JP2014080550A - Rubber composition for tread of high-performance wet tire, and high-performance wet tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for the tread of a high-performance wet tire, which can improve wet grip performance, dry grip performance, and wear resistance in a balanced manner, and a high-performance wet tire having the tread made using the rubber composition.SOLUTION: This invention relates to a rubber composition for the tread of a high-performance wet tire which contains a rubber component, carbon nanotube, and zinc oxide with an average primary particle diameter of 200 nm or less. The carbon nanotube is preferably carbon nanotube not subjected to graphitization treatment.

Description

The present invention relates to a rubber composition for a tread of a high-performance wet tire and a high-performance wet tire using the same.

Rubber compositions for treads of high-performance wet tires are strongly required to improve wet grip performance, dry grip performance (dry grip performance) and wear resistance in a well-balanced manner, ensuring these performances. Therefore, various devices have been conventionally made. For example, as a method for improving the wet grip performance, it is known to blend silica as a filler or to blend carbon black having a small particle size in a high filling.

However, these methods have room for improvement in that wear resistance decreases. Also, it has been proposed to ensure wet grip performance by blending aluminum hydroxide, but when blended in a large amount, the wear resistance tends to deteriorate significantly.

Therefore, as another method, a method using carbon black having a fine structure and a high structure has been studied. The fine particles can increase the hysteresis loss and improve the dry grip performance, and the high structure can increase the modulus and improve the wear resistance.

However, if carbon black with fine structure and high structure is used, the rubber becomes extremely hard, so the wet grip performance tends to decrease, and it is necessary to adjust the hardness of the rubber by increasing the amount of plasticizer. Also, the wear resistance tends to decrease due to the increase of the plasticizer. Thus, it has been difficult to improve the wet grip performance, the dry grip performance, and the wear resistance with a conventional method in a well-balanced manner.

Patent Document 1 describes a method for increasing the modulus using carbon nanotubes, but there is still room for improvement in terms of improving wet grip performance, dry grip performance, and wear resistance in a well-balanced manner. .

JP 2009-46547 A

The present invention has a rubber composition for a high-performance wet tire tread that can solve the above-mentioned problems and can improve wet grip performance, dry grip performance and wear resistance in a well-balanced manner, and a tread produced using the rubber composition. An object is to provide a high-performance wet tire.

The present invention relates to a rubber composition for a tread for a high-performance wet tire comprising a rubber component, carbon nanotubes, and zinc oxide having an average primary particle diameter of 200 nm or less.

The carbon nanotubes are preferably carbon nanotubes that have not been graphitized.

The fiber diameter of the carbon nanotube is preferably 5 to 200 nm.

The fiber length of the carbon nanotube is preferably 1 to 50 μm.

The bulk density of the carbon nanotube is preferably 0.03 g / cm ³ or more.

The carbon nanotubes are preferably vapor grown carbon fibers synthesized by chemical vapor deposition.

It is preferable that content of the said carbon nanotube with respect to 100 mass parts of said rubber components is 0.1-10 mass parts.

The rubber composition preferably contains an inorganic compound represented by the following formula (M).
kM ₁ · xSiO _y · zH ₂ O (M)
(In Formula (M), M ₁ is at least one metal selected from the group consisting of Al, Mg, Ti and Ca, an oxide or hydroxide of the metal, k is an integer of 1 to 5, x Is an integer from 0 to 10, y is an integer from 2 to 5, and z is an integer from 0 to 10.)

It is preferable that content of the said zinc oxide with respect to 100 mass parts of said rubber components is 0.1-10 mass parts.

The present invention also relates to a high-performance wet tire having a tread produced using the rubber composition.

According to the present invention, since it is a rubber composition for a tread of a high-performance wet tire containing a rubber component, carbon nanotubes, and zinc oxide having an average primary particle diameter of 200 nm or less, wet grip performance, dry grip performance, and abrasion resistance The sex can be improved in a well-balanced manner.

The rubber composition for a tread of the high performance wet tire tire of the present invention includes a rubber component, carbon nanotubes (CNT), and zinc oxide having an average primary particle diameter of 200 nm or less (fine particle zinc oxide).

