Motorcycle tires

Abstract

To provide a two-wheeled automobile tire with improved gripping performance during cornering after continuation of a long straight road.SOLUTION: A two-wheeled automobile tire has a tread part on which a tread rubber, which is divided into at least three parts in a tire width direction, is arranged. The tread rubber comprises a center rubber arranged on a midship part in the tire width direction, and a shoulder rubber arranged on both sides of the center rubber in the tire width direction. Both of the center rubber and the shoulder rubber have the content of silica of 80 parts by mass or more to 100 parts by mass of a rubber component. The content (Sc) of silica of the center rubber and the content (Ss) of silica of the shoulder rubber satisfy the following formula (1), the content (Pc) of a plasticizer of the center rubber and the content (Ps) of a plasticizer of the shoulder rubber satisfy the following formula (2), and the negative rate (Nc) of the center rubber and the negative rate (Ns) of the shoulder rubber satisfy the following formula (3): (1) Sc>Ss, (2) Pc<Ps, (3) Nc>Ns.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a tire for a two-wheeled vehicle. [Background technology]

[0002] The tread rubber of motorcycle tires has different parts that come into contact with the road surface when driving in a straight line and when turning. When driving in a straight line, it is mainly the center rubber that comes into contact with the road surface, and when turning, it is mainly the shoulder rubber that comes into contact with the road surface. Since performance according to each situation is required, the tread rubber often has different rubber properties between the center rubber and the shoulder rubber. Summary of the Invention [Problem to be solved by the invention]

[0003] Generally, to improve grip performance when cornering (turning), it is desirable to soften the shoulder rubber and increase its adhesion to the road surface. However, when there are consecutive straight roads, unlike the center rubber, the shoulder rubber, which is not in contact with the road surface, does not warm up easily, and if the rubber temperature is low it becomes hard, which creates anxiety when cornering after a series of straight roads.

[0004] SUMMARY OF THE PRESENT EMBODIMENTS The present invention has an object to provide a tire for a two-wheeled vehicle which solves the above-mentioned problems and has improved grip when cornering after a stretch of straight road. [Means for solving the problem]

[0005] The present invention relates to a tire for a two-wheeled vehicle having a tread portion in which a tread rubber is arranged divided into at least three parts in the tire width direction, The tread rubber includes a center rubber disposed in the center in the tire width direction and shoulder rubbers disposed on both sides of the center rubber in the tire width direction, The center rubber and the shoulder rubber each have a silica content of 80 parts by mass or more per 100 parts by mass of a rubber component, The silica content (Sc) of the center rubber and the silica content (Ss) of the shoulder rubber satisfy the following formula (1), The content of the plasticizer in the center rubber (Pc) and the content of the plasticizer in the shoulder rubber (Ps) satisfy the following formula (2), The negative ratio (Nc) of the center rubber and the negative ratio (Ns) of the shoulder rubber satisfy the following formula (3): (1) Sc>Ss (2) PC <Ps (3) Nc>Ns

[0006] The motorcycle tire preferably has a groove portion that passes through the boundary between the center rubber and the shoulder rubber and does not reach the tire equator.

[0007] In the above-mentioned tire for a motorcycle, it is preferable that the center rubber and the shoulder rubber each have a silica content of 90 parts by mass or more per 100 parts by mass of the rubber component.

[0008] In the above-mentioned tire for a motorcycle, the shoulder rubber preferably has a plasticizer content of 80 parts by mass or less relative to the rubber component.

[0009] In the above-mentioned tire for a two-wheeled vehicle, the shoulder rubber preferably has a styrene-butadiene rubber content of 70% by mass or more in 100% by mass of the rubber component.

[0010] In the above-mentioned tire for a two-wheeled vehicle, it is preferable that the center rubber has a solid plasticizer content of 1 to 30 parts by mass relative to the rubber component, and the shoulder rubber has a solid plasticizer content of 1 to 30 parts by mass relative to the rubber component.

[0011] The solid plasticizer is preferably a styrene-based resin.

[0012] In the above-mentioned tire for a two-wheeled vehicle, the shoulder rubber preferably has a liquid plasticizer content of 20 to 80 parts by mass relative to the rubber component.

[0013] Preferably, the liquid plasticizer is an oil. Effect of the Invention

[0014] According to the present invention, a two-wheeled vehicle tire has a tread portion in which a tread rubber is divided into at least three parts in the tire width direction, the tread rubber comprises a center rubber arranged in the center in the tire width direction and shoulder rubbers arranged on both sides of the center rubber in the tire width direction, and both the center rubber and the shoulder rubber have a silica content of 80 parts by mass or more per 100 parts by mass of rubber component, and the silica content (Sc) of the center rubber and the silica content (Ss) of the shoulder rubber, the plasticizer content (Pc) of the center rubber and the plasticizer content (Ps) of the shoulder rubber, the negative rate (Nc) of the center rubber and the negative rate (Ns) of the shoulder rubber each satisfy the formulas (1) to (3), thereby improving grip when cornering after a series of straight roads. [Brief description of the drawings]

