JP2017214508A - Tire rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire rubber composition that achieves both of wet grip performance and wear resistance.SOLUTION: A tire rubber composition contains aluminum alkoxide of 1-30 pts.mass relative to a diene rubber containing an aromatic vinyl-conjugated diene rubber of 100 pts.mass.SELECTED DRAWING: None

Description

  The present invention relates to a tire rubber composition that improves wet grip performance and wear resistance.

  An extremely high level of performance is required for pneumatic tires for high-performance automobiles running on circuits and the like. For example, competition wet tires are required to have high levels of stability on wet road surfaces (wet grip performance) and wear resistance. In order to improve wet grip performance, a rubber composition for tires containing both carbon black and silica is known. However, when part of the carbon black is replaced with silica, there is a problem that the wear resistance is lowered.

  Patent Document 1 proposes to improve wet grip performance with a rubber composition in which 5 to 150 parts by weight of aluminum hydroxide and carbon black and / or silica are blended with respect to 100 parts by weight of diene rubber. However, this rubber composition also has a problem that the wear resistance is similarly lowered.

JP 2005-213353 A

  An object of the present invention is to provide a rubber composition for tires that is compatible with wet grip performance and wear resistance.

  The rubber composition for tires of the present invention that achieves the above object is characterized in that 1 to 30 parts by mass of aluminum alkoxide is blended with 100 parts by mass of a diene rubber containing an aromatic vinyl-conjugated diene rubber.

  In the tire rubber composition of the present invention, aluminum alkoxide is blended in an amount of 1 to 30 parts by mass in 100 parts by mass of a diene rubber containing an aromatic vinyl-conjugated diene rubber as described above. Abrasion can be made compatible with the conventional level or more.

  The rubber composition for tire is formed by blending less than 120 parts by mass of silica and 20 parts by mass or more of carbon black with respect to 100 parts by mass of the diene rubber, and the carbon black with respect to 100% by mass in total of the silica and carbon black. The ratio is preferably 40% by mass or more. By blending silica and carbon black within such a range, it is possible to improve wet grip performance and durability of grip performance on dry road surfaces and wear resistance while achieving both wet grip performance and wear resistance. it can.

  Moreover, it is good to mix | blend 10-60 mass parts of hydrocarbon resins whose softening point is 60-180 degreeC with respect to 100 mass parts of said diene-type rubber | gum, and can make the wet grip performance still more excellent.

  The tire rubber composition described above is suitable for forming a tread for a pneumatic tire. A pneumatic tire made of the rubber composition for tires can achieve both wet grip performance and wear resistance at a higher level than ever.

  In the rubber composition for tires of the present invention, the rubber component is a diene rubber containing an aromatic vinyl conjugated diene rubber. Examples of the aromatic vinyl conjugated diene rubber include styrene butadiene rubber. The styrene butadiene rubber may be either solution polymerized styrene butadiene rubber or emulsion polymerized styrene butadiene rubber.

The amount of styrene in the styrene-butadiene rubber is not particularly limited, but is preferably 10 to 50% by mass, and preferably 15 to 45% by mass. If the styrene content of the styrene-butadiene rubber is less than 10% by mass, the rubber strength may be lowered and the grip performance may be reduced. Further, if the amount of styrene in the styrene-butadiene rubber exceeds 50% by mass, the wear resistance may be deteriorated. The amount of styrene in the styrene-butadiene rubber is measured by ¹ H-NMR.

The vinyl content of the styrene butadiene rubber is not particularly limited, but is preferably 5 to 80% by mass, more preferably 8 to 70% by mass. If the vinyl content of the styrene butadiene rubber is less than 5% by mass, grip performance may be reduced. On the other hand, if the vinyl content of the styrene butadiene rubber exceeds 80% by mass, it may become too hard and the grip performance may be reduced. The vinyl content of the styrene butadiene rubber is measured by ¹ H-NMR.

