Conjugated diene polymer, rubber composition, Anti-vibration rubber, transmission belt, conveyer belt, shoe sole, industrial material, and tire

Abstract

To provide a conjugated diene polymer capable of obtaining a rubber composition excellent in balance of compression set and durability under a low temperature, and a rubber composition using the conjugated diene polymer.SOLUTION: A conjugated diene polymer has a molecular weight distribution of less than 1.5 as measured by gel permeation chromatography (GPC), a peak-top molecular weight of the lowest molecular weight peak (A) in the molecular weight distribution curve of 300,000 or more, a single glass transition temperature (Tg) peak in differential scanning calorimetry (DSC) measurement, the Tg peak being -92°C or lower, and a nitrogen content of 80 ppm or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a conjugated diene polymer and a rubber composition, a vibration-proof rubber, a transmission belt, a conveyor belt, a shoe sole, an industrial material, and a tire. [Background technology]

[0002] Anti-vibration rubber, which constitutes the anti-vibration components of automobiles, trains, etc., is a material that is required to have small compression set and a low dynamic magnification, and rubber materials containing natural rubber have been proposed for some time (see, for example, Patent Document 1). Natural rubber has excellent dynamic magnification and mechanical strength, making it an essential material for anti-vibration rubber applications, and it is often blended with high-cis butadiene rubber, styrene butadiene rubber, etc. to meet other required properties.

[0003] On the other hand, the required properties of anti-vibration rubber have changed in recent years, and there is a trend toward improved compression set over a wide temperature range, especially at low temperatures, and improved durability (ozone resistance) of rubber products.Natural rubber is known to be prone to deterioration, particularly in terms of durability (ozone resistance) (see, for example, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 198647 [Non-patent literature]

[0005] [Non-Patent Document 1] Journal of the Society of Rubber Science and Technology of Japan, Vol. 53, No. 8, 1980, pp. 53-62, "Heat and Ozone Degradation" Summary of the Invention [Problem to be solved by the invention]

[0006] However, natural rubber, which is the main ingredient in vibration-isolating rubber, has a glass transition temperature (Tg) of around -60°C, and its compression set at low temperatures is still insufficient, leaving room for improvement. Natural rubber also has poor compatibility with the amine-based antioxidants commonly used in vibration-isolating rubber, which causes the antioxidant to bleed onto the surface of the rubber over time and wear away, resulting in a decrease in the durability of the rubber.

[0007] Therefore, an object of the present invention is to provide a conjugated diene polymer that, when blended with natural rubber, gives a rubber composition that is excellent in compression set at low temperatures and has high durability, and to provide a rubber composition using the conjugated diene polymer. Regarding the aforementioned compression set at low temperatures, specifically, the objective is to improve the compression set at 0°C, and regarding the improvement in durability, the objective is to improve the ozone resistance one year after the production of the rubber composition. [Means for solving the problem]

[0008] As a result of extensive investigations into solving the problems of the prior art described above, the present inventors have found that by using a conjugated diene polymer whose molecular weight distribution, the peak-top molecular weight of the lowest molecular weight peak (A) in the molecular weight distribution curve, the number of glass transition temperature peaks, the glass transition temperature peak, and the nitrogen content are all within specific ranges, when mixed with natural rubber to form a rubber composition, an excellent balance between compression set and durability at low temperatures can be achieved, leading to the completion of the present invention. That is, the present invention is as follows.

[0009] [1] The molecular weight distribution as measured by gel permeation chromatography (GPC) is less than 1.5, and the peak top molecular weight of the lowest peak (A) in the molecular weight distribution curve is 300,000 or more; There is one glass transition temperature Tg peak in differential scanning calorimetry (DSC) measurement, and the Tg peak is −92° C. or lower; Nitrogen content is 80 ppm or more, Conjugated diene polymer. [2] When a group of peaks located on the higher molecular weight side than the peak (A) is defined as a group of peaks (B), a peak area ratio of the group of peaks (B) to the sum of the area of ​​the peak (A) and the area of ​​the group of peaks (B) satisfies the following relationship: The conjugated diene polymer according to [1] above. Peak area ratio: 5%≦B / (A+B)≦15% [3] The denaturation rate is 70% or more, The conjugated diene polymer according to [1] or [2] above. [4] The content of aromatic vinyl monomer units is 1% by mass or more. The conjugated diene polymer according to any one of [1] to [3] above. [5] The content of the aromatic vinyl monomer block is 1% by mass or more and 7% by mass or less. The conjugated diene polymer according to [4] above. [6] all of the aromatic vinyl monomer units in the conjugated diene polymer constitute an aromatic vinyl monomer block in a blocked state; The conjugated diene polymer according to [5] above. [7] the aromatic vinyl monomer block is present at the polymerization initiation terminal of the conjugated diene polymer; The conjugated diene polymer according to [6] above. [8] The conjugated diene polymer according to any one of [1] to [7] above, Natural rubber and A rubber composition comprising: [9] A vibration-proof rubber containing the rubber composition according to [8].

[10] A power transmission belt containing the rubber composition according to [8].

[11] A conveyor belt containing the rubber composition according to [8].

[12] A shoe sole containing the rubber composition according to [8].

[13] An industrial material containing the rubber composition according to [8].

[14] A tire containing the rubber composition according to [8]. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a conjugated diene polymer from which a rubber composition having an excellent balance between compression set at low temperatures and durability can be obtained, and a rubber composition using the conjugated diene polymer. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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 the present invention is not limited to the following embodiments. The present invention can be implemented in various modifications within the scope of its gist.

[0012] [Conjugated diene polymer] The conjugated diene polymer of the present embodiment has a molecular weight distribution of less than 1.5 as measured by gel permeation chromatography (GPC), a peak top molecular weight of the lowest peak (A) in the molecular weight distribution curve of 300,000 or more, one glass transition temperature Tg peak as measured by differential scanning calorimetry (DSC), and the Tg peak is −92° C. or less, and a nitrogen content of 80 ppm or more. According to the above-mentioned configuration, it is possible to provide a conjugated diene polymer from which a rubber composition having an excellent balance between compression set and durability at low temperatures can be obtained.

[0013] The conjugated diene polymer of the present embodiment contains a structural unit derived from a conjugated diene compound (hereinafter also referred to as a "conjugated diene monomer unit"), and may contain a structural unit derived from an aromatic vinyl compound (hereinafter also referred to as an "aromatic vinyl monomer unit").

[0014] Examples of conjugated diene compounds include, but are not limited to, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene. Among these, from the viewpoint of industrial availability, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is particularly preferred. These may be used alone or in combination of two or more. Examples of aromatic vinyl compounds include, but are not limited to, styrene, p-methylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene. Among these, styrene is preferred from the viewpoint of industrial availability. These may be used alone or in combination of two or more.

[0015] (Aromatic vinyl monomer unit content) The conjugated diene polymer of this embodiment preferably has an aromatic vinyl monomer unit content of 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, from the viewpoint of ozone resistance of a rubber composition using the conjugated diene polymer of this embodiment. The presence of aromatic vinyl monomer units, which are polar monomers, in the conjugated diene polymer increases the polarity of the conjugated diene polymer, which tends to suppress the rate of surface deposition (bleeding) of an amine-based antioxidant when the conjugated diene polymer is used in a rubber composition, thereby improving the long-term ozone resistance of the rubber composition and its products. Furthermore, from the viewpoint of the compression set of the rubber composition at low temperatures, it is preferable that the Tg of the conjugated diene polymer is low, and from this viewpoint, the content of aromatic vinyl monomer units with high Tg is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 3% by mass or less. The content of aromatic vinyl monomer units is 1 It can be measured by H-NMR, specifically by the method described in the Examples below. The content of the aromatic vinyl monomer unit in the conjugated diene polymer of this embodiment can be controlled within the above-mentioned range by adjusting the amount of the aromatic vinyl compound added during polymerization.

