Tire rubber composition, and tire

Abstract

The purpose of the present invention is to provide: a tire rubber composition exhibiting excellent on-ice performance, on-snow performance and wet performance, and having excellent green strength; and a tire manufactured by using the tire rubber composition. The present invention relates to a tire rubber composition containing: a diene-based rubber including a modified conjugated diene-based rubber; silica; and a plasticizer, wherein the modified conjugated diene-based rubber satisfies a specific formula 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-based rubber in the diene-based rubber is more than 15 mass% and not more than 50 mass%, the content of silica is 30-90 parts by mass per 100 parts by mass of the diene-based rubber, and the content of the plasticizer is 30-80 parts by mass per 100 parts by mass of the diene-based rubber.

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] Japanese Patent Application Laid-Open No. 2020-29474

[0004] Recently, from the viewpoint of safety, etc., there has been a demand for further improvements in tire performance on ice (ICE braking), performance on snow (Snow braking), wet performance, green strength of rubber compositions before vulcanization, etc. In this context, the present inventors have studied the conventional rubber compositions for tires described in Patent Document 1 and the like, and have found that further improvements in the ice performance, snow performance, wet performance, and the green strength when made into tires are desirable.

[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 performance on ice, snow, and wet surfaces, and also has excellent green strength, and a tire manufactured using the rubber composition for tires.

[0006] As a result of intensive research to solve 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 optimizing the contents of silica and plasticizer, etc., and 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 for a tire comprising a diene rubber containing a modified conjugated diene rubber (A1), silica (B), and a plasticizer (C), 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 a proportion of the modified conjugated diene rubber (A1) in the diene rubber is more than 15% by mass and not more than 50% by mass, wherein the content of the silica (B) per 100 parts by mass of the diene rubber is 30 parts by mass or more and 90 parts by mass or less, and wherein the content of the plasticizer (C) per 100 parts by mass of the diene rubber is 30 parts by mass or more and 80 parts by mass or less. 4.7≦IVw 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 (mass%) of repeating units derived from styrene to the entire modified conjugated diene rubber, and Vn represents the proportion (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], wherein the modified conjugated diene rubber (A1) has a star structure with three or more branches, at least one branched 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 plasticizer (C) contains at least one selected from the group consisting of oil, a liquid polymer, and a thermoplastic resin. [4] The rubber composition for a tire according to any one of [1] to [3], wherein the plasticizer (C) comprises at least one selected from the group consisting of a liquid polymer and a vegetable oil, in an amount of 1 part by mass or more per 100 parts by mass of the diene rubber. [5] The rubber composition for a tire according to any one of [1] to [4], wherein the diene rubber further comprises a mixture of SBR and / or BR with a liquid polymer. [6] The rubber composition for a tire according to [5], wherein the liquid polymer contained in the mixture comprises a modified liquid polymer. [7] The rubber composition for a tire according to any one of [1] to [6], further comprising an epichlorohydrin rubber, the amount of the epichlorohydrin rubber being 1 part by mass or more and 25 parts by mass or less per 100 parts by mass of the diene rubber. [8] The rubber composition for a tire according to any one of [1] to [7], wherein the plasticizer (C) contains a thermoplastic resin, and the content of the thermoplastic resin is 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the diene rubber. [9] A tire produced using the rubber composition for a tire according to any one of [1] to [8].

[0008] As will be described below, according to the present invention, it is possible to provide a rubber composition for a tire which, when made into a tire, exhibits excellent performance on ice, on snow, and in wet conditions, and also has excellent green strength, 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. The manufacturing method of each component is not particularly limited unless otherwise specified. Examples include conventionally known methods. Regarding the rubber composition for tires, the ice performance, snow performance, and wet performance of a tire, as well as the green strength of the rubber composition before vulcanization, are also referred to simply as "ice performance," "snow performance," "wet performance," and "green strength," respectively. In this specification, powers of 10 are sometimes represented by E. For example, E+5 represents 10 to the fifth power. In this specification, silica (B) may be simply referred to as silica. The same applies to plasticizer (C), etc. In the present invention, when the standard for the proportion of a component is "in the diene rubber," the diene rubber refers to the entire diene rubber including the specific conjugated diene rubber. When the standard for the content of a component is "per 100 parts by mass of the diene rubber," 100 parts by mass of the diene rubber refers to 100 parts by mass of the total diene rubber including the specific conjugated diene rubber.

