JP2015174990A - pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having a high mileage, wet grip performance, and steering stability all improved in a well balanced manner.SOLUTION: The pneumatic tire includes a tread composed of the following rubber composition. The rubber composition comprises a rubber component, silica, and a liquid resin having a softening point of 7 to 15°C, in which natural rubber is included by 10 to 30 mass% in 100 mass% of the rubber component, and with respect to 100 parts by mass of the rubber component, the silica is included by 105 to 160 parts by mass, the liquid resin is included by 30 to 50 parts by mass, and oil and resins excluding the liquid resin are included in total by 0 to 5 parts by mass.

Description

The present invention relates to a pneumatic tire including a tread composed of a rubber composition.

As a rubber composition for an automobile tire, a rubber composition containing a conjugated diene polymer such as polybutadiene or butadiene-styrene copolymer and a filler such as carbon black or silica is used. In recent years, due to increasing interest in environmental issues, there has been a strong demand for lower fuel consumption for automobiles, and rubber compositions used for automobile tires are also required to have excellent fuel efficiency. .

As a method for improving fuel economy, for example, Patent Document 1 proposes a method using a diene rubber (modified rubber) modified with an organosilicon compound containing an amino group and an alkoxy group. However, in recent years, further improvement in fuel economy has been demanded due to an increase in interest in environmental problems. In addition, the performance required for rubber compositions for automobile tires includes wet grip performance and steering stability, but these performances are generally in contradiction to low fuel consumption, and each performance is It was difficult to obtain a high dimension and good balance.

JP 2000-344955 A

An object of the present invention is to solve the above-mentioned problems and to provide a pneumatic tire in which fuel economy, wet grip performance, and steering stability are improved in a well-balanced manner.

The present invention contains a rubber component, silica, and a liquid resin having a softening point of 7 to 15 ° C.
In 100% by mass of the rubber component, the content of natural rubber is 10 to 30% by mass,
The content of the silica with respect to 100 parts by mass of the rubber component is 105 to 160 parts by mass, the content of the liquid resin is 30 to 50 parts by mass, and the total content of the resin and the oil excluding the liquid resin is 0. The present invention relates to a pneumatic tire including a tread composed of a rubber composition that is ˜5 parts by mass.

It is preferable that the content (A) of the silica and the total content (B) of the resin and the oil satisfy the following formula (C).
0.27 ≦ (B) / (A) ≦ 0.42 (C)

The glass transition temperature of the rubber composition is preferably in the range of -17 to 7 ° C.

The silica preferably contains silica (I) having a nitrogen adsorption specific surface area of 100 m ² / g or less and silica (II) having a nitrogen adsorption specific surface area of 150 m ² / g or more.

It is preferable that the contents of silica (I) and (II) satisfy the following formula.
(Content of silica (I)) × 0.2 ≦ (content of silica (II)) ≦ (content of silica (I)) × 6.5

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.

（式（１）中、Ｒ^１は、水素原子、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、分岐若しくは非分岐の炭素数６〜３０のアリール基、又は水酸基を表す。Ｒ^２及びＲ^３は、同一若しくは異なって、水素原子、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、分岐若しくは非分岐の炭素数２〜３０のアルキニル基、分岐若しくは非分岐の炭素数６〜３０のアリール基、又は下記式（２）で表される基を表し、該アルキル基、該アルケニル基、該アルキニル基、該アリール基が有する水素原子が水酸基又はカルボキシル基で置換されていてもよい。Ｒ^１とＲ^２、Ｒ^１とＲ^３、又はＲ^２とＲ^３とで環構造を形成してもよい。ｎは、０〜８の整数を表す。）

（式（２）中、Ｒ^４は、分岐若しくは非分岐の炭素数１〜３０のアルキレン基を表す。Ｒ^５は、水素原子、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、分岐若しくは非分岐の炭素数６〜３０のアリール基、又は水酸基を表す。ｐは、０〜１０の整数を表す。） The rubber composition preferably contains a compound represented by the following formula (1).

(In Formula (1), R ¹ is a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, a branched or unbranched carbon number of 6; R ² and R ³ are the same or different and each represents a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched carbon group having 2 to 30 carbon atoms. An alkenyl group, a branched or unbranched alkynyl group having 2 to 30 carbon atoms, a branched or unbranched aryl group having 6 to 30 carbon atoms, or a group represented by the following formula (2): The hydrogen atom of the alkenyl group, the alkynyl group or the aryl group may be substituted with a hydroxyl group or a carboxyl group, and R ¹ and R ² , R ¹ and R ³ , or R ² and R ^{3 represent} a ring structure. Forming Good .n represents an integer of 0-8.)

(In formula (2), R ⁴ represents a branched or unbranched alkylene group having 1 to 30 carbon atoms. R ⁵ represents a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, branched or An unbranched alkenyl group having 2 to 30 carbon atoms, a branched or unbranched aryl group having 6 to 30 carbon atoms, or a hydroxyl group, and p represents an integer of 0 to 10.)

It is preferable that content of the compound represented by Formula (1) with respect to 100 mass parts of said silica is 0.1-20 mass parts.

According to the present invention, the rubber composition contains a specific amount of natural rubber, silica, and a liquid resin having a softening point of 7 to 15 ° C., and the total content of the resin and oil other than the liquid resin is a predetermined amount or less. Therefore, fuel efficiency, wet grip performance, and steering stability are improved in a well-balanced manner.

