JP6536638B2 - Rubber composition for cap tread and pneumatic tire - Google Patents

Description

The present invention relates to a rubber composition for a cap tread and a pneumatic tire.

In recent years, grip performance and wear resistance are particularly required for automobile tires, and techniques using modified SBR and specific silica have been proposed.

Also, as a technique for improving grip performance, a method of blending a large amount of plasticizer such as resin and a technique of blending a large amount of filler such as silica have been proposed as a technique of improving abrasion resistance. In such compounding systems, dispersion of silica is difficult and there is a problem that the desired abrasion resistance is not improved.

Furthermore, when traveling at high speed on a road such as an European outburn, high-speed grip performance and wear resistance in various temperature ranges are required, but there is no technology that is satisfactory yet. It is desired to provide a rubber composition having excellent abrasion resistance.

An object of the present invention is to solve the above problems and to provide a rubber composition for a cap tread excellent in grip performance and abrasion resistance at high speed running, and a pneumatic tire using the same.

The present invention comprises styrene butadiene rubber and / or butadiene rubber, isoprene rubber, filler, and plasticizer, and the total content of styrene butadiene rubber and butadiene rubber in 90 mass% of the rubber component is 90 mass% The content of isoprene rubber is 0.3 to 10% by mass, the content of silica in 100% by mass of filler is 80% by mass or more, and the content of silica relative to 100 parts by mass of rubber component is 110% The present invention relates to a rubber composition for a cap tread having a content of a plasticizer of 50 parts by mass or more.

The styrene butadiene rubber preferably has a vinyl content of 70 mol% or less.
The styrene butadiene rubber is preferably a modified styrene butadiene rubber having a functional group capable of interacting with silica.

The content of styrene butadiene in 100% by mass of the rubber component is preferably 80% by mass or more.
It is preferable that the content rate of the liquid plasticizer in 100 mass% of plasticizers is 20 mass% or less.
The content of silica having a nitrogen adsorption specific surface area of 190 m ² / g or more per 100 parts by mass of rubber is preferably 50 parts by mass or more.

The present invention also relates to a pneumatic tire having a cap tread made of the rubber composition and a base tread.
The rubber composition for the base tread used in the base tread preferably has a content of isoprene-based rubber in 20% by mass of the rubber component of 20% by mass or more.

According to the present invention, a styrene butadiene rubber and / or a butadiene rubber, an isoprene rubber, a filler and a plasticizer, and the total content of styrene butadiene rubber and butadiene rubber in the rubber component, and an isoprene rubber The rubber composition for a cap tread having a predetermined content of the content, the silica content in the filler, and the content of the silica and the plasticizer relative to the rubber component, so that the grip performance and the wear resistance at high speeds are remarkable. Can be improved.

[Cap tread]
The rubber composition for a cap tread of the present invention comprises styrene butadiene rubber and / or butadiene rubber, isoprene rubber, a filler and a plasticizer, and the total content of styrene butadiene rubber and butadiene rubber in the rubber component The content of isoprene-based rubber, the content of silica in the filler, and the content of silica and plasticizer with respect to the rubber component are predetermined amounts. And by satisfying all the above, it is possible to solve the conventionally difficult problem of improving the grip performance (low temperature road surface and high temperature road surface) and wear resistance in a well-balanced manner at high speed traveling. In addition, good wet grip performance can be obtained simultaneously.

In the present invention, a small amount of isoprene-based rubber is added as a rubber component to a compound containing a predetermined amount of a rubber component having a high content of SBR and / or BR, a filler having a high silica content, and a plasticizer. It becomes fine islands incompatible with the rubber component and improves the silica dispersion. It is expected that if there is an incompatible rubber component in the rubber matrix, a large amount of silica will be present at the interface, or the cross-linked form will change at the interface, but a small amount of isoprene based rubber is compounded. It is considered that the presence of the non-uniform region improves the dispersibility of the silica, and at high speeds, the grip performance on both the low temperature road surface and the high temperature road surface is remarkably improved in addition to the wear resistance.

