Conjugated diene polymer, rubber composition, and tire member

Abstract

Provided is a conjugated diene polymer having an inter-entanglement-point molecular weight of 2400 g / mol to 3000 g / mol (inclusive), a Mooney viscosity measured at 100 DEG C of 40 or more, a Mooney stress relaxation (MSR) of 0.8 or more, and a vinyl aromatic monomer unit content of 1% by mass to 18% by mass (inclusive).

Description

Technical Field

[0001] The present invention relates to a conjugated diene polymer, a rubber composition and a tire component. Background Art

[0002] Conventionally, there is a demand for longer life of automobile tires in order to reduce environmental load. One of the issues that hinder the longer life of tires is the growth of cracks due to repeated strains during driving and the deterioration of the sidewall due to the breakage of flying stones.

[0003] As a tire rubber composition that meets the above-mentioned demand for longer tire life, a rubber composition having high crack growth resistance and chipping resistance is required.

[0004] It is known that the chipping resistance of a tire is correlated with the elongation at break of a rubber composition. Therefore, in order to extend the life of a tire, it is necessary to improve the crack growth resistance and elongation at break of a rubber composition.

[0005] Generally, as a method for improving the fracture properties including elongation at break of a rubber composition, a method of increasing the molecular weight of the rubber can be cited. In addition, as a method for improving the crack growth property of a rubber composition, a method of using a high molecular weight and low branched polybutadiene is disclosed (for example, see Patent Document 1).

[0006] As described above, in order to improve the elongation at break and crack growth resistance of the rubber composition for a tire, it is considered preferable to use a rubber composition containing a high molecular weight and low branched polybutadiene.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2019-218503 Summary of the invention

[0010] Problems to be solved by the invention

[0011] However, high molecular weight polybutadiene has a high entanglement density between rubbers and therefore has insufficient energy dissipation properties. Therefore, a rubber composition using such high molecular weight polybutadiene has a problem that there is still room for improvement in crack growth resistance.

[0012] Therefore, an object of the present invention is to provide a conjugated diene polymer capable of obtaining a rubber composition having an excellent balance between elongation at break and crack growth resistance.

[0013] Means for solving problems

[0014] The present inventors have conducted intensive studies to solve the problems of the above-mentioned prior art and have found that the problems of the above-mentioned prior art can be solved by making the conjugated diene polymer have a specific molecular weight between entanglement points, a Mooney viscosity and a Mooney stress relaxation rate greater than or equal to a specified value, and a content of vinyl aromatic monomer units within a specified numerical range, thereby completing the present invention.

[0015] That is, the present invention is as follows. [1]

[0017] A conjugated diene polymer, wherein

[0018] The molecular weight between entanglement points is 2400 g / mol or more and 3000 g / mol or less,

[0019] The Mooney viscosity measured at 100° C. is 40 or more, and the Mooney stress relaxation rate (MSR) is 0.8 or more,

[0020] The content of the vinyl aromatic monomer unit is 1% by mass or more and 18% by mass or less. [2]

[0022] The conjugated diene polymer as described in the above [1], wherein the weight average molecular weight is 300,000 or more. [3]

[0024] The conjugated diene polymer as described in [1] or [2] above, wherein the nitrogen content is 70 ppm to 300 ppm, and the modification rate is 60% or more. [4]

[0026] The conjugated diene polymer according to any one of [1] to [3] above, wherein the Mooney stress relaxation ratio (MSR) is 0.80 or more and 1.80 or less. [5]

[0028] The conjugated diene polymer as described in any one of [1] to [4] above, wherein, among the content of the structure represented by the following formula (1): C1 mol %, the content of the structure represented by the following formula (2): C2 mol %, the content of the structure represented by the following formula (3): C3 mol %, and the content of the structure represented by the following formula (4): C4 mol %,

[0029] [Chemistry 1]

[0030]

[0031] The difference α between the value of (C2+C4) / (C1+C2+C3+C4) and the value of (C1+C2) / (C1+C2+C3+C4) is 0.1 or less. [6]

[0033] The conjugated diene polymer according to any one of [1] to [5] above, wherein

[0034] The nitrogen content is 90ppm or more and 300ppm or less.

[0035] The modification rate is more than 60%. [7]

[0037] The conjugated diene polymer according to any one of [1] to [6] above, wherein the conjugated diene polymer is a hydrogenated styrene-butylene copolymer having a hydrogenation rate of 50 mol% or more. [8]

[0039] A rubber composition comprising:

[0040] 100 parts by mass of a rubber component comprising 30 parts by mass or more of the conjugated diene polymer described in any one of [1] to [7] above and 30 parts by mass or more of a natural rubber; and

[0041] 30 parts by mass or more of carbon black. [9]

[0043] A tire component, comprising the rubber composition described in [8] above.

[0044] Effects of the Invention

[0045] According to the present invention, there can be provided a conjugated diene polymer capable of providing a rubber composition having an excellent balance between elongation at break and crack growth resistance. DETAILED DESCRIPTION

[0046] A specific embodiment of the present invention (hereinafter referred to as “this embodiment”) will be described in detail below.

[0047] It should be noted that the following embodiments are examples for explaining the present invention, and the present invention is not limited to the following embodiments. The present invention can be implemented by appropriately modifying the present invention within the scope of the gist thereof.

[0048] [Conjugated diene polymer]

[0049] In the conjugated diene polymer of this embodiment, the molecular weight between entanglement points is 2400 to 3000 g / mol, the Mooney viscosity (ML) measured at 100° C. is 40 or more, the Mooney stress relaxation rate (MSR) is 0.8 or more, and the content of the vinyl aromatic monomer unit is 1% by mass to 18% by mass.

[0050] In addition, in this specification, the structural element of a polymer is described as a "monomer unit", and before polymerization is described as a "compound".

[0051] As described above, in the conjugated diene polymer, by setting the molecular weight between entanglement points, Mooney viscosity (ML), Mooney stress relaxation ratio (MSR) and content of vinyl aromatic monomer units within predetermined numerical ranges, there is a tendency to obtain a rubber composition excellent in crack growth resistance and elongation at break.

[0052] The relationship between each structure and performance is described below.

[0053] (Molecular weight between entanglement points)

[0054] It is known that the following relationship holds true between the quasi-equilibrium elastic modulus Gn and the molecular weight Me between entanglement points (The Polymer Having the Highest Rubbery Plateau (Polymer Vol. 48, September (1999))).

[0055] Gn=cRT / Me

[0056] (c is the density, R is the gas constant, and T is the absolute temperature.)

[0057] The molecular weight between entanglement points is the molecular weight between entanglement points between molecular chains, and represents the molecular weight of a unit that loads stress.

[0058] In the conjugated diene polymer of the present embodiment, the molecular weight between entanglement points is determined by the following formula using the elastic modulus Gn at 27° C. as a variable.

[0059] Molecular weight between entanglement points = cRT / Gn···(1)

[0060] c: 0.9×10 6 (g / m 3 )

[0061] R: 8.31 (J / K / mol)

[0062] T: 300(K)

[0063] Gn: Elastic modulus at 27°C Gn (Pa)

[0064] In the above formula (1), the density in the general formula is taken as a constant. The reason is that, although the density of the polymer depends on the temperature and the molecular structure, the temperature is fixed at 27° C. when measuring the elastic modulus. In addition, in the conjugated diene polymer of the present embodiment, the content of the vinyl aromatic monomer unit that affects the density of the conjugated diene polymer is limited to 1% by mass or more and 18% by mass or less. It has been confirmed that when it is within this range, the density is approximately 0.9×106 (g / m 3 ) is also fine.

[0065] Specifically, the molecular weight between entanglement points of the conjugated diene polymer of the present embodiment can be measured by the method described in the examples described later.

[0066] In the conjugated diene polymer of the present embodiment, the molecular weight between entanglement points is 2400 to 3000 g / mol, preferably 2600 to 3000 g / mol, and more preferably 2700 to 3000 g / mol, from the viewpoint of crack growth resistance of the rubber composition.

[0067] The inventors have found in the process of various studies on the relationship between the crack growth resistance of the rubber composition and the structure of the conjugated diene polymer that the crack growth resistance of the rubber composition is correlated with the molecular weight between the entanglement points of the conjugated diene polymer. Regarding its mechanism, it has been confirmed through experiments that even if the molecular weight of the conjugated diene polymer changes, the effect on the crack growth of the rubber composition is very small, and the entanglement density and branch number of the conjugated diene polymer are dominant. That is, the lower the entanglement density of the conjugated diene polymer and the smaller the degree of branching, the better the crack growth resistance of the rubber composition. Therefore, by increasing the molecular weight between the entanglement points of the conjugated diene polymer, there is a tendency that the entanglement density of the polymer chains is easily reduced and the entropy elastic modulus is easily reduced. As a result, it is believed that the stress imparted to the conjugated diene polymer is easily dispersed and the crack growth resistance of the rubber composition is improved.

[0068] Examples of methods for controlling the molecular weight between entanglement points of the conjugated diene polymer of the present embodiment within a predetermined range include adjusting the content of the vinyl aromatic monomer unit of the conjugated diene polymer, the amount of 1,2-vinyl bonds in the conjugated diene polymer (hereinafter sometimes referred to as the vinyl bond amount), and the hydrogenation rate.

[0069] For example, in the polymerization process of the conjugated diene polymer, the molecular weight between entanglement points of the conjugated diene polymer can be increased by increasing the amount of styrene added as one of the vinyl aromatic compounds. On the other hand, the molecular weight between entanglement points of the conjugated diene polymer can be controlled in the direction of decreasing by decreasing the hydrogenation rate or by increasing the amount of 1,2-vinyl bonds in the conjugated diene polymer before hydrogenation.

[0070] Specifically, when the styrene content is 18% by mass, the molecular weight between entanglement points tends to be increased due to the high styrene content. Therefore, by adjusting the 1,2-vinyl bond amount in the conjugated diene polymer before hydrogenation to 50 to 80 mol% and the hydrogenation rate to 40 to 80 mol%, the target molecular weight between entanglement points tends to be obtained.

[0071] On the other hand, when the styrene content is 1% by mass, the molecular weight between entanglement points tends to be reduced due to the low styrene content. Therefore, by adjusting the 1,2-vinyl bond amount in the conjugated diene polymer before hydrogenation to 40 to 70 mol% and the hydrogenation rate to 50 to 90 mol%, the target molecular weight between entanglement points tends to be obtained.

[0072] The content of the vinyl aromatic monomer unit, the amount of 1,2-vinyl bonds, and the hydrogenation rate can be measured by the methods described in the examples below.

[0073] (Content of vinyl aromatic monomer units)

[0074] In the conjugated diene polymer of the present embodiment, the content of the vinyl aromatic monomer unit is 1% by mass or more and 18% by mass or less. From the perspective of fracture properties when the cross-linking rubber composition containing the conjugated diene polymer of the present embodiment and a cross-linking agent is used in a tire, the content of the vinyl aromatic monomer unit is 1% by mass or more and 18% by mass or less, preferably 6% by mass or more and 18% by mass or less, and more preferably 12% by mass or more and 18% by mass or less.

[0075] Examples of the vinyl aromatic compound constituting the vinyl aromatic monomer unit include, but are not limited to, styrene, p-methylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene.

[0076] Among these, styrene is preferred from the viewpoint of ease of industrial availability.

[0077] These may be used alone or in combination of two or more.

