JP7698236B2 - Rubber composition for tires and tires - Google Patents

Description

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

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

JP 2014-28902 A

Recently, from the viewpoint of safety, etc., there has been a demand for further improvements in wet performance, snow performance, abrasion resistance, etc., for tires. In addition, there has been a demand for further improvements in mixing processability and extrusion processability for rubber compositions for producing tires.
Under these circumstances, the present inventors have studied the rubber composition for tires described in Patent Document 1 and the like, and have found that further improvement is desirable in consideration of future expected increases in demand.

In view of the above, the present invention aims to provide a rubber composition for tires that exhibits excellent mixing processability and extrusion processability, and that exhibits excellent wet performance, snow performance and abrasion 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 a specific silane coupling agent, 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) A rubber composition comprising a rubber component (A) containing a modified conjugated diene rubber (A1), silica (B), and a silane coupling agent (C),
The modified conjugated diene rubber (A1) satisfies the following formulas (1) to (3) and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto,
The proportion of the modified conjugated diene rubber (A1) in the rubber component (A) is 25% by mass or more,
The rubber composition for tires, wherein the silane coupling agent (C) is 3-octanoylthio-1-propyltriethoxysilane or a polysiloxane represented by the average composition formula (C2) below:
IVw _10% ≦3.1×10 ^-6 ×Mw _10% -2.77 (1)
St+Vn≦50 (2)
4.7≦IVw _10% (3)
Mw _10% and IVw _10% in the formulas (1) and (3) 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.
In formula (2), St represents the proportion (mass%) of repeating units derived from styrene to the entire modified conjugated diene rubber, and Vn represents the proportion (mass%) of repeating units of 1,2-vinyl structure derived from conjugated diene to the entire modified conjugated diene rubber.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-b-c-de)/2} (C2)
In formula (C2), A represents a divalent organic group containing a sulfide group. B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms. C represents a hydrolyzable group. D represents an organic group containing a mercapto group. ^R1 represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. a to e satisfy the relational expressions 0≦a<1, 0<b<1, 0<c<3, 0<d<1, 0≦e<2, 0<2a+b+c+d+e<4.
(2) The modified conjugated diene rubber (A1) is
a star 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 the above (1), further comprising a main chain branched structure in the above portion.
(3) The rubber composition for tires according to the above (1) or (2), further comprising 20 to 50 parts by mass of a thermoplastic resin (D) per 100 parts by mass of the rubber component (A).
(4) The rubber composition for tires according to (3) above, wherein the thermoplastic resin (D) is at least two selected from the group consisting of terpene resins, C5/C9 resins, C9 resins, DCPD resins, DCPD/C9 resins, hydrogenated C5/C9 resins, hydrogenated C9 resins, hydrogenated DCPD resins, and hydrogenated DCPD/C9 resins, each in an amount of 20 parts by mass or less.
(5) The rubber composition for tires according to any one of (1) to (4) above, wherein the content of the silica (B) is 50 to 150 parts by mass per 100 parts by mass of the rubber component (A).
(6) A tire produced using the rubber composition for tires according to any one of (1) to (5) above.

As described below, the present invention provides a rubber composition for tires that exhibits excellent mixing processability and extrusion processability, and that exhibits excellent wet performance, snow performance and abrasion 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.
Furthermore, with respect to a rubber composition for tires, the wet performance, snow performance and wear resistance when made into a tire are also simply referred to as "wet performance", "snow performance" and "wear 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.

[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 rubber composition contains a rubber component (A) containing a modified conjugated diene rubber (A1), silica (B), and a silane coupling agent (C),
The modified conjugated diene rubber (A1) satisfies the formulas (1) to (3) described below and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto,
The proportion of the modified conjugated diene rubber (A1) in the rubber component (A) is 25% by mass or more,
In the rubber composition for tires, the silane coupling agent (C) is 3-octanoylthio-1-propyltriethoxysilane or a polysiloxane represented by the average composition formula (C2) described below.