In the rubber composition for a cap tread, the total content (total content) of SBR and BR in 100% by mass of the rubber component is 90% by mass or more from the viewpoint that sufficient grip performance (low temperature road surface and high temperature road surface) is obtained. Preferably it is 92 mass% or more, More preferably, it is 93 mass% or more.

The content (content) of SBR in 100% by mass of the rubber component is preferably 40% by mass or more, more preferably 60% by mass or more, from the viewpoint of obtaining sufficient grip performance (low temperature road surface and high temperature road surface). Preferably it is 70 mass% or more, Especially preferably, it is 80 mass% or more. In addition, the content of the SBR is preferably 98% by mass or less, more preferably 97% by mass or less from the viewpoint of wear resistance.

The content (content) of BR in 100% by mass of the rubber component is preferably 0 to 60% by mass from the viewpoint of achieving sufficient grip performance (low temperature road surface and high temperature road surface) and balance with low fuel consumption. More preferably, it is 0-50 mass%, More preferably, it is 10-30 mass%.

The usable SBR is not particularly limited, and, for example, emulsion-polymerized styrene butadiene rubber (E-SBR), solution-polymerized styrene butadiene rubber (S-SBR) and the like can be used. It may be either non-modified SBR or modified SBR. Among them, modified SBR having a functional group having an interaction with silica (silica interactive functional group) is preferable. Thereby, the grip performance (low temperature road surface and high temperature road surface) and wear resistance are improved. The position of the functional group may be at the main chain or at the end.

The above-mentioned silica interactive functional group is not particularly limited as long as it is a group having interaction (reactivity) with silica, and an amino group, an amido group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group , Urea, ether, carbonyl, oxycarbonyl, mercapto, sulfide, disulfide, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imide, hydrazo, azo, diazo, carboxyl And a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group and the like, and those having a substituent may be used. Among them, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted by an alkyl group having 1 to 6 carbon atoms), an alkoxy group (from an aspect of grip performance (low temperature road surface and high temperature road surface) and abrasion resistance) Preferably, a C1-C6 alkoxy group) and an alkoxy silyl group (preferably a C1-C6 alkoxy silyl group) are preferable.

（式（１）中、Ｒ^１、Ｒ^２及びＲ^３は、同一又は異なって、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）又はこれらの誘導体を表す。Ｒ^４及びＲ^５は、同一又は異なって、水素原子又はアルキル基を表す。Ｒ^４及びＲ^５は結合して窒素原子と共に環構造を形成してもよい。ｎは整数を表す。） As modified | denatured SBR, the styrene butadiene rubber modified | denatured with the compound (modifier) represented by following formula (1) is preferable. In particular, SBR in which the polymerization end (active end) of S-SBR is modified with a compound represented by the formula (1) is 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 these R ⁴ and R ⁵ are the same or different and each represents a hydrogen atom or an alkyl group R ⁴ and R ⁵ may combine to form a ring structure with a nitrogen atom, and n represents an integer. .)

In the above formula (1), an alkoxy group is preferable as R ¹ , R ² and R ³ (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms). As R ⁴ and R ⁵ , an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) is suitable. n is preferably 1 to 5, more preferably 2 to 4, and further preferably 3. When R ⁴ and R ⁵ combine to form a ring structure with a nitrogen atom, it is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (such as cyclohexyloxy group) and an aryloxy group (such as phenoxy group and benzyloxy group).

Specific examples of the compound represented by the above formula (1) include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxy Silane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane and the like can be mentioned. Among them, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane, 3-diethylaminopropyltrimethoxysilane, 3-diethylaminopropyl from the viewpoint of grip performance (low temperature road surface and high temperature road surface) and abrasion resistance. Triethoxysilane is preferred. These may be used alone or in combination of two or more.

The styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more. By setting the lower limit or more, sufficient grip performance (low temperature road surface and high temperature road surface) tends to be obtained. The styrene content is preferably 55% by mass or less, more preferably 45% by mass or less, and still more preferably 43% by mass or less. By making the upper limit or less, there is a tendency that good fuel consumption can be secured. In addition, in this specification, styrene content can be measured by the method of the below-mentioned Example.

The vinyl content of SBR is preferably 70 mol% or less, more preferably 65 mol% or less, still more preferably 60 mol% or less. By making the upper limit or less, there is a tendency that good fuel consumption can be secured. The vinyl content is preferably 5 mol% or more, more preferably 8 mol% or more, and still more preferably 10 mol% or more. By setting the lower limit or more, sufficient grip performance (low temperature road surface and high temperature road surface) tends to be obtained. In addition, in this specification, a vinyl content is a vinyl content (content rate of a vinyl bond) of a butadiene part, and can be measured by the method of the below-mentioned Example.

The BR is not particularly limited, and examples thereof include BR730 and BR51 manufactured by JSR Co., Ltd., BR1220 manufactured by Nippon Zeon Co., Ltd., high cis content BR such as BR130B, BR150B and BR710 manufactured by Ube Industries, Ltd., Nippon Zeon A low cis content BR or the like such as BR1250H manufactured by Co., Ltd. can be used. These may be used alone or in combination of two or more.

The cis content of BR is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. As a result, in addition to grip performance and abrasion resistance, good performance on snow and ice can be obtained.
In the present specification, the cis content is a value calculated by infrared absorption spectrum analysis.

In the rubber composition for a cap tread, the content (content) of isoprene-based rubber in 100% by mass of the rubber component is 0.3 to 10% by mass from the viewpoint of grip performance (low temperature road surface and high temperature road surface), Preferably it is 1.0-10 mass%, More preferably, it is 2.0-10 mass%. By blending a small amount of isoprene-based rubber, as described above, fine nonuniform regions are formed, and grip performance (low temperature road surface and high temperature road surface) and wear resistance are improved.

As isoprene-based rubbers that can be used, synthetic isoprene rubber (IR), natural rubber (NR), modified natural rubber and the like can be mentioned. NR includes deproteinized natural rubber (DPNR) and high purity natural rubber (HPNR), and as modified natural rubber, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber Etc. Moreover, as NR, for example, a common one in the tire industry such as SIR20, RSS # 3, TSR20 can be used. Among these, from the viewpoint of obtaining sufficient grip performance (low temperature road surface and high temperature road surface), NR and IR are preferable, and NR is more preferable.

Other rubber components may be blended, and examples thereof include styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), butyl rubber and the like.

The rubber composition for cap tread contains silica as a filler. By uniformly dispersing silica, good grip performance (low temperature road surface, high temperature road surface, wet road surface) and wear resistance can be provided. Examples of the silica include dry method silica (anhydrous silica), wet method silica (hydrous silica) and the like. Among them, wet method silica is preferable because it has many silanol groups. Silica may be used alone or in combination of two or more.

The content (content) of silica in 100% by mass of the filler is 80% by mass or more. By using a filler having a high silica content, good grip performance (low temperature road surface, high temperature road surface, wet road surface), wear resistance can be obtained, and balance with fuel efficiency can be improved. The content is preferably 85% by mass or more, more preferably 90% by mass or more. The upper limit is not particularly limited, and may be 100% by mass, but may be 99% by mass or less.

In the rubber composition for a cap tread, the content of silica is preferably 110 parts by mass or more, more preferably 120 parts by mass or more, and still more preferably 125 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting the value to the lower limit or more, sufficient grip performance (low temperature road surface, high temperature road surface, wet road surface) and abrasion resistance tend to be obtained. The upper limit of the content is not particularly limited, but is preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and still more preferably 200 parts by mass or less from the viewpoint of processability and fuel economy.

