rubber composition

Abstract

The present invention provides a tire composition that exhibits fuel efficiency and high wear resistance, while also providing good handling. [Solution] A rubber composition comprising, per 100 parts by mass of the total diene elastomer, 50 to 98 phr of at least one first diene elastomer selected from the group consisting of polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymer, isoprene copolymer and mixtures thereof, 2 to 50 phr of a second diene elastomer which is a block copolymer, and 50 to 200 phr of a filler, and satisfying four conditions including the following conditions. (1) The GPC of the block copolymer (X) has at least two peaks. (2) Among the block copolymers (X), block copolymer (A) showing the first peak has at least one polymer block mainly composed of a vinyl aromatic compound.

Description

Technical Field

[0001] The present invention relates to a rubber composition.

Background Art

[0002] Block copolymers using conjugated diene compounds and vinyl aromatic compounds have elasticity similar to natural rubber and synthetic rubber at room temperature, molding processability similar to thermoplastic resins at high temperatures, and are also excellent in weather resistance and heat resistance. Therefore, conventionally, as a resin modifier, it has been widely used in fields such as automotive parts, tire members, medical molded products, asphalt modifiers, footwear, molded products such as food containers, packaging materials, adhesive sheets, and household and industrial parts. As a tire member, a tire tread is typically expected to have excellent traction, handling, wet skid resistance, fuel efficiency performance, and good wear characteristics. These properties largely depend on the composition of the rubber composition used in the manufacture of the tire. To improve performance, tire compositions typically contain up to 20 phr or, in some cases, up to 75 phr of resin, which is, for example, a resin containing substituted or unsubstituted units derived from a cyclopentadiene homopolymer or copolymer, a terpene resin, or a rosin-derived substance including a rosin ester or oligoester resin. For example, Patent Document 1 discloses a rubber composition for a tire tread containing, in addition to a first diene elastomer, a hydrogenated copolymer of a block copolymer using a conjugated diene compound and a vinyl aromatic compound as a second diene elastomer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, hydrogenated block copolymers have drawbacks compared to resins and other materials, such as poor processability and limitations on the amount that can be added. Furthermore, in recent years, tire compositions have been required to be fuel-efficient and long-lasting in order to reduce environmental impact. Therefore, tire compositions are required to exhibit fuel efficiency and high wear resistance, while also providing good handling. [Means for solving the problem]

[0005] As a result of diligent research to solve the above problems, the inventors of the present invention have found that a rubber composition containing a block copolymer having a specific structure to be used as a second diene elastomer can solve the problems of the prior art described above, and have completed the present invention. In other words, the present invention is as follows.

[0006] [1] For every 100 parts by mass of the entire diene elastomer, At least one first diene elastomer selected from the group consisting of polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymer, isoprene copolymer and mixtures thereof, in an amount of 50 to 98 phr. A second diene elastomer which is a block copolymer in an amount of 2 to 50 phr, and A rubber composition containing a filler of 50 to 200 phr, A rubber composition wherein the block copolymer (X) contained in the second diene elastomer comprises vinyl aromatic monomer units and conjugated diene monomer units, and satisfies the following conditions. (1) The GPC of the block copolymer (X) has at least two peaks. (2) Among the block copolymers (X), block copolymer (A) showing the first peak has at least one polymer block mainly composed of a vinyl aromatic compound. (3) Among the block copolymers (X), block copolymer (B) showing a second peak has at least one polymer block mainly composed of a vinyl aromatic compound. (4) The ratio (Mn1 / Mn2) of the number average molecular weight (Mn1) of block copolymer (A) to the number average molecular weight (Mn2) of block copolymer (B) is 6.0 or greater. [2] The rubber composition according to [1] above, wherein the structure of the block copolymer (A) showing the first peak among the block copolymer (X) is represented as a1-b1-a2-b2. a1, a2: Blocks mainly composed of vinyl aromatic compounds b1, b2: Blocks mainly composed of conjugated diene compounds, or random copolymer blocks consisting of conjugated diene compounds and vinyl aromatic compounds. [3] The rubber composition according to [1] or [2] above, wherein at least one glass transition temperature of the first diene elastomer is in the range of -40°C or lower. [4] The rubber composition according to any one of the above [1] to [3], wherein the hydrogenation rate of the double bond derived from the conjugated diene compound of the block copolymer (X) is 65% or more. [5] The rubber composition according to any one of the above [1] to [4], wherein the structure of the block copolymer (A) showing the first peak among the block copolymer (X) is represented as a1-b1-a2-b2, and the number-average molecular weight of the b2 block is 20,000 or less. [6] The rubber composition according to any one of [1] to [5] above, wherein the conjugated diene compound that forms the conjugated diene monomer unit of the block copolymer (X) is isoprene and / or butadiene. [7] The rubber composition according to any one of the above [1] to [6], wherein the value after 10 seconds (10s hardness) of the block copolymer (X) measured in accordance with JIS K6253 on a durometer type A is 25 or less. [8] A rubber composition according to any of the above [1] to [7], wherein the instantaneous value (instantaneous hardness) measured on a durometer type A in accordance with JIS K6253 is 45 to 75. [9] The rubber composition according to any one of [1] to [8] above, wherein the block copolymer (A) and the block copolymer (B) have a random copolymer structure consisting of a vinyl aromatic compound and a conjugated diene compound.

[10] The rubber composition according to any one of the above [1] to [9], wherein the tanδ peak at 50°C or below in a viscoelasticity measurement (1 Hz) has two or more peaks, or has one main peak in addition to a shoulder peak. [Effects of the Invention]

[0007] According to the present invention, a rubber composition can be obtained that has good processability and excellent wear resistance, fuel efficiency, and handling properties. [Modes for carrying out the invention]

[0008] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). It should be noted that this embodiment is illustrative for explaining the present invention, and the present invention is not limited to the following content, but can be implemented in various ways within the scope of its gist.

[0009] The rubber composition in this embodiment is For every 100 parts by mass of the entire diene elastomer, A first diene elastomer selected from polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymer, isoprene copolymer and mixtures thereof in an amount of 5 to 95 phr, A second diene elastomer which is a block copolymer in an amount of 5-50 phr, and A rubber composition containing a filler of 50 to 200 phr, A rubber composition in which the block copolymer (X) contained in the second diene elastomer contains a vinyl aromatic monomer unit and a conjugated diene monomer unit and satisfies the following conditions. (1) The GPC of the block copolymer (X) has at least two peaks. (2) The block copolymer (A) showing the first peak among the block copolymers (X) has at least one polymer block mainly composed of a vinyl aromatic compound. (3) The block copolymer (B) showing the second peak among the block copolymers (X) has at least one polymer block mainly composed of a vinyl aromatic compound. (4) The ratio (Mn1 / Mn2) of the number average molecular weight (Mn1) of the block copolymer (A) to the number average molecular weight (Mn2) of the block copolymer (B) is 6.0 or more.

[0010] 〔First diene elastomer〕 As the first diene elastomer component, it includes at least one selected from the group consisting of polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymer, isoprene copolymer, and mixtures thereof, and examples thereof include "rubber" components commonly used in tire compositions. When natural rubber is included, this includes both natural rubber and its various raw and regenerated forms.

[0011] In this embodiment, the first diene elastomer component may be selected from, for example, butyl rubber, halogenated butyl rubber, and EPDM (ethylene propylene diene monomer rubber), and mixtures thereof. Further, the first diene elastomer component may be, for example, natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber, synthetic polyisoprene rubber, epoxidized natural rubber, polybutadiene rubber, for example, high cis-polybutadiene rubber, nitrile-hydrogenated butadiene rubber (HNBR), hydrogenated SBR, ethylene propylene diene monomer rubber, ethylene propylene rubber, maleic acid-modified ethylene propylene rubber, butyl rubber, isobutylene-aromatic vinyl or diene monomer copolymer, brominated NR, chlorinated NR, brominated isobutylene-p-methylstyrene copolymer, chloroprene rubber, epichlorohydrin homopolymer rubber, epichlorohydrin-ethylene oxide or allyl glycidyl ether copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer rubber, chlorosulfonated polyethylene, chlorinated polyethylene, maleic acid-modified chlorinated polyethylene, methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber, polysulfide rubber, vinylidene fluoride rubber, tetrafluoroethylene-propylene rubber, fluorinated silicone rubber, fluorinated phosphagen rubber, styrene elastomer, thermoplastic olefin elastomer, polyester elastomer, urethane elastomer, and polyamide elastomer.

[0012] The first diene elastomer may be coupled, star-branched, and / or functionalized with a coupling agent and / or star-branching or functionalizing agent. The end groups of the first diene elastomer may be functionalized to improve its affinity for fillers such as carbon black and / or silica. Coupling and / or star-branching or functionalization includes coupling with carbon black as a filler, which may include, for example, a functional group containing a C-Sn bond or an amination functional group such as benzophenone, a silanol functional group or a polysiloxane functional group with a silanol terminus, an alkoxysilane group, or a polyether group. The end chains of the first diene elastomer may be functionalized with silanol groups. In another embodiment, the first diene elastomer may be epoxide-functionalized (or epoxide-treated) and have epoxide functional groups.

[0013] The content of the first diene elastomer is 50 to 98 phr, preferably 55 to 96 phr, and more preferably 60 to 93 phr, per 100 parts by mass of the total diene elastomer. When the content of the first diene elastomer is 50 phr or more, abrasion resistance is good, and when it is 98 phr or less, wet grip performance is improved.

[0014] (tanδ peak in the viscoelasticity of the first diene elastomer) The first diene elastomer preferably has at least one tanδ peak in the range of -40°C or below in a viscoelasticity measurement (1 Hz), more preferably at least one tanδ peak in the range of -50°C or below, and even more preferably at least one tanδ peak in the range of -55°C or below. When the first diene elastomer has at least one tanδ peak below -40°C, the balance between abrasion resistance and wet grip performance of the rubber composition of this embodiment tends to improve.

[0015] [Second type of diene elastomer] The second diene elastomer contains a block copolymer (X). The block copolymer (X) contains vinyl aromatic monomer units and conjugated diene monomer units and satisfies the following conditions. (1) The GPC of the block copolymer (X) has at least two peaks. (2) Among the block copolymers (X), block copolymer (A) showing the first peak has at least one polymer block mainly composed of a vinyl aromatic compound. (3) Among the block copolymers (X), block copolymer (B) showing a second peak has at least one polymer block mainly composed of a vinyl aromatic compound. (4) The ratio (Mn1 / Mn2) of the number average molecular weight (Mn1) of block copolymer (A) to the number average molecular weight (Mn2) of block copolymer (B) is 6.0 or greater.

[0016] The content of the second diene elastomer is 2 to 50 phr, preferably 4 to 45 phr, and more preferably 7 to 40 phr, per 100 parts by mass of the total diene elastomer. When the content of the second diene elastomer is 2 phr or more, wet grip performance is improved, and when it is 50 phr or less, abrasion resistance is improved.

[0017] [Block copolymer (X)] The vinyl aromatic compounds that form the vinyl aromatic monomer units of the block copolymer (X) are not limited to the following, but examples include vinyl aromatic compounds such as styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, and N,N-diethyl-p-aminoethylstyrene. Among these, styrene, α-methylstyrene, and p-methylstyrene are preferred from the viewpoint of availability and productivity. These may be used individually or in combination of two or more.

[0018] The conjugated diene compound that forms the conjugated diene monomer unit of the block copolymer (X) can be any diolefin having a conjugated double bond, and is not limited to the following, but examples include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, farnesene, etc. Among these, 1,3-butadiene and isoprene are preferred from the viewpoint of availability and productivity. These may be used individually or in combination of two or more.

[0019] It is preferable that the block copolymer (X) has at least two peaks originating from the block copolymer (X) when gel permeation chromatography (GPC) is measured of a sample containing the block copolymer (X). Having at least two peaks from the block copolymer (X) tends to improve the processability of the rubber composition and improve the balance between abrasion resistance and wet grip performance.

[0020] The block copolymer (X) preferably has a ratio of the molecular weights of the first peak (the fastest elution peak) and the second peak (the second fastest elution peak) (Mn1 / Mn2) of 6.0 or higher in the GPC curve, more preferably 8.0 or higher, and even more preferably 10.0 or higher. When Mn1 / Mn2 is 6.0 or higher, the balance between the abrasion resistance and wet grip performance of the rubber composition tends to improve.

