JP6726972B2 - Rubber composition and tire - Google Patents

Description

The present invention relates to a rubber composition and a tire using the same. More specifically, it relates to a rubber composition using a vinyl cis-polybutadiene rubber and a tire using the same.

Conventionally, vinyl cis-polybutadiene rubber has been produced by using a predetermined catalyst in an inert organic solvent containing a hydrocarbon such as benzene, toluene and xylene as a main component, and converting 1,3-butadiene into cis-1, It is carried out by a method in which four polymerizations are carried out, and subsequently, syndiotactic-1,2 polymerizations (hereinafter sometimes simply referred to as "1,2 polymerizations").

Further, vinyl cis-polybutadiene rubber is desired to be improved in various properties depending on its use when it is made into a rubber composition. For example, in Patent Document 1, when 1,3-butadiene is cis-1,4 polymerized, dissolved 1,2-polybutadiene is premixed to obtain a rubber composition, thereby improving processability and Vinyl cis-polybutadiene rubbers having improved tensile stress are described.

JP, 2008-163144, A

However, in the vinyl cis-polybutadiene rubber described in Patent Document 1 which is the above-mentioned improved vinyl cis-polybutadiene rubber, further workability and tensile stress improvement when the rubber composition for tires is improved, It is industrially useful.

The present invention has been made in view of the above problems, and an object thereof is to provide a rubber composition having an excellent balance of processability and tensile stress and a tire having an excellent balance of fuel economy and crack growth resistance. And

In order to achieve the above object, the inventors of the present invention have conducted extensive studies and as a result, have determined that a vinyl cis-polybutadiene rubber blended in a rubber composition contains a specific amount of 1,2-polybutadiene having a specific melting point. Further, by containing a specific amount of 1,2-polybutadiene produced in the production process of vinyl cis-polybutadiene rubber, a rubber composition having excellent tensile stress while suppressing deterioration of processability is obtained. They have found that they can be manufactured and have reached the present invention.

That is, in the present invention, 1,2-polybutadiene (a) having a melting point of 95 to 110° C. is 4 to 20% by weight, and 1,2-polybutadiene (b) having a melting point of 150 to 230° C. is 10 to 15% by weight. 10 to 90 parts by weight of vinyl cis-polybutadiene rubber (A) and 90 to 10 parts by weight of a diene rubber (B) other than (A) to 100 parts by weight of a rubber component (A)+(B). And a rubber composition containing 10 to 100 parts by weight of a rubber reinforcing agent (C), and a tire using the same.

As described above, according to the present invention, it is possible to provide a rubber composition having an excellent balance between processability and tensile stress, and a tire having an excellent balance between low fuel consumption and crack growth resistance.

<Vinyl cis-polybutadiene rubber (A)>
The vinyl cis-polybutadiene rubber (A) used in the rubber composition of the present invention comprises 4 to 20% by weight of 1,2-polybutadiene (a) having a melting point of 95 to 110° C. in polybutadiene as a matrix component, and It contains 10 to 15% by weight of 1,2-polybutadiene (b) having a melting point of 150 to 230°C.

(1,2-polybutadiene (a))
In the vinyl cis-polybutadiene rubber (A), the melting point of 1,2-polybutadiene (a) is 95 to 110°C, preferably 95 to 105°C. When the melting point of 1,2-polybutadiene (a) is lower than 95°C, the tensile stress tends to decrease, and when it is higher than 110°C, the crack resistance tends to decrease, which is not preferable.

The content of 1,2-polybutadiene (a) is 4 to 20% by weight, preferably 4 to 10% by weight, and preferably 4 to 8% by weight, based on the vinyl cis-polybutadiene rubber (A). More preferable. If the content is more than 20% by weight, the workability tends to decrease, and if it is less than 4% by weight, the tensile stress tends to decrease, which is not preferable.

1,2-Polybutadiene (a) is a vinyl cis-produced by adding or synthesizing it in an inert organic solvent in the first step of the method for producing a vinyl cis-polybutadiene rubber (A) described later. The above content can be contained in the polybutadiene rubber (A).

(1,2-polybutadiene (b))
Further, the vinyl cis-polybutadiene rubber (A) used in the present invention is prepared by converting 1,3-butadiene to syndiotactic-1,2 in the third step of the method for producing the vinyl cis-polybutadiene rubber (A) described later. The 1,2-polybutadiene (b) can be contained by polymerizing.

