Rubber composition, tread rubber, and tire

Abstract

The present invention addresses the problem of providing a rubber composition which makes it possible to produce tires having improved wear resistance while attaining intact steering stability. This rubber composition comprises a rubber component, a reinforcing filler, and a liquid plasticizer, wherein the rubber component includes a polybutadiene rubber having a silica-reactive functional group derived from a functional compound represented by general formula (1) in an amount larger than 0 part by mass but not larger than 45 parts by mass per 100 parts by mass of the rubber component and includes a styrene / butadiene rubber in an amount of at least 55 parts by mass per 100 parts by mass of the rubber component.

Description

Rubber composition, tread rubber and tire

[0001] The present invention relates to a rubber composition, a tread rubber, and a tire.

[0002] BACKGROUND ART Conventionally, tire treads, particularly tire treads for motorcycles, have been required to have performance such as wear resistance, steering stability, and gripping ability, and various studies have been carried out to improve these performances.

[0003] For example, Patent Document 1 discloses a rubber composition for tires, which contains a rubber component containing a diene-based polymer modified with a polyfunctional compound having two or more epoxy groups in the molecule, silica, a specific silane coupling agent, and a coal-based resin and / or a petroleum-based resin, with the aim of improving fuel economy, handling stability, and grip performance.

[0004] Patent Document 2 discloses a motorcycle tire in which the tread rubber contains a rubber component containing a styrene-butadiene rubber and a modified conjugated diene polymer, and silica, with the rubber component containing styrene-butadiene rubber and a modified conjugated diene polymer being 40 to 120 parts by mass of a filler per 100 parts by mass of the rubber component, and the silica content in the filler is 80% by mass or more, with the aim of achieving both wet grip performance and abrasion resistance.

[0005] Furthermore, Patent Document 3 discloses a rubber composition for tires, which is intended to achieve both tire grip performance and ease of manufacturing, and which comprises a rubber component, a filler, and a softener, wherein the rubber component comprises at least one selected from styrene-butadiene rubber and butadiene rubber, the filler comprises silica and carbon black, the total content of the silica and the carbon black being 65 to 140 parts by mass per 100 parts by mass of the rubber component, the softener comprises a liquid softener component and a hydrogenated resin, the proportion of the hydrogenated resin in the total content of the softener being 40% by mass or more, and the hydrogenated resin has a softening point exceeding 110°C and a weight average molecular weight in terms of polystyrene of 200 to 1600 g / mol.

[0006] JP 2011-122090 A International Publication No. 2017 / 204236 JP 2022-187976 A

[0007] To further improve tire performance, it is necessary to achieve both steering stability and wear resistance of the tire. However, none of the above documents discusses achieving both steering stability and wear resistance of the tire. Therefore, there is a need for a technology that achieves both steering stability and wear resistance of the tire.

[0008] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a rubber composition that can improve the wear resistance while maintaining the steering stability of a tire. Another object of the present invention is to provide a tread rubber made of such a rubber composition, and to provide a tire that has improved wear resistance while maintaining steering stability.

[0009] The gist and configuration of the present invention to solve the above problems is as follows.

[0010] [1] A rubber composition comprising a rubber component, a reinforcing filler, and a liquid plasticizer, wherein the rubber component contains more than 0 parts by mass and not more than 45 parts by mass of a polybutadiene rubber having a silica-reactive functional group derived from a functional compound represented by the following general formula (1) per 100 parts by mass of the rubber component, and 55 parts by mass or more of a styrene-butadiene rubber per 100 parts by mass of the rubber component. [In general formula (1), A １ represents a monovalent epoxy group; R １ represents a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms); R ２ represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms), a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., having 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms), or a reactive group; R ３represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms) or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms); n is an integer of 0 to 2; ２ OR ３ If there is a ２ and / or OR ３ may be the same or different from one another; no active protons are included in the molecule and / or its partial condensation products.

[0011] [2] A in the general formula (1) １ is selected from a glycidoxy group, a 3,4-epoxycyclohexyl group, or a glycidyl group having a total of 3 to 8 carbon atoms, and the two terminal carbon atoms are in the epoxy ring, and the other end of the carbon chain is R １ The rubber composition according to [1], wherein the

[0012] [3] The rubber composition according to [1] or [2], wherein the reinforcing filler contains silica.

[0013] [4] The rubber composition according to [3], wherein the content of the silica is 70 parts by mass or more per 100 parts by mass of the rubber component.

[0014] [5] The rubber composition according to any one of [1] to [4], wherein the reinforcing filler contains carbon black.

[0015] [6] The rubber composition according to any one of [1] to [5], further comprising 25 parts by mass or less of a resin per 100 parts by mass of the rubber component.

[0016] [7] A tread rubber comprising the rubber composition according to any one of [1] to [6].

[0017] [8] A tire comprising the tread rubber according to [7].

[0018] [9] The tire according to [8], which is for a motorcycle.

[0019] According to the present invention, it is possible to provide a rubber composition that can improve the abrasion resistance while maintaining the steering stability of a tire. Furthermore, the present invention is also possible to provide a tread rubber made of such a rubber composition, and to provide a tire that has improved abrasion resistance while maintaining the steering stability.

[0020] The rubber composition, tread rubber, and tire of the present invention will be described in detail below by way of example based on embodiments thereof.

[0021] <Definitions> The compounds described herein may be derived in whole or in part from fossil resources, from biological resources such as plant resources, from recycled resources such as used tires, or from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0022] In the present invention, the term "liquid plasticizer" does not include the extender oil and resin of the oil extender contained in the rubber component.

