JP2003342423A - Rubber composition improved in wet grip property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire which enhances wet grip properties without impairing the rolling resistance of a tire. <P>SOLUTION: The rubber composition comprises a block copolymer (A) and a rubber component (B), where (A) is a block copolymer constituted of a polymer block, which is comprised of (a-1) at least one selected from the group consisting styrene, p-methylstyrene and α-methylstyrene and (a-2) isobutylene with a (a-1):(a-2) weight ratio of 5:95 to 45:55, and a polymer block comprising an aromatic vinyl compound as a monomer and (B) is at least one rubber component selected from the group consisting of a natural rubber, diene polymer rubbers and olefin polymer rubbers. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for tires containing a block copolymer, which can improve steering stability and braking property (wet grip property) particularly on a wet road surface.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for lower fuel consumption of automobiles, especially reduction of rolling resistance of tires, and from a safety point of view, it is possible to provide a tire having high grip performance on wet road surfaces, that is, high wet grip performance. A rubber composition is sought.

The wet grip property is related to the hysteresis loss (tan δ) of the tread rubber, and has a frequency of 1
It is known that the larger the tan δ at 0 ° C. at 0 Hz, the higher the wet grip property.

As a rubber composition for a tread used for such a pneumatic tire in the field of automobiles, Japanese Patent Application Laid-Open No. 11-80433 discloses polyisobutylene / p-.
A rubber composition for a tread comprising a bromide of a methylstyrene copolymer and a rubber component is disclosed. However, styrene-butadiene rubber (S
Since the vulcanization rates of BR), butadiene rubber (BR), and natural rubber (NR) are significantly different, there is a problem that processability and productivity are deteriorated. In addition, JP-A-11-3151
No. 71 discloses a rubber composition containing a styrene-isobutylene copolymer as a rubber component,
This is to add a styrene-isobutylene random copolymer as a plasticizer component, and improves the wet grip property by lowering the elastic modulus of the rubber composition. However, the addition of the plasticizer component has a problem that the hardness is lowered unlike the improvement of the wet grip property by selecting the rubber component. Further, the above publication does not describe a block copolymer. A rubber composition comprising a styrene-isobutylene block copolymer and a rubber component is described in JP-A No. 2001-247722, and since wet grip properties can be improved without affecting workability, it can be used for tires. It is disclosed that it is suitable as a wet grip improver for a rubber composition. However, unless added in a large amount, the effect of improving wet grip properties did not appear, and physical properties such as fracture properties tended to deteriorate.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition for tires which improves wet grip properties without impairing workability and breaking strength of tires.

[0006]

In order to solve the above problems, the inventors of the present invention have made extensive studies and as a result have completed the present invention. That is, the present invention is a rubber composition comprising the following block copolymer (A) and a rubber component (B). (A) at least one selected from the group consisting of styrene, p-methylstyrene and α-methylstyrene (a-
1) and isobutylene (a-2), (a-1):
(A-2) = 5: 95 to 45:55 (weight ratio), a block copolymer composed of a polymer block containing an aromatic vinyl compound as a monomer, (B)
At least one rubber component selected from the group consisting of natural rubber, diene polymer rubber and olefin polymer rubber.

A preferred embodiment is a rubber composition in which the rubber component (B) is crosslinked.

In a preferred embodiment, the content of the block copolymer (A) is 1 to 30% by weight based on 100% by weight of the total of the block copolymer (A) and the rubber component (B).

In a preferred embodiment, the aromatic vinyl compound is at least one monomer selected from the group consisting of styrene, α-methylstyrene, p-methylstyrene and indene.

In a preferred embodiment, the content of the polymer block containing an aromatic vinyl compound as a monomer in the block copolymer (A) is 10%.
It is 10 to 40% by weight with respect to 0% by weight.

The rubber composition of the present invention is suitably used for pneumatic tire treads.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition of the present invention is a rubber composition comprising the following block polymer (A) and rubber component (B). (A) at least one selected from the group consisting of styrene, p-methylstyrene and α-methylstyrene (a-
1) and isobutylene (a-2), (a-1):
(A-2) = 5: 95 to 45:55 (weight ratio), a block copolymer composed of a polymer block containing an aromatic vinyl compound as a monomer, (B)
At least one rubber component selected from the group consisting of natural rubber, diene polymer rubber and olefin polymer rubber.

