Conjugated diene polymer, method for producing conjugated diene polymer, rubber composition, rubber crosslinked product, and tire

Abstract

Provided is a conjugated diene polymer that satisfies formula (I).　(I) 1.6 < ML ÷ G' ÷ Mw × 1,000,000 < 3.6 (In formula (I), ML represents the Mooney viscosity (ML1+4,100°C) measured according to JIS K6300-1, G' represents the storage shear modulus measured at a temperature of 100°C, a frequency of 0.05 Hz, and a dynamic strain of 10%, and Mw represents the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography.)

Description

Conjugated diene polymers, methods for producing conjugated diene polymers, rubber compositions, rubber crosslinked products, and tires

[0001] The present invention relates to a conjugated diene polymer, and more specifically, to a conjugated diene polymer with excellent hot flow properties that can provide rubber crosslinked products with excellent low heat generation properties.

[0002] In recent years, due to growing concern about environmental issues, there has been a demand for polymers used in automobile tires that exhibit superior fuel efficiency. Tires obtained using a rubber composition in which silica is compounded as a filler into a conjugated diene polymer have improved low heat generation properties compared to tires obtained using conventionally used rubber compositions containing carbon black, thus resulting in tires with superior fuel efficiency.

[0003] Regarding conjugated diene polymers for providing such tires, Patent Document 1 describes a step of polymerizing isoprene monomers, or a monomer mixture containing isoprene and aromatic vinyl monomers, in an inert solvent with a polymerization initiator to form a polymer block (A) having active ends containing 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units; a step of mixing the polymer block (A) having active ends with 1,3-butadiene, or a monomer mixture containing 1,3-butadiene and aromatic vinyl monomers, and continuing the polymerization reaction to form a polymer block (B) having active ends containing 50 to 100% by weight of 1,3-butadiene monomer units and 0 to 50% by weight of aromatic vinyl monomer units, by connecting it to polymer block (A), thereby obtaining a conjugated diene polymer chain having active ends, comprising polymer block (A) and polymer block (B); and A method for producing a conjugated diene polymer is disclosed, characterized by comprising the step of reacting the active end of a conjugated diene polymer chain having the active end with a compound represented by a specific general formula (1).

[0004] Japanese Patent Publication No. 2016-30795

[0005] The conjugated diene polymer obtained by the technology described in Patent Document 1 can provide a rubber crosslinked product with excellent shape stability, low heat generation, and excellent wet grip. However, it has the problem of insufficient hot flowability, and the crumbs formed by solidification tend to stick together, resulting in unstable operability during solidification.

[0006] This invention has been made in view of the above circumstances, and aims to provide a conjugated diene polymer with excellent hot flow properties that can give a rubber crosslinked product with excellent low heat generation properties.

[0007] As a result of diligent research to achieve the above objective, the inventors discovered that the above objective can be achieved by a conjugated diene polymer satisfying a specific formula (I), and thus completed the present invention.

[0008] In other words, the present invention provides the following conjugated diene polymers, methods for producing conjugated diene polymers, rubber compositions, rubber crosslinked products, and tires.

[0009] [1] A conjugated diene polymer satisfying the following formula (I): 1.6 < ML ÷ G' ÷ Mw × 1,000,000 < 3.6 (I) (wherein ML is the Mooney viscosity measured according to JIS K6300-1) １＋４, 100°C) where G' represents the storage shear modulus measured under conditions of a temperature of 100°C, a frequency of 0.05 Hz, and a dynamic strain of 10%, and Mw represents the weight-average molecular weight in polystyrene terms measured by gel permeation chromatography.) [2] A method for producing a conjugated diene polymer according to [1], comprising: a polymerization step of polymerizing a monomer containing a conjugated diene compound using a polymerization initiator in an inert solvent to obtain a conjugated diene polymer chain having an active end; a coupling step of reacting the conjugated diene polymer chain having an active end with a coupling agent having an epoxy group or a carbonyl group to form a coupling polymer chain; and a modification step of reacting the coupling polymer chain with a nitrogen atom-containing silane compound, wherein the coupling agent is a compound consisting only of at least one heteroatom selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms, a carbon atom, and a hydrogen atom. [3] The method for producing a conjugated diene polymer according to [2], wherein the amount of nitrogen atom-containing silane compound used in the modification step is 0.1 to 5 moles per mole of the polymerization initiator used in the polymerization step. [4] The method for producing a conjugated diene polymer according to [2] or [3], wherein the total number of epoxy groups and carbonyl groups in the coupling agent used in the coupling step is 0.1 moles or more per mole of the polymerization initiator used in the polymerization step. [5] The method for producing a conjugated diene polymer according to any one of [2] to [4], wherein the number of epoxy groups and carbonyl groups per molecule of the coupling agent is 3 or more. [6] The method for producing a conjugated diene polymer according to any one of [2] to [5], wherein the number average molecular weight of the coupling agent is 300 or more. [7] A method for producing a conjugated diene polymer according to any one of [2] to [6], wherein in the modification step, the coupling polymer chain is reacted with a polyorganosiloxane, and then the coupling polymer chain reacted with the polyorganosiloxane is further reacted with the nitrogen atom-containing silane compound. [8] A rubber composition containing the conjugated diene polymer according to [1] and a filler. [9] The rubber composition according to [8] further containing a crosslinking agent.

[10] A crosslinked rubber product obtained by crosslinking the crosslinkable rubber composition described in [9].

[11] A tire comprising the crosslinked rubber product described in

[10] .

[0010] According to the present invention, it is possible to provide a conjugated diene polymer with excellent hot flow properties that can give a rubber crosslinked product with excellent low heat generation properties.

[0011] <Conjugated diene polymer> The conjugated diene polymer of the present invention satisfies the following formula (I): 1.6 < ML ÷ G' ÷ Mw × 1,000,000 < 3.6 (I) (wherein ML is the Mooney viscosity measured according to JIS K6300-1) １＋４ G' represents the storage shear modulus measured at 100°C, 0.05 Hz, and 10% dynamic strain, and Mw represents the weight-average molecular weight in polystyrene terms measured by gel permeation chromatography.

[0012] The inventors diligently studied how to achieve both hot flow and low heat generation in rubber crosslinked products, and as a result found that the balance between the Mooney viscosity ML, storage shear modulus G', and weight-average molecular weight Mw of a conjugated diene polymer affects both hot flow and low heat generation in rubber crosslinked products. Specifically, it was found that when the storage shear modulus G' and weight-average molecular weight Mw are within a certain range, if the Mooney viscosity ML is too small, the low heat generation of the rubber crosslinked product becomes insufficient, and if the Mooney viscosity ML is too large, the hot flow is insufficient. Furthermore, the inventors found that when the storage shear modulus G' and weight-average molecular weight Mw are increased, the appropriate range for Mooney viscosity ML also widens. Finally, it was found that when the conjugated diene polymer satisfies formula (I), both hot flow and low heat generation in rubber crosslinked products can be achieved.

[0013] The conjugated diene polymer of the present invention contains at least a conjugated diene monomer unit. Examples of conjugated diene compounds for forming the conjugated diene monomer unit include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Among these, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred. These may be used individually or in combination of two or more.

[0014] The content of conjugated diene monomer units in the conjugated diene polymer is not particularly limited, but is preferably 30 to 100% by weight, more preferably 50 to 99% by weight, and even more preferably 52 to 95% by weight. By setting the content of conjugated diene monomer units within the above range, the effects of the present invention become even more pronounced. From the viewpoint of obtaining the effects of the present invention at an extremely high level, the content of conjugated diene monomer units is preferably 65 to 95% by weight, and more preferably 75 to 90% by weight.

[0015] In conjugated diene polymers, the amount of vinyl bond in the conjugated diene monomer unit is preferably 1 to 90 mol%, more preferably 10 to 80 mol%, even more preferably 20 to 70 mol%, even more preferably 25 to 65 mol%, and particularly preferably 30 to 60 mol%. By setting the vinyl bond content in the conjugated diene monomer unit within the above range, the effects of the present invention become even more pronounced.

[0016] The conjugated diene polymer of the present invention is preferably a copolymer having aromatic vinyl monomer units in addition to conjugated diene monomer units. Examples of aromatic vinyl monomers for forming aromatic vinyl monomer units include styrene, methylstyrene, ethylstyrene, t-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, chlorostyrene, bromostyrene, methoxystyrene, dimethylaminomethylstyrene, dimethylaminoethylstyrene, diethylaminomethylstyrene, diethylaminoethylstyrene, cyanoethylstyrene, and vinylnaphthalene. Among these, styrene is preferred. These may be used individually or in combination of two or more.

[0017] The content of aromatic vinyl monomer units in the conjugated diene polymer is not particularly limited, but is preferably 0 to 70% by weight, more preferably 1 to 50% by weight, and even more preferably 5 to 48% by weight. By setting the content of aromatic vinyl monomer units within the above range, the effects of the present invention become even more pronounced. From the viewpoint of obtaining the effects of the present invention at an extremely high level, the content of aromatic vinyl monomer units is preferably 5 to 35% by weight, and more preferably 10 to 25% by weight.

[0018] The conjugated diene polymer of the present invention may have aromatic vinyl compound blocks. An aromatic vinyl compound block is a block formed by the continuous bonding of two or more aromatic vinyl monomer units. The proportion of aromatic vinyl compound blocks in the aromatic vinyl monomer units of the conjugated diene polymer is not particularly limited, but is preferably 10% or less, more preferably 8% or less, and even more preferably 6% or less. The lower limit of the proportion of aromatic vinyl compound blocks is not particularly limited, but may be 0.5% or more, 1% or more, or 2% or more.

[0019] Aromatic vinyl compound blocks can be classified into blocks with two or three consecutive aromatic vinyl monomer units (hereinafter sometimes referred to as "aromatic vinyl compound blocks (2-3 chains)") and blocks with four or more consecutive aromatic vinyl monomer units (hereinafter sometimes referred to as "aromatic vinyl compound blocks (4 or more chains)").

[0020] The proportion of aromatic vinyl compound blocks (2-3 chains) in the aromatic vinyl monomer units of the conjugated diene polymer is not particularly limited, but is preferably 7% or less, more preferably 6% or less, and even more preferably 4.5% or less. The lower limit of the proportion of aromatic vinyl compound blocks (2-3 chains) is not particularly limited, but may be 0.4% or more, 0.8% or more, or 1.6% or more.

[0021] The proportion of aromatic vinyl compound blocks (four or more chains) in the aromatic vinyl monomer units of the conjugated diene polymer is not particularly limited, but is preferably 3% or less, more preferably 2% or less, and even more preferably 1.5% or less. The lower limit of the proportion of aromatic vinyl compound blocks (four or more chains) is not particularly limited, but may be 0.1% or more, 0.2% or more, or 0.4% or more.

[0022] On the other hand, it is preferable that the conjugated diene polymer of the present invention has aromatic vinyl monomer units that do not form aromatic vinyl compound blocks (hereinafter sometimes referred to as "single aromatic vinyl monomer units"). The proportion of single aromatic vinyl monomer units in the aromatic vinyl monomer units of the conjugated diene polymer is preferably 90% or more, more preferably 92% or more, and even more preferably 94% or more. The upper limit of the proportion of single aromatic vinyl monomer units is not particularly limited, but may be 99.5% or less, 99% or less, or 98% or less.

[0023] The effects of the present invention become even more pronounced by setting the proportion of aromatic vinyl compound blocks and the proportion of individual aromatic vinyl monomer units within the above ranges. The proportion of aromatic vinyl compound blocks and the proportion of individual aromatic vinyl monomer units can be controlled by methods such as controlling the proportion of these compounds used at the start of polymerization when polymerizing monomers containing conjugated diene compounds and aromatic vinyl compounds; controlling the proportion of aromatic vinyl compounds in the added monomers and the timing of the addition when adding monomers; adjusting the amount of inert solvent relative to the amount of aromatic vinyl compound used; adjusting the type and amount of polar compounds added; controlling the polymerization temperature; and combining these methods.

