Motorcycle tire

Abstract

To provide a motorcycle tire excellent in traveling performance such as braking performance or turning performance during corner entry.SOLUTION: This motorcycle tire comprises a tread part in which tread rubber divided at least into three in a tire width direction is disposed. The tread rubber includes center rubber disposed in the center of the tire width direction, and shoulder rubber disposed on both sides of the center rubber in the tire width direction, and has a groove over the center rubber and the shoulder rubber. In both the center rubber and the shoulder rubber, a silica content with respect to 100 pts. mass of a rubber component is 70 pts. mass or more. A ratio (Si(S) / Si(C)) of the silica content Si(S) of the shoulder rubber to the silica content Si(C) of the center rubber is 0.80-0.95 inclusive. A ratio (M300(S) / M300(C)) of the 300% modulus M300(S)of the shoulder rubber to the 300% modulus M300(C) of the center rubber is 1.15-1.50 inclusive.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] The tread rubber of a tire for a two-wheeled vehicle contacts the road surface at different portions during straight running and turning. During straight running, mainly the center rubber contacts the road surface, and during turning, mainly the shoulder rubber contacts the road surface. Since performance according to each situation is required, the tread rubber often has different rubber physical properties between the center rubber and the shoulder rubber (such as in Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For a tire for a two-wheeled vehicle, it is desired to improve the running time on a racing course or the like by improving various performances during running such as the braking performance and turning performance when entering a corner.

[0005] An object of the present invention is to solve the above problems and provide a tire for a two-wheeled vehicle having excellent running performances such as braking performance and turning performance when entering a corner.

Means for Solving the Problems

[0006] The present invention is a tire for a two-wheeled vehicle having 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 disposed at the center in the tire width direction and shoulder rubbers disposed on both sides of the center rubber in the tire width direction, and has grooves extending across the center rubber and the shoulder rubbers. Both the center rubber and the shoulder rubbers have a silica content of 70 parts by mass or more with respect to 100 parts by mass of the rubber component. The ratio (Si(S) / Si(C)) of the silica content Si(S) of the shoulder rubber to the silica content Si(C) of the center rubber is 0.80 or more and 0.95 or less. The present invention relates to a motorcycle tire having a tread portion provided with a tread rubber divided into at least three parts in the tire width direction, wherein the tread rubber includes a center rubber disposed at the center in the tire width direction and shoulder rubbers disposed on both sides of the center rubber in the tire width direction, and has grooves extending across the center rubber and the shoulder rubbers, both the center rubber and the shoulder rubbers have a silica content of 70 parts by mass or more with respect to 100 parts by mass of the rubber component, the ratio (Si(S) / Si(C)) of the silica content Si(S) of the shoulder rubber to the silica content Si(C) of the center rubber is 0.80 or more and 0.95 or less, and the ratio (M300(S) / M300(C)) of the 300% modulus M300(S) of the shoulder rubber to the 300% modulus M300(C) of the center rubber is 1.15 or more and 1.50 or less.

Advantages of the Invention

[0007] The present invention is a motorcycle tire having a tread portion provided with a tread rubber divided into at least three parts in the tire width direction. The tread rubber includes a center rubber disposed at the center in the tire width direction and shoulder rubbers disposed on both sides of the center rubber in the tire width direction, and has grooves extending across the center rubber and the shoulder rubbers. Both the center rubber and the shoulder rubbers have a silica content of 70 parts by mass or more with respect to 100 parts by mass of the rubber component. The ratio (Si(S) / Si(C)) of the silica content Si(S) of the shoulder rubber to the silica content Si(C) of the center rubber is 0.80 or more and 0.95 or less. The ratio (M300(S) / M300(C)) of the 300% modulus M300(S) of the shoulder rubber to the 300% modulus M300(C) of the center rubber is 1.15 or more and 1.50 or less. Therefore, the running performance such as the braking performance and the cornering performance during corner entry can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0009] The motorcycle tire is a motorcycle tire having 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 arranged at the center in the tire width direction and shoulder rubbers arranged on both sides of the center rubber in the tire width direction, and has grooves extending across the center rubber and the shoulder rubbers. Both the center rubber and the shoulder rubber have a silica content of 70 parts by mass or more with respect to 100 parts by mass of the rubber component. The ratio (Si(S) / Si(C)) of the silica content Si(S) of the shoulder rubber to the silica content Si(C) of the center rubber is 0.80 or more and 0.95 or less. The ratio (M300(S) / M300(C)) of the 300% modulus M300(S) of the shoulder rubber to the 300% modulus M300(C) of the center rubber is 1.15 or more and 1.50 or less.

[0010] The mechanism by which the above-described effects are obtained by the motorcycle tire is not necessarily clear, but is presumed as follows. When a motorcycle turns, it runs with the body tilted, so the grounding location of the tread part is different when braking before approaching a corner and during turning. When braking before a corner, the center part of the tread is in contact with the ground. Therefore, from the perspective of enhancing braking performance, it is conceivable to increase the amount of filler (silica) in the center rubber and make it easier for heat to be generated by the center rubber. On the other hand, during turning, the shoulder rubber of the tread is in contact with the ground, and since it is necessary to generate a large reaction force to bend the direction of the vehicle body, it is considered desirable to enhance the polymer network and responsiveness of the shoulder rubber. In the above motorcycle tire, by satisfying the relational expression of the silica amount where the above Si(S) / Si(C) is 0.80 or more and 0.95 or less, it is considered possible to enhance the braking performance when entering a corner and the responsiveness during turning, thereby enhancing the turning performance. Also, by adjusting so as to satisfy the relational expression where the above M300(S) / M300(C) is 1.15 or more and 1.50 or less at the same time, and increasing the modulus of the shoulder rubber with respect to the modulus of the center rubber, it becomes possible to easily generate a large reaction force with the shoulder rubber, and it is considered possible to improve the turning performance. In addition, since the groove provided in the tread rubber is formed across the center rubber and the shoulder rubber, it becomes easier to transmit the deformation generated during braking by the center rubber to the shoulder rubber. Therefore, when the shoulder rubber comes into contact with the ground, the generation of the reaction force becomes faster, and it is considered that the turning performance is likely to be improved. Due to the above mechanisms, in the above motorcycle tire, it is possible to improve the running performance such as the braking performance and turning performance when entering a corner, and as a result, it is inferred that the running time is improved.

[0011] Thus, in the two-wheel vehicle tire having a tread portion provided with tread rubber divided into at least three parts in the tire width direction, by setting the parameters to "Si(S) / Si(C) is 0.80 or more and 0.95 or less" and "M300(S) / M300(C) is 1.15 or more and 1.50 or less", the problems (objectives) of improving running performance such as braking performance and turning performance during corner entry are solved. That is, the parameters "Si(S) / Si(C) is 0.80 or more and 0.95 or less" and "M300(S) / M300(C) is 1.15 or more and 1.50 or less" do not define the problems (objectives). The problem of the present application is to improve running performance such as braking performance and turning performance during corner entry, and the solution means therefor is to adopt a configuration that satisfies the parameters.

[0012] Hereinafter, as an embodiment of the two-wheel vehicle tire, an example of the two-wheel vehicle tire will be described based on the drawings, but it is not limited to the following. FIG. 1 is a tire meridian cross-sectional view including the tire rotation axis of the two-wheel vehicle tire according to an embodiment of the two-wheel vehicle tire.

[0013] The two-wheel vehicle tire 1 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 tire radial direction and inside the tread portion 2.

[0014] In the above cross-section, the tread surface 2A of the tread portion 2 that contacts the road surface is convex and curved in an arc shape outward in the tire radial direction. Further, the tread edge 2e, which is the outer end of the tread surface 2A in the tire axis direction, is located most outward in the tire axis direction.

[0015] In the tread portion 2, the tread rubber 9 is disposed on the radially outer side of 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. Further, the tread rubber 9 of this embodiment shows a tread portion composed of a plurality of divided tread members arranged in the tire width direction, and here, it is composed of each divided tread member made of two types of rubber compositions having different formulations.

[0016] 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. That is, two types of rubbers, the center rubber 9A and the shoulder rubber 9B, are arranged side by side from near 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 the normal line 12 erected on the tread surface 2A, but for example, they may be separated by a boundary line inclined outward or inward in the tire axial direction from the tread surface 2A toward the belt layer 7.

[0017] In this embodiment, the case where the tread rubber 9 is composed of two types of divided tread members (center rubber 9A and shoulder rubber 9B) has been described, but the number of types of the divided tread members is not particularly limited, and for example, it may be three types or five types.

[0018] FIG. 2 is a developed plan view showing a tread pattern of a tire for a two-wheeled vehicle according to an embodiment. The tire for a two-wheeled vehicle has a groove extending across the center rubber 9A and the shoulder rubber 9B.

[0019] In this specification, the groove extending across the center rubber 9A and the shoulder rubber 9B means a groove passing through the boundary 9D between the center rubber 9A and the shoulder rubber 9B. The groove extending across the center rubber 9A and the shoulder rubber 9B is not particularly limited as long as it has a shape passing through the boundary 9D.

