JP6907598B2 - Rubber composition for tires and pneumatic tires - Google Patents

Description

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

Pneumatic tires are strongly required to improve steering stability such as braking performance especially at high speeds. In textile coat compounds, a method of improving hardness and improving rigidity is known as a method of improving steering stability. In order to improve the rigidity, a method such as a high blending of filler can be mentioned, but in such a blending, the rolling resistance of the compound increases, so that heat generation increases and fuel efficiency is deteriorated. Therefore, it has been difficult to improve the steering stability and rolling resistance of the pneumatic tire at the same time.

As a composition for a tire having reduced rolling resistance (heat generation) when made into a tire, for example, Patent Document 1 contains a diene rubber and carbon black, and the diene rubber is a natural rubber and a conjugated diene. The content of the natural rubber in the diene rubber is 60% by mass or more, and the diene rubber contains a modified polymer obtained by reacting a nitron compound with a double bond of the polymer. The content of the modified polymer is 8 to 40% by mass, the content of the carbon black is 30 to 67 parts by mass with respect to 100 parts by mass of the diene rubber, and the nitrogen adsorption specific surface area of the carbon black is A rubber composition for undertread, which is 20 to 60 m ² / g, is disclosed (claim 1).

JP-A-2015-218240

When the present inventors examined the rubber composition for under tread described in Patent Document 1, it was found that it exhibits excellent rolling resistance performance when made into a tire, but it is not mentioned in Patent Document 1. Regarding steering stability, it was clarified that there is room for improvement.

Therefore, it is an object of the present invention to provide a rubber composition for a tire that exhibits excellent steering stability and rolling resistance performance when made into a tire, and a pneumatic tire using this rubber composition for a tire.

As a result of diligent studies to solve the above problems, the present inventors have made diene-based rubber and carbon black, and the diene-based rubber contains a specific amount of a specific aromatic vinyl-conjugated diene copolymer. A rubber composition for a tire containing, the content of the carbon black is within a specific range, and the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is within a specific range, is excellent in maneuvering when made into a tire. Knowing that it exhibits stability and rolling resistance, the present invention has been completed.
That is, the present inventors have found that the above problems can be solved by the following configuration.

式（Ｎ）中、Ｒ^１は水素原子又はアルキル基を表し、Ｒ^２はアルキレン基を表す。
［４］ 上記［１］〜［３］のいずれか１つに記載のタイヤ用ゴム組成物をアンダートレッドに配置した空気入りタイヤ。
［５］ 上記［１］〜［３］のいずれか１つに記載のタイヤ用ゴム組成物をカーカスコートゴムに配置した空気入りタイヤ。
［６］ 上記［１］〜［３］のいずれか１つに記載のタイヤ用ゴム組成物をタイゴムに配置した空気入りタイヤ。
［７］ 上記［１］〜［３］のいずれか１つに記載のタイヤ用ゴム組成物をビードインシュレーションゴムに配置した空気入りタイヤ。 [1] A rubber composition for a tire containing a diene-based rubber and carbon black.
The diene-based rubber contains 5 to 30% by mass of an aromatic vinyl-conjugated diene copolymer.
The content of the carbon black is 30 to 80 parts by mass with respect to 100 parts by mass of the diene rubber.
The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is 30 to 90 m ² / g.
The aromatic vinyl-conjugated diene copolymer is a copolymer of an aromatic vinyl compound and a conjugated diene compound, and the content of the repeating unit derived from the aromatic vinyl compound is 18% by mass or more. Among the repeating units derived from the conjugated diene compound, the ratio of the vinyl structure is 8 mol% or less, the ratio of the 1,4-trans structure is 75 mol% or less, and the ratio of the 1,4-cis structure is 17. A copolymer of an aromatic vinyl compound and a conjugated diene compound, which is ~ 90 mol% and has a glass transition temperature of −60 ° C. or lower.
Rubber composition for tires.
[2] The proportion of the 1,4-trans structure of the aromatic vinyl-conjugated diene copolymer is 70 mol% or less, and the proportion of the 1,4-cis structure is 30 to 85 mol%. The rubber composition for a tire according to [1].
[3] The aromatic vinyl-conjugated diene copolymer is composed of titanium halide, tin halide, cyclic silazane, alkoxysilane, epoxide, amine, ketone and a compound represented by the following formula (N) at the terminal. The rubber composition for a tire according to the above [1] or [2], which is an aromatic vinyl-conjugated diene copolymer modified with at least one modifier selected from the group.

In formula (N), R ¹ represents a hydrogen atom or an alkyl group, and R ² represents an alkylene group.
[4] A pneumatic tire in which the rubber composition for a tire according to any one of the above [1] to [3] is arranged on an undertread.
[5] A pneumatic tire in which the rubber composition for a tire according to any one of the above [1] to [3] is arranged on a carcass coated rubber.
[6] A pneumatic tire in which the tire rubber composition according to any one of the above [1] to [3] is arranged on a tie rubber.
[7] A pneumatic tire in which the rubber composition for a tire according to any one of the above [1] to [3] is arranged on a bead insulation rubber.

According to the present invention, it is possible to provide a rubber composition for a tire that exhibits excellent steering stability and rolling resistance performance when made into a tire, and a pneumatic tire using the rubber composition for a tire.

It is a partial cross-sectional schematic diagram of the tire which shows an example of embodiment of the pneumatic tire of this invention. It is a partial cross-sectional schematic diagram of the bead core of the tire which shows an example of embodiment of the pneumatic tire of this invention.

The rubber composition for a tire of the present invention and the pneumatic tire of the present invention will be described below.
In addition, the range represented by using "~" in this specification means the range including both ends described before and after "~" in the range.

[Rubber composition for tires]
The rubber composition for a tire of the present invention is a rubber composition for a tire containing a diene-based rubber and carbon black.
The diene-based rubber contains 5 to 30% by mass of a specific aromatic vinyl-conjugated diene copolymer.
The content of the carbon black is 30 to 80 parts by mass with respect to 100 parts by mass of the diene rubber.
The nitrogen adsorption specific surface area of the carbon black is 30 to 90 m ² / g.

The rubber composition for a tire of the present invention exhibits excellent steering stability and rolling resistance performance when made into a tire.

The reason for this has not been determined, but it is presumed to be as follows.
Since the aromatic vinyl-conjugated diene copolymer exhibits a low glass transition temperature (Tg) as compared with the content of the aromatic vinyl monomer, the mechanical properties of the rubber composition for tires containing the aromatic vinyl-conjugated diene copolymer are improved. , The glass transition temperature (Tg) can be lowered. As a result, compared to the case where the glass transition temperature (Tg) of the rubber composition for a tire is lowered by blending the conjugated diene polymer exemplified in isoprene rubber (IR), butadiene rubber (BR) and the like in the past. It is possible to improve the hardness, tensile properties (tensile strength at the time of cutting) and grip performance of the rubber composition, and to achieve both excellent steering stability performance and excellent rolling resistance performance when made into a tire. Conceivable.

