Method for producing polybutadiene composition

Abstract

Provided are a polybutadiene composition, a method for producing a rubber material with excellent crack growth resistance, and a crosslinked product. The polybutadiene composition is produced by a method comprising step Y of polymerizing 1,3-butadiene in the presence of 1,2-polybutadiene and a lanthanide-based catalyst. A polybutadiene composition comprises 1,2-polybutadiene and 1,4-polybutadiene, and can be obtained by polymerizing 1,3-butadiene in the presence of 1,2-polybutadiene and a lanthanide-based catalyst.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application incorporates the contents of Japanese Patent Application No. 2018-233795, filed on December 13, 2018. Technical Field

[0003] This disclosure relates to a polybutadiene composition, a method for manufacturing the same, and a crosslinked composite. More specifically, it relates to a polybutadiene composition containing 1,4-polybutadiene and 1,2-polybutadiene, and a method for manufacturing the same. Background Technology

[0004] Polybutadiene compositions containing 1,4-polybutadiene are manufactured by a method of cis-1,4-polymerization of 1,3-butadiene in the presence of a catalyst in an inert solvent such as a hydrocarbon (see, for example, Patent Document 1 and Patent Document 2). Patent Document 1 and Patent Document 2 disclose obtaining vinyl-cis-polybutadiene rubber by cis-1,4-polymerization of 1,3-butadiene in the presence of a cobalt-based or nickel-based catalyst, followed by 1,2-polymerization of 1,3-butadiene.

[0005] Prior art literature

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2008-163144

[0008] Patent Document 2: Japanese Patent Application Publication No. 2017-132954 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] Due to recent environmental concerns and increased awareness of resource conservation and energy saving, there is a demand for rubber materials with superior resistance to crack growth. Among polybutadiene rubbers, materials with even better resistance to crack growth than before are also ideal.

[0011] This disclosure is made in view of the aforementioned issues, and one of the objectives is to provide a polybutadiene composition and a method for manufacturing the same, which yields a rubber material with excellent resistance to crack growth.

[0012] Technical means to solve the problem

[0013] To address the aforementioned issues, according to this disclosure, the following polybutadiene compositions, methods for their manufacture, and crosslinking agents are provided.

[0014] [1] A method for manufacturing a polybutadiene composition, comprising step Y of polymerizing 1,3-butadiene in the presence of 1,2-polybutadiene and a lanthanide catalyst.

[0015] [2] A polybutadiene composition containing 1,2-polybutadiene and 1,4-polybutadiene, which can be obtained by polymerizing 1,3-butadiene in the presence of the 1,2-polybutadiene and a lanthanide catalyst.

[0016] [3] A crosslinked body is formed by crosslinking a rubber composition, said rubber composition containing a polybutadiene composition obtained by the manufacturing method according to [1] or a polybutadiene composition according to [2].

[0017] The effects of the invention

[0018] According to the polybutadiene composition and manufacturing method disclosed herein, polybutadiene rubber with excellent resistance to crack growth can be obtained. Detailed Implementation

[0019] The following provides a detailed description of matters relating to the manner of this disclosure. Furthermore, in this specification, the numerical range recorded using “~” means that the values ​​recorded before and after the “~” are included as lower and upper limits.

[0020] The polybutadiene composition disclosed herein is manufactured by a method comprising a step (hereinafter referred to as "step Y") of polymerizing 1,3-butadiene in the presence of 1,2-polybutadiene and a lanthanide catalyst. According to this method, a polybutadiene composition containing 1,4-polybutadiene and 1,2-polybutadiene can be obtained. The polybutadiene composition is preferably manufactured by a method comprising step X, together with step Y, further comprising step X to obtain 1,2-polybutadiene. Alternatively, this manufacturing method may further include step Z, which modifies the 1,4-polybutadiene, if necessary. Hereinafter, steps X, Y, and Z will be described in detail sequentially.

[0021] <Step X(1,2 aggregation steps)>

[0022] Step X is the step of producing 1,2-polybutadiene by polymerizing 1,3-butadiene in the presence of a cobalt-based catalyst. Step X includes: preparing a mixture of 1,3-butadiene and an organic solvent; polymerizing 1,3-butadiene in the presence of a cobalt-based catalyst (more specifically, 1,2-polymerization); and stopping the polymerization reaction. Furthermore, the 1,2-polybutadiene obtained by the polymerization reaction in step X will hereinafter also be referred to as "1,2-polybutadiene (A)". Furthermore, in this specification, "1,2-polymerization" refers to a polymerization in which the proportion of monomer units with a 1,2 bond configuration of 1,3-butadiene exceeds 50% by mass in the polybutadiene produced by the polymerization of 1,3-butadiene. "1,2-polybutadiene" refers to polybutadiene in which the proportion of monomer units with a 1,2 bond configuration of 1,3-butadiene exceeds 50% by mass.

[0023] (Preparation steps)

[0024] The organic solvent used in this step is a solvent whose main component is hydrocarbon or halogenated hydrocarbon. Specific examples of hydrocarbons include: saturated aliphatic hydrocarbons with 4 to 10 carbon atoms such as butane, pentane, hexane, and heptane; saturated alicyclic hydrocarbons with 6 to 20 carbon atoms such as cyclopentane and cyclohexane; monoolefins such as 1-butene and 2-butene; and aromatic hydrocarbons such as benzene, toluene, and xylene. Specific examples of halogenated hydrocarbons include: methylene chloride, chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene, 1,2-dichloroethane, chlorobenzene, bromobenzene, and chlorotoluene. Among these, hydrocarbons are preferably used as the organic solvent. Furthermore, the phrase "mainly composed of hydrocarbons or halogenated hydrocarbons" refers to the total amount of organic solvent used in this step, where hydrocarbons or halogenated hydrocarbons exceed 50% by mass, preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, particularly preferably 95% by mass or more.

[0025] In the mixture of 1,3-butadiene and the organic solvent, the amount of 1,3-butadiene is preferably 3% by mass or more, more preferably 5% by mass or more, relative to the total amount of 1,3-butadiene and the organic solvent. Furthermore, the amount of 1,3-butadiene is preferably 80% by mass or less, more preferably 50% by mass or less, and even more preferably 15% by mass or less, relative to the total amount of 1,3-butadiene and the organic solvent. The temperature for preparing the mixture of 1,3-butadiene and the organic solvent is preferably 10°C to 50°C, more preferably 30°C to 40°C.

[0026] (Aggregation Step)

[0027] In this step, a mixture of 1,3-butadiene obtained through the preparation steps and an organic solvent is used to perform 1,2-polymerization of 1,3-butadiene in an organic solvent mainly composed of hydrocarbons or halogenated hydrocarbons in the presence of a cobalt-based catalyst. This produces 1,2-syndiotactic polybutadiene.

[0028] The cobalt-based catalyst used contains a cobalt compound. The cobalt compound is preferably a cobalt salt, specifically including: cobalt halide salts such as cobalt chloride, cobalt bromide, and cobalt iodide; and organic acid cobalt salts such as cobalt octoate, cobalt tertiary carbonate, and cobalt naphthenate. Among these, organic acid cobalt salts are preferred as the cobalt compound in that they do not contain halogen atoms.

