Conjugated diene polymer and method for producing conjugated diene polymer

Abstract

Provided is a conjugated diene polymer which has an estimated glass transition temperature (estimated Tg) derived from a microstructure in the conjugated diene polymer of -72°C to -45°C inclusive, and has only one glass transition temperature (Tg) as determined by differential scanning calorimetry (DSC), wherein the difference between the extrapolated glass transition initiation temperature and the extrapolated glass transition end temperature of the glass transition temperature (Tg) is 15°C to 35°C inclusive.

Description

[Technical Field]

[0001] The present invention relates to a conjugated diene polymer and a method for producing a conjugated diene polymer. [Background technology]

[0002] One of the basic functions required for automobile tire treads is braking performance on road surfaces. With recent climate change, road surfaces can become wet due to sudden rainfall, or turn into icy or snowy surfaces due to sudden snowfall. In such environments, there is a demand for rubber materials used in tire treads that have excellent braking performance not only on dry road surfaces, but also on icy, snowy, and wet surfaces.

[0003] Generally, wet grip performance, which is a required characteristic of rubber for braking on wet roads, and low-temperature performance, which is a required characteristic of rubber for braking on snow, are in conflict with each other, and improving one performance tends to cause a deterioration in the other performance. Tire tread rubber is required to resolve this conflicting property.

[0004] Furthermore, rubber compositions have been known that reduce the modulus of elasticity at low temperatures to improve low-temperature performance and ensure high conformability of tread rubber to snowy road surfaces, and techniques have been proposed to lower the glass transition temperature of rubber materials in order to lower the glass transition temperature of the rubber composition.

[0005] On the other hand, a method of increasing the glass transition temperature of a rubber composition is known to improve wet grip performance, and a technique of increasing the glass transition temperature of a rubber material has been proposed to increase the glass transition temperature of a rubber composition.

[0006] For example, Patent Document 1 discloses a rubber composition containing silica and a modified conjugated diene polymer having a low glass transition temperature, which is obtained by reacting an alkoxysilane containing an amino group with the active terminal of a conjugated diene polymer, and proposes a technology for improving low-temperature performance.

[0007] Furthermore, Patent Document 2 discloses a rubber composition containing a conjugated diene polymer with a high glass transition temperature and silica, and proposes a technology for improving wet grip performance. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2021 / 005295 [Patent Document 2] Patent No. 3438317 Summary of the Invention [Problem to be solved by the invention]

[0009] In Europe and other regions, all-weather tires that can be used all year round are said to be gaining popularity, and there is a demand for rubber compositions that offer improved wet grip performance over a wide temperature range. However, the present inventors have conducted a detailed study of the conventional rubber compositions disclosed in Patent Documents 1 and 2 and have found that the conventional rubber compositions have a problem in that the balance between the wet grip performance and low temperature performance of the vulcanizates thereof needs to be improved. That is, a rubber composition containing a conjugated diene polymer is required to improve the wet grip performance of the vulcanizate thereof, without reducing flexibility at low temperatures, and to have excellent braking performance even on icy and snowy surfaces.

[0010] Therefore, an object of the present invention is to provide a conjugated diene polymer that can provide a tire having excellent wet grip performance and low-temperature performance, and a method for producing the conjugated diene polymer. [Means for solving the problem]

[0011] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, it was discovered that by providing a rubber having a predetermined physical property with respect to glass transition temperature, it is possible to obtain both wet grip performance and low temperature performance when vulcanized, and this discovery led to the completion of the present invention. That is, the present invention is as follows.

[0012] [1] A conjugated diene-based polymer having at least a first polymer segment and a second polymer segment, The first polymer segment contains a conjugated diene monomer unit and does not contain an aromatic vinyl monomer unit, and the vinyl bond amount Y in the bound conjugated diene in the first polymer segment is 1 (mol%) satisfies the following formula (2), 10≦Y 1 ≦45···(2) the second polymer segment contains conjugated diene monomer units and aromatic vinyl monomer units; The aforementioned The estimated glass transition temperature (estimated Tg) derived from the microstructure of the conjugated diene polymer is -72°C or higher -50 °C or less, It has only one glass transition temperature (Tg) as measured by differential scanning calorimetry (DSC), The conjugated diene polymer has a glass transition temperature (Tg) in which the difference between the extrapolated glass transition onset temperature and the extrapolated glass transition end temperature is 15°C or more and 35°C or less. [2] before The conjugated diene polymer according to [1] above, wherein the second polymer segment has an estimated glass transition temperature (estimated Tg) derived from the microstructure of the second polymer segment that is higher than -45°C and not higher than -5°C. [3] The conjugated diene polymer according to [1] or [2] above, wherein the molecular weight distribution, which is the ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn, is 1.7 or more and 2.5 or less. [4] the segment ratio of the first polymer segment is 20% by mass or more and 80% by mass or less; The conjugated diene polymer according to [2] or [3] above. [5] The conjugated diene polymer according to any one of [1] to [4] above, having a weight average molecular weight of 300,000 or more and 1,350,000 or less. [6] The conjugated diene polymer according to any one of [1] to [5] above, which contains a nitrogen atom. [7] The conjugated diene-based polymer according to [6] above, wherein the modification rate of the conjugated diene copolymer is 70% or more. [8] A method for producing the conjugated diene polymer according to any one of [2] to [7], Using two or more continuous reactors, a first polymerization step (P1) in which a conjugated diene compound, a polymerization initiator, and a polar substance are added to the continuous reactor to continuously form a first polymer segment of a conjugated diene-based polymer; a second polymerization step (P2) in which an aromatic vinyl compound and a polar substance are added to the continuous reactor to form a second polymer segment at the end of the first polymer segment; have, A method for producing a conjugated diene polymer. [9] The method for producing a conjugated diene polymer according to [8] above, further comprising a coupling step (P3) of reacting the conjugated diene polymer with a coupling agent after the second polymer step (P2).

[10] The method for producing a conjugated diene polymer according to [8] or [9] above, wherein the mass ratio of the conjugated diene compound added in the first polymerization step (P1) to the total amount of the conjugated diene compound and the aromatic vinyl compound added is 20 mass% or more and 80 mass% or less.

[11] The method for producing a conjugated diene-based polymer according to any one of [8] to

[10] above, wherein the polymerization reaction rate in the first polymerization step (P1) is 75% or more and 95% or less.

[12]

[12] The method for producing a conjugated diene polymer according to any one of [8] to

[11] above, wherein the mass ratio of the amount of aromatic vinyl compound added in the second polymerization step (P2) to the amount of conjugated diene compound added is 0.15 or more and 0.70 or less.

[13]

[13] The method for producing a conjugated diene-based polymer according to any one of [8] to

[12] above, wherein a polar substance is added in the second polymerization step (P2) in an amount greater than the amount of polar substance added in the first polymerization step (P1).

[14] The method for producing a conjugated diene polymer according to any one of [9] to

[13] above, wherein the coupling agent is an aminoalkoxysilane compound. [Effects of the Invention]

[0013] According to the present invention, a conjugated diene polymer can be provided, the vulcanizate of which exhibits both excellent wet grip performance and low-temperature performance. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The following embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented by appropriately modifying it within the scope of its gist.

[0015] [Conjugated diene polymer] The conjugated diene polymer of the present embodiment contains conjugated diene monomer units and aromatic vinyl monomer units.

[0016] The conjugated diene polymer of this embodiment has an estimated glass transition temperature (hereinafter sometimes referred to as estimated Tg) derived from the microstructure in the conjugated diene polymer of -72°C or higher and -45°C or lower. The estimated glass transition temperature (estimated Tg) is derived from the microstructure of the conjugated diene polymer, as will be described later. The conjugated diene polymer of the present embodiment has only one glass transition temperature (Tg) measured by differential scanning calorimetry (DSC), and the difference between the extrapolated glass transition onset temperature and the extrapolated glass transition end temperature of the glass transition temperature (Tg) is 15°C or more and 35°C or less.

[0017] According to the above-mentioned constitution, a conjugated diene polymer can be obtained which can give a vulcanizate that has both excellent wet grip performance and low-temperature performance.

[0018] (Conjugated diene compounds) Conjugated diene compounds forming 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, 1,3-butadiene and isoprene are preferred from the viewpoint of industrial availability. These compounds may be used alone or in combination of two or more. The conjugated diene compound is preferably 1,3-butadiene or isoprene, more preferably 1,3-butadiene, from the viewpoints of availability and ease of structural control during polymer synthesis.

[0019] (aromatic vinyl compounds) Examples of aromatic vinyl compounds that form aromatic vinyl 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 compounds may be used alone or in combination of two or more. Of the aromatic vinyl compounds, styrene is preferred from the viewpoints of availability and ease of structural control during polymer synthesis.

[0020] (microstructure) The microstructure in this specification refers to the composition of a polymer including the distinction of isomers in a conjugated diene polymer using an aromatic vinyl compound and a conjugated diene compound or in a polymer segment described below. In the conjugated diene polymer of this embodiment, the mass of the copolymer consisting of styrene and butadiene is preferably 70 mass% or more, more preferably 80 mass% or more, and even more preferably 90 mass% or more, based on the mass of the entire conjugated diene polymer.

[0021] <Amount of bound aromatic vinyl monomer units (X all )> The estimated Tg of the conjugated diene polymer of the present embodiment is derived from the microstructure of the conjugated diene polymer. An example of the microstructure is a conjugated diene polymer having a bonded aromatic vinyl monomer unit amount (X all ) are mentioned. The amount of bound aromatic vinyl monomer units (X all ) (mass %) is the mass fraction of bound aromatic vinyl monomer units relative to the total mass of the conjugated diene polymer of the present embodiment.

[0022] Here, the amount of bound aromatic vinyl monomer units can be calculated by measuring the ultraviolet absorption of the phenyl group in the portion of the conjugated diene polymer derived from an aromatic vinyl compound (hereinafter, sometimes referred to as "bound aromatic vinyl monomer units" or "aromatic vinyl monomer units"). Furthermore, when the conjugated diene polymer is composed of bound aromatic vinyl monomer units and bound conjugated diene monomer units, the amount of bound conjugated diene monomer units can be determined from the amount of bound aromatic vinyl monomer units obtained as described above. Specifically, it can be measured by the method described in the Examples below.

[0023] <Vinyl bond content in the bonded conjugated diene (Y all )> The estimated Tg of the conjugated diene polymer of the present embodiment is derived from the microstructure of the conjugated diene polymer. One example of the microstructure is the amount of vinyl bonds (Y all ) are mentioned. The vinyl bond content (Y all ) (mol %) is the molar fraction (mol %) of 1,2-bond units relative to the polymer units derived from the conjugated diene compound contained in the conjugated diene-based polymer of the present embodiment.

[0024] When the conjugated diene polymer of the present embodiment is a copolymer of butadiene and styrene, the vinyl bond content in the bound conjugated diene can be obtained by determining the vinyl bond content (1,2-bond content) in the bound butadiene by Hampton's method (RR Hampton, Analytical Chemistry, 21, 923 (1949)). Specifically, it can be measured by the method described in the examples below.

[0025] <Content of bound aromatic vinyl monomer unit blocks> The conjugated diene polymer of the present embodiment preferably has a small number or no blocks in which four or more linked aromatic vinyl monomer units are chained (hereinafter, sometimes referred to as linked aromatic vinyl monomer unit blocks). When the conjugated diene polymer of the present embodiment has few or no bound aromatic vinyl monomer unit blocks, it tends to be less likely to have two or more glass transition temperatures. When the conjugated diene polymer is a butadiene-styrene polymer, the content of the bound aromatic vinyl monomer unit block in the conjugated diene polymer can be measured by a known method in which the conjugated diene polymer is decomposed by the Kolthoff method (I.M. Kolthoff, et al., J. Polym. Sci. 1, 429 (1946)) and the amount of methanol-insoluble polystyrene is analyzed. The content of the bound aromatic vinyl monomer unit block measured by such a method is preferably 1.0% by mass or less, more preferably 0.1% by mass or less, based on the total amount of the conjugated diene polymer. By not including the bound aromatic vinyl monomer unit block in the conjugated diene copolymer or in the polymer segment described below, the conjugated diene polymer of this embodiment tends to exhibit continuous properties with temperature change. As a result, vulcanizates using the conjugated diene polymer of this embodiment tend to exhibit continuous changes over a wide temperature range and have excellent tensile strength.

[0026] (Method for estimating the glass transition temperature of conjugated diene polymers): Estimated glass transition temperature (estimated Tg) The glass transition temperature of the conjugated diene polymer of this embodiment can be calculated using the Gordon-Taylor equation (Gordon, M.; Taylor, J.S.J. Appl. Chem. 1952, 2, 493.), which is expanded to a system of two or more components according to the following formula (1): The value calculated by this method is referred to as the estimated glass transition temperature (estimated Tg).

[0027]

number

[0028] In the formula (1), the variable subscript i represents each component of the microstructure contained in the conjugated diene polymer, and Δα i is the difference in thermal expansion coefficient before and after the glass transition of the homopolymer of component i, w i is the mass ratio of component i in the conjugated diene polymer, Tg i is the glass transition temperature of the homopolymer of component i, ρ i is the density of the homopolymer of component i. Both literature values ​​and measured values ​​can be used. For example, when a conjugated diene polymer contains styrene, if one of the i's is a styrene component, Δα is calculated from the thermal expansion coefficient of polystyrene (J. BRANDRUP et al., Polymer Handbook, 3rd Group, (USA), John Wiley & Sons, Inc., 1966, VI-75). i =3.6×10 -4 K -1 , Tg from the measured glass transition temperature i = 105.3℃, and the measured density value is ρ i =1.02g / cm 3 can be used.

[0029] For example, when the conjugated diene polymer is a butadiene-styrene copolymer, the amount of bound aromatic vinyl monomer units X all (mass%), and the vinyl bond amount Y in the bound conjugated diene all (mol%) and the thermal expansion coefficients (Δai ), glass transition temperature (Tg i ), density (ρ i ) the estimated glass transition temperature (estimated Tg) can be calculated from the following formula (i).

[0030]

number

[0031] The amount of bound aromatic vinyl monomer units X relative to the denominator of the formula (i) all (mass%), vinyl bond content Y in the bonded conjugated diene all Since the effect of the product of (mol%) is very small, it can be approximated by the following formula (ii): Furthermore, the following formula (ii) can be approximated as the following formula (iii):

[0032]

number

[0033]

number

[0034] That is, in the case of a butadiene homopolymer or a butadiene-styrene copolymer, the physical properties of the conjugated diene polymer can be predicted by the above formula (iii) from the values ​​usually used in design.

[0035] According to the formula (1), the amount of bound aromatic vinyl monomer units X in the conjugated diene polymer of this embodiment is all (mass%), vinyl bond content Y in the bonded conjugated diene all The mass proportion of each microstructure component can be calculated from the microstructure, such as the amount of bound aromatic vinyl monomer units X (mol%), and the glass transition temperature (Tg) of the conjugated diene polymer can be estimated. all (mass%), vinyl bond content Y in the bonded conjugated diene allIt is a measure of the change in the glass transition temperature of a conjugated diene polymer relative to the change in the molecular weight (mol%). When the estimated Tg value is small, the glass transition temperature (Tg) of the conjugated diene polymer of this embodiment is low, and when the estimated Tg value is large, the glass transition temperature (Tg) of the conjugated diene polymer of this embodiment is high. For example, when the estimated Tg is -70°C, the glass transition temperature of the conjugated diene polymer is estimated to be -70°C, and when the estimated Tg is -45°C, the glass transition temperature of the conjugated diene polymer is estimated to be -45°C.

[0036] As described above, the estimated Tg value determined from the microstructure of a conjugated diene polymer is generally an indicator of the glass transition temperature of the conjugated diene polymer. However, the present inventors have found that when the relaxation temperature of a conjugated diene polymer near its actual glass transition temperature is wide, the viscoelasticity of the actual vulcanizate does not necessarily match the viscoelasticity based on the estimated glass transition temperature calculated from the microstructure. Specifically, when the difference in estimated Tg values ​​between the polymer segments described below is 33 or more, or when the mass ratio of the first polymer segment described below is in the range of 40 to 60, the discrepancy between the glass transition temperature (estimated Tg) estimated from the above formula (1) and the actually measured glass transition temperature (Tg) tends to become significant. Therefore, from the perspective of controlling the performance of a vulcanizate affected by the glass transition temperature, they have found that it is more effective to control the estimated Tg value calculated from the microstructure to a specific value than to control the actually measured glass transition temperature of the conjugated diene polymer to a specific value. The reason for this is thought to be that DSC (differential scanning calorimetry) measurements pick up small energy changes, so the entire glass transition temperature is pulled up at the start of relaxation in the low Tg portion of the conjugated diene polymer, making the measured glass transition temperature lower than the estimated glass transition temperature. For example, it has been experimentally confirmed that even if the microstructure of the entire conjugated diene polymer is the same, the glass transition temperature measured by DSC can differ by about 2 to 5°C depending on the differences in the microstructure of each segment.

[0037] The conjugated diene polymer of the present embodiment has an estimated Tg that satisfies the range of −72° C. or more and −45° C. or less, and therefore the measured glass transition temperature when vulcanized becomes an optimum value, and the balance between wet grip performance and low-temperature performance tends to be excellent.

