阅读说明：本技术 橡胶组合物、胎面橡胶和轮胎 (Rubber composition, tread rubber, and tire ) 是由 中谷健二 熊木健太郎 于 2019-10-04 设计创作，主要内容包括：本发明提供一种橡胶组合物,其已经在高水平实现了湿路面性能、耐磨耗性、低滚动阻力和耐断裂性之间的良好平衡。一种橡胶组合物,其包含填料和包含至少三种聚合物的橡胶组分,并且将其配置为使得：所述橡胶组分分离为至少两个聚合物相,即具有最高tanδ峰温度的聚合物相(1)和具有最低峰温度的聚合物相(2)；所述聚合物相(1)和所述聚合物相(2)彼此不相容；所述聚合物相(1)至少包含改性共轭二烯系聚合物(A1)和(A2)、和填料；改性共轭二烯系聚合物(A1)具有特定的重均分子量和特定的收缩因子(g’)；并且如果X为聚合物相(1)的填料浓度并且Y为聚合物相(1)的填料的平均聚集体面积,则X和Y满足式(1)：Y<4.8X+1200。(The present invention provides a rubber composition which has achieved a good balance among wet performance, wear resistance, low rolling resistance and fracture resistance at a high level. A rubber composition comprising a filler and a rubber component comprising at least three polymers, and configured such that: the rubber component separates into at least two polymer phases, namely a polymer phase (1) having the highest tan delta peak temperature and a polymer phase (2) having the lowest peak temperature; the polymer phase (1) and the polymer phase (2) are incompatible with each other; the polymer phase (1) contains at least modified conjugated diene polymers (a1) and (a2), and a filler; the modified conjugated diene polymer (A1) has a specific weight average molecular weight and a specific shrinkage factor (g'); and if X is the filler concentration of the polymer phase (1) and Y is the average aggregate area of the fillers of the polymer phase (1), then X and Y satisfy formula (1): y <4.8X + 1200.)

1. A rubber composition comprising a rubber component and a filler, wherein:

the rubber component includes at least a modified conjugated diene polymer (a1), a modified conjugated diene polymer (a2), and a third polymer that are different from each other;

the modified conjugated diene polymer (A1) has a weight-average molecular weight of 20X 10⁴～300×10⁴0.25 to 30 mass% of a polymer having a molecular weight of 200X 10 based on the total amount of the modified conjugated diene polymer (A1)⁴～500×10⁴The modified conjugated diene-based polymer of (1), and having a shrinkage factor (g') of less than 0.64;

the rubber component separates into at least two polymer phases: a polymer phase (1) having the highest peak temperature of tan delta temperature dispersion curve; and a polymer phase (2) having the lowest peak temperature;

the polymer phase (1) and the polymer phase (2) are incompatible with each other;

the polymer phase (1) includes at least the modified conjugated diene polymer (a1), the modified conjugated diene polymer (a2), and the filler; and is

When the concentration (%) of the filler in the polymer phase (1) is defined as X and the concentration (%) of the filler in the polymer phase (1) is defined as XAverage aggregate area (nm) of filler²) When defined as Y, X and Y satisfy the following formula (1):

Y<4.8X+1200 (1)。

2. the rubber composition according to claim 1, wherein the modified conjugated diene polymer (A1) and the modified conjugated diene polymer (A2) are each a modified styrene butadiene rubber.

3. The rubber composition according to claim 1 or 2, wherein the polymer phase (2) comprises a natural rubber, a synthetic isoprene rubber, or a butadiene rubber having a cis-1, 4 content of 90 mass% or more.

4. The rubber composition according to any one of claims 1 to 3, wherein X in the above formula (1) is more than 100.

5. The rubber composition according to any one of claims 1 to 4, wherein the difference between the glass transition temperatures (Tg) of the modified conjugated diene polymer (A1) and the modified conjugated diene polymer (A2) is 20 ℃ or more.

6. The rubber composition according to any one of claims 1 to 5, wherein the total amount of the modified conjugated diene polymer (A1) and the modified conjugated diene polymer (A2) is 50 parts by mass or more with respect to 100 parts by mass of the rubber component.

7. A tread rubber using the rubber composition according to any one of claims 1 to 6.

8. A tire using the rubber composition according to any one of claims 1 to 6.

Technical Field

The present disclosure relates to a rubber composition, a tread rubber, and a tire.

Background

Conventionally, inorganic fillers such as silica have been used to improve grip performance on wet road (hereinafter referred to as "wet performance"). However, such fillers also increase energy loss, making it difficult to reduce rolling resistance.

Further, in addition to wear resistance against abrasion with time due to driving, the tire is required to have fracture resistance against chipping or other damage of the tire rubber when driving on a rough road or the like.

For example, in order to provide a rubber composition for a tire tread, which is suitable for the production of a tire having an excellent balance between wet grip performance and low rolling resistance performance without impairing wear resistance of the tire, patent document 1 proposes a rubber composition for a tire tread, wherein the rubber composition comprises at least two kinds of diene rubbers as a rubber component, in which a tan δ temperature dispersion curve is bimodal, and a tan δ peak temperature on a high temperature side is in a range of-10 ℃ to-50 ℃, and a tan δ peak temperature on a low temperature side is lower than a peak temperature on a high temperature side by 10 ℃ or more; further comprising at least one reinforcing filler in a total amount of 30 to 90 parts by weight per 100 parts by weight of the rubber component; and in the above compound, the content of the high Tg rubber component [ compounding ratio of the high Tg rubber component ] in the binding rubber thereof is × 0.7 or less. However, in this case, it is not easy to achieve both low rolling resistance and wear resistance.

Reference list

Patent document

PTL 1: japanese patent laid-open No.8-27313

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present disclosure is to provide a rubber composition in which wet performance, wear resistance, low rolling resistance, and fracture resistance are highly balanced. Further, another object of the present disclosure is to provide a tread rubber and a tire in which wet performance, wear resistance, low rolling resistance, and fracture resistance are highly balanced.

Means for solving the problems

The rubber composition according to the present disclosure is a rubber composition comprising a rubber component and a filler, wherein:

the rubber component includes at least a modified conjugated diene polymer (a1), a modified conjugated diene polymer (a2), and a third polymer;

the modified conjugated diene polymer (A1) has a weight-average molecular weight of 20X 10⁴～300×10⁴0.25 to 30 mass% of a polymer having a molecular weight of 200X 10 based on the total amount of the modified conjugated diene polymer (A1)⁴～500×10⁴The modified conjugated diene-based polymer of (1), and having a shrinkage factor (g') of less than 0.64;

the rubber component separates into at least two polymer phases: a polymer phase (1) having the highest peak temperature of tan delta temperature dispersion curve; and a polymer phase (2) having the lowest peak temperature;

the polymer phase (1) and the polymer phase (2) are incompatible with each other;

the polymer phase (1) includes at least the modified conjugated diene polymer (a1), the modified conjugated diene polymer (a2), and the filler; and is

When the concentration of the filler in the polymer phase (1) is (are) reduced%) is defined as X and the average aggregate area (nm) of the filler in the polymer phase (1)²) When defined as Y, X and Y satisfy the following formula (1):

Y<4.8X+1200 (1)。

as a result, the wet performance, wear resistance, low rolling resistance, and fracture resistance can be highly balanced.

The tread rubber according to the present disclosure is a tread rubber using the above rubber composition.

As a result, the wet performance, wear resistance, low rolling resistance, and fracture resistance of the tread rubber can be highly balanced.

The tire according to the present disclosure is a tire using the above rubber composition.

As a result, the wet performance, wear resistance, low rolling resistance, and fracture resistance of the tire can be highly balanced.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present disclosure, a rubber composition in which wet performance, wear resistance, low rolling resistance, and fracture resistance are highly balanced can be provided. According to the present disclosure, it is possible to provide a tread rubber and a tire in which wet performance, wear resistance, low rolling resistance, and fracture resistance are highly balanced.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described. The description of these embodiments is intended to be illustrative of the disclosure and is not intended to limit the disclosure in any way.

In the following description, the modified conjugated diene-based polymer (a1) and the modified conjugated diene-based polymer (a2) may be represented as a component (a1) and a component (a2), respectively.

In this specification, unless otherwise indicated, numerical ranges are intended to include the lower and upper limits of those ranges. For example, 0.25 to 30 mass% means 0.25 mass% or more and 30 mass% or less.