[0021] In the GPC curve of the block copolymer (X), the ratio of the molecular weight of the first peak (which has the fastest elution) to the second peak (which has the second fastest elution) (Mn1 / Mn2) is preferably 100 or less, more preferably 80 or less, and even more preferably 60 or less, from the viewpoint of productivity.

[0022] In the following explanation, block copolymers that show the first peak in the GPC curve, which indicates the earliest elution, will be referred to as block copolymer (A), and block copolymers that show the second peak will be referred to as block copolymer (B).

[0023] <Block copolymer (A)> The block copolymer (A) (in this embodiment, also simply referred to as "copolymer (A)") has at least one polymer block mainly composed of a vinyl aromatic compound. The presence of at least one polymer block mainly composed of a vinyl aromatic compound in the block copolymer (A) tends to improve the abrasion resistance of the rubber composition.

[0024] In this specification, "main component" means that the target monomer unit is contained in the target polymer block in an amount exceeding 70% by mass and not exceeding 100% by mass, preferably between 80% by mass and 100% by mass, and more preferably between 90% by mass and 100% by mass. In this specification, "vinyl bond content" means the proportion of the conjugated diene before hydrogenation that is incorporated in the form of 1,2-bonds and 3,4-bonds, among the 1,2-bonds, 3,4-bonds and 1,4-bonds. The amount of vinyl bonding can be measured by nuclear magnetic resonance spectroscopy (NMR). The amount of vinyl bonding can be arbitrarily controlled by using polar compounds, etc., as described later.

[0025] The content of polymer blocks mainly composed of vinyl aromatic compounds in the block copolymer (A) is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more. When the content of polymer blocks mainly composed of vinyl aromatic compounds in the block copolymer (A) is 5% by mass or more, the abrasion resistance of the rubber composition of this embodiment tends to increase.

[0026] The structure of the block copolymer (A) is not limited to the following, but it is preferable to have a structure represented by the following general formula, for example. (a1-b1)o a1-b1-a2 a1-b1-a2-b2 a1-b1-a2-b2-a3 (a1-b1)pX In the above formula, a1, a2, and a3 represent blocks mainly composed of vinyl aromatic compounds, and b1 and b2 represent blocks mainly composed of conjugated diene compounds, or random copolymer blocks consisting of conjugated diene compounds and vinyl aromatic compounds. Hereafter, these will also be referred to as polymer blocks (a1), (a2), (a3), (b1), and (b2), respectively.

[0027] o is an integer greater than or equal to 1, preferably an integer between 1 and 10, more preferably an integer between 1 and 5. p is an integer greater than or equal to 2, preferably an integer between 2 and 11, more preferably an integer between 2 and 8. X represents a coupling agent residue. Here, a coupling agent residue refers to the residue after a coupling agent has been bonded, which is used to bond polymer blocks (b1) and polymer blocks (b2). The coupling agent is not limited to the following, but examples include polyhalogen compounds and acid esters, which will be described later.

[0028] The block copolymer (A) is more preferably represented by the structure a1-b1-a2-b2. When the block copolymer (A) has the structure a1-b1-a2-b2, its compatibility with the first diene elastomer is improved, and the abrasion resistance of the rubber composition of this embodiment tends to improve.

[0029] In the general formula representing the block copolymer (A) described above, (a1), (a2), and (a3) ​​each independently represent a polymer block mainly composed of a vinyl aromatic compound, and (b1) and (b2) each independently represent a polymer block mainly composed of a conjugated diene compound or a random copolymer block consisting of a vinyl aromatic compound and a conjugated diene compound.

[0030] When the block copolymer (A) is a1-b1-a2-b2, the number average molecular weight of the polymer block (b2) is preferably 20,000 or less, more preferably 17,000 or less, even more preferably 13,000 or less, and even more preferably 10,000 or less. When the number average molecular weight of the polymer block (b2) is 20,000 or less, the fuel efficiency of the rubber composition of this embodiment tends to improve.

[0031] The block copolymer (A) is preferably polymerized by stepwise polymerization. "Polymerized by stepwise polymerization" means that polymerization is carried out sequentially from one end to the opposite end of the final target polymer structure, without using a coupling reaction. It is preferable that the block copolymer (A) does not contain coupling agent residues. This prevents unintended contamination such as uncoupled polymers.

[0032] The number-average molecular weight (Mn1) of the block copolymer (A) is preferably 120,000 or more, more preferably 150,000 or more, and even more preferably 180,000 or more. When the number-average molecular weight (Mn1) of the block copolymer (A) is 120,000 or more, the abrasion resistance of the rubber composition tends to improve. The upper limit of the number average molecular weight (Mn1) of the block copolymer (A) is preferably 350,000 or less, more preferably 300,000 or less, and even more preferably 250,000 or less. When the number average molecular weight (Mn1) of the block copolymer (A) is 350,000 or less, the rubber composition of this embodiment tends to exhibit good processability. The number-average molecular weight (Mn1) of the block copolymer (A) can be measured by GPC. The number-average molecular weight (Mn1) of the hydrogenated copolymer (A) can be controlled to the above numerical range by adjusting conditions such as the amount of monomer added and the amount of polymerization initiator added during the polymerization process.

[0033] The total vinyl aromatic compound content in the block copolymer (A) is preferably 15% to 70% by mass, more preferably 20% to 60% by mass, and even more preferably 25% to 55% by mass. When the total vinyl aromatic compound content in the block copolymer (A) is 15% by mass or more, the rubber composition tends to have good fuel efficiency. When the total vinyl aromatic compound content in the block copolymer (A) is 70% by mass or less, the rubber composition tends to have low hardness. The total content of vinyl aromatic compounds in block copolymer (A) can be measured by proton nuclear magnetic resonance (1H-NMR) spectroscopy. Specifically, it can be measured by the method described in the examples below. The content of vinyl aromatic compounds in the block copolymer (A) can be controlled to the above numerical range by adjusting the amount of vinyl aromatic compounds added during the polymerization process.

[0034] The block copolymer (A) preferably has a random copolymer structure consisting of a vinyl aromatic compound and a conjugated diene compound. When the block copolymer (A) has a random copolymer structure consisting of a vinyl aromatic compound and a conjugated diene compound, the balance between the abrasion resistance and wet grip of the rubber composition tends to be good.

[0035] The weight fraction (RSa) of vinyl aromatic compounds in the random copolymer structure is preferably in the range of 10% to 70% by mass, more preferably in the range of 13% to 60% by mass, even more preferably in the range of 15% to 55% by mass, and still more preferably in the range of 17% to 45% by mass. When (RSa) is within the above range, the rubber composition of this embodiment tends to exhibit good wet grip. The vinyl aromatic content in the random copolymer structure of block copolymer (A) can be measured by nuclear magnetic resonance (NMR). Specifically, it can be measured by the method described in the examples below. The content of vinyl aromatic compounds in the random copolymer structure of block copolymer (A) can be controlled to the above numerical range by adjusting the amount and timing of addition of vinyl aromatic compounds during the polymerization process.

[0036] The amount of vinyl bonds (Va) of the conjugated diene monomer units in the block copolymer (A) is preferably in the range of 25% to 85%, more preferably in the range of 30% to 80%, and even more preferably in the range of 35% to 75%. When the amount of vinyl bonds (Va) of the conjugated diene monomer units in the block copolymer (A) is in the range of 25% to 85%, the rubber composition of this embodiment tends to be more flexible. In this embodiment, the vinyl bond content refers to the total content of 1,2-vinyl bonds (conjugated dienes incorporated into the polymer via 1,2-bonds) and 3,4-vinyl bonds (conjugated dienes incorporated into the polymer via 3,4-bonds) relative to the total conjugated diene (where, if 1,3-butadiene is used as the conjugated diene, it refers to the 1,2-vinyl bond content; if isoprene is used as the conjugated diene, it refers to the 3,4-vinyl bond content).

[0037] The vinyl bond content based on the conjugated diene before hydrogenation can be measured using nuclear magnetic resonance (NMR) spectroscopy. The microstructure (cis, trans, and vinyl ratios) derived from the conjugated diene compound monomer units in the block copolymer (A) can be arbitrarily altered by using polar compounds, etc., as described later.

[0038] The aliphatic double bonds derived from the conjugated diene compound in the block copolymer (A) are preferably hydrogenated, and the hydrogenation rate (also called the hydrogenation rate) of the aliphatic double bonds is preferably 65% ​​or more, more preferably 70% or more, and even more preferably 75% or more. When the block copolymer (A) is hydrogenated, the balance between abrasion resistance and wet grip of the rubber composition of this embodiment tends to be good.

[0039] The hydrogenation rate can be controlled, for example, by the amount of catalyst used during hydrogenation, and the hydrogenation rate can be controlled, for example, by the amount of catalyst used during hydrogenation, the amount of hydrogen feed, pressure, and temperature. The hydrogenation rate of double bonds derived from the conjugated diene compound in block copolymer (A) can be measured by nuclear magnetic resonance (NMR) spectroscopy.

[0040] <Block copolymer (B)> The block copolymer (B) (in this embodiment, also simply referred to as "copolymer (B)") has at least one polymer block mainly composed of a vinyl aromatic compound. The presence of at least one polymer block mainly composed of a vinyl aromatic compound in the block copolymer (B) tends to improve the abrasion resistance of the rubber composition.

[0041] The content of polymer blocks mainly composed of vinyl aromatic compounds in block copolymer (B) is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more. When the content of polymer blocks mainly composed of vinyl aromatic compounds in block copolymer (B) is 5% by mass or more, the strength of the rubber composition of this embodiment tends to increase.

[0042] The structure of the block copolymer (B) is not limited to the following, but it is preferable to have a structure represented by the following general formula, for example. d1 d1-e1 d1-e1-f1 (d1-e1)qY (d1-e1-f1)qY In the above formula, d1 represents a block mainly composed of vinyl aromatic compounds, e1 and f1 represent blocks mainly composed of conjugated diene compounds, or random copolymer blocks consisting of conjugated diene compounds and vinyl aromatic compounds. Hereinafter, these will also be referred to as polymer blocks (d1), (e1), and (f1), respectively.

[0043] The block copolymer (B) is more preferably represented by the d1-e1 structure. When the block copolymer (B) has the d1-e1 structure, the abrasion resistance of the rubber composition of this embodiment tends to increase.

[0044] In the general formula representing the block copolymer (B) described above, (d1) represents a polymer block mainly composed of a vinyl aromatic compound, and (e1) and (f1) independently represent a polymer block mainly composed of a conjugated diene compound or a random copolymer block consisting of a vinyl aromatic compound and a conjugated diene compound.

[0045] q is an integer greater than or equal to 2, preferably an integer between 2 and 11, more preferably an integer between 2 and 8. Y represents a coupling agent residue. Here, a coupling agent residue refers to the residue after a coupling agent has been bonded, which is used to bond polymer blocks (e1) and polymer blocks (f1). The coupling agent is not limited to the following, but examples include polyhalogen compounds and acid esters, which will be discussed later.

[0046] The block copolymer (B) is preferably polymerized by stepwise polymerization. "Polymerized by stepwise polymerization" means that polymerization is carried out sequentially from one end to the opposite end of the final target polymer structure, without using a coupling reaction. It is preferable that the block copolymer (B) does not contain coupling agent residues. This prevents unintended contamination such as uncoupled polymers.

[0047] The number average molecular weight (Mn2) of the block copolymer (B) is preferably 1000 or more from the viewpoint of productivity. The number average molecular weight (Mn2) of the block copolymer (B) is preferably 30,000 or less, more preferably 20,000 or less, and even more preferably 17,000 or less. When the number average molecular weight (Mn2) of the block copolymer (B) is 30,000 or less, the rubber composition of this embodiment tends to exhibit good processability. The number-average molecular weight (Mn2) of the block copolymer (B) can be measured by GPC. The number-average molecular weight (Mn2) of the hydrogenated copolymer (B) can be controlled to the above numerical range by adjusting conditions such as the amount of monomer added and the amount of polymerization initiator added during the polymerization process.

