Conjugated diene polymer, rubber composition, and tire component

Abstract

This conjugated diene polymer has an entanglement molecular weight of 2400 g / mol to 3000 g / mol, a Mooney viscosity measured at 100°C of 40 or higher, a Mooney stress relaxation (MSR) of 0.8 or higher, and a vinyl aromatic monomer unit content of 1 mass% to 18 mass%.

Description

[Technical Field]

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

[0002] To reduce environmental impact, there has long been a demand for longer lifespan automobile tires. One of the challenges hindering tire lifespan is crack growth due to repeated strain during driving, and deterioration of the sidewall due to chipping from flying stones.

[0003] As a rubber composition for tires that meets the demand for longer tire life as described above, a rubber composition having high crack growth resistance and chipping resistance is required. It is known that the chipping resistance of a tire is correlated with the elongation at break of the rubber composition. For this reason, improvements in the crack growth resistance and elongation at break of the rubber composition are required to extend the life of tires. Generally, methods for improving the breaking properties, including the elongation at break, of rubber compositions include increasing the molecular weight of the rubber. As a method for improving the crack growth properties of rubber compositions, a method utilizing high-molecular-weight, low-branched polybutadiene has been disclosed (see, for example, Patent Document 1). As described above, in order to improve the breaking elongation and crack growth resistance of a rubber composition for tires, it is considered preferable to use a rubber composition containing a high-molecular-weight, low-branched polybutadiene. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-218503 Summary of the Invention [Problem to be solved by the invention]

[0005] However, high molecular weight polybutadienes have a high entanglement density between rubber molecules, and therefore do not have sufficient energy dissipation properties. Therefore, rubber compositions using such high molecular weight polybutadienes have the problem that there is room for improvement in terms of crack growth resistance.

[0006] Therefore, an object of the present invention is to provide a conjugated diene polymer from which a rubber composition having an excellent balance between elongation at break and crack growth resistance can be obtained. [Means for solving the problem]

[0007] As a result of intensive research and investigation into solving the above-mentioned problems of the prior art, the present inventors have found that the above-mentioned problems of the prior art can be solved by making a conjugated diene polymer have a specific entanglement point molecular weight, a Mooney viscosity and a Mooney stress relaxation of predetermined values ​​or more, and a content of vinyl aromatic monomer units within a predetermined numerical range, and have thus completed the present invention. That is, the present invention is as follows.

[0008] [1] 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 (MSR) is 0.8 or more, The content of vinyl aromatic monomer units is 1% by mass or more and 18% by mass or less. Conjugated diene polymers. [2] The conjugated diene polymer according to [1] above, having a weight average molecular weight of 300,000 or more. [3] The conjugated diene polymer according to [1] or [2] above, having a nitrogen content of 70 ppm or more and 300 ppm or less and a modification rate of 60% or more. [4] The Mooney stress relaxation (MSR) is 0.80 or more and 1.80 or less. The conjugated diene polymer according to any one of [1] to [3] above. [5] 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%,

[0009] [ka]

[0010] The value of (C2+C4) / (C1+C2+C3+C4) and The difference α between the value of (C1+C2) / (C1+C2+C3+C4) and the value of (C1+C2) / (C1+C2+C3+C4) is 0.1 or less. The conjugated diene polymer according to any one of [1] to [4] above.

[0011] [6] The nitrogen content is 90 ppm or more and 300 ppm or less, The denaturation rate is 60% or more, The conjugated diene polymer according to any one of [1] to [5] above. [7] 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] 100 parts by mass of a rubber component containing 30 parts by mass or more of the conjugated diene polymer according to any one of [1] to [7] above and 30 parts by mass or more of natural rubber; 30 parts by mass or more of carbon black, A rubber composition comprising: [9] A tire component made of the rubber composition according to [8] above. [Effects of the Invention]

[0012] According to the present invention, a conjugated diene polymer can be provided that can give a rubber composition having an excellent balance between elongation at break and crack growth resistance. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. It should be noted that the following embodiments are merely examples for explaining the present invention, and the present invention is not limited to the following embodiments. The present invention can be practiced by appropriately modifying it within the scope of its gist.

[0014] [Conjugated diene polymer] The conjugated diene polymer of the present embodiment has an entanglement point molecular weight of 2400 to 3000 g / mol, a Mooney viscosity (ML) measured at 100°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 or more and 18% by mass or less. In this specification, the constituent elements of a polymer are referred to as "monomer units", and before polymerization they are referred to as "compounds".

[0015] As described above, by setting the molecular weight between entanglement points, Mooney viscosity (ML), Mooney stress relaxation (MSR), and content of vinyl aromatic monomer units in the conjugated diene polymer within predetermined numerical ranges, a rubber composition excellent in crack growth resistance and elongation at break tends to be obtained. The relationship between each structure and performance will be explained below.

[0016] (Molecular weight between entanglement points) The pseudo-equilibrium elastic modulus Gn and the molecular weight between entanglement points Me are Gn=cRT / Me (c is density, R is gas constant, and T is absolute temperature.) It is known that the following relationship holds (The Polymer Having the Highest Rubbery Plateau (Kobunshi Vol. 48, September issue (1999)). The molecular weight between entanglements is the molecular weight between entanglement points of molecular chains, and indicates the molecular weight of a unit that bears stress.

[0017] In the conjugated diene polymer of this embodiment, the entanglement molecular weight can be calculated by the following formula using the elastic modulus Gn at 27° C. as a variable. Molecular weight between entanglements = cRT / Gn (1) c:0.9×10 6 (g / m 3 ) R: 8.31 (J / K / mol) T:300(K) Gn: Elastic modulus Gn (Pa) at 27°C

[0018] In the formula (1), the density in the general formula is a constant. The reason for this is that although the density of a polymer depends on the temperature and the molecular structure, the temperature is constant at 27°C when measuring the elastic modulus, and in addition, the content of the vinyl aromatic monomer unit, which affects the density of the conjugated diene polymer of this embodiment, is specified to be 1% by mass or more and 18% by mass or less. In this range, the density can be reduced to 0.9 × 10 6 (g / m 3 ) and confirmed that it is acceptable to approximate it. Specifically, the entanglement point molecular weight of the conjugated diene polymer of the present embodiment can be measured by the method described in the examples below.

[0019] From the viewpoint of crack growth resistance of the rubber composition, the conjugated diene polymer of this embodiment has an entanglement molecular weight of 2400 to 3000 g / mol, preferably 2600 to 3000 g / mol, and more preferably 2700 to 3000 g / mol. The present inventors have conducted extensive research into the relationship between the crack growth resistance of rubber compositions and the structure of conjugated diene polymers, and have found a correlation between the crack growth resistance of rubber compositions and the entanglement molecular weight of the conjugated diene polymer. Regarding the mechanism, it has been experimentally confirmed that changing the molecular weight of the conjugated diene polymer has little effect on crack growth in rubber compositions, and that the entanglement density and number of branches of the conjugated diene polymer are dominant. In other words, the crack growth resistance of rubber compositions tends to improve as the entanglement density and degree of branching of the conjugated diene polymer decrease. Therefore, a high entanglement molecular weight of the conjugated diene polymer tends to reduce the entanglement density between polymer chains and decrease the entropy modulus. As a result, stress applied to the conjugated diene polymer is more easily dispersed, which is thought to improve the crack growth resistance of the rubber composition.

[0020] Methods for controlling the entanglement point molecular weight of the conjugated diene polymer of the present embodiment within a predetermined range include adjusting the content of vinyl aromatic monomer units in the conjugated diene polymer, the amount of 1,2-vinyl bonds (hereinafter sometimes referred to as the vinyl bond amount) in the conjugated diene polymer, and the hydrogenation rate. For example, the entanglement molecular weight of the conjugated diene polymer can be increased by increasing the amount of styrene, which is a vinyl aromatic compound, added in the polymerization process of the conjugated diene polymer. On the other hand, the entanglement molecular weight of the conjugated diene polymer can be controlled to be lower by decreasing the hydrogenation rate or increasing the amount of 1,2-vinyl bonds in the conjugated diene polymer before hydrogenation. Specifically, when the styrene content is 18% by mass, the molecular weight between entanglement points tends to increase due to the high styrene content, and therefore, by adjusting the amount of 1,2-vinyl bonds 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. On the other hand, when the styrene content is 1% by mass, the molecular weight between entanglement points tends to decrease due to the low styrene content, so the target molecular weight between entanglement points tends to be obtained by adjusting the amount of 1,2-vinyl bonds in the conjugated diene polymer before hydrogenation to 40 to 70 mol% and the hydrogenation rate to 50 to 90 mol%. The content of vinyl aromatic monomer units, the amount of 1,2-vinyl bonds, and the hydrogenation rate can be measured by the methods described in the Examples below.

[0021] (Vinyl aromatic monomer unit content) The conjugated diene polymer of this embodiment has a vinyl aromatic monomer unit content of 1% by mass or more and 18% by mass or less. From the viewpoint of the breaking properties when a rubber composition for crosslinking containing the conjugated diene polymer of this embodiment and a crosslinking 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. Examples of vinyl aromatic compounds constituting the vinyl aromatic monomer units include, but are not limited to, styrene, p-methylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene. Among these, styrene is preferred from the viewpoint of industrial availability. These may be used alone or in combination of two or more. The content of the vinyl aromatic monomer unit in the conjugated diene polymer of this embodiment can be controlled within the above numerical range by adjusting the amount of vinyl aromatic compound added in the polymerization step and the polymerization time.

