JP2013091758A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire, wherein dry-grip performance, wet-grip performance and chunking resistant performance can be improved well-balancedly; and to provide a pneumatic tire using the same.SOLUTION: A rubber composition for a tire comprises: a rubber component that contains 60 to 100 mass% of a styrene-butadiene rubber; and a resin obtained by copolymerizing a phenolic compound (a), a terpene compound (b), and an aromatic vinyl compound (c).

Description

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

Rubber compositions used for motorcycle tires (especially rubber compositions for treads) have high mechanical strength (anti-chunking performance) to suppress the occurrence of chunking (partial rubber peeling) during running. ) Is required. Various other performances such as dry grip performance and wet grip performance are also required for the rubber composition used for motorcycle tires, and various devices have been devised in order to ensure these performances.

Among them, it is widely known that the grip performance is improved by blending a resin, and a phenol-based resin or the like is suitably used (Patent Document 1). However, a rubber composition specialized in dry grip performance tends to sacrifice wet grip performance, and thus has a problem that it cannot sufficiently respond to changes in road surface conditions. Furthermore, rubber compositions specialized in grip performance tend to sacrifice the anti-chunking performance.

In order to improve wet grip performance, a technique of adding an oligomer such as styrene or α-methylstyrene or a terpene resin as a resin has been known.

When blending with oligomers such as styrene and α-methylstyrene, the improvement in wet grip performance depends on the amount added, and increasing the amount added improves wet grip performance but decreases dry grip performance and anti-chunking performance. There is a problem of doing. Further, although the terpene-based resin has an effect of improving the anti-chunking performance at an optimum amount, the effect of improving the wet grip performance is not as effective as that of an oligomer such as styrene or α-methylstyrene. Moreover, there is a tendency that sufficient dry grip performance cannot be obtained. On the other hand, when a phenol-based resin is blended, a good dry grip performance is obtained, but there is a problem that sufficient wet grip performance and anti-chunking performance cannot be obtained.

Therefore, blending these resins may improve the balance of dry grip performance, wet grip performance, and anti-chunking performance, but the compatibility of each resin with the polymer is different. It is difficult for the resin to be uniformly dispersed in the polymer, and the current situation is that the performance cannot be sufficiently improved with a simple blend.

JP-A-2005-350535

An object of the present invention is to solve the above problems and provide a rubber composition for a tire that can improve the dry grip performance, the wet grip performance, and the anti-chunking performance in a balanced manner, and a pneumatic tire using the same.

The present invention relates to a resin obtained by copolymerizing a rubber component containing 60 to 100% by mass of a styrene butadiene rubber with (a) a phenolic compound, (b) a terpene compound and (c) an aromatic vinyl compound. The rubber composition for tires containing these.

The phenolic compound (a) is phenol and / or alkylphenol, the terpene compound (b) is a cyclic unsaturated hydrocarbon having no hydroxyl group, and the aromatic vinyl compound (c) is styrene and / or alkyl-substituted styrene. It is preferable that

The terpene compound (b) is preferably at least one selected from the group consisting of α-pinene, β-pinene, 3-carene, limonene and dipentene.

It is preferable that the compounding quantity of resin is 5-50 mass parts with respect to 100 mass parts of rubber components.

The copolymerization ratio of the phenolic compound (a) in 100 mass% of the resin is 5 to 10 mass%, the copolymerization ratio of the terpene compound (b) is 70 to 85 mass%, and the aromatic vinyl compound (c). The copolymerization ratio is preferably 10 to 20% by mass.

The tire rubber composition preferably further contains carbon black.

The tire rubber composition is based on JIS K6251: 2010, using a dumbbell-shaped No. 3 test piece as a test piece, and a tensile strength TB (MPa) measured by carrying out a tensile test in a 23 ° C. atmosphere. TB × EB / 2 calculated from the elongation at break EB (%) is preferably 3500 or more.

The tire rubber composition is preferably used as a tread rubber composition.

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

The motorcycle tire is preferably a motocross tire.

