JP2016069628A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having operation stability, flex crack growth resistance, chip cut resistance and low fuel consumption which are improved excellently.SOLUTION: There is provided a pneumatic tire manufactured by using a rubber composition containing a hydrogenated copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound and having hydrogenation rate of a conjugated diene part of 75 mol% and carbon black having nitrogen adsorption specific surface area of 5 to 200 m/g and having the content of the hydrogenated polymer in the 100 mass% of a rubber component of 75 mass% or more and the content of the carbon black of 30 to 70 pts.mass based on 100 pts.mass of the rubber component.SELECTED DRAWING: None

Description

The present invention relates to a pneumatic tire manufactured using a predetermined rubber composition.

Among tires, particularly for sidewalls of heavy-duty tires such as trucks and buses, rubber compositions mainly composed of natural rubber and polybutadiene rubber have been used from the viewpoint of resistance to flex crack growth and strength.

In recent years, due to increasing interest in environmental issues, there has been a strong demand for lower fuel consumption for automobiles, and rubber compositions used for automobile tires are also required to have excellent fuel efficiency. .

Known methods for improving fuel efficiency include the use of low reinforcing fillers, weight loss of fillers, silica, etc. In these methods, for example, in the case of sidewalls, reinforcing properties As a result, the fracture properties such as rubber hardness (steering stability), flex crack growth resistance, and chip cut resistance deteriorate. In particular, since the sidewalls of heavy duty tires tend to generate heat, the above-described method has been adopted to suppress the heat generation. However, the breakdown characteristics are deteriorated, and both the breakdown characteristics and fuel efficiency are compatible. It was very difficult. As described above, it is difficult to satisfy both the fracture characteristics such as the rubber hardness, the bending crack growth resistance, and the chip cut resistance and the low fuel consumption.

As a method for improving fuel economy, for example, Patent Document 1 proposes a method using a diene rubber (modified rubber) modified with an organosilicon compound containing an amino group and an alkoxy group. It has not been studied to achieve both characteristics and low fuel consumption.

JP 2000-344955 A

An object of the present invention is to solve the above-mentioned problems and to provide a pneumatic tire in which steering stability, flex crack growth resistance, chip cut resistance, and fuel efficiency are well improved.

The present invention is a pneumatic tire produced using a rubber composition, wherein the rubber composition has a hydrogenation rate of a conjugated diene part obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound. 75% by mass or more of the hydrogenated copolymer and carbon black having a nitrogen adsorption specific surface area of 5 to 200 m ² / g, and the content of the hydrogenated copolymer in 100% by mass of the rubber component is 75% by mass. It is related with the pneumatic tire whose content of the said carbon black is 30-70 mass parts with respect to 100 mass parts of rubber components.

The hydrogenated copolymer preferably has a weight average molecular weight of 200,000 to 2,000,000.

It is preferable that the hydrogenation rate of the hydrogenated copolymer is 90 mol% or more.

The hydrogenated copolymer is preferably a hydrogenated styrene butadiene copolymer.

The hydrogenated styrene butadiene copolymer is preferably a hydrogenated styrene butadiene copolymer.

The hydrogenated styrene butadiene copolymer preferably has a styrene content of 5 to 40% by mass.

The rubber composition preferably further contains polybutadiene rubber.

The content of the polybutadiene rubber in 100% by mass of the rubber component is preferably 5 to 25% by mass.

A pneumatic tire having a sidewall produced using the rubber composition is preferable.

According to the present invention, a pneumatic tire manufactured using a rubber composition containing a specific amount of a specific hydrogenated copolymer having a hydrogenation rate of 75 mol% or more and carbon black having a specific nitrogen adsorption specific surface area. Therefore, it has good steering stability, resistance to flex crack growth, resistance to chip cut and low fuel consumption.

The pneumatic tire of the present invention is a conjugated diene obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound (hereinafter also referred to as a copolymer of an aromatic vinyl compound and a conjugated diene compound). Carbon black containing a hydrogenated copolymer having a hydrogenation rate of 75 mol% or more in a part of 75% by mass in 100% by mass of a rubber component and a nitrogen adsorption specific surface area of 5 to 200 m ² / g. Is produced using a rubber composition containing 30 to 70 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition in the present invention not only contains 30 to 70 parts by mass of carbon black having a specific nitrogen adsorption specific surface area with respect to 100 parts by mass of the rubber component, but the hydrogenation rate of the conjugated diene part is 75 mol% or more. By containing the specific hydrogenated copolymer in an amount of 75% by mass or more in 100% by mass of the rubber component, the steering stability, the flex crack growth resistance, the chip cut resistance and the low fuel consumption can be remarkably improved.

The rubber composition in the present invention is characterized in that it contains a hydrogenated copolymer in which the conjugated diene portion of a copolymer of an aromatic vinyl compound and a conjugated diene compound is hydrogenated as a rubber component. Since ordinary rubber has many double bond portions that serve as cross-linking reaction points, cross-linking density occurs, and this cross-linking density is considered to be a starting point of breakage due to stress concentration. In the present invention, the reactive sites for crosslinking are reduced by reducing the double bond portion by hydrogenation treatment. As a result, it is expected that the chip density and the like will be improved by reducing cross-linking density and reducing stress concentration.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, and the like. These may be used singly or may be used in combination of two or more, but among them, the viewpoints of practical aspects such as the availability of monomers and the effect of the present invention can be more suitably obtained. To styrene is particularly preferred.

Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, and the like. These may be used singly or may be used in combination of two or more, but among them, the viewpoints of practical aspects such as the availability of monomers and the effect of the present invention can be more suitably obtained. 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred.

As a copolymer of an aromatic vinyl compound and a conjugated diene compound, a copolymer of styrene and 1,3-butadiene (styrene butadiene copolymer) is preferable. Accordingly, a hydrogenated styrene butadiene copolymer is preferred as the hydrogenated copolymer. Furthermore, the hydrogenated styrene butadiene copolymer is preferably a hydrogenated styrene butadiene copolymer modified by a method described later.

The styrene-butadiene copolymer is not particularly limited in the order of copolymerization as long as it is a copolymer of styrene and 1,3-butadiene, and may be random copolymer or block copolymer, but random copolymer is preferable. . The same applies to a copolymer of an aromatic vinyl compound and a conjugated diene compound other than the styrene-butadiene copolymer.

