JP2011189808A - Tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire for a motorcycle superior in a balance of low fuel consumption performance, abrasion resistance and operating stability. <P>SOLUTION: This tire for the motorcycle has a tread part for arranging tread rubber divided into at least three parts in the tire width direction, wherein the tread rubber has center rubber arranged in the central part in the tire width direction and shoulder rubber arranged on both sides in the tire width direction of the center rubber, and the shoulder rubber includes a rubber component and silica on which the CTAB specific surface area is 180m<SP>2</SP>/g or more and the BET specific surface area is 185m<SP>2</SP>/g or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a motorcycle tire.

In recent years, from the viewpoint of environmental considerations and the like, improvement in fuel efficiency of tires has been demanded. Examples of a method for improving the fuel efficiency include a method using natural rubber as a rubber component and a method using silica as a reinforcing material (see, for example, Patent Document 1). However, when these methods are used, there is room for improvement in that although the fuel efficiency is improved, the wear resistance tends to deteriorate.

In recent years, a divided tread in which different types of rubber compositions are arranged in the tire width direction has been used for a tread portion of a motorcycle (MC) tire (see, for example, Patent Document 2). By using a split tread, a rubber composition (center rubber) with excellent wear resistance is arranged at the center of the tread, and a rubber composition (shoulder rubber) with excellent steering stability is arranged at the shoulder of the tread. Thus, both wear resistance and steering stability can be achieved. However, as the performance of vehicles increases, further improvement in wear resistance and steering stability is required.

JP 2008-31244 A JP 2009-46058 A

An object of the present invention is to solve the above-mentioned problems and to provide a tire for a motorcycle that is excellent in balance between low fuel consumption performance, wear resistance, and steering stability.

The present invention has a tread portion in which a tread rubber divided into at least three parts in the tire width direction is disposed, and the tread rubber is disposed in a center portion in the tire width direction, and the tire width of the center rubber. A tire for a motorcycle including a rubber component and silica having a CTAB specific surface area of 180 m ² / g or more and a BET specific surface area of 185 m ² / g or more. About.

The aggregate size of the silica is preferably 30 nm or more.

The amount of acetone extracted in 100% by mass of the shoulder rubber is preferably 8% by mass or more.

The shoulder rubber preferably has a tan δ of 0.06 to 0.25.

According to the present invention, since the shoulder rubber blended with silica having a CTAB specific surface area and a BET specific surface area of a specific value or more is used in the tread portion of a motorcycle tire, low fuel consumption performance, wear resistance and steering stability are achieved. Motorcycle tires with excellent balance can be provided.

It is a figure which shows a pore distribution curve. 1 is a tire meridian cross-sectional view including a tire rotation axis of a motorcycle tire according to an embodiment of the present invention. 1 is a tire meridian cross-sectional view showing a state in which a motorcycle tire according to an embodiment of the present invention is in contact with a road surface (exemplification in a contact surface). 1 is a tire meridian cross-sectional view showing a state in which a motorcycle tire according to an embodiment of the present invention is in contact with a road surface (exemplification outside a contact surface).

The tire for a motorcycle according to the present invention has a tread portion in which a tread rubber divided into at least three parts in the tire width direction is disposed, and the tread rubber is disposed in a center portion in the tire width direction, and the center rubber. A shoulder rubber disposed on both sides in the tire width direction of the rubber, wherein the shoulder rubber contains a rubber component and silica having a CTAB specific surface area of 180 m ² / g or more and a BET specific surface area of 185 m ² / g or more. To do.

The rubber component that can be used for the shoulder rubber is not particularly limited. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), epoxidized natural rubber (ENR), Examples thereof include diene rubbers such as acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used alone or in combination of two or more. Among these, NR and SBR are preferable, and NR and SBR are more preferably used in combination because the steering stability on the dry road surface and the wet road surface and the wear resistance can be compatible.

The NR is not particularly limited, and those commonly used in the rubber industry such as RSS # 3, TSR20, etc. can be used.

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

In the present invention, silica having a CTAB specific surface area of 180 m ² / g or more and a BET specific surface area of 185 m ² / g or more (hereinafter also referred to as “particulate silica”) is used. A good dispersion of such fine-particle silica in rubber can improve the wear resistance and fuel efficiency in a well-balanced manner.