(rubber composition)

The rubber composition according to the present disclosure includes a rubber composition including a rubber component and a filler, wherein:

the rubber component includes at least a modified conjugated diene polymer (a1), a modified conjugated diene polymer (a2), and a third polymer that are different from each other;

the weight-average molecular weight of the modified conjugated diene polymer (A1) was 20X 10⁴～300×10⁴0.25 to 30 mass% of a polymer having a molecular weight of 200X 10 based on the total amount of the modified conjugated diene polymer (A1)⁴～500×10⁴The modified conjugated diene-based polymer of (1), and having a shrinkage factor (g') of less than 0.64;

the rubber component separates into at least two polymer phases: a polymer phase (1) having the highest peak temperature of tan delta temperature dispersion curve; and a polymer phase (2) having the lowest peak temperature;

the polymer phase (1) and the polymer phase (2) are incompatible with each other;

the polymer phase (1) includes at least a modified conjugated diene polymer (a1), a modified conjugated diene polymer (a2), and a filler; and is

When the concentration (%) of the filler in the polymer phase (1) is defined as X and the average aggregate area (nm) of the filler in the polymer phase (1) is defined as²) When defined as Y, X and Y satisfy the following formula (1):

Y<4.8X+1200 (1)。

as a result, the wet performance, wear resistance, low rolling resistance, and fracture resistance can be highly balanced.

Polymer phase

The rubber component separates into at least two polymer phases: a polymer phase (1) having the highest peak temperature of tan delta temperature dispersion curve; and a polymer phase (2) having the lowest peak temperature, and the polymer phase (1) and the polymer phase (2) are incompatible with each other. Further, the polymer phase (1) includes at least the modified conjugated diene polymer (a1), the modified conjugated diene polymer (a2), and a filler. In addition, when the concentration (%) of the filler in the polymer phase (1) is defined as X and the average aggregate area (nm) of the filler in the polymer phase (1) is defined as²) When defined as Y, X and Y satisfy the following formula (1):

Y<4.8X+1200 (1)。

that is, in formula (1), when X and Y are described in the above units, Y is smaller than 4.8X +1200 on the right side. When this formula (1) is satisfied, the filler in the rubber composition is more distributed in the polymer phase (1), and the filler is more highly dispersed in the polymer phase (1). Therefore, the wet performance, wear resistance, low rolling resistance, and fracture resistance can be highly balanced.

When the rubber component includes only three types: when component (a1), component (a2), and the third polymer are used, as described above, polymer phase (1) includes component (a1), component (a2), and a filler, and polymer phase (2) includes the third polymer. In this case, the polymer phase (2) may or may not include a filler.

In the present disclosure, the tan δ temperature dispersion curve of the polymer phase was obtained by measurement under the condition of strain of 1% and frequency of 52Hz using a viscoelastic spectrometer manufactured by Toyo Seiki co.

In the present disclosure, the presence of polymer phase (1) and polymer phase (2) and the fact that these polymer phases are incompatible are confirmed using FIB-SEM. Specifically, a 4 μm × 4 μm area of the rubber composition was observed using FIB-SEM, and when there was a difference in the dyed state, it was defined that the polymer phase (1) and the polymer phase (2) were present, and these polymer phases were incompatible. In this case, they may be compatible by visual inspection.

In the present disclosure, the concentration of the filler in the polymer phase (1) is determined by the following steps 1 to 4.

Step 1: the amount (parts by mass) of the polymer present in the polymer phase (1) is determined. For example, when the rubber component includes three types: component (a1), component (a2), and the third polymer, the polymers present in polymer phase (1) include only two: component (a1) and component (a 2). Therefore, in this case, the total part by mass of the component (a1) and the component (a2) compounded into the rubber composition is the amount (part by mass) of the polymer present in the polymer phase (1).

And a step 2: the proportion (partition rate) of filler distributed (present) in the polymer phase (1) is determined. How to determine the distribution ratio of the filler will be mentioned later.

Step 3: the amount of filler included in the rubber composition is multiplied by the partition rate of the filler in the polymer phase (1). This value is the amount (parts by mass) of the filler distributed in the polymer phase (1).

And step 4: the amount (parts by mass) of the filler distributed determined in step 3 is divided by the amount (parts by mass) of the polymer in the polymer phase (1) determined in step 1, and then multiplied by 100. This value is the concentration (%) of filler in the polymer phase (1).

In the above-mentioned step 2, the distribution ratio (%) of the filler distributed in the polymer phase (1) is determined as a ratio of the area of the filler included in the polymer phase (1) to the total area of the fillers included in the entire polymer phase of the rubber composition. Specifically, it was determined by the following procedures 2-1 to 2-4.

Step 2-1: the smooth surface of a sample of the rubber composition cut by a microtome was measured using AFM in a measurement range of 2. mu. m.times.2. mu.m. The obtained AFM image is converted into multivalued images of the respective polymer phases and fillers by the histogram (for example, a ternary image in the case of the polymer phases (1) and (2)).

Step 2-2: based on the multivalued image, the area of the filler included in each polymer phase is determined.

Step 2-3: the sum of these filler areas is defined as the total area of filler included in the total polymer phase.

Step 2-4: the proportion (%) of the area of the filler included in the polymer phase (1) relative to the total area of the above fillers is defined as the partition rate (%) of the filler present in the polymer phase (1).

When the filler is at the interface between the polymer phases, the two points where three corresponding polymer phases are in contact with the filler are connected and the area of the filler is divided.

In the present disclosure, the average aggregate area of the filler in the polymer phase (1) is calculated by: the aggregate area of the filler portion in the polymer phase (1) was determined from an image obtained by FIB-SEM in a measurement range of 4 μm × 4 μm, and then the average aggregate area of the filler portion was calculated in number average (arithmetic average) from the entire surface area of the filler portion and the number of aggregates. In the calculation, particles in contact with the edge (side) of the image are not counted, and particles having a size of 20 pixels or less are considered as noise and are not counted.

In formula (1), X is not particularly limited as long as formula (1) is satisfied, and is, for example, 30 or more, 50 or more, 100 or more, 150 or more, or 200 or more. X is, for example, 350 or less, 300 or less, 250 or less, or 200 or less. The larger X, the higher the concentration of filler in the polymer phase (1) and the further improvement in wet road properties. When X is less than 50, the effect of the present disclosure is small, and therefore, X is preferably 50 or more.

In the rubber composition according to the present disclosure, it is preferable that X in the above formula (1) should be more than 100.

As a result, a further improved balance between low rolling resistance and wet performance can be achieved.

In formula (1), Y is not particularly limited as long as formula (1) is satisfied, and is, for example, 2000 or less, 1950 or less, 1750 or less, or 1600 or less. Y is, for example, 1000 or more, 1200 or more, 1300 or more, 1400 or more, 1500 or more, or 1600 or more. The smaller Y, the smaller the average aggregate area of the filler in the polymer phase (1), the more highly dispersed the filler in the polymer phase (1), and the further improvement in low rolling resistance.

< rubber component >

The rubber composition according to the present disclosure includes at least the modified conjugated diene polymer (a1), the modified conjugated diene polymer (a2), and the third polymer, which are different from each other, as rubber components.

Both the component (a1) and the component (a2) are polymers obtained by modifying a conjugated diene-based polymer.

The conjugated diene polymer is a polymer of one conjugated diene compound or a copolymer of two or more conjugated diene compounds. Alternatively, the conjugated diene polymer may be a copolymer of a conjugated diene compound and an aromatic vinyl compound.

Examples of the conjugated diene compound include, for example, compounds having 4 to 12 carbon atoms, such as 1, 3-butadiene, isoprene, 1, 3-pentadiene, 2, 3-dimethyl-1, 3-butadiene, 2-phenyl-1, 3-butadiene, 3-methyl-1, 3-pentadiene, 1, 3-hexadiene, and 1, 3-heptadiene. As the conjugated diene compound, 1, 3-butadiene and isoprene are preferable from the viewpoint of easiness of industrial applicability.

Examples of the aromatic vinyl compound include, for example, styrene, p-methylstyrene, α -methylstyrene, vinylxylenes, vinylnaphthalenes, diphenylethylenes, 1-vinylnaphthalenes, 3-vinyltoluenes, ethylvinylbenzenes, divinylbenzene, 4-cyclohexylstyrene, and 2,4, 6-trimethylstyrene. These aromatic vinyl compounds may be used alone or in combination of two or more. As the aromatic vinyl compound, styrene is preferable from the viewpoint of easiness of industrial applicability.

Examples of the conjugated diene-based polymer include, for example, Natural Rubber (NR), polybutadiene (BR), synthetic polyisoprene (IR), styrene butadiene copolymer (SBR), isoprene butadiene copolymer, ethylene butadiene copolymer, and propylene butadiene copolymer.

Modified conjugated diene Polymer (A1)

The weight-average molecular weight of the modified conjugated diene polymer (A1) was 20X 10⁴～300×10⁴0.25 to 30 mass% of a polymer having a molecular weight of 200X 10 based on the total amount of the modified conjugated diene polymer (A1)⁴～500×10⁴And has a shrinkage factor (g') of less than 0.64.

