JP2013018813A - Rubber composition for tire, and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire, well balancedly improved in rolling resistance, wear resistance and wet skid performance, improved particularly in heat aging resistance, and capable of maintaining wear resistance and wet skid over a long period until the last stage of wearing.SOLUTION: The composition contains a modified dienic rubber A modified dienic rubber A modified with a specific acrylamide compound, and a modified dienic rubber B modified with a specific silicon or tin compound and a specific modified compound or the modified compound, and is obtained by blending further sulfur and a specific compound to a blend rubber in which the whole of the rubber A and the rubber B has a weight-average molecular weight of 300,000 to 1,400,000.

Description

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

In recent years, the characteristics required for pneumatic tires for automobiles are various, such as low fuel consumption (rolling resistance characteristics), wear resistance of the tread and wet skid performance, and various properties are required to improve these performances. Ingenuity has been made.

However, in recent years, the required performance of tires has increased, and further improvement in wear resistance and wet skid performance of the tread portion is desired. As a method of satisfying these performances, a method of atomizing carbon black and improving wear resistance is known, but there is a problem that the hardness of rubber increases at the end of wear and wet skid performance decreases.

Further, Patent Document 1 discloses a rubber composition for a tread that uses amorphous silica spherical fine particles as a filler and has improved wet skid performance without deteriorating rolling resistance and wear resistance. There is still room for improvement in terms of improving these performances in a balanced manner. In addition, as with the use of atomized carbon black, the hardness of the rubber increases at the end of wear and the wet skid performance also decreases.

JP 2008-31244 A

The present invention solves the above-mentioned problems, improves the rolling resistance, wear resistance and wet skid performance in a well-balanced manner, and particularly improves the heat aging resistance and can maintain the wear resistance and wet skid for a long period until the end of wear. An object of the present invention is to provide a rubber composition and a pneumatic tire using the same.

（式中、Ｒ^１は水素又はメチル基を表す。Ｒ^２及びＲ^３はアルキル基を表す。ｎは整数を表す。）
下記式（ＩＩ）で表されるケイ素若しくはスズ化合物及び下記式（ＩＩＩ）で表される変性化合物、又は下記式（ＩＩＩ）で表される変性化合物で変性された変性ジエン系ゴムＢとを含み、かつ該変性ジエン系ゴムＡ及びＢ全体の重量平均分子量が３０万〜１４０万であり、
更に、硫黄と、下記式（ＩＶ）で表される化合物とを含むタイヤ用ゴム組成物に関する。

（式中、Ｒはアルキル基、アルケニル基、シクロアルケニル基又は芳香族炭化水素基を表す。Ｍはケイ素又はスズを表す。Ｘはハロゲンを表す。ａは０〜２の整数を表す。ｂは２〜４の整数を表す。）

（式中、Ｒ^４〜Ｒ^６は同一若しくは異なって炭素数が１〜８のアルキル基を表す。Ｒ^７〜Ｒ^１２は同一若しくは異なって炭素数が１〜８のアルコキシ基又はアルキル基を表す。ｐ〜ｒは同一若しくは異なって１〜８の整数を表す。）

（式中、Ａは、炭素数２〜１０のアルキレン基、Ｒ^１３及びＲ^１４は、同一若しくは異なって、チッ素原子を含む１価の有機基を表す。） The present invention relates to a modified diene rubber A modified with an acrylamide compound represented by the following formula (I):

(In the formula, R ¹ represents hydrogen or a methyl group. R ² and R ³ represent an alkyl group. N represents an integer.)
Including a silicon or tin compound represented by the following formula (II) and a modified compound represented by the following formula (III), or a modified diene rubber B modified with the modified compound represented by the following formula (III) And the weight average molecular weight of the modified diene rubbers A and B as a whole is 300,000 to 1,400,000.
Furthermore, it is related with the rubber composition for tires containing sulfur and the compound represented by following formula (IV).

(In the formula, R represents an alkyl group, an alkenyl group, a cycloalkenyl group or an aromatic hydrocarbon group. M represents silicon or tin. X represents a halogen. A represents an integer of 0 to 2. b represents Represents an integer of 2 to 4.)

(In the formula, R ^{4 to} R ⁶ are the same or different and represent an alkyl group having 1 to 8 carbon atoms. R ^{7 to} R ¹² are the same or different and represent an alkoxy group or alkyl group having 1 to 8 carbon atoms. P to r are the same or different and each represents an integer of 1 to 8.)

(In the formula, A represents an alkylene group having 2 to 10 carbon atoms, and R ¹³ and R ¹⁴ are the same or different and each represents a monovalent organic group containing a nitrogen atom.)

As the modified diene rubbers A and B, an activity having an alkali metal terminal obtained by polymerizing a conjugated diene monomer, or a conjugated diene monomer and an aromatic vinyl monomer using an alkali metal catalyst in a hydrocarbon solvent. A mixture obtained by reacting the acrylamide compound with the silicon or tin compound and the modifying compound or the modifying compound with respect to the conjugated diene polymer is preferred.

R ^{4 to} R ⁶ in the above modified compound are methyl group, ethyl group, propyl group or butyl group, R ^{7 to} R ¹² are methoxy group, ethoxy group, propoxy group or butoxy group, and p to r are integers of 2 to 5. Preferably there is.

It is preferable to satisfy the relationship of the sulfur content <the content of the compound represented by the formula (IV). Moreover, it is preferable that content of the compound represented by the said sulfur and said formula (IV) is 0.1-2 mass parts with respect to 100 mass parts of rubber components, respectively.

The rubber composition for tires of the present invention is an active conjugate having an alkali metal terminal obtained by polymerizing a conjugated diene monomer, or a conjugated diene monomer and an aromatic vinyl monomer using an alkali metal catalyst in a hydrocarbon solvent. The present invention relates to a diene polymer containing a mixture obtained by reacting two or more kinds of modifiers.