The CTAB (cetyltrimethylammonium bromide) specific surface area of the fine particle silica is 180 m ² / g or more, preferably 190 m ² / g or more, more preferably 195 m ² / g or more, and further preferably 200 m ² / g or more. When the CTAB specific surface area is less than 180 m ² / g, it tends to be difficult to obtain sufficient improvement in wear resistance. The CTAB specific surface area is preferably 600 m ² / g or less, more preferably 500 m ² / g or less, still more preferably 300 m ² / g or less, and particularly preferably 250 m ² / g or less. When the CTAB specific surface area exceeds 600 m ² / g, the dispersibility is inferior and aggregation occurs, so that the physical properties tend to decrease.
In addition, the CTAB specific surface area of a silica is measured based on ASTM D3765-92.

The BET specific surface area of the fine particle silica is 185 m ² / g or more, preferably 190 m ² / g or more, more preferably 200 m ² / g or more, still more preferably 210 m ² / g or more, particularly preferably 220 m ² / g or more. . When the BET specific surface area is less than 185 m ² / g, it tends to be difficult to obtain sufficient improvement in wear resistance. The BET specific surface area is preferably 600 m ² / g or less, more preferably 500 m ² / g or less, still more preferably 300 m ² / g or less, and particularly preferably 260 m ² / g or less. When the BET specific surface area exceeds 600 m ² / g, the dispersibility is inferior and aggregation occurs, so that the physical properties tend to decrease.
In addition, the BET specific surface area of a silica is measured according to ASTM D3037-81.

The aggregate size of the fine particle silica is preferably 30 nm or more, more preferably 35 nm or more, still more preferably 40 nm or more, particularly preferably 45 nm or more, and most preferably 50 nm or more. The aggregate size is preferably 100 nm or less, more preferably 80 nm or less, still more preferably 70 nm or less, and particularly preferably 65 nm or less. By having such an aggregate size, it is possible to provide excellent reinforcement, wear resistance, and steering stability while having good dispersibility.

The aggregate size is called the aggregate diameter or the maximum frequency Stokes equivalent diameter, and is the particle diameter when the aggregate of silica composed of a plurality of primary particles is regarded as one particle. It is equivalent. The aggregate size can be measured using a disk centrifugal sedimentation type particle size distribution measuring device such as BI-XDC (manufactured by Brookhaven Instruments Corporation).

Specifically, it can be measured by the following method using BI-XDC.
Add 3.2 g silica and 40 mL deionized water to a 50 mL tall beaker and place the beaker containing the suspension in an ice-filled crystallizer. Samples are prepared by disintegrating the suspension for 8 minutes using an ultrasonic probe (1500 watt 1.9 cm VIBRACEELL ultrasonic probe (Bioblock, used at 60% of maximum power)) in a beaker. A sample of 15 mL is introduced into a disk, stirred, and measured under conditions of fixed mode, analysis time of 120 minutes, density of 2.1.
In the recorder of the apparatus, the values of the passing diameter and the mode value of 16%, 50% (or median) and 84% by weight are recorded. (The derivative of the cumulative particle size curve gives the distribution curve its maximum abscissa called mode.)

（式中、ｍ_ｉは、Ｄ_ｉのクラスにおける粒子の全質量である） Using this disk centrifugal sedimentation type particle size analysis, silica was dispersed by ultrasonic disintegration in water, can measure the weight average diameter of the particles (aggregates), expressed as D _w (aggregate size) . After analysis (sedimentation for 120 minutes), the weight distribution of the particle size is calculated by a particle size distribution measuring device. The weight average diameter of the particle size, expressed as D _w is calculated by the following equation.

Where m _i is the total mass of the particles in the class D _i

The average primary particle diameter of the fine particle silica is preferably 25 nm or less, more preferably 22 nm or less, still more preferably 17 nm or less, and particularly preferably 14 nm or less. Although the minimum of this average primary particle diameter is not specifically limited, Preferably it is 3 nm or more, More preferably, it is 5 nm or more, More preferably, it is 7 nm or more. Although having such a small average primary particle size, the dispersibility of silica can be further improved by the structure like carbon black having the above-mentioned aggregate size, and the reinforcement and wear resistance can be further improved.
The average primary particle diameter of silica can be obtained by observing with a transmission or scanning electron microscope, measuring 400 or more primary particles of silica observed in the visual field, and calculating the average.

