JP2013159742A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire making rolling resistance compatible with wet grip in a combined rubber composition compound of a natural rubber and polybutadiene rubber.SOLUTION: A rubber composition for a tire contains: 100 pts.mass of a rubber component containing 10 to 65 mass% of polybutadiene in which a rate of a vinyl structure of a microstructure is ≥10%, and a ratio of cis-structure: trans-structure is 85:15 to 100:0 and 35 to 90 mass% of polyisoprene-based rubber; and 5 to 150 pts.mass of silica whose nitrogen adsorption specific surface area is 40 to 400 m/g.

Description

The present invention relates to a rubber composition for tires.

Tread rubber for studless tires, truck buses and light trucks is made of natural rubber or high-cis polybutadiene rubber as the main component because of its low glass transition temperature (Tg), flexibility and high strength. There are many.

For rubber compositions used in tires for studless tires, in order to improve grip performance on ice and snow, there is a method of reducing the hardness of rubber and reducing the modulus of elasticity (modulus) at low temperature and improving adhesive friction. . In particular, since the braking force on ice is greatly affected by the effective contact area of rubber with ice, it is often considered to use a flexible rubber in order to increase the braking force.

On the other hand, a method of simply reducing the hardness of the rubber by a method such as increasing the amount of oil is also conceivable, but there is a problem that a feeling of stability on ice or snow is lost and steering stability is deteriorated. Furthermore, with recent improvements in road maintenance, not only on ice and snow, but also on wet and dry road surfaces (wet grips) and low fuel consumption have been strongly demanded.

On the other hand, there is an increasing demand for low fuel consumption for rubber compositions used for truck and bus tires. In general, carbon black is used for rubber compositions used for truck and bus tires in order to ensure durability, but the use of silica is also demanded as fuel efficiency is reduced in recent years (patented) Reference 1).

However, the high-cis polybutadiene rubber, which is a natural rubber used for studless tires, truck buses, and light trucks, has a problem that it has poor reactivity with a silane coupling agent, and rolling resistance and wet grip cannot be achieved at the same time.

JP 2009-001720 A

An object of the present invention is to solve the above-mentioned problems and to provide a pneumatic tire that achieves both rolling resistance and wet grip in a rubber compounded combination of natural rubber and polybutadiene rubber.

In the present invention, the proportion of the microstructured vinyl structure is 10% or more, the polybutadiene having a cis structure: trans structure ratio of 85:15 to 100: 0, 10 to 65% by mass, and the polyisoprene rubber is 35 to 90%. The present invention relates to a tire rubber composition containing 5 to 150 parts by mass of silica having a nitrogen adsorption specific surface area of 40 to 400 m ² / g with respect to 100 parts by mass of a rubber component containing 5% by mass.

Furthermore, it is preferable that 0.5-20 mass parts of coupling agents which have a mercapto group are included with respect to 100 mass parts of silica.

（式（１）中、Ｒ^１０１〜Ｒ^１０３は、分岐若しくは非分岐の炭素数１〜１２のアルキル基、分岐若しくは非分岐の炭素数１〜１２のアルコキシ基、又は−Ｏ−（Ｒ^１１１−Ｏ）_ｚ−Ｒ^１１２（ｚ個のＲ^１１１は、分岐若しくは非分岐の炭素数１〜３０の２価の炭化水素基を表す。ｚ個のＲ^１１１はそれぞれ同一でも異なっていてもよい。Ｒ^１１２は、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、炭素数６〜３０のアリール基、又は炭素数７〜３０のアラルキル基を表す。ｚは１〜３０の整数を表す。）で表される基を表す。Ｒ^１０１〜Ｒ^１０３はそれぞれ同一でも異なっていてもよい。Ｒ^１０４は、分岐若しくは非分岐の炭素数１〜６のアルキレン基を表す。）

（式（２）及び（３）中、Ｒ^２０１は水素、ハロゲン、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、分岐若しくは非分岐の炭素数２〜３０のアルキニル基、又は該アルキル基の末端の水素が水酸基若しくはカルボキシル基で置換されたものを表す。Ｒ^２０２は分岐若しくは非分岐の炭素数１〜３０のアルキレン基、分岐若しくは非分岐の炭素数２〜３０のアルケニレン基、又は分岐若しくは非分岐の炭素数２〜３０のアルキニレン基を表す。Ｒ^２０１とＲ^２０２とで環構造を形成してもよい。） The coupling agent containing a mercapto group includes a compound represented by the following formula (1) and / or a binding unit A represented by the following formula (2) and a binding unit B represented by the following formula (3). A compound coupling agent is preferred.