[0078] The content of the vinyl aromatic monomer unit in the conjugated diene polymer of the present embodiment can be controlled within the above numerical range by adjusting the amount of the vinyl aromatic compound added and the polymerization time in the polymerization step.

[0079] (Conjugated diene monomer unit)

[0080] The conjugated diene polymer of the present embodiment contains a conjugated diene monomer unit.

[0081] As the conjugated diene compound constituting the conjugated diene monomer unit, for example, 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 can be mentioned, but are not limited thereto. Among these, 1,3-butadiene and isoprene are preferred from the perspective of ease of industrial availability, and 1,3-butadiene is more preferred.

[0082] These may be used alone or in combination of two or more.

[0083] (Mooney viscosity)

[0084] The Mooney viscosity (ML) of a conjugated diene polymer is an index including information such as the molecular weight, molecular weight distribution, degree of branching, and content of a softener of the conjugated diene polymer.

[0085] The Mooney viscosity of the conjugated diene polymer of the present embodiment measured at 100° C. is 40 or more, preferably 50 or more, and more preferably 60 or more, from the viewpoint of elongation at break when a cross-linked rubber composition containing the conjugated diene polymer and a cross-linking agent is used in a tire.

[0086] On the other hand, from the perspective of productivity of the rubber composition containing the conjugated diene polymer of the present embodiment and processability of the rubber composition mixed with a filler, etc., the Mooney viscosity measured at 100° C. is preferably 100 or less, more preferably 80 or less, and even more preferably 70 or less.

[0087] As a method for measuring the Mooney viscosity, the method specified in ISO 289 described later can be applied.

[0088] The Mooney viscosity of the conjugated diene polymer can be controlled within the above numerical range by adjusting the amount of the polymerization initiator added and the amount and type of the coupling agent added in the polymerization step of the conjugated diene polymer.

[0089] For example, as a method for increasing the Mooney viscosity of a conjugated diene polymer, there can be cited a method of reducing the amount of polymerization initiator added and increasing the molecular weight before the coupling process; a method of using a coupling agent with a large maximum coupling number. From the perspective of the crack growth resistance of the rubber composition, a conjugated diene polymer with a small branch structure ratio is preferred. Since the more branches there are, the higher the Mooney viscosity tends to be, so when the branch structure ratio is reduced and the Mooney viscosity is made above 40, by making the amount of polymerization initiator added to about 0.001g per 1g of conjugated diene polymer, there is a tendency to obtain the target conjugated diene polymer.

[0090] (Mooney stress relaxation rate)

[0091] The Mooney stress relaxation rate (MSR) of the conjugated diene polymer of the present embodiment is 0.8 or more. The larger the MSR, the faster the stress relaxation rate, and as a result, the energy dissipation is excellent. As with the molecular weight between entanglement points, the higher the energy dissipation, the less stress is concentrated, and thus there is a tendency for the crack growth resistance of the rubber composition to be improved.

[0092] From the viewpoint of the crack growth resistance of the rubber composition, the MSR of the conjugated diene polymer of the present embodiment is 0.8 or more, preferably 0.9 or more, and more preferably 1.0 or more.

[0093] As a method for controlling the MSR of the conjugated diene polymer to be 0.8 or more, a method of reducing the branching degree of the conjugated diene polymer or a method of reducing the Mooney viscosity is effective. Specifically, in an unbranched conjugated diene polymer, an MSR of about 1.4 can be obtained at a Mooney viscosity of 80.

[0094] Since the Mooney viscosity and MSR of the conjugated diene polymer are both determined by the molecular weight and the degree of branching, in order to make both of them fall within the desired numerical range, it is necessary to adjust the molecular weight and the degree of branching according to the contribution to the control of the Mooney viscosity and MSR. As a method that can be easily adopted, the molecular weight is adjusted by adjusting the amount of the polymerization initiator added so that the Mooney viscosity of the conjugated diene polymer falls within the desired range, and then the degree of branching is adjusted by selecting the coupling agent.

[0095] From the perspective of storage stability (cold flow) of the conjugated diene polymer, the MSR of the conjugated diene polymer is preferably 1.80 or less, more preferably 1.50 or less, and further preferably 1.30 or less. As a method for reducing the MSR, a method of increasing the degree of branching of the conjugated diene polymer or a method of increasing the Mooney viscosity, which is opposite to the above method, is effective.

[0096] By setting the MSR to 1.80 or less, the polymer molecular chains are sufficiently entangled with each other in practical use, and when the conjugated diene polymer is stored at room temperature, the shape obtained by molding can be maintained, and deformation under its own weight can be suppressed. Therefore, cold flowability is a barometer of the storage stability of the conjugated diene polymer, and is closely related to the MSR and Mooney viscosity of the conjugated diene polymer.

[0097] MSR can be measured by the method described in the examples below, and cold flow property can be evaluated by the method described in the examples below.

[0098] (Weight average molecular weight of conjugated diene polymer)

[0099] In the conjugated diene polymer of the present embodiment, the weight average molecular weight (Mw) determined by gel permeation chromatography (GPC) is preferably 300,000 or more, more preferably 400,000 or more, and even more preferably 440,000 or more.

[0100] When the Mw of the conjugated diene polymer is 300,000 or more, the sulfide tends to have high tensile strength.

[0101] The Mw of the conjugated diene polymer of the present embodiment is preferably 700,000 or less, more preferably 650,000 or less, and further preferably 600,000 or less. By setting the Mw to 700,000 or less, when the conjugated diene polymer of the present embodiment is used in a tire composition, the processability during kneading is excellent, the filler is fully dispersed, and the fuel efficiency performance is excellent.

[0102] The weight average molecular weight of the conjugated diene polymer can be calculated from the molecular weight in terms of polystyrene measured by GPC, and can be measured by the method described in Examples below.

[0103] The weight average molecular weight of the conjugated diene polymer can be controlled within the above numerical range by adjusting the amount of monomer added, polymerization time, polymerization temperature, polymerization initiator, and amount of polar compound added in the polymerization step.

[0104] (Glass transition temperature of conjugated diene polymer)

[0105] In the conjugated diene polymer of the present embodiment, the glass transition temperature (Tg) measured by a differential scanning calorimeter is preferably -50°C or lower, more preferably -55°C or lower, and further preferably -60°C or lower. When Tg is within the above range, the hysteresis loss of the sulfide containing the conjugated diene polymer is reduced, and there is a tendency that the fuel efficiency performance when the composition is used as a tire is excellent.

[0106] The Tg of the conjugated diene polymer can be measured by the method described in the examples below.

[0107] (Modification of conjugated diene polymers)

[0108] The conjugated diene polymer of the present embodiment preferably contains a tin atom, a nitrogen atom, or a silicon atom, and more preferably contains both a nitrogen atom and a silicon atom, from the viewpoint of fuel efficiency when used as a tire material.

[0109] In the present embodiment, a compound having a nitrogen atom is referred to as a modifier, and an operation of adding the modifier to a conjugated diene polymer is referred to as modification.

[0110] (Modification rate of conjugated diene polymer)

[0111] In the conjugated diene polymer of the present embodiment, the modification rate measured by the column adsorption GPC method is preferably 60% or more.

[0112] By setting the modification rate to 60% or more, when the sulfide containing carbon black and / or silica as a filler is used as a tire component, there is a tendency that excellent fuel efficiency performance can be obtained.

[0113] The modification rate of the conjugated diene polymer of the present embodiment is more preferably 70% or more, and further preferably 75% or more.

[0114] The modification rate can be measured by using a chromatograph capable of separating modified components containing a functional group from non-modified components.

[0115] Examples of methods using this chromatograph include a method using a gel permeation chromatography column filled with a polar compound such as silicon oxide that can adsorb specific functional groups and performing quantitative determination using an internal standard of a non-adsorbed component for comparison (column adsorption GPC method).

[0116] More specifically, the modification rate can be obtained as follows: the amount of adsorption on the silica column is measured based on the difference between the chromatogram obtained by measuring a sample solution containing the sample and a low molecular weight internal standard polystyrene using a polystyrene gel column and the chromatogram obtained by measuring a sample solution using a silica column, thereby obtaining the modification rate.

[0117] More specifically, the modification ratio can be measured by the method described in Examples.

[0118] In the conjugated diene polymer of the present embodiment, the modification ratio can be controlled by adjusting the amount of the modifier added and the reaction method, thereby being controlled within the above-mentioned numerical range.

[0119] For example, the following methods can be combined to control the polymerization conditions and thus control the modification rate as mentioned above: a method of using an organic lithium compound having at least one nitrogen atom in the molecule described later as a polymerization initiator to carry out polymerization; a method of copolymerizing a monomer having at least one nitrogen atom in the molecule; a method of using a modifier having the structural formula described later.

[0120] (Nitrogen content)

[0121] In the conjugated diene polymer of the present embodiment, the nitrogen content measured by micro nitrogen analysis is preferably 70 ppm or more and 300 ppm or less.

[0122] When the nitrogen content is 70 ppm or more, there is a tendency for excellent fuel efficiency to be exhibited. The nitrogen content is more preferably 90 ppm or more, and further preferably 110 ppm or more.

[0123] In the conjugated diene polymer of the present embodiment, when the terminal is modified, even if the number of nitrogen atoms contained in the modifier is fixed, the nitrogen content tends to decrease as the molecular chain is extended and the molecular weight increases.

[0124] From the viewpoint of processability, the nitrogen content of the conjugated diene polymer is preferably 300 ppm or less, more preferably 250 ppm or less, and even more preferably 200 ppm or less.

[0125] The nitrogen content can be measured by the method described in the examples below.

[0126] The nitrogen content can be controlled within the above numerical range by adjusting the type and addition amount of the modifier.

[0127] When comparing the same conjugated diene polymer, there is a tendency that the higher the modification rate, the higher the nitrogen content, but since the nitrogen content also depends on the type and molecular weight of the modifier, it is not necessarily related to the modification rate. As a result, as described above, the modification rate tends to affect the fuel efficiency when the conjugated diene polymer is used in a tire, and the nitrogen content tends to affect the tensile strength.

[0128] In the conjugated diene polymer of the present embodiment, as a method for controlling the modification rate and nitrogen content respectively, in the case of increasing the nitrogen content while maintaining the modification rate, the method of adding a modifier with a high nitrogen content is effective. By using the modifier with a high nitrogen content, when mixing the tire rubber composition using the conjugated diene polymer, the dispersion of the carbon black is promoted by utilizing hydrogen bonds to produce an effect with the carbon black, which has a tendency to improve fuel efficiency performance. Similarly, the method of adjusting the molecular weight can also be cited as a method for controlling the modification rate and nitrogen content of the conjugated diene polymer respectively. Specifically, by reducing the molecular weight of the conjugated diene polymer, the nitrogen content can be changed while maintaining the modification rate.

[0129] (Modifier)

[0130] The modifier is not particularly limited, and a conventionally known modifier can be used.

[0131] As the modifier, from the viewpoint of the fuel efficiency performance of the sulfide of the conjugated diene polymer of the present embodiment, a compound having a nitrogen atom is preferred, and a nitrogen group-containing alkoxysilane compound is more preferred.

