JP2010270176A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition causing less amount of a volatile organic compound (VOC) in kneading or the like on preparation of the rubber composition and excellent in low heat generation property (low fuel economy property) and heat resistance, and to provide a pneumatic tire using the rubber composition. <P>SOLUTION: The rubber composition includes (A) a rubber component containing either a modified conjugated diene (co)polymer (a-1) in which a terminal end of the molecule chain has a structure represented by formula (1) or a modified conjugated diene (co)polymer modified by another silicon-containing group, (B) 10 to 100 pts.mass of carbon black, based on 100 pts.mass of the rubber component, having a nitrogen adsorption ratio surface area (N<SB>2</SB>SA) of 20 to 100 m<SP>2</SP>/g, and (C) an organic crosslinking agent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

In recent years, with the social demands for energy and resource saving, in order to save the fuel consumption of automobiles, many demands for low loss and fracture resistant rubber materials have come to be demanded from the demand for tire durability. .
In order to improve the rolling resistance performance of tires, a technique using a low heat-generating rubber composition has become common, and as a technique for expressing the performance, modification by introducing a functional group that interacts with a filler The use of a polymer is a very effective means.
In order to improve the rolling resistance performance of tires, the method of reducing the filler for reinforcement does not prevent deterioration of durability, but by introducing a modifying group into the polymer used, both low loss and durability are achieved. It is known that can be realized. It is known that depending on the type of the modified functional group introduced into the polymer, the interaction with the reinforcing filler is different, and the obtained performance is also affected.

According to studies by the present inventors, it has been found that a modified polymer having a primary amino group introduced has a very high interaction with carbon black and gives a rubber composition excellent in low loss. Concerning the introduction of the primary amino group into the polymer, for example, a rubber component containing a conjugated diene polymer having a primary amino group and an alkoxysilyl group, and carbon black containing N ₂ SA of 30 to 100 m ² / g are contained. A rubber composition is disclosed (for example, see Patent Document 1).

JP 2006-307095 A

  However, in the above technique, since alkoxysilyl groups remain in the polymer, there is a concern that when the polymer is blended, there is a concern that it may be released into the atmosphere as an alcohol component. .

  Under such circumstances, the present invention has a small amount of volatile organic compound (VOC) generated during kneading at the time of preparation of the rubber composition, and is excellent in low exothermic property (low fuel consumption) and heat resistance. An object of the present invention is to provide a rubber composition excellent in properties and a pneumatic tire using the rubber composition.

The above problems are solved by the present invention described below. That is, the present invention
<1> (A) Modified conjugated diene (co) polymer (a-1) having a structure represented by the following general formula (1) and a structure represented by the following general formula (2): A rubber component containing at least one of the modified conjugated diene (co) polymer (a-2), and (B) a nitrogen adsorption ratio of 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component A rubber composition containing carbon black having a surface area (N ₂ SA) of 20 m ² / g or more and 100 m ² / g or less and (C) an organic crosslinking agent.

式中、Ｒ¹は炭素数１〜２０のヒドロカルビル基、Ｒ²は炭素数１〜１２のアルキレン基を示す。また（Polymer）−は変性共役ジエン（共）重合体のポリマー鎖である。

In the formula, R ¹ represents a hydrocarbyl group having 1 to 20 carbon atoms, and R ² represents an alkylene group having 1 to 12 carbon atoms. (Polymer)-is a polymer chain of a modified conjugated diene (co) polymer.

式中、Ｒ³は炭素数１〜２０のヒドロカルビル基、Ｒ⁴は炭素数１〜１２のアルキレン基、Ｒ⁵は炭素数１〜２０のヒドロカルビル基、炭素数２〜２０のヒドロカルビルカルボキシル基、−ＯＨ基及び炭素数５〜２０の１，３−ジカルボニル含有基のいずれかを示し、複数のＲ⁵はたがいに同一でも異なっていてもよい。ＭはＴｉ、Ｓｎ、Ａｌ、Ｓｉ及びＢｉのいずれかを示し、ｋは｛（Ｍの価数）−２｝であり、ｎは０または１である。また（Polymer）−は変性共役ジエン（共）重合体のポリマー鎖である。

In the formula, R ³ is a hydrocarbyl group having 1 to 20 carbon atoms, R ⁴ is an alkylene group having 1 to 12 carbon atoms, R ⁵ is a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyl carboxyl group having 2 to 20 carbon atoms,- One of an OH group and a 1,3-dicarbonyl-containing group having 5 to 20 carbon atoms is shown, and a plurality of R ⁵ may be the same or different. M represents any of Ti, Sn, Al, Si, and Bi, k is {(valence of M) −2}, and n is 0 or 1. (Polymer)-is a polymer chain of a modified conjugated diene (co) polymer.

<2> (A) One hydrocarbyloxy group and one reactive group are directly bonded to a silicon atom at the active end of a conjugated diene (co) polymer having an active end, and one Obtained by performing a hydrolysis reaction and a deprotection reaction after modifying a compound containing a bifunctional silicon atom in which a protected primary amino group is bonded to the silicon atom via an alkylene group. A rubber component containing a modified conjugated diene (co) polymer (a-1) having a terminal structure represented by the following general formula (1), and (B) 10 parts by mass or more and 100 parts by mass with respect to 100 parts by mass of the rubber component A rubber composition containing carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 20 m ² / g or more and 100 m ² / g or less, and (C) an organic crosslinking agent, in an amount of at most parts by mass.

式中、Ｒ¹は炭素数１〜２０のヒドロカルビル基、Ｒ²は炭素数１〜１２のアルキレン基を示す。また（Polymer）−は変性共役ジエン（共）重合体のポリマー鎖である。

In the formula, R ¹ represents a hydrocarbyl group having 1 to 20 carbon atoms, and R ² represents an alkylene group having 1 to 12 carbon atoms. (Polymer)-is a polymer chain of a modified conjugated diene (co) polymer.

<3> (A) (a) One hydrocarbyloxy group and one reactive group are directly bonded to a silicon atom at the active end of a conjugated diene (co) polymer having an active end, and A step of modifying by reacting a compound containing a bifunctional silicon atom in which one protected primary amino group is bonded to the silicon atom via an alkylene group, (b) titanium-based, tin-based A step of performing a condensation reaction involving the compound containing a bifunctional silicon atom in the presence of at least one condensation accelerator selected from aluminum, silicon, zirconium and bismuth, and (c) A rubber component containing a modified conjugated diene (co) polymer (a-2) represented by the following general formula (2) obtained by performing a step of performing a hydrolysis reaction and a deprotection reaction; For 100 parts by mass of rubber component 10 to 100 parts by mass of a carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 20 m ² / g to 100 m ² / g, and (C) an organic crosslinking agent. It is a composition.

式中、Ｒ³は炭素数１〜２０のヒドロカルビル基、Ｒ⁴は炭素数１〜１２のアルキレン基、Ｒ⁵は炭素数１〜２０のヒドロカルビル基、炭素数２〜２０のヒドロカルビルカルボキシル基、−ＯＨ基及び炭素数５〜２０の１，３−ジカルボニル含有基のいずれかを示し、複数のＲ⁵はたがいに同一でも異なっていてもよい。ＭはＴｉ、Ｓｎ、Ａｌ、Ｓｉ及びＢｉのいずれかを示し、ｋは｛（Ｍの価数）−２｝であり、ｎは０または１である。また（Polymer）−は変性共役ジエン（共）重合体のポリマー鎖である。

In the formula, R ³ is a hydrocarbyl group having 1 to 20 carbon atoms, R ⁴ is an alkylene group having 1 to 12 carbon atoms, R ⁵ is a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyl carboxyl group having 2 to 20 carbon atoms,- One of an OH group and a 1,3-dicarbonyl-containing group having 5 to 20 carbon atoms is shown, and a plurality of R ⁵ may be the same or different. M represents any of Ti, Sn, Al, Si, and Bi, k is {(valence of M) −2}, and n is 0 or 1. (Polymer)-is a polymer chain of a modified conjugated diene (co) polymer.

<4> The organic crosslinking agent is at least one selected from compounds represented by the following general formula (3) to general formula (5), formula (I), and formula (II): <1> to <3> The rubber composition according to any one of the above.

式中、Ｒ¹⁸、Ｒ¹⁹、Ｒ²⁰及びＲ²¹は、それぞれ独立に炭素数３〜１２の直鎖若しくは分岐鎖アルキル基または炭素数７〜１２のアラルキル基を示す。

In the formula, R ¹⁸ , R ¹⁹ , R ²⁰ and R ²¹ each independently represent a linear or branched alkyl group having 3 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms.

式中、Ｒ²²及びＲ²³は、それぞれ独立に炭素数７〜１２の直鎖若しくは分岐鎖アルキル基または炭素数７〜１２のアラルキル基を示し、Ｍ¹は２価以上の金属であり、ｎはＭ¹の金属の原子価に等しい数である。

In the formula, R ²² and R ²³ each independently represent a linear or branched alkyl group having 7 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms, M ¹ is a divalent or higher metal, n Is a number equal to the valence of the metal of M ¹ .

