Modified conjugated-diene-based polymer, rubber composition, crosslinked rubber, and method for producing tire

Abstract

A method for producing a modified conjugated-diene-based polymer, the method comprising: a first step, in which monomers including a conjugated-diene compound are polymerized in an inert solvent using a polymerization initiator to obtain conjugated-diene-based polymer chains each having an active terminal; and a second step, in which a polyorganosiloxane represented by general formula (1) is added to the conjugated-diene-based polymer chains each having an active terminal either continuously over 2-60 minutes or in a plurality of installments, thereby reacting the conjugated-diene-based polymer chains each having an active terminal with the polyorganosiloxane.

Description

Modified conjugated diene polymer, rubber composition, cross-linked rubber product, and method for producing tire

[0001] The present invention relates to a modified conjugated diene polymer, a rubber composition, a cross-linked rubber product, and a method for producing a tire.

[0002] In recent years, with the growing interest in environmental issues, polymers used in automobile tires are being required to have excellent fuel economy characteristics. Tires obtained using rubber compositions in which silica is blended as a filler with a conjugated diene polymer have improved low heat buildup compared to tires obtained using rubber compositions in which conventionally used carbon black is blended, and therefore can be tires with even more excellent fuel economy characteristics.

[0003] As a conjugated diene polymer for providing such tires, Patent Document 1 proposes a modified conjugated diene polymer obtained by modifying a conjugated diene polymer chain with polyorganosiloxane. According to the technology of Patent Document 1, the introduction of a modified structure with polyorganosiloxane improves affinity with silica, thereby enabling improvements in fuel economy.

[0004] WO 2003 / 102053

[0005] On the other hand, from the viewpoint of responding to recent environmental issues, there is a demand for improved productivity in producing modified conjugated diene polymers modified with polyorganosiloxanes.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a modified conjugated diene polymer that can produce a modified conjugated diene polymer having good fuel economy with high productivity.

[0007] The present inventors have conducted studies to achieve the above object, and have found that when reacting a specific polyorganosiloxane with a conjugated diene polymer chain having an active terminal, by adding such polyorganosiloxane continuously over a period of 2 to 60 minutes or by adding it in multiple divided portions, a modified conjugated diene polymer having good fuel economy can be produced with high productivity, leading to the completion of the present invention.

[0008] That is, the present invention provides the following [1] to [8]: [1] A method for producing a modified conjugated diene polymer, comprising: a first 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; and a second step of adding a polyorganosiloxane represented by the following general formula (1) to the conjugated diene polymer chain having an active end over a period of 2 to 60 minutes, either continuously or in multiple divided additions, thereby reacting the conjugated diene polymer chain having an active end with the polyorganosiloxane. (In the above general formula (1), R １ ~R ８ are hydrocarbon groups having 1 to 20 carbon atoms, and may be the same or different from each other. １ and X ４ represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a polar functional group having an atom of Group 15 or 16 of the periodic table, a halogen atom, or a hydrocarbon group having 1 to 20 carbon atoms which may have the polar functional group or a halogen atom, and these may be the same or different. ２ represents a polar functional group having an atom of Group 15 or 16 of the periodic table, a halogen atom, or a hydrocarbon group having 1 to 20 carbon atoms which may have the polar functional group or a halogen atom; X ２ When there are a plurality of X, they may be the same or different. ３ is a group containing 2 to 20 repeating alkylene glycol units, and X ３ A part of X may be a group derived from a group containing 2 to 20 repeating units of alkylene glycol, ３ When there are a plurality of X's, they may be the same or different. m is an integer of 1 to 200, n is an integer of 0 to 200, and k is an integer of 0 to 200. [2] The method for producing a modified conjugated diene polymer according to [1], wherein the polar functional group having an atom of Group 16 of the periodic table is a polar functional group having an oxygen atom. [3] The method for producing a modified conjugated diene polymer according to [1], wherein the polar functional group having an atom of Group 16 of the periodic table is a polar functional group having an oxygen atom. １ and X ４is a hydrocarbon group having 1 to 20 carbon atoms, ２ is a hydrocarbon group having 1 to 20 carbon atoms which may have an alkoxy group or an epoxy group. [4] A method for producing a modified conjugated diene polymer according to any one of [1] to [3], wherein the modified conjugated diene polymer contains an isoprene-containing block containing 80 to 100% by weight of isoprene units. [5] A method for producing a modified conjugated diene polymer according to any one of [1] to [4], wherein a total of 0.5 to 5.0 moles of a polar compound per mole of the polymerization initiator is added before the second step. [6] A method for producing a rubber composition, comprising obtaining a modified conjugated diene polymer by the production method according to any one of [1] to [5], and adding silica to the modified conjugated diene polymer. [7] A method for producing a rubber composition according to [6], further adding a crosslinking agent. [8] A method for producing a crosslinked rubber product, comprising obtaining a rubber composition by the production method according to [6] or [7], and crosslinking the rubber composition. [9] A method for producing a tire by obtaining a rubber composition by the production method according to [6] or [7], and crosslinking the rubber composition to produce a tire comprising a cross-linked rubber product of the rubber composition.

[0009] According to the present invention, it is possible to provide a method for producing a modified conjugated diene polymer that can produce a modified conjugated diene polymer having good fuel economy with high productivity.

[0010] <Method for producing modified conjugated diene polymer> The method for producing a modified conjugated diene polymer of the present invention includes a first 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, and a second step of adding a polyorganosiloxane represented by general formula (1) described below to the conjugated diene polymer chain having an active end over a period of 2 to 60 minutes, either continuously or in multiple divided additions, to the conjugated diene polymer chain having an active end, thereby reacting the conjugated diene polymer chain having an active end with the polyorganosiloxane.

[0011] <First Step> The first step of the production method of the present invention is a step of polymerizing a monomer containing a conjugated diene compound in an inert solvent using a polymerization initiator to obtain a conjugated diene-based polymer chain having an active terminal.

[0012] In the first step of the production method of the present invention, the conjugated diene compound used as a monomer to obtain a conjugated diene polymer chain having an active terminal is not particularly limited, but examples thereof include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, and 3-butyl-1,3-octadiene. Among these, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred. These conjugated diene compounds may be used alone or in combination of two or more.

[0013] Furthermore, in the first step of the production method of the present invention, an aromatic vinyl compound may be used together with the conjugated diene compound as a monomer for polymerization. Examples of aromatic vinyl compounds used as a monomer 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. The conjugated diene polymer chain having an active end obtained in the first step of the production method of the present invention preferably contains 50 to 100% by weight of conjugated diene monomer units, more preferably 52 to 98% by weight, and particularly preferably 55 to 84% by weight. Furthermore, preferably, the conjugated diene polymer chain contains 0 to 50% by weight of aromatic vinyl monomer units, more preferably 2 to 48% by weight, and particularly preferably 16 to 45% by weight.

[0014] Furthermore, in the first step of the production method of the present invention, a compound copolymerizable with the conjugated diene compound other than an aromatic vinyl compound may be used together with the conjugated diene compound. Examples of such compounds copolymerizable with the conjugated diene compound include linear olefin compounds such as ethylene, propylene, and 1-butene; cyclic olefin compounds such as cyclopentene and 2-norbornene; non-conjugated diene compounds such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate; and other (meth)acrylic acid derivatives such as (meth)acrylonitrile and (meth)acrylamide. The amount of these compounds copolymerizable with the conjugated diene compound, as monomer units, in the conjugated diene-based polymer chain having an active terminal obtained in the first step of the production method of the present invention is preferably 10% by weight or less, and more preferably 5% by weight or less.

[0015] The inert solvent used in the polymerization is not particularly limited as long as it is one that is commonly used in solution polymerization and does not inhibit the polymerization reaction. Specific examples of the inert solvent include chain aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; and ether compounds such as tetrahydrofuran and diethyl ether. These inert solvents may be used alone or in combination of two or more. The amount of the inert solvent used is not particularly limited, but is an amount that results in a monomer concentration of, for example, 1 to 50% by weight, preferably 10 to 40% by weight.

[0016] The polymerization initiator used in the polymerization is not particularly limited as long as it can polymerize a monomer containing a conjugated diene compound to give a conjugated diene polymer chain having an active terminal. Specific examples include polymerization initiators using an organic alkali metal compound, an organic alkaline earth metal compound, or a lanthanum series metal compound as a main catalyst. Examples of organic alkali metal compounds include organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; organic polyvalent lithium compounds such as dilithiomethane, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trillithiobenzene, and 1,3,5-tris(lithiomethyl)benzene; organic sodium compounds such as sodium naphthalene; and organic potassium 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, diketylbarium, etc. Examples of polymerization initiators using a lanthanum series metal compound as the main catalyst include polymerization initiators using a lanthanum series metal salt, such as lanthanum, cerium, praseodymium, neodymium, samarium, or gadolinium, as the main catalyst, which is composed of a lanthanum series metal salt formed from a carboxylic acid and a phosphorus-containing organic acid, etc., together with a co-catalyst such as an alkylaluminum compound, an organoaluminum hydride compound, or an organoaluminum halide compound. 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.The organic alkali metal compound may be used as an organic alkali metal amide compound by reacting it in advance with a secondary amine compound such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, piperidine, hexamethyleneimine, or heptamethyleneimine. By using the organic alkali metal amide compound as a polymerization initiator, the resulting cross-linked rubber product can have better wet grip properties and abrasion resistance. These polymerization initiators may be used alone or in combination of two or more.

[0017] Examples of organic alkali metal amide compounds include those obtained by reacting an organic alkali metal compound with a secondary amine compound. Among these, in the production method of the present invention, a compound represented by the following general formula (2) can be preferably used:

[0018] In general formula (2), M １ represents an alkali metal atom, R １１ , R １２ each independently represents an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, a protecting group for an amino group, or a group that can be hydrolyzed to generate a hydroxyl group; R １１ and R １２ may be bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, and when forming such a ring structure, they may form the ring structure together with, in addition to the nitrogen atom to which they are bonded, a heteroatom other than the nitrogen atom to which they are bonded.

[0019] The alkyl group is not particularly limited, but is preferably an alkyl group having 1 to 20 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Examples of such alkyl groups include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, and an n-decyl group.

[0020] The cycloalkyl group is not particularly limited, but is preferably a cycloalkyl group having 3 to 20 carbon atoms, and more preferably a cycloalkyl group having 3 to 12 carbon atoms. Examples of such cycloalkyl groups include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and a cyclododecyl group.

[0021] The aryl group is not particularly limited, but is preferably an aryl group having 6 to 12 carbon atoms, and more preferably an aryl group having 6 to 10 carbon atoms. Examples of such aryl groups include a phenyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0022] The aralkyl group is not particularly limited, but is preferably an aralkyl group having 7 to 13 carbon atoms, and more preferably an aralkyl group having 7 to 9 carbon atoms. Examples of such aralkyl groups include a benzyl group and a phenethyl group.

[0023] The protecting group for the amino group is not particularly limited, and may be any group that acts as a protecting group for the amino group, such as an alkylsilyl group. Examples of such alkylsilyl groups include a trimethylsilyl group, a triethylsilyl group, a triphenylsilyl group, a methyldiphenylsilyl group, an ethylmethylphenylsilyl group, and a tert-butyldimethylsilyl group. １１ and / or R １２ is a protecting group for an amino group, the protecting group for the amino group is removed, and the resulting conjugated diene rubber is formed at one end of the polymer chain by removing the protecting group for the amino group. １３ and / or R １４ It is possible to introduce a structure in which is a hydrogen atom.

[0024] The group capable of generating a hydroxyl group upon hydrolysis is not particularly limited, and may be, for example, a group that generates a hydroxyl group upon hydrolysis in the presence of an acid or the like, and examples thereof include alkoxyalkyl groups and groups containing an epoxy group. Examples of alkoxyalkyl groups include methoxymethyl groups, ethoxymethyl groups, ethoxyethyl groups, propoxymethyl groups, butoxymethyl groups, butoxyethyl groups, and propoxyethyl groups. Examples of groups containing an epoxy group include groups represented by the following general formula (3): -Z １ -Z ２ -E １ (3) In general formula (3), Z １ is an alkylene group or alkylarylene group having 1 to 10 carbon atoms, and Z ２ is a methylene group, a sulfur atom or an oxygen atom, E １ is a glycidyl group.

[0025] Also, R １１ and R １２ may be bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, and in this case, R １１ and R １２ and a nitrogen atom bonded thereto, an azetidine ring (R １１ and R １２ is a propylene group), a pyrrolidine ring (R １１ and R １２ butylene group), piperidine ring (R １１ and R １２ is a pentylene group), a hexamethyleneimine ring (R １１ and R １２ R is a hexylene group. １１ and R １２ When they are bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, the ring structure is preferably a 4- to 8-membered ring structure.

[0026] In addition, in the general formula (2), M １is an alkali metal atom, and examples of such alkali metal atoms include lithium, sodium, and potassium atoms. Among these, lithium atoms are preferred from the viewpoint of polymerization activity.

[0027] In the first step of the production method of the present invention, when a compound represented by general formula (2) is used as a polymerization initiator, the amine structure forming the organic alkali metal amide compound remains bonded to the polymerization initiation terminal of the polymer chain. Therefore, when a compound represented by general formula (2) is used as a polymerization initiator, a structure represented by the following general formula (4) is introduced into one terminal of the polymer chain forming the obtained conjugated diene rubber.

