JP2020059408A - tire - Google Patents

Abstract

To provide a tire excellent in dry steering stability and dry grip characteristics.SOLUTION: A tire includes a cap rubber and a base rubber as a tread rubber, in which a storage elastic modulus at 30°C of the base rubber is 10 MPa or more, the cap rubber contains a vulcanized rubber of a rubber composition containing a rubber component (A), a filler (B) and a softening agent (C), the rubber component (A) contains a modified conjugated diene-based polymer (A1), an extension oil added to the modified conjugated diene-based polymer (A1) is 10 pts.mass or less with respect to 100 pts.mass of the modified conjugated diene-based polymer (A1), a content of the filler (B) is 50 pts.mass or more and 130 pts.mass or less with respect to 100 pts.mass of the rubber component (A), the filler (B) contains at least carbon black, and the softening agent (C) contains 4 pts.mass or more of the softening agent having a softening point of 135°C or higher and 155°C or lower with respect to 100 pts.mass of the rubber component (A).SELECTED DRAWING: None

Description

  The present invention relates to a tire.

  From the viewpoint of improving vehicle safety, various studies have been conducted to improve the dry grip performance and wet grip performance of tires on a wet road surface. Further, with the recent increasing interest in environmental problems, there is an increasing demand for low fuel consumption of automobiles. In order to meet such requirements, it is required to reduce rolling resistance of tires. As a method of reducing the rolling resistance of a tire, it is common to use a rubber composition having excellent low loss performance for the tread.

  Conventionally, it has been a mainstream to provide a tire with high wet grip performance and low loss performance by using a modified styrene-butadiene copolymer rubber (SBR) as a rubber component or by adding an inorganic filler such as silica. there were.

  In recent years, by applying a rubber composition containing a large amount of a thermoplastic resin and a softening agent as a main rubber component to a tread rubber, a higher wet grip performance and a lower loss performance are realized. It has been known. (For example, Patent Document 1)

International Publication No. 2015/079703

  However, with the rubber composition as described in Patent Document 1, it is difficult to obtain a tire having a low elastic modulus of rubber and having sufficient dry steering stability, dry grip characteristics, and abrasion resistance.

  In view of the above problems, the present invention provides a tire having excellent dry steering stability and dry grip characteristics.

<1> A tire having a tread rubber, wherein the tread rubber includes a cap rubber having a ground contact surface and a base rubber provided radially inside the cap rubber, and the storage elasticity of the base rubber at 30 ° C. The rate E ′ is 10 MPa or more, the cap rubber contains a vulcanized rubber of a rubber composition containing a rubber component (A), a filler (B), and a softening agent (C), and the rubber component ( A) contains a modified conjugated diene polymer (A1), and the modified conjugated diene polymer (A1) has a weight average molecular weight of 20 × 10 ⁴ or more and 300 × 10 ⁴ or less. The combined (A1) contains a modified conjugated diene polymer having a molecular weight of 200 × 10 ⁴ or more and 500 × 10 ⁴ or less in an amount of 0.25% by mass or more and 30% by mass or less, and a contraction factor (g ′) of 0.64. Is less than, and The extending oil added to the modified conjugated diene polymer (A1) is 10 parts by mass or less based on 100 parts by mass of the modified conjugated diene polymer (A1), and the content of the filler (B) is The amount is 50 parts by mass or more and 130 parts by mass or less with respect to 100 parts by mass of the rubber component (A), the filler (B) contains at least carbon black, and the softening agent (C) is at least softened. The tire contains 4 parts by mass or more of a softening agent having a point of 135 ° C. or higher and 155 ° C. or lower with respect to 100 parts by mass of the rubber component (A).
<2> The tire according to <1>, wherein the filler (B) further contains an inorganic filler in a ratio of 10 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the rubber component.
<3> The tire according to <2>, wherein the inorganic filler is at least one selected from silica and aluminum hydroxide.
<4> The tire according to <3>, wherein the silica content in the filler (B) is 70% by mass or more.
<5> The tire according to any one of <1> to <4>, in which the total amount of the softening agent (C) with respect to 100 parts by mass of the rubber component (A) is 4 parts by mass or more and 30 parts by mass or less.
<6> The tire according to any one of <1> to <3>, in which the proportion of the carbon black in the filler (B) is 70% by mass or more.
<7> The tire according to <1> to <3>, <6>, in which the total amount of the softening agent (C) is 4 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber component (A). .
<8> The modified conjugated diene-based polymer (A1) has one or more coupling residues and a conjugated diene-based polymer chain bonded to the coupling residues, and one cup The tire according to any one of <1> to <7>, including a branch in which 5 or more conjugated diene-based polymer chains are bonded to a ring residue.
<9> The modified conjugated diene polymer (A1) has the following general formula (I):

[In the formula, D represents a conjugated diene-based polymer chain, R ¹ , R ² and R ³ each independently represent a single bond or an alkylene group having 1 to 20 carbon atoms, and R ⁴ and R ⁷ are , Each independently represents 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, and R ⁶ and R ¹⁰ Each independently represents 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 an integer of 1 to 3. , X ≦ m, p is 1 or 2, y is an integer of 1 to 3, y ≦ (p + 1), z is an integer of 1 or 2, and each of them is plural. ^D in the case ^{of, R 1 ~R 11, m,} p, x, y, and z are each independently i represents an integer of 0 to 6, j represents an integer of 0 to 6, k represents an integer of 0 to 6, (i + j + k) is an integer of 3 to 10, and ((x × i) + (y × j) + (z × k)) is an integer of 5 to 30, and A is a hydrocarbon group having 1 to 20 carbon atoms, or an oxygen atom, a nitrogen atom, a silicon atom, Which has at least one atom selected from the group consisting of a sulfur atom and a phosphorus atom, and represents an organic group having no active hydrogen], <1> to <8> It is the tire described.
<10> In the general formula (I), A is the following general formula (II):

[In the formula, B ¹ 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 ¹ , they are each independently],
The following general formula (III):

[In the formula, 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 an integer of 1 to 10, respectively. B ² and B ³ when a plurality of them are present are independent of each other],
The following general formula (IV):

[In the formula, 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 B ⁴ when there are a plurality of B ⁴ are each independently],
The following general formula (V):

[In the formula, 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 , they are each independent.] It is a tire as described in <9> represented by either.
<11> The modified conjugated diene-based polymer (A1) is a conjugated diene-based polymer represented by the following general formula (VI):

[Wherein, 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 are each independently And 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 is an alkyl group having 1 to 20 carbon atoms or a trialkyl group. Represents an alkylsilyl group, m represents an integer of 1 to 3, p represents 1 or 2, and when R ^{12 to} R ²² , m and p are present in plural, they are respectively independent, 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 hydrocarbon group having 1 to 20 carbon atoms or an oxygen atom. , A nitrogen atom, a silicon atom, a sulfur atom and a phosphorus atom, A tire according to any one of <1> to <10>, wherein the tire has at least one atom selected from the group, and represents a non-active hydrogen-containing organic group]. is there.
<12> The coupling agent represented by the general formula (VI) is tetrakis [3- (2,2-dimethoxy-1-aza-2-silacyclopentane) propyl] -1,3-propanediamine, tetrakis. At least one selected from the group consisting of (3-trimethoxysilylpropyl) -1,3-propanediamine and tetrakis (3-trimethoxysilylpropyl) -1,3-bisaminomethylcyclohexane, <11> The tire described in.

  According to the present invention, a tire having excellent dry steering stability and dry grip characteristics can be obtained.

〔tire〕
The present invention is a tire having a tread rubber, and the tread rubber includes a cap rubber having a ground contact surface and a base rubber provided inside the cap rubber in a radial direction.
Hereinafter, the base rubber and the cap rubber will be described in detail.

