Rubber composition and vulcanized rubber composition

Abstract

This rubber composition contains 10-150 parts by mass of carbon black with respect to 100 parts by mass of rubber components including at least one conjugated diene-based polymer, and contains a silica-based inorganic filler in an amount of 0-30 mass% with respect to the total amount of the filler. In the rubber components, 10 mass% or more thereof is a modified conjugated diene-based polymer. The modified conjugated diene-based polymer: (1) has a main chain branched structure having a branched structure in the main chain; (2) includes, in the main chain branched structure, a structure derived from at least one conjugated diene-based monomer, or a structure derived from at least one conjugated diene-based monomer and a structure derived from an aromatic vinyl-based monomer; (3) has, at at least one terminal, a terminal group having at least one carbonyl group and at least one substituted amino group per molecule; (4) has a Mooney viscosity of 30-120 as measured at 100°C; (5) has a branching degree (Bn) of not less than 1.1 but less than 4.0 as determined by a viscosity detector-provided GPC-light scattering method; (6) exhibits a chromatography shape having a single peak as measured by gel permeation chromatography (GPC) and has a molecular weight distribution of 1.60-3.00; and (7) has a hydrogenation rate of less than 10 mol%.

Description

Rubber composition and vulcanized rubber composition

[0001] The present invention relates to a composition of a modified conjugated diene polymer, and more particularly to a rubber composition and a vulcanized rubber composition containing a modified conjugated diene polymer.

[0002] BACKGROUND ART Conventionally, there has been an increasing demand for improved fuel economy in automobiles, and there has been a demand for improvements in the rubber materials used in automobile tires, particularly in the tire treads that come into contact with the road surface.

[0003] In particular, as required performance for tires for heavy loads used on large vehicles such as trucks and buses, tires with improved fuel efficiency with low energy loss are required in addition to conventional properties such as high strength and wear resistance for supporting high loads. Specifically, rubber materials used in tire treads for heavy loads are required to have rubber compositions with high tensile strength and excellent fuel economy.

[0004] As rubber materials that meet the above-mentioned requirements, for example, a modified conjugated diene polymer having a hydroxyl group at the end of the polymer chain and a composition thereof, a method for producing a conjugated diene polymer in which a hydrocarbyloxysilane compound is reacted with the end of the polymer chain and then a specific compound such as a hydrocarbyloxysilane compound is further reacted, and a composition thereof have been proposed (see, for example, Patent Documents 1 and 2).

[0005] However, for tires for heavy loads, rubber compositions containing carbon black are still preferably used from the viewpoint of durability and abrasion resistance, and there is a demand for rubber compositions containing carbon black as a filler that have improved fuel economy, abrasion resistance, and tensile strength. However, if the filler is not dispersed in the rubber composition in an adequate manner, there is a problem in that the fuel economy, abrasion resistance, and tensile strength are not fully exhibited.

[0006] On the other hand, rubber compositions containing carbon black are also preferably used for rubber products used as industrial goods from the viewpoints of durability and processability. For example, rubber materials containing natural rubber, which has excellent vibration-damping properties such as compression set and dynamic magnification, have been proposed as vibration-damping rubber for automobiles, trains, etc. (see, for example, Patent Document 3).

[0007] JP 2017-171806 A International Publication No. 03 / 046020 Pamphlet JP 2004-292679 A

[0008] However, recent rubber materials sometimes have insufficient vibration-damping properties, and in particular, when the dispersibility of the filler in a rubber composition containing carbon black is insufficient, there is a problem that the vibration-damping properties are not fully exhibited.

[0009] In addition, modified conjugated diene polymers, which are suitable for use in highly loaded tire treads and industrial products, have the problem that the bales, which are the product form, tend to flow easily (hereinafter referred to as "cold flow"), making the bales difficult to handle after storage.

[0010] In light of this background, it is desired to provide a rubber composition containing carbon black that is excellent in processability when made into a rubber composition containing carbon black, and in fuel economy, tensile strength, abrasion resistance, and vibration-damping properties when the rubber composition is vulcanized. However, the processability of a rubber composition and the tensile strength and abrasion resistance when vulcanized are in a mutually contradictory relationship, and it is difficult to achieve both.

[0011] Therefore, in order to solve the above-mentioned problems, the present invention aims to provide a rubber composition and a vulcanized rubber composition which contain carbon black and a modified conjugated diene polymer with reduced cold flow properties, and which have excellent processability as a rubber composition, and which, when vulcanized, achieve a high level of fuel economy, tensile strength, abrasion resistance, and vibration damping properties.

[0012] As a result of intensive research and investigation to solve the above-mentioned problems of the conventional art, the present inventors have found that a rubber composition containing 10 parts by mass or more and 150 parts by mass or less of carbon black per 100 parts by mass of a rubber component containing at least one conjugated diene polymer, and a silica-based inorganic filler content of 0% by mass or more and 30% by mass or less based on the total amount of fillers, wherein by using a specific or modified conjugated diene polymer in an amount of 10% by mass or more of the rubber component, the rubber composition has excellent processability and, when vulcanized, has excellent fuel economy, tensile strength, abrasion resistance, and vibration-damping properties, and have completed the present invention.

[0013] That is, the present invention is as follows: <1> A rubber composition containing 10 to 150 parts by mass of carbon black per 100 parts by mass of a rubber component containing at least one type of conjugated diene polymer, and a silica-based inorganic filler content of 0 to 30% by mass based on the total amount of fillers, wherein 10% by mass or more of the rubber component is a modified conjugated diene polymer, and the modified conjugated diene polymer (1) has a main chain branched structure having a branched structure in the main chain, (2) the main chain branched structure includes a structure derived from at least one type of conjugated diene monomer, or a structure derived from at least one type of conjugated diene monomer and a structure derived from an aromatic vinyl monomer, (3) has, at at least one end, an end group having at least one carbonyl group and at least one substituted amino group in the molecule, (4) has a Mooney viscosity measured at 100°C of 30 to 120, and (5) (5) A rubber composition having a branching degree (Bn) of 1.1 or more and less than 4.0 as measured by a GPC-light scattering method with a viscosity detector, (6) a chromatogram shape measured by gel permeation chromatography (GPC) is unimodal and a molecular weight distribution is 1.60 to 3.00, and (7) a hydrogenation rate of less than 10 mol%. <2> The rubber composition according to <1>, wherein the amount of 1,2-vinyl bonds in the conjugated diene units of the modified conjugated diene polymer is 10 mol% or more and 25 mol% or less. <3> The rubber composition according to <1> or <2>, wherein the amount of aromatic vinyl bonds in the modified conjugated diene polymer is 0 mass% or more and 10 mass% or less. <4> The rubber composition according to any one of <1> to <3>, wherein the glass transition temperature (Tg) of the modified conjugated diene polymer is -110°C to -80°C. <5> The rubber composition according to any one of <1> to <4>, wherein the modified conjugated diene polymer has a modification rate of 40% by mass or more as measured by column adsorption GPC. <6> The rubber composition according to any one of <1> to <5>, wherein the modified conjugated diene polymer has a hydrogenation rate of less than 5 mol%. <7> The rubber composition according to any one of <1> to <6>, wherein the modified conjugated diene polymer has a structure represented by the following formula (1) and / or formula (2): (In formula (1), P represents a conjugated diene polymer containing at least one conjugated diene monomer, and Ra and Rb each independently represent a hydrocarbon group having 1 to 20 carbon atoms.) (In formula (2), P represents a conjugated diene polymer containing at least one conjugated diene monomer, and Ra and Rb each independently represent a hydrocarbon group having 1 to 20 carbon atoms.) <8> The rubber composition according to any one of <1> to <7>, wherein a main chain branched structure of the modified conjugated diene polymer has a portion derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group, and the portion derived from the vinyl monomer containing an alkoxysilyl group or a halosilyl group has the branched structure. <9> The rubber composition according to <8>, wherein the portion derived from the vinyl monomer containing an alkoxysilyl group or a halosilyl group is a monomer unit derived from a compound represented by the following formula (3) or (4), and the branched structure in the main chain branched structure of the modified conjugated diene polymer has a branch point of a polymer chain by a monomer unit derived from a compound represented by the following formula (3) or (4): (In the formula, R １ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may have a branched structure in part, or an aryl group having 6 to 20 carbon atoms; R ２ ~R ３ each independently represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, which may have a branched structure in part, and when there are a plurality of R １ ~R ３ are each independent. １ represents an independent halogen atom, m represents an integer of 0 to 2, n represents an integer of 0 to 3, l represents an integer of 0 to 3, and (m+n+l) is 3. (In the formula, R ２ ~R ５ each independently represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, which may have a branched structure in part, and when there are a plurality of R ２ ~R ５ are each independent, and X ２~X ３ each independently represents a halogen atom, m represents an integer of 0 to 2, n represents an integer of 0 to 3, l represents an integer of 0 to 3, (m+n+l) is 3, a represents an integer of 0 to 2, b represents an integer of 0 to 3, c represents an integer of 0 to 3, and (a+b+c) is 3. <10> The main chain branched structure of the modified conjugated diene polymer has a monomer unit derived from a compound represented by formula (3), and in formula (3), R １ represents a hydrogen atom, and m represents 0. <11> The rubber composition according to <8> or <10>, wherein the main chain branched structure of the modified conjugated diene polymer has a monomer unit derived from the compound represented by formula (4), and in formula (4), m represents 0 and b represents 0. <12> The rubber composition according to <8> or <10>, wherein the main chain branched structure of the modified conjugated diene polymer has a monomer unit derived from the compound represented by formula (3), and in formula (3), R １ represents a hydrogen atom, m represents 0, n represents 3, and l represents 0. <13> The rubber composition according to <9> above, wherein the main chain branched structure of the modified conjugated diene polymer has monomer units derived from the compound represented by formula (4), and in formula (4), m represents 0, n represents 3, l represents 0, a represents 0, b represents 0, and c represents 3. <14> A vulcanized rubber composition obtained by vulcanizing the rubber composition according to any one of <1> to <13> above.

[0014] According to the present invention, it is possible to provide a rubber composition and a vulcanized rubber composition which use carbon black and a modified conjugated diene polymer with reduced cold flow properties, and which have excellent processability and which, when vulcanized, achieve a high level of fuel economy, tensile strength, abrasion resistance, and vibration-damping properties.

[0015] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail, but the present invention is not limited thereto and various modifications are possible within the scope of the present invention. Furthermore, throughout the specification, an expression in which numerical values ​​are connected by "to", for example, x to y (x and y are each numerical values), means a numerical range including x and y as the upper and lower limits.

[0016] <Rubber Composition> The rubber composition of this embodiment is a rubber composition containing 10 parts by mass or more and 150 parts by mass or less of carbon black relative to 100 parts by mass of a rubber component containing at least one type of conjugated diene polymer, and a content of a silica-based inorganic filler is 0% by mass or more and 30% by mass or less based on the total amount of the filler, wherein 10% by mass or more of the rubber component is a modified conjugated diene polymer, (1) having a main chain branched structure having a branched structure in the main chain, (2) the main chain branched structure includes a structure derived from at least one type of conjugated diene monomer, or a structure derived from at least one type of conjugated diene monomer and a structure derived from an aromatic vinyl monomer, (3) having, at at least one end, an end group having at least one carbonyl group and at least one substituted amino group in the molecule, (4) having a Mooney viscosity measured at 100°C of 30 to 120, and (5) (5) the degree of branching (Bn) measured by a GPC-light scattering method with a viscosity detector is 1.1 or more and less than 4.0, (6) the shape of the chromatogram measured by gel permeation chromatography (GPC) is unimodal and the molecular weight distribution is 1.60 to 3.00, and (7) the hydrogenation rate is less than 10 mol%. The modified conjugated diene polymer will be described later.

[0017] [Rubber Polymer Other than Modified Conjugated Diene Polymer in the Present Embodiment] As described above, the rubber composition of the present embodiment contains a rubber component containing at least one conjugated diene polymer and carbon black. In addition to the modified conjugated diene polymer described below, the rubber composition of the present embodiment can also use a rubber-like polymer other than the modified conjugated diene polymer (hereinafter, simply referred to as a "rubber-like polymer") in combination as the rubber component.

[0018] Such rubbery polymers are not particularly limited, but examples thereof include conjugated diene polymers such as conjugated diene polymers or hydrogenated products thereof, random copolymers of conjugated diene compounds and vinyl aromatic compounds or hydrogenated products thereof, and block copolymers of conjugated diene compounds and vinyl aromatic compounds or hydrogenated products thereof, non-diene polymers, and natural rubber.

[0019] Specific conjugated diene polymers are not particularly limited, but examples thereof include styrene-based elastomers such as butadiene rubber or hydrogenated products thereof, isoprene rubber or hydrogenated products thereof, styrene-butadiene rubber or hydrogenated products thereof, styrene-butadiene block copolymer or hydrogenated products thereof, and styrene-isoprene block copolymer or hydrogenated products thereof, and acrylonitrile-butadiene rubber or hydrogenated products thereof.

[0020] The non-diene polymer is not particularly limited, but examples thereof include olefin elastomers such as ethylene-propylene rubber, ethylene-propylene-diene rubber, ethylene-butene-diene rubber, ethylene-butene rubber, ethylene-hexene rubber, and ethylene-octene rubber, butyl rubber, brominated butyl rubber, acrylic rubber, fluororubber, silicone rubber, chlorinated polyethylene rubber, epichlorohydrin rubber, α,β-unsaturated nitrile-acrylate-conjugated diene copolymer rubber, urethane rubber, and polysulfide rubber.

[0021] The natural rubber is not particularly limited, but examples thereof include smoked sheets RSS3 to RSS5, SMR, and epoxidized natural rubber.

[0022] The various rubbery polymers described above may be modified rubbers to which polar functional groups such as hydroxyl groups, amino groups, etc. When used for tires, butadiene rubber, isoprene rubber, styrene-butadiene rubber, natural rubber, and butyl rubber are preferably used.

[0023] From the viewpoint of a balance between performance and processing characteristics, the weight average molecular weight of the rubber polymer is preferably 2,000 to 2,000,000, and more preferably 5,000 to 1,500,000. Furthermore, low molecular weight rubber polymers, so-called liquid rubbers, can also be used as the rubber polymer. These rubber polymers may be used alone or in combination of two or more.

[0024] In the present embodiment, when a rubber composition containing a modified conjugated diene polymer and a rubbery polymer is prepared, the ratio (mass ratio) of the modified conjugated diene polymer to the rubbery polymer (modified conjugated diene polymer / rubbery polymer) is preferably 10 / 90 or more and 100 / 0 or less, more preferably 20 / 80 or more and 90 / 10 or less, and even more preferably 40 / 60 or more and 80 / 20 or less. Therefore, the rubber component preferably contains 10 parts by mass or more and 100 parts by mass or less, more preferably 20 parts by mass or more and 90 parts by mass or less, and even more preferably 40 parts by mass or more and 80 parts by mass or less, relative to the total amount (100 parts by mass) of the rubber component. When the (modified conjugated diene polymer / rubbery polymer) content ratio is within the above-mentioned range, the vulcanized rubber composition obtained exhibits excellent abrasion resistance and tensile strength, a balance between fuel economy and wet skid resistance, and excellent vibration damping performance.

