tire

Abstract

Provided is a tire comprising a pair of beads, a pair of sidewalls, and a tread communicating with both sidewalls, the tread being divided into at least three sections in the tire width direction by a center part that includes the tire equatorial plane and a pair of shoulder parts that include the tread edges, wherein the tread rubber in the center part is vulcanized rubber with a rubber composition containing a rubber component including at least one type of modified styrene-butadiene copolymer rubber and at least 75 parts by mass of silica per 100 parts by mass of the rubber component, and additionally, ΔE' / E'4 is 0.900 or less, where ΔE' is the difference between the storage modulus E'0.1 of the tread rubber in the center part at 25°C and 0.1% strain and the storage modulus E'4 at 25°C and 4% strain. The tire exhibits excellent abrasion resistance and wet grip.

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] In the case of motorcycle tire treads, a tire has been developed that divides the tread into thirds across the tire width and uses two types of tread rubber to achieve a certain degree of compatibility between the performance required for straight-line driving and the performance required for cornering. For example, Patent Document 1 discloses a motorcycle tire including a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, the tread portion being divided into three in the tire width direction by a center portion including the tire equatorial plane and a pair of shoulder portions including the tread ends. In the motorcycle tire of Patent Document 1, the tread rubber of the center portion and the tread rubber of the shoulder portions both contain a rubber component including a styrene-butadiene rubber and a modified conjugated diene polymer, and silica, and contains 40 to 120 parts by mass of a filler per 100 parts by mass of the rubber component, and the silica content in the filler is 80% by mass or more. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 204236 Summary of the Invention [Problem to be solved by the invention]

[0004] In a two-wheel tire tread as shown in Patent Document 1, in addition to wear resistance, it is desired to achieve both dry grip performance (grip performance on dry road surfaces) and wet grip performance (grip performance on wet road surfaces). One of the means for achieving this high level of compatibility is tread division. The center rubber is required to achieve a high level of both wear resistance and wet grip performance, and improvements in the dispersion of fillers in the rubber have been studied. When the amount of filler in the rubber is small, the filler disperses better and the abrasion resistance improves, but it is difficult to improve wet grip performance. Therefore, there is room for further improvement in the technology for achieving a high level of wet grip without compromising abrasion resistance in the center rubber.

[0005] An object of the present invention is to provide a tire that is excellent in wear resistance and wet grip, and an object of the present invention is to achieve the object. [Means for solving the problem]

[0006] <1> A tire comprising a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, the tread portion being divided into at least three portions in the tire width direction by a center portion including a tire equatorial plane and a pair of shoulder portions including tread ends, The tread rubber of the center portion is a vulcanized rubber of a rubber composition containing a rubber component containing at least one modified styrene-butadiene copolymer rubber and 75 parts by mass or more of silica per 100 parts by mass of the rubber component, and the storage modulus E' of the tread rubber of the center portion at 25°C and strain of 0.1% 0.1 A tire in which ΔE' / E'4 is 0.900 or less, where ΔE' is the difference between the storage modulus E'4 at 25°C and 4% strain. The tire includes a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, the tread portion being divided into three portions in the tire width direction by a center portion including the tire equatorial plane and a pair of shoulder portions including tread ends, The tread rubber of the center portion is a vulcanized rubber of a rubber composition containing a rubber component containing at least one modified styrene-butadiene copolymer rubber and 75 parts by mass or more of silica per 100 parts by mass of the rubber component, and the storage modulus E' of the tread rubber of the center portion at 25°C and strain of 0.1% 0.1 and the storage modulus E'4 at 25° C. and a strain of 4%, ΔE', is preferably ΔE' / E'4 of 0.900 or less.

[0007] <2> The content of the silica in the rubber composition is 120 parts by mass or less per 100 parts by mass of the rubber component. <1> A tire as described in. <3> The rubber composition further contains carbon black, and a ratio of the silica to the total amount of the silica and the carbon black is 70 mass % or more. <1> or <2> A tire as described in.

[0008] <4> The rubber composition further contains 2 to 85 parts by mass of a softener based on 100 parts by mass of the rubber component. <1> ~ <3> 13. A tire according to any one of the preceding claims. <5> The softener contains a resin, and the resin is at least one selected from the group consisting of a C5 resin, a C9 resin, a C5-C9 resin, a terpene resin, a terpene-aromatic compound resin, a rosin resin, a dicyclopentadiene resin, and an alkylphenol resin. <4> A tire as described in. <6> The ratio of the resin to the total amount of the softener is 20 to 90 mass %. <5> A tire as described in.

[0009] <7> The rubber component further contains a modified butadiene rubber. <1> ~ <6> 13. A tire according to any one of the preceding claims. <8> The modified styrene-butadiene copolymer rubber has a weight average molecular weight of 20×10 4 More than 300 x 10 4 The molecular weight of the modified styrene-butadiene copolymer rubber is 200×10 or less relative to the total amount of the modified styrene-butadiene copolymer rubber. 4 Over 500 x 10 4The modified styrene-butadiene copolymer rubber is 0.25% by mass or more and 30% by mass or less, and the shrinkage factor (g') is less than 0.64. <1> ~ <7> 13. A tire according to any one of the preceding claims.

[0010] <9> The modified styrene-butadiene copolymer rubber has branches and a branching degree of 5 or more. <1> ~ <8> 13. A tire according to any one of the preceding claims. <10> The modified styrene-butadiene copolymer rubber has one or more coupling residues and a styrene-butadiene copolymer rubber chain bonded to the coupling residues, The branch includes a branch in which five or more of the styrene-butadiene copolymer rubber chains are bonded to one of the coupling residues. <10> A tire as described in. <11> The modified styrene-butadiene copolymer rubber is represented by the following formula (I): <1> ~ <10> 13. A tire according to any one of the preceding claims.

[0011] [ka]

[0012] In formula (I), D represents a styrene-butadiene copolymer rubber chain. 1 , R 2 and R 3 R each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. 4 and R 7 R each independently represents an alkyl group having 1 to 20 carbon atoms. 5 , R 8 , and R 9 R each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. 6 and R 10 R each independently represents an alkylene group having 1 to 20 carbon atoms. 11represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. m and x each independently represent an integer of 1 to 3, and x≦m. p represents 1 or 2. y represents an integer of 1 to 3, and y≦(p+1). z represents an integer of 1 or 2. i represents an integer of 0 to 6, j represents an integer of 0 to 6, k represents an integer of 0 to 6, and (i+j+k) is an integer of 3 to 10. ((x×i)+(y×j)+(z×k)) is an integer of 5 to 30. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, and a phosphorus atom, and having no active hydrogen. <12> In the formula (I), A is represented by the following formula (II), (III), (IV), or (V): <11> A tire as described in.

[0013] [ka]

[0014] [ka]

[0015] [ka]

[0016] [ka]

[0017] In formula (II), B 1 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms. a represents an integer of 1 to 10. In formula (III), B 2 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms; B 3 represents an alkyl group having 1 to 20 carbon atoms. a represents an integer of 1 to 10. In formula (IV), B 4represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms. a represents an integer of 1 to 10. In formula (V), B 5 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms. a represents an integer of 1 to 10. <13> The modified styrene-butadiene copolymer rubber is obtained by reacting a styrene-butadiene copolymer rubber with a coupling agent represented by the following formula (VI): <1> ~ <12> 13. A tire according to any one of the preceding claims.

[0018] [ka]

[0019] In formula (VI), R 12 , R 13 and R 14 R each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. 15 , R 16 , R 17 , R 18 and R 20 R each independently represents an alkyl group having 1 to 20 carbon atoms. 19 and R 22 R each independently represents an alkylene group having 1 to 20 carbon atoms. 21 represents an alkyl group or trialkylsilyl group having 1 to 20 carbon atoms, and m represents an integer of 1 to 3. p represents 1 or 2. i, j, and k each independently represent an integer of 0 to 6, with the proviso that (i+j+k) is an integer of 3 to 10. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, silicon atoms, sulfur atoms, and phosphorus atoms and having no active hydrogen.

[0020] <14> The coupling agent represented by the formula (VI) is at least one selected from the group consisting of tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, and tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane. <13> A tire as described in. <15> The content of the softener in the rubber composition is 72 parts by mass or less based on 100 parts by mass of the rubber component. <4> ~ <14> 13. A tire according to any one of the preceding claims. Effect of the Invention

[0021] According to the present invention, a tire having excellent wear resistance and wet grip performance can be provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The tire of the present invention comprises a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, and the tread portion is divided into at least three portions in the tire width direction by a center portion including the tire equatorial plane and a pair of shoulder portions including the tread ends. First, the structure of the tire will be described.

[0023] <Tire structure> Each bead portion usually has a bead core, and one or more carcass layers are provided between the pair of bead cores so as to extend in a toroidal shape. The carcass layer is made of a plurality of carcass cords covered with rubber. The sidewall portion extends radially outward from the bead portion on the side surface of the tire to reinforce and protect the side surface.

[0024] The tread portion extends across both sidewall portions. In the present invention, a split tread is used in which the tread portion is divided into a center portion and two shoulder portions sandwiching the center portion. The split tread is divided into at least three portions by a center portion including the tire equatorial plane and a pair of shoulder portions including the tread ends. The split tread may have an additional portion between the center portion and the shoulder portion, or the center portion may be divided into a plurality of portions. For example, the tread portion may be divided into a first shoulder portion, a second shoulder portion, a first center portion, a second center portion, a third shoulder portion, and a fourth shoulder portion in order from the tread ends. The divided tread is preferably divided into three by a center portion and a pair of shoulder portions. The tire equator is a latitude line of the tire that passes through the center of the tire in the width direction, and the surface in the tire circumferential direction that includes the tire equator is called the tire equatorial plane. More specifically, the center portion is the widthwise curve length (L C ) is the maximum length of the widthwise curve of the entire surface area of ​​the tread (L T The width direction curve length (L C ) is the maximum length of the widthwise curve of the entire surface area of ​​the tread (L T If the curvature length (L C ) is the maximum length of the widthwise curve of the entire surface area of ​​the tread (L T ) is 40 to 50%, it is advantageous in terms of achieving an excellent balance between wet grip properties and abrasion resistance. The widthwise curve length of the tread surface of the shoulder part (L S ) may be different between one shoulder part and the other shoulder part, but it is usually preferable that they are the same, and the curve length in the width direction of the shoulder part (one side) is L T It is preferable that the Lc content is (100-Lc) / 2%.

[0025] Hereinafter, the rubber constituting the tread portion may be referred to as "tread rubber." The rubber constituting the shoulder portion may be referred to as "tread rubber of the shoulder portion" or simply as "shoulder rubber." Moreover, the rubber constituting the center portion may be referred to as "tread rubber of the center portion" or simply as "center rubber." The rubber composition constituting the center rubber before vulcanization may be referred to as a rubber composition for the center rubber. In other words, the rubber obtained by vulcanizing the rubber composition for the center rubber is the center rubber.

[0026] <Tread rubber> The tread rubber (center rubber) of the center portion of the tire of the present invention has a storage modulus E' at 25°C and strain of 0.1%. 0.1 and the difference between the storage modulus E'4 at 25°C and strain 4% (E' 0.1 -E'4) is ΔE, and ΔE' / E'4 is 0.900 or less. The center rubber is a vulcanized rubber of a rubber composition containing a rubber component including at least one modified styrene-butadiene copolymer rubber and 75 parts by mass or more of silica per 100 parts by mass of the rubber component. The reason why the tire of the present invention has excellent wear resistance and wet grip performance due to the center rubber of the present invention having the above-mentioned configuration is not clear, but is presumed to be due to the following reasons. It is believed that the above rubber composition provides dispersion reinforcement of silica and improves abrasion resistance. It is believed that the tire has excellent wet performance because the rubber composition contains a large amount of silica. As a property of vulcanized rubber, the smaller ΔE' / E'4 indicates that the dispersibility of silica is improved. First, the vulcanized rubber characteristics of the center rubber will be described.

