JP2011079883A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition capable of highly balancing and improving wet grip performance, environmental performance (reduced rolling resistance, measures against petroleum resource exhaustion, CO<SB>2</SB>emission reduction) and durability performance (crack resistance, abrasion resistance), and a pneumatic tire using the same. <P>SOLUTION: The rubber composition comprises: at least three rubbers chosen from the group consisting of a natural rubber, an epoxidized natural rubber, an unmodified styrene butadiene rubber and butadiene rubber; and a modified styrene butadiene rubber modified by formula (1) (wherein R<SP>1</SP>, R<SP>2</SP>and R<SP>3</SP>are identical to or different from each other and each represents alkyl group, alkoxy group, silyloxy group, acetal group, carboxyl group, mercapto group or derivatives thereof; R<SP>4</SP>and R<SP>5</SP>are identical to or different from each other and each represents hydrogen atom, alkyl group or cyclic ether group; and n is an integer) or formula (2) (wherein R<SP>6</SP>, R<SP>7</SP>and R<SP>8</SP>are identical to or different from each other and each represents alkyl group, alkoxy group, silyloxy group, acetal group, carboxyl group, mercapto group or derivatives thereof; R<SP>9</SP>represents cyclic ether group; and p and q are each an integer). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

In recent years, rubber compositions for tire treads composed mainly of natural rubber or the like have been proposed from the viewpoints of depletion of petroleum resources, reduction of rolling resistance, and consideration for the environment (reduction of CO ₂ emissions). However, when only natural rubber is used as a rubber component, there is a problem that wet grip performance is inferior compared with a tread using conventional SBR or the like.

For this reason, attempts have been made to improve wet grip performance while using epoxidized natural rubber as a tread and actively working to cope with the depletion of petroleum resources and reduce CO ₂ emissions. However, with epoxidized natural rubber alone, compared to conventional SBR treads, especially when used in high-performance (high flatness) tires and tires for heavy-duty vehicles even in passenger cars, in terms of crack resistance and wear resistance. Further improvements are needed. As crack resistance performance, it is necessary to suppress the occurrence of cracks along the groove direction at the bottom of the tread groove (cracks generated by repeated deformation of the groove bottom).

Patent Documents 1 and 2 include a rubber for tire tread having high wear resistance, low rolling resistance, and good wet skid performance by blending a polybutadiene rubber modified with a silicon compound having an amino group and an alkoxy group. A composition is disclosed. However, even if such modified polybutadiene is used, wet grip performance, environmental performance (reduction of rolling resistance, response to depletion of petroleum resources, consideration for CO ₂ emissions) and durability performance (crack resistance performance, There is still room for improvement in terms of improving the wear resistance performance) in a high-dimensional and well-balanced manner.

JP 2000-159814 A JP 2000-344955 A

The present invention solves the above-mentioned problems, wet grip performance, environmental performance (reducing rolling resistance, dealing with exhaustion of petroleum resources, considering CO ₂ emissions), and durability performance (crack resistance performance, wear resistance performance). And a pneumatic tire using the rubber composition.

The present invention relates to three or more rubbers selected from the group consisting of natural rubber, epoxidized natural rubber, unmodified styrene butadiene rubber, and butadiene rubber, and a compound represented by the following formula (1) or (2) The present invention relates to a rubber composition containing a modified styrene butadiene rubber modified by the above.

（式中、Ｒ^１、Ｒ^２及びＲ^３は、同一若しくは異なって、アルキル基、アルコキシ基、シリルオキシ基、アセタール基、カルボキシル基、メルカプト基又はこれらの誘導体を表す。Ｒ^４及びＲ^５は、同一若しくは異なって、水素原子、アルキル基又は環状エーテル基を表す。ｎは整数を表す。）

(Wherein R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different and represents a hydrogen atom, an alkyl group or a cyclic ether group. N represents an integer.)

