Rubber composition for tires and tires

Abstract

The present invention addresses the problem of providing: a rubber composition for tires which exhibits excellent mixability and extrudability and gives tires having excellent wet performance, snow performance, and wear resistance; and a tire produced using the rubber composition for tires. This rubber composition for tires comprises a rubber component (A) including a modified conjugated diene-based rubber (A1), silica (B), and a silane coupling agent (C), wherein the component A1 is a conjugated diene-based rubber which satisfies a specific formula and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent to the silicon atom, the proportion of the component A1 in the component A is 25 mass% or higher, and the component C is 3-octanoylthio-1-propyltriethoxysilane or a polysiloxane represented by a specific average compositional formula.

Description

Technical Field

[0001] The present invention relates to a rubber composition for tires and a tire.

Background Art

[0002] Conventionally, a rubber composition for tires containing silica has been known from the viewpoint of performance improvement (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Recently, from the viewpoints of safety and the like, further improvements in wet performance, snow performance, abrasion resistance, etc. have been demanded for tires. In addition, further improvements in mixing processability and extrusion processability have also been demanded for the rubber composition for tires for manufacturing tires. Under such circumstances, when the present inventors examined the rubber composition for tires described in Patent Document 1 and the like, it became clear that further improvement is desirable in consideration of the requirements that will increase in the future.

[0005] Therefore, in view of the above circumstances, the present invention provides a rubber composition for tires that exhibits excellent mixing processability and extrusion processability, and exhibits excellent wet performance, snow performance, and abrasion resistance when made into a tire, and a tire manufactured using the above rubber composition for tires.

Means for Solving the Problems

[0006] As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by using a specific modified conjugated diene rubber as the rubber component and a specific silane coupling agent, and thus have arrived at the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0007] (1) A rubber composition (A) containing a rubber component (A) containing a modified conjugated diene rubber (A1), silica (B), and a silane coupling agent (C), wherein the modified conjugated diene rubber (A1) satisfies the following formulas (1) to (3) and has a modified group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, and is a conjugated diene rubber, the proportion of the modified conjugated diene rubber (A1) in the rubber component (A) is 25% by mass or more, the silane coupling agent (C) is 3-octanoylthio-1-propyltriethoxysilane or a polysiloxane represented by the average composition formula of the following formula (C2), a rubber composition for tires. IVw 10% ≦3.1×10 -6 ×Mw 10% -2.77 (1) St + Vn ≦ 50 (2) 4.7 ≦ IVw 10% (3) For Mw 10% and IVw 10% in formulas (1) and (3), it is as follows. For the modified conjugated diene rubber, gel permeation chromatography measurement is performed using a differential refractive index detector and a viscosity detector as detectors. Among the peaks of the chromatogram by the differential refractive index detector, the weight average molecular weight determined using the high molecular weight side portion having an area of 10% of the total peak area is defined as Mw 10% And among the peaks of the chromatogram by the viscosity detector, the weight average intrinsic viscosity determined using the high molecular weight side portion having an area of 10% of the total peak area is defined as IVw 10% However, the unit of the weight average intrinsic viscosity is dL / g. In formula (2), St represents the proportion (mass %) of the repeating unit derived from styrene with respect to the total amount of the modified conjugated diene rubber, and Vn represents the proportion (mass %) of the repeating unit of the 1,2-vinyl structure derived from the conjugated diene with respect to the total amount of the modified conjugated diene rubber. (A) a (B) b (C) c (D) d (R 1 ) e SiO (4-2a-b-c-d-e) / 2 (C2) In formula (C2), A represents a divalent organic group containing a sulfide group. B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms. C represents a hydrolyzable group. D represents an organic group containing a mercapto group. R 1 represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. a to e satisfy the relational expressions of 0 ≦ a < 1, 0 < b < 1, 0 < c < 3, 0 < d < 1, 0 ≦ e < 2, and 0 < 2a + b + c + d + e < 4. (2) The modified conjugated diene rubber (A1) has a star structure with three or more branches, and at least one branch chain of the star structure has a portion derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group, and in the above portion, has a further main chain branched structure, the tire rubber composition according to (1) above. (3) Further, the tire rubber composition according to (1) or (2) above, containing 20 to 50 parts by mass of a thermoplastic resin (D) with respect to 100 parts by mass of the rubber component (A). (4) The tire rubber composition according to (3) above, containing at least two selected from the group consisting of terpene resins, C5 / C9 resins, C9 resins, DCPD resins, DCPD / C9 resins, hydrogenated C5 / C9 resins, hydrogenated C9 resins, hydrogenated DCPD resins, and hydrogenated DCPD / C9 resins, each in a content of 20 parts by mass or less. (5) The tire rubber composition according to any one of (1) to (4) above, wherein the content of the silica (B) is 50 to 150 parts by mass with respect to 100 parts by mass of the rubber component (A). A tire manufactured using the rubber composition for tires according to any one of (1) to (5) above.

Advantages of the Invention

[0008] As described below, according to the present invention, there can be provided a rubber composition for tires that exhibits excellent mixing processability and extrusion processability, and excellent wet performance, snow performance, and abrasion resistance when formed into a tire, and a tire manufactured using the rubber composition for tires.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0010] The rubber composition for tires and the like of the present invention will be described below. In this specification, a numerical range represented using "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. Also, each component may be used alone or in combination of two or more. Here, when two or more of each component are used in combination, the content of that component refers to the total content unless otherwise specified. Also, for the rubber composition for tires, the wet performance, snow performance, and abrasion resistance when formed into a tire are simply referred to as "wet performance", "snow performance", and "abrasion resistance", respectively. Also, in this specification, a power of 10 may be represented by E. For example, E+5 represents 10 to the 5th power.

[0011] [I] Rubber Composition for Tires The rubber composition for tires of the present invention (hereinafter, also referred to as "the composition of the present invention") is A rubber component (A) containing a modified conjugated diene rubber (A1), silica (B), and a silane coupling agent (C), The above-mentioned modified conjugated diene rubber (A1) satisfies the following formulas (1) to (3) and is a conjugated diene rubber having a modified group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. The proportion of the above-mentioned modified conjugated diene rubber (A1) in the above-mentioned rubber component (A) is 25% by mass or more. The above-mentioned silane coupling agent (C) is 3-octanoylthio-1-propyltriethoxysilane or a polysiloxane represented by the average composition formula of formula (C2) described later, and is a rubber composition for tires.

[0012] Since the composition of the present invention has such a configuration, it is considered that the above-mentioned problems can be solved. The reason is not clear, but it is presumed to be as follows. The composition of the present invention contains, as a rubber component, a conjugated diene rubber (hereinafter also referred to as "specific conjugated diene rubber") that satisfies the following formulas (1) to (3) and has a modified group (hereinafter also referred to as "specific modified group") containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. Formula (1) defines the relationship between the weight average intrinsic viscosity on the high molecular weight side and the weight average molecular weight on the high molecular weight side. From the studies of the present inventors, it has been found that a rubber that satisfies formula (1) has excellent mixing processability. In addition, the specific modified group possessed by the specific conjugated diene rubber is considered to interact with silica. Further, the specific silane coupling agent contained in the composition of the present invention interacts with silica together with the above-mentioned specific modified group, and further interacts with the skeleton of the specific conjugated diene rubber and other rubber components. Therefore, in the composition of the present invention, the dispersibility of silica is extremely high, and this is considered to lead to excellent effects (extrusion processability, wet performance, snow performance, abrasion resistance).

