JP7439483B2 - motorcycle tires - Google Patents

Description

The present invention relates to a motorcycle tire.

In order to improve the high-speed durability of motorcycle tires, a method is known in which the tread portion is composed of a cap tread (cap layer) and a base tread (base layer) arranged inside the cap tread in the tire radial direction. (For example, see Patent Document 1).

In recent years, silica is sometimes added to cap treads to ensure wet grip performance, etc. However, silica has inferior reinforcing properties compared to carbon black, so if carbon black is reduced and silica is added, High-speed durability tends to decrease. Therefore, further improvement in high-speed durability is required.

Japanese Patent Application Publication No. 2007-223376

An object of the present invention is to solve the above-mentioned problems and provide a motorcycle tire with excellent high-speed durability.

The present invention includes a tread portion in which a cap tread and a base tread are laminated, and a cap tread rubber composition constituting the cap tread contains isoprene rubber, silica, and carbon black, and the cap tread rubber composition contains isoprene rubber, silica, and carbon black, and The content of the isoprene-based rubber is 25% by mass or more, the base tread rubber composition constituting the base tread contains the isoprene-based rubber, and the content of the isoprene-based rubber in 100% by mass of the rubber component is It relates to a two-wheeled vehicle tire having a hardness of 45% by mass or more and a hardness of 50 or more at 25°C.

In the cap tread rubber composition, the carbon black content/silica content is preferably 1/5 to 5/5.

It is preferable that the cap tread rubber composition contains styrene butadiene rubber, and in the cap tread rubber composition, the content of the styrene butadiene rubber/the content of the isoprene rubber is 20/80 to 50/50. .

The present invention includes a tread portion in which a cap tread and a base tread are laminated, and a cap tread rubber composition constituting the cap tread contains isoprene rubber, silica, and carbon black, and the cap tread rubber composition contains isoprene rubber, silica, and carbon black, and The content of the isoprene-based rubber is 25% by mass or more, the base tread rubber composition constituting the base tread contains the isoprene-based rubber, and the content of the isoprene-based rubber in 100% by mass of the rubber component is Since the two-wheeled vehicle tire has a hardness of 45% by mass or more and a hardness of 50 or more at 25° C., excellent high-speed durability can be obtained.

The present invention includes a tread portion in which a cap tread and a base tread are laminated, and a cap tread rubber composition constituting the cap tread contains isoprene rubber, silica, and carbon black, and the cap tread rubber composition contains isoprene rubber, silica, and carbon black, and The content of the isoprene-based rubber is 25% by mass or more, the base tread rubber composition constituting the base tread contains the isoprene-based rubber, and the content of the isoprene-based rubber in 100% by mass of the rubber component is It is a two-wheeled vehicle tire having a hardness of 45% by mass or more and a hardness at 25° C. of 50 or more.

In the above motorcycle tire, silica and carbon black are blended into the cap tread rubber composition, and a predetermined amount of isoprene-based rubber is blended into both the cap tread rubber composition and the base tread rubber composition. The tear strength is increased and the adhesion between the cap tread and the base tread is improved. Furthermore, by setting the hardness of the base tread rubber composition to a certain value or higher, even if a filler that is easily distributed to the isoprene rubber is present at the interface between the cap tread and the base tread, fracture will occur starting at the interface. It becomes difficult. It is presumed that these effects provide excellent durability even during high-speed driving where deformation occurs rapidly.

<Cap tread rubber composition>
The cap tread rubber composition contains isoprene rubber as a rubber component.
Examples of isoprene rubber include isoprene rubber (IR), epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, natural rubber (NR), deproteinized natural rubber (DPNR), and high purity natural rubber (UPNR). , epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, and the like. These may be used alone or in combination of two or more. Among them, NR is preferable.

The content of isoprene rubber in 100% by mass of the rubber component may be 25% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, Moreover, it is preferably 90% or less, more preferably 80% by mass or less, still more preferably 75% by mass or less, particularly preferably 60% by mass or less. Within the above range, better effects tend to be obtained.