D50 of the fine particle silica is preferably 7.0 μm or less, more preferably 5.5 μm or less, and further preferably 4.5 μm or less. When it exceeds 7.0 μm, it indicates that the dispersibility of silica is rather deteriorated. The D50 of the fine particle silica is preferably 2.0 μm or more, more preferably 2.5 μm or more, and further preferably 3.0 μm or more. When the average particle size is less than 2.0 μm, the aggregate size also becomes small, and it tends to be difficult to obtain sufficient dispersibility as fine particle silica.
Here, D50 is the median diameter of the fine-particle silica, and 50% by mass of the particles is smaller than the median diameter.

The proportion of fine particle silica having a particle size larger than 18 μm is preferably 6% by mass or less, more preferably 4% by mass or less, and further preferably 1.5% by mass or less. Thereby, the favorable dispersibility of a silica is obtained and desired performance is obtained.
The D50 of silica and the proportion of silica having a predetermined particle diameter are measured by the following method.

Aggregation of aggregates is evaluated by performing particle size measurements (using laser diffraction) on a suspension of silica that has been previously ultrasonically disintegrated. In this method, the disintegrability of silica (disintegration of silica of 0.1 to several tens of microns) is measured. Ultrasonic disintegration is performed using a Bioblock VIBRACEL acoustic generator (600 W) (used at 80% of maximum power) equipped with a 19 mm diameter probe. Particle size measurement is performed by laser diffraction on a Moulburn Mastersizer 2000 particle size analyzer.

Specifically, it is measured by the following method.
1 gram of silica is weighed in a pill box (height 6 cm and diameter 4 cm) and deionized water is added to bring the mass to 50 grams, which is an aqueous suspension containing 2% silica (this is 2 minutes To be homogenized by magnetic stirring). Ultrasonic disintegration is then performed for 420 seconds, and particle size measurements are taken after all of the homogenized suspension has been introduced into the particle size analyzer vessel.

The pore distribution width W of the pore volume of the fine particle silica is preferably 0.3 or more, more preferably 0.7 or more, still more preferably 1.0 or more, particularly preferably 1.3 or more, and most preferably 1. 5 or more. The pore distribution width W is preferably 5.0 or less, more preferably 4.0 or less, still more preferably 3.0 or less, and particularly preferably 2.0 or less. With such a broad porous distribution, the dispersibility of silica can be improved and desired performance can be obtained.
The pore distribution width W of the silica pore volume can be measured by the following method.

The pore volume of the particulate silica is measured by mercury porosimetry. A sample of silica is pre-dried in an oven at 200 ° C. for 2 hours, then removed from the oven and placed in a test container within 5 minutes and evacuated. The pore diameter (AUTOPORE III 9420 powder engineering porosimeter) is calculated with a contact angle of 140 ° and a surface tension γ of 484 dynes / cm (or N / m) according to the Washburn equation.

The pore distribution width W can be obtained by a pore distribution curve as shown in FIG. 1 represented by a function of pore diameter (nm) and pore volume (mL / g). That is, the value of the diameter Xs (nm) giving the peak value Ys (mL / g) of the pore volume is recorded, and then a straight line of Y = Ys / 2 is plotted, and this straight line intersects the pore distribution curve. Find points a and b. When the abscissas (nm) of the points a and b are Xa and Xb (Xa> Xb), the pore distribution width W corresponds to (Xa−Xb) / Xs.

The diameter Xs (nm) giving the peak value Ys of the pore volume in the pore distribution curve of the fine particle silica is preferably 10 nm or more, more preferably 15 nm or more, still more preferably 18 nm or more, and particularly preferably 20 nm or more. Further, it is preferably 60 nm or less, more preferably 35 nm or less, still more preferably 28 nm or less, and particularly preferably 25 nm or less. If it is in the said range, the fine particle silica excellent in the dispersibility and the reinforcing property can be obtained.

The amount of the fine particle silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 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, the steering stability on the dry road surface and the wet road surface may not be sufficiently improved. The amount of the fine particle silica is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 80 parts by mass or less. When the amount exceeds 150 parts by mass, it is necessary to add a large amount of oil in order to obtain an appropriate hardness, which may cause a decrease in wear resistance and aging due to oil loss.