The wet grip performance is considered to depend on the deformation near the surface of the tire. It is known that this deformation near the surface is vibration of a very high frequency, and if temperature-frequency conversion is used, the wet grip property greatly depends on the value of tan δ near 0 ° C. at 10 Hz, resulting in rolling resistance. Is tan δ near 60 ° C. at 10 Hz
It is known to greatly depend on the value of.

The block copolymer (A) of the present invention contains 10
Hz, the peak point of the loss tangent (tan δ) obtained by the dynamic viscoelasticity measurement in the tensile mode is around 0 ° C., the value is large, and it is effective in improving the wet grip property.
Further, the value of tan δ near 60 ° C. is small, and rolling resistance is not significantly deteriorated. Further, by using a polymer excellent in this property, it is possible to reduce the compounding amount in the rubber component, and it is possible to suppress deterioration of the breaking property of the rubber composition.

To achieve the object of the present invention, the tan δ at 10 Hz and 0 ° C. of the block copolymer (A) is preferably 0.5 or more, more preferably 0.7 or more.

The peak point of tan δ of the block copolymer (A) varies depending on the kind and amount of the monomer used, and usually appears at about -20 to about 100 ° C. In order for the peak point of tan δ to appear near 0 ° C., at least one kind (a-1) selected from the group consisting of styrene, p-methylstyrene and α-methylstyrene, and isobutylene (a-2).
The composition ratio of the polymer block consisting of (a-1): (a-
2) = 5: 95 to 45:55 (weight ratio) is preferable, and (a-1) :( a-2) = 15: 85 to 35: 6.
More preferably, it is 5. When (a-1) is smaller than 5, the peak point of tan δ is too low, and ta at 0 ° C.
If nδ is not improved and (a-1) exceeds 45, ta
The peak point of n δ is too high, and tan δ near 0 ° C. is not improved.

The polymer block containing an aromatic vinyl compound as a monomer of the block copolymer (A) of the present invention may or may not contain a monomer other than the aromatic vinyl compound. The content of the monomer other than the vinyl compound is preferably 30% by weight or less, more preferably 10% by weight or less. The content of the polymer block containing an aromatic vinyl compound as a monomer in the block copolymer (A) is preferably 10 to 40% by weight based on 100% by weight of the block copolymer (A), 15-3
It is more preferably 0% by weight. When the content of the polymer block containing an aromatic vinyl compound as a monomer exceeds 40% by weight, a high tan δ peak does not appear, and when it is less than 10% by weight, the mechanical properties are significantly deteriorated. As the aromatic vinyl-based monomer, it is preferable to use at least one monomer selected from the group consisting of styrene, α-methylstyrene, p-methylstyrene, and indene. From the viewpoint of cost, styrene, α -Methylstyrene,
Alternatively, it is particularly preferable to use a mixture thereof.

The block copolymer (A) of the present invention comprises at least one kind (a-1) selected from the group consisting of styrene, p-methylstyrene and α-methylstyrene and isobutylene (a-2). , (A-1): (a-2)
= 5: 95 to 45:55 (weight ratio), as long as it has a structure of a block copolymer composed of a polymer block and a polymer block containing an aromatic vinyl compound as a monomer. There is no particular limitation, and for example, any of block copolymers having a linear, branched, star-shaped structure, diblock copolymer, triblock copolymer, multiblock copolymer, etc. can be selected. Yes, it is sufficient to select a material that meets the requirements of mechanical characteristics and workability.

The number average molecular weight of the block copolymer (A) is not particularly limited, but from the viewpoint of physical properties and processability,
It is preferably 3,000 to 150,000,
Especially preferably, it is 5,000 to 100,000. When the number average molecular weight of the block copolymer (A) is lower than the above range, the physical properties of the composition are not sufficiently expressed,
On the other hand, when it exceeds the above range, it is disadvantageous in terms of workability.