The composition of the present invention has the above-mentioned structure and is therefore believed to be able to solve the above-mentioned problems. Although the reason for this is not clear, it is speculated to be 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 formulas (1) to (3) described below and has a modifying group (hereinafter also referred to as a "specific modifying group") that contains a nitrogen atom, a silicon atom, and an oxygen atom adjacent thereto. 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, and the inventors have found that rubber that satisfies formula (1) has excellent mixing processability. In addition, it is believed that the specific modifying group of the specific conjugated diene rubber interacts with silica. In addition, the specific silane coupling agent contained in the composition of the present invention interacts with silica together with the specific modifying group, and further interacts with the skeleton of the specific conjugated diene rubber and other rubber components. Therefore, in the composition of the present invention, the dispersibility of silica is extremely high, which is believed to lead to excellent effects (extrusion processability, wet performance, snow performance, abrasion resistance).

Below, we will explain each component contained in the composition of the present invention.

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

[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 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 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 conjugated diene rubber is preferably SBR because the effects of the present invention are more excellent.

[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 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.

[Formula (1)]
The specific conjugated diene rubber satisfies the following formula (1).
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, 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 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)

The Mw _10% and IVw _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, Mw _10% and IVw _10% in formula (1) will be explained 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 (manufactured by Tosoh Corporation under the trade names "TSKgel G4000HXL", "TSKgel G5000HXL", and "TSKgel G6000HXL") packed with polystyrene gel are connected together and used. The sample to be measured is dissolved in toluene to a concentration of 1 mg/mL to prepare a 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.

Methods for making the modified conjugated diene rubber satisfy formula (1) include, for example, changing the type and amount of the specific modifier or the type and amount of the specific branching agent in the manufacturing method of the present invention described below.

Mw _10% is preferably from 100,000 to 10,000,000, and more preferably from 1,000,000 to 5,000,000, because the effects of the present invention are more excellent.

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

St+Vn≦50 (2)

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

Because the effect of the present invention is better, St+Vn is preferably 10 to 45, and more preferably 25 to 45.

Because the effect of the present invention is better, St is preferably 5 to 40, more preferably 10 to 35, and even more preferably 15 to 30.

Because the effect of the present invention is better, Vn is preferably 5 to 30, and more preferably 10 to 20.

[Formula (3)]
The specific conjugated diene rubber satisfies the following formula (3).
4.7≦IVw _10% (3)

The method for determining IVw _10% is as described above.

The IVw _10% is preferably 8 or less, and more preferably 6 or less, because the effects of the present invention are more excellent.

[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 -30°C, and more preferably from -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.

[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 described above, n represents an integer of 3 or more. There is no particular upper limit to n, but it is preferable that n be 30 or less because the effects of the present invention are superior.

[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.

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

[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 process]
The polymerization step is a step of obtaining a conjugated diene-based polymer by polymerizing a monomer containing a conjugated diene by 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, with n-butyllithium being more preferred, because they provide superior effects for the present invention.

There is no particular limit to the amount of organolithium compound used, but it is preferable that it be 0.001 to 10 mol% relative to the monomer, as 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 compound>
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.

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

[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]
In the composition of the present invention, the content of silica is preferably 50 to 150 parts by mass, and more preferably 80 to 140 parts by mass, per 100 parts by mass of the rubber component, because the effects of the present invention are more excellent.

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

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

[Specific polysiloxane]
The polysiloxane represented by the average composition formula (C2) (hereinafter, also referred to as the "specific polysiloxane") will be described below.
The specific polysiloxane is a polysiloxane represented by the average composition formula (C2) below.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-b-c-de)/2} (C2)

In the above formula (C2), A represents a divalent organic group containing a sulfide group. B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms. C represents a hydrolyzable group. D represents an organic group containing a mercapto group. ^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.