The shoulder rubber may contain silica other than the fine particle silica. In this case, the total content of silica is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and still more preferably 45 parts by mass or more with respect to 100 parts by mass of the rubber component. The total 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. When the amount is less than the lower limit or exceeds the upper limit, there is a tendency similar to the amount of the fine particle silica described above.

The shoulder rubber preferably contains a silane coupling agent. As the silane coupling agent, a conventionally known silane coupling agent can be used. For example, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxy) (Silylbutyl) disulfide, sulfide type; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, etc. mercapto type; vinyltriethoxysilane, vinyltrimethoxysilane, etc. Vinyl type; amino type such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, etc .; γ-glycidoxypropyltriethoxysilane, γ- Glycid Glycidoxy systems such as xylpropyltrimethoxysilane and γ-glycidoxypropylmethyldiethoxysilane; Nitro systems such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; 3-chloropropyltrimethoxysilane; And chloro-based compounds such as 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, and the like. Of these, bis (3-triethoxysilylpropyl) disulfide is preferable from the viewpoint of good processability. 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 the total content of silica. If it is less than 1 part by mass, the workability tends to deteriorate. Further, the content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, with respect to 100 parts by mass of the total content of silica. When the amount exceeds 20 parts by mass, there is a tendency that an effect commensurate with the increase in cost cannot be obtained.

In addition to the above components, the rubber composition of the present invention includes fillers other than silica (carbon black, calcium carbonate, aluminum hydroxide, etc.), silane coupling agents, oils, tackifiers, antioxidants, and ozone degradation inhibitors. Additives as required such as anti-aging agents, vulcanizing agents, vulcanization accelerators, vulcanization acceleration aids, and the like may be appropriately blended.

The shoulder rubber preferably contains carbon black. Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited. By blending carbon black, it is possible to enhance the reinforcement.

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

The amount of acetone extracted in 100% by mass of the shoulder rubber (before vulcanization) is preferably 8% by mass or more, more preferably 10% by mass or more. The acetone extract is preferably 25% by mass or less, more preferably 22% by mass or less. If the acetone extract is within the above range, the effect of the present invention can be obtained satisfactorily.
In the present specification, the amount of acetone extracted from the shoulder rubber (before vulcanization) is a value measured by the method described in Examples described later.

The tan δ of the shoulder rubber (after vulcanization) is preferably 0.06 or more, more preferably 0.08 or more. The shoulder rubber has a tan δ of preferably 0.25 or less, more preferably 0.20 or less. When tan δ is within the above range, the effects of the present invention can be obtained satisfactorily.
In the present specification, tan δ of the shoulder rubber (after vulcanization) is a value measured by the method described in Examples described later.

The tire for a motorcycle of the present invention is manufactured by a normal method using the shoulder rubber. That is, a shoulder rubber blended with the above components is extruded into a desired shape at an unvulcanized stage, and molded together with other tire members on a tire molding machine by a normal method, whereby an unvulcanized tire Form. The tire for a motorcycle according to the present invention can be manufactured by heating and pressurizing the unvulcanized tire in a vulcanizer.

The motorcycle tire of the present invention is suitably used as a motorcycle tire.

Hereinafter, as an embodiment of the present invention, a motorcycle tire will be described with reference to the drawings. FIG. 2 is a tire meridian cross-sectional view including a tire rotation axis of a motorcycle tire according to an embodiment of the present invention.

The motorcycle tire 1 includes a carcass 6 that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 that is disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2. With.

In the cross section, the road surface of the tread portion 2 and the tread surface 2A to be installed are convex outward in the tire radial direction and extend in an arc shape. Further, the tread edge 2e which is the outer end of the tread surface 2A in the tire axial direction is located on the outermost side in the tire axial direction.

