Rubber composition for tires, and tire

Abstract

The purpose of the present invention is to provide: a rubber composition for tires which exhibit excellent resistance to thermal sagging, resistance to wear in circuit running, wet performance, and rolling performance; and a tire produced using the rubber composition. This rubber composition for tires comprises: a rubber component A including a modified conjugated-diene rubber A1; silica B; and a softener C comprising at least one member selected from the group consisting of thermoplastic resins and oils. The A1 is a conjugated-diene rubber satisfying a specific expression and having a modification group including a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto and accounts for 25 mass% or more of the A. The A as a whole has a glass transition temperature higher than -80°C but not higher than -45°C. The content of the B is 80-160 parts by mass per 100 parts by mass of the A. The content of the thermoplastic resin(s) is 30-80 parts by mass, excluding 80 parts by mass, per 100 parts by mass of the A, and the proportion of the thermoplastic resin(s) to the sum of the thermoplastic resin(s) and the oil(s) is 50 mass% or higher.

Description

Rubber composition for tires and tires

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

[0002] BACKGROUND ART Conventionally, rubber compositions for tires containing silica in order to improve performance have been known (for example, Patent Document 1).

[0003] JP 2014-28902 A

[0004] Recently, from the viewpoint of safety and the like, there has been a demand for further improvements in heat sagging resistance, circuit wear resistance (wear resistance under high severity conditions such as circuit driving), wet performance, etc. In addition, from the viewpoint of environmental issues and the like, there has also been a demand for further improvements in rolling performance. In this context, the present inventors have studied the rubber composition for tires described in Patent Document 1 and the like, and have found that further improvements are desirable in consideration of demands that are likely to increase in the future.

[0005] In view of the above circumstances, the present invention aims to provide a rubber composition for tires that, when made into a tire, exhibits excellent heat sagging resistance, circuit abrasion resistance, wet performance, and rolling performance, and a tire manufactured using the rubber composition for tires.

[0006] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a specific modified conjugated diene rubber as the rubber component and optimizing the contents of silica and thermoplastic resin, etc., and have arrived at the present invention. That is, the present inventors have found that the above-mentioned problems can be solved by the following configuration.

[0007] (1) A rubber component (A) containing a modified conjugated diene rubber (A1), silica (B), and a softener (C) consisting of at least one selected from the group consisting of a thermoplastic resin and an oil, wherein the modified conjugated diene rubber (A1) is a conjugated diene rubber that satisfies the following formulas (1) and (2) and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, wherein the proportion of the modified conjugated diene rubber (A1) in the rubber component (A) is 25% by mass or more, the glass transition temperature of the entire rubber component (A) is higher than -80°C and -45°C or less, the content of the silica (B) per 100 parts by mass of the rubber component (A) is 80 parts by mass or more and 160 parts by mass or less, and the content of the thermoplastic resin per 100 parts by mass of the rubber component (A) is 30 parts by mass or more and less than 80 parts by mass, A rubber composition for a tire, wherein the ratio of the thermoplastic resin to the total of the thermoplastic resin and the oil is 50 mass % or more. １０％ ≦3.1×10 －６ ×Mw １０％ −2.77 (1) St+Vn≦50 (2) Mw in formula (1) １０％ and IVw １０％ The weight average molecular weight (Mw) is determined by using the high molecular weight portion of the peak in the chromatogram obtained by the differential refractive index detector, which is 10% of the total area of ​​the peak. 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 area of ​​the entire peak, is defined as IVw. １０％where the unit of weight average intrinsic viscosity is dL / g. In formula (2), St represents the proportion (% by mass) of repeating units derived from styrene to the entire modified conjugated diene rubber, and Vn represents the proportion (% by mass) of repeating units of a 1,2-vinyl structure derived from a conjugated diene to the entire modified conjugated diene rubber. (2) The rubber composition for a tire according to (1) above, wherein the modified conjugated diene rubber (A1) has a star structure with three or more branches, at least one branch chain of the star structure has a moiety derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group, and the moiety has a further main chain branched structure. (3) The rubber composition for a tire according to (1) or (2), wherein the thermoplastic resin comprises at least one selected from the group consisting of a terpene resin, a C5 / C9 resin, a C9 resin, a DCPD resin, a DCPD / C9 resin, a hydrogenated C5 / C9 resin, a hydrogenated C9 resin, a hydrogenated DCPD resin, and a hydrogenated DCPD / C9 resin. (4) The rubber composition for a tire according to any one of (1) to (3), further comprising 0.2 parts by mass or more and 3.0 parts by mass or less of a thiuram vulcanization accelerator per 100 parts by mass of the rubber component (A). (5) The rubber composition for a tire according to any one of (1) to (4), wherein the content of the thermoplastic resin per 100 parts by mass of the rubber component (A) is 50 parts by mass or more and less than 80 parts by mass, and the proportion of the thermoplastic resin to the total of the thermoplastic resin and the oil is 80% by mass or more. (6) The rubber composition for a tire according to any one of (1) to (5) above, wherein the softener (C) contains two or more thermoplastic resins. (7) A tire produced using the rubber composition for a tire according to any one of (1) to (6) above.

[0008] As will be described below, according to the present invention, it is possible to provide a rubber composition for a tire that exhibits excellent heat sagging resistance, circuit abrasion resistance, wet performance, and rolling performance when made into a tire, and a tire manufactured using the rubber composition for a tire.

[0009] 1 is an example of a GPC chromatogram. 2 is a partial cross-sectional schematic view showing an example of an embodiment of a tire of the present invention.

[0010] The rubber composition for tires of the present invention will be described below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. Each component may be used alone, or two or more may be used in combination. When two or more components are used in combination, the content of the components refers to the total content unless otherwise specified. Furthermore, with regard to the rubber composition for tires, the heat sagging resistance, circuit wear resistance, wet performance, and rolling performance of the tire are also referred to simply as "heat sagging resistance," "circuit wear resistance," "wet performance," and "rolling performance," respectively. Furthermore, in this specification, powers of 10 are sometimes represented by E. For example, E+5 represents 10 to the fifth power.

