Rubber composition for tires and tires

Abstract

To provide a tire rubber composition for manufacturing tires with excellent wet grip, and a tire that is a vulcanized product of the tire rubber composition. [Solution] The tire rubber composition comprises a rubber component and a tackifier. The tackifier contains constituent units derived from isopropenyltoluene. The content ratio of the tackifier is 40 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the rubber component.

Description

Technical Field

[0001] The present invention relates to a rubber composition for tires and a tire.

Background Art

[0002] Conventionally, it is known that a tire is manufactured using a rubber composition for tires containing a rubber component and a tackifier.

[0003] As such a rubber composition for tires, for example, a rubber composition containing 100 parts by mass of styrene-butadiene rubber (SBR) and 2 parts by mass of a tackifier (aliphatic / aromatic copolymer type petroleum resin, Quintone G100B) has been proposed (see, for example, Example 1 of Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, from the viewpoint of safety, tires are required to have improved wet grip performance (braking performance on a wet road surface) that exhibits braking performance.

[0006] The present invention provides a rubber composition for tires for manufacturing a tire having excellent wet grip performance, and a tire that is a vulcanizate of the rubber composition for tires.

Means for Solving the Problems

[0007] The present invention [1] is a rubber composition for tires comprising a rubber component and a tackifier, wherein the tackifier comprises constituent units derived from isopropenyltoluene, and the content ratio of the tackifier is 40 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the rubber component.

[0008] The present invention [2] includes the tire rubber composition described in [1] above, wherein the tackifier comprises only constituent units derived from isopropenyltoluene.

[0009] The present invention [3] includes a tire which is a vulcanized product of the tire rubber composition described in [1] or [2] above. [Effects of the Invention]

[0010] In the rubber composition for tires of the present invention, the tackifier contains constituent units derived from isopropenyltoluene. Furthermore, the content ratio of the tackifier is 40 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the rubber component. Therefore, it is possible to manufacture tires with excellent wet grip.

[0011] The tire of the present invention is a vulcanized product of the tire rubber composition of the present invention. Therefore, it has excellent wet grip. [Modes for carrying out the invention]

[0012] 1. Rubber composition for tires The rubber composition for tires contains a rubber component and a tackifier.

[0013] <Rubber components> Examples of rubber components include diene-based rubbers.

[0014] Examples of diene rubbers include natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), and chloroprene rubber (CR).

[0015] As the rubber component, preferably, styrene butadiene rubber (SBR) can be mentioned.

[0016] The rubber component can be used alone or in combination of two or more kinds.

[0017] The content ratio of the rubber component is, for example, 62.5 parts by mass to 71.5 parts by mass, preferably 63.0 parts by mass to 71.0 parts by mass, more preferably 65.0 parts by mass to 67.0 parts by mass with respect to 100 parts by mass of the total amount of the rubber component and the tackifier.

[0018] <Tackifier> The tackifier is a polymer containing a structural unit derived from isopropenyl toluene.

[0019] Such a polymer is formed by polymerizing polymerization components.

[0020] (Polymerization components) The polymerization components include isopropenyl toluene as an essential component.

[0021] In addition, from the viewpoints of improving the compatibility with the rubber component, the wet grip modification performance, and the low rolling resistance, the polymerization components can also include other components copolymerizable with isopropenyl toluene.

[0022] Examples of the other components include α-methyl styrene, indene, vinyl toluene, and unsaturated aliphatic hydrocarbons.

[0023] Examples of the unsaturated aliphatic hydrocarbons include a C4 fraction and a C5 fraction.

[0024] The C4 fraction is obtained by refining and / or decomposing petroleum. The C4 fraction is a fraction having a boiling point range of usually -15°C or higher and 45°C or lower under normal pressure, and includes, for example, unsaturated aliphatic hydrocarbons having 4 carbon atoms that do not contain a conjugated double bond and unsaturated aliphatic hydrocarbons having 4 carbon atoms that contain a conjugated double bond.

[0025] Examples of carbon-4 unsaturated aliphatic hydrocarbons that do not contain conjugated double bonds include 1-butene, isobutene, and 2-butene.