[0024] The above proportions of aromatic vinyl compound blocks and aromatic vinyl monomer units were obtained using deuterated chloroform as the solvent. １ The ratio can be determined using the spectrum obtained by 1H-NMR measurement, based on the reference (Sardelis, K. Michels, H. J. Allen, G. Polymer, 1984, 25, 1011). Specifically, the above ratio can be determined by the method described in the examples.

[0025] Conjugated diene polymers may contain other monomer units besides those described above. Examples of other monomers constituting such monomer units include α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids or acid anhydrides such as acrylic acid, methacrylic acid, and maleic anhydride; unsaturated carboxylic acid esters such as methyl methacrylate, ethyl acrylate, and butyl acrylate; linear olefin compounds such as ethylene, propylene, and 1-butene; cyclic olefin compounds such as cyclopentene and 2-norbornene; and non-conjugated dienes such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene. These may be used individually or in combination of two or more.

[0026] The content of other monomer units in the conjugated diene polymer is preferably 10% by weight or less, and more preferably 5% by weight or less, based on the total amount of all monomers being 100% by weight.

[0027] When a conjugated diene polymer is composed of two or more monomer units, the bonding patterns of each monomer unit can be various, such as block-like, tapered, or random.

[0028] The conjugated diene polymer of the present invention is preferably obtained by a manufacturing method described later, which includes specific coupling and modification steps. That is, the conjugated diene polymer of the present invention preferably has a coupling structure derived from a coupling agent (C) described later and a modified structure derived from a nitrogen atom-containing silane compound.

[0029] The conjugated diene polymer of the present invention satisfies the following formula (I). Hereinafter, the value of ML ÷ G' ÷ Mw × 1,000,000 may be referred to as the "value of formula (I)". 1.6 < ML ÷ G' ÷ Mw × 1,000,000 < 3.6 (I) (In formula (I), ML is the Mooney viscosity (ML) measured according to JIS K6300-1) １＋４ G' represents the storage shear modulus measured at 100°C, 0.05 Hz, and 10% dynamic strain, and Mw represents the weight-average molecular weight in polystyrene terms measured by gel permeation chromatography.

[0030] One method for setting the value of formula (I) within the above range is to employ a manufacturing method described later, which includes specific coupling and modification steps.

[0031] The value of formula (I) is not particularly limited as long as it is greater than 1.6 and less than 3.6, but is preferably greater than 1.6 and 3.4 or less, more preferably greater than 1.6 and 3.0 or less, even more preferably greater than 1.6 and 2.7 or less, and particularly preferably greater than 1.6 and 2.5 or less. By setting the value of formula (I) within the above range, the effects of the present invention become even more pronounced. Furthermore, when extremely excellent low heat generation of the rubber crosslinked product is required, the value of formula (I) is preferably 2.4 or less, and more preferably 2.3 or less. As a method for setting the value of formula (I) within the above preferred range, one method is to set the type and amount of coupling agent and modifier used in the manufacturing method described later to within the preferred range described later.

[0032] In formula (I), ML is the Mooney viscosity (ML) of the conjugated diene polymer, as measured according to JIS K6300-1. １＋４ This represents (100°C). ML is not particularly limited as long as it satisfies formula (I), but is preferably 30 to 120, and more preferably 40 to 100.

[0033] In formula (I), G' represents the storage shear modulus of the conjugated diene polymer, measured under conditions of a temperature of 100°C, a frequency of 0.05 Hz, and a dynamic strain of 10%. G' is not particularly limited as long as it satisfies formula (I), but is preferably 20 to 100 and more preferably 28 to 90.

[0034] In formula (I), Mw represents the weight-average molecular weight in polystyrene terms, measured by gel permeation chromatography. Mw is not particularly limited as long as it satisfies formula (I), but is preferably 50,000 to 5,000,000, more preferably 100,000 to 3,000,000, particularly preferably 200,000 to 2,000,000, and most preferably 200,000 to 1,000,000. By setting Mw within the above range, the effects of the present invention become even more pronounced.

[0035] The molecular weight distribution of the conjugated diene polymer of the present invention, expressed as the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn), is preferably 1.1 to 3.0, more preferably 1.2 to 2.5, and particularly preferably 1.2 to 2.0.

[0036] The coupling rate of the conjugated diene polymer of the present invention is not particularly limited, but is preferably 10% by weight or more, more preferably 20% by weight or more, and also preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 75% by weight or less. The coupling rate is the weight fraction of polymer molecules having a molecular weight of 1.8 times or more the peak top molecular weight of the conjugated diene polymer chain having an active end, relative to the total amount of the final conjugated diene polymer. The molecular weight at this time is determined as the polystyrene-equivalent molecular weight by gel permeation chromatography.

[0037] <Method for Producing Conjugated Diene Polymers> The conjugated diene polymers of the present invention can preferably be produced by the following method for producing conjugated diene polymers. The present invention also relates to such a method for producing conjugated diene polymers.

[0038] A method for producing a conjugated diene polymer, comprising: a polymerization step of polymerizing a monomer containing a conjugated diene compound in an inert solvent using a polymerization initiator to obtain a conjugated diene polymer chain having an active end; a coupling step of reacting the conjugated diene polymer chain having an active end with a coupling agent having an epoxy group or a carbonyl group to form a coupling polymer chain; and a modification step of reacting the coupling polymer chain with a nitrogen atom-containing silane compound, described later, wherein the coupling agent is a compound consisting only of at least one heteroatom selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms, a carbon atom, and a hydrogen atom.

[0039] [Polymerization Process] In the polymerization process, monomers containing a conjugated diene compound are polymerized in an inert solvent using a polymerization initiator to obtain a conjugated diene polymer chain having an active end.

[0040] In the polymerization process, a conjugated diene compound is used as the monomer, and aromatic vinyl monomers and other monomers are further used as needed. The above-mentioned compounds can be used as the conjugated diene compound, aromatic vinyl monomer, and other monomers.

[0041] The inert solvent is not particularly limited as long as it is commonly used in solution polymerization and does not inhibit the polymerization reaction. Specific examples of inert solvents include linear aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; and aromatic hydrocarbons such as benzene, toluene, and xylene. These inert solvents may be used individually or in combination of two or more. The amount of inert solvent used is not particularly limited, but is such that the monomer concentration is, for example, 1 to 50% by weight, preferably 10 to 40% by weight.

[0042] Polymerization initiators are not particularly limited as long as they can polymerize monomers containing conjugated diene compounds to give conjugated diene polymer chains having active ends. Specific examples include polymerization initiators that primarily use organoalkali metal compounds, organoalkaline earth metal compounds, and lanthanum series metal compounds as catalysts. Examples of organoalkali metal compounds include organomonolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenithium; organopolyvalent lithium compounds such as dilithiomethane, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-tris(lithiomethyl)benzene; organosodium compounds such as sodium naphthalene; and organopotassium compounds such as potassium naphthalene. Examples of organic alkaline earth metal compounds include di-n-butylmagnesium, di-n-hexylmagnesium, diethoxycalcium, calcium distearate, di-t-butoxystrontium, diethoxybarium, diisopropoxybarium, diethylmercaptobarium, di-t-butoxybarium, diphenoxybarium, diethylaminobarium, barium distearate, and diketilbarium. Examples of polymerization initiators using lanthanum series metal compounds as the main catalyst include a salt of a lanthanum series metal, such as lanthanum, cerium, praseodymium, neodymium, samarium, or gadolinium, with a carboxylic acid or phosphorus-containing organic acid as the main catalyst, and a polymerization initiator consisting of this and co-catalysts such as alkylaluminum compounds, organoaluminum hydride compounds, and organoaluminum halide compounds. Among these polymerization initiators, organic monolithium compounds and organic polyvalent lithium compounds are preferably used, organic monolithium compounds are more preferably used, and n-butyllithium is particularly preferably used.

[0043] Furthermore, organoalkali metal compounds may be used as organoalkali metal amide compounds by reacting them beforehand with secondary amine compounds such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, piperidine, hexamethyleneimine, and heptamethyleneimine.

[0044] The method for adding the organic alkali metal amide compound as a polymerization initiator to the polymerization system is not particularly limited. One method is to first react the organic alkali metal compound with a secondary amine compound to obtain the organic alkali metal amide compound, and then mix this with a monomer containing a conjugated diene compound to proceed with the polymerization reaction. Alternatively, one can add the organic alkali metal compound and the secondary amine compound separately to the polymerization system and mix them with a monomer containing a conjugated diene compound to generate the organic alkali metal amide compound in the polymerization system, thereby proceeding with the polymerization reaction. The reaction conditions, such as the reaction temperature, are not particularly limited and can be, for example, according to the desired polymerization reaction conditions.

[0045] The amount of secondary amine compound used can be determined according to the amount of polymerization initiator added, but it is usually in the range of 0.01 to 1.5 millimoles, preferably 0.1 to 1.2 millimoles, and more preferably 0.5 to 1.0 millimoles, per millimole of organoalkali metal compound.

[0046] The amount of polymerization initiator used can be determined according to the molecular weight of the target conjugated diene polymer chain, but is usually in the range of 1 to 50 mmol, preferably 1.5 to 20 mmol, and more preferably 2 to 15 mmol per 1000 g of monomer.

[0047] The polymerization temperature is typically in the range of -80 to +150°C, preferably 0 to 100°C, and more preferably 30 to 90°C. Any polymerization method, such as batch or continuous, can be used, but when copolymerizing a conjugated diene compound with an aromatic vinyl compound, the batch method is preferred because it allows for easier control of the randomness of the bonding between the conjugated diene monomer units and the aromatic vinyl monomer units.

[0048] Furthermore, when polymerizing monomers containing conjugated diene compounds, it is preferable to add a polar compound to an inert organic solvent in order to adjust the vinyl bond content in the conjugated diene monomer units in the resulting conjugated diene polymer chain. Examples of polar compounds include ether compounds such as dibutyl ether, tetrahydrofuran, and 2,2-di(tetrahydrofuryl)propane; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; and phosphine compounds. Among these, ether compounds and tertiary amines are preferred, tertiary amines are more preferred, and tetramethylethylenediamine is particularly preferred. These polar compounds may be used individually or in combination of two or more. The amount of polar compound used should be determined according to the desired vinyl bond content, preferably 0.001 to 100 moles, more preferably 0.01 to 10 moles, per mole of polymerization initiator. When the amount of polar compound used is within this range, it is easy to adjust the vinyl bond content in the conjugated diene monomer units, and problems due to deactivation of the polymerization initiator are less likely to occur.

[0049] The vinyl bond content in the conjugated diene monomer units of the conjugated diene polymer chain having an active end obtained in the polymerization process is preferably 1 to 90% by weight, more preferably 3 to 80% by weight, and particularly preferably 5 to 70% by weight. By setting the vinyl bond content in the conjugated diene monomer units within the above range, the resulting rubber crosslinked product can be made to have superior low heat generation properties.

[0050] The polymerization step preferably comprises the steps of: polymerizing isoprene, or a monomer containing isoprene and an aromatic vinyl compound, in an inert solvent with a polymerization initiator to form a polymer block (A) having active ends containing 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units; and mixing the polymer block (A) having active ends with 1,3-butadiene, or a monomer containing 1,3-butadiene and an aromatic vinyl compound, and continuing the polymerization reaction to form a polymer block (B) having active ends containing 50 to 100% by weight of 1,3-butadiene monomer units and 0 to 50% by weight of aromatic vinyl monomer units, in a continuous manner with polymer block (A), thereby obtaining a conjugated diene polymer chain having active ends.

[0051] By employing such a process, the conjugated diene polymer chain having an active end obtained in the polymerization process can include a polymer block (A) containing 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units, and a polymer block (B) containing 50 to 100% by weight of 1,3-butadiene monomer units and 0 to 50% by weight of aromatic vinyl monomer units, which are formed in a continuous manner. Such embodiments will be described below.