  The Tg of the styrene butadiene rubber is not particularly limited, but is preferably −40 ° C. or higher, and preferably −35 to 0 ° C. When the Tg of the styrene butadiene rubber is lower than −40 ° C., the wet grip performance is lowered. Further, when the Tg of the styrene butadiene rubber is higher than 0 ° C., the wear resistance is deteriorated. In this specification, the Tg of styrene-butadiene rubber is measured by a differential scanning calorimetry (DSC) under a temperature increase rate condition of 20 ° C./min, and is set as the temperature at the midpoint of the transition region. When the styrene butadiene rubber is an oil-extended product, the glass transition temperature of the styrene butadiene rubber in a state in which no oil-extended component (oil) is contained is used.

  The weight average molecular weight (Mw) of the styrene butadiene rubber is 500,000 to 2,000,000, preferably 600,000 to 1,800,000. When the Mw of the styrene butadiene rubber is less than 500,000, the rubber strength is lowered. Moreover, when Mw exceeds 2 million, the workability of a rubber composition will deteriorate. In this specification, the weight average molecular weight (Mw) of the styrene butadiene rubber is measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

  The content of styrene butadiene rubber in 100% by mass of the diene rubber is preferably 30 to 100% by mass, and more preferably 50 to 100% by mass. When the content of the styrene butadiene rubber is less than 50% by mass, the wet performance is deteriorated.

  The rubber composition for tires of the present invention can contain other diene rubbers other than styrene butadiene rubber. Other diene rubbers include, for example, natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (low cis BR), high cis BR, high trans BR (trans bond content of butadiene portion 70 to 95%), styrene -Isoprene copolymer rubber, butadiene-isoprene copolymer rubber, solution polymerization random styrene-butadiene-isoprene copolymer rubber, emulsion polymerization random styrene-butadiene-isoprene copolymer rubber, emulsion polymerization styrene-acrylonitrile-butadiene copolymer rubber, acrylonitrile- Examples thereof include butadiene copolymer rubber, high vinyl SBR-low vinyl SBR block copolymer rubber, polyisoprene-SBR block copolymer rubber, and polystyrene-polybutadiene-polystyrene block copolymer.

  The rubber composition for tires of this invention mix | blends 1-30 mass parts of aluminum alkoxide with 100 mass parts of diene rubbers. By blending aluminum alkoxide, the wet grip performance can be improved to a level higher than the conventional level while maintaining wear resistance. The compounding amount of the aluminum alkoxide is preferably 4 to 26 parts by mass, more preferably 8 to 22 parts by mass with respect to 100 parts by mass of the diene rubber. When the blending amount of the aluminum alkoxide is less than 1 part by mass, the effect of improving the wet grip performance cannot be obtained sufficiently. Moreover, when the compounding quantity of aluminum alkoxide exceeds 30 mass parts, wet grip performance will decline on the contrary.

  Aluminum alkoxide is a white powder and is used as a reaction reagent and catalyst in organic synthesis. The alkoxy group of the aluminum alkoxide preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms. Examples of the alkoxy group include methoxy, ethoxy, propyloxy, isopropyloxy, butyloxy, s-butyloxy, t-butyloxy, isobutyloxy, pentyloxy, isoamyloxy, t-amyloxy, hexyloxy, cyclohexyloxy, cyclohexylmethyloxy, tetrahydrofuran Nyloxy, tetrahydropyranyloxy, 2-methoxyethyloxy, 3-methoxypropyloxy, 4-methoxybutyloxy, 2-butoxyethyloxy, methoxyethoxyethyloxy, methoxyethoxyethoxyethyloxy, 3-methoxybutyloxy, 2 -Methylthioethyloxy, trifluoromethyloxy and the like.