The method for producing the block copolymer (A) is not particularly limited, and a known polymerization method can be used. In order to obtain a block copolymer having a controlled structure, the following general formula is used. In the presence of the compound represented by (1),
At least one type (a-1) selected from the group consisting of styrene, p-methylstyrene and α-methylstyrene.
It is preferable to polymerize a monomer component containing isobutylene (a-2) and a monomer component containing an aromatic vinyl compound as a main component. (CR ¹ R ² X) _n R ³ (1) (In the formula, X represents a substituent selected from the group consisting of a halogen atom, an alkoxyl group having 1 to 6 carbon atoms and an acyloxyl group having 1 to 6 carbon atoms. R ¹ and R ² are, respectively,
It represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms.
R ¹ and R ² may be the same or different. Further, a plurality of R ¹ and R ² may be the same or different. R ³ represents a polyvalent aromatic hydrocarbon group or a polyvalent aliphatic hydrocarbon group which can have n substituents. n represents a natural number of 1 to 6. ) Examples of the halogen atom include chlorine, fluorine, bromine, iodine and the like. The alkoxyl group having 1 to 6 carbon atoms is not particularly limited, and examples thereof include a methoxy group, an ethoxy group, an n- or isopropoxy group, and the like. The acyloxyl group having 1 to 6 carbon atoms is not particularly limited, and examples thereof include an acetyloxy group and a propionyloxy group. The hydrocarbon group having 1 to 6 carbon atoms is not particularly limited, and examples thereof include a methyl group, an ethyl group and n-
Alternatively, an isopropyl group and the like can be mentioned.

The compound represented by the above general formula (1) serves as an initiator and is considered to generate a carbon cation in the presence of a Lewis acid or the like and serve as a starting point of cationic polymerization. Examples of the compound represented by the general formula (1) used in the present invention include the following compounds.

(1-chloro-1-methylethyl) benze
The C₆H_FiveC (CH₃)₂Cl 1,4-bis (1-chloro-1-methylethyl) benze
The 1,4-Cl (CH₃)₂CC₆H_FourC (CH₃)₂Cl 1,3-bis (1-chloro-1-methylethyl) benze
The 1,3-Cl (CH₃)₂CC₆H_FourC (CH₃)₂Cl 1,3,5-tris (1-chloro-1-methylethyl)
benzene 1,3,5- (ClC (CH₃)₂)₃C₆H₃ 1,3-bis (1-chloro-1-methylethyl) -5-
(Tert-butyl) Benzene 1,3- (C (CH₃)₂Cl)₂-5- (C
(CH₃)₃) C₆H₃ Among these, particularly preferred is 1-chloro-1-methyl.
Luethylbenzene [C ₆H_FiveC (CH₃)₂Cl], bis
(1-Chloro-1-methylethyl) benzene [C ₆H
_Four(C (CH₃)₂Cl)₂], Tris (1-chloro-1-
Methylethyl) benzene [(ClC (CH₃)₂)₃C₆H
₃]. [Note that 1-chloro-1-methylethylben
Zen is α-chloroisopropylbenzene, 2-chloro
-2-Propylbenzene or cumyl chloride
Called bis (1-chloro-1-methylethyl) benze
Is bis (α-chloroisopropyl) benzene, bis
(2-chloro-2-propyl) benzene or dicum
Also called luchloride, tris (1-chloro-1-me
Tylethyl) benzene is tris (α-chloroisopropene).
Pill) benzene, tris (2-chloro-2-propyl)
Also called benzene or tricumyl chloride
]].

In the above polymerization reaction, a Lewis acid catalyst can coexist. Any Lewis acid can be used as long as it can be used for cationic polymerization, such as TiCl ₄ , TiBr.
₄ , BCl ₃ , BF ₃ , BF ₃ · OEt ₂ , SnCl ₄ , SbCl ₅ ,
SbF ₅ , WCl ₆ , TaCl ₅ , VCl ₅ , FeCl ₃ , ZnB
Metal halides such as r ₂ , AlCl ₃ , AlBr ₃ ; Et ₂
Organic metal halides such as AlCl and EtAlCl ₂ can be preferably used. Above all, considering the catalytic ability and industrial availability, TiCl ₄ , B
Cl ₃ and SnCl ₄ are preferred.

The amount of the Lewis acid catalyst used is not particularly limited and can be set in consideration of the polymerization characteristics or the polymerization concentration of the monomers used.

In the above polymerization reaction, if necessary, an electron donor component may coexist. This electron donor component is believed to have the effect of stabilizing the growing carbocation during cationic polymerization.
The addition of an electron donor produces a polymer with a controlled structure with a narrow molecular weight distribution. The electron donor component that can be used is not particularly limited, and examples thereof include pyridines, amines, amides, sulfoxides, esters, and metal compounds having an oxygen atom bonded to a metal atom.

