MANUFACTURING PROCESS FOR AROMATIC VINYL DIENE COPOLYMER AND MANUFACTURING PROCESS FOR RUBBER COMPOSITION

Abstract

A process for producing an aromatic vinyl-diene copolymer, wherein the aromatic vinyl-diene copolymer is a copolymer of an aromatic vinyl and a diene, and wherein the aromatic vinyl-diene copolymer has a content of repeat units derived from an aromatic vinyl in an amount of 18 wt% or more, and among repeat units derived from a diene, a proportion of a vinyl structure of 8 mol% or less, a proportion of a 1,4-trans structure of 60 mol% or less and a proportion of a 1,4-cis structure of 40 to 95 mol%, wherein the process for producing the aromatic vinyl-diene copolymer comprises copolymerizing a monomer containing an aromatic vinyl and a diene using an initiator, wherein the initiator is prepared with an organolithium compound, an alkylaluminium, a barium alcoholate and at least one polar compound selected from the group consisting of water and an alcohol.

Description

Technical field

[0001] The present invention relates to a method for producing an aromatic vinyl diene copolymer and a method for producing a rubber composition. State of the art

[0002] Diene polymers such as a butadiene homopolymer (BR) and a styrene-butadiene copolymer (SBR) are known as rubber materials used in tires and the like. It should be noted that diene polymers are mainly produced by emulsion polymerization or solution polymerization. For example, patent document 1 describes a process for producing a diene (conjugated diene) polymer by solution polymerization, wherein the process includes the use of a catalyst composition containing: (a) a dialkoxybarium compound, (b) an organoaluminum compound, (c) an organolithium compound, and (d) an amine compound represented by general formula (I) or a diamine compound represented by general formula (II), and polymerizing a conjugated diene or a monomer formed from a conjugated diene and an aromatic vinyl compound in an inert organic solvent.Patent document 2 describes a process for producing an aromatic vinyl-diene copolymer by copolymerizing a monomer containing an aromatic vinyl and a diene using an initiator prepared from an organolithium compound, an alkylaluminum, and a metal alcoholate. Patent document 3 describes a process for producing a functionalized polymer in which a reactive chain end of the polymer is reacted with an imide compound. Patent document 4 describes a process for the homopolymerization of vinylaromatic monomers or block copolymerization of vinylaromatic monomers and dienes. List of literature on patent literature Patent Document 1: JP 2712622 B Patent document 2: US 2019 / 0 023 880 A1 Patent document 3: US 7,906,592 B2 Patent document 4: US 6,350,834 B1 Brief description of the invention: Technical problem

[0003] In recent years, for example, to improve the properties in low-temperature environments, a material with a low glass transition temperature (Tg) (e.g., -80 °C or lower) has been needed for a copolymer of an aromatic vinyl and a diene (aromatic vinyl-diene copolymer) (e.g., SBR). For example, a copolymer of an aromatic vinyl and a diene (e.g., SBR) produced by the process described in Patent Document 1 has a relatively high Tg, and there is a need for a material with a lower Tg.

[0004] In view of the circumstances described above, it is an object of the present invention to provide a method for producing an aromatic vinyl-diene copolymer, which produces an aromatic vinyl-diene copolymer with a low glass transition temperature, and a method for producing a rubber composition using the method. Solution to the problem

[0005] As a result of careful research into the problems described above, the inventors of the present invention have found that the problems described above can be solved by using an initiator prepared with an organolithium compound, an alkylaluminium, a barium alcoholate and at least one polar compound selected from the group consisting of water and an alcohol, and have thus completed the present invention. In other words, the inventors have discovered that the problems described above can be solved by the following configurations. (1) A process for producing an aromatic vinyl-diene copolymer, wherein the aromatic vinyl-diene copolymer is a copolymer of an aromatic vinyl and a diene and the aromatic vinyl-diene copolymer has a content of repeat units derived from an aromatic vinyl in an amount of 18 wt% or more, and among repeat units derived from a diene, a proportion of a vinyl structure of 8 mol% or less, a proportion of a 1,4-trans structure of 60 mol% or less and a proportion of a 1,4-cis structure of 40 to 95 mol%, wherein the process for producing the aromatic vinyl-diene copolymer includes copolymerizing a monomer containing an aromatic vinyl and a diene using an initiator, wherein the initiator is prepared with an organolithium compound, an alkylaluminium, a barium alcoholate and at least one polar compound selected from the group consisting of water and an alcohol. (2) A process for producing an aromatic vinyl-diene copolymer, wherein the aromatic vinyl-diene copolymer is a copolymer of an aromatic vinyl and a diene, wherein the aromatic vinyl-diene copolymer has a content of repeating units derived from an aromatic vinyl in an amount of 18 wt% or more, among repeating units derived from a diene, a proportion of a vinyl structure of 8 mol% or less, a proportion of a 1,4-trans structure of 60 mol% or less, and a proportion of a 1,4-cis structure of 40 to 95 mol%, and wherein the aromatic vinyl-diene copolymer has one end modified with at least one electrophile selected from the group consisting of titanium halide, tin halide, cyclic silazane, alkoxysilane, epoxide, amine, ketone, and a compound represented by formula (N) which will be described later, wherein the process for producing the aromatic vinyl-diene copolymer includes copolymerizing a monomer containing an aromatic vinyl and a diene using an initiator, wherein the initiator is prepared with an organolithium compound, an alkylaluminum, a barium alcoholate and at least one polar compound selected from the group consisting of water and an alcohol, and Subsequent termination of the polymerization using the electrophile. (3) The process for producing an aromatic vinyl-diene copolymer according to (1) or (2) above, wherein the proportion of a quantity of the polar compound in relation to a quantity of the organolithium compound, expressed as a molar ratio, is from 1 / 15 to 1 / 1. (4) A method for producing a rubber composition, including: Producing an aromatic vinyl diene copolymer using the process for producing an aromatic vinyl diene copolymer according to any of the preceding points (1) to (3), and mixing the obtained aromatic vinyl diene copolymer with a filler and obtaining a rubber composition. Advantageous effects of the invention

[0006] As described below, according to embodiments of the present invention, a method for producing an aromatic vinyl-diene copolymer, which generates an aromatic vinyl-diene copolymer with a low glass transition temperature, and a method for producing a rubber composition using the method can be provided. Brief description of the drawings Fig. Figure 1 is a schematic cross-sectional view representing a pneumatic tire according to an embodiment of the present invention. Description of embodiments

[0007] The process for producing an aromatic vinyl diene copolymer and the process for producing a rubber composition using the process for producing an aromatic vinyl diene copolymer according to embodiments of the present invention are described below.