  Examples of the aluminum alkoxide include aluminum alkyl alkoxide, cyclic aluminum oligomer, and aluminum chelate. Examples of the aluminum alkyl alkoxide include aluminum methoxide, aluminum ethoxide, aluminum isopropoxide, aluminum-n-butoxide, aluminum-s-butoxide, aluminum-t-butoxide, aluminum-n-hexyl, aluminum-n-octyl, Aluminum-n-decyl, aluminum-n-dodecyl, aluminum-cyclohexyl and the like can be mentioned. Examples of the aluminum chelate include diisopropoxy (ethylacetoacetate) aluminum and tris (ethylacetoacetate) aluminum. Especially, what has a C2-C5 alkyl alkoxy group is preferable.

  The rubber composition for tires of the present invention contains carbon black and silica. By blending carbon black and silica, the properties of the rubber composition including wet grip performance and wear resistance can be improved.

  The amount of carbon black is preferably 20 parts by mass or more, more preferably 20 to 120 parts by mass, and still more preferably 30 to 100 parts by mass with respect to 100 parts by mass of the diene rubber. Wear resistance can be maintained and improved by setting the blending amount of carbon black to 20 parts by mass or more.

  The amount of silica is preferably less than 120 parts by weight, more preferably 10 parts by weight or more and less than 120 parts by weight, and further preferably 20 to 100 parts by weight with respect to 100 parts by weight of the diene rubber. Wear resistance can be maintained and improved by making the compounding quantity of silica less than 120 mass parts.

  In the tire rubber composition of the present invention, the blending amount of carbon black and silica is within the above-described range, and the ratio of carbon black to 100% by mass of silica and carbon black is 40% by mass or more, preferably 50% by mass. That's it. Surprisingly, the amount of silica and carbon black that satisfies all of these requirements makes the wet grip performance, grip durability, and wear resistance of the dry road surface superior to conventional levels. be able to.

  Wet tires for competition are required to be able to handle all road conditions. If it is raining, use tires specialized for wet performance. However, when the road surface is wet but the rain stops, the road surface gradually dries out, so that the tire specialized for wet performance wears. On the other hand, a dry tire cannot exert a grip on a wet road surface. For this reason, wet tires are required to have a higher level of wet grip performance, wear resistance, and grip sustainability on a dry road surface. The rubber composition for tires of the present invention uses an aluminum alkoxide and makes the blending of silica and carbon black within a suitable range to achieve both wet grip performance, grip durability, and wear resistance on a dry road surface. be able to.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 200 to 400 m ² / g, more preferably 210 to 390 m ² / g. When N ₂ SA of carbon black is less than 200 m ² / g, grip performance is lowered. On the other hand, if the N ₂ SA of the carbon black exceeds 400 m ² / g, the wear resistance deteriorates. The N ₂ SA of carbon black is determined according to JIS K6217-2.

The N ₂ SA of silica is preferably 100 to 300 m ² / g, more preferably 110 to 290 m ² / g. When N ₂ SA of silica is less than 100 m ² / g, grip performance is deteriorated. If the N ₂ SA of silica exceeds 300 m ² / g, processing becomes difficult. N ₂ SA of silica is determined according to JIS K6217-2.

  As silica, silica usually used in a rubber composition for tires, for example, wet method silica, dry method silica, or surface-treated silica can be used.

  In the rubber composition for tires of the present invention, by adding a silane coupling agent together with silica, the dispersibility of silica can be improved and the reinforcement with diene rubber can be further enhanced. The silane coupling agent is preferably added in an amount of 2 to 20% by mass, more preferably 5 to 15% by mass, based on the amount of silica. When the compounding quantity of a silane coupling agent is less than 2 mass% of silica mass, the effect which improves the dispersibility of a silica is not fully acquired. Moreover, when a silane coupling agent exceeds 20 mass%, silane coupling agents will superpose | polymerize and it will become impossible to acquire a desired effect.