The above polymerization reaction can be carried out in an organic solvent as the case requires, and any organic solvent can be used without particular limitation as long as it does not substantially inhibit the cationic polymerization. Specifically, halogenated hydrocarbons such as methyl chloride, dichloromethane, chloroform, ethyl chloride, dichloroethane, n-propyl chloride, n-butyl chloride and chlorobenzene; benzene, toluene, xylene,
Alkylbenzenes such as ethylbenzene, propylbenzene and butylbenzene; linear aliphatic hydrocarbons such as ethane, propane, butane, pentane, hexane, heptane, octane, nonane and decane; 2-methylpropane,
2-methylbutane, 2,3,3-trimethylpentane,
Branched aliphatic hydrocarbons such as 2,2,5-trimethylhexane; cycloaliphatic hydrocarbons such as cyclohexane, methylcyclohexane, ethylcyclohexane; paraffin oil obtained by hydrogenating and refining petroleum fractions. it can.

These solvents may be used alone or in combination of two or more in consideration of the balance between the polymerization characteristics of the monomers constituting the block copolymer and the solubility of the resulting polymer.

The amount of the above solvent used is in the range of 1 to 1 in consideration of the viscosity of the resulting polymer solution and the ease of heat removal.
It is determined to be 50 wt%, preferably 3 to 35 wt%.

In carrying out the actual polymerization, the components are mixed under cooling, for example, at a temperature of -100 ° C or higher and lower than 0 ° C. In order to balance the energy cost and the stability of polymerization, a particularly preferable temperature range is -30 ° C to -80 ° C.

Examples of the rubber component (B) used in the rubber composition of the present invention include natural rubber, diene polymer rubber and olefin polymer rubber. As the diene polymer rubber, isoprene rubber, butadiene rubber, 1,2-
Examples are polybutadiene, styrene-butadiene rubber, chloroprene rubber, and nitrile rubber. Examples of the olefin rubber include butyl rubber, chlorinated butyl rubber, brominated butyl rubber, and ethylene-propylene-diene rubber. Among them, a homopolymer of a diene compound or a copolymer of a diene compound and an aromatic vinyl compound is preferable, and specifically, isoprene rubber, butadiene rubber,
Styrene butadiene rubber is especially preferred.

In the rubber composition of the present invention, it is preferable that the rubber component (B) is cross-linked, and a cross-linking agent and a cross-linking accelerator, which are usually used in the rubber industry, are appropriately blended to cross-link. can do. Examples of the cross-linking agent include sulfur, phenolic resins, metal oxides and peroxides.
These are usually about 0.
Used 5-10 parts. As the crosslinking accelerator, 2,2-
Examples thereof include dithiobisbenzothiazole, 1,3-diphenylguanidine, tetramethylthiuram disulfide, zinc dimethylthiocarbamate, and mercaptobenzothiazyl disulfide. These are usually rubber components 10
About 0.2 to 5 parts is used with respect to 0 parts by weight.

In the rubber composition of the present invention, in addition to the above, compounding agents which are generally used in the rubber industry, such as fillers, plasticizers and antiaging agents, are appropriately compounded according to the purpose and application. be able to. Examples of the filler include carbon black, silica, filler, calcium carbonate, mica, flake graphite and the like. Examples of plasticizers include petroleum-based process oils such as paraffinic process oils, naphthene-based process oils, aromatic process oils, dialkyl dibasic acids such as diethyl phthalate, dioctyl phthalate, and dibutyl adipate, liquid polybutene, liquid poly A low molecular weight liquid polymer such as isoprene is exemplified, and among them, liquid polybutene, liquid polyisoprene, and aromatic process oil are preferable from the viewpoint of compatibility with the rubber component.

The rubber component (B) in the rubber composition of the present invention
The content of the block copolymer (A) with respect to the total amount of the rubber component (B) and the block copolymer (A) is 10
The content of the block copolymer (A) is 1 to 0% by weight.
It is preferably 30% by weight, more preferably 5 to 15% by weight. When the content of the block copolymer increases, the breaking strength of the rubber composition tends to decrease.

