JP2013234252A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a rubber composition for a tire that can improve high mileage, wet grip performance, abrasion resistance and rubber strength by excellent balance; and a pneumatic tire using the rubber composition.SOLUTION: A rubber composition for tire includes: 30-120 pts.mass of silica, based on 100 pts.mass of a rubber component including 10-80 mass% of an epoxidized natural rubber in which an epoxidation rate is 7-15% by mole based on 100 mass% of the rubber component; and a silane coupling agent having a mercapto group based on 100 pts.mass of the silica.

Description

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

In recent years, due to increasing interest in environmental issues, there has been a strong demand for low fuel consumption for automobiles, and even for rubber compositions (tire rubber compositions) used for automobile tires, low fuel consumption has been achieved. There is a demand for excellence. As rubber compositions for tires, rubber compositions containing natural rubber, conjugated diene polymers such as polybutadiene and butadiene-styrene copolymers, and fillers such as carbon black and silica are used. .

As a method for improving fuel economy, for example, Patent Document 1 proposes a method using a diene rubber (modified rubber) modified with an organosilicon compound containing an amino group and an alkoxy group. However, when modified rubber is used, the reaction efficiency between silica and rubber (polymer) is improved and fuel efficiency is improved. On the other hand, the bond between silica and rubber becomes too dense, resulting in rubber strength and resistance. Abrasion may be reduced.

In addition, since the rubber composition for tires, especially the rubber composition for cap treads in contact with the road surface, is required to have excellent wet grip performance in terms of safety, it has low fuel consumption, rubber strength, and wear resistance. Therefore, there is a demand for a method for improving these performances at a high level in a well-balanced manner. However, in particular, low fuel consumption and wet grip performance are also contradictory performances, and the present situation is that a rubber composition for tires that has improved the above-described performance in a high-order and well-balanced manner has not yet been obtained.

JP 2000-344955 A

The present invention solves the above-mentioned problems, and provides a rubber composition for a tire that can improve fuel economy, wet grip performance, wear resistance, and rubber strength in a balanced manner, and a pneumatic tire using the rubber composition. With the goal.

In the present invention, 30 to 120 parts by mass of silica, mercapto group with respect to 100 parts by mass of rubber component containing 10 to 80% by mass of 100% by mass of epoxidized natural rubber having an epoxidation rate of 7 to 15% by mol. It is related with the rubber composition for tires which contains 0.5-20 mass parts of silane coupling agents which have this 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 silane coupling agent 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). It is preferable.

(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.)

The tire rubber composition preferably contains butadiene rubber and / or styrene butadiene rubber.

It is preferable that the nitrogen adsorption specific surface area of a silica is 40-400 m < ² > / g.

The tire rubber composition is preferably used as a cap tread rubber composition.

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

According to the present invention, 30 to 120 parts by mass of silica with respect to 100 parts by mass of rubber component containing 10 to 80% by mass of 100% by mass of epoxidized natural rubber having an epoxidation rate of 7 to 15 mol%, Since it is a rubber composition for tires containing 0.5 to 20 parts by mass of a silane coupling agent having a mercapto group with respect to 100 parts by mass of silica, it balances fuel economy, wet grip performance, wear resistance, and rubber strength. Can improve well.

The rubber composition for tires of the present invention has 30 to 30 parts by weight of silica with respect to 100 parts by weight of rubber component containing 10 to 80% by weight of 100% by weight of epoxidized natural rubber having an epoxidation rate of 7 to 15% by mole. 120 parts by mass and 0.5 to 20 parts by mass of a silane coupling agent having a mercapto group with respect to 100 parts by mass of silica.

By blending silica with epoxidized natural rubber with a specific epoxidation rate, fuel economy and wet grip performance can be improved in a better balance than when natural rubber or butadiene rubber is used with silica. The fuel economy, rubber strength (destructive property), and wear resistance can be improved in a more balanced manner than when butadiene rubber is used together with silica.

In the present invention, the combination of an epoxidized natural rubber having a specific epoxidation rate and a silane coupling agent having a mercapto group can synergistically improve fuel economy, wet grip performance, wear resistance, and rubber strength. In combination with epoxidized natural rubber with a specific epoxidation rate, a specific amount of silica and a silane coupling agent having a mercapto group are blended to improve fuel economy, wet grip performance, wear resistance, and rubber strength in a balanced manner. it can.

