JP2019059826A - Tire rubber composition and pneumatic tire - Google Patents

Abstract

To provide a tire rubber composition having excellent silica dispersibility and workability, and a pneumatic tire produced using the tire rubber composition.SOLUTION: A tire rubber composition contains a diene component, silica, and a mercapto-based silane coupling agent. The diene component contains at least one rubber component selected from the group consisting of natural rubber and isoprene rubber, and at least one polymer component selected from the group consisting of a styrene butadiene polymer and a butadiene polymer with a vinyl bond content of 50 mass% or more and with a weight average molecular weight of 100,000 or more. In the diene component, the rubber component content is 50 mass% or more and the polymer component content is 10 mass% or more relative to the rubber component content, the silica content is 30 pts.mass or more relative to the diene component 100 pts.mass, and the mercapto-based silane coupling agent content is 4 mass% or more relative to the silica content.SELECTED DRAWING: Figure 1

Description

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

In recent years, it has been required to reduce the heat buildup (hysteresis loss) of a tire from the viewpoint of low fuel consumption during vehicle travel. On the other hand, there is known a method of reducing heat buildup of a tire by blending silica with a rubber component constituting a tread portion of the tire.
However, since silica has a low affinity with the rubber component and the cohesiveness between the silicas is high, the silica does not disperse even if it is simply blended in the rubber component, and the effect of reducing heat generation is sufficiently obtained. There was a problem that I could not In particular, in the case of a rubber composition for a tire comprising a natural rubber such as a rubber composition for heavy load tires as a main rubber component, the dispersibility of the silica is particularly bad, and the above-mentioned problems are remarkable.

  Among these, for example, a rubber composition for a heavy load tire, which uses a natural rubber and a mercapto-based silane coupling agent in combination, is disclosed in the example of Patent Document 1. According to the patent document 1, it is described that the rubber composition for a tire can produce a tire excellent in silica dispersibility (silica dispersibility) and excellent in low heat buildup.

JP, 2016-30815, A

  Recently, due to environmental problems and resource problems, it is required to further reduce the heat buildup of the tire, and accordingly, the rubber composition for a tire containing silica is required to further improve the dispersibility of the silica (silica dispersibility). ing. Further, from the viewpoint of production efficiency, further improvement of the processability (reduction of viscosity) is also required.

  Under these circumstances, when the present inventor prepared the rubber composition for a tire referring to the example of Patent Document 1, the silica dispersibility and processability do not necessarily satisfy the level required nowadays It was revealed.

  Then, in view of the said situation, this invention aims at providing the pneumatic tire manufactured using the rubber composition for tires which is excellent in silica dispersibility and processability, and the said rubber composition for tires. Do.

As a result of intensive studies on the above problems, the present inventors found that at least one polymer selected from the group consisting of styrene butadiene polymers and butadiene polymers having a vinyl bond content of 50% by mass or more together with mercapto silane coupling agents. It discovered that the said subject was solvable by mix | blending a specific amount of a component, and came to this invention.
That is, the present inventor has found that the above problem can be solved by the following configuration.

(1) containing a diene-based component, silica and a mercapto-based silane coupling agent,
A styrene butadiene polymer, wherein the diene component is at least one rubber component selected from the group consisting of natural rubber and isoprene rubber, and a vinyl bond content is 50% by mass or more and a weight average molecular weight is 100,000 or more And at least one polymer component selected from the group consisting of
In the diene component, the content of the rubber component is 50% by mass or more,
The content of the polymer component is 10% by mass or more based on the content of the rubber component,
The content of the silica is 30 parts by mass or more with respect to 100 parts by mass of the diene component,
The rubber composition for tires whose content of the said mercapto type silane coupling agent is 4 mass% or more with respect to content of the said silica.
(2) The rubber composition for a tire according to the above (1), wherein the polymer component is a butadiene polymer having a vinyl bond content of 90% by mass or more and a weight average molecular weight of 100,000 or more.
(3) The mercapto silane coupling agent is a polysiloxane represented by an average composition formula of the formula (1) described later, or a repeating unit represented by a formula (A3) described later and a formula (A4) described later The rubber composition for tires according to the above (1) or (2), which is a copolymer having a repeating unit represented by
(4) A pneumatic tire comprising the rubber composition for a tire according to any one of (1) to (3) above in a cap tread.

  As described below, according to the present invention, it is possible to provide a rubber composition for a tire which is excellent in silica dispersibility and processability, and a pneumatic tire manufactured using the above rubber composition for a tire.

FIG. 1 is a schematic partial cross-sectional view of a tire representing an example of an embodiment of a pneumatic tire according to the present invention.

Below, the pneumatic tire manufactured using the rubber composition for tires of the present invention and the above-mentioned rubber composition for tires is explained.
In addition, the numerical range represented using "-" in this specification means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.
Further, each component contained in the rubber composition for a tire of the present invention may be used alone or in combination of two or more. Here, when using 2 or more types together about each component, content about the component points out total content, unless there is particular notice.

[Rubber composition for tire]
The rubber composition for a tire of the present invention (hereinafter, also simply referred to as "the composition of the present invention") contains a diene component, silica, and a mercapto silane coupling agent.
Here, the diene component is at least one rubber component selected from the group consisting of natural rubber and isoprene rubber, and has a vinyl bond content of 50% by mass or more and a weight average molecular weight of 100,000 or more. And at least one polymer component selected from the group consisting of styrene butadiene polymers and butadiene polymers.
Further, in the diene-based component, the content of the rubber component is 50% by mass or more, and the content of the polymer component is 10% by mass or more with respect to the content of the rubber component.
Moreover, content of the said silica is 30 mass parts or more with respect to 100 mass parts of said diene components.
Moreover, content of the said mercapto type silane coupling agent is 4 mass% or more with respect to content of the said silica.
Since the composition of the present invention has such a constitution, it can be considered that the above-mentioned effects can be obtained. Although the reason is not clear, it is presumed that it is as follows.

