Conjugated diene polymers and methods for producing the same, polymer compositions, crosslinked materials, and tires

Abstract

The conjugated diene polymer has a value α represented by numerical formula (i) of 0.65-0.97 when the composition ratio (molar ratio) of structural units represented by formulas (1)-(4) in the polymer is taken as p, q, r, and s, respectively. The conjugated diene polymer includes 25-75 mass% of a polymer (A1) having a multi-branched structure having four or more molecular chains, and the polymer (A1) has a functional group including at least one element selected from the group consisting of nitrogen, oxygen, and sulfur at a terminal portion and / or a branch point portion of the polymer. α = (p + (0.5 × r)) / (p + q + (0.5 × r) + s) ... (i)

Description

Cross-reference of related applications

[0001] This application is based on Japanese Patent Application No. 2021-41264, filed on March 15, 2021, and its contents are incorporated herein by reference. [Technical Field]

[0002] This disclosure relates to conjugated diene polymers, methods for producing the same, polymer compositions, crosslinked polymers, and tires. [Background technology]

[0003] Conjugated diene polymers obtained by polymerization using conjugated diene compounds have excellent properties such as heat resistance, abrasion resistance, mechanical strength, and moldability, and are therefore widely used in various industrial products such as pneumatic tires, vibration-damping rubber, and hoses.

[0004] In polymer compositions used in the manufacture of treads, sidewalls, etc., for pneumatic tires, it is known that inorganic fillers such as carbon black and silica are blended with conjugated diene polymers as reinforcing agents to improve the durability and wear resistance of the product. Furthermore, conventionally, conjugated diene polymers modified with compounds containing silicon or nitrogen have been used to increase the affinity between the conjugated diene polymer and the reinforcing agent (see, for example, Patent Documents 1 to 3).

[0005] In recent years, it has been proposed to obtain tire components with high strength and excellent wear resistance by using hydrogenated conjugated diene polymers having functional groups such as amino groups or alkoxysilyl groups at one or both ends (see Patent Document 4). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2008 / 123164 [Patent Document 2] Japanese Patent Application Publication No. 11-349632 [Patent Document 3] International Publication No. 2017 / 221943 [Patent Document 4] International Publication No. 2014 / 133097 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, due to environmental concerns and increased awareness of resource and energy conservation, there has been a growing demand to extend the lifespan of rubber products, increase their service life, and reduce their weight and size while maintaining their performance. Therefore, there is a need for materials that can produce cross-linked rubber (vulcanized rubber) that is stronger than conventional materials and also has excellent abrasion resistance.

[0008] However, generally speaking, wear resistance and strength are inversely related to processability; improving one tends to degrade the other. To manufacture higher quality rubber products such as tires, it is necessary for all of these properties to be excellent.

[0009] Furthermore, if the viscosity of the polymer solution is high, the fluidity of the polymer solution decreases. This raises concerns that smooth transfer of the polymer solution through piping or into containers may be difficult, and that hydrogen diffusion within the polymer solution may be low during hydrogenation reactions, leading to longer hydrogenation times. In such cases, it may be difficult to ensure sufficient productivity.

[0010] This disclosure has been made in view of the above-mentioned problems, and one of its objectives is to provide a conjugated diene polymer that can improve the strength and wear resistance of the crosslinked material and the processability of the polymer composition in a balanced manner, and that has a sufficiently low solution viscosity. [Means for solving the problem]

[0011] This disclosure provides the following conjugated diene polymers, methods for producing the same, polymer compositions, crosslinked products, and tires. [1] A conjugated diene polymer in which, when the constituent ratios (molar ratios) of the structural units represented by the following formula (1), the structural units represented by the following formula (2), the structural units represented by the following formula (3), and the structural units represented by the following formula (4) are p, q, r, and s, respectively, the value α represented by the following formula (i) is 0.65 to 0.97, wherein the conjugated diene polymer contains 25 to 75% by mass of a polymer (A1) having a highly branched structure with four or more molecular chains, and the polymer (A1) has a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, and sulfur, on one or both of the terminal portion and the branching point portion of the polymer (A1). α=(p+(0.5×r)) / (p+q+(0.5×r)+s) …(i) [ka]

[0012] [2] A method for producing a conjugated diene polymer, comprising: a polymerization step of 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) having an active end; a reaction step of reacting the conjugated diene polymer (I) with a compound [B] having four or more functional groups that can react with the active end to obtain a conjugated diene polymer (II); and a hydrogenation step of hydrogenating the conjugated diene polymer (II) such that the hydrogenation rate of structural units derived from the conjugated diene compound is 65 to 97%, wherein the reaction step is a step of reacting the conjugated diene polymer (I) with the compound [B] such that the conjugated diene polymer (II) contains 25 to 75% by mass of a polymer having a highly branched structure with four or more molecular chains, and at least one selected from the group consisting of the metal compound and the compound [B] contains at least one element selected from the group consisting of nitrogen, oxygen and sulfur.

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

[0014] The conjugated diene polymers of this disclosure can be used to obtain crosslinked materials that are high in strength and have excellent wear resistance. Furthermore, the conjugated diene polymers of this disclosure have sufficiently low solution viscosity and excellent productivity. Moreover, according to this disclosure, it is possible to obtain polymer compositions that are high in strength and have excellent wear resistance, while also having excellent processability (particularly Mooney viscosity and cold flow characteristics). [Modes for carrying out the invention]

[0015] The following details the matters related to the implementation of this disclosure. In this specification, numerical ranges indicated using "~" represent a range that includes the numbers indicated before and after "~" as the lower and upper limits, respectively.

[0016] [A] Conjugated diene polymers The conjugated diene polymer of this disclosure (hereinafter also referred to as "[A] conjugated diene polymer") has a value α represented by the following formula (i) of 0.65 to 0.97, where p, q, r, and s are the molar ratios of the structural units represented by formula (1), formula (2), formula (3), and formula (4) in the polymer, respectively. α=(p+(0.5×r)) / (p+q+(0.5×r)+s) …(i) [ka]

[0017] [A]Conjugated diene polymers are aggregates of polymers having structural units derived from conjugated diene compounds, and include polymers having a highly branched structure (i.e., branched polymers). Specifically, [A]conjugated diene polymers contain polymers (A1), which are branched polymers having a highly branched structure with four or more molecular chains, in an amount of 25 to 75% by mass relative to the total amount (100% by mass) of the [A]conjugated diene polymer. 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 and branching points. Such [A]conjugated diene polymers can be produced by a method including the following polymerization, reaction, and hydrogenation steps. Note that when polymer (A1) has a specific element in its terminal portion, polymer (A1) may have the specific element at all terminals (i.e., free ends), or it may have the specific element at some of its terminals. The branching point of a branched polymer refers to the branching point of the molecular chain; in other words, it is the end opposite the free end (i.e., the fixed end) of each molecular chain. Below, we will explain the method for producing [A] conjugated diene polymers, while also explaining the composition of [A] conjugated diene polymers.

[0018] <Polymerization process> This process involves polymerizing monomers containing a conjugated diene compound to obtain a conjugated diene polymer having an active end (hereinafter also referred to as "conjugated diene polymer (I)"). Conjugated diene polymer (I) is an aggregate of polymers having structural units derived from the conjugated diene compound and having an active end. Examples of conjugated diene compounds used for 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, and 2-chloro-1,3-butadiene. Among these, at least one selected from the group consisting of 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene is preferred, and at least one of 1,3-butadiene and isoprene is more preferred.

[0019] [A] The conjugated diene polymer may be a homopolymer of a conjugated diene compound, but from the viewpoint of a higher strength crosslinked body, it is preferable that it be a copolymer having structural units derived from an aromatic vinyl compound together with structural units derived from an aromatic vinyl compound. Examples of aromatic vinyl compounds used in polymerization include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, t-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, vinylxylene, vinylnaphthalene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene (e.g., 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene). Among these, styrene and α-methylstyrene are preferred as aromatic vinyl compounds.

[0020] [A] When the conjugated diene polymer is a copolymer of a conjugated diene compound and an aromatic vinyl compound, it is preferable that the copolymer contains 1,3-butadiene and styrene in its monomer composition, in terms of high living properties in anionic polymerization. This copolymer is preferable to have a random copolymerized portion in which the distribution of the conjugated diene compound and the aromatic vinyl compound is irregular, in terms of improving the dispersibility of inorganic fillers. [A] When the conjugated diene polymer is a random copolymer of a conjugated diene compound and an aromatic vinyl compound, it may further have a block portion consisting of the conjugated diene compound or the aromatic vinyl compound in addition to the random copolymerized portion.

[0021] [A] When the 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 greater than 0% by mass and less than or equal to 45% by mass of the total structural units constituting the [A] conjugated diene polymer. This range is preferable because it allows for the production of a crosslinked polymer with higher strength and wear resistance while maintaining good processability of the polymer composition, and also allows for a sufficiently low solution viscosity of the polymer. To achieve a sufficiently low solution viscosity of the polymer while increasing the strength of the crosslinked polymer and improving cold flow characteristics, the proportion of structural units derived from the aromatic vinyl compound is more preferably 2% by mass or more, and even more preferably 5% by mass or more, of the total structural units constituting the [A] conjugated diene polymer. Furthermore, from the viewpoint of lowering the Mooney viscosity of the polymer and suppressing a decrease in the wear resistance of the crosslinked material, the proportion of structural units derived from aromatic vinyl compounds is more preferably 40% by mass or less, even more preferably 38% by mass or less, and even more preferably 35% by mass or less, relative to the total structural units constituting the [A] conjugated diene polymer.

[0022] Furthermore, the proportion of structural units derived from aromatic vinyl compounds in the polymer is 1 These values ​​were measured by 1H-NMR. The conjugated diene compound and aromatic vinyl compound may be used individually or in combination of two or more.

[0023] [A] The monomers used in the polymerization reaction to obtain a conjugated diene polymer may include compounds other than the conjugated diene compound and the aromatic vinyl compound (hereinafter also referred to as "other monomers"). Examples of other monomers include acrylonitrile, methyl (meth)acrylate, and ethyl (meth)acrylate. The proportion of other monomers used is preferably 10% by mass or less, and more preferably 5% by mass or less, relative to the total amount of monomers used in polymerization.

[0024] Any polymerization method may be used, including solution polymerization, gas-phase polymerization, or bulk polymerization. Of these, solution polymerization is particularly preferred. Furthermore, either batch or continuous polymerization methods may be used. When using solution polymerization, one specific example of a polymerization method is to polymerize 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).