In the cap tread rubber composition, rubber components that can be used other than isoprene rubber include styrene-butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), and styrene-isoprene-butadiene copolymer rubber (SIBR). ) and other diene rubbers. These may be used alone or in combination of two or more. Among these, SBR is preferred.

The SBR is not particularly limited, and for example, emulsion polymerized styrene butadiene rubber (E-SBR), solution polymerized styrene butadiene rubber (S-SBR), etc. can be used. As commercially available products, products from Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

SBR may be either non-denatured SBR or modified SBR.
The modified SBR may be any SBR that has a functional group that interacts with a filler such as silica; for example, an end-modified SBR in which at least one end of the SBR is modified with a compound (modifier) having the above-mentioned functional group. SBR (terminally modified SBR having the above functional group at the end), main chain modified SBR having the above functional group in the main chain, main chain terminal modified SBR having the above functional group in the main chain and the end (for example, main chain modified SBR having the above functional group in the main chain) The main chain end-modified SBR which has the above-mentioned functional group and has at least one end modified with the above-mentioned modifier, or is modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and has a hydroxyl group. and terminal-modified SBR into which an epoxy group has been introduced.

Examples of the above functional groups include amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, and disulfide groups. group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group, etc. . Note that these functional groups may have a substituent. Among these, 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), an alkoxysilyl group ( An alkoxysilyl group having 1 to 6 carbon atoms is preferred.

Specific examples of compounds (modifiers) having the above functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, and 3-dimethylaminopropyltriethoxysilane. Examples include silane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane.

In addition, the above-mentioned modifiers include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; diglycidylated bisphenol A, etc. Polyglycidyl ethers of aromatic compounds having the above phenol groups; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; 4,4'-diglycidyl- Epoxy group-containing tertiary amines such as diphenylmethylamine, 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl orthotoluidine, tetraglycidylmethaxylene diglycidylamino compounds such as diamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane;

Amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidine carbonyl chloride, N,N-dimethylcarbamic acid chloride, N,N-diethylcarbamic acid chloride; 1 , 3-bis-(glycidyloxypropyl)-tetramethyldisiloxane, (3-glycidyloxypropyl)-pentamethyldisiloxane and other epoxy group-containing silane compounds;

(trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl]sulfide, (trimethylsilyl)[3 -(tributoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide sulfide group-containing silane compounds such as propoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide;

N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxy Silane, alkoxysilanes such as N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltriethoxysilane; 4-N,N-dimethylaminobenzophenone, 4-N,N- Di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino) ) Benzophenone, (thio)benzophenone compounds having an amino group and/or substituted amino group such as N,N,N',N'-bis-(tetraethylamino)benzophenone; 4-N,N-dimethylaminobenzaldehyde, 4- Benzaldehyde compounds having an amino group and/or substituted amino group such as N,N-diphenylaminobenzaldehyde, 4-N,N-divinylaminobenzaldehyde; N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N- N-substituted pyrrolidones such as phenyl-2-pyrrolidone, N-t-butyl-2-pyrrolidone, N-methyl-5-methyl-2-pyrrolidone; N-methyl-2-piperidone, N-vinyl-2-piperidone, N-substituted piperidones such as N-phenyl-2-piperidone; N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurirolactam, N-vinyl-ω-laurirolactam, N-substituted lactams such as N-methyl-β-propiolactam and N-phenyl-β-propiolactam;

N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5 -Triazine-2,4,6-triones, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3 -diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophene, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenyl) Also included are amino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, and the like.

The amount of styrene in SBR is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 37% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less. Within the above range, better effects tend to be obtained.
Note that the amount of styrene in SBR can be measured by ¹ H-NMR measurement.

The amount of vinyl in SBR is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 14% by mass or more, and preferably 40% by mass or less, more preferably 20% by mass or less. When the content is within the above range, better effects tend to be obtained.
Note that the vinyl content (1,2-bonded butadiene unit content) of SBR can be measured by infrared absorption spectroscopy.

