JP6352685B2 - Rubber composition, pneumatic tire and method for producing the rubber composition - Google Patents

Description

The present invention relates to a rubber composition, a pneumatic tire produced using the rubber composition, and a method for producing the rubber composition.

In recent years, in response to demands for lower fuel consumption in automobiles, tires with reduced rolling resistance and reduced heat generation have been developed, particularly with excellent fuel efficiency for treads with a high occupation ratio. Sex is required. As a method for improving the fuel efficiency of tire rubber compositions, replacement of carbon black, which has been used as a reinforcing filler, with silica, reducing the amount of reinforcing filler, and reinforcement with a large particle size However, these methods have a problem that the fracture performance and wear resistance are greatly reduced. If the amount of the filler for reinforcement is reduced, the wet grip performance is further reduced. In general, it is difficult to achieve compatibility between durability, durability such as fracture performance and wear resistance, and wet grip performance, which is a contradiction.

By using a modified polymer for silica that has a functional group that interacts with a silane coupling agent or silica, the dispersibility of silica is improved, or rubber and silica are chemically bonded to reduce fuel consumption and breakage performance. Improvements in performance such as wear resistance and wet grip performance have been attempted, but the demand for improvement is large, and there is a problem in that workability is lowered. Therefore, further improvement in these performance balances is desired.

The present invention solves the above problems, has a good workability, and can improve the fuel efficiency, wet grip performance, fracture performance and wear resistance in a well-balanced manner, and a rubber composition for tires and the rubber composition. It is an object of the present invention to provide a pneumatic tire produced as described above and a method for producing the rubber composition.

The present invention is a rubber composition containing a polymer obtained by homopolymerizing and / or copolymerizing a conjugated diene monomer I and a conjugated diene monomer II, respectively, which is formed in the rubber composition. The average length of the interface between the polymer phase (1) derived from the monomer I and the polymer phase (2) derived from the monomer II is 3 μm or more per 1 μm ² of the cross section of the rubber composition, or the polymer phases (1) and (2) Relates to a rubber composition for tires in which the cis bond content of double bonds in the structural units derived from the conjugated diene monomer I and monomer II in the polymer is 90 mol% or more, respectively.

In 100% by mass of the rubber component, the content of the structural unit derived from the monomer I and the content of the structural unit derived from the monomer II are each 20 to 80% by mass, and the structural unit and monomer derived from the monomer I The total content of the structural units derived from II is preferably 40% by mass or more, and the reinforcing filler is preferably contained in an amount of 10 to 150 parts by mass with respect to 100 parts by mass of the rubber component.

It is preferable that the monomer I and the monomer II are isoprene and butadiene.

It is preferable to contain a copolymer obtained by copolymerizing the monomer I and the monomer II.

It is preferable that the copolymer has a glass transition temperature of −100 to −40 ° C. and a weight average molecular weight of 150,000 to 2,000,000.

The copolymer is preferably obtained by coordination anionic polymerization with a transition metal-containing compound.

It is preferable to contain 5% by mass or more of the copolymer in 100% by mass of the rubber component.

It is preferable that the copolymer is a modified copolymer modified by adding a functional group having a chemical interaction with the reinforcing filler.

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

The present invention also includes the step of copolymerizing the conjugated diene monomer I and the conjugated diene monomer II by coordination anionic polymerization, and the step of kneading the copolymer obtained by the above step. It relates to the manufacturing method.

According to the present invention, homopolymerization and / or copolymerization of the monomers I and II in which the cis bond content of the double bond in the structural unit derived from the specific monomer I and the specific monomer II is a predetermined amount or more. The obtained polymer is contained, and the average length of the interface between the polymer phase (1) derived from the monomer I and the polymer phase (2) derived from the monomer II is a specific value or more, or the two polymer phases are compatible. Since it is a rubber composition for tires, it has good processability and can improve fuel economy, wet grip performance, fracture performance and wear resistance in a well-balanced manner.

Schematic diagram of the phase structure of two types of polymer phases formed from two types of monomers, respectively

The rubber composition for tires of the present invention comprises the monomers I and II in which the cis bond content of double bonds in the structural units derived from the conjugated diene monomer I and the conjugated diene monomer II is 90 mol% or more, respectively. It contains a polymer obtained by homopolymerization and / or copolymerization, and the average length of the interface between the polymer phase (1) derived from the monomer I and the polymer phase (2) derived from the monomer II is rubber. 3 μm or more per 1 μm ² cross section of the composition, or the polymer phases (1) and (2) are compatible.
In addition, when mixing 2 or more types of polymers, phase structures, such as complete compatibility, a sea-island structure, and a co-continuous structure, are formed according to the compatibility degree between polymers. For example, in the case of a sea-island structure, a polymer phase structure as shown in any of (a) to (c) of FIG. 1 is formed, and the closer the compatibility between the polymers, the closer to the phase structure of FIG. 1 (c). It is guessed. In the present specification, as used in the present specification, as shown in FIG. 1 (c), it means that it is non-uniform at the molecular level, but is uniform in an area of a specific size, and the interface cannot be discriminated. This means that the average length of the interface cannot be measured.
The interface length means the sum of the interface lengths of the polymer phases (1) and (2) in one mesh. For example, FIGS. 1 (a) and 1 (b) (the inside of the square is 1 mesh). Means the sum of the lengths of the boundaries of the polymer phases (1) and (2) (thick line portions in FIGS. 1A and 1B).

Homopolymerization and / or copolymerization of the monomers I and II in which the cis bond content of the double bond in the structural unit derived from the conjugated diene monomer I and the conjugated diene monomer II is 90 mol% or more, respectively. A rubber composition containing an obtained polymer and having an average length of an interface formed between a polymer phase (1) derived from a conjugated diene monomer I and a polymer phase (2) derived from a conjugated diene monomer II By making the cross section 1 μm ² or more 3 μm or more, the polymer phases (1) and (2) are finely dispersed, and the polymer phases (1) and (2) can form a uniform phase structure. In order to contribute to the improvement of the dispersibility of the agent and the like, it is presumed that the processability is improved and the fuel efficiency, wet grip performance, breakage performance and wear resistance can be improved.