1. 1. Diene-based rubber The diene-based rubber contains 5 to 30% by mass of a specific aromatic vinyl-conjugated diene copolymer (hereinafter, may be referred to as “specific aromatic vinyl-conjugated diene copolymer”).
Further, the content of the specific aromatic vinyl-conjugated diene copolymer in the diene-based rubber is preferably 10 because the steering stability when the rubber composition for a tire of the present invention is used as a tire is more excellent. It is by mass or more and less than 30% by mass, more preferably 10 to 30% by mass, and further preferably 15 to 25% by mass.
In the diene-based rubber, the total of the specific aromatic vinyl-conjugated diene copolymer and the other diene-based rubber is 100% by mass.

1.1) Specific aromatic vinyl-conjugated diene copolymer The above aromatic vinyl-conjugated diene copolymer (hereinafter, may be simply referred to as “specific copolymer”) is an aromatic vinyl compound and a conjugated diene compound. It is a copolymer with.
Here, the content of the repeating unit derived from the aromatic vinyl compound is 18% by mass or more.
Further, the ratio of each microstructure of the repeating unit derived from the conjugated diene compound is in a specific range.
Specifically, among the repeating units derived from the conjugated diene compound, the proportion of the vinyl structure is 8 mol% or less, the proportion of the 1,4-trans structure is 75 mol% or less, and the 1,4-cis structure. The proportion of is 17-90 mol%.
The glass transition temperature of the specific copolymer is −60 ° C. or lower.
The specific copolymer is preferably a solution-polymerized copolymer, and particularly preferably a solution-polymerized styrene-butadiene rubber (SBR), because the effect of the present invention is more excellent.
Hereinafter, the specific copolymer will be described in detail.

1.1.1) Monomer The specific copolymer is a copolymer of an aromatic vinyl compound and a conjugated diene compound. That is, the specific copolymer is a copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound. The specific copolymer may be a copolymer obtained by copolymerizing another monomer in addition to the aromatic vinyl compound and the conjugated diene compound.

1.1.1.1) Aromatic vinyl compound The above aromatic vinyl compound is not particularly limited, and is, for example, styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethyl. Styrene, 3-ethylstyrene, 4-ethylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, vinylnaphthalene, dimethylaminomethyl Examples thereof include styrene and dimethylaminoethylstyrene. Among these, at least one selected from the group consisting of styrene, α-methylstyrene and 4-methylstyrene is preferable, and styrene is more preferable, because the effect of the present invention is more excellent. These aromatic vinyl compounds may be used alone or in combination of two or more.

The content of the repeating unit derived from the aromatic vinyl compound (hereinafter, also referred to as “aromatic vinyl content”) in the specific copolymer is 18% by mass or more. Among them, it is preferably 20% by mass or more, more preferably 30% by mass or more, for the reason that the effect of the present invention is more excellent. The upper limit is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 90% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less.

1.1.1.2) Conjugated diene compound The conjugated diene compound is not particularly limited, and examples thereof include butadiene (for example, 1,3-butadiene), isoprene, and chloroprene. Among them, at least one selected from the group consisting of 1,3-butadiene and isoprene is preferable, and 1,3-butadiene is more preferable, because the effect of the present invention is more excellent. These conjugated diene compounds may be used alone or in combination of two or more.

The content of the repeating unit derived from the conjugated diene compound in the specific copolymer is preferably 82% by mass or less, more preferably 80% by mass or less, and further, for the reason that the effect of the present invention is more excellent. It is preferably 70% by mass or less. Further, the lower limit is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, for the reason that the effect of the present invention is more excellent.

1.1.1.3) Other Monomers As described above, the specific copolymer may be a copolymer obtained by copolymerizing other monomers in addition to the aromatic vinyl compound and the conjugated diene compound. .. Examples of the other monomer include α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and maleic anhydride, acid anhydrides, methyl methacrylate and acrylic acid. Unsaturated carboxylic acid esters such as ethyl and butyl acrylate, and unconjugated diene compounds such as 1,5-hexadien, 1,6-heptadiene, 1,7-octadien, dicyclopentadiene and 5-ethylidene-2-norbornene. Can be mentioned.

1.1.2) Microstructure 1.1.2.1) Vinyl structure In the above-mentioned specific copolymer, the proportion of the vinyl structure among the repeating units derived from the conjugated diene compound is 8 mol% or less, and the present invention It is preferably 5 mol% or less for the reason that the effect of the above is more excellent. The lower limit is not particularly limited and is 0 mol%.
Here, the ratio of the vinyl structure is a repetition having a vinyl structure (for example, 1,2-vinyl structure when the conjugated diene compound is 1,3-butadiene) among all the repeating units derived from the conjugated diene compound. The ratio (mol%) occupied by a unit.

11.2.2) 1,4-Trans structure In the above-mentioned specific copolymer, the proportion of the 1,4-trans structure among the repeating units derived from the conjugated diene compound is 75 mol% or less, and the present invention It is preferably 70 mol% or less, more preferably less than 70 mol%, and even more preferably 60 mol% or less, for the reason that the effect of the above is more excellent. The lower limit is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 10 mol% or more, more preferably 20 mol% or more, and further preferably 30 mol% or more.
Here, the ratio of the 1,4-trans structure means the ratio (mol%) of the repeating units having the 1,4-trans structure among all the repeating units derived from the conjugated diene compound.

11.2.3) 1,4-cis structure In the above-mentioned specific copolymer, the ratio of the 1,4-cis structure to the repeating units derived from the conjugated diene compound is 17 to 90 mol%. For better reasons of the effect of the invention, it is preferably 20-90 mol%, more preferably 25-85 mol%, even more preferably 30-85 mol%, even more preferably 40-75 mol%. be.
Here, the ratio of the 1,4-cis structure means the ratio (mol%) of the repeating units having the 1,4-cis structure to all the repeating units derived from the conjugated diene compound.

In the present specification, among the repeating units derived from the conjugated diene compound, "the ratio of vinyl structure (mol%), the ratio of 1,4-trans structure (mol%), and the ratio of 1,4-cis structure (mol). %) ”Is also expressed as“ vinyl / trans / cis ”.

11.3) Glass transition temperature The glass transition temperature (Tg) of the above-mentioned specific copolymer is −60 ° C. or lower, preferably −70 ° C. or lower, more preferably, for the reason that the effect of the present invention is more excellent. Is -80 ° C or lower. The lower limit is not particularly limited, but is preferably −100 ° C. or higher, more preferably −90 ° C. or higher, for the reason that the effect of the present invention is more excellent.
In the present specification, the glass transition temperature (Tg) is measured by a differential scanning calorimetry (DSC) at a heating rate of 10 ° C./min and calculated by the midpoint method. do.