The pneumatic tire of the present invention contains a rubber component, silica, and a liquid resin having a softening point of 7 to 15 ° C., and the content of natural rubber is 10 to 30% by mass in 100% by mass of the rubber component. The content of the silica with respect to 100 parts by mass of the rubber component is 105 to 160 parts by mass, the content of the liquid resin is 30 to 50 parts by mass, and the total content of the resin and the oil excluding the liquid resin is A tread composed of 0 to 5 parts by mass of a rubber composition is provided. Hereinafter, the rubber composition is also referred to as a rubber composition according to the present invention.

The rubber composition according to the present invention contains natural rubber (NR). Thereby, the effect of this invention is acquired suitably.
The NR is not particularly limited, and for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20, and the like can be used.

The content of NR in 100% by mass of the rubber component is 10% by mass or more, preferably 12% by mass or more, and more preferably 15% by mass or more. If it is less than 10% by mass, sufficient fuel economy and wet grip performance tend not to be obtained. The NR content is 30% by mass or less, preferably 28% by mass or less, and more preferably 25% by mass or less. When it exceeds 30 mass%, there exists a tendency for workability, wet grip performance, and steering stability to deteriorate. By making the content of NR within the above range, the effects of the present invention can be suitably obtained.

The rubber component that can be used other than the above NR is not limited, but for example, isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber ( And diene rubbers such as IIR). These rubber components may be used alone or in combination of two or more. Of these, BR and SBR are preferred because they exhibit a good balance between low fuel consumption, wet grip performance, and steering stability.

It is not particularly limited as BR, for example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B having high cis content such as BR150B, VCR412 manufactured by Ube Industries, Ltd., VCR617, etc. BR containing syndiotactic polybutadiene crystals can be used. Of these, the BR cis content is preferably 90% by mass or more because of its good wear resistance and low fuel consumption.

When the rubber composition according to the present invention contains BR, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 8% by mass or more. If the amount is less than 5% by mass, sufficient wear resistance and steering stability tend not to be obtained. The BR content is preferably 15% by mass or less, more preferably 10% by mass or less. If it exceeds 15% by mass, fuel economy tends to deteriorate.

The SBR is not particularly limited, and examples thereof include emulsion polymerization SBR (E-SBR), solution polymerization SBR (S-SBR), and modified SBR modified by a primary amino group. Among these, modified SBR is preferable because it has a high effect of improving wet grip performance, low fuel consumption, and steering stability.

As the modified SBR, those coupled with tin or silicon are preferably used. As a coupling method of the modified SBR, for example, an alkali metal (such as Li) or an alkaline earth metal (such as Mg) at the molecular chain terminal of the modified SBR is reacted with tin halide or silicon halide according to a conventional method. The method etc. are mentioned.

As the modified SBR, a copolymer of styrene and butadiene having a primary amino group or an alkoxysilyl group is also preferable. The primary amino group may be bonded to any of the polymerization initiation terminal, the polymerization termination terminal, the polymer main chain, and the side chain, but it can suppress the energy loss from the polymer terminal and improve the hysteresis loss characteristics. From the viewpoint, it is preferably introduced at the polymerization initiation terminal or the polymerization termination terminal.

Among the modified SBRs, those obtained by modifying the polymerization terminal (active terminal) of a styrene butadiene rubber (S-SBR), which is solution-polymerized, with a compound represented by the following formula (3) (modified S-SBR (JP 2010-2010)) The modified SBR)) described in Japanese Patent No. 111753 is preferably used. This makes it easy to control the molecular weight of the polymer, reduces the low molecular weight component that increases tan δ, and further strengthens the bond between silica and the polymer chain, further improving wet grip performance, fuel efficiency, and steering stability. .

（式（３）中、Ｒ^１１、Ｒ^１２及びＲ^１３は、同一若しくは異なって、アルキル基、アルコキシ基（好ましくは炭素数１〜８、より好ましくは炭素数１〜６、更に好ましくは炭素数１〜４のアルコキシ基）、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^１４及びＲ^１５は、同一若しくは異なって、水素原子又はアルキル基（好ましくは炭素数１〜４のアルキル基）を表す。ｎは整数（好ましくは１〜５、より好ましくは２〜４、更に好ましくは３）を表す。）

(In Formula (3), R <^11> , R < ¹² > and R <^13> are the same or different, and are an alkyl group and an alkoxy group (preferably having 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably having carbon atoms. 1 to 4 alkoxy group), a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (—SH), or a derivative thereof, R ¹⁴ and R ¹⁵ are the same or different and represent a hydrogen atom or an alkyl group. Represents a group (preferably an alkyl group having 1 to 4 carbon atoms), and n represents an integer (preferably 1 to 5, more preferably 2 to 4, more preferably 3).

As R ¹¹ , R ¹² and R ¹³ , an alkoxy group is desirable, and as R ¹⁴ and R ¹⁵ , a hydrogen atom is desirable. As a result, excellent wet grip performance, low fuel consumption, and steering stability can be obtained.

Specific examples of the compound represented by the above formula (3) include 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 2-dimethylaminoethyltrimethoxysilane, 3 -Diethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane and the like. These may be used alone or in combination of two or more.

Examples of the method for modifying the styrene butadiene rubber with the compound (modifier) represented by the above formula (3) are described in JP-B-6-53768, JP-B-6-57767, JP-T2003-514078, and the like. A conventionally known method such as a known method can be used. For example, a styrene butadiene rubber and a modifier may be brought into contact with each other. After a styrene butadiene rubber is synthesized by anionic polymerization, a predetermined amount of a modifier is added to the polymer rubber solution, and a polymerization terminal (active activity of the styrene butadiene rubber is activated. And a method in which a modifier is added to the styrene-butadiene rubber solution and reacted.

