Method for producing polybutadiene, polybutadiene, and polybutadiene composition

Abstract

To provide a polybutadiene that can give a rubber composition that is excellent in tensile stress and low heat buildup.SOLUTION: There is provided a method for producing a block polybutadiene in which a cis-1,4-polybutadiene structure and a syndiotactic-1,2-polybutadiene structure are bonded, the method comprising: a step X of aging a halogen-containing organoaluminum and a first alkylaluminum in the presence of water; and a step Y of polymerizing 1,3-butadiene by mixing a polymerization catalyst and a second alkylaluminum in the presence of the resulting aged solution, wherein in step Y or before step Y, 1,3-butadiene is mixed with carbon disulfide, and wherein the concentration (A) of the halogen-containing organoaluminum, the concentration (B) of the first alkylaluminum, and the molar ratio (C) of the second alkylaluminum satisfy the following: 0.2≤(A) / {(B)+(C)}≤3.0...(1), 0.01≤(C) / (B)≤1.0...(2).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing polybutadiene, polybutadiene, and a polybutadiene composition. [Background technology]

[0002] Conventionally, a method for producing a polybutadiene composition containing cis-1,4-polybutadiene and syndiotactic-1,2-polybutadiene involves cis-1,4-polymerizing 1,3-butadiene using a predetermined catalyst in an inert organic solvent containing a hydrocarbon such as benzene, toluene, or xylene as a main component, followed by syndiotactic-1,2-polymerization.

[0003] Furthermore, improvements in various properties of the polybutadiene composition obtained by the above method are desired depending on the application of the rubber composition when it is made into a rubber composition. For example, Patent Document 1 describes a method for producing a polybutadiene composition having improved tensile properties and crack resistance of the rubber composition by microparticulating a syndiotactic polybutadiene resin using a C4 fraction as a solvent.

[0004] Furthermore, Patent Document 2 describes a method for producing a polybutadiene composition with improved fatigue resistance by optimizing the ratio of the number of moles of halogen atoms in a halogen-containing organoaluminum to the number of moles of alkylaluminum. Also, Patent Document 3 describes a method for producing a polybutadiene composition that can impart excellent productivity and suitable rigidity to a rubber composition by adjusting the amount of catalyst used.

[0005] Furthermore, Patent Documents 4 and 5 describe polybutadiene compositions that have a boiling n-hexane insoluble content, a long chain branching index, and a branching degree within specific ranges, and that can impart excellent cold flow properties and elasticity.

[0006] Patent Document 6 describes a method for producing a polybutadiene composition, characterized in that a radical initiator is added after polymerization to bond cis-1,4-polybutadiene and syndiotactic-1,2-polybutadiene.

[0007] On the other hand, Patent Document 7 describes a diblock polybutadiene composed of a cis-1,4-polybutadiene structure and a syndiotactic-1,2-polybutadiene structure, and Non-Patent Document 1 describes a multiblock polybutadiene composed of a cis-1,4-polybutadiene structure and a syndiotactic-1,2-polybutadiene structure. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-044633 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-235865 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-227523 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-227522 [Patent Document 5] Japanese Patent Application Laid-Open No. 2014-025071 [Patent Document 6] Japanese Patent Application Laid-Open No. 2017-52860 [Patent Document 7] Special Publication No. 2016-536447 [Non-patent literature]

[0009] [Non-Patent Document 1] Macromolecules, 2009, Vol. 42, No. 20, 7642-7643 Summary of the Invention [Problem to be solved by the invention]

[0010] However, even in the various improved polybutadiene compositions described in Patent Documents 1 to 5, there is still room for improvement in terms of tensile stress and other physical properties when they are made into rubber compositions. Furthermore, a production method for obtaining a polybutadiene composition excellent in tensile stress and low heat buildup is not fully investigated in Patent Documents 6 and 7 and Non-Patent Document 1. Furthermore, Patent Document 6 has a problem in that it requires many steps to obtain a polybutadiene in which cis-1,4-polybutadiene and syndiotactic-1,2-polybutadiene are bonded together.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a polybutadiene composition that can give a rubber composition excellent in tensile stress and low heat buildup, and a polybutadiene that is a copolymer that gives rise to the polybutadiene composition, by a simple production method requiring few steps. [Means for solving the problem]

[0012] The present inventors have discovered that by using a halogen-containing organoaluminum and an alkylaluminum and carrying out the alkylaluminum addition process multiple times under specific conditions, polybutadiene, which is a block copolymer in which a cis-1,4-polybutadiene structure and a syndiotactic-1,2-polybutadiene structure are bonded, can be obtained, and that rubber compositions containing this polybutadiene exhibit excellent tensile stress and low heat buildup, leading to the present invention.

[0013] The present invention provides a method for producing polybutadiene, which produces a block polybutadiene having a cis-1,4-polybutadiene structure and a syndiotactic-1,2-polybutadiene structure (hereinafter also simply referred to as "block polybutadiene"), comprising the steps of: Step X: aging the halogen-containing organoaluminum and the first alkylaluminum in the presence of water; and a step Y of mixing 1,3-butadiene with a polymerization catalyst and a second alkylaluminum in the presence of the aged liquid obtained in the step X, and polymerizing the resulting mixture. In step Y or before step Y, mixing 1,3-butadiene with carbon disulfide, The present invention provides a production method in which the molar concentration (A) of the halogen-containing organoaluminum in the step X, the molar concentration (B) of the first alkylaluminum, and the molar concentration (C) of the second alkylaluminum in the step Y satisfy the following formulas (1) and (2): 0.2 ≦(A) / {(B)+(C)}≦ 3.0 ···(1) and, 0.01 ≦(C) / (B)≦ 1.0 ···(2).