(In the formula (1), R ^{101 to} R ¹⁰³ are each a branched or unbranched C 1-12 alkyl group, a branched or unbranched C 1-12 alkoxy group, or —O— (R ¹¹¹ — O) _z- R ¹¹² (z R ¹¹¹ represents a branched or unbranched divalent hydrocarbon group having 1 to 30 carbon atoms. The z R ^{111 s} may be the same as or different from each other. ¹¹² represents a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms. Z represents an integer of 1 to 30.) R ^{101 to} R ¹⁰³ may be the same as or different from each other, and R ¹⁰⁴ has 1 to 6 carbon atoms which are branched or unbranched. Represents an alkylene group of

(In the formulas (2) and (3), R ²⁰¹ is hydrogen, halogen, branched or unbranched alkyl group having 1 to 30 carbon atoms, branched or unbranched alkenyl group having 2 to 30 carbon atoms, branched or unbranched. Or an alkyl group substituted with a hydroxyl group or a carboxyl group, and R ²⁰² represents a branched or unbranched C 1-30 alkylene group, branched or It represents an unbranched C2-C30 alkenylene group or a branched or unbranched C2-C30 alkynylene group, and R ²⁰¹ and R ²⁰² may form a ring structure.)

According to the present invention, when the proportion of the vinyl structure of the polybutadiene contained is 10% or more, the reactivity with the silane coupling agent is improved, and the dispersibility of silica and the bonding force between silica and polybutadiene are improved. . Thereby, it is possible to achieve both reduction of rolling resistance and wet grip. Moreover, the coexistence degree of reduction of rolling resistance and wet grip improves by containing the coupling agent containing a mercapto group.

The rubber composition for tires of the present invention comprises 10 to 65% by mass of polybutadiene having a ratio of microstructure vinyl structure of 10% or more and a cis structure: trans structure ratio of 85:15 to 100: 0, and polyisoprene. 5 to 150 parts by mass of silica having a nitrogen adsorption specific surface area of 40 to 400 m ² / g is included with respect to 100 parts by mass of the rubber component containing 35 to 90% by mass of the rubber based.

The content of the polyisoprene rubber is 35% by mass or more, preferably 40% by mass or more, and more preferably 45% by mass or more. When the polyisoprene-based rubber is less than 35% by mass, the rubber breaking strength tends to be low, and the rubber grouping at the time of kneading tends to deteriorate and the productivity tends to deteriorate. The content of the polyisoprene rubber is 90% by mass or less, preferably 85% by mass or less. When the content of the polyisoprene rubber exceeds 90% by mass, sufficient flexibility and wear resistance tend not to be obtained.

Examples of the polyisoprene rubber include natural rubber (NR) and polyisoprene rubber (IR). NR is not particularly limited. For example, SIR20, RSS # 3, TSR20, deproteinized natural rubber (DPNR), high purity natural rubber (HPNR), epoxidized natural rubber (ENR), etc., which are common in the tire industry Can be used. Similarly, IR that is common in the tire industry can be used.

The content of polybutadiene is 10 to 65% by mass, but the lower limit is preferably 15% by mass or more, and more preferably 20% by mass or more. If it is less than 10% by mass, flexibility at low temperatures cannot be ensured, and on a studless tire, the performance on ice and snow is lowered, and the wear resistance tends to be lowered (including tires for trucks and buses). On the other hand, the upper limit is preferably 60% by mass or less. If it exceeds 65% by mass, the wet grip performance tends to decrease.

As the polybutadiene, a polybutadiene having a microstructure vinyl structure ratio of 10% or more and a cis structure: trans structure ratio of 85:15 to 100: 0 is used. The proportion of the vinyl structure is preferably 11% or more. If it is less than 10%, the reactivity with the coupling agent is poor, and the fuel economy and strength tend to decrease. The cis structure: trans structure ratio is more preferably 90:10 to 100: 0, and more preferably 93: 7 to 100: 0. When the cis structure is less than 85, the wear resistance tends to decrease.

The rubber composition for tires of the present invention may contain other rubber components. Other rubber components include styrene-butadiene copolymer rubber (SBR), other polybutadiene rubbers (BR), butadiene-isoprene copolymer rubber, butyl rubber, ethylene-propylene copolymer, ethylene-octene copolymer. Etc. Two or more of these rubber components may be used in combination. Among them, those containing 50% by mass or more of a structural unit derived from a conjugated diene compound can be suitably used from the viewpoint that fuel economy, wet grip performance, wear resistance and workability can be improved in a balanced manner. For these, BR and SBR are preferable.

The polybutadiene other than the above is not particularly limited, and examples thereof include butadiene rubber having a high cis content such as BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., and BR150B.

The rubber composition of the present invention contains silica. The silica is not particularly limited, and examples thereof include dry method silica (anhydrous silica) and wet method silica (hydrous silica). Wet silica is preferred because it has many silanol groups. Silica may be used alone or in combination of two or more.

