JP6701764B2 - Vinyl cis-polybutadiene rubber and method for producing the same - Google Patents

Description

  The present invention relates to a vinyl cis-polybutadiene rubber and a method for producing 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 of 4 polymerizations and then 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 a 1,3-butadiene is subjected to cis-1,4 polymerization, a dissolved 1,2-polybutadiene is mixed in advance to obtain a rubber composition, which has an extrudability. And vinyl cis-polybutadiene rubber with improved tensile stress. Further, Patent Documents 2 to 4 describe further improved vinyl cis-polybutadiene rubbers having excellent heat generation and crack resistance.

JP, 2008-163144, A JP2012-207052A JP 2012-214735 A JP 2012-214765 A

  However, the vinyl cis-polybutadiene rubbers described in Patent Documents 1 to 4, which are various improved vinyl cis-polybutadiene rubbers, are industrially useful for further improvement in crack resistance.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a vinyl cis-polybutadiene rubber excellent in crack resistance and a method for producing the same, when a rubber composition is prepared. .

  The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, by incorporating 1,2-polybutadiene having a specific peak top molecular weight (Mp) into a vinyl cis-polybutadiene rubber, The present invention has been found out that a vinyl cis-polybutadiene rubber having excellent crack resistance can be produced when it is made into a composition.

  That is, the present invention is a vinyl cis-polybutadiene rubber containing 1,2-polybutadiene (A) having a melting point of 60 to 150° C. and 1,2-polybutadiene (B) having a melting point of 160 to 230° C. , 1,2-polybutadiene (B) having a peak top molecular weight (Mp) of 10,000 or less.

  Further, the present invention is a method for producing the vinyl cis-polybutadiene rubber, which comprises 1,2-polybutadiene (A) having a melting point of 60 to 150° C., 1,3-butadiene, and a hydrocarbon as main components. And a catalyst comprising 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 catalyst consisting of 1,3-butadiene and cis-1,4 are polymerized in the second step, and 1,3-butadiene in the polymerization reaction mixture obtained in the second step is converted into syndiotactic-1, And a third step of polymerizing, wherein the polymerization temperature is adjusted to 50 to 100° C. in the third step.

  As described above, according to the present invention, it is possible to provide a vinyl cis-polybutadiene rubber excellent in crack resistance and a method for producing the same, when a rubber composition is formed.

<Vinyl cis-polybutadiene rubber>
The vinyl cis-polybutadiene rubber according to the present invention comprises 1,2-polybutadiene (A) having a melting point of 60 to 150° C. and 1,2-polybutadiene (having a melting point of 160 to 230° C.) in polybutadiene as a matrix component. B) is contained, and the peak top molecular weight (Mp) of 1,2-polybutadiene (B) is 10,000 or less.

(1,2-polybutadiene (A))
In the vinyl cis-polybutadiene rubber according to the present invention, the melting point of 1,2-polybutadiene (A) is 60 to 150°C, preferably 80 to 120°C, more preferably 95 to 99°C. preferable. If the melting point of 1,2-polybutadiene (A) is lower than 60° C. or higher than 150° C., crack resistance tends to deteriorate, which is not preferable.

  The content of 1,2-polybutadiene (A) is preferably 1 to 20% by weight, more preferably 2 to 10% by weight, particularly preferably 3 to 7% by weight, based on the vinyl cis-polybutadiene rubber. If the content is more than 20% by weight, the fuel economy tends to deteriorate, and if it is less than 1% by weight, the crack resistance tends to deteriorate, which is not preferable.

  1,2-Polybutadiene (A) is used in the vinyl cis-polybutadiene rubber produced by adding or synthesizing it in an inert organic solvent in the first step of the method for producing vinyl cis-polybutadiene rubber described below. Can contain the above content.

(1,2-polybutadiene (B))
In the vinyl cis-polybutadiene rubber according to the present invention, the melting point of 1,2-polybutadiene (B) is 160 to 230°C, preferably 170 to 220°C, and more preferably 175 to 210°C. preferable. When the melting point of 1,2-polybutadiene (B) is lower than 160° C., the die swell deteriorates, which is not preferable.