The hydrogenation rate of the hydrogenated copolymer (ratio of hydrogenation with respect to the conjugated diene part of the copolymer of aromatic vinyl compound and conjugated diene compound) is 75 mol% or more, preferably 80 mol% or more, More preferably, it is 90 mol% or more, More preferably, it is 93 mol% or more. When the hydrogenation rate is less than 75 mol%, it is difficult to improve fuel economy, chip cut resistance and flex crack growth resistance. The hydrogenation rate of the hydrogenated copolymer is preferably 99 mol% or less, more preferably 98 mol% or less. If the hydrogenation rate exceeds 99 mol%, the rubber composition may become hard.
Note that the hydrogenation rate can be calculated from the spectral reduction rate of the unsaturated bonds of the spectrum obtained by measuring the H ¹ -NMR.

The weight average molecular weight (Mw) of the hydrogenated copolymer is preferably 200,000 or more, more preferably 400,000 or more. If Mw is less than 200,000, good steering stability, flex crack growth resistance, chip cut resistance and low fuel consumption may not be obtained. The Mw of the hydrogenated copolymer is preferably 2,000,000 or less, more preferably 1,000,000 or less, and still more preferably 700,000 or less. When Mw exceeds 2,000,000, the workability tends to decrease.

In the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation), detector: differential refractometer, column: It can be determined in terms of standard polystyrene based on the measured value by TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the hydrogenated copolymer is preferably 50 or more, more preferably 60 or more, and still more preferably 80 or more. If it is less than 50, there is a possibility that good fuel economy, steering stability, resistance to flex crack growth and chip cut resistance cannot be obtained. The Mooney viscosity is preferably 120 or less, more preferably 110 or less, and still more preferably 100 or less. When it exceeds 120, workability tends to deteriorate.
In this specification, Mooney viscosity (ML _{1 + 4} , 100 ° C.) is a value obtained by measuring Mooney viscosity at 100 ° C. according to JIS K 6300.

When the hydrogenated copolymer is a hydrogenated styrene butadiene copolymer, the styrene content of the hydrogenated styrene butadiene copolymer is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass. % Or more, particularly preferably 20% by mass or more, and most preferably 25% by mass or more. If the styrene content is less than 5% by mass, sufficient fuel economy may not be obtained. Further, the styrene content of the hydrogenated styrene butadiene copolymer is preferably 40% by mass or less, more preferably 35% by mass or less. When the styrene content exceeds 40% by mass, sufficient steering stability, flex crack growth resistance and chip cut resistance cannot be obtained, and fuel efficiency may be deteriorated. When the styrene content is within the above range, the effect of the present invention can be more suitably obtained.
In addition, styrene content is measured by the method as described in the Example mentioned later.

The hydrogenated copolymer can be synthesized, for example, by subjecting a polymer obtained by polymerizing an aromatic vinyl compound and a conjugated diene compound to a hydrogenation treatment, and specifically, can be synthesized by the following method.

<Method for producing copolymer>
(Polymerization method)
There is no particular limitation on the polymerization method of the copolymer of the aromatic vinyl compound and the conjugated diene compound, and any of the solution polymerization method, the gas phase polymerization method, and the bulk polymerization method can be used, but the solution polymerization method is particularly preferable. Moreover, any of a batch type and a continuous type may be sufficient as the superposition | polymerization form.

When the solution polymerization method is used, the monomer concentration in the solvent (the total of styrene and 1,3-butadiene in the case of a styrene butadiene copolymer) is preferably 5% by mass or more, and more preferably 10% by mass or more. . When the monomer concentration in the solution is less than 5% by mass, the amount of the copolymer obtained is small and the cost tends to increase. The monomer concentration in the solvent is preferably 50% by mass or less, and more preferably 30% by mass or less. When the monomer concentration in the solvent exceeds 50% by mass, the solution viscosity becomes too high, stirring becomes difficult, and polymerization tends to be difficult.

(Polymerization initiator in anionic polymerization)
When anionic polymerization is performed, the polymerization initiator is not particularly limited, but an organic lithium compound is preferably used. As the organic lithium compound, those having an alkyl group having 2 to 20 carbon atoms are preferable. For example, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, tert- Octyl lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, 2-butyl-phenyl lithium, 4-phenyl-butyl lithium, cyclohexyl lithium, cyclopentyl lithium, reaction products of diisopropenylbenzene and butyl lithium, etc. Among these, n-butyllithium or sec-butyllithium is preferable from the viewpoints of availability, safety, and the like.

Moreover, you may perform a polymerization reaction in presence of the compound (R) obtained by mixing at least any one of said organolithium compounds, and the compound (B1) which has a functional group which interacts with a silica. By performing the polymerization in the presence of the compound (R), a functional group having an interaction with silica can be introduced into the polymerization initiation terminal of the copolymer. Thereby, the copolymer by which the start terminal was modified | denatured is obtained. In the present specification, the term “interaction” refers to an intermolecular force that forms a covalent bond between molecules or is weaker than a covalent bond (eg, ion-dipole interaction, dipole-dipole interaction, It means the formation of electromagnetic force between molecules such as hydrogen bonds and van der Waals forces. The “functional group that interacts with silica” refers to a group having at least one atom that interacts with silica, such as a nitrogen atom, a sulfur atom, a phosphorus atom, or an oxygen atom.

The compound (R) is preferably a reaction product of an organolithium compound and a nitrogen-containing compound such as a secondary amine compound. Specific examples of the nitrogen-containing compound include, for example, dimethylamine, diethylamine, dipropylamine, dibutylamine, dodecamethyleneimine, N, N′-dimethyl-N′-trimethylsilyl-1,6-diaminohexane, piperidine, pyrrolidine, Hexamethyleneimine, heptamethyleneimine, dicyclohexylamine, N-methylbenzylamine, di- (2-ethylhexyl) amine, diallylamine, morpholine, N- (trimethylsilyl) piperazine, N- (tert-butyldimethylsilyl) piperazine, 1, Examples include 3-ditrimethylsilyl-1,3,5-triazinane. In addition, when superposing | polymerizing in presence of a compound (R), a compound (R) is prepared by mixing an organic lithium compound and a compound (B1) previously, and the prepared compound (R) is made into a polymerization system. Polymerization may be carried out by adding to the above. Alternatively, the polymerization may be carried out by preparing the compound (R) by adding the organolithium compound and the compound (B1) to the polymerization system and mixing both in the polymerization system.

