JP6215684B2 - Tread rubber composition for motorcycle tire and motorcycle tire - Google Patents

Description

The present invention relates to a tread rubber composition for a motorcycle tire and a motorcycle tire produced using the tread rubber composition.

The rubber composition for treads used for motorcycle tires (tread rubber composition for motorcycle tires) suppresses the occurrence of chipping (partial rubber peeling) during running, so it has high mechanical strength (chipping resistance). Is required. Furthermore, the tread rubber composition for motorcycle tires is also required to have good grip performance (particularly wet grip performance).

By blending silica, good grip performance (particularly wet grip performance) can be obtained (for example, Patent Document 1). However, when silica is blended, there is a problem that the mechanical strength of the rubber composition is lowered and the chipping resistance is lowered.

JP 2011-089078 A

The present invention provides a tread rubber composition for a motorcycle tire that solves the above-mentioned problems and can improve grip performance (particularly wet grip performance) and chipping resistance in a well-balanced manner, and a motorcycle tire using the rubber composition for a tire tread. The purpose is to provide.

In the present invention, when a rubber component containing styrene-butadiene rubber and three or more particles adjacent to one particle are used as a branched particle Z, the average length of ZZ between branched particles including the branched particle Z W ¹ includes and the structure of silica 30～400Nm, based on 100 parts by mass of the rubber component, about tread rubber composition for a motorcycle tire comprising 5 to 50 parts by mass of the structure silica.

The present invention also relates to a tread rubber composition for two-wheeled vehicle tires obtained by kneading a rubber component containing styrene butadiene rubber and silica sol.

The tread rubber composition for motorcycle tires preferably contains carbon black.

When the above-mentioned structure silica has an average primary particle diameter of D, the average aspect ratio W ¹ / D of the inter-branched particle ZZ including the branched particles Z is preferably 3 to 100.

The average primary particle diameter D of the structure silica is preferably 5 to 1000 nm.

It is preferable that the tread rubber composition for a motorcycle tire includes 1 to 20 parts by mass of a silane coupling agent with respect to 100 parts by mass of silica.

The tread rubber composition for a motorcycle tire has a carbon black content of 30 to 200 parts by mass, a silica content of 5 to 100 parts by mass, and a total filler content of 50 to 100 parts by mass of the rubber component. It is preferably 250 parts by mass.

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

The motorcycle tire is preferably a motocross tire.

According to the present invention, since it is a tread rubber composition for a motorcycle tire containing a rubber component containing styrene-butadiene rubber and specific silica, grip performance (particularly wet grip performance) and chipping resistance can be improved in a well-balanced manner. By using the rubber composition in a tire tread, a motorcycle tire excellent in the above performance can be provided.

2 is a schematic diagram of branched particles Z. FIG. Outline of average primary particle diameter D of silica, average length of branched ZZ including branched particles Z (W ¹ ), and average length of branched ZZ not including branched particles Z (W ² ) It is a schematic diagram.

The tread rubber composition for a motorcycle tire according to the present invention includes a branch containing a branched particle Z when a rubber component containing a styrene butadiene rubber and a particle adjacent to one particle are three or more particles. and a structure silica having an average length ^{W 1} of the interparticle Z-Z is 30～400Nm (linear silica), with respect to 100 parts by mass of the rubber component includes 5 to 50 parts by mass of the structure silica.

In the conventional rubber composition containing granular silica, although the grip performance (particularly wet grip performance) can be improved, the mechanical strength of the rubber composition is lowered and the chipping performance is lowered. there were. On the other hand, the use of the structure silica reduces the occluder rubber (rubber which is encapsulated in the silica aggregate and cannot be distorted) generated by the aggregation of the silica particles, and local stress concentration, that is, local Distortion is reduced. Furthermore, the structure silica is oriented in the tread circumferential direction of the tire when the tire is highly stretched (during high strain) such as during sudden braking or sharp turning. As a result, while maintaining good grip performance (especially wet grip performance) obtained by blending silica, chipping performance can be improved, and grip performance (particularly wet grip performance) and chipping performance are well balanced. can get.

