JP6087495B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

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

In recent years, there has been a demand for a tire rubber composition to reduce rolling resistance and to exhibit excellent grip performance.

As a method for improving grip performance, a method using carbon black having a small particle diameter and a method using various softening agents are known. However, in both cases, the hysteresis loss increases, and the rolling resistance increases.

As a method for reducing rolling resistance, a method using hydrous silicic acid as a filler is known. However, when hydrous silicic acid is used, the storage elastic modulus of the rubber composition is reduced and grip performance is deteriorated as compared with the case of using carbon black having a comparable specific surface area. Although the storage elastic modulus can be increased by increasing the amount of hydrous silicic acid or increasing the specific surface area, the rolling resistance also increases. Thus, the reduction of rolling resistance and the improvement of grip performance are mutually contradictory, and there is still no rubber composition that can achieve both performances at a high level.

Further, the rubber composition for tires is also required to have a breaking strength. As a method for obtaining an excellent breaking strength, a method for increasing the filler is known, but the rolling resistance increases. Thus, it has been difficult to improve the fuel efficiency (low rolling resistance), grip performance, and breaking strength in a well-balanced manner.

Patent Document 1 proposes a technique that can obtain high grip performance by using a specific plasticizer, resin, etc., but has been studied about the point of improving fuel economy, grip performance, and breaking strength in a balanced manner. Absent.

JP 2004-137463 A

The object of the present invention is to solve the above-mentioned problems and to provide a rubber composition for tires that can improve fuel economy, grip performance, and breaking strength in a well-balanced manner, and a pneumatic tire using the same.

（式（１）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 relates to a tire rubber composition comprising a modified butadiene rubber modified with a compound represented by the following formula (1), silica, a resin having a softening point of -20 to 150 ° C, and a plasticizer having a freezing point of 10 ° C or lower.

(In the 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, a mercapto group, or a derivative thereof. R ⁴ and R ⁵ is the same or different and represents a hydrogen atom or an alkyl group, and n represents an integer.)

It is preferable that the resin content is 0.1 to 20 parts by mass and the plasticizer content is 0.1 to 20 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition contains natural rubber, and the content of the natural rubber in 100% by mass of the rubber component is preferably 50 to 90% by mass, and the content of the modified butadiene rubber is preferably 10 to 50% by mass.
The rubber composition contains 10 to 100 parts by mass of silica with respect to 100 parts by mass of the rubber component, and contains 0.8 parts by mass or more of a silane coupling agent with respect to 100 parts by mass of the silica. preferable.

The rubber composition is preferably obtained by blending a mixture of the resin and the plasticizer.
The rubber composition is preferably used as a tread.

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

According to the present invention, since it is a tire rubber composition containing a modified butadiene rubber modified with a specific compound, silica, a resin having a softening point of -20 to 150 ° C. and a plasticizer having a freezing point of 10 ° C. or less, low fuel consumption It is possible to provide a pneumatic tire with improved grip performance and breaking strength in a well-balanced manner.

（式（１）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（−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 rubber composition for tires of the present invention comprises a modified butadiene rubber (modified BR) modified with a compound represented by the following formula (1), silica, a resin having a softening point of -20 to 150 ° C, and a plastic having a freezing point of 10 ° C or less. Contains agents.

(In formula (1), R ¹ , R ² and R ³ are the same or different and are alkyl group, alkoxy group, silyloxy group, acetal group, carboxyl group (—COOH), 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, and n represents an integer.

Examples of the modified BR include those described in JP 2010-111753 A and the like.

In the formula (1), an alkoxy group is preferred as R ¹ , R ² and R ^{3 in} terms of obtaining excellent fuel economy, grip performance and breaking strength (preferably having 1 to 8 carbon atoms, more Preferably it is C1-C6, More preferably, it is C1-C4, Most preferably, it is C1-C2 alkoxy group. R ⁴ and R ⁵ are preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and still more preferably 3. By using a preferred compound, the aforementioned performance balance can be remarkably improved.

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

As a method for modifying the butadiene rubber with the compound represented by the formula (1), conventionally known methods such as the methods described in JP-B-6-53768 and JP-B-6-57767 can be used. For example, it can be modified by bringing the butadiene rubber into contact with the compound. Specifically, after the preparation of the butadiene rubber by anionic polymerization, a predetermined amount of the compound is added to the rubber solution, and the polymerization terminal of the butadiene rubber (active And the like, and the like.