[0013] Hereinafter, each component contained in the composition of the present invention will be described.

[0014] [1] Rubber component The composition of the present invention contains a rubber component including a specific conjugated diene rubber. The composition of the present invention may contain a rubber component other than the specific conjugated diene rubber.

[0015] [Specific conjugated diene rubber] The specific conjugated diene rubber satisfies the following formulas (1) and (2) described later and has a modified group (specific modified group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, and is a conjugated diene rubber.

[0016] 〔Skeleton〕 The skeleton of the specific conjugated diene rubber is a polymer having a repeating unit derived from a conjugated diene.

[0017] [Conjugated diene] Specific examples of the conjugated diene include butadiene (especially 1,3-butadiene), isoprene, chloroprene, and the like. From the reason that the effects of the present invention are more excellent, the above diene is preferably butadiene (especially 1,3-butadiene) or isoprene, and more preferably butadiene (especially 1,3-butadiene).

[0018] [Other monomers] The skeleton of the specific conjugated diene rubber may have a repeating unit other than the repeating unit derived from the conjugated diene. Examples of such a monomer (other monomers) that becomes such a repeating unit include vinyl monomers, alkenes (for example, ethylene, propylene, butene), and the like. Examples of the vinyl monomer include aromatic vinyl (for example, styrene), acrylonitrile, a specific branching agent described later, and the like.

[0019] [Specific example] Specific examples of the backbone include natural rubber (NR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), and the like. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene butadiene rubber (SBR) and styrene isoprene copolymer rubber. For the above reasons that the effects of the present invention are more excellent, the conjugated diene rubber is preferably SBR.

[0020] [Specific Modifying Group] As described above, the specific conjugated diene rubber has a modifying group (specific modifying group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent to the silicon atom. The specific modifying group may be present at the terminal, main chain, or side chain of the conjugated diene rubber. For the above reasons that the effects of the present invention are more excellent, the specific modifying group preferably contains a silicon atom and an oxygen atom adjacent to it as an alkoxysilyl group. The alkoxysilyl group is -Si(OR1) n (R2) 3-n (where R1 is an alkyl group, R2 is a hydrogen atom or an alkyl group, and n is an integer from 1 to 3). For the above reasons that the effects of the present invention are more excellent, the specific modifying group preferably contains a nitrogen atom as an amino group (primary to tertiary amino group). For the above reasons that the effects of the present invention are more excellent, the specific modifying group is preferably a group derived from a specific modifying agent described later.

[0021] [Formula (1)] The specific conjugated diene rubber satisfies the following formula (1). Formula (1) defines the relationship between the weight average intrinsic viscosity on the high molecular weight side and the weight average molecular weight on the high molecular weight side. Polymers with a small molecular size relative to their molecular weight, such as those having branches, tend to satisfy formula (1). The reason for limiting to the high molecular weight side is that the influence on the physical properties of the entire polymer is large.

[0022] IVw 10% ≦3.1×10 -6 ×Mw 10% -2.77 (1)

[0023] Mw in formula (1) 10% and IVw 10% are obtained as follows. For the modified conjugated diene rubber, gel permeation chromatography measurement is performed using a differential refractive index detector (RI detector) and a viscosity detector as detectors. Of the peaks in the chromatogram obtained by the differential refractive index detector, the weight-average molecular weight determined using the high molecular weight side portion having an area of 10% of the total peak area is defined as Mw 10% And of the peaks in the chromatogram obtained by the viscosity detector, the weight-average reduced viscosity determined using the high molecular weight side portion having an area of 10% of the total peak area is defined as IVw 10% However, the unit of the weight-average reduced viscosity is dL / g.

[0024] Hereinafter, Mw 10% and IVw 10% in formula (1) will be described more specifically.

[0025] As described above, gel permeation chromatography (GPC) measurement is performed on the modified conjugated diene rubber using a differential refractive index detector and a viscosity detector as detectors. The specific method of the GPC measurement is as follows.

[0026] Toluene containing 5 mmol / L of triethylamine is used as the eluent. Three columns filled with polystyrene gel (trade names "TSKgel G4000HXL", "TSKgel G5000HXL", and "TSKgel G6000HXL" manufactured by Tosoh Corporation) are connected and used. The sample for measurement is dissolved in toluene to a concentration of 1 mg / mL to prepare a measurement solution, 100 μL of the measurement solution is injected into the GPC measurement device, and the measurement is performed under the conditions of an oven temperature of 40°C and a toluene flow rate of 1 mL / min.

[0027] Of the peaks in the chromatogram obtained using a differential refractive index detector (horizontal axis: elution time, vertical axis: signal intensity) (peaks derived from the modified conjugated diene rubber), the portion on the high molecular weight side (the side with shorter elution time) that accounts for 10% of the total peak area is used to determine the weight average molecular weight. The obtained weight average molecular weight is designated as Mw 10% and this is used hereinafter.

[0028] Also, of the peaks in the chromatogram obtained using a viscosity detector (horizontal axis: elution time, vertical axis: signal intensity) (peaks derived from the modified conjugated diene rubber), the portion on the high molecular weight side (the side with shorter elution time) that accounts for 10% of the total peak area is used to determine the weight average intrinsic viscosity. The obtained weight average intrinsic viscosity is designated as IVw 10% and this is used hereinafter. The weight average intrinsic viscosity is defined as (Σ(ηi × Mi × Ni)) / (Σ(Mi × Ni)), where Mi is the molecular weight, Ni is the number of molecules, and ηi is the intrinsic viscosity at the molecular weight Mi.

[0029] Note that FIG. 1 shows an example of a GPC chromatogram (horizontal axis: elution time, vertical axis: signal intensity). Mw 10% and IVw 10% are determined using P1, which is the portion on the high molecular weight side (the side with shorter elution time) that accounts for 10% of the area of the entire peak P0.

[0030] As a method for causing the modified conjugated diene rubber to satisfy formula (1), for example, in the production method of the present invention described later, methods such as changing the type and amount of use of a specific modifier and the type and amount of use of a specific branching agent can be mentioned.

[0031] Mw 10% is preferably from 100,000 to 10,000,000, and more preferably from 1,000,000 to 5,000,000, for the reason that the effects of the present invention are more excellent.

[0032] [Formula (2)] The specific conjugated diene rubber satisfies the following formula (2).

[0033] St + Vn ≦ 50 (2)

[0034] In formula (2), St represents the proportion (mass %) of the repeating unit derived from styrene with respect to the entire specific conjugated diene rubber (hereinafter also referred to as the "styrene content"), and Vn represents the proportion (mass %) of the repeating unit of the 1,2-vinyl structure derived from conjugated diene (for example, butadiene) with respect to the entire specific conjugated diene rubber (hereinafter also referred to as the "vinyl content").

[0035] For the reason that the effects of the present invention are more excellent, St + Vn is preferably 10 to 45, and more preferably 25 to 45.

