Polymer composition, its manufacturing method, crosslinked product, and tire

Abstract

Provided is a polymer composition containing: (A) a conjugated diene polymer having a structural unit derived from a conjugated diene compound and a structural unit derived from an aromatic vinyl compound, the value α of the conjugated diene polymer, as represented by mathematical expression (i), is 0.60-0.98, where the composition ratio (molar ratio) in the polymer of the structural units represented by formulas (1), (2), (3) and (4) are p, q, r, s respectively; and (B) a hindered phenol compound having a molecular weight of 250-2000. A portion or all of the component (A) has a functional group including at least one element selected from the group consisting of nitrogen, oxygen, sulfur, and phosphorous.　α = (p + (0.5 × r)) / (p + q + (0.5 × r) + s) ... (i)

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to Japanese Patent Application No. 2022-35722, filed on March 8, 2022, the entire contents of which are incorporated herein by reference. The present disclosure relates to a polymer composition, a method for producing the same, a crosslinked product thereof, and a tire. [Background technology]

[0002] Conjugated diene polymers obtained by polymerization using conjugated diene compounds have various 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, anti-vibration rubber, and hoses.

[0003] It is known that polymer compositions used in the production of pneumatic tire treads, sidewalls, etc., contain inorganic fillers such as carbon black and silica as reinforcing agents together with conjugated diene polymers in order to improve the durability and abrasion resistance of the products. Furthermore, conjugated diene polymers modified with silicon- or nitrogen-containing compounds have been used in the past to increase the affinity between the conjugated diene polymers and the reinforcing agents (see, for example, Patent Documents 1 to 3).

[0004] In recent years, it has been proposed to obtain tire components with high strength and excellent wear resistance by using hydrogenated conjugated diene polymers, which are 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]

[0005] [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 Summary of the Invention [Problem to be solved by the invention]

[0006] In the production process of a conjugated diene polymer, when the solvent is removed from a polymer solution containing the conjugated diene polymer to recover the conjugated diene polymer, a desolvation operation such as steam stripping is usually performed. In this desolvation operation, it is difficult to strictly control the desolvation time in an actual process. On the other hand, variations in the desolvation time may result in unstable polymer quality, and there is a concern that such quality instability may lead to a decrease in the performance of the crosslinked product. In consideration of this point, a polymer that can exhibit stable physical properties despite variations in the desolvation time is desired.

[0007] However, when removing the solvent from a polymer solution containing a conjugated diene polymer into which a functional group has been introduced, it is expected that radical side reactions such as reactions between functional groups or elimination of the functional groups themselves may occur during the removal of the solvent, or that side reactions with metal residues (e.g., hydrogenation catalysts) may occur. Furthermore, there is a concern that the Mooney viscosity of the conjugated diene polymer may be easily changed due to variations in the time for removing the solvent due to such side reactions occurring during the removal of the solvent.

[0008] In the production process of conjugated diene polymers, adhesion of the conjugated diene polymer to equipment (e.g., adhesion to a drying oven) often becomes a problem in the process of drying the conjugated diene polymer. When polymer adhesion to equipment is likely to occur, there is a concern that volatile matter derived from the polymer that has adhered and remained on the equipment may cause contamination of the equipment or that the polymer remaining on the equipment may burn due to accumulated heat. This necessitates frequent cleaning of the equipment, which increases the process load in the production process and raises concerns about reduced productivity.

[0009] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a polymer composition that can reduce the process load and stabilize the quality in a production process of a conjugated diene-based polymer, and that can provide a crosslinked product with suppressed performance degradation. [Means for solving the problem]

[0010] The present disclosure provides the following polymer composition, a method for producing the same, a crosslinked product thereof, and a tire.

[0011] [1] A polymer composition comprising: (A) a conjugated diene polymer having a structural unit derived from a conjugated diene compound and a structural unit derived from an aromatic vinyl compound, wherein the value α represented by the following mathematical formula (i) is 0.60 to 0.98 when p, q, r, and s are the constituent ratios (molar ratios) in the polymer of a structural unit represented by the following formula (1), a structural unit represented by the following formula (2), a structural unit represented by the following formula (3), and a structural unit represented by the following formula (4), respectively; and (B) a hindered phenol compound having a molecular weight of 250 to 2,000, wherein part or all of the component (A) has a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, sulfur, and phosphorus. α=(p+(0.5×r)) / (p+q+(0.5×r)+s) …(i) [ka]

[0012] [2] A crosslinked product obtained by crosslinking the polymer composition of [1] above. [3] A tire having a tread, a sidewall, or both formed using the polymer composition of [1] above. [4] A method for producing the polymer composition according to [1] above, comprising the steps of: polymerizing a monomer containing a conjugated diene compound and an aromatic vinyl compound in the presence of an alkali metal or an alkaline earth metal, and hydrogenating the polymer to obtain a polymer solution containing the component (A); mixing the polymer solution with the component (B) to obtain a mixed liquid containing the component (A) and the component (B); and removing the solvent from the mixed liquid and drying it. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to reduce the process load and stabilize the quality in the production process of a conjugated diene-based polymer. Furthermore, by stabilizing the quality of the conjugated diene-based polymer in the production process, it is possible to obtain a crosslinked product in which performance degradation is suppressed. DETAILED DESCRIPTION OF THE INVENTION

[0014] Matters relating to the implementation of the present disclosure will be described in detail below. In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values before and after "to" as the lower and upper limits.

[0015] <Polymer composition> The polymer composition of the present disclosure (hereinafter also referred to as "the composition") contains (A) a conjugated diene polymer and (B) a hindered phenol compound having a molecular weight of 250 to 2,000. The components contained in the composition and the components that may be optionally blended are described in detail below.

[0016] <Component (A): Conjugated Diene Polymer> The conjugated diene polymer of component (A) (hereinafter also referred to as "(A) conjugated diene polymer") is a copolymer having structural units derived from a conjugated diene compound and structural units derived from an aromatic vinyl compound. The (A) conjugated diene polymer is a highly saturated polymer in which the value α, represented by the following mathematical formula (i), is 0.60 to 0.98, where p, q, r, and s are the constituent ratios (molar ratios) in the polymer of the structural units represented by the following formulas (1), (2), (3), and (4), respectively: α=(p+(0.5×r)) / (p+q+(0.5×r)+s) …(i) [ka]

[0017] The molecular structure of the (A) conjugated diene polymer is not particularly limited. The (A) conjugated diene polymer may be a linear polymer (hereinafter also referred to as a "linear polymer"), a polymer having a multi-branched structure (hereinafter also referred to as a "branched polymer"), or a mixture thereof. The (A) conjugated diene polymer preferably contains a branched polymer having four or more branches, since this allows for a crosslinked product to be obtained in which the change in Mooney viscosity of the conjugated diene polymer due to differences in the treatment time (hereinafter also referred to as the "removal time") when removing the solvent from a polymer solution containing the (A) conjugated diene polymer is small and deterioration in physical properties (for example, deterioration in strength, viscoelastic properties, and abrasion resistance) is suppressed.

[0018] A part or all of the conjugated diene polymer (A) contained in the present composition has a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, sulfur, and phosphorus (hereinafter also referred to as a "specific functional group").

[0019] In a polymer having a specific functional group (hereinafter also referred to as a "functional group-containing polymer"), the position of the specific functional group in the polymer is not particularly limited. Examples of functional group-containing polymers include polymers having a specific functional group in the molecular chain (i.e., between the ends of the molecular chain), at the ends of the molecular chain, or both. When the functional group-containing polymer has a specific functional group at the end of the molecular chain, the functional group-containing polymer may have the specific functional group at the polymerization initiation end, the polymerization termination end, or both the polymerization initiation end and the polymerization termination end. Furthermore, the functional group-containing polymer may have the specific functional group at some of the ends in one polymer molecule, or may have the specific functional group at all of the ends in one polymer molecule. In terms of enhancing the effect of improving various physical properties (e.g., mechanical strength, abrasion resistance, viscoelastic properties, fuel economy, etc.) of a crosslinked product obtained using the present composition, it is preferable that the functional group-containing polymer have the specific functional group at two or more ends.

[0020] Here, in this specification, the term "functional group" refers to a group having a specific structure within the molecule of an organic compound, and refers to an atomic group or bonding pattern that characterizes the compound. Examples of the specific functional group possessed by the functional group-containing polymer include a primary amino group, a secondary amino group, a tertiary amino group, a nitrogen-containing group formed by protecting two hydrogen atoms of a primary amino group, a nitrogen-containing group formed by protecting one hydrogen atom of a secondary amino group, a tertiary amino group, an imino group, a pyridyl group, a phosphorus-containing group formed by protecting two hydrogen atoms of a primary phosphino group, a phosphorus-containing group formed by protecting one hydrogen atom of a secondary phosphino group, a tertiary phosphino group, an epoxy group, a thioepoxy group, a hydroxyl group, an oxygen-containing group formed by protecting the hydrogen atom of a hydroxyl group, a thiol group, a sulfur-containing group formed by protecting the hydrogen atom of a thiol group, a nitrogen-containing heterocyclic group (for example, a group having a heterocyclic ring such as a pyridine ring or an imide ring), a hydrocarbyloxysilyl group, a hydrocarbyloxycarbonyl group, an ether bond, and a thioether bond.

[0021] As the functional group-containing polymer contained in the (A) conjugated diene polymer, a reaction product (hereinafter also referred to as a "modified polymer") between a conjugated diene polymer having an active terminal and a compound having a specific functional group and a reaction site with the active terminal of the conjugated diene polymer can be preferably used. The compound (hereinafter also referred to as a "modifier") having a specific functional group and a reaction site with the active terminal of the conjugated diene polymer may have one or more reaction sites with the active terminal. Specific examples of the specific functional group possessed by the modifier include the same groups and bonds as the specific functional groups possessed by the functional group-containing polymer. Such a modified polymer can be obtained by using a coupling agent or a terminal modifier, which is a compound having a specific functional group, as the modifier, as described below. Here, the modified polymer may be a polymer obtained by further using an initiating terminal modifier, described below, in addition to the coupling agent or terminal modifier in the reaction to obtain the modified polymer.

[0022] When the (A) conjugated diene polymer contains a functional group-containing polymer (preferably a modified polymer), the branched polymer and the functional group-containing polymer may be separate polymers having different molecular structures and physical properties. Furthermore, the (A) conjugated diene polymer may contain both a branched polymer and a functional group-containing polymer by virtue of the branched polymer having a specific functional group. From the viewpoint of minimizing the change in Mooney viscosity with respect to differences in desolvation time and stabilizing quality, the (A) conjugated diene polymer preferably contains a branched polymer having a specific functional group. From the viewpoint of improving blend properties such as tensile strength while stabilizing quality, the (A) conjugated diene polymer more preferably contains a branched polymer having specific functional groups at two or more ends, and even more preferably contains a branched polymer having specific functional groups at four or more ends.

[0023] (A) Conjugated diene polymer is an aggregate of polymers having structural units derived from conjugated diene compounds. Specific embodiments of (A) Conjugated diene polymer include the following embodiments [a1] to [a4]. [a1] An embodiment containing a branched polymer having four or more branches (hereinafter also referred to as a "first polymer") and one or more polymers selected from the group consisting of linear polymers and branched polymers having three or fewer branches (hereinafter also referred to as a "second polymer"), wherein the first polymer and the second polymer are functional group-containing polymers. [a2] An embodiment in which a first polymer and a second polymer are contained, and of the first polymer and the second polymer, the first polymer is a functional group-containing polymer. [a3] An embodiment containing a first polymer and a second polymer, wherein the second polymer is a functional group-containing polymer. [a4] An embodiment in which a second polymer is contained but a first polymer is not contained, and the second polymer is a functional group-containing polymer. Among these, an embodiment containing at least a second polymer, where the second polymer is a functional group-containing polymer, is more preferred, from the viewpoint of being able to enhance the effects of reducing the burden on the manufacturing process and improving the blend properties, and an embodiment containing a first polymer and a second polymer, where the first polymer and the second polymer are functional group-containing polymers is even more preferred.

[0024] The (A) conjugated diene polymer can be produced by a method including the following polymerization step and hydrogenation step. The (A) conjugated diene polymer may also be produced by a method including, in addition to the polymerization step and hydrogenation step, at least one of the following reaction step and modification step. Hereinafter, the molecular structure of the (A) conjugated diene polymer will be described together with the method for producing the (A) conjugated diene polymer.

[0025] <Polymerization process> The polymerization step is a step in which a monomer containing a conjugated diene compound and an aromatic vinyl compound is polymerized to obtain a conjugated diene polymer having an active terminal.

[0026] Conjugated diene compounds used in 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 one or both of 1,3-butadiene and isoprene are more preferred. The conjugated diene compounds may be used alone or in combination of two or more.

[0027] 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, one or both of styrene and α-methylstyrene are preferred as aromatic vinyl compounds. One or more aromatic vinyl compounds may be used alone or in combination.

[0028] The proportion of structural units derived from aromatic vinyl compounds in the (A) conjugated diene polymer is preferably more than 0% by mass and not more than 45% by mass relative to all structural units constituting the (A) conjugated diene polymer. By setting the proportion within the above range, it is possible to obtain a crosslinked product having high strength and excellent abrasion resistance while maintaining the processability of the polymer composition. The proportion of structural units derived from aromatic vinyl compounds is more preferably 2% by mass or more, and even more preferably 5% by mass or more, relative to all structural units constituting the (A) conjugated diene polymer. Furthermore, the proportion of structural units derived from aromatic vinyl compounds is more preferably 40% by mass or less, more preferably 38% by mass or less, and even more preferably 35% by mass or less, relative to all structural units constituting the (A) conjugated diene polymer. The content of structural units derived from aromatic vinyl compounds in the polymer is 1 The values were measured by H-NMR.

[0029] The (A) conjugated diene polymer is preferably a copolymer containing 1,3-butadiene and styrene in the monomer composition, because it has a high living property in anionic polymerization.

