JP2011144323A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for tires, which can improve low fuel cost property, wet grip performance, abrasion resistance and extrusion processability in good balance, and to provide a pneumatic tire using the same. <P>SOLUTION: The rubber composition for tires comprises a rubber component containing a dienic polymer modified with a compound represented by formula (1), silica, and a liquid resin having a softening point of -20 to 20°C, wherein the content of the silica is 10 to 150 pts.mass per 100 pts.mass of the rubber component, and the content of the liquid resin is 3 to 40 pts.mass per 100 pts.mass of the rubber component. In formula (1), R<SP>1</SP>, R<SP>2</SP>and R<SP>3</SP>are the same or different and are each alkyl, alkoxy, silyloxy, acetal, carboxyl, mercapto or their derivatives; R<SP>4</SP>and R<SP>5</SP>are the same or different and are each H or alkyl; and n is an integer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a rubber composition for tires and a pneumatic tire using the same.

Conventionally, vehicle fuel efficiency has been reduced by reducing the rolling resistance of tires (improving rolling resistance performance). In recent years, there has been an increasing demand for low fuel consumption of vehicles, and excellent low heat generation (low fuel consumption) for rubber compositions for producing treads with a high occupation ratio of tires among tire components. Sex) is required.

As a method for improving the low fuel consumption of the rubber composition, a method of reducing the reinforcing filler is known. However, when the amount of the reinforcing filler is reduced, the hardness of the rubber composition tends to decrease and wet grip performance and wear resistance tend to deteriorate, and the shape of the rubber composition does not stabilize, and the extrudability deteriorates. There was a trend.

In general, a softening agent such as aroma oil is added to the rubber composition for tires in order to improve the extrudability and wet grip performance. However, when the aroma oil is added, the rolling resistance increases and the fuel efficiency tends to deteriorate. Therefore, a method for improving the fuel economy, wet grip performance, abrasion resistance and extrusion processability in a well-balanced manner has been desired.

Patent Documents 1 to 4 propose to improve grip performance and the like using a resin (resin) such as an indene resin. However, these rubber compositions still have room for improvement in terms of improving fuel economy, wet grip performance, wear resistance, and extrusion processability in a well-balanced manner.

JP 2006-124601 A JP 2004-137463 A JP 2009-7454 A JP 2001-240704 A

An object of the present invention is to solve the above-mentioned problems and provide a rubber composition for a tire that can improve fuel economy, wet grip performance, wear resistance and extrusion processability in a well-balanced manner, and a pneumatic tire using the same. And

（式中、Ｒ^１、Ｒ^２及びＲ^３は、同一若しくは異なって、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、メルカプト基又はこれらの誘導体を表す。Ｒ^４及びＲ^５は、同一若しくは異なって、水素原子又はアルキル基を表す。ｎは整数を表す。） The present invention contains a rubber component containing a diene polymer modified with a compound represented by the following formula (1), silica, and a liquid resin having a softening point of -20 to 20 ° C. It is related with the rubber composition for tires whose content of the said silica is 10-150 mass parts and whose content of the said liquid resin is 3-40 mass parts with respect to 100 mass parts of components.

(Wherein 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, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different, and represents a hydrogen atom or an alkyl group. N represents an integer.)

The liquid resin is preferably at least one selected from the group consisting of a liquid coumarone indene resin, a liquid indene resin, and a liquid α-methylstyrene resin.

In 100% by mass of the rubber component, the content of the diene polymer modified with the compound represented by the formula (1) is preferably 10% by mass or more.

The diene polymer modified with the compound represented by the above formula (1) is preferably a styrene butadiene rubber and / or butadiene rubber modified with the compound represented by the above formula (1).

The nitrogen adsorption specific surface area of the silica is preferably 40 to 220 m ² / g.

The rubber composition is preferably used for a tread.

The present invention also relates to a pneumatic tire using the rubber composition.

