Conjugated diene polymers and their manufacturing methods, polymer compositions, crosslinks and tires

Abstract

A conjugated diene polymer, wherein when the structural units represented by formulas (1) to (4) are in the polymer in a molar ratio of p, q, r, and s respectively, the value α represented by formula (i) is 0.65 to 0.97, and the conjugated diene polymer is made as follows: containing 25% to 75% by mass of a polymer (A1) having a multi-branched structure having four or more molecular chains, wherein the polymer (A1) has a functional group comprising at least one element selected from the group consisting of nitrogen, oxygen, and sulfur in one or both of the end portion and the branch point portion of the polymer.

Description

[Technical Field]

[0001] This disclosure relates to a conjugated diene polymer, a method for manufacturing the same, polymer compositions, crosslinks, and tires. [Cross-Reference to Related Applications]

[0002] This application is based on Japanese Patent Application No. 2021-41264, filed on March 15, 2021, the contents of which are incorporated herein by reference. [Previous Technology]

[0003] Conjugated diene polymers obtained by polymerizing conjugated diene compounds are widely used in various industrial products such as pneumatic tires, vibration damping rubber, and hoses due to their excellent heat resistance, wear resistance, mechanical strength, and processability.

[0004] As polymer components used in the manufacture of pneumatic tires, such as the tread and sidewall, it is known that inorganic fillers such as carbon black or silica are formulated as reinforcing agents while formulating conjugated diene polymers to improve the durability or wear resistance of the product. Furthermore, conventionally, to improve the affinity between the conjugated diene polymer and the reinforcing agent, conjugated diene polymers modified with compounds containing silica or nitrogen have been used (for example, see Patent Documents 1 to 3).

[0005] In addition, in recent years, it has been proposed to use hydrides of conjugated diene polymers with functional groups such as amino or alkoxysilyl groups at one or both ends to obtain tire components with high strength and excellent wear resistance (see Patent Document 4). [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2008 / 123164 [Patent Document 2] Japanese Patent Publication No. 11-349632 [Patent Document 3] International Publication No. 2017 / 221943 [Patent Document 4] International Publication No. 2014 / 133097 [Summary of the Invention]

[0007] [Problem to be Solved by the Invention] Due to the current environmental conditions and increased awareness of resource conservation / energy saving, there is a desire to extend the lifespan of rubber products, increase their service life, or achieve product lightweighting or miniaturization while maintaining performance. Therefore, there is a need for a cross-linked material (vulcanized rubber) that can achieve greater strength and superior wear resistance than before.

[0008] However, generally speaking, abrasion resistance and strength are inversely related to processability; improving one tends to reduce the performance of the other. In order to manufacture higher quality rubber products such as tires, it is required that each of these properties is also excellent.

[0009] Furthermore, when the polymer solution has a high viscosity, the flowability of the polymer solution decreases. Therefore, it may be difficult to smoothly transfer the polymer solution in piping or to containers, or, in the case of a hydrogenation reaction, the hydrogen diffusivity within the polymer solution decreases, and the hydrogenation time becomes longer. In such cases, sufficient productivity cannot be guaranteed.

[0010] This disclosure was made in view of the aforementioned problems, one of the objectives of which is to provide a conjugated diene polymer that can uniformly improve the strength and wear resistance of crosslinked bodies, as well as the processability of polymer compositions, and has sufficiently low solution viscosity. [Means for Solving the Problems]

[0011] According to this disclosure, the following conjugated diene polymers, manufacturing methods thereof, polymer compositions, crosslinks and tires are provided. [1] A conjugated diene polymer, wherein when the structural units represented by the following formula (1), the following formula (2), the following formula (3) and the following formula (4) are respectively set as p, q, r and s, the value α represented by the following formula (i) is 0.65 to 0.97, and the conjugated diene polymer comprises 25% to 75% by mass of a polymer (A1) having a multi-branched structure having four or more molecular chains, wherein the polymer (A1) has a functional group comprising at least one element selected from the group consisting of nitrogen, oxygen and sulfur in one or both of the terminal portion and the branch point portion of the polymer (A1), α=(p+(0.5×r)) / (p+q+(0.5×r)+s)…(i) [Chemical 1]

[0012] [2] A method for manufacturing a conjugated diene polymer, comprising: a polymerization step, wherein a monomer containing a conjugated diene compound is polymerized in the presence of a metal compound having an alkali metal or an alkaline earth metal to obtain a conjugated diene polymer (I) having an active end; a reaction step, wherein the conjugated diene polymer (I) is reacted with a compound [B] having four or more functional groups capable of reacting with the active end to obtain a conjugated diene polymer (II); and a hydrogenation step, wherein hydrogen is added in such a manner that the hydrogenation rate of the structural units of the conjugated diene compound having the conjugated diene polymer (II) is 65% to 97%, wherein the reaction step is a step of reacting the conjugated diene polymer (I) with the compound [B] in such a manner that the conjugated diene polymer (II) contains 25% to 75% by mass of a polymer having a multi-branched structure having four or more molecular chains, wherein at least one element selected from the group consisting of the metal compound and the compound [B] comprises at least one element selected from the group consisting of nitrogen, oxygen and sulfur.

[0013] [3] A polymer composition comprising the conjugated diene polymer of [1] or the conjugated diene polymer obtained by the manufacturing method of [2], and an inorganic filler. [4] A crosslinked body formed by crosslinking the polymer composition of [3]. [5] A tire having one or both of a tread or a sidewall formed using the polymer composition of [3]. [Effects of the Invention]

[0014] According to the conjugated diene polymer disclosed herein, a crosslinked body with high strength and excellent wear resistance can be obtained. Furthermore, the solution viscosity of the conjugated diene polymer disclosed herein is sufficiently low, resulting in excellent manufacturability. Moreover, according to this disclosure, a crosslinked body with high strength and excellent wear resistance can be obtained, and a polymer composition with excellent processability (particularly Munich viscosity and cold flow characteristics) can be obtained.

Implementation Method

[0016] Hereinafter, matters related to the implementation of this disclosure will be explained in detail. Furthermore, in this specification, the numerical range recorded by "~" indicates the range including the numerical values ​​recorded before and after "~" as the lower limit and upper limit values.

[0017] 《[A] Conjugated Diene Polymers》 Regarding the conjugated diene polymers disclosed herein (hereinafter also referred to as "[A] conjugated diene polymers"), when the composition ratios (molar ratios) of the structural units represented by the following formula (1), the following formula (2), the following formula (3), and the following formula (4) in the polymer are respectively set as p, q, r, and s, the value α represented by the following formula (i) is 0.65 to 0.97. α=(p+(0.5×r)) / (p+q+(0.5×r)+s)…(i) [Chemical 2]

[0018] [A]conjugated diene polymers are aggregates of high molecules having structural units derived from conjugated diene compounds, including polymers with multi-branched structures (i.e., branched polymers). Specifically, [A]conjugated diene polymers include, relative to the total amount of [A]conjugated diene polymers (100% by mass), 25% to 75% by mass of a branched polymer containing four or more molecular chains, namely polymer (A1). Furthermore, polymer (A1) has at least one element selected from the group consisting of nitrogen, oxygen, and sulfur (hereinafter also referred to as "specific element") in one or both of its terminal portion and branch point portion. Such [A]conjugated diene polymers can be manufactured by a method including polymerization, reaction, and hydrogenation steps. Moreover, when polymer (A1) has a specific element in its terminal portion, polymer (A1) may have the specific element in all ends (i.e., free ends) or in only a portion of the ends. The branching point of a branched polymer refers to the branching part of the molecular chain; in other words, it is the end (i.e., the fixed end) on the side opposite to the free end of each molecular chain. The following will explain the manufacturing method of the [A] conjugated diene polymer while also describing its structure.

[0019] <Polymerization Step> This step involves polymerizing a monomer containing a conjugated diene compound to obtain a conjugated diene polymer (hereinafter also referred to as "conjugated diene polymer (I)") with active ends. Conjugated diene polymer (I) is an aggregate of polymers having structural units derived from a conjugated diene compound and having active ends. Examples of conjugated diene compounds used in the polymerization include: 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-heptadiene, 2-phenyl-1,3-butadiene, 3-methyl-1,3-pentadiene, 2-chloro-1,3-butadiene, etc. Of these, at least one is selected from the group consisting of 1,3-butadiene, isoprene and 2,3-dimethyl-1,3-butadiene, and more preferably at least any one of 1,3-butadiene and isoprene.

[0020] [A] The conjugated diene polymer may be a homopolymer of a conjugated diene compound, but from the viewpoint of a crosslinker with higher strength, it is preferred to be a copolymer having structural units derived from both conjugated diene compounds and aromatic vinyl compounds. Examples of aromatic vinyl compounds used in the polymerization include: styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-tert-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-tert-butylstyrene, 3-tert-butylstyrene, vinylxylene, vinylnaphthalene, vinylpyridine, diphenylethylene, and diphenylethylene containing a tertiary amino group (e.g., 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene). Among these, styrene and α-methylstyrene are preferred.

[0021] When the [A] conjugated diene polymer is a copolymer of a conjugated diene compound and an aromatic vinyl compound, in terms of high activity in anionic polymerization, it is preferable that the monomer composition includes a copolymer of 1,3-butadiene and styrene. In terms of improving the dispersibility of the inorganic filler, the copolymer is preferably a random copolymeric portion having an irregular distribution of the conjugated diene compound and the aromatic vinyl compound. When the [A] conjugated diene polymer is a random copolymer of a conjugated diene compound and an aromatic vinyl compound, it may have a block portion containing either a conjugated diene compound or an aromatic vinyl compound, while also having a random copolymeric portion.

[0022] When the [A]conjugated diene polymer is a copolymer of a conjugated diene compound and an aromatic vinyl compound, the proportion of structural units derived from the aromatic vinyl compound in the [A]conjugated diene polymer is preferably more than 0% by mass and less than 45% by mass relative to all structural units constituting the [A]conjugated diene polymer. By setting this range, it is preferable to obtain a crosslinked body with higher strength and excellent wear resistance while simultaneously achieving good processability of the polymer composition, and to sufficiently reduce the solution viscosity of the polymer. Regarding the aspects of sufficiently reducing the solution viscosity of the polymer, increasing the strength of the crosslinked body, and achieving good cold flow characteristics, the proportion of structural units derived from the aromatic vinyl compound is preferably more than 2% by mass, and more preferably more than 5% by mass relative to all structural units constituting the [A]conjugated diene polymer. Furthermore, from the perspective of reducing the Munich viscosity of the polymer and suppressing the reduction of the wear resistance of the crosslinked body, the proportion of structural units derived from aromatic vinyl compounds relative to all structural units constituting the [A] conjugated diene polymer is preferably 40% by mass or less, more preferably 38% by mass or less, and even more preferably 35% by mass or less.

[0023] Furthermore, the proportion of structural units derived from aromatic vinyl compounds in the polymer is determined by 1H-nuclear magnetic resonance (1H-NMR). Conjugated diene compounds and aromatic vinyl compounds may be used individually or in combination of two or more.

[0024] The monomers used in the polymerization reaction to obtain the [A]conjugated diene polymer may include compounds other than conjugated diene compounds and aromatic vinyl compounds (hereinafter also referred to as "other monomers"). Examples of other monomers include acrylonitrile, methyl methacrylate, ethyl methacrylate, etc. The proportion of other monomers used relative to the total amount of monomers used in the polymerization is preferably set to 10% by mass or less, more preferably 5% by mass or less.

[0025] As the polymerization method used, any one of solution polymerization, gas-phase polymerization, and bulk polymerization can be used, with solution polymerization being particularly preferred. Furthermore, as the polymerization form, either batch polymerization or continuous polymerization can be used. In the case of solution polymerization, as a specific example of a polymerization method, a method for polymerizing a monomer containing a conjugated diene compound in an organic solvent in the presence of a polymerization initiator and, if necessary, a randomizer (vinyl content adjuster).

[0026] As a polymerization initiator, a metal compound having an alkali metal or alkaline earth metal can be used. Among these, a compound having an alkali metal is preferred. Specific examples of alkali metal compounds include: alkyl lithium such as methyl lithium, ethyl lithium, n-propyl lithium, n-butyl lithium, dibutyl lithium, and tributyl lithium; 1,4-dilithiobutane, phenyl lithium, lithium stilbene, naphthyl lithium, 1,3-bis(1-lithium-1,3-dimethylpentyl)benzene, 1,3-epoxyphenylbis(3-methyl-1-phenylpentyl)dilithium, sodium naphthyl, potassium naphthyl, and potassium ethoxy. Among these, a lithium compound is preferred as the polymerization initiator.