(Method of anionic polymerization)
There is no restriction | limiting in particular as a method of anion-polymerizing using the said polymerization initiator and manufacturing a copolymer, A conventionally well-known method can be used.
Specifically, in an organic solvent inert to the reaction, for example, a hydrocarbon solvent such as an aliphatic, alicyclic, or aromatic hydrocarbon compound, for example, butyl lithium is used as a polymerization initiator, and a randomizer is used as necessary. By subjecting styrene, 1,3-butadiene and the like to anionic polymerization in the presence of styrene, a desired copolymer such as a styrene-butadiene copolymer can be obtained.

(Hydrocarbon solvents in anionic polymerization)
The hydrocarbon solvent is preferably one having 3 to 8 carbon atoms, such as propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene and trans-2. -Butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene and the like. These may be used alone or in combination of two or more.

(Randomizer in anionic polymerization)
The randomizer is a microstructure control of a conjugated diene moiety in a copolymer, for example, an increase in 1,2-bond in butadiene, an increase in 3,4-bond in isoprene, or the composition of monomer units in the copolymer. It is a compound having an action of controlling distribution, for example, randomizing styrene units and butadiene units in a styrene-butadiene copolymer. The randomizer is not particularly limited, and any known compound generally used as a conventional randomizer can be used. For example, dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, bistetrahydrofurylpropane, triethylamine, pyridine, N-methylmorpholine, N, N, N ′, N′-tetramethylethylenediamine, 1,2-di Examples include ethers such as piperidinoethane and tertiary amines. Further, potassium salts such as potassium-t-amylate and potassium-t-butoxide, and sodium salts such as sodium-t-amylate can also be used. These randomizers may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of randomizer used is preferably 0.01 molar equivalents or more, more preferably 0.05 molar equivalents or more per mole of the organic lithium compound. If the amount of randomizer used is less than 0.01 molar equivalent, the effect of addition tends to be small and it tends to be difficult to randomize. The amount of randomizer used is preferably 1000 molar equivalents or less, more preferably 500 molar equivalents or less, per mole of the organic lithium compound. If the amount of randomizer used exceeds 1000 molar equivalents, the reaction rate of the monomer changes greatly, and conversely, it tends to be difficult to randomize.

(Reaction temperature)
The reaction temperature during the anionic polymerization is not particularly limited as long as the reaction proceeds suitably, but it is usually preferably −10 ° C. to 100 ° C., more preferably 25 ° C. to 70 ° C.

(Modification process)
By the step of reacting the active terminal of the copolymer obtained in the above-mentioned polymerization step with the compound (B2) having a functional group that interacts with silica, it interacts with silica at the terminal end of polymerization of the copolymer. Functional groups can be introduced. As a result, a copolymer having a modified terminal end of polymerization is obtained. In the present invention, the term “terminal” means a portion other than the structure derived from a monomer having a carbon-carbon double bond that exists at the end of a molecular chain.

（式（１）中、Ａ^１は、窒素原子、リン原子及び硫黄原子からなる群より選択される少なくとも一種の原子を有し、活性水素を有さず、かつＲ^５に対して窒素原子、リン原子又は硫黄原子で結合する１価の官能基である。Ｒ^３及びＲ^４はヒドロカルビル基であり、Ｒ^５はヒドロカルビレン基であり、ｎは０〜２の整数である。但し、Ｒ^３及びＲ^４が複数存在する場合、複数のＲ^３及びＲ^４は、それぞれ同じでも異なっていてもよい。）
（ＩＩ）分子中に、環状エーテル基、（チオ）カルボニル基及びイソ（チオ）シアナート基からなる群より選択される少なくとも１種の官能基（ｘ１）と、窒素原子、リン原子、酸素原子及び硫黄原子からなる群より選択される少なくとも一種の原子（但し、窒素原子、リン原子及び硫黄原子は、少なくともいずれかが３置換のヒドロカルビルシリル基で保護されていてもよい。）を有し、かつ活性水素を有していない、前記官能基（ｘ１）とは異なる基（ｘ２）と、を各々１つ以上有する化合物（Ｂ２−２）；
（ＩＩＩ）分子中に、イソ（チオ）シアナート基を２つ以上有する化合物（Ｂ２−３）；
等が挙げられる。化合物（Ｂ２）としては、これらを一種単独で又は二種以上を組み合わせて使用することができる。なお、本明細書において、（チオ）カルボニル基は、カルボニル基及びチオカルボニル基を示し、イソ（チオ）シアナート基は、イソシアナート基及びイソチオシアナート基を示す。 As long as the copolymer used in the modification reaction (hereinafter also referred to as a terminal modification reaction) has an active terminal, the polymerization initiation terminal may be unmodified or modified. The compound (B2) is not particularly limited as long as it has a functional group that interacts with silica and can react with the polymerization active terminal. Preferable specific examples of compound (B2) include, for example, (I) compound (B2-1) represented by the following formula (1);

(In Formula (1), A ¹ has at least one atom selected from the group consisting of a nitrogen atom, a phosphorus atom, and a sulfur atom, does not have active hydrogen, and is a nitrogen atom with respect to R ⁵ ; R ³ and R ⁴ are hydrocarbyl groups, R ⁵ is a hydrocarbylene group, and n is an integer of 0 to 2, where R ³ and R ⁴ are monovalent functional groups bonded with a phosphorus atom or a sulfur atom. When a plurality of ³ and R ⁴ are present, the plurality of R ³ and R ⁴ may be the same or different.)
(II) In the molecule, at least one functional group (x1) selected from the group consisting of a cyclic ether group, a (thio) carbonyl group and an iso (thio) cyanate group, a nitrogen atom, a phosphorus atom, an oxygen atom, and At least one atom selected from the group consisting of sulfur atoms (provided that at least one of the nitrogen atom, phosphorus atom and sulfur atom may be protected by a tri-substituted hydrocarbylsilyl group); A compound (B2-2) having no active hydrogen and each having one or more groups (x2) different from the functional group (x1);
(III) Compound (B2-3) having two or more iso (thio) cyanate groups in the molecule;
Etc. As a compound (B2), these can be used individually by 1 type or in combination of 2 or more types. In the present specification, the (thio) carbonyl group represents a carbonyl group and a thiocarbonyl group, and the iso (thio) cyanate group represents an isocyanate group and an isothiocyanate group.

In the above formula (1), the hydrocarbyl group of R ³ and R ⁴ is a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or a 6 to 20 carbon atom. An aryl group is preferred.
R ⁵ is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms.
n is preferably 0 or 1 from the viewpoint of increasing the reactivity with the copolymer.
A ¹ has at least one atom selected from the group consisting of a nitrogen atom, a phosphorus atom and a sulfur atom (hereinafter also referred to as a specific atom), and binds to R ⁵ with these specific atoms. The specific atom is not bonded to active hydrogen, and may be protected with, for example, a trisubstituted hydrocarbylsilyl group. Here, “active hydrogen” refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably refers to a substance having a bond energy lower than that of polymethylene.