[0023] In this specification, examples of the "divalent hydrocarbon group" include a linear or branched alkylene group, an alkenylene group, an alkynylene group, a cycloalkylene group, an arylene group, and an aralkylene group (a divalent group having an alkylene group and an arylene group).

[0024] In this specification, the "aliphatic hydrocarbon group" may be either a straight-chain or branched type, and may have an unsaturated bond in its structure. That is, when the aliphatic hydrocarbon group has two or more carbon atoms, one or more -CH ２ -CH ２ Each - may independently be substituted by -CH=CH- or -C≡C-. Examples of the aliphatic hydrocarbon group include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a s-butyl group, a t-butyl group, a pentyl group, a hexyl group, a decyl group, and a dodecyl group; alkenyl groups such as a vinyl group, an allyl group, and a 1-butenyl group; and alkynyl groups such as an ethynyl group and a propynyl group.

[0025] In this specification, examples of the "aromatic hydrocarbon group" include a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a diphenylmethyl group, a diphenylethyl group, a diphenylpropyl group, a methylphenyl group, a dimethylphenyl group, an ethylphenyl group, and a propylphenyl group.

[0026] In this specification, the "alkyl group" may be a linear, branched, or cyclic alkyl group, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a tert-pentyl group, a neopentyl group, a 1,2-dimethylpropyl group, an n-hexyl group, an isohexyl group, a (n-)heptyl group, a (n-)octyl group, a (n-)nonyl group, a (n-)decyl group, a (n-)undecyl group, a (n-)dodecyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and a cyclononyl group. Examples of the "alkylene group" include a divalent group obtained by removing any one hydrogen atom from the "alkyl group".

[0027] In this specification, examples of an "alkenyl group" include an ethynyl group, a 1-propynyl group, a 2-propynyl group, a 2-butynyl group, a pentynyl group, a hexynyl group, a vinyl group, an allyl group, and an isopropenyl group. Examples of an "alkenylene group" include a divalent group obtained by removing any one hydrogen atom from the aforementioned "alkenyl group."

[0028] In this specification, examples of the "alkynyl group" include an ethynyl group, a propargyl group, a 2-butynyl group, a 3-butynyl group, a 2-pentynyl group, a 3-pentynyl group, a 4-pentynyl group, a 2-hexynyl group, a 3-hexynyl group, a 4-hexynyl group, a 5-hexynyl group, etc. Incidentally, examples of the "alkynylene group" include a divalent group obtained by removing any one hydrogen atom from the above-mentioned "alkynyl group".

[0029] In this specification, the term "aryl group" refers to a monovalent aromatic hydrocarbon group, which may be either monocyclic or polycyclic, and includes those having 6 to 18 carbon atoms, such as a phenyl group, a 1-naphthyl group, a 2-naphthyl group, an anthryl group, a phenanthryl group, a pyrenyl group, an indenyl group, and an indanyl group.

[0030] In this specification, the term "arylene group" refers to a divalent group having a monocyclic or polycyclic aromatic ring. Examples of the arylene group include a phenylene group, a naphthylene group, an anthranylene group, and a phenanthranylene group.

[0031] In this specification, examples of the "alkoxy group (alkyloxy group)" include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a 2-ethylhexyloxy group, an octyloxy group, and a nonyloxy group.

[0032] <Rubber Composition> The rubber composition of the present embodiment includes a rubber component, a reinforcing filler, and a liquid plasticizer, wherein the rubber component includes more than 0 part by mass and not more than 45 parts by mass of a polybutadiene rubber having a silica-reactive functional group generated from a functional compound represented by the following general formula (1), per 100 parts by mass of the rubber component, and includes 55 parts by mass or more of a styrene-butadiene rubber, per 100 parts by mass of the rubber component: [In general formula (1), A １ represents a monovalent epoxy group; R １ represents a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms); R ２ represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms), a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., having 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms), or a reactive group; R ３represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms) or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms); n is an integer of 0 to 2; ２ OR ３ If there is a ２ and / or OR ３ may be the same or different from one another; no active protons are included in the molecule and / or its partial condensation products.

[0033] The rubber composition can improve the abrasion resistance while maintaining the steering stability of the tire. In the rubber composition of the present embodiment, by containing a polybutadiene rubber having a silica-reactive functional group generated from the functional compound of the general formula (1), the dispersibility of the reinforcing filler in the rubber composition can be improved more than before, and it is thought that the abrasion resistance can be improved without deteriorating the steering stability of the tire to which the rubber composition is applied.

[0034] (Rubber Component) The rubber composition of this embodiment contains a rubber component, which provides rubber elasticity to the rubber composition. The rubber component contains a polybutadiene rubber having a silica-reactive functional group derived from the functional compound represented by the general formula (1) above, and a styrene-butadiene rubber. In addition to these, the rubber component may also contain other rubber components.

[0035] In the rubber composition of this embodiment, the rubber component may be partially or entirely oil-extended. When the rubber component is oil-extended, the extender oil is classified as a softener, which will be described later. In the present invention, the extender oil is not included in the liquid plasticizer.

[0036] [Polybutadiene rubber having silica-reactive functional groups derived from functional compounds represented by general formula (1)] The polybutadiene rubber (BR) contained in the rubber component has silica-reactive functional groups derived from the functional compounds represented by general formula (1). As described above, the presence of the silica-reactive groups in the butadiene rubber in the rubber composition increases the dispersibility of the reinforcing filler, and improves the wear resistance of the tire without reducing the steering stability.