The weight average molecular weight (Mw) of the component (A1) was 20X 10⁴～300×10⁴. The Mw is preferably 50X 10⁴Above, 64 × 10⁴Above, or 80X 10⁴The above. Further, the Mw is preferably 250X 10⁴Hereinafter, 180X 10⁴Below, or 150 × 10⁴The following. When Mw is 20X 10⁴In the above case, low rolling resistance and wet performance of the tire can be highly achieved at the same time. When Mw is 300X 10⁴The processability of the rubber composition is improved as follows.

For theThe conjugated diene-based polymer and the component (a1), the number average molecular weight, the weight average molecular weight, the molecular weight distribution, and the content of the specific high molecular weight component mentioned later were measured as follows. The chromatogram was measured using a GPC (gel permeation chromatography) measuring apparatus (trade name "HLC-8320 GPC" manufactured by Tosoh Corporation) equipped with three connected columns filled with a polystyrene-based gel and an RI detector (trade name "HLC-8020" manufactured by Tosoh Corporation) using a conjugated diene-based polymer or a modified conjugated diene-based polymer as a sample. Based on a calibration curve obtained by using a standard polystyrene, determined are a weight average molecular weight (Mw), a number average molecular weight (Mn), a molecular weight distribution (Mw/Mn), a peak molecular weight (Mp) of the modified conjugated diene-based polymer₁) Peak molecular weight (Mp) of conjugated diene polymer₂) The ratio (Mp) between them₁/Mp₂) And a molecular weight of 200X 10⁴～500×10⁴The modified conjugated diene polymer of (3). As an eluent, 5mmol/L triethylamine in THF (tetrahydrofuran) was used. As the column, three of "TSKgel supperoporehz-H" (trade name) manufactured by Tosoh Corporation were connected, and "TSKguardcolumn SuperMP (HZ) -H" (trade name) manufactured by Tosoh Corporation was connected to the former stage thereof as a protective column and used. 10 mg of the sample for measurement was dissolved in 10mL of THF to prepare a measurement solution, and 10. mu.L of the measurement solution was injected into a GPC measurement apparatus and measured under conditions of an oven temperature of 40 ℃ and a THF flow rate of 0.35 mL/min.

Peak molecular weight (Mp) was determined as follows₁And Mp₂). In the GPC curve obtained by the measurement, the peak detected as the component having the highest molecular weight is selected. For the selected peak, the molecular weight corresponding to the maximum of the peak is calculated and defined as the peak molecular weight.

The modified conjugated diene polymer (A1) contains 0.25 to 30 mass% of a polymer having a molecular weight of 200 × 10 with respect to the total amount (100 mass%) of the modified conjugated diene polymer (A1)⁴～500×10⁴The modified conjugated diene polymer (in the present specification, this may also be referred to as "a specific high molecular weight component"). When the content of the specific high-molecular weight component is within this range, low rolling resistance and wet performance of the tire can be highly achieved at the same time.

Further, the molecular weight was 200X 10⁴～500×10⁴The modified conjugated diene polymer (D) is obtained by modifying a polymer having a molecular weight of 500X 10 in the whole integral molecular weight distribution curve⁴Less than 200X 10 of molecular weight⁴The ratio of the active component to the active component.

In one example, component (a1) includes 1.0 mass% or more, 1.4 mass% or more, 1.75 mass% or more, 2.0 mass% or more, 2.15 mass% or more, or 2.5 mass% or more of a specific high molecular weight component. In one example, component (a1) includes 28% by mass or less, 25% by mass or less, 20% by mass or less, or 18% by mass or less of a specific high molecular weight component.

In the present specification, "molecular weight" refers to a molecular weight in terms of standard polystyrene obtained by GPC. In order to obtain the component (a1) in which the content of the specific high-molecular weight component is within this range, it is preferable to control the polymerization step and the reaction conditions in the reaction step, which will be mentioned later. For example, in the polymerization step, the amount of the organic monolithium compound used as a polymerization initiator may be adjusted, which will be mentioned later. Further, in the polymerization step, the method having the residence time distribution can be used for both the continuous and batch polymerization modes, that is, the time distribution of the growth reaction can be widened.

In one example, component (A1) has a molecular weight distribution (Mw/Mn) of 1.6 to 3.0.

The modified conjugated diene polymer (A1) has a shrinkage factor (g') of less than 0.64. In general, a polymer having a branched chain tends to have a smaller molecular size when compared with a linear polymer having the same absolute molecular weight, and the above-mentioned shrinkage factor (g') is an index of the ratio of the size occupied by the molecule when compared with a hypothetical linear polymer having the same absolute molecular weight. That is, as the degree of branching of the polymer increases, the shrinkage factor (g') tends to become smaller. In the present embodiment, the intrinsic viscosity is used as an index of the molecular sizeAssuming that the linear polymer follows the following relationship: intrinsic viscosity [ eta ]]＝-3.883M^0.771. The shrinkage factor (g') of the modified conjugated diene polymer of each absolute molecular weight was calculated, and the absolute molecular weight was adjusted to 100X 10⁴～200×10⁴The average value of the shrinkage factor (g ') at the time of curing is defined as the shrinkage factor (g') of the modified conjugated diene polymer. Here, a "branch" is formed by bonding other polymers directly or indirectly to one polymer. In addition, "degree of branching" refers to the number of polymers bonded to each other directly or indirectly for one branch. For example, when five conjugated diene-based polymer chains (to be mentioned later) are bonded to each other by linkage via a coupling residue (to be mentioned later), the branching degree is 5. Note that the coupling residue is a constituent unit of the modified conjugated diene-based polymer bonded to the conjugated diene-based polymer chain, and is, for example, a constituent unit derived from a coupling agent generated by a reaction between the conjugated diene-based polymer and the coupling agent, which will be mentioned later. Further, the conjugated diene-based polymer chain is a constituent unit of the modified conjugated diene-based polymer, and is, for example, a constituent unit of a conjugated diene-based polymer produced from a reaction between the conjugated diene-based polymer and a coupling agent, which will be mentioned later.

The shrinkage factor (g') is, for example, 0.63 or less, 0.60 or less, 0.59 or less, or 0.57 or less. Furthermore, the lower limit of the shrinkage factor (g') is not limited and may be at or below the detection limit. For example, it is 0.30 or more, 0.33 or more, 0.35 or more, 0.45 or more, 0.57 or more, or 0.59 or more. By using the component (A1) wherein the shrinkage factor (g') is within this range, the processability of the rubber composition is improved.

Since the shrinkage factor (g ') tends to depend on the degree of branching, for example, the degree of branching can be used as an index for controlling the shrinkage factor (g'). Specifically, when the degree of branching of the modified conjugated diene-based polymer is 6, the shrinkage factor (g ') thereof tends to be 0.59 to 0.63, and when the degree of branching of the modified conjugated diene-based polymer is 8, the shrinkage factor (g') thereof tends to be 0.45 to 0.59.

The measurement method of the shrinkage factor (g') is as follows. Modifying the conjugated diene polymerUsed as a sample and measured using a GPC measuring apparatus (trade name "GPCmax VE-2001" manufactured by Malvern Panalytical ltd.) equipped with three connected columns filled with polystyrene-based gel and using three detectors connected in order of a light scattering detector, an RI detector, and a viscosity detector (trade name "TDA 305" manufactured by Malvern Panalytical ltd.). Based on standard polystyrene, the absolute molecular weight is determined from the results of the light scattering detector and the RI detector, and the intrinsic viscosity is determined from the results of the RI detector and the viscosity detector. Linear polymers were used, provided they follow the following formula: intrinsic viscosity [ eta ]]＝-3.883M^0.771And the shrinkage factor (g') is calculated as a ratio of intrinsic viscosities corresponding to the respective molecular weights. As eluent, 5mmol/L triethylamine in THF was used. As the column, "TSKgel G4000 HXL", "TSKgel G5000 HXL", and "TSKgel G6000 HXL" (all trade names) manufactured by Tosoh Corporation were linked and used. 20 mg of the sample for measurement was dissolved in 10mL of THF to prepare a measurement solution, and 100. mu.L of the measurement solution was injected into a GPC measurement apparatus and measured under conditions of an oven temperature of 40 ℃ and a THF flow rate of 1 mL/min.

The amount of the extender oil added to component (A1) can be suitably adjusted, and is, for example, 1 to 40 parts by mass, 1 to 35 parts by mass, or 1 to 10 parts by mass with respect to 100 parts by mass of component (A1). In another example, the amount of the extender oil added to component (a1) is more than 0 part by mass and 10 parts by mass or less with respect to 100 parts by mass of component (a 1).

Examples of the extender oil include, for example, aromatic oil, naphthenic oil, paraffinic oil, and aromatic-substituted oil. Among the above, aromatic substituted oils having a polycyclic aromatic (PCA) component of 3 mass% or less according to the IP346 method are preferable from the viewpoint of environmental safety and prevention of oil bleeding and wet braking performance. Examples of fragrance alternative oils include RAE (residual Aromatic extracts) in addition to TDAE (treated dispersed Aromatic extracts) and MES (Mill Extraction solvents) described in Kautschuk Gummi Kunststoffe,52(12),799 (1999).