In particular, A ¹ is preferably a group capable of becoming an onium ion by the onium salt generator. When the compound (B2) has such a group (A ¹ ), excellent shape retention can be imparted to the modified copolymer.
Specific examples of A ¹ include, for example, a nitrogen-containing group in which two hydrogen atoms of a primary amino group are substituted by two protecting groups, and one hydrogen atom of a secondary amino group is substituted by one protecting group. A nitrogen-containing group, a tertiary amino group, an imino group, a pyridyl group, a phosphorus-containing group in which two hydrogen atoms of a primary phosphino group are substituted by two protecting groups, and one hydrogen atom of a secondary phosphino group is 1 Examples thereof include a phosphorus-containing group that is substituted by one protecting group, a tertiary phosphino group, and a sulfur-containing group in which one hydrogen atom of a thiol group is substituted by one protecting group. Among these, a group having a nitrogen atom is preferable from the viewpoint of good affinity with silica. The “protecting group” is a functional group that converts A ¹ into a functional group that is inactive with respect to the polymerization active terminal, and examples thereof include a trisubstituted hydrocarbylsilyl group.

Specific examples of the compound (B2-1) include a nitrogen-containing group in which two hydrogen atoms of a primary amine are substituted by two protecting groups, and one hydrogen atom of a secondary amine is substituted by one protecting group. Examples of the compound having a nitrogen-containing group or a tertiary amino group and an alkoxysilyl group are, for example, N, N-bis (trimethylsilyl) aminopropyltrimethoxysilane, N, N-bis (trimethylsilyl) aminopropylmethyl. Diethoxysilane, N, N ′, N′-tris (trimethylsilyl) -N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3- (4-trimethylsilyl-1-piperazino) propylmethyldimethoxysilane, Etc.

Examples of the compound having an imino group or pyridyl group and an alkoxysilyl group include N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine, N- (1-methylpropylidene). ) -3- (Triethoxysilyl) -1-propanamine, N- (4-N, N-dimethylaminobenzylidene) -3- (triethoxysilyl) -1-propanamine, N- (cyclohexylidene)- 3- (Triethoxysilyl) -1-propanamine and trimethoxysilyl compounds, methyldiethoxysilyl compounds, ethyldimethoxysilyl compounds, N- (3-trimethoxysilylpropyl) -4 corresponding to these triethoxysilyl compounds , 5-dihydroimidazole, N- (3-triethoxysilylpropyl) -4,5-dihydroimi Sol, N- (3-trimethoxysilylpropyl) -4,5-imidazole, N- (3-triethoxysilylpropyl) -4,5-imidazole, 3-hexamethyleneiminopropyltrimethoxysilane, 3-hexamethylene Examples include iminopropylmethyldimethoxysilane, and compounds obtained by replacing the alkyl group and alkanediyl group in the above compound with an alkyl group having 1 to 6 carbon atoms and an alkanediyl group having 1 to 6 carbon atoms, respectively.

A phosphorus-containing group in which two hydrogen atoms of a primary phosphino group are substituted by two protecting groups, a phosphorus-containing group in which one hydrogen atom of a secondary phosphino group is substituted by one protecting group, a tertiary phosphino group Or a compound having a sulfur-containing group in which one hydrogen atom of a thiol group is substituted with one protecting group and an alkoxysilyl group include P, P-bis (trimethylsilyl) phosphinopropylmethyldimethoxysilane, P , P-bis (trimethylsilyl) phosphinopropyltrimethoxysilane, 3-dimethylphosphinopropyltrimethoxysilane, 3-dimethylphosphinopropylmethyldimethoxysilane, 3-diphenylphosphinopropyltrimethoxysilane, 3-diphenylphosphinopropyl Triethoxysilane, 3- Phenylphosphinopropylmeryldimethoxysilane, S-trimethylsilylmercaptopropylmethyldimethoxysilane, S-trimethylsilylmercaptopropyltrimethoxysilane, S-trimethylsilylmercaptopropyltriethoxysilane, S-trimethylsilylmercaptopropylmethyldiethoxysilane, and the above compounds The compound etc. which replaced the alkyl group and the alkanediyl group with the C1-C6 alkyl group and the C1-C6 alkanediyl group, respectively can be mentioned. In addition, examples of the compound having an iso (thio) cyanate group include 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane.

In the compound (B2-2), the group (x2) is preferably a group containing a nitrogen atom that is not bonded to active hydrogen. Specific examples thereof include a compound having a cyclic ether group such as tetra Epoxyamine compounds such as glycidyl-1,3-bisaminomethylcyclohexane;
Examples of the compound having a (thio) carbonyl group include 4-aminoacetophenone such as 4-N, N-dimethylaminobenzophenone; bis (dihydrocarbylaminoalkyl) such as 1,7-bis (methylethylamino) -4-heptanone Ketones; dihydrocarbylaminoalkyl (meth) acrylates such as 2-dimethylaminoethyl acrylate; hydrocarbyl imidazolidinones such as 1,3-dimethyl-2-imidazolidinone; N-hydrocarbyl pyrrolidones such as 1-phenyl-2-pyrrolidone N-hydrocarbylcaptolactam such as N-methyl-ε-caprolactam; N-dihydrocarbylformamide such as N, N-diethylformamide; N, N-dihydrocarbylacetamide such as N, N-dimethylacetamide; N-dimethyl Acrylamide such as (meth) acrylamide; and the like;
Examples of the compound having an iso (thio) cyanate group include 3-isocyanatopropyltrimethoxysilane.

Examples of the compound (B2-3) include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and p-phenylene diene. Isocyanate, tris (isocyanatophenyl) thiophosphate, xylene diisocyanate, benzene-1,2,4-triisocyanate, naphthalene-1,2,5,7-tetraisocyanate, 1,4-phenylene diisothiate Examples include an isocyanate.