[0015] [Figure 1] 1 is a tire meridian cross-sectional view including a tire rotation axis of a tire for a two-wheeled vehicle according to one embodiment of the present invention. [Diagram 2] 1 is a developed plan view showing a tread pattern of a tire for a two-wheeled vehicle according to one embodiment of the present invention. FIG. [Diagram 3] FIG. 2 is a front view showing the attitude of the tire when traveling on an incline. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The tire for a two-wheeled vehicle of the present invention has a tread portion in which a tread rubber divided into at least three parts in the tire width direction is arranged, the tread rubber includes a center rubber arranged in the center in the tire width direction and shoulder rubbers arranged on both sides of the center rubber in the tire width direction, the center rubber and the shoulder rubber both have a silica content of 80 parts by mass or more per 100 parts by mass of rubber component, and the silica content (Sc) of the center rubber and the silica content (Ss) of the shoulder rubber, the plasticizer content (Pc) of the center rubber and the plasticizer content (Ps) of the shoulder rubber, the negative ratio (Nc) of the center rubber and the negative ratio (Ns) of the shoulder rubber satisfy the formulas (1) to (3), respectively. The tire has improved grip when cornering after a series of straight roads.

[0017] The reason why such an effect (mechanism) is obtained is not clear, but is presumed to be as follows. Adding 80 parts or more of silica to both the center rubber and the shoulder rubber enhances heat generation. Furthermore, by making the amount of silica in the center rubber larger than that in the shoulder rubber, the center rubber generates heat more easily than the shoulder rubber, and by making the negative rate of the center rubber larger than that of the shoulder rubber, it is believed that the center rubber generates heat more easily and transfers the generated heat to the shoulder rubber. As a result, even on a continuous straight road, it is believed that the shoulder rubber is sufficiently warmed and easily adheres to the road surface. Furthermore, by making the amount of plasticizer in the center rubber smaller than that of the shoulder rubber, it is believed that the heat generated in the center rubber is sufficiently transferred to the shoulder rubber, allowing the shoulder rubber to be sufficiently warmed. It is presumed that the above mechanism improves grip when cornering after a continuous straight road.

[0018] In this way, the motorcycle tire has a tread portion in which a tread rubber divided into at least three parts in the tire width direction, and the center rubber and the shoulder rubber each have a silica content of 80 parts by mass or more, Sc>Ss, and Pc<Ps」、「Nc> By using a structure of "Ns", the objective of improving grip when cornering after a long straight stretch of road is solved. In other words, "The silica content of both the center rubber and the shoulder rubber is 80 parts by mass or more", "Sc>Ss", "Pc<Ps」、「Nc> The parameter "Ns" does not define the problem (purpose); the problem of this application is to improve grip when cornering after a stretch of straight road, and the configuration that satisfies this parameter is used as a means to solve this problem.

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a tire for a motorcycle will be described below as one embodiment of the present invention with reference to the drawings. Fig. 1 is a tire meridian cross-sectional view including the tire rotation axis of a tire for a motorcycle according to one embodiment of the present invention.

[0020] The tire 1 for a two-wheeled vehicle includes a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a belt layer 7 disposed outside the carcass 6 in the radial direction of the tire and inside the tread portion 2.

[0021] In the above cross section, the tread surface 2A of the tread portion 2 that comes into contact with the road surface extends in a convex, arc-like curve toward the outside in the radial direction of the tire. Also, the tread edge 2e, which is the outermost end in the axial direction of the tread surface 2A, is located at the outermost position in the axial direction of the tire.

[0022] In the tread portion 2, a tread rubber 9 is disposed radially outside the belt layer 7. In this embodiment, the tread rubber 9 constitutes from the outer surface of the belt layer 7 to the tread surface 2A. In addition, in the tread rubber 9 of this embodiment, a tread portion constituted by a plurality of divided tread members disposed in the tire width direction is shown, and in this embodiment, each divided tread member is constituted by two types of rubber compositions having different blendings.

[0023] Specifically, it is composed of a center rubber 9A centered 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. In other words, two types of rubber, the center rubber 9A and the shoulder rubber 9B, are arranged side by side from the vicinity of the tire equator C toward both sides in the tire width direction. Note that the center rubber 9A and the shoulder rubber 9B are separated by a normal line 12 erected on the tread surface 2A, but they may also be separated by a boundary line that slopes from the tread surface 2A toward the belt layer 7, either outward or inward in the tire axial direction.

[0024] In this embodiment, the case has been described in which the tread rubber 9 is composed of two types of divided tread members (center rubber 9A and shoulder rubber 9B), but the number of types of divided tread members is not particularly limited, and may be, for example, three types or five types.

[0025] Fig. 2 is a developed plan view showing a tread pattern of a motorcycle tire according to one embodiment of the present invention. In Fig. 2, a motorcycle tire 1 has a plurality of grooves 11 formed on a tread surface 2A.

[0026] As shown in FIG. 2, the groove portion 11 includes a central longitudinal groove 11A that runs around the tire equator C, diagonal grooves 11B, 11B that extend symmetrically in a V-shape starting near the tire equator C and having one end edge E1 and the other end edge E2 of the tread portion 2 as opening ends, and are arranged side by side in the tire circumferential direction, and bypass grooves 11C that connect each of two adjacent diagonal grooves 11B, 11B in the circumferential direction.

