WO2020032208A1 - Tire - Google Patents

Abstract

The purpose of the present invention is to provide a tire that has a good dry handling performance and high belt durability and enables the reduction of rolling resistance. To solve this problem, the present invention pertains to a tire provided with a belt disposed in a tread part and consisting of one or more belt layers, characterized in that: a tread rubber forming the tread part comprises a rubber composition which contains a rubber component and a styrene-alkylene block copolymer having a total styrene content of 30 mass% or more; the belt layer comprises a belt coating rubber which coats a reinforcing cord; and the belt coating rubber has a ratio of 200% modulus M200 (MPa) to 50% modulus M50 (MPa) of 5.0 or less (M200/M50≤5.0).

Description

tire

The present invention relates to a tire.

か ら From the viewpoint of improving vehicle safety, various studies have been made to improve the braking performance and drivability of tires on various road surfaces such as wet road surfaces, ice and snow road surfaces as well as dry road surfaces. For example, in order to improve the performance on wet road surfaces, there is known a technique of using a rubber composition in which an aroma oil is blended with a rubber component such as natural rubber (NR) or butadiene rubber (BR) for a tread rubber (Patent Reference 1).

However, in the technique of blending the aroma oil as disclosed in Patent Document 1, since the compatibility between the aroma oil and the NR or BR is not high, the effect of improving the performance on a wet road surface is small, and the steering on a dry road surface is difficult. There were also problems such as a decrease in stability (dry handling).

In recent years, with respect to a case member such as a belt disposed on a tread portion of a tire and supporting a tire load, it is desired to reduce the rolling resistance of the tire from the viewpoint of improving fuel efficiency of an automobile. A technique is known in which the rigidity of the tire itself is reduced to reduce the input to the tread rubber of the tire.
However, when the rigidity of the case member is reduced, the tread rubber cannot be sufficiently deformed, and the performance of the tread rubber cannot be sufficiently exhibited. As a result, the grip performance of the tire cannot be sufficiently improved. In addition, if the rigidity of the belt is reduced, the crack propagation resistance and the like of the belt may be reduced, so that it is necessary to further improve the durability.

JP-A-5-269888

Therefore, an object of the present invention is to provide a tire that has excellent dry handling properties and belt durability, and that can reduce rolling resistance.

The gist of the present invention for solving the above-mentioned problems is as follows.
The tire of the present invention is a tire provided with a belt comprising one or more belt layers disposed on a tread portion. The tread rubber constituting the tread portion has a rubber component and a total styrene content of 30% by mass. And a styrene-alkylene block copolymer as described above, wherein the belt layer has a belt coating rubber covering a reinforcing cord, and the belt coating rubber has a 50% modulus M50 (MPa). ), The ratio of the 200% modulus value M200 (MPa) to 5.0 or less (M200 / M50 ≦ 5.0).
With the above configuration, the rolling resistance can be reduced while having excellent dry handling properties and belt durability.

で は In the tire of the present invention, the belt-coated rubber preferably has a dynamic storage modulus (E ′) at 25 ° C. at a strain of 1% of more than 12 MPa and less than 30 MPa. This is because grip performance on a dry road surface and a wet road surface can be improved, and a reduction in rolling resistance and an improvement in belt durability can be achieved at a higher level.

Further, in the tire of the present invention, the belt coating rubber, a rubber composition comprising a rubber component, and carbon black DBP absorption amount is 50 ~ 100 cm ³ / 100g, and the phenol resin, a methylene donor Is preferred. This is because the reduction of the rolling resistance and the improvement of the durability of the belt can be achieved at a higher level.

Further, in the tire of the present invention, the alkylene block of the styrene-alkylene block copolymer has-(CH ₂ -CH (C ₂ H ₅ ))-unit (A) and-(CH ₂ -CH ₂ ) -unit (B), and the total content of the unit (A) is at least 40% by mass based on the total mass of the alkylene blocks of the unit (A) and the unit (B) (unit (A) + unit (B)). And more preferably 50% by mass or more. This is because it is possible to achieve both a grip performance on a wet road surface and a reduction in rolling resistance while realizing excellent dry handling properties.

Further, in the tire of the present invention, in the rubber composition used for the tread rubber, the rubber component preferably contains natural rubber, and the content ratio of the natural rubber in the rubber component is preferably 50% by mass or more. . This is because cold resistance and reduction of rolling resistance can be improved.

Further, in the tire of the present invention, it is preferable that the total styrene content of the styrene-alkylene block copolymer is 50% by mass or more. This is because dry handling can be further improved.

According to the present invention, it is possible to provide a tire having excellent dry handling properties and belt durability, and capable of reducing rolling resistance.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing of one Embodiment of the tire of this invention.

Hereinafter, the tire of the present invention will be described in detail based on its embodiments.
FIG. 1 is a diagram schematically showing a cross section of an embodiment of the tire of the present invention. The tire of the present invention is a tire provided with a belt 6 including one or more belt layers 6a and 6b arranged on a tread portion 3, and in FIG. 1, a pair of bead portions 1 and a pair of sidewall portions 2 are provided. A radial carcass 5 extending in a toroidal shape between a tread portion 3, a bead core 4 embedded in the bead portion 1, and a tread portion 3 (more specifically, a tire radius of a crown portion of the radial carcass 5). And a belt 6 composed of two belt layers 6a and 6b (disposed outward in the direction of the belt).

In the illustrated example tire, the radial carcass 5 is composed of a single carcass ply, and further includes a body portion extending in a toroidal shape between a pair of bead cores 4 buried in the bead portion 1, Each bead core 4 includes a folded portion wound outward from the inside in the tire width direction to the outside in the tire width direction. The number of plies and the structure of the radial carcass 5 in the tire of the present invention are not limited thereto. It is not something that can be done. Here, the carcass ply constituting the radial carcass 5 is formed by covering a plurality of reinforcing cords with a covering rubber, and the reinforcing cords include organic fiber cords such as polyethylene terephthalate cords, nylon cords, rayon cords, and steel cords. A code may be used.

The belt 6 of the illustrated tire is composed of two belt layers 6a and 6b, and each of the belt layers 6a and 6b is usually a rubberized layer of a cord extending at an angle to the tire equatorial plane. Preferably, the belt layer is composed of a rubberized layer of a steel cord, and two belt layers 6a and 6b are laminated so that the cords constituting the belt layers 6a and 6b cross each other across the tire equatorial plane. The belt 6 is constituted.
Although the belt 6 in the figure includes two belt layers 6a and 6b, the number of belt layers constituting the belt 6 in the tire of the present invention may be one or more, and is not limited thereto. Not something.

The tire of the present embodiment is such that the tread rubber constituting the tread portion 3 is made of a rubber composition containing a rubber component and a styrene-alkylene block copolymer having a total styrene content of 30% by mass or more. ,
The belt layers 6a and 6b have a belt coating rubber covering the reinforcing cord, and the ratio of the 200% modulus M200 (MPa) to the 50% modulus M50 (MPa) of the belt coating rubber is 5.0 or less ( M200 / M50 ≦ 5.0).
With respect to the tread rubber, by including a specific styrene-alkylene block copolymer, the elastic modulus of the tread rubber can be increased, and the rolling resistance of the tire can be reduced, so that excellent dry handling properties can be obtained. And low rolling resistance can be realized. In addition, by setting the ratio of the 200% modulus value (MPa) to the 50% modulus value (MPa) of the belt coating rubber to a specific value (specifically, 5.0) or less, deterioration of the rolling resistance of the tire is reduced. In addition to the above, the durability of the belt can be greatly improved.

(Tread rubber)
In the tire of the present invention, the tread rubber is a rubber composition containing a rubber component and a styrene-alkylene block copolymer having a total styrene content of 30% by mass or more (hereinafter, referred to as a “rubber composition for tread”). Sometimes).

In the rubber composition for tread, the styrene-alkylene block copolymer is blended, the styrene block in the styrene-alkylene block copolymer, while acting as a filler in the tread rubber, polystyrene The presence of an alkylene block between the blocks reduces the friction between polystyrene blocks. As a result, the elastic modulus of the tread rubber can be increased, and the low-loss property can be improved (the rolling resistance of the tire can be reduced). Becomes

-Rubber component The rubber component of the rubber composition for a tread is not particularly limited, and a rubber component used in a known rubber composition can be used.
For example, the rubber component includes natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile butadiene rubber, chloroprene rubber, polyisoprene rubber, and modified products thereof. The rubber component may be used alone or in combination of two or more.

Among them, in the tread rubber composition, the rubber component preferably contains a natural rubber. This is because by including natural rubber as the rubber component, it is possible to improve the cold resistance and the low loss property (the effect of reducing the rolling resistance of the tire).
Furthermore, from the viewpoint of improving durability and low loss property, the content ratio of the natural rubber in the rubber component is preferably 50% by mass or more and 90% by mass or less, and more preferably 60% by mass or more. More preferably, it is 70% by mass or more.

In addition, the rubber component preferably contains at least one selected from the group consisting of unmodified SBR and modified SBR.
Further, the rubber component more preferably contains at least a modified conjugated diene-based polymer such as modified SBR. This is because it is possible to improve the low rolling resistance of the tire.

Here, as the modified conjugated diene-based polymer, for example, the following modified conjugated diene-based polymer (A) is preferable. The modified conjugated diene polymer (A) has a weight average molecular weight of 20 × 10 ⁴ or more and 300 × 10 ⁴ or less, and has a molecular weight of 200 × 10 ⁴ or more based on the total amount of the modified conjugated diene polymer (A). It contains a modified conjugated diene-based polymer of 10 ⁴ or more and 500 × 10 ⁴ or less in an amount of 0.25 mass% or more and 30 mass% or less, and a shrinkage factor (g ′) of less than 0.64. With this modified conjugated diene polymer (A), the low rolling resistance of the tire can be further improved.

The modified conjugated diene-based polymer (A) preferably has a branch and a degree of branching of 5 or more. In this case, the WET performance of the tire can be further improved.

Further, the modified conjugated diene-based polymer (A) has one or more coupling residues and a conjugated diene-based polymer chain bonded to the coupling residue, and the branch is composed of 1 The coupling residue preferably has a branch to which 5 or more of the conjugated diene-based polymer chains are bonded. In this case, the WET performance of the tire can be further improved.