As described above, the composition of the present invention contains a diene component, silica, and a mercapto silane coupling agent, and the diene component is at least one selected from the group consisting of natural rubber and isoprene rubber. The rubber composition of the present invention comprises at least one polymer component selected from the group consisting of styrene butadiene polymers and butadiene polymers, having a rubber component of a species and a vinyl bond content of 50% by mass or more and a weight average molecular weight of 100,000 or more.
Here, although the mercapto type silane coupling agent contributes to the improvement of the silica dispersibility, there is a problem that the processability is lowered when the mercapto type silane coupling agent is used in order to promote the generation of the radical of the rubber component. There is. On the other hand, since the composition of the present invention contains a polymer component having a high vinyl bond content, the vinyl bond of the polymer component reacts with the mercapto group of the mercapto silane coupling agent, and the generation of radicals is suppressed. As a result, the compositions of the present invention are believed to exhibit excellent processability.
In addition, since the composition of the present invention contains natural rubber and the like as the main rubber component, as described above, the dispersibility of silica is usually poor. However, in the composition of the present invention, the polymer component is bonded to the silica via the mercapto silane coupling agent, and the polymer component bonded to the silica in this way is compatible with the rubber component such as natural rubber. It is believed that silica is uniformly dispersed in the rubber component.
From the above reasons, it is presumed that the composition of the present invention exhibits excellent silica dispersibility and processability.

  Hereinafter, each component contained in the composition of this invention is explained in full detail.

[Diene-based component]
The diene component contained in the composition of the present invention is at least one rubber component selected from the group consisting of natural rubber and isoprene rubber, and has a vinyl bond content of 50% by mass or more and a weight average molecular weight of 100, And at least one polymer component selected from the group consisting of styrene butadiene polymer and butadiene polymer, which is more than 000 000.
Here, in the diene-based component, the content of the rubber component is 50% by mass or more, and the content of the polymer component is 10% by mass or more with respect to the content of the rubber component.

<Rubber component>
As described above, the diene-based component contained in the composition of the present invention contains at least one rubber component selected from the group consisting of natural rubber (NR) and isoprene rubber (IR).

(Molecular weight)
The weight average molecular weight (Mw) of NR or IR which is a rubber component is not particularly limited, but it is more excellent in silica dispersibility and processability, and, for reasons of excellent heat resistance, cold resistance and deterioration resistance, 200,000 to It is preferably 3,000,000, more preferably 300,000 to 2,000,000, and still more preferably 400,000 to 1,500,000.
In the present specification, the number average molecular weight (Mn) and the weight average molecular weight (Mw) are standard polystyrene equivalent values obtained by gel permeation chromatography (GPC) measurement under the following conditions.
Hereinafter, "the silica dispersibility and processability are more excellent, and the heat resistance, the cold resistance and the deterioration resistance are excellent" is also referred to as "the effect of the present invention is more excellent".
-Solvent: tetrahydrofuran-Detector: RI detector

(Content)
In the diene component, the content of the rubber component is 50% by mass or more. Especially, it is preferable that it is 60 mass% or more, it is more preferable that it is 70 mass% or more, and it is further more preferable that it is 80 mass% or more from the reason the effect of this invention is more excellent. The upper limit is preferably 90% or less because the effect of the present invention is more excellent.

<Polymer component>
As described above, the diene component contained in the composition of the present invention is selected from the group consisting of styrene butadiene polymer and butadiene polymer having a vinyl bond content of 50% by mass or more and a weight average molecular weight of 100,000 or more. At least one polymer component. The polymer component is preferably a butadiene polymer because the effects of the present invention are more excellent.

(Styrene unit content)
The styrene unit content of the styrene butadiene polymer which is a polymer component is not particularly limited, but is preferably 10 to 40% by mass, and more preferably 20 to 30% by mass because the effect of the present invention is more excellent. .
In addition, styrene unit content represents the ratio (mass%) of the repeating unit derived from styrene with respect to the whole styrene butadiene polymer.

(Vinyl bond content)
The vinyl bond content of the styrene butadiene polymer or butadiene polymer as the polymer component is 50% by mass or more. Among them, for the reason that the effect of the present invention is more excellent, the content is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and 90% by mass or more. Being particularly preferred. The upper limit is preferably 95% by mass or less because the effect of the present invention is more excellent.
In the present specification, the vinyl bond content of a styrene butadiene polymer refers to the ratio (% by mass) of repeating units having vinyl bonds derived from butadiene to the entire styrene butadiene polymer. Similarly, in the present specification, the vinyl bond content of a butadiene polymer refers to the ratio (% by mass) of repeating units having a vinyl bond derived from butadiene to the entire butadiene polymer.
For example, the styrene butadiene polymer has a styrene unit content of 40% by mass, a butadiene unit content (the ratio of the repeating unit derived from butadiene to the entire styrene butadiene polymer) is 60% by mass, and the repeating unit derived from butadiene When the proportion occupied by the repeating unit having a vinyl bond is 90% by mole, the vinyl bond content of the styrene butadiene polymer is 54% by mass (= 60% by mass × 0.9).

(Molecular weight)
Mw of the styrene butadiene polymer or butadiene polymer which is a polymer component is 100,000 or more. Especially, it is preferable that it is 100,000-2,000,000, and it is more preferable that it is 150,000-1,000,000 from the reason the effect of this invention is more excellent, 200,000-800, More preferably, it is 000.
The method of measuring the molecular weight is as described above.

(Stereoregularity)
The stereoregularity of the butadiene polymer, which is a polymer component, is not particularly limited, but is preferably syndiotactic because the effect of the present invention is more excellent.

(Melt mass flow rate)
The melt mass flow rate (MFR) of the styrene butadiene polymer or butadiene polymer as the polymer component is not particularly limited, but is preferably 1 to 100 g / 10 min, more preferably 2 to 10 g / 10 min, because the effect of the present invention is more excellent. It is more preferable that it is a minute, and it is further preferable that it is 3 to 5 g / 10 minutes.
The melt mass flow rate (MFR) is measured under the conditions of a temperature of 150 ° C. and a load of 21.2 N according to “Test method for melt mass flow rate (MFR) of plastic-thermoplastics” defined in JIS K 7210: 1999. And the value.

(Melting point)
The melting point of the styrene butadiene polymer or butadiene polymer which is the polymer component is not particularly limited, but is preferably 50 to 150 ° C., more preferably 60 to 100 ° C., because the effect of the present invention is more excellent. It is further more preferable that it is -90 degreeC. In addition, melting | fusing point points out melting | fusing point in 1 atmosphere.