[0027] [Storage modulus difference ΔE'] As described above, the storage modulus E' of the center rubber in the present invention is the storage modulus E' at 25°C and strain of 0.1%. 0.1 and the difference between the storage modulus E'4 at 25°C and strain 4% (E' 0.1 -E'4) is ΔE', and ΔE' / E'4 is 0.900 or less. If ΔE′ / E′4 exceeds 0.900, the wear resistance and wet grip performance of the tire cannot be improved. The smaller the ΔE' / E'4, the better the dispersion of silica in the vulcanized rubber matrix. 0.1 represents the storage modulus of the smallest possible strain. The storage modulus changes greatly with strain, but E'4 represents the storage modulus in the region beyond the inflection point where the change in storage modulus becomes mild. By taking a good look at the difference, you can get a good look at the degree of dispersion.

[0028] From the viewpoint of further improving the wear resistance and wet grip performance of the tire, ΔE' / E'4 of the center rubber is preferably 0.22 or more, more preferably 0.27 or more, even more preferably 0.32 or more, even more preferably 0.37 or more, and still more preferably 0.42 or more. The lower limit of ΔE' / E'4 of the center rubber is not particularly limited, but from the viewpoint of preventing aggregation of the filler in the vulcanized rubber, it is preferably 0.89 or less, more preferably 0.87 or less, and even more preferably 0.85 or less.

[0029] From the viewpoint of further improving the abrasion resistance and wet grip performance of the tire, the ΔE′ of the center rubber is preferably 10.0 or less, more preferably 8.0 or less, and further preferably 6.0 or less. There is no particular lower limit for ΔE' of the center rubber, but from the viewpoint of preventing aggregation of the filler in the vulcanized rubber, ΔE' of the center rubber is preferably 0.1 or more, more preferably 0.5 or more, even more preferably 1.0 or more, and still more preferably 1.5 or more.

[0030] Storage modulus E' of center rubber at 25℃ and strain of 0.1% 0.1From the viewpoint of dispersibility of the filler in the vulcanized rubber, it is preferably 6.7 N / mm or more, more preferably 6.8 N / mm or more, even more preferably 6.9 N / mm or more, even more preferably 7.0 N / mm or more, even more preferably 7.1 N / mm or more, even more preferably 7.2 N / mm or more, even more preferably 7.5 N / mm or more, even more preferably 7.8 N / mm or more, even more preferably 8.2 N / mm or more, even more preferably 8.5 N / mm or more, even more preferably 8.8 N / mm or more, even more preferably 9.1 N / mm or more, even more preferably 9.3 N / mm or more, even more preferably 9.5 N / mm or more, and even more preferably 9.9 N / mm or more. Storage modulus E' of center rubber at 25℃ and strain of 0.1% 0.1 is preferably 15.0 N / mm or less, more preferably 14.5 N / mm or less, even more preferably 13.8 N / mm or less, and even more preferably 13.3 N / mm or less. The storage modulus E' of the center rubber can be measured, for example, by using a viscoelasticity measuring device. Next, the rubber composition constituting the center rubber (rubber composition for the center rubber) will be described.

[0031] [Rubber composition] The rubber composition of the center rubber (rubber composition for center rubber) in the present invention contains a rubber component containing at least one type of modified styrene-butadiene copolymer rubber, and 75 parts by mass or more of silica per 100 parts by mass of the rubber component. When the rubber composition for the center rubber has the above-mentioned composition, ΔE′ / E′4 of the center rubber tends to be 0.900 or less. The rubber composition for the center rubber may further contain a rubber component other than the modified styrene-butadiene copolymer rubber, a filler other than silica, and various other components.

[0032] [Rubber component] In the rubber composition for the center rubber, the rubber component contains at least one type of modified styrene-butadiene copolymer rubber. When the rubber component constituting the center rubber contains a modified styrene-butadiene copolymer rubber, the ΔE′ / E′4 of the center rubber tends to be 0.900 or less.

[0033] (Modified styrene-butadiene copolymer rubber) The modified styrene-butadiene copolymer rubber in the present invention is not particularly limited as long as the styrene-butadiene copolymer rubber chain has a structure having a modifying group. For example, there may be mentioned a structure in which at least one end of a styrene-butadiene copolymer rubber chain has a modifying group containing a nitrogen atom and a silicon atom. The modified styrene-butadiene copolymer rubber contains nitrogen atoms and silicon atoms, which improves the processability of the rubber composition for the center rubber, and can further reduce the rolling resistance while improving the wet grip and abrasion resistance of the tire. The presence of nitrogen atoms in the modified styrene-butadiene copolymer rubber body can be confirmed by the presence or absence of adsorption to a specific column using the method described in the Examples below. The presence of silicon atoms in the modified styrene-butadiene copolymer rubber can be confirmed by metal analysis using the method described in the Examples below.

[0034] A modified styrene-butadiene copolymer rubber having a structure in which at least one end of a styrene-butadiene copolymer rubber chain has a modifying group containing a nitrogen atom and a silicon atom can be obtained by reacting, for example, a coupling agent containing a nitrogen atom and a silicon atom with a styrene-butadiene copolymer rubber.

[0035] At least one end of the styrene-butadiene copolymer rubber chain is preferably bonded to a silicon atom of each coupling residue. In this case, the ends of a plurality of styrene-butadiene copolymer rubbers may be bonded to one silicon atom. In addition, an end of the styrene-butadiene copolymer rubber chain and an alkoxy group or hydroxyl group having 1 to 20 carbon atoms may be bonded to one silicon atom, and as a result, the one silicon atom may constitute an alkoxysilyl group or silanol group having 1 to 20 carbon atoms.

[0036] The modified styrene-butadiene copolymer rubber preferably has a branched structure. In general, polymers having branches tend to have smaller molecular size compared to linear polymers of the same absolute molecular weight, and the shrinkage factor (g') is an index of the ratio of the molecular size to that of a linear polymer of the same assumed absolute molecular weight. In other words, the shrinkage factor (g') tends to be smaller as the degree of branching of a polymer increases. In this embodiment, intrinsic viscosity is used as an index of molecular size, and linear polymers have an intrinsic viscosity [η] = -3.883M 0.771 The shrinkage factor (g') for each absolute molecular weight of the modified styrene-butadiene copolymer rubber is calculated, and the shrinkage factor (g') is calculated when the absolute molecular weight is 100 x 10 4 ~200×10 4 The average value of the shrinkage factor (g') at this time is defined as the shrinkage factor (g') of the modified styrene-butadiene copolymer rubber. Here, the term "branched" refers to a structure formed by directly or indirectly bonding one polymer to another polymer. The "branching degree" is the number of polymers that are directly or indirectly bonded to each other per branch. For example, when five styrene-butadiene copolymer rubber chains described below are indirectly bonded to each other via coupling residues described below, the branching degree is 5. The coupling residue is a structural unit of a modified styrene-butadiene copolymer rubber that is bonded to a styrene-butadiene copolymer rubber chain, and is, for example, a structural unit derived from a coupling agent that is generated by reacting a styrene-butadiene copolymer rubber described later with a coupling agent. The styrene-butadiene copolymer rubber chain is a structural unit of a modified styrene-butadiene copolymer rubber, and is, for example, a structural unit derived from a styrene-butadiene copolymer rubber produced by reacting a styrene-butadiene copolymer rubber described later with a coupling agent.

[0037] The weight average molecular weight (Mw) of the modified styrene-butadiene copolymer rubber is 20×10 4 More than 300 x 10 4 It is preferable that: Weight average molecular weight is 20×10 4 When the weight average molecular weight is 300×10 or more, the wet grip performance of the tire is improved and the rolling resistance is easily reduced. 4 When the content is equal to or less than 1, the processability of the rubber composition for the center rubber can be improved. The weight average molecular weight of the modified styrene-butadiene copolymer rubber is 50×10 4 More preferably, 64×10 4 More preferably, it is 80×10 or more. 4 The weight average molecular weight of the modified styrene-butadiene copolymer rubber is preferably 250×10 or more. 4 It is more preferable that it is less than 180×10 4 More preferably, it is 150×10 4 Even more preferably, it is: In this specification, the term "molecular weight" refers to a standard polystyrene-equivalent molecular weight obtained by GPC (gel permeation chromatography). The weight average molecular weight of the modified styrene-butadiene copolymer rubber and the styrene-butadiene copolymer rubber described later are measured by the method described in the Examples described later.

[0038] The modified styrene-butadiene copolymer rubber has a molecular weight of 200 × 10 relative to the total amount (100 mass%) of the modified styrene-butadiene copolymer rubber. 4 Over 500 x 10 4 It is preferable that the modified styrene-butadiene copolymer rubber having a molecular weight of 200×10 or less is contained in an amount of 0.25% by mass or more and 30% by mass or less. 4 Over 500 x 10 4 The modified styrene-butadiene copolymer rubber described below is also referred to as a "specific high molecular weight component." When the content of the specific high molecular weight component in the total amount of the modified styrene-butadiene copolymer rubber is within the above range, the wet grip performance of the tire and reduced rolling resistance can both be achieved at a high level.

[0039] The content of the specific high molecular weight component in the total amount of the modified styrene-butadiene copolymer rubber is more preferably 1.0 mass% or more, even more preferably 1.4 mass% or more, even more preferably 1.75 mass% or more, even more preferably 2.0 mass% or more, even more preferably 2.15 mass% or more, and even more preferably 2.5 mass% or more. In addition, the content of the specific high molecular weight component in the total amount of the modified styrene-butadiene copolymer rubber is more preferably 28 mass% or less, even more preferably 25 mass% or less, even more preferably 20 mass% or less, and even more preferably 18 mass% or less. The modified styrene-butadiene copolymer rubber having a content of the specific high molecular weight component within the above range can be easily obtained by controlling the reaction conditions in the polymerization step and the reaction step in the production method described below. For example, in the polymerization step, the amount of the organic monolithium compound used as a polymerization initiator, which will be described later, may be adjusted. In addition, in the polymerization step, a method having a residence time distribution may be used in both continuous and batch polymerization modes. That is, the time distribution of the growth reaction may be broadened.

[0040] In the modified styrene-butadiene copolymer rubber, the molecular weight distribution (Mw / Mn), which is expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 1.6 to 3.0. When the molecular weight distribution of the modified styrene-butadiene copolymer rubber is in this range, the processability of the rubber composition for the center rubber can be improved. The number average molecular weight, weight average molecular weight, molecular weight distribution, and content of specific high molecular weight components for the modified styrene-butadiene copolymer rubber and the styrene-butadiene copolymer rubber described later are measured by the method described in the examples described later.

[0041] The modified styrene-butadiene copolymer rubber preferably has a shrinkage factor (g') of less than 0.64. By using a modified styrene-butadiene copolymer rubber having a shrinkage factor (g') of less than 0.64, the processability of the rubber composition for the center rubber can be improved. The shrinkage factor (g') of the modified styrene-butadiene copolymer rubber is more preferably 0.63 or less, further preferably 0.60 or less, even more preferably 0.59 or less, and further more preferably 0.57 or less. The lower limit of the shrinkage factor (g') of the modified styrene-butadiene copolymer rubber is not particularly limited and may be equal to or lower than the detection limit. The shrinkage factor (g') of the modified styrene-butadiene copolymer rubber is preferably 0.30 or more, more preferably 0.33 or more, even more preferably 0.35 or more, and even more preferably 0.45 or more.