Formula (C2) represents the average composition of the polysiloxane, i.e., the type of groups directly bonded to the Si atoms of the polysiloxane and the average number of each group.
In formula (C2), Si represents a Si atom of the polysiloxane. In addition, O in formula (C2) represents an O atom of the polysiloxane. Note that the O atom is a divalent group and is always bonded to two Si atoms (Si atoms of the polysiloxane). (4-2a-b-c-d-e)/2 in formula (C2) represents the average number of O atoms of the polysiloxane bonded to the Si atoms of the polysiloxane.
In formula (C2), A, B, C, D, and ^R1 each represent a group bonded to a Si atom of the polysiloxane. A is a divalent group and always bonds to two Si atoms (Si atoms of the polysiloxane). In formula (C2), a, b, c, d, and e each represent the average number of A, B, C, D, and ^R1 bonded to a Si atom of the polysiloxane.
As can be seen from the fact that the sum of the groups directly bonded to the Si atom of the polysiloxane (a×2+b+c+d+e+((4-2a-b-c-d-e)/2)×2) is 4 (the valence of the Si atom), no groups other than A, B, C, D, ^R1 and O are directly bonded to the Si atom of the polysiloxane. In addition, in calculating the above total, a and (4-2a-b-c-d-e)/2) are doubled because A and O are divalent groups.

Specific examples and preferred embodiments of the specific polysiloxane and its manufacturing method are as described in paragraphs [0038] to [0070] of JP 2019-156918 A, paragraphs [0020] to [0050] of WO 2014/129664 A, and paragraphs [0046] to [0099] of U.S. Patent Application Publication No. 2016/0002433 A, and the descriptions therein are incorporated by reference.

[Content]
In the composition of the present invention, the content of the specific silane coupling agent is preferably 1 to 20 mass%, more preferably 5 to 15 mass%, relative to the content of the above-mentioned silica, 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 commonly used in rubber compositions, such as fillers other than silica (preferably carbon black), silane coupling agents other than the specific silane coupling agent, thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, wax, processing aids, liquid polymers, thermoplastic resins, thermosetting resins, vulcanizing agents (e.g., sulfur), vulcanization accelerators (accelerators), and vulcanization activators.

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

[Specific examples]
Examples of the thermoplastic resin include coumarone resins (e.g., coumarone resin, coumarone-indene resin, coumarone-indene-styrene resin), phenol resins (e.g., phenol resin, phenol-acetylene resin, phenol-formaldehyde resin), xylene resins (e.g., xylene resin, xylene-acetylene resin, xylene-formaldehyde resin), rosin resins (e.g., rosin, rosin ester, hydrogenated rosin derivative), terpene resins (e.g., terpene resin, modified rosin ... Examples of the 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.

Because the effects of the present invention are more excellent, the thermoplastic resin preferably contains at least one type selected from the group consisting of terpene resins, C5/C9 resins, C9 resins, DCPD resins, DCPD/C9 resins, hydrogenated C5/C9 resins, hydrogenated C9 resins, hydrogenated DCPD resins, and hydrogenated DCPD/C9 resins, more preferably contains at least two types selected from the above group, and even more preferably contains at least two types selected from the above group in an amount of 20 parts by mass or less each.

[Content]
In the composition of the present invention, the content of the thermoplastic resin is preferably 20 to 50 parts by mass, and more preferably 25 to 35 parts by mass, per 100 parts by mass of the rubber component, because the effects of the present invention are more excellent.

[Carbon black]
The composition of the present invention preferably contains carbon black because the effects of the present invention are more excellent. The carbon black may be used alone or in combination of two or more 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. However, in order to obtain better effects of the present invention, the content of carbon black is preferably 1 to 100 parts by mass, and more preferably 2 to 30 parts by mass, per 100 parts by mass of the rubber component described above.

[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.

Figure 2 shows a partial cross-sectional schematic diagram of a tire representing 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 Figure 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 conventional method. The gas to be filled in 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 described in further 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 process>
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.

Methanol was then 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, and the solvent was removed by steam stripping. The resulting mixture was vacuum dried at 60°C for 24 hours to obtain a solid conjugated diene rubber. The resulting conjugated diene rubber is also referred to as conjugated diene rubber 1.

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

Formula (4)

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

Conjugated diene rubber 4 is a reaction product between a conjugated diene polymer, which is a copolymer of butadiene and styrene, and 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 to the nitrogen atom, which is derived from the modifier.