The content of silica is 5 parts by mass or more with respect to 100 parts by mass of the rubber component, preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 45 parts by mass or more. When the amount is less than 5 parts by mass, the effect of blending silica cannot be sufficiently obtained, and the wear resistance tends to decrease. The content of silica is 150 parts by mass or less, preferably 100 parts by mass or less. If it exceeds 150 parts by mass, the workability tends to deteriorate.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² / g or more, more preferably 50 m ² / g or more, and still more preferably 60 m ² / g or more. If it is less than 40 m < ² > / g, a reinforcement effect is small and there exists a tendency for abrasion resistance and fracture strength to fall. The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 400 m ² / g or less, more preferably 360 m ² / g or less, and still more preferably 300 m ² / g or less. When it exceeds 400 m < ² > / g, it will become difficult to disperse | distribute a silica and there exists a tendency for low-fuel-consumption property and workability to deteriorate. The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of the coupling agent having a mercapto group is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and further preferably 2 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 0.5 part by mass, the viscosity of the unvulcanized rubber composition tends to be high, and the processability tends to deteriorate. Further, 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, there is a tendency that an effect commensurate with the increase in cost cannot be obtained.

（式（１）中、Ｒ^１０１〜Ｒ^１０３は、分岐若しくは非分岐の炭素数１〜１２のアルキル基、分岐若しくは非分岐の炭素数１〜１２のアルコキシ基、又は−Ｏ−（Ｒ^１１１−Ｏ）_ｚ−Ｒ^１１２（ｚ個のＲ^１１１は、分岐若しくは非分岐の炭素数１〜３０の２価の炭化水素基を表す。ｚ個のＲ^１１１はそれぞれ同一でも異なっていてもよい。Ｒ^１１２は、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、炭素数６〜３０のアリール基、又は炭素数７〜３０のアラルキル基を表す。ｚは１〜３０の整数を表す。）で表される基を表す。Ｒ^１０１〜Ｒ^１０３はそれぞれ同一でも異なっていてもよい。Ｒ^１０４は、分岐若しくは非分岐の炭素数１〜６のアルキレン基を表す。）

（式（２）及び（３）中、Ｒ^２０１は水素、ハロゲン、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、分岐若しくは非分岐の炭素数２〜３０のアルキニル基、又は該アルキル基の末端の水素が水酸基若しくはカルボキシル基で置換されたものを表す。Ｒ^２０２は分岐若しくは非分岐の炭素数１〜３０のアルキレン基、分岐若しくは非分岐の炭素数２〜３０のアルケニレン基、又は分岐若しくは非分岐の炭素数２〜３０のアルキニレン基を表す。Ｒ^２０１とＲ^２０２とで環構造を形成してもよい。） The coupling agent having a mercapto group is not particularly limited as long as it has a mercapto group, but the compound represented by the following formula (1) and / or the binding unit A represented by the following formula (2) and the following formula A compound containing the binding unit B represented by (3) can be suitably used.

(In the formula (1), R ^{101 to} R ¹⁰³ are each a branched or unbranched C 1-12 alkyl group, a branched or unbranched C 1-12 alkoxy group, or —O— (R ¹¹¹ — O) _z- R ¹¹² (z R ¹¹¹ represents a branched or unbranched divalent hydrocarbon group having 1 to 30 carbon atoms. The z R ^{111 s} may be the same as or different from each other. ¹¹² represents a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms. Z represents an integer of 1 to 30.) R ^{101 to} R ¹⁰³ may be the same as or different from each other, and R ¹⁰⁴ has 1 to 6 carbon atoms which are branched or unbranched. Represents an alkylene group of

(In the formulas (2) and (3), R ²⁰¹ is hydrogen, halogen, branched or unbranched alkyl group having 1 to 30 carbon atoms, branched or unbranched alkenyl group having 2 to 30 carbon atoms, branched or unbranched. Or an alkyl group substituted with a hydroxyl group or a carboxyl group, and R ²⁰² represents a branched or unbranched C 1-30 alkylene group, branched or It represents an unbranched C2-C30 alkenylene group or a branched or unbranched C2-C30 alkynylene group, and R ²⁰¹ and R ²⁰² may form a ring structure.)

Hereinafter, the compound represented by Formula (1) is demonstrated.

By using the compound represented by Formula (1), silica is dispersed well, and the effects of the present invention are obtained well. In particular, wet grip performance and fuel efficiency can be greatly improved.

R ^{101 to} R ¹⁰³ are each a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or —O— (R ¹¹¹ —O) _z —R ¹¹² . Represents the group represented. From the viewpoint that the effect of the present invention can be obtained satisfactorily, at least one of R ^{101 to} R ¹⁰³ is preferably a group represented by —O— (R ¹¹¹ —O) _z —R ¹¹² , and two of them are — More preferably, it is a group represented by O— (R ¹¹¹ —O) _z —R ¹¹² , and one is a branched or unbranched C 1-12 alkoxy group.