The rubber composition containing the structure silica of the present invention can be produced, for example, by kneading a rubber component containing styrene butadiene rubber and silica sol.

[Rubber component]
In the present invention, styrene butadiene rubber (SBR) is used as the rubber component. Thereby, favorable grip performance (especially wet grip performance) and chipping resistance can be obtained.

The SBR is not particularly limited, and those generally used in the tire industry such as emulsion polymerization styrene butadiene rubber (E-SBR) and solution polymerization styrene butadiene rubber (S-SBR) can be used. Of these, E-SBR is preferable.

The content of SBR in 100% by mass of the rubber component is preferably 60% by mass or more, more preferably 80% by mass or more, and still more preferably 100% by mass. If the SBR content is less than 60% by mass, sufficient grip performance (particularly wet grip performance) and chipping resistance may not be obtained.

Examples of rubber components that can be used in addition to SBR in the present invention include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), and chloroprene rubber. And diene rubbers such as (CR) and butyl rubber (IIR). These rubber components may be used alone or in combination of two or more.

(Structural silica (linear silica))
In the structure silica (linear silica) used in the present invention, particles adjacent to one particle have three or more particles (hereinafter referred to as branched particles Z), and the branched particles Z and particles adjacent thereto. As a result, a branched structure is formed. The branched particle Z is a particle Z among the particles in FIG. 1, which is a schematic explanatory view of a branched particle, and is adjacent to three or more other particles. In addition, as structure silica, what has a branched structure (for example, FIG. 2) and what does not have are mentioned, However, Since the structured silica which does not have a branched structure will aggregate immediately, it does not exist substantially.

The average length (W ¹ in FIG. 2) of the ZZ between the branched particles including the branched particles Z of the structure silica is 30 nm or more, preferably 40 nm or more. If it is less than 30 nm, the effect of increasing the hysteresis loss due to the orientation of silica cannot be sufficiently obtained in the high elongation region, and sufficient grip performance (particularly wet grip performance) may not be obtained. W ¹ is 400 nm or less, preferably 200 nm or less, more preferably 100 nm or less. If it exceeds 400 nm, it becomes hard and sufficient grip performance (particularly wet grip performance) may not be obtained.

The average primary particle diameter of structure silica (D, see FIG. 2 which is a schematic explanatory diagram of structure silica containing branched particles) is preferably 5 nm or more, more preferably 7 nm or more. If it is less than 5 nm, sufficient chipping resistance may not be obtained. Further, D is preferably 1000 nm or less, more preferably 100 nm or less, and still more preferably 18 nm or less. If it exceeds 1000 nm, the stress does not increase sufficiently in the high elongation region, and the hysteresis loss does not increase, so that sufficient grip performance (particularly wet grip performance) may not be obtained.

The average aspect ratio (W ¹ / D) of ZZ between branched particles including the branched particles Z of structure silica is preferably 3 or more, more preferably 4 or more. If it is less than 3, the stress does not increase sufficiently in the high elongation region, and the hysteresis loss does not increase, so that sufficient grip performance (particularly wet grip performance) may not be obtained. Further, W ¹ / D is preferably 100 or less, more preferably 30 or less. When W ¹ / D exceeds 100, it may become hard and sufficient grip performance (particularly wet grip performance) may not be obtained.

In the present invention, D, W ¹ and W ¹ / D of silica can be measured by observation with a transmission electron microscope of silica dispersed in a vulcanized rubber composition. For example, in FIG. 2, W ¹ / D is 5 when the particle is a true sphere.

The content of the structure silica is 5 parts by mass or more, 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 5 mass parts, there exists a tendency for the effect which mix | blended structure silica is not fully acquired. Moreover, content of structure silica is 50 mass parts or less, Preferably it is 40 mass parts or less, More preferably, it is 30 mass parts or less. When it exceeds 50 parts by mass, the rigidity of the rubber composition increases, and the workability and grip performance (particularly wet grip performance) tend to deteriorate.