[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 diene rubber including a modified conjugated diene rubber (A1), silica (B), and a plasticizer (C), wherein 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 diene rubber is more than 15% by mass and not more than 50% by mass, the content of the silica (B) per 100 parts by mass of the diene rubber is 30 parts by mass or more and 90 parts by mass or less, and the content of the plasticizer (C) per 100 parts by mass of the diene rubber is 30 parts by mass or more and 80 parts by mass or less.

[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 not clear, but is thought to be roughly as follows. Generally, rubber compositions containing a large amount of plasticizer have low sheet strength, so green strength is necessary. On the other hand, the composition of the present invention contains a modified conjugated diene rubber (A1) as a rubber component. The modified conjugated diene rubber (A1) is a conjugated diene rubber that satisfies the following formula (1) and the following 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 (hereinafter, the modified conjugated diene rubber (A1) is also referred to as a "specific conjugated diene rubber"). 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 inventors' studies, it is believed that the high weight-average molecular weight and weight-average intrinsic viscosity of rubbers that satisfy formula (1) lead to improved green strength. Furthermore, from the investigations of the present inventors, it is believed that the specific modifying group of the specific conjugated diene rubber interacts with silica, and therefore the dispersibility of silica in the composition of the present invention is extremely high, which is believed to lead to excellent effects (on ice, on snow, and on wet surfaces) even when the composition of the present invention contains a plasticizer (C) within a predetermined range.

[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 diene rubber including a specific conjugated diene rubber as a rubber component. The composition of the present invention may further contain a diene rubber other than the specific conjugated diene rubber and / or a rubber component other than the diene rubber (non-diene rubber) as a rubber component. In the present invention, a preferred embodiment is that the rubber component is a solid rubber at 25°C.

[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 conjugated 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 of the specific conjugated diene rubber 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. The skeleton of the specific conjugated diene rubber is preferably SBR, as this provides better effects of the present invention.

[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 of the skeleton of the specific conjugated diene rubber, on the main chain, or on a side chain. For reasons of better effects of the present invention, 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] 4.7≦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％ In order to obtain a more excellent effect of the present invention, Mw is preferably from 100,000 to 10,000,000, and more preferably from 1,000,000 to 5,000,000. １０％ For the reason that the effects of the present invention (particularly green strength) are more excellent, the molecular weight is preferably more than 28,000,000 and not more than 10,000,000, and more preferably 3,000,000 to 5,000,000.

[0032] IVw １０％ is preferably 4.7 to 8, and more preferably 4.7 to 6, because the effects of the present invention are more excellent. １０％ is preferably more than 5.5 and not more than 8, because the effects of the present invention (especially green strength) 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] [Proportion of specific conjugated diene rubber] In the present invention, the proportion of the specific conjugated diene rubber in the diene rubber is more than 15% by mass and not more than 50% by mass. For reasons of better effects of the present invention, the proportion is preferably 20% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 40% by mass or less.

[0049] [Other Rubber Components] The rubber component may further contain a rubber component (other rubber component) other than the specific conjugated diene rubber.

[0050] (Other Diene Rubbers) Examples of diene rubbers (other diene rubbers) other than the specific conjugated diene rubber in the diene rubber that can be further contained in the composition of the present invention include natural rubber (NR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubbers (e.g., styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, etc.), isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), and chloroprene rubber (CR). From the viewpoint of achieving better effects of the present invention, the other diene rubber that can be further contained in the rubber component preferably contains natural rubber (NR) and / or butadiene rubber (BR), and more preferably contains natural rubber (NR) and butadiene rubber (BR). The proportion of the other diene rubber can be the remainder obtained by subtracting the range of the proportion of the specific conjugated diene rubber from 100% by mass.

[0051] (Non-diene Rubber) When the rubber component further contains a rubber component (non-diene rubber) other than the diene rubber as the other rubber component, examples of the non-diene rubber include epichlorohydrin rubber.

[0052] (Epichlorohydrin Rubber) When the rubber component further contains a non-diene rubber, the non-diene rubber preferably contains an epichlorohydrin rubber, from the viewpoint of achieving better effects of the present invention.

[0053] When the rubber component further contains epichlorohydrin rubber, the epichlorohydrin rubber is incompatible with diene rubber and therefore forms domains in the cured product after vulcanization, increasing surface roughness and providing appropriate flexibility, thereby further improving performance on ice. Furthermore, the chlorine contained in the epichlorohydrin rubber interacts with silica due to its high polarity, maintaining or further improving wet performance.

[0054] Examples of epichlorohydrin rubbers include one or more of epichlorohydrin homopolymers, epichlorohydrin-ethylene oxide copolymers, epichlorohydrin-propylene oxide copolymers, epichlorohydrin-allyl glycidyl ether copolymers, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymers, epichlorohydrin-propylene oxide-allyl glycidyl ether copolymers, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether copolymers, and epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether copolymers.