[0036] For the reason that the effects of the present invention are more excellent, St is preferably 5 to 40, more preferably 10 to 35, and even more preferably 15 to 30.

[0037] For the reason that the effects of the present invention are more excellent, Vn is preferably 5 to 30, and more preferably 10 to 20.

[0038] 〔Formula (3)〕 The specific conjugated diene rubber satisfies the following formula (3). 4.7 ≦ IVw 10% (3)

[0039] IVw 10% The method for obtaining it is as described above.

[0040] IVw 10% For the reason that the effects of the present invention are more excellent, it is preferably 8 or less, and more preferably 6 or less.

[0041] 〔Molecular weight〕 For the reason that the effects of the present invention are more excellent, the weight average molecular weight (Mw) of the specific conjugated diene rubber is preferably 100,000 to 2,000,000, and more preferably 200,000 to 1,300,000. The method for measuring the weight average molecular weight (Mw) of the specific conjugated diene rubber is the same as the above-described Mw, except that the entire peak is used. 10% It is the same.

[0042] 〔Glass transition temperature〕 The glass transition temperature (Tg) of the specific conjugated diene rubber is not particularly limited, but is preferably -100°C to -30°C, and more preferably -80°C to -45°C, because the effects of the present invention are more excellent. The glass transition temperature can be adjusted, for example, by the amount of styrene or the amount of vinyl. In this specification, the glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min and calculated by the midpoint method.

[0043] 〔Preferred embodiment 1〕 The specific conjugated diene rubber preferably has a star structure with three or more branches, more preferably a star structure with three or more branches having a specific modifying group as a branch point, and still more preferably a conjugated diene rubber represented by the following formula (A), because the effects of the present invention are more excellent.

[0044]

Chemical formula

[0045] In formula (A), X represents an n-valent group (specific modifying group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, P represents a conjugated diene polymer chain, and n represents an integer of 3 or more.

[0046] As described above, X represents an n-valent group (specific modifying group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. X preferably contains a silicon atom and an oxygen atom adjacent thereto as an alkoxysilyl group, because the effects of the present invention are more excellent. X preferably contains a nitrogen atom as an amino group, because the effects of the present invention are more excellent.

[0047] As described above, P represents a conjugated diene polymer chain. A plurality of Ps may be the same or different. The definition, specific examples, and preferred embodiments of the conjugated diene polymer chain are the same as those of the backbone of the specific conjugated diene rubber described above.

[0048] As described above, n represents an integer of 3 or more. The upper limit of n is not particularly limited, but for reasons of more excellent effects of the present invention, it is preferably 30 or less.

[0049] 〔Preferred embodiment 2〕 When the specific conjugated diene rubber has a star structure with three or more branches, at least one branch chain (conjugated diene polymer chain) of the star structure preferably has a portion derived from a specific branching agent described later, and in the above portion, it preferably has a further main chain branching structure for reasons of more excellent effects of the present invention. The main chain branching structure means a structure in which a branch chain (conjugated diene polymer chain) forms a branch point at a portion derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group, and further a polymer chain (for example, another conjugated diene polymer chain) extends from the branch point.

[0050] 〔Content〕 The proportion of the specific conjugated diene rubber in the rubber component is 25% by mass or more. For reasons of more excellent effects of the present invention, the above proportion is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more. The upper limit of the above proportion is not particularly limited and is 100% by mass.

[0051] [Production method of specific conjugated diene rubber] The production method of the specific conjugated diene rubber is not particularly limited, but for reasons of more excellent effects of the present invention, a method including the following steps (1) to (2) (hereinafter, also referred to as "the production method of the present invention") is preferred. (1) Polymerization step of obtaining a conjugated diene polymer by polymerizing a monomer containing a conjugated diene by anionic polymerization (2) By reacting the conjugated diene polymer obtained in the polymerization step with a compound containing a nitrogen atom and an alkoxysilyl group (hereinafter also referred to as "specific modifier"), a conjugated diene rubber having a specific modifying group is obtained. Modification step

[0052] 〔Polymerization step〕 The polymerization step is a step of obtaining a conjugated diene polymer by polymerizing a monomer containing a conjugated diene by anionic polymerization.

[0053] <Anionic polymerization> The anionic polymerization is not particularly limited, but from the reason that the effects of the present invention are more excellent, anionic polymerization using an organolithium compound as an initiator is preferably used.

[0054] The organolithium compound is not particularly limited, and specific examples thereof include mono-organolithium compounds such as n-butyllithium (n-BuLi), sec-butyllithium, tert-butyllithium, n-propyllithium, isopropyllithium, benzyllithium; 1,4-dilithiobutane, 1,5-dilithiopentane, 1,6-dilithiohexane, 1,10-dilithiodecane, 1,1-dilithiodiphenylene, dilithiopolybutadiene, dilithiopolyisoprene, 1,4-dilithiobenzene, 1,2-dilithio-1,2-diphenylethane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, 1,3,5-trilithio-2,4,6-triethylbenzene and other polyfunctional organolithium compounds. Among them, from the reason that the effects of the present invention are more excellent, mono-organolithium compounds of n-butyllithium, sec-butyllithium, and tert-butyllithium are preferred, and n-butyllithium is more preferred.

[0055] The amount of the organolithium compound used is not particularly limited, but from the reason that the effects of the present invention are more excellent, it is preferably 0.001 to 10 mol% based on the monomer.

[0056] <Monomer> Specific examples and preferred embodiments of the monomers containing conjugated dienes used in the coincidence process are the same as the conjugated dienes and other monomers in the backbone of the specific conjugated diene rubber described above.

[0057] (Specific branching agent) For the reason that the effects of the present invention are more excellent, the monomer preferably contains a vinyl monomer containing an alkoxysilyl group or a halosilyl group (hereinafter, also referred to as "specific branching agent"). For the reason that the effects of the present invention are more excellent, the specific branching agent is preferably an aromatic vinyl (especially styrene) containing an alkoxysilyl group or a halosilyl group, more preferably an aromatic vinyl containing an alkoxysilyl group, and even more preferably an aromatic vinyl containing a trialkoxysilyl group.

[0058] (1) Specific examples Specific examples of the aromatic vinyl containing an alkoxysilyl group include 1-(trimethoxysilyl)-4-vinylbenzene, 1,1-bis(4-trimethoxysilylphenyl)ethylene, and the like. In addition, examples of the aromatic vinyl containing a halosilyl group include trichloro(4-vinylphenyl)silane, 1,1-bis(4-trichlorosilylphenyl)ethylene, and the like.

[0059] (2) Dosage For the reason that the effects of the present invention are more excellent, the dosage of the specific branching agent is preferably 0.001 to 0.1% by mass, and more preferably 0.005 to 0.05% by mass, based on the conjugated diene.

[0060] <Polar compound> In the polymerization process, a polar compound may be added. Thereby, the monomers can be copolymerized randomly. In addition, the polar compound tends to be used also as a vinylating agent for controlling the microstructure of the conjugated diene. In addition, it also tends to be effective in promoting the polymerization reaction and the like.

