JP2019107979A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire excellent in durability under high temperature and high speed conditions while maintaining ice performance. A pneumatic tire including a tread block having an average sipe density of 1.0 cm/cm 2 or more and an average height of 0.6 to 2.0 cm, wherein the tread block has a mass of 30 to 50. % Isoprene-based rubber, 30-60 mass% butadiene rubber, and 5-30 mass% modified butadiene rubber 100 mass parts of the rubber component, 30-45 mass parts of carbon black, 20-40 mass parts of silica And a rubber composition for a cap tread containing 1.0 to 1.5 parts by mass of sulfur. [Selection diagram] None

Description

  The present invention relates to a pneumatic tire having a predetermined tread block.

  The tread of the conventional studless tire is provided with a tread block having a low hardness at both high and low temperatures and containing sipes in order to exert grip on a snowy and snowy road surface. However, such tread blocks are susceptible to chipping around sipes and have problems with durability at high temperatures and high speeds.

  In recent years, studless tires are also required to have durability that can withstand use outside of icy roads and use in summer. For example, although the method of covering a part of tread surface with the coating layer which consists of hard rubber is described in patent document 1, a structure is complicated, manufacturing efficiency is bad, and the improvement effect of durability is not enough either.

JP, 2009-154791, A

  An object of the present invention is to provide a pneumatic tire excellent in durability under high temperature and high speed conditions while maintaining the performance on ice.

The present invention is a pneumatic tire provided with a tread block having an average sipe density of 1.0 cm / cm ² or more and an average height of 0.6 to 2.0 cm, wherein the tread block is 30 to 50. 30 to 45 parts by mass of carbon black, 20 to 40 parts by mass of 100 parts by mass of a rubber component containing isoprene-based rubber, 30 to 60% by mass of butadiene rubber and 5 to 30% by mass of modified butadiene rubber The present invention relates to a pneumatic tire constituted of a rubber composition for a cap tread containing silica and 1.0 to 1.5 parts by mass of sulfur.

  The pneumatic tire of the present invention having a predetermined tread block is a pneumatic tire excellent in durability under high temperature and high speed conditions while maintaining the performance on ice.

The pneumatic tire according to the present invention is a pneumatic tire provided with a tread block having an average sipe density of 1.0 cm / cm ² or more and an average height of 0.6 to 2.0 cm, wherein the tread block is 30 to 45 parts by mass of carbon black, 20 to 50 parts by mass of 100 parts by mass of a rubber component containing 30 to 50% by mass of isoprene rubber, 30 to 60% by mass of butadiene rubber and 5 to 30% by mass of modified butadiene rubber The rubber composition is characterized by comprising a rubber composition for a cap tread containing 40 parts by mass of silica and 1.0 to 1.5 parts by mass of sulfur.

  By distributing the rubber component of the rubber composition for the cap tread to the isoprene rubber and the butadiene rubber and blending a small amount of the modified butadiene rubber, it is also possible to distribute the silica which tends to be unevenly distributed in the isoprene rubber phase to the butadiene rubber phase It is possible to increase the dispersibility of the butadiene rubber phase silica. As a result, the tensile stress (modulus) of the entire rubber composition can be reduced. In addition, by increasing the dispersibility of silica, tan δ at high temperature can be reduced.

  Furthermore, by incorporating more sulfur as a vulcanizing agent than usual, the crosslinking was increased and the molecular weight was increased, whereby the modulus of the entire rubber composition was improved. Here, since the decrease width of the modulus at high temperature is smaller in the high molecular weight polymer than in the low molecular weight polymer, the modulus rise is larger at low temperature, and as a result, the low temperature modulus of the rubber composition High temperature modulus and high temperature tan δ can be lowered.

  As a result of the above, according to the present invention, since the high temperature tan δ (for example, tan δ at 100 ° C.) is lowered, the equilibrium temperature of the tread surface at high speed running in summer (high temperature environment) can be around 100 ° C. This makes it difficult for the modulus (high temperature modulus) at 100 ° C. to drop from normal temperature, and the durability under high temperature and high speed conditions can be improved.

In the present specification, the "average sipe density" represents a value obtained by dividing the sum of the longitudinal distances of the sipe by the area of the entire contact surface. In the pneumatic tire according to the present embodiment, the average sipe density of the blocks may be 1.0 cm / cm ² or more, but it is preferably 1.3 cm / cm because the effects of the present invention can be favorably obtained. ^{It is 2} or more, more preferably 1.5 cm / cm ² or more. Although the upper limit is not particularly limited, it is usually 3.0 cm / cm ² or less.