  Although it does not restrict | limit especially as a silane coupling agent, A sulfur containing silane coupling agent is preferable, for example, bis- (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide Bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3- Mercaptopropyltrimethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyldimethylmethoxysilane, 2-mercaptoethyltriethoxysilane, 3-mercaptopropyltriethoxysilane, and Evonik Mercaptosilane compounds exemplified in JP-A 2006-249069 such as VP Si363 manufactured by the company, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-trimethoxy Ethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, dimethoxymethyl Silylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide, 3-octanoylthiopropyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltri Ethoxysilane, vinyltris (2-methoxyethoxy) silane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-amino Examples include propyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, and the like. The Further, the silane coupling agent is an organosilicon compound. As the organosilicon compound, polysiloxane, polysiloxane side chain, or both ends, one end, or both side chains and both ends are amino groups, epoxy groups, carbinol groups, or mercapto. Silicone oil introduced with one or more organic groups such as a group, carboxyl group, hydrogen group, polyether group, phenol group, silanol group, acrylic group, methacryl group or long chain alkyl group, condensed with one or more organic silanes Examples include silicone oligomers obtained by reaction. Of these, bis- (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide are preferable.

  The rubber composition for tires of the present invention can be made more excellent in wet grip performance by blending a hydrocarbon resin (resin) having a softening point of preferably 60 to 180 ° C. The softening point of the hydrocarbon resin is more preferably 80 to 160 ° C. When the softening point of the hydrocarbon resin is less than 60 ° C., the effect of improving the grip performance cannot be obtained. When the softening point of the hydrocarbon resin exceeds 180 ° C., it is difficult to disperse it in the rubber. The softening point of the hydrocarbon resin is measured according to JIS K6220-1 (ring and ball method).

  The blending amount of the hydrocarbon resin is preferably 10 to 60 parts by mass, and preferably 10 to 40 parts by mass with respect to 100 parts by mass of the diene rubber. Grip performance cannot fully be improved as the compounding quantity of hydrocarbon resin is less than 10 mass parts. Moreover, when the compounding quantity of hydrocarbon resin exceeds 60 mass parts, heat_generation | fever becomes excessive and grip sustainability will fall.

  The hydrocarbon resin is not particularly limited. For example, natural resins such as terpene resins and rosin resins, synthetic resins such as petroleum resins, coal resins, phenol resins, xylene resins, and the like can be used. These modified products are exemplified. Among these, terpene resins and / or petroleum resins are preferable, and modified products of terpene resins are particularly preferable.

  As the terpene resin, for example, α-pinene resin, β-pinene resin, limonene resin, hydrogenated limonene resin, dipentene resin, terpene phenol resin, terpene styrene resin, aromatic modified terpene resin, hydrogenated terpene resin and the like are suitable. Can be mentioned. Of these, aromatic modified terpene resins are preferred.

  The aromatic modified terpene resin is obtained by polymerizing a terpene and an aromatic compound. Examples of terpenes include α-pinene, β-pinene, dipentene, and limonene. Examples of the aromatic compound include styrene, α-methylstyrene, vinyl toluene, indene and the like. Of these, a styrene-modified terpene resin is preferable as the aromatic-modified terpene resin. Such an aromatic modified terpene resin has good compatibility with the diene rubber, and thus can improve the dynamic viscoelasticity of the rubber composition and improve the wet grip performance and the heat build-up.

Examples of petroleum resins include aromatic hydrocarbon resins or saturated or unsaturated aliphatic hydrocarbon resins, such as C ⁵ petroleum resins (such as isoprene, 1,3-pentadiene, cyclopentadiene, methylbutene, and pentene). aliphatic petroleum resins obtained by polymerizing fraction), C ⁹ petroleum resins (alpha-methyl styrene, o- vinyltoluene, m- vinyltoluene, p- vinyl polymerized aromatic petroleum resin fractions such as toluene) and C ⁵ -C ⁹ copolymer petroleum resin.