[0028] In general formula (4), R １３ , R １４ each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, a protecting group for an amino group, or a group that can generate a hydroxyl group upon hydrolysis; R １３ and R １４ may be bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, and when forming such a ring structure, they may form the ring structure together with, in addition to the nitrogen atom to which they are bonded, a heteroatom other than the nitrogen atom to which they are bonded.

[0029] R １３ , R １４ Examples of the alkyl group, cycloalkyl group, aryl group, aralkyl group, protecting group for amino group, or group capable of generating a hydroxyl group upon hydrolysis include R １１ , R １２ The same as R １３ and R １４ are bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded. １１ , R １２ It can be the same as R １３ , R １４ The hydrogen atom capable of becoming the hydroxyl group is introduced by removing the protecting group of the amino group.

[0030] In the production method of the present invention, when an organic alkali metal amide compound is used as a polymerization initiator, the resulting conjugated diene rubber can have an amine structure at one end and a specific structure derived from a modifier at the other end. As a result, due to the effect of such an amine structure, the resulting cross-linked rubber using the modified conjugated diene rubber has improved fuel economy.

[0031] The method for adding an organic alkali metal amide compound as a polymerization initiator to a polymerization system is not particularly limited, and a method can be used in which an organic alkali metal compound is reacted with a secondary amine compound in advance to obtain an organic alkali metal amide compound, which is then mixed with a monomer containing a conjugated diene compound to allow the polymerization reaction to proceed. Alternatively, a method can be used in which an organic alkali metal compound and a secondary amine compound are added separately to the polymerization system, and then mixed with a monomer containing a conjugated diene compound to generate an organic alkali metal amide compound in the polymerization system, thereby allowing the polymerization reaction to proceed. Reaction conditions such as reaction temperature are not particularly limited, and may be, for example, in accordance with the desired polymerization reaction conditions.

[0032] The amount of the secondary amine compound used may be determined depending on the intended amount of polymerization initiator to be added, but is usually in the range of 0.01 to 1.5 mmol, preferably 0.1 to 1.2 mmol, more preferably 0.5 to 1.0 mmol, per 1 mmol of the organic alkali metal compound.

[0033] The amount of the polymerization initiator used may be determined depending on 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, more preferably 2 to 15 mmol per 1000 g of monomer.

[0034] The polymerization temperature is usually in the range of −80 to +150° C., preferably 0 to 100° C., and more preferably 30 to 90° C. As the polymerization mode, any mode such as a batch mode or a continuous mode can be adopted, but when a conjugated diene compound and an aromatic vinyl compound are copolymerized, a batch mode is preferred in that it is easy to control the randomness of bonding between the conjugated diene monomer units and the aromatic vinyl monomer units.

[0035] In the first step of the production method of the present invention, it is preferable to carry out the polymerization in the presence of a polar compound when polymerizing a monomer containing a conjugated diene compound. Specifically, by using preferably 0.01 to 5.0 mol, more preferably 0.1 to 4.0 mol, and even more preferably 0.2 to 3.0 mol of a polar compound per mol of a polymerization initiator and carrying out the polymerization in the presence of such a polar compound, it is possible to suitably adjust the vinyl bond content in the conjugated diene monomer unit moiety contained in the conjugated diene polymer chain obtained in the first step. Specifically, the vinyl bond content in the conjugated diene monomer unit moiety contained in the conjugated diene polymer chain can be preferably 70 wt% or less, more preferably 68 wt% or less, and even more preferably 65 wt% or less. Furthermore, the lower limit of the vinyl bond content is not particularly limited, but is preferably 5 wt% or more, more preferably 10 wt% or more, and even more preferably 20 wt% or more. By setting the vinyl bond content in the conjugated diene monomer unit portion contained in the conjugated diene polymer chain within the above range, the vinyl bond content in the conjugated diene monomer unit portion contained in the finally obtained conjugated diene rubber can be set to 70% by weight or less, and this makes it possible to obtain a cross-linked rubber product with further improved fuel economy.

[0036] The method of polymerization in the presence of a polar compound is not particularly limited, but examples include a method in which a polar compound is added to an inert solvent used in polymerization and polymerization is carried out. Specific examples of polar compounds include ethers such as tetrahydrofuran, diethyl ether, dibutyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, and 2,2-di(tetrahydrofuryl)propane; tertiary amine compounds such as tetramethylethyleneamine, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium t-amyloxide and potassium t-butyloxide; and phosphine compounds such as triphenylphosphine. Among these, polar compounds capable of multidentate coordination are more preferred, and tetramethylethylenediamine is particularly preferred. These polar compounds may be used alone or in combination of two or more.

[0037] The peak top molecular weight (Mp), which is the peak in the lowest region of the molecular weight of the conjugated diene polymer chain having an active end obtained in the first step of the production method of the present invention, is not particularly limited, but is preferably 100,000 to 1,000,000, more preferably 150,000 to 700,000, and particularly preferably 150,000 to 500,000, as a value measured by gel permeation chromatography in terms of polystyrene.

[0038] Furthermore, the molecular weight distribution, which is expressed as the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the conjugated diene polymer chain having an active end obtained in the first step of the production method of the present invention, is not particularly limited, but is preferably 1.0 to 3.0, and more preferably 1.0 to 2.5. When the molecular weight distribution (Mw / Mn) of the conjugated diene polymer chain having an active end is within the above range, production of the conjugated diene rubber becomes easy.

[0039] In the production method of the present invention, in order to obtain a cross-linked rubber product with improved fuel economy, the first step preferably comprises the following steps: a step of polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound in an inert solvent using a polymerization initiator to form a polymer block (A) having an active end containing 80 to 100% by weight of isoprene monomer units, and a step of mixing the polymer block (A) having an active end 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 an active end 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 state with the polymer block (A), thereby obtaining a conjugated diene-based polymer chain having an active end.

[0040] By employing such a process, the conjugated diene polymer chain having an active terminal obtained in the first process and the resulting modified conjugated diene polymer can be made to contain an isoprene-containing block (A) containing 80 to 100% by weight of isoprene units, and more preferably, the resulting modified conjugated diene polymer can be made to contain a polymer block (A) containing 80 to 100% by weight of isoprene 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, formed in a continuous manner. Such an embodiment will be described below.

[0041] [Polymer Block (A)] The polymer block (A) in the conjugated diene polymer chain according to one embodiment of the present invention may contain 80 to 100% by weight of isoprene monomer units, preferably 80 to 100% by weight of isoprene monomer units and 0 to 20% by weight of aromatic vinyl monomer units, more preferably 85 to 97% by weight of isoprene monomer units and 3 to 15% by weight of aromatic vinyl monomer units, and even more preferably 89 to 95% by weight of isoprene monomer units and 5 to 11% by weight of aromatic vinyl monomer units. When the content of isoprene monomer units is within the above range, when silica is blended with the modified conjugated diene rubber, the affinity between the modified conjugated diene rubber and silica is improved, and the fuel economy of the cross-linked rubber obtained using this can be further improved.

[0042] The aromatic vinyl compound used to form the aromatic vinyl monomer units contained in the polymer block (A) may be the same as the aromatic vinyl compounds described above, and among these, styrene is preferred. These aromatic vinyl compounds may be used alone or in combination of two or more.

[0043] The polymer block (A) preferably consists of only isoprene monomer units, or isoprene monomer units and aromatic vinyl monomer units, but may contain other monomer units in addition to the isoprene monomer units or isoprene monomer units and aromatic vinyl monomer units, as desired. Examples of other compounds that can be used to form the other monomer units include conjugated diene compounds 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 alone or in combination of two or more. The content of other monomer units in the 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.

[0044] In the present invention, the polymer block (A) in the conjugated diene polymer chain is formed by polymerizing a monomer containing isoprene or a monomer containing isoprene and an aromatic vinyl compound in an inert solvent using a polymerization initiator. The formed polymer block (A) has an active terminal.

[0045] The inert solvent used in the polymerization of isoprene or a monomer containing isoprene and an aromatic vinyl compound to form polymer block (A) may be the same as the inert solvent described above. The amount of the inert solvent used is such that the monomer concentration is preferably 1 to 80% by weight, more preferably 10 to 50% by weight.

[0046] The polymerization initiator used to form the 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 terminal. Specific examples of the polymerization initiator include the same initiators as those described above.

[0047] The amount of the polymerization initiator used may be determined depending on 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 a monomer containing isoprene and an aromatic vinyl compound.

[0048] 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. The polymerization method may be any method, such as a batch method or a continuous method. Various bonding methods may be used, such as a block type, a tapered type, or a random type.

[0049] In the production method according to one embodiment of the present invention, it is preferable to polymerize isoprene or a monomer containing isoprene and an aromatic vinyl compound in the presence of a polar compound when forming the polymer block (A). Specifically, the polar compound is preferably used in an amount of 0.01 to 30 mol, more preferably 0.03 to 10 mol, and even more preferably 0.05 to 5 mol per mol of the polymerization initiator. By carrying out the polymerization in the presence of such a polar compound, the vinyl bond content of the isoprene monomer unit moiety in the polymer block (A) can be suitably adjusted. The vinyl bond content of the isoprene monomer unit moiety in the polymer block (A) is preferably 25% by weight or less, more preferably 20% by weight or less, and even more preferably 15% by weight or less. The lower limit of the vinyl bond content is not particularly limited, but is preferably 1% by weight or more, more preferably 5% by weight or more. By controlling the vinyl bond content of the isoprene monomer unit moiety within the above range, the fuel economy of the resulting cross-linked rubber can be further improved. The vinyl bond in the isoprene monomer unit portion may be either a 1,2-vinyl bond or a 3,4-vinyl bond.

[0050] The method for polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound in the presence of a polar compound is not particularly limited, but examples thereof include a method in which a polar compound is added to an inert solvent used for polymerization, and the like. The polar compound may be the same as the polar compounds described above.

[0051] The weight average molecular weight (Mw) of the polymer block (A), expressed as a polystyrene equivalent value measured by gel permeation chromatography, 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 the polymer block (A) is within the above range, the fuel economy of the obtained cross-linked rubber can be further improved.

[0052] The molecular weight distribution of the polymer block (A), which is expressed as the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (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 the polymer block (A) is within the above range, the production of the modified conjugated diene rubber becomes easier.

[0053] [Polymer Block (B)] The polymer block (B) in the conjugated diene polymer chain according to one embodiment of the present invention 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 preferably contains 52 to 98% by weight of 1,3-butadiene monomer units and 2 to 48% by weight of aromatic vinyl monomer units, and particularly preferably contains 55 to 84% by weight of 1,3-butadiene monomer units and 16 to 45% by weight of aromatic vinyl monomer units. When the content ratio of the 1,3-butadiene monomer units to the aromatic vinyl monomer units is within the above range, the production of the modified conjugated diene rubber becomes easier.

[0054] The aromatic vinyl compound used to constitute the aromatic vinyl monomer units contained in the polymer block (B) can be the same as the aromatic vinyl compounds described above, and among these, styrene is preferred.

[0055] Polymer block (B) preferably consists of 1,3-butadiene monomer units alone, or 1,3-butadiene monomer units and aromatic vinyl monomer units. However, as long as the essential properties of the present invention are not impaired, polymer block (B) may contain other monomer units in addition to 1,3-butadiene monomer units or 1,3-butadiene monomer units and aromatic vinyl monomer units, as desired. The other monomers used to form the other monomer units can be the same as the compounds exemplified for polymer block (A) above (with the exception of 1,3-butadiene). Furthermore, isoprene can also be used as the other monomer in polymer block (B). The content of the 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.

[0056] In one embodiment of the present invention, polymer block (B) in the conjugated diene polymer chain is formed contiguously with polymer block (A) by mixing polymer block (A) having the above-described active terminal with a monomer containing 1,3-butadiene or 1,3-butadiene and an aromatic vinyl compound and continuing the polymerization reaction. The formed polymer block (B) has an active terminal. Meanwhile, the active terminal disappears from polymer block (A).

[0057] The inert solvent used in the polymerization of the polymer block (A) with a monomer containing 1,3-butadiene or 1,3-butadiene and an aromatic vinyl compound to form the polymer block (B) is not particularly limited, and the same inert solvents as those described above can be used.

[0058] The amount of polymer block (A) having an active end used in forming polymer block (B) may be determined depending on the target 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 1,3-butadiene or the monomer containing 1,3-butadiene and an aromatic vinyl compound.

[0059] The method for mixing polymer block (A) with 1,3-butadiene or a monomer containing 1,3-butadiene and an aromatic vinyl compound is not particularly limited, and polymer block (A) having an active end may be added to a solution of 1,3-butadiene or a monomer containing 1,3-butadiene and an aromatic vinyl compound, or 1,3-butadiene or a monomer containing 1,3-butadiene and an aromatic vinyl compound may be added to a solution of polymer block (A) having an active end. From the viewpoint of controlling the polymerization, a method of adding polymer block (A) having an active end to a solution of 1,3-butadiene or a monomer containing 1,3-butadiene and an aromatic vinyl compound is preferred.

[0060] The polymerization temperature when polymerizing 1,3-butadiene or a monomer containing 1,3-butadiene 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. As the polymerization method, any method such as a batch method or a continuous method can be adopted. When the polymer block (B) is a copolymer chain, a batch method is preferred because it is easy to control the randomness of bonding.

[0061] When the polymer block (B) is formed into a copolymer chain, the bonding pattern of each monomer can be various bonding patterns, such as block, tapered, and random. Among these, the random bonding pattern is preferred. By using a random bonding pattern, the wet grip property and abrasion resistance of the resulting cross-linked rubber can be further improved. When the bonding pattern of 1,3-butadiene and the aromatic vinyl compound is random, it is preferable to polymerize 1,3-butadiene or 1,3-butadiene and the aromatic vinyl compound by continuously or intermittently supplying them into the polymerization system so that the ratio of the aromatic vinyl compound to the total amount of 1,3-butadiene and the aromatic vinyl compound in the polymerization system does not become too high.