According to the present invention, there is provided a tire rubber composition in which a predetermined amount of silica and a liquid resin having a specific softening point are blended with a rubber component containing a diene polymer modified with a specific compound. Therefore, by using the rubber composition for each member (particularly, tread) of the tire, it is possible to provide a pneumatic tire having improved fuel economy, wet grip performance, wear resistance, and extrusion processability in a well-balanced manner.

The present invention is a tire rubber composition in which a predetermined amount of silica and a liquid resin having a specific softening point are blended with a rubber component containing a diene polymer modified with a specific compound. By using these components in combination, fuel economy, wet grip performance, wear resistance and extrusion processability are improved in a well-balanced manner.

In the compound represented by the above formula (1), R ¹ , R ² and R ³ are the same or different and are an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (— SH) or derivatives thereof.
As said alkyl group, C1-C4 alkyl groups, such as a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, etc. are mentioned, for example.

Examples of the alkoxy group include alkoxy groups having 1 to 8 carbon atoms such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group and t-butoxy group (preferably having 1 to 6 carbon atoms). More preferably, C1-C4) etc. are mentioned. The alkoxy group includes a cycloalkoxy group (cycloalkoxy group having 5 to 8 carbon atoms such as cyclohexyloxy group) and an aryloxy group (aryloxy group having 6 to 8 carbon atoms such as phenoxy group and benzyloxy group). ) Is also included.

Examples of the silyloxy group include a silyloxy group substituted with an aliphatic group having 1 to 20 carbon atoms and an aromatic group (trimethylsilyloxy group, triethylsilyloxy group, triisopropylsilyloxy group, diethylisopropylsilyloxy group, t- Butyldimethylsilyloxy group, t-butyldiphenylsilyloxy group, tribenzylsilyloxy group, triphenylsilyloxy group, tri-p-xylylsilyloxy group, etc.).

Examples of the acetal group include groups represented by -C (RR ')-OR "and -O-C (RR')-OR". Examples of the former include a methoxymethyl group, an ethoxymethyl group, a propoxymethyl group, a butoxymethyl group, an isopropoxymethyl group, a t-butoxymethyl group, and a neopentyloxymethyl group. The latter includes a methoxymethoxy group, an ethoxy group, and the like. Methoxy group, propoxymethoxy group, i-propoxymethoxy group, n-butoxymethoxy group, t-butoxymethoxy group, n-pentyloxymethoxy group, n-hexyloxymethoxy group, cyclopentyloxymethoxy group, cyclohexyloxymethoxy group, etc. Can be mentioned.

R ¹ , R ² and R ³ are preferably alkoxy groups, and more preferably methoxy groups. Thereby, both wear resistance and low fuel consumption can be achieved.

In the compound represented by the above formula (1), R ⁴ and R ⁵ are the same or different and each represents a hydrogen atom, an alkyl group or a cyclic ether group.

Examples of the alkyl group for R ⁴ and R ⁵ include the same groups as the above alkyl groups.

As R ⁴ and R ⁵ , an alkyl group (preferably having 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms) is preferable, and an ethyl group is more preferable. Thereby, both wear resistance and low fuel consumption can be achieved.

As n (integer), 2-5 are preferable. Thereby, both wear resistance and low fuel consumption can be achieved. Furthermore, n is more preferably 2 to 4, and most preferably 3. If n is 1 or less, the denaturation reaction may be inhibited, and if n is 6 or more, the effect as a denaturing agent is reduced.