(Content)
The content of the polymer component is 10% by mass or more based on the content of the rubber component described above. The upper limit is preferably 100% by mass or less, more preferably 50% by mass or less, and still more preferably 30% by mass or less because the effect of the present invention is more excellent.
The content of the polymer component in the diene component (% by mass of the polymer component when the diene component is 100% by mass) is 5 to 40% by mass because the effect of the present invention is more excellent. Is preferable, 5 to 30% by mass is more preferable, and 10 to 20% by mass is more preferable.

<Other rubber components>
The diene-based component may further contain other rubber components that do not correspond to any of the above-described rubber components and polymer components.
As such other rubber components, butadiene rubber other than the above-mentioned polymer component, styrene butadiene rubber other than the above-mentioned polymer component, acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br- IIR, Cl-IIR), chloroprene rubber (CR) and the like.
The content of the other rubber component is not particularly limited, but it is preferably less than 30% by mass, more preferably less than 20% by mass, in the diene component, because the effect of the present invention is more excellent. More preferably, it is less than% by mass.

〔silica〕
The silica contained in the composition of the present invention is not particularly limited, and any conventionally known silica blended in rubber compositions for applications such as tires can be used.
Examples of the silica include wet silica, dry silica, fumed silica, diatomaceous earth and the like. As the above-mentioned silica, one type of silica may be used alone, or two or more types of silica may be used in combination.

<CTAB adsorption specific surface area>
Cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of silica is not particularly limited, for reasons that the effect of the present invention is more excellent, is preferably 100 to 300 m ² / g, it is 150 to 250 ² / g It is more preferable that it is 160-240 m < ² > / g more preferable.
Here, the CTAB adsorption specific surface area is a value measured according to JIS K 6217-3: 2001 "Part 3: Determination of specific surface area-CTAB adsorption method" according to JIS K 6217-3: 2001.

<Content>
In the composition of the present invention, the content of silica is at least 30 parts by mass with respect to 100 parts by mass of the diene component. The upper limit is not particularly limited, but is preferably 200 parts by mass or less, and more preferably 150 parts by mass or less because the effect of the present invention is more excellent.

[Mercapto-based silane coupling agent]
The mercapto type silane coupling agent (silane coupling agent having a mercapto group) contained in the composition of the present invention is not particularly limited as long as it is a silane compound having a mercapto group (-SH) and a hydrolysable group. In the present specification, a protected mercapto group whose mercapto group is protected does not correspond to a mercapto 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. Among them, an alkoxy group is preferable because the effect of the present invention is more excellent. When the hydrolyzable group is an alkoxy group, the carbon number of the alkoxy group is preferably 1 to 16, and more preferably 1 to 4. As a C1-C4 alkoxy group, a methoxy group, an ethoxy group, a propoxy group etc. are mentioned, for example.

The mercapto type silane coupling agent may have an organic functional group other than a mercapto group.
The organic functional group is not particularly limited, and examples thereof include an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group and an amino group.

  Specific examples of the mercapto-based silane coupling agent include mercaptopropyltrimethoxysilane and mercaptopropyltriethoxysilane.

<Preferred embodiment>
It is preferable that the said mercapto type silane coupling agent is a mercapto type silane coupling agent which has a polysiloxane structure (-Si-O-) from the reason which the effect of this invention is more excellent.
The mercapto silane coupling agent is more excellent in the effect of the present invention, and further, the compound represented by the formula (A1) described later, the formula (1) described later, because the heat resistance and the deterioration resistance are more excellent. Or a copolymer having a repeating unit represented by the formula (A3) described later and a repeating unit represented by the formula (A4) described later The compound is preferably a compound represented by the formula (A1), or more preferably the particular polysiloxane, and still more preferably the particular polysiloxane.

(Compound represented by formula (A1))

In the formula ^{(A1), R 11} represents an alkoxy group having 1 to 8 carbon atoms, among them, preferably an alkoxy group having 1 to 3 carbon atoms. As a C1-C3 alkoxy group, a methoxy group, an ethoxy group, etc. are mentioned, for example. In the case where l is an integer of 2 or more, a plurality of R ¹¹ may be identical to or different from each other.
In the formula ^{(A1), R 12} represents a straight-chain polyether group having 4 to 30 carbon atoms. The polyether group is a group having two or more ether bonds, and as a specific example thereof, for example, a group having a total of two or more structural units -R ^a -O-R ^b -can be mentioned. Here, R ^a and R ^b are each independently a linear or branched alkylene group, a linear or branched alkenylene group, a linear or branched alkynylene group, or a substituted or non-substituted Represents a substituted arylene group. Among them, a linear alkylene group is preferable. A plurality of R ¹² when m is 2 may be the same or different.
As a suitable aspect of a C4-C30 linear polyether group, the group represented by a following formula (A2) is mentioned, for example.

In the above formula (A2), R ²¹ represents a linear alkyl group, a linear alkenyl group, or a linear alkynyl group, and among them, a linear alkyl group is preferable. As said linear alkyl group, a C1-C20 linear alkyl group is preferable, and a C8-C15 linear alkyl group is more preferable. Specific examples of the linear alkyl group having 8 to 15 carbon atoms include octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group and the like, among which tridecyl group is preferable.
In the above formula (A2), R ²² represents a linear alkylene group, a linear alkenylene group or a linear alkynylene group, and a linear alkylene group is preferable among them. As said linear alkylene group, a C1-C2 linear alkylene group is preferable and ethylene group is more preferable.
In said formula (A2), p represents the integer of 1-10, and it is preferable that it is 3-7.
In the above formula (A2), * indicates a bonding position.

In the formula ^{(A1), R 13} represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.
In the formula ^{(A1), R 14} represents an alkylene group having 1 to 30 carbon atoms, among them preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 1 to 5 carbon atoms. As a specific example of a C1-C5 alkylene group, a methylene group, ethylene group, a propylene group etc. are mentioned, for example.
In said formula (A1), 1 represents the integer of 1-3, Especially, it is preferable that it is 3 from the reason the effect of this invention is more excellent. In said formula (A1), m represents the integer of 0-2. n represents an integer of 0 to 1; l, m and n satisfy the relational expression of l + m + n = 3.