（一般式（１−１）中、Ｒ^６は水素原子またはヒドロカルビル基であり、複数存在するＲ^６は同じであっても異なっていてもよい。Ａ^４、Ｒ^３、Ｒ^５及びｎは上記式（１）のＡ^１、Ｒ^３、Ｒ^５及びｎと同義である。） As the compound (B2), it is particularly preferable to use the compound (B2-1) in terms of strong affinity with silica. When using the silane compound (B2-1), for the purpose of adjusting the Mooney viscosity of the modified copolymer, together with the silane compound (B2-1), silicon tetrachloride, an epoxy-containing compound (for example, tetraglycidyl-1, 3-bisaminomethylcyclohexane and the like) may be used. The compound (B2) exemplified above has the same action in that it can obtain a modified copolymer in which the terminal end of polymerization is modified. Accordingly, even those not described in the examples described later can be used in the present invention. In addition, the structure represented by the following formula (1-1) is introduced into the polymer terminal by the reaction between the compound represented by the above formula (1) and the modified copolymer.

(In General Formula (1-1), R ⁶ is a hydrogen atom or a hydrocarbyl group, and a plurality of R ⁶ may be the same or different. A ⁴ , R ³ , R ⁵ and n are the same as above. (It is synonymous with A < ¹ >, R < ³ >, R < ⁵ > and n of Formula (1).)

The above terminal modification reaction can be performed as a solution reaction, for example. This solution reaction may be performed using a solution containing unreacted monomers after completion of the polymerization reaction in the polymerization step, and the copolymer contained in the solution is isolated and dissolved in a suitable solvent such as cyclohexane. You may do it above. The terminal modification reaction may be performed using either a batch system or a continuous system. At this time, the method for adding the compound (B2) is not particularly limited, and examples thereof include a method of adding all at once, a method of adding in divided portions, and a method of adding continuously.

The amount of the compound (B2) used for the terminal modification reaction may be appropriately set according to the type of the compound used for the reaction, but is preferably 0.8 with respect to the metal atom involved in the polymerization reaction possessed by the polymerization initiator. 1 molar equivalent or more, more preferably 0.3 molar equivalent or more. By setting it to 0.1 molar equivalent or more, the modification reaction can be sufficiently advanced, and the dispersibility of silica can be suitably improved.
The temperature of the terminal modification reaction is usually the same as the temperature of the polymerization reaction, preferably −20 to 150 ° C., more preferably 0 to 120 ° C., and particularly preferably 20 to 100 ° C. preferable. When the temperature of the modification reaction is low, the viscosity of the modified copolymer tends to increase. On the other hand, when the temperature of the modification reaction is high, the polymerization active terminal tends to be deactivated. The reaction time of the denaturation reaction is preferably 1 minute to 5 hours, more preferably 2 minutes to 1 hour.

(Reaction stopped)
The anionic polymerization can be stopped by adding a reaction terminator usually used in this field. Examples of such a reaction terminator include polar solvents having active protons such as alcohols such as methanol, ethanol and isopropanol or acetic acid and mixtures thereof, or polar solvents and nonpolar solvents such as hexane and cyclohexane. A mixed solution is mentioned. The amount of the reaction terminator added is usually about the same molar amount or twice the molar amount relative to the anionic polymerization initiator.

<Coupling>
In the method for producing the copolymer, a coupling agent may be added to the hydrocarbon solution of the copolymer from the start of the polymerization of the monomer to the recovery of the polymer described later. Examples of the coupling agent include compounds represented by the following formula (2-1).
R ¹ _a ML _4-a (2-1)
(In formula (2-1), R ¹ represents an alkyl group, an alkenyl group, a cycloalkenyl group or an aryl group, M represents a silicon atom or a tin atom, L represents a halogen atom or a hydrocarbyloxy group, and a represents Represents an integer of 0 to 2.)

As the coupling agent represented by the above formula (2-1), silicon tetrachloride, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, tin tetrachloride, methyltrichlorotin, dimethyldichlorotin, trimethylchlorotin, tetramethoxy Examples include silane, methyltrimethoxysilane, dimethoxydimethylsilane, methyltriethoxysilane, ethyltrimethoxysilane, dimethoxydiethylsilane, diethoxydimethylsilane, tetraethoxysilane, ethyltriethoxysilane, and diethoxydiethylsilane.

The amount of the coupling agent added is preferably 0.03 mol or more, more preferably 0.05 mol or more, per 1 mol of alkali metal derived from the alkali metal catalyst in order to improve the processability of the polymer. Moreover, in order to improve low fuel consumption, Preferably it is 0.4 mol or less, More preferably, it is 0.3 mol or less.

<Hydrogen addition method>
In the method for producing a hydrogenated copolymer, the copolymer described so far is hydrogenated to obtain a hydrogenated copolymer having a hydrogenation rate of 75 mol% or more. There is an advantage that heat resistance is improved by hydrogenating the copolymer. On the other hand, if the hydrogenation rate is low, the effects of improving fuel economy, bending crack growth resistance and chip cut resistance cannot be sufficiently obtained.

There are no particular limitations on the hydrogenation method and reaction conditions, and hydrogenation may be performed using known methods and known conditions. Usually, it is carried out in the presence of a hydrogenation catalyst at 20 to 150 ° C. under hydrogen pressure of 0.1 to 10 MPa. The hydrogenation rate can be arbitrarily selected by changing the amount of the hydrogenation catalyst, the hydrogen pressure during the hydrogenation reaction, the reaction time, and the like. As the hydrogenation catalyst, a compound containing any of metals in Group 4 to 11 of the periodic table can be used. For example, a compound containing Ti, V, Co, Ni, Zr, Ru, Rh, Pd, Hf, Re, and Pt atoms can be used as the hydrogenation catalyst. More specific hydrogenation catalysts include metallocene compounds such as Ti, Zr, Hf, Co, Ni, Pd, Pt, Ru, Rh, and Re; metals such as Pd, Ni, Pt, Rh, and Ru are carbon, A supported heterogeneous catalyst supported on a carrier such as silica, alumina, diatomaceous earth; a homogeneous Ziegler catalyst in which an organic salt of a metal element such as Ni or Co or an acetylacetone salt and a reducing agent such as organoaluminum is combined; Examples include organometallic compounds or complexes such as Ru and Rh; fullerenes and carbon nanotubes in which hydrogen is occluded.

Of these, metallocene compounds containing any of Ti, Zr, Hf, Co, and Ni are preferable in that they can be hydrogenated in a homogeneous system in an inert organic solvent. Furthermore, metallocene compounds containing any of Ti, Zr, and Hf are preferred. In particular, a hydrogenation catalyst obtained by reacting a titanocene compound with an alkyl lithium is preferable because it is an inexpensive and industrially useful catalyst. Specific examples include, for example, JP-A-1-275605, JP-A-5-271326, JP-A-5-271325, JP-A-5-222115, JP-A-11-292924, and JP-A-11-292924. JP 2000-37632 A, JP 59-133203 A, JP 63-5401 A, JP 62-218403 A, JP 7-90017 A, JP 43-19960 A, Mention may be made of the hydrogenation catalyst described in JP-B 47-40473. In addition, these hydrogenation catalysts can be used individually by 1 type or in combination of 2 or more types.