The content (HI) of 1,2-polybutadiene (b) is 10 to 15% by weight, preferably 12 to 14% by weight, based on the vinyl cis-polybutadiene rubber (A). If the content is more than 15% by weight, the workability, crack resistance and fuel economy will tend to decrease, and if it is less than 10% by weight, the tensile stress and crack resistance will tend to decrease, such being undesirable.

The melting point of 1,2-polybutadiene (b) is 150 to 230°C, preferably 180 to 220°C, more preferably 190 to 210°C. When the melting point of 1,2-polybutadiene (b) is lower than 150°C, the tensile stress tends to decrease.

The peak top molecular weight of the 1,2-polybutadiene (b) is preferably 100,000 to 400,000, more preferably 200,000 to 350,000. If the peak top molecular weight is larger than 400,000, the workability tends to decrease, and if it is smaller than 100,000, the tensile stress tends to decrease. In the present invention, the peak top molecular weight (Mp) is the peak top molecular weight in the elution curve obtained by gel permeation chromatography measurement, and can be calculated from a calibration curve obtained using polystyrene as a standard substance.

(Polybutadiene rubber)
In the vinyl cis-polybutadiene rubber (A) used in the present invention, the polybutadiene which is the matrix component is 1,3-butadiene in the second step of the method for producing the vinyl cis-polybutadiene rubber (A) described later. It is obtained by 1,4 polymerization. 20-60 are preferable and, as for the Mooney viscosity (ML1 ₊₄ , 100 degreeC) of polybutadiene, 20-35 are more preferable. Further, the cis-1,4 structure content of polybutadiene is preferably 90% or more, and particularly preferably 95% or more.

The weight average molecular weight of the polybutadiene as the matrix component is preferably 200,000 to 800,000, more preferably 400,000 to 650,000. Moreover, the ratio (Mw/Mn) of the weight average molecular weight and the number average molecular weight is preferably 2.00 to 5.00, and more preferably (2.20 to 3.50).

The polybutadiene obtained by cis-1,4 polymerization contains substantially no gel component.

<Method for producing vinyl cis-polybutadiene rubber (A)>
The method for producing the vinyl cis-polybutadiene rubber (A) used in the present invention is mainly composed of 1,2-polybutadiene (a) having a melting point of 95 to 110° C., 1,3-butadiene, and hydrocarbon. A first step of preparing a mixture with an inert organic solvent, and a mixture of water, an organoaluminum compound and a soluble cobalt compound in the mixture prepared in the first step, or an organoaluminum compound, a nickel compound and a fluorine compound A second step in which a catalyst is added to polymerize 1,3-butadiene with cis-1,4, and 1,3-butadiene in the polymerization reaction mixture obtained in the second step is polymerized with syndiotactic-1,2. And a third step.

(First step)
The 1,2-polybutadiene (a) having a melting point of 95 to 110° C., which is used in the method for producing the vinyl cis-polybutadiene rubber (A), is a cobalt compound, a general formula AlR ₃ (where R represents 1 to 10 carbon atoms). Which is 10 hydrocarbon groups) and carbon disulfide, and, if necessary, one selected from the group consisting of alcohol, aldehyde, ketone, ester, nitrile, sulfoxide, amide and phosphoric ester. Alternatively, it is produced by polymerizing 1,3-butadiene using a catalyst composed of two or more kinds of compounds. The 1,2-structure content of the 1,2-polybutadiene (a) is preferably 40 to 99%, particularly preferably 50 to 95%. The 1,2-polybutadiene (a) is preferably syndiotactic-1,2-polybutadiene.

In the method for producing vinyl cis-polybutadiene rubber (A), the addition amount of 1,2-polybutadiene (a) is 4 to 20% by weight based on the vinyl cis-polybutadiene obtained, and 4 to 10% by weight. %, more preferably 4 to 8% by weight. If the addition amount is more than 20% by weight, the workability tends to deteriorate, and if it is less than 4% by weight, the tensile stress tends to deteriorate, which is not preferable.

Examples of the inert organic solvent used in the method for producing the vinyl cis-polybutadiene rubber (A) include aromatic hydrocarbons such as toluene, benzene and xylene, aliphatic hydrocarbons such as n-hexane, butane, heptane and pentane, Alicyclic hydrocarbons such as cyclohexane and cyclopentane, olefin compounds and olefinic hydrocarbons such as cis-2-butene and trans-2-butene, mineral spirits, solvent solvents such as solvent naphtha and kerosene, and Examples thereof include halogenated hydrocarbon solvents such as methylene chloride. Further, the 1,3-butadiene monomer itself may be used as a polymerization solvent.