[0020] In FIG. 2, the motorcycle tire 1 is provided with a plurality of grooves 11 in the tread surface 2A, and a part of the grooves 11 is provided so as to straddle the center rubber 9A and the shoulder rubber 9B.

[0021] As shown in FIG. 2, in the motorcycle tire 1, the groove 11 includes a central longitudinal groove 11A that circulates on the tire equator C, and diagonal grooves 11B, 11B that symmetrically extend in a V-shape starting from the vicinity of the tire equator C and having the one edge E1 and the other edge E2 of the tread portion 2 as open ends, and are arranged side by side in the tire circumferential direction, and bypass grooves 11C that connect between two adjacent diagonal grooves 11B, 11B in the circumferential direction.

[0022] The tread surface 2A having a tread pattern composed of such grooves 11 is in a normal state where the tire 1 is mounted on a normal rim J and the normal internal pressure and the normal maximum load defined for the tire are applied. When the camber angle α is a predetermined angle, the contact surface where the tire 1 contacts the road surface L is within a predetermined range (not shown). 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.

[0023] In this specification, dimensions such as thickness are values measured in a normal state. The "normal state" refers to a state where the tire is mounted on a normal rim, filled with the normal internal pressure, and is in a no-load condition. Here, the "normal rim" is the rim defined for each tire in the standard system including the standard on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it is the standard rim in the applicable sizes described in the "JATMA YEAR BOOK"; in the case of ETRTO (The European Tyre and Rim Technical Organisation), it is the "Measuring Rim" described in the "STANDARDS MANUAL"; in the case of TRA (The Tire and Rim Association, Inc.), it is the "Design Rim" described in the "YEAR BOOK". Refer to JATMA, ETRTO, and TRA in this order, and follow the relevant standards if there are applicable sizes during the reference. In the case of a tire not defined by the standards, it refers to the rim with the smallest rim diameter and then the narrowest rim width among the rims that can be mounted on the tire and can hold the internal pressure, that is, the rim that does not cause air leakage between the rim and the tire. Also, the "normal internal pressure" refers to the air pressure defined for each tire in the standard system including the standard on which the tire is based. In the case of JATMA, it is the "maximum air pressure"; in the case of ETRTO, it is the "INFLATION PRESSURE"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Refer to JATMA, ETRTO, and TRA in this order, and follow the relevant standards if there are applicable sizes during the reference. In the case of a tire not defined by the standards, it refers to the normal internal pressure (however, 250 KPa or more) of another tire size (defined by the standards) with the normal rim described as the standard rim. In the case where there are multiple normal internal pressures of 250 KPa or more described, it refers to the minimum value among them.

[0024] The width GW of the groove 11 is preferably set in the range of 0.04 times or more and 0.12 times or less of the tread width WT. The depth of the groove 11 (not shown) is preferably set in the range of 0.06 times or more and 0.18 times or less of the tread width WT.

[0025] The depth of the groove 11 is preferably 2 mm or more, more preferably 3 mm or more, still more preferably 4 mm or more, and is preferably 12 mm or less, more preferably 10 mm or less, still more preferably 8 mm or less. When it is within the above range, the effect tends to be obtained more favorably.

[0026] Among the grooves 11, the depth G of the groove straddling the center rubber 9A and the shoulder rubber 9B (the depth of the groove at the interface between the center rubber 9A and the shoulder rubber 9B) is preferably 2 mm or more, more preferably 3 mm or more, still more preferably 4 mm or more, and is preferably 12 mm or less, more preferably 10 mm or less, still more preferably 8 mm or less.

[0027] The mechanism by which more effects can be obtained by adjusting the depth G of the groove straddling the center rubber 9A and the shoulder rubber 9B to 10 mm or less is not clear, but it is considered that by reducing the depth of the groove, the rigidity of the tread portion is increased and the responsiveness is likely to be improved.

[0028] In this specification, the depth of the groove is the radial distance of the tire in the tire diameter direction to the deepest part of the groove extending in an arbitrary direction that defines various tread patterns formed by partitioning on the tread rubber surface of the vulcanized tire. The depth of the groove is measured along the normal line of the surface obtained by extending the surface forming the ground contact surface of the outermost surface of the tread rubber, and means the distance from the surface obtained by extending the surface forming the ground contact surface to the deepest groove bottom, and refers to the maximum distance among the depths of the provided grooves.

[0029] The motorcycle tire 1 preferably has a groove 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 the tire 1 of FIG. 2, the groove 11 formed from the diagonal grooves 11B, 11B and the bypass grooves 11C connecting between the two diagonal grooves 11B, 11B crosses the boundary 9D between the center rubber 9A and the shoulder rubber 9B and is provided without extending to the tire equator C. When a groove extending from the center rubber to the shoulder rubber is provided in this way, the deformation generated during braking at the center rubber is likely to be transmitted to the shoulder rubber, and when the shoulder rubber comes into contact with the ground, the generation of reaction force becomes faster, and it is considered that the turning performance is likely to be improved. Also, it is considered that heat is likely to be generated at the center rubber and the generated heat is likely to be transferred to the shoulder rubber, and as a result, the braking performance is considered to be enhanced.

[0030] (Drug) Next, drugs that can be used in the center rubber composition constituting the center rubber and the shoulder rubber composition constituting the shoulder rubber will be described.

[0031] The above center rubber composition and the above shoulder rubber composition contain a rubber component. In this specification, the above rubber component is a component that contributes to crosslinking. Generally, a polymer having a weight average molecular weight (Mw) of 10,000 or more, and a polymer component that is not extracted by acetone corresponds to the rubber component. The above rubber component is in a solid state at 25°C.

[0032] The weight average molecular weight of the above rubber component is preferably 50,000 or more, more preferably 150,000 or more, still more preferably 200,000 or more, particularly preferably 270,000 or more, and is also preferably 2,000,000 or less, more preferably 1,500,000 or less, still more preferably 1,000,000 or less. When it is within the above range, the effect tends to be obtained more favorably.

[0033] In the present specification, the weight-average molecular weight (Mw) and the number-average molecular weight (Mn) can be determined by standard polystyrene conversion based on the measured values obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0034] The above rubber component may be an unmodified rubber or a modified rubber. Examples of the modified rubber include rubbers having a functional group that interacts with a filler such as silica. For example, a terminal-modified rubber (terminal-modified rubber having the above functional group at the terminal) in which at least one terminal of the rubber is modified with a compound (modifying agent) having the above functional group, a main-chain modified rubber having the above functional group in the main chain, a main-chain terminal-modified rubber having the above functional group in the main chain and at the terminal (for example, a main-chain terminal-modified rubber having the above functional group in the main chain and at least one terminal modified with the above modifying agent), and a terminal-modified rubber modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or an epoxy group introduced therein.

[0035] Examples of the above 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, an epoxy group, etc. These functional groups may have a substituent. Among them, an amino group (preferably an amino group in which the hydrogen atom of the 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), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferable.

[0036] Examples of the rubber component include diene rubbers. Examples of the diene rubbers include isoprene rubbers, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), etc. Further, examples of the rubber component include butyl rubbers, fluororubbers, etc. These rubber components may be subjected to modification treatment or hydrogenation treatment, and stretched rubbers stretched with oils, resins, liquid rubber components, etc. may also be used. These may be used alone or in combination of two or more. Among them, it is preferable to contain at least one of isoprene rubbers, BR, and SBR, and it is more preferable to contain at least SBR.

[0037] Examples of the isoprene rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, etc. As NR, for example, those generally used in the rubber industry such as SIR20, RSS#3, TSR20, etc. can be used. IR is not particularly limited, and for example, those generally used in the rubber industry such as IR2200, etc. can be used. Examples of the modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber, etc., examples of the modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc., and examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These may be used alone or in combination of two or more.

[0038] BR is not particularly limited, and for example, high-cis content high-cis BR, BR containing syndiotactic polybutadiene crystals, BR synthesized using a rare earth-based catalyst (rare earth BR), etc. can be used. These may be used alone or in combination of two or more. Among them, BR preferably contains high-cis BR having a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more. In the present specification, the cis content can be measured by infrared absorption spectroscopy.

[0039] When there is one type of BR, the cis content of BR means the cis content of that BR. When there are multiple types, it means the average cis content. The average cis content of BR can be calculated by {Σ(content of each BR × cis content of each BR)} / total content of all BRs. For example, in 100% by mass of the rubber component, if BR with a cis content of 90% by mass is 20% by mass and BR with a cis content of 40% by mass is 10% by mass, the average cis content of BR is 73.3% by mass (=(20×90 + 10×40) / (20 + 10)).

[0040] Either non-modified BR or modified BR can be used for BR. Examples of modified BR include modified BR into which functional groups similar to those of modified rubber are introduced. Also, hydrogenated butadiene polymers (hydrogenated BR) can be used for BR.