The modified conjugated diene polymer (A) has the following general formula (I):

[In the general formula (I), D represents a conjugated diene polymer chain, R ^1, R ² and R ³ is independently a single bond or an alkylene group having a carbon number of 1 ~ 20, R ⁴ And R ⁷ each independently represent an alkyl group having 1 to 20 carbon atoms; R ⁵ , R ⁸ and R ⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; ⁶ and R ¹⁰ each independently represent an alkylene group having 1 to 20 carbon atoms, R ¹¹ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and m and x each independently represent 1 to 3 represents an integer, x ≦ m, p represents 1 or 2, y represents an integer of 1 to 3, y ≦ (p + 1), and z represents an integer of 1 or 2. D, R ¹ to R ¹¹ , m, p, x, y, and z in the case where there are a plurality of groups are independent of each other, i is an integer of 0 to 6, and j is 0 to 6 Set Represents a number, k represents an integer of 0 to 6, (i + j + k) represents an integer of 3 to 10, and ((x × i) + (y × j) + (z × k)) represents 5 A is an integer of from 30 to 30, and A is a hydrocarbon group having 1 to 20 carbon atoms or at least one atom selected from the group consisting of oxygen, nitrogen, silicon, sulfur and phosphorus atoms. And an organic group having no active hydrogen]. In this case, the wear resistance of the tire can be improved.

Here, in the general formula (I), A is preferably represented by any of the following general formulas (II) to (V). In this case, by applying to a tire, low rolling resistance, WET performance, and wear resistance of the tire can be highly balanced.

Here, in the general formula (II), B ¹ represents a single bond or a hydrocarbon group having a carbon number of 1 ~ 20, a is an integer of 1 ~ 10, B ¹ in the case where there are plural, each be independent.
In the general 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, and a represents 1 to 10 carbon atoms. It shows an integer, and B ² and B ³ when there are a plurality of each are independent of each other.
Further, in the general 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, and when a plurality of B ⁴ are present, B ⁴ is each independently are doing.
Furthermore, in the general 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, and when there are a plurality of B ⁵ , be independent.

The modified conjugated diene-based polymer (A) is preferably obtained by reacting a conjugated diene-based polymer with a coupling agent represented by the following general formula (VI). By using the rubber composition containing the modified conjugated diene polymer (A1) reacted with the coupling agent in a tire, the wear resistance of the tire is improved, and the rolling resistance can be reduced.

In the general formula (VI), R ¹² , R ¹³ and R ¹⁴ each independently represent a single bond or an alkylene group having 1 to 20 carbon atoms, and R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ and R ²⁰ each independently represents an alkyl group having 1 to 20 carbon atoms, R ¹⁹ and R ²² each independently represent an alkylene group having 1 to 20 carbon atoms, and R ²¹ represents an alkyl group having 1 to 20 carbon atoms. , An alkyl group or a trialkylsilyl group, m represents an integer of 1 to 3, p represents an integer of 1 or 2, R ¹¹ to R ²² , m and p each represent a plurality of I, j, and k each independently represent an integer of 0 to 6, provided that (i + j + k) is an integer of 3 to 10, and A is a carbon atom having 1 to 20 carbon atoms. A hydrogen group, or an oxygen atom, a nitrogen atom, a silicon atom, having at least one atom selected from the group consisting of a sulfur atom and a phosphorus atom, It represents an organic group having no oxygen.
Here, in General Formula (VI), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of the organic group having no active hydrogen include active hydrogen such as a hydroxyl group (—OH), a secondary amino group (> NH), a primary amino group (—NH ₂ ), and a sulfhydryl group (—SH). Organic groups having no functional group.

Here, the coupling agent represented by the general formula (VI) is tetrakis [3- (2,2-dimethoxy-1-aza-2-silacyclopentane) propyl] -1,3-propanediamine, tetrakis ( It is preferably at least one selected from the group consisting of 3-trimethoxysilylpropyl) -1,3-propanediamine and tetrakis (3-trimethoxysilylpropyl) -1,3-bisaminomethylcyclohexane. In this case, the wear resistance of the tire can be further improved.

In general, a polymer having a branch tends to have a smaller molecular size when compared with a linear polymer having the same absolute molecular weight, and the shrinkage factor (g ′) is assumed to be the same. Is an index of the ratio of the size occupied by the molecule to the linear polymer which is the absolute molecular weight of the polymer. That is, as the degree of branching of the polymer increases, the shrinkage factor (g ′) tends to decrease. In the present embodiment, the intrinsic viscosity is used as an index of the size of the molecule, and the linear polymer is used according to the relational expression of intrinsic viscosity [η] = − 3.883M ^0.771 . The shrinkage factor (g ') at each absolute molecular weight of the modified conjugated diene-based polymer is calculated, and the average value of the shrinkage factor (g') at an absolute molecular weight of 100 × 10 ⁴ to 200 × 10 ⁴ is calculated. It is defined as a shrinkage factor (g ′) of the modified conjugated diene polymer. Here, the “branch” is formed by directly or indirectly bonding one polymer to another polymer. The “degree of branching” is the number of polymers directly or indirectly bonded to one branch. For example, when five conjugated diene-based polymer chains described below are indirectly bonded to each other via a coupling residue described later, the degree of branching is 5. The coupling residue is a structural unit of a modified conjugated diene-based polymer that is bonded to a conjugated diene-based polymer chain, and is, for example, to react a conjugated diene-based polymer described below with a coupling agent. Is a structural unit derived from a coupling agent. Further, the conjugated diene-based polymer chain is a constituent unit of the modified conjugated diene-based polymer, for example, produced by reacting a conjugated diene-based polymer and a coupling agent described below, derived from a conjugated diene-based polymer. It is a structural unit.
The shrinkage factor (g ′) is less than 0.64, preferably 0.63 or less, more preferably 0.60 or less, further preferably 0.59 or less, and even more preferably 0.57 or less. The lower limit of the shrinkage factor (g ′) is not particularly limited, and may be equal to or lower than the detection limit, but is preferably 0.30 or more, more preferably 0.33 or more, and still more preferably 0.35 or more. Yes, more preferably 0.45 or more, and even more preferably 0.59 or more. By using the modified conjugated diene-based polymer (A) having a shrinkage factor (g ′) within this range, the processability of the rubber composition is improved.
Since the contraction factor (g ′) tends to depend on the branching degree, for example, the contraction factor (g ′) can be controlled using the branching degree as an index. Specifically, when a modified conjugated diene-based polymer having a degree of branching of 6 is used, its shrinkage factor (g ′) tends to be 0.59 or more and 0.63 or less, and the modified conjugated diene having a degree of branching of 8 is used. In the case of a system polymer, the shrinkage factor (g ') tends to be 0.45 or more and 0.59 or less.

The measuring method of the contraction factor (g ′) is as follows. Using a modified conjugated diene polymer as a sample and a light scattering detector using a GPC measuring device (trade name “GPCmax VE-2001” manufactured by Malvern) in which three columns using polystyrene-based gel as a filler are connected. , RI detector, and viscosity detector (trade name “TDA305” manufactured by Malvern) are measured using three detectors connected in this order. Based on standard polystyrene, a light scattering detector and an RI detector are used. The absolute molecular weight is obtained from the result of the above, and the intrinsic viscosity is obtained from the result of the RI detector and the viscosity detector. The linear polymer is used according to the intrinsic viscosity [η] = − 3.883M ^0.771, and the shrinkage factor (g ′) is calculated as the ratio of the intrinsic viscosity corresponding to each molecular weight. As an eluent, THF containing 5 mmol / L triethylamine is used. The columns are used by connecting Tosoh's trade names “TSKgel G4000HXL”, “TSKgel G5000HXL”, and “TSKgel G6000HXL”. 20 mg of a sample for measurement is dissolved in 10 mL of THF to make a measurement solution, 100 μL of the measurement solution is poured into a GPC measuring device, and measurement is performed under the conditions of an oven temperature of 40 ° C. and a THF flow rate of 1 mL / min.

The modified conjugated diene polymer (A) preferably has a branch and a degree of branching of 5 or more. The modified conjugated diene-based polymer (A) has one or more coupling residues and a conjugated diene-based polymer chain bonded to the coupling residue. It is more preferable to include a branch in which 5 or more of the conjugated diene-based polymer chains are bonded to the coupling residue. The degree of branching is 5 or more, and the structure of the modified conjugated diene polymer is such that the branch contains a branch in which 5 or more conjugated diene polymer chains are bonded to one coupling residue. By specifying, the shrinkage factor (g ′) can be more reliably reduced to less than 0.64. The number of conjugated diene-based polymer chains bonded to one coupling residue can be confirmed from the value of shrinkage factor (g ′).
Further, the modified conjugated diene polymer (A) has a branch, and the degree of branching is more preferably 6 or more. The modified conjugated diene-based polymer (A) has one or more coupling residues and a conjugated diene-based polymer chain bonded to the coupling residue. It is more preferable to include a branch in which 6 or more of the conjugated diene-based polymer chains are bonded to the coupling residue. The structure of the modified conjugated diene-based polymer is such that the degree of branching is 6 or more, and the branch contains a branch in which 6 or more conjugated diene-based polymer chains are bonded to one coupling residue. By specifying, the contraction factor (g ′) can be reduced to 0.63 or less.
Furthermore, the modified conjugated diene-based polymer (A) has a branch, more preferably has a degree of branching of 7 or more, and still more preferably has a degree of branching of 8 or more. The upper limit of the degree of branching is not particularly limited, but is preferably 18 or less. The modified conjugated diene-based polymer (A) has one or more coupling residues and a conjugated diene-based polymer chain bonded to the coupling residue. It is even more preferable that the coupling residue includes a branch to which 7 or more of the conjugated diene-based polymer chains are bonded, and 8 or more of the conjugated diene to 1 of the coupling residue. It is particularly preferable to include a branch to which the system polymer chain is bonded. The degree of branching is 8 or more, and the structure of the modified conjugated diene polymer is such that the branch contains a branch in which 8 or more conjugated diene polymer chains are bonded to one coupling residue. By specifying, the contraction factor (g ′) can be reduced to 0.59 or less.

The modified conjugated diene polymer (A) preferably has a nitrogen atom and a silicon atom. In this case, the processability of the rubber composition is improved, and when applied to a tire, the low rolling resistance of the tire can be further improved while improving the WET performance and wear resistance of the tire. The modified conjugated diene-based polymer (A) has a nitrogen atom if the calculated modification rate is 10% or more according to the modification rate measurement method described below. Judge. It can be confirmed by the presence or absence of adsorption to a specific column.