The content of SBR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, particularly preferably 40% by mass or more, and preferably It is 75% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, particularly preferably 45% by mass or less. Within the above range, better effects tend to be obtained.

In the cap tread rubber composition, the SBR content (mass%)/isoprene rubber content (mass%) is preferably 20/80 or more, more preferably 40/60 or more, and preferably It is 50/50 or less. Within the above range, better effects tend to be obtained.

The cap tread rubber composition contains carbon black.
Carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, and the like. Commercially available products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Nippon Kayaku Carbon Co., Ltd., and Columbia Carbon Co., Ltd. can. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² /g or more, more preferably 100 m ² /g or more, even more preferably 114 m ² /g or more, and preferably 160 m ² /g. It is more preferably 140 m ² /g or less, still more preferably 125 m ² /g or less. Within the above range, better effects tend to be obtained.
Note that the N ₂ SA of carbon black is a value measured in accordance with JIS K6217-2:2001.

The content of carbon black is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and preferably 50 parts by mass or less, based on 100 parts by mass of the rubber component. More preferably it is 40 parts by mass or less, and still more preferably 35 parts by mass or less. Within the above range, better effects tend to be obtained.

The cap tread rubber composition contains silica.
Examples of silica include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and wet process silica is preferable because it has a large number of silanol groups. As commercially available products, products from EVONIK, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 100 m ² /g or more, more preferably 150 m ² /g or more, even more preferably 180 m ² /g or more, and preferably 250 m ² /g or less. , more preferably 220 m ² /g or less, still more preferably 200 m ² /g or less. Within the above range, better effects tend to be obtained.
Note that the nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, and preferably 100 parts by mass or less, more preferably 100 parts by mass of the rubber component. Preferably it is 80 parts by mass or less, more preferably 60 parts by mass or less. Within the above range, better effects tend to be obtained.

The total content of silica and carbon black is preferably 40 parts by mass or more, more preferably 60 parts by mass or more, even more preferably 70 parts by mass or more, and preferably 120 parts by mass, based on 100 parts by mass of the rubber component. parts, more preferably 100 parts by mass or less, still more preferably 90 parts by mass or less. Within the above range, better effects tend to be obtained.

In the cap tread rubber composition, the carbon black content (mass parts)/silica content (mass parts) is preferably 1/5 or more, more preferably 2/5 or more, and preferably 5/5 or more. /5 or less, more preferably 4/5 or less. Within the above range, better effects tend to be obtained.

It is preferable to use silica together with a silane coupling agent.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 3- Sulfide types such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto types such as NXT and NXT-Z manufactured by Momentive, vinyltriethoxysilane, and vinyl triethoxysilane. Vinyl type such as methoxysilane, amino type such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, glycidoxy such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. Examples include nitro types such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chloro types such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, products from EVONIK, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, and preferably 12 parts by mass or less, more preferably 8 parts by mass or less, based on 100 parts by mass of silica. It is. Within the above range, better effects tend to be obtained.

The cap tread rubber composition may contain an adhesive resin.
Adhesive resins include phenol resins, alkylphenol resins, terpene resins, coumaron resins, indene resins, coumaron indene resins, styrene resins, acrylic resins, rosin resins, which are commonly used in the tire industry. Aromatic hydrocarbon resins such as dicyclopentadiene resins (DCPD resins), aliphatic hydrocarbon resins such as C5 resins, C8 resins, C9 resins, and C5/C9 resins, and hydrogenation of these resins. Examples include things. Commercially available products include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Co., Ltd., Nippon Chemical Co., Ltd., and Japan Co., Ltd. Catalysts made by JXTG Energy Corporation, Nippon Zeon Corporation, Harima Kasei Co., Ltd., Toagosei Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of the adhesive resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, based on 100 parts by mass of the rubber component. It is. Within the above range, better effects tend to be obtained.

The cap tread rubber composition may contain wax.
The wax is not particularly limited, and includes petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable waxes and animal waxes; and synthetic waxes such as polymers of ethylene and propylene. As commercially available products, products from Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the rubber component. It is. Within the above range, better effects tend to be obtained.

