WO2025005123A1 - Rubber composition for tires, and tire - Google Patents

Abstract

The purpose of the present invention is to provide: a rubber composition for tires which exhibit excellent processability, wet performance, wear resistance, and chipping resistance; and a tire produced using the composition. This rubber composition for tires comprises a diene-based rubber including a modified conjugated-diene rubber, silica, a silane coupling agent, and an alkyltriethoxysilane, wherein the modified conjugated-diene rubber 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, the proportion of the modified conjugated-diene rubber in the diene-based rubber being 25 mass% or higher.

Description

Rubber composition for tires and tires

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

　Conventionally, rubber compositions for tires that contain silica in order to improve performance have been known (for example, Patent Document 1).

Patent No. 7196953

Recently, there has been a demand for further improvement in the processability of tires from the viewpoint of environmental issues, etc. In addition, there has been a demand for further improvement in wet performance, abrasion resistance, chipping resistance, etc. from the viewpoint of safety, etc.
Under these circumstances, 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 are desirable in terms of tire processability, and wet performance, abrasion resistance, and chipping resistance when made into a tire.

In view of the above circumstances, the present invention aims to provide a rubber composition for tires that has excellent processability and exhibits excellent wet performance, abrasion resistance, and chipping resistance when made into a tire, as well as a tire manufactured using the rubber composition for tires.

As a result of intensive research into the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by using a specific modified conjugated diene rubber as the rubber component and containing silica, a silane coupling agent and an alkyltriethoxysilane, 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.

[1]
The composition contains a diene rubber including a modified conjugated diene rubber (A1), silica, a silane coupling agent, and an alkyltriethoxysilane,
The modified conjugated diene rubber (A1) satisfies the following formula (1) and the following formula (2) and has a modifying group containing a nitrogen atom, a silicon atom and an oxygen atom adjacent thereto,
A rubber composition for tires, wherein the proportion of the modified conjugated diene rubber (A1) in the diene rubber is 25 mass % or more.
IVw _10% ≦3.1×10 ^-6 ×Mw _10% -2.77 (1)
IVw _10% ≧4.7 (2)
The IVw _10% in formula (1) and formula (2) and the Mw _10% in formula (1) are as follows.
The modified conjugated diene rubber is subjected to gel permeation chromatography measurement using a differential refractive index detector and a viscosity detector as detectors. The weight average molecular weight obtained using the high molecular weight side portion of the peak of the chromatogram obtained by the differential refractive index detector, which is 10% of the total peak area, is defined as Mw _10% . The weight average intrinsic viscosity obtained using the high molecular weight side portion of the peak of the chromatogram obtained by the viscosity detector, which is 10% of the total peak area, is defined as IVw _10% . The unit of weight average intrinsic viscosity is dL/g.
[2]
The modified conjugated diene rubber (A1) is
a star structure having three or more branches, at least one branch of which has a moiety derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group;
The rubber composition for a tire according to [1], wherein the portion further has a main chain branched structure.
[3]
The rubber composition for tires according to [1] or [2], wherein the silane coupling agent includes 3-octanoylthio-1-propyltriethoxysilane or a silane coupling agent having a mercapto group.
[4]
Further containing a thermoplastic resin,
The rubber composition for tires according to any one of [1] to [3], wherein the thermoplastic resin comprises at least one selected from the group consisting of terpene resins, C5/C9 resins, C5 resins, C9 resins, DCPD resins, DCPD/C9 resins, hydrogenated C5/C9 resins, hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated DCPD resins, and hydrogenated DCPD/C9 resins.
[5]
The rubber composition for tires according to [4], wherein the thermoplastic resin comprises at least two resins selected from the group consisting of terpene resins, C5/C9 resins, C5 resins, C9 resins, DCPD resins, DCPD/C9 resins, hydrogenated C5/C9 resins, hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated DCPD resins, and hydrogenated DCPD/C9 resins.
[6]
The rubber composition for tires according to [4] or [5], wherein the content of the thermoplastic resin is 50 parts by mass or less per 100 parts by mass of the diene rubber.
[7]
The rubber composition for tires according to any one of [1] to [6], wherein the content of the silica is 50 parts by mass or more per 100 parts by mass of the diene rubber.
[8]
A tire manufactured using the rubber composition for tires according to any one of [1] to [7].

As described below, the present invention can provide a rubber composition for tires that has excellent processability and exhibits excellent wet performance, abrasion resistance, and chipping resistance when made into a tire, as well as a tire manufactured using the rubber composition for tires.

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

The rubber composition for tires and the like 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.
In addition, each component may be used alone or in combination of two or more. When two or more components are used in combination, the content of the components refers to the total content unless otherwise specified.
In addition, the method for producing each component is not particularly limited unless otherwise specified, and may be, for example, a conventionally known method.
In addition, with respect to a rubber composition for tires, the processability, wet performance when made into a tire, wear resistance, and chipping resistance are also simply referred to as "processability,""wetperformance,""wearresistance," and "chipping resistance," respectively.
In addition, in this specification, a power of 10 may be represented as E. For example, E+5 represents 10 to the fifth power.
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 the total amount of the diene rubber including the specific conjugated diene rubber being 100 parts by mass.