The present invention also relates to a pneumatic tire having a tread produced using the rubber composition.

According to the present invention, a modified diene rubber A having a terminal modified with a specific acrylamide compound, a silicon or tin compound and a specific modified compound, or a modified diene rubber B modified with the modified compound, In addition, since the rubber composition for tires using the rubber A and B having a weight average molecular weight in a specific range and further containing sulfur and a specific compound, the rolling resistance, wear resistance and wet skid performance are well balanced. In addition to improvement, the heat aging resistance is particularly improved, and it becomes possible to maintain wear resistance and wet skid for a long time until the end of wear.

In the tire rubber composition of the present invention, as a rubber component, a blend having an overall weight average molecular weight composed of modified diene rubbers A and B described later in a specific range is used, and sulfur and a formula described later are used as a crosslinking agent. Since the compound represented by (IV) is used, the performance balance of rolling resistance, wear resistance and wet skid performance can be improved. In addition, wear resistance and wet skid can be maintained over a long period until the end of wear.

Such an improvement effect is presumed to be exhibited by the following functions.
In general, when a modified polymer is used, there is a concern that the rubber will deteriorate and the hardness will increase with the use of the tire, and both the wear resistance and wet skid performance will decrease at the end of wear. The blend of A and B has a strong interaction with both the carbon black and silica fillers and does not form a covalent bond with the filler. The rubber A terminal-modified with the acrylamide compound can enhance the interaction with silica and carbon black. However, the rubber A alone has many low-molecular components and cannot be expected to have a destructive effect on filler agglomerates. It is difficult to improve sex. On the other hand, in the present invention, the rubber B which is further end-modified with the above-described modifying compound is also used, so that the interaction with the filler, particularly silica, can be further strengthened. While having an action, terminal-modifying groups interact with each other to cause polymer coupling and increase the molecular weight. Therefore, the filler agglomerates are sufficiently destroyed, and the effect of improving the dispersibility of the filler by the rubbers A and B is efficiently and synergistically exhibited. Therefore, not only can the performance balance of rolling resistance, wear resistance and wet skid performance be improved synergistically, but also an increase in hardness can be suppressed. In addition, since the compound represented by formula (IV) is also used in the present invention, the deterioration of the rubber accompanying the use of the tire is remarkably suppressed, and the wet skid performance and the wear resistance are sufficiently maintained until the end of wear. Is done. Therefore, it is presumed that the above-described effects of the present invention are exhibited by exhibiting the above-described effects.

（式中、Ｒ^１は水素又はメチル基を表す。Ｒ^２及びＲ^３はアルキル基を表す。ｎは整数を表す。） The rubber composition of the present invention contains modified diene rubbers A and B, and the weight average molecular weight of the rubbers A and B as a whole is in a specific range.
The modified diene rubber A is a diene rubber modified with an acrylamide compound represented by the following formula (I). This is a diene rubber having a polymer terminal modified with an acrylamide compound.

(In the formula, R ¹ represents hydrogen or a methyl group. R ² and R ³ represent an alkyl group. N represents an integer.)

In the formula (I), R ² and R ³ are preferably alkyl groups having 1 to 4 carbon atoms. n is preferably an integer of 2 to 5.

Specific examples of the acrylamide compound include N, N-dimethylaminomethylacrylamide, N, N-ethylmethylaminomethylacrylamide, N, N-diethylaminomethylacrylamide, N, N-ethylpropylaminomethylacrylamide, N, N- Dipropylaminomethylacrylamide, N, N-butylpropylaminomethylacrylamide, N, N-dibutylaminomethylacrylamide, N, N-dimethylaminoethylacrylamide, N, N-ethylmethylaminoethylacrylamide, N, N-diethylaminoethyl Acrylamide, N, N-ethylpropylaminoethylacrylamide, N, N-dipropylaminoethylacrylamide, N, N-butylpropylaminoethylacrylamide, N, N-dibutyl Minoethylacrylamide, N, N-dimethylaminopropylacrylamide, N, N-ethylmethylaminopropylacrylamide, N, N-diethylaminopropylacrylamide, N, N-ethylpropylaminopropylacrylamide, N, N-dipropylaminopropylacrylamide N, N-butylpropylaminopropylacrylamide, N, N-dibutylaminopropylacrylamide, N, N-dimethylaminobutylacrylamide, N, N-ethylmethylaminobutylacrylamide, N, N-diethylaminobutylacrylamide, N, N -Ethylpropylaminobutylacrylamide, N, N-dipropylaminobutylacrylamide, N, N-butylpropylaminobutylacrylamide, N, N-dibutyl Mino butyl acrylamide; etc. These methacrylamide. Among these, N, N-dimethylaminopropylacrylamide is preferable from the viewpoint of improving the performance balance and maintaining wear resistance and wet skid until the end of wear.

（式中、Ｒはアルキル基、アルケニル基、シクロアルケニル基又は芳香族炭化水素基を表す。Ｍはケイ素又はスズを表す。Ｘはハロゲンを表す。ａは０〜２の整数を表す。ｂは２〜４の整数を表す。）

（式中、Ｒ^４〜Ｒ^６は同一若しくは異なって炭素数が１〜８のアルキル基を表す。Ｒ^７〜Ｒ^１２は同一若しくは異なって炭素数が１〜８のアルコキシ基又はアルキル基を表す。ｐ〜ｒは同一若しくは異なって１〜８の整数を表す。） The modified diene rubber B is a diene rubber modified with a silicon or tin compound represented by the following formula (II) and a modifying compound represented by the following formula (III), or represented by the following formula (III). A diene rubber modified with a modifying compound. The former is a diene rubber in which the terminal of a polymer coupled with a silicon or tin compound is modified with a modifying compound, and the latter is a diene rubber in which the polymer terminal is modified with a modifying compound.