[0025] [Filler] (Carbon Black) The carbon black contained in the rubber composition of the present embodiment is not particularly limited, but examples thereof include carbon blacks of various classes such as SRF, FEF, HAF, ISAF, and SAF. Among these, carbon blacks having a nitrogen adsorption specific surface area of ​​50 m ２ Carbon black having a carbon absorption of 80 mL / 100 g or more and a dibutyl phthalate (DBP) oil absorption of 80 mL / 100 g or less is preferred.

[0026] In the rubber composition of the present embodiment, the content of carbon black is preferably 10 parts by mass or more and 150 parts by mass or less, more preferably 25 parts by mass or more and 125 parts by mass or less, and even more preferably 30 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the rubber component.

[0027] In the crosslinked rubber composition of the present embodiment, the content of carbon black is preferably 10 parts by mass or more per 100 parts by mass of the rubber component from the viewpoint of achieving performance such as hardness and vibration damping properties required for industrial applications, and is preferably 150 parts by mass or less per 100 parts by mass of the rubber component from the viewpoint of dispersibility.

[0028] (Fillers other than carbon black) The rubber composition of this embodiment may contain fillers other than carbon black. The fillers other than carbon black are not particularly limited, but examples thereof include silica-based inorganic fillers, metal oxides, and metal hydroxides. Among these, silica is preferred. The fillers may be used alone or in combination of two or more.

[0029] The silica-based inorganic filler is not particularly limited and known fillers can be used, but SiO ２ or Si ３ Solid particles containing Al as a constituent unit are preferred, and SiO ２ or Si ３ Solid particles containing Al as the main component of the structural units are more preferred. Here, the main component refers to a component contained in the silica-based inorganic filler in an amount of 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more.

[0030] Specific silica-based inorganic fillers are not particularly limited, but examples thereof include inorganic fibrous materials such as silica, clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, and glass fiber. Other examples include silica-based inorganic fillers with hydrophobic surfaces and mixtures of silica-based inorganic fillers with non-silica-based inorganic fillers. Among these, silica and glass fiber are preferred, and silica is more preferred, from the viewpoints of strength and abrasion resistance. Examples of silica include dry silica, wet silica, and synthetic silicate silica. Among these silicas, wet silica is preferred.

[0031] From the viewpoint of obtaining practically good abrasion resistance and breaking strength of the vulcanized rubber composition, the nitrogen adsorption specific surface area determined by the BET adsorption method of the silica-based inorganic filler is 100 m ２ / g or more 300m ２ / g or less, and ２ / g or more 250m ２ / g or less. If necessary, a relatively small specific surface area (for example, a specific surface area of ​​200 m ２ / g or less) and a silica-based inorganic filler having a relatively large specific surface area (for example, 200 m２ / g or more) and a silica-based inorganic filler).

[0032] The content of the silica-based inorganic filler in the rubber composition is 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, based on the total amount of fillers. When the rubber composition contains a silica-based inorganic filler, the lower limit of the content can be 15% by mass or more, 10% by mass or more, or 5% by mass or more, based on the total amount of fillers.

[0033] In the rubber composition of this embodiment, the metal oxide refers to solid particles whose main constituent component is a structural unit represented by the chemical formula MxOy (M represents a metal atom, and x and y each independently represent an integer of 1 to 6). Examples of metal oxides include, but are not limited to, alumina, titanium oxide, magnesium oxide, and zinc oxide. Examples of metal hydroxides include, but are not limited to, aluminum hydroxide, magnesium hydroxide, and zirconium hydroxide.

[0034] [Modified Conjugated Diene Polymer] The rubber composition of the present embodiment contains a modified conjugated diene polymer that satisfies the following (1) to (7). (1) The polymer has a main chain branched structure having a branched structure in the main chain, (2) the main chain branched structure includes a structure derived from at least one conjugated diene monomer, or a structure derived from at least one conjugated diene monomer and a structure derived from an aromatic vinyl monomer, (3) at least one terminal has an end group having at least one carbonyl group and at least one substituted amino group in the molecule, (4) a Mooney viscosity measured at 100°C of 30 to 120, (5) a branching degree (Bn) measured by a GPC-light scattering method with a viscosity detector of 1.1 or more and less than 4.0, (6) a chromatogram measured by a gel permeation chromatograph (GPC) is unimodal and a molecular weight distribution is 1.60 to 3.00, and (7) a hydrogenation rate is less than 10 mol%.

[0035] Although not particularly limited, the modified conjugated diene polymer in this embodiment can be synthesized by polymerizing at least one modified conjugated diene monomer or copolymerizing a conjugated diene monomer and an aromatic vinyl monomer while adding a branching agent to synthesize a conjugated diene polymer having a main chain branched structure.

[0036] (Method for Producing Modified Conjugated Diene Polymer) The method for producing a modified conjugated diene polymer in this embodiment can include a polymerization and branching step of polymerizing a conjugated diene monomer using an organolithium compound as a polymerization initiator while adding a branching agent described below to obtain a conjugated diene polymer having a main chain branched structure, and a modification step of modifying the conjugated diene polymer with a modifying agent.

[0037] (Polymerization and branching step) in the method for producing a modified conjugated diene polymer is a step of, for example, using an organic monolithium compound as a polymerization initiator, polymerizing at least one conjugated diene compound, and adding a branching agent to obtain a conjugated diene polymer having a branched structure in its main chain. Hereinafter, the polymerization reaction in the polymerization and branching step is referred to as the "polymerization step," and the reaction with the branching agent is referred to as the "branching step."

[0038] In the polymerization step, it is preferable to carry out polymerization by a propagation reaction through a living anionic polymerization reaction, which can produce a conjugated diene polymer having an active terminal. In the subsequent branching step using a branching agent, main chain branching can be appropriately controlled, and a conjugated diene polymer with a high modification rate can be obtained.

[0039] The conjugated diene polymer may be a homopolymer obtained using a single conjugated diene compound as a monomer, or a polymer obtained using different types of conjugated diene compounds as monomers, that is, a copolymer.

[0040] (Conjugated Diene Monomer) Specific examples of the conjugated diene monomer in this embodiment are not particularly limited, but include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene. Among these, 1,3-butadiene and isoprene are preferred from the viewpoint of industrial availability. These may be used alone or in combination of two or more.

[0041] (Aromatic vinyl monomer) Examples of aromatic vinyl monomers in this embodiment include, but are not limited to, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene. Among these, styrene is preferred from the viewpoint of industrial availability. These may be used alone or in combination of two or more.

[0042] (Polymerization Initiator) At least an organic monolithium compound can be used as the polymerization initiator in this embodiment. The organic monolithium compound is not particularly limited, but examples thereof include low molecular weight compounds and solubilized oligomeric organic monolithium compounds. Furthermore, examples of the organic monolithium compound include compounds having a carbon-lithium bond, a nitrogen-lithium bond, and a tin-lithium bond in terms of the bonding mode between the organic group and the lithium. The amount of the organic monolithium compound used as the polymerization initiator is preferably determined based on the molecular weight of the target conjugated diene polymer.

[0043] The amount of a monomer such as a conjugated diene compound used relative to the amount of a polymerization initiator used is related to the degree of polymerization. That is, it tends to be related to the number average molecular weight and / or the weight average molecular weight. Therefore, to increase the molecular weight, it is advisable to adjust the amount of the polymerization initiator used in a direction to decrease, and to decrease the molecular weight, it is advisable to adjust the amount of the polymerization initiator used in a direction to increase.

[0044] The organic monolithium compound is preferably an alkyllithium compound having a substituted amino group or a dialkylaminolithium compound, because it can be used as a method for introducing nitrogen atoms into a conjugated diene polymer. In this case, a conjugated diene polymer having a nitrogen atom consisting of an amino group at the polymerization initiation terminal is obtained. The substituted amino group is an amino group that does not have an active hydrogen or has a structure in which the active hydrogen is protected.

[0045] The alkyllithium compound having an amino group without active hydrogen is not particularly limited, but examples thereof include 3-dimethylaminopropyllithium, 3-diethylaminopropyllithium, 4-(methylpropylamino)butyllithium, and 4-hexamethyleneiminobutyllithium.

[0046] The alkyllithium compound having an amino group with a structure in which an active hydrogen is protected is not particularly limited, but examples thereof include 3-bistrimethylsilylaminopropyllithium and 4-trimethylsilylmethylaminobutyllithium.

[0047] The dialkylaminolithium is not particularly limited, but examples thereof include lithium dimethylamide, lithium diethylamide, lithium dipropylamide, lithium dibutylamide, lithium di-n-hexylamide, lithium diheptylamide, lithium diisopropylamide, lithium dioctylamide, lithium-di-2-ethylhexylamide, lithium didecylamide, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide, lithium methylphenethylamide, lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, lithium morpholide, 1-lithioazacyclooctane, 6-lithio-1,3,3-trimethyl-6-azabicyclo[3.2.1]octane, and 1-lithio-1,2,3,6-tetrahydropyridine.

[0048] These organomonolithium compounds having a substituted amino group can also be used as solubilized oligomeric organomonolithium compounds by reacting them with a small amount of a polymerizable monomer, such as 1,3-butadiene, isoprene, or styrene.

[0049] The organic monolithium compound is preferably an alkyllithium compound from the viewpoints of industrial availability and ease of control of the polymerization reaction, in which case a conjugated diene polymer having an alkyl group at the polymerization initiation terminal can be obtained.

[0050] The alkyllithium compound is not particularly limited, but examples thereof include n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium. As the alkyllithium compound, n-butyllithium and sec-butyllithium are preferred from the viewpoints of industrial availability and ease of control of the polymerization reaction. These organomonolithium compounds may be used alone or in combination of two or more. Furthermore, they may be used in combination with other organometallic compounds.

[0051] Examples of other organometallic compounds include alkaline earth metal compounds, other alkali metal compounds, and other organometallic compounds.

[0052] Examples of alkaline earth metal compounds include, but are not limited to, organomagnesium compounds, organocalcium compounds, and organostrontium compounds, as well as alkaline earth metal alkoxides, sulfonates, carbonates, and amides.

[0053] Examples of organomagnesium compounds include dibutylmagnesium and ethylbutylmagnesium. Examples of other organometallic compounds include organoaluminum compounds.

[0054] (Polymerization Method) In the polymerization step of this embodiment, the polymerization reaction mode is not particularly limited, but examples thereof include a batchwise polymerization mode (also referred to as a "batch type") and a continuous polymerization mode.

[0055] In the continuous system, one or more connected reactors can be used. The continuous reactor may be, for example, a tank-type or tubular reactor equipped with an agitator. In the continuous system, preferably, the monomer, the inert solvent, and the polymerization initiator are continuously fed into the reactor, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is continuously discharged.

[0056] The batch reactor may be, for example, a tank-type reactor equipped with a stirrer. In the batch reactor, preferably, a monomer, an inert solvent, and a polymerization initiator are fed, and if necessary, a monomer is added continuously or intermittently during polymerization to obtain a polymer solution in the reactor, which is then discharged after the polymerization is completed.

[0057] (Polymerization Solvent) In the polymerization step of the conjugated diene polymer in this embodiment, the polymerization is preferably carried out in an inert solvent. The solvent is not particularly limited, but examples thereof include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific hydrocarbon solvents are not particularly limited, but examples thereof include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene, and hydrocarbons consisting of mixtures thereof.

[0058] By treating the impurities, that is, allenes and acetylenes, with an organometallic compound before subjecting the polymer to the polymerization reaction, a conjugated diene-based polymer having a high concentration of active ends tends to be obtained, and a modified conjugated diene-based polymer with a high modification rate tends to be obtained, which is preferable.

[0059] (Polar Compound) A polar compound may be added in the polymerization step. It tends to be usable as a vinylating agent for controlling the amount of 1,2-vinyl bonds in the conjugated diene polymer. It also tends to be effective in accelerating the polymerization reaction.

[0060] The polar compound is not particularly limited, and examples thereof include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium tert-butylate, and sodium amylate; and phosphine compounds such as triphenylphosphine.

[0061] These polar compounds may be used alone or in combination of two or more. The amount of the polar compound used is not particularly limited and can be selected depending on the purpose, etc., but is preferably 0.01 mol or more and 100 mol or less per mol of the polymerization initiator.

[0062] Such polar compounds (vinylating agents) can be used as modifiers for the microstructure of the conjugated diene polymer in an appropriate amount depending on the desired amount of 1,2 vinyl bonds.

[0063] (Polymerization temperature) The polymerization temperature in the polymerization step is preferably a temperature at which living anionic polymerization proceeds, and from the viewpoint of productivity, is more preferably 0°C or higher, and even more preferably 120°C or lower. By being in such a range, it tends to be possible to ensure a sufficient amount of the modifying agent reacting with the active terminals after the polymerization is completed. Even more preferably, it is 50°C or higher and 100°C or lower.

[0064] (Branching Step) The rubber composition of this embodiment includes a modified conjugated diene polymer having (1) a main chain branched structure in which the main chain has a branched structure, and (2) the main chain branched structure is a structure derived from at least one conjugated diene monomer, or a structure derived from at least one conjugated diene monomer and an aromatic vinyl monomer. The modified conjugated diene polymer can be obtained as a conjugated diene polymer having a main chain branched structure by adding a branching agent while polymerizing at least one conjugated diene monomer or copolymerizing a conjugated diene monomer and an aromatic vinyl monomer.

[0065] The amount of branching agent added in the branching step for forming a branched structure is not particularly limited and can be selected depending on the purpose, etc., but is preferably 0.02 mol or more and 0.5 mol or less, more preferably 0.03 mol or more and 0.4 mol or less, and even more preferably 0.03 mol or more and 0.3 mol or less, relative to 1 mol of the polymerization initiator.

[0066] The branching agent can be used in an appropriate amount depending on the desired number of branching points as branching points of the branched structure of the conjugated diene portion of the conjugated diene polymer.

[0067] In the branching step, the timing of adding the branching agent is not particularly limited and can be selected depending on the purpose, etc., but from the viewpoint of improving the absolute molecular weight and the modification rate of the conjugated diene-based polymer, the timing is preferably when the raw material conversion rate after the addition of the polymerization initiator is 20% or more, more preferably 40% or more, even more preferably 50% or more, still more preferably 65% ​​or more, and even more preferably 75% or more.

[0068] After the branching agent is added, the desired raw materials may be further added, and the polymerization step may be continued after branching, or the above-described process may be repeated.