[0016] (Aromatic vinyl block content) The aromatic vinyl monomer units in the conjugated diene polymer of the present embodiment preferably exist in the form of blocks from the viewpoint of Tg of the rubber composition. When the aromatic vinyl monomer units are present in the conjugated diene polymer in a block form rather than a random form, they form a microphase-separated structure with the conjugated diene segments, and the Tg of the entire conjugated diene polymer depends only on the conjugated diene segment structure. In other words, it becomes possible to introduce the aromatic vinyl monomer units without increasing the Tg of the conjugated diene polymer, which is preferable from the viewpoint of compression set at low temperatures. For the reasons described above, the content of the aromatic vinyl monomer block in the conjugated diene polymer of the present embodiment is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. It is more preferable that all of the aromatic vinyl monomer units in the conjugated diene polymer constitute an aromatic vinyl monomer block in a blocked state. The content of the aromatic vinyl monomer block in the conjugated diene polymer of this embodiment is preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of the dynamic magnification of the rubber composition of this embodiment. The aromatic vinyl monomer block can be present at any position in the molecular chain of the conjugated diene polymer of this embodiment. Specifically, the aromatic vinyl monomer block can be introduced into three locations: at the polymerization initiation end, inside the molecular chain, such as the center, and at the polymerization termination end. From the viewpoint of productivity, introduction at the polymerization initiation end or the polymerization termination end is preferred, and from the viewpoint of improving the modification rate of the conjugated diene polymer of this embodiment, introduction at the polymerization initiation end is more preferred. The aromatic vinyl monomer block content of the conjugated diene polymer can be measured by the method described in IM Kolthoff, et al., J. Polym. Sci. 1, 429 (1946), more specifically, by the method described in the Examples. The content of the aromatic vinyl monomer block in the conjugated diene polymer and the introduction site in the conjugated diene polymer can be controlled to the above-mentioned numerical range and introduction site by adjusting the amount and timing of addition of the aromatic vinyl compound in the polymerization step.

[0017] (1,2-vinyl bond content) The 1,2-vinyl bond content in the conjugated diene polymer of this embodiment is the molar ratio of the 1,2-vinyl bond content based on the content of conjugated diene monomer units, and is preferably 8 mol% or more, more preferably 13 mol% or more, and even more preferably 14 mol% or more from the viewpoint of productivity of the conjugated diene polymer. On the other hand, since an increase in the 1,2-vinyl bond content increases the Tg of the conjugated diene polymer, the 1,2-vinyl bond content is preferably 25 mol% or less, more preferably 22 mol% or less, and even more preferably 19 mol% or less from the viewpoint of low-temperature compression set of the rubber composition of this embodiment. The amount of 1,2-vinyl bonds is 1 It can be measured by H-NMR. The amount of 1,2-vinyl bonds can be controlled within the above range by adjusting the reaction initiation temperature, reaction termination temperature, and the type and amount of polar substance added during polymerization.

[0018] (The peak top molecular weight of the lowest molecular weight peak (A) in the molecular weight distribution curve measured by GPC) The conjugated diene polymer of this embodiment has a peak top molecular weight (Mp) of the lowest molecular weight peak (A) of 300,000 g / mol or more when measured by GPC (gel permeation chromatography). When the Mp of peak (A) is 300,000 g / mol or more, the polymers are sufficiently entangled, and the rubber composition of this embodiment tends to have excellent compression set at low temperatures. From the same viewpoint, the Mp of peak (A) is preferably 340,000 g / mol or more, and more preferably 380,000 g / mol or more. When the conjugated diene polymer of this embodiment is produced by an anionic polymerization process, the amount of polymerization initiator added and the amount of impurities in the system tend to be strictly controlled when the molecular weight is increased to an extremely high level. From the viewpoint of reducing the difficulty of this production control, the peak top molecular weight (Mp) of the peak (A) having the lowest molecular weight is preferably 500,000 g / mol or less, more preferably 460,000 g / mol or less, and even more preferably 420,000 g / mol or less. The peak top molecular weight (Mp) of the peak (A) having the lowest molecular weight when the conjugated diene polymer of the present embodiment is measured by GPC can be controlled to fall within the above-mentioned range by controlling the amount of the polymerization initiator and the coupling agent described below added.

[0019] (Area ratio of peak (B) which is located on the higher molecular weight side than peak (A)) From the viewpoint of cold flow resistance, the conjugated diene polymer of this embodiment preferably has one or more peaks on the higher molecular weight side than peak (A) having the lowest molecular weight. A group of peaks present on the higher molecular weight side than peak (A) is referred to as peak (B). In the peak waveform measured by a GPC RI detector, the area ratio (B / (A+B)) of peak (B) to the total area of ​​peak (A) and peak (B) is preferably 5% or more, more preferably 8% or more, and even more preferably 10% or more. In addition, from the viewpoint of the processability of the rubber composition of the present embodiment, the area ratio of the peak (B) is preferably 15% or less, more preferably 13% or less, and even more preferably 11% or less. The peak shape in the molecular weight distribution curve can be controlled simply and preferably by adjusting the method of adding a coupling agent to the polymerization active terminal. The abundance ratio and molecular weight of the polymer can be controlled as desired by adjusting the number of functional groups in the coupling agent, the amount added, and the type of coupling agent. The area ratio of the peak (B) when the conjugated diene polymer of the present embodiment is measured by GPC can be controlled to fall within the above-mentioned range by adjusting the amount of the polymerization initiator and the coupling agent described below added. Furthermore, the conjugated diene polymer contained in the peak (A) with the lowest molecular weight is preferably a polymer with a high linearity, and it is also preferable that the proportion of modified polymer is high. By modifying the terminal of the highly linear polymer, steric hindrance around the modifying group is small, and it is easy to interact with the functional group of the filler, which improves the dispersibility of the filler and tends to improve the dynamic magnification of the rubber composition of this embodiment.

[0020] (molecular weight distribution) The conjugated diene polymer of this embodiment has a molecular weight distribution (Mw / Mn) of less than 1.5 from the viewpoint of cold flow resistance, and from the same viewpoint, it is preferably 1.4 or less, more preferably 1.3 or less.

[0021] The number of peaks, molecular weight distribution, and peak top molecular weight of the conjugated diene polymer of this embodiment can be measured by gel permeation chromatography (GPC), specifically, by the method described in the Examples below.

[0022] (glass transition temperature) From the viewpoint of the compression set of the rubber composition of the present embodiment at low temperatures, the glass transition temperature of the conjugated diene polymer of the present embodiment has one peak and is −92° C. or lower, preferably −94° C. or lower, and more preferably −95° C. or lower. The glass transition temperature can be measured by differential scanning calorimetry (DSC), specifically by the method described in the examples below. The glass transition temperature of the conjugated diene polymer of the present embodiment can be controlled by adjusting the ratio of conjugated diene monomer units to aromatic vinyl monomer units in the conjugated diene polymer or the amount of 1,2-vinyl bonds, and the amount of 1,2-vinyl bonds can be controlled by adjusting the amount of polar substance added during polymerization or the polymerization temperature.

[0023] (nitrogen content) The conjugated diene polymer of this embodiment has a nitrogen content of 80 ppm or more, preferably 100 ppm or more, and more preferably 120 ppm or more, from the viewpoint of reducing the bleeding rate of the amine-based antioxidant in a rubber composition using the conjugated diene polymer of this embodiment and improving ozone resistance. The nitrogen content can be controlled within the above range by using a nitrogen atom-containing compound as a polymerization initiator, a coupling agent (to be described later), or a modifier in the polymerization step and adjusting the amounts of these used.

[0024] (coupling polymer) The conjugated diene polymer of the present embodiment may be a coupling polymer obtained by subjecting the active terminal of the conjugated diene polymer obtained through the polymerization step to a coupling reaction using a bifunctional or higher functional reactive compound (hereinafter also referred to as a "coupling agent"). In the coupling reaction step, a coupling agent is used to cause a coupling reaction at one active end of the conjugated diene polymer to obtain a conjugated diene polymer.

[0025] Examples of coupling agents include, but are not limited to, coupling agents having one or more functional groups such as an epoxy group, a carbonyl group, a carboxylic acid ester group, a carboxylic acid amide group, an acid anhydride group, a phosphate ester group, a phosphite ester group, an epithio group, a thiocarbonyl group, a thiocarboxylic acid ester group, a dithiocarboxylic acid ester group, a thiocarboxylic acid amide group, an imino group, an ethyleneimino group, a halogen group, an alkoxysilyl group, an isocyanate group, a thioisocyanate group, a conjugated diene group, and an arylvinyl group. Among the coupling agents, nitrogen atom-containing coupling agents can also be used as modifiers, which will be described later.

[0026] Examples of coupling agents include, but are not limited to, halogenated silane compounds such as silicon tetrachloride, silicon tetrabromide, silicon tetraiodide, monomethyltrichlorosilicon, monoethyltrichlorosilicon, monobutyltrichlorosilicon, monohexyltrichlorosilicon, monomethyltribromosilicon, and bistrichlorosilylethane; and halogenated silane compounds such as monochlorotrimethoxysilane, monobromotrimethoxysilane, dichlorodimethoxysilane, dibromodimethoxysilane, trichloromethoxysilane, and tribromomethoxysilane.

[0027] Further, examples include, but are not limited to, alkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, and alkyltriphenoxysilane; and compounds having an imino group and an alkoxysilyl group such as tristrimethoxysilylpropylamine, triethoxysilylpropylamine, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N-(1,3-dimethylbutylidene)-3-(tributoxysilyl)-1-propanamine, N-(1-methylpropylidene)-3-(triethoxysilyl)-1-propanamine, N-ethylidene-3-(triethoxysilyl)-1-propanamine, and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole.

