Conjugated diene-based polymer, polymer composition, crosslinked body, and tire

Abstract

This conjugated diene-based polymer comprises a structural unit derived from butadiene and a structural unit derived from an aromatic vinyl compound, wherein: the value α represented by expression (i) is 0.60-0.97; the proportion of the structural unit derived from an aromatic vinyl compound is 5-50 mass%; and the value θst calculated by expression (ii) from an 1H-NMR spectrum measured using deuterated chloroform as a solvent is greater than 4 mass% but less than 27 mass%.　Expression (i): α=(p+(0.5×r)) / (p+q+(0.5×r)+s) Expression (ii): θst=[(Σ(a) / Σ(a,b))×2.5]×100 (In expression (ii), Σ(a) represents an integrated value of a chemical shift range of 6.00≤σ<6.89, and Σ(a,b) represents an integrated value of a chemical shift range of 6.00≤σ≤8.00.)

Description

Conjugated diene polymer, polymer composition, crosslinked product, and tire

[0001] [Cross-reference to related applications] This application claims priority to Japanese Patent Application No. 2023-221073, filed on December 27, 2023, the entire contents of which are incorporated herein by reference. The present disclosure relates to a conjugated diene-based polymer, a polymer composition, a crosslinked product, and a tire.

[0002] Conjugated diene polymers obtained by polymerization using conjugated diene compounds have various good properties such as heat resistance, abrasion resistance, mechanical strength, moldability, etc., and are therefore widely used in various industrial products such as pneumatic tires, anti-vibration rubbers, hoses, etc. It has also been proposed to obtain high-strength, low-abrasion vulcanized rubber by using a hydrogenated conjugated diene polymer in which some of the unsaturated bonds in the conjugated diene polymer have been hydrogenated (see, for example, Patent Documents 1 and 2).

[0003] Furthermore, Patent Documents 1 and 2 propose obtaining tire components having high strength and excellent wear resistance by using a hydrogenated conjugated diene polymer having a functional group such as an amino group or an alkoxysilyl group at one or both ends.

[0004] International Publication No. WO 2014 / 133097 International Publication No. WO 2015 / 064646

[0005] The properties required for rubber for automobile tires include rolling resistance, strength, and wet grip performance. With recent environmental trends and growing consumer awareness of resource and energy conservation, there is a greater need than ever to further improve the rolling resistance and strength of rubber for automobile tires to improve automobile fuel economy. Rubber materials are also required to have good processability to increase productivity.

[0006] The present disclosure has been made in view of the above-mentioned problems, and a main object of the present disclosure is to provide a conjugated diene-based polymer that can improve the processability of a polymer composition and give a crosslinked product having a well-balanced improvement in rolling resistance, strength, and wet grip performance.

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have found that the above-mentioned problems can be solved by using a conjugated diene-based polymer having a specific structure. Specifically, the present disclosure provides the following conjugated diene-based polymer, polymer composition, crosslinked product, and tire.

[0008] [1] A conjugated diene polymer containing a structural unit derived from butadiene and a structural unit derived from an aromatic vinyl compound, wherein when the constituent ratios (molar ratios) in the polymer of the structural unit represented by the following formula (1), the structural unit represented by the following formula (2), the structural unit represented by the following formula (3), and the structural unit represented by the following formula (4) are p, q, r, and s, respectively, the value α represented by the following formula (i) is 0.60 or more and 0.97 or less, the proportion of the structural unit derived from the aromatic vinyl compound is 5% by mass or more and 50% by mass or less, and the ratio was measured using deuterated chloroform as a solvent. １ A conjugated diene-based polymer having a value θst calculated from a H-NMR spectrum by the following formula (ii) of more than 4 mass% and less than 27 mass%: α=(p+(0.5×r)) / (p+q+(0.5×r)+s) (i) θst=[(Σ(a) / Σ(a,b))×2.5]×100 (ii) (In formula (ii), Σ(a) represents the integral value in the chemical shift range of 6.00≦σ<6.89, and Σ(a,b) represents the integral value in the chemical shift range of 6.00≦σ≦8.00.)

[0009] [2] A polymer composition containing the conjugated diene polymer of [1] above and an antioxidant. [3] A crosslinked body obtained by crosslinking the polymer composition of [2] above. [4] A tire having a cap tread and / or a sidewall constituted by a cured product of the polymer composition of [2] above.

[0010] According to the present disclosure, it is possible to obtain a conjugated diene-based polymer that can improve the processability of a polymer composition and that can give a crosslinked product having a well-balanced improvement in rolling resistance, strength, and wet grip performance.

[0011] Matters related to the implementation of the present disclosure will be described in detail below. In this specification, a numerical range described using "to" indicates a range that includes the numerical values ​​described before and after "to" as the lower and upper limits. Unless otherwise specified, each component may be used alone or in combination of two or more.

[0012] <Conjugated Diene Polymer> The conjugated diene polymer of the present disclosure (hereinafter also referred to as "conjugated diene polymer (A)") contains a structural unit derived from butadiene (more specifically, 1,3-butadiene) and a structural unit derived from an aromatic vinyl compound. Furthermore, in the conjugated diene polymer (A), when the constituent ratios (molar ratios) in the polymer of the structural unit represented by the following formula (1), the structural unit represented by the following formula (2), the structural unit represented by the following formula (3), and the structural unit represented by the following formula (4) are respectively defined as p, q, r, and s, the value α represented by the following formula (i) is 0.60 or more and 0.97 or less: α=(p+(0.5×r)) / (p+q+(0.5×r)+s) (i)

[0013] If the value α represented by the above formula (i) is less than 0.60, the abrasion resistance of the crosslinked body obtained using the conjugated diene polymer tends to be insufficient. Also, if α exceeds 0.97, the vulcanization adhesion of the crosslinked body tends to deteriorate. From the viewpoint of obtaining a crosslinked body with a well-balanced improvement in abrasion resistance and vulcanization adhesion, α is preferably 0.65 or more, more preferably 0.70 or more, and even more preferably 0.75 or more. Also, α is preferably 0.96 or less, more preferably 0.95 or less.

[0014] The value α represented by the above mathematical formula (i) corresponds to the hydrogenation rate of the conjugated diene polymer. For example, when α is 0.60, the hydrogenation rate of the conjugated diene polymer is 60%. The hydrogenation rate and α of the conjugated diene polymer can be adjusted, for example, by adjusting the time of the hydrogenation reaction to obtain the conjugated diene polymer (A) or by controlling the cumulative amount of hydrogen supplied. In this specification, the hydrogenation rate is １ This is a value measured by a H-NMR device.

[0015] The conjugated diene polymer (A) is an aggregate of polymers having structural units derived from butadiene and structural units derived from an aromatic vinyl compound. Hereinafter, the structural units derived from butadiene will also be referred to simply as "butadiene units," and the structural units derived from an aromatic vinyl compound will also be referred to simply as "aromatic vinyl units."

[0016] Examples of aromatic vinyl compounds include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, t-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, vinylxylene, vinylnaphthalene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene (e.g., 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene). Preferred aromatic vinyl compounds are styrene and α-methylstyrene. Styrene is also preferred because of its high living properties in anionic polymerization when copolymerized with 1,3-butadiene.

[0017] In the conjugated diene polymer (A), the proportion of aromatic vinyl units is 5% by mass or more and 50% by mass or less. If the proportion of aromatic vinyl units is less than 5% by mass, the processability of the polymer composition containing the conjugated diene polymer, the strength of the crosslinked body, and wet grip performance tend to decrease. If the proportion of aromatic vinyl units exceeds 50% by mass, the rolling resistance of the crosslinked body tends to be insufficient. From the viewpoint of improving the processability of the polymer composition, the strength of the crosslinked body, the rolling resistance, and the wet grip performance in a well-balanced manner, the proportion of aromatic vinyl units is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more, based on the total amount of structural units contained in the conjugated diene polymer (A). Furthermore, the proportion of aromatic vinyl units is preferably 48% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less, based on the total amount of structural units contained in the conjugated diene polymer (A). The proportion of aromatic vinyl units in the conjugated diene polymer is １ This is a value measured by H-NMR.

[0018] The preferred range of the proportion of the aromatic vinyl units in the conjugated diene polymer (A) can be determined by appropriately combining the above-mentioned upper and lower limits. Specifically, the proportion of the aromatic vinyl units in the conjugated diene polymer (A) is preferably 10% by mass or more and 48% by mass or less, more preferably 15% by mass or more and 45% by mass or less, and even more preferably 20% by mass or more and 45% by mass or less.

[0019] The conjugated diene polymer (A) was measured using deuterated chloroform as a solvent. １ The value θst calculated from the H-NMR spectrum using the following formula (ii) is more than 4% by mass and less than 27% by mass: θst = [(Σ(a) / Σ(a,b)) × 2.5] × 100 (ii) (In formula (ii), Σ(a) represents the integral value in the chemical shift range of 6.00≦σ<6.89, and Σ(a,b) represents the integral value in the chemical shift range of 6.00≦σ≦8.00.)

[0020] Here, the conjugated diene polymer (A) measured using deuterated chloroform as a solvent１ The H-NMR spectrum shows a chemical shift corresponding to the number of consecutive aromatic vinyl units (hereinafter also referred to as "aromatic vinyl chain length"). Specifically, the chain state of aromatic vinyl units in the conjugated diene polymer (A) can be understood from the ratio of the integral value in the range (a) to the total integral value of each of the chemical shift ranges (a) to (c) below. In the explanation of (a) to (c), the symbol S represents a chemical shift (unit: ppm). "Short chain of aromatic vinyl compounds" means that one aromatic vinyl unit is interposed between butadiene units. (a) 8 or more chains of aromatic vinyl compounds: 6.00≦S<6.68 (b) 2 to 7 chains of aromatic vinyl compounds: 6.68≦S<6.89 (c) Short chain of aromatic vinyl compounds: 6.89≦S≦8.00

[0021] For example, when the aromatic vinyl compound is styrene, the ratio of the integral value in the range (a) to the sum of the integral values ​​in the ranges (a) to (c) is calculated, and this value is multiplied by 2.5, thereby making it possible to calculate the ratio of chains in which 8 or more styrene units are consecutive among the styrene units in the conjugated diene-based polymer (A).

[0022] If the θst of the conjugated diene polymer (A) is 4% by mass or less or exceeds 27% by mass, the processability of the polymer composition and the strength and wet grip performance of the crosslinked body obtained using the conjugated diene polymer (A) tend to be reduced. From the viewpoint of obtaining a crosslinked body exhibiting good low rolling resistance, strength, and wet grip performance, while also obtaining a conjugated diene polymer (A) that has excellent processability when made into a polymer composition, θst is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more. Furthermore, from the viewpoint of suppressing a reduction in the strength of the crosslinked body, θst is preferably 24% by mass or less, more preferably 20% by mass or less.