こ と Whether the modified conjugated diene polymer (A) has a silicon atom is determined by the following method. Using a modified conjugated diene-based polymer (0.5 g) as a sample, measurement was performed using an ultraviolet-visible spectrophotometer (trade name “UV-1800” manufactured by Shimadzu Corporation) in accordance with JIS K0101 44.3.1. It is quantified by molybdenum blue absorption spectrophotometry. Thus, when a silicon atom is detected (detection lower limit: 10 mass ppm), it is determined that the silicon atom is present.

It is preferable that at least one terminal of the conjugated diene-based polymer chain is bonded to a silicon atom of a coupling residue. In this case, the terminals of the plurality of conjugated diene-based polymer chains may be bonded to one silicon atom. Further, the terminal of the conjugated diene polymer chain and the alkoxy group or hydroxyl group having 1 to 20 carbon atoms are bonded to one silicon atom, and as a result, the one silicon atom is converted to an alkoxysilyl group having 1 to 20 carbon atoms. Or a silanol group.

The modified conjugated diene copolymer (A) can be an oil-extended polymer to which an extender oil has been added. The modified conjugated diene-based copolymer (A) may be non-oil-extended or oil-extended, but from the viewpoint of abrasion resistance, the Mooney viscosity measured at 100 ° C is 20 or more and 100 or more. And more preferably 30 to 80.

The method for measuring Mooney viscosity is as follows. Using a conjugated diene-based polymer or a modified conjugated diene-based polymer as a sample, Mooney viscosity is measured using an L-shaped rotor according to JIS K6300 using a Mooney viscometer (trade name “VR1132” manufactured by Ueshima Seisakusho Co., Ltd.). I do. The measurement temperature is 110 ° C. when a conjugated diene-based polymer is used as a sample, and 100 ° C. when a modified conjugated diene-based polymer is used as a sample. First, after preheating the sample at the test temperature for 1 minute, the rotor is rotated at 2 rpm, and the torque after 4 minutes is measured to obtain the Mooney viscosity (ML _{(1 + 4)} ).

The weight average molecular weight (Mw) of the modified conjugated diene polymer (A) is 20 × 10 ⁴ or more and 300 × 10 ⁴ or less, preferably 50 × 10 ⁴ or more, more preferably 64 × 10 ⁴ or more. And more preferably 80 × 10 ⁴ or more. The weight average molecular weight is preferably 250 × 10 ⁴ or less, more preferably 180 × 10 ⁴ or less, and even more preferably 150 × 10 ⁴ or less. When the weight-average molecular weight is 20 × 10 ⁴ or more, both low rolling resistance and wet performance of the tire can be highly compatible. When the weight average molecular weight is 300 × 10 ⁴ or less, the processability of the rubber composition is improved.

The number average molecular weight, the weight average molecular weight, the molecular weight distribution, and the content of the specific high molecular weight component with respect to the modified conjugated diene polymer (A) and the conjugated diene polymer described below are measured as follows. Using a conjugated diene-based polymer or a modified conjugated diene-based polymer as a sample, using a GPC measuring device (trade name “HLC-8320GPC” manufactured by Tosoh Corporation) in which three columns using polystyrene-based gel as a filler are connected. , An RI detector (trade name “HLC8020” manufactured by Tosoh Corporation) was used to measure the chromatogram, and the weight average molecular weight (Mw) and number average molecular weight (Mn) were determined based on a calibration curve obtained using standard polystyrene. ) and molecular weight distribution (Mw / Mn), a peak top molecular weight of the modified conjugated diene polymer and (Mp ₁₎ and a peak top molecular weight of the conjugated diene polymer (Mp ₂₎ and the ratio (Mp ₁ / Mp ₂₎ And a ratio of molecular weight of 200 × 10 ⁴ or more and 500 × 104 or less. As an eluent, THF (tetrahydrofuran) containing 5 mmol / L triethylamine is used. As the column, three TSKgel SuperMultipore HZ-H (trade name, manufactured by Tosoh Corporation) are connected, and a guard column is connected with a brand name, TSKguardcolumn SuperMP (HZ) -H (manufactured by Tosoh Corporation), as a guard column. 10 mg of a sample for measurement is dissolved in 10 mL of THF to make a measurement solution, 10 μL of the measurement solution is poured into a GPC measuring device, and measurement is performed under the conditions of an oven temperature of 40 ° C. and a THF flow rate of 0.35 mL / min.
The peak top molecular weights (Mp ₁ and Mp ₂ ) are determined as follows. In the GPC curve obtained by the measurement, the peak detected as the component having the highest molecular weight is selected. With respect to the selected peak, the molecular weight corresponding to the maximum value of the peak is calculated, and is set as the peak top molecular weight.
In addition, the ratio of the molecular weight of 200 × 10 ⁴ or more and 500 × 10 ⁴ or less is calculated by subtracting the ratio of the molecular weight of less than 200 × 10 ⁴ from the ratio of the total molecular weight of 500 × 10 ⁴ or less from the integrated molecular weight distribution curve. I do.

The modified conjugated diene polymer (A) is a modified conjugated diene polymer having a molecular weight of 200 × 10 ⁴ or more and 500 × 10 ⁴ or less with respect to the total amount (100% by mass) of the modified conjugated diene polymer (A). also referred to herein as "specific high molecular weight component."), and includes 10 ^4% by weight to 30% by weight. When the content of the specific high molecular weight component is within this range, it is possible to achieve a high level of both low rolling resistance and WET performance of the tire.
The modified conjugated diene-based polymer (A) contains a specific high molecular weight component, preferably at least 1.0% by mass, more preferably at least 1.4% by mass, further preferably at least 1.75% by mass, even more preferably at least 2.0% by mass. %, Particularly preferably at least 2.15% by mass, very preferably at least 2.5% by mass. Further, the modified conjugated diene-based polymer (A) preferably contains a specific high molecular weight component of 28% by mass or less, more preferably 25% by mass or less, further preferably 20% by mass or less, and still more preferably Contains 18% by mass or less.
In addition, in this specification, a "molecular weight" is a standard polystyrene equivalent molecular weight obtained by GPC (gel permeation chromatography). In order to obtain the modified conjugated diene-based polymer (A) in which the content of the specific high molecular weight component is in such a range, it is preferable to control reaction conditions in a polymerization step and a reaction step described later. For example, in the polymerization step, the amount of an organic monolithium compound to be described later used as a polymerization initiator may be adjusted. In the polymerization step, a method having a residence time distribution may be used in any of the continuous and batch polymerization modes, that is, the time distribution of the growth reaction may be broadened.

In the modified conjugated diene polymer (A), the molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is preferably 1.6 or more and 3.0 or less. If the molecular weight distribution of the modified conjugated diene polymer (A) is within this range, the processability of the rubber composition will be good.

The method for producing the modified conjugated diene-based polymer (A) is not particularly limited, but is a polymerization in which an organic monolithium compound is used as a polymerization initiator and at least the conjugated diene compound is polymerized to obtain a conjugated diene-based polymer. It is preferable to include a step and a reaction step of reacting a reactive compound having five or more functional groups (hereinafter, also referred to as a “coupling agent”) with the active terminal of the conjugated diene polymer. As the coupling agent, it is preferable to react a pentafunctional or more reactive compound having a nitrogen atom and a silicon atom.

The modified conjugated diene-based polymer (A) is preferably obtained by reacting a conjugated diene-based polymer with a coupling agent represented by the general formula (VI). By using the rubber composition containing the modified conjugated diene polymer (A) obtained by reacting with the coupling agent in a tire, it becomes possible to improve the wear resistance of the tire.
Here, in General Formula (VI), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of the organic group having no active hydrogen include active hydrogen such as a hydroxyl group (—OH), a secondary amino group (> NH), a primary amino group (—NH ₂ ), and a sulfhydryl group (—SH). Organic groups having no functional group.

The modified conjugated diene-based polymer (A) obtained by reacting the coupling agent represented by the general formula (VI) with a conjugated diene-based polymer is represented by, for example, the general formula (I).
In the general formula (I), D represents a conjugated diene polymer chain, and the weight average molecular weight of the conjugated diene polymer chain is preferably from 10 × 10 ⁴ to 100 × 10 ⁴ . The conjugated diene-based polymer chain is a constituent unit of the modified conjugated diene-based polymer, and is, for example, a structural unit derived from a conjugated diene-based polymer generated by reacting a conjugated diene-based polymer with a coupling agent. is there.
In formula (I), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of the organic group having no active hydrogen include active hydrogen such as a hydroxyl group (—OH), a secondary amino group (> NH), a primary amino group (—NH ₂ ), and a sulfhydryl group (—SH). And an organic group having no functional group.

Preferably, in the general formula (I), A is represented by the general formula (II) or (III), and k represents 0.
More preferably, in the general formula (I), A is represented by the general formula (II) or (III), k represents 0, and in the general formula (II) or (III), a is , 2 to 10.
Still more preferably, in the general formula (I), A is represented by the general formula (II), k represents 0, and in the general formula (II), a is an integer of 2 to 10. Show.

The content of the modified conjugated diene polymer (A) in the rubber component is preferably 25 to 40% by mass, more preferably 30 to 35% by mass. When the content of the modified conjugated diene polymer (A) in the rubber component is 25% by mass or more, when applied to a tire, the WET performance of the tire can be further improved. When the content of the modified conjugated diene polymer (A) in the rubber component is 40% by mass or less, the processability of the rubber composition is improved.

As the rubber component of the rubber composition for a tread, a modified SBR other than the modified conjugated diene polymer (A) can be used, or an unmodified SBR can be used. For example, examples of the other modified SBR include a modified (co) polymer as the polymer component P2 of WO2017 / 0777712, and modified polymers C and D described in Examples.

-Styrene-alkylene block copolymer The styrene-alkylene block copolymer in the tread rubber composition is a copolymer having a block derived from a styrene-based monomer and an alkylene block.
The styrene / alkylene block copolymer in the rubber composition for tread has a total styrene content of the styrene / alkylene block copolymer of 30% by mass or more based on the total mass of the styrene / alkylene block copolymer. . Thereby, the dry handling of the tire can be improved. The styrene-alkylene block copolymer may be used alone or in combination of two or more.

The total styrene content of the styrene / alkylene block copolymer (total content of blocks derived from the styrene monomer) may be appropriately adjusted, and is, for example, 30 to 60% by mass.
In the rubber composition for a tread, the total styrene content is preferably 50% by mass or more. When the total styrene content is 50% by mass or more, the dry handleability of the tire can be further improved.

The styrene content of the styrene-alkylene block copolymer and the content of the alkylene unit described below are determined by ¹ H-NMR integration ratio.