[0027] In the tread surface 2A having a tread pattern consisting of such grooves 11, when the tire 1 is mounted on a normal rim J and in a normal state where a normal internal pressure and a normal maximum load are applied to the tire, the contact surface where the tire 1 contacts the road surface L falls within a predetermined range (not shown) when the camber angle α is a predetermined angle. Note that the camber angle α refers to the inclination of the tire equatorial plane C with respect to the normal N of the contact surface L, as shown in FIG. 3.

[0028] It is preferable that the groove width GW of the groove 11 is set to 0.04 to 0.12 times the tread width WT, and the groove depth GH (not shown) is set to 0.06 to 0.18 times the tread width WT.

[0029] In the motorcycle tire 1, the negative rate (Nc) of the center rubber 9A and the negative rate (Ns) of the shoulder rubber 9B satisfy the following formula (3). (3) Nc>Ns

[0030] Nc / Ns is preferably 1.3 or more, more preferably 1.5 or more, even more preferably 1.8 or more, and particularly preferably 2.0 or more. The upper limit of Nc / Ns is preferably 5.0 or less, more preferably 4.5 or less, even more preferably 4.0 or less, and particularly preferably 3.5 or less. Within the above range, the effect tends to be better.

[0031] The negative ratio is the total groove area relative to the total area within the width of the contact area of ​​the tread. In this specification, it is the groove ratio (%) calculated by dividing the area of ​​the groove portion when the tire is pressed against the tire by the total contact area under normal internal pressure and normal load conditions, and the negative ratio (Nc) of the center rubber 9A is the groove ratio (%) at a camber angle of 0 degrees, and the negative ratio (Ns) of the shoulder rubber 9B is the groove ratio (%) at a camber angle of 40 degrees.

[0032] The negative ratio (Nc) of the center rubber 9A is preferably 5% or more, more preferably 10% or more, even more preferably 15% or more, and particularly preferably 16% or more, and is preferably 40% or less, more preferably 35% or less, even more preferably 30% or less, and particularly preferably 25% or less. Within the above ranges, the effect tends to be better obtained.

[0033] The negative ratio (Ns) of the shoulder rubber 9B is preferably 3% or more, more preferably 5% or more, even more preferably 7% or more, particularly preferably 8% or more, and is preferably 30% or less, more preferably 20% or less, even more preferably 15% or less, particularly preferably 10% or less. Within the above range, the effect tends to be better obtained.

[0034] The motorcycle tire 1 preferably has a groove portion 11 that passes through the boundary 9D between the center rubber 9A and the shoulder rubber 9B and does not reach the tire equator C. In FIG. 2, the groove portion 11 formed by the diagonal grooves 11B, 11B and the bypass groove 11C that connects the two diagonal grooves 11B, 11B is provided so as to cross the boundary 9D between the center rubber 9A and the shoulder rubber 9B and not to extend to the tire equator C. It is considered that the provision of a groove portion extending from the center rubber to the shoulder rubber in this way makes it easier for the center rubber to generate heat and to transfer the generated heat to the shoulder rubber. As a result, even on a continuous straight road, the shoulder rubber is sufficiently warmed up, so it is easier to adhere to the road surface, and it is presumed that the grip when cornering after a continuous straight road is improved.

[0035] (Drugs) Next, chemicals that can be used for the center rubber composition constituting the center rubber and the shoulder rubber composition constituting the shoulder rubber will be described.

[0036] Examples of rubber components that can be used in the center rubber and shoulder rubber compositions include isoprene-based rubber (isoprene rubber (IR), epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, natural rubber (NR), deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber)), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and butyl-based rubber.

[0037] These rubbers may be either unmodified or modified. The modified rubber may be a rubber having a functional group that interacts with a filler. Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, and an epoxy group. These functional groups may have a substituent. Among them, an amino group (preferably an amino group in which a hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms), and an amide group are preferred. These rubber components may be used alone or in combination of two or more kinds.

[0038] The center rubber and the shoulder rubber compositions contain a filler. The center rubber and shoulder rubber compositions contain silica as a filler. Other usable fillers include materials known in the rubber field, such as inorganic fillers such as carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica; and poorly dispersible fillers. Of these, carbon black is preferred.

[0039] Examples of silica that can be used in the center rubber and shoulder rubber compositions include dry process silica (anhydrous silica) and wet process silica (hydrated silica). Among these, wet process silica is preferred because it has a large number of silanol groups. Examples of silica that can be used include products from Degussa, Rhodia, Tosoh Silica, Solvay Japan, and Tokuyama.

[0040] When silica is contained, it is preferable to contain a silane coupling agent together with silica. As the silane coupling agent usable in the center rubber and shoulder rubber composition, any silane coupling agent conventionally used in combination with silica in the rubber industry can be used without any particular limitation, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, Examples of the mercapto-based compounds include 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z. Examples of the mercapto-based compounds include vinyltriethoxysilane and vinyltrimethoxysilane. Examples of the mercapto-based compounds include 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane. Examples of the glycidoxy-based compounds include γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane. Examples of the glycidoxy-based compounds include 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane. Examples of the nitro-based compounds include 3-nitropropyltriethoxysilane and 3-nitropropyltriethoxysilane. Examples of the chloro-based compounds include 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products include those from Degussa, Momentive, Shin-Etsu Silicone, Tokyo Chemical Industry, Azumax, and Dow Corning Toray. These may be used alone or in combination of two or more. Of these, sulfide-based and mercapto-based products are preferred.