[0052] [Polymer Block (A)] Polymer block (A) may contain 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units, but it is preferable that it contains 85 to 95% by weight of isoprene monomer units and 5 to 15% by weight of aromatic vinyl monomer units, and more preferably that it contains 89 to 95% by weight of isoprene monomer units and 5 to 11% by weight of aromatic vinyl monomer units. When the content ratio of isoprene monomer units and aromatic vinyl monomer units is within the above range, the affinity between the conjugated diene polymer and the filler is good, and the physical properties of the resulting rubber crosslinked product can be improved.

[0053] The aromatic vinyl compounds used to constitute the aromatic vinyl monomer units contained in polymer block (A) can be the same as the aromatic vinyl compounds described above, and among these, styrene is preferred. These aromatic vinyl compounds may be used individually or in combination of two or more.

[0054] The polymer block (A) is preferably composed of isoprene monomer units only, or isoprene monomer units and aromatic vinyl monomer units, but may optionally contain other monomer units in addition to isoprene monomer units, or isoprene monomer units and aromatic vinyl monomer units. Other compounds used to constitute other monomer units include conjugated dienes other than isoprene, such as 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene; α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids or acid anhydrides such as acrylic acid, methacrylic acid, and maleic anhydride; unsaturated carboxylic acid esters such as methyl methacrylate, ethyl acrylate, and butyl acrylate; and non-conjugated dienes such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene. Among these, 1,3-butadiene is preferred. These other monomers can be used individually or in combination of two or more. The content of other monomer units in polymer block (A) is preferably 20% by weight or less, more preferably 10% by weight or less, and even more preferably 6% by weight or less.

[0055] Polymer block (A) is formed by polymerizing isoprene, or a monomer containing isoprene and an aromatic vinyl compound, in an inert solvent with a polymerization initiator. The formed polymer block (A) has active ends.

[0056] To form polymer blocks (A), the same inert solvent as described above can be used for polymerization of isoprene, or a monomer containing isoprene and an aromatic vinyl compound. The amount of inert solvent used is such that the monomer concentration is preferably 1 to 80% by weight, and more preferably 10 to 50% by weight.

[0057] The polymerization initiator used to form polymer block (A) is not particularly limited, as long as it can polymerize isoprene, or a monomer containing isoprene and an aromatic vinyl compound, to give a polymer chain having an active end. Specific examples include those used with the polymerization initiator described above.

[0058] The amount of polymerization initiator used can be determined according to the target molecular weight, but is preferably in the range of 4 to 250 mmol, more preferably 6 to 200 mmol, and particularly preferably 10 to 70 mmol per 100 g of isoprene, or monomer containing isoprene and an aromatic vinyl compound.

[0059] The polymerization temperature when polymerizing isoprene, or a monomer containing isoprene and an aromatic vinyl compound, is preferably in the range of -80 to +150°C, more preferably 0 to 100°C, and even more preferably 20 to 90°C. Any polymerization method can be used, such as batch or continuous polymerization. Furthermore, various bonding patterns can be used, such as block-like, tapered, and random, with random bonding being preferred.

[0060] To adjust the vinyl bond content in the isoprene monomer units in polymer block (A), it is preferable to add a polar compound to the inert solvent during polymerization. The same polar compound as described above can be used. The amount of polar compound used should be determined according to the desired vinyl bond content, preferably 0.01 to 30 moles, and more preferably 0.05 to 10 moles, per mole of polymerization initiator. When the amount of polar compound used is within the above range, it is easy to adjust the vinyl bond content in the isoprene monomer units, and problems due to deactivation of the polymerization initiator are less likely to occur. Furthermore, by increasing the amount of polar compound used within the above range, the vinyl bond content in the isoprene monomer units can be increased.

[0061] The vinyl bond content in the isoprene monomer units in polymer block (A) is preferably 5 to 90% by weight, and more preferably 5 to 80% by weight. By setting the vinyl bond content in the isoprene monomer units within the above range, the low heat generation of the resulting rubber crosslinked product can be further improved. In this specification, the vinyl bond content in the isoprene monomer units refers to the ratio of the total amount of isoprene monomer units having a 1,2-structure and isoprene monomer units having a 3,4-structure in the isoprene monomer unit.

[0062] The weight-average molecular weight (Mw) of polymer block (A), measured by gel permeation chromatography in terms of polystyrene equivalent, is preferably 500 to 15,000, more preferably 1,000 to 12,000, and particularly preferably 1,500 to 10,000. When the weight-average molecular weight of polymer block (A) is within the above range, the low heat generation of the resulting rubber crosslinked product can be further improved.

[0063] Furthermore, the molecular weight distribution of polymer block (A), expressed as the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn), is preferably 1.0 to 1.5, and more preferably 1.0 to 1.3. When the molecular weight distribution value (Mw / Mn) of polymer block (A) falls within the above range, the production of conjugated diene polymers becomes easier.

[0064] [Polymer Block (B)] Polymer block (B) may contain 50 to 100% by weight of 1,3-butadiene monomer units and 0 to 50% by weight of aromatic vinyl monomer units, but it is preferable that it contains 52 to 95% by weight of 1,3-butadiene monomer units and 5 to 48% by weight of aromatic vinyl monomer units. When the content ratio of 1,3-butadiene monomer units and aromatic vinyl monomer units is within the above range, the production of conjugated diene polymers becomes easier.

[0065] The aromatic vinyl compounds used to constitute the aromatic vinyl monomer units contained in polymer block (B) can be the same as the aromatic vinyl compounds described above, and among these, styrene is preferred.

[0066] Polymer block (B) is preferably composed of only 1,3-butadiene monomer units, or 1,3-butadiene monomer units and aromatic vinyl monomer units. However, to the extent that the essential properties of the present invention are not impaired, it may optionally contain other monomer units in addition to 1,3-butadiene monomer units, or 1,3-butadiene monomer units and aromatic vinyl monomer units. The other monomers used to constitute the other monomer units are the same compounds exemplified in polymer block (A) described above (except for 1,3-butadiene). In polymer block (B), isoprene may also be used as the other monomer. The content of other monomer units in polymer block (B) is preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 35% by weight or less.

[0067] Polymer block (B) is formed in succession with polymer block (A) by mixing polymer block (A), which has the active ends described above, with 1,3-butadiene, or a monomer containing 1,3-butadiene and an aromatic vinyl compound, and continuing the polymerization reaction. The formed polymer block (B) has active ends. On the other hand, the active ends disappear from polymer block (A).

[0068] The inert solvent used for polymerization of polymer block (A) with polymer block (A) to form polymer block (B) is not particularly limited, and the same inert solvent as described above can be used.

[0069] The amount of polymer block (A) having an active end used when forming polymer block (B) can be determined according to the desired molecular weight, but is preferably in the range of 0.1 to 5 mmol, more preferably 0.15 to 2 mmol, and even more preferably 0.2 to 1.5 mmol per 100 g of monomer containing 1,3-butadiene, or 1,3-butadiene and an aromatic vinyl compound.

[0070] The method of mixing polymer block (A) with a monomer containing 1,3-butadiene, or 1,3-butadiene and an aromatic vinyl compound, is not particularly limited. Polymer block (A) having active ends may be added to a solution of 1,3-butadiene, or a monomer containing 1,3-butadiene and an aromatic vinyl compound, or polymer block (A) having active ends may be added to a solution of polymer block (A) having active ends. From the viewpoint of controlling polymerization, the method of adding polymer block (A) having active ends to a solution of 1,3-butadiene, or a monomer containing 1,3-butadiene and an aromatic vinyl compound is preferred.

[0071] The polymerization temperature when polymerizing 1,3-butadiene, or monomers containing 1,3-butadiene and aromatic vinyl compounds, is preferably in the range of -80 to +150°C, more preferably 0 to 100°C, and even more preferably 20 to 90°C. Any polymerization method can be used, such as batch or continuous polymerization. When the polymer block (B) is a copolymer chain, batch polymerization is preferred because it allows for easier control of the randomness of the bonds.

[0072] When the polymer block (B) is used as a copolymer chain, the bonding mode of each monomer can be various, such as block-like, tapered, and random. Among these, the random bond is preferred. By using a random bond, the low heat generation of the resulting rubber crosslinked product can be further improved. When the bonding mode of 1,3-butadiene and aromatic vinyl compound is random, it is preferable to continuously or intermittently supply 1,3-butadiene or 1,3-butadiene and aromatic vinyl compound into the polymerization system to polymerize them, so that the ratio of aromatic vinyl compound to the total amount of 1,3-butadiene and aromatic vinyl compound does not become too high.

[0073] To adjust the vinyl bond content in the 1,3-butadiene monomer units in polymer block (B), it is preferable to add a polar compound to the inert solvent during polymerization, similar to how the vinyl bond content in the isoprene monomer units in polymer block (A) is adjusted. However, if a sufficient amount of the polar compound to adjust the vinyl bond content in the 1,3-butadiene monomer units in polymer block (B) has been added to the inert solvent during the preparation of polymer block (A), it is not necessary to add a polar compound again. The same polar compound as described above can be used to adjust the vinyl bond content. The amount of the polar compound used should be determined according to the desired vinyl bond content, and should be adjusted to a range of preferably 0.01 to 100 moles, more preferably 0.1 to 30 moles, per mole of polymerization initiator used in the initial polymerization reaction (polymerization reaction to form the first polymer block (A)). When the amount of polar compounds used is within this range, it is easy to adjust the vinyl bond content in the 1,3-butadiene monomer unit, and problems due to deactivation of polymerization initiators are less likely to occur.

[0074] The vinyl bond content in the 1,3-butadiene monomer units in polymer block (B) is preferably 1 to 90% by weight, more preferably 3 to 80% by weight, and particularly preferably 5 to 70% by weight. By setting the vinyl bond content in the 1,3-butadiene monomer units in polymer block (B) within the above range, the resulting rubber crosslinked product can be made to have superior low heat generation properties.

[0075] In this way, a conjugated diene polymer chain having an active end, comprising polymer block (A) and polymer block (B), can be obtained. In one embodiment of the present invention, from the viewpoint of productivity, the conjugated diene polymer chain having an active end is preferably composed of polymer block (A) - polymer block (B), and the end of polymer block (B) is the active end; however, it may have multiple polymer blocks (A), or it may have other polymer blocks. For example, a conjugated diene polymer chain having an active end such as polymer block (A) - polymer block (B) - polymer block (A) can be mentioned. In this case, the active end is formed at the end of polymer block (A) formed following polymer block (B). When forming polymer block (A) on the active end side of a conjugated diene polymer chain, the amount of isoprene used is preferably 10 to 100 moles, more preferably 15 to 70 moles, and particularly preferably 20 to 35 moles, per mole of polymerization initiator used in the first polymerization reaction (polymerization reaction to form the first polymer block (A)).

[0076] In one embodiment of the present invention, the weight ratio of polymer block (A) to polymer block (B) in a conjugated diene polymer chain having an active end (if there are multiple polymer blocks (A) and polymer blocks (B), the weight ratio is based on the total weight of each) is preferably 0.001 to 0.1, more preferably 0.003 to 0.07, and particularly preferably 0.005 to 0.05, which is (weight of polymer block (A)) / (weight of polymer block (B)).

[0077] In a conjugated diene polymer chain having active ends and polymer block (A) and polymer block (B), the content ratio of total monomer units of isoprene monomer units and 1,3-butadiene monomer units to aromatic vinyl monomer units is preferably 50 to 100% by weight of total monomer units of isoprene monomer units and 1,3-butadiene monomer units, and 0 to 50% by weight of aromatic vinyl monomer units in the conjugated diene polymer chain having active ends, and more preferably 52 to 95% by weight of total monomer units of isoprene monomer units and 1,3-butadiene monomer units, and 5 to 48% by weight of aromatic vinyl monomer units. Furthermore, in a conjugated diene polymer chain having active ends and comprising polymer block (A) and polymer block (B), the vinyl bond content in the isoprene monomer unit and the 1,3-butadiene monomer unit is preferably within the same range as the vinyl bond content in the 1,3-butadiene monomer unit in polymer block (B) described above.

[0078] [Coupling Process] In the coupling process, a coupling polymer chain is formed by reacting a conjugated diene polymer chain having an active end with a specific coupling agent (hereinafter sometimes referred to as coupling agent (C)). This coupling reaction allows a coupling structure derived from coupling agent (C) to be introduced into the conjugated diene polymer.