[0041] From the perspective of obtaining more effects, it is desirable that at least one of the above center rubber (center rubber composition) and the above shoulder rubber (shoulder rubber composition) contains modified butadiene rubber (modified BR).

[0042] The mechanism by which more effects can be obtained by including modified BR in at least one of the center rubber and the shoulder rubber is not clear. However, by using modified BR, the affinity between the center rubber and the shoulder rubber during molding is increased, so it is considered that the force transmission at the interface becomes easier and the reaction force during turning is likely to occur.

[0043] As BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0044] SBR is not particularly limited. For example, emulsion polymerization styrene-butadiene rubber (E-SBR), solution polymerization styrene-butadiene rubber (S-SBR), etc. can be used. These can be used alone or in combination of two or more.

[0045] The styrene content of SBR is preferably 5% by mass or more, more preferably 20% by mass or more, still more preferably 24% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, still more preferably 36% by mass or less. When within the above ranges, the effects tend to be obtained more favorably. In the present specification, the styrene content can be measured by 1 1H-NMR measurement.

[0046] The styrene content of SBR means the styrene content of the SBR when there is one type of SBR, and means the average styrene content when there are multiple types. The average styrene content of SBR can be calculated by {Σ (content of each SBR × styrene content of each SBR)} / total content of all SBRs. For example, when in 100% by mass of the rubber component, 85% by mass of SBR has a styrene content of 40% by mass and 5% by mass of SBR has a styrene content of 25% by mass, the average styrene content of SBR is 39.2% by mass (=(85×40 + 5×25) / (85 + 5)).

[0047] The vinyl content of SBR is preferably 3% by mass or more, more preferably 10% by mass or more, still more preferably 17% by mass or more. The vinyl bond content is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less. When within the above ranges, the effects tend to be obtained more favorably. In the present specification, the vinyl content (1,2-bonded butadiene unit content) can be measured by infrared absorption spectroscopy.

[0048] The vinyl content (1,2-bonded butadiene unit content) of SBR is the ratio of vinyl bonds when the total mass of the butadiene part in SBR is 100 (unit: % by mass), and vinyl content [% by mass] + cis content [% by mass] + trans content [% by mass] = 100 [% by mass]. When there is one type of SBR, it means the vinyl content of the SBR, and when there are multiple types, it means the average vinyl content. The average vinyl content of SBR can be calculated by Σ{content of each SBR × (100 [mass%] - styrene content of each SBR [mass%]) × vinyl content of each SBR [mass%]} / Σ{content of each SBR × (100 [mass%] - styrene content of each SBR [mass%])}. For example, in 100 parts by mass of the rubber component, when there are 75 parts by mass of SBR with a styrene content of 40 mass% and a vinyl content of 30 mass%, 15 parts by mass of SBR with a styrene content of 25 mass% and a vinyl content of 20 mass%, and the remaining 10 parts by mass are other than SBR, the average vinyl content of SBR is 28 mass% (={75×(100 [mass%]-40 [mass%])×30 [mass%]+15×(100 [mass%]-25 [mass%])×20 [mass%])} / {75×(100 [mass%]-40 [mass%])+15×(100 [mass%]-25 [mass%])}).

[0049] As SBR, either non-modified SBR or modified SBR can be used. Examples of modified SBR include those with functional groups similar to modified rubber introduced. Also, as SBR, hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can be used.

[0050] As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. Also, those synthesized by known methods can be used.

[0051] The raw materials (monomers) of synthetic rubbers such as IR, SBR, and BR may be derived from underground resources such as petroleum and natural gas, or may be recycled from rubber products such as tires and non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited, and examples include styrene. Among them, it is preferable to use recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) as raw materials.

[0052] The method for producing recycled monomers is not particularly limited, and examples include being synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Also, the method for producing recycled naphtha is not particularly limited, and for example, rubber products such as tires may be decomposed under high temperature and high pressure, decomposed by microwaves, or extracted after mechanical pulverization.

[0053] Furthermore, the raw materials (monomers) of synthetic rubbers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to substances derived from natural resources such as plants. The biomass is not particularly limited, and examples include agricultural and forestry products, sugars, wood chips, plant residues after obtaining useful components, ethanol derived from plants, biomass naphtha, and the like.

[0054] The biomass-derived monomers (biomass monomers) are not particularly limited, and examples include biomass-derived butadiene and biomass-derived aromatic vinyls. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited, and examples thereof include styrene. Further, the method for producing the biomass monomer is not particularly limited, and examples thereof include those by biological and / or chemical and / or physical conversion of animals and plants. Fermentation by microorganisms is typical as the biological conversion, and examples of the chemical and / or physical conversion include those by a catalyst, high heat, high pressure, electromagnetic waves, a critical liquid, and combinations thereof.

[0055] The polymers synthesized from the biomass monomer components (biomass polymers) are not particularly limited, and examples thereof include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyls. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0056] Whether the raw material of the polymer is derived from biomass can be determined by pMC (percent Modern Carbon) measured in accordance with ASTM D6866-10.

[0057] pMC is the ratio of the 14 C concentration of the sample to the 14 C concentration of the standard modern carbon (modern standard reference), and is a value used as an index indicating the biomass ratio of a compound. The significance of this value will be described below.

[0058] In one mole (6.02×10 23 pieces) of carbon atoms, there are about 6.02×10 11 pieces, which is about one trillionth of ordinary carbon atoms, of 14C exists. 14 C is called a radioactive isotope, and its half-life is 5730 years and it decreases regularly. It takes 226,000 years for all of these to decay. Therefore, after carbon dioxide in the atmosphere and the like are taken up and fixed by plants and the like, in fossil fuels such as coal, oil, and natural gas, where more than 226,000 years are considered to have passed since the initial fixation, 14 all of the C element has decayed. Therefore, at present in the 21st century, fossil fuels such as coal, oil, and natural gas 14 contain no C element at all. Therefore, chemical substances produced using these fossil fuels as raw materials 14 also contain no C element at all.

[0059] On the other hand, 14 C is constantly generated by nuclear reactions of cosmic rays in the atmosphere, and a balance is maintained with the decrease due to radioactive decay. In the atmospheric environment of the earth, 14 the amount of C is a certain amount. Therefore, for substances derived from biomass resources that are circulating in the current environment, 14 the C concentration is about 1×10 -12 mol% with respect to the entire C atoms as described above. Therefore, by utilizing the difference between these values, the biomass ratio of a certain compound can be calculated.

[0060] This 14 C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 the C concentration ( 13 C / 12 C), 14 the C concentration ( 14 C / 12 C) is measured. In the measurement, 14 as a modern standard reference for the concentration of C, the 14The C concentration is adopted. As a specific reference substance, the oxalic acid standard provided by NIST (National Institute of Standards and Technology) is used. The specific activity of carbon in this oxalic acid (the radioactivity intensity of 14 C per gram of carbon) is separated for each carbon isotope, 13 and for 14 C, it is corrected to a fixed value, and the value obtained by applying the decay correction from 1950 AD to the measurement date is used as the value of the standard

[0061] C concentration (100%). The ratio of this value to the value of the actually measured sample is the pMC value.

[0061] Therefore, if the rubber is made of 100% biomass-derived substances, although there are regional differences, etc., currently in the normal state, it often does not reach 100, so it will show a value of about 110 pMC. On the other hand, for chemical substances derived from fossil fuels such as petroleum, when measuring this 14 C concentration, it will show a value of about 0 pMC (for example, 0.3 pMC). This value corresponds to the biomass ratio of 0% mentioned above.

[0062] From the above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in the rubber composition is suitable from the perspective of environmental protection.

[0063] The above center rubber composition and shoulder rubber composition contain a filler. The above center rubber composition and shoulder rubber composition contain silica as a filler. The fillers that can be used in addition to silica are not particularly limited, and materials known in the rubber field can be used. For example, inorganic fillers such as carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, biochar (BIO CHAR); poorly dispersible fillers, etc. can be mentioned. Among them, carbon black is preferred from the perspective of obtaining more effects.

[0064] In the above center rubber composition and shoulder rubber composition, the silica that can be used is not particularly limited. For example, silica prepared by the dry method (anhydrous silica), silica prepared by the wet method (hydrous silica), etc., which are common in the tire industry, can be used. The raw material of silica is not particularly limited. For example, it may be a raw material derived from a mineral such as quartz, or it may be a raw material derived from a living thing such as rice husk (for example, silica made from biomass materials such as rice husk as a raw material), or silica recycled from products containing silica may also be used. Among them, hydrous silica prepared by the wet method is preferred because it has many silanol groups. These silicas may be used alone or in combination of two or more.

[0065] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husk using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same manner as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0066] As the silica recycled from products containing silica, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter materials such as diatomaceous earth can be used. The recovery method is not particularly limited, and examples include pyrolysis and decomposition by electromagnetic waves. Among them, silica recovered from electronic components such as semiconductors or tires is preferred.