  The "sipe" is a groove having a width of 1.5 mm or less and a depth of 8 mm or less in the contact surface. The above-mentioned "longitudinal distance of sipes" refers to the distance in the longitudinal direction of the circumscribed rectangle that is the smallest area of the sipes. The above-mentioned "contact surface" refers to a surface which comes in contact with the road surface when a tire is mounted on a standard rim and filled with a standard internal pressure, placed vertically on a plane and subjected to a normal load.

  In the present specification, the “average height of the block” represents the average value of the tire radial direction distance from each point on the tread surface to the innermost tire radial direction depth at the bottom of the main groove of the tread. In the pneumatic tire according to the present embodiment, the average height of the blocks may be 0.6 to 2.0 cm, but the lower limit is preferably 0. 6, because the effects of the present invention can be favorably obtained. It is 8 cm or more, more preferably 1.0 cm or more, and the upper limit is preferably 1.6 cm or less, more preferably 1.4 cm or less.

  The "main groove" refers to a groove having a width of 2 mm or more and a depth of 9 mm or more in the ground contact surface, and having the largest width and depth.

  Examples of the isoprene rubber include natural rubber and polyisoprene rubber (IR). Examples of natural rubber include natural rubber (NR), modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high purity natural rubber (UPNR), etc. Also included.

  The NR is not particularly limited, and may be one commonly used in the tire industry, and examples thereof include SIR20, RSS # 3, and TSR20. Moreover, a thing common in the tire industry can also be used as said IR.

  The content of the isoprene-based rubber in the rubber component is 30% by mass or more, preferably 33% by mass or more, and more preferably 35% by mass or more. If it is less than 30% by mass, the processability at the time of mixing tends to deteriorate. The content of the isoprene rubber in the rubber component is 50% by mass or less, preferably 48% by mass or less, and more preferably 45% by mass or less. If it exceeds 50% by mass, the performance on ice tends to decrease.

  The butadiene rubber (BR) is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., High cis BR such as BR130B and BR150B manufactured by Ube Industries, Ltd., VCR412 manufactured by Ube Industries, Ltd. and VCR617 etc. And BR synthesized using a rare earth element-based catalyst such as BUNACB25 manufactured by LANXESS Corporation. One of these BRs may be used, or two or more thereof may be used in combination. Among them, high cis BR having a cis-1,4 bond content of 90% or more is preferable from the viewpoint of wear resistance and processability.

  The rare earth BR is a butadiene rubber synthesized using a rare earth catalyst and is characterized by having a high cis content and a low vinyl content. As the rare earth-based BR, those common in tire manufacture can be used.

  As the rare earth element catalyst used for the synthesis of the rare earth BR, known catalysts can be used. For example, a catalyst containing a lanthanum series rare earth compound, an organic aluminum compound, an aluminoxane, a halogen-containing compound, and optionally a Lewis base Etc. Among these, an Nd-based catalyst using a neodymium (Nd) -containing compound as the lanthanum series rare earth element compound is particularly preferable.

  Examples of the lanthanum series rare earth element compound include halides, carboxylates, alcoholates, thioalcoholates and amides of rare earth metals of atomic numbers 57 to 71. Among them, the Nd-based catalyst is preferable in that BR having a high cis content and a low vinyl content can be obtained.

The organoaluminum compound is represented by AlR ^a R ^b R ^c (wherein, R ^a , R ^b and R ^c are the same or different and each represents hydrogen or a hydrocarbon group having 1 to 8 carbon atoms). You can use one. Examples of the aluminoxane include chain aluminoxanes and cyclic aluminoxanes. As the halogen-containing compound, AlX _k R ^d _3-k (wherein, X is a halogen, R ^d is an alkyl group having 1 to 20 carbon atoms, an aryl group or an aralkyl group, k is 1, 1.5, 2 or 3) Aluminum halides represented by:) Strontium halides such as Me ₃ SrCl, Me ₂ SrCl ₂ , MeSrHCl ₂ , MeSrCl _{3 and the} like; metal halides such as silicon tetrachloride, tin tetrachloride and titanium tetrachloride . The Lewis base is used to complex a lanthanum series rare earth element compound, and acetylacetone, ketone, alcohol and the like are suitably used.