The rubber composition for tires of the present invention contains a polymer obtained by homopolymerization and / or copolymerization of conjugated diene monomer I and conjugated diene monomer II as a rubber component.
That is, (i) a monomer I and a monomer II homopolymer, (ii) a monomer I and a monomer II copolymer, (iii) the above (i) and (ii) Specific examples include those included together. As the polymer, those including a copolymer obtained by copolymerizing the monomer I and the monomer II are particularly preferable, and even if the homopolymer of the monomer I and / or the homopolymer of the monomer II is included, It does not have to be included.

Examples of the conjugated diene monomer I and the conjugated diene monomer II include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 1,3-hexadiene, and the like. Among them, 1,3-butadiene and isoprene are particularly preferable in that the effects of the present invention can be sufficiently obtained. When the monomer I and the monomer II are 1,3-butadiene and isoprene, respectively, the copolymer, the homopolymer of the monomer I, and the homopolymer of the monomer II are each a copolymer of 1,3-butadiene and isoprene. It corresponds to coalescence, polybutadiene rubber, polyisoprene rubber (may be natural rubber).

When the copolymer of monomers I and II, and the homopolymer of monomer I and the homopolymer of monomer II are included, the copolymer of monomers I and II is compatible with the two types of homopolymers. It is presumed that it acts as a compatibility improver for improving the polymer and contributes to fine dispersion of the polymer phase (1) derived from the monomer I and the polymer phase (2) derived from the monomer II.

The copolymer in the present invention is obtained by copolymerizing monomer I and monomer II. By copolymerizing different components of monomer I and monomer II, it becomes heterogeneous at the micro level such as molecules, but since it is copolymerized, it can be made uniform at the macro level such as rubber composition. It is speculated that it contributes to compatibilization of the polymer phase (1) derived from I and the polymer phase (2) derived from the monomer II.

<Copolymer>
First, the copolymer will be described.
The copolymer is not particularly limited as long as it is a copolymer obtained by a polymerization method to be described later, but the copolymer obtained by copolymerization is used in that the effect of the present invention is remarkably obtained. Further, a copolymer modified by adding a functional group chemically interacting with the reinforcing filler is particularly preferable.

A well-known thing can be used as said functional group, For example, the functional group which has an oxygen atom, a nitrogen atom, a silicon atom, etc. is mentioned. Examples of the functional group having an oxygen atom include an alkylene oxide group such as an epoxy group and a tetrahydrofuranyl group; a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, and a t-butoxy group. An alkoxy group such as a group; an alkoxyalkyl group such as a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, and an ethoxyethyl group; an alkoxyaryl group such as a methoxyphenyl group and an ethoxyphenyl group. Moreover, trialkyl silyloxy groups, such as a trimethyl silyloxy group, a triethyl silyloxy group, and t-butyl dimethyl silyloxy group, can be mentioned. Moreover, a hydroxyl group can be mentioned. Examples of the functional group having a nitrogen atom include dialkylaminoalkyl groups such as dimethylaminoethyl group and diethylaminoethyl group. Examples of the functional group having a silicon atom include a trialkylsilylalkyl group such as a trimethylsilylmethyl group. A functional group having an oxygen atom is preferable in that the effect of the present invention can be obtained satisfactorily, and an epoxy group is particularly preferable.

When the copolymer has an epoxy group, the degree of epoxidation of the modified copolymer is 100 mol% of the total double bonds in the copolymer, preferably 5 mol% or more, more preferably 10 mol% or more. It is. The degree of epoxidation is preferably 30 mol% or less, more preferably 20 mol% or less. If the degree of epoxidation is less than 5 mol%, the effects of the present invention may be reduced, and if it exceeds 30 mol%, fuel economy and wear resistance may be reduced. The degree of epoxidation can be measured by the method for measuring the degree of epoxidation in Examples described later.
In the present invention, the epoxidation method is not particularly limited, and examples thereof include a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, and a peracid method. For example, acetic acid and hydrogen peroxide And sulfuric acid (catalyst) are mixed and allowed to stand at 40 ° C. for about 1-2 days to produce peracetic acid, and the resulting peracetic acid and the solution after copolymerization of the above copolymer are mixed to epoxidize can do.

In addition to the structural unit based on the conjugated diene monomer I and the conjugated diene monomer II, the copolymer in the present invention may further include a structural unit based on another monomer. Examples of the other monomer include aromatic vinyl, vinyl nitrile, and unsaturated carboxylic acid ester. Examples of the aromatic vinyl include styrene, α-methylstyrene, vinyl toluene, vinyl naphthalene, divinyl benzene, trivinyl benzene, and divinyl naphthalene. Examples of the vinyl nitrile include acrylonitrile, and examples of the unsaturated carboxylic acid ester include methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. Among these, aromatic vinyl is preferable, and styrene is more preferable.

The cis bond content of the double bond in the structural unit derived from the conjugated diene monomer I and the conjugated diene monomer II in the copolymer is 90 mol% or more, preferably 92 mol% or more, respectively. Preferably it is 93 mol% or more, More preferably, it is 95 mol% or more. When the cis bond content is less than 90 mol%, fracture performance and wear resistance tend to deteriorate. The upper limit is not particularly limited.
In the present invention, the cis bond content is a value obtained by the measurement method of Examples described later.

The vinyl bond content of the double bond in the structural unit derived from the conjugated diene monomer I and the conjugated diene monomer II in the copolymer is preferably 5 mol% or less, more preferably 3 mol% or less. is there. When the vinyl bond content exceeds 5 mol%, the wear resistance tends to deteriorate. The lower limit is not particularly limited.
In addition, in this invention, vinyl bond content is a value obtained by the measuring method of the below-mentioned Example.