[0042] Since the shrinkage factor (g') tends to depend on the degree of branching, for example, the shrinkage factor (g') can be controlled using the degree of branching as an index. Specifically, for example, the shrinkage factor (g') of a modified styrene-butadiene copolymer rubber having a degree of branching of 6 tends to be 0.59 or more and 0.63 or less. Also, the shrinkage factor (g') of a modified styrene-butadiene copolymer rubber having a degree of branching of 8 tends to be 0.45 or more and 0.59 or less. The contraction factor (g') is measured by the method described in the Examples below.

[0043] The modified styrene-butadiene copolymer rubber has a branch and preferably has a branching degree of 5 or more. The modified styrene-butadiene copolymer rubber has one or more coupling residues and a styrene-butadiene copolymer rubber bonded to the coupling residue, and more preferably, the branching includes a branch in which 5 or more styrene-butadiene copolymer rubber chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene copolymer rubber so that the branching degree is 5 or more and the branching includes a branch in which 5 or more styrene-butadiene copolymer rubber chains are bonded to one coupling residue, the contraction factor (g') can be more reliably made less than 0.64. The number of styrene-butadiene copolymer rubber chains bonded to one coupling residue can be confirmed from the value of the contraction factor (g').

[0044] Moreover, the modified styrene-butadiene copolymer rubber has branches, and more preferably has a branching degree of 6 or more. Moreover, the modified styrene-butadiene copolymer rubber has one or more coupling residues and a styrene-butadiene copolymer rubber chain bonded to the coupling residue, and further preferably includes a branch in which 6 or more of the styrene-butadiene copolymer rubber chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene copolymer rubber so that the branching degree is 6 or more and the branching includes a branch in which 6 or more styrene-butadiene copolymer rubber chains are bonded to one coupling residue, the shrinkage factor (g') can be made 0.63 or less. Furthermore, the modified styrene-butadiene copolymer rubber has branches, and the branching degree is more preferably 7 or more, and even more preferably 8 or more. The upper limit of the branching degree is not particularly limited, but it is preferably 18 or less. The modified styrene-butadiene copolymer rubber has one or more coupling residues and a styrene-butadiene copolymer rubber chain bonded to the coupling residue, and further, it is more preferable that the branching includes a branch in which 7 or more styrene-butadiene copolymer rubber chains are bonded to one coupling residue, and it is particularly preferable that the branching includes a branch in which 8 or more styrene-butadiene copolymer rubber chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene copolymer rubber so that the branching degree is 8 or more and the branching includes a branch in which 8 or more styrene-butadiene copolymer rubber chains are bonded to one coupling residue, the shrinkage factor (g') can be made 0.59 or less.

[0045] The modified styrene-butadiene copolymer rubber preferably has a glass transition temperature (Tg) exceeding −50° C., more preferably from −30° C. to −20° C., and further preferably from −45° C. to −15° C. When the glass transition temperature (Tg) of the modified styrene-butadiene copolymer rubber is in the range of from −45° C. to −15° C., the wet grip performance of the tire can be further improved, the rolling resistance can be reduced, and the abrasion resistance can be further improved. The glass transition temperature is measured in accordance with ISO 22768:2006 by recording a DSC curve while increasing the temperature within a specified temperature range, and the peak top (inflection point) of the DSC differential curve is taken as the glass transition temperature.

[0046] The modified styrene-butadiene copolymer rubber can be an oil-extended polymer to which an extender oil is added. The modified styrene-butadiene copolymer rubber may be either non-oil-extended or oil-extended, but from the viewpoint of the wear resistance of the tire, the Mooney viscosity measured at 100° C. is preferably 20 or more and 100 or less, and more preferably 30 or more and 80 or less. The Mooney viscosity is measured by the method described in the examples described later.

[0047] The modified styrene-butadiene copolymer rubber is preferably represented by the following formula (I) from the viewpoint of further improving the wet grip performance and abrasion resistance of the tire.

[0048] [ka]

[0049] In formula (I), D represents a styrene-butadiene copolymer rubber chain. 1 , R 2 and R 3 R each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. 4 and R 7 R each independently represents an alkyl group having 1 to 20 carbon atoms. 5 , R 8 , and R 9 R each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. 6 and R 10 R each independently represents an alkylene group having 1 to 20 carbon atoms. 11 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. m and x each independently represent an integer of 1 to 3, and x≦m. p represents 1 or 2. y represents an integer of 1 to 3, and y≦(p+1). z represents an integer of 1 or 2. i represents an integer of 0 to 6, j represents an integer of 0 to 6, k represents an integer of 0 to 6, and (i+j+k) is an integer of 3 to 10. ((x×i)+(y×j)+(z×k)) is an integer of 5 to 30. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, and a phosphorus atom, and having no active hydrogen.

[0050] The weight average molecular weight of the styrene-butadiene copolymer rubber chain represented by D is 10 × 10 4 ~100×10 4 The styrene-butadiene copolymer rubber chain is a structural unit of the modified styrene-butadiene copolymer rubber, and is, for example, a structural unit derived from the styrene-butadiene copolymer rubber produced by reacting the styrene-butadiene copolymer rubber with a coupling agent.

[0051] In formula (I), D, R 4 , R 5 , and R 7 ~R 9 When there are multiple of each, D and R are multiple 4 , R 5 , and R 7 ~R 9 may be the same or different. In addition, when i, j, and k are 2 or more, and thus a plurality of the following partial structures (Ii), (Ij), and (Ik) are present in formula (I), the partial structures (Ii), (Ij), and (Ik) may be the same structure or different structures.

[0052] [ka]

[0053] [ka]

[0054] [ka]

[0055] The hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of organic groups that do not have active hydrogen include organic groups that do not have functional groups that have active hydrogen, such as a hydroxyl group (-OH), a secondary amino group (>NH), a primary amino group (-NH2), or a sulfhydryl group (-SH).

[0056] In the above formula (I), A is preferably represented by any one of the following formulas (II) to (V). When A is represented by any one of the formulas (II) to (V), the tire can have low rolling resistance, improved wear resistance, and improved wet grip performance.

[0057] [ka]

[0058] In formula (II), B 1 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms. a represents an integer of 1 to 10. When a is 2 or more, B 1 If there are multiple B 1 may be the same or different.

[0059] [ka]

[0060] In formula (III), B 2 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms; B 3 represents an alkyl group having 1 to 20 carbon atoms. a represents an integer of 1 to 10. When a is 2 or more, B 2 and B. 3 If there are multiple B 2 and B. 3 may be the same or different.

[0061] [ka]

[0062] In formula (IV), B4 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a is 2 or more, B 4 If there are multiple B 4 may be the same or different.

[0063] [ka]

[0064] In formula (V), B 5 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a is 2 or more, B 5 If there are multiple B 5 may be the same or different.

[0065] B in formulas (II) to (V) 1 , B 2 , B 4 and B. 5 With regard to the above, examples of the hydrocarbon group having 1 to 20 carbon atoms include an alkylene group having 1 to 20 carbon atoms.

[0066] In formula (I), it is preferable that A is represented by formula (II) or (III) and k is 0, and it is more preferable that A is represented by formula (II) or (III) and k is 0, and in formula (II) or (III), a is an integer of 2 to 10. In formula (I), a structure in which A is represented by formula (II) and k0, and in formula (II), a is an integer of 2 to 10, is even more preferable.

[0067] (Method of manufacturing modified styrene-butadiene copolymer rubber) The manufacturing method of the modified styrene-butadiene copolymer rubber is not particularly limited, but from the viewpoint of the ease of forming the branched structure described above, it is preferable to have the following steps. That is, it is preferable to have a polymerization step of polymerizing styrene and butadiene using an organic monolithium compound as a polymerization initiator to obtain a styrene-butadiene copolymer rubber, and a reaction step of reacting an active terminal of the styrene-butadiene copolymer rubber with a pentafunctional or higher reactive compound (hereinafter also referred to as a "specific coupling agent"). As the specific coupling agent, it is preferable to react a pentafunctional or higher reactive compound having a nitrogen atom and a silicon atom.

[0068] The reactive compound (coupling agent) is preferably a pentafunctional or higher reactive compound having a nitrogen atom and a silicon atom, and preferably has at least three silicon-containing functional groups. More preferably, the specific coupling agent is one in which at least one silicon atom constitutes an alkoxysilyl group or a silanol group having 1 to 20 carbon atoms.

[0069] The alkoxysilyl group of the specific coupling agent tends to react with, for example, the active terminal of the styrene-butadiene copolymer rubber, dissociating the alkoxylithium, and forming a bond between the terminal of the styrene-butadiene copolymer rubber chain and the silicon of the coupling residue. The value obtained by subtracting the number of SiO R subtracted by the reaction from the total number of SiO R of one molecule of the coupling agent is the number of alkoxysilyl groups of the coupling residue. In addition, the azasilacycle group of the coupling agent forms a >N-Li bond and a bond between the terminal of the styrene-butadiene copolymer rubber and the silicon of the coupling residue. In addition, the >N-Li bond tends to easily become >NH and LiOH due to water or the like during finishing. In addition, the alkoxysilyl group remaining unreacted in the coupling agent tends to easily become a silanol (Si-OH group) due to water or the like during finishing.

[0070] The specific coupling agent is preferably represented by formula (VI). In other words, the modified styrene-butadiene copolymer rubber is preferably obtained by reacting a styrene-butadiene copolymer rubber with a coupling agent represented by formula (VI). By forming the center rubber from a rubber composition containing the modified styrene-butadiene copolymer rubber obtained by reacting with the coupling agent, the wear resistance of the tire can be improved and the rolling resistance can be reduced.

[0071] [ka]

[0072] In formula (VI), R 12 , R 13 and R 14 R each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. 15 , R 16 , R 17 , R 18 and R 20 R each independently represents an alkyl group having 1 to 20 carbon atoms. 19 and R 22 R each independently represents an alkylene group having 1 to 20 carbon atoms. 21 represents an alkyl group or trialkylsilyl group having 1 to 20 carbon atoms, and m represents an integer of 1 to 3. p represents 1 or 2. i, j, and k each independently represent an integer of 0 to 6, with the proviso that (i+j+k) is an integer of 3 to 10. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, silicon atoms, sulfur atoms, and phosphorus atoms and having no active hydrogen.

[0073] In the formula (VI), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of the organic group that does not have an active hydrogen include organic groups that do not have a functional group that has an active hydrogen, such as a hydroxyl group (-OH), a secondary amino group (>NH), a primary amino group (-NH2), or a sulfhydryl group (-SH).

[0074] In formula (VI), A is preferably represented by any one of the above-mentioned formulas (II) to (V). When A has a structure represented by any one of formulas (II) to (V), a modified styrene-butadiene copolymer rubber having better performance can be obtained. The specific coupling agent preferably has a structure in which A is represented by formula (II) or (III) and k is 0 in formula (VI). In formula (VI), it is more preferable that A is represented by formula (II) or (III), k is 0, and in formula (II) or (III), a is an integer from 2 to 10, and it is even more preferable that A is represented by formula (II), k is 0, and in formula (II), a is an integer from 2 to 10.

[0075] Examples of such coupling agents include bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, tris(3-trimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, cyclopentane)propyl]-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, tris(3-trimethoxysilylpropyl)-methyl-1,3-propanediamine, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trismethoxysilylpropyl)-methyl-1,3-propanediamine, and the like. The above coupling agents may be used alone or in combination of two or more. Among these, the coupling agent represented by formula (VI) is particularly preferably tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, or tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane.

[0076] The amount of the compound represented by formula (VI) added as the coupling agent can be adjusted so that the mole number of the styrene-butadiene copolymer rubber to the mole number of the coupling agent reacts at a desired stoichiometric ratio, which tends to achieve a desired branching degree. The specific mole number of the polymerization initiator is preferably 5.0 times or more, more preferably 6.0 times or more, relative to the mole number of the coupling agent. In this case, in formula (VI), the number of functional groups of the coupling agent ((m-1)×i+p×j+k) is preferably an integer of 5 to 10, more preferably an integer of 6 to 10.