[0011] [I] Rubber Composition for Tire The rubber composition for tire of the present invention (hereinafter also referred to as "the composition of the present invention") comprises: a rubber component (A) containing a modified conjugated diene rubber (A1); silica (B); and a softener (C) consisting of at least one selected from the group consisting of a thermoplastic resin and an oil; the modified conjugated diene rubber (A1) is a conjugated diene rubber that satisfies the formula (1) and the formula (2) described later and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto; the proportion of the modified conjugated diene rubber (A1) in the rubber component (A) is 25% by mass or more; the glass transition temperature of the entire rubber component (A) is higher than -80°C and -45°C or less; the content of the silica (B) per 100 parts by mass of the rubber component (A) is 80 parts by mass or more and 160 parts by mass or less; the content of the thermoplastic resin per 100 parts by mass of the rubber component (A) is 30 parts by mass or more and less than 80 parts by mass; In the rubber composition for tires, the proportion of the thermoplastic resin relative to the total of the thermoplastic resin and the oil is 50% by mass or more.

[0012] The composition of the present invention is believed to be able to solve the above-mentioned problems because of its configuration. The reason for this is unclear, but is presumed to be as follows. The composition of the present invention contains, as a rubber component, a conjugated diene-based rubber (hereinafter also referred to as a "specific conjugated diene-based rubber") that satisfies the following formula (1) and formula (2) and has a modifying group (hereinafter also referred to as a "specific modifying 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. Studies by the present inventors have shown that rubbers that satisfy formula (1) have excellent processability. Furthermore, the specific modifying group possessed by the specific conjugated diene-based rubber is believed to interact with silica. Therefore, the dispersibility of silica in the composition of the present invention is extremely high, which is believed to lead to excellent effects (heat sagging resistance, circuit wear resistance, wet performance, and rolling performance). Furthermore, since the composition of the present invention contains a specific amount of thermoplastic resin, it is believed that an extremely high level of modulus (heat sagging resistance) and circuit abrasion resistance can be achieved.

[0013] Each component contained in the composition of the present invention will be described below.

[0014] [1] Rubber Component The composition of the present invention contains a rubber component containing 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 is a conjugated diene rubber that satisfies the formula (1) described later and the formula (2) described later, and has a modifying group (specific modifying group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto.

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

[0017] <Conjugated diene> Specific examples of the conjugated diene include butadiene (particularly 1,3-butadiene), isoprene, chloroprene, etc. The diene is preferably butadiene (particularly 1,3-butadiene) or isoprene, and more preferably butadiene (particularly 1,3-butadiene), because the effects of the present invention are more excellent.

[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 the monomer that forms such a repeating unit (other monomer) include vinyl monomers, alkenes (e.g., ethylene, propylene, butene), etc. Examples of the vinyl monomer include aromatic vinyls (e.g., styrene), acrylonitrile, and the specific branching agents described below.

[0019] <Specific Examples> Specific examples of the skeleton 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), etc. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR) and styrene-isoprene copolymer rubber. The conjugated diene rubber is preferably SBR because the effects of the present invention are more excellent.

[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 end, main chain, or side chain of the conjugated diene rubber. For the reason 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 the silicon atom as an alkoxysilyl group. The alkoxysilyl group is -Si(OR1) ｎ (R2) ３－ｎ(wherein R1 is an alkyl group, R2 is a hydrogen atom or an alkyl group, and n is an integer of 1 to 3). The specific modifying group preferably contains a nitrogen atom as an amino group (primary to tertiary amino group) because the effects of the present invention are more excellent. The specific modifying group is preferably a group derived from a specific modifying agent described below because the effects of the present invention are more excellent.

[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, and polymers having a small molecular size relative to their molecular weight, such as those having branches, tend to satisfy formula (1). The reason for limiting the formula to the high molecular weight side is that it has a large impact on the physical properties of the entire polymer.

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

[0023] Mw in formula (1) １０％ and IVw １０％ The weight average molecular weight (Mw) is determined by using a high molecular weight portion of the peak in the chromatogram obtained by the differential refractive index detector, which is 10% of the total area of ​​the peak. 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 area of ​​the entire peak, is defined as IVw. １０％ However, the unit of the weight average intrinsic viscosity is dL / g.

[0024] Hereinafter, Mw in formula (1) １０％ and IVw １０％ This will be explained in more detail.

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

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

[0027] The weight average molecular weight is determined by using the high molecular weight side (the side with a shorter elution time) which accounts for 10% of the area of ​​the entire peak (peak attributable to the modified conjugated diene rubber) in the chromatogram (horizontal axis: elution time, vertical axis: signal intensity) obtained by the differential refractive index detector. １０％ Let's say.

[0028] In addition, among the peaks (peaks attributable to the modified conjugated diene rubber) in the chromatogram (horizontal axis: elution time, vertical axis: signal intensity) obtained by the viscosity detector, the weight-average intrinsic viscosity is determined using the portion on the high molecular weight side (shorter elution time) which accounts for 10% of the total peak area. The weight-average intrinsic viscosity thus obtained is referred to as IVw １０％ The weight average intrinsic viscosity is defined as (Σ(ηi×Mi×Ni)) / (Σ(Mi×Ni)), where Ni is the number of molecules and ηi is the intrinsic viscosity at molecular weight Mi.

[0029] An example of a GPC chromatogram (horizontal axis: elution time, vertical axis: signal intensity) is shown in Figure 1. Mw １０％ and IVw １０％ Ask for.

[0030] Examples of a method for making the modified conjugated diene rubber satisfy formula (1) include a method of changing the type and amount of the specific modifier and the type and amount of the specific branching agent in the production method of the present invention described below.

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

[0032] IVw １０％ is preferably 2 to 8, and more preferably 4 to 6, because the effects of the present invention are more excellent.

[0033] [Formula (2)] The specific conjugated diene rubber satisfies the following formula (2).

[0034] St+Vn≦50 (2)

[0035] In formula (2), St represents the proportion (mass%) of repeating units derived from styrene relative to the entire specific conjugated diene rubber (hereinafter also referred to as the "styrene amount"), and Vn represents the proportion (mass%) of repeating units of a 1,2-vinyl structure derived from a conjugated diene (for example, butadiene) relative to the entire specific conjugated diene rubber (hereinafter also referred to as the "vinyl amount").