As the silica, fine particle silica having a nitrogen adsorption specific surface area (N ₂ SA) of 190 m ² / g or more can be suitably used. As a result, the abrasion resistance is significantly improved, and the performance balance with the grip performance is greatly improved.

The content of the fine particle silica is preferably 50 parts by mass or more, more preferably 80 parts by mass or more, from the viewpoint of wear resistance, with respect to 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and still more preferably 200 parts by mass or less from the viewpoint of processability and fuel economy.

The N ₂ SA of the fine particle silica is preferably 200 m ² / g or more, more preferably 210 m ² / g or more, and using more than 210 m ² / g is desirable in that abrasion resistance can be significantly improved. Further, the upper limit of N ₂ SA of silica is not particularly limited, but is preferably 400 m ² / g or less from the viewpoint of workability and processability. The nitrogen adsorption specific surface area of silica is a value measured by the BET method in accordance with ASTM D3037-81.

The CTAB (cetyltrimethyl ammonium bromide) specific surface area of the fine particle silica is preferably 150 m ² / g or more, more preferably 180 m ² / g or more, still more preferably 190 m ² / g from the viewpoint of abrasion resistance and performance on ice and snow It is above. The upper limit of the CTAB specific surface area is not particularly limited, but is preferably 400 m ² / g or less from the viewpoint of workability and processability. In addition, CTAB specific surface area is measured based on ASTMD3765-92.

When the rubber composition for cap tread contains silica, it is preferable to contain a silane coupling agent with silica.
As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry, and examples thereof include sulfides such as bis (3-triethoxysilylpropyl) disulfide, 3--3 Mercapto, such as mercaptopropyltrimethoxysilane, vinyl, such as vinyltriethoxysilane, amino, such as 3-aminopropyltriethoxysilane, glycidoxy of γ-glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxy Nitro type such as silane, chloro type such as 3-chloropropyltrimethoxysilane, and the like can be mentioned. Among them, sulfides are preferable, and bis (3-triethoxysilylpropyl) disulfide is more preferable.

The content of the silane coupling agent is preferably 1 part by mass or more, more preferably 3 parts by mass or more, with respect to 100 parts by mass of silica. By setting the lower limit or more, sufficient grip performance tends to be obtained. Further, the content of the silane coupling agent is preferably 15 parts by mass or less, more preferably 10 parts by mass or less. By setting the content to the upper limit or less, an effect commensurate with the amount to be blended tends to be obtained.

The rubber composition for cap tread preferably contains carbon black from the viewpoint of weatherability, grip performance (low temperature road surface and high temperature road surface), and abrasion resistance. Usable carbon blacks are not particularly limited, and common ones in the tire industry such as GPF, FEF, HAF, ISAF, and SAF can be used. These may be used alone or in combination of two or more.

The content of carbon black is preferably 1 part by mass or more, more preferably from the viewpoint that good weather resistance, grip performance (low temperature road surface and high temperature road surface) and abrasion resistance can be obtained relative to 100 parts by mass of the rubber component. 3 parts by mass or more. The content is preferably 30 parts by mass or less, more preferably 10 parts by mass or less from the viewpoint of low fuel consumption and processability.

The nitrogen adsorption specific surface area _(N 2 SA) of carbon black is good grip performance (low road and high temperature road), from the viewpoint of wear resistance is obtained, preferably ^{80 m} 2 / g or more, more preferably 100 m ² / It is more than g. From the viewpoint of processability, the carbon black N ₂ SA is preferably 200 m ² / g or less, more preferably 150 m ² / g or less. The nitrogen adsorption specific surface area of carbon black is measured by method A of JIS K6217.

The rubber composition for cap tread contains a plasticizer. Thereby, good grip performance (low temperature road surface and high temperature road surface) is imparted, and the performance balance with the abrasion resistance is significantly improved.