The vinyl content of the modified BR is preferably 35% by mass or less, more preferably 25% by mass or less, and still more preferably 20% by mass or less. When the vinyl content exceeds 35% by mass, the low exothermic property tends to be impaired. Although the minimum of the said vinyl content is not specifically limited, 1 mass% or more and 10 mass% or more may be sufficient. If it is less than 1% by mass, sufficient fuel economy may not be obtained.
The vinyl content (1,2-bond butadiene unit amount) can be measured by infrared absorption spectrum analysis.

The content of the modified BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more. If it is less than 10% by mass, sufficient fuel economy may not be obtained. The content is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 50% by mass or less. When it exceeds 90 mass%, there is a tendency that sufficient breaking strength cannot be obtained.

The rubber component that can be used in the present invention in addition to the modified BR is not particularly limited, and natural rubber (NR), epoxidized natural rubber (ENR), non-modified BR, styrene butadiene rubber (SBR), isoprene rubber (IR), Ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), halogenated butyl rubber (X-IIR), chloroprene rubber (CR), acrylonitrile (NBR), halides of copolymers of isomonoolefin and paraalkylstyrene Etc. can be used. Among these, NR is preferable because good fracture strength can be obtained and the aforementioned performance balance can be remarkably improved. Further, BR containing 1,2-syndiotactic polybutadiene crystal may be used.

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 preferably 50% by mass or more, more preferably 55% by mass or more. If it is less than 50% by mass, sufficient rubber strength and low fuel consumption tend not to be obtained. The content is preferably 90% by mass or less, more preferably 70% by mass or less. When it exceeds 90 mass%, glass transition temperature (Tg) will become large and there exists a tendency for rolling resistance to fall.

The rubber composition of the present invention contains a resin having a specific softening point and a plasticizer having a specific freezing point. In the compounding system containing the modified BR and silica, by using the resin and the plasticizer in combination, fuel economy, grip performance, and breaking strength can be remarkably improved.

The softening point of the resin is −20 ° C. or higher, preferably 0 ° C. or higher. If it is lower than -20 ° C, the fracture strength may be deteriorated. Moreover, this softening point is 150 degrees C or less, Preferably it is 120 degrees C or less, More preferably, it is 20 degrees C or less. If it exceeds 150 ° C., the fuel economy tends to be not sufficiently improved.
In this specification, the softening point is a temperature at which a sphere descends when a softening point defined in JIS K6220: 2001 is measured by a ring and ball softening point measuring apparatus.

The resin is not particularly limited as long as it satisfies the above softening point, and can be used without limitation, aromatic petroleum resin (resin by C9 fraction), coumarone indene resin, terpene resin, aromatic modified terpene resin, rosin Resin, phenol resin, petroleum resin (resin by C5 fraction), etc. are mentioned. Among these, coumarone indene resin is preferable from the viewpoint that excellent fuel economy, grip performance, and breaking strength can be obtained.

The content of the resin is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 0.1 parts by mass, the effect of improving the low heat build-up may not be sufficiently obtained. The resin content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. If it exceeds 20 parts by mass, sufficient fuel economy may not be obtained. Moreover, there exists a possibility that the workability | operativity in the fear of bloom, a kneading | mixing, and an extrusion process may deteriorate.

The freezing point of the plasticizer is preferably −100 ° C. or higher, more preferably −80 ° C. or higher. If it is less than -100 ° C, the fracture strength tends to deteriorate. The freezing point is 10 ° C. or lower, preferably 0 ° C. or lower. When it exceeds 10 degreeC, there exists a tendency for fracture strength to deteriorate. Moreover, there is a possibility that the effect of improving the grip performance cannot be obtained sufficiently.
In the present specification, the freezing point is a value measured by the following method.
A sample (plasticizer) is sealed in an aluminum cell, and the aluminum cell is inserted into a sample holder of a differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-60A), and then the sample holder is placed in a nitrogen atmosphere. An endothermic peak was observed while heating to 150 ° C. at 10 ° C./min, and the obtained endothermic peak was taken as the freezing point.