Among the above-mentioned inert organic solvents, toluene, cyclohexane, and a mixture of cis-2-butene and trans-2-butene are preferably used.

In the method for producing vinyl cis-polybutadiene rubber (A), 1,2-polybutadiene (a) having a melting point of 95 to 110° C., 1,3-butadiene, and an inert organic solvent containing hydrocarbon as a main component. The mixture of can be prepared by dissolving 1,2-polybutadiene (a) in a mixture of 1,3-butadiene and the inert organic solvent. When the 1,2-polybutadiene (a) is difficult to dissolve, it can be heated to 30 to 180° C. to dissolve it. Alternatively, the mixture may be prepared by synthesizing and dissolving 1,2-polybutadiene (a) in the mixture of 1,3-butadiene and an inert organic solvent using the above catalyst system.

(Second step)
Next, the concentration of water in the mixture prepared in the first step is adjusted. The concentration of water is preferably 0.1 to 1.4 mol, particularly preferably 0.2 to 1.2 mol, per mol of the organoaluminum compound used in cis-1,4 polymerization. Outside of this range, the catalytic activity decreases, the cis-1,4 structure content decreases, and the molecular weight becomes abnormally low or high, which is not preferable. Further, if the amount is out of the above range, it is not possible to suppress the generation of gel during the polymerization, so that the gel may adhere to the polymerization tank or the like and the continuous polymerization time cannot be extended, which is not preferable. A known method can be applied to the method for adjusting the water concentration. A method of adding and dispersing through a porous filter material (Japanese Patent Laid-Open No. 4-85304) is also effective.

An organoaluminum compound is added to the mixture obtained by adjusting the water concentration as described above. Examples of the organic aluminum compound include trialkyl aluminum, dialkyl aluminum chloride, dialkyl aluminum bromide, alkyl aluminum sesquichloride, alkyl aluminum sesquibromide, and alkyl aluminum dichloride.

Among the above organoaluminum compounds, trialkylaluminum represented by the general formula AlR ₃ (wherein R is a hydrocarbon group having 1 to 10 carbon atoms) can be preferably used. Examples of trialkylaluminum include trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, tripentylaluminum, trihexylaluminum, tricyclohexylaluminum, trioctyl. Aluminum, triphenyl aluminum, tri-p-tolyl aluminum, and tribenzyl aluminum can be mentioned. The alkyl groups in the trialkylaluminum may be the same or different from each other.

In addition to the above organoaluminum compounds, dialkylaluminum chlorides such as dimethylaluminum chloride and diethylaluminum chloride, organoaluminum halogen compounds such as sesquiethylaluminum chloride and ethylaluminum dichloride, diethylaluminum hydride, diisobutylaluminum hydride and sesquiethylaluminum hydride, etc. It is also possible to use the organoaluminum hydride compound.

Two or more kinds of these organoaluminum compounds may be used in combination.

When the cis-1,4 polymerization is carried out using a catalyst system composed of water, an organoaluminum compound and a soluble cobalt compound, the amount of the organoaluminum compound used is 0.1 mmol or more, and particularly 0 mol/mol of 1,3-butadiene. It is preferably 0.5 to 50 mmol. When cis-1,4 polymerization is carried out using a catalyst system composed of an organoaluminum compound, a nickel compound and a fluorine compound, it is 1×10 ⁻⁵ to 1×10 ⁻¹ mol per mol of 1,3-butadiene. It is preferable.

Then, a soluble cobalt compound is added to the mixture containing the organoaluminum compound to polymerize 1,3-butadiene with cis-1,4. The soluble cobalt compound is soluble in an inert organic solvent containing hydrocarbon as a main component or liquid 1,3-butadiene, or can be uniformly dispersed, for example, cobalt (II) acetylacetonate and cobalt. (III) Cobalt β-diketone complex such as acetylacetonate, cobalt β-keto acid ester complex such as cobalt acetoacetate ethyl ester complex, organic compound having 6 or more carbon atoms such as cobalt octoate, cobalt naphthenate and cobalt benzoate A cobalt salt of a carboxylic acid, a cobalt halide complex such as a cobalt chloride pyridine complex and a cobalt chloride ethyl alcohol complex is used. The amount of the soluble cobalt compound used is preferably 0.0005 mmol or more, and particularly preferably 0.001 mmol or more per mol of 1,3-butadiene. Further, the molar ratio (Al/Co) of the organic aluminum compound to the soluble cobalt compound is 10 or more, and particularly preferably 50 or more.