[0025] As polymerization initiators, metal compounds containing alkali metals or alkaline earth metals can be used. Of these, compounds containing alkali metals are preferred. Specific examples of metal compounds include alkyllithium compounds such as methyllithium, ethyllithium, n-propyllithium, n-butyllithium, sec-butyllithium, and t-butyllithium; 1,4-dilithiobutane, phenyllithium, stilbenithium, naphthyllithium, 1,3-bis(1-lithio-1,3-dimethylpentyl)benzene, 1,3-phenylenebis(3-methyl-1-phenylpentylidene)dilithium, sodium naphthyl, potassium naphthyl, and potassium ethoxy. Of these, lithium compounds are preferred as polymerization initiators.

[0026] Furthermore, the metal compound used as a polymerization initiator may be a metal amide compound having an alkali metal or alkaline earth metal. By carrying out polymerization to obtain a [A] conjugated diene polymer in the presence of a metal amide compound, an amino group (preferably a secondary or tertiary amino group) can be introduced to the polymerization initiation end of the conjugated diene polymer (more specifically, the free end portion of the branched polymer). The [A] conjugated diene polymer obtained by polymerization in the presence of a metal amide compound is preferable in that it exhibits a good balance between the strength and wear resistance of the crosslinked body and the processability of the polymer composition.

[0027] Among the metal amide compounds, it is preferable that the compound is obtained by mixing a lithium compound (for example, alkyllithium, etc.) with a compound having a nitrogen atom (hereinafter also referred to as the "starting-end modifier"). The starting-end modifier is preferably a secondary amine compound. Specific examples of secondary amine compounds include dimethylamine, diethylamine, dipropylamine, dibutylamine, dodecamethyleneimine, N,N'-dimethyl-N'-trimethylsilyl-1,6-diaminohexane, piperidine, pyrrolidine, hexamethyleneimine, heptamethyleneimine, dicyclohexylamine, N-methylbenzylamine, di-(2-ethylhexyl)amine, diallylamine, morpholine, N-(trimethylsilyl)piperazine, N-(tert-butyldimethylsilyl)-4-piperazine, and 1,3-ditrimethylsilyl-1,3,5-triazinan.

[0028] Furthermore, when polymerization is carried out in the presence of a metal amide compound, the metal amide compound may be prepared by pre-mixing the lithium compound and the starting modifier, and then the prepared metal amide compound may be added to the polymerization system and polymerization may be carried out. Alternatively, the lithium compound and the starting modifier may be added to the polymerization system, and the metal amide compound may be prepared by mixing the two in the polymerization system and then polymerization may be carried out. In the above polymerization, the amount of polymerization initiator used (total amount if two or more types are used) is preferably 0.01 to 20 mmol, and more preferably 0.05 to 15 mmol, per 100 g of monomer used for polymer synthesis.

[0029] Randomizers can be used to adjust the vinyl bond content, which represents the proportion of vinyl bonds in a polymer. Examples of randomizers include dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, 2,2-di(tetrahydrofuryl)propane, 2-(2-ethoxyethoxy)-2-methylpropane, triethylamine, pyridine, N-methylmorpholine, tetramethylethylenediamine, potassium dodecylbenzenesulfonate, and the like. These can be used individually or in combination of two or more.

[0030] Any organic solvent that is inert to the reaction can be used as the organic solvent for polymerization. For example, linear or cyclic aliphatic hydrocarbons, aromatic hydrocarbons, etc., can be used. Among these, hydrocarbons having 3 to 8 carbon atoms are preferred. Specific examples include propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis-2-butene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene, heptane, cyclopentane, methylcyclopentane, methylcyclohexane, 1-pentene, 2-pentene, cyclohexene, etc. The organic solvent can be used individually or in combination of two or more.

[0031] When solution polymerization is used, the monomer concentration in the reaction solvent is preferably 5 to 50% by mass, and more preferably 10 to 30% by mass, from the viewpoint of maintaining a balance between productivity and ease of polymerization control. The polymerization reaction temperature is preferably -20°C to 150°C, and more preferably 0 to 120°C. Furthermore, the polymerization reaction is preferably carried out under pressure sufficient to keep the monomer substantially in the liquid phase. Such pressure can be obtained by methods such as pressurizing the reactor with a gas inert to the polymerization reaction. By such a polymerization reaction, a conjugated diene polymer (I) having active ends can be obtained.

[0032] For the conjugated diene polymer (I) obtained by the above polymerization, the vinyl bond content in the structural units derived from 1,3-butadiene is preferably 15 to 85 mol%. A vinyl bond content of 15 mol% or more maintains flexibility and good processability in the resulting crosslinked material, and tends to exhibit excellent wear resistance in the low-slip region. Furthermore, the solution viscosity and Mooney viscosity of the polymer can be sufficiently reduced. The vinyl bond content of the conjugated diene polymer (I) is preferably 18 mol% or more, more preferably 20 mol% or more. Also, from the viewpoint of durability and cold flow characteristics of the crosslinked material obtained using the [A] conjugated diene polymer, the vinyl bond content of the conjugated diene polymer (I) is preferably 78 mol% or less, more preferably 65 mol% or less. In this specification, "vinyl bond content" refers to the percentage of structural units having 1,2-bonds relative to the total structural units derived from 1,3-butadiene in the conjugated diene polymer before hydrogenation. 1 This value is measured by an H-NMR instrument.

[0033] <Reaction Process> This step involves reacting the conjugated diene polymer (I) obtained by the polymerization step described above with a compound having four or more functional groups that can react with the active end 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 the conjugated diene compound.

[0034] [A] The [B] coupling agent used in the production of the conjugated diene polymer can be any compound having four or more reaction sites with the active end of the conjugated diene polymer, and is not particularly limited. Of these, a compound having at least one element selected from the group consisting of nitrogen, oxygen, sulfur, and silicon can be preferably used as the [B] coupling agent. When a compound having the above-mentioned specific element is used as the [B] coupling agent, it is preferable in that a crosslinked body can be obtained in which the strength and wear resistance of the crosslinked body and the processability of the polymer composition (more specifically, Mooney viscosity and cold flow) are further improved in a good balance.

[0035] [B]Specific examples of coupling agents include silicon-containing compounds such as tetrachlorosilane (silicon tetrachloride), tetramethoxysilane, and bis(trichlorosilyl)ethane.

[0036] Furthermore, as a coupling agent, a compound (hereinafter also referred to as "end modifier (b1)") can be used that has a functional group F containing at least one element (specific element) selected from the group consisting of nitrogen, oxygen, and sulfur, and has four or more reaction sites with the polymer chain obtained by the polymerization step. By using the end modifier (b1), a polymer having a functional group F at the branching point of the branched polymer can be obtained.

[0037] Specific examples of functional group F include, for example, primary amino groups, secondary amino groups, tertiary amino groups, protected primary amino groups, protected secondary amino groups, imino groups, nitrogen-containing heterocyclic groups (e.g., groups having heterocyclic rings such as pyridine rings and imide rings), hydroxyl groups, protected hydroxyl groups, thiol groups, protected thiol groups, and hydrocarbyloxysilyl groups. Functional group F is particularly preferably a nitrogen-containing functional group (nitrogen-containing group) in terms of its high effect in improving wear resistance, and it is especially preferable that it has at least one selected from the group consisting of primary amino groups, secondary amino groups, tertiary amino groups, and imino groups.

[0038] As the terminal modifier (b1), at least one compound selected from the group consisting of the compound represented by the following formula (5) and the compound represented by the following formula (6) can be preferably used. [Chemical formula] (In formula (5), R 1 and R 2 are each independently a hydrocarbyl group having 1 to 20 carbon atoms, R 3 is an alkanediyl group having 1 to 20 carbon atoms, A 1 is a group “*-C(R 5 )=N-” or a group “*-N=C(R 5 )-” (however, R 5 is a hydrogen atom or a hydrocarbyl group, and “*” indicates a bond that binds to R 4 ). R 4 is an m-valent hydrocarbon group having 1 to 20 carbon atoms, or an m-valent group having 1 to 20 carbon atoms that has at least one element selected from the group consisting of nitrogen, oxygen, and sulfur and to which no active hydrogen is bonded. n is an integer of 1 to 3, and m is an integer of 2 to 10. In the formula, a plurality of R 1 , R 2 , R 3 , A 1 , and n are the same or different. However, when m is 2 or 3, the sum of a plurality of n is m + 4 or more.) [Chemical formula] (In formula (6), R 6 , R 7 , R 10 and R 11 are each independently a hydrocarbyl group having 1 to 20 carbon atoms, R 8 and R 9 are each independently an alkanediyl group having 1 to 20 carbon atoms, A 2 is a group represented by the following formula (7), a group represented by the following formula (8), a group represented by the following formula (9), or a group represented by the following formula (10). w and p are each independently an integer of 1 to 3. However, A 2If the following equation (9) or equation (10) is true, then w and p are 3. In the equation, multiple R 6 , R 7 , R 10 , R 11 (These are either the same or different.) [ka] (In formula (7), R 12 , R 13 and R 15 Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, and R 14 and R 16 Each of these is an alkanediyl group having 1 to 20 carbon atoms, where q is an integer from 1 to 3 and r is an integer from 0 to 2. In the formula, multiple R 12 ~R 15 Each of these groups may be the same or different, and each of the multiple qs may be the same or different number. However, the sum of p, w, and q minus r is 6 or greater. "*" indicates a bond with the nitrogen atom in formula (6). [ka] (In formula (8), R 19 R is an alkanediyl group having 3 to 20 carbon atoms, and the nitrogen atom and silicon atom in the formula form a ring structure of 5 or more members. 17 and R 18 Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, and R 20 R is an alkanediyl group having 1 to 20 carbon atoms, and s is 1 or 2. In the formula, multiple R 17 , R 18 Each element may be identical or different. However, the sum of p, w, and s must be 7 or greater. "*" indicates a bond with the nitrogen atom in formula (6). [ka] (In formula (9), R 23 R is an alkanediyl group with 1 to 20 carbon atoms. 21 R is a hydrocarbylidene group having 1 to 20 carbon atoms. 22This is an alkanediyl or alkenediyl group having 1 to 20 carbon atoms, forming a ring structure of 5 or more members together with two adjacent nitrogen atoms. (* indicates a bond with the nitrogen atom in formula (6).) [ka] (In formula (10), R 26 R is a hydrocarbylene group having 1 to 20 carbon atoms. 24 and R 25 Each of these is independently a hydrocarbyl group having 1 to 20 carbon atoms, or R 24 and R 25 They are combined with each other R 24 and R 25 This represents a ring structure with 4 to 20 carbon atoms, formed together with the nitrogen atom to which it is bonded, or R 24 and R 25 They are combined with each other R 24 and R 25 The nitrogen atom to which it is bonded, and R 24 and R 25 This represents a ring structure of five or more members, composed of a nitrogen atom different from the nitrogen atom to which it is bonded, or a different nitrogen atom or oxygen atom. "*" indicates a bond with the nitrogen atom in formula (6).