[0036] St+Vn is preferably 10 to 45, and more preferably 25 to 45, because the effects of the present invention are more excellent.

[0037] St is preferably 5 to 40, more preferably 10 to 35, and even more preferably 15 to 30, because the effects of the present invention are more excellent.

[0038] Vn is preferably 5 to 30, and more preferably 10 to 20, because the effects of the present invention are more excellent.

[0039] [Molecular Weight] The weight average molecular weight (Mw) of the specific conjugated diene rubber is preferably 100,000 to 2,000,000, more preferably 200,000 to 1,300,000, because the effects of the present invention are more excellent. The method for measuring the weight average molecular weight (Mw) of the specific conjugated diene rubber is the same as that described above except that the entire peak is used. １０％ is the same as

[0040] [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, for reasons of better effects of the present invention. The glass transition temperature can be adjusted, for example, by the amount of styrene or vinyl. In this specification, the glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) at a temperature rise rate of 10°C / min and calculated by the midpoint method.

[0041] [Preferred Aspect 1] For reasons of better effects of the present invention, the specific conjugated diene rubber preferably has a star structure with three or more branches, more preferably has a star structure with three or more branches in which the specific modifying group is a branch point, and further preferably is a conjugated diene rubber represented by the following formula (A):

[0042]

[0043] 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.

[0044] 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.

[0045] As described above, P represents a conjugated diene polymer chain. Multiple 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 skeleton of the specific conjugated diene rubber described above.

[0046] As described above, n represents an integer of 3 or greater. There is no particular upper limit to n, but it is preferably 30 or less in order to obtain better effects of the present invention.

[0047] [Preferred Aspect 2] When the specific conjugated diene rubber has a star structure with three or more branches, at least one branched chain (conjugated diene polymer chain) of the star structure preferably has a moiety derived from a specific branching agent described below, and the moiety preferably has an additional main chain branched structure, for reasons of better effects of the present invention. Note that the main chain branched structure refers to a structure in which the branched chain (conjugated diene polymer chain) forms a branch point at a moiety derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group, and a polymer chain (for example, another conjugated diene polymer chain) further extends from the branch point.

[0048] [Content] The proportion of the specific conjugated diene rubber in the rubber component is 25% by mass or more. For reasons of better effects of the present invention, this 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 this proportion is not particularly limited, and is 100% by mass.

[0049] [Method for producing specific conjugated diene rubber] The method for producing the specific conjugated diene rubber is not particularly limited, but a method comprising the following steps (1) and (2) (hereinafter also referred to as the "production method of the present invention") is preferred because it provides better effects of the present invention: (1) a polymerization step of anionic polymerization of a monomer containing a conjugated diene to obtain a conjugated diene polymer; (2) a modification step of 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 the "specific modifier") to obtain a conjugated diene rubber having a specific modifying group.

[0050] [Polymerization Step] The polymerization step is a step of obtaining a conjugated diene-based polymer by anionic polymerization of a monomer containing a conjugated diene.

[0051] <Anionic Polymerization> The anionic polymerization is not particularly limited, but anionic polymerization using an organolithium compound as an initiator is preferred because it provides better effects of the present invention.

[0052] The organolithium compound is not particularly limited, and specific examples thereof include monoorganolithium compounds such as n-butyllithium (n-BuLi), sec-butyllithium, tert-butyllithium, n-propyllithium, isopropyllithium, and benzyllithium; and polyfunctional organolithium compounds such as 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-trillithiobenzene, and 1,3,5-trillithio-2,4,6-triethylbenzene. Among these, monoorganolithium compounds such as n-butyllithium, sec-butyllithium, and tert-butyllithium are preferred, with n-butyllithium being more preferred, because they provide better effects for the present invention.

[0053] The amount of the organolithium compound used is not particularly limited, but is preferably 0.001 to 10 mol % based on the monomer, because this provides a better effect of the present invention.

[0054] <Monomer> Specific examples and preferred embodiments of the conjugated diene-containing monomer used in the polymerization step are the same as those of the conjugated diene and other monomers in the skeleton of the specific conjugated diene-based rubber described above.

[0055] (Specific branching agent) The monomer preferably contains a vinyl monomer containing an alkoxysilyl group or a halosilyl group (hereinafter also referred to as "specific branching agent"), because the effects of the present invention are more excellent. The specific branching agent is preferably an aromatic vinyl (particularly 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, because the effects of the present invention are more excellent.

[0056] (1) Specific Examples Specific examples of aromatic vinyls containing an alkoxysilyl group include 1-(trimethoxysilyl)-4-vinylbenzene, 1,1-bis(4-trimethoxysilylphenyl)ethylene, etc. Specific examples of aromatic vinyls containing a halosilyl group include trichloro(4-vinylphenyl)silane, 1,1-bis(4-trichlorosilylphenyl)ethylene, etc.

[0057] (2) Amount Used The amount of the specific branching agent used is preferably 0.001 to 0.1% by mass, more preferably 0.005 to 0.05% by mass, based on the conjugated diene, for reasons of better effects of the present invention.

[0058] <Polar Compound> A polar compound may be added in the polymerization step. This allows the monomers to be copolymerized randomly. Polar compounds also tend to be usable as vinylating agents for controlling the microstructure of conjugated dienes. They also tend to be effective in accelerating the polymerization reaction.

[0059] Examples of polar compounds that can be used include ethers such as tetrahydrofuran, diethyl ether, dioxane, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate and sodium tert-butylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used alone or in combination of two or more.

[0060] (Amount Used) The amount of the polar compound used is preferably 0.01 moles or more and 100 moles or less per mole of the initiator, because the effects of the present invention are more excellent.

[0061] [Modification Step] The modification step is a step of reacting the conjugated diene polymer obtained in the polymerization step with a modifier (specific modifier) ​​containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, to obtain a conjugated diene rubber having a specific modifying group.