[0008] In the present patent specification, a numerical range specified using "from ... to ..." includes the first number as the lower limit and the last number as the upper limit.

[0009] Method for producing an aromatic vinyl-diene copolymer (“Method 1” according to an embodiment of the present invention) Method 1 according to an embodiment of the present invention is a method for producing an aromatic vinyl-diene copolymer, wherein the aromatic vinyl-diene copolymer is a copolymer of an aromatic vinyl and a diene, and wherein the aromatic vinyl-diene copolymer has a content of repeat units derived from an aromatic vinyl in an amount of 18 wt% or more, and among repeat units derived from a diene, a proportion of a vinyl structure of 8 mol% or less, a proportion of a 1,4-trans structure of 60 mol% or less, and a proportion of a 1,4-cis structure of 40 to 95 mol%, wherein the method for producing the aromatic vinyl-diene copolymer copolymerizes a monomer containing an aromatic vinyl and a diene,including the use of an initiator, wherein the initiator is prepared with an organolithium compound, an alkylaluminium, a barium alcoholate and at least one polar compound selected from the group consisting of water and an alcohol.

[0010] It is assumed that process 1 according to an embodiment of the present invention can achieve desired effects due to the use of the initiator (specific initiator) prepared with an organolithium compound, an alkylaluminum, a barium alkoxide, and at least one polar compound selected from the group consisting of water and an alcohol. Although the reason is not clear, it is assumed to be as follows. As described above, in process 1 according to an embodiment of the present invention, monomers are copolymerized with the specific initiator. The organolithium compound, the aluminum alkyl, and the barium alkoxide in the specific initiator stabilize the 1,4-structure (trans, cis) of the diene. Furthermore, a reaction product of the aluminum alkyl and the polar compound in the specific initiator particularly stabilizes the 1,4-cis structure of the diene.Consequently, the aromatic vinyl-diene copolymer obtained by method 1 according to one embodiment of the present invention has a high proportion of 1,4-structure and, in particular, a high proportion of 1,4-cis structure, which is relatively less likely to crystallize. It is assumed that, as a result, an aromatic vinyl-diene copolymer with a low glass transition temperature can be obtained when using method 1 according to one embodiment of the present invention. It should be noted that the essential difference from the method described in patent document 1 is the use of at least one polar compound selected from the group consisting of water and an alcohol, and that an aromatic vinyl-diene copolymer with a low glass transition temperature can be readily obtained according to method 1 according to one embodiment of the present invention.

[0011] Each of the components used in Method 1 according to an embodiment of the present invention is described in detail below. Specific initiator

[0012] As described above, in process 1 according to an embodiment of the present invention, a monomer is copolymerized using an initiator (specific initiator) prepared with an organolithium compound, an alkylaluminium, a barium alcoholate and at least one polar compound selected from the group consisting of water and an alcohol.

[0013] With a view to achieving an even lower glass transition temperature and excellent abrasion resistance, performance on ice, mechanical properties, wet performance, fuel economy, heat resistance, low-temperature resistance, deterioration resistance, contamination resistance, light resistance, and steering stability when forming a rubber product (e.g., tires), the specific initiator is preferably an initiator using aromatic divinyl. That is, the specific initiator is preferably an initiator prepared with an organolithium compound, an alkylaluminum, a barium alkoxide, at least one polar compound selected from the group consisting of water and an alcohol, and aromatic divinyl. In the following, “achieving an even lower glass transition temperature and achieving excellent abrasion resistance, performance on ice, mechanical properties, wet performance, fuel saving performance, heat resistance, low temperature resistance, deterioration resistance, contamination resistance, light resistance and steering stability when a rubber product (e.g. tires) is formed” is referred to as “achieving superior effects of the present invention”. Organolithium compound

[0014] Examples of organolithium compounds include monoorganolithium compounds such as n-butyllithium (n-BuLi), sec-butyllithium, tert-butyllithium, n-propyllithium, isopropyllithium, and benzyllithium; and polyfunctional organolithium compounds such as 1,4-dilithiobutane, 1,5-dilithiopentane, 1,6-dilithiohexane, 1,10-dilithiodecane, 1,1-dilithiodiphenylene, dilithiopolybutadiene, dilithiopolyisoprene, 1,4-dilithiobenzene, 1,2-dilithio-1,2-diphenylethane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-trilithio-2,4,6-triethylbenzene. In particular, monoorganolithium compounds such as n-butyllithium, sec-butyllithium and tert-butyllithium are preferred with a view to achieving superior effects of the present invention.

[0015] The amount of organolithium compound used to prepare the specific initiator is not subject to any particular limitations and is preferably from 0.001 to 10 mol% in relation to the amount of monomers to be polymerized, with a view to achieving superior effects of the present invention. Alkylaluminium

[0016] The alkylaluminum is not subject to any particular restrictions as long as it is a compound in which an alkyl group (open-chain, branched, cyclic) is bonded to an aluminum atom (Al). The number of carbons in the alkyl group is not subject to any particular restrictions; however, with a view to achieving superior effects of the present invention, the number is preferably from 1 to 20 and more preferably from 5 to 10.Specific examples of alkylaluminium include trimethylaluminium, triethylaluminium, triisopropylaluminium, tributylaluminium, triisobutylaluminium, tripropylaluminium, tributylaluminium, triisobutylaluminium, pentyldiethylaluminium, 2-methylpentyldiethylaluminium, dicyclohexylethylaluminium, tripentylaluminium, trihexylaluminium, trioctylaluminium, tri(2-ethylhexyl)aluminium, tricyclohexylaluminium, tricyclopentylaluminium, tri(2,2,4-trimethylpentyl)aluminium, tridodecylaluminium, tri(2-methylpentyl)aluminium, diisobutylaluminium hydride, dithylaluminium hydride, dipropylaluminium hydride, propylaluminium dihydride, and isobutylaluminium dihydride. Among these, trioctylaluminum is preferred with a view to achieving the superior effect of the present invention.