  The content (HI) of 1,2-polybutadiene (B) is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, and 10 to 15% by weight based on the vinyl cis-polybutadiene rubber. % Is particularly preferred. If the content is more than 25% by weight, workability tends to deteriorate, and if it is less than 1% by weight, crack resistance tends to deteriorate, which is not preferable.

  The peak top molecular weight (Mp) of 1,2-polybutadiene (B) is 10,000 or less, preferably 1,000 to 10,000, and particularly preferably 3,000 to 10,000. When the peak top molecular weight (Mp) is more than 10,000, crack resistance is deteriorated, which is not preferable. 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 (GPC) measurement, and can be calculated from a calibration curve obtained using polystyrene as a standard substance. .

  The 1,2-polybutadiene (B) is a vinyl-based resin produced by polymerizing 1,3-butadiene with syndiotactic-1,2 in the third step of the method for producing a vinyl-cis-polybutadiene rubber described later. The above content can be contained in the cis-polybutadiene rubber. The peak top molecular weight (Mp) of 1,2-polybutadiene (B) can be adjusted by adjusting the polymerization temperature of the syndiotactic-1,2 polymerization in the third step to 50 to 100°C. .

(Polybutadiene)
In the vinyl cis-polybutadiene rubber according to the present invention, the polybutadiene which is the matrix component is obtained by polymerizing 1,3-butadiene with cis-1,4 in the second step of the method for producing a vinyl cis-polybutadiene rubber described later. Obtained by 20-60 are preferable and, as for the Mooney viscosity (ML1 ₊₄ , 100 degreeC) of polybutadiene, 25-45 are more preferable. Further, the cis-1,4 structure content of polybutadiene is preferably 90% or more, and particularly preferably 95% or more.

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

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

(Graft)
Further, the vinyl cis-polybutadiene rubber according to the present invention preferably has a graft content of 5 to 25% by weight, more preferably 15 to 22% by weight. The graft body comprises 1,2-polybutadiene (A), which is obtained by cis-1,4 polymerization of 1,3-butadiene in dissolved 1,2-polybutadiene (A), and polybutadiene which is a matrix component. Is a partially chemically bonded substance. The graft body content of 5 to 25% by weight is preferable from the viewpoint of good fuel economy and balance with crack resistance.

<Method for producing vinyl cis-polybutadiene rubber>
As the method for producing the vinyl cis-polybutadiene rubber according to the present invention, 1,2-polybutadiene (A) having a melting point of 60 to 150° C., 1,3-butadiene, and an inert organic compound containing hydrocarbon as a main component are used. First step of preparing a mixture with a solvent, and 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. Then, the second step of polymerizing 1,3-butadiene with cis-1,4 and the third step of polymerizing 1,3-butadiene in the polymerization reaction mixture obtained in the second step with syndiotactic-1,2 And a step of adjusting the polymerization temperature to 50 to 100° C. in the third step.

(First step)
The 1,2-polybutadiene (A) having a melting point of 60 to 150° C., which is used in the method for producing a vinyl cis-polybutadiene rubber according to the present invention, is a cobalt compound, a general formula AlR ₃ (where R is 1 carbon atom). 1 to 10 hydrocarbon groups) and carbon disulfide, and optionally 1 selected from the group consisting of alcohols, aldehydes, ketones, esters, nitriles, sulfoxides, amides and phosphoric acid esters. It is produced by polymerizing 1,3-butadiene using a catalyst composed of one kind or 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 a vinyl cis-polybutadiene rubber according to the present invention, the addition amount of 1,2-polybutadiene (A) is preferably 1 to 20% by weight based on the obtained vinyl cis-polybutadiene rubber, 15% by weight is more preferable, and 3 to 10% by weight is particularly preferable. If the addition amount is more than 20% by weight, fuel economy tends to deteriorate, and if it is less than 1% by weight, crack resistance tends to deteriorate, which is not preferable.