[0022] (conjugated diene monomer units) The conjugated diene polymer of this embodiment contains conjugated diene monomer units. Conjugated diene compounds constituting the conjugated diene monomer units include, but are not limited to, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene. Among these, from the viewpoint of industrial availability, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred. These may be used alone or in combination of two or more.

[0023] (Mooney viscosity) The Mooney viscosity (ML) of a conjugated diene polymer is an index containing information such as the molecular weight, molecular weight distribution, degree of branching, and content of a softener of the conjugated diene polymer. 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 the elongation at break when a rubber composition for crosslinking containing the conjugated diene polymer and the crosslinking agent is used in a tire. On the other hand, from the viewpoints of productivity of the rubber composition containing the conjugated diene polymer of this embodiment and processability of the rubber composition blended with a filler or the like, the Mooney viscosity measured at 100°C is preferably 100 or less, more preferably 80 or less, and even more preferably 70 or less. The Mooney viscosity can be measured by the method specified in ISO289, which will be described later. The Mooney viscosity of the conjugated diene polymer can be controlled within the above-mentioned range by adjusting the amount of polymerization initiator added in the polymerization step of the conjugated diene polymer, and the amount and type of coupling agent added. For example, methods for increasing the Mooney viscosity of a conjugated diene polymer include reducing the amount of polymerization initiator added to increase the molecular weight before the coupling step, and using a coupling agent with a large maximum number of couplings. From the viewpoint of crack growth resistance of the rubber composition, a conjugated diene polymer with a low branched structure ratio is preferred. Since the more branches there are, the higher the Mooney viscosity tends to be. Therefore, when the Mooney viscosity is to be 40 or higher while reducing the branched structure ratio, the desired conjugated diene polymer tends to be obtained by adding about 0.001 g of polymerization initiator per 1 g of conjugated diene polymer.

[0024] (Mooney stress relaxation) The conjugated diene polymer of this embodiment has a Mooney stress relaxation (MSR) of 0.8 or more. The larger the MSR, the faster the stress relaxation rate, resulting in excellent energy dissipation. As with the interentanglement molecular weight, the higher the energy dissipation, the less stress concentrates, which tends to improve the crack growth resistance of the rubber composition. From the viewpoint of 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. Effective methods for controlling the MSR of a conjugated diene polymer to 0.8 or more include reducing the branching degree of the conjugated diene polymer and reducing the Mooney viscosity. Specifically, an unbranched conjugated diene polymer can achieve an MSR of about 1.4 at a Mooney viscosity of 80. Since both the Mooney viscosity and MSR of a conjugated diene polymer depend on the molecular weight and the degree of branching, in order to simultaneously bring both into the desired ranges, it is necessary to adjust the molecular weight and the degree of branching depending on their contribution to the control of the Mooney viscosity and MSR. An easily adoptable method is to adjust the molecular weight by adjusting the amount of polymerization initiator added so that the Mooney viscosity of the conjugated diene polymer falls within the desired range, and then adjust the degree of branching by selecting the type of coupling agent. From the viewpoint of the storage stability (cold flow property) 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 even more preferably 1.30 or less. As a method for lowering the MSR, a method of increasing the branching degree of the conjugated diene polymer or a method of increasing the Mooney viscosity, which are the opposite of the above-mentioned methods, are effective. When the MSR is 1.80 or less, the polymer molecular chains are entangled sufficiently for practical use, and when the conjugated diene polymer is stored at room temperature, the molded shape can be maintained and deformation due to its own weight can be suppressed. Therefore, the cold flow property is a barometer of the storage stability of the conjugated diene polymer, and is closely correlated with the MSR and Mooney viscosity of the conjugated diene polymer. The MSR can be measured by the method described in the Examples below, and the cold flow property can be evaluated by the method described in the Examples below.

[0025] (Weight-average molecular weight of conjugated diene polymer) The conjugated diene polymer of the present embodiment preferably has a weight average molecular weight (Mw) determined by gel permeation chromatography (GPC) of 300,000 or more, more preferably 400,000 or more, and even more preferably 440,000 or more. When the Mw of the conjugated diene polymer is 300,000 or more, the vulcanizate tends to have high tensile strength. The Mw of the conjugated diene polymer of the present embodiment is preferably not more than 700,000, more preferably not more than 650,000, and even more preferably not more than 600,000. When the conjugated diene polymer of the present embodiment has an Mw of not more than 700,000, when used in a tire composition, the processability during kneading is excellent, the filler is sufficiently dispersed, and the fuel economy performance is excellent. The weight average molecular weight of the conjugated diene polymer can be calculated from the polystyrene-equivalent molecular weight measured by GPC, and can be measured by the method described in the examples below. 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 in the polymerization step, the polymerization time, the polymerization temperature, and the amount of polymerization initiator and polar compound added.

[0026] (Glass transition temperature of conjugated diene polymer) The conjugated diene polymer of the present embodiment preferably has a glass transition temperature (Tg) measured by a differential scanning calorimeter of −50° C. or lower, more preferably −55° C. or lower, and even more preferably −60° C. or lower. When the Tg is within the above range, the hysteresis loss of a vulcanizate containing the conjugated diene polymer decreases, and when the vulcanizate is used as a tire composition, the fuel-saving performance tends to be excellent. The Tg of the conjugated diene polymer can be measured by the method described in the Examples below.

[0027] (Modification of conjugated diene polymer) From the viewpoint of fuel-saving performance when used as a tire material, 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. In this embodiment, the compound having a nitrogen atom is referred to as a modifier, and the addition of the modifier to the conjugated diene polymer is referred to as modification.

[0028] (Modification rate of conjugated diene polymer) The conjugated diene polymer of the present embodiment preferably has a modification rate of 60% or more as measured by column adsorption GPC. When the modification rate is 60% or more, excellent fuel economy performance tends to be obtained when the vulcanizate containing carbon black and / or silica as a filler is used as a tire component. The modification rate of the conjugated diene polymer of the present embodiment is more preferably 70% or more, and further preferably 75% or more. The degree of modification can be measured by chromatography, which can separate the modified component containing the functional group from the unmodified component. Examples of methods using this type of chromatography include a method in which a gel permeation chromatography column filled with a polar compound such as silica that adsorbs specific functional groups is used, and the non-adsorbed components are quantified using an internal standard for comparison (column adsorption GPC method). More specifically, the modification rate can be obtained by measuring the amount of a sample solution containing the sample and low-molecular-weight internal standard polystyrene adsorbed to the silica-based column from the difference between a chromatogram measured on a polystyrene-based gel column and a chromatogram measured on a silica-based column. More specifically, the modification rate can be measured by the method described in the Examples. In the conjugated diene polymer of this embodiment, the modification rate can be controlled by adjusting the amount of modifier added and the reaction method, and can thereby be controlled within the above-mentioned numerical range. For example, the above modification rate can be controlled by combining a method of polymerization using an organolithium compound having at least one nitrogen atom in the molecule described below as a polymerization initiator, a method of copolymerizing a monomer having at least one nitrogen atom in the molecule, and a method of using a modifying agent having a structural formula described below, and controlling the polymerization conditions.

[0029] (nitrogen content) The conjugated diene polymer of the present embodiment preferably has a nitrogen content of 70 ppm or more and 300 ppm or less as measured by nitrogen trace analysis. A nitrogen content of 70 ppm or more tends to exhibit excellent fuel economy performance, and a nitrogen content of 90 ppm or more is more preferable, and a nitrogen content of 110 ppm or more is even more preferable. When the conjugated diene polymer of the present embodiment is terminally modified, even if the number of nitrogen atoms contained in the modifier is constant, the nitrogen content tends to decrease as the molecular chain becomes longer and the molecular weight increases. 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, from the viewpoint of processability. The nitrogen content can be measured by the method described in the Examples below. The nitrogen content can be controlled within the above range by adjusting the type and amount of the modifier. When comparing the same conjugated diene polymers, the higher the modification rate, the higher the nitrogen content tends to be, but the nitrogen content does not necessarily correlate with the modification rate because it also depends on the type and molecular weight of the modifier. As a result, as described above, the modification rate tends to affect the fuel economy performance when the conjugated diene polymer is used in a tire, and the nitrogen content tends to affect the tensile strength. In the conjugated diene polymer of this embodiment, as a method for separately controlling the modification rate and the nitrogen content, when increasing the nitrogen content while maintaining the modification rate, a method of adding a modifier with a high nitrogen content is effective. By using this modifier with a high nitrogen content, the modifier acts through hydrogen bonding with carbon black when kneading a rubber composition for tires using the conjugated diene polymer, thereby promoting the dispersion of carbon black and tending to improve fuel economy performance. Similarly, a method of adjusting the molecular weight can also be mentioned as a method for separately controlling the modification rate and the nitrogen content of the conjugated diene polymer. Specifically, by lowering the molecular weight of the conjugated diene polymer, the nitrogen content can be changed while maintaining the modification rate.

[0030] (denaturant) The denaturant is not particularly limited, and any conventionally known denaturant can be used. As the modifier, from the viewpoint of the fuel-saving performance of the vulcanizate 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. 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-silacycloheptane, 2,2-dimethoxy-1-(3-dimethoxymethyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacycloheptane, 2,2-dimethoxy-1-(3-dimethoxymethyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(4-trimethoxysilylbutyl ...4-trimethoxysilylbutyl)-1-aza-2-silacyclohexane silylpropyl)-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, and 2-ethoxy-2-ethyl-1-(3- 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, Examples include 3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, 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-propanediamine, 3-(4-methylpiperazin-1-yl)propyltriethoxysilane.