[0026] An example of a carbon-4 unsaturated aliphatic hydrocarbon containing a conjugated double bond is 1,3-butadiene.

[0027] The C5 fraction is obtained by refining and / or cracking petroleum. The C5 fraction is a fraction with a boiling point range of typically -15°C to 45°C under normal pressure, and includes, for example, unsaturated aliphatic hydrocarbons with 5 carbon atoms that do not contain conjugated double bonds, and unsaturated aliphatic hydrocarbons with 5 carbon atoms that contain conjugated double bonds.

[0028] Examples of unsaturated aliphatic hydrocarbons with 5 carbon atoms that do not contain conjugated double bonds include 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, and 2-pentene.

[0029] Examples of unsaturated aliphatic hydrocarbons with 5 carbon atoms containing conjugated double bonds include isoprene, 1,3-pentadiene, and cyclopentadiene.

[0030] The C5 fraction preferably consists of a carbon-5 unsaturated aliphatic hydrocarbon containing a conjugated double bond.

[0031] Other ingredients can be used alone or in combination of two or more types.

[0032] When the polymerization component contains other components, the content of constituent units derived from isopropenyltoluene in the tackifier is, for example, 65 mol% to 99 mol%, preferably 80 mol% to 98 mol%, and more preferably 90 mol% to 97 mol%. In addition, the content of constituent units derived from other components in the tackifier is, for example, 1 mol% to 35 mol%, preferably 2 mol% to 20 mol%, and more preferably 3 mol% to 10 mol%.

[0033] The proportions of the above constituent units are as follows: 13 It can be measured by 13C-NMR spectroscopy.

[0034] Furthermore, all or part of the monomers constituting the polymerization component may be derived from fossil fuels or biomass.

[0035] Fossil fuels include petroleum, coal, natural gas, shale gas, or combinations thereof. Biomass refers to all renewable natural raw materials and their residues, including plant-derived or animal-derived materials such as fungi, yeasts, algae, and bacteria.

[0036] The polymerization component is preferably isopropenyltoluene or isopropenyltoluene and a C5 fraction. In other words, the tackifier (polymer) is preferably a homopolymer of isopropenyltoluene (a tackifier containing only structural units derived from isopropenyltoluene) or a copolymer of isopropenyltoluene and a C5 fraction (a tackifier containing structural units derived from isopropenyltoluene and structural units derived from the C5 fraction). From the viewpoint of wet grip and low rolling resistance, a homopolymer of isopropenyltoluene is more preferably used as the tackifier (polymer).

[0037] (Method of manufacturing tackifier) Tackifiers are obtained by polymerizing polymerization components. Specifically, polymerization components are polymerized at atmospheric pressure in the presence of a Friedel-Crafts catalyst.

[0038] Examples of Friedel-Crafts catalysts include phenolic complexes (e.g., boron trifluoride phenolate complexes).

[0039] The proportion of the Friedel-Crafts catalyst used is, for example, 0.01 to 1 part by mass per 100 parts by mass of the polymerization component.

[0040] The polymerization conditions include a polymerization temperature of, for example, -50°C to 50°C, and a polymerization time of, for example, 10 minutes to 10 hours.

[0041] Furthermore, the above reaction may be carried out in the presence or absence of a solvent. Preferably, the above reaction is carried out in the presence of a solvent.

[0042] Examples of solvents include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, ketones, and alkyl esters. Aromatic hydrocarbons are preferred as solvents. Examples of aromatic hydrocarbons include toluene and xylene. Toluene is preferred as an aromatic hydrocarbon.

[0043] Solvents can be used alone or in combination of two or more types.

[0044] After polymerization, the solvent and / or unreacted polymer components can be removed as needed.

[0045] This yields a tackifier (polymer) (a solution of the tackifier).

[0046] In the solution of the tackifier, the solid content concentration is, for example, 5% to 70% by mass, preferably 10% to 60% by mass.

[0047] (Physical properties of tackifiers) The softening point of the tackifier is, for example, 85°C to 150°C, preferably 87°C to 130°C, more preferably 89°C to 110°C, and even more preferably 98°C to 105°C.