  The rare earth element-based catalyst may be used in the form of silica, magnesia, magnesium chloride or the like even when used in the state of being dissolved in an organic solvent (n-hexane, cyclohexane, n-heptane, toluene, xylene, benzene etc.) in the polymerization of butadiene. It may be supported on a suitable carrier and used. The polymerization conditions may be either solution polymerization or bulk polymerization, the preferred polymerization temperature is -30 to 150 ° C., and the polymerization pressure may be optionally selected depending on other conditions.

  From the viewpoint of durability, the cis 1,4 bond content (cis content) of the rare earth BR is preferably 90% by mass or more, more preferably 93% by mass or more, and still more preferably 95% by mass or more.

  From the viewpoint of durability, the vinyl content of the rare earth BR is preferably 1.8% by mass or less, more preferably 1.5% by mass or less, still more preferably 1.0% by mass or less, and 0.8% by mass or less Particularly preferred. In the present specification, the vinyl content (1,2-bonded butadiene unit amount) and cis content (cis 1,4 bond content) of BR can be measured by infrared absorption spectroscopy.

  The content of BR in the rubber component is 30% by mass or more, preferably 40% by mass or more, and more preferably 50% by mass or more. If it is less than 30% by mass, the performance on ice tends to decrease. Moreover, content in the rubber component of BR is 60 mass% or less, 55 mass% or less is preferable, and 50 mass% or less is more preferable. If it exceeds 60% by mass, the processability tends to deteriorate.

（式（１）中、Ｒ¹、Ｒ²およびＲ³は、同一もしくは異なって、アルキル基、アルコキシ基、シリルオキシ基、アセタール基、カルボキシル基（−ＣＯＯＨ）、メルカプト基（−ＳＨ）またはこれらの誘導体を表す。Ｒ⁴およびＲ⁵は、同一もしくは異なって、水素原子またはアルキル基を表す。ｎは整数を表す。）
このような変性ＢＲとしては、例えば、日本ゼオン（株）製のＢＲ１２５０Ｈ（スズ変性）、住友化学工業（株）製のＳ変性ポリマー（シリカ用変性）等が挙げられる。 As modified BR, there are terminal modified BR and main chain modified BR, but terminal modified BR is preferable. The terminal-modified BR is not particularly limited, and can be selected according to the type of filler (carbon black, silica, etc.) that can be used, but tin-modified BR (tin-modified BR) because excellent low fuel consumption can be obtained. The modified BR (S modified BR) modified by the compound represented by the following formula (1) is preferable, and the tin modified BR is more preferable.

(In formula (1), R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (—SH) or R ⁴ and R ⁵ are the same or different and each represents a hydrogen atom or an alkyl group, and n is an integer.
Examples of such modified BR include BR 1250H (tin modified) manufactured by Nippon Zeon Co., Ltd., S modified polymer (modified for silica) manufactured by Sumitomo Chemical Co., Ltd., and the like.

  The tin-modified BR is not particularly limited, but is preferably a tin-modified BR which is polymerized by a lithium initiator and has a tin atom content of 50 to 3,000 ppm, a vinyl content of 5 to 50% by mass, and a molecular weight distribution of 2 or less.

  The tin-modified BR is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and the terminal of the tin-modified BR molecule is further bound by a tin-carbon bond. Is preferred. Examples of the lithium initiator include lithium compounds such as alkyllithium and aryllithium. Examples of tin compounds include tin tetrachloride and butyltin trichloride.

  The content of tin atoms in the tin-modified BR is preferably 50 ppm or more. Below 50 ppm, tan δ tends to increase. Further, the content of tin atoms is preferably 3000 ppm or less, more preferably 300 ppm or less. If it exceeds 3000 ppm, the processability of the kneaded material tends to deteriorate.

  The molecular weight distribution (Mw / Mn) of the tin-modified BR is preferably 2 or less. When Mw / Mn exceeds 2, tan δ tends to increase. The lower limit of the molecular weight distribution is not particularly limited, but is preferably 1 or more.

  The vinyl content of the tin-modified BR is preferably 5% by mass or more. If it is less than 5% by mass, it is difficult to produce tin-modified BR. The vinyl content is preferably 50% by mass or less, more preferably 20% by mass or less. If it exceeds 50% by mass, the dispersibility of the carbon black is poor, and the fuel economy, breaking resistance and breaking elongation tend to be lowered.