[0062] In the modification step, the active terminal of the conjugated diene polymer obtained in the polymerization step is thought to bond to the silicon atom of the specific modifying agent. For example, when the specific modifying agent contains an alkoxysilyl group, the active terminal is thought to bond to the silicon atom of the alkoxysilyl group, and the alkoxy group is thought to be released. Furthermore, when the conjugated diene polymer obtained in the polymerization step has a portion derived from a specific branching agent, in addition to the active terminal described above, the alkoxysilyl group or halosilyl group in the portion is thought to react with the specific modifying agent (e.g., alkoxysilyl group). Furthermore, the alkoxysilyl group or halosilyl group in the portion is thought to react with the active terminal of another conjugated diene polymer. As a result, a conjugated diene polymer having a portion derived from a specific branching agent will have a main chain branched structure (another conjugated diene polymer chain) in the portion.

[0063] <Specific Modifier> The specific modifier is a compound containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. For reasons of enhanced effects of the present invention, the specific modifier preferably contains the silicon atom and the oxygen atom adjacent thereto as an alkoxysilyl group (particularly, a trialkoxysilyl group) or a group containing a silazane structure (particularly, a cyclic silazane structure) in which an alkoxy group is bonded to the silicon atom of the silazane structure. Here, the silazane structure refers to a structure in which a silicon atom and a nitrogen atom are directly bonded (a structure having an Si—N bond). For reasons of enhanced effects of the present invention, the specific modifier preferably contains a nitrogen atom as a group containing an amino group (primary to tertiary amino group) or a silazane structure (particularly, a cyclic silazane structure). The specific modifier preferably has two or more (preferably three or more) moieties capable of reacting with an active terminal such as an alkoxysilyl group. When the specific modifier has a plurality of such moieties, the specific modifier functions as a coupling agent that connects conjugated diene-based polymers together.

[0064] (Specific Examples) Specific examples of the specific modifying agent 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 and tertiary amines having an alkoxysilyl group and a group containing a cyclic silazane structure, such as -(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, and bis(2-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-methyl-1,3-propanediamine.

[0065] (Amount Used) The amount of the specific modifier used is preferably 0.01 to 1% by mass, more preferably 0.02 to 0.2% by mass, based on the conjugated diene, for reasons of better effects of the present invention.

[0066] [Other Steps] The production method of the present invention may include steps (other steps) other than the steps described above. Examples of the other steps include a polymerization termination step of adding a polymerization terminator (e.g., methanol), and a solvent removal step of removing the solvent by steam stripping.

[0067] [Other Rubber Components] The rubber component may contain a rubber component (rubber component) other than the specific conjugated diene rubber. 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), and chloroprene rubber (CR). Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR) and styrene-isoprene copolymer rubber.

[0068] [Average Tg] The glass transition temperature of the entire rubber component (hereinafter also referred to as "average Tg") is greater than -80°C and less than -45°C. The average Tg of the rubber component is preferably greater than -75°C and less than -45°C, and more preferably greater than -70°C and less than -50°C, for reasons of better effects of the present invention. The average Tg of the rubber component is the sum (weighted average value of glass transition temperatures) of the glass transition temperatures (Tg) of each rubber component multiplied by the mass fraction of each rubber component.

[0069] [Molecular Weight] The 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.

[0070] [2] Silica The composition of the present invention contains silica. There are no particular limitations on the type of silica, and any conventionally known silica can be used. Examples of silica include wet silica, dry silica, fumed silica, and diatomaceous earth. Silica derived from biomass, such as rice husks, may also be used. The silica may be used alone or in combination of two or more types.

[0071] [CTAB] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​silica (hereinafter, "CTAB adsorption specific surface area" may be simply referred to as "CTAB") is not particularly limited, but in order to obtain a more excellent effect of the present invention, it is preferred to use a surface area of ​​100 to 300 m. ２ / g, and 150 to 200m ２Here, the CTAB adsorption specific surface area is a value measured in accordance with JIS K6430:2008, Appendix G.

[0072] [Content] In the composition of the present invention, the content of silica is 80 parts by mass or more and 160 parts by mass or less per 100 parts by mass of the rubber component. The content of silica is preferably 100 parts by mass or more and 140 parts by mass or less per 100 parts by mass of the rubber component, for the reason that the effects of the present invention are more excellent.

[0073] [3] Softener The composition of the present invention contains a softener comprising at least one selected from the group consisting of thermoplastic resins and oils.

[0074] [Thermoplastic Resin] The softener contains a thermoplastic resin. The softener preferably contains two or more types of thermoplastic resins, because this provides a better effect of the present invention.

[0075] [Specific Examples] Examples of thermoplastic resins include coumarone-based resins (e.g., coumarone resin, coumarone-indene resin, coumarone-indene-styrene resin), phenol-based resins (e.g., phenol resin, phenol-acetylene resin, phenol-formaldehyde resin), xylene-based resins (e.g., xylene resin, xylene-acetylene resin, xylene-formaldehyde resin), rosin-based resins (e.g., rosin, rosin ester, hydrogenated rosin derivative), terpene-based resins (e.g., terpene resin, modified Examples of suitable resins include aromatic terpene resins (such as aromatic modified terpene resins), terpene phenol resins, hydrogenated terpene resins, α-pinene resins, β-pinene resins, limonene resins, hydrogenated limonene resins, dipentene resins, and terpene styrene resins), styrene-based resins, petroleum-based resins (for example, C5 / C9-based resins, C9-based resins, DCPD (dicyclopentadiene)-based resins, DCPD / C9-based resins, hydrogenated C5 / C9-based resins, hydrogenated C9-based resins, hydrogenated DCPD-based resins, and hydrogenated DCPD / C9-based resins), and aliphatic saturated hydrocarbon-based resins.

[0076] 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, because this provides better effects of the present invention.

[0077] [Content] In the composition of the present invention, the content of the thermoplastic resin is 30 parts by mass or more and less than 80 parts by mass per 100 parts by mass of the rubber component. In the composition of the present invention, the content of the thermoplastic resin is preferably 50 parts by mass or more and less than 80 parts by mass per 100 parts by mass of the rubber component, for the reason that the effects of the present invention are more excellent.