[0069] The modified conjugated diene polymer of this embodiment is not particularly limited and may be a polymer of a conjugated diene monomer and a branching agent, or a copolymer of a conjugated diene monomer, a branching agent, and a monomer other than these. For example, when the conjugated diene monomer is butadiene or isoprene and is polymerized with a branching agent containing a vinyl aromatic moiety (i.e., an aromatic vinyl monomer), the polymer chain is a so-called polybutadiene or polyisoprene, and the branched portion contains a structure derived from the vinyl aromatic. Having such a structure improves the linearity per polymer chain, increases the crosslink density after vulcanization, and improves wear resistance. Therefore, the conjugated diene polymer of this embodiment is suitable for applications such as tires, resin modification, automotive interior and exterior parts, vibration-damping rubber, and footwear.

[0070] When the rubber composition of this embodiment is used for the tread of a highly loaded tire, the modified conjugated diene polymer is preferably a copolymer of a conjugated diene monomer and a branching agent.

[0071] (Modified Conjugated Diene Polymer) The modified conjugated diene polymer of this embodiment has (3) an end group at at least one end, the end group having at least one carbonyl group and at least one substituted amino group in the molecule. The modified conjugated diene polymer of this embodiment is, for example, a modified conjugated diene polymer modified with a modifying agent having at least one carbonyl group (>C=O group) and at least one substituted amino group in the molecule that reacts with the active end of the conjugated diene polymer. That is, the end group having at least one carbonyl group and at least one substituted amino group in the molecule that the modified conjugated diene polymer of this embodiment has is a group formed by modifying the active end with the above-mentioned modifying agent, and is a group derived from the structure of the modifying agent.

[0072] In the above-mentioned modifying agent, the carbonyl group and the substituted amino group may be adjacent or may be separated. Examples of compounds in which these functional groups are adjacent include amides, imides, ureas, and isocyanuric acids having a "-C(=O)-N<" bond. Among these, cyclic compounds are preferred, with N-substituted cyclic amides and N-substituted cyclic ureas being more preferred, and N-substituted cyclic ureas being particularly preferred. Examples of compounds in which the carbonyl group and the substituted amino group are separated include N-substituted aminoketones and N-substituted aminoaldehydes, with N-substituted aminoketones being preferred.

[0073] In the present embodiment, two or more types of modifiers may be used, and the modifiers may be added simultaneously or separately in the modification step. When two or more types of modifiers are used, the modified conjugated diene polymer in the present embodiment becomes a conjugated diene polymer in which two or more types of end groups have been modified.

[0074] The amount of the modifying agent used is not particularly limited and can be selected depending on the purpose, etc., but is preferably 0.10 mol or more and 3.00 mol or less, more preferably 0.30 mol or more and 2.00 mol or less, and still more preferably 0.50 mol or more and 1.50 mol or less, relative to 1 mol of the polymerization initiator.

[0075] In the present embodiment, the modifying agent having at least one carbonyl group and at least one substituted amino group in the molecule is not particularly limited, and examples of N-substituted cyclic amides include N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-t-butyl-2-pyrrolidone, N-methyl-2-piperidone, N-phenyl-2-piperidone, N-methyl-ε-caprolactam, and N-phenyl-ε-caprolactam.

[0076] The N-substituted cyclic ureas are not particularly limited, but examples thereof include 1,3-dimethylethyleneurea, 1,3-diethyl-2-imidazolidinone, and 1-methyl-3-ethyl-2-imidazolidinone.

[0077] The N-substituted aminoketones are not particularly limited, but examples thereof include 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, and the like.

[0078] The N-substituted aminoaldehydes are not particularly limited, but examples thereof include 4-N,N-dimethylaminobenzaldehyde.

[0079] [Structure of Terminal Group of Modified Conjugated Diene Polymer] In the modified conjugated diene polymer of the present embodiment, the terminal group having at least one carbonyl group and at least one substituted amino group in the molecule preferably has a structure (amino group or amide group) represented by the following formula (1) and / or the following formula (2):

[0080] (In formula (1), P represents a conjugated diene polymer containing at least one conjugated diene monomer, and R ａ and R ｂ each independently represents a hydrocarbon group having 1 to 20 carbon atoms.

[0081] (In formula (2), P represents a conjugated diene polymer containing at least one conjugated diene monomer, and R ａ and R ｂeach independently represents a hydrocarbon group having 1 to 20 carbon atoms.

[0082] The modified conjugated diene polymer of the present embodiment has the above-described terminal groups, and when the polymer is used in a rubber composition containing, in particular, carbon black as a filler, the terminal groups interact with or bond to functional groups on the surface of the carbon black, which tends to improve dispersion of the carbon black in the rubber composition, resulting in excellent fuel economy and dynamic magnification when vulcanized.

[0083] In the present embodiment, the modifying agent for forming the structure represented by formula (1) is not particularly limited, but examples thereof include 1,3-diethyl-2-imidazolinone, 1,3-dimethyl-2-imidazolinone, 1,3-dipropyl-2-imidazolinone, 1-methyl-3-ethyl-2-imidazolinone, 1-methyl-3-propyl-2-imidazolinone, 1-methyl-3-butyl-2-imidazolinone, and 1,3-dihydro-1,3-dimethyl-2H-imidazol-2-one.

[0084] In the present embodiment, the modifying agent represented by formula (2) is not particularly limited, but examples thereof include 1,3-diethyl-2-imidazolidinone, 1,3-dimethyl-2-imidazolidinone, 1,3-dipropyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, and 1-methyl-3-propyl-2-imidazolidinone.

[0085] (Modification Step) The method for producing a modified conjugated diene polymer in this embodiment may include a modification step (hereinafter also simply referred to as the "modification step") of modifying the conjugated diene polymer obtained through the polymerization and branching steps described above with the above-mentioned modifying agent.

[0086] In the modification step, one active end of the conjugated diene polymer is modified with the above-mentioned modifying agent to obtain a conjugated diene polymer. The reaction temperature in the modification step is preferably the same as the polymerization temperature of the conjugated diene polymer, more preferably 0° C. or higher and 120° C. or lower, and more preferably 50° C. or higher and 100° C. or lower. The reaction time in the modification step is preferably 10 seconds or longer, more preferably 30 seconds or longer.

[0087] The mixing in the modification step may be performed by mechanical stirring, stirring with a static mixer, etc. When the polymerization step is continuous, the modification step is also preferably continuous. The reactor used in the modification step may be, for example, a tank-type or tubular reactor equipped with a stirrer.

[0088] The modifying agent may be diluted with an inert solvent and continuously fed to the reactor. When the polymerization process is a batch process, the modifying agent may be directly added to the polymerization reactor, or may be transferred to a separate reactor for the modification process.

[0089] The time from the polymerization step to the modification step is preferably short, preferably within 10 minutes, more preferably within 5 minutes. In this case, a conjugated diene polymer with high modification efficiency tends to be obtained. The time from the polymerization step to the modification step refers to, for example, the time from the peak polymerization temperature to the addition of the modifier when the polymerization step is batchwise, and refers to the time from the addition of the modifier to the solution containing the conjugated diene polymer that has left the polymerization reactor when the polymerization step is continuous.

[0090] In this embodiment, after the modification step, a condensation reaction step of carrying out a condensation reaction in the presence of a condensation promoter may be further carried out.

[0091] The conjugated diene polymer of this embodiment may be hydrogenated at the conjugated diene portion in the conjugated diene polymer chain. The method for hydrogenating the conjugated diene portion of the conjugated diene polymer is not particularly limited, and known methods can be used. A suitable hydrogenation method includes a method in which gaseous hydrogen is blown into a polymer solution in the presence of a catalyst. The catalyst is not particularly limited, and examples include heterogeneous catalysts such as catalysts in which a noble metal is supported on a porous inorganic material; catalysts in which a salt of nickel, cobalt, or the like is solubilized and reacted with organoaluminum, and homogeneous catalysts such as catalysts using metallocenes such as titanocene. Among these, titanocene catalysts are preferred from the viewpoint of enabling selection of mild hydrogenation conditions. Furthermore, hydrogenation of aromatic groups can be carried out using a noble metal supported catalyst.

[0092] The hydrogenation catalyst is not particularly limited, but examples thereof include (1) supported heterogeneous hydrogenation catalysts in which a metal such as Ni, Pt, Pd, or Ru is supported on carbon, silica, alumina, diatomaceous earth, or the like, (2) so-called Ziegler-type hydrogenation catalysts which use a transition metal salt such as an organic acid salt or an acetylacetone salt of Ni, Co, Fe, Cr, or the like and a reducing agent such as an organoaluminum, and (3) so-called organometallic complexes such as organometallic compounds of Ti, Ru, Rh, Zr, etc. Furthermore, the hydrogenation catalyst is not particularly limited, but examples thereof include known hydrogenation catalysts described in JP-B Nos. 42-8704, 43-6636, 63-4841, 1-37970, 1-53851, 2-9041, and 8-109219. Preferred hydrogenation catalysts include a reaction mixture of a titanocene compound and a reducing organometallic compound.

[0093] The reaction temperature of the hydrogenation reaction is preferably the same as the polymerization temperature of the conjugated diene polymer, and is preferably from 0° C. to 120° C., more preferably from 50° C. to 100° C. The reaction time of the hydrogenation reaction is preferably 10 seconds or more, more preferably 30 seconds or more.

[0094] The hydrogenation reaction may be carried out by mechanical stirring, stirring with a static mixer, or the like. When the polymerization process is continuous, the hydrogenation reaction is preferably also continuous. The reactor used in the hydrogenation reaction may be, for example, a tank-type or tubular reactor equipped with a stirrer.

[0095] The hydrogenation catalyst may be diluted with an inert solvent and continuously supplied to the reactor. When the polymerization process is a batch process, the hydrogenation catalyst may be directly charged into the polymerization reactor and hydrogen may be blown in to carry out the hydrogenation reaction, or the hydrogenation catalyst may be transferred to another reactor and carried out the hydrogenation reaction.

[0096] In the method for producing a conjugated diene polymer of this embodiment, after the modification step, a deactivator, a neutralizer, etc. may be added to the polymer solution as needed.

[0097] The quenching agent is not particularly limited, but examples thereof include water; alcohols such as methanol, ethanol, and isopropanol; and the like.

[0098] The neutralizing agent is not particularly limited, but examples thereof include carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, mainly 10 carbon atoms); aqueous solutions of inorganic acids; and carbon dioxide gas.

[0099] In the method for producing a modified conjugated diene polymer in this embodiment, it is preferable to add a rubber stabilizer from the viewpoint of preventing gel formation after polymerization and improving stability during processing.

[0100] The rubber stabilizer is not limited to the following and any known stabilizer can be used, but preferred examples include antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (hereinafter also referred to as "BHT"), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol.

[0101] In order to further improve the productivity of the modified conjugated diene polymer of the present embodiment and the processability when it is made into a composition containing a filler or the like, a rubber softener can be added as needed.

[0102] The rubber softener is not particularly limited, but examples thereof include extender oil, liquid rubber, resin, etc. The method for adding the rubber softener to the conjugated diene polymer is not particularly limited, but a preferred method is to add the rubber softener to a conjugated diene polymer solution, mix them, and remove the solvent from the resulting polymer solution containing the rubber softener.

[0103] Preferred extender oils include, for example, aromatic oils, naphthenic oils, paraffin oils, etc. Among these, from the viewpoint of environmental safety, oil bleed prevention, and wet grip properties, aromatic substitute oils having a polycyclic aromatic (PCA) content of 3% by mass or less according to the IP346 method are preferred. Examples of aromatic substitute oils include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), etc. shown in Kautschuk Gummi Kunststoffe 52(12)799(1999), as well as RAE (Residual Aromatic Extracts).

[0104] Preferred liquid rubbers are not particularly limited, but examples thereof include liquid polybutadiene, liquid styrene-butadiene rubber, etc. The effect of adding liquid rubber is that it improves the processability of a composition containing a conjugated diene polymer and a filler, etc., and also shifts the glass transition temperature of the composition to a lower temperature, which tends to improve the abrasion resistance, low hysteresis loss, and low-temperature properties of a vulcanized product.

[0105] Preferred resins include, but are not limited to, aromatic petroleum resins, coumarone-indene resins, terpene resins, rosin derivatives (including tung oil resins), tall oil, tall oil derivatives, rosin ester resins, natural and synthetic terpene resins, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, mixed aliphatic-aromatic hydrocarbon resins, coumarin-indene resins, phenolic resins, p-tert-butylphenol-acetylene resins, phenol-formaldehyde resins, xylene-formaldehyde resins, monoolefin oligomers, diolefin oligomers, aromatic hydrocarbon resins, aromatic petroleum resins, hydrogenated aromatic hydrocarbon resins, cyclic aliphatic hydrocarbon resins, hydrogenated hydrocarbon resins, hydrocarbon resins, hydrogenated tung oil resins, hydrogenated oil resins, and esters of hydrogenated oil resins with monofunctional or polyfunctional alcohols. These resins may be used alone or in combination of two or more. When hydrogenating, all unsaturated groups may be hydrogenated, or some may remain.

[0106] The effect of adding the resin is to improve the processability of a composition obtained by blending the conjugated diene polymer with a filler or the like, and also to tend to improve the breaking strength of a vulcanized product. Furthermore, the glass transition temperature of the composition can be shifted to a higher temperature, which tends to improve the wet skid resistance.

[0107] The amount of rubber softener, such as extender oil, liquid rubber, or resin, added is not particularly limited, but is preferably 1 part by mass to 60 parts by mass, more preferably 5 parts by mass to 50 parts by mass, and even more preferably 10 parts by mass to 37.5 parts by mass, relative to 100 parts by mass of the modified conjugated diene polymer in this embodiment. When the rubber softener is added within the above range, the processability of a composition containing the conjugated diene polymer and a filler, etc., is improved, and the breaking strength and abrasion resistance of a vulcanized product tend to be improved.

[0108] (Solvent Removal Step) In the method for producing a modified conjugated diene polymer in this embodiment, a known method can be used as a method for obtaining the resulting modified conjugated diene polymer from the polymer solution. The method is not particularly limited, but examples thereof include a method of separating the solvent by steam stripping or the like, filtering the polymer, and then dehydrating and drying it to obtain the polymer, a method of concentrating the polymer in a flashing tank and then devolatilizing it using a vent extruder or the like, and a method of directly devolatilizing it using a drum dryer or the like.

[0109] (Mooney Viscosity) The modified conjugated diene polymer in this embodiment has (4) a Mooney viscosity measured at 100° C. of 30 to 120. Specifically, from the viewpoints of the productivity of the conjugated diene polymer, the processability when the polymer is made into a composition containing a filler or the like, and the abrasion resistance and breaking strength when the composition is made into a vulcanizate, the Mooney viscosity measured at 100° C. of the modified conjugated diene polymer in this embodiment is 30 or more and 120 or less, preferably 35 or more and 100 or less, and more preferably 40 or more and 90 or less.

[0110] When the Mooney viscosity measured at 100°C is 30 or more, the abrasion resistance and breaking strength of the vulcanized product are improved. When the Mooney viscosity measured at 100°C is 120 or less, problems in the production of the conjugated diene polymer are suppressed, and the processability is improved when the polymer is made into a composition containing a filler or the like.