[0031] (Monomer unit having an unsaturated group of a conjugated diene polymer) The conjugated diene polymer of the present embodiment preferably contains 10% by mass or more of conjugated diene monomer units and monomer units having an unsaturated group such as myrcene (monomer units that are not hydrogenated and remain as unsaturated groups when a portion of the conjugated diene is hydrogenated). The monomer unit having an unsaturated group is not limited to a conjugated diene monomer unit or myrcene, and may include other monomer units. Since the conjugated diene monomer unit and myrcene have a double bond, the conjugated diene polymer of the present embodiment has a crosslinkable unsaturated group due to the inclusion of these monomer units. 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. By having the content of conjugated diene monomer units and monomer units having an unsaturated group such as myrcene be 10% by mass or more, the conjugated diene polymer of this embodiment is excellent in terms of ease of crosslinking. On the other hand, by having the content of monomer units having an unsaturated group be 10% by mass or more, there is a tendency for the entanglement point molecular weight to be easily set to a certain level or more, which is preferable in terms of crack growth resistance. In addition, the Mooney viscosity tends to be low, which is also preferable in terms of the processability of the conjugated diene polymer. The content of conjugated diene monomer units and monomer units having an unsaturated group such as myrcene is more preferably 15% by mass or more, and even more preferably 20% by mass or more. The content of conjugated diene monomer units and monomer units 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 result in excellent weather resistance and resistance to deterioration over time. As the conjugated diene monomer unit or the monomer unit having an unsaturated group such as myrcene, the conjugated diene monomer unit is preferred from the viewpoint of economy and productivity. 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 below, and can be controlled to fall within the above-mentioned numerical range by adjusting the amount of the conjugated diene monomer unit or the monomer having an unsaturated group such as myrcene, which will be described later, added, or the hydrogenation rate of the conjugated diene monomer.

[0032] In the conjugated diene polymer of the present embodiment, when 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 %, it is preferable that 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. Here, the value of (C2+C4) / (C1+C2+C3+C4) means the hydrogenation rate, and the value of (C1+C2) / (C1+C2+C3+C4) means the amount of 1,2-vinyl bonds before hydrogenation.

[0033] [ka]

[0034] When the 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. The α is more preferably 0.09 or less, and even more preferably 0.08 or less.

[0035] Furthermore, 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 even more preferably 65 mol % or more. Also, it is preferably 90 mol % or less, more preferably 85 mol % or less, and even more preferably 80 mol % or less. In the conjugated diene polymer of the present embodiment, the hydrogenation rate of the structural units derived from the conjugated diene compound is 50 mol % or more, and therefore the vulcanizate tends to have excellent ozone resistance. By keeping the hydrogenation rate of the structural units derived from the conjugated diene compound at 90 mol% or less, the crosslink density after vulcanization increases, and the breaking strength and fuel economy performance of the vulcanized product tend to be excellent. The hydrogenation rate of the conjugated diene polymer of the present embodiment can be controlled by adjusting the amount of hydrogen added to the structural units derived from the conjugated diene compound. The temperature of the hydrogenation reaction is not particularly limited, but is preferably 60 to 105°C, and more preferably 70 to 100°C. The hydrogenation rate is 1 It can be measured by H-NMR.

[0036] The hydrogenation rate of the conjugated diene polymer of the present embodiment, and the inter- or intramolecular distribution of ethylene units, conjugated diene monomer units, monomer units having an unsaturated group such as myrcene, and vinyl aromatic monomer units are not particularly limited, and may be uniform, non-uniform, or distributed.

[0037] (Softener for conjugated diene polymers) The conjugated diene polymer of the present embodiment may contain a rubber softener as needed. The content of the rubber softener is preferably 30% by mass or less. In the conjugated diene polymer of this embodiment, the amount of rubber softener added is preferably 1 to 30 mass % from the viewpoint of improving processability when inorganic fillers and the like are blended during tire production. When the molecular weight of the conjugated diene polymer is high, for example, when the weight average molecular weight exceeds 1,000,000, it is preferable to add 15 to 30 mass% of the rubber softener. On the other hand, when a rubber composition containing a filler is prepared, from the viewpoint of increasing the degree of freedom in the amount of filler to be added, it is preferable to add 1 to 15 mass% of the rubber softener. The content of the rubber softener in the rubber composition using the conjugated diene polymer of this embodiment is more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of suppressing deterioration over time when made into a tire.

[0038] Examples of rubber softeners include, but are not limited to, extender oils, low-molecular-weight conjugated diene polymers, resins, etc., but extender oils are preferred from the viewpoints of processability, productivity, and economy. Also, from the viewpoint of the abrasion resistance of rubber compositions for tires, low-molecular-weight conjugated diene polymers that can contribute to crosslinking are preferred as rubber softeners. The method for adding a rubber softener to the conjugated diene polymer of the present embodiment is not limited to the following, but a preferred method is to add the rubber softener to a solution of the conjugated diene polymer, mix them, and then remove the solvent from the resulting polymer solution containing the rubber softener.

[0039] Preferred softeners include, but are not limited to, aromatic oils, naphthenic oils, paraffin oils, and the like. Among these, from the viewpoint of environmental safety, prevention of oil bleeding of the rubber composition, and wet grip properties, aromatic substitute oils having a polycyclic aromatic (PCA) content of 3 mass % or less according to the IP346 method are preferred. Examples of aroma substitute oils include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), and RAE (Residual Aromatic Extracts), as shown in Kautschuk Gummi Kunststoffe 52(12)799 (1999).

[0040] (Other additives) The conjugated diene polymer of the present embodiment may contain various additives such as an antioxidant, if necessary.

[0041] [Method for producing conjugated diene polymer] In one example of a method for producing the conjugated diene polymer of this embodiment, the conjugated diene polymer can be obtained by copolymerizing a conjugated diene compound with a vinyl aromatic compound, and hydrogenating the resulting conjugated diene polymer as needed.

[0042] Generally, when comparing the entanglement molecular weight of polybutadiene with that of polystyrene, polystyrene has a higher entanglement molecular weight. A similar trend is observed in the monomer ratio in conjugated diene polymers; as the content of vinyl aromatic monomer units increases, the entanglement molecular weight increases. On the other hand, when focusing on the bonding mode of the conjugated diene monomer, when the conjugated diene monomer is polymerized with a 1,2- or 3,4-bond (so-called vinyl bond), the entanglement molecular weight tends to be higher than with a 1,4-bond. Furthermore, when the conjugated diene monomer is hydrogenated, the entanglement molecular weight is higher than with a non-hydrogenated one. For this reason, in order to control the inter-entanglement molecular weight, it is appropriate to adjust the content of the vinyl aromatic monomer unit, the vinyl bond content of the conjugated diene monomer, and the hydrogenation rate. Of course, these factors also affect other properties of the conjugated diene polymer, so it is preferable to design them in a balance with the desired performance. For example, if the content of the vinyl aromatic monomer unit is set high, the inter-entanglement molecular weight can be increased even if the hydrogenation rate is low. Conversely, in the case of a conjugated diene polymer with a low content of vinyl aromatic monomer unit, the inter-entanglement molecular weight tends to more easily satisfy the requirements of this embodiment by setting the vinyl bond content and the hydrogenation rate high.

[0043] When the constituent components of the conjugated diene polymer of this embodiment are 1,3-butadiene as a conjugated diene compound and styrene as a vinyl aromatic compound, the proportion of styrene in the polymerization monomers is 1% by mass or more and 18% by mass or less. In order to control the entanglement point molecular weight 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, it is possible to improve the crack growth resistance of the rubber composition while also improving its breaking strength.

[0044] In the method for producing a conjugated diene polymer of the present embodiment, anionic polymerization is preferably carried out in the polymerization step from the viewpoint of easy control of the molecular structure. Also, it is preferable to hydrogenate (hydrogenate) a part or most of the double bonds in the conjugated diene polymer obtained by polymerizing at least a conjugated diene monomer.

[0045] Examples of methods for producing the conjugated diene polymer of the present embodiment include a method in which a conjugated diene monomer is polymerized by anionic polymerization using various additives and under various conditions, and if necessary, copolymerized with other monomers, followed by hydrogenation, as described in WO 96 / 05250, JP 2000-053706 A, WO 2003 / 085010 A, WO 2019 / 151126 A, WO 2019 / 151127 A, WO 2002 / 002663 A, and WO 2015 / 006179 A. The vinyl aromatic compound, ethylene, α-olefin, conjugated diene compound, and other monomers used during polymerization in the method for producing a conjugated diene polymer of the present embodiment can be the same as those described in the above-mentioned various documents. The polymerization step and the hydrogenation step may each be carried out in a batchwise or continuous manner.

[0046] (Polymerization process) In the polymerization step, a conjugated diene compound, a vinyl aromatic compound, and, if necessary, other monomers are polymerized using a polymerization initiator. The polymerization initiator used in the polymerization step includes an organic monolithium compound. The organomonolithium compound is not limited to the following, but examples thereof include low molecular weight compounds and solubilized oligomeric organomonolithium compounds. Furthermore, 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 mode between the organic group and the lithium.