The amount of bound styrene in SBR is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and particularly preferably 25% by mass or more. If it is less than 10% by mass, sufficient wet grip performance may not be obtained. The amount of bound styrene is preferably 35% by mass or less, more preferably 30% by mass or less. If it exceeds 35% by mass, fuel efficiency may be deteriorated. The amount of bound styrene is calculated by H ¹ -NMR measurement.

When the rubber composition according to the present invention contains SBR, the content of SBR in 100% by mass of the rubber component is preferably 35% by mass or more, more preferably 42% by mass or more, and further preferably 65% by mass or more. is there. If it is less than 35% by mass, sufficient handling stability tends to be not obtained. Further, the content of SBR is preferably 90% by mass or less, more preferably 80% by mass or less. If it exceeds 90% by mass, the fuel efficiency tends to deteriorate.

The ratio of BR and SBR content can be changed or set as appropriate according to the application, category, destination, size, etc. of the tire using the rubber composition according to the present invention as a tread rubber for a tire. .

The rubber composition according to the present invention contains silica. Examples of silica include silica prepared by a dry method (anhydrous silicic acid), silica prepared by a wet method (hydrous silicic acid), etc., and there are many silanol groups on the surface, and reaction with a silane coupling agent. Silica prepared by a wet method is preferred because it has many points.
Silica may be used alone or in combination of two or more, but preferably in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 20 m ² / g or more, more preferably 30 m ² / g or more, further preferably 40 m ² / g or more, particularly preferably 70 m ² / g or more, and most preferably. Is 110 m ² / g or more, most preferably 150 m ² / g or more. If it is less than 20 m ² / g, wet grip performance and steering stability tend to decrease. The N ₂ SA of silica is preferably 400 m ² / g or less, more preferably 360 m ² / g or less, still more preferably 220 m ² / g or less, and particularly preferably 200 m ² / g or less. When it exceeds 400 m ² / g, the silica is difficult to disperse, and the workability and fuel efficiency may be deteriorated.
In the present specification, N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

In the present invention, as silica, silica (I) having a nitrogen adsorption specific surface area (N ₂ SA) of 100 m ² / g or less, silica (II) having a nitrogen adsorption specific surface area (N ₂ SA) of 150 m ² / g or more, and It is preferable to contain. Thereby, better fuel efficiency can be obtained, and fuel economy, wet grip performance, and steering stability can be obtained in a more balanced manner.

N ₂ SA of silica (I) is 100 m ² / g or less, preferably 80 m ² / g or less, more preferably 60 m ² / g or less. When it exceeds 100 m < ² > / g, there exists a possibility that the effect by combined use of silica (I) and (II) may not fully be acquired. N ₂ SA of silica (I) is preferably 20 m ² / g or more, more preferably 30 m ² / g or more, and further preferably 40 m ² / g or more. If it is less than 20 m ² / g, sufficient reinforcing properties cannot be obtained, and sufficient wet grip performance and steering stability tend not to be obtained.

Although it does not specifically limit as silica (I), For example, Ultrazil 360 by a Degussa company, Z40 by a Rhodia company, RP80 by a Rhodia company etc. can be used. Silica (I) may be used alone or in combination of two or more.

The N ₂ SA of silica (II) is 150 m ² / g or more, preferably 160 m ² / g or more, more preferably 165 m ² / g or more. If it is less than 150 m ² / g, there is a risk that the combined effect of low fuel consumption and wet grip performance due to the combined use of silica (I) and (II) may not be obtained. Further, N ₂ SA of silica (II) is preferably 400 m ² / g or less, more preferably 360 m ² / g or less, still more preferably 240 m ² / g or less, and particularly preferably 200 m ² / g or less. When it exceeds 400 m ² / g, fuel economy and processability tend to deteriorate.

Although it does not specifically limit as silica (II), For example, Zeosyl 1205MP by Rhodia, Ultrazil VN3-G by Degussa, etc. can be used. Silica (II) may be used alone or in combination of two or more.

The content of silica (I) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 mass parts, there exists a tendency for rolling resistance not to reduce fully. The content of silica (I) is preferably 150 parts by mass or less, more preferably 115 parts by mass or less, still more preferably 100 parts by mass or less, still more preferably 70 parts by mass or less, and most preferably 50 parts by mass or less. Most preferably, it is 35 mass parts or less. If it exceeds 150 parts by mass, the strength, wet grip performance, and steering stability tend to decrease.

The content of silica (II) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 20 parts by mass or more, particularly preferably 50 parts by mass or more, with respect to 100 parts by mass of the rubber component. Preferably it is 70 mass parts or more. If it is less than 1 part by mass, the steering stability tends not to be sufficiently excellent. The content of silica (II) is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, and still more preferably 120 parts by mass or less. When it exceeds 150 parts by mass, the performance (particularly, low fuel consumption) of the present invention tends not to be obtained remarkably.

The content of silica (I) and the content of (II) preferably satisfy the following formula. Here, each content means the quantity (mass part) with respect to 100 mass parts of rubber components.
(Content of silica (I)) × 0.2 ≦ (content of silica (II)) ≦ (content of silica (I)) × 6.5
The content of silica (II) is preferably 0.2 times or more, more preferably 0.5 times or more of the content of silica (I). If it is less than 0.2 times, the steering stability tends to decrease. Further, the content of silica (II) is preferably 6.5 times or less, more preferably 6 times or less of the content of silica (I). When it exceeds 6.5 times, there is a tendency that the improvement effect of the low fuel consumption obtained when the above formula is satisfied is not seen.