(Base rubber)
The base rubber of the present invention is a rubber having a storage elastic modulus E ′ at 30 ° C. of 10 MPa or more. When the base rubber has the above storage elastic modulus, a tire having excellent dry steering stability and dry grip performance can be obtained. The storage elastic modulus E ′ is preferably 12 MPa or more, more preferably 15 MPa or more. However, if the storage elastic modulus E ′ is too high, the rubber tends to be hard, so the storage elastic modulus E ′ is preferably 35 MPa or less, and more preferably 30 MPa or less.
The storage elastic modulus E'of the vulcanized rubber obtained by vulcanizing the rubber composition at 145 ° C. for 33 minutes was measured at a temperature of 30 ° C., an initial strain of 2%, and a dynamic strain of 1 using a spectrometer manufactured by Ueshima Seisakusho. %, And the frequency was 52 Hz.

The rubber satisfying the above storage elastic modulus contains at least one rubber component selected from natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), and styrene-butadiene copolymer rubber (SBR). Is desirable. In particular, it is preferable to include at least SBR. The proportion of SBR in 100 parts by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, further preferably 50% by mass or more, and particularly preferably 70% by mass or more. The styrene content relative to 100 parts by mass of the rubber component is preferably 20% by mass or more, more preferably 25% by mass or more, and further preferably 30% by mass or more.
The rubber component of the base rubber may include an oil component. The content of the oil component is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 10 parts by mass or more and 40 parts by mass or less, and more preferably 20 parts by mass or more and 35 parts by mass with respect to 100 parts by mass of the rubber component. The following is more preferable.

  The rubber preferably contains at least one selected from carbon black and silica as a reinforcing component. In particular, it is more preferable to contain at least carbon black. The content of carbon black is preferably 20 parts by mass or more and 110 parts by mass or less, more preferably 40 parts by mass or more and 100 parts by mass or less, and 50 parts by mass or more and 90 parts by mass with respect to 100 parts by mass of the rubber component. It is more preferable that the amount is 60 parts by mass or more and 90 parts by mass or less. The particle size of carbon black is not particularly limited and can be selected from a wide range of grades.

  In the tire width direction cross-sectional view, the thickness at which the thickness of the base rubber becomes the maximum in the thickness in the region of 15% or less of the tread width from the tire equatorial plane to both tire width direction outer sides is It is preferably 0.1 times or more and 0.9 times or less with respect to the thickness of the tread rubber at the measured position. By setting it in the above range, the dry steering stability can be improved. In particular, the thickness of the base rubber with respect to the thickness of the tread rubber is more preferably 0.1 times or more and 0.5 times or less, further preferably 0.2 times or more and 0.3 times or less. When the thickness of the base rubber is in the above range, it is possible to improve steering stability, prevent the rigidity of the entire tire from becoming too high, and optimize the ground contact shape on the road surface.

(Cap rubber)
<Rubber composition>
The rubber composition used for the cap rubber of the present invention contains a vulcanized rubber of a rubber composition containing a rubber component (A), a filler (B) and a softening agent (C), and the rubber component (A) is used. Contains a modified conjugated diene polymer (A1), and the modified conjugated diene polymer (A1) has a weight average molecular weight of 20 × 10 ⁴ or more and 300 × 10 ⁴ or less, and the modified conjugated diene polymer (A A1) contains a modified conjugated diene polymer having a molecular weight of 200 × 10 ⁴ or more and 500 × 10 ⁴ or less in an amount of 0.25% by mass or more and 30% by mass or less, and a contraction factor (g ′) of less than 0.64. And the extender oil added to the modified conjugated diene polymer (A1) is 10 parts by mass or less based on 100 parts by mass of the modified conjugated diene polymer (A1), and the filler ( The content of B) is based on 100 parts by mass of the rubber component (A). Is 50 parts by mass or more and 130 parts by mass or less, the filler (B) contains at least carbon black, and the softening agent (C) has at least a softening point of 135 ° C. or more and 155 ° C. or less, 4 parts by mass or more is included with respect to 100 parts by mass of the rubber component (A).

  As the tread rubber, in addition to the above-mentioned base rubber having high rigidity, a modified conjugated diene polymer (A1) (hereinafter referred to as "modified polymer (A1)") is contained, and the softening point is within the above range. By providing the cap rubber using the rubber composition containing the softening agent, it is possible to obtain a tire having high dry steering stability and dry grip performance and excellent steering stability.

<Rubber component>
The rubber component (A) contains the modified polymer (A1). The ratio of the modified polymer (A1) in 100 parts by mass of the rubber component (A) is preferably 30 parts by mass or more and 100 parts by mass or less. When the modified polymer (A1) is in this range, a tire having high steering stability can be obtained. The ratio of the modified polymer (A1) is preferably 40 parts by mass or more, and more preferably 50 parts by mass or more. The ratio of the modified polymer (A1) is preferably 90 parts by mass or less, more preferably 85 parts by mass or less.

Examples of the rubber component other than the modified polymer (A1) include diene rubber such as natural rubber (NR) and synthetic diene rubber. Examples of the synthetic diene rubber include polyisoprene rubber (IR), polybutadiene rubber (BR), butadiene-isoprene copolymer rubber (BIR), styrene-isoprene copolymer rubber (SIR), styrene-butadiene-isoprene copolymer. Examples thereof include rubber (SBIR) and styrene-butadiene copolymer rubber (SBR) other than the modified polymer (A1). These synthetic diene rubbers may be unmodified rubbers or modified rubbers. As the diene rubber component other than the modified polymer (A1), only one type may be used, or two or more types may be blended and used.
The rubber component may contain a non-diene rubber and its modified rubber as long as the effects of the present invention are not impaired.

  Extending oil is added to the modified polymer (A1). The amount of extension oil added is 10 parts by mass or less based on 100 parts by mass of the modified polymer (A1). Preferably, the extension oil is added in an amount of more than 0 parts by mass, more preferably 0.1 parts by mass or more. When the amount of the extending oil added is 10 parts by mass or less, high steering stability can be obtained. Further, a tire having a low rolling resistance can be used.

Examples of the extender oil include aroma oil, naphthene oil, paraffin oil, aroma substitute oil and the like. Among these, an aromatic alternative oil having a polycyclic aromatic (PCA) component content of 3% by mass or less according to the IP346 method is preferable from the viewpoints of environmental safety and prevention of oil bleeding and wet braking properties. As an alternative oil for aroma, Kautschuk Gummi
In addition to TDAE (Treatment Distillate Aromatic Extracts) and MES (Mold Extraction Solvates) shown in Kunststoffe 52 (12) 799 (1999), RAE (Resistance Aromatic Extracts) are listed.

The modified polymer (A1) has a weight average molecular weight (Mw) of 20 × 10 ^{4 to} 300 × 10 ⁴ , and the modified polymer (A1) has a molecular weight of 200 × 10 ^{4 to} 500 × 10 ^4. The polymer is contained in an amount of 0.25% by mass or more and 30% by mass or less, and the contraction factor (g ') is less than 0.64.

When the weight average molecular weight (Mw) of the modified polymer (A1) is 20 × 10 ⁴ or more, the dry steering stability and dry grip performance of the tire can be improved. Mw is preferably 50 × 10 ⁴ or more, more preferably 64 × 10 ⁴ or more, and further preferably 80 × 10 ⁴ or more.
When Mw is 300 × 10 ⁴ or less, a rubber composition having good processability can be obtained. Mw is preferably 250 × 10 ⁴ or less, more preferably 180 × 10 ⁴ or less, and further preferably 150 × 10 ⁴ or less.