[0061] Examples of the polar compound include ethers such as tetrahydrofuran, diethyl ether, dioxane, dimethoxybenzene, 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, sodium tert-butyrate; phosphine compounds such as triphenylphosphine, etc. These can be used. These polar compounds may be used alone or in combination of two or more.

[0062] (Usage amount) The usage amount of the polar compound is preferably 0.01 mol or more and 100 mol or less per 1 mol of the initiator, because the effects of the present invention are more excellent.

[0063] 〔Modification step〕 The modification step is a step of obtaining a conjugated diene-based rubber having a specific modification group by reacting the conjugated diene-based polymer obtained in the polymerization step with a modifier (specific modifier) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto.

[0064] In the modification step, it is considered that the active terminal of the conjugated diene-based polymer obtained in the polymerization step binds to the silicon atom of the specific modifier. For example, when the specific modifier contains an alkoxysilyl group, it is considered that the above active terminal binds to the silicon atom of the alkoxysilyl group and the alkoxy group is eliminated. In addition, when the conjugated diene-based polymer obtained in the polymerization step has a portion derived from a specific branching agent, in addition to the above active terminal, the alkoxysilyl group or halosilyl group of the above portion is also considered to react with a specific modifier (for example, an alkoxysilyl group). Also, the alkoxysilyl group or halosilyl group of the above portion is considered to react with the active terminal of another conjugated diene-based polymer. As a result, the conjugated diene-based polymer having a portion derived from a specific branching agent has a main chain branched structure (another conjugated diene-based polymer chain) in the above portion.

[0065] <Specific modifier> The specific modifier is a compound containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. For the reason that the effects of the present invention are more excellent, the specific modifier preferably contains a silicon atom and an oxygen atom adjacent thereto as a group containing an alkoxysilyl group (particularly, a trialkoxysilyl group) or a group containing a silazane structure (particularly, a cyclic silazane structure), and an alkoxy group is bonded to the silicon atom of the silazane structure. Here, the silazane structure is intended to mean a structure in which a silicon atom and a nitrogen atom are directly bonded (a structure having a Si-N bond). For the reason that the effects of the present invention are more excellent, the specific modifier preferably contains a nitrogen atom as an amino group (primary to tertiary amino group) or a group containing a silazane structure (particularly, a cyclic silazane structure). The specific modifier preferably has two or more (preferably three or more) sites capable of reacting with an active terminal such as an alkoxysilyl group. When the specific modifier has a plurality of the above sites, the specific modifier functions as a coupling agent that connects conjugated diene polymers to each other.

[0066] (Specific examples) Specific examples of the specific modifier include tertiary amines having an alkoxysilyl group such as tris(3-trimethoxysilylpropyl)amine and tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, cyclic silazanes having an alkoxysilyl group such as 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, tertiary amines having a group containing an alkoxysilyl group-containing cyclic silazane structure such as tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine and tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)amine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, tertiary amines having a group containing an alkoxysilyl group and a cyclic silazane structure such as bis(2-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-methyl-1,3-propanediamine, and the like.

[0067] (Usage amount) The usage amount of the specific modifier is preferably 0.01 to 1% by mass, more preferably 0.02 to 0.2% by mass, based on the conjugated diene, because the effects of the present invention are more excellent.

[0068] 〔Other steps〕 The production method of the present invention may include steps other than the above-described steps (other steps). As other steps, there may be mentioned a polymerization termination step of adding a polymerization terminator (for example, methanol), a solvent removal step of removing the solvent by steam stripping, and the like.

[0069] [Other rubber components] The rubber component may contain a rubber component other than the specific conjugated diene rubber (rubber component). Examples of such other rubber components include natural rubber (NR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), and the like. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, and the like. The rubber component preferably contains BR for the reason that the effects of the present invention are more excellent. When the rubber component contains BR, the proportion of BR in the rubber component is preferably 10 to 50% by mass, and more preferably 20 to 40% by mass, for the reason that the effects of the present invention are more excellent.

[0070] [Molecular weight] A preferred embodiment of the weight average molecular weight (Mw) of the rubber component is the same as that of the specific conjugated diene rubber described above.

[0071] [2] Silica The composition of the present invention contains silica. The silica is not particularly limited, and any conventionally known silica can be used. Examples of the silica include wet silica, dry silica, fumed silica, diatomaceous earth, and the like. Silica derived from biomass such as rice husks may also be used. The above silica may be used alone or in combination of two or more kinds of silica.

[0072] [CTAB] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of silica (hereinafter, the "CTAB adsorption specific surface area" is also simply referred to as "CTAB") is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 100 to 300 m 2 / g, and more preferably 150 to 200 m 2 / g. Here, the CTAB adsorption specific surface area is a value measured according to Appendix G of JIS K6430:2008.

[0073] [Content] In the composition of the present invention, the content of silica is preferably 50 to 150 parts by mass, and more preferably 80 to 140 parts by mass, based on 100 parts by mass of the rubber component described above, for the reason that the effects of the present invention are more excellent.

[0074] [3] Specific silane coupling agent The composition of the present invention contains 3-octanoylthio-1-propyltriethoxysilane or a polysiloxane represented by the average composition formula of formula (C2) described below (hereinafter, collectively referred to as "specific silane coupling agent").

[0075] [3-Octanoylthio-1-propyltriethoxysilane] 3-Octanoylthio-1-propyltriethoxysilane is a compound represented by the following structural formula.

[0076] [Chemical formula]

[0077] [Specific polysiloxane] Hereinafter, the polysiloxane represented by the average composition formula of formula (C2) (hereinafter, also referred to as "specific polysiloxane") will be described. The specific polysiloxane is a polysiloxane represented by the average composition formula of the following formula (C2). (A) a (B) b (C) c (D)d (R 1 ) e SiO (4-2a-b-c-d-e) / 2 (C2)

[0078] In the above formula (C2), A represents a divalent organic group containing a sulfide group. B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms. C represents a hydrolyzable group. D represents an organic group containing a mercapto group. R 1 represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. a to e satisfy the relational expressions of 0 ≦ a < 1, 0 < b < 1, 0 < c < 3, 0 < d < 1, 0 ≦ e < 2, and 0 < 2a + b + c + d + e < 4.

[0079] Formula (C2) represents the average composition of the polysiloxane. That is, it represents the types of groups directly bonded to the Si atoms of the polysiloxane and the average number of each group. Si in formula (C2) represents the Si atom of the polysiloxane. Also, O in formula (C2) represents the O atom of the polysiloxane. Note that the O atom is a divalent group and is always bonded to two Si atoms (Si atoms of the polysiloxane). (4 - 2a - b - c - d - e) / 2 in formula (C2) represents the average number of O atoms of the polysiloxane bonded to the Si atoms of the polysiloxane. A, B, C, D, and R in formula (C2) 1 all represent groups bonded to the Si atoms of the polysiloxane. Note that A is a divalent group and is always bonded to two Si atoms (Si atoms of the polysiloxane). a, b, c, d, and e in formula (C2) are the average numbers of A, B, C, D, and R bonded to the Si atoms of the polysiloxane, respectively. 1 respectively. As can be seen from the fact that the sum of each group directly bonded to the Si atom of the polysiloxane (a×2 + b + c + d + e + ((4 - 2a - b - c - d - e) / 2)×2) becomes 4 (the valence of the Si atom), no group other than A, B, C, D, R 1 and O is directly bonded to the Si atom of the polysiloxane. In the calculation of the above sum, a and (4 - 2a - b - c - d - e) / 2) are doubled because A and O are divalent groups.