The content of the hydrogenated copolymer in 100% by mass of the rubber component is 75% by mass or more, preferably 80% by mass or more. When the content of the hydrogenated copolymer is less than 75% by mass, the effect of the present invention tends to be hardly obtained. Moreover, this content becomes like this. Preferably it is 95 mass% or less, More preferably, it is 90 mass% or less, More preferably, it is 85 mass% or less. When the content exceeds 95% by mass, the flex crack growth resistance and the chip cut resistance may be deteriorated.

Examples of other rubber components that can be used other than the hydrogenated copolymer include conventional styrene butadiene copolymer rubber (SBR), polybutadiene rubber (BR), butadiene isoprene copolymer rubber, and butyl rubber. Moreover, natural rubber (NR), an ethylene propylene copolymer, an ethylene octene copolymer, etc. can be mentioned. Of these, BR, NR, and SBR are preferable, and BR is particularly preferable in that the effects of the present invention can be sufficiently exhibited. Two or more of these rubber components may be used in combination. When the hydrogenated copolymer and BR are used in combination, the effects of the present invention are more remarkably exhibited.

The BR is not particularly limited. For example, BR 1220 manufactured by Nippon Zeon Co., Ltd., BR 150B manufactured by Ube Industries, Ltd., high cis blending amount BR, 1 such as VCR412, VCR617 manufactured by Ube Industries, Ltd. , 2-syndiotactic polybutadiene crystal (SPB) containing BR, BR synthesized by using a rare earth element-based catalyst (rare earth BR), and the like in the tire industry can be used.

The content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more. The content is preferably 25% by mass or less, more preferably 20% by mass or less. Within the above range, the effect of the present invention is remarkably exhibited.

The total content of the hydrogenated copolymer and BR in 100% by mass of the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more and 100% by mass. If it is less than 80% by mass, the effects of the present invention may not be sufficiently obtained.

The rubber composition in the present invention contains carbon black having a specific nitrogen adsorption specific surface area.

The carbon black has a nitrogen adsorption specific surface area (N ₂ SA) of 5 to 200 m ² / g. The lower limit is preferably 15 m ² / g or more, more preferably 50 m ² / g or more. Moreover, an upper limit becomes like this. Preferably it is 180 m < ² > / g or less, More preferably, it is 150 m < ² > / g or less, More preferably, it is 130 m < ² > / g or less, Most preferably, it is 100 m < ² > / g or less. If it is less than 5 m ² / g, a sufficient reinforcing effect may not be obtained, and if it exceeds 200 m ² / g, fuel economy may be reduced.
Incidentally, _N 2 SA of the carbon black in the present invention, JIS K 6217-2: measured according to 2001.

The carbon black has a dibutyl phthalate (DBP) oil absorption of preferably 50 ml / 100 g or more, more preferably 70 ml / 100 g or more, and even more preferably 90 ml / 100 g or more. The DBP oil absorption is preferably 200 ml / 100 g or less, more preferably 150 ml / 100 g or less. If it is less than 50 ml / 100 g, a sufficient reinforcing effect may not be obtained, and if it exceeds 200 ml / 100 g, the fuel efficiency may be lowered.
In addition, the DBP oil absorption of carbon black in the present invention is measured according to JIS K 6217-4: 2001.

The content of the carbon black is 30 parts by mass or more, preferably 35 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is 70 parts by mass or less, preferably 60 parts by mass or less, more preferably 55 parts by mass or less. Within the above range, good fuel economy, chip cut resistance and flex crack growth resistance can be obtained.

The rubber composition in the present invention may further contain a filler other than carbon black. Examples of other fillers include mica such as silica, calcium carbonate, and sericite, and white fillers such as aluminum hydroxide, magnesium oxide, magnesium hydroxide, clay, talc, alumina, titanium oxide, and mica.

In addition to the above components, the rubber composition in the present invention includes a vulcanizing agent such as sulfur; a thiazole vulcanization accelerator, a thiuram vulcanization accelerator, a sulfenamide vulcanization accelerator, and a guanidine vulcanization accelerator. Vulcanization accelerators such as agents; vulcanization activators such as stearic acid and zinc oxide; organic peroxides; processing aids such as extenders (oils) and lubricants; Can be used.

As the extending oil (oil), aromatic mineral oil (viscosity specific gravity constant (VGC value) 0.900 to 1.049), naphthenic mineral oil (VGC value 0. 850 to 0.899), paraffinic mineral oil (VGC value 0.790 to 0.849), and the like. The polycyclic aromatic content of the extender oil is preferably less than 3% by mass, more preferably less than 1% by mass. The polycyclic aromatic content is measured according to the British Petroleum Institute 346/92 method. Moreover, the aromatic compound content (CA) of the extending oil is preferably 20% by mass or more. These extending oils may be used in combination of two or more.

Examples of the vulcanization accelerator include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and thiazole vulcanization accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram monosulfide, tetramethylthiuram disulfide Thiuram vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N- Sulfenamide vulcanization accelerators such as oxyethylene-2-benzothiazole sulfenamide, N, N′-diisopropyl-2-benzothiazole sulfenamide; diphenylguanidine, diortolylguanidine, orthotolylbiguanidine, etc. Guani It can be mentioned emission-based vulcanization accelerator. Of these, sulfenamide-based vulcanization accelerators are preferable and N-cyclohexyl-2-benzothiazole sulfenamide is more preferable because the effects of the present invention can be more suitably obtained. It is also preferable to use a guanidine vulcanization accelerator in combination. 0.1-5 mass parts is preferable with respect to 100 mass parts of rubber components, and, as for the usage-amount of a vulcanization accelerator, More preferably, it is 0.2-4 mass parts.

Although it does not specifically limit as a vulcanizing agent, Sulfur can be used conveniently. The content of sulfur is preferably 0.5 to 5 parts by mass, more preferably 1 to 3 parts by mass with respect to 100 parts by mass of the rubber component. Thereby, the effect of this invention is acquired more suitably.