ス チ レ ン The styrene block of the styrene-alkylene block copolymer has a unit derived from a styrene monomer (polymerized styrene monomer). Examples of such a styrene-based monomer include styrene, α-methylstyrene, p-methylstyrene, and vinyl toluene. Among them, styrene is preferable as the styrene monomer.

The alkylene block of the styrene-alkylene block copolymer has an alkylene (divalent saturated hydrocarbon group) unit. Examples of such an alkylene unit include an alkylene group having 1 to 20 carbon atoms. The alkylene unit may have a linear structure, a branched structure, or a combination thereof. Examples of the linear structure alkylene unit include a — (CH ₂ —CH ₂ ) —unit (ethylene unit) and a — (CH ₂ —CH ₂ —CH ₂ —CH ₂ ) —unit (butylene unit). . Examples of the alkylene unit having a branched structure include a-(CH ₂ -CH (C ₂ H ₅ ))-unit (butylene unit). Among these, the alkylene unit preferably has a — (CH ₂ —CH (C ₂ H ₅ )) — unit.
The total content of the alkylene units may be appropriately adjusted, and is, for example, 40 to 70% by mass based on the total mass of the styrene / alkylene block copolymer.

In the rubber composition for a tread, the alkylene block of the styrene-alkylene block copolymer has-(CH ₂ -CH (C ₂ H ₅ ))-unit (A) and-(CH ₂ -CH ₂ ) -unit (B), and the total content of the unit (A) is at least 40% by mass based on the total mass of the alkylene blocks of the unit (A) and the unit (B) (unit (A) + unit (B)). Is preferably 50% by mass or more, and more preferably 65% by mass or more. This makes it possible to achieve both wet performance and reduced rolling resistance while having excellent dry handling properties.

Examples of the styrene / alkylene block copolymer include styrene / ethylene / butylene / styrene block copolymer (SEBS), styrene / ethylene propylene / styrene block copolymer (SEPS), and styrene / ethylene / ethylene propylene / styrene block. One or more types selected from the group consisting of copolymers (SEEPS) are mentioned.

In the rubber composition for a tread, it is preferable that the styrene / alkylene block copolymer is a styrene / ethylene butylene / styrene block copolymer.
This makes it possible to achieve both wet performance and reduced rolling resistance while having excellent dry handling properties. The ethylene butylene block of the styrene / ethylene butylene / styrene block copolymer is a block having the above-mentioned ethylene unit and butylene unit.

Further, the styrene-alkylene block copolymer may contain other structural units other than the styrene block and the alkylene block. Such other structural units include, for example, structural units having an unsaturated bond, such as-(CH ₂ -CH (CH = CH ₂ ))-units.

The method for preparing the styrene-alkylene block copolymer is not particularly limited, and a known method can be used. For example, a styrene-based monomer such as styrene and a conjugated diene compound such as 1,3-butadiene or an olefin such as butene are copolymerized to obtain a precursor copolymer, and the precursor copolymer is hydrogenated. And a styrene-alkylene block copolymer.
The styrene / alkylene block copolymer may be a commercially available product. Such commercially available products include, for example, JSR DYNARON (registered trademark) 8903P, 9901P, etc. of JSR Corporation.

The blending amount of the styrene-alkylene block copolymer in the rubber composition for a tread is not particularly limited, and may be appropriately adjusted.
For example, the amount of the styrene-alkylene block copolymer is 4 to 30 parts by mass based on 100 parts by mass of the rubber component. From the viewpoint of achieving both wet performance and reduced rolling resistance while having excellent dry handling properties, the blending amount of the styrene-alkylene block copolymer should be 8.5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. Is preferred.

In addition, the rubber composition for tread, in addition to the rubber component and the styrene-alkylene block copolymer, a filler, a vulcanization accelerator, a silane coupling agent, a thermoplastic resin, a vulcanizing agent and a glycerin fatty acid ester And one or more selected from the group consisting of:

-Filler As the filler, for example, silica, carbon black, aluminum oxide, clay, alumina, talc, mica, kaolin, glass balloon, glass beads, calcium carbonate, magnesium carbonate, magnesium hydroxide, calcium carbonate, magnesium oxide , Titanium oxide, potassium titanate, barium sulfate and the like. The filler may be used alone or in combination of two or more.

Further, it is preferable that the filler contains at least silica from the viewpoint of reinforcing property and reduction of low rolling resistance of the tire.
The silica is not particularly limited and can be appropriately selected depending on the purpose. Examples include wet silica (hydrous silicic acid), dry silica (silicic anhydride), calcium silicate, aluminum silicate and the like.

Further, the content of silica in the filler is not particularly limited, and can be appropriately adjusted according to the purpose. For example, the amount is preferably 50 to 100% by mass, more preferably 80 to 100% by mass, and particularly preferably 90 to 100% by mass based on the total mass of the filler.

The carbon black is not particularly limited. For example, carbon black of high, medium or low structure, such as SAF, ISAF, ISAF-HS, IISAF, HAF, FEF, GPF, SRF grade and the like can be mentioned.

The compounding amount of the filler in the rubber composition for tread is not particularly limited, and may be appropriately adjusted. For example, from the viewpoint of reducing the low rolling resistance of the tire and WET performance, the amount is preferably 20 to 120 parts by mass, more preferably 50 to 100 parts by mass with respect to 100 parts by mass of the rubber component.

Vulcanization Accelerator The tread rubber composition preferably contains a vulcanization accelerator in addition to the rubber component and the styrene-alkylene block copolymer. The vulcanization accelerator is, for example, at least one selected from guanidines, sulfenamides, thiazoles, thiourea and diethylthiourea. Each of these may be used alone or in combination of two or more.

配合 The amount of the vulcanization accelerator in the rubber composition for tread is not particularly limited, and can be appropriately adjusted depending on the purpose. For example, the amount is 0.1 to 20 parts by mass based on 100 parts by mass of the rubber component. When the amount is 0.1 part by mass or more, the effect of vulcanization is easily obtained, and when the amount is 20 parts by mass or less, excessive progress of vulcanization can be suppressed.

The guanidines are not particularly limited, and can be appropriately selected according to the purpose. For example, 1,3-diphenylguanidine, 1,3-di-o-tolyl guanidine, 1-o-tolyl biguanide, di-o-tolyl guanidine salt of dicatechol borate, 1,3-di-o-cumenyl guanidine , 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine and the like. Among them, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine and 1-o-tolylbiguanide are preferable in terms of high reactivity, and 1,3-diphenylguanidine is more preferable.

The sulfenamides are not particularly limited and can be appropriately selected according to the purpose. For example, N-cyclohexyl-2-benzothiazolesulfenamide, N, N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2 -Benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide, N-ethyl-2-benzothiazolylsulfenamide, N-propyl-2-benzothiazolylsulfenamide, N-butyl -2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N-octyl-2-benzothiazolylsulfenamide, N -2-ethylhexyl-2-benzothiazolylsulfenami , N-decyl-2-benzothiazolylsulfenamide, N-dodecyl-2-benzothiazolylsulfenamide, N-stearyl-2-benzothiazolylsulfenamide, N, N-dimethyl-2-benzothia Zolylsulfenamide, N, N-diethyl-2-benzothiazolylsulfenamide, N, N-dipropyl-2-benzothiazolylsulfenamide, N, N-dibutyl-2-benzothiazolylsulfenamide, N, N-dipentyl-2-benzothiazolylsulfenamide, N, N-dihexyl-2-benzothiazolylsulfenamide, N, N-dioctyl-2-benzothiazolylsulfenamide, N, N-di -2-ethylhexylbenzothiazolylsulfenamide, N, N-didodecyl-2-benzothiazolyls Fen'amido, N, etc. N- distearyl-2-benzothiazolyl sulfenamide and the like. Among these, N-cyclohexyl-2-benzothiazolylsulfenamide and N-tert-butyl-2-benzothiazolylsulfenamide are preferred because of their high reactivity.

The thiazoles are not particularly limited and can be appropriately selected according to the purpose. For example, 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, 2- (N, N-diethylthiocarbamoylthio) benzo Thiazole, 2- (4'-morpholinodithio) benzothiazole, 4-methyl-2-mercaptobenzothiazole, di- (4-methyl-2-benzothiazolyl) disulfide, 5-chloro-2-mercaptobenzothiazole, 2-mercapto Sodium benzothiazole, 2-mercapto-6-nitrobenzothiazole, 2-mercapto-naphtho [1,2-d] thiazole, 2-mercapto-5-methoxybenzothiazole, 6-amino-2-mercaptobenzothiazole and the like Can be Among these, 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide are preferable in terms of high reactivity.

The thiourea is a compound represented by NH ₂ CSNH ₂ .
The diethylthiourea is a compound represented by C ₂ H ₅ NHCSNHC ₂ H ₅ .

-Silane coupling agent When the rubber composition for tread contains silica as the filler, it is preferable that the rubber composition further includes a silane coupling agent. By using the silane coupling agent, it is possible to obtain a tire having more excellent workability during rubber processing and more excellent wear resistance. The silane coupling agents may be used alone or in combination of two or more.

The silane coupling agent is not particularly limited and can be appropriately selected depending on the purpose. For example, the formula (1): (R ¹ O) _3-p (R ² ) _p Si—R ³ —S _a Compound represented by —R ³ —Si (OR ¹ ) _3-r (R ² ) _r , formula (2): (R ⁴ O) _3-s (R ⁵ ) _s Si—R ⁶ —S _k —R ⁷ —S _k —R ⁶ —Si (OR ⁴ ) _3-t (R ⁵ ) _t and the like.

In the formula (1), R ¹ is each independently a straight-chain, cyclic or branched alkyl group having 1 to 8 carbon atoms, a straight-chain or branched alkoxyalkyl group having 2 to 8 carbon atoms, or a hydrogen atom. ² is each independently a linear, cyclic or branched alkyl group having 1 to 8 carbon atoms, and R ³ is each independently a linear or branched alkylene group having 1 to 8 carbon atoms. a is 2 to 6 on average, and p and r may be the same or different, and each is 0 to 3 on average. However, both p and r are not 3.