(Specific polysiloxane)
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-b-c-d-e) / 2} (1)
In Formula (1), A represents a divalent organic group containing a sulfide group, B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms, and C represents a hydrolyzable group. R ¹ represents an organic group containing a mercapto group, R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms, a to e are 0 ≦ a <1, 0 ≦ b <1, 0 <c <3 , 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4.

Formula (1) represents the average composition of polysiloxane. That is, it represents the type of group directly bonded to the Si atom of the polysiloxane and the average number of each group.
Si in Formula (1) represents the Si atom of polysiloxane. Moreover, O in Formula (1) represents the O atom of polysiloxane. The O atom is a divalent group and is bonded to two Si atoms (Si atoms of polysiloxane) without fail. (4-2a-b-c-d-e) / 2 in the formula (1) represents the average number of O atoms of the polysiloxane bonded to the Si atoms of the polysiloxane.
Each of A, B, C, D and R ¹ in the formula (1) represents a group to be bonded to the Si atom of the polysiloxane. Here, A is a divalent group and is bonded to two Si atoms (Si atoms of polysiloxane) without fail. In the formula (1), a, b, c, d and e each represent the average number of A, B, C, D and R ¹ bonded to the Si atom of the polysiloxane.
Because the sum (a × 2 + b + c + d + e + ((4−2a−b−c−d−e) / 2) × 2) of each group directly bonded to the Si atom of the polysiloxane is 4 (valence of Si atom) As can be seen, groups other than A, B, C, D, R ¹ and O are not directly bonded to the Si atom of the polysiloxane. In the above calculation of the sum, the reason for doubling a and (4-2a-b-c-d-e) / 2) is because A and O are divalent groups.

In the above formula (1), A represents a divalent organic group containing a sulfide group (hereinafter also referred to as “sulfide group-containing organic group”). Especially, it is preferable that it is group represented by following formula (2) from the reason which the effect of this invention is more excellent.
^* -(CH ₂ ) _n- S _x- (CH ₂ ) _n- ^* (2)
In said Formula (2), n represents the integer of 1-10, Especially, it is preferable that it is an integer of 2-4 from the reason the effect of this invention is more excellent.
In said Formula (2), x represents the integer of 1-6, Especially, it is preferable that it is an integer of 2-4 from the reason the effect of this invention is more excellent.
In the above formula (2), * indicates a bonding position.
Specific examples of the group represented by the formula (2) are, 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.
Because the effects of the present invention are more excellent, sulfide group contained in A is tetrasulfide group _- preferably a (-S 4).

  In said formula (1), B represents a C5-C10 monovalent hydrocarbon group, As a specific example, a hexyl group, an octyl group, a decyl group etc. are mentioned, for example.

In the above formula (1), C represents a hydrolyzable group, and specific examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, an alkenyloxy group and the like. Among them, a group represented by the following formula (3) is preferable because the effect of the present invention is more excellent.
^* -OR ² (3)
In the above formula (3), R ² is an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group (aryl alkyl group) or an alkenyl group having 2 to 10 carbon atoms having from 6 to 10 carbon atoms Among them, an alkyl group having 1 to 5 carbon atoms is preferable because the effect of the present invention is more excellent. As a specific example of the said C1-C20 alkyl group, a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, an octadecyl group etc. are mentioned, for example. As a specific example of said C6-C10 aryl group, a phenyl group, a tolyl group, etc. are mentioned, for example. As a specific example of the said C6-C10 aralkyl group, a benzyl group, a phenylethyl group, etc. are mentioned, for example. As a specific example of the said C2-C10 alkenyl group, a vinyl group, a propenyl group, a pentenyl group etc. are mentioned, for example.
In the above formula (3), * indicates a bonding position.

In the above formula (1), D represents an organic group containing a mercapto group. Especially, it is preferable that it is group represented by following formula (4) from the reason which the effect of this invention is more excellent.
^* -(CH ₂ ) _m- SH (4)
In said Formula (4), m represents the integer of 1-10, Especially, it is preferable that it is an integer of 1-5 from the reason the effect of this invention is more excellent.
In the above formula (4), * indicates a bonding position.
Specific examples of the group represented by the above formula (4) include ^* -CH ₂ SH, ^* -C ₂ H ₄ SH, ^* -C ₃ H ₆ SH, ^* -C ₄ H ₈ SH, ^* -C ₅ H ₁₀ SH, ^* -C ₆ H ₁₂ SH, ^* -C ₇ H ₁₄ SH, ^* -C ₈ H ₁₆ SH, ^* -C ₉ H ₁₈ SH, ^* -C ₁₀ H ₂₀ SH.

  In said Formula (1), E represents a C1-C4 monovalent hydrocarbon group.

  In the above formula (1), a to e are relational expressions of 0 ≦ a <1, 0 ≦ b <1, 0 <c <3, 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4. Meet.

  The specific polysiloxane preferably has a greater than 0 (0 <a), because the effect of the present invention is more excellent. That is, it is preferable to have a sulfide group-containing organic group. Among them, 0 <a ≦ 0.50 is preferable because the effect of the present invention is more excellent.

In the above formula (1), b is preferably 0.10 ≦ b ≦ 0.89, because the effect of the present invention is more excellent.
In the above formula (1), c is preferably 1.2 ≦ c ≦ 2.0, because the effect of the present invention is more excellent.
In the above formula (1), d is preferably 0.1 ≦ d ≦ 0.8 because the effect of the present invention is more excellent.

  In the above formula (1), A is a group represented by the above formula (2), and in the above formula (1), C is a group represented by the above formula (1). It is preferable that it is a polysiloxane which is a group represented by 3) and D in said Formula (1) is a group represented by said Formula (4).

The weight average molecular weight of the specific polysiloxane is preferably 500 to 2,300, and more preferably 600 to 1,500, because the effect of the present invention is more excellent. The molecular weight of the specific polysiloxane in the present application is determined in terms of polystyrene by gel permeation chromatography (GPC) using toluene as a solvent.
The mercapto equivalent of acetic acid / potassium iodide / potassium iodate addition-sodium thiosulfate solution titration method of the specific polysiloxane described above is preferably 550 to 700 g / mol, from the viewpoint of excellent vulcanization reactivity, and preferably 600 to 600 g / mol. More preferably, it is 650 g / mol.

