Rubber composition, method for manufacturing a rubber composition, and tire

Abstract

To provide a rubber composition excellent in fracture characteristics and ozone resistance.SOLUTION: A rubber composition contains a hydrogenated copolymer having a weight average molecular weight of 300,000 or more and 650,000 or less, a natural rubber, silica, and a silane coupling agent having a mercapto group. The hydrogenated copolymer has an aromatic vinyl unit and a conjugated diene unit. The conjugated diene unit contains 25 mol% or more of a 1,2-vinyl bond-containing conjugated diene unit based on the total amount of the conjugated diene unit. The proportion of a hydrogenated conjugated diene unit in the conjugated diene unit is 40 mol% or more and 90 mol% or less. The content of the hydrogenated copolymer is 20 mass% or more based on the total amount of rubber components. The content of the natural rubber is 30 mass% or more based on the total amount of the rubber components.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition, a method for producing a rubber composition, and a tire. [Background technology]

[0002] In recent years, from an environmental perspective, automobile tires are required to have high levels of fuel efficiency and mechanical strength. The fuel efficiency of tires is directly related to the fuel consumption of automobiles and therefore serves as an indicator of environmental impact, while the mechanical strength of tires is directly related to the tire's lifecycle and therefore has a significant impact on environmental impact.

[0003] To meet the above requirements, hydrogenated rubber polymers, which are rubber polymers to which hydrogen has been added, have become a popular rubber material for tires in recent years.

[0004] For example, Patent Documents 1 to 4 propose rubber compositions containing a rubber-like polymer having an ethylene chain structure and incorporating unsaturated groups that allow for intermolecular crosslinking, etc., for the purpose of increasing mechanical strength and compression set. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2017 / 150645 [Patent Document 2] International Publication No. 2019 / 151126 [Patent Document 3] International Publication No. 2019 / 151127 [Patent Document 4] International Publication No. 2019 / 078083 [Overview of the project] [Problems that the invention aims to solve]

[0006] In recent years, rubber compositions used for tires have been increasingly required to have high mechanical strength, such as ozone resistance and fracture resistance, in order to extend the product lifecycle from an environmental perspective. It has long been known that using natural rubber as the main raw material for tire rubber compositions can provide excellent mechanical strength, and by blending natural rubber with SBR or high-sys BR, it is possible to adjust various physical properties such as fuel efficiency.

[0007] However, blending natural rubber with SBR or high-sys BR did not provide sufficient ozone resistance. To address this issue, methods are being explored to blend hydrogenated SBR and other materials with natural rubber, which have superior ozone resistance.

[0008] However, in blends of natural rubber and hydrogenated SBR, natural rubber, which contains many double bonds in its constituent units, preferentially crosslinks and reinforces the material. As a result, hydrogenated SBR, which has fewer double bonds, is less likely to crosslink and reinforce the material, leading to a problem where the mechanical strength, or fracture properties, of the blend are insufficient. Furthermore, it has become clear that depending on the blending ratio, sufficient ozone resistance cannot be obtained even when hydrogenated SBR is blended with natural rubber. [Means for solving the problem]

[0009] In order to solve the problems of the prior art described above, the present inventors conducted diligent research and studies and found that a rubber composition with excellent fracture properties and ozone resistance can be obtained by including a silane coupling agent having a mercapto group and blending natural rubber and a predetermined partially hydrogenated SBR with appropriate hydrogenation in a specific ratio, thus completing the present invention.

[0010] In other words, the present invention is as follows. [1] It comprises a hydrogenated copolymer having a weight-average molecular weight of 300,000 or more and 650,000 or less, natural rubber, silica, and a silane coupling agent having a mercapto group. The hydrogenated copolymer has an aromatic vinyl unit and a conjugated diene unit, the conjugated diene unit contains a conjugated diene unit having a 1,2-vinyl bond in an amount of 25 mol% or more based on the total amount of the conjugated diene units, the proportion of the hydrogenated conjugated diene unit in the conjugated diene unit is 40 mol% or more and 90 mol% or less, the content of the hydrogenated copolymer is 20% by mass or more based on the total amount of the rubber component, the content of the natural rubber is 30% by mass or more based on the total amount of the rubber component, A rubber composition. [2] The hydrogenated copolymer has a molecular weight distribution of 1.20 to 1.75, The rubber composition according to [1]. [3] The nitrogen content of the hydrogenated copolymer is 15 ppm or more and 170 ppm or less, The rubber composition according to [1] or [2]. [4] The absolute value of the melt viscosity difference between the hydrogenated copolymer and the natural rubber at a temperature of 160 ° C and a shear rate of 12.16 s-1 is 10,000 (Pa·s) or less, The rubber composition according to any one of [1] to [3]. [5] The content of the silane coupling agent is 1 to 10 parts by mass with respect to 100 parts by mass of the silica, The rubber composition according to any one of [1] to [4]. [6] A first kneading step of kneading a rubber composition containing a hydrogenated copolymer, a natural rubber, silica, and a silane coupling agent having a mercapto group; A second kneading step of kneading the kneaded product obtained in the kneading step and a vulcanizing agent, A method for producing a rubber composition. [7] Using any one of the rubber compositions of [1] to [5], A tire. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a rubber composition that is excellent in terms of fracture properties and ozone resistance. [Modes for carrying out the invention]

[0012] The following describes in detail embodiments for carrying out the present invention (hereinafter referred to as "this embodiment"). However, this embodiment is merely an example for explaining the present invention, and the present invention is not limited to the following embodiments. It can be modified as appropriate without changing its essence.

[0013] 1. Rubber composition The rubber composition of this embodiment comprises a hydrogenated copolymer having a weight-average molecular weight of 300,000 to 650,000, natural rubber, silica, and a silane coupling agent having a mercapto group, wherein the hydrogenated copolymer has aromatic vinyl units and conjugated diene units, the conjugated diene units contain 25 mol% or more of conjugated diene units having a 1,2-vinyl bond relative to the total amount of conjugated diene units, the proportion of hydrogenated conjugated diene units in the conjugated diene units is 40 mol% to 90 mol%, the content of the hydrogenated copolymer is 20% by mass or more relative to the total amount of rubber components, and the content of the natural rubber is 30% by mass or more relative to the total amount of rubber components. The rubber composition of this embodiment may also contain other components as needed. Each component will be described in detail below.

[0014] Here, an aromatic vinyl unit refers to a constituent unit based on an aromatic vinyl compound, and similarly, a conjugated diene unit refers to a constituent unit based on a conjugated diene compound.

[0015] 1.1. Hydrogenated copolymer The hydrogenated copolymer in this embodiment has a weight-average molecular weight of 300,000 or more and 650,000 or less, and contains aromatic vinyl units and conjugated diene units, which will be described later. Here, a hydrogenated copolymer means a copolymer in which some of the constituent units of the copolymer have been reduced by hydrogenation.

[0016] The following provides a detailed explanation of the constituent units and average molecular weight of hydrogenated copolymers.

[0017] (Aromatic vinyl units) The aromatic vinyl compounds that constitute the aromatic vinyl unit are not limited to the following, but include, for example, styrene, p-methylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene. Among these, styrene is preferred from the viewpoint of ease of industrial availability. These may be used individually or in combination of two or more.

[0018] (Conjugated diene units) The conjugated diene compounds constituting the conjugated diene unit are not limited to the following, but examples include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene. Among these, 1,3-butadiene and isoprene are preferred from the viewpoint of ease of industrial availability, and 1,3-butadiene is more preferred. These may be used individually or in combination of two or more.

[0019] (Conjugated diene units having 1,2-vinyl bonds) The content of conjugated diene units having 1,2-vinyl bonds in the conjugated diene units is 25 mol% or more, preferably 35 mol% to 55 mol%, and more preferably 45 mol% to 55 mol% based on the total amount of conjugated diene units. Herein, in this specification, "conjugated diene units having 1,2-vinyl bonds" in the hydrogenated copolymer also includes conjugated diene units in which the 1,2-vinyl bonds have been reduced by hydrogenation. In other words, after hydrogenation, some of the 1,2-vinyl bonds are reduced to ethyl groups rather than so-called "vinyl bonds," but the term represents a structure in which it is assumed that 1,2-vinyl bonds were formed before hydrogenation.

[0020] The method for adjusting the content of conjugated diene units having 1,2-vinyl bonds is not particularly limited, but for example, the amount of conjugated diene units having 1,2-vinyl bonds in the conjugated diene units can be adjusted by adjusting the amount of polar compound added in the polymerization step described later.

[0021] (Hydrogenation rate of hydrogenated copolymers) The hydrogenated copolymer of this embodiment contains hydrogenated conjugated diene units, and the proportion of hydrogenated conjugated diene units in the total conjugated diene units (hereinafter also referred to as the hydrogenation rate or hydrogenation rate) is 40% or more and 90% or less, more preferably 50% or more and 85%, and even more preferably 60% or more and 80% or less.