As described above, the use of fine particle and high structure carbon black can improve the dry grip performance and wear resistance, but the rubber becomes extremely hard and there is room for improvement in that the wet grip performance is reduced. there were. In addition, there is room for improvement in that an increase in the amount of plasticizer is required, leading to a decrease in wear resistance. On the other hand, in the present invention, by using the rubber component, CNT, and fine particle zinc oxide in combination, the dry grip performance and the wear resistance can be improved without significantly hardening the rubber. While ensuring, dry grip performance and wear resistance can be improved. Further, since it is not necessary to increase the amount of plasticizer, it is possible to prevent a decrease in wear resistance due to an increase in the plasticizer. By these actions, a better result than the conventional one can be obtained in the average time at the time of circuit evaluation.

The CNT is preferably CNT that has not been graphitized. Since the non-graphitized CNT has a lower orientation than the graphitized CNT, the wet grip performance, the dry grip performance, and the wear resistance can be improved on the entire surface of the tire tread. Further, from the viewpoint of suppressing an increase in cost, the CNT is preferably a vapor grown carbon fiber synthesized by a chemical vapor deposition method (CVD method).

The fiber diameter of the CNT is preferably 5 nm or more, more preferably 7 nm or more, still more preferably 10 nm or more, preferably 200 nm or less, more preferably 100 nm or less, still more preferably 80 nm or less. If it is less than 5 nm, it is difficult to sufficiently disperse in the kneading step, and the reinforcing property may be lowered. If it exceeds 200 nm, sufficient wet grip performance and dry grip performance may not be exhibited.

The fiber length of CNT is preferably 1 μm or more, more preferably 2 μm or more, preferably 50 μm or less, more preferably 30 μm or less, still more preferably 20 μm or less, and particularly preferably 8 μm or less. If it is less than 1 μm, sufficient modulus cannot be secured, and good wear resistance may not be obtained. When it exceeds 50 μm, it is difficult to sufficiently disperse in the kneading step, and the reinforcing property may be lowered.

The fiber diameter and fiber length of CNT are the average values determined by image analysis of transmission micrographs.

The bulk density of the CNT is preferably 0.03 g / cm ³ or more, more preferably 0.04 g / cm ³ or more, further preferably 0.05 g / cm ³ or more. If it is less than 0.03 g / cm ³ , the bulk is too high, and the workability at the time of feeding into the weighing and kneading apparatus tends to be poor. The upper limit of the bulk density is not particularly limited, but is preferably 0.50 g / cm ³ or less, more preferably 0.10 g / cm ³ or less.

The content of CNT is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, preferably 10 parts by mass or less, more preferably 5 parts by mass or less, with respect to 100 parts by mass of the rubber component. It is. If it is less than 0.1 parts by mass, sufficient wet grip performance and dry grip performance may not be exhibited. When it exceeds 10 parts by mass, CNTs are difficult to disperse and wear resistance tends to be reduced.

The rubber composition of the present invention contains zinc oxide having a specific average primary particle size (fine particle zinc oxide). By blending the fine particle zinc oxide together with the CNT, the dispersibility of the fine particle zinc oxide and the dispersibility of the CNT can be synergistically improved, and wet grip performance, dry grip performance and wear resistance can be improved in a well-balanced manner.

The average primary particle diameter of the fine particle zinc oxide is 200 nm or less, preferably 150 nm or less, more preferably 140 nm or less, and still more preferably 130 nm or less. If it exceeds 200 nm, the effect of improving the dispersibility of CNTs cannot be sufficiently obtained, and the dispersion failure becomes the core of blow, and blowout is likely to occur. The average primary particle diameter of the fine particle zinc oxide is preferably 20 nm or more, more preferably 30 nm or more. If it is less than 20 nm, CNTs tend to be sufficiently difficult to disperse due to aggregation of particles of fine zinc oxide.

In the present invention, the average primary particle diameter of zinc oxide is the primary particle diameter when converted from a BET specific surface area measured by the BET method to a true spherical particle model.
Here, the primary particle diameter when converted from the BET specific surface area to the true spherical particle model can be calculated by the following relational expression. When primary particles are regarded as ideal spheres, the relationship represented by the following formula is established among the surface area (S), volume (V), density (ρ) and specific surface area (SSA) of one particle. To do.
SSA = 1 / (V · ρ) × S
Here, since V and S are physical quantities that are uniquely determined by the particle diameter, the particle diameter can be obtained from the specific surface area and density. The density can be easily determined by, for example, a commercially available pycnometer.

The content of the fine zinc oxide is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and still more preferably 0.3 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.1 parts by mass, the effect of improving the dispersibility of CNTs tends to be insufficient. Further, the content of the fine zinc oxide is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, still more preferably 7 parts by mass or less, and particularly preferably 4 parts by mass or less. When the amount exceeds 10 parts by weight, the fine zinc oxide is difficult to disperse, and the aggregate of fine zinc oxide becomes the core of the blow, which may cause blowout.