According to the present invention, a tire containing a specific amount of styrene butadiene rubber and a resin obtained by copolymerizing (a) a phenolic compound, (b) a terpene compound and (c) an aromatic vinyl compound. Pneumatic tire with excellent balance of dry grip performance, wet grip performance and anti-chunking performance by using the rubber composition for a tire member (particularly tread (cap tread)) (Tires for motorcycles) can be provided. In addition, in this specification, when it only describes as grip performance, it shall include both dry grip performance and wet grip performance.

The rubber composition for tires of the present invention is a copolymer of a rubber component containing 60 to 100% by mass of styrene butadiene rubber, (a) a phenol compound, (b) a terpene compound, and (c) an aromatic vinyl compound. And a resin obtained.

In the present invention, styrene butadiene rubber (SBR) is used as the rubber component. The SBR is not particularly limited, and for example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR) and the like can be used. Among these, E-SBR is preferable because the effects of the present invention can be suitably obtained.

25 mass% or more is preferable and, as for the styrene content rate in SBR, 30 mass% or more is more preferable. If it is less than 25 mass%, there is a tendency that sufficient grip performance (particularly wet grip performance) cannot be obtained. The styrene content is preferably 60% by mass or less, and more preferably 50% by mass or less. When it exceeds 60% by mass, not only the wear resistance and chunking resistance are lowered, but also the temperature dependency is increased, and the performance change with respect to the temperature change tends to increase.

The content of SBR in 100% by mass of the rubber component is 60% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. If it is less than 60% by mass, sufficient grip performance (particularly wet grip performance) tends to be not obtained. Further, the upper limit of the SBR content is not particularly limited, and may be 100% by mass.

The rubber component other than SBR that can be used in the present invention is not particularly limited. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber Examples thereof include diene rubbers such as (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and butyl rubber (IIR). A rubber component may be used independently and may use 2 or more types together.

In the present invention, a resin obtained by copolymerizing (a) a phenol compound, (b) a terpene compound and (c) an aromatic vinyl compound is used.

(A) The phenolic compound is not particularly limited as long as it has a phenolic hydroxyl group. For example, phenol, alkylphenol, alkoxyphenol (the number of carbon atoms of the alkoxy group is the same as that of the alkyl group), chlorine atom. And monovalent phenols such as halogenated phenols containing halogen atoms such as bromine atoms and unsaturated hydrocarbon group-containing phenols. Among these, from the viewpoint that dry grip performance, wet grip performance, and anti-chunking performance can be improved in a well-balanced manner, an alkylphenol in which at least one of phenol, o, m, and p positions is substituted with an alkyl group is preferable, and an alkylphenol (particularly, p Alkylphenols in which the position is substituted with an alkyl group are more preferred.

Carbon number of the alkyl group in the alkylphenol is preferably 1 to 10, more preferably 1 to 5.
Specific examples of the alkylphenol include, for example, methylphenol, ethylphenol, butylphenol, t-butylphenol, octylphenol, nonylphenol, decylphenol, and dinonylphenol, and any of o, m, and p positions may be substituted. Of these, t-butylphenol and methylphenol are preferable.

Examples of the alkoxyphenol include methoxyphenol substituted with an alkoxy group corresponding to the alkyl group of the aforementioned alkylphenol.
Examples of the halogenated phenol include chlorophenol and bromophenol.

Examples of the unsaturated hydrocarbon group-containing phenol include compounds having at least one hydroxyphenyl group in one molecule and at least one of the hydrogen atoms of the phenyl group substituted with an unsaturated hydrocarbon group. . Examples of the unsaturated bond in the unsaturated hydrocarbon group include a double bond and a triple bond. Examples of the unsaturated hydrocarbon group include alkenyl groups having 2 to 10 carbon atoms. Specific examples of the unsaturated substituent-containing phenol include isopropenyl phenol and butenyl phenol. These phenolic compounds may be used alone or in combination of two or more.