Further, instead of the soluble cobalt compound, a nickel compound and a fluorine compound may be added to a mixture containing an organoaluminum compound to polymerize 1,3-butadiene with cis-1,4. In this case, water may or may not be added as a component of the cis-1,4 polymerization catalyst.

As the nickel compound, nickel salts or complexes are preferably used. Particularly preferred are nickel halides such as nickel chloride and nickel bromide, nickel salts of inorganic acids such as nickel nitrate, nickel octylate, nickel acetate, nickel carboxylate having 1 to 18 carbon atoms such as nickel octoate, Nickel naphthenate, nickel malonate, nickel bisacetylacetonate and trisacetylacetonate, nickel complexes such as acetoacetic acid ethyl ester, nickel halide triarylphosphine complexes, trialkylphosphine complexes, pyridine complexes and picoline complexes Examples include organic base complexes and various complexes such as ethyl alcohol complexes. The amount of the nickel compound used is preferably 1×10 ⁻⁷ to 1×10 ⁻³ mol per mol of 1,3-butadiene.

As the fluorine compound, a complex of an ether of boron trifluoride, an alcohol, or a mixture thereof, or a mixture of an ether of hydrogen fluoride, an alcohol, or a complex thereof is preferably used. Particularly preferred are boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, hydrogen fluoride diethyl etherate, and hydrogen fluoride dibutyl etherate. The amount of the fluorine compound used is preferably 1×10 ⁻⁴ to 1 mol per mol of 1,3-butadiene.

The temperature for cis-1,4 polymerization of 1,3-butadiene is more than 0°C and 100°C or less, preferably 10 to 100°C, and more preferably 20 to 100°C. The polymerization time is preferably in the range of 10 minutes to 2 hours. It is preferable to carry out cis-1,4 polymerization so that the polymer concentration after cis-1,4 polymerization becomes 5 to 26% by weight. Polymerization is performed by stirring and mixing the solution in a polymerization tank (polymerizer). As the polymerization tank used for the polymerization, a polymerization tank equipped with a high-viscosity liquid stirring device, for example, the device described in JP-B-40-2645 can be used.

At the time of cis-1,4 polymerization, known molecular weight regulators, for example, non-conjugated dienes such as cyclooctadiene, arene and methylallene (1,2-butadiene), or α-olefins such as ethylene, propylene and butene-1. Kinds can be used. Further, in order to further suppress the formation of gel during polymerization, a known gelation inhibitor can be used.

(Third step)
Next, 1,3-butadiene in the polymerization reaction mixture obtained in the second step is polymerized with syndiotactic-1,2. At that time, 1,3-butadiene may or may not be added to the obtained cis-1,4 polymer. In addition, during the 1, 2 polymerization, an organoaluminum compound and carbon disulfide represented by the general formula AlR ₃ (wherein R is a hydrocarbon group having 1 to 10 carbon atoms), and a soluble cobalt compound Is preferably added to polymerize 1,3-butadiene with 1,2, and water may be added to the polymerization system during 1,2 polymerization. Further, carbon disulfide has a small influence on the cis-1,4 polymerization and remains in the solution even after the completion of the polymerization, so that it may be added in the first step or the second step.

As the organoaluminum compound represented by the general formula AlR ₃ , trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, triphenylaluminum and the like are preferable. The organoaluminum compound is preferably 0.1 mmol or more, and particularly preferably 0.5 to 50 mmol per mol of 1,3-butadiene. The concentration of carbon disulfide is 20 mmol/L or less, particularly preferably 0.01 to 10 mmol/L. As an alternative to carbon disulfide, known phenyl isothiocyanate or xanthogenic acid compounds may be used. Water is preferably added to the polymerization system after contacting 1,3-butadiene with the organoaluminum compound. The amount of water added is preferably 0.1 to 1.5 mol per mol of the organoaluminum compound.

In the present invention, the content (HI) of the 1,2-polybutadiene (b) can be adjusted by adjusting the addition amount of the soluble cobalt compound in the third step. The amount of the soluble cobalt compound added in the third step is preferably 0.005 mmol or more per mol of 1,3-butadiene remaining after the second step. Further, as the soluble cobalt compound, the same one as described in the second step can be used. When the polymerization activity is low, the soluble cobalt compound may be added more than usual.