[0029] The proportion of cobalt compound used is preferably set to a molar ratio of 1,3-butadiene to cobalt atoms in the cobalt compound (1,3-butadiene / Co) of 15,000 or more. Setting the 1,3-butadiene / Co molar ratio to 5,000 or more helps to prevent the molecular weight of 1,2-polybutadiene (A) from becoming too low, which is preferable in this respect. Furthermore, the proportion of cobalt compound used is preferably set to a molar ratio of 1,3-butadiene / Co of 150,000 or less. Setting the 1,3-butadiene / Co molar ratio to 150,000 or less helps to suppress the reduction of polymerization activity, which is preferable in this respect. A molar ratio of 1,3-butadiene / Co is more preferably 10,000 or more. Furthermore, a molar ratio of 1,3-butadiene / Co is more preferably 100,000 or less.

[0030] The cobalt-based catalyst used in step X preferably contains a phosphine compound and an organoaluminum compound along with the cobalt compound. The phosphine compound is preferably a phosphine compound having a branched aliphatic hydrocarbon group with 3 or more carbon atoms, or an alicyclic hydrocarbon group with 5 or more carbon atoms, and two aromatic hydrocarbon groups. The branched aliphatic hydrocarbon group with 3 or more carbon atoms is preferably a branched alkyl group with 3 to 10 carbon atoms. The alicyclic hydrocarbon group with 5 or more carbon atoms is preferably a substituted or unsubstituted cycloalkyl group with 5 to 10 carbon atoms. The aromatic hydrocarbon group is preferably phenyl.

[0031] Preferred examples of phosphine compounds include: diphenylcyclohexylphosphine, diphenylisopropylphosphine, diphenylisobutylphosphine, diphenyltert-butylphosphine, diphenylcyclopentylphosphine, diphenyl(4-methylcyclohexyl)phosphine, diphenylcycloheptylphosphine, and diphenylcyclooctylphosphine. Furthermore, one or more phosphine compounds can be used alone or in combination. The preferred proportion of the phosphine compound relative to 1 mole of the cobalt compound is 1 to 5 moles, more preferably 1.5 to 4 moles.

[0032] Examples of organoaluminum compounds include aluminoxanes (such as methylaluminoxane) and compounds formed by contacting trialkylaluminum with water (hereinafter referred to as "aluminum hydride compounds"). Aluminoxanes can be pre-synthesized or synthesized in a polymerization system. Regarding aluminum hydride compounds, the contact method between trialkylaluminum and water can involve contacting water in any of its states—vapor, liquid, or solid (ice)—with an inert organic solvent solution of trialkylaluminum. Alternatively, contact can be made in a dissolved, dispersed, or emulsified state in an inert organic solvent, or in a gaseous or mist state present in an inert gas.

[0033] In cobalt-based catalysts, the proportion of organoaluminum compounds used is preferably set to a molar ratio of 1,3-butadiene to aluminum atoms in the organoaluminum compound (1,3-butadiene / Al) of 500 or more. If the 1,3-butadiene / Al molar ratio is 500 or more, the reaction proceeds readily and sufficiently. Furthermore, the proportion of organoaluminum compounds used is preferably set to a 1,3-butadiene / Al molar ratio of 4,000 or less. If the 1,3-butadiene / Al molar ratio is 4,000 or less, there is a tendency to improve polymerization activity, which is preferable in this respect. More preferably, the 1,3-butadiene / Al ratio is 800 or less. Furthermore, more preferably, the 1,3-butadiene / Al ratio is 2,000 or less.

[0034] The reaction temperature in 1,2-polymerization is typically -20°C to 80°C, preferably 10°C to 60°C. The reaction time is preferably 5 minutes to 6 hours, more preferably 10 minutes to 3 hours. The polymerization reaction can be batch or continuous. The concentration of 1,3-butadiene in the reaction solution is typically 5% to 80% by mass, preferably 8% to 25% by mass. Furthermore, to prevent deactivation of the catalyst and polymer, measures can be taken to suppress the introduction of deactivating compounds such as oxygen, water, or carbon dioxide into the polymerization system.

[0035] (Stop step)

[0036] In step X, preferably, an organoaluminum compound is added to the polymerization system after the syndiotactic-1,2 polymerization reaction has reached the desired reaction conversion rate, thereby stopping the 1,2 polymerization reaction.

[0037] Organoaluminum compounds used as the stop of 1,2 polymerization reactions include, for example, trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-tert-butylaluminum, tripentylaluminum, trihexylaluminum, tricyclohexylaluminum, trioctylaluminum, and other alkylaluminum compounds.

[0038] Aluminum hydride compounds such as diethylaluminum hydride, di-n-propylaluminum hydride, di-n-butylaluminum hydride, diisobutylaluminum hydride, dihexylaluminum hydride, diisohexylaluminum hydride, dioctylaluminum hydride, and diisooctylaluminum hydride. Among these, the organoaluminum compound used to stop the 1,2 polymerization reaction is preferably at least one selected from the group consisting of diisobutylaluminum hydride, triethylaluminum, triisobutylaluminum, and diethylaluminum hydride. Furthermore, two or more organoaluminum compounds can be used alone or in combination.

[0039] When the 1,2 polymerization reaction is stopped, the proportion of the organoaluminum compound used is preferably 1 mole or more, more preferably 5 moles or more, relative to 1 mole of the cobalt compound used in the 1,2 polymerization reaction. Furthermore, the proportion of the organoaluminum compound used is preferably 20 moles or less, more preferably 15 moles or less, relative to 1 mole of the cobalt compound used in the 1,2 polymerization reaction. By setting the proportion of the organoaluminum compound within the aforementioned range, it is preferable that the molecular weight of 1,2-polybutadiene (A) does not become too high, or that the molecular weight of 1,4-polybutadiene, as the matrix component, does not become too low. The temperature at which the polymerization reaction is stopped is typically -20°C to 80°C, preferably 10°C to 60°C. In the 1,2 polymerization reaction, the reaction conversion rate is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more.

[0040] According to step X, 1,2-syndiotactic polybutadiene can be manufactured as 1,2-polybutadiene (A). The melting point of the resulting 1,2-polybutadiene (A) is preferably 60°C or higher, more preferably 100°C or higher, and even more preferably 130°C or higher. Furthermore, the melting point of 1,2-polybutadiene (A) is preferably 150°C or lower, more preferably 145°C or lower, and even more preferably 140°C or lower. By setting the melting point of 1,2-polybutadiene (A) to 60°C or higher, low fuel efficiency and anti-skid properties can be sufficiently ensured, which is preferred in this respect. Furthermore, by setting the melting point of 1,2-polybutadiene (A) to 150°C or lower, the processability of the rubber composition can be sufficiently ensured, which is preferred in this respect.