[0062] In one embodiment of the present invention, similar to the formation of polymer block (A), when forming polymer block (B), it is preferable to polymerize a monomer containing 1,3-butadiene or 1,3-butadiene and an aromatic vinyl compound in the presence of a polar compound. Specifically, by using preferably 0.01 to 5.0 mol, more preferably 0.1 to 4.0 mol, and even more preferably 0.2 to 3.0 mol of polar compound per mol of polymerization initiator and conducting polymerization in the presence of such a polar compound, it is possible to suitably adjust the vinyl bond content of the 1,3-butadiene monomer unit moiety in polymer block (B), and as a result, it is possible to suitably adjust the vinyl bond content of the conjugated diene monomer unit moiety contained in the final conjugated diene-based rubber. The vinyl bond content of the 1,3-butadiene monomer unit moiety in polymer block (B) is preferably 70 wt% or less, more preferably 68 wt% or less, and even more preferably 65 wt% or less. The lower limit of the vinyl bond content is not particularly limited, but is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 20% by weight or more.

[0063] The method for polymerizing 1,3-butadiene or a monomer containing 1,3-butadiene and an aromatic vinyl compound in the presence of a polar compound is not particularly limited, and examples include a method in which the polar compound is added to an inert solvent used for polymerization and then polymerization is carried out. In this case, the polar compound may be added so that the sum of the amount of polar compound added during the formation of polymer block (A) and the amount of polar compound newly added falls within the above-mentioned range. Therefore, if a polar compound is added during the formation of polymer block (A) in an amount sufficient to adjust the vinyl bond content of the 1,3-butadiene monomer unit portion in polymer block (B), it is not necessary to add a new polar compound. Furthermore, the same polar compounds as those described above can be used as the polar compound.

[0064] In this manner, a conjugated diene polymer chain having an active end, which includes 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 terminal of polymer block (B) is the active terminal. However, the conjugated diene polymer chain may have a plurality of polymer blocks (A) or may have other polymer blocks. For example, a conjugated diene polymer chain having an active end may be exemplified by polymer block (A)-polymer block (B)-polymer block (A). In this case, the active terminal is formed at the terminal of polymer block (A) formed subsequent to polymer block (B). When polymer block (A) is formed on the active terminal side of the conjugated diene polymer chain, the amount of isoprene used is preferably 10 to 100 mol, more preferably 20 to 90 mol, and particularly preferably 30 to 70 mol, per mol of the polymerization initiator used in the initial polymerization reaction (polymerization reaction to form the first polymer block (A)).

[0065] The weight ratio of polymer block (A) to polymer block (B) in the conjugated diene polymer chain having an active end obtained in one embodiment of the present invention (when a plurality of polymer blocks (A) and polymer blocks (B) are present, the weight ratio is based on the total weight of the respective polymer blocks) is (weight of polymer block (A)) / (weight of polymer block (B)), and is preferably 0.001 to 0.2, more preferably 0.005 to 0.1, and particularly preferably 0.008 to 0.05. By setting the weight ratio of polymer block (A) to polymer block (B) within the above range, the obtained cross-linked rubber product can have improved fuel economy.

[0066] The content ratio of the total monomer units of isoprene monomer units and 1,3-butadiene monomer units and the aromatic vinyl monomer units in the conjugated diene polymer chain having an active end, which has polymer block (A) and polymer block (B), is preferably 50 to 100% by weight of the total monomer units of isoprene monomer units and 1,3-butadiene monomer units and 0 to 50% by weight of the aromatic vinyl monomer units, more preferably 52 to 98% by weight of the total monomer units of isoprene monomer units and 1,3-butadiene monomer units and 2 to 48% by weight of the aromatic vinyl monomer units, and particularly preferably 55 to 84% by weight of the total monomer units of isoprene monomer units and 1,3-butadiene monomer units and 16 to 45% by weight of the aromatic vinyl monomer units. In addition, in the conjugated diene polymer chain having an active end, which has the polymer block (A) and the polymer block (B), the vinyl bond contents in the isoprene monomer units and the 1,3-butadiene monomer units are preferably in the same range as the vinyl bond content in the 1,3-butadiene monomer units in the above-mentioned polymer block (B).

[0067] The above-described polar compound may be further added before the second step of the present invention. Specifically, the amount of the polar compound added before the second step, more specifically the total amount of the polar compound added in the first step, is preferably 0.5 to 5.0 mol, more preferably 0.6 to 4.0 mol, and particularly preferably 0.9 to 3.0 mol, relative to 1 mol of the polymerization initiator, whereby the association state of the conjugated diene polymer chains having active ends can be suitably adjusted, and as a result, the maximum power load of the stirrer in the second step can be suitably adjusted.

[0068] <Second Step> The second step of the production method of the present invention is a step of reacting the conjugated diene-based polymer chain having an active terminal obtained in the first step with the polyorganosiloxane represented by the following general formula (1) by continuously adding the polyorganosiloxane to the conjugated diene-based polymer chain having an active terminal over a period of 2 to 60 minutes or by adding the polyorganosiloxane in multiple divided portions. (In the above general formula (1), R１ ~R ８ are hydrocarbon groups having 1 to 20 carbon atoms, and may be the same or different from each other. １ and X ４ represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a polar functional group having an atom of Group 15 or 16 of the periodic table, a halogen atom, or a hydrocarbon group having 1 to 20 carbon atoms which may have the polar functional group or a halogen atom, and these may be the same or different. ２ represents a polar functional group having an atom of Group 15 or 16 of the periodic table, a halogen atom, or a hydrocarbon group having 1 to 20 carbon atoms which may have the polar functional group or a halogen atom; X ２ When there are a plurality of X, they may be the same or different. ３ is a group containing 2 to 20 repeating alkylene glycol units, and X ３ A part of X may be a group derived from a group containing 2 to 20 repeating units of alkylene glycol, ３ When there are a plurality of m, they may be the same or different. m is an integer of 1 to 200, n is an integer of 0 to 200, and k is an integer of 0 to 200.

[0069] R in general formula (1) １ ~R ８ is a hydrocarbon group having 1 to 20 carbon atoms, preferably an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, which may be the same or different. Examples of alkyl groups having 1 to 6 carbon atoms include methyl groups, ethyl groups, n-propyl groups, isopropyl groups, butyl groups, pentyl groups, hexyl groups, and cyclohexyl groups. Examples of aryl groups having 6 to 12 carbon atoms include phenyl groups and methylphenyl groups. Among these, from the viewpoint of ease of production of the polyorganosiloxane itself, methyl groups and ethyl groups are preferred, and methyl groups are more preferred.

[0070] X in general formula (1) １and X ４ represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a polar functional group having an atom of Group 15 or 16 of the periodic table, a halogen atom, or a hydrocarbon group having 1 to 20 carbon atoms which may have the polar functional group or a halogen atom, and these may be the same or different. １ and X ４ The alkyl group is preferably any group selected from the group consisting of alkyl groups having 1 to 6 carbon atoms, aryl groups having 6 to 12 carbon atoms, hydrocarbon groups having 1 to 5 carbon atoms and an alkoxy group (hydrocarbon groups having a total of 1 to 5 carbon atoms, including the carbon atoms constituting the alkoxy group), and hydrocarbon groups having 4 to 12 carbon atoms and an epoxy group (hydrocarbon groups having a total of 4 to 12 carbon atoms, including the carbon atoms constituting the epoxy group). A hydrocarbon group having 4 to 12 carbon atoms and an epoxy group, or an alkyl group having 1 to 6 carbon atoms, is more preferred, and an alkyl group having 1 to 6 carbon atoms is even more preferred. Examples of alkyl groups having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and cyclohexyl. Among these, from the viewpoint of ease of production of the polyorganosiloxane itself, methyl and ethyl groups are preferred, and methyl groups are more preferred.

[0071] X in general formula (1) ２ represents a polar functional group having an atom of Group 15 or 16 of the periodic table, a halogen atom, or a hydrocarbon group having 1 to 20 carbon atoms which may have the polar functional group or a halogen atom; X ２ When there are a plurality of X, they may be the same or different. ２is preferably a hydrocarbon group having 1 to 20 carbon atoms which may have a polar functional group having an oxygen atom, more preferably a hydrocarbon group having 1 to 20 carbon atoms which may have an alkoxy group or an epoxy group, even more preferably a hydrocarbon group having 1 to 5 carbon atoms which has an alkoxy group, or a hydrocarbon group having 4 to 12 carbon atoms which has an epoxy group, and even more preferably a hydrocarbon group having 4 to 12 carbon atoms which has an epoxy group. In this case, the hydrocarbon group having an alkoxy group and the hydrocarbon group having an epoxy group preferably have the number of carbon atoms including the number of carbon atoms constituting the alkoxy group or the epoxy group within the above range, and the alkoxy group and the epoxy group are preferably ２ Furthermore, the hydrocarbon group constituting the hydrocarbon group having an alkoxy group or the hydrocarbon group having an epoxy group may contain an ether bond or a thioether bond in addition to the alkoxy group or the epoxy group.

[0072] Examples of the hydrocarbon group having 1 to 5 carbon atoms and an alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, and a butoxy group. Among these, from the viewpoint of ease of production of the polyorganosiloxane itself, a methoxy group and an ethoxy group are preferred.

[0073] Examples of the hydrocarbon group having 4 to 12 carbon atoms and containing an epoxy group include a group represented by the following general formula (5): -Z ３ -Z ４ -E ２ (5) In general formula (5), Z ３ is an alkylene group or alkylarylene group having 1 to 10 carbon atoms, and Z ４ is a methylene group, a sulfur atom, or an oxygen atom, and E ２ is a hydrocarbon group having 2 to 10 carbon atoms and an epoxy group (a hydrocarbon group having a total of 2 to 10 carbon atoms including the carbon atoms constituting the epoxy group).

[0074] The group represented by formula (5) includes Z ４ is preferably an oxygen atom, and Z ４ is an oxygen atom, and E２ is more preferably a glycidyl group, and Z ３ is an alkylene group having 1 to 10 carbon atoms (preferably an alkylene group having 1 to 3 carbon atoms), and Z ４ is an oxygen atom, and E ２ is a glycidyl group is particularly preferred.

[0075] X ３ is a group containing 2 to 20 repeating alkylene glycol units, and X ３ A part of X may be a group derived from a group containing 2 to 20 repeating units of alkylene glycol, ３ When there are a plurality of repeating units, they may be the same or different. As the group containing 2 to 20 repeating units of alkylene glycol, a group represented by the following general formula (6) is preferred. In the general formula (6), t is an integer of 2 to 20, and X ５ is an alkylene group or alkylarylene group having 2 to 10 carbon atoms, and R １５ is a hydrogen atom or a methyl group, and X ６ is an alkoxy group or an aryloxy group having 1 to 10 carbon atoms. Among these, t is an integer of 2 to 8, and X ５ is an alkylene group having 3 carbon atoms, and R １５ is a hydrogen atom, and X ６ is preferably a methoxy group.

[0076] In the polyorganosiloxane represented by the general formula (1), m is an integer of 1 to 200, preferably an integer of 20 to 150, and more preferably an integer of 30 to 120. When m is 1 or more, the fuel economy of the resulting cross-linked rubber can be further improved. Furthermore, when m is 200 or less, the polyorganosiloxane represented by the general formula (1) itself becomes easier to produce, and its viscosity does not become too high, making it easier to handle.

[0077] In the polyorganosiloxane represented by the general formula (1), n ​​is an integer of 0 to 200, preferably an integer of 0 to 150, more preferably an integer of 0 to 120. k is an integer of 0 to 200, preferably an integer of 0 to 150, more preferably an integer of 0 to 130. The total number of m, n, and k is 1 or more, preferably 3 to 400, more preferably 20 to 300, and particularly preferably 30 to 250. When the total number of m, n, and k is 1 or more, the reaction between the polyorganosiloxane represented by the general formula (1) and the conjugated diene polymer chain having an active terminal proceeds easily. Furthermore, when the total number of m, n, and k is 400 or less, the polyorganosiloxane represented by the general formula (1) itself is easily produced, and its viscosity does not become too high, making it easy to handle.

[0078] In the second step of the production method of the present invention, the amount of polyorganosiloxane represented by the general formula (1) used is, relative to 1 mole of the polymerization initiator used in the polymerization in the first step described above, converted into a polar functional group such as an epoxy group or a halogen atom in the polyorganosiloxane, preferably 0.1 moles or more, more preferably 0.15 moles or more, even more preferably 0.2 moles or more, particularly preferably 0.3 moles or more, and also preferably 2 moles or less, more preferably 1.5 moles or less, even more preferably 1 mole or less, particularly preferably 0.8 moles or less. When the amount of polyorganosiloxane used is within the above range, the fuel economy of the obtained rubber cross-linked product can be further improved.

[0079] In the second step of the production method of the present invention, when reacting the polyorganosiloxane represented by the general formula (1) with the conjugated diene polymer chain having an active terminal obtained in the first step, it is preferable to continuously add the polyorganosiloxane represented by the general formula (1) to the conjugated diene polymer chain having an active terminal over a period of 2 to 60 minutes, or to add it in portions in several times and react them.