1.1.4) Molecular Weight The molecular weight of the specific copolymer is a weight average molecular weight (Mw) and is not particularly limited, but is preferably 1,000 to 1,000,000 for the reason that the effect of the present invention is more excellent. It is more preferably 2,000 to 5,000,000, and even more preferably 3,000 to 2,000,000.
The molecular weight of the specific copolymer is a number average molecular weight (Mn) and is not particularly limited, but is preferably 500 to 5,000,000, more preferably 1 for the reason that the effect of the present invention is more excellent. It is 3,000 to 2,500,000, more preferably 1,500 to 1,000,000.
In the present specification, the number average molecular weight (Mn) and the weight average molecular weight (Mw) are standard polystyrene-equivalent values obtained by gel permeation chromatography (GPC) measurement under the following conditions.
-Solvent: Tetrahydrofuran-Detector: Differential refractive index (RI) detector

1.1.5) Preferable Aspects As a preferred embodiment of the above-mentioned specific copolymer, for example, titanium halide, tin halide, cyclic silazane, alkoxysilane, epoxide, amine, ketone and the formula described later ( Examples thereof include an embodiment modified with at least one modifier (hereinafter, also referred to as “specific modifier”) selected from the group consisting of the compounds represented by N). In the case of the above aspect, the effect of the present invention, particularly the rolling resistance performance is more excellent.
When the specific modifier is titanium halide, tin halide or a compound represented by the formula (N) described later, it is presumed that the terminal of the specific copolymer interacts with carbon black, and the specific modifier is used. When the specific copolymer is cyclic silazane, alkoxysilane or amine, the terminal of the specific copolymer is presumed to interact with silica, and when the specific modifier is epoxide or ketone, the terminal of the specific copolymer is silica or carbon black. Is presumed to interact with.

For the reason that the effect of the present invention is more excellent, the specific modifier is preferably cyclic silazane, N-methylpyrrolidone, alkoxysilane or a compound represented by the formula (N) described later, and more preferably N-methylpyrrolidone or It is an alkoxysilane, more preferably N-methylpyrrolidone.

11.5.1) Specific denaturing agents Each specific denaturing agent will be described below.

11.5.1.1) Titanium Halogenate The titanium halide is not particularly limited, but for example, TiCl ₃ , TiBr ₃ , Ti (OC ₂ H ₅ ) Cl ₂ , Ti (OC ₄ H ₉ ) Cl ₂ , TiCl ₄ , Ti (OC ₂ H ₅ ) Cl ₃ , Ti (OC ₄ H ₉ ) Cl _{3, and the} like.
The titanium halide, for reasons that the effect of the present invention is more excellent, and preferably is at least one selected from the group consisting of TiCl 3 _(trichloro titanium) and TiCl 4 _(titanium tetrachloride), more preferably tetrachloro It is titanium.

11.5.1.2) Tin Halogenate The tin halide is not particularly limited, and examples thereof include tin fluoride, tin chloride, tin bromide, tin iodide, and tin astatinate.

11.5.1.3) Cyclic sirazan The cyclic sirazan is not particularly limited as long as it is a cyclic sirazan, but is preferably a compound represented by the following formula (S) for the reason that the effect of the present invention is more excellent. be.
In the present specification, silazane refers to a compound having a structure in which a silicon atom and a nitrogen atom are directly bonded (a compound having a Si—N bond).

In the above formula (S), R _{1 to} R ₃ independently represent a hydrogen atom or a substituent. Specific examples of the substituent are the same as R in the formula (P) described later.
R ₁ is preferably an alkyl group (preferably 1 to 10 carbon atoms), an alkylsilyl group (preferably 1 to 10 carbon atoms) or an aromatic hydrocarbon group (preferably 1 to 10 carbon atoms) because the effect of the present invention is more excellent. Has 6 to 18 carbon atoms).
R ₂ is, for reasons that the effect of the present invention is more excellent, it is preferably an alkoxy group (preferably, 1 to 10 carbon atoms).
In the above formula (S), L represents a divalent organic group.
Examples of the divalent organic group include a substituted or unsubstituted aliphatic hydrocarbon group, a substituted or unsubstituted aromatic hydrocarbon group, -O-, -S-, -SO _2- , and -N (R). )-(R: alkyl group), -CO-, -NH-, -COO-, -CONH-, and combinations thereof.
The substituted or unsubstituted aliphatic hydrocarbon group is, for example, an alkylene group, preferably an alkylene group having 1 to 8 carbon atoms.
The substituted or unsubstituted aromatic hydrocarbon group is, for example, an arylene group, preferably an arylene group having 6 to 12 carbon atoms.
The above combinations are, for example, alkylene group (-C _m H _{2m O-:} m is a positive integer), alkyleneoxy group and an alkylene carbonyl group, and the like.
L is preferably an alkylene group, more preferably an alkylene group having 1 to 10 carbon atoms, for the reason that the effect of the present invention is more excellent.

Examples of the compound represented by the above formula (S) include Nn-butyl-1,1-dimethoxy-2-azasilacyclopentane and N-phenyl-1,1-dimethoxy-2-azasilacyclopentane. , N-Trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-diethoxy-2-azasilacyclopentane and the like.
The silicon atom of cyclic silazane is considered to exhibit electrophilicity.

1.1.5.1.4) Alkoxysilane The alkoxysilane is not particularly limited as long as it is a compound having an alkoxysilyl group, and is, for example, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, tetraethoxysilane, and the like. Methyltriethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3 -Glysidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, N, N-bistrimethylsilyl-3-aminopropyltrimethoxysilane and N, N-bistrimethylsilyl-3-aminopropyltriethoxysilane, etc. Can be mentioned.
The number of alkoxy groups in the alkoxysilyl group is not particularly limited, but is preferably two or more for the reason that the effect of the present invention is more excellent.
The silicon atom of alkoxysilane is considered to exhibit electrophilicity.

1.1.5.1.5) Epoxide The epoxide is not particularly limited as long as it is a compound having an oxacyclopropane (oxylane) structure, and is, for example, ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, styrene oxide, 1 -Phenylpropylene oxide, methylglycidyl ether, ethylglucidyl ether, glycidyl isopropyl ether, butyl glycidyl ether, 1-methoxy-2-methylpropylene oxide, allyl glycidyl ether, 2-ethyloxyl glycidyl ether, phenylglycidyl ether, p-tert -Butylphenyl glycidyl ether, lauryl alcohol glycidyl ether, stearyl glycidyl ether, palmityl glycidyl ether, myristyl glycidyl ether, lauryl glycidyl ether, capryl glycidyl ether, caproyl glycidyl ether and the like.

1.1.5.1.6) Amine The amine has an amino group (-NR ₂ : R represents a hydrogen atom or a hydrocarbon group. The two Rs may be the same or different). The compound is not particularly limited as long as it has, but it is preferably an aziridine for the reason that the effect of the present invention is more excellent.
Examples of the aziridine include N-methyl aziridine, N-ethyl aziridine, N-isopropyl aziridine, N-phenyl aziridine, N- (4-methylphenyl) aziridine and N-methyl-2-methyl aziridine.

11.5.1.7) Ketone The above-mentioned ketone is not particularly limited as long as it is a compound having a ketone group (> C = O), and examples thereof include acetone, benzophenone and derivatives thereof.
Examples of the benzophenone derivative include N, N, N', N'-tetramethyl-4,4'-diaminobenzophenone, N, N, N', N'-tetraethyl (4,4'-diamino)-. Benzophenone, N, N-dimethyl-1-aminobenzoquinone, N, N, N', N'-tetramethyl-1,3-diaminobenzoquinone, N, N-dimethyl-1-aminoanthraquinone, N, N, N' , N'-tetramethyl-1,4-diaminoanthraquinone and 4,4'-diacetylbenzophenone.

