Method for producing modified conjugated diene polymer, modified conjugated diene polymer, polymer composition, crosslinked product, tire and compound

Abstract

According to the present invention, a modified conjugated diene polymer is produced by a method which comprises a step for polymerizing a monomer that contains a conjugated diene compound in the presence of a polymerization initiator which contains a silicon-containing initiator that has a group F2 and an alkali metal element or an alkaline earth metal element. F2: a *1-Si(R1)n(Y1)3-n group (wherein R1 represents a hydrocarbyl group having 1 to 20 carbon atoms; Y1 represents a -OR2 group or a -NR3R4 group; each of R2, R3 and R4 independently represents a hydrocarbyl group having 1 to 20 carbon atoms; and n is an integer of 0 to 2).

Description

Method for producing modified conjugated diene polymer, modified conjugated diene polymer, polymer composition, crosslinked product, and tire

[0001] [Cross-reference to related applications] This application claims priority to Japanese Patent Application No. 2021-183755, filed on November 10, 2021, the entirety of which is incorporated herein by reference. The present disclosure relates to a method for producing a modified conjugated diene-based polymer, a modified conjugated diene-based polymer, a polymer composition, a crosslinked product, and a tire.

[0002] Conjugated diene polymers obtained by polymerization using conjugated diene compounds have various 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 a reinforcing agent such as carbon black or silica is blended with a conjugated diene polymer to improve the durability and abrasion resistance of rubber compositions used in pneumatic tire treads, sidewalls, etc. Furthermore, modified conjugated diene polymers obtained by modifying a conjugated diene polymer with a silicon- or nitrogen-containing compound have been used to increase the affinity between the conjugated diene polymer and the reinforcing agent (see, for example, Patent Documents 1 to 3).

[0004] International Publication No. 2008 / 123164 Japanese Patent Application Laid-Open No. 11-349632 International Publication No. 2017 / 221943

[0005] Due to recent environmental conditions, growing awareness of resource and energy conservation, and increasing consumer demand for driving performance, there is a demand for rubber materials for automobile tires that offer even better fuel efficiency (rolling resistance) than ever before.

[0006] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a modified conjugated diene polymer from which a crosslinked product excellent in fuel economy performance can be obtained.

[0007] The present disclosure provides the following method for producing a modified conjugated diene polymer, a modified conjugated diene polymer, a polymer composition, a crosslinked product, and a tire.

[0008] [1] A method for producing a modified conjugated diene polymer, comprising a step of polymerizing a monomer containing a conjugated diene compound in the presence of a polymerization initiator, wherein the polymerization initiator comprises a silicon-containing initiator having an alkali metal element or an alkaline earth metal element and a group F2 shown below. F2: group "* １ -Si(R １ ) ｎ (Y １ ) ３－ｎ ” (R １ is a hydrocarbyl group having 1 to 20 carbon atoms. １ is the group "-OR ２ " or the group "-NR ３ R ４ ". R ２ , R ３ and R ４ are each independently a hydrocarbyl group having 1 to 20 carbon atoms. n is an integer of 0 to 2. When n is 0 or 1, multiple Y １ are the same or different. When n is 2, a plurality of R １ are the same or different. １ " represents the bond to the carbon atom.)

[0009] [2] A modified conjugated diene polymer represented by the following formula (3): (In formula (3), X ２ is a group represented by the following formula (4-1) or formula (4-2): １ is a hydrocarbon group having 1 to 20 carbon atoms and a valence of (i+k), or has at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom, does not have active hydrogen, and is a group "-Si(R １ ) ｎ (Y １ ) ３－ｎ " and a group represented by the following formula (4-2) via a carbon atom. R １ is a hydrocarbyl group having 1 to 20 carbon atoms. １ is the group "-OR ２ " or the group "-NR ３ R ４ ". R ２ , R ３ and R ４are each independently a hydrocarbyl group having 1 to 20 carbon atoms. n is an integer of 0 to 2. When n is 0 or 1, multiple Y １ are the same or different. When n is 2, a plurality of R １ are the same or different, and i and k are each independently an integer of 1 to 6, provided that i+k≦10 is satisfied. ２ If there are multiple X ２ are the same or different. The group "-Si(R １ ) ｎ (Y １ ) ３－ｎ When there are a plurality of groups "-Si(R １ ) ｎ (Y １ ) ３－ｎ " are the same or different.) (In formula (4-1), Z １ represents a single bond, an alkanediyl group having 1 to 8 carbon atoms, or the group "* ３ -Ar １ -W １ -" (Ar １ is a divalent aromatic ring group. １ is a single bond or a methylene group. ３ " is Q １ represents a bond with .) ６ and R ７ are each independently a hydrocarbylene group having 1 to 10 carbon atoms. １ and Q ２ are each independently a nitrogen atom or —CR １０ -. However, Z １ If is a single bond, Q １ is a nitrogen atom. １０ represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms. Poly represents a modified or unmodified conjugated diene polymer chain. "*" represents a bond. In formula (4-2), Z ２ represents a single bond, an alkanediyl group having 1 to 8 carbon atoms, or the group "* ４ -Ar １ -W １ -" (Ar １ is a divalent aromatic ring group. １ is a single bond or a methylene group. ４ " is -NR１１ - represents a bond with . １１ represents a hydrogen atom, a hydrocarbyl group having 1 to 20 carbon atoms, or a trihydrocarbylsilyl group. Poly represents a modified or unmodified conjugated diene polymer chain. "*" represents a bond.

[0010] [3] A polymer composition containing the modified conjugated diene polymer obtained by the production method of [1] above, or the modified conjugated diene polymer of [2] above, and at least one selected from the group consisting of silica and carbon black. [4] A crosslinked product obtained by crosslinking the polymer composition of [3] above. [5] A tire having a tread or a sidewall, or both, formed using the polymer composition of [3] above.

[0011] According to the modified conjugated diene polymer of the present disclosure, a crosslinked product having excellent fuel economy performance can be obtained.

[0012] The modified conjugated diene polymer of the present disclosure can be produced by a method including a step of polymerizing a monomer containing a conjugated diene compound in the presence of a polymerization initiator (hereinafter also referred to as a "polymerization step"). In the polymerization step for producing the modified conjugated diene polymer of the present disclosure, a compound having an alkali metal element or an alkaline earth metal element and the group F2 shown below (hereinafter also referred to as a "silicon-containing initiator") is used as the polymerization initiator. F2: Group "*" １ -Si(R １ ) ｎ (Y １ ) ３－ｎ ” (R １ is a hydrocarbyl group having 1 to 20 carbon atoms. １ is the group "-OR ２ " or the group "-NR ３ R ４ ". R ２ , R ３ and R ４ are each independently a hydrocarbyl group having 1 to 20 carbon atoms. n is an integer of 0 to 2. When n is 0 or 1, multiple Y １ are the same or different. When n is 2, a plurality of R １ are the same or different. １" represents a bond to a carbon atom constituting a hydrocarbon group.) Hereinafter, matters related to the embodiments of the present disclosure will be described in detail.

[0013] <Silicon-Containing Initiator> In the production method of the present disclosure, a modified conjugated diene polymer having a group F2 introduced at the terminal of the polymer (more specifically, the polymerization initiation terminal) can be obtained by polymerizing a monomer in the presence of a silicon-containing initiator. The modified conjugated diene polymer has a structure derived from the silicon-containing initiator at its terminal, which enables it to form a covalent bond or interact with a filler such as silica or carbon black. In this specification, "interaction" refers to the formation of an intermolecular force weaker than a covalent bond (for example, an electromagnetic force acting between molecules such as an ion-dipole interaction, a dipole-dipole interaction, a hydrogen bond, or a van der Waals force).

[0014] (Regarding Group F2) Group F2 has a structure in which one or more hydrocarbyloxy groups or dihydrocarbylamino groups are bonded to a silicon atom. １ , R ２ , R ３ and R ４ Examples of the hydrocarbyl group having 1 to 20 carbon atoms represented by R include an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms. １ , R ２ , R ３ and R ４ Among these, alkyl groups having 1 to 20 carbon atoms are preferred, and alkyl groups having 1 to 10 carbon atoms are more preferred.

[0015] The silicon atom in group F2 is bonded to a carbon atom. The carbon atom to which the silicon atom in group F2 is bonded is preferably an element constituting a hydrocarbon group. Specifically, the silicon atom in group F2 may be bonded to a chain hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group. n is preferably 1 or 2, more preferably 2, from the viewpoint of achieving both productivity during polymer production and fuel economy of the crosslinked body.

[0016] The silicon-containing initiator preferably further has the following group F1, in that this can further enhance the effect of improving fuel economy performance: F1: at least one group selected from the group consisting of a tertiary amino group and a protected secondary amino group By polymerizing monomers in the presence of a silicon-containing initiator having groups F1 and F2, a modified conjugated diene polymer having groups F1 and F2 introduced at the polymerization initiation terminal can be obtained.

[0017] (Regarding Group F1) When group F1 is a tertiary amino group, the hydrocarbon group bonded to the nitrogen atom may be any of a chain hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. The protected secondary amino group may be a group "-NR ２０ -" is an example. ２０ is preferably a silyl functional group, and the group "-SiR ２１ R ２２ R ２３ ” (R ２１ , R ２２ and R ２３ are each independently a hydrocarbyl group having 1 to 20 carbon atoms), and are particularly preferably a trihydrocarbylsilyl group.

[0018] The number of groups F1 and F2 in the silicon-containing initiator is not particularly limited. The number of groups F1 in the silicon-containing initiator is preferably 0 to 6, more preferably 1 to 3, and even more preferably 1 or 2. The number of groups F2 in the silicon-containing initiator is preferably 1 to 6, more preferably 1 to 3, and even more preferably 1 or 2. The total number of groups F1 and F2 is preferably 1 to 10, more preferably 2 to 10, and even more preferably 2 to 5.

[0019] The silicon-containing initiator can be obtained, for example, by mixing at least one metal compound selected from the group consisting of alkali metal compounds and alkaline earth metal compounds with a compound having group F2 (hereinafter also referred to as "compound [M]"). Alternatively, the silicon-containing initiator may be obtained by mixing a metal element (e.g., lithium element, sodium element, potassium element) with compound [M]. Of these, compounds obtained by mixing a metal compound with compound [M] are preferably used as the silicon-containing initiator.

[0020] (Regarding the Metal Compound) The metal compound is a nitrogen-free compound having an alkali metal element or an alkaline earth metal element. A compound in which a hydrocarbon group is bonded to an alkali metal element or an alkaline earth metal element can be preferably used as the metal compound. Examples of such a metal compound include alkali metal compounds such as methyl lithium, ethyl lithium, n-propyl lithium, n-butyl lithium, sec-butyl lithium, t-butyl lithium, 1,4-dilithiobutane, phenyl lithium, stilbene lithium, naphthyl lithium, 1,3-bis(1-lithio-1,3-dimethylpentyl)benzene, 1,3-phenylenebis(3-methyl-1-phenylpentylidene)dilithium, naphthyl sodium, and naphthyl potassium.

[0021] Examples of alkaline earth metals include alkylarylmagnesiums such as dimethylmagnesium, diethylmagnesium, di(n-propyl)magnesium, di(n-butyl)magnesium, di(sec-butyl)magnesium, di(t-butyl)magnesium, diphenylmagnesium, bis(stilbene)magnesium, dinaphthylmagnesium, and methylphenylmagnesium.