[0078] In the composition of the present invention, the content of the thermoplastic resin is preferably 40 to 120% by mass relative to the specific conjugated diene rubber, for the reason that the effects of the present invention are more excellent.

[0079] [Oil] The softener may contain oil.

[0080] [Content] In the composition of the present invention, the content of oil is preferably 0 to 40 parts by mass, and more preferably 5 to 35 parts by mass, per 100 parts by mass of the rubber component, because the effects of the present invention are more excellent.

[0081] [Resin Ratio] In the composition of the present invention, the ratio of the thermoplastic resin to the total of the thermoplastic resin and the oil (hereinafter also referred to as "resin ratio") is 50% by mass or more. The resin ratio is preferably 80% by mass or more because the effects of the present invention are more excellent. The upper limit of the resin ratio is not particularly limited, and is 100% by mass.

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

[0083] [Silane Coupling Agent] The composition of the present invention preferably contains a silane coupling agent, because the effects of the present invention are more excellent.

[0084] The silane coupling agent is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group. The hydrolyzable group is not particularly limited, but examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Of these, an alkoxy group is preferred because the effects of the present invention are more excellent. When the hydrolyzable group is an alkoxy group, the number of carbon atoms in the alkoxy group is preferably 1 to 16, and more preferably 1 to 4, because the effects of the present invention are more excellent. Examples of alkoxy groups having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, and a propoxy group.

[0085] The organic functional group is not particularly limited, but is preferably a group capable of forming a chemical bond with an organic compound, such as an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, a sulfide group, a mercapto group, a blocked mercapto group (protected mercapto group) (e.g., an octanoylthio group), and the like. Among these, a sulfide group (particularly a disulfide group or a tetrasulfide group), a mercapto group, or a blocked mercapto group is preferred because the effects of the present invention are more excellent. The silane coupling agent may be used alone or in combination of two or more.

[0086] The silane coupling agent is preferably a sulfur-containing silane coupling agent, since this provides a better effect of the present invention.

[0087] Specific examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, and 3-octanoylthio-1-propyltriethoxysilane. One of these may be used alone, or two or more may be used in combination.

[0088] [Content] In the composition of the present invention, the content of the silane coupling agent is not particularly limited, but is preferably 2 to 20 parts by mass per 100 parts by mass of the rubber component described above, because this provides better effects of the present invention.

[0089] Furthermore, in the composition of the present invention, the content of the silane coupling agent is preferably 1 to 20 mass %, more preferably 5 to 15 mass %, relative to the content of the silica described above, because this provides better effects of the present invention.

[0090] [Carbon Black] The composition of the present invention preferably contains carbon black because the effects of the present invention are more excellent. The carbon black may be used alone or in combination of two or more types. The carbon black is not particularly limited, and various grades of carbon black such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, and SRF may be used.

[0091] [N ２ SA] The nitrogen adsorption specific surface area (N ２SA) is not particularly limited, but is preferably 50 to 200 m because the effect of the present invention is more excellent. ２ / g, and 70 to 150m ２ Here, the nitrogen adsorption specific surface area (N2SA) is a value obtained by measuring the amount of nitrogen adsorbed onto the surface of carbon black in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0092] [Content] In the composition of the present invention, the content of carbon black is not particularly limited, but in order to achieve better effects of the present invention, the content is preferably 1 to 100 parts by mass, and more preferably 2 to 30 parts by mass, per 100 parts by mass of the rubber component described above.

[0093] [Vulcanization Accelerator] The composition of the present invention preferably contains a vulcanization accelerator, for the reason that the effects of the present invention are more excellent. Examples of vulcanization accelerators include sulfenamide-based, thiuram-based, and guanidine-based accelerators.

[0094] In the composition of the present invention, the content of the vulcanization accelerator is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 3 to 6 parts by mass, per 100 parts by mass of the rubber component, for reasons of better effects of the present invention.

[0095] [Preferred embodiment] The vulcanization accelerator preferably contains a thiuram vulcanization accelerator because this provides better effects of the present invention.

[0096] In the composition of the present invention, the content of the thiuram vulcanization accelerator is preferably 0.2 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of the rubber component, because the effects of the present invention are more excellent. In the composition of the present invention, the content of the thiuram vulcanization accelerator is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, and even more preferably 0.5 to 2% by mass, based on the specific conjugated diene rubber, because the effects of the present invention are more excellent.

[0097] [5] Method for Preparing Rubber Composition for Tires The method for producing the composition of the present invention is not particularly limited, and specific examples thereof include a method in which the above-mentioned components are kneaded using known methods and devices (e.g., a Banbury mixer, a kneader, a 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 the sulfur and the vulcanization accelerator at a high temperature (preferably 100 to 160°C), cool the mixture, and then mix in the sulfur or vulcanization accelerator. In addition, the composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0098] [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, or other gases.

[0099] Fig. 2 shows a partial cross-sectional schematic view of a tire showing one example of an embodiment of the tire of the present invention, although the tire of the present invention is not limited to the embodiment shown in Fig. 2.

[0100] In Figure 2, reference numeral 1 denotes a bead portion, reference numeral 2 denotes a sidewall portion, and reference numeral 3 denotes a tire tread portion. A carcass layer 4 having fiber cords embedded therein is mounted between the pair of left and right bead portions 1, and the ends of this carcass layer 4 are folded back and wound up around a bead core 5 and a bead filler 6 from the inside to the outside of the tire. In the tire tread portion 3, a belt layer 7 is disposed around the entire circumference of the tire on the outside of the carcass layer 4. In the bead portion 1, a rim cushion 8 is disposed in the portion that contacts the rim. At least one of reference numerals 2-3, 5-6, and 8 (preferably reference numeral 3) is formed from the composition of the present invention described above.

[0101] The tire of the present invention can be manufactured, for example, by a conventionally known method. The gas to be filled into the tire can be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0102] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0103] [Synthesis of Conjugated Diene Rubber] Each conjugated diene rubber was synthesized as follows.