[0030] From the viewpoint of improving various physical properties (e.g., mechanical strength, abrasion resistance, viscoelastic properties, etc.) of the crosslinked body obtained using the present composition, the (A) conjugated diene polymer preferably has a random copolymerization portion in which the distribution of the conjugated diene compound and the aromatic vinyl compound is irregular. When the (A) conjugated diene polymer is a random copolymer of a conjugated diene compound and an aromatic vinyl compound, the (A) conjugated diene polymer may further have a chain portion of the conjugated diene compound formed by further adding a conjugated diene compound after random copolymerization of the conjugated diene compound and the aromatic vinyl compound.

[0031] The (A) conjugated diene polymer may have a polymer block portion mainly composed of an aromatic vinyl compound. When the (A) conjugated diene polymer has a polymer block portion mainly composed of an aromatic vinyl compound, this is preferable because it can suppress an increase in the contact area with equipment due to the flow of the polymer during the drying treatment of the (A) conjugated diene polymer, thereby suppressing adhesion of the polymer to equipment.

[0032] The position of the polymer block portion mainly composed of an aromatic vinyl compound in the (A) conjugated diene polymer is not particularly limited. The (A) conjugated diene polymer may have the polymer block portion mainly composed of an aromatic vinyl compound at the end of the molecular chain, or may have the polymer block portion in the molecular chain (between the ends). In terms of simplifying the production process of the (A) conjugated diene polymer and obtaining the effect of suppressing adhesion of the polymer to equipment, it is preferable that the (A) conjugated diene polymer have the polymer block portion mainly composed of an aromatic vinyl compound at the end of the molecular chain.

[0033] The polymer block portion mainly composed of an aromatic vinyl compound preferably contains structural units derived from an aromatic vinyl compound in an amount of 80 mass % or more, more preferably 85 mass % or more, and even more preferably 90 mass % or more, of all structural units constituting the polymer block portion.

[0034] When the (A) conjugated diene polymer has a polymerized block portion mainly composed of an aromatic vinyl compound, the polymerized block portion may account for 35 mass % or more, or 40 mass % or more of the total amount of structural units derived from the aromatic vinyl compound contained in the (A) conjugated diene polymer. Also, it is preferable that 80 mass % or more, or 90 mass % or more of the total amount of structural units derived from the conjugated diene compound contained in the (A) conjugated diene polymer constitute random copolymerized portions.

[0035] The monomers used in the polymerization reaction to obtain the (A) conjugated diene polymer may contain compounds other than conjugated diene compounds and aromatic vinyl compounds (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, of the total amount of monomers used in the polymerization.

[0036] The polymerization method used may be any of solution polymerization, gas phase polymerization, and bulk polymerization. Of these, solution polymerization is particularly preferred. Furthermore, the polymerization may be carried out in either a batch or continuous manner. When using solution polymerization, a specific example of the polymerization method is a method in which a monomer containing a conjugated diene compound and an aromatic vinyl compound is polymerized in an organic solvent in the presence of a polymerization initiator and, if necessary, a vinyl content adjuster (hereinafter also referred to as a "randomizer").

[0037] As the polymerization initiator, a metal compound containing an alkali metal or alkaline earth metal can be used. Among these, compounds containing an alkali metal are preferred. Specific examples of metal compounds include alkyllithium such as methyllithium, ethyllithium, n-propyllithium, n-butyllithium, sec-butyllithium, and t-butyllithium; 1,4-dilithiobutane, phenyllithium, stilbenelithium, naphthyllithium, 1,3-bis(1-lithio-1,3-dimethylpentyl)benzene, 1,3-phenylenebis(3-methyl-1-phenylpentylidene)dilithium, naphthylsodium, naphthylpotassium, and ethoxypotassium. Among these, lithium compounds are preferred.

[0038] The metal compound used as the polymerization initiator may be a metal amide compound containing an alkali metal or an alkaline earth metal. By carrying out polymerization to obtain (A) conjugated diene polymer in the presence of a metal amide compound, an amino group (preferably a secondary amino group or a tertiary amino group) can be introduced into the polymerization initiation terminal of the conjugated diene polymer (in the case of a branched polymer, the free terminal portion). (A) conjugated diene polymer obtained by polymerizing monomers in the presence of a metal amide compound is preferred in that it can further increase the strength of the crosslinked product and can enhance the effect of improving the fuel economy of the crosslinked product when used in tires.

[0039] Among metal amide compounds, compounds obtained by mixing a lithium compound (e.g., alkyllithium) with a compound having a nitrogen atom (hereinafter also referred to as an "initial terminal modifier") are preferred. The initial terminal modifier is preferably a secondary amine compound. Specific examples thereof include dimethylamine, diethylamine, dipropylamine, dibutylamine, dodecamethyleneimine, N,N'-dimethyl-N'-trimethylsilyl-1,6-diaminohexane, piperidine, pyrrolidine, hexamethyleneimine, heptamethyleneimine, dicyclohexylamine, N-methylbenzylamine, di-(2-ethylhexyl)amine, diallylamine, morpholine, N-(trimethylsilyl)piperazine, N-(tert-butyldimethylsilyl)-4-piperazine, and 1,3-ditrimethylsilyl-1,3,5-triazinane.

[0040] When polymerization is carried out in the presence of a metal amide compound, the metal amide compound may be prepared by premixing a lithium compound with an initiating terminal modifier, and the prepared metal amide compound may then be added to a polymerization system to carry out polymerization. Alternatively, the lithium compound and the initiating terminal modifier may be added to the polymerization system, and the two may then be mixed in the polymerization system to prepare a metal amide compound, followed by polymerization. The amount of polymerization initiator used in polymerization is preferably 0.01 to 20 mmol, more preferably 0.05 to 15 mmol, per 100 g of monomer used in polymer synthesis.

[0041] The randomizer can be used for the purpose of adjusting the vinyl bond content, which represents the content of vinyl bonds in a polymer. Examples of the randomizer 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, and potassium dodecylbenzenesulfonate. The randomizer can be used alone or in combination of two or more.

[0042] As the organic solvent used in the polymerization, an organic solvent inert to the polymerization reaction can be preferably used. Specific examples of the organic solvent used in the polymerization include linear or cyclic aliphatic hydrocarbons and aromatic hydrocarbons. Among these, hydrocarbons having 3 to 8 carbon atoms are preferred, and specific examples thereof include propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis-2-butene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene, heptane, cyclopentane, methylcyclopentane, methylcyclohexane, 1-pentene, 2-pentene, and cyclohexene. The organic solvent can be used alone or in combination of two or more.

[0043] When solution polymerization is performed, the monomer concentration in the reaction solvent is preferably 5 to 50% by mass, more preferably 10 to 30% by mass, from the viewpoint of maintaining a balance between productivity and ease of polymerization control. The temperature of the polymerization reaction is preferably -20°C to 150°C, more preferably 0 to 120°C. The polymerization reaction is preferably carried out under a pressure sufficient to maintain the monomers substantially in a liquid phase. Such a pressure can be obtained by, for example, pressurizing the reactor with a gas inert to the polymerization reaction. A conjugated diene polymer having an active terminal can be obtained by such a polymerization reaction.

[0044] In the conjugated diene polymer obtained by the above polymerization, the vinyl bond content in the structural units derived from 1,3-butadiene is preferably 15 to 85 mol %. By making the vinyl bond content 15 mol % or more, the flexibility of the obtained crosslinked body is maintained and the processability is good. In addition, the abrasion resistance in the low slip region tends to be excellent. The vinyl bond content is preferably 20 mol % or more, more preferably 25 mol % or more. From the viewpoint of durability, the vinyl bond content of the conjugated diene polymer is preferably 75 mol % or less, more preferably 65 mol % or less. In this specification, the "vinyl bond content" is a value indicating the content ratio of structural units having 1,2-bonds to all structural units derived from 1,3-butadiene contained in the conjugated diene polymer before hydrogenation. The vinyl bond content is 1 It is measured by H-NMR equipment.

[0045] <Reaction process> The reaction step is a step in which the conjugated diene polymer obtained in the polymerization step is reacted with a compound (hereinafter also referred to as a "coupling agent") having four or more functional groups capable of reacting with the active terminals of the conjugated diene polymer. By the reaction between the conjugated diene polymer having active terminals and the coupling agent, four or more molecular chains of the conjugated diene polymer are bonded to one molecule of the coupling agent, thereby obtaining a polymer containing a branched polymer with four or more branches as the conjugated diene polymer (A).

[0046] As the coupling agent, a compound having at least one element selected from the group consisting of nitrogen, oxygen, sulfur, phosphorus, tin, and silicon (hereinafter also referred to as "specific element") can be preferably used. When a compound having a specific element is used as the coupling agent, it is preferable in that the strength of the obtained crosslinked body can be further increased.

[0047] Specific examples of such coupling agents include tetrachlorosilane, bis(trichlorosilyl)ethane, etc. Furthermore, as the coupling agent, compounds having functional groups (hereinafter also referred to as "functional group F1") such as a nitrogen-containing group in which two hydrogen atoms of a primary amino group are protected, a nitrogen-containing group in which one hydrogen atom of a secondary amino group is protected, a tertiary amino group, an imino group, a nitrogen-containing heterocyclic group (for example, a group having a heterocycle such as a pyridine ring or an imide ring), a hydroxyl group, an oxygen-containing group in which the hydrogen atom of a hydroxyl group is protected, a sulfur-containing group in which the hydrogen atom of a thiol group is protected, or a hydrocarbyloxysilyl group can also be used as a functional group having a specific element.

[0048] Specific examples of coupling agents having the functional group F1 include N,N,N',N'-tetra(3-trimethoxysilylpropyl)ethylenediamine, N,N,N',N'-tetra(3-triethoxysilylpropyl)ethylenediamine, N,N,N'-tris(3-trimethoxysilylpropyl)-N'-methyl-ethylenediamine, N,N,N',N'-tetra(3-trimethoxysilylpropyl)-1,3-propanediamine, N,N,N',N'-tetra(3-trimethoxysilylpropyl)-1,4-butanediamine, bis(3-trimethoxysilylpropyl)-[2-(dimethylamino)ethyl]amine, bis(3-trimethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silacyclopentane)ethyl]amine, bis(3-triethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silacyclopentane)ethyl]amine, and bis(3-triethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silacyclopentane)ethyl]amine.

[0033] Examples of the amine include N,N-bis(3-trimethoxysilylpropyl)-[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, N,N-bis(3-trimethoxysilylpropyl)-3-imidazolylpropylamine, bis(3-trimethoxysilylpropyl)-(3-dimethylaminopropyl)amine, and compounds represented by the following formulas (M-1) to (M-4). [ka] (In formula (M-1), R 20 represents a hydrogen atom or an alkyl group. n1 represents an integer of 1 to 8.

[0049] When reacting a conjugated diene polymer having an active end with a coupling agent, it is preferable to use a polymer obtained using an initiation end-modifying agent as the conjugated diene polymer having an active end, thereby obtaining a polymer having a nitrogen-containing functional group at its terminal as a branched polymer having 4 or more branches. By using a polymer composition containing a branched polymer having a nitrogen-containing functional group at its terminal and having 4 or more branches as the (A) conjugated diene polymer, the strength and viscoelastic properties of the crosslinked body obtained from the polymer composition can be made even better.

[0050] The reaction between the conjugated diene polymer having an active terminal and the coupling agent is preferably carried out as a solution reaction. The amount of coupling agent used (the total amount when two or more types are used) can be appropriately set so that the content of branched polymers with four or more branches in the (A) conjugated diene polymer falls within the desired range. From the viewpoint of suppressing polymer adhesion to equipment during the production process of the (A) conjugated diene polymer (particularly the drying process), thereby suppressing equipment contamination due to polymer retention and heat accumulation combustion of the retained polymer, suppressing changes in Mooney viscosity due to differences in desolvation time and achieving quality stabilization, and from the viewpoint of obtaining a high-strength crosslinked product through stabilization of polymer quality, the amount of coupling agent used is preferably 0.01 mol or more, more preferably 0.02 mol or more, per mol of metal atoms involved in polymerization in the polymerization initiator (i.e., metal compound). The amount of the coupling agent used is preferably 0.2 mol or less, more preferably 0.1 mol or less, per mol of the metal atom involved in the polymerization of the polymerization initiator, from the viewpoint of adjusting the coupling rate to a desired value to obtain a polymer composition exhibiting good processability and to obtain a crosslinked product having excellent viscoelastic properties. Note that one type of coupling agent may be used alone, or two or more types may be used in combination.

[0051] In the coupling reaction, the reaction temperature is usually in the same range as that in the polymerization reaction. Specifically, it is preferably -20°C to 150°C, and more preferably 0 to 120°C. If the reaction temperature is low, the viscosity of the polymer after the reaction tends to increase, while if the reaction temperature is high, the active polymerization terminals are likely to be deactivated. The reaction time is preferably 1 minute to 5 hours, and more preferably 2 minutes to 1 hour.

[0052] The above coupling reaction can produce a pre-hydrogenated conjugated diene polymer (A) containing a branched polymer with four or more branches. The conjugated diene polymer after the coupling reaction may contain a linear polymer. The linear polymer contained in the polymer solution after the coupling reaction is an unreacted polymer that has not reacted with the coupling agent among the linear polymers contained in the conjugated diene polymer having an active end.

[0053] <Denaturation process> When the conjugated diene polymer obtained in the polymerization step or the reaction step has a specific functional group, the polymer may be directly subjected to the subsequent hydrogenation step. Furthermore, the conjugated diene polymer obtained in the polymerization step or the reaction step, regardless of whether it has a specific functional group, may be subjected to a treatment before the hydrogenation step in which the active terminals of the conjugated diene polymer are reacted with a compound (excluding coupling agents; hereinafter, also referred to as a "terminal modifier") that has a specific functional group and is capable of reacting with the active terminals of the conjugated diene polymer. By performing such a treatment, when the conjugated diene polymer obtained in the polymerization step or the reaction step contains a polymer having an active terminal, it is possible to incorporate into the conjugated diene polymer (A) a polymer in which the molecular chain of the linear conjugated diene polymer is bonded to the terminal modifier (i.e., having a specific functional group). The terminal modifier is a compound that differs from the coupling agent in that it has 1 to 3 reactive sites with the active terminals of the conjugated diene polymer.