In the formula (2), R ⁴ is each independently a straight-chain, cyclic or branched alkyl group having 1 to 8 carbon atoms, a straight-chain or branched alkoxyalkyl group having 2 to 8 carbon atoms, or a hydrogen atom. ⁵ is each independently a linear, cyclic or branched alkyl group having 1 to 8 carbon atoms, and R ⁶ is each independently a linear or branched alkylene group having 1 to 8 carbon atoms. R ⁷ is the formula ^{(-S-R 8 -S -)} , (- R 9 -S m1 -R 10 -) and _{^{(-R 11 -S m2 -R 12 -S}} m3 -R 13 -) either Wherein each of R ⁸ to R ¹³ is a divalent hydrocarbon group having 1 to 20 carbon atoms, a divalent aromatic group, or a divalent organic group containing a hetero element other than sulfur and oxygen. , M1, m2, and m3 may be the same or different and each have an average value of 1 or more and less than 4.), k is independently 1 to 6 as an average value, and s and t are each The average value is 0-3. However, s and t are not both 3.

Examples of the silane coupling agent represented by the formula (1) include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, and bis (3-methyldimethoxysilylpropyl) tetrasulfide. Sulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (3-methyldimethoxysilylpropyl) disulfide, bis (2 -Triethoxysilylethyl) disulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-methyldimethoxysilylpropyl) trisulfide, bis 2-triethoxysilylethyl) trisulfide, bis (3-monoethoxydimethylsilylpropyl) tetrasulfide, bis (3-monoethoxydimethylsilylpropyl) trisulfide, bis (3-monoethoxydimethylsilylpropyl) disulfide, bis ( 3-monomethoxydimethylsilylpropyl) tetrasulfide, bis (3-monomethoxydimethylsilylpropyl) trisulfide, bis (3-monomethoxydimethylsilylpropyl) disulfide, bis (2-monoethoxydimethylsilylethyl) tetrasulfide, bis (2-monoethoxydimethylsilylethyl) trisulfide, bis (2-monoethoxydimethylsilylethyl) disulfide and the like can be mentioned.

The silane coupling agent represented by the formula (2) includes, for example, an average composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S ₂ — (CH ₂ ) ₆ —S ₂ — (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ , average composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S ₂ — (CH ₂ ) ₁₀ —S ₂ — (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ , average composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S ₃ — (CH ₂ ) ₆ —S ₃ — (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ , average composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S ₄ — (CH ₂ ) ₆ —S ₄ — (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ , Average composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S— (CH ₂ ) ₆ —S ₂ — (CH ₂ ) ₆ —S— (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ , average composition formula ( CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S— (CH ₂ ) ₆ —S _2.5 — (CH ₂ ) ₆ —S— (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ , average Composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S— (CH ₂ ) ₆ —S ₃ — (CH ₂ ) ₆ —S— (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ , average composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S— (CH ₂ ) ₆ —S ₄ — (CH ₂ ) ₆ —S— (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ , average composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S— (CH ₂ ) ₁₀ —S ₂ — (CH ₂ ) ₁₀ —S— (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ , average composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S ₄ — (CH ₂ ) ₆ —S ₄ — (CH ₂ ) ₆ —S ₄ — (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ , average composition formula ( CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S ₂ — (CH ₂ ) ₆ —S ₂ — (CH ₂ ) ₆ —S ₂ — (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ And the average composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S— (CH ₂ ) ₆ —S ₂ — (CH ₂ ) ₆ —S ₂ — (CH ₂ ) ₆ —S— (CH ₂ ) _3- Si (OCH ₂ CH ₃ ) ₃ .

Examples of the silane coupling agent include Si363 (ethoxy (3-mercaptopropyl) bis (3,6,9,12,15-pentaoxaoctacosan-1-yloxy) silane manufactured by Evonik Degussa, and [C ₁₃ H ₂₇ O (CH ₂ CH ₂ O) ₅ ] ₂ (CH ₃ CH ₂ O) Si (CH ₂ ) ₃ SH).

配合 The amount of the silane coupling agent in the tread rubber composition may be appropriately adjusted. For example, the amount is 2 parts by mass or more based on 100 parts by mass of the rubber component. From the viewpoint of improving the reactivity of silica, the amount is preferably 2 to 20 parts by mass, more preferably 4 to 12 parts by mass, per 100 parts by mass of the rubber component.

The ratio of the blending amount (mass) of the silane coupling agent to the blending amount (mass) of the silica (the blending amount of the silane coupling agent / the blending amount of silica) is not particularly limited, and is appropriately adjusted depending on the purpose. However, it is preferably 0.01 to 0.20, more preferably 0.03 to 0.20, and particularly preferably 0.04 to 0.10. When this ratio is 0.01 or more, the effect of reducing the heat build-up of the rubber composition can be easily obtained, and when it is 0.20 or less, the production cost of the rubber composition can be reduced and the economic efficiency can be improved.

-Vulcanizing agent The vulcanizing agent is not particularly limited, and can be appropriately selected depending on the purpose. For example, sulfur and the like can be mentioned. The vulcanizing agents may be used alone or in combination of two or more.

The amount of the vulcanizing agent is not particularly limited and can be appropriately adjusted depending on the purpose. For example, the amount is 0.1 to 2.0 parts by mass, and 1.0 to 2.0 parts by mass with respect to 100 parts by mass of the rubber component. It is more preferably, and particularly preferably 1.2 to 1.8 parts by mass.

-Thermoplastic resin The rubber composition for a tread comprises, in addition to the rubber component and the styrene / alkylene block copolymer, a C5 resin, a C5 to C9 resin, a C9 resin, a terpene resin, a terpene-aromatic. It may further include a thermoplastic resin selected from the group consisting of a compound resin, a rosin resin, a dicyclopentadiene resin, an alkylphenol resin, and a partially hydrogenated resin thereof. Each of these may be used alone or in combination of two or more. The thermoplastic resin does not include the styrene-alkylene block copolymer described above.

配合 The blending amount of the thermoplastic resin is not particularly limited and can be appropriately adjusted depending on the purpose. For example, it is 5 to 50 parts by mass with respect to 100 parts by mass of the rubber component.

The C5 resin refers to a C5 synthetic petroleum resin and means a resin obtained by polymerizing a C5 fraction using a Friedel Crafts type catalyst such as AlCl ₃ or BF ₃ . Specifically, copolymers containing isoprene, cyclopentadiene, 1,3-pentadiene, 1-pentene and the like as main components, copolymers of 2-pentene and dicyclopentadiene, and 1,3-pentadiene as main components And the like.

The C5-C9 resin refers to a C5-C9 synthetic petroleum resin, and means a resin obtained by polymerizing a C5-C11 fraction using a Friedel-Crafts type catalyst such as AlCl ₃ or BF ₃ . For example, a copolymer containing styrene, vinyltoluene, α-methylstyrene, indene, or the like as a main component may be used. Among them, C5 to C9 resins having a small amount of C9 or more are preferable because of excellent compatibility with the rubber component. Specifically, a resin in which the ratio of C9 or more components in the C5 to C9 resin is less than 50% by mass is preferable, and a resin in which the ratio is 40% by mass or less is more preferable. In addition, those partially hydrogenated (for example, Alcon (registered trademark) of Arakawa Chemical Industry Co., Ltd.) are also included.

C9-based resin refers to C9-based synthetic petroleum resin and means a resin obtained by polymerizing a C9 fraction using a Friedel-Crafts type catalyst such as AlCl ₃ or BF ₃ . For example, a copolymer containing indene, methylindene, α-methylstyrene, vinyltoluene or the like as a main component can be used. In addition, those partially hydrogenated (for example, Alcon (registered trademark) of Arakawa Chemical Industry Co., Ltd.) and the like can also be mentioned.

The terpene-based resin can be obtained by blending turpentine oil obtained simultaneously with obtaining rosin from a pine tree or a polymerization component separated therefrom, and polymerizing using a Friedel-Crafts type catalyst. For example, β-pinene resin, α-pinene resin and the like can be mentioned.

The terpene-aromatic compound resin can be obtained by reacting a terpene with various phenols using a Friedel-Crafts type catalyst or further condensing it with formalin. For example, terpene-phenol resins and the like can be mentioned. Among the terpene-phenol resins, a resin in which the phenol component in the terpene-phenol resin is less than 50% by mass is preferable, and a resin in which the phenol component is 40% by mass or less is more preferable.

テ ル The terpene as a raw material is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include monoterpene hydrocarbons such as α-pinene and limonene. Among these, those containing α-pinene are preferable, and α-pinene is more preferable.

The rosin resin is not particularly limited and can be appropriately selected depending on the purpose. For example, natural resin rosins such as gum rosin, tall oil resin, and wood rosin contained in raw pine tar and tall oil; modified rosin; Rosin derivatives and the like can be mentioned. Specific examples of the modified rosin derivative include polymerized rosin, partially hydrogenated rosin; glycerin ester rosin, partially hydrogenated rosin and completely hydrogenated rosin; pentaerythritol ester rosin, partially hydrogenated rosin and completely hydrogenated rosin And the like.

The dicyclopentadiene resin can be obtained by polymerizing dicyclopentadiene using a Friedel-Crafts type catalyst such as AlCl ₃ or BF ₃ . Specific examples of commercially available dicyclopentadiene resins include Quinton 1920 (manufactured by Nippon Zeon), Quinton 1105 (manufactured by Nippon Zeon), and Marcarez M-890A (manufactured by Maruzen Petrochemical).

The alkylphenol-based resin is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include an alkylphenol-acetylene resin such as a p-tert-butylphenol-acetylene resin, and an alkylphenol-formaldehyde resin having a low polymerization degree. Can be

-Glycerin fatty acid ester When the rubber composition for tread contains silica as a filler, it is preferable that the tread rubber composition further contains a glycerin fatty acid ester composition, and the glycerin fatty acid ester is an ester of glycerin and two or more fatty acids. Among the two or more fatty acids constituting the glycerin fatty acid ester, the most fatty acid component is 10 to 90% by mass in the total fatty acid, and the monoester component is 50 to 100% by mass in the glycerin fatty acid ester. More preferably, the composition contains a glycerin fatty acid ester composition.
When the glycerin fatty acid ester composition is included, the processability of the rubber composition is improved, and the effect of reducing the rolling resistance of the tire can be further improved by applying the rubber composition to the tire.

The glycerin fatty acid ester is an ester of glycerin and two or more fatty acids. The glycerin fatty acid ester is a compound in which at least one of the three OH groups of glycerin and the COOH group of the fatty acid are ester-bonded.
Here, the glycerin fatty acid ester may be a glycerin fatty acid monoester (monoester component) obtained by esterifying one molecule of glycerin and one molecule of fatty acid, or a glycerin fatty acid diester obtained by esterifying one molecule of glycerin and two molecules of fatty acid. Diester component), glycerin fatty acid triester (ester component) obtained by esterifying one molecule of glycerin and three molecules of fatty acid, or a mixture thereof, but glycerin fatty acid monoester is preferred. When the glycerin fatty acid ester is a mixture of glycerin fatty acid monoester, glycerin fatty acid diester, and glycerin fatty acid triester, the content of each ester can be measured by gel permeation chromatography (GPC). The two fatty acids constituting the glycerin fatty acid diester and the three fatty acids constituting the glycerin fatty acid triester may be the same or different.