[0080] In this case, the polyorganosiloxane represented by the general formula (1) is usually added continuously over 2 to 60 minutes to a polymer solution obtained by dissolving a conjugated diene polymer chain having an active terminal in an inert solvent capable of dissolving it, while stirring with a stirrer or the like, or a method of adding it in multiple installments is adopted. In addition, as the inert solvent used in this case, it is preferable to use an inert solvent that can dissolve both the conjugated diene polymer chain having an active terminal and the polyorganosiloxane represented by the general formula (1), and the inert solvents described above can be used. Furthermore, in this case, the polyorganosiloxane represented by the general formula (1) is preferably added continuously or in installments to the polymerization solution used in the polymerization to obtain the conjugated diene polymer chain having an active terminal, which is a simple and preferred method.

[0081] According to the present invention, by continuously adding a polyorganosiloxane represented by general formula (1) to a conjugated diene polymer chain having an active terminal over a period of 2 to 60 minutes or by adding the polyorganosiloxane in multiple installments, the resulting modified conjugated diene polymer can be produced with high productivity while exhibiting good fuel economy. Specifically, when reacting a polyorganosiloxane represented by general formula (1) with a conjugated diene polymer chain having an active terminal, as described above, this is usually done by mixing the components in an inert solvent capable of dissolving them using a stirrer or the like. However, the maximum power load of the stirrer during mixing can be reduced, thereby enabling a reduction in the energy required for production. Furthermore, it is possible to carry out the reaction under relatively high polymer concentration conditions for the inert solvent used while suppressing an increase in the maximum power load of the stirrer. As a result, productivity can be improved. The reason for this is not entirely clear, but it is believed that the rate of production of multi-branched products having two or more branches can be reduced by adding the polyorganosiloxane represented by general formula (1) to the conjugated diene polymer chain having an active terminal continuously over a period of 2 to 60 minutes or by adding it in multiple divided portions.

[0082] In a method of continuously adding a polyorganosiloxane represented by the general formula (1) to a conjugated diene polymer chain having an active terminal over 2 to 60 minutes, the polyorganosiloxane represented by the general formula (1) used for modification may be added substantially continuously, at a constant addition rate (constant addition amount), or preferably at short intervals of 1 second to less than 2 minutes, more preferably at short intervals of 1 second to 60 seconds, a constant amount may be added intermittently and continuously. In addition, when adding continuously, it is preferable to add continuously at a constant addition rate (constant addition amount) or to add a constant amount intermittently, but for example, it may be added continuously or intermittently while varying the addition amount within a range of ±200%.

[0083] The addition time when the polyorganosiloxane represented by general formula (1) is continuously added to the conjugated diene polymer chain having an active terminal is 2 to 60 minutes, preferably 3 to 50 minutes, more preferably 4 to 40 minutes, and even more preferably 5 to 30 minutes. If the addition time when continuously adding is too short, the effect of reducing the maximum power load of the stirrer cannot be obtained, and productivity decreases. On the other hand, if the addition time when continuously adding is too long, the production time increases and productivity decreases.

[0084] In addition, in a method of adding a polyorganosiloxane represented by the general formula (1) to a conjugated diene polymer chain having an active terminal in multiple divided portions, the polyorganosiloxane represented by the general formula (1) used for modification may be divided into two or more portions and then added in portions. For example, when adding in two divided portions, a predetermined amount may be added in the first stage, the modification reaction may proceed, and then, after a predetermined interval, the remainder may be added in the second stage. Similarly, when adding in three divided portions, a predetermined amount may be added in the first stage, the modification reaction may proceed, and then, after a predetermined interval, a further predetermined amount may be added in the second stage, the modification reaction may proceed, and then, after a predetermined interval, the remainder may be added in the third stage. The same procedure may be followed when adding in four or more divided portions.

[0085] The amount added at each addition timing in divided addition is not particularly limited, and may be the same or different amounts at each addition timing, but from the viewpoint of a high effect of improving productivity, it is preferable to add the same amount at each addition timing or to add the largest amount in the first stage. For example, when adding in two divided additions, it is preferable that the ratio of the amount added in the first stage to the amount added in the second stage be 55:45 to 80:20 (weight ratio).

[0086] From the viewpoint of improving productivity, the addition time at each addition timing in divided addition is preferably less than 2 minutes, more preferably 1 second to less than 1 minute. From the viewpoint of improving productivity, the interval between each addition timing (the interval between the Nth stage divided addition and the N+1th stage divided addition) is preferably 1 to 30 minutes, more preferably 2 to 25 minutes, and even more preferably 5 to 20 minutes.

[0087] In the second step of the present invention, it is preferable to add the entire amount of the polyorganosiloxane represented by the general formula (1) used for modification continuously, or to add the entire amount of the polyorganosiloxane represented by the general formula (1) used for modification in parts, but it is also possible to adopt a method in which a part is added continuously and the rest is added in parts. In this case, it is also possible to adopt a method in which the polyorganosiloxane is first added continuously and then added in parts, or it is also possible to adopt a method in which the polyorganosiloxane is first added in parts and then added continuously.

[0088] In addition, when the polyorganosiloxane represented by the general formula (1) used for modification is added continuously or in portions, the polyorganosiloxane represented by the general formula (1) may be added directly without being dissolved in an inert solvent, or the polyorganosiloxane represented by the general formula (1) may be dissolved in an inert solvent in which it can be dissolved and added in the form of a solution. In this case, the solution concentration is preferably in the range of 1 to 50 wt%.

[0089] In the second step, the polyorganosiloxane represented by general formula (1) is added continuously or in portions to the conjugated diene polymer chain having an active terminal, thereby reacting the polyorganosiloxane represented by general formula (1) with the conjugated diene polymer chain having an active terminal. The reaction temperature is usually 0 to 120° C., preferably 30 to 90° C. The reaction time in the second step is not particularly limited, but is preferably 2 to 120 minutes, more preferably 5 to 60 minutes.

[0090] The timing for starting the continuous or divided addition of the polyorganosiloxane represented by general formula (1) to the conjugated diene polymer chains having active terminals is not particularly limited, but it is preferable to start when the polymerization reaction is not complete and the solution containing the conjugated diene polymer chains having active terminals also contains a monomer, more specifically, when the solution containing the conjugated diene polymer chains having active terminals contains 100 ppm or more, more preferably 300 to 50,000 ppm of a monomer.

[0091] After reacting the polyorganosiloxane represented by general formula (1) with the conjugated diene polymer chain having an active terminal, it is preferable to add a polymerization terminator such as an alcohol such as methanol, ethanol, or isopropanol, or water to deactivate the unreacted active terminal.

[0092] After deactivating the active ends of the conjugated diene polymer chains, if desired, an antioxidant such as a phenolic stabilizer, a phosphorus-based stabilizer, or a sulfur-based stabilizer, a crumb-forming agent, and a scale inhibitor are added to the reaction solution, and then the inert solvent is separated from the reaction solution by direct drying or steam stripping, etc., to recover the modified conjugated diene rubber. Note that, before separating the inert solvent from the reaction solution, an extender oil may be mixed with the polymerization solution, and the modified conjugated diene rubber may be recovered as an oil-extended rubber.

[0093] Examples of extender oils used when recovering modified conjugated diene rubber as oil-extended rubber include paraffinic, aromatic, and naphthenic petroleum-based softeners, plant-based softeners, synthetic softeners using plant-derived resources, and fatty acids. When a petroleum-based softener is used, it is preferable that the content of polycyclic aromatics extracted by the IP346 method (a testing method of the Institute Petroleum in the UK) is less than 3%. When an extender oil is used, the amount used is preferably 5 to 100 parts by weight, more preferably 10 to 60 parts by weight, and even more preferably 15 to 50 parts by weight per 100 parts by weight of modified conjugated diene rubber.

[0094] The weight average molecular weight (Mw) of the modified conjugated diene rubber is preferably 50,000 to 5,000,000, more preferably 75,000 to 3,000,000, and particularly preferably 100,000 to 1,000,000, as measured by gel permeation chromatography in terms of polystyrene.

[0095] The molecular weight distribution of the modified conjugated diene rubber, which is expressed as the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 1.1 to 3.0, more preferably 1.2 to 2.5, and particularly preferably 1.2 to 2.2. By adjusting the molecular weight distribution (Mw / Mn) of the modified conjugated diene rubber within the above range, the fuel economy of the obtained cross-linked rubber can be further improved.

[0096] Mooney viscosity (ML) of modified conjugated diene rubber １＋４ , 100°C) is preferably 20 to 150, more preferably 30 to 120, and particularly preferably 35 to 90. When the modified conjugated diene rubber is used as an oil-extended rubber, it is preferable that the Mooney viscosity of the oil-extended rubber be within the above range.

[0097] The glass transition temperature (Tg) of the modified conjugated diene rubber is not particularly limited, but is preferably 20° C. to −110° C., more preferably 10° C. to −70° C., particularly preferably 0° C. to −60° C., and most preferably −10° C. to −45° C. The glass transition temperature of the modified conjugated diene rubber of the present invention can be appropriately adjusted, for example, by adjusting the aromatic vinyl monomer unit content in the modified conjugated diene rubber and the vinyl bond content in the modified conjugated diene monomer unit portion.

[0098] In the production method of the present invention, the conjugated diene polymer chain that has been reacted with the polyorganosiloxane represented by general formula (1) after the second step may be further reacted with a hydrocarbyloxysilane compound.

[0099] Such hydrocarbyloxysilane compounds are not particularly limited, but can be silicon-containing compounds having at least one hydrocarbyloxy group, and do not fall under the category of polyorganosiloxanes represented by general formula (1), but preferably compounds having at least one group containing a nitrogen atom in addition to the hydrocarbyloxy group, and more preferably such a group containing a primary amino group having an active hydrogen atom and / or a group containing a secondary amino group having an active hydrogen atom.The hydrocarbyloxysilane compounds act as modifiers by reacting the hydrocarbyloxy group with the conjugated diene polymer chain having an active end or the reaction residue produced by the reaction of the conjugated diene polymer chain having an active end with the polyorganosiloxane represented by general formula (1).

[0100] Such a hydrocarbyloxysilane compound is not particularly limited, but a compound represented by the following general formula (7) can be suitably used. In the above general formula (7), R １６ is a hydrocarbyl group, A １ is a hydrocarbyloxy group, and A ２ is a group containing a nitrogen atom, 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.

[0101] R in the above general formula (7) １６ is a hydrocarbyl group, and examples thereof include alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, and aralkyl groups, 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, with a methyl group and an ethyl group being more preferred.

[0102] A in the above general formula (7) １ is a hydrocarbyloxy group, and examples thereof 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; aryloxy groups such as phenoxy and naphthoxy; and aralkyloxy groups such as benzyloxy. Of these, from the viewpoint of reactivity, alkoxy and aryloxy groups are preferred, alkoxy groups are more preferred, and methoxy and ethoxy groups are particularly preferred.

[0103] A in the above general formula (7) ２is a group containing a nitrogen atom, and is not particularly limited as long as it is a group containing a nitrogen atom, but is preferably an organic group having a nitrogen atom, and examples thereof include a 3-aminopropyl group, a 4-aminobutyl group, a 3-(2-aminoethylamino)propyl group, a 2-dimethylaminoethyl group, a 3-dimethylaminopropyl group, a 3-diethylaminopropyl group, a 3-dipropylaminopropyl group, a 3-dibutylaminopropyl group, a 3-phenylmethylaminopropyl group, a 3-(4-methylpiperazinyl)propyl group, an N,N-bis(trimethylsilyl)aminopropyl group, an N,N-bis(triethylsilyl)aminopropyl group, and an N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyl group. Among these, from the viewpoint of being able to further improve the fuel economy of the obtained rubber cross-linked product, a group containing 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, is preferred. The term "active hydrogen atom" refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably has a bond energy lower than that of the carbon-hydrogen bond of a polymethylene chain.

[0104] In the compound represented by the general formula (7), 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. From the viewpoint of reactivity with the conjugated diene polymer chain reacted with the polyorganosiloxane represented by the general formula (1) that has undergone the second step, preferably, p is an integer of 0 to 1, q is an integer of 2 to 3, and r is an integer of 1 to 2, and more preferably, p = 0, q = 3, and r = 1. When p is 2, two R groups are contained in one molecule of the compound represented by the general formula (7). １６ Similarly, when q is 2 or 3, a plurality of A groups contained in one molecule of the compound represented by general formula (7) may be the same or different from each other. １ The groups represented by may be the same or different from each other, and when r is 2 or 3, a plurality of A ２The groups represented by the formula (I) may be the same or different from each other.