式中、Ｒ²⁴、Ｒ²⁵、Ｒ²⁶及びＲ²⁷は、それぞれ独立に炭素数３〜１２の直鎖若しくは分岐鎖アルキル基または炭素数７〜１２のアラルキル基を示す。

In the formula, R ²⁴ , R ²⁵ , R ²⁶ and R ²⁷ each independently represent a linear or branched alkyl group having 3 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms.

<5> The rubber according to any one of <1> to <4>, wherein the organic crosslinking agent is at least one selected from compounds represented by the following formula (I), formula (II), and formula (III): It is a composition.

<6> A conjugated diene (co) polymer having an active terminal obtained by anionic polymerization of a conjugated diene compound alone or a conjugated diene compound and an aromatic vinyl compound using an organic alkali metal compound as a polymerization initiator The rubber composition according to any one of <2> to <5>.

<7> The compound containing the bifunctional silicon atom is N, N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane, N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane, or N, N-bis (trimethylsilyl). ) Aminoethylmethyldimethoxysilane, N, N-bis (trimethylsilyl) aminoethylmethyldiethoxysilane, 1-trimethylsilyl-2-ethoxymethyl-1-aza-2-silacyclopentane and 3- (2,2,5 <2> to <6>, which is at least one selected from 5-tetramethyl (1-aza-2,5-disilacyclopentane) -1-yl) propylmethyldiethoxysilane. It is a rubber composition.

<8> The condensation accelerator used in the step (b) is at least one selected from an alkoxide, carboxylate and acetylacetonate complex salt of a metal selected from titanium, tin and aluminum, or a mixed salt thereof. The rubber composition according to any one of <3> to <7>.

<9> The rubber component (A) is at least one of a modified conjugated diene (co) polymer (a-1) and a modified conjugated diene (co) polymer (a-2) in a proportion of 10% by mass or more. The rubber composition according to any one of <1> to <8>.

<10> The rubber component (A) contains at least one of the modified conjugated diene (co) polymer (a-1) and the modified conjugated diene (co) polymer (a-2) in a proportion of 50% by mass or more. It is a rubber composition as described in <9>.

<11> A pneumatic tire using the rubber composition according to any one of <1> to <10>.

<12> The pneumatic tire according to <11>, wherein the rubber composition according to any one of <1> to <10> is used as at least one selected from a tread rubber, a side rubber, a side reinforcing rubber, and a bead filler rubber. It is.

  According to the present invention, the amount of volatile organic compound (VOC) generated is small at the time of kneading at the time of preparation of the rubber composition, and it has excellent low heat build-up (low fuel consumption) and excellent heat resistance. A rubber composition and a pneumatic tire using the rubber composition can be provided.

Hereinafter, the present invention will be described with reference to embodiments.
<Rubber composition>
First, the rubber composition of this embodiment is demonstrated.
The rubber composition of this embodiment comprises (A) a rubber component containing at least one of a modified conjugated diene (co) polymer (a-1) and a modified conjugated diene (co) polymer (a-2); B) of 100 parts by weight or less than 10 parts by mass relative to the rubber component 100 parts by weight of carbon black is nitrogen adsorption specific surface area (N ₂ SA) of 20 m ² / g or more 100 m ² / g or less, (C And) an organic cross-linking agent.
In the present embodiment, the conjugated diene (co) polymer includes a conjugated diene polymer and a conjugated diene copolymer.

  That is, in a rubber composition obtained by using a specific organic crosslinking agent together with a modified conjugated diene (co) polymer having a specific structure that is excellent in low heat generation and does not generate a volatile organic compound (VOC), The structure is considered to have at least one of a C—S—C bond (monosulfide bond) and a C—C bond, and heat resistance can be improved in addition to the above characteristics.

(Modified conjugated diene (co) polymer (a-1))
The structure of the modified conjugated diene (co) polymer (a-1) in this embodiment is represented by the following general formula (1).

式中、Ｒ¹は炭素数１〜２０のヒドロカルビル基、Ｒ²は、炭素数１〜１２のアルキレン基を示す。なお、（Polymer）−は変性共役ジエン（共）重合体のポリマー鎖である。

In the formula, R ¹ represents a hydrocarbyl group having 1 to 20 carbon atoms, and R ² represents an alkylene group having 1 to 12 carbon atoms. (Polymer)-is a polymer chain of a modified conjugated diene (co) polymer.

In the general formula (1), the hydrocarbyl group having 1 to 20 carbon atoms represented by R ¹ includes an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms. And an aralkyl group having 7 to 20 carbon atoms, and among them, an alkyl group having 1 to 20 carbon atoms is preferable. The alkyl group having 1 to 20 carbon atoms may be linear, branched or cyclic, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec -Butyl group, tert-butyl group, various pentyl groups, various hexyl groups, various octyl groups, various decyl groups, various dodecyl groups, various tetradecyl groups, various hexadecyl groups, various octadecyl groups, various icosyl groups, cyclopentyl group, cyclohexyl group And methylcyclopentyl group, cyclopentylmethyl group, methylcyclohexyl group, cyclohexylmethyl group and the like. Among these, a methyl group and an ethyl group are preferable from the viewpoint of availability of raw materials.

On the other hand, R ² is an alkylene group having 1 to 12 carbon atoms, and this alkylene group may be linear, branched or cyclic, and specific examples thereof include a methylene group, an ethylene group, and propane. -1,3-diyl group, butane-1,3-diyl group, butane-1,4-diyl group, pentane-1,3-diyl group, pentane-1,5-diyl group, hexane-1,3- Diyl group, hexane-1,6-diyl group, heptane-1,3-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane- 1,10-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,4-diyl group and the like can be mentioned. Among these, an ethylene group and a propane-1,3-diyl group are preferable from the viewpoint of availability of raw materials and performance.

The modified conjugated diene (co) polymer (a-1) in the present embodiment can be efficiently produced according to the following production method.
That is, one hydrocarbyloxy group and one reactive group are directly bonded to a silicon atom at the active end of a conjugated diene (co) polymer having an active end, and one protected second group is protected. A compound containing a bifunctional silicon atom in which a single amino group is bonded to the silicon atom via an alkylene group is reacted and modified, and then subjected to a hydrolysis reaction and a deprotection reaction, whereby the general formula (1 The modified conjugated diene (co) polymer (a-1) having a terminal structure represented by (II) can be obtained.

-Conjugated diene (co) polymer having active terminal-
The conjugated diene (co) polymer having an active terminal used in the above production method is obtained by copolymerizing a diene monomer alone or with another monomer, and the production method is not particularly limited. However, any of solution polymerization method, gas phase polymerization method and bulk polymerization method can be used, but the solution polymerization method is particularly preferable. Moreover, any of a batch type and a continuous type may be sufficient as the superposition | polymerization form.
The active site metal present in the molecule of the conjugated diene (co) polymer is preferably one selected from alkali metals and alkaline earth metals, preferably alkali metals, and particularly preferably lithium metal.

In the solution polymerization method, for example, an organic alkali metal compound, particularly a lithium compound is used as a polymerization initiator, and a conjugated diene compound alone or a conjugated diene compound and an aromatic vinyl compound are anionically polymerized to produce a target polymer. Can do.
Furthermore, it is also effective to mix a halogen-containing monomer and activate a halogen atom in the polymer with an organometallic compound. For example, it is also effective to lithiate the bromine moiety of a copolymer containing an isobutylene unit, a paramethylstyrene unit and a parabromomethylstyrene unit to form an active site.

Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, and the like. Is mentioned. These may be used singly or in combination of two or more. Among these, 1,3-butadiene, isoprene and 2,3-dimethyl-1,3-butadiene are particularly preferable.
Examples of the aromatic vinyl compound used for copolymerization with these conjugated diene compounds include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, and 4-cyclohexane. Xylstyrene, 2,4,6-trimethylstyrene and the like can be mentioned. These may be used alone or in combination of two or more, and among these, styrene is particularly preferable.

Furthermore, when copolymerization is carried out using a conjugated diene compound and an aromatic vinyl compound as monomers, the use of 1,3-butadiene and styrene, respectively, makes practical use such as the availability of monomers, and The anionic polymerization characteristics are particularly preferable because of excellent living characteristics and the like.
When the solution polymerization method is used, the monomer concentration in the solvent is preferably in the range of 5 to 50% by mass, more preferably in the range of 10 to 30% by mass. In addition, when copolymerizing using a conjugated diene compound and an aromatic vinyl compound, the content of the aromatic vinyl compound in the charged monomer mixture is preferably in the range of 0 to 55% by mass.

  The lithium compound of the polymerization initiator is not particularly limited, but hydrocarbyl lithium and lithium amide compounds are preferably used. When the former hydrocarbyl lithium is used, it has a hydrocarbyl group at the polymerization initiation terminal and the other terminal. A conjugated diene (co) polymer having a polymerization active site is obtained. When the latter lithium amide compound is used, a conjugated diene (co) polymer having a nitrogen-containing group at the polymerization initiation terminal and the other terminal being a polymerization active site is obtained.