The rubber composition in the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The rubber composition in the present invention can be used for each member (tread, sidewall, carcass, belt, bead, etc.) of a tire, and is particularly preferably used as a sidewall of a tire.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing a hydrogenated copolymer and, if necessary, a rubber composition containing the above-mentioned various compounding agents, extruded in accordance with the shape of each tire member such as a sidewall at an unvulcanized stage, An unvulcanized tire is formed by shaping | molding with another tire member with a normal method on a tire molding machine. The pneumatic tire of the present invention is obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

The pneumatic tire of the present invention is preferably used as a tire for passenger cars, heavy duty tires for trucks and buses, two-wheeled vehicle tires, competition tires, and the like, and particularly preferably used as a heavy duty tire.

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

Hereinafter, various chemicals used at the time of synthesis and polymerization will be described together. In addition, the chemical | medical agent refine | purified according to the usual method as needed.
n-hexane: styrene manufactured by Kanto Chemical Co., Ltd .: butadiene manufactured by Kanto Chemical Co., Ltd .: 1,3-butadiene TMEDA manufactured by Tokyo Chemical Industry Co., Ltd .: N, N, N ′, N manufactured by Kanto Chemical Co., Ltd. '-Tetramethylethylenediamine n-butyllithium solution: 1.6M n-butyllithium hexane solution 2,6-di-tert-butyl-p-cresol manufactured by Kanto Chemical Co., Ltd .: manufactured by Ouchi Shinsei Chemical Co., Ltd. No crack 200
Alcohol: Methanolamine-based modifier manufactured by Tokyo Chemical Industry Co., Ltd .: N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane

Moreover, the evaluation method of the obtained copolymer is demonstrated collectively below.

(Measurement of hydrogenation rate of conjugated diene part of copolymer)
A solution having a concentration of 15% by mass was prepared using carbon tetrachloride as a solvent, and calculated from the spectrum reduction rate of the unsaturated bond part of 100 MHz H ¹ -NMR.

(Measurement of styrene content)
H ¹ -NMR was measured at 25 ° C. using a JEOL JNM-A 400 NMR apparatus, and phenyl protons based on 6.5 to 7.2 ppm styrene units and 4.9 to 5.4 ppm butadiene were obtained from the spectrum. The styrene content was determined from the ratio of vinyl protons based on units.

(Measurement of weight average molecular weight (Mw), number average molecular weight (Mn))
The weight average molecular weight (Mw) and number average molecular weight (Mn) of the copolymer were determined by gel permeation chromatography (GPC) (GPC-8000 series, manufactured by Tosoh Corporation), detector: differential refractometer, column: Tosoh Corporation ) Obtained from TSKGEL SUPERMULTIPORE HZ-M, manufactured by TSKGEL, based on standard polystyrene conversion. Moreover, when the copolymer has a modifying group, Mw and Mn were measured before carrying out the modification treatment. This is because when a copolymer having a modifying group is measured, the modifying group and the silica gel of the column interact, and accurate Mw and Mn cannot be obtained.

(Mooney viscosity (ML _{1 + 4} ))
The Mooney viscosity of the polymer was measured at 100 ° C. according to JIS K 6300 (1994).

<Example of copolymer production>
Synthesis Example 1 (Synthesis of copolymer (1): hydrogenation rate 0 mol%, SBR)
In a heat-resistant reaction vessel sufficiently purged with nitrogen, add 2000 ml of n-hexane, 60 g of styrene, 140 g of 1,3-butadiene, 0.93 g of TMEDA, and 0.45 mmol of n-butyllithium, and stir at 50 ° C. for 5 hours to carry out the polymerization reaction. went. Thereafter, alcohol was added to stop the reaction, 1 g of 2,6-tert-butyl-p-cresol was added to the reaction solution, and then copolymer (1) was obtained by reprecipitation purification. The obtained copolymer (1) had a weight average molecular weight (Mw) of 490,000 and a styrene content of 30% by mass.

Synthesis Example 2 (Synthesis of copolymer (2): hydrogenation rate 60 mol%, hydrogenated SBR)
A copolymer (2) was obtained by the same formulation as the copolymer (1) except that the obtained polymer was hydrogenated. That is, after the polymerization conversion reaction in the copolymer (1), alcohol is not added to stop the polymerization reaction, and then the mixture is stirred for 20 minutes while supplying hydrogen gas at a pressure of 0.4 MPa-Gauge. Reaction with terminal lithium gave lithium hydride. Hydrogenation was performed using a catalyst mainly composed of titanocene dichloride at a hydrogen gas supply pressure of 0.7 MPa-Gauge, a reaction temperature of 90 ° C. When the amount of hydrogen absorption reaches an integrated amount that achieves the target hydrogenation rate, the reaction temperature is brought to room temperature, the hydrogen pressure is returned to normal pressure, the reaction vessel is withdrawn from the reaction vessel, the reaction solution is stirred into water, and the solvent is steamed. The copolymer (2) was obtained by removing by stripping. The resulting copolymer (2) had a hydrogenation rate of 60 mol% and a weight average molecular weight (Mw) of 450,000.

Synthesis Example 3 (Synthesis of copolymer (3): hydrogenation rate 80 mol%, hydrogenated SBR)
A copolymer (3) was obtained by the same formulation as the copolymer (2) except that the cumulative amount of hydrogen suction was adjusted so as to achieve the target hydrogenation rate. The resulting copolymer (3) had a hydrogenation rate of 80 mol% and a weight average molecular weight (Mw) of 480,000.

Synthesis Example 4 (Synthesis of copolymer (4): hydrogenation rate 95 mol%, hydrogenated SBR)
A copolymer (4) was obtained by the same formulation as the copolymer (2) except that the integrated amount of hydrogen suction was adjusted so as to achieve the target hydrogenation rate. The resulting copolymer (4) had a hydrogenation rate of 95 mol% and a weight average molecular weight (Mw) of 450,000.

Synthesis Example 5 (Synthesis of copolymer (5): hydrogenation rate 95 mol%)
A copolymer (5) was obtained by the same formulation as the copolymer (2) except that the cumulative amount of hydrogen suction was adjusted so as to achieve the target hydrogenation rate. The resulting copolymer (5) had a weight average molecular weight (Mw) of 2,000,000 and a hydrogenation rate of 95 mol%.

Synthesis Example 6 (Synthesis of copolymer (6): hydrogenation rate 95 mol%)
A copolymer (6) was obtained by the same formulation as the copolymer (2) except that the cumulative amount of hydrogen suction was adjusted so as to achieve the target hydrogenation rate. The resulting copolymer (6) had a weight average molecular weight (Mw) of 200,000 and a hydrogenation rate of 95 mol%.