[0132] Examples of the nitrogen group-containing alkoxysilane compound include, but are not limited to, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(4-trimethoxysilylbutyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacyclohept ...3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(4-trimethoxysilylbutyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacycloheptane, 2,2-dimethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclohexane, 1-(3-Dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy-2-methyl-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-ethoxy-2-ethyl-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy-2-methyl-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane silacyclopentane, and 2-ethoxy-2-ethyl-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, tris(3-trimethoxysilylpropyl)amine, tris(3-methyldimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-methyldiethoxysilylpropyl)amine, tris(trimethoxysilylmethyl)amine, tris(2-trimethoxysilylethyl)amine, and tris(4-trimethoxysilylbutyl)amine, tetrakis[3-(2,2-dimethoxy-1-aza -2-silacyclopentane)propyl]-1,3-propylenediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propylenediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, and N-(3-(bis(3-(trimethoxysilyl)propyl)amino)propyl)-N-methyl-N-(3-(methyl(3-(trimethoxysilyl)propyl)amino)propyl)-N-(3-(trimethoxysilyl)propyl)-1,3-propylenediamine, 3-(4-methylpiperazin-1-yl)propyltriethoxysilane.

[0133] (Unsaturated group-containing monomer unit of conjugated diene polymer)

[0134] The conjugated diene polymer of the present embodiment preferably contains 10% by mass or more of a conjugated diene monomer unit and a monomer unit having an unsaturated group such as myrcene (a monomer unit remaining as an unsaturated group without hydrogenation when a part of the conjugated diene is hydrogenated).

[0135] The monomer unit having an unsaturated group is not limited to a conjugated diene monomer unit or myrcene, and other monomer units may be included.

[0136] Since the conjugated diene monomer units and myrcene have double bonds, the conjugated diene polymer of the present embodiment has a cross-linkable unsaturated group by having these monomer units.

[0137] The content of the monomer unit having an unsaturated group in the conjugated diene polymer of the present embodiment is closely related to the iodine value.

[0138] By making the content of the monomer unit having an unsaturated group such as the conjugated diene monomer unit and myrcene 10% or more by mass, the conjugated diene polymer of the present embodiment is excellent in terms of crosslinking ease. In contrast, by making the content of the monomer unit having an unsaturated group 10% or more by mass, it is also easy to set the molecular weight between entanglement points to a certain value or more, which is preferred from the perspective of crack growth resistance. In addition, since the Mooney viscosity is easily reduced, it is also preferred from the perspective of processability of the conjugated diene polymer.

[0139] The content of the conjugated diene monomer unit and the monomer unit having an unsaturated group such as myrcene is more preferably 15% by mass or more, and even more preferably 20% by mass or more.

[0140] The content of the conjugated diene monomer unit and the monomer unit having an unsaturated group such as myrcene is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, which tends to improve weather resistance and resistance to aging.

[0141] As the conjugated diene monomer unit and the monomer unit having an unsaturated group such as myrcene, a conjugated diene monomer unit is preferred from the viewpoint of economic efficiency and productivity.

[0142] The content of the monomer unit having an unsaturated group in the conjugated diene polymer of the present embodiment can be measured by the NMR measurement method described in the examples described below, and can be controlled within the above numerical range by adjusting the added amount of the conjugated diene monomer unit described below, the monomer having an unsaturated group such as myrcene, and the hydrogenation rate of the conjugated diene monomer.

[0143] In the conjugated diene polymer of the present embodiment, when the content of the structure represented by the following formula (1) is set to C1 mol%, the content of the structure represented by the following formula (2) is set to C2 mol%, the content of the structure represented by the following formula (3) is set to C3 mol%, and the content of the structure represented by the following formula (4) is set to C4 mol%, the difference α between the value of (C2+C4) / (C1+C2+C3+C4) and the value of (C1+C2) / (C1+C2+C3+C4) is preferably less than 0.1.

[0144] Here, the value of (C2+C4) / (C1+C2+C3+C4) refers to the hydrogenation rate, and the value of (C1+C2) / (C1+C2+C3+C4) refers to the 1,2-vinyl bond amount before hydrogenation.

[0145] [Chemistry 2]

[0146]

[0147] When α is 0.1 or less, the conjugated diene polymer of the present embodiment has less entanglement, and the rubber composition using the conjugated diene polymer of the present embodiment tends to exhibit excellent crack growth resistance. α is more preferably 0.09 or less, and even more preferably 0.08 or less.

[0148] When the conjugated diene polymer of the present embodiment is a hydrogenated product, the hydrogenation rate of the structural unit derived from the conjugated diene compound, for example, butadiene, is preferably 50 mol% or more, more preferably 60 mol% or more, and further preferably 65 mol% or more.

[0149] Moreover, it is preferably 90 mol% or less, more preferably 85 mol% or less, and further preferably 80 mol% or less.

[0150] In the conjugated diene polymer of the present embodiment, when the hydrogenation rate of the structural unit derived from the conjugated diene compound is 50 mol% or more, there is a tendency that the sulfide thereof has excellent ozone resistance.

[0151] By setting the hydrogenation rate of the structural unit derived from the conjugated diene compound to 90 mol% or less, the crosslinking density after vulcanization increases, and there is a tendency for the breaking strength and fuel efficiency of the vulcanized product to be excellent.

[0152] The hydrogenation rate of the conjugated diene polymer of the present embodiment can be controlled by adjusting the amount of hydrogen added relative to the structural unit derived from the conjugated diene compound.

[0153] The temperature of the hydrogenation reaction is not particularly limited, but is preferably 60 to 105°C, more preferably 70 to 100°C.

[0154] The hydrogenation rate can be used 1 The measurement was performed by H-NMR.

[0155] The hydrogenation rate of the conjugated diene polymer of the present embodiment, the distribution of the ethylene unit, the conjugated diene monomer unit, the monomer unit having an unsaturated group such as myrcene, and the vinyl aromatic monomer unit between molecules and within molecules is not particularly limited, and may be uniform, non-uniform, or distributed.

[0156] (Softener for conjugated diene polymer)

[0157] The conjugated diene polymer of the present embodiment may contain a rubber softener as necessary.

[0158] The content of the rubber softener is preferably 30% by mass or less.

[0159] In the conjugated diene polymer of the present embodiment, the amount of the rubber softener added is preferably 1 to 30% by mass from the viewpoint of improving processability when an inorganic filler or the like is blended during tire production.

[0160] When the molecular weight of the conjugated diene polymer is high, for example, when the weight average molecular weight exceeds 1,000,000, the amount of the rubber softener added is preferably 15 to 30% by mass. On the other hand, from the perspective of increasing the degree of freedom in the amount of the filler compounded when the rubber composition is compounded with a filler, the amount of the rubber softener added is preferably 1 to 15% by mass.

[0161] From the viewpoint of suppressing aging degradation when manufactured into a tire, the content of the rubber softener in the rubber composition using the conjugated diene polymer of this embodiment is more preferably 20 mass % or less, further preferably 10 mass % or less, and even more preferably 5 mass % or less.

[0162] As the rubber softener, for example, extender oil, low molecular weight conjugated diene polymer, resin, etc. can be cited but are not limited thereto. From the aspects of processability, productivity, and economy, extender oil is preferred. In addition, from the aspect of wear resistance of the tire rubber composition, the rubber softener is preferably a low molecular weight conjugated diene polymer that can contribute to crosslinking.

[0163] As a method for adding the rubber softener to the conjugated diene polymer of the present embodiment, the following method is preferred but not limited to: adding the rubber softener to a solution of the conjugated diene polymer, mixing to prepare a polymer solution containing the rubber softener, and then removing the solvent.

[0164] Preferred softeners include, but are not limited to, aromatic oils, cycloparaffin oils, paraffin oils, and the like.

[0165] Among these, alternative aromatic oils having a polycyclic aromatic (PCA) content of 3% by mass or less based on the IP346 method are preferred from the viewpoints of environmental safety, prevention of oil bleeding of the rubber composition, and wet grip properties.

[0166] As alternative aromatic oils, for example, TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), and the like described in Kautschuk Gummi Kunststoffe 52 (12) 799 (1999), and RAE (Residual Aromatic Extracts) can be cited.

[0167] (Other additives)

[0168] The conjugated diene polymer of the present embodiment may contain various additives such as an antioxidant as necessary.

[0169] [Method for producing conjugated diene polymer]

[0170] In the method for producing the conjugated diene polymer of the present embodiment, the conjugated diene polymer can be obtained, for example, by copolymerizing a conjugated diene compound and a vinyl aromatic compound and, if necessary, hydrogenating the obtained conjugated diene polymer.

[0171] Generally, if the molecular weight between entanglement points of polybutadiene is compared with the molecular weight between entanglement points of polystyrene, the molecular weight between entanglement points of polystyrene is larger. The same tendency is observed in the monomer ratio in the conjugated diene polymer. If the content of the vinyl aromatic monomer unit increases, the molecular weight between entanglement points increases. On the other hand, if the bonding mode of the conjugated diene monomer is focused on, when the conjugated diene monomer is polymerized using 1,2- or 3,4-bonding (so-called vinyl bonding), there is a tendency for the molecular weight between entanglement points to increase compared to 1,4-bonding. In addition, if hydrogenation is performed, the molecular weight between entanglement points increases compared to non-hydrogenation.

[0172] Therefore, in order to control the molecular weight between entanglement points, it is appropriate to adjust the content of the vinyl aromatic monomer unit, the vinyl bonding amount of the conjugated diene monomer, and the hydrogenation rate. Of course, these factors will also have an impact on other properties of the conjugated diene polymer, so it is preferably designed in a manner that is balanced with the required performance. For example, if the content of the vinyl aromatic monomer unit is set high, the molecular weight between entanglement points can be increased even if the hydrogenation rate is low. On the contrary, in the case of a conjugated diene polymer with a small content of vinyl aromatic monomer units, by setting the vinyl bonding amount and the hydrogenation rate high, there is a tendency that the molecular weight between entanglement points easily meets the conditions of this embodiment.

[0173] In the case where the constituent components of the conjugated diene polymer of the present embodiment are 1,3-butadiene as a conjugated diene compound and styrene as a vinyl aromatic compound, the proportion of styrene in the polymerized monomer is 1% by mass or more and 18% by mass or less. In order to control the molecular weight between entanglement points of the conjugated diene polymer within a desired range, the proportion of styrene is preferably 10% by mass or more, more preferably 15% by mass or more. By controlling the amount of styrene within the above range, there is a tendency to achieve an increase in the breaking strength while improving the crack growth resistance of the rubber composition.

[0174] In the method for producing the conjugated diene polymer of the present embodiment, anionic polymerization is preferably performed in the polymerization step because the molecular structure can be easily controlled. In addition, it is preferred that part or most of the double bonds in the conjugated diene polymer obtained by polymerizing at least the conjugated diene monomer be hydrogenated.

[0175] As a method for producing the conjugated diene polymer of the present embodiment, for example, as described in International Publication No. 96 / 05250, Japanese Patent Application Publication No. 2000-053706, International Publication No. 2003 / 085010, International Publication No. 2019 / 151126, International Publication No. 2019 / 151127, International Publication No. 2002 / 002663, and International Publication No. 2015 / 006179, a method of polymerizing a conjugated diene monomer by anionic polymerization in the presence of various additives and conditions, copolymerizing with other monomers as needed, and then hydrogenating.

[0176] As the vinyl aromatic compound, ethylene, α-olefin, conjugated diene compound, and other monomers used in the polymerization in the method for producing the conjugated diene polymer of the present embodiment, the same monomers as those described in the above-mentioned various documents can be used.

[0177] The polymerization step and the hydrogenation step can be carried out by either a batch method or a continuous method.

[0178] (Polymerization process)

[0179] In the polymerization step, a conjugated diene compound, a vinyl aromatic compound, and, if necessary, other monomers are polymerized using a polymerization initiator.