[0047] The amount of the organic monolithium compound used as the polymerization initiator is preferably determined depending on the target structure and molecular weight of the conjugated diene polymer of the present embodiment. The amount of a monomer such as a conjugated diene compound used relative to the amount of a polymerization initiator used is related to the degree of polymerization of the conjugated diene polymer, that is, the number average molecular weight and / or weight average molecular weight of the conjugated diene polymer. Therefore, in order to increase the molecular weight, it is advisable to adjust the amount of polymerization initiator used in a direction to decrease it, and in order to decrease the molecular weight, it is advisable to adjust the amount of polymerization initiator used in a direction to increase it.

[0048] The organomonolithium compound as a polymerization initiator is preferably an alkyllithium compound having a substituted amino group or a dialkylaminolithium compound, from the viewpoint that it is used as one method for introducing nitrogen atoms into a conjugated diene polymer. In this case, a conjugated diene polymer having a nitrogen atom consisting of an amino group at the polymerization initiation terminal is obtained. The substituted amino group is an amino group that does not have an active hydrogen or has a structure in which the active hydrogen is protected.

[0049] Examples of alkyllithium compounds having an amino group that does not have an active hydrogen include, but are not limited to, 3-dimethylaminopropyllithium, 3-diethylaminopropyllithium, 4-(methylpropylamino)butyllithium, and 4-hexamethyleneiminobutyllithium.

[0050] Examples of alkyllithium compounds having an amino group with a structure in which an active hydrogen is protected include, but are not limited to, 3-bistrimethylsilylaminopropyllithium and 4-trimethylsilylmethylaminobutyllithium.

[0051] Examples of dialkylaminolithiums include, but are not limited to, lithium dimethylamide, lithium diethylamide, lithium dipropylamide, lithium dibutylamide, lithium di-n-hexylamide, lithium diheptylamide, lithium diisopropylamide, lithium dioctylamide, lithium-di-2-ethylhexylamide, lithium didecylamide, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide, lithium methylphenethylamide, lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, lithium morpholide, 1-lithioazacyclooctane, 6-lithio-1,3,3-trimethyl-6-azabicyclo[3.2.1]octane, and 1-lithio-1,2,3,6-tetrahydropyridine.

[0052] These organomonolithium compounds having a substituted amino group can also be used as solubilized oligomeric organomonolithium compounds by reacting them with a small amount of a polymerizable monomer, such as 1,3-butadiene, isoprene, or styrene.

[0053] The organomonolithium compound used as the polymerization initiator is preferably an alkyllithium compound from the viewpoints of industrial availability and ease of control of the polymerization reaction. In this case, a conjugated diene polymer having an alkyl group at the polymerization initiation terminal can be obtained. Examples of the alkyllithium compound include, but are not limited to, n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium. As the alkyllithium compound, n-butyllithium and sec-butyllithium are preferred from the viewpoints of industrial availability and ease of control of the polymerization reaction.

[0054] The above-mentioned organomonolithium compounds may be used alone or in combination of two or more, and may also be used in combination with other organometallic compounds.

[0055] Examples of the other organometallic compounds include alkaline earth metal compounds, other alkali metal compounds, and other organometallic compounds. Alkaline earth metal compounds include, but are not limited to, organomagnesium compounds, organocalcium compounds, and organostrontium compounds, as well as alkaline earth metal alkoxides, sulfonates, carbonates, and amides. Organomagnesium compounds include, for example, dibutylmagnesium and ethylbutylmagnesium. Other examples of organometallic compounds include organoaluminum compounds.

[0056] The polymerization reaction mode in the polymerization step is not limited to the following, but examples thereof include a batchwise polymerization mode (also called a "batch type") and a continuous polymerization mode. In the continuous process, one or more connected reactors can be used, and examples of the continuous reactor include a tank-type reactor and a tubular reactor equipped with a stirrer. In the continuous method, preferably, a monomer, an inert solvent, and a polymerization initiator are continuously fed into a reactor, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is continuously discharged. The batch reactor may be, for example, a tank-type reactor equipped with a stirrer. In the batchwise process, preferably, a monomer, an inert solvent, and a polymerization initiator are fed to a reactor, and if necessary, a monomer is added continuously or intermittently during the polymerization to obtain a polymer solution in the reactor, and the polymer solution is discharged after the polymerization is completed. In the method for producing a conjugated diene polymer of this embodiment, in order to obtain a polymer having active ends at a high rate, a continuous method is preferred, which allows the polymer to be continuously discharged and subjected to the next reaction in a short time.

[0057] In the polymerization step of the conjugated diene polymer of this embodiment, the polymerization is preferably carried out in an inert solvent. The inert solvent is not limited to the following, but examples thereof include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. 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.

[0058] By treating the impurities, that is, allenes and acetylenes, with an organometallic compound before carrying out the polymerization step, a conjugated diene polymer having a high concentration of active ends tends to be obtained, and also a conjugated diene polymer with a high modification rate tends to be obtained after the modification step, so it is preferable to treat the impurities with the organometallic compound.

[0059] In the polymerization step, a polar compound may be added. This allows the vinyl aromatic compound and the conjugated diene compound to be randomly copolymerized. Furthermore, polar compounds tend to be useful as vinylating agents for controlling the microstructure of the conjugated diene moiety. Furthermore, polar compounds tend to be effective in accelerating the polymerization reaction.

[0060] Examples of polar compounds include, 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, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium tert-butylate, and sodium amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used alone or in combination of two or more.

[0061] The amount of polar compound used is not particularly limited and can be selected depending on the purpose, but is preferably 0.01 moles or more and 10 moles or less per mole of the polymerization initiator. Adding a polar compound in an amount of 0.01 to 10 moles per mole of polymerization initiator increases the amount of 1,2-vinyl bonds in the conjugated diene polymer, while decreasing the amount of 1,4-vinyl bonds. A high amount of 1,2-vinyl bonds in the conjugated diene polymer tends to increase the inter-entanglement molecular weight of the conjugated diene polymer. Even when the content of vinyl aromatic monomer units is relatively low, the inter-entanglement molecular weight of the conjugated diene polymer of this embodiment tends to be easily controlled within a numerical range of 2,400 to 3,000 g / mol. The conjugated diene polymer thus obtained, which has a low content of vinyl aromatic monomer units and a high amount of 1,2-vinyl bonds, tends to produce a vulcanizate with excellent crack growth resistance and fuel-saving performance.

[0062] Such polar compounds (vinylating agents) can be used in an appropriate amount depending on the desired amount of 1,2-vinyl bonds as modifiers for the microstructure of the conjugated diene portion of the conjugated diene polymer. Many polar compounds also have an effective randomizing effect in the copolymerization of a conjugated diene compound and a vinyl aromatic compound, and tend to be used as modifiers for adjusting the distribution of the vinyl aromatic compound and the amount of styrene blocks.

[0063] An example of a method for randomizing the copolymerization of a conjugated diene compound and a vinyl aromatic compound is a method described in JP-A-59-140211, in which a copolymerization reaction is initiated with the entire amount of styrene and a portion of 1,3-butadiene, and the remaining 1,3-butadiene is intermittently added during the copolymerization reaction.

[0064] The polymerization temperature in the polymerization step is preferably a temperature at which living anionic polymerization proceeds, and from the viewpoint of productivity, is more preferably 0° C. or higher, and is preferably 120° C. or lower, and more preferably 50° C. or higher and 100° C. or lower. By setting the temperature within this range, it tends to be possible to ensure a sufficient amount of modifying agent to react with the active terminals after the completion of polymerization.

[0065] (Branching process) In the method for producing a conjugated diene polymer of this embodiment, a step of adjusting the branching degree of the conjugated diene polymer may be further carried out. As a method for increasing the branching degree of a conjugated diene polymer, for example, a method using a compound derived from a vinyl monomer containing an alkoxysilyl group and / or a halosilyl group, that is, a branching agent, can be mentioned. The branching agent is added during the polymerization step, and then the monomer is added to continue the polymerization reaction, thereby extending the polymer chains branched at the branching points.Furthermore, a modifying agent, a coupling agent, or the like may be added thereafter to carry out a modification step.

[0066] (Denaturation process) The active terminals of the polymer obtained through the above-mentioned polymerization step and, if necessary, a branching step using a predetermined branching agent are subjected to a modification step using the above-mentioned coupling agent or a modifying agent having a nitrogen atom-containing group.

[0067] (deactivator, neutralizer) In the method for producing a conjugated diene polymer of the present embodiment, after the modification step, a deactivator, a neutralizer, etc. may be added to the polymer solution as needed. The quenching agent is not limited to the following, but examples thereof include water; alcohols such as methanol, ethanol, and isopropanol; and the like. Examples of neutralizing agents include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, mainly 10 carbon atoms); aqueous solutions of inorganic acids; and carbon dioxide gas.

[0068] (Hydrogenation process) The method for producing a conjugated diene polymer of the present embodiment is not particularly limited, but may include a step of hydrogenating a conjugated diene polymer so that the hydrogenation rate is 50 mol % or more and 90 mol % or less, as described above. The hydrogenation rate can be controlled, for example, by adjusting the amount of hydrogen used during hydrogenation, and the hydrogenation rate can be controlled, for example, by adjusting the amount of hydrogen fed, pressure, temperature, etc. The hydrogenation rate of the conjugated diene polymer can be measured by proton nuclear magnetic resonance ( 1 It can be measured by H-NMR.

[0069] (Addition of rubber stabilizer) In the method for producing a conjugated diene polymer of this embodiment, it is preferable to add a rubber stabilizer from the viewpoint of preventing gel formation after polymerization and improving stability during processing. Known rubber stabilizers can be used, and examples thereof include, but are not limited to, antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (hereinafter also referred to as "BHT"), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol) propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol.