[0039] (The compound represented by formula (5) above) In equation (5) above, R 1 , R 2 Examples of the hydrocarbyl group include alkyl groups with 1 to 20 carbon atoms, allyl groups, cycloalkyl groups with 3 to 20 carbon atoms, and aryl groups with 6 to 20 carbon atoms. 3 The alkanediyl group preferably has 1 to 10 carbon atoms, and more preferably 2 to 10 carbon atoms. 3 It is preferably linear in shape. A 1 R possessed 5 Regarding the hydrocarbyl group, R 1 and R 2 The explanation applies. n is preferably 2 or 3, and more preferably 3, in terms of its high effect in improving silica dispersibility.

[0040] R4 Examples of a hydrocarbon group with an m-valence include chain hydrocarbons having 1 to 20 carbon atoms, alicyclic hydrocarbons having 3 to 20 carbon atoms, or groups obtained by removing m hydrogen atoms from aromatic hydrocarbons having 6 to 20 carbon atoms. Specific examples of aromatic hydrocarbons include, for example, a ring structure represented by the following formula (C1), and a polycyclic structure formed by linking two or more such ring structures (e.g., a biphenyl group). [ka] (In equation (C1), r1 is an integer between 0 and 5.)

[0041] R 4 However, preferred specific examples of an m-valent group having 1 to 20 carbon atoms and possessing at least one element selected from the group consisting of nitrogen, oxygen, and sulfur, and to which no active hydrogen is bonded, 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 fused rings such as pyridine, pyrimidine, pyrazine, quinoline, naphthalidine, furan, and thiophene, or groups obtained by removing m hydrogen atoms from the ring portion of a structure in which multiple such monocyclic or fused rings are linked together. m is an integer from 2 to 10. From the viewpoint of processability of the polymer composition, m is preferably 2 to 6.

[0042] Specific examples of compounds represented by formula (5) above include, for example, the compounds represented by formulas (M-1) to (M-4) below. R in formula (M-1) below 27 n1 represents a hydrogen atom or an alkyl group, and n1 represents an integer from 1 to 8. [ka]

[0043] (The compound represented by formula (6) above) In equations (6) and (7) to (10) above, R 6 , R 7 , R 10 , R 11 , R 12 , R 13 , R15 , R 17 , R 18 , R 24 and R 25 Examples of the hydrocarbyl group having 1 to 20 carbon atoms for R 8 , R 9 , R 14 , R 16 , R 20 , R 21 , R 22 , R 23 and R 24 Examples of the alkanediyl group, alkenediyl group, and hydrocarbylidene group having 1 to 20 carbon atoms for R 19 are preferably those having 1 to 10 carbon atoms, more preferably 2 to 10 carbon atoms. R In the above formula (8), the ring structure formed by R 19 , a nitrogen atom, and a silicon atom is preferably a 5- to 7-membered ring, more preferably a 5- or 6-membered ring. In the above formula (9), the ring structure formed by R 21 , R 22 and two adjacent nitrogen atoms is preferably a 5- to 12-membered ring, more preferably a 5- to 7-membered ring. In the above formula (10), when R 24 and R 25 are combined with each other and represent a ring structure having 4 to 20 carbon atoms formed together with the nitrogen atom to which R 24 and R 25 are bonded, the ring structure preferably has 4 to 9 carbon atoms, more preferably 4 to 6 carbon atoms. R 24 and R 25 are combined with each other and represent a ring structure having 4 to 20 carbon atoms formed together with the nitrogen atom to which R 24 and R 25 are bonded, and R 24 and R 25 are bonded, and R 24 and R 25 ​​​​When referring to a ring structure of 5 or more members, which is composed of a nitrogen atom or oxygen atom different from the nitrogen atom to which it is bonded, the ring structure is preferably a 5 to 10-membered ring, more preferably a 5 to 7-membered ring. Specific examples of the above-mentioned ring structure of 5 or more members include, for example, a piperazine ring structure and a morpholine ring structure. w, p, and q are preferably 2 or 3, and more preferably 3, in terms of their high effect in improving silica dispersibility. For the same reason, s is preferably 2.

[0044] A specific example of the compound represented by formula (6) above is A in formula (6) above. 2 Examples of compounds in which the group represented by formula (7) above is N,N,N',N'-tetra(3-trimethoxysilylpropyl)ethylenediamine, N,N,N',N'-tetra(3-triethoxysilylpropyl)ethylenediamine, N,N,N'-tris(3-trimethoxysilylpropyl)-N'-methylethylenediamine, 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. A in equation (6) above 2 Examples of compounds in which the group represented by formula (8) above is bis(3-trimethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silacyclopentane)ethyl]amine, bis(3-triethoxysilylpropyl)-[2-(2,2-diethoxy-1-aza-2-silacyclopentane)ethyl]amine, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, bis(3-trimethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silacyclohexane)ethyl]amine, bis(3-trimethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silacyclooctane)ethyl]amine, etc.; A in equation (6) above 2Examples of compounds in which the group represented by the above formula (9) is N,N-bis(3-trimethoxysilylpropyl)-3-imidazolylpropylamine, etc. A in equation (6) above 2 Examples of compounds in which the group is represented by the above formula (10) include bis(3-trimethoxysilylpropyl)-(3-dimethylaminopropyl)amine, etc.

[0045] When a metal amide compound is used as a polymerization initiator in the polymerization step described above, a compound that does not contain nitrogen, oxygen, or sulfur (for example, the silicon-containing compound described above) may be used as the [B] coupling agent, or the end modifier (b1) may be used. On the other hand, when a metal amide compound is not used as a polymerization initiator in the polymerization step described above, the end modifier (b1) is used as the [B] coupling agent. Of these, it is preferable to use a metal amide compound as a polymerization initiator in the polymerization step described above and a silicon-containing compound (for example, silicon tetrachloride, etc.) as the [B] coupling agent in this step, or to use a metal amide compound as a polymerization initiator in the polymerization step described above and the end modifier (b1) as the [B] coupling agent in this step, in order to further improve the strength and wear resistance of the resulting crosslinked material and the processability of the polymer composition.

[0046] The reaction between the conjugated diene polymer (I) having an active end and the [B] coupling agent is preferably carried out as a solution reaction. The proportion of [B] coupling agent used (total amount if two or more types are used) can be appropriately set so that the content of polymer (A1) is within the desired range. Specifically, from the viewpoint of obtaining a crosslinked material exhibiting high strength and excellent wear resistance, as well as a polymer composition with excellent processability, the proportion of [B] coupling agent used is preferably 0.01 moles or more, and more preferably 0.05 moles or more, per mole of metal atoms involved in polymerization in the polymerization initiator (i.e., metal compound). Furthermore, from the viewpoint of adjusting the coupling rate to a desired value, suppressing a decrease in processability, and ensuring productivity by sufficiently lowering the solution viscosity of the polymer, the proportion of [B] coupling agent used is preferably 0.7 moles or less, and more preferably 0.5 moles or less, per mole of metal atoms involved in polymerization in the polymerization initiator. Note that one type of [B] coupling agent may be used alone, or two or more types may be used in combination.

[0047] The reaction temperature in the coupling reaction is usually the same as that of the polymerization reaction, preferably between -20°C and 150°C, and more preferably between 0°C and 120°C. If the reaction temperature is low, the viscosity of the polymer after the reaction tends to increase, and if the reaction temperature is high, the polymerization active ends tend to be deactivated. The reaction time is preferably between 1 minute and 5 hours, and more preferably between 2 minutes and 1 hour.

[0048] In the above coupling reaction, the coupling rate can be set according to the proportion of the polymer (A1) before hydrogenation present in the conjugated diene polymer (II), 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 material with high strength and excellent wear resistance, the coupling rate is preferably 25% or more, and more preferably 30% or more. Furthermore, from the viewpoint of obtaining a polymer composition with good processability and from the viewpoint of ensuring productivity by sufficiently lowering the solution viscosity of the polymer, the coupling rate is preferably 75% or less, and more preferably 70% or less.

[0049] In this specification, "coupling rate" refers to the proportion (mass%) of coupling polymers having two or more molecular chains among the polymers contained in the reaction system after reacting a linear conjugated diene polymer having an active end with a compound that can react with the active end. Specifically, it means the proportion (mass%) of polymers in which two or more linear molecular chains are bonded via the [B] coupling agent or end-modifying agent (c) among the total amount of polymers used in the reaction with the [B] coupling agent or end-modifying agent (c) (i.e., linear polymers contained in the conjugated diene polymer (I)). The coupling rate can be calculated from the peak area ratio of the GPC curve obtained using gel permeation chromatography (GPC). Similarly, the proportion of coupling polymers having four or more molecular chains can also be calculated from the peak area ratio of the GPC curve obtained using gel permeation chromatography (GPC).

[0050] The above coupling reaction can yield a conjugated diene polymer (II). The conjugated diene polymer (II) preferably contains a linear or branched polymer with three or fewer branches (i.e., the polymer (A2)) together with the polymer (A1) before hydrogenation. This linear or branched polymer with three or fewer branches is either a polymer in which three or fewer linear molecular chains are linked via a [B] coupling agent or terminal modifier (c) from among the polymers contained in the conjugated diene polymer (I), an unreacted polymer that did not react with the [B] coupling agent and terminal modifier (c), or both. In the conjugated diene polymer (II), the ratio of a polymer having a multi-branched structure with four or more molecular chains (i.e., the polymer (A1)) before hydrogenation to a linear or branched polymer with three or fewer branches can be appropriately set by adjusting the amount of [B] coupling agent used, the number of functional groups of the [B] coupling agent used, etc., so that the ratios of polymer (A1) and polymer (A2) in the [A] conjugated diene polymer are in the desired proportions.

[0051] Furthermore, when isolating the conjugated diene polymer contained in the reaction solution, this can be done by known desolvation methods such as steam stripping and drying operations such as heat treatment.