[0023] The preferred range of θst of the conjugated diene polymer (A) can be determined by appropriately combining the above-mentioned upper and lower limits. Specifically, θst of the conjugated diene polymer (A) is preferably 5% by mass or more and 24% by mass or less, more preferably 7% by mass or more and 24% by mass or less, and even more preferably 10% by mass or more and 20% by mass or less.

[0024] The conjugated diene polymer (A) may be a molecular aggregate of linear polymers (hereinafter also referred to as "linear polymers"), or may be a molecular aggregate of polymers having a branched structure (hereinafter also referred to as "branched polymers"), or may contain a branched polymer in addition to a linear polymer. In order to obtain a crosslinked product that exhibits good wet grip performance and is more excellent in abrasion resistance, the conjugated diene polymer (A) preferably contains a branched polymer, and more preferably contains a polymer having a multibranched structure with four or more molecular chains (hereinafter also referred to as "polymer (A1)").

[0025] The proportion of polymer (A1) in the conjugated diene polymer (A) is preferably 15% by mass or more and 75% by mass or less, based on the total amount of the conjugated diene polymer (A). When the content of polymer (A1) is within the above range, the processability of the polymer composition containing the conjugated diene polymer (A) can be maintained at a good level. From the viewpoint of improving the rolling resistance and strength of the crosslinked product while maintaining good processability of the polymer composition, the proportion of polymer (A1) is more preferably 18% by mass or more, and even more preferably 20% by mass or more, based on the total amount of the conjugated diene polymer (A). Furthermore, the proportion of polymer (A1) is more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less, based on the total amount of the conjugated diene polymer (A). The proportion (% by mass) of polymer (A1) in the conjugated diene polymer (A) can be calculated by separating the components of the branched polymer waveform in a GPC curve obtained using gel permeation chromatography (GPC).

[0026] The preferred range of the proportion of the polymer (A1) in the conjugated diene polymer (A) can be determined by appropriately combining the above-mentioned upper and lower limits. Specifically, the proportion of the polymer (A1) in the conjugated diene polymer (A) is more preferably 18% by mass or more and 70% by mass or less, and even more preferably 20% by mass or more and 65% by mass or less.

[0027] Next, the structure of the conjugated diene polymer (A) will be described in more detail while explaining the production method of the conjugated diene polymer (A). The conjugated diene polymer (A) can be produced, for example, by a method comprising the polymerization step and hydrogenation step shown below, and optionally comprising the reaction step shown below after the polymerization step and before the hydrogenation step. Polymerization step: A step of polymerizing a monomer including 1,3-butadiene and an aromatic vinyl compound to obtain a conjugated diene polymer having an active end. Reaction step: A step of reacting a conjugated diene polymer having an active end with a compound having four or more functional groups capable of reacting with the active end of the conjugated diene polymer (hereinafter also referred to as "coupling agent (B)"). Hydrogenation step: A step of hydrogenating (hereinafter also referred to as "hydrogenation") the conjugated diene polymer.

[0028] Hereinafter, the conjugated diene polymer obtained by the polymerization step will also be referred to as a "conjugated diene polymer (I)," and the conjugated diene polymer obtained by the reaction step will also be referred to as a "conjugated diene polymer (II)." Each step will be described below.

[0029] <Polymerization process>

[0030] In the polymerization reaction to obtain the conjugated diene polymer (A), only 1,3-butadiene and an aromatic vinyl compound may be used as monomers. Alternatively, compounds other than 1,3-butadiene and an aromatic vinyl compound (hereinafter also referred to as "other monomers") may be used in combination. Examples of other monomers include conjugated diene compounds other than 1,3-butadiene, acrylonitrile, methyl (meth)acrylate, and ethyl (meth)acrylate. Examples of conjugated diene compounds other than 1,3-butadiene include isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. The proportion of other monomers used is preferably 10% by mass or less, and more preferably 5% by mass or less, based on the total amount of monomers used in the polymerization.

[0031] The polymerization method used may be any of solution polymerization, gas phase polymerization, emulsion polymerization, and bulk polymerization. Of these, solution polymerization is particularly preferred. The polymerization method may be either batch or continuous. In the case of solution polymerization, a specific example of the polymerization method is a method in which monomers containing 1,3-butadiene and an aromatic vinyl compound are polymerized in an organic solvent in the presence of a polymerization initiator and, if necessary, a randomizer (vinyl content adjuster).

[0032] As the polymerization initiator, a metal compound containing an alkali metal or alkaline earth metal can be used. Of these, a compound containing an alkali metal is preferred. Specific examples of the metal compound include alkyllithium such as methyllithium, ethyllithium, n-propyllithium, n-butyllithium, sec-butyllithium, and t-butyllithium; 1,4-dilithiobutane, phenyllithium, stilbenelithium, naphthyllithium, 1,3-bis(1-lithio-1,3-dimethylpentyl)benzene, 1,3-phenylenebis(3-methyl-1-phenylpentylidene)dilithium, naphthylsodium, naphthylpotassium, and ethoxypotassium. Of these, a lithium compound is preferred as the polymerization initiator.

[0033] Furthermore, the metal compound used as the polymerization initiator may be a metal amide compound containing an alkali metal or alkaline earth metal. By carrying out polymerization to obtain the conjugated diene polymer (A) in the presence of a metal amide compound, an amino group can be introduced into the polymerization initiation terminal of the conjugated diene polymer (for example, the free terminal portion of a branched polymer). The amino group introduced into the polymerization initiation terminal of the conjugated diene polymer is preferably a secondary amino group or a tertiary amino group. The conjugated diene polymer (A) obtained by polymerization in the presence of a metal amide compound is preferred in that the crosslinked product has excellent strength and abrasion resistance, while the polymer composition has good processability.

[0034] Among metal amide compounds, a compound obtained by mixing a lithium compound (e.g., alkyllithium, etc.) with a compound having a nitrogen atom (hereinafter also referred to as an "initiation end modifier") is preferred. The initiation end modifier is preferably a secondary amine compound. Specific examples of secondary amine compounds include dimethylamine, diethylamine, dipropylamine, dibutylamine, dodecamethyleneimine, N,N'-dimethyl-N'-trimethylsilyl-1,6-diaminohexane, piperidine, pyrrolidine, hexamethyleneimine, heptamethyleneimine, dicyclohexylamine, N-methylbenzylamine, di-(2-ethylhexyl)amine, diallylamine, morpholine, N-(trimethylsilyl)piperazine, N-(tert-butyldimethylsilyl)-4-piperazine, and 1,3-ditrimethylsilyl-1,3,5-triazinane.

[0035] When polymerization is carried out in the presence of a metal amide compound, a lithium compound and an initiation end modifier may be mixed in advance to prepare a metal amide compound, and the prepared metal amide compound may then be added to a polymerization system to carry out polymerization. Alternatively, a lithium compound and an initiation end modifier may be added to a polymerization system, and the two may then be mixed in the polymerization system to prepare a metal amide compound, followed by polymerization. In the polymerization, the amount of polymerization initiator used (the total amount when two or more types are used) is preferably 0.01 to 20 mmol, more preferably 0.05 to 15 mmol, per 100 g of monomer used to synthesize the polymer.

[0036] The randomizer can be used for the purpose of adjusting the vinyl bond content, which represents the content of vinyl bonds in a polymer, etc. Examples of the randomizer include ether compounds such as dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, 2,2-di(tetrahydrofuryl)propane, and 2-(2-ethoxyethoxy)-2-methylpropane; amine compounds such as triethylamine, pyridine, N-methylmorpholine, and tetramethylethylenediamine; and potassium compounds such as potassium alkoxides, potassium phenoxide, potassium salts of organic carboxylic acids, potassium salts of organic sulfonic acids (e.g., potassium dodecylbenzenesulfonate), and potassium salts of organic phosphorous acids.

[0037] During polymerization, the aromatic vinyl chain length (i.e., θst) can be controlled by adding a potassium compound together with a polymerization initiator. For example, by adding a potassium compound together with a polymerization initiator to the polymerization system, the aromatic vinyl compound introduced into the conjugated diene polymer (A) can be randomly arranged or short chains of the aromatic vinyl compound can be provided. This allows the proportion of the aromatic vinyl chain length (styrene chain length when styrene is used) in the conjugated diene polymer (A) to be adjusted to fall within a desired range.

[0038] As the organic solvent used in the polymerization, an organic solvent inert to the reaction is preferably used. Examples of the organic solvent that can be used include linear or cyclic aliphatic hydrocarbons and aromatic hydrocarbons. Among these, hydrocarbons having 3 to 8 carbon atoms are preferred, and specific examples thereof include propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis-2-butene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene, heptane, cyclopentane, methylcyclopentane, methylcyclohexane, 1-pentene, 2-pentene, and cyclohexene.

[0039] When solution polymerization is performed, the monomer concentration in the reaction solvent is preferably 5 to 50% by mass, and more preferably 10 to 30% by mass, from the viewpoint of maintaining a balance between productivity and ease of polymerization control. The temperature of the polymerization reaction is preferably −20° C. to 150° C., and more preferably 0 to 120° C. Furthermore, the polymerization reaction is preferably carried out under a pressure sufficient to maintain the monomers substantially in a liquid phase. Such a pressure can be obtained by, for example, pressurizing the reactor with a gas inert to the polymerization reaction. By such a polymerization reaction, a conjugated diene-based polymer having an active terminal (i.e., conjugated diene-based polymer (I)) can be obtained.

[0040] The conjugated diene polymer (I) obtained by the polymerization preferably has a vinyl bond content of 5 to 70 mol% in the structural units derived from 1,3-butadiene. By setting the vinyl bond content to 5 mol% or more, the flexibility of the obtained crosslinked product tends to be maintained and the processability tends to be good. The vinyl bond content of the conjugated diene polymer (I) is more preferably 10 mol% or more, even more preferably 15 mol% or more, and even more preferably 20 mol% or more. In addition, the vinyl bond content of the conjugated diene polymer (I) is more preferably 60 mol% or less, even more preferably 50 mol% or less, from the viewpoint of ensuring the rolling resistance of the crosslinked product while maintaining the processability of the polymer composition containing the conjugated diene polymer (A). In this specification, the "vinyl bond content" is a value indicating the content ratio of structural units having 1,2-bonds to all structural units derived from 1,3-butadiene contained in the conjugated diene polymer before hydrogenation. The vinyl bond content is １ This is a value measured by a H-NMR device.