[0080] Specific examples and preferred embodiments of the specific polysiloxane and its production method are as described in paragraphs

[0038] to

[0070] of JP-A No. 2019-156918, paragraphs

[0020] to

[0050] of WO 2014 / 129664, and paragraphs

[0046] to

[0099] of US Patent Application Publication No. 2016 / 0002433, which are incorporated herein by reference.

[0081] [Content] In the composition of the present invention, the content of the specific silane coupling agent is preferably 1 to 20% by mass, more preferably 5 to 15% by mass, based on the content of the silica described above, because the effects of the present invention are more excellent.

[0082] [4] Optional components The composition of the present invention may contain, if necessary, components other than the above-described components (optional components). Examples of such components include fillers other than silica (preferably carbon black), silane coupling agents other than the specific silane coupling agent, thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, waxes, processing aids, liquid polymers, thermoplastic resins, thermosetting resins, vulcanizing agents (e.g., sulfur), vulcanization accelerators (accelerators), vulcanization activators, and various other additives commonly used in rubber compositions.

[0083] [Thermoplastic resin] The composition of the present invention preferably contains a thermoplastic resin because the effects of the present invention are more excellent. The composition of the present invention preferably contains two or more thermoplastic resins because the effects of the present invention are more excellent.

[0084] 〔Specific examples〕 Examples of the thermoplastic resin include coumarone resins (e.g., coumarone resin, coumarone-indene resin, coumarone-indene-styrene resin), phenol resins (e.g., phenol resin, phenol-acetylene resin, phenol-formaldehyde resin), xylene resins (e.g., xylene resin, xylene-acetylene resin, xylene-formaldehyde resin), rosin resins (e.g., rosin, rosin ester, hydrogenated rosin derivative), terpene resins (e.g., terpene resin, modified terpene resin (such as aromatic-modified terpene resin), terpene phenol resin, hydrogenated terpene resin, α-pinene resin, β-pinene resin, limonene resin, hydrogenated limonene resin, dipentene resin, terpene styrene resin), styrene resins, petroleum resins (e.g., C5 / C9 resin, C9 resin, DCPD (dicyclopentadiene) resin, DCPD / C9 resin, hydrogenated C5 / C9 resin, hydrogenated C9 resin, hydrogenated DCPD resin, hydrogenated DCPD / C9 resin), aliphatic saturated hydrocarbon resins, and the like.

[0085] For the reason that the effects of the present invention are more excellent, the thermoplastic resin preferably contains at least one selected from the group consisting of terpene resins, C5 / C9 resins, C9 resins, DCPD resins, DCPD / C9 resins, hydrogenated C5 / C9 resins, hydrogenated C9 resins, hydrogenated DCPD resins, and hydrogenated DCPD / C9 resins. More preferably, it contains at least two selected from the above group, and even more preferably, it contains at least two selected from the above group in a content of 20 parts by mass or less each.

[0086] [Content] In the composition of the present invention, for the reason that the effects of the present invention are more excellent, the content of the thermoplastic resin is preferably 20 to 50 parts by mass, more preferably 25 to 35 parts by mass, based on 100 parts by mass of the above-described rubber component.

[0087] [Carbon Black] The composition of the present invention preferably contains carbon black because the effects of the present invention are more excellent. The above carbon black may be used alone as one kind of carbon black or in combination of two or more kinds of carbon black. The above carbon black is not particularly limited, and for example, various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, SRF, etc. can be used.

[0088] [N2SA] The nitrogen adsorption specific surface area (N2SA) of the above carbon black is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 50 to 200 m 2 / g, and more preferably 70 to 150 m 2 / g. Here, the nitrogen adsorption specific surface area (N2SA) is a value measured according to JIS K6217-2:2001 "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method" for the amount of nitrogen adsorbed on the carbon black surface.

[0089] [Content] In the composition of the present invention, the content of carbon black is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 1 to 100 parts by mass, and more preferably 2 to 30 parts by mass with respect to 100 parts by mass of the above-mentioned rubber component.

[0090] [5] Method for preparing rubber composition for tire The production method of the composition of the present invention is not particularly limited, and specific examples thereof include, for example, a method of kneading the above-mentioned respective components using a known method and apparatus (for example, Banbury mixer, kneader, roll, etc.). When the composition of the present invention contains sulfur or a vulcanization accelerator, it is preferable to first mix the components other than sulfur and the vulcanization accelerator at a high temperature (preferably 100 to 160 ° C), cool, and then mix sulfur or the vulcanization accelerator. In addition, the composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0091] [II] Tire The tire of the present invention is a tire manufactured using the composition of the present invention described above. The tire of the present invention is preferably a pneumatic tire and can be filled with air, an inert gas such as nitrogen, and other gases.

[0092] Figure 2 shows a schematic partial cross-sectional view of a tire representing an example of an embodiment of the tire of the present invention. However, the tire of the present invention is not limited to the embodiment shown in Figure 2.

[0093] In Figure 2, reference numeral 1 represents the bead portion, reference numeral 2 represents the sidewall portion, and reference numeral 3 represents the tire tread portion. Also, between the pair of left and right bead portions 1, a carcass layer 4 in which a fiber cord is embedded is mounted, and the end portion of this carcass layer 4 is folded back from the inside of the tire to the outside around the bead core 5 and the bead filler 6 and wound up. Also, in the tire tread portion 3, a belt layer 7 is disposed over the entire circumference of the tire outside the carcass layer 4. Also, in the bead portion 1, a rim cushion 8 is disposed at the portion in contact with the rim. Note that at least any one of reference numerals 2 to 3, 5 to 6, and 8 (preferably reference numeral 3) is formed of the composition of the present invention described above.

[0094] The tire of the present invention can be manufactured, for example, according to a conventionally known method. Also, as the gas to be filled in the tire, in addition to normal air or air with adjusted oxygen partial pressure, an inert gas such as nitrogen, argon, or helium can be used.

Example

[0095] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[0096] [Synthesis of conjugated diene rubber] Each conjugated diene rubber was synthesized as follows.

[0097] [Conjugated diene rubber 1]

[0098] [Polymerization step] Into an autoclave equipped with a stirrer, under a nitrogen atmosphere, 1000 g / h of cyclohexane, 0.023 g / h of tetramethylethylenediamine, 176.4 g / h of 1,3-butadiene, 0.406 g / h of 1-butene, and 23.6 g / h of styrene were charged. Then, n-butyllithium was continuously added at 1.43 mmol / h, and polymerization was initiated at 70°C. When the polymerization was sufficiently stable, 1-(trimethoxysilyl)-4-vinylbenzene (branching agent) was added at 0.02 g / h and stirred to react. The branching agent corresponds to the specific branching agent described above.

[0099] [Modification step] To the solution flowing out from the reactor outlet, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine (modifying agent) was added at 0.08 g / h and stirred to react.