(B) The terpene compound is a hydrocarbon represented by a composition of (C ₅ H ₈ ) _n and an oxygen-containing derivative thereof, and includes monoterpene (C ₁₀ H ₁₆ ), sesquiterpene (C ₁₅ H ₂₄ ), diterpene ( And compounds having terpenes classified as C ₂₀ H ₃₂ ) as the basic skeleton. The terpene compound is not particularly limited, but is preferably a cyclic unsaturated hydrocarbon, and is preferably a compound having no hydroxyl group.

Specific examples of the terpene compound include α-pinene, β-pinene, 3-carene (δ-3-carene), dipentene, limonene, myrcene, allocymene, ocimene, α-ferrandrene, α-terpinene, and γ-terpinene. , Terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol and the like. Of these, α-pinene, β-pinene, 3-carene (δ-3-carene), dipentene, and limonene are preferable because dry grip performance, wet grip performance, and anti-chunking performance can be improved in a balanced manner. Pinene, β-pinene, and 3-carene are more preferable. These terpene compounds may be used alone or in combination of two or more.

(C) The aromatic vinyl compound is not particularly limited as long as it is a compound having an aromatic ring and a vinyl group. For example, styrene; α-methylstyrene, α-ethylstyrene, 4-cyclohexylstyrene, 2,4, Examples include alkyl-substituted styrene such as 6-trimethylstyrene and t-butylstyrene. Other examples include 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, and the like. These may be used alone or in combination of two or more. Of these, styrene and alkyl-substituted styrene are preferable, alkyl-substituted styrene is more preferable, and α-methylstyrene is still more preferable from the viewpoint that dry grip performance, wet grip performance, and chunking resistance can be improved in a balanced manner. These aromatic vinyl compounds may be used alone or in combination of two or more.

5-10 mass% is preferable and, as for the copolymerization ratio of the phenol type compound (a) in the said resin (100 mass%), 5-8 mass% is more preferable. If it is less than 5% by mass, sufficient grip performance tends not to be obtained, and if it exceeds 10% by mass, sufficient anti-chunking performance tends to be not obtained.

The copolymerization ratio of the terpene compound (b) is preferably 70 to 85% by mass, and more preferably 75 to 85% by mass. If the amount is less than 70% by mass, sufficient anti-chunking performance tends not to be obtained, and if it exceeds 85% by mass, sufficient grip performance tends not to be obtained.

10-20 mass% is preferable and, as for the copolymerization ratio of an aromatic vinyl type compound (c), 15-20 mass% is more preferable. If it is less than 10% by mass, sufficient wet grip performance tends not to be obtained, and if it exceeds 20% by mass, sufficient dry grip performance and anti-chunking performance tend not to be obtained.

The softening point of the resin is not particularly limited, but is preferably 30 to 180 ° C, more preferably 40 to 160 ° C, and still more preferably 50 to 150 ° C. If the softening point is less than 30 ° C, the effect of improving wet grip performance tends to be small, and if it exceeds 180 ° C, the effect of improving dry grip performance tends to be small.
The softening point of the resin is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1: 2001 is measured with a ring and ball softening point measuring device.

Although the weight average molecular weight Mw of the said resin is not specifically limited, 300-5000 are preferable and 300-2000 are more preferable. If Mw is less than 300, the effect of improving wet grip performance tends to be small, and if it exceeds 5000, dry grip performance tends to deteriorate.
In this specification, Mw is a value converted from standard polystyrene using a gel permeation chromatograph (GPC).

The resin can be synthesized by copolymerizing (a), (b) and (c) by a known method. For example, prepared by dropping a phenol compound, a terpene compound and an aromatic vinyl compound in an arbitrary order in an organic solvent such as toluene in the presence of a catalyst such as BF ₃ and reacting them at a predetermined temperature and time. it can.

5-50 mass parts is preferable with respect to 100 mass parts of rubber components, as for the compounding quantity of resin, 6-40 mass parts is more preferable, 8-35 mass parts is more preferable, and 20-30 mass parts is especially preferable. If it is less than 5 parts by mass, sufficient dry grip performance, wet grip performance and anti-chunking performance tend to be not obtained, and if it exceeds 50 parts by mass, the anti-chunking performance and wet grip performance tend to be lowered.