In the present invention, epoxidized natural rubber (ENR) having an epoxidation rate of 7 to 15 mol% is used as the rubber component. Thereby, low fuel consumption, wet grip performance, wear resistance, and rubber strength can be improved in a well-balanced manner. In addition, you may use it in combination with ENR whose epoxidation rate is outside the above range.

The ENR is not particularly limited as long as the epoxidation rate is an ENR within the above range, and may be a commercially available epoxidized natural rubber or an epoxidized natural rubber (NR). The method for epoxidizing natural rubber is not particularly limited, and examples thereof include a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, a peracid method, and the like (Japanese Patent Publication No. 4-26617, Japanese Patent Application Laid-Open No. Hei 2). No. 110182, British Patent No. 2113692, etc.). Examples of the peracid method include a method of reacting natural rubber with an organic peracid such as peracetic acid or performic acid. In addition, epoxidized natural rubber having various epoxidation rates can be prepared by adjusting the amount of organic peracid and the reaction time.
In the present invention, the epoxidation rate is the ratio (mol%) of the number of epoxidized double bonds to the total number of double bonds in the rubber before being epoxidized. Moreover, in this invention, an epoxidation rate is a value obtained by the measuring method as described in the Example mentioned later.

The natural rubber to be epoxidized is not particularly limited. For example, SIR20, RSS # 3, TSR20, deproteinized natural rubber (DPNR), high-purity natural rubber (HPNR), and the like used in the tire industry are used. it can.

The epoxidation rate of ENR is 7 mol% or more, preferably 8 mol% or more, more preferably 9 mol% or more. If the epoxidation rate is less than 7 mol%, the modification effect on the rubber composition is not sufficient, and there is a tendency that low fuel consumption, wet grip performance, wear resistance, and rubber strength cannot be improved in a balanced manner. The epoxidation rate is 15 mol% or less, preferably 14 mol% or less, more preferably 12 mol% or less. When the epoxidation rate exceeds 15 mol%, fuel economy and rubber strength tend to deteriorate. When the epoxidation rate is within the above range, low fuel consumption, wet grip performance, wear resistance, and rubber strength can be obtained in a well-balanced manner.

The content of ENR in 100% by mass of the rubber component is 10% by mass or more, preferably 15% by mass or more, more preferably 25% by mass or more, and further preferably 40% by mass or more. If it is less than 10% by mass, fuel economy, wet grip performance, wear resistance, and rubber strength tend to be lowered. The content of ENR is 80% by mass or less, preferably 75% by mass or less. When it exceeds 80% by mass, wet grip performance and wear resistance tend to be lowered.

Examples of rubber components other than ENR used in the rubber composition include diene rubbers. For example, NR, butadiene rubber (BR), styrene butadiene rubber (SBR), epoxidized styrene butadiene rubber (ESBR), isoprene rubber ( IR), butyl rubber (IIR), halogenated butyl rubber (X-IIR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), styrene-isoprene-butadiene copolymer rubber (SIBR) and the like can be used. In addition to diene rubbers, ethylene-propylene copolymers, ethylene-octene copolymers, and the like can be used. These rubber components may be used alone or in combination of two or more. Among these, those containing 50% by mass or more of structural units derived from conjugated diene compounds can be suitably used from the viewpoint that fuel economy, cut resistance, rubber strength and processability can be improved in a balanced manner. For this reason, BR and SBR are more preferable, and BR is more preferable because of its good wear resistance.

The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B having a high cis content such as BR150B, VCR412 manufactured by Ube Industries, Ltd. Commonly used in the tire industry, such as BR containing syndiotactic polybutadiene crystals, can be used. Of these, the BR cis content is preferably 90% by mass or more because of its good wear resistance.

When the rubber composition of the present invention contains BR, the content of BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more. If it is less than 10% by mass, the cut resistance, wear resistance, and low fuel consumption tend to decrease. The BR content is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 35% by mass or less. When it exceeds 50% by mass, wet grip performance and rubber strength tend to decrease.