（式中、Ｒ^６、Ｒ^７及びＲ^８は、同一若しくは異なって、アルキル基、アルコキシ基、シリルオキシ基、アセタール基、カルボキシル基、メルカプト基又はこれらの誘導体を表す。Ｒ^９は、環状エーテル基を表す。ｐ及びｑは整数を表す。）

(Wherein R ⁶ , R ⁷ and R ⁸ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁹ is a cyclic ether group. P and q represent integers.

The rubber composition contains 10 to 20% by mass of natural rubber, 1 to 5% by mass of epoxidized natural rubber, 15 to 60% by mass of modified styrene butadiene rubber, and 20 to 40% of butadiene rubber in 100% by mass of the rubber component. It is preferable to contain by mass.

In the rubber composition, the total content of natural rubber, epoxidized natural rubber, modified styrene butadiene rubber, non-modified styrene butadiene rubber and butadiene rubber in 100% by mass of the rubber component is preferably 100% by mass.

The rubber composition preferably contains 45 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.
The rubber composition preferably has an epoxidation rate of epoxidized natural rubber of 10 to 50 mol%.

The rubber composition is preferably a tread rubber composition.

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

According to the present invention, three or more kinds of rubber selected from the group consisting of natural rubber, epoxidized natural rubber, non-modified styrene butadiene rubber, and butadiene rubber, and modified styrene butadiene rubber modified with a specific compound, Because it contains a rubber composition, it has wet grip performance, environmental performance (reduction of rolling resistance, response to petroleum resource depletion, consideration for CO ₂ emissions) and durability performance (crack resistance performance, wear resistance performance) Can be improved in a well-balanced manner in a high dimension, and a pneumatic tire using the rubber composition can be provided.

The rubber composition of the present invention comprises three or more rubbers selected from the group consisting of natural rubber (NR), epoxidized natural rubber (ENR), unmodified styrene butadiene rubber (SBR), and butadiene rubber (BR). And a modified styrene butadiene rubber (modified SBR) modified with the compound represented by the above formula (1) or (2).

In the compound represented by the above formula (1), R ¹ , R ² and R ³ are the same or different and are an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (— SH) or derivatives thereof. Examples of the alkyl group include an alkyl group having 1 to 4 carbon atoms (preferably having 1 to 3 carbon atoms) such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a t-butyl group. Etc. Examples of the alkoxy group include alkoxy groups having 1 to 8 carbon atoms such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group and t-butoxy group (preferably having 1 to 6 carbon atoms). More preferably, C1-C4) etc. are mentioned. The alkoxy group includes a cycloalkoxy group (cycloalkoxy group having 5 to 8 carbon atoms such as cyclohexyloxy group) and an aryloxy group (aryloxy group having 6 to 8 carbon atoms such as phenoxy group and benzyloxy group). ) Is also included.

Examples of the silyloxy group include a silyloxy group substituted with an aliphatic group having 1 to 20 carbon atoms and an aromatic group (trimethylsilyloxy group, triethylsilyloxy group, triisopropylsilyloxy group, diethylisopropylsilyloxy group, t- Butyldimethylsilyloxy group, t-butyldiphenylsilyloxy group, tribenzylsilyloxy group, triphenylsilyloxy group, tri-p-xylylsilyloxy group, etc.).

Examples of the acetal group include groups represented by -C (RR ')-OR "and -O-C (RR')-OR". Examples of the former include a methoxymethyl group, an ethoxymethyl group, a propoxymethyl group, a butoxymethyl group, an isopropoxymethyl group, a t-butoxymethyl group, and a neopentyloxymethyl group. The latter includes a methoxymethoxy group, an ethoxy group, and the like. Methoxy group, propoxymethoxy group, i-propoxymethoxy group, n-butoxymethoxy group, t-butoxymethoxy group, n-pentyloxymethoxy group, n-hexyloxymethoxy group, cyclopentyloxymethoxy group, cyclohexyloxymethoxy group, etc. Can be mentioned. As R ¹ , R ^2, and R ³ , an alkoxy group and an alkyl group are preferable because fuel efficiency (rolling resistance) can be remarkably improved.

In the compound represented by the formula (1), examples of the alkyl group of R ⁴ and R ⁵ include the same groups as the alkyl group.