[0105] Specific examples of the compound represented by the general formula (7) are not particularly limited, but include, for example, A ２ is a group containing a primary amino group having an active hydrogen atom and / or a secondary amino group having an active hydrogen atom, such as 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, and 3-aminopropyltriethoxysilane. ２ compounds having a 3-aminopropyl group; A such as 4-aminobutyldimethylmethoxysilane, 4-aminobutylmethyldimethoxysilane, 4-aminobutyltrimethoxysilane, 4-aminobutyldimethylethoxysilane, 4-aminobutylmethyldiethoxysilane, and 4-aminobutyltriethoxysilane; ２ compounds having a 4-aminobutyl group; A 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 thereof include compounds having a 3-(2-aminoethylamino)propyl group;

[0106] In addition, A in the general formula (7) ２ is a group 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, such as 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropylmethyldimethoxysilane, 3-dimethylaminopropyldimethylmethoxysilane, 3-dimethylaminopropyltriethoxysilane, 3-dimethylaminopropylmethyldiethoxysilane, and 3-dimethylaminopropyldimethylethoxysilane.２ compounds having a 3-dimethylaminopropyl group; A such as 3-diethylaminopropyltrimethoxysilane, 3-diethylaminopropylmethyldimethoxysilane, 3-diethylaminopropyldimethylmethoxysilane, 3-diethylaminopropyltriethoxysilane, 3-diethylaminopropylmethyldiethoxysilane, and 3-diethylaminopropyldimethylethoxysilane; ２ compounds having a 3-diethylaminopropyl group; A such as 3-dipropylaminopropyltrimethoxysilane, 3-dipropylaminopropylmethyldimethoxysilane, 3-dipropylaminopropyldimethylmethoxysilane, 3-dipropylaminopropyltriethoxysilane, 3-dipropylaminopropylmethyldiethoxysilane, and 3-dipropylaminopropyldimethylethoxysilane; ２ compounds having a 3-dipropylaminopropyl group; A such as 3-dibutylaminopropyltrimethoxysilane, 3-dibutylaminopropylmethyldimethoxysilane, 3-dibutylaminopropyldimethylmethoxysilane, 3-dibutylaminopropyltriethoxysilane, 3-dibutylaminopropylmethyldiethoxysilane, and 3-dibutylaminopropyldimethylethoxysilane; ２ compounds having a 3-dibutylaminopropyl group; A such as 3-phenylmethylaminopropyltrimethoxysilane, 3-phenylmethylaminopropylmethyldimethoxysilane, 3-phenylmethylaminopropyldimethylmethoxysilane, 3-phenylmethylaminopropyltriethoxysilane, 3-phenylmethylaminopropylmethyldiethoxysilane, and 3-phenylmethylaminopropyldimethylethoxysilane; ２compounds having a 3-phenylmethylaminopropyl group; A 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 a compound having a 3-(4-methylpiperazinyl)propyl group as the aryl group;

[0107] A such as N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, and N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane ２ compounds having an N,N-bis(trimethylsilyl)aminopropyl group; A such as N,N-bis(triethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(triethylsilyl)aminopropylmethyldimethoxysilane, and N,N-bis(triethylsilyl)aminopropylmethyldiethoxysilane; ２ compounds having an N,N-bis(triethylsilyl)aminopropyl group; 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 thereof include compounds having an N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyl group;

[0108] Furthermore, as the hydrocarbyloxysilane compound, a compound represented by the following general formula (8) can also be suitably used. In the above general formula (8), A ３ is a hydrocarbyloxy group, and R １７ represents a hydrocarbon group which may have a substituent, and R １８ and R １９ each independently represents a hydrocarbon group which may have a substituent, R １８ and R １９ may be bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, and when forming such a ring structure, they may form a ring structure together with the nitrogen atom to which they are bonded and a heteroatom other than the nitrogen atom to which they are bonded. s is an integer of 0 to 2.

[0109] A in the above general formula (8) ３ is a hydrocarbyloxy group, and examples thereof 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; aryloxy groups such as phenoxy and naphthoxy; and aralkyloxy groups such as benzyloxy. Of these, from the viewpoint of reactivity, alkoxy and aryloxy groups are preferred, alkoxy groups are more preferred, and methoxy and ethoxy groups are particularly preferred.

[0110] In the above general formula (8), s (i.e., A ３ The number of groups represented by the formula (8) is an integer of 0 to 2, and it is preferable that s is 2. When s is 2 in the formula (8), two A groups are contained in one molecule of the compound represented by the formula (8). ３ The groups represented by the formula (I) may be the same or different from each other.

[0111] In the above general formula (8), R １７ represents a hydrocarbon group which may have a substituent. １７The hydrocarbon group which can be R is not particularly limited, but examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; alkenyl groups such as vinyl and allyl; alkynyl groups such as ethynyl and propynyl; aryl groups such as phenyl and naphthyl; and aralkyl groups such as benzyl. Among these, alkyl and aryl groups are preferred, alkyl groups are more preferred, and methyl and ethyl groups are particularly preferred. Furthermore, R １７ The hydrocarbon group represented by the formula (8) may have a substituent other than the hydrocarbon group, and the substituent is not particularly limited, but examples thereof include a carbonyl group-containing group such as a carboxyl group, an acid anhydride group, a hydrocarbylcarbonyl group, an alkoxycarbonyl group, and an acyloxy group, an epoxy group, an oxy group, a cyano group, an amino group, and a halogen group. When s in the formula (8) is 0, two R １７ The groups represented by the formula (I) may be the same or different from each other.

[0112] In the above general formula (8), R １８ and R １９ each independently represents a hydrocarbon group which may have a substituent, R １８ and R １９ may be bonded to each other to form a ring structure, and may form a ring structure together with the nitrogen atom to which they are bonded. When these form a ring structure, they may also form a ring structure together with the nitrogen atom to which they are bonded and a heteroatom other than the nitrogen atom to which they are bonded. １８ and R １９ When they are not bonded to each other, R １８ and R １９The hydrocarbon group which can be R is not particularly limited, but examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; alkenyl groups such as vinyl and allyl; alkynyl groups such as ethynyl and propynyl; aryl groups such as phenyl and naphthyl; and aralkyl groups such as benzyl. Among these, alkyl and aryl groups are preferred, alkyl groups are more preferred, and methyl and ethyl groups are particularly preferred. Furthermore, R １８ and R １９ When they are bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, R １８ and R １９ The divalent hydrocarbon group formed by bonding is not particularly limited, but examples thereof include alkylene groups such as an n-butylene group (when forming a 1-pyrrolidine group together with the nitrogen atom to which they are bonded in general formula (8)), an n-pentylene group (when forming a 1-piperidine group), and a butadienylene group (when forming a 1-pyrrole group). １８ and R １９ When they are bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, the ring structure is preferably a 4- to 8-membered ring structure.

[0113] Also, R １８ and R １９ The hydrocarbon group represented by the formula (I) may have a substituent other than the hydrocarbon group, regardless of whether a ring structure is formed or not, and the substituent is not particularly limited, but examples thereof include carbonyl group-containing groups such as a carboxyl group, an acid anhydride group, a hydrocarbylcarbonyl group, an alkoxycarbonyl group, and an acyloxy group, an epoxy group, an oxy group, a cyano group, an amino group, and a halogen group. １８ and R １９ are bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, the atoms forming the ring structure may include heteroatoms other than carbon atoms and the nitrogen atoms to which they are bonded, and examples of such heteroatoms include nitrogen atoms and oxygen atoms.

[0114] Particularly preferred compounds represented by the general formula (8) are those represented by the formula R １８ and R １９ are bonded to each other to form a piperazine ring structure together with the nitrogen atom to which they are bonded. More specifically, compounds represented by the following general formula (9) are particularly preferred. By using a compound having such a structure as the compound represented by general formula (8), the obtained cross-linked rubber product can be one that is particularly improved in fuel economy. In the above general formula (9), A ３ , R １７ , and s are the same as those in the general formula (8), R ２０ represents a hydrocarbon group.

[0115] R in the above general formula (9) ２０ represents a hydrocarbon group. ２０ The hydrocarbon group which can be the alkyl group is not particularly limited, but examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; alkenyl groups such as vinyl and allyl; alkynyl groups such as ethynyl and propynyl; aryl groups such as phenyl and naphthyl; and aralkyl groups such as benzyl. Of these, alkyl and aryl groups are preferred, alkyl groups are more preferred, and methyl groups are particularly preferred.

[0116] Specific examples of the compound represented by the general formula (8) 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, 2-methoxy-2-methyl-8-(4-methylpiperazinyl)methyl-1,6-dioxa-2-silacyclooctane, etc. These compounds represented by the general formula (8) may be used alone or in combination of two or more.

[0117] The amount of the hydrocarbyloxysilane compound used is not particularly limited, but is preferably 0.1 to 5 mol, more preferably 0.2 to 2 mol, and even more preferably 0.4 to 1.5 mol per mol of active end of the conjugated diene polymer chain having an active end obtained in step 1. By setting the amount of the hydrocarbyloxysilane compound used within the above range, the obtained cross-linked rubber product can be one with further improved fuel economy.

[0118] The method for reacting the hydrocarbyloxysilane compound with the conjugated diene polymer chain obtained by reacting the polyorganosiloxane represented by general formula (1) that has undergone the second step described above is not particularly limited, but examples include mixing them in an inert solvent in which each is soluble. The inert solvents described above can be used as the inert solvent used in this reaction. In addition, a simple and preferred method is to add the hydrocarbyloxysilane compound to the reaction solution used in the second step described above to react the polyorganosiloxane represented by general formula (1) with the conjugated diene polymer chain having an active terminal. In addition, the hydrocarbyloxysilane compound is preferably dissolved in an inert solvent and added to the polymerization system, with the solution concentration preferably in the range of 1 to 50 wt%. The reaction temperature is not particularly limited, but is typically 0 to 120°C. The reaction time is also not particularly limited, but is typically 1 minute to 1 hour.

[0119] Even when a hydrocarbyloxysilane compound is reacted, it is preferable to add a polymerization terminator such as water or an alcohol such as methanol, ethanol, or isopropanol after the reaction of the hydrocarbyloxysilane compound to deactivate the unreacted active terminals, as described above. Similarly, an antioxidant such as a phenolic stabilizer, a phosphorus-based stabilizer, or a sulfur-based stabilizer, a crumb-forming agent, or a scale inhibitor is added to the reaction solution, and the inert solvent is then separated from the reaction solution by direct drying or steam stripping to recover the modified conjugated diene rubber. Before separating the inert solvent from the reaction solution, an extender oil may be mixed with the polymerization solution, and the modified conjugated diene rubber may be recovered as an oil-extended rubber.

[0120] <Rubber Composition> The rubber composition of the present invention is a composition containing silica in addition to a rubber component containing the modified conjugated diene rubber obtained by the above-described production method of the present invention.

[0121] The rubber composition of the present invention may contain rubbers other than the modified conjugated diene rubber obtained by the production method of the present invention described above. Examples of other rubbers include natural rubber (which may be modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), and grafted 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, or which may 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, acrylonitrile-styrene-butadiene copolymer rubber, butyl rubber (IIR), ethylene-propylene copolymer, chloroprene rubber, nitrile chloroprene rubber, and nitrile isoprene rubber, all of which are other than the modified conjugated diene rubber obtained by the production method 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 alone or in combination of two or more, such as natural rubber and polybutadiene rubber, or natural rubber and styrene-butadiene copolymer rubber.

[0122] In the rubber composition of the present invention, the modified conjugated diene rubber obtained by the production method of the present invention preferably accounts for 10 to 100% by weight, and particularly preferably 50 to 100% by weight, of the rubber component in the rubber composition. By including the modified conjugated diene rubber obtained by the production method of the present invention in the rubber component in such a proportion, a cross-linked rubber product with improved fuel economy can be obtained.

[0123] Examples of silica used in the present invention include dry process white carbon, wet process white carbon, colloidal silica, precipitated silica, calcium silicate, and aluminum silicate. Among these, wet process white carbon, which is mainly composed of hydrous silicic acid, is preferred. Carbon-silica dual phase filler, in which silica is supported on the surface of carbon black, may also be used. These silicas may be used alone or in combination of two or more. The nitrogen adsorption specific surface area of ​​the silica used (measured by the BET method in accordance with ASTM D3037-81) is preferably 20 to 400 m ２ / g, more preferably 50 to 220 m ２ / g, particularly preferably 80 to 170 m ２ The pH of the silica is preferably 5 to 10.

[0124] The silica used in the present invention preferably has a dibutyl phthalate (DBP) absorption value in the range of about 100 to about 400, particularly in the range of about 150 to about 300.

[0125] The silica used in the present invention preferably has an average ultimate particle size in the range of 0.01 to 0.05 μm as measured by electron microscopy, but the average ultimate particle size of the silica is not limited to this range and may be smaller or larger.

[0126] The silica used in the present invention may be, for example, any of a variety of commercially available silicas, including Hi-Sil 210, Hi-Sil 233, and Hi-Sil 243LD manufactured by PPG Industries, Zeosil 1115MP, Zeosil 1165MP, Zeosil 165GR, and Zeosil Premium 200MP manufactured by Solvay, and ULTRASIL VN2 and ULTRASIL VN3 manufactured by Evonik.

[0127] The amount of silica compounded in the rubber composition of the present invention is preferably 10 to 250 parts by weight, more preferably 15 to 150 parts by weight, and even more preferably 20 to 130 parts by weight, per 100 parts by weight of the rubber component in the rubber composition. By setting the amount of silica compounded within the above range, the fuel economy of the obtained cross-linked rubber product can be further improved.

[0128] The rubber composition of the present invention may further contain a silane coupling agent from the viewpoint of further improving fuel economy. 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 (e.g., 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. Specific examples of the silane coupling agent include bis(3-(triethoxysilyl)propyl)disulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-(triethoxysilyl)propyl)tetrasulfide, γ-mercaptopropyltriethoxysilane, 3-[ ethoxybis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silyl]-1-propanethiol, 3-octanoylthio-1-propyl-triethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, γ-trimethoxysilylpropylbenzothiazyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-thiocyanatopropyl triethoxysilane, vinyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 3-trimethoxysilylpropyl methacrylate monosulfide, γ-glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-chloropropyltrimethoxysilane. Other examples that can be used include NXT-Z100, NXT-Z30, NXT-Z45, NXT-Z60, NXT-Z45, and NXT manufactured by Momentive Performance Materials, and Si69, Si75, and VP Si363 manufactured by Evonik. These silane coupling agents can be used alone or in combination of two or more. One or more of these silane coupling agents may be oligomerized in advance and used in the oligomerized state.The amount of the silane coupling agent to be added is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight, per 100 parts by weight of silica.