[0014] The present invention also provides polybutadiene and polybutadiene compositions obtained by the above-mentioned production method. [Effects of the Invention]

[0015] According to the present invention, a block polybutadiene capable of giving a rubber composition excellent in tensile stress and low heat buildup, and a polybutadiene composition containing the block polybutadiene, can be provided by a simple production method requiring few steps. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described below based on preferred embodiments thereof.

[0017] <Production method of polybutadiene> The method for producing polybutadiene according to the present embodiment is a method for producing polybutadiene, which produces a block polybutadiene having a cis-1,4-polybutadiene structure and a syndiotactic-1,2-polybutadiene structure, and includes the steps of: Step X: aging the halogen-containing organoaluminum and the first alkylaluminum in the presence of water; and a step Y of mixing 1,3-butadiene with a polymerization catalyst and a second alkylaluminum in the presence of the aged liquid obtained in the step X, and polymerizing the resulting mixture. In step Y or before step Y, mixing 1,3-butadiene with carbon disulfide, The molar concentration (A) of the halogen-containing organoaluminum in the step X, the molar concentration (B) of the first alkylaluminum, and the molar concentration (C) of the second alkylaluminum in the step Y satisfy the following formulas (1) and (2): 0.2 ≦(A) / {(B)+(C)}≦ 3.0 ···(1) and, 0.01 ≦(C) / (B)≦ 1.0 ···(2).

[0018] First, the step X will be described. In step X, a halogen-containing organoaluminum and a first alkylaluminum are reacted in the presence of water. This reaction is called aging. This step produces an aluminoxane compound, which serves as a co-catalyst for cis-1,4-polymerization in step Y. Here, the block polybutadiene in the present invention refers to a polybutadiene having a cis-1,4-polybutadiene block and a syndiotactic-1,2-polybutadiene block in one molecule. The presence of these blocks in the polybutadiene obtained by the present invention can be confirmed by measuring hexane solubility or DSC measurement. The production method of this embodiment produces a block polybutadiene in which the cis-1,4-polybutadiene block and the syndiotactic-1,2-polybutadiene block are covalently bonded at their chain ends.

[0019] In step X, mixing the halogen-containing organoaluminum and the first alkylaluminum in an inert organic solvent in the presence of water is preferred from the viewpoints of the efficiency of producing the aluminoxane compound and preventing gel formation. Examples of inert organic solvents 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; the olefin compounds and olefinic hydrocarbons such as cis-2-butene and trans-2-butene; hydrocarbon solvents such as mineral spirits, solvent naphtha, and kerosene; and halogenated hydrocarbon solvents such as methylene chloride. Alternatively, 1,3-butadiene monomer itself may be used as the 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.

[0020] In this step X, it is preferable to adjust the water concentration in the inert organic solvent before adding the halogen-containing organoaluminum and the first alkylaluminum to the inert organic solvent in order to efficiently produce the aluminoxane compound. The water concentration is preferably 0.1 to 2.5 mol, more preferably 0.15 to 2.3 mol, and particularly preferably 0.2 to 1.9 mol per mol of the total amount of the halogen-containing organoaluminum and the first alkylaluminum used in step X. By maintaining the water to organoaluminum ratio at or above the lower limit, it is possible to prevent a decrease in the catalytic activity of cis-1,4-polymerization, a decrease in the cis-1,4 structure content, and an abnormally high or low molecular weight. Furthermore, by maintaining the water to organoaluminum ratio at or below the upper limit, it is possible to suppress the generation of gel during polymerization, prevent adhesion of gel to the polymerization vessel, and extend the continuous polymerization time. Known methods can be used to adjust the water concentration. A method of adding and dispersing the water through a porous filter (see JP 4-85304 A) is also effective.

[0021] To the mixture containing water and an inert organic solvent obtained by adjusting the water concentration as described above, a halogen-containing organoaluminum compound and a first alkylaluminum compound are added as organoaluminum compounds. The halogen-containing organoaluminum is preferably an alkylaluminum halide. The alkylaluminum halide is represented by the general formula: AlR 1 n X 3-n (However, R 1 is a hydrocarbon group having 1 to 10 carbon atoms, and n is the number 1 or 2. X is a halogen atom. Examples of the halogen atom represented by X include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of halogen-containing organoaluminums when X is a chlorine atom include dimethylaluminum chloride, diethylaluminum chloride, methylaluminum dichloride, and ethylaluminum dichloride. The alkyl groups in the alkylaluminum may be the same or different. One or more halogen-containing organoaluminums may be used in combination.

[0022] The first alkylaluminum has the general formula AlR 2 3 (However, R 2 is a hydrocarbon group having 1 to 10 carbon atoms). Examples of alkylaluminum include trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, tripentylaluminum, trihexylaluminum, tricyclohexylaluminum, trioctylaluminum, triphenylaluminum, tri-p-tolylaluminum, and tribenzylaluminum. The alkyl groups in the alkylaluminum may be the same or different. The first alkylaluminum may be used alone or in combination of two or more.

[0023] In step X, in addition to the halogen-containing organoaluminum and the first alkylaluminum, organoaluminum hydride compounds such as diethylaluminum hydride, diisobutylaluminum hydride and sesquiethylaluminum hydride can also be used.

[0024] The total amount of the first alkylaluminum and halogen-containing organoaluminum used is preferably 0.1 mmol or more, and particularly preferably 0.5 to 50 mmol, per mole of 1,3-butadiene used as a monomer in step Y. This amount is particularly preferred when polymerization is performed with a catalyst system using a soluble cobalt compound.