(In the formula, R represents an alkyl group, an alkenyl group, a cycloalkenyl group or an aromatic hydrocarbon group. M represents silicon or tin. X represents a halogen. A represents an integer of 0 to 2. b represents Represents an integer of 2 to 4.)

(In the formula, R ^{4 to} R ⁶ are the same or different and represent an alkyl group having 1 to 8 carbon atoms. R ^{7 to} R ¹² are the same or different and represent an alkoxy group or alkyl group having 1 to 8 carbon atoms. P to r are the same or different and each represents an integer of 1 to 8.)

The silicon compound and tin compound represented by the formula (II) function as a diene rubber coupling agent. Examples of the silicon compound include tetrachlorosilicon, tetrabromosilicon, methyltrichlorosilicon, butyltrichlorosilicon, dichlorosilicon, and bistrichlorosilylsilicon. Examples of the tin compound include tetrachlorotin, tetrabromotin, methyltrichlorotin, butyltrichlorotin, dichlorotin, and bistrichlorosilyltin.

In the formula (III), R ^{4 to} R ⁶ are preferably a methyl group, an ethyl group, a propyl group or a butyl group, R ^{7 to} R ¹² are preferably a methoxy group, an ethoxy group, a propoxy group or a butoxy group, and p to r are An integer of 2 to 5 is preferable. Thereby, the performance balance can be improved, and the wear resistance and wet skid can be maintained until the end of wear.

Specific examples of the modified compound represented by the formula (III) include 1,3,5-tris (3-trimethoxysilylpropyl) isocyanurate, 1,3,5-tris (3-triethoxysilylpropyl) isocyanate. Nurate, 1,3,5-tris (3-tripropoxysilylpropyl) isocyanurate, 1,3,5-tris (3-tributoxysilylpropyl) isocyanurate, and the like. Among these, 1,3,5-tris (3-trimethoxysilylpropyl) isocyanurate is preferable because it improves the performance balance and can maintain wear resistance and wet skid until the end of wear.

The modified diene rubbers A and B can be obtained, for example, by separately preparing the rubbers A and B and then mixing them. In this case, the modified diene rubbers A and B can be prepared by the following production methods.

The modified diene rubber A is an active conjugated diene heavy polymer having an alkali metal terminal obtained by polymerizing a conjugated diene monomer or a conjugated diene monomer and an aromatic vinyl monomer using an alkali metal catalyst in a hydrocarbon solvent. It can be prepared by reacting the acrylamide compound represented by the above formula (I) with the union.

Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 1,3-pentadiene (piperine), 2,3-dimethyl-1,3-butadiene, 1,3-hexadiene, and the like. Of these, 1,3-butadiene and isoprene are preferred from the viewpoint of the physical properties of the resulting polymer and the availability for industrial implementation.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyl toluene, vinyl naphthalene, divinyl benzene, trivinyl benzene, and divinyl naphthalene. Of these, styrene is preferred from the viewpoint of the physical properties of the polymer obtained and the availability for industrial implementation.

The hydrocarbon solvent is not particularly limited as long as it does not deactivate the alkali metal catalyst, and examples thereof include aliphatic hydrocarbons, aromatic hydrocarbons, and alicyclic hydrocarbons. Specific examples include propane, n-butane, iso-butane, n-pentane, iso-pentane, n-hexane, cyclohexane, benzene, toluene and xylene having 3 to 12 carbon atoms.

Examples of the alkali metal catalyst include metals such as lithium, sodium, potassium, rubidium, and cesium, and hydrocarbon compounds containing these metals. Preferred alkali metal catalysts include lithium or sodium compounds having 2 to 20 carbon atoms, specifically, ethyl lithium, n-propyl lithium, iso-propyl lithium, n-butyl lithium, sec- Examples include butyl lithium, t-octyl lithium, n-decyl lithium, and phenyl lithium.

As the polymerization monomer, only a conjugated diene monomer may be used, or a conjugated diene monomer and an aromatic vinyl monomer may be used in combination. When the conjugated diene monomer and the aromatic vinyl monomer are used in combination, the ratio by weight of the conjugated diene monomer / aromatic vinyl monomer is preferably 50/50 to 90/10, more preferably 55/45 to 85/15. It is.

In the polymerization, it is possible to use commonly used ones such as alkali metal catalysts, hydrocarbon solvents, randomizers, vinyl bond content regulators of conjugated diene units, and the production method of the polymer is not particularly limited. .

In order to adjust the vinyl bond content of the conjugated diene part, various compounds can be used as the Lewis basic compound, but an ether compound or a tertiary amine is preferable from the viewpoint of easy availability in industrial practice. . Examples of the ether compound include cyclic ethers such as tetrahydrofuran, tetrahydropyran, and 1,4-dioxane; aliphatic monoethers such as diethyl ether and dibutyl ether; and aliphatic diethers such as ethylene glycol dimethyl ether. Examples of the tertiary amine compound include triethylamine and tripropylamine.

The amount used when the modified diene rubber A is produced by adding the acrylamide compound to the active conjugated diene polymer having an alkali metal terminal is the alkali metal catalyst used when adding the alkali metal. The amount is usually 0.05 to 10 mol, preferably 0.2 to 2 mol, per mol.

Since the reaction between the acrylamide compound and the active conjugated diene polymer having an alkali metal terminal occurs rapidly, the reaction temperature and reaction time can be selected in a wide range, but generally room temperature to 100 ° C., several seconds to several It's time. The reaction may be performed by bringing the active conjugated diene polymer and the acrylamide compound into contact. For example, a diene polymer is prepared using an alkali metal catalyst, and the acrylamide compound is placed in the polymer solution. Examples include a method of adding a constant amount.

After completion of the reaction, the coagulation method used in the production of rubber by ordinary solution polymerization such as addition of a coagulant or steam coagulation from the reaction solvent is used as it is, and the coagulation temperature is not limited at all. The resulting modified diene rubber A has an acrylamide compound introduced at the molecular end.