[0022] Among these, the metal compound used to obtain the silicon-containing initiator is preferably a lithium compound, more preferably at least one selected from the group consisting of alkyllithium and aryllithium, and particularly preferably alkyllithium (methyllithium, ethyllithium, n-propyllithium, n-butyllithium, sec-butyllithium, t-butyllithium, etc.). Note that as the metal compound, one type may be used alone, or two or more types may be used in combination.

[0023] (Regarding Compound [M]) Compound [M] is an initiator modifier that modifies the initial terminal of a conjugated diene polymer. Compound [M] preferably has groups F1 and F2. Compound [M] preferably has, in addition to group F2 or to groups F1 and F2, at least one group (hereinafter also referred to as "group F3") selected from the group consisting of a monovalent cyclic group having a structure in which a halogen atom or a methyl group is bonded to an aromatic ring, a secondary amino group, and a halogenated alkyl group. When compound [M] has group F3, the hydrogen atom in the methyl group bonded to the aromatic ring, the active hydrogen of the secondary amino group, or the halogen atom of the aromatic ring or halogenated alkyl group bonded to the halogen atom becomes a reactive site with the metal compound, and the hydrogen atom or halogen atom is replaced with a metal element, thereby efficiently producing a silicon-containing initiator. From the viewpoint of efficiently producing a silica-containing initiator, the secondary amino group as group F3 preferably constitutes the ring skeleton of a nitrogen-containing aliphatic heterocycle.

[0024] In this specification, the term "active hydrogen" refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably refers to a hydrogen atom having a bond energy lower than that of the carbon-hydrogen bond of polymethylene.

[0025] The compound [M] is not particularly limited as long as it has the group F2. Specifically, the compound [M] is preferably a compound represented by the following formula (1): (In formula (1), X １ is a group represented by the following formula (2-1) or formula (2-2): １is a hydrocarbon group having 1 to 20 carbon atoms and a valence of (i+k), or has at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom, does not have active hydrogen, and is a group "-Si(R １ ) ｎ (Y １ ) ３－ｎ " and a group represented by the following formula (2-2) via a carbon atom. R １ is a hydrocarbyl group having 1 to 20 carbon atoms. １ is the group "-OR ２ " or the group "-NR ３ R ４ ". R ２ , R ３ and R ４ are each independently a hydrocarbyl group having 1 to 20 carbon atoms. n is an integer of 0 to 2. When n is 0 or 1, multiple Y １ are the same or different. When n is 2, a plurality of R １ are the same or different, and i and k are each independently an integer of 1 to 6, provided that i+k≦10 is satisfied. １ If there are multiple X １ are the same or different. The group "-Si(R １ ) ｎ (Y １ ) ３－ｎ When there are a plurality of groups "-Si(R １ ) ｎ (Y １ ) ３－ｎ " are the same or different.) (In formula (2-1), R ５ R is a hydrogen atom, a halogenated alkyl group having 1 to 8 carbon atoms, or a monovalent cyclic group having a structure in which a halogen atom or a methyl group is bonded to an aromatic ring. ６ and R ７ are each independently a hydrocarbylene group having 1 to 10 carbon atoms. １ and Q ２ are each independently a nitrogen atom or —CR １０ -. However, R ５ If is a hydrogen atom, Q １ is a nitrogen atom. １０is a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms. "*" represents a bond. In formula (2-2), R ８ R is a hydrogen atom, a halogenated alkyl group having 1 to 8 carbon atoms, or a monovalent cyclic group having a structure in which a halogen atom or a methyl group is bonded to an aromatic ring. ９ is a hydrocarbyl group or a trihydrocarbylsilyl group having 1 to 20 carbon atoms, provided that R ８ When is a hydrogen atom, R ９ is a hydrocarbyl group having 1 to 20 carbon atoms. "*" represents a bond.

[0026] In formula (1), X １ is a group represented by formula (2-1), X １ From the viewpoint of obtaining a crosslinked product having excellent fuel economy performance, R preferably has a nitrogen-containing heterocycle, and more preferably has a nitrogen-containing heterocycle containing a tertiary nitrogen atom. ６ and R ７ The hydrocarbylene group having 1 to 10 carbon atoms represented by the formula (I) is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms, more preferably a methylene group or an ethylene group.

[0027] Q １ and Q ２ The group represented by -CR １０ -, then R １０ The hydrocarbyl group having 1 to 20 carbon atoms represented by the formula (I) is preferably a linear or branched alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. １０ Among these, Q is preferably a hydrogen atom or a methyl group. １ and Q ２ is preferably a nitrogen atom. １ and Q ２ Q of ２ is a tertiary nitrogen atom, or Q １ and Q ２ It is particularly preferred that both are tertiary nitrogen atoms.

[0028] R ５ and R ８ is a group corresponding to group F3.５ and R ８ Examples of halogenated alkyl groups having 1 to 8 carbon atoms represented by the formula (I) include groups in which any hydrogen atom in an alkyl group having 1 to 8 carbon atoms is substituted with a halogen atom. The alkyl group having 1 to 8 carbon atoms substituted with a halogen atom may be linear or branched. Among these, alkyl groups having 1 to 6 carbon atoms are preferred, and alkyl groups having 1 to 4 carbon atoms are more preferred. Examples of halogen atoms include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a chlorine atom or a bromine atom being preferred.

[0029] R ５ and R ８ When the group represented by the formula (I) is a monovalent cyclic group having a structure in which a halogen atom or a methyl group is bonded to an aromatic ring (hereinafter also referred to as "monovalent cyclic group E"), examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, etc., and among these, a benzene ring or a naphthalene ring is preferred. In the monovalent cyclic group E, the aromatic ring may further have a substituent other than a halogen atom and a methyl group. Examples of such a substituent include an N,N-dialkylamino group. Examples of the halogen atom bonded to the aromatic ring include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a chlorine atom or a bromine atom being preferred, and a bromine atom being more preferred.

[0030] R ５ and R ８Specific examples of the monovalent cyclic group E are a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 2-bromophenyl group, a 3-bromophenyl group, a 4-bromophenyl group, a 2-N,N-dimethylamino-3-methylphenyl group, a 2-N,N-dimethylamino-4-methylphenyl group, a 2-N,N-dimethylamino-5-methylphenyl group, a 2-methyl-3-N,N-dimethylaminophenyl group, a 3-N,N-dimethylamino-4-methylphenyl group, Examples thereof include a phenyl group, a 3-N,N-dimethylamino-5-methylphenyl group, a 2-N,N-dimethylamino-3-bromophenyl group, a 2-N,N-dimethylamino-4-bromophenyl group, a 2-N,N-dimethylamino-5-bromophenyl group, a 2-bromo-3-N,N-dimethylaminophenyl group, a 3-N,N-dimethylamino-4-bromophenyl group, a 3-N,N-dimethylamino-5-bromophenyl group, a 5-bromonaphthalenyl group, and a 5-bromoanthracenyl group.

[0031] From the viewpoint of reactivity with metal compounds, R ５ is preferably a hydrogen atom, a monovalent cyclic group E, or a halogenated alkyl group having 1 to 8 carbon atoms, and more preferably a hydrogen atom, a monovalent cyclic group having a structure in which a bromine atom is bonded to an aromatic ring, a bromoalkyl group having 1 to 8 carbon atoms, or a chloroalkyl group having 1 to 8 carbon atoms. ８ is preferably a monovalent cyclic group E or a halogenated alkyl group having 1 to 8 carbon atoms, and more preferably a monovalent cyclic group having a structure in which a bromine atom is bonded to an aromatic ring, a bromoalkyl group having 1 to 8 carbon atoms, or a chloroalkyl group having 1 to 8 carbon atoms.

[0032] R ９ The hydrocarbyl group having 1 to 20 carbon atoms represented by the formula (I) is preferably an alkyl group having 1 to 20 carbon atoms, more preferably a linear or branched alkyl group having 1 to 20 carbon atoms. Examples of the trihydrocarbylsilyl group include a trimethylsilyl group and a triethylsilyl group.

[0033] X １ In order to enhance the reactivity of X with the metal compound, １Among these, X is preferably a group represented by formula (2-1). １ It is believed that by introducing a bulky structure into the compound [M], the side reaction between the metal compound and the group F2 is suppressed when the metal compound and the compound [M] are mixed, and thus the silica-containing initiator can be produced efficiently.

[0034] A １ is an (i+k)-valent hydrocarbyl group, examples of which include groups in which (i+k) hydrogen atoms have been removed from a chain hydrocarbon having 1 to 20 carbon atoms, an alicyclic hydrocarbon having 3 to 20 carbon atoms, or an aromatic hydrocarbon having 6 to 20 carbon atoms. Of these, groups in which (i+k) hydrogen atoms have been removed from a chain hydrocarbon are preferred.

[0035] A １ is an (i+k)-valent group having 1 to 20 carbon atoms, having at least one atom selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms, and having no active hydrogen, specific examples include an (i+k)-valent heterocyclic group, an (i+k)-valent group having a tertiary amine structure, etc. The heterocyclic group is preferably a conjugated system, and examples thereof include a monocyclic or fused ring such as pyridine, pyrimidine, pyrazine, quinoline, naphthalidine, furan, thiophene, etc., or a group in which (i+k) hydrogen atoms have been removed from the ring portion of a structure in which a plurality of such monocyclic or fused rings are linked together.

[0036] (i+k) is an integer of 2 to 10. From the viewpoint of processability of the polymer composition, (i+k) is preferably 2 to 6. １ ) ｎ (Y １ ) ３－ｎ ", the explanation of group F2 applies. １ represents the group "-Si(R １ ) ｎ (Y １ ) ３－ｎ and the group represented by the following formula (2-2) through a carbon atom, and more specifically, it is preferable that they are bonded through the same or different carbon atoms constituting the hydrocarbon group.

[0037] Specific examples of the compound [M] include compounds represented by the following formulas (M-1) to (M-30). As the compound [M], one type may be used alone, or two or more types may be used in combination.

[0038] Among the above, compounds having groups F1, F2, and F3 can be preferably used as the compound [M], since they can give crosslinked products with better fuel economy performance. Specifically, the compounds represented by the above formulas (M-1) to (M-7) and (M-10) to (M-29) can be preferably used.

[0039] The compound [M] can be synthesized by appropriately combining standard methods in organic chemistry. ２ and a compound in which "G １ -A １ -(Si(R １ ) ｎ (Y １ ) ３－ｎ ) ｋ ” (G １ is a halogen atom) in the presence of a base, １ In addition, a compound in which the nitrogen atom of the group represented by the formula (2-2) is bonded to a hydrogen atom and a compound in which "G １ -A １ -(Si(R １ ) ｎ (Y １ ) ３－ｎ ) ｋ " in the presence of a base, to form a compound represented by formula (1) represented by X １ The compound represented by the formula (2-2) can be obtained. These synthesis reactions can be carried out, for example, in an appropriate organic solvent, in the presence of a catalyst as needed. However, the synthesis method for compound [M] is not limited to the above method.

[0040] <Polymerization Step> Next, details of the polymerization carried out using a silicon-containing initiator will be described. Examples of conjugated diene compounds used in the polymerization include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-heptadiene, 2-phenyl-1,3-butadiene, 3-methyl-1,3-pentadiene, and 2-chloro-1,3-butadiene. Among these, 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene are preferred.

[0041] The modified conjugated diene polymer of the present disclosure may be a homopolymer of a conjugated diene compound, but from the viewpoint of increasing the strength of the rubber, it is preferably a copolymer of a conjugated diene compound and an aromatic vinyl compound. Examples of aromatic vinyl compounds used in the polymerization include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-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, 4-t-butylstyrene, vinylxylene, vinylnaphthalene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylenes (e.g., 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene). Among these, styrene and α-methylstyrene are preferred as aromatic vinyl compounds.

