JP2013234254A - 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, mechanical strength and a filler gel fraction by excellent balance; and a pneumatic tire using the rubber composition.SOLUTION: A rubber composition for a tire includes: 20-80 pts.mass of silica and 2-20 pts.mass of carbon black, based on 100 pts.mass of a rubber component including 80-100 mass% of an epoxidized natural rubber in which an epoxidation rate is 2-8% by mole based on 100% by mole of the rubber component; and 4-12 pts.mass of a silane coupling agent 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 in a rubber composition, a method of reducing the amount of reinforcing filler is known. However, in this case, there is a problem that the mechanical strength is lowered. Further, as another method for improving fuel economy, a method of replacing carbon black as a filler with silica is known, but in this case as well, there is a problem that mechanical strength is lowered.

Further, in Patent Documents 1 to 3, for the purpose of improving fuel economy, in a compound containing silica, by adding a specific polar group to rubber, it has an affinity for silica, thereby improving the dispersibility of silica. Although a method for obtaining a rubber composition excellent in fuel efficiency is described, provision of other methods is also demanded.

JP 2001-114939 A JP 2005-126604 A JP 2005-325206 A

An object of the present invention is to solve the above-mentioned problems and provide a rubber composition for a tire that can improve fuel economy, mechanical strength, and filler gel fraction in a well-balanced manner, and a pneumatic tire using the rubber composition. And

In the present invention, 20 to 80 parts by mass of silica and carbon black are added to 100 parts by mass of a rubber component containing 80 to 100% by mass of 100% by mass of epoxidized natural rubber having an epoxidation rate of 2 to 8% by mol. It is related with the rubber composition for tires containing 2-20 mass parts, and 4-12 mass parts of silane coupling agents 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 is preferably used as a pre-tapping rubber composition.

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

According to the present invention, 20 to 80 parts by mass of silica with respect to 100 parts by mass of the rubber component containing 80 to 100% by mass in 100% by mass of the epoxidized natural rubber having an epoxidation rate of 2 to 8% by mol, Since it is a rubber composition for tires containing 2 to 20 parts by mass of carbon black and 4 to 12 parts by mass of silane coupling agent with respect to 100 parts by mass of silica, low fuel consumption, mechanical strength, filler gel fraction Can improve in a well-balanced manner.

The rubber composition for tires of the present invention has 20 to 20 parts by weight of silica with respect to 100 parts by weight of rubber component containing 80 to 100% by weight of 100% by weight of epoxidized natural rubber having an epoxidation rate of 2 to 8% by mole. 80 parts by mass, 2-20 parts by mass of carbon black, and 4-12 parts by mass of the silane coupling agent with respect to 100 parts by mass of silica.

When a specific amount of silica, carbon black, silane coupling agent is blended with natural rubber together with a specific amount of silica, carbon black, silane coupling agent together with epoxidized natural rubber of a specific epoxidation rate In addition, the fuel economy, mechanical strength, and filler gel fraction can be improved in a more balanced manner.

In the present invention, epoxidized natural rubber (ENR) having an epoxidation rate of 2 to 8 mol% is used as the rubber component. Thereby, low fuel consumption, mechanical strength, and filler gel fraction can be improved in a 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 2 mol% or more, preferably 3 mol% or more. If the epoxidation rate is less than 2 mol%, the modification effect on the rubber composition is not sufficient, the gel amount in the rubber composition does not increase sufficiently, and the fuel economy, mechanical strength, and filler gel fraction are balanced. Cannot improve well. The epoxidation rate is 8 mol% or less, preferably 7 mol% or less. If the epoxidation rate exceeds 8 mol%, the fuel efficiency and mechanical strength deteriorate. When the epoxidation ratio is within the above range, low fuel consumption, mechanical strength, and filler gel fraction can be obtained in a well-balanced manner.

The content of ENR in 100% by mass of the rubber component is 80% by mass or more, preferably 85% by mass or more, more preferably 95% by mass or more, and further preferably 100% by mass. If it is less than 80% by mass, the fuel economy, mechanical strength, and filler gel fraction are lowered. If the epoxidation rate is ENR within the above range, two or more kinds may be used in combination.

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.