[0077] In the method for producing the modified styrene-butadiene copolymer rubber, the polymerization step is preferably polymerization by a propagation reaction by a living anionic polymerization reaction, which can obtain a styrene-butadiene copolymer rubber having an active terminal and a modified styrene-butadiene copolymer rubber with a high modification rate. The styrene-butadiene copolymer rubber is obtained by copolymerizing at least styrene and butadiene styrene-butadiene copolymer rubber.

[0078] The amount of organic monolithium compound used as a polymerization initiator is preferably determined according to the molecular weight of the target styrene-butadiene copolymer rubber or modified styrene-butadiene copolymer rubber. The amount of monomer such as conjugated diene compound used relative to the amount of polymerization initiator used is related to the degree of polymerization, that is, related to the number average molecular weight and / or weight average molecular weight. Therefore, in order to increase the molecular weight, it is good to adjust the amount of polymerization initiator to decrease, and in order to decrease the molecular weight, it is good to adjust the amount of polymerization initiator to increase. From the viewpoint of industrial availability and ease of control of polymerization reaction, the organic monolithium compound is preferably an alkyllithium compound. In this case, a styrene-butadiene copolymer rubber having an alkyl group at the polymerization initiation terminal is obtained. Examples of the alkyllithium compound include n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium. From the viewpoint of industrial availability and ease of control of polymerization reaction, n-butyllithium and sec-butyllithium are preferred as the alkyllithium compound. These organic monolithium compounds may be used alone or in combination of two or more.

[0079] In the polymerization step, examples of the polymerization reaction mode include batch and continuous polymerization reaction modes. In the continuous mode, one or more connected reactors can be used. For the continuous mode, for example, a tank type or a tube type with a stirrer is used. In the continuous mode, preferably, a monomer, an inert solvent, and a polymerization initiator are continuously fed into the reactor, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is continuously discharged. For the batch mode, for example, a tank type with a stirrer is used. In the batch mode, preferably, a monomer, an inert solvent, and a polymerization initiator are fed, and if necessary, a monomer is continuously or intermittently added during polymerization, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is discharged after the polymerization is completed. In this embodiment, in order to obtain a styrene-butadiene copolymer rubber having a high proportion of active ends, a continuous mode is preferred, which allows the polymer to be continuously discharged and subjected to the next reaction in a short time.

[0080] The polymerization step is preferably carried out in an inert solvent. Examples of the solvent include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific examples of the hydrocarbon solvent include, but are not limited to, aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene, and hydrocarbons consisting of mixtures thereof. By treating the impurities, ie, allenes and acetylenes, with an organometallic compound before subjecting the mixture to the polymerization reaction, a styrene-butadiene copolymer rubber having a high concentration of active terminals tends to be obtained, and a modified styrene-butadiene copolymer rubber having a high modification rate tends to be obtained, which is preferable.

[0081] In the polymerization step, a polar compound may be added. By adding the polar compound, the aromatic vinyl compound can be randomly copolymerized with the conjugated diene compound, and the polar compound tends to be usable as a vinylizing agent for controlling the microstructure of the conjugated diene portion. Examples of the polar compounds that can be used include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium tert-butylate, and sodium tert-amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used alone or in combination of two or more.

[0082] In the polymerization step, from the viewpoint of productivity, the polymerization temperature is preferably 0° C. or higher, more preferably 120° C. or lower, and particularly preferably 50° C. or higher and 100° C. or lower. By keeping the temperature within such a range, there is a tendency that the amount of the coupling agent reacting with the active terminal after the polymerization is completed can be sufficiently ensured.

[0083] The amount of bound conjugated diene in the styrene-butadiene copolymer rubber or modified styrene-butadiene copolymer rubber is not particularly limited, but is preferably from 40% by mass to 100% by mass, and more preferably from 55% by mass to 80% by mass. In addition, the amount of bound aromatic vinyl in the styrene-butadiene copolymer rubber or the modified styrene-butadiene copolymer rubber is not particularly limited, but is preferably 0% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 45% by mass or less, even more preferably 30% by mass or more and 45% by mass or less, particularly preferably 35% by mass or more and 45% by mass or less, extremely preferably 39% by mass or more and 45% by mass or less, and most preferably 40% by mass or more and 45% by mass or less. When the amount of bound conjugated diene and the amount of bound aromatic vinyl are within the above ranges, the wet grip performance and wear resistance of the tire can be improved. The amount of bound aromatic vinyl can be measured by ultraviolet absorption of the phenyl group, and the amount of bound conjugated diene can also be calculated from the amount. Specifically, the amount is measured according to the method described in the examples below.

[0084] The reaction temperature in the reaction step is preferably the same as the polymerization temperature of the styrene-butadiene copolymer rubber, more preferably from 0° C. to 120° C., and further preferably from 50° C. to 100° C. In addition, the temperature change from the end of the polymerization step to the addition of the coupling agent is preferably 10° C. or less, more preferably 5° C. or less. The reaction time in the reaction step is preferably 10 seconds or more, more preferably 30 seconds or more. From the viewpoint of the coupling rate, the time from the end of the polymerization step to the start of the reaction step is preferably shorter, and more preferably within 5 minutes.

[0085] The mixing in the reaction step may be performed by mechanical stirring, stirring with a static mixer, or the like. When the polymerization step is a continuous process, it is preferable that the reaction step is also a continuous process. The reactor used in the reaction step may be, for example, a tank type or a tube type equipped with a stirrer. The coupling agent may be diluted with an inert solvent and continuously fed to the reactor. When the polymerization step is a batch process, the coupling agent may be added to the polymerization reactor, or may be transferred to another reactor to carry out the reaction step.

[0086] In order to obtain a modified styrene-butadiene copolymer rubber having a specific high molecular weight component, the molecular weight distribution (Mw / Mn) of the styrene-butadiene copolymer rubber is preferably 1.5 to 2.5, more preferably 1.8 to 2.2. In addition, it is preferable that the obtained modified styrene-butadiene copolymer rubber (A2) has a single peak in the molecular weight curve by GPC. When the peak molecular weight of the modified styrene-butadiene copolymer rubber by GPC is Mp1 and the peak molecular weight of the styrene-butadiene copolymer rubber is Mp2, it is preferable that the following formula is satisfied. (Mp1 / Mp2)<1.8×10-12×(Mp2-120×10 4 ) 2 +2 Mp2 is 20 x 10 4 Over 80×10 4 Below, Mp1 is 30 x 10 4 Over 150 x 10 4 The following is more preferred: Mp1 and Mp2 are determined by the method described in the Examples below.

[0087] The modification rate of the modified styrene-butadiene copolymer rubber is preferably 30% by mass or more, more preferably 50% by mass or more, and further preferably 70% by mass or more. When the modification rate is 30% by mass or more, the tire can have improved wear resistance and reduced rolling resistance. The modification rate is measured by the method described in the examples below.

[0088] After the reaction step, a deactivator, neutralizing agent, etc. may be added to the copolymer solution as necessary. Examples of deactivators include, but are not limited to, water; alcohols such as methanol, ethanol, isopropanol, etc. Examples of neutralizing agents include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, with 10 being the main carbon atom); aqueous solutions of inorganic acids, and carbon dioxide gas. In addition, from the viewpoint of preventing gel formation after polymerization and improving stability during processing, it is preferable to add an antioxidant such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol) propionate, or 2-methyl-4,6-bis[(octylthio)methyl]phenol to the modified styrene-butadiene copolymer rubber.

[0089] In order to further improve the processability of the modified styrene-butadiene copolymer rubber, an extender oil can be added to the modified conjugated diene copolymer as necessary. The method of adding the extender oil to the modified styrene-butadiene copolymer rubber is not limited to the following, but a method of adding the extender oil to the polymer solution, mixing, and desolvating the oil-extended copolymer solution is preferred. Examples of the extender oil include aromatic oil, naphthene oil, paraffin oil, etc. Among these, from the viewpoint of environmental safety, prevention of oil bleeding, and wet performance, aromatic substitute oils having a polycyclic aromatic (PCA) component of 3 mass% or less according to the IP346 method are preferred. Examples of the aromatic substitute oil include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), etc. shown in Kautschuk Gummi Kunststoffe 52 (12) 799 (1999), as well as RAE (Residual Aromatic Extracts).

[0090] The amount of the extending oil added is not particularly limited, but is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and particularly preferably 12 parts by mass or less, relative to 100 parts by mass of the modified styrene-butadiene copolymer rubber. The amount of the extending oil added is preferably 1% by mass or more, more preferably 3% by mass or more, and particularly preferably 5% by mass or more, relative to 100 parts by mass of the modified styrene-butadiene copolymer rubber.

[0091] The modified styrene-butadiene copolymer rubber can be obtained from the polymer solution by a known method, such as a method of separating the solvent by steam stripping or the like, filtering the polymer, and then dehydrating and drying it to obtain the polymer, a method of concentrating the polymer in a flashing tank and then devolatilizing the polymer with a vent extruder or the like, and a method of directly devolatilizing the polymer with a drum dryer or the like.

[0092] The content of the modified styrene-butadiene copolymer rubber in the rubber component of the rubber composition for the center rubber is preferably 20 to 70 mass%, more preferably 30 to 50 mass%. When the content of the modified styrene-butadiene copolymer rubber in the rubber component is 20 mass% or more, the wet grip performance of the tire can be further improved. Also, when the content of the modified styrene-butadiene copolymer rubber in the rubber component is 70 mass% or less, the processability of the rubber composition for the center rubber can be improved.

[0093] The rubber component of the rubber composition for the center rubber preferably further contains a rubber component (other rubber component) other than the modified styrene-butadiene copolymer rubber. The other rubber component may be at least one selected from the group consisting of natural rubber, butadiene rubber, styrene-butadiene copolymer rubber, and isoprene rubber (synthetic isoprene rubber). By including the other rubber component, the wet grip property and abrasion resistance of the tire can be improved, and the rolling resistance can be reduced. The other rubber component may be an unmodified rubber or a modified rubber. The other rubber component is preferably a modified or unmodified butadiene rubber, and more preferably a modified butadiene rubber. In other words, the rubber component of the rubber composition for the center rubber preferably contains a modified styrene-butadiene copolymer rubber and further a modified or unmodified butadiene rubber, and more preferably contains a modified styrene-butadiene copolymer rubber and further a modified butadiene rubber.

[0094] [Filler] The rubber composition for the center rubber contains 75 parts by mass or more of silica as a filler based on 100 parts by mass of the rubber component. When the content of silica in the rubber composition for the center rubber is 75 parts by mass or more per 100 parts by mass of the rubber component, the tire has excellent wet grip property. From the viewpoint of further improving the wet grip performance of the tire, the content of silica in the rubber composition for the center rubber is preferably 78 parts by mass or more, more preferably 82 parts by mass or more, even more preferably 85 parts by mass or more, and still more preferably 87 parts by mass or more, per 100 parts by mass of the rubber component. From the viewpoint of processability of the rubber composition, the content of silica in the rubber composition for the center rubber is preferably 120 parts by mass or less, more preferably 117 parts by mass or less, even more preferably 115 parts by mass or less, even more preferably 112 parts by mass or less, and even more preferably 108 parts by mass or less, per 100 parts by mass of the rubber component.

[0095] Examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc., and among these, wet silica is preferred. These silicas may be used alone or in combination of two or more. The wet silica may be precipitated silica, which is obtained by growing primary silica particles by reacting the reaction solution at a relatively high temperature in a neutral to alkaline pH range in the early stages of production, and then controlling the reaction solution to the acidic side to aggregate the primary particles.