11.5.1.8) Compound represented by formula (N) The compound represented by the above-mentioned formula (N) is a compound represented by the following formula (N).

In the above formula (N), R ¹ represents a hydrogen atom or an alkyl group, and R ² represents an alkylene group. The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, and the alkylene group is preferably an alkylene group having 2 to 10 carbon atoms.

As a non-limiting specific example of the compound represented by the above formula (N), N-methylpyrrolidone (in the above formula (N), R ₁ is a methyl group and R ₂ is a propylene group) is used. Can be mentioned.

1.1.6) Method for Producing Specified Aromatic Vinyl-conjugated Diene Copolymer The method for producing the specific aromatic vinyl-conjugated diene copolymer is not particularly limited, and a conventionally known method can be used. The method for setting the aromatic vinyl content, the ratio of the microstructure and the glass transition temperature within a specific range is not particularly limited, and for example, the type of the monomer to be polymerized, the amount ratio of the monomer, the type of the initiator, and the amount ratio of the initiator. By adjusting the reaction temperature and the like, the aromatic vinyl content, the ratio of the microstructure and the glass transition temperature can be set in a specific range.

11.6.1) Preferable Embodiment As a preferred embodiment of the method for producing the above-mentioned specific copolymer, for example, an initiator prepared by using an organic lithium compound, an alkylaluminum and a metal alcoholate (hereinafter, "specification"). An initiator may be used to copolymerize a monomer containing an aromatic vinyl compound and a conjugated diene compound (hereinafter, may be referred to as a “specific copolymer synthesis method”). The specific copolymer synthesized using this synthesis method exhibits better mechanical properties and wear resistance when made into a tire.

11.6.1.1) Specified Initiator As described above, in the above-mentioned method for synthesizing the specified copolymer, an initiator (specified initiator) prepared using an organic lithium compound, alkylaluminum and metal alcoholate is used. used. Since a specific initiator is used in the above-mentioned method for synthesizing the specific copolymer, the ratio of the vinyl structure to the repeating units derived from the conjugated diene compound in the obtained specific copolymer is, for example, 8 mol% or less. It is thought that it can be suppressed to.

The specific initiator is preferably prepared by further using an aromatic divinyl compound for the reason that the effect of the present invention is more excellent. That is, the specific initiator is preferably prepared using an organic lithium compound, an alkylaluminum, a metallic alcoholate, and an aromatic divinyl compound. When an aromatic divinyl compound is used in preparing the specific initiator, the obtained specific copolymer becomes branched and its molecular weight increases. As a result, the mechanical properties and wear resistance of the tire using the rubber composition containing the specific copolymer are further improved.

11.6.1.1.1) Organolithium compound The organolithium compound is not particularly limited as long as it is an organometal compound having a carbon-lithium bond, and is, for example, n-butyllithium, sec-butyllithium, and the like. Monoorganolithium compounds such as tert-butyllithium, n-propyllithium, iso-propyllithium and benzyllithium, and 1,4-dilithiobutane, 1,5-dilithiopentane, 1,6-dilithiohexane, 1,10- Dilithiodecane, 1,1-dilithiodiphenylene, dilithiopolybutadiene, dilithiopolyisoprene, 1,4-dilithiobenzene, 1,2-dilithio-1,2-diphenylethane, 1,4-dilithio-2-ethyl Examples thereof include polyfunctional organolithium compounds such as cyclohexane, 1,3,5-trilithiobenzene and 1,3,5-trilithio-2,4,6-triethylbenzene.
The organolithium compound is preferably at least one selected from the group consisting of n-butyllithium, sec-butyllithium and tert-butyllithium, and more preferably tert-, for the reason that the effect of the present invention is more excellent. It is butyllithium.

The amount of the organolithium compound used in the preparation of the specific initiator is not particularly limited, but is preferably 0.001 to 10 mol% with respect to the monomer to be polymerized for the reason that the effect of the present invention is more excellent.

11.6.1.1.12) Alkyl aluminum The alkyl aluminum is not particularly limited as long as it is a compound in which an alkyl group (chain, branched or cyclic) is bonded to an aluminum atom (Al). The number of carbon atoms of the alkyl group is not particularly limited, but is preferably 1 to 20, and more preferably 1 to 10 for the reason that the effect of the present invention is more excellent.
Examples of the alkylaluminum include trimethylaluminum, triethylaluminum, triisopropylaluminum, tributylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, triisobutylaluminum, pentyldiethylaluminum, 2-methylpentyl-diethylaluminum, and dicyclohexylethyl. Aluminum, tripentyl aluminum, trihexyl aluminum, trioctyl aluminum, tri (2-ethylhexyl) aluminum, tricyclohexyl aluminum, tricyclopentyl aluminum, tri (2,2,4-trimethylpentyl) aluminum, tridodecyl aluminum, tri (2) -Methylpentyl) Aluminum, diisobutylaluminum hydride, diethylaluminum hydride, dipropylaluminum hydride, propylaluminum dihydride, isobutylaluminum dihydride and the like.
The alkylaluminum is preferably trioctylaluminum because the effect of the present invention is more excellent.

The ratio of alkylaluminum to the organic lithium compound used in the preparation of the specific initiator is not particularly limited, but is preferably 0.1 to 50 molar equivalents, more preferably 0, for the reason that the effect of the present invention is more excellent. .5 to 10 molar equivalents. Here, 1 mol equivalent means the amount when 1 mol of alkylaluminum is added when 1 mol of the organic lithium compound is used. That is, the ratio of alkylaluminum to the organic lithium compound used in the preparation of the specific initiator is not particularly limited, but is preferably 10 to 5000 mol%, more preferably 50, for the reason that the effect of the present invention is more excellent. ~ 1000 mol%.

11.6.1.1.13) Metal Alkoxide The metal alcoholate (metal alkoxide) is not particularly limited as long as it is a compound in which the hydrogen of the hydroxy group of the alcohol is replaced with a metal.
The alcohol is not particularly limited as long as it is a compound in which a hydrogen atom of a chain, branched or cyclic hydrocarbon is substituted with a hydroxy group, but the carbon number of the alcohol is preferable because the effect of the present invention is more excellent. Is 1 to 30, more preferably 1 to 20.
The metal is not particularly limited, and examples thereof include alkali metals, alkaline earth metals, transition metals (metals of Group 3 to 11 of the IUPAC Periodic Table), aluminum, germanium, tin, antimony, and the like, and the effects of the present invention can be mentioned. Is preferably an alkaline earth metal, more preferably barium, for reasons of superiority.

The metal alcoholate is preferably barium alcoholate (also referred to as "barium alkoxide") because the effect of the present invention is more excellent.
Non-limiting specific examples of the barium alkoxide include barium dimethoxydo, barium diethoxydo, barium dipropoxide, barium dibutoxide and barium bis (2-ethylhexoxide).