[0041] The vinyl bond content of the conjugated diene polymer (A) before hydrogenation is calculated by multiplying the value β represented by the following formula (iii) by 100, where p, q, r, and s are the constituent ratios (molar ratios) of the structural unit represented by the above formula (1), the structural unit represented by the above formula (2), the structural unit represented by the above formula (3), and the structural unit represented by the above formula (4) contained in the conjugated diene polymer (A), respectively: β=(p+q) / (p+q+(0.5×r)+s) (iii) Note that, in the conjugated diene polymer (A) before hydrogenation, typically p=0 and r=0.

[0042] That is, the value β represented by the above mathematical formula (iii) corresponds to the vinyl bond content of the conjugated diene polymer before hydrogenation. For example, when the β of the conjugated diene polymer (A) is 0.05, the vinyl bond content of the conjugated diene polymer before hydrogenation is 5 mol%. In order to achieve both the processability of the polymer composition containing the conjugated diene polymer (A) and the rolling resistance of the crosslinked body, the β of the conjugated diene polymer (A) is preferably 0.05 or more and 0.70 or less. β is more preferably 0.10 or more, even more preferably 0.15 or more, and even more preferably 0.20 or more. β is more preferably 0.60 or less, and even more preferably 0.50 or less.

[0043] The preferred range of β of the conjugated diene polymer (A) can be determined by appropriately combining the above-mentioned upper and lower limits. Specifically, β of the conjugated diene polymer (A) is preferably 0.10 or more and 0.60 or less, more preferably 0.15 or more and 0.60 or less, and even more preferably 0.20 or more and 0.50 or less.

[0044] <Reaction Step> Examples of the coupling agent (B) used in the reaction step include compounds having four or more reaction sites with the active terminal of the conjugated diene polymer and having at least one element selected from the group consisting of nitrogen, oxygen, sulfur, silicon, titanium, and tin.

[0045] Specific examples of the coupling agent (B) include compounds containing silicon, titanium, or tin, such as tetrachlorosilane (silicon tetrachloride), tetramethoxysilane, bis(trichlorosilyl)ethane, titanium tetrachloride, and tin tetrachloride.

[0046] In addition, as the coupling agent (B), a compound having a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, and sulfur and having four or more reaction sites with the polymer chain obtained by the polymerization step (hereinafter also referred to as "terminal modifier (b1)") can also be used. By using the terminal modifier (b1), it is possible to obtain a polymer in which a functional group having one or more of nitrogen, oxygen, and sulfur is introduced into the branching point portion of the branched polymer. Specific examples of the terminal modifier (b1) include, for example, the compounds described in paragraphs 0029 to 0035 of WO 2020 / 196899 and the compounds described in paragraphs 0030 to 0033 of WO 2020 / 179705.

[0047] The reaction between the conjugated diene polymer (I) and the coupling agent (B) (i.e., the coupling reaction) is preferably carried out as a solution reaction. The proportion of the coupling agent (B) used (the total amount when two or more types are used) can be appropriately set so that the proportion of the polymer (A1) in the conjugated diene polymer (A) is within the desired range. Specifically, from the viewpoint of obtaining a crosslinked product exhibiting excellent abrasion resistance while maintaining good processability of the polymer composition, the proportion of the coupling agent (B) used is preferably 0.01 mol or more, more preferably 0.05 mol or more, per mol of the metal atom involved in the polymerization of the polymerization initiator (i.e., the metal compound). Furthermore, from the viewpoint of suppressing a decrease in the processability of the polymer composition, the proportion of the coupling agent (B) used is preferably 0.7 mol or less, more preferably 0.5 mol or less, per mol of the metal atom involved in the polymerization of the polymerization initiator.

[0048] The reaction temperature in the coupling reaction is usually the same as that in the polymerization reaction, and is preferably -20°C to 150°C, and more preferably 0 to 120°C. If the reaction temperature is low, the viscosity of the polymer after the reaction tends to increase, while if the reaction temperature is high, the active polymerization terminals are likely to be deactivated. The reaction time is preferably 1 minute to 5 hours, and more preferably 2 minutes to 1 hour.

[0049] A conjugated diene polymer (II) can be obtained by the above coupling reaction. The conjugated diene polymer (II) preferably contains a linear or branched polymer having 3 or less branches, together with a polymer having a molecular chain with 4 or more branches (i.e., the polymer (A1) before hydrogenation). This linear or branched polymer having 3 or less branches is mainly an unreacted polymer contained in the conjugated diene polymer (I) that has not reacted with the coupling agent (B). In the conjugated diene polymer (II), the ratio of the polymer having a multibranched structure having 4 or more molecular chains (i.e., the polymer (A1) before hydrogenation) to the linear or branched polymer having 3 or less branches can be appropriately set by adjusting the amount of coupling agent (B) used, the number of functional groups of the coupling agent (B) used, etc., so that the ratios of the polymer (A1) and the linear or branched polymer in the conjugated diene polymer (A) are respectively desired ratios.

[0050] When the conjugated diene polymer contained in the reaction solution is isolated, it can be isolated by a known solvent removal method such as steam stripping and a drying procedure such as heat treatment.

[0051] <Modification Step> The conjugated diene polymer (II) obtained above may be subjected directly to the subsequent hydrogenation step. Alternatively, prior to the hydrogenation step, a treatment may be performed in which the polymerization terminal of the linear polymer contained in the conjugated diene polymer (II) is reacted with a terminal-modifying agent (hereinafter referred to as "terminal-modifying agent (c)"). The terminal-modifying agent (c) is preferably a compound containing at least one element selected from the group consisting of nitrogen, oxygen, phosphorus, silicon, and sulfur and capable of reacting with the active terminal of the linear polymer. In this case, a linear or branched polymer having at most three branches and having a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, phosphorus, silicon, and sulfur can be introduced into the conjugated diene polymer (A). That is, by performing the subsequent hydrogenation step, a conjugated diene polymer (A) having a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, phosphorus, silicon, and sulfur can be obtained. Furthermore, by introducing a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, phosphorus, silicon, and sulfur into the conjugated diene polymer (A), it is possible to improve the rolling resistance of a crosslinked body obtained using the conjugated diene polymer (A). The terminal modifier (c) differs from the coupling agent (B) in that it has three or less reaction sites with the active terminals of the conjugated diene polymer (I).

[0052] Specific examples of the functional group having at least one element selected from the group consisting of nitrogen, oxygen, phosphorus, silicon, and sulfur include a primary amino group, a secondary amino group, a tertiary amino group, a protected primary amino group, a protected secondary amino group, an imino group, a nitrogen-containing heterocyclic group (e.g., a group having a heterocycle such as a pyridine ring or an imide ring), a hydroxyl group, a protected hydroxyl group, a thiol group, a protected thiol group, a hydrocarbyloxysilyl group, a phosphino group, etc. In terms of a high effect of improving abrasion resistance, the conjugated diene polymer (A) preferably has a nitrogen-containing functional group (nitrogen-containing group), and particularly preferably has at least one selected from the group consisting of a primary amino group, a secondary amino group, a tertiary amino group, and an imino group.

[0053] A preferred example of the terminal-modifying agent (c) is at least one selected from the group consisting of compounds represented by the following formula (5) and compounds represented by the following formula (6). (In formula (5), A １１ has at least one element selected from the group consisting of nitrogen, oxygen, phosphorus, and sulfur, does not have active hydrogen, and R ３５ is a monovalent functional group bonded to R at a carbon atom contained in a nitrogen, oxygen, phosphorus, or sulfur atom, or a carbonyl group, or is a (thio)epoxy group. ３３ and R ３４ are each independently a hydrocarbyl group. ３５ is a hydrocarbylene group. t is an integer of 0 to 2. However, when t is 2, multiple R ３３ When t is 0 or 1, multiple R ３４ are the same or different.) (In formula (6), A １２ has at least one element selected from the group consisting of nitrogen, oxygen, phosphorus, sulfur, and silicon, does not have active hydrogen, and R ３９ R is a monovalent functional group bonded to R via nitrogen, oxygen, phosphorus, sulfur, or silicon, or a hydrocarbyl group having 1 to 20 carbon atoms. ３９ is a single bond or a hydrocarbylene group. ３６ and R ３７ are each independently a hydrocarbyl group. ３８ is a hydrocarbylene group. u is 0 or 1. When u is 0, multiple R ３７ are the same or different.)

[0054] In the above formulas (5) and (6), R ３３ , R ３４ , R ３６ , R ３７ and A when it is a hydrocarbyl group. １２ With respect to R, the hydrocarbyl group is preferably a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. ３５ and R３９ The hydrocarbylene group in R is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms. ３８ The hydrocarbylene group represented by the following formula is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms. t is preferably 0 or 1.

[0055] A １１ is the monovalent functional group, A １１ at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur and silicon, and １２ is the monovalent functional group, A １２ At least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon may be protected, for example, by a tri-substituted hydrocarbylsilyl group. In this specification, active hydrogen refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably refers to one having a bond energy lower than that of the carbon-hydrogen bond of polymethylene. The term "(thio)epoxy group" encompasses epoxy groups and thioepoxy groups.

[0056] A １１ may be a group that can be converted into an onium ion by an onium salt generating agent. １１ ) can impart excellent shape retention to the polymer. １１Specific examples of include a nitrogen-containing group in which two hydrogen atoms of a primary amino group are replaced by two protecting groups, a nitrogen-containing group in which one hydrogen atom of a secondary amino group is replaced by one protecting group, a tertiary amino group, an imino group, a pyridyl group, a phosphorus-containing group in which two hydrogen atoms of a primary phosphino group are replaced by two protecting groups, a phosphorus-containing group in which one hydrogen atom of a secondary phosphino group is replaced by one protecting group, a tertiary phosphino group, an epoxy group, a thioepoxy group, a group in which the hydrogen atom of a hydroxyl group is replaced by a protecting group, a sulfur-containing group in which the hydrogen atom of a thiol group is replaced by a protecting group, a hydrocarbyloxycarbonyl group, etc. Among these, in terms of good affinity with silica, a group having a nitrogen atom is preferred, and a tertiary amino group or a nitrogen-containing group in which two hydrogen atoms of a primary amino group are replaced by two protecting groups is more preferred.The protecting group is, for example, A １１ , A １２ is a functional group that is converted into a functional group that is inactive to the polymerization active terminal. The onium salt generating agent is a Bronsted acid or a compound that generates a Bronsted acid upon contact with water.

[0057] Specific examples of the terminal modifying agent (c) include compounds represented by the above formula (5), such as N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-dimethylaminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-(4-trimethylsilyl-1-piperazino)propylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyltriethoxysilane.