The SBR is not particularly limited, and 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.

When the rubber composition of the present invention contains SBR, the content of SBR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 25% by mass or more. If it is less than 10% by mass, the wet grip performance tends to decrease. The content of the SBR is preferably 60% by mass or less, more preferably 50% by mass or less. If it exceeds 60% by mass, the wear resistance, fuel efficiency and rubber strength tend to decrease.

The rubber composition of the present invention contains silica. Thereby, low fuel consumption, wet grip performance, wear resistance, and rubber strength can be improved in a well-balanced manner. Examples of the silica include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferred because it has many silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² / g or more, more preferably 100 m ² / g or more, and further preferably 150 m ² / g or more. If it is less than 40 m < ² > / g, there exists a tendency for wet grip performance, rubber strength, and abrasion resistance to deteriorate. The N ₂ SA is preferably 400 m ² / g or less, more preferably 360 m ² / g or less, still more preferably 250 m ² / g or less, and particularly preferably 200 m ² / g or less. If it exceeds 400 m ² / g, the fuel efficiency tends to deteriorate.
The _N 2 SA of silica is a value measured by the BET method in accordance with ASTM D3037-81.

The content of silica is 30 parts by mass or more, preferably 50 parts by mass or more, more preferably 60 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 30 parts by mass, sufficient wet grip performance, rubber strength, and abrasion resistance may not be obtained. The content is 120 parts by mass or less, preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and still more preferably 75 parts by mass or less. If it exceeds 120 parts by mass, the fuel efficiency and mechanical strength (particularly the fuel efficiency) tend to deteriorate.

The rubber composition of the present invention contains a silane coupling agent having a mercapto group. Thereby, low fuel consumption, wet grip performance, wear resistance, and rubber strength can be improved in a well-balanced manner.

（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。） Examples of the silane coupling agent having a mercapto group include 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 compound containing can be used conveniently. Especially, the compound containing the bond unit A shown by following formula (2) and the bond unit B shown by following formula (3) is more preferable.

(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 the formula (1), silica is well dispersed, and low fuel consumption, wet grip performance, wear resistance, and rubber strength can be improved in a balanced manner.

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, methoxy group, ethoxy group, n-propoxy group, 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.

By using the compound containing the bond unit A represented by the formula (2) and the bond unit B represented by the formula (3), the silica is well dispersed, fuel efficiency, wet grip performance, wear resistance, The rubber strength can be improved in a well-balanced manner.

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.

Content of the silane coupling agent which has a mercapto group is 0.5 mass part or more with respect to 100 mass parts of silica, Preferably it is 1 mass part or more, Preferably it is 3 mass parts or more. If the amount is less than 0.5 parts by mass, silica cannot be sufficiently dispersed, resulting in poor fuel economy, wet grip performance, wear resistance, and rubber strength. Moreover, this content is 20 mass parts or less, Preferably it is 15 mass parts or less, Preferably it is 10 mass parts or less. If it exceeds 20 parts by mass, fuel economy, wet grip performance, wear resistance, and rubber strength will deteriorate.

The rubber composition of this invention may contain silane coupling agents other than the silane coupling agent which has a mercapto group with the silane coupling agent which has a mercapto group. Examples of the silane coupling agent other than the silane coupling agent having a mercapto group include sulfide, vinyl, amino, glycidoxy, nitro, and chloro silane coupling agents. Among these, a sulfide system is preferable because the effects of the present invention can be obtained satisfactorily.

As the sulfide-based silane coupling agent, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3- Triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, and 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide are preferable, and bis (3-triethoxysilylpropyl) tetrasulfide is more preferable.

When a silane coupling agent other than a silane coupling agent having a mercapto group is blended, the preferred total content of the silane coupling agent is the same as the content of the silane coupling agent having a mercapto group.