[0022] The hydrogenated copolymer of this embodiment tends to exhibit superior ozone resistance when vulcanized, due to the hydrogenation rate of the conjugated diene units being 40% or more. In polymerization using butadiene as the conjugated diene compound, 1,2-vinyl bonds and 1,4-bonds are formed, but since the 1,2-vinyl bonds are more reactive, the hydrogenation reaction occurs faster and proceeds preferentially. Therefore, by increasing the hydrogenation rate of the hydrogenated polymer to 40% or more, the amount of 1,2-vinyl bonds remaining as unreacted double bonds tends to decrease. In other words, because the amount of 1,2-vinyl bonds, which are highly reactive and therefore easily react with ozone, and thus prone to ozone degradation, is reduced, the ozone resistance of the hydrogenated copolymer can be ensured. On the other hand, by having a hydrogenation rate of 90% or less of the conjugated diene units, the co-crosslinking properties when blended with other types of rubber such as natural rubber are improved, forming a good crosslinking network, which tends to result in superior fracture characteristics and fuel efficiency when vulcanized.

[0023] Here, the hydrogenation rate described above can be controlled by the amount of hydrogen added to the conjugated diene units, and the hydrogenation rate is not particularly limited, but for example, 1 It can be measured using 1H-NMR.

[0024] Furthermore, the temperature of the hydrogenation reaction is not particularly limited, but is preferably 60 to 105°C, and more preferably 70 to 100°C.

[0025] (Weight-average molecular weight of hydrogenated copolymers) The hydrogenated copolymer of this embodiment has a weight-average molecular weight (Mw) determined by gel permeation chromatography (GPC) of 300,000 to 650,000, preferably 350,000 to 600,000, and more preferably 400,000 to 550,000. The preferred range of weight-average molecular weight may vary slightly depending on the type of tire material into which the hydrogenated copolymer is blended and the other rubber types blended. When the Mw of the hydrogenated copolymer is 300,000 or more, the vulcanized product of the hydrogenated copolymer of this embodiment tends to have high fracture strength. Furthermore, when the Mw of the hydrogenated copolymer is 650,000 or less, the productivity of the hydrogenated copolymer tends to be high, and the resulting rubber composition tends to have good processability.

[0026] The weight-average molecular weight of the hydrogenated copolymer can be calculated from the polystyrene-converted molecular weight measured by GPC, and can be measured by the method described in the examples below. The weight-average molecular weight of the hydrogenated copolymer can be controlled to the above numerical range by adjusting polymerization conditions such as the amount of monomer added, polymerization time, and polymerization temperature during the polymerization process.

[0027] (Molecular weight distribution of hydrogenated copolymers) The molecular weight distribution of the hydrogenated copolymer in this embodiment is preferably 1.20 to 1.75, more preferably 1.25 to 1.75, and even more preferably 1.30 to 1.75. As a result, the vulcanized product of the hydrogenated copolymer in this embodiment tends to have good processability.

[0028] The molecular weight distribution of the hydrogenated copolymer can be controlled to the above numerical range by adjusting the type of coupling agent and polymerization conditions such as the polymerization temperature during the polymerization process.

[0029] (Modification of hydrogenated copolymers) In this embodiment, the hydrogenated copolymer preferably contains tin atoms, nitrogen atoms, or silicon atoms, and more preferably contains both nitrogen atoms and silicon atoms, from the viewpoint of fuel efficiency when used in tires.

[0030] In this embodiment, a compound having a nitrogen atom and reacting with the polymerization active end and / or polymerization initiator is referred to as a modifier, and the addition of the modifier to the hydrogenated copolymer is referred to as modification. Furthermore, when a coupling agent is used and the coupling agent contains a nitrogen atom, modification can be achieved by increasing the molecular weight of the growing molecular chain and / or branching the molecular chain of the polymer through coupling.

[0031] (nitrogen content) In this embodiment, the hydrogenated copolymer preferably has a nitrogen content of 15 ppm or more and 170 ppm or less as measured by trace nitrogen analysis. Furthermore, from the viewpoint of fuel efficiency, the nitrogen content of the hydrogenated copolymer is more preferably 17 ppm or more, even more preferably 19 ppm or more, and even more preferably 21 ppm or more. On the other hand, from the viewpoint of processability, the nitrogen content of the hydrogenated copolymer is preferably 150 ppm or less, more preferably 130 ppm or less, and even more preferably 110 ppm or less.

[0032] The nitrogen content can be measured by methods such as trace nitrogen analysis, and more specifically, by the method described in the examples below. When comparing using the same polymer, the nitrogen content tends to be higher as the proportion of constituent units to which the modifying agent is attached among the constituent units of the hydrogenated copolymer (hereinafter also referred to as the modification rate) increases. However, the nitrogen content also depends on the type and molecular weight of the modifying agent, so it does not necessarily correlate with the modification rate.

[0033] The modification rate tends to affect fuel efficiency when hydrogenated polymers are used in tires, while the nitrogen content tends to affect fracture strength. There are no particular limitations on the method of separately controlling the modification rate and nitrogen content, but for example, when increasing the nitrogen content while maintaining the modification rate, adding a modification agent with a high nitrogen content is effective. By using this modification agent with a high nitrogen content, the silanization of the silane coupling agent is promoted when the rubber composition is kneaded for tires, which tends to result in tires with high fracture strength.

[0034] (Melting viscosity of hydrogenated copolymers) In this embodiment, the absolute value of the difference in melt viscosity between the hydrogenated copolymer and natural rubber under the conditions of a temperature of 160°C and a shear rate of 12.16 s⁻¹ is preferably 10,000 (Pa·s) or less, more preferably 9,000 (Pa·s) or less, and even more preferably 8,000 (Pa·s) or less. When comparing compositions with the same composition ratio of hydrogenated copolymer to natural rubber, it can be confirmed that ozone resistance tends to be good when the difference in melt viscosity between the hydrogenated copolymer and natural rubber under the above conditions is 10,000 (Pa·s) or less.

[0035] When the absolute value of the melt viscosity difference under the above conditions is 9,000 (Pa·s) or less, the vulcanized product of the hydrogenated copolymer of this embodiment tends to exhibit even better ozone resistance. When a vulcanized product is made by blending hydrogenated copolymer and natural rubber, the natural rubber phase, which has many double bonds, tends to be susceptible to ozone degradation, while the hydrogenated copolymer phase, which has few double bonds, tends to be less susceptible. However, when the absolute value of the melt viscosity difference between the hydrogenated copolymer and natural rubber of this embodiment under the above conditions is within the above range, even when the hydrogenated copolymer content is relatively small, the hydrogenated copolymer can be finely dispersed during kneading. Therefore, when a vulcanized product is made, it is thought that the growth of cracks due to ozone degradation of the natural rubber phase is suppressed. This increases the degree of freedom in compounding the rubber composition.

[0036] The melt viscosity of hydrogenated copolymers generally tends to increase with higher hydrogenation rates and decrease with lower hydrogenation rates. Furthermore, the melt viscosity tends to increase with higher molecular weight and decrease with lower molecular weight. Since natural rubber exhibits different melt viscosities depending on its type, it is preferable to set the molecular weight and hydrogenation rate of the hydrogenated copolymer so that its melt viscosity is close to that of the natural rubber being blended. Therefore, it is advisable to adjust the hydrogenation rate and molecular weight to minimize the difference in melt viscosity between the blended natural rubber and the copolymer. For example, when setting the hydrogenation rate to 90%, this can be controlled within the above range by increasing branching if the molecular weight is the same, or decreasing the molecular weight if the number of branches is the same. When setting the hydrogenation rate to 40%, this can be controlled within the above range by decreasing branching if the molecular weight is the same, or increasing the molecular weight if the number of branches is the same. This allows for adjustment of the melt viscosity difference.

[0037] (Denaturant) The hydrogenated copolymer of this embodiment is preferably modified with a modifying agent. The modifying agent is not particularly limited, and for example, conventionally known modifying agents can be used. Furthermore, from the viewpoint of fuel efficiency, the vulcanized product of the hydrogenated copolymer in this embodiment is preferably a compound having both nitrogen atoms and silicon atoms, and more preferably a nitrogen group-containing alkoxysilane compound.

[0038] Such nitrogen-containing alkoxysilane compounds include, but are not limited to, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(4-trimethoxysilylbutyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacycloheptane, and 2,2-dimethoxy-1-(3-dimethoxysilylpropyl) Toxymethylsilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy,2-methyl-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-ethoxy,2-ethyl-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy,2-methyl-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, and 2-ethoxy,2-ethyl-1- (3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, tris(3-trimethoxysilylpropyl)amine, tris(3-methyldimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-methyldiethoxysilylpropyl)amine, tris(trimethoxysilylmethyl)amine, tris(2-trimethoxysilylethyl)amine, and tris(4-trimethoxysilylbutyl)amine, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1, Examples include 3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, and N1-(3-(bis(3-(trimethoxysilyl)propyl)amino)propyl)-N1-methyl-N3-(3-(methyl(3-(trimethoxysilyl)propyl)amino)propyl)-N3-(3-(trimethoxysilyl)propyl)-1,3-propanediamine and 3-(4-methylpiperazine-1-yl)propyltriethoxysilane.These may be used individually or in combination of two or more types.