[0079] The coupling agent (C) is a compound having an epoxy group or a carbonyl group, and consisting only of at least one heteroatom selected from the group consisting of oxygen, nitrogen, and sulfur atoms, a carbon atom, and a hydrogen atom. Each coupling agent (C) can be used alone or in combination of two or more.

[0080] The coupling agent (C) may have only an epoxy group or a carbonyl group, or it may have both an epoxy group and a carbonyl group. It is preferable that the coupling agent (C) has an epoxy group. By using a coupling agent (C) having an epoxy group, the resulting rubber crosslinked product can be made to have superior low heat generation properties.

[0081] The number of epoxy groups and carbonyl groups (number of functional groups) per molecule of the coupling agent (C) is not particularly limited as long as it is 1 or more, but is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, and preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less.

[0082] The coupling agent (C) is preferably a polymer having an epoxy group or a carbonyl group. Such a coupling agent (C) can usually be prepared by (co)polymerizing an unsaturated monomer having 2 to 20 carbon atoms and, if necessary, by modification. For example, by (co)polymerizing a monomer having a functional group such as a glycidyl group or a carboxyl group as the unsaturated monomer, a polymer containing monomer units having an epoxy group or a carbonyl group can be obtained as the coupling agent (C). Alternatively, for example, by modifying the polymer with an epoxidizing agent, a polymer in which an epoxy group has been introduced, i.e., a polymer containing monomer units having an epoxy group, can be obtained as the coupling agent (C).

[0083] Examples of unsaturated monomers that can be used to prepare polymers as coupling agents (C) include, but are not limited to, ester compounds of acrylic acid or methacrylic acid with one-terminated alkyl-blocked polyalkylene glycols such as 1,2-butadiene, 1,3-butadiene, 1,4-isoprene, 3,4-isoprene, 1,2-isoprene, styrene, methyl methacrylate, vinyl glycidyl ether, glycidyl methacrylate, 3,4-oxycyclohexyl methacrylate, dimethylaminostyrene, 4-vinylstyrene, acrylonitrile, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, methoxypolyester glycol methacrylate, and ethoxypolyethylene polypropylene glycol methacrylate.

[0084] When modifying polymers with epoxidizing agents, for example, it is preferable to react an oxidizing agent such as peracetic acid, hydrogen peroxide, or perbenzoic acid with the double bond portion of a conjugated diene polymer (rubber or resin). The degree of epoxidation can be quantitatively determined, for example, by dissolving the sample in hydrochloric acid-dioxane and then titrating it with sodium hydroxide.

[0085] As polymers used as coupling agents (C), epoxidized polybutadiene, epoxidized polyisoprene, butadiene-dimethylaminopropyl methacrylate copolymer, epoxidized butadiene-dimethylaminomethylstyrene copolymer, poly(meth)acrylate, and polymethyl(meth)acrylate are preferred from the viewpoint of making the effects of the present invention even more pronounced.

[0086] Other coupling agents (C) besides polymers include epoxidized oils and fats such as epoxidized soybean oil and epoxidized linseed oil; alicyclic epoxy compounds such as 4,5-epoxycyclohexane-1,2-dicarboxylate di2-ethylhexyl and 4,5-epoxycyclohexane-1,2-dicarboxylate di(9,10-epoxystearyl); and amine-based aromatic epoxy compounds such as N-[2-methyl-4-(oxyranylmethoxy)phenyl]-N-(oxyranylmethyl)-oxiranmethaneamine, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane and tetraglycidyl-1,3-bisaminomethylcyclohexane.

[0087] The number-average molecular weight of the coupling agent (C) is preferably 300 or more, more preferably 400 or more, even more preferably 500 or more, particularly preferably 1,000 or more, and also preferably 100,000 or less, more preferably 10,000 or less, and even more preferably 5,000 or less, from the viewpoint of making the effects of the present invention even more pronounced.

[0088] In the coupling step, the coupling reaction in which the conjugated diene polymer chain having an active end reacts with the coupling agent (C) is preferably carried out by adding the coupling agent (C) to the polymerization solution containing the conjugated diene polymer chain having an active end obtained in the polymerization step. The coupling reaction is preferably carried out under reaction conditions of a reaction temperature of 0 to 150°C and a reaction time of 0.5 to 20 hours. The amount of coupling agent (C) used is preferably 0.01 to 10 molar equivalents, and more preferably 0.02 to 1 molar equivalent, relative to the polymerization initiator.

[0089] Furthermore, it is preferable to adjust the amount of coupling agent (C) used according to the number of epoxy groups and carbonyl groups (number of functional groups) per molecule of coupling agent (C). The total number of epoxy groups and carbonyl groups in the coupling agent used in the coupling step (product of the amount of coupling agent used and the number of functional groups) is preferably 0.1 moles or more, more preferably 0.15 moles or more, even more preferably 0.2 moles or more, preferably 1.0 mole or less, more preferably 0.9 moles or less, even more preferably 0.8 moles or less, particularly preferably 0.7 moles or less, and most preferably 0.6 moles or less.

[0090] [Modification Process] The modification process involves reacting a coupling polymer chain with a nitrogen atom-containing silane compound. This modification reaction allows for the introduction of a modified structure derived from the nitrogen atom-containing silane compound into the conjugated diene polymer.

[0091] The nitrogen atom-containing silane compound is not particularly limited as long as it has a silane structure and contains a nitrogen atom. Examples of nitrogen atom-containing silane compounds include the compound represented by general formula (1) and the compound represented by general formula (2), which will be described later. The effects of the present invention become even more pronounced when the modified structures derived from these nitrogen atom-containing silane compounds are introduced into the conjugated diene polymer of the present invention. Note that one nitrogen atom-containing silane compound may be used alone, or two or more may be used in combination.

[0092] General formula (1) is as follows. (In general formula (1), R １ is a hydrocarbyl group, and A １ is a hydrocarbyloxy group, and A ２ is a nitrogen atom-containing group, p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, and p+q+r=4.)

[0093] R in general formula (1) １ is a hydrocarbyl group, and examples thereof include an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, and an aralkyl group, with an alkyl group having 1 to 6 carbon atoms being preferred. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group, a pentyl group, and a hexyl group. Among these, a methyl group and an ethyl group are more preferred.

[0094] A in general formula (1) １ is a hydrocarbyloxy group, and examples thereof include alkoxy groups such as a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, and a tert-butoxy group; alkenyloxy groups such as a vinyloxy group and an allyloxy group; aryloxy groups such as a phenoxy group and a naphthoxy group; and aralkyloxy groups such as a benzyloxy group. Among these, from the viewpoint of reactivity, alkoxy groups and aryloxy groups are preferred, alkoxy groups are more preferred, and methoxy groups and ethoxy groups are particularly preferred.

[0095] A in the above general formula (1) ２The group is not particularly limited as long as it contains a nitrogen atom, but it is preferably an organic group having a nitrogen atom, for example, 3-aminopropyl group, 4-aminobutyl group, 3-(2-aminoethylamino)propyl group, 2-dimethylaminoethyl group, 3-dimethylaminopropyl group, 3-diethylaminopropyl group, 3-dipropylaminopropyl group, 3-dibutylaminopropyl group, 3-phenylmethylaminopropyl group, 3-(4-methylpiperazinyl)propyl group, N,N-bis(trimethylsilyl)aminopropyl group, N,N-bis(triethylsilyl)aminopropyl group, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyl group, and the like. Among these, it is preferable that the group contains a primary amino group having an active hydrogen atom and / or a secondary amino group having an active hydrogen atom, such as a 3-aminopropyl group, a 4-aminobutyl group, or a 3-(2-aminoethylamino)propyl group, in order to further improve the low heat generation of the resulting rubber crosslinked product. It is even more preferable that the group contains both a primary amino group having an active hydrogen atom and a secondary amino group having an active hydrogen atom. Note that "active hydrogen atom" refers to a hydrogen atom bonded to an atom other than a carbon atom, and it is preferable that the bond energy is lower than that of the carbon-hydrogen bond in the polymethylene chain.

[0096] In the compound represented by the general formula (1) above, p is an integer from 0 to 2, q is an integer from 1 to 3, r is an integer from 1 to 3, and p + q + r = 4. From the viewpoint of reactivity, preferably p is an integer from 0 to 1, q is an integer from 2 to 3, and r is an integer from 1 to 2, and more preferably p = 0, q = 3, r = 1. Note that when p is 2, there are 2 R in one molecule of the compound represented by general formula (1). １ The groups represented by may be the same or may be different from each other. Similarly, when q is 2 or 3, there may be multiple A groups in one molecule of the compound represented by general formula (1). １ The groups represented by may be the same or may be different from each other, and when r is 2 or 3, there may be multiple A groups in one molecule of the compound represented by general formula (1). ２The bases represented by may be the same or they may be different from each other.

[0097] Specific examples of compounds represented by general formula (1) are not particularly limited, but for example, A in general formula (1) ２ However, as a compound containing a primary amino group having an active hydrogen atom and / or a secondary amino group having an active hydrogen atom, A is a compound such as 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane, etc. ２ Examples include compounds having a 3-aminopropyl group; such as 4-aminobutyldimethylmethoxysilane, 4-aminobutylmethyldimethoxysilane, 4-aminobutyltrimethoxysilane, 4-aminobutyldimethylethoxysilane, 4-aminobutylmethyldiethoxysilane, and 4-aminobutyltriethoxysilane. ２ Examples include compounds having a 4-aminobutyl group; such as 3-(2-aminoethylamino)propyldimethylmethoxysilane, 3-(2-aminoethylamino)propylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propyldimethylethoxysilane, 3-(2-aminoethylamino)propylmethyldiethoxysilane, and 3-(2-aminoethylamino)propyltriethoxysilane. ２ Examples include compounds having a 3-(2-aminoethylamino)propyl group; and so on.

[0098] Also, A in general formula (1) ２ However, as a compound whose group is other than a group containing a primary amino group having an active hydrogen atom and / or a secondary amino group having an active hydrogen atom, A is a compound such as 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropylmethyldimethoxysilane, 3-dimethylaminopropyldimethylmethoxysilane, 3-dimethylaminopropyltriethoxysilane, 3-dimethylaminopropylmethyldiethoxysilane, and 3-dimethylaminopropyldimethylethoxysilane.２ Examples include compounds having a 3-dimethylaminopropyl group; such as 3-diethylaminopropyltrimethoxysilane, 3-diethylaminopropylmethyldimethoxysilane, 3-diethylaminopropyldimethylmethoxysilane, 3-diethylaminopropyltriethoxysilane, 3-diethylaminopropylmethyldiethoxysilane, and 3-diethylaminopropyldimethylethoxysilane. ２ Examples include compounds having a 3-diethylaminopropyl group; such as 3-dipropylaminopropyltrimethoxysilane, 3-dipropylaminopropylmethyldimethoxysilane, 3-dipropylaminopropyldimethylmethoxysilane, 3-dipropylaminopropyltriethoxysilane, 3-dipropylaminopropylmethyldiethoxysilane, and 3-dipropylaminopropyldimethylethoxysilane. ２ Examples include compounds having a 3-dipropylaminopropyl group; such as 3-dibutylaminopropyltrimethoxysilane, 3-dibutylaminopropylmethyldimethoxysilane, 3-dibutylaminopropyldimethylmethoxysilane, 3-dibutylaminopropyltriethoxysilane, 3-dibutylaminopropylmethyldiethoxysilane, and 3-dibutylaminopropyldimethylethoxysilane. ２ Examples include compounds having a 3-dibutylaminopropyl group; such as 3-phenylmethylaminopropyltrimethoxysilane, 3-phenylmethylaminopropylmethyldimethoxysilane, 3-phenylmethylaminopropyldimethylmethoxysilane, 3-phenylmethylaminopropyltriethoxysilane, 3-phenylmethylaminopropylmethyldiethoxysilane, and 3-phenylmethylaminopropyldimethylethoxysilane. ２Examples include compounds having a 3-phenylmethylaminopropyl group; such as 3-(4-methylpiperazinyl)propyltrimethoxysilane, 3-(4-methylpiperazinyl)propylmethyldimethoxysilane, 3-(4-methylpiperazinyl)propyldimethylmethoxysilane, 3-(4-methylpiperazinyl)propyltriethoxysilane, 3-(4-methylpiperazinyl)propylmethyldiethoxysilane, and 3-(4-methylpiperazinyl)propyldimethylethoxysilane. ２ Examples include compounds having a 3-(4-methylpiperazinyl)propyl group; such as N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, and N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane. ２ Examples include compounds having an N,N-bis(trimethylsilyl)aminopropyl group; such as N,N-bis(triethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(triethylsilyl)aminopropylmethyldimethoxysilane, and N,N-bis(triethylsilyl)aminopropylmethyldiethoxysilane. ２ Examples include compounds having an N,N-bis(triethylsilyl)aminopropyl group; such as N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane. ２ Examples include compounds having an N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyl group.