[0111] The Mooney viscosity is measured by using a conjugated diene polymer in the form of a plate prepared by pressing, setting the sample in the apparatus, preheating the sample at 100°C for 1 minute, rotating the rotor at 2 rpm, measuring the torque after 4 minutes, and using the measured value as the Mooney viscosity (ML(1+4)). More specifically, it can be measured by the method described in the examples below. The Mooney viscosity of the conjugated diene polymer can be controlled within the above-mentioned range by, for example, controlling the conditions such as the temperature in the polymerization step or adjusting the degree of branching in the branching step.

[0112] (Branching Degree (Bn)) The modified conjugated diene polymer in this embodiment has a branching degree (Bn) of 1.1 or more and less than 4.0 as measured by (5) a GPC-light scattering method with a viscosity detector. Specifically, from the viewpoints of processability, abrasion resistance, and breaking strength, the modified conjugated diene polymer in this embodiment has a branching degree (Bn) of 1.1 or more and less than 4.0 as measured by a GPC-light scattering method with a viscosity detector.

[0113] The degree of branching (Bn) being less than 4.0 means that the modified conjugated diene polymer in this embodiment has substantially less than four polymer chains with a branched structure relative to the longest polymer main chain.

[0114] The degree of branching (Bn) of a conjugated diene polymer is defined as g' = 6Bn / {(Bn+1)(Bn+2)}, where g' is a shrinkage factor measured by GPC-light scattering method with a viscosity detector. Generally, polymers having branches tend to have smaller molecular size compared to linear polymers with the same absolute molecular weight.

[0115] The shrinkage factor (g') is a measure of the ratio of the molecular size to that of a linear polymer of the same assumed absolute molecular weight. That is, the greater the degree of branching of a polymer, the smaller the shrinkage factor (g') tends to be.

[0116] In this embodiment, the intrinsic viscosity is used as an index of molecular size for this shrinkage factor. For linear polymers, the intrinsic viscosity [η] is 10 －３．８８３ ×M ０．７７１ In the above formula, M is the absolute molecular weight.

[0117] However, the contraction factor represents the rate of decrease in molecular size, and does not accurately represent the branched structure of the polymer. Therefore, the degree of branching (Bn) of the conjugated diene polymer is calculated using the value of the contraction factor (g') at each absolute molecular weight of the conjugated diene polymer. The calculated "degree of branching (Bn)" accurately represents the number of polymers that are directly or indirectly bonded to each other with respect to the longest main chain structure.

[0118] The calculated branching degree (Bn) is an index that represents the branching structure of a conjugated diene polymer. For example, in the case of a typical four-branched star polymer (four polymer chains connected to the center), two polymer chain arms are bonded to the longest highly branched main chain structure, and the branching degree (Bn) is evaluated as 2.

[0119] In the case of a typical six-branched star polymer, four polymer chain arms are attached to the longest highly branched main chain structure, and the degree of branching (Bn) is evaluated as four.

[0120] The conjugated diene polymer of the present embodiment desirably has a degree of branching (Bn) of 1.1 or more and less than 4.0. In such a case, this means that the conjugated diene polymer has a star polymer structure having branches similar to a star polymer structure with less than 6 branches from a linear chain.

[0121] Here, "branch" refers to a structure formed by direct or indirect bonding of one polymer to another polymer, and "degree of branching (Bn)" refers to the number of polymers that are directly or indirectly bonded to each other in the longest main chain structure.

[0122] When the degree of branching (Bn) is 1.1 or more and less than 4.0, the modified conjugated diene-based polymer of the present embodiment exhibits good interaction with fillers while suppressing cold flow of bales, which are the product form of the conjugated diene copolymer, and tends to have excellent fuel economy and dynamic magnification when vulcanized.

[0123] The degree of branching (Bn) of the modified conjugated diene polymer in this embodiment is 1.1 or more and less than 4.0, preferably 1.2 or more and less than 3.9, more preferably 1.3 or more and less than 3.8, and even more preferably 1.4 or more and less than 3.7. A conjugated diene polymer having a degree of branching (Bn) within this range tends to be excellent in fuel economy and dynamic magnification when vulcanized.

[0124] The degree of branching of the modified conjugated diene polymer can be controlled to 1.1 or more and less than 4.0 by combining the amount of branching agent and the amount of terminal modifier added. Specifically, the degree of branching can be controlled by the number of functional groups of the branching agent, the amount of branching agent added, the timing of adding the branching agent, and the number of functional groups and the amount of nitrogen-containing modifier added.

[0125] (Molecular Weight Distribution) The modified conjugated diene polymer of this embodiment (6) has a unimodal chromatographic shape measured by gel permeation chromatography (GPC), and a molecular weight distribution of 1.60 to 3.00. Specifically, the modified conjugated diene polymer of this embodiment has a unimodal chromatographic shape measured by gel permeation chromatography (GPC). A unimodal chromatographic shape means that the chromatographic shape of gel permeation chromatography (GPC) measured by the method described in the Examples below has one peak derived from the polymer, and the peak shape has no valley.

[0126] The GPC chromatogram of the modified conjugated diene polymer can be controlled, for example, by using a continuous polymerization method as the polymerization mode and appropriately controlling the type and amount of branching agent added in the branching step and the type and amount of terminal modifier added in the modification step. More specifically, this can be achieved by the method described in the examples below.

[0127] The modified conjugated diene polymer in this embodiment has a molecular weight distribution (Mw / Mn), expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), of 1.60 to 3.00. A conjugated diene polymer having a molecular weight distribution in this range tends to have excellent abrasion resistance and breaking strength when the composition containing a filler or the like is vulcanized. The molecular weight distribution is more preferably 1.65 to 2.70, and even more preferably 1.70 to 2.50.

[0128] The number average molecular weight, weight average molecular weight, and molecular weight distribution of the modified conjugated diene polymer can be measured by the method described in the Examples below. The number average molecular weight, weight average molecular weight, and molecular weight distribution of the conjugated diene polymer can be controlled within the above-mentioned ranges, for example, by controlling conditions such as temperature in the polymerization step or by adjusting the branching degree in the branching step.

[0129] The modified conjugated diene polymer of this embodiment has (7) a hydrogenation rate of less than 10 mol%. The hydrogenation rate in this embodiment refers to the hydrogenation rate relative to the double bonds in the structural units derived from the conjugated diene compound in the modified conjugated diene polymer. A modified conjugated diene polymer having a hydrogenation rate in this range exhibits high phase separation when formed into a composition with other rubber components, such as natural rubber, and when kneaded with a filler to form a composition, the effect of the terminal modified group is exerted, tending to result in excellent filler dispersibility. From this viewpoint, a hydrogenation rate of less than 5 mol% is more preferable, even more preferably less than 3 mol%, and a non-hydrogenated form is even more preferable.

[0130] The hydrogenation rate of the modified conjugated diene polymer was measured using a nuclear magnetic resonance spectrometer ( １ It can be measured using 1 H-NMR by the method described in the Examples below.

[0131] The hydrogenation rate can be controlled within the above range by appropriately controlling the amount of hydrogen added to the double bond in the structural unit derived from the conjugated diene compound, the amount of hydrogenation catalyst in the hydrogenation reaction, hydrogen pressure, reaction temperature, reaction time, etc. More specific details will be described in the examples below.

[0132] [1,2 Vinyl Bond Content] The 1,2 vinyl bond content of the modified conjugated diene polymer in this embodiment is preferably 25 mol% or less, more preferably 23 mol% or less, even more preferably 22 mol% or less, and even more preferably 20 mol% or less. There are no particular restrictions on the lower limit of the 1,2 vinyl bond content, but it is more preferably 7 mol% or more, even more preferably 10 mol% or more, and even more preferably 12 mol% or more. There are no particular restrictions on the combination of the upper and lower limits of the 1,2 vinyl bond content, but it is preferably 10 mol% or more and 25 mol% or less, more preferably 10 mol% or more and 25 mol% or less, and even more preferably 12 mol% or more and 22 mol% or less.

[0133] The microstructure of the modified conjugated diene polymer can be measured using a Fourier transform infrared spectrophotometer by the method described in the examples below.

[0134] The amount of 1,2 vinyl bonds can be controlled within the above-mentioned specific range by adjusting the amount of polar substance added in the polymerization step. While increasing the amount of polar compound added not only increases the amount of 1,2 vinyl bonds but also has the effect of accelerating the polymerization reaction, when a composition containing a filler or the like is formed, the breaking strength and abrasion resistance tend to deteriorate, and it is therefore necessary to adjust the amount of polar substance added to control the amount of 1,2 vinyl bonds within a specific range. More specific details will be described in the Examples below.

[0135] [Aromatic Vinyl Bond Content] The aromatic vinyl bond content of the modified conjugated diene polymer in this embodiment is preferably 0% by mass or more and 10% by mass or less. The upper limit of the aromatic vinyl bond content of the conjugated diene polymer is more preferably 7% by mass or less, even more preferably 6% by mass or less, and still more preferably 5% by mass or less.

[0136] The aromatic vinyl bond content can be controlled by adjusting the addition ratio of the conjugated diene monomer and the aromatic vinyl compound in the polymerization step described above. More specific details will be described in the examples below.

[0137] The aromatic vinyl bond content of the conjugated diene polymer can be measured using an ultraviolet spectrophotometer by the method described in the examples below.

[0138] By setting the aromatic vinyl bond amount within a specific range, when a composition containing a filler or the like is prepared, the breaking strength and abrasion resistance tend to be improved.

[0139] [Glass Transition Temperature (Tg)] The glass transition temperature of the conjugated diene polymer of the present embodiment is preferably within the range of −110° C. to −80° C. The lower limit of the glass transition temperature of the conjugated diene polymer is more preferably −105° C. or higher, even more preferably −103° C. or higher, and still more preferably −100° C. or higher.

[0140] The upper limit of the glass transition temperature is more preferably −82° C. or lower, even more preferably −84° C. or lower, and even more preferably −86° C. or lower.

[0141] The glass transition temperature tends to increase as the above-mentioned 1,2 vinyl bond content and aromatic vinyl bond content increase, and can be controlled by controlling the 1,2 vinyl bond content and aromatic vinyl bond content within appropriate ranges, as will be described more specifically in the Examples below.

[0142] The glass transition temperature of the conjugated diene polymer can be measured using a differential scanning calorimeter (DSC) by the method described in the examples below.

[0143] By adjusting the glass transition temperature to a specific range, when a composition containing a filler or the like is prepared, the breaking strength and abrasion resistance tend to be improved.

[0144] [Modification Ratio] The modified conjugated diene polymer in this embodiment preferably has a modification ratio of 40% by mass or more. The term "modification ratio" is sometimes used in this specification, and refers to the mass ratio of conjugated diene polymer having a nitrogen atom-containing functional group to the total amount of conjugated diene polymer. The modification ratio can be measured by chromatography, which can separate functional group-containing modified components from unmodified components.

[0145] Examples of such methods using chromatography include a method in which a gel permeation chromatography column is used, packed with a polar substance such as silica that adsorbs specific functional groups, and the non-adsorbed components are quantitatively determined using an internal standard for comparison (column adsorption GPC method).

[0146] More specifically, the modification rate can be obtained by measuring the amount of a sample solution containing the sample and a low-molecular-weight internal standard polystyrene adsorbed to the silica column from the difference between a chromatogram measured on a polystyrene-based gel column and a chromatogram measured on a silica-based column.

[0147] More specifically, the modification rate can be measured by the method described in the Examples.

[0148] In the modified conjugated diene polymer of this embodiment, the modification rate can be controlled by adjusting the amount of modifier added and the reaction method, and thereby the modification rate can be controlled to 40% by mass or more.

[0149] [Branched Structure] The modified conjugated diene polymer in this embodiment preferably has a main chain branched structure having a portion derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group, and the portion derived from the vinyl monomer containing an alkoxysilyl group or a halosilyl group has the branched structure. Specifically, the modified conjugated diene polymer in this embodiment preferably has a portion derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group in a part of the polymer chain, and the portion derived from the vinyl monomer containing an alkoxysilyl group or a halosilyl group has a branched structure.

[0150] The branched structure has one or more branching points, preferably three or more branching points, and more preferably four or more branching points, in the portion derived from the vinyl monomer containing an alkoxysilyl group or a halosilyl group.

[0151] Furthermore, the branch points forming the branched structure preferably have at least one polymer chain, more preferably have two or more polymer chains that are not the main chain, and even more preferably have four or more polymer chains that are not the main chain.

[0152] In particular, in the case of a branched structure consisting of a vinyl monomer containing an alkoxysilyl group or a halosilyl group, when signal detection is performed by Si-NMR, a peak derived from the branched structure is detected in the range of −45 ppm to −65 ppm, more specifically in the range of −50 ppm to −60 ppm.

[0153] In a preferred aspect of the conjugated diene polymer of this embodiment, the end of the polymer chain is modified with a nitrogen-containing modifying agent, and a portion of the polymer chain has a moiety derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group. The method for obtaining a modified conjugated diene polymerization having a further branched structure in the moiety derived from the vinyl monomer containing an alkoxysilyl group or a halosilyl group can be achieved by adjusting the number of functional groups of the nitrogen-containing modifying agent and the amount added. The branched structure can be controlled by adjusting the number of functional groups of the branching agent, the amount added of the branching agent, and the timing of addition of the branching agent. That is, in this specification, the "moiety derived from a vinyl monomer" refers to a structure in which the alkoxy group and / or halogen of the vinyl monomer, which is the branching agent described below, serves as a leaving group to substitute the polymerization active end, and the polymer chain is bonded to the silicon of the vinylsilane, and the vinyl group of the vinylsilane is polymerized as an aromatic vinyl compound. When a vinyl monomer containing multiple alkoxy groups and / or halogens is used as a branching agent, the resulting "portion derived from the vinyl monomer" may have multiple polymer chains bonded to the silicon of the vinylsilane.

[0154] In order to obtain a conjugated diene polymerization having a portion derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group in a part of the polymer chain, and having a further branched structure in the portion derived from the vinyl monomer containing an alkoxysilyl group or a halosilyl group, for example, there can be mentioned a method in which polymerization is carried out using an organolithium compound as a polymerization initiator, a branching agent that imparts a specific branching point is added during or after the polymerization, and after the polymerization is continued, modification is carried out using a modifying agent that imparts a specific branching rate.

[0155] [Branching Agent Structure] In the modified conjugated diene polymer of the present embodiment, the moiety derived from the vinyl monomer containing an alkoxysilyl group or a halosilyl group is preferably a monomer unit derived from a compound represented by the following formula (3) or (4), and the polymer chain preferably has a branching point due to the monomer unit derived from the compound represented by the following formula (3) or (4). The modified conjugated diene polymer is more preferably a conjugated diene polymer obtained using a branching agent described below, and even more preferably a modified conjugated diene polymer in which at least one end of the conjugated diene polymer has been modified with a modifying agent having an amino group and an amide group.