  The tire rubber composition of the present invention can contain other fillers other than carbon black and silica. Examples of other fillers include inorganic fillers such as clay, aluminum hydroxide, calcium carbonate, mica, talc, aluminum hydroxide, aluminum oxide, titanium oxide, and barium sulfate, and organic fillers such as cellulose, lecithin, lignin, and dendrimer. Can be illustrated.

  In addition to the above components, the rubber composition for tires of the present invention includes a vulcanization or crosslinking agent, a vulcanization accelerator, an antioxidant, a processing aid, a plasticizer, a liquid polymer, a thermosetting resin, Various compounding agents generally used in tire rubber compositions such as thermoplastic resins can be blended. Such a compounding agent can be kneaded by a general method to obtain a rubber composition for tires, which can be used for vulcanization or crosslinking. The compounding amounts of these compounding agents can be the conventional general compounding amounts as long as they do not contradict the purpose of the present invention. The tire rubber composition for a tire tread can be prepared by mixing each of the above components using a known rubber kneading machine such as a Banbury mixer, a kneader, or a roll.

  The rubber composition for tires of the present invention can be suitably used as a rubber composition for treads of pneumatic tires. A pneumatic tire having a tread portion made of this rubber composition can improve the balance of wet grip performance and wear resistance during high speed running on a circuit or the like to a conventional level or higher. In addition, by making the blending amount of silica and carbon black within the suitable range, while maintaining both wet grip performance and wear resistance, wet grip performance on dry road surfaces, durability of the grip performance and wear resistance are excellent. Can be

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  Ingredients excluding sulfur and vulcanization accelerators for 11 types of tire rubber compositions (Examples 1 to 8 and Comparative Examples 1 to 3) having the composition shown in Table 1 with the compounding ingredients shown in Table 2 as common ingredients Was mixed for 6 minutes using a 1.8 L closed Banbury mixer, discharged from the mixer at 150 ° C., and then cooled to room temperature. Then, the rubber composition for tires was prepared by mixing again for 3 minutes using a 1.8 liter closed Banbury mixer, and after discharge | releasing and mixing sulfur and a vulcanization accelerator with an open roll.

  A pneumatic tire having a tire size of 195 / 55R15 was manufactured using the tire rubber composition obtained above for a tire tread portion. About these pneumatic tires, wet grip performance, wet grip performance on a dry road surface, durability of wet grip performance on a dry road surface, and wear resistance of a dry road surface were evaluated by the following methods.

Wet grip performance The resulting pneumatic tires are assembled on rims of size 15 x 6 J, filled with air pressure 200 kPa, mounted on four wheels of a test vehicle, and the test driver is in a wet condition circuit course (about 2 km per lap) The lap time for each lap when the lap was continuously run for 10 laps was measured. The obtained results are shown in “Wet Grip Performance” of Table 1 by calculating the reciprocal of the average lap time and using the value of Comparative Example 1 as 100. A larger index means faster average lap time and better wet grip performance.

Wet grip performance on dry road surface and its sustainability The obtained pneumatic tires are assembled on rims of size 15 x 6 J, filled with air pressure 200 kPa, mounted on four wheels of the test vehicle, and the test driver dries the road surface. The lap time for each lap when the circuit course (1 lap of about 2 km) was continuously run for 10 laps was measured. The obtained results are shown in “Wet grip performance (on dry road surface)” in Table 1 by calculating the reciprocal of the average lap time and taking the value of Comparative Example 1 as 100. The larger this index, the faster the average lap time, and the better the wet grip performance on the dry road surface.

  Moreover, when the circuit course which consists of a dry road surface was circulated, the time when the average lap time of 9th to 10th lap was delayed was measured with respect to the average lap time of 3rd to 4th lap, and the reciprocal number was calculated. The obtained results are shown in “Sustainability (on dry road surface)” in Table 1 as an index with the value of Comparative Example 1 as 100. The larger this index is, the less the average lap time is decreased, which means that the wet grip performance on the dry road surface is excellent.