[0070] (Desolvation process) In the method for producing a conjugated diene polymer of this embodiment, a known method can be used to obtain the resulting polymer from the polymer solution. The method is not particularly limited, but examples thereof include a method in which the solvent is separated by steam stripping or the like, the polymer is filtered, and then the polymer is dehydrated and dried to obtain the polymer, a method in which the polymer is concentrated in a flashing tank and then devolatilized using a vent extruder or the like, and a method in which the polymer is directly devolatilized using a drum dryer or the like.

[0071] [Rubber composition] The rubber composition of this embodiment contains 100 parts by mass of a rubber component containing 30 parts by mass or more of the conjugated diene polymer of this embodiment described above and 30 parts by mass or more of natural rubber, and 30 parts by mass or more of carbon black. The rubber composition of the present embodiment has the above-described structure, and thus has an excellent balance between elongation at break and crack growth resistance. The rubber composition of the present embodiment may further contain other rubbers in addition to the conjugated diene polymer of the present embodiment described above. The conjugated diene polymer of the present embodiment, natural rubber, and other rubbers may be collectively referred to as a rubber component.

[0072] (carbon black) The carbon black is not particularly limited, and for example, carbon black of various classes such as SRF, FEF, HAF, ISAF, SAF, etc. Among these, from the viewpoint of extrusion moldability and rolling resistance characteristics, carbon black having a nitrogen adsorption specific surface area of ​​50 m 2 / g or more, and a dibutyl phthalate (DBP) oil absorption of 80 mL / 100 g or more is preferred. From the viewpoint 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 even more preferably 50 parts by mass or more, per 100 parts by mass of the rubber component, and from the viewpoint of improving the fuel economy performance of the rubber composition, the content is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less. 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 resulting vulcanizate. 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 the ozone resistance of the resulting vulcanizate.

[0073] The other rubbers are not particularly limited and can be appropriately selected depending on the purpose of the rubber composition. Examples include styrene-butadiene rubber (emulsion polymerization tire or solution polymerization type), polyisoprene, butadiene rubber (high-cis polybutadiene, low-cis polybutadiene, syndiotactic-1,2-polybutadiene, acrylonitrile-butadiene rubber (NBR), chloroprene rubber, ethylene-α-olefin copolymer rubber such as ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), butyl rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber, etc. These other rubbers may be used alone or in combination of two or more. As another method for mixing the rubber, the rubber may be mixed in a dry state after polymerization of the conjugated diene polymer, or may be mixed in a solution state during polymerization of the conjugated diene polymer.

[0074] The rubber composition of the present embodiment may contain a crosslinking agent. The content of the crosslinking agent in the rubber composition of this embodiment is preferably 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the rubber component. From the viewpoint of high tensile strength and a high crosslinking rate in the rubber composition, the content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.5 parts by mass or more. On the other hand, from the viewpoint of suppressing uneven crosslinking and high tensile strength, the content is preferably 20 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less. The crosslinking agent is not particularly limited and can be appropriately selected depending on 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 compound-based crosslinking agents, oxime-nitrosamine-based crosslinking agents, etc. These may be used alone or in combination of two or more. When the rubber composition of the present embodiment is used as a tire composition, among these, sulfur-based cross-linking agents (vulcanizing agents) are more preferable, and sulfur is particularly more preferable.

[0075] The rubber composition of the present embodiment may contain a vulcanizing agent, and may further contain a vulcanization accelerator in combination. 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.

[0076] Furthermore, the rubber composition of the present embodiment may contain various additives other than those described above, such as other softeners, fillers, heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, and lubricants. As other softeners, known softeners can be used. Other fillers include, but are not limited to, calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate. Known materials can be used as the heat stabilizer, antistatic agent, weather stabilizer, antioxidant, colorant, and lubricant.

[0077] (vulcanizate) The rubber composition of the present embodiment is suitably used as a vulcanizate. By vulcanizing a rubber composition containing natural rubber and carbon black, a vulcanizate exhibiting excellent breaking strength can be obtained inexpensively. The vulcanizate may contain, in addition to the conjugated diene polymer of this embodiment, natural rubber, and carbon black, an inorganic filler such as silica, 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 these to form a rubber composition, which is then heated and vulcanized. 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, but an example is a method for identification using NMR. For example, as previously reported (JSR TECHNICAL REVIEW No. 126 / 2019), 13By using C-NMR, it is possible to quantitatively calculate the ratio of styrene units, 1,2-vinyl bond amounts, 1,4-vinyl bond amounts, 1,4-cis bond amounts, and isoprene units contained in the rubber composition.

[0078] (silica) The rubber composition of the present embodiment may contain silica. The content of silica in the rubber composition is preferably 30 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the rubber component containing the conjugated diene polymer of the present embodiment and natural rubber. From the viewpoint of improving grip performance and handling stability when the rubber composition of the present embodiment is used in a tire, the content of silica is preferably 60 parts by mass or more, more preferably 65 parts by mass or more, and even more preferably 75 parts by mass or more, per 100 parts by mass of the rubber component. Also, from the viewpoint of improving fuel economy performance when used in a tire, the content is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less. Although the silica is not particularly limited and known silica can be used, solid particles containing SiO2 or Si3Al as a structural unit are preferred, and solid particles containing SiO2 or Si3Al as a main component of the structural unit are more preferred. Here, the main component refers to a component contained in the silica in an amount of 50 mass % or more, preferably 70 mass % or more, and more preferably 80 mass % or more. Examples of silica include, but are not limited to, silicon dioxide, clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, and inorganic fibrous materials such as glass fiber. An example of a commercially available silica product is "Ultrasil 7000GR" manufactured by Evonik Degussa. As the silica, a silica-based inorganic filler whose surface has been made hydrophobic can be used, and the silica-based inorganic filler may be used in combination with an inorganic filler other than a silica-based inorganic filler. Among these, silicon dioxide and glass fiber are preferred from the viewpoint of strength and abrasion resistance, and silicon dioxide is more preferred. Examples of silica include dry silica, wet silica, and synthetic silicate silica. Among these, wet silica is more preferred from the viewpoint of achieving an excellent balance between the effect of improving fracture properties and wet grip properties. In the rubber composition of the present embodiment, when a silica-based inorganic filler is contained from the viewpoint of obtaining practically good abrasion resistance and fracture characteristics, the nitrogen adsorption specific surface area of ​​the silica-based inorganic filler determined by the BET adsorption method is 100 m 2 / g or more 300m 2 / g or less is preferable, and 170m 2 / g or more 250m 2 / g or less is more preferable. If necessary, a relatively small specific surface area (for example, a specific surface area of ​​200 m 2 / g) and those with a relatively large specific surface area (e.g., 200m 2 This allows for a high level of balance between good abrasion resistance and fracture properties and fuel-saving properties.

[0079] (Silane coupling agent) The rubber composition of the present embodiment may contain a silane coupling agent from the viewpoint of improving the dispersibility of the filler and improving the tensile strength of the crosslinked product. The silane coupling agent is preferably a compound that has the function of strengthening the interaction between the rubber component and the inorganic filler, has groups that have affinity or bonding properties for both the rubber component and the filler, and has a sulfur-bonding moiety and an alkoxysilyl group or silanol group moiety in one molecule. 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, S-[3-(triethoxysilyl)-propyl]octanethioate, condensates of S-[3-(triethoxysilyl)-propyl]octanethioate with [(triethoxysilyl)-propyl]thiol, mercaptosilanes having at least one thiol functional group (—SH), and silanes bearing at least one masked thiol group. The content of the silane coupling agent in the rubber composition of the present embodiment is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 1.0 part by mass or more, per 100 parts by mass of the rubber component containing the conjugated diene polymer of the present embodiment and natural rubber, and is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. When the content of the silane coupling agent is within the above range, the effect of adding the silane coupling agent tends to be more pronounced.

[0080] (softener) The rubber composition of the present embodiment preferably contains 100 parts by mass of a rubber component containing the conjugated diene polymer of the present embodiment and natural rubber, and 1 part by mass or more and 60 parts by mass or less of a softener. The softener is not particularly limited and examples thereof include extender oils, low-molecular-weight conjugated diene polymers, resins, etc., but extender oils are preferred from the viewpoints of processability, productivity, and economy. Also, low-molecular-weight conjugated diene polymers that can contribute to crosslinking are preferred from the viewpoint of the abrasion resistance of rubber compositions for tires. Preferred softeners include, but are not limited to, aromatic oils, naphthenic oils, paraffin oils, and the like. Among these, from the viewpoints of environmental safety, prevention of oil bleeding, and wet grip properties, aromatic substitute oils having a polycyclic aromatic (PCA) content of 3 mass % or less according to the IP346 method are preferred. Examples of aroma substitute oils include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), and RAE (Residual Aromatic Extracts), as shown in Kautschuk Gummi Kunststoffe 52(12)799 (1999). 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 even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component from the viewpoint of processability, and is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less from the viewpoint of abrasion resistance.