[0099] The general formula (2) is as follows: In general formula (2), A ３ R is a hydrocarbyloxy group, ２ R represents a hydrocarbon group which may have substituents, ３ and R ４ Each of these independently represents a hydrocarbon group which may have substituents, and R ３ and R ４ These atoms may bond to each other, forming a ring structure with the nitrogen atom to which they bond. In the case of forming such a ring structure, they may also form the ring structure with heteroatoms other than the nitrogen atom to which they bond. s is an integer between 0 and 2.

[0100] A in general formula (2) ３ The group is a hydrocarbyloxy group, and examples include alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, and tert-butoxy; alkenyloxy groups such as vinyloxy and allyloxy; allyloxy groups such as phenoxy and naphthoxy; and aralkyloxy groups such as benzyloxy. Among these, from the viewpoint of reactivity, alkoxy and allyloxy groups are preferred, alkoxy groups are more preferred, and methoxy and ethoxy groups are particularly preferred.

[0101] In general formula (2), s (that is, in general formula (2), A ３ The number of groups represented by is an integer from 0 to 2, and it is preferable that s is 2. When s in general formula (2) is 2, two A are contained in one molecule of the compound represented by general formula (2). ３ The bases represented by may be the same or they may be different from each other.

[0102] In general formula (2), R ２ R represents a hydrocarbon group which may have substituents. ２The hydrocarbon groups that can become R are not particularly limited, but include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups; alkenyl groups such as vinyl and allyl groups; alkynyl groups such as ethynyl and propynyl groups; aryl groups such as phenyl and naphthyl groups; and aralkyl groups such as benzyl groups. Among these, alkyl and aryl groups are preferred, alkyl groups are more preferred, and methyl and ethyl groups are particularly preferred. ２ The hydrocarbon group represented by may have substituents other than hydrocarbon groups, and while not particularly limited, examples of substituents include carbonyl group-containing groups such as carboxyl groups, acid anhydride groups, hydrocarbyl carbonyl groups, alkoxycarbonyl groups, and acyloxy groups, as well as epoxy groups, oxy groups, cyano groups, amino groups, halogen groups, etc. Furthermore, when s in general formula (2) is 0, two R groups are contained in one molecule of the compound represented by general formula (2). ２ The bases represented by may be the same or they may be different from each other.

[0103] In general formula (2), R ３ and R ４ Each of these independently represents a hydrocarbon group which may have substituents, and R ３ and R ４ These atoms may bond to each other to form a ring structure, and may also form a ring structure with the nitrogen atom to which they are bonded. Furthermore, when they form a ring structure, they may form a ring structure with heteroatoms other than the nitrogen atom to which they are bonded. ３ and R ４ If they do not combine with each other, R ３ and R ４The hydrocarbon groups that can become R are not particularly limited, but include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups; alkenyl groups such as vinyl and allyl groups; alkynyl groups such as ethynyl and propynyl groups; aryl groups such as phenyl and naphthyl groups; and aralkyl groups such as benzyl groups. Among these, alkyl and aryl groups are preferred, alkyl groups are more preferred, and methyl and ethyl groups are particularly preferred. ３ and R ４ When these atoms bond to each other and form a ring structure with the nitrogen atom to which they bond, R ３ and R ４ The divalent hydrocarbon group formed by the bonding of these is not particularly limited, but examples include alkylene groups such as n-butylene groups (when they form a 1-pyrrolidine group together with the nitrogen atom to which they are bonded in general formula (2)), n-pentylene groups (when they form a 1-piperidine group), and butadienylene groups (when they form a 1-pyrrole group). ３ and R ４ When these atoms bond to each other and form a ring structure with the nitrogen atoms to which they bond, a 4- to 8-membered ring structure is preferred.

[0104] Also, R ３ and R ４ The hydrocarbon group represented by may have substituents other than hydrocarbon groups, regardless of whether or not a ring structure is formed, and the substituents are not particularly limited, but examples include carbonyl group-containing groups such as carboxyl groups, acid anhydride groups, hydrocarbyl carbonyl groups, alkoxycarbonyl groups, and acyloxy groups, as well as epoxy groups, oxy groups, cyano groups, amino groups, halogen groups, etc. Furthermore, R ３ and R ４ When these atoms bond to each other and form a ring structure with the nitrogen atom to which they bond, the atoms forming that ring structure may include heteroatoms other than carbon atoms and the nitrogen atom to which they bond. Examples of such heteroatoms include nitrogen atoms and oxygen atoms.

[0105] As a compound represented by general formula (2), particularly preferred is R ３ and R ４ Examples include compounds in which hydrocarbon groups represented by are bonded to each other, forming a piperazine ring structure together with the nitrogen atoms to which they are bonded. More specifically, compounds represented by the following general formula (3) are particularly preferred. By using a compound having such a structure as represented by general formula (2), the resulting rubber crosslinked product can be made to have particularly low exothermic properties. In the above general formula (3), A ３ , R ２ , and s all represent the same things as in the general formula (2) above, R ５ This represents a hydrocarbon group.

[0106] R in general formula (3) ５ R represents a hydrocarbon group. ５ The hydrocarbon groups that can be formed are not particularly limited, but include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups; alkenyl groups such as vinyl and allyl groups; alkynyl groups such as ethynyl and propynyl groups; aryl groups such as phenyl and naphthyl groups; and aralkyl groups such as benzyl groups. Among these, alkyl and aryl groups are preferred, alkyl groups are more preferred, and methyl groups are particularly preferred.

[0107] Specific examples of compounds represented by general formula (2) include 2,2-dimethoxy-8-(4-methylpiperazinyl)methyl-1,6-dioxa-2-silacyclooctane, 2,2-diethoxy-8-(4-methylpiperazinyl)methyl-1,6-dioxa-2-silacyclooctane, 2,2-dimethoxy-8-(N,N-diethylamino)methyl-1,6-dioxa-2-silacyclooctane, and 2-methoxy-2-methyl-8-(4-methylpiperazinyl)methyl-1,6-dioxa-2-silacyclooctane. Compounds represented by general formula (2) may be used individually or in combination of two or more.

[0108] In the modification step, the amount of nitrogen atom-containing silane compound used is not particularly limited, but is preferably 0.1 mole or more, more preferably 0.2 mole or more, even more preferably 0.3 mole or more, even more preferably 0.6 mole or more, especially preferably 0.8 mole or more, particularly preferably 1 mole or more, and also preferably 5 mole or less, more preferably 4.5 mole or less, even more preferably 4 mole or less, particularly preferably 3.5 mole or less, and most preferably 3 mole or less. By using nitrogen atom-containing silane compound in such amounts, the conjugated diene polymer yields a rubber crosslinked product with particularly excellent low heat generation properties. Furthermore, from the viewpoint of achieving extremely excellent hot flow properties of the conjugated diene polymer and low heat generation properties of the rubber crosslinked product, it is preferable that the amount of nitrogen atom-containing silane compound used is more than 1 mole, more preferably 1.3 mole or more, and even more preferably 1.6 mole or more, per mole of polymerization initiator used in the polymerization step.

[0109] In the modification step, a modifying agent other than the nitrogen atom-containing silane compound may be further reacted before or after the reaction of the coupling polymer chain with the nitrogen atom-containing silane compound. In particular, it is preferable to react the coupling polymer chain with a modifying agent other than the nitrogen atom-containing silane compound, and then further react the coupling polymer chain that has been reacted with the modifying agent with the nitrogen atom-containing silane compound. Through this modification reaction, a modified structure derived from the nitrogen atom-containing silane compound can be introduced into the conjugated diene polymer via a modified structure derived from the modifying agent other than the nitrogen atom-containing silane compound.

[0110] When a nitrogen atom-containing silane compound is added to a polymerization solution containing a coupling polymer chain (which may be a coupling polymer chain that has been reacted with a modifying agent other than a nitrogen atom-containing silane compound), the active site of the coupling polymer chain reacts with the compound represented by the nitrogen atom-containing silane compound.

[0111] The reaction between a coupling polymer chain (which may be a coupling polymer chain reacted with a modifying agent other than a nitrogen atom-containing silane compound) and a nitrogen atom-containing silane compound typically proceeds in which a detachable group, such as an alkoxy group, is detached from the nitrogen atom-containing silane compound and reacts with the active site of the coupling polymer chain, forming a bond between the coupling polymer chain and the silicon atom in the nitrogen atom-containing silane compound.

[0112] The method for reacting a coupling polymer chain (which may be a coupling polymer chain reacted with a modifying agent other than a nitrogen atom-containing silane compound) with a nitrogen atom-containing silane compound is not particularly limited, but one example is mixing them in solvents in which each can dissolve. The solvent used in this process can be one of those exemplified as an inert solvent used in the polymerization step. In this case, it is convenient and preferable to add the nitrogen atom-containing silane compound to the polymerization solution containing the coupling polymer chain. Furthermore, it is preferable to dissolve the nitrogen atom-containing silane compound in an inert solvent before adding it to the polymerization system, and the solution concentration is preferably in the range of 1 to 50% by weight. The reaction temperature is not particularly limited, but is usually 0 to 120°C, and the reaction time is not particularly limited, but is usually 1 minute to 1 hour.

[0113] Other than nitrogen atom-containing silane compounds, polyorganosiloxanes are preferred as modifying agents, and polyorganosiloxanes represented by the following general formula (4) are more preferred. In general formula (4), R ２１ ~R ２８ This is an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and these may be the same or different from each other. ２１ and X ２４ This group is selected from the group consisting of C1-C6 alkyl groups, C6-C12 aryl groups, C1-C5 alkoxy groups, and C4-C12 groups containing epoxy groups, and these groups may be identical or different from each other. ２２ X is a group having 4 to 12 carbon atoms that contains an alkoxy group having 1 to 5 carbon atoms or an epoxy group, and there are multiple X２２ They may be identical or different from one another. ２３ This is a group containing 2 to 20 repeating units of alkylene glycol, X ２３ When there are multiple values, they may be identical or different from one another. m is an integer between 3 and 200, n is an integer between 0 and 200, k is an integer between 0 and 200, and m + n + k is 3 or greater.

[0114] In general formula (4), R in general formula (4) ２１ ~R ２８ , X ２１ and X ２４ Examples of C1-C6 alkyl groups that can constitute the compound include methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and cyclohexyl groups. Examples of C6-C12 aryl groups include phenyl and methylphenyl groups. Among these, methyl and ethyl groups are preferred from the viewpoint of ease of production of the polyorganosiloxane represented by general formula (4).

[0115] In general formula (4), X ２１ , X ２２ and X ２４ Examples of alkoxy groups having 1 to 5 carbon atoms that can constitute the compound include methoxy, ethoxy, propoxy, isopropoxy, and butoxy groups. Among these, methoxy and ethoxy groups are preferred from the viewpoint of ease of production of the polyorganosiloxane represented by general formula (4).