  As the S-modified BR, those described in JP-A-2010-111753 etc. may be mentioned.

In the formula (1), an alkoxy group is preferable as R ¹ , R ² and R ³ from the viewpoint that excellent fuel economy and breaking resistance can be obtained (preferably having 1 to 8 carbon atoms, more preferably carbon). 1 to 4 alkoxy groups). As R ⁴ and R ⁵ , an alkyl group is suitable (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and further preferably 3. By using the preferred compounds, the effects of the present invention can be obtained well.

  Specific examples of the compound represented by the formula (1) include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane and the like. Among these, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 3-diethylaminopropyltrimethoxysilane are preferable in that the above-mentioned performance can be improved well. These may be used alone or in combination of two or more.

  As a method for modifying butadiene rubber with the compound represented by the formula (1), conventionally known methods such as the methods described in Japanese Patent Publication No. 6-53768, Japanese Patent Publication No. 6-57767, etc. can be used. For example, it can be modified by contacting butadiene rubber with the compound, and specifically, after preparation of butadiene rubber by anionic polymerization, a predetermined amount of the compound is added to the rubber solution to polymerize the terminal of butadiene rubber (activity And the like, and the like.

  The vinyl content of the S-modified BR is preferably 35% by mass or less, more preferably 30% by mass or less. If the vinyl content exceeds 35% by mass, fuel economy may be reduced. The lower limit of the vinyl content is not particularly limited, but is preferably 1% by mass or more, and more preferably 20% by mass or more. If the amount is less than 1% by mass, the heat resistance and the deterioration resistance may be reduced.

  The weight average molecular weight (Mw) of the S-modified BR is preferably at least 100,000, more preferably at least 400,000. If it is less than 100,000, sufficient breaking strength and bending fatigue resistance may not be obtained. Mw is preferably 2,000,000 or less, more preferably 800,000 or less. If it exceeds 2,000,000, the processability may be reduced to cause dispersion failure, and a sufficient breaking strength may not be obtained.

  The content of the modified BR in 100% by mass of the rubber component is 5% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more. If it is less than 5% by mass, the performance on ice tends to decrease. Moreover, content in the rubber component of modified BR is 30 mass% or less, 27 mass% or less is preferable, and 25 mass% or less is more preferable.

  The rubber composition for the cap tread may contain rubber components other than the isoprene rubber, BR and modified BR. Other rubber components include styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) and the like.

  It is preferable to contain carbon black from the viewpoint that the reinforcing property, the ultraviolet ray deterioration resistance and the durability of the rubber composition are improved. Examples of carbon black include SAF, ISAF, HAF, FF, FEF, GPF, etc., which are generally used in tire manufacture, and carbon black can be used alone or in combination of two or more. .

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 20 m ² / g or more, more preferably 35 m ² / g or more, and still more preferably 70 m ² / g or more. When N ₂ SA is less than 20 m ² / g, sufficient reinforcement may not be obtained. Also, N ₂ SA of carbon black is preferably not more than 200 meters ² / g, more preferably at most 150m ² / g. If it exceeds 200 m ² / g, it tends to be difficult to disperse well, and the processability tends to deteriorate. Incidentally, N ₂ SA of the carbon black is a value measured by the A method of JIS K 6217-2.

  Content with respect to 100 mass parts of rubber components of carbon black is 30 mass parts or more, and 35 mass parts or more are preferable. When the content of carbon black is less than 30 parts by mass, sufficient reinforcement may not be obtained. In addition, the content of carbon black is 45 parts by mass or less, and preferably 40 parts by mass or less. When the content of carbon black exceeds 45 parts by mass, it tends to be difficult to disperse well, and the processability tends to deteriorate.

  The inclusion of silica is preferable in that the wet braking performance and the low heat buildup of the tire are improved. Examples of the silica include dry method silica (anhydrous silica), wet method silica (hydrous silica) and the like, but wet method silica is preferable because it has many silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 50 m ² / g or more, more preferably 80 m ² / g or more, and still more preferably 100 m ² / g or more. If the N ₂ SA is less than 50 m ² / g, sufficient reinforcement may not be obtained. The N ₂ SA of the silica is preferably not more than 500 meters ² / g, more preferably at most 300m ² / g. If it exceeds 500 m ² / g, the processability may be significantly deteriorated. The nitrogen adsorption specific surface area of silica is a value measured by the BET method in accordance with ASTM D3037-81.