[0096] In addition, silica has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 60 to 200 m 2 It is preferable that the molecular weight is 1 / g. CTAB is 200m 2 When the tensile strength is 1 / g or less, the rolling resistance is reduced and the processability and workability of the rubber composition are not likely to decrease. Silica CTAB is 80m 2 / g or more is more preferable, and 100m 2 More preferably, it is 130m 2 / g or more, and more preferably 140m 2 / g or more is more preferable. Also, the CTAB of silica is 190m 2 / g or less is more preferable, and 185m 2 It is more preferable that the molecular weight is / g.

[0097] Cetyltrimethylammonium bromide adsorption specific surface area (CTAB) (m 2 / g) means a value measured in accordance with ASTM D3765-92. However, since ASTM D3765-92 is a method for measuring the CTAB of carbon black, in the present invention, the standard product IRB#3 (83.0 m 2 Instead of cetyltrimethylammonium bromide (hereinafter abbreviated as CE-TRAB) (1000 mg / g), a cetyltrimethylammonium bromide (hereinafter abbreviated as CE-TRAB) standard solution was separately prepared, and the silica OT (di-2-ethylhexyl sodium sulfosuccinate) solution was standardized with this solution. The adsorption cross section of one molecule of CE-TRAB on the silica surface was determined to be 0.35 nm 2 is the specific surface area (m2) calculated from the amount of CE-TRAB adsorbed. 2 / g) is taken as the value of CTAB. This is because the surfaces of carbon black and silica are different, and it is considered that there is a difference in the amount of CE-TRAB adsorbed even with the same surface area.

[0098] The filler may further contain a reinforcing filler other than silica, and examples thereof include metal oxides other than silica and carbon black. The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. Among these, ISAF and SAF grade carbon black are preferred from the viewpoint of improving the abrasion resistance of the center rubber. These carbon blacks may be used alone or in combination of two or more.

[0099] The content of carbon black in the rubber composition for the center rubber is not particularly limited, but is preferably in the range of 1 to 15 parts by mass, and more preferably in the range of 3 to 10 parts by mass, per 100 parts by mass of the rubber component. By making the content of carbon black 1 part by mass or more per 100 parts by mass of the rubber component, the wear resistance of the tire is further improved, and by making the content 15 parts by mass or less, the rolling resistance of the tire is unlikely to increase.

[0100] The ratio of silica to the total amount of silica and carbon black (referred to as silica ratio) is preferably 70 mass % or more. A silica ratio of 70% by mass can contribute to improving the low loss properties of the center rubber (and thus reducing rolling resistance) and improving abrasion resistance. From the viewpoint of processability of the rubber composition, the silica ratio is preferably equal to or less than 99 mass %. From the viewpoint of improving the wear resistance of the tire while improving the processability of the rubber composition, the silica ratio is more preferably 75 to 98 mass%, even more preferably 79 to 97 mass%, and even more preferably 83 to 96 mass%.

[0101] (Silane coupling agent) The rubber composition for the center rubber may contain a silane coupling agent in order to improve the compounding effect of silica. As the silane coupling agent, a compound represented by the following formula (VII), a compound represented by the following formula (VIII), a compound represented by the following formula (IX), and a compound represented by the following formula (X) are preferred. These silane coupling agents may be used alone or in combination of two or more.

[0102] Formula (VII) has the following structure: A m B 3-m Si-(CH2) a -S b -(CH2) a -SiA m B 3-m (VII) In the formula (VII), A is C n H 2n+1 O (n is an integer of 1 to 3) or a chlorine atom, B is an alkyl group having 1 to 3 carbon atoms, m is an integer of 1 to 3, a is an integer of 1 to 9, and b is an integer of 1 or greater. However, when m is 1, B may be the same as or different from each other, and when m is 2 or 3, A may be the same as or different from each other.

[0103] Examples of the compound represented by formula (VII) include bis(3-triethoxysilylpropyl) tetrasulfide, bis(3-trimethoxysilylpropyl) tetrasulfide, bis(3-methyldimethoxysilylpropyl) tetrasulfide, bis(3-triethoxysilylethyl) tetrasulfide, bis(3-triethoxysilylpropyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, and bis(3-triethoxysilylpropyl) trisulfide.

[0104] Formula (VIII) is the following structure: A m B 3-m Si-(CH2) c -Y (VIII) In the formula (VIII), A is C n H 2n+1 O (n is an integer of 1 to 3) or a chlorine atom, B is an alkyl group having 1 to 3 carbon atoms, Y is a mercapto group, a vinyl group, an amino group, a glycidoxy group or an epoxy group, m is an integer of 1 to 3, and c is an integer of 0 to 9. However, when m is 1, B may be the same as or different from each other, and when m is 2 or 3, A may be the same as or different from each other.

[0105] Examples of the compound represented by formula (VIII) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyl-di(tridecane-1-oxy-13-penta(ethylene oxide))ethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, etc. Examples of commercially available products of these include the product name "VP Si363" manufactured by Evonik Degussa.

[0106] Formula (IX) has the following structure: A m B 3-m Si-(CH2) a -S b -Z (IX) In the formula (IX), A is C n H 2n+1 O (n is an integer of 1 to 3) or a chlorine atom, B is an alkyl group having 1 to 3 carbon atoms, Z is a benzothiazolyl group, an N,N-dimethylthiocarbamoyl group or a methacryloyl group, m is an integer of 1 to 3, a is an integer of 1 to 9, and b is an integer of 1 or more and may have a distribution. However, when m is 1, B may be the same as or different from each other, and when m is 2 or 3, A may be the same as or different from each other.

[0107] Examples of the compound represented by formula (IX) include 3-trimethoxysilylpropyl-N,N-dimethylcarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, and 3-trimethoxysilylpropyl methacryloyl monosulfide.

[0108] Formula (X) is the following structure: R 31 x R 32 y R 33 z Si-R34 -S-CO-R 35 (X) In the formula (X), R 31 is R 36 O-, R 36 C(=O)O-, R 36 R 37 C=NO-, R 36 R 37 NO-, R 36 R 37 N- and -(OSiR 36 R 37 ) n (OSiR 35 R 36 R 37 ) and has 1 to 18 carbon atoms. 36 and R 37 are each independently selected from an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, and an aryl group, have 1 to 18 carbon atoms, and n is 0 to 10. R 32 is selected from hydrogen, or an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, and an aryl group having 1 to 18 carbon atoms. R 33 is -[O(R 38 O) m ] 0.5 -(However, R 38 is selected from an alkylene group and a cycloalkylene group and has 1 to 18 carbon atoms, and m is 1 to 4. x, y, and z satisfy the relationship: x+y+2z=3, 0≦x≦3, 0≦y≦2, 0≦z≦1. R 34 is selected from an alkylene group, a cycloalkylene group, a cycloalkylalkylene group, an alkenylene group, an arylene group, and an aralkylene group, and has 1 to 18 carbon atoms. R 35 is selected from an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an aryl group, and an aralkyl group, and has 1 to 18 carbon atoms.

[0109] For the compound represented by formula (X), in formula (X), R32 , R 35 , R 36 and R 37 In the above, the alkyl group may be linear or branched, and examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and an isopropyl group. The alkenyl group may be linear or branched, and examples of the alkenyl group include a vinyl group, an allyl group, and a methanyl group. Examples of the cycloalkyl group include a cyclohexyl group and an ethylcyclohexyl group, examples of the cycloalkenyl group include a cyclohexenyl group and an ethylcyclohexenyl group, and examples of the aryl group include a phenyl group and a tolyl group. Furthermore, R 5 In the above formula, examples of the aralkyl group include a phenethyl group.

[0110] In the above formula (X), R 34 and R 38 In the above, the alkylene group may be linear or branched, and examples of the alkylene group include a methylene group, an ethylene group, a trimethylene group, and a propylene group. Examples of the cycloalkylene group include a cyclohexylene group. 34 In the above, the alkenylene group may be linear or branched, and examples of the alkenylene group include a vinylene group, a propenylene group, etc. In addition, examples of the cycloalkylalkylene group include a cyclohexylmethylene group, etc., examples of the arylene group include a phenylene group, etc., and examples of the aralkylene group include a xylylene group, etc. In the above formula (X), R 33 In the above, -[O(R 38 O) m ] 0.5 Examples of the - group include a 1,2-ethanedioxy group, a 1,3-propanedioxy group, a 1,4-butanedioxy group, a 1,5-pentanedioxy group, and a 1,6-hexanedioxy group. The compound represented by the above formula (X) can be synthesized in the same manner as described in JP-A-2001-505225, and is also available under the trade name "NXT" (R 31 =C2H5O, R 34 =C3H6,R35 =C7H 15 , x=3, y=0, z=0: 3-octanoylthio-propyltriethoxysilane) and other commercially available products can also be used.

[0111] Among the compounds represented by the above formula (VII), (VIII), (IX) or (X), the compounds represented by the above formula (VIII) and the compounds represented by the above formula (X) are preferred.

[0112] The amount of the silane coupling agent in the rubber composition for the center rubber is preferably 1 part by mass or more, more preferably 4 parts by mass or more, and is preferably 20 parts by mass or less, and even more preferably 12 parts by mass or less, per 100 parts by mass of silica, from the viewpoint of improving the dispersibility of the silica in the rubber matrix.

[0113] [Softener] The rubber composition for the center rubber preferably contains a softener. By including a softener in the rubber composition for the center rubber, the center rubber can be softened, thereby achieving excellent wet grip properties and improving the processability and workability of the rubber composition. The softener may include oil, resin, and the like. The content of the softener in the rubber composition for the center rubber is preferably 2 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, still more preferably 30 parts by mass or more, even more preferably 35 parts by mass or more, even more preferably 40 parts by mass or more, and even more preferably 45 parts by mass or more, per 100 parts by mass of the rubber component. The content of the softener in the rubber composition for the center rubber is, per 100 parts by mass of the rubber component, preferably 85 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 78 parts by mass or less, even more preferably 72 parts by mass or less, and even more preferably 68 parts by mass or less. By setting the content of the softener to 2 parts by mass or more per 100 parts by mass of the rubber component, the wet grip performance of the tire can be improved, and by setting the content to 85 parts by mass or less, a decrease in the rigidity of the tire can be suppressed. The "content of the softener in the rubber composition for the center rubber" includes not only the content of the softener blended together with the rubber component as a softener, but also the content of the extender oil blended in advance in the rubber component.

[0114] (oil) Examples of oils include mineral oils derived from minerals, aromatic oils derived from petroleum, paraffin oils, naphthenic oils, palm oils derived from natural products, and octyl oleate.

[0115] (resin) As the resin, it is preferable to use a thermoplastic resin. When the rubber composition for the center rubber contains a thermoplastic resin as a softener, the wet grip performance of the tire can be improved and the rolling resistance can be reduced.

[0116] Examples of the resin include C5 resin, C5-C9 resin, C9 resin, dicyclopentadiene resin, terpene phenol resin, terpene resin, rosin resin, and alkylphenol resin. Among them, at least one selected from the group consisting of C5 resins, C5-C9 resins, C9 resins, dicyclopentadiene resins, rosin resins, and alkylphenol resins is preferable. When the resin contains at least one of C5 resin, C5-C9 resin, C9 resin, dicyclopentadiene resin, terpene phenol resin, terpene resin, rosin resin, and alkylphenol resin, the wet grip performance of the tire can be further improved.

[0117] Among the resins, C5 resins, C5-C9 resins and C9 resins are particularly preferred. C5-C9 resins and C9 resins have high compatibility with natural rubber, and further increase the effect of increasing the elastic modulus of the rubber composition in the low strain region and the effect of decreasing the elastic modulus of the vulcanized rubber in the high strain region, thereby further improving the wet grip performance of the tire. The resins may be used alone or in combination of two or more.