In the compound represented by the formula (1), examples of the cyclic ether group of R ⁴ and R ⁵ include an oxirane group, an oxetane group, an oxolane group, an oxane group, an oxepane group, an oxocan group, an oxonan group, an oxecan group, Cyclic ether group having one ether bond such as oxet group and oxol group, cyclic ether group having two ether bonds such as dioxolane group, dioxane group, dioxepane group and dioxecan group, and three ether bonds such as trioxane group Examples include cyclic ether groups. Among these, a C2-C7 cyclic ether group having one ether bond is preferable, and a C3-C5 cyclic ether group having one ether bond is more preferable. The cyclic ether group preferably has no unsaturated bond in the ring skeleton.

As n (integer), 1-5 are preferable from the reason of the heat-resistant stability of a compound. Furthermore, n is more preferably 2 to 4, and most preferably 3. When n is 0, it is difficult to bond a silicon atom and a nitrogen atom, and when n is 6 or more, the effect as a modifier is reduced.

Specific examples of the compound represented by the above formula (1) include 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, Aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethylbutoxysilane, 3-aminopropylmethyldibutoxysilane, dimethylaminomethyltrimethoxysilane, 2-dimethyl Aminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 4-dimethylaminobutyltrimethoxysilane, dimethylaminomethyldimethoxymethylsilane, 2-dimethylaminoethyldimethoxy Methylsilane, 3-dimethylaminopropyldimethoxymethylsilane, 4-dimethylaminobutyldimethoxymethylsilane, dimethylaminomethyltriethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 4-dimethylaminobutyl Triethoxysilane, dimethylaminomethyldiethoxymethylsilane, 2-dimethylaminoethyldiethoxymethylsilane, 3-dimethylaminopropyldiethoxymethylsilane, 4-dimethylaminobutyldiethoxymethylsilane, diethylaminomethyltrimethoxysilane, 2- Diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 4-diethylaminobutyltrimethoxysilane, diethylamino Tildimethoxymethylsilane, 2-diethylaminoethyldimethoxymethylsilane, 3-diethylaminopropyldimethoxymethylsilane, 4-diethylaminobutyldimethoxymethylsilane, diethylaminomethyltriethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane 4-diethylaminobutyltriethoxysilane, diethylaminomethyldiethoxymethylsilane, 2-diethylaminoethyldiethoxymethylsilane, 3-diethylaminopropyldiethoxymethylsilane, 4-diethylaminobutyldiethoxymethylsilane, the following formulas (3) to ( 10) and the like. These may be used alone or in combination of two or more. Of these, 3-aminopropyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, and a compound represented by the following formula (3) are preferred because fuel economy (rolling resistance) can be remarkably improved.

In the compound represented by the above formula (2), R ⁶ , R ⁷ and R ⁸ are the same as R ¹ , R ² and R ³ in the compound represented by the above formula (1).

In the compound represented by the above formula (2), examples of the cyclic ether group of R ⁹ include the same groups as the cyclic ether groups of R ⁴ and R ⁵ in the compound represented by the above formula (1). Among these, a C2-C7 cyclic ether group having one ether bond is preferable, and a C2-C4 cyclic ether group having one ether bond is more preferable. The cyclic ether group preferably has no unsaturated bond in the ring skeleton.

As p (integer), 1-5 are preferable from the reason of the heat-resistant stability of a compound. Further, p is more preferably from 2 to 4, and most preferably 3. When p is 0, the compound is unstable and mass production is difficult, and when p is 6 or more, the effect as a denaturant is diminished.

q (integer) is preferably 1 to 5 because of the heat stability of the compound. Furthermore, q is more preferably 1 to 3, and most preferably 1. When q is 0, the compound is unstable and mass production is difficult, and when q is 6 or more, the effect as a denaturing agent is reduced.