The glass transition temperature (Tg) of the copolymer is preferably −100 ° C. or higher, more preferably −95 ° C. or higher, preferably −40 ° C. or lower, more preferably −50 ° C. or lower, and further preferably −86. C. or lower, particularly preferably −89 ° C. or lower. If the Tg is less than -100 ° C, the wet grip performance may be deteriorated, and if it exceeds -40 ° C, the wear resistance may be deteriorated.
In the present invention, Tg is a value obtained by the measurement method of Examples described later.

The weight average molecular weight (Mw) of the copolymer is preferably 150,000 or more, more preferably 200,000 or more, still more preferably 400,000 or more, and particularly preferably 550,000 or more. The Mw is preferably 2,000,000 or less, more preferably 1,500,000 or less, and still more preferably 1,200,000 or less. If the Mw is less than 150,000, fuel economy, wet grip performance, fracture performance, and wear resistance tend to deteriorate, and if it exceeds 2,000,000, workability and wet grip performance during kneading. Tend to get worse.
In the present invention, Mw is a value obtained by the measurement method of Examples described later.

The content of structural units derived from the conjugated diene monomer I and the conjugated diene monomer II in 100% by mass of the copolymer is preferably 20% by mass or more, more preferably 30% by mass or more, and still more preferably 40%. It is at least mass%. In addition, each content is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, and particularly preferably 50% by mass or less. If the content of the structural unit is less than 20% by mass or exceeds 80% by mass, the effects of the present invention may not be sufficiently obtained. For example, when monomer I is 1,3-butadiene and monomer II is isoprene, if the content of the structural unit derived from 1,3-butadiene is less than 20% by mass, the wear resistance tends to deteriorate, If it exceeds 80% by mass, the wet grip performance tends to deteriorate. Moreover, when the content of the structural unit derived from isoprene is less than 20% by mass, wet grip performance tends to deteriorate, and when it exceeds 80% by mass, wear resistance tends to deteriorate.
In addition, in this invention, content of a structural unit is a value obtained by the measuring method of the below-mentioned Example.

The total content of structural units derived from the conjugated diene monomer I and the conjugated diene monomer II in 100% by mass of the copolymer is preferably 40% by mass or more, more preferably 60% by mass or more, and still more preferably 80%. It is at least 100% by mass, particularly preferably 100% by mass. There exists a possibility that the effect of this invention may not fully be acquired as this content is less than 40 mass%.

In the rubber composition for tires of the present invention, the content of the copolymer in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 3% by mass or more, and further preferably 5% by mass or more. More preferably, it is 15% by mass or more, particularly preferably 20% by mass or more, most preferably 35% by mass or more, and may be 100% by mass. There exists a possibility that the effect of this invention may not fully be acquired as this content is less than 1 mass%.

In the polymerization for preparing the copolymer, the polymerization procedure is not particularly limited, and all the monomers may be polymerized at one time, or the monomers may be sequentially added and polymerized. The monomer components are the conjugated diene monomers I and II described above, and other monomers may be used in combination.

The copolymerization can be carried out by a conventional method, for example, radical polymerization, anionic polymerization, cationic polymerization, coordination anionic polymerization, coordination cationic polymerization, etc. Coordinating anionic polymerization is preferable because it is high in abrasion resistance and fracture strength.

The polymerization method is not particularly limited, and any of a solution polymerization method, an emulsion polymerization method, a gas phase polymerization method, and a bulk polymerization method can be used. Among these, the solution polymerization method is preferable. Further, the polymerization type may be either a batch type or a continuous type.

The coordination anionic polymerization can be carried out in a suitable solvent in the presence of a coordination anionic polymerization initiator. As the coordination anion polymerization initiator, any conventional one can be suitably used. Examples of such a coordination anion polymerization initiator include transitions such as a lanthanoid compound, a titanium compound, a cobalt compound, and a nickel compound. The catalyst which is a metal containing compound is mentioned. Coordination anionic polymerization initiators can be used alone or in admixture of two or more. If desired, an aluminum compound or a boron compound can be further used as a promoter.

The lanthanoid compound is not particularly limited as long as it contains any of the elements (lanthanoids) having an atomic number of 57 to 71. Among these lanthanoid compounds, neodymium is preferable in that a polymer having a high cis content can be obtained. . Examples of lanthanoid compounds include carboxylates, β-diketone complexes, alkoxides, phosphates or phosphites, halides, and the like of these elements. Of these, carboxylates, alkoxides, and β-diketone complexes are preferred because of easy handling. Examples of the titanium compound include a cyclopentadienyl group, an indenyl group, a substituted cyclopentadienyl group, or a substituted indenyl group, and three substituents selected from a halogen, an alkoxyl group, and an alkyl group. Examples of the titanium-containing compound include titanium-containing compounds having one alkoxysilyl group from the viewpoint of catalyst performance. Examples of the cobalt compound include cobalt halides, carboxylates, β-diketone complexes, organic base complexes, and organic phosphine complexes. Examples of the nickel compound include nickel halides, carboxylates, β-diketone complexes, and organic base complexes. The catalyst used as a coordination anionic polymerization initiator can be used alone or in combination of two or more. The amount of the polymerization initiator used in the coordination anionic polymerization is not particularly limited. For example, it is preferably used in an amount of about 0.05 to 35 mmol, and about 0.05 to 0.2 mmol per 100 g of all monomers to be subjected to polymerization. More preferably it is used.

Examples of the aluminum compound used as a cocatalyst include organic aluminoxanes, halogenated organoaluminum compounds, organoaluminum compounds, and hydrogenated organoaluminum compounds. Examples of organic aluminoxanes include alkylaluminoxanes (such as methylaluminoxane, ethylaluminoxane, propylaluminoxane, butylaluminoxane, isobutylaluminoxane, octylaluminoxane, hexylaluminoxane), and examples of halogenated organoaluminum compounds include alkyl halides. Aluminum compounds (dimethylaluminum chloride, diethylaluminum chloride, methylaluminum dichloride, ethylaluminum dichloride, etc.), and organic aluminum compounds such as alkylaluminum compounds (trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, etc.) , Hydrogenated organoaluminum The object, for example, hydrogenated alkylaluminum compounds (diethyl aluminum hydride, and diisobutyl aluminum hydride) and the like. Examples of the boron compound include compounds containing anionic species such as tetraphenylborate, tetrakis (pentafluorophenyl) borate, and (3,5-bistrifluoromethylphenyl) borate. These promoters can also be used alone or in combination of two or more.