[0116] In general formula (4), X ２１ , X ２２ and X ２４ Examples of C4-C12 groups containing epoxy groups that can constitute this include the group represented by the following general formula (5): -Z ３ -Z ４ -E ２ (5)

[0117] In general formula (5), Z ３ is an alkylene group having 1 to 10 carbon atoms, or an alkylarylene group, Z ４is a methylene group, a sulfur atom, or an oxygen atom, and E ２ is a hydrocarbon group having 2 to 10 carbon atoms and having an epoxy group.

[0118] As the group represented by general formula (5), Z ４ is preferably an oxygen atom, more preferably Z ４ is an oxygen atom, and E ２ is a glycidyl group, still more preferably Z ３ is an alkylene group having 1 to 3 carbon atoms, Z ４ is an oxygen atom, and E ２ is a glycidyl group, which is particularly preferred.

[0119] In general formula (4), X ２１ and X ２４ are preferably, among the above, a C4-C12 group containing an epoxy group, or a C1-C6 alkyl group. Further, X ２２ is preferably, among the above, a C4-C12 group containing an epoxy group. Furthermore, it is more preferred that X ２１ and X ２４ are alkyl groups having 1 to 6 carbon atoms, and X ２２ is a C4-C12 group containing an epoxy group.

[0120] In general formula (4), X ２３ , that is, as a group containing a repeating unit of 2 to 20 alkylene glycols, a group represented by the following general formula (6) is preferred.

[0121]

[0122] In general formula (6), t is an integer of 2 to 20, X ２５ is an alkylene group having 2 to 10 carbon atoms or an alkylarylene group, R ２９ is a hydrogen atom or a methyl group, X ２６ is an alkoxy group having 1 to 10 carbon atoms or an aryloxy group. Among these, it is preferred that t is an integer of 2 to 8, X ２５ is an alkylene group having 3 carbon atoms, R ２９ is a hydrogen atom, and X ２６ is a methoxy group.

[0123] In general formula (4), m is an integer between 3 and 200, preferably between 20 and 150, and more preferably between 30 and 120. When m is 3 or greater, the hot flow properties of the conjugated diene polymer are further improved. When m is 200 or less, the production of the polyorganosiloxane represented by general formula (4) becomes easier, and its viscosity does not become too high, making it easier to handle.

[0124] In general formula (4), n is an integer from 0 to 200, preferably an integer from 0 to 150, more preferably an integer from 0 to 120. k is an integer from 0 to 200, preferably an integer from 0 to 150, more preferably an integer from 0 to 130. The sum of m, n, and k is 3 or more, preferably 3 to 400, more preferably 20 to 300, and particularly preferably 30 to 250. When the sum of m, n, and k is 3 or more, the reaction between the polyorganosiloxane represented by general formula (4) and the coupling polymer chain proceeds easily. Furthermore, when the sum of m, n, and k is 400 or less, the production of the polyorganosiloxane represented by general formula (4) itself becomes easier, and its viscosity does not become too high, making it easy to handle.

[0125] The amount of modifying agent other than nitrogen atom-containing silane compounds used in the modification step is not particularly limited. When a polyorganosiloxane represented by general formula (4) is used as a modifying agent other than nitrogen atom-containing silane compounds, the amount used is preferably such that the amount of reactive groups of the polyorganosiloxane side chains (such as alkoxy groups or epoxy groups in general formula (4)) is 0.1 to 3 moles, more preferably 0.2 to 2 moles, per mole of polymerization initiator used in the polymerization step.

[0126] The method for reacting the coupling polymer chain with a modifying agent other than a nitrogen atom-containing silane compound is not particularly limited, but one example is mixing them in solvents in which each can be dissolved. The solvent used in this process can be one of those exemplified as an inert solvent used in the polymerization step. Furthermore, a simple and preferred method is to add the modifying agent other than a nitrogen atom-containing silane compound to the polymerization solution containing the coupling polymer chain. In this case, it is preferable to dissolve the modifying agent other than a nitrogen atom-containing silane compound in an inert solvent and add it to the polymerization system, with the solution concentration preferably in the range of 1 to 50% by weight. The reaction temperature is not particularly limited, but is usually 0 to 120°C, and the reaction time is not particularly limited, but is usually 1 minute to 1 hour.

[0127] In the modification step, the coupling polymer chain is reacted with a nitrogen atom-containing silane compound (and any other modifying agent used as needed), and then, if necessary, a known polymerization inhibitor is added to deactivate the reaction system. Furthermore, if desired, antioxidants such as phenolic stabilizers, phosphorus stabilizers, and sulfur stabilizers, as well as crummaging agents and scale inhibitors, are added to the reaction solution. Subsequently, the polymerization solvent is separated from the reaction solution by direct drying or steam stripping, and the conjugated diene polymer is recovered. Alternatively, before separating the polymerization solvent from the reaction solution, a spreading oil may be mixed with the polymerization solution, and the conjugated diene polymer may be recovered as oil-spread rubber.

[0128] Examples of spreading oils used when recovering conjugated diene polymers as oil-expandable rubber include paraffinic, aromatic, and naphthenic petroleum-based softeners, plant-based softeners, and fatty acids. When using petroleum-based softeners, it is preferable that the content of polycyclic aromatics extracted by the IP346 method (the testing method of THE INSTITUTE PETROLEUM in the UK) is less than 3%. When using a spreading oil, the amount used is preferably 5 to 100 parts by weight, more preferably 10 to 60 parts by weight, and even more preferably 20 to 50 parts by weight, per 100 parts by weight of the conjugated diene polymer.

[0129] The conjugated diene polymer obtained by the above manufacturing method usually has a coupling structure derived from the coupling agent (C) and a modified structure derived from the nitrogen atom-containing silane compound introduced into it. However, within a range that does not hinder the effects of the present invention, it may also contain, for example, a polymer with only a coupling structure derived from the coupling agent (C) introduced, a polymer with only a modified structure derived from the nitrogen atom-containing silane compound introduced, or a polymer with neither structure introduced.

[0130] <Rubber Composition> The rubber composition of the present invention is a composition containing the conjugated diene polymer of the present invention described above and a filler.

[0131] The rubber composition of the present invention preferably contains silica as a filler. Examples of silica include dry-process white carbon, wet-process white carbon, colloidal silica, and precipitated silica. Among these, wet-process white carbon, which mainly consists of hydrated silicic acid, is preferred. Alternatively, a carbon-silica dual-phase filler, in which silica is supported on the surface of carbon black, may be used. These silicas can be used individually or in combination of two or more. The nitrogen adsorption specific surface area of ​​the silica used (measured by the BET method according to ASTM D3037-81) is preferably 50 to 300 m². ２ / g, more preferably 80 to 220m ２ / g, particularly preferably 100 to 170m ２ The amount is / g. Furthermore, the pH of the silica is preferably between 5 and 10.

[0132] The amount of silica in the rubber composition of the present invention is 10 to 200 parts by weight, preferably 30 to 150 parts by weight, and more preferably 50 to 130 parts by weight, per 100 parts by weight of the rubber component in the rubber composition. By setting the amount of silica within the above range, the processability of the rubber composition is improved, and the low heat generation of the resulting crosslinked rubber can be further enhanced.

[0133] The rubber composition of the present invention may further contain a silane coupling agent from the viewpoint of further improving low heat generation. The silane coupling agent is not particularly limited, and various silane coupling agents can be used, but in the present invention, sulfide-based, mercapto-based, protected mercapto-based (for example, those having a carbonylthio group), thiocyanate-based, vinyl-based, amino-based, methacrylate-based, glycidoxy-based, nitro-based, epoxy-based, or chloro-based silane coupling agents can be suitably used. For example, bis(3-(triethoxysilyl)propyl) disulfide, bis(3-triethoxysilylpropyl) trisulfide, bis(3-(triethoxysilyl)propyl) tetrasulfide, γ-mercaptopropyltriethoxysilane, 3-[ Examples include ethoxybis(3,6,9,12,15-pentaoxacosan-1-yloxy)silyl]-1-propanthol, 3-octanoylthio-1-propyl-triethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, γ-trimethoxysilylpropylbenzothiazyltetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-thiocyanatetopropyltriethoxysilane, vinyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 3-trimethoxysilylpropyl methacrylate monosulfide, γ-glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-chloropropyltrimethoxysilane. In addition, NXT-Z100, NXT-Z30, NXT-Z45, NXT-Z60, NXT-Z45, and NXT from Momentive Performance Materials, and Si69, Si75, and VP Si363 from Evonik can also be used. These silane coupling agents can be used individually or in combination of two or more. The amount of silane coupling agent to be blended is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight, per 100 parts by weight of silica.

[0134] The rubber composition of the present invention may contain carbon as a filler. Examples of carbon include furnace black, acetylene black, thermal black, channel black, and graphite. Among these, furnace black is preferred. These carbon blacks can be used individually or in combination of two or more. The amount of carbon black added is usually 120 parts by weight or less per 100 parts by weight of the rubber component in the rubber composition.

[0135] The method for adding the filler to the rubber component containing the conjugated diene polymer of the present invention is not particularly limited, and methods such as adding it to a solid rubber component and kneading it (dry kneading method) or adding it to a solution containing the conjugated diene polymer and solidifying and drying it (wet kneading method) can be applied.

[0136] The rubber composition of the present invention preferably further contains a crosslinking agent. Examples of crosslinking agents include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyvalent amine compounds, and alkylphenol resins having methylol groups. Among these, sulfur is preferably used. The amount of crosslinking agent added is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 4 parts by weight, per 100 parts by weight of the rubber component in the rubber composition.

[0137] In addition to the above components, the rubber composition of the present invention may contain, in accordance with conventional methods, compounding agents such as crosslinking promoters, crosslinking activators, antioxidants, fillers (excluding the above-mentioned silica and carbon black), surfactants, process oils, plasticizers, lubricants, tackifiers, and compatibilizers in the required amounts.

[0138] When sulfur or a sulfur-containing compound is used as a crosslinking agent, it is preferable to use a crosslinking accelerator and a crosslinking activator in combination. Examples of crosslinking accelerators include sulfenamide-based crosslinking accelerators; guanidine-based crosslinking accelerators; thiourea-based crosslinking accelerators; thiazole-based crosslinking accelerators; thiram-based crosslinking accelerators; dithiocarbamate-based crosslinking accelerators; xanthogenic acid-based crosslinking accelerators; and the like. Among these, those containing sulfenamide-based crosslinking accelerators are preferred. These crosslinking accelerators can be used individually or in combination of two or more. The amount of crosslinking accelerator added is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 4 parts by weight, per 100 parts by weight of the rubber component in the rubber composition.

[0139] Examples of crosslinking activators include higher fatty acids such as stearic acid; zinc oxide; and the like. These crosslinking activators can be used individually or in combination of two or more. The amount of crosslinking activator added is preferably 0.05 to 20 parts by weight, and particularly preferably 0.5 to 15 parts by weight, per 100 parts by weight of the rubber component in the rubber composition.

[0140] The rubber composition of the present invention may contain resins. Examples include C5 petroleum resins, C5 / C9 petroleum resins, C9 petroleum resins, dicyclopentadiene resins, terpene resins, terpene phenol resins, aromatically modified terpene resins, alkylphenol-acetylene resins, rosin resins, rosin ester resins, indene resins, C9 resins containing indene, α-methylstyrene-indene copolymer resins, coumaron-indene resins, farnesene resins, and polylimonene resins. These resins may be modified or hydrogenated. These resins can be used individually or in combination of two or more. The amount of resin added is preferably 0.1 to 80 parts by weight, and particularly preferably 1 to 70 parts by weight, per 100 parts by weight of the rubber component in the rubber composition.

[0141] The rubber composition of the present invention may contain other rubbers besides the conjugated diene polymer of the present invention described above. Examples of these other rubbers include natural rubber, polyisoprene rubber, emulsion-polymerized styrene-butadiene copolymer rubber, solution-polymerized styrene-butadiene copolymer rubber, polybutadiene rubber (which may be high-cis-BR or low-cis-BR; it may also be polybutadiene rubber containing crystalline fibers made of 1,2-polybutadiene polymer), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, and acrylonitrile-styrene-butadiene copolymer rubber, excluding the conjugated diene polymer of the present invention described above. Among these, natural rubber, polyisoprene rubber, polybutadiene rubber, and solution-polymerized styrene-butadiene copolymer rubber are preferred. These rubbers can be used individually or in combination of two or more.