[0100] Thereafter, methanol was added as a polymerization terminator to obtain a solution containing a conjugated diene rubber.

[0101] To the obtained solution, Irganox 1520L (manufactured by BASF) was added as an antioxidant at 1.14 parts by mass per 100 parts by mass of the conjugated diene rubber. Then, the solvent was removed by steam stripping and vacuum dried at 60°C for 24 hours to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is also referred to as conjugated diene rubber 1.

[0102] Conjugated diene rubber 1 is a reaction product of a conjugated diene polymer, which is a copolymer of butadiene, styrene, and a branching agent, and a modifying agent, and is a modified conjugated diene rubber having a modified group (specific modified group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto derived from the modifying agent. The conjugated diene rubber 1 has a star structure with three or more branches having a modifying group as a branching point, and the branched chain bonded to the modifying group has a portion derived from a branching agent, and in the portion derived from the branching agent, it has a further main chain branched structure (conjugated diene polymer chain).

[0103] 〔Conjugated diene rubber 2〕 Except for changing the usage amounts of the respective components as described in Table 1, a solid conjugated diene rubber was obtained according to the same procedure as that for the conjugated diene rubber 1. The obtained conjugated diene rubber is also referred to as the conjugated diene rubber 2.

[0104] The conjugated diene rubber 2 is a reaction product of a conjugated diene polymer, which is a copolymer of butadiene, styrene and a branching agent, and a modifying agent, and is a modified conjugated diene rubber having a modifying group (specific modifying group) containing a nitrogen atom, a silicon atom and an oxygen atom adjacent thereto, derived from the modifying agent. The conjugated diene rubber 2 has a star structure with three or more branches having a modifying group as a branching point, and the branched chain bonded to the modifying group has a portion derived from a branching agent, and in the portion derived from the branching agent, it has a further main chain branched structure (conjugated diene polymer chain).

[0105] 〔Conjugated diene rubber 4〕 2,000 g of cyclohexane, 31.6 g of tetrahydrofuran, 122 g of styrene and 320 g of 1,3-butadiene were charged into a nitrogen-substituted autoclave reactor having an internal volume of 5 liters. After adjusting the temperature of the contents of the reactor to 10°C, 4.75 mmol of n-butyllithium was added as a polymerization initiator to initiate polymerization. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85°C. When the polymerization conversion rate reached 99% (20 minutes after the start of polymerization), 10 g of 1,3-butadiene was added over 2 minutes, and then 2.12 mmol of the compound (modifying agent) of the following formula (4) was added and reacted for 15 minutes. The modifying agent corresponds to the specific modifying agent described above. To the obtained solution, 3.96 g of 2,6-di-tert-butyl-p-cresol was added. Then, the solvent was removed by steam stripping, and a solid conjugated diene rubber was obtained by drying with a hot roll adjusted to 110°C. The obtained conjugated diene rubber is also referred to as conjugated diene rubber 4.

[0106] Formula (4)

Chemical formula

[0107] In formula (4), R 1 is a hydrocarbyl group having 1 to 20 carbon atoms, R 2 is a hydrocarbyloxy group having 1 to 20 carbon atoms, R 3 is an alkanediyl group having 1 to 20 carbon atoms, A 2 is a group “*-C(R 5 )=N-” or a group “*-N=C(R 5 )-” (wherein R 5 is a hydrogen atom or a hydrocarbyl group, and “*” indicates a bond that binds to R 4 ). R 4 is an m-valent hydrocarbyl group having 1 to 20 carbon atoms, or an m-valent group having 1 to 20 carbon atoms that has at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom and does not have an active hydrogen. n is an integer of 1 to 3, and m is an integer of 2 to 10. In the formula, a plurality of R 1 , R 2 , R 3 , A 2 , and n may be the same or different.

[0108] Conjugated diene rubber 4 is a reaction product of a conjugated diene polymer that is a copolymer of butadiene and styrene and a modifier, and is a modified conjugated diene rubber having a modified group (specific modified group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto derived from the modifier.

[0109] 〔Conjugated diene rubber 5〕 A solid conjugated diene rubber was obtained according to the same procedure as that of the conjugated diene rubber 1, except that the amounts of the respective components were changed as described in Table 1. The obtained conjugated diene rubber is also referred to as the conjugated diene rubber 5.

[0110] The conjugated diene rubber 5 is a reaction product of a conjugated diene polymer, which is a copolymer of butadiene, styrene and a branching agent, and a modifier, and is a modified conjugated diene rubber having a modified group (specific modified group) containing a nitrogen atom, a silicon atom and an oxygen atom adjacent thereto, derived from the modifier. The conjugated diene rubber 5 has a star structure with three or more branches having the modified group as a branch point, and the branched chain bonded to the modified group has a portion derived from the branching agent, and in the portion derived from the branching agent, it has a further main chain branched structure (conjugated diene polymer chain).

[0111] 〔Conjugated diene rubber 6〕 Into an autoclave equipped with a stirrer, 4000 g of cyclohexane, 8.1 g of 2,2 - bis(tetrahydrofuryl)propane, 352.1 g of 1,3 - butadiene and 131.7 g of styrene were charged under a nitrogen atmosphere. After that, 4.1 mL of n - butyllithium (1.60 mol / L hexane solution) was added as an initiator, and polymerization was started at 40°C. Ten minutes after the start of polymerization, 184.3 g of 1,3 - butadiene and 15.1 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 60°C. After the continuous addition was completed, the polymerization reaction was continued for another 20 minutes. After confirming that the polymerization conversion rate was in the range of 95% to 100%, then, 0.08 mmol of 1,6 - bis(trichlorosilyl)hexane was added in the state of a 20% by mass cyclohexane solution and reacted for 10 minutes. Further, 0.027 mmol of polyorganosiloxane A represented by the following formula (9) was added in the state of a 20% by mass xylene solution and reacted for 30 minutes. Then, as a polymerization terminator, an amount of methanol corresponding to twice the molar amount of the used n - butyllithium was added to obtain a solution containing solution - polymerized SBR. And 5.96 g of 2,6 - di - tert - butyl - p - cresol was added to the obtained solution. Next, the solvent was removed by steam stripping and dried with a hot roll adjusted to 110°C to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is also referred to as conjugated diene rubber 6. [Chemical formula]

[0112] In the above formula (9), X1, X4, R1~R3 and R5~R8 are methyl groups. In the above formula (9), m is 80 and k is 120. In the above formula (9), X2 is a group represented by the following formula (10) (where * represents the bonding position).

[0113] [Chemical formula]

[0114] [Table 1]

[0115] [[Weight average molecular weight, weight average intrinsic viscosity, styrene content, vinyl content, glass transition temperature]] For the conjugated diene rubbers (conjugated diene rubbers 1 to 2 and conjugated diene rubbers 4 to 6) synthesized as described above, Mw, Mw 10% , IVw, IVw 10% , St, Vn, and the glass transition temperature (Tg) are shown in Table 2. Similarly, the conjugated diene rubber 3 (NS612) described later is also shown in Table 2. Note that in Table 2, the "right side" of formula (1) is the right side of formula (1), which is "3.1×10 -6 ×Mw 10% -2.77". Also, in Table 2, the "satisfied or not" of formula (1) represents the satisfaction or non-satisfaction of formula (1). Specifically, "A" represents that formula (1) is satisfied, and "B" represents that formula (1) is not satisfied. Also, in Table 2, "St + Vn" of formula (2) represents the above-described St + Vn.