[I] Rubber Composition for Tires The rubber composition for tires of the present invention (hereinafter also referred to as the "composition of the present invention") is
The composition contains a diene rubber including a modified conjugated diene rubber (A1), silica, a silane coupling agent, and an alkyltriethoxysilane,
The modified conjugated diene rubber (A1) satisfies the formula (1) and formula (2) described later and has a modifying group containing a nitrogen atom, a silicon atom and an oxygen atom adjacent thereto,
In the rubber composition for tires, the proportion of the modified conjugated diene rubber (A1) in the diene rubber is 25 mass % or more.

It is believed that the composition of the present invention, having such a structure, can solve the above-mentioned problems. Although the reason for this is not clear, it is believed to be roughly as follows.
The composition of the present invention contains, as a rubber component, a conjugated diene rubber (hereinafter also referred to as a "specific conjugated diene rubber") that satisfies the formula (1) and the formula (2) described below and has a modified group (hereinafter also referred to as a "specific modified group") containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. It is considered that the specific modified group of the specific conjugated diene rubber interacts with silica. In addition, the formula (1) specifies 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, but the inventors' studies have found that the specific conjugated diene rubber has room for improvement in wet performance, abrasion resistance, and chipping resistance, and may have slightly reduced processability. The above-mentioned decrease in processability was thought to be caused by an increase in viscosity in the rubber composition. Therefore, it is considered that the processability of the composition of the present invention is improved by applying an alkyltriethoxysilane to the specific conjugated diene rubber, which also leads to improvements in wet performance, abrasion resistance, and chipping resistance.

The components contained in the composition of the present invention are explained below.

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

[Specific conjugated diene rubber]
The specific conjugated diene rubber is a conjugated diene rubber that satisfies the formula (1) described below and the formula (2) described below and has a modifying group (specific modifying group) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto.

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

<Conjugated dienes>
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.

<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 (other monomer) that becomes such a repeating unit include vinyl monomers, alkenes (e.g., ethylene, propylene, butene), etc. Examples of the vinyl monomer include aromatic vinyl (e.g., styrene), acrylonitrile, and the specific branching agent described later.

<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), chloroprene rubber (CR), etc. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene butadiene rubber (SBR), styrene isoprene copolymer rubber, etc.
The skeleton of the specific conjugated diene rubber is preferably SBR, since this provides better effects of the present invention.

[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 any one of the terminals, main chain, or side chain of the skeleton of the specific conjugated diene rubber.
For the reason that the effect of the present invention is more excellent, the specific modifying group preferably contains a silicon atom and an oxygen atom adjacent thereto as an alkoxysilyl group. The alkoxysilyl group is a group represented by -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 this provides better effects of the present invention.
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.

[Equation (1), Equation (2)]
The specific conjugated diene rubber satisfies the following formulas (1) and (2).
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. The reason for limiting the molecular weight to the high molecular weight side is that it has a large effect on the physical properties of the entire polymer.

IVw _10% ≦3.1×10 ^-6 ×Mw _10% -2.77 (1)
IVw _10% ≧4.7 (2)

The IVw _10% in formula (1) and formula (2) and the Mw _10% in formula (1) are determined as follows.
The modified conjugated diene rubber is subjected to gel permeation chromatography measurement using a differential refractive index detector (RI detector) and a viscosity detector as detectors. The weight average molecular weight obtained using the high molecular weight side portion of the peak of the chromatogram obtained by the differential refractive index detector, which is 10% of the total peak area, is defined as Mw _10% . In addition, the weight average intrinsic viscosity obtained using the high molecular weight side portion of the peak of the chromatogram obtained by the viscosity detector, which is 10% of the total peak area, is defined as IVw _10% . However, the unit of weight average intrinsic viscosity is dL/g.

Hereinafter, IVw _10% in formula (1) and formula (2) and Mw _10% in formula (1) will be described in more detail.

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.

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

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 differential refractive index detector, the weight average molecular weight is determined using the portion on the high molecular weight side (the side with the shorter elution time) that accounts for 10% of the total peak area. The weight average molecular weight obtained is designated as Mw _10% .

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 calculated using the portion on the high molecular weight side (shorter elution time) which occupies 10% of the total area of the peaks. The weight-average intrinsic viscosity thus obtained is designated as _IVw10% .
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.

An example of a GPC chromatogram (horizontal axis: elution time, vertical axis: signal intensity) is shown in Figure 1. Mw _10% and IVw _10% are calculated using P1, which is a portion on the high molecular weight side (shorter elution time) that has an area of 10% of the area of P0, which is the entire peak.

As a method for making the modified conjugated diene rubber satisfy formula (1), for example, 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 later can be mentioned.

[Mw10%]
Mw _10% is preferably from 100,000 to 10,000,000, more preferably from 2.0×10 ⁶ (2,000,000) to 5,000,000, and even more preferably from 2,000,000 to 3,000,000, because the effects of the present invention are more excellent.

[IVw _10% ]
Because the effects of the present invention are more excellent, IVw _10% is preferably 4.7 or more and 6.0 or less, and more preferably 4.7 to 5.0.

[Formula (3)]
For the reason that the effects of the present invention are more excellent, it is preferable that the specific conjugated diene rubber further satisfies the following formula (3).

30≦St+Vn≦90 (3)

In formula (3), St represents the ratio (mass%) of repeating units derived from styrene to the entire specific conjugated diene rubber (hereinafter also referred to as the "styrene amount"), and Vn represents the ratio (mass%) of repeating units of 1,2-vinyl structure derived from conjugated diene (e.g., butadiene) to the entire specific conjugated diene rubber (hereinafter also referred to as the "vinyl amount").

It is preferable that St+Vn is greater than 30 and not greater than 75, because this provides a better effect of the present invention.