[0041] The weight-average molecular weight (Mw) of 1,2-polybutadiene (A) converted from polystyrene by gel permeation chromatography (GPC) is preferably 50,000 or more, more preferably 70,000 or more, and particularly preferably 100,000 or more. Furthermore, the weight-average molecular weight (Mw) of 1,2-polybutadiene (A) is preferably 500,000 or less, more preferably 400,000 or less, and particularly preferably 300,000 or less. If the weight-average molecular weight of 1,2-polybutadiene (A) is less than 50,000, the abrasion resistance of the crosslinked compound tends to decrease easily; if it exceeds 400,000, the processability of the rubber composition tends to decrease easily.

[0042] The content of 1,2-vinyl bonds in 1,2-polybutadiene (A) is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, particularly preferably 95% or more. In particular, if the content of 1,2-vinyl bonds is 90% or more, the low fuel efficiency performance of the crosslinked body obtained using the polybutadiene composition is better, and this is preferred in this respect. Furthermore, the 1,2-vinyl bond content is a value determined using an infrared spectrophotometer.

[0043] <Step Y (cis-1,4 polymerization step)>

[0044] In step Y, 1,4-polybutadiene is produced as the matrix component of the polybutadiene composition by polymerizing 1,2-polybutadiene in the presence of a lanthanide catalyst (cis-1,4 polymerization). In this step, the 1,2-polybutadiene (A) produced in step X is preferably used as the 1,2-polybutadiene. To simplify the manufacturing process, it is preferable to polymerize 1,3-butadiene by adding a lanthanide catalyst to the reaction mixture obtained in step X. Furthermore, in step Y, isoprene can be polymerized in addition to 1,3-butadiene by adding isoprene during cis-1,4 polymerization. Moreover, in this specification, "cis-1,4 polymerization" refers to a polymerization in which the proportion of monomer units with cis-1,4 bond patterns in the polybutadiene produced by the polymerization of 1,3-butadiene exceeds 50% by mass. The term "1,4-polybutadiene" refers to polybutadiene in which the proportion of monomer units with a 1,4 bond pattern (including cis-1,4 bonds and trans-1,4 bonds) exceeds 50% by mass.

[0045] The lanthanide catalyst used in step Y contains a lanthanide compound. A lanthanide compound is a compound containing at least one element belonging to the lanthanides. Alternatively, the lanthanide compound may be a product of the reaction between a lanthanide compound and a Lewis base. The lanthanide element in the lanthanide compound is preferably at least one selected from the group consisting of neodymium, praseodymium, cerium, lanthanum, gadolinium, and samarium, with neodymium being particularly preferred. Specific examples of lanthanide compounds include: lanthanide carboxylates, alkoxides, β-diketone complexes, phosphates, or phosphites.

[0046] Specific examples of lanthanide carboxylates can be listed as formula (1); "(R 1 The compound represented by "-CO2)3M" (where M is a lanthanide element, R...) 1 (A monovalent hydrocarbon group having 1 to 20 carbon atoms). In formula (1), R 1 Preferably, it is a saturated or unsaturated monovalent chain hydrocarbon group, and more preferably a straight-chain or branched alkyl or cycloalkyl group. The carbonyl group in formula (1) and R... 1 It possesses primary, secondary, or tertiary carbon atom bonds. M is preferably neodymium, praseodymium, cerium, lanthanum, gadolinium, or samarium, and more preferably neodymium.

[0047] Specific examples of compounds represented by formula (1) include: salts of octanoic acid, 2-ethylhexanoic acid, oleic acid, stearic acid, benzoic acid, naphthenic acid, and tertiary carbonic acid (manufactured by Shell Chemicals, a carboxylic acid in which the carboxyl group is bonded to a tertiary carbon atom). Among these, the compound represented by formula (1) is preferably a salt of tertiary carbonic acid, 2-ethylhexanoic acid, or naphthenic acid.

[0048] As a specific example of lanthanide alkoxides, equation (2) can be listed; (R 2 The compound represented by O)3M (where M is a lanthanide element, R) 2 (A monovalent hydrocarbon group having 1 to 20 carbon atoms). In formula (2), as R 2 Examples include: monovalent chain hydrocarbon groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groups, etc. R 2 Preferably, it is a monovalent aromatic hydrocarbon group. As the group "R" in formula (2) 2 Specific examples of "O-" include: 2-ethylhexylalkoxy, oleylalkoxy, stearylalkoxy, phenoxy, benzylalkoxy, etc. Among these, the "R" group... 2 "O-" is preferably 2-ethyl-hexylalkoxy or benzylalkoxy. The description of M and preferred examples can be applied to the description of formula (1).

[0049] Specific examples of β-diketone complexes of lanthanides include: acetylacetone complexes, benzoylacetone complexes, propionitrile-acetone complexes, valerate-acetone complexes, ethylacetylacetone complexes, etc. Among these, acetylacetone complexes or ethylacetylacetone complexes are preferred.

[0050] Specific examples of phosphates or phosphites of lanthanides include salts of bis(2-ethylhexyl) phosphate, bis(1-methylheptyl) phosphate, bis(p-nonylphenyl) phosphate, bis(polyethylene glycol-p-nonylphenyl) phosphate, (1-methylheptyl)(2-ethylhexyl) phosphate, (2-ethylhexyl)(p-nonylphenyl) phosphate, 2-ethylhexylphosphonic acid mono-2-ethylhexyl, 2-ethylhexylphosphonic acid mono-p-nonylphenyl, bis(2-ethylhexyl)phosphinic acid, bis(1-methylheptyl)phosphinic acid, bis(p-nonylphenyl)phosphinic acid, (1-methylheptyl)(2-ethylhexyl)phosphinic acid, (2-ethylhexyl)(p-nonylphenyl)phosphinic acid, etc. Among these, salts of bis(2-ethylhexyl) phosphate, bis(1-methylheptyl) phosphate, 2-ethylhexylphosphonic acid mono-2-ethylhexyl, or bis(2-ethylhexyl)phosphinic acid are preferred as phosphates or phosphites.

[0051] As for the lanthanide compounds used in step Y, these are preferably carboxylates or phosphates, more preferably carboxylates. Among these, neodymium phosphates or neodymium carboxylates are more preferred, and carboxylates such as neodymium tertiary carbonates or neodymium 2-ethylhexanoate are particularly preferred.

[0052] To ensure the lanthanide compound is soluble in a solvent or for long-term stable storage, it is preferable to mix the lanthanide compound with a Lewis base or to react the lanthanide compound with a Lewis base to generate a reaction product. The amount of Lewis base used is preferably 0 to 30 moles, more preferably 1 to 10 moles, relative to 1 mole of the lanthanide element in the lanthanide compound. Specific examples of Lewis bases include: acetylacetone, tetrahydrofuran, pyridine, N,N-dimethylformamide, thiophene, diphenyl ether, triethylamine, organophosphorus compounds, monohydric or dihydric alcohols, etc. Furthermore, in step Y, one or more lanthanide compounds may be used alone or in combination.