[0028] Furthermore, examples thereof include, but are not limited to, 2-[3-(trimethoxysilyl)propyl]-1,3-dimethylimidazolidinone, 2-[3-(trimethoxysilyl)propyl]-1,3-(bistrimethylsilyl)imidazolidinone, 2-(diethoxydiethylsilyl)-1,3-diethylimidazolidinone, 2-(triethoxysilyl)-1,4-diethylpiperazine, 2-(dimethoxymethylsilyl)-1,4-dimethylpiperazine, 5-(triethoxysilyl)-1,3-dipropylhexahydropyrimidine, 5-(dieth ...ethylhexahydropyrimidine, 5-(diethoxysilyl)-1,3-dipropylhexahydropyrimidine, 5-(diethoxysilyl)-1,3-diethylhexahydropyrimidine, 5-(diethoxysilyl)-1,3-diethylhexahydropyrimidine, 5-(diethoxysilyl)-1,3-diethylhexahydropyrimidine, 5-(diethoxysilyl)-1,3-diethylhexahydropyrimidine, 5-(diethoxysilyl)-1 {2-[3-(2-dimethylaminoethyl)-2-(ethyldimethoxysilyl)-imidazolidinone-1-yl]-ethyl}-dimethylamine, 5-(trimethoxysilyl)-1,3-bis-(2-methoxyethyl)-hexahydropyrimidine, 5-(ethyldimethoxysilyl)-1,3-bis-(2-trimethylsilylethyl)-hexahydropyrimidine-1,3-dimethylimidazolidinone, 2-(3-diethoxyethylsilyl-propyl)-1,3-diethylimidazolidinone Non, 2-(3-triethoxysilyl-propyl)-1,4-diethylpiperazine, 2-(3-dimethoxymethylsilyl-propyl)-1,4-dimethylpiperazine, 5-(3-triethoxysilyl-propyl)-1,3-dipropylhexahydropyrimidine, 5-(3-diethoxyethylsilyl-propyl)-1,3-diethylhexahydropyrimidine, {2-[3-(2-dimethylaminoethyl)-2-(3-ethyldimethoxysilyl-propyl)-imidazolidinon-1-yl]-ethyl}-dimethylamine, 5-(3-trimethoxysilyl-propyl)-1,4-diethylpiperazine, 5-(3-triethoxysilyl-propyl)-1,3-dipropylhexahydropyrimidine, 5-(3-diethoxyethylsilyl-propyl)-1,3-diethylhexahydropyrimidine, {2-[3-(2-dimethylaminoethyl)-2-(3-ethyldimethoxysilyl-propyl)-imidazolidinon-1-yl]-ethyl}-dimethylamine, 2-(Diethoxyethylsilyl)-1,3-bis(triethylsilyl)imidazolidinone, 2-(Diethoxyethylsilyl)-1,4-bis(trimethylsilyl)piperazine, 2-(Dimethoxymethylsilyl)-1,4-bis(trimethylsilyl)piperazine, 2-(Diethoxy ...Examples include 4-bis(trimethylsilyl)piperazine and 5-(triethoxysilyl)-1,3-bis(tripropylsilyl)hexahydropyrimidine.

[0029] Furthermore, although not limited to the following, for example, [3-(1-hexamethyleneimino)propyl]triethoxysilane, [3-(1-hexamethyleneimino)propyl]trimethoxysilane, [2-(1-hexamethyleneimino)ethyl]triethoxysilane, [2-(1-hexamethyleneimino)ethyl]trimethoxysilane, [3-(1-pyrrolidinyl)propyl]triethoxysilane, [3-(1-pyrrolidinyl)propyl]trimethoxysilane, [3-(1-heptamethyleneimino)propyl]triethoxysilane, [3-(1-do [decamethyleneimino)propyl]triethoxysilane, [3-(1-hexamethyleneimino)propyl]diethoxymethylsilane, [3-(1-hexamethyleneimino)propyl]diethoxyethylsilane, N-[3-(triethoxysilyl)propyl]-N,N'-diethyl-N'-trimethylsilyl-ethane-1,2-diamine, N-[2-(trimethoxysilanyl)ethyl]-N,N',N'-trimethylethane-1,2-diamine, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, and the like.

[0030] Furthermore, examples of the epoxy compounds include, but are not limited to, tetraglycidyl meta-xylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, etc. Furthermore, examples of the isocyanate compounds include, but are not limited to, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, diphenylethane diisocyanate, 1,3,5-benzene triisocyanate, etc.

[0031] In addition, examples thereof include, but are not limited to, 3-(4-methylpiperazin-1-yl)propyltriethoxysilane, 1-[3-(diethoxyethylsilyl)propyl]-4-methylpiperazine, 1-[3-(trimethoxysilyl)propyl]-3-methylimidazolidinone, 1-[3-(diethoxysilyl)propyl]-3-ethylimidazolidinone, 1-[3-(triethoxysilyl)propyl]-3-methylhexahydropyrimidine, 1-[3-(di 3-[3-(trimethoxysilyl)propyl]-3-methylhexahydropyrimidine, 3-[3-(tributoxysilyl)propyl]-1-methyl-1,2,3,4-tetrahydropyrimidine, 3-[3-(dimethoxymethylsilyl)propyl]-1-ethyl-1,2,3,4-tetrahydropyrimidine, 1-(2-ethoxyethyl)-3-[3-(trimethoxysilyl)propyl]imidazolidinone, (2-{3-[3-(trimethylsilyl)propyl]tetra hydropyrimidin-yl}ethyl)dimethylamine, 1-[3-(triethoxysilyl)propyl]-4-(trimethylsilyl)piperazine, 1-[3-(dimethoxymethylsilyl)propyl]-4-(trimethylsilyl)piperazine, 1-[3-(tributoxysilyl)propyl]-4-(trimethylsilyl)piperazine, 1-[3-(diethoxyethylsilyl)propyl]-3-(triethylsilyl)imidazolidinone, 2-(trimethoxysilanilide

[0033] Examples of suitable silyl groups include 1-[3-(triethoxysilyl)propyl]-1,3-dimethylimidazolidinone, 1-[3-(triethoxysilyl)propyl]-3-(trimethylsilyl)imidazolidinone, 1-[3-(dimethoxymethylsilyl)propyl]-3-(trimethylsilyl)hexahydropyrimidine, 1-[3-(triethoxysilyl)propyl]-3-(trimethylsilyl)hexahydropyrimidine, and 1-[4-(triethoxysilyl)propyl]-4-(trimethylsilyl)piperazine.

[0032] (modified polymer) The conjugated diene polymer of the present embodiment is a modified polymer. In this specification, a conjugated diene polymer modified with a nitrogen-containing compound is referred to as a modified polymer. The degree of modification can be defined by two things: the nitrogen content and the modification rate, which will be described later. The nitrogen content, which contributes to the polarity of the conjugated diene polymer, is 80 ppm or more for the conjugated diene polymer of this embodiment. A high nitrogen content increases the polarity of the conjugated diene polymer, which tends to reduce the bleeding rate of the amine-based antioxidant in the rubber composition using the conjugated diene polymer of this embodiment and improve ozone resistance. The nitrogen content is preferably 100 ppm or more, and more preferably 120 ppm. The nitrogen content can be measured by the method described in the examples below.

[0033] Methods for modifying conjugated diene polymers include, but are not limited to, a method using a polymerization initiator containing a nitrogen-containing compound, a method using a nitrogen-containing compound as a polymerization monomer, a method using the aforementioned nitrogen atom-containing coupling agent, a method of reacting a non-coupling nitrogen-containing compound with the reaction terminal, a method of modifying the double bonds of a polymerized conjugated diene polymer by reacting a nitrogen-containing compound with the double bonds of the polymerized conjugated diene polymer, etc. The nitrogen content can be controlled within the above-mentioned numerical range by adjusting the amount of these added.

[0034] Examples of the polymerization initiator containing a nitrogen-containing compound include, but are not limited to, reaction products of nitrogen-containing compounds such as dimethylamine, diethylamine, dibutylamine, dipropylamine, diheptylamine, dihexylamine, dioctylamine, di(2-ethylhexyl)amine, didecylamine, ethylpropylamine, ethylbutylamine, ethylbenzylamine, methylphenethylamine, piperidine, hexamethyleneimine, azacyclooctane, 1,3,3-trimethyl-6-azabicyclo[3.2.1]octane, 1,2,3,6-tetrahydropyridine, and 3,5-dimethylpiperidine with organic lithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, n-propyllithium, and i-propyllithium.