[0156] In the formula, R １ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may have a branched structure in part, or an aryl group having 6 to 20 carbon atoms; R ２ ~R ３ each independently represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, which may have a branched structure in part, and when there are a plurality of R1 to R3, each of them is independent. １ represents an independent halogen atom; m represents an integer of 0 to 2; n represents an integer of 0 to 3; l represents an integer of 0 to 3; and (m+n+l) is 3.

[0157] In the formula, R ２ ~R ５ each independently represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, which may have a branched structure in part, and when there are a plurality of R ２ ~R ５ are each independent, and X ２ ~X ３ each independently represents a halogen atom, m represents an integer of 0 to 2, n represents an integer of 0 to 3, l represents an integer of 0 to 3, (m+n+l) is 3, a represents an integer of 0 to 2, b represents an integer of 0 to 3, c represents an integer of 0 to 3, and (a+b+c) is 3.

[0158] The branching agent represented by formula (3) is not particularly limited, but examples thereof include trimethoxy(4-vinylphenyl)silane, triethoxy(4-vinylphenyl)silane, tripropoxy(4-vinylphenyl)silane, tributoxy(4-vinylphenyl)silane, triisopropoxy(4-vinylphenyl)silane, trimethoxy(3-vinylphenyl)silane, triethoxy(3-vinylphenyl)silane, tripropoxy(3-vinylphenyl)silane, tributoxy(3-vinylphenyl)silane, triisopropoxy(3-vinylphenyl)silane, (2-vinylphenyl)silane, trimethoxy(2-vinylphenyl)silane, triethoxy(2-vinylphenyl)silane, tripropoxy(2-vinylphenyl)silane, tributoxy(2-vinylphenyl)silane, triisopropoxy(2-vinylphenyl)silane, dimethoxymethyl(4-vinylphenyl)silane, diethoxymethyl(4-vinylphenyl)silane, dipropoxymethyl(4-vinylphenyl)silane, dibutoxymethyl(4-vinylphenyl)silane, diisopropoxymethyl(4-vinylphenyl)silane, dimethoxymethyl(3 -vinylphenyl)silane, diethoxymethyl(3-vinylphenyl)silane, dipropoxymethyl(3-vinylphenyl)silane, dibutoxymethyl(3-vinylphenyl)silane, diisopropoxymethyl(3-vinylphenyl)silane, dimethoxymethyl(2-vinylphenyl)silane, diethoxymethyl(2-vinylphenyl)silane, dipropoxymethyl(2-vinylphenyl)silane, dibutoxymethyl(2-vinylphenyl)silane, diisopropoxymethyl(2-vinylphenyl)silane, dimethylmethoxy(4-vinylphenyl)silane (4-vinylphenyl)silane, dimethylethoxy(4-vinylphenyl)silane, dimethylpropoxy(4-vinylphenyl)silane, dimethylbutoxy(4-vinylphenyl)silane, dimethylisopropoxy(4-vinylphenyl)silane, dimethylmethoxy(3-vinylphenyl)silane, dimethylethoxy(3-vinylphenyl)silane, dimethylpropoxy(3-vinylphenyl)silane, dimethylbutoxy(3-vinylphenyl)silane, dimethylisopropoxy(3-vinylphenyl)silane, dimethylmethoxy(2-vinylphenyl)silane,Dimethylethoxy(2-vinylphenyl)silane, dimethylpropoxy(2-vinylphenyl)silane, dimethylbutoxy(2-vinylphenyl)silane, dimethylisopropoxy(2-vinylphenyl)silane, trimethoxy(4-isopropenylphenyl)silane, triethoxy(4-isopropenylphenyl)silane, tripropoxy(4-isopropenylphenyl)silane, tributoxy(4-isopropenylphenyl)silane, triisopropoxy(4-isopropenylphenyl)silane, trimethoxy(3-isopropenylphenyl) ) silane, triethoxy(3-isopropenylphenyl)silane, tripropoxy(3-isopropenylphenyl)silane, tributoxy(3-isopropenylphenyl)silane, triisopropoxy(3-isopropenylphenyl)silane, trimethoxy(2-isopropenylphenyl)silane, triethoxy(2-isopropenylphenyl)silane, tripropoxy(2-isopropenylphenyl)silane, tributoxy(2-isopropenylphenyl)silane, triisopropoxy(2-isopropenylphenyl)silane, dimethoxymethyl (4-isopropenylphenyl)silane, diethoxymethyl(4-isopropenylphenyl)silane, dipropoxymethyl(4-isopropenylphenyl)silane, dibutoxymethyl(4-isopropenylphenyl)silane, diisopropoxymethyl(4-isopropenylphenyl)silane, dimethoxymethyl(3-isopropenylphenyl)silane, diethoxymethyl(3-isopropenylphenyl)silane, dipropoxymethyl(3-isopropenylphenyl)silane, dibutoxymethyl(3-isopropenylphenyl)silane, diisoprop dimethoxymethyl(2-isopropenylphenyl)silane, diethoxymethyl(2-isopropenylphenyl)silane, dipropoxymethyl(2-isopropenylphenyl)silane, dibutoxymethyl(2-isopropenylphenyl)silane, diisopropoxymethyl(2-isopropenylphenyl)silane, dimethylmethoxy(4-isopropenylphenyl)silane, dimethylethoxy(4-isopropenylphenyl)silane, dimethylpropoxy(4-isopropenylphenyl)silane,Dimethylbutoxy(4-isopropenylphenyl)silane, dimethylisopropoxy(4-isopropenylphenyl)silane, dimethylmethoxy(3-isopropenylphenyl)silane, dimethylethoxy(3-isopropenylphenyl)silane, dimethylpropoxy(3-isopropenylphenyl)silane, dimethylbutoxy(3-isopropenylphenyl)silane, dimethylisopropoxy(3-isopropenylphenyl)silane, dimethylmethoxy(2-isopropenylphenyl)silane, dimethylethoxy(2-isopropenylphenyl)silane, dimethylpropoxy(2-isopropenylphenyl)silane, dimethylbutoxy(2-isopropenylphenyl)silane, dimethylisopropoxy(2-isopropenylphenyl)silane, trichloro(4-vinylphenyl)silane, trichloro(3- vinylphenyl)silane, trichloro(2-vinylphenyl)silane, tribromo(4-vinylphenyl)silane, tribromo(3-vinylphenyl)silane, tribromo(2-vinylphenyl)silane, dichloromethyl(4-vinylphenyl)silane, dichloromethyl(3-vinylphenyl)silane, dichloromethyl(2-vinylphenyl)silane, dibromomethyl(4-vinylphenyl)silane, dibromomethyl(3-vinylphenyl)silane, dibromomethyl(2-vinylphenyl)silane, dimethylchloro(4-vinylphenyl)silane, dimethylchloro(3-vinylphenyl)silane, dimethylchloro(2-vinylphenyl)silane, dimethylbromo(4-vinylphenyl)silane, dimethylbromo(3-vinylphenyl)silane, and dimethylbromo(2-vinylphenyl)silane.

[0159] Among these, trimethoxy(4-vinylphenyl)silane, triethoxy(4-vinylphenyl)silane, tripropoxy(4-vinylphenyl)silane, tributoxy(4-vinylphenyl)silane, triisopropoxy(4-vinylphenyl)silane, trimethoxy(3-vinylphenyl)silane, triethoxy(3-vinylphenyl)silane, tripropoxy(3-vinylphenyl)silane, tributoxy(3-vinylphenyl)silane, triisopropoxy(3-vinylphenyl)silane, and trichloro(4-vinylphenyl)silane are preferred, and trimethoxy(4-vinylphenyl)silane, triethoxy(4-vinylphenyl)silane, tripropoxy(4-vinylphenyl)silane, and tributoxy(4-vinylphenyl)silane, triisopropoxy(4-vinylphenyl)silane are more preferred.

[0160] The branching agent represented by formula (4) is not particularly limited, and examples thereof include 1,1-bis(4-trimethoxysilylphenyl)ethylene, 1,1-bis(4-triethoxysilylphenyl)ethylene, 1,1-bis(4-tripropoxysilylphenyl)ethylene, 1,1-bis(4-tripentoxysilylphenyl)ethylene, 1,1-bis(4-triisopropoxysilylphenyl)ethylene, 1,1-bis(3-trimethoxysilylphenyl)ethylene, 1,1-bis(3-triethoxysilylphenyl)ethylene, 1,1-bis(3-trippropoxysilylphenyl)ethylene, 1,1-bis(3-tripentoxysilylphenyl)ethylene, 1,1-bis(3-triisopropoxysilylphenyl)ethylene, 1,1-bis(2-trimethoxysilylphenyl)ethylene, 1,1-bis(2-triethoxysilylphenyl)ethylene, 1,1-bis(4-(dimethylmethoxysilyl)phenyl)ethylene, 1,1-bis(4-(diethylmethoxysilyl)phenyl)ethylene, 1,1-bis(4-(dipropylmethoxysilyl)phenyl)ethylene, 1,1-bis(4-(dimethylethoxysilyl)phenyl)ethylene, 1,1-bis(4-(diethylethoxysilyl)phenyl)ethylene, and 1,1-bis(4-(dipropylethoxysilyl)phenyl)ethylene, 1,1-bis(4-(methyldimethoxysilyl)phenyl)ethylene, 1,1-bis(4-(ethyldiethoxysilyl)phenyl)ethylene.

[0161] Among these, 1,1-bis(4-trimethoxysilylphenyl)ethylene, 1,1-bis(4-triethoxysilylphenyl)ethylene, 1,1-bis(4-tripropoxysilylphenyl)ethylene, 1,1-bis(4-tripentoxysilylphenyl)ethylene, and 1,1-bis(4-triisopropoxysilylphenyl)ethylene are preferred, and 1,1-bis(4-trimethoxysilylphenyl)ethylene is more preferred.

[0162] The modified conjugated diene polymer in this embodiment has a main chain branch structure having a monomer unit derived from the compound represented by the above formula (3), and in formula (3), R １ It is preferred that m represents a hydrogen atom and m represents 0. This increases the number of branches, suppresses cold flow of bales, which are the product form of the conjugated diene polymer, and provides excellent processability when vulcanized, resulting in excellent abrasion resistance and breaking strength when vulcanized.

[0163] The modified conjugated diene polymer in this embodiment has a main chain branched structure having a monomer unit derived from the compound represented by the above formula (4), and in formula (4), it is preferred that m and b represent 0. This provides an effect of improving abrasion resistance and processability.

[0164] The modified conjugated diene polymer in this embodiment has a main chain branch structure having a monomer unit derived from the compound represented by the above formula (3), and in formula (3), R １ It is more preferred that m represents a hydrogen atom, n represents 3, and 1 represents 0. This improves the modification rate and the branching degree, suppresses cold flow in bales that are the product form of the conjugated diene polymer, and also improves fuel-saving performance, abrasion resistance, and processability.

[0165] The modified conjugated diene polymer in this embodiment has a main chain branched structure having a monomer unit derived from the compound represented by the above formula (4), and in formula (4), it is preferred that m represents 0, n represents 3, l represents 0, a represents 0, b represents 0, and c represents 3. This suppresses cold flow in bales, which are the finished product form of the conjugated diene polymer, and also provides the effects of improving abrasion resistance and processability.

[0166] <Rubber Composition, Vulcanized Rubber Composition> The rubber composition of the present embodiment can be vulcanized to form a vulcanized rubber composition. In other words, the vulcanized rubber composition of the present embodiment is a composition obtained by vulcanizing a rubber composition containing a modified conjugated diene-based polymer.

[0167] (Silane Coupling Agent) When silica is compounded as a filler, the rubber composition of this embodiment may contain a silane coupling agent. The silane coupling agent has the function of strengthening the interaction between the rubber component and the inorganic filler, and has groups that have affinity or bonding properties for both the rubber component and the silica-based inorganic filler. A compound having a sulfur-bonding moiety and an alkoxysilyl group or a silanol group moiety in one molecule is preferred. Examples of such compounds include, but are not limited to, bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, and bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide.

[0168] In the rubber composition of this embodiment, the content of the silane coupling agent is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 20 parts by mass or less, and even more preferably 1.0 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the silica-based inorganic filler. When the content of the silane coupling agent is within the above range, the above-mentioned effect of the addition of the silane coupling agent tends to be more pronounced.

[0169] (Rubber Softener) The rubber composition of the present embodiment may contain a rubber softener from the viewpoint of improving its processability.

[0170] The amount of rubber softener added is expressed as the total amount including the amount of rubber softener previously contained in the conjugated diene polymer or other rubber-like polymers, and the amount of rubber softener added when preparing a crosslinked rubber composition, per 100 parts by mass of the rubber component containing the conjugated diene polymer.

[0171] As the rubber softener, mineral oil or a liquid or low molecular weight synthetic softener is suitable.

[0172] Mineral oil-based rubber softeners, known as process oils or extender oils, which are used to soften rubber, increase its volume, and improve its processability, are mixtures of aromatic rings, naphthenic rings, and paraffin chains; those in which the carbon number of the paraffin chains accounts for 50% or more of the total carbons are called paraffinic; those in which the carbon number of the naphthenic rings accounts for 30% to 45% of the total carbons are called naphthenic; and those in which the aromatic carbon number accounts for more than 30% of the total carbons are called aromatic. When the conjugated diene polymer of this embodiment is a copolymer of a conjugated diene compound and a vinyl aromatic compound, it is preferable to use a rubber softener having an appropriate aromatic content, as this tends to be compatible with the copolymer.

[0173] In the rubber composition of this embodiment, the content of the rubber softener is preferably 0 to 100 parts by mass, more preferably 5 to 90 parts by mass, and even more preferably 10 to 80 parts by mass, per 100 parts by mass of the rubber component. When the content of the rubber softener is 100 parts by mass or less, per 100 parts by mass of the rubber component, bleeding out tends to be suppressed and stickiness of the surface of the rubber composition tends to be suppressed.

[0174] (Method for Producing Rubber Composition) The method for producing the rubber composition of this embodiment is not particularly limited, and examples thereof include a method of melt-kneading a conjugated diene polymer with other rubbery polymers, carbon black, silica-based inorganic fillers or other fillers, and additives such as a silane coupling agent and a rubber softener using a general mixer such as an open roll, a Banbury mixer, a kneader, a single-screw extruder, a twin-screw extruder, or a multi-screw extruder, or a method of dissolving and mixing the components and then removing the solvent by heating. Of these, melt-kneading methods using a roll, a Banbury mixer, a kneader, or an extruder are preferred from the viewpoints of productivity and good kneading ability. Furthermore, either a method of kneading the rubber component with other fillers, a silane coupling agent, and additives all at once or a method of mixing them in multiple batches can be applied.