The rubber composition of the present invention can be arbitrarily selected from fillers conventionally used in rubber compositions for tires such as carbon black, silica, calcium carbonate, etc. in addition to CNTs. Of these, carbon black and silica are preferably used.

The carbon black is not particularly limited, and for example, carbon black produced by an oil furnace method widely used in the world can be used. Moreover, about carbon black, you may use together the thing from which two or more types of colloidal characteristics differ.

The N ₂ SA (nitrogen adsorption specific surface area) of carbon black is preferably 100 m ² / g or more, more preferably 105 m ² / g or more, still more preferably 110 m ² / g or more, preferably 600 m ² / g or less. More preferably, it is 550 m < ² > / g or less, More preferably, it is 530 m < ² > / g or less. If it is less than 100 m < ² > / g, there exists a tendency for wet grip performance and dry grip performance to fall. If it exceeds 600 m ² / g, good dispersion is difficult to obtain, and the wear resistance tends to decrease.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

The carbon black content is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more, preferably 80 parts by mass or less, more preferably 100 parts by mass of the rubber component. Is 50 parts by mass or less, more preferably 40 parts by mass or less. If it is less than 10 parts by mass, sufficient wet grip performance and dry grip performance may not be exhibited. If it exceeds 80 parts by mass, the carbon black is difficult to disperse, and the wear resistance tends to decrease.

The total content of CNT and carbon black is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, and preferably 170 parts by mass or less with respect to 100 parts by mass of the rubber component. More preferably, it is 150 mass parts or less, More preferably, it is 120 mass parts or less. If it is less than 30 parts by mass, sufficient wet grip performance and dry grip performance may not be exhibited. When it exceeds 170 parts by mass, CNT and carbon black are difficult to disperse, and wear resistance tends to be reduced.

The silica is not particularly limited, and, for example, dry method silica (anhydrous silica), wet method silica (hydrous silica) and the like widely used in the world can be used.

The cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of silica is preferably 100 to 300 m ² / g because good wet grip performance, dry grip performance and wear resistance can be obtained. Moreover, it is preferable that the dibutyl phthalate oil absorption (DBP) of a silica is 150-300 mL / 100g for the same reason.
In addition, the cetyltrimethylammonium bromide adsorption specific surface area of silica is a value measured according to ASTM D3765-80, and the dibutyl phthalate oil absorption is a value measured according to the method described in JIS K 6221 6.1.2 A method.

The content of silica is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, preferably 100 parts by mass or less, more preferably 80 parts by mass or less with respect to 100 parts by mass of the rubber component. If it is less than 30 parts by mass, sufficient wet grip performance and dry grip performance may not be exhibited. When the amount exceeds 100 parts by mass, silica is difficult to disperse and wear resistance tends to be reduced.

Silica is preferably used in combination with a silane coupling agent. As the silane coupling agent, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide and the like are suitable. The content of the silane coupling agent is preferably 5 to 20 parts by mass with respect to 100 parts by mass of silica.

In the present invention, it is preferable to use an inorganic compound represented by the following formula (M) as the filler. Thereby, wet grip performance and dry grip performance can be improved more.
kM ₁ · xSiO _y · zH ₂ O (M)
(In Formula (M), M ₁ is at least one metal selected from the group consisting of Al, Mg, Ti and Ca, an oxide or hydroxide of the metal, and k is 1 to 5 (preferably 1). -3, more preferably 1), x is an integer of 0-10 (preferably 0-5, more preferably 0), y is an integer of 2-5, z is 0-10 (preferably 0-5). , More preferably an integer of 0).

Examples of the inorganic compound represented by the above formula (M) include alumina, alumina hydrate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, talc, titanium white, titanium black, calcium oxide, calcium hydroxide, and aluminum magnesium oxide. Clay, pyrophyllite, bentonite, aluminum silicate, magnesium silicate, calcium silicate, aluminum calcium silicate, magnesium silicate and the like. These inorganic compounds may be used alone or in combination of two or more. Of these inorganic compounds, aluminum hydroxide, magnesium hydroxide, clay, alumina, and alumina hydrate are preferable, and aluminum hydroxide is more preferable because wet grip performance and dry grip performance can be further improved.