[0048] The total vinyl aromatic compound content in the block copolymer (B) is preferably 15% to 70% by mass, more preferably 20% to 60% by mass, and even more preferably 25% to 55% by mass. When the total vinyl aromatic compound content in the block copolymer (B) is 15% by mass or more, the rubber composition tends to have good fuel efficiency. When the total vinyl aromatic compound content in the block copolymer (B) is 70% by mass or less, the rubber composition tends to have lower hardness.

[0049] The total content of vinyl aromatic compounds in block copolymer (B) can be measured by proton nuclear magnetic resonance (1H-NMR) spectroscopy. Specifically, it can be measured by the method described in the examples below.

[0050] The content of vinyl aromatic compounds in block copolymer (B) can be controlled to the above numerical range by adjusting the amount of vinyl aromatic compounds added during the polymerization process.

[0051] The block copolymer (B) preferably has a random copolymer structure consisting of a vinyl aromatic compound and a conjugated diene compound. When the block copolymer (B) has a random copolymer structure consisting of a vinyl aromatic compound and a conjugated diene compound, the balance between the abrasion resistance and wet grip of the rubber composition tends to be good.

[0052] The weight fraction (RSb) of the vinyl aromatic compound in the random copolymer structure is preferably in the range of 10% to 70% by mass, more preferably in the range of 13% to 60% by mass, even more preferably in the range of 15% to 55% by mass, and still more preferably in the range of 17% to 45% by mass. When (RSb) is within the above range, the rubber composition of this embodiment tends to exhibit good wet grip. The vinyl aromatic content in the random copolymer structure of block copolymer (B) can be measured by nuclear magnetic resonance (NMR). Specifically, it can be measured by the method described in the examples below. The content of vinyl aromatic compounds in the random copolymer structure of block copolymer (B) can be controlled to the above numerical range by adjusting the amount and timing of addition of vinyl aromatic compounds during the polymerization process.

[0053] The amount of vinyl bonds (Vb) of the conjugated diene monomer units in the block copolymer (B) is preferably in the range of 25% to 85%, more preferably in the range of 30% to 80%, and even more preferably in the range of 35% to 75%. When the amount of vinyl bonds (Vb) of the conjugated diene monomer units in the block copolymer (B) is in the range of 25% to 85%, the rubber composition of this embodiment tends to be more flexible.

[0054] In this embodiment, the vinyl bond content refers to the total content of 1,2-vinyl bonds (conjugated dienes incorporated into the polymer via 1,2-bonds) and 3,4-vinyl bonds (conjugated dienes incorporated into the polymer via 3,4-bonds) relative to the total conjugated diene (where, if 1,3-butadiene is used as the conjugated diene, it refers to the 1,2-vinyl bond content; if isoprene is used as the conjugated diene, it refers to the 3,4-vinyl bond content).

[0055] The vinyl bond content based on the conjugated diene before hydrogenation can be measured using nuclear magnetic resonance (NMR) spectroscopy. The microstructure (cis, trans, and vinyl ratios) derived from the conjugated diene compound monomer units in the block copolymer (B) can be arbitrarily altered by using polar compounds, etc., as described later.

[0056] The aliphatic double bonds derived from the conjugated diene compound in the block copolymer (B) are preferably hydrogenated, and the hydrogenation rate (also called the hydrogenation rate) of the aliphatic double bonds is preferably 65% ​​or more, more preferably 70% or more, and even more preferably 75% or more. When the block copolymer (B) is hydrogenated, the balance between abrasion resistance and wet grip of the rubber composition of this embodiment tends to be good.

[0057] The hydrogenation rate can be controlled, for example, by the amount of catalyst used during hydrogenation, and the hydrogenation rate can be controlled, for example, by the amount of catalyst used during hydrogenation, the amount of hydrogen feed, pressure, and temperature. The hydrogenation rate of double bonds derived from the conjugated diene compound in block copolymer (B) can be measured by nuclear magnetic resonance (NMR) spectroscopy.

[0058] The aliphatic double bonds derived from the conjugated diene compound in the block copolymer (X) are preferably hydrogenated, and the hydrogenation rate (also called the hydrogenation rate) of the aliphatic double bonds is preferably 65% ​​or more, more preferably 70% or more, and even more preferably 75% or more. When the block copolymer (X) is hydrogenated, the balance between abrasion resistance and wet grip of the rubber composition of this embodiment tends to be good.

[0059] (Mass ratio of block copolymer (A) to block copolymer (B) in copolymer (X)) The mass ratio (A) / (B) of copolymer (X) to copolymer (A) is preferably 85 / 15 to 30 / 70, more preferably 70 / 30 to 40 / 60, and even more preferably 65 / 35 to 45 / 55. The rubber composition of this embodiment tends to exhibit good processability when copolymer (A) in copolymer (X) is 85% by mass or less. The rubber composition of this embodiment tends to exhibit improved fuel efficiency when copolymer (A) is 30% by mass or more.

[0060] (Hardness of copolymer (X)) The 10s hardness of copolymer (X) measured at 10 seconds using a durometer type A according to JIS K6253 is preferably 25 or less, more preferably 22 or less, and even more preferably 20 or less. When the 10s hardness of copolymer (X) is 25 or less, the wet grip performance of the rubber composition tends to improve.

[0061] (tanδ peak in the viscoelasticity of copolymer (X)) The copolymer (X) preferably has at least one tanδ peak in the range of -30°C to 40°C in viscoelasticity measurements (1 Hz), more preferably has a tanδ peak in the range of -25°C to 30°C, and even more preferably has a tanδ peak in the range of -20°C to 25°C. When the copolymer (X) has at least one tanδ peak in the range of -30°C to 40°C, the wet grip performance of the rubber composition of this embodiment tends to improve.

[0062] (Method for producing block copolymer (A) and block copolymer (B)) The methods for producing copolymer (A) and copolymer (B) are not limited to the following, but include, for example, the methods described in Japanese Patent Publication No. 36-19286, Japanese Patent Publication No. 43-17979, Japanese Patent Publication No. 46-32415, Japanese Patent Publication No. 49-36957, Japanese Patent Publication No. 48-2423, Japanese Patent Publication No. 48-4106, Japanese Patent Publication No. 51-49567, Japanese Patent Publication No. 59-166518, etc.

[0063] Furthermore, the methods for producing copolymer (A) and copolymer (B) are not limited to the following, but include: (1) a method of solution polymerization of copolymer (A) and copolymer (B) and mixing the solutions containing the polymers; (2) a method of desolventing and decatalyzing copolymer (A) and copolymer (B) and then mixing them; (3) a method of adding the polymerization initiator in two stages during the polymerization reaction; (4) a method of adding a denaturing agent that reacts with the living ends or a protic reagent such as alcohol as a polymerization inhibitor during the polymerization reaction in a molar amount insufficient for the living ends to stop the reaction of some of the living ends; and (5) a method of adding an equimolar amount of a denaturing agent or a protic reagent such as alcohol as a polymerization inhibitor to the living ends after the polymerization reaction to stop the reaction of all living ends, and then adding a polymerization initiator and monomer to the solution and carrying out polymerization. In method (1) above, either a method in which the polymerization solutions of copolymer (A) and copolymer (B) are mixed before the hydrogenation reaction and then the hydrogenation reaction is carried out, or a method in which copolymer (A) and copolymer (B) are hydrogenated separately and then their respective solutions are mixed, can be applied. Furthermore, the mixing ratio of copolymer (A) and copolymer (B) can be controlled by adjusting the concentration of each polymerization solution and the amount of each solution mixed. In the method described in (3) above, the mixing ratio of copolymer (A) and copolymer (B) can be arbitrarily controlled by adjusting the feed rate of the vinyl aromatic compound and the conjugated diene compound, the amount of polymerization initiator added in two stages, the timing of the second stage of polymerization initiator addition, and so on. In the method described in (4) above, the mixing ratio and structure of copolymer (A) and copolymer (B) can be arbitrarily controlled by adjusting the feed rate and feed composition of the vinyl aromatic compound and the conjugated diene compound, the amount and timing of the addition of the modifier or polymerization inhibitor added during the process, etc. Copolymer (A) is a low molecular weight material with minimal molecular entanglement. Therefore, mixing it before desolventing, as in methods (1), (3), (4), and (5) above, allows for a higher rate of desolventing and finishing processes. The methods described in (3) and (4) above allow for the simultaneous production of copolymer (A) and copolymer (B), and since the production process can be reduced compared to the case where copolymer (A) and copolymer (B) are produced separately, production efficiency can be improved.

[0064] When producing a copolymer of styrene and butadiene by batch polymerization using a tank reactor equipped with a stirring device and a jacket, if copolymer (A) is a1-b1-a2-b2 and copolymer (B) is d1-e1, it is preferable that the b2 block and the e1 block have the same structure and the same molecular weight, that the a2 block and the d1 block are composed of the same vinyl aromatic compound, and that the molecular weight of the a2 block is greater than the molecular weight of the d1 block.

[0065] Furthermore, when polymerization is carried out by the method described in (3) above, the timing of the addition of the second-stage initiator depends on the ratio of the molecular weights of block a2 and block d1, and it is preferable that the addition is made when the polymerization transfer rate of the vinyl aromatic compound in block a2 reaches 100 × (molecular weight of block d1) / (molecular weight of block a2) (%).

[0066] The copolymer before hydrogenation is not limited to the following, but can be obtained, for example, by a method of living anionic polymerization using a predetermined monomer with a polymerization initiator such as an organoalkali metal compound in a hydrocarbon solvent. The hydrocarbon solvent is not particularly limited and includes, for example, aliphatic hydrocarbons such as n-butane, isobutane, n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclohexane, cycloheptane, and methylcycloheptane; and aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene.

[0067] Generally, organic alkali metal compounds known to exhibit anionic polymerization activity towards conjugated diene compounds and vinyl aromatic compounds can be used as polymerization initiators. Examples include aliphatic hydrocarbon alkali metal compounds having 1 to 20 carbon atoms, aromatic hydrocarbon alkali metal compounds having 1 to 20 carbon atoms, and organic amino alkali metal compounds having 1 to 20 carbon atoms. The alkali metals included in the polymerization initiator are not limited to those listed below, but examples include lithium, sodium, and potassium. Note that one or more alkali metals may be present in a single molecule.

[0068] Polymerization initiators include, but are not limited to, n-propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, n-pentyllithium, n-hexyllithium, benzyllithium, phenyllithium, tolyllithium, reaction products of diisopropenylbenzene and sec-butyllithium, and reaction products of divinylbenzene, sec-butyllithium and a small amount of 1,3-butadiene.

[0069] Furthermore, lithium compounds containing 1-(t-butoxy)propyllithium and a fraction of isoprene monomers inserted therein to improve solubility, as disclosed in U.S. Patent No. 5,708,092, siloxy group-containing alkyllithiums such as 1-(t-butyldimethylsiloxy)hexyllithium disclosed in British Patent No. 2,241,239, amino group-containing alkyllithiums disclosed in U.S. Patent No. 5,527,753, diisopropylamide lithium, and aminolithium compounds such as hexamethyldisilazidolithium can also be used.

[0070] The amount of lithium compound used as a polymerization initiator depends on the molecular weight of the target copolymer, but is preferably 0.005 to 6.4 phr (parts by mass per 100 parts by mass of monomer), and more preferably 0.005 to 2.6 phr.

[0071] When copolymerizing a conjugated diene compound and a vinyl aromatic compound using an organoalkali metal compound as a polymerization initiator, tertiary amine compounds or ether compounds can be added to adjust the content of vinyl bonds (1,2-bonds or 3,4-bonds) in the conjugated diene monomer units incorporated into the copolymer, or to adjust the random copolymerization properties between the conjugated diene compound and the vinyl aromatic compound.

[0072] The tertiary amine compound is not particularly limited, but examples include the compound represented by the following formula. R1R2R3N (In the formula, R1, R2, and R3 are hydrocarbon groups having 1 to 20 carbon atoms or hydrocarbon groups having a tertiary amino group.) The compounds represented by the above formula are not limited to the following, but include, for example, trimethylamine, triethylamine, tributylamine, N,N-dimethylaniline, N-ethylpiperidine, N-methylpyrrolidine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, 1,2-dipiperidinoethane, trimethylaminoethylpiperazine, N,N,N',N'',N''-pentamethylethylenetriamine, and N,N'-dioctyl-p-phenylenediamine. Among these, N,N,N',N'-tetramethylethylenediamine is preferred.