[0058] Specific examples of the compound represented by the above formula (6) include 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1,2-azasilolidine, 2,2-diethoxy-1-(3-trimethoxysilylpropyl)-1,2-azasilolidine, 2,2-dimethoxy-1-phenyl-1,2-azasilolidine, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, 2-(2,2-dimethoxy-1,2-azasilolidine-1-yl)-N,N-diethylethane-1-amine, 2-(2,2-dimethoxy-1,2-azasilolidine-1-yl)-N,N-dimethylethane-1-amine, and 3-(2,2-dimethoxy-1,2-azasilolidine-1-yl)-N,N-diethylpropan-1-amine. The terminal modifying agent (c) may be used alone or in combination of two or more.

[0059] The reaction between the conjugated diene polymer (II) and the terminal-modifying agent (c) can be carried out, for example, as a solution reaction. This solution reaction may be carried out either batchwise or continuously. In this case, the method of adding the terminal-modifying agent (c) is not particularly limited, and examples thereof include a method of adding the terminal-modifying agent all at once, a method of adding the terminal-modifying agent in portions, and a method of adding the terminal-modifying agent continuously.

[0060] The amount of the terminal modifier (c) used may be appropriately set depending on the type of compound used in the reaction. The amount of the terminal modifier (c) used is preferably 0.05 mol or more, more preferably 0.1 mol or more, relative to 1 mol of the metal atom involved in the polymerization reaction of the polymerization initiator. By using the terminal modifier (c) in an amount of 0.1 molar equivalent or more, the modification reaction can be sufficiently promoted, and the dispersibility of the inorganic filler can be suitably improved. In addition, the amount of the terminal modifier (c) is preferably 1.0 mol or less, more preferably 0.8 mol or less, relative to 1 mol of the metal atom involved in the polymerization reaction of the polymerization initiator.

[0061] The reaction temperature for the terminal modification reaction is usually the same as the temperature for the polymerization reaction, and is preferably −20 to 150° C., more preferably 0 to 120° C., and even more preferably 20 to 100° C. If the temperature for the modification reaction is low, the viscosity of the polymer solution tends to increase. If the temperature for the modification reaction is high, the polymerization active terminals tend to be deactivated. The reaction time for the terminal modification is preferably 1 minute to 5 hours, and more preferably 2 minutes to 1 hour.

[0062] The coupling rate of the conjugated diene polymer obtained by the reaction step and the modification step can be appropriately set depending on the proportion of polymer (A1) in the final product conjugated diene polymer (A), the molecular weight of the conjugated diene polymer (I), the number of functional groups of the coupling agent (B), etc. From the viewpoint of obtaining a crosslinked product having excellent abrasion resistance, the coupling rate is preferably 15% or more, more preferably 20% or more. Furthermore, from the viewpoint of obtaining a polymer composition having excellent processability and from the viewpoint of sufficiently lowering the solution viscosity of the polymer to ensure productivity, the coupling rate is preferably 75% or less, more preferably 70% or less.

[0063] In this specification, the term "coupling rate" refers to the proportion (mass%) of polymers having two or more molecular chains among the polymers contained in the reaction system after reacting a linear conjugated diene polymer having an active terminal with a compound capable of reacting with the active terminal. Specifically, it refers to the proportion (mass%) of polymers to which two or more linear molecular chains are bonded via the coupling agent (B) or the terminal modifier (c) among the total amount of polymers used in the reaction with the coupling agent (B) or the terminal modifier (c) (i.e., the linear polymers contained in the conjugated diene polymer (I)). The coupling rate can be calculated from the peak area ratio of the GPC curve obtained using gel permeation chromatography (GPC).

[0064] <Hydrogenation Step> In this step, the conjugated diene polymer obtained in the reaction step or modification step is hydrogenated. Any method and conditions for the hydrogenation reaction can be used as long as a conjugated diene polymer with a desired hydrogenation rate is obtained. Examples of such hydrogenation methods include a method using a catalyst containing an organometallic compound of titanium as the main component as a hydrogenation catalyst; a method using a catalyst composed of an organometallic compound of iron, nickel, or cobalt and an organometallic compound such as alkylaluminum; a method using an organic complex of an organometallic compound such as ruthenium or rhodium; and a method using a catalyst in which a metal such as palladium, platinum, ruthenium, cobalt, or nickel is supported on a support such as carbon, silica, or alumina. Among various methods, a method in which hydrogenation is carried out under mild conditions of low pressure and low temperature using a homogeneous catalyst comprising a titanium organometallic compound alone or a titanium organometallic compound and an organometallic compound of lithium, magnesium or aluminum (for example, the catalysts described in JP-B-63-4841 and JP-B-1-37970) is preferred from an industrial viewpoint, and is also suitable because of its high hydrogenation selectivity to the double bond of butadiene.

[0065] The hydrogenation of the conjugated diene polymer is preferably carried out using a solvent that is inert to the catalyst and that the conjugated diene polymer is soluble in. Preferred solvents include chain aliphatic hydrocarbons such as n-pentane, n-hexane, and n-octane; cyclic aliphatic hydrocarbons such as cyclohexane and cycloheptane; aromatic hydrocarbons such as benzene and toluene; and ethers such as diethyl ether and tetrahydrofuran. The solvent used for hydrogenation may be one of the above compounds, or a mixture containing them as the main component.

[0066] The hydrogenation reaction is generally carried out by maintaining the conjugated diene polymer at a predetermined temperature in a hydrogen or inert atmosphere, adding a hydrogenation catalyst with or without stirring, and then introducing hydrogen gas to pressurize to a predetermined pressure. An inert atmosphere refers to an atmosphere that does not react with the substances involved in the hydrogenation reaction, and examples include atmospheres of helium, neon, argon, etc. Air and oxygen are not preferred because they oxidize the catalyst and cause catalyst deactivation. Nitrogen is also not preferred because it acts as a catalyst poison during the hydrogenation reaction and reduces hydrogenation activity. In particular, it is most suitable for the hydrogenation reactor to have an atmosphere of hydrogen gas alone.

[0067] The hydrogenation reaction process can be any of a batch process, a continuous process, and a combination thereof. When a titanocene diaryl compound is used as the hydrogenation catalyst, it may be added to the reaction solution either alone or as a solution in an inert organic solvent. When the catalyst is used as a solution, the inert organic solvent used can be any solvent that does not react with the substances involved in the hydrogenation reaction. Preferably, the inert organic solvent used is the same solvent as the solvent used in the hydrogenation reaction. The preferred amount of catalyst added is 0.02 to 20 mmol per 100 g of the conjugated diene polymer before hydrogenation.

[0068] A preferred method for obtaining the conjugated diene polymer (A) is to solution polymerize a monomer containing 1,3-butadiene and an aromatic vinyl compound in the presence of a polymerization initiator, add a coupling agent (B) to the resulting polymer solution to carry out a coupling reaction, add a terminal modifier (c) as needed, and then subject the solution to a hydrogenation step. In this case, the conjugated diene polymer (A) is obtained by removing the solvent from the resulting solution. The polymer can be isolated by known solvent removal methods such as steam stripping and drying procedures such as heat treatment.

[0069] The weight average molecular weight (Mw) of the conjugated diene polymer (A) measured using GPC in terms of polystyrene is preferably 1.5×10 ５ ~2.0 x 10 ６The Mw of the conjugated diene polymer (A) is more preferably 1.8 × 10 ５ More preferably, it is 2.0 × 10 ５ The Mw is more preferably 1.6×10 ６ More preferably, 1.4 × 10 ６ The weight average molecular weight of the conjugated diene polymer referred to here is a value determined from all peaks of a GPC curve measured by GPC before hydrogenation. Hereinafter, it is also referred to as "total weight average molecular weight."

[0070] Furthermore, the molecular weight distribution (weight average molecular weight / number average molecular weight) of the total amount of the conjugated diene polymer (A) measured by GPC is preferably 1.1 or more and 4.0 or less. A molecular weight distribution of 1.1 or more is preferred in terms of excellent processability of the polymer composition, and a molecular weight distribution of 4.0 or less is preferred in terms of sufficiently improving the low hysteresis loss of the obtained crosslinked product. The molecular weight distribution of the conjugated diene polymer (A) is more preferably 1.20 or more, and even more preferably 1.23 or more. The molecular weight distribution of the conjugated diene polymer (A) is more preferably 3.5 or less, and even more preferably 3.0 or less.

[0071] The conjugated diene polymer (A) preferably has a peak top molecular weight of the smallest peak (hereinafter also referred to as "first peak weight average molecular weight") measured by GPC of 0.8 × 10 ５ ~1.0 x 10 ６ The first peak weight average molecular weight is in the range of 0.8 × 10 ５ When the first peak weight average molecular weight is 0.9×10 or more, the effect of improving the strength and abrasion resistance of the resulting crosslinked product can be sufficiently enhanced, while the processability can be further improved, which is preferable. ５ or more, and more preferably 1.0 × 10 ５ In order to improve processability and viscoelasticity, the first peak weight average molecular weight is more preferably 8.0 × 10 ５ is preferably 5.0 × 10 or less. ５The first weight average peak molecular weight is a value determined from a GPC curve measured by GPC before hydrogenation.

[0072] <Polymer Composition> The polymer composition of the present disclosure may contain, together with the conjugated diene polymer (A), various components other than the conjugated diene polymer (A). Examples of components that may be blended into the polymer composition of the present disclosure include one or more of an antioxidant, an inorganic filler (silica, carbon black, other fillers), other rubber components, a resin, a silane coupling agent, a crosslinking agent, and an extender oil.

[0073] [C] Antiaging Agent As the antiaging agent, it is possible to use known additives that are blended into rubber as components that inhibit deterioration of vulcanized rubber due to oxygen, ozone, heat, etc. Examples of the antiaging agent include quinoline-based antiaging agents, amine-based antiaging agents, and phenol-based antiaging agents.

[0074] Specific examples of these include quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline oligomers (for example, dimers, trimers, tetramers, etc.), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. Examples of the amine-based antiaging agent include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N,N'-dicyclohexyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-isopropyl-N'-p-phenylenediamine, phenyl-α-naphthylamine, 4,4'-dioctyldiphenylamine, styrenated diphenylamine, poly(2,2,4-trimethyl-1,2-dihydroquinoline), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine. Examples of phenolic antioxidants include 2,6-di-t-butyl-4-methylphenol, styrenated phenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0075] In the present composition, the content of the antioxidant is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 8 parts by mass, and even more preferably 0.2 to 7 parts by mass, per 100 parts by mass of the rubber component (including the conjugated diene polymer (A); the same applies hereinafter) contained in the polymer composition.

[0076] In this specification, the "rubber component" contained in the polymer composition refers to a polymer that can be cured to obtain a cured product exhibiting rubber elasticity by curing, etc. The cured product exhibits the property of undergoing large deformation under a small force at room temperature (for example, deformation that stretches to more than twice its original size when stretched at room temperature) and rapidly returning to almost its original shape when the force is removed.