The plasticizer is not particularly limited, and phosphorus such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, tris (2-ethylhexyl) phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate Acid ester compounds; phthalic acid ester compounds such as diisodecyl phthalate, butyl benzyl phthalate, diisononyl phthalate; trimellitic acid ester compounds such as tris (2-ethylhexyl) trimellitate; dibutyl adipate, diisobutyl adipate, bis (2-ethylhexyl) Adipate, diisodecyl adipate, bis (2-ethylhexyl) azelate, bis (2-ethylhexyl) sebacate Aliphatic dibasic acid ester-based compounds, such as ricinoleic acid ester compounds such as methyl acetyl ricinoleate; acid ester compounds such as glyceryl triacetate; sulfonamide compounds such as N- butyl benzenesulfonamide; and the like. Of these, aliphatic dibasic acid ester-based compounds and phosphate ester-based compounds are preferred from the viewpoint that excellent fuel economy, grip performance, and breaking strength can be obtained. Bis (2-ethylhexyl) sebacate, tributyl phosphate, tris (2-Ethylhexyl) phosphate is more preferred, and bis (2-ethylhexyl) sebacate is even more preferred.

The content of the plasticizer is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 0.1 parts by mass, the effect of improving the low heat build-up may not be sufficiently obtained. The resin content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. If it exceeds 20 parts by mass, sufficient fuel economy may not be obtained. There is also the risk of bloom.

The total content of the resin and the plasticizer is preferably 3 parts by mass or more, more preferably 8 parts by mass or more with respect to 100 parts by mass of the rubber component. The total content is preferably 20 parts by mass or less, more preferably 12 parts by mass or less. Within the above range, good fuel economy, grip performance and breaking strength can be obtained.

The content of the plasticizer in the total 100 mass% of the resin and the plasticizer is preferably 20 mass% or more, more preferably 40 mass% or more, preferably 80 mass% or less, more preferably 60 mass% or less. is there. Within the above range, excellent fuel economy, grip performance, and breaking strength can be obtained.

The resin and the plasticizer are preferably used as a mixture of the resin and the plasticizer. As a result, it is possible to dispel the concern about the reduction in fuel efficiency due to poor dispersion and the decrease in breaking strength due to the formation of aggregates, and excellent fuel economy and breaking strength can be obtained.

The said mixture can be adjusted by mixing the said resin and the said plasticizer by a well-known method, for example, what is necessary is just to mix at the temperature (for example, 50-200 degreeC) which can melt | dissolve the said resin and the said plasticizer.

Examples of the silica include, but are not limited to, dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and 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 30 m ² / g or more, and more preferably 150 m ² / g or more. If it is less than 30 m < ² > / g, there exists a tendency for reinforcement property to be small and for abrasion resistance to fall. Further, the _N 2 SA is preferably from 300 meters ² / g or less, more preferably 200m ² / g. When it exceeds 300 m < ² > / g, the dispersibility of a silica is bad and there exists a tendency for low-fuel-consumption property to deteriorate.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The average primary particle diameter of silica is preferably 10 nm or more, more preferably 15 nm or more. If it is less than 10 nm, fuel economy and processability tend to deteriorate. The average primary particle size is preferably 40 nm or less, more preferably 30 nm or less. If it exceeds 40 nm, the fracture strength tends to decrease.
In addition, the average primary particle diameter of silica can be calculated | required from the average value which observes a silica with an electron microscope, measures a particle diameter about 50 arbitrary particles, for example.

The content of silica is preferably 10 parts by mass or more, more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, the fuel economy, grip performance, and breaking strength may not be improved in a well-balanced manner. The content is preferably 100 parts by mass or less, more preferably 40 parts by mass or less. When the amount exceeds 100 parts by mass, it is difficult to disperse silica in rubber, and the processability of rubber tends to deteriorate. Moreover, there is a possibility that sufficient fuel efficiency cannot be obtained.

In the present invention, it is preferable to use a silane coupling agent. Examples of the silane coupling agent include sulfide, mercapto, vinyl, amino, glycidoxy, nitro, and chloro silane coupling agents. Among these, a sulfide system is preferable because the effects of the present invention can be obtained satisfactorily.

As sulfide-based silane coupling agents, bis (3-triethoxysilylpropyl) tetrasulfide and bis (2-triethoxysilylethyl) tetrasulfide are used because of low fuel economy, grip performance and good breaking strength. Bis (3-triethoxysilylpropyl) disulfide and bis (2-triethoxysilylethyl) disulfide are preferable.

The content of the silane coupling agent is preferably 0.8 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more, and preferably 15 parts by mass or less with respect to 100 parts by mass of silica. More preferably, it is 10 parts by mass or less. Within the above range, good fuel economy, grip performance and breaking strength can be obtained.