In this invention, it is preferable to mix | blend the granular silica conventionally mix | blended with the rubber composition with the structure silica. Thereby, grip performance (especially wet grip performance) can be improved more. Examples of the particulate silica include dry method silica (anhydrous silica), wet method silica (hydrous silica), and the like. Of these, wet-process silica is preferred because it has many silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of the granular silica is preferably 40 m ² / g or more, more preferably 70 m ² / g or more, and further preferably 110 m ² / g or more. When it is less than 40 m ² / g, chipping resistance tends to be lowered. Also, _N 2 SA of the particulate silica is preferably 220 m ² / g or less, and more preferably not more than 200m ² / g. When it exceeds 220 m < ² > / g, it will become difficult to disperse | distribute a granular silica and there exists a possibility that workability may deteriorate.
Incidentally, _N 2 SA of the particulate silica is a value determined by the BET method in accordance with ASTM D3037-93.

The content of silica (total content of structure silica and granular silica) is preferably 5 parts by mass or more, more preferably 10 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 5 parts by mass, sufficient grip performance (particularly wet grip performance) and chipping resistance may not be obtained. The content of the structure silica is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 60 parts by mass or less. When the amount exceeds 100 parts by mass, the rigidity of the rubber composition increases, and the workability and grip performance (particularly wet grip performance) tend to deteriorate.

(Silane coupling agent)
In the present invention, it is preferable to use a silane coupling agent together with silica (structure silica, and granular silica when used). The silane coupling agent is not particularly limited, and those conventionally used in the tire field can be used. For example, sulfide-based, mercapto-based, vinyl-based, amino-based, glycidoxy-based, nitro-based, chloro-based silane coupling Agents and the like. Among them, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, etc. A sulfide system can be preferably used. Of these, bis (3-triethoxysilylpropyl) tetrasulfide is preferable. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of silica. When the content of the silane coupling agent is less than 1 part by mass, sufficient chipping resistance tends to be not obtained. The content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less with respect to 100 parts by mass of silica. When the content of the silane coupling agent exceeds 20 parts by mass, the blending effect of the silane coupling agent as much as the content cannot be obtained, and the cost tends to be high.
In addition, 100 mass parts of silica means the total amount of both, when using a granular silica with a structure silica.

(Carbon black)
In the present invention, it is preferable to use carbon black. Thereby, a good chipping resistance can be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 70 m ² / g or more, and more preferably 120 m ² / g or more. If it is less than 70 m < ² > / g, there exists a possibility that sufficient reinforcement property cannot be obtained and sufficient chipping-proof performance may not be obtained. The _N 2 SA is preferably 200 meters ² / g or less, more preferably 160 m ² / g. When it exceeds 200 m ² / g, the wet grip performance tends to decrease.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

Carbon black has a dibutyl phthalate oil absorption (DBP) of preferably 50 ml / 100 g or more, and more preferably 100 ml / 100 g or more. If it is less than 50 ml / 100 g, sufficient reinforcement cannot be obtained, and sufficient chipping resistance may not be obtained. The DBP of carbon black is preferably 200 ml / 100 g or less, and more preferably 135 ml / 100 g or less. If it exceeds 200 ml / 100 g, the wet grip performance may be reduced.
The DBP of carbon black is measured according to JIS K6217-4: 2001.

The content of carbon black is preferably 30 parts by mass or more, more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 30 parts by mass, sufficient reinforcing properties cannot be obtained, and sufficient chipping resistance may not be obtained. The content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 100 parts by mass or less. If it exceeds 200 parts by mass, the wet grip performance may be reduced.

The content of silica in 100% by mass of the total of silica (total of structure silica and granular silica) and carbon black is preferably 10% by mass or more, more preferably 20% by mass or more. The content of the silica is preferably 60% by mass or less, more preferably 50% by mass or less. If it is in the said range, a grip performance (especially wet grip performance) and chipping-proof performance can be improved in a high dimension and with a good balance.

In the present invention, clay, calcium carbonate, mica, and the like can be used as the filler in addition to the structure silica, granular silica, and carbon black.