[Conjugated diene rubber 5]
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 5.

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) containing a nitrogen atom, a silicon atom and an oxygen atom adjacent thereto, which is derived from the modifier.
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 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 6]
In a stirrer-equipped autoclave, 4000 g of cyclohexane, 8.1 g of 2,2-di(tetrahydrofuryl)propane, 352.1 g of 1,3-butadiene, and 131.7 g of styrene were charged under a nitrogen atmosphere, and then 4.1 mL of n-butyllithium (1.60 mol/L hexane solution) was added as an initiator, and polymerization was started at 40°C. 10 minutes after the start of polymerization, 184.3 g of 1,3-butadiene and 15.1 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 60°C. After the continuous addition was completed, the polymerization reaction was continued for another 20 minutes, and after it was confirmed that the polymerization conversion rate was in the range of 95% to 100%, 0.08 mmol of 1,6-bis(trichlorosilyl)hexane was added in the form of a cyclohexane solution with a concentration of 20% by mass, and the reaction was allowed to proceed for 10 minutes. Further, 0.027 mmol of polyorganosiloxane A represented by the following formula (9) was added in the form of a xylene solution with a concentration of 20% by mass, and allowed to react for 30 minutes. Thereafter, methanol was added in an amount equivalent to twice the molar amount of n-butyllithium used as a polymerization terminator to obtain a solution containing solution-polymerized SBR. Then, 5.96 g of 2,6-di-tert-butyl-p-cresol was added to the obtained solution. Next, the solvent was removed by steam stripping, and the mixture was dried with a heat roll adjusted to 110°C to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is also referred to as conjugated diene rubber 6.

In the above formula (9), X ₁ , X ₄ , R ₁ to R ₃ and R _to R ₈ are methyl groups. In the above formula (9), m is 80 and k is 120. In the above formula (9), X ₂ is a group represented by the following formula (10) (wherein * represents a bonding position).

[Weight average molecular weight, weight average intrinsic viscosity, styrene content, vinyl content, glass transition temperature]
For the conjugated diene rubbers (conjugated diene rubbers 1 to 2 and conjugated diene rubbers 4 to 6) synthesized as described above, Mw, _Mw10% , IVw, _IVw10% , St, Vn, and glass transition temperature (Tg) are shown in Table 2. The same is true for conjugated diene rubber 3 (NS612) described later.
In Table 2, the "right side" of formula (1) represents the value of the right side of formula (1), which is "3.1×10 ^-6 ×Mw _10% -2.77".
In addition, in Table 2, "Suitable" of formula (1) indicates whether formula (1) is satisfied or not, and specifically, "A" indicates that formula (1) is satisfied, and "B" indicates that formula (1) is not satisfied.
In addition, in Table 2, "St+Vn" in formula (2) represents the above-mentioned St+Vn.

As shown in Table 2, all of the conjugated diene rubbers 1 and 2 satisfy the formulas (1) to (3). 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 fall under the above-mentioned specific conjugated diene rubber.
On the other hand, as shown in Table 2, neither conjugated diene rubber 3 nor conjugated diene rubber 6 satisfies formula (1), and therefore does not fall under the above-mentioned specific conjugated diene rubber. Also, as shown in Table 2, conjugated diene rubber 4 satisfies formula (1) but does not satisfy formula (2), and therefore does not fall under the above-mentioned specific conjugated diene rubber. Also, as shown in Table 2, conjugated diene rubber 5 satisfies formulas (1) and (2), but does not satisfy formula (3), and therefore does not fall under the above-mentioned specific conjugated diene rubber.

[Synthesis of polysiloxane]
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, measurement of the mercapto equivalent by the acetic acid/potassium iodide/potassium iodate addition-sodium thiosulfate solution titration method revealed that the equivalent was 730 g/mol, confirming that the mercapto group content was as set. From the above, it is represented by the following average composition formula. Therefore, the obtained polysiloxane corresponds to the above-mentioned specific polysiloxane.
(-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 2.