[0067] When silica crystallizes, it is insoluble in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, the crystallization of silica in rice husk ash can be suppressed (see, for example, Japanese Patent Application Laid-Open No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.).

[0068] Amorphous silica extracted from rice husk can be a commercially available product from Wilmar or the like.

[0069] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 50 m 2 / g or more, more preferably 100 m 2 / g or more, still more preferably 150 m 2 / g or more. Also, the upper limit of the N2SA of the silica is not particularly limited, but is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, still more preferably 250 m 2 / g or less. When within the above range, the effect tends to be obtained more favorably. In addition, in this specification, the N2SA of the silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0070] It is preferable that the above center rubber composition and shoulder rubber composition further contain a silane coupling agent. The silane coupling agent is not particularly limited, and those known in the rubber field can be used. For example, 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, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, etc. of the sulfide type, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto type such as NXT and NXT-Z manufactured by Momentive, vinyltriethoxysilane, vinyltrimethoxysilane, etc. of the vinyl type, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, etc. of the amino type, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. of the glycidoxy type, 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, etc. of the nitro type, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, etc. of the chloro type, and the like. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azmax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0071] Examples of carbon black that can be used in the above center rubber composition and shoulder rubber composition are not particularly limited, and include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw material of carbon black may be a biomass material such as lignin or vegetable oil, or a pyrolysis oil obtained by thermally decomposing waste tires. Also, the manufacturing method of carbon black may be by combustion such as the furnace method, by hydrothermal carbonization (HTC), or by thermal decomposition of methane such as the thermal black method. As commercial products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbia Carbon Company, etc. can be used. These may be used alone or in combination of two or more.

[0072] The nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 80 m 2 / g or more, more preferably 120 m 2 / g or more, and even more preferably 140 m 2 / g or more. Also, the above N2SA is preferably 300 m 2 / g or less, more preferably 250 m 2 / g or less, and even more preferably 200 m 2 / g or less. When within the above range, the effect tends to be obtained more favorably. In this specification, the nitrogen adsorption specific surface area of carbon black is determined according to JIS K6217-2:2001.

[0073] Examples of the above-mentioned difficult-to-disperse filler include microfibrillated plant fiber, short fibrous cellulose, gel-like compounds, etc. Among them, microfibrillated plant fiber is preferable.

[0074] As the microfibrillated plant fiber, cellulose microfibril is preferable from the viewpoint of obtaining good reinforcing properties. The cellulose microfibril is not particularly limited as long as it is derived from natural products. For example, resource biomass such as fruits, grains, and root vegetables, wood, bamboo, hemp, jute, kenaf, and pulp, paper, cloth, agricultural crop residues, food waste, and sewage sludge obtained from these as raw materials, waste biomass such as rice straw, wheat straw, and thinned wood, and unused biomass such as sea squirts, and cellulose produced by acetic acid bacteria, etc. These microfibrillated plant fibers may be used alone or in combination of two or more.

[0075] In the present specification, the cellulose microfibril typically means a cellulose fiber having an average fiber diameter within a range of 10 μm or less, and more typically a cellulose fiber having a fine structure with an average fiber diameter of 500 nm or less formed by an aggregation of cellulose molecules. A typical cellulose microfibril is formed, for example, as an aggregate of cellulose fibers having the above-mentioned average fiber diameter.

[0076] It is desirable that the above-mentioned center rubber composition and shoulder rubber composition contain a plasticizer. In the present specification, the plasticizer is a material that imparts plasticity to the rubber component, and is a concept including both a plasticizer that is liquid at 25°C and a plasticizer that is solid at 25°C. Examples of the plasticizer include resin components, oils, liquid polymers, ester-based plasticizers, etc. These plasticizers may be derived from mineral resources such as petroleum and natural gas, may be derived from biomass, or may be derived from naphtha recycled from rubber products or non-rubber products. Also, low-molecular-weight hydrocarbon components obtained by pyrolyzing and extracting used tires and products containing various components may be used as plasticizers. These plasticizers may be used alone or in combination of two or more.

[0077] Specific examples of the plasticizer include oils, liquid polymers, resins, etc. These may be used alone or in combination of two or more. Examples of the oil include mineral oil, vegetable oil, animal oil, etc. From the perspective of life cycle assessment, it is also possible to use waste oil after being used in a rubber mixer or an engine, or refined waste cooking oil used in a restaurant.

[0078] In this specification, the mineral oil refers to an oil derived from mineral resources such as petroleum and natural gas. Examples of the mineral oil include paraffinic oil (mineral oil), naphthenic oil, aromatic oil, etc. Specific examples of the mineral oil include, for example, MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), etc. It is also possible to use an oil with a low content of polycyclic aromatic (polycyclic aromatic compound: PCA) compounds for environmental protection. Examples of the low-PCA-content oil include MES, TDAE, heavy naphthenic oil, etc.

[0079] In this specification, vegetable oils include, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grape seed oil, wood wax, etc. Furthermore, as vegetable oils, there are also refined oils (such as salad oil) obtained by refining the above oils, transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidation polymerized oils obtained by oxidizing the above oils, waste cooking oils recovered from those used as edible oils, etc. Note that the vegetable oil may be liquid or solid at 25°C. These vegetable oils may be used alone or in combination of two or more.

[0080] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which the hydroxy group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited, and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a multimer of trimer or higher. Note that acylglycerols of dimer or higher can be obtained by thermal polymerization, oxidation polymerization, etc. Also, the acylglycerol may be liquid or solid at 25°C.

[0081] As a method for confirming whether the above acylglycerol is contained in the rubber composition, although not particularly limited, 1 it can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, at room temperature 1When measuring 1H-NMR and setting the signal of tetramethylsilane (TMS) to 0.00 ppm, signals around 5.26 ppm, around 4.28 ppm, and around 4.15 ppm were observed, and these signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" means a range of ±0.10 ppm.

[0082] The fatty acid is not particularly limited and may be an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0083] Among them, it is desirable that the fatty acid contains a fatty acid with few double bonds, that is, a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As the vegetable oil containing such a fatty acid, for example, a vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or a vegetable oil subjected to modification such as transesterification may be used. In addition, in order to produce a vegetable oil containing such a fatty acid, plants may be improved by variety improvement, genetic recombination, genome editing, etc.

[0084] As the oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0085] Examples of the liquid polymer include a liquid diene polymer (liquid rubber) and a liquid farnesene polymer at 25°C. Examples of the liquid rubber include a liquid styrene-butadiene copolymer (liquid SBR), a liquid butadiene polymer (liquid BR), a liquid isoprene polymer (liquid IR), a liquid styrene-isoprene copolymer (liquid SIR), a liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), a liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), and the like. These may have a modified terminal or main chain with a polar group. Further, hydrogenated products thereof can also be used.

[0086] The above liquid diene polymer preferably has a polystyrene-reduced weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 1.0×10 3 ~5.0×10 4 and more preferably 3.0×10 3 ~1.5×10 4 . The lower or upper limit of Mw of the liquid diene polymer may also be 4500 or 8500. In the present specification, the Mw of the liquid diene polymer is a polystyrene-reduced value measured by gel permeation chromatography (GPC).

[0087] Examples of the liquid diene polymer include products of Sartomer Company and Kuraray Co., Ltd.

[0088] As the above resin, as a tire formulation, a resin (resin) commonly used can be used, which may be liquid or solid at 25°C. For example, aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, acrylic resins, etc. can be mentioned. Further, the resin may be a hydrogenated resin (hydrogenated resin). These may be used alone or in combination of two or more. Also, the resin itself may be a copolymer of monomer components from a plurality of sources. Among them, aromatic vinyl polymers, petroleum resins, terpene resins, and hydrogenated resins thereof are desirable.

[0089] When using a resin that is solid at 25°C, the softening point of the above resin is preferably 50°C or higher, more preferably 55°C or higher, still more preferably 60°C or higher, and particularly preferably 85°C or higher. Also, it is preferably 160°C or lower, more preferably 150°C or lower, still more preferably 140°C or lower, and particularly preferably 100°C or lower. When within the above range, the effect tends to be obtained better. When the resin is liquid at 25°C, the softening point is preferably 20°C or lower, preferably 10°C or lower, and preferably 0°C or lower. In the case of a hydrogenated resin, it is desirable that the softening point is the same as above. Note that the softening point of the above resin is the temperature at which the ball drops, measured with a ring and ball softening point measuring device for the softening point defined in JIS K6220-1:2001.

[0090] The above aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a structural unit. For example, resins obtained by polymerizing α-methylstyrene and / or styrene can be mentioned. Specifically, homopolymers of styrene (styrene resins), homopolymers of α-methylstyrene (α-methylstyrene resins), copolymers of α-methylstyrene and styrene, copolymers of styrene and other monomers, etc. can be mentioned.

[0091] The above-mentioned coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain). Examples of monomer components other than coumarone and indene contained in the skeleton include styrene, α-methylstyrene, methyl indene, vinyl toluene, and the like.