[0055] When the rubber component further contains an epichlorohydrin rubber, the epichlorohydrin rubber preferably contains a copolymer of epichlorohydrin and ethylene oxide, from the viewpoint of achieving better effects of the present invention (particularly performance on ice).

[0056] When the rubber component further contains an epichlorohydrin rubber, from the viewpoint of achieving better effects of the present invention and excellent abrasion resistance, the epichlorohydrin rubber preferably has a Mooney viscosity at 100°C of 65 to 100. The Mooney viscosity at 100°C can be measured in accordance with JIS K6300-1:2013.

[0057] When the rubber component further contains an epichlorohydrin rubber, the content of the epichlorohydrin rubber is preferably 1 part by mass or more and 25 parts by mass or less, and more preferably 5 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the diene rubber, from the viewpoint of better effects of the present invention.

[0058] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) of rubber components other than the specific conjugated diene rubber, and of the liquid polymer described below, can be expressed as standard polystyrene-equivalent values ​​obtained by gel permeation chromatography (GPC) measurement under the following conditions: Solvent: tetrahydrofuran Detector: RI detector

[0059] [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.

[0060] [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.

[0061] <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.

[0062] 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.

[0063] 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.

[0064] <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.

[0065] (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.

[0066] (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.

[0067] (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.

[0068] <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.

[0069] 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.

[0070] (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.

[0071] [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.

[0072] 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.

[0073] <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.

[0074] (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.

[0075] (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.

[0076] [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.

[0077] [Average Tg] The glass transition temperature of the entire rubber component (hereinafter also referred to as "average Tg") is not particularly limited, but for reasons of better effects of the present invention, it is preferably higher than -90°C and lower than -45°C, and more preferably higher than -85°C and lower than -50°C. The average Tg of the rubber component is the sum (weighted average value of glass transition temperatures) obtained by multiplying the glass transition temperature (Tg) of each rubber component by the mass fraction of each rubber component.

[0078] [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.

[0079] [2] Silica The composition of the present invention contains silica [silica (B)]. 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. Biomass-derived silica such as rice husks may also be used. The silica may be one type alone or two or more types in combination.

[0080] [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 ２ Here, the CTAB adsorption specific surface area is a value measured in accordance with JIS K6430:2008, Appendix G.

[0081] [Content] In the composition of the present invention, the content of silica is 30 parts by mass or more and 90 parts by mass or less relative to 100 parts by mass of the diene rubber. For the reason that the effects of the present invention are more excellent, the content of silica is preferably 50 parts by mass or more and less than 80 parts by mass, and more preferably 60 parts by mass or more and 75 parts by mass or less relative to 100 parts by mass of the diene rubber.

[0082] [3] Plasticizer The composition of the present invention contains a plasticizer [plasticizer (C)]. In the present invention, the plasticizer is not particularly limited as long as it is a compound that can plasticize or soften the rubber component. In the present invention, the plasticizer does not fall under the category of the above-mentioned rubber component.

[0083] The plasticizer includes softeners, lubricants, and extender oils that can be added to general rubber compositions and are used to plasticize rubber. However, the plasticizer does not include wax. In a preferred embodiment, the plasticizer is liquid at 25°C, or, if solid at 25°C, has a softening point of 160°C or lower.

[0084] The plasticizer preferably contains at least one selected from the group consisting of oil, liquid polymer, and thermoplastic resin, for the reason that the effects of the present invention are more excellent.

[0085] In addition, the plasticizer preferably contains at least one selected from the group consisting of liquid polymers and vegetable oils, because this provides better effects of the present invention (particularly, performance on ice, performance on snow, etc.).

[0086] The plasticizer preferably contains a thermoplastic resin, because this provides better effects of the present invention (particularly wet performance and green performance).

[0087] [Oil] Examples of oils include aromatic oils, naphthenic oils, paraffin oils, and vegetable oils. The oil preferably contains aromatic oils and / or vegetable oils because the effects of the present invention are more excellent. The aromatic oil is not particularly limited as long as it is an aromatic oil that can be generally used in rubber compositions. The vegetable oil is not particularly limited as long as it is an oil derived from a plant. For both, examples include conventionally known aromatic oils and vegetable oils.