[0116] [[Table 2]]

[0117] As shown in Table 2, all of the conjugated diene rubbers 1 to 2 satisfy formulas (1) to (3). Also, as described above, all of the conjugated diene rubbers 1 to 2 are modified conjugated diene rubbers having specific modifying groups. Therefore, all of the conjugated diene rubbers 1 to 2 correspond to the above-described specific conjugated diene rubbers. On the other hand, as shown in Table 2, since both the conjugated diene rubber 3 and the conjugated diene rubber 6 do not satisfy formula (1), they do not correspond to the above-described specific conjugated diene rubbers. Also, as shown in Table 2, although the conjugated diene rubber 4 satisfies formula (1) but does not satisfy formula (2), it does not correspond to the above-described specific conjugated diene rubbers. Also, as shown in Table 2, although the conjugated diene rubber 5 satisfies formulas (1) to (2) but does not satisfy formula (3), it does not correspond to the above-described specific conjugated diene rubbers.

[0118] [Synthesis of Polysiloxane] 107.8 g (0.2 mol) of bis(triethoxysilylpropyl)tetrasulfide (KBE-846 manufactured by Shin-Etsu Chemical Co., Ltd.), 190.8 g (0.8 mol) of γ-mercaptopropyltriethoxysilane (KBE-803 manufactured by Shin-Etsu Chemical Co., Ltd.), 442.4 g (1.6 mol) of octyltriethoxysilane (KBE-3083 manufactured by Shin-Etsu Chemical Co., Ltd.), and 190.0 g of ethanol were placed in a 2 L separable flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer. Then, a mixed solution of 37.8 g (2.1 mol) of 0.5 N hydrochloric acid and 75.6 g of ethanol was added dropwise at room temperature. Thereafter, the mixture was stirred at 80°C for 2 hours. Then, it was filtered, 17.0 g of 5% KOH / EtOH solution was added dropwise, and the mixture was stirred at 80°C for 2 hours. Then, it was concentrated under reduced pressure and filtered to obtain 480.1 g of a brown transparent liquid polysiloxane. As a result of measurement by GPC, the average molecular weight was 840, and the average degree of polymerization was 4.0 (set degree of polymerization 4.0). Also, as a result of measuring the mercapto equivalent by the acetic acid / potassium iodide / potassium iodate addition-sodium thiosulfate solution titration method, it was 730 g / mol, and it was confirmed that the mercapto group content was as set. From the above, it is represented by the following average composition formula. Therefore, the obtained polysiloxane corresponds to the specific polysiloxane described above. (-C3H6-S4-C3H6-) 0.071 (-C8H 17 ) 0.571 (-OC2H5) 1.50 (-C3H6SH) 0.286 SiO 0.75 The obtained polysiloxane is also referred to as silane coupling agent 2.

[0119] [Preparation of Rubber Composition for Tires] Each component in Tables 3 to 4 below was mixed in the composition (parts by mass) shown in the same table. Specifically, first, the components other than sulfur and vulcanization accelerators in Tables 3 to 4 were mixed in a 1.8 L sealed mixer under the condition of 160 °C or lower for 5 minutes, and the masterbatch was discharged. Then, sulfur and vulcanization accelerators were added to the above masterbatch and mixed using an open roll under the condition of 100 °C or lower to produce rubber compositions for each tire.

[0120] [Evaluation] The following evaluations were performed on the obtained rubber compositions for each tire.

[0121] 〔Wet performance〕 Using the obtained rubber compositions for each tire, test tires were produced with a tire size of 245 / 40R19 and subjected to a wet braking test. Specifically, four of each test tire were mounted on a passenger car with a displacement of 2300 cc, and the braking distance from an initial speed of 100 km / h was measured on a water-sprinkled asphalt road surface. Then, the reciprocal of the braking distance was indexed with the standard example as 100. The results are shown in Tables 3 to 4. A larger index means better wet performance. In practical use, the index is preferably 100 or more.

[0122] 〔Snow performance〕 Using the obtained rubber compositions for each tire, test tires were produced with a tire size of 245 / 40R19 and subjected to a braking test on snow. Specifically, four of each test tire were mounted on a passenger car with a displacement of 2300 cc, and the braking distance from an initial speed of 40 km / h was measured on a snow-packed road surface. Then, the reciprocal of the braking distance was indexed with the standard example as 100. The results are shown in Tables 3 to 4. A larger index means better snow performance. In practical use, the index is preferably 100 or more.

[0123] 〔Abrasion resistance〕 The obtained rubber compositions for each tire were press-vulcanized at 160 °C for 40 minutes in a mold (15 cm × 15 cm × 0.2 cm) to produce each vulcanized rubber sheet. Regarding the obtained vulcanized rubber sheet, using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho), in accordance with JIS K 6264-2:2005, with an additional force of 4.0 kg / cm3 (=39 N), a slip rate of 30%, a wear test time of 4 minutes, and a wear test was conducted under the condition that the test temperature was room temperature, and the wear mass was measured. Then, the index was calculated as follows. The results are shown in Tables 3 to 4. The larger the index, the less the wear amount, which means excellent wear resistance. In practical use, the index is preferably 100 or more. Index = (wear mass of Comparative Example 4 / wear mass of each example) × 100

[0124] 〔Mixing processability〕 For each of the obtained rubber compositions for tires, in accordance with JIS K6300-1:2013, using an L-shaped rotor, the Mooney viscosity was measured under the conditions of a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 100°C. The reciprocals of the Mooney viscosities are shown in Tables 3 to 4. The results are expressed as an index with Comparative Example 4 being 100. The larger the index, the lower the viscosity, which means excellent mixing processability. In practical use, the index is preferably 100 or more.

[0125] 〔Extrusion processability〕 An unvulcanized rubber sheet (thickness: 2 mm) was prepared by cold pressing each of the obtained rubber compositions for tires. For the obtained unvulcanized rubber sheet, in accordance with JIS K6251:2010, a JIS No. 3 dumbbell-shaped test piece (thickness 2 mm) was punched out, and the 300% modulus was measured under the conditions of a temperature of 20°C and a tensile speed of 500 mm / min. The results are shown in Tables 3 to 4. The results are expressed as an index with Comparative Example 4 being 100. The larger the index, the more excellent the extrusion processability (green strength). In practical use, the index is preferably 100 or more.