Moreover, as a solvent used for coordination anion polymerization, any can be suitably used as long as it does not deactivate the coordination anion polymerization initiator or stop the polymerization reaction. Any of the solvents can be used. Examples of the polar solvent include ether solvents such as tetrahydrofuran, and examples of the nonpolar solvent include chain hydrocarbons such as hexane, heptane, octane and pentane, cyclic hydrocarbons such as cyclohexane, benzene and toluene. And aromatic hydrocarbons such as xylene. These solvents can be used alone or in admixture of two or more.

The reaction temperature during the polymerization is not particularly limited as long as the reaction proceeds suitably, but is usually preferably −10 ° C. to 100 ° C., more preferably 25 ° C. to 90 ° C. The reaction time varies depending on the charged amount, the reaction temperature, and other conditions, but usually, for example, about 3 hours is sufficient.

The coordination 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 thereof and nonpolar solvents such as hexane and cyclohexane. A mixed solution is mentioned. The addition amount of the reaction terminator is usually about the same molar amount or about twice the molar amount relative to the coordination anionic polymerization initiator.

After the termination of the polymerization reaction, the copolymer can be easily removed by removing the solvent from the polymerization solution by a conventional method, or pouring the polymerization solution into one or more times the amount of alcohol and precipitating the copolymer. It can be isolated.

The weight average molecular weight (Mw) of the copolymer can be controlled by adjusting the amount of monomer and polymerization initiator charged during polymerization. For example, if the total monomer / coordination anionic polymerization initiator ratio is increased, Mw can be increased, and conversely, if it is decreased, Mw can be decreased. The same applies to the number average molecular weight (Mn) of the copolymer.

<Homopolymer>
Next, the homopolymer will be described.
A cis bond of a double bond in a structural unit derived from the conjugated diene monomer I and the conjugated diene monomer II in the homopolymer of the conjugated diene monomer I and the homopolymer of the conjugated diene monomer II in the present invention Each content is preferably 90 mol% or more, more preferably 95 mol% or more, and still more preferably 97 mol% or more. When the cis bond content is less than 90 mol%, fracture performance and wear resistance tend to deteriorate. The upper limit is not particularly limited.

The vinyl bond content of the double bond in the structural unit derived from the conjugated diene monomer I and the conjugated diene monomer II in the homopolymer of the conjugated diene monomer I and the homopolymer of the conjugated diene monomer II is Each is preferably 5 mol% or less, more preferably 3 mol% or less. When the vinyl bond content exceeds 5 mol%, the wear resistance tends to deteriorate. The lower limit is not particularly limited.

The Tg of the homopolymer of the conjugated diene monomer I and the homopolymer of the conjugated diene monomer II is preferably −120 ° C. or higher, more preferably −115 ° C. or higher, respectively. Is −40 ° C. or lower, more preferably −50 ° C. or lower. When the Tg is less than -120 ° C, wet grip performance tends to deteriorate, and when it exceeds -40 ° C, wear resistance tends to deteriorate. In particular, when the monomer I is 1,3-butadiene and the monomer II is isoprene, the Tg of the polybutadiene rubber (the homopolymer of the monomer I) is preferably −120 to −80 ° C., more preferably −115 to − The Tg of polyisoprene rubber (which may be a homopolymer of monomer II or natural rubber) is preferably −90 to −40 ° C., more preferably −80 to −50 ° C.

The Mw of the homopolymer of the conjugated diene monomer I and the homopolymer of the conjugated diene monomer II is preferably 150,000 or more, more preferably 200,000 or more, still more preferably 300,000 or more, particularly Preferably it is 400,000 or more. The upper limit of the Mw is not particularly limited, but is preferably 2,000,000 or less, more preferably 1,500,000 or less, and still more preferably 1,200,000 or less. If it is less than 150,000, the wear resistance tends to deteriorate, and if it exceeds 2,000,000, the workability during kneading tends to deteriorate.

The homopolymer of the conjugated diene monomer I and the homopolymer of the conjugated diene monomer II in the present invention are those polymerized by a conventional method such as a polymerization method of the copolymer. The production method is not particularly limited, but the polymer is preferably polymerized by coordinated anionic polymerization in the same manner as the copolymer, in that the cis bond content of the polymer is high and the wear resistance and fracture strength are excellent. A commercial product may be used as long as it is polymerized by the above polymerization method. As a commercially available product, those commonly used in the tire industry can be used. For example, when monomers I and II are 1,3-butadiene and isoprene, as polybutadiene rubber, BR1220 manufactured by Nippon Zeon Co., Ltd., Ube Industries, Ltd. UBEPOL BR130B, BR150B manufactured by Co., Ltd., and the like. Examples of polyisoprene rubber include Nipol IR2200 manufactured by Nippon Zeon Co., Ltd., JSR IR2200 manufactured by JSR Co., Ltd., and the like. When any of the above monomers is isoprene, natural rubber (NR) can also be used as the homopolymer, and the NR is not particularly limited. For example, SIR20, RSS # 3, TSR20, desorption Common materials in the tire industry such as protein natural rubber (DPNR), high-purity natural rubber (HPNR), epoxidized natural rubber (ENR) and the like can be used.

In the tire rubber composition of the present invention, in 100% by mass of the rubber component, the homopolymer of the conjugated diene monomer I and the homopolymer of the conjugated diene monomer II are each preferably less than 50% by mass, more preferably Is 45 mass% or less, more preferably 35 mass% or less, and may be 0 mass%. Within the above range, the effects of the present invention can be obtained satisfactorily.