[0041] Examples of carbon black that can be used in the center rubber and shoulder rubber compositions include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. These may be used alone or in combination of two or more. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like.

[0042] The center rubber and shoulder rubber compositions preferably contain a plasticizer. The plasticizer is not particularly limited, but examples thereof include liquid plasticizers having liquid plasticity at 25° C., such as oil and liquid resin, and solid plasticizers having solid plasticity at 25° C., such as resin (polymer (solid resin) in a solid state at 25° C.). These plasticizers may be used alone or in combination of two or more.

[0043] The oil is not particularly limited, and may be any conventionally known oil, such as paraffin-based process oil, aromatic process oil, naphthenic process oil, low PCA (polycyclic aromatic) process oil such as TDAE or MES, vegetable oil, or a mixture thereof. As a commercially available oil, the Diana Process Oil AH series manufactured by Idemitsu Kosan Co., Ltd. may be used.

[0044] The liquid resin is not particularly limited, but examples thereof include liquid aromatic vinyl polymers, coumarone-indene resins, indene resins, terpene resins, rosin resins, and hydrogenated products thereof.

[0045] The liquid aromatic vinyl polymer includes a resin obtained by polymerizing α-methylstyrene and / or styrene, and specific examples thereof include liquid resins such as a homopolymer of styrene, a homopolymer of α-methylstyrene, and a copolymer of α-methylstyrene and styrene.

[0046] Liquid coumarone-indene resins include resins containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain), and monomer components that may be contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0047] The liquid indene resin may be a liquid resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

[0048] Examples of liquid terpene resins include resins obtained by polymerizing terpene compounds such as α-pinene, β-pinene, camphene, and dipentene, and liquid terpene resins such as terpene phenol, which is a resin obtained using a terpene compound and a phenolic compound as raw materials.

[0049] Examples of liquid rosin resins include liquid rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0050] The above-mentioned resin (solid resin in a solid state at 25° C.) is not particularly limited, and examples thereof include solid styrene-based resins, coumarone-indene resins, terpene-based resins, pt-butylphenol acetylene resins, acrylic-based resins, dicyclopentadiene-based resins (DCPD-based resins), C5-based petroleum resins, C9-based petroleum resins, C5C9-based petroleum resins, etc. These may be used alone or in combination of two or more.

[0051] The solid styrene-based resin is a solid polymer using a styrene-based monomer as a constituent monomer, and examples thereof include polymers polymerized with a styrene-based monomer as the main component (50% by mass or more).Specific examples thereof include homopolymers obtained by polymerizing each of the styrene-based monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more kinds of styrene-based monomers, and copolymers of a styrene-based monomer and another monomer that can be copolymerized therewith. Examples of other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene-isoprene, olefins such as 1-butene and 1-pentene, α,β-unsaturated carboxylic acids or acid anhydrides thereof such as maleic anhydride, and the like.

[0052] The solid coumarone-indene resin may be a solid resin having the same constitutional units as the above-mentioned liquid coumarone-indene resin.

[0053] Examples of solid terpene resins include polyterpene, terpene phenol, and aromatic modified terpene resin. Examples of solid polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin made from terpene compounds, as well as solid resins such as hydrogenated terpene resins obtained by hydrogenating the terpene resins. Examples of solid terpene phenols include solid resins obtained by copolymerizing a terpene compound with a phenolic compound, and solid resins obtained by hydrogenating the resins, specifically solid resins obtained by condensing a terpene compound, a phenolic compound, and formalin. Examples of solid aromatic modified terpene resins include solid resins obtained by modifying a terpene resin with an aromatic compound, and solid resins obtained by hydrogenating the resins.

[0054] The solid pt-butylphenol acetylene resin may be a solid resin obtained by subjecting pt-butylphenol to a condensation reaction with acetylene.

[0055] The solid acrylic resin is not particularly limited, and examples thereof include solvent-free acrylic solid resins. Examples of monomer components constituting the solid acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives. In addition, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used as monomer components constituting the solid acrylic resin, together with (meth)acrylic acid and (meth)acrylic acid derivatives. The solid acrylic resin may be a resin composed only of (meth)acrylic components, or a resin containing components other than (meth)acrylic components as constituent elements. In addition, the solid acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, etc.

[0056] The center rubber and the shoulder rubber compositions preferably contain sulfur. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc.

[0057] The center rubber and the shoulder rubber compositions preferably contain a vulcanization accelerator. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. Of these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

[0058] The center rubber and shoulder rubber compositions may contain wax, antioxidants, stearic acid, zinc oxide, vulcanizing agents other than sulfur (organic crosslinking agents, etc.), and the like.

[0059] In the tire, the silica content (Sc) of the center rubber and the silica content (Ss) of the shoulder rubber satisfy the following formula (1). (1) Sc>Ss

[0060] Sc / Ss is preferably 1.10 or more, more preferably 1.11 or more, and even more preferably 1.13 or more. The upper limit of Sc / Ss is preferably 1.50 or less, more preferably 1.40 or less, even more preferably 1.35 or less, and particularly preferably 1.30 or less. Within the above range, the effect tends to be better obtained.