[0142] In the rubber composition of the present invention, the conjugated diene polymer of the present invention preferably accounts for 10 to 100% by weight of the rubber component in the rubber composition, and particularly preferably accounts for 50 to 100% by weight. By including the conjugated diene polymer of the present invention in the rubber component in such proportions, the effects of the present invention become even more pronounced.

[0143] To obtain the rubber composition of the present invention, each component can be kneaded according to a conventional method. For example, the components, excluding heat-unstable components such as crosslinking agents and crosslinking accelerators, can be kneaded with a conjugated diene polymer, and then the heat-unstable components such as crosslinking agents and crosslinking accelerators can be mixed into the kneaded mixture to obtain the desired composition. The kneading temperature for the components, excluding heat-unstable components, and the conjugated diene polymer is preferably 80 to 200°C, more preferably 120 to 180°C, and the kneading time is preferably 30 seconds to 30 minutes. Furthermore, the mixing of the kneaded mixture with the heat-unstable components is usually carried out after cooling to 100°C or below, preferably 80°C or below.

[0144] <Cross-linked rubber product> The cross-linked rubber product of the present invention is obtained by cross-linking the rubber composition of the present invention described above. The cross-linked rubber product of the present invention can be manufactured by using the rubber composition of the present invention and, for example, molding it using a molding machine corresponding to the desired shape, such as an extruder, injection molding machine, compressor, or roll, and then heating it to perform a cross-linking reaction and fix the shape as a cross-linked product. In this case, cross-linking may be performed after molding or simultaneously with molding. The molding temperature is usually 10 to 200°C, preferably 25 to 120°C. The cross-linking temperature is usually 100 to 200°C, preferably 130 to 190°C, and the cross-linking time is usually 1 minute to 24 hours, preferably 2 minutes to 12 hours, and particularly preferably 3 minutes to 6 hours.

[0145] Furthermore, depending on the shape and size of the crosslinked rubber material, even if the surface is crosslinked, the interior may not be sufficiently crosslinked. In such cases, further heating may be performed to carry out secondary crosslinking.

[0146] For heating, you can appropriately select a common method used for crosslinking rubber, such as press heating, steam heating, oven heating, or hot air heating.

[0147] <Applications> The conjugated diene polymer, rubber composition, and rubber crosslinked product of the present invention can be used in a variety of applications, such as: materials for various parts of a tire, including the cap tread, base tread, carcass, sidewall, and bead; materials for hoses, belts, mats, vibration-damping rubber, and other various industrial products; impact resistance modifiers for resins; resin film cushioning agents; shoe soles; rubber shoes; golf balls; toys; and more.

[0148] In particular, the conjugated diene polymer of the present invention exhibits excellent hot-flow properties, which effectively prevents the adhesion of crumbs formed by solidification, and provides a rubber crosslinked material with excellent low heat generation, making it suitable for use in tire manufacturing. Specifically, the conjugated diene polymer, rubber composition, and rubber crosslinked material of the present invention can be suitably used in various tire parts such as the tread, carcass, sidewall, and bead in all-season tires, high-performance tires, and studless tires, and is particularly suitable for use as a tread material in fuel-efficient tires due to its excellent low heat generation properties.

[0149] The present invention will be described below based on more detailed examples, but the present invention is not limited to these examples. In the following, "parts" refers to weight unless otherwise specified. Furthermore, the tests and evaluations were carried out according to the following.

[0150] [Mooney viscosity (ML)] Mooney viscosity (ML) of conjugated diene polymers １＋４ The temperature (at 100°C) was measured according to JIS K6300-1.

[0151] [Storage Shear Modulus (G')] The storage shear modulus (G') of the conjugated diene polymer was measured using a rubber process analyzer PREMIER® RPA (manufactured by Alpha Technologies) on a bale of approximately 7 g of the conjugated diene polymer, under the conditions of a temperature of 100°C, a frequency of 0.05 Hz, and a dynamic strain of 10%.

[0152] [Weight-average molecular weight (Mw)] The weight-average molecular weight (Mw) of the conjugated diene polymer was determined by obtaining a chart based on the molecular weight in polystyrene terms using gel permeation chromatography (GPC), and then determining the weight-average molecular weight (Mw) based on the obtained chart. The specific measurement conditions for gel permeation chromatography were as follows: Measuring instrument: High-performance liquid chromatograph (Tosoh Corporation, product name "HLC-8320GPC") Column: Two polystyrene columns manufactured by Tosoh Corporation, product name "GMH-HR-H", were connected in series. Detector: Differential refractometer (RI) Eluent: Tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, special grade, containing stabilizer) Column temperature: 40°C Flow rate: 1.0 mL / min Sample solution concentration: 1.0 mg / mL Sample solution injection volume: 5 μL Molecular weight calculation method: Fourteen types of standard polystyrene with known molecular weights were analyzed by GPC, and the common logarithm of the molecular weight against the retention time of each standard polystyrene was plotted. A fifth-order polynomial approximation formula was calculated from the obtained plots and used as a calibration curve. Conjugated diene polymers were analyzed, and the polystyrene-equivalent molecular weight of the conjugated diene polymers was determined from the obtained retention time and the precaution curve. Standard polystyrene: PL2012-1001, P2012-2001, P2012-5001, PL2012-7001, PL2012-9001, PL2013-2001, PL2013-4001, PL2013-6001, PL2013-7001, PL2013-8001, PL2013-9001, PL2014-0001, PL2014-1001, PL2014-5001 (all manufactured by Agilent Technologies)

[0153] [Styrene unit content and vinyl bond content in conjugated diene monomer units] The styrene unit content and the vinyl bond content in conjugated diene monomer units are as follows: １ Measured by 1H-NMR.

[0154] [Ratio of individual styrene units and styrene blocks in a styrene unit] The ratio of individual styrene units and styrene blocks in a styrene unit was determined using the following references, with deuterated chloroform as the solvent. １ The result was obtained by H-NMR. １The 6.0–7.7 ppm peaks in the H-NMR spectrum were identified as styrene-derived peaks, and of these, the 6.0–7.0 ppm peaks were identified as styrene block-derived peaks. The ratio of the styrene block-derived peak area to the styrene-derived peak area was calculated, and this value was multiplied by 2.5 and expressed as a percentage to determine the proportion of styrene block. １ Of the 1H-NMR spectra, peaks from 6.9 to 7.0 ppm were considered to originate from styrene blocks (2-3 chains). The ratio of the peak area originating from styrene blocks (2-3 chains) to the peak area originating from styrene was calculated, and this value was multiplied by 2.5 and expressed as a percentage to determine the proportion of styrene blocks (2-3 chains). １ In the 1H-NMR spectrum, peaks between 6.0 and 6.9 ppm were considered to originate from styrene blocks (four or more chains). The ratio of the peak area originating from styrene blocks (four or more chains) to the peak area originating from styrene was calculated, and this value was multiplied by 2.5 and expressed as a percentage to determine the proportion of styrene blocks (four or more chains). Reference: Sardelis, K. Michels, H. J. Allen, G. Polymer, 1984, 25, 1011

[0155] [Hot Flow Properties of Conjugated Diene Polymers (Adhesion of Clams Formed by Solidification)] For approximately 7 g of a bale of conjugated diene polymer, tanδ was measured using a rubber process analyzer PREMIER® RPA (manufactured by Alpha Technologies) under the conditions of a temperature of 100°C, a frequency of 0.05 Hz, and a dynamic strain of 10%. The tanδ values ​​for the Examples and Comparative Examples 1-2 are shown as an index with the measured value of Comparative Example 3 set to 100. The smaller this index, the better the hot flow properties of the conjugated diene polymer.

[0156] [Low Heat Generation Properties of Crosslinked Rubber Materials] Test specimens of crosslinked rubber materials with a length of 50 mm, a width of 12.7 mm, and a thickness of 2 mm were prepared. Using an ARES-G2 manufactured by T.A. Instruments, the tanδ of the crosslinked rubber material test specimens was measured under the conditions of a temperature of 60°C, a frequency of 10 Hz, and a dynamic strain of 2.5%. The tanδ values ​​for the Examples and Comparative Examples 1 and 2 are shown as an index with the measured value of Comparative Example 3 set to 100. The smaller this index, the better the low heat generation properties of the crosslinked rubber material can be judged to be.

[0157] In the examples and comparative examples, the following coupling agents and modifiers were used: Coupling agent C1: Epoxylated 1,2-polybutadiene (number average molecular weight 1000, number of epoxy groups per molecule 5) Coupling agent C2: N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane (number average molecular weight 480, number of epoxy groups per molecule 4) Coupling agent C3: Epoxylated linseed oil (number average molecular weight 1000, total number of epoxy and carbonyl groups per molecule 9) Coupling agent C4: Polymethyl methacrylate (number average molecular weight 2500, number of carbonyl groups per molecule 15) Coupling agent C5: Tin tetrachloride Polyorganosiloxane: Polyorganosiloxane represented by the following formula (7) (modifier 1) Modifier (a): 3-aminopropyltrimethoxysilane Modifier (b): 3-diethylaminopropyltrimethoxysilane Modifier (c): 2,2-dimethoxy-8-(4-methylpiperazinyl)methyl-1,6-dioxa-2-silacyclooctane Modifier (d): 3-(2-aminoethylamino)propyltrimethoxysilane

[0158] [Example 1] (Polymerization process) 70.0 g of cyclohexane and 0.77 mmol of tetramethylethylenediamine were added to an 800 ml ampoule bottle purged with nitrogen, and then 7.69 mmol of n-butyllithium (an amount such that the amount of tetramethylethylenediamine as a polar compound was 0.10 moles per mole of n-butyllithium) was added. Next, 27.9 g of isoprene and 2.1 g of styrene were slowly added, and the mixture was reacted in the ampoule bottle at 50°C for 120 minutes to obtain a polymer block (A) having active ends. The weight-average molecular weight (Mw) of this polymer block (A) was 6,500, the molecular weight distribution (Mw / Mn) was 1.10, the styrene monomer unit content was 7.0% by weight, the isoprene monomer unit content was 93.0% by weight, and the vinyl bond content was 7.7% by weight.

[0159] In an autoclave equipped with a stirrer, 4000 g of cyclohexane, 2.69 mmol of tetramethylethylenediamine, 474 g of 1,3-butadiene, and 126 g of styrene were charged under a nitrogen atmosphere. The entire amount of the polymer block (A) with active ends obtained above was then added, and polymerization was started at 50°C (the amount of tetramethylethylenediamine present in the reaction system as a polar compound was 0.45 moles per mole of n-butyllithium used). Ten minutes after the start of polymerization, 376 g of 1,3-butadiene and 24 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 75°C. After the continuous addition was completed, the polymerization reaction was continued for another 10 minutes to obtain a polymerization solution containing conjugated diene polymer chains with active ends. The polymerization conversion rate was in the range of 95% to 100%.

[0160] (Coupling step) To the polymerization solution containing the conjugated diene polymer chain having an active end obtained above, 0.57 mmol of coupling agent C1 (an amount equivalent to 0.074 times the molar amount of n-butyllithium used) was added and the mixture was reacted for 60 minutes to obtain a polymerization solution containing the coupling polymer chain.

[0161] (Modification step) To the polymerization solution containing the coupling polymer chain obtained above, 2.44 g of polyorganosiloxane was added in the form of a 40% by weight xylene solution (X of polyorganosiloxane). ２ An amount equivalent to 0.6 times the molar amount of n-butyllithium used was added and the mixture was reacted for 30 minutes. Next, 7.69 mmol of denaturant (a) (equivalent to 1.0 times the molar amount of n-butyllithium used) was added and the mixture was reacted for 10 minutes. Then, methanol equivalent to 2 times the molar amount of n-butyllithium used was added as a polymerization inhibitor to obtain a solution containing the conjugated diene polymer. To this solution, 0.15 parts of Irganox 1520L (manufactured by BASF) was added as an antioxidant per 100 parts of the conjugated diene rubber, the solvent was removed by steam stripping, and the mixture was vacuum dried at 60°C for 24 hours to obtain a solid conjugated diene polymer. The obtained conjugated diene polymers were measured and evaluated according to the method described above, including Mooney viscosity (ML), storage shear modulus (G'), weight-average molecular weight (Mw), styrene unit content, vinyl bond content in conjugated diene monomer units, proportion of styrene individual units and styrene blocks in styrene units, and hot flow properties. The results are shown in Table 1.