[0052] <Modification process> The conjugated diene polymer (II) obtained above may be subjected to the subsequent hydrogenation step as is. Alternatively, before the hydrogenation step, a treatment may be performed in which the polymerization termination ends of the linear polymer contained in the conjugated diene polymer (II) are reacted with the end modifier (c). Preferably, the end modifier (c) is a compound that has at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, and that can react with the active ends of the linear polymer. In this case, a linear or branched polymer with three or fewer branches can be obtained, having a functional group containing at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon. Note that the end modifier (c) differs from the [B] coupling agent in that it has three or fewer reaction sites with the active ends of the conjugated diene polymer (I).

[0053] A preferred example of the terminal denaturant (c) is at least one selected from the group consisting of compounds represented by the following formula (11) and compounds represented by the following formula (12). [ka] (In formula (11), A 11 It has at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, and does not have active hydrogen, and R 35 It is a monovalent functional group bonded to nitrogen, phosphorus, oxygen, sulfur, silicon, or a carbon atom contained in the carbonyl group, or a (thio)epoxy group. 33 and R 34 These are, independently, hydrocarbyl groups. 35 is a hydrocarbylene group. t is an integer from 0 to 2. However, if t is 2, multiple R in the formula 33 These are either identical or different from each other. If t is 0 or 1, multiple R in the expression34 They are either identical or different from one another. [ka] (In formula (12), A 12 It has at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, and does not have active hydrogen, and R 39 It is a monovalent functional group bonded to it by nitrogen, phosphorus, oxygen, sulfur, or silicon, or a hydrocarbyl group having 1 to 20 carbon atoms. 36 and R 37 These are, independently, hydrocarbyl groups. 38 This is a hydrocarbylene group. 39 is a single bond or a hydrocarbylene group. u is 0 or 1. However, if u is 0, multiple R in the formula 37 They are either identical or different from one another.

[0054] In equations (11) and (12) above, R 33 , R 34 , R 36 , R 37 , and A in the case of a hydrocarbyl group 12 Regarding this, the hydrocarbyl group is preferably a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. R 35 and R 39 The hydrocarbylene group is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms. 38 The hydrocarbylene group represented is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms. t is preferably 0 or 1.

[0055] A 11 When the above monovalent functional group is A 11 At least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, and A 12When the above monovalent functional group is A 12 At least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon may be protected by, for example, a trisubstituted hydrocarbylsilyl group. In this specification, active hydrogen refers to a hydrogen atom bonded to an atom other than a carbon atom, preferably one with a bond energy lower than the carbon-hydrogen bond of polymethylene. (Thio)epoxy group means encompassing epoxy groups and thioepoxy groups.

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

[0057] Specific examples of the terminal denaturant (c) include compounds represented by the above formula (11), such as N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-dimethylaminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-(4-trimethylsilyl-1-piperazino)propylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyltriethoxysilane.

[0058] Specific examples of compounds represented by formula (12) above include, for example, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1,2-azacyloridine, 2,2-diethoxy-1-(3-trimethoxysilylpropyl)-1,2-azacyloridine, 2,2-dimethoxy-1-phenyl-1,2-azacyloridine, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, 2-(2,2-dimethoxy-1,2-azacyloridine-1-yl)-N,N-diethylethane-1-amine, 2-(2,2-dimethoxy-1,2-azacyloridine-1-yl)-N,N-dimethylethane-1-amine, and 3-(2,2-dimethoxy-1,2-azacyloridine-1-yl)-N,N-diethylpropane-1-amine. The terminal denaturing agent (c) may be used alone or in combination of two or more types.

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

[0060] The amount of 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 moles or more, more preferably 0.1 moles or more, per mole of metal atoms involved in the polymerization reaction in the polymerization initiator. By using an amount of terminal modifier (c) of 0.1 molar equivalents or more, the modification reaction can be sufficiently advanced, and the dispersibility of the inorganic filler can be suitably improved. Furthermore, the amount of terminal modifier (c) is preferably 1.0 mole or less, more preferably 0.8 mole or less, per mole of metal atoms involved in the polymerization reaction in the polymerization initiator.

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

[0062] <Hydrogenation process> In this step, the conjugated diene polymer obtained by the above reaction or modification step is hydrogenated (hereinafter also referred to as "hydrogenation"). Any method and conditions for the hydrogenation reaction can be used as long as a conjugated diene polymer with the desired hydrogenation rate is obtained. Examples of such hydrogenation methods include: using a catalyst mainly composed of titanium organometallic compounds as a hydrogenation catalyst; using a catalyst consisting of organometallic compounds of iron, nickel, and cobalt and organometallic compounds such as alkylaluminum; using organic complexes of organometallic compounds such as ruthenium and rhodium; and using a catalyst in which metals such as palladium, platinum, ruthenium, cobalt, and nickel are supported on a carrier such as carbon, silica, or alumina. Among the various methods, the hydrogenation method using a titanium organometallic compound alone, or a homogeneous catalyst consisting of a titanium organometallic compound and a lithium, magnesium, or aluminum organometallic compound (for example, the catalysts described in Japanese Patent Publication No. 63-4841 and Japanese Patent Publication No. 1-37970), under mild conditions of low pressure and low temperature, is industrially preferred and also suitable due to its high hydrogenation selectivity to the double bond of butadiene.

[0063] Hydrogenation of conjugated diene polymers is preferably carried out using a solvent that is inert to the catalyst and in which the conjugated diene polymer is soluble. Preferred solvents include chain aliphatic hydrocarbons such as n-pentane, n-hexane, and n-octane; cyclic aliphatic hydrocarbons such as cyclohexane and cycloheptane; aromatic hydrocarbons such as benzene and toluene; and ethers such as diethyl ether and tetrahydrofuran. The solvent used for hydrogenation may be one of the above compounds or a mixture in which they are the main components.

[0064] Hydrogenation reactions are generally carried out by maintaining a conjugated diene polymer at a predetermined temperature under a hydrogen or inert atmosphere, adding a hydrogenation catalyst with or without stirring, and then introducing hydrogen gas to pressurize to a predetermined pressure. An inert atmosphere means an atmosphere that does not react with the substances involved in the hydrogenation reaction, and examples include helium, neon, and argon. Air and oxygen are undesirable because they oxidize the catalyst and lead to catalyst deactivation. Nitrogen is also undesirable because it acts as a catalyst poison during the hydrogenation reaction and reduces hydrogenation activity. In particular, an atmosphere of hydrogen gas alone is most preferable inside the hydrogenation reactor.

[0065] The hydrogenation reaction process can be used as a batch process, a continuous process, or a combination thereof. When a titanocenediaryl compound is used as the hydrogenation catalyst, it may be added directly to the reaction solution or as a solution in an inert organic solvent. When the catalyst is used as a solution, any inert organic solvent that does not react with the substances involved in the hydrogenation reaction can be used. Preferably, the same solvent used in the hydrogenation reaction is used. The preferred amount of catalyst to add is 0.02 to 20 mmol per 100 g of the conjugated diene polymer before hydrogenation.

[0066] [A] When the constituent ratios (molar ratios) of the structural units represented by formula (1), formula (2), formula (3), and formula (4) in the polymer are p, q, r, and s, respectively, the value α represented by the following formula (i) is between 0.65 and 0.97. α=(p+(0.5×r)) / (p+q+(0.5×r)+s) …(i) [ka]

[0067] [A] In conjugated diene polymers, the value α represented by the above formula (i) is more preferably 0.70 or higher, even more preferably 0.75 or higher, even more preferably 0.80 or higher, and particularly preferably 0.85 or higher, in order to obtain a crosslinked material with superior abrasion resistance. The value α represented by the above formula (i) corresponds to the hydrogenation rate of the conjugated diene polymer. For example, if α is 0.65, the hydrogenation rate of the conjugated diene polymer is 65%. Furthermore, α is more preferably 0.96 or lower, and even more preferably 0.93 or lower, in terms of forming a crosslinked structure and improving processability. The hydrogenation rate of the polymer and α can be adjusted, for example, by adjusting the time of the hydrogenation reaction or controlling the cumulative amount of hydrogen supplied. In this specification, the hydrogenation rate 1 These values ​​were measured using an H-NMR spectrometer.

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

[0069] [A] For conjugated diene polymers, the weight-average molecular weight (Mw) in polystyrene terms, measured using gel permeation chromatography (GPC), is preferably 1.5 × 10¹⁶, from the viewpoint of obtaining a crosslinked material with high strength and excellent abrasion resistance. 5 ~2.0×10 6 The Mw of the conjugated diene polymer is more preferably 1.8 × 10⁻⁶. 5 The above, and more preferably 2.0 × 10 5 That is all. Furthermore, Mw is more preferably 1.6 × 10 6More preferably 1.4 × 10 6 The following applies. Note that the weight-average molecular weight of the conjugated diene polymer referred to here is the value obtained from all peaks of the GPC curve measured by GPC before hydrogenation. Hereafter, this will also be referred to as the "total weight-average molecular weight."

[0070] 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., aggregates of different molecular weights) measured by GPC is preferably 1.1 or more and 4.0 or less. A molecular weight distribution of 1.1 or more is preferable in terms of excellent processability, and a molecular weight distribution of 4.0 or less is preferable in that the low hysteresis loss properties of the resulting crosslinked material can be sufficiently improved. The molecular weight distribution of the [A]conjugated diene polymer is more preferably 1.20 or more, and even more preferably 1.23 or more. Furthermore, the molecular weight distribution is more preferably 3.5 or less, and even more preferably 3.0 or less.

[0071] [A] For conjugated diene polymers, the peak top molecular weight of the peak with the smallest molecular weight, as measured by GPC (hereinafter also referred to as the "1st peak molecular weight"), is preferably 0.8 × 10⁻⁶. 5 ~1.0×10 6 It is within this range. The 1st peak molecular weight is 0.8 × 10⁻⁶. 5 The above is preferable because it allows for sufficiently high improvement in the strength and wear resistance of the resulting crosslinked material while also providing superior processability. The 1st peak molecular weight is more preferably 0.9 × 10⁶. 5 The above, and more preferably 1.0 × 10 5 That concludes the explanation. Furthermore, in order to improve processability and viscoelastic properties, the 1st peak molecular weight is more preferably 8.0 × 10⁻⁶. 5 The following, and more preferably 5.0 × 10 5 The results are as follows. Note that the 1st peak molecular weight is the value obtained from the GPC curve measured by GPC before hydrogenation.

[0072] The [A] conjugated diene polymer obtained by the above process contains 25 to 75% by mass of polymer (A1), which has a highly branched structure with four or more molecular chains and a functional group containing at least one specific element selected from the group consisting of nitrogen, oxygen, and sulfur, at either the terminal portion and / or branching point portion of polymer (A1). Preferably, polymer (A1) has a structure in which four or more molecular chains are bonded to a structure derived from a [B] coupling agent having at least one element selected from the group consisting of nitrogen, oxygen, sulfur, and silicon.