Specific examples of the compound represented by the above formula (1) include 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, Aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethylbutoxysilane, 3-aminopropylmethyldibutoxysilane, dimethylaminomethyltrimethoxysilane, 2-dimethyl Aminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 4-dimethylaminobutyltrimethoxysilane, dimethylaminomethyldimethoxymethylsilane, 2-dimethylaminoethyldimethoxy Methylsilane, 3-dimethylaminopropyldimethoxymethylsilane, 4-dimethylaminobutyldimethoxymethylsilane, dimethylaminomethyltriethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 4-dimethylaminobutyl Triethoxysilane, dimethylaminomethyldiethoxymethylsilane, 2-dimethylaminoethyldiethoxymethylsilane, 3-dimethylaminopropyldiethoxymethylsilane, 4-dimethylaminobutyldiethoxymethylsilane, diethylaminomethyltrimethoxysilane, 2- Diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 4-diethylaminobutyltrimethoxysilane, diethylamino Tildimethoxymethylsilane, 2-diethylaminoethyldimethoxymethylsilane, 3-diethylaminopropyldimethoxymethylsilane, 4-diethylaminobutyldimethoxymethylsilane, diethylaminomethyltriethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane 4-diethylaminobutyltriethoxysilane, diethylaminomethyldiethoxymethylsilane, 2-diethylaminoethyldiethoxymethylsilane, 3-diethylaminopropyldiethoxymethylsilane, 4-diethylaminobutyldiethoxymethylsilane, and the like. These may be used alone or in combination of two or more.

Examples of the modification method of the diene polymer by the compound represented by the above formula (1) (modifier) include conventional methods such as those described in JP-B-6-53768 and JP-B-6-57767. A known method can be used. For example, a diene polymer and a modifier may be brought into contact with each other. A method of polymerizing a diene polymer and adding a predetermined amount of the modifier to the diene polymer solution, or modifying the diene polymer solution. The method of adding an agent and making it react is mentioned.

The diene polymer to be modified is not particularly limited, and isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber. Examples include diene-based synthetic rubbers such as (NBR) and butyl rubber (IIR). These may be used alone or in combination of two or more. Among these, BR and SBR are preferable, and SBR is more preferable because of good co-crosslinking properties with adjacent members, fracture characteristics, fuel efficiency, and grip performance.

When the modified diene polymer is a modified styrene butadiene rubber (modified SBR), the vinyl content of the modified SBR is preferably 70% by mass or less, more preferably 60% by mass or less, and still more preferably 50% by mass or less. When the vinyl content exceeds 70% by mass, low heat build-up tends to be impaired. The vinyl content is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. When the vinyl content is less than 5% by mass, the wet grip performance tends to deteriorate.
The vinyl content (1,2-bond butadiene unit amount) can be measured by infrared absorption spectrum analysis.

The content of the modified diene polymer in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 35% by mass or more, and further preferably 55% by mass or more. If it is less than 10% by mass, sufficient wet grip performance may not be ensured. The content of the modified diene polymer is preferably 85% by mass or less, more preferably 75% by mass or less, and preferably 65% by mass or less. If it exceeds 85% by mass, kneadability and breaking strength tend to deteriorate.

The rubber component that can be used in the present invention other than the modified diene polymer is not particularly limited, and examples thereof include diene rubbers such as the above-mentioned diene synthetic rubber, natural rubber (NR), and epoxidized natural rubber (ENR). Diene rubbers may be used alone or in combination of two or more. Of these, NR and BR are preferable because they show wet grip performance and wear resistance in a well-balanced manner.

The NR is not particularly limited, and for example, SIR20, RSS # 3, TSR20, deproteinized natural rubber (DPNR), high-purity natural rubber (HPNR), and the like can be used in the tire industry.

The content of NR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 7% by mass or more. If it is less than 5% by mass, kneadability and breaking strength tend to deteriorate. The NR content is preferably 90% by mass or less, more preferably 85% by mass or less. When it exceeds 90 mass%, there is a possibility that sufficient low exothermic property cannot be obtained.

The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B having a high cis content such as BR150B, VCR412 manufactured by Ube Industries, Ltd. Commonly used in the tire industry, such as BR containing syndiotactic polybutadiene crystals, can be used.

The content of BR in 100% by mass of the rubber component is preferably 80% by mass or less, more preferably 60% by mass or less. When it exceeds 80 mass%, there exists a tendency for workability, breaking strength, and wet grip performance to deteriorate.