[0038] The conjugated diene polymer of this embodiment has a lower limit of the estimated Tg derived from the microstructure of −72° C. or higher, preferably −70° C. or higher, and more preferably −68° C. or higher. When the lower limit of the estimated Tg is within the above range, the wet grip performance of the vulcanizate of the conjugated diene polymer of this embodiment tends to be improved. The upper limit of the estimated Tg value is −45° C. or less, preferably −48° C. or less, and more preferably −50° C. or less. When the upper limit of the estimated Tg is within the above range, the low-temperature performance of the vulcanizate of the conjugated diene polymer of the present embodiment tends to be improved.

[0039] The estimated Tg can be controlled within the above-mentioned range by adjusting the microstructure of the conjugated diene polymer. For example, when the conjugated diene polymer of the present embodiment is a butadiene-styrene copolymer, the bound styrene amount X of the conjugated diene polymer can be calculated by the above-mentioned formula (iii). all (mass%), vinyl bond content in bound butadiene Y all By adjusting the (mol%), it is possible to control the content within the above-mentioned range.

[0040] (polymer segment) The conjugated diene polymer of the present embodiment preferably has two or more polymer segments. The polymer segment refers to a portion of a conjugated diene polymer that is composed of conjugated diene monomer units and aromatic vinyl monomer units, or that is composed of conjugated diene monomer units. Furthermore, in the conjugated diene polymer of this embodiment, the polymer segment preferably has a small number or no blocks in which four or more linked aromatic vinyl monomer units are chained. If there are blocks in which four or more linked aromatic vinyl monomer units are chained, the Tg width tends to be wide. This is preferable from the viewpoint of increasing the difference between the extrapolated glass transition onset temperature and the extrapolated glass transition end temperature, but it tends to cause the glass transition temperature measured by DSC to be easily divided into two. The multiple polymer segments contained in the conjugated diene polymer of this embodiment have different microstructures. Each polymer segment may differ, for example, in the amount of bound aromatic vinyl monomer units or the amount of vinyl bonds in the bound conjugated diene. Each polymer segment can be distinguished by the method described in the Examples below.

[0041] <First polymer segment> The conjugated diene polymer of this embodiment preferably has a first polymer segment that does not contain an aromatic vinyl monomer unit and a second polymer segment that contains an aromatic vinyl monomer unit. As a result, the estimated Tg value of the first polymer segment is smaller than the estimated Tg value of the conjugated diene polymer of this embodiment (the value of formula (1) for the entire polymer). In this case, the estimated Tg of the first polymer segment is calculated by substituting each component of the microstructure of the conjugated diene polymer into formula (1). When the conjugated diene polymer is a butadiene-styrene copolymer or a butadiene homopolymer, the estimated Tg of the conjugated diene polymer is calculated by multiplying the bound styrene amount X of the conjugated diene polymer by formula (iii). all (mass%), vinyl bond content in bound butadiene Y all It is calculated from (mol%).

[0042] It is preferred that the first polymer segment does not contain an aromatic vinyl monomer unit, and that the vinyl bond amount Y1 (mol %) in the bonded conjugated diene satisfies the following formula (2). 10≦Y1≦45 (2) The lower limit of Y1 is more preferably greater than 10, even more preferably 12 or more, and even more preferably 15 or more. The upper limit of Y1 is more preferably less than 45, even more preferably 43 or less, and even more preferably 40 or less. By satisfying the formula (2), the flexibility of the conjugated diene polymer of the present embodiment in the low temperature range is improved, and the vulcanizate thereof tends to have excellent abrasion resistance. The vinyl bond amount Y1 (mol %) in the bonded conjugated diene can be controlled within the above numerical range by adjusting the amount of polar substance added in the first polymerization step for producing the first polymer segment.

[0043] <Second polymer segment> As described above, the conjugated diene polymer of the present embodiment preferably has a first polymer segment that does not contain an aromatic vinyl monomer unit and a second polymer segment that contains an aromatic vinyl monomer unit. The second polymer segment has an estimated Tg value greater than that of the conjugated diene polymer of this embodiment. In such a case, the estimated Tg of the second polymer segment is calculated by substituting each component of the microstructure of the second polymer segment into the above formula (1). When the conjugated diene polymer is a butadiene-styrene copolymer or a butadiene homopolymer, the estimated Tg of the conjugated diene polymer is calculated by multiplying the bound styrene amount X of the conjugated diene polymer by the above formula (iii). all (mass%), vinyl bond content in bound butadiene Y all It is calculated from (mol%).

[0044] The second polymer segment preferably has an estimated Tg of higher than −45° C. and not higher than −5° C. The estimated Tg of the second polymer segment is calculated by the above-mentioned formula (1) when the amount of bound aromatic vinyl monomer units X all (mass%), vinyl bond content Y in the bonded conjugated diene all It can be determined from the microstructure such as (mol%).

[0045] In the conjugated diene polymer of this practical embodiment, the lower limit of the estimated Tg of the second polymer segment is preferably higher than -45°C, more preferably -44°C or higher, and even more preferably -43°C or higher. The upper limit of the estimated Tg of the second polymer segment is preferably −5° C. or lower, more preferably −10° C. or lower, and even more preferably −15° C. or lower. When the estimated Tg of the second polymer segment is in the above-mentioned range, the conjugated diene polymer of the present embodiment tends to have increased hysteresis loss in the high temperature range, and the vulcanizate thereof tends to have excellent wet grip performance.

[0046] The estimated Tg of the second polymer segment of the conjugated diene polymer of this embodiment, calculated by the above formula (1), can be controlled to fall within the above-mentioned numerical range by adjusting the microstructure of the second polymer segment.

[0047] The conjugated diene polymer of this embodiment may contain a polymer segment other than the first polymer segment and the second polymer segment. For example, after synthesis of the first and second polymer segments, the conjugated diene polymer may contain a third polymer segment made of a conjugated diene compound in order to increase the reactivity of the conjugated diene polymer with a coupling agent. The polymer segments may be bonded to each other directly or via a coupling agent.

[0048] (polymer segment ratio) The polymer segment ratio in the conjugated diene polymer represents the average mass fraction of each polymer segment relative to the entire conjugated diene polymer. The ratios of the first and second polymer segments in the conjugated diene polymer of this embodiment are defined as the ratios of the masses of the polymer segments obtained in the first polymerization step (P1), which is a step for preparing the first polymer segment, and the second polymerization step (P2), which is a step for forming the second polymer segment, to the total mass of the conjugated diene polymer. In the first polymer segment ratio (r1) and the second polymer segment ratio (r2) in the conjugated diene-based polymer of this embodiment, the segment ratio (r1) of the first polymer segment is preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and even more preferably 40% by mass or more and 60% by mass or less. When the lower limit of the first polymer segment ratio (r1) satisfies the above range, the ratio of the first polymer segment in the conjugated diene polymer of this embodiment falls within a preferred range, and when vulcanized, the conjugated diene polymer has improved flexibility at low temperatures, and the vulcanized product tends to have excellent wear resistance. Also, when the first polymer segment ratio (r1) satisfies the above upper limit, the ratio of the second polymer segment (r2) in the conjugated diene polymer falls within a preferred range, and wet grip performance tends to be excellent.

[0049] In the conjugated diene polymer of this embodiment, the segment ratio (r1) of the first polymer segment can be controlled within the above-mentioned numerical range by adjusting the polymerization conditions, such as the amount of monomer added and polymerization time, in the first polymerization step (P1).

[0050] The method for introducing multiple polymer segments into the molecule of the conjugated diene-based polymer of this embodiment is not particularly limited, but examples thereof include a method using a continuous solution polymerization method in which multiple reactors are arranged in series, as described below, and sequentially adding a conjugated diene compound, an aromatic vinyl compound, a polar substance, and a solvent to each reactor. The sequentially added substances may be the same or different between reactors.

[0051] (Glass transition temperature (Tg), and the difference between the extrapolated glass transition onset temperature and the extrapolated glass transition finish temperature) The conjugated diene polymer of this embodiment has only one glass transition temperature (Tg) measured by differential scanning calorimetry (DSC), and the difference between the extrapolated glass transition onset temperature and the extrapolated glass transition end temperature of the glass transition temperature (Tg) is from 15° C. to 35° C. A single conjugated diene polymer undergoes glass transition over a wide temperature range, that is, has a region in which it relaxes from an elastic state to a viscous state over a wide temperature range, so that its vulcanizate easily becomes viscous in the low temperature range, resulting in excellent low-temperature performance. In addition, the elastic region of the vulcanizate continues even in the high temperature range, resulting in excellent wet grip performance, resulting in an excellent balance between these two properties.

[0052] As described above, the conjugated diene polymer of this embodiment has only one glass transition temperature (Tg) as measured by DSC. In order to have only one glass transition temperature (Tg), it is effective to ensure that the conjugated diene polymer does not contain isolated aromatic vinyl monomer units (aromatic vinyl monomer blocks, segments consisting only of aromatic vinyl monomer units) or that random conjugated diene polymers with a high proportion of aromatic vinyl monomer units are not locally distributed unevenly. For example, if only 30% by mass from the end of a conjugated diene polymer contains bonds of aromatic vinyl monomer units, and 40% by mass of that is aromatic vinyl monomer units, the conjugated diene polymer will have two glass transition temperatures. Having one glass transition temperature (Tg) means that the conjugated diene polymer is not phase-separated, and tends to exhibit good low-temperature properties when vulcanized.

[0053] The glass transition temperature (Tg) of the conjugated diene polymer of this embodiment is approximately halfway between the extrapolated glass transition onset temperature and the extrapolated glass transition end temperature in differential scanning calorimetry (DSC). The measured Tg value is preferably −75°C or higher, more preferably −70°C or higher. The glass transition temperature (Tg) of the conjugated diene polymer of this embodiment is preferably −45°C or lower, more preferably −50°C or lower. The glass transition temperature (Tg) may be within a range that combines any of the above upper and lower limits. The glass transition temperature (Tg) of the conjugated diene polymer of this embodiment is measured in accordance with ISO 22768:2006. More specifically, a DSC curve is recorded by differential scanning calorimetry (DSC) while increasing the temperature within a predetermined temperature range, and the inflection point of the DSC curve is taken as the glass transition temperature. Specifically, it can be measured by the method described in the Examples below. The conjugated diene polymer of the present embodiment may contain plasticizing components such as resins and process oils described below, but these components must be removed in the DSC measurement for determining the Tg of the conjugated diene polymer of the present embodiment.

[0054] The glass transition temperature (Tg) of a conjugated diene polymer varies depending on the amount of bound aromatic vinyl monomer units in the conjugated diene polymer and the amount of vinyl bonds in the bound conjugated diene. Specifically, the glass transition temperature (Tg) increases when the amount of bound aromatic vinyl monomer units and the amount of vinyl bonds in the bound conjugated diene are increased, whereas the glass transition temperature (Tg) decreases when the amount of bound aromatic vinyl monomer units and the amount of vinyl bonds in the bound conjugated diene are decreased. In the conjugated diene polymer of this embodiment, the estimated Tg can be controlled to a suitable range by adjusting the microstructure, thereby controlling the actually measured glass transition temperature (Tg) to a preferred range.

[0055] The conjugated diene polymer of this embodiment has an extrapolated glass transition onset temperature of a glass transition temperature (Tg) of preferably −90° C. or higher, more preferably −85° C. or higher. The extrapolated glass transition onset temperature is preferably −60° C. or lower, more preferably −65° C. or lower. When the extrapolated glass transition onset temperature is within the above range, the vulcanizate of the conjugated diene polymer of this embodiment tends to have even more excellent tensile properties. The conjugated diene polymer of this embodiment has an extrapolated glass transition end temperature of a glass transition temperature (Tg) of preferably −70° C. or higher, more preferably −65° C. or higher. The extrapolated glass transition end temperature is preferably −40° C. or lower, more preferably −45° C. or lower. When the extrapolated glass transition end temperature is within the above range, the vulcanizate of the conjugated diene polymer of this embodiment tends to have even more excellent low hysteresis loss properties.

[0056] The conjugated diene polymer of this embodiment has only one glass transition temperature (Tg) as measured by DSC, and the difference between the extrapolated glass transition onset temperature and the extrapolated glass transition end temperature of the glass transition temperature is 15° C. or more and 30° C. or less. As a result, when vulcanized, the hysteresis loss in the temperature range higher than the glass transition temperature is high, resulting in excellent wet grip performance, and a wide range of flexibility is obtained at temperatures lower than the glass transition temperature, tending to result in excellent low-temperature performance. From the viewpoint of achieving both wet grip performance and low-temperature performance, the conjugated diene polymer of this embodiment is a conjugated diene polymer having, for only one glass transition temperature, a difference between the extrapolated glass transition onset temperature and the extrapolated glass transition end temperature of 15°C or more. The lower limit of the difference between the extrapolated glass transition onset temperature and the extrapolated glass transition end temperature is preferably 15.5°C or more, more preferably 18°C ​​or more. The upper limit is preferably 35°C or less, more preferably 30°C or less.

[0057] The extrapolated glass transition onset temperature varies depending on the vinyl bond content Y1 in the bonded conjugated diene of the first polymer segment. Specifically, the extrapolated glass transition onset temperature increases as the vinyl bond content Y1 in the bonded conjugated diene increases. On the other hand, the extrapolated glass transition onset temperature decreases as the bonded aromatic vinyl monomer unit content X1 in the first polymer segment and the vinyl bond content Y1 in the bonded conjugated diene decrease. For example, when Y1 is 20 (mol%), the extrapolated glass transition onset temperature is −76.5° C., whereas when Y1 is 15 (mol%), the extrapolated glass transition onset temperature is −78.0° C. The extrapolated glass transition end temperature varies depending on the amount of bound aromatic vinyl monomer units X2 in the second polymer segment, the amount of vinyl bonds Y2 in the bound conjugated diene, and the second polymer segment ratio r2. Specifically, the extrapolated glass transition end temperature increases with an increase in the amount of bound aromatic vinyl monomer units X2 and the amount of vinyl bonds Y2 in the bound conjugated diene, or an increase in the second polymer segment ratio r2. On the other hand, the extrapolated glass transition end temperature decreases with a decrease in the amount of bound aromatic vinyl monomer units X2 and the amount of vinyl bonds Y2 in the bound conjugated diene, or a decrease in the second polymer segment ratio r2. For example, when r2 is 50 (mass%) and the value calculated by the formula (iii) is −23, the extrapolated glass transition end temperature is −53.0°C, and when r2 is 50 (mass%) and the value calculated by the formula (3) is −43, the extrapolated glass transition onset temperature is −58.0°C. When the value calculated by the above formula (iii) is -38 and r2 is 55, the extrapolated glass transition end temperature is -46.0°C.

[0058] (Weight average molecular weight) The weight average molecular weight (Mw) of the conjugated diene polymer of the present embodiment measured by GPC measurement method is preferably 27×10 4 More preferably, it is 30×10 4 More preferably, it is 40×10 4 or more, and even more preferably 45×10 4When the lower limit of the weight average molecular weight measured by GPC measurement method falls within the above range, the vulcanizate tends to have excellent abrasion resistance. The weight average molecular weight is preferably 135×10 4 or less, and more preferably 90×10 4 Less than 70 × 10, more preferably 4 When the upper limit of the weight average molecular weight falls within the above range, the dispersibility of the filler in the vulcanizate tends to be even better. The weight-average molecular weight may be within a range that combines any of the upper and lower limits. The weight-average molecular weight of the conjugated diene polymer can be measured by GPC measurement, specifically, by the method described in the examples below.

[0059] (number average molecular weight) The number average molecular weight of the conjugated diene polymer of the present embodiment measured by GPC measurement method is preferably 17×10 4 More preferably, it is 19×10 or more. 4 or more, and more preferably 23×10 4 When the lower limit of the number average molecular weight measured by GPC measurement method is within the above range, the vulcanizate tends to have excellent abrasion resistance. In addition, the number average molecular weight is preferably 80×10 4 or less, more preferably 50×10 4 or less, and more preferably 40×10 4 The number average molecular weight may be determined by any combination of the upper and lower limits. The number average molecular weight of the conjugated diene polymer can be measured by GPC measurement, specifically, by the method described in the Examples below. When the upper limit of the number average molecular weight satisfies the above range, the dispersibility of the filler in the vulcanizate tends to be even better. The number average molecular weight may be determined by any combination of the upper and lower limits. The number average molecular weight of the conjugated diene polymer can be measured by GPC measurement, specifically, by the method described in the Examples below.

[0060] The weight average molecular weight and number average molecular weight of the conjugated diene polymer can be controlled within the above-mentioned ranges by adjusting the ratio between the amount of polymerization initiator used and the amount of monomer used, and the type and amount of coupling agent used.

[0061] (molecular weight distribution) The molecular weight distribution of the conjugated diene polymer of this embodiment is expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). The conjugated diene polymer of this embodiment preferably has a molecular weight distribution of 1.7 or more and 2.5 or less. A conjugated diene polymer having a molecular weight distribution in this range tends to have better processability when made into a vulcanizate. The molecular weight distribution of the conjugated diene polymer of the present embodiment is more preferably 1.75 or more, and even more preferably 1.8 or more, and more preferably 2.4 or less, and even more preferably 2.2 or less.