  The weight average molecular weight of the modified polymer (A1), the number average molecular weight (Mn) described below, and the content of the specific high molecular weight component are measured as follows. Using a modified polymer as a sample, a GPC (gel permeation chromatography) measuring device (trade name “HLC-8320GPC” manufactured by Tosoh Corporation) in which three columns having polystyrene gel as a filler were connected, RI was used. The chromatogram is measured using a detector (trade name “HLC-8020” manufactured by Tosoh Corporation). The eluent is THF (tetrahydrofuran) containing 5 mmol / L triethylamine. As the column, three Tosoh product name "TSKgel SuperMultipore HZ-H" are connected, and a Tosoh product name "TSKguardcolumn SuperMP (HZ) -H" is used as a guard column in the preceding stage. 10 mg of a sample for measurement is dissolved in 10 mL of THF to prepare a measurement solution, and 10 μL of the measurement solution is injected into a GPC measurement 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 modified polymer (A1) is a modified 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 polymer (hereinafter, “specific high molecular weight component”). (Also referred to as). 0.25 mass% or more and 30 mass% or less. When the content is within the above range, the dry steering stability and dry grip performance of the tire can be improved.

Further, the ratio of the modified polymer having a molecular weight of 200 × 10 ^{4 to} 500 × 10 ⁴ is obtained by subtracting the ratio of the molecular weight of less than 200 × 10 ⁴ from the ratio of the molecular weight of 500 × 10 ⁴ or less from the integral molecular weight distribution curve. calculate.

  The modified polymer (A1) contains a specific high molecular weight component, preferably 1.0% by mass or more, more preferably 1.4% by mass or more, more preferably 1.75% by mass or more, further preferably 2.0% by mass. It is contained in an amount of at least mass%, more preferably at least 2.15 mass%, and particularly preferably at least 2.5 mass%. The modified polymer (A1) contains a specific high molecular weight component in a proportion of preferably 28% by mass or less, more preferably 25% by mass or less, further preferably 20% by mass or less, and particularly preferably 18% by mass or less.

  In the modified polymer (A1), 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. When the modified polymer (A1) has a molecular weight distribution within this range, the rubber composition has good processability.

The contraction factor (g ') of the modified polymer (A1) is less than 0.64. In general, a branched polymer tends to have a smaller molecular size when compared with a linear polymer having the same absolute molecular weight. That is, as the degree of branching of the polymer increases, the contraction factor (g ') tends to decrease. In the present invention, the intrinsic viscosity is used as an index of the size of the molecule, and the linear polymer is used as the one that follows the relational expression of intrinsic viscosity [η] = − 3.883M ^0.771 . The contraction factor (g ') at each absolute molecular weight of the modified polymer was calculated, and the average value of the contraction factor (g') when the absolute molecular weight was 100 × 10 ⁴ to 200 × 10 ⁴ was calculated as the modified polymer. The contraction factor (g ′) of Here, the "branch" is formed by directly or indirectly binding one polymer to another polymer. The “branching degree” is the number of polymers directly or indirectly bonded to one branch. For example, the degree of branching is 5 when the five SBR chains described below are bound to each other indirectly via a coupling residue. The coupling residue is a constitutional unit of the modified polymer, which is bonded to the conjugated diene polymer chain. For example, it is a structural unit derived from the coupling agent, which is produced by reacting SBR with the coupling agent. The conjugated diene polymer chain is a constituent unit of the modified polymer. For example, it is a structural unit derived from a conjugated diene polymer, which is produced by reacting SBR with a coupling agent.

  The contraction factor (g ') is preferably 0.63 or less, more preferably 0.60 or less, still more preferably 0.59 or less, and particularly preferably 0.57 or less. The lower limit of the contraction factor (g ′) is not particularly limited and may be equal to or lower than the detection limit value, preferably 0.30 or more, more preferably 0.33 or more, more preferably 0.35 or more, It is preferably 0.45 or more, more preferably 0.57 or more, and particularly preferably 0.59 or more. By using the modified polymer having the shrinkage factor (g ') in 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 the modified polymer (A1) having a branching degree of 6 is used, the contraction factor (g ′) thereof tends to be 0.59 to 0.63, and the branching degree is 8. When the modified polymer (A1) is used, the contraction factor (g ') tends to be 0.45 to 0.59.

The method for measuring the contraction factor (g ') is as follows. Using a modified polymer as a sample and a GPC measuring device (trade name "GPCmax VE-2001" manufactured by Malvern Co., Ltd.) in which three columns having polystyrene-based gel as a filler are connected, a light scattering detector and RI detection are used. And a viscosity detector (trade name "TDA305" manufactured by Malvern Co., Ltd.) are connected in this order, and measurement is performed using the results of the light scattering detector and the RI detector based on standard polystyrene. The absolute molecular weight and the intrinsic viscosity are obtained from the results 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 ′) as the ratio of the intrinsic viscosities corresponding to each molecular weight is calculated. The eluent is THF containing 5 mmol / L of triethylamine. As the column, the product names “TSKgel G4000HXL”, “TSKgel G5000HXL”, and “TSKgel G6000HXL” manufactured by Tosoh Corporation are connected and used. 20 mg of a sample for measurement is dissolved in 10 mL of THF to prepare a measurement solution, and 100 μL of the measurement solution is injected 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 polymer (A1) preferably has a branch and a degree of branching of 5 or more. Further, the modified polymer (A1) has one or more coupling residues and an SBR chain bonded to the coupling residue, and further, the branch is one coupling residue. On the other hand, it is more preferable to include a branch in which 5 or more SBR chains are bound. The degree of branching is 5 or more, and the structure of the modified polymer (A1) is specified so that the branching includes a branch in which 5 or more SBR chains are bonded to one coupling residue. By this, the contraction factor (g ') can be more surely made less than 0.64. The number of conjugated diene polymer chains bonded to one coupling residue can be confirmed from the value of the contraction factor (g ').

  Further, the modified polymer (A1) has a branch, and it is more preferable that the degree of branching is 6 or more. Further, the modified polymer (A1) has one or more coupling residues and an SBR chain bonded to the coupling residue, and further, the branch is one coupling residue. It is more preferred to include a branch to which 6 or more SBR chains are bound. The degree of branching is 6 or more, and the structure of the modified polymer (A1) is specified such that the branching has 6 or more SBR chains bonded to one coupling residue. Thus, the contraction factor (g ') can be reduced to 0.63 or less.

  Further, the modified polymer (A1) has a branch, and the branching degree is more preferably 7 or more, and further preferably 8 or more. The upper limit of the branching degree is not particularly limited, but is preferably 18 or less. Further, the modified polymer (A1) has one or more coupling residues and an SBR chain bonded to the coupling residue, and further, the branch is one coupling residue. On the other hand, it is even more preferable to include a branch in which 7 or more SBR chains are bonded, and it is more preferable to include a branch in which 8 or more SBR chains are bonded to one coupling residue. Particularly preferred. Shrinkage by specifying the structure of the modified polymer so that the degree of branching is 8 or more, and the branch includes a branch in which 8 or more SBR chains are bonded to one coupling residue. The factor (g ') can be 0.59 or less.

  In the rubber composition according to the present invention, the modified polymer (A1) has a branch and has one or more coupling residues and a styrene-butadiene rubber chain bonded to the coupling residues. It is preferable that 5 or more of the styrene-butadiene rubber chains are bonded to one coupling residue. As a result, the dry steering stability and dry grip performance of the tire can be improved.

In the rubber composition according to the present invention, the modified polymer (A1) has the following general formula (I):


[In the general formula (I), D represents a styrene-butadiene rubber chain, R ¹ , R ² and R ³ each independently represent a single bond or an alkylene group having 1 to 20 carbon atoms, and R ⁴ and R 3 ⁷ independently represents 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, R ⁶ and R ¹⁰ independently represents 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 It 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, When a plurality of D, R ^{1 to} R ¹¹ , m, p, x, y, and z are independent of each other, i is It shows the integer of 0-6, j shows the integer of 0-6, k shows the integer of 0-6, (i + j + k) is the integer of 3-10, ((xxi) + (Y × j) + (z × k)) is an integer of 5 to 30, and A is a hydrocarbon group having 1 to 20 carbon atoms, or an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom and phosphorus. Represents an organic group having at least one atom selected from the group consisting of atoms and having no active hydrogen].
As a result, the dry steering stability and dry grip performance of the tire can be improved.