Examples of the branched or unbranched alkyl group having 1 to 12 carbon atoms (preferably 1 to 5 carbon atoms) represented by R ^{101 to} R ¹⁰³ include, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and n-butyl. Group, iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group and the like.

Examples of the branched or unbranched alkoxy group having 1 to 12 carbon atoms (preferably 1 to 5 carbon atoms) of R ^{101 to} R ¹⁰³ include, for example, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, n- Examples include butoxy, iso-butoxy, sec-butoxy, tert-butoxy, pentyloxy, hexyloxy, heptyloxy, 2-ethylhexyloxy, octyloxy, nonyloxy and the like.

In —O— (R ¹¹¹ —O) _z —R ¹¹² of R ^{101 to} R ¹⁰³ , R ¹¹¹ represents a branched or unbranched carbon number of 1 to 30 (preferably having 1 to 15 carbon atoms, more preferably 1 carbon number). To 3) a divalent hydrocarbon group.
Examples of the hydrocarbon group include a branched or unbranched alkylene group having 1 to 30 carbon atoms, a branched or unbranched alkenylene group having 2 to 30 carbon atoms, and a branched or unbranched alkynylene group having 2 to 30 carbon atoms. And an arylene group having 6 to 30 carbon atoms. Of these, a branched or unbranched alkylene group having 1 to 30 carbon atoms is preferable.

Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms (preferably 1 to 15 carbon atoms, more preferably 1 to 3 carbon atoms) of R ¹¹¹ include, for example, a methylene group, an ethylene group, a propylene group, and a butylene group. Pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and the like.

Examples of the branched or unbranched carbon atoms 2-30 alkenylene group (preferably 2 to 15 carbon atoms, more preferably 2 to 3 carbon atoms) of R ^111, for example, vinylene group, propenylene group, 2-propenylene Group, 1-butenylene group, 2-butenylene group, 1-pentenylene group, 2-pentenylene group, 1-hexenylene group, 2-hexenylene group, 1-octenylene group and the like.

Examples of the branched or unbranched carbon atoms 2-30 alkynylene group (preferably 2 to 15 carbon atoms, more preferably 2 to 3 carbon atoms) of R ^111, for example, ethynylene group, propynylene group, butynylene group, pentynylene group Hexynylene group, heptynylene group, octynylene group, noninylene group, decynylene group, undecynylene group, dodecynylene group and the like.

Examples of the arylene group having 6 to 30 carbon atoms (preferably 6 to 15 carbon atoms) of R ¹¹¹ include a phenylene group, a tolylene group, a xylylene group, and a naphthylene group.

z represents an integer of 1 to 30 (preferably 2 to 20, more preferably 3 to 7, further preferably 5 to 6).

R ¹¹² represents a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms. Represent. Of these, a branched or unbranched alkyl group having 1 to 30 carbon atoms is preferable.

Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms (preferably 3 to 25 carbon atoms, more preferably 10 to 15 carbon atoms) of R ¹¹² include, for example, a methyl group, an ethyl group, an n-propyl group, Isopropyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl , Dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, octadecyl group and the like.

Examples of the branched or unbranched alkenyl group having 2 to 30 carbon atoms (preferably 3 to 25 carbon atoms, more preferably 10 to 15 carbon atoms) for R ¹¹² include, for example, a vinyl group, a 1-propenyl group, and 2-propenyl. Group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 2-pentenyl group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group Group, pentadecenyl group, octadecenyl group and the like.

Examples of the aryl group having 6 to 30 carbon atoms (preferably 10 to 20 carbon atoms) of R ¹¹² include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group.

Examples of the aralkyl group having 7 to 30 carbon atoms (preferably 10 to 20 carbon atoms) of R ¹¹² include a benzyl group and a phenethyl group.

Specific examples of the group represented by —O— (R ¹¹¹ —O) _z —R ¹¹² include, for example, —O— (C ₂ H ₄ —O) ₅ —C ₁₁ H ₂₃ , —O— (C _{2 H 4 -O) 5 -C 12 H} 25, -O- (C 2 H 4 -O) 5 -C 13 H 27, -O- (C 2 H 4 -O) 5 -C 14 H 29, -O _{- (C 2 H 4 -O)} 5 -C 15 H 31, -O- (C 2 H 4 -O) 3 -C 13 H 27, -O- (C 2 H 4 -O) 4 -C 13 H _{27, -O- (C 2 H 4} -O) 6 -C 13 H 27, such as _{-O- (C 2 H 4 -O)} 7 -C 13 H 27 and the like. Among _{these, -O- (C 2 H 4 -O} ) 5 -C 11 H 23, -O- (C 2 H 4 -O) 5 -C 13 H 27, -O- (C 2 H 4 -O) 5 _{-C 15 H 31, -O- (C} 2 H 4 -O) 6 -C 13 H 27 are preferable.