  As the hydrocarbyl lithium, those having a hydrocarbyl group having 2 to 20 carbon atoms are preferable, for example, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-octyl lithium, n-decyl. Examples include lithium, phenyl lithium, 2-naphthyl lithium, 2-butyl-phenyl lithium, 4-phenyl-butyl lithium, cyclohexyl lithium, cyclopentyl lithium, a reaction product of diisopropenylbenzene and butyl lithium, and the like. Of these, n-butyllithium is particularly preferred.

  On the other hand, examples of the lithium amide compound include lithium hexamethylene imide, lithium pyrrolidide, lithium piperide, lithium heptamethylene imide, lithium dodecamethylene imide, lithium dimethyl amide, lithium diethyl amide, lithium dibutyl amide, lithium dipropyl amide, and lithium disulfide. Heptylamide, lithium dihexylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium-N-methylpiverazide, lithium ethylpropylamide, lithium ethylbutyramide, lithium ethylbenzylamide, lithium methylphenethylamide, etc. Is mentioned. Among these, from the viewpoint of the interaction effect on carbon black and the ability of initiating polymerization, cyclic lithium amides such as lithium hexamethylene imide, lithium pyrrolidide, lithium piperidide, lithium heptamethylene imide, and lithium dodecamethylene imide are preferable. In particular, lithium hexamethylene imide and lithium pyrrolidide are suitable.

In general, these lithium amide compounds prepared from a secondary amine and a lithium compound can be used for polymerization, but can also be prepared in a polymerization system (in-situ). The amount of the polymerization initiator used is preferably selected in the range of 0.2 to 20 mmol per 100 g of monomer.
There is no restriction | limiting in particular as a method of manufacturing the conjugated diene (co) polymer by anionic polymerization using the said lithium compound as a polymerization initiator, A conventionally well-known method can be used.

  Specifically, in an organic solvent inert to the reaction, for example, a hydrocarbon solvent such as an aliphatic, alicyclic or aromatic hydrocarbon compound, the conjugated diene compound or the conjugated diene compound and the aromatic vinyl compound are The desired conjugated diene (co) polymer can be obtained by anionic polymerization in the presence of a randomizer to be used, if desired, using a lithium compound as a polymerization initiator.

  The hydrocarbon solvent is preferably one having 3 to 8 carbon atoms, such as propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene and trans-2. -Butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene and the like. These may be used alone or in combination of two or more.

The randomizer used as desired is control of the microstructure of the conjugated diene (co) polymer, such as an increase in 1,2 bonds in the butadiene moiety in the butadiene-styrene copolymer, an increase in 3,4 bonds in the isoprene polymer, etc. Or a compound having a function of controlling composition distribution of monomer units in a conjugated diene compound-aromatic vinyl compound copolymer, for example, randomizing butadiene units, styrene units in a butadiene-styrene copolymer, etc. . The randomizer is not particularly limited, and any one of known compounds generally used as a conventional randomizer can be appropriately selected and used. Specifically, dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, oxolanylpropane oligomers [especially those containing 2,2-bis (2-tetrahydrofuryl) -propane, etc.], triethylamine, pyridine N-methylmorpholine, N, N, N ′, N′-tetramethylethylenediamine, ethers such as 1,2-dipiperidinoethane, and tertiary amines. Further, potassium salts such as potassium-t-amylate and potassium-t-butoxide, and sodium salts such as sodium-t-amylate can also be used.
One of these randomizers may be used alone, or two or more thereof may be used in combination. The amount used is preferably selected in the range of 0.01 to 1000 molar equivalents per mole of the lithium compound.

The temperature in this polymerization reaction is preferably selected in the range of 0 to 150 ° C, more preferably in the range of 20 to 130 ° C. The polymerization reaction can be carried out under generated pressure, but it is usually desirable to operate at a pressure sufficient to keep the monomer in a substantially liquid phase. That is, the pressure depends on the particular material being polymerized, the polymerization medium used and the polymerization temperature, but higher pressures can be used if desired, such pressure being a gas that is inert with respect to the polymerization reaction. Can be obtained by an appropriate method such as pressurizing.
In this polymerization, it is desirable to use all raw materials involved in the polymerization, such as a polymerization initiator, a solvent, and a monomer, from which reaction inhibitors such as water, oxygen, carbon dioxide, and protic compounds have been removed.
In addition, when obtaining a polymer as an elastomer, it is preferable that the glass transition temperature (Tg) calculated | required by the differential thermal analysis method of the polymer or copolymer obtained is the range of -95 degreeC--15 degreeC. By setting the glass transition temperature within the above range, it is possible to suppress the increase in viscosity and obtain a polymer that is easy to handle.

-Compounds containing functional silicon atoms-
In the production method, one hydrocarbyloxy group and one reactive group are directly bonded to a silicon atom at the active end of the conjugated diene (co) polymer obtained as described above. In addition, a compound containing a bifunctional silicon atom in which one protected primary amino group is bonded to the silicon atom via an alkylene group (hereinafter sometimes referred to as “modifier”) is reacted. To perform a denaturing reaction.
Examples of the modifier include silicon compounds represented by general formula (6), general formula (7), and general formula (8).

式中、Ｒ⁶〜Ｒ¹⁶は、それぞれ独立に炭素数１〜２０のヒドロカルビル基、Ｒ¹⁷は炭素数１〜１２のアルキレン基、Ａ¹及びＡ²は、それぞれ独立に反応性基であって、ハロゲン原子または炭素数１〜２０のヒドロカルビルオキシ基を示し、Ｒ¹及びＲ²は前記と同じである。

In the formula, R ^{6 to} R ¹⁶ are each independently a hydrocarbyl group having 1 to 20 carbon atoms, R ¹⁷ is an alkylene group having 1 to 12 carbon atoms, and A ¹ and A ² are each independently a reactive group. Represents a halogen atom or a hydrocarbyloxy group having 1 to 20 carbon atoms, and R ¹ and R ² are the same as defined above.

The hydrocarbyl groups of carbon number 1 to 20, R ¹ in the general formula (1) is as described for R ³ in the general formula (2). Examples of the alkylene group having 1 to 12 carbon atoms represented by R ¹⁷ include a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-1,3-diyl group, and a butane-1,4-diyl group. , Pentane-1,3-diyl group, pentane-1,5-diyl group, hexane-1,3-diyl group, hexane-1,6-diyl group, heptane-1,3-diyl group, heptane-1, 7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,4-diyl group Etc.

When the reactive groups A ¹ and A ² in the modifier are hydrocarbyloxy groups, examples of the modifier include N, N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane and N, N-bis (trimethylsilyl). Aminopropylmethyldiethoxysilane, N, N-bis (trimethylsilyl) aminoethylmethyldimethoxysilane, N, N-bis (trimethylsilyl) aminoethylmethyldiethoxysilane, 1-trimethylsilyl-2,2-ethoxymethyl-1-aza -2-silacyclopentane and 3- (2,2,5,5-tetramethyl (1-aza-2,5-disilacyclopentane) -1-yl) propylmethyldiethoxysilane .

When the reactive groups A ¹ and A ² are halogen atoms, examples of the modifier include N, N-bis (trimethylsilyl) aminopropylmethylmethoxychlorosilane, N, N-bis (trimethylsilyl) aminopropylmethyl. Examples include ethoxychlorosilane, N, N-bis (trimethylsilyl) aminoethylmethylmethoxychlorosilane, N, N-bis (trimethylsilyl) aminoethylmethylethoxychlorosilane, and the like.

  Preferred examples of the modifier include N, N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane, N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane, 1-trimethylsilyl-2,2-ethoxymethyl-1 -Aza-2-silacyclopentane, 3- (2,2,5,5-tetramethyl (1-aza-2,5-disilacyclopentan-1-yl) propylmethyldiethoxysilane.

These modifiers may be used alone or in combination of two or more. The modifier may be a partial condensate.
Here, the partial condensate refers to a product in which a part (but not all) of Si-OR as a modifier is Si-O-Si bonded by condensation.
In the modification reaction, it is preferable that the conjugated diene (co) polymer to be used has at least 10% of polymer chains having a living property.

In the modification reaction with the modifying agent, the amount of the modifying agent is preferably in the range of 0.5 to 200 mmol / kg · conjugated diene (co) polymer. The content is more preferably in the range of 1 to 100 mmol / kg · conjugated diene (co) polymer, and particularly preferably in the range of 2 to 50 mmol / kg · conjugated diene (co) polymer. Here, the conjugated diene (co) polymer means the mass of only a polymer not containing an additive such as an anti-aging agent added at the time of production or after production. By making the usage-amount of a modifier into the said range, it is excellent in the dispersibility of carbon black, and the mechanical characteristics after a vulcanization, abrasion resistance, and low exothermic property are improved.
In addition, the addition method of the modifier is not particularly limited, and examples thereof include a batch addition method, a division addition method, a continuous addition method, and the like. preferable.