The rubber composition of the present invention preferably contains carbon black. Thereby, wet grip performance, abrasion resistance, and rubber strength can be further improved. Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited. Carbon black may be used independently and may use 2 or more types together.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² / g or more, and more preferably 90 m ² / g or more. If it is less than 50 m ² / g, sufficient reinforcing properties cannot be obtained, and sufficient wet grip performance, wear resistance, and rubber strength may not be obtained. The _N 2 SA is preferably 150 meters ² / g or less, more preferably 130m ² / g. When it exceeds 150 m ² / g, heat generation increases, and fuel economy tends to deteriorate.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

The dibutyl phthalate oil absorption (DBP) of carbon black is preferably 50 ml / 100 g or more, more preferably 90 ml / 100 g or more. If it is less than 50 ml / 100 g, sufficient reinforcement cannot be obtained, and sufficient wet grip performance, wear resistance, and rubber strength may not be obtained. The DBP of carbon black is preferably 200 ml / 100 g or less, and more preferably 125 ml / 100 g or less. When it exceeds 200 ml / 100 g, the heat generation becomes large and the fuel efficiency tends to deteriorate.
The DBP of carbon black is measured according to JIS K 6217-4: 2001.

The content of carbon black is preferably 3 parts by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 3 parts by mass, sufficient wet grip performance, wear resistance, and rubber strength may not be obtained. The content is preferably 80 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 20 parts by mass or less. If it exceeds 80 parts by mass, heat generation will increase and fuel economy tends to deteriorate.

When carbon black is contained, the total content of silica in 100% by mass of silica and carbon black is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more. By setting the content to 50% by mass or more, the effect of the present invention can be obtained more suitably. On the other hand, the total content is preferably 95% by mass or less.

The rubber composition of the present invention preferably contains an alkaline fatty acid metal salt. Since the alkaline fatty acid metal salt neutralizes the acid used during the ENR synthesis, it can prevent deterioration due to heat during ENR kneading and vulcanization. It can also prevent reversion. In addition, by adding an alkaline fatty acid metal salt to the rubber composition of the present invention, wear resistance obtained by combining ENR having a specific epoxidation rate, silica, and a silane coupling agent having a mercapto group, etc. The improvement effect can be increased.

Examples of the metal in the alkaline fatty acid metal salt include sodium, potassium, calcium, barium, magnesium, zinc and the like. Among them, there are many in nature, the environmental load is small, and the heat resistance effect is large. From the viewpoint of compatibility with the epoxidized natural rubber, calcium, zinc and barium are preferable, and calcium is more preferable. Specific examples of alkaline fatty acid metal salts include sodium stearate, magnesium stearate, calcium stearate, barium stearate and other metal stearates, sodium oleate, magnesium oleate, calcium oleate, barium oleate and other oleic acids Examples thereof include metal salts. Of these, calcium stearate and calcium oleate are preferred because they are excellent in aging resistance and heat resistance, have high compatibility with epoxidized natural rubber, and are relatively inexpensive.

The content of the alkaline fatty acid metal salt is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of ENR. If it is less than 0.5 parts by mass, the wear resistance and heat resistance tend not to be sufficiently improved. The content of the alkaline fatty acid metal salt is preferably 12 parts by mass or less, more preferably 8 parts by mass or less, and still more preferably 7 parts by mass or less. When it exceeds 12 parts by mass, the wear resistance, rubber strength, and low fuel consumption tend to deteriorate.

In addition to the above-mentioned components, the rubber composition of the present invention includes compounding agents generally used in the production of rubber compositions, for example, reinforcing fillers such as calcium carbonate, aluminum hydroxide, alumina, clay and talc, oxidation Zinc, stearic acid, processing aids, various anti-aging agents, softening agents such as oil, aromatic petroleum resins, vulcanizing agents such as wax and sulfur, vulcanization accelerators and the like can be appropriately blended.

Although it does not specifically limit as a softener which can be used by this invention, For example, mineral oils, such as aromatic oil, a process oil, paraffin oil, will be mentioned if it is oil. These softeners may be used alone or in combination of two or more.

In the present invention, the amount of oil is preferably 1 to 15 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component, because the effects of the present invention can be suitably obtained. . Here, the amount of oil contained in the oil-extended rubber is also included in the amount of oil blended.

Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Etc. These vulcanization accelerators may be used alone or in combination of two or more. Of these, sulfenamide vulcanization accelerators are preferred.

Examples of the sulfenamide vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N -Dicyclohexyl-2-benzothiazolylsulfenamide (DCBS) and the like.