[0037] The rubber component contains more than 0 parts by mass and not more than 45 parts by mass of a polybutadiene rubber having a silica-reactive functional group derived from a functional compound represented by the general formula (1) above, per 100 parts by mass of the rubber component. The rubber component contains the polybutadiene rubber in the above range, resulting in a rubber composition that can improve abrasion resistance while maintaining tire steering stability. From the viewpoint of improving abrasion resistance, the rubber composition of this embodiment preferably contains 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more of the polybutadiene rubber having a silica-reactive functional group derived from a functional compound represented by the general formula (1) above, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of a balance between maintaining steering stability and improving abrasion resistance, the rubber composition preferably contains 40 parts by mass or less, more preferably 35 parts by mass or less, of the polybutadiene rubber having a silica-reactive functional group derived from a functional compound represented by the general formula (1) above, per 100 parts by mass of the rubber component.

[0038] The polybutadiene rubber preferably has a cis bond content of at least 95% (e.g., 95%, 96%, 97%, 98%, 99% or more), a glass transition temperature (Tg) of less than -101°C (e.g., -102°C, -103°C, -104°C, -105°C, -106°C, -107°C, -108°C, -109°C, -110°C, -111°C, -112°C or less), preferably less than -101°C or -110°C (e.g., -102°C, -103°C, -104°C, -105°C, -106°C, -107°C, -108°C, -109°C, or -110°C), and has silica-reactive functional groups. In certain embodiments, the Tg of the polybutadiene rubber is less than -101°C and greater than or equal to -110°C. The cis bond content refers to the cis 1,4-bond content. The cis 1,4-bond content and vinyl bond content in this specification are determined by the following formula: ２The cis content of the polybutadiene rubber is measured by FTIR (Fourier Transform Infrared Spectroscopy) in which the polybutadiene rubber is dissolved in a 1,4-dimethylaminopropylamine and then subjected to FTIR. More preferably, the polybutadiene rubber has a cis 1,4-bond content of at least 98% (e.g., 98%, 99% or more) or at least 99% (e.g., 99%, 99.5% or more). Because the polybutadiene rubber has a high cis bond content (i.e., at least 95% as described above), the vinyl bond content can be low. In certain embodiments, the polybutadiene rubber has a vinyl bond content of less than 4% (e.g., 3.9%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, etc.), preferably less than 3% (e.g., 2.5%, 2%, 1.5%, 1%, 0.5%, etc.), and more preferably less than 2% (e.g., 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, etc.). In certain embodiments, the polybutadiene rubber used in the rubber composition has a Tg of -105°C or lower (e.g., -105°C, -106°C, -107°C, -108°C, -109°C or lower), for example, -105 to -110°C. In certain embodiments, the polybutadiene rubber contains less than 3% by weight (e.g., 3%, 2%, 1%, or less), preferably less than 1% by weight (e.g., 1%, 0.5%, or less) or 0% by weight of syndiotactic 1,2-polybutadiene. Generally, according to one embodiment, one or more polybutadiene rubbers having a cis-bond content of at least 95%, a Tg of less than -101°C, and silica-reactive functional groups can be used. In certain embodiments, the polybutadiene rubber consists solely of one polybutadiene having a cis-bond content of at least 95% (e.g., 95%, 96%, 97%, 98%, 99%, or more) and a Tg of less than -101°C. In preferred embodiments, the amount of any polybutadiene rubber having a high vinyl content (i.e., about 70% as described above) is less than 25 parts by weight (per 100 parts by weight of the total rubber composition), more preferably less than 10 parts by weight, and even more preferably less than 5 parts by weight or 0 parts by weight.

[0039] As described above, the polybutadiene rubber may be a polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than −101° C., and silica-reactive functional groups. In certain embodiments, the Tg of the polybutadiene rubber is less than −101° C. and greater than or equal to −110° C. (e.g., −102° C., −103° C., −104° C., −105° C., −106° C., −107° C., −108° C., −109° C., −110° C.), or between −105° C. and −110° C. (e.g., −105° C., −106° C., −107° C., −108° C., −109° C., −110° C.).

[0040] The weight average molecular weight (Mw) of the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101°C, preferably less than -101°C and greater than or equal to -110°C, and having silica-reactive functional groups may vary. In certain embodiments, the polybutadiene rubber has a cis bond content of at least 95%, a Tg of less than -101°C, more preferably less than -101°C and at least -110°C, and the polybutadiene rubber having silica-reactive functional groups has a weight average molecular weight (Mw) of 450,000 to 700,000 g / mol (e.g., 450,000, 500,000, 550,000, 600,000, 650,000, or 700,000 g / mol), preferably a Mw of 500,000 to 650,000 g / mol (e.g., 500,000, 525,000, 550,000, 575,000, 600,000, 625,000, or 650,000 g / mol). Mw ranges varying within the aforementioned ranges, such as 500,000 to 600,000 g / mol, 550,000 to 600,000 g / mol, 450,000 to 600,000 g / mol, and 500,000 to 700,000 g / mol, may also be utilized in certain embodiments. The polybutadiene rubber having silica-reactive functional groups preferably has a number average molecular weight (Mn) of 180,000 to 300,000 g / mol (e.g., 180,000, 200,000, 220,000, 240,000, 250,000, 260,000, 280,000, or 300,000 g / mol), and more preferably has an Mn of 200,000 to 280,000 g / mol (e.g., 200,000, 220,000, 240,000, 250,000, 260,000, or 280,000). Ranges of Mn varying within the aforementioned ranges, such as 200,000 to 250,000 g / mol, 230,000 to 280,000 g / mol, 180,000 to 280,000 g / mol, and 200,000 to 280,000 g / mol, may also be utilized in certain embodiments.In certain embodiments, the polybutadiene rubber has a cis bond content of at least 95%, a Tg of less than -101°C, preferably less than -101°C and equal to or greater than -110°C, and has silica-reactive functional groups, and the polybutadiene rubber preferably has a Mw of 450,000 to 700,000 g / mol (or within the aforementioned ranges, as described above) and a Mn of 180,000 to 300,000 g / mol (or within the aforementioned ranges, as described above). The aforementioned Mw and Mn values ​​for the polybutadiene rubber refer to values ​​measured by GPC using standard polystyrene. Similarly, the aforementioned Mw and Mn values ​​for the polybutadiene rubber refer to the bound Mw and bound Mn, not the base polymer values.