[0027] Furthermore, the metal compound used as the polymerization initiator can also be a metal amide compound containing an alkali metal or alkaline earth metal. By carrying out polymerization to obtain [A]conjugated diene polymers in the presence of a metal amide compound, amine groups (preferably secondary or tertiary amine groups) can be introduced into the polymerization initiation end of the conjugated diene polymer (more specifically, the free end portion of the branched polymer). The [A]conjugated diene polymers obtained by polymerization in the presence of a metal amide compound exhibit better balanced performance in terms of the strength and wear resistance of the crosslinked body and the processability of the polymer composition.

[0028] As a metal amine compound, it is preferably a compound obtained by mixing a lithium compound (e.g., alkyllithium) with a compound having a nitrogen atom (hereinafter also referred to as a "starting-end modifier"). The starting-end modifier is preferably a secondary amine compound. Specific examples of secondary amine compounds include: dimethylamine, diethylamine, dipropylamine, dibutylamine, dodecylmethyleneimine, 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, 1,3-di-trimethylsilyl-1,3,5-triazacyclohexane, etc.

[0029] Furthermore, when polymerization is carried out in the presence of a metalloamine compound, the metalloamine compound can be prepared by pre-mixing a lithium compound and an initiator, and then the prepared metalloamine compound can be added to the polymerization system for polymerization. Alternatively, the metalloamine compound can be prepared by adding a lithium compound and an initiator to the polymerization system and mixing them in the polymerization system for polymerization. During the polymerization, the amount of polymerization initiator used (the total amount when using two or more) is preferably set to 0.01 mmol to 20 mmol, more preferably 0.05 mmol to 15 mmol, relative to 100 g of monomer used in the synthesis of the polymer.

[0030] Randomizing agents can be used to adjust the vinyl bond content, which indicates the percentage of vinyl bonds in a polymer. Examples of randomizing agents include: dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, 2,2-di(tetrahydrofuranyl)propane, 2-(2-ethoxyethoxy)-2-methylpropane, triethylamine, pyridine, N-methylmorpholine, tetramethylethylenediamine, potassium dodecylbenzenesulfonate, etc. These can be used alone or in combination of two or more.

[0031] As the organic solvent used in the polymerization, any organic solvent that is inert in the reaction can be used, such as chain or cyclic aliphatic hydrocarbons, aromatic hydrocarbons, etc. Among these, hydrocarbons with 3 to 8 carbon atoms are preferred. Specific examples include: propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propylene, 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, cyclohexene, etc. Furthermore, one or more organic solvents can be used alone or in combination as organic solvents.

[0032] In the case of solution polymerization, from the viewpoint of maintaining a balance between productivity and ease of polymerization control, the monomer concentration in the reaction solvent is preferably 5% to 50% by mass, more preferably 10% to 30% by mass. The polymerization temperature is preferably -20°C to 150°C, more preferably 0°C to 120°C. Furthermore, the polymerization reaction is preferably carried out at a pressure sufficient to substantially maintain the monomer in a liquid phase. This pressure can be obtained by pressurizing the reactor using a gas that is inert for the polymerization reaction. Through this polymerization reaction, a conjugated diene polymer (I) with active terminals can be obtained.

[0033] For the conjugated diene polymer (I) obtained by the polymerization, the vinyl bond content in the structural units derived from 1,3-butadiene is preferably 15 mol% to 85 mol%. By setting the vinyl bond content to 15 mol% or more, the obtained crosslinked body maintains flexibility, has good processability, and tends to have excellent wear resistance in low-slip regions. Furthermore, the solution viscosity and Munich viscosity of the polymer can be sufficiently reduced. The vinyl bond content of the conjugated diene polymer (I) is preferably 18 mol% or more, and more preferably 20 mol% or more. In addition, from the viewpoint of the durability and cold flow characteristics of the crosslinked body obtained using the [A] conjugated diene polymer, the vinyl bond content of the conjugated diene polymer (I) is preferably 78 mol% or less, and more preferably 65 mol% or less. Furthermore, in this specification, "vinyl bond content" refers to the proportion of structural units having 1,2-bonds relative to all structural units derived from 1,3-butadiene in the unhydrogenated conjugated diene polymer, and is a value obtained by measuring using a 1H-NMR apparatus.

[0034] <Reaction Step> In this step, the following steps are performed: the conjugated diene polymer (I) obtained by the polymerization step is reacted with a compound having four or more functional groups capable of reacting with the active ends of the conjugated diene polymer (I) (hereinafter also referred to as "[B] coupling agent" or "compound [B]") to obtain a conjugated diene polymer (II). The conjugated diene polymer (II) is an aggregate of polymers having structural units derived from conjugated diene compounds.

[0035] The [B] coupling agent used in the manufacture of [A] conjugated diene polymers is not particularly limited as long as it is a compound having four or more reaction sites with the active ends of the conjugated diene polymer. Among these, a compound having at least one element selected from the group consisting of nitrogen, oxygen, sulfur, and silicon is preferably used as the [B] coupling agent. When a compound having the aforementioned specific element is used as the [B] coupling agent, it is preferable to obtain a crosslinked body in which the strength and wear resistance of the crosslinked body and the processability of the polymer composition (more specifically, Munich viscosity and cold flow) are improved in a more balanced manner.

[0036] Specific examples of coupling agents for [B] include silicon-containing compounds such as tetrachlorosilane (silicon tetrachloride), tetramethoxysilane, bis(trichlorosilyl)ethane, etc.

[0037] Additionally, as a [B] coupling agent, a compound having a functional group F comprising at least one element selected from the group consisting of nitrogen, oxygen, and sulfur (a specific element) and having four or more reaction sites with the polymer chain obtained by the polymerization step may also be used (hereinafter, also referred to as "terminal modifier (b1)"). By using the terminal modifier (b1), a polymer having a functional group F at the branching point portion in the branched polymer can be obtained.

[0038] Specific examples of functional group F include: primary amino group, secondary amino group, tertiary amino group, protected primary amino group, protected secondary amino group, imine group, nitrogen-containing heterocyclic group (e.g., a group having a pyridine ring, acetoimine ring, or other heterocyclic ring), hydroxyl group, protected hydroxyl group, thiol group, protected thiol group, alkyloxysilyl group, etc. Regarding functional group F, in terms of its high effect on improving wear resistance, it is preferable to have a nitrogen-containing functional group (nitrogen-containing group), and particularly preferably to have at least one selected from the group consisting of primary amino group, secondary amino group, tertiary amino group, and imine group.

[0039] As an end modifier (b1), at least one compound selected from the group consisting of the compound represented by formula (5) and the compound represented by formula (6) can be used. [Chemistry 3] (In formula (5), R1 and R2 are each independently a hydrocarbon group with 1 to 20 carbon atoms, R3 is an alkyl diol with 1 to 20 carbon atoms, and A1 is a group "*-C(R5)=N-" or a group "*-N=C(R5)-" (where R5 is a hydrogen atom or a hydrocarbon group, and "*" indicates a bond bonded to R4). R4 is a hydrocarbon group with 1 to 20 carbon atoms in m valence, or a hydrocarbon group with 1 to 20 carbon atoms in m valence that has at least one element selected from the group consisting of nitrogen, oxygen and sulfur and has no active hydrogen bonded to that element. n is an integer from 1 to 3, and m is an integer from 2 to 10. In the formula, multiple R1, R2, R3, A1, and n may be the same or different. In the case where m is 2 or 3, the sum of multiple n is m+4 or more.) [Chemistry 4] (In formula (6), R6, R7, R10 and R11 are each independently a hydrocarbon group having 1 to 20 carbon atoms, R8 and R9 are each independently an alkyldiyl group having 1 to 20 carbon atoms, and A2 is a group represented by formula (7), formula (8), formula (9), or formula (10). w and p are each independently an integer from 1 to 3. Wherein, when A2 is formula (9) or formula (10), w and p are 3. In the formula, multiple R6, R7, R10, and R11 may be the same or different.) [Chem.5] (In formula (7), R12, R13 and R15 are each an independent hydrocarbon group with 1 to 20 carbon atoms, R14 and R16 are each an independent alkyldiyl group with 1 to 20 carbon atoms, q is an integer from 1 to 3, and r is an integer from 0 to 2. In the formula, multiple R12 to R15 are either the same group or different groups, and multiple q are either the same number or different numbers. Among them, the sum of p, w and q minus r is 6 or more. "*" indicates a bond with the nitrogen atom in formula (6).) [Chemical Engineering 6] (In formula (8), R19 is an alkyldiyl group with 3 to 20 carbon atoms, forming a ring structure with 5 or more members with the nitrogen and silicon atoms in the formula; R17 and R18 are each an alkyl group with 1 to 20 carbon atoms, R20 is an alkyldiyl group with 1 to 20 carbon atoms, and s is 1 or 2. In the formula, multiple R17 and R18 are the same or different. Among them, the total of p, w and s is 7 or more. "*" indicates a bond with the nitrogen atom in formula (6).) [Chemical Engineering 7] (In formula (9), R23 is an alkyldiyl group with 1 to 20 carbon atoms, R21 is a hydrocarbylidene group with 1 to 20 carbon atoms, R22 is an alkyldiyl or alkenediyl group with 1 to 20 carbon atoms, forming a ring structure with 5 or more members with the two adjacent nitrogen atoms; "*" indicates a bond with the nitrogen atom in formula (6).[Chem. 8] ​​(In formula (10), R26 is a hydrocarbon group with 1 to 20 carbon atoms, and R24 and R25 are each independently hydrocarbon groups with 1 to 20 carbon atoms, or represent a ring structure with 4 to 20 carbon atoms formed by R24 and R25 bonded together with the nitrogen atoms bonded to R24 and R25, or represent a ring structure with 5 or more members formed by R24 and R25 bonded together with the nitrogen atoms bonded to R24 and R25, and nitrogen atoms or oxygen atoms different from the nitrogen atoms bonded to R24 and R25. "*" indicates a bond with the nitrogen atom in formula (6).)

[0040] (The compound represented by formula (5)) In formula (5), the hydrocarbon groups of R1 and R2 can be, for example, alkyl groups with 1 to 20 carbon atoms, allyl groups, cycloalkyl groups with 3 to 20 carbon atoms, aryl groups with 6 to 20 carbon atoms, etc. The alkyl diel group of R3 is preferably 1 to 10 carbon atoms, more preferably 2 to 10 carbon atoms. R3 is preferably linear. The description of R1 and R2 applies to the hydrocarbon group of R5 possessed by A1. In terms of improving the dispersibility of silicon dioxide, N is preferably 2 or 3, more preferably 3.

[0041] As the m-valent hydrocarbon group of R4, examples include groups formed by removing m hydrogen atoms from chain hydrocarbons having 1 to 20 carbon atoms, alicyclic hydrocarbons having 3 to 20 carbon atoms, or aromatic hydrocarbons having 6 to 20 carbon atoms. Specific examples of aromatic hydrocarbons include ring structures represented by the following formula (C1), and polycyclic structures formed by linking two or more of these ring structures (e.g., biphenyl). [Chemical 9] (In formula (C1), r1 is an integer from 0 to 5.)

[0042] As a preferred specific example, when R4 is an m-valent group having 1 to 20 carbon atoms and having at least one element selected from the group consisting of nitrogen, oxygen, and sulfur, and having no active hydrogen atoms bonded to that element, examples include m-valent heterocyclic groups and m-valent groups having a tertiary amine structure. The heterocyclic group is preferably a conjugated system, and examples include monocyclic or condensed rings such as pyridine, pyrimidine, pyrazine, quinoline, naphthidine, furan, and thiophene, or groups formed by removing m hydrogen atoms from the ring portion of a structure formed by linking multiple such monocyclic or condensed rings. m is an integer from 2 to 10. From the viewpoint of the processability of the polymer composition, m is preferably 2 to 6.