  The specific polysiloxane preferably has 2 to 50 siloxane units (-Si-O-) because the effect of the present invention is more excellent.

  In addition, metal (for example, Sn, Ti, Al) other than a silicon atom does not exist in frame | skeleton of the said specific polysiloxane.

The method for producing the specific polysiloxane is not particularly limited, but as a first preferred embodiment, an organosilicon compound represented by the following formula (6) and an organosilicon compound represented by the following formula (7) Methods of hydrolytic condensation. In a second preferred embodiment, an organosilicon compound represented by the following formula (5), an organosilicon compound represented by the following formula (6), and an organosilicon represented by the following formula (7) The method of carrying out hydrolysis condensation with a compound is mentioned. Moreover, as a 3rd suitable aspect, the organosilicon compound represented by following formula (5), the organosilicon compound represented by following formula (6), and organosilicon represented by following formula (7) The method of carrying out the hydrolysis condensation of a compound and the organosilicon compound represented by following formula (8) is mentioned.
Among them, the second preferred embodiment is preferable because the effect of the present invention is more excellent.

In the above formula (5), R ⁵¹ represents an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, and among these, the reason why the effect of the present invention is more excellent Therefore, it is preferable that it is a C1-C5 alkyl group. As a specific example of the said C1-C20 alkyl group, a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, an octadecyl group etc. are mentioned, for example. As a specific example of the said C6-C10 aryl group, a phenyl group, a tolyl group, a naphthyl group etc. are mentioned, for example. As a specific example of a C2-C10 alkenyl group, a vinyl group, a propenyl group, a pentenyl group etc. are mentioned, for example.
In said Formula (5), R ⁵² represents a C1-C10 alkyl group or a C6-C10 aryl group. As a specific example of the said C1-C10 alkyl group, a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group etc. are mentioned, for example. Specific examples of the aryl group of the carbon number 6 to 10 is as defined above R ^51.
In the above formula (5), the definition of n and preferred embodiments are the same as the above n.
In the above formula (5), the definition and preferred embodiments of x are the same as the above x.
In said formula (5), y represents the integer of 1-3.

  As specific examples of the organosilicon compound represented by the above formula (5), for example, bis (trimethoxysilylpropyl) tetrasulfide, bis (triethoxysilylpropyl) tetrasulfide, bis (trimethoxysilylpropyl) disulfide, bis (Triethoxysilylpropyl) disulfide and the like.

In the above formula (6), the definition, the specific example and the preferred embodiment of R ⁶¹ are the same as the above R ⁵¹ .
In the above formula (6), the definition, specific examples and preferred embodiments of R ⁶² are the same as the above R ⁵² .
In the above formula (6), the definition of z is the same as the above y.
In said formula (6), p represents the integer of 5-10.

  Specific examples of the organic silicon compound represented by the above formula (6) include, for example, pentyltrimethoxysilane, pentylmethyldimethoxysilane, pentyltriethoxysilane, pentylmethyldiethoxysilane, hexyltrimethoxysilane, hexylmethyldimethoxysilane Hexyltriethoxysilane, hexylmethyldiethoxysilane, octyltrimethoxysilane, octylmethyldimethoxysilane, octyltriethoxysilane, octylmethyldiethoxysilane, decyltrimethoxysilane, decylmethyldimethoxysilane, decyltriethoxysilane, decylmethylethoxysilane Diethoxysilane etc. are mentioned.

The formula (7), the definition of R ^71, specific examples and preferred embodiments are the same as above R ^51.
In the above formula (7), the definition, specific examples and preferred embodiments of R ⁷² are the same as the above R ⁵² .
In the above formula (7), the definition of m and the preferred embodiment are the same as the above m.
In the above formula (7), the definition of w is the same as the above y.

  Specific examples of the organic silicon compound represented by the above formula (7) include, for example, α-mercaptomethyltrimethoxysilane, α-mercaptomethylmethyldimethoxysilane, α-mercaptomethyltriethoxysilane, α-mercaptomethylmethyldi Examples include ethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltriethoxysilane, and γ-mercaptopropylmethyldiethoxysilane.

In said Formula (8), the definition of R ⁸¹ , an example, and a suitable aspect are the same as said R ⁵¹ .
In the above formula (8), the definition, the specific example and the preferred embodiment of R ⁸² are the same as the above R ⁵² .
In the above formula (8), the definition of v is the same as the above y.
In said formula (8), q represents the integer of 1-4.

  Specific examples of the organic silicon compound represented by the above formula (8) include, for example, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, methylethyldiethoxysilane, propyltrimethoxysilane, propylmethyldimethoxysilane, Propylmethyldiethoxysilane and the like can be mentioned.

  A solvent may be used when necessary in producing the specific polysiloxane. The solvent is not particularly limited, but specific examples thereof include aliphatic hydrocarbon solvents such as pentane, hexane, heptane and decane, ether solvents such as diethyl ether, tetrahydrofuran and 1,4-dioxane, formamide, dimethylformamide, N And amide solvents such as methyl pyrrolidone, aromatic hydrocarbon solvents such as benzene, toluene and xylene, alcohol solvents such as methanol, ethanol and propanol.

A catalyst may be used when necessary in producing the specific polysiloxane. Examples of the catalyst include acidic catalysts such as hydrochloric acid and acetic acid, Lewis acid catalysts such as ammonium fluoride, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium acetate, potassium acetate, sodium hydrogencarbonate, sodium hydrogencarbonate, potassium hydrogencarbonate and potassium hydrogencarbonate And alkali metal salts such as calcium carbonate, sodium methoxide and sodium ethoxide, and amine compounds such as triethylamine, tributylamine, pyridine and 4-dimethylaminopyridine.
The catalyst is preferably not an organometallic compound containing Sn, Ti or Al as a metal. When such an organic metal compound is used, a metal is introduced into the polysiloxane skeleton to obtain the specific polysiloxane (a metal other than a silicon atom (for example, Sn, Ti, Al) is not present in the skeleton). I can not do it.