In the present invention, a plasticizer is a material that imparts plasticity to a rubber component, and, for example, a liquid plasticizer (process oil, extension oil, vegetable oil, animal oil and other oils and fats (oil); synthetic liquid ester plasticizer, liquid polymer Liquid resin such as liquid resin), wax, solid resin and the like. Specifically, it is a component extracted from a rubber composition using acetone.

In the rubber composition for a cap tread, the content of the plasticizer is 50 parts by mass or more, preferably 60 parts by mass or more, more preferably 65 parts by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of processability. is there. The upper limit of the content is not particularly limited, but is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 100 parts by mass or less from the viewpoint of good abrasion resistance and fracture resistance.

Oils include petroleum oils and the like. Specifically, in addition to paraffinic process oils, naphthenic process oils, and aromatic process oils, treated distillate aromatic extracts (TDAE (treated distillate aromatic extracts)), solvent residue aromatic extracts ( (SRAE) alternative aroma oils such as solvent residues aromatic extracts, mild extraction solvates (MES), and the like. Among them, TDAE is preferred.

The content (content) of the liquid plasticizer in 100% by mass of the plasticizer is preferably 30% by mass or less, more preferably 20% by mass or less from the viewpoint of grip performance (low temperature road surface and high temperature road surface) and abrasion resistance. More preferably, it is 18% by mass or less. The lower limit of the content is not particularly limited, and may be 0% by mass, preferably 1% by mass or more, and more preferably 3% by mass or more.
The liquid plasticizer is a plasticizer in a liquid state at 25 ° C.

As solid resin and liquid resin, for example, styrene resin, petroleum resin and / or coal resin (C5 system, C9 system, C5 / C9 system etc.), indene resin, coumarone indene resin, terpene resin, natural resin etc. Can be mentioned.

Examples of the C5-based resins include olefins in the C5 fraction obtained by naphtha decomposition, and aliphatic petroleum resins mainly composed of diolefins. Examples of the C9 resin include vinyl petroleum in the C9 fraction obtained by naphtha decomposition, indene, and aromatic petroleum resin having methyl indene as a main raw material.

The softening point of C5, C9 and C5 / C9 resins is preferably 0 ° C. or more, more preferably 20 ° C. or more, still more preferably 50 ° C. or more, particularly preferably 80 ° C. or more from the viewpoint of grip performance . The softening point is preferably 150 ° C. or less, more preferably 130 ° C. or less.

The content of the solid resin or liquid resin is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more from the viewpoint of grip performance (low temperature road surface and high temperature road surface) and abrasion resistance. Particularly preferably, it is 60 parts by mass or more. The upper limit of the content is not particularly limited, but is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 100 parts by mass or less.
The solid resin and the liquid resin are respectively a resin in a solid state at 25 ° C. and a resin in a liquid state.

A vulcanizing agent and a vulcanization accelerator are usually blended in the rubber composition for cap tread. The vulcanizing agent and the vulcanization accelerator are not particularly limited, and those common in the tire industry can be used.

As a vulcanizing agent, sulfur is preferable and powdered sulfur is more preferable. Also, sulfur and another vulcanizing agent may be used in combination. Other vulcanizing agents include, for example, Tackirol V200 manufactured by Taoka Chemical Industry Co., Ltd., DURALINK HTS (1,6-hexamethylene-sodium dithiosulfate dihydrate) manufactured by Flexis, and KA9188 manufactured by LANXESS. Sulfur-containing vulcanizing agents such as (1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane) and organic peroxides such as dicumyl peroxide can be mentioned.

The content of the vulcanizing agent is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 15 parts by mass or less, more preferably 100 parts by mass of the rubber component. It is 5 parts by mass or less.

As the vulcanization accelerator, guanidines, sulfenamides, thiazoles, thiurams, dithiocarbamates, thioureas and xanthogenates are preferable. Although these may be used independently, it is desirable to combine 2 or more types according to a use. Among them, it is preferable to use at least a guanidines vulcanization accelerator.