[0025] In step X, the first alkylaluminum and the halogen-containing organoaluminum are preferably mixed in an inert organic solvent in the presence of water and then aged. From the viewpoint of the efficiency of producing the aluminoxane compound, the aging time is preferably 0.1 to 360 minutes, more preferably 1 to 120 minutes, and particularly preferably 3 to 90 minutes. The aging temperature is preferably -10 to 80°C, more preferably -5 to 60°C, and particularly preferably 0 to 50°C. Step X is preferably carried out in the absence of a polymerization catalyst, in order to successfully obtain a block polybutadiene.

[0026] In step X, 1,3-butadiene, a monomer used as a reaction substrate, may be premixed with an inert organic solvent, and water, a first alkylaluminum, and a halogen-containing organoaluminum may be added to the mixture. Alternatively, 1,3-butadiene may be added to the inert organic solvent simultaneously with or after the addition of water, the first alkylaluminum, or the halogen-containing organoaluminum. Alternatively, in step Y, the aged solution obtained in step X may be mixed with 1,3-butadiene, a polymerization catalyst, and a second alkylaluminum. Preferably, in step X, an inert organic solvent and 1,3-butadiene are premixed, and water, a first alkylaluminum, and a halogen-containing organoaluminum are added to the mixture, from the viewpoints of the efficiency of aluminoxane compound production and prevention of gel formation.

[0027] In this production method, in the step Y, carbon disulfide is mixed with 1,3-butadiene in addition to the polymerization catalyst and the second alkylaluminum, or carbon disulfide is mixed with 1,3-butadiene before the step Y. Carbon disulfide is a co-catalyst for syndiotactic 1,2-polymerization, and therefore, in this step, the polymerization catalyst and the second alkylaluminum are mixed with 1,3-butadiene in the presence of carbon disulfide in the step Y, and syndiotactic 1,2-polymerization can proceed when the polymerization catalyst and the second alkylaluminum are mixed with 1,3-butadiene. In this production method, it is preferable in terms of production efficiency of block polybutadiene to add carbon disulfide to 1,3-butadiene in advance before adding the polymerization catalyst (soluble cobalt compound) to 1,3-butadiene, and it is particularly preferable to add carbon disulfide to 1,3-butadiene in advance before adding the second alkyl aluminum and the polymerization catalyst to 1,3-butadiene in step Y. In this production method, it is preferable from the viewpoint of production efficiency of block polybutadiene to add a polymerization catalyst to 1,3-butadiene in a state in which carbon disulfide and the aged liquid after step X have been mixed in advance. The concentration of carbon disulfide in the polymerization liquid containing an inert organic solvent and 1,3-butadiene and subjected to polymerization in step Y is preferably 0.01 to 20 mmol / L, particularly preferably 0.1 to 1 mmol / L. As an alternative to carbon disulfide, known phenyl isothiocyanate or xanthogenic acid compounds may be used.

[0028] (Process Y) Step Y is a step of polymerizing 1,3-butadiene by mixing a polymerization catalyst and a second alkylaluminum in the presence of the aged liquid obtained in step X. This second alkylaluminum is mixed with 1,3-butadiene without being premixed with water and / or halogenated organoaluminum.

[0029] Examples of polymerization catalysts include soluble cobalt compounds. Examples of soluble cobalt compounds include those that are soluble in or uniformly dispersible in an inert medium primarily composed of a hydrocarbon solvent or in liquid 1,3-butadiene. Examples include cobalt β-diketone complexes such as cobalt(II) acetylacetonate and cobalt(III) acetylacetonate; cobalt β-keto acid ester complexes such as cobalt acetic acid ester complex; cobalt salts of organic carboxylic acids having 6 or more carbon atoms such as cobalt octoate, cobalt naphthenate, and cobalt benzoate; and cobalt halide complexes such as cobalt chloride pyridine complex and cobalt chloride ethyl alcohol complex. When using a soluble cobalt compound, the amount used, calculated as cobalt atoms in the soluble cobalt compound, is preferably 0.001 mmol or more, and more preferably 0.005 mmol or more, per mole of 1,3-butadiene. The amount of the soluble cobalt compound used is usually 1 millimole or less per mole of 1,3-butadiene in terms of cobalt atom.

[0030] In step Y, the polymerization catalyst and the second alkylaluminum may be added to 1,3-butadiene simultaneously or at different times. When they are added at different times, either the second alkylaluminum or the polymerization catalyst may be added first.

[0031] The molar ratio (Al / Co) of the total of the first alkylaluminum, the second alkylaluminum, and the halogen-containing organoaluminum to the soluble cobalt compound is preferably 10 or more, and particularly preferably 50 or more. This molar ratio is usually 2000 or less.

[0032] The second alkylaluminum can be any of the compounds described above. The second alkylaluminum added in this step may be the same as or different from the first alkylaluminum added in step X. The molar concentration (C) of the second alkylaluminum added in step Y is preferably in the following molar ratio relative to the molar concentration (A) of the halogen-containing organoaluminum added in step X and the molar concentration (B) of the first alkylaluminum. 0.2 ≦(A) / {(B)+(C)}≦ 3.0 ···(1), and, 0.01 ≦(C) / (B)≦ 1.0 ···(2) Here, the molar concentration (A) of the halogen-containing organoaluminum, the molar concentration (B) of the first alkylaluminum, and the molar concentration (C) of the second alkylaluminum all refer to concentrations obtained by dividing the added moles by the volume of the polymerization liquid used for polymerization in step Y, and refer to concentrations based on the volume of the polymerization liquid after carbon disulfide, the second alkylaluminum, and the polymerization catalyst have been added in step Y.