[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.

[Wet performance]
Using each of the rubber compositions for tires obtained, test tires were prepared with a tire size of 245/40R19 and subjected to a wet braking test. Specifically, four test tires were mounted on a passenger car with an engine displacement of 2300cc, and the braking distance from an initial speed of 100km/h was measured on an asphalt road surface sprayed with water. The reciprocal of the braking distance was then indexed with the standard example being set at 100.
The results are shown in Tables 3 and 4. A higher index value indicates better wet performance. In practice, an index value of 100 or more is preferable.

[Snow performance]
Using each of the rubber compositions for tires obtained, test tires were manufactured with a tire size of 245/40R19, and subjected to a braking test on snow. Specifically, four test tires were mounted on a passenger car with an engine displacement of 2300cc, and the braking distance from an initial speed of 40km/h on a packed snow road surface was measured. The reciprocal of the braking distance was then indexed, with the standard example being set at 100.
The results are shown in Tables 3 and 4. A higher index value indicates better snow performance. For practical purposes, an index value of 100 or more is preferable.

[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 produce each vulcanized rubber sheet. The obtained vulcanized rubber sheets were subjected to an abrasion test using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) in accordance with JIS K 6264-2:2005 under conditions of load of 4.0 kg/ ^cm3 (=39 N), slip rate of 30%, abrasion test time of 4 minutes, and test temperature of room temperature, and the abrasion mass was measured. Then, the index was calculated as follows.
The results are shown in Tables 3 and 4. A larger index indicates a smaller amount of wear and better wear resistance. For practical purposes, an index of 100 or more is preferable.
Index = (Wear mass of Comparative Example 4/Wear mass of each Example) x 100

[Mixing processability]
For each of the obtained rubber compositions for tires, the Mooney viscosity was measured in accordance with JIS K6300-1:2013 using an L-shaped rotor under conditions of a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 100°C.
The reciprocal of the Mooney viscosity is shown in Tables 3 and 4. The results are expressed as an index with Comparative Example 4 being 100. The larger the index, the smaller the viscosity and the better the mixability and processability. For practical purposes, an index of 100 or more is preferable.

[Extrusion processability]
Each of the obtained rubber compositions for tires was cold pressed to prepare an unvulcanized rubber sheet (thickness: 2 mm). From the obtained unvulcanized rubber sheet, a JIS No. 3 dumbbell-shaped test piece (thickness: 2 mm) was punched out in accordance with JIS K6251:2010, and the 300% modulus was measured under conditions of a temperature of 20° C. and a tensile speed of 500 mm/min.
The results are shown in Tables 3 and 4. The results are expressed as an index, with Comparative Example 4 being 100. A larger index means better extrusion processability (green strength). For practical purposes, an index of 100 or more is preferable.

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

Silane coupling agent 2: Polysiloxane synthesized as described above (corresponding to a specific silane coupling agent)
Anti-aging agent (6C): Nocrac 6C (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
Wax: Sunnock (Ouchi Shinko Chemical Industry Co., Ltd.)
Stearic acid: Beads Stearic Acid YR (manufactured by NOF Corporation)
・Zinc oxide: Three types of zinc oxide (manufactured by Seido Chemical Industry Co., Ltd.)
Vulcanization accelerator (CZ): Sancerer CM-G (sulfenamide type) manufactured by Sanshin Chemical Industry Co., Ltd.
・Vulcanization accelerator (DPG): Sumitomo Chemical Co., Ltd. Soxinol D-G (guanidine type)
Sulfur: Shikoku Chemical Industry Co., Ltd. Myucron OT-20