[0048] If the above softening point falls within the above range, wet grip performance can be improved.

[0049] The above softening point can be measured by the ring-and-ball method (in accordance with JIS K2207).

[0050] The number-average molecular weight (Mn) of the tackifier is, for example, 400 to 2000, preferably 500 to 1200, more preferably 600 to 1000, and even more preferably 700 to 900, based on standard polystyrene measurements by gel permeation chromatography (GPC).

[0051] If the above number-average molecular weight (Mn) is within the above range, wet grip performance can be improved.

[0052] The weight-average molecular weight (Mw) of the tackifier is, for example, 500 to 5000, preferably 800 to 3000, more preferably 900 to 2000, even more preferably 1000 to 1500, and particularly preferably 1120 to 1300, as measured by gel permeation chromatography (GPC) on a standard polystyrene basis.

[0053] If the weight-average molecular weight (Mw) is within the above range, wet grip performance can be improved.

[0054] The z-average molecular weight (Mz) of the tackifier is, for example, 500 to 3000, preferably 1000 to 2000, more preferably 1200 to 1800, and even more preferably 1660 to 1750, as measured by gel permeation chromatography (GPC) on a standard polystyrene basis.

[0055] If the average molecular weight (Mz) of z is within the above range, wet grip performance can be improved.

[0056] Furthermore, in the tackifier, the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) is, for example, 1.10 to 2.00, preferably 1.20 to 1.80, more preferably 1.30 to 1.60, and even more preferably 1.50 to 1.55.

[0057] If the above ratio falls within the above range, wet grip performance can be improved.

[0058] Adhesion agents can be used alone or in combination of two or more types.

[0059] The proportion of the tackifier is 40 parts by mass or more, preferably more than 40 parts by mass, more preferably 45 parts by mass or more, even more preferably 48 parts by mass or more, particularly preferably 49 parts by mass or more, and 60 parts by mass or less, preferably 55 parts by mass or less, more preferably 52 parts by mass or less, and even more preferably 51 parts by mass or less, per 100 parts by mass of the rubber component.

[0060] If the tackifier content is above the lower limit mentioned above, wet grip performance can be significantly improved. Furthermore, if the tackifier content is above the lower limit mentioned above, rolling resistance can be improved.

[0061] On the other hand, if the proportion of tackifier is below the lower limit mentioned above, it will not be possible to sufficiently improve wet grip performance.

[0062] Furthermore, if the tackifier content is below the upper limit mentioned above, wet grip performance can be significantly improved. Also, if the tackifier content is above the lower limit mentioned above, rolling resistance can be improved.

[0063] On the other hand, if the proportion of tackifier exceeds the above upper limit, the dispersibility of the tackifier decreases, resulting in a decrease in wet grip performance.

[0064] The proportion of the tackifier is, for example, 28.0 to 37.5 parts by mass, preferably 30.0 to 36.0 parts by mass, and more preferably 32.0 to 34.0 parts by mass, per 100 parts by mass of the total amount of rubber components and tackifier.

[0065] <Additives> The rubber composition for tires may contain additives in appropriate proportions as needed. Examples of additives include inorganic fillers, rubber reinforcing agents, softeners, crosslinking agents, crosslinking aids, antioxidants, processing aids, alkoxysilane compounds, surfactants, reaction inhibitors, colorants, dispersants, flame retardants, plasticizers, antioxidants, scorch inhibitors, UV absorbers, antistatic agents, lubricants, antifungal agents, scouring accelerators, dyes (e.g., disperse dyes, acid dyes), inorganic and organic pigments, surfactants, paints, compounds for foaming (e.g., foaming agents, foaming aids), and defoaming agents.

[0066] <Preparation of rubber composition for tires> A rubber composition for tires is obtained by blending and kneading a rubber component, a tackifier, and additives as needed.

[0067] 2. Tires A tire is a vulcanized product of a tire rubber composition. Such a tire is obtained by vulcanizing a tire rubber composition.