The rubber composition of the present invention preferably contains carbon black. As a result, good reinforcing properties can be obtained, and low fuel consumption, grip performance, and breaking strength can be obtained well. Carbon black is not particularly limited, and examples thereof include GPF, HAF, ISAF, and SAF.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 30 m ² / g or more, and more preferably 70 m ² / g or more. If it is less than 30 m ² / g, there is a tendency that sufficient reinforcing properties cannot be obtained. Preferably 250 meters ² / g or less, more preferably 150 meters ² / g, more preferably not more than ^90m 2 / g. If it exceeds 250 m ² / g, processability and fuel efficiency tend to deteriorate.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

The content of carbon black is preferably 10 parts by mass or more, more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 10 parts by mass, sufficient reinforcement may not be obtained. The content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 30 parts by mass or less. When it exceeds 60 parts by mass, there is a possibility that sufficient low fuel efficiency cannot be obtained.

The total content of silica and carbon black is preferably 20 parts by mass or more, more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. The total content is preferably 120 parts by mass or less, more preferably 60 parts by mass or less. Within the above range, good fuel economy, grip performance and breaking strength can be obtained.

The content of silica in a total of 100% by mass of silica and carbon black is preferably 30% by mass or more, more preferably 50% by mass or more, preferably 90% by mass or less, more preferably 70% by mass or less. . Within the above range, low fuel consumption, grip performance, and breaking strength can be obtained in a high level and in a well-balanced manner.

In addition to the above components, the rubber composition of the present invention includes vulcanization agents such as stearic acid, various anti-aging agents, zinc oxide, wax, oil, and sulfur, which are commonly used in the production of rubber compositions. An agent, a vulcanization accelerator, and the like can be appropriately blended.

The rubber composition of 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, kneader, open roll or the like and then vulcanizing. The rubber composition can be used for each member of a tire such as a sidewall and a tread, and is particularly preferably used for a tread (particularly a base tread).

The pneumatic tire of the present invention can be produced by a usual method using the rubber composition. That is, the rubber composition containing the above components is extruded in accordance with the shape of each member (tread, etc.) of the tire at an unvulcanized stage, and is then used on a tire molding machine together with other tire members. By molding with, an unvulcanized tire can be formed. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

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.
NR: TSR20
BR (1): Modified butadiene rubber (modified BR) manufactured by Sumitomo Chemical Co., Ltd. (vinyl content: 15% by mass, R ¹ , R ² and R ³ = —OCH ₃ , R ⁴ and R ⁵ = —CH ₂ CH ₃ , modified with n = 3 compound)
BR (2): Nipol BR1220 (vinyl content: 1% by mass, non-modified) manufactured by Nippon Zeon Co., Ltd.
Carbon black: Seast NH (N ₂ SA: 74 m ² / g) manufactured by Tokai Carbon Co., Ltd.
Silica: ULTRASIL VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g, average primary particle size: 15 nm)
Silane coupling agent: Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by 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.
Resin (1): NOVARES C10 manufactured by Rutgers Chemicals (coumarone indene resin, softening point: 5 to 15 ° C.)
Resin (2): NOVARES C100 manufactured by Rutgers Chemicals (coumarone indene resin, softening point: 95 to 105 ° C.)
Resin (3): NOVARES C140 (Coumarone indene resin, softening point: 135-145 ° C.) manufactured by Rutgers Chemicals
Resin (4): NOVARES C160 manufactured by Rutgers Chemicals (coumarone indene resin, softening point: 155 to 165 ° C.)
Pre-blend (1) to (6): Production Example 1 below
Plasticizer (1): Bis (2-ethylhexyl) sebacate manufactured by Daihachi Chemical Industry Co., Ltd. (DOS, freezing point: −62 ° C.)
Plasticizer (2): Tris (2-ethylhexyl) phosphate manufactured by Daihachi Chemical Industry Co., Ltd. (TOP, freezing point: −70 ° C. or less)
Plasticizer (3): Tributyl phosphate manufactured by Daihachi Chemical Industry Co., Ltd. (TBP, freezing point: −80 ° C. or less)
Plasticizer (4): Ethyl phthalyl ethyl glycolate manufactured by Daihachi Chemical Industry Co., Ltd. (Freezing point: 13 ° C.)
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.

(Production Example 1)
In accordance with the following mixing ratio, the resin (resins (1) to (3)) and the plasticizer (plasticizer (1)) are mixed, and then heated and mixed at 130 ° C. to 150 ° C. to dissolve them. ) To (6) were prepared. In addition, after confirming that the peak of the single resin had disappeared using the DSC spectrum, it was used for rubber kneading.
Pre-blend (1) Resin (1): Plasticizer (1) = 1: 1
Pre-blend (2) Resin (2): Plasticizer (1) = 1: 1
Pre-blend (3) Resin (3): Plasticizer (1) = 1: 1
Pre-blend (4) Resin (1): Plasticizer (1) = 3: 7
Pre-blend (5) Resin (2): Plasticizer (1) = 3: 7
Pre-blend (6) Resin (3): Plasticizer (1) = 3: 7
In addition, the said mixing ratio represents the ratio of the mass part of a chemical | medical agent.