In the present embodiment, after the modification reaction is performed on the active terminal of the conjugated diene (co) polymer in this way, the hydrolysis reaction and the deprotection reaction are performed, so that the hydrocarbyloxy group or halogen bonded to the Si atom is obtained. A hydrolyzable functional group such as an atom is converted into a hydroxyl group, and the protected primary amino group is deprotected to convert it into a free primary amine.
The hydrolysis reaction is preferably performed by adding a basic compound and water. Basic compound and water may be added at the same time, but first add basic compound or basic compound aqueous solution to polymerization reaction system and confirm that pH is 9-13, preferably 10-11. Then, a molar amount of water more than the molar amount of Li of the initiator, for example, 2 to 4 times the molar amount of water is added, and the polymerization reaction system is stirred, for example, for 10 minutes to several hours until hydrolysis is completed. Is good.

As the basic compound, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are preferable from the viewpoint of cost, and sodium hydroxide is particularly preferable.
In this way, after completion of the hydrolysis reaction and deprotection reaction, an isopropanol solution of 2,6-di-t-butyl-p-cresol (BHT) or the like is added to the polymerization reaction system to stop the polymerization reaction.
Thereafter, a modified conjugated diene having a molecular chain terminal having a structure represented by the general formula (1) is obtained by performing a desolvation treatment such as steam stripping to reduce the partial pressure of the solvent by blowing water vapor or a vacuum drying treatment. A (co) polymer (a-1) is obtained.

(Modified conjugated diene (co) polymer (a-2))
The structure of the modified conjugated diene (co) polymer (a-2) in this embodiment is represented by the following general formula (2).

式中、Ｒ³は炭素数１〜２０のヒドロカルビル基、Ｒ⁴は炭素数１〜１２のアルキレン基、Ｒ⁵は炭素数１〜２０のヒドロカルビル基、炭素数２〜２０のヒドロカルビルカルボキシル基、−ＯＨ基または炭素数５〜２０の１，３−ジカルボニル含有基を示し、複数のＲ⁵はたがいに同一でも異なっていてもよい。ＭはＴｉ、Ｓｎ、Ａｌ、ＳｉまたはＢｉを示し、ｋは｛（Ｍの価数）−２｝であり、ｎは０または１である。
なお、（Polymer）−は変性共役ジエン（共）重合体のポリマー鎖である。

In the formula, R ³ is a hydrocarbyl group having 1 to 20 carbon atoms, R ⁴ is an alkylene group having 1 to 12 carbon atoms, R ⁵ is a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyl carboxyl group having 2 to 20 carbon atoms,- An OH group or a 1,3-dicarbonyl-containing group having 5 to 20 carbon atoms is shown, and a plurality of R ⁵ may be the same or different. M represents Ti, Sn, Al, Si or Bi, k is {(valence of M) −2}, and n is 0 or 1.
(Polymer)-is a polymer chain of a modified conjugated diene (co) polymer.

The hydrocarbyl group having 1 to 20 carbon atoms represented by R ³ and the hydrocarbyl group having 1 to 20 carbon atoms out of R ⁵ are as described for R ¹ in the general formula (1). Further, an alkylene group having 1 to 12 carbon atoms represented by R ⁴ are as described in the R ² of the general formula (1).

The modified conjugated diene (co) polymer (a-2) in the present embodiment can be efficiently produced according to the following production method.
That is, (a) one hydrocarbyloxy group and one reactive group are directly bonded to a silicon atom at the active end of a conjugated diene (co) polymer having an active end, and one protection A step of reacting a compound containing a bifunctional silicon atom in which the primary amino group formed is bonded to the silicon atom via an alkylene group, and (b) titanium-based, tin (tin) -based, A step of performing a condensation reaction involving the aforementioned compound containing a bifunctional silicon atom in the presence of at least one condensation accelerator selected from aluminum, silicon, zirconium and bismuth, and (c) water addition A modified conjugated diene (co) polymer (a-2) represented by the general formula (2) can be obtained by performing a step of performing a decomposition reaction and a deprotection reaction.
In addition, in the manufacturing method of this modified conjugated diene (co) polymer (a-2), it manufactures the above-mentioned modified conjugated diene (co) polymer (a-1) until the modification reaction step of (a) step. In the production method, the bifunctional silicon used in the step (a) in the presence of the condensation accelerator is used as the step (b) after the modification reaction step in the step (a). A step of performing a condensation reaction involving a compound containing an atom is applied.

-Condensation accelerator-
The condensation accelerator used in the step (b) is preferably at least one metal compound selected from titanium, tin, aluminum, silicon, zirconium and bismuth. More specifically, tetravalent titanium alkoxides, carboxylates and acetylacetonate complex salts, or mixed salts thereof are preferably cited as the titanium system, and divalent tin dicarboxylic acid { In particular, bis (hydrocarbyl carboxylic acid) salt}, divalent carboxylic acid tin dicarboxylate {including bis (hydrocarbyl carboxylic acid)} salt), bis (β-diketonate), alkoxy halide, monocarboxylic acid Preferred examples include salt hydroxide. The hydrocarbyl group bonded to tin preferably has 4 or more carbon atoms, and particularly preferably has 4 to 8 carbon atoms.
Further, preferred examples of the aluminum system include trivalent aluminum alkoxides, carboxylates and acetylacetonate complex salts, or mixed salts thereof.
From the above, as the condensation accelerator, at least one selected from metal alkoxides, carboxylates and acetylacetonate complex salts selected from titanium, tin and aluminum, or a mixed salt thereof is preferable.

Of the above-mentioned condensation accelerators, titanium is particularly preferred, and titanium (Ti) alkoxides, carboxylates and acetylacetonate complex salts are preferably used.
Specific condensation accelerators include tetrakis (2-ethyl-1,3-hexanediolato) titanium, tetrakis (2-methyl-1,3-hexanediolato) titanium, tetrakis (2-propyl-1,3). -Hexanediolato) titanium, tetrakis (2-butyl-1,3-hexanediolato) titanium, tetrakis (1,3-hexanediolato) titanium, tetrakis (1,3-pentanediolato) titanium, tetrakis (2 -Methyl-1,3-pentanediolato) titanium, tetrakis (2-ethyl-1,3-pentanediolato) titanium, tetrakis (2-propyl-1,3-pentanediolato) titanium, tetrakis (2-butyl) -1,3-pentanediolato) titanium, tetrakis (1,3-heptanediolato) titanium, tetrakis (2-methyl-1,3- Butanediolato) titanium, tetrakis (2-ethyl-1,3-heptanediolato) titanium, tetrakis (2-propyl-1,3-heptanediolato) titanium, tetrakis (2-butyl-1,3-heptanediolato) titanium, tetrakis (2- Ethylhexoxy) titanium, tetramethoxy titanium, tetraethoxy titanium, tetra-n-propoxy titanium, tetraisopropoxy titanium, tetra-n-butoxy titanium, tetra-n-butoxy titanium oligomer, tetraisobutoxy titanium, tetra-sec-butoxy titanium , Tetra-tert-butoxytitanium, bis (oleate) bis (2-ethylhexanoate) titanium, titanium dipropoxybis (triethanolamate), titanium dibutoxybis (triethanolamate), tita Tributoxy systemate, titanium tripropoxy systemate, titanium tripropoxyacetylacetonate, titanium dipropoxybis (acetylacetonate), titanium tripropoxy (ethylacetoacetate), titanium propoxyacetylacetonatebis (ethylacetoacetate), titanium Tributoxyacetylacetonate, titanium dibutoxybis (acetylacetonate), titanium tributoxyethylacetoacetate, titaniumbutoxyacetylacetonatebis (ethylacetoacetate), titanium tetrakis (acetylacetonate), titanium diacetylacetonatebis (ethyl) Acetoacetate), bis (2-ethylhexanoate) titanium oxide, bis (laurate) titanium oxide, bis (naphthenate) ) Titanium oxide, bis (stearate) titanium oxide, bis (oleate) titanium oxide, bis (linoleate) titanium oxide, tetrakis (2-ethylhexanoate) titanium, tetrakis (laurate) titanium, tetrakis (naphthenate) titanium, tetrakis (Stearate) titanium, tetrakis (oleate) titanium, tetrakis (linoleate) titanium, titanium di-n-butoxide (bis-2,4-pentanedionate), titanium oxide bis (tetramethylheptanedionate), titanium oxide bis ( Pentanedionate), titanium tetra (lactate) and the like.
Among these, tetrakis (2-ethyl-1,3-hexanediolato) titanium, tetrakis (2-ethylhexoxy) titanium, and titanium di-n-butoxide (bis-2,4-pentanedionate) are preferable.