[0042] When the modified conjugated diene polymer of the present disclosure is a copolymer of a conjugated diene compound and an aromatic vinyl compound, it is preferably a polymer containing 1,3-butadiene and styrene in the monomer composition, in view of its high living property in anionic polymerization. The copolymer preferably has a random copolymerization portion in which the distribution of the conjugated diene compound and the aromatic vinyl compound is irregular, in view of achieving a well-balanced improvement in hysteresis loss at low and high temperatures. The copolymer may further have a block portion composed of a conjugated diene compound or an aromatic vinyl compound.

[0043] When the modified conjugated diene polymer of the present disclosure is a copolymer of a conjugated diene compound and an aromatic vinyl compound, the proportion of the aromatic vinyl compound used is preferably 3 to 55 mass%, more preferably 5 to 50 mass%, based on the total amount of the conjugated diene compound and the aromatic vinyl compound used in the polymerization, from the viewpoint of achieving a good balance between the low hysteresis loss property and the wet skid resistance of the resulting crosslinked product. １ The value is measured by H-NMR. The conjugated diene compound and the aromatic vinyl compound may each be used alone or in combination of two or more.

[0044] In the polymerization, compounds other than conjugated diene compounds and aromatic vinyl compounds (hereinafter also referred to as "other monomers") may be used as 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.

[0045] The polymerization method used in this step may be any of solution polymerization, gas phase polymerization, and bulk polymerization. Among these, solution polymerization is particularly preferred. The polymerization method may be either batch or continuous. When solution polymerization is used, a specific example of the polymerization method is to polymerize a monomer containing a conjugated diene compound in a solvent (preferably an organic solvent) in the presence of a polymerization initiator and, if necessary, a vinyl content adjuster (hereinafter also referred to as a "randomizer").

[0046] As the polymerization initiator, only a silicon-containing initiator may be used. Alternatively, a compound having an alkali metal element or an alkaline earth metal element and not having group F2 (hereinafter also referred to as "other initiators") may be used together with the silicon-containing initiator. Examples of other initiators include the alkali metal compounds and alkaline earth metal compounds described above, as well as compounds obtained by mixing at least one selected from the group consisting of alkali metal compounds and alkaline earth metal compounds with a compound not having group F2 (hereinafter also referred to as "initiation terminal modifier").

[0047] Examples of the initiation terminal modifying agent not having the group F2 include nitrogen-containing compounds, and secondary amine compounds can be preferably used. Specific examples of such nitrogen-containing compounds include linear or cyclic secondary amine compounds, such as 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)piperazine, 1,3-ditrimethylsilyl-1,3,5-triazinane, N-trimethylsilylpiperazine, 1,3,3-trimethyl-6-azabicyclo[3.2.1]octane, and 1-propyl-3-azabicyclo[3.2.2]nonane.

[0048] In the polymerization, the amount of polymerization initiator used (total amount of silicon-containing initiator and other initiators) is preferably 0.01 to 20 mmol, and more preferably 0.05 to 15 mmol, per 100 g of monomer used in the synthesis of the modified conjugated diene polymer. Furthermore, the amount of silicon-containing initiator used among the polymerization initiators is preferably 50 mol % or more, more preferably 60 mol % or more, and even more preferably 80 mol % or more, based on the total amount of polymerization initiator (i.e., metal compound) used in the polymerization of the monomer.

[0049] Examples of methods for polymerization in the presence of a silicon-containing initiator include [1A] a method in which a metal compound and a compound [M] are mixed in advance to synthesize a silicon-containing initiator outside the system, and the resulting silicon-containing initiator is mixed with a monomer to carry out polymerization; and [2A] a method in which a silicon-containing initiator is synthesized inside the system by mixing a metal compound and a compound [M] in a reactor containing a monomer, and then polymerization is carried out. Both of these methods are included in the embodiment of "polymerizing a monomer containing a conjugated diene compound in the presence of a silicon-containing initiator obtained by mixing a metal compound and a compound [M]." From the viewpoint of simplifying the operation, method [2A] is preferred, and from the viewpoint of improving the low hysteresis loss performance of the resulting crosslinked product and improving fuel economy, method [1A] is preferred.

[0050] When using method [1A] as a method for polymerization in the presence of a silicon-containing initiator, compound [M] and a metal compound may be mixed in an organic solvent. The organic solvent used to generate the silicon-containing initiator may be any organic solvent that is inert to compound [M] and the metal compound, such as an aliphatic hydrocarbon, an alicyclic hydrocarbon, or an aromatic hydrocarbon. Furthermore, when generating the silicon-containing initiator using compound [M] and a metal compound, a catalyst (e.g., a tertiary amine compound) may be used as needed. In method [1A], the temperature is preferably −20° C. to 150° C., more preferably 0° C. to 120° C.

[0051] When the silicon-containing initiator is generated outside the system by premixing the metal compound and compound [M], some of the monomer may be present. The presence of a monomer when mixing the metal compound and compound [M] increases the efficiency of incorporation of group F2 of the silicon-containing initiator into the modified conjugated diene polymer, which is advantageous in that it further enhances the effect of improving fuel economy in the crosslinked product. Examples of monomers added when generating the silicon-containing initiator include conjugated diene compounds and aromatic vinyl compounds. The conjugated diene compound is preferably at least one of butadiene and isoprene, and the aromatic vinyl compound is preferably at least one of styrene and α-styrene.

[0052] When the silicon-containing initiator obtained by premixing the metal compound and the compound [M] is added to a reactor containing the monomer, the method for adding the silicon-containing initiator is not particularly limited, and examples thereof include a method of adding all at once, a method of adding in portions, and a method of adding continuously. When the silicon-containing initiator is added all at once to the reactor, it is preferable in that the molecular weight distribution of the resulting modified conjugated diene polymer can be narrowed. When the silicon-containing initiator is added in portions to the reactor, it tends to be possible to improve the processability of the resulting modified conjugated diene polymer while increasing the efficiency of introducing the silicon-containing initiator into the polymerization terminal.

[0053] When the silicon-containing initiator is added in portions to the reactor, the second or subsequent addition of the silicon-containing initiator may be carried out before the start of monomer polymerization, or after the start of monomer polymerization.From the viewpoint of increasing the efficiency of introducing the silicon-containing initiator into the polymerization terminal, the second or subsequent addition of the silicon-containing initiator is carried out after the start of monomer polymerization, that is, it is preferable to add the silicon-containing initiator to the reactor after the polymerization is initiated by the initial addition of the silicon-containing initiator.When the silicon-containing initiator is added in portions, the mass ratio of the first addition amount to the total amount added from the second addition onwards is preferably 9:1 to 1:1.

[0054] The randomizer can be used for the purpose of adjusting the vinyl bond content, which represents the content of vinyl bonds in a polymer. As the randomizer, it is preferable to use a compound that contains at least one element of oxygen and nitrogen, and does not contain active hydrogen, an alkali metal element, or an alkaline earth metal element. Note that the randomizer differs from the polymerization initiator in that it does not contain any alkali metal element or alkaline earth element.

[0055] Examples of the randomizer include nitrogen-containing compounds such as triethylamine, pyridine, N-methylmorpholine, and tetramethylethylenediamine. Examples of the oxygen-containing compounds include dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, 2,2-di(2-tetrahydrofuryl)propane, and 2-(2-ethoxyethoxy)-2-methylpropane. One type of randomizer can be used alone, or two or more types can be used in combination.

[0056] When a randomizer is used in polymerization, the timing of adding the randomizer to the reactor is not particularly limited and can be appropriately set within a range that does not impair the fuel economy of the resulting modified conjugated diene polymer. The method of adding the randomizer is not particularly limited, and examples thereof include a method of adding the randomizer all at once, a method of adding it in portions, and a method of adding it continuously.

[0057] Specific examples of the order of addition of the components, including the randomizer, include the following [1B] to [4B]. The randomizer may be added by one of the following [1B] to [4B], or by a combination of two or more of them. [1B] An embodiment in which, in the method [1A] above, the randomizer is added to the reactor together with the monomer before adding the silicon-containing initiator to the reactor. [2B] An embodiment in which, in the method [1B] above, the randomizer is added to the reactor together with the monomer and compound [M] before adding the metal compound to the reactor. [3B] An embodiment in which, in the method [1B] above, the randomizer is added to the reactor after adding the monomer, compound [M], and metal compound to the reactor. [4B] An embodiment in which, in the method [1A] above, the randomizer is added to the reactor after adding the monomer and silicon-containing initiator to the reactor.

[0058] Among the above, the embodiment [3B], i.e., when the embodiment includes a step of adding a randomizer after adding a metal compound to a reactor (hereinafter also referred to as a "post-addition step"), is preferred in that it can prevent the molecular weight distribution of the resulting modified conjugated diene polymer from becoming broad. Specific embodiments when this step includes a post-addition step include [3B-1] an embodiment in which the randomizer is added all at once to a reactor containing a monomer, compound [M], and a metal compound, and [3B-2] an embodiment in which a metal compound is added to a reactor containing a monomer, compound [M], and a randomizer to initiate polymerization, and then the randomizer is additionally added (i.e., the randomizer is added in portions). Of these, the embodiment [3B-1] is preferred in that it can achieve the effect of preventing the molecular weight distribution of the resulting modified conjugated diene polymer from becoming broad while requiring fewer steps.

[0059] As the organic solvent used in the polymerization, an organic solvent that does not participate in the polymerization reaction can be preferably used. Specific examples of the organic solvent used in the polymerization include aliphatic hydrocarbons, alicyclic 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.

[0060] 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. Furthermore, the polymerization reaction is preferably carried out under a pressure sufficient to maintain the monomers substantially in a liquid phase. Such a pressure can be obtained by, for example, pressurizing the inside of a reactor with a gas that does not participate in the polymerization reaction.

[0061] By such a polymerization reaction, a modified conjugated diene polymer having a group F2 at one end and an active end at the other end can be obtained. The weight average molecular weight (Mw) of the resulting modified conjugated diene polymer, measured by gel permeation chromatography (GPC) in terms of polystyrene, is preferably 5.0 × 10 ４ ~1.0 x 10 ６ Mw is 5.0 × 10 ４ When the crosslinked body has a viscosity of 1.0×10 or more, the crosslinked body can have a sufficient tensile strength, low heat buildup, and abrasion resistance, which is preferable. ６ It is preferable that the Mw is 8.0×10 or less in that the processability of the polymer composition containing the modified conjugated diene polymer can be improved. ４ ~8.0 x 10５ and more preferably 1.0 × 10 ５ ~5.0 x 10 ５ The Mw of the modified conjugated diene polymer referred to here represents the weight average molecular weight (total weight average molecular weight) based on all peaks of the GPC curve.

[0062] The vinyl bond content of the modified conjugated diene polymer having an active terminal is preferably 15 to 70 mol%. A vinyl bond content of 15 mol% or more is preferable in that the grip properties can be improved, and a vinyl bond content of 70 mol% or less is preferable in that the deterioration of the abrasion resistance of the obtained vulcanized rubber can be suppressed. The vinyl bond content is more preferably 20 mol% or more, even more preferably 30 mol% or more, and even more preferably 40 mol% or more. Furthermore, the vinyl bond content is preferably 70 mol% or less, and more preferably 68 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 of butadiene in the modified conjugated diene polymer, １ This is a value measured by H-NMR.