[0088] [Liquid Polymer] Examples of liquid polymers include liquid butyl rubber, liquid isoprene rubber, liquid butadiene rubber, and liquid styrene-butadiene rubber. The liquid polymer may be a modified liquid polymer (modified liquid polymer), and examples of modified liquid polymers include epoxy-modified liquid polymers, carboxy-modified liquid polymers, amine-modified liquid polymers, alkoxysilyl-modified liquid polymers, hydroxyl-group-modified liquid polymers, siloxane-modified liquid polymers, and mercapto-group-modified liquid polymers. When the liquid polymer is a modified liquid polymer, examples of the modifying group possessed by the modified liquid polymer include an epoxy group, a carboxy group, an amino group (—NH ２ ), imino group (—NH—), alkoxysilyl group, trialkylsilyl group, hydroxyl group, polysiloxane group, mercapto group, and combinations thereof.

[0089] The liquid polymer preferably contains an alkoxysilyl-modified liquid polymer because the effects of the present invention are more excellent. The alkoxysilyl-modified liquid polymer is a liquid polymer having an alkoxysilyl group. Examples of the alkoxy group in the alkoxysilyl group include a methoxy group and an ethoxy group. The alkoxysilyl group in the alkoxysilyl-modified liquid polymer can be bonded to the main chain of the alkoxysilyl-modified liquid polymer directly or via a divalent linking group. The divalent linking group is not particularly limited. The alkoxysilyl group in the alkoxysilyl-modified liquid polymer may be a trialkoxysilyl group, a dialkoxysilyl group, or a monoalkoxysilyl group. When the alkoxysilyl group is a dialkoxysilyl group or a monoalkoxysilyl group, the dialkoxysilyl group or the like may further have a modifying group represented by the formula: *-R-X. X in the modifying group represents a functional group such as an amino group, a mercapto group, an epoxy group, a carboxy group, a hydroxyl group, or an N-trialkylsilyl-imino group. X is preferably an amino group or an N-trialkylsilyl-imino group, because the effects of the present invention are more excellent. The alkyl group bonded to the silicon atom of the N-trialkylsilyl-imino group is not particularly limited. Examples include alkyl groups having 1 to 10 carbon atoms, such as methyl and ethyl groups. R in the modifying group represents a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include alkylene groups having 1 to 6 carbon atoms. The "*" in the modifying group represents the bonding position. The modifying group represented by the above formula can be bonded to the silicon atom in the dialkoxysilyl group or the like directly or via a divalent linking group. The divalent linking group is not particularly limited. The liquid polymer preferably contains a dialkoxysilyl-modified liquid polymer having a modifying group represented by the formula: *-R-X, because the effects of the present invention are more excellent. ２ or *-R-NH-Si(alkyl) ３ More preferably, the liquid polymer contains a dialkoxysilyl-modified polymer having a modifying group represented by the formula: *-R-NH ２ or *-R-NH-Si(alkyl) ３It is more preferable that the liquid butadiene rubber contains a dialkoxysilyl-modified liquid butadiene rubber having a modifying group represented by the following formula:

[0090] The liquid polymer preferably contains a liquid butadiene rubber because the effects of the present invention are more excellent. The liquid butadiene rubber may be either an unmodified liquid butadiene rubber or a modified liquid butadiene rubber, or may contain both.

[0091] The weight average molecular weight (Mw) of the liquid polymer is preferably 3,000 or more and less than 100,000, and more preferably 5,000 or more and less than 80,000, for reasons of superior effects of the present invention.

[0092] [Thermoplastic Resin] 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 rosin ... 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.

[0093] 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.

[0094] The softening point of the thermoplastic resin is preferably 60 to 160° C., because this provides a better effect of the present invention. The softening point can be measured in accordance with JIS K6220-1:2015.

[0095] [Preferred Aspect 3] In one preferred aspect, the diene rubber as the rubber component further contains a mixture of SBR (styrene butadiene rubber) and / or BR (butadiene rubber) with a liquid polymer, because this enhances the effects of the present invention. That is, when the diene rubber as the rubber component further contains SBR and / or BR and the plasticizer contains a liquid polymer, the diene rubber as the rubber component preferably contains a mixture in which at least some or all of the SBR and / or at least some or all of the BR are premixed with at least some or all of the liquid polymer, and more preferably contains a mixture obtained by premixing all of the BR with at least some or all of the liquid polymer. The mixture may be solid or liquid at 25°C. The method for obtaining the mixture is not particularly limited. For example, a conventionally known mixing method may be used.

[0096] In the above-mentioned preferred embodiment 3, the liquid polymer contained in the mixture preferably contains a modified liquid polymer (modified liquid polymer) because the effects of the present invention are more excellent. The modified liquid polymer is the same as described above.