The average primary particle diameter of the inorganic compound is preferably 0.5 μm or more, more preferably 0.8 μm or more. If the thickness is less than 0.5 μm, it is difficult to disperse the inorganic compound, and the wear resistance tends to decrease. The average primary particle size is preferably 10 μm or less, more preferably 5 μm or less. When it exceeds 10 μm, the inorganic compound becomes a fracture nucleus and wear resistance tends to decrease.
In the present invention, the average primary particle size of the inorganic compound is a number average particle size and is measured by a transmission electron microscope.

The content of the inorganic compound is preferably 10 parts by mass or more, more preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, there is a possibility that the effect of improving wet grip performance and dry grip performance cannot be obtained sufficiently. The content of the inorganic compound is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less. If it exceeds 60 parts by mass, poor dispersion may occur and wear resistance may be reduced.

Among the total content of the inorganic compound, carbon black and silica, 100% by mass, the content of the inorganic compound is 10 to 60% by mass, the content of carbon black is 0 to 50% by mass, and the content of silica is 40 to 90%. It is preferable that it is mass%. By adjusting within the above range, good wet grip performance, dry grip performance and wear resistance can be obtained.

Examples of rubber components that can be used in the present invention include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), and ethylene propylene diene rubber ( EPDM), diene rubbers such as chloroprene rubber (CR) and acrylonitrile butadiene rubber (NBR). A rubber component may be used independently and may use 2 or more types together. Of these, NR, BR, and SBR are preferable, and SBR is more preferable because wet grip performance, dry grip performance, and wear resistance can be improved in a well-balanced manner.

The SBR is not particularly limited, and for example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR), and the like can be used.

The styrene content of SBR is preferably 20% by mass or more, and more preferably 25% by mass or more. If it is less than 20% by mass, sufficient wet grip performance and dry grip performance tend not to be obtained. Moreover, 60 mass% or less is preferable and, as for the styrene content rate of SBR, 50 mass% or less is more preferable. When it exceeds 60% by mass, not only the wear resistance decreases, but also the temperature dependency increases, and the performance change with respect to the temperature change tends to increase.

The content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 60% by mass or more. When it is less than 50% by mass, sufficient heat resistance tends to be not obtained. The upper limit of the content of SBR is not particularly limited, and may be 100% by mass.

In addition to the above components, the rubber composition of the present invention includes compounding agents generally used in the production of rubber compositions such as softeners, stearic acid, various anti-aging agents, resins, tackifiers, waxes, additives. A sulfur accelerator or the like can be appropriately blended.

Although it does not specifically limit as a softener which can be used by this invention, For example, mineral oils, such as aromatic oil, process oil, paraffin oil, will be mentioned if it is oil. A low molecular weight liquid polymer may be used as a softening agent. These may be used alone or in combination of two or more. Among these, it is preferable to use a liquid polymer because wet grip performance, dry grip performance and wear resistance can be improved in a well-balanced manner.

Examples of the liquid polymer include liquid SBR, liquid BR, liquid IR, and liquid SIR. The reason that wet grip performance, dry grip performance, and wear resistance can be improved in a well-balanced manner, and that good processability is also obtained. Therefore, liquid SBR and liquid IR are preferable, and liquid SBR is more preferable.

The number average molecular weight (Mn) of the liquid polymer is preferably 1.0 × 10 ^{3 to} 2.0 × 10 ⁵ , more preferably 2.0 × 10 ^{3 to} 1.0 × 10 ⁵ , and still more preferably 3.0. It is * 10 < ³ > -2.0 * 10 < ⁴ >. If it is less than 1.0 × 10 ³ , the fracture characteristics are deteriorated and sufficient durability may not be ensured. On the other hand, when it exceeds 2.0 × 10 ⁵ , the viscosity of the polymerization solution becomes too high, and the productivity may be deteriorated.

In this specification, the number average molecular weight (Mn) is a gel permeation chromatograph (GPC) (GPC-8000 series manufactured by Tosoh Corp., detector: differential refractometer, column: TSKGEL manufactured by Tosoh Corp. It is calculated | required by standard polystyrene conversion based on the measured value by SUPERMULTIPORE HZ-M).

The content of the liquid polymer is preferably 15 parts by mass or more, more preferably 35 parts by mass or more, and further preferably 45 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 15 parts by mass, the effect of blending the liquid polymer may not be sufficiently obtained. Further, the content of the liquid polymer is preferably 100 parts by mass or less, more preferably 80 parts by mass or less. If it exceeds 100 parts by mass, the wear resistance may be reduced.