[0063] The polymerization can be terminated, for example, by reacting a modified conjugated diene polymer having an active end with an alcohol or hydrogen. Alternatively, a terminal modifier or coupling agent may be reacted with the modified conjugated diene polymer having an active end. Here, the terminal modifier is a compound having a functional group that covalently bonds with or interacts with a filler and that can react with the active end of the polymer. By reacting a modified conjugated diene polymer having an active end with a terminal modifier, a modified conjugated diene polymer can be obtained in which a functional group that covalently bonds with or interacts with a filler has been introduced into the polymerization termination end. In this specification, the term "active end" refers to a portion (more specifically, a metal end) that is present at the end of the molecular chain and is not derived from a monomer having a carbon-carbon double bond.

[0064] The terminal modifier is not particularly limited as long as it has a functional group that covalently bonds or interacts with the filler (especially silica) and can react with the active terminal of the modified conjugated diene polymer. Among the terminal modifiers, compounds having one or more atoms selected from the group consisting of nitrogen, sulfur, phosphorus, oxygen, and silicon, and no active hydrogen bonded to the atom, are preferred. In particular, terminal modifiers are preferably compounds having one or more functional groups selected from the group consisting of amino groups, groups having a carbon-nitrogen double bond, nitrogen-containing heterocyclic groups, phosphino groups, cyclic ether groups, cyclic thioether groups, protected hydroxyl groups, protected thiol groups, and hydrocarbyloxysilyl groups, and capable of reacting with the active terminal of the polymer. The amino group is preferably a protected primary amino group, secondary amino group, or tertiary amino group. Such compounds are not particularly limited, but for example, one or more of the compounds described in JP 2003-171418 A and WO 2021 / 112167 A can be suitably used.

[0065] Examples of coupling agents include dibutyldichlorosilicon, methyltrichlorosilicon, methyldichlorosilicon, tetrachlorosilicon (silicon tetrachloride), silicon tetrabromide, silicon tetraiodide, trichloromethoxysilane, tribromomethoxysilane, trimethoxysilane, tetramethoxysilane, tetrachlorotin (tin tetrachloride), tetrabromotin, trichlorobutyltin, trichloromethyltin, trichloroethyltin, trichlorophenyltin, trichlorooctyltin, trichlorophosphine, divinylbenzene, and trichloropropane. Furthermore, as the coupling agent, a polyfunctional compound having one or more atoms selected from the group consisting of nitrogen, sulfur, and oxygen, to which no active hydrogen is bonded, and having a plurality of reaction sites with the active terminal of the modified conjugated diene polymer (e.g., tetraglycidyl-1,3-bisaminomethylcyclohexane, N,N,N',N'-tetra(3-trimethoxysilylpropyl)ethylenediamine, bis(3-trimethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silacyclopentane)ethyl]amine, etc.) may be used.

[0066] The reaction between the modified conjugated diene polymer having an active terminal and the terminal-modifying agent or coupling agent can be carried out, for example, as a solution reaction. This solution reaction may be carried out using a solution containing unreacted monomers after the polymerization reaction has been completed, or the modified conjugated diene polymer contained in the solution may be isolated and dissolved in an appropriate solvent such as cyclohexane before the reaction. The reaction may be carried out batchwise or continuously. In this case, the method for adding the terminal-modifying agent and the coupling agent is not particularly limited, and examples thereof include a method of adding them all at once, a method of adding them in portions, and a method of adding them continuously.

[0067] The amounts of the terminal modifier and coupling agent used may be appropriately determined depending on the type of compound used in the reaction. The amount of the terminal modifier and coupling agent used is preferably 0.1 molar equivalent or more, more preferably 0.3 to 1.5 molar equivalents, relative to the metal element contained in the polymerization initiator that participates in the polymerization reaction. The reaction temperature is usually the same as the polymerization reaction temperature, preferably −20 to 150°C, and more preferably 0 to 120°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 more likely to be deactivated. The reaction time is preferably 1 minute to 5 hours, more preferably 2 minutes to 1 hour.

[0068] The modified conjugated diene polymer contained in the reaction solution can be isolated by a known solvent removal method such as steam stripping and a drying procedure such as heat treatment.

[0069] The weight average molecular weight of the modified conjugated diene polymer after the termination of the polymerization reaction is preferably 1.5 × 10 in terms of polystyrene as determined by GPC, from the viewpoint of obtaining a crosslinked product having high strength and excellent fuel economy. ５ ~2.0 x 10 ６ and more preferably 1.8 × 10 ５ ~1.5 x 10 ６ and more preferably 2.0 × 10 ５ ~1.2 × 10 ６The weight average molecular weight of the modified conjugated diene polymer referred to here represents the weight average molecular weight (total weight average molecular weight) based on all peaks of the GPC curve measured by GPC.

[0070] The molecular weight distribution (Mw / Mn) of the modified conjugated diene polymer, which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by GPC, is preferably 4.0 or less, more preferably 3.5 or less, and is usually 1.0 or more.

[0071] According to the production method including the above polymerization step and modification step, a modified conjugated diene polymer represented by the following formula (3) can be obtained. (In formula (3), X ２ is a group represented by the following formula (4-1) or formula (4-2): １ , R １ , Y １ , n, i, and k have the same meanings as in formula (1). ２ If there are multiple X ２ are the same or different.) (In formula (4-1), Z １ represents a single bond, an alkanediyl group having 1 to 8 carbon atoms, or the group "* ３ -Ar １ -W １ -" (Ar １ is a divalent aromatic ring group. １ is a single bond or a methylene group. ３ " is Q １ represents a bond with .) ６ , R ７ , Q １ and Q ２ is the same as formula (2-1). １ If is a single bond, Q １ represents a nitrogen atom. Poly represents a modified or unmodified conjugated diene polymer chain. "*" represents a bond. In formula (4-2), Z ２ represents a single bond, an alkanediyl group having 1 to 8 carbon atoms, or the group "* ４ -Ar １ -W １ -" (Ar １is a divalent aromatic ring group. １ is a single bond or a methylene group. ４ " is -NR １１ - represents a bond with . １１ represents a hydrogen atom, a hydrocarbyl group having 1 to 20 carbon atoms, or a trihydrocarbylsilyl group. Poly represents a modified or unmodified conjugated diene polymer chain. "*" represents a bond.

[0072] In formula (3), A １ , R １ , Y １ , n, i, and k are the same as those in formula (1). The modified or unmodified conjugated diene polymer chain in formula (4-1) and formula (4-2) has a structure corresponding to the conjugated diene polymer produced by the above polymerization step.

[0073] The reaction mechanism when a monomer is polymerized in the presence of a silicon-containing initiator will be explained using a specific example. １ is the formula (2-1), and R ５ When a compound is used in which R is a group in which a halogen atom is bonded to an aromatic ring, ５ The halogen atom in R is replaced by a metal atom (alkali metal or alkaline earth metal). ５ Polymerization is initiated from the reactive site formed on the metal compound. For example, n-butyllithium is used as the metal compound, and X in formula (1) is used as the silicon-containing initiator. １ is the formula (2-1), and R ５ The reaction scheme when a compound in which is a 4-bromophenyl group is used is shown in the following formula (6): In formula (6), the wavy line represents a conjugated diene polymer chain.

[0074] Further, as the silicon-containing initiator, X in formula (1) １ is the formula (2-1), and R ５ When a compound in which a methyl group is bonded to an aromatic ring is used, R ５ One hydrogen atom in the methyl group in R is replaced by a metal atom. ５For example, n-butyllithium is used as the metal compound, and X in formula (1) is used as the silicon-containing initiator. １ is the formula (2-1), and R ５ The reaction scheme when a compound in which is a 4-methylphenyl group is used is shown in the following formula (7): In formula (7), the wavy line represents a conjugated diene polymer chain.

[0075] Other examples of silicon-containing initiators include those represented by the formula (1) X １ is the formula (2-1) and Q １ is a nitrogen atom and R ５ is a hydrogen atom or a halogenated alkyl group, or a compound in which R ５ When a compound is used in which Q is a halogenated alkyl group, the conjugated diene polymer chain is connected directly or via an alkanediyl group to Q in formula (4-1). １ It is possible to obtain a modified conjugated diene polymer having a structure in which the following is bonded:

[0076] <Polymer Composition> The polymer composition of the present disclosure may contain various components in addition to the modified conjugated diene polymer (hereinafter also referred to as "modified conjugated diene polymer (A)").

[0077] [B] Silica The polymer composition of the present disclosure can contain [B] silica. The blending amount of [B] silica is preferably in the range of 20 to 120 parts by mass, and more preferably in the range of 30 to 100 parts by mass, per 100 parts by mass of the rubber component containing the modified conjugated diene-based polymer [A]. When the blending amount of [B] silica is 20 parts by mass or more per 100 parts by mass of the rubber component, the low loss properties, fracture properties, and abrasion resistance of the polymer composition can be sufficiently improved, and when it is 120 parts by mass or less, the processability of the polymer composition can be sufficiently improved.

[0078] 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. The cured product exhibits the property of undergoing large deformation under small force at room temperature (for example, stretching 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.

[0079] The silica [B] is not particularly limited, and examples thereof include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred. The silica [B] may be used alone or in combination of two or more. The BET specific surface area (measured in accordance with ISO 5794 / 1) of the silica [B] is 40 to 350 m. ２ / g, and 80 to 350 m ２ / g is more preferable, and 120 to 350m ２ / g is particularly preferred. Silica having a BET specific surface area in this range has the advantage of being able to achieve both rubber reinforcement and dispersibility in the modified conjugated diene polymer (A). Examples of such silica include "Nipsil AQ" (BET specific surface area = 205 m), manufactured by Tosoh Silica Corporation. ２ / g), "Nipsil KQ", product name "Ultrasil VN3" (BET specific surface area = 175 m), manufactured by Degussa ２ Commercially available products such as PEG-100 / g can be used.

[0080] The silica contained in the polymer composition may be a mixture of two or more types having different specific surface areas. Specifically, CTAB (cetyltrimethylammonium bromide) having a specific surface area of ​​180 m ２ / g or more, BET specific surface area is 185m ２ / g or more, and an aggregate size of 45 nm or more; and a CTAB specific surface area of ​​95 m ２ / g or less, BET specific surface area is 100m ２ The CTAB specific surface area of ​​the silica is measured in accordance with ASTM D3765-92.

[0081] One embodiment of the polymer composition has a CTAB specific surface area of ​​180 m ２ / g or more, BET specific surface area is 185m ２ / g or more, and an aggregate size of 45 nm or more; and a CTAB specific surface area of ​​95 m ２ / g or less, BET specific surface area is 100m ２The combined use of such first silica and second silica enables the first silica, which has a small average primary particle size but a relatively large aggregate size, to be well dispersed in the rubber component, improving the dispersibility of the silica and enabling excellent rubber breaking strength, abrasion resistance, fuel economy and processability to be obtained.

[0082] 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 180 m ２ If the CTAB specific surface area is less than 350 m / g, it tends to be difficult to obtain sufficient improvement in rubber breaking 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 350 m ２ If the density exceeds 1 / g, the dispersibility becomes poor and aggregation occurs, and the physical properties tend to deteriorate.

[0083] 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 185 m ２ If the specific surface area is less than 1 / g, it may be difficult to obtain sufficient improvement in rubber 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 350 m ２ If the specific surface area exceeds 1 / g, the dispersibility is poor and the particles aggregate, 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.

[0084] The aggregate size of the first silica is 45 nm or more, preferably 50 nm or more, more preferably 55 nm or more, and even more preferably 60 nm or more. 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. By having such an aggregate size, it is possible to 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.

[0085] 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. Although it has such a small average primary particle diameter, the carbon black-like structure having the above aggregate size can further improve the dispersibility (processability) of the silica, thereby further improving fuel economy and wear 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 in the field of view, and averaging the measured values.