The rubber composition of the present invention contains silica. Thereby, low fuel consumption, mechanical strength, and filler gel fraction can be improved in a 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 100 m ² / g or more, more preferably 150 m ² / g or more, and further preferably 165 m ² / g or more. If it is less than 100 m < ² > / g, there exists a tendency for mechanical strength 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 20 parts by mass or more, preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 20 parts by mass, sufficient mechanical strength and filler gel fraction may not be obtained. The content is 80 parts by mass or less, preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and still more preferably 50 parts by mass or less. If it exceeds 80 parts by mass, the fuel efficiency and mechanical strength (particularly the fuel efficiency) tend to deteriorate.

The rubber composition of the present invention preferably contains a silane coupling agent together with silica. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, sulfide type, mercapto type, vinyl type, amino type, glycidoxy type, nitro type And chloro-based silane coupling agents. These silane coupling agents may be used alone or in combination of two or more. Among these, from the reason that the effects of the present invention can be obtained satisfactorily, sulfide type and mercapto type are preferable, and mercapto type (silane coupling agent having a mercapto group) is more preferable.

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.

（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 the fuel economy, mechanical strength, and filler gel fraction 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), silica is well dispersed, fuel efficiency, mechanical strength, filler gel fraction Can be improved in a more 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.

The content of the silane coupling agent is 4 parts by mass or more with respect to 100 parts by mass of silica. If the amount is less than 4 parts by mass, the silica cannot be sufficiently dispersed, and the fuel economy, mechanical strength, and filler gel fraction (particularly mechanical strength) deteriorate. Moreover, content of this silane coupling agent is 12 mass parts or less, Preferably it is 10 mass parts or less. When the amount exceeds 12 parts by mass, a coupling effect commensurate with the increase in the amount of the silane coupling agent cannot be obtained sufficiently, and the reinforcing property, fuel efficiency and mechanical strength are lowered, and the cost tends to be increased.

The rubber composition of the present invention contains carbon black. Thereby, low fuel consumption, mechanical strength, and filler gel fraction can be improved in a balanced manner. Carbon blacks that can be used include 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 thermal black (thermal carbon black) such as MT; channel black (channel carbon black) such as EPC, MPC and CC; graphite and the like. 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 5 m ² / g or more, more preferably 20 m ² / g or more, further preferably 40 m ² / g or more, and particularly preferably 60 m ² / g or more. If it is less than 5 m ² / g, sufficient reinforcing properties cannot be obtained, and sufficient mechanical strength and filler gel fraction may not be obtained. The _N 2 SA is preferably 200 meters ² / g or less, more preferably 150 meters ² / g, still more preferably 120 m ² / g or less, particularly preferably 100 m ² / g. If it exceeds 200 m ² / g, the dispersibility is poor and the fuel efficiency tends to deteriorate.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

The carbon black dibutyl phthalate oil absorption (DBP) is preferably 5 ml / 100 g or more, and more preferably 60 ml / 100 g or more. If it is less than 5 ml / 100 g, sufficient reinforcing properties cannot be obtained, and sufficient mechanical strength and filler gel fraction may not be obtained. The DBP of carbon black is preferably 300 ml / 100 g or less, more preferably 180 ml / 100 g or less, still more preferably 130 ml / 100 g or less, particularly preferably 90 ml / 100 g or less. If it exceeds 300 ml / 100 g, the dispersibility is poor 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 2 parts by mass or more, preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 2 parts by mass, sufficient reinforcing properties cannot be obtained, and sufficient mechanical strength and filler gel fraction cannot be obtained. The content is 20 parts by mass or less, preferably 15 parts by mass or less, more preferably 10 parts by mass or less. If it exceeds 20 parts by mass, heat generation will increase and fuel economy tends to deteriorate.

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. On the other hand, the total content is preferably 95% by mass or less.
When the total content is within the above range, the effects of the present invention can be obtained more suitably.

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, improvement in mechanical strength and the like obtained by combining ENR, silica, carbon black, and silane coupling agent with a specific epoxidation rate The 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 mechanical strength 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 5 parts by mass or less. When it exceeds 12 parts by mass, mechanical strength, 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.