  Examples of the inert organic solvent used in the method for producing a vinyl cis-polybutadiene rubber according to the present invention include aromatic hydrocarbons such as toluene, benzene and xylene, and 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 halogenated hydrocarbon solvents such as methylene chloride. Further, 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 a vinyl cis-polybutadiene rubber according to the present invention, an inert organic solvent containing 1,2-polybutadiene (A) having a melting point of 60 to 150° C., 1,3-butadiene and a hydrocarbon as main components. The mixture with can be prepared by dissolving 1,2-polybutadiene (A) in a mixture of 1,3-butadiene and the above-mentioned 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 is lowered, the cis-1,4 structure content is lowered, and the molecular weight is abnormally low or high, which is not preferable. Further, if the amount is out of the above range, the generation of gel during polymerization cannot be suppressed, 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/dispersing through a porous filter material (Japanese Patent Laid-Open No. 4-85304) is also effective.

  The 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 the 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.

  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 consisting of water, an organoaluminum compound and a soluble cobalt compound, the amount of the organoaluminum compound used is 0.1 mmol or more, 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 consisting 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. Preferably.

  Next, 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, cobalt octoate, cobalt naphthenate and cobalt benzoate having 6 or more carbon atoms Cobalt salts of carboxylic acids, cobalt halides such as cobalt chloride pyridine complex and cobalt chloride ethyl alcohol complex are used. The amount of the soluble cobalt compound used is preferably 0.001 mmol or more, and particularly preferably 0.005 mmol or more per 1 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, etc. 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 is 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, a known gelation inhibitor can be used in order to further suppress the generation of gel during polymerization.

(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. Further, during the 1, 2 polymerization, an organoaluminum compound represented by the general formula AlR ₃ (wherein R is a hydrocarbon group having 1 to 10 carbon atoms) and carbon disulfide, and, if necessary, It is preferable to add a soluble cobalt compound to polymerize 1,3-butadiene 1,2, and water may be added to the polymerization system during 1,2 polymerization. Further, carbon disulfide has a small effect on 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 above 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, a known phenyl isothiocyanate or a xanthate compound 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. As the soluble cobalt compound, the same one as described in the second step can be used.

  In the third step, the temperature of 1,2 polymerization is 50 to 100°C, preferably 60 to 90°C, and particularly preferably 70 to 85°C. In the present invention, the peak top molecular weight (Mp) of the obtained 1,2-polybutadiene (B) can be adjusted by adjusting the polymerization temperature in the third step to 50 to 100°C.

  The 1,2-butadiene polymerization system is 1-50 parts by weight, preferably 1-20 parts by weight, of 1,3-butadiene per 100 parts by weight of the cis-1,4 polymer obtained in the second step. Can be 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 2 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. Polymerization is performed by stirring and mixing the polymerization solution in a polymerization tank (polymerizer). As the polymerization tank used for the 1,2 polymerization, the viscosity is further increased during the 1,2 polymerization, and the polymer is apt to adhere to the polymerization tank. Any device 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 anti-aging agent, 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 the vinyl cis-polybutadiene rubber.

  The polymerization reaction is performed by adding a large amount of alcohol such as methanol and ethanol or a polar solvent such as water to the polymerization solution, polymerizing an inorganic acid such as hydrochloric acid and sulfuric acid, an organic acid 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. The vinyl cis-polybutadiene rubber produced is then separated, washed and subsequently dried according to the usual methods.

<Rubber composition>
The vinyl cis-polybutadiene rubber of the present invention is, for example, a tire tread such as a cap tread in a tire, a side reinforcing layer of a run flat tire, a carcass, a belt, a chafer, a base tread, a bead, a stiffener, an inner liner, or a vibration proof. It can also be used for industrial products such as rubber, hoses, belts, rubber rolls, rubber coolers and shoe sole rubbers, other composites, adhesives, and modifiers for plastics. In particular, when used as a rubber composition for a tire, it has better crack resistance than before.

  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 base rubber and the vulcanized product produced by the method for producing a vinyl cis-polybutadiene rubber according to the present invention were measured as follows.