The temperature of 1,2 polymerization is preferably -5 to 100°C, particularly preferably -5 to 80°C. The polymerization system for 1,2 polymerization is 1 to 50 parts by weight, preferably 1 to 20 parts by weight of 1,3-butadiene per 100 parts by weight of the cis-1,4 polymer obtained in the second step. Is preferably added. Thereby, the yield of 1,2-polybutadiene (b) at the time of 1,2 polymerization can be increased. The polymerization time is preferably in the range of 10 minutes to 2 hours. It is preferable to carry out 1,2 polymerization so that the polymer concentration after 1,2 polymerization is 9 to 29% by weight. The polymerization is performed by stirring and mixing the polymerization solution in a polymerization tank (polymerization vessel). As the polymerization tank used for the 1,2 polymerization, the viscosity becomes higher during the 1,2 polymerization, and the polymer is easily attached, so that the polymerization tank is equipped with a high-viscosity liquid stirring device, for example, it is described in Japanese Patent Publication No. 40-2645. Different devices can be used.

After the polymerization reaction reaches a predetermined polymerization rate, a known antioxidant can be added according to a conventional method. As the antioxidant, phenol-based 2,6-di-t-butyl-p-cresol (BHT), phosphorus-based trinonylphenyl phosphite (TNP), and sulfur-based 4,6-bis(octylthio) are used. Methyl)-o-cresol and dilauryl-3,3'-thiodipropionate (TPL). These may be used alone or in combination of two or more, and the addition amount of the antioxidant is 0.001 to 5 parts by weight with respect to 100 parts by weight of vinyl cis-polybutadiene (A).

The polymerization reaction is carried out by adding a large amount of alcohol such as methanol and ethanol or a polar solvent such as water to the polymerization solution, inorganic acids such as hydrochloric acid and sulfuric acid, organic acids such as acetic acid and benzoic acid, or hydrogen chloride gas. Stop using a method known per se, such as a method of introducing into a solution. Then, the vinyl cis-polybutadiene (A) thus produced is separated, washed and then dried according to a conventional method.

<Rubber composition>
The rubber composition of the present invention comprises a rubber component (A)+(10 to 90 parts by weight of the vinyl cis-polybutadiene rubber (A) and 90 to 10 parts by weight of a diene rubber (B) other than (A). 10 to 100 parts by weight of the rubber reinforcing agent (C) is mixed with 100 parts by weight of B).

(Diene rubber (B) other than (A))
In the present invention, the diene rubber other than (A) as the component (B) is, for example, at least one diene rubber selected from natural rubber, isoprene rubber, butadiene rubber, emulsion polymerization or solution polymerization styrene-butadiene rubber. Rubber can be used, and it is particularly preferable to use natural rubber and butadiene rubber. When the component (B) is mixed with the component (A), it may be mixed at the time of kneading such as Banbury, roll, etc. which is usually performed, or it may be prepared by previously mixing and drying in a solution state after polymerization. May be.

The ratio of the component (A) to the component (B) is preferably 10 to 90 parts by weight of the component (A) and 90 to 10 parts by weight of the component (B), and particularly 10 to 60 parts by weight of the component (A). When the amount of the component (B) is 90 to 40 parts by weight, the rubber composition for a tire is most suitable.

(Rubber reinforcing agent (C))
In the present invention, as the rubber reinforcing agent as the component (C), various carbon black, white carbon, activated calcium carbonate, inorganic reinforcing agents such as ultrafine magnesium silicate, syndiotactic-1,2-polybutadiene resin, polyethylene Organic reinforcing agents such as resins, polypropylene resins, high styrene resins, phenol resins, lignin, modified melamine resins, coumarone indene resins and petroleum resins can be mentioned.
Particularly preferred is carbon black having a particle size of 90 nm or less and a dibutyl phthalate (DBP) oil absorption of 70 ml/100 g or more, and examples thereof include FEF, FF, GPF, SAF, ISAF, SRF, HAF.

The mixing ratio of the component (C) is preferably 10 to 100 parts by weight, and more preferably 20 to 60 parts by weight, based on 100 parts by weight of the rubber component (A)+(B). When the amount of the component (C) is less than 20, the tensile stress tends to decrease, and when it exceeds 60, the workability tends to deteriorate.

(Other ingredients)
The rubber composition of the present invention is usually used in the rubber industry such as other components such as vulcanizing agent, vulcanization aid, antioxidant, filler, process oil, zinc white, stearic acid, etc., if necessary. Chemicals may be kneaded.

As the vulcanizing agent, known vulcanizing agents such as sulfur, organic peroxides, resin vulcanizing agents, and metal oxides such as magnesium oxide are used.

As the vulcanization accelerator, known vulcanization accelerators such as aldehydes, ammonias, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates and xanthates can be used.

Examples of the filler include calcium carbonate, basic magnesium carbonate, clay, Lissajous, diatomaceous earth, regenerated rubber and powdered rubber.