Specific examples of the compound represented by the above formula (2) include 3-glycidoxypropyltrimethoxysilane (compound represented by the following formula (11)), 3-glycidoxypropylmethyldimethoxysilane, 3- Glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethylmethyldimethoxysilane, 2-glycidoxyethyltriethoxysilane, 2 -Glycidoxyethylmethyldiethoxysilane, 4-glycidoxybutyltrimethoxysilane, 4-glycidoxybutylmethyldimethoxysilane, 4-glycidoxybutyltriethoxysilane, 4-glycidoxybutylmethyldiethoxysilane , Glycidoxymethyltrimethoxysilane, glycidoxy Triethoxysilane, include compounds represented by the following formula (12) to (15). These may be used alone or in combination of two or more. Among these, 3-glycidoxypropyltrimethoxysilane (a compound represented by the following formula (11)) is preferable because fuel saving performance (rolling resistance) can be remarkably improved.

Methods for modifying styrene butadiene rubber (SBR) with the compound (modifier) represented by the above formula (1) or (2) are described in JP-B-6-53768, JP-B-6-57767, and the like. A conventionally known method such as the above method can be used. For example, SBR may be brought into contact with a modifier, such as a method of polymerizing SBR and adding a predetermined amount of the modifier to the polymer rubber solution, a method of reacting by adding a modifier to the SBR solution, and the like. Can be mentioned.

The styrene butadiene rubber (SBR) to be modified is not particularly limited, and those commonly used in the tire industry can be used.

By containing the modified SBR, the rubber composition of the present invention can achieve good wear resistance, crack resistance, wet grip performance, and reduction in rolling resistance. With regard to wear resistance and crack resistance, particularly when used in high performance (high flatness) tires and tires for heavy-duty vehicles even in passenger cars, good performance is exhibited.

The cis content of the modified SBR is preferably 35% by mass or less, more preferably 30% by mass or less, and still more preferably 25% by mass or less. When the cis content exceeds 35% by mass, the extrusion processability tends to be inferior. The cis content of the modified SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more. If it is less than 10% by mass, the wear resistance tends to deteriorate.
The cis content (cis-1,4-bonded butadiene unit amount) can be measured by infrared absorption spectrum analysis.

The vinyl content of the modified SBR is preferably 70% by mass or less, more preferably 65% by mass or less, and still more preferably 60% by mass or less. When the vinyl content exceeds 70% by mass, low heat build-up tends to be impaired. The vinyl content of the modified SBR is preferably 45% by mass or more, more preferably 50% by mass or more, and further preferably 55% by mass or more. If it is less than 45% by mass, the wear resistance tends not to be sufficiently improved.
The vinyl content (1,2-bond butadiene unit amount) can be measured by infrared absorption spectrum analysis.

The content of the modified SBR in 100% by mass of the rubber component is preferably 15% by mass or more, more preferably 20% by mass or more, and further preferably 25% by mass or more. If it is less than 15% by mass, the wet grip performance tends to be lowered, and further, the rolling resistance tends not to be sufficiently reduced. The content of the modified SBR is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 45% by mass or less, and particularly preferably 43% by mass or less. When it exceeds 60% by mass, kneading workability tends to be remarkably deteriorated.

Examples of rubber components other than the modified SBR used in the rubber composition include diene rubbers. For example, NR, ENR, BR, SBR, isoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR). ), Halogenated butyl rubber (X-IIR), chloroprene rubber (CR), acrylonitrile (NBR), a halide of a copolymer of isomonoolefin and paraalkylstyrene, and the like. Above all, we have a high-level balance between wet grip performance, environmental performance (reduction of rolling resistance, response to depletion of petroleum resources, consideration for CO ₂ emissions) and durability performance (crack resistance, wear resistance). From the viewpoint of good improvement, it is preferable to use NR, ENR, BR together with the modified SBR, and it is more preferable to use NR, ENR, BR, SBR together with the modified SBR.

The NR is not particularly limited, and for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20, and the like can be used.

The content of NR in 100% by mass of the rubber component is preferably 7% by mass or more, more preferably 10% by mass or more. If it is less than 7% by mass, the breaking strength tends to decrease. The content of NR is preferably 30% by mass or less, more preferably 20% by mass or less. If it exceeds 30% by mass, the wet grip performance tends to decrease.