[0039] (Hydrogenated copolymer softener) The hydrogenated copolymer of this embodiment may contain a rubber softener as needed. The rubber softener content is preferably 30% by mass or less relative to the total amount of the hydrogenated copolymer. In the hydrogenated copolymer of this embodiment, from the viewpoint of improving processability when inorganic fillers, etc., are blended during tire manufacturing, the amount of rubber softener added is preferably 1 to 30% by mass. When the molecular weight of the hydrogenated copolymer is high, for example, when the weight-average molecular weight exceeds 1 million, it is preferable to add 15 to 30% by mass of rubber softener. On the other hand, from the viewpoint of increasing the degree of freedom in blending when a rubber composition containing fillers is made, it is preferable to add 1 to 15% by mass of rubber softener. From the viewpoint of suppressing deterioration over time when made into tires, the rubber softener content in the rubber composition using the hydrogenated copolymer of this embodiment is more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0040] While not particularly limited, examples of rubber softeners include stretching oils, low-molecular-weight rubbery polymers, and resins. From the viewpoint of processability, productivity, and economic efficiency, stretching oils are preferred. Furthermore, from the viewpoint of abrasion resistance in tire rubber compositions, low-molecular-weight rubbery polymers that can contribute to crosslinking are preferred.

[0041] The method for adding the rubber softener to the rubbery polymer of this embodiment is not limited to the following, but a preferred method is to add the rubber softener to the rubbery polymer solution, mix it to obtain a polymer solution containing the rubber softener, and then desolvate the resulting solution.

[0042] Among these, preferred softening agents include, but are not limited to, essential oils, naphthenic oils, paraffin oils, etc. Of these, essential oil substitutes with a polycyclic aromatic (PCA) component content of 3% by mass or less according to the IP346 method are preferred from the viewpoint of environmental safety, as well as from the viewpoint of preventing oil bleeding and wet grip characteristics.

[0043] Examples of aromatic oil substitutes are not limited to TDAE (Treated Distillate Aromatic Extracts) and MES (Mild Extraction Solvate), as shown in Kautschuk Gummi Kunststoffe 52(12)799(1999), as well as RAE (Residual Aromatic Extracts).

[0044] (Other additives) The rubbery polymer of this embodiment may contain various other additives, such as antioxidants, as needed.

[0045] [Method for producing hydrogenated copolymers] The method for producing the hydrogenated copolymer of this embodiment comprises a polymerization step of copolymerizing a conjugated diene monomer and an aromatic vinyl monomer, and a hydrogenation step of hydrogenating the obtained copolymer to a hydrogenation rate of 40% to 90%. Furthermore, it may include a branching step, a coupling step, a desolvation step, and other steps as needed. Each step will be described in detail below.

[0046] In the method for producing the hydrogenated copolymer of this embodiment, from the viewpoint of easy control of the molecular structure, it is preferable to carry out anionic polymerization in the polymerization step. Furthermore, in the hydrogenation step, a portion or most of the double bonds of the conjugated diene units in the copolymer obtained by copolymerizing the conjugated diene monomer and the aromatic vinyl monomer are hydrogenated (hydrogenated).

[0047] The method for producing the hydrogenated copolymer of this embodiment is not particularly limited, but examples include a method in which a conjugated diene monomer and an aromatic vinyl monomer are copolymerized by anionic polymerization under various additives and conditions, followed by hydrogenation, as described in International Publication No. 96 / 05250, Japanese Patent Publication No. 2000-053706, International Publication No. 2003 / 085010, International Publication No. 2019 / 151126, International Publication No. 2019 / 151127, International Publication No. 2002 / 002663, and International Publication No. 2015 / 006179.

[0048] The aromatic vinyl monomers, ethylene, α-olefins, conjugated diene monomers, and other monomers used in polymerization in the hydrogenated copolymer production method of this embodiment can be the same as those described in the various documents mentioned above.

[0049] The polymerization and hydrogenation processes described above may be carried out in either a batch or continuous manner.

[0050] (Polymerization process) In the polymerization process, a polymerization initiator is used to polymerize the conjugated diene compound, aromatic vinyl compound, and, if necessary, other monomers.

[0051] The polymerization initiator used in the polymerization process is not particularly limited, but examples include organic monolithium compounds. Examples of organic monolithium compounds are not limited to the following, but examples include low molecular weight compounds or solubilized oligomer organic monolithium compounds. Furthermore, examples of organic monolithium compounds are not particularly limited, but in terms of the bonding mode between their organic group and lithium, for example, compounds having a carbon-lithium bond, compounds having a nitrogen-lithium bond, and compounds having a tin-lithium bond.

[0052] The amount of organic monolithium compound used as a polymerization initiator is preferably determined by the target structure of the hydrogenated copolymer and the molecular weight of the hydrogenated copolymer. The amount of monomers such as conjugated diene compounds used relative to the amount of polymerization initiator is related to the degree of polymerization. That is, it tends to affect the number-average molecular weight and / or weight-average molecular weight. Therefore, in order to increase the molecular weight of the hydrogenated copolymer, it is good to adjust the amount of polymerization initiator to decrease, and in order to decrease the molecular weight of the hydrogenated copolymer, it is good to adjust the amount of polymerization initiator to increase.

[0053] The organic monolithium compound is not particularly limited from the viewpoint of being used as one method for introducing a nitrogen atom into a polymer, but for example, alkyllithium compounds having a substituted amino group or dialkylaminolithium are preferred. In this case, a polymer having a nitrogen atom consisting of an amino group at the polymerization initiation end is obtained. A 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.

[0054] Alkyl lithium compounds having an amino group that does not possess active hydrogen are not limited to the following, but examples include 3-dimethylaminopropyllithium, 3-diethylaminopropyllithium, 4-(methylpropylamino)butyllithium, and 4-hexamethyleneiminobutyllithium.

[0055] Alkyllithium compounds having an amino group with a structure that protects active hydrogen include, but are not limited to, 3-bistrimethylsilylaminopropyllithium and 4-trimethylsilylmethylaminobutyllithium.

[0056] Examples of dialkylaminolithium 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-lithiazacyclooctane, 6-lithio-1,3,3-trimethyl-6-azabicyclo[3.2.1]octane, and 1-lithio-1,2,3,6-tetrahydropyridine.

[0057] These organomonolithium compounds having substituted amino groups can also be used as solubilized oligomeric organomonolithium compounds by reacting small amounts of polymerizable monomers, such as 1,3-butadiene, isoprene, and styrene.

[0058] From the viewpoint of ease of industrial availability and ease of control of the polymerization reaction, alkyllithium compounds are preferred as organic monolithium compounds. In this case, a copolymer having an alkyl group at the polymerization initiation end is obtained.

[0059] The alkyllithium compounds mentioned above are not limited to the following, but examples include n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenilithium. From the viewpoint of ease of industrial availability and ease of controlling the polymerization reaction, n-butyllithium and sec-butyllithium are preferred as alkyllithium compounds.

[0060] These organic monolithium compounds may be used individually or in combination of two or more. They may also be used in combination with other organometallic compounds.

[0061] Other organometallic compounds include, but are not limited to, alkaline earth metal compounds, other alkali metal compounds, and other organometallic compounds.

[0062] Examples of such alkaline earth metal compounds include, but are not limited to, organomagnesium compounds, organocalcium compounds, and organostrontium compounds. Compounds of alkaline earth metal alkoxides, sulfonates, carbonates, and amides are also examples.

[0063] Examples of organomagnesium compounds include, but are not limited to, dibutylmagnesium and ethylbutylmagnesium. Examples of other organometallic compounds include organoaluminum compounds.

[0064] In the polymerization process, the polymerization reaction mode is not limited to the following, but examples include batch mode (also called "batch reaction") and continuous reaction mode.

[0065] In a continuous reactor, one or more connected reactors can be used. Continuous reactors include, for example, tank-type or tubular-type reactors equipped with stirrers. Preferably, monomers, inert solvents, and polymerization initiators are continuously fed into the reactor, a polymer solution containing the polymer is obtained within the reactor, and the polymer solution is continuously discharged.

[0066] Batch reactors, for example, are tank-type reactors equipped with stirrers. In a batch reactor, monomers, an inert solvent, and a polymerization initiator are preferably fed into the reactor, and monomers are added continuously or intermittently during polymerization as needed, to obtain a polymer solution containing the polymer within the reactor, and the polymer solution is discharged after polymerization is complete.

[0067] In the hydrogenated copolymer production method of this embodiment, a continuous process is preferred in order to obtain a polymer having a high proportion of active ends, which allows the polymer to be continuously discharged and subjected to the next reaction in a short time.