[0097] For reasons of achieving better effects of the present invention, the plasticizer preferably contains at least one oil selected from the group consisting of aromatic oil, naphthenic oil, and paraffin oil, and at least one selected from the group consisting of vegetable oil, liquid polymer, and thermoplastic resin; more preferably, the plasticizer contains aromatic oil, vegetable oil, liquid polymer, and thermoplastic resin; and even more preferably, the plasticizer contains aromatic oil, vegetable oil, modified liquid polymer, and thermoplastic resin, and the modified liquid polymer is a mixture with SBR and / or BR as the rubber component.

[0098] [Content] In the present invention, the content of the plasticizer per 100 parts by mass of the diene rubber is 30 parts by mass or more and 80 parts by mass or less. For the reason that the effects of the present invention are more excellent, the content of the plasticizer is preferably 40 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the diene rubber.

[0099] When the plasticizer contains at least one oil selected from the group consisting of aromatic oil, naphthenic oil, and paraffin oil, the content of the at least one oil selected from the group consisting of aromatic oil, naphthenic oil, and paraffin oil (when two or more oils are used, the total content; the same applies hereinafter) is preferably 30 parts by mass or more and 80 parts by mass or less, and more preferably 30 parts by mass or more and 60 parts by mass or less, per 100 parts by mass of diene rubber, for reasons of better effects of the present invention.

[0100] When the plasticizer contains at least one selected from the group consisting of a liquid polymer and a vegetable oil, the content of the at least one selected from the group consisting of a liquid polymer and a vegetable oil is preferably 1 part by mass or more, and more preferably 5 parts by mass or more and 40 parts by mass or less, per 100 parts by mass of the diene rubber, for reasons of better effects of the present invention.

[0101] When the plasticizer contains a vegetable oil, the content of the vegetable oil is preferably 5 parts by mass or more and 20 parts by mass or less, and more preferably 5 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the diene rubber, because this will provide better effects of the present invention.

[0102] When the plasticizer contains a liquid polymer, the content of the liquid polymer is preferably 5 to 20 parts by mass, more preferably 5 to 15 parts by mass, per 100 parts by mass of diene rubber, because the effects of the present invention are more excellent. When the plasticizer contains an unmodified liquid polymer, the content of the unmodified liquid polymer is preferably 5 to 20 parts by mass, more preferably 5 to 15 parts by mass, per 100 parts by mass of diene rubber, because the effects of the present invention are more excellent. When the plasticizer contains a modified liquid polymer (including when the modified liquid polymer is a mixture as described above), the content of the modified liquid polymer is preferably 5 to 20 parts by mass, more preferably 5 to 15 parts by mass, per 100 parts by mass of diene rubber, because the effects of the present invention are more excellent.

[0103] When the plasticizer contains a thermoplastic resin, the content of the thermoplastic resin is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 5 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the diene rubber, for reasons of better effects of the present invention.

[0104] [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), thermally expandable microcapsules, silane coupling agents, stearic acid, zinc oxide (zinc white), antioxidants, waxes, processing aids, thermosetting resins, vulcanizing agents (e.g., sulfur), vulcanization accelerators (accelerators), and vulcanization activators.

[0105] [Silane Coupling Agent] The composition of the present invention preferably further contains a silane coupling agent, because the effects of the present invention are more excellent.

[0106] 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.

[0107] 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.

[0108] The silane coupling agent is preferably a sulfur-containing silane coupling agent, since this provides a better effect of the present invention.

[0109] 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.

[0110] [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 diene rubber, because this provides better effects of the present invention.

[0111] 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.

[0112] [Carbon Black] The composition of the present invention preferably further 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, can be used.

[0113] [N ２ SA] The nitrogen adsorption specific surface area (N ２ SA) 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 / g. Here, the nitrogen adsorption specific surface area (N ２ SA) is the amount of nitrogen adsorption on the surface of carbon black measured in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0114] [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, it is preferably 1 to 100 parts by mass, and more preferably 2 to 30 parts by mass, per 100 parts by mass of the diene rubber described above.

[0115] [Vulcanization Accelerator] The composition of the present invention preferably further 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.

[0116] [Content] 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 diene rubber, for reasons of better effects of the present invention.

[0117] [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.

[0118] [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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0123] [Synthesis of Conjugated Diene Rubber] Each conjugated diene rubber was synthesized as follows.

[0124] [Conjugated Diene Rubber 4] <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 stirred to allow the reaction to proceed. The branching agent corresponds to the specific branching agent described above.

[0125] <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.

[0126] Thereafter, methanol was added as a polymerization terminator to obtain a solution containing a conjugated diene rubber.

[0127] 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 4.

[0128] The conjugated diene rubber 4 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 4 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).