[0054] A preferred specific example of the terminal modifying agent is at least one selected from the group consisting of compounds represented by the following formula (5) and compounds represented by the following formula (6). [ka] (In formula (5), A 11 has at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, and sulfur, does not have active hydrogen, and R 35 R is a monovalent functional group bonded to R at a carbon atom contained in a nitrogen, phosphorus, oxygen, sulfur, or carbonyl group, or is a (thio)epoxy group. 33 and R 34 are each independently a hydrocarbyl group. 35 is a hydrocarbylene group, and t is an integer of 0 to 2. However, when t is 2, multiple R 33 are the same or different. When t is 0 or 1, multiple R 34 are the same or different from each other.) [ka] (In formula (6), A 12 has at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, and sulfur, does not have active hydrogen, and R 39 R is a monovalent functional group bonded to R via nitrogen, phosphorus, oxygen, or sulfur, or a hydrocarbyl group having 1 to 20 carbon atoms. 36 and R 37 are each independently a hydrocarbyl group. 38 is a hydrocarbylene group. 39 is a single bond or a hydrocarbylene group. u is 0 or 1. However, when u is 0, multiple R 37 are the same or different from each other.)

[0055] In the above formulas (5) and (6), R 33 , R 34 , R 36 , R 37 and A when it is a hydrocarbyl group. 12 With regard to the above, 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 38 and R 39 The hydrocarbylene group represented by the formula (I) is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms. 38 The hydrocarbylene group represented by the following formula is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms. t is preferably 0 or 1.

[0056] A 11 When A is the monovalent functional group, 11 at least one element selected from the group consisting of nitrogen, phosphorus, oxygen and sulfur, and 12 When A is the monovalent functional group, 12 At least one element selected from the group consisting of nitrogen, phosphorus, oxygen, and sulfur may be protected, for example, by a tri-substituted hydrocarbylsilyl group. In this specification, active hydrogen refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably refers to one having a bond energy lower than that of the carbon-hydrogen bond of polymethylene. The term "(thio)epoxy group" encompasses both epoxy and thioepoxy groups.

[0057] A 11 may be a group that can be converted into an onium ion by an onium salt generating agent. 11 ) can provide the polymer with excellent shape retention. 11Specific examples of include a nitrogen-containing group in which two hydrogen atoms of a primary amino group are protected, a nitrogen-containing group in which one hydrogen atom of a secondary amino group is protected, a tertiary amino group, an imino group, a pyridyl group, a phosphorus-containing group in which two hydrogen atoms of a primary phosphino group are protected, a phosphorus-containing group in which one hydrogen atom of a secondary phosphino group is protected, a tertiary phosphino group, an epoxy group, a thioepoxy group, an oxygen-containing group in which the hydrogen atom of a hydroxyl group is protected, a sulfur-containing group in which the hydrogen atom of a thiol group is protected, and a hydrocarbyloxycarbonyl group. Among these, a group having a nitrogen atom is preferred in terms of good affinity with silica, and a tertiary amino group or a nitrogen-containing group in which two hydrogen atoms of a primary amino group are protected is more preferred. The protected group is, for example, A 11 , A 12 is a group converted into a functional group that is inactive to the polymerization active terminal. The onium salt generating agent is a Bronsted acid or a compound that generates a Bronsted acid upon contact with water.

[0058] Specific examples of the terminal modifying agent include compounds represented by formula (5), such as N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-dimethylaminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-(4-trimethylsilyl-1-piperazino)propylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyltriethoxysilane.

[0059] Specific examples of the compound represented by formula (6) include 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1,2-azasilolidine, 2,2-diethoxy-1-(3-trimethoxysilylpropyl)-1,2-azasilolidine, 2,2-dimethoxy-1-phenyl-1,2-azasilolidine, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, 2-(2,2-dimethoxy-1,2-azasilolidine-1-yl)-N,N-diethylethan-1-amine, 2-(2,2-dimethoxy-1,2-azasilolidine-1-yl)-N,N-dimethylethan-1-amine, and 3-(2,2-dimethoxy-1,2-azasilolidine-1-yl)-N,N-diethylpropan-1-amine. The terminal modifying agent may be used alone or in combination of two or more.

[0060] The reaction between the conjugated diene polymer having an active terminal and the terminal-modifying agent can be carried out, for example, as a solution reaction. This solution reaction may be carried out using either a batch system or a continuous system. In this case, the method of adding the terminal-modifying agent is not particularly limited, and examples thereof include a method of adding the terminal-modifying agent all at once, a method of adding the terminal-modifying agent in portions, and a method of adding the terminal-modifying agent continuously.

[0061] The amount of the terminal modifier used may be appropriately determined depending on the type of compound used in the reaction, but is preferably 0.05 moles or more, more preferably 0.1 moles or more, per mole of metal atoms involved in the polymerization reaction of the polymerization initiator. By using an amount of the terminal modifier of 0.1 molar equivalents or more, the modification reaction can be sufficiently promoted, and the effect of improving the dispersibility of the inorganic filler can be enhanced. Furthermore, the amount of the terminal modifier is preferably 1.0 moles or less, more preferably 0.8 moles or less, per mole of metal atoms involved in the polymerization reaction of the polymerization initiator.

[0062] In the modification reaction using a terminal modifying agent, the reaction temperature is usually the same as the polymerization reaction temperature, and is 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. Furthermore, if the modification reaction temperature is high, the polymerization active terminals are likely to be deactivated. The reaction time for terminal modification is preferably 1 minute to 5 hours, and more preferably 2 minutes to 1 hour.

[0063] The coupling rate of the (A) conjugated diene polymer can be set depending on the proportion of branched polymers present in the (A) conjugated diene polymer, the molecular weight of the conjugated diene polymer having an active end, the number of functional groups of the coupling agent used, etc. From the viewpoint of suppressing changes in Mooney viscosity due to differences in the desolvation time of the (A) conjugated diene polymer and stabilizing quality, the coupling rate of the (A) conjugated diene polymer is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. Furthermore, from the viewpoint of obtaining a polymer composition with good processability and a crosslinked product with excellent viscoelastic properties, the coupling rate of the (A) conjugated diene polymer is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less.

[0064] In this specification, the term "coupling ratio" refers to the proportion (mass %) of linear conjugated diene polymers having active terminals used in the reaction of a linear conjugated diene polymer having active terminals with a modifier. Specifically, it refers to the proportion (mass %) of polymers in which two or more linear conjugated diene polymer molecular chains are bonded via a coupling agent or a terminal modifier to the total amount of polymer (more specifically, an aggregate of linear polymers having active terminals) used in the reaction with the coupling agent or terminal modifier. The coupling ratio can be calculated from the peak area ratio of a GPC curve obtained using gel permeation chromatography (GPC) by separating the waveform of a molecule in which two or more linear conjugated diene polymer molecular chains are bonded.

[0065] In addition, when the conjugated diene polymer having an active end obtained by the polymerization step is not subjected to either the reaction step or the modification step, the conjugated diene polymer having an active end may be reacted with a polymerization terminator such as an alcohol, and then the subsequent hydrogenation step may be carried out. In this case, it is preferable to use an initiation end-modifying agent in the polymerization step to obtain a conjugated diene polymer having a specific functional group.

[0066] <Hydrogenation process> In the hydrogenation step, the conjugated diene polymer obtained in the polymerization step, reaction step, 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 having a desired hydrogenation rate is obtained. Examples of such hydrogenation methods include a method using a catalyst containing an organometallic compound of titanium as the main component as a hydrogenation catalyst; a method using a catalyst composed of an organometallic compound of iron, nickel, or cobalt and an organometallic compound such as alkylaluminum; a method using an organic complex of an organometallic compound such as ruthenium or rhodium; and a method using a catalyst in which a metal such as palladium, platinum, ruthenium, cobalt, or nickel is supported on a support such as carbon, silica, or alumina. Among the various methods, a method in which hydrogenation is carried out under mild conditions of low pressure and low temperature using a homogeneous catalyst composed of a titanium organometallic compound alone or a titanium organometallic compound together with an organometallic compound of lithium, magnesium or aluminum (for example, the catalysts described in Japanese Patent Publication Nos. 63-4841 and 1-37970) is industrially preferred, and is also suitable because of its high hydrogenation selectivity to the double bond of butadiene.

[0067] The hydrogenation of a conjugated diene polymer is preferably carried out using a solvent that is inert to the catalyst and that dissolves the conjugated diene polymer. Preferred solvents include chain aliphatic hydrocarbons such as n-pentane, n-hexane, and n-octane; cyclic aliphatic hydrocarbons such as cyclohexane and cycloheptane; aromatic hydrocarbons such as benzene and toluene; and ethers such as diethyl ether and tetrahydrofuran. The solvent used for hydrogenation may be one of the above compounds or a mixture containing them as the main component.

[0068] The hydrogenation reaction is generally carried out by maintaining the conjugated diene polymer at a predetermined temperature in a hydrogen or inert atmosphere, adding a hydrogenation catalyst with or without stirring, and then introducing hydrogen gas to pressurize to a predetermined pressure. An inert atmosphere refers to an atmosphere that does not react with the substances involved in the hydrogenation reaction, and examples include helium, neon, and argon. Air and oxygen are undesirable because they oxidize the catalyst and cause catalyst deactivation. Nitrogen is also undesirable because it acts as a catalyst poison during the hydrogenation reaction and reduces hydrogenation activity. In particular, it is most suitable for the hydrogenation reactor to have an atmosphere of hydrogen gas alone.

[0069] The hydrogenation reaction process can be any of a batch process, a continuous process, and a combination thereof. When a titanocene diaryl compound is used as the hydrogenation catalyst, it may be added to the reaction solution either as is or as a solution in an inert organic solvent. When the catalyst is used as a solution, the inert organic solvent used can be any solvent that does not react with the substances involved in the hydrogenation reaction. The inert organic solvent is preferably the same solvent as that used in the hydrogenation reaction. The preferred amount of catalyst added is 0.02 to 20 mmol per 100 g of the conjugated diene polymer before hydrogenation.

[0070] In the (A) conjugated diene polymer, when the constituent ratios (molar ratios) of the structural unit represented by the above formula (1), the structural unit represented by the formula (2), the structural unit represented by the formula (3), and the structural unit represented by the formula (4) in the polymer are p, q, r, and s, respectively, the value α represented by the mathematical formula (i) is 0.60 or more and 0.98 or less. α=(p+(0.5×r)) / (p+q+(0.5×r)+s) …(i)

[0071] If the α value of the (A) conjugated diene polymer is less than 0.60, the amount of unsaturated bonds in the (A) conjugated diene polymer is large, resulting in a large change in Mooney viscosity due to differences in desolvation time. This tends to destabilize the quality of the (A) conjugated diene polymer or increase the heat-storage combustibility of the (A) conjugated diene polymer attached to equipment. Furthermore, the instability of the quality of the (A) conjugated diene polymer may result in a decrease in the strength and viscoelastic properties of the crosslinked product. If the α value of the (A) conjugated diene polymer is more than 0.98, crosslinking cannot be sufficiently promoted, which tends to result in a decrease in the strength and viscoelastic properties of the crosslinked product. Furthermore, it tends to be difficult to ensure adhesion when the crosslinked product is laminated with other conjugated diene material sheets and vulcanized. From these perspectives, the α value of the (A) conjugated diene polymer is more preferably 0.65 or more, even more preferably 0.70 or more, and even more preferably 0.75 or more. The value α of the conjugated diene polymer (A) is more preferably 0.97 or less, even more preferably 0.95 or less, and even more preferably 0.92 or less.

[0072] The value α represented by the mathematical formula (i) corresponds to the hydrogenation rate of the conjugated diene polymer. For example, when α is 0.60, the hydrogenation rate of the conjugated diene polymer is 60%. The hydrogenation rate of the conjugated diene polymer and the value α can be adjusted by adjusting the hydrogenation reaction time or controlling the cumulative amount of hydrogen supplied. In this specification, the hydrogenation rate is 1 These are values measured by a H-NMR apparatus. Regarding p, q, r, and s in formula (i), when the constituent ratios of the structural units of formulas (1) to (4) in the polymer are expressed in mole percent, p, q, r, and s can each take a value of 0 to 100% (with the proviso that the total value of p, q, r, and s is 100% or less).

[0073] A preferred method for obtaining (A) a conjugated diene polymer is to solution-polymerize a monomer containing 1,3-butadiene and styrene in the presence of a polymerization initiator (preferably a metal amide compound), add a coupling agent to the resulting polymer solution to carry out a coupling reaction, then add preferably a terminal modifier, and then subject the polymer to a hydrogenation step. This method is preferred because it can obtain a crosslinked product excellent in various physical properties (strength, abrasion resistance, viscoelastic properties, vulcanization adhesion, etc.), and is also industrially useful.

[0074] The weight average molecular weight (Mw) of the (A) conjugated diene polymer, measured using gel permeation chromatography (GPC) in terms of polystyrene, is preferably 1.5 × 10 in order to obtain a crosslinked product having high strength and excellent abrasion resistance. 5 ~2.0×10 6 The Mw of the conjugated diene polymer is more preferably 1.8 × 10 5 More preferably, it is 2.0×10 5 More preferably, Mw is 1.6×10 or more. 6 or less, more preferably 1.4 × 10 6 The weight average molecular weight of the conjugated diene polymer referred to here is a value determined from all peaks of a GPC curve measured by GPC before hydrogenation. Hereinafter, it is also referred to as "total average molecular weight."

[0075] Furthermore, the molecular weight distribution (ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (weight average molecular weight / number average molecular weight)) of the total amount of polymer (i.e., aggregate of different molecular weights) measured by GPC for (A) conjugated diene polymer is preferably 1.1 or more and 4.0 or less. A molecular weight distribution of 1.1 or more is preferred in terms of excellent processability, and a molecular weight distribution of 4.0 or less is preferred in terms of sufficiently improving the low hysteresis loss of the obtained crosslinked product. The molecular weight distribution of (A) conjugated diene polymer is more preferably 1.2 or more. The molecular weight distribution of (A) conjugated diene polymer is more preferably 3.5 or less, and even more preferably 3.0 or less.