In the tire rubber composition of the present invention, the total content of the conjugated diene monomer I homopolymer and the conjugated diene monomer II homopolymer is preferably 90% by mass or less in 100% by mass of the rubber component. More preferably, it is 85 mass% or less, More preferably, it is 65 mass% or less, and may be 0 mass%. When the total content exceeds 90% by mass, the blended amount of the copolymer is too small, and the effects of the present invention may not be sufficiently obtained.

In the rubber composition for tires of the present invention, the content of the structural unit derived from the conjugated diene monomer I and the conjugated diene monomer II is preferably 20% by mass or more, more preferably 30%, in 100% by mass of the rubber component. It is at least 40% by mass, more preferably at least 40% by mass. In addition, each content is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, and particularly preferably 50% by mass or less. If the content of the structural unit is less than 20% by mass or exceeds 80% by mass, the effects of the present invention may not be sufficiently obtained. For example, when monomer I is 1,3-butadiene and monomer II is isoprene, if the content of the structural unit derived from 1,3-butadiene is less than 20% by mass, the wear resistance tends to deteriorate, If it exceeds 80% by mass, the wet grip performance tends to deteriorate. Moreover, when the content of the structural unit derived from isoprene is less than 20% by mass, wet grip performance tends to deteriorate, and when it exceeds 80% by mass, wear resistance tends to deteriorate.

In the tire rubber composition of the present invention, the total content of structural units derived from the conjugated diene monomer I and the conjugated diene monomer II in 100% by mass of the rubber component is preferably 40% by mass or more, more preferably 60%. It is at least 80% by mass, more preferably at least 80% by mass, particularly preferably at least 100% by mass. There exists a possibility that the effect of this invention may not fully be acquired as this content is less than 40 mass%.

The average length of the interface between the polymer phase (1) derived from the monomer I and the polymer phase (2) derived from the monomer II formed in the tire rubber composition of the present invention is 1 μm ² in cross section of the rubber composition. 3 μm or more per unit or the above polymer phases (1) and (2) are compatible. The average length of the interface is preferably 3.3 μm or more, more preferably 3.5 μm or more, and still more preferably 4.0 μm or more. The upper limit is not particularly limited, and may be a compatible state in which the average length cannot be measured. If it is less than 3 μm, the dispersibility of the polymer phase is poor and the effects of the present invention cannot be sufficiently obtained.
In the present invention, the average length of the interface is a value obtained by the measurement method of Examples described later.

In the tire rubber composition of the present invention, in addition to the polymer obtained by homopolymerization and / or copolymerization of the conjugated diene monomer I and the conjugated diene monomer II, other rubber components may be blended. The other rubber components include styrene butadiene rubber (SBR), ethylene-propylene rubber (EPM), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), Examples thereof include an ethylene-octene copolymer. These rubber components may be used in combination of two or more. From the viewpoint that fuel economy, wet grip performance, wear resistance and processability can be improved in a well-balanced manner, those containing 50% by mass or more of a conjugated diene-derived constitutional unit can be preferably used. Is preferably SBR containing 50% by mass or more.

The tire rubber composition of the present invention preferably contains silica as a reinforcing filler. The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silica), wet process silica (hydrous silica), and the like, and wet process silica is preferable because it has many silanol groups. Silica may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² / g or more, more preferably 50 m ² / g or more, further preferably 60 m ² / g or more, particularly preferably 100 m ² / g or more, and most preferably. Is 150 m ² / g or more. The N ₂ SA is preferably 400 m ² / g or less, more preferably 360 m ² / g or less, still more preferably 300 m ² / g or less, particularly preferably 250 m ² / g or less, and most preferably 200 m ² / g. It is as follows. If it is less than 40 m ² / g, the reinforcing effect is small, and the wear resistance and fracture performance tend to be reduced. If it exceeds 400 m ² / g, silica becomes difficult to disperse, resulting in poor fuel economy and workability. Tend to.
The _N 2 SA of silica is a value determined by the BET method in accordance with ASTM D3037-93.

The content of silica is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 45 parts by mass or more, and particularly preferably 60 parts by mass or more with respect to 100 parts by mass of the rubber component. Moreover, this content becomes like this. Preferably it is 150 mass parts or less, More preferably, it is 100 mass parts or less, More preferably, it is 90 mass parts or less. When the content is less than 10 parts by mass, the effect of blending silica is not sufficiently obtained, and the wear resistance tends to be reduced. When the content exceeds 150 parts by mass, the workability tends to be deteriorated.

In the present invention, it is preferable to use a silane coupling agent in combination with silica. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, bis (3-triethoxysilylpropyl) tetrasulfide, 3-trimethoxysilyl Sulfide type such as propylbenzothiazolyl tetrasulfide, mercapto type such as 3-mercaptopropyltrimethoxysilane, vinyl type such as vinyltriethoxysilane, amino type such as 3-aminopropyltriethoxysilane, γ-glycidoxy Examples thereof include glycidoxy type of propyltriethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, and chloro type such as 3-chloropropyltrimethoxysilane. Among these, from the viewpoint of reinforcing effect and the like, a sulfide system is preferable, and bis (3-triethoxysilylpropyl) tetrasulfide is more preferable. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of silica. Moreover, this content becomes like this. Preferably it is 20 mass parts or less, More preferably, it is 15 mass parts or less. When the amount is less than 1 part by mass, the viscosity of the unvulcanized rubber composition tends to be high, and the processability tends to deteriorate. When the amount exceeds 20 parts by mass, an effect commensurate with the increase in cost tends not to be obtained.

The tire rubber composition of the present invention may contain other reinforcing fillers in addition to silica. Examples of other reinforcing fillers include carbon black, calcium carbonate, talc, alumina, clay, water. Examples thereof include aluminum oxide and mica, and carbon black is particularly preferable from the viewpoint of reinforcement.

Carbon black includes furnace black (furnace carbon black) such as SAF, ISAF, N339, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF and ECF; acetylene black (acetylene carbon black); FT And thermal black (thermal carbon black) such as MT; channel black (channel carbon black) such as EPC, MPC and CC; graphite and the like. These can be used alone or in combination of two or more.