[0073] Furthermore, linear ether compounds, cyclic ether compounds, and the like can be used as ether compounds. Examples of linear ether compounds include dimethyl ether, diethyl ether, diphenyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, and other ethylene glycol dialkyl ether compounds, as well as diethylene glycol dialkyl ether compounds such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol dibutyl ether. Examples of cyclic ether compounds include tetrahydrofuran, dioxane, 2,5-dimethyloxolane, 2,2,5,5-tetramethyloxolane, 2,2-bis(2-oxolanyl)propane, and alkyl ethers of furfuryl alcohol.

[0074] The amount of tertiary amine compound or ether compound used is preferably 0.1 to 4 (moles / mol of alkali metal), more preferably 0.2 to 3 (moles / mol of alkali metal) relative to the polymerization initiator of the organoalkali metal compound.

[0075] In the manufacturing process of copolymer (A) and copolymer (B), sodium alkoxide may be present during copolymerization. The sodium alkoxide is not limited to the following, but examples include compounds represented by the following formula. Sodium alkoxides having an alkyl group with 3 to 6 carbon atoms are particularly preferred, and sodium t-butoxide and sodium t-pentoxide are more preferred. NaOR (In the formula, R is an alkyl group having 2 to 12 carbon atoms.)

[0076] The amount of sodium alkoxide used in the polymerization process of copolymers (A) and (B) is preferably 0.01 or more and less than 0.1 (molar ratio) relative to the vinyl bond amount adjusting agent (tertiary amine compound or ether compound), more preferably 0.01 or more and less than 0.08 (molar ratio), even more preferably 0.03 or more and less than 0.08 (molar ratio), and even more preferably 0.04 or more and less than 0.06 (molar ratio). When the amount of sodium alkoxide is within the above range, it tends to be possible to produce copolymers with a high productivity rate that have a copolymer block containing conjugated diene monomer units with a high vinyl bond amount and a polymer block mainly composed of vinyl aromatic monomer units with a narrow molecular weight distribution, and that have a narrow molecular weight distribution.

[0077] The copolymerization method of a conjugated diene compound and a vinyl aromatic compound using an organoalkali metal compound as a polymerization initiator is not particularly limited and may be batch polymerization, continuous polymerization, or a combination thereof. The polymerization temperature is not particularly limited, but is usually 0 to 180°C, preferably 30 to 150°C.

[0078] The time required for polymerization varies depending on the conditions, but is usually within 48 hours, preferably 0.1 to 10 hours. Polymerization is also preferably carried out under an inert gas atmosphere such as nitrogen gas. The polymerization pressure is not particularly limited and should be within a range sufficient to maintain the monomer and solvent in the liquid phase within the above polymerization temperature range.

[0079] Furthermore, a coupling agent with two or more functional groups may be added in the required amount at the end of polymerization to carry out the coupling reaction. The coupling agent with two or more functional groups is not particularly limited, and known agents can be used. Examples of difunctional coupling agents include, but are not limited to, dihalogen compounds such as dimethyldichlorosilane and dimethyldibromosilane, and acid esters such as methyl benzoate, ethyl benzoate, phenyl benzoate, and phthalates. Examples of polyfunctional coupling agents with three or more functional groups include, but are not limited to, 1,1,1,2,2-pentachloroethane, perchloroethane, pentachlorobenzene, perchlorobenzene, octabromodiphenyl ether, decabromodiphenyl ether, polyalcohols with three or more valent properties, polyvalent epoxy compounds such as epoxidized soybean oil and diglycidylbisphenol A, epoxy group-containing compounds with two to six functional properties, carboxylic acid esters, polyvinyl compounds such as divinylbenzene, silicon halide compounds represented by the formula R1(4-n)SiXn (where R1 is a hydrocarbon group having 1 to 20 carbon atoms, X is a halogen, and n is an integer of 3 or 4), and tin halide compounds. Examples of silicon halide compounds include, but are not limited to, methylsilyl trichloride, t-butylsilyl trichloride, silicon tetrachloride, and their brominated products. Examples of tin halide compounds include, but are not limited to, methyltin trichloride, t-butyltin trichloride, and polyvalent halogen compounds such as tin tetrachloride. Dimethyl carbonate and diethyl carbonate can also be used.

[0080] Copolymer (A) and copolymer (B) may be obtained by adding a modifying agent that generates a functional group-containing atomic group to the living end of a block copolymer obtained by the method described above. Examples of functional group-containing atomic groups include, but are not limited to, atomic groups containing at least one functional group selected from the group consisting of hydroxyl group, carbonyl group, thiocarbonyl group, acid halide group, acid anhydride group, carboxyl group, thiocarboxylate group, aldehyde group, thioaldehyde group, carboxylic acid ester group, amide group, sulfonic acid group, sulfonic acid ester group, phosphoric acid group, phosphoric acid ester group, amino group, imino group, nitrile group, pyridyl group, quinoline group, epoxy group, thioepoxy group, sulfide group, isocyanate group, isothiocyanate group, silicon halide group, silanol group, alkoxysilicon group, tin halide group, alkoxytin group, and phenyltin group.

[0081] Modifying agents that generate functional group-containing atomic groups include, but are not limited to, tetraglycidylmetoxylendiamine, tetraglycidyl-1,3-bisaminomethylcyclohexane, ε-caprolactone, δ-valerolactone, 4-methoxybenzophenone, γ-glycidoxyethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyldimethylphenoxysilane, bis(γ-glycidoxypropyl)methylpropoxysilane, 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, N,N'-dimethylpropyleneurea, N-methylpyrrolidone, and the like. The amount of modifying agent added is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and even more preferably 0.3 to 10 parts by mass, per 100 parts by mass of the copolymer before modification. The addition reaction temperature for the denaturing agent is preferably 0 to 150°C, more preferably 20 to 120°C. The time required for the denaturation reaction varies depending on the denaturation reaction conditions, but is preferably within 24 hours, and more preferably 0.1 to 10 hours.

[0082] Copolymer (A) is preferably produced by carrying out a hydrogenation step after the polymerization step described above, or after the modification step described above. The hydrogenation catalyst used to produce copolymer (A) is not particularly limited, and for example, hydrogenation catalysts described in Japanese Patent Publication No. 42-8704, Japanese Patent Publication No. 43-6636, Japanese Patent Publication No. 63-4841, Japanese Patent Publication No. 1-37970, Japanese Patent Publication No. 1-53851, Japanese Patent Publication No. 2-9041, etc., can be used. Preferred hydrogenation catalysts include mixtures of titanocene compounds and / or reducing organometallic compounds. The titanocene compounds are not particularly limited, but examples include the compounds described in Japanese Patent Publication No. 8-109219, and specifically include compounds having at least one ligand having a (substituted) cyclopentadienyl structure, an indenyl structure, and a fluorenyl structure, such as biscyclopentadienyl titanium dichloride and monopentamethylcyclopentadienyl titanium trichloride. Reducing organometallic compounds are not particularly limited, but examples include organoalkali metal compounds such as organolithium, organomagnesium compounds, organoaluminum compounds, organoboron compounds, and organozinc compounds. The reaction temperature for hydrogenation is typically 0 to 200°C, preferably 30 to 150°C. The pressure of the hydrogen used in the hydrogenation reaction is preferably 0.1 to 15 MPa, more preferably 0.2 to 10 MPa, and even more preferably 0.3 to 5 MPa. The reaction time for hydrogenation is usually 3 minutes to 10 hours, preferably 10 minutes to 5 hours. Hydrogenation reactions can be carried out in batch processes, continuous processes, or a combination of both.

[0083] Copolymer (B) may be produced by carrying out a hydrogenation step after the polymerization step described above, or after the modification step described above. The hydrogenation catalyst used to produce copolymer (B) is not particularly limited, and for example, hydrogenation catalysts described in Japanese Patent Publication No. 42-8704, Japanese Patent Publication No. 43-6636, Japanese Patent Publication No. 63-4841, Japanese Patent Publication No. 1-37970, Japanese Patent Publication No. 1-53851, Japanese Patent Publication No. 2-9041, etc., can be used. Preferred hydrogenation catalysts include mixtures of titanocene compounds and / or reducing organometallic compounds. The titanocene compounds are not particularly limited, but examples include the compounds described in Japanese Patent Publication No. 8-109219, and specifically include compounds having at least one ligand having a (substituted) cyclopentadienyl structure, an indenyl structure, and a fluorenyl structure, such as biscyclopentadienyl titanium dichloride and monopentamethylcyclopentadienyl titanium trichloride. Reducing organometallic compounds are not particularly limited, but examples include organoalkali metal compounds such as organolithium, organomagnesium compounds, organoaluminum compounds, organoboron compounds, and organozinc compounds. The reaction temperature for hydrogenation is typically 0 to 200°C, preferably 30 to 150°C. The pressure of the hydrogen used in the hydrogenation reaction is preferably 0.1 to 15 MPa, more preferably 0.2 to 10 MPa, and even more preferably 0.3 to 5 MPa. The reaction time for hydrogenation is usually 3 minutes to 10 hours, preferably 10 minutes to 5 hours. Hydrogenation reactions can be carried out in batch processes, continuous processes, or a combination of both.

[0084] Catalyst residue may be removed from the reaction solution after the hydrogenation step, if necessary. When hydrogenated copolymers are produced by anionic living polymerization, the polymerization initiators and the metal atom-containing compounds in the hydrogenation catalysts used in the aforementioned hydrogenation reaction tend to react with moisture in the air during the desolvent removal process, etc., to form specific metal compounds that remain in the hydrogenated copolymer.

[0085] The method for reducing the amount of residual metal in the rubber composition and its cured product of this embodiment is not particularly limited and can be any conventionally known method. For example, a method of neutralizing the hydrogenation catalyst residue by adding water and carbon dioxide after the hydrogenation reaction of copolymers (A) and (B); or a method of neutralizing the hydrogenation catalyst residue by adding an acid in addition to water and carbon dioxide. Specifically, the method described in Japanese Patent Application No. 2014-557427 can be applied. Even when these metal removal methods are used, water containing hydroxides of metal compounds is mixed in during the desolventing process of copolymers (A) and (B), so it is common for about 1 to 15 ppm to be present. Therefore, it is preferable to remove 20% or more of the amount of metal added to copolymers (A) and (B), more preferably 30% or more, even more preferably 40% or more, even more preferably 50% or more, and even more preferably 60% or more.

[0086] Furthermore, it is possible to reduce the amount of residual metal in copolymers (A) and (B) by reducing the amount of polymerization initiator and hydrogenation catalyst added. However, reducing the amount of polymerization initiator increases the molecular weight of copolymers (A) and (B), and if it falls outside the aforementioned preferred molecular weight range, the heat resistance of the cured product tends to decrease. Also, when performing the hydrogenation reaction, reducing the amount of hydrogenation catalyst leads to a longer hydrogenation reaction time and a higher hydrogenation reaction temperature, which tends to significantly reduce productivity.

[0087] Methods for separating copolymers (A) and (B) from the solvent are not limited to the following, but include, for example, adding a polar solvent that is a poor solvent for copolymers (A) and (B), such as acetone or alcohol, to a solution of copolymers (A) and (B) to precipitate and recover the copolymers (A) and (B); adding a solution of copolymers (A) and (B) to hot water under stirring and removing the solvent by steam stripping; or directly heating a solution of copolymers (A) and (B) to remove the solvent by distillation.

[0088] Copolymer (A) and copolymer (B) may contain antioxidants on their surface and / or inside, for example, by adding antioxidants during manufacturing.