[0062] (Mooney viscosity) The Mooney viscosity of the modified conjugated diene polymer of this embodiment, measured at 100°C, is preferably 30 or more and 150 or less, more preferably 60 or more and 130 or less, and even more preferably 60 or more and 115 or less. When the Mooney viscosity is within the above range, the fluidity of the conjugated diene copolymer of this embodiment decreases, resulting in excellent moldability, and the fracture properties and abrasion resistance of the vulcanizate thereof tend to be further improved. The Mooney viscosity of the conjugated diene polymer of this embodiment can be measured by the method described in the examples below.

[0063] (denaturation rate) The conjugated diene polymer of the present embodiment preferably has a nitrogen atom, and more specifically, preferably has a modifying group having a nitrogen atom. In this specification, the term "modification rate" refers to the content, expressed in mass %, of a conjugated diene polymer component having a specific functional group in the polymer molecule that has affinity or binding reactivity with a filler relative to the total amount of the conjugated diene polymer mixture, when a conjugated diene polymer is modified with a nitrogen atom-containing modifying agent to obtain a mixture of modified and unmodified conjugated diene polymers. Therefore, when the specific functional group contains a nitrogen atom, the term "modification rate" refers to the mass ratio of the nitrogen atom-containing conjugated diene polymer relative to the total amount of the conjugated diene polymer mixture.

[0064] For example, when a conjugated diene polymer containing a modified conjugated diene polymer is obtained by reacting a nitrogen atom-containing modifying agent with the terminal end of a conjugated diene polymer, the modification rate is the mass ratio of the conjugated diene polymer having a nitrogen atom-containing functional group resulting from the nitrogen atom-containing modifying agent to the total amount of the conjugated diene polymer.

[0065] The degree of modification can be measured by chromatography, which can separate functional group-containing modified components from unmodified components. Examples of such chromatographic methods include a method in which a gel permeation chromatography column is used, packed with a polar substance such as silica that adsorbs specific functional groups, and the non-adsorbed components are quantified using an internal standard for comparison. More specifically, the modification rate can be obtained by measuring the amount of a sample adsorbed to a silica column from the difference between a chromatogram obtained by measuring a sample solution containing a sample and a low-molecular-weight internal standard polystyrene on a polystyrene gel column and a chromatogram obtained by measuring a sample solution on a silica column. More specifically, the modification rate can be measured by the method described in the Examples.

[0066] In the conjugated diene polymer of this embodiment, the modification rate can be controlled by adjusting the amount of the modifier added and the reaction method. For example, a desired modification rate can be achieved 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.

[0067] From the viewpoint of low hysteresis loss of the vulcanizate, the conjugated diene polymer of the present embodiment preferably has a modification rate of 60% or more, more preferably 65% ​​or more, and even more preferably 70% or more, relative to the total amount of the conjugated diene polymer.

[0068] [Method for producing conjugated diene polymer] The method for producing the conjugated diene polymer of the present embodiment is not limited to the following: For example, the process may include a first polymerization step (P1) using two or more continuous reactors, in which a conjugated diene compound, a polymerization initiator, and a polar substance are added to the continuous reactors to continuously form a first polymer segment of a conjugated diene-based polymer, and a second polymerization step (P2) in which an aromatic vinyl compound and a polar substance are added to the continuous reactors to form a second polymer segment at the end of the first polymer segment. The continuous reactor preferably has two or more reactors.

[0069] (Polymerization initiator) As the polymerization initiator, at least an organic monolithium compound can be used. 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. The amount of the organic monolithium compound used as the polymerization initiator is preferably determined depending on the molecular weight of the target conjugated diene polymer or modified conjugated diene polymer. The amount of a monomer such as a conjugated diene compound used relative to the amount of a polymerization initiator used is related to the degree of polymerization, that is, tends to be related to the number average molecular weight and the weight average molecular weight. 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.

[0070] When a nitrogen atom is introduced into a conjugated diene-based polymer using a polymerization initiator, the organomonolithium compound is preferably an alkyllithium compound having a substituted amino group or a dialkylaminolithium, from the viewpoint that the organomonolithium compound is used as one method for introducing a nitrogen atom into a conjugated diene-based 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. 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. 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. 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. 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.

[0071] The polymerization initiator may be one produced by reacting an aromatic vinyl compound and / or a conjugated diene compound having a substituted amino group with an organic monolithium compound, or may be one capable of introducing a functional group into one end of a polymer chain. The organomonolithium compound is preferably an alkyllithium compound from the viewpoints of industrial availability and ease of control of the polymerization reaction, in which case a conjugated diene polymer having an alkyl group at the polymerization initiation terminal can be obtained. 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. These organomonolithium compounds may be used alone or in combination of two or more, or may be used in combination with other organometallic compounds. 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. Examples of organomagnesium compounds include dibutylmagnesium and ethylbutylmagnesium. Examples of other organometallic compounds include organoaluminum compounds.

[0072] In the method for producing a conjugated diene polymer of this embodiment, a coupling step (P3) of reacting the conjugated diene polymer with a coupling agent may be carried out after the second polymerization step (P2).

[0073] The weight-average molecular weight of the conjugated diene polymer before the coupling step (P3) can be controlled by adjusting the amount of polymerization initiator used relative to the conjugated diene compound and aromatic vinyl compound, and the weight-average molecular weight tends to decrease as the amount of polymerization initiator used decreases. The amount of polymerization initiator used is preferably 0.15 mol or more and 1.5 mol or less, assuming that the total mass of the conjugated diene compound and aromatic vinyl compound used is 100 kg.

[0074] (polar substance) A polar substance may be added in the polymerization step. The polar substance allows the aromatic vinyl compound to be randomly copolymerized with the conjugated diene compound, and the polar substance tends to be usable as a vinylating agent for controlling the microstructure of the conjugated diene portion. The polar substance also tends to be effective in accelerating the polymerization reaction.

[0075] Examples of polar substances 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 substances may be used alone or in combination of two or more. The amount of polar substance used is not particularly limited and can be selected depending on the purpose, but is preferably 0.01 moles or more and 100 moles or less per mole of the polymerization initiator.

[0076] Such polar substances (vinylating agents) can be used in an appropriate amount depending on the desired vinyl bond amount as an agent for adjusting the microstructure of the conjugated diene portion of the conjugated diene polymer. Many polar substances simultaneously exhibit an effective randomizing effect in the copolymerization of a conjugated diene compound and an aromatic vinyl compound, and tend to be able to adjust the randomness of the aromatic vinyl monomer units and conjugated diene monomer units in each polymer segment. As a method for randomizing the conjugated diene monomer units and the aromatic vinyl monomer units, for example, as described in JP-A-59-140211, a copolymerization reaction may be initiated with all of the styrene and a portion of the 1,3-butadiene, and the remaining 1,3-butadiene may be intermittently added during the copolymerization reaction. The 1,3-butadiene added here is added to obtain a high modification rate in the coupling step (P3), and does not necessarily have to form a polymer segment.

[0077] The polymerization temperature in the polymerization step is preferably a temperature at which living anionic polymerization proceeds, and from the viewpoint of productivity, it is preferably 0°C or higher, and more preferably 120°C or lower. By keeping it in this range, it tends to be possible to ensure a sufficient amount of modifying agent reacting with the active terminals after the polymerization is completed. It is even more preferably 50°C or higher and 100°C or lower.

[0078] (Polymer segment polymerization process) In a preferred embodiment of the method for producing a conjugated diene-based polymer of the present embodiment, the polymerization step is carried out in a continuous reactor system using two or more continuous reactors, and as described above, a first polymerization step (P1) for obtaining a first polymer segment and a second polymerization step (P2) for obtaining a second polymer segment are carried out. The first polymerization step (P1) and the second polymerization step (P2) can each be carried out using one or two or more connected reactors. The reactor may be of any shape, such as a tank type with an agitator or a tubular type. It is not essential that the first polymerization step (P1) and the second polymerization step (P2) be assigned to each reactor; for example, the second polymerization step (P2) may be set to start downstream of the first reactor. Each reactor may have a temperature control function.

[0079] In a continuous reactor system, one or two or more connected reactors can be used. The continuous reactor may be, for example, a tank-type or tubular reactor equipped with a stirrer. In a continuous reactor system, preferably, the monomers, the inert solvent, and the polymerization initiator are continuously fed to the reactor, a polymer solution containing a conjugated diene polymer is obtained in the reactor, and the conjugated diene polymer solution is continuously discharged.

[0080] In a continuous reactor system, when continuous tank reactors connected in series are used, new monomers, inert solvents, and polar substances are added to the piping connecting the reactors, or when tubular reactors are used, they are added to the middle of the reactors, thereby allowing a polymer segment different from that synthesized in the previous polymerization step to be introduced into the conjugated diene polymer. Furthermore, by changing the polymerization temperature in the reactor, the bonding form of the conjugated diene compound changes, allowing a different polymer segment to be introduced into the conjugated diene polymer.

[0081] In the method for producing a conjugated diene polymer according to this embodiment, a continuous system is preferred to obtain the conjugated diene polymer, since the polymer can be continuously discharged and subjected to the next reaction in a short time. More preferably, a reaction system in which continuous tank reactors are connected in series is used, thereby increasing the residence time distribution within the reactor and the molecular weight distribution of each polymer segment. Additionally, the randomization effect of the aromatic vinyl compound is enhanced. This suppresses microphase separation of the conjugated diene polymer when vulcanized, resulting in a single glass transition temperature, and also tends to result in excellent wet grip performance and low-temperature performance.

[0082] In the first polymerization step (P1) for producing the first polymer segment, a conjugated diene compound, a polymerization initiator, and a polar substance are added to a reactor and polymerized continuously. The conjugated diene polymer solution after the first polymerization step (P1) is continuously distilled from the reactor and sent to the next step. The liquid is preferably sent to, for example, the second polymerization step (P2) for forming the second polymer segment.

[0083] In the second polymerization step (P2) for the second polymer segment, one or two or more connected reactors are used, as in the polymerization step (P1). An aromatic vinyl compound and an additional polar substance are added to the conjugated diene-based polymer of the first polymer segment obtained in the first polymerization step (P1), and polymerization is continuously carried out. The conjugated diene polymer solution after the second polymerization step (P2) is continuously distilled from the reactor and sent to the next step. The destination of the solution is preferably, for example, the coupling step (P3) described below.

[0084] The conjugated diene polymer of the present embodiment can also be produced by the following method. That is, to form a first polymer segment and a second polymer segment in a conjugated diene-based polymer, two or more continuous polymerization methods may be used. For example, in the first polymerization step (P1) for producing the first polymer segment, an aromatic vinyl compound, a conjugated diene compound, a polymerization initiator, and a polar substance are added to a first reactor and polymerized continuously, while in the second polymerization step (P2) for forming the second polymer segment, no additional aromatic vinyl compound is added to the second reactor and any subsequent reactors, and the conditions for the polymerization steps in the respective reactors are changed, thereby enabling the conjugated diene-based polymer of the present embodiment to be produced.

[0085] Specifically, as described below, the polymerization reaction rate in the first reactor in the first polymerization step (P1) is reduced, and the conjugated diene compound and aromatic vinyl compound that remain unreacted in the first polymerization step (P1) are polymerized in the second polymerization step (P2) or later, thereby forming a first polymer segment and a second polymer segment in the conjugated diene polymer. More specifically, by setting the polymerization reaction rate to 60% or less in the first polymerization step (P1), the above-mentioned production method becomes easier. According to the method described in WO 2018 / 128285, the molecular weight distribution of the conjugated diene polymer decreases. When the molecular weight distribution of the conjugated diene polymer is 1.7 or more, the processability of the vulcanized product tends to be excellent.

[0086] In the method for producing a conjugated diene polymer of this embodiment, it is preferable that, in the second polymerization step (P2) following the first polymerization step (P1), an aromatic vinyl compound and an additional polar substance are added to the conjugated diene polymer of the first polymer segment obtained in the first polymerization step (P1) and polymerization is carried out continuously. Unlike a production method in which an aromatic vinyl compound is added to the first polymerization step (P1) and then the second polymerization step (P2) is carried out, this production method can improve the polymerization reaction rate in the first polymerization step, can make the molecular weight distribution of the conjugated diene polymer 1.7 or more, and tends to result in vulcanizates having excellent processability.

[0087] In the method for producing a conjugated diene polymer of this embodiment, the polymerization reaction rate in the first polymerization step (P1) is preferably 75% or more and 95% or less, more preferably 80% or more and 94% or less, and even more preferably 85% or more and 93% or less. By performing continuous polymerization using two or more continuous reactors and achieving the above-mentioned polymerization reaction rate, the molecular weight distribution of the conjugated diene polymer tends to increase, and the processability of the vulcanizate thereof tends to be improved.

[0088] In the method for producing a conjugated diene polymer of this embodiment, the mass ratio of the conjugated diene compound added in the first polymerization step (P1) to the total amount of the conjugated diene compound and the aromatic vinyl compound added is preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and even more preferably 40% by mass or more and 60% by mass or less. By carrying out the polymerization step within the above range, the ratio of the first polymer segment to the conjugated diene-based polymer can be preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and even more preferably 40% by mass or more and 60% by mass or less. When the ratio of the first polymer segment satisfies the above range, the vulcanizate tends to have excellent abrasion resistance.

[0089] The polymerization reaction rate in the first polymerization step (P1) can be calculated using the following formula (7). For example, the polymerization reaction rate in the first polymerization step (P1) can be calculated from the solid amount of the conjugated diene-based polymer per hour after the first polymerization step (P1) relative to the total amount of the conjugated diene compound and the aromatic vinyl compound added per hour in the first polymerization step (P1). The amount of solids (m1) in the conjugated diene polymer solution can be determined from the amount of nonvolatile components in the polymer solution flowing through the outlet of the first polymerization step (P1) in a unit time. Specifically, the entire volume of the polymer solution flowing through the outlet of the first polymerization step (P1) is collected for 3 minutes, and a polymerization terminator is immediately added. The solution is then transferred to a heat-resistant dish or similar and dried in an oven at 140°C for 30 minutes or more. The mass M1 of the remaining solid matter is then measured. The solid amount (m1) is calculated by combining the following equations (7) and (8).

[0090]

number

[0091]

number

[0092] In the second polymerization step (P2) for forming the second polymer segment, it is preferable to add an aromatic vinyl compound as described above. By controlling the mass ratio of the amount of aromatic vinyl compound added to the amount of conjugated diene compound added in the second polymerization step (P2), the proportion of aromatic vinyl monomer units in the second polymer segment can be controlled, which tends to make it possible to maintain the elastic properties of the conjugated diene polymer in the high temperature range. Specifically, the lower limit of the mass ratio is preferably 0.15 or more, more preferably 0.25 or more, and even more preferably 0.30 or more. By increasing the amount of aromatic vinyl compound added in the second polymerization step (P2), the amount of bound aromatic vinyl monomer units in the second polymer segment in the conjugated diene polymer increases, and the wet grip performance of the vulcanizate tends to be excellent. The upper limit of the mass ratio of the amount of aromatic vinyl compound added to the amount of conjugated diene compound added in the second polymerization step (P2) is preferably 0.70 or less, more preferably 0.65 or less, and even more preferably 0.60 or less. By adjusting the amount of aromatic vinyl compound added in the second polymerization step (P2) to fall within a predetermined range, the amount of bound aromatic vinyl monomer units in the second polymer segment in the conjugated diene polymer can be adjusted to fall within a desired range, and the resulting vulcanizate tends to have excellent handling stability.

[0093] In the second polymerization step (P2), one or more polar substances may be added, which increases the vinyl bond amount Y2 in the bonded conjugated diene of the second polymer segment and tends to improve the wet grip performance of the vulcanizate.

[0094] The amount of polar substance added in the second polymerization step (P2) is not particularly limited and can be selected depending on the purpose, etc., but it is preferably 0.01 to 100 moles per mole of polymerization initiator, including the polar substance added in the first polymerization step (P1). Furthermore, from the viewpoint of reacting the bound aromatic vinyl compound in the second polymerization step (P2) and not forming blocks of the bound aromatic vinyl compound monomer, it is preferable that the amount of polar substance added in the second polymerization step (P2) be greater than that in the first polymerization step (P1). While not particularly limited, it is preferably more than 1.0 times and less than 25 times, more preferably 1.5 times or more and less than 20 times.

[0095] In producing the conjugated diene polymer of this embodiment, a predetermined step may be included before or after the first polymerization step (P1) and before or after the second polymerization step (P2). For example, a polymerization step for forming a polymer segment different from the first polymer segment and the second polymer segment may be included.

[0096] From the viewpoint of the modification rate in the coupling step described later, the polymerization steps are preferably carried out in the order of the first polymerization step (P1) and the second polymerization step (P2), but are not limited thereto. For example, after carrying out the second polymerization step (P2), the first polymerization step (P1) is carried out at a high polymerization temperature without adding an aromatic vinyl compound, thereby obtaining a modified conjugated diene-based polymer in which the coupling step is carried out after the second polymer segment and the first polymer segment. From the viewpoint of reaction controllability, it is preferable that the conversion rate is high in each polymerization step.