[0017] The proportion of alkylaluminum in relation to the organolithium compound used in the preparation of the specific initiator is not subject to any particular limitations; however, to achieve the superior effects of the present invention, the proportion is preferably from 0.1 to 50 molar equivalents and more preferably from 0.5 to 10 molar equivalents. It should be noted that 1 molar equivalent refers to the amount at the time 1 mole of alkylaluminum is added in a case where 1 mole of an organolithium compound is used. That is to say, the proportion of alkylaluminum in relation to the organolithium compound used in the preparation of the specific initiator is not subject to any particular limitations; however, to achieve the superior effects of the present invention, the proportion is preferably from 10 to 5000 mol% and more preferably from 50 to 1000 mol%. Metal alcoholate

[0018] The metal alcoholate (metal alkoxide) according to the present invention is a barium alcoholate.

[0019] In other embodiments not covered by the scope of protection, examples of the metal of the metal alcoholate may include alkali metals, other alkaline earth metals, transition metals (metals of groups 3 to 11), aluminium, germanium, tin and antimony.

[0020] The alcohol is not subject to any particular restrictions as long as it is a compound in which a hydrogen atom of an open-chain, branched, or cyclic hydrocarbon is substituted by a hydroxyl group. The number of carbon atoms in the alcohol is not subject to any particular restrictions; however, for the sake of achieving superior effects of the present invention, the number is preferably from 1 to 30, and more preferably from 1 to 20.

[0021] With a view to achieving superior effects of the present invention, the metal alcoholate is barium alcoholate (barium alkoxide). Examples of barium alkoxide include barium dimethoxide, barium diethoxide, barium dipropoxide, barium dibutoxide, and barium bis(2-ethylhexoxide).

[0022] The proportion of barium alkoxide in relation to the organolithium compound used in the preparation of the specific initiator is not subject to any particular limitations; however, to achieve the superior effects of the present invention, the proportion is preferably from 0.01 to 5 molar equivalents and more preferably from 0.1 to 3 molar equivalents. It should be noted that 1 molar equivalent refers to the amount at the time 1 mole of barium alkoxide is added in a case where 1 mole of an organolithium compound is used. That is to say, the proportion of barium alkoxide in relation to the organolithium compound used in the preparation of the specific initiator is not subject to any particular limitations; however, to achieve the superior effects of the present invention, the proportion is preferably from 1 to 500 mol% and more preferably from 10 to 300 mol%. Polar connection

[0023] As described above, in method 1 according to an embodiment of the present invention, at least one polar compound selected from the group consisting of water and an alcohol is used for the preparation of the specific initiator.

[0024] The alcohol is not subject to any particular restrictions as long as it is a compound in which a hydrogen atom of an open-chain, branched, or cyclic hydrocarbon is substituted by a hydroxyl group. The number of carbon atoms in the alcohol is not subject to any particular restrictions; however, for the sake of achieving superior effects of the present invention, the number is preferably from 1 to 30, and more preferably from 1 to 20. For the sake of achieving superior effects of the present invention, the polar compound is preferably water.

[0025] The proportion of the polar compound relative to the organolithium compound used in the preparation of the specific initiator is not subject to any particular restrictions; however, to achieve superior effects of the present invention, the proportion, expressed as a molar ratio, is preferably from 1 / 100 to 1 / 1, more preferably from 1 / 50 to 1 / 2, even more preferably from 1 / 20 to 1 / 4, and most preferably from 1 / 14 to 1 / 6. Hereinafter, the “proportion (molar ratio) of the polar compound relative to the organolithium compound used in the preparation of the specific initiator” is also referred to as “polar compound / Li”.

[0026] Furthermore, the proportion of the polar compound relative to the alkylaluminium used in the preparation of the specific initiator is not subject to any particular restrictions; however, to achieve superior effects of the present invention, the proportion, expressed as a molar ratio, is preferably from 1 / 100 to 1 / 0.1, more preferably from 1 / 50 to 1 / 0.2, even more preferably from 1 / 20 to 1 / 0.3, and particularly preferably from 1 / 10 to 1 / 0.5. Hereinafter, the “proportion (molar ratio) of the polar compound relative to the alkylaluminium used in the preparation of the specific initiator” is also referred to as “polar compound / Al”.

[0027] It should be noted that an amine compound can be used instead of the polar compound described above. Here, the amine compound is defined as a compound with an amino group (-NH2, -NHR, -NR2). Here, R represents a substituent. Two R-molecules of -NR2 can be identical or different. The substituent is not subject to any special restrictions as long as it is a monovalent substituent. Examples include hydrocarbon groups, each of which may contain a halogen atom, a hydroxyl group, a nitro group, a carboxyl group, an alkoxy group, an amino group, a mercapto group, an acyl group, an imide group, a phosphino group, a phosphinyl group, a silyl group, or a heteroatom.

[0028] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the heteroatom of the hydrocarbon group that can contain a heteroatom include an oxygen atom, nitrogen atom, sulfur atom, and phosphorus atom. Examples of hydrocarbon groups that can contain a heteroatom include aliphatic hydrocarbon groups, aromatic hydrocarbon groups, and groups containing a combination of these. The aliphatic hydrocarbon group can exist in the form of a straight chain, a branched chain, or a ring. Specific examples of the aliphatic hydrocarbon group include straight-chain or branched alkyl groups (especially those with 1 to 30 carbon atoms), straight-chain or branched alkenyl groups (especially those with 2 to 30 carbon atoms), and straight-chain or branched alkynyl groups (especially those with 2 to 30 carbon atoms). Examples of the aromatic hydrocarbon group include aromatic hydrocarbon groups with 6 to 18 carbon atoms each, such as a phenyl group, a tolyl group, a xylyl group and a naphthyl group.

[0029] Furthermore, an alkylaluminoxane can be used instead of the alkylaluminium and the polar compound. Aromatic Divinyl

[0030] Aromatic divinyl is not subject to any particular restrictions as long as it is an aromatic compound with two vinyl groups. Among these, with a view to achieving the superior effects of the present invention, aromatic vinyl is preferably divinylbenzene.