Examples of the branched or unbranched alkylene group having 1 to 6 carbon atoms (preferably 1 to 5 carbon atoms) of R ¹⁰⁴ include the same groups as the branched or unbranched alkylene group having 1 to 30 carbon atoms of R ^111. Can give.

Examples of the compound represented by the formula (1) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the following formula: The compound represented by the following formula (Si363 manufactured by EVONIK-DEGUSSA) and the like can be used, and a compound represented by the following formula can be preferably used. These may be used alone or in combination of two or more.

Next, the compound containing the bond unit A represented by the formula (2) and the bond unit B represented by the formula (3) will be described.

The compound containing the bond unit A represented by the formula (2) and the bond unit B represented by the formula (3) is more viscous during processing than a polysulfide silane such as bis- (3-triethoxysilylpropyl) tetrasulfide. The rise is suppressed. This is presumably because the increase in Mooney viscosity is small because the sulfide portion of the bond unit A is a C—S—C bond and is thermally stable compared to tetrasulfide and disulfide.

Moreover, the shortening of the scorch time is suppressed as compared with mercaptosilane such as 3-mercaptopropyltrimethoxysilane. This is because the bonding unit B has a structure of mercaptosilane, but the —C ₇ H ₁₅ part of the bonding unit A covers the —SH group of the bonding unit B, so that it does not easily react with the polymer and scorch is less likely to occur. This is probably because of this.

In the silane coupling agent having the above structure, the content of the bond unit A is preferably 30 from the viewpoint that the effect of suppressing the increase in viscosity during processing and the effect of suppressing the shortening of the scorch time can be enhanced. It is at least mol%, more preferably at least 50 mol%, preferably at most 99 mol%, more preferably at most 90 mol%. Further, the content of the bond unit B is preferably 1 mol% or more, more preferably 5 mol% or more, further preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less, More preferably, it is 55 mol% or less. Further, the total content of the binding units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably 100 mol%.
The content of the bond units A and B is an amount including the case where the bond units A and B are located at the terminal of the silane coupling agent. The form in which the bonding units A and B are located at the end of the silane coupling agent is not particularly limited, as long as the units corresponding to the formulas (2) and (3) indicating the bonding units A and B are formed. .

Examples of the halogen for R ²⁰¹ include chlorine, bromine, and fluorine.

^Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms of R ²⁰¹ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert- Examples thereof include a butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, and a decyl group. The number of carbon atoms of the alkyl group is preferably 1-12.

^Examples of the branched or unbranched C 2-30 alkenyl group of R ²⁰¹ include a vinyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, and 2-pentenyl. Group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group and the like. The alkenyl group preferably has 2 to 12 carbon atoms.

^Examples of the branched or unbranched alkynyl group having 2 to 30 carbon atoms of R ²⁰¹ include ethynyl group, propynyl group, butynyl group, pentynyl group, hexynyl group, heptynyl group, octynyl group, nonynyl group, decynyl group, undecynyl group, And dodecynyl group. The alkynyl group preferably has 2 to 12 carbon atoms.

Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms of R ²⁰² include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, Examples include dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and the like. The alkylene group preferably has 1 to 12 carbon atoms.

^Examples of the branched or unbranched C2-C30 alkenylene group of R202 include vinylene group, 1-propenylene group, 2-propenylene group, 1-butenylene group, 2-butenylene group, 1-pentenylene group and 2-pentenylene. Group, 1-hexenylene group, 2-hexenylene group, 1-octenylene group and the like. The alkenylene group preferably has 2 to 12 carbon atoms.

Examples of branched or unbranched alkynylene group having 2 to 30 carbon atoms R ^202, ethynylene group, propynylene group, butynylene group, pentynylene group, hexynylene group, heptynylene group, octynylene group, nonynylene group, decynylene group, undecynylene group, And dodecynylene group. The alkynylene group preferably has 2 to 12 carbon atoms.

In the compound containing the bond unit A represented by the formula (2) and the bond unit B represented by the formula (3), the repetition of the total of the repeating number (x) of the bonding unit A and the repeating number (y) of the bonding unit B The number (x + y) is preferably in the range of 3 to 300. Within this range, since the mercaptosilane of the bond unit B is covered by —C ₇ H ₁₅ of the bond unit A, it is possible to suppress the scorch time from being shortened and to have good reactivity with silica and rubber components. Can be secured.