[0061] In the tire, the plasticizer content (Pc) of the center rubber and the plasticizer content (Ps) of the shoulder rubber satisfy the following formula (2). (2) PC <Ps

[0062] Ps / Pc is preferably 1.00 or more, more preferably 1.03 or more, even more preferably 1.05 or more, and particularly preferably 1.07 or more. The lower limit of Ps / Pc is preferably 1.30 or less, more preferably 1.21 or less, even more preferably 1.14 or less, particularly preferably 1.12 or less, and most preferably 1.11 or less. Within the above range, the effect tends to be better obtained.

[0063] (Sc / Ss)×(Ps / Pc)×(Nc / Ns) is preferably 1.80 or more, more preferably 1.87 or more, even more preferably 2.06 or more, particularly preferably 2.00 or more, and most preferably 2.29 or more. The lower limit of (Sc / Ss)×(Ps / Pc)×(Nc / Ns) is preferably 3.00 or less, more preferably 2.52 or less, even more preferably 2.45 or less, and particularly preferably 2.40 or less. Within the above range, the effect tends to be better obtained.

[0064] [Center rubber (center rubber composition)] The center rubber composition constituting the center rubber preferably contains the SBR as a rubber component from the viewpoint of gripping properties when cornering after a straight stretch of road.

[0065] The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. Commercially available products include those from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc.

[0066] In the center rubber composition, the content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass. When it is within the above range, the effect tends to be better obtained.

[0067] The styrene content of SBR is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 35% by mass or more, and particularly preferably 40% by mass or more. The upper limit of the styrene content is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. Within the above range, the effect tends to be better obtained. In this specification, the styrene content of SBR is 1 It is calculated by H-NMR measurement.

[0068] The vinyl content of the SBR is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 47% by mass or more. The vinyl content is preferably 65% ​​by mass or less, more preferably 60% by mass or less. Within the above range, the effect tends to be better obtained. The vinyl content (amount of 1,2-bonded butadiene units) can be measured by infrared absorption spectroscopy.

[0069] In the center rubber composition, the content of the filler is preferably 90 parts by mass or more, more preferably 100 parts by mass or more, even more preferably 105 parts by mass or more, and particularly preferably 110 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 200 parts by mass or less, more preferably 170 parts by mass or less, and even more preferably 150 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0070] In the center rubber composition, the content of silica is 80 parts by mass or more, preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and even more preferably 100 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 130 parts by mass or less, and particularly preferably 120 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0071] In the center rubber composition, the nitrogen adsorption specific surface area (N2SA) of silica is preferably 80 m 2 / g or more, more preferably 120m 2 / g or more, more preferably 150m 2 / g or more, particularly preferably 175m 2 / g or more. The N2SA of the silica is preferably 250m 2 / g or less, more preferably 200m 2 When the content is within the above range of not more than 1 / g, the effect tends to be better. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0072] In the center rubber composition, the content of the silane coupling agent is preferably 1 to 15 parts by mass, and more preferably 3 to 10 parts by mass, based on 100 parts by mass of silica.

[0073] In the center rubber composition, the carbon black content is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and particularly preferably 10 parts by mass or more, based on 100 parts by mass of the rubber component. The carbon black content is 15 parts by mass or less, preferably 13 parts by mass or less, and more preferably 12 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0074] In the center rubber composition, the nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 80 m 2 / g or more, more preferably 110m 2 / g or more, more preferably 130m 2 / g or more, particularly preferably 140m 2 The upper limit of the N2SA of the carbon black is not particularly limited, but is preferably 200 m 2 / g or less, more preferably 180m 2 / g or less, more preferably 160m 2 / g or less. The nitrogen adsorption specific surface area of ​​carbon black is determined by Method A of JIS K6217.

[0075] In the center rubber composition, the silica content is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total content of silica and carbon black (100% by mass). The upper limit of the silica content is preferably 95% by mass or less, more preferably 93% by mass or less. Within the above range, the effect tends to be better obtained.

[0076] In the center rubber composition, the content of the plasticizer (total amount of the liquid plasticizer and solid plasticizer) is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 45 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the total content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 75 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0077] From the viewpoint of gripping property when cornering after a stretch of railroad, the center rubber composition is preferably blended with a liquid plasticizer having liquid plasticity at 25° C., and more preferably contains the oil. As the oil used in the center rubber composition, paraffin-based process oil and aromatic process oil are preferably used.

[0078] In the center rubber composition, the content of the liquid plasticizer is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 35 parts by mass or more, and particularly preferably 40 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less. Within the above range, the effect tends to be better obtained. The content of the oil is also preferably within a similar range. The content of the liquid plasticizer and oil includes the amount of oil contained in the rubber (oil-extended rubber).

[0079] From the viewpoint of grip when cornering after a stretch of straight road, the center rubber composition preferably contains a solid plasticizer having solid-state plasticity at 25°C, and more preferably contains a solid resin such as the solid styrene-based resin.