Moreover, as a specific tin-based condensation accelerator, for example, tin 2-ethylhexanoate {[CH ₃ (CH ₂ ) ₃ CH (C ₂ H ₅ ) CO ₂ ] ₂ Sn (divalent)} can be mentioned. .
Specific aluminum-based condensation accelerators include, for example, triethoxyaluminum, tri-n-propoxyaluminum, triisopropoxyaluminum, tri-n-butoxyaluminum, tri-sec-butoxyaluminum, tri-tert-butoxyaluminum, Aluminum dibutoxy systemate, aluminum dibutoxyacetylacetonate, aluminum butoxybis (acetylacetonate), aluminum dibutoxyethylacetoacetate, aluminum tris (acetylacetonate), aluminum tris (ethylacetoacetate), tris (2-ethyl) Hexanoate) aluminum, tris (laurate) aluminum, tris (naphthenate) aluminum, tris (stearate) aluminum Tris (oleate) aluminum, tris (linolate) aluminum, and the like.

Specific examples of bismuth-based condensation accelerators include, for example, tris (2-ethylhexanoate) bismuth, tris (laurate) bismuth, tris (naphthenate) bismuth, tris (stearate) bismuth, tris (oleate) bismuth. , Tris (linoleate) bismuth and the like.
Specific zirconium-based condensation accelerators include, for example, tetra-n-propoxyzirconium, tetraisopropoxyzirconium, tetra-n-butoxyzirconium, tetra-sec-butoxyzirconium, tetra-tert-butoxyzirconium, tetra (2- Ethylhexyl) zirconium, zirconium tributoxy systemate, zirconium tributoxyacetylacetonate, zirconium dibutoxybis (acetylacetonate), zirconium tributoxyethylacetoacetate, zirconium butoxyacetylacetonatebis (ethylacetoacetate), zirconium tetrakis (acetyl) Acetonate), zirconium diacetylacetonate bis (ethyl acetoacetate), bis (2-ethylhexa) Ate) zirconium oxide, bis (laurate) zirconium oxide, bis (naphthenate) zirconium oxide, bis (stearate) zirconium oxide, bis (oleate) zirconium oxide, bis (linoleate) zirconium oxide, tetrakis (2-ethylhexanoate) Zirconium, tetrakis (laurate) zirconium, tetrakis (naphthenate) zirconium, tetrakis (stearate) zirconium, tetrakis (oleate) zirconium, tetrakis (linoleate) zirconium, tetraethoxyzirconium and the like can be mentioned.

  In the condensation reaction in the present embodiment, the condensation accelerator and water are used in combination. Water is preferably used in the form of a solution such as a simple substance or alcohol, or a dispersed micelle in a hydrocarbon solvent, and if necessary, in the reaction system such as adsorbed water on the solid surface or hydrated water of hydrate. Water that is potentially contained in a compound capable of releasing water can also be used effectively. Accordingly, it is also preferable to use a compound that can easily release water, such as a solid having adsorbed water or a hydrate, in combination with the condensation accelerator.

The condensation accelerator and water may be added separately to the reaction system or mixed immediately before use as a mixture, but long-term storage of the mixture is not preferable because it causes decomposition of the metal compound.
In addition, water may be charged into the reaction system as a solution of an organic solvent compatible with water such as alcohol, or water is directly injected and dispersed in the hydrocarbon solution using various chemical engineering techniques. You may let them. Water may be added by steam stripping or the like after completion of the condensation reaction.

The amount of the condensation accelerator used is preferably such that the number of moles of the condensation accelerator is in the range of 0.1 to 10 as the molar ratio to the total amount of hydrocarbyloxy groups present in the reaction system. A range of ˜5 is particularly preferred. By setting the use amount of the condensation accelerator within the above range, the condensation reaction proceeds efficiently.
Further, the number of moles of water is preferably 0.1 or more as a molar ratio to the total amount of hydrocarboxysilyl groups present in the reaction system. The upper limit depends on the purpose and reaction conditions, but there should be 0.5 to 3 molar equivalents of effective water based on the amount of hydrocarboxysilyl groups bound to the polymer active site before the condensation treatment. Is preferred.
Moreover, it is preferable to perform the condensation reaction using the said condensation accelerator at the temperature of 20 degreeC or more, and the range of 30-120 degreeC is more preferable. The reaction time is preferably in the range of 0.5 minutes to 10 hours, more preferably in the range of 0.5 minutes to 5 hours, still more preferably in the range of about 0.5 to 120 minutes, and further preferably in the range of 3 to 60 minutes. .
In addition, the pressure of the reaction system at the time of the condensation reaction is usually in the range of 0.01 to 20 MPa, preferably in the range of 0.05 to 10 MPa.

In this embodiment, there is no restriction | limiting in particular about the form of a condensation reaction, You may carry out by a continuous type using apparatuses, such as a batch type reactor, or a multistage continuous type reactor. Moreover, you may perform this condensation reaction and a desolvent simultaneously.
After performing the condensation reaction in this way, a hydrolysis reaction and a deprotection reaction are performed as step (c). This hydrolysis reaction and deprotection reaction can be carried out in the same manner as described in the production of the modified conjugated diene (co) polymer (a-1) described above.
(C) After completion of the hydrolysis reaction and deprotection reaction in the step, as in the case of the modified conjugated diene (co) polymer (a-1), 2,6-di-t-butyl-p-cresol is used. An isopropanol solution of (BHT) or the like is added to the polymerization reaction system to stop the polymerization reaction. Then, the modified conjugated diene (co) having a molecular chain terminal having a structure represented by the general formula (2) by performing a desolvation process such as steam stripping, a drying process such as hot roll drying or vacuum drying. A polymer (a-2) is obtained.

(Rubber component)
The rubber component (A) in the rubber composition of the present embodiment is obtained by the above-described production method, and the molecular chain terminal is a modified conjugated diene (co) polymer (a-1) represented by the general formula (1). ) May be used singly or in combination of two or more kinds, or a modified conjugated diene (co) polymer (a-2) represented by the general formula (2) may be used singly. And two or more kinds may be used in combination. Alternatively, one or more modified conjugated diene (co) polymer (a-1) and one or more modified conjugated diene (co) polymer (a-2) may be used in combination.
The content of at least one of the modified conjugated diene (co) polymers (a-1) and (a-2) in the rubber component (A) is preferably 10% by mass or more, and more preferably 50% by mass or more. . When the content of the modified conjugated diene (co) polymer is 10% by mass or more, the effect of the present embodiment is exhibited well.

  The other rubber components used in combination with at least one of the modified conjugated diene (co) polymers (a-1) and (a-2) used in the rubber composition of the present embodiment include natural rubber and synthetic isoprene rubber. Butadiene rubber, styrene-butadiene rubber, ethylene-α-olefin copolymer rubber, ethylene-α-olefin-diene copolymer rubber, acrylonitrile-butadiene copolymer rubber, chloroprene rubber, halogenated butyl rubber, and mixtures thereof. . Further, some of them may have a branched structure by using a polyfunctional type, for example, a modifier such as tin tetrachloride or silicon tetrachloride.

The modified conjugated diene (co) polymers (a-1) and (a-2) used in the rubber composition of the present embodiment have a weight average molecular weight (Mw) in the range of 50 × 10 ³ to 1,000 × 10 ³ . it is preferably, and more preferably in the range of ^{100 × 10 3 ~600 × 10 3} . Moreover, it is preferable that molecular weight distribution (Mw / Mn) is 5 or less, and it is more preferable that it is 3 or less. By making the weight average molecular weight of the modified conjugated diene (co) polymer within the above range, it is possible to obtain an excellent fracture resistance by suppressing a decrease in elastic modulus and an increase in hysteresis loss of the vulcanizate, and a modified conjugated diene ( Excellent kneading workability of the rubber composition containing the (co) polymer can be obtained. Also, by making the molecular weight distribution of the modified conjugated diene (co) polymer within the above range, even if the modified conjugated diene (co) polymer is blended with the rubber composition, the workability of the rubber composition is reduced. The kneading is easy and the physical properties of the rubber composition can be sufficiently improved.
Here, the weight average molecular weight (Mw) and the molecular weight distribution were measured by GPC [manufactured by Tosoh Corporation, HLC-8020] using a refractometer as a detector, and were shown in terms of polystyrene using monodisperse polystyrene as a standard. The column is GMHXL [manufactured by Tosoh], and the eluent is tetrahydrofuran.

Further, the modified conjugated diene (co) polymers (a-1) and (a-2) used in the rubber composition of the present embodiment have a vinyl bond content in the conjugated diene part, which improves the durability of the rubber composition. From the viewpoint, it is preferably 50% or less, and more preferably 30% or less.
The vinyl bond content was determined by an infrared method (Morello method).

  The Japan Rubber Association aims to reduce the generation of volatile organic compounds (VOC) to the current 65%. Therefore, in the rubber composition of the present embodiment, the amount of volatile organic compound (VOC) generated by the following method is preferably 65% or less, more preferably 50% or less, and 35 % Or less is particularly preferable. If the amount of VOC generated exceeds the current 65%, bubbles may be generated in the rubber material in the extrusion process, and the burden on the environment increases, which is not preferable.