[0033] In this embodiment, it is important that in step Y, 1,3-butadiene is mixed with a polymerization catalyst (particularly a soluble cobalt compound) and a second alkyl aluminum in the presence of the aging solution obtained in step X and carbon disulfide. In this configuration, satisfying (1) and (2) results in a block polybutadiene and a polybutadiene composition that can provide a rubber composition with excellent tensile stress and low heat buildup. Under these circumstances, the following phenomenon is presumed to occur in this embodiment. When the second alkyl aluminum is added, the alkyl aluminum that has not yet become an aluminoxane compound mixes with the soluble cobalt compound, making syndiotactic 1,2-polymerization more likely to proceed than cis-1,4-polymerization. Meanwhile, when the second alkyl aluminum is mixed with water contained in the polymerization solution, it converts to aluminoxane, which is thought to switch from syndiotactic 1,2-polymerization to cis-1,4-polymerization at the same catalytic active site. Furthermore, the presence of a previously prepared aging solution is thought to promote this switch. It is believed that such switching causes a cis-1,4-polybutadiene chain to extend from the end of a syndiotactic-1,2-polybutadiene chain, resulting in a block polybutadiene. In the production method of the present invention, by using a halogen-containing organoaluminum, a first alkylaluminum, and a second alkylaluminum in a specific ratio such as (1) and (2), the phenomenon of syndiotactic-1,2-polymerization and cis-1,4-polymerization occurring simultaneously can occur (specifically, the phenomenon of switching between syndiotactic-1,2-polymerization and cis-1,4-polymerization during the polymer growth process). Compared to polybutadiene compositions consisting of cis-1,4-polybutadiene and syndiotactic-1,2-polybutadiene, the block polybutadiene obtained by the present invention has a cis-1,4-polybutadiene structure and a syndiotactic-1,2-polybutadiene structure in a single polymer, making the two structures more compatible with each other. Therefore, even if the amount of syndiotactic-1,2-polybutadiene structure in the composition is the same, the dispersibility of the syndiotactic-1,2-polybutadiene crystal structure in the cis-1,4-polybutadiene structure in the composition is improved, which leads to low heat buildup and improved tensile stress when used in a rubber composition. Therefore, for example, when the block polybutadiene obtained by the present production method is contained in a polybutadiene composition together with cis-1,4-polybutadiene and syndiotactic-1,2-polybutadiene, the block polybutadiene acts as a compatibilizer between the cis-1,4-polybutadiene and the syndiotactic-1,2-polybutadiene, thereby achieving the above-mentioned excellent effects. According to the production method of the present invention, the ratio of the cis-1,4-polybutadiene structure to the syndiotactic-1,2-polybutadiene structure in a block polybutadiene or a polybutadiene composition containing the same can be adjusted, and block polybutadiene and polybutadiene compositions having desired physical properties can be easily produced.

[0034] In the production method of this embodiment, cis-1,4-polybutadiene is usually obtained in addition to the block polybutadiene. In the production method of this embodiment, syndiotactic-1,2-polybutadiene may also be obtained.

[0035] In the present invention, if the amount of the second alkyl aluminum used is too small relative to the amount of the first alkyl aluminum used, specifically if the (C) / (B) ratio is less than 0.01, syndiotactic 1,2-polymerization and cis-1,4-polymerization do not occur simultaneously, and therefore block polybutadiene cannot be obtained. In order to achieve the above-mentioned effects by ensuring that the proportion of syndiotactic 1,2-polybutadiene structures in the block polybutadiene and polybutadiene composition obtained by the production method of this embodiment is at a certain level or higher, it is particularly preferable to set the (C) / (B) ratio to 0.05 or greater. Furthermore, if the amount of the second alkyl aluminum used is too large relative to the amount of the first alkyl aluminum used, specifically if the (C) / (B) ratio is greater than 1.0, syndiotactic 1,2-polymerization and cis-1,4-polymerization do not occur simultaneously, and therefore block polybutadiene cannot be obtained. Setting (C) / (B) to 0.5 or less is preferred because it is easy to make the cis-1,4-polybutadiene structure in the block polybutadiene and polybutadiene composition obtained by the production method of this embodiment equal to or greater than a certain amount, and it is easy to obtain low heat buildup and tensile stress in rubber compositions using these.

[0036] Furthermore, in (1), if (A) / {(B)+(C)} is less than 0.2, the proportion of cis-1,4-polybutadiene structures in the block polybutadiene and polybutadiene composition obtained by the production method of this embodiment will be reduced, and the above-mentioned effects will not be obtained and processability will be impaired. From this viewpoint, (A) / {(B)+(C)} is more preferably 0.5 or more. On the other hand, if the (A) / {(B) + (C)} ratio in the block polybutadiene and polybutadiene composition obtained by the production method of this embodiment is greater than 3.0, syndiotactic 1,2-polymerization is difficult to occur, the proportion of syndiotactic 1,2-polybutadiene structures in the syndiotactic 1,2-polybutadiene and block polybutadiene is reduced, the above-mentioned effects are not obtained, and the crack resistance of rubber compositions using these is deteriorated. From this viewpoint, the (A) / {(B) + (C)} ratio is more preferably 2 or less.

[0037] In order to enhance the above-mentioned effect, the concentration (A) of the halogen-containing organoaluminum in the polymerization solution used for polymerization in step Y is preferably 0.1 mmol / L or more and 10 mmol / L or less, and more preferably 1 mmol / L or more and 5 mmol / L or less.

[0038] In order to enhance the above-mentioned effect, the concentration (B) of the first alkyl aluminum in the polymerization liquid used for polymerization in step Y is preferably 0.1 mmol / L or more and 10 mmol / L or less, and more preferably 1 mmol / L or more and 5 mmol / L or less.

[0039] In order to enhance the above-mentioned effect, the concentration (C) of the second alkyl aluminum in the polymerization liquid used for polymerization in step Y is preferably 0.01 mmol / L or more and 10 mmol / L or less, and more preferably 0.1 mmol / L or more and 1 mmol / L or less.