The N ₂ SA of the carbon black is preferably 5 m ² / g or more, more preferably 50 m ² / g or more, and still more preferably 90 m ² / g or more. The N ₂ SA is preferably 200 m ² / g or less, more preferably 150 m ² / g or less, still more preferably 120 m ² / g or less, and particularly preferably 100 m ² / g or less. If it is less than 5 m ² / g, the reinforcing effect tends to be small and the wear resistance tends to decrease. If it exceeds 200 m ² / g, the dispersibility is poor, and the hysteresis loss tends to increase and the fuel efficiency tends to decrease. .
The N ₂ SA is a value measured according to JIS K6217-2: 2001.

Carbon black has a dibutyl phthalate (DBP) absorption amount of preferably 5 ml / 100 g or more, more preferably 80 ml / 100 g or more, and further preferably 100 ml / 100 g or more. The DBP absorption amount is preferably 300 ml / 100 g or less, more preferably 180 ml / 100 g or less, and still more preferably 150 ml / 100 g or less. When the amount is less than 5 ml / 100 g, the reinforcing effect is small and the wear resistance tends to decrease. When the amount exceeds 300 ml / 100 g, the dispersibility is poor, and the hysteresis loss increases and the fuel efficiency tends to decrease.
The DBP absorption is a value measured according to JIS K6217-4: 2001.

As commercial products of carbon black, Toast Carbon Co., Ltd. Seast 6, Seast 7HM, Seast KH, Mitsubishi Chemical Corporation Dia Black N339, Dia Black I, Degussa CK3, Special Black 4A, etc. should be used. Can do.

The content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. Moreover, this content becomes like this. Preferably it is 60 mass parts or less, More preferably, it is 30 mass parts or less, More preferably, it is 15 mass parts or less. If it is less than 1 part by mass, sufficient reinforcing properties may not be obtained, and if it exceeds 60 parts by mass, the fuel economy tends to deteriorate.

The content of the reinforcing filler is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and still more preferably 60 parts by mass or more with respect to 100 parts by mass of the rubber component. Moreover, this content becomes like this. Preferably it is 150 mass parts or less, More preferably, it is 120 mass parts or less, More preferably, it is 100 mass parts or less. If the amount is less than 10 parts by mass, the reinforcing property may not be sufficiently obtained, and if it exceeds 150 parts by mass, the workability may be deteriorated.

In addition to the above components, the rubber composition for tires of the present invention includes compounding agents generally used in the tire industry, such as extender oils such as oil, wax, zinc oxide, anti-aging agent, sulfur and the like. Materials such as a vulcanizing agent and a vulcanization accelerator can be appropriately blended.

Examples of the extending oil include aromatic mineral oil (viscosity specific gravity constant (VGC value): 0.900 to 1.049), and naphthenic mineral oil (VGC value: 0.00). 850 to 0.899), paraffinic mineral oil (VGC value: 0.790 to 0.849), and the like. The polycyclic aromatic content of the extending 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. Thiuram vulcanization accelerators such as disulfides; 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 and N, N'-diisopropyl-2-benzothiazole sulfenamide; diphenylguanidine, diortolylguanidine, orthotolylbiguanidine What guanidine-based vulcanization accelerator can be exemplified. These vulcanization accelerators may be used alone or in combination of two or more. The content of the vulcanization accelerator is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the rubber component.

As a method for producing the rubber composition of the present invention, a known method, for example, a method of kneading each component with a known mixer such as a roll or Banbury can be used.

As kneading conditions, when additives other than the vulcanizing agent and the vulcanization accelerator are blended, the kneading temperature is usually 50 to 200 ° C., preferably 80 to 190 ° C., and the kneading time is usually 30 seconds. -30 minutes, preferably 1-30 minutes. When blending a vulcanizing agent and a vulcanization accelerator, the kneading temperature is usually 100 ° C. or lower, preferably room temperature to 80 ° C. A composition containing a vulcanizing agent and a vulcanization accelerator is usually used after vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200 ° C, preferably 140 to 180 ° C.

The rubber composition for tires of the present invention can be used for each member of a tire, and can be particularly suitably used for a tread (cap tread).

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition blended with various additives as necessary is extruded according to the shape of the tire tread, etc. at the unvulcanized stage, and molded by a normal method on a tire molding machine, Bonding together with other tire members forms an unvulcanized tire. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce the pneumatic tire of the present invention.

The pneumatic tire of the present invention can be suitably used as a heavy load tire for passenger car tires, buses, trucks, and the like.

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

Hereinafter, various chemicals used in the production examples will be described together. In addition, the chemical | medical agent refine | purified according to the usual method as needed.
Isoprene: Isoprene (special grade) manufactured by Tokyo Chemical Industry Co., Ltd.
1,3-butadiene: Takachiho Kogyo Co., Ltd. 1,3-butadiene cyclohexane: Kanto Chemical Co., Ltd. cyclohexane (special grade)
Versatic acid neodymium (III): Versatic acid neodymium trioctylaluminum manufactured by Nichia Corporation: Trioctylaluminum (hexane solution) manufactured by Sigma-Aldrich
tert-butyl chloride: tert-butyl chloride hexane manufactured by Tokyo Chemical Industry Co., Ltd .: normal hexane manufactured by Kanto Chemical Co., Ltd. (special grade)
Dibutylhydroxytoluene: dibutylhydroxytoluene isopropanol manufactured by Tokyo Chemical Industry Co., Ltd .: isopropanol manufactured by Kanto Chemical Co., Ltd. (special grade)
Acetic acid: Wako Pure Chemical Industries, Ltd. (Reagent grade 1, active ingredient 98%)
Hydrogen peroxide solution: Wako Pure Chemical Industries, Ltd. (active ingredient 35%)
Sulfuric acid: Wako Pure Chemical Industries, Ltd. (active ingredient 98%)
Methanol: Methanol manufactured by Wako Pure Chemical Industries, Ltd. (reagent grade 1)
Tetramethylethylenediamine: n-butyllithium manufactured by Kanto Chemical Co., Ltd .: 1.6M n-butyllithium hexane solution 2,6-tert-butyl-p-cresol manufactured by Kanto Chemical Co., Ltd .: Ouchi Shinsei Chemical Industry Co., Ltd. ) No crack 200

<Analysis of polymer>
The polymer obtained as described below was analyzed by the following method.