Although it does not specifically limit as resin which can be used by this invention, It is preferable to mix | blend an aromatic petroleum resin. Aromatic petroleum resins include phenolic resins, coumarone indene resins, styrene resins, rosin resins, DCPD resins, and the like. Among these, a coumarone indene resin is preferable because the effects of the present invention can be more suitably obtained.

Coumarone indene resin is a resin containing coumarone and indene as a monomer component constituting the skeleton (main chain) of the resin, and monomer components contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, Examples thereof include methylindene and vinyltoluene.

The softening point of the aromatic petroleum resin is preferably 70 ° C. or higher, more preferably 80 ° C. or higher. If it is less than 70 ° C., sufficient wear resistance may not be obtained. The softening point is preferably 170 ° C. or lower, more preferably 140 ° C. or lower, and still more preferably 120 ° C. or lower. If it exceeds 170 ° C., the wet grip performance and the dry grip performance tend to decrease.
The softening point of the aromatic petroleum resin is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1: 2001 is measured with a ring and ball softening point measuring device.

The content of the aromatic petroleum resin is preferably 10 parts by mass or more, more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, there is a possibility that the effect of improving wet grip performance and dry grip performance cannot be obtained sufficiently. Moreover, this content becomes like this. Preferably it is 60 mass parts or less, More preferably, it is 40 mass parts or less. If it exceeds 60 parts by mass, the temperature dependency increases, and the performance change with respect to the temperature change tends to increase.

Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Etc. These may be used alone or in combination of two or more. Of these, sulfenamides and thiazoles are preferable, and sulfenamides and thiazoles are more preferably used in combination.

Examples of the sulfenamide vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N -Dicyclohexyl-2-benzothiazolylsulfenamide (DCBS) and the like. Of these, N-cyclohexyl-2-benzothiazolylsulfenamide is preferable.

0.1-5 mass parts is preferable with respect to 100 mass parts of rubber components, and, as for content of a sulfenamide-type vulcanization accelerator, 0.5-2.5 mass parts is more preferable.

Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and the like. Of these, 2-mercaptobenzothiazole is preferable.

0.1-3 mass parts is preferable with respect to 100 mass parts of rubber components, and, as for content of a thiazole type vulcanization accelerator, 0.2-1 mass part is more preferable.

As a method for producing the rubber composition for tires of the present invention, known methods can be used. For example, the above components are kneaded using a rubber kneader such as an open roll or a Banbury mixer, and then vulcanized. Etc. can be manufactured.

The rubber composition of the present invention can be used for a tread (cap tread) of a high-performance wet tire. In addition, the high-performance wet tire in this specification is a pneumatic tire that is particularly excellent in wet grip performance, and includes a concept for a competition tire for a wet road surface used in a competition vehicle.

The high-performance wet tire of the present invention is produced by a normal method using the rubber composition. That is, the rubber composition containing the above components is extruded in accordance with the shape of the tread at an unvulcanized stage and molded together with other tire members on a tire molding machine by a normal method. Form a vulcanized tire. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
SBR: NS522 manufactured by Nippon Zeon Co., Ltd. (styrene content: 39% by mass, 37.5 parts by mass of oil with respect to 100 parts by mass of rubber solid content)
Carbon black 1: Seast 9 (SAF, N ₂ SA: 142 m ² / g) manufactured by Tokai Carbon Co., Ltd.
Carbon black 2: Seast 6 manufactured by Tokai Carbon Co., Ltd. (ISAF, N ₂ SA: 119 m ² / g)
Carbon nanotube 1: VGCF manufactured by Showa Denko Co., Ltd. (gas phase carbon fiber synthesized by CVD method (with graphitization treatment), fiber diameter: 150 nm, fiber length: 10 to 20 μm, bulk density: 0.04 g / cm ³ )
Carbon nanotube 2: VGCF-X (shown by Showa Denko KK) (gas phase carbon fiber synthesized by CVD method (no graphitization treatment), fiber diameter: 10 to 15 nm, fiber length: 3 μm, bulk density: 0. 08 g / cm ³ )
Silica: Nipsil VN3 (N ₂ SA: 175 m ² / g) manufactured by Nippon Silica Kogyo Co., Ltd.
Aluminum hydroxide: Heidilite H-43 (average primary particle size: 1 μm) manufactured by Showa Denko KK
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Oil: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Liquid SBR: L-SBR-820 (Mn: 8500) manufactured by Kuraray
Resin: Escron G90 (Coumarone Indene resin, softening point: 90 ° C.) manufactured by Nikko Chemical Co., Ltd.
Zinc oxide 1: 2 types of zinc oxide manufactured by Mitsui Kinzoku Co., Ltd. (average primary particle size: 400 nm)
Zinc oxide 2: Zincock Super F-2 (average primary particle size: 65 nm) manufactured by Hakusui Tech Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Sulfur: Powder sulfur vulcanization accelerator made by Karuizawa Sulfur Co., Ltd. CZ: Noxeller CZ (N-cyclohexyl-2-benzothiazylsulfenamide) made by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator M: Noxeller M (2-mercaptobenzothiazole) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<Method for producing rubber composition>
In accordance with the formulation shown in Table 1, materials other than sulfur and a vulcanization accelerator were kneaded using 1.7 L Banbury manufactured by Kobe Steel. Sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tread shape, bonded together with other tire members on a tire molding machine, vulcanized at 150 ° C. for 30 minutes, and a test tire (tire size: 215). / 45R17).