For example, NXT-Z30, NXT-Z45, NXT-Z60, etc. manufactured by Momentive are used as the compound containing the binding unit A represented by the formula (2) and the coupling unit B represented by the formula (3). Can do. These may be used alone or in combination of two or more.

The content of the silane coupling agent having a mercapto group is preferably 0.5 parts by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 0.5 part by mass, the viscosity of the unvulcanized rubber composition is high, and good processability may not be ensured. Moreover, content of the silane coupling agent which has a mercapto group becomes like this. Preferably it is 20 mass parts or less, More preferably, it is 10 mass parts or less. If it exceeds 20 parts by mass, the rubber strength and wear resistance tend to decrease.

In the rubber composition of the present invention, other silane coupling agents can be used in combination with the silane coupling agent having a mercapto group. Thereby, the improvement effect of each performance can be heightened. Examples of other silane coupling agents include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2- Triethoxysilylethyl) tetrasulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3 -Triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetras Fido, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3- Examples include mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazole tetrasulfide, and bis (3-triethoxysilylpropyl) tetrasulfide can be preferably used. .

The content of the other silane coupling agent is preferably 0.5 parts by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 0.5 part by mass, the viscosity of the unvulcanized rubber composition is high, and good processability may not be ensured. Moreover, content of another silane coupling agent becomes like this. Preferably it is 20 mass parts or less, More preferably, it is 10 mass parts or less. If it exceeds 20 parts by mass, the rubber strength and wear resistance tend to decrease.

The total content of the silane coupling agent is preferably 0.5 parts by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 0.5 part by mass, the viscosity of the unvulcanized rubber composition is high, and good processability may not be ensured. Moreover, the total content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. If it exceeds 20 parts by mass, the rubber strength and wear resistance tend to decrease.

In the tire rubber composition of the present invention, in addition to the above-mentioned components, additives generally used in the production of rubber compositions can be appropriately blended. Known additives can be used, such as sulfur vulcanizing agents; thiazole vulcanization accelerators, thiuram vulcanization accelerators, sulfenamide vulcanization accelerators, guanidine vulcanization accelerators. Vulcanization accelerators such as stearic acid and zinc oxide; organic peroxides; fillers such as carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide and mica; Examples include processing aids such as lubricants; anti-aging agents.

Carbon black includes furnace black (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF and ECF; acetylene black (acetylene carbon black); FT and MT Thermal black (thermal carbon black) such as: Channel black (channel carbon black) such as EPC, MPC and CC; Graphite and the like. These can be used alone or in combination of two or more.

The content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 1 part by mass, sufficient reinforcement may not be obtained. The content of carbon black is preferably 60 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 15 parts by mass or less, and most preferably 10 parts by mass or less. If it exceeds 60 parts by mass, the fuel efficiency tends to deteriorate.

Nitrogen adsorption specific surface area _(N 2 SA) of carbon black is usually 5 to 200 m ² / g, the lower limit is preferably ^{50 m} 2 / g, the upper limit is 150 meters ² / g. Carbon black has a dibutyl phthalate (DBP) absorption amount of usually 5 to 300 ml / 100 g, preferably a lower limit of 80 ml / 100 g and an upper limit of 180 ml / 100 g. If the N ₂ SA or DBP absorption amount of the carbon black is less than the lower limit of the above range, the reinforcing effect tends to be small and the wear resistance tends to decrease. If the upper limit of the above range is exceeded, dispersibility is poor and hysteresis loss increases. There is a tendency for fuel efficiency to decrease. The nitrogen adsorption specific surface area is measured according to ASTM D4820-93, and the DBP absorption is measured according to ASTM D2414-93. As a commercial product, Tokai Carbon Co., Ltd. trade name Seast 6, Seast 7HM, Seast KH, Degussa trade name CK3, Special Black 4A, etc. can be used.

As the extending oil, aromatic mineral oil (viscosity specific gravity constant (VGC value) 0.900 to 1.049), naphthenic mineral oil (VGC value 0.850 to 0) 899), paraffinic mineral oil (VG value 0.790 to 0.849), and the like. The polycyclic aromatic content of the extender oil is preferably less than 3% by mass, more preferably less than 1% by mass. The polycyclic aromatic content is measured according to the British Petroleum Institute 346/92 method. Moreover, the aromatic compound content (CA) of the extending oil is preferably 20% by mass or more. These extending oils may be used in combination of two or more.

Examples of the vulcanization accelerator include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and thiazole vulcanization accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram monosulfide, tetramethylthiuram disulfide Thiuram vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N- Sulfenamide vulcanization accelerators such as oxyethylene-2-benzothiazole sulfenamide, N, N′-diisopropyl-2-benzothiazole sulfenamide; diphenylguanidine, diortolylguanidine, orthotolylbiguanidine, etc. Guani Can be mentioned emission-based vulcanization accelerator, its amount is preferably from 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component, more preferably from 0.2 to 3 parts by weight.