In the present invention, the reinforcing filler can be arbitrarily selected from those conventionally used in tire rubber compositions such as carbon black, silica, calcium carbonate, alumina, clay and talc. Of these, carbon black is preferable.

By using carbon black, it is possible to improve grip performance, and to improve wear resistance, anti-chunking performance and steering stability. As the carbon black, for example, those generally used in the tire industry such as GPF, HAF, ISAF, and SAF can be used.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² / g or more, more preferably 100 m ² / g or more, still more preferably 120 m ² / g or more. When N ₂ SA is less than 50 m ² / g, sufficient wear resistance, anti-chunking performance, and grip performance tend not to be obtained. The N ₂ SA of the carbon black is preferably 200 m ² / g or less, more preferably 160 m ² / g or less. When N ₂ SA exceeds 200 m ² / g, the dispersibility of carbon black tends to be poor, and the wear resistance and chunking resistance tend to be reduced.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by JISK6217-2: 2001.

The content of carbon black is preferably 70 parts by mass or more, more preferably 80 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 70 parts by mass, sufficient wear resistance, anti-chunking performance, and grip performance tend not to be obtained. Further, the carbon black content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 120 parts by mass or less with respect to 100 parts by mass of the rubber component. When it exceeds 200 parts by mass, the workability and the dispersibility of carbon black are poor, and the wear resistance and the chunking resistance tend to decrease.

In the present invention, it is preferable to blend a softener from the viewpoint of grip performance and the like.
Although it does not specifically limit as a softening agent, Oils, such as mineral oil, are mentioned. Examples of the oil include process oils such as paraffinic process oil, aroma based process oil, and naphthenic process oil.

In particular, it is preferable to use a liquid diene polymer as a part or all of the softening agent from the viewpoint of excellent performance balance between durability (anti-chunking performance) and grip performance. In the present invention, the liquid diene polymer is a diene polymer in a liquid state at normal temperature (25 ° C.).

The liquid diene polymer preferably has a polystyrene-reduced weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 1.0 × 10 ^{3 to} 2.0 × 10 ⁵ . 5 × 10 ^{3 to} 6.0 × 10 ⁴ is more preferable, 2.0 × 10 ^{3 to} 2.0 × 10 ⁴ is further preferable, and 3.0 × 10 ^{3 to} 1.5 × 10 ⁴ is more preferable. ⁴ is particularly preferred. If it is less than 1.0 × 10 ³ , the anti-chunking performance is lowered, and there is a possibility that sufficient durability cannot be secured. On the other hand, if it exceeds 2.0 × 10 ⁵ , the viscosity of the polymerization solution becomes too high, and the productivity may be deteriorated.
In this specification, the weight average molecular weight (Mw) is a gel permeation chromatograph (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL manufactured by Tosoh Corporation. It is a value obtained by standard polystyrene conversion based on the measured value by SUPERMALTPORE HZ-M).

Examples of the liquid diene polymer include a liquid styrene butadiene copolymer (liquid SBR), a liquid butadiene polymer (liquid BR), a liquid isoprene polymer (liquid IR), a liquid styrene isoprene copolymer (liquid SIR), and the like. It is done. Among these, liquid SBR and liquid IR are preferably used, and liquid SBR is more preferably used because durability (chunking resistance) and grip performance can be obtained in a well-balanced manner. These liquid diene polymers may be used alone or in combination of two or more.

The vinyl content of the liquid SBR is preferably 10% by mass or more, more preferably 20% by mass or more. If the vinyl content is less than 10% by mass, sufficient grip performance may not be obtained. The vinyl content is preferably 90% by mass or less, more preferably 75% by mass or less. When the vinyl content exceeds 90% by mass, wear resistance and chunking resistance tend to deteriorate.
The vinyl content of the liquid SBR can be measured by infrared absorption spectrum analysis.