In one example, the weight average molecular weight of the SBR chain represented by D in the general formula (I) is 10 × 10 ^{4 to} 100 × 10 ⁴ . The SBR chain is a structural unit of the modified polymer (A1) and is, for example, a structural unit derived from SBR produced by reacting SBR with a coupling agent.

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 hydroxyl group (—OH), secondary amino group (> NH), primary amino group (—NH ₂ ), sulfhydryl group (—SH) and the like. And an organic group having no functional group.

In the rubber composition according to the present invention, in the general formula (I), A is the following general formulas (II) to (V):


[In the general formula (II), B ¹ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, a represents an integer of 1 to 10, and when there are a plurality of B ^1's , each independently represents B ¹ ; ing;
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 an integer of 1 to 10. And B ² and B ³ when a plurality of them are present are each independent;
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 B ⁴ when a plurality of them are present, each independently. Is;
In formula (V), B ⁵ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, a represents an integer of 1 to 10, and B ⁵ in the case where a plurality of them are present, each independently. Is present].
As a result, the dry steering stability and dry grip performance of the tire can be improved.

  In one example, in the general formula (I), A is represented by the general formula (II) or (III), and k represents 0. In another example, in the general formula (I), A is represented by the general formula (II) or (III), k is 0, and in the general formula (II) or (III), a Represents an integer of 2 to 10. In still another example, in the general formula (I), A is represented by the general formula (II), k is 0, and in the general formula (II), a is an integer of 2 to 10. Indicates.

Regarding B ¹ , B ² , B ⁴ , and B ^{5 in the} general formulas (II) to (V), examples of the hydrocarbon group having 1 to 20 carbon atoms include an alkylene group having 1 to 20 carbon atoms.

  The modified polymer (A1) preferably has a nitrogen atom and a silicon atom. In this case, the processability of the rubber composition becomes good, and when applied to a tire, the dry steering stability and dry grip performance of the tire can be improved. Regarding the modified polymer (A1) having a nitrogen atom, it is judged that the modified polymer (A1) has a nitrogen atom when the calculated modification rate is 10% or more by the modification rate measuring method described later. .

  It is judged by the following method that the modified polymer (A1) has a silicon atom. Using 0.5 g of the modified polymer as a sample, it was measured using an ultraviolet-visible spectrophotometer (trade name “UV-1800” manufactured by Shimadzu Corporation) in accordance with JIS K 0101 44.3.1, and molybdenum blue was measured. Quantify by absorptiometry. As a result, when silicon atoms are detected (lower limit of detection: 10 mass ppm), it is determined that they have silicon atoms.

  In one example, the SBR chain has at least one of its ends attached to a silicon atom, which each has a coupling residue. In this case, the ends of a plurality of SBR chains may be bonded to one silicon atom. Further, the end of the SBR 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 an alkoxysilyl group or silanol group having 1 to 20 carbon atoms. May be configured.

  The amount of bonded conjugated diene in the modified polymer (A1) is preferably 40 to 100% by mass, more preferably 55 to 80% by mass. When the amount of the conjugated conjugated diene is within the above range, the dry steering stability and the dry grip performance of the tire can be improved when the rubber composition is applied to the tire.

  The amount of bound styrene in the modified polymer (A1) is preferably 35% by mass or more. When the amount of the bound aromatic vinyl is 35% by mass or more, the dry steering stability and the dry grip performance of the tire can be improved when the rubber composition is applied to the tire.

  The amount of bound aromatic vinyl can be measured by ultraviolet absorption of a phenyl group, and the amount of bound conjugated diene can also be obtained from this. Specifically, it measures according to the following. Using the modified polymer as a sample, 100 mg of the sample is made up to 100 mL with chloroform and dissolved to obtain a measurement sample. The amount of bound styrene (% by mass) with respect to 100% by mass of the sample is measured by the amount of absorption of the ultraviolet absorption wavelength (near 254 nm) by the phenyl group of styrene (Shimadzu Corporation spectrophotometer "UV-2450"). .

  In the modified polymer (A1), the amount of vinyl bond in the conjugated diene bond unit is preferably 10 to 75 mol%, more preferably 20 to 65 mol%.

For the modified polymer (A1), the method of Hampton [R. R. [Hampton, Analytical Chemistry, 21, 923 (1949)], the vinyl bond content (1,2-bond content) in the butadiene bond unit can be determined. Specifically, it is as follows. Using the modified polymer as a sample, 50 mg of the sample is dissolved in 10 mL of carbon disulfide to obtain a measurement sample. Using a solution cell, the infrared spectrum was measured in the range of 600 to 1000 cm ^-1 , and the microstructure of the butadiene moiety, that is, the 1,2-vinyl bond, was determined according to the calculation formula of the above Hampton method by the absorbance at a predetermined wave number. The amount (mol%) is determined (Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation).

  The modified polymer (A1) preferably has a Tg higher than −50 ° C., more preferably −45 to −15 ° C. When the Tg of the modified polymer (A1) is in the range of −45 to −15 ° C., the dry steering stability and dry grip performance of the tire can be improved when the rubber composition is applied to the tire.

  Regarding Tg, according to ISO 22768: 2006, the DSC curve is recorded while increasing the temperature in a predetermined temperature range, and the peak top (Influence point) of the DSC differential curve is taken as Tg. Specifically, it is as follows. Using the modified polymer as a sample, in accordance with ISO 22768: 2006, using a differential scanning calorimeter "DSC3200S" manufactured by Mac Science Co., Ltd., the temperature was raised from -100 ° C to 20 ° C / min under the flow of 50 mL / min of helium. While the DSC curve is recorded, the peak top (Infection point) of the DSC differential curve is taken as Tg.

  The Mooney viscosity of the modified polymer (A1) measured at 100 ° C. is, for example, 20 to 100, or 30 to 80.

The method of measuring the Mooney viscosity is as follows. Using the modified polymer as a sample, a Mooney viscometer (trade name "VR1132" manufactured by Ueshima Seisakusho) is used to measure the Mooney viscosity using an L-shaped rotor in accordance with JIS K6300. The measurement temperature is 100 ° C. First, the sample is preheated 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)} ).

-Method for synthesizing modified polymer (A1) The method for synthesizing modified polymer (A1) is not particularly limited. For example, styrene-butadiene is prepared by polymerizing at least butadiene using an organic monolithium compound as a polymerization initiator. A synthetic method having a polymerization step of obtaining a rubber and a reaction step of reacting a pentafunctional or higher functional reactive compound (hereinafter, also referred to as “coupling agent”) with an active terminal of the styrene-butadiene rubber Can be mentioned.

  Examples of the polymerization step include polymerization by growth reaction by living anion polymerization reaction. Thereby, a styrene-butadiene rubber having an active terminal can be obtained, and a modified polymer (A1) having a high modification rate can be obtained.

  The amount of the organic monolithium compound used as the polymerization initiator can be adjusted according to the target molecular weight of the modified polymer. Decreasing the polymerization initiator increases the molecular weight, while increasing the polymerization initiator decreases the molecular weight.

  The organomonolithium compound is preferably an alkyllithium compound from the viewpoint of industrial availability and easy control of the polymerization reaction. In this case, SBR having an alkyl group at the polymerization initiation terminal is obtained.

  Examples of the alkyl lithium compound include n-butyl lithium, sec-butyl lithium, tert-butyl lithium, n-hexyl lithium, benzyl lithium, phenyl lithium, and stilbene lithium. These organic monolithium compounds may be used alone or in combination of two or more.

  In the polymerization step, a batch or continuous polymerization reaction mode can be appropriately selected and used.

  An inert solvent may be used in the polymerization step.