As a method for producing a rubber composition by blending other rubber components and additives with a conjugated diene polymer, a known method, for example, kneading each component with a known mixer such as a roll or Banbury. Can be used.

As kneading conditions, when additives other than the vulcanizing agent and the vulcanization accelerator are blended, the kneading temperature is usually 50 to 200 ° C., preferably 80 to 190 ° C., and the kneading time is usually 30 seconds. -30 minutes, preferably 1-30 minutes.

When blending a vulcanizing agent and a vulcanization accelerator, the kneading temperature is usually 100 ° C. or lower, preferably room temperature to 80 ° C. A composition containing a vulcanizing agent and a vulcanization accelerator is usually used after vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200 ° C, preferably 140 to 180 ° C.

The rubber composition of the present invention has an excellent balance between low fuel consumption, rolling resistance and wet grip performance, wear resistance, and processability, and can provide a remarkable improvement effect of these performances.

The rubber composition of the present invention can be suitably used for each member of a tire, and can be particularly suitably used for a tread.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, if necessary, a rubber composition in which various additives are blended with a rubber component is extruded in accordance with the shape of the tread of the tire at an unvulcanized stage, and molded by a normal method on a tire molding machine. And it bonds together with another tire member, and forms an unvulcanized tire. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce the pneumatic tire of the present invention.

The pneumatic tire of the present invention can be suitably used as a studless tire for passenger cars or a tire for trucks and buses.

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

Production Example 1 <Synthesis of Polybutadiene Rubber B>
Hereinafter, various chemicals used at the time of synthesis and polymerization will be described together. In addition, the chemical | medical agent refine | purified according to the usual method as needed.
THF: anhydrous tetrahydrofuran butadiene manufactured by Kanto Chemical Co., Ltd .: 1,3-butadiene n-butyllithium solution manufactured by Tokyo Chemical Industry Co., Ltd .: 1.6M n-butyllithium hexane solution 2,6- manufactured by Kanto Chemical Co., Ltd. Di-tert-butyl-p-cresol: Nocrack 200 manufactured by Ouchi Shinsei Chemical Co., Ltd.
Cyclohexane: manufactured by Kanto Chemical Co., Inc.

To a 3 L pressure-resistant vessel sufficiently purged with nitrogen, 18000 mL of n-hexane, 2000 g of butadiene, and 5 mmol of THF were added, and the temperature was raised to 40 ° C. Next, after adding 11 mL of n-butyllithium solutions, it heated up at 50 degreeC and stirred for 3 hours. Next, 1 mL of methanol and 0.1 g of 2,6-tert-butyl-p-cresol are added to the reaction solution, and then aggregates are collected from the polymer solution by steam stripping, and the obtained aggregates are recovered for 24 hours. The polybutadiene rubber B was obtained by drying under reduced pressure.

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
Natural rubber: TSR20
Polybutadiene rubber A: Ubepol BR150B manufactured by Ube Industries, Ltd.
(Mw = 437,000, Mn = 19.0 million, Mw / Mn = 2.3,
Vinyl structure = 1.2%, cis structure: trans structure = 98.2: 1.8)
Polybutadiene rubber B: Rubber polymerized in Production Example 1 (Mw = 21,000, Mn = 24,000, Mw / Mn = 1.11.
(Vinyl structure = 13.9%, cis structure: trans structure = 17.8: 82.2)
Polybutadiene rubber C: Ubepol MBR manufactured by Ube Industries, Ltd.
(Mw = 523,000, Mn = 21,000, Mw / Mn = 2.5,
(Vinyl structure = 11.4%, cis structure: trans structure = 97.7: 2.3)
Silica: Ultrasil VN3-G (N ₂ SA: 175 m ² / g) manufactured by Degussa
Silane coupling agent A: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Silane coupling agent B: NXT-Z45 manufactured by Momentive (copolymer of bond unit A and bond unit B (in the above general formulas (1) and (2), bond unit A: 55 mol%, bond unit B: 45 mol%)
Carbon black: Dia Black N339 manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 96 m ² / g, DBP absorption: 124 ml / 100 g)
Oil: X-140 manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Antigen 3C manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Beads manufactured by NOF Corporation Zinc stearate Zinc oxide: Zinc flower No. 1 manufactured by Mitsui Kinzoku Mining Co., Ltd. Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd. 1: Soxinol CZ manufactured by Sumitomo Chemical Co., Ltd.
Vulcanization accelerator 2: Soxinol D manufactured by Sumitomo Chemical Co., Ltd.