[0035] Furthermore, examples of non-coupling nitrogen-containing compounds include, but are not limited to, 1,3-diethyl-2-imidazolinone, 1,3-dimethyl-2-imidazolinone, 1,3-dipropyl-2-imidazolinone, 1-methyl-3-ethyl-2-imidazolinone, 1-methyl-3-propyl-2-imidazolinone, 1-methyl-3-butyl-2-imidazolinone, 1,3-dihydro-1,3-dimethyl-2H-imidazol-2-one, N-methyl-2-pyrrolidone, 1-phenyl-2-pyrrolidone, and N-methyl-ε-caprolactam.

[0036] (denaturation rate) In this specification, unless otherwise specified, the "modification ratio" represents the mass ratio of the polymer having a nitrogen atom-containing functional group to the total amount of the conjugated diene polymer. For example, when a nitrogen atom-containing modifying agent is reacted with the terminal end of a polymer, the mass ratio of the polymer having a nitrogen atom-containing functional group due to the nitrogen atom-containing modifying agent to the total amount of the polymer is expressed as the modification rate. As mentioned above, the nitrogen atom-containing coupling agent is also included in the nitrogen atom-containing modifying agent. On the other hand, when a polymer is branched using a branching agent containing a nitrogen atom, the resulting copolymer will also have a nitrogen atom-containing functional group, and therefore this branched polymer will also be counted as a polymer having a nitrogen atom-containing functional group when calculating the modification rate. That is, in this specification, the polymer having a nitrogen atom-containing functional group refers to a polymer having a nitrogen atom-containing functional group formed by a nitrogen atom-containing modifying agent and a branched polymer formed by a branching agent having a nitrogen atom-containing functional group, and the total mass ratio of these is the "modification rate."

[0037] From the viewpoint of dynamic magnification, the conjugated diene polymer of the present embodiment has a modification rate (hereinafter also simply referred to as "modification rate") measured by a column adsorption GPC method described later, of preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more, relative to the total amount of the conjugated diene polymer. On the other hand, since it is difficult to remove impurities during polymerization, from the viewpoint of increasing productivity, the modification rate is preferably 99% or less, more preferably 97% or less, even more preferably 95% or less, and even more preferably 93% or less. The modification rate can be controlled by keeping the amount of modifier added and the polymerization temperature low, thereby suppressing the deactivation of living ends.

[0038] The modification rate of the conjugated diene polymer of the present embodiment can be measured, for example, by chromatography, which can separate functional group-containing modified components from unmodified components. Examples of methods using this type of chromatography include a method in which a gel permeation chromatography column filled with a polar substance such as silica that adsorbs specific functional groups is used, and the non-adsorbed components are quantified using an internal standard for comparison (column adsorption GPC method). More specifically, the modification rate can be determined by measuring the amount of adsorption onto the 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 the sample solution on a silica column. More specifically, the modification rate can be measured by the method described in the Examples. The modification rate of the conjugated diene polymer of this embodiment can be controlled within the above-mentioned range by, for example, controlling the amount of the modifying agent added and the polymerization reaction temperature to prevent deactivation of the active terminals.

[0039] [Method for producing conjugated diene polymer] The conjugated diene polymer of this embodiment is obtained by carrying out a polymerization step in which an aromatic vinyl compound and a conjugated diene compound are polymerized using a predetermined polymerization initiator. Preferably, a coupling reaction step and / or a modification reaction step may be carried out using the above-mentioned coupling agent or modifying agent, followed by a hydrogenation step. A branching step may be carried out using a branching agent before the coupling reaction step or the modification step.

[0040] (Polymerization process) The polymerization method for the conjugated diene polymer of the present embodiment is not limited to the following, but living anionic polymerization is preferred, and adiabatic polymerization is preferred. From the viewpoint of increasing the reaction rate and improving productivity, the reaction temperature is preferably a polymerization initiation temperature of 25°C to 60°C, more preferably 25°C to 55°C, and even more preferably 25°C to 50°C. From the viewpoint of increasing the polymerization addition rate of the monomer, the polymerization termination temperature is preferably 65°C or higher, more preferably 68°C or higher, and even more preferably 70°C or higher. On the other hand, from the viewpoint of increasing the modification rate, the temperature is preferably 95°C or lower, more preferably 85°C or lower, even more preferably 82°C or lower, and even more preferably 80°C or lower.

[0041] As the polymerization initiator used in the polymerization step, 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 structure of the target conjugated diene polymer and the molecular weight of the 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, i.e., tends to be related to the number average molecular weight and / or weight average molecular weight, and peak top 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.

[0042] As the organic monolithium compound, an alkyllithium compound having a substituted amino group or a dialkylaminolithium is preferred from the viewpoint that it can be used as one method for introducing nitrogen atoms into a conjugated diene polymer. In this case, a conjugated diene polymer having a nitrogen atom consisting of an amino group at the polymerization initiation terminal is obtained.

[0043] 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.

[0044] 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. The organic monolithium compound is preferably an alkyllithium compound from the viewpoints of industrial availability and ease of control of the polymerization reaction, in which case a copolymer 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.

[0045] In the polymerization step, the polymerization reaction mode is not limited to the following, but examples thereof include a batchwise (also called a "batch type") and a continuous polymerization reaction mode. In the continuous system, one or more connected reactors can be used. The continuous reactor may be, for example, a tank-type or tubular reactor equipped with a stirrer. In the continuous system, preferably, the monomer, the inert solvent, and the polymerization initiator are continuously fed into the reactor, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is continuously discharged. The batch reactor may be, for example, a tank-type reactor equipped with a stirrer. In the batch reactor, preferably, a monomer, an inert solvent, and a polymerization initiator are fed, and if necessary, a monomer is added continuously or intermittently during polymerization to obtain a polymer solution in the reactor, which is then discharged after the polymerization is completed. In the method for producing a conjugated diene polymer of the present embodiment, in order to obtain a conjugated diene polymer having active ends at a high rate, a continuous method is preferred, which allows the polymer to be continuously discharged and subjected to the next reaction in a short time.

[0046] In the polymerization step of the conjugated diene polymer of this embodiment, the polymerization is preferably carried out in an inert solvent. Examples of the inert solvent include, but are not limited to, hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Examples of the hydrocarbon solvent include, but are not limited to, aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; and hydrocarbons consisting of mixtures thereof.

[0047] The inert solvent is preferred because, by treating impurities such as allenes and acetylenes with an organometallic compound before subjecting the polymer to the polymerization reaction, a conjugated diene-based polymer having a high concentration of active ends tends to be obtained, and a modified conjugated diene-based polymer with a high modification rate tends to be obtained.

[0048] In the polymerization step, a polar substance (polar compound) may be added. The addition of a polar substance allows the aromatic vinyl compound to be randomly copolymerized with the conjugated diene compound. Polar substances tend to be used as vinylating agents to control the microstructure of the conjugated diene portion. They also tend to be effective in accelerating the polymerization reaction. 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 30 moles or less per mole of the polymerization initiator. Such polar substances (vinylating agents) can be used in an appropriate amount depending on the desired amount of 1,2-vinyl bonds as modifiers for the microstructure of the conjugated diene moiety in the conjugated diene polymer. Many polar substances also have an effective randomizing effect in the copolymerization of a conjugated diene compound and an aromatic vinyl compound, and tend to be used as modifiers for adjusting the distribution of the aromatic vinyl compound and the amount of styrene blocks.

[0049] As a method for randomizing the conjugated diene compound and the aromatic vinyl compound, for example, as described in JP-A-59-140211, a copolymerization reaction may be initiated with the entire amount of styrene and a portion of 1,3-butadiene, and the remaining 1,3-butadiene may be intermittently added during the copolymerization reaction.

[0050] (Coupling process, modification process, hydrogenation process) The active terminals of the conjugated diene polymer obtained through the above-mentioned polymerization step and, if necessary, a branching step using a predetermined branching agent may be subjected to a coupling reaction using the above-mentioned coupling agent or a modification reaction using a modifying agent having a nitrogen atom-containing group. When a nitrogen atom-containing coupling agent is used, the coupling reaction and the modification reaction proceed simultaneously. In addition, a hydrogenation step in which a hydrogenation reaction is carried out may be carried out as needed.

[0051] (Deactivator addition process, neutralizer addition process) In the method for producing a conjugated diene polymer of this embodiment, a deactivator, a neutralizer, etc. may be added to the polymer solution as needed. The quenching agent is not limited to the following, but examples thereof include water; alcohols such as methanol, ethanol, and isopropanol; and the like. Examples of neutralizing agents include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, mainly 10 carbon atoms); aqueous solutions of inorganic acids; and carbon dioxide gas.