On the other hand, the modified diene rubber B is an active conjugated diene having an alkali metal terminal obtained by polymerizing a conjugated diene monomer or a conjugated diene monomer and an aromatic vinyl monomer using an alkali metal catalyst in a hydrocarbon solvent. (A) reacting a silicon or tin compound (coupling agent) represented by the above formula (II) and then a modifying compound represented by the above formula (III) with respect to the polymer, or ( b) It can be prepared by reacting a modifying compound represented by the above formula (III).

An active conjugated diene polymer having an alkali metal terminal is obtained in the same manner as in the preparation of the modified diene rubber A. Moreover, in said (a), a silicon or tin compound is normally used in 0.01-0.4 equivalent of halogen atoms with respect to 1 equivalent of terminal alkali metal atoms of an active conjugated diene type polymer. The coupling reaction is usually performed in the range of 20 ° C to 100 ° C. Furthermore, the reaction of the modifying compound in the above (a) and (b) can be carried out by the same method as the reaction of the acrylamide compound described above. The resulting modified diene rubber B has a modified compound introduced at the molecular end.

The modified diene rubbers A and B are preferably a mixture obtained by preparing the rubbers A and B in one batch. In this case, for example, the active conjugated diene polymer having an alkali metal terminal is prepared by reacting the acrylamide compound, the silicon or tin compound and the modifying compound, or the modifying compound. it can.

Specifically, an active conjugated diene polymer having an alkali metal terminal is prepared by the same method as described above, and (c) an acrylamide compound is added to the polymer solution, and then a silicon or tin compound is added as necessary. (Coupling agent) is added, and then a modifying compound is added, or (d) an acrylamide compound, a modifying compound, and, if necessary, a silicon or tin compound are simultaneously added to the polymer solution, etc. The above mixture is obtained.

In this case, the reaction with the acrylamide compound and the modifying compound and the coupling reaction can be carried out in the same manner as described above. The resulting mixture contains a modified diene rubber A in which an acrylamide compound is introduced at the molecular end and a modified diene rubber B in which a modified compound is introduced at the molecular end.

The modified diene rubbers A and B used in the rubber composition of the present invention have a weight average molecular weight (weight average molecular weight measured for the entire composition comprising the modified diene rubbers A and B) of both rubbers of 300,000. Above, preferably 500,000 or more, more preferably 600,000 or more. The (Mw) is 1.4 million or less, preferably 1.2 million or less, more preferably 1 million or less. Within the above range, the performance balance can be improved and the wear resistance and wet skid can be maintained until the end of wear.

The total molecular weight distribution (Mw / Mn) of the modified diene rubbers A and B is preferably 4 or less, more preferably 3.5 or less, and still more preferably 3 or less. If it exceeds 4, the dispersibility of the filler tends to deteriorate, and tan δ tends to increase (rolling resistance characteristics deteriorate).

In the present specification, the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the above-mentioned rubbers and the aromatic vinyl polymer described later are the gel permeation chromatograph (GPC) (GPC- manufactured by Tosoh Corporation). 8000 series, detector: differential refractometer, column: TSKEL SUPERMALTPORE HZ-M manufactured by Tosoh Corp.

As the modified diene rubbers A and B, the modified butadiene rubber (modified BR) and the modified styrene butadiene rubber (modified SBR) can be used because the performance balance can be improved and the wear resistance and wet skid can be maintained until the end of wear. Preferably, modified SBR is more preferable.

When the modified diene rubbers A and B are modified SBR, the vinyl bond content in the entire butadiene portion of the rubbers A and B is preferably 20% by mass or more, more preferably 25% by mass or more. A modified diene rubber of less than 20% by mass tends to be difficult to polymerize (manufacture). The vinyl bond amount is preferably 60% by mass or less, more preferably 55% by mass or less. When it exceeds 60 mass%, the dispersibility of the filler tends to deteriorate. In the present specification, the vinyl bond amount (1,2-bond butadiene unit amount) can be measured by infrared absorption spectrum analysis.

When the modified diene rubbers A and B are modified SBR, the total styrene content of the rubbers A and B is preferably 10% by mass, more preferably 15% by mass or more, and further preferably 25% by mass or more. If it is less than 10% by mass, the wet skid performance tends to deteriorate. Moreover, this styrene content becomes like this. Preferably it is 50 mass% or less, More preferably, it is 45 mass% or less. When it exceeds 50 mass%, there exists a tendency for abrasion resistance to deteriorate. In the present specification, the styrene content is calculated by ¹ H-NMR measurement.

In the rubber composition of the present invention, the blending ratio (A / B (mass ratio)) of the modified diene rubbers A and B is preferably 5/95 to 95/5, more preferably 10/90 to 90/10, More preferably, it is 20 / 80-80 / 20. When it is less than the lower limit, the rolling resistance characteristic is lowered, and when it exceeds the upper limit, the wear resistance is lowered, and the performance balance tends to be deteriorated.

In the rubber composition, the total content of the modified diene rubbers A and B in 100% by mass of the rubber component is preferably 2% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more. is there. If it is less than 2% by mass, rolling resistance characteristics and wear resistance may not be sufficiently improved. The upper limit of the total content is not particularly limited, and may be 100% by mass, but is preferably 90% by mass or less, more preferably 80% by mass or less.

Examples of other rubber components that can be used in the present invention include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), and chloroprene rubber (CR). ), Butyl rubber (IIR), halogenated butyl rubber (X-IIR), styrene-isoprene-butadiene copolymer rubber (SIBR) and the like can be used. Especially, it is preferable to use SBR and BR from the point that compatibility is high and the said performance balance is excellent.

As the SBR, those generally used in the tire industry such as emulsion polymerization styrene butadiene rubber (E-SBR) and solution polymerization styrene butadiene rubber (S-SBR) can be used. As BR, BR having a high cis content, BR containing a syndiotactic polybutadiene crystal, or the like can be used.