[0118] C5 resin refers to C5 synthetic petroleum resin, and examples of the C5 resin include aliphatic petroleum resins obtained by polymerizing a C5 fraction obtained by thermal cracking of naphtha in the petrochemical industry using a Friedel-Crafts catalyst such as AlCl3 or BF3. The C5 fraction usually includes olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. As the C5 resin, commercially available products can be used, and examples thereof include the aliphatic petroleum resin "ESCOLETS (registered trademark) 1000 series" manufactured by ExxonMobil Chemical Company, "A100, B170, M100, R100" of the "Quinton (registered trademark) 100 series" manufactured by Zeon Corporation, and "T-REZ RA100" manufactured by Tonen Chemical Industry Co., Ltd.

[0119] The C5-C9 resin refers to a C5-C9 synthetic petroleum resin. Examples of the C5-C9 resin include solid polymers obtained by polymerizing petroleum-derived C5 fraction and C9 fraction using Friedel-Crafts catalysts such as AlCl3 and BF3. More specifically, copolymers mainly composed of styrene, vinyltoluene, α-methylstyrene, indene, etc. are included. As the C5-C9 resin, a resin with a small amount of C9 or more components is preferable from the viewpoint of compatibility with rubber components. Here, "a small amount of C9 or more components" means that the amount of C9 or more components in the total amount of the resin is less than 50 mass%, preferably 40 mass% or less. As the C5-C9 resin, commercially available products can be used, and examples thereof include the product name "Quinton (registered trademark) G100B" (manufactured by Nippon Zeon Co., Ltd.), the product name "ECR213" (manufactured by ExxonMobil Chemical Co., Ltd.), and the product name "T-REZ RD104" (manufactured by Tonen Chemical Co., Ltd.).

[0120] The C9 resin is, for example, a resin obtained by polymerizing aromatic compounds having 9 carbon atoms, the main monomers of which are vinyltoluene, alkylstyrene, and indene, which are C9 fractions by-produced together with basic petrochemical raw materials such as ethylene and propylene by thermal decomposition of naphtha in the petrochemical industry. Specific examples of the C9 fraction obtained by thermal decomposition of naphtha include vinyltoluene, α-methylstyrene, β-methylstyrene, γ-methylstyrene, o-methylstyrene, p-methylstyrene, and indene. The C9 resin is obtained by polymerizing aromatic compounds having 9 carbon atoms, the main monomers being vinyltoluene, alkylstyrene, and indene, which are C9 fractions by-produced together with basic petrochemical raw materials such as ethylene and propylene by thermal decomposition of naphtha in the petrochemical industry. Specific examples of the C9 fraction obtained by thermal decomposition of naphtha include vinyltoluene, α-methylstyrene, β-methylstyrene, γ-methylstyrene, o-methylstyrene, p-methylstyrene, and indene. The C9 resin is obtained by polymerizing aromatic compounds having 9 carbon atoms, such as styrene, which is a C8 fraction, together with the C9 fraction. 10 The fractions methylindene, 1,3-dimethylstyrene, and even naphthalene, vinylnaphthalene, vinylanthracene, p-tert-butylstyrene are used as raw materials, and these C8-C 10The fractions and the like can be copolymerized as a mixture with, for example, a Friedel-Crafts catalyst to obtain the C9 resin. The C9 resin may be a modified petroleum resin modified with a compound having a hydroxyl group, an unsaturated carboxylic acid compound, or the like. Commercially available products can be used as the C9 resin. For example, examples of unmodified C9 petroleum resins include those under the trade names "Nippon Oil Neopolymer (registered trademark) L-90", "Nippon Oil Neopolymer (registered trademark) 120", "Nippon Oil Neopolymer (registered trademark) 130", and "Nippon Oil Neopolymer (registered trademark) 140" (manufactured by JX Nippon Oil & Energy Corporation).

[0121] The dicyclopentadiene resin is a petroleum resin produced from dicyclopentadiene obtained by dimerizing cyclopentadiene as the main raw material. As the dicyclopentadiene resin, commercially available products can be used, and examples thereof include "1105, 1325, 1340" and the like in the "Quinton (registered trademark) 1000 series", which is an alicyclic petroleum resin manufactured by Zeon Corporation.

[0122] Terpene phenol resins can be obtained, for example, by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing with formalin. There are no particular limitations on the terpenes used as raw materials, and monoterpene hydrocarbons such as α-pinene and limonene are preferred, and those containing α-pinene are more preferred, and α-pinene is particularly preferred. As the terpene phenol resin, commercially available products can be used, such as those under the trade names "Tamanol 803L" and "Tamanol 901" (manufactured by Arakawa Chemical Industries Co., Ltd.), the trade names "YS Polystar (registered trademark) U" series, "YS Polystar (registered trademark) T" series, "YS Polystar (registered trademark) S" series, "YS Polystar (registered trademark) G" series, "YS Polystar (registered trademark) N" series, "YS Polystar (registered trademark) K" series, and "YS Polystar (registered trademark) TH" series (manufactured by Yasuhara Chemical Co., Ltd.).

[0123] Terpene resins are solid resins obtained by blending turpentine oil obtained at the same time as obtaining rosin from pine trees, or a polymerization component separated from the same, and polymerizing the blend using a Friedel-Crafts catalyst, and examples of such resins include β-pinene resin, α-pinene resin, etc. As the terpene resin, commercially available products can be used, such as the "YS Resin" series (PX-1250, TR-105, etc.) manufactured by Yasuhara Chemical Co., Ltd. and the "Picolite" series (A115, S115, etc.) manufactured by Hercules.

[0124] Rosin resin is the residue remaining after collecting balsams such as pine resin (pine tar), which is the sap of plants of the pine family, and distilling turpentine essential oil. It is a natural resin whose main component is rosin acid (abietic acid, palustric acid, isopimaric acid, etc.), as well as modified resins and hydrogenated resins obtained by modifying, hydrogenating, etc., the natural resin rosin, its polymerized rosin, and partially hydrogenated rosin; glycerin ester rosin, its partially hydrogenated rosin, fully hydrogenated rosin, and polymerized rosin; pentaerythritol ester rosin, its partially hydrogenated rosin, and polymerized rosin, etc. Natural resin rosins include gum rosin, tall oil rosin, wood rosin, etc., contained in raw pine tar and tall oil. The rosin resin may be a commercially available product, such as "Neotoru 105" (manufactured by Harima Chemical Co., Ltd.), "SN Tack 754" (manufactured by San Nopco Ltd.), "Lime Resin No. 1", "Pensel A" and "Pensel AD" (manufactured by Arakawa Chemical Industries, Ltd.), "Polypale" and "Pentalin C" (manufactured by Eastman Chemical Co., Ltd.), and "Hi-Rosin (registered trademark) S" (manufactured by Taisho Matsu Oil Co., Ltd.).

[0125] The alkylphenol resin can be obtained, for example, by condensation reaction of alkylphenol and formaldehyde under a catalyst. Commercially available products can be used as the alkylphenol resin, such as "Hitanol 1502P" (alkylphenol formaldehyde resin, manufactured by Hitachi Chemical Co., Ltd.), "Tackirol 201" (alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), "Tackirol 250-I" (brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), "Tackirol 250-III" (brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), "R7521P", "SP1068", "R7510PJ", "R7572P" and "R7578P" (manufactured by SI GROUP INC.).

[0126] The ratio of the resin in the total amount of the softener is preferably 20 to 90 mass %. When the ratio of the resin in the total amount of the softener is 20% by mass or more, the wet grip performance of the tire is improved, and when it is 90% by mass or less, the decrease in the elastic modulus of the center rubber can be suppressed. The proportion of the resin in the total amount of the softener is more preferably from 20 to 70 mass %, further preferably from 20 to 50 mass %, and even further preferably from 20 to 35 mass %.

[0127] In addition to the rubber components, fillers, softeners, and silane coupling agents described above, the rubber composition for the center rubber may contain compounding agents commonly used in the rubber industry, such as stearic acid, antioxidants, zinc oxide (zinc oxide), vulcanization accelerators, vulcanizing agents, etc., appropriately selected within a range that does not impair the object of the present invention.

[0128] The component compositions of the shoulder rubber rubber composition constituting the shoulder rubber and other rubber compositions such as rubber compositions constituting other tire parts are not particularly limited. The other rubber composition may contain the rubber components, fillers, softeners, and silane coupling agents that the rubber composition for the center rubber may contain, and may also contain stearic acid, antioxidants, zinc oxide (zinc white), vulcanization accelerators, vulcanizing agents, etc. The rubber component of the other rubber composition may not contain a modified styrene-butadiene copolymer rubber. Also, the content of silica in the rubber composition may be 75 parts by mass or less (including 0 part by mass) per 100 parts by mass of the rubber component.

[0129] From the viewpoint of grip, the total amount of the softener in the rubber composition for the shoulder rubber is preferably greater than the total amount of the softener in the rubber composition for the center. The rubber composition for the shoulder rubber does not have to contain a modified styrene-butadiene copolymer rubber as a rubber component.

[0130] The tire of the present invention can be used for various purposes, not limited to applications such as two-wheeled vehicles and four-wheeled vehicles, but the effects of the present invention can be easily achieved by using it for two-wheeled vehicles in particular. When used as a motorcycle tire, it may be a front tire or a rear tire, but in the present invention, since it is possible to achieve high levels of both wet grip performance and wear resistance of the tread, the effects of the present invention are particularly likely to be achieved when applied to a rear tire. The type of motorcycle is not particularly limited and can be appropriately selected depending on the purpose. Examples of such vehicles include racing motorcycles, motorcycles for general public roads, on-road motorcycles, off-road motorcycles, etc. Among these, motorcycles in which the effects of the present invention are particularly likely to be realized are preferred for general public roads and on-road motorcycles, and more preferred are motorcycles for general public roads. EXAMPLES

[0131] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0132] <Preparation of Rubber Composition> (1) Comparative Example 1 and Examples 1 to 2 A rubber composition for a tread of a shoulder portion was prepared in the compounding ratio (parts by mass) shown in Table 1, and a rubber composition for a tread of a center portion was prepared in the compounding ratio (parts by mass) shown in Table 2. (2) Comparative Examples 2 to 4 and Examples 3 to 6 A rubber composition for a tread of a shoulder portion is prepared in the compounding ratio (parts by mass) shown in Table 1, and a rubber composition for a tread of a center portion is prepared in the compounding ratio (parts by mass) shown in Table 2.

[0133] [Rubber composition for shoulder rubber] (1) Comparative Example 1 and Examples 1 to 2 According to the compounding recipe shown in Table 1, a rubber composition for shoulder rubber was produced using a conventional Banbury mixer. (2) Comparative Examples 2 to 4 and Examples 3 to 6 According to the compounding recipe shown in Table 1, a rubber composition for shoulder rubber is produced using a conventional Banbury mixer. The ingredients in Table 1 are as follows: BR: Polybutadiene rubber: manufactured by JSR Corporation, product name "BR01" SBR: Styrene-butadiene copolymer rubber, manufactured by JSR Corporation, emulsion-polymerized styrene-butadiene copolymer rubber, product name "HP755B" Carbon black: Asahi Carbon Co., Ltd., product name "ASAHI#105" Silica: Tosoh Silica Corporation, product name "Nipsil AQ" Softener: Tonen Chemical Co., Ltd., product name "T-REZ RD104" and JX Nippon Oil & Energy Corporation, product name "Oil A / O MIX" Antiaging agent: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., includes at least the product name "Nocrac 6C." Vulcanization package: Contains stearic acid, zinc oxide, thiuram accelerator, and vulcanizing agent.

[0134] In addition, the "total amount of softener" in Table 1 means the total amount of 30 parts by mass of the softener in the compounding components and 32 parts by mass of the oil extender in the rubber component.