As a method for preparing the rubber composition of the present invention, a conventionally known method may be adopted. For example, first, the block copolymer (A), the rubber component (B), and a crosslinking agent and a crosslinking accelerator. Various compounding agents other than the above are mixed with a tumbler, a Henschel mixer, a riboblender, etc., and then kneaded with an extruder, bumper, roll, or the like. At this time, the kneading temperature is
It is desirable to appropriately change the temperature from room temperature to 200 ° C. depending on the composition ratio of the block copolymer (A) and the rubber component (B).
This is because the glass transition temperature of the polymer block containing the aromatic vinyl compound of the block copolymer (A) as a monomer is usually 100 ° C. or higher, and therefore the proportion of the block copolymer (A) in the composition. This is because, when is high, the respective components are not sufficiently mixed. Therefore, it is preferable to knead at a higher temperature as the blending amount of the block copolymer (A) is higher. When it is desired to obtain a crosslinked rubber, after kneading, a crosslinking agent and a crosslinking accelerator are added and further kneaded using the above apparatus. At this time, the kneading temperature is preferably 80 ° C to 120 ° C for the purpose of suppressing the reaction of the crosslinking agent. further,
If necessary, the rubber composition can be molded and crosslinked by using a press machine, an injection molding machine or the like.

The structure and size of the tire using the rubber composition of the present invention are not particularly limited and can be selected as required. The wet grip, which is the object of the present invention, is most required for tires for passenger cars, and it is desirable to use it for this. When the tire tread has a multi-layer structure, it is preferable to use the rubber composition of the present invention at least in the outermost layer. Further, since the rubber composition of the present invention has a good grip on a wet road surface, it can be used also for a shoe sole for general footwear.

[0036]

The present invention will be described in more detail with reference to the following examples. It should be noted that the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention. Various measuring methods and the like will be described prior to the examples.

(Measurement of Dynamic Viscoelasticity) The dynamic viscoelastic property was converted into a sheet by hot press molding, and the obtained sheet was measured by JI.
According to SK-6394 (Dynamic property test method for vulcanized rubber and thermoplastic rubber), one 40 mm × 5 mm × 2 mm test piece was cut out and used, with a frequency of 10 Hz and a strain of 0.
It was measured in the tensile mode under the condition of 1%. The equipment used is
A dynamic viscoelasticity measuring device DVA-200 (manufactured by IT Measurement and Control Co., Ltd.). At this time, the frequency is 10Hz
This is because the wet gripping property correlates with the tan δ value at 10 Hz and 0 ° C. when the time-temperature conversion rule of viscoelasticity is used. The larger the value, the better the wet gripping property. Is known to be good. In addition, the rolling resistance is 10
It is known that there is a correlation with the tan δ value at Hz and 60 ° C., and the smaller the value, the better the rolling resistance.

(Production Example) [Polystyrene-poly (isobutylene-co-styrene) -polystyrene-triblock copolymer (isobutylene of the middle block: styrene =
Production of 90:10 (weight ratio) (A-2)] In a 2 L reaction vessel equipped with a stirrer, 145 mL of methylcyclohexane (dried with molecular sieves), n-
Butyl chloride (dried with molecular sieves) 150 mL, dicumyl chloride 0.170 g, α
-Picolin (2-methylpyridine) 0.15 mL was added. After cooling the reaction vessel to -70 ° C, isobutylene 4
7.5 mL and 7.8 mL styrene were added. Furthermore, 3.2 mL of titanium tetrachloride was added to start polymerization, and -7
The solution was reacted at 0 ° C. for 3.0 hours while stirring. Next, 9.8 mL of styrene was further added to the reaction solution, the reaction was continued for another 90 minutes, and then a large amount of methanol was added to stop the reaction. After removing the solvent and the like from the reaction solution, the polymer was dissolved in toluene and washed twice with water. This toluene solution was added to a methanol mixture to precipitate a polymer, and the obtained polymer was vacuum dried at 60 ° C. for 24 hours to obtain a block copolymer.

The number average molecular weight was measured by a 510-type GPC system manufactured by Waters (chloroform was used as a solvent and the flow rate was 1 mL / min), and the value in terms of polystyrene was shown. Styrene content in polymer is ¹ H-NM
It was calculated from the integration ratio of the R spectrum.

Other block bodies (A-1,
A-3 to A-7) were similarly synthesized by changing the charging ratio of isobutylene and styrene.