The content of silica is 105 parts by mass or more, preferably 107 parts by mass or more, more preferably 115 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 105 parts by mass, a sufficient reinforcing effect due to the inclusion of silica cannot be obtained, and sufficient wet grip performance and steering stability tend not to be obtained. The content of silica is 160 parts by mass or less, preferably 155 parts by mass or less, more preferably 140 parts by mass or less. When it exceeds 160 parts by mass, it becomes difficult for silica to be uniformly dispersed in the rubber composition, and the fuel efficiency tends to deteriorate. By making the content of silica within the above range, the effect of the present invention can be suitably obtained. Here, the content of silica means the total content when two or more types of silica are used.

In this invention, it is preferable to mix | blend a silane coupling agent with a silica. As the silane coupling agent, conventionally known silane coupling agents can be used, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxy). Silylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) ) Disulfide, bis (3-trimethoxysilylpropyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-trie Sulfide systems such as xylsilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2- Mercapto series such as mercaptoethyltrimethoxysilane and 2-mercaptoethyltriethoxysilane, vinyl series such as vinyltriethoxysilane and vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane and other amino-based, γ-glycidoxypropyltrie Glycidoxy systems such as toxisilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, 3-nitropropyltrimethoxysilane, 3-nitropropyltri Examples thereof include nitro series such as ethoxysilane, and chloro series such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane. In addition, said silane coupling agent may be used independently and may be used in combination of 2 or more type. Among these, a sulfide-based silane coupling agent is preferable because bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide are more preferable because the effects of the present invention can be obtained more suitably. preferable.

When the rubber composition which concerns on this invention contains a silane coupling agent, Preferably content of a silane coupling agent is 1-20 mass parts with respect to 100 mass parts of silica, More preferably, it is 2-18. It is a mass part, More preferably, it is 5-16 mass part.

The rubber composition according to the present invention contains a liquid resin having a specific softening point. By using the liquid resin together with a rubber component containing a specific amount of NR and a specific amount of silica, fuel economy, wet grip performance, and steering stability can be improved in a well-balanced manner.

The liquid resin is usually a thermoplastic resin having a weight average molecular weight of several hundred to several thousand, and is a resin that can be given tackiness by blending with natural rubber or synthetic rubber. Examples of the liquid resin include petroleum-based or coal-based resin liquids such as coumarone indene resin, indene resin, α-methylstyrene resin, vinyltoluene resin, and polyisopentane resin. Other liquid resins include coumarone resin, naphthene resin, phenolic resin, terpene resin, terpene-phenolic resin, rosin, rosin ester, hydrogenated rosin derivative, hydrogenated terpene resin, natural resin liquids, and alkylphenol-formaldehyde resins. Synthetic resins such as C5 petroleum resins, C9 petroleum resins, aliphatic petroleum resins, xylene-formaldehyde resins, phenol-modified C9 petroleum resins, carboxylic acid-modified C9 petroleum resins, and dicyclopentadiene-modified C9 petroleum resins. Liquid materials can also be used. Among them, from the viewpoint that the effects of the present invention can be obtained satisfactorily, the liquid resin is preferably at least one selected from the group consisting of liquid coumarone indene resin, liquid indene resin, and liquid α-methylstyrene resin. Liquid coumarone indene resin is more preferred.

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

The softening point of the liquid resin is 7 ° C or higher, preferably 8 ° C or higher, more preferably 9 ° C or higher. If it is lower than 7 ° C, wet grip performance and steering stability may not be improved. The softening point of the liquid resin is 15 ° C. or lower, preferably 13 ° C. or lower, more preferably 11 ° C. or lower. If it exceeds 15 ° C., the exothermic property of the liquid resin increases, and there is a tendency that the fuel efficiency cannot be sufficiently improved.
In this specification, the softening point is a temperature at which a sphere descends when a softening point defined in JIS K 6220-1: 2001 is measured with a ring and ball softening point measuring apparatus.

Content of the said liquid resin is 30 mass parts or more with respect to 100 mass parts of rubber components, Preferably it is 32 mass parts or more. If it is less than 30 parts by mass, the effect of blending the liquid resin cannot be sufficiently obtained, and sufficient wet grip performance and steering stability may not be obtained. Moreover, content of the said liquid resin is 50 mass parts or less, Preferably it is 49 mass parts or less, More preferably, it is 37 mass parts or less. If it exceeds 50 parts by mass, fuel economy and steering stability may be deteriorated. By setting the content of the liquid resin within the above range, the effects of the present invention can be suitably obtained.

Since the liquid resin has a function of softening the rubber composition, the use of the liquid resin reduces the content of softening components such as oil (softening components other than the liquid resin) in the rubber composition. This can improve the balance of fuel efficiency, wet grip performance, and handling stability. In the rubber composition according to the present invention, a resin or oil other than the liquid resin may be contained, but the total content of the resin and oil other than the liquid resin is preferably as small as possible. Specifically, the rubber component It is 5 parts by mass or less, preferably 4 parts by mass or less, more preferably 2 parts by mass or less with respect to 100 parts by mass. When the amount exceeds 5 parts by mass, fuel economy, wet grip performance, and steering stability are deteriorated, and the balance of these three performances may be deteriorated. A lower limit is 0 mass part (it does not contain substantially).
In addition, examples of the resin other than the liquid resin include the above resin having a softening point higher than that of the above liquid resin.