Component (a1) may be an oil-extended polymer with added extender oil, and may be either non-oil-extended or oil-extended.

Preferably, component (a1) should have branches and a degree of branching of 5 or more. Further, it is more preferable that the component (a1) should have one or more coupling residues and conjugated diene-based polymer chains bonded to such coupling residues, and further, the above-mentioned branched chain should include a branched chain in which five or more such conjugated diene-based polymer chains are bonded to one such coupling residue. By specifying the structure of the modified conjugated diene polymer so that the degree of branching is 5 or more and the branches include those in which five or more conjugated diene polymer chains are bonded to one coupling residue, the shrinkage factor (g') can be made less than 0.64 more reliably. Note that the number of conjugated diene-based polymer chains bonded to one coupling residue can be confirmed from the value of the shrinkage factor (g').

Further, it is more preferable that the component (a1) should have branches and a branching degree of 6 or more. In addition, it is still more preferable that the component (a1) should have one or more coupling residues and conjugated diene-based polymer chains bonded to such coupling residues, and further, the above-mentioned branched chain should include a branched chain in which six or more such conjugated diene-based polymer chains are bonded to one such coupling residue. The shrinkage factor (g') can be made 0.63 or less by defining the structure of the modified conjugated diene polymer so that the degree of branching is 6 or more and the branches include branches in which six or more conjugated diene polymer chains are bonded to one coupling residue.

Further, it is still more preferable that component (a1) should have branches and a branching degree of 7 or more, and it is even more preferable that the branching degree should be 8 or more. Although the upper limit of the degree of branching is not particularly limited, it is preferably 18 or less. In addition, it is even more preferable that the component (a1) should have one or more coupling residues and conjugated diene-based polymer chains to such coupling residues, and further, the above-mentioned branches should include branches in which seven or more such conjugated diene-based polymer chains are bonded to one such coupling residue, and it is even more preferable that the above-mentioned branches should include branches in which eight or more such conjugated diene-based polymer chains are bonded to one such coupling residue. The shrinkage factor (g') can be made 0.59 or less by specifying the structure of the modified conjugated diene polymer so that the degree of branching is 8 or more and the branches include a branch in which eight or more conjugated diene polymer chains are bonded to one coupling residue.

Preferably, the modified conjugated diene polymer (a1) should be represented by the following general formula (I):

[ formula 1]

[ in the general formula (I), D represents a conjugated diene polymer chain; r¹、R²And R³Each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms; r⁴And R⁷Each independently represents an alkyl group having 1 to 20 carbon atoms; r⁵、R⁸And R⁹Each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; r⁶And R¹⁰Each independently represents an alkylene group having 1 to 20 carbon atoms; r¹¹Represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; m and x each independently represent an integer of 1 to 3, and x is not more than m; p represents 1 or 2, y represents an integer of 1-3, and y is less than or equal to (p + 1); z represents 1 or 2; when D, R¹～R¹¹M, p, x, y and z are independent of each other when they are present in plural; i represents an integer of 0 to 6, j represents an integer of 0 to 6, k represents an integer of 0 to 6, and (i + j + k) is an integer of 3 to 10; (x × i) + (y × j) + (z × k)) is an integer of 5 to 30; and A represents a hydrocarbon group having 1 to 20 carbon atoms or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom and a phosphorus atom and having no active hydrogen.]。

As a result, the wet performance, wear resistance, low rolling resistance, and fracture resistance can be more highly balanced.

In one example, in the general formula (I), the conjugated diene-based polymer represented by DThe weight average molecular weight of the chain was 10X 10⁴～100×10⁴. The conjugated diene polymer chain is a constituent unit of the modified conjugated diene polymer, and is, for example, a constituent unit derived from a conjugated diene polymer generated by a reaction between the conjugated diene polymer and a coupling agent.

In the general formula (I), the hydrocarbon group represented by A encompasses saturated, unsaturated, aliphatic and aromatic hydrocarbon groups. Examples of the above organic group having no active hydrogen include, for example, organic groups having no functional group having active hydrogen, such as hydroxyl group (-OH), secondary amino group(s) ((s))>NH), primary amino group (-NH)₂) And mercapto (-SH).

In the general formula (I), it is preferable that a should be represented by any one of the following general formulae (II) to (V): [ formula 2]

[ in the general formula (II), B¹Represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms; a represents an integer of 1 to 10; and when B¹When present in plural, they are independent of each other;

in the general formula (III), B²Represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms; b is³Represents an alkyl group having 1 to 20 carbon atoms; a represents an integer of 1 to 10; and when B²And B³When each is present in plural, they are independent of each other;

in the general formula (IV), B⁴Represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms; a represents an integer of 1 to 10; and when B⁴When present in plural, they are independent of each other; and is

In the general formula (V), B⁵Represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms; a represents an integer of 1 to 10; and when B⁵When plural are present, they are independent of each other.]。

As a result, the wet performance, wear resistance, low rolling resistance, and fracture resistance can be more highly balanced.

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

For B in the formulae (II) to (V)¹、B²、B⁴And B⁵Examples of the hydrocarbon group having 1 to 20 carbon atoms include alkylene groups having 1 to 20 carbon atoms.

Preferably, component (a1) should have nitrogen atoms and silicon atoms. In this case, processability of the rubber composition becomes good, and when applied to a tire, low rolling resistance can be further improved while wet braking performance and wear resistance of the tire are improved. Note that, as to whether or not the component (a1) has a nitrogen atom, by a measurement method of a modification ratio which will be described later, when the calculated modification ratio is 10% or more, it is determined that the component (a1) has a nitrogen atom.

Whether or not component (a1) has a silicon atom is determined by the following method. 0.5g of the modified conjugated diene-based polymer was used as a sample and measured using an ultraviolet-visible spectrophotometer (trade name "UV-1800" manufactured by Shimadzu Corporation) in accordance with JIS K010144.3.1, and silicon atoms were quantified by molybdenum blue absorption spectrophotometry. As a result, when silicon atoms were determined (lower detection limit: 10 mass ppm), it was determined that the sample had silicon atoms.

In one example, at least one terminal of each conjugated diene-based polymer chain is bonded to a silicon atom which the coupling residue has. In this case, the ends of the plurality of conjugated diene 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 may be bonded to one silicon atom, resulting in one silicon atom constituting an alkoxysilyl group or silanol group having 1 to 20 carbon atoms.

The conjugated diene polymer or the conjugated diene contained in the component (A1) is, for example, 40 to 100 mass% or 55 to 80 mass%. When the conjugated diene content is within the above range, the rubber composition can more highly balance wet performance, wear resistance, low rolling resistance and fracture resistance when applied to a tire.

The content of the conjugated diene polymer or the conjugated aromatic vinyl group in the component (a1) is, for example, 0 mass% or more, 20 mass% or more, or 35 mass% or more. The content of the bound aromatic vinyl group in the conjugated diene polymer or the component (a1) is, for example, 60 mass% or less or 45 mass% or less. When the bound aromatic vinyl content is within the above range, the wet performance, wear resistance, low rolling resistance and fracture resistance can be more highly balanced when the rubber composition is applied to a tire.

The bound aromatic vinyl content can be measured by ultraviolet absorption of phenyl groups, and based thereon, the bound conjugated diene content can also be determined. Specifically, the measurement was performed according to the following method. The modified conjugated diene-based polymer was used as a sample, and 100mg of the sample was diluted to 100ml with chloroform and dissolved in chloroform to prepare an assay sample. The bound styrene content (% by mass) with respect to 100% by mass of the sample was measured based on the absorption amount of a phenyl group of styrene at an ultraviolet absorption wavelength (about 254nm) (spectrophotometer "UV-2450" manufactured by Shimadzu Corporation).

In the conjugated diene polymer or the component (A1), the vinyl bond content in the conjugated diene bonding units is, for example, 10 to 75 mol%, or 20 to 65 mol%.

When the component (A1) is a copolymer of butadiene and styrene, the vinyl bond content (1, 2-bond content) in the butadiene bonding units can be determined by the Hampton method [ R.R. Hampton, Analytical Chemistry,21,923(1949)]To be determined. Specifically, the method is as follows. The modified conjugated diene-based polymer was used as a sample, and 50mg of the sample was dissolved in 10mL of carbon disulfide to prepare a measurement sample. Using a solution pool at 600-1000 cm^-1And based on the absorbance at a given wavenumber, according to the formula of the Hampton method described aboveTo determine the microstructure of the butadiene portion, i.e., the 1, 2-vinyl bond content (mol%) (Fourier transform infrared spectroscopy "FT-IR 230" manufactured by JASCO Corporation).