  Content with respect to 100 mass parts of rubber components of a silica is 20 mass parts or more, and 25 mass parts or more are preferable. When the content of silica is less than 20 parts by mass, the grip performance tends to be lowered. Moreover, 40 mass parts or less are preferable, and, as for content of a silica, 35 mass parts or less are more preferable. When the content of silica exceeds 40 parts by mass, the processability may be deteriorated.

  When silica is contained, it is preferable to use a silane coupling agent in combination. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry, for example, Si75, Si266 (bis (3-triethoxysilylpropyl) manufactured by Evonik Degussa ) Disulfide), sulfide type such as Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by the same company, 3-mercaptopropyltrimethoxysilane, mercapto such as NXT-Z100 manufactured by Momentive, NXT-Z45, and NXT Systems (silane coupling agents having a mercapto group), vinyl systems such as vinyltriethoxysilane, amino systems such as 3-aminopropyltriethoxysilane, glycidoxy systems of γ-glycidoxypropyltriethoxysilane, 3-nitropropyl Trimethoxysilane Nitro-based, chloro system such as 3-chloropropyl trimethoxysilane. These may be used alone or in combination of two or more. Among them, a sulfide type and a mercapto type are preferable from the viewpoint of strong bonding with silica and excellent in low heat buildup.

  From a viewpoint of silica dispersibility, 2 mass parts or more are preferable, and, as for content with respect to 100 mass parts of silicas in the case of containing a silane coupling agent, 3 mass parts or more are more preferable. Moreover, from a viewpoint of cost, 25 mass parts or less are preferable, and 20 mass parts or less are more preferable.

  The rubber composition according to the present embodiment can contain an inorganic potassium salt in order to improve extrusion processability. As an inorganic potassium salt, the potassium salt etc. which are chosen 1 or more types from the group which consists of potassium carbonate, potassium hydrogencarbonate, and potassium tetraborate are mentioned, for example, and potassium tetraborate is preferable.

  The content of the inorganic potassium salt is preferably 0.3 parts by weight or more, more preferably 0.4 parts by weight or more, with respect to 100 parts by weight of silica, from the viewpoint of extrusion processability. From the viewpoint of wear resistance, the amount is preferably 1.45 parts by weight or less, more preferably 1 part by weight or less, with respect to 100 parts by weight of silica.

  The sulfur is not particularly limited, and any sulfur common in the tire industry can be used, and powdered sulfur is preferable. The content of sulfur relative to 100 parts by mass of the rubber component is 1.0 parts by mass or more, preferably 1.1 parts by mass or more. When the content of sulfur is less than 1.0 part by mass, crosslinking may be insufficient, and the effect of the present invention may not be exhibited without increasing the molecular weight of the rubber composition. Further, the content of sulfur is 1.5 parts by mass or less, preferably 1.3 parts by mass or less. When the content of sulfur exceeds 1.5 parts by mass, the crosslink density tends to be too high, and the durability tends to decrease.

  The rubber composition according to the present embodiment may contain, in addition to the components described above, compounding agents generally used for producing a rubber composition, for example, reinforcing fillers other than carbon black and silica, zinc oxide, stearic acid, A softener, an adhesive resin, an antiaging agent, a wax, a vulcanizing agent other than sulfur, a vulcanization accelerator and the like can be appropriately contained.

  The reinforcing filler other than the carbon black and the silica is not particularly limited, and examples thereof include aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, talc and the like, and it is also possible to use these white fillers alone. It is also possible to use in combination of species or more.

  From a viewpoint of processability, 0.2 mass part or more is preferable, and, as for content with respect to 100 mass parts of rubber components in the case of containing a stearic acid, 1 mass part or more is more preferable. Moreover, from the viewpoint of the vulcanization rate, 10 parts by mass or less is preferable, and 5 parts by mass or less is more preferable.

  The content relative to 100 parts by mass of the rubber component in the case of containing zinc oxide is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more from the viewpoint of processability. Moreover, from a viewpoint of abrasion resistance performance, 10 mass parts or less are preferable, and 5 mass parts or less are more preferable.