[0068] Furthermore, the polymerization step of the hydrogenated copolymer in this embodiment is preferably carried out in an inert solvent. The inert solvent is not particularly limited, but examples include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific hydrocarbon solvents are not limited to the following, but examples include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; and hydrocarbons consisting of aromatic hydrocarbons such as benzene, toluene, and xylene, and mixtures thereof.

[0069] Treating impurities such as allenes and acetylenes with organometallic compounds before carrying out the polymerization process tends to yield polymers with a high concentration of active ends, and further processing through the modification step tends to yield modified copolymers with a high modification rate, which is therefore preferable.

[0070] In the polymerization process, polar compounds (polar substances) may be added. This allows for random copolymerization of aromatic vinyl compounds with conjugated diene compounds, and these compounds tend to be used as vinylizing agents to control the microstructure of the conjugated diene portion. They also tend to be effective in accelerating the polymerization reaction.

[0071] The polar compounds are not limited to the following, but examples include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium-tert-amylate, potassium-tert-butyrate, sodium-tert-butyrate, and sodium amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used individually or in combination of two or more.

[0072] The amount of such polar compounds used is not particularly limited and can be selected according to the purpose, for example, but it is preferably 0.01 moles or more and 10 moles or less per mole of polymerization initiator. Adding polar compounds within the range of 0.01 moles or more and 10 moles or less tends to increase the amount of 1,2-vinyl bonds in the conjugated diene compound and, conversely, decrease the amount of 1,4-bonds.

[0073] Such polar compounds (vinylating agents) can be used in appropriate amounts depending on the desired amount of 1,2-vinyl bonds, as modifiers of the microstructure of the conjugated diene moiety in the polymer. Many polar compounds also have an effective randomization effect in copolymerization of conjugated diene compounds and aromatic vinyl compounds, and tend to be used as modifiers for adjusting the distribution of aromatic vinyl compounds and the amount of styrene block.

[0074] One method for randomizing the conjugated diene compound and aromatic vinyl compound is, for example, as described in Japanese Patent Publication No. 59-140211, to initiate a copolymerization reaction with all of the styrene and a portion of the 1,3-butadiene, and then intermittently add the remaining 1,3-butadiene during the copolymerization reaction.

[0075] The polymerization temperature in the polymerization process is preferably the temperature at which living anionic polymerization proceeds, and from the viewpoint of productivity, it is more preferably 0°C or higher, and even more preferably 120°C or lower. Within this range, it tends to be possible to ensure a sufficient amount of denaturing agent to react with the active ends after polymerization is complete. Even more preferably, it is 50°C to 100°C.

[0076] (Branching process) The method for producing a hydrogenated copolymer in this embodiment may include a branching step to adjust the degree of branching of the hydrogenated copolymer. One method for increasing the degree of branching of a hydrogenated polymer is to use a compound derived from a vinyl monomer containing an alkoxysilyl group and / or a halosilyl group as a branching agent. By adding the branching agent during the polymerization step and then adding monomers to continue polymerization, the branched polymer chains at the branching points can be extended. After that, a modification step may be performed by adding a modifying agent, a coupling agent, etc.

[0077] (Coupling process) The method for producing the hydrogenated copolymer of this embodiment may include the following coupling step. The coupling step is a step in which the active ends of the polymer obtained through the polymerization step and, if necessary, the branching step using a predetermined branching agent are subjected to a coupling reaction with the coupling agent described above or a modifying agent having a nitrogen atom-containing group.

[0078] (Inactivating agent, neutralizing agent) In the method for producing the hydrogenated copolymer of this embodiment, after the coupling step, an inactivator, neutralizing agent, etc., may be added to the polymer solution as needed. Examples of inactivators 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 branched carboxylic acids with 9 to 11 carbon atoms, mainly centered around 10); aqueous solutions of inorganic acids; and carbon dioxide.

[0079] (Hydrogenation process) The method for producing a hydrogenated copolymer of this embodiment includes a step of hydrogenating to a hydrogenation rate of 40% to 90%. The hydrogenation rate is not particularly limited, but can be controlled, for example, by adjusting the amount of hydrogen added during hydrogenation. The hydrogenation rate is not particularly limited, but can be controlled, for example, by the amount of hydrogen feed, pressure, and temperature. The hydrogenation rate of the obtained hydrogenated copolymer is not particularly limited, but can be controlled, for example, by proton nuclear magnetic resonance ( 1 It can be measured by the 1H-NMR method.

[0080] (Addition of rubber stabilizer) In the method for producing the hydrogenated copolymer of this embodiment, it is preferable to add a rubber stabilizer from the viewpoint of preventing gel formation after polymerization and improving stability during processing. The rubber stabilizer is not limited to the following and any known ones can be used, but examples of antioxidants include 2,6-di-tert-butyl-4-hydroxytoluene (hereinafter also referred to as "BHT"), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propinate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol.

[0081] (Solvent removal process) In the method for producing the hydrogenated copolymer of this embodiment, known methods can be used to obtain the polymer from the polymer solution. These methods are not particularly limited, but examples include: separating the solvent by steam stripping, filtering the polymer, and then dehydrating and drying it; concentrating the solution in a flushing tank and then defoliating it with a vent extruder; or directly defoliating it with a drum dryer.

[0082] (Hydrogenated copolymer content) The hydrogenated copolymer content is 20% by mass or more relative to the total amount of rubber components, preferably 20% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 60% by mass or less, and even more preferably 40% by mass or more and 50% by mass or less. In this embodiment, the hydrogenated copolymer content is preferably 20% by mass or more from the viewpoint of fuel efficiency, fracture characteristics, and ozone resistance. Furthermore, in this embodiment, the hydrogenated copolymer content is preferably 70% by mass or less from the viewpoint of processability and ozone resistance.

[0083] Here, "rubber component" refers to the component in a rubber composition that has rubber elasticity. The rubber component in this embodiment includes the hydrogenated copolymer and natural rubber described above, and may also include other components as needed.

[0084] The method for adjusting the hydrogenated copolymer content in the rubber composition is not particularly limited, but for example, it can be adjusted by changing the amount of hydrogenated copolymer blended into the rubber composition.

[0085] The wax added to tire compound ensures ozone resistance by blooming onto the surface of the vulcanized material, forming a uniform thin film of wax on the surface and physically blocking ozone. However, since wax and hydrogenated copolymers have similar molecular structures and are highly compatible, if the content of hydrogenated copolymers increases, the blooming of the wax onto the surface of the vulcanized material is suppressed, making it difficult to form a uniform wax film and tending to worsen ozone resistance. For this reason, it is preferable that the content of hydrogenated copolymers be within the above range.

[0086] 1.2. Natural rubber The rubber composition in this embodiment contains natural rubber, the amount of which is 30% by mass or more of the total amount of rubber components, preferably 40% by mass or more and 80% by mass or less, and more preferably 50% by mass or more and 70% by mass or less. In particular, a natural rubber content of 30% by mass or more tends to improve processability during mixing and improve the balance of physical properties. Furthermore, a natural rubber content of 80% by mass or less tends to result in excellent ozone resistance.

[0087] The method for adjusting the natural rubber content in a rubber composition is not particularly limited, but it can be adjusted, for example, by changing the amount of natural rubber blended into the rubber composition.

[0088] Other rubbers that can be used besides the rubber components mentioned above are not particularly limited and can be appropriately selected depending on the purpose. Examples include styrene-butadiene rubber (emulsion polymerization tires and solution polymerization types), natural rubber, polyisoprene, butadiene rubber (high-cis polybutadiene, low-cis polybutadiene, syndiotactic 1,2-polybutadiene, acrylonitrile-butadiene rubber (NBR), chloroprene rubber, ethylene-α-olefin copolymer rubbers such as ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), butyl rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber, etc. These may be used individually or mixed in combination of two or more. Mixing may be done by mixing dry polymers after polymerization or by mixing in solution during polymerization.

[0089] 1.3. Silica The rubber composition of this embodiment contains silica. The silica content is preferably 40 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the rubber component containing the hydrogenated copolymer of this embodiment. From the viewpoint of improving grip performance and handling stability when the rubber composition of this embodiment is used in a tire, 40 parts by mass or more is preferred, 50 parts by mass or more is more preferred, and 60 parts by mass or more is even more preferred. Furthermore, from the viewpoint of improving fuel efficiency when used in a tire, 100 parts by mass or less is preferred, 90 parts by mass or less is more preferred, and 80 parts by mass or less is even more preferred. Such silica is not particularly limited, but known silicas can be used, for example.

[0090] The method for adjusting the silica content is not particularly limited, but for example, it can be adjusted by changing the amount of silica blended into the rubber composition.

[0091] Among these, solid particulate silica containing SiO2 or Si3Al as a constituent unit is preferred, and more preferably, SiO2 or Si3Al is the main component of the constituent unit. Here, "main component" means that it is present in 50% by mass or more of the silica, and more preferably 70% by mass or more, and more preferably 80% by mass or more. Furthermore, solid particulate silica is preferred.

[0092] Examples of such silica include, but are not limited to, silica, clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, and inorganic fibrous materials such as glass fibers.