The ENR is not particularly limited, and may be a commercially available epoxidized natural rubber, an epoxidized natural rubber, or a liquid epoxidized natural rubber. Examples of a method for epoxidizing natural rubber include a method of reacting natural rubber with an organic peracid such as peracetic acid or performic acid.

The epoxidation rate of ENR is preferably 10 mol% or more, and preferably 20 mol% or more. When the epoxidation rate is less than 10 mol%, there is a tendency that rolling resistance cannot be sufficiently reduced. Moreover, it is preferable that an epoxidation rate is 50 mol% or less, and it is more preferable that it is 30 mol% or less. When the epoxidation rate exceeds 50 mol%, kneading workability tends to deteriorate.

The content of ENR in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 3% by mass or more. If it is less than 1% by mass, the rolling resistance tends not to be sufficiently reduced. The content of ENR is preferably 7% by mass or less, more preferably 5% by mass or less. If it exceeds 7 mass%, the breaking strength tends to decrease.

When the rubber composition of the present invention contains ENR, good wet grip performance is obtained along with good environmental performance (reduction in rolling resistance, response to petroleum resource depletion, consideration for CO ₂ emissions). Can do. Moreover, rolling resistance can be effectively reduced by using modified SBR and ENR together.

The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B and other high cis content BR, VCR412 manufactured by Ube Industries, Inc., VCR617, etc. BR containing syndiotactic polybutadiene crystals can be used. Although the cis content of BR is not particularly limited, it is preferably 93% by mass or more because it has good wear resistance and crack resistance.

The content of BR in 100% by mass of the rubber component is preferably 17% by mass or more, more preferably 20% by mass or more, and further preferably 25% by mass or more. If it is less than 17% by mass, the crack resistance tends to deteriorate. The content of BR is preferably 43% by mass or less, more preferably 40% by mass or less, and still more preferably 38% by mass or less. When it exceeds 43 mass%, kneading workability tends to deteriorate.

The SBR (non-modified styrene butadiene rubber) is not particularly limited, and examples thereof include emulsion polymerization SBR (E-SBR) and solution polymerization SBR (S-SBR), and the reason that kneadability is good. Therefore, E-SBR is preferable.

The cis content of SBR is preferably 25% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less. When the cis content exceeds 25% by mass, the extrusion processability tends to be inferior. The cis content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 13% by mass or more. If it is less than 13% by mass, the wear resistance tends to deteriorate.
The cis content (cis-1,4-bonded butadiene unit amount) can be measured by infrared absorption spectrum analysis.

The vinyl content of SBR is preferably 25% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less. When the vinyl content exceeds 25% by mass, the low exothermic property tends to be impaired. The vinyl content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 13% by mass or more.
If it is less than 13% by mass, the wear resistance tends not to be sufficiently improved.
The vinyl content (1,2-bond butadiene unit amount) can be measured by infrared absorption spectrum analysis.

The content of SBR in 100% by mass of the rubber component is preferably 17% by mass or more, more preferably 20% by mass or more. If it is less than 17% by mass, wet grip performance and kneading workability tend to deteriorate. The content of SBR is preferably 43% by mass or less, more preferably 35% by mass or less. When it exceeds 43 mass%, there exists a tendency for reduction of rolling resistance not to be seen.

When the content of the modified SBR, NR, ENR, BR, and SBR in 100% by mass of the rubber component is within the above-mentioned preferable ranges, respectively, wet grip performance and environmental performance (reducing rolling resistance and dealing with depletion of petroleum resources) , CO ₂ emission considerations) and durability performance (crack resistance performance, wear resistance performance) can be improved at a higher level and in a well-balanced manner.

In the present invention, the total content of modified SBR, NR, ENR, BR, and SBR in 100% by mass of the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass. . If the total content is less than 80% by mass, sufficient rubber physical properties may not be obtained.