[0080] In the center rubber composition, the content of the solid plasticizer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above range, the effect tends to be better obtained. The content of solid resin such as solid styrene-based resin is also preferably within the same range.

[0081] The softening point of the solid resin used in the center rubber composition is preferably 160° C. or lower, more preferably 130° C. or lower, even more preferably 110° C. or lower, and particularly preferably 96° C. or lower. The lower limit is preferably 60° C. or higher, more preferably 70° C. or higher, even more preferably 80° C. or higher, and particularly preferably 85° C. or higher. Within the above range, the effect tends to be better obtained. In this specification, the softening point of a solid resin is the temperature at which the ball drops when the softening point as specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0082] The center rubber composition preferably contains sulfur. In the center rubber composition, the sulfur content is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 1.5 parts by mass or more, and particularly preferably 2.0 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0083] The center rubber composition preferably contains a vulcanization accelerator. In the center rubber composition, the content of the vulcanization accelerator is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, even more preferably 3.0 parts by mass or more, and particularly preferably 3.5 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 4.0 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0084] [Shoulder rubber (shoulder rubber composition)] The shoulder rubber composition constituting the shoulder rubber preferably contains the SBR as a rubber component from the viewpoint of gripping properties when cornering after a series of straight roads.

[0085] In the shoulder rubber composition, the content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass. When it is within the above range, the effect tends to be better obtained.

[0086] The styrene content and vinyl content of the SBR used in the shoulder rubber composition are preferably in the same range as those used in the center rubber composition. In addition, the SBR used in the shoulder rubber composition can be preferably the same as that used in the center rubber composition.

[0087] In the shoulder rubber composition, the content of the filler is preferably 85 parts by mass or more, more preferably 90 parts by mass or more, even more preferably 95 parts by mass or more, and particularly preferably 100 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 200 parts by mass or less, more preferably 170 parts by mass or less, and even more preferably 150 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0088] In the shoulder rubber composition, the content of silica is 80 parts by mass or more, preferably 85 parts by mass or more, more preferably 88 parts by mass or more, and even more preferably 90 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 130 parts by mass or less, and particularly preferably 120 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0089] As the silica used in the shoulder rubber composition, the silica used in the center rubber composition can be preferably used. The N2SA of the silica used in the shoulder rubber composition is preferably in the same range as that used in the center rubber composition.

[0090] The shoulder rubber composition preferably contains a silane coupling agent together with silica. The content of the silane coupling agent in the shoulder rubber composition is preferably in the same range as the content of the silane coupling agent used in the center rubber composition.

[0091] In the shoulder rubber composition, the carbon black content is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and particularly preferably 10 parts by mass or more, based on 100 parts by mass of the rubber component. The carbon black content is 15 parts by mass or less, preferably 13 parts by mass or less, and more preferably 12 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0092] The N2SA of the carbon black used in the shoulder rubber composition is preferably in the same range as that used in the center rubber composition described above.

[0093] In the shoulder rubber composition, the silica content is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total content of silica and carbon black (100% by mass). The upper limit of the silica content is preferably 95% by mass or less, more preferably 93% by mass or less. Within the above range, the effect tends to be better obtained.

[0094] In the shoulder rubber composition, the content of the plasticizer (the total amount of the liquid plasticizer and the solid plasticizer) is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 45 parts by mass or more, relative to 100 parts by mass of the rubber component. The upper limit of the total content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 75 parts by mass or less. Within the above range, the effect tends to be obtained better. In particular, when the amount of plasticizer in the shoulder rubber is large, the rubber becomes too hard when the shoulder rubber cools and hardens during straight running, and the shoulder part does not warm up sufficiently even if heat is transferred from the center part. For example, by adjusting the amount to 80 parts by mass or less, such a problem can be prevented, and it is presumed that the grip performance during cornering after a series of straight roads is improved.

[0095] From the viewpoint of gripping property when cornering after a continuous road, the shoulder rubber composition is preferably blended with a liquid plasticizer having liquid plasticity at 25° C., and more preferably contains the oil. As the oil used in the shoulder rubber composition, it is preferable to use a paraffin-based process oil or an aromatic process oil.

[0096] In the shoulder rubber composition, the content of the liquid plasticizer is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 35 parts by mass or more, and particularly preferably 40 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, and particularly preferably 60 parts by mass or less. Within the above range, the effect tends to be better obtained. The content of the oil is also preferably within a similar range. The content of the liquid plasticizer and oil includes the amount of oil contained in the rubber (oil-extended rubber).

[0097] From the viewpoint of gripping performance when cornering after a stretch of straight road, the shoulder rubber composition preferably contains a solid plasticizer having solid-state plasticity at 25°C, and more preferably contains a solid resin such as the solid styrene-based resin.

[0098] In the shoulder rubber composition, the content of the solid plasticizer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above range, the effect tends to be better obtained. The content of solid resin such as solid styrene-based resin is also preferably within the same range.

[0099] As the solid resin usable for the shoulder rubber composition, the same resin as that used for the center rubber composition can be preferably used. When the solid resin is used for the shoulder rubber composition, the softening point of the solid resin used is preferably in the same range as that used for the center rubber composition.