As guanidines vulcanization accelerator, 1,3-diphenyl guanidine, 1,3-di-o-tolyl guanidine, 1-o-tolylbiguanide, di-o-tolyl guanidine salt of dicatechol borate, 1,3- Examples include 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, 1,3-di-o-tolyl guanidine and 1-o-tolylbiguanide are particularly preferable in terms of high reactivity.

0.1-10 mass parts is preferable with respect to 100 mass parts of rubber components, and, as for content of a vulcanization accelerator, 0.2-7 mass parts is more preferable.

In the rubber composition for the cap tread, in addition to the above-mentioned materials, various materials generally used in the tire industry such as anti-aging agent, surfactant, zinc oxide, stearic acid, wax, etc. are suitably blended. It is also good.

As a method for producing a rubber composition for a cap tread, a known method can be used. For example, the above-mentioned components are kneaded using a rubber kneading apparatus such as an open roll or a Banbury mixer and then vulcanized. It can be manufactured.

[Base tread]
By using a base tread in addition to the cap tread made from the rubber composition for cap treads, it is possible to provide a pneumatic tire having a tread of a multilayer structure. As a rubber composition (rubber composition for base treads) used for a base tread, although a conventionally well-known thing containing a predetermined | prescribed rubber component, a filler, etc. can be used, what contains isoprene type rubber is preferable. Thereby, the difference in the rubber physical property between the cap / base of the tread can be reduced, and the improvement of the breaking performance and the reduction of noise can be realized.

In the rubber composition for base tread, the content (content) of isoprene-based rubber in 100% by mass of the rubber component is preferably 20% by mass or more, and 30% by mass or more from the viewpoint of steering stability, processability, etc. More preferably, 40% by mass or more is more preferable. The upper limit of the content is not particularly limited. Examples of usable isoprene rubbers include the same as described above.

[Pneumatic tire]
The rubber composition for the cap tread and the pneumatic tire using the rubber composition for the base tread can be produced by using the rubber composition according to a conventional method. That is, the rubber composition for the cap tread and the rubber composition for the base tread, in which various additives are compounded if necessary, are extruded according to the shape of the member at the unvulcanized stage, and the tire forming machine is manufactured. After forming an unvulcanized tire by molding in a conventional manner and bonding with other tire members, a tire can be manufactured by heating and pressing in a vulcanizer.

The pneumatic tire of the present invention can be suitably used as a studless tire, and can be applied to, for example, tires for passenger cars, tires for trucks and buses, tires for two-wheeled vehicles, high-performance tires and the like.

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

Hereinafter, various medicines used by an example and a comparative example are summarized and explained.
NR: TSR
BR: High cis BR (cis content: 96% by mass)
Modified SBR: Production Example 1
Silica 1: N ₂ SA 240 m ² / g, CTAB ²⁰⁰ m ² / g
Silica 2: N ₂ SA ₂₀₀ m ² / g, CTAB 155 m ² / g
Silica 3: N ₂ SA 175 m ² / g, CTAB 175 m ² / g
Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide carbon black: N ₂ SA 114 m ² / g
Oil: TDAE oil resin: C5 / C9 resin (softening point 86 ° C)
Stearic acid: Commercially available anti-aging agent: N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine zinc oxide: zinc oxide two sulfur: powdered sulfur vulcanization accelerator 1: N, N ' -Diphenylguanidine vulcanization accelerator 2: N-cyclohexyl-2-benzothiazolylsulfenamide