[0104] [Conjugated diene rubber 1]

[0105] <Polymerization Step> An autoclave equipped with a stirrer was charged under a nitrogen atmosphere with 1000 g / h (hour), tetramethylethylenediamine 0.023 g / h, 1,3-butadiene 176.4 g / h, 1-butene 0.406 g / h, and styrene 23.6 g / h, and then n-butyllithium was continuously added at 1.43 mmol / h, and polymerization was initiated at 70°C. Once the polymerization was sufficiently stabilized, 1-(trimethoxysilyl)-4-vinylbenzene (branching agent) was added at 0.02 g / h, and the mixture was allowed to react with stirring. The branching agent corresponds to the specific branching agent described above.

[0106] <Modification Step> To the solution flowing out from the outlet of the reactor, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine (modifier) ​​was added at 0.08 g / h, and the mixture was stirred to react.

[0107] Thereafter, methanol was added as a polymerization terminator to obtain a solution containing a conjugated diene rubber.

[0108] To the resulting solution, 1.14 parts by mass of Irganox 1520L (manufactured by BASF) was added as an antioxidant per 100 parts by mass of the conjugated diene rubber, and the solvent was then removed by steam stripping. The resulting mixture was vacuum dried at 60°C for 24 hours to obtain a solid conjugated diene rubber. The resulting conjugated diene rubber is also referred to as conjugated diene rubber 1.

[0109] The conjugated diene rubber 1 is a reaction product of a conjugated diene polymer, which is a copolymer of butadiene, styrene, and a branching agent, with a modifier, and is a modified conjugated diene rubber having a modifying group (specific modifying group) derived from the modifier, which includes a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. The conjugated diene rubber 1 has a star structure with three or more branches with the modifying group as a branching point, and the branched chain bonded to the modifying group has a portion derived from the branching agent, and the portion derived from the branching agent has a further main chain branched structure (conjugated diene polymer chain).

[0110] [Conjugated diene rubber 2] A solid conjugated diene rubber was obtained in the same manner as for conjugated diene rubber 1, except that the amount of each component used was changed as shown in Table 1. The obtained conjugated diene rubber is also referred to as conjugated diene rubber 2.

[0111] 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, with a modifier, and is a modified conjugated diene rubber having a modifying group (specific modifying group) derived from the modifier, which includes a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. The conjugated diene rubber 2 has a star structure with three or more branches with the modifying group as a branching point, and the branched chain bonded to the modifying group has a portion derived from the branching agent, and the portion derived from the branching agent has a further main chain branched structure (conjugated diene polymer chain).

[0112] [Conjugated Diene Rubber 3] A solid conjugated diene rubber was obtained in the same manner as for Conjugated Diene Rubber 1, except that the amount of each component used was changed as shown in Table 1. The obtained conjugated diene rubber is also referred to as Conjugated Diene Rubber 3.

[0113] The conjugated diene rubber 3 is a reaction product of a conjugated diene polymer, which is a copolymer of butadiene, styrene, and a branching agent, with a modifier, and is a modified conjugated diene rubber having a modifying group (specific modifying group) derived from the modifier, which includes a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. The conjugated diene rubber 3 has a star structure with three or more branches with the modifying group as a branching point, and the branched chain bonded to the modifying group has a portion derived from the branching agent, and the portion derived from the branching agent has a further main chain branched structure (conjugated diene polymer chain).

[0114]

[0115] [Comparative Conjugated Diene Rubber] 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-purged 5-liter autoclave reactor. After adjusting the temperature of the reactor contents 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, with the maximum temperature reaching 85°C. When the polymerization conversion reached 99% (20 minutes after the start of polymerization), 10 g of 1,3-butadiene was added over 2 minutes, followed by the addition of 2.12 mmol of a compound (modifier) ​​represented by the following formula (4), and the reaction was continued for 15 minutes. The modifier corresponds to the specific modifier described above. 3.96 g of 2,6-di-tert-butyl-p-cresol was added to the resulting solution. Next, the solvent was removed by steam stripping, and the mixture was dried with a heated roll adjusted to 110° C. to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is also referred to as a comparative conjugated diene rubber.

[0116] Formula (4)

[0117] In formula (4), R １ is a hydrocarbyl group having 1 to 20 carbon atoms, and R ２ is a hydrocarbyloxy group having 1 to 20 carbon atoms, and R ３ is an alkanediyl group having 1 to 20 carbon atoms, and A ２ is the group "*-C(R ５ )=N-" or the group "*-N=C(R ５ ) -" (However, R５ is a hydrogen atom or a hydrocarbyl group, and * is R ４ ) indicates that the bond is bonded to 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 and having at least one atom selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms and having no active hydrogen. n is an integer of 1 to 3, and m is an integer of 2 to 10. In the formula, multiple R １ , R ２ , R ３ , A ２ , n may be the same or different.

[0118] The comparative conjugated diene rubber is a reaction product of a conjugated diene polymer, which is a copolymer of butadiene and styrene, with a modifier, and is a modified conjugated diene rubber having a modifying group (specific modifying group) derived from the modifier and containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto.

[0119] [Weight-average molecular weight, weight-average intrinsic viscosity, styrene content, vinyl content, glass transition temperature] The conjugated diene rubbers synthesized as described above (conjugated diene rubbers 1 to 3, comparative conjugated diene rubbers) were measured for Mw, Mw １０％ , IVw, IVw １０％ , St, Vn, and glass transition temperature (Tg) are shown in Table 2. The same is true for E581 and NS612, which will be described later. In Table 2, the "right side" of formula (1) refers to the right side of formula (1), "3.1 × 10 －６ ×Mw １０％ In Table 2, "Suitable / Incompatible" in formula (1) indicates whether formula (1) is satisfied, and specifically, "A" indicates that formula (1) is satisfied, and "B" indicates that formula (1) is not satisfied. In Table 2, "St+Vn" in formula (2) indicates the above-mentioned St+Vn.