[0097] (Coupling step (P3)) In the method for producing the conjugated diene polymer of the present embodiment, a step of coupling the active terminals of the conjugated diene polymer obtained through the above-described polymerization step using a coupling agent, for example, a reactive compound having three or more functionalities, and / or a step of modifying the active terminals using a modifying agent having a nitrogen atom-containing group (preferably, a coupling agent having a nitrogen atom-containing group) may be carried out. Hereinafter, the step of performing coupling and / or modification will be referred to as the coupling step (P3). In the coupling step (P3), one active end of the conjugated diene polymer is subjected to a modification reaction with a coupling agent or a modifying agent having a nitrogen atom to obtain a modified conjugated diene polymer.

[0098] <Coupling agent> In the method for producing a conjugated diene polymer of the present embodiment, the coupling agent used in the coupling step may have any structure as long as it is a tri- or higher functional reactive compound, but is preferably a tri- or higher functional reactive compound having a silicon atom.

[0099] Examples of the tri- or higher functional reactive compound having a silicon atom include, but are not limited to, halogenated silane compounds, epoxylated silane compounds, vinylated silane compounds, alkoxysilane compounds, and alkoxysilane compounds containing a nitrogen-containing group, with aminoalkoxysilane compounds being preferred.

[0100] Examples of halogenated silane compounds that serve as coupling agents include, but are not limited to, methyltrichlorosilane, tetrachlorosilane, tris(trimethylsiloxy)chlorosilane, tris(dimethylamino)chlorosilane, hexachlorodisilane, bis(trichlorosilyl)methane, 1,2-bis(trichlorosilyl)ethane, 1,2-bis(methyldichlorosilyl)ethane, 1,4-bis(trichlorosilyl)butane, and 1,4-bis(methyldichlorosilyl)butane.

[0101] Examples of the epoxidized silane compound that serves as a coupling agent include, but are not limited to, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and epoxy-modified silicone.

[0102] <Modifiers Having Nitrogen Atom-Containing Groups> Examples of the nitrogen atom-containing modifying agent include, but are not limited to, isocyanate compounds, isothiocyanate compounds, isocyanuric acid derivatives, nitrogen atom group-containing carbonyl compounds, nitrogen atom group-containing vinyl compounds, and nitrogen atom group-containing epoxy compounds.

[0103] In the modifying agent having a nitrogen atom-containing group, the nitrogen atom-containing group is preferably an amine compound having no active hydrogen, and examples thereof include tertiary amine compounds, protected amine compounds in which the active hydrogen is substituted with a protecting group, imine compounds represented by the general formula -N=C, and alkoxysilane compounds bonded to the nitrogen atom-containing group.

[0104] Examples of isocyanate compounds that are modifying agents having a nitrogen atom-containing group include, but are not limited to, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate (C-MDI), phenyl isocyanate, isophorone diisocyanate, hexamethylene diisocyanate, butyl isocyanate, and 1,3,5-benzene triisocyanate.

[0105] Examples of isocyanuric acid derivatives that are modifying agents having a nitrogen atom-containing group include, but are not limited to, 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate, 1,3,5-tris(3-triethoxysilylpropyl)isocyanurate, 1,3,5-tri(oxiran-2-yl)-1,3,5-triazinane-2,4,6-trione, 1,3,5-tris(isocyanatomethyl)-1,3,5-triazinane-2,4,6-trione, and 1,3,5-trivinyl-1,3,5-triazinane-2,4,6-trione.

[0106] Examples of carbonyl compounds that are modifying agents having a nitrogen atom-containing group include, but are not limited to, 1,3-dimethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 1-methyl-3-(2-methoxyethyl)-2-imidazolidinone, N-methyl-2-pyrrolidone, N-methyl-2-piperidone, N-methyl-2-quinolone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(dimethylamino)benzophenone, methyl 2-pyridyl ketone, methyl-4-pyridyl ketone, propyl-2-pyridyl ketone, di-4-pyridyl ketone, 2-benzoylpyridine, N,N,N',N'-tetramethylurea, N,N-dimethyl-N',N'-diphenylurea, N,N-methyl diethylcarbamate, N,N-diethylacetamide, N,N-dimethyl-N',N'-dimethylaminoacetamide, N,N-dimethylpicolinic acid amide, and N,N-dimethylisonicotinic acid amide.

[0107] Examples of vinyl compounds that are modifying agents having a nitrogen atom-containing group include, but are not limited to, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-methylmaleimide, N-methylphthalimide, N,N-bistrimethylsilyl acrylamide, morpholinoacrylamide, 3-(2-dimethylaminoethyl)styrene, (dimethylamino)dimethyl-4-vinylphenylsilane, 4,4'-vinylidenebis(N,N-dimethylaniline), 4,4'-vinylidenebis(N,N-diethylaniline), 1,1-bis(4-morpholinophenyl)ethylene, and 1-phenyl-1-(4-N,N-dimethylaminophenyl)ethylene.

[0108] The epoxy compound, which is a modifying agent having a nitrogen atom-containing group, is not limited to the following, but examples thereof include hydrocarbon compounds containing an epoxy group bonded to an amino group, and may further have an epoxy group bonded to an ether group. Such epoxy compounds include, but are not limited to, epoxy compounds represented by general formula (a).

[0109] [ka]

[0110] In the formula (a), R is a divalent or higher organic group having at least one polar group selected from a divalent or higher hydrocarbon group, or a polar group having oxygen such as an ether, epoxy, or ketone, a polar group having sulfur such as a thioether or thioketone, or a polar group having nitrogen such as a tertiary amino group or an imino group.

[0111] The divalent or higher valent hydrocarbon group is a saturated or unsaturated hydrocarbon group that may be linear, branched, or cyclic, and includes an alkylene group, an alkenylene group, a phenylene group, etc. Preferably, it is a hydrocarbon group having 1 to 20 carbon atoms. Examples include methylene, ethylene, butylene, cyclohexylene, 1,3-bis(methylene)-cyclohexane, 1,3-bis(ethylene)-cyclohexane, o-, m-, p-phenylene, m-, p-xylene, and bis(phenylene)-methane groups.

[0112] In the formula (a), R 1 , R 4 is a hydrocarbon group having 1 to 10 carbon atoms, and R 1 , R 4 may be the same or different from each other. In the formula (a), R 2 , R 5 is hydrogen or a hydrocarbon group having 1 to 10 carbon atoms, and R 2 , R 5 may be the same or different from each other. In the formula (a), R 3 is a hydrocarbon group having 1 to 10 carbon atoms, or a structure of the following formula (a1): R 1 , R 2 , R 3 may be bonded to each other to form a cyclic structure. Also, R 3 When R is a hydrocarbon group, it may be bonded to R to form a cyclic structure. 3The N bonded to R may be directly bonded to the N bonded to R. In the formula (a), n is an integer of 1 or more, and m is 0 or an integer of 1 or more.

[0113] [ka]

[0114] In the formula (a1), R 1 , R 2 is R in the formula (a) 1 , R 2 is defined similarly to R 1 , R 2 may be the same or different from each other.

[0115] The epoxy compound, which is a modifying agent having a nitrogen atom-containing group, is preferably one having an epoxy group-containing hydrocarbon group, more preferably one having a glycidyl group-containing hydrocarbon group.

[0116] The epoxy group-containing hydrocarbon group bonded to the amino group or ether group is not particularly limited, but examples thereof include a glycidylamino group, a diglycidylamino group, and a glycidoxy group. More preferred epoxy compounds as the modifying agent are epoxy group-containing compounds having a glycidylamino group or a diglycidylamino group, and a glycidoxy group, respectively, and examples thereof include compounds represented by the following general formula (a2):

[0117] [ka]

[0118] In the formula (a2), R is defined as R in the formula (a), 6 is a hydrocarbon group having 1 to 10 carbon atoms or a structure of the following formula (a3): R 6 When R is a hydrocarbon group, it may be bonded to R to form a cyclic structure. In this case, R 6The N bonded to R may be directly bonded to the N bonded to R. In formula (a2), n is an integer of 1 or more, and m is 0 or an integer of 1 or more.

[0119] [ka]

[0120] As the epoxy compound which is a modifying agent having a nitrogen atom-containing group, a compound having one or more diglycidylamino groups and one or more glycidoxy groups in the molecule is particularly preferred.

[0121] The epoxy compound used as the modifying agent having a nitrogen atom-containing group is not limited to the following, but examples thereof include N,N-diglycidyl-4-glycidoxyaniline, 1-N,N-diglycidylaminomethyl-4-glycidoxy-cyclohexane, 4-(4-glycidoxyphenyl)-(N,N-diglycidyl)aniline, 4-(4-glycidoxyphenoxy)-(N,N-diglycidyl)aniline, 4-(4-glycidoxybenzyl)-(N,N-diglycidyl)aniline, 4-(N,N'-diglycidyl-2-piperazinyl)-glycidoxybenzene, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m- Examples of the diglycidylaminomethyl cyclohexane include xylylenediamine, 4,4-methylene-bis(N,N-diglycidylaniline), 1,4-bis(N,N-diglycidylamino)cyclohexane, N,N,N',N'-tetraglycidyl-p-phenylenediamine, 4,4'-bis(diglycidylamino)benzophenone, 4-(4-glycidylpiperazinyl)-(N,N-diglycidyl)aniline, 2-[2-(N,N-diglycidylamino)ethyl]-1-glycidylpyrrolidine, N,N-diglycidylaniline, 4,4'-diglycidyl-dibenzylmethylamine, N,N-diglycidylaniline, N,N-diglycidylorthotoluidine, and N,N-diglycidylaminomethylcyclohexane. Of these, particularly preferred are N,N-diglycidyl-4-glycidoxyaniline and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[0122] In order to effectively and reliably achieve the effects of this embodiment, the modifying agent is preferably an alkoxysilane compound having a nitrogen atom-containing group.Examples of such modifiers include, but are not limited to, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropylmethyldimethoxysilane, 3-diethylaminopropyltriethoxysilane, 3-morpholinopropyltrimethoxysilane, 3-piperidinopropyltriethoxysilane, 3-hexamethyleneiminopropylmethyldiethoxysilane, 3-(4-methyl-1-piperazino)propyltriethoxysilane, 1-[3-(triethoxysilyl)-propyl]-3-methylhexahydropyrimidine, 3-(4-trimethylsilyl ... bis(3-triethoxysilylpropyl)methylamine, bis(3-triethoxysilylpropyl)methylamine, bis(3-triethoxysilylpropyl)methylamine, tris(trimethoxysilyl)amine, Tris(3-trimethoxysilylpropyl)amine, N,N,N',N'-tetra(3-trimethoxysilylpropyl)ethylenediamine, 3-isocyanatopropyltrimethoxysilane, 3-cyanopropyltrimethoxysilane, 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-(4-trimethoxysilylbutyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(4-trimethoxysilylpropyl ... 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane, 2,2-diethoxy-1-butyl-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-methyl-1-aza-2-silacyclopentane, 2,2-dimethoxy-8-(4-methylpiperazinyl)methyl-1,6-dioxa-2-silacyclooctane, 2,2-dimethoxy-8-(N,N-diethylamino)methyl-1,6-dioxa-2-silacyclooctane, and the like.

[0123] Particularly preferred examples of the alkoxysilane compound having a nitrogen atom-containing group include the following: Specifically, tris(3-trimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-tripropoxysilylpropyl)amine, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine (also referred to as "N,N,N',N'-tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine"), tris(3-trimethoxysilylpropyl) -[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, tris(3-trimethoxysilylpropyl)-[3-(1-methoxy-2-methyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, bis(3-triethoxysilylpropyl)-[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-ethoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, tetraethoxysilylpropyl Tris(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, tetrakis(3-trimethoxysilylpropyl)-1,6-hexamethylenediamine, pentakis(3-trimethoxysilylpropyl)-diethylenetriamine, tris(3-trimethoxysilylpropyl)-methyl-1,3-propanediamine, tetrakis[3-(2,2-dimethoxy -1-aza-2-silacyclopentane)propyl]silane, bis(3-trimethoxysilylpropyl)-bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]silane, tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)silane, tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]silane, 3-tris[2-(2,2-dimethoxy-1-aza-2-silacyclopentane)ethoxy]silyl-1-trimethoxysilylpropane, 1-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-3,4,5-tris(3-trimethoxysilylpropyl)-cyclohexane, 1-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-3,4,5-tris(3-trimethoxysilylpropyl)-cyclohexane, 3,4,5-tris(3-trimethoxysilylpropyl)-cyclohexyl-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]ether, (3-trimethoxysilylpropyl)phosphate, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]phosphate. ,

[0124] Also, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)phosphate, tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]phosphate, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N-(1,3-dimethylbutylidene)-3-(trimethoxysilyl)-1-propanamine, N-benzylidene-3-(triethoxysilyl)propan-1-amine, N- benzylidene-3-(trimethoxysilyl)propan-1-amine, 1,1-(1,4-phenylene)bis(N-(3(triethoxysilyl)propyl)methanamine), 1,1-(1,4-phenylene)bis(N-(3(trimethoxysilyl)propyl)methanamine), 2-methoxy-2-methyl-1-(benzylideneaminoethyl)-1-aza-2-silacyclopentane, and 2-methoxy-2-methyl-1-(4-methoxybenzylideneaminoethyl)-1-aza-2-silacyclopentane.

[0125] Furthermore, 1-methyl-4-[3-(trimethoxysilyl)propyl]piperazine, 1-methyl-4-[3-(triethoxysilyl)propyl]piperazine, 1-methyl-4-[3-(methyldimethoxysilyl)propyl]piperazine, 3,3'-(1,1,3,3-tetramethoxydisiloxane-1,3-diyl)bis(N,N-dimethylpropan-1-amine), 3,3'-(1,1,3,3-tetraethoxydisiloxane-1,3-diyl)bis(N,N-dimethylpropan-1-amine), 3,3'-(1,1,3,3-tetrapropoxydisiloxane-1,3-diyl)bis(N,N-dimethylpropan-1-amine), 3,3'-(1,1,3,3-tetramethoxydisiloxane-1,3-diyl)bis(N,N-dimethylpropan-1-amine),

[0033] Examples of suitable siloxanes include 3,3'-(1,1,3,3-tetramethoxydisiloxane-1,3-diyl)bis(N,N-diethylpropan-1-amine), 3,3'-(1,1,3,3-tetraethoxydisiloxane-1,3-diyl)bis(N,N-diethylpropan-1-amine), 3,3'-(1,1,3,3-tetraethoxydisiloxane-1,3-diyl)bis(N,N-diethylpropan-1-amine).

[0126] Furthermore, 3,3'-(1,1,3,3-tetrapropoxydisiloxane-1,3-diyl)bis(N,N-diethylpropan-1-amine), 3,3'-(1,1,3,3-tetraethoxydisiloxane-1,3-diyl)bis(N,N-dipropylpropan-1-amine), 3,3'-(1,1,3,3-tetrapropoxydisiloxane-1,3-diyl)bis(N,N-dipropylpropan-1-amine), 3,3'-(1,1,3,3-tetrapropoxydisiloxane-1,3-diyl)bis(N,N-dipropylpropan-1-amine), Methoxydisiloxane-1,3-diyl)bis(N,N-diethylmethane-1-amine), 3,3'-(1,1,3,3-tetraethoxydisiloxane-1,3-diyl)bis(N,N-diethylmethane-1-amine), 3,3'-(1,1,3,3-tetrapropoxydisiloxane-1,3-diyl)bis(N,N-diethylmethane-1-amine), 3,3'-(1,1,3,3-tetramethoxydisiloxane-1,3-diyl)bis(N,N-dimethyl dimethylmethan-1-amine), 3,3'-(1,1,3,3-tetramethoxydisiloxane-1,3-diyl)bis(N,N-dipropylmethan-1-amine), 3,3'-(1,1,3,3-tetrapropoxydisiloxane-1,3-diyl)bis(N,N-dimethylmethan-1-amine), 3,3'-(1,1,3,3-tetrapropoxydisiloxane-1,3-diyl)bis(N,N-dipropylmethan-1-amine), 3,3'-(1,1,3,3-tetraethoxydisiloxane-1,3-diyl)bis(N,N-dimethyl 1,3-bis(3-(1H-imidazol-1-yl)propyl)1,1,3,3-tetramethoxydisiloxane, 1,3-bis(3-(1H-imidazol-1-yl)propyl)1,1,3,3-tetraethoxydisiloxane, and 1,3-bis(3-(1H-imidazol-1-yl)propyl)1,1,3,3-tetrapropoxydisiloxane.