[0129] [Conjugated Diene Rubber 5] A solid conjugated diene rubber was obtained in the same manner as for Conjugated Diene Rubber 4, except that the amounts of each component used were changed as shown in Table 1. The obtained conjugated diene rubber is also referred to as Conjugated Diene Rubber 5.

[0130] 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, 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 5 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).

[0131] [Conjugated diene rubber 2 (comparison)] A solid conjugated diene rubber was obtained in the same manner as for conjugated diene rubber 4, except that the amounts of each component used were changed as shown in Table 1. The obtained conjugated diene rubber is also referred to as conjugated diene rubber 2.

[0132] 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).

[0133] [Conjugated Diene Rubber 3 (Comparative)] A solid conjugated diene rubber was obtained in the same manner as for Conjugated Diene Rubber 4, except that the amounts of each component used were changed as shown in Table 1. The obtained conjugated diene rubber is also referred to as Conjugated Diene Rubber 3.

[0134] 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).

[0135]

[0136] [Weight-average molecular weight, weight-average intrinsic viscosity, styrene content, vinyl content, and glass transition temperature] The conjugated diene rubbers synthesized as described above (conjugated diene rubbers 4 and 5, and conjugated diene rubbers (comparison) 2 and 3) were measured for Mw, Mw １０％ , IVw, IVw １０％ , St, Vn, and St+Vn are shown in Table 2. The same is true for NS612 (described later) used as conjugated diene rubber 1 (comparison). In Table 2, the "right side" of formula (1) refers to the right side of formula (1), "3.1 × 10 －６ ×Mw １０％ The "left side" of formula (1) is "4.7". In Table 2, "applicability" of formula (1) indicates whether formula (1) is applicable or not. Specifically, "A" indicates the IVw １０％ represents that formula (1) is satisfied, and "B" represents IVw １０％ does not satisfy the formula (1). In Table 2, "St+Vn" in the formula (2) represents the above-mentioned St+Vn.

[0137]

[0138] As shown in Table 2, all of the conjugated diene rubbers 4 and 5 satisfy the formulas (1) and (2). Furthermore, as described above, all of the conjugated diene rubbers 4 and 5 are modified conjugated diene rubbers having a specific modifying group. Therefore, all of the conjugated diene rubbers 4 and 5 fall under the specific conjugated diene rubber described above. As shown in Table 2, the conjugated diene rubbers 1 and 2 (comparison) satisfy the formula (2) but do not satisfy the formula (1), and therefore do not fall under the specific conjugated diene rubber described above. The conjugated diene rubber 3 (comparison) satisfies the formula (1) but does not satisfy the formula (2), and therefore does not fall under the specific conjugated diene rubber described above. Furthermore, as described above, the conjugated diene rubbers 2 and 3 (comparison) are modified conjugated diene rubbers having a specific modifying group.

[0139] [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.

[0140] [Production of Tires] Each of the obtained rubber compositions for tires was used in the tread portion of a tire to produce test tires having a tire size of 245 / 40R19.

[0141] [Evaluation] The following evaluations were carried out for each of the obtained rubber compositions for tires and each of the test tires. When each of the obtained test tires was subjected to a braking test, the following braking test method was carried out by mounting four test tires on a passenger car with an engine displacement of 2300 cc.

[0142] [Ice Performance] A professional test driver drives the vehicle on an icy test course and evaluates its braking / driving performance, lane change performance, cornering performance, etc. This evaluation is based on an index rating, with the standard example being assigned a standard value of 100. The higher the index, the better the ice performance.

[0143] [Snow Performance] A professional test driver drives the vehicle on a test course on snowy roads and evaluates its braking / driving performance, lane change performance, cornering performance, etc. This evaluation is based on an index rating, with the standard example being assigned a standard value of 100. The higher the index, the better the snow performance.

[0144] [Wet Performance] In the wet braking test, the braking distance was measured from an initial speed of 100 km / h on an asphalt road surface sprinkled with water. The reciprocal of the distance was indexed, with the standard example being set at 100, and the results are shown in Tables 3 and 4. In the present invention, an index of over 100 indicates excellent wet performance. A larger value indicates better wet performance.

[0145] [Green Strength] Using each of the obtained rubber compositions (unvulcanized), JIS No. 3 dumbbell-shaped test pieces (thickness: 2 mm) were punched out in accordance with JIS K6251:2017, and the 300% modulus was measured under conditions of a temperature of 20°C and a tensile speed of 500 mm / min. The 300% modulus was indexed, with the standard example being set at 100, and is shown in Tables 3 and 4. In the present invention, an index of more than 100 indicates excellent green strength. A larger value indicates better green strength.