The ratio (B) / (A) of the silica content (A), the resin (including the liquid resin) and the total oil content (B) is preferably 0.27 or more, and 0.28 or more. It is more preferable that Further, (B) / (A) is preferably 0.42 or less, more preferably 0.38 or less, and further preferably 0.36 or less. Thereby, low fuel consumption, wet grip performance, and steering stability can be improved in a more balanced manner. Here, each content means the quantity (mass part) with respect to 100 mass parts of rubber components. Moreover, content (A) of a silica means a total content, when using 2 or more types of silica.

（式（１）中、Ｒ^１は、水素原子、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、分岐若しくは非分岐の炭素数６〜３０のアリール基、又は水酸基（−ＯＨ）を表す。Ｒ^２及びＲ^３は、同一若しくは異なって、水素原子、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、分岐若しくは非分岐の炭素数２〜３０のアルキニル基、分岐若しくは非分岐の炭素数６〜３０のアリール基、又は下記式（２）で表される基を表し、該アルキル基、該アルケニル基、該アルキニル基、該アリール基が有する水素原子が水酸基（−ＯＨ）又はカルボキシル基（−ＣＯＯＨ）で置換されていてもよい。Ｒ^１とＲ^２、Ｒ^１とＲ^３、又はＲ^２とＲ^３とで環構造を形成してもよい。ｎは、０〜８の整数を表す。）

（式（２）中、Ｒ^４は、分岐若しくは非分岐の炭素数１〜３０のアルキレン基を表す。Ｒ^５は、水素原子、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、分岐若しくは非分岐の炭素数６〜３０のアリール基、又は水酸基（−ＯＨ）を表す。ｐは、０〜１０の整数を表す。） In the present invention, it is further preferable to use a compound represented by the following formula (1). Thereby, the effect of this invention is acquired more suitably.

(In Formula (1), R ¹ is a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, a branched or unbranched carbon number of 6; Represents an aryl group of ˜30, or a hydroxyl group (—OH), R ² and R ³ are the same or different and are a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched carbon; An alkenyl group having 2 to 30 carbon atoms, a branched or unbranched alkynyl group having 2 to 30 carbon atoms, a branched or unbranched aryl group having 6 to 30 carbon atoms, or a group represented by the following formula (2); The hydrogen atom of the alkyl group, the alkenyl group, the alkynyl group, or the aryl group may be substituted with a hydroxyl group (—OH) or a carboxyl group (—COOH) R ¹ and R ² , R ¹ and R ^3, also May also form a ring with R ² and ^{R 3} .n represents an integer of 0-8.)

(In formula (2), R ⁴ represents a branched or unbranched alkylene group having 1 to 30 carbon atoms. R ⁵ represents a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, branched or Represents an unbranched alkenyl group having 2 to 30 carbon atoms, a branched or unbranched aryl group having 6 to 30 carbon atoms, or a hydroxyl group (—OH), and p represents an integer of 0 to 10.

Examples of the branched or unbranched alkyl group of R ¹ having 1 to 30 carbon atoms (preferably 3 to 25 carbon atoms, more preferably 10 to 20 carbon atoms, and further preferably 15 to 20 carbon atoms) include, for example, a methyl group , Ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group , Nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, octadecyl group and the like.

Examples of the branched or unbranched alkenyl group of R ¹ having 2 to 30 carbon atoms (preferably 3 to 25 carbon atoms, more preferably 10 to 20 carbon atoms, still more preferably 15 to 20 carbon atoms) include, for example, a vinyl group 1-propenyl group, 2-propenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 2-pentenyl group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group, decenyl group, undecenyl Group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, octadecenyl group and the like.

Examples of the branched or unbranched aryl group having 6 to 30 carbon atoms (preferably 6 to 10 carbon atoms) of R ¹ include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group.

As R ^1, a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a hydroxyl group (-OH) are preferred, the alkyl group is more preferable.

R ² and R ³ branched or unbranched 1 to 30 carbon atoms (preferably 1 to 25 carbon atoms, more preferably 1 to 20 carbon atoms, still more preferably 1 to 10 carbon atoms, particularly preferably 1 to 1 carbon atoms). Examples of the alkyl group of 5) include the same groups as the branched or unbranched alkyl group having 1 to 30 carbon atoms of R ¹ .

R ² and R ³ branched or unbranched 2 to 30 carbon atoms (preferably 2 to 25 carbon atoms, more preferably 2 to 20 carbon atoms, still more preferably 2 to 10 carbon atoms, particularly preferably 2 to 2 carbon atoms). Examples of the alkenyl group of 5) include the same groups as the branched or unbranched C 2-30 alkenyl group of R ¹ .

R ² and R ³ branched or unbranched 2 to 30 carbon atoms (preferably 2 to 25 carbon atoms, more preferably 2 to 20 carbon atoms, still more preferably 2 to 10 carbon atoms, particularly preferably 2 to 2 carbon atoms). Examples of the alkynyl group of 5) include an ethynyl group, a propynyl group, a butynyl group, a pentynyl group, a hexynyl group, a heptynyl group, an octynyl group, a nonynyl group, a decynyl group, an undecynyl group, and the like.

Examples of the branched or unbranched aryl group having 6 to 30 carbon atoms (preferably 6 to 10 carbon atoms) of R ² and R ³ include, for example, the above branched or unbranched aryl group having 6 to 30 carbon atoms of R ^1. The same group can be mentioned.