St is preferably greater than 10 and less than 50 because this provides a better effect of the present invention.

Vn is preferably greater than 0 and equal to or less than 40, because this provides a better effect of the present invention.

[Molecular weight]
The weight average molecular weight (Mw) of the specific conjugated diene rubber is preferably from 100,000 to 2,000,000, and more preferably from 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 for the above-mentioned Mw _10% , except that the entire peak is used.

[Glass transition temperature]
The glass transition temperature (Tg) of the specific conjugated diene rubber is not particularly limited, but is preferably from -100°C to 0°C, and more preferably from -80°C to -10°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.

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

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.

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 this provides a better effect of the present invention.
X preferably contains a nitrogen atom as an amino group because the effect of the present invention is more excellent.

As described above, P represents a conjugated diene polymer chain. A plurality of P's 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.

As mentioned above, n represents an integer of 3 or more. There is no particular upper limit to n, but it is preferably 30 or less because the effects of the present invention are more excellent.

[Preferred embodiment 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 portion derived from a specific branching agent described later, and the portion preferably has a further main chain branched structure, for reasons of better effects of the present invention.
The main chain branched structure refers to a structure in which a branched chain (conjugated diene polymer chain) forms a branch point at a portion derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group, and a polymer chain (e.g., another conjugated diene polymer chain) extends from the branch point.

[Proportion of specific conjugated diene rubber]
In the present invention, the proportion of the specific conjugated diene rubber in the diene rubber is 25% by mass or more.
The above ratio is preferably 30% by mass or more, and more preferably 50% by mass or more and 90% by mass or less, because the effects of the present invention are more excellent.

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

(Other diene rubbers)
Examples of diene rubbers other than the specific conjugated diene rubber in the diene rubber (other diene rubbers) which the composition of the present invention may further contain include natural rubber (NR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber (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), chloroprene rubber (CR), etc.
The other diene rubber may be modified. However, the modification in the modified other diene rubber [modified conjugated diene rubber (A2)] does not include a specific modified group. The modified other diene rubber may have, for example, an epoxy group or a polysiloxane group.
From the viewpoint of achieving superior effects of the present invention, the other diene rubber that the rubber component can further contain preferably contains natural rubber (NR), butadiene rubber (BR) or SBR, more preferably contains NR, BR and SBR, and further preferably contains unmodified NR, unmodified BR, unmodified SBR and modified SBR.
The proportion of the other diene rubber in the diene rubber can be the remainder obtained by subtracting the range of the proportion of the specific conjugated diene rubber from 100% by mass.

In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) of the rubber components other than the specific conjugated diene rubber can be standard polystyrene equivalent values obtained by gel permeation chromatography (GPC) measurement under the following conditions.
Solvent: Tetrahydrofuran Detector: RI detector

[Method of producing specific conjugated diene rubber]
The method for producing the specific conjugated diene rubber is not particularly limited, but because the effects of the present invention are superior, a method including the following steps (1) and (2) (hereinafter also referred to as the "production method of the present invention") is preferred.
(1) a polymerization step in which a monomer containing a conjugated diene is polymerized by anionic polymerization to obtain a conjugated diene polymer; (2) a modification step in which the conjugated diene polymer obtained in the polymerization step is reacted with a compound containing a nitrogen atom and an alkoxysilyl group (hereinafter also referred to as a "specific modifier") to obtain a conjugated diene rubber having a specific modifying group.

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

<Anionic Polymerization>
The anionic polymerization is not particularly limited, but anionic polymerization using an organolithium compound as an initiator is preferred because the effects of the present invention are more excellent.

The organolithium compound is not particularly limited, but specific examples include mono-organolithium compounds such as n-butyllithium (n-BuLi), sec-butyllithium, tert-butyllithium, n-propyllithium, iso-propyllithium, 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-trilithiobenzene, and 1,3,5-trilithio-2,4,6-triethylbenzene. Among these, mono-organolithium compounds such as n-butyllithium, sec-butyllithium, and tert-butyllithium are preferred because they provide better effects for the present invention, with n-butyllithium being more preferred.

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

<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.

(Specific branching agent)
The monomer preferably contains a vinyl monomer containing an alkoxysilyl group or a halosilyl group (hereinafter also referred to as a "specific branching agent") because this provides a superior effect of the present invention.
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, for reasons that the effects of the present invention are more excellent.

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

(2) Amount Used The amount of the specific branching agent used is preferably 0.001 to 0.1% by mass, and more preferably 0.005 to 0.05% by mass, based on the conjugated diene, because this provides a better effect of the present invention.

<Polar Compounds>
In the polymerization step, a polar compound may be added. This allows the monomers to be randomly copolymerized. In addition, polar compounds tend to be usable as vinylating agents for controlling the microstructure of conjugated dienes. In addition, polar compounds tend to be effective in promoting polymerization reactions.

Examples of the polar compound 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.

(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.

[Modification step]
The modification step is a step of obtaining a conjugated diene rubber having a specific modifying group by 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.

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

<Specific Modifier>
The specific modifier is a compound containing a nitrogen atom, a silicon atom and an oxygen atom adjacent thereto.
For the reason that the effect of the present invention is more excellent, the specific modifier preferably contains a silicon atom and an 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 a 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 a Si-N bond).
The specific modifying agent 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) because the effects of the present invention are more excellent.
The specific modifying agent preferably has two or more (preferably three or more) sites capable of reacting with an active terminal such as an alkoxysilyl group. When the specific modifying agent has a plurality of such sites, the specific modifying agent functions as a coupling agent that connects conjugated diene polymers together.