[0092] The above-mentioned coumarone resin is a resin containing coumarone as the main monomer component constituting the resin skeleton (main chain).

[0093] The above-mentioned indene resin is a resin containing indene as the main monomer component constituting the resin skeleton (main chain).

[0094] As the above-mentioned phenol resin, for example, known polymers such as those obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural in the presence of an acid or alkali catalyst can be used. Among them, those obtained by reacting with an acid catalyst (such as novolak-type phenol resins) are preferred.

[0095] Examples of the above-mentioned rosin resin include rosin-based resins typified by natural rosin, polymerized rosin, modified rosin, their ester compounds, and their hydrogenated products.

[0096] Examples of the above-mentioned petroleum resin include C5-based resin, C9-based resin, C5 / C9-based resin, dicyclopentadiene (DCPD) resin, C9 / DCPD resin, and their hydrogenated products. Among them, DCPD resin, hydrogenated DCPD resin, C9 / DCPD resin, and C9 / hydrogenated DCPD resin are preferred.

[0097] The above terpene resin is a polymer containing terpenes as constituent units. For example, there are polyterpene resins obtained by polymerizing terpene compounds, aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds, and the like. Examples of aromatic modified terpene resins include terpene phenol resins using terpene compounds and phenolic compounds as raw materials, terpene styrene resins using terpene compounds and styrene compounds as raw materials, and terpene phenol styrene resins using terpene compounds, phenolic compounds and styrene compounds as raw materials. Examples of terpene compounds include α-pinene, β-pinene, etc., examples of phenolic compounds include phenol, bisphenol A, etc., and examples of aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.). Among them, aromatic modified terpene resins are preferred.

[0098] The above acrylic resin is a polymer containing acrylic monomers as constituent units. For example, there are styrene acrylic resins such as styrene acrylic resins obtained by copolymerizing an aromatic vinyl monomer component and an acrylic monomer component having a carboxyl group. Among them, a solvent-free carboxyl group-containing styrene acrylic resin can be preferably used.

[0099] As the above resin, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, ExxonMobil, KRATON, Nippon Paint Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., Tago Chemical Industries Co., Ltd., etc. can be used.

[0100] From the perspective of sustainability, it is desirable to use plant-derived plasticizers such as the above plant-derived oils and farnesene-based polymers as the above plasticizer.

[0101] The farnesene-based polymer is a polymer obtained by polymerizing farnesene and has a structural unit based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene), but (E)-β-farnesene having the following structure is preferred.

Chemical formula

[0102] The farnesene-based polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer). These may be used alone or in combination of two or more. Among them, a copolymer of farnesene and a vinyl monomer is preferred.

[0103] Examples of vinyl monomers include aromatic vinyl compounds such as styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-t-butyl-2-methylstyrene, vinyl ethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, 4-t-butylstyrene, vinylxylene, vinylnaphthalene, vinyltoluene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene, and conjugated diene compounds such as butadiene and isoprene. These may be used alone or in combination of two or more. Among them, butadiene is preferred. That is, as the farnesene-vinyl monomer copolymer, a copolymer of farnesene and butadiene (farnesene-butadiene copolymer) is preferred.

[0104] In the farnesene-vinyl monomer copolymer, the copolymerization ratio by mass (farnesene / vinyl monomer) of farnesene and the vinyl monomer is preferably 40 / 60 to 90 / 10.

[0105] Farnesene-based polymers with a weight average molecular weight (Mw) of 3000 or more and 300,000 or less can be preferably used. The Mw of the farnesene-based polymer is preferably 8000 or more, more preferably 10000 or more, and preferably 100,000 or less, more preferably 60,000 or less, and still more preferably 50,000 or less. When within the above range, the effects tend to be more preferably obtained.

[0106] The farnesene-based polymer may be in a liquid state or a solid state at 25°C. Among them, a liquid farnesene-based polymer in a liquid state at 25°C is desirable.

[0107] The above rubber composition may further contain vulcanized rubber particles. The vulcanized rubber particles are particles made of vulcanized rubber. Specifically, rubber powder etc. specified in JIS K 6316:2017 can be used. From the viewpoints of environmental consideration and cost, recycled rubber powder produced from crushed waste tires etc. is preferable. These may be used alone or in combination of two or more.

[0108] The vulcanized rubber particles are not particularly limited, and may be non-modified vulcanized rubber particles or modified vulcanized rubber particles.

[0109] As commercially available products of vulcanized rubber particles, for example, products of Lehigh, Murakami Rubber Industry Co., Ltd. etc. can be used.

[0110] In the above center rubber composition and shoulder rubber composition, the content of the vulcanized rubber particles is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, still more preferably 10 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less, with respect to 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably.

[0111] The above center rubber composition and shoulder rubber composition preferably contain an anti-aging agent from the viewpoints of crack resistance, ozone resistance etc.

[0112] The anti-aging agent is not particularly limited, but examples include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, and polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercial products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys, etc. can be used.

[0113] The above center rubber composition and shoulder rubber composition preferably contain stearic acid. As the stearic acid, conventionally known ones can be used, and for example, products of NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Corporation, Chiba Fatty Acids Co., Ltd., etc. can be used.

[0114] The above center rubber composition and shoulder rubber composition preferably contain zinc oxide. As the zinc oxide, those conventionally known can be used. For example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0115] The above center rubber composition and shoulder rubber composition may be blended with wax. The wax is not particularly limited, and any of those usually used in the tire industry can be preferably used. For example, mineral waxes, plant-derived waxes, etc. can be mentioned. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among them, mineral waxes are preferable. Examples of plant-derived waxes include rice wax, carnauba wax, candelilla wax, etc. Examples of mineral waxes include paraffin wax, microcrystalline wax, these selected special waxes, etc., and paraffin wax is preferable. Note that the wax according to this embodiment does not contain stearic acid. As the wax, those commercially available from, for example, Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. can be used. These waxes may be used alone or in combination of two or more.

[0116] In the above center rubber composition and shoulder rubber composition, it is preferable to blend sulfur as a crosslinking agent in terms of forming appropriate crosslinking chains in the polymer chain and imparting good performance.

[0117] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc. generally used in the rubber industry. As commercial products, products of Tsuruimi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexsys Co., Nippon Karyu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0118] The above center rubber composition and shoulder rubber composition preferably contain a vulcanization accelerator. The type of the vulcanization accelerator is not particularly limited, and those commonly used can be used. Examples of the vulcanization accelerator include benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; 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, N-t-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among them, sulfenamide-based, guanidine-based, and benzothiazole-based vulcanization accelerators are preferred.

[0119] In addition to the above components, the above center rubber composition and shoulder rubber composition may be appropriately blended with compounding agents commonly used in the tire industry, such as release agents and other materials.

[0120] In this specification, various materials containing carbon atoms (such as rubber, oil, resin, vulcanization accelerator, anti-aging agent, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the above-mentioned compound from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process of synthesizing methane from carbon dioxide may be converted.

[0121] In the above motorcycle tire, the ratio (Si(S) / Si(C)) of the silica content Si(S) (the silica content in the shoulder rubber composition) of the shoulder rubber to the silica content Si(C) (the silica content in the center rubber composition) of the center rubber is 0.80 or more and 0.95 or less. The Si(S) / Si(C) is preferably 0.85 or more, more preferably 0.88 or more, and still more preferably 0.90 or more. The upper limit is preferably 0.94 or less, more preferably 0.93 or less, and still more preferably 0.92 or less. When within the above range, the effect tends to be obtained more favorably.

[0122] 〔Center rubber (center rubber composition)〕 The center rubber composition constituting the center rubber preferably contains the above SBR as a rubber component.

[0123] In the above center rubber composition, the content of the above SBR in 100% by mass of the rubber component is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass. When within the above range, the effect tends to be obtained more favorably.

[0124] When the above center rubber composition contains BR, the content of the above BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0125] When the above center rubber composition contains an isoprene-based rubber, the content of the above isoprene-based rubber in 100% by mass of the rubber component is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0126] In the above center rubber composition, the content of the above silica is 70 parts by mass or more, preferably 80 parts by mass or more, more preferably 90 parts by mass or more, and still more preferably 100 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 120 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0127] In the above center rubber composition, the content of the above carbon black is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and still more preferably 7 parts by mass or more with respect to 100 parts by mass of the rubber component, and is also preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0128] In the above center rubber composition, the content of the above filler (total amount of fillers such as carbon black and silica) is preferably 80 parts by mass or more, more preferably 100 parts by mass or more, and still more preferably 110 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 200 parts by mass or less, more preferably 160 parts by mass or less, and still more preferably 130 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0129] In the above center rubber composition, the content of the above silane coupling agent is preferably 0.1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more with respect to 100 parts by mass of silica. The upper limit of the content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0130] In the above center rubber composition, the content of the above plasticizer (total amount of plasticizer) is preferably 2 parts by mass or more, more preferably 35 parts by mass or more, still more preferably 38 parts by mass or more, with respect to 100 parts by mass of the rubber component. The upper limit is preferably 123 parts by mass or less, more preferably 93 parts by mass or less, still more preferably 76 parts by mass or less, and even more preferably 73 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. Note that the content of the plasticizer includes the amount of oil and resin contained in the oil-extended rubber and resin-extended rubber.