According to the formulation shown in Tables 1-2, the chemicals were kneaded and blended to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 15 minutes to obtain a vulcanized rubber composition.
Further, the unvulcanized rubber composition is formed into a tread shape and bonded together with other tire members to form an unvulcanized tire, press vulcanized at 170 ° C. for 10 minutes, and a test tire ( Size 195 / 65R15) was produced.

The obtained vulcanized rubber composition and the test tire were evaluated by the following test methods, and the results are shown in Tables 1-2.

(Rolling resistance)
Loss tangent of the vulcanized rubber sheet at 70 ° C. under the conditions of a frequency of 10 Hz, an initial strain of 10% and a dynamic strain of 2% using the viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. tan δ) was measured, and Comparative Example 1 was set to 100, and tan δ of each formulation was expressed as an index (rolling resistance index) by the following calculation formula. In addition, it shows that it is excellent in low heat generation, so that heat_generation | fever is so small that a rolling resistance index | exponent is large.
(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(destruction strength)
Measure the breaking strength (TB) and elongation at break (EB) of No. 3 dumbbell-shaped test piece made of the above vulcanized rubber composition according to JIS K6251 “vulcanized rubber and thermoplastic rubber-how to determine tensile properties” The fracture energy (TB × EB / 2) was calculated from the obtained measurement results. And the comparative example 1 was set to 100, and the destruction energy of each mixing | blending was each indicated by the index | exponent with the following formulas. The larger the breaking strength index, the higher the mechanical strength and the better the breaking strength.
(Fracture strength index) = (Fracture energy of each formulation) / (Fracture energy of Comparative Example 1) × 100

(Grip performance)
Using the test tire, the vehicle was run on a dry asphalt road test course. The test driver evaluated the stability of control during steering at that time, and the comparative example 1 was set to 100 and displayed as an index. The larger the value, the higher the grip performance on the dry road surface.

In an embodiment using a modified butadiene rubber modified with a specific compound, silica, a resin having a softening point of -20 to 150 ° C., and a plasticizer having a freezing point of 10 ° C. or less, fuel economy, grip performance, and breaking strength are improved in a well-balanced manner. It was done.
In particular, it has been clarified that excellent performance can be obtained when the resin (1) is used as the resin, and that the above-described performance balance can be remarkably improved by using a resin having a low softening point. Further, it was revealed that rolling resistance and breaking strength can be further improved by using a blend of resin and plasticizer in advance, and the above-mentioned performance balance can be obtained at a high level. When the resin and the plasticizer were blended at 1: 1, particularly excellent performance was obtained.

Claims (6)

A rubber component containing natural rubber and a modified butadiene rubber modified with a compound represented by the following formula (1), silica, a coumarone indene resin having a softening point of -20 to 150 ° C, and a plasticizer having a freezing point of 10 ° C or lower Including
The content of the natural rubber in 100% by mass of the rubber component is 50 to 90% by mass, and the content of the modified butadiene rubber is 10 to 50% by mass.
The plasticizer is an aliphatic dibasic acid ester-based compound or the rubber composition for a tire is a phosphoric ester compound.

(In Formula (1), R ¹ , R ² and R ³ are the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group or a mercapto group. R ⁴ and R ⁵ are the same. Or, differently, it represents a hydrogen atom or an alkyl group, and n represents an integer.) The tire use according to claim 1, wherein the content of the coumarone indene resin is 0.1 to 20 parts by mass and the content of the plasticizer is 0.1 to 20 parts by mass with respect to 100 parts by mass of the rubber component. Rubber composition. 10 to 100 parts by mass of silica with respect to 100 parts by mass of the rubber component,
The tire rubber composition according to claim 1 or 2, comprising 0.8 parts by mass or more of a silane coupling agent with respect to 100 parts by mass of the silica. The tire rubber composition according to any one of claims 1 to 3, obtained by blending a mixture of the coumarone indene resin and the plasticizer. The rubber composition for a tire according to any one of claims 1 to 4, which is used as a tread. The pneumatic tire produced using the rubber composition in any one of Claims 1-5.