(Specific example)
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 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.

(Amount used)
The amount of the specific modifier used is preferably 0.01 to 1% by mass, and more preferably 0.02 to 0.2% by mass, based on the conjugated diene, because this provides a better effect of the present invention.

[Other steps]
The manufacturing method of the present invention may include steps (other steps) other than the steps described above.
Other steps include a polymerization terminating step in which a polymerization terminator (e.g., methanol) is added, and a solvent removal step in which the solvent is removed by steam stripping.

[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.

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

[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 is preferably 100 to 300 ^{m 2} /g, and more preferably 150 to 200 m ² /g, for reasons of superior effects of the present invention.
Here, the CTAB adsorption specific surface area is a value measured in accordance with JIS K6430:2008 Annex G.

[Content]
The content of silica is preferably 50 parts by mass or more, and more preferably 60 parts by mass or more and 120 parts by mass or less, per 100 parts by mass of the diene rubber, because the effects of the present invention are more excellent.

[3] Silane Coupling Agent The composition of the present invention contains a silane coupling agent.

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, and examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Of these, an alkoxy group is preferable 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 the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, and a propoxy group.

The organic functional group is not particularly limited, but is preferably a group capable of forming a chemical bond with an organic compound. Examples of the organic functional group include an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, a sulfide group, a mercapto group, and a blocked mercapto group (protected mercapto group) (for example, a thioester group such as an octanoylthio group). Among these, a sulfide group (particularly a disulfide group or a tetrasulfide group), a mercapto group, and a blocked mercapto group are preferred because they provide better effects of the present invention.
The silane coupling agents may be used alone or in combination of two or more kinds.

The silane coupling agent preferably contains a sulfur-containing silane coupling agent, because this provides a better effect of the present invention.

Examples of the silane coupling agent include sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)tetrasulfide (Si69), bis(3-trimethoxysilylpropyl)tetrasulfide, and bis(3-triethoxysilylpropyl)disulfide;
Thioester-based silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane (NXT);
Examples of the silane coupling agents include silane coupling agents having a mercapto group, such as mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, and mercapto group-containing polysiloxane-based silane coupling agents.

The above-mentioned silane coupling agent having a mercapto group may further have a sulfide group in addition to the mercapto group. The silane coupling agent having a mercapto group does not include a silane coupling agent (e.g., Si69) that has only a sulfide group as an organic functional group.

Examples of the mercapto group-containing polysiloxane-based silane coupling agent include sulfur-containing silane coupling agents represented by the following average composition formula (X).
In this specification, the average composition formula (X) may be referred to as "formula (X)". The sulfur-containing silane coupling agent represented by the average composition formula (X) may be referred to as "the silane coupling agent represented by formula (X)".

[Sulfur-containing silane coupling agent represented by average composition formula (X)]
The silane coupling agent represented by formula (X) preferably has a polysiloxane skeleton, which may be linear, branched, or three-dimensional, or a combination thereof.
Formula (X) is as follows:
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-b-c-de)} /2 (X)
In formula (X), A represents a divalent organic group containing a sulfide group. B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms. C represents a hydrolyzable group. D represents an organic group containing a mercapto group. ^R1 represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. a to e satisfy the following relational expressions: 0≦a<1, 0<b<1, 0<c<3, 0<d<1, 0≦e<2, 0<2a+b+c+d+e<4.

[A]
A represents a divalent organic group containing a sulfide group, and may have a heteroatom such as an oxygen atom, a nitrogen atom, or a sulfur atom.
A is preferably a group represented by the following formula (A1).
*-(CH2)n-Sx-(CH2)n-* (A1)
In formula (A1), n represents an integer of 1 to 10, x represents an integer of 1 to 6, and * represents a bonding position.
Specific examples of A represented by formula (A1) include, for example, *-CH ₂ -S ₂ -CH ₂ -*, *-C ₂ H ₄ -S ₂ -C ₂ H ₄ -*, *-C ₃ H ₆ -S ₂ -C ₃ H ₆ -*, *-C ₄ H ₈ -S ₂ -C ₄ H ₈ -*, *-CH ₂ -S ₄ -CH ₂ -*, *-C ₂ H ₄ -S ₄ -C ₂ H ₄ -*, *-C ₃ H ₆ -S ₄ -C ₃ H ₆ -*, *-C ₄ H ₈ -S ₄ -C ₄ H ₈ -*, and the like.

[B]
B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms. B is preferably a monovalent hydrocarbon group having 6 to 10 carbon atoms, more preferably 8 to 10 carbon atoms. Examples include a hexyl group, an octyl group, and a decyl group.

[C]
C represents a hydrolyzable group. Examples of C include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. C is preferably a group represented by the following formula (C1).
*-OR ² (C1)
In formula (C1), * indicates a bonding position. ^R2 represents an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group (arylalkyl group) having 6 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, and among these, an alkyl group having 1 to 5 carbon atoms is preferable. Specific examples of the alkyl group having 1 to 5 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group.

[D]
D represents an organic group containing a mercapto group. D is preferably a group represented by the following formula (D1).
*-(CH ₂ ) _m -SH (D1)
In formula (D1), m represents an integer of 1 to 10, and preferably an integer of 1 to 5. In the formula, * indicates a bonding position.
Examples of the group represented _by formula (D1) include _{* -CH2SH ,} * _-C2H4SH , * _{-C3H6SH , * -C4H8SH} , * _-C5H10SH , _{* -C6H12SH ,} * _{-C7H14SH ,} * _-C8H16SH , * _-C9H18SH , _and * _-C10H20SH .