R ² and R ³ include a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkyl group having 1 to 30 carbon atoms substituted with a hydroxyl group or a carboxyl group, a hydroxyl group or a carboxyl group. A branched or unbranched aryl group having 6 to 30 carbon atoms substituted with a group and a group represented by the above formula (2) are preferable, and the above alkyl group substituted with an alkyl group, a hydroxyl group or a carboxyl group is more preferable. A combination of the alkyl group and the alkyl group substituted with a hydroxyl group or a carboxyl group is more preferable.

n represents an integer of 0 to 8, but n is preferably 0 to 3 and is preferably 0 because the fuel economy, wet grip performance, and steering stability can be improved in a balanced manner. Is more preferable.

Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms (preferably 1 to 15 carbon atoms, more preferably 1 to 3 carbon atoms) of R ⁴ include, for example, a methylene group, an ethylene group, a propylene group, and a butylene group. Pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and the like.

Branched or unbranched having 1 to 30 carbon atoms of R ⁵ (preferably having a carbon number of 3 to 25, more preferably 10 to 20 carbon atoms) Examples of the alkyl group, for example, the number of carbon atoms of branched or unbranched ^{R 1} above The group similar to the alkyl group of 1-30 can be mentioned.

Branched or unbranched carbon atoms 2 to 30 R ⁵ (preferably having a carbon number of 3 to 25, more preferably 10 to 20 carbon atoms) Examples of the alkenyl group, for example, the number of carbon atoms of branched or unbranched ^{R 1} above The group similar to a 2-30 alkenyl group can be mentioned.

Examples of the branched or unbranched aryl group having 6 to 30 carbon atoms (preferably 6 to 10 carbon atoms) of R ⁵ are the same as the branched or unbranched aryl group having 6 to 30 carbon atoms of R ¹ . The group can be mentioned.

R ⁵ is preferably a branched or unbranched alkyl group having 1 to 30 carbon atoms.

p represents an integer of 0 to 10; however, p is preferably 0 to 3 and preferably 0 because the fuel economy, wet grip performance, and steering stability can be improved in a balanced manner. Is more preferable.

Examples of the compound represented by the above formula (1) include N, N-dimethylformamide, octadecanamide, N- (4-hydroxyphenyl) octadecanamide, ε-caprolactam, sarcosine, N-lauroyl sarcosine, and N-octadecyl. Sarcosine, N, N′-ethylenebisoctadecanamide, N- (1-oxooctadecyl) sarcosine and the like can be mentioned. These may be used alone or in combination of two or more.

When the rubber composition according to the present invention contains the compound represented by the above formula (1), the content of the compound represented by the above formula (1) is preferably 0.00 with respect to 100 parts by mass of silica. 1 mass part or more, More preferably, it is 0.5 mass part or more, More preferably, it is 1 mass part or more. If it is less than 0.1 part by mass, the effect obtained by blending the compound represented by the formula (1) may not be sufficiently obtained. The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less with respect to 100 parts by mass of silica. When the amount exceeds 20 parts by mass, the hardness after vulcanization is lowered, and the steering stability may be deteriorated.

In the present invention, in addition to the compound represented by the formula (1), an amino acid derivative is preferably further blended. Thereby, the dispersibility of silica can be improved more favorably, and while maintaining good workability and workability, fuel economy, wet grip performance, and steering stability can be improved in a balanced manner.

In the case where an amino acid derivative is further added in addition to the compound represented by the above formula (1), HT254 manufactured by Schill + Seilacher, which is commercially available as a mixture of the compound represented by the above formula (1) and the amino acid derivative. Etc. may be used.

When the rubber composition according to the present invention contains the compound represented by the above formula (1), the total content of the compound represented by the above formula (1) and the amino acid derivative is based on 100 parts by mass of silica. Preferably it is 0.2 mass part or more, More preferably, it is 1 mass part or more. There exists a possibility that the effect acquired by mix | blending the compound represented by the said Formula (1) as it is less than 0.2 mass part cannot fully be acquired. The total content is preferably 15 parts by mass or less, more preferably 11 parts by mass or less, and still more preferably 5 parts by mass or less with respect to 100 parts by mass of silica. If it exceeds 15 parts by mass, the hardness after vulcanization may be reduced, and the steering stability may be deteriorated.

The rubber composition according to the present invention may contain additives other than the chemicals described above. Known additives can be used, such as sulfur vulcanizing agents; thiazole vulcanization accelerators, thiuram vulcanization accelerators, sulfenamide vulcanization accelerators, guanidine vulcanization accelerators. Vulcanization accelerators such as stearic acid and zinc oxide; organic peroxides such as dicumyl peroxide and ditertiary butyl peroxide; reinforcing agents such as carbon black; calcium carbonate, talc and alumina And fillers such as clay, aluminum hydroxide and mica; processing aids; anti-aging agents; and lubricants.

Examples of the sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. The content of sulfur is preferably 0.1 to 15 parts by mass, more preferably 0.3 to 10 parts by mass, and still more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component. It is.

Examples of the vulcanization accelerator include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and thiazole vulcanization accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram monosulfide, tetramethylthiuram. Thiuram vulcanization accelerators such as disulfides; N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N -Sulfenamide vulcanization accelerators such as oxyethylene-2-benzothiazole sulfenamide and N, N'-diisopropyl-2-benzothiazole sulfenamide; diphenylguanidine, diortolylguanidine, orthotolylbiguanidine What guanidine-based vulcanization accelerator and the like. Of these, sulfenamide-based vulcanization accelerators are preferable and N-cyclohexyl-2-benzothiazole sulfenamide is more preferable because the effects of the present invention can be more suitably obtained. It is also preferable to use a guanidine vulcanization accelerator in combination. The content of the vulcanization accelerator is preferably 0.1 to 7 parts by mass and more preferably 1 to 6 parts by mass with respect to 100 parts by mass of the rubber component.