[0129] The rubber composition of the present invention may further contain carbon black such as furnace black, acetylene black, thermal black, channel black, and graphite. Of these, furnace black is preferred. These carbon blacks may be used alone or in combination of two or more. The amount of carbon black is usually 120 parts by weight or less per 100 parts by weight of the rubber component in the rubber composition.

[0130] The method for adding silica to the rubber component containing the modified conjugated diene rubber obtained by the production method of the present invention is not particularly limited, and may include a method of adding silica to a solid rubber component and kneading it (dry kneading method) or a method of adding silica to a solution containing the conjugated diene rubber and coagulating and drying it (wet kneading method).

[0131] The rubber composition of the present invention preferably further contains a crosslinking agent. Examples of crosslinking agents include sulfur-containing compounds such as sulfur and sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, and alkylphenol resins having methylol groups. Of these, sulfur is preferably used. The amount of crosslinking agent blended 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.

[0132] In addition to the above components, the rubber composition of the present invention may contain, in accordance with conventional methods, the necessary amounts of additives such as crosslinking accelerators, crosslinking activators, antioxidants, fillers (excluding the above-mentioned silica and carbon black), activators, process oils, plasticizers, lubricants, compatibilizers, and surfactants. Examples of process oils include petroleum-based softeners such as paraffinic, aromatic, and naphthenic softeners, plant-based softeners, synthetic softeners made from plant-derived resources, and fatty acids. When using petroleum-based softeners, it is preferable that the polycyclic aromatic content extracted by the IP346 method (a testing method of the Institute Petroleum in the UK) is less than 3%.

[0133] When sulfur or a sulfur-containing compound is used as the 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; thiuram-based crosslinking accelerators; dithiocarbamic acid-based crosslinking accelerators; and xanthogenic acid-based crosslinking accelerators. Among these, those containing sulfenamide-based crosslinking accelerators are preferred. These crosslinking accelerators may be used alone or in combination of two or more. The amount of crosslinking accelerator blended 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.

[0134] Examples of crosslinking activators include higher fatty acids such as stearic acid, zinc oxide, etc. These crosslinking activators may be used alone or in combination of two or more. The amount of crosslinking activator blended 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.

[0135] In addition, the rubber composition of the present invention may contain a resin in addition to the rubber component. By incorporating a resin, it is possible to impart tackiness to the rubber composition and increase the dispersibility of the filler in the rubber composition. As a result, improvements in the wet grip properties and abrasion resistance of the resulting cross-linked rubber can be expected. Furthermore, similar to the effect of a plasticizer, it is also possible to improve the processability of the rubber composition. Examples of resins include C5 petroleum resins, C5 / C9 petroleum resins, C9 petroleum resins, dicyclopentadiene resins, terpene resins, terpene phenol resins, aromatic-modified terpene resins, alkylphenol-acetylene resins, rosin resins, rosin ester resins, indene resins, C9 resins containing indene, α-methylstyrene-indene copolymer resins, coumarone-indene resins, farnesene resins, and polylimonene resins. These resins may be modified or hydrogenated. These resins may be used alone or in combination of two or more. The amount of the resin to be mixed is preferably 50 parts by weight or less, and more preferably 25 parts by weight or less, per 100 parts by weight of the rubber component in the rubber composition.

[0136] To obtain the rubber composition of the present invention, the components may be kneaded according to a conventional method. For example, the components excluding thermally unstable components such as crosslinking agents and crosslinking accelerators are kneaded with a conjugated diene rubber, and then the kneaded mixture is mixed with thermally unstable components such as crosslinking agents and crosslinking accelerators to obtain the desired composition. The kneading temperature for the components excluding thermally unstable components and the conjugated diene rubber is preferably 80 to 200°C, more preferably 120 to 180°C, and the kneading time is preferably 30 seconds to 30 minutes. The kneaded mixture is usually mixed with the thermally unstable components after cooling to 100°C or less, preferably 80°C or less.

[0137] <Rubber Cross-Linked 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 produced by using the rubber composition of the present invention, for example, molding it into a desired shape using a molding machine such as an extruder, injection molding machine, compressor, or roll, and then heating it to cause a cross-linking reaction, thereby fixing the shape as a cross-linked rubber product. In this case, cross-linking may be carried out after molding in advance, 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.

[0138] Depending on the shape, size, etc. of the cross-linked rubber, the surface may be cross-linked but the interior may not be sufficiently cross-linked, so secondary cross-linking may be carried out by further heating.

[0139] The heating method may be appropriately selected from common methods used for crosslinking rubber, such as press heating, steam heating, oven heating, and hot air heating.

[0140] The cross-linked rubber product of the present invention thus obtained has good fuel economy because it is obtained using the modified conjugated diene rubber obtained by the production method of the present invention described above, and by making use of these properties, it can be used in a variety of applications, for example, as materials for various tire parts such as cap tread, base tread, carcass, sidewalls, and bead portions in tires; materials for hoses, belts, mats, anti-vibration rubber, and various other industrial products; impact modifiers for resins; resin film cushioning agents; shoe soles; rubber shoes; golf balls; toys; etc. In particular, the cross-linked rubber product of the present invention has good fuel economy and can therefore be suitably used as a tire material, particularly as a material for fuel-efficient tires, and is most suitable for tread applications.

[0141] The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. In the following, "parts" are by weight unless otherwise specified. Tests and evaluations were carried out according to the following methods.

[0142] [Peak Top Molecular Weight (Mp), Weight Average Molecular Weight (Mw), and Molecular Weight Distribution (Mw / Mn)] The peak top molecular weight (Mp), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the modified conjugated diene polymer were determined based on a chart obtained by gel permeation chromatography (GPC) based on the molecular weight converted into polystyrene. Specific measurement conditions for gel permeation chromatography were as follows. Measuring instrument: High performance liquid chromatograph (manufactured by Tosoh Corporation, trade name "HLC-8320") Column: Two polystyrene columns manufactured by Tosoh Corporation, trade name "GMH-HR-H", were connected in series. Detector: Differential refractometer Eluent: Tetrahydrofuran Column temperature: 40°C

[0143] [Styrene unit content, vinyl bond content] The styrene unit content and vinyl bond content are １ Measured by H-NMR.

[0144] [Mooney Viscosity] Measured using a Mooney viscometer (manufactured by Shimadzu Corporation) in accordance with JIS K6300-1 (2013). Note that for rubber that was not made into oil-extended rubber, the Mooney viscosity was measured in an un-oil-extended state.

[0145] [Maximum Power Load of Stirrer] In the polymerization and modification reactions used to produce a modified conjugated diene polymer, the power load of the stirrer used in the polymerization and modification reactions was continuously recorded, and the maximum power load, which was the value at which the power load reached its maximum, was determined to evaluate the production efficiency of the modification reaction. For the maximum power load, the values ​​for Examples 1 to 10 and Comparative Example 1 are expressed as an index with the measured value for Comparative Example 1 set to 100; the values ​​for Examples 11 to 13 and Comparative Example 2 are expressed as an index with the measured value for Comparative Example 2 set to 100; the values ​​for Examples 14 and 15 and Comparative Example 3 are expressed as an index with the measured value for Comparative Example 3 set to 100; and the values ​​for Reference Examples 1 to 3 are expressed as an index with the measured value for Reference Example 1 set to 100. The smaller the index, the lower the power load required to produce a modified conjugated diene polymer, resulting in excellent energy efficiency. Furthermore, the higher the polymer concentration can be produced while achieving high energy efficiency, and therefore, it can be determined that high productivity can be achieved.

[0146] [Ratio of Multibranched Polymers] In the elution curve obtained by gel permeation chromatography of the modified conjugated diene polymer under the above conditions, the area ratio of the peak portion having a peak top molecular weight 1.8 times or more the peak top molecular weight of the peak with the smallest molecular weight relative to the total elution area was defined as the area ratio of the peak portion derived from multibranched polymers with two or more branches, and this area ratio was calculated as the ratio of multibranched polymers. Regarding the ratio of multibranched polymers, for Examples 1 to 10 and Comparative Example 1, the measured value for Comparative Example 1 is expressed as an index of 100; for Examples 11 to 13 and Comparative Example 2, the measured value for Comparative Example 2 is expressed as an index of 100; for Examples 14 and 15 and Comparative Example 3, the measured value for Comparative Example 3 is expressed as an index of 100; and for Reference Examples 1 to 3, the measured value for Reference Example 1 is expressed as an index of 100. It can be determined that the smaller this index, the easier the bale formation and the better the productivity.

[0147] [Fuel Economy of Cross-Linked Rubber Product] The low heat buildup of the cross-linked rubber product was evaluated by measuring tan δ at 60°C using an ARES-G2 (manufactured by TA Instruments) on a test piece of the cross-linked rubber product having a length of 50 mm, a width of 12.7 mm and a thickness of 2 mm under conditions of a dynamic strain of 2.0% and 10 Hz. With regard to the values ​​of tan δ, for Examples 1 to 10 and Comparative Example 1, the value is expressed as an index relative to the measured value of Comparative Example 1 being 100; for Examples 11 to 13 and Comparative Example 2, the value is expressed as an index relative to the measured value of Comparative Example 2 being 100; for Examples 14 and 15 and Comparative Example 3, the value is expressed as an index relative to the measured value of Comparative Example 3 being 100; and for Reference Examples 1 to 3, the value is expressed as an index relative to the measured value of Reference Example 1 being 100. The smaller the index, the better the fuel economy.

[0148] Example 1 (Production of Polymer Block (A)) 218.1 parts of cyclohexane, 7.5 parts of styrene, and 0.3 parts of tetramethylethylenediamine were placed in a nitrogen-purged vessel, and the internal temperature of the vessel was adjusted to 50°C. Next, 1.64 parts of n-butyllithium was added, followed by the addition of 92.5 parts of isoprene over 80 minutes. The mixture was then allowed to react for 15 minutes, yielding a solution containing polymer block (A) having an active terminal. This polymer block (A) had a weight-average molecular weight (Mw) of 6,500, a molecular weight distribution (Mw / Mn) of 1.10, a styrene unit content of 7.5%, an isoprene unit content of 92.5%, and a vinyl bond content of 7.0%.

[0149] (Production of Modified Conjugated Diene Polymer) 455.6 parts of cyclohexane, 36.0 parts of styrene, 24.0 parts of 1,3-butadiene, and 0.026 parts of tetramethylethylenediamine were charged into an autoclave equipped with a stirrer under a nitrogen atmosphere. To detoxify impurities that may deactivate the polymerization, normal butyllithium was added to the autoclave as a scavenger. Then, 5.3 parts of the resulting solution containing polymer block (A) having active terminals (1.6 parts of polymer block (A) used) was added, and polymerization was initiated at 40°C. Twenty minutes after the start of polymerization, 3.8 parts of styrene and 21.3 parts of 1,3-butadiene were continuously added over 20 minutes. Thereafter, 2.3 parts of styrene and 12.8 parts of 1,3-butadiene were continuously added over 30 minutes. The maximum temperature during the polymerization reaction was 70°C. After a series of continuous additions, the mixture was stirred for 30 minutes. After confirming that the polymerization conversion rate was in the range of 95% to 100%, the addition of the polyorganosiloxane represented by the following formula (10) was started. The polyorganosiloxane was used in the state of a 40% by weight xylene solution, and was added continuously and at a constant rate over 5 minutes from the start of addition under stirring with a stirrer. The total amount of polyorganosiloxane added was 0.129 parts (equivalent to 0.450 moles of epoxy groups in the polyorganosiloxane per mole of n-butyllithium used). Then, under stirring with a stirrer, a modification reaction was carried out for 30 minutes from the start of addition of the polyorganosiloxane. Thereafter, methanol was added in an amount equivalent to twice the moles of the n-butyllithium used as a polymerization terminator to obtain a solution containing a modified conjugated diene-based polymer. In Example 1, the concentration of the modified conjugated diene polymer in the solution containing the modified conjugated diene polymer (final polymer concentration) was 18% by weight.To this solution, 0.20 parts of Irganox 1520L (manufactured by Ciba Specialty Chemicals) was added as an antioxidant per 100 parts of the modified conjugated diene polymer. Next, 25 parts of process oil (manufactured by ENEOS Corporation, trade name: Aromax T-DAE) was added as an extender oil per 100 parts of the modified conjugated diene polymer. The mixture was stirred, and the solvent was removed by steam stripping. A solid modified conjugated diene polymer was obtained by hot air drying. The styrene unit content, vinyl bond content, peak top molecular weight (Mp), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), Mooney viscosity, and content ratio of multi-branched units of the resulting modified conjugated diene polymer, as well as the maximum power load of the stirrer during the modification reaction with polyorganosiloxane, were measured. The results are shown in Table 1.