[0077] [D] Silica The polymer composition of the present disclosure may contain silica as an inorganic filler. The blending amount of silica is preferably in the range of 20 to 150 parts by mass, more preferably in the range of 30 to 130 parts by mass, per 100 parts by mass of the rubber component contained in the polymer composition. When the blending amount of silica is 20 parts by mass or more per 100 parts by mass of the rubber component, the low hysteresis loss, fracture properties, and abrasion resistance of the polymer composition can be sufficiently improved, and when it is 150 parts by mass or less, the processability of the polymer composition can be sufficiently improved.

[0078] The silica is not particularly limited, and examples thereof include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred. The BET specific surface area of ​​the silica (measured in accordance with ISO 5794 / 1) is 40 to 350 m. ２ / g, and 80 to 350 m ２ / g is more preferable, and 120 to 350m ２ / g is particularly preferred. Silica having a BET specific surface area in this range has the advantage of being able to achieve both rubber reinforcing properties and dispersibility in the conjugated diene polymer (A). Examples of such silica include "Nipsil AQ" (BET specific surface area = 205 m), manufactured by Tosoh Silica Corporation. ２ / g), "Nipsil KQ", product name "Ultrasil VN3" (BET specific surface area = 175 m), manufactured by Degussa ２ Commercially available products such as PEG-100 / g can be used.

[0079] The silica contained in the polymer composition of the present disclosure may be a combination of two or more types of silica having different specific surface areas. ２ / g or more, BET specific surface area is 185m ２ / g or more and an aggregate size of 45 nm or more; and a first silica having a CTAB specific surface area of ​​95 m ２ / g or less, BET specific surface area is 100m ２ A second silica having a viscosity of 1 / g or less may be used in combination.

[0080] The polymer composition of the present disclosure has a CTAB specific surface area of ​​180 m ２ / g or more, BET specific surface area is 185m ２ / g or more and an aggregate size of 45 nm or more; and a first silica having a CTAB specific surface area of ​​95 m ２ / g or less, BET specific surface area is 100m ２ The combined use of such first silica and second silica enables the first silica, which has a small average primary particle size but a relatively large aggregate size, to be well dispersed in the rubber component, improving the dispersibility of the silica and providing excellent fracture strength, abrasion resistance, fuel economy and processability.

[0081] [E] Carbon Black The polymer composition of the present disclosure preferably contains carbon black as an inorganic filler from the viewpoint of the fracture properties and abrasion resistance of the polymer composition. The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. The nitrogen adsorption specific surface area (N ２ SA) is not particularly limited. In order to obtain the effects of the present disclosure more fully, it is preferable to use a value of 50 to 200 m. ２ / g is preferred, and 70 to 150m ２ / g is more preferable. ２ SA) is the amount of nitrogen adsorption on the surface of the carbon black measured in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method." The amount of carbon black mixed is preferably in the range of 1 to 150 parts by mass, more preferably in the range of 5 to 120 parts by mass, per 100 parts by mass of the rubber component contained in the polymer composition.

[0082] [Other Fillers] The composition of the present disclosure may contain other fillers as inorganic fillers in addition to the silica and carbon black described above. Examples of such other fillers include alumina (Al), such as γ-alumina and α-alumina. ２ O ３ alumina monohydrate (Al), boehmite, diaspore, etc. ２ O ３ ・H ２ O), aluminum hydroxides such as gibbsite and bayerite [Al(OH) ３ ], aluminum carbonate [Al ２ (CO ３ ) ３ ], magnesium hydroxide [Mg(OH) ２ ], magnesium oxide (MgO), magnesium carbonate (MgCO ３ ), talc (3MgO.4SiO ２ ・H ２ O), attapulgite (5MgO.8SiO ２ ・9H ２ O), titanium white (TiO ２ ), titanium black (TiO ２ｎ－１ ), calcium oxide (CaO), calcium hydroxide [Ca(OH) ２ ], magnesium aluminum oxide (MgO.Al ２ O ３ ), clay (Al ２ O ３ 2SiO ２ ), kaolin (Al ２ O ３ 2SiO ２ ・2H ２ O), pyrophyllite (Al ２ O ３ 4SiO ２ ・H ２ O), bentonite (Al ２ O ３ 4SiO ２ ・2H ２ O), aluminum silicate (Al ２ SiO ５ , Al ４ 3SiO ４ ・5H ２ O, etc.), magnesium silicate (Mg ２ SiO４ , MgSiO ３ etc.), calcium silicate (Ca ２ SiO ４ etc.), calcium aluminum silicate (Al ２ O ３ CaO 2SiO ２ etc.), magnesium calcium silicate (CaMgSiO ４ ), calcium carbonate (CaCO ３ ), zirconium oxide (ZrO ２ ), zirconium hydroxide [ZrO(OH) ２ ・nH ２ O], zirconium carbonate [Zr(CO ３ ) ２ ], crystalline aluminosilicates containing hydrogen, alkali metals or alkaline earth metals to compensate for the charge, such as various zeolites, and the like.

[0083] In the polymer composition of the present disclosure, the blending amount of inorganic filler (silica, carbon black, and other fillers) is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, per 100 parts by mass of the rubber component contained in the polymer composition. The blending amount of filler is preferably 150 parts by mass or less, more preferably 130 parts by mass or less. When the blending amount of filler in the polymer composition is within the above range, when the polymer composition of the present disclosure is used for manufacturing a tire tread, low rolling resistance, braking performance on wet road surfaces, handling performance on dry road surfaces, and abrasion resistance of the tire can be improved while simultaneously achieving even higher levels of compatibility.

[0084] [F] Other Rubber Component The polymer composition of the present disclosure may contain only the conjugated diene polymer (A) as the rubber component. Furthermore, in addition to the conjugated diene polymer (A), the composition may contain a rubber component (hereinafter also referred to as the other rubber component) different from the conjugated diene polymer (A) as long as the effects of the present disclosure are not impaired. Examples of the other rubber component include one or more diene rubbers selected from natural rubber, isoprene rubber, butadiene rubber, emulsion-polymerized styrene-butadiene rubber, solution-polymerized styrene-butadiene rubber, butyl rubber, halogenated butyl rubber, and ethylene-propylene rubber. Among these, at least one selected from natural rubber, butadiene rubber, and styrene-butadiene rubber is preferred as the other rubber component. The manner in which the other rubber component and the conjugated diene polymer (A) are mixed is not particularly limited. For example, the other rubber component and the conjugated diene polymer (A) may be mixed during kneading using a Banbury mixer, roll mixer, or the like, as is commonly done. Alternatively, other rubber components may be added to the conjugated diene polymer (A) in a solution state after polymerization.

[0085] The amount of the other rubber components to be blended is preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 40% by mass or less, based on the total amount of the rubber components (the conjugated diene polymer (A) and the other rubber components) contained in the polymer composition.

[0086] In the present disclosure, from the viewpoint of further improving dry grip performance, wet grip performance, and blowout resistance, a liquid rubber may be used as part or all of the other rubber components.

[0087] Examples of liquid rubbers include liquid polyisoprene (liquid IR), liquid polybutadiene (liquid BR), liquid styrene-butadiene copolymer (liquid SBR), and liquid ethylene-propylene copolymer (liquid EP). For example, liquid SBR having a weight average molecular weight of 1,000 to 100,000, preferably 2,000 to 80,000, can be used. Note that the weight average molecular weight referred to in this specification refers to the weight average molecular weight in terms of polystyrene as analyzed by gel permeation chromatography (GPC). The liquid rubber used in this disclosure refers to one that has fluidity at 23°C.

[0088] Resin [G] The polymer composition of the present disclosure may contain a thermoplastic or thermosetting resin (hereinafter also simply referred to as "resin (G)"). From the viewpoint of obtaining a vulcanized rubber with excellent properties such as strength, abrasion resistance, and crack growth resistance, the resin (G) is preferably at least one selected from the group consisting of styrene-based resins, polyethylene, C5-based resins, C9-based resins, C5 / C9-based resins, dicyclopentadiene (DCPD)-based resins, dicyclopentadiene / C9-based resins, alkylphenol-based resins, terpene-based resins, hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated dicyclopentadiene-based resins, hydrogenated dicyclopentadiene / C9-based resins, and hydrogenated terpene-based resins. Thermoplastic resins are particularly preferably used as the resin (G) because of their high effect of improving various properties such as strength, abrasion resistance, and crack growth resistance.

[0089] Here, the styrene-based resin is a polymer obtained using a styrene-based monomer, and in particular, a polymer having structural units derived from a styrene-based monomer in an amount of 20 mass% or more relative to the total amount of monomer units possessed by the styrene-based resin is preferred. Examples of the styrene-based monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene. Of these, the styrene-based monomer is preferably at least one of styrene and α-methylstyrene.

[0090] The styrene-based resin may be a homopolymer obtained by polymerizing one type of styrene-based monomer, or a copolymer obtained by copolymerizing two or more types of styrene-based monomers. The styrene-based resin may also be a copolymer obtained by using a styrene-based monomer and another monomer copolymerizable with the styrene-based monomer. Examples of the other monomer include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene, butadiene, and isoprene, olefins such as 1-butene and 1-pentene, and α,β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof.

[0091] As the styrene-based resin, a block polymer (thermoplastic elastomer) having a conjugated diene polymer block as a soft segment and a polystyrene-based block as a hard segment can also be used.

[0092] Specific examples of the block polymer include styrene-butadiene block copolymers, styrene-isoprene block copolymers, epoxidized styrene-butadiene block copolymers, block copolymers in which a portion of the conjugated diene polymer block contained in a styrene-butadiene block copolymer or a styrene-isoprene block copolymer has been hydrogenated, etc. More specifically, styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-ethylene-butylene-styrene block copolymers (SEBS), and epoxidized styrene-butadiene-styrene block copolymers, as well as hydrogenated products of these copolymers, etc. can be preferably used.

[0093] Examples of polyethylene include low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), etc. C5 resins are produced by catalyzing a C5 fraction with a Friedel-Crafts catalyst (AlCl ３ or BF ３It is a solid polymer (C5 synthetic petroleum resin) obtained by polymerization using isoprene, cyclopentadiene, 1,3-pentadiene, 1-pentene, etc. Specific examples of C5 resins include copolymers mainly composed of isoprene, cyclopentadiene, 1,3-pentadiene, 1-pentene, etc., copolymers of 2-pentene and dicyclopentadiene, and polymers mainly composed of 1,3-pentadiene.

[0094] C9 resins were prepared by subjecting C9 fraction to Friedel-Crafts catalyst (AlCl ３ or BF ３ A solid polymer (C9 synthetic petroleum resin) obtained by polymerization using a methyl indene, methyl indene, coumarone, vinyl toluene, etc. is a specific example of a C9 resin.