[0043] Specific examples of compounds represented by formula (5) may include compounds represented by formulas (M-1) to (M-4) below. In formula (M-1) below, R27 represents a hydrogen atom or an alkyl group, and n1 represents an integer from 1 to 8. [Chemical 10]

[0044] (The compound represented by formula (6)) In formulas (6) and (7) to (10), the hydrocarbon groups of R6, R7, R10, R11, R12, R13, R15, R17, R18, R24 and R25 that have 1 to 20 carbon atoms can be, for example, alkyl groups with 1 to 20 carbon atoms, allyl groups, cycloalkyl groups with 3 to 20 carbon atoms, aryl groups with 6 to 20 carbon atoms, etc. The alkyldiyl, alkyldiyl, and alkylyl groups of R8, R9, R14, R16, R20, R21, R22, R23 and R24 that have 1 to 20 carbon atoms are preferably 1 to 10 carbon atoms, more preferably 2 to 10 carbon atoms. R19 is preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms. In formula (8), the ring structure formed by R19, nitrogen atoms, and silicon atoms is preferably a 5- to 7-membered ring, more preferably a 5- or 6-membered ring. In formula (9), the ring structure formed by R21, R22, and two adjacent nitrogen atoms is preferably a 5- to 12-membered ring, more preferably a 5- to 7-membered ring. In formula (10), when R24 and R25 represent a ring structure with 4 to 20 carbon atoms formed by the combination of R24 and R25 and the nitrogen atoms bonded to R24 and R25, the ring structure is preferably 4 to 9 carbon atoms, more preferably 4 to 6 carbon atoms. In the case where R24 and R25 represent a ring structure of 5 or more members formed by the combination of R24 and R25 with nitrogen atoms bonded to R24 and R25, and nitrogen atoms or oxygen atoms different from those bonded to R24 and R25, the ring structure is preferably a 5- to 10-membered ring, more preferably a 5- to 7-membered ring. Specific examples of the 5- or more-membered ring structure include piperazine ring structures, morpholine ring structures, etc. Regarding the high improvement effect on silicon dioxide dispersibility, w, p, and q are preferably 2 or 3, more preferably 3. For the same reason, s is preferably 2.

[0045] As a specific example of the compound represented by the formula (6), the compound in which A2 in the formula (6) is the group represented by the formula (7) can be listed as follows: N,N,N',N'-tetra(3-trimethoxysilylpropyl)ethylenediamine, N,N,N',N'-tetra(3-triethoxysilylpropyl)ethylenediamine, N,N,N'-tris(3-trimethoxysilylpropyl)-N'-methyl-ethylenediamine, N,N,N',N'-tetra(3-trimethoxysilylpropyl)-1,3-propanediamine, N,N,N',N'-tetra(3-trimethoxysilylpropyl)-1,4-butanediamine, bis(3-trimethoxysilylpropyl)-[2-(dimethylamino)ethyl]amine, etc. Compounds in which A2 in formula (6) is a base represented by formula (8) include, for example: bis(3-trimethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silazopentanyl)ethyl]amine, bis(3-triethoxysilylpropyl)-[2-(2,2-diethoxy-1-aza-2-silazopentanyl)ethyl]amine, bis(3-trimeth ... Compounds in which A2 in formula (6) is a group represented by formula (9) include, for example, N,N-bis(3-trimethoxysilylpropyl)-3-imidazolylpropylamine; compounds in which A2 in formula (6) is a group represented by formula (10) include, for example, bis(3-trimethoxysilylpropyl)-(3-dimethylaminopropyl)amine.

[0046] When a metalloamine compound is used as the polymerization initiator in the polymerization step, a compound that does not contain any of nitrogen, oxygen, and sulfur (e.g., the silicon-containing compound) can be used as the [B] coupling agent, or an end modifier (b1) can be used. On the other hand, when a metalloamine compound is not used as the polymerization initiator in the polymerization step, an end modifier (b1) is used as the [B] coupling agent. Among these, in terms of further improving the strength and wear resistance of the obtained crosslinked body and the processability of the polymer composition, it is preferable to use a metalloamine compound as the polymerization initiator in the polymerization step and a silicon-containing compound (e.g., silicon tetrachloride) as the [B] coupling agent in this step, or to use a metalloamine compound as the polymerization initiator in the polymerization step and an end modifier (b1) as the [B] coupling agent in this step.

[0047] The reaction between the conjugated diene polymer (I) with active terminals and the [B] coupling agent is preferably carried out in the form of a solution reaction. The proportion of the [B] coupling agent used (the total amount when two or more are used) can be appropriately set to a range where the proportion of the polymer (A1) is within the desired range. Specifically, from the viewpoint of obtaining a crosslinked body exhibiting high strength and excellent wear resistance, and at the same time obtaining a polymer composition with excellent processability, the proportion of the [B] coupling agent used is preferably 0.01 mol or more, and more preferably 0.05 mol or more, relative to 1 mol of the metal atoms participating in polymerization of the polymerization initiator (i.e., the metal compound). Furthermore, from the viewpoint of adjusting the coupling rate to a desired value, suppressing the reduction in processability, and sufficiently reducing the solution viscosity of the polymer to ensure productivity, the proportion of the [B] coupling agent used is preferably 0.7 mol or less, and more preferably 0.5 mol or less, relative to 1 mol of the metal atoms participating in polymerization of the polymerization initiator. Furthermore, as a [B] coupling agent, it can be used alone or in combination with two or more.

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

[0049] In the coupling reaction, the coupling rate can be set according to the proportion of the unhydrogenated polymer (A1) present in the conjugated diene polymer (II), or the molecular weight of the conjugated diene polymer (I), the number of functional groups of the [B] coupling agent, etc. From the viewpoint of obtaining a crosslinked body with high strength and excellent wear resistance, the coupling rate is preferably 25% or more, and more preferably 30% or more. In addition, from the viewpoint of obtaining a polymer composition with good processability and from the viewpoint of sufficiently reducing the solution viscosity of the polymer to ensure productivity, the coupling rate is preferably 75% or less, and more preferably 70% or less.

[0050] Furthermore, in this specification, "coupling rate" refers to the proportion (mass %) of coupled polymers having two or more molecular chains in the reaction system after reacting a linear conjugated diene polymer with an active end and a compound capable of reacting with the active end. Specifically, it refers to the proportion (mass %) of polymers with two or more linear molecular chains bonded by the [B] coupling agent or end-modifier (c) in the total amount of polymers used in the reaction with the [B] coupling agent or end-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 a gel permeation chromatograph (GPC). Similarly, the proportion of coupled polymers having four or more molecular chains can also be calculated from the peak area ratio of the GPC curve obtained using a gel permeation chromatograph (GPC).

[0051] A conjugated diene polymer (II) can be obtained by the coupling reaction. The conjugated diene polymer (II) preferably contains a linear or three-branched (i.e., the pre-hydrogenated polymer (A2)) branched polymer (i.e., the pre-hydrogenated polymer (A1)) along with a pre-hydrogenated polymer (A1). The linear or three-branched branched polymer is a polymer contained in the conjugated diene polymer (I) that has three or fewer linear molecular chains bonded by a [B] coupling agent or a terminal modifier (c), or an unreacted polymer that has not reacted with the [B] coupling agent and the terminal modifier (c), or both. In conjugated diene polymers (II), the ratio of polymers with a multi-branched structure having four or more molecular chains (i.e., the unhydrogenated polymer (A1)) to linear or branched polymers with three or fewer branches can be appropriately set by adjusting the amount of [B] coupling agent used or the functional group of the [B] coupling agent used, in such a way that the ratio of polymer (A1) and polymer (A2) in the [A] conjugated diene polymer is respectively the desired ratio.

[0052] Furthermore, in the case of separating conjugated diene polymers contained in the reaction solution, this can be done, for example, by known solvent removal methods such as steam stripping and drying operations such as heat treatment.

[0053] <Modification Step> The obtained conjugated diene polymer (II) can be directly supplied to the next hydrogenation step. Alternatively, prior to the hydrogenation step, a treatment can be performed to react the polymerization terminus of the linear polymer contained in the conjugated diene polymer (II) with a terminal modifier (c). As the terminal modifier (c), a compound having at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon and capable of reacting with the active terminus of the linear polymer can be used. In this case, a linear or three-branched or less branched polymer having a functional group containing at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon can be obtained. Furthermore, the terminal modifier (c) differs from the [B] coupling agent in that the reaction point with the active terminus of the conjugated diene polymer (I) is three or less.

[0054] As a preferred specific example of the end modifier (c), at least one of the group consisting of compounds represented by formula (11) and compounds represented by formula (12) can be listed. [Formula 11] (In formula (11), A11 is a monovalent functional group or (thio)epoxy group bonded to a carbon atom contained in nitrogen, phosphorus, oxygen, sulfur and silicon, without active hydrogen, and relative to R35. R33 and R34 are each independently hydrocarbon groups. R35 is an extended hydrocarbon group. t is an integer from 0 to 2. Wherein, when t is 2, the plurality of R33 in the formula are the same or different from each other. When t is 0 or 1, the plurality of R34 in the formula are the same or different from each other.) [Chem. 12] (In formula (12), A12 is a monovalent functional group or a hydrocarbon group with 1 to 20 carbon atoms bonded to R39 by nitrogen, phosphorus, oxygen, sulfur and silicon, without active hydrogen. R36 and R37 are each a hydrocarbon group independently. R38 is an extended hydrocarbon group. R39 is a single bond or an extended hydrocarbon group. u is 0 or 1. In the case where u is 0, the multiple R37s in the formula are the same or different from each other.)

[0055] In formulas (11) and (12), for R33, R34, R36, R37 and A12 when they are hydrocarbon groups, the hydrocarbon group is preferably a straight-chain or branched alkyl group with 1 to 20 carbon atoms, a cycloalkyl group with 3 to 20 carbon atoms, or an aryl group with 6 to 20 carbon atoms. The hydrocarbon group represented by R35 and R39 is preferably a straight-chain or branched alkyldiyl group with 1 to 20 carbon atoms, a cycloalkyl group with 3 to 20 carbon atoms, or an aryl group with 6 to 20 carbon atoms. The hydrocarbon group represented by R38 is preferably a straight-chain or branched alkyldiyl group with 1 to 20 carbon atoms. t is preferably 0 or 1.

[0056] When A11 is the monovalent functional group, A11 may contain at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon. When A12 is the monovalent functional group, A12 may contain at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, for example, protected by a trisubstituted alkyl silyl group. Furthermore, in this specification, active hydrogen refers to a hydrogen atom bonded to an atom other than a carbon atom, preferably a hydrogen atom with a bonding energy lower than the carbon-hydrogen bond of polymethylene. (Thio)epoxy group refers to a group containing both epoxy groups and thioepoxy groups.

[0057] A11 can also be a group that can become a onium ion by an onium salt generating agent. By having this group (A11) in the end modifier (c), the polymer can be endowed with excellent shape retention. Specific examples of A11 include: nitrogen-containing groups formed by replacing two hydrogen atoms of a primary amine group with two protecting groups, nitrogen-containing groups formed by replacing one hydrogen atom of a secondary amine group with one protecting group, tertiary amine group, imine group, pyridyl group, phosphorus-containing groups formed by replacing two hydrogen atoms of a primary phosphine group with two protecting groups, phosphorus-containing groups formed by replacing one hydrogen atom of a secondary phosphine group with one protecting group, tertiary phosphine group, epoxy group, thioepoxy group, groups formed by replacing hydrogen atoms of a hydroxyl group with protecting groups, sulfur-containing groups formed by replacing hydrogen atoms of a thiol group with protecting groups, hydrocarbon oxycarbonyl group, etc. Of these, those with good affinity for silicon dioxide are preferably nitrogen-containing groups, more preferably tertiary amine groups, or nitrogen-containing groups formed by replacing two hydrogen atoms of a primary amine group with two protecting groups. Furthermore, the protecting group refers to a functional group that converts Al1 or Al2 into an inert functional group relative to the polymerization active end. Furthermore, the onium salt forming agent is Bronsted acid or a compound that forms Bronsted acid by contacting water.

[0058] Specific examples of the end modifier (c) and compounds represented by the formula (11) include, for example, 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-piperazinyl)propylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, etc.