[0120]

[0121] As shown in Table 2, all of the conjugated diene rubbers 1 to 3 satisfy the formulas (1) and (2). As described above, all of the conjugated diene rubbers 1 to 3 are modified conjugated diene rubbers having a specific modifying group. Therefore, all of the conjugated diene rubbers 1 to 3 fall under the above-mentioned specific conjugated diene rubber. As shown in Table 2, the comparative conjugated diene rubber satisfies the formula (1). As described above, the comparative conjugated diene rubber is a modified conjugated diene rubber having a specific modifying group. However, as shown in Table 2, the comparative conjugated diene rubber does not satisfy the formula (2), and therefore does not fall under the above-mentioned specific conjugated diene rubber. As shown in Table 2, both E581 and NS612 do not satisfy the formula (1), and therefore do not fall under the above-mentioned specific conjugated diene rubber.

[0122] [Preparation of Rubber Composition for Tire] The components in Tables 3 to 4 below were mixed in the compositions (parts by mass) shown in the tables. Specifically, first, the components in Tables 3 to 4 other than sulfur and vulcanization accelerator were mixed in a 1.8 L internal mixer at 160°C or lower for 5 minutes, and a master batch was released. Thereafter, sulfur and vulcanization accelerator were added to the master batch, and the mixture was mixed using an open roll at 100°C or lower to produce each rubber composition for tire.

[0123] [Evaluation] The following evaluations were carried out for each of the obtained rubber compositions for tires.

[0124] [Heat Sagging Resistance] Using each of the obtained rubber compositions for tires, test tires were produced with a tire size of 245 / 40R19. The tires were mounted on a front-wheel drive vehicle with an engine displacement of 2300cc via the applicable rim, and the front-wheel drive vehicle was driven around a test course with a lap length of 10km for two laps. The test driver evaluated the controllability during steering using a sensory evaluation, and the result was expressed as an index, with the standard example being 100. The results are shown in Tables 3 and 4. The higher the index, the better the dry handling stability and heat sagging resistance. For practical purposes, an index of 105 or higher is preferred.

[0125] [Circuit Wear Resistance] Using each of the obtained rubber compositions for tires, test tires were produced with a tire size of 245 / 40R19. The tires were mounted on a front-wheel drive vehicle with an engine displacement of 2300 cc via the applicable rim, and a test driver drove the front-wheel drive vehicle five laps on a circuit with a lap length of 3.6 km. The tire profiles were measured before and after the run, and the amount of wear was calculated from the difference. The reciprocal of this was expressed as an index, with the standard example being 100. The results are shown in Tables 3 and 4. In this evaluation, the higher the index, the higher the circuit wear resistance. In practice, an index of 105 or higher is preferable.

[0126] [Wet Performance] Using each of the obtained rubber compositions for tires, test tires with a tire size of 245 / 40R19 were produced and subjected to a braking test. The braking test was carried out by mounting four test tires of each type on a passenger car with an engine displacement of 2300 cc. The wet braking test was carried out by measuring the braking distance from an initial speed of 100 km / h on an asphalt road surface sprinkled with water. The reciprocal of the distance was then indexed, with the standard example being set at 100, and the results are shown in Tables 3 and 4. A larger value indicates better performance. In practice, an index of 103 or more is preferred.

[0127] [Rolling Performance] Each of the obtained rubber compositions for tires was press-vulcanized in a mold (15 cm x 15 cm x 0.2 cm) at 160°C for 40 minutes to produce a vulcanized rubber sheet. The resulting vulcanized rubber sheets were then measured for tan δ (60°C) in accordance with JIS K6394:2007 using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) under conditions of an elongation deformation strain rate of 10%±2%, a frequency of 20 Hz, and a temperature of 60°C, and the reciprocal of tan δ (60°C) was calculated. The results are shown in Tables 3 and 4. The results are expressed as an index, with the reciprocal of tan δ (60°C) of the reference example being set to 100. A larger index indicates better rolling performance (low rolling resistance). For practical purposes, an index of 102 or greater is preferred.

[0128]

[0129]

[0130] Details of each component in Tables 3 and 4 are as follows: Conjugated diene rubbers 1 to 3: Conjugated diene rubbers 1 to 3 synthesized as described above Comparative conjugated diene rubbers: Comparative conjugated diene rubbers synthesized as described above E581: E581 manufactured by Asahi Kasei Corporation (terminally modified solution polymerized SBR having a hydroxy group at the end, Tg: -27°C) (does not satisfy formula (1) and therefore does not fall under the category of the specific conjugated diene rubber described above) NS612: NS612 manufactured by Nippon Zeon Co., Ltd. (solution polymerized SBR, Tg: -60°C) (does not satisfy formula (1) and therefore does not fall under the category of the specific conjugated diene rubber described above) BR: Nipol BR1220 manufactured by Nippon Zeon Co., Ltd. (butadiene rubber, Tg: -106°C) (does not have a specific modifying group and therefore does not fall under the category of the specific conjugated diene rubber described above) Carbon black: Seast 3 manufactured by Tokai Carbon Co., Ltd. (HAF carbon black, nitrogen adsorption specific surface area (N ２ SA): 79m ２ / g) Silica: ZEOSIL 1165MP manufactured by Solvay (CTAB adsorption specific surface area: 160 m ２ / g) 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. Oil: Extract No. 4 S manufactured by Showa Shell Sekiyu K.K. Silane coupling agent (Si69): Si69 manufactured by Evonik Corporation Zinc white: Zinc white 3 types (manufactured by Seido Chemical Industry Co., Ltd.) Stearic acid: Beads Stearic Acid YR (manufactured by Nippon Oil & Fats Co., Ltd.) Anti-aging agent: Nocrac 6C (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Wax: Sannock (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Vulcanization accelerator (CZ): Sancerer CM-G (sulfenamide type) manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator (TBzTD): Sancerer TBZTD (thiuram type) manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator (DPG): Soxinol D-G (guanidine type) manufactured by Sumitomo Chemical Co., Ltd. Sulfur: Myucron OT-20 manufactured by Shikoku Chemical Industry Co., Ltd.

[0131] In Tables 3 and 4, "average Tg" represents the glass transition temperature of the entire rubber component. Also, in Tables 3 and 4, "resin ratio" represents the resin ratio described above.