The content of the vulcanization accelerator is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts per 100 parts by mass of the rubber component. It is below mass parts. By adjusting within the above range, the effect of the present invention can be obtained more suitably.

As a method for producing the rubber composition of the present invention, known methods can be used. For example, the above components are kneaded using a rubber kneader such as an open roll, a Banbury mixer, a closed kneader, and then added. It can be manufactured by a method of sulfurating.

The rubber composition of the present invention can be suitably used for each member of a tire, and in particular, can be suitably applied to a cap tread of a pneumatic tire.

A cap tread is a surface layer portion of a tread having a multilayer structure. In the case of a tread having a two-layer structure, the tread includes a surface layer (cap tread) and an inner surface layer (base tread).

A tread having a multilayer structure is produced by pasting a sheet into a predetermined shape, or by inserting it into two or more extruders and forming it into two or more layers at the head outlet of the extruder. Can do.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing various additives as necessary is extruded in accordance with the shape of a cap tread or the like at an unvulcanized stage, molded by a normal method on a tire molding machine, etc. After being bonded together with the tire member to form an unvulcanized tire, the tire can be manufactured by heating and pressing in a vulcanizer.

The pneumatic tire of the present invention is preferably used as a tire for passenger cars, a tire for trucks and buses, a tire for motorcycles, a tire for competition, and the like, and more preferably used as a tire for passenger cars.

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 the production examples will be described together.
High ammonia type natural rubber latex: Hytex made by Nomura Trading Co., Ltd.
Nonionic emulsifier: Emulgen 106 manufactured by Kao Corporation
Hydrogen peroxide: Hydrogen peroxide manufactured by Wako Pure Chemical Industries, Ltd. (reagent grade 1, active ingredient 35%)
Acetic anhydride: Acetic anhydride manufactured by Wako Pure Chemical Industries, Ltd. (Reagent grade 1, active ingredient 93%)
Ammonia: Ammonia water manufactured by Wako Pure Chemical Industries, Ltd. (Reagent grade 1, active ingredient 25%)

The following evaluation was performed on the ENR obtained by the following production example.
(Epoxidation rate)
The epoxidation rate was determined by dissolving the obtained dry rubber (ENR) in deuterated chloroform and analyzing it by nuclear magnetic resonance (NMR (JNM-ECA series manufactured by JEOL Ltd.)) spectroscopic analysis. It calculated using the following calculation formulas from the ratio of the integral value h (ppm) of a bond part and an aliphatic part.
(Epoxidation rate E%) = 3 × h (2.69) / (3 × h (2.69) + 3 × h (5.14) + h (0.87)) × 100

Production Example 1 (Preparation of ENR (1) (10 mol%))
1750 g of high ammonia type natural rubber latex (solid content 60%) was placed in a 5 L glass container, stirred with a stirring blade, and diluted with 1500 g of distilled water so that the solid content would be 30%. To this, 21 g of a nonionic emulsifier was added with stirring. Next, 215 g of hydrogen peroxide and 230 g of acetic anhydride were reacted in another container to prepare peracetic acid, and the prepared peracetic acid was slowly added to the 5 L glass container. After the addition, the mixture was reacted at room temperature for 30 minutes, neutralized with ammonia, only the rubber component was coagulated with methanol, washed with tap water, and dried to prepare ENR (1). The epoxidation rate of the obtained ENR (1) was 10 mol%.

Production Example 2 (Preparation of ENR (2) (3 mol%))
1750 g of high ammonia type natural rubber latex (solid content 60%) was placed in a 5 L glass container, stirred with a stirring blade, and diluted with 1500 g of distilled water so that the solid content would be 30%. To this, 21 g of a nonionic emulsifier was added with stirring. Next, 65 g of hydrogen peroxide and 70 g of acetic anhydride were reacted in another container to prepare peracetic acid, and the prepared peracetic acid was slowly added to the 5 L glass container. After the addition, the mixture was reacted at room temperature for 30 minutes, neutralized with ammonia, only the rubber component was coagulated with methanol, washed with tap water, and dried to prepare ENR (2). The epoxidation rate of the obtained ENR (2) was 3 mol%.