[0073] [A] The conjugated diene polymer preferably includes a linear or branched polymer (A2) with three or fewer branches, together with polymer (A1). More specifically, polymer (A2) is a hydrogenated polymer of the conjugated diene polymer (I) obtained by the polymerization step above, in which three or fewer linear molecular chains are linked via a [B] coupling agent or terminal modifier (c), or a hydrogenated unreacted polymer that did not react with the [B] coupling agent and terminal modifier (c), or both. From the viewpoint of obtaining a crosslinked material with higher strength and abrasion resistance, polymer (A2) preferably has a functional group containing at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon. Furthermore, from the viewpoint of obtaining a crosslinked material with higher strength and abrasion resistance, polymer (A2) preferably includes a linear polymer having a secondary or tertiary amino group at one terminal portion and a functional group containing at least one specific element selected from the group consisting of nitrogen, oxygen, and sulfur at the other terminal portion. A linear polymer with modified ends in this manner can be obtained by using a metal amide compound as a polymerization initiator in the polymerization step and performing the modification step described above.

[0074] [A] The proportion of polymer (A1) in the conjugated diene polymer is 25 to 75% by mass, when the amount of [A] conjugated diene polymer is set to 100% by mass. By having the proportion of polymer (A1) to [A] conjugated diene polymer within the above range, an excellent balance can be achieved between the strength and wear resistance of the crosslinked material and the processability of the polymer composition. Furthermore, by reducing the viscosity of the polymer solution, sufficient productivity can be ensured by smoothly transferring the polymer solution through piping or into containers during the polymer manufacturing process, and by shortening the hydrogenation time during the hydrogenation process. The proportion of polymer (A1) to [A] conjugated diene polymer is preferably 28% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 50% by mass or more. In addition, the proportion of polymer (A1) to [A] conjugated diene polymer is preferably 73% by mass or less, and more preferably 70% by mass or less.

[0075] [A] The proportion of polymer (A2) in the conjugated diene polymer is preferably 25 to 75% by mass when the amount of [A] conjugated diene polymer is taken as 100% by mass. The proportion of polymer (A2) relative to the [A] conjugated diene polymer is preferably 27% by mass or more, and more preferably 30% by mass or more. Furthermore, 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, even more preferably 60% by mass or less, and even more preferably 50% by mass or less. The proportions (by mass) of polymer (A1) and polymer (A2) in the [A] conjugated diene polymer can be calculated by separating the waveforms of the coupling polymers in the GPC curve obtained using GPC.

[0076] <Polymer composition> The polymer composition of this disclosure may contain, along with the [A]conjugated diene polymer, various components other than the [A]conjugated diene polymer.

[0077] [D] Silica The polymer composition in this disclosure 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, per 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 per 100 parts by mass of the rubber component, the low hysteresis loss, fracture properties, and abrasion resistance of the polymer composition can be sufficiently improved, and if it is 120 parts by mass or less, the processability of the polymer composition can be sufficiently improved.

[0078] The [D] silica used in the polymer composition of this disclosure is not particularly limited, and examples include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc., with wet silica being preferred among these. These silicas may be used individually or in combination of two or more. The BET specific surface area of ​​the silica (measured in accordance with ISO 5794 / 1) is 40 to 350 m². 2 The range of / g is preferred, and is 80 to 350m 2 A range of / g is even more preferable, between 120 and 350 m 2 A range of / g is particularly preferred. Silica with a BET specific surface area in this range has the advantage of being able to achieve both rubber reinforcing properties and dispersibility in [A] conjugated diene polymers. An example of such silica is "Nipsil AQ" manufactured by Tosoh Silica Co., Ltd. (BET specific surface area = 205 m²). 2 / g), "Nipsil KQ", manufactured by Degussa, product name "Ultrazil VN3" (BET specific surface area = 175m²) 2 Commercially available products such as ( / g) can be used.

[0079] The silica contained in the polymer composition in this disclosure may be a combination of two or more types with different specific surface areas. Specifically, CTAB with a specific surface area of ​​180 m² 2 / g or more, BET specific surface area 185m² 2 The first silica has a specific surface area of ​​95 m² or more and an aggregate size of 45 nm or more, and the CTAB specific surface area is 95 m². 2 / g or less, BET specific surface area of ​​100m 2It may also be used in combination with secondary silica, which is less than or equal to / g.

[0080] The polymer composition in this disclosure has a CTAB specific surface area of ​​180 m². 2 / g or more, BET specific surface area 185m² 2 The first silica has a specific surface area of ​​95 m² or more and an aggregate size of 45 nm or more, and the CTAB specific surface area is 95 m². 2 / g or less, BET specific surface area of ​​100m 2 It contains secondary silica at a concentration of less than / g. By using such primary and secondary silica in combination, it becomes possible to effectively disperse the primary silica, which has a small average primary particle size but a relatively large aggregate size, within the rubber component. This improves the dispersibility of silica and allows for excellent fracture strength, wear resistance, low fuel consumption, and processability.

[0081] The specific surface area of ​​the first silica with CTAB (cetyltrimethylammonium bromide) is preferably 190 m². 2 / g or more, more preferably 195m 2 / g or more, more preferably 197m 2 It is 1 / g or more. The specific surface area of ​​the CTAB is 180m². 2 If the value is less than / g, it tends to be difficult to obtain sufficient improvement in fracture strength and wear resistance. The CTAB specific surface area of ​​the first silica is preferably 350 m². 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 It is less than / g. The specific surface area of ​​CTAB is 350m². 2 When the amount exceeds [amount] / g, dispersibility deteriorates and aggregation occurs, leading to a tendency for physical properties to decline. The CTAB specific surface area of ​​silica is measured in accordance with ASTM D3765-92.

[0082] The BET specific surface area of ​​the first silica is preferably 190 m². 2 / g or more, more preferably 195m 2 / g or more, more preferably 210m 2 The BET specific surface area is 185 m² or more. 2If the value is less than / g, it tends to be difficult to obtain sufficient improvements in fracture strength and wear resistance. The BET specific surface area of ​​the first silica is preferably 350 m². 2 / g or less, more preferably 300m 2 / g or less, more preferably 260m 2 It is less than / g. The specific surface area of ​​BET is 350m². 2 When the concentration exceeds [amount] / g, dispersibility deteriorates and aggregation occurs, leading to a tendency for physical properties to decline. The BET specific surface area of ​​silica is measured according to ASTM D3037-81.

[0083] The aggregate size of the first silica is 45 nm or larger, preferably 50 nm or larger, more preferably 55 nm or larger, and even more preferably 60 nm or larger. Alternatively, the aggregate size of the first silica is preferably 100 nm or smaller, more preferably 80 nm or smaller, even more preferably 70 nm or smaller, and particularly preferably 67 nm or smaller. Having such aggregate sizes allows for good dispersibility (processability) while providing excellent fuel efficiency and wear resistance. The aggregate size of silica can be measured by the method described in Japanese Patent Application Publication No. 2011-140613.

[0084] The average primary particle diameter 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 diameter of the first silica is preferably 3 nm or more, more preferably 5 nm or more, and even more preferably 7 nm or more. Despite having such a small average primary particle diameter, the carbon black-like structure with the aggregate size described above can further improve the dispersibility (processability) of the silica, thereby further improving fuel efficiency and wear resistance. The average primary particle diameter of silica can be determined by observing the silica with a transmission or scanning electron microscope, measuring the particle diameter of 400 or more primary silica particles observed within the field of view, and averaging the results.

[0085] The CTAB specific surface area of ​​the second silica is preferably 10 m². 2 / g or more, more preferably 20m2 / g or more, more preferably 30m 2 It is 10 m² or more. The specific surface area of ​​the CTAB is 10 m². 2 If the amount is less than / g, the reinforcing properties will be low, and it may become difficult to ensure the mechanical strength and wear resistance required for polymer compositions used in tire manufacturing. The CTAB specific surface area of ​​the second silica is preferably 80 m². 2 / g or less, more preferably 60m 2 / g or less, more preferably 50m 2 It is less than / g. The specific surface area of ​​CTAB is 95m². 2 If the concentration exceeds [amount] / g, the dispersibility of silica may deteriorate, making it difficult to improve fracture strength and wear resistance.

[0086] The BET specific surface area of ​​the second silica is preferably 10 m². 2 / g or more, more preferably 20m 2 / g or more, more preferably 30m 2 The BET specific surface area of ​​the second silica is 10 m² or more. 2 If the value is less than / g, the reinforcing properties will be low, and it may be difficult to ensure the mechanical strength and wear resistance required for polymer compositions used in tire manufacturing. The BET specific surface area of ​​the second silica is preferably 85m². 2 / g or less, more preferably 60m 2 / g or less, more preferably 50m 2 It is less than / g. The specific surface area of ​​BET is 100m². 2 If the concentration exceeds [amount] / g, the dispersibility of silica may deteriorate, making it difficult to improve fracture strength and wear resistance.

[0087] The average primary particle diameter of the second silica is preferably 20 nm or more, more preferably 25 nm or more, even more preferably 30 nm or more, particularly preferably 35 nm or more, and most preferably 55 nm or more. Alternatively, the average primary particle diameter of the second silica is preferably 500 nm or less, more preferably 200 nm or less, even more preferably 100 nm or less, and particularly preferably 70 nm or less. Having such an average primary particle diameter improves fracture strength and wear resistance.

[0088] [E] Carbon Black The polymer composition of this disclosure preferably contains [E] carbon black as an inorganic filler, from the viewpoint of fracture properties and wear resistance of the polymer composition. The carbon black is not particularly limited, and examples include GPF, FEF, HAF, ISAF, and SAF grade carbon black. The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited. In order to obtain the effects of this disclosure more fully, it is 50 to 200 m 2 / g is preferred, and 70-150m 2 / g is more preferable. Nitrogen adsorption specific surface area (N2SA) is the value obtained by measuring the amount of nitrogen adsorbed onto the carbon black surface according to JIS K6217-2:2001 "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method". Carbon black may be used alone or two or more types may be used in combination. The amount of carbon black blended is preferably in the range of 1 to 150 parts by mass, and more preferably in the range of 5 to 120 parts by mass, per 100 parts by mass of [A] conjugated diene polymer.