[0031] The proportion of aromatic divinyl relative to the organolithium compound used in the preparation of the specific initiator is not subject to any particular limitations; however, to achieve the superior effects of the present invention, the proportion is preferably from 0.1 to 5 molar equivalents and more preferably from 0.3 to 3 molar equivalents. It should be noted that 1 molar equivalent refers to the amount at the time 1 mole of aromatic divinyl is added in a case where 1 mole of an organolithium compound is used. That is to say, the proportion of aromatic divinyl relative to the organolithium compound used in the preparation of the specific initiator is not subject to any particular limitations; however, to achieve the superior effects of the present invention, the proportion is preferably from 10 to 500 mol% and more preferably from 30 to 300 mol%. Method for producing a specific initiator

[0032] The method for preparing the specific initiator is not subject to any particular restrictions, and examples include a method in which the organolithium compound, the alkylaluminium, the barium alkoxide, and the polar compound, as described above, are dissolved in a solvent. Among these, to achieve superior effects of the present invention, the polar compound is preferably added after the organolithium compound, the alkylaluminium, and the barium alkoxide have been mixed.

[0033] The type of solvent is not subject to any particular restrictions, and for example an organic solvent may be used; however, in order to achieve superior effects according to the present invention, a solvent other than alcohol is preferred. Monomer

[0034] The monomers used in process 1 according to one embodiment of the present invention include an aromatic vinyl and a diene. It should be noted that the monomer used in process 1 according to one embodiment of the present invention may, in addition to the aromatic vinyl and the diene, further comprise another monomer. Aromatic vinyl

[0035] The aromatic vinyl is not subject to any particular restrictions, and examples include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, vinylnaphthalene, dimethylaminomethylstyrene, and dimethylaminoethylstyrene. Of these, styrene, α-methylstyrene, and 4-methylstyrene are preferred with a view to achieving superior effects of the present invention, and styrene is more preferred. Such an aromatic vinyl can be used alone, or a combination of two or more types can be used. Serve

[0036] The diene is not subject to any particular restrictions, and examples include butadiene (e.g., 1,3-butadiene), isoprene, and chloroprene. Among these, 1,3-butadiene is preferred with a view to achieving superior effects of the present invention. Such a diene can be used alone, or a combination of two or more types can be used. Other monomer

[0037] As described above, the monomer used in process 1 according to an embodiment of the present invention can be a copolymer with which another monomer has been copolymerized in addition to the aromatic vinyl and the diene. Examples of such a monomer include unsaturated α- and β-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.

[0038] Next, the structure and the like of the aromatic vinyl diene copolymer obtained by process 1 according to an embodiment of the present invention (hereinafter also referred to as "Copolymer 1 according to an embodiment of the present invention") will be described in detail below. Copolymerization of the monomer

[0039] As described above, in process 1 according to an embodiment of the present invention, a monomer comprising an aromatic vinyl and a diene is copolymerized using a specific initiator. The specific initiator and the monomer are as described above.

[0040] The copolymerization process of the monomer is not subject to any particular restrictions, and examples include a process in which the monomer described above is added to an organic solvent solution containing the specific initiator described above and is stirred in a temperature range of 0 to 120 °C (preferably 30 to 100 °C).

[0041] The method for terminating the polymerization is not subject to any particular limitations, and examples include a method for adding alcohol (in particular methanol) to the polymerization solution. Furthermore, the polymerization can be terminated by using a specific electrophile such as method 2 according to an embodiment of the present invention described below. Aromatic vinyl content

[0042] The content of repeating units derived from an aromatic vinyl (hereinafter also referred to as "aromatic vinyl content") in copolymer 1 according to one embodiment of the present invention is 18 wt% or more. Of these, the content is preferably 20 wt% or more, and more preferably 25 wt% or more, in order to achieve superior effects of the present invention. The upper limit is not subject to any particular restrictions; however, in order to achieve superior effects of the present invention, the upper limit is preferably 90 wt% or less, more preferably 70 wt% or less, and even more preferably 60 wt% or less. Salary

[0043] The content of repeat units derived from a diene (hereinafter also referred to as the "diene content") in copolymer 1 according to an embodiment of the present invention is preferably 82 wt% or less, more preferably 80 wt% or less, and more preferably 75 wt% or less, in order to achieve superior effects of the present invention. The lower limit, in order to achieve superior effects of the present invention, is preferably 10 wt% or more, more preferably 30 wt% or more, and more preferably 40 wt% or more. Microstructure

[0044] The microstructure of copolymer 1 according to an embodiment of the present invention is described below. Vinyl structure

[0045] In copolymer 1 according to an embodiment of the present invention, the proportion of the vinyl structure among the repeating units derived from a diene is 8 mol% or less. For the sake of achieving superior effects of the present invention, the proportion of these is preferably 7 mol% or less, more preferably 6 mol% or less, more preferably 5 mol% or less, and particularly preferably 4 mol% or less. The lower limit is not subject to any particular restrictions and may be 0 mol%. It should be noted that the fraction of the vinyl structure refers to a fraction (mol-%) of repeating units with a vinyl structure (e.g., 1,2-vinyl structure in a case where the diene is 1,3-butadiene) among all repeating units derived from diene. 1,4-trans structure

[0046] In copolymer 1 according to an embodiment of the present invention, the proportion of the repeating units derived from a diene is 60 mol% or less. Among these, the proportion is preferably 50 mol% or less, and more preferably 40 mol% or less, in order to achieve superior effects of the present invention. The lower limit is not subject to any particular restrictions; however, in order to achieve superior effects of the present invention, the lower limit is preferably 1 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more. It should be noted that the proportion of 1,4-trans structure refers to a proportion (mol-%) of repeat units with a 1,4-trans structure among all repeat units derived from diene. 1,4-cis structure

[0047] In the copolymer according to one embodiment of the present invention, the proportion of the repeating units derived from dienes is 40 to 95 mol%. Of these, the proportion is preferably 50 mol% or more, more preferably 60 mol% or more, more preferably 65 mol% or more, more preferably 70 mol% or more, particularly preferably 75 mol% or more, and most preferably 80 mol% or more, in order to achieve superior effects of the present invention. The upper limit of the proportion of the 1,4-cis structure is preferably 90 mol% or less.