[0059] Specific examples of compounds represented by formula (12) include, for example: 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1,2-azasilcyclopentane, 2,2-diethoxy-1-(3-trimethoxysilylpropyl)-1,2-azasilcyclopentane, 2,2-dimethoxy-1-phenyl-1,2-azasilcyclopentane, 1-trimethylsilyl-2,2-dimethoxysilane Methoxy-1-aza-2-silazopentanyl, 2-(2,2-dimethoxy-1,2-azasilazopentanyl-1-yl)-N,N-diethylethane-1-amine, 2-(2,2-dimethoxy-1,2-azasilazopentanyl-1-yl)-N,N-dimethylethane-1-amine, 3-(2,2-dimethoxy-1,2-azasilazopentanyl-1-yl)-N,N-diethylpropane-1-amine, etc. As end-modifiers (c), one can be used alone, or two or more can be used in combination.

[0060] The reaction between the conjugated diene polymer (II) and the end modifier (c) can be carried out, for example, in the form of a solution reaction. This solution reaction can be carried out using either a batch reaction or a continuous reaction. In this case, there are no particular restrictions on the method of adding the end modifier (c), and methods such as simultaneous addition, intermittent addition, and continuous addition can be listed.

[0061] The amount of the terminal modifier (c) used can be appropriately set according to the type of compound used in the reaction. The amount of terminal modifier (c) used is preferably 0.05 mol or more, and more preferably 0.1 mol or more, relative to 1 mol of metal atoms participating in the polymerization reaction in the polymerization initiator. By setting the amount of terminal modifier (c) to 0.1 mol equivalent or more, the modification reaction can be fully carried out, thereby better improving the dispersibility of the inorganic filler. Furthermore, the amount of terminal modifier (c) is preferably 1.0 mol or less, and more preferably 0.8 mol or less, relative to 1 mol of metal atoms participating in the polymerization reaction in the polymerization initiator.

[0062] The reaction temperature of the end-modification reaction is usually the same as that of the polymerization reaction, preferably -20℃ to 150℃, more preferably 0℃ to 120℃, and even more preferably 20℃ to 100℃. If the temperature of the modification reaction is low, the viscosity of the polymer solution tends to increase. In addition, if the temperature of the modification reaction is high, the polymeric active ends are easily deactivated. The reaction time for end-modification is preferably 1 minute to 5 hours, more preferably 2 minutes to 1 hour.

[0063] <Hydrogenation Step> In this step, the conjugated diene polymer obtained by the aforementioned reaction step or modification step is hydrogenated (hereinafter also referred to as "hydrogenation"). Regarding the method and conditions of the hydrogenation reaction, any method and conditions can be used as long as a conjugated diene polymer with the desired hydrogenation rate can be obtained. Examples of such hydrogenation methods include: methods using a catalyst with a titanium organometallic compound as the main component as the hydrogenation catalyst; methods using a catalyst containing organometallic compounds such as iron, nickel, and cobalt, and organometallic compounds such as alkylaluminum; methods using organometallic complexes containing organometallic compounds such as ruthenium and rhodium; and methods using a catalyst in which metals such as palladium, platinum, ruthenium, cobalt, and nickel are supported on a carrier such as carbon, silicon dioxide, or alumina. Among various methods, the method of hydrogenation under mild conditions of low pressure and low temperature, using only an organometallic compound of titanium, or using a homogeneous catalyst containing an organometallic compound of titanium and organometallic compounds of lithium, magnesium and aluminum (e.g., the catalysts described in Japanese Patent Publication No. 63-4841 and Japanese Patent Publication No. 1-37970), is better for industrial applications. In addition, the hydrogenation selectivity for the double bond of butadiene is also appropriately increased.

[0064] The hydrogenation of conjugated diene polymers is preferably carried out using a solvent that is inert to the catalyst and soluble in the conjugated diene polymer. 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 can be one of the aforementioned compounds or a mixture thereof as a main component.

[0065] Hydrogenation reactions are generally carried out by maintaining a conjugated diene polymer at a specified temperature in a hydrogen or inert environment, adding a hydrogenation catalyst with or without stirring, and then introducing hydrogen gas and pressurizing to a specified pressure. An inert environment refers to an environment that does not react with the substances participating in the hydrogenation reaction; examples include environments with helium, neon, and argon. Air or oxygen is undesirable because it oxidizes the catalyst, leading to catalyst deactivation. Additionally, nitrogen is undesirable because it acts as a catalyst poison during the hydrogenation reaction, reducing hydrogenation activity. Ideally, the hydrogenation reactor should contain a hydrogen-only environment.

[0066] The hydrogenation reaction process can utilize any of the batch process, continuous process, or combinations thereof. Furthermore, when using a diaryl terephthalene compound as the hydrogenation catalyst, it can be added directly to the reaction solution alone, or in the form of a solution of an inert organic solvent. When using the catalyst in solution form, the inert organic solvent used can be any solvent that does not react with the substances participating in the hydrogenation reaction. Preferably, it is the same solvent used in the hydrogenation reaction. Additionally, the preferred amount of catalyst added is 0.02 mmol to 20 mmol per 100 g of the conjugated diene polymer before hydrogenation.

[0067] [A] In conjugated diene polymers, when the composition ratios (molar ratios) of the structural units represented by the following formula (1), the following formula (2), the following formula (3), and the following formula (4) in the polymer are respectively set as p, q, r, and s, the value α represented by the following formula (i) is 0.65 or more and 0.97 or less. α=(p+(0.5×r)) / (p+q+(0.5×r)+s)…(i) [Chemistry 13]

[0068] [A] In terms of obtaining a crosslinked body with better wear resistance in conjugated diene polymers, the value α represented by the formula (i) is preferably 0.70 or more, more preferably 0.75 or more, more preferably 0.80 or more, and particularly preferably 0.85 or more. Furthermore, the value α represented by the formula (i) corresponds to the hydrogenation rate of the conjugated diene polymer. For example, when α is 0.65, the hydrogenation rate of the conjugated diene polymer is 65%. Additionally, from the viewpoint of forming a crosslinked structure or improving processability, α is preferably 0.96 or less, and more preferably 0.93 or less. Furthermore, the hydrogenation rate of the polymer and α can be adjusted, for example, by adjusting the hydrogenation reaction time or controlling the cumulative hydrogen supply. In this specification, the hydrogenation rate is a value obtained by measurement using a 1H-NMR apparatus.

[0069] A preferred method for obtaining [A]conjugated diene polymers involves solution polymerization of a monomer containing 1,3-butadiene in the presence of a polymerization initiator (preferably a metalloamine compound). After adding a [B] coupling agent to the obtained polymer solution for a coupling reaction, an end-modifier (c) is added as needed, followed by a hydrogenation step. This is useful industrially. In this case, the [A]conjugated diene polymer is obtained by removing the solvent from the obtained solution. The polymer can be separated, for example, by known solvent removal methods such as steam stripping and drying operations such as heat treatment.

[0070] For [A] conjugated diene polymers, from the viewpoint of obtaining crosslinked bodies with high strength and excellent wear resistance, the weight-average molecular weight (Mw) of polystyrene, as determined by gel permeation chromatography (GPC), is preferably 1.5 × 10⁵ to 2.0 × 10⁶. The Mw of the conjugated diene polymer is more preferably 1.8 × 10⁵ or more, and even more preferably 2.0 × 10⁵ or more. Furthermore, the Mw is more preferably 1.6 × 10⁶ or less, and even more preferably 1.4 × 10⁶ or less. Moreover, the weight-average molecular weight of the conjugated diene polymer described herein is a value obtained from the total peak value of the GPC curve measured by GPC before hydrogenation. Hereinafter, it is also referred to as "total weight-average molecular weight".

[0071] Furthermore, for the [A]conjugated diene polymer, the molecular weight distribution (weight average molecular weight / number average molecular weight) of the total amount of polymer (i.e., an aggregate of different molecular weights) as determined by GPC is preferably 1.1 or higher and 4.0 or lower. A molecular weight distribution of 1.1 or higher is preferable in terms of excellent processability, while a molecular weight distribution of 4.0 or lower is preferable in terms of sufficiently improving the low hysteresis loss of the obtained crosslinked body. The molecular weight distribution of the [A]conjugated diene polymer is more preferably 1.20 or higher, and even more preferably 1.23 or higher. In addition, this molecular weight distribution is more preferably 3.5 or lower, and even more preferably 3.0 or lower.

[0072] For [A]conjugated diene polymers, the peak molecular weight (hereinafter also referred to as "1st peak molecular weight") of the smallest molecular weight measured by GPC is preferably in the range of 0.8 × 10⁵ to 1.0 × 10⁶. When the 1st peak molecular weight is 0.8 × 10⁵ or higher, the strength and wear resistance of the obtained crosslinked body can be significantly improved, and the processability is also better. The 1st peak molecular weight is more preferably 0.9 × 10⁵ or higher, and more preferably 1.0 × 10⁵ or higher. In addition, in terms of improving processability and viscoelastic properties, the 1st peak molecular weight is more preferably 8.0 × 10⁵ or lower, and more preferably 5.0 × 10⁵ or lower. Furthermore, the 1st peak molecular weight is a value obtained from the GPC curve measured by GPC before hydrogenation.

[0073] The [A]conjugated diene polymer obtained by the above steps comprises 25% to 75% by mass of polymer (A1), wherein polymer (A1) contains a multi-branched structure having four or more molecular chains, and one or both of the terminal portion and the branch point portion of polymer (A1) have a functional group containing at least one specific element selected from the group consisting of nitrogen, oxygen, and sulfur. Polymer (A1) is preferably a structure having four or more molecular chains bonded to a structural bond derived from a [B] coupling agent, wherein the [B] coupling agent has at least one element selected from the group consisting of nitrogen, oxygen, sulfur, and silicon.

[0074] [A] The conjugated diene polymer preferably comprises a linear or three-branched or less branched polymer (A2) in addition to the polymer (A1). More specifically, the polymer (A2) is a hydride of the conjugated diene polymer (I) obtained by the polymerization step, which has three or less linear molecular chains bonded by the coupling agent (B) or the end modifier (c), or a hydride of an unreacted polymer that has not reacted with the coupling agent (B) and the end modifier (c), or both. From the viewpoint of obtaining a crosslinked body with higher strength and excellent wear resistance, the polymer (A2) preferably has a functional group comprising at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur and silicon. Furthermore, from the viewpoint of obtaining a crosslinked body with higher strength and excellent wear resistance, polymer (A2) preferably comprises a linear polymer having a secondary or tertiary amine group at one end and a functional group comprising at least one specific element selected from the group consisting of nitrogen, oxygen, and sulfur at the other end. Such a linear polymer with modified ends can be obtained by using a metalloamine compound as a polymerization initiator in the polymerization step and performing the modification step.

[0075] When the amount of the [A]conjugated diene polymer is set to 100% by mass, the proportion of polymer (A1) in the [A]conjugated diene polymer is 25% to 75% by mass. By having the proportion of polymer (A1) to [A]conjugated diene polymer within the aforementioned range, an excellent balance can be achieved between the strength and abrasion resistance of the crosslinked body and the processability of the polymer composition. Furthermore, due to the reduction in polymer solution viscosity, the transfer of the polymer solution in piping or to a container can be smoothly carried out during the polymer manufacturing process, or the hydrogenation time can be shortened during the hydrogenation process, thereby ensuring sufficient productivity. The proportion of polymer (A1) to [A]conjugated diene polymer is preferably 28% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, and even more preferably 50% by mass or more. Additionally, the proportion of polymer (A1) to [A]conjugated diene polymer is preferably 73% by mass or less, more preferably 70% by mass or less.

[0076] When the amount of the [A] conjugated diene polymer is set to 100% by mass, the proportion of polymer (A2) in the [A] conjugated diene polymer is preferably 25% to 75% by mass. The proportion of polymer (A2) relative to the [A] conjugated diene polymer is preferably 27% by mass or more, more preferably 30% by mass or more. In addition, the proportion of polymer (A2) relative to the [A] conjugated diene polymer is preferably 72% by mass or less, more preferably 70% by mass or less, further preferably 60% by mass or less, and even more preferably 50% by mass or less. Furthermore, the proportion (by mass) of polymer (A1) and polymer (A2) in the [A] conjugated diene polymer can be calculated by component separation of the waveform of the coupled polymer in the GPC curve obtained using GPC.

[0077] <Polymer Composition> The polymer composition disclosed herein may contain various components other than [A] conjugated diene polymers.