Examples of the carbon black include furnace black, acetylene black, thermal black, channel black, and graphite. Carbon blacks include channel carbon blacks such as EPC, MPC and CC; furnace carbon blacks such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF and ECF; FT and MT Thermal carbon black such as acetylene carbon black is exemplified. One or more of these can be used.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 5 to 200 m ² / g. The lower limit is preferably 50 m ² / g, and more preferably 80 m ² / g. It is preferable that the upper limit is 150 meters ² / g, and more preferably 130m ² / g. Carbon black has a dibutyl phthalate (DBP) absorption amount of preferably 5 to 300 ml / 100 g. The nitrogen adsorption specific surface area is measured according to ASTM D4820-93, and the DBP absorption is measured according to ASTM D2414-93. As a commercial item, Mitsubishi Chemical Corporation trade name Dia Black N220, Tokai Carbon Co., Ltd. trade name Seast 6, Seast 7HM, Seast KH, Degussa Corporation trade name CK3, Special Black 4A, etc. can be used.

When the rubber composition according to the present invention contains carbon black, the content of carbon black is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the rubber component. In order to increase the strength, the content is more preferably 2 parts by mass or more, and still more preferably 3 parts by mass or more. Moreover, in order to improve low fuel consumption, More preferably, it is 30 mass parts or less, More preferably, it is 8 mass parts or less.

The rubber composition according to the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The glass transition temperature (tan δ peak temperature) of the rubber composition (after vulcanization) according to the present invention is preferably in the range of −17 to 7 ° C. By setting the glass transition temperature of the rubber composition within the above range, the glass transition temperature of the rubber composition and the softening point of the liquid resin are close to each other, and the effects of the present invention can be exhibited more remarkably. In addition, there exists a possibility that sufficient wet grip performance and steering stability may not be acquired as it is less than -17 degreeC. Moreover, when it exceeds 7 degreeC, there exists a possibility that sufficient low fuel consumption may not be obtained. The glass transition temperature is more preferably −16 ° C. or higher, and further preferably −15 ° C. or higher. The glass transition temperature is more preferably −7 ° C. or lower, and further preferably −9 ° C. or lower.
The glass transition temperature can be measured by a viscoelastic temperature dispersion measurement test.

The rubber composition according to the present invention has a high level of balance between low fuel consumption, wet grip performance, and steering stability.

The rubber composition according to the present invention is suitably used as a tire tread. In the case of a tread having a two-layer structure, it is composed of a surface layer (cap tread) and an inner surface layer (base tread), and the rubber composition according to the present invention can be used for both a cap tread and a base tread. It is suitably used as a tread.

A tread having a multilayer structure is manufactured by a method in which a sheet is bonded to a predetermined shape, or a method in which two or more extruders are loaded and two or more layers are formed at the head outlet of the extruder. Can do.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing natural rubber, silica, a liquid resin having a softening point of 7 to 15 ° C., and, if necessary, the above-described various compounding agents is matched to the shape of each tire member such as a tread at an unvulcanized stage. The unvulcanized tire is formed by extruding and molding together with other tire members by a normal method on a tire molding machine. The pneumatic tire of the present invention is obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

The pneumatic tire of the present invention is preferably used as a tire for passenger cars, a tire for trucks and buses, a tire for motorcycles, a tire for competition, and the like, and particularly preferably used as a tire for passenger cars.

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

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
Natural rubber (NR): TSR20
Butadiene rubber (BR): Ubepol BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass)
Styrene butadiene rubber (SBR): HPR355 (modified S-SBR, manufactured by JSR Corporation, bound styrene content: 28% by mass, vinyl content: 56% by mass, Tg: −27 ° C., compound represented by formula (3) (R ¹¹ = methoxy group, R ¹² = methoxy group, R ¹³ = methoxy group, R ¹⁴ = hydrogen atom, R ¹⁵ = hydrogen atom, n = 3 in formula (3))
Carbon black: Diablack N220 manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 111 m ² / g, DBP absorption: 115 ml / 100 g)
Silica (I): Ultrazil 360 manufactured by Degussa (N ₂ SA: 50 m ² / g)
Silica (II): Ultrazil VN3-G (N ₂ SA: 175 m ² / g) manufactured by Degussa
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Oil: X-140 manufactured by Japan Energy Co., Ltd.
Resin (1): NOVARES C10 (liquid coumarone indene resin, softening point of about 10 ° C.) manufactured by Rutgers Chemical Co.
Resin (2): SA85 manufactured by Arizona Chemical (softening point: about 85 ° C.)
Resin (3): Piccola Stick A5 manufactured by Eastman Chemical Company (softening point approx. 5 ° C)
Compound (1): HT254 (fatty acid amide-based processing aid (fatty acid amide (compound represented by the above formula (1) (N- (1-oxooctadecyl) sarcosine)) and amino acid derivative) manufactured by Schill + Seilacher, ( Fatty acid amide content: 25-50% by mass))
Compound (2): Lauroyl sarcosine wax manufactured by Tokyo Chemical Industry Co., Ltd .: Sannoc N manufactured by Ouchi Shinsei Chemical Co., Ltd.
Anti-aging agent: Antigen 3C manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Beads manufactured by NOF Corporation Zinc stearate zinc oxide: Zinc flower No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. (1): Sumitomo Soxinol CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Chemical Co., Ltd.
Vulcanization accelerator (2): Soxinol D (1,3-diphenylguanidine) manufactured by Sumitomo Chemical Co., Ltd.