[0089] Antioxidants include, but are not limited to, phenolic antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, amine-based antioxidants, and the like. Specifically, 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butyl-phenyl)propionate, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane], tris-(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 4,4'-butylidene-bis-(3-methyl-6-t-butylphenol), 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methyl [Propionyloxy(2-phenyl)propionyloxy)-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane, triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)1,3,5-triazine, pentaerythrityl-tetrakis[3 -(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamamide), 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3,5-di-t-butyl-4 -Hydroxybenzylphosphonate ethyl) calcium and polyethylene wax (50%) mixture, octylated diphenylamine, 2,4-bis[(octylthio)methyl]-o-cresol, isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, butyrate, 3,3-bis(3-t-butyl-4-hydroxyphenyl)ethylene ester, 1,1,3-tris-(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-tris(4-t-butyl-3-hydroxy-2,Examples include 6-dimethylbenzyl isocyanurate, 2-t-butyl-6-(3'-t-butyl-5'-methyl-2'-hydroxybenzyl)-4-methylphenyl acrylate, and 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)-ethyl]-4,6-di-t-pentylphenyl acrylate.

[0090] The polymerization inhibitor is not particularly limited, but examples include alcohols such as water, methanol, ethanol, isopropanol, 2-ethylhexanol, heptanol, and mixtures thereof.

[0091] Copolymer (A) and / or copolymer (B) may be pelletized. These may be pelletized individually or as a mixture. Examples of pelletizing methods include: extruding copolymer (A) and / or copolymer (B) in strand form from a single-screw or twin-screw extruder and cutting them underwater with a rotating blade installed in front of the die; extruding copolymer (A) and / or (B) in strand form from a single-screw or twin-screw extruder, water-cooling or air-cooling, and then cutting them with a strand cutter; melting and mixing in an open roll or Banbury mixer, forming into a sheet with a roll, further cutting the sheet into strips, and then cutting into cubic pellets with a pelletizer. The size and shape of the copolymer (A) and / or copolymer (B) pellets are not particularly limited.

[0092] Copolymer (A) and / or copolymer (B) may, if necessary, be compounded with a pellet blocking inhibitor in the pellets for the purpose of preventing pellet blocking. Examples of pellet blocking inhibitors, but not limited to the following, include calcium stearate, magnesium stearate, zinc stearate, polyethylene, polypropylene, ethylene bisstearylamide, talc, amorphous silica, etc. From the viewpoint of ion migration, EBS, polyethylene, and polypropylene are preferred as pellet blocking inhibitors.

[0093] The preferred amount of pellet blocking inhibitor is 500 to 6000 ppm relative to copolymer (A) and / or (B), and a more preferred amount is 1000 to 5000 ppm. The pellet blocking inhibitor is preferably incorporated on the surface of the pellets, but it can also be included to some extent inside the pellets.

[0094] (Molecular weight distribution of block copolymer (A) and block copolymer (B)) The molecular weight distribution (Mwa / Mna) of copolymer (A) is preferably 1.01 to 8.0, more preferably 1.01 to 6.0, and even more preferably 1.01 to 5.0. When the molecular weight distribution is within the above range, the dimensional stability of the rubber composition of this embodiment tends to be good.

[0095] The shape of the molecular weight distribution of copolymer (A) measured by GPC is not particularly limited; it may have a polymodal molecular weight distribution with two or more peaks, or a monomodal molecular weight distribution with one peak. A monomodal molecular weight distribution of copolymer (A) is preferable. When the molecular weight distribution of copolymer (A) is monomodal, the rubber composition tends to have excellent heat resistance. The weight-average molecular weight (Mwa) and molecular weight distribution (Mwa / Mna; ratio of weight-average molecular weight (Mwa) to number-average molecular weight (Mna)) of copolymer (A) can be determined using the molecular weight of the peaks in the chromatogram measured by GPC using the method described in the examples below, and a calibration curve (created using the peak molecular weight of standard polystyrene) obtained from measurements of commercially available standard polystyrene.

[0096] The molecular weight distribution (Mwb / Mnb) of copolymer (B) is preferably 1.01 to 8.0, more preferably 1.01 to 6.0, and even more preferably 1.01 to 5.0. When the molecular weight distribution is within the above range, the dimensional stability of the rubber composition of this embodiment tends to be good.

[0097] The shape of the molecular weight distribution of copolymer (B) measured by GPC is not particularly limited; it may have a polymodal molecular weight distribution with two or more peaks, or a monomodal molecular weight distribution with one peak. A monomodal molecular weight distribution of copolymer (B) is preferable. When the molecular weight distribution of copolymer (B) is monomodal, the rubber composition tends to have excellent heat resistance. The weight-average molecular weight (Mwb) and molecular weight distribution [Mwb / Mnb; ratio of weight-average molecular weight (Mwb) to number-average molecular weight (Mnb)] of copolymer (B) can be determined using the molecular weight of the peaks in the chromatogram measured by GPC using the method described in the examples below, and a calibration curve (created using the peak molecular weight of standard polystyrene) obtained from measurements of commercially available standard polystyrene.

[0098] (Any resin component) The rubber composition of this embodiment may contain any other resin component in addition to the solid rubber component described above. If the composition of this embodiment contains any resin component other than the solid rubber component described above, the amount is preferably less than 25 parts by mass of the resin component per 100 parts by mass of the solid rubber component, more preferably less than 20 parts by mass, even more preferably less than 15 parts by mass, even more preferably less than 10 parts by mass, and even more preferably less than 5 parts by mass. For example, it is preferably 0.5 to 5 parts by mass, and more preferably 0 parts by mass.

[0099] Other optional resin components that can be used selectively include, for example, cyclopentadiene homopolymer or copolymer resins (referred to as CPD), dicyclopentadiene homopolymer or copolymer resins (referred to as DCPD or (D)CPD), terpene homopolymer or copolymer resins, rosin-derived resins, rosin / rosin esters, pinene homopolymer or copolymer resins, C5 fraction homopolymer or copolymer resins, C9 fraction homopolymer or copolymer resins, α-methylstyrene homopolymer or copolymer resins, and combinations thereof, as well as substituted or unsubstituted resins of these resins. The aforementioned optional resin components are preferably (D)CPD / vinyl aromatic copolymer resin, (D)CPD / terpene copolymer resin, terpene / phenol copolymer resin, (D)CPD / pinene copolymer resin, pinene / phenol copolymer resin, (D)CPD / C5 fraction copolymer resin, (D)CPD / C9 fraction copolymer resin, terpene / vinyl aromatic copolymer resin, terpene / phenol copolymer resin, pinene / vinyl aromatic copolymer resin, pinene / phenol resin, C5 fraction / vinyl aromatic copolymer resin, and combinations thereof. In particular, terpene resins, rosin esters, and oligoester resins are preferred.

[0100] (Any plasticizer component) The rubber composition of this embodiment may further contain any plasticizer component. "Plasticizer" (also referred to as process oil) refers to petroleum-derived process oils and synthetic plasticizers used to stretch the solid rubber component described above and improve the processability of the rubber composition of this embodiment. Examples of plasticizers, though not limited to the following, include fatty acid esters, hydrocarbon process oils, tall oil pitch and modified tall oil pitch, and combinations thereof. The amount of plasticizer is preferably 0 to 35 parts by mass, more preferably 5 to 25 parts by mass, and even more preferably less than 20 parts by mass, per 100 parts by mass of the solid rubber component. The plasticizer is more preferably a modified tall oil pitch selected from the group consisting of pitch esters, decarboxylated tall oil pitch, tall oil pitch soap, heat-treated tall oil pitch, and heat and catalyst-treated tall oil pitch. Plasticizers include both extender oils contained in the solid rubber component and process oils added during mixing. Suitable process oils include aromatic oils, paraffinic oils, naphthenic oils, low PCA oils such as MES, TDAE, and heavy naphthenic oils, as well as vegetable oils such as sunflower oil, soybean oil, and safflower oil. Examples of low PCA oils include those with a polycyclic aromatic content of less than 3% by weight. Suitable vegetable oils include, for example, soybean oil, sunflower oil, and rapeseed oil in the form of esters containing some degree of unsaturation.

[0101] In this embodiment, the rubber composition preferably contains the above-mentioned arbitrary resins and plasticizers in total at 70 parts by mass or less, more preferably 65 parts by mass or less, and most preferably 60 parts by mass or less, per 100 parts by mass of the solid rubber component. This tends to reduce the processability and hardness of the rubber composition.

[0102] (Coupling agent) The rubber composition of this embodiment may further contain a coupling agent. The coupling agent is a substance that can promote stable chemical and / or physical interactions between two types of substances that would not normally interact, for example, between a filler such as silica and a solid rubber component. The coupling agent may be pre-mixed with or reacted with the filler particles, or it may be added to the rubber mixture during the rubber / silica processing stage, i.e., the mixing stage. Examples of coupling agents include, but are not limited to, sulfur-based coupling agents, organic peroxide-based coupling agents, inorganic coupling agents, polyamine coupling agents, resin coupling agents, sulfur compound-based coupling agents, oxime-nitrosamine-based coupling agents, and sulfur. In particular, those that are at least bifunctional are preferred. Examples of such coupling agents include organosilanes or polyorganosiloxanes. In particular, silane sulfides, silane polysulfides, and combinations thereof are preferred. The amount of coupling agent added is preferably 1 to 20 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 3 to 15 parts by mass, per 100 parts by mass of the solid rubber component.

[0103] (Filler) The rubber composition of this embodiment may further contain 50 to 200 parts by mass of filler per 100 parts by mass of solid rubber component. Examples of fillers, but not limited to those listed below, include calcium carbonate, carbon nanotubes, clay, mica, silica, silicate, talc, titanium dioxide, alumina, zinc oxide, starch, wood flour, carbon black, or mixtures thereof, with an average particle size of 0.0001 μm to 100 μm. Other fillers, but not limited to those listed below, include granular fillers such as ultra-high molecular weight polyethylene (UHMWPE), granular polymer gels, and plasticized starch composite fillers, which are known in the art. The filler may be surface-treated, for example, silica material coated with or reacted with a terpene-derived silane, such as the alkoxyterpene epoxysilane disclosed in U.S. Patent No. 4,738,892. Furthermore, the filler may be treated in the presence of a functional moiety such as at least one of organosilane, organotitanate, or organozirconate. Specifically, prior to being incorporated into the rubber composition, the filler may first be surface-treated with a coupling agent such as aminosilane, hexamethyldisilazane (HMDS), or vinyltriethoxysilane, or physically coated or covered with a resin. The rubber composition of this embodiment may further contain 5 to 100 parts by mass of carbon black per 100 parts by mass of solid rubber component. The iodine adsorption amount of carbon black is typically in the range of 9 to 145 g / kg, and the DBP value is in the range of 34 to 150 cm³ / 100 g. The rubber composition of this embodiment preferably contains 5 to 125 parts by mass, more preferably 20 to 60 parts by mass, even more preferably 30 to 50 parts by mass, and even more preferably 40 to 45 parts by mass of filler per 100 parts by mass of solid rubber component.

[0104] (Crosslinking agent) The solid rubber components in the rubber composition of this embodiment may be crosslinked by adding curing agents, such as sulfur, metals, metal oxides such as zinc oxide, peroxides, organometallic compounds, radical initiators, fatty acids, and other substances common in the art. Zinc oxide is added, for example, in an amount of about 5 parts by mass per 100 parts by mass of solid rubber component to form a zinc halide, which then acts as a catalyst for the vulcanization of the rubber compound. Known curing methods can be applied, including peroxide curing systems, resin curing systems, and polymer crosslinking by heat or radiation. Accelerators, activators, and retarders can also be used in the curing process. The amount of crosslinking agent added is preferably 0.3 to 10 parts by mass, more preferably 0.5 to 5.0 parts by mass, and even more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the solid rubber component.

[0105] (Other additives) The rubber composition of this embodiment may also contain other components known in the art, such as curing aids like sulfur donors, accelerators, activators and retarders, processing additives, pigments, fatty acids, zinc oxide, waxes, antioxidants and ozone degradation inhibitors, and various other additives such as compounding accelerators. It is preferable that these other additives are present in amounts of 10 parts by mass or less per 100 parts by mass of the solid rubber component.

[0106] (Method for molding rubber compositions) The rubber composition of this embodiment can be molded by methods known to those skilled in the art of rubber mixing. For example, the components of the rubber composition are typically mixed in two steps, which consist of at least one non-production step followed by a production mixing step. The final curing agent, such as a sulfur vulcanizing agent, is typically mixed in the final stage, conventionally referred to as the "production" mixing stage, but this final mixing is performed at a lower temperature than the mixing temperature in the preceding non-production mixing stage, i.e., the final target temperature. The rubber composition can be subjected to a thermomechanical mixing process. This thermomechanical mixing process generally involves machining in a mixer or extruder for a period of time suitable for creating a temperature environment of 140°C to 190°C. The appropriate duration of the thermomechanizing process varies depending on the operating conditions and the volume and properties of the components, but it is preferable to perform the thermomechanizing process for, for example, 1 to 20 minutes.