[0076] The peak top molecular weight of the smallest peak (hereinafter also referred to as "first peak molecular weight") of the (A) conjugated diene polymer measured by GPC is preferably 0.8 × 10 5 ~1.0×10 6 The first peak molecular weight is in the range of 0.8 × 10 5 When the first peak molecular weight is 0.9×10 or more, the strength and abrasion resistance of the resulting crosslinked product can be sufficiently increased, while the viscoelastic properties and processability can be improved. 5 or more, and more preferably 1.0 × 10 5 In addition, from the viewpoint of improving the viscoelastic properties and processability, the first peak molecular weight is more preferably 8.0 × 10 5 More preferably, it is 5.0 × 10 5 The first peak molecular weight is a value determined from a GPC curve measured by GPC before hydrogenation.

[0077] The conjugated diene polymer (A) preferably contains, together with a branched polymer having four or more branches, one or more polymers (second polymers) selected from the group consisting of linear polymers and branched polymers having three or less branches. More specifically, the second polymer is a hydrogenated product of the conjugated diene polymer obtained in the polymerization step, or a hydrogenated product of the conjugated diene polymer obtained in the reaction step that has not reacted with the coupling agent. From the viewpoint of increasing the strength of the crosslinked product, the second polymer preferably has specific functional groups at some or all of its terminals, and more preferably has specific functional groups at all of its terminals. For example, a linear polymer having modified terminals can be obtained by using a metal amide compound as a polymerization initiator in the polymerization step and performing the modification step.

[0078] The proportion of the branched polymer having four or more branches in the (A) conjugated diene polymer is preferably 10% by mass or more relative to the total amount (100% by mass) of the (A) conjugated diene polymer. Having the proportion of the branched polymer having four or more branches in the (A) conjugated diene polymer within the above range is preferred in that it suppresses changes in Mooney viscosity due to differences in the desolvation time of the (A) conjugated diene polymer and enables quality stabilization. The proportion of the branched polymer having four or more branches in the (A) conjugated diene polymer is more preferably 15% by mass or more, and even more preferably 20% by mass or more. Furthermore, from the viewpoints of improving the processability of the polymer composition and the viscoelastic properties of the crosslinked product, the proportion of the branched polymer having four or more branches in the (A) conjugated diene polymer is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less. The proportion (mass%) of branched polymers having four or more branches in the (A) conjugated diene polymer can be calculated by separating the waveform of a coupling polymer (a molecule in which four or more linear conjugated diene polymers are bonded) from a GPC curve obtained using GPC.

[0079] The proportion of the modified polymer in the (A) conjugated diene polymer is preferably 60% by mass or more relative to the total amount of the (A) conjugated diene polymer. When the proportion of the modified polymer in the (A) conjugated diene polymer is within the above range, the strength, abrasion resistance, viscoelastic properties, and fuel economy of the resulting crosslinked product can be improved. The proportion of the modified polymer in the (A) conjugated diene polymer is more preferably 70% by mass or more, and even more preferably 80% by mass or more. The proportion (mass%) of the modified polymer in the (A) conjugated diene polymer is a value calculated by adding the proportion of linear polymers having a partial structure derived from the terminal modifier and the coupling rate. The reaction rate of the terminal modifier in the reaction between the conjugated diene polymer having an active terminal and the terminal modifier can be calculated by subjecting the polymer solution after the modification reaction with the terminal modifier to gas chromatography and quantifying the amount of unreacted terminal modifier.

[0080] The nitrogen content of the (A) conjugated diene polymer is preferably 50 ppm or more relative to the total amount of the (A) conjugated diene polymer. The nitrogen content of the (A) conjugated diene polymer within the above range is preferable because it allows for the production of a crosslinked polymer excellent in various properties, such as strength, viscoelasticity, and abrasion resistance, while fully reducing the burden on the production process. From this perspective, the nitrogen content of the (A) conjugated diene polymer is more preferably 60 ppm or more, and even more preferably 80 ppm or more, relative to the total amount of the (A) conjugated diene polymer. Furthermore, the nitrogen content of the (A) conjugated diene polymer is preferably 500 ppm or less, and more preferably 450 ppm or less, relative to the total amount of the (A) conjugated diene polymer. The nitrogen content of the polymer is a value measured in accordance with the chemiluminescence method of JIS K2609:1998 (Crude oil and petroleum products - Nitrogen content test method). Details of the measurement method follow the method described in the Examples below.

[0081] The nitrogen-containing conjugated diene polymer (A) can be obtained by using, in producing the polymer, a method of using a nitrogen-containing compound (preferably a secondary amine compound) as an initiation terminal modifier, a method of polymerizing using a nitrogen-containing monomer, a method of using a nitrogen-containing compound as a terminal modifier, or a method of using a nitrogen-containing compound as a coupling agent, or by combining two or more of these methods.

[0082] <Component (B): Hindered phenol compound> The composition contains a hindered phenol compound (hereinafter also referred to as "compound (B)") having a molecular weight of 250 to 2,000. Herein, the term "hindered phenol compound" refers to a compound having a partial structure (hereinafter also referred to as "hindered phenol structure") in which groups having one or more carbon atoms are bonded to the carbons on both sides of the carbon atom bonded to the hydroxyl group (i.e., at the two ortho positions relative to the hydroxyl group) among the carbons constituting an aromatic ring (preferably a benzene ring) to which a hydroxyl group is bonded.

[0083] In the hindered phenol structure, the groups having one or more carbon atoms bonded to the carbons on both sides of the carbon to which the hydroxyl group is bonded (hereinafter also referred to as "specific groups Xb") are not particularly limited as long as the molecular weight of compound (B) falls within the above-mentioned range. Examples of specific groups Xb include saturated or unsaturated chain hydrocarbon groups having 1 to 40 carbon atoms, saturated or unsaturated alicyclic hydrocarbon groups having 3 to 40 carbon atoms, and aromatic hydrocarbon groups having 6 to 40 carbon atoms, as well as groups in which one or more of the methylene groups and hydrogen atoms in these hydrocarbon groups have been replaced with functional groups (e.g., hydroxyl groups, (meth)acryloyl groups, -O-, -S-, etc.). (A) In the process for producing a conjugated diene polymer (particularly in the drying treatment of the polymer), from the viewpoint of suppressing the heat accumulation combustion of the polymer adhering to and remaining on the equipment, suppressing the change in Mooney viscosity due to the variation in the desolvation time, thereby stabilizing the quality, and obtaining a crosslinked product exhibiting good properties, at least one of the two specific groups Xb in the hindered phenol structure preferably has 2 or more carbon atoms, more preferably 4 or more carbon atoms.

[0084] At least one of the two specific groups Xb in the hindered phenol structure of the compound (B) is preferably bonded to a carbon constituting the aromatic ring via a tertiary carbon, i.e., the compound (B) preferably has a carbon bonded to at least one of the carbons on both sides of the carbon in the aromatic ring to which a hydroxyl group is bonded, and the carbon is a quaternary carbon.

[0085] Examples of such hindered phenol compounds include N-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, tetrakis{methylene-3-(3',5'-di-t-butyl-4-hydroxyphenyl)propionate}methane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, distearyl(4-hydroxy-3-methyl-5-t-butylbenzyl)malonate, and triethylene glycol. -bis{3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate}, 1,6-hexanediol-bis{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate}, 2,4-bis-(N-octylthio)-6-(4-hydroxyphenyl)-3,5-di-t-butyl-anilino-1,3,5-triazine, 2,2-thiodiethylenebis{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate}, 2,2-thiodiethylenebis Bis(4-methyl-6-t-butylphenol), 2,2'-methylenebis-(4-ethyl-6-t-butylphenol), N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3,5-di-t-butyl tris(3,5-di-t-butyl-4-hydroxybenzyl)sulfide, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 2,4-bis{(octylthio)methyl}-O-cresol, isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, N,N'-bis{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionylhydrazine, and (meth)acrylate compounds having a hindered phenol structure.

[0086] An example of a (meth)acrylate compound having a hindered phenol structure is a compound represented by the following formula (7). [ka] (In formula (7), R 1 ~R 5 are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. 6 is a hydrogen atom or a methyl group.

[0087] In equation (7), R 1 ~R 5 Examples of the alkyl group having 1 to 10 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, and a 1,1-dimethylpropyl group. 1 and R 2 In terms of a high stabilizing effect and ease of production, R is preferably a bulky alkyl group with large steric hindrance, such as an isopropyl group, a sec-butyl group, a tert-butyl group, or a 1,1-dimethylpropyl group. 3 and R 4 R is preferably a tert-butyl group or a 1,1-dimethylpropyl group from the viewpoint of suppressing the reaction of forming a quinoid structure accompanied by hydrogen abstraction. 5 is preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group.

[0088] Among the (B) compounds, hindered phenol compounds having an unsaturated group are particularly preferred because they can effectively suppress facility contamination caused by volatile matter and bleed-out products during the drying process of the polymer, stabilize quality by suppressing changes in Mooney viscosity due to variations in desolvation time, effectively reduce the process load in the process of producing the (A) conjugated diene polymer, and effectively improve various properties such as the strength, abrasion resistance, and viscoelastic properties of the crosslinked product, or fuel economy when used in tires. When the (B) compound has an unsaturated group, examples of the unsaturated group include a vinyl group, a (meth)acryloyl group, and a vinylphenyl group. Of these, the hindered phenol compound having an unsaturated group as the (B) component preferably has a (meth)acryloyl group, and more preferably a compound represented by formula (7). Among these, in formula (7), R 1 and R2 is a tert-butyl group, R 3 and R 4 is a methyl group, R 5 and R 6 is a hydrogen atom, or R 1 ~R 4 is a tert-pentyl group, R 5 is a methyl group, R 6 is a hydrogen atom is preferred.

[0089] The molecular weight of the (B) compound is 250 to 2,000. If the molecular weight of the hindered phenol compound incorporated into the present composition is less than 250, the hindered phenol compound tends to migrate to the mixed solvent phase during the solvent removal step, resulting in a tendency for the amount of the hindered phenol compound remaining in the polymer to decrease. This raises concerns that the heat storage combustion of polymer components adhering to the equipment and the volatilization of the components may not be sufficiently suppressed during the polymer drying process. This necessitates frequent treatments to remove the components adhering to the equipment, increasing the process load. Furthermore, if the molecular weight of the hindered phenol compound exceeds 2,000, the compatibility with the (A) conjugated diene polymer may decrease, resulting in a decrease in performance. From these viewpoints, the molecular weight of the (B) compound is preferably 300 or more, more preferably 350 or more. Furthermore, the molecular weight of the (B) compound is preferably 1,800 or less, more preferably 1,500 or less, and even more preferably 1,200 or less.

[0090] The blending amount of the (B) compound (the total amount when two or more compounds are used) is preferably 0.1 to 2.2 parts by mass per 100 parts by mass of the (A) conjugated diene polymer. By blending the (B) compound in an amount of 0.1 part by mass or more, the change in Mooney viscosity with respect to differences in the desolvation time can be further reduced. Furthermore, the heat-storage combustibility of the (A) conjugated diene polymer can be reduced during the drying treatment of the (A) conjugated diene polymer. Furthermore, the effect of improving various properties, such as the strength and viscoelasticity of the crosslinked polymer, and the fuel economy performance when used in tires, can be enhanced. From these viewpoints, the blending amount of the (B) compound is more preferably 0.2 to 100 parts by mass, and even more preferably 0.4 to 100 parts by mass, of the (A) conjugated diene polymer. Furthermore, by blending the (B) compound in an amount of 2.2 parts by mass or less, the effect of suppressing facility contamination due to volatile matter and bleed-out products during the drying treatment of the polymer can be enhanced. Furthermore, the blending amount of the (B) compound tends to suppress a decrease in the strength of the crosslinked polymer obtained using the composition and a decrease in the fuel economy performance when used in tires. The amount of the compound (B) to be blended is more preferably 1.8 parts by mass or less, even more preferably 1.4 parts by mass or less, and even more preferably 1.0 part by mass or less, relative to 100 parts by mass of the conjugated diene polymer (A). As the compound (B), one type may be used alone, or two or more types may be used in combination.

[0091] <Other ingredients> In addition to the conjugated diene polymer (A) and the compound (B), the present composition may further contain the following components.

[0092] (C) Component: specific stabilizer The composition may further contain, as component (C), at least one compound selected from the group consisting of phosphorus-based stabilizers and organic sulfur-based stabilizers, having a molecular weight of 250 to 2,000 (hereinafter also referred to as the "(C) specific stabilizer"). By including the (C) specific stabilizer in the composition together with the (B) compound, a smaller amount of additive can be used to achieve the effect of minimizing the change in Mooney viscosity relative to the solvent removal time, thereby improving quality stability, and the effect of suppressing the heat accumulation combustion and volatilization of components due to adhesion of the (A) conjugated diene polymer to equipment during the drying process of the (A) conjugated diene polymer. This allows for a well-balanced improvement in equipment contamination and the performance of the crosslinked product.

[0093] The (C) specific stabilizer can be a known compound as a phosphorus-based antioxidant or an organic sulfur-based antioxidant, and has a molecular weight within the range of 250 to 2,000. Specific examples of these include phosphorus-based stabilizers having a molecular weight of 250 to 2,000, such as tris(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4'-bisphenylene phosphite, tris(nonylphenyl)phosphite, distearyl pentaerythritol diphosphite, bis(2,4,di-t-butylphenyl)pentaerythritol phosphite, bis(2,6,di-t-butyl-4-methylphenyl)pentaerythritol phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, and tetrakis(2,4-di-t-butylphenyl)4,4'-bisphenylene-diphosphite. The phosphorus-based stabilizers may be used alone or in combination of two or more.

[0094] Specific examples of organic sulfur stabilizers having a molecular weight of 250 to 2,000 include organic thioacid compounds such as didodecylthiodipropionate, ditetradecylthiodipropionate, dioctadecylthiodipropionate, 2,2-bis[[3-(dodecylthio)propionic acid]-1,3-propanediyl, pentaerythritol tetrakis(3-dodecylthiopropionate), and thiobis(N-phenyl-β-naphthylamine). The organic sulfur stabilizers can be used alone or in combination of two or more.