In the present invention, silica is used. By blending silica with the modified diene polymer, good low heat buildup and high rubber strength can be obtained, and both low fuel consumption and wear resistance can be achieved. The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² / g or more, more preferably 50 m ² / g or more. If it is less than 40 m < ² > / g, there exists a tendency for a fracture characteristic to fall. Further, N ₂ SA of silica is preferably 220 m ² / g or less, more preferably 200 m ² / g or less. When it exceeds 220 m ² / g, low exothermic property and kneading workability tend to deteriorate.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica is 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 45 parts by mass, and still more preferably 65 parts by mass with respect to 100 parts by mass of the rubber component. If the content of silica is less than 10 parts by mass, sufficient effects due to the blending of silica tend not to be obtained. Moreover, content of a silica is 150 mass parts or less, Preferably it is 120 mass parts or less, More preferably, it is 100 mass parts or less, More preferably, it is 85 mass parts or less. When the content of silica exceeds 150 parts by mass, silica becomes difficult to disperse and kneadability tends to deteriorate.

Silica is preferably used in combination with a silane coupling agent. 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 sulfide systems such as bis (3-triethoxysilylpropyl) disulfide, 3- Mercapto type such as mercaptopropyltrimethoxysilane, vinyl type such as vinyltriethoxysilane, amino type such as 3-aminopropyltriethoxysilane, glycidoxy type of γ-glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxy Examples thereof include nitro compounds such as silane and chloro compounds such as 3-chloropropyltrimethoxysilane. These may be used alone or in combination of two or more. Among these, sulfide type is preferable, and bis (3-triethoxysilylpropyl) disulfide is more preferable.

The content of the silane coupling agent is preferably 5 parts by mass or more, more preferably 8 parts by mass or more with respect to 100 parts by mass of the silica. If it is less than 5 mass parts, there exists a tendency for a fracture characteristic to fall large. The content of the silane coupling agent is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, with respect to 100 parts by mass of the silica. When the amount exceeds 15 parts by mass, effects such as an increase in fracture characteristics and a reduction in rolling resistance due to the addition of the silane coupling agent tend not to be obtained.

The rubber composition of the present invention contains a liquid resin having a specific softening point. By using the liquid resin as an alternative to oil, it is possible to improve the fuel efficiency, fracture characteristics and extrusion processability in a well-balanced manner while maintaining the hardness. This effect is considered due to the compatibility of the liquid resin with the rubber component and the viscosity characteristics of the liquid resin.

Examples of the liquid resin include liquid petroleum-based or coal-based resins such as liquid coumarone indene resin, liquid indene resin, liquid α-methylstyrene resin, liquid vinyltoluene resin, and liquid polyisopentane resin. Among these, at least one selected from the group consisting of liquid coumarone indene resin, liquid indene resin, and liquid α-methylstyrene resin is preferable, and liquid coumarone indene resin is more preferable.

The softening point of the liquid resin is −20 ° C. or higher, preferably −5 ° C. or higher, more preferably 0 ° C. or higher. When the temperature is lower than -20 ° C, the viscosity of the liquid resin becomes too low, and the kneadability with the rubber component tends to deteriorate. The softening point of the liquid resin is 20 ° C. or lower, preferably 18 ° C. or lower, more preferably 17 ° C. or lower. If it exceeds 20 ° C., the exothermic property of the liquid resin increases, and the fuel efficiency tends to deteriorate.
In this specification, the softening point is a temperature at which a sphere descends when the softening point defined in JIS K 6220 is measured with a ring and ball softening point measuring device.

The content of the liquid resin is 3 parts by mass or more, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, and particularly preferably 18 parts by mass with respect to 100 parts by mass of the rubber component. More than a part. If it is less than 3 parts by mass, the extrudability and fuel efficiency may not be sufficiently improved. The content of the liquid resin is 40 parts by mass or less, preferably 35 parts by mass or less, and more preferably 30 parts by mass or less with respect to 100 parts by mass of the rubber component. When it exceeds 40 mass parts, there exists a tendency for abrasion resistance to deteriorate.