[0131] In the above center rubber composition, the content of the solid plasticizer in a solid state at 25°C is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, with respect to 100 parts by mass of the rubber component. The upper limit is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0132] In the above center rubber composition, the content of the above resin in a solid state at 25°C is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, with respect to 100 parts by mass of the rubber component. The upper limit is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0133] In the above center rubber composition, the content of the liquid plasticizer in a liquid state at 25°C is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 33 parts by mass or more, with respect to 100 parts by mass of the rubber component. The upper limit is preferably 118 parts by mass or less, more preferably 88 parts by mass or less, still more preferably 71 parts by mass or less, and even more preferably 68 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. Note that the content of the liquid plasticizer includes the amount of oil contained in the oil-extended rubber and the amount of liquid resin of the resin-extended rubber extended with the liquid resin.

[0134] In the above center rubber composition, the content of the above oil is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 33 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 118 parts by mass or less, more preferably 88 parts by mass or less, still more preferably 71 parts by mass or less, and even more preferably 68 parts by mass or less. When it is within the above range, the effect tends to be obtained better. Note that the content of the oil also includes the amount of oil contained in the oil-extended rubber.

[0135] In the above center rubber composition, the content of the above antioxidant is preferably 0.2 parts by mass or more, more preferably 2.0 parts by mass or more, still more preferably 3.4 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 10.0 parts by mass or less, more preferably 6.0 parts by mass or less.

[0136] In the above center rubber composition, the content of the above stearic acid is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, still more preferably 2.0 parts by mass or more, based on 100 parts by mass of the rubber component, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0137] In the above center rubber composition, the content of the above zinc oxide is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, still more preferably 2.0 parts by mass or more, based on 100 parts by mass of the rubber component, and is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less.

[0138] In the above center rubber composition, the content of the above wax is preferably 0.5 parts by mass or more, more preferably 1.6 parts by mass or more, based on 100 parts by mass of the rubber component, and is preferably 8.0 parts by mass or less, more preferably 5.0 parts by mass or less.

[0139] In the above center rubber composition, the sulfur content is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, still more preferably 2.0 parts by mass or more, based on 100 parts by mass of the rubber component. The sulfur content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, still more preferably 2.2 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0140] In the above center rubber composition, the content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization rate and crosslink density. However, based on 100 parts by mass of the rubber component, it is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, still more preferably 1.4 parts by mass or more. The upper limit is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, still more preferably 5.0 parts by mass or less.

[0141] 〔Shoulder rubber (shoulder rubber composition)〕 The shoulder rubber composition constituting the shoulder rubber preferably contains the above SBR as a rubber component.

[0142] In the above shoulder rubber composition, the content of the above SBR in 100% by mass of the rubber component is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass. When within the above range, the effect tends to be obtained more favorably.

[0143] Although the mechanism by which more effect is obtained by blending 70% by mass or more of SBR into the shoulder rubber is not clear, it is considered that by including a predetermined amount of SBR, a domain of the styrene part is generated in the system, making it easier to transmit force at the styrene part and easier to generate a reaction force with the shoulder rubber.

[0144] When the above shoulder rubber composition contains BR, the content of the above BR in 100% by mass of the rubber component is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0145] When the above shoulder rubber composition contains an isoprene rubber, the content of the above isoprene rubber in 100% by mass of the rubber component is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0146] In the above shoulder rubber composition, the content of the above silica is 70 parts by mass or more, preferably 80 parts by mass or more, more preferably 85 parts by mass or more, still more preferably 90 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 180 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 120 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0147] In the above shoulder rubber composition, the content of the above carbon black is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 7 parts by mass or more, based on 100 parts by mass of the rubber component, and is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0148] In the above shoulder rubber composition, the content of the above filler (total amount of fillers such as carbon black and silica) is preferably 80 parts by mass or more, more preferably 85 parts by mass or more, still more preferably 90 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 180 parts by mass or less, more preferably 140 parts by mass or less, still more preferably 110 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0149] In the above shoulder rubber composition, the content of the above silane coupling agent is preferably 0.1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, particularly preferably 7 parts by mass or more with respect to 100 parts by mass of silica. The upper limit of the content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less, particularly preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0150] In the above shoulder rubber composition, the content of the above plasticizer (total amount of plasticizer) is preferably 2 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 23 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 85 parts by mass or less, more preferably 78 parts by mass or less, still more preferably 63 parts by mass or less, even more preferably 61 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably. Note that the content of the plasticizer also includes the amount of oil and resin contained in oil-extended rubber and resin-extended rubber.

[0151] In the above shoulder rubber composition, the content of the above solid plasticizer in a solid state at 25°C is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, still more preferably 8 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0152] In the above shoulder rubber composition, the content of the resin that is in a solid state at 25°C is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, and still more preferably 8 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0153] In the above shoulder rubber composition, the content of the liquid plasticizer that is in a liquid state at 25°C is preferably 2 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 58 parts by mass or less, more preferably 55 parts by mass or less, and still more preferably 53 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, the content of the liquid plasticizer includes the amount of oil contained in the oil-extended rubber and the amount of the liquid resin of the resin-extended rubber extended with the liquid resin.

[0154] In the above shoulder rubber composition, the content of the oil is preferably 2 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 58 parts by mass or less, more preferably 55 parts by mass or less, and still more preferably 53 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, the content of the oil includes the amount of oil contained in the oil-extended rubber.

[0155] In the above shoulder rubber composition, the content of the anti-aging agent is preferably 0.2 parts by mass or more, more preferably 2.0 parts by mass or more, and still more preferably 3.4 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 10.0 parts by mass or less, more preferably 6.0 parts by mass or less.

[0156] In the above shoulder rubber composition, the content of the stearic acid is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, still more preferably 2.0 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component.

[0157] In the above shoulder rubber composition, the content of the zinc oxide is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, still more preferably 2.0 parts by mass or more, and preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, based on 100 parts by mass of the rubber component.

[0158] In the above shoulder rubber composition, the content of the wax is preferably 0.5 parts by mass or more, more preferably 1.6 parts by mass or more, and preferably 8.0 parts by mass or less, more preferably 5.0 parts by mass or less, based on 100 parts by mass of the rubber component.

[0159] In the above shoulder rubber composition, the content of the sulfur is preferably 1.0 parts by mass or more, more preferably 1.5 parts by mass or more, still more preferably 2.0 parts by mass or more, based on 100 parts by mass of the rubber component. The content of the sulfur is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, still more preferably 2.2 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0160] In the above shoulder rubber composition, the content of the above vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization rate and crosslink density. However, based on 100 parts by mass of the rubber component, it is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, still more preferably 1.4 parts by mass or more. The upper limit is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, still more preferably 5.0 parts by mass or less.

[0161] Both the center rubber (center rubber composition) and the shoulder rubber (shoulder rubber composition) have a plasticizer content (total amount of plasticizer) of 2 parts by mass or more and 85 parts by mass or less with respect to 100 parts by mass of the rubber component, and the aromatic vinyl polymer ratio P(S) in the plasticizer contained in the shoulder rubber (shoulder rubber composition) (= amount of aromatic vinyl polymer contained in the shoulder rubber / amount of plasticizer contained in the shoulder rubber) is preferably greater than the aromatic vinyl polymer ratio P(C) in the plasticizer contained in the center rubber (= amount of aromatic vinyl polymer contained in the center rubber / amount of plasticizer contained in the center rubber) (P(C) < P(S)).

[0162] The mechanism by which more effects can be obtained by adjusting the plasticizer content of both the center rubber and the shoulder rubber to 2 parts by mass or more and 85 parts by mass or less and P(C) < P(S) is not clear. However, by containing a predetermined amount of plasticizer, the compatibility between the rubber compositions at the interface between the center rubber and the shoulder rubber is enhanced, and the force is more easily transmitted between the interfaces of the center rubber and the shoulder rubber. Furthermore, by making the ratio of the aromatic vinyl polymer in the plasticizer higher in the shoulder rubber, the shoulder rubber is more likely to warm up and the road surface followability is enhanced, so it is considered possible to improve the responsiveness during cornering.

[0163] In the above center rubber (center rubber composition) and shoulder rubber (shoulder rubber composition), the lower limit of the plasticizer content with respect to 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 23 parts by mass or more, and the upper limit is preferably 50 parts by mass or less, more preferably 45 parts by mass or less. When within the above range, the effect tends to be obtained better.

[0164] Regarding the above P(C) < P(S), P(S) / P(C) is preferably 1.3 or more, more preferably 1.7 or more, still more preferably 1.9 or more, and is preferably 4.8 or less, more preferably 4.1 or less, still more preferably 3.8 or less. When within the above range, the effect tends to be obtained better.