[0180] Examples of the polymerization initiator used in the polymerization step include organic monolithium compounds and the like.

[0181] Examples of the organic monolithium compound include, but are not limited to, low molecular weight compounds and soluble oligomer organic monolithium compounds.

[0182] In addition, examples of the organic monolithium compound include compounds having a carbon-lithium bond, compounds having a nitrogen-lithium bond, and compounds having a tin-lithium bond in terms of the bonding form between the organic group and the lithium.

[0183] The amount of the organic monolithium compound used as a polymerization initiator is preferably determined according to the structure and molecular weight of the target conjugated diene polymer of the present embodiment.

[0184] The amount of the monomer such as the conjugated diene compound used relative to the amount of the polymerization initiator used is related to the degree of polymerization of the conjugated diene polymer, that is, to the number average molecular weight and / or weight average molecular weight of the conjugated diene polymer.

[0185] Therefore, in order to increase the molecular weight, the amount of the polymerization initiator used can be adjusted in the direction of decreasing, and in order to decrease the molecular weight, the amount of the polymerization initiator used can be adjusted in the direction of increasing.

[0186] From the viewpoint of using it as a method for introducing nitrogen atoms into a conjugated diene polymer, the organic monolithium compound as a polymerization initiator is preferably an alkyllithium compound having a substituted amino group or dialkyllithium amide.

[0187] In this case, a conjugated diene polymer having a nitrogen atom constituting an amino group at the polymerization initiation terminal can be obtained.

[0188] The substituted amino group is an amino group having no active hydrogen or having a structure in which the active hydrogen is protected.

[0189] Examples of the alkyl lithium compound having an amino group (which has no active hydrogen) include, but are not limited to, 3-dimethylaminopropyl lithium, 3-diethylaminopropyl lithium, 4-(methylpropylamino)butyl lithium, and 4-hexamethyleneiminobutyl lithium.

[0190] Examples of the alkyl lithium compound having an amino group with active hydrogen protected include, but are not limited to, 3-bistrimethylsilylaminopropyllithium and 4-trimethylsilylmethylaminobutyllithium.

[0191] Examples of the dialkyl lithium amide include, but are not limited to, dimethyl lithium amide, diethyl lithium amide, dipropyl lithium amide, dibutyl lithium amide, di-n-hexyl lithium amide, diheptyl lithium amide, diisopropyl lithium amide, dioctyl lithium amide, di-2-ethylhexyl lithium amide, didecyl lithium amide, ethylpropyl lithium amide, ethylbutyl lithium amide, ethylbenzyl lithium amide, methylphenethyl lithium amide, hexamethylene imide, pyrrolidinyl lithium, piperidine lithium, heptamethylene imide, morpholine lithium, 1-lithioazacyclooctane, 6-lithio-1,3,3-trimethyl-6-azabicyclo[3.2.1]octane, and 1-lithio-1,2,3,6-tetrahydropyridine.

[0192] These organic monolithium compounds having a substituted amino group may be reacted with a small amount of a polymerizable monomer such as 1,3-butadiene, isoprene, styrene, etc., and used as an organic monolithium compound of a soluble oligomer.

[0193] From the viewpoint of ease of industrial availability and ease of polymerization reaction control, the organic monolithium compound as the polymerization initiator is preferably an alkyllithium compound. In this case, a conjugated diene polymer having an alkyl group at the polymerization initiation terminal can be obtained.

[0194] Examples of the alkyl lithium compound include, but are not limited to, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, n-hexyl lithium, benzyl lithium, phenyl lithium, and stilbene lithium.

[0195] As the alkyl lithium compound, n-butyl lithium and sec-butyl lithium are preferred from the viewpoint of ease of industrial availability and ease of polymerization reaction control.

[0196] The above-mentioned organic monolithium compounds may be used alone or in combination of two or more, or may be used in combination with other organic metal compounds.

[0197] Examples of the other organic metal compounds include alkaline earth metal compounds, other alkali metal compounds, and other organic metal compounds.

[0198] Examples of the alkaline earth metal compound include, but are not limited to, organomagnesium compounds, organocalcium compounds, and organostrontium compounds, and examples also include alkoxides, sulfonates, carbonates, and amide compounds of alkaline earth metals.

[0199] Examples of the organic magnesium compound include dibutyl magnesium and ethylbutyl magnesium.

[0200] Examples of other organometallic compounds include organoaluminum compounds.

[0201] Examples of the polymerization reaction mode of the polymerization step include, but are not limited to, batch-wise (also referred to as "batch-wise") and continuous polymerization reaction modes.

[0202] In the continuous type, one or two or more connected reactors can be used. For example, a tank type or a tube type reactor equipped with a stirrer is used as the continuous type reactor.

[0203] In the continuous method, it is preferred that the monomer, the inert solvent and the polymerization initiator are continuously charged into a reactor, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is continuously discharged.

[0204] As the batch reactor, for example, a tank reactor equipped with a stirrer is used.

[0205] In the batch method, preferably, monomers, an inert solvent and a polymerization initiator are loaded into a reactor, monomers are added continuously or intermittently during polymerization as required, a polymer solution is obtained in the reactor, and the polymer solution is discharged after completion of the polymerization.

[0206] In the method for producing the conjugated diene polymer of the present embodiment, in order to obtain a polymer having an active terminal at a high ratio, a continuous method is preferably used in which the polymer can be continuously discharged and supplied to the subsequent reaction in a short time.

[0207] The polymerization step of the conjugated diene polymer according to the present embodiment is preferably performed in an inert solvent.

[0208] Examples of the inert solvent include, but are not limited to, hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons.

[0209] Examples of hydrocarbon solvents include, but are not limited to, 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.

[0210] Before the polymerization step is carried out, by treating allenes and acetylenes as impurities with an organic metal compound, there is a tendency to obtain a conjugated diene polymer with a high concentration of active terminals, and there is a tendency to obtain a conjugated diene polymer with a high modification rate after the modification step, so it is preferred to treat the impurities with the above-mentioned organic metal compound.

[0211] In the polymerization process, a polar compound may be added. Thus, a vinyl aromatic compound and a conjugated diene compound can be randomly copolymerized. In addition, the polar compound has a tendency to be used as a vinylating agent for controlling the microstructure of the conjugated diene portion. In addition, there is a tendency to have an effect in the promotion of the polymerization reaction.

[0212] As polar compounds, there can be mentioned, but are not limited to, ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, 2,2-bis(2-tetrahydrofuranyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidylethane, trimethylamine, triethylamine, pyridine, quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butoxide, sodium tert-butoxide, sodium amylate; phosphine compounds such as triphenylphosphine, etc.

[0213] These polar compounds may be used alone or in combination of two or more.

[0214] The amount of the polar compound used is not particularly limited and may be selected depending on the purpose etc., but is preferably 0.01 mol or more and 10 mol or less per 1 mol of the polymerization initiator.

[0215] By adding a polar compound in a range of 0.01 mol to 10 mol relative to 1 mol of the polymerization initiator, the 1,2-vinyl bond amount in the conjugated diene polymer increases; on the contrary, the 1,4-vinyl bond amount decreases. By increasing the 1,2-vinyl bond amount in the conjugated diene polymer, there is a tendency that the molecular weight between entanglement points of the conjugated diene polymer is easily increased, and even when the content of the vinyl aromatic monomer unit is relatively small, there is a tendency that the molecular weight between entanglement points of the conjugated diene polymer of this embodiment is easily controlled within a numerical range of 2400 g / mol to 3000 g / mol. There is a tendency that a sulfide having excellent crack growth resistance and fuel efficiency performance can be obtained from the conjugated diene polymer having a low content of vinyl aromatic monomer units and a high 1,2-vinyl bond amount thus obtained.

[0216] Such polar compounds (vinylating agents) can be used in appropriate amounts as regulators of the microstructure of the conjugated diene portion of the conjugated diene polymer according to the desired 1,2-vinyl bond amount. Most polar compounds have an effective randomizing effect in the copolymerization of conjugated diene compounds and vinyl aromatic compounds, and tend to be used as regulators of the distribution of vinyl aromatic compounds and regulators of the styrene block amount.

[0217] As a method for randomizing the copolymerization of the conjugated diene compound and the vinyl aromatic compound, for example, there is a method of initiating a copolymerization reaction using the total amount of styrene and a part of 1,3-butadiene and intermittently adding the remaining 1,3-butadiene during the copolymerization reaction as described in JP-A-59-140211.

[0218] The polymerization temperature in the polymerization step is preferably a temperature for performing living anionic polymerization, and is more preferably 0° C. or higher, preferably 120° C. or lower, and more preferably 50° C. or higher and 100° C. or lower from the viewpoint of productivity. By setting the temperature in this range, there is a tendency that the amount of reaction of the modifier with respect to the active terminal after the completion of the polymerization can be sufficiently ensured.

[0219] (Branching process)

[0220] In the method for producing a conjugated diene polymer according to the present embodiment, a step of adjusting the degree of branching of the conjugated diene polymer may be further performed.

[0221] As a method of increasing the degree of branching of the conjugated diene polymer, for example, there is mentioned a method of using a branching agent which is a compound derived from a vinyl monomer containing an alkoxysilyl group and / or a halosilyl group.

[0222] By adding a branching agent in the polymerization process and then adding monomers to continue the polymerization reaction, the polymer chain branched at the branching point can be extended. In addition, a modifier, coupling agent, etc. can be added thereafter to carry out a modification process.

[0223] (Modification process)

[0224] The active ends of the polymer obtained after the polymerization step and, if necessary, the branching step using a predetermined branching agent are subjected to a modification step using the coupling agent or the modifying agent having a nitrogen atom-containing group.

[0225] (Deactivator, Neutralizer)

[0226] In the method for producing a conjugated diene polymer according to the present embodiment, a deactivator, a neutralizer, and the like may be added to the polymer solution after the modification step, as necessary.

[0227] Examples of the deactivating agent include, but are not limited to, water; alcohols such as methanol, ethanol, and isopropanol; and the like.

[0228] Examples of the neutralizing agent include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and neodecanoic acid (a mixture of multi-branched carboxylic acids having 9 to 11 carbon atoms, with 10 being the center); aqueous solutions of inorganic acids; and carbon dioxide.

[0229] (Hydrogenation process)

[0230] The method for producing the conjugated diene polymer of the present embodiment is not particularly limited, and may include a step of hydrogenating the conjugated diene polymer so that the hydrogenation rate becomes 50 mol% or more and 90 mol% or less as described above.

[0231] The hydrogenation rate can be controlled by adjusting the amount of hydrogen during hydrogenation, and the hydrogenation rate can be controlled by adjusting the amount of hydrogen added, pressure, and temperature. The hydrogenation rate of the conjugated diene polymer can be measured by proton nuclear magnetic resonance ( 1 H-NMR) method.

[0232] (Addition of rubber stabilizer)

[0233] In the method for producing the conjugated diene polymer of the present embodiment, it is preferred to add a rubber stabilizer from the viewpoint of preventing gel formation after polymerization and improving stability during processing.

[0234] As the rubber stabilizer, known substances can be used, and antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (hereinafter also referred to as "BHT"), octadecyl 3-(4'-hydroxy-3',5'-di-tert-butylphenol) propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol can be mentioned but are not limited thereto.