[0086] 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. 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 the mechanical strength and abrasion resistance required for a polymer composition for obtaining rubber for tires. ２ / g or less, more preferably 60m ２ / g or less, more preferably 50m ２ / g or less. CTAB specific surface area is 95 m ２ If the silica content exceeds 1 / g, the dispersibility of the silica may be deteriorated, making it difficult to improve the rubber breaking strength and abrasion resistance.

[0087] 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 10 m 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 obtaining rubber for tires. ２ / g or less, more preferably 60m ２ / g or less, more preferably 50m ２ / g or less. BET specific surface area is 100 m ２ If the silica content exceeds 1 / g, the dispersibility of the silica may be deteriorated, making it difficult to improve the rubber breaking strength and abrasion resistance.

[0088] 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 average primary particle size 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, rubber breaking strength and abrasion resistance can be improved.

[0089] [C] Carbon Black The polymer composition of the present disclosure preferably contains [C] carbon black from the viewpoint of the fracture properties and abrasion resistance of the polymer composition. The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. The nitrogen adsorption specific surface area (N ２ SA) is not particularly limited, but is preferably 50 to 200 m because it is superior in terms of the effects of the present disclosure. ２ / g is preferred, and 70 to 150m ２ / g is more preferable. ２SA) is the amount of nitrogen adsorption on the surface of the carbon black measured in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method." These carbon blacks may be used alone or in combination of two or more. The amount of carbon black blended 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 modified conjugated diene polymer [A].

[0090] [Other Fillers] The polymer composition of the present disclosure may contain other fillers in addition to the silica (B) and carbon black (C). Examples of such other fillers include alumina (Al), such as γ-alumina and α-alumina. ２ O ３ alumina monohydrate (Al), boehmite, diaspore, etc. ２ O ３ ・H ２ O), aluminum hydroxides such as gibbsite and bayerite [Al(OH) ３ ], aluminum carbonate [Al ２ (CO ３ ) ３ ], magnesium hydroxide [Mg(OH) ２ ], magnesium oxide (MgO), magnesium carbonate (MgCO ３ ), talc (3MgO.4SiO ２ ・H ２ O), attapulgite (5MgO.8SiO ２ ・9H ２ O), titanium white (TiO ２ ), titanium black (TiO ２ｎ－１ ), calcium oxide (CaO), calcium hydroxide [Ca(OH) ２ ], magnesium aluminum oxide (MgO.Al ２ O ３ ), clay (Al ２ O ３ 2SiO ２ ), kaolin (Al ２ O ３ 2SiO ２ ・2H ２ O), pyrophyllite (Al ２ O ３ 4SiO２ ・H ２ O), bentonite (Al ２ O ３ 4SiO ２ ・2H ２ O), aluminum silicate (Al ２ SiO ５ , Al ４ 3SiO ４ ・5H ２ O, etc.), magnesium silicate (Mg ２ SiO ４ , MgSiO ３ etc.), calcium silicate (Ca ２ SiO ４ etc.), calcium aluminum silicate (Al ２ O ３ CaO 2SiO ２ etc.), magnesium calcium silicate (CaMgSiO ４ ), calcium carbonate (CaCO ３ ), zirconium oxide (ZrO ２ ), zirconium hydroxide [ZrO(OH) ２ ・nH ２ O], zirconium carbonate [Zr(CO ３ ) ２ ], crystalline aluminosilicates containing hydrogen, alkali metals or alkaline earth metals to compensate for the charge, such as various zeolites, and the like.

[0091] In the polymer composition of the present disclosure, the blending amount of the filler containing silica [B] and carbon black [C] 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. Furthermore, the blending amount of the filler containing silica [B] and carbon black [C] is preferably 150 parts by mass or less, more preferably 130 parts by mass or less. When the blending amount of the filler in the polymer composition is within the above range, application of the polymer composition to a tire tread can achieve an even higher level of compatibility between low rolling resistance, braking performance on wet roads, handling performance on dry roads, and abrasion resistance of the tire.

[0092] [D] Other Rubber Components In the present disclosure, the rubber component other than the modified conjugated diene-based polymer [A] can be, for example, at least one diene-based rubber selected from natural rubber, isoprene rubber, butadiene rubber, emulsion-polymerized styrene-butadiene rubber, solution-polymerized styrene-butadiene rubber, butyl rubber, halogenated butyl rubber, and ethylene-propylene rubber. Among these, it is preferable to include at least one of natural rubber, butadiene rubber, and styrene-butadiene rubber. When mixing component [D] with component [A], they may be mixed during kneading as is typically done with a Banbury mixer, roll, or the like, or they may be mixed in advance in the solution state after polymerization and dried before use.

[0093] The ratio of the component [A] to the component [D] is preferably 5 to 45 parts by mass of the component [A] and 65 to 95 parts by mass of the component [D] relative to 100 parts by mass of the rubber components [A] + [D], and more preferably 10 to 40 parts by mass of the component [A] and 60 to 90 parts by mass of the component [D]. In particular, when the component (A) is 15 to 35 parts by mass and the component [D] is 65 to 85 parts by mass, this is the optimum polymer composition for producing rubber for tires.

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

[0095] Examples of liquid rubber include liquid polyisoprene (liquid IR), liquid polybutadiene (liquid BR), liquid styrene-butadiene copolymer (liquid SBR), and liquid ethylene-propylene copolymer (liquid EP). For example, liquid SBR having a weight-average molecular weight of 1,000 to 100,000, preferably 2,000 to 80,000, can be used. The weight-average molecular weight refers to the weight-average molecular weight in terms of polystyrene analyzed by gel permeation chromatography (GPC). Liquid rubber refers to one that has fluidity at 23°C.

[0096] [E] Thermoplastic / Thermosetting Resin The polymer composition of the present disclosure may contain a [E] thermoplastic / thermosetting resin (hereinafter also simply referred to as "resin [E]"). From the viewpoint of obtaining a crosslinked product with excellent properties such as strength, abrasion resistance, and crack growth resistance, the resin [E] 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 resin [E], one type may be used alone, or two or more types may be used in combination.

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

[0098] The styrene-based resin may be a homopolymer obtained by polymerizing one type of styrene-based monomer, or a copolymer obtained by copolymerizing two or more types of styrene-based monomers. The styrene-based resin may also be a copolymer obtained by using a styrene-based monomer and another monomer copolymerizable with the styrene-based monomer. Examples of the other monomer include unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate; dienes such as chloroprene, butadiene, and isoprene; olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof; and the like.

[0099] The softening point of the styrene-based resin is preferably 30°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher. When the softening point is 30°C or higher, the effect of improving crack growth resistance in crosslinked rubber tends to be easily obtained. Furthermore, the softening point of the styrene-based resin is preferably 160°C or lower, more preferably 130°C or lower, and even more preferably 100°C or lower. When the softening point is 160°C or lower, the dispersibility of the resin becomes good, and crack growth resistance, abrasion resistance, and breaking strength tend to be easily improved. 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 when the sample softens and a ball placed on the sample drops onto the bottom plate.

[0100] The styrene-based resin may also 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 preferred 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.

[0101] 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, and more preferably 30% by mass or more. Furthermore, the content of the conjugated diene units is preferably 80% by mass or less, and more preferably 70% by mass or less.

[0102] The content of the polystyrene block in the block polymer is preferably 20% by mass or more, from the viewpoint of increasing 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.

[0103] 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 contained in 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 as the block polymers, since they have sufficient crosslinking points.

[0104] Examples of polyethylene include low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), etc. C5 resins are produced by catalyzing a C5 fraction with a Friedel-Crafts catalyst (AlCl ３ or BF ３It is a solid polymer (C5 synthetic petroleum resin) obtained by polymerization using isoprene, cyclopentadiene, 1,3-pentadiene, 1-pentene, etc. Specific examples of C5 resins include copolymers mainly composed of isoprene, cyclopentadiene, 1,3-pentadiene, 1-pentene, etc., copolymers of 2-pentene and dicyclopentadiene, and polymers mainly composed of 1,3-pentadiene.

[0105] C9 resins were prepared by subjecting C9 fraction to Friedel-Crafts catalyst (AlCl ３ or BF ３ C5 / C9 resins are solid polymers (C9 synthetic petroleum resins) obtained by polymerization using a Friedel-Crafts catalyst (AlCl) or the like. Specific examples of C9 resins include copolymers containing indene, methylindene, vinyltoluene, or the like as the main component. C5 / C9 resins are produced by polymerization of C5 to C9 fractions using a Friedel-Crafts catalyst (AlCl). ３ or BF ３ It is a solid polymer (C5 / C9 synthetic petroleum resin) obtained by polymerization using a copolymer of vinyl toluene, indene, or the like. Specific examples of C5 / C9 resins include copolymers mainly composed of vinyl toluene, indene, or the like. From the viewpoint of compatibility with rubber components, C5 / C9 resins with a small amount of C9 or higher components are preferred. Specifically, the C5 / C9 resin preferably contains less than 50% by mass, and more preferably 40% by mass or less, of the total amount of the resin containing C9 or higher components.

[0106] 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.) manufactured by 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.

[0107] 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.

[0108] A representative example of a terpene-aromatic compound resin is a terpene-phenol resin. This terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing them with formalin. There are no particular limitations on the terpenes used as raw materials; monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred. In the present disclosure, a terpene-phenol resin with a low ratio of phenolic components is preferred. Here, "low ratio of phenolic components" refers to a phenolic component content of less than 50% by mass, preferably 40% by mass or less, of the total resin. Using a terpene-aromatic compound resin, particularly a terpene-phenol resin, as the resin [E] can further improve handling performance. As the terpene-aromatic compound resin, commercially available products can be used, such as those sold under the trade names "Tamanol 803L" and "Tamanol 901" (manufactured by Arakawa Chemical Industries, Ltd.), and the "YS Polystar (registered trademark)" series (manufactured by Yasuhara Chemical Co., Ltd.).

[0109] The blending ratio of the [E] resin is preferably 1 part by mass or more per 100 parts by mass of the rubber component contained in the polymer composition. By blending 1 part by mass or more of the [E] resin, the effect of improving the abrasion resistance, breaking strength, and crack growth resistance of the crosslinked product obtained using the polymer composition by adding the [E] resin can be sufficiently enhanced, which is suitable. The blending ratio of the [E] 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 various performance properties of the rubber composition well, the blending ratio of the [E] 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 polymer composition. Note that the [E] resin may be used alone or in combination of two or more types.

[0110] [F] Silane Coupling Agent In the present disclosure, the dispersibility of silica can be further improved by blending a silane coupling agent. The silane coupling agent used is not particularly limited, but a sulfur-containing silane coupling agent is preferred. Examples of sulfur-containing silane coupling agents include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, γ-mercaptopropyltriethoxysilane, and 3-octanoylthiopropyltriethoxysilane.

[0111] The amount of silane coupling agent blended is preferably 1 to 20 parts by mass per 100 parts by mass of silica. If the amount of silane coupling agent blended is less than 1 part by mass, the blended amount may be too small to sufficiently improve the dispersibility of silica. On the other hand, if the amount of silane coupling agent blended is more than 20 parts by mass, the processability and elongation at break may decrease. The amount of silane coupling agent blended is more preferably 5 to 15 parts by mass per 100 parts by mass of silica.

[0112] [G] Crosslinking Agent The polymer composition of the present disclosure may contain a crosslinking agent [G]. By containing the crosslinking agent [G] in the polymer composition of the present disclosure, 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 typically being 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 polymer composition.