[0100] The shoulder rubber composition preferably contains sulfur. In the shoulder rubber composition, the sulfur content is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 1.5 parts by mass or more, and particularly preferably 2.0 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0101] The shoulder rubber composition preferably contains a vulcanization accelerator. In the shoulder rubber composition, the content of the vulcanization accelerator is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, even more preferably 3.5 parts by mass or more, and particularly preferably 3.5 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 4.0 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0102] The shoulder rubber composition may contain wax, antioxidant, stearic acid, zinc oxide, sulfur, vulcanization accelerator, and organic crosslinking agent, and for example, those used in the center rubber composition can be preferably used. When these materials are used in the shoulder rubber composition, the content of the materials is preferably in the same range as the content of the materials used in the center rubber composition.

[0103] The center rubber and shoulder rubber compositions can be produced by a general method, i.e., by kneading the above-mentioned components in a Banbury mixer, kneader, open roll, etc., and then vulcanizing the components.

[0104] As for the kneading conditions of the center rubber and shoulder rubber composition, in the base kneading step in which additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100°C or lower, preferably room temperature to 80°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200°C, preferably 140 to 180°C.

[0105] The motorcycle tire of the present invention is manufactured by a normal method using a center rubber and a shoulder rubber composition. That is, the center rubber composition and the shoulder rubber composition containing the above-mentioned components are extruded in an unvulcanized state according to the shape of the center rubber and the shoulder rubber, and molded together with other tire components in a normal method on a tire building machine to form an unvulcanized tire. The unvulcanized tire is heated and pressurized in the vulcanizer to obtain a tire. EXAMPLES

[0106] The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0107] The various chemicals used in the examples and comparative examples will be collectively described below. SBR: Asahi Kasei Corporation's Tufuden 4850 (S-SBR, styrene content 40% by mass, vinyl content 47% by mass, oil-extended rubber containing 50 parts by mass of oil per 100 parts by mass of rubber solids) Carbon black: Show Black N110 (N2SA142m) manufactured by Cabot Japan Co., Ltd. 2 / g) Silica: ULTRASIL VN3 (N2SA175m) manufactured by Evonik 2 / g) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Oil: Diana Process NH-70 (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd. Styrene-based resin: Sylvatraxx 4401 manufactured by Arizona Chemical Co. (copolymer of α-methylstyrene and styrene, softening point 85°C, Tg 43°C) Wax: Ozoace 0355 made by Nippon Seiro Co., Ltd. Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Stearic acid: Camellia made by NOF Corporation Zinc oxide: Ginrei R manufactured by Toho Zinc Co., Ltd. Sulfur: HK-200-5 (powdered sulfur containing 5% oil by mass) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noccela NS-G (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0108] Examples and Comparative Examples According to the compounding recipes shown in each table, chemicals other than sulfur and vulcanization accelerator were kneaded at 60 rpm for 4 minutes using a Banbury mixer to obtain a kneaded product. Next, sulfur and vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded using a two-axis open roll to obtain an unvulcanized rubber sheet (thickness: 4 mm). According to the specifications in each table, the obtained unvulcanized rubber sheet was processed into the shape of tread rubber (center rubber, shoulder rubber), bonded with other tire components, and vulcanized at 170°C for 15 minutes to obtain a test tire having the structure shown in Figures 1 to 2.

[0109] The test tires thus produced were subjected to the following evaluations, and the results are shown in the tables.

[0110] <Negative rate (groove ratio)> For each test tire, the tire was mounted on a regular rim under conditions of an internal pressure of 290 kPa and a load of 1.3 kN, and the groove ratio (%) was calculated by dividing the area of ​​the groove when the tire was pressed against the rim by the total contact area. The negative ratio (Nc) of the center rubber was defined (measured) as the groove ratio (%) at a camber angle of 0 degrees, and the negative ratio (Ns) of the shoulder rubber was defined (measured) as the groove ratio (%) at a camber angle of 40 degrees.

[0111] <Grip when cornering after a long straight stretch of road> The test tires were mounted on the following test vehicle, and the grip of the tire (rear wheel) was evaluated on an actual vehicle by comparing the time when driving on a circuit with a straight road:corner ratio of 20:1 with the reference tire using the following formula to see how much the time was improved. The reference tire was a commercially available tire that did not fall under the scope of the present invention and had the slowest time. A higher value indicates better grip of the tire (rear wheel) when cornering after a series of straight roads. (Grip index when cornering after a straight road)=[(Driving time of reference tire−Driving time of each test tire) / (Driving time of reference tire−Driving time of Comparative Example 1)]×100 (Test vehicle) Motorcycle with a displacement of 750cc Tires (front and rear): 120 / 70ZR17, 180 / 55ZR17 Rims: (front wheel) MT3.50x17, (rear wheel) MT5.50x17 Internal pressure: (front wheel) 250kPa, (rear wheel) 290kPa

[0112] [Table 1]

[0113] [Table 2]

[0114] [Table 3]

[0115] As can be seen from each table, the example tires in which the silica content in the center rubber and shoulder rubber was 80 parts by mass or more and which satisfied the above formulas (1) to (3) had excellent grip when cornering after a series of straight roads. [Explanation of symbols]