When blending SBR (non-modified), the content of the SBR is preferably 30% by mass or more, more preferably 40% by mass, and still more preferably 50% by mass or more. There exists a tendency for workability to deteriorate that it is less than 30 mass%. The content is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. When it exceeds 90% by mass, silica is difficult to disperse, and the balance between wet skid performance and wear resistance tends to be deteriorated.
In addition, the suitable amount of styrene of SBR (non-modified) is the same as that when the modified diene rubbers A and B are modified SBR.

When using modified SBR or non-modified SBR in the present invention, the total content of all SBRs in 100% by mass of the rubber component is preferably 75% by mass or more, more preferably 85% by mass or more, and further preferably 95% by mass. As mentioned above, Most preferably, it is 100 mass%. If it is less than 75% by mass, the wear resistance tends to decrease.

When blending BR (non-modified), the content of the BR is preferably 5% by mass or more, more preferably 10% by mass or more. If it is less than 5% by mass, the wear resistance tends to deteriorate. The content is preferably 40% by mass or less, more preferably 30% by mass or less. When it exceeds 40 mass%, there exists a tendency for wet skid performance to fall.

The rubber composition of the present invention preferably contains carbon black and / or silica (preferably both components) as a filler. In the present invention, by using the modified diene rubbers A and B as the rubber component and sulfur and the compound (IV) as the crosslinking agent, the dispersibility of fillers such as silica and carbon black can be remarkably improved. In addition, the wear resistance and wet skid can be maintained until the end of wear.

By adding carbon black, the reinforcing property can be improved and the wear resistance can be further improved. The carbon black is not particularly limited, and GPF, FEF, HAF, ISAF, SAF, and the like can be used. Carbon black may be used independently and may be used in combination of 2 or more type.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² / g or more, more preferably 100 m ² / g or more. If it is less than 50 m < ² > / g, there exists a tendency for sufficient reinforcement property not to be acquired. Also, _N 2 SA of carbon black is preferably not more than 200 meters ² / g, more preferably at most 150m ² / g. If it exceeds 200 m ² / g, the carbon black is difficult to disperse and the rolling resistance characteristics tend to deteriorate.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by JISK6217-2: 2001.

Carbon black has a dibutyl phthalate (DBP) oil absorption of preferably 60 ml / 100 g or more, more preferably 100 ml / 100 g or more. If it is less than 60 ml / 100 g, sufficient reinforcement may not be obtained. The DBP oil absorption of carbon black is preferably 150 ml / 100 g or less, more preferably 120 ml / 100 g or less. If it exceeds 150 ml / 100 g, processability and dispersibility tend to decrease.
In addition, the DBP oil absorption amount of carbon black is calculated | required by JISK6217-4: 2001.

The content of carbon black is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and still more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 10 parts by mass, sufficient reinforcing properties tend not to be obtained. The carbon black content is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 60 parts by mass or less. When it exceeds 100 parts by mass, the carbon black is difficult to disperse, and the rolling resistance characteristic tends to deteriorate.

By blending silica, the rolling resistance characteristics can be improved while enhancing the reinforcement. Examples of the silica include silica manufactured by a wet method, silica manufactured by a dry method, and the like. Silica may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 120 m ² / g or more, more preferably 150 m ² / g or more. There exists a tendency for sufficient reinforcement property not to be acquired as it is less than 120 m < ² > / g. Further, N ₂ SA of silica is preferably 250 m ² / g or less, more preferably 200 m ² / g or less. When it exceeds 250 m ² / g, since the dispersibility of silica is lowered, the hysteresis loss is increased, and the rolling resistance characteristic tends to be deteriorated.
The _N 2 SA of silica is a value determined by the BET method in accordance with ASTMD3037-81.

The content of silica is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, and further preferably 35 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 20 parts by mass, sufficient reinforcing properties tend not to be obtained. The silica content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 70 parts by mass or less. When the amount exceeds 120 parts by mass, the dispersibility of silica is lowered, and thus rolling resistance characteristics tend to deteriorate.

In the rubber composition of the present invention, the total content of carbon black and silica is preferably 40 parts by mass or more, more preferably 70 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 40 parts by mass, sufficient reinforcing properties tend not to be obtained. The total content is preferably 150 parts by mass or less, more preferably 110 parts by mass or less. If it exceeds 150 parts by mass, the dispersibility of the filler tends to decrease.

When both carbon black and silica fillers are contained, the content of silica in the carbon black and silica is preferably 45% by mass or more, more preferably 50% by mass or more. On the other hand, the content is preferably 90% by mass or less, more preferably 80% by mass or less. Within the above range, the effects of the present invention are sufficiently obtained.

In the present invention, a silane coupling agent may be used in combination with silica. Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and the like. Of these, bis (3-triethoxysilylpropyl) tetrasulfide is preferred because it has a high reinforcing effect.

The content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 1 part by mass, not only the coupling effect is insufficient and the wet skid performance is not sufficiently obtained, but also the wear resistance tends to be lowered. The content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. When it exceeds 20 parts by mass, the rubber composition becomes hard and the wet skid performance tends to decrease.

In the present invention, sulfur (crosslinking agent) is used.
Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

The sulfur content is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and still more preferably 0.3 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 0.1 parts by mass, the vulcanization rate will be slow, and the productivity may be deteriorated. The content is preferably 2.0 parts by mass or less, more preferably 1.9 parts by mass or less, and still more preferably 1.8 parts by mass or less. If it exceeds 2.0 parts by mass, the rubber physical property change after aging may be increased.

In the present invention, a compound (crosslinking agent) represented by the following formula (IV) is used. By blending the compound represented by the formula (IV), the rubber composition can have a CC bond having high binding energy and high thermal stability. Therefore, heat aging resistance is improved, and wet skid performance and wear resistance can be maintained until the end of wear.