  Examples of the inert solvent include aliphatic hydrocarbons such as butane, pentane, hexane and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane and methylcyclohexane; aromatics such as benzene, toluene and xylene. Examples include hydrocarbons. The inert solvent may be used alone or in combination of two or more.

  Before using an inert solvent for the polymerization reaction, it may be treated with an organometallic compound in order to remove impurities such as arenes and acetylenes in the inert solvent.

  A polar compound may be used in the polymerization step. By using a polar compound, styrene can be randomly copolymerized with butadiene. The polar compound can also be used as a vinylating agent for controlling the microstructure of the conjugated diene part.

  Examples of polar compounds include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis (2-oxolanyl) propane; tetra. Tertiary amine compounds such as methylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine and quinuclidine; alkali metal alkoxides such as potassium-tert-amylate, potassium-tert-butyrate, sodium-tert-butyrate and sodium amylate. Compounds: phosphine compounds such as triphenylphosphine, and the like. The polar compounds may be used alone or in combination of two or more.

  The polymerization temperature in the polymerization step may be appropriately adjusted, and is, for example, 0 to 120 ° C. or 50 to 100 ° C. from the viewpoint of sufficiently securing the reaction amount of the coupling agent with respect to the active terminal after the polymerization is completed.

  Examples of the coupling agent include pentafunctional or higher reactive compounds having a nitrogen atom and a silicon atom. The reactive compound preferably has at least 3 silicon-containing functional groups. The coupling agent is preferably one in which at least one silicon atom constitutes an alkoxysilyl group having 1 to 20 carbon atoms or a silanol group. The coupling agents may be used alone or in combination of two or more.

  The alkoxysilyl group contained in the coupling agent tends to react with the active terminal of SBR to dissociate the alkoxylithium, thereby forming a bond between the terminal of the SBR chain and silicon of the coupling residue. The value obtained by subtracting the SiOR number subtracted by the reaction from the total number of SiOR contained in one molecule of the coupling agent is the number of alkoxysilyl groups contained in the coupling residue. The azasilacycle group of the coupling agent forms a> N-Li bond and a bond between the SBR terminal and the silicon of the coupling residue. The> N-Li bond tends to easily become> NH and LiOH due to water or the like at the time of finishing. Further, in the coupling agent, the unreacted residual alkoxysilyl group can easily become silanol (Si-OH group) due to water or the like at the time of finishing.

In the rubber composition according to the present invention, the modified polymer (A1) is a styrene-butadiene rubber represented by the following general formula (VI):


[In the general formula ^{(VI), R 12, R} 13 and R ¹⁴ is independently a single bond or an alkylene group having a carbon number of ^{1~20, R 15, R 16,} R 17, R 18 and R ²⁰ Are each independently an alkyl group having 1 to 20 carbon atoms, R ¹⁹ and R ²² are each independently an alkylene group having 1 to 20 carbon atoms, and R ²¹ is an alkyl group having 1 to 20 carbon atoms, Represents an alkyl group or a trialkylsilyl group, m represents an integer of 1 to 3, p represents 1 or 2, and R ^{12 to} R ²² , m and p are independently present when a plurality of them are present. And 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 hydrocarbon group having 1 to 20 carbon atoms, or At least one selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom and a phosphorus atom. Have the atoms and is preferably formed by reacting a coupling agent represented by an organic group having no active hydrogen.
As a result, when the rubber composition is applied to a tire, the dry steering stability and dry grip performance of the tire can be improved.

In formula (VI), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. The organic group having no active hydrogen, for example, a hydroxyl group (-OH), a secondary amino group (> NH), primary amino (-NH _2), an active hydrogen such as a sulfhydryl group (-SH) Examples thereof include an organic group that does not have a functional group that has.

  In one example, in the general formula (VI), A is represented by the general formula (II) or (III), and k represents 0. In another example, in the general formula (VI), A is represented by the general formula (II) or (III), k is 0, and in the general formula (II) or (III), a Represents an integer of 2 to 10. In still another example, in the general formula (VI), A is represented by the general formula (II), k is 0, and in the general formula (II), a is an integer of 2 to 10. Indicates.

  Examples of such a coupling agent include tetrakis [3- (2,2-dimethoxy-1-aza-2-silacyclopentane) propyl] -1,3-propanediamine and tetrakis (3-trimethoxysilylpropyl). ) -1,3-Propanediamine, Tetrakis (3-trimethoxysilylpropyl) -1,3-bisaminomethylcyclohexane, bis (3-trimethoxysilylpropyl)-[3- (2,2-dimethoxy-1-) Aza-2-silacyclopentane) propyl] amine, tris (3-trimethoxysilylpropyl) amine, tris (3-triethoxysilylpropyl) amine, tris (3-trimethoxysilylpropyl)-[3- (2, 2-dimethoxy-1-aza-2-silacyclopentane) propyl] -1,3-propanediamine Tris (3-trimethoxysilylpropyl) -methyl-1,3-propanediamine, bis [3- (2,2-dimethoxy-1-aza-2-silacyclopentane) propyl]-(3-trismethoxysilylpropyl ) -Methyl-1,3-propanediamine and the like.

  The addition amount of the compound represented by the general formula (VI) as the coupling agent can be adjusted so that the number of moles of SBR and the number of moles of the coupling agent are reacted in a desired stoichiometric ratio, This tends to achieve the desired degree of branching. The specific number of moles of the polymerization initiator is, for example, 5.0 times or more, or 6.0 times or more the mole number of the coupling agent. In this case, in the general formula (VI), the number of functional groups ((m−1) × i + p × j + k) of the coupling agent is an integer of 5 to 10, or an integer of 6 to 10.

  The reaction temperature in the reaction step may be appropriately adjusted, and is, for example, 0 to 120 ° C, or 50 to 100 ° C. The temperature change from the polymerization step to the addition of the coupling agent is, for example, 10 ° C. or lower, or 5 ° C. or lower.

  The reaction time in the reaction step may be appropriately adjusted, and is, for example, 10 seconds or longer, or 30 seconds or longer. The time from the end of the polymerization step to the start of the reaction step is preferably shorter from the viewpoint of the coupling rate, and is, for example, 5 minutes or less.

  The mixing in the reaction step may be mechanical stirring, stirring with a static mixer, or the like.

  In order to obtain the modified polymer (A1) having a specific high molecular weight component, the molecular weight distribution (Mw / Mn) of SBR may be 1.5 to 2.5, or 1.8 to 2.2. Moreover, it is preferable that the obtained component (A1) has a single peak in the molecular weight curve by GPC.

In one example, when the peak molecular weight by GPC of the modified polymer (A1) is Mp ₁ and the peak molecular weight of SBR is Mp ₂ , the following formula is established.
(Mp ₁ / Mp ₂ ) <1.8 × 10 −12 × (Mp ₂ −120 × 10 ⁴ ) ² +2

In one example, Mp ₂ is 20 × 10 ⁴ to 80 × 10 ⁴ , and Mp ₁ is 30 × 10 ^{4 to} 150 × 10 ⁴ .

  The modification ratio of the modified polymer (A1) is, for example, 30% by mass or more, 50% by mass or more, or 70% by mass or more. When the modification rate is 30% by mass or more, when the rubber composition is applied to the tire, the dry steering stability and the dry grip performance of the tire can be improved.