Wear resistance of dry road surface The pneumatic tires obtained above are assembled on rims of size 15 x 6 J, filled with air pressure 200 kPa, mounted on four wheels of a test vehicle, and the test driver is made of dry road surface The circuit course (about 2 km per lap) was run continuously for 10 laps, and then the groove depth in the tread of the pneumatic tire was measured. The obtained results are shown in “Abrasion resistance (on dry road surface)” in Table 1 as an index with the value of Comparative Example 1 being 100. It means that the higher the index is, the better the abrasion resistance of the road surface that has been dried.

In Table 1, the types of raw materials used are as follows.
SBR: emulsion-polymerized styrene butadiene rubber, Nipol 1739 manufactured by Nippon Zeon Co., Ltd., styrene content 40 mass%, vinyl content 14%, glass transition temperature -31 ° C., weight average molecular weight 720,000, styrene butadiene rubber 00 mass Oil-extracted product with 37.5 parts by mass of oil component added to silica: Silos Zeosil 1165MP, N ₂ SA = 165 m ² / g
・ Carbon black, Toast carbon company's seast 9, N ₂ SA = 142 m ² / g
Aluminum hydroxide: Showa Denko Co., Ltd. Heidilite H-43
Aluminum alkoxide-1: Aluminum ethoxide, aluminum ethoxide manufactured by Kawaken Fine Chemical Co., Ltd. Aluminum alkoxide-2: Aluminum isopropoxide, Kawaken Fine Chemical PADM
Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide, Si69 manufactured by Evonik
Resin: Aromatic modified terpene resin having a softening point of 145 ° C., YS Resin T-145 manufactured by Yasuhara Chemical Co., Ltd.
・ Oil: Extract No. 4 S manufactured by Showa Shell Sekiyu KK

In addition, the kind of raw material used in Table 2 is shown below.
-Zinc flower: Zinc oxide 3 types manufactured by Shodo Chemical Industry Co., Ltd.-Stearic acid: Beads stearic acid YR manufactured by NOF Corporation
-Anti-aging agent: 6PPD manufactured by Flexis
・ Sulfur: Fine powder sulfur with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd. ・ Vulcanization accelerator-1: Vulcanization accelerator CBS, Noxeller CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.
-Vulcanization accelerator-2: Vulcanization accelerator DPG, Nouchira D manufactured by Ouchi Shinsei Chemical Co., Ltd.

  As is clear from Table 1, it was confirmed that the rubber compositions for tires of Examples 1 to 8 were excellent in wet grip performance and wear resistance. In addition, it was confirmed that the rubber compositions for tires of Examples 1 to 6 were excellent in wet grip performance on a dry road surface and its sustainability.

  The rubber composition for tires of Comparative Example 2 is inferior in wear resistance because aluminum hydroxide is blended in place of aluminum alkoxide.

  In the rubber composition for tires of Comparative Example 3, since the compounding amount of aluminum alkoxide exceeds 30 parts by mass, the wet grip performance is deteriorated.

Claims (5)

  A tire rubber composition comprising 1 to 30 parts by mass of an aluminum alkoxide in 100 parts by mass of a diene rubber containing an aromatic vinyl-conjugated diene rubber.   Silica is less than 120 parts by weight and carbon black is blended by 20 parts by mass or more with respect to 100 parts by mass of the diene rubber, and the ratio of the carbon black to the total of 100% by mass of the silica and carbon black is 40% by mass or more The tire rubber composition according to claim 1, wherein:   The rubber composition for tires according to claim 1 or 2, comprising 10 to 60 parts by mass of a hydrocarbon resin having a softening point of 60 to 180 ° C with respect to 100 parts by mass of the diene rubber. .   The tire rubber composition according to any one of claims 1 to 3, which is formed by forming a tread of a pneumatic tire.   A pneumatic tire comprising the rubber composition for a tire according to any one of claims 1 to 4.