In the present invention, the amount of oil is preferably 15 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably, with respect to 100 parts by mass of the rubber component, because the effects of the present invention can be suitably obtained. 2 parts by mass or less, particularly preferably 0 part by mass (substantially free). 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 among them, it can be suitably used as a rubber composition for pretapping that covers a cord in a carcass ply or a belt ply.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. In other words, carcass cords and belt cords are coated at an unvulcanized stage using a rubber composition containing various additives as necessary, and extruded according to the shape of the tire carcass ply and / or belt. Then, the tire can be manufactured by molding in a normal method on a tire molding machine, bonding together with other tire members to form an unvulcanized tire, and then heating and pressing in the 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) (1 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, hydrogen peroxide 22 g and acetic anhydride 23 g 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 1 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) (5 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, 108 g of hydrogen peroxide and 115 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 5 mol%.

Production Example 4 (Preparation of ENR (4) (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 (4). The epoxidation rate of the obtained ENR (4) was 10 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 1 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 5 mol%
ENR (4): ENR (4) produced in Production Example 4 and having an epoxidation rate of 10 mol%
BR: Ubepol BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass)
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 N326 (N ₂ SA: 81 m ² / g, DBP: 75 ml / 100 g) manufactured by Cabot Japan
Anti-aging agent: Antigen 3C manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Beads manufactured by NOF Corporation Tsubaki stearate Calcium stearate: Calcium stearate manufactured by NOF Corporation Zinc oxide: Zinc Hana No. 1 manufactured by Mitsui Kinzoku Co., Ltd. Sulfur: manufactured by Tsurumi Chemical Powder sulfur vulcanization accelerator (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 5, 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.
The obtained unvulcanized rubber composition is coated with a carcass cord, formed into a carcass shape, bonded together with other tire members on a tire molding machine, and press vulcanized at 160 ° C. for 20 minutes. Thus, a test tire (tire size: 195 / 65R15) was obtained.

The following evaluation was performed about the obtained unvulcanized rubber composition, the vulcanized rubber composition, and the test tire. The results are shown in Tables 1-5. In Tables 1 and 2, the reference comparative example is Comparative Example 1, and in Tables 3 to 5, the reference comparative example is Comparative Example 17.

(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

(Mechanical 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. It shows that it is excellent in mechanical strength, so that an index | exponent is large.
(Mechanical strength index) = (Mechanical strength of each formulation) / (Mechanical strength of reference comparative example) × 100

(Filler gel fraction)
About 0.5 g of an unvulcanized rubber composition was taken, finely cut, and the mass was accurately measured (Rg). Next, the mass of a 100-mesh stainless steel basket was precisely weighed (Kg), and the weighed sample was transferred to the cage to measure the mass (Rg + Kg). This was immersed in a bottle with a stopper containing 100 mL of toluene and left at 23 ° C. for 24 hours. Next, the basket is pulled up, dried at 23 ° C. for 24 hours, and then dried under reduced pressure for 24 hours so as to become a constant weight at 70 ° C., and the toluene-insoluble matter is accurately weighed together with the cage (Gg + Kg). The filler gel fraction was determined.
Filler gel fraction (mass%) = 100 × [GR × (filler mass / total rubber composition mass)] / [R × (rubber mass / rubber composition total mass)]
However,
Filler part by mass: Total mass part of rubber composition of silica and carbon black in each formulation of Tables 1 to 5 Total part of rubber composition: Total part by mass of total composition of each formulation in Tables 1 to 5: Tables 1 to 5 Using the filler gel fraction of each formulation obtained by the above formula for the total mass parts of the rubber components of each formulation, the filler gel fraction (index) of each formulation was indicated by an index from the following formula.
(Filler gel fraction (index)) = (Filler gel fraction of each formulation) / (Filler gel fraction of reference comparative example) × 100
In addition, the larger the index, the higher the filler gel fraction, indicating that the interaction between the filler (carbon black, silica) and the rubber component is stronger.

From the results of Tables 1 to 5, examples containing specific amounts of epoxidized natural rubber having a specific epoxidation rate, silica, carbon black, and a silane coupling agent are low fuel consumption, mechanical strength, filler gel The fraction was improved in a well-balanced manner.

Claims (4)

20 to 80 parts by mass of silica and 2 to 20 carbon black with respect to 100 parts by mass of rubber component containing 80 to 100% by mass of 100% by mass of epoxidized natural rubber having an epoxidation rate of 2 to 8 mol% A rubber composition for a tire containing 4 to 12 parts by mass of a silane coupling 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, which is used as a rubber composition for pre-tapping. The pneumatic tire produced using the rubber composition in any one of Claims 1-3.