[0053] The proportion of lanthanide compounds used in step Y is preferably 0.00001 mmol to 1.0 mmol, more preferably 0.0001 mmol to 0.5 mmol, relative to 100 g of 1,3-butadiene used in step Y. Setting the proportion of lanthanide compounds to 0.00001 mmol or more significantly improves polymerization activity, which is preferable in this respect. Furthermore, setting the proportion of lanthanide compounds to 1.0 mmol or less prevents the catalyst concentration from becoming too high, eliminating the need for a deashing step, which is also preferable in this respect.

[0054] The lanthanide catalyst used in step Y is preferably a combination of lanthanide compounds and organoaluminum compounds and halogen compounds.

[0055] As an organoaluminum compound, at least one selected from the group consisting of aluminum oxanes, alkyl aluminum compounds, and aluminum hydride compounds is preferred. Among these, it is particularly preferred to use at least one compound selected from the group consisting of alkyl aluminum compounds and aluminum hydride compounds (hereinafter referred to as "aluminum compound (L)") in combination with an aluminum oxane.

[0056] As preferred specific examples of the aluminum oxanes used in this step, compounds represented by formula (3) and formula (4) below can be listed. Alternatively, associative aluminum oxanes described in Fine Chemicals, 23, (9) 5 (1994), Journal of the American Chemical Society, 115, 4971 (1993), and Journal of the American Chemical Society, 117, 6465 (1995) can also be used.

[0057] [Chemistry 1]

[0058]

[0059] (In equations (3) and (4), R) 3 and R 4 Each R is an independent monovalent hydrocarbon group having 1 to 20 carbon atoms, and k and m are independent integers greater than 2. The multiple Rs in equation (3) 3 They can be the same or different. When m is 2 or more, the multiple R's in equation (4) can be... 4 They can be the same or different.

[0060] R in equation (3) 3 and R in equation (4) 4Examples of such compounds include: methyl, ethyl, propyl, butyl, isobutyl, tert-butyl, hexyl, isohexyl, octyl, isooctyl, etc. Among these, methyl, ethyl, isobutyl, or tert-butyl are preferred, with methyl being particularly preferred. k and m are preferably integers from 4 to 100.

[0061] Specific examples of aluminum oxanes include: methylaluminoxane (hereinafter also referred to as "MAO"), ethylaluminoxane, n-propylaluminoxane, n-butylaluminoxane, isobutylaluminoxane, tert-butylaluminoxane, hexylaluminoxane, isohexylaluminoxane, etc. Among these, MAO is preferred. Furthermore, one type of aluminum oxane can be used alone, or two or more types can be used in combination.

[0062] The preferred proportion of aluminum oxane used in the lanthanide catalyst is 1 to 500 moles of aluminum (Al) relative to 1 mole of the lanthanide compound used in the 1,4 polymerization reaction, more preferably 3 to 250 moles, and even more preferably 5 to 200 moles. By setting the proportion of aluminum oxane within the aforementioned range, it is unnecessary to include steps for inhibiting the decrease in catalyst activity and removing catalyst residues, which is preferable in this respect.

[0063] Specific examples of aluminum compounds (L) include alkylaluminum compounds and aluminum hydride compounds illustrated in the description of the stopping step. Furthermore, aluminum compounds (L) can be used alone or in combination of two or more. Among these, the aluminum compound (L) is preferably at least one selected from the group consisting of diisobutylaluminum hydride, triethylaluminum, triisobutylaluminum, and diethylaluminum hydride. When preparing a lanthanide catalyst, the preferred ratio of aluminum compound (L) is 1 to 700 moles, more preferably 3 to 500 moles, relative to 1 mole of the lanthanide compound used in the 1,4 polymerization reaction.

[0064] The halogen compound used as a component of a lanthanide catalyst is preferably a chlorinated compound, more preferably at least one selected from the group consisting of silicon chloride compounds and chlorinated hydrocarbon compounds. Examples of silicon chloride compounds used include trimethylsilyl chloride, triethylsilyl chloride, and dimethylsilyl dichloride. Among these, trimethylsilyl chloride is preferably used as the silicon chloride compound. Specific examples of chlorinated hydrocarbon compounds include methyl chloride, butyl chloride, hexyl chloride, octyl chloride, chloroform, dichloromethane, and benzyl chloride. Among these, methyl chloride, chloroform, or dichloromethane is preferred.

[0065] When preparing lanthanide catalysts, the preferred proportion of the halogen compound used is a molar ratio (halogen atom / lanthanide compound) of 0.5 to 3 halogen atoms relative to 1 mole of the lanthanide compound, more preferably 1.0 to 2.5, and even more preferably 1.2 to 1.8. A molar ratio of halogen atoms / lanthanide compound of 0.5 or higher is preferred as it sufficiently enhances the activity of the polymerization catalyst. Furthermore, a molar ratio of 3 or lower avoids the halogen compound from becoming a catalyst poison, which is also preferred in this respect.

[0066] In step Y, the reaction temperature for 1,4-polymerization is preferably set to -30°C to 200°C, more preferably to 0°C to 150°C. The form of the polymerization reaction is not particularly limited; it can be carried out using a batch reactor or a multi-stage continuous reactor, etc., in a continuous manner. When using a polymerization solvent for the 1,4-polymerization of 1,3-butadiene, the monomer concentration in the solvent is preferably set to 5% to 50% by mass, more preferably 7% to 35% by mass. Furthermore, from the viewpoint of producing 1,4-polybutadiene and preventing the deactivation of 1,4-polybutadiene with active ends, it is preferable to implement measures to prevent the introduction of compounds with deactivating effects, such as oxygen, water, or carbon dioxide, into the polymerization system.

[0067] 1,4-Polybutadiene with active ends (hereinafter also referred to as "1,4-polybutadiene (B)") can be obtained through the 1,4 polymerization reaction. The weight-average molecular weight (Mw) of the obtained 1,4-polybutadiene (B), converted from polystyrene obtained by GPC, is preferably 50,000 or more, more preferably 100,000 or more, and particularly preferably 150,000 or more. Furthermore, the weight-average molecular weight (Mw) of 1,4-polybutadiene (B) is preferably 2,000,000 or less, more preferably 1,500,000 or less, and particularly preferably 1,000,000 or less. If the weight-average molecular weight of 1,4-polybutadiene (B) is less than 50,000, the abrasion resistance of the crosslinked compound tends to decrease easily; if it exceeds 2,000,000, the processability of the rubber composition tends to decrease easily.

[0068] Regarding 1,4-polybutadiene (B), from the viewpoint of ease of manufacture, the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) is preferably 1.1 or more, more preferably 2.0 or more, and even more preferably 2.1 or more. Furthermore, the Mw / Mn ratio of 1,4-polybutadiene (B) is preferably 4.0 or less, more preferably 3.5 or less. If the Mw / Mn ratio of 1,4-polybutadiene (B) is 4.0 or less, the resulting crosslinked body exhibits better destructive properties and lower heat generation characteristics, which is preferable in this respect.