Synthesis Example 7 (Synthesis of copolymer (7): hydrogenation rate: 95 mol%, hydrogenated modified SBR)
In a heat-resistant reaction vessel sufficiently purged with nitrogen, add 2000 ml of n-hexane, 60 g of styrene, 140 g of 1,3-butadiene, 0.93 g of TMEDA, and 0.45 mmol of n-butyllithium, and stir at 50 ° C. for 5 hours to carry out the polymerization reaction. went. Thereafter, 0.15 mol of an amine-based modifier was added and stirred at 0 ° C. for 1 hour. Regarding the subsequent steps, a copolymer (7) was obtained by the same formulation as the copolymer (2) except that the integrated amount of hydrogen suction was adjusted. The resulting copolymer (7) had a hydrogenation rate of 95 mol% and a weight average molecular weight (Mw) before modification of 440,000.

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
Copolymers (1) to (7): Synthetic polybutadiene rubber by the above method: Ubepol BR150B manufactured by Ube Industries, Ltd.
Carbon Black 1: Show Black N330 manufactured by Cabot Japan Co., Ltd. (N ₂ SA: 75 m ² / g, DBP oil absorption: 102 ml / 100 g)
Carbon Black 2: Show Black N220 (N ₂ SA: 125 m ² / g, DBP oil absorption: 115 ml / 100 g) manufactured by Cabot Japan
Oil: X-140 manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Antigen 3C manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Beads manufactured by NOF Corporation Zinc stearate Zinc oxide: Zinc flower No. 1 manufactured by Mitsui Kinzoku Mining Co., Ltd. Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. 1: Soxinol CZ (N-cyclohexyl-2-benzothiazole sulfenamide) manufactured by Sumitomo Chemical Co., Ltd.
Vulcanization accelerator 2: Soxinol D (1,3-diphenylguanidine) manufactured by Sumitomo Chemical Co., Ltd.

(Examples and Comparative Examples)
According to the blending content shown in Table 2, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150 ° C. using a 1.7 L Banbury mixer manufactured by Kobe Steel Co., Ltd. Obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized with a 0.5 mm thick mold at 170 ° C. for 20 minutes to obtain a vulcanized rubber composition.
Further, the obtained unvulcanized rubber composition was molded into a sidewall shape, and bonded together with other tire members on a tire molding machine to form an unvulcanized tire, and vulcanized at 170 ° C. for 12 minutes, A test tire (size: 195 / 65R15) was produced.

<Evaluation items and test methods>
The following evaluation was performed about the obtained vulcanized rubber composition and the tire for a test. The results are shown in Table 2.

(Low fuel consumption index)
Using a spectrometer manufactured by Ueshima Seisakusho, tan δ of the vulcanized rubber composition was measured at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 50 ° C. The reciprocal value of tan δ was expressed as an index with Comparative Example 1 being 100. Larger values indicate lower rolling resistance and better fuel efficiency.

(Rubber hardness index)
The rubber hardness was measured with a type A durometer in accordance with JIS K 6253 “Method for testing hardness of vulcanized rubber and thermoplastic rubber”. The rubber hardness index was calculated by the following calculation formula, assuming that the rubber hardness of Comparative Example 1 was 100. The higher the rubber hardness index, the better the steering stability.
(Rubber hardness index) = (Rubber hardness of each compound) / (Rubber hardness of Comparative Example 1) × 100

(Bending crack growth resistance index)
According to JIS K 6260 “Dematcher bending crack growth test method for vulcanized rubber and thermoplastic rubber”, a crack of 1 mm is generated in the vulcanized rubber composition at a room temperature of 25 ° C., and this crack grows by 1 mm. The number of bends up to was measured. In addition, this measurement was performed twice, the average value was set to 100, and the bending crack growth resistance index was calculated by the following formula. Moreover, the larger the value, the better the resistance to flex crack growth. 70% and 110% indicate the elongation with respect to the length of the original vulcanized rubber composition.
(Bending crack growth index) = (Number of bendings for each formulation) / (Number of bendings for Comparative Example 1) × 100

(Chip cut resistance index)
Each test piece cut out from the test tire was subjected to air heat aging in a gear oven tester at 80 ° C. for 10 days, and then subjected to a tensile test according to JIS K 6251 to determine the breaking strength (TB) and the breaking strength of the test piece. The time elongation (EB) was measured. And the numerical value of the product (TBxEB) of the obtained breaking strength and elongation at break (TBxEB) was calculated, and the product was indexed according to the following calculation formula to evaluate the chip cut resistance. The higher the index, the better.
(Chip cut resistance index) = (TB × EB of each formulation) / (TB × EB of Comparative Example 1) × 100

From Table 2, an example using a rubber composition containing a hydrogenated styrene butadiene copolymer having a hydrogenation rate of 75 mol% or more and 75 mass% or more in a rubber component of 100 mass% and a specific amount of carbon black. In 1 to 8, it became clear that fuel economy, steering stability, chip cut resistance, and flex crack growth resistance can be improved satisfactorily.

Claims (9)

A pneumatic tire produced using a rubber composition,
The rubber composition is obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound, a hydrogenated copolymer having a conjugated diene portion hydrogenation rate of 75 mol% or more, and a nitrogen adsorption specific surface area of 5 ~ ²⁰⁰ m ² / g carbon black,
The content of the hydrogenated copolymer in 100% by mass of the rubber component is 75% by mass or more,
The pneumatic tire whose content of the said carbon black is 30-70 mass parts with respect to 100 mass parts of rubber components. The pneumatic tire according to claim 1, wherein the hydrogenated copolymer has a weight average molecular weight of 200,000 to 2,000,000. The pneumatic tire according to claim 1 or 2, wherein a hydrogenation rate of the hydrogenated copolymer is 90 mol% or more. The pneumatic tire according to any one of claims 1 to 3, wherein the hydrogenated copolymer is a hydrogenated styrene butadiene copolymer. The pneumatic tire according to claim 4, wherein the hydrogenated styrene butadiene copolymer is a hydrogenated modified styrene butadiene copolymer. The pneumatic tire according to claim 4 or 5, wherein the hydrogenated styrene-butadiene copolymer has a styrene content of 5 to 40% by mass. The pneumatic tire according to claim 1, wherein the rubber composition further contains a polybutadiene rubber. The pneumatic tire according to claim 7, wherein the content of the polybutadiene rubber in 100% by mass of the rubber component is 5 to 25% by mass. The pneumatic tire according to any one of claims 1 to 8, which is a pneumatic tire having a sidewall produced using the rubber composition.