You may mix | blend carbon black with the said rubber composition. Thereby, reinforcement is obtained, and wear resistance and extrusion processability can be further improved. As the carbon black, for example, those generally used in the tire industry such as GPF, HAF, ISAF, and SAF can be used.

When carbon black is used, the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably 30 m ² / g or more, more preferably 70 m ² / g or more. When N ₂ SA is less than 30 m ² / g, there is a tendency that sufficient reinforcing properties cannot be obtained. Also, _N 2 SA of carbon black is preferably 250 meters ² / g or less, and more preferably not more than 150m ² / g. When N ₂ SA exceeds 250 m ² / g, the viscosity of the unvulcanized rubber composition becomes very high and the kneading processability tends to deteriorate or the fuel efficiency tends to deteriorate.
Note that N ₂ SA of carbon black is obtained by JIS K6217, method A on page 7.

The content of carbon black is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 5 parts by mass, sufficient reinforcing properties tend not to be obtained. The carbon black content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, still more preferably 30 parts by mass or less, and particularly preferably 15 parts by mass or less with respect to 100 parts by mass of the rubber component. . If it exceeds 60 parts by mass, the fuel efficiency tends to deteriorate.

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 reinforcing fillers such as clay, zinc oxide, stearic acid, various anti-aging agents, aromas Oils such as oil, waxes, vulcanizing agents such as sulfur, vulcanization accelerators and the like can be appropriately blended.

The liquid resin has an action of softening the rubber composition. Therefore, by using the liquid resin, the content of oil in the rubber composition can be reduced, and the fuel efficiency can be further improved.

The oil content is preferably 3 parts by mass or less, more preferably 1 part by mass or less, still more preferably 0.1 parts by mass or less, particularly preferably 0 parts by mass (not contained) with respect to 100 parts by mass of the rubber component. It is.

The rubber composition of the present invention can be used for each member used in a tire, and among these, it is preferably used for a tread (cap tread and base tread), and more preferably used for a cap tread.

As a method for producing the rubber composition of the present invention, a known method can be employed, and examples thereof include a method of kneading the above components using a rubber kneading device such as a Banbury mixer or an open roll.

Using the rubber composition of the present invention, the pneumatic tire of the present invention can be produced by an ordinary method. That is, a tire member such as a tread can be produced using the rubber composition, bonded together with other members, and heated and pressurized on a tire molding machine. A tread can be produced by a method of pasting a rubber composition in a sheet shape into a predetermined shape, a method of charging two or more extruders, and forming two layers at the head outlet of the extruder. it can.

The pneumatic tire of the present invention can be used for passenger cars, trucks, buses and the like.

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.
Modified SBR (SBR (1)): Modified styrene butadiene rubber manufactured by Sumitomo Chemical Co., Ltd. (vinyl content: 58 mass%, R ¹ , R ² and R ³ = —OCH ₃ , R ⁴ and R ⁵ = —CH ₂ CH ₃ , n = 3)
Non-modified SBR (SBR (2)): Non-modified styrene butadiene rubber manufactured by Sumitomo Chemical Co., Ltd. (vinyl content: 53% by mass, containing 37.5 parts by mass of oil with respect to 100 parts by mass of rubber solid content)
BR: Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.
NR: RSS # 3
Silica: Ultrasil VN3 manufactured by Evonik Degussa (average primary particle size: 15 nm, N ₂ SA: 175 m ² / g)
Carbon black: Dia Black I (N220, N ₂ SA: 114 m ² / g) manufactured by Mitsubishi Chemical Corporation
Silane coupling agent: Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa
Zinc oxide: Zinc Hana No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Stearic acid “Kashiwa” manufactured by NOF Corporation
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Aroma oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Liquid resin (1): NOVARES C10 (liquid coumarone indene resin, softening point: 5 to 15 ° C.) manufactured by Rutgers Chemicals
Liquid resin (2): NOVARES TL10 manufactured by Rutgers Chemicals (liquid resin mainly composed of α-methylstyrene and indene, softening point: 5 to 15 ° C.)
Solid resin: NOVARES C90 (Coumarone indene resin, softening point: 85-95 ° C.) manufactured by Rutgers Chemicals
Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. (1): Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator (2): Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-3 and Comparative Examples 1-5
According to the formulation shown in Table 1, using a 1.7 L Banbury mixer, materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes at 150 ° C. to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 80 ° C. using a biaxial open roll to obtain an unvulcanized rubber composition. Further, the obtained unvulcanized rubber composition is molded into a cap tread shape, bonded together with other tire members on a tire molding machine, and vulcanized at 150 ° C. for 30 minutes, so that a test tire (size: 195 / 65R15).