The method of measuring the modification rate is as follows. The modified polymer is used as a sample and applied to a GPC column having a silica gel as a filler, and the property of adsorbing the modified basic polymer component is applied. A sample solution containing a sample and a low molecular weight internal standard polystyrene was adsorbed on a silica column by measuring the difference between the chromatogram measured with a polystyrene column and the chromatogram measured with a silica column to determine the denaturation rate. Ask. Specifically, it is as shown below.
Preparation of sample solution: A sample solution is prepared by dissolving 10 mg of sample and 5 mg of standard polystyrene in 20 mL of THF.
GPC measurement conditions using a polystyrene-based column: using Tosoh's trade name “HLC-8320GPC”, using 5 mmol / L of triethylamine-containing THF as an eluent, injecting 10 μL of the sample solution into the apparatus, and using a column oven A chromatogram is obtained using a RI detector under the conditions of a temperature of 40 ° C. and a THF flow rate of 0.35 mL / min. For the column, three Tosoh product name "TSKgel SuperMultipore HZ-H" are connected, and a Tosoh product name "TSKguardcolumn SuperMP (HZ) -H" is used as a guard column in front of it.
GPC measurement conditions using a silica-based column: using Tosoh Corporation trade name "HLC-8320GPC", using THF as an eluent, injecting 50 μL of a sample solution into the apparatus, column oven temperature 40 ° C, THF flow rate A chromatogram is obtained using an RI detector at 0.5 ml / min. As the column, the product names “Zorbax PSM-1000S”, “PSM-300S”, and “PSM-60S” are connected and used, and the product name “DIOL 4.6 × 12.5 mm 5micron” is used as a guard column in the preceding stage. Connect and use.
Calculation method of denaturation ratio: The total peak area of the chromatogram using the polystyrene column is 100, the peak area of the sample is P1, the peak area of the standard polystyrene is P2, and the peak area of the chromatogram of the silica column is The denaturation rate (%) is calculated from the following formula, with the whole being 100, the peak area of the sample being P3, and the peak area of the standard polystyrene being P4.
Denaturation rate (%) = [1- (P2 × P3) / (P1 × P4)] × 100
(However, P1 + P2 = P3 + P4 = 100)

  After the reaction step, a deactivating agent, a neutralizing agent and the like may be added to the copolymer solution, if necessary. Examples of the quenching agent include water; alcohols such as methanol, ethanol, and isopropanol. Examples of the neutralizing agent include carboxylic acids such as stearic acid, oleic acid, versatic acid (a mixture of carboxylic acids having 9 to 11 carbon atoms and 10 mainly), an aqueous solution of an inorganic acid, carbonic acid. Gas etc. are mentioned.

  The modified polymer (A1) is, for example, 2,6-di-tert-butyl-4-hydroxytoluene (BHT), from the viewpoint of preventing gel formation after polymerization and improving the stability during processing. Add an antioxidant such as n-octadecyl-3- (4'-hydroxy-3 ', 5'-di-tert-butylphenol) propinate, 2-methyl-4,6-bis [(octylthio) methyl] phenol. It is preferable.

<Filler>
The rubber composition used for the cap rubber of the present invention contains a filler (B) that reinforces the rubber composition. In the present invention, the filler (B) contains at least carbon black.

(Carbon black)
The carbon black is not particularly limited and can be appropriately selected according to the purpose. The carbon black is preferably, for example, FEF, SRF, HAF, ISAF or SAF grade, and more preferably HAF, ISAF or SAF grade.

  In the present invention, as the filler (B), an inorganic filler may be added in addition to carbon black. Examples of the inorganic filler include metal oxides such as silica, aluminum hydroxide, alumina, and titania. In particular, at least one selected from silica and aluminum hydroxide is preferable.

(silica)
The silica is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Among them, wet silica is preferable.
As such silica, commercially available products such as Tosoh Silica Co., Ltd., trade names "Nipsil AQ" and "Nipsil KQ", manufactured by Evonik, trade name "Ultrasil VN3" can be used. One type of silica may be used alone, or two or more types may be used in combination.
In the rubber composition of the present invention, a silane coupling agent may be added to improve the dispersibility of silica.

(Aluminum hydroxide)
Aluminum hydroxide is not particularly limited, and examples thereof include gibbsite and bayerite. As such aluminum hydroxide, commercially available products such as "Hijilite" manufactured by Showa Denko KK can be used.

  In the present invention, the content of the filler in the rubber composition is 50 parts by mass or more and 130 parts by mass or less with respect to 100 parts by mass of the rubber component (A). If the content of the filler is less than 50 parts by mass, the strength of the rubber after vulcanization will decrease. The content of the filler is preferably 55 parts by mass or more, and more preferably 60 parts by mass or more with respect to 100 parts by mass of the rubber component (A). On the other hand, when the content of the filler exceeds 130 parts by mass, the viscosity of the rubber composition increases and the workability deteriorates. The content of the filler is preferably 125 parts by mass or less, and more preferably 120 parts by mass or less with respect to 100 parts by mass of the rubber component (A).

  In one example of the present invention, as the filler (B), an inorganic filler may be contained in a proportion of 10 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the rubber component (A). The content of the inorganic filler is preferably 15 parts by mass or more, and more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component (A). Further, the content of the inorganic filler is preferably 65 parts by mass or less, and more preferably 60 parts by mass or less, relative to 100 parts by mass of the rubber component (A). By adding the inorganic filler in the above proportion, not only the dry steering stability and the dry grip performance of the tire but also the wet grip performance can be improved.

  In this case, the proportion of silica in the filler (B) is preferably 70% by mass or more. The silica content is more preferably 75% by mass or more, further preferably 80% by mass or more. When the proportion of silica in the filler (B) is 70% by mass or more, the wet grip performance of the tire can be improved. In view of processability, the silica content is preferably 95% by mass or less.

  In another example of the present invention, the proportion of carbon black in the filler (B) may be 70% by mass or more. The proportion of carbon black is more preferably 75% by mass or more, and further preferably 80% by mass or more. With the above ratio, the dry steering stability and dry grip performance of the tire can be further improved.

<Softener>
The rubber composition used for the cap rubber of the present invention contains at least a softening agent having a softening point of 135 ° C. or higher and 155 ° C. as the softening agent (C).
Examples of the softening agent having the softening point include butylphenol acetylene resin, terpene resin, terpene phenol resin, C9 resin and the like. In particular, butylphenol acetylene resin and terpene phenol resin are preferably used.

  The amount of the softening agent having a softening point of 135 ° C. or higher and 155 ° C. is 4 parts by mass or more based on 100 parts by mass of the rubber component (A). If the blending amount is less than 4 parts by mass, the viscosity of the unvulcanized rubber becomes high and the workability and workability deteriorate. The blending amount of the softening agent is preferably 7 parts by mass or more, and more preferably 10 parts by mass or more, relative to 100 parts by mass of the rubber component (A).

  Further, in the present invention, the extender oil contained in the rubber component such as the modified polymer (A1) is also included in the softening agent (C). Further, as the softening agent (C), mineral oil derived from minerals, aromatic oil derived from petroleum, paraffin oil, naphthene oil, palm oil derived from natural products and the like may be included. Among these, from the viewpoint of improving the wet grip performance of the tire, it is preferable to use a mineral-derived softening agent and petroleum-derived process oil.

In many examples of inorganic fillers relative to carbon black as the filler (B), the compounding amount of the softening agent (C) is in the range of 4 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the rubber component (A). Is preferred. By blending the softening agent in an amount of 30 parts by mass or less, it is possible to suppress the decrease in the rigidity of the rubber composition.
In many examples of carbon black with respect to the inorganic filler as the filler (B), the compounding amount of the softening agent (C) is 4 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber component (A). It is preferably in the range of. By blending the softening agent in an amount of 60 parts by mass or less, it is possible to suppress a decrease in the rigidity of the rubber composition.

<Various ingredients>
In the rubber composition of the present invention, in addition to the components described above, for example, various components usually used in the rubber industry such as a vulcanizing agent, a vulcanization accelerator, zinc white, stearic acid, an antioxidant, and a wax. Can be appropriately selected and blended within a range that does not impair the object of the present invention. Commercially available products can be suitably used as these various components.