Examples of the antiaging agent include amine-ketone-based, imidazole-based, amine-based, phenol-based, sulfur-based and phosphorus-based agents.

The process oil may be any of aromatic type, naphthene type and paraffin type.

The rubber composition of the present invention can be obtained by kneading the above components using a Banbury, an open roll, a kneader, a twin-screw kneader or the like which is commonly used.

The vulcanized rubber composition obtained by vulcanizing the rubber composition of the present invention makes use of the improved tensile stress, tire applications such as studless tires, snow tires and all-season tires, and also for large tire applications. Applicable.

The rubber composition according to the present invention can be used in various parts of a tire such as a sidewall, a cap tread, a base tread, a side reinforcing rubber, and a beat filler, and it is particularly preferably used in a sidewall of a tire.

The tire using the rubber composition according to the present invention is preferably a pneumatic tire, and as a gas to be filled, air having normal or adjusted oxygen partial pressure, nitrogen, and inert gas such as argon and helium are used. There is gas, etc.

When the rubber composition according to the present invention is used for a sidewall of a tire, the rubber composition according to the present invention containing each component is processed in an unvulcanized stage and attached by a usual method on a tire molding machine. A green tire can be obtained by molding. A tire can be obtained by heating and pressing this raw tire with a vulcanizer.

Further, the rubber composition according to the present invention can be used for anti-vibration rubber, seismic isolation rubber, belt (belt conveyor), rubber crawler, various hoses, moran, etc., as well as tire applications.

Hereinafter, the present invention will be specifically described based on Examples, but these do not limit the object of the present invention. The physical properties of the vinyl cis-polybutadiene rubber (A) and the rubber composition were measured as follows.

<Vinyl cis-polybutadiene rubber (A)>
1. Mooney viscosity (ML ₁₊₄ , 100°C)
The Mooney viscosity (ML ₁₊₄ , 100° C.) was measured by a Mooney viscometer (manufactured by Shimadzu Corporation, SMV-202) at a value of 4 minutes for preheating at 100° C. according to JIS K6300.

2. Low Melting Point SPB (1,2-Polybutadiene (a)) Content The low melting point SPB (1,2-polybutadiene (a)) content was calculated using the following formula (1).
Content of low-melting point SPB (1,2-polybutadiene (a))=amount of low-melting point SPB added in polymerization system/amount of obtained vinyl cis-polybutadiene rubber (A)×100 (1)

3. High melting point SPB (1,2-polybutadiene (b)) content (HI)
The heat of fusion measured by a differential scanning calorimeter (DSC-50 manufactured by Shimadzu Corporation) and the measured H.V. I. The H. I. It was calculated from the calibration curve. Measured H. I. 2 g of vinyl cis-polybutadiene rubber was subjected to boiling extraction with a Soxhlet extractor for 4 hours in 200 ml of n-hexane, and the extraction residue was shown in parts by weight.

4. Melting point of high melting point SPB (1,2-polybutadiene (b)) The melting point of high melting point SPB (1,2-polybutadiene (b)) shows a value when the sample is about 10 mg and the heating rate is 10° C./min. It was measured by a scanning calorimeter (manufactured by Shimadzu Corporation, DSC-50).

<Rubber composition>
1. Processability The processability was evaluated from the Mooney viscosity (ML ₁₊₄ , 100°C) of the secondary compound. The index was calculated by setting Comparative Example 2 to 100. The higher the value, the better the workability.

<Vulcanized product>
1. Tensile stress (M300)
The tensile stress M300 was measured according to JIS6251. Further, the index was calculated by setting Comparative Example 1 to 100. The larger the value, the higher the tensile stress.