[0068] Known methods exist for vulcanizing tire rubber compositions. Specifically, first, a vulcanizing agent (e.g., a sulfur-based compound, a peroxide-based crosslinking agent) is added to the tire rubber composition. Next, the mixture is molded using a known molding method (e.g., mold molding), and then heated. This process produces a tire, which is a vulcanized product of the tire rubber composition.

[0069] Examples of such tires include pneumatic tires, solid tires, airless tires, and retreaded tires. Furthermore, such tires are suitably used for various purposes, such as fuel-efficient tires, all-season tires, high-performance tires, snow tires, and studless tires.

[0070] 3. Effects In the rubber composition for tires, the tackifier contains constituent units derived from isopropenyltoluene. Furthermore, the tackifier content is 40 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the rubber component. Therefore, tires with excellent wet grip can be manufactured.

[0071] Specifically, Example 1 of the rubber composition in Patent Document 1 contains 100 parts by mass of styrene-butadiene rubber (SBR) and 2 parts by mass of a tackifier (aliphatic / aromatic copolymer petroleum resin, Quinton G100B). Furthermore, in Patent Document 1, the content ratio of the tackifier is limited from the viewpoint of suppressing the occurrence of cracks due to ultraviolet light.

[0072] On the other hand, we found that wet grip performance tends to improve when the proportion of tackifiers is increased.

[0073] In particular, we found that when the tackifier contains structural units derived from isopropenyltoluene, the wet grip performance is significantly improved compared to when the tackifier contains structural units derived from aliphatic / aromatic copolymer petroleum resin (Example 1 of Patent Document 1).

[0074] Tires are vulcanized products of rubber compositions for tires. Therefore, they offer excellent wet grip. [Examples]

[0075] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Unless otherwise specified, "parts" and "%" are based on mass. Furthermore, specific numerical values ​​such as blending ratios (content), physical properties, and parameters used in the following description may be replaced with the corresponding upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than") of the blending ratios (content), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0076] <Details of ingredients> Details of the abbreviations used in each example and comparative example are described below. SBR: Solution-polymerized polystyrene-butadiene rubber (manufactured by ENEOS Materials, product name "SL552") IPT: Isopropenyltoluene αMS: α-methylstyrene C5:C5 fraction Quinton G100B: Aliphatic / aromatic copolymer petroleum resin, manufactured by Zeon Corporation.

[0077] <Manufacturing of tackifiers (polymers)> Manufacturing Example 1 (Isopropenyltoluene Monopolymer) A 1270 ml autoclave equipped with stirring blades was subjected to a polymerization reaction at 5°C. A mixture of the polymerization component (isopropenyltoluene) and dehydrated purified toluene (polymerization component / toluene = 1 / 1 (volume ratio)) and a Friedel-Crafts catalyst (boron trifluoride phenolate complex diluted 10-fold with dehydrated purified toluene (1.7 times the phenol equivalent)) were continuously supplied to the first stage. The polymerization reaction was carried out at 5°C. The supply rate of the polymerization component and toluene mixture was 1.0 liter / hour, and the supply rate of the Friedel-Crafts catalyst was 105 milliliters / hour. A reaction mixture was obtained.

[0078] Next, the reaction mixture was transferred to a second autoclave, and the polymerization reaction was continued at 5°C. When the total residence time in the first and second autoclaves reached 2 hours, the reaction mixture was continuously discharged from the autoclaves. When the residence time reached three times the total residence time, 1 liter of the reaction mixture was collected to terminate the polymerization reaction. After polymerization was complete, a 1 N aqueous NaOH solution was added to the collected reaction mixture to deash the catalyst residue. Furthermore, the reaction mixture was washed five times with a large amount of water, and then the solvent and unreacted polymerization components were removed under reduced pressure using an evaporator to obtain a tackifier (polymer).

[0079] Manufacturing Example 2 (Isopropenyltoluene Single Polymer) A tackifier (polymer) was obtained based on the same procedure as in Manufacturing Example 1, except that the supply rate of the Friedel-Crafts catalyst was changed to 82 ml / hour.