(Production Example 1: Synthesis of Modified SBR)
The inside of a 20 l stainless steel polymerization reactor is washed, dried, and replaced with dry nitrogen, and 10.2 kg of hexane (specific gravity 0.68 g / cm ³ ), 547 g of 1,3-butadiene, 173 g of styrene, tetrahydrofuran 6. 1 ml was charged into the polymerization reactor. Next, 13.1 mmol of n-butyllithium was introduced as an n-hexane solution to initiate polymerization.
The stirring speed was 130 rpm, the temperature in the polymerization reactor was 70 ° C., and copolymerization of 1,3-butadiene and styrene was performed for 3 hours while continuously feeding the monomers into the polymerization reactor. The feed amount of 1,3-butadiene in the entire polymerization was 821 g, and the feed amount of styrene was 259 g. Next, the obtained polymer solution was stirred at a stirring speed of 130 rpm, 11.1 mmol of 3-diethylaminopropyltriethoxysilane was added, and stirred for 15 minutes. To the polymer solution was added 20 ml of a hexane solution containing 0.54 ml of methanol, and the polymer solution was further stirred for 5 minutes.
Polymer solution containing 1.8 g of 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, pentaerythrityl tetrakis (3-lauryl thiopropionate) 0.9 g) was added, then the modified SBR was recovered from the polymer solution by steam stripping.
The obtained modified SBR had a styrene content of 25% by mass, a vinyl content of 28% by mole, Mw / Mn = 1.1, and Mw of 600,000.

The molecular weight, styrene content and vinyl content of the obtained polymer were analyzed by the following method.
Molecular weight
The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) under the following conditions (1) to (8). Then, the molecular weight distribution (Mw / Mn) of the polymer was determined from the measured Mw and Mn.
(1) Device: HLC-8020 manufactured by Tosoh Corporation
(2) Separation column: GMH-XL (two in series) manufactured by Tosoh Corp.
(3) Measurement temperature: 40 ° C
(4) Carrier: tetrahydrofuran (5) Flow rate: 0.6 mL / min (6) Injection amount: 5 μL
(7) Detector: Differential refraction (8) Molecular weight standard: Standard polystyrene

<Vinyl content (unit: mol%)>
The amount of vinyl bonds in the polymer was determined from the absorption intensity near 910 cm ^−1, which is the absorption peak of vinyl groups, by infrared spectroscopy.

<Styrene content (unit: mass%)>
The content of styrene units of the polymer was determined from the refractive index according to JIS K6383 (1995).

[Manufacturing method of rubber composition for cap tread]
The materials described in the base kneading step were kneaded for 5 minutes under the condition of 150 ° C. using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd. according to the contents of the formulation shown in Table 1 to obtain a kneaded product . Next, the chemicals described in the finishing and kneading step were added to the obtained kneaded product, and kneaded using an open roll for 5 minutes at 80 ° C. to obtain an unvulcanized rubber composition.

[Manufacturing method of rubber composition for base tread]
Materials other than sulfur and a vulcanization accelerator are knead | mixed for 5 minutes on the conditions of 150 degreeC using the 1.7 L Banbury mixer made from Kobe Steel, Ltd. according to the compounding content shown in Table 2 for 5 minutes, and the kneaded material is Obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded using an open roll for 5 minutes at 80 ° C. to obtain an unvulcanized rubber composition.

[Manufacturing method of test tire]
According to Tables 1-2, the obtained rubber composition for unvulcanized cap tread is molded into a cap tread, and the rubber composition for unvulcanized base tread is molded into a shape of a base tread. They were bonded together with the members to form an unvulcanized tire, which was vulcanized at 170 ° C. for 10 minutes to produce a test tire (size: 195 / 65R15, studless tire for passenger car).

[Evaluation]
The test tires were evaluated by the following method, and the results are shown in Table 1.