In the tread portion 2, a tread rubber 9 is disposed on the outer side in the radial direction of the belt layer 7. In the present embodiment, the tread rubber 9 constitutes from the outer surface of the belt layer 7 to the tread surface 2A. Moreover, in the tread rubber 9 of this embodiment, the tread part comprised by the some division | segmentation tread member distribute | arranged to the tire width direction is shown, Here, each produced with two types of rubber compositions from which a mixing | blending differs. It consists of a divided tread member. Specifically, it is composed of a center rubber 9A centering on the tire equator C and a pair of shoulder rubbers 9B adjacent to the center rubber 9A and extending to the tread edge 2e. That is, two types of rubber, center rubber 9A and shoulder rubber 9B, are arranged side by side from the vicinity of the tire equator C toward both sides in the tire width direction. The center rubber 9A and the shoulder rubber 9B are separated by a normal line 12 standing on the tread surface 2A. For example, the center rubber 9A and the shoulder rubber 9B are inclined outward or inward in the tire axial direction from the tread surface 2A toward the belt layer 7. What was divided by the boundary line may be used.

In the present embodiment, the shoulder rubber 9A constituting the tread rubber 9 contains fine particle silica. Thereby, low fuel consumption performance, wear resistance, and steering stability can be given to the motorcycle tire 1 in a well-balanced manner.

In the present embodiment, the case where the tread rubber 9 is configured by two types of divided tread members (center rubber 9A and shoulder rubber 9B) has been described. However, the number of types of the divided tread members is not particularly limited. There may be five types.

As shown in FIG. 3, the division position (boundary line) between the center rubber 9A and the shoulder rubber 9B is the contact surface (normal inner pressure is filled and the tread rubber 9 is applied to the road surface 100 under a normal load. It is preferable to be inside the width X of the (contact portion). Thereby, compared with the case where the said division | segmentation position is the outer side of the width | variety X of a contact surface (refer FIG. 4), a transient characteristic (connection of the grip performance when a tire collapses at the time of cornering) is good. In the examples described later, the state shown in FIG. 3 is expressed as “inside the ground plane”, and the state shown in FIG. 4 is expressed as “outside the ground plane”.

In this specification, the normal load is the maximum of a single wheel at the applicable size described in the industrial standards and standards effective in the area where the tire is manufactured, sold or used, such as JATMA, TRA, ETRTO, etc. The load (maximum load capacity) is meant, and the normal internal pressure means the air pressure corresponding to the maximum load capacity.

When the tread portion 2 is constituted by a cap tread portion and a base tread portion, the tread rubber 9 is preferably disposed on the cap tread portion. Thereby, the improvement effect of low fuel consumption performance, wear resistance, and steering stability can be easily obtained.

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
SBR: SBR1502 manufactured by Sumitomo Chemical Co., Ltd.
Silica (1): VN3 manufactured by Degussa (BET specific surface area: 175 m ² / g)
Silica (2): Zeosil Premium 200MP manufactured by Rhodia (CTAB specific surface area 200 m ² / g, BET specific surface area: 220 m ² / g, average primary particle size: 10 nm, aggregate size: 65 nm, D50: 4.2 μm, 18 μm Of particles exceeding 1.0 mass: 1.0 mass%, pore distribution width W: 1.57, diameter Xs giving pore volume peak value in pore distribution curve Xs: 21.9 nm)
Carbon black: Dia Black I (N220, N ₂ SA: 114 m ² / g) manufactured by Mitsubishi Chemical Corporation
Oil: Aromatic oil silane coupling agent manufactured by Idemitsu Kosan Co., Ltd .: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunnock S manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Stearic acid: Zinc oxide manufactured by NOF Corporation: Zinc Hua No. 1 manufactured by Mitsui Kinzoku Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. NS: Ouchi Shinsei Chemical Industry Co., Ltd. Noxeller NS made
Vulcanization accelerator DPG: Noxeller D manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-2 and Comparative Examples 1-2
In accordance with the formulation shown in Table 1, using a Banbury mixer, chemicals other than sulfur and vulcanization accelerator were kneaded for 4 minutes at 160 ° C. to obtain a kneaded product. Next, using a biaxial open roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 2 minutes at 100 ° C. to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was press vulcanized at 160 ° C. for 20 minutes to obtain a vulcanized rubber composition.
Further, the obtained unvulcanized rubber composition is processed into a tread shape, bonded to another tire member, and vulcanized at 160 ° C. for 20 minutes, thereby having a structure shown in FIG. I got a tire.