[0052] (rubber stabilizer addition process) In the method for producing a conjugated diene polymer of the present embodiment, it is preferable to add a rubber stabilizer from the viewpoint of preventing gel formation after polymerization and improving stability during processing. In the method for producing a conjugated diene polymer of this embodiment, it is preferable to add a hindered phenol-based antioxidant as a rubber stabilizer. In the conjugated diene polymer of this embodiment, from the viewpoint of preventing gelation due to heat generation during kneading, the hindered phenol antioxidant is added in an amount of preferably 0.55 parts by mass or more, more preferably 0.60 parts by mass or more, and even more preferably 0.65 parts by mass or more, per 100 parts by mass of the conjugated diene polymer, while from the viewpoint of cost, the amount is preferably 1.5 parts by mass or less, more preferably 1.4 parts by mass or less.

[0053] Furthermore, hindered phenol-based antioxidants can be further classified into sulfur-containing hindered phenol-based antioxidants and sulfur-free hindered phenol-based antioxidants. In the conjugated diene polymer of this embodiment, from the viewpoints of suppressing gelation during kneading and suppressing oxidative degradation, the sulfur-containing hindered phenol-based antioxidant is preferably added in an amount of 0.10 parts by mass or more, more preferably 0.15 parts by mass or more, even more preferably 0.20 parts by mass or more, and even more preferably 0.25 parts by mass or more, relative to 100 parts by mass of the conjugated diene polymer. On the other hand, from the viewpoint of odor, the sulfur-containing hindered phenol-based antioxidant is preferably added in an amount of 1.0 part by mass or less, more preferably 0.9 parts by mass or less, and even more preferably 0.8 parts by mass or less. Furthermore, from the viewpoint of suppressing deterioration due to heat or sunlight after production, the sulfur-free hindered phenol antioxidant is added in an amount of preferably 0.2 part by mass or more, more preferably 0.3 part by mass or more, even more preferably 0.4 part by mass or more, even more preferably 0.5 part by mass or more, and even more preferably 0.6 part by mass or more, relative to 100 parts by mass of the conjugated diene polymer. On the other hand, from the viewpoint of colorability such as yellowing of the molded article, the sulfur-free hindered phenol antioxidant is added in an amount of preferably 1.0 part by mass or less, more preferably 0.95 part by mass or less, and even more preferably 0.9 part by mass or less.

[0054] In order to sufficiently reduce the risk of gelation and achieve excellent productivity in the conjugated diene polymer of this embodiment, it is preferable to add 0.55 parts by mass or more of a hindered phenol-based antioxidant per 100 parts by mass of the conjugated diene-based polymer, and it is more preferable to add 0.1 part by mass or more and 1.0 part by mass or less of a sulfur-containing hindered phenol-based antioxidant or 0.35 part by mass or more and 1.0 part by mass or less of a sulfur-free hindered phenol-based antioxidant per 100 parts by mass of the conjugated diene-based polymer. The hindered phenol-based antioxidants may be used alone or in combination of two or more.Similarly, it is preferable to use one or more sulfur-containing hindered phenol-based antioxidants and one or more sulfur-free hindered phenol-based antioxidants in combination, and two or more of each may be used in combination.

[0055] Examples of the hindered phenol compound include, but are not limited to, N-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, tetrakis{methylene-3-(3',5'-di-t-butyl-4-hydroxyphenyl)propionate}methane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, distearyl(4-hydroxy-3-methyl-5-t-butylbenzyl)malonate, tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, and tetrakis(2-methyl-4-hydroxy-5-t-butylphenyl)propionate. Ethylene glycol bis{3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate}, 1,6-hexanediol bis{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate}, 2,4-bis-(N-octylthio)-6-(4-hydroxyphenyl)-3,5-di-t-butyl-anilino-1,3,5-triazine, 2,2-thiodiethylene bis{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate}, 2 ,2-thiobis(4-methyl-6-t-butylphenol), 2,2'-methylenebis-(4-ethyl-6-t-butylphenol), N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3,5-di- t-butyl-4-hydroxybenzyl) sulfide, tris(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate, 2,4-bis{(octylthio)methyl}-o-cresol, isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, N,N'-bis{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionylhydrazine, and (meth)acrylate compounds having a hindered phenol structure.

[0056] (Desolvation process) In the method for producing a conjugated diene polymer of this embodiment, a known method can be used to obtain the resulting conjugated diene polymer from the polymer solution. Examples of the method include, but are not limited to, a method in which the solvent is separated by steam stripping or the like, the conjugated diene polymer is then filtered, and the resulting polymer is then dehydrated and dried to obtain a conjugated diene polymer, a method in which the polymer is concentrated in a flashing tank and then devolatilized using a vent extruder or the like, and a method in which the polymer is directly devolatilized using a drum dryer or the like.

[0057] [Rubber composition] The rubber composition of the present embodiment contains the conjugated diene-based polymer of the present embodiment and natural rubber, and optionally contains other rubber components, fillers, silane coupling agents, rubber softeners, crosslinking agents, and predetermined additives, which will be described later.

[0058] (Other rubber components) Examples of rubber components other than the conjugated diene polymer of this embodiment include, but are not limited to, synthetic rubbers, and examples of synthetic rubbers include isoprene rubber, butadiene rubber and its hydrides, styrene butadiene rubber and its hydrides, nitrile rubber and its hydrides, urethane rubber, butyl rubber and its halides, ethylene-propylene-diene rubber (EPDM), chloroprene rubber, acrylic rubber, silicone rubber, and fluororubber.

[0059] (filler) The rubber composition of this embodiment preferably contains 10 parts by mass or more, and more preferably 15 parts by mass or more, of a filler per 100 parts by mass of the rubber component containing the conjugated diene polymer of this embodiment, from the viewpoints of rigidity and compression set. On the other hand, from the viewpoints of sufficiently dispersing the filler and ensuring that the rubber composition of this embodiment has practically sufficient processability and mechanical strength, the content of the filler is preferably 300 parts by mass or less, more preferably 250 parts by mass or less, even more preferably 200 parts by mass or less, and even more preferably 100 parts by mass or less, per 100 parts by mass of the rubber component containing the conjugated diene polymer of this embodiment.

[0060] Examples of fillers include, but are not limited to, silica-based inorganic fillers, carbon black, calcium carbonate, titanium oxide, aluminum hydroxide, and clay. These may be used alone or in combination of two or more. Furthermore, fillers other than those mentioned above may also be contained.

[0061] From the viewpoint of the dynamic magnification of the rubber composition, the filler used in the rubber composition of the present embodiment preferably contains 40% by mass or more of carbon black, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0062] The silica-based inorganic filler is not limited to the following and any known filler can be used, but for example, 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 50 mass% or more, preferably 70 mass% or more, and more preferably 80 mass% or more. Specific 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. Other examples include silica-based inorganic fillers whose surfaces have been made hydrophobic, and mixtures of silica-based inorganic fillers and inorganic fillers other than silica-based inorganic fillers. Among these, silica and glass fiber are preferred, and silica is more preferred, from the viewpoints of strength, abrasion resistance, etc. Examples of silica include dry silica, wet silica, and synthetic silicate silica.

[0063] 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 with a nitrogen adsorption specific surface area of ​​50 m 2 / g or more and a dibutyl phthalate (DBP) oil absorption of 80 mL / 100 g or less is preferred. The calcium carbonate is not particularly limited, but examples thereof include calcium carbonate having an average particle size of 0.04 μm to 8.0 μm and an oil absorption of 10 to 35 g per 100 g of calcium carbonate. The filler may contain fillers other than the above-mentioned fillers, such as metal oxides and metal hydroxides. Metal oxides are compounds 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 the main component of the structural unit. Examples of metal oxides include, but are not limited to, alumina, titanium oxide, magnesium oxide, and zinc oxide. Examples of metal hydroxides include, but are not limited to, aluminum hydroxide, magnesium hydroxide, and zirconium hydroxide.

[0064] (Silane coupling agent) The rubber composition of the present embodiment may contain a silane coupling agent. The silane coupling agent has the function of strengthening the interaction between the rubber component and the inorganic filler, and has groups that have affinity or bonding properties for both the rubber component and the silica-based inorganic filler. Preferably, the silane coupling agent is a compound that has a sulfur-bonding moiety and an alkoxysilyl group or silanol group moiety in one molecule. Examples of such compounds include, but are not limited to, bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, and bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide. 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 inorganic filler. When the content of the silane coupling agent is within the above range, the effect of the addition of the silane coupling agent tends to be more pronounced.

[0065] (rubber softener) The rubber composition of the present embodiment may contain a rubber softener as needed. The rubber additive may be added to the conjugated diene polymer of the present embodiment described above. The rubber softener is preferably added from the viewpoint of further improving the productivity of the conjugated diene polymer and the processability of the rubber composition containing a filler or the like. Examples of rubber softeners include, but are not limited to, extender oil, liquid rubber, and resin. The method of adding a rubber softener to a conjugated diene polymer or a conjugated diene polymer composition is not limited to the following, but a preferred method is to add a rubber softener to a conjugated diene polymer solution, mix them, and remove the solvent from the resulting polymer solution containing the rubber softener.