Preferably component (A1) has a Tg of above-50 ℃ and still more preferably has a Tg of-45 to-15 ℃. When the component (A1) has a Tg in the range of-45 to-15 ℃, wet performance, wear resistance, low rolling resistance and fracture resistance can be further highly achieved when applied to a tire.

For Tg, according to ISO 22768: 2006, a DSC curve is recorded when the temperature is raised in a given temperature range, and the peak top (inflection point) of the DSC differential curve is defined as Tg. The details are as follows. The modified conjugated diene-based polymer was used as a sample, and while the temperature was increased from-100 ℃ at 20 ℃/min under a helium cycle of 50 ml/min, and the peak top (inflection point) of the DSC differential curve was defined as Tg, the modified conjugated diene-based polymer was prepared in accordance with ISO 22768: 2006 a DSC curve was recorded using a differential scanning calorimeter "DSC 3200S" manufactured by MAC Science ltd.

In the rubber composition according to the present disclosure, it is preferable that the difference between the glass transition temperatures (Tg) of the modified conjugated diene polymer (a1) and the modified conjugated diene polymer (a2) should be 20 ℃ or more.

As a result, the wear resistance can be further improved.

In one example, the difference in Tg between component (A1) and component (A2) is 20 to 40 ℃.

The component (A1) has a Mooney viscosity, measured at 100 ℃, of, for example, 20 to 100 or 30 to 80.

The Mooney viscosity was measured as follows. Using the conjugated diene-based polymer or the modified conjugated diene-based polymer as a sample, the mooney viscosity was measured in accordance with JIS K6300 using a mooney viscometer with an L-shaped rotor (trade name "VR 1132" manufactured by Ueshima sesakasho co., ltd.). When the conjugated diene-based polymer was used as a sample, the measurement temperature was 110 ℃, and when the modified conjugated diene-based polymer was used as a sample, the measurement temperature was 100 ℃. First, the sample is preheated at the test temperature for 1 minute, then the rotor is rotated at 2rpm, the torque after 4 minutes is measured and definedIs Mooney viscosity (ML)₍₁₊₄₎)。

In one embodiment, component (a1) is a modified styrene butadiene rubber.

In the rubber composition according to the present disclosure, it is preferable that the modified conjugated diene polymer (a1) and the modified conjugated diene polymer (a2) should each be a modified styrene butadiene rubber.

As a result, a further improved balance between low rolling resistance and wet performance can be achieved.

Method for synthesizing modified conjugated diene polymer (a1)

The synthesis method of the component (a1) is not particularly limited, and for example, a synthesis method having: a polymerization step in which an organic monolithium compound is used as a polymerization initiator, and at least one conjugated diene compound is polymerized to obtain a conjugated diene-based polymer; and a reaction step in which a pentafunctional or higher-reactivity compound (hereinafter, this may also be referred to as a coupling agent) is allowed to react with the active terminal of the conjugated diene-based polymer.

Examples of the polymerization step include, for example, polymerization by a growth reaction with a living anion polymerization reaction. As a result, a conjugated diene-based polymer having an active end can be obtained, and the component (a1) having a high modification rate can be obtained.

The amount of the organic monolithium compound used as the polymerization initiator may be adjusted according to the target molecular weight of the conjugated diene-based polymer or the modified conjugated diene-based polymer. When the amount of the polymerization initiator is decreased, the molecular weight is increased; on the other hand, when the amount of the polymerization initiator increases, the molecular weight decreases.

From the viewpoint of ease of industrial applicability and ease of controlling the polymerization reaction, the organic monolithium compound is preferably an alkyllithium compound. In this case, a conjugated diene polymer having an alkyl group at the polymerization initiating terminal is obtained.

Examples of alkyl lithium compounds include, for example, n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenedium. These organic monolithium compounds may be used alone or in combination of two or more.

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

In the polymerization step, an inert solvent may be used.

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

Before the inert solvent is used in the polymerization reaction, it may be treated with an organometallic compound to remove impurities such as propadiene and acetylene from the inert solvent.

In the polymerization step, a polar compound may be used. By using the polar compound, the aromatic vinyl compound can be randomly copolymerized with the conjugated diene compound. In addition, polar compounds can also be used as vinylating agents (vinylating agents) which are used to control the microstructure of the conjugated diene moiety.

Examples of the polar compound include, for example, ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2, 2-bis (2-oxolanyl) propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium amylate; phosphine compounds, such as triphenylphosphine. These 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 ℃ or 50 to 100 ℃ from the viewpoint of ensuring a sufficient reaction amount of the coupling agent for the active terminal after the polymerization is ended.

Examples of the coupling agent include, for example, pentafunctional or more reactive compounds having a nitrogen atom or a silicon atom. Preferably, the reactive compound should have at least three silicon-containing functional groups. The coupling agent is preferably a coupling agent in which at least one silicon atom constitutes an alkoxysilyl group or a silanol group having 1 to 20 carbon atoms, and more preferably a compound represented by the general formula (VI), which will be described later. These coupling agents may be used alone or in combination of two or more.

The alkoxysilyl group possessed by the coupling agent tends to react with, for example, the active terminal possessed by the conjugated diene-based polymer, dissociating the lithium alkoxide and forming a bond between the terminal of the conjugated diene-based polymer chain and the silicon of the coupling residue. The number of alkoxysilyl groups possessed by the coupling residue is obtained by subtracting the number of SiOR groups reduced by the reaction from the total number of SiOR groups possessed by one molecule of the coupling agent. Further, the nitrogen heterocyclic ring group of the coupling agent forms a bond between > N-Li bond and the terminal of the conjugated diene polymer and silicon of the coupling residue. Note that the > N — Li bond tends to easily become > NH and LiOH due to water or the like at the time of completion. Further, in the coupling agent, the remaining unreacted alkoxysilyl group can easily become silanol (Si — OH group) due to water or the like at the time of completion.

Preferably, the modified conjugated diene polymer (a1) should be prepared by reacting a conjugated diene polymer with a coupling agent represented by the following general formula (VI):

[ formula 3]

[ in the general formula (VI), R¹²、R¹³And R¹⁴Each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms; r¹⁵、R¹⁶、R¹⁷、R¹⁸And R²⁰Each independently represents an alkyl group having 1 to 20 carbon atoms; r¹⁹And R²²Each independently represents an alkylene group having 1 to 20 carbon atoms; r²¹Represents a compound having 1 to 20 carbon atomsAlkyl or trialkylsilyl groups; m represents an integer of 1 to 3; p represents 1 or 2; when R is¹²～R²²M and p are independent of each other when they are present in plural; 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 represents a hydrocarbon group having 1 to 20 carbon atoms or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom and a phosphorus atom and having no active hydrogen.]。

As a result, the wet performance, wear resistance, low rolling resistance, and fracture resistance can be more highly balanced.

In the general formula (VI), the hydrocarbon group represented by A encompasses saturated, unsaturated, aliphatic and aromatic hydrocarbon groups. Examples of the organic group having no active hydrogen include, for example, a group free of a functional group having active hydrogen such as a hydroxyl group (-OH), a secondary amino group (- (OH), a salt (-COO-), a salt (->NH), primary amino group (-NH)₂) And mercapto (-SH), and the like.

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

Examples of such coupling agents include, for example, tetrakis [3- (2, 2-dimethoxy-1-aza-2-silacyclopentane) propyl ] -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, and bis [3- (2, 2-dimethoxy-1-aza-2-silacyclopentane) propyl ] - (3-trimethoxysilylpropyl) -methyl-1, 3-propanediamine.

The amount of the compound represented by the general formula (VI) added as a coupling agent may be adjusted so that the number of moles of the conjugated diene-based polymer and the number of moles of the coupling agent react in a desired stoichiometric ratio, thereby tending to achieve a desired degree of branching. The number of moles of the polymerization initiator is specifically, for example, 5.0 times or more or 6.0 times or more the number of moles of the coupling agent. In this case, in the general formula (VI), the number of functional groups of the coupling agent ((m-1). times.i + p.times.j + k) 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 ℃ or 50 to 100 ℃. The temperature change from the end of the polymerization step to the addition of the coupling agent is, for example, 10 ℃ or less or 5 ℃ or less.

The reaction time in the reaction step may be appropriately adjusted, and is, for example, 10 seconds or more or 30 seconds or more. From the viewpoint of the coupling ratio, it is preferable that the time from the end of the polymerization step to the start of the reaction step should be shorter and, for example, 5 minutes or less.

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

In order to obtain the component (A1) having the above-mentioned specific high molecular weight component, the molecular weight distribution (Mw/Mn) of the conjugated diene polymer may be 1.5 to 2.5 or 1.8 to 2.2. In addition, it is preferable that the obtained component (a1) should have a molecular weight curve by GPC in which a single peak is detected.