Examples 1-8 and Comparative Examples 1-9
In accordance with the contents shown in Tables 1 and 2, materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes at 150 ° C. using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., and mixed. A kneaded paste was obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized with a 0.5 mm thick mold at 170 ° C. for 20 minutes to obtain a vulcanized rubber composition.
Further, the obtained unvulcanized rubber composition is molded into a tread shape and bonded together with other tire members on a tire molding machine to form an unvulcanized tire, which is vulcanized at 170 ° C. for 12 minutes, and tested. Tires (size: 195 / 65R15) were manufactured.
The obtained tire was used and evaluated according to the following method. The results are shown in Tables 1 and 2.

<Evaluation items and test methods>
The tan δ of the vulcanized rubber composition was measured at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 50 ° C. using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd. The reciprocal value of tan δ was expressed as an index with Comparative Example 1 being 100. Larger values indicate lower rolling resistance and better fuel efficiency.
Wear resistance index tire size 195 / 65R15, mounted on a domestic FF car, measure the groove depth of the tire tread after mileage 8000km, calculate the mileage when the tire groove depth decreases by 1mm It was indexed by the following formula.
(Driving distance when 1 mm groove depth decreases) ÷ (traveling distance when tire groove of Comparative Example 1 decreases by 1 mm) × 100, the larger the index, the better the wear resistance.
A tensile test was conducted according to the rubber strength index JIS K6251 to measure the elongation at break. The measurement results are shown as an index with Comparative Example 1 as 100. The larger the index, the greater the breaking strength.
(Rubber strength index) = (Fracture strength of each compound) / (Fracture strength of Comparative Example 1) × 100
Wet grip performance index Each test tire was mounted on all wheels of a vehicle (domestic FF2000cc), and a braking distance from an initial speed of 100 km / h was determined on a wet asphalt road surface. The result is expressed as an index. The larger the value, the better the wet skid performance (wet grip performance). The index was calculated by the following formula.
(Wet grip performance index) = (Brake distance of Comparative Example 1) / (Brake distance of each formulation) × 100
Dry steering stability index prototype tires were mounted on all domestic FF2000cc wheels, and steering stability was evaluated by sensory evaluation of the driver on the test course. The evaluation was made by making the comparative example 1 100 points. The greater the score, the better the steering stability.

In Examples 1 to 3, the effect of adding polybutadiene C (particularly low heat build-up and wet grip) is obtained with respect to Comparative Examples 1 and 2.
In Example 3, with respect to Comparative Examples 1-2 and 7-9, the effect of polybutadiene C is obtained by blending silica.
In Example 4, compared with Comparative Examples 3 to 4, polybutadiene C is a rubber composition in which a silica compound and a mercapto silane coupling agent are combined, and a synergistic effect in performance is obtained.
In Comparative Examples 5 to 6, results are obtained in which the performance is biased outside the prescribed amount.

Claims (3)

A rubber containing 10 to 65 mass% of polybutadiene having a ratio of microstructure vinyl structure of 10% or more, and having a cis structure: trans structure ratio of 85:15 to 100: 0, and 35 to 90 mass% of polyisoprene rubber. A rubber composition for tires containing 5 to 150 parts by mass of silica having a nitrogen adsorption specific surface area of 40 to 400 m ² / g with respect to 100 parts by mass of the component. Furthermore, the rubber composition for tires of Claim 1 which contains 0.5-20 mass parts of coupling agents which have a mercapto group with respect to 100 mass parts of silica. The coupling agent containing a mercapto group includes a compound represented by the following formula (1) and / or a binding unit A represented by the following formula (2) and a binding unit B represented by the following formula (3). The rubber composition for tires according to claim 2, which is a compound coupling agent.

(In the formula (1), R ^{101 to} R ¹⁰³ are each a branched or unbranched C 1-12 alkyl group, a branched or unbranched C 1-12 alkoxy group, or —O— (R ¹¹¹ — O) _z- R ¹¹² (z R ¹¹¹ represents a branched or unbranched divalent hydrocarbon group having 1 to 30 carbon atoms. The z R ^{111 s} may be the same as or different from each other. ¹¹² represents a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms. Z represents an integer of 1 to 30.) R ^{101 to} R ¹⁰³ may be the same as or different from each other, and R ¹⁰⁴ has 1 to 6 carbon atoms which are branched or unbranched. Represents an alkylene group of

(In the formulas (2) and (3), R ²⁰¹ is hydrogen, halogen, branched or unbranched alkyl group having 1 to 30 carbon atoms, branched or unbranched alkenyl group having 2 to 30 carbon atoms, branched or unbranched. Or an alkyl group substituted with a hydroxyl group or a carboxyl group, and R ²⁰² represents a branched or unbranched C 1-30 alkylene group, branched or It represents an unbranched C2-C30 alkenylene group or a branched or unbranched C2-C30 alkynylene group, and R ²⁰¹ and R ²⁰² may form a ring structure.)