[0235] (Desolventization process)

[0236] In the method for producing the conjugated diene polymer of the present embodiment, a known method can be used as a method for extracting the obtained polymer from the polymer solution. The method is not particularly limited, and examples thereof include: a method of separating the solvent by steam stripping, filtering out the polymer, and further dehydrating and drying it to obtain the polymer; a method of concentrating using a flash tank and further devolatilizing using a venting extruder; and a method of directly devolatilizing using a rotary dryer.

[0237] [Rubber composition]

[0238] The rubber composition of the present embodiment contains 100 parts by mass of a rubber component containing 30 parts by mass or more of the conjugated diene polymer of the present embodiment and 30 parts by mass or more of natural rubber, and 30 parts by mass or more of carbon black.

[0239] The rubber composition of the present embodiment has the above-mentioned configuration and is excellent in the balance between elongation at break and crack growth resistance.

[0240] The rubber composition of the present embodiment may further contain other rubbers in addition to the conjugated diene polymer of the present embodiment. The conjugated diene polymer of the present embodiment, natural rubber, and other rubbers may be collectively described as a rubber component.

[0241] (Carbon Black)

[0242] The carbon black is not particularly limited, and various grades of carbon black such as SRF, FEF, HAF, ISAF, and SAF can be used. Among these, carbon black having a nitrogen adsorption specific surface area of ​​50 m2 is preferred from the perspective of extrusion moldability and rolling resistance characteristics. 2 / g or more and a carbon black with a dibutyl phthalate (DBP) oil absorption of 80mL / 100g or more.

[0243] From the perspective of the breaking strength of the rubber composition, the content of carbon black is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and further preferably 50 parts by mass or more relative to 100 parts by mass of the rubber component. In addition, from the perspective of improving the fuel efficiency of the rubber composition, the content of carbon black is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and further preferably 80 parts by mass or less.

[0244] The content of natural rubber in the rubber composition of the present embodiment is preferably 30 parts by mass or more per 100 parts by mass of the rubber component, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more from the viewpoint of the tear strength of the obtained vulcanizate.

[0245] The content of the conjugated diene polymer in the rubber composition of the present embodiment is preferably 30 parts by mass or more per 100 parts by mass of the rubber component, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more from the viewpoint of ozone resistance of the obtained vulcanizate.

[0246] There are no particular limitations on other rubbers, and they can be appropriately selected according to the purpose of the rubber composition. Examples include styrene-butadiene rubber (emulsion polymerization type, solution polymerization type), polyisoprene, butadiene rubber (high cis polybutadiene, low cis polybutadiene, syndiotactic-1,2-polybutadiene), nitrile rubber (NBR), chloroprene rubber, ethylene-α-olefin copolymer rubbers such as ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), butyl rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber, and the like.

[0247] These other rubbers may be used alone or in combination of two or more.

[0248] As a method of mixing the other rubber, the other rubber may be mixed in a dry state after the polymerization of the conjugated diene polymer, or may be mixed in a solution state during the polymerization of the conjugated diene polymer.

[0249] The rubber composition of the present embodiment may contain a cross-linking agent.

[0250] The content of the crosslinking agent in the rubber composition of the present embodiment is preferably 0.1 to 20 parts by mass relative to 100 parts by mass of the rubber component. From the perspective of high tensile strength and high crosslinking speed in the rubber composition, it is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 1.5 to 10 parts by mass. On the other hand, from the perspective of suppressing uneven crosslinking and high tensile strength, it is preferably 20 to 30 parts by mass, more preferably 5 to 30 parts by mass, and even more preferably 3 to 30 parts by mass.

[0251] The crosslinking agent is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include sulfur-based crosslinking agents, organic peroxide-based crosslinking agents, inorganic crosslinking agents, polyamine crosslinking agents, resin crosslinking agents, sulfur-containing compound-based crosslinking agents, oxime-nitrosoamine-based crosslinking agents, etc. These can be used alone or in combination of two or more.

[0252] When the rubber composition of the present embodiment is used as a composition for a tire, a sulfur-based crosslinking agent (vulcanizing agent) is more preferred among these, and sulfur is more preferred in particular.

[0253] The rubber composition of the present embodiment may contain a vulcanizing agent, and may further contain a vulcanization accelerator.

[0254] Examples of the vulcanization accelerator include, but are not limited to, guanidine-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, sulfenamide-based, thiourea-based, thiuram-based, dithiocarbamate-based, and xanthate-based compounds.

[0255] The rubber composition of the present embodiment may contain various additives other than those described above, such as a softener, a filler, a heat stabilizer, an antistatic agent, a weather stabilizer, an antioxidant, a colorant, and a lubricant.

[0256] As other softeners, known softeners can be used.

[0257] Examples of other fillers include, but are not limited to, calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate.

[0258] As the heat stabilizer, the antistatic agent, the weather stabilizer, the anti-aging agent, the colorant, and the lubricant, known materials can be used.

[0259] (Sulfide)

[0260] The rubber composition of the present embodiment can be preferably used in the form of a vulcanized product. By vulcanizing the rubber composition containing natural rubber and carbon black, a vulcanized product having excellent breaking strength can be obtained at low cost.

[0261] The sulfide may contain, in addition to the conjugated diene polymer, natural rubber and carbon black of the present embodiment, an inorganic filler such as silicon oxide, a rubber component other than the conjugated diene polymer and natural rubber, a silane coupling agent, a rubber softener, wax, a vulcanizing agent, a vulcanization accelerator and a vulcanization aid, and can be obtained by mixing them to form a rubber composition and then heating and vulcanizing it.

[0262] The method for identifying the type and content ratio of the rubber component contained in the rubber composition of the present embodiment is not particularly limited, and an example thereof is a method of identifying by using NMR.

[0263] For example, as described in the existing report (JSR TECHNICAL REVIEW No. 126 / 2019), solid 13 C-NMR quantitatively calculates the styrene units, the amount of 1,2-vinyl bonds, the amount of 1,4-vinyl bonds, the amount of 1,4-cis bonds, and the ratio of isoprene units contained in the rubber composition.

[0264] (Silicon Oxide)

[0265] The rubber composition of the present embodiment may contain silica.

[0266] The content of silica in the rubber composition is preferably 30 parts by mass or more and 100 parts by mass or less relative to 100 parts by mass of the rubber component containing the conjugated diene polymer of the present embodiment and natural rubber.

[0267] From the perspective of improving the grip performance and handling stability when the rubber composition of the present embodiment is used in a tire, the content of silicon oxide is preferably 60 parts by mass or more, more preferably 65 parts by mass or more, and further preferably 75 parts by mass or more relative to 100 parts by mass of the rubber component. In addition, from the perspective of improving the fuel efficiency when used in a tire, it is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and further preferably 80 parts by mass or less.

[0268] Silicon oxide is not particularly limited, and known substances can be used, preferably solid particles containing SiO2 or Si3Al as structural units, more preferably solid particles containing SiO2 or Si3Al as the main component of the structural unit. Here, the main component refers to a component containing 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more in silicon oxide.

[0269] Examples of silicon oxide include, but are not limited to, silicon dioxide, clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, and inorganic fibrous substances such as glass fibers.

[0270] As a commercial product of silicon oxide, the trade name "Ultrasil 7000GR" manufactured by Evonik Degussa is mentioned, for example.

[0271] In addition, as silicon oxide, a silicon oxide-based inorganic filler whose surface is hydrophobized may be used, and the silicon oxide-based inorganic filler may be used in combination with an inorganic filler other than silicon oxide-based fillers.

[0272] Among these, silica and glass fiber are preferred from the viewpoint of strength and abrasion resistance, and silica is more preferred.

[0273] Examples of silicon oxide include dry silicon oxide, wet silicon oxide, and synthetic silicate silicon oxide. Among these, wet silicon oxide is more preferred because of its excellent balance between the effect of improving the breaking characteristics and the wet grip characteristics.

[0274] In the rubber composition of the present embodiment, in order to obtain practically good wear resistance and fracture characteristics, when a silica-based inorganic filler is contained, the nitrogen adsorption specific surface area of ​​the silica-based inorganic filler determined by the BET adsorption method is preferably 100 m 2 / g above 300m 2 / g or less, more preferably 170m 2 / g above 250m 2 / g or less.

[0275] In addition, the specific surface area can be smaller (for example, the specific surface area is less than 200m 2 / g) of silicon oxide-based inorganic fillers and larger specific surface areas (e.g., specific surface areas of 200 m 2 In this way, it is possible to achieve a high balance between good wear resistance and fracture characteristics and fuel efficiency characteristics.

[0276] (Silane coupling agent)

[0277] The rubber composition of the present embodiment may contain a silane coupling agent from the viewpoint of improving the dispersibility of the filler and increasing the tensile strength of the crosslinked body.

[0278] The silane coupling agent is preferably a compound having a function of strengthening the interaction between the rubber component and the inorganic filler, having a group having affinity or bonding properties with the rubber component and the filler, respectively, and having a sulfur bonding portion and an alkoxysilyl group or a silanol group portion in one molecule.

[0279] Examples of such compounds include, but are not limited to, bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide, 3-octanoylthiopropyltriethoxysilane, a condensate of 3-octanoylthiopropyltriethoxysilane and [(triethoxysilyl)-propyl]thiol, mercaptosilanes having at least one thiol functional group (-SH), and silanes carrying at least one masked mercapto group.

[0280] The content of the silane coupling agent in the rubber composition of the present embodiment is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 1.0 parts by mass or more, relative to 100 parts by mass of the rubber component containing the conjugated diene polymer of the present embodiment and the natural rubber. In addition, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 15 parts by mass or less.

[0281] When the content of the silane coupling agent is within the above range, the above-mentioned addition effect by the silane coupling agent tends to be more remarkable.

[0282] (Softener)

[0283] The rubber composition of the present embodiment preferably contains 100 parts by mass of a rubber component including the conjugated diene polymer of the present embodiment and a natural rubber, and 1 part by mass to 60 parts by mass of a softener.

[0284] The softener is not particularly limited, and examples thereof include extender oil, low molecular weight conjugated diene polymers, resins, etc., and extender oil is preferred from the perspective of processability, productivity, and economy. In addition, from the perspective of the wear resistance of the tire rubber composition, low molecular weight conjugated diene polymers that can contribute to crosslinking are preferred.

[0285] Preferred softeners include, but are not limited to, aromatic oils, cycloparaffin oils, paraffin oils, and the like.

[0286] Among these, alternative aromatic oils having a polycyclic aromatic (PCA) content of 3% by mass or less based on the IP346 method are preferred from the viewpoints of environmental safety, prevention of oil bleeding, and wet grip properties.

[0287] As alternative aromatic oils, for example, TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), and the like described in Kautschuk Gummi Kunststoffe 52 (12) 799 (1999), and RAE (Residual Aromatic Extracts) can be cited.

[0288] In the rubber composition of the present embodiment, the content of the softener is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and further preferably 10 parts by mass or more, based on 100 parts by mass of the rubber component from the aspect of processability. In addition, from the aspect of wear resistance, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and further preferably 40 parts by mass or less.

[0289] (Method for producing rubber composition)

[0290] The rubber composition of the present embodiment can be produced by mixing the conjugated diene polymer of the present embodiment, a rubber component composed of natural rubber and other rubbers, carbon black, silica, other fillers, a crosslinking agent, a silane coupling agent, a softener and other additives.

[0291] Regarding the method of mixing the conjugated diene polymer of the present embodiment, natural rubber and other rubber components, crosslinking agents, silica, carbon black or other fillers, silane coupling agents, softeners and other additives, examples include but are not limited to melt mixing methods using common mixers such as open mills, Banbury mixers, kneaders, single-screw extruders, twin-screw extruders, multi-screw extruders, etc.; and methods of dissolving and mixing the components and then heating to remove the solvent.