（式中、Ａは、炭素数２〜１０のアルキレン基、Ｒ^１３及びＲ^１４は、同一若しくは異なって、チッ素原子を含む１価の有機基を表す。）

(In the formula, A represents an alkylene group having 2 to 10 carbon atoms, and R ¹³ and R ¹⁴ are the same or different and each represents a monovalent organic group containing a nitrogen atom.)

The alkylene group for A is not particularly limited, and examples thereof include linear, branched, and cyclic groups. Among them, a linear alkylene group is preferable.

2-10 are preferable and, as for carbon number of an alkylene group, 4-8 are more preferable. When the carbon number of the alkylene group is 1, thermal stability is poor, and there is a tendency that the effect of having the alkylene group is not obtained. When the alkylene group has 11 or more carbon atoms, —S—S—A—S There is a tendency that formation of a crosslinked chain represented by -S- becomes difficult.

Examples of the alkylene group satisfying the above conditions include ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, decamethylene group and the like. Among these, a hexamethylene group is preferred because a cross-link represented by -S-S-ASS- is formed smoothly between the polymers and is thermally stable.

R ¹³ and R ¹⁴ are not particularly limited as long as they are monovalent organic groups containing a nitrogen atom, and those containing at least one aromatic ring are preferred, and N—C (= Those containing a linking group represented by S)-are more preferred.

R ¹³ and R ¹⁴ may be the same or different from each other, but are preferably the same for reasons such as ease of production.

Examples of the compound satisfying the above conditions include 1,2-bis (N, N′-dibenzylthiocarbamoyldithio) ethane, 1,3-bis (N, N′-dibenzylthiocarbamoyldithio) propane, 1, 4-bis (N, N′-dibenzylthiocarbamoyldithio) butane, 1,5-bis (N, N′-dibenzylthiocarbamoyldithio) pentane, 1,6-bis (N, N′-dibenzylthio) Carbamoyldithio) hexane, 1,7-bis (N, N′-dibenzylthiocarbamoyldithio) heptane, 1,8-bis (N, N′-dibenzylthiocarbamoyldithio) octane, 1,9-bis (N , N′-dibenzylthiocarbamoyldithio) nonane, 1,10-bis (N, N′-dibenzylthiocarbamoyldithio) decane and the like. Among these, 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane is preferable because it is thermally stable and has excellent polarizability.

The content of the compound represented by the formula (IV) is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and further preferably 0.3 parts by mass with respect to 100 parts by mass of the rubber component. That's it. If the amount is less than 0.1 part by mass, the effect of improving the compound represented by formula (IV) may not be sufficiently obtained. The content is preferably 2.0 parts by mass or less, more preferably 1.9 parts by mass or less, and still more preferably 1.8 parts by mass or less. If it exceeds 2.0 parts by mass, the fracture characteristics may deteriorate.

The rubber composition of the present invention preferably satisfies the relationship of sulfur content (mass) <content (mass) of the compound represented by formula (IV). If the amount of sulfur is more than the amount of the compound of formula (IV), the effect of blending the compound represented by formula (IV) may not be sufficiently obtained. Here, the content of sulfur / the content (mass ratio) of the compound represented by the formula (IV) is preferably 0.05 or more, more preferably 0.1 or more. If it is less than 0.05, the vulcanization rate tends to be slow. The mass ratio is preferably 0.95 or less, more preferably 0.9 or less.

In addition to the above components, the rubber composition of the present invention may appropriately contain additives as required, such as softeners such as oil, anti-aging agents, vulcanization accelerators, vulcanization accelerators and the like.

The tire rubber composition of the present invention has an alkali metal terminal activity obtained by polymerizing a conjugated diene monomer or a conjugated diene monomer and an aromatic vinyl monomer using an alkali metal catalyst in a hydrocarbon solvent. What contains the mixture obtained by making 2 or more types of modifiers react with respect to a conjugated diene type polymer is also mentioned.

That is, in the above description, a mixture obtained by reacting a specific modifier with the active conjugated diene polymer has been described. However, the present invention is not limited to such a form, and two or more arbitrary modifiers are used. A mixture obtained by reacting is also included in the present invention. The mixture can be obtained by, for example, reacting two or more conventionally known terminal modifiers in one batch with an active conjugated diene polymer having an alkali metal terminal prepared by the same method as described above. By using such a mixture prepared in one batch, the effect of improving the performance balance can be obtained.

The rubber composition of the present invention can be used as a tire member such as a tread, a sidewall, and an inner liner, and in particular, it can be suitably used as a tread from the viewpoint that both wear resistance and wet skid can be achieved before and after deterioration. Moreover, the tire using this can be applied suitably for a passenger car, a commercial vehicle, a two-wheeled vehicle, etc.

The rubber composition of the present invention can be produced by a general method such as a method of kneading the above components with a kneader such as a Banbury mixer, a kneader, or an open roll, and then vulcanizing the rubber component, filler (reinforcing) Agent), silane coupling agent and softener mixing step 1, mixture obtained in step 1, stearic acid, zinc oxide and anti-aging agent mixing step 2, and mixture obtained in step 2 It is preferable to manufacture by the manufacturing method which has the kneading | mixing process including the process 3 which mixes a vulcanizing agent and a vulcanization accelerator. In general, the steps 1 and 2 are not separately kneaded but kneaded in one step. In the present invention, chemicals such as anti-aging agent, zinc oxide and stearic acid lower the reaction efficiency of the silane coupling agent. Therefore, it is preferable to knead these components and, if necessary, the wax in the step 2.