  A silane coupling agent having a mercapto group [eg, an organosilicon compound represented by the formula (7)] and a silane cup having a sulfide group or a mercapto group as an organosilicon compound used in producing the specific polysiloxane When using a silane coupling agent other than a ring agent [for example, an organosilicon compound represented by Formula (6) or Formula (8)], a silane coupling agent having a mercapto group and a silane having a sulfide group or a mercapto group The mixing ratio (molar ratio) with the silane coupling agent other than the coupling agent (silane coupling agent having a mercapto group / silane coupling agent other than a silane coupling agent having a sulfide group or a mercapto group) is not particularly limited. It is preferable to be 1.1 / 8.9 to 6.7 / 3.3 because the effect is better. Ku, and more preferably 1.4 / 8.6 to 5.0 / 5.0.

  As an organosilicon compound used when manufacturing the said specific polysiloxane, the silane coupling agent which has a mercapto group [For example, the organosilicon compound represented by Formula (7)], and the silane coupling agent which has a sulfide group [ For example, when using the organosilicon compound represented by the formula (5) in combination, the mixing ratio (molar ratio) of the silane coupling agent having a mercapto group to the silane coupling agent having a sulfide group (silane having a mercapto group) Coupling agent / silane coupling agent having a sulfide group) is preferably 2.0 / 8.0 to 8.9 / 1.1, because the effect of the present invention is more excellent, and 2.5 / 2. It is more preferable that it is 7.5-8.0 / 2.0.

  As an organosilicon compound used when manufacturing the said specific polysiloxane, the silane coupling agent which has a mercapto group [for example, the organosilicon compound represented by Formula (7)], the silane coupling agent which has a sulfide group [ For example, a silane coupling agent other than the organosilicon compound represented by the formula (5) and / or a silane coupling agent having a sulfide group or a mercapto group [e.g. When the organosilicon compound] is used in combination, the amount of the silane coupling agent having a mercapto group is preferably 10.0 to 73.0% in the total amount (mol) of the three formers. The amount of the silane coupling agent having a sulfide group is preferably 5.0 to 67.0% of the total amount of the front three. The amount of the silane coupling agent other than the silane coupling agent having a sulfide group or a mercapto group is preferably 16.0 to 85.0% in the total amount of the preceding three.

(Copolymer having a repeating unit represented by the formula (A3) and a repeating unit represented by the formula (A4)

In the above formulas (A3) and (A4), R ³¹ and R ⁴¹ each independently represent an alkylene group having 1 to 5 carbon atoms, and specific examples thereof include a methylene group, an ethylene group and a propylene group Be Among these, a propylene group is preferable. Plural R ³¹ and R ⁴¹ may be the same or different.
In the above formulas (A3) and (A4), R ³² and R ⁴² each independently represent a linear or branched C 1 to C 30 alkylene group, or a linear or branched C 2 to 30 carbon atoms. Or an linear or branched alkynyl group having 2 to 30 carbon atoms, and among them, one having 3 to 20 carbon atoms is preferable. When R ³² is terminal, R ³² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or A linear or branched alkynyl group having 2 to 30 carbon atoms is represented, and among them, those having 3 to 20 carbon atoms are preferable. If R ⁴² is ^terminated, the definition of ^{R 42,} specific examples and preferred embodiments are the same as above ^{R 32.} Plural R ³² and R ⁴² may be the same or different.
In formulas (A3) and (A4), each of R ³³ and R ⁴³ independently represents a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkyl group Alkenyl group having 2 to 30 carbon atoms, linear or branched alkynyl group having 2 to 30 carbon atoms, linear or branched alkyl group having 1 to 30 carbon atoms, and having a hydroxyl group or a carboxyl group at one end Or a linear or branched alkenyl group having 2 to 30 carbon atoms which has a hydroxyl group or a carboxyl group at the end. R ⁴³ is preferably a group having a hydroxyl group at the end. R ³² and R ³³ may form a ring with R ³² and R ³³ . R ⁴² and R ⁴³ may form a ring with R ⁴² and R ⁴³ . The plurality of R ³³ and R ⁴³ may be the same or different.
R ³⁴ represents an alkyl group having 1 to 13 carbon atoms, and among them, an alkyl group having 3 to 10 carbon atoms is preferable. As a specific example of a C3-C10 alkyl group, a hexyl group, a heptyl group, an octyl group etc. are mentioned, for example. Plural R ³⁴ may be the same or different.

<Content>
In the composition of the present invention, the content of the mercapto silane coupling agent is 4% by mass or more with respect to the content of silica described above. Especially, it is preferable that it is 5-30 mass% because it is more excellent in the effect of this invention, it is more preferable that it is 6-20 mass%, and it is further more preferable that it is 7-15 mass%.
In the composition of the present invention, the content of the mercapto silane coupling agent is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the diene component, because the effect of the present invention is more excellent. It is more preferable that it is 20 mass parts, and it is further more preferable that it is 3-15 mass parts.

[Optional component]
The composition of the present invention may further contain other components (optional components) as needed, as long as the effects and purposes of the composition are not impaired.
Examples of the above optional components include carbon black, silane coupling agents other than mercapto silane coupling agents, terpene resins (preferably, aromatic modified terpene resins), thermally expandable microcapsules, fillers, zinc oxide (zinc oxide) Commonly used in rubber compositions such as stearic acid, anti-aging agents, waxes, processing aids, oils, liquid polymers, thermosetting resins, vulcanizing agents (eg sulfur), vulcanization accelerators, etc. Additives and the like.

<Carbon black>
The composition of the present invention preferably contains carbon black because the effect of the present invention is more excellent.
The carbon black is not particularly limited. For example, various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, SRF, etc. Can be used.
Nitrogen adsorption specific surface area of the carbon black _(N 2 SA) is not particularly limited, for the reasons the effects of the present invention is more excellent, is preferably 50 to 200 m ² / g, it is 70~150m ² / g Is more preferred.
Here, the nitrogen adsorption specific surface area (N ₂ SA) refers to the nitrogen adsorption amount on the surface of carbon black according to JIS K 6217-2: 2001 "Part 2: Determination of specific surface area-nitrogen adsorption method-single point method" It is a measured value.