[0150] (Production of Rubber Composition and Cross-Linked Rubber Product) In a 250 ml Brabender mixer, 70 parts of the modified conjugated diene polymer obtained above (amount as polymer excluding extender oil) and 30 parts of butadiene rubber (manufactured by Nippon Zeon Co., Ltd., trade name "Nipol BR1220") were masticated for 30 seconds, and then 50 parts of silica (manufactured by Solvay, trade name "Zeosil 1165MP"), 10 parts of process oil (manufactured by ENEOS Corporation, trade name "Aromax T-DAE"), and 6.0 parts of a silane coupling agent (manufactured by Evonik Co., Ltd., trade name "Si69") were added, and the mixture was kneaded for 1.5 minutes at an initial temperature of 110°C. 25 parts of "N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine" (trade name "Nocrac 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 3.0 parts of zinc oxide, 2.0 parts of stearic acid, and 2.0 parts of an antioxidant, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, were added, and the mixture was further kneaded for 2.5 minutes, and then the kneaded mixture was discharged from the mixer. The temperature of the kneaded mixture at the end of kneading was 150°C. After cooling to room temperature, the kneaded mixture was again kneaded for 3 minutes in the Brabender type mixer with an initial temperature of 110°C, and then the kneaded mixture was discharged from the mixer. Next, 1.50 parts of sulfur, 1.8 parts of N-cyclohexyl-2-benzothiazolylsulfenamide (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noccela CZ-G"), and 1.5 parts of 1,3-diphenylguanidine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noccela D") were added to the obtained kneaded product and kneaded with an open roll at 50°C to obtain a rubber composition. The obtained rubber composition was then molded into a sheet with an open roll at 50°C, and the obtained sheet-shaped rubber composition was press-crosslinked at 160°C for 20 minutes to prepare test pieces of the cross-linked rubber. The obtained cross-linked rubber was used to evaluate fuel economy. The results are shown in Table 1.

[0151] [Example 2] A modified conjugated diene polymer and a cross-linked rubber were obtained and evaluated in the same manner as in Example 1, except that the polyorganosiloxane represented by the above formula (10) (40 wt% xylene solution) was added continuously and at a constant rate under stirring with a stirrer over 14 minutes from the start of addition. The results are shown in Table 1.

[0152] [Example 3] A modified conjugated diene polymer was obtained in the same manner as in Example 1, except that the addition of the polyorganosiloxane represented by the above formula (10) (a xylene solution with a concentration of 40% by weight) was carried out continuously and at a uniform speed over a period of 20 minutes from the start of addition while stirring with a stirrer, and the amount of process oil added was changed to 20 parts per 100 parts of the modified conjugated diene polymer, and a cross-linked rubber product was obtained in the same manner as in Example 1, except that the amount of process oil added during the production of the rubber composition and the cross-linked rubber product was changed to 13.5 parts, and evaluations were similarly performed. The results are shown in Table 1.

[0153] [Example 4] A modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Example 1, except that the polyorganosiloxane represented by the above formula (10) (40 wt% xylene solution) was added continuously and at a constant rate under stirring with a stirrer over a period of 33 minutes from the start of addition, and the modification reaction was carried out for 35 minutes from the start of addition of the polyorganosiloxane, and the evaluation was similarly carried out. The results are shown in Table 1.

[0154] Example 5 A modified conjugated diene polymer was obtained in the same manner as in Example 1, except that the amount of tetramethylethylenediamine added and the amount of the solution containing the polymer block (A) having an active terminal were changed, and the polyorganosiloxane represented by the above formula (10) (40 wt % xylene solution) was added in three separate times. Specifically, except that 0.027 parts of tetramethylethylenediamine and 5.7 parts of a solution containing a polymer block (A) having an active terminal (the amount of polymer block (A) used was 1.72 parts) were charged, the polymerization reaction was carried out in the same manner as in Example 1, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.047 parts of polyorganosiloxane (40 wt% concentration xylene solution) were added within 1 minute under stirring with a stirrer (in terms of epoxy groups in the polyorganosiloxane, an amount equivalent to 0.150 moles per mole of n-butyllithium used) (first-stage addition), and a modification reaction was carried out for 10 minutes under stirring with a stirrer. Next, after the 10-minute modification reaction, 0.047 parts of polyorganosiloxane (40 wt% concentration xylene solution) were added within 1 minute under stirring with a stirrer (second-stage addition), and a modification reaction was carried out for 10 minutes under stirring with a stirrer. Furthermore, after 10 minutes of modification reaction, 0.047 parts of polyorganosiloxane (40 wt% xylene solution) was added within 1 minute under stirring with a stirrer (third-stage addition), and the modification reaction was carried out under stirring with a stirrer. Then, under stirring with a stirrer, the modification reaction was carried out for 40 minutes from the start of the addition of the polyorganosiloxane. Then, except for changing the amount of tetramethylethylenediamine added and the amount of the solution containing the polymer block (A) having an active terminal, and changing the method of adding the polyorganosiloxane (40 wt% xylene solution) as described above, a modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Example 1, and were evaluated in the same manner. The results are shown in Table 1.

[0155] [Example 6] A modified conjugated diene polymer was obtained in the same manner as in Example 1, except that the amount of tetramethylethylenediamine added was changed and the addition of the polyorganosiloxane (40 wt% xylene solution) represented by the above formula (10) was performed in two separate batches. Specifically, except that 0.025 parts of tetramethylethylenediamine was added, the polymerization reaction was carried out in the same manner as in Example 1, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.064 parts of polyorganosiloxane (40 wt% xylene solution) were added within 1 minute under stirring with a stirrer (equivalent to 0.225 moles of epoxy groups in the polyorganosiloxane per mole of n-butyllithium used) (first-stage addition), and the modification reaction was carried out for 10 minutes under stirring with a stirrer. Next, after 10 minutes of modification reaction, 0.064 parts of polyorganosiloxane (40 wt% xylene solution) was added within 1 minute under stirring with a stirrer (second-stage addition), and the modification reaction was carried out under stirring with a stirrer. Then, under stirring with a stirrer, the modification reaction was carried out for 30 minutes from the start of the addition of polyorganosiloxane. Then, except for changing the amount of tetramethylethylenediamine added and changing the method of adding polyorganosiloxane (40 wt% xylene solution) as described above, a modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 1.

[0156] Example 7 The amount of tetramethylethylenediamine added was changed to 0.026 parts, and the amount of polyorganosiloxane (40 wt% xylene solution) represented by the above formula (10) added in the first stage was 0.079 parts (equivalent to 0.275 moles of epoxy groups in the polyorganosiloxane, per mole of n-butyllithium used), and the amount of polyorganosiloxane (40 wt% xylene solution) added in the second stage was 0.050 parts (equivalent to 0.175 moles of epoxy groups in the polyorganosiloxane, per mole of n-butyllithium used), except that a modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Example 6 and evaluated in the same manner. The results are shown in Table 1.

[0157] Example 8 The amount of tetramethylethylenediamine added was changed to 0.029 parts, the amount of the solution containing the polymer block (A) having an active terminal added was changed to 6.3 parts (1.9 parts as the amount of polymer block (A) used), and the amount of polyorganosiloxane (40 wt% xylene solution) added in the first stage was changed to 0.102 parts (equivalent to 0.300 moles per mole of n-butyllithium used, calculated as the epoxy groups in the polyorganosiloxane), and the amount of polyorganosiloxane (40 wt% xylene solution) added in the second stage was changed to 0.051 parts (equivalent to 0.150 moles per mole of n-butyllithium used, calculated as the epoxy groups in the polyorganosiloxane), except that a modified conjugated diene polymer and a cross-linked rubber were obtained and evaluated in the same manner as in Example 6. The results are shown in Table 1.

[0158] [Example 9] A modified conjugated diene polymer and a cross-linked rubber product were obtained and evaluated in the same manner as in Example 8, except that the amount of cyclohexane used as the solvent was changed to 426.3 parts. The results are shown in Table 1. In Example 9, the concentration of the modified conjugated diene polymer in the solution containing the modified conjugated diene polymer (final polymer concentration) was 19% by weight.

[0159] [Example 10] A modified conjugated diene polymer and a cross-linked rubber product were obtained and evaluated in the same manner as in Example 8, except that the amount of cyclohexane used as the solvent was changed to 400.0 parts. The results are shown in Table 1. In Example 10, the concentration of the modified conjugated diene polymer in the solution containing the modified conjugated diene polymer (final polymer concentration) was 20% by weight.

[0160] Comparative Example 1 A modified conjugated diene polymer was obtained in the same manner as in Example 6, except that the polyorganosiloxane represented by formula (10) (40 wt. % xylene solution) was added all at once. Specifically, a polymerization reaction was carried out in the same manner as in Example 1, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.129 parts (equivalent to 0.450 moles of epoxy groups in the polyorganosiloxane per mole of n-butyllithium used) of the polyorganosiloxane (40 wt. % xylene solution) was added within 1 minute under stirring with a mixer, and the modification reaction was carried out for 30 minutes under stirring with a mixer. Then, a modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Example 6, and evaluated in the same manner. The results are shown in Table 1.

[0161] Example 11 (Production of Modified Conjugated Diene Polymer) 455.6 parts of cyclohexane, 16.0 parts of styrene, 44.0 parts of 1,3-butadiene, and 0.146 parts of tetramethylethylenediamine were charged into an autoclave equipped with a stirrer under a nitrogen atmosphere. To detoxify impurities that may deactivate the polymerization, normal butyllithium was added as a scavenger to the autoclave. Then, 9.8 parts of the solution containing the polymer block (A) having an active end obtained in Example 1 (2.96 parts of polymer block (A) used) was added, and polymerization was initiated at 40°C. Ten minutes after the start of polymerization, 5.0 parts of styrene and 35.0 parts of 1,3-butadiene were continuously added over 40 minutes. The maximum temperature during the polymerization reaction was 70°C. After a series of continuous additions, the mixture was stirred for 20 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, the addition of the polyorganosiloxane represented by the above formula (10) was started. Specifically, after confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.119 parts of polyorganosiloxane (equivalent to 0.225 moles of epoxy groups in the polyorganosiloxane per mole of n-butyllithium used) was added within 1 minute in a 40 wt% xylene solution under stirring with a stirrer (first-stage addition), and a modification reaction was carried out for 10 minutes under stirring with a stirrer. Next, after the 10-minute modification reaction, 0.119 parts of polyorganosiloxane was added within 1 minute in a 40 wt% xylene solution under stirring with a stirrer (second-stage addition), and a modification reaction was carried out under stirring with a stirrer. Then, under stirring with a stirrer, the modification reaction was carried out for 30 minutes from the start of the addition of the polyorganosiloxane. Thereafter, methanol was added as a polymerization terminator in an amount equivalent to twice the molar amount of n-butyllithium used to obtain a solution containing a modified conjugated diene polymer. In Example 11, the concentration of the modified conjugated diene polymer in the solution containing the modified conjugated diene polymer (final polymer concentration) was 18 wt%.Then, 0.20 parts of Irganox 1520L (manufactured by Ciba Specialty Chemicals) was added to this solution as an antioxidant per 100 parts of the modified conjugated diene polymer, and the solvent was removed by steam stripping, followed by hot air drying to obtain a solid modified conjugated diene polymer. The styrene unit content, vinyl bond content, peak top molecular weight (Mp), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), Mooney viscosity, and content ratio of multi-branched polymers of the obtained modified conjugated diene polymer, as well as the maximum power load of the stirrer during the modification reaction with polyorganosiloxane, were measured and the results are shown in Table 2.

[0162] (Production of Rubber Composition and Cross-Linked Rubber Product) A rubber composition and a cross-linked rubber product were produced in the same manner as in Example 1, except that the modified conjugated diene polymer obtained above was used and that the amount of process oil added during the production of the rubber composition and the cross-linked rubber product was changed to 25 parts, and the obtained cross-linked rubber product was used to evaluate fuel economy. The results are shown in Table 2.

[0163] Example 12 A second stage of addition of polyorganosiloxane represented by the above formula (10) (40 wt% xylene solution) was carried out, and the modification reaction was carried out for 30 minutes under stirring with a stirrer. Then, within 1 minute under stirring with a stirrer, 0.226 parts of 2,2-dimethoxy-8-(4-methylpiperazinyl)methyl-1,6-dioxa-2-silacyclooctane (a compound represented by the above general formula (9)) as hydrocarbyloxirane compound A was added in a 50 wt% xylene solution (an amount equivalent to 1.00 moles per mole of n-butyllithium used) and the reaction was carried out for 15 minutes. A modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Example 11, and evaluated in the same manner. The results are shown in Table 2.

[0164] Example 13 A second stage of addition of polyorganosiloxane represented by formula (10) (40 wt% xylene solution) was carried out, and the modification reaction was carried out for 30 minutes under stirring with a stirrer. Further, within 1 minute under stirring with a stirrer, 0.165 parts of 3-(2-aminoethylamino)propyltrimethoxysilane (a compound represented by general formula (7) above) as hydrocarbyloxirane compound B was added in a 50 wt% xylene solution (an amount equivalent to 1.00 mole per mole of n-butyllithium used). A modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Example 11, and evaluated in the same manner. The results are shown in Table 2.

[0165] Comparative Example 2 A modified conjugated diene polymer was obtained in the same manner as in Example 11, except that the polyorganosiloxane represented by formula (10) (40 wt. % xylene solution) was added all at once. Specifically, a polymerization reaction was carried out in the same manner as in Example 11, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.238 parts (equivalent to 0.450 moles of epoxy groups in the polyorganosiloxane per mole of n-butyllithium used) of the polyorganosiloxane (40 wt. % xylene solution) was added within 1 minute under stirring with a mixer, and the modification reaction was carried out for 20 minutes under stirring with a mixer. Then, a modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Example 11, and evaluated in the same manner. The results are shown in Table 2.