[0040] The temperature at which syndiotactic 1,2-polymerization and cis-1,4-polymerization are carried out in step Y is preferably 0°C to 100°C, more preferably 10 to 100°C, and particularly preferably 20 to 100°C. The polymerization time (average residence time) is preferably in the range of 10 minutes to 2 hours.

[0041] The polymerization in step Y is preferably carried out so that the polymer concentration after polymerization is 5 to 26% by mass. The polymerization tank used in step Y may be one tank or two or more tanks connected together. The polymerization is carried out by stirring and mixing the solution in the polymerization tank (polymerization vessel). The polymerization tank used for polymerization may be a polymerization tank equipped with a high-viscosity liquid stirring device, such as the device described in JP-B-40-2645.

[0042] (anti-aging agent) After the polymerization reaction has reached a predetermined polymerization rate, a known antioxidant can be added in accordance with a conventional method. Examples of antioxidants include phenol-based 2,6-di-t-butyl-p-cresol (BHT), phosphorus-based trinonylphenyl phosphite (TNP), and sulfur-based 4,6-bis(octylthiomethyl)-o-cresol and dilauryl-3,3'-thiodipropionate (TPL). These may be used alone or in combination. The antioxidant is added in an amount of 0.001 to 5 parts by weight per 100 parts by weight of the polybutadiene composition.

[0043] The resulting polybutadiene composition is then separated, washed, and subsequently dried according to conventional methods. The polybutadiene composition produced by the production method according to this embodiment comprises a boiling n-hexane-insoluble component and a boiling n-hexane-soluble component. In the polybutadiene composition, the boiling n-hexane-insoluble component corresponds to syndiotactic 1,2-polybutadiene and the block polybutadiene. On the other hand, the boiling n-hexane-soluble component corresponds to cis 1,4-polybutadiene.

[0044] <Polybutadiene and polybutadiene composition> The polybutadiene and polybutadiene composition of this embodiment are obtained by the production method of this embodiment described above. The polybutadiene composition of this embodiment contains cis-1,4-polybutadiene in addition to a block polybutadiene having a cis-1,4-polybutadiene structure and a syndiotactic-1,2-polybutadiene structure. The polybutadiene composition of this embodiment may further contain syndiotactic-1,2-polybutadiene.

[0045] (cis-1,4-polybutadiene) In the polybutadiene composition according to this embodiment, cis-1,4-polybutadiene is the matrix component. The cis-1,4-polybutadiene is produced by exclusively cis-1,4-polymerizing 1,3-butadiene at catalytically active sites of a part of the polymerization catalyst in step Y of the method for producing the polybutadiene composition, which will be described later. The Mooney viscosity (ML 1+4 , 100°C) is preferably 20 to 60, more preferably 25 to 45. Furthermore, the cis-1,4-structure content of the cis-1,4-polybutadiene does not necessarily have to be 100% as long as it falls within the boiling n-hexane soluble content range, but the cis-1,4-structure content is preferably 90% or more, and particularly preferably 95% or more.

[0046] The weight-average molecular weight of the cis-1,4-polybutadiene is preferably 100,000 to 800,000, more preferably 300,000 to 600,000. The ratio of the weight-average molecular weight to the number-average molecular weight (Mw / Mn) is preferably 2.00 to 5.00, more preferably 2.20 to 3.50. These weight-average molecular weights can be measured by analyzing the hexane-soluble components of the polybutadiene composition by gel permeation chromatography (GPC). Examples 1 to 3 described below satisfy the weight-average molecular weight of 300,000 to 600,000 and the ratio of the weight-average molecular weight to the number-average molecular weight (Mw / Mn) of 2.20 to 3.50.

[0047] (Block polybutadiene) The block polybutadiene of this embodiment is obtained by syndiotactic-1,2-polymerizing 1,3-butadiene and subsequently cis-1,4-polymerizing it within the same molecule in step Y of the method for producing a polybutadiene composition described above. The block polybutadiene of the present invention has a cis-1,4-polybutadiene structure (cis-1,4-polybutadiene block) and a syndiotactic-1,2-polybutadiene structure (syndiotactic-1,2-polybutadiene block). The block polybutadiene having a cis-1,4-polybutadiene structure and a syndiotactic-1,2-polybutadiene structure obtained by the present invention is typically a block polybutadiene having a structure in which the cis-1,4-polybutadiene block and the syndiotactic-1,2-polybutadiene block, which are repeating structures with different regioselectivities, are linked by covalent bonding at their chain ends. The presence of block polybutadiene in the polybutadiene composition can be confirmed by the cis-1,4-bond content and vinyl-1,2-bond content obtained by Fourier transform infrared spectroscopy (FT-IR measurement) of the boiling n-hexane-insoluble matter of the polybutadiene composition, the ΔH and melting point values ​​obtained by differential scanning calorimetry (DSC measurement), and NMR measurement.

[0048] (syndiotactic 1,2-polybutadiene) Syndiotactic 1,2-polybutadiene is produced by syndiotactic 1,2-polymerization of 1,3-butadiene exclusively at catalytically active sites of a part of the polymerization catalyst in step Y of the method for producing a polybutadiene composition described below. The presence of syndiotactic 1,2-polybutadiene in the polybutadiene composition in addition to the block polybutadiene can be confirmed by DSC measurement or NMR measurement.

[0049] The melting point of the polybutadiene composition is preferably 150 to 230°C, more preferably 180 to 220°C, and even more preferably 190 to 210°C. When the melting point is within this range, the tensile stress tends to be improved. The melting point can be measured by the method described in the examples below.