[0113] The polymer composition may contain a process oil commonly used to extend elastomers. The process oil may be added to the polymer composition, for example, by directly adding the oil during rubber compounding. Suitable process oils include various oils known in the art, such as aromatic oils, paraffinic oils, naphthenic oils, and vegetable oils, as well as oils with a low content of polycyclic aromatic compounds (low PCA oils), such as mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), special residual aromatic extracts (SRAE), and heavy naphthenic oils. Examples of commercially available MES, TDAE, and SRAE include Catenex SNR (heavy paraffin obtained by dewaxing distillate oil with a solvent) manufactured by Shell as an MES, Vivatec 500 manufactured by H&R Wasag AG as a TDAE, and NC140 manufactured by Japan Energy Corp. The amount of process oil to be blended is preferably 10 to 100 parts by mass per 100 parts by mass of the total amount of polymer components contained in the polymer composition.

[0114] In addition to the components described above, the polymer composition may contain various additives that are generally used in polymer compositions for producing rubber for tires, such as antioxidants, zinc oxide, stearic acid, softeners, vulcanization accelerators, silane coupling agents, compatibilizers, vulcanization aids, processing aids, scorch inhibitors, etc. 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.

[0115] The polymer composition of the present disclosure can be applied to various rubber products as a crosslinked body by kneading the polymer components, filler, and other components blended as necessary using a kneader such as an open kneader (e.g., a roll) or an internal kneader (e.g., a Banbury mixer), molding the mixture, and then crosslinking (vulcanizing). Specifically, the crosslinked body of the present disclosure can be applied to various applications, such as tire applications such as tire treads, undertreads, carcasses, sidewalls, and bead portions; sealing materials such as packings, gaskets, weatherstrips, and O-rings; interior and exterior skin materials for various vehicles such as automobiles, ships, aircraft, and railways; building materials; vibration-proof rubbers for industrial machinery and equipment; various hoses and hose covers such as diaphragms, rolls, radiator hoses, and air hoses; belts such as power transmission belts; linings; dust boots; medical device materials; fenders; insulating materials for electric wires; and other industrial products.

[0116] According to the method for producing a modified conjugated diene polymer of the present disclosure, it is possible to obtain a modified conjugated diene polymer for obtaining a crosslinked product having excellent physical properties required for tire applications, such as fuel economy and strength. Therefore, the polymer composition containing the modified conjugated diene polymer obtained according to the present disclosure can be suitably used, in particular, as a material for a tire tread, a sidewall, or both.

[0117] Tires can be manufactured by conventional methods, for example, by mixing the polymer composition in a kneader, forming a sheet, and then disposing the sheet in a predetermined position (for example, on the outside of the carcass in the case of a sidewall) and vulcanizing the sheet in a conventional manner to form a tread rubber or a sidewall rubber, thereby obtaining a pneumatic tire.

[0118] According to the present disclosure described above in detail, the following means are provided. [Means 1] A method for producing a modified conjugated diene polymer, comprising a step of polymerizing a monomer containing a conjugated diene compound in the presence of a polymerization initiator, wherein the polymerization initiator comprises a silicon-containing initiator having an alkali metal element or an alkaline earth metal element and the group F2 described above. [Means 2] A method for producing a modified conjugated diene polymer according to [Means 1], wherein the silicon-containing initiator further has at least one group selected from the group consisting of a tertiary amino group and a protected secondary amino group. [Means 3] A method for producing a modified conjugated diene polymer according to [Means 1] or [Means 2], wherein the silicon-containing initiator is a compound obtained by mixing at least one metal compound selected from the group consisting of alkali metal compounds and alkaline earth metal compounds with a compound [M] having the group F2. [Means 4] The method for producing a modified conjugated diene polymer according to [Means 3], wherein the compound [M] has at least one selected from the group consisting of a monovalent cyclic group having a structure in which a halogen atom or a methyl group is bonded to an aromatic ring, a secondary amino group, and a halogenated alkyl group. [Means 5] The method for producing a modified conjugated diene polymer according to [Means 3] or [Means 4], wherein the compound [M] is a compound represented by formula (1). [Means 6] The method for producing a modified conjugated diene polymer according to any of [Means 3] to [Means 5], wherein the silicon-containing initiator obtained by premixing the metal compound and the compound [M] is mixed with the monomer. [Means 7] The method for producing a modified conjugated diene polymer according to any of [Means 3] to [Means 5], wherein the silicon-containing initiator is produced by mixing the compound [M] and the metal compound in a reactor containing the monomer. [Means 8] A method for producing a modified conjugated diene polymer according to [Means 7], wherein a vinyl content adjuster, which is a compound having at least one of oxygen and nitrogen and having no active hydrogen, alkali metal element, or alkaline earth metal element, is added to a reactor after the metal compound has been added to the reactor. [Means 9] A method for producing a modified conjugated diene polymer according to any of [Means 1] to [Means 8], comprising a step of adding the silicon-containing initiator to the reactor after initiating polymerization of the monomer.[Means 10] A modified conjugated diene polymer represented by the above formula (3). [Means 11] A polymer composition containing a modified conjugated diene polymer obtained by the production method described in any one of [Means 1] to [Means 9], or the modified conjugated diene polymer described in [Means 10], and at least one selected from the group consisting of silica and carbon black. [Means 12] A crosslinked body obtained by crosslinking the polymer composition described in [Means 11]. [Means 13] A tire in which a tread or a sidewall, or both, are formed using the polymer composition described in [Means 11].

[0119] Hereinafter, specific explanations will be given based on examples, but the present disclosure is not limited to these examples. In the examples and comparative examples, "parts" and "%" are based on mass unless otherwise specified. The methods for measuring various physical properties of polymers and rubbers are shown below.

[0120] [Characteristics of polymer and rubber] Vinyl bond content (mol%): 400 MHz １ Measured by H-NMR. Bound styrene content (mass%): 400 MHz １ Measured by H-NMR measurement. Weight average molecular weight (Mw): A chart based on the molecular weight converted to polystyrene was obtained by gel permeation chromatography (GPC), and the weight average molecular weight (Mw) was determined based on this chart. Specific measurement conditions for GPC are as follows. (GPC measurement conditions) Measuring instrument: HLC-8020 (manufactured by Tosoh Corporation) Column: Two GMH-HR-H (manufactured by Tosoh Corporation) connected in series Detector: Differential refractometer RI-8020 (manufactured by Tosoh Corporation) Eluent: Tetrahydrofuran Column temperature: 40°C Flow rate: 1.0 mL / min Sample concentration: 10 mg / 20 ml The molecular weight of the polymer was measured using the polymer after the polymerization reaction had been stopped. The "1st peak weight average molecular weight" refers to the peak top molecular weight of the peak with the smallest molecular weight. Mooney viscosity (ML １＋４ , 100°C): Measured in accordance with JIS K6300-1:2013 using an L rotor under conditions of 1 minute preheating, 4 minutes rotor operation time, and a temperature of 100°C.

[0121] Synthesis of Compound [M] Synthesis Example 1 Synthesis of N-(3-(tert-butoxydimethylsilyl)propyl)piperazine (Compound M-7) 10.5 g of chloro-(3-chloropropyl)dimethylsilane and 180 mL of dichloromethane were placed in a nitrogen-purged two-neck flask having an internal volume of 300 mL. After the temperature of the contents of the reactor was adjusted to 0°C, a mixture of 8.7 g of tert-butyl alcohol and 5.3 g of N-methylimidazole was slowly added dropwise. After the dropwise addition, the mixture was stirred for 2 hours while maintaining the temperature of the reactor at 0°C. Next, the reaction solution was filtered to remove N-methylimidazole hydrochloride. The dichloromethane in the filtrate was removed using a rotary evaporator, yielding 12.0 g of tert-butoxy-(3-chloropropyl)dimethylsilane in a yield of 93%. Next, 14.9 g of piperazine, 7.5 g of diisopropylethylamine, 12.0 g of tert-butoxy-(3-chloropropyl)dimethylsilane, and 55 mL of toluene were added to a nitrogen-purged recovery flask with an internal volume of 100 mL. The reactor was heated to reflux the toluene and then stirred for 5.5 hours. The reactor was then cooled in a refrigerator for 16 hours, and the reaction solution was filtered. Low-boiling components were removed from the filtrate using a rotary evaporator, and then vacuum distillation was carried out to obtain 2.9 g of the target compound M-7 in a yield of 19%.

[0122] <Synthesis of Modified Conjugated Diene Polymer> [Example 1: Synthesis of Modified Conjugated Diene Polymer A-1 and Its Physical Properties] A nitrogen-purged 5-liter autoclave reactor was charged with 2,000 g of cyclohexane, 2.64 mmol of N-(3-(tert-butoxydimethylsilyl)propyl)piperazine (compound M-7), 0.25 g of 2,2-di(tetrahydrofuryl)propane as a vinyl content adjuster (randomizer), and 80 g of styrene and 300 g of 1,3-butadiene as monomers. The temperature of the reactor content was adjusted to 20°C, and then 3.12 mmol of n-butyllithium was added to initiate polymerization. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 71°C. After the polymerization conversion reached 99% (35 minutes after the start of polymerization), 20 g of 1,3-butadiene was added over 1 minute (additional butadiene). To the obtained polymer solution, 3.52 g of 2,6-di-tert-butyl-p-cresol was added as an antioxidant. Thereafter, the solvent was removed by steam stripping, and the resulting mixture was dried using a heated roll adjusted to 130°C to obtain a modified conjugated diene polymer (hereinafter also referred to as "Polymer A-1"). Various physical properties of Polymer A-1 are shown in Table 2.

[0123] [Example 2: Synthesis of modified conjugated diene polymer A-2 and its physical properties] A modified conjugated diene polymer (hereinafter also referred to as "polymer A-2") was obtained in the same manner as in Example 1, except that 2.64 mmol of 1-(piperidin-4-yl)-3-(N,N-diethylaminodimethylsilyl)propane (compound M-9) was used instead of N-(3-(tert-butoxydimethylsilyl)propyl)piperazine (compound M-7). Various physical property values ​​of polymer A-2 are shown in Table 2.

[0124] Example 3 Synthesis of Modified Conjugated Diene Polymer A-3 and Its Physical Properties A nitrogen-purged 5-liter autoclave reactor was charged with 2,000 g of cyclohexane, 2.64 mmol of N-(3-(tert-butoxydimethylsilyl)propyl)piperazine (compound M-7), 0.25 g of 2,2-di(tetrahydrofuryl)propane as a vinyl content adjuster (randomizer), and 80 g of styrene and 300 g of 1,3-butadiene as monomers. The temperature of the reactor content was adjusted to 20°C, and then 3.12 mmol of n-butyllithium was added to initiate polymerization. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 74°C. After the polymerization conversion reached 99% (41 minutes after the start of polymerization), 20 g of 1,3-butadiene was added over 1 minute. Thereafter, 0.78 mmol of silicon tetrachloride was added. To the obtained polymer solution, 3.52 g of 2,6-di-tert-butyl-p-cresol was added as an antioxidant. Thereafter, the solvent was removed by steam stripping, and the resulting mixture was dried using a heated roll adjusted to 130°C to obtain a modified conjugated diene polymer (hereinafter also referred to as polymer A-3). Various physical properties of polymer A-3 are shown in Table 2.

[0125] [Example 4: Synthesis of modified conjugated diene polymer A-4 and its physical properties] A modified conjugated diene polymer (hereinafter also referred to as "polymer A-4") was obtained in the same manner as in Example 3, except that 0.78 mmol of tin tetrachloride was added instead of silicon tetrachloride. Various physical properties of polymer A-4 are shown in Table 2.