[0166] Example 14 (Production of Modified Conjugated Diene Polymer) 500.4 parts of cyclohexane, 15.0 parts of styrene, 37.1 parts of 1,3-butadiene, and 0.016 parts of tetramethylethylenediamine were charged into an autoclave equipped with a stirrer under a nitrogen atmosphere. To detoxify impurities that may deactivate the polymerization, normal butyllithium was added as a scavenger to the autoclave. Then, 8.8 parts of the solution containing the polymer block (A) having an active terminal obtained in Example 1 (2.66 parts of polymer block (A) used) was added, and polymerization was initiated at 55°C. 12 minutes after the start of polymerization, 3.3 parts of 1,3-butadiene were continuously added over 4 minutes. One minute later, 17.8 parts of 1,3-butadiene were continuously added over 17 minutes. Furthermore, 13.4 parts of 1,3-butadiene were continuously added over 18 minutes. Further, 13.4 parts of 1,3-butadiene were added continuously over 35 minutes. The maximum temperature during the polymerization reaction was 80°C. After the series of continuous additions, the mixture was stirred for 30 minutes. After confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.053 parts of tetramethylethylenediamine was added and stirred for 5 minutes. Then, 0.002 parts of 1,6-bis(trichlorosilyl)hexane was added and allowed to react for 10 minutes. Thereafter, the addition of the polyorganosiloxane represented by the above formula (10) was started. Specifically, 0.143 parts of polyorganosiloxane (equivalent to 0.300 moles of epoxy groups in the polyorganosiloxane per mole of n-butyllithium used, converted into epoxy groups in the polyorganosiloxane) was added within 1 minute in a 40% by weight xylene solution under stirring with a stirrer (first-stage addition), and the modification reaction was carried out for 10 minutes under stirring with a stirrer. Next, after 10 minutes of modification reaction, 0.143 parts of polyorganosiloxane was added in a 40 wt% xylene solution under stirring with a stirrer within 1 minute (second stage addition), and the modification reaction was carried out under stirring with a stirrer. Then, under stirring with a stirrer, the modification reaction was carried out for 30 minutes from the start of the addition of polyorganosiloxane.Further, within 1 minute under stirring with a stirrer, 0.148 parts of hydrocarbyloxirane compound B (amount equivalent to 1.00 mole per mole of n-butyllithium used) was added to a 50 wt % xylene solution, and the mixture was allowed to react for 15 minutes. Thereafter, methanol was added as a polymerization terminator in an amount equivalent to twice the moles of n-butyllithium used, to obtain a solution containing a modified conjugated diene polymer. In Example 14, the concentration of the modified conjugated diene polymer in the solution containing the modified conjugated diene polymer (final polymer concentration) was 16.7 wt %. To this solution, 0.20 parts of Irganox 1520L (manufactured by Ciba Specialty Chemicals) was added as an antioxidant per 100 parts of the modified conjugated diene polymer, and 0.20 parts of Irganox 1076 (manufactured by Ciba Specialty Chemicals) was added per 100 parts of the modified conjugated diene polymer. The solvent was then removed by steam stripping, and the resulting solid modified conjugated diene polymer was obtained by hot air drying. The styrene unit content, vinyl bond content, peak top molecular weight (Mp), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), Mooney viscosity, and content ratio of multi-branched polymers of the resulting modified conjugated diene polymer, as well as the maximum power load of the stirrer during the modification reaction with polyorganosiloxane, were measured. The results are shown in Table 3.

[0167] (Production of Rubber Composition and Cross-Linked Rubber Product) In a 250 ml Banbury mixer, 50 parts of natural rubber, 30 parts of the modified conjugated diene polymer obtained above, and 20 parts of butadiene rubber (manufactured by Nippon Zeon Co., Ltd., trade name "Nipol BR1220") were masticated for 30 seconds. Next, 25 parts of silica (manufactured by Solvay, trade name "Zeosil 1165MP"), 25 parts of carbon black (manufactured by Tokai Carbon Co., Ltd., trade name "Seat 9H"), and 2.0 parts of a silane coupling agent: bis(3-(triethoxysilyl)propyl)tetrasulfide (manufactured by Evonik, trade name "Si69") were added and kneaded for 1.5 minutes at a starting temperature of 110°C, after which 3 parts of zinc oxide, 2 parts of stearic acid, and 2 parts of an antioxidant: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac 6C") were added and kneaded for an additional 2.5 minutes, and the kneaded product was discharged from the mixer. The temperature of the kneaded product at the end of kneading was 150°C. The kneaded product was cooled to room temperature and then kneaded again in the Banbury mixer at a starting temperature of 110°C for 3 minutes, after which the kneaded product was discharged from the mixer. Next, the resulting kneaded mixture was kneaded using an open roll at 50°C with a mixture of 1.75 parts of sulfur, 1.0 part of a crosslinking accelerator: N-(tert-butyl)-2-benzothiazole sulfenamide (manufactured by Sanshin Chemical Industry Co., Ltd., trade name "Suncerer NS-G"), and 0.53 parts of a crosslinking accelerator: 1,3-diphenylguanidine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noccelaer D"), and then a sheet-like rubber composition was taken out. The resulting rubber composition was press-crosslinked at 160°C for 7 minutes, and test pieces of the crosslinked rubber were prepared and evaluated for fuel economy. The results are shown in Table 3.

[0168] After it was confirmed that the polymerization conversion rate was in the range of 95% to 100%, a modified conjugated diene polymer and a cross-linked rubber product were obtained in the same manner as in Example 14, except that tetramethylethylenediamine was not added, and then the evaluations were carried out in the same manner. The results are shown in Table 3.

[0169] Comparative Example 3 A modified conjugated diene polymer was obtained in the same manner as in Example 15, except that the polyorganosiloxane represented by formula (10) (40 wt. % xylene solution) was added all at once. Specifically, a polymerization reaction was carried out in the same manner as in Example 15, and after adding 1,6-bis(trichlorosilyl)hexane, 0.286 parts of the polyorganosiloxane (40 wt. % xylene solution) was added within 1 minute under stirring with a mixer. (This amount corresponds to 0.600 moles of epoxy groups in the polyorganosiloxane per mole of n-butyllithium used.) The modification reaction was carried out for 20 minutes under stirring with a mixer. A modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Example 15, and evaluated in the same manner. The results are shown in Table 3.

[0170] Reference Example 1 (Production of Modified Conjugated Diene Polymer) 400.0 parts of cyclohexane, 16.0 parts of styrene, 44.0 parts of 1,3-butadiene, and 0.092 parts of tetramethylethylenediamine were charged into an autoclave equipped with a stirrer under a nitrogen atmosphere. To detoxify impurities that may deactivate the polymerization, normal butyllithium was added as a scavenger to the autoclave. Then, 6.5 parts of the solution containing the polymer block (A) having an active end obtained in Example 1 (1.96 parts of polymer block (A) used) were added, and polymerization was initiated at 40°C. Ten minutes after the start of polymerization, 5.0 parts of styrene and 35.0 parts of 1,3-butadiene were continuously added over 40 minutes. The maximum temperature during the polymerization reaction was 60°C. After the series of continuous additions, the mixture was stirred for 20 minutes. After confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.004 parts of 1,6-bis(trichlorosilyl)hexane was added and the reaction was allowed to proceed for 10 minutes. Thereafter, 0.192 parts (equivalent to 1.28 moles per mole of n-butyllithium used) of hydrocarbyl oxirane compound A was added to a 50 wt% xylene solution within 1 minute under stirring with a stirrer, and the modification reaction was allowed to proceed for 25 minutes under stirring with a stirrer. Then, methanol was added as a polymerization terminator in an amount equivalent to twice the molar amount of n-butyllithium used to obtain a solution containing a modified conjugated diene polymer. In Reference Example 1, the concentration of the modified conjugated diene polymer in the solution containing the modified conjugated diene polymer (final polymer concentration) was 20 wt%. Then, 0.20 parts of Irganox 1520L (manufactured by Ciba Specialty Chemicals) was added to this solution as an antioxidant per 100 parts of the modified conjugated diene polymer, and the solvent was removed by steam stripping, followed by hot air drying to obtain a solid modified conjugated diene polymer. The styrene unit content, vinyl bond content, peak top molecular weight (Mp), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), Mooney viscosity, and content ratio of multi-branched bodies of the obtained modified conjugated diene polymer, as well as the maximum power load of the stirrer during the modification reaction with polyorganosiloxane, were measured and the results are shown in Table 4.

[0171] (Production of Rubber Composition and Cross-Linked Rubber Product) A rubber composition and a cross-linked rubber product were produced in the same manner as in Example 11, except that the modified conjugated diene polymer obtained above was used, and the obtained cross-linked rubber product was used to evaluate fuel economy. The results are shown in Table 4.

[0172] Reference Example 2 A modified conjugated diene polymer was obtained in the same manner as in Reference Example 1, except that the addition of hydrocarbyl oxirane compound A was changed from a lump-sum addition to a continuous addition. Specifically, a polymerization reaction was carried out in the same manner as in Reference Example 1, and after adding 1,6-bis(trichlorosilyl)hexane, hydrocarbyl oxirane compound A was added continuously and at a constant rate as a 50 wt % xylene solution over 21 minutes from the start of addition under stirring with a stirrer. The total amount of hydrocarbyl oxirane compound B added was 0.192 parts (equivalent to 1.28 moles per mole of n-butyllithium used). Then, under stirring with a stirrer, a modification reaction was carried out for 25 minutes from the start of addition of hydrocarbyl oxirane compound A. A modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Reference Example 1, and evaluated in the same manner. The results are shown in Table 4.

[0173] A modified conjugated diene polymer and a cross-linked rubber were obtained in the same manner as in Reference Example 2, except that the addition of hydrocarbyloxirane compound A (40 wt % xylene solution) was carried out continuously and at a constant rate over 4 minutes from the start of addition under stirring with a stirrer, and were evaluated in the same manner. The results are shown in Table 4.

[0174]

[0175]

[0176]

[0177]

[0178] As shown in Tables 1, 2, and 3, when reacting a polyorganosiloxane represented by general formula (1) with a conjugated diene polymer chain having an active terminal, the polyorganosiloxane represented by general formula (1) was added continuously over 2 to 60 minutes or in multiple divided additions. In Examples 1 to 15, the maximum power load of the agitator in the modification reaction could be reduced, thereby enabling the production of modified conjugated diene polymers at low power loads, resulting in excellent energy efficiency and, further, production at higher polymer concentrations while maintaining high energy efficiency. Furthermore, the resulting modified conjugated diene polymers had good fuel economy. In particular, as is clear from the results of Examples 9 and 10, the maximum power load of the agitator could be kept low even when the polymer concentration was increased.

[0179] In addition, from the results of Table 4, when another silane-based modifier is used instead of the polyorganosiloxane represented by the general formula (1) (Reference Examples 1 to 3), even if continuous addition or divided addition is performed, the maximum power load of the stirrer does not decrease, but rather increases. Therefore, it can be said that the effect of continuous addition or divided addition is a unique effect when using a polyorganosiloxane represented by the general formula (1).

Claims

1. A method for producing a modified conjugated diene polymer, comprising: a first 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; and a second step of reacting the conjugated diene polymer chain having an active end with a polyorganosiloxane represented by the following general formula (1) by adding the polyorganosiloxane to the conjugated diene polymer chain having an active end over a period of 2 to 60 minutes, either continuously or in multiple divided additions: (In the above general formula (1), R １ ~R ８ are hydrocarbon groups having 1 to 20 carbon atoms, and may be the same or different from each other. １ and X ４ represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a polar functional group having an atom of Group 15 or 16 of the periodic table, a halogen atom, or a hydrocarbon group having 1 to 20 carbon atoms which may have the polar functional group or a halogen atom, and these may be the same or different. ２ represents a polar functional group having an atom of Group 15 or 16 of the periodic table, a halogen atom, or a hydrocarbon group having 1 to 20 carbon atoms which may have the polar functional group or a halogen atom; X ２ When there are a plurality of X, they may be the same or different. ３ is a group containing 2 to 20 repeating alkylene glycol units, and X ３ A part of X may be a group derived from a group containing 2 to 20 repeating units of alkylene glycol, ３ When there are a plurality of m, they may be the same or different. m is an integer of 1 to 200, n is an integer of 0 to 200, and k is an integer of 0 to 200.

2. The method for producing a modified conjugated diene polymer according to claim 1, wherein the polar functional group having an atom of Group 16 of the periodic table is a polar functional group having an oxygen atom.

3. The above X １ and X ４ is a hydrocarbon group having 1 to 20 carbon atoms, ２ The method for producing a modified conjugated diene polymer according to claim 1 or 2, wherein is a hydrocarbon group having 1 to 20 carbon atoms which may have an alkoxy group or an epoxy group.

4. A method for producing a modified conjugated diene polymer according to any one of claims 1 to 3, wherein the modified conjugated diene polymer contains an isoprene-containing block containing 80 to 100% by weight of isoprene units.

5. The method for producing a modified conjugated diene polymer according to any one of claims 1 to 4, wherein a total of 0.5 to 5.0 moles of polar compound per mole of polymerization initiator is added before the second step.

6. A method for producing a rubber composition, which comprises obtaining a modified conjugated diene polymer by the method according to any one of claims 1 to 5, and adding silica to the modified conjugated diene polymer.

7. The method for producing a rubber composition according to claim 6, further comprising adding a crosslinking agent.

8. A method for producing a cross-linked rubber product, which comprises obtaining a rubber composition by the method according to claim 6 or 7 and cross-linking said rubber composition.

9. A method for producing a tire, comprising obtaining a rubber composition by the method of producing a tire according to claim 6 or 7, and crosslinking the rubber composition to produce a tire comprising a crosslinked rubber product of the rubber composition.

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