[0135] [Table 1]

[0136] [Rubber composition for center rubber] (1) Comparative Example 1 and Examples 1 to 2 According to the compounding recipe shown in Table 2, a rubber composition for a center rubber was produced using a conventional Banbury mixer. (2) Comparative Examples 2 to 4 and Examples 3 to 6 According to the compounding recipe shown in Table 2, a rubber composition for the center rubber is produced using a conventional Banbury mixer. The ingredients in Table 2 are as follows:

[0137] 1. Rubber component (1) BR: butadiene rubber, manufactured by JSR Corporation, product name "BR01" (2) Modified BR: Modified butadiene rubber, manufactured by JSR Corporation, product name "JSR BR54" (3) SBR: styrene-butadiene copolymer rubber, manufactured by JSR Corporation, emulsion-polymerized styrene-butadiene copolymer rubber, product name "HP755B", containing 37.5 parts by mass of oil per 100 parts by mass of rubber component, bound styrene content = 39.5% by mass, bound vinyl content = 38.5% by mass (4) Modified SBR: Modified styrene-butadiene copolymer rubber synthesized by the following method, containing 10.0 parts by mass of oil per 100 parts by mass of rubber component, weight average molecular weight (Mw) = 85.2 × 10 4 , molecular weight 200×10 4 Over 500 x 10 4 Percentage below = 4.6% Shrinkage factor (g') = 0.59, glass transition temperature (Tg) = -25℃

[0138] 2. Fillers CB: Carbon black, manufactured by Asahi Carbon Co., Ltd., product name "ASAHI#105" Silica: Tosoh Silica Corporation, product name "Nipsil AQ", CTAB165

[0139] 3.Other Ingredients Oil: JX Nippon Oil & Energy Corporation, product name "A / O MIX" Resin: C5-C9 resin Silane coupling agent: Shin-Etsu Chemical Co., Ltd., product name "ABC-856" Antiaging agent: At least N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, product name "Nocrac 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization package: Contains guanidine vulcanization accelerators, thiuram vulcanization accelerators, sulfide vulcanization accelerators, stearic acid, zinc oxide and sulfur.

[0140] The synthesized modified styrene-butadiene copolymer rubber is analyzed for the amount of bound styrene, the microstructure of the butadiene portion, the molecular weight, the shrinkage factor (g'), the Mooney viscosity, the glass transition temperature (Tg), the modification rate, the presence or absence of nitrogen atoms, and the presence or absence of silicon atoms by the following methods.

[0141] (1) Bound styrene content The modified styrene-butadiene copolymer rubber is used as a sample, and 100 mg of the sample is dissolved in chloroform to make a measuring sample. The amount of bound styrene (mass%) relative to 100 mass% of the sample is measured based on the amount of absorption of ultraviolet light by the phenyl group of styrene (near 254 nm) (Shimadzu Corporation spectrophotometer "UV-2450").

[0142] (2) Microstructure of butadiene part (1,2-vinyl bond content) The modified styrene-butadiene copolymer rubber was used as a sample, and 50 mg of the sample was dissolved in 10 mL of carbon disulfide to prepare a measurement sample. The infrared spectrum was recorded from 600 to 1000 cm using a solution cell. -1The absorbance at a predetermined wave number is measured in the range of 100 to 200 nm, and the microstructure of the butadiene portion, i.e., the amount of 1,2-vinyl bonds (mol%) is calculated according to the formula of Hampton's method (method described in R.R. Hampton, Analytical Chemistry 21, 923 (1949)) (Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation).

[0143] (3)Molecular weight Using styrene-butadiene copolymer rubber or modified styrene-butadiene copolymer rubber as a sample, a GPC measuring device (manufactured by Tosoh Corporation under the trade name "HLC-8320GPC") with three columns packed with polystyrene gel was used to measure the chromatogram using an RI detector (manufactured by Tosoh Corporation under the trade name "HLC8020"). Based on the calibration curve obtained using standard polystyrene, the weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw / Mn), peak top molecular weight (Mp1) of the modified styrene-butadiene copolymer rubber, peak top molecular weight (Mp2) of the styrene-butadiene copolymer rubber, and the ratio (Mp1 / Mp2) of the modified styrene-butadiene copolymer rubber, and the molecular weight of the modified styrene-butadiene copolymer rubber were calculated. 4 Over 500 x 10 4 The following ratios and are calculated. The eluent used is THF (tetrahydrofuran) containing 5 mmol / L triethylamine. Three columns, Tosoh Corporation's "TSKgel SuperMultiporeHZ-H" (trade name), are connected, with a Tosoh Corporation's "TSKguardcolumn SuperMP(HZ)-H" (trade name) connected in front of them as a guard column. 10 mg of the sample to be measured is dissolved in 10 mL of THF to make the measurement solution, and 10 μL of the measurement solution is injected into the GPC measurement device and measured under conditions of an oven temperature of 40°C and a THF flow rate of 0.35 mL / min. The above peak top molecular weights (Mp1 and Mp2) are determined as follows. In the GPC curve obtained by measurement, a peak detected as the highest molecular weight component is selected. For the selected peak, the molecular weight corresponding to the maximum value of the peak is calculated and used as the peak top molecular weight. In addition, the molecular weight of the above 200 × 10 4 Over 500 x 104 The following ratios are calculated from the integral molecular weight distribution curve of 500×10 4 The molecular weight is 200 x 10 based on the percentage of the whole. 4 It is calculated by subtracting the percentage that is less than that.

[0144] (4) Contraction factor (g') Using modified styrene-butadiene copolymer rubber as a sample, a GPC measuring device (Malvern's product name "GPCmax VE-2001") with three columns packed with polystyrene gel is used to measure using three detectors connected in that order: a light scattering detector, an RI detector, and a viscosity detector (Malvern's product name "TDA305"). Based on standard polystyrene, the absolute molecular weight is obtained from the results of the light scattering detector and the RI detector, and the intrinsic viscosity is obtained from the results of the RI detector and the viscosity detector. Linear polymer has an intrinsic viscosity [η] = -3.883M 0.771 The shrinkage factor (g') is calculated as the ratio of the intrinsic viscosity corresponding to each molecular weight. The eluent is THF containing 5 mmol / L triethylamine. The columns used are Tosoh Corporation's "TSKgel G4000HXL", "TSKgel G5000HXL", and "TSKgel G6000HXL". 20 mg of the sample to be measured is dissolved in 10 mL of THF to prepare a measurement solution, and 100 μL of the measurement solution is injected into the GPC measurement device and measured under conditions of an oven temperature of 40°C and a THF flow rate of 1 mL / min.

[0145] (5) Mooney viscosity Using styrene-butadiene copolymer rubber or modified styrene-butadiene copolymer rubber as a sample, a Mooney viscometer (trade name "VR1132" manufactured by Ueshima Seisakusho Co., Ltd.) is used to measure the Mooney viscosity in accordance with JIS K6300 using an L-shaped rotor. The measurement temperature is 110°C when the sample is styrene-butadiene copolymer rubber, and 100°C when the sample is modified styrene-butadiene copolymer rubber. First, the sample is preheated at the test temperature for 1 minute, and then the rotor is rotated at 2 rpm, and the torque is measured after 4 minutes to determine the Mooney viscosity (ML (1+4))

[0146] (6) Glass transition temperature (Tg) Using modified styrene-butadiene copolymer rubber as a sample, a differential scanning calorimeter "DSC3200S" manufactured by Mac Science Corporation was used in accordance with ISO 22768:2006. A DSC curve was recorded while heating from -100°C at 20°C / min under a helium flow of 50 mL / min, and the peak top (inflection point) of the DSC differential curve was taken as the glass transition temperature.

[0147] (7) Denaturation rate Using modified styrene-butadiene copolymer rubber as a sample, the measurement is made by applying the property of the modified basic polymer component being adsorbed to a GPC column packed with silica-based gel. The amount of the sample solution containing the sample and low molecular weight internal standard polystyrene adsorbed to the silica-based column is measured from the difference between the chromatogram measured with a polystyrene-based column and the chromatogram measured with a silica-based column, and the modification rate is calculated. Specifically, it is as shown below. Preparation of sample solution: Dissolve 10 mg of sample and 5 mg of standard polystyrene in 20 mL of THF to prepare a sample solution.

[0148] GPC measurement conditions using a polystyrene column: Tosoh Corporation's product name "HLC-8320GPC" is used, 5 mmol / L triethylamine-containing THF is used as the eluent, 10 μL of the sample solution is injected into the device, and a chromatogram is obtained using an RI detector under the conditions of a column oven temperature of 40°C and a THF flow rate of 0.35 mL / min. Three Tosoh Corporation's product name "TSKgel SuperMultiporeHZ-H" columns are connected, and a Tosoh Corporation product name "TSKguardcolumn SuperMP(HZ)-H" is connected in front of them as a guard column.

[0149] GPC measurement conditions using a silica column: Tosoh Corporation's "HLC-8320GPC" is used, THF is used as the eluent, 50 μL of the sample solution is injected into the device, and a chromatogram is obtained using an RI detector under the conditions of a column oven temperature of 40°C and a THF flow rate of 0.5 ml / min. The columns used are "Zorbax PSM-1000S", "PSM-300S", and "PSM-60S", and a guard column "DIOL 4.6 × 12.5 mm 5 micron" is connected to the front of the column. How to calculate the modification rate: The total peak area of ​​the chromatogram using a polystyrene column is set to 100, the peak area of ​​the sample is set to P1, the peak area of ​​the standard polystyrene is set to P2, and the total peak area of ​​the chromatogram using a silica column is set to 100, the peak area of ​​the sample is set to P3, and the peak area of ​​the standard polystyrene is set to P4. Then, calculate the modification rate (%) from the following formula. Denaturation rate (%) = [1-(P2 x P3) / (P1 x P4)] x 100 (where P1+P2=P3+P4=100)

[0150] (8) Presence or absence of nitrogen atom The same measurement as in (7) above is carried out, and when the calculated modification rate is 10% or more, it is determined that the compound contains a nitrogen atom.

[0151] (9) Presence or absence of silicon atoms 0.5 g of modified styrene-butadiene copolymer rubber is used as a sample, and measured using an ultraviolet-visible spectrophotometer (Shimadzu Corporation's product name "UV-1800") in accordance with JIS K 0101 44.3.1, and quantified using molybdenum blue absorptiometry. If silicon atoms are detected (detection limit 10 mass ppm), it is determined that the rubber contains silicon atoms.

[0152] (Synthesis of modified styrene-butadiene copolymer rubber) The polymerization reactor was a tank-type pressure vessel with an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom, an outlet at the top, and a jacket for temperature control. 1,3-butadiene, which had been previously dehydrated, was mixed at 17.2 g / min, styrene at 10.5 g / min, and n-hexane at 145.3 g / min. In a static mixer installed in the middle of the piping supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.117 mmol / min, mixed, and then continuously supplied to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.019 g / min and n-butyllithium as a polymerization initiator at a rate of 0.242 mmol / min were fed to the bottom of the polymerization reactor, which was being vigorously mixed with a stirrer, to continue the polymerization reaction continuously. The temperature of the polymerization solution at the top outlet of the reactor was controlled to be 75°C. When the polymerization was sufficiently stabilized, a small amount of the polymer solution before the addition of the coupling agent was withdrawn from the top outlet of the reactor, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of polymer, after which the solvent was removed, and the Mooney viscosity at 110°C and various molecular weights were measured.