The glycerin fatty acid ester is an ester of glycerin and two or more fatty acids, and may be a glycerin fatty acid diester or a glycerin fatty acid triester obtained by esterifying two or more fatty acids with one molecule of glycerin. A mixture of a glycerin fatty acid monoester obtained by esterifying one kind of one fatty acid molecule of the two or more kinds of fatty acids and a glycerin fatty acid monoester obtained by esterifying one molecule of glycerin and one kind of other fatty acid molecule. It is preferable that

As the two or more fatty acids that are the raw materials of the glycerin fatty acid ester (that is, the constituent fatty acids of the glycerin fatty acid ester), from the viewpoints of processability of the rubber composition, reduction of low rolling resistance of the tire, improvement of breaking characteristics, and the like, Fatty acids having 8 to 22 carbon atoms are preferred, fatty acids having 12 to 18 carbon atoms are more preferred, fatty acids having 14 to 18 carbon atoms are still more preferred, and fatty acids having 16 carbon atoms and fatty acids having 18 carbon atoms are preferred. Is even more preferred. Further, among the two or more fatty acids that are the raw materials of the glycerin fatty acid ester, one of the most fatty acid component and the second most fatty acid component is a fatty acid having 16 carbon atoms and the other is a fatty acid having 18 carbon atoms. More preferred.

Further, when the glycerin fatty acid ester is an ester of glycerin, a fatty acid having 16 carbon atoms, and a fatty acid having 18 carbon atoms, the mass ratio of the fatty acid having 16 carbon atoms to the fatty acid having 18 carbon atoms (carbon number: 16 (A fatty acid / a fatty acid having 18 carbon atoms) is preferably in the range of 90/10 to 10/90, more preferably in the range of 80/20 to 20/80, and even more preferably in the range of 75/25 to 25/75. When the mass ratio of the fatty acid having 16 carbon atoms to the fatty acid having 18 carbon atoms is in this range, the processability of the rubber composition, the reduction in low rolling resistance of the tire, and the breaking characteristics can be further improved.

The constituent fatty acids of the glycerin fatty acid ester may be linear or branched, but are preferably linear, and may be either saturated or unsaturated fatty acids, but are preferably saturated fatty acids.

As the constituent fatty acids of the glycerin fatty acid ester, specifically, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, linoleic acid, linolenic acid, araginic acid, Arachidonic acid, behenic acid and the like are mentioned, and among these, lauric acid, myristic acid, palmitic acid and stearic acid are preferable, and palmitic acid and stearic acid are more preferable.

Specific examples of the glycerin fatty acid ester include lauric acid monoglyceride, myristic acid monoglyceride, palmitic acid monoglyceride, and stearic acid monoglyceride, and more preferably palmitic acid monoglyceride and stearic acid monoglyceride.

In the rubber composition for tread, the amount of the glycerin fatty acid ester composition is, from the viewpoint of processability of the rubber composition, based on 100 parts by mass of the silica, preferably 0.5 parts by mass or more, more preferably 1 part by mass. Parts or more, more preferably 1.5 parts by mass or more, and, from the viewpoint of the breaking properties of the rubber composition, based on 100 parts by mass of the silica, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, It is even more preferably at most 5 parts by mass.

-Other components The rubber composition for treads, in addition to the components described above, components commonly used in the rubber industry, for example, an antioxidant, a vulcanization accelerator, an organic acid compound, etc., the purpose of the present invention. Can be appropriately selected and contained within a range not inconsistent with the above.

A known method can be used for the method of using the tread rubber composition for the tread rubber. For example, it can be manufactured by molding a green tire using the above rubber composition for a tread rubber and vulcanizing the green tire according to a conventional method.

(Belt coating rubber)
In the tire of the present invention, the belt layers 6a and 6b have a belt coating rubber covering the reinforcing cord, and the belt coating rubber has a 200% modulus value M200 (MPa) with respect to a 50% modulus value M50 (MPa). The ratio is not more than 5.0 (M200 / M50 ≦ 5.0).

M50 is a parameter related to the elasticity of the vulcanized rubber in a low strain range. Therefore, with respect to M50, in order to suppress deformation of the belt portion of the tire, for example, while adjusting the type and content of carbon black in the belt coating rubber described later, the phenol resin or methylene donor in the belt coating rubber described later is supplied. It must be as high as possible by incorporating the body. On the other hand, M200 is a parameter related to the elasticity of the vulcanized rubber in a high strain range. Therefore, for M200, from the viewpoint of suppressing crack growth, it is necessary to reduce the concentration of stress at the tip of the crack, for example, by adjusting the type and content of carbon black described later, it is necessary to lower the value .
By setting the ratio of the size of the M200 to the size of the M50 in the belt coating rubber to 5.0 or less (M200 / M50 ≦ 5.0), reduction in rolling resistance and improvement in belt durability are realized. it can. Further, from the same viewpoint, M200 / M50 of the belt coating rubber is preferably 4.8 or less.
The 50% modulus is the tensile stress (MPa) at 50% elongation of the vulcanized rubber, and the 200% modulus is the tensile stress (MPa) at 200% elongation of the vulcanized rubber. That is. These values can be measured according to JIS K 6251 (2010).

Further, the specific numerical range of the belt coating rubber M50 and the M200 is not particularly limited, but from the viewpoint of reducing the rolling resistance at a higher level and realizing the durability of the belt, M50 is 1.8 MPa. As described above, M200 is preferably 10.5 MPa or less.

The belt-coated rubber preferably has a dynamic storage modulus (E ′) at 25 ° C. at a strain of 1% of more than 12 MPa and less than 30 MPa, more preferably 13 to 25 MPa. This is because grip performance on a dry road surface and a wet road surface can be further improved, and a reduction in rolling resistance and an improvement in belt durability can be achieved at a higher level.
By making the dynamic storage elastic modulus (E ') at a strain of 1% at 25 ° C. of the belt coating rubber more than 12 MPa, the strength of the belt coating rubber can be increased, and the durability of the belt can be further improved. Since the input to the tread rubber is improved, the grip performance on a dry road surface and a wet road surface can be further improved. On the other hand, by setting the dynamic storage elastic modulus (E ′) of the belt-coated rubber at 25 ° C. at a strain of 1% to less than 30 MPa, an increase in rolling resistance can be suppressed.

Here, the belt coating rubber is composed of a rubber composition for belt coating (hereinafter, may be referred to as “rubber composition for belt coating”).
Other conditions are not particularly limited as long as the above-mentioned relationship of M200 / M50 ≦ 5.0 can be satisfied for the rubber composition for belt coating.
For example, from the viewpoint of reducing the rolling resistance at a higher level and realizing the durability of the belt, the rubber composition for the belt coating includes a rubber component, carbon black, a phenol resin, and a methylene donor. Can be used.

-Rubber component The rubber component contained in the rubber composition for belt coating is not particularly limited, and can be appropriately changed depending on required performance.
For example, from the viewpoint that excellent crack propagation resistance and wear resistance can be obtained, natural rubber or a diene-based synthetic rubber is used alone, or natural rubber and a diene-based synthetic rubber are used in combination. Can be.
The rubber component can be composed of 100% of the diene rubber, but may contain a rubber other than the diene rubber as long as the object of the present invention is not impaired. From the viewpoint that excellent crack propagation resistance and wear resistance can be obtained, the content of the diene rubber in the rubber component is preferably 30% by mass or more, and more preferably 40% by mass or more. More preferably, it is even more preferably 50% by mass or more.

Here, as the diene-based synthetic rubber, polybutadiene rubber (BR), isoprene rubber (IR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) And the like.
Examples of the non-diene rubber include ethylene propylene diene rubber (EPDM), ethylene propylene rubber (EPM), and butyl rubber (IIR).
These synthetic rubbers may be used alone or as a blend of two or more. These rubbers may be modified with a modifying group.

-Carbon black The carbon black that can be contained in the rubber composition for belt coating is not particularly limited, and can be appropriately changed according to required performance.
For example, from the viewpoint of more excellent durability can be obtained, as the carbon black, DBP (dibutyl phthalate) absorption is preferably used as the 50 ~ 100cm ³ / 100g.
A DBP absorption 50 ~ 100cm ³ / 100g, by using the low structure carbon black, it is possible to achieve both adequate flexibility and reinforcement of the belt coating rubber, belt such as excellent crack growth resistance Durability can be obtained. When the DBP absorption exceeds 100 cm ^3/100 g, because the structure is high, too high a reinforcing of the belt coating rubber, it is not possible to obtain sufficient durability for flexibility is reduced. The DBP absorption of carbon black is preferably at 90cm ^3/100 g or less, more preferably 80 cm ^3/100 g or less.
The structure of carbon black refers to the size of a structure (aggregate of carbon black particles) formed as a result of fusion and connection of spherical carbon black particles.
The DBP absorption of carbon black is the amount of DBP (dibutyl phthalate) absorbed by 100 g of carbon black, and can be measured according to JIS K 6217-4 (2008).

As for the carbon black is preferably a nitrogen adsorption specific surface area (N ₂ SA) is 70 ~ 90m ² / g, and more preferably 75 ~ 85m ² / g. Since the structure of the carbon black can be further optimized, the rolling resistance can be reduced and the durability of the belt can be further improved.
Incidentally, the nitrogen adsorption specific surface area can be measured by a single point method in accordance with ISO4652-1, for example, after immersing degassed carbon black in liquid nitrogen, adsorbed on the carbon black surface at equilibrium The measured amount of nitrogen is measured, and the specific surface area (m ² / g) can be calculated from the measured value.

Further, the type of the carbon black is not particularly limited. For example, any hard carbon produced by an oil furnace method can be used. Among these, it is preferable to use HAF grade carbon black from the viewpoint of achieving a higher level of both the reduction in rolling resistance and the durability of the belt.

The content of the carbon black is preferably 35 to 45 parts by mass with respect to 100 parts by mass of the rubber component. By setting the content of the carbon black to 100 parts by mass of the rubber component and 35 parts by mass or more, higher reinforcing properties and crack propagation resistance can be obtained, and by 45 parts by mass or less. Further, the rolling resistance can be further improved.