[0107] (Application) The rubber composition of this embodiment can be applied to various applications, such as tire applications including tire treads, undertreads, carcasses, sidewalls, and bead sections; sealing materials such as packings, gaskets, weatherstrips, and O-rings; interior and exterior surface materials for various vehicles such as automobiles, ships, aircraft, and railways; building materials; vibration-damping rubbers for industrial machinery and equipment; various hoses and hose covers such as diaphragms, rolls, radiator hoses, and air hoses; belts such as power transmission belts; linings; dust boots; medical equipment materials; fenders; insulating materials for electric wires; and other industrial products. In particular, the crosslinked polymer obtained using the rubber composition of this embodiment has an excellent balance of rigidity, wear resistance, and viscoelastic properties, making it suitable for use as a material for tire treads and sidewalls.

[0108] (Hardness of the rubber composition of this embodiment) The instantaneous hardness (instantaneous value) of the rubber composition of this embodiment, measured according to JIS K6253 using a durometer type A, is preferably 45 to 75, and more preferably 50 to 70. When the instantaneous hardness of the rubber composition of this embodiment is 45 to 75, the balance between wet grip performance and abrasion resistance tends to improve.

[0109] (Shape of the tanδ peak of the rubber composition of this embodiment) The rubber composition of this embodiment preferably has two or more tanδ peaks at 50°C or below in viscoelasticity measurements (1 Hz), or has one main peak plus a shoulder peak. When the tanδ peak of the rubber composition of this embodiment exhibits the above shape, it tends to have an excellent balance between abrasion resistance and wet grip performance. [Examples]

[0110] 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.

[0111] [Method for determining the structure of the first diene elastomer, block copolymer (A), and block copolymer (B), and method for measuring their physical properties] ((1) Content of vinyl aromatic monomer units (styrene) in the first diene elastomer, block copolymer (A), and block copolymer (B)) The copolymer before hydrogenation was used and measured by proton nuclear magnetic resonance (1H-NMR). The measurement was performed using a JNM-LA400 (manufactured by JEOL), with deuterated chloroform as the solvent, a sample concentration of 50 mg / mL, an observation frequency of 400 MHz, tetramethylsilane as the chemical shift reference, a pulse delay of 2.904 seconds, 64 scans, a pulse width of 45°, and a measurement temperature of 26°C. The styrene content was calculated using the integrated total styrene aromatic signal in the spectrum at 6.2–7.5 ppm.

[0112] ((2) Amount of vinyl bonding in the first diene elastomer, block copolymer (A), and block copolymer (B)) The amount of vinyl bonding was measured using proton nuclear magnetic resonance (1H-NMR) spectroscopy with the copolymer before hydrogenation. The measurement conditions and the method for processing the measurement data were the same as in (1) above. The amount of vinyl bonds in copolymer (A) and copolymer (B) is calculated by determining the integral value per H for each bond type from the integral values ​​of the signals attributed to 1,4-bonds and 1,2-bonds, and then dividing the integral value of the 1,2-bond by the sum of the integral values ​​of the 1,4-bonds and 1,2-bonds (1,2-bonds are the case for butadiene; in the case of isoprene, it would be 3,4-bonds).

[0113] ((3) Content of vinyl aromatic monomer units in random polymer blocks (RS) and content of polymer blocks mainly composed of vinyl aromatic monomer units (BS)) The following abbreviations are defined: BSa: Content of polymer blocks mainly consisting of vinyl aromatic monomer units in copolymer (A) BSb: Content of polymer blocks mainly composed of vinyl aromatic monomer units of copolymer (B) RSa: Mass fraction of vinyl aromatic monomer units in random polymer blocks of copolymer (A) RSb: Mass fraction of vinyl aromatic monomer units in random polymer blocks of copolymer (B) Copolymer (A) and copolymer (B) were used as measurement samples, and the vinyl aromatic monomer units contained in each were distinguished from those derived from "polymer blocks mainly composed of vinyl aromatic monomer units" and those derived from "random copolymer structures consisting of vinyl aromatic compounds and conjugated diene compounds" using proton nuclear magnetic resonance (1H-NMR, ECS400, JOEL RESONABCE). Deuterated chloroform was used as the solvent, the sample concentration was 50 mg / mL, the observation frequency was 400 MHz, tetramethylsilane was used as the chemical shift reference, the pulse delay was 2.904 seconds, the number of scans was 256, and the measurement temperature was 23°C. After calculating the random and blocky aromatics from the integrated intensity of the signals attributed to aromatics, and then the integrated value per 1H for each bonding mode, the total styrene content was calculated, and the styrene content in the random polymer blocks (hereinafter referred to as random styrene content) (RSa)(RSb) and the styrene block content in the copolymer (BSa)(BSb) were calculated. The calculation method is as follows. Styrene block strength (b-St strength) = (cumulative value from 6.9 ppm to 6.3 ppm) / 2 Random styrene strength (r-St strength) = (cumulative value from 7.5 ppm to 6.9 ppm) - 3 × (b - St) Ethylene-butylene strength (EB strength) = Total cumulative value - 3 × {(b-St intensity) + (r-St intensity)} / 8 Styrene block content (BS) =104×(b-St strength) / [104×{(b-St strength)+(r-St strength)}+56×(EB strength)] Random Styrene Amount (RS) =104×(r-St strength) / {104×(r-St strength)+56×(EB strength)}

[0114] ((4) Number average molecular weight (Mn)) The number-average molecular weights of the first diene elastomer, copolymer (A), and copolymer (B) were measured using GPC [instrument: Tosoh HLC8220, column TSKgel SuperH-RC x 2]. Tetrahydrofuran was used as the solvent. The measurements were performed at a temperature of 35°C. A calibration curve was created using commercially available standard polystyrene with a known weight-average molecular weight, and the number-average molecular weight, converted to polystyrene equivalent, was determined. Here, in the table, the number-average molecular weight of copolymer (A) is denoted as (Mn1), and the number-average molecular weight of copolymer (B) is denoted as (Mn2).

[0115] ((5) Mass ratio of block copolymer (A) and block copolymer (B)) Using GPC (Glass Propagation) [equipment: Tosoh HLC8220, column: TSKgel SuperH-RC x 2], the ratio of copolymer (A) to copolymer (B) was measured using a mixture of copolymer (A) and copolymer (B). Tetrahydrofuran was used as the solvent. The measurements were performed at a temperature of 35°C. The mass ratios of copolymer (A) and copolymer (B) were calculated from the area ratio of the peaks derived from copolymer (A) and copolymer (B).

[0116] ((6) Hydrogenation rate) The hydrogenation rates of copolymer (A) and copolymer (B) were measured using a nuclear magnetic resonance spectrometer (BRUKER, DPX-400). The measurements were performed using hydrogenated copolymers, which are copolymers obtained after hydrogenation, by proton nuclear magnetic resonance (1H-NMR). Specifically, the integral values ​​of the signals originating from the residual double bonds at 4.5–5.5 ppm and the signals originating from the hydrogenated conjugated dienes were calculated, and their ratio was determined.

[0117] (Separation of block copolymer (A) and block copolymer (B), which are constituent components of block aggregate (X)) The resin composition was separated into a low-molecular-weight copolymer (A) and a high-molecular-weight copolymer (B) using GPC [equipment: Waters ACQUITY UPLC H-Class, columns: Waters ACQUITY APC XT900 (2.5 μm, 4.6 × 150 mm), Waters ACQUITY APC XT200 (2.5 μm, 4.6 × 75 mm), Waters ACQUITY APC XT125 (2.5 mm, 4.6 × 75 mm) in series]. Chloroform was used as the solvent. Based on the GPC measurement chart, the low-molecular-weight and high-molecular-weight peaks were separated into their respective components.

[0118] (Block copolymer (A) and block copolymer (B)) Copolymers (A1) to (A11) and copolymers (B1) to (B11) were manufactured as follows.

[0119] <Synthesis example 1: Copolymer (A1)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added. Next, 0.047 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 1.4 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 63 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added, and polymerization was carried out for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 1 part by mass of styrene and a cyclohexane solution (20% by mass) containing 4 parts by mass of butadiene were added, and polymerization was carried out for 15 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 33% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 16% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 10,000, and a number-average molecular weight (Mn1) of 200,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A1).

[0120] <Synthesis example 2: Copolymer (A2)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added. Next, 0.047 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 1.4 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 63 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added, and polymerization was carried out for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 1 part by mass of styrene and a cyclohexane solution (20% by mass) containing 4 parts by mass of butadiene were added, and polymerization was carried out for 15 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 33% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 16% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 10,000, and a number-average molecular weight (Mn1) of 200,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer. A hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C, and the reaction was stopped midway. The hydrogenation rate of the obtained hydrogenated copolymer was 50%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A2).

[0121] <Synthesis example 3: Copolymer (A3)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added. Next, 0.047 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 1.4 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 63 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added, and polymerization was carried out for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 1 part by mass of styrene and a cyclohexane solution (20% by mass) containing 4 parts by mass of butadiene were added, and polymerization was carried out for 15 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 33% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 16% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 10,000, and a number-average molecular weight (Mn1) of 200,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer. A hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C, and the reaction was stopped midway. The hydrogenation rate of the obtained hydrogenated copolymer was 80%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A3).

[0122] <Synthesis example 4: Copolymer (A4)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added. Next, 0.047 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 1.4 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 63 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added, and polymerization was carried out for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 1 part by mass of styrene and a cyclohexane solution (20% by mass) containing 4 parts by mass of butadiene were added, and polymerization was carried out for 15 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 33% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 16% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 10,000, and a number-average molecular weight (Mn1) of 200,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer. A hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C, and the reaction was stopped midway. The hydrogenation rate of the obtained hydrogenated copolymer was 90%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A4).

[0123] <Synthesis example 5: Copolymer (A5)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added. Next, 0.032 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 1.4 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 63 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added, and polymerization was carried out for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 1 part by mass of styrene and a cyclohexane solution (20% by mass) containing 4 parts by mass of butadiene were added, and polymerization was carried out for 15 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 33% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 16% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 15,000, and a number-average molecular weight (Mn1) of 300,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A5).

[0124] <Synthesis Example 6: Copolymer (A6)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added. Next, 0.080 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 1.4 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 63 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added, and polymerization was carried out for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 1 part by mass of styrene and a cyclohexane solution (20% by mass) containing 4 parts by mass of butadiene were added, and polymerization was carried out for 15 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 33% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 16% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 0.6 million, and a number-average molecular weight (Mn1) of 120,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A6).

[0125] <Synthesis Example 7: Copolymer (A7)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added. Next, 0.047 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 1.4 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 14 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 57 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Next, a cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added, and polymerization was carried out for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 2.6 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 10.4 parts by mass of butadiene were added, and polymerization was carried out for 15 minutes. Subsequently, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 33% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 16% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 25,000, and a number-average molecular weight (Mn1) of 200,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A7).

[0126] <Synthesis example 8: Copolymer (A8)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added. Next, 0.080 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 1.4 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 17 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 67 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 8 parts by mass of styrene (20% by mass) was added, and polymerization was carried out for 15 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 33% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 16% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 0,000, and a number-average molecular weight (Mn1) of 200,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A8).

[0127] <Synthesis Example 9: Copolymer (A9)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added. Next, 0.053 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 1.4 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 39.5 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 39.5 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added, and polymerization was carried out for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 2.5 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 2.5 parts by mass of butadiene were added, and polymerization was carried out for 15 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 40% by mass, a styrene content (Sa) of 58% by mass, a random styrene content (RSa) of 50% by mass, a styrene block content (BSa) of 16% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 7,500, and a number-average molecular weight (Mn1) of 150,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A9).