(Synthesis example 1)
Into a 1.5 L stainless steel autoclave equipped with helical wings and having been subjected to nitrogen substitution, 2.7 g of low melting point SPB (1,2-polybutadiene (v) component: RB830 manufactured by JSR Corporation) and 100 ml of cyclohexane were charged, and the autoclave was sealed, Then, 600 ml of a raw material solution (FB) was prepared by pressure-feeding 500 ml of a mixed solution of 1,3-butadiene and 2-butene (weight ratio 50:50). Water (H ₂ O) and carbon disulfide (CS ₂ ) shown in Table 1 were added to the raw material solution using a syringe, and then the autoclave was heated to 60° C. and stirred at 500 rpm for 30 minutes, The low melting point SPB was completely dissolved. After cooling the autoclave to 25° C., diethylaluminum chloride and triethylaluminum (molar ratio 3:1) shown in Table 1 were added using a syringe, and the mixture was stirred for 5 minutes. Next, 1,5-cyclooctadiene (COD) shown in Table 1 was added using a syringe, and the temperature was raised to 45°C. Thereafter, cobalt octoate (Co(Oct) ₂ ) shown in Table 1 was added using a syringe, and cis-1,4 polymerization was carried out at 45° C. for 20 minutes. Triethylaluminum (TEA) shown in Table 2 was added to the obtained polymerization reaction mixture using a syringe and held for 2 minutes, and then cobalt octoate (Co(Oct) ₂ ) shown in Table 2 was added using a syringe. Then, the syndiotactic-1,2 polymerization was carried out at 45° C. for 20 minutes. A polymerization terminator was added to the obtained polymerization reaction mixture to terminate the syndiotactic-1,2 polymerization. Then, the autoclave was cooled and depressurized, and the polymerization reaction mixture was taken out into a vat. The vinyl cis-polybutadiene described in Synthesis Example 1 was obtained by charging the whole vat into a vacuum dryer heated to 100° C. and removing unreacted butadiene and solvent. Table 3 shows the physical properties of the obtained vinyl cis-polybutadiene.

(Comparative Synthesis Example 1)
3.0 g of low melting point SPB (1,2-polybutadiene (a) component: RB830 manufactured by JSR Co.) was added to a 5.0 L stainless steel autoclave equipped with helical wings and finished with Chisso substitution, and 1,3-butadiene and 2- 2000 ml of a mixed solution of butene and cyclohexane (weight ratio 32:31:36) was pressure fed, and the autoclave was closed to prepare a raw material solution. Water (H ₂ O) and carbon disulfide (CS ₂ ) shown in Table 1 were added to the raw material solution using a syringe, and then the autoclave was heated to 60° C. and stirred at 500 rpm for 30 minutes, The low melting point SPB was completely dissolved. After cooling the autoclave to 25° C., diethylaluminum chloride shown in Table 1 was added using a syringe and stirred for 5 minutes. Then, 1,5-cyclooctadiene (COD) and dilauryl-3,3′-thiodipropionate (TPL) shown in Table 1 were added using a syringe, and the temperature was raised to 60°C. Then, it added using the cobalt octoate (Co(Oct) ₂ ) syringe shown in Table 1, and implemented cis-1,4 polymerization for 20 minutes at 60 degreeC. Triethylaluminum (TEA) shown in Table 2 was added to the obtained polymerization reaction mixture using a syringe and held for 2 minutes, and then cobalt octoate (Co(Oct) ₂ ) shown in Table 2 was added using a syringe. Then, syndiotactic-1,2 polymerization was carried out at 40° C. for 20 minutes. A polymerization terminator was added to the obtained polymerization reaction mixture to terminate the syndiotactic-1,2 polymerization. Then, the autoclave was cooled and depressurized, and the polymerization reaction mixture was taken out into a vat. The vinyl cis-polybutadiene described in Comparative Synthesis Example 1 was obtained by charging the whole vat into a vacuum dryer heated to 100° C. and removing unreacted butadiene and solvent. Table 3 shows the physical properties of the obtained vinyl cis-polybutadiene.

(Comparative Synthesis Example 2)
Into a 1.5 L stainless steel autoclave equipped with helical wings and having completed the nitrogen substitution, 2.7 g of low melting point SPB (1,2-polybutadiene (a) component: RB830 manufactured by JSR Corporation) and 100 ml of cyclohexane were charged, and the autoclave was sealed, Then, 600 ml of a raw material solution (FB) was prepared by pressure-feeding 500 ml of a mixed solution of 1,3-butadiene and 2-butene (weight ratio 50:50). Water (H ₂ O) and carbon disulfide (CS ₂ ) shown in Table 1 were added to the raw material solution using a syringe, and then the autoclave was heated to 60° C. and stirred at 500 rpm for 30 minutes, The low melting point SPB was completely dissolved. After cooling the autoclave to 25° C., diethylaluminum chloride and triethylaluminum (molar ratio 3:1) shown in Table 1 were added using a syringe, and the mixture was stirred for 5 minutes. Then, 1,5-cyclooctadiene (COD) shown in Table 1 was added using a syringe, and the temperature was raised to 45°C. Thereafter, cobalt octoate (Co(Oct) ₂ ) shown in Table 1 was added using a syringe, and cis-1,4 polymerization was carried out at 45° C. for 20 minutes. Triethylaluminum (TEA) shown in Table 2 was added to the obtained polymerization reaction mixture using a syringe and held for 2 minutes, and then cobalt octoate (Co(Oct) ₂ ) shown in Table 2 was added using a syringe. Then, the syndiotactic-1,2 polymerization was carried out at 45° C. for 20 minutes. A polymerization terminator was added to the obtained polymerization reaction mixture to terminate the syndiotactic-1,2 polymerization. Then, the autoclave was cooled and depressurized, and the polymerization reaction mixture was taken out into a vat. The vinyl cis-polybutadiene described in Comparative Synthesis Example 2 was obtained by charging the whole vat into a vacuum dryer heated to 100° C. and removing unreacted butadiene and solvent. Table 3 shows the physical properties of the obtained vinyl cis-polybutadiene.