The ratio of the metal alcoholate to the organolithium compound used in the preparation of the specific initiator is not particularly limited, but is preferably 0.01 to 5 molar equivalents, more preferably 0, for the reason that the effect of the present invention is more excellent. .1 to 3 molar equivalents. Here, 1 mol equivalent means the amount when 1 mol of the metal alcoholate is added when 1 mol of the organic lithium compound is used. That is, the ratio of the metal alcoholate to the organic lithium compound used in the preparation of the specific initiator is not particularly limited, but is preferably 1 to 500 mol%, more preferably 10 for the reason that the effect of the present invention is more excellent. ~ 300 mol%.

11.6.1.1.4) Aromatic divinyl compound The aromatic divinyl compound is not particularly limited as long as it is an aromatic compound having two vinyl groups, but for the reason that the effect of the present invention is more excellent, It is preferably divinylbenzene.

The ratio of the aromatic divinyl compound to the organolithium compound used in the preparation of the specific initiator is not particularly limited, but is preferably 0.1 to 5 molar equivalents, more preferably, for the reason that the effect of the present invention is more excellent. Is 0.3 to 3 molar equivalents. Here, 1 mol equivalent means the amount when 1 mol of aromatic divinyl is added when 1 mol of the organolithium compound is used. That is, the ratio of the aromatic divinyl compound to the organolithium compound used in the preparation of the specific initiator is not particularly limited, but is preferably 10 to 500 mol%, more preferably, for the reason that the effect of the present invention is more excellent. Is 30-300 mol%.

11.6.1.1.5) Method for preparing the specific initiator The method for preparing the specific initiator is not particularly limited, but a method for dissolving the above-mentioned organic lithium compound, alkylaluminum, metal alcoholate, etc. in a solvent. And so on.
The solvent is not particularly limited, but is preferably an organic solvent, and more preferably an organic solvent other than alcohol for the reason that the effect of the present invention is more excellent.

11.6.1.2) Monomer The monomer (mixture) contains an aromatic vinyl compound and a conjugated diene compound. Specific examples and preferred embodiments of the aromatic vinyl compound and the conjugated diene compound are as described above.
The proportion of the aromatic vinyl compound in the monomer is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 18% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass. That is all. The upper limit is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 90% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less.
The proportion of the conjugated diene compound in the monomer is not particularly limited, but is preferably 82% by mass or less, more preferably 80% by mass or less, still more preferably 70% by mass, for the reason that the effect of the present invention is more excellent. % Or less. The lower limit is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 10% by mass or more, more preferably 30% by mass or more, and further preferably 40% by mass or more.
The monomer may contain yet another monomer in addition to the aromatic vinyl compound and the conjugated diene compound. Specific examples of such monomers are the same as those of the "other monomers" described above.

11.6.1.2.1) Monomer Copolymerization As described above, in the method of the present invention, a monomer containing an aromatic vinyl compound and a conjugated diene compound is copolymerized using a specific initiator. The specific initiator and monomer are as described above.

The copolymerization method of the monomer is not particularly limited, but a method of adding the above-mentioned monomer to the above-mentioned organic solvent solution containing the specific initiator and stirring in a temperature range of 0 to 120 ° C. (preferably 30 to 100 ° C.) and the like. Can be mentioned.

The ratio of the organolithium compound in the specific initiator to the monomer is not particularly limited, but is preferably 0.001 to 10 mol% for the reason that the effect of the present invention is more excellent.

When copolymerizing the monomers, a phenol compound and / or an amine compound may be added to the copolymerization system (for example, the organic solvent solution containing the above-mentioned specific initiator). Among them, it is preferable to add a phenol compound to the copolymerization system because the effect of the present invention is more excellent. When a phenol compound is added to the copolymer system, the proportion of 1,4-cis structure among the repeating units derived from the conjugated diene compound increases in the obtained aromatic vinyl-conjugated diene copolymer.
Here, the phenol compound is intended to be a compound having a phenolic hydroxyl group or a metal salt thereof. Further, the amine compound is intended to be a compound having an _{amino group (-NH 2} , -NHR, -NR _2). Here, R represents a substituent. Specific examples and preferred embodiments of the substituent are the same as R in the formula (P) described later. Two R a -NR ₂ can be the same or different.
Examples of the phenol compound include compounds represented by the following formula (P).

In the above formula (P), X ¹ represents a hydrogen atom or a metal atom. Examples of the metal atom include a sodium atom and a potassium atom.
In the above formula (P), R represents a hydrogen atom or a substituent. The plurality of Rs may be the same or different.
The above-mentioned substituent is not particularly limited as long as it is a monovalent substituent, and for example, a halogen atom, a hydroxy group, a nitro group, a carboxy group, an alkoxy group, an amino group, a mercapto group, an acyl group, an imide group, a phosphino group, and the like. Examples thereof include a phosphinyl group, a silyl group, and a hydrocarbon group which may have a hetero atom.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
Examples of the heteroatom of the hydrocarbon group which may have the heteroatom include an oxygen atom, a nitrogen atom, a sulfur atom and a phosphorus atom.
Examples of the hydrocarbon group which may have the heteroatom include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a group in which these are combined.
The aliphatic hydrocarbon group may be linear, branched or cyclic. Examples of the aliphatic hydrocarbon group include a linear or branched alkyl group, a linear or branched alkenyl group, and a linear or branched alkynyl group. Here, the linear or branched alkyl group preferably has 1 to 30 carbon atoms, and the linear or branched alkenyl group preferably has 2 to 30 carbon atoms. The linear or branched alkynyl group preferably has 2 to 30 carbon atoms.
Examples of the aromatic hydrocarbon group include an aromatic hydrocarbon group having 6 to 18 carbon atoms such as a phenyl group, a tolyl group, a xsilyl group, and naphthyl.
In the above formula (P), X represents a hydrogen atom, ^one -OX group or a substituent. X ¹ is as described above. Moreover, the specific example of the substituent is the same as R in the above-mentioned formula (P).

The amount of the phenol compound added to the reaction system is not particularly limited, but is preferably 0.01 to 90 mol%, more preferably 0. It is 1 to 80 mol%.

The method for terminating the polymerization is not particularly limited, and examples thereof include a method of adding alcohol, preferably methanol, to the polymerization solution.
The method for terminating the polymerization is selected from titanium halide, tin halide, cyclic silazane, alkoxysilane, epoxide, amine, ketone and a compound represented by the following formula (N) because the effect of the present invention is more excellent. A method of terminating the polymerization using an electrophile (hereinafter, may be referred to as a “specific electrophile”) is preferable.
That is, the method for synthesizing the specific copolymer is preferably a method of copolymerizing a monomer containing an aromatic vinyl compound and a conjugated diene compound using a specific initiator, and then terminating the polymerization using a specific electrophile. ..
The definition, specific examples and preferred embodiments of the specific electrophile are the same as those of the specific modifier described above.
By terminating the polymerization with a specific electrophile, a copolymer having a terminal modified with a specific electrophile (specific modifier) can be obtained.
The amount of the specific electrophile with respect to the specific initiator is not particularly limited.
The ratio of the electrophile to the organolithium compound (specific electrophile / organolithium compound) is not particularly limited, but is preferably 0.1 to 10 in terms of molar ratio for the reason that the effect of the present invention is more excellent. More preferably, it is 1 to 5.
The ratio of the specific electrophile to the alkylaluminum (alkylAl) (specific electrophile / alkylAl) is not particularly limited, but is preferably 0.1 in terms of molar ratio for the reason that the effect of the present invention is more excellent. It is 10, and more preferably 1 to 5.
Further, the ratio of the electrophile to the metal alcoholate (electrophile / metal alcoholate) is not particularly limited, but for the reason that the effect of the present invention is more excellent, the molar ratio is preferably 0.1 to 20 and more. It is preferably 1 to 10.