The total content of the filler (preferably the total content of structure silica, granular silica and carbon black) is preferably 50 parts by mass or more, more preferably 70 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, sufficient reinforcing properties cannot be obtained, and sufficient chipping resistance may not be obtained. The content is preferably 250 parts by mass or less, more preferably 180 parts by mass or less, and still more preferably 120 parts by mass or less. If it exceeds 250 parts by mass, the wet grip performance may be reduced.

(Softener)
Softeners include petroleum-based softeners such as process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, and petroleum jelly, and fatty oil-based softeners such as soybean oil, palm oil, castor oil, linseed oil, rapeseed oil, and coconut oil. Agents, waxes such as tall oil, sub, beeswax, carnauba wax and lanolin, and fatty acids such as linoleic acid, palmitic acid, stearic acid and lauric acid. As the process oil, for example, a paraffin process oil, an aroma process oil, a naphthenic process oil, or the like can be used. Of these, petroleum softeners are preferred, process oils are more preferred, and aroma based process oils are even more preferred. The compounding amount of the softening agent is preferably 10 to 100 parts by mass, more preferably 20 to 50 parts by mass with respect to 100 parts by mass of the rubber component. When the blending amount of the softening agent is within the above range, better grip performance (particularly wet grip performance) and chipping resistance can be obtained.

(Vulcanization accelerator)
The rubber composition of the present invention can contain a vulcanization accelerator. Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine, aldehyde-ammonia, imidazoline, and xanthate vulcanization accelerators. Is mentioned. These may be used alone or in combination of two or more. Of these, sulfenamide vulcanization accelerators are preferred.

Examples of the sulfenamide vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N And '-dicyclohexyl-2-benzothiazolylsulfenamide (DZ). Of these, CBS is preferable.

The amount of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and further preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component. The amount of the vulcanization accelerator is preferably 6 parts by mass or less, more preferably 4 parts by mass or less. When the blending amount of the vulcanization accelerator is within the above range, better grip performance (particularly wet grip performance) and chipping resistance can be obtained.

(Vulcanization aid)
The rubber composition of the present invention can contain a vulcanization aid. As the vulcanization aid, stearic acid, zinc oxide (zinc white) or the like can be used.

(Other ingredients)
In the rubber composition of the present invention, various compounding agents and additives blended for tires or general rubber compositions such as other reinforcing agents, plasticizers and vulcanizing agents can be blended. Moreover, the content of these compounding agents and additives can also be set to general amounts.

<Method for producing rubber composition>
The rubber composition of the present invention can be produced by a conventionally known production method, and the production method is not limited. For example, it can be produced by kneading each of the above components using a kneading machine such as a Banbury mixer or a kneading roll under ordinary methods and conditions.

In particular, the silica sol is preferably kneaded with a rubber component containing SBR in a rubber kneading apparatus from the viewpoint that the rubber composition of the present invention in which the structure silica is formed can be easily produced.
(I) A rubber component containing SBR, silica sol, and, if necessary, carbon black, silane coupling agent, zinc oxide, stearic acid, softener, anti-aging agent, wax, etc. at 80 to 180 ° C. (preferably 90 A base kneading step of kneading at ˜170 ° C. for 3 to 10 minutes,
(II) a final kneading step of kneading the kneaded material obtained by the base kneading step, the vulcanizing agent, and the vulcanization accelerator at 30 to 70 ° C. (preferably 40 to 60 ° C.) for 3 to 10 minutes;
(III) A production method including a vulcanization step of vulcanizing the unvulcanized rubber composition obtained by the finish kneading step at 150 to 190 ° C. (preferably 150 to 180 ° C.) for 5 to 30 minutes is more preferable.

The preferable compounding amount (silica conversion) of silica sol is the same as that of the above-mentioned structure silica.

In the kneading step (such as the base kneading step) for forming the structure silica, if each component is kneaded in toluene, which is a good solvent for rubber, the W ^{1 of} the structure silica tends to become excessively long. It is preferable to knead without using.