[0050] The syndiotactic 1,2-polybutadiene structure is preferably 1 to 50% by mass, more preferably 5 to 20% by mass, and particularly preferably 7 to 15% by mass in the polybutadiene composition. This range is preferable because it allows processability, tensile strength, and crack resistance to be all achieved. In the polybutadiene composition of the present invention, the syndiotactic 1,2-polybutadiene structure includes the structure in the block polybutadiene, and when the polybutadiene composition contains syndiotactic 1,2-polybutadiene, it also includes the structure in the syndiotactic 1,2-polybutadiene. In this specification, the proportion of the syndiotactic 1,2-polybutadiene structure can be determined as the crystalline component content based on the enthalpy of fusion in the polybutadiene composition.

[0051] Furthermore, in order to more easily achieve both tensile stress and low heat buildup when made into a rubber composition, and to more easily achieve both processability and crack resistance, the polybutadiene composition preferably has a boiling n-hexane insoluble content of 0.1 to 50 mass%, more preferably 1 to 45 mass%, and particularly preferably 1 to 20 mass%.

[0052] Furthermore, in order to more easily achieve both tensile strength and low heat buildup when the polybutadiene composition is made into a rubber composition by maintaining a certain level of cis-1,4-bond content in the block polybutadiene, the cis-1,4-bond content in the boiling n-hexane insoluble matter is preferably 10 to 90 mass%, more preferably 50 to 80 mass%. Furthermore, the vinyl-1,2-bond content in the boiling n-hexane insoluble matter is preferably 10 to 90 mass%, even more preferably 20 to 50 mass%. The vinyl-1,2-bond content in the boiling n-hexane insoluble matter can be determined using FT-IR as described in the Examples below. The cis-1,4-bond content in the boiling n-hexane insoluble matter can be determined using FT-IR as described in the Examples below.

[0053] The present inventors have discovered that block polybutadienes and polybutadiene compositions produced by a specific manufacturing method exhibit excellent tensile strength and low heat buildup when incorporated into rubber compositions. However, defining the structure and composition of block polybutadienes and polybutadiene compositions that impart low heat buildup and tensile stress when incorporated into rubber compositions requires the establishment of new evaluation methods and the development of new methods for measuring physical properties, which requires enormous costs and time. Therefore, in order to obtain patents quickly, the applicant decided to define block polybutadienes and polybutadiene compositions containing the same by their manufacturing methods. As described above, at the time of filing this application, there were circumstances that made it impossible or impractical to define the structure and composition of block polybutadienes and polybutadiene compositions.

[0054] <Rubber composition> The rubber composition contains the polybutadiene and the polybutadiene composition. The rubber composition preferably further contains a rubber component other than the polybutadiene composition and a reinforcing material.

[0055] Examples of rubber components other than the polybutadiene composition include high-cis polybutadiene rubber, low-cis polybutadiene rubber, natural rubber (NR), polyisoprene rubber (IR), emulsion-polymerized or solution-polymerized styrene butadiene rubber (SBR), ethylene propylene diene rubber (EPDM), nitrile rubber (NBR), butyl rubber (IIR), and chloroprene rubber (CR).

[0056] Examples of reinforcing materials include inorganic reinforcing agents such as carbon black, silica, activated calcium carbonate, and ultrafine magnesium silicate, and organic reinforcing agents such as syndiotactic-1,2-polybutadiene resin, polyethylene resin, polypropylene resin, high styrene resin, phenolic resin, lignin, modified melamine resin, coumarone-indene resin, and petroleum resin, with 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 being particularly preferred, such as FEF, FF, GPF, SAF, ISAF, SRF, and HAF. Examples of silica include dry-process silicic anhydride and wet-process silicic acid hydrate and synthetic silicates.

[0057] The polybutadiene composition and the reinforcing material can be kneaded using a Banbury mixer, an open roll mixer, a kneader, a twin-screw mixer, or the like.

[0058] Furthermore, compounding agents that are normally used in the rubber industry, such as vulcanizing agents, vulcanization aids, antioxidants, process oils, zinc oxide, and stearic acid, may be mixed into the rubber composition as needed.

[0059] 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 aid, known vulcanization aids such as aldehydes, ammonia, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates, and xanthates are used. As the antiaging agent, amine-ketone, imidazole, amine, phenol, sulfur, and phosphorus-based agents can be used. As the process oil, any of aromatic, naphthenic, and paraffinic types can be used.

[0060] The polybutadiene and polybutadiene composition obtained by the present invention can be used for, for example, tire components such as cap treads in tires, side reinforcing layers of run-flat tires, carcasses, belts, chafers, base treads, beads, stiffeners, inner liners, etc., industrial products such as vibration-isolating rubber, hoses, belts, rubber rolls, rubber coolers, shoe sole rubber, other composites, adhesives, plastic modifiers, etc. In particular, when used as a rubber composition for tires, it can exhibit superior tensile stress and low heat buildup compared to conventional rubber compositions. [Example]

[0061] The present invention will be described in detail below based on examples, but the present invention is not limited thereto. The physical properties of the raw rubber and vulcanizate of the polybutadiene composition produced by the method for producing a polybutadiene composition according to the present invention were measured as follows.

[0062] <Polybutadiene composition> (1) Mass % of block polybutadiene and syndiotactic 1,2-polybutadiene in the polybutadiene composition (content of boiling n-hexane insoluble matter) The residue of the extraction after 2 g of the polybutadiene composition was subjected to Soxhlet extraction with 200 ml of n-hexane for 4 hours was taken as the boiling n-hexane insoluble matter, and the mass % of this residue in the polybutadiene composition was taken as the boiling n-hexane insoluble matter content (the total proportion of block polybutadiene and syndiotactic 1,2-polybutadiene in the polybutadiene composition).