[0116] 1. Motorcycle tyres 2 Tread section 2A Tread surface 2e Tread edge 3 Sidewall 4 Bead section 5 Bead Core 6. Carcass 7 Belt layer 8 Bead Apex 9 Tread rubber 9A Center rubber 9B Shoulder Rubber C Tire Equator 12 Normal 9D Boundary between center rubber 9A and shoulder rubber 9B 11 Groove 11A Center groove 11B Diagonal groove 11C Bypass groove E1 One edge E2 The other edge α Camber angle N Normal L Road surface (touching surface) GW groove width WT tread width

Claims

1. A tire for a two-wheeled vehicle having a tread portion in which a tread rubber is divided into at least three parts in the tire width direction, The tread rubber includes a center rubber disposed in the center in the tire width direction and shoulder rubbers disposed on both sides of the center rubber in the tire width direction, The center rubber and the shoulder rubber each have a silica content of 80 parts by mass or more per 100 parts by mass of a rubber component, the silica content (Sc) of the center rubber and the silica content (Ss) of the shoulder rubber satisfy the following formula (1), the content (Pc) of the plasticizer in the center rubber and the content (Ps) of the plasticizer in the shoulder rubber satisfy the following formula (2), the negative ratio (Nc) of the center rubber and the negative ratio (Ns) of the shoulder rubber satisfy the following formula (3), A tire for a two-wheeled automobile, in which the silica content (Sc) of the center rubber, the silica content (Ss) of the shoulder rubber, the plasticizer content (Pc) of the center rubber, the plasticizer content (Ps) of the shoulder rubber, the negative ratio (Nc) of the center rubber, and the negative ratio (Ns) of the shoulder rubber satisfy the following formula (4): (1) Sc>Ss (2) Pc<Ps (3) Nc>Ns (4) 1.80≦(Sc / Ss)×(Ps / Pc)×(Nc / Ns)≦3.00

2. A tire for a two-wheeled vehicle having a tread portion in which tread rubber is divided into at least three parts in the tire width direction, The tread rubber includes a center rubber disposed in the center in the tire width direction and shoulder rubbers disposed on both sides of the center rubber in the tire width direction, The center rubber and the shoulder rubber each have a silica content of 80 parts by mass or more per 100 parts by mass of a rubber component, the silica content (Sc) of the center rubber and the silica content (Ss) of the shoulder rubber satisfy the following formula (1), the content (Pc) of the plasticizer in the center rubber and the content (Ps) of the plasticizer in the shoulder rubber satisfy the following formula (2), A tire for a two-wheeled vehicle, wherein the negative ratio (Nc) of the center rubber and the negative ratio (Ns) of the shoulder rubber satisfy the following formula (3): (1) 1.10≦Sc / Ss≦1.30 (2) Pc<Ps (3) Nc>Ns

3. A tire for a two-wheeled vehicle having a tread portion in which tread rubber is divided into at least three parts in the tire width direction, The tread rubber includes a center rubber disposed in the center in the tire width direction and shoulder rubbers disposed on both sides of the center rubber in the tire width direction, The center rubber and the shoulder rubber each have a silica content of 80 parts by mass or more per 100 parts by mass of a rubber component, the silica content (Sc) of the center rubber and the silica content (Ss) of the shoulder rubber satisfy the following formula (1), the content (Pc) of the plasticizer in the center rubber and the content (Ps) of the plasticizer in the shoulder rubber satisfy the following formula (2), the negative ratio (Nc) of the center rubber and the negative ratio (Ns) of the shoulder rubber satisfy the following formula (3), A tire for a two-wheeled automobile, wherein the content (Pc) of the plasticizer in the center rubber and the content (Ps) of the plasticizer in the shoulder rubber satisfy the following formula (4): (1) Sc>Ss (2) Pc<Ps (3) Nc>Ns (4) Ps / Pc≦1.30

4. 4. The tire for a two-wheeled vehicle according to claim 1, further comprising a groove portion that passes through a boundary between the center rubber and the shoulder rubber and does not reach the tire equator.

5. The tire for a two-wheeled vehicle according to any one of claims 1 to 4, wherein the center rubber and the shoulder rubber each have a silica content of 90 parts by mass or more per 100 parts by mass of the rubber component.

6. The tire for a two-wheeled vehicle according to any one of claims 1 to 5, wherein the shoulder rubber has a plasticizer content of 80 parts by mass or less relative to the rubber component.

7. The tire for a two-wheeled vehicle according to any one of claims 1 to 6, wherein the shoulder rubber has a styrene-butadiene rubber content of 70 mass% or more based on 100 mass% of the rubber component.

8. The center rubber has a solid plasticizer content of 1 to 30 parts by mass relative to the rubber component, The tire for a two-wheeled vehicle according to any one of claims 1 to 7, wherein the shoulder rubber has a solid plasticizer content of 1 to 30 parts by mass relative to the rubber component.

9. 9. A tire for a two-wheeled vehicle according to claim 8, wherein the solid plasticizer is a styrene-based resin.

10. The tire for a two-wheeled vehicle according to any one of claims 1 to 9, wherein the shoulder rubber has a liquid plasticizer content of 20 to 80 parts by mass relative to the rubber component.

11. 11. A tire for a two-wheeled vehicle according to claim 10, wherein the liquid plasticizer is oil.

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