The styrene content of the liquid SBR is preferably 10% by mass or more, more preferably 15% by mass or more. If the styrene content is less than 10% by mass, sufficient grip performance may not be obtained. The styrene content is preferably 60% by mass or less, more preferably 45% by mass or less. When the styrene content exceeds 60% by mass, the softening point becomes high, the rubber becomes hard, and the grip performance may be deteriorated.
Incidentally, styrene content of the liquid SBR ^is calculated by H 1 -NMR measurement.

In the present invention, the oil content is preferably 20 parts by mass or more, more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 20 parts by mass, the effect of addition may not be obtained. The oil content is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 50 parts by mass or less. When it exceeds 100 parts by mass, the wear resistance and the chunking resistance tend to deteriorate.
Here, the oil content includes the amount of oil contained in the oil-extended rubber.

The content of the liquid diene polymer is preferably 5 parts by mass or more, 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 grip performance tends not to be obtained. Further, the content of the liquid diene polymer is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. When it exceeds 50 parts by mass, the wear resistance and the chunking resistance tend to deteriorate.

The total content of the resin, oil, and liquid diene polymer is preferably 50 parts by mass or more, more preferably 75 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 50 parts by mass, there is a tendency that sufficient grip performance cannot be obtained. The total content is preferably 180 parts by mass or less, more preferably 140 parts by mass or less, and still more preferably 100 parts by mass or less. When it exceeds 180 parts by mass, the wear resistance and the chunking resistance tend to deteriorate.

Further, the ratio of the blending amount of carbon black and the total content of the resin, oil and liquid diene polymer (the blending amount of carbon black / the total content of the resin, oil and liquid diene polymer) is 1 0.1 to 1.6 is preferable, 1.1 to 1.5 is more preferable, and 1.1 to 1.3 is still more preferable.

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 zinc oxide, stearic acid, various anti-aging agents, tackifiers, waxes, sulfur and the like. Vulcanizing agents, vulcanization accelerators and the like can be appropriately blended.

As a method for producing the rubber composition for tires of the present invention, known methods can be used. For example, the above components are kneaded using a rubber kneader such as an open roll or a Banbury mixer, and then vulcanized. Etc. can be manufactured.

The rubber composition of the present invention can be used for each member of a tire, and among these, it is preferably used for a tread portion, and particularly preferably used for a cap tread. By using it for the cap tread, an excellent performance balance of dry grip performance, wet grip performance and anti-chunking performance can be obtained.

The rubber composition of the present invention (after vulcanization) was measured based on JIS K6251: 2010 by using a dumbbell-shaped No. 3 test piece as a test piece and performing a tensile test in an atmosphere at 23 ° C. TB × EB / 2 (MPa ·%) calculated from TB (MPa) and elongation at break EB (%) is preferably 3500 or more, and more preferably 4000 or more. The upper limit of TB × EB / 2 is not particularly limited, and the higher the better.
When TB × EB / 2 is within the above range, good anti-chunking performance can be ensured.

The rubber composition (after vulcanization) of the present invention preferably has a hardness measured with a hardness meter in an atmosphere of 25 ° C. based on JIS K6253: 2006, preferably from 50 to 75. It is more preferable. When the hardness is within the above range, good grip performance can be secured while maintaining good steering stability.

The pneumatic tire (two-wheeled vehicle tire) of the present invention is 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 tire member such as a tread at an unvulcanized stage, and is molded together with the other tire members by a normal method on a tire molding machine. By doing so, an unvulcanized tire is formed. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire. Also, a motorcycle tire may be manufactured by an STW method in which a strip is wound.

The motorcycle tire of the present invention is used as a motorcycle tire, and particularly preferably used as a motocross tire.

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

Production Examples 1-4
<Chemicals used>
The chemicals used for resin synthesis are shown below. In addition, the chemical | medical agent refine | purified according to the usual method as needed.
Toluene: Kanto Chemical Co., Ltd. α-Pinene: Tokyo Chemical Industry Co., Ltd. 3-Calene: Tokyo Chemical Industry Co., Ltd. pt-butylphenol: Wako Pure Chemical Industries, Ltd. Styrene: Tokyo Chemical Industry Co., Ltd. ) Α-methylstyrene: manufactured by Tokyo Chemical Industry Co., Ltd. Boron trifluoride (BF ₃ ): manufactured by Tokyo Chemical Industry Co., Ltd. Sodium carbonate: manufactured by Tokyo Chemical Industry Co., Ltd.