[0089] [Other fillers] The compositions of this disclosure may include, in addition to the above-mentioned [D] silica and [E] carbon black, other fillers as inorganic fillers. Such other fillers include alumina (Al2O3) such as γ-alumina and α-alumina, alumina monohydrate (Al2O3·H2O) such as boehmite and diaspore, 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 white (TiO2), titanium black (TiO2) 2n-1), calcium oxide (CaO), calcium hydroxide [Ca(OH)2], 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.) Examples include calcium silicate (Ca2SiO4, etc.), aluminum calcium silicate (Al2O3·CaO·2SiO2, etc.), magnesium calcium silicate (CaMgSiO4), calcium carbonate (CaCO3), zirconium oxide (ZrO2), zirconium hydroxide [ZrO(OH)2·nH2O], zirconium carbonate [Zr(CO3)2], and various zeolites, as well as crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals to correct the charge.

[0090] In the polymer composition of this disclosure, the amount of inorganic filler ([D] silica, [E] carbon black, and other fillers) is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, per 100 parts by mass of rubber component ([A] including conjugated diene polymer), and the amount of filler is preferably 150 parts by mass or less, more preferably 130 parts by mass or less. If the amount of filler in the polymer composition is within the above range, when the polymer composition of this disclosure is applied to the manufacture of tire treads, it is possible to further improve the low rolling resistance of the tire, braking performance on wet roads, handling performance on dry roads, and wear resistance while achieving a high level of balance.

[0091] [F] Other rubber components The compositions of this disclosure may contain only a [A] conjugated diene polymer as the rubber component. Alternatively, in addition to the [A] conjugated diene polymer, a rubber component different from the [A] conjugated diene polymer (hereinafter also referred to as [F] component) may be contained, to the extent that it does not impair the effects of this disclosure. As the [F] component, for example, one or more diene rubbers selected from natural rubber, isoprene rubber, butadiene rubber, emulsion polymerized styrene-butadiene rubber, solution polymerized styrene-butadiene rubber, butyl rubber, halogenated butyl rubber, and ethylene-propylene rubber can be used. Among these, it is preferable to contain at least one selected from natural rubber, butadiene rubber, and styrene-butadiene rubber. The manner in which the [F] component and the [A] conjugated diene polymer are mixed is not particularly limited. For example, the [F] component and the [A] conjugated diene polymer may be mixed during kneading using a Banbury mixer or rolls, as is commonly done. Alternatively, the [F] component may be added to the [A] conjugated diene polymer in a solution state after polymerization.

[0092] The amount of component [F] is preferably 80% by mass or less, and more preferably 60% by mass or less, relative to the total amount of rubber components ([A] conjugated diene polymer and component [F]) contained in the polymer composition. In this specification, "rubber component" contained in the polymer composition refers to a polymer from which a cured product exhibiting rubber elasticity can be obtained by thermosetting. The cured product exhibits the property of undergoing large deformation with a small force at room temperature (for example, deformation that stretches to more than twice its original size when stretched at room temperature), and rapidly returning to almost its original shape when the force is removed.

[0093] In this disclosure, liquid rubber may be used as part or all of the other rubber components, from the viewpoint of further improving dry grip performance, wet grip performance, and blowout resistance.

[0094] Examples of liquid rubber 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 with a weight-average molecular weight of 1,000 to 100,000, preferably 2,000 to 80,000, can be used. In this specification, weight-average molecular weight refers to the weight-average molecular weight on a polystyrene basis, as analyzed by gel permeation chromatography (GPC). The liquid rubber used in this disclosure refers to a material that is fluid at 23°C.

[0095] [G]Thermoplastic resin The polymer composition of this disclosure may contain [G] thermoplastic resin. From the viewpoint of obtaining a crosslinked material with excellent properties in terms of strength, abrasion resistance and crack growth resistance, the thermoplastic resin is preferably at least one selected from the group consisting of styrene resins, polyethylene, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene resins, alkylphenol resins, and terpene resins. The thermoplastic resin may be used alone or in combination of two or more types.

[0096] Here, the styrene-based resin is a polymer obtained using a styrene-based monomer, and among these, it is preferable that the polymer contains 20% by mass or more of structural units derived from the styrene-based monomer 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, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene. Of these, it is preferable that the styrene-based monomer is at least one of styrene and α-methylstyrene.

[0097] Styrene resins may be homopolymers obtained by polymerizing one type of styrene monomer, or copolymers obtained by copolymerizing two or more types of styrene monomers. Styrene resins may also be copolymers obtained using a styrene monomer and other monomers that can copolymerize with the styrene monomer. Examples of other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, acrylics, and unsaturated carboxylic acids such as methacrylic acid; unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate; dienes such as chloroprene and butadiene isoprene; olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or their acid anhydrides, etc.

[0098] The softening point of styrene-based resins 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, there is a tendency to obtain an improved crack growth resistance effect in the crosslinked material. Furthermore, the softening point of styrene-based resins 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 dispersibility of the resin is good, and there is a tendency to improve crack growth resistance, abrasion resistance, and tensile strength. In this disclosure, the softening point of styrene-based resins is the value measured using a ring-type softening point measuring device according to the method specified in JIS K 6220-1:2015, and is the temperature at which the sample softens and the sphere placed on the sample falls onto the bottom plate.

[0099] As the styrene-based resin, a block polymer (thermoplastic elastomer) having a conjugated diene polymer block as a soft segment and a polystyrene-based block as a hard segment can also be used. Using such a block polymer is preferable because it can further improve crack growth resistance. In addition, the conjugated diene polymer block in the above block polymer may have some of the carbon-carbon double bonds in the structural unit derived from the conjugated diene compound hydrogenated.

[0100] Examples of conjugated diene compounds constituting the above-mentioned conjugated diene polymer block include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. These conjugated diene compounds can be used individually or in combination of two or more. Among these, it is preferable that the conjugated diene compound be at least one of 1,3-butadiene and isoprene. The content of conjugated diene units in the block polymer is preferably 20% by mass or more, and more preferably 30% by mass or more. Furthermore, the content of conjugated diene units is preferably 80% by mass or less, and more preferably 70% by mass or less.

[0101] The content of polystyrene blocks in the above block polymer is preferably 20% by mass or more, in order to achieve higher tensile strength. Furthermore, the content of polystyrene blocks is preferably 80% by mass or less, and more preferably 70% by mass or less. The respective content ratios of polystyrene blocks, conjugated diene polymer blocks, and conjugated diene units in the block polymer are as follows: 1 It can be calculated by the integration ratio of the H-NMR spectrum.

[0102] Specific examples of the block polymers mentioned above include styrene-butadiene block copolymers, styrene-isoprene block copolymers, epoxidized styrene-butadiene block copolymers, and block copolymers obtained by hydrogenating a portion of the conjugated diene polymer block of a styrene-butadiene block copolymer or styrene-isoprene block copolymer. More specifically, examples include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene-butylene-styrene block copolymer (SBBS), and epoxidized styrene-butadiene-styrene block copolymers, as well as hydrogenated versions of these copolymers. Among these block polymers, SBS or SIS, which have a conjugated diene polymer block in which the soft segment is not hydrogenated, or epoxidized styrene-butadiene-styrene block copolymer can be preferably used due to their ease of crosslinking.

[0103] 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 a C5 fraction using a Friedel-Crafts type catalyst (such as AlCl3 or BF3). Specific examples of C5 resins include copolymers mainly composed of isoprene, cyclopentadiene, 1,3-pentadiene, 1-pentene, copolymers of 2-pentene and dicyclopentadiene, and polymers mainly composed of 1,3-pentadiene.

[0104] C9 resins are solid polymers (C9 synthetic petroleum resins) obtained by polymerizing a C9 fraction using a Friedel-Crafts type catalyst (such as AlCl3 or BF3). Specific examples of C9 resins include copolymers mainly composed of indene, methylindene, vinyltoluene, etc. C5 / C9 resins are solid polymers (C5 / C9 synthetic petroleum resins) obtained by polymerizing C5-C9 fractions using a Friedel-Crafts type catalyst (such as AlCl3 or BF3). Specific examples of C5 / C9 resins include copolymers mainly composed of vinyltoluene, indene, etc. For C5 / C9 resins, resins with a low concentration of C9 and above components are preferable from the viewpoint of compatibility with rubber components. Specifically, for C5 / C9 resins, it is preferable that the amount of C9 and above components in the total resin is less than 50% by mass, and more preferably 40% by mass or less.

[0105] Dicyclopentadiene resins are petroleum resins that use dicyclopentadiene from the C5 fraction as the main raw material. Specific examples of dicyclopentadiene resins include the "Marcaretz 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 alkylphenol-formaldehyde resins.

[0106] Terpene resins are solid resins obtained by polymerizing turpentine oil, which is obtained simultaneously when rosin is obtained from pine trees, or polymer components separated therefrom, using a Friedel-Crafts type catalyst. Examples include β-pinene resin and α-pinene resin. Commercially available terpene resins can be used, such as the "YS Resin" series (PX-1250, TR-105, etc.) from Yasuhara Chemical Co., Ltd., and the "PicoLite" series (A115, S115, etc.) from Hercules Corporation.

[0107] A typical example of a terpene-aromatic compound resin is terpene-phenol resin. This terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Friedel-Crafts type catalyst, or by further condensation with formalin. There are no particular restrictions on the terpenes used as raw materials, but monoterpene hydrocarbons such as α-pinene and limonene are preferred, those containing α-pinene are more preferred, and α-pinene is particularly preferred. In this disclosure, a terpene-phenol resin with a low proportion of phenol components is preferred. Here, "low proportion of phenol components" means that the phenol component in the total amount of resin is less than 50% by mass, preferably 40% by mass or less. Furthermore, if a terpene-aromatic compound resin, particularly a terpene-phenol resin, is used as the [G] thermoplastic resin, handling performance can be further improved. Commercially available terpene-aromatic compound resins can be used. Examples of commercially available products include the product names "Tamanol 803L" and "Tamanol 901" (manufactured by Arakawa Chemical Industries, Ltd.), and the "YS Polystar (registered trademark)" series (manufactured by Yasuhara Chemical Co., Ltd.).

[0108] The amount of thermoplastic resin added is preferably 1 part by mass or more per 100 parts by mass of rubber component in the polymer composition. By adding 1 part by mass or more of thermoplastic resin, the crosslinked body obtained using the polymer composition can be sufficiently improved by the addition of thermoplastic resin, which is preferable. The amount of thermoplastic resin added is more preferably 3 parts by mass or more per 100 parts by mass of rubber component, and even more preferably 7 parts by mass or more. Furthermore, from the viewpoint of maintaining the various properties of the polymer composition well, the amount of thermoplastic resin added is preferably 50 parts by mass or less per 100 parts by mass of rubber component in the polymer composition, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less. Note that one type of thermoplastic resin may be used alone, or two or more types may be used in combination.