[0078] [D]Silica The polymer composition disclosed herein may contain [D]silica as an inorganic filler. The amount of [D]silica is preferably in the range of 20 to 120 parts by mass, and more preferably in the range of 30 to 100 parts by mass, relative to 100 parts by mass of the rubber component (including [A]conjugated diene polymer) contained in the polymer composition. If the amount of [D]silica is 20 parts by mass or more relative to 100 parts by mass of the rubber component, the low hysteresis loss, destructive properties, and abrasion resistance of the polymer composition can be sufficiently improved; conversely, if it is 120 parts by mass or less, the processability of the polymer composition can be sufficiently improved.

[0079] There are no particular limitations on the [D] silica used in the polymer composition disclosed herein. Examples include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc., of which wet silica is preferred. One type of silica may be used alone, or two or more may be used in combination. Furthermore, the Brunauer-Emmett-Teller (BET) specific surface area of ​​the silica (measured according to International Organization for Standardization (ISO) 5794 / 1) is preferably in the range of 40 m² / g to 350 m² / g, more preferably in the range of 80 m² / g to 350 m² / g, and particularly preferably in the range of 120 m² / g to 350 m² / g. Silicon dioxide with a BET specific surface area in this range has the following advantages: it can balance rubber reinforcement and dispersibility in [A] conjugated diene polymers. Commercially available silicon dioxide products such as Tosoh Silicon Dioxide Co., Ltd.'s trade name "Nipsil AQ" (BET specific surface area = 205 m² / g) and "Nipsil KQ" and Degussa's trade name "Ultrasil VN3" (BET specific surface area = 175 m² / g) are examples.

[0080] The polymer composition disclosed herein may contain two or more types of silicon dioxide with different specific surface areas. Specifically, it may also contain a first type of silicon dioxide with a CTAB specific surface area of ​​180 m² / g or more, a BET specific surface area of ​​185 m² / g or more, and an aggregate size of 45 nm or more, and a second type of silicon dioxide with a CTAB specific surface area of ​​95 m² / g or less and a BET specific surface area of ​​100 m² / g or less.

[0081] The polymer composition disclosed herein contains a first silica with a CTAB specific surface area of ​​180 m² / g or more, a BET specific surface area of ​​185 m² / g or more, and an aggregate size of 45 nm or more, and a second silica with a CTAB specific surface area of ​​95 m² / g or less and a BET specific surface area of ​​100 m² / g or less. By using both the first and second silica, the first silica, which has a small average primary particle size but a relatively large aggregate size, can be well dispersed in the rubber component, improving the dispersibility of silica, thereby obtaining excellent breaking strength, abrasion resistance, low oil consumption, and processability.

[0082] The CTAB (hexadecyltrimethylammonium bromide) specific surface area of ​​the first silicon dioxide is preferably 190 m² / g or more, more preferably 195 m² / g or more, and even more preferably 197 m² / g or more. When the CTAB specific surface area is less than 180 m² / g, it tends to be difficult to obtain sufficient improvement in breaking strength and wear resistance. The CTAB specific surface area of ​​the first silicon dioxide is preferably 350 m² / g or less, more preferably 300 m² / g or less, and even more preferably 250 m² / g or less. When the CTAB specific surface area exceeds 350 m² / g, the dispersibility is poor and it will agglomerate, thus tending to reduce physical properties. Furthermore, the CTAB specific surface area of ​​silicon dioxide is determined according to American Society for Testing and Materials (ASTM) D3765-92.

[0083] The BET specific surface area of ​​the first silicon dioxide is preferably 190 m² / g or more, more preferably 195 m² / g or more, and even more preferably 210 m² / g or more. When the BET specific surface area is less than 185 m² / g, it tends to be difficult to achieve sufficient improvement in breaking strength and wear resistance. The BET specific surface area of ​​the first silicon dioxide is preferably 350 m² / g or less, more preferably 300 m² / g or less, and even more preferably 260 m² / g or less. When the BET specific surface area exceeds 350 m² / g, the dispersibility is poor, and it tends to agglomerate, thus tending to reduce physical properties. Furthermore, the BET specific surface area of ​​silicon dioxide is determined according to ASTM D3037-81.

[0084] The aggregate size of the first silica is 45 nm or more, preferably 50 nm or more, more preferably 55 nm or more, and even more preferably 60 nm or more. Furthermore, the aggregate size of the first silica is preferably 100 nm or less, more preferably 80 nm or less, even more preferably 70 nm or less, and particularly preferably 67 nm or less. By having this aggregate size, excellent low oil consumption and wear resistance can be imparted while maintaining good dispersibility (processability). Moreover, the aggregate size of the silica can be determined by the method described in Japanese Patent Application Publication No. 2011-140613.

[0085] The average primary particle size of the first silica is preferably 25 nm or less, more preferably 22 nm or less, even more preferably 17 nm or less, and particularly preferably 14 nm or less. Furthermore, the average primary particle size of the first silica is preferably 3 nm or more, more preferably 5 nm or more, and even more preferably 7 nm or more. Although it has such a small average primary particle size, the dispersibility (processability) of silica can be further improved by the carbon black-like structure with the aforementioned aggregate size, thereby further improving low oil consumption and wear resistance. Moreover, the average primary particle size of silica can be determined by observing silica with a transmission or scanning electron microscope, measuring the particle size of more than four hundred primary silica particles observed in the field of view, and averaging them.

[0086] The CTAB specific surface area of ​​the second silica is preferably 10 m² / g or more, more preferably 20 m² / g or more, and even more preferably 30 m² / g or more. When the CTAB specific surface area is less than 10 m² / g, the reinforcing properties decrease, and it may become difficult to ensure the mechanical strength or abrasion resistance required for the polymer composition used in tire manufacturing. The CTAB specific surface area of ​​the second silica is preferably 80 m² / g or less, more preferably 60 m² / g or less, and even more preferably 50 m² / g or less. When the CTAB specific surface area exceeds 95 m² / g, the dispersibility of the silica deteriorates, and it may become difficult to improve the breaking strength and abrasion resistance.

[0087] The BET specific surface area of ​​the second silica is preferably 10 m² / g or more, more preferably 20 m² / g or more, and even more preferably 30 m² / g or more. When the BET specific surface area of ​​the second silica is less than 10 m² / g, the reinforcing properties decrease, and it may sometimes become difficult to ensure the mechanical strength or abrasion resistance required for the polymer composition used in tire manufacturing. The BET specific surface area of ​​the second silica is preferably 85 m² / g or less, more preferably 60 m² / g or less, and even more preferably 50 m² / g or less. When the BET specific surface area exceeds 100 m² / g, the dispersibility of the silica deteriorates, and it may become difficult to improve breaking strength and abrasion resistance.

[0088] The average primary particle size of the second silicon dioxide is preferably 20 nm or more, more preferably 25 nm or more, further preferably 30 nm or more, particularly preferably 35 nm or more, and most preferably 55 nm or more. Furthermore, the average primary particle size of the second silicon dioxide is preferably 500 nm or less, more preferably 200 nm or less, further preferably 100 nm or less, and particularly preferably 70 nm or less. Having this average primary particle size improves breaking strength and wear resistance.

[0089] [E] Carbon black From the viewpoint of the destructive properties and abrasion resistance of the polymer composition, the polymer composition disclosed herein preferably contains [E] carbon black as an inorganic filler. The type of carbon black is not particularly limited, but examples include: general purpose furnace black (GPF), fast extruding furnace black (FEF), high abrasion furnace black (HAF), intermediate super abrasion furnace black (ISAF), and super abrasion furnace black (SAF). The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited. For more fully obtaining the effects of this disclosure, a value of 50 m² / g to 200 m² / g is preferred, and more preferably 70 m² / g to 150 m² / g is more preferred. Nitrogen adsorption specific surface area (N2SA) is the value of nitrogen adsorption on the surface of carbon black determined according to Japanese Industrial Standards (JIS) K6217-2:2001 "Part 2: Methods for determining specific surface area - Nitrogen adsorption method - Single point method". Carbon black can be used alone or in combination with two or more types. Furthermore, the amount of carbon black prepared relative to 100 parts by mass of the [A]conjugated diene polymer is preferably in the range of 1 to 150 parts by mass, more preferably in the range of 5 to 120 parts by mass.

[0090] [Other fillers] In addition to the aforementioned [D]silica and [E]carbon black, the composition disclosed herein may also contain other fillers as inorganic fillers. Other fillers mentioned include: alumina (Al2O3) such as γ-alumina and α-alumina, alumina monohydrate such as boehmite and diaspore (Al2O3·H2O), aluminum hydroxide [Al(OH)3] such as gibbsite and bayerite, aluminum carbonate [Al2(CO3)3], magnesium hydroxide [Mg(OH)2], magnesium oxide (MgO), magnesium carbonate (MgCO3), talc (3MgO·4SiO2·H2O), attapulgite (5MgO·8SiO2·9H2O), titanium dioxide (TiO2), titanium black (TiO2n-1), calcium oxide (CaO), calcium hydroxide [Ca(OH)2], and magnesium aluminum oxide. (MgO·Al2O3), clay (Al2O3·2SiO2), kaolin (Al2O3·2SiO2·2H2O), pyrophyllite (Al2O3·4SiO2·H2O), bentonite (Al2O3·4SiO2·2H2O), aluminum silicate (Al2SiO5·Al4·3SiO4·5H2O, etc.), magnesium silicate (Mg2SiO4, MgSiO3, etc.), calcium silicate (Ca2SiO4, etc.), calcium aluminum silicate (Al2O3·CaO·2SiO2, etc.), calcium magnesium silicate (CaMgSiO4), calcium carbonate (CaCO3), zirconium oxide (ZrO2), zirconium hydroxide [ZrO(OH)2·nH2O], zirconium carbonate [Zr(CO3)2], and various zeolites, including crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals with corrective charges.

[0091] In the polymer composition disclosed herein, the amount of inorganic fillers ([D] silica, [E] carbon black and other fillers) is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, relative to 100 parts by mass of rubber component (including [A] conjugated diene polymer). Furthermore, the amount of fillers is preferably 150 parts by mass or less, more preferably 130 parts by mass or less. If the amount of fillers in the polymer composition is within the aforementioned range, when the polymer composition disclosed herein is applied to tire tread manufacturing applications, improvements can be made to the tire's low rolling resistance, braking performance on wet roads, handling performance on dry roads, and wear resistance to a greater extent.

[0092] [F] Other Rubber Components The composition disclosed herein may contain only [A] conjugated diene polymer as a rubber component. In addition to containing [A] conjugated diene polymer, other rubber components (hereinafter also referred to as [F] components) different from [A] conjugated diene polymers may be used, without impairing the effects of this disclosure. As [F] component, for example, one or more diene rubbers selected from natural rubber, isoprene rubber, butadiene rubber, emulsified styrene-butadiene rubber, solution-polymerized styrene-butadiene rubber, butyl rubber, halogenated butyl rubber, and ethylene-propylene rubber may be used. Among these, it is preferred to contain at least one selected from natural rubber, butadiene rubber, and styrene-butadiene rubber. There are no particular limitations on the manner in which [F] component is mixed with [A] conjugated diene polymer. For example, [F] component and [A] conjugated diene polymer may be mixed during normal mixing using a Banbury mixer or rollers. Alternatively, the [F] component can be added to the [A] conjugated diene polymer in solution after polymerization.

[0093] Relative to the total amount of rubber components ([A] conjugated diene polymer and [F] component) contained in the polymer composition, the amount of [F] component is preferably 80% by mass or less, more preferably 60% by mass or less. Furthermore, in this specification, "rubber component" contained in the polymer composition refers to a polymer that can be thermocured to obtain a cured material exhibiting rubber elasticity. This cured material exhibits the following properties: it undergoes large deformation with a small force at room temperature (e.g., elongates to more than twice its original shape when stretched at room temperature), and rapidly returns to approximately its original shape upon removal of the force.

[0094] In this disclosure, from the viewpoint of further improving dry grip performance, wet grip performance and crack resistance, liquid rubber may also be used as part or all of the other rubber components.

[0095] 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 may have a weight-average molecular weight of 1,000 to 100,000, preferably 2,000 to 80,000. Furthermore, the weight-average molecular weight mentioned in this specification refers to the weight-average molecular weight converted from polystyrene analyzed by gel permeation chromatography (GPC). The liquid rubber used in this disclosure refers to a rubber that is fluid at 23°C.