Production Example 3 (Preparation of ENR (3) (8 mol%))
1750 g of high ammonia type natural rubber latex (solid content 60%) was placed in a 5 L glass container, stirred with a stirring blade, and diluted with 1500 g of distilled water so that the solid content would be 30%. To this, 21 g of a nonionic emulsifier was added with stirring. Next, 172 g of hydrogen peroxide and 185 g of acetic anhydride were reacted in another container to prepare peracetic acid, and the prepared peracetic acid was slowly added to the 5 L glass container. After the addition, the mixture was reacted at room temperature for 30 minutes, neutralized with ammonia, only the rubber component was coagulated with methanol, washed with tap water, and dried to prepare ENR (3). The epoxidation rate of the obtained ENR (3) was 8 mol%.

Production Example 4 (Preparation of ENR (4) (13 mol%))
1750 g of high ammonia type natural rubber latex (solid content 60%) was placed in a 5 L glass container, stirred with a stirring blade, and diluted with 1500 g of distilled water so that the solid content would be 30%. To this, 21 g of a nonionic emulsifier was added with stirring. Next, 280 g of hydrogen peroxide and 300 g of acetic anhydride were reacted in another container to prepare peracetic acid, and the prepared peracetic acid was slowly added to the 5 L glass container. After the addition, the mixture was reacted at room temperature for 30 minutes, neutralized with ammonia, only the rubber component was coagulated with methanol, washed with tap water, and dried to prepare ENR (4). The epoxidation rate of the obtained ENR (4) was 13 mol%.

Production Example 5 (Preparation of ENR (5) (25 mol%))
1750 g of high ammonia type natural rubber latex (solid content 60%) was placed in a 5 L glass container, stirred with a stirring blade, and diluted with 1500 g of distilled water so that the solid content would be 30%. To this, 21 g of a nonionic emulsifier was added with stirring. Next, 538 g of hydrogen peroxide and 575 g of acetic anhydride were reacted in another container to prepare peracetic acid, and the prepared peracetic acid was slowly added to the 5 L glass container. After the addition, the mixture was reacted at room temperature for 30 minutes, neutralized with ammonia, only the rubber component was coagulated with methanol, washed with tap water, and dried to prepare ENR (5). The epoxidation rate of the obtained ENR (5) was 25 mol%.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR20
ENR (1): ENR (1) produced in Production Example 1 and having an epoxidation rate of 10 mol%
ENR (2): ENR (2) produced in Production Example 2 and having an epoxidation rate of 3 mol%
ENR (3): ENR (3) produced in Production Example 3 and having an epoxidation rate of 8 mol%
ENR (4): ENR (4) produced in Production Example 4 and having an epoxidation rate of 13 mol%
ENR (5): ENR (5) produced in Production Example 5 and having an epoxidation rate of 25 mol%
BR: Ubepol BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass)
SBR: SBR1502 manufactured by Sumitomo Chemical Co., Ltd.
Silica: Ultrasil VN3-G (N ₂ SA: 175 m ² / g) manufactured by Evonik Degussa
Silane coupling agent 1: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Evonik Degussa
Silane coupling agent 2: Si363 manufactured by Evonik Degussa
Silane coupling agent 3: NXT-Z45 manufactured by Momentive (compound containing bonding unit A and bonding unit B (bonding unit A: 55 mol%, bonding unit B: 45 mol%))
Carbon Black: Show Black N220 (N ₂ SA: 111 m ² / g, DBP: 115 ml / 100 g) manufactured by Cabot Japan
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 Co., Ltd. Beads of calcium stearate Calcium stearate: Calcium stearate manufactured by NOF Co., Ltd. Zinc oxide: Zinc Hua No. 1 manufactured by Mitsui Kinzoku Mining Co., Ltd. Wax: Ouchi Shinsei Chemical Industry Co., Ltd. ) Sannok N made
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. (1): Soxinol CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Sumitomo Chemical Co., Ltd.
Vulcanization accelerator (2): Soxinol D (1,3-diphenylguanidine) manufactured by Sumitomo Chemical Co., Ltd.