-VOC measurement method A sample is treated with a siloxane hydrolysis reagent consisting of 0.2N toluenesulfonic acid / 0.24N water in a solvent consisting of 15% n-butanol and 85% toluene, and remains in the unvulcanized rubber composition. The stoichiometric amount of ethanol from [EtOSi] is measured by headspace / gas chromatography.

(Carbon black)
In the rubber composition of the present embodiment, carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 20 m ² / g or more and 100 m ² / g or less with respect to 100 parts by mass of the (A) rubber component. Is used at a ratio of 10 parts by mass or more and 100 parts by mass or less.
The modified conjugated diene (co) polymers (a-1) and (a-2) used in the rubber composition of this embodiment have a free primary amino group at the end of the molecular chain. The amino group exhibits a very high interaction particularly with respect to carbon black having N ₂ SA of 100 m ² / g or less, and gives a rubber composition excellent in low heat generation performance (low fuel consumption performance), but N ₂ SA is 100 m. ^The effect is not sufficiently exhibited for carbon black exceeding ² / g. If N ₂ SA is less than 20 m ² / g, the reinforcing property is insufficient and sufficient durability cannot be obtained. The N ₂ SA is preferably not more than 20 m ² / g or more 95 m ² / g, more preferably not more than 25 m ² / g or more 90m ² / g. The N ₂ SA is a value measured according to JIS K 6217-2: 2001.

Examples of such carbon black include HAF, FEF, GPF, SRF, N339, IISAF-HS (N285), and the like.
Further, if the content of the carbon black is less than 10 parts by mass with respect to 100 parts by mass of the rubber component (A), a sufficient reinforcing effect cannot be obtained, and if it exceeds 100 parts by mass, kneading and extrusion become difficult. The content of carbon black is preferably 20 parts by weight or more and 80 parts by weight or less, more preferably 30 parts by weight or more and 70 parts by weight or less.

(Organic crosslinking agent)
The rubber composition of this embodiment contains the above-mentioned (A) rubber component and (B) carbon black, and (C) an organic crosslinking agent. Here, the organic crosslinking agent is an organic compound other than sulfur that crosslinks a conjugated diene (co) polymer to form a three-dimensional network structure.
Examples of the organic crosslinking agent in the present embodiment include, but are not limited to, organic sulfur-containing compounds, organic peroxides, quinonedioximes, organic polyvalent amines, modified phenolic resins, and tetrachloro-p-benzoquinone. .

  In the present embodiment, it is necessary for improving the heat resistance of the rubber composition that the crosslinked structure in the rubber composition after crosslinking has at least one of a C—S—C bond and a C—C bond. That is, the cross-linked structure of rubber includes a polysulfide bond with S of 3 or more, a disulfide bond with S of 2, and a monosulfide bond with S, but these polysulfide bonds and disulfide bonds are easily broken by heat. If a crosslinked structure is formed only by bonding, the heat resistance of the rubber composition cannot be sufficiently ensured. Therefore, in the rubber composition of the present embodiment, it is considered that the crosslinked structure has at least one of a C—S—C bond and a C—C bond, and as the ratio of polysulfide bonds and disulfide bonds in the crosslinked structure decreases, the rubber The heat resistance of the composition will be improved.

  In order to have at least one of a C—S—C bond and a C—C bond in the crosslinked structure, the organic crosslinking agent in the present embodiment includes the following general formulas (3) to (5) and formulas: It is desirable that it is at least one selected from the compounds represented by (I) and formula (II).

上記式中、Ｒ¹⁸、Ｒ¹⁹、Ｒ²⁰及びＲ²¹は、それぞれ独立に炭素数３〜１２の直鎖若しくは分岐鎖アルキル基または炭素数７〜１２のアラルキル基を示す。

In the above formula, R ¹⁸ , R ¹⁹ , R ²⁰ and R ²¹ each independently represent a linear or branched alkyl group having 3 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms.

上記式中、Ｒ²²及びＲ²³は、それぞれ独立に炭素数７〜１２の直鎖若しくは分岐鎖アルキル基または炭素数７〜１２のアラルキル基を示し、Ｍ¹は２価以上の金属であり、ｎはＭ¹の金属の原子価に等しい数である。

In the above formula, R ²² and R ²³ each independently represent a linear or branched alkyl group having 7 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms, M ¹ is a divalent or higher metal, n is a number equal to the valence of the metal of M ¹ .

上記式中、Ｒ²⁴、Ｒ²⁵、Ｒ²⁶及びＲ²⁷は、それぞれ独立に炭素数３〜１２の直鎖若しくは分岐鎖アルキル基または炭素数７〜１２のアラルキル基を示す。

In the above formula, R ²⁴ , R ²⁵ , R ²⁶ and R ²⁷ each independently represent a linear or branched alkyl group having 3 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms.

In the general formula (3), R ¹⁸ , R ¹⁹ , R ²⁰ and R ²¹ each independently represent a linear or branched alkyl group having 3 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms, Examples of the 3-12 linear or branched alkyl group include a 2-ethylhexyl group, an isopropyl group, an isobutyl group, a dodecyl group, and the like, and examples of the aralkyl group having 7 to 12 carbon atoms include a benzyl group. It is done. When the carbon number of R ^{18 to} R ²¹ is 2 or less, the dispersion into the rubber component is deteriorated and the heat resistance is deteriorated, and when the carbon number is 13 or more, the vulcanization speed may be extremely delayed.
Specifically, examples of the compound of the general formula (3) include tetrakis-2-ethylhexyl thiuram disulfide, tetrakis-isopropyl thiuram disulfide, tetrakis-isobutyl thiuram disulfide, tetrakis-dodecyl thiuram disulfide, tetrakis-benzyl thiuram disulfide and the like.

In General Formula (4), R ²² and R ²³ each independently represent a linear or branched alkyl group having 7 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms, and a linear chain having 7 to 12 carbon atoms. Alternatively, examples of the branched alkyl group include a 2-ethylhexyl group and a dodecyl group, and examples of the aralkyl group having 7 to 12 carbon atoms include a benzyl group. When the carbon number of R ^{22 to} R ²³ is 6 or less, the dispersion into the rubber component is deteriorated and the heat resistance is deteriorated, and when the carbon number is 13 or more, the vulcanization speed may be extremely delayed. M ¹ is a metal having a valence of 2 or more, and n is a number equal to the valence of the metal of M ^1. Examples of the metal include zinc, antimony, iron, copper, nickel, lead, tellurium, and the like. Among these, zinc is preferable. Specifically, examples of the compound of the general formula (4) include 2-ethylhexyl dithiocarbamate zinc, dodecyl dithiocarbamate zinc, and benzyldithiocarbamate zinc.

In the general formula (5), R ²⁴ , R ²⁵ , R ²⁶ and R ²⁷ each independently represent a linear or branched alkyl group having 3 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms. Examples of the 3-12 linear or branched alkyl group include a 2-ethylhexyl group, an isopropyl group, an isobutyl group, a dodecyl group, and the like, and examples of the aralkyl group having 7 to 12 carbon atoms include a benzyl group. It is done. When the carbon number of R ^{24 to} R ²⁷ is 2 or less, the dispersion into the rubber component is deteriorated and the heat resistance is deteriorated. When the carbon number is 13 or more, the vulcanization speed may be extremely delayed. Specifically, as the compound of the general formula (5), 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) -hexane, 1,6-bis (N, N′-di (2-ethylhexyl) ) Thiocarbamoyldithio) -hexane and the like.

  Among the compounds represented by the general formula (3) to the general formula (5), the compound represented by the general formula (5) is preferable from the viewpoint of heat resistance, fracture resistance and cost, and among them, the following formula (III) ) Is most preferred.

  Therefore, the organic crosslinking agent used in the present embodiment is specifically at least one selected from the compounds represented by the formula (I) and the formula (II) and the compound represented by the formula (III). It is particularly desirable that

The total amount of at least one compound selected from the compounds represented by formulas (3) to (5), (I) and (II) is 0.5 parts by mass with respect to 100 parts by mass of the rubber component. The content is preferably 10 parts by mass or less, more preferably 1 part by mass or more and 6 parts by mass or less. By setting the total blending amount of these compounds in the above range, the ratio of C—S—C bonds and C—C bonds in the crosslinked structure of the rubber composition may be sufficient to ensure desired heat resistance. it can.
In particular, when using at least one compound selected from the compounds represented by the formula (I) and the formula (II) and the compound represented by the formula (III) as the organic crosslinking agent, the total blending amount is 100 masses of the rubber component. It is preferable to set it as 0.5 mass part or more and 10 mass parts or less with respect to a part.

(Other ingredients)
The rubber composition of the present embodiment is preferably sulfur crosslinkable, and sulfur is suitably used as a vulcanizing agent. As the amount used, it is preferable to blend 0.1 to 10 parts by mass of sulfur (total amount of sulfur and sulfur donors) with respect to 100 parts by mass of the rubber component. This is because within this range, the necessary elastic modulus and strength of the vulcanized rubber composition can be ensured and fuel efficiency can be obtained. In this respect, it is more preferable to blend 0.5 to 5 parts by mass of the sulfur content.