[0175] The rubber composition of this embodiment can be a vulcanized rubber composition (hereinafter sometimes referred to as a "vulcanized composition") vulcanized with a vulcanizing agent. The vulcanizing agent is not particularly limited, but examples thereof include radical generators such as organic peroxides and azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. Examples of sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, and polymeric polysulfur compounds. In the rubber composition of this embodiment, the content of the vulcanizing agent is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the rubber component. Conventional vulcanization methods can be used, and the vulcanization temperature is preferably 120°C or more and 200°C or less, and more preferably 140°C or more and 180°C or less.

[0176] During vulcanization, a vulcanization accelerator may be used as needed. The vulcanization accelerator may be a conventionally known material, and is not particularly limited. Examples of the vulcanization accelerator include sulfenamide-based, guanidine-based, thiuram-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, thiourea-based, and dithiocarbamate-based vulcanization accelerators. The vulcanization aid is also not particularly limited. Examples of the vulcanization accelerator include zinc oxide and stearic acid. The content of the vulcanization accelerator is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the rubber component.

[0177] The rubber composition of this embodiment may contain various additives other than those described above, such as softeners and fillers, heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, and lubricants, as long as the object of the present invention is not impaired. Known softeners can be used as the other softeners. Specific examples of other fillers include, but are not limited to, calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate. Known materials can be used as the heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, and lubricants.

[0178] The rubber composition of the present embodiment is suitably used as a rubber composition for tires. That is, the tire of the present embodiment contains the rubber composition or vulcanized rubber composition of the present embodiment.

[0179] The rubber composition for tires is not particularly limited, and can be used in various tire parts such as treads, carcasses, sidewalls, beads, etc., of various tires such as fuel-efficient tires, all-season tires, high-performance tires, studless tires, tires for vehicles carrying heavy loads, etc. In particular, the rubber composition for tires has an excellent balance of abrasion resistance, breaking strength, low hysteresis loss, and wet skid resistance when vulcanized, and is therefore suitably used for the treads of fuel-efficient tires, high-performance tires, and tires for vehicles carrying heavy loads.

[0180] In addition to being used for tires, the rubber composition of the present embodiment has industrial applicability as well, for example, vibration-damping rubber, vibration-isolating rubber, conveyor belts, shoe soles such as outsoles for shoes, weather strips for automobiles, packings and gaskets, sealing materials, waterproof sheets, engine mounts, air springs, rubber gloves, medical and sanitary products, hoses for industrial and various uses, battery cases, adhesives, electric wire coatings, window frame rubber, rubber stoppers, rubber rollers, and materials for various industrial products.

[0181] Hereinafter, the present embodiment will be described in more detail with reference to specific examples and comparative examples, but the present embodiment is not limited to the following examples and comparative examples.

[0182] Various physical properties in the examples and comparative examples were measured by the methods shown below.

[0183] (Physical Property 1) Mooney Viscosity Using a conjugated diene polymer (before modification) or a conjugated diene polymer modified with a substituted amino group-containing modifier (hereinafter also referred to as a "modified conjugated diene polymer" and, together with the conjugated diene polymer, also referred to as a "(modified) conjugated diene polymer") as a sample, the Mooney viscosity was measured using a Mooney viscometer (trade name "VR1132" manufactured by Ueshima Seisakusho Co., Ltd.) with an L-shaped rotor in accordance with ISO 289. The measurement temperature was 100°C. First, the sample was preheated at the test temperature for 1 minute, and then the rotor was rotated at 2 rpm. The torque after 4 minutes was measured and recorded as the Mooney viscosity (ML (physical property 1)). Table 1 shows the measurement results of the Mooney viscosity before modification (100°C) and the Mooney viscosity after modification (100°C).

[0184] (Physical Property 2) Microstructure of Conjugated Diene Polymer (1,2 Vinyl Bond Amount) When the (modified) conjugated diene polymer is polybutadiene, the (modified) conjugated diene polymer is used as a sample, and 50 mg of the sample is dissolved in 10 mL of carbon disulfide to prepare a measurement sample. Using a solution cell, the infrared spectrum is measured from 600 to 1000 cm －１ The absorbance at a predetermined wave number was measured in the range of 100 to 1500, and the 1,2-vinyl bond content (mol %) of the conjugated diene polymer was determined according to the calculation formula of the Morero method (the method described in D. Morero, A. Santambrogio, L. Porri, F. Clampelli: Chim. e Ind., 41, 758 (1959)). (Measuring device: Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation.)

[0185] When the (modified) conjugated diene polymer was a styrene-butadiene copolymer, the measurement was carried out in the same manner as in the case of polybutadiene described above, and the microstructure of the butadiene portion, i.e., the 1,2-vinyl bond content (mol %) was determined from the absorbance at a predetermined wave number according to the calculation formula of the Hampton method (the method described in R.R. Hampton, Analytical Chemistry 21, 923 (1949)).

[0186] (Physical Property 3) Bound Styrene Amount (Styrene Amount; Aromatic Vinyl Bond Amount) 100 mg of a (modified) conjugated diene polymer was used as a sample, and chloroform was added to a measuring solution to make 100 mL of the sample, and the resultant solution was dissolved to prepare a measurement sample. The bound styrene amount (mass%) relative to 100 mass% of the modified conjugated diene polymer sample was measured based on the amount of absorption of ultraviolet light by the phenyl group of styrene (near 254 nm) (using a spectrophotometer "UV-2450" manufactured by Shimadzu Corporation).

[0187] (Physical Property 4) Glass Transition Temperature DSC measurement was carried out on the (modified) conjugated diene polymer as a sample using a differential scanning calorimeter ("DSC3500" manufactured by NETZSCH) in accordance with ISO 22768: 2006. A DSC curve was recorded while heating from -130°C at 20°C / min under a helium flow of 50 mL / min, and the peak top (inflection point) of the DSC differential curve was taken as the glass transition temperature (Tg).

[0188] (Physical Property 5) Degree of Branching (Bn) The degree of branching (Bn) of a (modified) conjugated diene polymer was measured by a GPC-light scattering method with a viscosity detector as follows: Using a (modified) conjugated diene polymer as a sample, a gel permeation chromatography (GPC) measuring device (manufactured by Malvern under the trade name "GPCmax VE-2001") having three columns connected together, each packed with a polystyrene gel, was used to measure using three detectors connected in this order: a light scattering detector, an RI detector, and a viscosity detector (manufactured by Malvern under the trade name "TDA305"). Based on standard polystyrene, the absolute molecular weight was determined from the results of the light scattering detector and the RI detector, and the intrinsic viscosity was determined from the results of the RI detector and the viscosity detector.

[0189] The linear polymer has an intrinsic viscosity [η] = 10 －３．８８３ ×M ０．７７１The shrinkage factor (g') was calculated as the ratio of intrinsic viscosity corresponding to each molecular weight. In this formula, M represents the absolute molecular weight. The obtained shrinkage factor (g') was then used to calculate the degree of branching (Bn), defined as g' = 6Bn / {(Bn + 1)(Bn + 2)}. Tetrahydrofuran (hereinafter also referred to as "THF") containing 5 mmol / L of triethylamine was used as the eluent. Tosoh Corporation's "TSKgel G4000HXL," "TSKgel G5000HXL," and "TSKgel G6000HXL" columns were used. 20 mg of the sample to be measured was dissolved in 10 mL of THF to prepare a measurement solution, and 100 μL of the measurement solution was injected into the GPC measurement device. Measurement was performed at an oven temperature of 40°C and a THF flow rate of 1 mL / min.

[0190] (Physical Property 6) Molecular Weight (Weight Average Molecular Weight, Number Average Molecular Weight, Mw / Mn) Measurement Condition 1: A (modified) conjugated diene polymer was used as a sample, and a chromatogram was measured using a GPC measurement device (trade name "HLC-8320GPC" manufactured by Tosoh Corporation) in which three columns packed with polystyrene gel were connected together, and an RI detector (trade name "HLC8020" manufactured by Tosoh Corporation).The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) were determined based on a calibration curve obtained using standard polystyrene.

[0191] The eluent used was tetrahydrofuran (THF) containing 5 mmol / L triethylamine. Three columns, manufactured by Tosoh Corporation under the trade name "TSKgel SuperMultiporeHZ-H," were connected, and a guard column, manufactured by Tosoh Corporation under the trade name "TSKguardcolumn SuperMP(HZ)-H," was connected in front of the columns.

[0192] 10 mg of the sample to be measured was dissolved in 10 mL of THF to prepare a measurement solution, and 10 μL of the measurement solution was injected into a GPC measurement device and measured under conditions of an oven temperature of 40° C. and a THF flow rate of 0.35 mL / min.

[0193] Among the various samples measured under the above-mentioned measurement condition 1, samples whose molecular weight distribution (Mw / Mn) value was less than 1.6 were measured again under the following measurement condition 2. For samples whose molecular weight distribution value was 1.6 or more when measured under measurement condition 1, the value measured under measurement condition 1 was used.

[0194] Measurement condition 2: A conjugated diene polymer or a coupled conjugated diene polymer was used as a sample, and a chromatogram was measured using a GPC measurement device in which three columns packed with polystyrene gel were connected together, and the weight average molecular weight (Mw) and number average molecular weight (Mn) were determined based on a calibration curve using standard polystyrene.

[0195] The eluent used was THF containing 5 mmol / L triethylamine. The columns used were a guard column manufactured by Tosoh Corporation under the trade name "TSKguard column Super H-H," and columns manufactured by Tosoh Corporation under the trade names "TSKgel Super H5000," "TSKgel Super H6000," and "TSKgel Super H7000."

[0196] An RI detector (trade name "HLC8020" manufactured by Tosoh Corporation) was used under conditions of an oven temperature of 40° C. and a THF flow rate of 0.6 mL / min. 10 mg of a sample to be measured was dissolved in 20 mL of THF to prepare a measurement solution, and 20 μL of the measurement solution was injected into a GPC measurement device for measurement.

[0197] (Property 7) Modification Ratio The modification ratio of a (modified) conjugated diene polymer was measured by a column adsorption GPC method as follows: Using a coupled conjugated diene polymer as a sample, the measurement was carried out by utilizing the adsorption property of the modified basic polymer component in a GPC column packed with silica gel.

[0198] The amount of a sample solution containing the sample and low-molecular-weight internal standard polystyrene adsorbed onto the silica-based column was measured by subtracting the chromatogram measured on the polystyrene-based column from the chromatogram measured on the silica-based column, and the modification rate was calculated.

[0199] Specifically, the measurements were carried out under the measurement condition 1 in (Property 4) above. For samples whose molecular weight distribution was 1.6 or more, the measurements were carried out under the measurement condition 3 below, and for samples whose molecular weight distribution was less than 1.6, the measurements were carried out under the measurement condition 4 below.

[0200] Preparation of sample solution: 10 mg of sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a sample solution.

[0201] Measurement condition 3: GPC measurement conditions using a polystyrene column: Using a Tosoh Corporation product name "HLC-8320GPC," 10 μL of the sample solution was injected into the apparatus using 5 mmol / L triethylamine-containing THF as the eluent, and a chromatogram was obtained using an RI detector under the conditions of a column oven temperature of 40° C. and a THF flow rate of 0.35 mL / min. Three Tosoh Corporation product name "TSKgel SuperMultiporeHZ-H" columns were connected, and a Tosoh Corporation product name "TSKguardcolumn SuperMP(HZ)-H" was connected in front of them as a guard column.

[0202] Measurement condition 4: THF containing 5 mmol / L triethylamine was used as the eluent, and 20 μL of the sample solution was injected into the device and measured. The columns used were a guard column manufactured by Tosoh Corporation under the trade name "TSKguard column Super H-H," and columns manufactured by Tosoh Corporation under the trade names "TSKgel Super H5000," "TSKgel Super H6000," and "TSKgel Super H7000." A chromatogram was obtained using an RI detector (Tosoh Corporation HLC8020) at a column oven temperature of 40 °C and a THF flow rate of 0.6 mL / min.

[0203] GPC measurement conditions using a silica-based column: Tosoh Corporation's product name "HLC-8320GPC" was used, THF was used as the eluent, 50 μL of the sample solution was injected into the device, and a chromatogram was obtained using an RI detector under the conditions of a column oven temperature of 40 ° C. and a THF flow rate of 0.5 ml / min. The columns were connected and used with product names "Zorbax PSM-1000S", "PSM-300S", and "PSM-60S", and a guard column "DIOL 4.6 × 12.5 mm 5 micron" was connected to the front stage.

[0204] Calculation method of modification rate: The total peak area of ​​the chromatogram using a polystyrene-based column was set to 100, the peak area of ​​the sample was set to P1, the peak area of ​​the standard polystyrene was set to P2, and the total peak area of ​​the chromatogram using a silica-based column was set to 100, the peak area of ​​the sample was set to P3, and the peak area of ​​the standard polystyrene was set to P4. The modification rate (%) was calculated using the following formula.

[0205] Denaturation rate (%) = [1 - (P2 x P3) / (P1 x P4)] x 100 (where P1 + P2 = P3 + P4 = 100)

[0206] (Physical Property 8) Hydrogenation Ratio A (modified) conjugated diene polymer containing no antioxidant was used as a sample, and 50 mg of the sample was dissolved in 1 mL of deuterated chloroform to prepare a measurement sample. １ Measurement was carried out using a H-NMR (trade name "JNM-LA400" manufactured by JEOL Ltd.) under conditions of an observation frequency of 400 MHz, a pulse delay of 2.904 seconds, an accumulation number of 64, a pulse width of 45°, and a measurement temperature of 26°C. From the chemical shifts using TMS (tetramethylsilane) as a reference substance, the hydrogenation rate of double bonds in structural units derived from 1,3-butadiene was determined from the constituent ratios (mol %) of 1,4-bond structural units derived from 1,3-butadiene, 1,2-bond structural units, hydrogenated 1,4-bond structural units, and hydrogenated 1,2-bond structural units.

[0207] (Synthesis Example 1) Modified Conjugated Diene Polymer (Sample 1) Two tank-type pressure vessels each having an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom and an outlet at the top, and equipped with a stirrer as a tank-type reactor and a jacket for temperature control were connected together as polymerization reactors.

[0208] 1,3-butadiene, from which moisture had been removed in advance, was mixed at 30.8 g / min and n-hexane at 189.3 g / min. In a static mixer installed midway through the pipe supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.072 mmol / min, mixed, and then continuously fed to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.027 mmol / min and n-butyllithium as a polymerization initiator at a rate of 0.205 mmol / min were fed to the bottom of the first reactor, which was being vigorously mixed with a stirrer, and the internal temperature of the reactor was maintained at 78°C.

[0209] The polymer solution was continuously withdrawn from the top of the first reactor and continuously fed to the bottom of the second reactor, where the reaction continued at 78°C. It was then further fed to a static mixer from the top of the second reactor. Once the polymerization was sufficiently stabilized, trimethoxy(4-vinylphenyl)silane (abbreviated as "BS-1" in the table) was added as a branching agent from the bottom of the second reactor at a rate of 0.030 mmol / min while 1,3-butadiene was polymerized. This allowed for the polymerization and branching reactions to occur, yielding a conjugated diene polymer with a branched structure. Once the polymerization and branching reactions were stabilized, a small amount of the conjugated diene polymer solution before the addition of the modifier was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of polymer. The solvent was then removed, and the Mooney viscosity of the resulting conjugated diene polymer was measured. The measurement results are shown in Table 1.