[0063] (2) Proportion of syndiotactic 1,2-polybutadiene structure in the polybutadiene composition (melting enthalpy change (ΔH)) The melting enthalpy change (ΔH) (unit: J / g) of the crystalline component was measured from the peak area of ​​the endothermic curve using a differential scanning calorimeter (DSC) (DSC7000X manufactured by Hitachi High-Tech Science Corporation, heating rate: 10°C, atmospheric gas: nitrogen) for 5 mg of the polybutadiene composition. The syndiotactic 1,2-polybutadiene content was determined by measuring ΔH in the same manner for known mixtures of syndiotactic 1,2-polybutadiene and cis-1,4-polybutadiene (UBEPOL VCR450, manufactured by UBE Elastomers Corp., UBEPOL VCR800, manufactured by UBE Elastomers Corp., UBEPOL VCR412, and UBEPOL VCR617, manufactured by UBE Elastomers Corp.) and creating a calibration curve. Based on this calibration curve, the amount of syndiotactic 1,2-polybutadiene corresponding to the ΔH obtained above was determined. The proportion of syndiotactic 1,2-polybutadiene in the mixtures of various known syndiotactic 1,2-polybutadienes and cis-1,4-polybutadienes used to draw the calibration curve was determined from the boiling n-hexane insoluble content in the mixtures of various known syndiotactic 1,2-polybutadienes and cis-1,4-polybutadienes. (3) Ratio of syndiotactic 1,2-polybutadiene structure in block polybutadiene and syndiotactic 1,2-polybutadiene The ratio obtained by dividing the amount of syndiotactic 1,2-polybutadiene obtained in (2) above by the boiling n-hexane insoluble matter obtained above was defined as the proportion of syndiotactic 1,2-polybutadiene structures in the block polybutadiene and syndiotactic 1,2-polybutadiene.

[0064] (4) Melting point The polybutadiene composition was determined from the peak temperature of the endothermic curve measured with a differential scanning calorimeter (DSC) (DSC7000X, manufactured by Hitachi High-Tech Science Corporation, heating rate 10°C, nitrogen atmosphere gas).

[0065] (5) cis-1,4-bond content and (6) vinyl-1,2-bond content of boiling n-hexane insoluble matter Infrared absorption spectroscopy (JASCO FT / IR6600) was used to measure the peak at 734 cm -1 (cis), 967cm -1 (Trans), 912cm -1 The cis-1,4-bond content (mol%) was calculated from the (vinyl) absorption intensity ratio using the following formula: The absorption intensity ratio is the ratio of absorption peak intensities (peak areas). cis-1,4-bond content (mol%) = 4.73 × 734 cm -1 Intensity of absorption peak / (4.73 × 734 cm -1 Intensity of absorption peak at +967cm -1 Absorption peak intensity + 0.61 × 912 cm -1 (intensity of absorption peak of Vinyl-1,2-bond content (mol%) = 0.61 × 912 cm -1 Intensity of absorption peak / (4.73 × 734 cm -1 Intensity of absorption peak at +967cm -1 Absorption peak intensity + 0.61 × 912 cm -1 (intensity of absorption peak of

[0066] <Rubber composition> 100% tensile stress The 100% tensile stress was measured in accordance with JIS-K6251 and expressed as an index, with Comparative Example 1 in Table 2 being set at 100. The larger the index, the more excellent the properties.

[0067] Low heat generation (tanδ(60℃)) Measurements were made using a viscoelasticity measuring device (Ueshima Seisakusho, VR-7130) at a temperature range of -60°C to 80°C, a frequency of 16 Hz, and a dynamic strain of 0.5%. Tan δ at 60°C was used as an index of fuel economy. Comparative Example 1 in Table 2 was set at 100 and expressed as an index. The fuel economy (tan δ(60°C)) is calculated so that the smaller the numerical value, the better the characteristics, but in Table 2, the index is converted so that the higher the index, the better the characteristics (fuel economy).

[0068] Example 1 A 1.5 L stainless steel autoclave equipped with a helical impeller and purged with nitrogen was charged with 300 mL of cyclohexane, sealed, and then 300 mL of 1,3-butadiene was pumped in to produce 600 mL of raw solution. Water and carbon disulfide were added to the raw solution using a syringe to achieve concentrations of 5.19 mmol / L and 0.36 mmol / L, respectively. The autoclave was then heated to 25°C and stirred for 30 minutes. Diethylaluminum chloride and triethylaluminum were added using a syringe to achieve concentrations of 2.36 mmol / L and 2.53 mmol / L, respectively. The solution was stirred for 5 minutes and then heated to 55°C. Next, cobalt octoate (Co(Oct)2) was added using a syringe to a concentration of 65 μmol / L, and triethylaluminum was added using a syringe to a concentration of 0.22 mmol / L, and the mixture was allowed to react at 60°C for 20 minutes. Thereafter, the autoclave was cooled and depressurized, and the polybutadiene composition was removed from the stainless steel autoclave and dried at 100°C for 2 hours. The composition of the polybutadiene composition obtained in Example 1 and the composition of the n-hexane insoluble matter are shown in Table 1. The value of (A) / {(B)+(C)} in Example 1 was 0.86. The value of (C) / (B) in Example 1 was 0.087.

[0069] Example 2 A 1.5 L stainless steel autoclave equipped with a helical impeller and purged with nitrogen was charged with 300 mL of cyclohexane and sealed. 300 mL of 1,3-butadiene was then pumped in to produce 600 mL of raw solution. Water and carbon disulfide were added to the raw solution using a syringe to achieve concentrations of 5.19 mmol / L and 0.36 mmol / L, respectively. The autoclave was then heated to 25°C and stirred for 30 minutes. Diethylaluminum chloride and triethylaluminum were added using a syringe to achieve concentrations of 2.36 mmol / L and 2.20 mmol / L, respectively. The solution was stirred for 5 minutes and then heated to 55°C. Next, cobalt octoate (Co(Oct)2) was added using a syringe to a concentration of 65 μmol / L, and triethylaluminum was added using a syringe to a concentration of 0.55 mmol / L, and the mixture was allowed to react at 60°C for 20 minutes. Thereafter, the autoclave was cooled and depressurized, and the polybutadiene composition was removed from the stainless steel autoclave and dried at 100°C for 2 hours. The composition of the polybutadiene composition and the composition of the n-hexane insoluble matter of Example 2 are shown in Table 1. The value of (A) / {(B)+(C)} in Example 2 was 0.81. The value of (C) / (B) in Example 2 was 0.233.