[0069] The content of the cis-1,4 structure in 1,4-polybutadiene (B) is preferably 70% or more, more preferably 80% or more, and even more preferably 89% or more, particularly preferably 93% or more. In particular, if the content of the cis-1,4 structure is 89% or more, the crosslinked body obtained using the polybutadiene composition exhibits better crack growth resistance and abrasion resistance, which is preferred. According to step Y, as the polybutadiene composition, a mixture of 1,4-polybutadiene (B) and 1,2-syndiotactic polybutadiene as the matrix component can be obtained.

[0070] In the polybutadiene composition obtained in step Y, the content of 1,2-polybutadiene (A) relative to the total amount of the polybutadiene composition is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more. Furthermore, the content of 1,2-polybutadiene (A) relative to the total amount of the polybutadiene composition is preferably 30% by mass or less, more preferably 23% by mass or less, and even more preferably 15% by mass or less. In the polybutadiene composition, a content of 5% by mass or more of 1,2-polybutadiene (A) sufficiently improves the processability of the rubber composition, which is preferable in this respect. Furthermore, a content of 30% by mass or less of 1,2-polybutadiene (A) sufficiently improves the abrasion resistance of the crosslinked body obtained using the rubber composition, which is preferable in this respect.

[0071] <Step Z (Modification Step)>

[0072] In step Y, an anti-aging agent (e.g., 2,4-di-tert-butyl-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, etc.) can be added to the polymerization system immediately after the cis-1,4 polymerization reaction reaches the desired conversion rate, according to conventional methods. Alternatively, the polymerization ends of 1,4-polybutadiene (B) can be modified using an alkoxysilane compound before adding the anti-aging agent. Through this modification reaction, the active ends of 1,4-polybutadiene (B) react with the alkoxysilane compound to obtain 1,4-polybutadiene with silicon-containing groups introduced into the polymerization ends. That is, according to this step, a polybutadiene composition containing end-modified 1,4-polybutadiene can be manufactured.

[0073] The alkoxysilane compound used in the modification step (hereinafter also referred to as "alkoxysilane compound (S)") is preferably a compound having at least one alkoxysilane group and capable of reacting with the active terminal of 1,4-polybutadiene (B). Among these, in terms of high reactivity with the active terminal, the alkoxysilane compound (S) is preferably an alkoxysilane compound having at least one functional group selected from the group consisting of epoxy, isocyanate, carbonyl, and cyano groups. Furthermore, the alkoxysilane compound (S) may be a partial condensate or a mixture of the alkoxysilane compound and a partial condensate.

[0074] Specific examples of alkoxysilane compounds (S) include alkoxysilane compounds containing epoxy groups such as: 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, (2-glycidoxyethyl)methyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl)methyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane, etc.

[0075] Examples of alkoxysilane compounds containing isocyanate groups include: 3-isocyanate propyltrimethoxysilane, 3-isocyanate propyltriethoxysilane, 3-isocyanate propylmethyldiethoxysilane, 3-isocyanate propyltriisopropoxysilane, etc.

[0076] Examples of alkoxysilane compounds containing a carbonyl group include: 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, 3-(meth)acryloyloxypropyltriisopropoxysilane, etc.

[0077] Examples of alkoxysilane compounds containing a cyano group include: 3-cyanopropyltriethoxysilane, 3-cyanopropyltrimethoxysilane, 3-cyanopropylmethyldiethoxysilane, and 3-cyanopropyltriisopropoxysilane. Furthermore, as an alkoxysilane compound (S), one or more can be used alone or in combination. "(meth)acryloyl" refers to a compound containing both an "acryloyl" and a "methacryloyl" group.

[0078] During the modification reaction, the proportion of alkoxysilane compound (S) used relative to 1 mole of lanthanide compound used in step Y is preferably 0.01 moles or more, more preferably 0.1 moles or more. If it is less than 0.01 moles, the modification reaction may not proceed sufficiently, and the dispersibility of the filler may not be adequately improved. Furthermore, the proportion of alkoxysilane compound (S) used relative to 1 mole of lanthanide compound used in step Y is preferably 200 moles or less, more preferably 150 moles or less. Even if it exceeds 200 moles, the modification reaction will saturate, and the cost of the used portion will increase. There are no particular limitations on the method of adding alkoxysilane compound (S), and examples include: adding it all at once, adding it separately, or adding it continuously.

[0079] The modification reaction is preferably carried out in solution. The solution obtained through step Y, containing unreacted monomers, can be used directly. This is preferable in terms of simplifying the manufacturing process. Furthermore, the form of the modification reaction is not particularly limited; it can be carried out using a batch reactor, a multi-stage continuous reactor, or an online mixer, etc., in a continuous manner. The modification reaction is preferably carried out before any subsequent operations such as solvent removal, water treatment, heat treatment, and polymer separation, which may be performed after the polymerization reaction.

[0080] The temperature of the modification reaction is preferably set to be the same as the polymerization temperature of 1,4-polybutadiene. Specifically, it is preferably set to 20°C to 100°C, and more preferably to 40°C to 90°C. If the temperature is too low, the viscosity of the polymer tends to increase; if the temperature is too high, the active ends of the polymerization are easily deactivated, which is undesirable. The reaction time of the modification reaction is preferably set to 5 minutes to 5 hours, and more preferably to 15 minutes to 1 hour. In the manufacturing method of this disclosure, if the modification reaction is not carried out, and if the 1,4-polymerization carried out in step Y is completed and the modification reaction is carried out, an existing anti-aging agent or reaction stopper can be added in the solvent removal step as needed after the modification reaction.

[0081] In the case of end modification of 1,4-polybutadiene (B) using step Z, a compound (hereinafter also referred to as a "condensation catalyst") that undergoes a condensation reaction with and is consumed by the residues of the alkoxysilane compound (S) introduced at the active end is further added in the solvent removal step after the modification reaction. Specific examples of condensation catalysts include those containing at least one element from Groups 4A, 2B, 3B, 4B, and 5B of the periodic table. By adding a condensation catalyst, the condensation reaction of the residues of the alkoxysilane compound (S) can be more effectively promoted, resulting in 1,4-polybutadiene with excellent processability, low-temperature properties, and wear resistance.

[0082] As a condensation catalyst, it is preferred to include at least one element selected from the group consisting of titanium, tin, zirconium, bismuth, and aluminum. Specific examples include titanium-containing condensation catalysts such as tetramethoxytitanium, tetraethoxytitanium, tetraisopropoxytitanium, tetratert-butoxytitanium, tributoxystearate titanium, and tripropoxyethyl acetoacetate titanium; tin-containing condensation catalysts such as bis(n-octanoate)tin, bis(2-ethylhexanoate)tin, and bis(laurate)tin; zirconium-containing condensation catalysts such as tetraethoxyzirconium, tetra-n-propoxyzirconium, and tetratert-butoxyzirconium; bismuth-containing condensation catalysts such as tri(2-ethylhexanoate)bismuth and tri(laurate)bismuth; and aluminum-containing condensation catalysts such as triethoxyaluminum, tri-n-propoxyaluminum, triisopropoxyaluminum, and dibutoxyethyl acetoacetate aluminum.