<Synthesis method>
A three-necked flask equipped with a thermometer, a stirrer, a cooler, and a Dean-Stark trap was thoroughly purged with nitrogen, and 200 g of toluene was added thereto. To this, 10 g of pt-butylphenol was added, followed by stirring and refluxing for 2 hours. As a catalyst, 1.2 g of BF ₃ gas was added, and 76 g of α-pinene was added dropwise over a period of about 90 minutes, and then 14 g of styrene was added dropwise over a period of about 30 minutes, while stirring at 40 ° C. for 60 minutes under nitrogen. Polymerization was performed. After completion of the reaction, 1.2 g of sodium carbonate dissolved in 100 ml of water was added to stop the reaction, and the catalyst was removed by repeating washing with water. Toluene and unreacted monomers were removed by distillation under reduced pressure to obtain the intended resin A.
Resins B to D were synthesized in the same manner as Resin A, except that 3-carene was used instead of α-pinene, α-methylstyrene was used instead of styrene, and the addition amount was changed to the amount shown in Table 1.
Table 1 shows the composition, softening point, and molecular weight of the synthesized resin. The molecular weight and softening point were measured by the following methods.

(Measurement of weight average molecular weight (Mw), number average molecular weight (Mn))
Mw and Mn are based on values measured by gel permeation chromatograph (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation). Was obtained by standard polystyrene conversion.

(Softening point)
The softening point was determined by measuring the softening point defined in JIS K 6220-1: 2001 with a ring-and-ball type softening point measuring device and setting the temperature at which the sphere descended as the softening point.

Examples and Comparative Examples <Chemicals Used>
Various chemicals used in Examples and Comparative Examples will be described together.
SBR: Nipol 9548 (manufactured by Nippon Zeon Co., Ltd., E-SBR, styrene content: 35% by mass, 37.5 parts by mass of oil with respect to 100 parts by mass of rubber component)
Carbon black: Seast 9 SAF (manufactured by Tokai Carbon Co., Ltd., N ₂ SA: 142 m ² / g)
Liquid SBR: RAICON 100 (manufactured by Sartomer, styrene content: 20% by mass, vinyl content: 70% by mass, Mw: 5000)
Oil: Diana Process AH-24 (made by Idemitsu Kosan Co., Ltd.)
Resins A to D: Synthetic resin E in Production Examples 1 to 4: Kristalex 3085 (α-methylstyrene resin, manufactured by Eastman Chemical Co.)
Resin F: YS Resin PX1250 (terpene resin, manufactured by Yasuhara Chemical Co., Ltd.)
Resin G: Koresin (pt-butylphenol resin, manufactured by BASF)
Zinc oxide: Zinc oxide (Mitsui Metal Mining Co., Ltd.)
Stearic acid: Stearic acid “椿” (manufactured by NOF Corporation)
Anti-aging agent: Antigen 6C (manufactured by Sumitomo Chemical Co., Ltd.) (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine)
Wax: Sunnock N (Ouchi Shinsei Chemical Co., Ltd.)
Sulfur: Powdered sulfur (manufactured by Karuizawa Sulfur Co., Ltd.)
Vulcanization accelerator: Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

<Method for producing rubber composition>
According to the formulation shown in Table 2, materials other than sulfur and a vulcanization accelerator were kneaded at 130 ° C. for 5 minutes using a 1.7 L Banbury manufactured by Kobe Steel Co., Ltd. to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded at 120 ° C. for 2 minutes using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized at 150 ° C. for 30 minutes to obtain a vulcanized rubber composition.

<Tire manufacturing method>
The obtained unvulcanized rubber composition was molded into a tread shape, and bonded together with other tire members on a tire molding machine, and press vulcanized at 150 ° C. for 30 minutes to give a test tire (motocross tire). ) (Tire size: 120 / 80-19).