[0081] (Method of manufacturing rubber composition) The rubber composition of the present embodiment can be produced by mixing the conjugated diene polymer of the present embodiment, natural rubber, and a rubber component made of other rubber, and various additives such as carbon black, silica, other fillers, crosslinking agents, silane coupling agents, and softeners. The method for mixing the conjugated diene polymer of this embodiment, rubber components including natural rubber and other rubbers, crosslinking agents, silica, carbon black and other fillers, silane coupling agents, softeners and other additives is not limited to the following, but examples thereof include a melt-kneading method using a general mixer such as an open roll, a Banbury mixer, a kneader, a single-screw extruder, a twin-screw extruder or a multi-screw extruder, and a method in which the components are dissolved and mixed and then the solvent is removed by heating. Among these methods, melt-kneading using a roll, a Banbury mixer, a kneader, or an extruder is preferred from the viewpoints of productivity and good kneading ability. Also applicable are a method of kneading the rubber component, the filler, the silane coupling agent, and the additives all at once, and a method of mixing them in several batches.

[0082] [Application] The rubber composition of the present embodiment can be used, preferably as a crosslinkable rubber composition, for tire components, interior and exterior materials for automobiles, vibration-proof rubber, belts, footwear, foams, various industrial products, and the like. Among these, it is preferably used for tire components. Examples of tire components include various tires such as fuel-efficient tires, all-season tires, high-performance tires, snow tires, and studless tires; and tire components such as tire treads, carcasses, sidewalls, and bead portions. In particular, the rubber composition of the present embodiment has an excellent balance of crack growth resistance, fuel-saving performance, and elongation at break when vulcanized, and is therefore suitably used as a material for tire treads and sidewalls of fuel-saving tires. A known method can be used to manufacture a tire. For example, components typically used in tire manufacturing, such as at least one carcass layer selected from the group consisting of an unvulcanized rubber composition for crosslinking and cords, a belt layer, and a tread layer, are laminated on a tire-building drum in this order, and the drum is removed to form a green tire. The green tire is then heated and vulcanized in a conventional manner to manufacture a desired tire (e.g., a pneumatic tire). [Example]

[0083] Hereinafter, the present embodiment will be described in more detail with reference to specific examples and comparative examples, but the present embodiment is not limited to the following examples and comparative examples. Various physical properties in the examples and comparative examples were measured by the methods shown below.

[0084] (Microstructure of butadiene portion of conjugated diene polymer before hydrogenation (1,2-vinyl bond content)) 50 mg of the conjugated diene polymer before hydrogenation was dissolved in 10 mL of carbon disulfide to prepare a measurement sample. Using a solution cell, infrared spectra were recorded from 600 to 1000 cm -1The absorbance at a predetermined wave number was measured in the range of 100 Hz to 100 Hz, and the microstructure of the butadiene moiety, i.e., the 1,2-vinyl bond content (mol%) was determined according to the calculation formula of Hampton's method (method described in R.R. Hampton, Analytical Chemistry 21, 923 (1949)). The measuring device used was a Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation.

[0085] (Weight-average molecular weight of conjugated diene polymer) The chromatogram was measured using a GPC measuring device equipped with three columns packed with polystyrene gel connected together, and the weight-average molecular weight of the conjugated diene polymer was determined based on a calibration curve using standard polystyrene. The eluent used was tetrahydrofuran (THF) containing 5 mmol / L triethylamine. The columns used were a guard column manufactured by Tosoh Corporation under the trade name "TSKguardcolumn SuperH-H" and columns manufactured by Tosoh Corporation under the trade names "TSKgel SuperH5000," "TSKgel SuperH6000," and "TSKgel SuperH7000." An RI detector (trade name "HLC8020" manufactured by Tosoh Corporation) was used under conditions of an oven temperature of 40°C and a THF flow rate of 0.6 mL / min. 10 mg of the sample to be measured was dissolved in 20 mL of THF to prepare a measurement solution, and 20 μL of the measurement solution was injected into the GPC measurement device and measured.

[0086] (Modification rate of conjugated diene polymer) The modification rate of the conjugated diene polymer was measured by a column adsorption GPC method as follows: The measurement was carried out by utilizing the property of the conjugated diene polymer modified with a nitrogen atom-containing functional group to be adsorbed onto a column. The amount of a sample solution containing the sample and low-molecular-weight internal standard polystyrene adsorbed onto the silica-based column was measured by subtracting the chromatogram measured on the polystyrene-based column from the chromatogram measured on the silica-based column, and the modification rate was calculated. Specifically, it is as follows: <Preparation of sample solution>: 10 mg of the sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a sample solution. <GPC measurement conditions using a polystyrene column> THF containing 5 mmol / L triethylamine was used as the eluent, and 20 μL of the sample solution was injected into the instrument for measurement. The guard column used was a Tosoh Corporation "TSKguardcolumn SuperH-H" (trade name), and columns were Tosoh Corporation "TSKgel SuperH5000," "TSKgel SuperH6000," and "TSKgel SuperH7000" (trade names). The column oven temperature was 40°C, and the THF flow rate was 0.6 mL / min. A chromatogram was obtained using an RI detector (Tosoh Corporation HLC8020). <GPC measurement conditions using a silica column>: A Tosoh HLC-8320GPC column was used, and 50 μL of the sample solution was injected into the column using THF as the eluent. Chromatograms were obtained using an RI detector at a column oven temperature of 40°C and a THF flow rate of 0.5 mL / min. Zorbax PSM-1000S, PSM-300S, and PSM-60S columns were used, with a DIOL 4.6 x 12.5 mm 5 micron guard column connected to the column. <Calculation method of denaturation rate>: The total peak area of ​​the chromatogram using the polystyrene column was set to 100, the peak area of ​​the sample was set to P1, the peak area of ​​the standard polystyrene was set to P2, and the total peak area of ​​the chromatogram using the silica column was set to 100, the peak area of ​​the sample was set to P3, and the peak area of ​​the standard polystyrene was set to P4. The modification rate (%) was calculated using the following formula. Denaturation rate (%) = [1-(P2 x P3) / (P1 x P4)] x 100 (However, P1+P2=P3+P4=100)

[0087] (Hydrogenation rate of conjugated diene polymer) A large amount of methanol was added to the reaction solution of the conjugated diene polymer after the hydrogenation reaction, and the conjugated diene polymer before hydrogenation and the hydrogenated conjugated diene polymer were precipitated and recovered. Next, the hydrogenated conjugated diene polymer was extracted with acetone, and the hydrogenated conjugated diene polymer was dried under vacuum. This, 1 The hydrogenation rate was measured using the sample for H-NMR measurement. 1 The conditions for H-NMR measurement are as follows: <Measurement conditions> Measuring equipment: JNM-LA400 (JEOL) Solvent: deuterated chloroform Measurement sample: Samples taken before and after hydrogenation of polymer Sample concentration: 50mg / mL Observation frequency: 400MHz Chemical shift standard: TMS (tetramethylsilane) Pulse delay: 2.904 seconds Number of scans: 64 Pulse width: 45° Measurement temperature: 26℃

[0088] (Styrene content of conjugated diene polymer (mass%)) A 100 mg sample of a conjugated diene polymer was dissolved in chloroform to prepare a measurement sample. The amount of styrene (mass%) in the sample was measured based on the amount of absorption of ultraviolet light (near 254 nm) by the phenyl group of styrene (measuring device: Shimadzu UV-2450 spectrophotometer).

[0089] (glass transition temperature of conjugated diene polymer (°C)) The glass transition temperature of the conjugated diene polymer sample was measured using a differential scanning calorimeter in accordance with JIS K6240.

[0090] (Nitrogen content of conjugated diene polymer) The conjugated diene polymer was used as a sample, and the nitrogen content was measured using a trace nitrogen analyzer (Nitto Seiko Analytech TN-2100H).

[0091] (Mooney viscosity (ML) of conjugated diene polymer) Using the conjugated diene polymer as a sample, the Mooney viscosity was measured according to the method specified in ISO289. In Tables 1 to 3 below, the Mooney viscosity values ​​measured at 100° C. are shown in ML.

[0092] (Mooney Stress Relaxation (MSR) of Conjugated Diene Polymers) Using a conjugated diene polymer as a sample, the Mooney viscosity (ML) was measured at 100° C., and then the rotation of the rotor was stopped and the decay of the torque applied to the rotor was measured for 30 seconds. The relaxation time versus the decay of the Mooney viscosity value was plotted logarithmically, and the slope was calculated as the Mooney stress relaxation (MSR).

[0093] (Cold flow property of conjugated diene polymer (rating 1)) A 10 cm cube was cut out from the conjugated diene polymer as an evaluation sample. A 1 kg weight was placed on the evaluation sample and then left for 30 minutes. The rate of change in height of the evaluation sample before and after placing the weight for 30 minutes was taken as cold flow property and evaluated according to the following criteria. ○: Height change rate is less than 10% △: Height change rate is 10% or more but less than 15% ×: Height change rate is 15% or more From the viewpoint of maintaining moldability of the conjugated diene polymer during storage, the more excellent the rating, the more preferable it is, followed by the more excellent the rating.

[0094] (Molecular weight between entanglement points of conjugated diene polymer) The conjugated diene polymer was used as a sample, and the modulus of elasticity Gn at 27° C. was measured using ARES-G2 manufactured by TA Instruments. The molecular weight between entanglement points was calculated from the obtained elastic modulus Gn and the following formula. Molecular weight between entanglement points = cRT / Gn c: 0.9×10 6 (g / m 3 ) R: 8.31 (J / K / mol) T: 300 (K) Gn: Elastic modulus measured by ARES (Pa) <Measurement conditions of ARSE-G2> Mode: Compression mode Strain: 0.05% Frequency: 1 Hz The measurement sample used was a conjugated diene polymer pressed to a thickness of 1 mm and punched into a circular shape with a diameter of 10 mm.