  Examples of the softener include liquid polymers, oils, low temperature plasticizers and the like. The plasticizer components may be used alone or in combination of two or more. Among them, it is preferable to use a liquid polymer because the abrasion resistance and the grip performance can be improved in a well-balanced manner.

  Examples of the liquid polymer include liquid SBR, liquid BR, liquid IR, liquid SIR and the like. Among them, it is preferable to use liquid SBR, in particular, because the durability performance and the grip performance can be improved in a well-balanced manner.

  Examples of the oil include mineral oil such as aromatic oil, process oil, paraffin oil and the like. Among them, it is preferable to use process oil because of the reduction of environmental load.

  Examples of low temperature plasticizers include liquid components such as dioctyl phthalate (DOP), dibutyl phthalate (DBP), tris (2 ethylhexyl) phosphate (TOP), bis (2 ethylhexyl) sebacate (DOS) and the like.

  The content with respect to 100 parts by mass of the rubber component in the case of containing the softener is preferably 15 to 250 parts by mass, and is preferably 20 to 200 parts by mass because the effect as the softener is sufficiently obtained. More preferable.

  Examples of the adhesive resin include cyclopentadiene resins, coumarone resins, petroleum resins (aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins, etc.), phenolic resins, rosin derivatives and the like. And aromatic petroleum resins are preferred.

  Examples of the aromatic petroleum resin include the following aromatic vinyl resins and C9 petroleum resins other than aromatic vinyl resins, and the like, with preference given to aromatic vinyl resins.

  In the aromatic vinyl resin, examples of the aromatic vinyl monomer (unit) include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2 , 4,6-trimethylstyrene or the like may be used, and may be a homopolymer of each monomer or a copolymer of two or more monomers. Moreover, you may denature these.

  As an aromatic vinyl resin, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferable because it is economical, easy to process, and excellent in wet grip performance. Preferably, a copolymer of α-methylstyrene and styrene is more preferable. As the aromatic vinyl-based resin, for example, commercially available products such as SYLVARES SA 85 manufactured by Arizona Chemical Co., SA 100, SA 120, SA 140, R2336 manufactured by Eastman Chemical Co., etc. are suitably used. As a copolymer of α-methylstyrene and styrene, for example, SYLVATRAXX4401 manufactured by Arizona Chemical Co., Ltd. is preferably used.

  From the viewpoint of wet grip performance, the content of the aromatic petroleum resin is preferably 2 parts by mass or more, and more preferably 5 parts by mass or more, with respect to 100 parts by mass of the rubber component. Further, from the viewpoint of wear resistance and fuel economy, 50 parts by mass or less is preferable, 40 parts by mass or less is more preferable, and 30 parts by mass or less is more preferable.

  The anti-aging agent is not particularly limited, and those used in the field of rubber can be used, and examples thereof include quinoline-based, quinone-based, phenol-based and phenylene diamine-based anti-aging agents.

  In the case of containing an antiaging agent, the content relative to 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 0.8 parts by mass or more. Further, the content of the antioxidant is preferably 3.0 parts by mass or less.

  The content with respect to 100 parts by mass of the rubber component in the case of containing a wax is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more from the viewpoint of the weather resistance of the rubber. Moreover, from a viewpoint of whitening of the tire by bloom, 10 mass parts or less are preferable, and 5 mass parts or less are more preferable.

  As a vulcanizing agent other than sulfur, for example, Tackilol V200 manufactured by Taoka Chemical Industry Co., Ltd., DURALINK HTS (1,6-hexamethylene-sodium dithiosulfate dihydrate) manufactured by Flexex, manufactured by LANXESS A vulcanizing agent containing a sulfur atom such as KA9188 (1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane), an organic peroxide such as dicumyl peroxide, and the like can be mentioned.

  As a vulcanization accelerator, for example, sulfenamide type, thiazole type, thiuram type, thiourea type, guanidine type, dithiocarbamic acid type, aldehyde-amine type or aldehyde-ammonia type, imidazoline type, and xanthate type vulcanization accelerator Etc. These vulcanization accelerators may be used alone or in combination of two or more. Among them, a sulfenamide vulcanization accelerator, a thiazole vulcanization accelerator, and a guanidine vulcanization accelerator are preferable, and a sulfenamide vulcanization accelerator is more preferable.