[0292] Among these methods, melt kneading methods using rolls, Banbury mixers, kneaders, and extruders are preferred from the perspective of productivity and good kneading properties. In addition, any of a method in which the rubber component is kneaded with a filler, a silane coupling agent, and an additive at one time or a method in which the rubber component is mixed in multiple batches may be used.

[0293] [use]

[0294] The rubber composition of the present embodiment can be preferably used as a cross-linking rubber composition for tire parts, automobile interior and exterior materials, anti-vibration rubber, belts, shoes, foams, various industrial products, and the like.

[0295] Among these, it can be preferably used for tire parts.

[0296] Examples of tire components include various tires such as fuel-efficient tires, all-season tires, high-performance tires, snow tires, and studless tires; and parts of the tire such as the tire tread, tire carcass, sidewalls, and bead portions.

[0297] In particular, the rubber composition of the present embodiment has an excellent balance among crack growth resistance, fuel efficiency performance, and elongation at break when it is made into a vulcanizate, and therefore can be suitably used as a material for tire treads and sidewalls of fuel-efficient tires.

[0298] As a method for manufacturing a tire, a known method can be used. For example, at least one tire carcass layer, belt layer, tread layer, and other components commonly used in tire manufacturing, selected from the group consisting of an unvulcanized cross-linking rubber composition and a cord, are sequentially laminated on a tire molding drum, and the drum is removed to produce a green tire. Next, the green tire is heated and vulcanized according to a conventional method, thereby producing a desired tire (e.g., a pneumatic tire).

[0299] Example

[0300] The present embodiment will be described in more detail below with reference to specific examples and comparative examples, but the present embodiment is not limited to the following examples and comparative examples.

[0301] Various physical properties in Examples and Comparative Examples were measured by the methods shown below.

[0302] (Microstructure of butadiene portion of conjugated diene polymer before hydrogenation (1,2-vinyl bond content))

[0303] 50 mg of the conjugated diene polymer before hydrogenation was dissolved in 10 mL of carbon disulfide to prepare a measurement sample.

[0304] Use a solution dish at 600-1000cm -1 The infrared spectrum was measured in the range of , and the microstructure of the butadiene part, that is, the amount of 1,2-vinyl bonds (mol %), was obtained from the absorbance at a specified wave number according to the calculation formula of the Hampton method (RR Hampton, Analytical Chemistry 21, 923 (1949)). As a measuring device, a Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation was used.

[0305] (Weight average molecular weight of conjugated diene polymer)

[0306] The chromatogram was measured using a GPC measuring apparatus to which three columns using polystyrene-based gel as a filler were connected, and the weight average molecular weight of the conjugated diene polymer was determined based on a calibration curve obtained using standard polystyrene.

[0307] As the eluent, THF (tetrahydrofuran) added with 5 mmol / L triethylamine was used.

[0308] As the columns, guard columns: trade name "TSKguardcolumn SuperH-H" manufactured by Tosoh Corporation, and columns: trade names "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgelSuperH7000" manufactured by Tosoh Corporation were used.

[0309] An RI detector (trade name "HLC8020" manufactured by Tosoh Corporation) was used under the conditions of an oven temperature of 40°C and a THF flow rate of 0.6 mL / min.

[0310] 10 mg of a measurement sample 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.

[0311] (Modification rate of conjugated diene polymer)

[0312] The modification rate of the conjugated diene polymer was measured by the column adsorption GPC method as follows: The measurement was performed by utilizing the property that the conjugated diene polymer modified with the nitrogen atom-containing functional group is adsorbed on the column.

[0313] The adsorption amount on the silica column was measured from the difference between the chromatogram obtained by measuring a sample solution containing the sample and low molecular weight internal standard polystyrene using a polystyrene column and the chromatogram obtained by measuring a silica column, and the modification rate was obtained.

[0314] Specifically, it is as follows.

[0315] <Preparation of sample solution>:

[0316] 10 mg of a sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a sample solution.

[0317] <GPC Measurement Conditions Using a Polystyrene Column>

[0318] THF with 5 mmol / L triethylamine added was used as the eluent, and 20 μL of the sample solution was injected into the device for measurement. For the column, a guard column: a trade name "TSKguardcolumn SuperH-H" manufactured by Tosoh Corporation, and a column: a trade name "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgelSuperH7000" manufactured by Tosoh Corporation were used. The chromatogram was obtained by using an RI detector (HLC8020 manufactured by Tosoh Corporation) at a column box temperature of 40°C and a THF flow rate of 0.6 mL / min.

[0319] <GPC measurement conditions using silica column>:

[0320] A product named "HLC-8320GPC" manufactured by Tosoh Corporation was used, THF was used as an 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 box temperature of 40°C and a THF flow rate of 0.5 ml / min. As for the column, a product named "Zorbax PSM-1000S", "PSM-300S", and "PSM-60S" were connected and used, and a product named "DIOL 4.6×12.5 mm 5 micron" was connected as a guard column in the front section.

[0321] <Calculation method of modification rate>:

[0322] The overall peak area of ​​the chromatogram obtained using a polystyrene column is set to 100, the peak area of ​​the sample is set to P1, and the peak area of ​​the standard polystyrene is set to P2. The overall peak area of ​​the chromatogram obtained using a silica column is set to 100, the peak area of ​​the sample is set to P3, and the peak area of ​​the standard polystyrene is set to P4, and the modification rate (%) is calculated by the following formula.

[0323] Modification rate (%) = [1-(P2×P3) / (P1×P4)]×100

[0324] (where P1+P2=P3+P4=100)

[0325] (Hydrogenation rate of conjugated diene polymer)

[0326] A large amount of methanol is added to the reaction liquid of the conjugated diene polymer after the hydrogenation reaction, thereby precipitating the conjugated diene polymer before hydrogenation and the hydrogenated conjugated diene polymer, and the resulting products are recovered.

[0327] Next, the hydrogenated conjugated diene polymer was extracted with acetone, and the hydrogenated conjugated diene polymer was vacuum dried.

[0328] Use it as 1 The hydrogenation rate of the sample subjected to the H-NMR measurement was measured.

[0329] 1 The conditions for H-NMR measurement are as follows.

[0330] <Measurement Conditions>

[0331] Measuring equipment: JNM-LA400 (manufactured by JEOL)

[0332] Solvent: deuterated chloroform

[0333] Measurement samples: Extracts of polymers before and after hydrogenation

[0334] Sample concentration: 50 mg / mL

[0335] Observation frequency: 400MHz

[0336] Chemical shift standard: TMS (tetramethylsilane)

[0337] Pulse delay: 2.904 seconds

[0338] Scan times: 64 times

[0339] Pulse width: 45°

[0340] Measurement temperature: 26℃

[0341] (Styrene Amount of Conjugated Diene Polymer (Mass %))

[0342] The conjugated diene polymer was used as a sample, and 100 mg of the sample was fixed to 100 mL with chloroform and dissolved to prepare a measurement sample. The amount of styrene in the sample (mass %) was measured by the absorption of the ultraviolet absorption wavelength (near 254 nm) caused by the phenyl group of styrene (measuring device: spectrophotometer "UV-2450" manufactured by Shimadzu Corporation).

[0343] (Glass transition temperature of conjugated diene polymer (°C))

[0344] The conjugated diene polymer was used as a sample and the glass transition temperature was measured using a differential scanning calorimeter in accordance with JIS K6240.

[0345] (Nitrogen content of conjugated diene polymer)

[0346] The conjugated diene polymer was used as a sample, and the nitrogen content was measured using a micro nitrogen analyzer (Nitto Seiko Analytech TN-2100H).

[0347] (Mooney viscosity (ML) of conjugated diene polymer)

[0348] The Mooney viscosity was measured using a conjugated diene polymer as a sample according to the method specified in ISO289.

[0349] In the following Tables 1 to 3, the value of the Mooney viscosity measured at 100° C. is described as ML.

[0350] (Mooney stress relaxation ratio (MSR) of conjugated diene polymers)

[0351] The Mooney viscosity (ML) of the conjugated diene polymer was measured at 100° C., and then the rotation of the rotor was stopped and the attenuation of the torque applied to the rotor was measured for 30 seconds.

[0352] The relaxation time and the decay of the Mooney viscosity were plotted using double logarithm, and the slope was calculated as the Mooney stress relaxation rate (MSR).

[0353] (Cold Flow Properties of Conjugated Diene Polymers (Evaluation 1))

[0354] Using the conjugated diene polymer as a sample, a 10 cm square cubic sample was cut out to prepare an evaluation sample.

[0355] After placing a 1 kg weight on the evaluation sample and leaving it for 30 minutes, the change rate of the height of the evaluation sample before and after the weight was placed for 30 minutes was regarded as cold flowability and evaluated according to the following criteria.

[0356] 0:Height change rate is less than 10%

[0357] △: The height change rate is 10% or more and less than 15%

[0358] ×: The height change rate is 15% or more

[0359] From the aspect of maintaining the moldability during the storage of the conjugated diene polymer, 〇 is preferred, and △ is secondarily preferred.

[0360] (Molecular weight between entanglement points of conjugated diene polymer)

[0361] Using the conjugated diene polymer as a specimen, measure the elastic modulus Gn at 27 °C using ARES-G2 manufactured by TA Instrument.

[0362] Calculate the molecular weight between entanglement points based on the obtained elastic modulus Gn and the following formula.

[0363] Molecular weight between entanglement points = cRT / Gn

[0364] c: 0.9×10 6 (g / m 3 )

[0365] R: 8.31 (J / K / mol)

[0366] T: 300 (K)

[0367] Gn: Elastic modulus measured by ARES (Pa)

[0368] <Measurement conditions of ARSE-G2>

[0369] Mode: Compression mode

[0370] Strain: 0.05%

[0371] Frequency: 1 Hz

[0372] Use a substance obtained by pressing the conjugated diene polymer into a thickness of 1 mm and stamping it into a circle with a diameter of 10 mm as the measurement specimen.

[0373] [Manufacture of conjugated diene polymer]

[0374] (Preparation of hydrogenation catalyst)

[0375] Prepare the hydrogenation catalyst used in the preparation of the conjugated diene polymer in the following examples and comparative examples by the method of the following production example.

[0376] <Production example>

[0377] Into a nitrogen-purged reaction vessel, 1 liter of dried and purified cyclohexane was placed, 100 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added, and an n-hexane solution containing 200 mmol of trimethylaluminum was added while stirring thoroughly. The mixture was reacted at room temperature for about 3 days to obtain a hydrogenation catalyst (TC-1).

[0378] (Polymerization of Conjugated Diene Polymer)

[0379] <(Example 1) Conjugated Diene Polymer A1>

[0380] A temperature-controllable autoclave having an internal volume of 43 L and equipped with a stirrer and a jacket was used as a reactor. 3,956.0 g of 1,3-butadiene from which impurities had been removed in advance, 344.0 g of styrene, 25,800 g of cyclohexane, and 7.8 g of 2,2-di(2-tetrahydrofuryl)propane as a polar compound were added to the reactor, and the internal temperature of the reactor was maintained at 42°C.

[0381] Next, 1.7 g of n-butyllithium was supplied to the reactor as a polymerization initiator.