[0048] It should be noted that the proportion of 1,4-cis structure refers to the proportion (mol-%) of repeat units with a 1,4-cis structure among all diene-derived repeat units.

[0049] It should be noted that among the repeating units derived from dien, the “proportion of vinyl structure (mol-%), proportion of 1,4-trans structure (mol-%), proportion of 1,4-cis structure (mol-%)” is also referred to as “vinyl / trans / cis”. Glass transition temperature

[0050] To achieve superior effects of the present invention, the glass transition temperature (Tg) of copolymer 1 according to one embodiment of the present invention is preferably -80 °C or less. Below this, the glass transition temperature (Tg) is preferably -85 °C or less, and more preferably -90 °C or less, to achieve superior effects of the present invention. The lower limit is not subject to any particular restrictions; however, to achieve superior effects of the present invention, the lower limit is preferably -100 °C or higher.

[0051] It should be noted that in the present description the glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) at a temperature rise rate of 20 °C / minute and calculated using the midpoint method. Molecular weight

[0052] The molecular weight of copolymer 1 according to an embodiment of the present invention is not subject to any particular restrictions; However, to achieve superior effects of the present invention, the weight-averaged molecular weight (Mw) is preferably from 1000 to 10000000, more preferably from 2000 to 5000000, and even more preferably from 3000 to 2000000. Furthermore, to achieve superior effects of the present invention, the number-averaged molecular weight (Mn) is preferably from 500 to 5000000, more preferably from 1000 to 2500000, and even more preferably from 1500 to 1000000. It should be noted that in this description, the number-averaged molecular weight (Mw) and the weight-averaged molecular weight (Mn) are each values ​​obtained by gel permeation chromatography (GPC) measurement, calibrated with a polystyrene standard, under the following conditions. becomes. • Solvent: Tetrahydrofuran • Detector: RI detector

[0053] Method for producing an aromatic vinyl diene copolymer (“Method 2” according to an embodiment of the present invention)

[0054] Method 2 according to an embodiment of the present invention is a method for producing an aromatic vinyl-diene copolymer, wherein the aromatic vinyl-diene copolymer is a copolymer of an aromatic vinyl and a diene, wherein the aromatic vinyl-diene copolymer has a content of repeating units derived from an aromatic vinyl in an amount of 18 wt% or more, among which repeating units derived from a diene there is a proportion of a vinyl structure of 8 mol% or less, a proportion of a 1,4-trans structure of 60 mol% or less, and a proportion of a 1,4-cis structure of 40 to 95 mol%, and wherein the aromatic vinyl-diene copolymer has an end modified with at least one electrophile selected from the group consisting of titanium halide, tin halide, cyclic silazane, alkoxysilane, epoxide, amine, ketone, and a compound.which is represented by the formula (N) below (hereinafter also referred to as the “specific electrophile”), wherein the process for preparing the aromatic vinyl-diene copolymer includes copolymerizing a monomer containing an aromatic vinyl and a diene using an initiator, wherein the initiator is prepared with an organolithium compound, an alkylaluminium, a barium alkoxide and at least one polar compound selected from the group consisting of water and an alcohol, and subsequent termination of the polymerization using the electrophile.

[0055] Method 2 according to an embodiment of the present invention is identical to method 1 according to an embodiment of the present invention described above, except that the polymerization of the monomers is terminated using the specific electrophile. The structure and the like (in particular aromatic vinyl content, diene content, microstructure, glass transition temperature and molecular weight) of the aromatic vinyl-diene copolymer obtained by method 2 according to an embodiment of the present invention (hereinafter also referred to as “Copolymer 2 according to an embodiment of the present invention”) are identical to those of Copolymer 1 according to an embodiment of the present invention described above, except that the end is modified with a specific electrophile.Since copolymer 2, according to one embodiment of the present invention, has an end modified with the specific electrophile, the end interacts with the filler, and copolymer 2 achieves excellent abrasion resistance, ice performance, mechanical properties, wet performance, fuel economy performance, heat resistance, low temperature resistance, deterioration resistance, contamination resistance, light resistance, and steering stability when a rubber product (e.g., tires) is formed. It should be noted that in a case where the specific electrophile is a titanium halide, a tin halide, or a compound represented by formula (N) described below, the end of copolymer 2 according to one embodiment of the present invention is assumed to interact with carbon black. In a case where the specific electrophile is a cyclic silazane, an alkoxysilane, or an amine, the end of copolymer 2 according to one embodiment of the present invention is assumed to interact with silica. In a case where the specific electrophile is an epoxide or a ketone, the end of copolymer 2 according to one embodiment of the present invention is assumed to interact with silica or carbon black.

[0056] With a view to achieving superior effects of the present invention, the specific electrophile is preferably a cyclic silazane, an alkoxysilane or a compound represented by formula (N) described below, and a cyclic silazane is more preferred. Specific electrophile

[0057] Each of the specific electrophiles is described below. titanium halide

[0058] The titanium halide is not subject to any particular restrictions, and examples include TiCl3, TiBr3, Ti(OC2Hs)Cl2, Ti(OC4H9)Cl2, TiCl4, Ti(OC2H5)Cl3, and Ti(OC4H9)Cl3. Among these, TiCl3 (trichlorotitanium) and TiCl4 (tetrachlorotitanium) are preferred with a view to achieving superior effects of the present invention, and tetrachlorotitanium is more preferred. tin halide

[0059] The tin halide is not subject to any special restrictions, and examples include tin fluoride, tin chloride, tin bromide, tin iodide, and tin astatide. Cyclic silazane

[0060] Cyclic silazane is not subject to any special restrictions as long as it is a silazane in a cyclic form.

[0061] It should be noted that "Silazan" is intended to mean a compound that has a structure in which a silicon atom and a nitrogen atom are directly bonded (a compound with a Si-N bond).

[0062] With a view to achieving superior effects of the present invention, the cyclic silazane is preferably a compound represented by the following formula (S).

[0063] In the formula above (S), R1 to R3 each independently represent a hydrogen atom or a substituent. Specific examples of the substituent are identical to those of R in the formula (P) described below.

[0064] With a view to achieving superior effects of the present invention, R1 is preferably an alkyl group (preferably with 1 to 10 carbons), an alkylsilyl group (preferably with 1 to 10 carbons) or an aromatic hydrocarbon group (preferably with 6 to 18 carbons).