[0095] [Production of conjugated diene polymer] (Preparation of hydrogenation catalyst) The hydrogenation catalyst used for preparing the conjugated diene polymer in the following Examples and Comparative Examples was prepared by the method of the following Production Example. <Production Example> 1 liter of dried and purified cyclohexane was charged into a nitrogen-substituted reaction vessel, 100 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added, and a n-hexane solution containing 200 mmol of trimethylaluminum was added while stirring sufficiently, and reacted at room temperature for about 3 days to obtain a hydrogenation catalyst (TC-1).

[0096] (Polymerization of conjugated diene polymer) <(Example 1) Conjugated diene polymer A1> An autoclave with an internal volume of 43 L, equipped with a stirrer and a jacket and capable of temperature control, was used as a reactor. 3,956.0 g of 1,3-butadiene, 344.0 g of styrene, 25,800 g of cyclohexane, and 7.8 g of 2,2-bis(2-tetrahydrofuryl)propane as a polar compound, which had been purified of impurities in advance, were put into the reactor, and the internal temperature of the reactor was maintained at 42°C. Subsequently, 1.7 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction started, the temperature inside the reactor began to rise due to heat generated by the polymerization. When the temperature rise stopped, 2.8 g of the modifier 1,3-dimethyl-2-imidazolidinone was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was withdrawn and dried to obtain a conjugated diene polymer before hydrogenation. 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 (Ti basis) per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C, thereby obtaining a conjugated diene polymer A1. The hydrogenation rate of the obtained conjugated diene polymer A1 was 68 mol %. To the resulting conjugated diene polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the conjugated diene polymer A1 are shown in Table 1.

[0097] <(Example 2) Conjugated Diene Polymer A2> A temperature-controllable autoclave having an internal volume of 43 L, equipped with a stirrer and a jacket, was used as a reactor, and 3,569.0 g of 1,3-butadiene, 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, from which impurities had been removed in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. Subsequently, 1.6 g of n-butyllithium was supplied as a polymerization initiator to the reactor. After the polymerization reaction started, the temperature inside the reactor began to rise due to heat generated by the polymerization. When the temperature rise stopped, 2.6 g of the modifier 1,3-dimethyl-2-imidazolidinone was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was withdrawn and dried to obtain a conjugated diene polymer before hydrogenation. 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 (Ti basis) per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C, thereby obtaining conjugated diene polymer A2. The hydrogenation rate of the obtained conjugated diene polymer A2 was 68 mol %. To the resulting conjugated diene polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the conjugated diene polymer A2 are shown in Table 1.

[0098] <(Example 3) Conjugated Diene Polymer A3> A temperature-controllable autoclave having an internal volume of 43 L, equipped with a stirrer and a jacket, was used as a reactor, and 4,171.0 g of 1,3-butadiene, 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, from which impurities had been removed in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. Subsequently, 1.8 g of n-butyllithium was supplied as a polymerization initiator to the reactor. After the polymerization reaction started, the temperature inside the reactor began to rise due to heat generated by the polymerization. When the temperature rise stopped, 2.9 g of the modifier 1,3-dimethyl-2-imidazolidinone was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was withdrawn and dried to obtain a conjugated diene polymer before hydrogenation. 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 (Ti basis) per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C, thereby obtaining a conjugated diene polymer A3. The hydrogenation rate of the obtained conjugated diene polymer A3 was 68 mol %. To the resulting conjugated diene polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the conjugated diene polymer A3 are shown in Table 1.

[0099] <( Reference example 4) Conjugated diene polymer A4> The production conditions other than the amount of hydrogenation were the same as in Example 1, and a conjugated diene polymer A4 was obtained. The analytical values ​​of the conjugated diene polymer A4 are shown in Table 1.

[0100] <(Example 5) Conjugated Diene Polymer A5> The production conditions other than the amount of hydrogenation were the same as in Example 1, and a conjugated diene polymer A5 was obtained. The analytical values ​​of the conjugated diene polymer A5 are shown in Table 1.

[0101] <(Example 6) Conjugated Diene Polymer A6> Conjugated diene polymer A6 was obtained in the same manner as in Example 1, except that the amount of n-butyllithium as a polymerization initiator added was changed to 1.3 g and the amount of 1,3-dimethyl-2-imidazolidinone as a modifying agent added was changed to 2.1 g. The analytical values ​​of the conjugated diene polymer A6 are shown in Table 1.

[0102] <(Example 7) Conjugated Diene Polymer A7> Conjugated diene polymer A7 was obtained in the same manner as in Example 1, except that the amount of n-butyllithium as a polymerization initiator added was changed to 3.0 g and the amount of 1,3-dimethyl-2-imidazolidinone as a modifying agent added was changed to 4.9 g. The analytical values ​​of the conjugated diene polymer A7 are shown in Table 1.

[0103] <(Example 8) Conjugated Diene Polymer A8> A conjugated diene polymer A8 was obtained in the same manner as in Example 1, except that the amount of the modifying agent, 1,3-dimethyl-2-imidazolidinone, added was changed to 1.6 g. The analytical values ​​of the conjugated diene polymer A8 are shown in Table 1.

[0104] <(Example 9) Conjugated Diene Polymer A9> 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, 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, all of which had been previously subjected to impurity removal, were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. Subsequently, 4.1 g of n-butyllithium was supplied as a polymerization initiator to the reactor. After the polymerization reaction started, the temperature inside the reactor began to rise due to heat generated by the polymerization. When the temperature rise stopped, 6.4 g of the modifier 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilolidine was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was withdrawn and dried to obtain a conjugated diene polymer before hydrogenation. 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 (Ti basis) per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C, thereby obtaining a conjugated diene polymer A9. The hydrogenation rate of the obtained conjugated diene polymer A9 was 68 mol %. To the resulting conjugated diene polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the conjugated diene polymer A9 are shown in Table 1.

[0105] <( Reference example 10) Conjugated diene polymer A10 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. The analytical values ​​of the conjugated diene polymer A10 are shown in Table 2.

[0106] <(Example 11) Conjugated Diene Polymer A11> 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 modifying agent upon completion of the polymerization. The analytical values ​​of the conjugated diene polymer A11 are shown in Table 2.

[0107] <( Reference example 12) Conjugated diene polymer A12 A conjugated diene polymer A12 was obtained in the same manner as in Example 5, except that the amount of polar compound 2,2-di(2-tetrahydrofuryl)propane added was changed to 8.1 g and the amount of hydrogenation was changed. The analytical values ​​of the conjugated diene polymer A12 are shown in Table 2.

[0108] <(Example 13) Conjugated Diene Polymer A13> Conjugated diene polymer A13 was obtained in the same manner as in Example 1, except that the amount of n-butyllithium as the polymerization initiator was changed to 4.1 g, the amount of 2,2-di(2-tetrahydrofuryl)propane as the polar compound was changed to 11.3 g, and the modifying agent was changed to 1-methyl-4-[3-(triethoxysilyl)propyl]piperazine to 4.1 g. The analytical values ​​of the conjugated diene polymer A13 are shown in Table 2.

[0109] <(Example 14) Conjugated Diene Polymer A14> Conjugated diene polymer A14 was obtained in the same manner as in Example 9, except that the amount of polar compound 2,2-di(2-tetrahydrofuryl)propane added was changed to 18.5 g and the amount of modifying agent 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilolidine added was changed to 3.9 g. The analytical values ​​of the conjugated diene polymer A14 are shown in Table 2.

[0110] <(Example 15) Conjugated Diene Polymer A15> Conjugated diene polymer A15 was obtained in the same manner as in Example 9, except that the amount of n-butyllithium as the polymerization initiator was changed to 2.2 g, the amount of 2,2-di(2-tetrahydrofuryl)propane as the polar compound was changed to 9.9 g, and the amount of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilolidine as the modifying agent was changed to 3.4 g. The analytical values ​​of the conjugated diene polymer A15 are shown in Table 2.

[0111] <( Reference example 16) Conjugated diene polymer A16 A temperature-controllable autoclave having an internal volume of 43 L and equipped with a stirrer and a jacket was used as a reactor, and 3,999.0 g of 1,3-butadiene, 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, from which impurities had been removed in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. Subsequently, 8.1 g of n-butyllithium was supplied as a polymerization initiator to the reactor. After the polymerization reaction started, the temperature inside the reactor began to rise due to heat generated by the polymerization. When the temperature rise stopped, 1.6 g of silicon tetrachloride, a modifier, was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was withdrawn and dried to obtain a conjugated diene polymer before hydrogenation. 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 (Ti basis) per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 40 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C, thereby obtaining a conjugated diene polymer A16. The hydrogenation rate of the obtained conjugated diene polymer A16 was 55 mol %. To the resulting conjugated diene polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the conjugated diene polymer A16 are shown in Table 2.

[0112] <(Example 17) Conjugated Diene Polymer A17> A conjugated diene polymer A17 was obtained in the same manner as in Example 1, except that the amount of the modifying agent, 1,3-dimethyl-2-imidazolidinone, added was changed to 1.9 g. The analytical values ​​of the conjugated diene polymer A17 are shown in Table 2.

[0113] <(Example 18) Conjugated Diene Polymer A18> 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. The analytical values ​​of the conjugated diene polymer A18 are shown in Table 2.