[0066] Examples of the extender oil include aromatic oil, naphthenic oil, paraffin oil, etc. Among these, from the viewpoint of environmental safety, oil bleeding prevention, and wet grip properties, aromatic substitute oils having a polycyclic aromatic (PCA) component content of 3 mass% or less according to the IP346 method are preferred. Examples of aromatic substitute oils include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), etc., as shown in Kautschuk Gummi Kunststoffe 52(12)799(1999), as well as RAE (Residual Aromatic Extracts).

[0067] The liquid rubber is not limited to the following, but examples thereof include liquid polybutadiene and liquid styrene-butadiene rubber. The effect of adding liquid rubber is that it improves the processability of a rubber composition containing a conjugated diene polymer and a filler, etc., and also tends to shift the glass transition temperature of the rubber composition to a lower temperature, thereby improving the abrasion resistance and low-temperature properties of a vulcanized product.

[0068] Examples of the resin 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, various hydrocarbon resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, and 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. When hydrogenating, all of the unsaturated groups may be hydrogenated, or some may remain. The effects of adding a resin include an effect of improving the processability of a rubber composition blended with the conjugated diene-based polymer of this embodiment and a filler, etc., as well as an effect of improving the breaking strength of a vulcanized product. Furthermore, the glass transition temperature of the rubber composition of this embodiment can be shifted to a higher temperature, which tends to improve the tensile properties at high temperatures.

[0069] The amount of extender oil, liquid rubber, resin, or the like added as a rubber softener is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, relative to 100 parts by mass of the conjugated diene-based polymer of this embodiment. When the rubber softener is added within the above range, the processability of the rubber composition containing the conjugated diene polymer of this embodiment and a filler, etc., is improved, and the breaking strength and abrasion resistance of the vulcanized product tend to be improved.

[0070] (Rubber bale molding) The conjugated diene polymer and rubber composition of the present embodiment can be formed into a rubber bale molded article. The rubber bale molded body is a mass of a conjugated diene polymer or a rubber composition obtained by compression molding, and can be obtained, for example, by extruding a conjugated diene polymer or a rubber composition using an extruder, cutting it to obtain crumbs, and then compression molding the crumbs.

[0071] (Crosslinked composition) The rubber composition of the present embodiment may be a crosslinked composition that has been subjected to a crosslinking treatment with a crosslinking agent. Examples of crosslinking agents include, but are not limited to, radical generators such as organic peroxides and azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. The sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, polymeric polysulfur compounds, and the like. In the rubber composition of this embodiment, the content of the crosslinking agent is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the rubber component containing the conjugated diene-based polymer of this embodiment. As the vulcanization method, a conventionally known method can be applied, and the vulcanization temperature is preferably 120°C or more and 200°C or less, and more preferably 140°C or more and 180°C or less.

[0072] In the crosslinking, a vulcanization accelerator may be used as needed. 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. The vulcanization aid may include, but is not limited to, zinc oxide, stearic acid, and triallyl isocyanurate. The content of the vulcanization accelerator is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, per 100 parts by mass of the rubber component containing the conjugated diene polymer of the present embodiment.

[0073] Examples of organic peroxides include, but are not limited to, 1,3-bis(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexene-3, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,2'-bis(tert-butylperoxy)-p-isopropylbenzene, dicumyl peroxide, di-tert-butyl peroxide, tert-butyl peroxide, peroxide, p-menthane peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, dilauroyl peroxide, diacetyl peroxide, tert-butyl peroxybenzoate, 2,4-dichlorobenzoyl peroxide, p-chlorobenzoyl peroxide, benzoyl peroxide, di(tert-butylperoxy)perbenzoate, n-butyl-4,4-bis(tert-butylperoxy)valerate, and tert-butylperoxyisopropyl carbonate.

[0074] (Uses of rubber compositions) The rubber composition of the present embodiment is used for, for example, vibration-proof rubber, vibration-damping materials, various rubber belts such as transmission belts and conveyor belts, shoe soles, various industrial materials, automobile interiors, hoses, tires, etc. Materials for these various applications contain the rubber composition of the present embodiment.

[0075] (Method of manufacturing rubber composition) The rubber composition of this embodiment is obtained by mixing the conjugated diene rubber of this embodiment, natural rubber, and, if necessary, a filler, a silane coupling agent, a rubber softener, a crosslinking agent, and predetermined additives. The mixing method is not limited to the following, but examples thereof include a melt-kneading method using a general mixer such as an open roll, a Banbury mixer, a kneader, a single-screw extruder, a twin-screw extruder, or a multi-screw extruder, and a method in which the components are dissolved and mixed and then the solvent is removed by heating. Among these, 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. Also applicable are a method of kneading the rubber component, other fillers, silane coupling agent, and additives all at once, and a method of mixing them in several batches. After the mixing step, a predetermined crosslinking reaction is carried out to obtain a crosslinked composition.

[0076] (Other additives) The rubber composition of the present embodiment may contain various additives other than those described above, such as softeners and fillers, heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, lubricants, and tackifiers, within the scope of the present embodiment. As other softeners, known softeners can be used. Known materials can be used for the heat stabilizer, antistatic agent, weather stabilizer, antioxidant, colorant, and lubricant. [Example]

[0077] Hereinafter, the present embodiment will be described in more detail with reference to specific examples and comparative examples, application examples and comparative application examples, but the present invention is not limited in any way by the following examples and comparative examples, application examples and comparative application examples.

[0078] Here, specific examples of conjugated diene polymers are referred to as "Examples" and "Comparative Examples", and specific examples of rubber compositions are referred to as "Application Examples" and "Application Comparative Examples".

[0079] Various physical properties in the Examples, Comparative Examples, Application Examples and Application Comparative Examples were measured by the methods shown below.

[0080] [Physical property measurement method] [Peak top molecular weight of peak (A), area ratio of peak (B), molecular weight distribution] The chromatogram was measured using a GPC measuring device with three columns connected together, each packed with polystyrene gel, and the peak top molecular weight (Mp) of the lowest molecular weight peak (A) was determined based on a calibration curve using standard polystyrene. In the obtained molecular weight distribution curve, the group of peaks on the higher molecular weight side than peak (A) was designated as peak (B), and the area ratio of peak (B) (B / (A+B)) was calculated. The molecular weight distribution of the conjugated diene polymer was also determined. The specific measurement conditions are shown below. 20 μL of the measurement solution below was injected into the GPC measurement device and the measurement was carried out. (Measurement conditions) Device: Tosoh Corporation, product name "HLC-8320GPC" Eluent: 5mmol / L triethylamine in tetrahydrofuran (THF) Guard column: Tosoh Corporation's product name "TSKguardcolumn SuperH-H" Separation column: Tosoh Corporation product names "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" connected in this order. Oven temperature: 40°C Flow rate: 0.6mL / min Detector: RI detector (product name "HLC8020" manufactured by Tosoh Corporation) Measurement solution: 10 mg of sample dissolved in 20 mL of THF (Calculation method for the area ratio of peak (B)) In the molecular weight distribution curve obtained by the RI detector, the area ratio of peak (B) was calculated according to the following formula. Peak (B) area ratio = Peak (B) area / (Peak (B) area + Peak (A) area) × 100 (%)

[0081] [Modification rate of conjugated diene polymer] The modification rate was measured by the column adsorption GPC method, utilizing the property of the modified polymer to be adsorbed onto a column, as follows. The amount of adsorption onto the silica-based column was measured by subtracting the chromatogram of a sample solution containing the sample and low-molecular-weight internal standard polystyrene measured using a column packed with polystyrene-based gel from the chromatogram measured using a column packed with silica-based gel, and the modification rate was calculated. (GPC measurement conditions using a polystyrene column) The GPC measurement conditions using a polystyrene column are as follows: 20 μL of the measurement solution below was injected into the GPC measurement device and the measurement was carried out. Device: Tosoh Corporation, product name "HLC-8320GPC" Eluent: THF containing 5mmol / L triethylamine Guard column: Tosoh Corporation's product name "TSKguardcolumn SuperH-H" Column: Tosoh Corporation product names "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" connected in this order Oven temperature: 40°C Flow rate: 0.6mL / min Detector: RI detector (Tosoh HLC8020) Measurement solution: 10 mg of sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a sample solution. (GPC measurement conditions using a silica column) The conditions for GPC measurement using a silica column are as follows: 50 μL of the measurement solution below was injected into the GPC measurement device and measurement was carried out. Device: Tosoh Corporation, product name "HLC-8320GPC" Eluent:THF Guard column: GL Sciences product name "DIOL 4.6 x 12.5 mm 5 micron" Separation column: Agilent Technologies' Zorbax PSM-1000S, PSM-300S, and PSM-60S columns connected in this order Oven temperature: 40℃, Flow rate: 0.5mL / min Detector: RI detector (Tosoh HLC8020) (Calculation method of denaturation rate): The total peak area of ​​the chromatogram using the polystyrene column was set to 100, the peak area of ​​the sample was set to P1, the peak area of ​​the standard polystyrene was set to P2, and the total peak area of ​​the chromatogram using the silica column was set to 100, the peak area of ​​the sample was set to P3, and the peak area of ​​the standard polystyrene was set to P4. The modification rate (%) was calculated using the following formula. Denaturation rate (%) = [1-(P2 x P3) / (P1 x P4)] x 100 (However, P1+P2=P3+P4=100)

[0082] [Glass transition temperature (Tg)] Measurements were performed using a conjugated diene polymer as a sample according to ISO 22768:2006. 10 mg of sample was placed in a dedicated aluminum pan, and a Hitachi High-Tech Science DSC7020 differential scanning calorimeter was used as the measurement device. The sample was heated from 30°C to 160°C at 20°C / min and held for 2 minutes, then cooled from 160°C to -120°C at 10°C / min. The DSC curve was recorded while the temperature was then increased from -120°C to 100°C at 10°C / min. The glass transition temperature was determined as the peak top (inflection point) of the DSC differential curve resulting from the glass transition of the conjugated diene polymer when the temperature was increased from -120°C to 100°C.