  The rubber composition of the present embodiment includes various chemicals usually used in the rubber industry, for example, vulcanizing agents other than sulfur, vulcanization accelerators, and process oils, as desired, as long as the purpose of the present embodiment is not impaired. , Plasticizers, anti-aging agents, anti-scorch agents, zinc white, stearic acid, thermosetting resins, thermoplastic resins, and the like.

  The vulcanization accelerator is not particularly limited. For example, M (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide), CZ (N-cyclohexyl-2-benzothiazylsulfenamide) And guanidine vulcanization accelerators such as DPG (diphenylguanidine), etc., and the amount used is 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component. A range is preferable, More preferably, it is the range of 0.2-3.0 mass parts.

  Examples of the process oil used as a softening agent that can be used in the rubber composition of the present embodiment include paraffinic, naphthenic, and aromatic oils. Aromatics are used for applications that place importance on tensile strength and wear resistance, and naphthenic or paraffin types are used for uses that place importance on hysteresis loss and low-temperature characteristics. The amount used is preferably in the range of 0 to 100 parts by mass with respect to 100 parts by mass of the rubber component. If it is 100 mass parts or less, it can suppress that the tensile strength of vulcanized rubber and low heat generating property (low fuel consumption property) deteriorate.

  Further, examples of the anti-aging agent that can be used in the rubber composition of the present embodiment include 3C (N-isopropyl-N′-phenyl-p-phenylenediamine, 6C [N- (1,3-dimethylbutyl) -N ′). -Phenyl-p-phenylenediamine], AW (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline), high-temperature condensate of diphenylamine and acetone, etc. The range of 0.1-6.0 mass parts is preferable with respect to 100 mass parts of rubber components, and the range of 0.3-5.0 mass parts is more preferable.

  The rubber composition of the present embodiment is obtained by kneading using a kneading machine such as a Banbury mixer, a roll, an internal mixer or the like according to the above compounding prescription, vulcanizing after molding, for example, pneumatic Used for various industrial rubber products such as tire components, belt conveyors, rubber hoses and the like. In particular, each member of the tire is used as a tread rubber, a side rubber, a side reinforcing layer rubber, a bead filler rubber, or the like.

<Pneumatic tire>
The pneumatic tire of this embodiment is manufactured by a manufacturing method of a normal pneumatic tire or a pneumatic run-flat tire using the rubber composition as a tread rubber, a sidewall, a side reinforcing layer rubber, a bead filler rubber, or the like. Is done. That is, as described above, the rubber composition of the present embodiment containing various chemicals is processed into each member at an unvulcanized stage, and pasted and molded by a normal method on a tire molding machine, and a raw tire is molded. Is done. The green tire is heated and pressed in a vulcanizer to obtain a tire.
The tire according to the present embodiment thus obtained has reduced rolling resistance during normal running and improved fuel efficiency. Moreover, if it is used for the side reinforcing layer or bead filler of the run flat tire, run flat durability is improved in addition to low fuel consumption during normal driving.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
<Evaluation of rubber composition>
Σtanδ (28 to 150 ° C) based on the volatilization amount of alcohol from the unvulcanized rubber composition and the dynamic loss tangent (tanδ) of the vulcanized rubber composition was measured according to the following method.
(1) Alcohol volatilization amount A siloxane hydrolysis reagent consisting of (0.2 mol / liter toluenesulfonic acid) / (0.24 mol / liter water) in a solvent consisting of 15% by mass n-butanol and 85% by mass toluene. Samples were processed and the stoichiometric amount of ethanol from [EtOSi] remaining in the test unvulcanized rubber composition was measured by headspace / gas chromatography.
(2) Method of measuring Σtanδ (28 to 150 ° C) From a slab sheet having a thickness of 2 mm obtained by vulcanizing the rubber composition under the conditions of 160 ° C and 12 minutes, a sheet having a width of 5 mm and a length of 40 mm was obtained. A sample was cut out. About this sample, a tangent loss tan δ was measured under the measurement conditions of a distance between chucks of 10 mm, an initial strain of 200 μm, a dynamic strain of 1%, a frequency of 52 Hz, and a measurement start temperature of 25 to 200 ° C. using a spectrometer manufactured by Ueshima Seisakusho. The relationship between temperature and tan δ is graphed, the area of the portion surrounded by the tan δ curve and each perpendicular to the x-axis indicating 28 ° C. and 150 ° C. is obtained, and the value is Σtan δ (28 to 150 ° C.).

<Evaluation of tire>
(Run flat durability)
Each test tire (tyre size 215 / 45ZR17) is assembled with rims at normal pressure, filled with 230 kPa of internal pressure, left in a room at 38 ° C. for 24 hours, then the valve core is removed and the internal pressure is set to atmospheric pressure. A drum running test was conducted under the conditions of 4.17 kN (425 kg), speed 89 km / h, and room temperature 38 ° C. The travel distance until failure of each test tire was measured, and the travel distance of Comparative Example 5 or 7 was taken as 100, and the index was displayed by the following formula. The larger the index, the better the run flat durability.
Run-flat durability (index) = (travel distance of test tire / travel distance of tire of Comparative Example 5 or 7) × 100

<Production of modified / unmodified conjugated diene copolymer>
(Modified conjugated diene copolymer BR-a)
Into a nitrogen-substituted 5 L autoclave, 1.4 kg of cyclohexane, 250 g of 1,3-butadiene and 0.0285 mmol of 2,2-ditetrahydrofurylpropane were injected as a cyclohexane solution under nitrogen, and 2.85 mmol of n-butyl was added thereto. After adding lithium (BuLi), polymerization was carried out in a 50 ° C. warm water bath equipped with a stirrer for 4.5 hours. The reaction conversion of 1,3-butadiene was almost 100%. Next, this polymer solution was kept at a temperature of 60 ° C., 2.85 mmol of N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane was added and reacted for 15 minutes, and then the polymer solution was brought to a temperature of 60 ° C. While keeping it, 2.85 mmol of tetrakis (2-ethyl-1,3-hexanediolato) titanium was added and further stirred for 15 minutes to react. Thereafter, the resultant was taken out in a methanol solution containing 1.3 g of 2,6-di-tert-butyl-p-cresol, and after the polymerization was stopped, the solvent was removed by steam stripping, and the resultant was dried with a roll at 110 ° C. Diene copolymer BR-a was obtained.

(Modified conjugated diene copolymer BR-b)
In the production of the modified conjugated diene copolymer BR-a, instead of using 2.85 mmol of tetrakis (2-ethyl-1,3-hexanediolato) titanium, 2.85 mmol of tin 2-ethylhexanoate was used. In the same manner as in the production of the modified conjugated diene copolymer BR-a, a modified conjugated diene copolymer BR-b was obtained.

(Modified conjugated diene copolymer BR-c)
In the production of the modified conjugated diene copolymer BR-a, instead of 2.85 mmol of tetrakis (2-ethyl-1,3-hexanediolato) titanium, 2.85 mmol of tris (stearate) aluminum was used. A modified conjugated diene copolymer BR-c was obtained in the same manner as in the production of the modified conjugated diene copolymer BR-a.

(Modified conjugated diene copolymer BR-d)
Into a nitrogen-substituted 5 L autoclave, 1.4 kg of cyclohexane, 250 g of 1,3-butadiene and 0.0285 mmol of 2,2-ditetrahydrofurylpropane were injected as a cyclohexane solution under nitrogen, and 2.85 mmol of n-butyl was added thereto. After adding lithium (BuLi), polymerization was carried out in a 50 ° C. warm water bath equipped with a stirrer for 4.5 hours. The reaction conversion of 1,3-butadiene was almost 100%. Next, this polymer solution was kept at a temperature of 60 ° C., 2.85 mmol of N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane was added, and the mixture was reacted for 30 minutes. A sodium hydroxide (NaOH) aqueous solution was added little by little, and when the pH reached 10.5, water was added in a molar amount 3 times that of lithium (Li), and the mixture was stirred for 30 minutes. Thereafter, the resultant was taken out in a methanol solution containing 1.3 g of 2,6-di-tert-butyl-p-cresol, and after the polymerization was stopped, the solvent was removed by steam stripping, and the resultant was dried with a roll at 110 ° C. A diene copolymer BR-d was obtained.

(Modified conjugated diene copolymer BR-e)
Into a nitrogen-substituted 5 L autoclave, 1.4 kg of cyclohexane, 250 g of 1,3-butadiene and 0.0285 mmol of 2,2-ditetrahydrofurylpropane were injected as a cyclohexane solution under nitrogen, and 2.85 mmol of n-butyl was added thereto. After adding lithium (BuLi), polymerization was carried out in a 50 ° C. warm water bath equipped with a stirrer for 4.5 hours. The reaction conversion of 1,3-butadiene was almost 100%. Next, this polymer solution was kept at a temperature of 60 ° C., and 2.85 mmol of N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane was added and reacted for 30 minutes. Thereafter, the resultant was taken out in a methanol solution containing 1.3 g of 2,6-di-tert-butyl-p-cresol, and after the polymerization was stopped, the solvent was removed by steam stripping, and the resultant was dried with a roll at 110 ° C. A diene copolymer BR-e was obtained.