The rubber composition of the present invention preferably contains silica. Thereby, improvement of wet grip performance and reduction of rolling resistance can be aimed at. Examples of the silica include, but are not limited to, dry method silica (anhydrous silicic acid), wet method silica (anhydrous silicic acid), and the like, and wet method silica is preferable because it has many silanol groups. Silica may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of the silica is preferably 100 m ² / g or more, more preferably 120 m ² / g or more. If it is less than 100 m ² / g, the reinforcing property is not sufficient, and the wear resistance of the tire tends to deteriorate. Further, N ₂ SA of silica is preferably 300 m ² / g or less, more preferably 250 m ² / g or less. When it exceeds 300 m < ² > / g, the dispersibility of a silica will fall and there exists a tendency for heat_generation | fever to deteriorate.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

When the rubber composition of the present invention contains silica, the content of silica is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. Most preferably, it is 45 parts by mass or more. If it is less than 20 parts by mass, it tends to be impossible to achieve both improvement of wet grip performance and reduction of rolling resistance. The content of the silica is preferably 60 parts by mass or less, more preferably 55 parts by mass or less. When it exceeds 60 parts by mass, the viscosity at the time of kneading increases and the workability tends 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, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-tri Ethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilyl) Butyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) Trisulfi Bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4 -Triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropylbenzothiazoli And sulfide systems such as tetratetrasulfide and 3-triethoxysilylpropylbenzothiazole tetrasulfide. Moreover, mercapto type, vinyl type, glycidoxy type, nitro type, chloro type and the like can also be mentioned. Of these, bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide are preferably used from the viewpoint of the reinforcing effect and processability of the silane coupling agent. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 3 parts by mass or more and more preferably 7 parts by mass or more with respect to 100 parts by mass of the silica. If it is less than 3 parts by mass, the fracture strength tends to be greatly reduced. Moreover, 15 mass parts or less are preferable, and, as for content of this silane coupling agent, 10 mass parts or less are more preferable. When the amount exceeds 15 parts by mass, effects such as an increase in fracture strength and a reduction in rolling resistance due to the addition of the silane coupling agent tend not to be obtained.

The rubber composition of the present invention preferably contains carbon black. As a result, both wet grip performance and wear resistance can be improved. Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² / g or more, and more preferably 100 m ² / g or more. If it is less than 80 m < ² > / g, there exists a tendency for grip performance and abrasion resistance to fall. Further, the nitrogen adsorption specific surface area of carbon black is preferably 280 m ² / g or less, and more preferably 200 m ² / g or less. If it exceeds 280 m ² / g, good dispersion is difficult to obtain, and the wear resistance tends to decrease.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

When the rubber composition of the present invention contains carbon black, the content of carbon black is preferably 10 parts by mass or more, more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, the wear resistance tends to deteriorate. The carbon black content is preferably 35 parts by mass or less, more preferably 30 parts by mass or less. When it exceeds 35 parts by mass, processability and fuel efficiency (rolling resistance) tend to deteriorate.

When the rubber composition of the present invention contains carbon black and silica, the ratio of carbon black to silica (silica / carbon black) is preferably 1.5 or more, more preferably 1.67 or more. If it is less than 1.5, there is a tendency that environmental performance (reduction of rolling resistance, response to oil resource depletion, consideration for CO ₂ emissions) cannot be sufficiently improved. Silica / carbon black is preferably 2.5 or less, more preferably 2.25 or less. If it exceeds 2.5, the balance between rolling resistance and grip performance may be deteriorated.

The rubber composition of the present invention preferably contains oil or a plasticizer. Thereby, kneading | mixing and extrusion workability become favorable. As the oil, for example, paraffinic process oil, aroma based process oil, naphthenic process oil, and the like can be used. Among these, paraffinic process oil is preferably used because the compatibility between the modified SBR and silica is improved. Specific examples of the paraffinic process oil include PW-32, PW-90, PW-150, and PS-32 manufactured by Idemitsu Kosan Co., Ltd. Specific examples of the aroma-based process oil include AC-12, AC-460, AH-16, AH-24, and AH-58 manufactured by Idemitsu Kosan Co., Ltd.