[0095] C5 / C9 resins are produced by subjecting C5 to C9 fractions to Friedel-Crafts catalyst (AlCl ３ or BF ３ It is a solid polymer (C5 / C9 synthetic petroleum resin) obtained by polymerization using a copolymer of vinyl toluene, indene, or the like. Specific examples of C5 / C9 resins include copolymers mainly composed of vinyl toluene, indene, or the like. From the viewpoint of compatibility with rubber components, C5 / C9 resins with a small amount of C9 or higher components are preferred. Specifically, the C5 / C9 resin preferably contains less than 50% by mass, and more preferably 40% by mass or less, of the total amount of the resin containing C9 or higher components.

[0096] Dicyclopentadiene (DCPD)-based resins are petroleum resins that use dicyclopentadiene in the C5 fraction as the main raw material. Specific examples of dicyclopentadiene-based resins include the "Marukarets M" series (M-890A, M-845A, M-990A, etc.) manufactured by Maruzen Petrochemical Co., Ltd.

[0097] Dicyclopentadiene / C9 resin is a petroleum resin made primarily from dicyclopentadiene (DCPD) in the C5 fraction and the C9 fraction. Specific examples of dicyclopentadiene / C9 resins include ENEOS Corporation's product name "EP-140."

[0098] Examples of alkylphenol-based resins include alkylphenol-acetylene resins such as p-tert-butylphenol-acetylene resin, and alkylphenol-formaldehyde resins with a low degree of polymerization.

[0099] Terpene resins are solid resins obtained by blending turpentine oil, which is obtained simultaneously when rosin is obtained from pine trees, or a polymerization component separated from the turpentine oil, and polymerizing the blend using a Friedel-Crafts catalyst, and examples of such resins include β-pinene resin and α-pinene resin. Commercially available terpene resins can be used, and examples include the "Picolite" series (A115, S115, etc.) manufactured by Hercules.

[0100] A representative example of a terpene-aromatic compound resin is a terpene-phenol resin. This terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing them with formalin. There are no particular limitations on the terpenes used as raw materials; monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred. In the present disclosure, a terpene-phenol resin with a low ratio of phenolic components is preferred. Here, "low ratio of phenolic components" refers to a phenolic component content of less than 50% by mass, preferably 40% by mass or less, of the total resin. Using a terpene-aromatic compound resin, particularly a terpene-phenol resin, as resin (G) can further improve handling performance. As the terpene-aromatic compound resin, commercially available products can be used, for example, trade names "Tamanol 803L" and "Tamanol 901" (manufactured by Arakawa Chemical Industries, Ltd.), trade name "SYLVATRAXX4202" (manufactured by Arizona Chemical Co., Ltd.), etc.

[0101] Hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated dicyclopentadiene resins, hydrogenated dicyclopentadiene / C9 resins, and hydrogenated terpene resins (hereinafter collectively referred to as "hydrogenated resins") are resins obtained by hydrogenating raw material resins. Commercially available hydrogenated resins can be used. For example, hydrogenated C5 resins include those under the trade name "Impera (registered trademark) E1780" (manufactured by Eastman Co.); hydrogenated C9 resins include those under the trade name "Alcon M135" (manufactured by Arakawa Chemical Industries, Ltd.); hydrogenated dicyclopentadiene resins include those under the trade name "Oppera PR-120" (manufactured by ExxonMobil Corporation) and "T-REZ HA125" (manufactured by ENEOS Corporation); and hydrogenated dicyclopentadiene / C9 resins include those under the trade name "T-REZ PR803" (manufactured by ENEOS Corporation).

[0102] The blending ratio of resin (G) is preferably 1 part by mass or more per 100 parts by mass of the rubber component contained in this blend. Blending 1 part by mass or more of resin (G) is preferable because the effect of improving abrasion resistance, breaking strength, and crack growth resistance due to the addition of resin (G) can be sufficiently enhanced in the crosslinked product obtained using this blend. The blending ratio of resin (G) is more preferably 3 parts by mass or more, and even more preferably 7 parts by mass or more per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of maintaining various performance properties of the blend well, the blending ratio of resin (G) is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less per 100 parts by mass of the rubber component contained in this blend.

[0103] [H] Silane Coupling Agent In the polymer composition of the present disclosure, the dispersibility of silica can be further improved by blending a silane coupling agent together with silica. There are no particular restrictions on the silane coupling agent used. Among them, sulfur-containing silane coupling agents are preferred, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, γ-mercaptopropyltriethoxysilane, and 3-octanoylthiopropyltriethoxysilane.

[0104] The amount of the silane coupling agent is preferably 1 to 20 parts by mass per 100 parts by mass of silica. When the amount of the silane coupling agent is 1 part by mass or more, the amount is sufficient and the dispersibility of the silica can be sufficiently improved. Furthermore, when the amount of the silane coupling agent is 20 parts by mass or less, the processability and elongation at break of the polymer composition can be maintained good. The amount of the silane coupling agent is more preferably 5 to 15 parts by mass per 100 parts by mass of silica.

[0105] [I] Crosslinking Agent The polymer composition of the present disclosure may contain a crosslinking agent. By containing a crosslinking agent in the polymer composition of the present disclosure, a crosslinked product with sufficiently improved strength and abrasion resistance can be obtained. Examples of crosslinking agents include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, and alkylphenol resins having methylol groups, with sulfur typically being used. The amount of crosslinking agent is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the total amount of rubber components contained in the polymer composition.

[0106] [J] Extender Oil The polymer composition of the present disclosure may contain a process oil commonly used to extend elastomers as an oil for oil extension (extender oil). The method for adding the process oil is not particularly limited. For example, the process oil may be dispersed in a conjugated diene polymer solution after polymerization and then desolvated to form an oil-extended rubber, or the process oil may be directly added to the polymer composition during kneading using a Banbury mixer or roll mixer. Preferred process oils include various oils known in the art, such as aromatic oils, paraffinic oils, naphthenic oils, vegetable oils, and oils with a low content of polycyclic aromatic compounds (low PCA oils), such as mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), special residual aromatic extracts (SRAE), and heavy naphthenic oils. Examples of commercially available MES, TDAE, and SRAE include Catenex SNR (heavy paraffin obtained by dewaxing distillate oil with a solvent) manufactured by Shell as an MES, Vivatec 500 manufactured by H&R Wasag AG as a TDAE, and NC140 manufactured by Japan Energy Corp. The amount of process oil to be blended is preferably 10 to 100 parts by mass per 100 parts by mass of the total amount of polymer components contained in the polymer composition.

[0107] In addition to the components described above, the polymer composition may contain various additives that are generally used in polymer compositions for obtaining vulcanized rubber, such as zinc oxide, stearic acid, softeners, vulcanization accelerators, compatibilizers, vulcanization aids, processing aids, scorch inhibitors, etc. The amounts of these additives added may be appropriately selected depending on the various components, as long as they do not impair the effects of the present disclosure.

[0108] The polymer composition of the present disclosure can be applied to various rubber products as a crosslinked body by kneading the rubber component and other components blended as necessary using a kneader such as an open kneader (e.g., a roll) or an internal kneader (e.g., a Banbury mixer), molding the mixture, and then crosslinking (vulcanizing). Specifically, the crosslinked body can be applied to various applications, such as tire applications such as tire treads, undertreads, carcasses, sidewalls, and bead portions; sealing materials such as packings, gaskets, weatherstrips, and O-rings; interior and exterior skin materials for various vehicles such as automobiles, ships, aircraft, and railways; building materials; vibration-proof rubbers for industrial machinery and equipment; various hoses and hose covers such as diaphragms, rolls, radiator hoses, and air hoses; belts such as power transmission belts; linings; dust boots; medical device materials; fenders; insulating materials for electric wires; and other industrial products.

[0109] The conjugated diene polymer (A) can provide a crosslinked product having excellent physical properties required for tire applications, such as strength, rolling resistance, wet grip performance, etc. Therefore, a polymer composition containing the conjugated diene polymer can be suitably used particularly as a material for a tire cap tread, a sidewall, or both.

[0110] Tires can be manufactured by conventional methods, for example, by mixing the polymer composition in a kneader, forming a sheet, and then disposing the sheet in a predetermined position (for example, on the outside of the carcass in the case of a sidewall) and vulcanizing the sheet in a conventional manner to form a tread or a sidewall, thereby obtaining a pneumatic tire.

[0111] According to the present disclosure described above in detail, the following means are provided: [Means 1] A conjugated diene-based polymer containing a structural unit derived from butadiene and a structural unit derived from an aromatic vinyl compound, wherein, when the constituent ratios (molar ratios) in the polymer of the structural unit represented by the above formula (1), the structural unit represented by the above formula (2), the structural unit represented by the above formula (3), and the structural unit represented by the above formula (4) are p, q, r, and s, respectively, the value α represented by the above formula (i) is 0.60 or more and 0.97 or less, the proportion of the structural unit derived from the aromatic vinyl compound is 5% by mass or more and 50% by mass or less, and the ratio is measured using deuterated chloroform as a solvent. １ A conjugated diene polymer having a θst value calculated from an H-NMR spectrum by the above formula (ii) of more than 4% by mass and less than 27% by mass. [Means 2] The conjugated diene polymer of [Means 1], having a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, phosphorus, silicon, and sulfur. [Means 3] The conjugated diene polymer of [Means 1] or [Means 2], containing 15% by mass or more and 75% by mass or less of a polymer having a multibranched structure having four or more molecular chains. [Means 4] The conjugated diene polymer of any of [Means 1] to [Means 3], having a proportion of structural units derived from aromatic vinyl compounds of 25% by mass or more and 50% by mass or less. [Means 5] The conjugated diene polymer of any of [Means 1] to [Means 3], having a β value represented by the above formula (iii) of 0.05 to 0.70. [Means 6] A polymer composition containing the conjugated diene polymer of any of [Means 1] to [Means 5], and an antioxidant. [Means 7] The polymer composition of [Means 6] further containing a resin. [Means 8] The polymer composition of [Means 6] or [Means 7] further containing an extender oil. [Means 9] The polymer composition of any of [Means 6] to [Means 8] further containing an inorganic filler. [Means 10] The polymer composition of [Means 9], wherein the inorganic filler comprises silica and further contains a silane coupling agent. [Means 11] A crosslinked product obtained by crosslinking the polymer composition of any of [Means 6] to [Means 10]. [Means 12] A tire in which one or both of a cap tread and a sidewall are constituted by a cured product of the polymer composition of any of [Means 6] to [Means 10].

[0112] The following provides a detailed explanation based on examples. However, the present disclosure is not limited to these examples. In the examples and comparative examples, "parts" and "%" are by mass unless otherwise specified. The methods for measuring various physical properties of the polymer are shown below.