<Examples and Comparative Examples>
In accordance with the formulation shown in Tables 1 and 2, materials other than sulfur and vulcanization accelerator were kneaded for 3 minutes under a condition of 150 ° C. using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., and mixed. A kneaded paste was obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized with a 0.5 mm thick mold at 170 ° C. for 20 minutes to obtain a sheet-like vulcanized rubber composition.
Further, the obtained unvulcanized rubber composition was molded into a tread shape, and bonded together with other tire members on a tire molding machine to form an unvulcanized tire, and press vulcanized at 160 ° C. for 20 minutes, A test tire (size: 195 / 65R15) was produced.

The following evaluation was performed using the obtained vulcanized rubber composition and test tire. The test results are shown in Tables 1 and 2. In the following evaluation, the reference comparative example of Table 1 was set as Comparative Example 1-1, and the reference comparative example of Table 2 was set as Comparative Example 2-1.

(Viscoelastic temperature dispersion measurement test)
Vulcanization obtained by the above method using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho under the conditions of a frequency of 10 Hz, an initial strain of 10%, an amplitude of ± 0.25%, and a heating rate of 2 ° C./min. A temperature distribution curve of tan δ of the rubber composition was prepared, and a temperature corresponding to the largest tan δ value in the obtained temperature distribution curve was measured as a tan δ peak temperature (Tg (° C.)). The tan δ peak temperature corresponds to the glass transition temperature of the rubber composition (after vulcanization).

(Wet grip performance)
Each test tire was mounted on all wheels of a vehicle (domestic FF2000cc), and a braking distance from an initial speed of 100 km / h was determined on a wet asphalt road surface. The result is expressed as an index. The larger the number, the better the wet skid performance (wet grip performance). The index was calculated by the following formula.
Wet skid performance index = (braking distance of reference comparative example) / (braking distance of each formulation) × 100

(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, and the standard The index was expressed as an index when the comparative example was 100. A larger index indicates better fuel efficiency.

(Maneuvering stability)
A sensory test was performed on a test course in a normal passenger car (2000 CC) equipped with the manufactured test tire. The reference comparative example is 100, and the higher the score, the better the steering stability.

As shown in Tables 1 and 2, by using a predetermined amount of a rubber component containing a predetermined amount of natural rubber, silica, and a liquid resin having a softening point of 7 to 15 ° C., low fuel consumption, wet grip performance, steering The performance balance of stability can be remarkably improved. In particular, the performance balance could be remarkably improved by using two specific types of silica in combination or using the compound represented by the above formula (1).

Claims (8)

Containing a rubber component, silica, and a liquid resin having a softening point of 7 to 15 ° C .;
In 100% by mass of the rubber component, the content of natural rubber is 10 to 30% by mass,
The content of the silica with respect to 100 parts by mass of the rubber component is 105 to 160 parts by mass, the content of the liquid resin is 30 to 50 parts by mass, and the total content of the resin and the oil excluding the liquid resin is 0. A pneumatic tire provided with a tread composed of a rubber composition of ˜5 parts by mass. The pneumatic tire according to claim 1, wherein the content (A) of the silica and the total content (B) of the resin and the oil satisfy the following formula (C).
0.27 ≦ (B) / (A) ≦ 0.42 (C) The pneumatic tire according to claim 1 or 2, wherein the rubber composition has a glass transition temperature in the range of -17 to 7 ° C. ^2. The pneumatic tire according to claim 1, wherein the silica includes silica (I) having a nitrogen adsorption specific surface area of 100 m ² / g or less and silica (II) having a nitrogen adsorption specific surface area of 150 m ² / g or more. The pneumatic tire according to claim 4, wherein the contents of silica (I) and (II) satisfy the following formula.
(Content of silica (I)) × 0.2 ≦ (content of silica (II)) ≦ (content of silica (I)) × 6.5 The pneumatic tire according to any one of claims 1 to 5, 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 pneumatic tire according to any one of claims 1 to 6, wherein the rubber composition contains a compound represented by the following formula (1).

(In Formula (1), R ¹ is a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, a branched or unbranched carbon number of 6; R ² and R ³ are the same or different and each represents a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched carbon group having 2 to 30 carbon atoms. An alkenyl group, a branched or unbranched alkynyl group having 2 to 30 carbon atoms, a branched or unbranched aryl group having 6 to 30 carbon atoms, or a group represented by the following formula (2): The hydrogen atom of the alkenyl group, the alkynyl group or the aryl group may be substituted with a hydroxyl group or a carboxyl group, and R ¹ and R ² , R ¹ and R ³ , or R ² and R ^{3 represent} a ring structure. Forming Good .n represents an integer of 0-8.)

(In formula (2), R ⁴ represents a branched or unbranched alkylene group having 1 to 30 carbon atoms. R ⁵ represents a hydrogen atom, a branched or unbranched alkyl group having 1 to 30 carbon atoms, branched or An unbranched alkenyl group having 2 to 30 carbon atoms, a branched or unbranched aryl group having 6 to 30 carbon atoms, or a hydroxyl group, and p represents an integer of 0 to 10.) The pneumatic tire according to claim 7, wherein the content of the compound represented by the formula (1) with respect to 100 parts by mass of silica is 0.1 to 20 parts by mass.