[0096] [G] Thermoplastic Resin The polymer composition disclosed herein may contain [G] thermoplastic resin. As a thermoplastic resin, from the viewpoint of obtaining a crosslinker with superior strength, abrasion resistance, and crack growth resistance, it is preferably selected from at least one group consisting of styrene-based resins, polyethylene, C5-based resins, C9-based resins, C5 / C9-based resins, dicyclopentadiene-based resins, alkylphenol-based resins, and terpene-based resins. As a thermoplastic resin, one type may be used alone, or two or more types may be used in combination.

[0097] Here, the styrene-based resin is a polymer obtained using styrene-based monomers, preferably a polymer having 20% ​​by mass or more structural units derived from styrene-based monomers relative to the total amount of monomer units in the styrene-based resin. Examples of styrene-based monomers include: styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, phosphochlorostyrene, m-chlorostyrene, p-chlorostyrene, etc. The styrene-based monomer is preferably at least one of styrene and α-methylstyrene from these.

[0098] Styrene-based resins can be homopolymers polymerized from one styrene-based monomer, or copolymers copolymerized from two or more styrene-based monomers. Additionally, styrene-based resins can also be copolymers obtained using styrene-based monomers and other monomers that can be copolymerized with styrene-based monomers. Examples of other monomers include: acrylonitrile, methacrylonitrile, and other acrylonitrile derivatives; acrylic acids, methacrylic acid, and other unsaturated carboxylic acids; methyl acrylate, methyl methacrylate, and other unsaturated carboxylic acid esters; dienes such as chloroprene, butadiene, and isoprene; olefins such as 1-butene and 1-pentene; and α,β-unsaturated carboxylic acids or their anhydrides, such as maleic anhydride.

[0099] The softening point of the styrene-based resin is preferably 30°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher. When the softening point is 30°C or higher, the crosslinked material tends to easily achieve improved resistance to crack growth. Furthermore, the softening point of the styrene-based resin is preferably 160°C or lower, more preferably 130°C or lower, and even more preferably 100°C or lower. When the softening point is 160°C or lower, the resin dispersibility becomes good, and there is a tendency for improved resistance to crack growth, abrasion resistance, and tensile strength. Moreover, in this disclosure, the softening point of the styrene-based resin is a value obtained by measuring using a ring-and-ball softening point measuring device according to the method specified in JIS K6220-1:2015, and is the temperature at which the ball placed on the sample softens and descends to the bottom plate.

[0100] As a styrene-based resin, a block polymer (thermoplastic elastomer) having conjugated diene polymer blocks as soft segments and polystyrene blocks as hard segments can also be used. Using such a block polymer further improves the resistance to crack growth. Furthermore, in the conjugated diene polymer blocks of the block polymer, a portion of the carbon-carbon double bonds originating from the structural units of the conjugated diene compound can be hydrogenated.

[0101] Examples of conjugated diene compounds constituting the block of the conjugated diene polymer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. One or more of these conjugated diene compounds may be used alone or in combination. Preferably, at least one of 1,3-butadiene and isoprene is used. The proportion of conjugated diene units in the block polymer is preferably 20% by mass or more, more preferably 30% by mass or more. Furthermore, the proportion of conjugated diene units is preferably 80% by mass or less, more preferably 70% by mass or less.

[0102] In terms of further improving the fracture strength, the content of polystyrene blocks in the block polymer is preferably 20% by mass or more. Furthermore, the content of polystyrene blocks is preferably 80% by mass or less, and more preferably 70% by mass or less. Moreover, the respective contents of polystyrene blocks, conjugated diene polymer blocks, and conjugated diene units in the block polymer can be calculated by the integral ratio of the 1H-NMR spectrum.

[0103] Specific examples of the block polymers include: styrene-butadiene block copolymers, styrene-isoprene block copolymers, epoxides of styrene-butadiene block copolymers, and block copolymers obtained by hydrogenating a portion of the conjugated diene polymer blocks of styrene-butadiene block copolymers or styrene-isoprene block copolymers. More specifically, examples include: styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-butadiene-butene-styrene block copolymers (SBBS), epoxides of styrene-butadiene-styrene block copolymers, and hydrides of these copolymers. Regarding ease of crosslinking, SBS or SIS having conjugated diene polymer blocks with unhydrogenated soft segments, or epoxides of styrene-butadiene-styrene block copolymers, are preferably used among these.

[0104] Examples of polyethylene include: low-density polyethylene (LDPE), high-density polyethylene (HDPE), and linear low-density polyethylene (LLDPE). C5 resins are solid polymers (C5 synthetic petroleum resins) obtained by polymerizing C5 fractions using Friedel-Crafts type catalysts (AlCl3 or BF3, etc.). Specific examples of C5 resins include: copolymers with isoprene, cyclopentadiene, 1,3-pentadiene, 1-pentene, etc. as main components; copolymers of 2-pentene and dicyclopentadiene; polymers with 1,3-pentadiene as the main component, etc.

[0105] C9 series resins are solid polymers (C9 series synthetic petroleum resins) obtained by polymerizing the C9 fraction using a Fridell-Quaft type catalyst (AlCl3 or BF3, etc.). Specific examples of C9 series resins include copolymers with indene, methyl indene, vinyltoluene, etc., as main components. C5 / C9 series resins are solid polymers (C5 / C9 series synthetic petroleum resins) obtained by polymerizing the C5 to C9 fractions using a Fridell-Quaft type catalyst (AlCl3 or BF3, etc.). Specific examples of C5 / C9 series resins include copolymers with vinyltoluene, indene, etc., as main components. In C5 / C9 series resins, from the viewpoint of compatibility with rubber components, it is preferable to have a lower content of C9 or higher components. Specifically, in C5 / C9 series resins, the content of C9 or higher components in the total resin volume is preferably less than 50% by mass, more preferably less than 40% by mass.

[0106] Dicyclopentadiene resins refer to petroleum resins that use dicyclopentadiene from the C5 fraction as the main raw material. Specific examples of dicyclopentadiene resins include the "Marukarez M" series (M-890A, M-845A, M-990A, etc.) from Maruzen Petrochemical Co., Ltd. Examples of alkylphenol resins include alkylphenol-acetylene resins such as p-tert-butylphenol-acetylene resin, and low-polymerization-degree alkylphenol-formaldehyde resin.

[0107] Terpene resins are solid resins obtained by polymerizing turpentine oil, which is obtained simultaneously with rosin from pine trees, or by blending polymer components separated from pine trees, using Fridell-Quaft type catalysts. Examples include β-pinene resins and α-pinene resins. Commercially available products can be used as terpene resins, for example, the "YS Resin" series (PX-1250, TR-105, etc.) manufactured by Yasuhara Chemical Co., Ltd., and the "PICCOLYTE" series (A115, S115, etc.) manufactured by Hercules Co., Ltd.

[0108] As a representative example of a terpene-aromatic compound resin, a terpene-phenol resin can be cited. This terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Fridell-Quaft catalyst, or by further condensation using formalin. There are no particular limitations on the terpenes used as raw materials, but monoterpenes such as α-pinene or limonene are preferred, more preferably containing α-pinene, and especially preferably α-pinene. In this disclosure, a terpene-phenol resin with a low phenol content is preferred. Here, "low phenol content" means that the phenol content in the total resin is less than 50% by mass, preferably less than 40% by mass. Furthermore, if a terpene-aromatic compound resin, especially a terpene-phenol resin, is used as a [G] thermoplastic resin, the processing performance can be further improved. Commercially available terpene-aromatic compound resins can be used. Commercially available products include, for example, "Tamanol 803L", "Tamanol 901" (manufactured by Arakawa Chemical Industry Co., Ltd.), and the "YS Polystar" series (registered trademark) (manufactured by Yasuhara Chemical Co., Ltd.).

[0109] The amount of thermoplastic resin is preferably 1 part by mass or more relative to 100 parts by mass of the rubber component contained in the polymer composition. By incorporating 1 part by mass or more of thermoplastic resin, the improvement effect of adding thermoplastic resin on abrasion resistance, tensile strength, and crack growth resistance in the crosslinked body obtained using the polymer composition can be sufficiently improved. The amount of thermoplastic resin is more preferably 3 parts by mass or more relative to 100 parts by mass of the rubber component, and more preferably 7 parts by mass or more. In addition, from the viewpoint of maintaining the various properties of the polymer composition well, the amount of thermoplastic resin is preferably 50 parts by mass or less relative to 100 parts by mass of the rubber component contained in the polymer composition, more preferably 30 parts by mass or less, and more preferably 25 parts by mass or less. Furthermore, the thermoplastic resin can be used alone or in combination of two or more.

[0110] [H]Silane Coupling Agent In this disclosure, a silane coupling agent can be formulated together with silica to further improve the dispersibility of silica. There are no particular limitations on the silane coupling agent used. Preferably, it is a sulfur-containing silane coupling agent, such as: bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, γ-mercaptopropyltriethoxysilane, 3-octylthiopropyltriethoxysilane, etc.

[0111] The preferred amount of silane coupling agent is 1 to 20 parts by mass relative to 100 parts by mass of silicon dioxide. If the amount of silane coupling agent is less than 1 part by mass, the amount is too small and may not sufficiently improve the dispersibility of silicon dioxide. Conversely, if it exceeds 20 parts by mass, the processability and elongation at break may sometimes deteriorate. The preferred amount of silane coupling agent is 5 to 15 parts by mass relative to 100 parts by mass of silicon dioxide.

[0112] [I] Crosslinking Agent The polymer composition disclosed herein may contain a crosslinking agent. By containing a crosslinking agent in the polymer composition disclosed herein, a crosslinked body with sufficiently improved strength and abrasion resistance can be obtained. Examples of crosslinking agents include sulfur, sulfur halide, organic peroxides, quinone dioximes, organic polyamine compounds, and alkylphenol resins containing hydroxymethyl groups, with sulfur being commonly used. The amount of crosslinking agent is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of the total amount of rubber components contained in the polymer composition.

[0113] [J] Filler oil: In the polymer composition disclosed herein, the oil used for filling (filler oil) can be a process oil commonly used for filling elastomers. There are no particular limitations on the method of adding the process oil. For example, the process oil can be formulated into the polymerized conjugated diene polymer solution in the form of an oil-filled rubber by solvent extraction after spreading, or the process oil can be directly added to the polymer composition during mixing using a Bamboo mixer or rollers. As preferred process oils, various oils known in the art can be listed, such as aromatic oils, paraffinic oils, naphthenic oils, vegetable oils, and oils with low polycyclic aromatic hydrocarbon (PCA) content (low-polycyclic aromatic hydrocarbon (PCA) oils), such as mild extraction solvents (MES), treated distillate aromatic extracts (TDAE), special residual aromatic extracts (SRAE), and heavy naphthenic oils. Examples of commercially available MES, TDAE, and SRAE include Shell's Catenex SNR (a heavy paraffin obtained by dewaxing distillate oil using a solvent) as an MES, H&R Wasag AG's Vivatec 500 as a TDAE, and Japan Energy Corp.'s NC140 as an SRAE. The preferred amount of process oil is 10 to 100 parts by mass relative to 100 parts by mass of the total polymer components contained in the polymer composition.

[0114] In addition to the components mentioned above, the polymer composition may also contain various additives commonly used in polymer compositions for obtaining vulcanized rubber, such as anti-aging agents, zinc oxide, stearic acid, softeners, vulcanization accelerators, silane coupling agents, compatibilizers, vulcanization aids, processing aids, and scorch inhibitors. The amounts of these additives can be appropriately selected based on the various components without impairing the effects of this disclosure.

[0115] In addition to polymer components and inorganic fillers, the polymer composition disclosed herein also uses open mixing machines (e.g., rollers) and closed mixing machines (e.g., Bambury mixing machines) to mix the components as needed, and then crosslinks (vulcanizes) after molding and processing, thereby enabling it to be used as a crosslinked body in various rubber products. Specifically, the crosslinked material can be applied to tire applications such as tire tread, under tread, carcass, sidewall, and bead part; sealing materials such as liner, gasket, weather strip, and O-ring; inner and outer packaging materials for various vehicles such as automobiles, ships, airplanes, and railways; building materials; vibration-damping rubber for industrial machinery or equipment; various hoses and hose covers such as diaphragms, rollers, radiator hoses, and air hoses; belts such as power transmission belts; linings; dust boots; medical machine materials; fenders; electrical insulation materials; and other industrial products.