In one example, when the peak molecular weight by GPC of component (A1) is defined as Mp₁And the peak molecular weight of the conjugated diene polymer is defined as Mp₂Then, the following formula is maintained.

(Mp₁/Mp₂)<1.8×10-12×(Mp₂-120×10⁴)²+2

In one example, Mp₂Is 20X 10⁴～80×10⁴And Mp₁Is 30 x 10⁴～150×10⁴。

The modification ratio of the component (a1) is, for example, 30 mass% or more, 50 mass% or more, or 70 mass% or more. When the modification ratio is 30% by mass or more, when the rubber composition is applied to a tire, the low rolling resistance can be further improved while improving the wear resistance of the tire.

The modification ratio was measured as follows. Using the modified conjugated diene-based polymer as a sample, measurement was performed by applying the property that the modified basic polymer component was adsorbed on a GPC column filled with a silica-based gel. The adsorption amount on the silica-based column was measured from the difference between the chromatogram obtained by measuring a sample solution containing a sample and low-molecular-weight internal standard polystyrene on the polystyrene-based column and the chromatogram obtained by measuring the sample solution on the silica-based column, thereby determining the modification rate. Specifically, the measurement was performed as follows.

Preparation of sample solution: 10 mg of the sample and 5mg of standard polystyrene were dissolved in 20mL of THF to prepare a sample solution.

GPC measurement conditions using polystyrene-based columns: using "HLC-8320 GPC" (trade name) manufactured by Tosoh Corporation and THF using 5mmol/L triethylamine as an eluent, 10. mu.L of the sample solution was injected into the apparatus under conditions of a column temperature of 40 ℃ and a THF flow rate of 0.35 mL/min, and a chromatogram was obtained using an RI detector. As the column, three of "TSKgel supperoporehz-H" (trade name) manufactured by Tosoh Corporation were connected, and "TSKguardcolumn SuperMP (HZ) -H" (trade name) manufactured by Tosoh Corporation was connected to the former stage thereof as a protective column and used.

GPC measurement conditions using silica-based columns: using "HLC-8320 GPC" (trade name) manufactured by Tosoh Corporation and using THF as an eluent, 50 μ L of the sample solution was injected into the apparatus under conditions of a column temperature of 40 ℃ and a THF flow rate of 0.5 mL/min, and a chromatogram was obtained using an RI detector. As the column, "Zorbax PSM-1000S", "PSM-300S" and "PSM-60S" (all trade names) were attached and used, and "DIOL 4.6X 12.5mm 5 micron" (trade name) was attached as a protective column to its front stage and used.

The calculation method of the modification rate comprises the following steps: the modification ratio (%) was determined according to the following formula, in which the entire peak area of a chromatogram using a polystyrene-based column was defined as 100, the peak area of a sample was defined as P1, the peak area of a standard polystyrene was defined as P2, the entire peak area of a chromatogram using a silica-based column was defined as 100, the peak area of a sample was defined as P3, and the peak area of a standard polystyrene was defined as P4.

Modification rate (%) ([ 1- (P2 × P3)/(P1 × P4) ] × 100

(note that P1+ P2 is P3+ P4 is 100.)

After the reaction step, a quencher, a neutralizer, or the like may be added to the copolymer solution, if desired. Examples of quenchers include, for example, water and alcohols such as methanol, ethanol, and isopropanol. Examples of the neutralizing agent include, for example, carboxylic acids such as stearic acid, oleic acid and versatic acid (a mixture of highly branched carboxylic acids having 9 to 11, mainly 10 carbon atoms); an aqueous solution of a mineral acid; and carbon dioxide.

From the viewpoints of preventing gel formation after polymerization and improving stability during processing, it is preferable to add an antioxidant to component (a1), such as 2, 6-di-t-butyl-4-hydroxytoluene (BHT), n-octadecyl-3- (4' -hydroxy-3 ',5' -di-t-butylphenol) propionate, and 2-methyl-4, 6-bis [ (octylthio) methyl ] phenol.

In order to further improve the processability of the component (A1), a filling oil may be added to the modified conjugated diene-based copolymer, if necessary. As a method of adding a filling oil to the modified conjugated diene-based polymer, for example, a method in which a filling oil is added to a polymer solution and mixed to form an oil-extended copolymer solution, which is then desolventized, can be cited.

As a method for obtaining component (a1) from the polymer solution, a known method can be used. Examples of such a method include a method in which after separating the solvent by steam stripping or the like, the polymer is filtered out and further dehydrated and dried to obtain a polymer; a method in which the polymer solution is concentrated in a washing tank and further devolatilized with a vented extruder or the like; a method in which the polymer solution is directly devolatilized by a drum dryer or the like.

The amount of the component (a1) in the rubber component can be appropriately adjusted, and is, for example, 10 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, or 50 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, for example, the amount of the component (a1) is 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less with respect to 100 parts by mass of the rubber component.

In the rubber composition according to the present disclosure, it is preferable that the total amount (to be mentioned later) of the modified conjugated diene polymer (a1) and the modified conjugated diene polymer (a2) should be 50 parts by mass or more with respect to 100 parts by mass of the rubber component.

As a result, the filler can be distributed more in the polymer phase (1), and the filler can be dispersed more highly in the polymer phase (1).

Modified conjugated diene Polymer (A2)

The modified conjugated diene polymer (a2) is a modified conjugated diene polymer different from the modified conjugated diene polymer (a 1). However, both the component (a1) and the component (a2) are modified conjugated diene-based polymers, and therefore, they are included in the polymer phase (1).

Examples of the conjugated diene-based polymer as the base polymer of component (a2) include, for example, the above-mentioned polybutadiene (BR), synthetic polyisoprene (IR), styrene butadiene copolymer (SBR), isoprene butadiene copolymer, ethylene butadiene copolymer, and propylene butadiene copolymer.

In one embodiment, component (a2) is a modified styrene butadiene rubber.

The modified SBR as the component (a2) may be different from the component (a1), and thus publicly known modified SBR may be used. Examples thereof include modified SBR as described in, for example, Japanese patent laid-open No.2017-190457, International publication No. WO2016/194316, International publication No. WO 2017/077712, and International publication No. WO2017/077714.

The modifier used for obtaining the modified SBR as the component (a2) may be appropriately selected from publicly known modifiers and used. Preferably, the modifier should be one or more selected from the group consisting of alkoxysilane compounds, hydrocarbyloxysilane compounds, and combinations thereof, because they have a high interaction with the filler (e.g., silica).

Examples of the alkoxysilane compound include, for example, N- (1, 3-dimethylbutylidene) -3- (triethoxysilyl) -1-propylamine, tetramethoxysilane, tetraethoxysilane, tetra-N-propoxysilane, tetraisopropoxysilane, tetra-N-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, ethyltriisopropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltripropoxysilane, propyltriisopropoxysilane, butyltrimethoxysilane, butyltriethoxysilane, phenyltrimethoxysilane, propyltriisopropoxysilane, butyltrimethoxysilane, butyl, Phenyltriethoxysilane, dimethyldimethoxysilane, methylphenyldimethoxysilane, dimethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and divinyldiethoxysilane. Among the above, N- (1, 3-dimethylbutylidene) -3- (triethoxysilyl) -1-propylamine, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane and the like can be mentioned. These alkoxysilane compounds may be used alone or in combination of two or more.

Examples of the hydrocarbyloxysilane compound include, for example, [ N, N-bis (trimethylsilyl) - (3-amino-1-propyl) ] (methyl) (diethoxy) silane, N1, N1, N7-tetramethyl-4- ((trimethoxysilyl) methyl) -1,7 heptane, 2- ((hexyl-dimethoxysilyl) methyl) -N1, N1, N3, N3-2-pentamethylpropane-1, 3-diamine, N1- (3- (dimethylamino) propyl-N3, N3-dimethyl-N1- (3- (trimethoxysilyl) propyl) propane-1, 3-diamine, 4- (3- (dimethylamino) propyl) -N1, n1, N7, N7-tetramethyl-4- ((trimethoxysilyl) methyl) heptane-1, 7-diamine, N-dimethyl-2- (3- (dimethoxymethylsilyl) propoxy) ethylamine, N-bis (trimethylsilyl) -2- (3- (trimethoxysilyl) propoxy) ethylamine, N-dimethyl-2- (3- (trimethoxysilyl) propoxy) ethylamine, and N, N-dimethyl-3- (3- (trimethoxysilyl) propoxy) propan-1-amine.

Examples of the modifier suitable for obtaining the modified SBR as component (a2) by anionic polymerization include, for example, at least one compound selected from the group consisting of 3, 4-bis (trimethylsiloxy) -1-vinylbenzene, 3, 4-bis (trimethylsiloxy) benzaldehyde, 3, 4-bis (t-butyldimethylsiloxy) benzaldehyde, 2-cyanopyridine, 1, 3-dimethyl-2-imidazolidinone, and 1-methyl-2-pyrrolidone.