[0041]

[Table 1] (Examples 1 to 4, Comparative Examples 1 to 4) As the rubber component (B), a styrene-butadiene copolymer rubber (JSR SL
552, manufactured by JSR, abbreviated as SBR hereinafter. ), Butadiene rubber (JSR BR01, manufactured by JSR, hereinafter abbreviated as BR) is used, and the total amount thereof is 100 parts by weight together with 10% by weight of the block copolymers (A-1 to A-7) prepared in Production Examples. Compounding agents such as a filler, a plasticizer, a vulcanizing agent, a vulcanization accelerator, and an antioxidant were kneaded at a compounding ratio shown in Table 2 to obtain a tire compound. For the kneading, a Labo Plastomill (manufactured by Toyo Seiki Co., Ltd.) was used. First, the compounding agents other than the vulcanizing agent and the vulcanization accelerator were kneaded at 80 ° C. and 100 rpm, and the temperature was raised by shearing heat generation to 150 ° C. It was discharged when it became.
Next, add a crosslinking agent and a crosslinking accelerator, set at 30 ° C,
Knead at 80 rpm and increase the temperature by shear heat generation to 90
It was discharged when it reached ℃. The rubber composition thus obtained was compression molded at 150 ° C. to prepare a sheet. The moldability was extremely good. The obtained sheet was used to evaluate the dynamic viscoelastic properties. The results are shown in Table 3.

[0042]

[Table 2] (Abbreviations in the table) Nipseal AQ: Silica-Nippon Si-69: Degussa stearic acid: Nippon Oil & Fats Co., Ltd. Zinc oxide: Mitsui Mining & Smelting Co., Ltd. Wax: Sunnock N, Ouchi Shinko Chemical Co., Ltd. 810NA, Ouchi Shinko Chemical Co., Ltd. DPG: Knockseller D, Ouchi Shinko Chemical Co., Ltd. Sulfur: Kawagoe Chemical Co., Ltd. TBBS: Knock Setter NS, Ouchi Shinko Chemical Co., Ltd. CB: Asahi # 78, Asahi Carbon Co., Ltd. Company Alomax 3: Fuji Kosan Co., Ltd.

[0043]

[Table 3] In Examples 1 to 4, the weight ratio of styrene (a-1) and isobutylene (a-2) was (a-1) :( a-
2) = 10: 90, 20:80, 30:70, 40: 6
Although it is a block copolymer of 0, the tan δ at 0 ° C. is 0.019 to 0.039 higher than that of Comparative Example 1 containing no block copolymer (A), and the wet grip property is improved. Further, Comparative Example 2 has (a-1): (a-
2) = 0: 100 block copolymer, but only tan δ at 0 ° C. was improved by 0.01, and
Compared with No. 4, the wet grip property improving effect is insufficient. Comparative Example 3 is a block copolymer of (a-1) :( a-2) = 50: 50, but has a tan δ of 0.01 at 0 ° C.
However, the wet grip property improving effect is insufficient as compared with Examples 1 to 4. Further, in both Comparative Example 2 and Comparative Example 3, tan δ at 60 ° C. is from Examples 1 to 4.
The rolling resistance is worse than the above and rolling resistance is worse. Comparative Example 4 is a mere copolymer of styrene (a-1) and isobutylene (a-2) having no polystyrene block, and although it has improved tan δ at 0 ° C., it is not a block, The tan δ at ° C is high, and the rolling resistance is significantly deteriorated.

[0044]

EFFECTS OF THE INVENTION The rubber composition of the present invention has an excellent balance of contradictory properties such as wet grip property and rolling resistance by blending a specific block copolymer with a rubber component which has been conventionally used for a tire. Can be used as a pneumatic tire.

Claims (6)

[Claims] 1. A rubber composition comprising the following block copolymer (A) and a rubber component (B). (A) at least one selected from the group consisting of styrene, p-methylstyrene and α-methylstyrene (a-
1) and isobutylene (a-2), (a-1):
(A-2) = 5: 95 to 45:55 (weight ratio), a block copolymer composed of a polymer block containing an aromatic vinyl compound as a monomer, (B)
At least one rubber component selected from the group consisting of natural rubber, diene polymer rubber and olefin polymer rubber. 2. The rubber composition according to claim 1, wherein the rubber component (B) is crosslinked. 3. The content of the block copolymer (A) is 1 to 30% by weight based on 100% by weight of the total of the block copolymer (A) and the rubber component (B). Item 3. The rubber composition according to item 1 or 2. 4. The aromatic vinyl compound is styrene, α-
The rubber composition according to any one of claims 1 to 3, which is at least one monomer selected from the group consisting of methylstyrene, p-methylstyrene, and indene. 5. The content of a polymer block containing an aromatic vinyl compound as a monomer in the block copolymer (A) is 10 to 4 relative to 100% by weight of the block copolymer (A).
The rubber composition according to claim 1, wherein the rubber composition is 0% by weight. 6. A pneumatic tire tread comprising the rubber composition according to any one of claims 1 to 5.