The cap tread rubber composition may contain oil.
Examples of the oil include process oil, vegetable oil, or a mixture thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, etc. can be used. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Commercially available products include Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., JXTG Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu Co., Ltd., Fuji Kosan Co., Ltd., etc. products can be used. These may be used alone or in combination of two or more.

The oil content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and preferably 40 parts by mass or less, more preferably 40 parts by mass or more, based on 100 parts by mass of the rubber component. Preferably it is 30 parts by mass or less. Within the above range, better effects tend to be obtained.

The cap tread rubber composition may also include an anti-aging agent.
Examples of anti-aging agents 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; -isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, etc. p-phenylenediamine-based anti-aging agents; quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methylphenol; Monophenolic anti-aging agents such as styrenated phenol; bis-, tris-, and polyphenol-based aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, etc. Examples include inhibitors. As commercially available products, products from Seiko Kagaku Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., Flexis Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of the anti-aging agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 6 parts by mass or less, more preferably 3 parts by mass, based on 100 parts by mass of the rubber component. below. Within the above range, better effects tend to be obtained.

The cap tread rubber composition may contain stearic acid.
As the stearic acid, conventionally known ones can be used, and commercially available products such as those manufactured by NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., and Chiba Fatty Acid Corporation can be used. These may be used alone or in combination of two or more.

The content of stearic acid is preferably 1 part by mass or more, more preferably 2 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. be. Within the above range, better effects tend to be obtained.

The cap tread rubber composition may contain zinc oxide.
As zinc oxide, conventionally known ones can be used, and commercially available products include Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd. You can use products such as These may be used alone or in combination of two or more.

The content of zinc oxide is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 6 parts by mass or less, based on 100 parts by mass of the rubber component. be. When the content is within the above range, better effects tend to be obtained.

The cap tread rubber composition may contain sulfur.
Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc. commonly used in the rubber industry. As commercially available products, products manufactured by Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis, Nippon Kanditsu Kogyo Co., Ltd., Hosoi Chemical Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of sulfur is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 6 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the rubber component. . Within the above range, better effects tend to be obtained.

The cap tread rubber composition may contain a vulcanization accelerator.
Examples of the vulcanization accelerator include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis (2-benzothiazolyl disulfide); Thiuram-based vulcanization accelerators such as -ethylhexyl)thiuram disulfide (TOT-N); N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide ( TBBS), sulfenamide-based vulcanization accelerators such as N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide; diphenylguanidine, diorthotolylguanidine, ortho Guanidine-based vulcanization accelerators such as tolylbiguanidine can be mentioned. As commercially available products, products from Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of the vulcanization accelerator is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and preferably 8 parts by mass or less, more preferably 8 parts by mass or less, based on 100 parts by mass of the rubber component. is 5 parts by mass or less. Within the above range, better effects tend to be obtained.

In addition to the above components, the cap tread rubber composition contains additives commonly used in the tire industry, such as organic peroxides; calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. Fillers; etc. may be further blended. The content of these additives is preferably 0.1 to 200 parts by mass based on 100 parts by mass of the rubber component.

The cap tread rubber composition can be produced, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing the mixture.

As for the kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the final kneading step of kneading the vulcanizing agent and vulcanization accelerator, the kneading temperature is usually 120°C or less, preferably 85 to 110°C. Further, a composition obtained by kneading a vulcanizing agent and a vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. Vulcanization time is usually 5 to 15 minutes.

<Base tread rubber composition>
The base tread rubber composition can be manufactured using the same chemicals and in the same manner as the cap tread rubber composition.

The base tread rubber composition contains isoprene rubber as a rubber component.
The content of isoprene rubber in 100% by mass of the rubber component may be 45% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and preferably 90% by mass or less. , more preferably 80% by mass or less. Within the above range, better effects tend to be obtained.

The base tread rubber composition preferably contains SBR as a rubber component.
The content of SBR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and preferably 55% by mass or less, more preferably 40% by mass or less, even more preferably It is 30% by mass or less. Within the above range, better effects tend to be obtained.