[0041] In certain embodiments disclosed herein, as noted above, the at least one polybutadiene rubber may be an oil-extended rubber. In other preferred embodiments disclosed herein, the at least one polybutadiene rubber is a non-oil-extended rubber (i.e., the BR is not extended with oil).

[0042] In the rubber composition disclosed herein, by using a polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101°C, preferably less than -101 to -110°C, and having silica-reactive functional groups, it is possible, in certain embodiments, to improve abrasion resistance and handling stability compared to a control rubber composition using a non-functionalized polybutadiene having a cis bond content of at least 95% and a Tg of less than -101°C.

[0043] -Functionalized Compound- The polybutadiene rubber contained in the rubber composition of this embodiment has a silica-reactive functional group derived from a functional compound represented by the following general formula (1): According to a specific embodiment, the polybutadiene rubber contains a silica-reactive functional group containing a silicon-containing functional group having a siloxy group (e.g., a hydrocarbyloxysilane-containing compound), and the compound optionally contains a monovalent group having at least one functional group. Such a silicon-containing functional group may be added by reacting an active end of the polymer chain with a compound having the following general formula (1): [In general formula (1), A １represents a monovalent epoxy group; R １ represents a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms); R ２ represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms), a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., having 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms), or a reactive group; R ３ represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms) or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms); n is an integer of 0 to 2; ２ OR ３ If there is a ２ and / or OR ３ may be the same or different from one another; no active protons are included in the molecule and / or its partial condensation products.

[0044] A partial condensation product refers to a product in which some (but not all) of the SiOR groups in the hydrocarbyloxysilane compound have been converted to SiOSi bonds through condensation. In certain embodiments, at least one of the following is satisfied: (a) R １ represents a divalent hydrocarbon group having 1 to 20 carbon atoms, 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 2 to 3 carbon atoms (e.g., 2 or 3 carbon atoms); (b) R ３represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, 6 carbon atoms), or 1 to 2 carbon atoms (e.g., 2 or 3 carbon atoms), or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms or 6 to 8 carbon atoms; (c) R ２ represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, 6 carbon atoms), or 1 to 2 carbon atoms (e.g., 2 or 3 carbon atoms), or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or 6 to 8 carbon atoms; in certain such embodiments, each of (a), (b), and (c) is satisfied, and R １ , R ３ , and R ２ is selected from one of the above groups.

[0045] The particular epoxy group present in general formula (1) that functionalizes the compound may vary. In certain embodiments, the epoxy group (i.e., A in general formula (1) above) １ ) is a glycidoxy group, a 3,4-epoxycyclohexyl group, or a glycidyl group having a total of 3 to 8 (e.g., 3, 4, 5, 6, 7, or 8), preferably 3 to 6 (e.g., 3, 4, 5, or 6) carbon atoms (the two terminal carbon atoms are in the epoxy ring and the other end of the carbon chain is R １ In this embodiment, the polybutadiene rubber is bonded to an epoxy group (i.e., A １ The polybutadiene rubber has silica-reactive functional groups resulting from the use of a functionalized compound of general formula (1) in which the epoxy group (i.e., A) is selected from glycidyl groups. １ In certain embodiments, the polybutadiene rubber has silica-reactive groups resulting from the use of a functionalized compound of general formula (1) in which the epoxy groups (i.e., A) are selected from 3,4-epoxycyclohexyl groups. １) is a glycidyl group having a total of 3 to 8 (e.g., 3, 4, 5, 6, 7, or 8), preferably 3 to 6 (e.g., 3, 4, 5, or 6) carbons (the two terminal carbons are in the epoxy ring and the other end of the carbon chain is R ｃ The silica-reactive functional groups are generated by using a functionalizing compound of formula (1) selected from: Non-limiting specific examples of such functionalized compounds of general formula (1) containing epoxy groups include 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, (2-glycidoxyethyl)methyldimethoxysilane, (2-glycidoxyethyl)methyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl)methyldimethoxysilane, (3-glycidoxypropyl)methyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl(methyl)diethoxysilane, and the like. Among these, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethoxydiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane are particularly preferred.

[0046] In the above general formula (1), A １ represents a monovalent epoxy group (a group containing an epoxy bond). １ is preferably selected from a glycidoxy group, a 3,4-epoxycyclohexyl group, or a glycidyl group having a total of 3 to 8 carbon atoms. In this specification, the term "epoxy group" refers to a group having an oxirane ring structure, and includes a glycidoxy group, an epoxycyclohexyl group, a glycidyl group, a glycidyloxy group-substituted alkyl group, etc. Furthermore, the glycidyl group having a total of 3 to 8 carbon atoms includes a glycidyl group, a glycidyloxy group-substituted alkyl group, etc., and specific examples thereof include a glycidyl group, a 2-glycidoxyethyl group, a 3-glycidoxypropyl group, etc.