<Vinyl cis-polybutadiene rubber>
1. 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 to polymerization system/amount of vinyl cis-polybutadiene rubber obtained×100 (1)

2. 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) in accordance with JIS K6300, at a temperature of 100° C. for 1 minute of preheating and 4 minutes.

3. High melting point SPB (1,2-polybutadiene (B)) content (HI)
An infrared spectrum is measured, a microstructure is calculated from an absorption intensity ratio of cis 740 cm ⁻¹ , trans 967 cm ⁻¹ , vinyl 910 cm ⁻¹ , and 1,2-polybutadiene (A), 1,2-polybutadiene (B), The content of each vinyl 1,2-structure of the vinyl cis-polybutadiene rubber was calculated.
The amount (g) of 1,2-polybutadiene (B) was calculated by substituting the calculated vinyl 1,2-structure content, the polymerization conditions, and the numerical values obtained from the results into the following formula (2).
(Amount (g) of 1,2-polybutadiene (A))*(Content of vinyl 1,2-structure of 1,2-polybutadiene (A))+{(Yield of vinyl cis-polybutadiene rubber (g)-( 1,2-polybutadiene (A) amount (g)-(1,2-polybutadiene (B) amount (g))}*0.01+(1,2-polybutadiene (B) amount (g))*(1, 2-Polybutadiene (B) vinyl 1,2-structure content) = (Vinyl cis-polybutadiene rubber yield (g)) * (Vinyl cis-polybutadiene rubber vinyl 1,2-structure content)・Formula (2)
By substituting the calculated amount (g) of 1,2-polybutadiene (B) into the following formula (3), the H.V. I. The amount was calculated.
(HI amount of vinyl cis-polybutadiene rubber (%))=(1,2-polybutadiene (B) amount (g))/(yield of vinyl cis-polybutadiene rubber (g)*100... Formula (3)

4. High melting point SPB (1,2-polybutadiene (B)) peak top molecular weight (Mp)
The peak top molecular weight (Mp) of the high melting point SPB (1,2-polybutadiene (B)) was obtained by dissolving the n-hexane insoluble matter recovered by Soxhlet extraction with ortho-dichlorobenzene (ODCB) at 145° C. and then filtering with heat. The product was subjected to high temperature GPC measurement (GPC/V2000 type manufactured by Waters) at 145° C., and the peak top molecular weight (Mp) of SPB was calculated from a calibration curve obtained using polystyrene as a standard substance.

<Vulcanized product>
1. Crack resistance The crack resistance was measured by using a constant elongation fatigue tester (Kamishima Seisakusho) to make a crack of 0.5 mm in the center of a vulcanized test piece (width 12 mm, height 110 mm, thickness 2 mm) and strain 50 %, the number of times when the crack growth length reached 1.0 mm was measured under the condition of 300 times/minute. Comparative Example 1 is set to 100, and the larger the index value, the better the crack resistance.

(Example 1)
Vinyl cis-polybutadiene rubber was produced under the conditions shown in Tables 1 and 2. Specifically, an amount of low melting point SPB (1,2-polybutadiene (A) component: RB830 manufactured by JSR Co.) and 450 ml of cyclohexane shown in Table 1 were added to a 1.5 L stainless steel autoclave equipped with helical wings and having been subjected to nitrogen substitution. 900 ml of a raw material solution (FB) was prepared by charging and sealing the autoclave, and then 450 ml of 1,3-butadiene was pressure-fed. Water (H ₂ O) was added to the raw material solution so as to have the concentration shown in Table 1 by using a syringe, and then the autoclave was heated to 60° C. and stirred at 500 rpm for 30 minutes to obtain low melting point SPB. It was completely dissolved. After cooling the autoclave to 25° C., diethylaluminum chloride and triethylaluminum (molar ratio 3:1) were added using a syringe so as to have the concentrations shown in Table 1, and the mixture was stirred for 5 minutes. Next, 1,5-cyclooctadiene (COD) was added using a syringe so as to have the concentrations shown in Table 1, and the temperature was raised to 45°C. Cobalt octoate (Co(Oct) ₂ ) was added using a syringe so as to have the concentrations shown in Table 1, and cis-1,4 polymerization was carried out at 45° C. for 20 minutes. Triethylaluminum (TEA) was added to the obtained polymerization reaction mixture using a syringe so that the concentration thereof was shown in Table 2, and the mixture was kept for 2 minutes, and then cobalt octoate was used so that the concentration thereof was shown in Table 2. The mixture was added and held for another 2 minutes, and further carbon disulfide (CS ₂ ) was added using a syringe so that the concentration was as shown in Table 2, and syndiotactic-1,2 polymerization was carried out at 78° C. for 5 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 rubber described in 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 rubber.