The base tread rubber composition preferably contains carbon black.
The content of carbon black is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 60 parts by mass or more, and preferably 120 parts by mass or less, based on 100 parts by mass of the rubber component. The amount is more preferably 100 parts by mass or less, and still more preferably 80 parts by mass or less. Within the above range, better effects tend to be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 10 m ² /g or more, more preferably 25 m ² /g or more, even more preferably 35 m ² /g or more, and preferably 80 m ² /g. Below, it is more preferably 60 m ² /g or less, and still more preferably 50 m ² /g or less. Within the above range, better effects tend to be obtained.

The base tread rubber composition may contain silica, wax, stearic acid, anti-aging agent, zinc oxide, sulfur, vulcanization accelerator, etc. in addition to the above-mentioned components. These contents are the same as those explained for the cap tread rubber composition above.

<Motorcycle tires>
The motorcycle tire of the present invention is manufactured by a conventional method using the cap tread rubber composition and the base tread rubber composition.
That is, the cap tread rubber composition and the base tread rubber composition are extruded in the unvulcanized stage to fit the shapes of the cap tread and base tread, respectively, and then placed on a tire molding machine together with other tire components. An unvulcanized tire is formed by molding in a conventional manner. By heating and pressurizing this unvulcanized tire in a vulcanizer, a two-wheeled vehicle tire having a tread portion in which a cap tread and a base tread are laminated is obtained.

Note that when the tread portion is composed of a center rubber disposed at the center in the width direction of the tire and shoulder rubber disposed on both sides of the center rubber in the width direction of the tire, the above-mentioned cap is attached to the cap layer of the center rubber. It is preferable to use the above base tread rubber composition in the base layer of the center rubber.

In the two-wheeled vehicle tire, the base tread rubber composition has a hardness of 50 or more at 25°C. The upper limit is not particularly limited, but is preferably 60 or less, more preferably 55 or less, even more preferably 52 or less.

In the two-wheeled vehicle tire, it is preferable that the cap tread rubber composition and the base tread rubber composition have a small difference in hardness at 25°C. More specifically, the hardness difference is preferably 20 or less, more preferably 18 or less, even more preferably 16 or less, particularly preferably 15 or less, and may be 0 (the hardness is substantially the same). Within the above range, better effects tend to be obtained.
Further, it is preferable that the hardness of the base tread rubber composition at 25°C is smaller than the hardness of the cap tread rubber composition at 25°C.

The hardness of the rubber composition can be adjusted by adjusting the content of fillers such as silica and carbon black, the content of sulfur, the content of vulcanization accelerators, the content of softeners such as oil; It can be adjusted by using methods such as using fillers. Specifically, the hardness after vulcanization can be increased by increasing the amount of fillers, sulfur, and vulcanization accelerators, reducing the amount of softeners, and using fillers with small particle sizes, and adjustments can be made in line with these trends. It is possible.
Further, the hardness of the rubber composition can be measured by the method described in Examples after vulcanization.

The motorcycle tire described above can be suitably used as a motorcycle tire.

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

Below, various chemicals used in Examples and Comparative Examples will be explained.

<Chemicals used in cap tread rubber composition>
SBR (1): JSR0122 manufactured by JSR Corporation (styrene content: 37% by mass, vinyl content: 14% by mass, contains 34 parts by mass of oil per 100 parts by mass of rubber solid content)
NR:TSR20
BR: Ubepol BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass)
Carbon black (1): N220 (N ₂ SA: 114 m ² /g) manufactured by Cabot Japan Co., Ltd.
Silica: ULTRASIL VN3 manufactured by EVONIK (N ₂ SA: 180 m ² /g)
Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by EVONIK
Oil (1): A/O mix manufactured by Sankyo Yuka Kogyo Co., Ltd.
Sulfur: Powdered sulfur vulcanization accelerator (1) manufactured by Tsurumi Chemical Industry Co., Ltd.: Noxeler NS (N-tert-butyl-2-benzothiazylsulfenamide (TBBS) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) )