[0065] With a view to achieving superior effects of the present invention, R2 is preferably an alkoxy group (preferably with 1 to 10 carbon atoms).

[0066] In the above formula (S), L represents a divalent organic group.

[0067] Examples of the divalent organic group include substituted or unsubstituted aliphatic hydrocarbon groups (e.g., an alkylene group, preferably with 1 to 8 carbon atoms), substituted or unsubstituted aromatic hydrocarbon groups (e.g., an arylene group, preferably with 6 to 12 carbon atoms), -O-, -S-, -SO2-, -N(R)-(R: alkyl group), -CO-, -NH-, -COO-, -CONH- and groups having a combination of these (e.g., alkylenoxy groups (-C m H 2m O-: m is a positive integer), alkylenoxycarbonyl groups and alkylenecarbonyloxy groups).

[0068] With a view to achieving superior effects of the present invention, L is preferably an alkylene group (preferably with 1 to 10 carbon atoms).

[0069] Examples of the compound represented by the above formula (S) include Nn-butyl-1,1-dimethoxy-2-azasilacyclopentane, N-phenyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane and N-trimethylsilyl-1,1-diethoxy-2-azasilacyclopentane. It should be noted that the silicon atom of the cyclic silazane is assumed to be electrophilic. alkoxysilane

[0070] Alkoxysilane is not subject to any special restrictions as long as it is a compound with an alkoxysilyl group, and examples include tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, N,N-bistrimethylsilyl-3-aminopropyltrimethoxysilane, and N,N-bistrimethylsilyl-3-aminopropyltriethoxysilane.

[0071] The number of alkoxy groups in the alkoxysilyl group is not subject to any particular restrictions; however, in order to achieve superior effects of the present invention, the number is preferably 2 or more.

[0072] It should be noted that the silicon atom of the alkoxysilane is assumed to be electrophilic. epoxy

[0073] The epoxide is not subject to any particular restrictions as long as it is a compound with an oxacyclopropane (oxirane) structure. Specific examples of the epoxide include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, styrene oxide, 1-phenylpropylene oxide, methyl glycidyl ether, ethyl glycidyl ether, glycidyl isopropyl ether, butyl glycidyl ether, 1-methoxy-2-methylpropylene oxide, allyl glycidyl ether, 2-ethyloxyglycidyl ether, phenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, lauryl alcohol glycidyl ether, stearyl glycidyl ether, palmityl glycidyl ether, myristyl glycidyl ether, lauryl glycidyl ether, capryl glycidyl ether, and caproyl glycidyl ether. Amin

[0074] The amine is not subject to any particular restrictions as long as it is a compound with an amino group (-NR2: R represents a hydrogen atom or a hydrocarbon group. The two R molecular parts can be the same or different). Among these, the amine is preferably aziridine with a view to achieving superior effects of the present invention; examples of aziridine include N-methylaziridine, N-ethylaziridine, N-isopropylaziridine, N-phenylaziridine, N-(4-methylphenyl)aziridine, and N-methyl-2-methylaziridine. Ketone

[0075] The ketone is not subject to any special restrictions as long as it is a compound with a ketone group (-CO-). Specific examples of the ketone include acetone, benzophenone, and derivatives thereof.

[0076] Examples of benzophenone derivatives include N,N,N',N'-tetramethyl-4,4'-diaminobenzophenone, N,N,N',N'-tetraethyl(4,4'-diamino)-benzophenone, N,N-dimethyl-1-aminobenzoquinone, N,N,N',N'-tetramethyl-1,3-diaminobenzoquinone, N,N-dimethyl-1-aminoanthraquinone, N,N,N',N'-tetramethyl-1,4-diaminoanthraquinone, and 4,4'-diacetylbenzophenone. Connection, represented by formula (N)

[0077] A compound represented by the formula (N) below is described below.

[0078] In the above formula (N) R 1 for a hydrogen atom or an alkyl group (preferably with 1 to 10 carbons) and R 2 for an alkylene group (preferably with 2 to 10 carbons).

[0079] Specific examples of the compound represented by the above formula (N) include N-methylpyrrolidone (in the above formula (N) R1 is a methyl group and R2 is a propylene group).

[0080] The amount of the specific electrophile in relation to the amount of the specific initiator is not subject to any particular restrictions; however, the ratio of the specific electrophile to the organolithium compound (specific electrophile / organolithium compound), expressed as a molar ratio, is preferably from 0.1 to 10 and more preferably from 1 to 5 with a view to achieving superior effects of the present invention.

[0081] With a view to achieving superior effects of the present invention, the ratio of the specific electrophile to the alkylaluminium (alkyl Al) (specific electrophile / alkyl Al), expressed as a molar ratio, is preferably from 0.1 to 10 and more preferably from 1 to 5.

[0082] With a view to achieving superior effects of the present invention, the ratio of the specific electrophile to the barium alkoxide (specific electrophile / barium alkoxide), expressed as a molar ratio, is preferably from 0.1 to 20 and more preferably from 1 to 10. Method for producing a rubber composition

[0083] The method for producing a rubber composition according to an embodiment of the present invention is a method for producing a rubber composition that includes: Producing the copolymer 1 according to an embodiment of the present invention or the copolymer 2 according to an embodiment of the present invention, as described above (hereinafter also collectively referred to as "copolymer according to an embodiment of the present invention") using method 1 according to an embodiment of the present invention or Method 2 according to an embodiment of the present invention described above (hereinafter also referred to collectively as "method according to an embodiment of the present invention"), and Mixing the copolymer, as obtained according to one embodiment of the present invention, with a filler and obtaining a rubber composition. Production of copolymers

[0084] The production of copolymers (process 1 according to an embodiment of the present invention or process 2 according to an embodiment of the present invention) is as described above. Mix

[0085] Mixing is a step to obtain a rubber composition in which the copolymer, as obtained according to one embodiment of the present invention, and a filler are mixed. filler

[0086] The filler used in the mixing process is not subject to any particular restrictions; however, with a view to achieving superior effects of the present invention, it is preferably carbon and / or silica.