[0127] Among coupling modifiers having a group containing a nitrogen atom, examples of protected amine compounds in which active hydrogen is substituted with a protecting group include compounds having alkoxysilanes and protected amines in the molecule. Examples of such compounds include, but are not limited to, N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethylmethyldiethoxysilane, N,N-bis(triethylsilyl)aminopropylmethyldiethoxysilane, 3-(4-trimethylsilyl-1-piperazino)propyltriethoxysilane, and 3-(3-triethylsilyl-1-imidazolidinyl)propylmethyldiethoxysilane. silane, 3-(3-trimethylsilyl-1-hexahydropyrimidinyl)propyltrimethoxysilane, 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-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane, 2,2-diethoxy-1-butyl-1-aza-2-silacyclopentane, and 2,2-dimethoxy-1-methyl-1-aza-2-silacyclopentane.

[0128] Further, for example, N-(1,3-dimethylbutylidene)-3-methyl(dimethoxysilyl)-1-propanamine, N-(1,3-dimethylbutylidene)-3-methyl(diethoxysilyl)-1-propanamine, N-(1-methylethylidene)-3-(triethoxysilyl)-1-propanamine, N-(1-methylethylidene)-3-(trimethoxysilyl)-1-propanamine, N-(1-methylethylidene)-3-methyl(dimethoxysilyl)-1-propanamine, N-(1-methylethylidene)-3-methyl N-ethylidene-3-(triethoxysilyl)-1-propanamine, N-ethylidene-3-(trimethoxysilyl)-1-propanamine, N-ethylidene-3-methyl(dimethoxysilyl)-1-propanamine, N-ethylidene-3-methyl(diethoxysilyl)-1-propanamine, N-(1-methylpropylidene)-3-(triethoxysilyl)-1-propanamine, N-(1-methylpropylidene)-3-(trimethoxysilyl)-1-propanamine , N-(1-methylpropylidene)-3-methyl(dimethoxysilyl)-1-propanamine, N-(1-methylpropylidene)-3-methyl(diethoxysilyl)-1-propanamine, N-benzylidene-3-methyl(dimethoxysilyl)propan-1-amine, N-benzylidene-3-methyl(diethoxysilyl)propan-1-amine, N-4-methylbenzylidene-3-(triethoxysilyl)propan-1-amine, N-4-methylbenzylidene-3-(trimethoxysilyl)propan-1-amine, N- 4-Methylbenzylidene-3-methyl(dimethoxysilyl)propan-1-amine, N-4-methylbenzylidene-3-methyl(diethoxysilyl)propan-1-amine, N-naphthylidene-3-(triethoxysilyl)propan-1-amine, N-naphthylidene-3-(trimethoxysilyl)propan-1-amine, N-naphthylidene-3-methyl(dimethoxysilyl)propan-1-amine, 1,1-(1,4-phenylene)bis(N-(3-methyl(dimethoxysilyl)propyl)methanamine), 1,1-(1,4-phenylene)bis(N-(3-methyl(diethoxysilyl)propyl)methanamine), 2-ethoxy-2-methyl-1-(benzylideneaminoethyl)-1-aza-2-silacyclopentane, and 2-methoxy-2-methyl-1-(methylisobutylideneaminoethyl)-1-aza-2-silacyclopentane, 1-trimethylsilyl-4-[3-(trimethoxysilyl)propyl]piperazine, and 1-trimethylsilyl-4-[3-(triethoxysilyl)propyl]piperazine.

[0129] In the method for producing a conjugated diene polymer of the present embodiment, when a coupling step is performed, it is more preferable to use a modifier having a nitrogen atom-containing group represented by any one of the following formulas (A) to (D) in the coupling step. These may be used alone or in combination of two or more.

[0130] [ka]

[0131] where R 10 , R 11 are hydrocarbon groups having 1 to 12 carbon atoms, which may contain unsaturated bonds, and may be the same or different from each other; R 12 is a hydrocarbon group having 1 to 20 carbon atoms. R 8 , R 9 are aliphatic hydrocarbon groups having 1 to 6 carbon atoms, which may contain unsaturated bonds, and may be the same or different. R 7 is a hydrocarbon group containing Si, O, or N and having 1 to 20 carbon atoms which may be substituted with an organic group not having active hydrogen, and which may have an unsaturated bond. a is an integer of 1 to 3.

[0132] [ka]

[0133] In the formula (B), A represents a hydrocarbon group having 1 to 20 carbon atoms or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, and a phosphorus atom, and having no active hydrogen. R 13 , R 14 , and R 15 each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. R 16 , R 17 , R 18 , R 19 , and R 21 each independently represents an alkyl group having 1 to 20 carbon atoms. R 20 , and R 22 each independently represents an alkylene group having 1 to 20 carbon atoms. R 23 each independently represents an alkyl group having 1 to 20 carbon atoms or a trialkylsilyl group. Each b independently represents an integer of 1 to 3, each c independently represents 1 or 2, i represents an integer of 0 to 6, j represents an integer of 0 to 6, k represents an integer of 0 to 6, and the sum of i, j, and k is an integer of 4 to 10.

[0134] [ka]

[0135] However, in formula (C), R 24 , R 25 , R 26 , R 27 , R 28 , and R 29 are each independently an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms. R 30 , R 31 , and R 32 are each independently an alkylene group having 1 to 20 carbon atoms. s, t, and u each independently represent an integer of 1 to 3, and the sum of s, t, and u is an integer of 4 or greater.

[0136] [ka]

[0137] However, in formula (D), B 1 and B 2 are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms which may or may not contain an oxygen atom. R 33 ~R 36 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms. L 1 ~L 4 are each independently a divalent, trivalent, or tetravalent alkylsilyl group substituted with an alkyl group having 1 to 10 carbon atoms, or a monovalent hydrocarbon group having 1 to 20 carbon atoms; 1 and L 2 And, L 3 and L 4 may be linked to each other to form a ring having 1 to 5 carbon atoms, and L 1 and L 2 And, L 3 and L 4 When are linked to each other to form a ring, the formed ring may contain 1 to 3 heteroatoms of one or more kinds selected from the group consisting of N, O, and S.

[0138] Specifically, in the formula (D), B 1 and B 2 are each independently an alkylene group of 1 to 10 carbon atoms, and R 33 ~R 36 are each independently an alkyl group having 1 to 10 carbon atoms, and L 1 ~L 4 are each independently a tetravalent alkylsilyl group substituted with an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 10 carbon atoms, or L 1 and L 2 And, L 3 and L 4 may be linked to each other to form a ring having 1 to 3 carbon atoms, and L 1 and L 2And, L 3 and L 4 When they are linked to each other to form a ring, the ring formed may contain 1 to 3 heteroatoms of one or more kinds selected from the group consisting of N, O and S.

[0139] Examples of the coupling modifier represented by formula (A) include, but are not limited to, 1-methyl-4-[3-(trimethoxysilyl)propyl]piperazine, 1-methyl-4-[3-(triethoxysilyl)propyl]piperazine, 1-propyl-4-[3-(trimethoxysilyl)propyl]piperazine, 1-propyl-4-[3-(triethoxysilyl)propyl]piperazine, 1-trimethylsilyl-4-[3-(trimethoxysilyl)propyl]piperazine, and 1-trimethylsilyl-4-[3-(triethoxysilyl)propyl]piperazine.

[0140] Among these, from the viewpoint of enhancing the reactivity and interaction between the conjugated diene polymer of the present embodiment and an inorganic filler such as silica, and from the viewpoint of enhancing processability, those in which a is 3 in the formula (A) are preferred.

[0141] In the coupling step using the coupling modifier represented by formula (A), the reaction temperature and reaction time are not particularly limited, but the reaction is preferably carried out at a temperature of 0°C or higher and 120°C or lower, and for 30 seconds or longer.

[0142] The amount of the coupling modifier represented by formula (A) added is preferably in a range such that the total number of moles of alkoxy groups bonded to silyl groups in the compound represented by formula (A) is 0.2 to 2.0 times the number of moles of the polymerization initiator added, more preferably 0.3 to 1.5 times, and even more preferably 0.4 to 1.0 times. From the viewpoint of achieving a more preferable range for the molecular weight of the resulting modified conjugated diene polymer, the amount is preferably 0.2 times or more, and from the viewpoint of storage stability during long-term storage, the amount is preferably 2.0 times or less.

[0143] More specifically, the amounts of the polymerization initiator and the coupling modifier represented by the formula (A) added may be adjusted so that the number of moles of the coupling modifier represented by the formula (A) is preferably 0.1 to 1.0 times the number of moles of the polymerization initiator.

[0144] In the formula (B), A is preferably represented by any one of the following formulae (I) to (IV).

[0145] [ka]

[0146] In the formula (I), D 1 represents a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms, and h represents an integer of 1 to 10. When a plurality of D 1 are each independent of each other.

[0147] [ka]

[0148] In the formula (II), D 2 represents a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms. 3 represents an alkyl group having 1 to 20 carbon atoms. h represents an integer of 1 to 10. When a plurality of D 2 and D 3 are each independent of each other.

[0149] [ka]

[0150] In the formula (III), D 4 represents a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms. h represents an integer of 1 to 10. When there are multiple D 4 are each independent of each other.

[0151] [ka]

[0152] In the formula (IV), D 5 represents a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms. h represents an integer of 1 to 10. When there are multiple D 5 are each independent of each other.

[0153] In the formula (B), when A is represented by formula (I), examples of the coupling modifier include, but are not limited to, tris(3-trimethoxysilylpropyl)amine, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)amine, tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, tris(3-ethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)-[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]amine, bis[3-(2,2-diethoxy-1- aza-2-silacyclopentane)propyl]-(3-triethoxysilylpropyl)amine, tris[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]amine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, bis(3-trimethoxysilylpropyl)-bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)-1,3-propanediamine.

[0154] Further, for example, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tris(3-trimethoxysilylpropyl)-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl] tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, tetrakis(3-triethoxysilylpropyl)-1,3-propanediamine, and tris(3-triethoxysilylpropyl)-[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine.

[0155] Further, for example, bis(3-triethoxysilylpropyl)-bis[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tris[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-(3-triethoxysilylpropyl)-1,3-propanediamine, tetrakis[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tris(3-triethoxysilylpropyl)-[3-(1-ethoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, bis(3-triethoxysilylpropyl)-[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, bis[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-ethoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, bis[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-(3-triethoxysilylpropyl)-[3-(1-ethoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, tris[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-ethoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-propanediamine, and tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane.

[0156] Furthermore, for example, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, bis(3-trimethoxysilylpropyl)-bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tris(3-trimethoxysilylpropyl) bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, and bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-bisaminomethylcyclohexane.

[0157] Furthermore, for example, tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, tetrakis(3-triethoxysilylpropyl)-1,3-propanediamine, tris(3-triethoxysilylpropyl)-[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, bis(3-triethoxysilylpropyl)-1,3-propanediamine, tris[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tris(3-triethoxysilylpropyl)-[3-(1-ethoxy-2-trimethylsilylpropyl)-bis[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, tris[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-(3-triethoxysilylpropyl)-1,3-propanediamine, tetrakis[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tris(3-triethoxysilylpropyl)-[3-(1-ethoxy-2-trimethylsilylpropyl) bis(3-triethoxysilylpropyl)-[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-ethoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, bis[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-(3-triethoxysilylpropyl)-[3-(1-ethoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, bis[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-(3-triethoxysilylpropyl)-[3-(1-ethoxy-2- trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, tris[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-[3-(1-ethoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-1,3-bisaminomethylcyclohexane, tetrakis(3-trimethoxysilylpropyl)-1,6-hexamethylenediamine, and pentakis(3-trimethoxysilylpropyl)-diethylenetriamine.

[0158] In the formula (B), when A is represented by formula (II), examples of the coupling modifier include, but are not limited to, tris(3-trimethoxysilylpropyl)-methyl-1,3-propanediamine, bis(2-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-methyl-1,3-propanediamine, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl), Tris(3-triethoxysilylpropyl)-methyl-1,3-propanediamine, Bis(2-triethoxysilylpropyl)-[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-methyl-1,3-propanediamine, Bis[3-(2,2-diethoxy-1-aza-2-silacyclopentane)propyl]-(3-triethoxysilylpropyl)-methyl-1,3-propanediamine, N 1 ,N 1 '-(Propane-1,3-diyl)bis(N 1 -methyl-N 3 ,N 3 -bis(3-(trimethoxysilyl)propyl)-1,3-propanediamine), and N 1 -(3-(bis(3-(trimethoxysilyl)propyl)amino)propyl)-N 1 -methyl-N 3 -(3-(methyl(3-(trimethoxysilyl)propyl)amino)propyl)-N 3 -(3-(trimethoxysilyl)propyl)-1,3-propanediamine.

[0159] In the formula (B), when A is represented by formula (III), examples of the coupling modifier include, but are not limited to, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]silane, tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)silane, tris[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trimethoxysilylpropyl)silane, ]-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]silane, bis(3-trimethoxysilylpropyl)-bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]silane, (3-trimethoxysilyl)-[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)-bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]silane propyl]silane, bis[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)-bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]silane, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]silane, bis(3-trimethoxysilylpropyl)-[3-(1-methoxy-2-trimethylsilyl-1-sila- 2-azacyclopentane)propyl]-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]silane, bis[3-(1-methoxy-2-trimethylsilyl-1-sila-2-azacyclopentane)propyl]-bis(3-trimethoxysilylpropyl)silane, and bis(3-trimethoxysilylpropyl)-bis[3-(1-methoxy-2-methyl-1-sila-2-azacyclopentane)propyl]silane.

[0160] In the formula (B), when A is represented by formula (IV), examples of the coupling modifier include, but are not limited to, 3-tris[2-(2,2-dimethoxy-1-aza-2-silacyclopentane)ethoxy]silyl-1-(2,2-dimethoxy-1-aza-2-silacyclopentane)propane and 3-tris[2-(2,2-dimethoxy-1-aza-2-silacyclopentane)ethoxy]silyl-1-trimethoxysilylpropane.

[0161] The amount of the modifier represented by formula (B) to be added is preferably determined based on the ratio of the number of moles of the polymerization initiator to the number of moles of the modifier represented by formula (B) to be added, which allows the conjugated diene polymer and the modifier to react in a desired stoichiometric ratio.

[0162] More specifically, the amounts of the polymerization initiator and the coupling modifier represented by formula (B) added may be adjusted so that the ratio of the moles of the coupling modifier represented by formula (B) to the moles of the polymerization initiator is preferably 0.012 to 1.0, more preferably 0.02 to 0.5. In this case, the number of functional groups in the modifier in formula (B) (for example, when i and j are 2 or more, and there are multiple w and x, and when f and g are equal, then f × i + (g + 1) × j + k) is preferably an integer of 5 to 10, more preferably an integer of 6 to 10. From the viewpoint of keeping the molecular weight of the resulting modified conjugated diene polymer within a preferred range, the ratio is preferably 0.012 or more. From the viewpoint of storage stability during long-term storage, the ratio is preferably 0.2 or less.

[0163] Among these, from the viewpoint of enhancing the reactivity and interaction between the modified conjugated diene polymer and the inorganic filler such as silica, and from the viewpoint of enhancing processability, it is preferable that i, j, and k in the formula (B) are all 3.

[0164] Examples of the coupling modifier represented by formula (C) include, but are not limited to, 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.

[0165] In the coupling step using the coupling modifier represented by formula (C), the reaction temperature and reaction time are not limited to the following, but are preferably from 0°C to 120°C, and the reaction is preferably carried out for 30 seconds or more.

[0166] The amount of coupling modifier represented by formula (C) added is preferably in a range such that the total number of moles of alkoxy groups bonded to silyl groups in the compound represented by formula (C) is 0.1 to 2.0 times the number of moles of polymerization initiator added, more preferably 0.2 to 1.0 times, and even more preferably 0.3 to 0.5 times. From the viewpoint of the molecular weight of the resulting modified conjugated diene polymer, the amount is preferably 0.1 times or more. Furthermore, from the viewpoint of storage stability during long-term storage, the amount is preferably 2.0 times or less.

[0167] Examples of the coupling modifier represented by formula (D) include 3,3'-(1,1,3,3-tetramethoxydisiloxane-1,3-diyl)bis(N,N-dimethylpropan-1-amine), 3,3'-(1,1,3,3-tetraethoxydisiloxane-1,3-diyl)bis(N,N-dimethylpropan-1-amine), 3,3'-(1,1,3,3-tetrapropoxydisiloxane-1,3-diyl)bis(N,N-dimethylpropan-1-amine), 3,3'-(1,1,3,3-tetramethoxydisiloxane-1,3-diyl)bis(N,N-diethylpropan-1-amine), 3,3'-(1,1,3,3-tetramethyldisiloxane-1,3-diyl)bis(N,N-dimethyl ... methoxydisiloxane-1,3-diyl)bis(N,N-dipropylpropan-1-amine), 3,3'-(1,1,3,3-tetraethoxydisiloxane-1,3-diyl)bis(N,N-diethylpropan-1-amine).

[0168] In the coupling step using the coupling modifier represented by formula (D), the reaction temperature and reaction time are not particularly limited, but the reaction is preferably carried out at a temperature of 0°C or higher and 120°C or lower, and for 30 seconds or longer.

[0169] The amount of coupling modifier represented by formula (D) added is preferably in a range such that the total number of moles of alkoxy groups bonded to silyl groups in the compound represented by formula (D) is 0.25 to 2.0 times the number of moles of polymerization initiator added, more preferably 0.3 to 1 time, and even more preferably 0.35 to 0.5 times. From the viewpoints of the molecular weight of the resulting modified conjugated diene polymer and storage stability during long-term storage, it is preferably 2.0 times or less.