[0095] The amount of the (C) specific stabilizer (the total amount when two or more types are used) is preferably 0.01 to 2.0 parts by mass per 100 parts by mass of the (A) conjugated diene polymer. The amount of the (C) specific stabilizer is more preferably 0.02 parts by mass or more, and even more preferably 0.05 parts by mass or more, per 100 parts by mass of the (A) conjugated diene polymer. The amount of the (C) specific stabilizer is more preferably 1.5 parts by mass or less, and even more preferably 1.2 parts by mass or less, per 100 parts by mass of the (A) conjugated diene polymer. By setting the amount of the (C) specific stabilizer within the above range, it is possible to achieve the effects of further minimizing changes in Mooney viscosity with respect to variations in the desolvation time and suppressing the effects of heat accumulation combustion and volatilization of components due to adhesion of the (A) conjugated diene polymer to equipment during drying treatment, while reducing the amount of the (B) compound added. As the (C) specific stabilizer, only a phosphorus-based stabilizer may be used, only an organic sulfur-based stabilizer may be used, or a phosphorus-based stabilizer and an organic sulfur-based stabilizer may be used in combination.

[0096] (D) Component: inorganic filler The composition may contain an inorganic filler. Examples of inorganic fillers include silica and carbon black, as well as fillers other than silica and carbon black (hereinafter also referred to as "other fillers"). The inorganic filler blended in the composition preferably includes one or both of silica and carbon black.

[0097] (D-1) Ingredient: Silica The composition may contain silica. The amount of silica is preferably 20 to 120 parts by mass, more preferably 30 to 100 parts by mass, per 100 parts by mass of the rubber component containing the (A) conjugated diene polymer. When the amount of silica is 20 parts by mass or more per 100 parts by mass of the rubber component, the low hysteresis loss, fracture properties, and abrasion resistance of the polymer composition can be sufficiently improved, and when the amount is 120 parts by mass or less, the processability of the polymer composition can be sufficiently improved.

[0098] In this specification, the "rubber component" contained in the polymer composition refers to a polymer that can be cured to give a cured product exhibiting rubber elasticity by heat curing, etc. The cured product exhibits the property of undergoing large deformation under 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.

[0099] The silica is not particularly limited, and examples thereof include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred. As the silica, one type may be used alone, or two or more types may be used in combination. The BET specific surface area of the silica (measured in accordance with ISO 5794 / 1) is 40 to 350 m 2 / g, and 80 to 350m 2 / g is more preferable, and 120 to 350m 2 / g is particularly preferred. Silica having a BET specific surface area in this range has the advantage of being able to achieve both rubber reinforcement and dispersibility in the modified diene polymer (A). Examples of such silica include "Nipsil AQ" (BET specific surface area = 205 m), manufactured by Tosoh Silica Corporation. 2 / g), "Nipsil KQ" manufactured by Degussa, trade name "Ultrasil VN3" (BET specific surface area = 175 m 2 Commercially available products such as PEG-100 / g can be used.

[0100] The silica blended in the present composition may be a combination of two or more types with different specific surface areas. Specifically, CTAB (cetyltrimethylammonium bromide) with a specific surface area of 180 m 2 / g or more, BET specific surface area is 185m 2 / g or more, aggregate size of 45nm or more, and CTAB specific surface area of 95m 2 / g or less, BET specific surface area is 100m 2 The CTAB specific surface area of the silica may be measured in accordance with ASTM D3765-92.

[0101] This composition has a CTAB specific surface area of 180m 2 / g or more, BET specific surface area is 185m 2 / g or more, aggregate size of 45nm or more, and CTAB specific surface area of 95m 2 / g or less, BET specific surface area is 100m 2 The rubber composition may contain a second silica having an average primary particle size of 1 / 2 g or less. By using such a first silica and a second silica in combination, it becomes possible to satisfactorily disperse the first silica, which has a small average primary particle size but a relatively large aggregate size, in the rubber component. This improves the dispersibility of the silica, and provides excellent fracture strength, abrasion resistance, fuel economy, and processability.

[0102] The CTAB specific surface area of the first silica is preferably 190 m 2 / g or more, more preferably 195m 2 / g or more, more preferably 197m 2 / g or more. CTAB specific surface area is 180m 2 If the CTAB specific surface area of the first silica is less than 350 m / g, it may be difficult to obtain sufficient improvements in fracture strength and abrasion resistance. 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 / g or less. CTAB specific surface area is 350m 2 If the amount exceeds 1 / g, the dispersibility becomes poor and aggregation occurs easily, which tends to deteriorate the physical properties.

[0103] The BET specific surface area of the first silica is preferably 190 m 2 / g or more, more preferably 195m 2 / g or more, more preferably 210m 2 / g or more. BET specific surface area is 185m 2 If the BET specific surface area is less than 350 m / g, it may be difficult to obtain sufficient improvements in breaking strength and abrasion resistance. 2 / g or less, more preferably 300m 2 / g or less, more preferably 260m 2 / g or less. BET specific surface area is 350m 2 If the BET specific surface area of silica exceeds 1 / g, the dispersibility is poor and the silica is prone to aggregation, which tends to result in a deterioration in physical properties. The BET specific surface area of silica is measured in accordance with ASTM D3037-81.

[0104] The aggregate size of the first silica is 45 nm or more, preferably 50 nm or more, more preferably 55 nm or more, and even more preferably 60 nm or more. The aggregate size is preferably 100 nm or less, more preferably 80 nm or less, even more preferably 70 nm or less, and particularly preferably 67 nm or less. Having such an aggregate size can provide excellent fuel economy and abrasion resistance while maintaining good dispersibility (processability). The aggregate size of silica can be measured by the method described in JP 2011-140613 A.

[0105] 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. The lower limit of the average primary particle diameter is not particularly limited, but 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 dispersibility (processability) of the silica can be further improved by the carbon black-like structure having the above aggregate size, thereby further improving fuel economy and abrasion resistance. The average primary particle diameter of the silica can be determined by observing the silica with a transmission or scanning electron microscope, measuring the particle diameters of 400 or more primary silica particles observed within the field of view, and averaging the measured values.

[0106] The CTAB specific surface area of the second silica is preferably 10 m 2 / g or more, more preferably 20m 2 / g or more, more preferably 30m 2 / g or more. CTAB specific surface area is 10m 2 If the CTAB specific surface area is less than 80 m / g, the reinforcing effect will be low, and it may be difficult to ensure sufficient mechanical strength and abrasion resistance required for a polymer composition for tire production. 2 / g or less, more preferably 60m 2 / g or less, more preferably 50m 2 / g or less. CTAB specific surface area is 95m 2 If it exceeds 1 / g, the dispersibility of silica may be deteriorated, making it difficult to improve the breaking strength and abrasion resistance.

[0107] The BET specific surface area of the second silica is preferably 10 m 2 / g or more, more preferably 20m 2 / g or more, more preferably 30m 2 / g or more. BET specific surface area is 10m 2 If the BET specific surface area is less than 85 m / g, the reinforcing effect will be low, and it may be difficult to ensure the mechanical strength and abrasion resistance required for a polymer composition for tire production. 2 / g or less, more preferably 60m2 / g or less, more preferably 50m 2 / g or less. BET specific surface area is 100m 2 If it exceeds 1 / g, the dispersibility of silica may be deteriorated, making it difficult to improve the breaking strength and abrasion resistance.

[0108] The average primary particle size 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.The upper limit of the average primary particle size is not particularly limited, but is preferably 500 nm or less, more preferably 200 nm or less, even more preferably 100 nm or less, particularly preferably 70 nm or less.By having such an average primary particle size, it is possible to ensure sufficient fracture strength and wear resistance.

[0109] (D-2) Component: Carbon black From the viewpoint of the fracture properties and abrasion resistance of the polymer composition, the present composition preferably contains carbon black. The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited, and is preferably 50 to 200 m 2 / g is preferred, and 70 to 150m 2 / g is more preferred. The nitrogen adsorption specific surface area (N2SA) is the amount of nitrogen adsorbed onto the surface of carbon black measured in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method." One type of carbon black may be used alone, or two or more types may be used in combination. The amount of carbon black in the composition is preferably in the range of 1 to 150 parts by mass, more preferably 5 to 120 parts by mass, per 100 parts by mass of the (A) conjugated diene polymer.

[0110] (D-3) Ingredient: Other fillers The composition may contain other inorganic fillers in addition to silica and carbon black. Examples of such 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 dioxide (TiO2), and titanium black (TiO 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 silicates (Al2SiO5, Al4·3SiO4·5H2O, etc.), magnesium silicates (Mg2SiO4, MgSiO3, etc.) , calcium silicate (Ca2SiO4, etc.), calcium aluminum silicate (Al2O3·CaO·2SiO2, etc.), calcium magnesium silicate (CaMgSiO4), calcium carbonate (CaCO3), zirconium oxide (ZrO2), zirconium hydroxide [ZrO(OH)2·nH2O], zirconium carbonate [Zr(CO3)2], and crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals to compensate for the charge, such as various zeolites.

[0111] In the present composition, the blending amount of the inorganic filler containing silica and carbon black is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, per 100 parts by mass of the rubber component containing the conjugated diene polymer (A). The blending amount of the inorganic filler is preferably 150 parts by mass or less, more preferably 130 parts by mass or less, per 100 parts by mass of the rubber component containing the conjugated diene polymer (A). When the blending amount of the inorganic filler in the present composition is within the above range, when the present composition is applied to a tire tread, the tire can have a better balance of low rolling resistance, braking performance on wet roads, handling performance on dry roads, and abrasion resistance.

[0112] (E) Component: Other rubber components The present composition may contain only the conjugated diene polymer (A) as the rubber component. Alternatively, the composition may contain, in addition to the conjugated diene polymer (A), a rubber component other than the conjugated diene polymer (hereinafter also referred to as "other rubber component"), as long as the effects of the present disclosure are not impaired. Examples of the other rubber component include at least one diene rubber selected from natural rubber, isoprene rubber, butadiene rubber, emulsion-polymerized or solution-polymerized styrene-butadiene rubber, butyl rubber, halogenated butyl rubber, and ethylene-propylene rubber. Among these, natural rubber, butadiene rubber, and styrene-butadiene rubber are preferred as the other rubber component. The manner in which the other rubber component and the conjugated diene polymer (A) are mixed is not particularly limited. For example, the other rubber component and the conjugated diene polymer (A) may be mixed during kneading using a Banbury mixer or roll mixer, as is commonly done. Alternatively, the other rubber component may be mixed with a polymer solution containing the conjugated diene polymer (A) after polymerization, followed by a desolvation and drying process.

[0113] The amount of the other rubber components added is preferably 80% by mass or less, and more preferably 60% by mass or less, based on the total amount of the rubber components ((A) conjugated diene polymer and other rubber components) contained in the polymer composition.

[0114] In the present composition, a liquid rubber may be used as part or all of the other rubber components in order to further improve dry grip performance, wet grip performance and blowout resistance.

[0115] Examples of liquid rubbers include liquid polyisoprene (liquid IR), liquid polybutadiene (liquid BR), liquid styrene-butadiene copolymer (liquid SBR), and liquid ethylene-propylene copolymer (liquid EP). For example, liquid SBR having a weight-average molecular weight of 1,000 to 100,000, preferably 2,000 to 80,000, can be used. In this specification, the weight-average molecular weight refers to the weight-average molecular weight in terms of polystyrene analyzed by gel permeation chromatography (GPC). The liquid rubber used in this composition is one that has fluidity at 23°C.

[0116] ·(F) Component: Thermoplastic / Thermosetting resin The present composition may contain a thermoplastic / thermosetting resin (hereinafter, also simply referred to as "(F) resin"). From the viewpoint of obtaining a crosslinked product with excellent properties such as strength, abrasion resistance, and crack growth resistance, the (F) resin is preferably at least one selected from the group consisting of styrene-based resins, polyethylene, C5-based resins, C9-based resins, C5 / C9-based resins, dicyclopentadiene-based resins, alkylphenol-based resins, and terpene-based resins. As the (F) resin, one type may be used alone, or two or more types may be used in combination.

[0117] Here, the styrene-based resin is a polymer obtained using a styrene-based monomer, and in particular, a polymer having structural units derived from a styrene-based monomer in an amount of 20 mass% or more relative to the total amount of monomer units possessed by the styrene-based resin is preferred. Examples of the styrene-based monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc. Of these, the styrene-based monomer is preferably at least one of styrene and α-methylstyrene.

[0118] The styrene-based resin may be a homopolymer obtained by polymerizing one type of styrene-based monomer, or a copolymer obtained by copolymerizing two or more types of styrene-based monomers. The styrene-based resin may also be a copolymer obtained by using a styrene-based monomer and another monomer copolymerizable with the styrene-based monomer. Examples of other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene-isoprene, olefins such as 1-butene and 1-pentene, and α,β-unsaturated carboxylic acids or their acid anhydrides such as maleic anhydride.

[0119] The softening point of the styrene-based resin is preferably 30°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher. A softening point of 30°C or higher tends to improve the crack growth resistance of the crosslinked body. The softening point of the styrene-based resin is preferably 160°C or lower, more preferably 130°C or lower, and even more preferably 100°C or lower. A softening point of 160°C or lower tends to improve the dispersibility of the resin, and to improve the crack growth resistance, abrasion resistance, and breaking strength. In the present disclosure, the softening point of the styrene-based resin is a value measured using a ring and ball softening point analyzer according to the method specified in JIS K 6220-1:2015, and is the temperature at which the sample softens and a ball placed on the sample drops to the bottom plate.

[0120] The styrene-based resin may be a block polymer (thermoplastic elastomer) having a conjugated diene polymer block as a soft segment and a polystyrene block as a hard segment. The use of such a block polymer is preferable because it can further enhance the effect of improving crack growth resistance. The conjugated diene polymer block of the block polymer may have some of the carbon-carbon double bonds in the structural unit derived from the conjugated diene compound hydrogenated.