1.2) Diene-based rubber other than the specific copolymer The diene-based rubber other than the specific copolymer is a diene-based rubber and is not particularly limited as long as it is other than the specific copolymer.
Examples of the diene rubber other than the specific copolymer include aromatic vinyl-conjugated diene copolymers other than the specific copolymer, non-aromatic vinyl-conjugated diene copolymers, and conjugated diene (co) polymers. , And natural rubber.
Examples of the aromatic vinyl-conjugated diene copolymer other than the specific copolymer include styrene-butadiene rubber (SBR) other than the specific copolymer. The styrene-butadiene rubber (SBR) may be a solution-polymerized styrene-butadiene rubber (S-SBR) or an emulsion-polymerized styrene-butadiene rubber (E-SBR), but a solution-polymerized styrene-butadiene rubber (S-SBR) is preferable. Is.
Examples of the non-aromatic vinyl-conjugated diene copolymer include acrylonitrile butadiene rubber (NBR), butyl rubber (isobutylene isoprene rubber) (IIR), and halogenated butyl rubber (Br-IIR, Cl-IIR).
Examples of the conjugated diene (co) polymer include isoprene rubber (IR), butadiene rubber (BR), and chloroprene rubber (CR).
As the diene-based rubber other than the specific copolymer, it is preferable to use natural rubber (NR).

2. Carbon Black The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is 30 to 90 m ² / g.
Further, since the rolling resistance when the rubber composition for a tire of the present invention is used as a tire becomes smaller, the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably 30 to 70 m ² / g. , More preferably 30 to 50 m ² / g.
Here, for the nitrogen adsorption specific surface area (N ₂ SA), the amount of nitrogen adsorbed on the carbon black surface is described in JIS K 6217-2: 2001 "Part 2: Method of determining the specific surface area-Nitrogen adsorption method-Single point method". Therefore, it is a measured value.

The content of the carbon black is 30 to 80 parts by mass with respect to 100 parts by mass of the diene rubber.
Further, since the rolling resistance when the rubber composition for a tire of the present invention is used as a tire becomes smaller, the content of the carbon black is preferably 30 to 70 mass by mass with respect to 100 parts by mass of the diene rubber. Parts, more preferably 35 to 65 parts by mass.

3. 3. Additives other than diene rubber and carbon black The tire rubber composition of the present invention contains, if necessary, additives other than the diene rubber and carbon black, as long as the object of the present invention is not impaired. be able to.
Examples of the additive include a filler other than the carbon black (for example, carbon black or silica other than the carbon black), a silane coupling agent, zinc oxide (zinc oxide), stearic acid, an adhesive resin, and a base material. Common for rubber compositions such as kneading accelerators, antiaging agents, waxes, processing aids, aroma oils, liquid polymers, terpene resins, thermosetting resins, vulcanizing agents (eg sulfur), vulcanization accelerators, etc. Examples include various additives used in.

4. Method for Producing Rubber Composition for Tire The method for producing the rubber composition for tire of the present invention is not particularly limited, and specific examples thereof include, for example, a known method and apparatus (for example, a Banbury mixer, etc.) for each of the above-mentioned components. A method of kneading using a kneader, a roll, etc.) can be mentioned. When the rubber composition for a tire of the present invention contains sulfur or a vulcanization accelerator, components other than sulfur and the vulcanization accelerator are first mixed at a high temperature (preferably 40 to 160 ° C.) and then cooled. , Sulfur or vulcanization accelerators are preferably mixed.
Further, the rubber composition for a tire of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

5. Applications of Rubber Compositions for Tires The rubber compositions for tires of the present invention are used in the production of pneumatic tires. Among them, it is preferably used for under treads of pneumatic tires, carcass coated rubbers, tie rubbers, or bead insulation rubbers.

[Pneumatic tires]
The pneumatic tire of the present invention is a pneumatic tire manufactured by using the above-mentioned rubber composition for a tire of the present invention. Among them, it is preferable that the tire is a pneumatic tire in which the rubber composition for a tire of the present invention is used for an under tread, a carcass coated rubber, a tie rubber, or a bead insulation rubber.
FIG. 1 shows a schematic partial cross-sectional view of a tire showing an example of an embodiment of the pneumatic tire of the present invention, but the pneumatic tire of the present invention is not limited to the embodiment shown in FIG.

In FIG. 1, reference numeral 1 represents a bead portion, reference numeral 2 represents a sidewall portion, and reference numeral 3 represents a tire tread portion.
Further, a carcass layer 4 in which a fiber cord is embedded is mounted between the pair of left and right bead portions 1, and the end portion of the carcass layer 4 is placed around the bead core 5 and the bead filler 6 from the inside to the outside of the tire. It is folded back and rolled up.
Further, in the tire tread 3, the belt layer 7 is arranged on the outside of the carcass layer 4 over one circumference of the tire, and the under tread 9 is arranged so as to cover the belt layer 7.
Further, in the bead portion 1, the rim cushion 8 is arranged at a portion in contact with the rim.

Further, FIG. 2 shows an enlarged schematic view of the bead core of reference numeral 5.
In FIG. 2, reference numeral G represents a bead insulation rubber, reference numeral W represents a bead wire, and reference numeral C represents a bead cover rubber.

The pneumatic tire of the present invention can be manufactured, for example, according to a conventionally known method. Further, as the gas to be filled in the tire, an inert gas such as nitrogen, argon or helium can be used in addition to normal or adjusted oxygen partial pressure.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[Synthesis of aromatic vinyl-conjugated diene copolymer]
(Synthesis Example 1) Terminal-denatured SBR (SBR-1)
n-BuLi (manufactured by Kanto Chemical Co., Inc .: 1.60 mol / L (hexane solution), 18 mL, 28.8 mmol), barium bis (2-ethylhexoxide) (Ba (OCH ₂ CH (C ₂ H ₅ ) CH ₂₎ CH ₂ CH ₂ CH ₃ ) ₂ ) (Strem Chemicals: 1M (toluene / hexane solution) 7.5mL), trioctylaluminum (Aldrich: 25wt% (hexane solution), 45mL) and cyclohexane (Kanto Chemical) Of the initiator solution (corresponding to the specified initiator described above) prepared using (manufactured by Kanto Chemical Co., Inc .: 10 mL), 60 mL of 1,3-butadiene (708 g, 13098 mmol) and styrene (manufactured by Kanto Chemical Co., Inc .: 300 g, 2883 mmol) ) And 4-tert-butylpyrocatechol (4.79 g, 28.8 mmol) in a cyclohexane (4.24 kg) solution, and stirred at 60 ° C. for 14 hours. After cooling to room temperature, methanol (manufactured by Kanto Chemical Co., Inc .: 3.44 g) was added to terminate the polymerization. The resulting solution was removed and concentrated under reduced pressure. The concentrated solution was poured into methanol (5 L) to separate the methanol-insoluble component. As a result, a styrene-butadiene copolymer (SBR) (895 g; Mn = 360,000; Mw = 500,000; Mw / Mn = 1.4) was obtained in a yield of 88%. It was estimated by IR analysis that vinyl / trans / cis = 3/62/35. The aromatic vinyl content (content of the repeating unit derived from styrene) was 31% by mass, and the glass transition temperature was −84 ° C.