[0128] <Synthesis Example 10: Copolymer (A10)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added. Next, 0.064 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.9 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 79 parts by mass of butadiene was added, and polymerization was carried out for 45 minutes. Next, a cyclohexane solution (20% by mass) containing 8 parts by mass of styrene was added, and polymerization was carried out for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 5 parts by mass of butadiene was added, and polymerization was carried out for 15 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 16% by mass, a random styrene content (RSa) of 0% by mass, a styrene block content (BSa) of 16% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 7,500, and a number-average molecular weight (Mn1) of 150,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A8).

[0129] <Synthesis Example 11: Copolymer (A11)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution containing 20 parts by mass of styrene (20% by mass) and a cyclohexane solution containing 80 parts by mass of butadiene (20% by mass) were added. Next, 0.064 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.9 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 60 minutes. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 20% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 0% by mass, a molecular weight of the fourth block (b2 block molecular weight) of 0,000, and a number average molecular weight (Mn1) of 200,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (A11).

[0130] <Synthesis Example 12: Copolymer (B1)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene was added. Next, 0.92 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.6 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 64 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 36% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 20% by mass, and a number-average molecular weight (Mn1) of 10,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B1).

[0131] <Synthesis Example 13: Copolymer (B2)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene was added. Next, 0.92 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.6 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 64 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 36% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 20% by mass, and a number-average molecular weight (Mn1) of 10,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer. A hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C, and the reaction was stopped midway. The hydrogenation rate of the obtained hydrogenated copolymer was 50%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B2).

[0132] <Synthesis Example 14: Copolymer (B3)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene was added. Next, 0.92 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.6 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 64 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 36% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 20% by mass, and a number-average molecular weight (Mn1) of 10,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer. A hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C, and the reaction was stopped midway. The hydrogenation rate of the obtained hydrogenated copolymer was 80%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B3).

[0133] <Synthesis Example 15: Copolymer (B4)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene was added. Next, 0.92 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.6 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 64 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 36% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 20% by mass, and a number-average molecular weight (Mn1) of 10,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer. A hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C, and the reaction was stopped midway. The hydrogenation rate of the obtained hydrogenated copolymer was 90%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B4).

[0134] <Synthesis Example 16: Copolymer (B5)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene was added. Next, 0.64 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.6 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 64 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 36% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 20% by mass, and a number-average molecular weight (Mn1) of 15,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B5).

[0135] <Synthesis Example 17: Copolymer (B6)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene was added. Next, 1.60 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.4 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 64 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 36% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 20% by mass, and a number-average molecular weight (Mn1) of 0.6 million. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B6).

[0136] <Synthesis Example 18: Copolymer (B7)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene was added. Next, 0.38 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.8 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 64 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 36% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 20% by mass, and a number-average molecular weight (Mn1) of 25,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B7).

[0137] <Synthesis Example 19: Copolymer (B8)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene was added. Next, 1.28 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.8 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 40 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 40 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. Subsequently, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 40% by mass, a styrene content (Sa) of 60% by mass, a random styrene content (RSa) of 50% by mass, a styrene block content (BSa) of 20% by mass, and a number-average molecular weight (Mn1) of 10,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B8).

[0138] <Synthesis Example 20: Copolymer (B9)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene was added. Next, 0.92 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.8 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 80 parts by mass of butadiene was added, and polymerization was carried out for 45 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 40% by mass, a styrene content (Sa) of 20% by mass, a random styrene content (RSa) of 0% by mass, a styrene block content (BSa) of 20% by mass, and a number-average molecular weight (Mn1) of 10,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B9).

[0139] <Synthesis Example 21: Copolymer (B10)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene was added. Next, 0.24 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.8 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 15 minutes. Subsequently, a cyclohexane solution (20% by mass) containing 16 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 64 parts by mass of butadiene were added, and polymerization was carried out for 45 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 36% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 20% by mass, and a number-average molecular weight (Mn1) of 40,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B10).

[0140] <Synthesis example 22: Copolymer (B11)> Batch polymerization was carried out using a tank-type reactor (internal volume 10L) equipped with a stirring device and jacket. A cyclohexane solution (20% by mass) containing 20 parts by mass of styrene and a cyclohexane solution (20% by mass) containing 80 parts by mass of butadiene were added. Next, 0.46 parts by mass of n-butyllithium per 100 parts by mass of total monomer and 0.8 moles of N,N,N',N'-tetramethylethylenediamine per mole of n-butyllithium were added, and polymerization was carried out at 70°C for 50 minutes. After that, methanol was added to stop the polymerization reaction. The polymer obtained as described above had a vinyl bond content (Va) of 60% by mass, a styrene content (Sa) of 20% by mass, a random styrene content (RSa) of 20% by mass, a styrene block content (BSa) of 0% by mass, and a number-average molecular weight (Mn1) of 20,000. Furthermore, the hydrogenation catalyst prepared as described above was added to the obtained copolymer at a concentration of 100 ppm (Ti-based) per 100 parts by mass of copolymer, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.7 MPa and a temperature of 80°C. The hydrogenation rate of the obtained hydrogenated copolymer was 98%. Next, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer to 100 parts by mass of the hydrogenated copolymer to obtain copolymer (B11).

[0141] [Manufacturing Examples 1-11, Comparative Manufacturing Examples 1-3]

[0142] [Method for measuring the physical properties and characteristics of block copolymer (X)] ((1) Viscoelasticity measurement of block copolymer (X) (tanδ peak)) The dynamic viscoelastic spectrum was measured using the method described below, and the peak temperature of the loss coefficient tanδ (tanδ peak temperature) was obtained. First, the copolymer (X) was formed into a 2 mm thick sheet, then cut into pieces 10 mm wide and 35 mm long to be used as the sample for measurement. The sample for measurement was set in the torsion-type geometry of the ARES device (manufactured by TA Instruments Co., Ltd., product name), and measurements were taken under the following conditions: effective measurement length of 25 mm, strain of 0.5%, frequency of 1 Hz, measurement range from -100°C to 100°C, and heating rate of 3°C / min.

[0143] ((2) 10s hardness of block copolymer (X)) In accordance with JIS K6253, the value after 10 seconds (10s hardness) was measured using a durometer type A.

[0144] (Manufacturing of block copolymer (X)) Copolymers (X1) to (X14) were prepared by mixing copolymers (A1) to (A11) and hydrogenated copolymers (B1) to (B11) in solution according to Tables 1 and 2, desolventing, and then forming them into pellets.

[0145] [Table 1]

[0146] [Table 2]

[0147] (Glass transition temperature) Using the first diene elastomer as a sample, DSC measurements were performed using a differential scanning calorimeter (product name "DSC3200S" manufactured by MacScience Corporation) in accordance with ISO 22768:2006. Under a helium flow of 50 mL / min, the DSC curve was recorded while increasing the temperature from -100°C at 20°C / min, and the peak top (inflection point) of the DSC differential curve was defined as the glass transition temperature.

[0148] (Production of the first diene elastomer) <Synthesis Example 23: Diene Elastomer (Y1)> Two tank-type pressure vessels, each with an internal volume of 10 L, a ratio of internal height (L) to diameter (D) (L / D) of 4.0, an inlet at the bottom, an outlet at the top, and equipped with a stirrer and a jacket for temperature control, were connected together as polymerization branching reactors. 1,3-butadiene, styrene, and n-hexane, from which water had been removed beforehand, were continuously supplied to the bottom of the first reactor at rates of 18.5 g / min, 6.2 g / min, and 117.4 g / min, respectively, while being mixed. Immediately before the mixed solution entered the first reactor, n-butyllithium was continuously added at a rate of 0.096 mmol / min using a static mixer to inactivate any remaining impurities. Simultaneously with the supply of 1,3-butadiene, styrene, n-hexane, and n-butyllithium, 2,2-bis(2-oxolanil)propane as a polar compound and n-butyllithium as a polymerization initiator were supplied to the bottom of the first reactor at rates of 0.049 mmol / min and 0.202 mmol / min, respectively, while the reaction solution was vigorously stirred with a stirrer. The temperature inside the first reactor was maintained at 82°C. The conjugated diene polymer solution produced by the polymerization reaction in the first reactor was continuously withdrawn from the top of the first reactor and continuously supplied to the bottom of the second reactor. Once the polymerization was sufficiently stable, trimethoxy(4-vinylphenyl)silane was supplied from the bottom of the second reactor at a rate of 0.006 mmol / min as a branching agent while copolymerizing 1,3-butadiene and styrene, and an additional 1,3-butadiene was added at a rate of 6.2 g / min to carry out the polymerization branching step. The temperature inside the second reactor was maintained at 86°C. A small amount of the conjugated diene polymer solution was withdrawn from the outlet of the second reactor, and antioxidant (BHT) was added so that the antioxidant content was 0.2 g per 100 g of conjugated diene polymer, after which the solvent was removed.

[0149] Next, the conjugated diene polymer solution that flowed out from the top of the second reactor was supplied to a static mixer. Furthermore, the conjugated diene polymer was coupled to the conjugated diene polymer solution flowing continuously through the static mixer by continuously adding 1-methyl-4-(3-(trimethoxysilyl)propyl)piperazine at a rate of 0.104 mmol / min and tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine at a rate of 0.003 mmol / min as coupling modifiers. At this time, the time from when the coupling modifier was added to the polymer solution flowing out from the outlet of the second reactor was 4.8 minutes, and the temperature of the polymer solution at the time of addition of the coupling modifier was 68°C. In addition, the difference between the temperature of the polymer solution at the outlet of the second reactor and the temperature of the polymer solution when the coupling modifier was added was 2°C.

[0150] Next, to the polymer solution that flowed out of the static mixer, an n-hexane solution of antioxidant (BHT) was continuously added at a rate of 0.055 g / min, so that the antioxidant (BHT) content was 0.2 g per 100 g of polymer, thereby terminating the coupling reaction. The solvent was removed by steam stripping, and the mixture was formed into a veil to obtain the diene elastomer (Y1). The diene elastomer (Y1) had a number-average molecular weight of 311,000, a vinyl bond content of 20%, a styrene content of 20 wt%, and a glass transition temperature of -60°C.

[0151] <Synthesis Example 24: Diene Elastomer (Y2)> Two tank-type pressure vessels, each with an internal volume of 10 L, a ratio of internal height (L) to diameter (D) (L / D) of 4.0, an inlet at the bottom, an outlet at the top, and equipped with a stirrer and a jacket for temperature control, were connected together as polymerization branching reactors. 1,3-butadiene, styrene, and n-hexane, from which water had been removed beforehand, were continuously supplied to the bottom of the first reactor at rates of 16.2 g / min, 9.2 g / min, and 117.4 g / min, respectively, while being mixed. Immediately before the mixed solution entered the first reactor, n-butyllithium was continuously added at a rate of 0.045 mmol / min using a static mixer to inactivate any remaining impurities. Simultaneously with the supply of 1,3-butadiene, styrene, n-hexane, and n-butyllithium, 2,2-bis(2-oxolanil)propane as a polar compound and n-butyllithium as a polymerization initiator were supplied to the bottom of the first reactor at rates of 0.045 mmol / min and 0.202 mmol / min, respectively, while the reaction solution was vigorously stirred with a stirrer. The temperature inside the first reactor was maintained at 83°C. The conjugated diene polymer solution produced by the polymerization reaction in the first reactor was continuously withdrawn from the top of the first reactor and continuously supplied to the bottom of the second reactor. Once the polymerization was sufficiently stable, trimethoxy(4-vinylphenyl)silane was supplied from the bottom of the second reactor at a rate of 0.011 mmol / min as a branching agent while copolymerizing 1,3-butadiene and styrene, and an additional 1,3-butadiene was added at a rate of 5.4 g / min to carry out the polymerization branching step. The temperature inside the second reactor was maintained at 88°C. A small amount of the conjugated diene polymer solution was withdrawn from the outlet of the second reactor, and antioxidant (BHT) was added so that the antioxidant content was 0.2 g per 100 g of conjugated diene polymer, after which the solvent was removed.

[0152] Next, the conjugated diene polymer solution that flowed out from the top of the second reactor was supplied to a static mixer. Furthermore, the conjugated diene polymer was coupled to the conjugated diene polymer solution flowing continuously through the static mixer by continuously adding 1-methyl-4-(3-(trimethoxysilyl)propyl)piperazine at a rate of 0.104 mmol / min and tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine at a rate of 0.003 mmol / min as coupling modifiers. At this time, the time from when the coupling modifier was added to the polymer solution flowing out from the outlet of the second reactor was 4.8 minutes, and the temperature of the polymer solution at the time of addition of the coupling modifier was 68°C. In addition, the difference between the temperature of the polymer solution at the outlet of the second reactor and the temperature of the polymer solution when the coupling modifier was added was 2°C.