(Unmodified conjugated diene copolymer BR-f)
Into a nitrogen-substituted 5 L autoclave, 1.4 kg of cyclohexane, 250 g of 1,3-butadiene and 0.0285 mmol of 2,2-ditetrahydrofurylpropane were injected as a cyclohexane solution under nitrogen, and 2.85 mmol of n-butyl was added thereto. After adding lithium (BuLi), polymerization was carried out in a 50 ° C. warm water bath equipped with a stirrer for 4.5 hours. The reaction conversion of 1,3-butadiene was almost 100%. The polymer solution was taken out in a methanol solution containing 1.3 g of 2,6-di-tert-butyl-p-cresol, and after the polymerization was stopped, the solvent was removed by steam stripping, and dried with a roll at 110 ° C., An unmodified conjugated diene copolymer BR-f was obtained.

<Examples 1-9 and Comparative Examples 1-8>
Using the modified / unmodified conjugated diene copolymers BR-a to BR-f obtained above, rubber compositions were produced in accordance with the formulations shown in Table 1 (selecting the formulations 1 to 3 as appropriate). Specifically, it was obtained by kneading with a Banbury mixer according to the above-mentioned formulation, and vulcanized by a conventional method after molding.

About the obtained rubber composition, alcohol volatilization amount and vulcanized rubber physical property, (SIGMA) tan (delta) (28-150 degreeC) were calculated | required.
Next, these rubber compositions were disposed on the side reinforcing layers, and pneumatic run-flat tires for passenger cars having tire sizes of 215 / 45ZR17 were manufactured according to ordinary methods, and the run-flat durability of these tires was evaluated. .
These results are summarized in Tables 2 and 3. In Tables 2 and 3, I, II, and III described as organic crosslinking agents represent compounds represented by Formula (I), Formula (II), and Formula (III), respectively.

As shown in Tables 2 to 3, the rubber composition containing the specific modified conjugated diene polymer, carbon black, and specific organic cross-linking agent according to Examples has no alcohol volatilization when kneaded, and Σ of tan δ It can be seen that in pneumatic tires having relatively small values and actually using these rubber compositions as side reinforcing layers and bead fillers, heat generation of the tire during run flat running is small, and run flat durability can be improved. .
On the other hand, in the comparative example in which at least one of the specific modified conjugated diene polymer, carbon black, and the specific organic crosslinking agent is not used, not only alcohol volatilization may occur during kneading, but also Even sufficient run-flat durability cannot be obtained.

Claims (12)

(A) Modified conjugated diene (co) polymer (a-1) having a structure represented by the following general formula (1) and a modified conjugate having a structure represented by the following general formula (2): A rubber component containing at least one of the diene (co) polymer (a-2), and (B) a nitrogen adsorption specific surface area (N) of 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component ₂ A rubber composition containing carbon black having a SA of 20 m ² / g or more and 100 m ² / g or less, and (C) an organic crosslinking agent.

(In the formula, R ¹ represents a hydrocarbyl group having 1 to 20 carbon atoms, R ² represents an alkylene group having 1 to 12 carbon atoms, and (Polymer) − is a polymer chain of a modified conjugated diene (co) polymer. )

Wherein R ³ is a hydrocarbyl group having 1 to 20 carbon atoms, R ⁴ is an alkylene group having 1 to 12 carbon atoms, R ⁵ is a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyl carboxyl group having 2 to 20 carbon atoms, Any one of —OH group and C1-C20 1,3-dicarbonyl-containing group, and a plurality of R ⁵ may be the same or different, and M is Ti, Sn, Al, Si and Bi. Wherein k is {(valence of M) −2}, n is 0 or 1. (Polymer) − is a polymer chain of a modified conjugated diene (co) polymer.) (A) One hydrocarbyloxy group and one reactive group are directly bonded to the silicon atom at the active end of the conjugated diene (co) polymer having an active end, and one protected The following general formula obtained by reacting a compound containing a bifunctional silicon atom in which a primary amino group is bonded to the silicon atom via an alkylene group, followed by hydrolysis and deprotection. A rubber component containing the modified conjugated diene (co) polymer (a-1) having a terminal structure represented by (1), and (B) 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the rubber component. A rubber composition containing carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 20 m ² / g or more and 100 m ² / g or less, and (C) an organic crosslinking agent.

(In the formula, R ¹ represents a hydrocarbyl group having 1 to 20 carbon atoms, R ² represents an alkylene group having 1 to 12 carbon atoms, and (Polymer) − is a polymer chain of a modified conjugated diene (co) polymer. ) (A) (a) one hydrocarbyloxy group and one reactive group are directly bonded to a silicon atom at the active end of a conjugated diene (co) polymer having an active end, and A step of modifying by reacting a compound containing a bifunctional silicon atom in which a protected primary amino group is bonded to the silicon atom via an alkylene group; (b) titanium-based, tin-based, aluminum-based , A step of performing a condensation reaction involving the compound containing a bifunctional silicon atom in the presence of at least one condensation accelerator selected from silicon, zirconium and bismuth, and (c) a hydrolysis reaction And a rubber component containing a modified conjugated diene (co) polymer (a-2) represented by the following general formula (2) obtained by performing a step of performing a deprotection reaction, and (B) the rubber component 100 10 parts by mass The amount of 100 parts by weight or more, and carbon black nitrogen adsorption specific surface area (N ₂ SA) is less than 20 m ² / g or more 100 m ² / g, the rubber composition containing the (C) organic cross-linking agents .

Wherein R ³ is a hydrocarbyl group having 1 to 20 carbon atoms, R ⁴ is an alkylene group having 1 to 12 carbon atoms, R ⁵ is a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyl carboxyl group having 2 to 20 carbon atoms, Any one of —OH group and C1-C20 1,3-dicarbonyl-containing group, and a plurality of R ⁵ may be the same or different, and M is Ti, Sn, Al, Si and Bi. Wherein k is {(valence of M) −2}, n is 0 or 1. (Polymer) − is a polymer chain of a modified conjugated diene (co) polymer.) The said organic crosslinking agent is at least 1 type chosen from the compound represented by following General formula (3) thru | or General formula (5), Formula (I), and Formula (II), The any one of Claims 1-3 The rubber composition as described in 2.

(In the formula, R ¹⁸ , R ¹⁹ , R ²⁰ and R ²¹ each independently represents a linear or branched alkyl group having 3 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms.)

(In the formula, R ²² and R ²³ each independently represent a linear or branched alkyl group having 7 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms, M ¹ is a divalent or higher metal, n is a number equal to the valence of the metal of M ^1. )

(In the formula, R ²⁴ , R ²⁵ , R ²⁶ and R ²⁷ each independently represents a linear or branched alkyl group having 3 to 12 carbon atoms or an aralkyl group having 7 to 12 carbon atoms.)

The rubber composition according to any one of claims 1 to 4, wherein the organic crosslinking agent is at least one selected from compounds represented by the following formula (I), formula (II), and formula (III).

  The conjugated diene (co) polymer having an active terminal is obtained by anionic polymerization of a conjugated diene compound alone or a conjugated diene compound and an aromatic vinyl compound using an organic alkali metal compound as a polymerization initiator. Item 6. The rubber composition according to any one of Items 2 to 5.   The compound containing a bifunctional silicon atom is N, N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane, N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane, or N, N-bis (trimethylsilyl) aminoethyl. Methyldimethoxysilane, N, N-bis (trimethylsilyl) aminoethylmethyldiethoxysilane, 1-trimethylsilyl-2-ethoxymethyl-1-aza-2-silacyclopentane and 3- (2,2,5,5-tetra The rubber composition according to any one of claims 2 to 6, which is at least one selected from methyl (1-aza-2,5-disilacyclopentane) -1-yl) propylmethyldiethoxysilane. .   The condensation accelerator used in the step (b) is at least one selected from alkoxides of metal selected from titanium, tin and aluminum, carboxylates and acetylacetonate complex salts, or mixed salts thereof. The rubber composition according to any one of 3 to 7.   The said (A) rubber component contains at least any one of a modified conjugated diene (co) polymer (a-1) and a modified conjugated diene (co) polymer (a-2) in a proportion of 10% by mass or more. The rubber composition according to any one of 1 to 8.   The said (A) rubber component contains at least any one of a modified conjugated diene (co) polymer (a-1) and a modified conjugated diene (co) polymer (a-2) in a proportion of 50% by mass or more. 9. The rubber composition according to 9.   A pneumatic tire using the rubber composition according to claim 1.   The pneumatic tire according to claim 11, wherein the rubber composition according to any one of claims 1 to 10 is used as at least one selected from a tread rubber, a side rubber, a side reinforcing rubber, and a bead filler rubber.