[0093] Commercially available silica products include, but are not limited to, the "Ultrasil 7000GR" product manufactured by Evonik Degussa.

[0094] Other examples include silica-based inorganic fillers with hydrophobic surfaces, and mixtures of silica-based inorganic fillers and non-silica-based inorganic fillers. Among these, silica and glass fibers are preferred from the viewpoint of strength and abrasion resistance, with silica being more preferred. Such silica is not particularly limited, but examples include dry silica, wet silica, and synthetic silicate silica. Among these, wet silica is even more preferred from the viewpoint of having an excellent balance between the effect of improving fracture properties and wet skid resistance.

[0095] In the rubber composition of this embodiment, from the viewpoint of obtaining practically good abrasion resistance and fracture characteristics, the nitrogen adsorption specific surface area obtained by the BET adsorption method of silica-based inorganic filler is 100 m². 2 / g or more 300m 2 It is preferable that it be less than or equal to / g, and 170m 2 / g or more 250m 2 It is more preferable that the value be less than or equal to / g.

[0096] Also, if necessary, a relatively small specific surface area (for example, a specific surface area of ​​200 m²) 2Silica-based inorganic fillers (less than / g) and those with a relatively large specific surface area (for example, 200m 2 It can be used in combination with silica-based inorganic fillers (at a concentration of / g or higher). This tends to achieve a highly balanced combination of good wear resistance and fracture characteristics with low hysteresis loss.

[0097] 1.4. Silane coupling agents The rubber composition of this embodiment contains a silane coupling agent having a mercapto group (-SH). By blending silica and a silane coupling agent having a mercapto group (-SH) together with the hydrogenated copolymer of this embodiment, the reinforcing properties are improved, and a rubber composition with an excellent balance between fuel efficiency and fracture characteristics tends to be obtained.

[0098] When blending hydrogenated copolymers with other types of rubber such as natural rubber, using a silane coupling agent without mercapto groups (-SH) tends to worsen fracture properties because the natural rubber, which has many double bonds, reacts preferentially and is reinforced first. This results in insufficient reinforcement of the hydrogenated copolymer and an uneven distribution of crosslinks. On the other hand, when blending hydrogenated copolymers with other types of rubber such as natural rubber, using a silane coupling agent with mercapto groups (-SH) tends to improve fracture properties because its high reactivity allows for sufficient reinforcement of the hydrogenated copolymer, forming a good crosslink network.

[0099] The silane coupling agent having a mercapto group (-SH) is not particularly limited, but for example, Si363 from Evonik DeGussa, and NXT-Z30, NXT-Z45, and NXT-Z60 from Momentive can be used. These may be used alone or in combination of two or more.

[0100] The rubber composition of the present embodiment may contain a silane coupling agent having no mercapto group (—SH). The silane coupling agent having no mercapto group (—SH) is not particularly limited, and for example, Si266, Si69, Si75 manufactured by Evonik Degussa, NXT manufactured by Momentive, etc. can be used.

[0101] The content of the silane coupling agent in the rubber composition of the present embodiment is preferably 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of silica. From the viewpoint of fuel consumption performance, the content of the silane coupling agent is more preferably 2 parts by mass or more, further preferably 3 parts by mass or more, and even more preferably 4 parts by mass or more. From the viewpoint of manufacturing cost, the content of the silane coupling agent is preferably 9 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 7 parts by mass or less. When the content of the silane coupling agent is 1 part by mass or more, it tends to have excellent fuel consumption performance, and when the content of the silane coupling agent is 10 parts by mass or less, it tends to have excellent processability.

[0102] The method for adjusting the content of the silane coupling agent having a mercapto group is not particularly limited. For example, it can be adjusted by changing the blending amount of the above silane coupling agent with respect to the rubber composition.

[0103] 1.5. Carbon Black The rubber composition of the present embodiment preferably contains 1 part by mass or more and 100 parts by mass or less of carbon black with respect to 100 parts by mass of the rubber component containing the hydrogenated copolymer of the present embodiment.

[0104] The carbon black is not particularly limited, and examples thereof include carbon blacks of each class such as SRF, FEF, HAF, ISAF, SAF, etc. Among these, from the viewpoints of extrusion moldability and rolling resistance characteristics, the nitrogen adsorption specific surface area is 50 m 2Carbon black with a concentration of 1 / g or more and a dibutyl phthalate (DBP) oil absorption capacity of 80 mL / 100 g or more is preferred. From the viewpoint of improving wear resistance, the amount of carbon black blended is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. Furthermore, from the viewpoint of improving fuel efficiency, it is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 20 parts by mass or less.

[0105] 1.6. Softeners The rubber composition of this embodiment preferably contains 1 to 60 parts by mass of a softening agent per 100 parts by mass of the rubber component containing the hydrogenated copolymer of this embodiment. The softening agent is not particularly limited and examples include drawable oil, low molecular weight rubbery polymer, and resin, but drawable oil is preferred from the viewpoint of processability, productivity, and economy. Furthermore, a low molecular weight rubbery polymer that can contribute to crosslinking is preferred from the viewpoint of wear resistance of the rubber composition for tires.

[0106] Examples of such preferred spreading oils include, but are not limited to, aromatic oils, naphthenic oils, and paraffinic oils. Among these, aromatic substitute oils with a polycyclic aromatic (PCA) component content of 3% by mass or less according to the IP346 method are preferred from the viewpoint of environmental safety, as well as from the viewpoint of preventing oil bleeding and wet grip characteristics. Examples of aromatic substitute oils are not particularly limited, but 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).

[0107] In the rubber composition of this embodiment, the amount of softening agent is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of abrasion resistance, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less.

[0108] 1.7. Sulfurization aids The rubber composition of this embodiment may contain a vulcanization aid, and such vulcanization aids are not particularly limited, but examples include stearic acid and zinc oxide. These may be used individually or in combination of two or more.

[0109] 1.8. Crosslinking Agents The rubber composition of this embodiment contains a crosslinking agent, and preferably contains 0.1 parts by mass to 20 parts by mass of the crosslinking agent per 100 parts by mass of the rubber component containing the hydrogenated copolymer of this embodiment. The crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose. Examples include sulfur-based crosslinking agents (vulcanizing agents), organic peroxide-based crosslinking agents, inorganic crosslinking agents, polyamine crosslinking agents, resin crosslinking agents, sulfur compound-based crosslinking agents, oxymo-nitrosamine-based crosslinking agents, etc., and these may be used in combination. Among these, sulfur-based crosslinking agents (vulcanizing agents) are more preferred for tire rubber compositions. Among sulfur-based crosslinking agents, sulfur is particularly preferred.

[0110] The crosslinking agent content in the rubber composition of this embodiment is preferably 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of rubber component. From the viewpoint of high tensile strength and high crosslinking speed, 0.1 parts by mass or more is preferred, 0.5 parts by mass or more is more preferred, and 1.5 parts by mass or more is even more preferred. On the other hand, from the viewpoint of suppressing uneven crosslinking and high tensile strength, 20 parts by mass or less is preferred, 5 parts by mass or less is more preferred, and 3 parts by mass or less is even more preferred.

[0111] 1.9. Vulcanization accelerators In the rubber composition of this embodiment, a vulcanizing agent may be used in combination with a vulcanizing accelerator. The vulcanizing accelerator is not particularly limited, but examples include compounds such as guanidine, aldehyde amine, aldehyde ammonia, thiazole, sulfenamide, thiourea, thiuram, dithiocarbamate, and xantate compounds.

[0112] 1.10. Other Ingredients Furthermore, the rubber composition of this embodiment may also contain various additives other than those described above, such as other softeners and fillers, heat stabilizers, antistatic agents, weather stabilizers, anti-aging agents, colorants, and lubricants. The other softeners are not particularly limited, but for example, known softeners can be used. The other fillers are not particularly limited, but examples include calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate. The heat stabilizers, antistatic agents, weather stabilizers, anti-aging agents, colorants, and lubricants are not particularly limited, but for example, known materials can be used.

[0113] (vulcanizate) The rubber composition of this embodiment is suitably used as a vulcanized product. Here, a vulcanized product refers to a product that can be obtained by mixing rubber components such as hydrogenated copolymers or natural rubber with inorganic fillers such as silica or carbon black, rubber components other than the hydrogenated copolymers or natural rubber of this embodiment, a silane coupling agent having a mercapto group, a silane coupling agent not having a mercapto group, a rubber softener, a wax, a vulcanizing agent, a vulcanization accelerator, and a vulcanization aid to form a rubber composition, and then heating and vulcanizing it.

[0114] The method for identifying the types and proportions of rubber components contained in the rubber composition of this embodiment is not particularly limited, but for example, 13 C-Nuclear magnetic resonance analysis ( 13 It can be identified using 1C-NMR. For example, in previously published literature (JSR TECHNICAL REVIEW No. 126 / 2019), solid 13 The document states that by using 1C-NMR, the amount of styrene units, 1,2-vinyl bonds, 1,4-trans bonds, 1,4-cis bonds, and isoprene units contained in the rubber composition can be quantitatively calculated, and the above identification can be performed by referring to this document.