<Evaluation method>
(Dry grip performance)
The prepared test tire was mounted on all the wheels of a motorcycle for motocross (CRF450R manufactured by Honda Motor Co., Ltd.), and the vehicle was run for 10 laps on the motocross test course (dry asphalt road surface). At that time, the test driver evaluated the stability of the control at the time of steering. Larger values indicate better dry grip performance.

(Chunking resistance)
Based on JIS K6251: 2010, a dumbbell-shaped No. 3 test piece was prepared from the obtained vulcanized rubber composition, and a tensile test was performed using the test piece in an atmosphere at 23 ° C. to obtain a breaking strength TB (MPa ), Elongation at break EB (%) was measured. And TB * EB / 2 (MPa *%) was computed. The result shows an actual measurement value, and the result of Comparative Example 1 is shown as an index with the result being 100. TB × EB / 2, the larger the index, the better the anti-chunking performance.

(Wet grip performance)
The prepared test tire is mounted on all the wheels of a motorcycle for motocross (CRF450R manufactured by Honda Motor Co., Ltd.), and 10 laps are carried out on a motocross test course (wet asphalt road surface) where water is sprayed to make the road wet. A real car was run. At that time, the test driver evaluated the stability of the control at the time of steering. Larger values indicate better wet grip performance.

(hardness)
Using the obtained vulcanized rubber composition, the hardness of the rubber was measured using a hardness meter in a 25 ° C. atmosphere based on JIS K6253: 2006 (Shore-A measurement). It shows that it is so hard that a numerical value is large.

From the results of Table 2, in Comparative Examples 2 to 4 containing a resin of α-methylstyrene, terpene, and pt-butylphenol, the balance of dry grip performance, wet grip performance and anti-chunking performance is inferior to that of the examples. It was. Also in Comparative Example 5 where these were blended, the performance balance was quite poor.

On the other hand, it contains a specific amount of styrene butadiene rubber and (a) a phenol compound, (b) a terpene compound and (c) resins (resins A to D) obtained by copolymerizing an aromatic vinyl compound. As a result, dry grip performance, wet grip performance, and anti-chunking performance were improved at the same time, and it became clear that these performance balances could be remarkably improved.

Claims (10)

A rubber component containing 60 to 100% by mass of styrene butadiene rubber and a resin obtained by copolymerizing (a) a phenol compound, (b) a terpene compound and (c) an aromatic vinyl compound. Rubber composition for tires. The phenolic compound (a) is phenol and / or alkylphenol, the terpene compound (b) is a cyclic unsaturated hydrocarbon having no hydroxyl group, and the aromatic vinyl compound (c) is styrene and / or alkyl-substituted styrene. The rubber composition for tires according to claim 1, wherein The tire rubber composition according to claim 2, wherein the terpene compound (b) is at least one selected from the group consisting of α-pinene, β-pinene, 3-carene, limonene and dipentene. The rubber composition for a tire according to any one of claims 1 to 3, wherein the amount of the resin is 5 to 50 parts by mass with respect to 100 parts by mass of the rubber component. The copolymerization ratio of the phenolic compound (a) in 100% by mass of the resin is 5 to 10% by mass, the copolymerization ratio of the terpene compound (b) is 70 to 85% by mass, and the copolymerization of the aromatic vinyl compound (c). The rubber composition for tires according to any one of claims 1 to 4, wherein a polymerization ratio is 10 to 20% by mass. Furthermore, the rubber composition for tires in any one of Claims 1-5 containing carbon black. From rupture strength TB (MPa) and elongation at break EB (%) measured using a dumbbell-shaped No. 3 test piece as a test piece and performing a tensile test in a 23 ° C. atmosphere based on JIS K6251: 2010 TB * EB / 2 calculated is 3500 or more, The rubber composition for tires in any one of Claims 1-6. The tire rubber composition according to any one of claims 1 to 7, which is used as a tread rubber composition. A tire for a motorcycle using the rubber composition according to any one of claims 1 to 8. The tire for a motorcycle according to claim 9, which is a tire for motocross.