[0121] Examples of conjugated diene compounds constituting the conjugated diene polymer block include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. The conjugated diene compounds may be used singly or in combination of two or more. Among these, the conjugated diene compound is preferably at least one of 1,3-butadiene and isoprene. The content of the conjugated diene units in the block polymer is preferably 20% by mass or more, more preferably 30% by mass or more. Furthermore, the content of the conjugated diene units is preferably 80% by mass or less, more preferably 70% by mass or less.

[0122] The content of the polystyrene block in the block polymer is preferably 20% by mass or more, in order to increase the breaking strength. The content of the polystyrene block is preferably 80% by mass or less, and more preferably 70% by mass or less. The respective contents of the polystyrene block, the conjugated diene polymer block, and the conjugated diene unit in the block polymer are as follows: 1 It can be calculated from the integral ratio of the H-NMR spectrum.

[0123] Specific examples of the block polymer include styrene-butadiene block copolymers, styrene-isoprene block copolymers, epoxidized styrene-butadiene block copolymers, and block copolymers in which a portion of the conjugated diene polymer block of a styrene-butadiene block copolymer or a styrene-isoprene block copolymer has been hydrogenated. More specifically, examples include styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-butadiene-butylene-styrene block copolymers (SBBS), and epoxidized styrene-butadiene-styrene block copolymers, as well as hydrogenated products of these copolymers. Among these, SBS or SIS having a conjugated diene polymer block in which the soft segment is not hydrogenated, or epoxidized styrene-butadiene-styrene block copolymers are preferred because of their ease of crosslinking.

[0124] Examples of polyethylene include low-density polyethylene (LDPE), high-density polyethylene (HDPE), and linear low-density polyethylene (LLDPE). C5 resins are solid polymers (C5 synthetic petroleum resins) obtained by polymerizing C5 fractions using a Friedel-Crafts catalyst (such as AlCl3 or BF3). Specific examples of C5 resins include copolymers primarily composed of isoprene, cyclopentadiene, 1,3-pentadiene, and 1-pentene, copolymers of 2-pentene and dicyclopentadiene, and polymers primarily composed of 1,3-pentadiene.

[0125] The C9 resin is a solid polymer (C9 synthetic petroleum resin) obtained by polymerizing a C9 fraction using a Friedel-Crafts catalyst (such as AlCl3 or BF3). Specific examples of the C9 resin include copolymers containing indene, methylindene, vinyltoluene, etc. as the main component. The C5 / C9 resin is a solid polymer (C5 / C9 synthetic petroleum resin) obtained by polymerizing a C5 to C9 fraction using a Friedel-Crafts catalyst (such as AlCl3 or BF3). Specific examples of the C5 / C9 resin include copolymers containing vinyltoluene, indene, etc. as the main component. From the viewpoint of compatibility with rubber components, C5 / C9 resins with a low content of C9 or higher components are preferred. Specifically, the C5 / C9 resin preferably contains less than 50% by mass, and more preferably 40% by mass or less, of the C9 or higher components in the total amount of the resin.

[0126] Dicyclopentadiene-based resins are petroleum resins that use dicyclopentadiene in C5 fractions as the main raw material. Specific examples of dicyclopentadiene-based resins include the "Marukarets M" series (M-890A, M-845A, M-990A, etc.) from Maruzen Petrochemical Co., Ltd. Examples of alkylphenol-based resins include alkylphenol-acetylene resins such as p-tert-butylphenol-acetylene resins, and low-polymerization alkylphenol-formaldehyde resins.

[0127] Terpene resins are solid resins obtained by blending turpentine oil, which is obtained simultaneously when rosin is obtained from pine trees, or a polymerization component separated from this, and polymerizing the blend using a Friedel-Crafts catalyst, and examples of such resins include β-pinene resin and α-pinene resin. Commercially available terpene resins can be used, and examples include the "YS Resin" series (PX-1250, TR-105, etc.) manufactured by Yasuhara Chemical Co., Ltd. and the "Picolite" series (A115, S115, etc.) manufactured by Hercules.

[0128] A representative example of a terpene-aromatic compound resin is a terpene-phenol resin. This terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst or by further condensing them with formalin. There are no particular limitations on the terpenes used as raw materials; monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred. Furthermore, a terpene-phenol resin with a low phenol content is preferred. Here, "a low phenol content" refers to a phenol content of less than 50% by mass, preferably 40% by mass or less, of the total resin. Using a terpene-aromatic compound resin, particularly a terpene-phenol resin, as the (F) resin can further improve handling performance. Commercially available terpene-aromatic compound resins can be used. Examples of commercially available products include those sold under the trade names "Tamanol 803L" and "Tamanol 901" (manufactured by Arakawa Chemical Industries, Ltd.), and those sold under the trade name "YS Polystar (registered trademark)" series (manufactured by Yasuhara Chemical Co., Ltd.).

[0129] The blending ratio of the (F) resin is preferably 1 part by mass or more per 100 parts by mass of the rubber component contained in the composition. By blending 1 part by mass or more of the (F) resin, the effect of improving the abrasion resistance, breaking strength, and crack growth resistance of the crosslinked product obtained using the composition can be sufficiently enhanced, which is suitable. The blending ratio of the (F) resin is more preferably 3 parts by mass or more, and even more preferably 7 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of maintaining the various performance properties of the composition well, the blending ratio of the (F) resin is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less, per 100 parts by mass of the rubber component contained in the composition. Note that, as the (F) resin, one type may be used alone, or two or more types may be used in combination.

[0130] Component (G): Silane coupling agent The composition may further enhance the dispersibility of silica by blending a silane coupling agent. The silane coupling agent used is not particularly limited. Preferred silane coupling agents are sulfur-containing silane coupling agents, such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropylbenzothiazoletetrasulfide, γ-mercaptopropyltriethoxysilane, and 3-octanoylthiopropyltriethoxysilane.

[0131] The amount of silane coupling agent is preferably 1 to 20 parts by mass per 100 parts by mass of silica contained in the composition. If the amount of silane coupling agent is less than 1 part by mass, there is a concern that the effect of improving the dispersibility of silica will be reduced due to the small amount. On the other hand, if the amount of silane coupling agent is more than 20 parts by mass, the processability of the polymer composition and the elongation at break of the crosslinked product may decrease. The amount of silane coupling agent is more preferably 5 to 15 parts by mass per 100 parts by mass of silica contained in the composition.

[0132] Component (H): Crosslinking agent The present composition may contain a crosslinking agent. By including the crosslinking agent in the present composition, a crosslinked product with improved strength and abrasion resistance can be obtained. Examples of crosslinking agents include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, and alkylphenol resins having methylol groups, with sulfur being typically used. The amount of crosslinking agent blended 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 present composition.

[0133] ·(I) Component: Extender oil The composition may contain a process oil commonly used to extend elastomers as an oil for oil extension (extender oil). The method for adding the process oil is not particularly limited. For example, the process oil may be dispersed in a conjugated diene polymer solution after polymerization and then desolvated to form an oil-extended rubber. Alternatively, the process oil may be directly added to the polymer composition during kneading to obtain a rubber compound (compounded rubber). Suitable process oils include various oils known in the art, such as aromatic oils, paraffinic oils, naphthenic oils, vegetable oils, and oils with a low content of polycyclic aromatic compounds (low PCA oils), such as mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), special residual aromatic extracts (SRAE), and heavy naphthenic oils. Examples of commercially available MES, TDAE, and SRAE include Catenex SNR (heavy paraffin obtained by dewaxing distillate oil with a solvent) manufactured by Shell as MES, Vivatec 500 manufactured by H&R Wasag AG as TDAE, and NC140 manufactured by Japan Energy Corp. 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.

[0134] In addition to the components described above, the composition may contain various additives that are commonly used in polymer compositions for obtaining vulcanized rubber, such as zinc oxide, stearic acid, softeners, vulcanization accelerators, compatibilizers, vulcanization aids, processing aids, and scorch inhibitors. The blending ratios of these additives may be appropriately selected depending on the various components, as long as the effects of the present disclosure are not impaired.

[0135] <<Method for producing polymer composition>> The present composition can be obtained by mixing the (A) conjugated diene polymer with the (B) compound. The manner in which the (A) conjugated diene polymer and the (B) compound are mixed to obtain the present composition is not particularly limited. From the viewpoint of suppressing changes in the Mooney viscosity of the (A) conjugated diene polymer obtained by desolvation due to differences in the desolvation time of the (A) conjugated diene polymer, and suppressing heat-accumulating combustion and volatilization of components due to equipment contamination during drying treatment, the present composition is preferably obtained by adding the (B) compound to a polymer solution containing the (A) conjugated diene polymer after polymerization, thereby mixing the (A) conjugated diene polymer with the (B) compound, and then removing the solvent and drying.

[0136] Specifically, the present composition is preferably produced by a method including the following steps A, B, and C. Step A: A step of polymerizing a monomer containing a conjugated diene compound and an aromatic vinyl compound in the presence of an alkali metal or an alkaline earth metal, followed by hydrogenation, to obtain (A) a polymer solution containing a conjugated diene-based polymer. Step B: A step of mixing the polymer solution obtained in Step A with the compound (B) to obtain a mixed solution containing the conjugated diene polymer (A) and the compound (B). Step C: A step of removing the solvent from the mixed solution obtained in Step B and drying it.

[0137] Step A includes the polymerization step and hydrogenation step described above, and optionally includes one or both of a reaction step and a modification step. The above explanations apply to the details of each step.

[0138] In step B, from the viewpoint of simplifying the production process, it is preferable to use the polymer solution containing the conjugated diene polymer (A) obtained in step A as is and mix the polymer solution with the compound (B). The amount of the compound (B) is as described above. When the specific stabilizer (C) is blended into the composition, the specific stabilizer (C) may be blended during kneading to obtain a blended composition (so-called compounded rubber), thereby mixing the conjugated diene polymer (A) and the specific stabilizer (C). Alternatively, the specific stabilizer (C) may be added to the polymer solution in step B, thereby mixing the conjugated diene polymer (A) and the specific stabilizer (C). The latter (the embodiment in which the specific stabilizer (C) is added to the polymer solution in step B) is preferable, as it can sufficiently enhance the effect of blending the specific stabilizer (C). When the specific stabilizer (C) is added to the polymer solution in step B, the specific stabilizer (C) may be added to the polymer solution simultaneously with the compound (B), or may be added to the polymer solution before or after the addition of the compound (B). The amount of the compound (C) is as described above.

[0139] There are no particular limitations on the method for removing the solvent from the mixed liquid containing the conjugated diene polymer (A) and the compound (B) and drying the mixed liquid in step C. The solvent can be removed from the mixed liquid and dried by, for example, a known desolvation procedure such as steam stripping and a drying procedure such as heat treatment.

[0140] According to Steps A to C, a solid polymer composition from which the solvent has been removed (hereinafter also referred to as "polymer composition P") can be obtained as one embodiment of the present composition. Polymer composition P may be in the form of solid particles (crumbs), or may be a rubber bale obtained by compression molding the crumbs into a desired shape (for example, a rectangular parallelepiped shape). In polymer composition P, the total content of (A) the conjugated diene polymer, (B) the compound, and (I) the extender oil, which is optionally blended, is preferably 95% by mass or more, more preferably 97% by mass or more, based on the total mass of the composition.

[0141] By blending the above-mentioned various components (e.g., components (D) to (I)) with the obtained polymer composition P as needed, a polymer composition or blended composition (hereinafter also referred to as "polymer composition Q") that can serve as a blended composition can be obtained as another embodiment of the present composition. The blended composition can be obtained by mixing the polymer composition P with various additives (e.g., components (D) to (I)) that are optionally used in polymer compositions for obtaining vulcanized rubber, and kneading the mixture using a kneader, preferably an open kneader (e.g., a roll) or an internal kneader (e.g., a Banbury mixer). The blended rubber thus obtained is molded and then crosslinked (vulcanized) to obtain a crosslinked product (i.e., vulcanized rubber).

[0142] A crosslinked product obtained using the polymer composition of the present disclosure, which contains (A) a conjugated diene polymer and (B) a compound, can be used in various rubber products. Specifically, the crosslinked product obtained using the composition can be used in tire applications such as tire treads, undertreads, carcasses, sidewalls, and bead portions; sealants such as packings, gaskets, weatherstrips, and O-rings; interior and exterior skin materials for various vehicles such as automobiles, ships, aircraft, and trains; building materials; vibration-proof rubbers for industrial machinery and equipment; various hoses and hose covers such as diaphragms, rolls, radiator hoses, and air hoses; belts such as power transmission belts; linings; dust boots; medical equipment materials; fenders; insulating materials for electric wires; and other industrial products.

[0143] The polymer composition of the present disclosure, which contains a conjugated diene polymer (A) and a compound (B), can suppress adhesion of the conjugated diene polymer (A) to equipment during drying treatment, and can also suppress heat accumulation combustion and volatilization of components due to the polymer adhered to the equipment, thereby reducing the process load in the production process and producing a crosslinked product having excellent physical properties required for tire applications, such as tensile strength, abrasion resistance, and viscoelasticity. Therefore, the polymer composition containing a conjugated diene polymer (A) and a compound (B) can be suitably used, in particular, as a material for tire treads, sidewalls, or both.

[0144] Tires can be manufactured by conventional methods, for example, by mixing the polymer composition in a kneader, forming a sheet, and then arranging the sheet in a predetermined position (for example, on the outside of the carcass in the case of a sidewall) and vulcanizing the sheet in a conventional manner to form a tread or a sidewall, thereby obtaining a pneumatic tire.