[0165] The above center rubber composition and shoulder rubber composition are kneaded using a rubber kneading apparatus such as an open roll or a Banbury mixer for each of the above components, and then a crosslinked rubber composition is obtained by a method such as crosslinking.

[0166] As the kneading conditions, in the base kneading step of kneading additives other than the vulcanizing agent and the vulcanization accelerator, the kneading temperature is preferably 50°C or higher, more preferably 190°C or higher, and preferably 200°C or lower, more preferably 190°C or lower. The kneading time is preferably 30 seconds or longer, more preferably 1 minute or longer, and preferably 30 minutes or shorter. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is preferably 100°C or lower, more preferably 80°C or lower, and preferably room temperature or lower. Further, the composition kneaded with the vulcanizing agent and the vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is preferably 120°C or higher, more preferably 140°C or higher, and preferably 200°C or lower, more preferably 180°C or lower.

[0167] The above motorcycle tire is manufactured by a usual method using the center rubber and the shoulder rubber composition. That is, the center rubber composition and the shoulder rubber composition containing the above components are extruded in an unvulcanized state according to the shapes of the center rubber and the shoulder rubber, and together with other tire members, an unvulcanized tire is formed by molding in a usual manner on a tire molding machine. The tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

[0168] The ratio (M300(S) / M300(C)) of the 300% modulus M300(S) [MPa] of the above shoulder rubber (shoulder rubber composition after vulcanization) to the 300% modulus M300(C) [MPa] of the above center rubber (center rubber composition after vulcanization) is 1.15 or more and 1.50 or less. The above M300(S) / M300(C) is preferably 1.17 or more, more preferably 1.19 or more, and is preferably 1.37 or less, more preferably 1.32 or less. When it is within the above range, the effect tends to be preferably obtained.

[0169] The 300% modulus M300(C) of the above center rubber (center rubber composition after vulcanization) is preferably 4.3 MPa or more, more preferably 5.8 MPa or more, still more preferably 6.3 MPa or more, and is preferably 9.0 MPa or less, more preferably 8.0 MPa or less, still more preferably 7.5 MPa or less. When it is within the above range, the effect tends to be preferably obtained.

[0170] The 300% modulus M300(S) of the above shoulder rubber (shoulder rubber composition after vulcanization) is preferably 5.9 MPa or more, more preferably 6.7 MPa or more, still more preferably 7.5 MPa or more, and is preferably 11.1 MPa or less, more preferably 9.0 MPa or less, still more preferably 8.3 MPa or less. When it is within the above range, the effect tends to be preferably obtained.

[0171] In addition, in this specification, the 300% modulus (M300) of the rubber composition means M300 of the rubber composition after vulcanization. M300 is a value measured by a method based on JIS K6251:2010.

[0172] M300 can be adjusted by the chemicals (especially rubber components, fillers, plasticizers such as oils and resins, and the type and amount of vulcanizing agents) compounded in the rubber composition. For example, increasing the amount of the filler, decreasing the amount of the plasticizer, increasing the amount of sulfur, or increasing the amount of the vulcanization accelerator tends to increase the value of M300.

[0173] It is desirable that the ratio (70°C E*(S) / 70°C E*(C)) of the complex elastic modulus 70°C E*(S) [MPa] of the above shoulder rubber (vulcanized shoulder rubber composition) to the complex elastic modulus 70°C E*(C) [MPa] of the above center rubber (vulcanized center rubber composition) at 70°C exceeds 0.75 and is less than 1.25. The above 70°C E*(S) / 70°C E*(C) preferably exceeds 0.85, more preferably exceeds 0.91, still more preferably exceeds 1.00, and preferably is less than 1.20, more preferably is less than 1.15, still more preferably is less than 1.10. When within the above range, there is a tendency that the effect can be preferably obtained.

[0174] Although the mechanism by which more effects can be obtained by adjusting 70°C E*(S) / 70°C E*(C) to exceed 0.75 and be less than 1.25 is not clear, it is considered that by reducing the difference in rubber hardness between the center rubber and the shoulder rubber during cornering, it is possible to suppress a large change in the amount of deformation at the interface between the center rubber and the shoulder rubber, improve the handling stability, and make it easier to enhance the turning performance.

[0175] The complex elastic modulus 70°C E*(C) of the above center rubber (vulcanized center rubber composition) at 70°C is preferably 6.6 MPa or more, more preferably 6.8 MPa or more, still more preferably 7.0 MPa or more, and preferably 9.9 MPa or less, more preferably 9.0 MPa or less, still more preferably 8.5 MPa or less. When within the above range, there is a tendency that the effect can be preferably obtained.

[0176] The complex elastic modulus 70°C E*(S) of the above shoulder rubber (vulcanized shoulder rubber composition) at 70°C is preferably 5.8 MPa or more, more preferably 6.4 MPa or more, still more preferably 7.0 MPa or more, and preferably 7.8 MPa or less, more preferably 7.6 MPa or less, still more preferably 7.4 MPa or less. When within the above range, there is a tendency that the effect can be preferably obtained.

[0177] In this specification, the 70°C E* of the rubber composition means the 70°C E* of the vulcanized rubber composition. The 70°C E* is a value obtained by performing a viscoelasticity test on the vulcanized rubber composition. The 70°C E* of the rubber composition (after vulcanization) is the complex elastic modulus in the elongation mode at a temperature of 70°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz. Note that the 70°C E* is measured by cutting out a sample with a width of 4 mm, a length of 20 mm, and a thickness of 1 mm from the tire, and the longitudinal direction of the sample is made to coincide with the tangential direction of the tire circumferential direction.

[0178] The adjustment of the 70°C E* can be carried out, for example, mainly by changing the type and blending amount of the rubber component, the type and blending amount of the filler, and the blending amount of the plasticizer. Specifically, with an increase in the filler amount and a decrease in the plasticizer amount, the 70°C E* tends to increase.

[0179] It is desirable that the ratio (30°C E*(S) / 30°C E*(C)) of the complex elastic modulus 30°C E*(S) [MPa] at 30°C of the above shoulder rubber (vulcanized shoulder rubber composition) to the complex elastic modulus 30°C E*(C) [MPa] at 30°C of the above center rubber (vulcanized center rubber composition) exceeds 0.75 and is less than 1.25. The above 30°C E*(S) / 30°C E*(C) is preferably more than 0.85, more preferably more than 0.91, still more preferably more than 1.08, and is preferably less than 1.20, more preferably less than 1.20, still more preferably less than 1.15. When within the above range, the effect tends to be preferably obtained.

[0180] The mechanism by which more effects can be obtained by adjusting the above 30°C E*(S) / 30°C E*(C) to exceed 0.75 and be less than 1.25 is not clear, but it is considered that by reducing the difference in rubber hardness between the center rubber and the shoulder rubber during straight running, it is possible to suppress a large change in the amount of deformation at the interface between the center rubber and the shoulder rubber, improve the handling stability, and make it easier to enhance the turning performance.

[0181] The complex elastic modulus 30°C E*(C) of the above center rubber (vulcanized center rubber composition) is preferably 6.5 MPa or more, more preferably 9.2 MPa or more, still more preferably 9.9 MPa or more, and is preferably 16.3 MPa or less, more preferably 13.0 MPa or less, still more preferably 11.0 MPa or less. When it is within the above range, the effect tends to be preferably obtained.

[0182] The complex elastic modulus 30°C E*(S) of the above shoulder rubber (vulcanized shoulder rubber composition) is preferably 8.0 Pa or more, more preferably 9.2 MPa or more, still more preferably 10.9 MPa or more, and is preferably 11.7 MPa or less, more preferably 111.5 MPa or less, still more preferably 11.3 MPa or less. When it is within the above range, the effect tends to be preferably obtained.

[0183] In this specification, 30°C E* of the rubber composition means 30°C E* of the vulcanized rubber composition. 30°C E* is a value obtained by performing a viscoelasticity test on the vulcanized rubber composition. 30°C E* of the rubber composition (after vulcanization) is the complex elastic modulus at a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, and an elongation mode. It should be noted that 30°C E* is measured by cutting out a sample with a width of 4 mm, a length of 20 mm, and a thickness of 1 mm from the tire, and the longitudinal direction of the sample is made to coincide with the tangential direction of the tire circumferential direction.

[0184] The adjustment of 30°C E* can be adjusted, for example, mainly by changing the type and blending amount of the rubber component, the type and blending amount of the filler, and the blending amount of the plasticizer. Specifically, with an increase in the filler amount and a decrease in the plasticizer amount, 30°C E* tends to increase.

Examples

[0185] Based on the examples, the present invention will be specifically described, but the present invention is not limited only to these.