Preferably, the above modifier should be an amino moiety of a lithium amide compound used as a polymerization initiator in anionic polymerization. Examples of such lithium amide compounds include, for example, lithium hexamethyleneimide, lithium pyrrolidine, lithium piperidine, lithium heptamethyleneimide, lithium dodecamethyleneimide, lithium dimethylamide, lithium diethylamide, lithium dibutylamide, lithium dipropylamide, lithium dihexylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium N-methylpiperazine, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide, lithium methylphenylethylamide, and combinations thereof. For example, the modifier as the amino moiety of lithium hexamethyleneimine is hexamethyleneimine, the modifier as the amino moiety of lithium pyrrolidinium is pyrrolidine, and the modifier as the amino moiety of lithium piperidinium is piperidine.

Examples of the modifier suitable for obtaining a modified SBR as component (A2) by coordination polymerization include, for example, at least one compound selected from the group consisting of 2-cyanopyridine and 3, 4-bistrimethylsilyloxybenzaldehyde.

Examples of the modifier suitable for obtaining the modified SBR as the component (A2) by emulsion polymerization include, for example, at least one compound selected from the group consisting of 3, 4-bistrimethylsilyloxybenzaldehyde and 4-hexamethyleneiminoalkylstyrene. Preferably, these modifiers which are preferably used in the emulsion polymerization should be copolymerized during the emulsion polymerization as monomers comprising nitrogen atoms and/or silicon atoms.

The modified SBR as the component (a2) has a modification ratio of, for example, 30% or more, 35% or more, or 70% or more. The higher the modification ratio, the more the filler is distributed into the polymer phase (1) when the filler comprises silica, and the more the wet performance can be improved.

The Tg of component (A2) is, for example, at most-40 ℃ at most, -50 ℃ at most, or at most-60 ℃. The Tg of component (A2) is, for example, -70 ℃ or higher, -60 ℃ or higher, or-50 ℃ or higher.

The amount of the component (a2) in the rubber component may be appropriately adjusted, and is, for example, 10 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, or 50 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, for example, the amount of the component (a2) is 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less with respect to 100 parts by mass of the rubber component.

Third Polymer

The third polymer is a polymer other than the component (a1) and the component (a 2). The third polymer may be appropriately selected, and examples thereof include, for example, Natural Rubber (NR), polybutadiene (BR), synthetic polyisoprene (IR), styrene butadiene copolymer (SBR), isoprene butadiene copolymer, ethylene butadiene copolymer, and propylene butadiene copolymer.

In one embodiment, the third polymer is one selected from the group consisting of natural rubber, synthetic isoprene rubber, and butadiene rubber having a cis-1, 4 content of 90 mass% or more (high-cis BR).

In the rubber composition according to the present disclosure, it is preferable that the polymer phase (2) should include natural rubber, synthetic isoprene rubber, or butadiene rubber having a cis-1, 4 content of 90 mass% or more (high-cis BR).

As a result, the difference between the Tg of the polymer phase (1) and that of the lowest peak temperature is large, which ensures that these phases are incompatible.

The amount of the third polymer in the rubber component may be appropriately adjusted, and is, for example, 10 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, 50 parts by mass or more, 60 parts by mass or more, or 70 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, for example, the amount of the third polymer in the rubber component is 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, 30 parts by mass or less, or 20 parts by mass or less with respect to 100 parts by mass of the rubber component.

< Filler >

The rubber composition according to the present disclosure includes a filler. Examples of the filler include, for example, silica, carbon black, aluminum hydroxide, clay, alumina, talc, mica, kaolin, glass spheres, glass beads, calcium carbonate, magnesium hydroxide, magnesium oxide, titanium oxide, potassium titanate, and barium sulfate.

In one embodiment, the filler is silica and carbon black. In another example, the filler is silica.

The silica may be appropriately selected according to the purpose, and examples thereof include, for example, wet silica (hydrated silicate), dry silica (silicic anhydride), calcium silicate, and aluminum silicate. These silicas may be used alone or in combination of two or more.

The BET specific surface area of the silica can be suitably selected, and is, for example, 40 to 350m²/g、80～300m²A/g, or 150 to 280m²/g。

The BET specific surface area is a specific surface area determined by a BET method, and in the present disclosure, it refers to a value measured according to ASTM D4820-93.

The proportion of silica in the filler can be appropriately adjusted, and is, for example, 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, or 95 mass% or more with respect to the total mass of the filler. For example, the proportion of silica in the filler is 100 mass% or less, less than 100 mass%, 95 mass% or less, 90 mass% or less, 80 mass% or less, 70 mass% or less, 60 mass% or less, or 50 mass% or less with respect to the total mass of the filler.

Examples of the carbon black include, for example, high-structure carbon black, medium-structure carbon black or low-structure carbon black having a grade such as SAF, ISAF-HS, IISAF, N339, HAF, FEF, GPF, or SRF. These carbon blacks may be used alone or in combination of two or more.

The BET specific surface area of the carbon black may be appropriately selected, and is, for example, 40 to 350m²(ii)/g or 80 to 200m²/g。

The proportion of carbon black in the filler can be appropriately adjusted, and is, for example, 1 mass% or more, 2 mass% or more, 3 mass% or more, 4 mass% or more, 5 mass% or more, 10 mass% or more, 20 mass% or more, or 30 mass% or more with respect to the total mass of the filler. For example, the proportion of carbon black in the filler is 100% by mass or less, less than 100% by mass, 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less with respect to the total mass of the filler.

The compounding amount of the filler can be appropriately adjusted, and is, for example, 50 to 120 parts by mass with respect to 100 parts by mass of the rubber component.

In addition to the rubber component and the filler, components generally used in the rubber industry, such as styrene alkylene block copolymers, thermoplastic resins, softeners, vulcanization accelerators, silane coupling agents, vulcanizing agents, glycerin fatty acid esters, anti-aging agents, vulcanization accelerator auxiliaries, and organic acid compounds, may be appropriately selected and contained in the rubber composition according to the present disclosure, within a range that does not conflict with the gist of the present disclosure.

(Process for producing rubber composition)

The method for producing the rubber composition according to the present disclosure is not particularly limited, and components such as a rubber component and a filler can be compounded using a known compounding method.

The rubber composition according to the present disclosure is suitable for a tire, and more suitable for a tire tread rubber.

(Tread rubber)

The tread rubber according to the present disclosure is a tread rubber using the above rubber composition.

As a result, the wet performance, wear resistance, low rolling resistance, and fracture resistance of the tread rubber can be highly balanced.

(tire)

The tire according to the present disclosure is a tire using the above rubber composition.

As a result, the wet performance, wear resistance, low rolling resistance, and fracture resistance of the tire can be highly balanced.

Examples

Hereinafter, the present disclosure will be described in further detail with reference to examples, but these examples are only intended to illustrate the present disclosure and do not limit the present disclosure in any way. Unless otherwise specified, the compounding amount means parts by mass.

The materials used in the examples are as follows.

A rubber component:

natural Rubber (NR): "SIR 20" (trade name) manufactured by indonesia;

high-cis BR: "JSR" manufactured by JSR CORPORATION(BR01 is a registered trademark in japan, other countries, or both) "(trade name);

modified SBR (3): "Tufdene F3440" (trade name) manufactured by Asahi Kasei Corporation, styrene content of 35.5 mass%, vinyl content of 40 mass%, and weight average molecular weight of 100X 10⁴Not corresponding to component (a1) but corresponding to component (a 2). Tg ═ 25 ℃; and

unmodified SBR: "HP 755B" (trade name) manufactured by JSR CORPORATION, a solution polymerized styrene butadiene copolymer, Tg ═ 18 ℃.

Filling:

carbon black: "# 78" (trade name) manufactured by Asahi Carbon co., ltd.;

silica 1: manufactured by Tosoh Silica Corporation "(Nipsil is a registered trademark in Japan, other countries, or both) AQ "CTAB 165 (trade name), BET specific surface area of 205; and

silica 2: CTAB79 manufactured by Tosoh Silica Corporation.

And (3) the other:

silane coupling agent: bis (3-triethoxysilylpropyl) disulfide, "Si 75" (trade name) manufactured by Evonik Industries AG;

C₅-C₉a resin system: manufactured by Zeon Corporation "(Quinton is a registered trademark in japan, other countries, or both) G100B ";

zinc stearate: "307564" (trade name) manufactured by Sigma-Aldrich;

anti-aging agent (6 PPD): n- (1, 3-dimethylbutyl) -N' -phenyl-p-phenylenediamine, NOCRAC 6C (trade name), manufactured by Ouchi Shinko Chemical Industrial co., ltd.;

vulcanization accelerator (1) (DPG): 1, 3-diphenylguanidine, manufactured by Sumitomo Chemical co.(SOXINOL is a registered trademark in Japan, other countries, or both) D-G "(trade name);

vulcanization accelerator (2) (MBTS): bis (2-benzothiazolyl) persulfide manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.,) "(NOCCELER is a registered trademark in japan, other countries, or both) DM-P "(trade name); and

vulcanization accelerator (3) (CBS): from OuchiN-Cyclohexylbenzothiazole-2-sulfenamide manufactured by Shinko Chemical Industrial Co., Ltd "(NOCCELER is a registered trademark in Japan, other countries, or both) CZ-G "(trade name).