[0047] The glycidyl groups having a total of 3 to 8 carbon atoms are preferably glycidyl groups having 3 to 6 carbon atoms.

[0048] In the general formula (1), n ​​is an integer of 0 to 2, preferably an integer of 1 to 2, and more preferably 1. When n is an integer of 1 to 2, the polybutadiene rubber having a silica-reactive functional group generated from the compound represented by general formula (1) can further improve the dispersibility of the reinforcing filler, and can further improve the wear resistance of a tire to which the rubber composition of this embodiment is applied, which is preferable.

[0049] [Styrene-butadiene rubber] The rubber component contains styrene-butadiene rubber (SBR). The rubber component contains 55 parts by mass or more of the styrene-butadiene rubber per 100 parts by mass of the rubber component. When the rubber component contains 55 parts by mass or more of the styrene-butadiene rubber per 100 parts by mass of the rubber component, a rubber composition is obtained that can improve abrasion resistance while maintaining the steering stability of the tire. From the viewpoint of improving steering stability, the rubber component contains 55 parts by mass or more of the styrene-butadiene rubber per 100 parts by mass of the rubber component, preferably 60 parts by mass or more, and more preferably 65 parts by mass or more. Furthermore, from the viewpoint of abrasion resistance, the rubber component contains preferably 90 parts by mass or less of the styrene-butadiene rubber per 100 parts by mass of the rubber component, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less.

[0050] The styrene-butadiene rubber may be unmodified, modified, or a blend of unmodified and modified styrene-butadiene rubbers. The styrene-butadiene rubber may also be oil-extended.

[0051] The styrene-butadiene rubber preferably has a styrene content of 5 to 50% by mass, more preferably 8 to 45% by mass. If the styrene content of the styrene-butadiene rubber is 5% by mass or more, the abrasion resistance of the rubber composition is further improved. The styrene unit can be determined by an infrared method (Morello method).

[0052] [Other Rubbers] The rubber component may further contain other rubbers, and the content of the other rubbers in the rubber component is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and may even be 0% by mass. Examples of such other rubbers include natural rubber (NR), polybutadiene rubber other than polybutadiene rubber having a silica-reactive functional group derived from a functional compound represented by general formula (1), isoprene rubber (IR), chloroprene rubber (CR), styrene-isoprene rubber (SIR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), halogenated butyl rubber, etc. These other rubbers may be used alone or in combination of two or more.

[0053] (Reinforcing Filler) The rubber composition of this embodiment contains a reinforcing filler. The reinforcing filler reinforces the rubber composition and can improve the fracture properties of the rubber composition. The reinforcing filler may be used alone or in combination of two or more.

[0054] In the rubber composition of this embodiment, the total content of the reinforcing filler is preferably 65 parts by mass or more and 140 parts by mass or less per 100 parts by mass of the rubber component. By including the reinforcing filler in the above range, it is possible to improve abrasion resistance while maintaining steering stability. The total content of the reinforcing filler is preferably 70 parts by mass or more, and more preferably 80 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, the total content of the reinforcing filler is more preferably 120 parts by mass or less, and even more preferably 100 parts by mass or less, per 100 parts by mass of the rubber component.

[0055] [Silica] In the rubber composition of the present embodiment, the reinforcing filler preferably contains silica, which can contribute to maintaining the steering stability of a tire to which the rubber composition is applied.

[0056] The content of silica in the rubber composition is preferably 70 parts by mass or more per 100 parts by mass of the rubber component. When the content of silica is 70 parts by mass or more per 100 parts by mass of the rubber component, handling stability can be improved, which can contribute to maintaining handling stability. From the viewpoint of improving handling stability, the content of silica is more preferably 75 parts by mass or more per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of a balance between maintaining handling stability and improving abrasion resistance, the content of silica is preferably 100 parts by mass or less, more preferably 95 parts by mass or less, and even more preferably 90 parts by mass or less per 100 parts by mass of the rubber component.

[0057] Silica has a nitrogen adsorption specific surface area (BET method) of 80m ２ / g or more 330m ２ The nitrogen adsorption specific surface area (BET method) of silica is preferably less than 80 m ２ / g or more, a tire using the rubber composition can be sufficiently reinforced. ２ When the specific surface area is less than 100 m / g, the elastic modulus of the rubber composition does not become too high, and the deterioration of the steering stability of a tire using the rubber composition can be suppressed. ２ / g or more, and ２ / g or more, and ２ / g or more, and ２ / g or more, and ２ / g or more, and ２ / g or more, and ２ / g or more, and ２ From the viewpoint of maintaining the steering stability of the tire at a higher level, the nitrogen adsorption specific surface area (BET method) of the silica is more preferably 300 m ２ / g or less, and ２ / g or less is more preferable, and 270m ２ It is more preferable that the tensile strength is 1 / g or less.

[0058] The silica preferably has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 150 m ２ / g or more, more preferably 150 to 300m ２ / g, and even more preferably 150 to 250 m ２ / g, particularly preferably 150 to 220 m ２ / g. CTAB is 150m ２ When the CTAB is 300 m / g or more, a tire to which the rubber composition is applied can be sufficiently reinforced. ２ When the modulus of elasticity of the rubber composition is not too high, deterioration in the steering stability of a tire using the rubber composition can be suppressed.

[0059] Examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate, and among these, wet silica is preferred. These silicas may be used alone or in combination of two or more.