[0115] 2. Method for producing rubber composition

[0116] In the method for producing the rubber composition of this embodiment, the method for mixing the rubber components, crosslinking agent, silica, carbon black, silane coupling agent having a mercapto group, softener, and other fillers is not limited to the following, but for example, a melt-mixing method using a general mixer such as an open roll, Banbury mixer, kneader, single-screw extruder, twin-screw extruder, or multi-screw extruder can be used, and a method in which the solvent is heated off after dissolving and mixing each component can be used. Of these, the melt-mixing method using a roll, Banbury mixer, kneader, or extruder is preferred in terms of productivity and good mixing performance.

[0117] Furthermore, while both a method of kneading the rubber component, other fillers, the silane coupling agent, and additives all at once, and a method of mixing them in multiple steps are applicable, a method comprising a first kneading step of kneading the rubber component, silica, the silane coupling agent, and additives, and a second kneading step of kneading the mixture obtained in the first kneading step with the sulfurizing agent is preferred.

[0118] In the first kneading step, in which the rubber component, silica, the silane coupling agent, and additives are kneaded together, the temperature reached during kneading is preferably 140°C or higher, more preferably 150°C or higher, and even more preferably 155°C or higher, from the viewpoint of fuel efficiency. The inventors have found that when kneading the hydrogenated copolymer and the silane coupling agent having a mercapto group, the preferred temperature tends to be reached in a short time. The ease with which the kneading temperature rises leads to improved production efficiency and also serves as an indicator to confirm the progress of the reaction between the two.

[0119] Furthermore, from the viewpoint of processability, the temperature reached during the first kneading step, in which the rubber components, fillers, silane coupling agents, and additives are kneaded, is preferably 170°C or lower, more preferably 165°C or lower, and even more preferably 160°C or lower. Since silane coupling agents having mercapto groups (-SH) are highly reactive, depending on the structure of the rubber being kneaded, crosslinking may progress during kneading, which can easily worsen processability. However, in the case of hydrogenated copolymers, there are fewer double bonds that react with the silane coupling agent, so good processability is observed even at high kneading temperatures.

[0120] Next, as a second mixing step, it is preferable to cool the resulting mixture after the first mixing step in which the rubber components, filler, silane coupling agent, and additives are mixed, and then mix in the vulcanizing agent. The temperature of the mixture is preferably cooled to 80°C or lower, more preferably to 70°C or lower. By mixing in the vulcanizing agent after such cooling, the vulcanizing agent can be crosslinked while dispersed throughout the composition. A crosslinked rubber composition is obtained by heating the composition containing the vulcanizing agent to preferably 150°C, more preferably to about 160°C.

[0121] 3.Applications The rubber composition of this embodiment can be used as a crosslinking rubber composition in applications such as tire components, automotive interior and exterior parts, vibration-damping rubber, belts, footwear, foams, and various industrial products. Among these, it is particularly suitable for use in tire components.

[0122] The tire components are not particularly limited, but can be used in various tire parts such as the tire tread, carcass, sidewall, and bead, including fuel-efficient tires, all-season tires, high-performance tires, snow tires, and studless tires. In particular, as a tire component, it is suitable for use in the tire treads of fuel-efficient tires, high-performance tires, and snow tires because, when vulcanized, it offers an excellent balance of wear resistance, fuel efficiency, wet skid resistance, and snow performance.

[0123] Conventional known or commonly used methods can be used to manufacture the tire. Such methods are not particularly limited, but for example, at least one carcass layer, belt layer, tread layer, and other components commonly used in tire manufacturing, selected from the group consisting of an unvulcanized crosslinking rubber composition and cords, are sequentially laminated onto a tire molding drum, and the drum is removed to obtain a green tire. Then, the green tire is heated and vulcanized according to a conventional method to produce a desired tire (e.g., a pneumatic tire). [Examples]

[0124] The embodiment will be described in more detail below with reference to specific examples and comparative examples, but this embodiment is not limited in any way to the following examples and comparative examples. Furthermore, the various physical properties in the examples and comparative examples were measured by the methods shown below.

[0125] First, the method for measuring the physical properties of hydrogenated copolymers and rubber compositions produced by the manufacturing examples described later will be explained in detail, followed by a detailed explanation of each manufacturing example, each example, and each comparative example.

[0126] (Microstructure of the butadiene portion of the copolymer before hydrogenation (amount of 1,2-vinyl bonds)) 50 mg of the copolymer before hydrogenation was dissolved in 10 mL of carbon disulfide to prepare the measurement sample. The infrared absorption spectrum was measured using a solution cell at 600–1000 cm⁻¹. -1 Measurements were taken within a specified range, and the microstructure of the butadiene portion, i.e., the amount of 1,2-vinyl bonds (mol%), was determined by the absorbance at a predetermined wavenumber according to the calculation formula of Hampton's method (as described in RRHampton, Analytical Chemistry 21,923 (1949)) (measurement device: Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation).

[0127] (Weight-average molecular weight of copolymers) A GPC analyzer consisting of three connected columns packed with polystyrene gel was used to measure chromatograms, and the weight-average molecular weight of the copolymer was determined based on a calibration curve using standard polystyrene. The eluent used was 5 mmol / L triethylamine-containing THF. The columns used were: guard column: "TSKguardcolumn SuperH-H" (manufactured by Tosoh Corporation), and columns: "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" (manufactured by Tosoh Corporation). An RI detector ("HLC8020" (manufactured by Tosoh Corporation) was used under conditions of oven temperature 40°C and THF flow rate 0.6 mL / min. 10 mg of the sample for measurement was dissolved in 20 mL of THF to prepare the measurement solution, and 20 μL of the measurement solution was injected into the GPC analyzer for measurement.

[0128] (Hydrogenation rate of copolymer) After the hydrogenation reaction, an excess amount of methanol was added to the reaction solution of the copolymer to precipitate and recover both the pre-hydrogenation copolymer and the hydrogenated copolymer. Next, the hydrogenated copolymer was extracted with acetone and then vacuum-dried. This was then used to... 1 The sample was used for H-NMR measurement, and the hydrogenation rate was determined. 1 The conditions for H-NMR measurement are described below. <Measurement conditions> Measuring instrument: JNM-LA400 (manufactured by JEOL) Solvent: Deuterated chloroform Measurement samples: Samples taken before and after hydrogenation of the polymer. Sample concentration: 50 mg / mL Observation frequency: 400MHz Chemical shift standard: TMS (tetramethylsilane) Pulse delay: 2.904 seconds Number of scans: 64 Pulse width: 45° Measurement temperature: 26℃

[0129] (Styrene content of copolymer (mass%)) The copolymer was used as the sample. 100 mg of the sample was dissolved in chloroform to a volume of 100 mL and used as the measurement sample. The amount of styrene (mass%) in the sample was measured by the amount of ultraviolet absorption at a wavelength (around 254 nm) by the phenyl group of styrene (measurement device: Shimadzu Corporation UV-2450 spectrophotometer).

[0130] (Nitrogen content of copolymer) The copolymer was used as a sample, and its nitrogen content was measured using a trace nitrogen analyzer (Nitto Seiko Analytech TN-2100H).

[0131] [Manufacturing of copolymers] (Preparation of hydrogenation catalyst) The hydrogenation catalyst used in preparing the copolymer in the production example described later was prepared by the method of production example α below. <Manufacturing example α> One liter of dried and purified cyclohexane was charged into a nitrogen-purged reaction vessel, 100 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added, and while stirring thoroughly, an n-hexane solution containing 200 mmol of trimethylaluminum was added and the mixture was reacted at room temperature for about 3 days to obtain a hydrogenation catalyst (TC-1).

[0132] (polymerization of copolymers) <(Production Example 1) Copolymer A1> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 3,046 g of 1,3-butadiene, 344.0 g of styrene, 25,800 g of cyclohexane, and 3.76 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 2.2 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature stopped rising, an additional 909.9 g of 1,3-butadiene (hereinafter also referred to as additional butadiene) was added. Once the temperature rise in the reactor due to the reaction heat of the added butadiene had subsided, 2.3 g of the denaturing agent 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azacyloridine (denaturing agent 1) was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was removed and dried to obtain the copolymer before hydrogenation.

[0133] Subsequently, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the copolymer solution before hydrogenation at a concentration of 60 ppm (Ti-based) per 100 parts by mass of the copolymer before hydrogenation. The hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain copolymer A1. The hydrogenation rate of the obtained copolymer A1 was 70 mol%.

[0134] To the resulting copolymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the resulting copolymer A1 are shown in Table 1.

[0135] <(Production Example 2) Copolymer A2> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 3,046 g of 1,3-butadiene, 344.0 g of styrene, 25,800 g of cyclohexane, and 8.14 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 4.7 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature rise stopped, an additional 909.9 g of 1,3-butadiene was added. Once the temperature rise inside the reactor due to the reaction heat of the added butadiene had stopped, 5.0 g of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azacyloridine, a denaturing agent, was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain the copolymer before hydrogenation.