(Wet grip performance)
The test tire was mounted on a domestic FR vehicle with a displacement of 2000 cc, and the vehicle was run for 10 laps on a wet asphalt road test course. The test driver evaluated the stability of the control at the time of steering at that time, and the comparative example 1 was set to 100 and indicated as an index. The larger the value, the higher the grip performance on the wet road surface.

(Grip performance during dry-up)
The test tire was mounted on a 2000 cc domestic FR vehicle, and the vehicle traveled 10 laps on a dry asphalt road test course. The test driver evaluated the stability of the control at the time of steering at that time, and the comparative example 1 was set to 100 and indicated as an index. The larger the value, the higher the grip performance on the dry road surface.

(Abrasion resistance during dry-up)
The test tire was mounted on a domestic FR vehicle with a displacement of 2000 cc, and the vehicle was run for 30 laps on a test course on a road surface (dry up road surface) that changed from a wet road surface to a dry road surface. The remaining groove amount of the tire tread rubber at that time was measured, and the index was displayed with Comparative Example 1 as 100. The larger the value, the greater the remaining groove amount and the higher the wear resistance.

From the results shown in Table 1, the examples in which CNT and zinc oxide having a specific average primary particle size (zinc oxide 2) are used in combination have synergistically improved wet grip performance, dry grip performance, and wear resistance. The performance was obtained in a well-balanced and high dimension.

Claims (10)

A rubber composition for a tread for a high-performance wet tire, comprising a rubber component, carbon nanotubes, and zinc oxide having an average primary particle diameter of 200 nm or less. The rubber composition for a tread of a high-performance wet tire according to claim 1, wherein the carbon nanotube is a carbon nanotube that has not been graphitized. The rubber composition for a tread of a high-performance wet tire according to claim 1 or 2, wherein the carbon nanotube has a fiber diameter of 5 to 200 nm. The rubber composition for a tread of a high-performance wet tire according to any one of claims 1 to 3, wherein the carbon nanotube has a fiber length of 1 to 50 µm. The rubber composition for a tread of a high-performance wet tire according to any one of claims 1 to 4, wherein the carbon nanotube has a bulk density of 0.03 g / cm ³ or more. The rubber composition for a tread of a high performance wet tire according to any one of claims 1 to 5, wherein the carbon nanotube is a vapor grown carbon fiber synthesized by a chemical vapor deposition method. The rubber composition for a tread of a high-performance wet tire according to any one of claims 1 to 6, wherein a content of the carbon nanotube with respect to 100 parts by mass of the rubber component is 0.1 to 10 parts by mass. The rubber composition for a tread of a high performance wet tire according to any one of claims 1 to 7, comprising an inorganic compound represented by the following formula (M).
kM ₁ · xSiO _y · zH ₂ O (M)
(In Formula (M), M ₁ is at least one metal selected from the group consisting of Al, Mg, Ti and Ca, an oxide or hydroxide of the metal, k is an integer of 1 to 5, x Is an integer from 0 to 10, y is an integer from 2 to 5, and z is an integer from 0 to 10.) The rubber composition for a tread of a high-performance wet tire according to any one of claims 1 to 8, wherein the content of the zinc oxide with respect to 100 parts by mass of the rubber component is 0.1 to 10 parts by mass. A high-performance wet tire having a tread produced using the rubber composition according to claim 1.