[0146]

[0147] Details of each component in Tables 3 and 4 are as follows: NR: Natural rubber. SIR20 manufactured by PT. KIRANA SAPTA, Tg: -65°C. Conjugated diene rubber 1 (comparison): 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). Conjugated diene rubbers 2-3 (comparison): Conjugated diene rubbers 2-3 synthesized as described above. Conjugated diene rubbers 4-5: Conjugated diene rubbers 4-5 synthesized as described above. BR: Nipol BR1220 manufactured by Nippon Zeon Co., Ltd. (polybutadiene rubber, Tg: -106°C).

[0148] Plasticizer-containing BR1: BR extended with liquid BR. BRX5000, manufactured by Zeon Corporation. Contains 40 parts by mass of liquid (low molecular weight) BR at 25°C per 100 parts by mass of solid BR at 25°C. The BR and liquid BR contained in plasticizer-containing BR1 are unmodified. Plasticizer C1 (liquid BR): Liquid butadiene rubber. Mw is 38,000. Liquid at 25°C. Plasticizer C2 (vegetable oil): Showa Pure Sunflower Oil Olein Rich, manufactured by Showa Sangyo Co., Ltd. Liquid at 25°C.

[0149] Epichlorohydrin rubber: Hydrin C2000L manufactured by Nippon Zeon Co., Ltd., epichlorohydrin-ethylene oxide copolymer, Mooney viscosity at 100°C = 70

[0150] Plasticizer C3 (thermoplastic resin): Terpene resin: YS Resin TO125 (aromatic modified terpene resin, softening point: 125°C) manufactured by Yasuhara Chemical Co., Ltd. Plasticizer-containing BR2: BR extended with liquid BR modified with aminopropyldimethoxysilyl groups. Plasticizer-containing BR2 was produced by mixing 100 parts by mass of BR (trade name NIPOL BR 1220, manufactured by Zeon Corporation) that is solid at 25°C with 40 parts by mass of BR that is liquid (low molecular weight) at 25°C and modified with aminopropyldimethoxysilyl groups. The method for producing liquid BR modified with aminopropyldimethoxysilyl groups is as follows. A thoroughly dried 5-L autoclave was purged with nitrogen and charged with 4,100 g of hexane, 92 mL of n-butyllithium (1.60 mol / L hexane solution), and 0.25 mL of 2,2-di(2-tetrahydrofuryl)propane. 762 g of butadiene was added sequentially under stirring, and polymerization was carried out at room temperature for 1 hour. Subsequently, 59 g of N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane was added to terminate the polymerization reaction, yielding a polymer solution. The resulting solution was removed and concentrated under reduced pressure. The concentrated solution was poured into methanol (5.0 L), and the methanol-insoluble components were separated to yield a modified liquid polymer. The weight-average molecular weight of the resulting modified polymer was 9,500. The resulting modified liquid polymer was BR that contained N-trimethylsilyl-3-iminopropyldimethoxysilyl groups as aminopropyldimethoxysilyl groups and was liquid at 25°C.

[0151] Carbon black (HAF): SEAT 3 (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) Silane coupling agent Si69: Si69 manufactured by Evonik Corporation Stearic acid: Beads stearic acid YR manufactured by NOF Corporation Zinc oxide: Three types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd. Antioxidant: 6PPD manufactured by Eastman Corporation

[0152] Plasticizer C4 (oil): Aromatic oil. Extract No. 4 S manufactured by Showa Shell Sekiyu K.K. Liquid at 25°C. Plasticizer C5: Liquid BR modified with aminopropyldimethoxysilyl groups. Produced in the same manner as the liquid BR modified with aminopropyldimethoxysilyl groups contained in the plasticizer-containing BR2.

[0153] Sulfur: Myucron OT-20 manufactured by Shikoku Chemical Industry Co., Ltd. Vulcanization accelerator CZ: Sancerer CM-G (sulfenamide type) manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator DPG: Soxinol D-G (guanidine type) manufactured by Sumitomo Chemical Co., Ltd. Vulcanization accelerator DPG (Soxsil D-G manufactured by Sumitomo Chemical Co., Ltd.)