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

(Acetone extract)
The mass of the unvulcanized rubber composition was measured before and after extraction, and the acetone extract was determined by the following formula. Extraction was performed by immersing the unvulcanized rubber composition in acetone all day and night.
Acetone extract = (mass of unvulcanized rubber composition before extraction−mass of unvulcanized rubber composition after extraction) / mass of unvulcanized rubber composition before extraction × 100

(hardness)
According to JIS-K6301, the JIS-A hardness of the vulcanized rubber composition at 25 ° C. was measured.

(Viscoelastic properties)
Using the viscoelastic spectrometer “VES-F-3” manufactured by Iwamoto Seisakusho Co., Ltd., the above vulcanized rubber composition under the conditions of a temperature of 50 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 0.5%. Loss tangent (tan δ) was measured.

The following evaluation was performed using the test tire. The results are shown in Table 2. In Table 2, the unit structure means that the tread rubber is not divided, and the multiple structure means that the tread rubber is divided (including the center rubber and the shoulder rubber). Means.

(Rolling resistance)
The test tire was filled with normal internal pressure, and rolling resistance was measured according to the measurement method of ISO18164. And the rolling resistance of the comparative example 1 was set to 100, and the rolling resistance of each sample was shown as a rolling resistance index | exponent by the following formula. The smaller the value, the lower the rolling resistance and the better the fuel efficiency.
(Rolling resistance index) = (Rolling resistance of each sample) / (Rolling resistance of Comparative Example 1) × 100

(Abrasion resistance)
The test tire filled with the regular internal pressure is mounted on a Majesty (displacement: 250cc, front tire: 120 / 80-14 D305, rear tire: 150 / 70-13 D305) manufactured by Yamaha Motor Co., Ltd. I ran on the circuit at 200km. Then, the amount of decrease in the groove depth of each tire after traveling 200 km was measured, and the travel distance when the groove depth decreased by 1 mm was calculated. Then, the traveling distance of the comparative example 1 was set to 100, and the traveling distance of each sample was displayed as an index according to the following calculation formula. It shows that it is excellent in abrasion resistance, so that a numerical value is large.
(Wear resistance index) = (travel distance of each sample) / (travel distance of Comparative Example 1) × 100

(Maneuvering stability)
The Majesty traveled the circuit and conducted a sensory evaluation of steering stability on wet asphalt surfaces. The evaluation results are shown by relative evaluation with the steering stability of Comparative Example 1 as 3.5 points. It shows that steering stability is so favorable that a numerical value is large. The ± 0.1 point is a difference that can be seen by a professional evaluation rider, and the ± 0.2 point is a difference that can be seen by an amateur evaluation rider.

From Table 2, the steering stability of Example 1 using the shoulder rubber containing fine particle silica was improved as compared with Comparative Example 1 while maintaining the wear resistance and the low fuel consumption performance. Moreover, while using shoulder rubber containing fine particle silica and the tan δ of the center rubber being smaller than the tan δ of the sheller rubber, the Example 2 has low fuel consumption performance while maintaining the wear resistance as compared with the Comparative Example 1. Maneuvering stability has been improved. On the other hand, in Comparative Example 2 using a shoulder rubber not containing fine particle silica, steering stability was deteriorated as compared with Comparative Example 1.

DESCRIPTION OF SYMBOLS 1 Motorcycle tire 2 Tread part 2A Tread surface 2e Tread edge 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 8 Bead apex 9 Tread rubber 9A Center rubber 9B Shoulder rubber 100 Road surface X Width of ground surface

Claims (4)

It has a tread portion in which tread rubber divided into at least three parts in the tire width direction is arranged,
The tread rubber includes a center rubber disposed in a center portion in a tire width direction, and shoulder rubber disposed on both sides in the tire width direction of the center rubber,
A tire for a motorcycle, wherein the shoulder rubber contains a rubber component and silica having a CTAB specific surface area of 180 m ² / g or more and a BET specific surface area of 185 m ² / g or more. The tire for a motorcycle according to claim 1, wherein the aggregate size of the silica is 30 nm or more. The tire for two-wheeled vehicles according to claim 1 or 2 whose acetone extraction part in said shoulder rubber 100 mass% is 8 mass% or more. The tire for a motorcycle according to any one of claims 1 to 3, wherein tan δ of the shoulder rubber is 0.06 to 0.25.

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