[0126] [Example 5: Synthesis of modified conjugated diene polymer A-5 and its physical properties] A modified conjugated diene polymer (hereinafter also referred to as "polymer A-5") was obtained in the same manner as in Example 1, except that 0.02 g of divinylbenzene was further added as a monomer. Various physical properties of polymer A-5 are shown in Table 2.

[0127] [Example 6: Synthesis of modified conjugated diene polymer A-6 and its physical properties] A modified conjugated diene polymer (hereinafter also referred to as "polymer A-6") was obtained in the same manner as in Example 1, except that the amount of butadiene used in the reactor was 400 g, the amount of styrene used was 0 g, and the amount of additional butadiene used was 0 g. Various physical property values ​​of polymer A-6 are shown in Table 2 below.

[0128] Example 7 Synthesis of Modified Conjugated Diene Polymer A-7 and Its Physical Properties A nitrogen-purged 5-liter autoclave reactor was charged with 2,000 g of cyclohexane, 2.64 mmol of N-(3-(tert-butoxydimethylsilyl)propyl)piperazine (compound M-7), 80 g of styrene as monomers, and 300 g of 1,3-butadiene. The temperature of the reactor content was adjusted to 20°C, and then 3.12 mmol of n-butyllithium was added. Thereafter, 0.25 g of 2,2-di(tetrahydrofuryl)propane was charged as a vinyl content adjuster (randomizer). The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 73°C. After the polymerization conversion reached 99% (36 minutes after the start of the polymerization), 20 g of 1,3-butadiene was added over 1 minute. To the obtained polymer solution, 3.52 g of 2,6-di-tert-butyl-p-cresol was added as an antioxidant. Thereafter, the solvent was removed by steam stripping, and the mixture was dried using a heated roll adjusted to 130°C to obtain a modified conjugated diene copolymer (hereinafter also referred to as "Polymer A-7"). Various physical properties of Polymer A-7 are shown in Table 2.

[0129] Example 8 Synthesis of Modified Conjugated Diene Polymer A-8 and Its Physical Properties A modified conjugated diene polymer (hereinafter also referred to as "Polymer A-8") was obtained in the same manner as in Example 7, except that 2.64 mmol of N-(3-(triethoxysilyl)propyl)piperazine (Compound M-2) was used instead of N-(3-(tert-butoxydimethylsilyl)propyl)piperazine (Compound M-7) and the amount of n-butyllithium added was changed to 9.36 mmol. The physical properties of Polymer A-8 are shown in Table 2.

[0130] Example 9 Synthesis of Modified Conjugated Diene Polymer A-9 and Its Physical Properties (1) Synthesis of Polymerization Initiator 312 g of cyclohexane was added to a nitrogen-purged 500 mL flask, and 4.00 mmol of N-(3-(tert-butoxydimethylsilyl)propyl)piperazine (compound M-7) was further added and dissolved. 4.00 mmol of n-butyllithium was added thereto, and the mixture was reacted at room temperature for 60 minutes to obtain initiator solution I-1. (2) Synthesis of Polymer 1,760 g of cyclohexane, 0.25 g of 2,2-di(tetrahydrofuryl)propane as a vinyl content adjuster (randomizer), and 80 g of styrene and 300 g of 1,3-butadiene as monomers were charged into a nitrogen-purged 5-liter autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, polymerization was initiated by adding initiator solution I-1 so that the amount of polymerization initiator (lithiated compound M-7) was 3.12 mmol. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 72°C. After the polymerization conversion reached 99% (48 minutes after the start of polymerization), 20 g of 1,3-butadiene was added over 1 minute. 3.52 g of 2,6-di-tert-butyl-p-cresol was added as an antioxidant to the resulting polymer solution containing the modified conjugated diene polymer. The solvent was then removed by steam stripping, and the mixture was dried using a heated roll adjusted to 130°C, yielding a modified conjugated diene copolymer (hereinafter also referred to as "polymer A-9"). Table 2 shows the physical properties of polymer A-9.

[0131] Example 10 Synthesis of Modified Conjugated Diene Polymer A-10 and Its Physical Properties (1) Synthesis of Polymerization Initiator 250 g of cyclohexane was added to a nitrogen-purged 500 mL flask, and 3.20 mmol of N-(3-(tert-butoxydimethylsilyl)propyl)piperazine (compound M-7) was further added and dissolved therein. 3.20 mmol of n-butyllithium was added thereto, and the mixture was reacted at room temperature for 60 minutes. Thereafter, 2.18 g of isoprene was added, and the mixture was further reacted at 40°C for 30 minutes to obtain initiator solution I-2. (2) Synthesis of Polymer 1,750 g of cyclohexane, 0.25 g of 2,2-di(tetrahydrofuryl)propane as a vinyl content adjuster (randomizer), and 80 g of styrene and 300 g of 1,3-butadiene as monomers were charged into a nitrogen-purged 5-liter autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, the entire amount of initiator solution I-2 obtained above was added to initiate polymerization. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 76°C. After the polymerization conversion reached 99% (43 minutes after the start of polymerization), 20 g of 1,3-butadiene was added over 1 minute. To the resulting polymer solution, 3.52 g of 2,6-di-tert-butyl-p-cresol was added as an antioxidant. Thereafter, the solvent was removed by steam stripping, and the mixture was dried using a heated roll adjusted to 130°C to obtain a modified conjugated diene copolymer (hereinafter also referred to as "polymer A-10"). Various physical properties of polymer A-10 are shown in Table 2.

[0132] Example 11 Synthesis of Modified Conjugated Diene Polymer A-11 and Its Physical Properties (1) Synthesis of Polymerization Initiator 312 g of cyclohexane was added to a nitrogen-purged 500 mL flask, and 4.00 mmol of 1-(4-bromophenyl)-4-(3-ethoxydimethylsilyl)propyl)piperazine (Compound M-14) and 0.092 g of tetramethylethylenediamine were added and dissolved therein. 4.00 mmol of n-butyllithium was added thereto, and the mixture was reacted at 20°C for 60 minutes to obtain initiator solution I-3.

[0133] (2) Polymer Synthesis A 5-liter autoclave reactor purged with nitrogen was charged with 1,760 g of cyclohexane, 0.25 g of 2,2-di(tetrahydrofuryl)propane as a vinyl content adjuster (randomizer), and 80 g of styrene and 300 g of 1,3-butadiene as monomers. After adjusting the temperature of the reactor contents to 20°C, initiator solution I-3 was added so that the amount of polymerization initiator (lithiated compound M-14) was 3.12 mmol, thereby initiating polymerization. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 72°C. After the polymerization conversion reached 99% (48 minutes after the start of polymerization), 20 g of 1,3-butadiene was added over 1 minute. 3.52 g of 2,6-di-tert-butyl-p-cresol was added as an antioxidant to the resulting polymer solution. Thereafter, the solvent was removed by steam stripping, and the resulting mixture was dried using a heated roll adjusted to 130°C to obtain a modified conjugated diene copolymer (hereinafter also referred to as "polymer A-11"). Various physical properties of polymer A-11 are shown in Table 2.

[0134] Example 12: Synthesis and Properties of Modified Conjugated Diene Polymer A-12 (1) Synthesis of Polymerization Initiator Initiator solution I-1 was obtained in the same manner as in Example 9. (2) Synthesis of Polymer A nitrogen-purged 5-liter autoclave reactor was charged with 1,760 g of cyclohexane, 0.25 g of 2,2-di(tetrahydrofuryl)propane as a vinyl content adjuster (randomizer), and 80 g of styrene and 300 g of 1,3-butadiene as monomers. After adjusting the temperature of the reactor contents to 20°C, polymerization was initiated by adding initiator solution I-1 so that the amount of polymerization initiator (lithiated compound M-7) was 2.42 mmol. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 72°C. After the polymerization conversion reached 80% (42 minutes after the start of polymerization), initiator solution I-1 was further added in an amount equivalent to 0.70 mmol of the lithiated compound M-7. After the polymerization conversion reached 99% (48 minutes after the start of polymerization), 20 g of 1,3-butadiene was added over 1 minute. 3.52 g of 2,6-di-tert-butyl-p-cresol was added as an antioxidant to the obtained polymer solution. The solvent was then removed by steam stripping, and the mixture was dried using a heated roll adjusted to 130°C, yielding a modified conjugated diene copolymer (hereinafter also referred to as "Polymer A-12"). The physical properties of Polymer A-12 are shown in Table 2.

[0135] Comparative Example 1: Synthesis of Modified Conjugated Diene Polymer B-1 and Its Physical Properties A nitrogen-purged 5-liter autoclave reactor was charged with 2,000 g of cyclohexane, 0.25 g of 2,2-di(tetrahydrofuryl)propane as a vinyl content adjuster (randomizer), and 80 g of styrene and 300 g of 1,3-butadiene as monomers. The temperature of the reactor contents was adjusted to 20°C, and then 3.12 mmol of n-butyllithium was added to initiate polymerization. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 72°C. After the polymerization conversion reached 99% (38 minutes after the start of polymerization), 20 g of 1,3-butadiene was added over 1 minute. Thereafter, 1.1 g of 3-(N,N-bistrimethylsilyl)aminopropylmethyldiethoxysilane (compound Mod-1) was added. To the obtained polymer solution, 3.52 g of 2,6-di-tert-butyl-p-cresol was added as an antioxidant. Thereafter, the solvent was removed by steam stripping, and the mixture was dried using a heated roll adjusted to 130°C to obtain a modified conjugated diene copolymer (hereinafter also referred to as "Polymer B-1"). Various physical properties of Polymer B-1 are shown in Table 2.

[0136] Comparative Example 2: Synthesis of modified conjugated diene polymer B-2 and its physical properties A modified conjugated diene polymer (hereinafter also referred to as "polymer B-2") was obtained in the same manner as in Example 1, except that 2.64 mmol of N-(tert-butyldimethylsilyl)piperazine (compound Mod-2) was used instead of N-(3-(tert-butoxydimethylsilyl)propyl)piperazine (compound M-7). The physical properties of polymer B-2 are shown in Table 2.

[0137]

[0138] In Table 1, the abbreviations of the compounds are as follows: R-1: 2,2-ditetrahydrofurylpropane M-2: N-(3-(triethoxysilyl)propyl)piperazine M-7: N-(3-(tert-butoxydimethylsilyl)propyl)piperazine M-9: 1-(piperidin-4-yl)-3-(N,N-diethylaminodimethylsilyl)propane M-14: 1-(4-bromophenyl)-4-(3-ethoxydimethylsilyl)propyl)piperazine Mod-1: 3-(N,N-bistrimethylsilyl)aminopropylmethyldiethoxysilane Mod-2: N-(tert-butyldimethylsilyl)piperazine

[0139] In Examples 9 to 12, polymerization was carried out by using an initiator solution obtained by mixing n-butyllithium and compound [M] in cyclohexane and adding the initiator solution to cyclohexane containing a monomer and a randomizer. In Example 12, the initiator solution was further added in two separate portions. In Table 1, for Example 12, the upper portion of the amount of polymerization initiator added represents the amount added in the first portion, and the lower portion represents the amount added in the second portion.

[0140]

[0141] <Production of Polymer Composition and Crosslinked Body> Using each of the modified conjugated diene polymers A-1 to A-12, B-1, and B-2 produced above, the components were blended according to the formulation shown in Table 3 below, and the blend was kneaded to produce a polymer composition. The values ​​in Table 3 are in parts by mass. Kneading was performed as follows. Using a plastomill (capacity: 250 ml) equipped with a temperature control device, the modified conjugated diene polymer, butadiene rubber, silica, a silane coupling agent, an extender oil, stearic acid, an antioxidant, and zinc oxide were blended and kneaded in the first stage at a filling rate of 72% and a rotation speed of 60 rpm. Next, in the second stage of kneading, the blend obtained above was cooled to room temperature, and then sulfur and a vulcanization accelerator were blended and kneaded. The resulting polymer composition was molded and vulcanized in a vulcanization press at 160°C for a predetermined time to obtain a crosslinked body (vulcanized rubber). The rolling resistance was evaluated as follows, and the results are shown in Table 3.