[0116] According to the [A] conjugated diene polymer, a crosslinked body with good physical properties such as tensile strength and wear resistance required for tire applications can be obtained. Therefore, polymer compositions containing the [A] conjugated diene polymer can be particularly preferably used as materials for tire treads, sidewalls, or both.

[0117] Tire manufacturing can be carried out using conventional methods. For example, polymer components are mixed using a mixer, and the sheet-like components are placed in a designated location (e.g., the outer side of the frame in the case of the sidewall) and vulcanized according to conventional methods to form the tread or sidewall, thereby obtaining a pneumatic tire. [Example]

[0118] Hereinafter, specific descriptions will be given based on examples, but this disclosure is not limited to these examples. Furthermore, unless otherwise specified, "parts" and "%" in the examples and comparative examples are mass references. The following shows methods for determining various physical properties of polymers.

[0119] [Polymer Characteristic Evaluation] • Vinyl bond content (moles %): Determined by 1H-NMR at 400 MHz for the unhydrogenated polymer. • Bonded styrene content (%): Determined by 1H-NMR at 400 MHz for the unhydrogenated polymer. • First Peak Average Molecular Weight: For the unhydrogenated polymer, a graph of molecular weight based on polystyrene conversion was obtained using a gel permeation chromatography (GPC, product name: HLC-8020 (manufactured by Tosoh)). The molecular weight was determined by the holding time of the longest-held peak in the obtained GPC curve. Specific measurement conditions are as follows: (Measurement Conditions) Column: Two GMH-HR-H (manufactured by Tosoh) columns connected in series. Detector: Differential refractometer RI-8020 (manufactured by Tosoh) Dissolution solution: Tetrahydrofuran Column temperature: 40°C Flow rate: 1.0 ml / min Sample concentration: 10 mg / 20 ml • Total Weight Average Molecular Weight: For the unhydrogenated polymer, the total peak value of the GPC curve obtained using GPC (HLC-8020 (manufactured by Tosoh)) was calculated using polystyrene conversion. Measurement conditions were the same as described above. • Coupling rate (mass%): For the unhydrogenated polymer, the proportion of coupled polymers with two or more molecular chains is calculated from the peak area ratio of the GPC curve obtained using GPC (HLC-8020 (product name, manufactured by Tosoh Corporation)). • Hydrogenation rate and α: Calculated using tetrachloroethylene as a solvent by 1H-NMR spectroscopy measured with a 100 MHz instrument. • Polymer (Al) content (mass%): For the unhydrogenated polymer, the content is calculated by component separation of the waveforms of coupled polymers with four or more branches in the GPC curve obtained using GPC (HLC-8020 (product name, manufactured by Tosoh Corporation)).

[0120] <Synthesis of Hydrogenated Conjugated Diene Polymers> [Example 1: Synthesis and Properties of Hydrogenated Conjugated Diene Polymer A] In a 50-liter autoclave reactor purged with nitrogen, 25900 g of cyclohexane, 65 g of tetrahydrofuran, 370 g of styrene, 3219 g of 1,3-butadiene, and 63 mmol of piperidine were added. After adjusting the temperature of the reactor contents to 42°C, a cyclohexane solution containing n-butyllithium (86 mmol) was added to initiate polymerization. Polymerization was carried out under insulated conditions. After confirming that the polymerization conversion reached 99%, 111 g of 1,3-butadiene was added, and polymerization was continued for 3 minutes to obtain a reaction solution containing the polymer. 10 mmol of silicon tetrachloride was added to the obtained reaction solution, and the reaction was carried out for 5 minutes. Next, the reaction solution was set at a temperature above 80°C. After introducing hydrogen into the system, 1.64 g of diethylaluminum chloride, 3.67 g of bis(n-5-cyclopentadienyl)titanium (furfuryloxy) chloride, and 1.67 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 while maintaining a hydrogen pressure above 0.7 MPa to allow the reaction to reach the specified hydrogen accumulation value. The reaction solution was then restored to room temperature and pressure, and extracted from the reaction vessel to obtain a polymer solution. The obtained polymer solution was stripped by steam to remove the solvent, and dried using a hot roller heated to 130°C to obtain hydrogenated conjugated diene polymer A. The polymerization formulation of hydrogenated conjugated diene polymer A is shown in Table 1, and the various physical properties of the obtained hydrogenated conjugated diene polymer A are shown in Table 3.

[0121] [Synthesis and properties of hydrogenated conjugated diene polymers B, D, K, N, Q, R, and T in Examples 2, 4-11, 14-17, and Comparative Examples 1-3: Examples 2, 4-17, 14-17, and Comparative Examples 1-3] Except for changes to the polymerization formulation as described in Tables 1 and 2, and changes to the hydrogenation rate as described in Tables 3 and 4, hydrogenated conjugated diene polymers B, D, K, N, Q, R, and T were obtained by the same method as in Example 1. Furthermore, no starting-end modifier was used in Example 4 and Comparative Example 1. The various physical properties of the obtained hydrogenated conjugated diene polymers B, D, K, N, Q, R, and T are shown in Tables 3 and 4.

[0122] [Example 3: Synthesis and Properties of Hydrogenated Conjugated Diene Polymer C] In a 50-liter autoclave reactor purged with nitrogen, 25900 g of cyclohexane, 65 g of tetrahydrofuran, 370 g of styrene, 3219 g of 1,3-butadiene, and 63 mmol of piperidine were added. After adjusting the temperature of the reactor contents to 42°C, a cyclohexane solution containing n-butyllithium (86 mmol) was added to initiate polymerization. Polymerization was carried out under insulated conditions. After confirming that the polymerization conversion reached 99%, 111 g of 1,3-butadiene was added, and polymerization was continued for 3 minutes to obtain a reaction solution containing the polymer. 10 mmol of silicon tetrachloride was added to the obtained reaction solution, and the reaction was carried out for 5 minutes. Then, 28 mmol of N,N-dimethylaminopropyltriethoxysilane was added, and the reaction was carried out for 15 minutes. Next, the reaction solution was set at a temperature above 80°C. After introducing hydrogen into the system, 1.64 g of diethylaluminum chloride, 3.67 g of bis(n-5-cyclopentadienyl)titanium (furfuryloxy) chloride, and 1.67 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 at a hydrogen pressure above 0.7 MPa to allow the reaction to reach the specified hydrogen accumulation value. The reaction solution was then restored to room temperature and pressure, and extracted from the reaction vessel to obtain a polymer solution. The obtained polymer solution was stripped by steam to remove the solvent, and dried using a hot roller heated to 130°C to obtain hydrogenated conjugated diene polymer C. The polymerization formulation of hydrogenated conjugated diene polymer C is shown in Table 1, and the various physical properties of the obtained hydrogenated conjugated diene polymer C are shown in Table 3.

[0123] [Example 12 and Comparative Example 4: Synthesis and Properties of Hydrogenated Conjugated Diene Polymer L and Hydrogenated Conjugated Diene Polymer U] Except for the change in polymerization formulation as described in Table 2, hydrogenated conjugated diene polymer L and hydrogenated conjugated diene polymer U were obtained by the same method as in Example 1. Furthermore, no starting-end modifier was used in Comparative Example 4. The various physical properties of the obtained hydrogenated conjugated diene polymer L and hydrogenated conjugated diene polymer U are shown in Table 4.

[0124] [Example 13: Synthesis and Properties of Hydrogenated Conjugated Diene Polymer M] In a 50-liter autoclave reactor purged with nitrogen, 25900 g of cyclohexane, 65 g of tetrahydrofuran, 0.74 g of potassium dodecylbenzenesulfonate, 740 g of styrene, 2849 g of 1,3-butadiene, and 63 mmol of piperidine were added. After adjusting the temperature of the reactor contents to 42°C, a cyclohexane solution containing n-butyllithium (43 mmol) was added to initiate polymerization. Polymerization was carried out under insulated conditions. After confirming that the polymerization conversion reached 99%, 111 g of 1,3-butadiene was added, and polymerization was continued for 3 minutes to obtain a reaction solution containing the polymer. 2.6 mmol of silicon tetrachloride was added to the obtained reaction solution, and the reaction was carried out for 5 minutes. Then, 24 mmol of N,N-dimethylaminopropyltriethoxysilane was added, and the reaction was carried out for 15 minutes. Next, the reaction solution was set at a temperature above 80°C. After introducing hydrogen into the system, 1.64 g of diethylaluminum chloride, 3.67 g of bis(n-5-cyclopentadienyl)titanium (furfuryloxy) chloride, and 1.67 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 at a hydrogen pressure above 0.7 MPa to allow the reaction to reach the specified hydrogen accumulation value. The reaction solution was then restored to room temperature and pressure, and extracted from the reaction vessel to obtain a polymer solution. The obtained polymer solution was stripped by steam to remove the solvent, and dried using a hot roller heated to 130°C to obtain the hydrogenated conjugated diene polymer M. The polymerization formulation of the hydrogenated conjugated diene polymer M is shown in Table 2, and the various physical properties of the obtained hydrogenated conjugated diene polymer M are shown in Table 4.

[0125] [Table 1] Example 1 2 3 4 5 6 7 8 9 10 11 Types of hydrogenated conjugated diene polymers A B C D E F G H I J K Polymerization formulation solvent Cyclohexane (g) 25900 25900 25900 25900 25900 25900 25900 25900 25900 25900 25900 Vinyl content modifier Tetrahydrofuran (g) 65 65 65 65 65 65 65 65 26 65 65 V-1 (g) - - - - - - - - - - - Polymer monomer Styrene (g) 370 370 370 370 370 370 370 925 370 370 370 Butadiene (g) 3219 3219 3219 3219 3219 3219 3219 2664 3219 3219 3219 Adding butadiene (g) 111 111 111 111 111 111 111 111 111 111 111 Polymerization initiator n-Butyllithium (mmol) 86 86 86 86 86 86 86 86 86 66 43 (Initial modifier) Piperidine (mmol) 63 - 63 - 63 63 63 63 63 48 32 INI-1 (mmol) - 63 - - - - - - - - - End-of-phase modifier Mod-1 (mmol) - - 28 - - - - - - - - Coupling agent Silicon tetrachloride (mmol) 10 10 10 - - 8.6 10 10 10 10 2.6 Mod-2 (mmol) - - - 10 10 - - - - - -

[0126] [Table 2] Example Comparative example 12 13 14 15 16 17 1 2 3 4 Types of hydrogenated conjugated diene polymers L M N O P Q R S T U Polymerization formulation solvent Cyclohexane (g) 25900 25900 25900 25900 25900 25900 25900 25900 25900 25900 Vinyl content modifier Tetrahydrofuran (g) 65 65 65 389 1684 13 65 65 65 65 V-1 (g) - 0.74 - - - - - - - - Polymer monomer Styrene (g) 370 740 1480 370 370 370 370 370 370 370 Butadiene (g) 3219 2849 2109 3219 3219 3219 3219 3219 3219 3219 Adding butadiene (g) 111 111 111 111 111 111 111 111 111 111 Polymerization initiator n-Butyllithium (mmol) 43 43 86 86 86 86 86 86 86 43 (Initial modifier) Piperidine (mmol) 32 32 63 63 63 63 - 63 63 - INI-1 (mmol) - - - - - - - - - - End-of-phase modifier Mod-1 (mmol) twenty four twenty four - - - - - - - twenty two Coupling agent Silicon tetrachloride (mmol) 2.6 2.6 10 10 10 10 10 16 0.86 2.6 Mod-2 (mmol) - - - - - - - - - -

[0127] In Tables 1 and 2, "-" indicates compounds for which the corresponding column was not used. The abbreviations for vinyl content modifiers, starting-end modifiers, ending-end modifiers, and coupling agents are as follows: V-1: Potassium dodecylbenzenesulfonate; INI-1: n-Ter-butyldimethylsilyl-4-piperazine; Mod-1: N,N-dimethylaminopropyltriethoxysilane; Mod-2: Compound represented by the following formula (Mod-2) [Chemical 14]