  The content of the carbon black is not particularly limited, but is preferably 1 to 100 parts by mass, and more preferably 5 to 50 parts by mass with respect to 100 parts by mass of the diene component because the effect of the present invention is more excellent. Is more preferred.

[Use]
The compositions of the present invention are suitably used in the manufacture of tires, in particular heavy duty tires.

[Pneumatic tire]
The pneumatic tire of the present invention is a pneumatic tire (particularly, a heavy load tire) manufactured using the composition of the present invention described above. Among them, a pneumatic tire in which the composition of the present invention is disposed in a tire tread (cap tread) is preferable.
Although FIG. 1 shows a partial cross-sectional schematic view of a tire that represents an example of an embodiment of the pneumatic tire according to the present invention, the pneumatic tire according to the present invention is not limited to the embodiment shown in FIG.

In FIG. 1, the pneumatic tire comprises a pair of left and right bead portions 1 and side wall portions 2 and a tire tread portion 3 connected to both side wall portions 2, and a carcass cord in which a steel cord is embedded between the pair of left and right bead portions 1 The layer 4 is mounted, and the end of the carcass layer 4 is wound around the bead core 5 and the bead filler 6 from inside to 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 over the entire circumference of the tire. Belt cushions 8 are disposed at both ends of the belt layer 7. An inner liner 9 is provided on the inner surface of the pneumatic tire in order to prevent air filled inside the tire from leaking to the outside of the tire, and a tie rubber 10 for bonding the inner liner 9 is used together with the carcass layer 4 It is laminated between the inner liner 9 and the inner liner 9.
The tire tread portion 3 is formed of the composition of the present invention described above.

  The pneumatic tire of the present invention can be manufactured, for example, according to a conventionally known method. Moreover, as a gas with which the tire is filled, an inert gas such as nitrogen, argon, helium or the like can be used in addition to a normal air or air whose oxygen partial pressure is adjusted.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

[Preparation of rubber composition for tire]
The components shown in Table 1 below were blended at the proportions (parts by mass) shown in the same Table. When the rubber component is an oil-extended product, the parts by mass of the rubber components in Table 1 below represent the amount (parts by mass) of the net rubber excluding the oil-extended oil.
Specifically, among the components shown in Table 1 below, the components other than sulfur and the vulcanization accelerator were raised to about 140 ° C. using a 1.7-liter closed Banbury mixer, and then 5 minutes After mixing, it was discharged and cooled to room temperature to obtain a masterbatch. Furthermore, using the above-mentioned Banbury mixer, the obtained masterbatch was mixed with sulfur and a vulcanization accelerator to obtain a rubber composition for a tire.

[Evaluation]
The obtained rubber composition for a tire was evaluated as follows.

<Pane effect>
The obtained rubber composition for a tire (unvulcanized) is placed in a strain shear stress measuring machine (RPA 2000, manufactured by α-Technology Co., Ltd.), vulcanized at 170 ° C. for 10 minutes, and then strain of 0.28% strain. The shear modulus G 'and the strain shear modulus G' at a strain of 30.0% were measured, and the difference G '0.28 (MPa)-G' 30.0 (MPa) was calculated as the Payne effect.
The results are shown in Table 1. The results are expressed as an index with a standard example as 100. The smaller the index, the better the silica dispersibility. It is preferable that it is 95 or less practically.

<Viscosity>
With respect to the obtained rubber composition for a tire, the Mooney viscosity is measured under the conditions of a preheating time of 1 minute, a rotation time of the rotor of 4 minutes, and a test temperature of 100 ° C. according to JIS K6300-1: 2013. did.
The results are shown in Table 1. The results are expressed as an index with a standard example as 100. The smaller the index, the smaller the viscosity and the better the processability.

The details of each component in Table 1 are as follows.
NR: TSR 20 (Tg: -62 ° C)
Tufdene 1000: styrene butadiene rubber (styrene unit content: 18% by mass, vinyl bond content: 8.2% by mass, Mw: 290,000, manufactured by Asahi Kasei Corporation)
-NS116: styrene butadiene rubber (styrene unit content: 23% by mass, vinyl bond content: 56% by mass, Mw: 510,000, manufactured by Nippon Zeon Co., Ltd.)
· RB 810: syndiotactic 1,2-polybutadiene (butadiene polymer) (vinyl bond content: 90% by mass, MFR: 3 g / 10 minutes (150 ° C., 21.2 N), melting point: 71 ° C., specific gravity: 0.90 , Mw: 230,000, manufactured by JSR Corporation)
· RB 820: syndiotactic 1,2-polybutadiene (butadiene polymer) (vinyl bond content: 92% by mass, MFR: 3 g / 10 minutes (150 ° C., 21.2 N), melting point: 95 ° C., specific gravity: 0.91 , Mw: 220,000, manufactured by JSR Corporation)

Silica: ULTRASIL 9100 GR (CTAB adsorption specific surface area: 200 m ² / g, manufactured by Evonik)
Carbon black: Show black N 339 (manufactured by Cabot Japan Ltd.)
-Stearic acid: beads stearic acid (made by NOF Corporation)
・ Zinc flower: 3 kinds of zinc oxide (made by Shodo Chemical Industry Co., Ltd.)
・ Anti-aging agent: Ozonone 6C (made by SEIKO CHEMICAL Co., Ltd.)

Si69: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide)
Si 263: Si 263 (3-mercaptopropyltriethoxysilane)
-Specific polysiloxane: Specific polysiloxane synthesized as follows: Bis (triethoxysilylpropyl) tetrasulfide (Shin-Etsu Chemical Co., Ltd. KBE-846 in a 2 L separable flask equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer) ) 107.8 g (0.2 mol), γ-mercaptopropyltriethoxysilane (Shin-Etsu Chemical KBE-803) 190.8 g (0.8 mol), octyltriethoxysilane (Shin-Etsu Chemical KBE-3083) 442. After 4 g (1.6 mol) and 190.0 g of ethanol were put in, a mixed solution of 37.8 g (2.1 mol) of 0.5 N hydrochloric acid and 75.6 g of ethanol was dropped at room temperature. Then, it stirred at 80 degreeC for 2 hours. Then, after filtration, 17.0 g of a 5% KOH / EtOH solution was dropped, and the mixture was stirred at 80 ° C. for 2 hours. Thereafter, concentration under reduced pressure and filtration gave 480.1 g of a brown clear liquid polysiloxane. As a result of measurement by GPC, the average molecular weight was 840, and the average degree of polymerization was 4.0 (set degree of polymerization 4.0). Moreover, as a result of measuring a mercapto equivalent by acetic acid / potassium iodide / potassium iodate addition-sodium thiosulfate solution titration method, it is 730 g / mol and it was confirmed as it is mercapto group content as setting. As mentioned above, it shows with the following 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
Let the obtained polysiloxane be a specific polysiloxane.
-NXT-Z45: NXT-Z 45 (manufactured by Momentive, Inc.) (a copolymer having a repeating unit represented by the above-mentioned formula (A3) and a repeating unit represented by the above-mentioned formula (A4))