[0145] According to the present disclosure described above, the following means are provided. [Means 1] A polymer composition comprising: (A) a conjugated diene polymer having a structural unit derived from a conjugated diene compound and a structural unit derived from an aromatic vinyl compound, wherein the value α represented by the above mathematical formula (i) is 0.60 to 0.98 when the constituent ratios (molar ratios) in the polymer of the structural unit represented by the above formula (1), the structural unit represented by the above formula (2), the structural unit represented by the above formula (3), and the structural unit represented by the above formula (4) are p, q, r, and s, respectively; and (B) a hindered phenol compound having a molecular weight of 250 to 2,000, wherein part or all of the component (A) has a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, sulfur, and phosphorus. [Means 2] The polymer composition according to [Means 1], wherein the content of the component (B) is 0.1 to 2.2 parts by mass per 100 parts by mass of the component (A). [Means 3] The polymer composition according to [Means 1] or [Means 2], wherein the proportion of nitrogen contained in the component (A) is 50 ppm or more based on the total amount of the component (A). [Means 4] The polymer composition according to any one of [Means 1] to [Means 3], wherein the component (A) has a polymer block portion containing 80 mass % or more of structural units derived from an aromatic vinyl compound. [Means 5] The polymer composition according to any one of [Means 1] to [Means 4], which contains a branched polymer having 4 or more branches as the component (A). [Means 6] The polymer composition according to [Means 5], wherein the proportion of the branched polymer having 4 or more branches is 15% by mass or more based on the total amount of the component (A). [Means 7] The polymer composition according to any one of [Means 1] to [Means 6], wherein the molecular weight of the component (B) is 350 to 1,200. [Means 8] The polymer composition according to any one of [Means 1] to [Means 7], which contains a compound having a carbon-carbon unsaturated bond as the component (B). [Means 9] The polymer composition according to any one of [Means 1] to [Means 8], further comprising at least one component selected from the group consisting of phosphorus-based stabilizers and organic sulfur-based stabilizers, the component having a molecular weight of 250 to 2,000. [Means 10] The polymer composition according to any one of [Means 1] to [Means 9], wherein the value α is 0.75 to 0.92. [Means 11] The polymer composition according to any one of [Means 1] to [Means 10], wherein the total content of the component (A), the component (B), and an optionally blended extender oil is 95 mass% or more based on the total mass of the composition. [Means 12] The polymer composition according to any one of [Means 1] to [Means 10], further comprising an inorganic filler. [Means 13] A crosslinked body obtained by crosslinking the polymer composition according to any one of [Means 1] to [Means 10] and [Means 12]. [Means 14] A tire in which a tread, a sidewall, or both are formed using the polymer composition according to any one of [Means 1] to [Means 10] and [Means 12]. [Means 15] A method for producing the polymer composition according to any one of [Means 1] to [Means 12], comprising the steps of: polymerizing a monomer containing a conjugated diene compound and an aromatic vinyl compound in the presence of an alkali metal or an alkaline earth metal, and hydrogenating the polymer to obtain a polymer solution containing the component (A); mixing the polymer solution with the component (B) to obtain a mixed liquid containing the component (A) and the component (B); and removing the solvent from the mixed liquid and drying it. [Example]

[0146] The present disclosure will be specifically explained below based on examples, but the present disclosure is not limited to these examples. In the examples and comparative examples, "parts" and "%" are by mass unless otherwise specified. The methods for measuring various physical properties of the polymer are shown below.

[0147] [Polymer Characterization] Vinyl bond content (mol%): For the polymer before hydrogenation, 1 1H-NMR was used to measure the Bound styrene content (%): For the polymer before hydrogenation, 400MHz 1 1H-NMR was used to measure the First peak molecular weight: For the polymer before hydrogenation, a chart based on the molecular weight converted to polystyrene was obtained using a gel permeation chromatograph (GPC, product name: HLC-8020, manufactured by Tosoh Corporation), and the first peak molecular weight was determined from the retention time of the peak with the longest retention time in the obtained GPC curve. The specific measurement conditions are as follows: (Measurement conditions) Column: Two GMH-HR-H columns (manufactured by Tosoh Corporation) were connected in series. Detector: Differential refractometer RI-8020 (Tosoh Corporation) Eluent: tetrahydrofuran Column temperature: 40℃ Flow rate: 1.0mL / min Sample concentration: 10mg / 20mL Total average molecular weight: The total average molecular weight was calculated in terms of polystyrene from all peaks in the GPC curve obtained using GPC (product name: HLC-8020, manufactured by Tosoh Corporation) for the polymer before hydrogenation. The measurement conditions were the same as above. Coupling rate (mass%): The coupling rate (mass%) was calculated from the peak area ratio of the waveform of molecules in which two or more linear conjugated diene polymer molecular chains were bonded, which was obtained using GPC (product name: HLC-8020, manufactured by Tosoh Corporation) for the polymer before hydrogenation. Hydrogenation rate and α: Measured using ethylene tetrachloride as a solvent with a 100MHz device 1 Calculated from H-NMR spectrum. Content (mass%) of polymers with four or more branches: The polymer before hydrogenation was used for GPC (product name: HLC-8020, manufactured by Tosoh Corporation) to obtain a GPC curve, from which the waveforms of molecules in which molecular chains of linear conjugated diene polymers with four or more branches were separated into components, and the content was calculated from the peak area ratio. Modified polymer content (mass%): Calculated by adding the coupling ratio (C / E) to the ratio of linear polymer modified with the terminal modifier (W1) (modified polymer content = W1 + C / E). The ratio W1 was calculated using the following formula from the number of moles of polymerization initiator (M1) and coupling agent (M2) used in polymer production, the number of moles of terminal modifier consumed during modification with the terminal modifier (M3), and the coupling ratio (C / E). W1[%]=(100-C / E)×M3 / (M1-4×M2) The number of moles (M3) of the terminal modifier consumed during modification with the terminal modifier was calculated by quantifying the amount of unreacted terminal modifier by gas chromatography measurement of the polymer solution after the modification reaction. Nitrogen content (ppm): Measured according to the chemiluminescence method of JIS K2609:1998 (Crude oil and petroleum products - Nitrogen content test method). Specifically, using a trace total nitrogen analyzer (Mitsubishi Chemical Analytech "TN-2100H"), the sample was thermally decomposed under argon gas flow, then burned and oxidized in an oxygen atmosphere. The resulting nitric oxide was reacted with ozone gas under dehydrating conditions, and the detected luminescence intensity was measured in the range of 590 to 2500 nm. The nitrogen content was calculated from the area of ​​the luminescence intensity.

[0148] <Production of Conjugated Diene Polymer> [Production Example 1: Production of Hydrogenated Conjugated Diene Polymer A-1 and Its Properties] A 50-liter autoclave reactor with a nitrogen-purged atmosphere was charged with 25,900 g of cyclohexane, 65 g of tetrahydrofuran, 0.6 g of potassium dodecylbenzenesulfonate, 740 g of styrene, 2,849 g of 1,3-butadiene, and 30 mmol of piperidine. The temperature of the reactor contents was adjusted to 42°C, and a cyclohexane solution containing n-butyllithium (39 mmol) was added to initiate polymerization. The polymerization was carried out under adiabatic conditions. After the polymerization conversion reached 99%, 111 g of 1,3-butadiene was added (additional butadiene) and the polymerization was continued for an additional 3 minutes to obtain a reaction solution containing a polymer. 2.0 mmol of tetrachlorosilane was added to the resulting reaction solution and the reaction was continued for 5 minutes. 28 mmol of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was then added and the reaction was continued for 15 minutes. Next, the reaction solution was heated to 80°C or higher, hydrogen was introduced into the system, and the reaction was carried out for 1 hour. A small amount of the polymer solution was withdrawn from the reaction vessel and used for analysis to obtain a pre-hydrogenated conjugated diene polymer. Subsequently, 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, and the hydrogenation reaction was carried out while maintaining a hydrogen pressure of 1.0 MPa. After the reaction, hydrogen was supplied until a predetermined hydrogen accumulation value was reached while maintaining a hydrogen pressure of 0.7 MPa or higher. The reaction solution was then returned to room temperature and pressure and withdrawn from the reaction vessel, yielding a polymer solution containing hydrogenated conjugated diene polymer A-1. A small amount of the resulting polymer solution was withdrawn, the solvent was removed by steam stripping, and the solution was dried using a heated roll adjusted to 130°C to obtain hydrogenated conjugated diene polymer A-1. The polymerization recipe for the hydrogenated conjugated diene polymer A-1 is shown in Table 1, and various physical properties of the hydrogenated conjugated diene polymer A-1 are shown in Table 3.

[0149] [Production Examples 2 to 11, Production Examples 13 to 15, and Comparative Production Examples 1 to 5: Production of Hydrogenated Conjugated Diene Polymers and Their Properties] Polymer solutions containing hydrogenated conjugated diene polymers A-2 to A-11, A-13 to A-18, A-21, and A-22 were obtained in the same manner as in Production Example 1, except that the polymerization recipe was changed as shown in Tables 1 and 2 and the hydrogenation rate was changed as shown in Tables 3 and 4. Hydrogenated conjugated diene polymers A-2 to A-11, A-13, A-21, and A-22 were produced in Production Examples 2 to 11 and 13 to 15, respectively, and hydrogenated conjugated diene polymers A-14 to A-18 were produced in Comparative Production Examples 2 to 5, respectively. Various physical properties of the hydrogenated conjugated diene polymers A-2 to A-11, A-13 to A-18, A-21, and A-22 are shown in Tables 3 and 4.

[0150] [Production Example 12: Production of Hydrogenated Conjugated Diene Polymer A-12 and Its Properties] A 50-liter autoclave reactor purged with nitrogen was charged with 25,900 g of cyclohexane, 600 g of styrene, 65 g of tetrahydrofuran, and 30 mmol of piperidine. A cyclohexane solution containing 39 mmol of n-butyllithium was added, and polymerization was carried out under adiabatic conditions at a polymerization initiation temperature of 40°C. After the polymerization conversion reached 99% or higher, the reaction solution was cooled to 30°C, and 700 g of styrene and 2,289 g of 1,3-butadiene were added for further polymerization. After the polymerization conversion reached 99% or higher, 111 g of 1,3-butadiene was added and polymerization was continued for an additional 3 minutes to obtain a reaction solution containing a polymer. 2.0 mmol of tetrachlorosilane was added to the resulting reaction solution and reacted for 5 minutes. 28 mmol of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was then added and reacted for 15 minutes. The reaction solution was then heated to 80°C or higher, and hydrogen was introduced into the system, followed by a 1-hour reaction. A small amount of the polymer solution was withdrawn from the reaction vessel to obtain a pre-hydrogenated conjugated diene polymer. 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, and the hydrogenation reaction was carried out while maintaining a hydrogen pressure of 1.0 MPa. After the reaction, hydrogen was supplied until a predetermined integrated hydrogen value was reached while maintaining a hydrogen pressure of 0.7 MPa or higher. The reaction solution was then returned to room temperature and pressure and withdrawn from the reaction vessel to obtain a polymer solution containing hydrogenated conjugated diene polymer A-12. A small amount of the resulting polymer solution was withdrawn, the solvent was removed by steam stripping, and the solution was dried on a heated roll heated to 130°C to obtain hydrogenated conjugated diene polymer A-12. The polymerization formulation for hydrogenated conjugated diene polymer A-12 is shown in Table 2, and various physical properties of hydrogenated conjugated diene polymer A-12 are shown in Table 4.

[0151] Comparative Production Examples 6 and 7: Production of Hydrogenated Conjugated Diene Polymers A-19 and A-20 and Their Properties Polymer solutions containing hydrogenated conjugated diene polymers A-19 and A-20 were obtained in the same manner as in Production Example 12, except that the polymerization recipe was changed as shown in Table 2 and the hydrogenation rate was changed as shown in Table 4. Table 4 shows the physical properties of the hydrogenated conjugated diene polymers A-19 and A-20.

[0152] [Table 1]

[0153] [Table 2]

[0154] In Tables 1 and 2, "-" means that the compound in the corresponding column was not used. The abbreviations for the vinyl content adjuster, initiation terminal modifier, terminal modifier and coupling agent are as follows. V-1: Potassium dodecylbenzenesulfonate INI-1: piperidine Md-1: N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane Cp-1: Tetrachlorosilane

[0155] [Table 3]

[0156] [Table 4]

[0157] <Production of polymer composition and crosslinked product> [Example 1] Production of polymer composition P To the polymer solution containing the hydrogenated conjugated diene polymer A-1 obtained in Production Example 1, 0.2 parts by mass of hindered phenol compound B-1 and 0.3 parts by mass of hindered phenol compound B-2 as component (B) and 0.3 parts by mass of phosphate ester compound C-1 as component (C) were mixed per 100 parts by mass of the hydrogenated conjugated diene polymer A-1. The resulting mixture was steam stripped for 2 hours to remove the solvent, and then dried using a heated roll adjusted to 130 ° C. to obtain polymer composition P-1 containing hydrogenated conjugated diene polymer A-1, hindered phenol compound B-1, hindered phenol compound B-2, and phosphate ester compound C-1. The formulation of polymer composition P-1 is shown in Table 5.

[0158] -Production of polymer composition Q and crosslinked product Using the polymer composition P-1 produced above, the components were blended according to the formulation shown in Table 7, and the blend was kneaded to produce polymer composition Q-1. Kneading was performed as follows. Using a plastomill (capacity: 250 mL) equipped with a temperature control device, in the first stage of kneading, polymer composition P-1, silica, carbon black, a silane coupling agent, an extender oil, stearic acid, zinc oxide, and an antioxidant were blended and kneaded at a filling rate of 72% and a rotation speed of 60 rpm. In the second stage of kneading, the blend obtained above was cooled to room temperature, and then a vulcanization accelerator and sulfur were blended and kneaded. The kneaded polymer composition Q-1 was molded and vulcanized in a vulcanization press at 160°C for a predetermined time to obtain a crosslinked product (vulcanized rubber). The manufacturing process was evaluated by measuring the MV change rate due to the extension of the desolvation time, the heat accumulation combustion suppression ability, volatility, and equipment adhesion, and the compound properties were evaluated by measuring the tensile strength, abrasion resistance, rolling resistance, and vulcanization adhesion of the resulting crosslinked products. The results are shown in Table 8.