[R ¹ ]
^R1 represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. Examples of ^R1 include a methyl group, an ethyl group, a propyl group, and a butyl group.

[a to e]
a to e satisfy the relational expressions 0≦a<1, 0<b<1, 0<c<3, 0<d<1, 0≦e<2, 0<2a+b+c+d+e<4.
a is preferably greater than 0, and more preferably 0<a≦0.50.
Preferably, b satisfies 0.10≦b≦0.89.
Preferably, c satisfies 1.2≦c≦2.0.
d is preferably in the range of 0.1≦d≦0.8.

The silane coupling agent is used because it provides a superior effect of the present invention.
It is preferable that the composition contains 3-octanoylthio-1-propyltriethoxysilane or a silane coupling agent having a mercapto group,
It is more preferable that the composition contains 3-octanoylthio-1-propyltriethoxysilane or a silane coupling agent represented by formula (X):
It is more preferable that the silane compound contains 3-octanoylthio-1-propyltriethoxysilane.

[Content]
The content of the silane coupling agent in the composition of the present invention is not particularly limited, but the content of the silane coupling agent is preferably 2 to 20 mass % of the above-mentioned silica content, and more preferably 5 to 15 mass %, because the effects of the present invention are more excellent.

[4] Alkyltriethoxysilane The composition of the present invention contains an alkyltriethoxysilane.
It is believed that by containing alkyltriethoxysilane in the composition of the present invention, the dispersibility of silica in the composition of the present invention is improved, resulting in excellent processability, wet performance, abrasion resistance, and chipping resistance.

The alkyltriethoxysilane may, for example, be a compound represented by the following formula (Y).
R ¹ -Si-(OCH ₂ CH ₃ ) ₃ (Y)
In formula (Y), ^R1 represents an alkyl group having 7 to 20 carbon atoms. Examples of the alkyl group having 7 to 20 carbon atoms include a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group. Of these, an octyl group and a nonyl group are preferred because they provide better effects of the present invention.

[Content]
In the composition of the present invention, the content of alkyltriethoxysilane is not particularly limited, but in order to obtain a more excellent effect of the present invention, it is preferably 0.1 to 15.0 mass% of the above-mentioned silica content, and more preferably 0.5 to 10.0 mass%.
Further, the content of alkyltriethoxysilane is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5.0 parts by mass, and even more preferably 0.8 to 2.0 parts by mass, per 100 parts by mass of the diene rubber, because the effects of the present invention are more excellent.

[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 that are generally used in rubber compositions, such as fillers other than silica (preferably carbon black), thermoplastic resins, oils, 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.

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

[Specific examples]
Examples of the thermoplastic resin 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 terpene resin), (aromatic modified terpene resins, etc.), terpene phenol resins, hydrogenated terpene resins, α-pinene resins, β-pinene resins, limonene resins, hydrogenated limonene resins, dipentene resins, terpene styrene resins), styrene-based resins, petroleum-based resins (for example, C5/C9-based resins, C5-based resins, C9-based resins, DCPD (dicyclopentadiene)-based resins, DCPD/C9-based resins, hydrogenated C5/C9-based resins, hydrogenated C5-based resins, hydrogenated C9-based resins, hydrogenated DCPD-based resins, hydrogenated DCPD/C9-based resins), aliphatic saturated hydrocarbon-based resins, and the like.

The thermoplastic resin preferably contains at least one type selected from the group consisting of terpene resins, C5/C9 resins, C5 resins, C9 resins, DCPD resins, DCPD/C9 resins, hydrogenated C5/C9 resins, hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated DCPD resins, and hydrogenated DCPD/C9 resins, because this provides better effects for the present invention, and more preferably contains at least two types selected from the above group.
When at least one type selected from the above group is included, it is preferable to include at least one type selected from the group consisting of terpene resins, C5/C9 resins, C5 resins, and DCPD resins, because the effects of the present invention are more excellent.
When at least two types selected from the above group are included, the combination is preferably a combination of a terpene resin and a C5/C9 resin because the effect of the present invention is more excellent. The terpene resin is not particularly limited. For example, a conventionally known terpene resin can be mentioned. The same applies to the C5/C9 resin.

[Content]
In the composition of the present invention, the content of the thermoplastic resin (when two or more kinds of thermoplastic resins are used, the total content thereof) is not particularly limited. However, in order to obtain better effects of the present invention, the content is preferably 0 to 50 parts by mass, and more preferably 1 to 30 parts by mass, per 100 parts by mass of the diene rubber described above.

[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 kinds.
The carbon black is not particularly limited, and various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, and SRF can be used.

[ _N2SA ]
The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is not particularly limited, but in order to obtain a superior effect of the present invention, it is preferably 50 to 200 m ² /g, and more preferably 70 to 150 m ² /g.
The nitrogen adsorption specific surface area (N ₂ SA) is the amount of nitrogen adsorbed on the surface of carbon black measured according to JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method".

[Content]
In the composition of the present invention, the content of carbon black is not particularly limited, but because the effects of the present invention are more excellent, 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 diene rubber described above.

[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 of kneading the above-mentioned components using a known method or device (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 the sulfur or the vulcanization accelerator.
The composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[II] Tire The tire of the present invention is a tire manufactured using the above-mentioned composition of the present invention. 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.