When the said rubber composition contains oil or a plasticizer, 10 mass parts or more are preferable with respect to 100 mass parts of rubber components, and 20 mass parts or more are more preferable. When it is less than 10 parts by mass, kneading workability tends to deteriorate. On the other hand, the amount is preferably 35 parts by mass or less, more preferably 25 parts by mass or less, with respect to 100 parts by mass of the rubber component. When it exceeds 35 parts by mass, heat generation increases, and fuel efficiency may be deteriorated.

In addition to the rubber component, silica, silane coupling agent, carbon black, oil, and plasticizer, the rubber composition of the present invention includes a compounding agent that is generally used in the production of a rubber composition, such as clay reinforcement. Fillers, zinc oxide, stearic acid, various anti-aging agents, waxes, sulfur and other vulcanizing agents, vulcanization accelerators, and the like can be appropriately blended.

Examples of the vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N′-dicyclohexyl-2- Examples include benzothiazolylsulfenamide (DZ), mercaptobenzothiazole (MBT), dibenzothiazolyl disulfide (MBTS), and diphenylguanidine (DPG). Among these, TBBS is preferable because it is thermally stable and has excellent dispersibility in the rubber composition, and it is more preferable to use TBBS and DPG in combination.

As a method for producing the rubber composition of the present invention, a known method can be used. For example, the above components are kneaded using a rubber kneader such as an open roll or a Banbury mixer, and then vulcanized. Can be manufactured.

Although the rubber composition of the present invention can be used for each member of a tire, it can be suitably applied to a tread. The tread can be used for a tread having a single layer structure, but can also be used for a cap tread having a multilayer structure (such as a two-layer structure including a cap tread and a base tread). The tread can be produced by pasting a sheet into a predetermined shape, or by inserting it into two or more extruders and forming it in two layers at the head outlet of the extruder.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, if necessary, a rubber composition containing various additives is extruded into a tread shape at an unvulcanized stage, molded by a normal method on a tire molding machine, and other tire members The tires can be produced by pasting together to form an unvulcanized tire and then heating and pressing in a vulcanizer.

The tire of the present invention is suitably used as a passenger car tire, bus tire, truck tire, and the like.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: RSS # 3 made by Tef Binhague
BR: BR150B manufactured by Ube Industries, Ltd. (cis content 93% by mass)
SBR: ZBR 1502 manufactured by Nippon Zeon (cis content: 14% by mass, vinyl content: 15% by mass, non-modified)
Modified SBR: Modified styrene butadiene rubber manufactured by Sumitomo Chemical Co., Ltd. (cis content: 28 mass%, vinyl content 56 mass%, R ¹ , R ² and R ³ = —OCH ₃ , R ⁴ and R ⁵ = —CH ₂ CH ₃ , n = 3)
ENR: ENR25 manufactured by Guthrie Polymer SDN, BHD (epoxidation rate: 25 mol%)
Carbon black: Show Black N220 (N ₂ SA 125 m ² / g) manufactured by Cabot Japan
Silica: Ultrazil (N ₂ SA 210 m ² / g) manufactured by Degussa
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Mineral oil: PS-32 (paraffinic process oil) manufactured by Idemitsu Kosan Co., Ltd.
Zinc oxide: Zinc Hua 1 manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. (1): Noxeller CZ manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator (2): Noxeller NS manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator (3): Noxeller DPG manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-17 and Comparative Examples 1-8
In accordance with the formulation shown in Tables 1 to 3, materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes at 150 ° C. using a 1.7 L 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 an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized with a 2 mm thick mold at 170 ° C. for 15 minutes to obtain a vulcanized rubber composition.

(Rolling resistance performance)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), tan δ of each vulcanized rubber composition was measured under conditions of a temperature of 50 ° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz. With the rolling resistance index of the reference formulation (Comparative Example 1 (Table 1) or Comparative Example 4 (Tables 2 and 3)) as 100, the rolling resistance performance was indicated by an index according to the following formula. The smaller the rolling resistance index, the lower the rolling resistance and the better the rolling resistance performance.
(Rolling resistance index) = (tan δ of each formulation / tan δ of the standard formulation) × 100