[0128] [Table 3] Polymer properties Example 1 2 3 4 5 6 7 8 9 10 11 Types of polymers A B C D E F G H I J K Bonded styrene content (wt%) 10 10 10 10 10 10 10 25 10 10 10 Vinyl bond content (mol%) 34 34 34 34 34 34 34 34 27 34 34 1st peak molecular weight (×10) 4 ) 10 10 10 10 10 10 10 10 10 13 20 Total weight average molecular weight (×10) 4 ) 35 35 35 35 35 20 35 35 35 40 35 Coupling rate (wt%) 60 60 60 60 60 50 60 60 60 60 30 Hydrogenation rate (%) 88 88 88 88 88 88 80 88 88 88 88 α 0.88 0.88 0.88 0.88 0.88 0.88 0.80 0.88 0.88 0.88 0.88 Polymer (A1) content (wt%) 57 57 57 57 57 48 57 57 57 57 29

[0129] [Table 4] Polymer properties Implementation Examples Comparative example 12 13 14 15 16 17 1 2 3 4 Types of polymers L M N O P Q R S T U Bonded styrene content (wt%) 10 20 40 10 10 10 10 10 10 10 Vinyl bond content (mol%) 34 34 34 55 78 20 34 34 34 34 1st peak molecular weight (×10) 4 ) 20 20 10 10 10 10 10 10 10 20 Total weight average molecular weight (×10) 4 ) 35 35 35 35 35 35 35 40 12 35 Coupling rate (wt%) 30 30 60 60 60 60 60 90 5 30 Hydrogenation rate (%) 88 85 88 88 88 88 88 88 88 91 α 0.88 0.85 0.88 0.88 0.88 0.88 0.88 0.88 0.88 0.91 Polymer (A1) content (wt%) 29 28 57 57 57 57 57 87 4 29

[0130] <Manufacturing of Polymer Compositions and Crosslinkers> Using the hydrogenated conjugated diene polymers A to Q and R to U respectively, the components were formulated according to the formulation shown in Table 5 and then mixed to manufacture polymer compositions. The mixing was carried out as follows. Using a plastomill (capacity: 250 ml) equipped with a temperature control device, the hydrogenated modified conjugated diene polymers (A to Q, R to U), silica, carbon black, silane coupling agent, filler oil, stearic acid, zinc oxide, and anti-aging agent were mixed as the first stage of mixing at a filler ratio of 72% and a rotation speed of 60 rpm to obtain a compound as polymer composition A. Next, as the second stage of mixing, the obtained compound was cooled to room temperature, and a vulcanization accelerator and sulfur were added and mixed to obtain polymer composition B. The obtained polymer composition B was molded and vulcanized at 160°C under pressure for a specified time to obtain a crosslinked body (vulcanized rubber). Furthermore, solution viscosity, processability, cold flow, tensile strength, and abrasion resistance were evaluated as follows. The results are shown in Tables 6 and 7.

[0131] (1) Solution viscosity: The sample obtained by dissolving 29 g of polymer in 171 g of cyclohexane was used as the test sample. The viscosity of the solution was measured using a Toki Industrial Viscometer TVB-10 at a temperature of 60°C. Furthermore, the smaller the value of the solution viscosity, the better the flowability of the polymer solution, the easier it is to transfer in piping or to a container, or the higher the hydrogen diffusivity in the polymer solution during hydrogenation, thereby shortening the hydrogenation time and ensuring sufficient productivity. From this point of view, it is excellent. Based on the obtained solution viscosity value, the solution viscosity was determined using the following criteria from A to D. A (Extremely good): less than 1000 mP·s B (Good): more than 1000 mP·s and less than 2000 mP·s C (Allowable level): more than 2000 mP·s and less than 3000 mP·s D (Poor): more than 3000 mP·s

[0132] (2)Munich viscosity: The polymer was used as the test sample, and the measurement was performed according to JIS K6300 using an L rotor under the conditions of 1 minute of preheating, 4 minutes of rotor operation time, and 100°C. The index was evaluated using Comparative Example 1 as the benchmark. It can be said that the smaller the value, the smaller the Munich viscosity and the better the processability. Based on the obtained Munich viscosity value, the Munich viscosity was determined using the following judgment criteria A to D. A: less than 70 B: 70 or more and less than 85 C: 85 or more and less than 100 D: 100 or more

[0133] (3)Cold flow (C / F): The cold flow was measured by extruding the polymer through a 1 / 4-inch orifice at a pressure of 3.5 psi and a temperature of 70°C. To establish a stable condition, the extrusion speed was measured after 10 minutes and expressed in grams per minute (g / min). Furthermore, a smaller cold flow value indicates better shape stability (storage stability) and superior processability. Based on the obtained cold flow value, the cold flow was judged using the following criteria from A to D: A: less than 0.1 g / min B: less than 0.2 g / min and greater than 0.1 g / min C: less than 0.3 g / min and greater than 0.2 g / min D: greater than 0.3 g / min

[0134] (4) Tensile strength: The cross-linked body was used as the test specimen, and a tensile test was performed according to JISK 6251:2010. Here, a dumbbell-shaped No. 3 specimen was used as the test specimen, and the stress at fracture (TB) and elongation at fracture (EB) were measured at room temperature. It is shown that the larger the values ​​of TB and EB, the greater the fracture strength, the higher the mechanical strength of the material, and the better. The evaluation was based on the value of TB, and the index was evaluated using Comparative Example 1 as the benchmark. It can be said that the larger the value, the greater the tensile strength, and the better the strength. Based on the obtained tensile strength value, the tensile strength was determined using the following judgment criteria A to D. A: 110 or more B: 100 or more and less than 110 C: 80 or more and less than 100 D: less than 80

[0135] (5) Abrasion resistance: The cross-linked body was used as the test sample, and the abrasion amount was measured at 50°C and 15% slip rate using a Lamborn abrasion tester (manufactured by Shimada Giken Co., Ltd.) according to JIS K6264-2:2005. The index based on Comparative Example 1 was used for evaluation. The smaller the value, the less abrasion amount and the better the abrasion resistance. Based on the obtained abrasion amount value, the abrasion resistance was judged using the following judgment criteria A to D. A: less than 90 B: less than 95 and above 90 C: less than 100 and above 95 D: above 100

[0136] [Table 5] Formula (phr) Hydrogenated conjugated diene polymers 100 Silicon dioxide*1) 38 Carbon black *2) 37 Silane coupling agent *3) 3.2 Filler oil * 4) 34 stearic acid 2.0 Zinc oxide 3.0 Anti-aging agent*5) 1.0 Vulcanization accelerator CZ *6) 1.8 Vulcanization accelerator D *7) 1.5 sulfur 1.5 *1) Rhodia's ZEOSIL 1165MP *2) Tokai Carbon's Seast 3 *3) Evonik's Si75 *4) ENEOS's T-DAE process oil *5) Seiko Chemical's Ozonone 6C *6) Ouchi Shinsei Chemical Co., Ltd.'s Nocceler CZ *7) Ouchi Shinsei Chemical Co., Ltd.'s Nocceler D

[0137] [Table 6] Feature Evaluation Example 1 2 3 4 5 6 7 8 9 10 11 Types of polymers A B C D E F G H I J K solution viscosity B B B B B A A B C C C Munich viscosity B C C B B A B C B B B Cold flow B A B B B C C B B A C Tensile strength B B A B A C C A B A B Abrasion resistance B A A A A C C B A B A

[0138] [Table 7] Feature Evaluation Example Comparative example 12 13 14 15 16 17 1 2 3 4 Types of polymers L M N O P Q R S T U solution viscosity C C B A A C B D A C Munich viscosity B B C B B C B C B C Cold flow C B A C C B C A D D Tensile strength A A A B C A C B D B Abrasion resistance A A C B B A D B D B

[0139] As shown in Tables 6 and 7, it can be seen that the polymer compositions of Examples 1 to 17 can improve the solution viscosity, Munich viscosity, cold flow characteristics, tensile strength, and abrasion resistance of the polymers in a balanced manner. Among these, the tensile strength and abrasion resistance of the crosslinked polymer compositions of Examples 3, 5, 12, 13, and 17 are all rated "A", and the processability evaluation based on Munich viscosity of the polymer compositions of Examples 5, 12, and 13 is further rated "B", thus achieving a balance of various properties.

[0140] In contrast, in Comparative Example 1, where the ends of the polymer chains in the branched polymer were not modified by either the initiating modifier or the terminal modifier (b1), the abrasion resistance of the crosslinked body was rated as "D". In Comparative Example 2, where the content of polymer (A1) in the hydrogenated conjugated diene polymer was as high as 87% by mass, the solution viscosity was rated as "D". In Comparative Example 3, where the content of polymer (A1) in the [A]conjugated diene polymer was low, the cold flow characteristics, tensile strength, and abrasion resistance of the crosslinked body were rated as "D". In Comparative Example 4, where the ends of the polymer chains in the branched polymer were not modified by either the initiating modifier or the terminal modifier (b), although the tensile strength and abrasion resistance of the crosslinked body were improved, the cold flow characteristics were rated as "D". Thus, compared with the examples, the polymer compositions of Comparative Examples 1 to 4 all showed poor results. [Simplified Explanation of the Diagram]

[0015] None

Claims

1. A conjugated diene polymer, wherein when the structural units represented by formula (1), formula (2), formula (3), and formula (4) are respectively set as p, q, r, and s in the polymer, the value α represented by the following formula (i) is 0.65 to 0.97, and the conjugated diene polymer comprises 30% to 75% by mass of a polymer (A1) having a multi-branched structure having four or more molecular chains, wherein the polymer (A1) has a functional group comprising at least one element selected from the group consisting of nitrogen, oxygen, and sulfur at at least the branch point portion of the polymer (A1), α = (p + (0.5 × r)) / (p + q + (0.5 × r) + s) ... (i) 2. The conjugated diene polymer as claimed in claim 1, having structural units derived from aromatic vinyl compounds.

3. The conjugated diene polymer as described in claim 2, wherein, The proportion of structural units derived from aromatic vinyl compounds is greater than 0% by mass and less than 45% by mass.

4. The conjugated diene polymer as described in claim 1 or claim 2, wherein, The polymer (A1) has a structure in which four or more molecular chains are bonded to a structure derived from a coupling agent, the coupling agent having at least one element selected from the group consisting of nitrogen, oxygen, sulfur and silicon.

5. The conjugated diene polymer as described in claim 1 or claim 2, wherein, The polymer (A1) has secondary or tertiary amino groups at its terminal portions.

6. The conjugated diene polymer as claimed in claim 1 or claim 2, further comprising linear or branched polymers with three or fewer branches (A2).

7. The conjugated diene polymer as claimed in claim 6, wherein, The polymer (A2) comprises a linear polymer having a secondary or tertiary amine group at one end and a functional group comprising at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur and silicon at the other end.

8. A method for manufacturing a conjugated diene polymer, comprising: The polymerization step involves polymerizing a monomer containing a conjugated diene compound in the presence of a metal compound having an alkali metal or alkaline earth metal to obtain a conjugated diene polymer (I) with active ends; a reaction step involves reacting the conjugated diene polymer (I) with a compound [B] having four or more functional groups capable of reacting with the active ends to obtain a conjugated diene polymer (II); and a hydrogenation step involves hydrogenating the conjugated diene polymer (II) in such a way that the hydrogenation rate of the structural units of the conjugated diene compound is 65% to 97%, wherein the reaction step involves reacting the conjugated diene polymer (I) with the compound [B] in such a way that the conjugated diene polymer (II) contains 30% to 75% by mass of a polymer containing a multi-branched structure having four or more molecular chains, wherein at least the metal compound and the compound [B] contain at least one element selected from the group consisting of nitrogen, oxygen, and sulfur.

9. A method for manufacturing a conjugated diene polymer as described in claim 8, wherein, The metal compound is a metal amide compound containing an alkali metal or an alkaline earth metal.

10. A method for manufacturing a conjugated diene polymer as described in claim 8 or claim 9, wherein, The conjugated diene polymer (II) further comprises a linear or branched polymer with fewer than three branches, and after the reaction step and before the hydrogenation step, it further comprises the following step: by reacting a compound having at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur and silicon and capable of reacting with the active end and the linear polymer in the conjugated diene polymer (II), to obtain a linear or branched polymer having a functional group comprising at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur and silicon.

11. A polymer composition comprising a conjugated diene polymer as described in any one of claims 1 to 7, or a conjugated diene polymer obtained by a method for manufacturing a conjugated diene polymer as described in any one of claims 8 to 10, and an inorganic filler.

12. A crosslinked body formed by crosslinking a polymer composition as claimed in claim 11.

13. A tire having one or both of a tread or a sidewall formed using a polymer composition as described in claim 11.