[0154] As can be seen from Tables 3 and 4, all of Examples 1 to 10, which contain specific amounts of specific conjugated diene rubber, specific amounts of silica, and specific amounts of plasticizer (C), exhibited excellent ice performance, snow performance, wet performance, and green strength. Comparing Examples 1 and 2 (comparison between embodiments differing only in the type of rubber component), Example 1 exhibited better ice performance and snow performance than Example 2. IVw １０％ and Mw １０％Example 2, which contained a specific conjugated diene rubber with a higher TRP content, exhibited better green strength than Example 1. Furthermore, comparing Example 1 with Examples 3, 4, and 7 (comparisons between embodiments that differ only in the type of plasticizer (C)), Examples 3 and 4, in which the plasticizer (C) contained a liquid polymer or vegetable oil, exhibited better ice performance and snow performance than Example 1. Example 3 also exhibited better green strength. Example 7, in which the plasticizer (C) contained a thermoplastic resin, exhibited better wet performance and green strength than Example 1. Furthermore, when the composition of the present invention contained BR as another rubber component, comparing Example 1 with Examples 5 and 8 (comparisons between embodiments that differ only in whether BR was a mixture with a liquid polymer), Examples 5 and 8, in which BR was a mixture with a liquid polymer, exhibited better ice performance, snow performance, and green strength. Furthermore, comparing Example 3 with Example 9 (comparison between embodiments in which the liquid polymer was unmodified or modified), Example 9, which contained a modified liquid polymer, showed better ice performance. Furthermore, when the composition of the present invention contained BR as the other diene rubber and the BR was a mixture with a liquid polymer, comparing Example 5 with Example 8 (comparison between embodiments in which the liquid polymer was unmodified or modified), Example 8, which contained a modified liquid polymer, showed better ice performance, snow performance, wet performance, and green strength. Furthermore, comparing Example 1 with Example 6 (comparison between embodiments in which the only difference was the epichlorohydrin), Example 6, which further contained epichlorohydrin, showed better ice performance. Furthermore, among Examples 1 to 10, Example 10, which contained vegetable oil and a thermoplastic resin as plasticizers, contained BR as the other diene rubber, and was a mixture of the BR with a modified liquid polymer, showed the best ice performance, snow performance, and green strength.

[0155] On the other hand, the following tires were insufficient in at least one of ice performance, snow performance, wet performance, and green strength: the standard example containing conjugated diene rubber 1 (comparison) instead of the specific conjugated diene rubber; comparative examples 1 and 2 containing conjugated diene rubber 2 or 3 (comparison), which is a modified diene rubber other than the specific conjugated diene rubber, instead of the specific conjugated diene rubber; comparative example 3 in which the content of plasticizer (C) per 100 parts by mass of diene rubber is less than 30 parts by mass; comparative example 4 in which the content of plasticizer (C) per 100 parts by mass of diene rubber is more than 80 parts by mass; comparative example 5 in which the content of silica per 100 parts by mass of diene rubber is less than 30 parts by mass; comparative example 6 in which the content of silica per 100 parts by mass of diene rubber is more than 90 parts by mass; comparative example 7 in which the specific conjugated diene rubber is contained but its content in the diene rubber is 15% by mass or less; and comparative example 8 in which the specific conjugated diene rubber is contained but its content in the diene rubber is more than 50% by mass.

[0156] 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 composition for tires comprising a diene rubber containing a modified conjugated diene rubber (A1), silica (B), and a plasticizer (C), 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 diene rubber is more than 15% by mass and not more than 50% by mass, the content of the silica (B) relative to 100 parts by mass of the diene rubber is 30 parts by mass or more and 90 parts by mass or less, and the content of the plasticizer (C) relative to 100 parts by mass of the diene rubber is 30 parts by mass or more and 80 parts by mass or less. 4.7≦IVw 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 or 2, wherein the plasticizer (C) comprises at least one selected from the group consisting of oils, liquid polymers and thermoplastic resins.

4. A rubber composition for tires according to any one of claims 1 to 3, wherein the plasticizer (C) contains at least one kind selected from the group consisting of liquid polymers and vegetable oils in an amount of 1 part by mass or more per 100 parts by mass of the diene rubber.

5. A rubber composition for tires according to any one of claims 1 to 4, wherein the diene rubber further comprises a mixture of SBR and / or BR with a liquid polymer.

6. The rubber composition for tires according to claim 5, wherein the liquid polymer contained in the mixture includes a modified liquid polymer.

7. The rubber composition for tires according to any one of claims 1 to 6, further comprising an epichlorohydrin rubber, the content of the epichlorohydrin rubber being 1 part by mass or more and 25 parts by mass or less per 100 parts by mass of the diene rubber.

8. A rubber composition for tires according to any one of claims 1 to 7, wherein the plasticizer (C) contains a thermoplastic resin, and the content of the thermoplastic resin is 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the diene rubber.

9. A tire manufactured using the rubber composition for tires according to any one of claims 1 to 8.

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