(Abrasion resistance)
Vulcanized rubber specimens for lamborn abrasion test obtained from each vulcanized rubber composition under the conditions of load load of 2.5 kg, temperature of 20 ° C., slip rate of 40%, test time of 2 minutes with a lamborn abrasion tester. The amount of volume loss of each blend was calculated, and the wear resistance index of the reference blend (Comparative Example 1 (Table 1) or Comparative Example 4 (Tables 2 and 3)) was calculated. Assuming 100, the wear resistance performance was indicated by an index according to the following formula. The larger the wear resistance index, the better the wear resistance.
(Abrasion resistance performance index) = (volume loss amount of reference blend / volume loss amount of each blend) × 100

(Wet grip performance)
Using a portable skid tester manufactured by Stanley, the maximum friction coefficient of each vulcanized rubber composition was measured according to the method of ASTM E303-83, and the reference blend (Comparative Example 1 (Table 1) or Comparative Example 4 (Table The wet grip performance index of 2, 3)) was set to 100, and the index was expressed by the following formula. The larger the wet grip performance index, the better the wet grip performance.
(Wet grip performance index) = (Numerical value of each formulation / Numerical value of standard formulation) × 100

(Crack resistance)
In accordance with JIS K 6252 “Vulcanized Rubber and Thermoplastic Rubber—How to Obtain Tear Strength”, tear strength (N / mm) was measured, and the tear strength index of the reference formulation (Comparative Example 1 (Table 1) or Example 2 (Tables 2 and 3)) was set to 100, and the tear strength was expressed as an index by the following formula. The larger the tear strength index, the greater the tear strength and the better the crack resistance.
(Tear Strength Index) = (Tear Strength of Each Formulation / Tear Strength of Reference Formula) × 100

From Table 1, in Example 1 containing four types of rubber components of modified SBR, NR, BR, and ENR, Comparative Examples 1 to 2 containing modified SBR and two types of rubber components of NR, BR, and ENR Compared with 3, it was excellent in all of rolling resistance performance, wear resistance performance, wet grip performance, and crack resistance performance. Further, by containing NR and ENR, it is possible to cope with the depletion of petroleum resources and to consider CO ₂ emissions.

From Tables 2 and 3, the examples containing the five types of rubber components modified SBR, NR, BR, ENR, and SBR are more resistant to rolling resistance and resistance than the comparative examples not containing the five types of rubber components. It was excellent in all of wear performance, wet grip performance, and crack resistance performance. Further, by containing NR and ENR, it is possible to cope with the depletion of petroleum resources and to consider CO ₂ emissions. Moreover, when the amount of NR increased, the crack resistance performance decreased, and when the amount of BR increased, the crack resistance performance tended to improve.

Claims (7)

Modified by a compound represented by the following formula (1) or (2) and at least three kinds of rubbers selected from the group consisting of natural rubber, epoxidized natural rubber, non-modified styrene butadiene rubber, and butadiene rubber A rubber composition containing a modified styrene butadiene rubber.

(Wherein R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different and represents a hydrogen atom, an alkyl group or a cyclic ether group. N represents an integer.)

(Wherein R ⁶ , R ⁷ and R ⁸ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁹ is a cyclic ether group. P and q represent integers. The rubber component contains 7 to 30% by mass of natural rubber, 1 to 7% by mass of epoxidized natural rubber, 15 to 60% by mass of modified styrene butadiene rubber, and 17 to 43% by mass of butadiene rubber in 100% by mass of the rubber component. The rubber composition according to 1. The rubber composition according to claim 1 or 2, wherein the total content of natural rubber, epoxidized natural rubber, modified styrene butadiene rubber, unmodified styrene butadiene rubber and butadiene rubber in 100% by mass of the rubber component is 100% by mass. . The rubber composition according to any one of claims 1 to 3, comprising 20 parts by mass or more of silica with respect to 100 parts by mass of the rubber component. The rubber composition according to any one of claims 1 to 4, wherein the epoxidized natural rubber has an epoxidation rate of 10 to 50 mol%. The rubber composition according to any one of claims 1 to 5, wherein the rubber composition is a rubber composition for treads. The pneumatic tire which has a tread produced using the rubber composition in any one of Claims 1-6.