[0109] [H] Silane coupling agent In this disclosure, the dispersibility of silica can be further enhanced by combining it with a silane coupling agent. The silane coupling agent used is not particularly limited. Among them, sulfur-containing silane coupling agents are preferred, such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropylbenzothiazoletetrasulfide, γ-mercaptopropyltriethoxysilane, and 3-octanoylthiopropyltriethoxysilane.

[0110] The amount of silane coupling agent is preferably 1 to 20 parts by mass per 100 parts by mass of silica. If the amount of silane coupling agent is less than 1 part by mass, the amount may be too small to sufficiently improve the dispersibility of silica. Conversely, if it exceeds 20 parts by mass, the processability and elongation at break may deteriorate. The amount of silane coupling agent is more preferably 5 to 15 parts by mass per 100 parts by mass of silica.

[0111] [I] Crosslinking agent The polymer composition of this disclosure may contain a crosslinking agent. By containing a crosslinking agent in the polymer composition of this disclosure, a crosslinked body with sufficiently improved strength and abrasion resistance can be obtained. Examples of crosslinking agents include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyvalent amine compounds, alkylphenol resins having methylol groups, etc., and sulfur is usually used. The amount of crosslinking agent is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the total amount of rubber components contained in the polymer composition.

[0112] [J] Extension oil The polymer composition of this disclosure may contain a process oil commonly used for oil-expanding elastomers as an oil for oil-expanding (expanding oil). The method of adding the process oil is not particularly limited. For example, the process oil may be spread into the conjugated diene polymer solution after polymerization and then desoluble to be incorporated as an oil-expandable rubber, or the process oil may be incorporated into the polymer composition by directly adding the process oil during kneading with a Banbury mixer or rolls. Preferred process oils include various oils known in the industry, such as aromatic oils, paraffinic oils, naphthenic oils, vegetable oils, and oils with a low content of polycyclic aromatic compounds (low PCA oils), such as mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), special residual aromatic extracts (SRAE), and heavy naphthenic oils. Examples of commercially available MES, TDAE, and SRAE include Shell's Catenex SNR (heavy paraffin obtained by dewaxing distillate oil with 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 amount of process oil blended is preferably 10 to 100 parts by mass per 100 parts by mass of the total amount of polymer components contained in the polymer composition.

[0113] In addition to the components described above, the polymer composition may contain various additives commonly used in polymer compositions for obtaining vulcanized rubber, such as antioxidants, 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 depending on the components, as long as they do not impair the effects of the disclosed material.

[0114] The polymer composition disclosed herein can be applied to various rubber products as a crosslinked body by mixing polymer components and inorganic fillers, as well as components added as needed, using a mixer such as an open-type mixer (e.g., a roll mixer) or a closed-type mixer (e.g., a Banbury mixer), and then crosslinking (vulcanizing) after molding. Specifically, the above crosslinked body can be applied to tire applications such as tire treads, undertreads, carcasses, sidewalls, and bead sections; sealing materials such as packings, gaskets, weatherstrips, and O-rings; interior and exterior surface materials for various vehicles such as automobiles, ships, aircraft, and railways; building materials; vibration-damping rubber for industrial machinery and equipment; various hoses and hose covers such as diaphragms, rolls, radiator hoses, and air hoses; belts such as power transmission belts; linings; dust boots; medical equipment materials; fenders; insulating materials for electric wires; and other industrial products.

[0115] [A] Conjugated diene polymers can be used to obtain crosslinked materials with good physical properties required for tire applications, such as tensile strength and abrasion resistance. Therefore, polymer compositions containing [A] conjugated diene polymers can be suitably used as materials for tire treads, sidewalls, or both.

[0116] Tires can be manufactured according to conventional methods. For example, a polymer composition can be mixed in a kneader to form a sheet, which can then be placed in a predetermined position (for example, outside the carcass in the case of a sidewall) according to conventional methods and vulcanized to form a tread or sidewall, thereby obtaining a pneumatic tire. [Examples]

[0117] The following will provide a detailed explanation based on the examples. However, this disclosure is not limited to these examples. In the examples and comparative examples, "parts" and "%" refer to mass unless otherwise specified. The methods for measuring various physical properties of polymers are shown below.

[0118] [Polymer property evaluation] • Vinyl bond content (mol%): For the polymer before hydrogenation, at 400 MHz 1 It was measured by 1H-NMR. • Bound styrene content (%): For polymer before hydrogenation, at 400 MHz 1 It was measured by 1H-NMR. • 1st peak average molecular weight: For the polymer before hydrogenation, a chart based on the molecular weight in polystyrene equivalent was obtained using a gel permeation chromatograph (GPC, product name: HLC-8020 (product name (Tosoh Corporation))), and the average molecular weight was determined from the retention time of the peak with the longest retention time in the obtained GPC curve. The specific measurement conditions are as follows. (Measurement conditions) Two GMH-HR-H columns (manufactured by Tosoh Corporation) were connected in series. Detector: Differential refractometer RI-8020 (manufactured by Tosoh Corporation) Eluent: Tetrahydrofuran Column temperature: 40℃ Flow rate: 1.0ml / min Sample concentration: 10 mg / 20 ml • Total weight-average molecular weight: For the polymer before hydrogenation, this was determined from all peaks of the GPC curve obtained using GPC (HLC-8020 (product name (manufactured by Tosoh Corporation))) and converted to polystyrene equivalent. The measurement conditions were the same as above. • Coupling rate (mass%): For the polymer before hydrogenation, the proportion of coupling polymers having two or more molecular chains was calculated from the peak area ratio of the GPC curve obtained using GPC (HLC-8020 (product name (manufactured by Tosoh Corporation))). • Hydrogenation rate and measurement were performed using α:tetrachloride ethylene as the solvent and a 100 MHz instrument. 1 It was calculated from the H-NMR spectrum. • Polymer (A1) content (mass%): For the polymer before hydrogenation, this was calculated by separating the waveforms of coupling polymers with four or more branches in the GPC curve obtained using GPC (HLC-8020 (product name (manufactured by Tosoh Corporation))).

[0119] <Synthesis of hydrogenated conjugated diene polymers> [Example 1: Synthesis and properties of hydrogenated conjugated diene polymer A] 25,900 g of cyclohexane, 65 g of tetrahydrofuran, 370 g of styrene, 3,219 g of 1,3-butadiene, and 63 mmol of piperidine were charged into a nitrogen-purged autoclave reactor. After adjusting the temperature of the reactor contents to 42°C, polymerization was started by adding a cyclohexane solution containing n-butyllithium (86 mmol). Polymerization was carried out under adiabatic conditions. After confirming that the polymerization conversion rate reached 99%, 111 g of 1,3-butadiene was added, and polymerization was continued for a further 3 minutes to obtain a reaction solution containing the polymer. 10 mmol of silicon tetrachloride was added to the obtained reaction solution and reacted for 5 minutes. Next, the reaction mixture was heated to over 80°C, hydrogen was introduced into the system, and then 1.64 g of diethylaluminum chloride, 3.67 g of bis(η5-cyclopentadienyl)titanium(furfuryloxy)chloride, and 1.67 g of n-butyllithium were added. 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 of 0.7 MPa or higher until the predetermined hydrogen cumulative value was reached. The reaction mixture was then returned to room temperature and atmospheric pressure and withdrawn from the reaction vessel to obtain the polymer solution. The obtained polymer solution was desolvated by steam stripping and dried using a hot roll 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.

[0120] [Examples 2, 4-11, 14-17 and Comparative Examples 1-3: Synthesis and properties of hydrogenated conjugated diene polymers B, D-K, N-Q, R-T] Hydrogenated conjugated diene polymers B, D-K, N-Q, and R-T were obtained using the same method as in Example 1, except that the polymerization formulation was modified as shown in Tables 1 and 2, and the hydrogenation rate was modified as shown in Tables 3 and 4. In Example 4 and Comparative Example 1, no starting modifier was used. The various physical properties of the obtained hydrogenated conjugated diene polymers B, D-K, N-Q, and R-T are shown in Tables 3 and 4.

[0121] [Example 3: Synthesis and properties of hydrogenated conjugated diene polymer C] 25,900 g of cyclohexane, 65 g of tetrahydrofuran, 370 g of styrene, 3,219 g of 1,3-butadiene, and 63 mmol of piperidine were charged into a nitrogen-purged autoclave reactor. After adjusting the temperature of the reactor contents to 42°C, polymerization was started by adding a cyclohexane solution containing n-butyllithium (86 mmol). Polymerization was carried out under adiabatic conditions. After confirming that the polymerization conversion rate reached 99%, 111 g of 1,3-butadiene was added and polymerization was continued for a further 3 minutes to obtain a reaction solution containing the polymer. 10 mmol of silicon tetrachloride was added to the obtained reaction solution and reacted for 5 minutes, and then 28 mmol of N,N-dimethylaminopropyltriethoxysilane was added and reacted for 15 minutes. Next, the reaction mixture was heated to over 80°C, hydrogen was introduced into the system, and then 1.64 g of diethylaluminum chloride, 3.67 g of bis(η5-cyclopentadienyl)titanium(furfuryloxy)chloride, and 1.67 g of n-butyllithium were added. 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 of 0.7 MPa or higher until the predetermined hydrogen cumulative value was reached. The reaction mixture was then returned to room temperature and atmospheric pressure and withdrawn from the reaction vessel to obtain the polymer solution. The obtained polymer solution was desolvated by steam stripping and dried using a hot roll 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.

[0122] [Example 12 and Comparative Example 4: Synthesis of Hydrogenated Conjugated Diene Polymers L and U and Their Physical Properties] Hydrogenated conjugated diene polymers L and U were obtained using the same method as in Example 1, except that the polymerization formulation was modified as shown in Table 2. In Comparative Example 4, no starting modifier was used. The various physical properties of the obtained hydrogenated conjugated diene polymers L and U are shown in Table 4.