[0087] During mixing, a component other than the copolymer according to an embodiment of the present invention or the filler can be mixed. Examples of such an additional component include various additives commonly used in rubber compositions, such as silane adhesion promoters, zinc oxide (zinc bloom), stearic acid, adhesive resins, peptization agents, aging retarders, waxes, processing aids, flavor oils, liquid polymers, terpene resins, thermosetting resins, vulcanizing agents (e.g., sulfur), and vulcanization accelerators. Furthermore, the rubber composition may contain an additional rubber component besides the polymer, according to one embodiment of the present invention.Examples of such a different rubber component include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), a styrene-butadiene rubber (SBR) other than the polymer according to one embodiment of the present invention, acrylonitrile butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR) and chloroprene rubber (CR). Application

[0088] The copolymer described above according to one embodiment of the present invention and the rubber composition obtained by the above-described method for producing a rubber composition according to one embodiment of the present invention (hereinafter also referred to as "composition according to one embodiment of the present invention") can be widely used for rubber products such as tires, conveyor belts, and hoses. In particular, use in tires is preferred. pneumatic tires

[0089] The pneumatic tire according to one embodiment of the present invention is one that is manufactured using the composition according to one embodiment of the present invention described above. In particular, the pneumatic tire is preferably a pneumatic tire in which the composition according to one embodiment of the present invention is used (provided) in the tire tread (crown tread). Fig. Figure 1 is a schematic cross-sectional partial view of a pneumatic tire, representing a pneumatic tire according to an embodiment of the present invention; however, the present invention is not limited to the embodiment shown in Fig. 1 illustrated embodiment limited.

[0090] In Fig.Reference 1 denotes a bead section, reference 2 denotes a sidewall section, and reference 3 denotes a tire tread section. Furthermore, a carcass layer 4, in which a fiberglass thread is embedded, is embedded between a left / right pair of bead sections 1, and ends of the carcass layer 4 are wrapped around bead cores 5 and a bead filler 6 by folding from an inside to an outside of the tire. In the tire tread section 3, a belt layer 7 is provided along the entire circumference of the tire on the outside of the carcass layer 4. Additionally, in one section of each of the bead sections 1 that abuts a rim, a wheel flange pad 8 is provided. It should be noted that the tire tread section 3 is formed from the composition according to an embodiment of the present invention described above.

[0091] The pneumatic tire according to one embodiment of the present invention can, for example, be manufactured in accordance with a known method. Furthermore, an inert gas such as nitrogen, argon, or helium, or the like, can be used as the gas with which the pneumatic tire is filled, in addition to normal air or air whose oxygen partial pressure is adjusted. [Example]

[0092] One embodiment of the present invention is described in more detail below with reference to examples. However, an embodiment of the present invention is not limited to these examples. Production of an aromatic vinyl diene copolymer

[0093] Aromatic vinyl diene copolymers were prepared as described below. Comparative example 1: SBR

[0094] n-BuLi (available from Kant°Chemical Co., Inc.: 1.60 mol / L (hexane solution), 18 mL, 28.8 mmol), barium bis(2-ethylhexoxide) (Ba(OCH2CH(C2Hs)CH2CH2CH2CH3)2) (available from STREM: 1M (toluene / hexane solution) 7.5 mL), trioctylaluminum (available from Aldrich: 25 wt% (hexane solution), 45 mL) and cyclohexane (available from Kanto Chemical Co., Inc.: 10 mL) were mixed, and an initiator solution (not the specific initiator described above) was prepared. 60 mL of the obtained initiator solution were added to a cyclohexane solution (4.23 kg) consisting of a mixture of 1,3-butadiene (708 g, 13098 mmol) and styrene (380 g, 3649 mmol) and stirred at 60 °C for 14 hours. After the mixture was cooled to room temperature, methanol (available from Kanto Chemical Co., Inc.: 3.44 g) was added and the polymerization was stopped. The resulting solution was taken off and concentrated under reduced pressure. The concentrated solution was poured into methanol (5 L) to remove a methanol-insoluble component. A styrene-butadiene copolymer (SBR) was obtained. Example 1: SBR

[0095] n-BuLi (available from Kant°Chemical Co., Inc.: 1.60 mol / L (hexane solution), 18 mL, 28.8 mmol), barium bis(2-ethylhexoxide) (Ba(OCH2CH(C2Hs)CH2CH2CH2CH3)2) (available from STREM: 1M (toluene / hexane solution) 7.5 mL), trioctylaluminum (available from Aldrich: 25 wt% (hexane solution), 45 mL) and cyclohexane (available from Kanto Chemical Co., Inc.: 10 mL) were mixed, then 0.035 mL of water (ratio (molar ratio) of the amount of water added to the amount of n-BuLi: 1 / 15) was added as a polar compound, and an initiator solution (corresponding to the specific initiator described above) was prepared. 60 mL of the obtained initiator solution were added to a cyclohexane solution (4.24 kg) consisting of a mixture of 1,3-butadiene (708 g, 13098 mmol) and styrene (380 g, 3649 mmol) and stirred at 60 °C for 14 hours. After the mixture was cooled to room temperature, methanol (available from Kanto Chemical Co., Inc.: 3.58 g) was added and the polymerization was stopped. The resulting solution was taken off and concentrated under reduced pressure. The concentrated solution was poured into methanol (5 L) to remove a methanol-insoluble component. A styrene-butadiene copolymer (SBR) was obtained. Example 2: SBR

[0096] An SBR was obtained by a process identical to that of Example 1, except that the ratio (molar ratio) of the amount of water added in relation to the amount of n-BuLi was changed from 1 / 15 to 1 / 12. Example 3: SBR

[0097] An SBR was obtained by a process identical to that of Example 1, except that the ratio (molar ratio) of the amount of water added in relation to the amount of n-BuLi was changed from 1 / 15 to 1 / 5. Example 4: End-modified SBR with titanium halide

[0098] An SBR was obtained by a process identical to that of Example 2, except that the polymerization was terminated by the addition of tetrachlorotitanium (available from Aldrich: 14.7 g) instead of methanol. The SBR obtained was a styrene-butadiene copolymer with the end modified with a titanium halide (terminal titanium halide-modified SBR). Example 5: Terminally modified SBR with tin halide