[0153] Next, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine diluted to 2.74 mmol / L as a coupling agent was continuously added at a rate of 0.0302 mmol / min (n-hexane solution containing 5.2 ppm water) to the polymer solution flowing out from the outlet of the reactor, and the polymer solution to which the coupling agent was added was mixed by passing through a static mixer to undergo a coupling reaction. At this time, it took 4.8 minutes for the coupling agent to be added to the polymer solution flowing out from the outlet of the reactor, the temperature was 68°C, and the difference between the temperature in the polymerization process and the temperature before the modifier was added was 7°C. An antioxidant (BHT) was continuously added to the polymer solution that had undergone the coupling reaction at 0.055 g / min (n-hexane solution) so that the amount was 0.2 g per 100 g of polymer, and the coupling reaction was terminated. Simultaneously with the antioxidant, oil (JOMO Process NC140 manufactured by JX Nippon Oil & Energy Corporation) was continuously added so that the amount was 10.0 g per 100 g of polymer, and mixed with a static mixer. The solvent was removed by steam stripping to obtain a modified styrene-styrene-butadiene copolymer rubber (modified SBR). It was confirmed by the above method that the modified SBR obtained contained nitrogen atoms and silicon atoms. The modified SBR has a "degree of branching," which corresponds to the number of branches estimated from the number of functional groups of the coupling agent and the amount added, of 8 (this can also be confirmed from the shrinkage factor value), and the "number of SiO R residues," which corresponds to the total number of SiO R per molecule of coupling agent minus the number of SiO R reduced by reaction, is 4.

[0154] <Tire manufacturing> (1) Comparative Example 1 and Examples 1 to 2 Using each rubber composition for tread, a prototype motorcycle tire (size: 180 / 55ZR17) was produced in a conventional manner, which had a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, and the tread portion was divided into three in the tire width direction by a center portion including the tire equatorial plane and a pair of shoulder portions including the tread ends, and the tread of the motorcycle tire was formed from the rubber composition.

[0155] (2) Comparative Examples 2 to 4 and Examples 3 to 6 Using each prepared rubber composition for tread, a prototype motorcycle tire (size: 180 / 55ZR17) was produced in a conventional manner, having a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, with the tread portion being divided into three in the tire width direction by a center portion including the tire equatorial plane and a pair of shoulder portions including the tread ends, and the tread of the motorcycle tire was formed from the rubber composition.

[0156] <Evaluation> (1) Comparative Example 1 and Examples 1 to 2 For each rubber composition for tread used in the tread of a two-wheeled tire, the abrasion resistance and wet grip property were evaluated as follows.

[0157] (2) Comparative Examples 2 to 4 and Examples 3 to 6 For each rubber composition for tread used in the tread of a two-wheeled tire, the abrasion resistance and wet grip property are evaluated as follows.

[0158] 1. Abrasion resistance (1) Comparative Example 1 and Examples 1 to 2 A test rider drove the vehicle 3,500 km at 80 km / h on a paved test course. After the run, the remaining tread depth was measured and the tire's wear resistance was evaluated based on the remaining tread depth. The evaluation results are shown in the "Wear Resistance" column in Table 2. The evaluation result of Comparative Example 1 was set at 100, and an index was calculated as a relative evaluation. A higher index indicates higher abrasion resistance. The acceptable range is 110 or higher.

[0159] (2) Comparative Examples 2 to 4 and Examples 3 to 6 A test rider drives the vehicle 3,500 km at 80 km / h on a paved test course. After the run, the remaining tread depth is measured and the tire's wear resistance is evaluated based on the remaining tread depth. The evaluation results are shown in the "Wear Resistance" column in Table 2. The evaluation result of Comparative Example 1 was set to 100, and an index was calculated as a relative evaluation. A higher index indicates higher abrasion resistance. The acceptable range is 110 or higher.

[0160] 2. Wet grip (grip on wet surfaces) (1) Comparative Example 1 and Examples 1 to 2 A test rider performed various driving tests on a wet road course and evaluated the wet grip of the tires while driving. The evaluation results are shown in the "Wet Performance" column in Table 2. The evaluation result of Comparative Example 1 was set as 100, and an index was calculated as a relative evaluation. The higher the index, the better the tire's wet grip. The acceptable range is 102 or above.

[0161] (2) Comparative Examples 2 to 4 and Examples 3 to 6 A test rider performs various driving exercises on a wet road course and evaluates the feeling of the wet grip of the tire while driving. The evaluation results are shown in the "Wet Grip" column of Table 2. The evaluation result of Comparative Example 1 is set as 100, and an index is calculated as a relative evaluation. The higher the index, the better the tire's wet grip. The acceptable range is 102 or above.

[0162] 3. Storage modulus (E') and loss tangent (tan δ) of center rubber (1) Comparative Example 1 and Examples 1 to 2 Using vulcanized rubber test pieces obtained by vulcanizing the rubber compositions for the center rubber of the Examples and Comparative Examples, the dynamic elastic modulus (E') and loss tangent (tan δ) of the center rubber were measured using a viscoelasticity measuring device. Dynamic elastic modulus is the storage modulus E' at 25°C, frequency 52Hz, and strain 0.1% 0.1 The storage modulus E'4 at 25°C, frequency 52Hz, and strain 4% was measured, and the difference ΔE' (=E' 0.1 -E'4) was calculated. ΔE' / E'4 was calculated from the obtained E'4 and ΔE'. The loss tangent (tan δ) of the center rubber was measured at a temperature of 30°C, a strain of 1%, and a frequency of 52Hz. The higher the value, the better the grip.

[0163] (2) Comparative Examples 2 to 4 and Examples 3 to 6 Using vulcanized rubber test pieces obtained by vulcanizing the rubber compositions for the center rubber of the Examples and Comparative Examples, the dynamic elastic modulus (E') and loss tangent (tan δ) of the center rubber are measured using a viscoelasticity measuring device. Dynamic elastic modulus is the storage modulus E' at 25°C, frequency 52Hz, and strain 0.1% 0.1 The storage modulus E'4 at 25°C, frequency 52Hz, and strain 4% was measured, and the difference ΔE' (=E' 0.1 -E'4) is calculated. Calculate ΔE' / E'4 from E'4 and ΔE'. The loss tangent (tan δ) of the center rubber is measured under the following conditions: temperature 30°C, strain 1%, and frequency 52Hz. The higher the value, the better the grip.

[0164] The amount of SBR in Table 2 is an amount including 70 parts by mass of the rubber component and 26 parts by mass of the extender oil, and the amount of modified SBR is an amount including 70 parts by mass of the rubber component and 7 parts by mass of the extender oil. In Table 2, "total amount of oil" means the sum of the amount of oil in the compounded components and the amount of oil extended in the rubber component. "Total amount of softener" means the total amount of oil plus the amount of resin.

[0165] [Table 2]

[0166] The results in Table 2 show that the Examples exhibit excellent and well-balanced effects in terms of abrasion resistance, wet grip performance, and rolling resistance, compared to the samples of each Comparative Example. [Industrial Applicability]

[0167] According to the present invention, it is possible to provide a tire that has excellent grip performance on wet road surfaces, while enabling reduced rolling resistance and improved wear resistance.

Claims

1. A tire comprising a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, the tread portion being divided into at least three portions in the tire width direction by a center portion including a tire equatorial plane and a pair of shoulder portions including tread ends, The tread rubber of the center portion is a vulcanized rubber of a rubber composition containing a rubber component containing at least one modified styrene-butadiene copolymer rubber and 75 parts by mass or more of silica per 100 parts by mass of the rubber component, and the storage modulus E' of the tread rubber of the center portion at 25°C and strain of 0.1% ０．１ and storage modulus E' at 25°C and strain 4% ４ The difference between these is ΔE', and ΔE' / E' ４ A tire having a tread area of ​​0.900 or less, The tire, wherein the rubber component further comprises a modified butadiene rubber.

2. The tire according to claim 1, wherein the content of the silica in the rubber composition is 120 parts by mass or less per 100 parts by mass of the rubber component.

3. The tire according to claim 1 or 2, wherein the rubber composition further contains carbon black, and a ratio of the silica to a total amount of the silica and the carbon black is 70 mass % or more.

4. The tire according to any one of claims 1 to 3, wherein the rubber composition further comprises 2 to 85 parts by mass of a softener based on 100 parts by mass of the rubber component.

5. The softener includes a resin, and the resin is ５ based resin, C ９ based resin, C ５ -C ９ 5. The tire according to claim 4, wherein the resin is at least one selected from the group consisting of terpene-based resins, terpene-aromatic compound-based resins, rosin-based resins, dicyclopentadiene resins, and alkylphenol-based resins.

6. The tire according to claim 5, wherein the ratio of the resin to the total amount of the softener is 20 to 90 mass %.

7. The modified styrene-butadiene copolymer rubber has a weight average molecular weight of 20×10 ４ Above 300 x 10 ４ The molecular weight of the modified styrene-butadiene copolymer rubber is 200×10 or less relative to the total amount of the modified styrene-butadiene copolymer rubber. ４ Above 500 x 10 ４ The tire according to any one of claims 1 to 6, comprising 0.25 mass % or more and 30 mass % or less of a modified styrene-butadiene copolymer rubber having a shrinkage factor (g') of less than 0.

64.

8. The tire according to any one of claims 1 to 7, wherein the modified styrene-butadiene copolymer rubber has branches and a degree of branching of 5 or more.

9. The modified styrene-butadiene copolymer rubber has one or more coupling residues and a styrene-butadiene copolymer rubber chain bonded to the coupling residues, The tire according to claim 8, wherein the branches include branches in which five or more of the styrene-butadiene copolymer rubber chains are bonded to one of the coupling residues.

10. The tire according to any one of claims 1 to 9, wherein the modified styrene-butadiene copolymer rubber is represented by the following formula (I): 【Chemistry 1】 [In formula (I), D represents a styrene-butadiene copolymer rubber chain. １ , R ２ and R ３ R each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. ４ and R ７ R each independently represents an alkyl group having 1 to 20 carbon atoms. ５ , R ８ , and R ９ R each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. ６ and R １０ R each independently represents an alkylene group having 1 to 20 carbon atoms. １１ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. m and x each independently represent an integer of 1 to 3, and x≦m. p represents 1 or 2. y represents an integer of 1 to 3, and y≦(p+1). z represents an integer of 1 or 2. i represents an integer of 0 to 6, j represents an integer of 0 to 6, k represents an integer of 0 to 6, and (i+j+k) is an integer of 3 to 10. ((x×i)+(y×j)+(z×k)) is an integer of 5 to 30. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, and a phosphorus atom, and having no active hydrogen.

11. The tire according to claim 10, wherein in the formula (I), A is represented by the following formula (II), the following formula (III), the following formula (IV), or the following formula (V): 【Chemistry 2】 【Chemistry 3】 【Chemistry 4】 【Chemistry 5】 [In formula (II), B １ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms. a represents an integer of 1 to 10. In formula (III), B ２ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms; B ３ represents an alkyl group having 1 to 20 carbon atoms. a represents an integer of 1 to 10. In formula (IV), B ４ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms. a represents an integer of 1 to 10. In formula (V), B ５ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms. a represents an integer of 1 to 10.

12. The tire according to any one of claims 1 to 11, wherein the modified styrene-butadiene copolymer rubber is obtained by reacting a styrene-butadiene copolymer rubber with a coupling agent represented by the following formula (VI): 【Chemistry 6】 [In formula (VI), R １２ , R １３ and R １４ R each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. １５ , R １６ , R １７ , R １８ and R ２０ R each independently represents an alkyl group having 1 to 20 carbon atoms. １９ and R ２２ R each independently represents an alkylene group having 1 to 20 carbon atoms. ２１ represents an alkyl group or a trialkylsilyl group having 1 to 20 carbon atoms, m represents an integer of 1 to 3, p represents 1 or 2, i, j, and k each independently represent an integer of 0 to 6, with the proviso that (i+j+k) is an integer of 3 to 10, and A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, and a phosphorus atom, and having no active hydrogen.]

13. The tire according to claim 12, wherein the coupling agent represented by formula (VI) is at least one selected from the group consisting of tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, and tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane.

14. The tire according to any one of claims 4 to 13, wherein the content of the softener in the rubber composition is 72 parts by mass or less per 100 parts by mass of the rubber component.

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