[0136] Subsequently, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the copolymer solution before hydrogenation at a concentration of 60 ppm (Ti-based) per 100 parts by mass of the copolymer before hydrogenation. The hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain copolymer A2. The hydrogenation rate of the obtained copolymer A2 was 70 mol%.

[0137] To the resulting copolymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the resulting copolymer A2 are shown in Table 1.

[0138] <(Production Example 3) Copolymer A3> Copolymer A3 was obtained using the same manufacturing conditions as in Manufacturing Example 1, except for the amount of hydrogenation. The analytical values ​​of the obtained copolymer A3 are shown in Table 1.

[0139] <(Production Example 4) Copolymer A4> Copolymer A4 was obtained using the same manufacturing conditions as in Manufacturing Example 2, except for the amount of hydrogenation. The analytical values ​​of the obtained copolymer A4 are shown in Table 1.

[0140] <(Production Example 5) Copolymer A5> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 3,013 g of 1,3-butadiene, 387.0 g of styrene, 25,800 g of cyclohexane, and 1.64 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 1.0 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature rise stopped being observed, an additional 900.0 g of 1,3-butadiene was added. Once the temperature rise inside the reactor due to the reaction heat of the added butadiene had stopped, a portion of the polymerization solution was removed and dried to obtain the copolymer before hydrogenation.

[0141] Subsequently, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the copolymer solution before hydrogenation at a concentration of 60 ppm (Ti-based) per 100 parts by mass of the copolymer before hydrogenation. The hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain copolymer A5.

[0142] The hydrogenation rate of the obtained copolymer A5 was 74 mol%. To the solution of the obtained copolymer, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the obtained copolymer A5 are shown in Table 1.

[0143] <(Production Example 6) Copolymer A6> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 3,013 g of 1,3-butadiene, 387.0 g of styrene, 25,800 g of cyclohexane, and 4.95 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 2.9 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature rise stopped, an additional 900.0 g of 1,3-butadiene was added. Once the temperature rise inside the reactor due to the reaction heat of the added butadiene had stopped, 3.2 g of tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine (modifier 2), which is a denaturing agent, was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain the copolymer before hydrogenation.

[0144] Subsequently, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the copolymer solution before hydrogenation at a concentration of 60 ppm (Ti-based) per 100 parts by mass of the copolymer before hydrogenation. The hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain copolymer A6. The hydrogenation rate of the obtained copolymer A6 was 74 mol%.

[0145] To the resulting copolymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the resulting copolymer A6 are shown in Table 1.

[0146] <(Production Example 7) Copolymer A7> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 3,013 g of 1,3-butadiene, 387.0 g of styrene, 25,800 g of cyclohexane, and 2.99 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 1.8 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature stopped rising, an additional 900.0 g of 1,3-butadiene was added. Once the temperature rise in the reactor due to the reaction heat of the added butadiene had subsided, 0.2 g of the denaturing agent 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azacyloridine and 2.6 g of 1,3-dimethyl-2-imidazolidinone (denaturing agent 3) were added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was removed and dried to obtain the copolymer before hydrogenation.

[0147] Subsequently, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the copolymer solution before hydrogenation at a concentration of 60 ppm (Ti-based) per 100 parts by mass of the copolymer before hydrogenation. The hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain copolymer A7. The hydrogenation rate of the obtained copolymer A7 was 74 mol%.

[0148] To the resulting copolymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the resulting copolymer A7 are shown in Table 1.

[0149] <(Production Example 8) Copolymer A8> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 3,013 g of 1,3-butadiene, 387.0 g of styrene, 25,800 g of cyclohexane, and 3.73 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 2.2 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature rise stopped, an additional 900.0 g of 1,3-butadiene was added. Once the temperature rise inside the reactor due to the reaction heat of the added butadiene had stopped, 0.7 g of tetramethylsilane (modifier 4), a denaturing agent, was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was removed and dried to obtain the copolymer before hydrogenation.

[0150] Subsequently, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the copolymer solution before hydrogenation at a concentration of 60 ppm (Ti-based) per 100 parts by mass of the copolymer before hydrogenation. The hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain copolymer A8. The hydrogenation rate of the obtained copolymer A8 was 74 mol%.

[0151] To the resulting copolymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the resulting copolymer A8 are shown in Table 2.

[0152] <(Production Example 9) Copolymer A9> Copolymer A9 was obtained in the same manner as in Production Example 1, except that the amount of the denaturing agent, 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azacyloridine, was changed to 1.8 g. The analytical values ​​of the obtained copolymer A9 are shown in Table 2.

[0153] <(Production Example 10) Copolymer A10> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 2,881 g of 1,3-butadiene, 559.0 g of styrene, 25,800 g of cyclohexane, and 9.77 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 2.8 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature rise stopped, an additional 860.4 g of 1,3-butadiene was added. Once the temperature rise inside the reactor due to the reaction heat of the added butadiene had stopped, 2.9 g of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azacyloridine, a denaturing agent, was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain the copolymer before hydrogenation.

[0154] Subsequently, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the copolymer solution before hydrogenation at a concentration of 60 ppm (Ti-based) per 100 parts by mass of the copolymer before hydrogenation. The hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain copolymer A10. The hydrogenation rate of the obtained copolymer A10 was 67 mol%.

[0155] To the resulting copolymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the resulting copolymer A10 are shown in Table 2.

[0156] <(Production Example 11) Copolymer A11> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 2,152 g of 1,3-butadiene, 1,505 g of styrene, 25,800 g of cyclohexane, and 3.13 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 3.2 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature rise stopped, an additional 642.9 g of 1,3-butadiene was added. Once the temperature rise inside the reactor due to the reaction heat of the added butadiene had stopped, 3.4 g of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azacyloridine, a denaturing agent, was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain the copolymer before hydrogenation.

[0157] Subsequently, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the copolymer solution before hydrogenation at a concentration of 60 ppm (Ti-based) per 100 parts by mass of the copolymer before hydrogenation. The hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain copolymer A11. The hydrogenation rate of the obtained copolymer A11 was 64 mol%.

[0158] To the resulting copolymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the resulting copolymer A11 are shown in Table 2.

[0159] <(Production Example 12) Copolymer B1> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 3,046 g of 1,3-butadiene, 344.0 g of styrene, 25,800 g of cyclohexane, and 3.41 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 2.0 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature rise stopped, an additional 909.9 g of 1,3-butadiene was added. Once the temperature rise inside the reactor due to the reaction heat of the added butadiene had stopped, 2.1 g of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azacyloridine, a denaturing agent, was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was extracted and dried to obtain the copolymer before hydrogenation.

[0160] Subsequently, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the copolymer solution before hydrogenation at a concentration of 60 ppm (Ti-based) per 100 parts by mass of the copolymer before hydrogenation. The hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain copolymer B1. The hydrogenation rate of the obtained copolymer B1 was 40 mol%.

[0161] To the resulting copolymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the resulting copolymer B1 are shown in Table 2.

[0162] <(Production Example 13) Copolymer B2> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 3,046 g of 1,3-butadiene, 344.0 g of styrene, 25,800 g of cyclohexane, and 10.69 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 6.2 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature stopped rising, an additional 909.9 g of 1,3-butadiene was added. Once the temperature rise in the reactor due to the reaction heat of the added butadiene had subsided, 6.6 g of the denaturing agent 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azacyloridine was added to the reactor and stirred for 5 minutes. A portion of the polymerization solution was removed and dried to obtain the copolymer before hydrogenation.

[0163] Subsequently, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the copolymer solution before hydrogenation at a concentration of 60 ppm (Ti-based) per 100 parts by mass of the copolymer before hydrogenation. The hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain copolymer B2. The hydrogenation rate of the obtained copolymer B2 was 70 mol%.

[0164] To the resulting copolymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the resulting copolymer B2 are shown in Table 2.

[0165] <(Production Example 14) Copolymer B3> A temperature-controlled autoclave with an internal volume of 43 L, equipped with a stirrer and jacket, was used as the reactor. 3,046 g of 1,3-butadiene, 344.0 g of styrene, 25,800 g of cyclohexane, and 3.76 g of 2,2-di(2-tetrahydrofuryl)propane (as a polar substance), which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 42°C. Subsequently, 2.2 g of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. When the temperature rise stopped, an additional 909.9 g of 1,3-butadiene was added. Once the temperature rise inside the reactor due to the reaction heat of the added butadiene had stopped, 2.3 g of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azacyloridine, a denaturing agent, was added to the reactor and stirred for 5 minutes. Methanol was added to this copolymer solution as a reaction stopper, and then a portion of the polymerization solution was removed and dried to obtain the copolymer before hydrogenation.

[0166] To the obtained copolymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The analytical values ​​of the obtained copolymer B3 are shown in Table 2.