(Examples and Comparative Examples)
In accordance with the formulation shown in Tables 1 to 3, materials other than sulfur and a vulcanization accelerator were kneaded for 3 minutes at 150 ° C. using a Banbury mixer to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 80 ° C. using a biaxial 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 was molded into a cap tread shape, bonded together with other tire members on a tire molding machine, press vulcanized at 160 ° C. for 20 minutes, and a test tire ( Tire size: 195 / 65R15) was obtained.

The following evaluation was performed about the obtained vulcanized rubber composition and the tire for a test. The results are shown in Tables 1-3. In Tables 1 to 3, the reference comparative example is Comparative Example 1.

(Low fuel consumption)
Rolling resistance when the manufactured test tire was run at a speed (80 km / h) under the conditions of a rim (15 × 6JJ), internal pressure (230 kPa) and load (3.43 kN) using a rolling resistance tester. The rolling resistance index of the reference comparative example was taken as 100, and the rolling resistance of each formulation was displayed as an index according to the following calculation formula. In addition, it shows that rolling resistance can be reduced and a fuel-consumption property is excellent, so that a rolling resistance index | exponent is large.
(Rolling resistance index) = (Rolling resistance of the reference comparative example) / (Rolling resistance of each formulation) × 100

(Wet grip performance)
The manufactured test tire was mounted on all wheels of a test vehicle (domestic FF2000cc), and the brake was stepped on the wet asphalt road surface while traveling at an initial speed of 100 km / h to measure the braking distance. And the wet grip performance index | exponent of the reference | standard comparative example was set to 100, and the braking distance of each mixing | blending was displayed as an index | exponent with the following formula. In addition, it shows that wet grip performance is so favorable that a wet grip performance index | exponent is large.
(Wet grip performance index) = (braking distance of reference comparative example) / (braking distance of each formulation) × 100

(Abrasion resistance)
The manufactured test tire was mounted on all wheels of a test vehicle (domestic FF2000cc) and traveled on an actual vehicle, and the change in the groove depth of the tread pattern before and after traveling 30000 km was calculated. Then, the wear resistance index of the reference comparative example was set to 100, and the change in groove depth of each formulation was displayed as an index by the following calculation formula. In addition, it shows that it is excellent in abrasion resistance, so that an abrasion resistance index | exponent is large.
(Abrasion resistance index) = (Change in groove depth of reference comparative example) / (Change in groove depth of each composition) × 100

(Rubber strength)
A tensile test was performed in accordance with JIS K6251 to measure elongation at break. The measurement results are shown as an index with the reference comparative example as 100. The larger the index, the better the rubber strength (breaking strength).
(Rubber strength index) = (breaking elongation of each compound) / (breaking elongation of reference comparative example) × 100

From the result of Tables 1-3, 30-120 mass of silica is carried out with respect to 100 mass parts of rubber components containing 10-80 mass% of epoxidized natural rubber whose epoxidation rate is 7-15 mol% in 100 mass% of rubber components. Examples, which contain 0.5 to 20 parts by mass of a silane coupling agent having a mercapto group with respect to 100 parts by mass of silica, can improve fuel economy, wet grip performance, wear resistance, and rubber strength in a balanced manner. It was.

By comparing the epoxidized natural rubber having an epoxidation rate of 7 to 15 mol% with the silane coupling agent having a mercapto group, the fuel efficiency and the wetness were compared. It was found that the grip performance, wear resistance, and rubber strength can be improved synergistically.

Claims (6)

Silane cup having 30 to 120 parts by mass of silica and mercapto group with respect to 100 parts by mass of rubber component containing 10 to 80% by mass of epoxidized natural rubber having an epoxidation rate of 7 to 15 mol% in 100% by mass of rubber component A tire rubber composition containing 0.5 to 20 parts by mass of a ring agent with respect to 100 parts by mass of silica. The silane coupling agent is a compound containing 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 tire rubber composition according to claim 1.

(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.) The rubber composition for tires according to claim 1 or 2 containing butadiene rubber and / or styrene butadiene rubber. The tire rubber composition according to any one of claims 1 to 3, wherein the silica has a nitrogen adsorption specific surface area of 40 to 400 m ² / g. The tire rubber composition according to any one of claims 1 to 4, which is used as a rubber composition for a cap tread. The pneumatic tire produced using the rubber composition in any one of Claims 1-5.