[0170] The method for producing a conjugated diene-based polymer of the present embodiment may include a condensation reaction step in which a condensation promoter is added to cause a condensation reaction after and / or before the coupling step.

[0171] In the method for producing a conjugated diene polymer of the present embodiment, after the coupling step, a deactivator and / or a neutralizer may be added to the polymer solution, if necessary. Examples of the quenching agent include, but are not limited to, water and alcohols such as methanol, ethanol, and isopropanol. Examples of neutralizing agents include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a mixture of highly branched carboxylic acids having 9 to 11 carbon atoms, with 10 carbon atoms as the main component), aqueous solutions of inorganic acids, and carbon dioxide gas.

[0172] A rubber stabilizer is preferably added to the conjugated diene polymer of the present embodiment from the viewpoint of preventing gel formation after polymerization and improving stability during processing. The rubber stabilizer is not limited to the following and known stabilizers can be used, but preferred are antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol) propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol.

[0173] (Process for obtaining from polymer solution) The method for producing a conjugated diene polymer of this embodiment may include a step of obtaining the obtained conjugated diene polymer from a polymer solution. A known method can be used to obtain the conjugated diene polymer from the polymer solution, and the following methods may also be used, for example. Examples of methods include a method in which the solvent is separated by steam stripping or the like, and then the conjugated diene polymer is filtered and then dehydrated and dried to obtain a conjugated diene polymer; a method in which the conjugated diene polymer is obtained by concentrating the polymer in a flashing tank and then devolatilizing it using a vent extruder or the like; and a method in which the conjugated diene polymer is obtained by directly devolatilizing it using a drum dryer or the like.

[0174] (Step of Obtaining Extended Conjugated Diene Polymer) In the method for producing a conjugated diene polymer of the present embodiment, at least one selected from the group consisting of an extender oil, a liquid rubber, and a resin may be further added to the produced conjugated diene polymer to form an extended conjugated diene polymer. The extended conjugated diene polymers include not only oil-extended conjugated diene polymers containing oil, but also those containing liquid polybutadiene and various resins other than oil. This can further improve the processability of the conjugated diene polymer.

[0175] The method for adding the extender oil to the conjugated diene polymer is not limited to the following method, but a method in which the extender oil is added to a conjugated diene polymer solution, mixed, and the resulting extended polymer solution is desolvated is preferred. Examples of extender oils include aromatic oils, naphthenic oils, paraffin oils, and vegetable oils. The vegetable oils can be selected from the group consisting of linseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, castor oil, tung oil, pine oil, sunflower oil, palm oil, olive oil, coconut oil, peanut oil, and grapeseed oil. Among these, aromatic substitute oils having a polycyclic aromatic (PCA) content of 3% by mass or less according to the IP346 method are preferred from the standpoints of environmental safety, oil bleeding prevention, and wet grip performance. 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).

[0176] Examples of liquid rubber include, but are not limited to, liquid polybutadiene and liquid styrene-butadiene rubber. Examples of resins include, but are not limited to, aromatic petroleum resins, coumarone-indene resins, terpene resins, rosin derivatives (including tung oil resins), tall oil, tall oil derivatives, rosin ester resins, natural and synthetic terpene resins, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, mixed aliphatic-aromatic hydrocarbon resins, coumarin-indene resins, phenolic resins, p-tert-butylphenol-acetylene resins, phenol-formaldehyde resins, xylene-formaldehyde resins, monoolefin oligomers, diolefin oligomers, hydrogenated aromatic hydrocarbon resins, cyclic aliphatic hydrocarbon resins, hydrogenated hydrocarbon resins, hydrogenated tung oil resins, hydrogenated oil resins, and esters of hydrogenated oil resins with monofunctional or polyfunctional alcohols. These resins may be used alone or in combination of two or more. In the case of hydrogenation, all of the unsaturated groups may be hydrogenated, or some of them may remain. The amount of at least one selected from the group consisting of extender oil, liquid rubber, and resin is not particularly limited, but is preferably 1 to 60 parts by mass, more preferably 10 to 60 parts by mass, and even more preferably 15 to 37.5 parts by mass, relative to 100 parts by mass of the conjugated diene-based polymer of the present embodiment.

[0177] [Rubber composition] The conjugated diene polymer of this embodiment can be made into a rubber composition by adding a filler (hereinafter, sometimes referred to as the rubber composition of this embodiment). The rubber composition of this embodiment includes a rubber component containing the conjugated diene polymer of this embodiment and 5.0 to 150 parts by mass of a filler per 100 parts by mass of the rubber component. The rubber component preferably contains 10 parts by mass or more of the conjugated diene polymer of this embodiment per 100 parts by mass of the total rubber component. Dispersing a filler in the rubber component containing the conjugated diene polymer of this embodiment can provide a rubber composition with superior processability during vulcanization, and the vulcanizate exhibits superior low hysteresis loss, fracture properties, and abrasion resistance. Furthermore, when the rubber component contains the conjugated diene polymer of this embodiment in a predetermined proportion, the low hysteresis loss, processability, and abrasion resistance tend to be further improved.

[0178] Examples of fillers include, but are not limited to, silica-based inorganic fillers, carbon black, metal oxides, and metal hydroxides. Among these, silica-based inorganic fillers are preferred. In particular, when the rubber composition of this embodiment is used for vulcanized rubber applications such as tires, automobile parts such as anti-vibration rubber, and shoes, it is preferred to contain a silica-based inorganic filler. Such fillers may be used alone or in combination of two or more.

[0179] The silica-based inorganic filler is not particularly limited and any known filler can be used, but 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-based inorganic filler in an amount of more than 50 mass%, preferably 70 mass% or more, and more preferably 80 mass% or more.

[0180] Examples of silica-based inorganic fillers include, but are not limited to, inorganic fibrous materials such as silica, clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, and glass fiber. Surface-hydrophobized silica-based inorganic fillers and mixtures of silica-based inorganic fillers with non-silica-based inorganic fillers may also be used. Among these, silica or glass fiber is preferred, and silica is more preferred, from the viewpoint of further improving the strength and abrasion resistance of the rubber composition of this embodiment. Examples of silica include, but are not limited to, dry silica, wet silica, and synthetic silicate silica. Among these silicas, wet silica is preferred from the viewpoint of further improving the breaking strength of the rubber composition.

[0181] From the viewpoint of more reliably obtaining a rubber composition having practically good abrasion resistance and breaking strength, 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, and 170m 2 / g or more 250m 2 / g or less. If necessary, a relatively small specific surface area (for example, a specific surface area of ​​200 m 2 / g) silica-based inorganic filler and a relatively large specific surface area (e.g., 200 m 2 / g or more) may be used in combination with silica-based inorganic fillers. 2 When a silica-based inorganic filler (at least 1000 saturates / g) is used, the rubber composition of the present embodiment further improves the dispersibility of silica, and as a result, tends to have even better abrasion resistance, breaking strength, and low hysteresis loss.

[0182] Examples of carbon black include, but are not limited to, carbon blacks of various classes such as SRF, FEF, HAF, ISAF, and SAF. Among these, carbon blacks having a nitrogen adsorption specific surface area of ​​50 m or more as determined by the BET adsorption method are preferred. 2 / g or more and a dibutyl phthalate (DBP) oil absorption of 80 mL / 100 g or less is preferred.

[0183] Metal oxides include those with the chemical formula M x O y (M represents a metal atom, and x and y each independently represent an integer of 1 to 6.) As long as the solid particles have as the main component of the structural unit, there are no particular limitations, but examples include alumina, titanium oxide, magnesium oxide, and zinc oxide.

[0184] Examples of metal hydroxides include, but are not limited to, aluminum hydroxide, magnesium hydroxide, and zirconium hydroxide.

[0185] The content of the filler in the rubber composition of this embodiment is preferably 5.0 parts by mass to 150 parts by mass, more preferably 20 parts by mass to 100 parts by mass, and even more preferably 30 parts by mass to 90 parts by mass, per 100 parts by mass of the rubber component. When the filler satisfies the above range, the rubber composition tends to have even more excellent processability during vulcanization, and the vulcanizate thereof tends to have even more excellent low hysteresis loss, fracture properties, and abrasion resistance.

[0186] From the viewpoint of reliably imparting the performance required for applications such as tires, such as dry grip performance and conductivity, the rubber composition of this embodiment preferably contains 0.5 parts by mass to 100 parts by mass of carbon black relative to 100 parts by mass of the rubber component containing the conjugated diene polymer of this embodiment. From the same viewpoint, the rubber composition preferably contains 3.0 parts by mass to 100 parts by mass, and even more preferably 5.0 parts by mass to 50 parts by mass, of carbon black relative to 100 parts by mass of the rubber component containing the conjugated diene polymer of this embodiment.

[0187] The rubber composition of the present embodiment may further contain a silane coupling agent. When the rubber composition contains a silane coupling agent, the interaction between the rubber component and the filler can be further improved. The silane coupling agent is preferably, but not limited to, a compound having a sulfur bond and an alkoxysilyl group or a silanol group in one molecule. Examples of such compounds include, but are not limited to, bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, and bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide.

[0188] In the rubber composition of this embodiment, the content of the silane coupling agent is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and even more preferably 1.0 to 15 parts by mass, relative to 100 parts by mass of the filler. When the content of the silane coupling agent is within the above range, the interaction between the rubber component and the filler tends to be further improved.

[0189] The rubber composition of the present embodiment may contain, as a rubber component, a rubbery polymer other than the conjugated diene-based polymer of the present embodiment (hereinafter simply referred to as a "rubbery polymer"). Examples of rubbery polymers include, but are not limited to, conjugated diene polymers and hydrogenated products thereof, random copolymers of conjugated diene compounds and vinyl aromatic compounds and hydrogenated products thereof, block copolymers of conjugated diene compounds and vinyl aromatic compounds and hydrogenated products thereof, non-diene polymers, and natural rubber. Examples of rubber-like polymers include, but are not limited to, styrene-based elastomers such as butadiene rubber and hydrogenated products thereof, isoprene rubber and hydrogenated products thereof, styrene-butadiene rubber and hydrogenated products thereof, styrene-butadiene block copolymers and hydrogenated products thereof, and styrene-isoprene block copolymers and hydrogenated products thereof, as well as acrylonitrile-butadiene rubber and hydrogenated products thereof. Examples of non-diene polymers include, but are not limited to, olefin elastomers such as ethylene-propylene rubber, ethylene-propylene-diene rubber, ethylene-butene-diene rubber, ethylene-butene rubber, ethylene-hexene rubber, and ethylene-octene rubber, butyl rubber, brominated butyl rubber, acrylic rubber, fluororubber, silicone rubber, chlorinated polyethylene rubber, epichlorohydrin rubber, α,β-unsaturated nitrile-acrylate-conjugated diene copolymer rubber, urethane rubber, and polysulfide rubber. Examples of natural rubber include, but are not limited to, smoked sheets RSS3 to 5, SMR, and epoxidized natural rubber.

[0190] The rubbery polymer may be a modified rubber to which a polar functional group such as a hydroxyl group or an amino group has been added. When the rubber composition of the present embodiment is used for a tire, the rubbery polymer is preferably at least one selected from the group consisting of butadiene rubber, isoprene rubber, styrene-butadiene rubber, natural rubber, and butyl rubber.

[0191] From the viewpoint of the balance between the abrasion resistance, breaking strength, low hysteresis loss, and processability of the rubber composition, the weight average molecular weight of the rubber polymer is preferably 2,000 to 2,000,000, and more preferably 5,000 to 1,500,000. Furthermore, a low molecular weight rubber polymer, so-called liquid rubber, can also be used as the rubber polymer. These rubber polymers may be used alone or in combination of two or more.

[0192] When the rubber composition of this embodiment further contains the above-described rubbery polymer in addition to the conjugated diene polymer of this embodiment, the content ratio (mass ratio) of the conjugated diene polymer to the rubbery polymer (conjugated diene polymer / rubbery polymer) is preferably 10 / 90 to 100 / 0, more preferably 20 / 80 to 99 / 1, and even more preferably 30 / 70 to 95 / 5. That is, the rubber component contains preferably 10 to 100 parts by mass, more preferably 20 to 90 parts by mass, and even more preferably 30 to 80 parts by mass of the conjugated diene polymer of this embodiment per 100 parts by mass of the total rubber component. When the proportion of the conjugated diene polymer of this embodiment in the rubber component is within the above range, the vulcanizate of the rubber composition tends to have even better wear resistance and low hysteresis loss.

[0193] In order to further improve the processability of the rubber composition of the present embodiment, a rubber softener may be added in addition to the rubber component. As the rubber softener, the same ones as those exemplified as those contained in the above-mentioned conjugated diene polymer can be used, but mineral oil or liquid or low-molecular weight synthetic softeners are preferred. Mineral oil-based rubber softeners, also known as process oils or extender oils, are used to soften rubber components, increase their volume, and improve their processability. These softeners are mixtures of aromatic rings, naphthenic rings, and paraffin chains. Among these, softeners in which 50% or more of the total carbon atoms belong to paraffin chains are called paraffinic, those in which 30% to 45% of the total carbon atoms belong to naphthenic rings are called naphthenic, and those in which more than 30% of the total carbon atoms belong to aromatic carbons are called aromatic. The rubber composition of this embodiment preferably contains a rubber softener with an appropriate aromatic content. The inclusion of such a rubber softener further improves compatibility with conjugated diene polymers. The content of the rubber softener in the rubber composition of this embodiment is expressed as the total amount of the rubber softener added in advance to the conjugated diene polymer or rubber-like polymer and the rubber softener added when preparing the rubber composition. In the rubber composition of this embodiment, the content of the rubber softener is preferably 0 to 100 parts by mass, more preferably 10 to 90 parts by mass, and even more preferably 30 to 90 parts by mass, per 100 parts by mass of the rubber component. By having the content of the rubber softener be 100 parts by mass or less per 100 parts by mass of the rubber component, bleeding out can be suppressed, and stickiness on the surface of the rubber composition can be further suppressed.

[0194] The rubber composition can be produced by mixing a conjugated diene polymer, a rubbery polymer, a filler, a silane coupling agent, a rubber softener, and the like. The mixing method is not particularly limited, but examples include melt-kneading methods 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 methods in which the components are dissolved and mixed and then the solvent is removed by heating. Of these, melt-kneading methods using a roll, a Banbury mixer, a kneader, or an extruder are preferred from the viewpoints of productivity and good kneading ability. The rubber component, the filler, the silane coupling agent, and the additives may be kneaded all at once, or may be mixed in multiple batches.

[0195] The rubber composition of the present embodiment may be vulcanized with a vulcanizing agent to form a vulcanizate. The vulcanizing agent is not particularly limited, but examples thereof include radical generators such as organic peroxides and azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. Examples of sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, and polymeric polysulfur compounds.

[0196] In the rubber composition of this embodiment, the content of the vulcanizing agent is preferably 0.01 to 20 parts by mass, and more preferably 0.1 to 15 parts by mass, per 100 parts by mass of the rubber component. A conventionally known method can be used as the vulcanization method. The vulcanization temperature is preferably 120°C to 200°C, and more preferably 140°C to 180°C.

[0197] When vulcanizing the rubber composition, a vulcanization accelerator and / or a vulcanization aid may be used as necessary. As the vulcanization accelerator, a conventionally known material can be used, and examples thereof include, but are not limited to, sulfenamide-based, guanidine-based, thiuram-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, thiourea-based, and dithiocarbamate-based vulcanization accelerators. Furthermore, examples of the vulcanization aid include, but are not limited to, zinc oxide and stearic acid. The content of each of the vulcanization accelerator and the vulcanization aid is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the rubber component.

[0198] The rubber composition of the present embodiment may contain various additives such as softeners other than those described above, other fillers, heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, and lubricants, within the range that does not impair the effects of the present embodiment. Known softeners can be used as the softener. Examples of other fillers include, but are not limited to, calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate. Known materials can be used as the heat stabilizer, antistatic agent, weather stabilizer, antioxidant, colorant, and lubricant.

[0199] The rubber composition of the present embodiment is suitably used as a rubber composition for tires. The rubber composition of the present embodiment is not particularly limited, but can be suitably used for various tire parts such as fuel-efficient tires, all-season tires, high-performance tires, and studless tires, including treads, carcasses, sidewalls, and bead portions.

[0200] In addition, the numerical ranges described above as preferred ranges, etc., may be replaced with numerical ranges that arbitrarily combine the values ​​described as upper limits and the values ​​described as lower limits, unless otherwise specified. [Example]

[0201] Hereinafter, the present embodiment will be described in more detail with reference to specific examples and comparative examples, but the present invention is not limited to the following examples and comparative examples in any way.

[0202] Various physical properties in the examples and comparative examples were measured by the methods shown below.