[0132] As can be seen from Tables 3 and 4, all of Examples 1 to 12, which contain a rubber component with an average Tg within a specific range containing a specific amount of specific conjugated diene rubber, a specific amount of silica, and a specific amount of thermoplastic resin, and in which the resin ratio is within a specific range, exhibited excellent heat sagging resistance, circuit wear resistance, wet performance, and rolling performance. Comparing Examples 1 to 4 (comparison of embodiments differing only in the type of rubber component), Examples 1 to 2 and Example 4, in which the St + Vn of the specific conjugated diene rubber was 30 or more, exhibited better wet performance. In particular, the IVw of the specific conjugated diene rubber １０％Examples 1 and 4, in which the σ is 4.5 or higher, exhibited better circuit abrasion resistance. Furthermore, comparing Examples 4 to 6 (comparison between embodiments differing only in the carbon black and silica contents), Examples 4 and 6, in which the silica content per 100 parts by mass of the rubber component was 100 parts by mass or more, exhibited better wet performance and rolling performance. Furthermore, comparing Examples 4 to 6 (comparison between embodiments differing only in the carbon black and silica contents), Examples 4 to 5, in which the silica content per 100 parts by mass of the rubber component was 140 parts by mass or less, exhibited better heat sagging resistance and circuit abrasion resistance. Furthermore, comparing Example 4 and Example 7 (comparison between embodiments differing only in the type of thermoplastic resin), Example 4, in which the thermoplastic resin contained a terpene resin, exhibited better circuit abrasion resistance, wet performance, and rolling performance. Furthermore, comparing Example 4 with Example 8 (comparison between embodiments where only the vulcanization accelerator was different), Example 8, which contained 0.2 to 3.0 parts by mass of thiuram vulcanization accelerator per 100 parts by mass of the rubber component, showed better heat sagging resistance, circuit wear resistance, and rolling performance. Similarly, comparing Example 11 with Example 12 (comparison between embodiments where only the vulcanization accelerator was different), Example 12, which contained 0.2 to 3.0 parts by mass of thiuram vulcanization accelerator per 100 parts by mass of the rubber component, showed better heat sagging resistance, circuit wear resistance, and rolling performance. Furthermore, comparing Example 4 with Example 9 and Example 10 (comparison between embodiments where the resin ratio was different), Examples 9 and 10, which had a resin ratio of 60% or more by mass, showed better wet performance. Among them, Example 9, in which the resin ratio was 90% by mass or less, exhibited better heat sagging resistance, circuit wear resistance, and rolling performance. Furthermore, from a comparison between Example 9 and Example 11 (comparison between embodiments in which only the type of thermoplastic resin was different), Example 11, in which the thermoplastic resin contained a terpene resin and a C5 / C9 resin, exhibited better circuit wear resistance, wet performance, and rolling performance.

[0133] On the other hand, the following Comparative Examples were insufficient in at least one of heat sagging resistance, circuit abrasion resistance, wet performance, and rolling performance: a standard example that did not contain a specific conjugated diene rubber; Comparative Example 1 that contained a specific conjugated diene rubber but in which the content of the specific conjugated diene rubber in the rubber component was less than 25% by mass; Comparative Example 2 that contained a comparative conjugated diene rubber that was a modified diene rubber other than the specific conjugated diene rubber instead of the specific conjugated diene rubber; Comparative Example 3 in which the average Tg of the rubber component exceeded −45° C.; Comparative Example 4 in which the average Tg of the rubber component was −80° C. or lower; Comparative Example 5 in which the content of the thermoplastic resin per 100 parts by mass of the rubber component was less than 30 parts by mass; Comparative Example 6 in which the content of the thermoplastic resin per 100 parts by mass of the rubber component was 80 parts by mass or more; Comparative Example 7 in which the content of silica per 100 parts by mass of the rubber component was less than 80 parts by mass; and Comparative Example 8 in which the content of silica per 100 parts by mass of the rubber component exceeded 160 parts by mass.

[0134] REFERENCE SIGNS LIST 1 Bead portion 2 Sidewall portion 3 Tire tread portion 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion

Claims

1. A rubber component (A) containing a modified conjugated diene rubber (A1), silica (B), and a softener (C) consisting of at least one selected from the group consisting of a thermoplastic resin and an oil, wherein the modified conjugated diene rubber (A1) is a conjugated diene rubber which satisfies the following formulas (1) and (2) and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, wherein the proportion of the modified conjugated diene rubber (A1) in the rubber component (A) is 25% by mass or more, the glass transition temperature of the entire rubber component (A) is greater than -80°C and less than -45°C, the content of the silica (B) per 100 parts by mass of the rubber component (A) is 80 parts by mass or more and 160 parts by mass or less, and the content of the thermoplastic resin per 100 parts by mass of the rubber component (A) is 30 parts by mass or more and less than 80 parts by mass, A rubber composition for tires, wherein the ratio of the thermoplastic resin to the total of the thermoplastic resin and the oil is 50 mass % or more. １０％ ≦3.1×10 －６ ×Mw １０％ −2.77 (1) St + Vn≦50 (2) Mw in formula (1) １０％ and IVw １０％ The weight average molecular weight (Mw) is calculated by using the high molecular weight portion of the peak of the chromatogram obtained by the differential refractive index detector, which is 10% of the total area of ​​the peak. 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％ where 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.

2. The rubber composition for tires according to claim 1, wherein the modified conjugated diene rubber (A1) has a star structure with three or more branches, at least one branch of the star structure has a moiety derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group, and the moiety has a further main chain branch structure.

3. The rubber composition for tires according to claim 1, wherein the thermoplastic resin comprises 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.

4. The rubber composition for tires according to claim 1, further comprising 0.2 parts by mass or more and 3.0 parts by mass or less of a thiuram vulcanization accelerator per 100 parts by mass of the rubber component (A).

5. The rubber composition for tires according to claim 1, wherein the content of the thermoplastic resin per 100 parts by mass of the rubber component (A) is 50 parts by mass or more and less than 80 parts by mass, and the ratio of the thermoplastic resin to the total of the thermoplastic resin and the oil is 80 mass% or more.

6. The rubber composition for tires according to claim 1, wherein the softener (C) contains two or more types of thermoplastic resins.

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

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