(Measurement of weight average molecular weight Mw)
The weight average molecular weight Mw of the polymer is determined by gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M, manufactured by Tosoh Corporation). It calculated | required by standard polystyrene conversion based on the measured value.

(Structural identification of copolymer)
The structure of the polymer was identified using a JNM-ECA series device manufactured by JEOL Ltd. From the measurement results, the content of structural units derived from monomer I and monomer II, the cis bond content, and the vinyl bond content in the polymer were calculated.

(Measurement of glass transition temperature (Tg))
The glass transition temperature (Tg) should be measured in accordance with JIS-K7121, using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan while raising the temperature at a heating rate of 10 ° C / min. The glass transition onset temperature was determined.

(Measurement of degree of epoxidation)
Several places of the obtained copolymer were sampled, and the measurement was performed using a ¹ H-NMR apparatus of JNM-ECA series manufactured by JEOL Ltd.
The degree of epoxidation (%) was calculated by the following formula.
Epoxidation degree (%) = B / (A + B) × 100
(In the formula, A is an integrated value of a peak derived from a cis proton (5.0-5.2 ppm), and B in the formula is an integrated value of a peak derived from an epoxy group proton (2.6-2.8 ppm)). Represents the value.)

<Preparation of catalyst solution>
The 200 ml glass container was purged with nitrogen, 21 ml of isoprene / cyclohexane solution (3.0 mol / L), 6 ml of neodymium (III) versatic acid / cyclohexane solution (0.4 mol / L), trioctyl aluminum / hexane solution (0.5 mol / L) L) 52 ml was added and stirred. After stirring at 80 ° C. for 30 minutes, 5 ml of a tert-butyl chloride / cyclohexane solution (1 mol / L) was added and stirred at 60 ° C. to obtain a catalyst solution.

<Preparation of peracetic acid>
Peracetic acid was prepared by mixing 97.5 g of 35% hydrogen peroxide, 30 g of acetic acid, and 2 g of sulfuric acid and leaving at 40 ° C. for 1 day.

<Production Example 1 (Synthesis of Copolymer 1)>
3 L pressure-resistant stainless steel container was replaced with nitrogen, and 2 L of cyclohexane, 80 g of 1,3-butadiene (monomer I), 80 g of isoprene (monomer II), and 15 ml of a trioctylaluminum / cyclohexane solution (0.5 mol / L) were added. After stirring for 30 minutes, 10 ml of the catalyst solution was added, and stirring was further performed while maintaining 80 ° C. After 3 hours, 10 ml of 0.01M-BHT (dibutylhydroxytoluene) / isopropanol solution was added dropwise to complete the reaction. After cooling, the reaction solution was added to 3 L of methanol separately prepared, and the precipitate thus obtained was air-dried overnight and further dried under reduced pressure for 2 days to obtain 155 g of copolymer 1. The polymerization conversion rate (percentage of “dry weight / charge amount”) was almost 100%.

<Production Example 2 (Synthesis of Copolymer 2)>
3 L pressure-resistant stainless steel container was replaced with nitrogen, and 2 L of cyclohexane, 80 g of 1,3-butadiene (monomer I), 80 g of isoprene (monomer II), and 15 ml of a trioctylaluminum / cyclohexane solution (0.5 mol / L) were added. After stirring for 30 minutes, 10 ml of the catalyst solution was added, and stirring was further performed while maintaining 80 ° C. After 3 hours, 10 ml of 0.01M-BHT (dibutylhydroxytoluene) / isopropanol solution was added dropwise to complete the reaction, and 35 g of the above peracetic acid was slowly added, and the heater and controller were adjusted so that the reaction temperature reached 60 ° C. The reaction was carried out by stirring for 30 minutes with a propeller stirrer while adjusting at. The reaction solution was cooled and then added to 3 L of methanol separately prepared, and the precipitate thus obtained was air-dried overnight and further dried under reduced pressure for 2 days to obtain a copolymer 2. The polymerization conversion rate (percentage of “dry weight / charge amount”) was almost 100%. The degree of epoxidation was 15 mol%.

<Production Example 3 (Synthesis of Copolymer 3)>
A 3 L pressure-resistant stainless steel container was replaced with nitrogen, and 2 L of hexane, 50 g of 1,3-butadiene (monomer I), 50 g of isoprene (monomer II), 0.3 mmol of tetramethylethylenediamine and 0.25 mmol of n-butyllithium were added, and 0 Stir at 48 ° C. for 48 hours. Thereafter, 0.1 g of 2,6-tert-butyl-p-cresol was added to the reaction solution, and then the solution was added to 3 L of methanol separately prepared, and the precipitate thus obtained was air-dried overnight, The copolymer 3 was obtained by drying under reduced pressure for 2 days. The polymerization conversion rate (percentage of “dry weight / charge amount”) was almost 100%.

Analysis results (Mw, Tg, each cis bond content, each vinyl bond content, each of the copolymers 1 to 3 obtained in the above Production Examples 1 to 3 and the homopolymers 1 and 2 used in the examples. Table 1 shows the content of structural units and the degree of epoxidation).

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
Copolymers 1-3: Prepared in the above production examples Homopolymer 1: UBEPOL BR150B manufactured by Ube Industries, Ltd.
Homopolymer 2: Nipol IR2200 manufactured by Nippon Zeon Co., Ltd.
Silica: Ultrasil VN3-G (N ₂ SA: 175 m ² / g) manufactured by Degussa
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Carbon black: Dia Black N339 manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 96 m ² / g, DBP absorption: 124 ml / 100 g)
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 (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 vulcanized at 170 ° C. for 12 minutes to obtain a vulcanized rubber composition (test rubber composition).
The obtained unvulcanized rubber composition and test rubber composition were evaluated by the following test methods, and the results are shown in Table 2.