[0113] [Evaluation of polymer properties] Vinyl bond content (mol%): For the polymer before hydrogenation, １ Bound styrene content (%): The polymer before hydrogenation was measured by 1H-NMR at 400 MHz. １ Column: Two GMH-HR-H columns (manufactured by Tosoh Corporation) were connected in series. Detector: Differential refractometer RI-8020 (manufactured by Tosoh Corporation) Eluent: Tetrahydrofuran Column temperature: 40°C Flow rate: 1.0 ml / min Sample concentration: 10 mg / 20 mL Total weight-average molecular weight: For the polymer before hydrogenation, a chart based on the molecular weight in terms of polystyrene was obtained using a gel permeation chromatograph (GPC, product name: HLC-8020 (manufactured by Tosoh Corporation)), and the 1st peak average molecular weight was determined from the retention time of the peak with the longest retention time in the obtained GPC curve. The specific measurement conditions are as follows. (Measurement conditions) Column: Two GMH-HR-H columns (manufactured by Tosoh Corporation) were connected in series. Detector: Differential refractometer RI-8020 (manufactured by Tosoh Corporation) Eluent: Tetrahydrofuran Column temperature: 40°C Flow rate: 1.0 ml / min Sample concentration: 10 mg / 20 mL Total weight-average molecular weight: For the polymer before hydrogenation, the total weight-average molecular weight was determined in terms of polystyrene from all peaks in the GPC curve obtained using GPC (HLC-8020 (manufactured by Tosoh Corporation)). The measurement conditions were the same as above. Coupling rate (mass%): The proportion of coupling polymers having two or more molecular chains was calculated from the peak area ratio of the GPC curve obtained using GPC (HLC-8020 (product name (manufactured by Tosoh Corporation))) for the polymer before hydrogenation. Hydrogenation rate and α: Measured using a 400 MHz device with deuterated chloroform as a solvent. １It was calculated from the H-NMR spectrum. Content of polymer (A1): It was calculated by separating the waveform of a coupling polymer having four or more branches in a GPC curve obtained using GPC (HLC-8020 (product name (manufactured by Tosoh Corporation)) for the polymer before hydrogenation. Styrene sequence length ratio (mass%): The styrene sequence length ratio θst, which is the ratio of chains in which 8 or more styrene structural units are connected to all styrene structural units in the polymer, was calculated as follows. １ From the H-NMR spectrum, the ratio of the integral value Σ(a) in the range (a) to the total integral value Σ(a, b, c) in each of the following chemical shift ranges (a) to (c) was calculated, and this value was multiplied by 2.5 to obtain the styrene sequence length content θst [wt %] (see the following mathematical formula (ii)): (a) 8 or more aromatic vinyl compound chains: 6.00≦S<6.68 (b) 2 to 7 aromatic vinyl compound chains: 6.68≦S<6.89 (c) short aromatic vinyl compound chains: 6.89≦S≦8.00 θst=[(Σ(a) / Σ(a, b, c))×2.5]×100 ...(ii)

[0114] <Production of Hydrogenated Conjugated Diene Polymer> [Example 1: Synthesis and Properties of Hydrogenated Conjugated Diene Polymer A-1] A nitrogen-purged 50-liter autoclave reactor was charged with 25,800 g of cyclohexane, 26 g of tetrahydrofuran, 0.32 g of potassium dodecylbenzenesulfonate, 1,505 g of styrene, and 2,709 g of 1,3-butadiene. After adjusting the temperature of the reactor contents to 45°C, a cyclohexane solution containing n-butyllithium (34 mmol) was added to initiate polymerization. The polymerization was carried out under adiabatic conditions. After confirming that the polymerization conversion rate had reached 99%, 86 g of 1,3-butadiene was added (additional butadiene), and the polymerization was continued for an additional 3 minutes to obtain a reaction solution containing a polymer. 2.0 mmol of tetrachlorosilane was added to the resulting reaction solution, and the reaction was continued for 5 minutes. 26 mmol of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was then added, and the reaction was continued for 15 minutes. Next, the reaction solution was heated to 80°C or higher, and hydrogen was introduced into the system, allowing the reaction to proceed for 1 hour. A small amount of the polymer solution was withdrawn from the reaction vessel, and a pre-hydrogenated conjugated diene polymer was obtained for analysis. Thereafter, 3.56 g of diethylaluminum chloride, 2.72 g of bis(η5-cyclopentadienyl)titanium(furfuryloxy)chloride, and 1.23 g of n-butyllithium were added, and the hydrogenation reaction was carried out while maintaining a hydrogen pressure of 1.0 MPa. After the reaction, hydrogen was supplied until a predetermined integrated hydrogen value was reached while maintaining a hydrogen pressure of 0.7 MPa or higher, and the reaction solution was then returned to room temperature and pressure and withdrawn from the reaction vessel, yielding a polymer solution containing hydrogenated conjugated diene polymer A-1. A small amount of the resulting polymer solution was withdrawn, subjected to steam stripping to remove the solvent, and dried using a heated roll adjusted to 130°C, yielding hydrogenated conjugated diene polymer A-1. The polymerization recipe for the hydrogenated conjugated diene polymer A-1 is shown in Table 1, and various physical properties of the hydrogenated conjugated diene polymer A-1 are shown in Table 3.

[0115] [Examples 2, 3, 5 to 12, Comparative Examples 3 to 5: Production of hydrogenated conjugated diene polymers A-2, A-3, A-5 to A-12, A-15 to A-17, and their physical properties] Polymer solutions containing hydrogenated conjugated diene polymers A-2, A-3, A-5 to A-12, and A-15 to A-17 were obtained in the same manner as in Example 1, except that the polymerization recipe was changed as shown in Tables 1 and 2, and the hydrogenation rate was changed as shown in Tables 3 and 4. The physical properties of the hydrogenated conjugated diene polymers A-2, A-3, A-5 to A-12, and A-15 to A-17 are shown in Tables 3 and 4.

[0116] Example 4: Synthesis and Properties of Hydrogenated Conjugated Diene Polymer A-4 A 50-liter autoclave reactor purged with nitrogen was charged with 25,800 g of cyclohexane, 26 g of tetrahydrofuran, 0.86 g of potassium dodecylbenzenesulfonate, 645 g of styrene, and 645 g of 1,3-butadiene. The temperature of the reactor contents was adjusted to 45°C, and a cyclohexane solution containing n-butyllithium (39 mmol) was added to initiate polymerization. The polymerization was carried out under adiabatic conditions. When the temperature of the contents reached 55°C (corresponding to the point at which the polymerization conversion rate reached 30%), 3,010 g of 1,3-butadiene (additional amount) was added to the reactor at a constant feed rate over 10 minutes. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85°C. It was confirmed that the polymerization conversion rate had reached 99%, and a reaction liquid containing a polymer was obtained. 2.3 mmol of tetrachlorosilane was added to the resulting reaction solution and reacted for 5 minutes. 29 mmol of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was then added and reacted for 15 minutes. The reaction solution was then heated to 80°C or higher, hydrogen was introduced into the system, and the reaction was continued for 1 hour. A small amount of the polymer solution was withdrawn from the reaction vessel to obtain a pre-hydrogenated conjugated diene polymer for analysis. Thereafter, 4.08 g of diethylaluminum chloride, 3.56 g of bis(η5-cyclopentadienyl)titanium(furfuryloxy)chloride, and 1.61 g of n-butyllithium were added, and the hydrogenation reaction was carried out while maintaining a hydrogen pressure of 1.0 MPa. After the reaction, hydrogen was supplied until a predetermined integrated hydrogen value was reached while maintaining a hydrogen pressure of 0.7 MPa or higher, and the reaction was continued. The reaction solution was then returned to room temperature and pressure and withdrawn from the reaction vessel to obtain a polymer solution containing hydrogenated conjugated diene polymer A-4. A small amount of the obtained polymer solution was withdrawn, the solvent was removed by steam stripping, and the solution was dried with a heated roll adjusted to 130°C to obtain a hydrogenated conjugated diene polymer A-4. The polymerization formulation of the hydrogenated conjugated diene polymer A-4 is shown in Table 1, and various physical property values ​​of the hydrogenated conjugated diene polymer A-4 are shown in Table 3.

[0117] Comparative Example 1: Production of hydrogenated conjugated diene polymer A-13 and its physical properties A polymer solution containing hydrogenated conjugated diene polymer A-13 was obtained in the same manner as in Example 4, except that the polymerization recipe was changed as shown in Table 2 and the hydrogenation rate was changed as shown in Table 4. The physical properties of the hydrogenated conjugated diene polymer A-13 are shown in Table 4.

[0118] Comparative Example 2: Synthesis and Properties of Hydrogenated Conjugated Diene Polymer A-14 A 50-liter autoclave reactor purged with nitrogen was charged with 25,800 g of cyclohexane, 26 g of tetrahydrofuran, 1,505 g of styrene, and 2,709 g of 1,3-butadiene. The temperature of the reactor contents was adjusted to 45°C, and a cyclohexane solution containing n-butyllithium (34 mmol) was added to initiate polymerization. The polymerization was carried out under adiabatic conditions. After confirming that the polymerization conversion had reached 99%, 86 g of 1,3-butadiene was added (additional butadiene), and the polymerization was continued for an additional 3 minutes to obtain a reaction solution containing a polymer. 2.0 mmol of tetrachlorosilane was added to the resulting reaction solution and the reaction was continued for 5 minutes, followed by the addition of 26 mmol of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane and the reaction was continued for 15 minutes. The reaction solution was then heated to 80°C or higher, hydrogen was introduced into the system, and the reaction was continued for 1 hour. A small amount of the polymer solution was withdrawn from the reaction vessel, and a pre-hydrogenated conjugated diene polymer was obtained for analysis. Thereafter, 3.56 g of diethylaluminum chloride, 2.72 g of bis(η5-cyclopentadienyl)titanium(furfuryloxy)chloride, and 1.23 g of n-butyllithium were added, and a hydrogenation reaction was carried out while maintaining a hydrogen pressure of 1.0 MPa. After the reaction, hydrogen was supplied until a predetermined integrated hydrogen value was reached while maintaining a hydrogen pressure of 0.7 MPa or more, and the reaction solution was then returned to room temperature and pressure and withdrawn from the reaction vessel, yielding a polymer solution containing hydrogenated conjugated diene polymer A-14. A small amount of the obtained polymer solution was withdrawn, subjected to steam stripping to remove the solvent, and dried using a heated roll adjusted to 130°C, yielding hydrogenated conjugated diene polymer A-14. The polymerization recipe for the hydrogenated conjugated diene polymer A-14 is shown in Table 2, and various physical properties of the hydrogenated conjugated diene polymer A-14 are shown in Table 4.