(Comparative Example 1)
Vinyl cis-polybutadiene rubber was produced under the conditions shown in Tables 1 and 2. Specifically, a 1.5 L stainless steel autoclave equipped with helical wings and having been subjected to nitrogen substitution was charged with 2.7 g of low melting point SPB (1,2-polybutadiene (A) component: RB830 manufactured by JSR Co.) and 100 ml of cyclohexane. Was sealed, and then 500 ml of a mixed solution of 1,3-butadiene and 2-butene (weight ratio 50:50) was pressure-fed to prepare 600 ml of a raw material solution (FB). Water (H ₂ O) and carbon disulfide (CS ₂ ) were added to the raw material solution using a syringe so as to have the concentrations shown in Table 1, and then the autoclave was heated to 60° C. and stirred at 500 rpm for 30 minutes. By doing so, the low melting point SPB was completely dissolved. After cooling the autoclave to 25° C., diethylaluminum chloride and triethylaluminum (molar ratio 3:1) were added using a syringe so as to have the concentrations shown in Table 1, and the mixture was stirred for 5 minutes. Next, 1,5-cyclooctadiene (COD) was added using a syringe so as to have the concentrations shown in Table 1, and the temperature was raised to 45°C. Cobalt octoate (Co(Oct) ₂ ) was added using a syringe so as to have the concentrations shown in Table 1, and cis-1,4 polymerization was carried out at 45° C. for 20 minutes. Triethylaluminum (TEA) was added to the obtained polymerization reaction mixture using a syringe so as to have the concentration shown in Table 2, and the mixture was held for 2 minutes, and then cobalt octoate was used so as to have the concentration shown in Table 2 using the syringe. After the addition, 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 rubber described in Comparative 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 rubber.

  According to Table 4, the vinyl cis-polybutadiene rubbers obtained in Example 1 and Comparative Example 1 were kneaded in a plastomill with the addition of carbon black, natural rubber, zinc white, process oil, stearic acid and an antioxidant. After that, secondary mixing was performed by adding a vulcanization accelerator and sulfur on a roll to prepare a compound. Further, this compound was molded, press-vulcanized at 160° C. to obtain a vulcanized product, and then crack resistance was measured. Table 5 shows the results of measuring the physical properties of the vulcanizates.

  From the above, it can be seen that the vulcanizates according to the examples have improved crack resistance as compared with the vulcanizates of the comparative examples.

Claims (4)

A vinyl cis-polybutadiene rubber containing 1,2-polybutadiene (A) having a melting point of 60 to 150°C and 1,2-polybutadiene (B) having a melting point of 160 to 230°C.
The vinyl-cis-polybutadiene rubber, wherein the 1,2-polybutadiene (B) has a peak top molecular weight (Mp) of 10,000 or less. The vinyl cis-polybutadiene according to claim 1 , wherein the content (HI) of 1,2-polybutadiene (B) is 1 to 25% by weight based on the vinyl cis-polybutadiene. Rubber. A first step of preparing a mixture of 1,2-polybutadiene (A) having a melting point of 60 to 150° 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. , 4 second step of polymerizing,
A third step of polymerizing 1,3-butadiene in the polymerization reaction mixture obtained in the second step with syndiotactic-1,2,
In the third step, the polymerization temperature is adjusted to 70 to 85 °C, and a method for producing vinyl cis-polybutadiene. The method for producing vinyl cis-polybutadiene according to claim 3, wherein the organoaluminum compound is trialkylaluminum and dialkylaluminum chloride.