[0162] [Production of rubber composition and crosslinked rubber product] In a 250 ml Banbury mixer, 100 parts of a conjugated diene polymer are kneaded for 30 seconds, followed by 50 parts of silica (Solvay, trade name "Zeosil 1165MP") and process oil (ENEOS, trade name "Aromax"). Twenty parts of T-DAE and 6.0 parts of the silane coupling agent: bis(3-(triethoxysilyl)propyl) tetrasulfide (manufactured by Evonik, trade name "Si69") were added, and the mixture was kneaded for 1.5 minutes starting at 110°C. Then, 25 parts of silica (manufactured by Solvay, trade name "Zeosil 1115MP"), 3 parts of zinc oxide, 2 parts of stearic acid, and 2 parts of the antioxidant: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (manufactured by Ouchi Shinko Chemical Industry, trade name "Nocrac 6C") were added, and the mixture was kneaded for a further 2.5 minutes, after which the mixture was discharged from the mixer. The temperature of the mixture at the end of kneading was 150°C. After the mixture was cooled to room temperature, it was kneaded again in a Bravender-type mixer for 2 minutes starting at 110°C, and then the mixture was discharged from the mixer. Next, in an open roll oven at 50°C, a mixture of 1.4 parts sulfur, 1.2 parts crosslinking accelerator: N-tert-butyl-2-benzothiazolyl sulfenamide (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noxellar NS-P"), and 1.2 parts 1,3-diphenylguanidine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noxellar D") was added to the obtained kneaded mixture and a sheet-like rubber composition was extracted. This rubber composition was press-crosslinked at 160°C for 20 minutes to prepare test specimens of crosslinked rubber. The low heat generation properties of the test specimens of crosslinked rubber were evaluated according to the method described above. The results are shown in Table 1.

[0163] [Example 1-1] Except for changing the amount of modifying agent (a) to 3.85 mmol (an amount equivalent to 0.5 moles of n-butyllithium used) in the modification step, a conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 1. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0164] [Example 1-2] Except for changing the amount of modifying agent (a) to 15.38 mmol (an amount equivalent to 2.0 times the molar amount of n-butyllithium used) in the modification step, a conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 1. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0165] [Examples 1-3] Except for changing the amount of modifying agent (a) to 23.07 mmol (an amount equivalent to 3.0 times the molar amount of n-butyllithium used) in the modification step, a conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 1. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0166] [Example 2] Except that in the modification step, 7.69 mmol of modification agent (b) (an amount equivalent to 1.0 mole of n-butyllithium used) was used instead of modification agent (a), the same procedure as in Example 1 was followed to obtain a conjugated diene polymer, a rubber composition, and a rubber crosslinked product. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0167] [Example 3] Except that in the modification step, 7.69 mmol of modification agent (c) (an amount equivalent to 1.0 mole of n-butyllithium used) was used instead of modification agent (a), the same procedure as in Example 1 was followed to obtain a conjugated diene polymer, a rubber composition, and a rubber crosslinked product. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0168] [Example 4] Except that in the modification step, 7.69 mmol of modifying agent (d) (an amount equivalent to 1.0 mole of n-butyllithium used) was used instead of modifying agent (a), the same procedure as in Example 1 was followed to obtain a conjugated diene polymer, a rubber composition, and a rubber crosslinked product. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0169] [Example 5] In the coupling step, 0.58 mmol of coupling agent C2 (an amount equivalent to 0.075 times the molar amount of n-butyllithium used) was used instead of coupling agent C1. Except for this, the procedure was the same as in Example 3 to obtain a conjugated diene polymer, a rubber composition, and a rubber crosslinked product. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0170] [Example 6] In the coupling step, 0.21 mmol of coupling agent C3 (an amount equivalent to 0.027 times the molar amount of n-butyllithium used) was used instead of coupling agent C1. Except for this, the procedure was the same as in Example 2 to obtain a conjugated diene polymer, a rubber composition, and a rubber crosslinked product. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0171] [Example 7] In the coupling step, 0.15 mmol of coupling agent C4 (an amount equivalent to 0.02 times the molar amount of n-butyllithium used) was used instead of coupling agent C1. Except for this, the procedure was the same as in Example 4 to obtain a conjugated diene polymer, a rubber composition, and a rubber crosslinked product. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0172] [Example 8] Except for changing the amount of coupling agent C1 used in the coupling step to 0.28 mmol (an amount equivalent to 0.037 times the molar amount of n-butyllithium used), a conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 2. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0173] [Example 8-1] Except that the amount of coupling agent C1 was changed to 0.88 mmol (equivalent to 0.114 times the molar amount of n-butyllithium used) in the coupling step, and the amount of modifying agent (b) was changed to 23.07 mmol (equivalent to 3 times the molar amount of n-butyllithium used) in the modification step, a conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 1. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0174] [Example 8-2] Except that the amount of coupling agent C1 was changed to 0.88 mmol (equivalent to 0.114 times the molar amount of n-butyllithium used) in the coupling step, and the amount of modifying agent (b) was changed to 15.38 mmol (equivalent to 2 times the molar amount of n-butyllithium used) in the modification step, a conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 1. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0175] [Example 9] Except for changing the amount of modifying agent (b) to 3.85 mmol (an amount equivalent to 0.5 times the molar amount of n-butyllithium used) in the modification step, a conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 2. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0176] [Example 10] Except for changing the amount of modifying agent (d) to 3.85 mmol (an amount equivalent to 0.5 times the molar amount of n-butyllithium used) in the modification step, a conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 4. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0177] [Example 11] To the polymerization solution containing the coupling polymer chain obtained in the same manner as in Example 1, 7.69 mmol of the modifying agent (c) (an amount equivalent to 1.0 mole of the n-butyllithium used) was added and the mixture was reacted for 10 minutes. Thereafter, methanol equivalent to 2 moles of the n-butyllithium used was added as a polymerization inhibitor to obtain a solution containing the conjugated diene polymer. Except for using the obtained solution containing the conjugated diene polymer, a conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 1. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0178] [Example 12] In the polymerization step, 7.69 mmol of n-butyllithium (represented as "BuLi" in Table 2) was used instead of the polymer block (A) having an active end, except that the procedure was the same as in Example 3 to obtain a conjugated diene polymer, a rubber composition, and a rubber crosslinked product. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0179] [Comparative Example 1] A polymerization solution containing a coupling polymer chain was obtained in the same manner as in Example 12, except that 1.12 mmol of coupling agent C1 (an amount equivalent to 0.146 times the molar amount of n-butyllithium used) was used in the coupling step. A methanol equivalent to 2 times the molar amount of n-butyllithium used was added to the obtained polymerization solution containing the coupling polymer chain as a polymerization inhibitor to obtain a solution containing a conjugated diene polymer. A conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 1, except that the obtained solution containing the conjugated diene polymer was used. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0180] [Comparative Example 2] To a polymerization solution containing a conjugated diene polymer chain having an active end obtained in the same manner as in Example 12, 2.44 g of polyorganosiloxane was added in the form of a 40% by weight xylene solution (X of polyorganosiloxane). ２An amount equivalent to 0.6 times the molar amount of n-butyllithium used was added and the mixture was reacted for 30 minutes. Next, 7.69 mmol of denaturant (b) (equivalent to 1.0 times the molar amount of n-butyllithium used) was added and the mixture was reacted for 10 minutes. Then, methanol equivalent to 2 times the molar amount of n-butyllithium used was added as a polymerization inhibitor to obtain a solution containing the conjugated diene polymer. The conjugated diene polymer, rubber composition, and rubber crosslinked product were obtained in the same manner as in Example 1, except that the obtained solution containing the conjugated diene polymer was used. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0181] [Comparative Example 3] A polymerization solution containing a conjugated diene polymer chain having an active end, obtained in the same manner as in Example 1, was reacted with 0.58 mmol of coupling agent C5 for 60 minutes to obtain a polymerization solution containing a coupling polymer chain.

[0182] To the polymerization solution containing the coupling polymer chain obtained above, 7.69 mmol of the modifying agent (b) (equivalent to 1.0 mole of the n-butyllithium used) was added and the mixture was reacted for 10 minutes. Subsequently, methanol equivalent to 2 moles of the n-butyllithium used was added as a polymerization inhibitor to obtain a solution containing the conjugated diene polymer. Except for using the obtained solution containing the conjugated diene polymer, a conjugated diene polymer, a rubber composition, and a rubber crosslinked product were obtained in the same manner as in Example 1. The obtained conjugated diene polymer and rubber crosslinked product were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0183]

[0184]

[0185] As is clear from Tables 1 and 2, conjugated diene polymers with a value of formula (I) greater than 1.6 and less than 3.6 were able to provide rubber crosslinked products with excellent hot flow and low heat generation properties (Examples 1-12, 1-1, 1-2, 1-3, 8-1, and 8-2). On the other hand, conjugated diene polymers with a value of formula (I) of 1.6 or less provided rubber crosslinked products with poor low heat generation properties (Comparative Example 1). Furthermore, conjugated diene polymers with a value of formula (I) of 3.6 or more had poor hot flow properties (Comparative Examples 2-3).

Claims

A conjugated diene polymer satisfying the following formula (I). 1.6 < ML÷G'÷Mw×1,000,000 < 3.6 (I) (In formula (I), ML is the Mooney viscosity (ML) measured according to JIS K6300-1. １＋４ G' represents the storage shear modulus measured at 100°C, 0.05 Hz, and 10% dynamic strain, and Mw represents the weight-average molecular weight in polystyrene terms measured by gel permeation chromatography. 　 A method for producing a conjugated diene polymer according to claim 1, A polymerization step involves polymerizing monomers containing a conjugated diene compound in an inert solvent using a polymerization initiator to obtain a conjugated diene polymer chain having an active end, A coupling step is performed to form a coupling polymer chain by reacting the conjugated diene polymer chain having the active end with a coupling agent having an epoxy group or a carbonyl group. The coupling polymer chain is further modified by reacting it with a nitrogen atom-containing silane compound. A method for producing a conjugated diene polymer, wherein the coupling agent is a compound consisting only of at least one heteroatom selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms, a carbon atom, and a hydrogen atom. 　 The method for producing a conjugated diene polymer according to claim 2, wherein the amount of nitrogen atom-containing silane compound used in the modification step is 0.1 to 5 moles per mole of the polymerization initiator used in the polymerization step. 　 A method for producing a conjugated diene polymer according to claim 2 or 3, wherein the total number of epoxy groups and carbonyl groups in the coupling agent used in the coupling step is 0.1 moles or more per mole of the polymerization initiator used in the polymerization step. 　 A method for producing a conjugated diene polymer according to any one of claims 2 to 4, wherein the number of epoxy groups and carbonyl groups per molecule of the coupling agent is 3 or more. 　 A method for producing a conjugated diene polymer according to any one of claims 2 to 5, wherein the number average molecular weight of the coupling agent is 300 or more. 　 A method for producing a conjugated diene polymer according to any one of claims 2 to 6, wherein in the modification step, the coupling polymer chain is reacted with a polyorganosiloxane, and then the coupling polymer chain reacted with the polyorganosiloxane is further reacted with the nitrogen atom-containing silane compound. 　 A rubber composition comprising a conjugated diene polymer according to claim 1 and a filler. 　 The rubber composition according to claim 8, further containing a crosslinking agent. 　 A crosslinked rubber product obtained by crosslinking the crosslinkable rubber composition described in claim 9. 　 A tire comprising the rubber crosslinking material described in claim 10.

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