FIG. 2 shows a schematic partial cross-sectional view of a tire that represents one example of an embodiment of a tire of the present invention. However, the tire of the present invention is not limited to the embodiment shown in FIG. 2.

In FIG. 2, reference numeral 1 denotes a bead portion, reference numeral 2 denotes a sidewall portion, and reference numeral 3 denotes a tire tread portion.
Between the pair of left and right bead portions 1, a carcass layer 4 having fiber cords embedded therein is installed, and the ends of this carcass layer 4 are folded back and wrapped around the bead cores 5 and bead fillers 6 from the inside to the outside of the tire.
In the tire tread portion 3, a belt layer 7 is disposed on the outer side of the carcass layer 4 around one circumference of the tire.
In addition, a rim cushion 8 is disposed in the bead portion 1 at a portion that comes into contact with the rim.
At least one of the components 2, 3, 5, 6 and 8 (preferably the component 3) is made of the composition of the present invention.

The tire of the present invention can be manufactured, for example, according to a conventionally known method. In addition, 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.

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

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

[Conjugated diene rubber 1]

<Polymerization step>
In a stirrer-equipped autoclave, cyclohexane 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 were charged under a nitrogen atmosphere, and n-butyllithium was continuously added at 1.43 mmol/h to initiate polymerization at 70° C. When the polymerization was sufficiently stabilized, 1-(trimethoxysilyl)-4-vinylbenzene (branching agent) was added at 0.02 g/h and reacted with stirring. The branching agent corresponds to the specific branching agent described above.

<Modification step>
To the solution flowing out from the reactor outlet, 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.

Then, methanol was added as a polymerization terminator to obtain a solution containing conjugated diene rubber.

To the resulting solution, 1.14 parts by mass of Irganox 1520L (manufactured by BASF) was added as an anti-aging agent per 100 parts by mass of conjugated diene rubber, after which the solvent was removed by steam stripping and the 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.

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 a branching agent, and the portion derived from the branching agent has a further main chain branched structure (conjugated diene polymer chain).

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

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) containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto, which is derived from the modifier.
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 a branching agent, and the portion derived from the branching agent has a further main chain branched structure (conjugated diene polymer chain).

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

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) containing a nitrogen atom, a silicon atom and an oxygen atom adjacent thereto, which is derived from the modifier.
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 a branching agent, and the portion derived from the branching agent has a further main chain branched structure (conjugated diene polymer chain).

[Weight average molecular weight, weight average intrinsic viscosity, styrene content, vinyl content, glass transition temperature]
For the conjugated diene rubbers synthesized as described above (conjugated diene rubbers 1 and 2, conjugated diene rubber 3 (comparison)), Mw, Mw10 _% , IVw, IVw10 _% , St, Vn, St+Vn, and Tg are shown in Table 2. Table 2 also shows NS560 used as conjugated diene rubber 4 (comparison) and Nipol 1502 used as conjugated diene rubber 5 (comparison). Details of NS560 and the like will be described later.
In Table 2, the "right side" represents the value of the right side of formula (1), which is "3.1×10 ^-6 ×Mw _10% -2.77".
In Table 2, "Suitable" of formula (1) indicates whether formula (1) is satisfied or not. Specifically, "A" indicates that IVw _10% satisfies formula (1), and "B" indicates that IVw _10% does not satisfy formula (1).
In Table 2, "Suitable" of formula (2) indicates whether formula (2) is satisfied or not. Specifically, "A" indicates that IVw _10% satisfies formula (2), and "B" indicates that IVw _10% does not satisfy formula (2).
In Table 2, "St+Vn" in formula (3) represents the above-mentioned St+Vn.

As shown in Table 2, all of the conjugated diene rubbers 1 and 2 satisfy the formula (1) and the formula (2). As described above, all of the conjugated diene rubbers 1 and 2 are modified conjugated diene rubbers having a specific modifying group. Therefore, all of the conjugated diene rubbers 1 and 2 correspond to the above-mentioned specific conjugated diene rubber.
On the other hand, as shown in Table 2, the conjugated diene rubber 3 (comparison) does not satisfy the formula (2), and therefore does not fall under the above-mentioned specific conjugated diene rubber.
Conjugated diene rubber 4 (comparison) does not satisfy formula (1) and formula (2), and therefore does not fall under the above-mentioned specific conjugated diene rubber.
Conjugated diene rubber 5 (comparison) satisfies formula (2) but does not satisfy formula (1), and therefore does not fall under the above-mentioned specific conjugated diene rubber. Note that conjugated diene rubber 5 (comparison) is unmodified as described below.

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

[evaluation]
The following evaluations were carried out for each of the obtained rubber compositions for tires. The results are shown in Tables 3 and 4.

[Processability]
For each of the obtained rubber compositions for tires, the Mooney viscosity at 100° C. was measured in accordance with JIS K6300-1:2013.
The results were expressed as an index with the Mooney viscosity of the standard example being 100.
In the present invention, the processability is considered to be excellent when the index is greater than 105. A larger index indicates better processability.

[Wet 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 each vulcanized rubber sheet. Then, for each of the obtained vulcanized rubber sheets, tan δ (0°C) was measured in accordance with JIS K6394:2007 using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho, Ltd.) under conditions of an elongation deformation rate of 10% ± 2%, a frequency of 20 Hz, and a temperature of 0°C, and the reciprocal of tan δ (0°C) was calculated.
The results were expressed as an index with tan δ (0° C.) of the standard example being set at 100.
In the present invention, wet performance is considered to be excellent when the index is 100 or more. A larger index indicates better wet performance.