[Examples 1 to 7, Comparative Examples 1 to 10]
<Base rubber>
Each component is kneaded with a compounding composition shown in Tables 1 and 2 below to prepare a rubber composition for a base rubber. The details of the components in the table will be described later.
The storage elastic moduli of the base rubbers in Tables 1 and 2 are the vulcanized rubbers obtained by vulcanizing each rubber composition at 145 ° C. for 33 minutes, using a spectrometer manufactured by Ueshima Seisakusho at a temperature of 30 ° C. and an initial strain. The values are measured under the conditions of 2%, dynamic strain 1%, and frequency 52 Hz.
(1) Base rubber 1

(2) Base rubber 2

<Cap rubber>
Each component is kneaded with a compounding composition shown in Tables 3 to 5 below to prepare a rubber composition for a cap rubber. The details of the components in the table are as follows.

1. Rubber component (1) Natural rubber (NR)
SIR20
(2) SBR1 (modified polymer (A1))
The synthesis method and physical properties will be described in detail below.
(3) SBR2
Product name "T0150" manufactured by JSR Corporation. Oil extension 34 phr.
(4) SBR3
Product name "HP755B" manufactured by JSR Corporation. Oil extension of 37.5 phr.
(5) SBR4
Product name "T0143" manufactured by JSR Corporation. Oil extension 27.3 phr.
(6) SBR5
Asahi Kasei Corp., trade name "Tuffden 2830". Oil extension of 37.5 phr.
(7) BR
Product name "BR01" manufactured by JSR Corporation

2. Filler (1) Carbon black 1 (CB1)
N550, Cabot's product name "SHOW BLACK N550"
(2) Carbon black 2 (CB2)
N234, Cabot's product name "VULCAN 7H"
(3) Carbon black 3 (CB3)
Asahi Carbon Co., Ltd., product name "Cast 7H"
(4) Silica Tosoh Silica Co., Ltd., trade name "Nipsil AQ"
(5) Aluminum hydroxide manufactured by Showa Denko KK, trade name "Heidilite H-43M"

3. Softening agent In Tables 3 and 4, the total of the blending amount of the extender oil contained in the rubber component and the blending amount of the following softening agent is expressed as "total softening agent amount".
(1) Softener 1
Butylphenol acetylene resin (manufactured by BASF, trade name "KORESIN", softening point 143 ° C)
(2) Softener 2
Terpene phenol resin (Yasuhara Chemical Co., Ltd., YS Polystar S145, softening point 145 ° C)
(3) Softener 3
Kumaron indene resin (Rutgers, trade name "C160", softening point 170 ° C)
(4) Softener 4
C5 resin (manufactured by Zeon Corporation, trade name "QUINTONE A100", softening point 120 ° C)

4. Silane coupling agent Product name "Si69" manufactured by Evonik Industries
5. Stearic acid manufactured by Shin Nippon Rika Co., Ltd., product name "Stearic acid 50S"
6. Wax made by Nippon Seiro Co., Ltd., product name "Ozoace 701"
7. Anti-aging agent (1) PPD
Ouchi Shinko Chemical Industry Co., Ltd., product name "NOXCELLER PPD"
(2) TMDQ
Product name "Nocrac 224" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
8. Zinc Hua Huxui Tech Co., Ltd., product name "No. 3 Zinc Hua"
9. Vulcanization accelerator (1) DPG
Ouchi Shinko Chemical Industry Co., Ltd., product name "NOXCELLER D"
(2) MBTS
Ouchi Shinko Kagaku Kogyo Co., Ltd., product name "NOXCELLER DM-P"
(3) CBS
Ouchi Shinko Chemical Industry Co., Ltd., product name "NOXCELLER CZ-G"
(4) NS
Ouchi Shinko Chemical Industry Co., Ltd., product name "NOXCELLER NS"
10. Sulfur (vulcanizing agent)
Sulfur: Tsurumi Chemical Co., Ltd., trade name "powdered sulfur"

[SBR1 (Method for producing modified polymer (A1)]
The internal volume is 10 L, the internal height (L) to diameter (D) ratio (L / D) is 4.0, the bottom has an inlet, the top has an outlet, and a tank reactor with a stirrer. The tank type pressure vessel having a stirrer and a temperature control jacket was used as a polymerization reactor. The water content was previously removed, and 1,3-butadiene was mixed under the conditions of 17.2 g / min, styrene 10.5 g / min, and n-hexane 145.3 g / min. In a static mixer provided in the middle of a pipe for supplying the mixed solution to the inlet of the reaction group, n-butyllithium for residual impurity inactivation treatment was added and mixed at 0.117 mmol / min, and then mixed at the bottom of the reaction group. It was fed continuously. Further, polymerization in which 2,2-bis (2-oxolanyl) propane is used as a polar substance at a rate of 0.019 g / min and n-butyllithium is used as a polymerization initiator at a rate of 0.242 mmol / min with a stirrer. It was supplied to the bottom of the reactor to continuously continue the polymerization reaction. The temperature was controlled so that the temperature of the polymerization solution at the outlet of the top of the reactor was 75 ° C.

  Next, in the polymer solution flowing out from the outlet of the reactor, 0.0302 mmol / min of tetrakis (3-trimethoxysilylpropyl) -1,3-propanediamine diluted to 2.74 mmol / L as a coupling agent ( The polymer solution to which the coupling agent was added was continuously added at a rate of water containing 5.2 ppm of n-hexane solution), and the polymer solution was mixed by passing through a static mixer to cause a coupling reaction. At this time, the time until the coupling agent was added to the polymerization solution flowing out from the outlet of the reactor was 4.8 minutes and the temperature was 68 ° C., the temperature in the polymerization step and the temperature until the modifier was added. Was 7 ° C. The antioxidant (BHT) was continuously added to the polymer solution subjected to the coupling reaction at 0.055 g / min (n-hexane solution) so that the amount was 0.2 g per 100 g of the polymer, and the coupling reaction was completed. did. At the same time with the antioxidant, 10.0 g of oil (JOMO process NC140 manufactured by JX Nikko Nisseki Energy Co., Ltd.) was continuously added to 100 g of the polymer, and mixed with a static mixer. The solvent was removed by steam stripping to obtain a modified polymer (SBR1).

The physical properties of the obtained SBR1 were measured by the methods described above. The results are summarized below.
An oil content of 8.0 parts by mass is included with respect to 100 parts by mass of the rubber component,
-Weight average molecular weight (Mw) = 85.2 × 10 ⁴ ,
・ Ratio of “specific high molecular weight component” (SBR having a molecular weight of 200 × 10 ⁴ or more and 500 × 10 ⁴ or less) = 4.6%,
• Contraction factor (g ') = 0.59.
In addition, SBR1 has a “branching degree” corresponding to the number of branches assumed from the number of functional groups of the coupling agent and the amount added (which can be confirmed from the value of the contraction factor), and SiOR contained in one molecule of the coupling agent. The "number of SiOR residues" corresponding to a value obtained by subtracting the number of SiORs subtracted by the reaction from the total number of is 4.

<Manufacture of tires>
A tread rubber is produced by combining the prepared rubber composition for base rubber and the rubber composition for cap rubber of Examples and Comparative Examples. Using the obtained tread rubber, a tire is manufactured according to a conventional method. In Tables 3 to 5, the notation "Yes" indicates that the base rubber was used. In Comparative Example 1, neither of the base rubbers 1 and 2 is used.

[Evaluation]
For Examples 1 to 7 and Comparative Examples 1 to 10, the dry grip performance and dry steering stability of the test tires are evaluated by the following methods. Moreover, about Examples 1-5 and Comparative Examples 1-7, the wet grip performance, rolling resistance, and abrasion resistance are evaluated by the following methods.

1. Dry Grip Performance The test tires of the rubber compositions of each Example and Comparative Example were mounted on a test vehicle, and the running performance of the tire during running is shown by the driver's feeling rating in an actual vehicle test on a dry road surface.
The evaluation results are shown in Tables 3-5. In Tables 3 and 4, the tire feeling of Comparative Example 1 is indexed with the feeling score being 100. In Table 5, the tire feeling of Comparative Example 8 is indexed with the feeling score being 100. The larger the index value, the better the dry grip performance.