[0210] Next, 1,3-dimethylimidazolidinone (abbreviated as "A" in the table) was continuously added as a modifying agent to the polymer solution flowing out from the outlet of the reactor at a rate of 0.155 mmol / min, and the mixture was mixed using a static mixer to carry out a modification reaction. At this time, it took 4.8 minutes for the modifying agent to be added to the polymer solution flowing out from the outlet of the reactor, the temperature was 76°C, and the difference between the temperature in the polymerization step and the temperature before the addition of the modifying agent was 2°C.

[0211] Next, an antioxidant (BHT) was continuously added to the modified polymer solution at a rate of 0.055 g / min (n-hexane solution) to give 0.2 g per 100 g of polymer, and the modification reaction was terminated. The solvent was then removed by steam stripping to obtain a modified conjugated diene-based polymer (Sample 1) having a four-branched structure derived from trimethoxy(4-vinylphenyl)silane (the compound represented by formula (3) above) in a portion of its main chain. Various physical properties of the sample were measured. The measurement results are shown in Table 1.

[0212] The structure of the modified conjugated diene polymer was identified by comparing the molecular weight measured by GPC with the branching degree measured by GPC with a viscometer for the polymer before the addition of the branching agent, the polymer before modification after the addition of the branching agent, and the polymer in each step after the addition of the modifier. The structure of each sample was similarly identified.

[0213] (Synthesis Examples 2 to 9) Modified conjugated diene polymers (Samples 2 to 9) Modified conjugated diene polymers (Samples 2 to 9) were obtained in the same manner as Synthesis Example 1, except that the production conditions of Examples 2 to 9 shown in Table 1 were changed from those of Example 1. Various physical properties of the samples were measured. The measurement results are shown in Table 1. In the table, "BS-2" to "BS-3" and "B" shown as branching agents and modifiers respectively represent the following compounds. "BS-2": dimethylmethoxy(4-vinylphenyl)silane "BS-3": 1,1-bis(4-(methyldimethoxysilyl)phenyl)ethylene (compound represented by the above formula (4)) "B": N-methyl-2-pyrrolidone

[0214] (Preparation of hydrogenation catalyst) A tank-type pressure vessel equipped with a stirrer, which had been previously purged with nitrogen, an internal volume of 5 L, and an internal height (L) to diameter (D) ratio (L / D) of 4.0, was used as a preparation vessel. 3,200 g of cyclohexane, which had been previously purified and had moisture removed, was fed into the preparation vessel. Next, 250 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added. While thoroughly stirring, 500 mmol of trimethylaluminum (1.4 mol / L, normal hexane solution) was added, and the mixture was allowed to react at room temperature for 3 days to obtain a hydrogenation catalyst.

[0215] (Synthesis Example 10) Modified Conjugated Diene Polymer (Sample 10) Two tank-type pressure vessels each having an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom and an outlet at the top, and equipped with a stirrer as a tank-type reactor and a jacket for temperature control were connected together as polymerization reactors.

[0216] 1,3-butadiene, from which moisture had been removed in advance, was mixed at 30.8 g / min and n-hexane at 189.3 g / min. In a static mixer installed midway through the pipe supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.072 mmol / min, mixed, and then continuously fed to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.027 mmol / min and n-butyllithium as a polymerization initiator at a rate of 0.205 mmol / min were fed to the bottom of the first reactor, which was being vigorously mixed with a stirrer, and the internal temperature of the reactor was maintained at 78°C.

[0217] The polymer solution was continuously withdrawn from the top of the first reactor and continuously fed to the bottom of the second reactor, where the reaction continued at 78°C. It was then further fed to a static mixer from the top of the second reactor. Once the polymerization was sufficiently stabilized, trimethoxy(4-vinylphenyl)silane (abbreviated as "BS-1" in the table) was added as a branching agent from the bottom of the second reactor at a rate of 0.030 mmol / min while 1,3-butadiene was polymerized. This allowed for the polymerization and branching reactions to occur, yielding a conjugated diene polymer with a branched structure. Once the polymerization and branching reactions were stabilized, a small amount of the conjugated diene polymer solution before the addition of the modifier was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of polymer. The solvent was then removed, and the Mooney viscosity of the resulting conjugated diene polymer was measured. The measurement results are shown in Table 1.

[0218] Next, 1,3-dimethylimidazolidinone (abbreviated as "A" in the table) was continuously added as a modifying agent to the polymer solution flowing out from the outlet of the reactor at a rate of 0.155 mmol / min, and the mixture was mixed using a static mixer to carry out a modification reaction. At this time, it took 4.8 minutes for the modifying agent to be added to the polymer solution flowing out from the outlet of the reactor, the temperature was 76°C, and the difference between the temperature in the polymerization step and the temperature before the addition of the modifying agent was 2°C.

[0219] Next, one tank-type pressure vessel of the same type as that used as the polymerization reactor was connected as a hydrogenation reactor, and the polymer solution after the modification reaction was continuously supplied to the bottom of the hydrogenation reactor. Furthermore, the hydrogenation catalyst synthesized above was continuously added at a rate of 30 ppm / min based on titanium atoms and hydrogen at a rate of 768 ml / min (corresponding to a hydrogenation rate of 6 mol% relative to the double bonds derived from butadiene in the conjugated diene polymer) per 100 parts by mass of the conjugated diene polymer, thereby continuously carrying out a hydrogenation reaction. The pressure in the hydrogenation reactor at this time was 0.50 MPa, and the temperature inside the reactor was 75°C.

[0220] Once the hydrogenation reaction had stabilized, an antioxidant (BHT) was continuously added to the hydrogenated polymer solution at a rate of 0.055 g / min (n-hexane solution) to give 0.2 g per 100 g of polymer, thereby terminating the hydrogenation reaction. The solvent was then removed by steam stripping to obtain a modified conjugated diene polymer (Sample 10) in which a portion of the main chain had a four-branched structure derived from trimethoxy(4-vinylphenyl)silane (the compound represented by formula (3) above) and in which the conjugated diene polymer had been partially hydrogenated. Various physical properties of the sample were measured. The measurement results are shown in Table 1.

[0221] Comparative Synthesis Example 1 Conjugated Diene Polymer (Sample 11) Two tank-type pressure vessels each having an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom and an outlet at the top, and equipped with a stirrer as a tank-type reactor and a jacket for temperature control were connected together as polymerization reactors.

[0222] 1,3-butadiene, from which moisture had been removed in advance, was mixed at 30.8 g / min and n-hexane at 189.3 g / min. In a static mixer installed midway through the pipe supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.072 mmol / min, mixed, and then continuously fed to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.027 mmol / min and n-butyllithium as a polymerization initiator at a rate of 0.205 mmol / min were fed to the bottom of the first reactor, which was being vigorously mixed with a stirrer, and the internal temperature of the reactor was maintained at 78°C.

[0223] The polymer solution was continuously withdrawn from the top of the first reactor and continuously fed to the bottom of the second reactor, where the reaction continued at 78°C, and then fed to a static mixer from the top of the second reactor. When the polymerization reaction was sufficiently stabilized, a small amount of the conjugated diene polymer solution was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of polymer, followed by removal of the solvent, and the Mooney viscosity of the conjugated diene polymer was measured. The measurement results are shown in Table 2.

[0224] Next, an antioxidant (BHT) was continuously added to the modified polymer solution at a rate of 0.055 g / min (n-hexane solution) so that the amount was 0.2 g per 100 g of polymer. The solvent was then removed by steam stripping to obtain a modified conjugated diene polymer (Sample 11), and various physical properties were measured. The measurement results are shown in Table 2.

[0225] (Comparative Synthesis Examples 2 and 3) Conjugated diene-based polymers (samples 12 and 13) The production conditions of Comparative Synthesis Example 1 were changed to those of Comparative Synthesis Examples 2 and 3 shown in Table 2, and when the polymerization reaction was sufficiently stabilized, a branching agent was added to carry out a polymerization reaction and a branching reaction to obtain a conjugated diene-based polymer having a branched structure. Thereafter, conjugated diene-based polymers (samples 12 and 13) were obtained in the same manner as in Comparative Example 1, except that no modifier was added, and various physical properties were measured. The measurement results are shown in Table 2.

[0226] Comparative Synthesis Example 4 Modified Conjugated Diene Polymer (Sample 14) A modified conjugated diene polymer (Sample 14) was obtained in the same manner as in Comparative Synthesis Example 1, except that the production conditions of Comparative Synthesis Example 1 were changed to those of Comparative Synthesis Example 4 shown in Table 2, and once the polymerization reaction had stabilized sufficiently, a modifier was added and the polymerization reaction and modification reaction to obtain a conjugated diene polymer were carried out, and various physical properties were measured. The measurement results are shown in Table 2.

[0227] (Comparative Synthesis Examples 5 and 6) Modified conjugated diene polymers (samples 15 and 16) The production conditions of Comparative Synthesis Examples 5 and 6 shown in Table 2 were changed from those of Comparative Synthesis Example 1, and when the polymerization reaction was sufficiently stable, a branching agent was added, and a polymerization reaction and branching reaction were carried out to obtain a conjugated diene polymer having a branched structure. Thereafter, modified conjugated diene polymers (samples 15 and 16) were obtained in the same manner as in Comparative Synthesis Example 1, except that when the polymerization reaction and branching reaction were sufficiently stable, the modifier was added, and various physical properties were measured. The measurement results are shown in Table 2. "BS-4" shown as a branching agent in the table represents the following compound. "BS-4": 1,1-bis(4-trimethoxysilylphenyl)ethylene

[0228] Comparative Synthesis Example 7: Modified Conjugated Diene Polymer (Sample 17) A tank-type pressure vessel equipped with a stirrer and a temperature-control jacket, which had an internal volume of 10 L and an internal height (L) to diameter (D) ratio (L / D) of 4.0, was used as the polymerization reactor. 1,050 g of 1,3-butadiene and 4,780 g of n-hexane, from which moisture had been removed in advance, were fed into the reactor and mixed with stirring. Next, 0.01 mmol of 2,2-bis(2-oxolanyl)propane was added as a polar substance to the reactor, and the internal temperature of the reactor was controlled to 45°C while continuing to stir. After confirming that the internal temperature of the reactor had stabilized at 45°C while stirring, the warm water in the reactor jacket was drained, and 10.66 mmol of n-butyllithium was added as a polymerization initiator to initiate the polymerization reaction. After the initiation of polymerization, the internal temperature of the reactor gradually rose, peaking at 95°C after 21 minutes. Two minutes after the peaking, 1.33 mmol of trimethoxy(4-vinylphenyl)silane (abbreviated as "BS-1" in the table) was added as a branching agent, and a branching reaction was carried out for 5 minutes. Thereafter, 6.40 mmol of 1,3-dimethylimidazolidinone (abbreviated as "A" in the table) was added as a modifying agent, and a modification reaction was carried out for 5 minutes. After the modification reaction, 10.00 mmol of ethyl alcohol was added to completely quench the reaction. Next, an antioxidant (BHT) was added to the polymer solution in an amount of 0.2 g per 100 g of polymer. The solvent was then removed by steam stripping to obtain a modified conjugated diene-based polymer (Sample 17) containing a 4-branched structure, and various physical properties of the sample were measured. The measurement results are shown in Table 2.

[0229] Comparative Synthesis Example 8 Conjugated Diene Polymer (Sample 18) High-cis BR manufactured by UBE Elastomers Co., Ltd., trade name "UBEPOL BR150" (Mooney viscosity (100°C): 43, 1,2-vinyl bond content: 1 mol%) was prepared as (Sample 18).

[0230] (Comparative Synthesis Example 9) Modified Conjugated Diene Polymer (Sample 19) The production conditions of Comparative Synthesis Example 1 were changed to those of Comparative Synthesis Example 9 shown in Table 2, and when the polymerization reaction was sufficiently stable, a branching agent was added, and a polymerization reaction and branching reaction were carried out to obtain a conjugated diene polymer having a branched structure. Thereafter, a modified conjugated diene polymer (Sample 19) was obtained in the same manner as in Comparative Synthesis Example 1, except that when the polymerization reaction and branching reaction were sufficiently stable, the modifier was added, and various physical properties were measured. The measurement results are shown in Table 2. In the table, "BS-3" shown as a branching agent represents the following compound. "BS-3": 1,1-bis(4-(methyldimethoxysilyl)phenyl)ethylene

[0231] Comparative Synthesis Example 10 Modified Conjugated Diene Polymer (Sample 20) Two tank-type pressure vessels each having an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom and an outlet at the top, and equipped with a stirrer as a tank-type reactor and a jacket for temperature control were connected together as polymerization reactors.

[0232] 1,3-butadiene, from which moisture had been removed in advance, was mixed at 30.8 g / min and n-hexane at 189.3 g / min. In a static mixer installed midway through the pipe supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.072 mmol / min, mixed, and then continuously fed to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.027 mmol / min and n-butyllithium as a polymerization initiator at a rate of 0.205 mmol / min were fed to the bottom of the first reactor, which was being vigorously mixed with a stirrer, and the internal temperature of the reactor was maintained at 78°C.

[0233] The polymer solution was continuously withdrawn from the top of the first reactor and continuously fed to the bottom of the second reactor, where the reaction continued at 78°C. It was then fed to a static mixer from the top of the second reactor. Once the polymerization was sufficiently stabilized, trimethoxy(4-vinylphenyl)silane (abbreviated as "BS-1" in the table) was added as a branching agent from the bottom of the second reactor at a rate of 0.030 mmol / min while 1,3-butadiene was polymerized. This allowed for the polymerization and branching reactions to occur, yielding a conjugated diene polymer with a branched structure. Once the polymerization and branching reactions were stabilized, a small amount of the conjugated diene polymer solution before the addition of the modifier was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of polymer. The solvent was then removed, and the Mooney viscosity of the resulting conjugated diene polymer was measured. The measurement results are shown in Table 2.

[0234] Next, 1,3-dimethylimidazolidinone (abbreviated as "A" in the table) was continuously added as a modifying agent to the polymer solution flowing out from the outlet of the reactor at a rate of 0.155 mmol / min, and the mixture was mixed using a static mixer to carry out a modification reaction. At this time, it took 4.8 minutes for the modifying agent to be added to the polymer solution flowing out from the outlet of the reactor, the temperature was 76°C, and the difference between the temperature in the polymerization step and the temperature before the addition of the modifying agent was 2°C.