The following evaluation was performed using the obtained unvulcanized rubber composition and the test tire. The results are shown in Table 1.

(Low fuel consumption)
Using a rolling resistance tester, the rolling resistance when the test tire was run at a rim (15 × 6JJ), internal pressure (230 kPa), load (3.43 kN), speed (80 km / h) was measured, The fuel efficiency index of Comparative Example 2 was set to 100, and the index was displayed by the following formula. A larger value indicates lower rolling resistance and better fuel efficiency.
(Low fuel efficiency index) = (Rolling resistance of Comparative Example 2) / (Rolling resistance of each formulation) × 100

(Wet grip performance)
A braking distance from an initial speed of 100 km / h was determined on a wet asphalt road surface using a vehicle equipped with the test tire. And the wet grip performance index | exponent of the comparative example 2 was set to 100, and the index display was carried out with the following formula. It shows that it is excellent in wet grip performance, so that a value is large.
(Wet grip performance index) = (Brake distance of Comparative Example 2) / (Brake distance of each formulation) × 100

(Abrasion resistance)
The vehicle equipped with the test tire was run, and the change in pattern groove depth before and after running 30000 km was determined. Then, the travel distance when the groove depth decreased by 1 mm was calculated, and the index was displayed by the following calculation formula with the abrasion resistance index of Comparative Example 2 as 100. It shows that it is excellent in abrasion resistance, so that a value is large.
(Abrasion resistance index) = (travel distance of each formulation) / (travel distance of Comparative Example 2) × 100

(Extrudability)
The roughness of the rubber skin (surface shape) of the unvulcanized rubber composition formed into a sheet using an open roll was visually observed and evaluated on a 5-point scale. The closer to 5, the better the extrudability.

From Table 1, the examples in which the silica component, the silane coupling agent, and the liquid resin were blended in a predetermined amount with respect to the rubber component containing the modified diene polymer, while maintaining the extrusion processability as compared with the comparative example. Improved fuel economy, wet grip performance and wear resistance in a well-balanced manner. On the other hand, since the comparative example did not contain a predetermined amount of the above components, the balance of each performance was poor.

Claims (7)

A rubber component containing a diene polymer modified with a compound represented by the following formula (1), silica, and a liquid resin having a softening point of -20 to 20 ° C,
A rubber composition for tires, in which the silica content is 10 to 150 parts by mass and the liquid resin content is 3 to 40 parts by mass with respect to 100 parts by mass of the rubber component.

(Wherein 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, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different, and represents a hydrogen atom or an alkyl group. N represents an integer.) The tire rubber composition according to claim 1, wherein the liquid resin is at least one selected from the group consisting of a liquid coumarone indene resin, a liquid indene resin, and a liquid α-methylstyrene resin. The rubber composition for a tire according to claim 1 or 2, wherein the content of the diene polymer modified with the compound represented by the formula (1) is 10% by mass or more in 100% by mass of the rubber component. The diene polymer modified with the compound represented by the formula (1) is a styrene butadiene rubber and / or butadiene rubber modified with the compound represented by the formula (1). The rubber composition for tires in any one. The tire rubber composition according to claim 1, wherein the silica has a nitrogen adsorption specific surface area of 40 to 220 m ² / g. The rubber composition for a tire according to any one of claims 1 to 5, which is used for a tread. A pneumatic tire using the rubber composition according to claim 1.