With respect to the modified conjugated diene polymer (A1), the bound styrene content, the microstructure of the butadiene portion, the molecular weight, the shrinkage factor (g'), the Mooney viscosity, the Tg, the modification ratio, the presence or absence of a nitrogen atom, and the presence or absence of a silicon atom were analyzed according to the methods described above.

< Synthesis of modified SBR (1) -component (A1) >

As the polymerization reactor, a tank-type pressure vessel having a stirrer and a jacket for temperature control, which had an internal volume of 10L, a ratio (L/D) of an internal height (L) to a diameter (D) of 4.0, an inlet at the bottom and an outlet at the top, was used. The pre-dehydrated 1, 3-butadiene, styrene and n-hexane were mixed under conditions of 17.2 g/min, 10.5 g/min and 145.3 g/min, respectively. In a static mixer provided in the middle of a pipe for supplying the mixed solution to the inlet of the reactor, n-butyllithium for inerting residual impurities was added and mixed at a rate of 0.117 mmol/min, and then the resultant mixture was continuously supplied to the bottom of the reactor. Further, 2-bis (2-oxocyclopentyl) propane as a polar substance and n-butyllithium as a polymerization initiator were added to the bottom of the polymerization reactor at rates of 0.019 g/min and 0.242 mmol/min, respectively, where they were vigorously mixed with a stirrer to continuously perform polymerization. The temperature was controlled so that the temperature of the polymerization solution at the outlet of the top of the reactor was 75 ℃. When the polymerization was sufficiently stabilized, a small amount of the polymer solution before the addition of the coupling agent was extracted from the outlet at the top of the reactor to add 0.2g of an antioxidant (BHT) per 100g of the polymer, then the solvent was removed, and the Mooney viscosity at 110 ℃ and various molecular weights were measured. Next, tetrakis (3-trimethoxysilylpropyl) -1, 3-propanediamine diluted to 2.74mmol/L as a coupling agent was continuously added at a rate of 0.0302 mmol/min to the polymer solution (n-hexane solution containing 5.2ppm of water) flowing out of the outlet of the reactor. The polymer solution to which the coupling agent has been added is mixed by a static mixer and subjected to a coupling reaction. At this time, the time from the outflow of the polymer solution from the outlet of the reactor until the addition of the coupling agent was 4.8 minutes, the temperature was 68 ℃, and the difference between the temperature during the polymerization step and the temperature until the addition of the modifier was 7 ℃. To the polymer solution having undergone the coupling reaction, an antioxidant (BHT) was continuously added at a rate of 0.2g and 0.055 g/min (n-hexane solution) per 100g of the polymer to terminate the coupling reaction. While serving as an antioxidant, OIL ("JOMO Process NC 140" (trade name) manufactured by JX NIPPON OIL & Energy CORPORATION) was continuously added at 10.0g per 100g of the polymer, and mixed with a static mixer. The solvent was removed by steam stripping to obtain modified SBR (1) as component (a 1).

When the modified SBR (1) was analyzed by the above-described method, the respective values were as follows, and they corresponded to the component (a 1):

the bound styrene content was 35 mass%;

vinyl bond content (1, 2-bond content) 42 mol%;

Mw＝85.2×10⁴g/mol；

Mn＝38.2×10⁴g/mol；

Mw/Mn＝2.23；

peak molecular weight (Mp)₁)＝96.8×10⁴g/mol；

Ratio between peak molecular weights (Mp)₁/Mp₂)＝3.13；

The proportion of "specific high molecular weight component" was 4.6%;

the puncturing factor (g') is 0.59;

mooney viscosity (100 ℃ C.) > 65;

tg ═ 24 ℃; and

the modification rate was 80%.

Further, the modified SBR (1) has a nitrogen atom and a silicon atom.

For modified SBR (1), "degree of branching" corresponding to the number of branches assumed based on the number of functional groups and the amount of addition of the coupling agent was 8 (this can also be confirmed by the value of the shrinkage factor), and "number of SiOR residues" corresponding to the value obtained by subtracting the number of SiOR reduced by the reaction from the total number of SiOR possessed by one molecule of the coupling agent was 4.

< Synthesis of modified SBR (2) -component (A2) >

To a dry, nitrogen-purged 800mL pressure-resistant glass vessel were added a cyclohexane solution of 1, 3-butadiene and a cyclohexane solution of styrene so as to attain 67.5g of 1, 3-butadiene and 7.5g of styrene, 0.6mmol of 2, 2-bis (tetrahydrofuryl) propane and 0.8mmol of n-butyllithium were added, and then polymerization was carried out at 50 ℃ for 1.5 hours. To the polymerization reaction system in which the polymerization conversion at this time had reached almost 100%, 0.72mmol of [ N, N-bis (trimethylsilyl) - (3-amino-1-propyl) ] (methyl) (diethoxy) silane was added, and the modification reaction was carried out at 50 ℃ for 30 minutes. Thereafter, 2mL of a 5 mass% isopropanol solution of 2, 6-di-t-butyl-p-cresol (BHT) was added to stop the reaction, and the resultant was dried according to a conventional method to obtain a modified SBR. In the microstructure of the modified SBR, the bound styrene content was 10 mass%, the vinyl bond content in the butadiene portion was 40%, and the peak molecular weight was 200,000. Further, Tg was-60 ℃.

< preparation and evaluation of rubber composition >

The rubber compositions of example 1 and comparative example 1 were manufactured using a general banbury mixer according to the formulations described in tables 1 and 2. The rubber compositions of examples 2 to 7 and comparative examples 2 to 5 were produced using a common banbury mixer. Further, by using these rubber compositions as tread rubbers, pneumatic radial tires for passenger cars having a size of 195/65R15 were produced. With respect to the rubber composition or the tire, the wet performance, the wear resistance, the low rolling resistance and the fracture resistance were evaluated according to the following methods. Each evaluation is described in table 1.

For each rubber composition, the peak temperature of the tan δ temperature dispersion curve of the polymer phase (1) and the polymer phase (2), the filler concentration in the polymer phase (1), and the average aggregate area of the filler in the polymer phase (1) were determined by the above-mentioned methods.

< Wet road Property >

For example 1 and comparative example 1, vulcanized rubber that can be matched with a measuring tool having a long diameter of 40mm and a short diameter of 20mm was prepared, and a frictional force generated when the rubber was pressed against a road surface of a fixed wet iron plate and moved back and forth was detected with a load cell, and a dynamic friction coefficient was calculated. The calculations were performed for examples 2 to 7 and comparative examples 2 to 5.

< wear resistance >

After vulcanizing the rubber composition at 145 ℃ for 33 minutes, the rubber composition was vulcanized in accordance with JIS K6264-2: 2005 abrasion loss was measured at 23 ℃ using a lambert abrader. The wear resistance was expressed as an index by taking the reciprocal of the amount of wear and defining the value of comparative example 1 as 100. The larger the index value, the less the amount of wear and the more excellent the wear resistance.

< Low Rolling resistance >

For example 1 and comparative example 1, the index was calculated based on tan δ at 50 ℃. For examples 2-7 and comparative examples 2-5, indices were calculated. The smaller the index value, the lower the rolling resistance and the more excellent the low rolling resistance.

< fracture resistance >

For example 1 and comparative example 1, a tensile test was conducted at room temperature on the rubber compositions in accordance with JIS-K6251, and the breaking stress of the vulcanized rubber compositions was calculated from the obtained results. The rubber compositions of examples 2 to 7 and comparative examples 2 to 5 were subjected to a tensile test at room temperature in accordance with JIS-K6251, and the breaking stress of the vulcanized rubber compositions was measured. Each fracture resistance was expressed as an index by defining comparative example 1 as 100. The larger the index value, the more excellent the fracture resistance.

[ Table 1]

^*In table 2, in comparative example 5, natural rubber is the third polymer, and high-cis BR is the fourth polymer.

As described in table 2, by the rubber composition according to the present disclosure, wet performance, wear resistance, low rolling resistance, and fracture resistance can be highly balanced.

Industrial applicability

According to the present disclosure, a rubber composition in which wet performance, wear resistance, low rolling resistance, and fracture resistance are highly balanced can be provided. According to the present disclosure, it is possible to provide a tire in which wet performance, wear resistance, low rolling resistance, and fracture resistance are highly balanced.