-Phenol resin The phenol resin that can be contained in the rubber composition for belt coating is not particularly limited, and can be appropriately changed according to required performance.
The rubber composition for belt coating contains a phenolic resin together with a methylene donor described below, thereby improving the 50% modulus value (M50) of the belt coating rubber, reducing the rolling resistance of the tire, and improving the belt coating. The reinforcement of rubber can be improved and excellent belt durability can be realized.

Here, the phenol resin is not particularly limited, and can be appropriately selected according to required performance. For example, those produced by subjecting a phenol such as phenol, cresol, resorcin, or tert-butylphenol or a mixture thereof to formaldehyde to a condensation reaction in the presence of an acid catalyst such as hydrochloric acid and oxalic acid are exemplified.
It is. The phenol resin may be a modified phenol resin. For example, the phenol resin may be modified with an oil such as rosin oil, tall oil, cashew oil, linoleic acid, oleic acid, and linoleic acid.
In addition, about the above-mentioned phenol resin, one kind may be included alone, or a plurality of kinds may be mixed and included.

Further, the content of the phenol resin in the rubber composition for belt coating is preferably 2 to 10 parts by mass, more preferably 3 to 7 parts by mass with respect to 100 parts by mass of the rubber component. . By setting the content of the phenol resin to 100 parts by mass of the rubber component and 2 parts by mass or more, the durability of the belt can be further improved, and by 10 parts by mass or less, deterioration of the rolling resistance is suppressed. it can.

-Methylene donor The methylene donor that can be contained in the rubber composition for belt coating is not particularly limited, and can be appropriately changed according to required performance.
By including the melamine donor as a curing agent for the phenolic resin, the 50% modulus value (M50) of the belt coating rubber is improved, and the reinforcing property of the rubber composition is improved while maintaining the rolling resistance reduction effect. Can be done.

Here, the methylene donor is not particularly limited, and can be appropriately selected depending on required performance. For example, hexamethylenetetramine, hexamethoxymethylolmelamine, pentamethoxymethylolmelamine, hexamethoxymethylmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, hexakis- (methoxymethyl) melamine, N, N ', N "-trimethyl-N , N ', N "-trimethylolmelamine, N, N', N" -trimethylolmelamine, N-methylolmelamine, N, N '-(methoxymethyl) melamine, N, N', N "-tributyl-N , N ', N "-trimethylolmelamine, paraformaldehyde, etc. Among these methylene donors, selected from the group consisting of hexamethylenetetramine, hexamethoxymethylmelamine, hexamethoxymethylolmelamine and paraformaldehyde, at least It is preferable that the species.
Note that these methylene donors may be used alone or in combination.

Further, in the rubber composition for belt coating, the ratio of the content of the phenol resin to the content of the methylene donor is preferably 0.6 to 0.6 from the viewpoint of reducing rolling resistance and achieving a higher level of belt durability. It is preferably 7, and more preferably 1 to 5. When the ratio of the content of the phenol resin to the content of the methylene donor is 0.6 or more, M50 is sufficiently improved, and durability such as crack propagation resistance can be improved. In the case of 7 or less, the rolling resistance does not deteriorate.

-Other components In addition, the rubber composition for belt coating, besides the above-mentioned rubber component, carbon black, phenol resin and methylene donor, may contain other components to such an extent that the effects of the invention are not impaired. it can.
As other components, for example, fillers other than the carbon black, antioxidants, crosslinking accelerators, crosslinking agents, crosslinking accelerators, silane coupling agents, stearic acid, antiozonants, surfactants and the like Additives commonly used in the rubber industry can be included as appropriate.

Examples of the filler include silica and other inorganic fillers.
Among them, it is preferable that the filler contains silica. This is because the reduction of the rolling resistance and the durability of the belt can both be achieved at a higher level.

Examples of the silica include wet silica, colloidal silica, calcium silicate, and aluminum silicate.
Among the above, the silica is preferably wet silica, and more preferably precipitated silica. This is because these silicas have high dispersibility and can further improve the low rolling resistance and wear resistance of the tire. Precipitated silica means that in the early stage of production, the reaction solution is allowed to react at a relatively high temperature in a neutral to alkaline pH range to grow primary silica particles, and then to the acidic side to aggregate the primary particles. Is the silica obtained as a result.
The content of the silica is not particularly limited, but is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of achieving an excellent rolling resistance reduction effect. More preferably, it is 10 parts by mass.

In addition, as the inorganic filler, for example, an inorganic compound represented by the following formula (3) can be used.
nM · xSiO _Y · zH ₂ O (3)
(Wherein M is a metal selected from the group consisting of aluminum, magnesium, titanium, calcium and zirconium, oxides or hydroxides of these metals, hydrates thereof, and carbonates of these metals) N, x, y, and z are each an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10.)

Examples of the inorganic compound of the above formula (3) include alumina (Al ₂ O ₃ ) such as γ-alumina and α-alumina; alumina monohydrate (Al ₂ O ₃ .H ₂ O) such as boehmite and diaspore; And aluminum hydroxide [Al (OH) ₃ ] such as bayerite; aluminum carbonate [Al ₂ (CO ₃ ) ₃ ], magnesium hydroxide [Mg (OH) ₂ ], magnesium oxide (MgO), magnesium carbonate (MgCO ₃₎ ), talc _{(3MgO · 4SiO 2 · H 2} O), attapulgite _{(5MgO · 8SiO 2 · 9H 2} O), titanium white (TiO _2), titanium black (TiO _2n-1), calcium oxide (CaO), hydroxide Calcium [Ca (OH) ₂ ], aluminum magnesium oxide (MgO.Al ₂ O ₃ ), clay (Al ₂ O ₃ .2SiO ₂ ), kaolin (Al ₂ O ₃ .2SiO ₂ .2H ₂ O), pyrophyllite (Al ₂ O ₃ · 4SiO ₂ · H ₂ O), bentonite (Al ₂ O ₃ · 4SiO ₂ · 2H ₂ O), magnesium silicate (Mg ₂ SiO ₄ , MgSiO ₃ etc.), aluminum calcium silicate (Al ₂ O ₃・ CaO ・ 2SiO ₂ etc.), magnesium calcium silicate (CaMgSiO ₄ ), calcium carbonate (CaCO ₃ ), zirconium oxide (ZrO ₂₎ ), Zirconium hydroxide [ZrO (OH) ₂ .nH ₂ O], zirconium carbonate [Zr (CO ₃ ) ₂ ], various types of zeolites such as hydrogen, alkali- or alkaline-earth metals that correct charge Aluminosilicates and the like can be mentioned.

公 知 As the anti-aging agent, known agents can be used, and there is no particular limitation. For example, a phenolic antioxidant, an imidazole antioxidant, an amine antioxidant and the like can be mentioned. These antioxidants can be used alone or in combination of two or more.

公 知 A known crosslinking accelerator can be used, and is not particularly limited. For example, thiazole vulcanization accelerators such as 2-mercaptobenzothiazole and dibenzothiazyldisulfide; N-cyclohexyl-2-benzothiazylsulfenamide, Nt-butyl-2-benzothiazylsulfenamide and the like Sulphenamide-based vulcanization accelerators; guanidine-based vulcanization accelerators such as diphenylguanidine; tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetradodecylthiuram disulfide, tetraoctylthiuram disulfide, tetrabenzylthiuram disulfide, Thiuram-based vulcanization accelerators such as pentamethylenethiuram tetrasulfide; dithiocarbamate-based vulcanization accelerators such as zinc dimethyldithiocarbamate; zinc dialkyldithiophosphate; .

The crosslinking agent is not particularly limited. For example, sulfur, bismaleimide compounds and the like can be mentioned.
With respect to the type of the bismaleimide compound, for example, N, N'-o-phenylenebismaleimide, N, N'-m-phenylenebismaleimide, N, N'-p-phenylenebismaleimide, N, N '-( 4,4'-diphenylmethane) bismaleimide, 2,2-bis- [4- (4-maleimidophenoxy) phenyl] propane, bis (3-ethyl-5-methyl-4-maleimidophenyl) methane and the like are exemplified. Can be. In the present invention, N, N'-m-phenylenebismaleimide, N, N '-(4,4'-diphenylmethane) bismaleimide and the like can be suitably used.

架橋 Examples of the cross-linking accelerator include zinc white (ZnO) and fatty acids. The fatty acid may be a saturated or unsaturated, linear or branched fatty acid, and the number of carbon atoms of the fatty acid is not particularly limited. For example, a fatty acid having 1 to 30, preferably 15 to 30 carbon atoms, More specifically, naphthenic acids such as cyclohexanoic acid (cyclohexanecarboxylic acid) and alkylcyclopentane having a side chain; hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acids such as neodecanoic acid), dodecanoic acid, and tetradecane Saturated fatty acids such as acid, hexadecanoic acid and octadecanoic acid (stearic acid); unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid and linolenic acid; and resin acids such as rosin, tall oil acid and abietic acid. These may be used alone or in combination of two or more. In the present invention, zinc white and stearic acid can be suitably used.

In addition, when silica is contained as the filler, it is preferable to further contain a silane coupling agent. This is because the reinforcing effect and the low heat generation effect of silica can be further improved. In addition, a well-known thing can be used suitably as a silane coupling agent. The preferred content of the silane coupling agent varies depending on the type of the silane coupling agent and the like, but is preferably in the range of 2 to 25% by mass, and more preferably in the range of 2 to 20% by mass based on silica. More preferably, it is particularly preferably 5 to 18% by mass. If the content is less than 2% by mass, the effect as a coupling agent is not sufficiently exhibited, and if it exceeds 25% by mass, gelation of the rubber component may be caused.

The method for producing the rubber composition for belt coating is not particularly limited, and each component (rubber component, carbon black, phenol resin, methylene donor and other components) constituting the rubber composition is It can be obtained by blending and kneading.
Further, in the production of the rubber composition for belt coating, kneading of each of the components can be kneaded at the same time, or any of the components can be kneaded in advance, and the remaining components can be kneaded. . These conditions can be appropriately changed according to the performance required of the rubber composition.

For example, from the viewpoint of reducing the rolling resistance and the durability of the belt at a higher level, it is preferable to mix and knead the rubber component and the carbon black before kneading with the phenol resin. Since the phenolic resin has a strong interaction with the carbon black, the reaction between the rubber component and the carbon black may decrease when the phenolic resin is added simultaneously. Therefore, prior to kneading with the phenol resin, the rubber component and the carbon black are blended and kneaded, so that the dispersibility and reinforcement of the carbon black are improved, the rolling resistance is reduced, and the belt durability is improved. At a higher level.