[0159] (1) MV change rate due to extension of desolvation time Polymer composition P' was obtained in the same manner as in the production of polymer composition P, except that the steam stripping time was changed from 2 hours to 8 hours. The Mooney viscosity (MV) of polymer composition P and polymer composition P' was measured, and the measured MV values ​​(MV-P, MV-P') were obtained. Mooney viscosity was measured in accordance with JIS K6300-1 using an L rotor, with a preheating time of 1 minute, a rotor operation time of 4 minutes, and a temperature of 100°C. Using the MV measurement values ​​(MV-P, MV-P'), the MV change rate was calculated using the following formula. MV change rate = MV-P' / MV-P The smaller the obtained MV change rate value and the closer it is to 1.0, the better the quality stability in the solvent removal process and the more useful it is in reducing the burden on process management.The values ​​were graded AA to C according to the following criteria. AA: 0.8 or more and less than 1.2 A: 1.2 or more and less than 1.5 B: 1.5 or more and less than 2.0 C: 2.0 or more or less than 0.8

[0160] (2) Heat storage and combustion suppression 350 g of polymer composition P was cut into 0.5 cm squares to obtain angular crumbs. The angular crumbs were placed in a 10 cm diameter stainless steel wire mesh, and a thermocouple for temperature measurement was placed in a gear oven so that it was in contact with the angular crumbs. The gear oven was set to 170°C and heated with ventilation for 8 hours, and the maximum temperature reached as indicated by the thermocouple was measured. The lower the maximum temperature reached, the greater the effect of suppressing heat accumulation and combustion. This reduces the risk of heat accumulation and ignition of polymer composition crumbs that adhere to or remain on the inside and outside of the drying oven or extruder during the manufacturing process, and can be considered useful in reducing process load, such as by reducing the frequency of equipment cleanup. Based on the maximum temperature reached, the heat accumulation and combustion suppression ability was evaluated as A to C using the following criteria. A: Maximum temperature is less than 180°C B: The maximum temperature is between 180°C and 210°C and is within the allowable range. C: The maximum temperature is 210°C or higher, which is unacceptable.

[0161] (3) Volatility Using 10 mg of polymer composition P, the 0.5 wt% thermal weight loss temperature (Td0.5) was determined in a thermogravimetric analyzer at a temperature increase rate of 5°C / min from 40°C under an air flow of 200 mL / min. The measured temperature at which the weight loss of polymer composition P reached 0.5 wt% was defined as the 0.5 wt% thermal weight loss temperature (Td0.5). A higher Td0.5 is more effective in suppressing volatile components around the drying oven and extruder during the manufacturing process, thereby reducing the process load by preventing deterioration of the working environment at the manufacturing site and reducing the frequency of equipment cleanup. Volatility was evaluated based on Td0.5, with a scale of A to C, according to the following criteria: A: 280℃ or higher B: 170℃ or higher and lower than 280℃, within the acceptable range C: Less than 170°C, unacceptable

[0162] (4) Adhesion to equipment (adhesion to apron) In the above "Production of polymer composition P", instead of subjecting the polymer composition after solvent removal by steam stripping to a drying treatment using a heated roll adjusted to 130°C, the polymer composition after solvent removal was placed on a SUS wire gauze and heated in a hot air thermostatic chamber at 120°C for 1 hour to a hot air drying treatment. The state of the dried polymer composition P when recovered from the SUS wire gauze was observed, and the equipment adhesion was evaluated as AA to C according to the following evaluation criteria. AA: 99% or more of the polymer composition was recovered, and no adhesion of the polymer composition to the wire mesh was observed. A: 97% or more but less than 99% of the polymer composition was recovered, and adhesion of the polymer composition to the wire mesh was small. B: 95% or more but less than 97% of the polymer composition was recovered, and a large amount of the polymer composition adhered to the wire mesh. C: The recovery rate of the polymer composition was less than 95%, and a very large amount of the polymer composition adhered to the wire mesh. If the rating is AA to B, it can be determined that the equipment adhesion in the drying step using a band dryer, extruder, etc. during the production of the polymer composition is at a practical level. If the rating is C, it can be determined that it does not reach a practical level.

[0163] (5) Tensile strength The crosslinked body was used as a measurement sample and subjected to a tensile test in accordance with JIS K6251:2010. Here, a dumbbell No. 3 was used as the test sample, and the stress at break (TB) and elongation at break (EB) were measured at room temperature. The larger the TB and EB values, the higher the breaking strength, indicating that the mechanical strength of the material is high and good. Evaluation was performed based on the TB value, and was evaluated using an index based on Comparative Example 1. The larger the value, the higher the tensile strength, indicating that the strength is good. From the obtained tensile strength value, the tensile strength was rated as AA to C according to the following criteria. AA: 110 or more A: 100 or more and less than 110 B: Between 80 and 100, within the acceptable range C: Under 80

[0164] (6) Abrasion resistance The crosslinked body was used as a measurement sample and measured at 25°C under a load of 10 N using a DIN abrasion tester (manufactured by Toyo Seiki Co., Ltd.) in accordance with JIS K6264-2:2005. The rolling resistance was evaluated using an index based on Comparative Example 1. The larger the index, the higher and better the abrasion resistance. From the obtained index, the abrasion resistance was rated as A to C according to the following criteria. A: 115 or more B: 105 or more and less than 115, within the acceptable range C: Less than 105

[0165] (7) Rolling resistance The crosslinked body was used as a measurement sample and measured using a dynamic spectrometer (manufactured by Rheometrics, Inc., USA) under conditions of tensile dynamic strain of 0.7%, angular velocity of 100 radians per second, and 50°C. The rolling resistance was evaluated using an index based on Comparative Example 2. The larger the index, the lower the rolling resistance and the better it is. From the obtained index, the rolling resistance was rated as AA to C according to the following criteria. AA: 125 or more A: 115 or more and less than 125 B: 105 or more and less than 115, within the acceptable range C: Less than 105

[0166] (8) Vulcanization adhesion A pre-vulcanization sheet of polymer composition Q formed into a sheet and a pre-vulcanization sheet containing natural rubber as the main component were laminated together with PET films sandwiched between the edges, and the laminate was vulcanized at 170°C for 15 minutes to obtain a laminated vulcanizate in which the portions not sandwiched by the PET film were vulcanized and bonded together. A strip-shaped sample piece was taken from the laminated vulcanizate, extending from the portion sandwiched with PET to the portion not sandwiched, so that the adhesive strength could be measured across a width of 15 mm. The PET film was then removed to prepare a test piece. A vulcanized sheet formed from polymer composition Q was placed on one side of an autograph testing machine equipped with a thermostatic chamber, and a vulcanized sheet of natural rubber was placed on the other side. The two sheets were then chucked together, and a peel test was carried out in an atmosphere of 70°C at a speed of 50 mm / min to measure adhesive strength. The adhesive strength values ​​obtained were evaluated as an index based on Comparative Example 1. The higher the value, the higher the adhesive strength and the better the vulcanization adhesion. From the obtained index, the vulcanization adhesion was evaluated as AA to C according to the following criteria. AA: 140 or more A: 110 or more and less than 140 B: 90 or more and less than 110 C: Less than 90

[0167] [Examples 2 to 15, Comparative Examples 1 to 7] Polymer compositions P-2 to P-22 were produced as polymer composition P in the same manner as in Example 1, except that polymer solutions containing hydrogenated conjugated diene polymers A-2 to A-22 were used instead of the polymer solution containing hydrogenated conjugated diene polymer A-1, and the types and amounts of additives were as shown in Tables 5 and 6. In producing polymer composition P, polymer solutions containing hydrogenated conjugated diene polymers A-2 to A-13, A-21, and A-22, respectively, were used in Examples 2 to 15, and polymer solutions containing hydrogenated conjugated diene polymers A-14 to A-20, respectively, were used in Comparative Examples 1 to 7. Furthermore, polymer compositions Q-2 to Q-22 were produced by blending and kneading the components according to the formulation shown in Table 7 in the same manner as in Example 1, except that polymer compositions P-2 to P-22 were used instead of polymer composition P-1. Furthermore, crosslinked bodies were produced using the produced polymers Q-2 to Q-22, and various evaluations were performed in the same manner as in Example 1. The results are shown in Tables 8 and 9.

[0168] [Table 5]

[0169] [Table 6]

[0170] In Tables 5 and 6, "-" means that the compound in the corresponding column was not used. The abbreviations for the additives are as follows: B-1: n-Octadecyl-3-(4-hydroxyl-3,5-di-t-butylphenyl)-propionate B-2: 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate B-3: Pentaerythritol tetrakis[3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate] C-1: Tris(2,4-di-tert-butylphenyl)phosphite C-2: 2,2-bis({[3-(dodecylthio)propionyl]oxy}methyl)-1,3-propanediyl bis[3-(dodecylthio)propionate] H-1: 2,6-di-tert-butyl-4-methylphenol

[0171] [Table 7]

[0172] [Table 8]

[0173] [Table 9]

[0174] As shown in Tables 8 and 9, the polymer compositions of Examples 1 to 15 were evaluated as "AA," "A," or "B" in terms of the MV change rate due to the extension of the desolvation time, the heat-accumulation combustion suppression ability, the volatility, and the equipment adhesion. From these results, it can be said that the polymer compositions of Examples 1 to 15 can reduce the load in the production process and have good quality stability. Furthermore, the crosslinked products obtained from the polymer compositions of Examples 1 to 15 were excellent in terms of the tensile strength, abrasion resistance, rolling resistance, and vulcanization adhesion, because the change in the Mooney viscosity of the polymer during the production process was suppressed, and thus the crosslinked products obtained from the polymer compositions of Examples 1 to 15 were also excellent in terms of the tensile strength, abrasion resistance, rolling resistance, and vulcanization adhesion, and were excellent in various compounding properties.

[0175] In contrast, the polymer compositions of Comparative Examples 1 and 7, which contained unmodified hydrogenated conjugated diene polymers A-14 and A-20, respectively, were favorable in the manufacturing process evaluation (MV change rate with extended desolvation time, heat accumulation combustion suppression, volatility, and equipment adhesion), but were rated "C" in one or more of the compounding properties (tensile strength, abrasion resistance, rolling resistance, and vulcanization adhesion), and were inferior to Examples 1 to 15. Furthermore, the polymer compositions of Comparative Examples 2 and 3, which did not contain a hindered phenol compound having a molecular weight of 250 or more, and the polymer compositions of Comparative Examples 4 and 5, which contained hydrogenated conjugated diene polymers with hydrogenation rates of 5% and 43%, respectively, were rated "C" in one or more of the manufacturing process evaluations, and were inferior in terms of manufacturing process load and quality stability. Furthermore, the compounding properties were also rated "C" in one or more of the evaluation items. The polymer composition of Comparative Example 6, which contained the hydrogenated conjugated diene polymer A-19 having a hydrogenation rate of 99%, was evaluated as good in the manufacturing process, but was evaluated as "C" in the tensile strength, rolling resistance, and vulcanization adhesion, indicating poor compounding properties.

[0176] From the above results, it has become clear that a polymer composition in which the value of α represented by the above formula (1) is 0.60 or more and 0.98 or less, which contains a conjugated diene-based polymer having conjugated diene compound units and aromatic vinyl compound units, and a hindered phenol compound having a molecular weight of 250 to 2,000, and in which part or all of the macromolecules constituting the conjugated diene-based polymer have a specific functional group containing at least one element selected from the group consisting of nitrogen, oxygen, sulfur and phosphorus, can reduce the process load and stabilize the quality in the production process of the conjugated diene-based polymer, and can produce a crosslinked product in which performance degradation is suppressed.

Claims

1. (A) A conjugated diene-based polymer having a structural unit derived from a conjugated diene compound and a structural unit derived from an aromatic vinyl compound, wherein the value α represented by the following mathematical formula (i) is 0.60 to 0.98 when the constituent ratios (molar ratios) in the polymer of the structural unit represented by the following formula (1), the structural unit represented by the following formula (2), the structural unit represented by the following formula (3), and the structural unit represented by the following formula (4) are respectively p, q, r, and s; (B) Hindered phenol compound having a molecular weight of 250 to 2,000 Contains a part or all of the component (A) has a functional group containing at least one element selected from the group consisting of nitrogen and oxygen, A polymer composition comprising, as the component (B), a compound having a (meth)acryloyl group. α=(p+(0.5×r)) / (p+q+(0.5×r)+s)…(i) 【Chemical 1】

2. 2. The polymer composition according to claim 1, wherein the content of the component (B) is 0.1 to 2.2 parts by mass per 100 parts by mass of the component (A).

3. 2. The polymer composition according to claim 1, wherein the proportion of nitrogen contained in the component (A) is 50 ppm or more based on the total amount of the component (A).

4. The polymer composition according to claim 1, wherein the component (A) has a polymer block portion containing 80% by mass or more of structural units derived from an aromatic vinyl compound.

5. The polymer composition according to claim 1 , comprising, as the component (A), a branched polymer having four or more branches.

6. The polymer composition according to claim 5 , wherein the proportion of the branched polymer having 4 or more branches is 15% by mass or more based on the total amount of the component (A).

7. 2. The polymer composition according to claim 1, wherein the molecular weight of the component (B) is 350 to 1,200.

8. 2. The polymer composition according to claim 1, further comprising at least one component selected from the group consisting of phosphorus-based stabilizers and organic sulfur-based stabilizers, the component having a molecular weight of 250 to 2,000.

9. 2. The polymer composition according to claim 1, wherein the value α is from 0.75 to 0.

92.

10. 2. The polymer composition according to claim 1, wherein the total content of the component (A), the component (B), and the optionally blended extender oil is 95% by mass or more based on the total mass of the composition.

11. The polymer composition according to claim 1, further comprising an inorganic filler.

12. A crosslinked product obtained by crosslinking the polymer composition according to any one of claims 1 to 9 and 11.

13. A tire having a tread, a sidewall, or both formed using the polymer composition according to any one of claims 1 to 9 and 11.

14. A method for producing the polymer composition according to any one of claims 1 to 11, comprising: a step of polymerizing a monomer including a conjugated diene compound and an aromatic vinyl compound in the presence of an alkali metal or an alkaline earth metal, followed by hydrogenation to obtain a polymer solution including the component (A); a step of mixing the polymer solution with the component (B) to obtain a mixed solution containing the component (A) and the component (B); a step of removing the solvent from the mixed liquid and drying it; A method for producing a polymer composition, comprising:

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