[0060] In the rubber composition of this embodiment, when both silica and carbon black described below are contained, the ratio of silica in the total content of silica and carbon black is preferably 50% by mass or more and 95% by mass or less. When the ratio of silica in the total content of silica and carbon black is within the above range, the tire can maintain a higher level of steering stability while improving wear resistance. From the viewpoint of maintaining steering stability, the ratio of silica in the total content of silica and carbon black is more preferably 70% by mass or more, and even more preferably 85% by mass or more.

[0061] [Carbon Black] The rubber composition of the present embodiment preferably contains carbon black. Carbon black can improve the fracture properties of the rubber composition. Furthermore, the rubber composition of the present embodiment more preferably contains silica and carbon black.

[0062] The content of carbon black in the rubber composition is preferably more than 0 parts by mass and not more than 20 parts by mass per 100 parts by mass of the rubber component. By having the content of carbon black be more than 0 parts by mass and not more than 20 parts by mass per 100 parts by mass of the rubber component, deterioration in handling stability can be suppressed and abrasion resistance can be improved.

[0063] The nitrogen adsorption specific surface area of ​​carbon black (N ２ SA) is not particularly limited and can be selected appropriately depending on the purpose, but ２ / g or more. ２ SA) is 70m ２ / g or more, the abrasion resistance can be improved satisfactorily. ２ SA) can be measured in accordance with JIS K 6217-2:2001.

[0064] The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. These carbon blacks may be used alone or in combination of two or more.

[0065] [Other Reinforcing Fillers] The reinforcing filler may contain other reinforcing fillers in addition to the above-mentioned silica and carbon black. Examples of other reinforcing fillers include, but are not limited to, clay, talc, calcium carbonate, aluminum hydroxide, etc. When these other reinforcing fillers are contained, the content thereof can be appropriately changed within a range that does not impair the effects of the present invention.

[0066] (Softener) A softener is a compound that has the effect of softening a rubber composition. Examples of softeners include liquid plasticizers and resins, which will be described later, and extender oils contained in the oil extender contained in the rubber component. In the present invention, the liquid plasticizer does not include the extender oil and resin contained in the rubber component.

[0067] In the rubber composition of the present embodiment, the total content of the softeners is preferably 40 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the rubber component. When the total content of the softeners is within the above range, the tire can maintain its steering stability and improve its wear resistance.

[0068] [Liquid Plasticizer] The rubber composition of the present embodiment contains a liquid plasticizer. By containing the liquid plasticizer in the rubber composition, it is possible to improve the abrasion resistance while maintaining the steering stability of the tire. Here, the liquid plasticizer is liquid at 25°C (room temperature).

[0069] Examples of liquid plasticizers include oils. Examples of such oils include, but are not limited to, petroleum-based softeners such as aromatic oils, paraffinic oils, and naphthenic oils; and plant-based softeners such as palm oil, castor oil, cottonseed oil, and soybean oil. Among these, petroleum-based softeners such as aromatic oils, paraffinic oils, and naphthenic oils are preferred.

[0070] The amount of the liquid plasticizer is preferably 5 parts by mass or more, and more preferably 9 parts by mass or more, per 100 parts by mass of the rubber component from the viewpoint of improving abrasion resistance, and is preferably 30 parts by mass or less, and more preferably 26 parts by mass or less, per 100 parts by mass of the rubber component from the viewpoint of suppressing deterioration in handling stability.

[0071] [Resin] The rubber composition of the present embodiment preferably further contains a resin. When the rubber composition contains a resin, deterioration in handling stability can be suppressed. As the resin, C ５ based resin, C ５ -C ９ based resin, C ９ Examples of the resins include terpene-based resins, terpene-based resins (including terpene-aromatic compound-based resins), dicyclopentadiene-based resins, and alkylphenol-based resins. These resins may be used alone or in combination of two or more. The resins may also be hydrogenated.

[0072] C ５ As a resin based on C, there is C obtained by thermal decomposition of naphtha in the petrochemical industry.５ and aliphatic petroleum resins obtained by (co)polymerizing the distillate. ５ The fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. ５ Commercially available resins can be used.

[0073] C ５ -C ９ The C-based resin is ５ -C ９ It refers to synthetic petroleum resin, ５ -C ９ Examples of the resin include petroleum-derived C ５ -C １１ The fraction was treated with AlCl ３ , B.F. ３ Examples of the solid polymers include those obtained by polymerization using a Friedel-Crafts catalyst such as C ５ -C ９ Examples of the C-based resin include copolymers containing styrene, vinyltoluene, α-methylstyrene, indene, etc. as the main component. ５ -C ９ As the resin, ９ Resins containing less of the above components are preferred from the viewpoint of compatibility with the rubber component. ９ "Low amount of the above components" means that the C ９ This means that the above components are contained in an amount of less than 50% by mass, preferably 40% by mass or less. ５ -C ９ Commercially available resins can be used.

[0074] C ９ The C-based resin is ９ This refers to synthetic petroleum resins, such as AlCl ３ or BF ３ Using a Friedel-Crafts type catalyst such as C ９ It refers to a solid polymer obtained by polymerizing the fraction. ９Examples of the resin include copolymers containing indene, α-methylstyrene, vinyltoluene, etc. as main components.

[0075] Terpene resins are solid resins obtained by blending turpentine, which is obtained simultaneously with the extraction of rosin from pine trees, or polymerization components separated therefrom, and polymerizing them using a Friedel-Crafts catalyst. Examples include β-pinene resin and α-pinene resin. Terpene resins also include terpene-aromatic compound resins, representative examples of which include terpene-phenol resin and styrene-terpene resin. Terpene-phenol resins can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing the terpene with formalin. Styrene-terpene resins can be obtained by reacting styrene with terpenes using a Friedel-Crafts catalyst. The terpenes used as raw materials are not particularly limited; monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred.