[0083] The polybutadiene composition of this disclosure can be obtained by removing the solvent from the obtained solution and separating the polybutadiene. The polybutadiene can be separated, for example, by existing solvent removal methods such as steam stripping and drying operations such as heat treatment.

[0084] The polybutadiene composition obtained by the manufacturing method is preferably a composition in which 5% to 30% by mass of 1,2-syndiotactic polybutadiene with a melting point of 60°C to 150°C is contained in the 1,4-polybutadiene as the matrix component, relative to the total amount of 1,4-polybutadiene and 1,2-polybutadiene. In this case, it is preferably used as a material to obtain a vulcanized rubber with better resistance to crack growth. Furthermore, when the 1,4-polybutadiene contained in the polybutadiene composition is end-modified by step Z, a polybutadiene composition containing 1,4-polybutadiene with alkoxysilane compound (S) residues introduced at the end and 1,2-syndiotactic polybutadiene can be obtained. In this case, the polybutadiene composition is preferably used as a material to obtain a vulcanized rubber with excellent resistance to crack growth and better low fuel efficiency.

[0085] In the polybutadiene composition, the content of cis-1,4 bonds is preferably 55% or more, more preferably 65% ​​or more, and even more preferably 75% or more. If the content of cis-1,4 bonds is 55% or more, the resulting crosslinked body exhibits better resistance to crack growth and abrasion. Furthermore, the content of cis-1,4 bonds in the polybutadiene composition is preferably 95% or less, more preferably 92% or less, and even more preferably 90% or less.

[0086] In the polybutadiene composition, the content of 1,2 bonds is preferably 40% or less, more preferably 30% or less, and even more preferably 25% or less. Furthermore, the content of 1,2 bonds in the polybutadiene composition is preferably 5% or more, more preferably 8% or more.

[0087] The Mooney viscosity (ML1+4, 100°C) of the polybutadiene composition is preferably 10 or more, more preferably 20 or more. Furthermore, the Mooney viscosity (ML1+4, 100°C) of the polybutadiene composition is preferably 150 or less, more preferably 100 or less. A Mooney viscosity (ML1+4, 100°C) of 10 or more ensures adequate rubber properties, particularly destructive characteristics. Additionally, a Mooney viscosity (ML1+4, 100°C) of 150 or less allows for good workability and allows for uniform mixing with various compounding agents, which is preferable in this respect. Moreover, in this specification, the Mooney viscosity (ML1+4, 100°C) is a value determined according to JIS K6300-1:2013.

[0088] From the viewpoint of ease of manufacture, the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) in the obtained polybutadiene composition is preferably 1.1 or more, more preferably 2.0 or less, and even more preferably 2.1 or more. Furthermore, the Mw / Mn ratio of the polybutadiene composition is preferably 4.0 or less, more preferably 3.5 or less. Having an Mw / Mn ratio of 4.0 or less in the polybutadiene composition results in better destructive properties of the resulting crosslinked body, which is preferable in this respect.

[0089] <Rubber Composition>

[0090] The rubber composition contains a polybutadiene composition obtained by the manufacturing method and may contain other components as needed. The other components are described below.

[0091] Inorganic fillers may also be incorporated into the rubber composition of the present invention. Examples of inorganic fillers include silica and carbon black. Examples of silica include wet silica (hydrated silicic acid), dry silica (silicic anhydride), colloidal silica, precipitated silica, calcium silicate, and aluminum silicate. Wet silica is preferred.

[0092] Examples of carbon black include general purpose furnace black (GPF), fast extrusion furnace black (FEF), high abrasion furnace black (HAF), intermediate super abrasion furnace black (ISAF), and super abrasion furnace black (SAF), but are not particularly limited. In addition to silica and carbon black, various reinforcing fillers such as clay and calcium carbonate can also be incorporated into the rubber composition as inorganic fillers. The proportion of inorganic fillers in the rubber composition is preferably 25 to 130 parts by mass, more preferably 30 to 110 parts by mass, relative to 100 parts by mass of the total amount of rubber components in the rubber composition.

[0093] Rubber compositions typically contain crosslinking agents. Examples of crosslinking agents include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, and alkylphenol resins containing hydroxymethyl groups; sulfur is commonly used. The amount of sulfur incorporated is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of the total amount of rubber components in the rubber composition.

[0094] Other rubber components different from polybutadiene may also be formulated into the rubber composition. The types of these other rubber components are not particularly limited, but examples include: styrene-butadiene rubber (SBR), natural rubber (NR), isoprene rubber (IR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, etc. From the viewpoint of fully obtaining the improved fuel efficiency and other performance benefits caused by the formulation of other rubber components, the amount of other rubber components is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, relative to 100 parts by mass of the total polymer components contained in the rubber composition. Furthermore, from the viewpoint of obtaining a crosslinked body with sufficiently improved crack growth resistance through the formulation of the polybutadiene composition, the amount of other rubber components is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, relative to 100 parts by mass of the total polymer components contained in the rubber composition.

[0095] In addition to the aforementioned components, various additives commonly used in rubber compositions may be formulated into the rubber composition, such as anti-aging agents, zinc oxide, stearic acid, softeners, vulcanization accelerators, silane coupling agents, compatibilizers, vulcanization aids, process oils, processing aids, and scorch inhibitors. Their formulation ratios can be appropriately selected based on the various components without impairing the effects of this disclosure.

[0096] <Crosslinkers>

[0097] The rubber composition disclosed herein, apart from polymer components and inorganic fillers, uses a mixing machine such as an open mixing machine (e.g., roller) or a closed mixing machine (e.g., a Banbury mixer) to mix the components as needed, and then crosslinks (vulcanizes) after molding and processing, thereby enabling it to be used as a crosslinked body in various rubber products. Specifically, it can be applied to tire applications such as tire tread, under tread, carcass, sidewall, and bead part; sealing materials such as liner, gasket, weather strip, and O-ring; inner and outer packaging materials for various vehicles such as automobiles, ships, airplanes, and railways; building materials; vibration damping rubber for industrial machinery or equipment; various hoses and hose covers such as diaphragms, rollers, radiator hoses, and air hoses; belts for power transmission; linings; dust boots; medical equipment materials; fenders; electrical insulation materials; and other industrial products.

[0098] According to the polybutadiene composition, a crosslinked body with excellent resistance to crack growth, low fuel efficiency, and excellent rigidity can be manufactured. Therefore, the polybutadiene composition is particularly preferred for use as a material for the tread and sidewall of tires. Tire manufacturing can be carried out according to conventional methods. For example, a rubber composition containing rubber components and other components to be formulated as needed is mixed using a mixer, and the sheet-like material is placed in a specified position and vulcanized according to conventional methods to form tread rubber or sidewall rubber, thereby obtaining a pneumatic tire.

[0099] Example

[0100] The following detailed description is based on examples, but this disclosure is not limited to these examples. Furthermore, unless otherwise specified, "parts" and "%" in the examples and comparative examples refer to mass. The following shows methods for determining various physical properties of the polymer.

[0101] [Menner viscosity]: Measured according to JISK6300-1:2013, using an L rotor, under the conditions of 1 minute preheating, 4 minutes rotor operation time, and 100°C.