[0070] Example 3 A 1.5 L stainless steel autoclave equipped with a helical impeller and purged with nitrogen was charged with 300 mL of cyclohexane and sealed. 300 mL of 1,3-butadiene was then pumped in to produce 600 mL of raw solution. Water and carbon disulfide were added to the raw solution using a syringe to achieve concentrations of 5.19 mmol / L and 0.36 mmol / L, respectively. The autoclave was then heated to 25°C and stirred for 30 minutes. Diethylaluminum chloride and triethylaluminum were added using a syringe to achieve concentrations of 2.36 mmol / L and 1.93 mmol / L, respectively. The solution was stirred for 5 minutes and then heated to 55°C. Next, cobalt octoate (Co(Oct)2) was added using a syringe to a concentration of 65 μmol / L, and triethylaluminum was added using a syringe to a concentration of 0.84 mmol / L, and the mixture was allowed to react at 60°C for 20 minutes. Thereafter, the autoclave was cooled and depressurized, and the polybutadiene composition was removed from the stainless steel autoclave and dried at 100°C for 2 hours. The composition of the polybutadiene composition and the composition of the n-hexane insoluble matter of Example 3 are shown in Table 1. The value of (A) / {(B)+(C)} in Example 3 was 0.85. The value of (C) / (B) in Example 3 was 0.435.

[0071] [Table 1]

[0072] In Examples 1 to 3, the cis-1,4-bond content and vinyl-1,2-bond content values ​​obtained by FT-IR measurement of the boiling n-hexane-insoluble matter, and the melting point values ​​obtained by DSC measurement, confirmed that the boiling n-hexane-insoluble matter in the polybutadiene contained block polybutadiene having a cis-1,4-polybutadiene structure (cis-1,4-polybutadiene block) and a regular syndiotactic-1,2-polybutadiene structure (cis-1,4-polybutadiene block). In the table above, BR-1 is a high-cis-butadiene rubber whose main component is cis-1,4-polybutadiene. BR-2 is a commercially available vinyl-cis-polybutadiene, VCR412 (manufactured by UBE Elastomers Co., Ltd.).

[0073] Examples 4 to 6 The polybutadiene compositions obtained in Examples 1 to 3, BR-1, and BR-2 were subjected to primary blending in a plastomill, where carbon black, natural rubber, zinc oxide, process oil, stearic acid, and an antioxidant were added and kneaded according to Table 2 below, and then secondary blending was performed using a roll to add a vulcanization accelerator and sulfur, to prepare rubber compositions. In Table 2, the components were blended so that the proportions of syndiotactic 1,2-polybutadiene structures in the compositions of Examples 4 to 6 and Comparative Examples 1 and 2 were the same. The compound was then molded and press-vulcanized at 150°C to obtain a vulcanizate, after which stress and low heat buildup were measured. The results of measuring the physical properties of the vulcanizate are shown in Table 2.

[0074] [Table 2]

[0075] In Table 2, natural rubber is RSS#2 (ML 1+4 , adjusted to 100°C = 70°C). VivaTec 500 manufactured by H&R was used as the process oil. Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. was used as the antioxidant. Sancerer NS manufactured by Sanshin Chemical Industry Co., Ltd. was used as the vulcanization accelerator.

[0076] As shown in Table 2, Examples 4 to 6 had improved tensile strength and low heat buildup compared to Comparative Example 1, which was obtained by the present production method and did not contain a polybutadiene rubber component. On the other hand, it is clear that when a polybutadiene composition not containing a syndiotactic-1,2-polybutadiene structure is used as in Comparative Example 2, no tensile stress can be obtained.

Claims

1. A method for producing polybutadiene, which produces a block polybutadiene having a cis-1,4-polybutadiene structure and a syndiotactic-1,2-polybutadiene structure, comprising the steps of: Step X: aging the halogen-containing organoaluminum and the first alkylaluminum in the presence of water; and a step Y of mixing 1,3-butadiene with a polymerization catalyst and a second alkylaluminum in the presence of the aged liquid obtained in the step X, and polymerizing the resulting mixture, In step Y or before step Y, 1,3-butadiene is mixed with carbon disulfide; A method for producing polybutadiene, wherein the molar concentration (A) of the halogen-containing organoaluminum in the step X, the molar concentration (B) of the first alkylaluminum, and the molar concentration (C) of the second alkylaluminum in the step Y satisfy the following formulas (1) and (2): 0.2≦(A) / {(B)+(C)}≦3.0...(1) and, 0.01≦(C) / (B)≦1.0 (2).

2. 2. The method for producing polybutadiene according to claim 1, wherein the polymerization catalyst is a soluble cobalt compound.

3. The method for producing polybutadiene according to claim 1, wherein a polybutadiene composition containing 1 to 50% by mass of a syndiotactic 1,2-polybutadiene structure is produced.

4. 3. The method for producing polybutadiene according to claim 1, wherein a polybutadiene composition containing cis-1,4-polybutadiene in addition to the block polybutadiene is produced.

5. 3. A block polybutadiene obtained by the method according to claim 1 or 2.

6. A polybutadiene composition obtained by the production method according to claim 1 or 2.

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