[0119] Comparative Example 6: Production of hydrogenated conjugated diene polymer A-18 and its physical properties A polymer solution containing hydrogenated conjugated diene polymer A-18 was obtained in the same manner as in Comparative Example 2, except that the polymerization recipe was changed as shown in Table 2 and the hydrogenation rate was changed as shown in Table 4. The physical properties of the hydrogenated conjugated diene polymer A-18 are shown in Table 4.

[0120]

[0121]

[0122] In Tables 1 and 2, "-" means that the compound in the corresponding column was not used. The abbreviations for the vinyl content adjuster, terminal modifier, and coupling agent are as follows: V-1: potassium dodecylbenzenesulfonate Compound 1: N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane Compound 2: tetrachlorosilane

[0123]

[0124]

[0125] <Production and Evaluation of Polymer Compositions and Crosslinked Products (1)> Using each of the hydrogenated conjugated diene polymers A-1 to A-18 produced above, the components were blended according to the formulation shown in Table 5, and the blends were kneaded to produce polymer compositions. Kneading was performed as follows. Using a plastomill (capacity: 250 mL) equipped with a temperature control device, in the first stage of kneading, the hydrogenated modified conjugated diene polymers (A-1 to A-18), silica, carbon black, a silane coupling agent, an extender oil, stearic acid, zinc oxide, and an antioxidant were blended and kneaded at a filling rate of 72% and a rotation speed of 60 rpm to obtain polymer composition A. Next, in the second stage of kneading, the obtained polymer composition A was cooled to room temperature, and then a vulcanization accelerator and sulfur were blended and kneaded to obtain polymer composition B. The obtained polymer composition B was molded and vulcanized in a vulcanization press at 160°C for a predetermined time to obtain a crosslinked product (vulcanized rubber). The processability, rolling resistance, strength and wet grip performance were evaluated as follows, and the results are shown in Tables 6 and 7.

[0126] (1) Processability: Using rubber before vulcanization (polymer composition B) as a measurement sample, Mooney viscosity was measured in accordance with JIS K6300 using an L rotor under the conditions of 1 minute of preheating, 4 minutes of rotor operation time, and a temperature of 100°C. Expressed as an index with Comparative Example 1 set to 100, a value of 110 or more was evaluated as "A," a value of 90 or more but less than 110 was evaluated as "B," a value of 80 or more but less than 90 was evaluated as "C," and a value of less than 80 was evaluated as "D." A larger index value indicates a smaller Mooney viscosity and better processability.

[0127] (2) Rolling resistance (50°C tan δ): Using a vulcanized rubber as a measurement sample, the ratio of loss modulus G" to storage modulus G' (50°C tan δ) was measured using a shear-type dynamic spectrometer (manufactured by TA Instruments) under conditions of an angular velocity of 100 radians per second, a temperature of 50°C, and a shear strain of 3%. Expressed as an index with Comparative Example 1 set to 100, a value of 110 or more was evaluated as "A," a value of 90 or more but less than 110 was evaluated as "B," a value of 80 or more but less than 90 was evaluated as "C," and a value of less than 80 was evaluated as "D." A higher index value indicates better rolling resistance.

[0128] (3) Strength (TB*EB): Vulcanized rubber was used as the test sample and a tensile test was conducted in accordance with JIS K6251:2010. Here, a dumbbell-shaped No. 3 was used as the test sample, and the stress at break (TB, unit: MPa) and elongation at break (EB, unit: %) were measured at room temperature. The larger the TB and EB values, the higher the break strength and the better the mechanical strength of the material. The strength was calculated according to the formula (TB*EB) / 2. Expressed as an index with Comparative Example 1 set to 100, a value of 110 or more was rated "A," a value of 90 or more but less than 110 was rated "B," a value of 80 or more but less than 90 was rated "C," and a value of less than 80 was rated "D." A higher index value indicates higher strength and better performance.

[0129] (4) Wet grip performance (0 ° C tan δ): Using a vulcanized rubber as a measurement sample, the loss factor (tan δ (0 ° C)) was measured using an ARES-RDA (manufactured by TA Instruments) under conditions of a shear strain of 0.14%, an angular velocity of 100 radians per second, and 0 ° C. The measurement results were expressed as an index with Comparative Example 2 set to 100. If the index was 110 or more, it was evaluated as "A", if it was 90 or more but less than 110, it was evaluated as "B", if it was 80 or more but less than 90, it was evaluated as "C", and if it was less than 80, it was evaluated as "D". The higher the index value, the better the wet grip performance.

[0130]

[0131] The details in Table 5 are as follows: *1) ZEOSIL 1165MP manufactured by Rhodia *2) SEAST 3 manufactured by Tokai Carbon *3) Si75 manufactured by Evonik *4) T-DAE process oil manufactured by ENEOS *5) Ozonone 6C manufactured by Seiko Chemical Co., Ltd. *6) Noccela CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. *7) Noccela D manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0132]

[0133]

[0134] As shown in Table 6, the hydrogenated conjugated diene polymers of Examples 1 to 12 were able to improve the processability of the polymer composition, as well as the strength, rolling resistance, and wet grip performance of the crosslinked product in a well-balanced manner. Of these, Examples 1 to 3, 5 to 9, 11, and 12 were rated "A" or "B" in all four evaluation items, demonstrating a good balance of various properties.

[0135] In contrast, as shown in Table 7, Comparative Example 1, in which the θst of the hydrogenated conjugated diene polymer exceeded 50% by mass, and Comparative Example 4, in which α was less than 0.6, were rated "D" for strength. Furthermore, Comparative Example 2, in which θst was 4% by mass or less, and Comparative Example 3, in which α was greater than 0.97, did not receive a "D" in the evaluation results, but were overall inferior to Examples 1 to 12. Comparative Example 5, in which the bound styrene content exceeded 50% by mass, was rated "D" for rolling resistance, and Comparative Example 6, in which the bound styrene content was less than 5% by mass, was rated "D" for processability and wet grip performance.

[0136] <Production and Evaluation of Polymer Compositions and Crosslinked Products (2)> Using each of the hydrogenated conjugated diene polymers A-1 to A-18 produced above, the components were blended according to the formulations shown in Tables 8 to 11, and the blends were kneaded to produce polymer compositions. Kneading was carried out in the same manner as in Examples 1 to 12 and Comparative Examples 1 to 6. Furthermore, processability, rolling resistance, strength, and wet grip performance were evaluated in the same manner as in Examples 1 to 12 and Comparative Examples 1 to 6. The results are shown in Tables 8 to 11. In Tables 8 to 11, "-" means that the compound in the corresponding column was not used.

[0137]

[0138]

[0139]

[0140]

[0141] Details in Tables 8 to 11 are as follows. *1) to *7) Same as the explanation in Table 5 *8) Resin 1: T-REZ PR802 (C5 / C9 resin) manufactured by ENEOS Corporation *9) Resin 2: T-REZ PR803 (hydrogenated DCPD / C9 resin) manufactured by ENEOS Corporation *10) Resin 3: SYLVARES SA85 (α-methylstyrene resin) manufactured by Kraton Corporation SBR: HPR355R manufactured by ENOES Materials NR: RSS#3

[0142] As shown in Tables 8 and 9, Examples 13 to 41, which used the hydrogenated conjugated diene polymers A-1 to A-12 produced in Examples 1 to 12, achieved a well-balanced improvement in the processability of the polymer composition, and the rolling resistance, strength, and wet grip performance of the crosslinked product, even in systems in which non-hydrogenated SBR was used in combination. In contrast, Comparative Examples 7 to 19, which used the hydrogenated conjugated diene polymers A-13 to A-18 produced in Comparative Examples 1 to 6, were not rated "A" in any of the evaluation items or were rated "D" in one of the evaluation items, and were generally inferior to Examples 13 to 41.

[0143] Furthermore, as shown in Tables 10 and 11, Examples 42 to 70, which used the hydrogenated conjugated diene polymers A-1 to A-12 produced in Examples 1 to 12, were able to improve the processability of the polymer composition, and the rolling resistance, strength, and wet grip performance of the crosslinked product in a well-balanced manner, even in systems in which natural rubber was used in combination. In contrast, Comparative Examples 20 to 32, which used the hydrogenated conjugated diene polymers A-13 to A-18 produced in Comparative Examples 1 to 6, were not rated "A" in any of the evaluation items or were rated "D" in one of the evaluation items, and were generally inferior to Examples 42 to 70.

Claims

1. A conjugated diene polymer containing a structural unit derived from butadiene and a structural unit derived from an aromatic vinyl compound, wherein when the composition ratios (molar ratios) of the structural unit represented by the following formula (1), the structural unit represented by the following formula (2), the structural unit represented by the following formula (3), and the structural unit represented by the following formula (4) in the polymer are p, q, r, and s, respectively, the value α represented by the following mathematical formula (i) is 0.60 or more and 0.97 or less, the proportion of the structural unit derived from the aromatic vinyl compound is 5% by mass or more and 50% by mass or less, and measured using deuterated chloroform as a solvent １ a conjugated diene polymer in which the value θst calculated by the following mathematical formula (ii) from the 1H-NMR spectrum is more than 4% by mass and less than 27% by mass. α = (p + (0.5 × r)) / (p + q + (0.5 × r) + s) …(i) θst = [(Σ(a) / Σ(a, b)) × 2.5] × 100 …(ii) (In formula (ii), Σ(a) represents the integral value in the chemical shift range of 6.00 ≤ σ < 6.89, and Σ(a, b) represents the integral value in the chemical shift range of 6.00 ≤ σ ≤ 8.00.) 2. The conjugated diene polymer according to claim 1, having a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, phosphorus, silicon, and sulfur.

3. The conjugated diene polymer according to claim 1, containing 15% by mass or more and 75% by mass or less of a polymer having a multi-branched structure with four or more molecular chains.

4. The conjugated diene polymer according to claim 1, wherein the proportion of the structural unit derived from the aromatic vinyl compound is 25% by mass or more and 50% by mass or less.

5. The conjugated diene polymer according to claim 1, wherein the value β represented by the following formula (iii) is 0.05 or more and 0.70 or less. β = (p + q) / (p + q + (0.5 × r) + s) …(iii) 6. A polymer composition containing the conjugated diene polymer according to claim 1 and an antioxidant.

7. The polymer composition according to claim 6, further containing a resin.

8. The polymer composition according to claim 6, further containing an extender oil.

9. The polymer composition according to claim 6, further containing an inorganic filler.

10. The polymer composition according to claim 9, wherein the inorganic filler contains silica and further contains a silane coupling agent.

11. A crosslinked product obtained by crosslinking the polymer composition according to any one of claims 6 to 10.

12. A tire in which one or both of the cap tread and the sidewall are constituted by a cured product of the polymer composition according to any one of claims 6 to 10.

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