[0083] [Styrene Content of Conjugated Diene Polymer] Using a conjugated diene polymer as a sample, 1 The amount of bound styrene was measured by 1 H-NMR measurement. 1 The conditions for H-NMR measurement are as follows: <Measurement conditions> Measuring equipment: JNM-LA400 (JEOL) Solvent: deuterated chloroform Measurement sample: Conjugated diene polymer Sample concentration: 50mg / mL Observation frequency: 400MHz Chemical shift standard: TMS (tetramethylsilane) is contained at 0.05% by mass relative to deuterated chloroform. Pulse delay: 2.904 seconds Number of scans: 64 Pulse width: 45° Measurement temperature: 26℃

[0084] [Styrene block content] The content of the aromatic vinyl monomer block (styrene block) was measured according to the osmium tetroxide decomposition method described in I. M. Kolthoff, et al., J. Polym. Sci. 1, 429 (1946). More specifically, 0.050 g of the conjugated diene polymer was dissolved in 10 mL of chloroform, to which 16 mL of a 69% by weight aqueous solution of tert-butyl hydroperoxide and 4.0 mL of a 0.050% by weight chloroform solution of osmium tetroxide were added. The mixture was refluxed in a 90°C bath for 12 minutes to carry out an oxidative decomposition reaction. After completion of the reaction, the reaction solution was cooled, and 200 mL of methanol was added to the reaction solution with stirring to precipitate the styrene block component, which was then filtered through a 5 μm glass filter. The styrene block content was determined by dividing the mass of the resulting product by the total mass of the styrene-butadiene copolymer rubber.

[0085] [Nitrogen content] The conjugated diene polymer was used as a sample, and the nitrogen content was measured using a trace nitrogen analyzer (Nitto Seiko Analytech TN-2100H).

[0086] [Evaluation of cold flow properties] The stabilizer-containing conjugated diene polymers obtained in the examples and comparative examples were used as measurement samples. The cold flow property was evaluated by applying a load of 1 kg to a sample of 40 mm × 40 mm × thickness (H0) 50 mm at 25°C and leaving it for 60 minutes, and calculating the change in thickness (H60) from the thickness (%) using the following formula, and indexing the change in thickness. Thickness change rate (%) = (H0-H60) x 100 / H0 The analysis results are expressed as an index, with a higher number indicating less susceptibility to cold flow (better).

[0087] [Production of Conjugated Diene Polymer] (Example 1) Polymer 1 As shown in Table 1, a 40 L internal volume, temperature-controllable autoclave equipped with a stirrer and a jacket was used as a reactor. 3,000 g of 1,3-butadiene, from which impurities had been removed in advance, 0 g of styrene, 23,000 g of cyclohexane, and 196.9 mmol of tetrahydrofuran (THF) as a polar substance were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. As a polymerization initiator, 19.7 mmol of n-butyllithium was fed to the reactor. After the polymerization reaction started, the temperature inside the reactor rose due to heat generated by the polymerization, and the final temperature inside the reactor was 83°C. 0.18 g of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane was added as a modifier to this polymer solution, and after reacting for 3 minutes, 1.57 g of 1,3-dimethyl-2-imidazolidinone was added as a modifier and reacted for 15 minutes. Then, 15 mol of water was added as a reaction terminator. To the obtained polymer solution, 21.0 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate (stabilizer 1) and 9.0 g of 4,6-bis(octylthiomethyl)-o-cresol (stabilizer 2) were added as antioxidants, and the conjugated diene polymer solution was then dropped into warm water to remove the solvent. The solution was then dried in a dryer to obtain polymer 1. The obtained polymer 1 was analyzed by the above-mentioned method, and the results are shown in Table 1.

[0088] (Examples 2 to 4, 8 to 11, Comparative Examples 1, 2, 4, 5) Polymers 2 to 4, 8 to 11, 12, 13, 15, 16 As shown in Tables 1 and 2, each conjugated diene polymer (polymers 2 to 4, 8 to 11, 12, 13, 15, and 16) was obtained in the same manner as in Example 1, except that the amounts of styrene and 1,3-butadiene added, the amounts of polymerization initiator and polar substance added, and the type and amount of modifier added were changed. The stabilizers shown in Tables 1 and 2 were added to the obtained solutions of each conjugated diene polymer, and then the conjugated diene polymer solutions were dropped into warm water to remove the solvent, followed by drying in a dryer to obtain conjugated diene polymer (polymers 2 to 4, 8 to 11, 12, 13, 15, and 16) compositions, respectively. The obtained polymers 2 to 4, 8 to 11, 12, 13, 15 and 16 were analyzed by the above-mentioned methods, and the results are shown in Tables 1 and 2.

[0089] (Example 5) Polymer 5 As shown in Table 1, a 40 L internal volume, temperature-controllable autoclave equipped with a stirrer and a jacket was used as a reactor. 2,910 g of 1,3-butadiene, from which impurities had been removed in advance, 23,000 g of cyclohexane, and 185.6 mmol of tetrahydrofuran (THF) as a polar substance were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. As a polymerization initiator, 18.6 mmol calculated as n-butyllithium was supplied to the reactor. After the polymerization reaction began, the temperature inside the reactor rose due to heat generated by the polymerization, and the final temperature inside the reactor was 82°C. 0.18 g of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane was added to this polymer solution and allowed to react for 10 minutes. 129 g of styrene was then added and the reaction was continued for 5 minutes, and 1.55 g of 1,3-dimethyl-2-imidazolidinone (compound 2) was added and allowed to react for 15 minutes. 16 mol of water was then added as a reaction terminator. To the obtained polymer solution, 21.0 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate (stabilizer 1) and 9.0 g of 4,6-bis(octylthiomethyl)-o-cresol (stabilizer 2) were added as antioxidants, and the conjugated diene polymer solution was then dropped into warm water to remove the solvent, followed by drying in a dryer to obtain polymer 5 having a block styrene structure. The obtained polymer 5 was analyzed by the above-mentioned method, and the results are shown in Table 1.

[0090] (Examples 6 and 7) Polymers 6 and 7 As shown in Table 1, each conjugated diene polymer (polymers 6 and 7) was obtained in the same manner as in Example 5, except that the amounts of styrene and 1,3-butadiene added, the amounts of polymerization initiator and polar substance added, and the type and amount of modifier added were changed. The stabilizers shown in Tables 1 and 2 were added to the obtained solutions of each conjugated diene polymer, and then the conjugated diene polymer solutions were dropped into warm water to remove the solvent, followed by drying in a dryer to obtain conjugated diene polymer (polymers 6 and 7) compositions, respectively. The obtained polymers 6 and 7 were analyzed by the above-mentioned methods, and the results are shown in Table 1.

[0091] (Comparative Example 3) Polymer 14 Polymer 14 was produced under the same conditions as in Example 1, except that the polymerization initiation temperature was 70° C. The obtained polymer 14 was analyzed by the above-mentioned method, and the results are shown in Table 2.