(Synthesis Example 2) N-Methylpyrrolidone Terminal Denatured SBR (SBR-2)
n-BuLi (manufactured by Kanto Chemical Co., Inc .: 1.60 mol / L (hexane solution), 18 mL, 28.8 mmol), barium bis (2-ethylhexoxide) (Ba (OCH ₂ CH (C ₂ H ₅ ) CH ₂₎ CH ₂ CH ₂ CH ₃ ) ₂ ) (Strem Chemicals: 1M (toluene / hexane solution) 7.5mL), trioctylaluminum (Aldrich: 25wt% (hexane solution), 45mL) and cyclohexane (Kanto Chemical) Of the initiator solution (corresponding to the specified initiator described above) prepared using (manufactured by Kanto Chemical Co., Inc .: 10 mL), 60 mL was added to 1,3-butadiene (721 g, 13330 mmol) and styrene (manufactured by Kanto Chemical Co., Inc .: 300 g, 2883 mmol). ) And 4-tert-butylpyrocatechol (4.79 g, 28.8 mmol) in a cyclohexane (4.24 kg) solution and stirred at 60 ° C. for 24 hours. After cooling to room temperature, N-methylpyrrolidone (8.41 g) was added to terminate the polymerization. The resulting solution was removed and concentrated under reduced pressure. The concentrated solution was poured into methanol (5 L) to separate the methanol-insoluble component. As a result, a styrene-butadiene copolymer (N-methylpyrrolidone terminally modified SBR) whose terminal was modified with N-methylpyrrolidone (915 g; Mn = 248,000; Mw = 621,000; Mw / Mn = 2.5. ) Was obtained in a yield of 90%. It was estimated by IR analysis that vinyl / trans / cis = 6/40/54. The aromatic vinyl content (content of the repeating unit derived from styrene) was 24% by mass, and the glass transition temperature was −89 ° C.

(Synthesis Example 3) Alkoxysilane end-modified SBR (SBR-3)
n-BuLi (manufactured by Kanto Chemical Co., Inc .: 1.60 mol / L (hexane solution), 18 mL, 28.8 mmol), barium bis (2-ethylhexoxide) (Ba (OCH ₂ CH (C ₂ H ₅ ) CH ₂₎ CH ₂ CH ₂ CH ₃ ) ₂ ) (Strem Chemicals: 1M (toluene / hexane solution) 7.5mL), trioctylaluminum (Aldrich: 25wt% (hexane solution), 45mL) and cyclohexane (Kanto Chemical) Of the initiator solution (corresponding to the specified initiator described above) prepared using (manufactured by Kanto Chemical Co., Inc .: 10 mL), 60 mL was added to 1,3-butadiene (721 g, 13330 mmol) and styrene (manufactured by Kanto Chemical Co., Inc .: 300 g, 2883 mmol). ) And 4-tert-butylpyrocatechol (4.79 g, 28.8 mmol) in a cyclohexane (4.24 kg) solution, and stirred at 60 ° C. for 14 hours. After cooling to room temperature, a mixed solution of N, N-bistrimethylsilyl-3-aminopropyltrimethoxysilane (22.4 g) and lithium diisopropylamide (made by Aldrich (2M solution): 10 mL) in cyclohexane (10 mL) was added and polymerized. Stopped. The resulting solution was removed and concentrated under reduced pressure. The concentrated solution was poured into methanol (5 L) to separate the methanol-insoluble component. As a result, 81% of the styrene-butadiene copolymer (alkoxysilane terminal-modified SBR) (827 g; Mn = 350,000; Mw = 490,000; Mw / Mn = 1.4) whose terminal was modified with alkoxysilane. Was obtained in the yield of. It was estimated by IR analysis that vinyl / trans / cis = 4/61/35. The aromatic vinyl content (content of the repeating unit derived from styrene) was 26% by mass, and the glass transition temperature was −85 ° C.

[Standard Examples 1 and 2, Examples 1 to 6 and Comparative Examples 1 and 2]
<Preparation of rubber composition>
The components shown in Tables 1 and 2 below were blended in proportions (parts by mass) shown in Tables 1 and 2 below.
Specifically, first, among the components shown in Tables 1 and 2 below, the components excluding sulfur and the vulcanization accelerator were mixed in a Banbury mixer at 80 ° C. for 5 minutes. Next, using a roll, sulfur and a vulcanization accelerator were mixed to obtain a rubber composition (unvulcanized).

<Manufacturing of vulcanized rubber sheet>
Each of the obtained rubber compositions (unvulcanized) was press-vulcanized in a mold (15 cm × 15 cm × 0.2 cm) at 160 ° C. for 15 minutes to prepare a vulcanized rubber sheet.

<Hardness>
The vulcanized rubber sheet prepared as described above is hard at 20 ° C. in accordance with JIS K 6253-: 2012 "Vulcanized rubber and thermoplastic rubber-How to determine hardness-Part 3: Durometer hardness". (Hardness of type A rubber meter) was measured.
The results are shown in Tables 1 and 2 ("Hardness" column).
The results are represented by an index with the hardness of Standard Example 1 as 100 for Table 1, and as an index with the hardness of Standard Example 2 as 100 for Table 2. The larger the index, the better the steering stability when tired.

<300% modulus>
Regarding the vulcanized rubber sheet prepared as described above, in accordance with JIS K 6251: 2010 "Vulcanized rubber and thermoplastic rubber-How to obtain tensile properties", JIS No. 3 dumbbell type test piece (thickness 2 mm) was punched out and the temperature was increased. 300% modulus (tensile stress at 300% elongation) was measured under the conditions of 20 ° C. and a tensile speed of 500 mm / min.
The results are shown in Tables 1 and 2 ("300% modulus" column).
The results are represented by an index with 300% modulus of Standard Example 1 as 100 in Table 1 below, and by an index with 300% modulus of Standard Example 2 as 100 in Table 2 below. The larger the index, the better the steering stability when tired.

<Strength at cutting>
Regarding the vulcanized rubber sheet prepared as described above, in accordance with JIS K 6251: 2010 "Vulcanized rubber and thermoplastic rubber-How to obtain tensile properties", JIS No. 3 dumbbell type test piece (thickness 2 mm) was punched out and the temperature was increased. The cutting strength (cutting tensile stress) was evaluated under the conditions of 20 ° C. and a tensile speed of 500 mm / min.
The results are shown in Tables 1 and 2 (column of "strength at cutting").
The results are represented by an index with the cutting strength of Standard Example 1 as 100 for Table 1 below, and as an index with the cutting strength of Standard Example 2 as 100 for Table 2 below. The larger the index, the better the steering stability when tired.