In the case of such a production method including steps 1 to 3, the kneading temperature in step 1 is preferably 130 to 160 ° C, the kneading temperature in step 2 is preferably 130 to 155 ° C, and the kneading temperature in step 3 is 70 to 120 ° C. preferable. When the kneading temperature exceeds the respective upper limit value, the rubber tends to deteriorate.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing the above components is extruded in accordance with the shape of a tire component (such as a tread) at an unvulcanized stage, and is used together with other tire members on a tire molding machine in a usual manner. An unvulcanized tire is formed by molding. A pneumatic tire can be manufactured by heating and pressing the unvulcanized tire in a vulcanizer.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described.
Modified diene rubbers A and B: Production Examples 1 to 10 below (oil amount of each rubber: 15% by mass)
SBR: SBR1502 manufactured by JSR Corporation (styrene content: 23.5% by mass)
BR: BR130B manufactured by Ube Industries, Ltd.
Silica: Ultrazil VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Carbon Black: Dia Black I (N ₂ SA: 114 m ² / g, DBP oil absorption: 114 ml / 100 g) manufactured by Mitsubishi Chemical Corporation
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Oil: JOMO process X140 manufactured by Japan Energy Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Anti-aging agent: NOCRACK 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Stearic acid: Zinc oxide manufactured by NOF Co., Ltd .: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Seimisulfur manufactured by Nippon Kiboshi Kogyo Co., Ltd. (60% insoluble matter due to carbon disulfide, oil content) Insoluble sulfur containing 10% by mass)
Vulcanization accelerator TBBS: Noxeller NS manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator DPG: NOCELLER D manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Crosslinking agent: Vulcuren VP KA9188 (1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane) manufactured by LANXESS

(Production Example 1)
A stainless steel polymerization reactor having an internal volume of 20 liters was washed, dried, and substituted with dry nitrogen, and then 548 g of 1,3-butadiene, 235 g of styrene, 8.89 g of tetrahydrofuran, 10.2 kg of hexane, n-butyllithium (n-hexane) Solution 5.22 mmol) was added and polymerization was carried out at 65 ° C. for 3 hours with stirring. After completion of the polymerization, 1.57 mmol (0.245 g) of N, N-dimethylaminopropylacrylamide and 3.66 mmol (2.251 g) of 1,3,5-tris (3-trimethoxysilylpropyl) isocyanurate were added. . After reacting for 30 minutes with stirring, 10 ml of methanol was added, and the mixture was further stirred for 5 minutes. Thereafter, the contents of the polymerization reaction vessel are taken out, 10 g of 2,6-di-t-butyl-p-cresol (Sumitomo Chemical's BHT: the same applies hereinafter) and 141 g of oil are added to evaporate most of the hexane. After that, the mixture was dried under reduced pressure at 55 ° C. for 12 hours to obtain a rubber mixture 1.

(Production Example 2)
Manufactured except for changing N, N-dimethylaminopropylacrylamide to 0.52 mmol (0.082 g) and 1,3,5-tris (3-trimethoxysilylpropyl) isocyanurate to 4.70 mmol (2.894 g). In the same manner as in Example 1, rubber mixture 2 was obtained.

(Production Example 3)
Manufactured except for changing N, N-dimethylaminopropylacrylamide to 4.70 mmol (0.734 g) and 1,3,5-tris (3-trimethoxysilylpropyl) isocyanurate to 0.52 mmol (0.322 g). In the same manner as in Example 1, rubber mixture 3 was obtained.

(Production Example 4)
Tetrahydrofuran (31.12 g), n-butyllithium (n-hexane solution 18.28 mmol), N, N-dimethylaminopropylacrylamide (1.83 mmol (0.286 g)), 1,3,5-tris (3-tri A rubber mixture 4 was obtained in the same manner as in Production Example 1 except that the amount of methoxysilylpropyl) isocyanurate was changed to 16.45 mmol (10.131 g).

(Production Example 5)
Tetrahydrofuran (31.12 g), n-butyllithium (n-hexane solution 18.28 mmol), N, N-dimethylaminopropylacrylamide (16.45 mmol (2.57 g)), 1,3,5-tris (3-tri A rubber mixture 5 was obtained in the same manner as in Production Example 1 except that the amount of methoxysilylpropyl) isocyanurate was changed to 1.83 mmol (1.126 g).

(Production Example 6)
4.15 g of tetrahydrofuran, n-butyllithium (2.44 mmol of n-hexane solution), 0.24 mmol (0.038 g) of N, N-dimethylaminopropylacrylamide, 1,3,5-tris (3-tris A rubber mixture 6 was obtained in the same manner as in Production Example 1 except that methoxysilylpropyl) isocyanurate was changed to 2.19 mmol (1.351 g).

(Production Example 7)
4.15 g of tetrahydrofuran, n-butyllithium (2.44 mmol of n-hexane solution), 2.19 mmol (0.343 g) of N, N-dimethylaminopropylacrylamide, 1,3,5-tris (3-tri A rubber mixture 7 was obtained in the same manner as in Production Example 1 except that the amount of methoxysilylpropyl) isocyanurate was changed to 0.24 mmol (0.15 g).

(Production Example 8)
4.15 g of tetrahydrofuran, n-butyllithium (2.44 mmol of n-hexane solution), 0 mmol (0 g) of N, N-dimethylaminopropylacrylamide, 1,3,5-tris (3-trimethoxysilylpropyl) A rubber mixture 8 was obtained in the same manner as in Production Example 1, except that the isocyanurate was changed to 2.44 mmol (1.501 g).

(Production Example 9)
4.15 g of tetrahydrofuran, n-butyllithium (2.44 mmol of n-hexane solution), 2.44 mmol (0.381 g) of N, N-dimethylaminopropylacrylamide, 1,3,5-tris (3-tris A rubber mixture 9 was obtained in the same manner as in Production Example 1 except that methoxysilylpropyl) isocyanurate was changed to 0 mmol (0 g).

<Examples and Comparative Examples>
According to the contents shown in Tables 1 and 2 (the amount of sulfur indicates the amount of pure sulfur contained in Seymisulfur), using the 1.7 L Banbury mixer, out of the ingredients, the material shown in step 1 at 150 ° C. The mixture was kneaded for 3 minutes to obtain a kneaded product. Next, the material shown in Step 2 was added to the kneaded product obtained in Step 1, and kneaded at 140 ° C. for 3 minutes to obtain a kneaded product. Subsequently, the material shown in Step 3 was added to the kneaded material obtained in Step 2, and kneaded at 80 ° C. for 3 minutes using an open roll to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was press vulcanized at 150 ° C. for 20 minutes to obtain a vulcanized rubber sheet.