[0092] (Example 12) Polymer 17 As shown in Table 1, a 40 L internal volume autoclave equipped with a stirrer and a jacket and capable of temperature control was used as a reactor. 129 g of styrene, from which impurities had been removed in advance, 23,000 g of cyclohexane, and 185.6 mmol of tetrahydrofuran (THF) as a polar substance were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. As a polymerization initiator, 18.6 mmol calculated as n-butyllithium was supplied to the reactor. After the polymerization reaction began, the temperature inside the reactor rose due to heat generated by the polymerization. When this stopped, 2,910 g of 1,3-butadiene was added to the reactor and the reaction continued. The final temperature inside the reactor was 85°C. 0.18 g of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane was added to the polymer solution and allowed to react for 10 minutes. 129 g of styrene was then added and the reaction continued for 5 minutes. 1.55 g of 1,3-dimethyl-2-imidazolidinone (compound 2) was then added and the reaction continued for 15 minutes. 16 mol of water was then added as a reaction terminator. To the obtained polymer solution, 21.0 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate (stabilizer 1) and 9.0 g of 4,6-bis(octylthiomethyl)-o-cresol (stabilizer 2) were added as antioxidants, and the conjugated diene polymer solution was then dropped into warm water to remove the solvent. The mixture was then dried in a dryer to obtain polymer 17 having a block styrene structure. The obtained polymer 17 was analyzed by the above-mentioned method, and the results are shown in Table 1.

[0093] (Example 13) Polymer 18 Polymer 18 was obtained according to the same polymerization procedure as in Example 12 and in the amounts of reagents added shown in Table 1. The obtained polymer 18 was analyzed by the above-mentioned methods, and the results are shown in Table 1.

[0094] [Table 1]

[0095] [Table 2]

[0096] [Production of Rubber Composition] (Application Examples 1 to 13), (Application Comparative Examples 1 to 5) Conjugated diene polymers 1 to 18 and natural rubber shown in Tables 1 and 2 were used as raw rubbers, and rubber compositions containing each raw rubber were obtained according to the formulation shown below. When the conjugated diene polymer of Example 1 was used, it was designated as Application Example 1, and when the conjugated diene polymer of Comparative Example 1 was used, it was designated as Application Comparative Example 1. Similarly, the example numbers and comparative example numbers correspond to the application example numbers and comparative application example numbers, respectively. <Rubber composition> Raw material rubber (conjugated diene polymer 1-18) 50.0 parts by mass Natural rubber: 50.0 parts by mass Carbon black (manufactured by Tokai Carbon Co., Ltd., Shist SO (N550)): 50.0 parts by mass Naphthenic oil (Idemitsu Kosan Co., Ltd., Diana Process NM-280): 10.0 parts by mass Zinc white: 5.0 parts by mass Stearic acid: 1.0 parts by mass Antioxidant (Nocrac 6C): 2.0 parts by mass Anti-aging agent (Nocrac MB): 1.0 parts by mass Wax (Ouchi Shinko Chemical Co., Ltd., Sunnock N): 2.0 parts by mass Sulfur: 2.5 parts by mass Vulcanization accelerator (N-(tert-butyl)-2-benzothiazole sulfenamide): 1.5 parts by mass Total: 175.0 parts by mass

[0097] The above materials were kneaded in the following manner to obtain a rubber braid. In the first stage of mixing, a closed mixer (capacity: 0.3 L) equipped with a temperature control device was used to mix raw rubber, filler (carbon black), oil (naphthenic oil), wax (Sunnoc N), zinc oxide, stearic acid, and antioxidants (Nocrac 6C, Nocrac MB) at a filling rate of 65% and rotor rotation speeds of 50 / 57 rpm. The temperature of the internal mixer was controlled, and the discharge temperature (compound) was 150°C to obtain a conjugated diene polymer composition. After cooling, the mixture was kneaded in the second stage using an open roll set at 70°C, after which sulfur and a vulcanization accelerator were added and kneaded. Thereafter, it was molded into a predetermined shape and vulcanized in a vulcanization press at 160°C for 20 minutes. After vulcanization, the physical properties of the rubber composition were measured. The results of the physical property measurements are shown in Tables 3 and 4. After vulcanization as described above, the physical properties of the vulcanized rubber composition were measured by the following methods.

[0098] [Physical Properties of Rubber Composition] ((1) Compression set at low temperatures) According to the measurement method of JIS K6262, the compression set was measured after cooling for 72 hours in an environment of 0°C. The analysis results are expressed as an index, with a higher index indicating better compression set performance at low temperatures.

[0099] ((2) Durability (ozone resistance one year after production of rubber composition) The durability of the rubber composition was evaluated by measuring its ozone resistance after one year of use. Furthermore, samples were aged in a high-temperature thermostatic chamber to simulate the condition of the rubber composition one year after its production. A sample with accelerated aging was obtained by leaving the rubber composition in a thermostatic chamber at 100° C. for one week. The ozone resistance was evaluated as follows. Evaluation was carried out in accordance with JIS K6259 using an ozone weather meter OSM-NH manufactured by Suga Test Instruments Co., Ltd. Dynamic testing was carried out at an ozone concentration of 50 pphm, a temperature of 40°C, a tensile strain of 10%, and a frequency of 0.5 Hz, and the time until the sample broke was expressed as an index. The larger the index number, the longer the time until the sample breaks, indicating excellent durability.

[0100] ((3) Processability: Mooney viscosity of composition) A portion of the kneaded rubber composition was taken out before molding, and the Mooney viscosity was measured. Using a Mooney viscometer VR1130 manufactured by Ueshima Seisakusho Co., Ltd., the viscosity was measured after preheating at 100°C for 1 minute and then rotating the rotor at 2 revolutions per minute for 4 minutes in accordance with JIS K6300-1. When the Mooney viscosity of a rubber composition is high, the rubber composition tends to be poorly cohesive during kneading and tends to break when formed into a sheet, making it poor in processability and undesirable for practical use. The analysis results are expressed as an index, with a higher index value indicating better processability.

[0101] ((4) Dynamic magnification) The static spring constant and dynamic spring constant of the rubber composition were measured in accordance with JIS K6385, and the dynamic spring ratio (dynamic spring constant / static spring constant) was calculated. The measuring device used was ACUMEN (registered trademark) 3 manufactured by MTS. The analysis results are expressed as an index, with a higher index value indicating a better dynamic magnification.

[0102] [Table 3]

[0103] [Table 4]

[0104] The combined index values ​​showed that the conjugated diene polymers obtained in Examples 1 to 13 and the rubber compositions of Application Examples 1 to 13 had a better balance between low-temperature compression set and durability than the conjugated diene polymers obtained in Comparative Examples 1 to 5 and the rubber compositions of Application Comparative Examples 1 to 5. [Industrial Applicability]

[0105] The conjugated diene polymer and rubber composition of the present invention have industrial applicability as vibration-proof rubber, vibration-damping rubber material, vibration-isolating rubber, tires, packings and gaskets, sealing materials, conveyor belts, power transmission belts, shoe outsoles and shoe midsoles, automobile weather strips, glass runs, trunk lids, railway vehicle components, aircraft components, waterproof sheets, engine mounts, air springs, rubber gloves, medical and sanitary products, hoses for industrial and various uses, battery cases, adhesives, wire coatings, window frame rubber, rubber rolls, rubber rollers for office automation equipment and spinning, etc., keypads, keyboard covers, underwater goggles, swimming caps, container bags, marine-related parts, indoor flooring materials, artificial muscle materials, and materials for various industrial products.

Claims

1. The molecular weight distribution as measured by gel permeation chromatography (GPC) is less than 1.5, and the peak top molecular weight of the lowest peak (A) in the molecular weight distribution curve is 300,000 or more, There is one peak of glass transition temperature Tg in differential scanning calorimetry (DSC) measurement, and the Tg peak is −92° C. or lower; The nitrogen content is 80 ppm or more. Conjugated diene polymer.

2. When the peak group located on the higher molecular weight side than the peak (A) is defined as the peak group (B), a peak area ratio of the group of peaks (B) to the sum of the area of ​​the peak (A) and the area of ​​the group of peaks (B) satisfies the following relationship: The conjugated diene polymer according to claim 1 . Peak area ratio: 5%≦B / (A+B)≦15%

3. The denaturation rate is 70% or more. The conjugated diene polymer according to claim 1 .

4. The content of aromatic vinyl monomer units is 1% by mass or more. The conjugated diene polymer according to claim 1 .

5. the content of the aromatic vinyl monomer block is 1% by mass or more and 7% by mass or less; The conjugated diene polymer according to claim 4.

6. all of the aromatic vinyl monomer units in the conjugated diene polymer constitute an aromatic vinyl monomer block in a blocked state; The conjugated diene polymer according to claim 5 .

7. the aromatic vinyl monomer block is present at the polymerization initiation terminal of the conjugated diene polymer; The conjugated diene polymer according to claim 6 .

8. The conjugated diene polymer according to any one of claims 1 to 7, Natural rubber and A rubber composition comprising:

9. A vibration-isolating rubber comprising the rubber composition according to claim 8.

10. A power transmission belt comprising the rubber composition according to claim 8.

11. A conveyor belt comprising the rubber composition according to claim 8.

12. A shoe sole comprising the rubber composition according to claim 8.

13. An industrial material comprising the rubber composition according to claim 8.

14. A tire comprising the rubber composition according to claim 8.

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