The tire of the present invention is not particularly limited except that the above-described tread rubber and belt coating rubber are used.
In addition, the tire of the present invention may be vulcanized after molding using an unvulcanized rubber composition, or molded using semi-vulcanized rubber that has undergone a preliminary vulcanization step, depending on the type of tire to be applied. Thereafter, the vulcanization may be further performed by main vulcanization.
Further, the tire of the present invention is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire is not only normal or oxygen-adjusted air, but also inert gas such as nitrogen, argon, helium and the like. Gas can be used.

本 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples below.

(Preparation of rubber composition for tread)
Under the conditions shown in Table 1, rubber compositions 1 to 3 for tread were prepared, and composition 4 was prepared. For the preparation of the rubber compositions 1 to 3 for the tread, each component is divided and kneaded in two stages (first stage of kneading, last stage of kneading). Regarding the preparation of the rubber composition 4 for tread, each component was divided and kneaded in two stages (first stage of kneading, last stage of kneading). The amount of each component is shown as an amount (parts by mass) relative to 100 parts by mass of the rubber component.

* 11: RSS # 3
* 12: Modified styrene-butadiene copolymer rubber produced using N, N-bis (trimethylsilyl) -3- [diethoxy (methyl) silyl] propylamine as a modifier, Tg = −62 ° C. Details are as follows.
A 1,3-butadiene cyclohexane solution and a styrene cyclohexane solution were added to a dried and nitrogen-purged 800 mL pressure-resistant glass container so as to obtain 1,3-butadiene 67.5 g and styrene 7.5 g. After 0.6 mmol of tetrahydrofurylpropane was added, and 0.8 mmol of n-butyllithium was added, polymerization was carried out at 50 ° C. for 1.5 hours. At this time, 0.72 mmol of N, N-bis (trimethylsilyl) -3- [diethoxy (methyl) silyl] propylamine as a modifier was added to the polymerization reaction system in which the polymerization conversion rate was almost 100%, and the mixture was added at 50 ° C. For 30 minutes. Thereafter, 2 mL of a 5% by mass solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was added to stop the reaction, followed by drying according to a conventional method to obtain a modified styrene-butadiene copolymer rubber. . As a result of measuring the microstructure of the resulting modified SBR, the amount of bound styrene was 10% by mass, the amount of vinyl bond in the butadiene portion was 40%, and the peak molecular weight was 200,000.
* 13: “# 80” manufactured by Asahi Carbon Co., Ltd.
* 14: “Nipsil AQ” manufactured by Tosoh Silica Industry Co., Ltd., BET specific surface area = 210 m ² / g
* 15: Bis (3-triethoxysilylpropyl) tetrasulfide, “Si69” manufactured by Evonik Degussa
* 16: C ₅ -C ₉ resins, JXTG energy Ltd. "T-REZ RD104"
* 17: A styrene-alkylene block copolymer having a total styrene content of 53% by mass, “DYNARON (registered trademark) 9901P” manufactured by JSR Corporation, a ratio of the unit (A) to the unit (A) + the unit (B) 70 mass. %
Silica: NipSil (registered trademark) AQ manufactured by Tosoh Silica Corporation
* 18: Styrene / alkylene block copolymer having a total styrene content of 35% by mass, “DYNARON (registered trademark) 8903P” manufactured by JSR Corporation, ratio of unit (A) to unit (A) + unit (B) 70 mass %
* 19: Styrene / alkylene block copolymer having a total styrene content of 15% by mass, "DYNARON (registered trademark) 8600P" manufactured by JSR Corporation, ratio of unit (A) to unit (A) + unit (B) 68 mass %
* 20: Microcrystalline wax, "Ozoace 0701" manufactured by Nippon Seiro Co., Ltd.
* 101: Total amount of "Nocrack 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. and "Nonflex RD-S" manufactured by Seiko Chemical Co., Ltd. * 102: 1,3-Diphenylguanidine (Ouchi Shinko Chemical Industry Co., Ltd.) “Noxeller D” manufactured by K.K.), di-2-benzothiazolyl disulfide (“Noxeller DM” manufactured by Ouchi Shinko Chemical Co., Ltd.), and N-cyclohexyl-2-benzothiazole sulfenamide (III) Total amount with "Sancellar CM-G" manufactured by Shin Chemical Co., Ltd.)

(Preparation of rubber composition for belt coating)
Under the conditions shown in Table 2, rubber compositions A to C for belt coating were prepared. In addition, about the compounding quantity of each component, it shows with the quantity (mass part) with respect to 100 mass parts of rubber components.
For M50, M200, and E 'in Table 2, vulcanized rubber obtained by vulcanizing the rubber composition for belt coating at 145 ° C. for 33 minutes was measured. M50 and M200 were measured in accordance with JIS K 6251 (2010), and E 'was measured using a spectrometer manufactured by Ueshima Seisakusho under the conditions of initial load of 160 mg and frequency of 52 Hz. went.

* 21: RSS # 3
* 22: HAF grade carbon black, Asahi Carbon Co., Ltd. "Asahi # 70L", DBP absorption amount: 75cm ³ / 100g, nitrogen adsorption specific surface area: 81m ² / g
* 23: GPF grade carbon black, Asahi Carbon Co., Ltd. "Asahi NPG", DBP absorption amount: 89cm ³ / 100g, nitrogen adsorption specific surface area: 28m ² / g
* 24: Sumitomo Bakelite Co., Ltd. “Sumilite Resin PR-50235”
* 25: Hexamethoxymethylmelamine, "CYREZ 964" manufactured by ALLNEX
* 26: “Nipsil AQ” manufactured by Tosoh Silica Industry Co., Ltd., BET specific surface area = 210 m ² / g
* 27: 2,2′-methylenebis (4-methyl-6-tert-butylphenol), “Nocrack NS-6” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
* 28: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, “Nocrack 6C” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
* 29: 1,3-Diphenylguanidine, “Noxeller D” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
* 30: Complex salt in which part of the organic acid in the cobalt salt of the organic acid is replaced with boric acid, "Manobond C" manufactured by OMG, cobalt content: 22.0% by mass
* 31: “BMI-RB” manufactured by Daiwa Chemical Industry Co., Ltd.

<Samples 1 to 12>
A pneumatic tire (size: 195 / 60R15) of each sample is prepared by combining the rubber composition for tread and the rubber composition for belt coating shown in Table 3. In addition, about the pneumatic tire of each sample, the manufacturing conditions other than the tread rubber and the belt coating rubber are all the same.

<Evaluation>
(1) Rolling resistance The tire of each sample is rotated at a speed of 80 km / hr by a rotating drum, the load is set to 4.82 kN, and the rolling resistance coefficient is measured by a measuring instrument.
The evaluation is represented by an index when the rolling resistance coefficient of the tire of Sample 7 is set to 100, and a smaller index value indicates a lower rolling resistance and a better result.

(2) Dry handling The tire of each sample is mounted on a test vehicle, and the actual handling on a dry road is used to evaluate the handling during running based on the driver's feeling.
The evaluation is represented by an index when the feeling score of the tire of Sample 7 is set to 100, and the larger the index value, the higher the steering stability (dry handling property) on a dry road surface.

(3) belt durability (crack propagation resistance)
A test piece of 2 mm x 50 mm x 6 mm is cut out from the belt coating rubber of the tire of each sample, and a small hole is made in the center thereof to form an initial crack. Thereafter, a stress is repeatedly applied in the long side direction to the test piece under the conditions of 2.0 MPa, a frequency of 6 Hz, and an ambient temperature of 80 ° C. Then, for each test piece, the number of repetitions from the application of the repeated stress to the breakage of the test piece is measured, and then the common logarithm of the number of repetitions is calculated. In addition, the measurement test up to the fracture is performed four times for each test piece to calculate a common logarithm, and an average thereof is defined as an average common logarithm.
The evaluation is shown as an index when the average common logarithm of the test piece of Sample 7 is 100, and the larger the average common logarithm of the test piece is, the more excellent the crack growth resistance is. Table 3 shows the evaluation results.

From the results in Table 3, the samples 11 and 12 corresponding to the present invention show higher effects in all of the rolling resistance, dry handling properties and belt durability than the samples of the respective comparative examples.
In addition, each sample of the comparative example shows a value inferior to the example in at least one evaluation item.

According to the present invention, it is possible to provide a tire having excellent dry handling properties and belt durability, and capable of reducing rolling resistance.

1: bead part 2: side wall part 3: tread part 4: bead core 5: radial carcass 6: belt 6a, 6b: belt layer

Claims (7)

1. A belt comprising at least one belt layer disposed on a tread portion,
   The tread rubber constituting the tread portion is composed of a rubber composition containing a rubber component and a styrene-alkylene block copolymer having a total styrene content of 30% by mass or more,
   The belt layer has a belt coating rubber covering a reinforcing cord, and the belt coating rubber has a ratio of a 200% modulus M200 (MPa) to a 50% modulus M50 (MPa) of 5.0 or less (M200 / M50). ≦ 5.0).
2. 2. The tire according to claim 1, wherein the belt coating rubber has a dynamic storage modulus (E ′) at a strain of 1% at 25 ° C. of more than 12 MPa and less than 30 MPa.
3. The belt coating rubber is a rubber component, and carbon black DBP absorption amount is 50 ~ 100 cm ³ / 100g, and a phenol resin, characterized by comprising a rubber composition containing a methylene donor, claim The tire according to 1 or 2.
4. The alkylene block of the styrene-alkylene block copolymer has-(CH ₂ -CH (C ₂ H ₅ ))-unit (A) and-(CH ₂ -CH ₂ ) -unit (B), 4. The composition according to claim 1, wherein the total content of (A) is at least 40% by mass based on the total mass (unit (A) + unit (B)) of the alkylene blocks of units (A) and (B). A tire according to any one of the preceding claims.
5. The total content of the unit (A) is 50% by mass or more based on the total mass of the alkylene blocks of the units (A) and (B) (unit (A) + unit (B)). The tire described in the above.
6. The rubber composition used in the tread rubber, wherein the rubber component contains a natural rubber, and a content ratio of the natural rubber in the rubber component is 50% by mass or more. A tire according to any one of the preceding claims.
7. The tire according to any one of claims 1 to 6, wherein the total styrene content of the styrene-alkylene block copolymer is 50% by mass or more.

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