In this specification, silica sol refers to a colloidal solution in which silica is dispersed in a solvent. The silica sol is not particularly limited, but a colloidal solution in which elongated silica is dispersed in a solvent is preferable because a structure silica can be suitably formed. A colloidal solution in which elongated silica is dispersed in an organic solvent (organo Silica sol) is more preferable. Here, the elongated silica means a silica (secondary particle) having a chain shape in which a plurality of primary particles such as a spherical shape and a granular shape are connected. It may be linear or branched.

The solvent for dispersing silica is not particularly limited, but alcohols such as methanol and isopropanol are preferable, and isopropanol is more preferable.

The average particle diameter of the primary particles constituting the silica (secondary particles) contained in the silica sol is preferably 1 to 100 nm, more preferably 5 to 80 nm.
The average particle size of the primary particles was determined by visually measuring the particle size (average diameter) of 50 primary particles in a photograph taken with a transmission electron microscope JEM2100FX manufactured by JEOL. .

In addition, when the silica (secondary particles) has an elongated shape, the average diameter of the primary particles is an average value of thicknesses (diameters) measured at arbitrary 50 locations of the silica (secondary particles) in the electron micrograph. In the case where the silica (secondary particles) has a bead shape with a constriction, it can be obtained as an average value of the diameters of 50 bead beads in an electron micrograph. When each rosary has a major axis and a minor axis, that is, when each rosary is elongated, the minor axis is measured.

The average particle diameter of silica (secondary particles) contained in the silica sol is preferably 20 to 300 nm, more preferably 30 to 150 nm. The average particle diameter of silica (secondary particles) can be measured by a dynamic light scattering method, and specifically, can be measured by the following method.
The average particle diameter of silica (secondary particles) was measured with a laser particle analysis system ELS-8000 (cumulant analysis) manufactured by Otsuka Electronics Co., Ltd. The measurement conditions are a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and an integration count of 100. The refractive index of water (1.333) is input as the refractive index of the dispersion solvent. The measurement concentration was usually about 5 × 10 ⁻³ mass%.

The silica (secondary particles) is, for example, a method described in claim 2 of International Publication No. WO 00/15552 and the disclosure of the specification related thereto, Japanese Patent No. 2803134, Japanese Patent No. 2926915. It can be produced according to the method described in claim 2 of the publication and the disclosure part of the specification related thereto.

Specific examples of the silica (secondary particles) that can be used in the present invention include “Snowtex-OUP” (average secondary particle size: 40 to 100 nm) manufactured by Nissan Chemical Industries, Ltd., “Snowtex”. -UP "(average secondary particle size: 40 to 100 nm)," Snowtex PS-M "(average secondary particle size: 80 to 150 nm)," Snowtex PS-MO "(average secondary particle size: 80-150 nm), “Snowtex PS-S” (average secondary particle size: 80-120 nm), “Snowtex PS-SO” (average secondary particle size: 80-120 nm), “IPA-ST-” UP ”(average secondary particle size: 40 to 100 nm),“ Quartron PL-7 ”(average secondary particle size: 130 nm) manufactured by Fuso Chemical Industries, Ltd., and the like. Among these, IPA-ST-UP is preferable because it can form the structure silica suitably.

By using the rubber composition of the present invention thus obtained for a tire tread, a two-wheeled vehicle tire with improved grip performance (particularly wet grip performance) and chipping resistance can be obtained.

<Motorcycle tires>
The motorcycle tire of the present invention is manufactured by a usual method using the rubber composition.
That is, by extruding a rubber composition containing the above components in accordance with the shape of a tread or the like at an unvulcanized stage, and molding it with a tire molding machine by a normal method along with other tire members, Form an unvulcanized tire. A motorcycle tire is obtained by heating and pressurizing the unvulcanized tire in a vulcanizer. Further, 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.