[0080] Production Example 3 (Copolymer of Isopropenyltoluene and C5 fraction) A tackifier (polymer) was obtained based on the same procedure as in Manufacturing Example 1. However, the polymerization components were changed to isopropenyl toluene and C5 fraction, and their mass ratio was set to 90 / 10.

[0081] Manufacturing Example 4 (Homopolymer of α-methylstyrene) A tackifier (polymer) was obtained based on the same procedure as in Manufacturing Example 1, except that the polymerization component was changed to α-methylstyrene. In addition, the supply rate of the Friedel-Crafts catalyst was changed to 90 ml / hour.

[0082] Manufacturing Example 5 (Homopolymer of α-methylstyrene) A tackifier (polymer) was obtained based on the same procedure as in Manufacturing Example 1, except that the polymerization component was changed to α-methylstyrene. In addition, the supply rate of the Friedel-Crafts catalyst was changed to 56 ml / hour.

[0083] <Preparation of rubber composition for tires> Examples 1 to 5 and Comparative Examples 1 to 14 Based on the information in Tables 2 and 3, the rubber components and tackifiers were blended and kneaded for 5 minutes at a temperature of 160°C and a rotor speed of 40 rpm using a Laboplast Mill [Model 4C150, manufactured by Toyo Seiki Seisakusho Co., Ltd.]. This prepared a rubber composition for tires. <Rating> [Constituent units of each component] The constituent units of each component in the tackifier (polymer) of each manufacturing example are determined based on the following conditions: 13 The results were obtained by analyzing the 1C-NMR spectrum. The results are shown in Table 1. {conditions} Equipment: Bruker BioSpin AVANCE III cryo-500 nuclear magnetic resonance spectrometer Measured nucleus: 13C (125MHz) Measurement mode: Single-pulse proton broadband decoupling Pulse width: 45° (5.00 μsec) Points: 64k Measurement range: 250 ppm (-55 to 195 ppm) Repeat time: 5.5 seconds Total number of times: 128 Measurement solvent: Orthodichlorobenzene / benzene-d6 (4 / 1 (volume ratio)) Sample concentration: 60 mg / 0.6 mL Measurement temperature: 120℃ Window function: exponential (BF: 1.0Hz) Chemical shift criterion: δδ signal 29.73 ppm

[0084] [Softening point] The tackifier (polymer) for each manufacturing example was measured using the ring-sphere method in accordance with JIS K2207. The results are shown in Table 1.

[0085] [Number-average molecular weight (Mn), weight-average molecular weight (Mw), z-average molecular weight (Mz), and degree of dispersion (Mw / Mn)] For each tackifier (polymer) of the manufacturing agent, the number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz) in terms of standard polystyrene were measured by gel permeation chromatography (GPC) based on the following measurement conditions, and the Mw / Mn ratio was calculated. The results are shown in Table 1. {Measurement conditions} Equipment: GPC HLC-8320 (manufactured by Tosoh Corporation) Solvent: Tetrahydrofuran Columns: TSKgel G7000 x 1, TSKgel G4000 x 2, TSKgel G2000 x 1 (all manufactured by Tosoh Corporation) Flow rate: 1.0ml / min Sample: 20 mg / mL tetrahydrofuran solution Column temperature: 40℃ Detector: Differential refractive index detector Injection volume: 50μl

[0086] [Viscoelasticity (wet grip and low rolling resistance)] A predetermined amount of the tire rubber composition for each example and comparative example was filled into a SUS mold. Using a manual hot press (PEWR-30, manufactured by Shinto Metal Industries Co., Ltd.) set to a heating plate of 150°C, the mixture was pressurized at a gauge pressure of 9 MPa for 4 minutes. Then, it was transferred to a cooling plate set to 20°C and compressed at a gauge pressure of 9 MPa for 3 minutes. This produced a measuring press sheet measuring 65 mm in length, 65 mm in width, and 2 mm in thickness. Next, test pieces were prepared by punching out pieces with a width of 3 mm from the measuring press sheet.

[0087] Using a rheometer (DVA-225, manufactured by IT Measurement & Control Co., Ltd.), the tanδ peak intensity, tanδ peak value at 0°C (tanδ(0°C)), and tanδ peak value at 60°C (tanδ(60°C)) were measured on the test specimens under the conditions of tensile mode, frequency of 1 Hz, strain setting of 0.05%, and heating rate of 3°C / min.