  As a sulfenamide-type vulcanization accelerator, for example, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N -Dicyclohexyl-2-benzothiazolylsulfenamide (DCBS) etc. are mentioned. Among them, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS) and N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) are preferable.

  Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and di-2-benzothiazolyl disulfide. Among them, 2-mercaptobenzothiazole is preferable.

  Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1, 3-di-o-cumenyl guanidine, 1,3-di-o-biphenyl guanidine, 1,3-di-o-cumenyl-2-propionyl guanidine and the like. Among these, 1,3-diphenylguanidine is preferable.

  The content with respect to 100 parts by mass of the rubber component in the case of containing a vulcanization accelerator is preferably 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more from the viewpoint of acceleration of vulcanization. Moreover, from a viewpoint of processability, 5 mass parts or less are preferable, and 3 mass parts or less are more preferable.

  The rubber composition for a cap tread according to the present invention can be produced by a known method. For example, it can manufacture by the method etc. which knead | mix the said each component using rubber-kneading apparatuses, such as an open roll, a Banbury mixer, and a closed-type kneader, and it vulcanizes after that.

  The pneumatic tire of the present invention can be manufactured by the usual method using the rubber composition. That is, a member obtained by extruding the unvulcanized rubber composition obtained by kneading the above-mentioned components in accordance with the shape of a tire tread is bonded together with other tire members on a tire molding machine, and the ordinary method is used. By molding, an unvulcanized tire is formed, and the unvulcanized tire is heated and pressurized in a vulcanizer, whereby the pneumatic tire of the present invention can be obtained.

  Although the category of the pneumatic tire according to the present invention is not particularly limited, it is a pneumatic tire excellent in durability under high temperature and high speed conditions while maintaining the performance on ice, and therefore it is used for winter for studless tires, snow tires, etc. It is preferable to use a tire or an all-season tire.

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

Hereinafter, various medicines used in Examples and Comparative Examples are collectively shown.
NR: TSR20
BR: BR150B (Hicis BR, cis-1, 4 bond content: 96%) manufactured by Ube Industries, Ltd.
S-modified BR: Reference to Preparation Example 1 below: Tin-modified BR: BR 1250H manufactured by Nippon Zeon Co., Ltd. (polymerization using lithium as an initiator, vinyl content: 10 to 13% by mass, cis content: 45% by mass, Mw / Mn : 1.5, tin atom content: 250 ppm, tin end modified BR)
Carbon black: Show black N 220 (N ₂ SA: 111 m ² / g) manufactured by Cabot Japan Ltd.
Silica 1: Ultrasil VN3 (N ₂ SA: 175 m ² / g) manufactured by Evonik Degussa
Silica 2: Zeosil 115 GR (N ₂ SA: 105 m ² / g) manufactured by Rhodia
Silane coupling agent: Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa
Aromatic petroleum resin: Sylvatra xx 4401 (a main component of α-methylstyrene, softening point: 85 ° C., SP value: around 9.0) manufactured by Arizona Chemical Co.
Wax: Ozo Ace 0355 manufactured by Nippon Seiwa Co., Ltd.
Anti-aging agent 1: Antigen 6C (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Anti-aging agent 2: Antage RD (polymer of 2,2,4-trimethyl-1,2-dihydroquinoline) manufactured by Kawaguchi Chemical Industry Co., Ltd.
Inorganic potassium salt: potassium tetraborate tetrahydrate stearic acid manufactured by Wako Pure Chemical Industries, Ltd. stearic acid: stearic acid “Nagi” manufactured by NOF Corporation
Zinc oxide: Zinc white oil 2 manufactured by Mitsui Mining & Smelting Co., Ltd. 1: Diana Process NH-70S manufactured by Idemitsu Kosan Co., Ltd.
Oil 2: Diana Process Oil PA32 manufactured by Idemitsu Kosan Co., Ltd.
Sulfur: Seimi sulfur (manufactured by Nippon Denryoku Kogyo Co., Ltd.) (Insoluble sulfur of 60% or more of insoluble matter by carbon disulfide, oil content: 5% by mass, the value in Table 1 is pure sulfur content)
Vulcanization accelerator 1: Noccellar CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Co., Ltd.
Vulcanization accelerator 2: Noxceler D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Co., Ltd.
Vulcanization accelerator 3: Noccellar M (2-mercaptobenzothiazole) manufactured by Ouchi Shinko Chemical Co., Ltd.