[0102] [Molecular weight distribution]: Determined using a gel permeation chromatograph (trade name: VISCOTEK GPCmax, manufactured by Malvern) with a differential refractometer as the detector, under the following conditions, and calculated as a conversion value for standard polystyrene.

[0103] Tube String: Two tubes, trade name "GMHHR-H" (manufactured by Tosoh Corporation); Tube String Temperature: 38℃

[0104] Mobile phase: tetrahydrofuran; Flow rate: 1.0 ml / min

[0105] Sample concentration: 10mg / 20ml

[0106] [Cis-1,4 bond content and 1,2-vinyl bond content]: Measured using an infrared spectrophotometer (trade name: FT / IR-4100 series, manufactured by Jasco Spectrophotometer) with a ZnSe prism at a wavenumber of 1000 cm⁻¹. -1 ~600cm -1 .

[0107] [1,2-Polybutadiene content]: The content α of 1,2-syndiotactic polybutadiene is calculated according to the following calculation formulas (1) to (4). Furthermore, the abbreviations in calculation formulas (1) to (4) have the following meanings.

[0108] Q1: Input amount of 1,3-butadiene (for syndiotactic-1,2 polymerization)

[0109] Q2: 1,2-Polybutadiene production amount

[0110] Q3: Amount of unreacted 1,3-butadiene in 1,2 polymerization

[0111] Q4: Input amount of 1,3-butadiene (for cis-1,4 polymerization)

[0112] Q5: 1,4-Polybutadiene production amount

[0113] Q2 = Q1 × (reaction conversion rate of syndiotactic-1,2 polymerization)···(1)

[0114] Q3=Q1-Q2···(2)Q5=(Q3+Q4)×(conversion rate of cis-1,4 polymerization)···(3)

[0115] Content rate α=(Q2÷(Q2+Q5))×100···(4)

[0116] 1. Manufacturing and Evaluation of Polybutadiene Rubber

[0117] [Example 1]

[0118] 1.5 kg of cyclohexane and 50 g of 1,3-butadiene were added to a nitrogen-purified 3L autoclave. Catalyst composition A was prepared by mixing a dichloride solution containing 0.02 mmol of cobalt chloride, a dichloride solution containing 0.04 mmol of diphenylcyclohexylphosphine, and a toluene solution containing 0.6 mmol of methylaluminoxane (MAO), and reacting at 30°C for 60 minutes. Catalyst composition A was added to the autoclave and reacted at 30°C for 1 hour (syndiotactic-1,2 polymerization) to obtain a polymer solution. Furthermore, the conversion rate of the added 1,3-butadiene was approximately 75%. Then, to stop the polymerization reaction, a toluene solution containing 0.2 mmol of diisobutylaluminum hydrogenation was added to the autoclave, and the mixture was stirred for 15 minutes.

[0119] Next, 250 g of 1,3-butadiene was added to the resulting polymer solution. Meanwhile, catalyst composition B was prepared by reacting 4.5 mmol of 1,3-butadiene with a cyclohexane solution containing 0.037 mmol of neodymium tert-carbonate (Nd(ver)3), a toluene solution containing 1.2 mmol of MAO, a toluene solution containing 2.86 mmol of diisobutylaluminum hydrogenation, and a toluene solution containing 0.045 mmol of trimethylsilyl chloride (Me3SiCl) at 30°C for 60 minutes. Catalyst composition B was then added to the autoclave and reacted at 70°C for 1 hour (cis-1,4 polymerization) to obtain a polymer solution. Furthermore, the conversion rate of the added 1,3-butadiene was approximately 100%.

[0120] Subsequently, to determine the various physical properties of the polybutadiene rubber obtained through the reaction, 200 g of polymer solution was drawn from the polymer solution, and a toluene solution containing 1.5 g of 2,4-di-tert-butyl-p-cresol was added to the drawn polymer solution to stop the polymerization reaction. Then, the solvent was removed by steam stripping, and the product was dried using a roller at 110°C. The resulting dried product was taken as polybutadiene rubber P. The various physical properties of polybutadiene rubber P were determined, showing a 1,2-polybutadiene content of 11%, a 1,2-polybutadiene melting point of 137°C, a 1,2-polybutadiene weight-average molecular weight (Mw) of 140,000, a Menner viscosity (ML1+4, 100°C) of 57, a molecular weight distribution (Mw / Mn) of 3.14, a cis-1,4 bond content of 87.6%, and a 1,2-vinyl bond content of 11.1%.

[0121] [Example 2 and Comparative Example 1]

[0122] The polymerization formulations for the 1,2 polymerization in Example 1 are shown in Table 1 below, and the polymerization formulations for the cis-1,4 polymerization are shown in Table 2 below. Except for this aspect, the same procedures as in Example 1 were performed to obtain polybutadiene rubber Q and polybutadiene rubber R, respectively. Furthermore, the measurement results of the various physical properties of the obtained polybutadiene rubber Q and polybutadiene rubber R are shown in Table 3 below. In Table 3, Comparative Example 2 shows the measurement results of commercially available polybutadiene rubber (trade name "BR01", manufactured by JSR Corporation).

[0123] [Table 1]

[0124]

[0125] [Table 2]

[0126]

[0127] The abbreviations in Tables 1 and 2 have the following meanings.

[0128] CoCl2: Cobalt chloride

[0129] PCH: Diphenylcyclohexylphosphine

[0130] AlBuH: Diisobutylaluminum hydride

[0131] NdVer: Neodymium tert-carbonate

[0132] MeSiCl: Trimethylsilyl chloride

[0133] [Table 3]

[0134]

[0135] [Example 3]

[0136] To obtain a modified polybutadiene rubber containing 1,4-polybutadiene (hereinafter referred to as "modified polybutadiene rubber"), the remaining polymer solution from Example 1 was treated as follows. A toluene solution containing 1.62 mmol of 3-glycidoxypropyl(dimethoxy)methylsilane (hereinafter referred to as "GOPDMS") was added to the polymer solution at a temperature maintained at 70°C, and the reaction was carried out for 30 minutes to obtain a reaction solution. Then, a toluene solution containing 1.5 g of 2,4-di-tert-butyl-p-cresol was added to the reaction solution to obtain a modified polymer solution (yield: 1.6 kg). Next, 5 L of an aqueous solution adjusted to pH 10 using sodium hydroxide was added to the modified polymer solution, and a solvent removal and condensation reaction was carried out at 110°C for 1 hour. The solution was then dried using a roller at 110°C, and the resulting dried product was taken as modified polybutadiene rubber S. The Menner viscosity of modified polybutadiene rubber S is shown in Table 4 below.

[0137] [Example 4 and Comparative Example 3]

[0138] In Example 3, except that the polymer solutions of Example 2 and Comparative Example 1 were used instead of the polymer solution of Example 1, and the amount of GOPDMS used was changed as described in Table 4 below, the same operation as in Example 3 was performed to obtain modified polybutadiene rubber T and modified polybutadiene rubber U. The Menner viscosity of the obtained modified polybutadiene rubber T and modified polybutadiene rubber U is shown in Table 4 below. Furthermore, in Table 4, in Comparative Example 4, commercially available polybutadiene rubber (trade name "BR01", manufactured by JSR Corporation) was used.