(Average length of interface)
A sample having a thickness of 500 nm was prepared from the obtained rubber composition for test using a microtome (Ultra Microtome EM VC6 manufactured by LEICA), and this sample was dyed with osmium tetroxide. The structure of the polymer phase was observed for the sample after dyeing using a transmission electron microscope JEM2100F manufactured by JEOL. The observed image was divided into 1 μm square mesh, and the length of the interface of the polymer phase in the mesh was measured. When the interface cannot be discriminated as shown in FIG. 1 (c), it was considered as compatible, and five meshes were measured, and the average value was taken as the average length of the interface. It shows that the dispersibility of a polymer phase is so high that the average length of an interface is long.

(Destructive performance)
A test piece was cut out from the obtained rubber composition for testing, and a tensile test was conducted using a No. 3 dumbbell according to JIS K6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”. The strength (TB) and elongation at break (EB) were measured, the value of TB × EB / 2 was taken as the breaking strength, and the result of Comparative Example 1 was taken as 100, and each formulation was indicated by an index according to the following formula. The larger the index, the better the fracture performance.
(Fracture strength index) = (TB of each formulation × EB / 2) / (TB of comparative example 1 × EB / 2) × 100

(Kneading processability)
About the obtained unvulcanized rubber composition, according to JIS K6300-1, the Mooney viscosity of the unvulcanized rubber composition was measured at 130 ° C., the Mooney viscosity of Comparative Example 1 was set to 100, and measured according to the following formula. The results are displayed as an index. The larger the index, the lower the viscosity and the easier the processing (excellent processability).
(Mooney viscosity index) = (Mooney viscosity of Comparative Example 1) / (Mooney viscosity of each formulation example) × 100

(Low fuel consumption)
Using a spectrometer manufactured by Ueshima Seisakusho, tan δ of each formulation was measured under conditions of an initial strain of 10%, a dynamic strain of 1%, and a temperature of 70 ° C. Each formulation was displayed as an index according to the following calculation formula with the value of tan δ of Comparative Example 1 being 100. The larger the index, the lower the rolling resistance and the better the fuel efficiency.
(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Wet grip performance)
Using a viscoelasticity measuring device manufactured by Rheometrics, tan δ was measured under the conditions of a frequency of 10 Hz, a strain of 0.1%, and a temperature of 0 ° C., and tan δ of Comparative Example 1 was set to 100, and each formulation was displayed as an index. It shows that it is excellent in wet grip performance, so that an index value is large.
(Wet grip performance index) = (tan δ of each formulation) / (tan δ of Comparative Example 1) × 100

(Abrasion resistance)
A Lambourn abrasion tester (manufactured by Iwamoto Seisakusho) was used to conduct a Lambourn abrasion test for 5 minutes under the conditions of a load of 2.5 kgf, a temperature of 20 ° C., and a slip rate of 20%. The volume loss amount of each rubber composition for test was measured, and Comparative Example 1 was set to 100, and each compound was indexed by the following calculation formula. It shows that it is excellent in abrasion resistance, so that an index | exponent is large.
(Lambourn wear index) = (volume loss amount of Comparative Example 1) / (volume loss amount of each formulation) × 100

Obtained by homopolymerization and / or copolymerization of the monomers I and II in which the cis bond content of the double bond in the structural unit derived from the conjugated diene monomer I and the conjugated diene monomer II is not less than a predetermined amount. The polymer contains a polymer, the average length of the interface between the polymer phase (1) derived from the monomer I and the polymer phase (2) derived from the monomer II is a specific value or more, or the two polymer phases are compatible. The examples had good processability and markedly improved the performance balance of low fuel consumption, wet grip performance, fracture performance and wear resistance.

Claims (8)

A rubber composition containing a copolymer obtained by copolymerizing a conjugated diene monomer I and a conjugated diene monomer II,
The average length of the interface between the polymer phase (1) derived from the conjugated diene monomer I and the polymer phase (2) derived from the conjugated diene monomer II formed in the rubber composition is 1 μm in cross section of the rubber composition. 3 μm or more per ² or the polymer phase (1) and the polymer phase (2) are compatible.
The cis bond content of the double bond in the structural unit derived from the conjugated diene monomer I and the conjugated diene monomer II in the copolymer is 90 mol% or more, respectively.
Ri modified copolymer der which is modified by the copolymer to impart a functional group having chemically interact with the reinforcing fillers,
The conjugated diene monomer I and the conjugated diene monomer II is, isoprene and butadiene der Ru tire rubber composition. In 100% by mass of the rubber component, the content of the structural unit derived from the conjugated diene monomer I and the content of the structural unit derived from the conjugated diene monomer II are each 20 to 80% by mass, and the conjugated diene system. The total content of the structural unit derived from the monomer I and the structural unit derived from the conjugated diene monomer II is 40% by mass or more, and the reinforcing filler is included in an amount of 10 to 150 parts by mass with respect to 100 parts by mass of the rubber component. The tire rubber composition according to claim 1. In 100% by mass of the copolymer, the content of structural units derived from the conjugated diene monomer I is 40 to 60% by mass, and the content of structural units derived from the conjugated diene monomer II is 40 to 60% by mass. The tire rubber composition according to claim 1 or 2. The rubber composition for tires according to any one of claims 1 to 3, wherein the copolymer has a glass transition temperature of -100 to -40 ° C and a weight average molecular weight of 150,000 to 2,000,000. The rubber composition for a tire according to any one of claims 1 to 4, wherein the copolymer is obtained by coordination anionic polymerization with a transition metal-containing compound. The rubber composition for a tire according to any one of claims 1 to 5, wherein the copolymer is contained in an amount of 5% by mass or more in 100% by mass of the rubber component. The pneumatic tire produced using the rubber composition for tires in any one of Claims 1-6. 7. The method according to claim 1, comprising a step of copolymerizing the conjugated diene monomer I and the conjugated diene monomer II by coordination anionic polymerization, and a step of kneading the copolymer obtained by the step. A method for producing a rubber composition for a tire.

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