[0382] After the polymerization reaction started, the temperature in the reactor began to rise due to the heat generated by the polymerization. After the temperature rise was completed, 2.8 g of 1,3-dimethyl-2-imidazolidinone was added to the reactor as a modifier and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain a conjugated diene polymer before hydrogenation.

[0383] Thereafter, the hydrogenation catalyst (TC-1) prepared in the above <Production Example> was added to the conjugated diene polymer solution before hydrogenation in an amount of 60 ppm based on Ti per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes under the conditions of a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain a conjugated diene polymer A1.

[0384] The hydrogenation rate of the obtained conjugated diene polymer A1 was 68 mol%.

[0385] To the obtained conjugated diene polymer solution, 12.6 g of n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants.

[0386] Table 1 shows the analysis values ​​of the conjugated diene polymer A1.

[0387] <(Example 2) Conjugated Diene Polymer A2>

[0388] A temperature-controllable autoclave having an internal volume of 43 L and equipped with a stirrer and a jacket was used as a reactor. 3,569.0 g of 1,3-butadiene from which impurities had been removed in advance, 731.0 g of styrene, 25,800 g of cyclohexane, and 7.8 g of 2,2-di(2-tetrahydrofuryl)propane as a polar compound were added to the reactor, and the temperature inside the reactor was maintained at 42°C.

[0389] Next, 1.6 g of n-butyllithium was supplied to the reactor as a polymerization initiator.

[0390] After the polymerization reaction started, the temperature in the reactor began to rise due to the heat generated by the polymerization. After the temperature rise was completed, 2.6 g of 1,3-dimethyl-2-imidazolidinone was added to the reactor as a modifier and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain a conjugated diene polymer before hydrogenation.

[0391] Thereafter, the hydrogenation catalyst (TC-1) prepared in the above <Production Example> was added to the conjugated diene polymer solution before hydrogenation in an amount of 60 ppm based on Ti per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes under the conditions of a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain a conjugated diene polymer A2.

[0392] The hydrogenation rate of the obtained conjugated diene polymer A2 was 68 mol%.

[0393] To the obtained conjugated diene polymer solution, 12.6 g of n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants.

[0394] Table 1 shows the analysis values ​​of the conjugated diene polymer A2.

[0395] <(Example 3) Conjugated Diene Polymer A3>

[0396] A temperature-controllable autoclave with an internal volume of 43 L and equipped with a stirrer and a jacket was used as a reactor. 4,171.0 g of 1,3-butadiene from which impurities had been removed in advance, 129.0 g of styrene, 25,800 g of cyclohexane, and 8.2 g of 2,2-di(2-tetrahydrofuryl)propane as a polar compound were added to the reactor, and the temperature inside the reactor was maintained at 42°C.

[0397] Next, 1.8 g of n-butyllithium was supplied to the reactor as a polymerization initiator.

[0398] After the polymerization reaction started, the temperature in the reactor began to rise due to the heat generated by the polymerization. After the temperature rise was completed, 2.9 g of 1,3-dimethyl-2-imidazolidinone was added to the reactor as a modifier and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain a conjugated diene polymer before hydrogenation.

[0399] Thereafter, the hydrogenation catalyst (TC-1) prepared in the above <Production Example> was added to the conjugated diene polymer solution before hydrogenation in an amount of 60 ppm based on Ti per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes under the conditions of a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain a conjugated diene polymer A3.

[0400] The hydrogenation rate of the obtained conjugated diene polymer A3 was 68 mol%.

[0401] To the obtained conjugated diene polymer solution, 12.6 g of n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants.

[0402] Table 1 shows the analysis values ​​of the conjugated diene polymer A3.

[0403] <(Example 4) Conjugated Diene Polymer A4>

[0404] The production conditions other than the amount of hydrogenation were the same as in Example 1 to obtain a conjugated diene polymer A4.

[0405] Table 1 shows the analysis values ​​of the conjugated diene polymer A4.

[0406] <(Example 5) Conjugated Diene Polymer A5>

[0407] The production conditions other than the amount of hydrogenation were the same as in Example 1 to obtain a conjugated diene polymer A5.

[0408] Table 1 shows the analysis values ​​of the conjugated diene polymer A5.

[0409] <(Example 6) Conjugated Diene Polymer A6>

[0410] A conjugated diene polymer A6 was obtained in the same manner as in Example 1 except that the added amount of n-butyllithium as a polymerization initiator was changed to 1.3 g and the added amount of 1,3-dimethyl-2-imidazolidinone as a modifier was changed to 2.1 g.

[0411] Table 1 shows the analysis values ​​of the conjugated diene polymer A6.

[0412] <(Example 7) Conjugated Diene Polymer A7>

[0413] A conjugated diene polymer A7 was obtained in the same manner as in Example 1 except that the added amount of n-butyllithium as the polymerization initiator was changed to 3.0 g and the added amount of 1,3-dimethyl-2-imidazolidinone as the modifier was changed to 4.9 g.

[0414] Table 1 shows the analysis values ​​of the conjugated diene polymer A7.

[0415] <(Example 8) Conjugated Diene Polymer A8>

[0416] A conjugated diene polymer A8 was obtained in the same manner as in Example 1 except that the added amount of 1,3-dimethyl-2-imidazolidinone as a modifier was changed to 1.6 g.

[0417] Table 1 shows the analysis values ​​of the conjugated diene polymer A8.

[0418] <(Example 9) Conjugated Diene Polymer A9>

[0419] A temperature-controllable autoclave having an internal volume of 43 L and equipped with a stirrer and a jacket was used as a reactor. 3,956.0 g of 1,3-butadiene from which impurities had been removed in advance, 344.0 g of styrene, 25,800 g of cyclohexane, and 18.3 g of 2,2-di(2-tetrahydrofuryl)propane as a polar compound were added to the reactor, and the internal temperature of the reactor was maintained at 42°C.

[0420] Next, 4.1 g of n-butyllithium was supplied to the reactor as a polymerization initiator.

[0421] After the polymerization reaction started, the temperature in the reactor began to rise due to the heat generated by the polymerization. After the temperature rise was completed, 6.4 g of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilacyclopentane was added to the reactor as a modifier and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain a conjugated diene polymer before hydrogenation.

[0422] Thereafter, the hydrogenation catalyst (TC-1) prepared in the above <Production Example> was added to the conjugated diene polymer solution before hydrogenation in an amount of 60 ppm based on Ti per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes under the conditions of a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain a conjugated diene polymer A9.

[0423] The hydrogenation rate of the obtained conjugated diene polymer A9 was 68 mol%.

[0424] To the obtained conjugated diene polymer solution, 12.6 g of n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants.

[0425] Table 1 shows the analysis values ​​of the conjugated diene polymer A9.

[0426] <(Example 10) Conjugated Diene Polymer A10>

[0427] A conjugated diene polymer A10 was obtained in the same manner as in Example 1 except that the amount of the polar compound 2,2-di(2-tetrahydrofuryl)propane added was changed to 4.9 g.

[0428] Table 2 shows the analysis values ​​of the conjugated diene polymer A10.

[0429] <(Example 11) Conjugated Diene Polymer A11>

[0430] A conjugated diene polymer A11 was obtained in the same manner as in Example 1 except that 2.0 g of ethanol was added instead of the modifier when the polymerization was completed.

[0431] Table 2 shows the analysis values ​​of the conjugated diene polymer A11.

[0432] <(Example 12) Conjugated Diene Polymer A12>

[0433] A conjugated diene polymer A12 was obtained in the same manner as in Example 5 except that the amount of the polar compound 2,2-di(2-tetrahydrofuryl)propane added was changed to 8.1 g and the amount of hydrogenation was changed.

[0434] Table 2 shows the analysis values ​​of the conjugated diene polymer A12.

[0435] <(Example 13) Conjugated diene polymer A13>

[0436] A conjugated diene polymer A13 was obtained in the same manner as in Example 1 except that the added amount of the polymerization initiator n-butyllithium was 4.1 g, the added amount of the polar compound 2,2-di(2-tetrahydrofuryl)propane was 11.3 g, and the modifier was changed to 4.1 g of 1-methyl-4-[3-(triethoxysilyl)propyl]piperazine.

[0437] Table 2 shows the analysis values ​​of the conjugated diene polymer A13.

[0438] <(Example 14) Conjugated Diene Polymer A14>

[0439] A conjugated diene polymer A14 was obtained in the same manner as in Example 9 except that the amount of the polar compound 2,2-di(2-tetrahydrofuryl)propane added was changed to 18.5 g and the amount of the modifier 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilacyclopentane added was changed to 3.9 g.

[0440] Table 2 shows the analysis values ​​of the conjugated diene polymer A14.

[0441] <(Example 15) Conjugated diene polymer A15>

[0442] The conjugated diene polymer A15 was obtained in the same manner as in Example 9 except that the added amount of the polymerization initiator n-butyl lithium was changed to 2.2 g, the added amount of the polar compound 2,2-di(2-tetrahydrofuryl)propane was changed to 9.9 g, and the added amount of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilacyclopentane as a modifier was changed to 3.4 g.

[0443] Table 2 shows the analysis values ​​of the conjugated diene polymer A15.

[0444] <(Example 16) Conjugated Diene Polymer A16>

[0445] A temperature-controllable autoclave having an internal volume of 43 L and equipped with a stirrer and a jacket was used as a reactor. 3,999.0 g of 1,3-butadiene from which impurities had been removed in advance, 301.0 g of styrene, 25,800 g of cyclohexane, and 59.9 g of 2,2-di(2-tetrahydrofuryl)propane as a polar compound were added to the reactor, and the temperature inside the reactor was maintained at 42°C.

[0446] Next, 8.1 g of n-butyllithium was supplied to the reactor as a polymerization initiator.

[0447] After the polymerization reaction started, the temperature in the reactor began to rise due to heat generation caused by the polymerization. After the temperature rise was completed, 1.6 g of silicon tetrachloride as a modifier was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain a conjugated diene polymer before hydrogenation.

[0448] Thereafter, the hydrogenation catalyst (TC-1) prepared in the above <Production Example> was added to the conjugated diene polymer solution before hydrogenation in an amount of 60 ppm based on Ti per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 40 minutes under the conditions of a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain a conjugated diene polymer A16.

[0449] The hydrogenation rate of the obtained conjugated diene polymer A16 was 55 mol%.

[0450] To the obtained conjugated diene polymer solution, 12.6 g of n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants.

[0451] Table 2 shows the analysis values ​​of the conjugated diene polymer A16.

[0452] <(Example 17) Conjugated Diene Polymer A17>

[0453] A conjugated diene polymer A17 was obtained in the same manner as in Example 1 except that the added amount of 1,3-dimethyl-2-imidazolidinone as a modifier was changed to 1.9 g.

[0454] Table 2 shows the analysis values ​​of the conjugated diene polymer A17.

[0455] <(Example 18) Conjugated diene polymer A18>

[0456] A conjugated diene polymer A18 was obtained in the same manner as in Example 1 except that the amount of the polar compound 2,2-di(2-tetrahydrofuryl)propane added was changed to 1.8 g.

[0457] Table 2 shows the analysis values ​​of the conjugated diene polymer A18.

[0458] <(Comparative Example 1) Conjugated Diene Polymer B1>

[0459] A temperature-controllable autoclave having an internal volume of 43 L and equipped with a stirrer and a jacket was used as a reactor. 3,956.0 g of 1,3-butadiene from which impurities had been removed in advance, 344.0 g of styrene, 25,800 g of cyclohexane, and 19.9 g of 2,2-di(2-tetrahydrofuryl)propane as a polar compound were added to the reactor, and the internal temperature of the reactor was maintained at 42°C.