[0123] [Example 13: Synthesis and properties of hydrogenated conjugated diene polymer M] In a nitrogen-purged autoclave reactor with a volume of 50 liters, 25,900 g of cyclohexane, 65 g of tetrahydrofuran, 0.74 g of potassium dodecylbenzenesulfonate, 740 g of styrene, 2,849 g of 1,3-butadiene, and 63 mmol of piperidine were charged. After adjusting the temperature of the reactor contents to 42°C, polymerization was started by adding a cyclohexane solution containing n-butyllithium (43 mmol). Polymerization was carried out under adiabatic conditions. After confirming that the polymerization conversion rate reached 99%, 111 g of 1,3-butadiene was added and polymerization was continued for a further 3 minutes to obtain a reaction solution containing the polymer. 2.6 mmol of silicon tetrachloride was added to the obtained reaction solution and reacted for 5 minutes, and then 24 mmol of N,N-dimethylaminopropyltriethoxysilane was added and reacted for 15 minutes. Next, the reaction mixture was heated to over 80°C, hydrogen was introduced into the system, and then 1.64 g of diethylaluminum chloride, 3.67 g of bis(η5-cyclopentadienyl)titanium(furfuryloxy)chloride, and 1.67 g of n-butyllithium were added. 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 of 0.7 MPa or higher until the predetermined hydrogen cumulative value was reached, and the reaction mixture was returned to room temperature and atmospheric pressure and withdrawn from the reaction vessel to obtain a polymer solution. The obtained polymer solution was desolvated by steam stripping and dried using a hot roll 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.

[0124] [Table 1]

[0125] [Table 2]

[0126] In Tables 1 and 2, "-" indicates that the compound in the corresponding column was not used. The abbreviations for vinyl content modifiers, start-end modifiers, end-end modifiers, and coupling agents are as follows: V-1: Potassium dodecylbenzenesulfonate INI-1:Nt-Butyldimethylsilyl-4-piperazine Mod-1: N,N-dimethylaminopropyltriethoxysilane Mod-2: Compounds represented by the following formula (Mod-2) [ka]

[0127] [Table 3]

[0128] [Table 4]

[0129] <Manufacturing of polymer compositions and crosslinked materials> Using the hydrogenated conjugated diene polymers A-Q and R-U produced above, polymer compositions were manufactured by blending each component according to the formulations shown in Table 5 and kneading them. The kneading was carried out by the following method. Using a Plastmill (capacity: 250 ml) equipped with a temperature control device, the first stage of kneading was performed at a filling rate of 72% and a rotation speed of 60 rpm, blending the hydrogenated modified conjugated diene polymers (A-Q, R-U), silica, carbon black, silane coupling agent, spreading oil, stearic acid, zinc oxide, and antioxidant to obtain polymer composition A. Next, in the second stage of kneading, after cooling the obtained blend to room temperature, a vulcanization accelerator and sulfur were added and kneaded to obtain polymer composition B. The obtained polymer composition B was molded and vulcanized at 160°C for a predetermined time using a vulcanization press 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.

[0130] (1) Solution viscosity: A sample was prepared by dissolving 29 g of polymer in 171 g of cyclohexane. The viscosity of the solution was measured using a Toki Sangyo TVB-10 viscometer at a temperature of 60°C. A lower solution viscosity indicates better fluidity of the polymer solution, making it easier to transfer in pipes and to containers. It also improves hydrogen diffusion in the polymer solution during the hydrogenation reaction, shortening the hydrogenation time and ensuring sufficient productivity. The obtained solution viscosity values ​​were judged from A to D according to the following criteria. A (Excellent): Less than 1000 mP·s B (Good): 1000 mP·s or more and less than 2000 mP·s C (acceptable level): 2000 mP·s or more and less than 3000 mP·s D (defective): 3000mP·s or more

[0131] (2) Mooney viscosity: The polymer was used as the sample for measurement, and the viscosity was measured in accordance with JIS K6300 using an L rotor under the conditions of preheating for 1 minute, rotor operating time for 4 minutes, and temperature of 100°C. It was evaluated as an index based on Comparative Example 1, and a smaller value indicates lower Mooney viscosity and better processability. From the obtained Mooney viscosity values, the Mooney viscosity was judged from A to D according to the following criteria. A: Less than 70 B: 70 or higher, less than 85 C: 85 or higher, less than 100 D:100 or more

[0132] (3) Cold Flow (C / F): Cold flow was measured by extruding the polymer through a 1 / 4-inch orifice at a pressure of 3.5 pounds / square inch and a temperature of 70°C. After standing for 10 minutes to allow it to reach a steady state, the extrusion rate was measured and expressed as grams per minute (g / min). A smaller cold flow value indicates better dimensional stability (storage stability) and superior processability. The obtained cold flow values ​​were judged as A to D according to the following criteria. A: Less than 0.1g / min B: Less than 0.2g / min, 0.1g / min or more C: Less than 0.3g / min, 0.2g / min or more D: 0.3g / min or more

[0133] (4) Tensile Strength: Tensile tests were performed on the crosslinked material as a test sample in accordance with JIS K6251:2010. Here, a dumbbell-shaped sample No. 3 was used as the test sample, and the stress at fracture (TB) and elongation at fracture (EB) were measured at room temperature. Larger values ​​for TB and EB indicate greater fracture strength and higher mechanical strength of the material. The evaluation was performed using the TB value and was evaluated as an index based on Comparative Example 1. A larger value indicates greater tensile strength and better strength. The tensile strength was judged from A to D based on the following criteria. A: 110 or more B: 100 or more, less than 110 C: 80 or more, less than 100 D: Less than 80

[0134] (5) Abrasion resistance: The cross-linked material was used as the measurement sample, and the amount of abrasion was measured at a temperature of 50°C with a slip ratio of 15% using a Lambourne type abrasion tester (manufactured by Shimada Giken Co., Ltd.) in accordance with JIS K6264-2:2005. The abrasion was evaluated as an index based on Comparative Example 1, and a smaller value indicates less abrasion and better abrasion resistance. The abrasion resistance was judged from A to D based on the obtained abrasion values ​​according to the following criteria. A: Less than 90 B: Less than 95, 90 or more C: Less than 100, 95 or higher D:100 or more

[0135] [Table 5]

[0136] [Table 6]

[0137] [Table 7]

[0138] As shown in Tables 6 and 7, the polymer compositions of Examples 1 to 17 were found to provide a balanced improvement in the solution viscosity, Mooney viscosity, and cold flow characteristics of the polymer, as well as the tensile strength and abrasion resistance of the crosslinked material. Of these, the polymer compositions of Examples 3, 5, 12, 13, and 17 all received an "A" rating for both the tensile strength and abrasion resistance of the crosslinked material, and the polymer compositions of Examples 5, 12, and 13 also received a "B" rating for processability based on Mooney viscosity, demonstrating a good balance of various properties.

[0139] In contrast, the polymer composition of Comparative Example 1, in which the ends of the polymer chains of the branched polymer were not modified by either the starting end modifier or the end modifier (b1), received a rating of "D" for the abrasion resistance of the crosslinked body. Comparative Example 2, in which the content of polymer (A1) in the hydrogenated conjugated diene polymer was high at 87% by mass, received a rating of "D" for the solution viscosity. Furthermore, Comparative Example 3, in which the content of polymer (A1) in the [A] conjugated diene polymer was low, received a rating of "D" for the cold flow characteristics, as well as for the tensile strength and abrasion resistance of the crosslinked body. Comparative Example 4, in which the ends of the polymer chains of the branched polymer were not modified by either the starting end modifier or the end modifier (b), showed improved tensile strength and abrasion resistance of the crosslinked body, but received a rating of "D" for the cold flow characteristics. Thus, all of the polymer compositions of Comparative Examples 1 to 4 performed worse than the examples.

Claims

1. A conjugated diene polymer in which, when the constituent ratios (molar ratios) of the structural units represented by the following formula (1), the structural units represented by the following formula (2), the structural units represented by the following formula (3), and the structural units represented by the following formula (4) are p, q, r, and s, respectively, the value α represented by the following formula (i) is between 0.65 and 0.

97. The aforementioned conjugated diene polymer contains 30 to 75% by mass of a polymer (A1) having a highly branched structure with four or more molecular chains. The polymer (A1) is a conjugated diene polymer having a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, and sulfur at one or both of the terminal portion and the branching point portion of the polymer (A1). α=(p+(0.5×r)) / (p+q+(0.5×r)+s)…(i) 【Chemistry 1】

2. The conjugated diene polymer according to claim 1, having structural units derived from an aromatic vinyl compound.

3. The conjugated diene polymer according to claim 2, wherein the proportion of structural units derived from aromatic vinyl compounds is greater than 0% by mass and less than or equal to 45% by mass.

4. The polymer (A1) has a structure in which four or more molecular chains are bonded to a structure derived from the coupling agent. The coupling agent comprises at least one element selected from the group consisting of nitrogen, oxygen, sulfur, and silicon, as a conjugated diene polymer according to any one of claims 1 to 3.

5. The polymer (A1) is a conjugated diene polymer according to any one of claims 1 to 4, wherein the polymer has a secondary amino group or a tertiary amino group at its terminal portion.

6. A conjugated diene polymer according to any one of claims 1 to 5, further comprising a linear or branched polymer (A2) with three or fewer branches.

7. The conjugated diene polymer according to claim 6, wherein the polymer (A2) comprises a linear polymer having a secondary or tertiary amino group at one terminal portion and a functional group at the other terminal portion containing at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon.

8. A polymerization step to obtain a conjugated diene polymer (I) having an active end by polymerizing a monomer containing a conjugated diene compound in the presence of a metal compound having an alkali metal or alkaline earth metal, A reaction step to obtain a conjugated diene polymer (II) by reacting the conjugated diene polymer (I) with a compound [B] having four or more functional groups that can react with the active end; A hydrogenation step is performed in which the conjugated diene polymer (II) is hydrogenated so that the hydrogenation rate of structural units derived from the conjugated diene compound is 65 to 97%, Includes, The reaction step involves reacting the conjugated diene polymer (I) with compound [B] such that the conjugated diene polymer (II) contains 30 to 75% by mass of a polymer having a highly branched structure with four or more molecular chains. A method for producing a conjugated diene polymer, wherein at least one selected from the group consisting of the metal compound and compound [B] contains at least one element selected from the group consisting of nitrogen, oxygen, and sulfur.

9. The method for producing a conjugated diene polymer according to claim 8, wherein the metal compound is a metal amide compound having an alkali metal or an alkaline earth metal.

10. The aforementioned conjugated diene polymer (II) further comprises a linear or branched polymer with three or fewer branches, A method for producing a conjugated diene polymer according to claim 8 or 9, further comprising the step of 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, with a linear polymer in the conjugated diene polymer (II), to obtain 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.

11. A polymer composition comprising a conjugated diene polymer according to any one of claims 1 to 7 and an inorganic filler.

12. A crosslinked body obtained by crosslinking the polymer composition according to claim 11.

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

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