[0142] Rolling resistance (50°C tan δ): Using vulcanized rubber as a measurement sample, the loss factor (tan δ (50°C)) was measured using an ARES-RDA (manufactured by TA Instruments) under conditions of a shear strain of 1.0%, an angular velocity of 100 radians per second, and 50°C. The measurement results are shown as an index, with Comparative Example 1 set at 100. The larger the value, the smaller the energy loss and the better the rolling resistance (fuel economy).

[0143]

[0144] In Table 3, the trade names used for each component are as follows: *1: BR01 manufactured by ENEOS Materials, *2: ZEOSIL 1165MP manufactured by Solvay, *3: Si75 manufactured by Evonik, *4: Process oil T-DAE manufactured by ENEOS, *5: 500S manufactured by New Japan Chemical Co., Ltd., *6: Zinc oxide type 2 manufactured by Seido Chemical Co., Ltd., *7: Ozonone 6C manufactured by Seiko Chemical Co., Ltd., *8: Noccela D manufactured by Ouchi Shinko Chemical Industry Co., Ltd., *9: Noccela CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd., *10) Kinkain brand finely powdered sulfur 200 mesh manufactured by Tsurumi Chemical Industry Co., Ltd.

[0145] As can be seen from the results in Table 3, the polymer compositions of Examples 1 to 12 showed a significant improvement in 50°C tan δ compared to the polymer compositions of Comparative Examples 1 and 2. These results confirmed that modified conjugated diene polymers obtained using silicon-containing initiators can produce crosslinked rubbers with excellent rolling resistance (fuel economy). In particular, Examples 9 to 12, which used initiator solutions obtained by pre-mixing compound [M] and a metal compound, tended to provide crosslinked products with improved rolling resistance. Furthermore, a comparison between Example 1 and Example 2 showed that the use of a compound further having group F1 as a silicon-containing initiator tended to provide crosslinked products with improved rolling resistance.

Claims

1. The method includes a step of polymerizing a monomer containing a conjugated diene compound in the presence of a polymerization initiator, The polymerization initiator comprises a silicon-containing initiator having an alkali metal element or an alkaline earth metal element and a group F2 shown below. F2: Base “* １ -Si(R １ ) ｎ (Y １ ) ３－ｎ ” (R １ is a hydrocarbyl group having 1 to 20 carbon atoms. １ is the group "-OR ２ " or the group "-NR ３ R ４ ". R ２ , R ３ and R ４ are each independently a hydrocarbyl group having 1 to 20 carbon atoms. n is an integer of 0 to 2. When n is 0 or 1, multiple Y １ are the same or different. When n is 2, multiple R １ are the same or different. １ " represents the bond to the carbon atom.)

2. 2. The method for producing a modified conjugated diene polymer according to claim 1, wherein the silicon-containing initiator further has at least one group selected from the group consisting of a tertiary amino group and a protected secondary amino group.

3. 2. The method for producing a modified conjugated diene polymer according to claim 1, wherein the silicon-containing initiator is a compound obtained by mixing at least one metal compound selected from the group consisting of alkali metal compounds and alkaline earth metal compounds with the compound [M] having the group F2.

4. 4. The method for producing a modified conjugated diene-based polymer according to claim 3, wherein the compound [M] has at least one selected from the group consisting of a monovalent cyclic group having a structure in which a halogen atom or a methyl group is bonded to an aromatic ring, a secondary amino group, and a halogenated alkyl group.

5. The method for producing a modified conjugated diene polymer according to claim 3 , wherein the compound [M] is a compound represented by the following formula (1): 【Chemistry 1】 (In formula (1), X １ is a group represented by the following formula (2-1) or formula (2-2): １ is a hydrocarbon group having 1 to 20 carbon atoms and a valence of (i+k), or has at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom, does not have active hydrogen, and is a group "-Si(R １ ) ｎ (Y １ ) ３－ｎ " and a group represented by the following formula (2-2) via a carbon atom. R １ is a hydrocarbyl group having 1 to 20 carbon atoms. １ is the group "-OR ２ " or the group "-NR ３ R ４ ". R ２ , R ３ and R ４ are each independently a hydrocarbyl group having 1 to 20 carbon atoms. n is an integer of 0 to 2. When n is 0 or 1, multiple Y １ are the same or different. When n is 2, multiple R １ are the same or different, and i and k are each independently an integer of 1 to 6, provided that i+k≦10 is satisfied. １ If there are multiple X １ are the same or different. The group "-Si(R １ ) ｎ (Y １ ) ３－ｎ When there are a plurality of groups "-Si(R １ ) ｎ (Y １ ) ３－ｎ " are the same or different.) 【Chemistry 2】 (In formula (2-1), R ５ R is a hydrogen atom, a halogenated alkyl group having 1 to 8 carbon atoms, or a monovalent cyclic group having a structure in which a halogen atom or a methyl group is bonded to an aromatic ring. ６ and R ７ are each independently a hydrocarbylene group having 1 to 10 carbon atoms. １ and Q ２ are each independently a nitrogen atom or —CR １０ -. However, R ５ If is a hydrogen atom, Q １ is a nitrogen atom. １０ is a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms. "*" represents a bond. In formula (2-2), R ８ R is a hydrogen atom, a halogenated alkyl group having 1 to 8 carbon atoms, or a monovalent cyclic group having a structure in which a halogen atom or a methyl group is bonded to an aromatic ring. ９ is a hydrocarbyl group or a trihydrocarbylsilyl group having 1 to 20 carbon atoms, provided that R ８ When is a hydrogen atom, R ９ is a hydrocarbyl group having 1 to 20 carbon atoms. "*" represents a bond.

6. The method for producing a modified conjugated diene-based polymer according to claim 3 , wherein the silicon-containing initiator obtained by premixing the metal compound and the compound [M] is mixed with the monomer.

7. The method for producing a modified conjugated diene-based polymer according to claim 3, wherein the silicon-containing initiator is produced by mixing the compound [M] and the metal compound in a reactor containing the monomers.

8. 8. The method for producing a modified conjugated diene polymer according to claim 7, wherein a vinyl content adjuster which is a compound having at least one of oxygen and nitrogen and having no active hydrogen, alkali metal element, or alkaline earth metal element is added to the reactor after the metal compound is added to the reactor.

9. 2. The method for producing a modified conjugated diene-based polymer according to claim 1, further comprising the step of adding the silicon-containing initiator to the reactor after initiating polymerization of the monomer.

10. A modified conjugated diene polymer represented by the following formula (3): 【Transformation 3】 (In formula (3), X ２ is a group represented by the following formula (4-1) or formula (4-2): １ is a hydrocarbon group having 1 to 20 carbon atoms and a valence of (i+k), or has at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom, does not have active hydrogen, and is a group "-Si(R １ ) ｎ (Y １ ) ３－ｎ " and a group represented by the following formula (4-2) via a carbon atom. R １ is a hydrocarbyl group having 1 to 20 carbon atoms. １ is the group "-OR ２ " or the group "-NR ３ R ４ ". R ２ , R ３ and R ４ are each independently a hydrocarbyl group having 1 to 20 carbon atoms. n is an integer of 0 to 2. When n is 0 or 1, multiple Y １ are the same or different. When n is 2, multiple R １ are the same or different, and i and k are each independently an integer of 1 to 6, provided that i+k≦10 is satisfied. ２ If there are multiple X ２ are the same or different. The group "-Si(R １ ) ｎ (Y １ ) ３－ｎ When there are a plurality of groups "-Si(R １ ) ｎ (Y １ ) ３－ｎ " are the same or different.) 【Chemistry 4】 (In formula (4-1), Z １ represents a single bond, an alkanediyl group having 1 to 8 carbon atoms, or the group "* ３ -Ar １ -W １ -" (Ar １ is a divalent aromatic ring group. １ is a single bond or a methylene group. ３ " is Q １ represents a bond with .) ６ and R ７ are each independently a hydrocarbylene group having 1 to 10 carbon atoms. １ and Q ２ are each independently a nitrogen atom or —CR １０ -. However, Z １ If is a single bond, Q １ is a nitrogen atom. １０ represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms. Poly represents a modified or unmodified conjugated diene polymer chain. "*" represents a bond. In formula (4-2), Z ２ represents a single bond, an alkanediyl group having 1 to 8 carbon atoms, or the group "* ４ -Ar １ -W １ -" (Ar １ is a divalent aromatic ring group. １ is a single bond or a methylene group. ４ " is -NR １１ - represents a bond with . １１ represents a hydrogen atom, a hydrocarbyl group having 1 to 20 carbon atoms, or a trihydrocarbylsilyl group. Poly represents a modified or unmodified conjugated diene polymer chain. "*" represents a bond.

11. A polymer composition comprising a modified conjugated diene polymer obtained by the production method according to any one of claims 1 to 9, or the modified conjugated diene polymer according to claim 10, and at least one selected from the group consisting of silica and carbon black.

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

13. A tire having a tread or a sidewall, or both, formed from the polymer composition of claim 11.

14. A compound represented by the following formula (1): 【Transformation 5】 (In formula (1), X 1 is a group represented by the following formula (2-1) or formula (2-2). A 1 is an (i+k)-valent hydrocarbon group having 1 to 20 carbon atoms, or an (i+k)-valent group having 1 to 20 carbon atoms which has at least one atom selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms, has no active hydrogen, and is bonded via a carbon atom to the group "-Si(R 1 ) n (Y 1 ) 3-n " and the group represented by the following formula (2-2). R 1 is a hydrocarbyl group having 1 to 20 carbon atoms. Y 1 is a group "-OR 2 " or a group "-NR 3 R 4 ". R 2 , R 3 , and R 4 are each independently a hydrocarbyl group having 1 to 20 carbon atoms. n is an integer of 0 to 2. When n is 0 or 1, a plurality of Y 1 are the same or different. When n is 2, the multiple R 1 s are the same or different. i and k are each independently an integer of 1 to 6, provided that i+k≦10 is satisfied. In the formula, when there are multiple X 1 s, the multiple X 1 s are the same or different. When there are multiple groups "-Si(R 1 ) n (Y 1 ) 3-n ", the multiple groups "-Si(R 1 ) n (Y 1 ) 3-n " are the same or different. 【Transformation 6】 (In formula (2-1), R 5 is a hydrogen atom, a halogenated alkyl group having 1 to 8 carbon atoms, or a monovalent cyclic group having a structure in which a halogen atom or a methyl group is bonded to an aromatic ring. R 6 and R 7 are each independently a hydrocarbylene group having 1 to 10 carbon atoms. Q 1 and Q 2 are each independently a nitrogen atom or —CR 10 —, provided that when R 5 is a hydrogen atom, Q 1 is a nitrogen atom. R 10 is a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms. “*” represents a bond.) In formula (2-2), R 8 is a hydrogen atom, a halogenated alkyl group having 1 to 8 carbon atoms, or a monovalent cyclic group having a structure in which a halogen atom or a methyl group is bonded to an aromatic ring. R 9 is a hydrocarbyl group or trihydrocarbylsilyl group having 1 to 20 carbon atoms. However, when R 8 is a hydrogen atom, R 9 is a hydrocarbyl group having 1 to 20 carbon atoms. "*" represents a bond.

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