[0153] Next, to the polymer solution that flowed out of the static mixer, an n-hexane solution of antioxidant (BHT) was continuously added at a rate of 0.055 g / min, so that the antioxidant (BHT) content was 0.2 g per 100 g of polymer, thereby terminating the coupling reaction. The solvent was removed by steam stripping, and the mixture was formed into a veil to obtain the diene elastomer (Y1). The diene elastomer (Y2) had a number-average molecular weight of 315,000, a vinyl bond content of 20%, a styrene content of 30 wt%, and a glass transition temperature of -47°C.

[0154] <Synthesis Example 25: Diene Elastomer (Y3)> Two tank-type pressure vessels, each with an internal volume of 10 L, a ratio of internal height (L) to diameter (D) (L / D) of 4.0, an inlet at the bottom, an outlet at the top, and equipped with a stirrer and a jacket for temperature control, were connected together as polymerization branching reactors. 1,3-butadiene, styrene, and n-hexane, from which water had been removed beforehand, were continuously supplied to the bottom of the first reactor at rates of 13.0 g / min, 12.7 g / min, and 117.4 g / min, respectively, while being mixed. Immediately before the mixed solution entered the first reactor, n-butyllithium was continuously added at a rate of 0.096 mmol / min using a static mixer to inactivate any remaining impurities. Simultaneously with the supply of 1,3-butadiene, styrene, n-hexane, and n-butyllithium, 2,2-bis(2-oxolanil)propane as a polar compound and n-butyllithium as a polymerization initiator were supplied to the bottom of the first reactor at rates of 0.049 mmol / min and 0.260 mmol / min, respectively, while the reaction solution was vigorously stirred with a stirrer. The temperature inside the first reactor was maintained at 82°C. The conjugated diene polymer solution produced by the polymerization reaction in the first reactor was continuously withdrawn from the top of the first reactor and continuously supplied to the bottom of the second reactor. Once the polymerization was sufficiently stable, trimethoxy(4-vinylphenyl)silane was supplied from the bottom of the second reactor at a rate of 0.006 mmol / min as a branching agent while copolymerizing 1,3-butadiene and styrene, and an additional 1,3-butadiene was added at a rate of 4.6 g / min to carry out the polymerization branching step. The temperature inside the second reactor was maintained at 86°C. A small amount of the conjugated diene polymer solution was withdrawn from the outlet of the second reactor, and antioxidant (BHT) was added so that the antioxidant content was 0.2 g per 100 g of conjugated diene polymer, after which the solvent was removed.

[0155] Next, the conjugated diene polymer solution that flowed out from the top of the second reactor was supplied to a static mixer. Furthermore, the conjugated diene polymer was coupled to the conjugated diene polymer solution flowing continuously through the static mixer by continuously adding 1-methyl-4-(3-(trimethoxysilyl)propyl)piperazine at a rate of 0.104 mmol / min and tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine at a rate of 0.003 mmol / min as coupling modifiers. At this time, the time from when the coupling modifier was added to the polymer solution flowing out from the outlet of the second reactor was 4.8 minutes, and the temperature of the polymer solution at the time of addition of the coupling modifier was 68°C. In addition, the difference between the temperature of the polymer solution at the outlet of the second reactor and the temperature of the polymer solution when the coupling modifier was added was 2°C.

[0156] Next, to the polymer solution that flowed out of the static mixer, an n-hexane solution of antioxidant (BHT) was continuously added at a rate of 0.055 g / min, so that the antioxidant (BHT) content was 0.2 g per 100 g of polymer, thereby terminating the coupling reaction. The solvent was removed by steam stripping, and the mixture was formed into a veil to obtain the diene elastomer (Y1). The diene elastomer (Y3) had a number-average molecular weight of 312,000, a vinyl bond content of 40%, a styrene content of 40 wt%, and a glass transition temperature of -25°C.

[0157] [Manufacturing of rubber compositions] The components were mixed using the materials and methods described below to obtain a rubber composition.

[0158] • First diene elastomer; copolymer (Y1)~(Y3): 70 parts by mass • Butadiene rubber (BR (product name "BR150" manufactured by Ube Industries): 30 parts by mass) • Second diene elastomer; copolymer (X1)~(X14): 5~20 parts by mass • Silica (Evonik Degussa product name "Ultrasil 7000GR", nitrogen adsorption specific surface area 170 m² / g): 75.0 parts by mass • Silane coupling agent (Evonik Degussa, "Si75", bis(triethoxysilylpropyl) disulfide): 6.0 parts by mass • Carbon black (manufactured by Tokai Carbon Co., Ltd., Seast KH (N339)): 5.0 parts per liter • Softener (SRAE oil (manufactured by JX Energy Corporation, product name "PF30")): 32 parts by mass ·Zinc white: 2.5 parts by mass Stearic acid: 2.0 parts by mass • Wax, Sunnock: 1.5 parts by mass • Anti-aging agent (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine): 2.0 parts by mass ·Sulfur: 2.2 parts by mass • Vulcanization accelerator 1 (N-cyclohexyl-2-benzothiadylsulfinamide): 1.7 parts by mass • Vulcanization accelerator 2 (diphenylguanidine): 2.0 parts by mass

[0159] (Mixing method) Using a sealed kneader (capacity 0.5L) equipped with a temperature control device, the first stage of kneading involved mixing all materials except sulfur and vulcanization accelerators under conditions of a 65% filling rate and a rotor rotation speed of 50-90 rpm. During this process, the temperature of the sealed mixer was controlled, and the resulting mixture was obtained at a discharge temperature of 150-160°C. Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature and then mixed again to improve the dispersion of the reinforcing filler. In this case as well, the discharge temperature of the mixture was adjusted to 150-160°C by controlling the temperature of the mixer. After cooling, in the third stage of kneading, the mixture was kneaded in an open roll oven set to 70°C with a vulcanization accelerator and sulfur to obtain an unvulcanized rubber composition. Subsequently, the mixture was molded and vulcanized using a vulcanization press at 160°C for a predetermined vulcanization time to obtain the vulcanized rubber composition. The vulcanization time was set to the 90% vulcanization time of the unvulcanized rubber composition plus 5 minutes. The rubber composition after vulcanization was evaluated by the following method.

[0160] [Evaluation of physical properties of rubber compositions] (Handling: Wet grip performance (tanδ at 0°C)) The rubber compositions obtained in the examples and comparative examples were measured using a viscoelasticity tester "ARES" manufactured by Rheometrics Scientific, Inc., with tanδ measured in torsion mode at 0°C, a frequency of 10 Hz, and a strain of 1%, and this value was used as an indicator of wet grip performance. The measurement results of the rubber composition in Comparative Example 4 were standardized to 100, and higher values ​​were evaluated as indicating better performance. Values ​​exceeding 100 were evaluated as having superior wet grip properties.

[0161] (Fuel efficiency (tanδ at 50°C)) The rubber compositions obtained in the examples and comparative examples were measured using a viscoelasticity tester "ARES" manufactured by Rheometrics Scientific, Inc., with tanδ measured in torsion mode at 50°C, a frequency of 10 Hz, and a strain of 1%, and this value was used as an indicator of fuel efficiency. The values ​​are shown as an index with the measured values ​​of Comparative Example 4 set to 100 as the baseline. A higher index indicates a smaller adverse effect on viscoelastic properties (RR) and better performance. Values ​​exceeding 100 were evaluated as having superior fuel efficiency.

[0162] The rubber compositions of the examples and comparative examples were evaluated by measuring the tanδ peak shape in torsion mode using a viscoelasticity tester "ARES" manufactured by Rheometrics Scientific Corporation at 50°C, a frequency of 10 Hz, and a strain of 1%.

[0163] (Processability (Moony viscosity of the compound)) Each rubber composition before vulcanization was used as a sample for measurement, and the Mooney viscosity ML1+4 was measured using an L-rotor in accordance with JIS K6300-1:2013, under the conditions of 1 minute preheating, 4 minutes rotor operation time, and a temperature of 100°C. In Table 2 below, the values ​​are shown as an index with the measured value of Comparative Example 4 set to 100 as the baseline, and a larger index indicates better processability. Values ​​exceeding 100 were evaluated as having excellent processability.

[0164] (Abrasion resistance) The resin compositions of the examples and comparative examples were measured for abrasion resistance by the DIN abrasion test method of JIS K6246-2 using a DIN abrasion tester (manufactured by Ueshima Seisakusho Co., Ltd.). The measurement result of Comparative Example 4 was standardized with 100, and a higher value was evaluated as indicating better performance. Those with a value exceeding 100 were evaluated as having excellent abrasion resistance.

[0165] (Hardness of the rubber composition) According to JIS K6253, the instantaneous value of the rubber composition of the present embodiment was measured using a durometer type A.

[0166] The evaluation results of the rubber compositions obtained in the examples and comparative examples are shown in Tables 3 to 5 below.

[0167]

Table 3

[0168]

Table 4

[0169]

Table 5

[0170] From the results shown in the above table, it can be seen that the rubber compositions of the present embodiment (Examples 1 to 16) have good processability and are rubber compositions excellent in abrasion resistance, fuel efficiency performance, and handling performance.

Claims

1. For every 100 parts by mass of the entire diene elastomer, A first diene elastomer selected from the group consisting of polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymer, isoprene copolymer and mixtures thereof, in an amount of 50 to 98 phr. A second diene elastomer which is a block copolymer in an amount of 2 to 50 phr, and A rubber composition comprising 50 to 200 phr of filler, A rubber composition wherein the block copolymer (X) contained in the second diene elastomer comprises vinyl aromatic monomer units and conjugated diene monomer units, and satisfies the following conditions. (1) The GPC of the block copolymer (X) has at least two peaks. (2) Among the block copolymers (X), block copolymer (A) showing the first peak has at least one polymer block mainly composed of a vinyl aromatic compound. (3) Among the block copolymers (X), block copolymer (B) showing the second peak has at least one polymer block mainly composed of a vinyl aromatic compound. (4) The ratio (Mn1 / Mn2) of the number average molecular weight (Mn1) of block copolymer (A) to the number average molecular weight (Mn2) of block copolymer (B) is 6.0 or greater.

2. The rubber composition according to claim 1, wherein the structure of the block copolymer (A) showing the first peak among the block copolymer (X) is represented as a1-b1-a2-b2. a1, a2: Blocks mainly composed of vinyl aromatic compounds b1, b2: Blocks mainly composed of conjugated diene compounds, or random copolymer blocks consisting of conjugated diene compounds and vinyl aromatic compounds.

3. The rubber composition according to claim 1 or 2, wherein at least one glass transition temperature of the first diene elastomer is in the range of -40°C or lower.

4. The rubber composition according to claim 1 or 2, wherein the hydrogenation rate of the double bond derived from the conjugated diene compound of the block copolymer (X) is 65% or more.

5. The rubber composition according to claim 1 or 2, wherein the structure of the block copolymer (A) showing the first peak among the block copolymer (X) is represented as a1-b1-a2-b2, and the number-average molecular weight of the b2 block is 20,000 or less.

6. The rubber composition according to claim 1 or 2, wherein the conjugated diene compound that forms the conjugated diene monomer unit of the block copolymer (X) is isoprene and / or butadiene.

7. The rubber composition according to claim 1 or 2, wherein the value of the block copolymer (X) after 10 seconds (10s hardness) measured on a durometer type A according to JIS K6253 is 25 or less.

8. The rubber composition according to claim 1 or 2, wherein the instantaneous value (instantaneous hardness) measured on a durometer type A in accordance with JIS K6253 is 45 to 75.

9. The rubber composition according to claim 1 or 2, wherein the block copolymer (A) and the block copolymer (B) have a random copolymer structure consisting of a vinyl aromatic compound and a conjugated diene compound.

10. The rubber composition according to claim 1 or 2, wherein the tanδ peak at 50°C or below in a viscoelasticity measurement (1 Hz) has two or more peaks, or has one main peak plus a shoulder peak.

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