[0167] [Table 1]

[0168] [Table 2]

[0169] (Preparation of rubber compositions, evaluation of physical properties) Using copolymers A1 to A11 obtained in Production Examples 1 to 11 shown in Tables 1 to 2, copolymers B1 to B3 obtained in Production Examples 12 to 14, and natural rubber and high-cis polybutadiene as raw material rubber components, rubber compositions containing each raw material rubber were obtained according to the formulations shown in Tables 3 to 5.

[0170] In Tables 3 to 5, the amount of each compounding agent added is shown as parts per 100 parts by mass of rubber component excluding rubber softeners (hereinafter also referred to as parts per 100 rubber or [phr]).

[0171] (Ingredients) The following materials were used, as shown in Tables 3-5. ·Copolymers A1~A11, B1~B3 • Natural rubber (NR): RSS No. 3 (Producer: UNIMAC RUBBER CO., LTD. (Thailand), Supplier: Marubeni Techno Rubber) • High-cis polybutadiene (High-cis BR): UBEPOL U150 manufactured by Ube Industries, Ltd. • Silica: Evonik Degussa 7000GR (N2SA: 170m 2 / g) • Carbon: Diablack N339 (N2SA: 96m) manufactured by Mitsubishi Chemical Corporation. 2 ( / g, DBP absorption: 124 mL / 100 g) • Oil: Process NC140 manufactured by JX Nippon Oil & Energy Corporation • Silane coupling agent 1: Si363 manufactured by Evonik DeGussa • Silane coupling agent 2: Si75 manufactured by Evonik DeGussa • Silane coupling agent 3: Si69 manufactured by Evonik DeGussa • Anti-aging agent: Nocrack 6C manufactured by Ouchi Shinko Chemical Co., Ltd. • Stearic acid: Bead stearic acid "Tsubaki" manufactured by NOF Corporation • Zinc oxide: Three types of zinc oxide manufactured by Hakusui Tech Co., Ltd. • Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. • Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industries, Ltd. • Vulcanization accelerator 1: Vulcanization accelerator: Noxellar CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. • Vulcanization accelerator 2: Noxellar D manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0172] (Evaluation of rubber composition) First, rubber compositions for each example and comparative example were prepared using the above materials according to the formulations described in Tables 3 to 5. Then, using a sealed kneader (capacity 0.3L) equipped with a temperature control device, the raw rubber, silica, carbon, silane coupling agent, softener, zinc oxide, and stearic acid were kneaded in the first stage under conditions of a filling rate of 65% and a rotor rotation speed of 30 to 50 rpm. At this time, the temperature of the sealed mixer was controlled, and each rubber composition (formulation) was obtained at a discharge temperature of 135 to 175°C.

[0173] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature, an antioxidant was added, and the mixture was kneaded again to improve the dispersion of silica. In this case as well, the discharge temperature of the mixture was adjusted to 135-175°C by controlling the temperature of the mixer. After cooling, in the third stage of mixing, sulfur and vulcanization accelerators 1 and 2 were added and kneaded in an open roll mixer set to 70°C.

[0174] The mixture was then molded and vulcanized at 160°C using a vulcanizing press to obtain the vulcanized rubber composition. The fuel efficiency, fracture characteristics, processability, and ozone resistance of the vulcanized rubber composition were evaluated using the evaluation methods and criteria described later. The vulcanization time was calculated by adding 5 minutes to the T90 (minutes) of each sample measured using the method described later. Specifically, the evaluation was performed using the method described below. The evaluation results are shown in Tables 3 to 5.

[0175] [Table 3]

[0176] [Table 4]

[0177] [Table 5]

[0178] (Evaluation method) <Evaluation 1: Fuel efficiency> Viscoelastic parameters were measured in torsion mode using the "ARES" viscoelasticity testing machine manufactured by Rheometrics Scientific. Tanδ, measured at 50°C, frequency of 10Hz, and strain of 3%, was used as an indicator of fuel efficiency performance. The fuel efficiency performance of the reference example was quantified as 100, and the evaluation was made according to the following [evaluation criteria]. [Evaluation Criteria] 5. The fuel efficiency index of the vulcanized material is 110 or higher. 4. The fuel efficiency index of the vulcanized material is 105 or higher but less than 110. 3. The fuel efficiency index of the vulcanized material is 95 or higher and less than 105. 2: The fuel efficiency index of the vulcanized material is 90 or higher but less than 95. 1: The fuel efficiency index of the vulcanized material is less than 90.

[0179] <Rating 2: Destructive properties> Tensile strength TB (MPa) and fracture elongation EB (%) were measured in accordance with the tensile testing method of JIS K6251. TB × EB / 2 (MPa·%) was calculated, and the fracture characteristics of the reference example were quantified as 100. The evaluation was then made according to the following [evaluation criteria]. [Evaluation Criteria] 5. The fuel efficiency index of the vulcanized material is 110 or higher. 4. The fuel efficiency index of the vulcanized material is 105 or higher but less than 110. 3. The fuel efficiency index of the vulcanized material is 95 or higher and less than 105. 2: The fuel efficiency index of the vulcanized material is 90 or higher but less than 95. 1: The fuel efficiency index of the vulcanized material is less than 90.

[0180] <Evaluation 3: Processability> The mixture obtained above, after the second stage of kneading and before the third stage of kneading, was used as a sample. Using a Mooney viscometer, the viscosity was measured after preheating to 130°C for 1 minute in accordance with JIS K6300-1, and then rotating the rotor at 2 revolutions per minute for 4 minutes. The reference example was assigned a numerical value of 100, and the evaluation was made according to the following criteria. [Evaluation Criteria] 5. The fuel efficiency index of the vulcanized material is 110 or higher. 4. The fuel efficiency index of the vulcanized material is 105 or higher but less than 110. 3. The fuel efficiency index of the vulcanized material is 95 or higher and less than 105. 2: The fuel efficiency index of the vulcanized material is 90 or higher but less than 95. 1: The fuel efficiency index of the vulcanized material is less than 90.

[0181] <Rating 4: Ozone resistance> In accordance with the static ozone degradation test method of JIS K6259, a JIS No. 5 dumbbell piece was attached to a stretching jig at an elongation rate of 20%, and a static ozone degradation test was conducted at an ozone concentration of 50 pphm and a temperature of 40°C for 48 hours. The results were then evaluated visually according to the following criteria. [Evaluation Criteria] 5: No cracks are visible. 4: There are one to ten cracks smaller than 1 mm. 3: There are between 10 and 20 cracks smaller than 1 mm. 2: Cracks between 1mm and 3mm in size are observed. 1: Cracks larger than 3mm are visible.

Claims

1. Hydrogenated copolymer having a weight-average molecular weight of 300,000 or more and 650,000 or less, Natural rubber and Silica and, A silane coupling agent having a mercapto group, The hydrogenated copolymer has aromatic vinyl units and conjugated diene units, The conjugated diene units contain 25 mol% or more of conjugated diene units having 1,2-vinyl bonds relative to the total amount of the conjugated diene units. The proportion of hydrogenated conjugated diene units in the aforementioned conjugated diene units is 40 mol% or more and 85 mol% or less. The hydrogenated copolymer content is 20% by mass or more relative to the total amount of rubber components. The amount of natural rubber is 30% by mass or more relative to the total amount of rubber components. Temperature 160℃, shear rate 12.16s -1 The absolute value of the difference in melt viscosity between the hydrogenated copolymer and the natural rubber under the specified conditions is 9,000 (Pa·s) or less. Rubber composition.

2. The hydrogenated copolymer has a molecular weight distribution of 1.20 to 1.

75. The rubber composition according to claim 1.

3. The nitrogen content of the hydrogenated copolymer is 15 ppm or more and 170 ppm or less. The rubber composition according to claim 1 or claim 2.

4. The content of the silane coupling agent is 1 to 10 parts by mass per 100 parts by mass of silica. The rubber composition according to any one of claims 1 to 3.

5. A first kneading step of kneading a rubber composition comprising a hydrogenated copolymer having a weight-average molecular weight of 300,000 or more and 650,000 or less, natural rubber, silica, and a silane coupling agent having a mercapto group, The process includes a second kneading step in which the mixture obtained in the first step is kneaded with a vulcanizing agent. A method for producing a rubber composition, The hydrogenated copolymer has aromatic vinyl units and conjugated diene units, The conjugated diene units contain 25 mol% or more of conjugated diene units having 1,2-vinyl bonds relative to the total amount of the conjugated diene units. The proportion of hydrogenated conjugated diene units in the aforementioned conjugated diene units is 40 mol% or more and 85 mol% or less. The hydrogenated copolymer content is 20% by mass or more relative to the total amount of rubber components. The amount of natural rubber is 30% by mass or more relative to the total amount of rubber components. Temperature 160℃, shear rate 12.16s -1 The absolute value of the difference in melt viscosity between the hydrogenated copolymer and the natural rubber under the specified conditions is 9,000 (Pa·s) or less. A method for producing a rubber composition.

6. A rubber composition made according to any one of claims 1 to 4, tire.

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