[0099] An SBR was obtained by a process identical to that of Example 2, except that the polymerization was terminated by the addition of tin chloride (SnCl4) (available from Kanto Chemical Co., Inc.: 18.9 g) instead of methanol. The SBR obtained was a styrene-butadiene copolymer with the end modified with a tin halide (terminal tin halide-modified SBR). Example 6: SBR modified end-stage with cyclic silazane

[0100] An SBR was obtained by a process identical to that of Example 2, except that the polymerization was terminated by adding a mixed cyclohexane solution (10 ml) of N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane (structure below) (17.0 g) and lithium diisopropylamide (available from Aldrich (2 M solution): 11 ml) instead of methanol. The SBR obtained was a styrene-butadiene copolymer with the end modified with a cyclic silazane (terminal silazane-modified SBR). Example 7: SBR modified end-to-end with alkoxysilane

[0101] An SBR was obtained by a process identical to that of Example 2, except that the polymerization was terminated by adding a mixed cyclohexane solution (10 ml) of N,N-bistrimethylsilyl-3-aminopropyltrimethoxysilane (22.2 g) and lithium diisopropylamide (available from Aldrich (2 M solution): 11 ml) instead of methanol. The SBR obtained was a styrene-butadiene copolymer with the end modified with an alkoxysilane (terminal alkoxysilane-modified SBR). Example 8: SBR modified end-to-end with N-methylpyrrolidone

[0102] An SBR was obtained by a process identical to that of Example 2, except that the polymerization was terminated by adding N-methylpyrrolidone (8.48 g) instead of methanol. The SBR obtained was a styrene-butadiene copolymer with the end modified by N-methylpyrrolidone (terminal N-methylpyrrolidone-modified SBR).

[0103] For the aromatic vinyl diene copolymers obtained, the content of aromatic vinyl (content of repeat units derived from styrene), vinyl / trans / cis, Tg and molecular weight are listed in Table 1 below. [Table 1-I] Table 1 Polar connection / Li Electrophile Anaromatic vinyl content [mass %] Comparative example 1 - Methanol 28 Example 1 1 / 15 Methanol 27 Example 2 1 / 12 Methanol 28 Example 3 1 / 5 Methanol 26 Example 4 1 / 12 titanium halide 28 Example 5 1 / 12 tin halide 29 Example 6 1 / 12 Cyclic silazane 28 Example 7 1 / 12 alkoxysilane 26 Example 8 1 / 12 NMP 28 [Table 1-II] Table 1 Microstructure [mol-%] Tg[°C] Molecular weight Vinyl structure 1,4-trans structure 1,4-cis structure Mn Mw / Mn Comparative example 1 7 46 47 -78 136000 1,8 Example 1 6 36 58 -84 128000 1,6 Example 2 4 11 85 -92 110400 1,7 Example 3 5 33 62 -83 110000 1,8 Example 4 5 11 84 -86 108000 1,7 Example 5 6 11 83 -87 120000 1,8 Example 6 6 8 86 -90 115000 1,5 Example 7 4 12 84 -88 102000 1,8 Example 8 5 10 85 -89 160000 1,6

[0104] As can be seen from Table 1, each of the examples 1 to 8 that used a specific initiator exhibited a high proportion of 1,4-cis structure and a low glass transition temperature. Among these, each of the examples 2 to 8 in which the polar compound / Li ratio was 1 / 14 or greater exhibited a higher proportion of 1,4-cis structure and a lower glass transition temperature. Among these, each of the examples 2 and 4 to 8 in which the polar compound / Li ratio was 1 / 6 or less exhibited an even higher proportion of 1,4-cis structure and an even lower glass transition temperature. List of reference symbols 1 bead section 2 Side wall section 3 Tire tread section 4 Carcass layer 5 bead core 6 bead fillers 7th belt layer 8 wheel rim pads

Claims

[1] A process for producing an aromatic vinyl-diene copolymer, wherein the aromatic vinyl-diene copolymer is a copolymer of an aromatic vinyl and a diene, and wherein the aromatic vinyl-diene copolymer has a content of repeat units derived from an aromatic vinyl in an amount of 18 wt% or more, and among repeat units derived from a diene, a proportion of a vinyl structure of 8 mol% or less, a proportion of a 1,4-trans structure of 60 mol% or less and a proportion of a 1,4-cis structure of 40 to 95 mol%, wherein the process for producing the aromatic vinyl-diene copolymer comprises copolymerizing a monomer containing an aromatic vinyl and a diene using an initiator, wherein the initiator is prepared with an organolithium compound, an alkylaluminium, a barium alcoholate and at least one polar compound selected from the group consisting of water and an alcohol. [2] Method for producing an aromatic vinyl-diene copolymer, wherein the aromatic vinyl-diene copolymer is a copolymer of an aromatic vinyl and a diene, wherein the aromatic vinyl-diene copolymer has a content of repeat units derived from an aromatic vinyl in an amount of 18 wt% or more, among repeat units derived from a diene a proportion of a vinyl structure of 8 mol% or less, a proportion of a 1,4-trans structure of 60 mol% or less and a proportion of a 1,4-cis structure of 40 to 95 mol%, and wherein the aromatic vinyl diene copolymer has one end modified with at least one electrophile selected from the group consisting of titanium halide, tin halide, cyclic silazane, alkoxysilane, epoxide, amine, ketone and a compound represented by the formula (N) below, the process for producing the aromatic vinyl diene copolymer comprises: Copolymerization of a monomer containing an aromatic vinyl and a diene, using an initiator, wherein the initiator is prepared with an organolithium compound, an alkylaluminum, a barium alkoxide and at least one polar compound selected from the group consisting of water and an alcohol; and Subsequent termination of the polymerization using the electrophile: where in formula (N) R 1 stands for a hydrogen atom or an alkyl group and R 2 stands for an alkylene group. [3] Method for producing an aromatic vinyl-diene copolymer according to claim 1 or 2, wherein the proportion of an amount of the polar compound in relation to an amount of the organolithium compound, expressed as a molar ratio, is from 1 / 15 to 1 / 1. [4] Method for producing a rubber composition, comprising: Producing an aromatic vinyl diene copolymer using the process for producing an aromatic vinyl diene copolymer according to any one of claims 1 to 3, and Mixing the resulting aromatic vinyl diene copolymer with a filler to obtain a rubber composition.

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