[0203] [(Property 1) Amount of bound aromatic vinyl monomer units (amount of bound styrene)] (Bound styrene content of conjugated diene polymer X all ) A conjugated diene polymer containing no rubber softener was used as a sample, and 100 mg of the sample was dissolved in chloroform to make a total volume of 100 mL to prepare a measurement sample. The amount of bound styrene (mass %) relative to 100 mass % of the sample conjugated diene polymer was measured based on the amount of absorption of ultraviolet light (around 254 nm) by the phenyl group of styrene (measuring device: Shimadzu Corporation spectrophotometer "UV-2450").

[0204] (Amount of bound styrene in the first polymer segment X1) The bound styrene amount was calculated in the same manner as for the bound styrene amount in the segment of the conjugated diene polymer, except that the sample was changed from the conjugated diene polymer to the first polymer segment.

[0205] (Amount of bound styrene in the second polymer segment X2) The segment ratio (r1) of the first polymer segment and the segment ratio (r2) of the second polymer segment were calculated by the method described below, and the amount of bound styrene in the conjugated diene polymer X calculated from the measurement was all Using the amount of bound styrene X1 in the first polymer segment and the amount of bound styrene X2 in the second polymer segment, the amount of bound styrene X2 in the second polymer segment was calculated from the following formula (9).

[0206]

number

[0207] [(Property 2) Amount of vinyl bonds in bound conjugated diene (amount of 1,2-vinyl bonds in bound butadiene)] (Vinyl bond amount Y of conjugated diene polymer all ) A conjugated diene polymer containing no rubber softener was used as a sample, and 50 mg of the sample was dissolved in 10 mL of carbon disulfide to prepare a measurement sample. The infrared spectrum of each sample was measured from 600 to 1000 cm -1 The measurement was carried out using a Fourier transform infrared spectrophotometer (manufactured by JASCO Corporation under the trade name "FT-IR230"). According to the Hampton method (method described in R.R. Hampton, Analytical Chemistry 21, 923 (1949)), the amount of 1,2-vinyl bonds (mol %) in the bound butadiene was determined from the absorbance at a predetermined wave number.

[0208] (Amount of vinyl bond in first polymer segment Y1) The vinyl bond amount was calculated in the same manner as for the bound vinyl amount of the conjugated diene polymer, except that the sample was changed from the conjugated diene polymer to the first polymer segment. In the table, when the numerical range of formula (2) is satisfied, it is indicated by "○", and when it is not satisfied, it is indicated by "×".

[0209] (Amount of vinyl bonds in the second polymer segment Y2) The segment ratio (r1) of the first polymer segment and the segment ratio (r2) of the second polymer segment were calculated by the method described below, and the amount of bound styrene in the conjugated diene polymer X calculated from the measurement was all , the bound styrene amount X1 in the first polymer segment, the bound styrene amount X2 in the second polymer segment, and the vinyl bond amount Y in the conjugated diene polymer. all Using the vinyl bond amount Y1 in the first polymer segment and the vinyl bond amount Y2 in the second polymer segment, the vinyl bond amount Y2 in the second polymer segment was calculated according to the following formula (10).

[0210]

number

[0211] [(Property 3) Polymer Segment Ratio] (First polymer segment ratio r1) The first polymer segment ratio was calculated using the following formula (11). The ratio of the polymer segment in the first polymerization step (P1) for producing the first polymer segment was calculated from the solid amount of the conjugated diene polymer per hour after the first polymerization step (P1) relative to the total amount of the conjugated diene compound and the aromatic vinyl compound added per hour in polymerizing the conjugated diene polymer. The amount of solids in the conjugated diene polymer solution was determined from the amount of nonvolatile components in the polymer solution flowing through the outlet of the first polymerization step (P1) per unit time. The total amount of the polymer solution flowing through the outlet of the first polymerization step (P1) was collected for 3 minutes, and a polymerization terminator was immediately added.Then, the solution was transferred to a heat-resistant dish and dried in an oven at 140°C for 30 minutes or more, and the mass M1 of the remaining solid matter was measured. Here, the solid content m1 and the first polymer segment ratio (r1) were calculated using formula (11).

[0212]

number

[0213] (Second polymer segment ratio r2) The second polymer segment ratio (r2) was calculated using the following formula (12). The second polymer segment ratio in the second polymerization step (P2) for forming the second polymer segment was calculated from the difference between the solid amount of the conjugated diene polymer per hour after the second polymerization step (P2) and the solid amount of the conjugated diene polymer per hour after the first polymerization step (P1), relative to the total amount of the conjugated diene compound and the aromatic vinyl compound added per hour in polymerizing the conjugated diene polymer. The amount of solids in the conjugated diene polymer solution was determined from the amount of nonvolatile components in the polymer solution flowing through the second polymerization step (P2) outlet per unit time. The entire amount of polymer solution flowing through the outlet of the second polymerization step (P2) was collected for 3 minutes, and a polymerization terminator was immediately added. The solution was then transferred to a heat-resistant dish and dried in an oven at 140°C for 30 minutes or more. The mass M2 of the remaining solid matter was measured. The second polymer segment ratio r2 was calculated using equation (12) from the solid matter mass M1 and the solid matter mass M2 obtained in the first polymerization step (P1) described above.

[0214]

number

[0215] [(Property 4) Estimated Glass Transition Temperature] The estimated glass transition temperature of the conjugated diene polymer was calculated using the above formula (iii).

[0216] [(Physical properties 5) Molecular weight] Using a conjugated diene polymer as a sample, a chromatogram was measured using a GPC measurement apparatus (manufactured by Tosoh Corporation under the trade name "HLC-8320GPC") in which three columns packed with polystyrene gel were connected together, and an RI detector (manufactured by Tosoh Corporation under the trade name "HLC8020"), and the weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) were determined based on a calibration curve obtained using standard polystyrene. The eluent used was tetrahydrofuran (THF) containing 5 mmol / L triethylamine. Three columns, "TSKgel SuperMultiporeHZ-H" manufactured by Tosoh Corporation, were connected, and a "TSKguardcolumn SuperMP(HZ)-H" manufactured by Tosoh Corporation was connected in front of them as a guard column. 10 mg of the sample to be measured was dissolved in 10 mL of THF to prepare a measurement solution, and 10 μL of the measurement solution was injected into a GPC measurement device and measured under conditions of an oven temperature of 40° C. and a THF flow rate of 0.35 mL / min.

[0217] [(Property 6) Polymer Mooney Viscosity] The conjugated diene polymer was used as a sample and the Mooney viscosity was measured using a Mooney viscometer (manufactured by Ueshima Seisakusho Co., Ltd., trade name "VR1132") in accordance with ISO 289 using an L-shaped rotor at a measurement temperature of 100°C. First, the sample was preheated at the test temperature for 1 minute, and then the rotor was rotated at 2 rpm. After 4 minutes, the torque was measured to determine the Mooney viscosity (ML (1+4) ) was decided.

[0218] [(Property 7) Glass transition temperature (Tg)] When the conjugated diene polymer was an oil-extended product, the conjugated diene polymer after extraction of the extended oil was used as a sample, and a DSC heating curve was recorded in accordance with ISO 22768:2006 using a differential scanning calorimeter "DSC3200S" manufactured by Mac Science, Inc., by cooling from 20°C at 20°C / min to -120°C under a helium flow of 50 mL / min, and then heating from -120°C at 10°C / min, and the only inflection point observed between -100°C and -20°C on the DSC heating curve was taken as the glass transition temperature.

[0219] The extrapolated glass transition onset temperature was determined as the temperature at the intersection of a straight line extending from the low-temperature baseline toward the high-temperature side and a tangent drawn at the point where the gradient of the step-like change in the glass transition curve is maximum.

[0220] The extrapolated glass transition finish temperature was determined as the temperature at the intersection of a line drawn by extending the high-temperature baseline toward the low-temperature side and a tangent drawn at the point where the gradient of the step-like portion of the glass transition curve is maximum.

[0221] [(Property 8) Modification rate] The modification rates of the conjugated diene polymers of the examples and comparative examples were measured by column adsorption GPC as follows. The conjugated diene polymer was used as a sample and the measurement was carried out by applying the adsorption property of the modified basic polymer component to a GPC column packed with silica gel. 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. <Preparation of sample solution>: 10 mg of the sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF (tetrahydrofuran) to prepare a sample solution. <GPC measurement conditions using polystyrene column>: Using a Tosoh Corporation product name "HLC-8320GPC," 10 μL of the sample solution was injected into the instrument using THF containing 5 mmol / L triethylamine as the eluent, and a chromatogram was obtained using an RI detector under the following conditions: column oven temperature 40°C, THF flow rate 0.35 mL / min. Three columns, "TSKgel SuperMultiporeHZ-H" manufactured by Tosoh Corporation, were connected, and a "TSKguardcolumn SuperMP(HZ)-H" manufactured by Tosoh Corporation was connected in front of them as a guard column. <GPC measurement conditions using a silica column> GPC measurements were carried out using a Tosoh Corporation product name "HLC-8320GPC" and an RI detector (Tosoh Corporation product name "HLC8020"). THF was used as the eluent, and 50 μL of the sample solution was injected into the device, and a chromatogram was obtained under the conditions of a column oven temperature of 40° C. and a THF flow rate of 0.5 ml / min. The columns used were Agilent Zorbax PSM-1000S, PSM-300S, and PSM-60S, connected in this order, with a DIOL 4.6 x 12.5 mm 5 micron guard column connected in front of them. <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 × p3) / (p1 × p4)] × 100 (where p1+p2=p3+p4=100)

[0222] [Production of Conjugated Diene Polymer] Example 1 Two tank-type pressure vessels with an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom and an outlet at the top, and an agitator-equipped tank-type reactor equipped with an agitator and a jacket for temperature control were connected together as polymerization reactors. Pre-dehydrated 1,3-butadiene and normal hexane were mixed at 18.8 g / min and 163.4 g / min, respectively, to obtain a mixed solution. A static mixer was installed midway through the pipe supplying this mixed solution to the reactor inlet, and n-butyllithium (0.104 mmol / min) was added to inactivate remaining impurities. After mixing, the mixture was continuously fed to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane (polar substance) was added at a rate of 0.027 mmol / min, and n-butyllithium (polymerization initiator) was added at a rate of 0.239 mmol / min to the bottom of the first reactor, which was vigorously mixed with a stirrer. The reactor internal temperature was maintained at 78°C. After the polymerization reaction stabilized, a small amount of conjugated diene polymer was withdrawn from the top of the reactor, and 0.2 g of antioxidant (BHT) was added per 100 g of polymer. Thereafter, the solvent was removed, and the vinyl bond amount (Y1) in the bound conjugated diene in the first polymer segment was measured.

[0223] Next, the polymer solution was continuously fed from the top of the first reactor to the bottom of the second reactor, and further, to the second reactor, 1,3-butadiene was added at a rate of 10.6 g / min, styrene at 4.5 g / min, normal hexane at 41.9 g / min, and 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.415 mmol / min, with stirring, and the reaction was continued at 78°C.

[0224] Next, to the polymer solution flowing out from the top of the second reactor, coupling agents 1-methyl-4-[3-(trimethoxysilyl)propyl]piperazine (referred to as "Coupling Agent A" in the table) were added at a rate of 0.097 mmol / min, and tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine (referred to as "Coupling Agent B" in the table) were added at a rate of 0.010 mmol / min continuously, and the mixture was mixed using a static mixer to carry out a coupling reaction. At this time, it took 4.8 minutes for the coupling agent to be added to the polymer solution flowing out from the reactor outlet, and the temperature was 68°C, and the difference between the temperature during the polymerization process and the temperature before the coupling agent was added was 2°C. After the coupling reaction, a small amount of the conjugated diene polymer solution was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of polymer. After that, the solvent was removed, and the bound styrene content (X), vinyl bond content (Y), glass transition temperature, extrapolated glass transition onset temperature, and end temperature were identified.

[0225] Next, an antioxidant (BHT) was continuously added to the polymer solution at a rate of 0.055 g / min (n-hexane solution) to give 0.2 g per 100 g of polymer, and the coupling reaction was terminated. Simultaneously with the antioxidant, SRAE oil (JOMO Process NC140, manufactured by JX Nippon Oil & Energy Corporation) was continuously added as a rubber softener to give 5.0 g per 100 g of polymer, and the mixture was mixed in a static mixer. The solvent was removed by steam stripping to obtain a conjugated diene polymer (A1), whose molecular weight, Mooney viscosity, and modification rate were determined.

[0226] Example 2 To the first reactor, 1,3-butadiene was added at 15.8 g / min and normal hexane at 156.0 g / min, and 2,2-bis(2-oxolanyl)propane as a polar substance was added at a rate of 0.072 mmol / min, and to the second reactor, 1,3-butadiene was added at 14.0 g / min, styrene at 4.4 g / min, normal hexane at 49.9 g / min, and 2,2-bis(2-oxolanyl)propane as a polar substance was added at a rate of 0.370 mmol / min. The other conditions were the same as in Example 1, and a conjugated diene polymer (A2) was obtained.

[0227] Example 3 To the first reactor, 1,3-butadiene was added at 19.8 g / min and normal hexane at 165.6 g / min, and 2,2-bis(2-oxolanyl)propane as a polar substance was added at a rate of 0.145 mmol / min, and to the second reactor, 1,3-butadiene was added at 7.2 g / min, styrene at 4.2 g / min, normal hexane at 33.2 g / min, and 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.253 mmol / min, and the internal temperature of the second reactor was set to 78° C. Other conditions were the same as in Example 1, and a conjugated diene polymer (A3) was obtained.

[0228] Example 4 To the first reactor, 1,3-butadiene was added at 18.8 g / min and normal hexane at 163.4 g / min, and 2,2-bis(2-oxolanyl)propane as a polar substance was added at a rate of 0.023 mmol / min, and the temperature inside the first reactor was raised to 82°C. Further, to the second reactor, 1,3-butadiene was added at 11.2 g / min, styrene at 5.3 g / min, normal hexane at 44.8 g / min, and 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.153 mmol / min. The other conditions were the same as in Example 1, and a conjugated diene polymer (A4) was obtained.

[0229] Example 5 As coupling agents, 1-methyl-4-[3-(trimethoxysilyl)propyl]piperazine (referred to as "coupling agent A" in the table) was continuously added at a rate of 0.110 mmol / min, and tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine (referred to as "coupling agent B" in the table) was continuously added at a rate of 0.007 mmol / min. Other conditions were the same as in Example 1, and a conjugated diene polymer (A5) was obtained.

[0230] Example 6 The polymerization initiator added to the first reactor was n-butyllithium at 0.193 mmol / min, and the polar substance added to the second reactor was 2,2-bis(2-oxolanyl)propane at 0.019 mmol / min, and the coupling agent added to the second reactor was 2,2-bis(2-oxolanyl)propane at 0.298 mmol / min. The other conditions were the same as in Example 1, and a conjugated diene polymer (A6) was obtained.

[0231] Example 7 The polymerization initiator added to the first reactor was n-butyllithium at 0.343 mmol / min, the polar substance was 2,2-bis(2-oxolanyl)propane at 0.033 mmol / min, the second reactor was 2,2-bis(2-oxolanyl)propane at 0.596 mmol / min, and the coupling agent was 1-methyl-4-[3-(trimethoxysilyl)propyl]piperazine (referred to as "coupling agent A" in the table) at a rate of 0.173 mmol / min. The other conditions were the same as in Example 1, and a conjugated diene polymer (A7) was obtained.

[0232] Example 8 To the first reactor, n-butyllithium was added as a polymerization initiator at a rate of 0.198 mmol / min, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.019 mmol / min, and to the second reactor, 2,2-bis(2-oxolanyl)propane was added at a rate of 0.298 mmol / min, and 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (referred to as "coupling agent C" in the table) was added continuously as a coupling agent at a rate of 0.052 mmol / min. The other conditions were the same as in Example 1, and a conjugated diene polymer (A8) was obtained.

[0233] Example 9 The polymerization initiator added to the first reactor was n-butyllithium at 0.130 mmol / min, the polar substance 2,2-bis(2-oxolanyl)propane at 0.015 mmol / min, the second reactor was 2,2-bis(2-oxolanyl)propane at 0.235 mmol / min, and the coupling agent tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine (referred to as "coupling agent B" in the table) was continuously added at a rate of 0.017 mmol / min. SRAE oil (JOMO Process NC140 manufactured by JX Nippon Oil & Energy Corporation) was continuously added as a rubber softener so that 25.0 g per 100 g of polymer. The other conditions were the same as in Example 1, and a conjugated diene polymer (A9) was obtained.

[0234] Example 10 1,3-butadiene was continuously added to the second reactor at a rate of 13.8 g / min, styrene at a rate of 2.7 g / min, and normal hexane at a rate of 46.6 g / min. The other conditions were the same as in Example 4, and a conjugated diene polymer (A10) was obtained.

[0235] ( Reference example 11) As a polar substance to be added to the first reactor, 2,2-bis(2-oxolanyl)propane was continuously added at a rate of 0.266 mmol / min, and to the second reactor, 2,2-bis(2-oxolanyl)propane was continuously added at a rate of 0.176 mmol / min. Other conditions were the same as in Example 1, and a conjugated diene polymer (A11) was obtained.