[0076] Dicyclopentadiene resins include, for example, AlCl ３ or BF ３ This refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as

[0077] The alkylphenol resin refers to a phenol resin having an alkyl group, and examples thereof include alkylphenol-acetylene resins such as p-tert-butylphenol-acetylene resin, and alkylphenol-formaldehyde resins with a low degree of polymerization.

[0078] The rubber composition of this embodiment preferably contains 25 parts by mass or less of the resin per 100 parts by mass of the rubber component. When the resin is contained in an amount of 25 parts by mass or less per 100 parts by mass of the rubber component, the tire can maintain a higher level of steering stability while further improving wear resistance. The rubber composition more preferably contains 20 parts by mass or less of the resin per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of improving steering stability, the rubber composition preferably contains 5 parts by mass or more of the resin per 100 parts by mass of the rubber component, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more.

[0079] (Styrenic Thermoplastic Elastomer) The rubber composition of this embodiment may contain a styrene-based thermoplastic elastomer (TPS). The styrene-based thermoplastic elastomer (TPS) has a styrene-based polymer block (hard segment) and a conjugated diene-based polymer block (soft segment). The styrene-based polymer portion forms physical crosslinks to serve as crosslinking points, while the conjugated diene-based polymer block imparts rubber elasticity. The double bonds of the conjugated diene-based polymer block (soft segment) may be partially or completely hydrogenated. Note that the styrene-based thermoplastic elastomer (TPS) is thermoplastic, while the rubber component (preferably, a diene-based rubber) is not thermoplastic. Therefore, in this specification, the styrene-based thermoplastic elastomer (TPS) is not included in the rubber component. The content of the styrene-based thermoplastic elastomer (TPS) is preferably in the range of 1 to 30 parts by mass per 100 parts by mass of the rubber component.

[0080] Examples of the styrene-based thermoplastic elastomer (TPS) include styrene / butadiene / styrene (SBS) block copolymers, styrene / isoprene / styrene (SIS) block copolymers, styrene / butadiene / isoprene / styrene (SBIS) block copolymers, styrene / isoprene (SI) block copolymers, styrene / butadiene / isoprene (SBI) block copolymers, styrene / ethylene / butylene / styrene (SEBS) block copolymers, styrene / ethylene / propylene / styrene (SEPS) block copolymers, styrene / ethylene / ethylene / propylene / styrene (SEEPS) block copolymers, styrene / ethylene / butylene (SEB) block copolymers, styrene / ethylene / propylene (SEP) block copolymers, and styrene / ethylene / ethylene / propylene (SEEP) block copolymers.

[0081] (Other Components) The rubber composition of the present embodiment may contain the above-described rubber component, reinforcing filler, softener, and styrene-based thermoplastic elastomer, as well as various components commonly used in the rubber industry, such as silane coupling agents, antioxidants, stearic acid, zinc oxide (zinc white), vulcanization accelerators, and vulcanizing agents, as needed, selected appropriately within the scope of the present invention. Commercially available products can be suitably used as these compounding ingredients.

[0082] Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N ,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, etc. The content of the silane coupling agent is preferably in the range of 2 to 20 parts by mass, more preferably in the range of 5 to 15 parts by mass, per 100 parts by mass of silica.

[0083] Examples of the antioxidant include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6C), 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), N,N'-diphenyl-p-phenylenediamine (DPPD), etc. The content of the antioxidant is not particularly limited, but is preferably in the range of 0.1 to 15 parts by mass, and more preferably in the range of 1 to 10 parts by mass, per 100 parts by mass of the rubber component.

[0084] Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiuram-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators. Examples of the vulcanizing agent include sulfur. The total content of the vulcanization system (vulcanization package) containing the vulcanization accelerator, vulcanizing agent, and stearic acid is not particularly limited, and is preferably in the range of 1 to 25 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of the rubber component.

[0085] (Method for Producing Rubber Composition) The method for producing the rubber composition is not particularly limited, but the rubber composition can be produced, for example, by blending the above-described rubber component, reinforcing filler, and liquid plasticizer with various components appropriately selected as necessary, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0086] The kneading conditions are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, etc., as well as the kneading temperature, the kneading time, the type of kneading device, etc., can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc., which are usually used for kneading rubber compositions.

[0087] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, the heat-in time, and the heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roller typically used for heat-in of a rubber composition.

[0088] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

[0089] The vulcanization equipment, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of equipment for vulcanization include a molding vulcanizer using a mold used for vulcanizing rubber compositions. The vulcanization temperature is, for example, about 100 to 190°C.

[0090] (Uses) The rubber composition of the present embodiment can be used for various tires, and can be used for tires for both motorcycles and automobiles, but is preferably used for motorcycle tires, and particularly preferably used as a tread rubber for motorcycle tires. The rubber composition of the present embodiment can also be used in the center portion and shoulder portion of the tire tread. Since motorcycle tires require steering stability and wear resistance, the rubber composition for tires of the present invention is particularly suitable.

[0091] <Tread Rubber> The tread rubber of this embodiment is characterized by being made of the rubber composition described above. Since the tread rubber of this embodiment is made of the rubber composition described above, it is possible to improve the wear resistance while maintaining the steering stability of the tire. The tread rubber of this embodiment may be applied to new tires or retread tires. The tread rubber of this embodiment is particularly suitable as a tread rubber for motorcycle tires. Since motorcycle tires require steering stability and wear resistance, the tread rubber of this embodiment is particularly suitable.