[0235] Next, one tank-type pressure vessel of the same type as that used as the polymerization reactor was connected as a hydrogenation reactor, and the polymer solution after the modification reaction was continuously supplied to the bottom of the hydrogenation reactor. Furthermore, the hydrogenation catalyst synthesized above was continuously added at a rate of 30 ppm / min (based on elemental titanium) per 100 parts by mass of the conjugated diene polymer, and hydrogen was continuously added at a rate of 1,536 ml / min (corresponding to a hydrogenation rate of 12 mol% relative to the double bonds derived from butadiene in the conjugated diene polymer), to continuously carry out a hydrogenation reaction. The pressure in the hydrogenation reactor at this time was 0.50 MPa, and the temperature inside the reactor was 75°C.

[0236] Once the hydrogenation reaction had stabilized, an antioxidant (BHT) was continuously added to the hydrogenated polymer solution at a rate of 0.055 g / min (n-hexane solution) to give 0.2 g per 100 g of polymer, thereby terminating the hydrogenation reaction. The solvent was then removed by steam stripping to obtain a modified conjugated diene polymer (Sample 20) in which a portion of the main chain had a four-branched structure derived from trimethoxy(4-vinylphenyl)silane (the compound represented by formula (3) above) and in which the conjugated diene polymer had been partially hydrogenated. Various physical properties of the sample were measured. The measurement results are shown in Table 2.

[0237] Comparative Synthesis Example 11: Modified conjugated diene polymer (sample 21) A modified conjugated diene polymer (sample 21) was obtained in the same manner as in Comparative Synthesis Example 10, except that the hydrogenation rate during the hydrogenation reaction was changed from 1536 ml / min to 4470 ml / min (corresponding to a hydrogenation rate of 35 mol% relative to the double bonds derived from butadiene in the conjugated diene polymer) compared to the production conditions of Comparative Synthesis Example 10, and various physical properties were measured. The measurement results are shown in Table 2.

[0238]

[0239]

[0240] Examples 1 and 2 and Comparative Example 10 Using Samples 1 and 18 shown in Tables 1 and 2 as raw rubbers, rubber compositions containing the respective raw rubbers were obtained according to the formulations shown in Table 3.

[0241] (Carbon compounding, kneading method Examples 1 and 2 and Comparative Example 10) Rubber compositions were obtained by kneading the materials shown in Table 3 by the following method. Using an internal kneader (internal volume 0.3 L) equipped with a temperature control device, raw rubber (samples 1 and 18), carbon black, (silica, silane coupling agent), SRAE oil, zinc oxide, and stearic acid were kneaded in the first stage of kneading under conditions of a filling rate of 65% and a rotor rotation speed of 30 to 50 rpm. During this process, the temperature of the internal mixer was controlled, and each rubber composition (compound) was obtained at a discharge temperature of 155 to 160°C.

[0242] Next, in the second stage of mixing, the compound obtained above was cooled to room temperature, and then an antioxidant was added. The compound was then mixed again to improve the dispersion of the carbon black. Again, the temperature of the mixer was controlled to 155-160°C to adjust the discharge temperature of the compound to 155-160°C. After cooling, in the third stage of mixing, sulfur and vulcanization accelerator 1 were added and mixed using an open roll set at 70°C. The mixture was then molded and vulcanized in a vulcanization press at 160°C for 30 minutes. The rubber compositions before and after vulcanization were evaluated. Specifically, the evaluations were performed using the following methods. The results are shown in Table 4.

[0243] Comparative Examples 1 and 2 Using Sample 1 shown in Table 1 as the raw rubber, rubber compositions containing the raw rubber were obtained according to the formulation shown in Table 3.

[0244] (Silica compounding, kneading method Comparative Examples 1 and 2) The materials shown in Table 3 were kneaded by the following method to obtain a rubber composition. Using an internal kneader (inner capacity 0.3 L) equipped with a temperature control device, in the first stage of kneading, raw rubber (Sample 1), (carbon black), silica, silane coupling agent, SRAE oil, zinc oxide, and stearic acid were kneaded under conditions of a filling rate of 65% and a rotor rotation speed of 30 to 50 rpm. During this process, the temperature of the internal mixer was controlled, and a rubber composition (compound) was obtained at a discharge temperature of 155 to 160°C.

[0245] Next, in the second stage of mixing, the compound obtained above was cooled to room temperature, and then an antioxidant was added. The compound was then mixed again to improve the dispersion of the silica. Again, the temperature of the mixer was controlled to 155-160°C to adjust the discharge temperature of the compound to 155-160°C. After cooling, in the third stage of mixing, sulfur and vulcanization accelerators 2 and 3 were added and mixed using an open roll set at 70°C. The mixture was then molded and vulcanized in a vulcanization press at 160°C for 20 minutes. The rubber compositions before and after vulcanization were evaluated. Specifically, the evaluations were performed using the following methods. The results are shown in Table 4.

[0246] (Evaluation 1) Cold Flow Property Samples 1 and 18 were cut out from the bale to a sample size of L x W x H = 40 mm x 40 mm x 50 mm, and a 1 kg load was placed on each sample, which was then left to stand for 24 hours in a 40°C environment. After standing for 24 hours, the height (H) of the sample was measured, and the average retention rate of two samples was calculated. The result of Comparative Example 10 was set to 100, and this was indexed. A higher index indicates better cold flow property. The results are shown in Table 4.

[0247] (Evaluation 2) Mooney Viscosity of Blend The blend obtained above after the second stage kneading but before the third stage kneading was used as a sample, and after preheating at 130°C for 1 minute, the rotor was rotated at 2 revolutions per minute for 4 minutes, and the viscosity was measured using a Mooney viscometer in accordance with ISO 289. The result of Comparative Example 10 was set to 100, and the results were indexed. A smaller index indicates better processability. The results are shown in Table 4.

[0248] (Evaluation 3) Sheet Condition The compound obtained above after the second stage mixing but before the third stage mixing was used as a sample, and was passed three times through a 10-inch open roll temperature-controlled at 70°C under conditions of a guide width of 200 mm and a clearance of 2.5 mm. The edge and surface conditions of the rubber composition sheet were visually evaluated as follows. The results are shown in Table 4.

[0249] ◎: Edges and surface are smooth; ◯: Edges are slightly rough, but the surface is smooth; △: Edges are significantly rough and the surface is rough; ×: Edges and surface are severely rough, making sheet molding difficult.

[0250] (Evaluation 4) Tensile Strength The tensile strength was measured in accordance with the tensile testing method of JIS K6251, and the results were indexed, with the result of Comparative Example 10 being set at 100. A larger index indicates better tensile strength. The results are shown in Table 4.

[0251] (Evaluation 5) Payne Effect The storage modulus (G') was measured using a viscoelasticity tester "ARES" manufactured by Rheometrics Scientific in a torsion mode at a temperature of 50°C, a frequency of 10 Hz, and a strain of 0.1%. ０．１ ) and the storage modulus (G') measured at 10% strain １０ ) to the difference ΔG' (G' ０．１ -G'１０ The Payne effect was calculated and indexed, with the result of Comparative Example 10 being set at 100. The smaller the index, the better the dispersion of the filler. The results are shown in Table 4.

[0252] (Evaluation 6) Fuel Economy Using a viscoelasticity tester "ARES" manufactured by Rheometrics Scientific, tan δ was measured in torsion mode at a temperature of 50°C, a frequency of 10 Hz, and a strain of 3%. This was used as an index of fuel economy, and the result of Comparative Example 10 was set to 100. The smaller the index, the better the fuel economy. The results are shown in Table 4.

[0253] (Evaluation 7) Abrasion Resistance Using an Acron abrasion tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), the amount of abrasion was measured at a load of 44.4 N and 1,000 revolutions in accordance with JIS K6264-2, and the result of Comparative Example 10 was indexed as 100. The smaller the index, the better the abrasion resistance. The results are shown in Table 4.

[0254] (Evaluation 8) Dynamic Spring Ratio The static spring constant and dynamic spring constant of the crosslinked rubber composition were measured using ACUMEN3 manufactured by MTS in accordance with JIS K6385, and the dynamic spring ratio (dynamic spring constant / static spring constant) was calculated and indexed, with the result of Comparative Example 10 set to 100. The smaller the index, the more excellent the vibration-damping properties. The results are shown in Table 4.

[0255] Carbon black: "Seast KH (N550)" manufactured by Tokai Carbon Co., Ltd. Silica: "Ultrasil 7000GR" manufactured by Evonik Degussa Co., Ltd. Nitrogen adsorption specific surface area: 170 m ２ / g Silica silane coupling agent: "Si75" manufactured by Evonik Degussa Bis(triethoxysilylpropyl)disulfide SRAE oil: "NC140" manufactured by JX Nippon Oil & Energy Corporation Antioxidant: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine Vulcanization accelerator 1: N-(tert-butyl)-2-benzothiazolesulfenamide Vulcanization accelerator 2: N-cyclohexyl-2-benzothiazylsulfinamide Vulcanization accelerator 3: diphenylguanidine

[0256]

[0257] As shown in Table 4, it was confirmed that Examples 1 and 2 containing carbon black had lower compound viscosity and better processability than Comparative Examples 1 and 2 containing silica, and also had good filler dispersion and were excellent in tensile strength, fuel economy, abrasion resistance, and dynamic magnification.

[0258] (Examples 3 to 11, Comparative Examples 3 to 13) Samples 2 to 21 shown in Tables 1 and 2 were used as raw rubbers, and rubber compositions containing the respective raw rubbers were obtained according to the compounding conditions and kneading method of Example 1, except that the conjugated diene polymer sample 1 shown in Example 1 in Table 3 was changed to samples 2 to 21, respectively.

[0259] The physical properties were evaluated according to the above-mentioned (Evaluation 1) to (Evaluation 8), and the results are shown in Tables 5 and 6. The evaluations of Example 1 and Comparative Example 10 are also shown.

[0260]

[0261]

[0262] As shown in Tables 5 and 6, it was confirmed that Examples 1 and 3 to 11 were superior in cold flow resistance compared with Comparative Examples 3 to 13, and that the Mooney viscosity of the compound when vulcanized was low, indicating good processability, and that the Payne effect when vulcanized was low, and that the fuel economy, tensile strength, and dynamic magnification were excellent.

Claims

1. A rubber composition comprising 10 to 150 parts by mass of carbon black per 100 parts by mass of a rubber component containing at least one conjugated diene polymer, and a silica-based inorganic filler content of 0 to 30% by mass based on the total amount of fillers, wherein 10% by mass or more of the rubber component is a modified conjugated diene polymer, wherein the modified conjugated diene polymer: (1) has a main chain branched structure having a branched structure in the main chain; (2) the main chain branched structure includes a structure derived from at least one conjugated diene monomer, or a structure derived from at least one conjugated diene monomer and a structure derived from an aromatic vinyl monomer; (3) has, at at least one end, a terminal group having at least one carbonyl group and at least one substituted amino group in the molecule; (4) has a Mooney viscosity measured at 100°C of 30 to 120; and (5) (5) A rubber composition having a branching degree (Bn) of 1.1 or more and less than 4.0 as measured by a GPC-light scattering method with a viscosity detector; (6) A chromatogram measured by a gel permeation chromatograph (GPC) having a unimodal shape and a molecular weight distribution of 1.60 to 3.00; and (7) A hydrogenation rate of less than 10 mol%.

2. The rubber composition according to claim 1, wherein the amount of 1,2 vinyl bonds in the conjugated diene units of said modified conjugated diene polymer is 10 mol % or more and 25 mol % or less.

3. The rubber composition according to claim 1, wherein the amount of aromatic vinyl bonds in the modified conjugated diene polymer is 0% by mass or more and 10% by mass or less.

4. The rubber composition according to claim 1, wherein the glass transition temperature (Tg) of the modified conjugated diene polymer is -110°C to -80°C.

5. The rubber composition according to claim 1, wherein the modified conjugated diene polymer has a modification rate of 40% by mass or more as measured by column adsorption GPC.

6. The rubber composition according to claim 1, wherein the modified conjugated diene polymer has a hydrogenation rate of less than 5 mol %.

7. The rubber composition according to claim 1, wherein the modified conjugated diene polymer has a structure represented by the following formula (1) and / or the following formula (2). (In formula (1), P represents a conjugated diene polymer containing at least one conjugated diene monomer, and Ra and Rb each independently represent a hydrocarbon group having 1 to 20 carbon atoms.) (In formula (2), P represents a conjugated diene polymer containing at least one conjugated diene monomer, and Ra and Rb each independently represent a hydrocarbon group having 1 to 20 carbon atoms.) 8. The rubber composition according to claim 1, wherein the main chain branched structure of the modified conjugated diene polymer has a portion derived from a vinyl monomer containing an alkoxysilyl group or a halosilyl group, and the portion derived from the vinyl monomer containing an alkoxysilyl group or a halosilyl group has the branched structure.

9. The rubber composition according to claim 7, wherein the portion derived from the vinyl monomer containing an alkoxysilyl group or a halosilyl group is a monomer unit derived from a compound represented by the following formula (3) or (4), and the branched structure in the main chain branched structure of the modified conjugated diene polymer has a polymer chain branch point formed by the monomer unit derived from the compound represented by the following formula (3) or (4). (In the formula, R １ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may have a branched structure in part, or an aryl group having 6 to 20 carbon atoms; R ２ ~R ３ each independently represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, which may have a branched structure in part, and when there are a plurality of R １ ~R ３ are each independent. １ represents an independent halogen atom, m represents an integer of 0 to 2, n represents an integer of 0 to 3, l represents an integer of 0 to 3, and (m+n+l) is 3. (In the formula, R ２ ~R ５ each independently represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, which may have a branched structure in part, and when there are a plurality of R ２ ~R ５ are each independent, and X ２ ~X ３ each independently represents a halogen atom, m represents an integer of 0 to 2, n represents an integer of 0 to 3, l represents an integer of 0 to 3, (m+n+l) is 3, a represents an integer of 0 to 2, b represents an integer of 0 to 3, c represents an integer of 0 to 3, and (a+b+c) is 3.

10. The main chain branch structure of the modified conjugated diene polymer has a monomer unit derived from the compound represented by formula (3), and in formula (3), R １ The rubber composition according to claim 9 , wherein represents a hydrogen atom and m represents 0.

11. The rubber composition according to claim 9, wherein the main chain branched structure of the modified conjugated diene polymer has a monomer unit derived from the compound represented by formula (4), and in formula (4), m represents 0 and b represents 0.

12. The main chain branch structure of the modified conjugated diene polymer has a monomer unit derived from the compound represented by formula (3), and in formula (3), R １ The rubber composition according to claim 9 , wherein: represents a hydrogen atom; m represents 0; n represents 3; and 1 represents 0.

13. The rubber composition according to claim 9, wherein the main chain branching structure of the modified conjugated diene polymer has a monomer unit derived from the compound represented by formula (4), wherein in formula (4), m represents 0, n represents 3, l represents 0, a represents 0, b represents 0, and c represents 3.

14. A vulcanized rubber composition obtained by vulcanizing the rubber composition according to any one of claims 1 to 13.

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