<Examples and Comparative Examples>
Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
SBR: Nipol 1502 manufactured by Nippon Zeon Co., Ltd. (E-SBR, styrene content: 23.5% by mass)
Carbon black: N110 (N ₂ SA: 144 m ² / g, DBP absorption: 115 ml / 100 g) manufactured by Cabot Japan
Silica A: Organosilica sol IPA-ST-UP manufactured by Nissan Chemical Industries, Ltd. (elongated isopropanol-dispersed silica sol (average particle diameter of silica (secondary particles) measured by dynamic light scattering method: 40 to 100 nm)) (Silica content: 15% by mass) (The amount shown in Table 1 indicates the amount of silica in the organosilica sol.)
Silica B: Ultrasil VN3 manufactured by Degussa (granular silica, N ₂ SA: 175 m ² / g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Evonik Degussa
Aroma oil: Diana Process Oil X140 (Aroma Process Oil) manufactured by Japan Energy
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Three types of zinc oxide (average primary particle size: 1.0 μm) manufactured by Hakusui Tech Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd .: Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

In accordance with the composition shown in Table 1, materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes at 80 to 180 ° 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 5 minutes at 50 ° C. using an open roll to obtain an unvulcanized rubber composition.
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).
The performance of the obtained test tire was evaluated by the following test method.

<Evaluation items and test methods>
(Wet grip performance, chipping resistance)
The test tires were 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 an unpaved off-road course under wet conditions. The following five levels of sensory evaluation were performed on the grip performance at this time.
5: Very good, 4: Good, 3: Normal, 2: Slightly inferior, 1: Inferior In addition, the following five-step sensory evaluation was performed on chipping resistance according to the appearance of the test tire after running.
5: Very good, 4: Good, 3: Normal, 2: Slightly inferior, 1: Inferior

(Average primary particle diameter, average length and average aspect ratio of silica)
A sample was cut out from the tread of the test tire, and the silica dispersed in the sample was observed with a transmission electron microscope, and the average primary particle diameter (D) of silica and the average of Z-Z between branched particles including branched particles Z. 2 (W ¹ in FIG. 2), the average length of the inter-branched particles ZZ not including the branched particles Z (W ² in FIG. ² ), the average aspect ratio of the ZZ between the branched particles including the branched particles Z (W ¹ / D), the average aspect ratio (W ² / D) of ZZ between the branched particles not containing the branched particles Z was calculated. The numerical value was an average value obtained by measuring 30 locations. In Examples 2 and 4, since silica A and silica B were used in combination, granular silica was also present together with structure silica in the rubber composition. Therefore, only structure silica was observed with a transmission electron microscope and evaluated.

As shown in Table 1, Examples including a rubber component containing styrene butadiene rubber and specific silica were able to improve the grip performance (particularly wet grip performance) and chipping resistance in a well-balanced manner.

Z branch particles

Claims (8)

When the rubber component containing styrene butadiene rubber and three or more particles adjacent to one particle are used as the branched particle Z, the average length W ^{1 of the} ZZ between the branched particles including the branched particle Z is 30. Containing ~ 400 nm structure silica and carbon black ,
Wherein the rubber component 100 parts by weight of 5 to 50 parts by mass of the structure silica, viewed 50-100 parts by weight containing the carbon black,
A tread rubber composition for a motorcycle tire , wherein the silica content in the total of 100% by mass of silica and carbon black is 10 to 50% by mass . The tread rubber composition for a motorcycle tire according to claim 1 , wherein the tread rubber composition is obtained by kneading a rubber component containing styrene butadiene rubber and silica sol. The structure silica has an average primary particle diameter is defined as D, the average aspect ratio W ^{1 /} D branch intergranular Z-Z including the branch particles Z are as defined in claim 1 or 2 is of 3 to 100 A tread rubber composition for motorcycle tires. The tread rubber composition for a motorcycle tire according to any one of claims 1 to 3, wherein the average primary particle diameter D of the structure silica is 5 to 1000 nm. The tread rubber composition for a motorcycle tire according to any one of claims 1 to 4 , comprising 1 to 20 parts by mass of a silane coupling agent with respect to 100 parts by mass of silica. Per 100 parts by mass of the rubber component, shea content 5 to 100 parts by weight of silica, tread rubber for a motorcycle tire according to any one of claims 1 to 5 Total amount of filler is 50 to 250 parts by weight Composition. A two-wheeled vehicle tire having a tread produced using the rubber composition according to any one of claims 1 to 6 . The motorcycle tire according to claim 7, which is a motocross tire.

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