<Chemicals used in base tread rubber composition>
SBR (2): JSR1502 manufactured by JSR Corporation (styrene content: 24% by mass, vinyl content: 16% by mass)
NR:TSR20
Carbon black (2): N660 (N ₂ SA: 35 m ² /g) manufactured by Cabot Japan Co., Ltd.
Oil (2): PS-32 (mineral oil) manufactured by Idemitsu Kosan Co., Ltd.
Sulfur: Powdered sulfur vulcanization accelerator (2) manufactured by Tsurumi Chemical Industry Co., Ltd.: Noxela CZ (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

<Examples and comparative examples>
According to the formulation shown in Table 1, materials other than sulfur and the vulcanization accelerator were kneaded for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., and the kneaded product was mixed. Obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded for 5 minutes at 80°C using an open roll. A base tread rubber composition was obtained.
The unvulcanized cap tread rubber composition is molded into the shape of a cap tread, and the unvulcanized base tread rubber composition is molded into the shape of a base tread, and then bonded together with other tire components on a tire molding machine. A sulfurized tire was formed and vulcanized at 170° C. for 10 minutes to obtain a test tire (two-wheel vehicle tire).

The following evaluations were performed using the above test tires. The results are shown in Table 1.

(hardness)
A test piece was cut from the cap tread and base red rubber of the above test tire, and tested according to JIS K6253-3 (2012) "Vulcanized rubber and thermoplastic rubber - How to determine hardness - Part 3: Durometer hardness". The hardness at 25° C. (JIS-A hardness) was measured using a type A durometer.

(High speed durability)
The above test tire was attached to a drum testing machine, the rotational speed was gradually increased from 100 km/h, the speed at which failure occurred was measured, and the results were expressed as an index with Comparative Example 1 set as 100 (high-speed durability index). The larger the index, the greater the speed at which fracture occurs, indicating superior high-speed durability.

From Table 1, the cap tread rubber composition contains isoprene rubber, silica, and carbon black, the content of isoprene rubber in 100 mass % of the rubber component is 25% by mass or more, and the base tread rubber composition contains Examples containing isoprene-based rubber, in which the content of isoprene-based rubber in 100% by mass of the rubber component was 45% by mass or more, and the hardness at 25° C. was 50 or more, had excellent high-speed durability.

Claims (5)

Equipped with a tread section in which a cap tread and a base tread are laminated,
The cap tread rubber composition constituting the cap tread contains isoprene rubber, silica, and carbon black, and the content of the isoprene rubber in 100 mass % of the rubber component is 25% by mass or more,
The base tread rubber composition constituting the base tread contains isoprene-based rubber, the content of the isoprene-based rubber in 100% by mass of the rubber component is 45% by mass or more, and the hardness at 25 ° C. is 50 or more. ,
A two-wheeled vehicle tire in which the hardness of the base tread rubber composition at 25°C is smaller than the hardness of the cap tread rubber composition at 25°C . Equipped with a tread section in which a cap tread and a base tread are laminated,
The cap tread rubber composition constituting the cap tread contains isoprene rubber, silica, and carbon black, and the content of the isoprene rubber in 100 mass % of the rubber component is 25% by mass or more,
The base tread rubber composition constituting the base tread contains isoprene-based rubber, the content of the isoprene-based rubber in 100% by mass of the rubber component is 45% by mass or more, and the hardness at 25 ° C. is 50 or more and 53 or less. A motorcycle tire. The two-wheeled vehicle tire according to claim 1 or 2 , wherein in the cap tread rubber composition, the content of the carbon black/the content of the silica is 1/5 to 5/5. The cap tread rubber composition contains styrene butadiene rubber,
The motorcycle tire according to any one of claims 1 to 3, wherein in the cap tread rubber composition, the content of the styrene-butadiene rubber/the content of the isoprene rubber is 20/80 to 50/50. The motorcycle tire according to any one of claims 1 to 4, wherein the cap tread rubber composition contains oil, and the content of the oil is 20 parts by mass or more based on 100 parts by mass of the rubber component.