<Abrasion resistance>
The test tire was mounted on a domestic FF 2000 cc car, and the groove depth of the tire tread portion after a traveling distance of 5000 km at a speed of 100 to 150 km / hour was measured. The travel distance when the tire groove depth decreased by 1 mm was calculated, and was indexed according to the following equation. The higher the index, the better the wear resistance.
(Abrasion resistance index) = (traveling distance when the groove depth decreases by 1 mm) / (traveling distance when the tire groove of Comparative Example 1 decreases by 1 mm) × 100

<Low temperature high speed grip performance>
Install the test tire on a domestic 2000cc FF car and drive on a road surface at 0 ° C to 3 ° C without snow and ice on the Hokkaido Asahikawa test course, and apply the lock brake at a speed of 160 km / h before stopping The required stopping distance was measured. Assuming that Comparative Example 1 is 100, the following equation was used. The larger the index, the better the braking performance at low temperatures.
(Low temperature high speed grip performance index) = (stop distance of Comparative Example 1) / (stop distance of each composition) × 100

<High temperature high speed grip performance>
The test was conducted under the same conditions as the above evaluation method of low-temperature high-speed grip performance except that the road temperature was 45 ° C., and the index was expressed by the following equation. The larger the index, the better the braking performance at high temperatures.
(High-temperature high-speed grip performance index) = (Stop distance of Comparative Example 1) / (Stop distance of each composition) × 100

<Low temperature wet grip performance>
The test was conducted under the same conditions as in the evaluation method for low-temperature high-speed grip performance except that the vehicle was driven on a wet road surface, and the index was expressed by the following equation. The larger the index, the better the wet grip performance at low temperatures.
(Low temperature wet grip performance index) = (stop distance of Comparative Example 1) / (stop distance of each composition) × 100

From Tables 1 to 2, the total content of SBR and BR in the rubber component and the content of isoprene-based rubber in the filler containing SBR and / or BR, isoprene-based rubber, filler, and plasticizer The tire of the example using the rubber composition for a cap tread having a silica content of 50% and a content of silica and a plasticizer relative to the rubber component is a grip performance at high speeds (low temperature road surface and high temperature road surface). And wear resistance was very good. Furthermore, the wet grip performance was also good.

On the other hand, Comparative Examples 1 and 3 which do not contain or contain a large amount of isoprene rubber (the amount of SBR and BR is small) and Comparative Example 2 which has a small amount of silica have inferior balance of grip performance and abrasion resistance, , Wet grip performance was also inferior. Furthermore, Comparative Example 4 with a small amount of plasticizer was difficult to knead and form because of poor processability, and could not be evaluated. From the above results, it has become clear that a very excellent performance balance can be obtained only in the case where a specific component of the present invention is blended in a predetermined amount of the present application.

Claims (6)

A styrene butadiene rubber and / or a butadiene rubber, an isoprene rubber, a filler and a plasticizer,
The total content of styrene butadiene rubber and butadiene rubber in 100 mass% of the rubber component is 90 mass% or more, and the content of isoprene rubber is 0.3 to 8 mass%,
The silica content in 100% by mass of the filler is 80% by mass or more,
A cap tread made of a rubber composition for a cap tread, wherein the content of silica is 130 parts by mass or more and the content of a plasticizer is 50 parts by mass or more with respect to 100 parts by mass of the rubber component,
A pneumatic tire comprising: a base tread made of a rubber composition for a base tread having a content of isoprene-based rubber in 20% by mass of a rubber component of 20% by mass or more . The pneumatic tire according to claim 1, wherein the styrene butadiene rubber has a vinyl content of 70 mol% or less. The pneumatic tire according to claim 1 or 2, wherein the styrene butadiene rubber is a modified styrene butadiene rubber having a functional group capable of interacting with silica. The pneumatic tire according to any one of claims 1 to 3, wherein the content of styrene butadiene rubber in 100% by mass of the rubber component is 80% by mass or more. The pneumatic tire according to any one of claims 1 to 4, wherein the content of the liquid plasticizer in 100% by mass of the plasticizer is 20% by mass or less. The pneumatic tire according to any one of claims 1 to 5, wherein the content of the silica having a nitrogen adsorption specific surface area of 190 m ² / g or more per 100 parts by mass of the rubber component is 50 parts by mass or more.