Oil: Extract No. 4 S (Showa Shell Sekiyu KK)
Sulfur: fine powder sulfur with gold oxide oil (sulfur content 95.24% by mass, manufactured by Tsurumi Chemical Industry Co., Ltd.)
・ Vulcanization accelerator CZ: Nouchi cellar CZ-G manufactured by Ouchi Shinko Chemical Co., Ltd.

As can be seen from Table 1, an example using a mercapto silane coupling agent and at least one polymer component selected from the group consisting of a styrene butadiene polymer having a vinyl bond content of 50% by mass or more and a butadiene polymer in combination Comparative Examples 1 to 6 exhibited excellent silica dispersibility as compared with the standard example and the comparative example 3 which contain a mercapto type silane coupling agent but do not contain the above-mentioned polymer component. Among them, Examples 2 to 6 in which the vinyl bond content of the polymer component is 80% by mass or more showed more excellent silica dispersibility and processability. Among them, Examples 2 to 3 and 5 to 6 in which the melting point of the above-mentioned polymer component is 90 ° C. or less showed further excellent silica dispersibility and processability.
From the comparison of Examples 2 and 3 (comparison of embodiments in which only the content of the polymer component differs), the content of the polymer component is 20% by mass or more with respect to the content of the rubber component, It showed better silica dispersibility and processability.
In addition, from the comparison between Examples 2 and 5 and 6 (comparison of embodiments in which only the type of mercapto-based silane coupling agent differs), the mercapto-based silane coupling agent is the above-mentioned specific polysiloxane or the above-mentioned formula Examples 5 and 6, which are copolymers having the repeating unit represented by (A3) and the repeating unit represented by the above-mentioned formula (A4), showed better processability. Among them, Example 5 in which the mercapto-based silane coupling agent is the specific polysiloxane described above exhibited further excellent silica dispersibility and processability.

On the other hand, Comparative Example 2 which contains the above-mentioned polymer component but does not contain a mercapto type silane coupling agent has insufficient silica dispersibility.
Moreover, although the mercapto type silane coupling agent and the above-mentioned polymer component are used together, the silica dispersibility is insufficient in Comparative Example 4 in which the content of the above-mentioned polymer component is less than 10% by mass with respect to the content of the rubber component. Met.

  From the comparison between the standard example, the comparative examples 1 and 2 and the example 2, the mercapto type silane coupling agent and the mercapto type silane coupling agent are compared with the standard example and the comparative examples 1 and 2 which do not contain the above polymer component. Example 2 in which the above polymer component was used in combination showed excellent processability.

DESCRIPTION OF SYMBOLS 1 bead part 2 side wall part 3 tire tread part 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt cushion 9 inner liner 10 tie rubber

Claims (4)

Containing a diene component, silica, and a mercapto silane coupling agent,
A styrene butadiene polymer, wherein the diene component is at least one rubber component selected from the group consisting of natural rubber and isoprene rubber, and a vinyl bond content is 50% by mass or more and a weight average molecular weight is 100,000 or more And at least one polymer component selected from the group consisting of
In the diene-based component, the content of the rubber component is 50% by mass or more,
The content of the polymer component is 10% by mass or more based on the content of the rubber component,
The content of the silica is 30 parts by mass or more with respect to 100 parts by mass of the diene component,
The rubber composition for tires which is content of 4 mass% or more with respect to content of the said mercapto type | system | group silane coupling agent.   The rubber composition for a tire according to claim 1, wherein the polymer component is a butadiene polymer having a vinyl bond content of 90% by mass or more and a weight average molecular weight of 100,000 or more. The mercapto based silane coupling agent is a polysiloxane represented by an average composition formula of the following formula (1), or a repeating unit represented by the following formula (A3) and a repeating unit represented by the following formula (A4) The rubber composition for a tire according to claim 1 or 2, which is a copolymer having:
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-b-c-d-e) / 2} (1)
In Formula (1), A represents a divalent organic group containing a sulfide group, B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms, and C represents a hydrolyzable group. R ¹ represents an organic group containing a mercapto group, R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms, a to e are 0 ≦ a <1, 0 ≦ b <1, 0 <c <3 , 0 <d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4.
Wherein (A3) and ^{(A4), R 31} and ^{R 41} each independently represents an alkylene group having 1 to 5 carbon atoms.
R ³² and R ⁴² each independently represent a linear or branched alkylene group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a linear or branched chain -Like represents a C2-C30 alkynylene group. When R ³² is terminal, R ³² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or It represents a linear or branched alkynyl group having 2 to 30 carbon atoms. When R ⁴² is a terminal, R ⁴² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or It represents a linear or branched alkynyl group having 2 to 30 carbon atoms.
R ³³ and R ⁴³ each independently represent a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, a straight chain A linear or branched alkynyl group having 2 to 30 carbon atoms or a linear or branched alkyl group having 1 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at the end, or a linear or branched group It is a C2-C30 alkenyl group which has a hydroxyl group or a carboxyl group at the terminal.
R ³² and R ³³ may form a ring with R ³² and R ³³ .
R ⁴² and R ⁴³ may form a ring with R ⁴² and R ⁴³ .
R ³⁴ represents an alkyl group having 1 to 13 carbon atoms.
Plural R ³¹ , R ³² , R ³³ , R ³⁴ , R ⁴¹ , R ⁴² and R ⁴³ may be the same or different.   The pneumatic tire which arrange | positioned the rubber composition for tires of any one of Claims 1-3 to the cap tread.