[Wear resistance]
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 prepare each vulcanized rubber sheet. Then, for each of the obtained vulcanized rubber sheets, the amount of wear was measured under conditions of a load of 15.0 kg (147.1 N) and a slip ratio of 25% using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) in accordance with JIS K6264-2:2005.
The results were expressed as an index, with the reciprocal of the amount of wear of the control sample taken as 100.
In the present invention, the abrasion resistance is considered to be excellent when the index is more than 100. A larger index indicates better abrasion resistance.

[Chipping resistance]
Each of the rubber compositions for tires was used in the tire tread to form a pneumatic tire by vulcanization molding. The pneumatic tire was mounted on a wheel having a rim size of 16×7J, and the tire was mounted on a test vehicle with an air pressure of 350 kPa. The tire was then driven on an unpaved road for 1,000 km, and the number of external damages was counted by visually observing the tire.
The results were expressed as an index, with the reciprocal of the number of lesions in the control case set at 100.
In the present invention, chipping resistance is considered to be excellent when the index is more than 100. A larger index indicates better chipping resistance.

Details of each component in Tables 3 and 4 are as follows.
NR: Natural rubber. SIR20 manufactured by PT. KIRANA SAPTA, Tg: -62°C. Unmodified conjugated diene rubbers 1-2: Conjugated diene rubbers 1-2 synthesized as described above (corresponding to the specific conjugated diene rubbers described above because they satisfy formulas (1) and (2)).
Conjugated diene rubber 3 (comparison): Conjugated diene rubber 3 synthesized as described above (does not satisfy formula (2) and therefore does not fall under the specific conjugated diene rubber described above)
Conjugated diene rubber 4 (comparison): NS560 (terminal-modified SBR) manufactured by Zeon Corporation (does not satisfy formula (1) and formula (2) and therefore does not fall under the above-mentioned specific conjugated diene rubber)
Conjugated diene rubber 5 (comparison): Nipol 1502 manufactured by Zeon Corporation (an unmodified SBR that does not satisfy formula (1) and therefore does not fall under the above-mentioned specific conjugated diene rubber)
BR: Nipol BR1220 manufactured by Zeon Corporation (polybutadiene rubber, Tg: -107°C)
Carbon black: Seast 3 manufactured by Tokai Carbon Co., Ltd. (HAF carbon black, nitrogen adsorption specific surface area (N ₂ SA): 79 m 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: ENEOS Corporation, product name RD104
C5 resin: ENEOS Corporation, product name RA100
・DCPD/C9 resin: Manufactured by Shanghai Yida Chemical Co., Ltd., product name RT-1102D
Silane coupling agent 1 (Si69): Si69 manufactured by Evonik. Bis(3-triethoxysilylpropyl)tetrasulfide. Silane coupling agent 2 (NXT): A silane coupling agent having a thioester group. 3-octanoylthio-1-propyltriethoxysilane (structure shown below) (manufactured by Momentive Performance Materials, Inc.)
Silane coupling agent 3: A silane coupling agent having a polysiloxane skeleton and having a sulfide group and a mercapto group, represented by the following average composition formula: Average composition formula: (-C ₃ H ₆ -S ₄ -C ₃ H ₆ -) _0.071 (-C ₈ H ₁₇ ) _0.571 (-OC ₂ H ₅ ) _1.50 (-C ₃ H ₆ SH) _0.286 SiO _0.75 .
Silane coupling agent 3 was prepared as follows.
A 2L separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer was charged with 107.8g (0.2mol) of bis(triethoxysilylpropyl)tetrasulfide (KBE-846, manufactured by Shin-Etsu Chemical Co., Ltd.), 190.8g (0.8mol) of γ-mercaptopropyltriethoxysilane (KBE-803, manufactured by Shin-Etsu Chemical Co., Ltd.), 442.4g (1.6mol) of octyltriethoxysilane (KBE-3083, manufactured by Shin-Etsu Chemical Co., Ltd.), and 190.0g of ethanol, and then a mixed solution of 37.8g (2.1mol) of 0.5N hydrochloric acid and 75.6g of ethanol was dropped at room temperature. Then, the mixture was stirred at 80°C for 2 hours. Then, the mixture was filtered, and 17.0g of a 5% KOH/EtOH solution was dropped and stirred at 80°C for 2 hours. Thereafter, the mixture was concentrated under reduced pressure and filtered to obtain 480.1 g of a brown transparent liquid polysiloxane. Measurement by GPC revealed that the average molecular weight was 840 and the average degree of polymerization was 4.0 (predetermined degree of polymerization: 4.0). Furthermore, the mercapto equivalent was measured by the acetic acid/potassium iodide/potassium iodate addition-sodium thiosulfate solution titration method to find that it was 730 g/mol, confirming that the mercapto group content was as set. From the above, the obtained polysiloxane is represented by the following average composition formula. Therefore, the obtained polysiloxane corresponds to the sulfur-containing silane coupling agent represented by the above-mentioned average composition formula (X).
(-C ₃ H ₆ -S ₄ -C ₃ H ₆ -) _0.071 (-C ₈ H ₁₇ ) _0.571 (-OC ₂ H ₅ ) _1.50 (-C ₃ H ₆ SH) _0.286 SiO _0.75
The obtained polysiloxane is also referred to as silane coupling agent 3.
Alkyltriethoxysilane: Octyltriethoxysilane (KBE-3083, manufactured by Shin-Etsu Chemical Co., Ltd.)
Oil: Showa Shell Sekiyu Extract No. 4 S
Sulfur: Shikoku Chemical Industry Co., Ltd. Myucron OT-20
Vulcanization accelerator: Sancerer CM-G (sulfenamide type) manufactured by Sanshin Chemical Industry Co., Ltd.