Further, using the obtained unvulcanized rubber composition, it was molded into a shape of a tread having a thickness of 10 mm, bonded to another tire part, and vulcanized at 170 ° C. for 15 minutes for testing. A tire was manufactured (tire size: 215 / 45ZR17).

(Deterioration conditions)
The test tire produced above was thermally deteriorated in an oven at 80 ° C. for 168 hours, and the obtained tire was used as a deteriorated sample (test tire after heat deterioration).

The following evaluation was performed using the obtained vulcanized rubber sheet and test tire (Fresh, after heat deterioration). The test results are shown in Tables 1 and 2.

(Rolling resistance index)
For the vulcanized rubber sheet, tan δ of each formulation was measured under the conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2% using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.). The tan δ of 1 was set to 100, and the index was expressed by the following calculation formula. The larger the index, the smaller the rolling resistance and the better the fuel efficiency.
(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Wet skid performance)
A test tire or a test tire after heat deterioration was mounted on all wheels of a vehicle (domestic FF2000cc), and a braking distance from an initial speed of 100 km / h on a wet asphalt road surface was determined. The braking distance of Comparative Example 1 (Fresh) was set to 100, and the index was displayed by the following calculation formula. The larger the index, the better the wet skid performance.
Wet skid performance = (braking distance of comparative example 1) / (braking distance of each formulation) × 100
Wet skid performance after heat deterioration = (braking distance of Comparative Example 1) / (braking distance of each formulation (after heat deterioration)) × 100

(Abrasion resistance)
The test tire or the test tire after heat deterioration was mounted on all the wheels of the vehicle (domestic FF2000cc), and the vehicle traveled on the test course, and the change in the pattern groove search before and after traveling 30000 km was obtained. In Comparative Example 1 (Fresh), the change in groove search was set to 100, and an index was displayed according to the following formula. The higher the index, the better the wear resistance.
Abrasion resistance = (change in groove search of Comparative Example 1) / (change in groove search of each composition) x 100
Wear resistance after thermal deterioration = (change in groove search in Comparative Example 1) / (change in groove search in each formulation (after heat deterioration)) × 100

From Table 2, from the results of Comparative Example 1 that does not include both rubbers A and B, Comparative Example 11 that includes only rubber B, Comparative Example 12 that includes only rubber A, and Comparative Example 2 that includes only rubber A and B, both rubber components , The balance of rolling resistance, wear resistance, and wet skid performance is synergistically improved, and in particular, there is a synergistic effect on wear resistance and rolling resistance characteristics. The abrasion resistance was insufficient.

On the other hand, from Table 1, in the examples in which rubbers A and B and KA9188 are used in combination, the performance balance is improved, and the wet skid performance and wear resistance after thermal deterioration are remarkable due to the combined effect of KA9188. It became clear that it improved.

Claims (7)

A modified diene rubber A modified with an acrylamide compound represented by the following formula (I):

(In the formula, R ¹ represents hydrogen or a methyl group. R ² and R ³ represent an alkyl group. N represents an integer.)
Including a silicon or tin compound represented by the following formula (II) and a modified compound represented by the following formula (III), or a modified diene rubber B modified with the modified compound represented by the following formula (III) And the weight average molecular weight of the modified diene rubbers A and B as a whole is 300,000 to 1,400,000.
Furthermore, the rubber composition for tires containing sulfur and the compound represented by following formula (IV).

(In the formula, R represents an alkyl group, an alkenyl group, a cycloalkenyl group or an aromatic hydrocarbon group. M represents silicon or tin. X represents a halogen. A represents an integer of 0 to 2. b represents Represents an integer of 2 to 4.)

(In the formula, R ^{4 to} R ⁶ are the same or different and represent an alkyl group having 1 to 8 carbon atoms. R ^{7 to} R ¹² are the same or different and represent an alkoxy group or alkyl group having 1 to 8 carbon atoms. P to r are the same or different and each represents an integer of 1 to 8.)

(In the formula, A represents an alkylene group having 2 to 10 carbon atoms, and R ¹³ and R ¹⁴ are the same or different and each represents a monovalent organic group containing a nitrogen atom.) The modified diene rubbers A and B are active conjugates having an alkali metal terminal obtained by polymerizing a conjugated diene monomer or a conjugated diene monomer and an aromatic vinyl monomer using an alkali metal catalyst in a hydrocarbon solvent. The tire rubber composition according to claim 1, which is a mixture obtained by reacting the acrylamide compound, the silicon or tin compound and the modifying compound, or the modifying compound with a diene polymer. R ^{4 to} R ⁶ in the modified compound are methyl group, ethyl group, propyl group or butyl group, R ^{7 to} R ¹² are methoxy group, ethoxy group, propoxy group or butoxy group, and p to r are integers of 2 to 5. The rubber composition for tires according to claim 1 or 2. The rubber composition for tires according to any one of claims 1 to 3 which satisfies the relation of content of said sulfur <content of a compound denoted by said formula (IV). The tire content according to any one of claims 1 to 4, wherein the content of the sulfur and the compound represented by the formula (IV) is 0.1 to 2 parts by mass with respect to 100 parts by mass of the rubber component. Rubber composition. 2 types of active conjugated diene polymer having an alkali metal terminal obtained by polymerizing a conjugated diene monomer or a conjugated diene monomer and an aromatic vinyl monomer using an alkali metal catalyst in a hydrocarbon solvent A tire rubber composition comprising a mixture obtained by reacting the above modifier. The pneumatic tire which has a tread produced using the rubber composition in any one of Claims 1-6.