[0088] Furthermore, in order to clearly demonstrate the improvement in wet grip and low rolling resistance due to the incorporation of tackifiers, the scores for tanδ(0°C) and tanδ(60°C) were calculated based on the following equations (1) and (2). A higher score for tanδ(0°C) indicates superior wet grip. Similarly, a higher score for tanδ(60°C) indicates superior low rolling resistance. The results are shown in Tables 2 and 3. Score for tanδ(0℃) = tanδ(0℃) of each example or comparative example / tanδ(0℃) of comparative example 1 × 100 (1) Score for tanδ(60℃) = tanδ(60℃) of Comparative Example 1 / tanδ(60℃) of each example or comparative example × 100 (2)

[0089] <Consideration> Examples 1, 2, and Comparative Examples 2 to 4 all use the tackifier from Production Example 1. On the other hand, as shown in Table 4, the content ratio of the tackifier to 100 parts by mass of rubber component is 10 parts by mass, 20 parts by mass, 30 parts by mass, 40 parts by mass, and 50 parts by mass for Comparative Example 2, Comparative Example 3, Comparative Example 4, Example 1, and Example 2, respectively.

[0090] The higher the proportion of tackifier, the higher the tanδ(0℃) score, indicating that a higher proportion of tackifier improves wet grip performance.

[0091] Furthermore, Comparative Examples 12 to 14 all used Quinton G100B as the tackifier. On the other hand, as shown in Table 5, the content ratio of the tackifier to 100 parts by mass of rubber component was 20 parts by mass, 30 parts by mass, and 40 parts by mass for Comparative Example 12, Comparative Example 13, and Comparative Example 14, respectively.

[0092] The higher the proportion of tackifier, the higher the tanδ(0℃) score, indicating that a higher proportion of tackifier improves wet grip performance.

[0093] However, the degree of improvement in wet grip differs between using the tackifier of Manufacturing Example 1 (a tackifier containing constituent units derived from isopropenyltoluene) and using Quinton G100B.

[0094] In more detail, when using the tackifier of Manufacturing Example 1, the tanδ(0°C) score for Comparative Example 2, where the tackifier is 20 parts by mass per 100 parts by mass of rubber component, is 131, while the tanδ(0°C) score for Example 1, where the tackifier is 40 parts by mass per 100 parts by mass of rubber component, is 344. In other words, increasing the amount of tackifier from 20 parts by mass to 40 parts by mass increases the tanδ(0°C) score by 2.6 times.

[0095] On the other hand, when Quinton G100B was used, the tanδ(0°C) score for Comparative Example 12, where the tackifier was 20 parts by mass per 100 parts by mass of rubber component, was 125, while the tanδ(0°C) score for Comparative Example 14, where the tackifier was 40 parts by mass per 100 parts by mass of rubber component, was 257. In other words, increasing the amount of tackifier from 20 parts by mass to 40 parts by mass resulted in a 2.1-fold increase in the tanδ(0°C) score.

[0096] In other words, when using the tackifier of Production Example 1 (a tackifier containing constituent units derived from isopropenyltoluene), the degree of improvement in wet grip performance by increasing the amount of tackifier (to 40 parts by mass or more) is greater compared to when using Quinton G100B.

[0097] This is also true when using Production Examples 2 and 3, which are tackifiers containing constituent units derived from isopropenyltoluene, as shown in Table 5.

[0098] [Table 1]

[0099] [Table 2]

[0100] [Table 3]

[0101] [Table 4]

[0102] [Table 5]

Claims

1. It contains rubber components and tackifiers. The tackifier contains constituent units derived from isopropenyltoluene, A rubber composition for tires in which the content ratio of the tackifier is 40 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the rubber component.

2. The tire rubber composition according to claim 1, wherein the tackifier comprises only constituent units derived from isopropenyltoluene.

3. A tire that is a vulcanized product of the tire rubber composition according to claim 1 or 2.

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