As can be seen from Tables 3 and 4, all of Examples 1 to 13, which contain a diene rubber containing a specific amount of a specific conjugated diene rubber, silica, a silane coupling agent, and an alkyltriethoxysilane, exhibited excellent processability, wet performance, abrasion resistance, and chipping resistance.
Comparing Example 1 and Example 2 (comparison between embodiments in which the IVw _10% of the specific conjugated diene rubber 1 is different), Example 1 in which the IVw _10% of the specific conjugated diene rubber 1 is small showed better processability.
Comparing Example 1 and Example 3 (comparison between embodiments differing only in the rubber component content), Example 1, in which the ratio of the specific conjugated diene rubber in the diene rubber was 50 mass% or more, showed superior processability, abrasion resistance, and heat chipping resistance.
In addition, from a comparison of Examples 4 to 7 (a comparison between embodiments that differ only in that a thermoplastic resin is further contained), Example 5, which further contains a thermoplastic resin and in which the thermoplastic resin contains a terpene resin and a C5/C9 resin, exhibited better wet performance.
Moreover, comparing Examples 4, 8 and 9 (comparison between embodiments differing only in the type of silane coupling agent), Example 8, which contained a silane coupling agent having a thioester group, showed superior processability.
Comparing Examples 5, 10 and 11 (comparison between embodiments in which only the type of silane coupling agent is different), Example 10, in which the silane coupling agent contains NXT, exhibited better processability than Examples 5 and 11.
In comparison with Examples 12, 10, and 13 (comparison between embodiments differing only in the amount of alkyltriethoxysilane), Example 10 exhibited better processability, wet performance, and abrasion resistance than Example 12, and better abrasion resistance and chipping resistance than Example 13.

On the other hand, the standard example containing a modified diene rubber other than the specific conjugated diene rubber instead of the specific conjugated diene rubber and not containing alkyltriethoxysilane, Comparative Example 1 containing no alkyltriethoxysilane, Comparative Example 2 containing a modified diene rubber other than the specific conjugated diene rubber instead of the specific conjugated diene rubber, and Comparative Examples 3 and 4 in which the content of the specific conjugated diene rubber in the diene rubber was less than 25% by mass were insufficient in at least one of the processability, wet performance, abrasion resistance, and chipping resistance.

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 (8)

The composition contains a diene rubber including a modified conjugated diene rubber (A1), silica, a silane coupling agent, and an alkyltriethoxysilane,
The modified conjugated diene rubber (A1) satisfies the following formula (1) and the following formula (2) and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto,
A rubber composition for tires, wherein the proportion of the modified conjugated diene rubber (A1) in the diene rubber is 25 mass % or more.
IVw _10% ≦3.1×10 ^-6 ×Mw _10% -2.77 (1)
IVw _10% ≧4.7 (2)
The IVw _10% in formula (1) and formula (2) and the Mw _10% in formula (1) are as follows.
The modified conjugated diene rubber is subjected to gel permeation chromatography measurement using a differential refractive index detector and a viscosity detector as detectors. The weight average molecular weight obtained using the high molecular weight side portion of the peak of the chromatogram obtained by the differential refractive index detector, which is 10% of the total peak area, is defined as Mw _10% . The weight average intrinsic viscosity obtained using the high molecular weight side portion of the peak of the chromatogram obtained by the viscosity detector, which is 10% of the total peak area, is defined as IVw _10% . The unit of weight average intrinsic viscosity is dL/g. The modified conjugated diene rubber (A1) is
a star-shaped structure having three or more branches, at least one branch of which has a moiety derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group;
The rubber composition for a tire according to claim 1 , wherein the portion further has a main chain branched structure. The rubber composition for tires according to claim 1 or 2, wherein the silane coupling agent includes 3-octanoylthio-1-propyltriethoxysilane or a silane coupling agent having a mercapto group. Further containing a thermoplastic resin,
The rubber composition for a tire according to any one of claims 1 to 3, wherein the thermoplastic resin comprises at least one selected from the group consisting of terpene resins, C5/C9 resins, C5 resins, C9 resins, DCPD resins, DCPD/C9 resins, hydrogenated C5/C9 resins, hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated DCPD resins, and hydrogenated DCPD/C9 resins. The rubber composition for tires according to claim 4, wherein the thermoplastic resin comprises at least two selected from the group consisting of terpene resins, C5/C9 resins, C5 resins, C9 resins, DCPD resins, DCPD/C9 resins, hydrogenated C5/C9 resins, hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated DCPD resins, and hydrogenated DCPD/C9 resins. The rubber composition for tires according to claim 4 or 5, wherein the content of the thermoplastic resin is 50 parts by mass or less per 100 parts by mass of the diene rubber. The rubber composition for tires according to any one of claims 1 to 6, wherein the content of the silica is 50 parts by mass or more per 100 parts by mass of the diene rubber. A tire manufactured using the rubber composition for tires according to any one of claims 1 to 7.

Images