[0114] <(Comparative Example 1) Conjugated Diene Polymer B1> A temperature-controllable autoclave having an internal volume of 43 L, equipped with a stirrer and a jacket, was used as a reactor, and 3,956.0 g of 1,3-butadiene, 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, all of which had been previously subjected to impurity removal, were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. Subsequently, 4.4 g of n-butyllithium was supplied as a polymerization initiator to the reactor. After the polymerization reaction started, the temperature inside the reactor began to rise due to heat generated by the polymerization. When the temperature rise stopped, 4.8 g of the modifier 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilolidine was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was withdrawn and dried to obtain a conjugated diene polymer before hydrogenation. 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 (Ti basis) per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C, thereby obtaining a conjugated diene polymer B1. The hydrogenation rate of the obtained conjugated diene polymer B1 was 68 mol %. To the resulting conjugated diene polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the conjugated diene polymer B1 are shown in Table 3.

[0115] <(Comparative Example 2) Conjugated Diene Polymer B2> 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. The analytical values ​​of the conjugated diene polymer B2 are shown in Table 3.

[0116] <(Comparative Example 3) Rubbery Polymer B3> 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. The analytical values ​​of the conjugated diene polymer B3 are shown in Table 3.

[0117] <(Comparative Example 4) Conjugated Diene Polymer B4> A temperature-controllable autoclave having an internal volume of 43 L, equipped with a stirrer and a jacket, was used as a reactor, and 3,956.0 g of 1,3-butadiene, 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, all of which had been previously removed of impurities, were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. Subsequently, 12.6 g of n-butyllithium was supplied as a polymerization initiator to the reactor. After the temperature rise in the reactor was completed, 20.2 g of the modifier 1,3-dimethyl-2-imidazolidinone was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was withdrawn and dried to obtain a conjugated diene polymer before hydrogenation. 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 (Ti basis) per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C, thereby obtaining conjugated diene polymer B4. The hydrogenation rate of the obtained conjugated diene polymer B4 was 68 mol %. To the resulting solution of conjugated diene polymer B4, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the conjugated diene polymer B4 are shown in Table 3.

[0118] <(Comparative Example 5) Conjugated Diene Polymer B5> Conjugated diene polymer B5 was obtained in the same manner as in Example 1, except that the amount of hydrogenation was changed. The analytical values ​​of the conjugated diene polymer B5 are shown in Table 3.

[0119] <(Comparative Example 6) Conjugated Diene Polymer B6> 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. The analytical values ​​of the conjugated diene polymer B6 are shown in Table 3.

[0120] <(Comparative Example 7) Conjugated Diene Polymer B7> Conjugated diene polymer B7 was obtained in the same manner as in Comparative Example 1, except that the amount of the polymerization initiator n-butyllithium added was changed to 6.8 g, the amount of the polar compound 2,2-di(2-tetrahydrofuryl)propane added was changed to 30.4 g, and the amount of the modifying agent 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilolidine added was changed to 7.3 g. The analytical values ​​of the conjugated diene polymer B7 are shown in Table 3.

[0121] [Table 1]

[0122] [Table 2]

[0123] [Table 3]

[0124] [Examples 19 to 21, Reference Example 22, Examples 23 to 27, Reference Example 28, Examples 29 to 30, Reference Example 31, Examples 32 to 34, Reference Example 35, Examples 36 to 37), [Comparative Examples 8 to 14] (Preparation of rubber composition for crosslinking, evaluation of physical properties) Examples 1 to 3 shown in Tables 1 to 3 3, Reference Example 4, Examples 5 to 9, Reference Example 10, Example 11, Reference Example 12, Example 15, Reference Example 16, Example 17 to Conjugated diene polymers A1 to A18 obtained in 18 and conjugated diene polymers B1 to B7 obtained in Comparative Examples 1 to 7 were mixed according to the formulations shown below to obtain rubber compositions for crosslinking containing the respective raw rubbers. The compounding conditions are shown below.

[0125] (Combination conditions) The amount of each compounding ingredient added in Tables 4 to 6 is shown in parts by mass per 100 parts by mass of the rubber component not including any rubber softener. Conjugated diene polymers: A1 to A18, B1 to B7 Natural rubber: RSS3 High cis-butadiene: Manufactured by UBE Corporation Silica: Evonik Degussa VN3 (N2SA: 175m 2 / g) Carbon black: Diablack N339 (N2SA: 96m) manufactured by Mitsubishi Chemical Corporation 2 / g, DBP absorption: 124mL / 100g) Softener: Diana Process AH-24 (aroma oil) manufactured by Idemitsu Kosan Co., Ltd. Silane coupling agent: Si69 manufactured by Evonik Degussa Anti-aging agent: Nocrac 6C manufactured by Ouchi Shinko Chemical Co., Ltd. Stearic acid: NOF Corporation's "Tsubaki" stearic acid beads Zinc oxide: Three types of zinc oxide manufactured by Hakusui Tech Co., Ltd. Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0126] (Mixing method and evaluation of moldability of rubber composition) The above materials were kneaded by the following method to obtain a rubber composition for crosslinking. According to the formulations shown in Tables 4 to 6, rubber compositions of the examples and comparative examples were prepared. Using an internal mixer (capacity: 0.3 L) equipped with a temperature control device, the rubber component, silica, carbon black, silane coupling agent, softener, zinc oxide, and stearic acid were mixed in the first stage of mixing at a filling rate of 65% and a rotor rotation speed of 30 to 50 rpm. At this time, the temperature of the internal mixer was controlled so that the discharge temperature was 155 to 160°C, and each rubber composition (compound) was obtained. Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature, and then an antioxidant was added and mixed again to improve the dispersion of the silica. In this case, the discharge temperature of the mixture was also adjusted to 155 to 160°C by controlling the temperature of the mixer. After cooling, in the third stage of kneading, sulfur and a vulcanization accelerator were added and kneaded using an open roll set at 70° C. After kneading, the moldability of the rubber composition was evaluated based on the surface roughness of the sheet of the rubber composition for crosslinking discharged from the open roll. Thereafter, the rubber composition was molded and vulcanized at 160°C in a vulcanizing press, and the vulcanized rubber composition was evaluated. The vulcanization time was determined by adding 5 minutes to the 90% vulcanization time of each sample measured by the method described below. Specifically, the evaluation was carried out by the following methods. The evaluation results are shown in Tables 4 to 6.

[0127] <Evaluation 2: Crack growth resistance of rubber composition> The crack growth resistance of the rubber composition was evaluated by measuring the number of times a No. 5 dumbbell made of the rubber composition with an initial crack was stretched at 100% strain and 300 rpm using an FT-3132 manufactured by Kitahama Seisakusho until it broke. In Tables 4 to 6, the fatigue resistance of Comparative Example 8 is quantified as 100. The conjugated diene polymer of this embodiment is intended to exhibit excellent crack growth resistance, and a value of 120 or more is required.

[0128] <Evaluation 3: Breaking Elongation> The tensile strength was measured in accordance with the tensile test method of JIS K6251. In Tables 4 to 6, the breaking elongation of Comparative Example 8 is quantified as 100. The conjugated diene polymer of the present embodiment is intended to exhibit an excellent balance between crack growth resistance and breaking elongation, and a value of 50 or more is required.

[0129] <Evaluation 4: Fuel-saving performance of rubber composition> Viscoelastic parameters were measured in torsion mode using a viscoelasticity tester "ARES-G2" manufactured by TA Instruments. Tan δ measured at 50°C, a frequency of 10 Hz, and a strain of 3% was used as an index of fuel-saving performance, and was quantified assuming that the fuel-saving performance of Comparative Example 8 was 100.

[0130] [Table 4]

[0131] [Table 5]

[0132] [Table 6]

[0133] As shown in Tables 4 to 6, Examples 19 to 21, Reference Example 22, Examples 23 to 27, Reference Example 28, Examples 29 to 30, Reference Example 31, Examples 32 to 34, Reference Example 35, Examples 36 to It was found that No. 37 was superior to Comparative Examples 8 to 14 in the evaluation of crack growth resistance and elongation at break, and also had a good balance of these properties.

[0134] This application is based on a Japanese patent application (Patent Application No. 2022-108011) filed with the Japan Patent Office on July 4, 2022, the contents of which are incorporated herein by reference. [Industrial Applicability]

[0135] The conjugated diene polymer of the present invention has industrial applicability in fields such as tire casing components such as tire treads and sidewalls, interior and exterior materials for automobiles, vibration-proof rubber, belts, footwear, foams, and various industrial products.

Claims

1. 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 (MSR) is 0.8 or more, The content of vinyl aromatic monomer units is 1% by mass or more and 18% by mass or less, In the case where the content of the structure represented by the following formula (1): C 1 mol %, the content of the structure represented by the following formula (2): C 2 mol %, the content of the structure represented by the following formula (3): C 3 mol %, and the content of the structure represented by the following formula (4): C 4 mol %, 【Chemistry 1】 The value of (C2+C4) / (C1+C2+C3+C4), The difference α between the value of (C1+C2) / (C1+C2+C3+C4) and the value of (C1+C2) / (C1+C2+C3+C4) is 0.1 or less. Conjugated diene polymers.

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

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

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

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

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

7. 100 parts by mass of a rubber component containing 30 parts by mass or more of the conjugated diene polymer according to any one of claims 1 to 6 and 30 parts by mass or more of natural rubber; 30 parts by mass or more of carbon black, containing Rubber composition.

8. A tire component comprising the rubber composition according to claim 7.

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