As can be seen from Tables 3 and 4, all of Examples 1 to 7, which contain a rubber component containing a specific amount of a specific conjugated diene rubber, silica, and a specific silane coupling agent, exhibited excellent wet performance, snow performance, abrasion resistance, mix processability, and extrusion processability.
Comparing Example 1 and Example 2 (comparison between embodiments in which only the type of specific silane coupling agent is different), Example 1 in which the specific silane coupling agent is 3-octanoylthio-1-propyltriethoxysilane exhibited better mixing processability and extrusion processability. Also, comparing Example 1 and Example 2 (comparison between embodiments in which only the type of specific silane coupling agent is different), Example 2 in which the specific silane coupling agent is a specific polysiloxane exhibited better wet performance.
In addition, comparing Example 1 with Example 3 (comparison between embodiments differing only in the type of specific conjugated diene rubber), Example 3, in which the specific conjugated diene rubber had an St+Vn of 40 or more, showed better wet performance. In addition, comparing Example 1 with Example 3 (comparison between embodiments differing only in the type of specific conjugated diene rubber), Example 1, in which the specific conjugated diene rubber had an St+Vn of less than 40, showed better snow performance.
In addition, in comparison between Example 1 and Example 4 (comparison between embodiments having different ratios of the specific conjugated diene rubber in the rubber component), Example 4, in which the ratio is 50% by mass or more, exhibited better wet performance, snow performance, abrasion resistance and extrusion processability. In comparison between Example 1 and Example 4 (comparison between embodiments having different ratios of the specific conjugated diene rubber in the rubber component), Example 1, in which the ratio is less than 50% by mass, exhibited better mixing processability.
In addition, comparing Example 1 with Examples 5 to 6 (comparison between embodiments with and without a thermoplastic resin), Examples 5 to 6 containing a thermoplastic resin showed better wet performance and abrasion resistance. Among them, Example 6, which contains at least two kinds selected from the group consisting of terpene resin, C5/C9 resin, C9 resin, DCPD resin, DCPD/C9 resin, hydrogenated C5/C9 resin, hydrogenated C9 resin, hydrogenated DCPD resin, and hydrogenated DCPD/C9 resin as the thermoplastic resin, each in an amount of 20 parts by mass or less, showed even better wet performance, snow performance, and abrasion resistance.

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

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 (6)

The rubber composition contains a rubber component (A) containing a modified conjugated diene rubber (A1), silica (B), and a silane coupling agent (C),
The modified conjugated diene rubber (A1) satisfies the following formulas (1) to (3) and has a modifying group containing a nitrogen atom, a silicon atom, and an oxygen atom adjacent to the silicon atom ,
The proportion of the modified conjugated diene rubber (A1) in the rubber component (A) is 25% by mass or more,
The rubber composition for tires, wherein the silane coupling agent (C) is 3-octanoylthio-1-propyltriethoxysilane or a polysiloxane represented by the average composition formula (C2) below:
IVw _10% ≦3.1×10 ^-6 ×Mw _10% -2.77 (1)
St+Vn≦50 (2)
4.7≦IVw _10% (3)
Mw _10% and IVw _10% in the formulas (1) and (3) 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 , using toluene containing 5 mmol/L triethylamine as an eluent, under the condition of 40° C. 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.
In formula (2), St represents the proportion (mass%) of repeating units derived from styrene to the entire modified conjugated diene rubber, and Vn represents the proportion (mass%) of repeating units of 1,2-vinyl structure derived from conjugated diene to the entire modified conjugated diene rubber.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-b-c-de)/2} (C2)
In formula (C2), A represents a divalent organic group containing a sulfide group. B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms. C represents a hydrolyzable group. D represents an organic group containing a mercapto group. ^R1 represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. 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. 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 further contains 20 to 50 parts by mass of a thermoplastic resin (D) per 100 parts by mass of the rubber component (A). The rubber composition for tires according to claim 3, wherein the thermoplastic resin (D) is at least two selected from the group consisting of terpene resin, C5/C9 resin, C9 resin, DCPD resin, DCPD/C9 resin, hydrogenated C5/C9 resin, hydrogenated C9 resin, hydrogenated DCPD resin, and hydrogenated DCPD/C9 resin, each in an amount of 20 parts by mass or less. The rubber composition for tires according to claim 1, wherein the content of the silica (B) is 50 to 150 parts by mass per 100 parts by mass of the rubber component (A). A tire manufactured using the rubber composition for tires according to any one of claims 1 to 5.

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