[0092] <Tire> The tire of this embodiment is characterized by including the above-described tread rubber. Because the tire of this embodiment includes the above-described tread rubber, the tire has improved wear resistance while maintaining the steering stability of the tire.

[0093] The tire of this embodiment can be used as a variety of tires, including tires for two-wheeled vehicles and tires for four-wheeled vehicles, but is particularly suitable as a tire for two-wheeled vehicles, which require steering stability and wear resistance, making the tire of this embodiment particularly suitable.

[0094] The tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, depending on the type of tire to be applied, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization step or the like and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0095] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0096] <Synthesis of Modified Polybutadiene Rubber (Modified BR)> Modified polybutadiene rubber was synthesized using (3-glycidoxypropyl)-methyldimethoxysilane as a modifier.

[0097] <Preparation of Rubber Composition> Rubber compositions were prepared by kneading the ingredients according to the formulations shown in Table 1 using a conventional kneading device.

[0098] <Evaluation of Rubber Composition> Tires (size: 190 / 55ZR17) were produced using the prepared rubber compositions by the following method, and motorcycle tire treads were formed and evaluated by the following method. The results are shown in Table 1. Tires were produced by molding the obtained unvulcanized rubber compositions into a tread shape, laminating them with other tire components, and vulcanizing them at 160°C for 15 minutes.

[0099] (1) Steering Stability The manufactured tires were mounted on a test vehicle, and in an actual vehicle test on a dry road surface, the steering stability was expressed as a driver's feeling rating, and the feeling rating of the tire of Comparative Example 1 was expressed as an index, with the feeling rating being 100. The larger the index value, the more excellent the steering stability. Note that an index value of 95 or more was considered to have maintained steering stability.

[0100] (2) Wear Resistance The prepared tires were mounted on a test vehicle, and a test rider drove the vehicle 3,500 km at 80 km / h on a paved test course. The remaining groove depth after the run was measured, and the wear resistance of the tire was evaluated based on the remaining groove depth. The evaluation result of the comparative example was expressed as an index, with 100 being used.

[0101]

[0102] *1 SBR: Styrene-butadiene rubber, manufactured by ENEOS Materials Corporation, trade name "SSBR HP755B", oil-extended rubber containing 37.5 parts by mass of extender oil (liquid softener component, liquid at 25 ° C) per 100 parts by mass of rubber component, the middle row indicates the content of rubber component, and the bottom row indicates the content of extender oil. *2 BR: Butadiene rubber, manufactured by ENEOS Materials Corporation, trade name "BR54" *3 Modified BR: Modified butadiene rubber, modified polymer synthesized by the method described above *4 Carbon black: manufactured by Asahi Carbon Co., Ltd., trade name "Asahi #105", nitrogen adsorption specific surface area (BET method) = 140 m ２ / g *5 Silica: Tosoh Silica Corporation, trade name "Nipsil AQ", nitrogen adsorption specific surface area (BET method) = 222 m ２ / g, *6 Oil: Liquid plasticizer component, manufactured by JX Nippon Oil & Energy Corporation, trade name "A / O MIX" *7 C ５ C ９ Resin: ENEOS Corporation, trade name "T-REZ RD104", softening point = 104 ° C. * 8 Coupling agent: Shin-Etsu Chemical Co., Ltd., trade name "ABC-856" * 9 Other chemicals: total amount including wax, antioxidant, and workability improver * 10 Vulcanization package: total amount including vulcanization accelerator, sulfur, and stearic acid

[0103] It can be seen from Table 1 that the rubber compositions of the examples according to the present invention can improve the wear resistance while maintaining the steering stability of the tire.

[0104] According to the present invention, it is possible to provide a rubber composition that can improve the abrasion resistance while maintaining the steering stability of a tire.

Claims

1. A rubber composition comprising a rubber component, a reinforcing filler, and a liquid plasticizer, wherein the rubber component contains more than 0 parts by mass and not more than 45 parts by mass of polybutadiene rubber having a silica-reactive functional group derived from a functional compound represented by the following general formula (1) per 100 parts by mass of the rubber component, and 55 parts by mass or more of styrene-butadiene rubber per 100 parts by mass of the rubber component. [In general formula (1), A １ represents a monovalent epoxy group; R １ represents a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms); R ２ represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms), a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., having 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms), or a reactive group; R ３ represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms) or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms); n is an integer of 0 to 2; ２ OR ３ If there is a ２ and / or OR ３ may be the same or different from one another; no active protons are included in the molecule and / or its partial condensation products.

2. A in the general formula (1) １ is selected from a glycidoxy group, a 3,4-epoxycyclohexyl group, or a glycidyl group having a total of 3 to 8 carbon atoms, and the two terminal carbon atoms are in the epoxy ring, and the other end of the carbon chain is R １ The rubber composition according to claim 1, wherein the rubber composition is bonded to 3. The rubber composition of claim 1, wherein said reinforcing filler comprises silica.

4. The rubber composition according to claim 3, wherein the content of said silica is 70 parts by mass or more per 100 parts by mass of said rubber component.

5. The rubber composition of claim 1, wherein said reinforcing filler comprises carbon black.

6. The rubber composition according to claim 1, further comprising 25 parts by mass or less of a resin per 100 parts by mass of the rubber component.

7. A tread rubber comprising the rubber composition according to claim 1.

8. A tire comprising the tread rubber according to claim 7.

9. The tire according to claim 8, which is for a motorcycle.

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