Production Example 1: Synthesis of S-modified BR
Into a nitrogen-substituted autoclave reactor, hexane, 1,3-butadiene, tetrahydrofuran and ethylene glycol diethyl ether were charged. Next, bis (diethylamino) methylvinylsilane and n-butyllithium were introduced as a cyclohexane solution and an n-hexane solution, respectively, to initiate polymerization. The stirring speed was 130 rpm, the temperature in the reactor was 65 ° C., and the polymerization of 1,3-butadiene was performed for 3 hours while continuously feeding the monomers into the reactor. Next, the obtained polymer solution was stirred at a stirring speed of 130 rpm, N- (3-dimethylaminopropyl) acrylamide was added, and a reaction was performed for 15 minutes. After completion of the polymerization reaction, 2,6-di-tert-butyl-p-cresol was added. Next, the solvent was removed by steam stripping, followed by drying with a heat roll adjusted to 110 ° C. to obtain S-modified BR (vinyl content: 10% by mass, cis content: 40% by mass, Mw: 400,000) .

(Example and Comparative Example)
According to the compounding contents shown in Table 1, various chemicals except sulfur and a vulcanization accelerator were kneaded at 150 ° C. for 5 minutes in a Banbury mixer. Sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneading was carried out at 170 ° C. for 12 minutes using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into the shape of a tread, laminated together with other tire members on a tire molding machine, press-cured for 20 minutes under conditions of 170 ° C., and a studless tire for test was obtained. .

  The unvulcanized rubber composition is extruded into a shape of a tire tread by an extruder equipped with a die having a predetermined shape, and is bonded together with other tire members to form an unvulcanized tire, and the condition of 170 ° C. The test tire (size: 195 / 65R15, studless tire) was manufactured by press curing for 12 minutes under. The sipe density and height of the tread block in each test tire are shown in Table 1.

  The following evaluation was performed about the obtained rubber composition for a test, and the tire for a test. The evaluation results are shown in Table 1.

<Tension stress measurement test>
A dumbbell-like No. 4 test piece described in JIS K 6251 "Tensile test method for vulcanized rubber" was produced from each of the test rubber compositions. Next, using these test pieces, according to the method described in JIS K 6251, tensile stress M300 (normal temperature) at 300% elongation at normal temperature and tensile stress M300 (100 ° C) at 300% elongation at 100 ° C. Was measured. Furthermore, the reduction rate of the tensile stress at 100 ° C. to the tensile stress at normal temperature was calculated. The lower the reduction rate, the better the durability. The performance target value is 32% or less.

<Durability test>
Using a drum tester, with a standard rim (6.0 J), an internal pressure (260 kPa), a load (4.56 kN), and a road surface temperature of 80 ° C, on the drum, the speed is 230 km / h and the tread rubber is used. The running time until peeling damage occurred was measured. The results were indexed using Comparative Example 1 as 100. The larger the index, the better the durability at high temperature and high speed running.

Performance test on ice
The studless tire for the above test was attached to a domestic 2000cc FR car, and 10 laps of the car were run on a test track on an ice road surface. At that time, the test driver evaluated the stability of the control at the time of steering, and set the index of Comparative Example 1 to 100. The larger the index, the better the performance on ice (gripping performance on ice).

<Wet grip performance test>
The studless tire for the above test was attached to a domestic 2000cc FR car, and 10 laps of the vehicle were run on a test course on a wet asphalt road surface. At that time, the test driver evaluated the stability of the control at the time of steering, and set the index of Comparative Example 1 to 100. The larger the index, the better the wet grip performance.

  From the results of Table 1, it can be seen that the pneumatic tire of the present invention is a pneumatic tire excellent in durability under high temperature and high speed conditions while maintaining the performance on ice.

Claims (1)

A pneumatic tire comprising a tread block having an average sipe density of 1.0 cm / cm ² or more and an average height of 0.6 to 2.0 cm,
The tread block is
100 parts by mass of a rubber component containing 30 to 50% by mass of isoprene-based rubber, 30 to 60% by mass of butadiene rubber, and 5 to 30% by mass of modified butadiene rubber,
The pneumatic tire comprised with the rubber composition for cap treads containing 30-45 mass parts carbon black, 20-40 mass parts silica, and 1.0-1.5 mass parts sulfur.