[0236] ( Reference example 12) To the first reactor, 1,3-butadiene was added at 13.8 g / min and styrene at 4.4 g / min simultaneously, normal hexane was added at 104.8 g / min, and 2,2-bis(2-oxolanyl)propane was added as a polar substance at a rate of 0.003 mmol / min, and the internal temperature of the first reactor was raised to 65°C. Furthermore, to the second reactor, 1,3-butadiene was added at 2.9 g / min, no additional styrene was added, normal hexane was added at 9.5 g / min, and 2,2-bis(2-oxolanyl)propane as an additional polar substance was added at a rate of 0.020 mmol / min. The internal temperature of the second reactor was raised to 65°C, and as a coupling agent, 1-methyl-4-[3-(trimethoxysilyl)propyl]piperazine (referred to as "coupling agent A" in the table) was added at a rate of 0.087 mmol / min, and tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine (referred to as "coupling agent B" in the table) was added continuously at a rate of 0.009 mmol / min. The other conditions were the same as in Example 1, and a conjugated diene polymer (A12) was obtained.

[0237] Example 13 The polymerization initiator added to the first reactor was n-butyllithium at 0.370 mmol / min, the polar substance added to the second reactor was 2,2-bis(2-oxolanyl)propane at 0.036 mmol / min, and the other conditions were the same as in Example 7, to obtain a conjugated diene polymer (A13).

[0238] Example 14 The polymerization initiator added to the first reactor was n-butyllithium at 0.062 mmol / min, the polar substance 2,2-bis(2-oxolanyl)propane at 0.007 mmol / min, the second reactor was 2,2-bis(2-oxolanyl)propane at 0.094 mmol / min, and the coupling agent tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine (referred to as "coupling agent B" in the table) was continuously added at a rate of 0.008 mmol / min. SRAE oil (JOMO Process NC140 manufactured by JX Nippon Oil & Energy Corporation) was continuously added as a rubber softener to 100 g of polymer at a rate of 37.5 g. The other conditions were the same as in Example 9, and a conjugated diene polymer (A14) was obtained.

[0239] Example 15 To the first reactor, 1,3-butadiene was added at 21.4 g / min, normal hexane at 170.3 g / min, and 2,2-bis(2-oxolanyl)propane as a polar substance at 0.054 mmol / min. To the second reactor, 1,3-butadiene was added at 9.2 g / min, styrene at 3.5 g / min, normal hexane at 36.8 g / min, and 2,2-bis(2-oxolanyl)propane at 0.394 mmol / min. The other conditions were the same as in Example 1, and a conjugated diene polymer (A15) was obtained.

[0240] Example 16 To the first reactor, 1,3-butadiene was added at 15.4 g / min, normal hexane at 166.0 g / min, and 2,2-bis(2-oxolanyl)propane was added at 0.072 mmol / min as a polar substance, and to the second reactor, 1,3-butadiene was added at 12.6 g / min, styrene at 5.3 g / min, normal hexane at 48.2 g / min, and 2,2-bis(2-oxolanyl)propane at 0.340 mmol / min, and the polymerization temperature of the second reactor was 80° C. The other conditions were the same as in Example 1, and a conjugated diene polymer (A16) was obtained.

[0241] (Reference Example 1) To the first reactor, 1,3-butadiene was added at 22.3 g / min and styrene at 4.2 g / min simultaneously, normal hexane was added at 178.8 g / min, 2,2-bis(2-oxolanyl)propane was added as a polar substance at a rate of 0.101 mmol / min, and the temperature inside the first reactor was set to 68° C. To the second reactor, 1,3-butadiene was added at 7.4 g / min, no additional styrene was added, normal hexane was added at 26.7 g / min, and no additional polar substance was added, and the temperature inside the second reactor was set to 73° C. The other conditions were the same as in Example 1, and a conjugated diene polymer (B1) was obtained.

[0242] (Comparative Example 1) A conjugated diene polymer (B2) was obtained in the same manner as in Example 1, except that 2,2-bis(2-oxolanyl)propane was added as a polar substance to the first reactor at a rate of 0.266 mmol / min, and 1,3-butadiene was added to the second reactor at a rate of 9.7 g / min, additional styrene at 5.4 g / min, normal hexane at 41.3 g / min, and 2,2-bis(2-oxolanyl)propane as an additional polar substance at a rate of 0.156 mmol / min.

[0243] (Comparative Example 2) The step of adding a coupling agent was not carried out, and other conditions were the same as in Reference Example 1 to obtain a conjugated diene polymer (B3).

[0244] (Comparative Example 3) Conjugated diene polymer (B4) was obtained in the same manner as in Reference Example 1, except that n-butyllithium was continuously added to the first reactor at a rate of 0.343 mmol / min as a polymerization initiator, 2,2-bis(2-oxolanyl)propane at a rate of 0.124 mmol / min and normal hexane at a rate of 109.2 g / min as polar substances, and 1-methyl-4-[3-(trimethoxysilyl)propyl]piperazine (referred to as "coupling agent A" in the table) as a coupling agent at a rate of 0.173 mmol / min.

[0245] Comparative Example 4 To the first reactor, n-butyllithium was continuously added at a rate of 0.198 mmol / min as a polymerization initiator, 2,2-bis(2-oxolanyl)propane at a rate of 0.070 mmol / min as a polar substance, and 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (referred to as "coupling agent C" in the table) at a rate of 0.052 mmol / min as a coupling agent, and then SRAE oil (JOMO Process NC140, manufactured by JX Nippon Oil & Energy Corporation) was continuously added as a rubber softener so that 25.0 g was added per 100 g of polymer. A conjugated diene polymer (B5) was obtained in the same manner as in Reference Example 1.

[0246] (Comparative Example 5) A conjugated diene polymer (B6) was obtained in the same manner as in Reference Example 1, except that n-butyllithium was continuously added to the first reactor at a rate of 0.130 mmol / min as a polymerization initiator, 2,2-bis(2-oxolanyl)propane at a rate of 0.055 mmol / min as a polar substance, and tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine (referred to as "coupling agent B" in the table) at a rate of 0.017 mmol / min as a coupling agent, and then SRAE oil (JOMO Process NC140, manufactured by JX Nippon Oil & Energy Corporation) was continuously added as a rubber softener so that 37.5 g was added per 100 g of polymer.

[0247] [Table 1]

[0248] [Table 2]

[0249] [Table 3]

[0250] [Examples 17 to 26, Reference Examples 27-28, Examples 29-32), [Reference Example 2], [Comparative Examples 6 to 10] Using the conjugated diene polymers A1 to A16 and B1 to B6 shown in Tables 1 to 3 as raw material rubbers, rubber compositions containing each raw material rubber were obtained according to the formulation shown below. Conjugated diene polymers (A1 to A16, B1 to B6): 100 parts by mass (oil excluded) Silica (product name "Ultrasil 7000GR" manufactured by Evonik Degussa, nitrogen adsorption specific surface area 170 m2 / g): 85.0 parts by mass carbon black (Product name "Seast 7HM (N234)" manufactured by Tokai Carbon Co., Ltd.): 2.0 parts by mass Silane coupling agent (trade name "Si69" manufactured by Evonik Degussa, bis(triethoxysilylpropyl)tetrasulfide): 6.8 parts by mass S-RAE Oil (Product name "Process NC140" manufactured by JX Nippon Oil & Energy Corporation): 40 parts by mass Zinc white: 2.4 parts by mass Stearic acid: 1.25 parts by mass Antioxidant (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine): 3.5 parts by mass Sulfur: 1.0 parts by mass Vulcanization accelerator 1 Tetrabenzyl thiuram disulfide: 0.5 parts by mass Vulcanization accelerator 2 N-(tert-butyl)-2-benzothiazolesulfenamide: 2.5 parts by mass Total: 246.95 parts by mass

[0251] The above materials were kneaded by the following method to obtain a rubber composition. In the first stage of mixing, raw rubbers (A1 to A16, B1 to B6), fillers (silica, carbon black), silane coupling agent, process oil, zinc oxide, and stearic acid were mixed at a filling rate of 65% and a rotor rotation speed of 30 to 50 rpm using an internal mixer (capacity: 0.3 L) equipped with a temperature control device. The temperature of the internal mixer was controlled, and the discharge temperature was kept at 145 to 150°C to obtain each rubber composition (compound).

[0252] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature, and then the 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 120°C by controlling the temperature of the mixer. After cooling, in the third stage of kneading, sulfur and vulcanization accelerators 1 and 2 were added and kneaded using an open roll set at 70°C. Thereafter, the product was molded and vulcanized in a vulcanization press at 160°C for 20 minutes. The rubber composition before vulcanization and the rubber composition after vulcanization were evaluated. Specifically, the evaluation was carried out by the following method. The evaluation results are shown in Tables 4 to 6.

[0253] [Evaluation 1-3: Viscoelastic parameters] Viscoelastic parameters were measured in torsion mode using a viscoelastic testing machine "ARES" manufactured by Rheometrics Scientific. Each measurement value was indexed, with the result for the rubber composition of Reference Example 2 being set at 100.

[0254] (Evaluation 1: Low hysteresis loss) Tan δ measured at 50°C, a frequency of 10 Hz, and a strain of 3% was used as an index of low hysteresis loss. The larger the index, the better the low hysteresis loss property, and an index value of 85 or more was determined to have sufficiently low hysteresis loss property.

[0255] (Evaluation 2: Wet grip performance) Tan δ measured at 0°C, a frequency of 10 Hz, and a strain of 1% was used as an index of wet grip performance. The larger the index, the better the wet grip performance. Furthermore, when the index value is 130 or more, it is determined that the tire has sufficient wet grip properties.

[0256] (Evaluation 3: Low temperature performance) The storage modulus G' measured at -20°C, a frequency of 10 Hz, and a strain of 1% was used as an index of low-temperature performance. The larger the index, the better the low-temperature properties. Furthermore, when the index value is 65 or more, it is determined that the material has sufficient low-temperature properties.

[0257] [Evaluation 4: Abrasion resistance] Using an Acron abrasion tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), the amount of wear was measured at a load of 44.4 N and 1000 revolutions in accordance with JIS K6264-2, and the result of Reference Example 2 was indexed as 100. The larger the index, the better the abrasion resistance. Furthermore, when the value was 70 or higher, it was determined that the wear resistance was sufficient.

[0258] [Evaluation 5: Processability] With respect to the unvulcanized conjugated diene polymers produced by the methods shown in the Examples and Comparative Examples, the polymers were formed into a sheet shape with rolls immediately after being discharged from the pressure kneader (immediately after the first stage of kneading by the pressure kneader was completed and the polymers were discharged), and the cohesion (shape) of the sheet was visually observed and evaluated by a panelist on a scale of 1 to 5 based on the following criteria. The cohesion is an index of the processability of the vulcanized product. The larger the index, the better the processability. Furthermore, when the score was 4 or higher, it was determined that the workability was sufficient. <Evaluation criteria> 1: The edge of the sheet is less than 50% smooth, and workability is very poor. 2: More than 50% but not more than 60% of the edge of the sheet is smooth, and workability is poor. 3: The edge of the sheet is smooth by more than 60% but not more than 80%, and has good processability. 4: The edge of the sheet is smooth by more than 80% but not more than 90%, and has excellent processability. 5: 90% of the edges of the sheet are super smooth, making it extremely easy to process.

[0259] [Evaluation 6: Wet grip performance and low temperature characteristics] The sum of the indices calculated in the evaluations 2 and 3 was used as the wet grip performance and low-temperature characteristic index. The larger the index, the better the wet grip performance and low temperature characteristics.

[0260] [Table 4]

[0261] [Table 5]

[0262] [Table 6]

[0263] As shown in Tables 4 to 6, the rubber compositions of conjugated diene polymers of Examples 17 to 32, which used conjugated diene polymers A1 to A16 satisfying the estimated Tg, were found to have superior low-temperature properties when vulcanized compared to the rubber composition of Comparative Example 6, which used conjugated diene polymer B2.

[0264] As shown in Tables 4 to 6, the rubber compositions of conjugated diene polymers of Examples 17 to 21, 23, 27 to 29, 31 and 32, which used conjugated diene polymers A1 to A5, A7, A11 to A13, A15 and A16, in which the difference between the extrapolated glass transition end temperature and the onset temperature satisfies the range of 15°C or more and 35°C or less, were found to have an excellent balance of wet grip performance and low temperature properties when vulcanized, compared to the rubber composition of Reference Example 2, which used conjugated diene polymer B1.

[0265] As shown in Tables 4 to 6, the rubber composition of Example 22 using conjugated diene polymer A6 was found to have an excellent balance of wet grip performance and low temperature properties when vulcanized, compared to the rubber composition of Comparative Example 7 using conjugated diene polymer B3.

[0266] When the rubber compositions of Example 23 and Comparative Example 8, Example 24 and Comparative Example 9, and Example 25 and Comparative Example 10 were compared, it was found that the rubber compositions of Example 23 and Comparative Example 8, Example 24 and Comparative Example 9, and Example 25 and Comparative Example 10, respectively, exhibited an excellent balance between wet grip performance and low temperature properties when vulcanized.

[0267] Furthermore, as shown in Tables 4 to 6, the rubber compositions of Examples 17 to 24, 26, 27, 29, 31, and 32, which used conjugated diene polymers A1 to A8, A10, A11, A13, A15, and A16, each having a molecular weight distribution of 1.7 or more and 2.5 or less, were found to have excellent processability when vulcanized.

[0268] Furthermore, as shown in Tables 4 to 6, the rubber compositions of Examples 17 to 21 and Examples 23 to 32, which used conjugated diene polymers A1 to A5 and A7 to A16, were found to have excellent low hysteresis loss properties when vulcanized, compared to the rubber composition of Comparative Example 7, which used conjugated diene polymer B3.

[0269] This application is based on a Japanese patent application (Patent Application No. 2023-072838) filed with the Japan Patent Office on April 27, 2023, the contents of which are incorporated herein by reference. [Industrial Applicability]

[0270] The conjugated diene polymer of the present invention has industrial applicability as a material in fields such as tire treads, interior and exterior parts of automobiles, vibration-proof rubber, belts, footwear, foams, and various industrial goods.

Claims

1. A conjugated diene-based polymer having at least a first polymer segment and a second polymer segment, The first polymer segment contains a conjugated diene monomer unit and does not contain an aromatic vinyl monomer unit, and the vinyl bond amount Y 1 (mol %) in the bound conjugated diene in the first polymer segment satisfies the following formula (2): 10≦Y 1 ≦45 (2) the second polymer segment contains conjugated diene monomer units and aromatic vinyl monomer units; an estimated glass transition temperature (estimated Tg) derived from the microstructure of the conjugated diene polymer is −72° C. or higher and −50° C. or lower; has only one glass transition temperature (Tg) as measured by differential scanning calorimetry (DSC); the difference between the extrapolated glass transition onset temperature and the extrapolated glass transition end temperature of the glass transition temperature (Tg) is 15°C or more and 35°C or less; Conjugated diene polymer.

2. The estimated glass transition temperature (estimated Tg) derived from the microstructure of the second polymer segment is higher than -45°C and not higher than -5°C. The conjugated diene polymer according to claim 1 .

3. a molecular weight distribution, which is the ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn, of 1.7 or more and 2.5 or less; The conjugated diene polymer according to claim 1 .

4. the segment ratio of the first polymer segment is 20% by mass or more and 80% by mass or less; The conjugated diene polymer according to claim 2 .

5. The weight average molecular weight is 300,000 or more and 1,350,000 or less. The conjugated diene polymer according to claim 1 .

6. containing a nitrogen atom, The conjugated diene polymer according to claim 1 .

7. The modification rate of the conjugated diene copolymer is 70% or more. The conjugated diene polymer according to claim 6 .

8. A method for producing the conjugated diene polymer according to claim 2, Two or more continuous reactors are used, a first polymerization step (P1) in which a conjugated diene compound, a polymerization initiator, and a polar substance are added to the continuous reactor to continuously form a first polymer segment of a conjugated diene-based polymer; a second polymerization step (P2) in which an aromatic vinyl compound and a polar substance are added to the continuous reactor to form a second polymer segment at the end of the first polymer segment; have, A method for producing a conjugated diene polymer.

9. The method further includes a coupling step (P3) of reacting the conjugated diene-based polymer with a coupling agent after the second polymer step (P2). The method for producing the conjugated diene polymer according to claim 8.

10. a mass ratio of the conjugated diene compound added in the first polymerization step (P1) to the total amount of the conjugated diene compound and the aromatic vinyl compound added is 20 mass% or more and 80 mass% or less; The method for producing the conjugated diene polymer according to claim 8.

11. The polymerization reaction rate of the first polymerization step (P1) is 75% or more and 95% or less. The method for producing the conjugated diene polymer according to claim 8.

12. In the second polymerization step (P2), the mass ratio of the amount of the aromatic vinyl compound added to the amount of the conjugated diene compound added is 0.15 or more and 0.70 or less. The method for producing the conjugated diene polymer according to claim 8.

13. In the second polymerization step (P2), a polar substance is added in an amount greater than the amount of polar substance added in the first polymerization step (P1). The method for producing the conjugated diene polymer according to claim 8.

14. The coupling agent is an aminoalkoxysilane compound. The method for producing the conjugated diene polymer according to claim 9 .

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