2. Dry steering stability The test tire is mounted on a test vehicle, and the dry steering stability is shown by the driver's feeling rating in an actual vehicle test on a dry road surface.
The evaluation results are shown in Tables 3-5. In Tables 3 and 4, the tire feeling of Comparative Example 1 is indexed with the feeling score being 100. In Table 5, the tire feeling of Comparative Example 8 is indexed with the feeling score being 100. The larger the index value, the better the dry steering stability.

3. Wet grip performance A vulcanized rubber test piece is cut out from a trial tire. At room temperature, the resistance value is measured by rubbing each test piece on a wet concrete road surface with a British Portable Skid Tester (BPST). In Tables 3 and 4, the value of Comparative Example 1 is set to 100 and displayed as an index. The larger the index value, the larger the resistance value, indicating that the wet grip performance is excellent.

4. Rolling resistance For the vulcanized rubber obtained by vulcanizing each rubber composition at 145 ° C. for 33 minutes, the loss tangent (tan δ) was measured by a Ueshima Seisakusho spectrometer, temperature 40 ° C., initial strain 2%, dynamic strain 1%. , The frequency is 52 Hz. The reciprocal of the rolling resistance of Comparative Example 1 is set to 100 and displayed as an index. The larger the index value, the lower the rolling resistance and the better the fuel economy. The evaluation results are shown in Tables 3 and 4.

5. Abrasion resistance After running 10,000 km on a paved road surface with an actual vehicle using a trial tire, the residual groove is measured and the running distances required for the tread to wear 1 mm are compared. The trial tire of Comparative Example 1 is set to 100 and displayed as an index. The larger the value of the wear resistance index, the better the wear resistance. The evaluation results are shown in Tables 3 and 4.

  In each of the examples, a tire having high dry steering stability and dry grip performance can be obtained. In particular, as shown in Table 4, by using SBR1 (modified polymer (A1)) and by providing a cap rubber using a rubber composition containing a softening agent having a softening point of 135 to 155 ° C., rolling resistance is low, A tire having excellent abrasion resistance can be obtained.

  As a tread rubber, in addition to a base rubber having high rigidity, a cap rubber using a rubber composition containing a specific modified conjugated diene polymer and further containing a softening agent having a softening point of 135 to 155 ° C. It is possible to obtain a tire having high dry grip performance and excellent dry steering stability.

Claims (12)

A tire having a tread rubber,
The tread rubber includes a cap rubber having a grounding surface, and a base rubber provided radially inside the cap rubber,
The storage elastic modulus E ′ of the base rubber at 30 ° C. is 10 MPa or more,
The cap rubber is
A vulcanized rubber of a rubber composition containing a rubber component (A), a filler (B), and a softening agent (C),
The rubber component (A) contains a modified conjugated diene polymer (A1), and the modified conjugated diene polymer (A1) has a weight average molecular weight of 20 × 10 ⁴ or more and 300 × 10 ⁴ or less, The conjugated diene-based polymer (A1) contains a modified conjugated diene-based polymer having a molecular weight of 200 × 10 ⁴ or more and 500 × 10 ⁴ or less in an amount of 0.25% by mass or more and 30% by mass or less, and a contraction factor (g ′). Is less than 0.64, and the extender oil added to the modified conjugated diene polymer (A1) is 10 parts by mass or less based on 100 parts by mass of the modified conjugated diene polymer (A1). Yes,
The content of the filler (B) is 50 parts by mass or more and 130 parts by mass or less with respect to 100 parts by mass of the rubber component (A),
The filler (B) contains at least carbon black,
The tire, wherein the softening agent (C) contains at least 4 parts by mass of a softening agent having a softening point of 135 ° C. or higher and 155 ° C. or lower with respect to 100 parts by mass of the rubber component (A).   The tire according to claim 1, wherein the filler (B) further contains an inorganic filler in a ratio of 10 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the rubber component.   The tire according to claim 2, wherein the inorganic filler is at least one selected from silica and aluminum hydroxide.   The tire according to claim 3, wherein the proportion of the silica in the filler (B) is 70% by mass or more.   The tire according to any one of claims 1 to 4, wherein a total amount of the softening agent (C) with respect to 100 parts by mass of the rubber component (A) is 4 parts by mass or more and 30 parts by mass or less.   The tire according to any one of claims 1 to 3, wherein a proportion of the carbon black in the filler (B) is 70% by mass or more.   The tire according to any one of claims 1 to 3, wherein a total amount of the softening agent (C) is 4 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber component (A). The modified conjugated diene-based polymer (A1) has one or more coupling residues and a conjugated diene-based polymer chain bonded to the coupling residues,
The tire according to any one of claims 1 to 7, which comprises a branch in which five or more conjugated diene-based polymer chains are bonded to one coupling residue. The modified conjugated diene polymer (A1) has the following general formula (I):

[In the formula, D represents a conjugated diene-based polymer chain, R ¹ , R ² and R ³ each independently represent a single bond or an alkylene group having 1 to 20 carbon atoms, and R ⁴ and R ⁷ are , Each independently represents 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, and R ⁶ and R ¹⁰ Each independently represents 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 an integer of 1 to 3. , X ≦ m, p is 1 or 2, y is an integer of 1 to 3, y ≦ (p + 1), z is an integer of 1 or 2, and each of them is plural. ^D in the case ^{of, R 1 ~R 11, m,} p, x, y, and z are each independently i represents an integer of 0 to 6, j represents an integer of 0 to 6, k represents an integer of 0 to 6, (i + j + k) is an integer of 3 to 10, and ((x × i) + (y × j) + (z × k)) is an integer of 5 to 30, and A is a hydrocarbon group having 1 to 20 carbon atoms, or an oxygen atom, a nitrogen atom, a silicon atom, It has at least 1 sort (s) of atom selected from the group consisting of a sulfur atom and a phosphorus atom, and represents an organic group having no active hydrogen]. Tires listed. In the general formula (I), A is the following general formula (II):

[In the formula, B ¹ 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 ¹ , they are each independently],
The following general formula (III):

[In the formula, 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 an integer of 1 to 10, respectively. B ² and B ³ when a plurality of them are present are independent of each other],
The following general formula (IV):

[In the formula, 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 B ⁴ when there are a plurality of B ⁴ are each independently],
The following general formula (V):

[In the formula, 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 , they are each independently]. The tire according to claim 9, which is represented by any one. The modified conjugated diene-based polymer (A1) is a conjugated diene-based polymer represented by the following general formula (VI):

^Wherein, R ^{12, R 13} and ^{R 14} is independently a single bond or an alkylene group having a carbon number of ^{1~20, R 15, R 16,} R 17, R 18 and ^{R 20} are each independently And 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 is an alkyl group having 1 to 20 carbon atoms or a trialkyl group. Represents an alkylsilyl group, m represents an integer of 1 to 3, p represents 1 or 2, and when R ^{12 to} R ²² , m and p are present in plural, they are each independent, 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 hydrocarbon group having 1 to 20 carbon atoms or an oxygen atom. , A nitrogen atom, a silicon atom, a sulfur atom and a phosphorus atom, It shows the organic group which has at least 1 type of atom selected from, and does not have active hydrogen.], The coupling agent represented by any one of Claims 1-10. tire.   The coupling agent represented by the general formula (VI) is tetrakis [3- (2,2-dimethoxy-1-aza-2-silacyclopentane) propyl] -1,3-propanediamine, tetrakis (3-). The compound according to claim 11, which is at least one selected from the group consisting of trimethoxysilylpropyl) -1,3-propanediamine and tetrakis (3-trimethoxysilylpropyl) -1,3-bisaminomethylcyclohexane. tire.