[0126]

Table 3

[0127]

Table 4

[0128] Details of each component in Tables 3 to 4 are as follows. · Conjugated diene rubber 1 - 2: Conjugated diene rubber 1 - 2 synthesized as described above · Conjugated diene rubber 3: NS612 manufactured by Nippon Zeon Co., Ltd. (solution - polymerized SBR, Tg: - 60°C) · Conjugated diene rubber 4 - 6: Conjugated diene rubber 4 - 6 synthesized as described above · BR: Nipol BR1220 manufactured by Nippon Zeon Co., Ltd. (butadiene rubber, Tg: - 106°C) · CB: Seast 3 manufactured by Tokai Carbon Co., Ltd. (HAF carbon black, nitrogen adsorption specific surface area (N2SA): 79 m 2 / g) · Silica: ZEOSIL 1165MP manufactured by Solvay (CTAB adsorption specific surface area: 160 m 2 / g) · Oil: Oil · Terpene resin: YS Resin TO125 manufactured by Yasuhara Chemical Co., Ltd. (aromatic - modified terpene resin, softening point: 125°C) · C5 / C9 resin: HC - 3100 manufactured by Guangzhou Ecopower New Material Co., Ltd. · Comparative silane coupling agent: Si69 manufactured by Evonik (not corresponding to specific silane coupling agents) · Silane coupling agent 1: 3 - octanoylthio - 1 - propyltriethoxysilane (the following compound) (corresponding to specific silane coupling agents)

[0129]

Chemical formula

[0130] As can be seen from Tables 3 to 4, Examples 1 to 7 containing a rubber component containing a specific amount of a specific conjugated diene rubber, silica, and a specific silane coupling agent all exhibited excellent wet performance, snow performance, abrasion resistance, mixing processability, and extrusion processability. From the comparison between Example 1 and Example 2 (comparison between aspects where only the type of the specific silane coupling agent is different), Example 1 in which the specific silane coupling agent is 3-octanoylthio-1-propyltriethoxysilane exhibited better mixing processability and extrusion processability. Also, from the comparison between Example 1 and Example 2 (comparison between aspects where only the type of the specific silane coupling agent is different), Example 2 in which the specific silane coupling agent is a specific polysiloxane exhibited better wet performance. Also, from the comparison between Example 1 and Example 3 (comparison between aspects where only the type of the specific conjugated diene rubber is different), Example 3 in which the St+Vn of the specific conjugated diene rubber is 40 or more exhibited better wet performance. Also, from the comparison between Example 1 and Example 3 (comparison between aspects where only the type of the specific conjugated diene rubber is different), Example 1 in which the St+Vn of the specific conjugated diene rubber is less than 40 exhibited better snow performance. Also, from the comparison between Example 1 and Example 4 (comparison between aspects where the ratio of the specific conjugated diene rubber in the rubber component is different), Example 4 in which the above ratio is 50% by mass or more exhibited better wet performance, snow performance, abrasion resistance, and extrusion processability. Also, from the comparison between Example 1 and Example 4 (comparison between aspects where the ratio of the specific conjugated diene rubber in the rubber component is different), Example 1 in which the above ratio is less than 50% by mass exhibited better mixing processability. In addition, from the comparison between Example 1 and Examples 5 to 6 (comparison between different modes with different presence or absence of thermoplastic resin), Examples 5 to 6 containing thermoplastic resin showed more excellent wet performance and abrasion resistance. Among them, Example 6 containing at least two selected from the group consisting of terpene resin, C5 / C9 resin, C9 resin, DCPD resin, DCPD / C9 resin, hydrogenated C5 / C9 resin, hydrogenated C9 resin, hydrogenated DCPD resin, and hydrogenated DCPD / C9 resin in a content of 20 parts by mass or less each showed even more excellent wet performance, snow performance and abrasion resistance.

[0131] On the other hand, in the standard example not containing a specific conjugated diene rubber and a specific silane coupling agent, Comparative Examples 1 and 3 to 5 containing a specific silane coupling agent but not containing a specific conjugated diene rubber, Comparative Example 2 containing a specific amount of a specific conjugated diene rubber but not containing a specific silane coupling agent, and Comparative Example 6 containing a specific conjugated diene rubber and a specific silane coupling agent but having a proportion of the specific conjugated diene rubber in the rubber component of less than 25% by mass, at least one of wet performance, snow performance, abrasion resistance, mixing processability and extrusion processability was insufficient.

Explanation of Signs

[0132] 1 Bead part 2 Sidewall part 3 Tire tread part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion

Claims

1. The rubber composition contains a rubber component (A) containing a modified conjugated diene rubber (A1), silica (B), and a silane coupling agent (C), The modified conjugated diene rubber (A1) satisfies the following formulas (1) to (3) and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent to the silicon atom, The proportion of the modified conjugated diene rubber (A1) in the rubber component (A) is 25% by mass or more, The rubber composition for tires, wherein the silane coupling agent (C) is 3-octanoylthio-1-propyltriethoxysilane or a polysiloxane represented by the average composition formula (C2) below: [Vw １０％ ≦3.1×10 －６ ×Mw １０％ -2.77 (1) St+Vn≦50 (2) 4.7≦IVw １０％ (3) Mw in formulas (1) and (3) １０％ and IVw １０％ The details are as follows: The modified conjugated diene rubber is subjected to gel permeation chromatography measurement using a differential refractive index detector and a viscosity detector as detectors at 40° C. using toluene containing 5 mmol / L triethylamine as an eluent. The weight average molecular weight (Mw) was calculated using the high molecular weight portion of the chromatogram peak that was 10% of the total peak area. １０％ The weight-average intrinsic viscosity determined using the high molecular weight portion of the peak in the chromatogram obtained by the viscosity detector, which is 10% of the total peak area, is defined as IVw １０％ Here, the unit of the weight average intrinsic viscosity is dL / g. In formula (2), St represents the proportion (mass%) of repeating units derived from styrene to the entire modified conjugated diene rubber, and Vn represents the proportion (mass%) of repeating units of 1,2-vinyl structure derived from conjugated diene to the entire modified conjugated diene rubber. (A) ａ (B) ｂ (C) ｃ (D) ｄ (R １ ) ｅ SiO （４－２ａ－ｂ－ｃ－ｄ－ｅ）／２ (C2) In formula (C2), A represents a divalent organic group containing a sulfide group. B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms. C represents a hydrolyzable group. D represents an organic group containing a mercapto group. R １ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms, and a to e satisfy the relational expressions 0≦a<1, 0<b<1, 0<c<3, 0<d<1, 0≦e<2, 0<2a+b+c+d+e<4.

2. The modified conjugated diene rubber (A1) is a star-shaped structure having three or more branches, at least one branch of which has a moiety derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group; The rubber composition for a tire according to claim 1 , wherein the portion further has a main chain branched structure.

3. The rubber composition for tires according to claim 1, further comprising 20 to 50 parts by mass of a thermoplastic resin (D) per 100 parts by mass of the rubber component (A).

4. 4. The rubber composition for tires according to claim 3, wherein the thermoplastic resin (D) is at least two selected from the group consisting of terpene resins, C5 / C9 resins, C9 resins, DCPD resins, DCPD / C9 resins, hydrogenated C5 / C9 resins, hydrogenated C9 resins, hydrogenated DCPD resins, and hydrogenated DCPD / C9 resins, each in an amount of 20 parts by mass or less.

5. The rubber composition for tires according to claim 1, wherein the content of the silica (B) is 50 to 150 parts by mass per 100 parts by mass of the rubber component (A).

6. A tire produced using the rubber composition for tires according to any one of claims 1 to 5.

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