The vinyl cis-polybutadiene rubbers obtained in Synthesis Example 1 and Comparative Synthesis Examples 1 and 2 are kneaded in a plastomill according to Table 4 with carbon black, natural rubber, process oil, zinc white, stearic acid and an antioxidant added. The primary formulation was carried out, and then the secondary formulation was carried out by adding a vulcanization accelerator and sulfur on a roll to prepare a secondary formulation. The Mooney viscosity (ML ₁₊₄ , 100° C.) of this secondary compound was measured to evaluate the processability. Furthermore, this secondary compound was molded and press-vulcanized at 160° C. to obtain a vulcanized product, and then the tensile stress (M300) was measured. Table 5 shows the results of measuring the physical properties of the compound and the vulcanized product.

From the above, it can be seen that the blends and vulcanizates according to the Examples are improved in tensile stress and workability as compared with the blends and vulcanizates of Comparative Examples.

<Evaluation of low fuel consumption>
Next, Example 1 and Comparative Examples 1 and 2 were evaluated for fuel economy. The loss tangent (tan δ) was measured at a temperature of 50° C., a frequency of 15 Hz and a strain of 5% using a viscoelasticity measuring device manufactured by Rheometrics. The results are shown in Table 6. As a result, the reciprocal of tan δ was expressed as an index with Comparative Example 1 as 100. The larger the index value, the better the fuel economy.

<Evaluation of tire side rubber crack growth resistance>
Next, an evaluation test was performed on crack growth resistance when the rubber compositions according to Example 1 and Comparative Examples 1 and 2 were used in the tread portion of the tire. First, each of the rubber compositions according to Example 1 and Comparative Example 1 was used to manufacture a pneumatic tire having a size of 195/65R15. A side rubber portion of the obtained tire was preliminarily provided with a scratch of 1 mm, and then the tire was run on a drum, and the length of the grown crack was measured after a certain period of time. The results are shown in Table 6. The result was expressed as an index by taking the reciprocal of the crack length with the crack length of Comparative Example 1 being 100. The larger the index value, the better the crack growth resistance.

As a result of the evaluation, when the rubber composition according to Example 1 was used, the fuel economy was not significantly deteriorated, and the crack growth resistance was significantly improved. In addition, H. I. In Comparative Example 2 in which the amount was increased, the fuel economy was deteriorated and the crack growth resistance was not improved.

Claims (4)

Rubber based on 100 parts by weight of a rubber component (A)+(B) consisting of 10 to 90 parts by weight of vinyl cis-polybutadiene rubber (A) and 90 to 10 parts by weight of a diene rubber (B) other than (A). A rubber composition comprising 10 to 100 parts by weight of a reinforcing agent (C) , wherein the vinyl cis-polybutadiene rubber (A) is based on the vinyl cis-polybutadiene rubber (A). A rubber composition containing 4 to 20% by weight of 1,2-polybutadiene (a) having a melting point of 95 to 110° C. and 10 to 15% by weight of 1,2-polybutadiene (b) having a melting point of 150 to 230° C. Stuff. The vinyl cis-polybutadiene rubber (A) is
A first step of preparing a mixture of 1,2-polybutadiene (a) having a melting point of 95 to 110° C., 1,3-butadiene, and an inert organic solvent containing hydrocarbon as a main component;
Water, a catalyst composed of an organoaluminum compound and a soluble cobalt compound, or a catalyst composed of an organoaluminum compound, a nickel compound and a fluorine compound is added to the mixture prepared in the first step to add 1,3-butadiene to cis-1. , The second step of polymerizing 4;
The third step of polymerizing 1,3-butadiene in the polymerization reaction mixture obtained in the second step, which is syndiotactic-1,2, is obtained by a production method comprising: Rubber composition. A tire using the rubber composition according to claim 1. A tire using the rubber composition according to claim 1 or 2 for a sidewall.