<Storage modulus>
The vulcanized rubber sheet prepared as described above has a storage elastic modulus (E) under the conditions of initial strain 10%, amplitude ± 2%, frequency = 20 Hz, and temperature 20 ° C. by a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.). '(20 ° C.)) was measured.
The results are shown in Tables 1 and 2 below (column of "storage elastic modulus").
The results are represented by an index with E'(20 ° C.) of Standard Example 1 as 100 for Table 1 below, and as an index with E'(20 ° C.) of Standard Example 2 as 100 for Table 2 below. did. The larger the index, the better the steering stability performance when tired.

<Rolling resistance performance>
For each of the obtained vulcanized rubber sheets, a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used under the conditions of initial strain of 10%, amplitude of ± 2%, frequency of 20 Hz, and temperature of 60 ° C. )) Was measured.
The results are shown in Tables 1 and 2 below (in the "Rolling resistance performance" column).
The results are represented by an index with tan δ (60 ° C.) of Standard Example 1 as 100 in Table 1 below, and as an index with tan δ (60 ° C.) of Standard Example 2 as 100 in Table 2 below. The smaller the index, the better the rolling resistance performance when used as a tire.

<Diene rubber>
<< Specific copolymer >>
SBR-1: End-denatured SBR synthesized in Synthesis Example 1 (aromatic vinyl content 31% by mass; vinyl / trans / cis = 3/62/35; glass transition temperature -84 ° C)
SBR-2: N-methylpyrrolidone terminally modified SBR synthesized in Synthesis Example 2 (aromatic vinyl content 24% by mass; vinyl / trans / cis = 6/40/54; glass transition temperature -89 ° C)
SBR-3: Alkoxysilane terminal-modified SBR synthesized in Synthesis Example 3 (aromatic vinyl content 26% by mass; vinyl / trans / cis = 4/61/35; glass transition temperature -85 ° C)

<< Diene rubber other than specific copolymer >>
SBR-4: SBR (Nipol 1502, manufactured by Zeon Corporation; glass transition temperature -53 ° C)
NR: Natural rubber TSR20

<Carbon black>
CB-1: THAIBLACK N660 (manufactured by Thai Carbon Black Public; N ₂ SA 35m ² / g)
CB-2: Show Black N339 (manufactured by Cabot Japan; N ₂ SA 85m ² / g)

<Additive>
Silica: ZEOSIL 1165MP (manufactured by Rhodia)
Silane coupling agent: Si363 (manufactured by Evonik Degussa)
Anti-aging agent: Santoflex 6PPD (manufactured by Flexis)
Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
Stearic acid: Stearic acid (manufactured by NOF CORPORATION)
Vulcanization accelerator: Noxeller NS-P (NS) (manufactured by Ouchi Shinko Kagaku Co., Ltd.)
Sulfur: Muclon OT-20 (manufactured by Shikoku Kasei Kogyo Co., Ltd.)

[Explanation of results]
<Standard Example 1, Examples 1 and 2>
As can be seen from Table 1, Examples 1 and Example containing a specific aromatic vinyl-conjugated diene copolymer as compared with Standard Example 1 not containing a specific aromatic vinyl-conjugated diene copolymer. In No. 2, the hardness, 300% modulus indicating steering stability performance, cutting strength and storage elastic ratio were all equal to or higher than each other, and steering stability performance was excellent. Further, Examples 1 and 2 were also excellent in rolling resistance performance as compared with Standard Example 1.

<Examples 1 and 2>
Example 2 using a specific aromatic vinyl-conjugated diene copolymer end-modified with N-methylpyrrolidone was carried out using a specific aromatic vinyl-conjugated diene copolymer having an unmodified end. Compared with Example 1, the rolling resistance performance was more excellent.

<Standard Example 2, Examples 3, 6>
As can be seen from Table 2, Examples 3 and 6 containing a specific aromatic vinyl-conjugated diene copolymer are compared with Standard Example 2 not containing a specific aromatic vinyl-conjugated diene copolymer. , Hardness, 300% modulus indicating steering stability performance, cutting strength and storage elastic ratio were all equal to or higher than each other, and steering stability performance was excellent. Further, Examples 3 and 6 were also excellent in rolling resistance performance as compared with Standard Example 2.

<Examples 3 and 6>
Example 6 using a specific aromatic vinyl-conjugated diene copolymer having the terminal modified with alkoxysilane is Example 3 using a specific aromatic vinyl-conjugated diene copolymer having an unmodified end. The rolling resistance performance was superior to that of ~ 5.

<Examples 3 to 5, Comparative Examples 1 and 2>
Examples 3 to 5 in which the content of the specific aromatic vinyl-conjugated diene copolymer is 5 to 30% by mass of the diene-based rubber have rolling resistance performance as compared with Comparative Examples 1 and 2 containing 50% by mass or more. Was excellent.

1 bead part 2 sidewall part 3 tire tread part 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 rim cushion 9 under tread G bead insulation rubber W bead wire C bead cover rubber

Claims (7)

A rubber composition for tires containing a diene rubber and carbon black.
The diene-based rubber contains 5 to 30% by mass of an aromatic vinyl-conjugated diene copolymer.
The content of the carbon black is 30 to 80 parts by mass with respect to 100 parts by mass of the diene rubber.
The carbon black has a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 90 m ² / g.
The aromatic vinyl-conjugated diene copolymer is a copolymer of an aromatic vinyl compound and a conjugated diene compound, and the content of the repeating unit derived from the aromatic vinyl compound is 18% by mass or more. Among the repeating units derived from the conjugated diene compound, the proportion of the vinyl structure is 8 mol% or less, the proportion of the 1,4-trans structure is 10 mol% or more and 75 mol% or less, and the 1,4-cis structure. Is a copolymer of an aromatic vinyl compound and a conjugated diene compound, the ratio of which is 17 to 90 mol% and the glass transition temperature is −60 ° C. or lower.
Rubber composition for tires. According to claim 1, the proportion of the 1,4-trans structure of the aromatic vinyl-conjugated diene copolymer is 70 mol% or less, and the proportion of the 1,4-cis structure is 30 to 85 mol%. The rubber composition for tires described. The aromatic vinyl-conjugated diene copolymer is selected from the group consisting of titanium halide, tin halide, cyclic silazane, alkoxysilane, epoxide, amine, ketone and a compound represented by the following formula (N) at the terminal. The rubber composition for a tire according to claim 1 or 2, which is an aromatic vinyl-conjugated diene copolymer modified with at least one modifier.

In formula (N), R ¹ represents a hydrogen atom or an alkyl group, and R ² represents an alkylene group. A pneumatic tire in which the rubber composition for a tire according to any one of claims 1 to 3 is arranged on an undertread. A pneumatic tire in which the rubber composition for a tire according to any one of claims 1 to 3 is arranged on a carcass coated rubber. A pneumatic tire in which the rubber composition for a tire according to any one of claims 1 to 3 is arranged on a tie rubber. A pneumatic tire in which the rubber composition for a tire according to any one of claims 1 to 3 is arranged on a bead insulation rubber.

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