[0186] The various chemicals used in the examples and comparative examples will be collectively described below. SBR1: Tough Den 3830 manufactured by Asahi Kasei Corporation (styrene content 36% by mass, vinyl content 23% by mass, containing 37.5% by mass of oil based on 100 parts by mass of rubber solid content) SBR2: Tough Den 4850 manufactured by Asahi Kasei Corporation (styrene content 40% by mass, vinyl content 47% by mass, containing 50% by mass of oil based on 100 parts by mass of rubber solid content) BR: BR150B manufactured by Ube Industries, Ltd. (cis content 98% by mass) Carbon black: Show Black N110 (N2SA 142 m 2 / g) manufactured by Cabot Japan Ltd. Silica: ULTRASIL VN3 (N2SA 175 m 2 / g) manufactured by Evonik 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. Aromatic vinyl polymer: Sylvatraxx 4401 (copolymer of α-methylstyrene and styrene, softening point 85°C, Tg 43°C) manufactured by Arizona Chemical Wax: Oz Ace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Stearic acid: Tsubaki manufactured by NOF Corporation Zinc oxide: Ginrei R manufactured by Toho Zinc Co., Ltd. Sulfur: HK-200-5 (powder sulfur containing 5% by mass of oil) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Nocceler NS-G (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Vulcanization accelerator 2: Nocceler D (1,3-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0187] (Examples and Comparative Examples) According to the compounding formulations shown in each table, using a Banbury mixer, chemicals other than sulfur and vulcanization accelerators are kneaded at 60 rpm for 4 minutes to obtain a kneaded product. Sulfur and vulcanization accelerators are added to the kneaded product, and it is kneaded using a twin-screw open roll to obtain an unvulcanized rubber sheet (thickness: 4 mm). According to the specifications in each table, the unvulcanized rubber sheet is processed into the shape of tread rubber (center rubber, shoulder rubber), bonded to other tire members, and vulcanized at 170 °C for 15 minutes to obtain a test tire (with grooves spanning the center rubber and shoulder rubber) having the structure shown in FIGS. 1 to 2.

[0188] The following evaluations are performed using the test tire. The results are shown in each table. Note that the reference comparative example is Comparative Example 1.

[0189] <Viscoelasticity test> From inside the rubber layers of the center rubber and shoulder rubber of each test tire, viscoelasticity measurement samples with a length of 40 mm × width of 3 mm × thickness of 0.5 mm are taken such that the tire circumferential direction is the long side, and the E* values of the center rubber and shoulder rubber are obtained as measurement values under the conditions of a temperature of 30 °C or 70 °C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, and an elongation mode using an RSA series manufactured by TA Instruments. Note that the thickness direction of the sample is the tire radial direction.

[0190] <300% Modulus (M300)> From the samples taken from inside the rubber layers of the center rubber and shoulder rubber of each test tire, test pieces in the shape of No. 7 dumbbell with a thickness of 1 mm are prepared, and a tensile test is carried out at 20 °C based on JIS K6251:2010 to measure the 300% modulus (M300).

[0191] <Running performance (Cornering performance during cornering)> Regarding the grip performance of the tire (rear wheel), as an in-vehicle evaluation, the time when running on a circuit is compared with the reference tire by the following formula to obtain a relative value indicating how much it is reduced. The reference tire is a commercially available tire that does not fall under the present invention and has the slowest time. A higher numerical value indicates better cornering performance. (Cornering Performance Index) = [(Running time of reference tire - Running time of each test tire) / (Running time of reference tire - Running time of Comparative Example 1)] × 100 (Test vehicle) A motorcycle with a displacement of 750 cc Tires (front and rear): 120 / 70ZR17, 180 / 55ZR17 Rims: (front wheel) MT3.50x17, (rear wheel) MT5.50x17 Inner pressure: (front wheel) 250 kPa, (rear wheel) 290 kPa

[0192] [Table 1]

[0193] [Table 2]

[0194] The tire of the present invention (1) is a motorcycle tire having a tread portion provided with a tread rubber divided into at least three parts in the tire width direction, The tread rubber includes a center rubber disposed at the center in the tire width direction and shoulder rubbers disposed on both sides of the center rubber in the tire width direction, and has grooves extending across the center rubber and the shoulder rubbers, Both the center rubber and the shoulder rubbers have a silica content of 70 parts by mass or more per 100 parts by mass of the rubber component, The ratio (Si(S) / Si(C)) of the silica content Si(S) of the shoulder rubber to the silica content Si(C) of the center rubber is 0.80 or more and 0.95 or less, The tire for a two-wheeled vehicle is such that the ratio (M300(S) / M300(C)) of the 300% modulus M300(S) of the shoulder rubber to the 300% modulus M300(C) of the center rubber is 1.15 or more and 1.50 or less.

[0195] The present invention (2) is the tire for a two-wheeled vehicle according to the present invention (1), wherein the depth G of the groove is 10 mm or less.

[0196] The present invention (3) is the tire for a two-wheeled vehicle according to the present invention (1) or (2), wherein the ratio (70°C E*(S) / 70°C E*(C)) of the complex elastic modulus 70°C E*(S) of the shoulder rubber at 70°C to the complex elastic modulus 70°C E*(C) of the center rubber at 70°C exceeds 0.75 and is less than 1.25.

[0197] The present invention (4) is the tire for a two-wheeled vehicle in any combination of the present inventions (1) to (3), wherein the ratio (30°C E*(S) / 30°C E*(C)) of the complex elastic modulus 30°C E*(S) of the shoulder rubber at 30°C to the complex elastic modulus 30°C E*(C) of the center rubber at 30°C exceeds 0.75 and is less than 1.25.

[0198] In the present invention (5), both the center rubber and the shoulder rubber have a plasticizer content of 2 parts by mass or more and 85 parts by mass or less with respect to 100 parts by mass of the rubber component. The present invention (5) is the tire for a two-wheeled vehicle in any combination of the present inventions (1) to (4), wherein the aromatic vinyl polymer ratio P(S) in the plasticizer contained in the shoulder rubber is larger than the aromatic vinyl polymer ratio P(C) in the plasticizer contained in the center rubber.

[0199] The present invention (6) is the tire for a two-wheeled vehicle in any combination of the present inventions (1) to (5), wherein the content of styrene-butadiene rubber in the shoulder rubber is 70% by mass or more in 100% by mass of the rubber component.

[0200] The tire (7) of the present invention is a tire for a two-wheeled vehicle which is any combination of any one of the present inventions (1) to (6) in which at least one of the center rubber and the shoulder rubber contains a modified butadiene rubber.

Explanation of Signs

[0201] 1 Tire for two-wheeled vehicle 2 Tread portion 2A Tread surface 2e Tread edge 3 Sidewall portion 4 Bead portion 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 portion 11A Central longitudinal groove 11B Oblique groove 11C Bypass groove E1 One edge E2 The other edge α Camber angle N Normal L Road surface (contact surface) GW Groove width WT Tread width

Claims

1. A tire for a two-wheeled vehicle having a tread portion provided with a tread rubber divided into at least three parts in the tire width direction, wherein the tread rubber includes a center rubber disposed at the center in the tire width direction and shoulder rubbers disposed on both sides of the center rubber in the tire width direction, and has grooves extending across the center rubber and the shoulder rubbers, both the center rubber and the shoulder rubbers have a silica content of 70 parts by mass or more with respect to 100 parts by mass of the rubber component, the ratio (Si(S) / Si(C)) of the silica content Si(S) of the shoulder rubber to the silica content Si(C) of the center rubber is 0.80 or more and 0.95 or less, and the ratio (M300(S) / M300(C)) of the 300% modulus M300(S) of the shoulder rubber to the 300% modulus M300(C) of the center rubber is 1.15 or more and 1.50 or less, a tire for a two-wheeled vehicle.

2. The tire for a two-wheeled vehicle according to claim 1, wherein the depth G of the groove is 10 mm or less.

3. The tire for a two-wheeled vehicle according to claim 1, wherein the ratio (70°C E*(S) / 70°C E*(C)) of the complex elastic modulus 70°C E*(S) of the shoulder rubber at 70°C to the complex elastic modulus 70°C E*(C) of the center rubber at 70°C exceeds 0.75 and is less than 1.

25.

4. The tire for a two-wheeled vehicle according to claim 1, wherein the ratio (30°C E*(S) / 30°C E*(C)) of the complex elastic modulus 30°C E*(S) of the shoulder rubber at 30°C to the complex elastic modulus 30°C E*(C) of the center rubber at 30°C exceeds 0.75 and is less than 1.

25.

5. both the center rubber and the shoulder rubbers have a plasticizer content of 2 parts by mass or more and 85 parts by mass or less with respect to 100 parts by mass of the rubber component, and the aromatic vinyl polymer ratio P(S) in the plasticizer contained in the shoulder rubber is greater than the aromatic vinyl polymer ratio P(C) in the plasticizer contained in the center rubber, the tire for a two-wheeled vehicle according to claim 1.

6. The tire for a two-wheeled vehicle according to claim 1, wherein the content of styrene-butadiene rubber in 100% by mass of the rubber component of the shoulder rubber is 70% by mass or more.

7. The tire for a two-wheeled vehicle according to claim 1, wherein at least one of the center rubber and the shoulder rubbers contains a modified butadiene rubber.

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