[0460] Next, 4.4 g of n-butyllithium was supplied to the reactor as a polymerization initiator.

[0461] After the polymerization reaction started, the temperature in the reactor began to rise due to the heat generated by the polymerization. After the temperature rise was completed, 4.8 g of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilacyclopentane was added to the reactor as a modifier and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain a conjugated diene polymer before hydrogenation.

[0462] Thereafter, the hydrogenation catalyst (TC-1) prepared in the above <Production Example> was added to the conjugated diene polymer solution before hydrogenation in an amount of 60 ppm based on Ti per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes under the conditions of a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain a conjugated diene polymer B1.

[0463] The hydrogenation rate of the obtained conjugated diene polymer B1 was 68 mol%.

[0464] To the obtained conjugated diene polymer solution, 12.6 g of n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants.

[0465] Table 3 shows the analysis values ​​of the conjugated diene polymer B1.

[0466] <(Comparative Example 2) Conjugated Diene Polymer B2>

[0467] A conjugated diene polymer B2 was obtained in the same manner as in Example 2 except that the amount of butadiene added was changed to 3225.0 g and the amount of styrene added was changed to 1075.0 g.

[0468] Table 3 shows the analysis values ​​of the conjugated diene polymer B2.

[0469] <(Comparative Example 3) Rubber-like polymer B3>

[0470] A conjugated diene polymer B3 was obtained in the same manner as in Example 10 except that the amount of the polar compound 2,2-di(2-tetrahydrofuryl)propane added was changed to 3.1 g.

[0471] Table 3 shows the analysis values ​​of the conjugated diene polymer B3.

[0472] <(Comparative Example 4) Conjugated Diene Polymer B4>

[0473] A temperature-controllable autoclave having an internal volume of 43 L and equipped with a stirrer and a jacket was used as a reactor. 3,956.0 g of 1,3-butadiene from which impurities had been removed in advance, 344.0 g of styrene, 25,800 g of cyclohexane, and 10.6 g of 2,2-di(2-tetrahydrofuryl)propane as a polar compound were added to the reactor, and the internal temperature of the reactor was maintained at 42°C.

[0474] Next, 12.6 g of n-butyllithium was supplied to the reactor as a polymerization initiator.

[0475] After the temperature rise in the reactor was completed, 20.2 g of 1,3-dimethyl-2-imidazolidinone was added to the reactor as a modifier, and the mixture was stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain a conjugated diene polymer before hydrogenation.

[0476] Thereafter, the hydrogenation catalyst (TC-1) prepared in the above <Production Example> was added to the conjugated diene polymer solution before hydrogenation in an amount of 60 ppm based on Ti per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes under the conditions of a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain a conjugated diene polymer B4.

[0477] The hydrogenation rate of the obtained conjugated diene polymer B4 was 68 mol%.

[0478] To the obtained solution of the conjugated diene polymer B4, 12.6 g of n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants.

[0479] Table 3 shows the analysis values ​​of the conjugated diene polymer B4.

[0480] <(Comparative Example 5) Conjugated Diene Polymer B5>

[0481] A conjugated diene polymer B5 was obtained in the same manner as in Example 1 except that the amount of hydrogenation was changed.

[0482] Table 3 shows the analysis values ​​of the conjugated diene polymer B5.

[0483] <(Comparative Example 6) Conjugated Diene Polymer B6>

[0484] A conjugated diene polymer B6 was obtained in the same manner as in Example 3 except that the amount of butadiene added was changed to 4300.0 g and the amount of styrene added was changed to 0 g.

[0485] Table 3 shows the analysis values ​​of the conjugated diene polymer B6.

[0486] <(Comparative Example 7) Conjugated Diene Polymer B7>

[0487] A conjugated diene polymer B7 was obtained in the same manner as in Comparative Example 1 except that the added amount of the polymerization initiator n-butyllithium was changed to 6.8 g, the added amount of the polar compound 2,2-di(2-tetrahydrofuryl)propane was changed to 30.4 g, and the added amount of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilacyclopentane as a modifier was changed to 7.3 g.

[0488] Table 3 shows the analysis values ​​of the conjugated diene polymer B7.

[0489]

[0490]

[0491]

[0492] [Examples 19 to 37], [Comparative Examples 8 to 14]

[0493] (Preparation and physical property evaluation of cross-linking rubber composition)

[0494] Conjugated diene polymers A1 to A18 obtained in Examples 1 to 18 and conjugated diene polymers B1 to B7 obtained in Comparative Examples 1 to 7 shown in Tables 1 to 3 were used to obtain crosslinking rubber compositions containing the respective raw material rubbers in the following blending ratios.

[0495] The mixing conditions are as follows.

[0496] (Mixing conditions)

[0497] The addition amount of each compounding agent in Tables 4 to 6 is expressed as parts by mass relative to 100 parts by mass of the rubber component excluding the rubber softener.

[0498] Conjugated diene polymers: A1~A18, B1~B7

[0499] Natural rubber: RSS3

[0500] · High cis-butadiene: manufactured by UBE Co., Ltd.

[0501] Silicon oxide: VN3 (N2SA: 175m 2 / g)

[0502] Carbon black: Diablack N339 (N2SA: 96m 2 / g, DBP absorption value: 124mL / 100g)

[0503] Softener: DIANA Process AH-24 (aromatic oil) manufactured by Idemitsu Kosan Co., Ltd.

[0504] Silane coupling agent: Si69 manufactured by Evonik Degussa

[0505] Anti-aging agent: NOCRAC 6C manufactured by Ouchi Shinko Chemical Co., Ltd.

[0506] · Stearic acid: Beads Stearic Acid "Tsubaki" manufactured by NOF Corporation

[0507] Zinc oxide: Zinc Oxide III manufactured by Hakusui Tech Co., Ltd.

[0508] Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.

[0509] ・Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd.

[0510] Vulcanization accelerator: NOCCELER CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0511] (Kneading method and evaluation of moldability of rubber composition)

[0512] The above materials were kneaded by the following method to obtain a rubber composition for cross-linking.

[0513] According to the formulations described in Tables 4 to 6, rubber compositions of Examples and Comparative Examples were prepared.

[0514] A closed mixer (content 0.3 L) equipped with a temperature control device was used as the first stage of mixing to mix the rubber component, silica, carbon black, silane coupling agent, softener, zinc oxide and stearic acid at a filling rate of 65% and a rotor speed of 30 to 50 rpm.

[0515] At this time, the temperature of the internal mixer was controlled to obtain each rubber composition (compound) at a discharge temperature of 155 to 160°C.

[0516] Next, as the second stage of kneading, the mixture obtained above was cooled to room temperature, an antioxidant was added, and kneading was performed again to improve the dispersion of silicon oxide. In this case, the discharge temperature of the mixture was adjusted to 155-160°C by temperature control of the mixer.

[0517] After cooling, as the third stage of kneading, sulfur and a vulcanization accelerator were added and kneaded in an open roll mill set at 70° C. After kneading, the moldability of the rubber composition was evaluated based on the surface roughness of the cross-linking rubber composition sheet discharged from the open roll mill.

[0518] Thereafter, the rubber composition was molded and vulcanized at 160° C. using a press vulcanizer, and the vulcanized rubber composition was evaluated.

[0519] The curing time was set to a value obtained by adding 5 minutes to the 90% curing time of each sample measured by the method described later.

[0520] Specifically, the evaluation was performed by the following method. The evaluation results are shown in Tables 4 to 6.

[0521] <Evaluation 2: Crack Growth Resistance of Rubber Composition>

[0522] A dumbbell-shaped specimen No. 5 of the rubber composition with initial cracks was stretched under the conditions of a strain of 100% and 300 rpm using FT-3132 manufactured by Kitahama Seisakusho, and the number of times until fracture was measured to evaluate the crack growth resistance of the rubber composition.

[0523] In Tables 4 to 6, the fatigue resistance of Comparative Example 8 is numerically expressed as 100. The conjugated diene polymer of the present embodiment aims to achieve a value of 120 or more in order to exhibit excellent crack growth resistance.

[0524] <Evaluation 3: Elongation at break>

[0525] The tensile strength was measured according to the tensile test method of JIS K6251.

[0526] In Tables 4 to 6, the elongation at break of Comparative Example 8 is numerically expressed as 100. The conjugated diene polymer of the present embodiment aims to achieve a value of 50 or more in order to show an excellent balance between crack growth resistance and elongation at break.

[0527] <Evaluation 4: Fuel-saving performance of rubber composition>

[0528] Viscoelastic parameters were measured in torsional vibration mode using a viscoelasticity tester "ARES-G2" manufactured by TA Instruments. Tan δ measured at 50°C, 10 Hz, and 3% strain was used as an index of fuel efficiency, and the fuel efficiency of Comparative Example 8 was 100 and numerically expressed.

[0529]

[0530]

[0531]

[0532] As shown in Tables 4 to 6, it can be seen that Examples 19 to 37 are superior to Comparative Examples 8 to 14 in the evaluation of crack growth resistance and elongation at break, and that the balance of these characteristics is also good.

[0533] This application is based on the Japanese patent application (Japanese Patent Application No. 2022-108011) filed with the Japan Patent Office on July 4, 2022, the contents of which are incorporated into this specification by reference.

[0534] Industrial Applicability

[0535] The conjugated diene polymer of the present invention has industrial applicability in the fields of tire treads, sidewalls and other tire casing parts, automobile interior and exterior materials, anti-vibration rubber, belts, shoes, foams, various industrial products, and the like.

Claims

1. A conjugated diene polymer, wherein: The molecular weight between entanglement points is 2400 g / mol or more and 3000 g / mol or less. The Mooney viscosity measured at 100° C. is 40 or more, and the Mooney stress relaxation rate (MSR) is 0.8 or more, The content of the vinyl aromatic monomer unit is 1% by mass or more and 18% by mass or less.

2. The conjugated diene polymer according to claim 1, wherein The weight average molecular weight is 300,000 or more.

3. The conjugated diene polymer according to claim 1, wherein The nitrogen content is 70 ppm or more and 300 ppm or less, and the modification rate is 60% or more.

4. The conjugated diene polymer according to claim 1, wherein The Mooney stress relaxation ratio (MSR) is 0.80 or more and 1.80 or less.

5. The conjugated diene polymer according to claim 1, wherein Among the content of the structure represented by the following formula (1): C1 mol%, the content of the structure represented by the following formula (2): C2 mol%, the content of the structure represented by the following formula (3): C3 mol%, and the content of the structure represented by the following formula (4): C4 mol%, [Chemistry 1] The difference α between the value of (C2+C4) / (C1+C2+C3+C4) and the value of (C1+C2) / (C1+C2+C3+C4) is 0.1 or less.

6. The conjugated diene polymer according to claim 1, wherein The nitrogen content is 90ppm or more and 300ppm or less. The modification rate is more than 60%.

7. The conjugated diene polymer according to claim 1, wherein The conjugated diene polymer is a hydrogenated styrene-butylene copolymer having a hydrogenation rate of 50 mol% or more.

8. A rubber composition comprising: 100 parts by mass of a rubber component comprising 30 parts by mass or more of the conjugated diene polymer according to any one of claims 1 to 7 and 30 parts by mass or more of a natural rubber; and 30 parts by mass or more of carbon black. 9 . A tire component, comprising the rubber composition according to claim 8 .

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