[0139] [Table 4]

[0140]

[0141] 2. Preparation and evaluation of carbon black-blended rubber compositions

[0142] [Example 5]

[0143] In addition to 100 parts of a rubber component containing 60% modified polybutadiene rubber S (Example 3) and 40% natural rubber, 60 parts of carbon black (trade name "DIABLACK N339 for Rubber," manufactured by Mitsubishi Chemical Corporation), 10 parts of T-DAE process oil, 2 parts of stearic acid, 1 part of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (trade name "Nocrac 6C," manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) as an anti-aging agent, 3 parts of zinc oxide, 1 part of CZ (trade name "Nocceler CZ-G," manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) as a vulcanization accelerator, and 1.2 parts of sulfur were mixed using a plastomill to obtain a carbon black-blended rubber composition. The carbon black-blended rubber composition was then vulcanized at 160°C for 12 minutes to obtain a carbon black-blended vulcanized rubber. The properties of the carbon black-blended vulcanized rubber were evaluated using the evaluation methods (1) to (3) shown below. The blending formulations and evaluation results are shown in Table 5 below.

[0144] (1) Resistance to crack growth

[0145] The obtained rubber composition was calendered into a sheet and then vulcanized at 160°C for a specified time using a vulcanizing press to produce a sheet containing a 2 mm thick cross-linked rubber. The resulting sheet was then die-cut to produce a dumbbell-shaped test piece conforming to Type IV as described in ASTM D638. In this die-cutting, the length direction of the dumbbell was aligned with the grain direction of the sheet, and a crack extending in the opposite grain direction was formed at the center of the dumbbell's length.

[0146] For the obtained test pieces, a constant elongation fatigue test was conducted under the conditions of 100% elongation, a test temperature of 23°C, and a rotation speed of 300 cpm, and the number of cycles until the test piece fractured was determined. The result is expressed as an index with Comparative Example 6 set to 100; the larger the value, the better the resistance to crack growth.

[0147] (2) Rigidity (M300)

[0148] Vulcanized rubber was used as the test specimen, and tensile tests were performed according to JIS K6251:2010. A dumbbell-shaped No. 3 specimen was used as the test sample, and the tensile stress (M300) at 300% elongation was measured at room temperature. The value is expressed as an index with Comparative Example 2 set to 100; the larger the value, the better the rigidity.

[0149] (3) Low fuel efficiency (50℃ tanδ)

[0150] Vulcanized rubber was used as the test sample, and the measurements were performed using an ARES-RDA (manufactured by TA Instruments) at a shear strain of 1.0%, an angular velocity of 100 radians per second, and a temperature of 50°C. The values ​​are expressed as an index with Comparative Example 2 set to 100; a higher value indicates lower energy loss and better low hysteresis loss characteristics.

[0151] [Example 6, Comparative Examples 5 to 8]

[0152] Except for changing the formulation to the one shown in Table 5 below, the compounding was performed in the same manner as in Example 5, thereby obtaining a carbon black compounded rubber composition. Furthermore, using the obtained carbon black compounded rubber composition, carbon black compounded vulcanized rubber was manufactured in the same manner as in Example 5, and its physical properties were evaluated. These results are shown in Table 5 below. In Table 5 below, the abbreviations for polybutadiene have the following meanings.

[0153] S: Modified polybutadiene rubber of Example 3

[0154] T: Modified polybutadiene rubber of Example 4

[0155] U: Modified polybutadiene rubber of Comparative Example 3

[0156] BR01: Trade name "BR01", butadiene rubber manufactured by JSR Corporation.

[0157] RB840: Trade name "RB840", 1,2-polybutadiene manufactured by JSR Corporation.

[0158] VCR412: Trade name "VCR412", vinyl cis-polybutadiene (1,2-polybutadiene content 12.0% by mass) manufactured by Ube Industries, Ltd.

[0159] [Table 5]

[0160]

[0161] As shown in Table 5, the carbon black-blended vulcanized rubbers of Examples 5 and 6 achieved better evaluation results in terms of rigidity, low fuel efficiency, and resistance to crack growth compared to the vulcanized rubbers of Comparative Examples 5 and 6. Furthermore, compared to Comparative Example 7, the carbon black-blended vulcanized rubbers of Examples 5 and 6 exhibited superior resistance to crack growth; compared to Comparative Example 8, they showed superior low fuel efficiency and resistance to crack growth. In particular, regarding resistance to crack growth, Example 5 showed approximately 5.3 times that of Comparative Example 5, 3.3 times that of Comparative Example 6, approximately 4.3 times that of Comparative Example 7, and approximately 4.6 times that of Comparative Example 8; while Example 6 showed approximately 4.4 times that of Comparative Example 5, approximately 2.7 times that of Comparative Example 6, approximately 3.6 times that of Comparative Example 7, and approximately 3.9 times that of Comparative Example 8, demonstrating a significant improvement.

[0162] Based on the above, it is clear that the manufacturing method of the polybutadiene rubber composition according to this disclosure can obtain a vulcanized rubber with excellent rigidity, low fuel efficiency, and excellent resistance to crack growth.

Claims

1. A method for manufacturing a polybutadiene composition, comprising step Y of polymerizing 1,3-butadiene in the presence of 1,2-polybutadiene and a lanthanide catalyst.

2. The method for manufacturing the polybutadiene composition according to claim 1, further comprising step X of polymerizing 1,3-butadiene in the presence of a cobalt-based catalyst to obtain the 1,2-polybutadiene.

3. The method for manufacturing the polybutadiene composition according to claim 2, wherein in step X, an organoaluminum compound is added and polymerization is stopped.

4. The method for manufacturing the polybutadiene composition according to claim 2 or 3, wherein step Y is a step of polymerizing 1,3-butadiene by adding the lanthanide catalyst to the reaction mixture obtained by step X.

5. The method for manufacturing the polybutadiene composition according to claim 2 or 3, wherein the cobalt-based catalyst contains a cobalt compound, a phosphine compound, and an organoaluminum compound.

6. A method for manufacturing a polybutadiene composition according to any one of claims 1 to 3, wherein the 1,2-polybutadiene is 1,2-syndiotactic polybutadiene.

7. The method for manufacturing the polybutadiene composition according to any one of claims 1 to 3, wherein the lanthanide catalyst contains lanthanide compounds, organoaluminum compounds, and halogen compounds.

8. A method for manufacturing a polybutadiene composition according to any one of claims 1 to 3, wherein step Y is the step of obtaining 1,4-polybutadiene with active ends. This further includes step Z, which involves reacting the active ends of the 1,4-polybutadiene with an alkoxysilane compound.

9. A method for manufacturing a polybutadiene composition according to any one of claims 1 to 3, wherein the polybutadiene composition obtained by step Y contains 5% to 30% by mass of the 1,2-polybutadiene.

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