Crosslinked rubber composition, method for producing a crosslinked rubber composition

Abstract

A crosslinked product of a rubber composition that includes 100 mass parts of a rubber component (A) including 10-100 mass% (inclusive) of a hydrogenated conjugated diene polymer and having an iodine value of 10-370 (inclusive) and 10-120 mass parts (inclusive) of carbon black (B), the hydrogenated conjugated diene polymer having a hydrogenation rate of 10-99% (inclusive), the content of aromatic vinyl monomer blocks being less than 5 mass%, the weight-average molecular weight being 150,000-1,500,000 (inclusive), and the change in Shore A hardness before and after heating for 72 hours at 100°C in air satisfying formula (1) below.　(1) -10 < (Shore A hardness after heating) - (Shore A hardness before heating) < 5

Description

[Technical Field]

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

[0002] For vibration-damping rubber in automobiles, trains, and other vehicles, rubber materials containing natural rubber with excellent vibration-damping properties such as compression set and dynamic magnification have been proposed (see, for example, Patent Document 1). Furthermore, when heat resistance and ozone resistance are required, rubber materials containing rubber with excellent heat resistance and ozone resistance, such as ethylene-propylene-diene rubber (EPDM), have been proposed (see, for example, Patent Document 2). Moreover, as a rubber material with an excellent balance of heat resistance and vibration-damping properties, rubber compositions containing hydrogenated styrene-butadiene block copolymer have been proposed (see, for example, Patent Document 3). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2004-292679 [Patent Document 2] Japanese Patent Publication No. 2018-119096 [Patent Document 3] Japanese Patent Publication No. 2018-35253 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, rubber materials containing EPDM have the problem of sometimes having insufficient vibration damping properties. Furthermore, rubber compositions containing hydrogenated styrene-butadiene block copolymers have the problem of having insufficient vibration damping properties if styrene domains are formed. Therefore, there is a need for a rubber composition that achieves both vibration damping properties and heat resistance while maintaining sufficient processability and ozone resistance for practical use.

[0005] Therefore, in view of the problems of the prior art described above, the present invention aims to provide a crosslinked rubber composition that has an excellent balance of vibration damping properties and heat resistance. [Means for solving the problem]

[0006] As a result of diligent research to solve the problems of the prior art described above, the present inventors have found that a crosslinked rubber composition with excellent vibration damping properties and heat resistance can be obtained by using a rubber component (A) containing a hydrogenated conjugated diene polymer having a specific structure and carbon black (B) as a filler, and by setting the change in hardness before and after predetermined heating conditions within a specific range. This has led to the completion of the present invention. In other words, the present invention is as follows:

[0007] [1] 100 parts by mass of rubber component (A) containing 10% to 100% by mass of a hydrogenated conjugated diene polymer and having an iodine value of 10 to 370, Carbon black (B) 30 parts by mass or more and 50 parts by mass or less, A product comprising a crosslinked rubber composition which is a crosslinked rubber composition comprising, The hydrogenated conjugated diene polymer has a hydrogenation rate of 10% to 90%, an aromatic vinyl monomer block content of less than 5% by mass, and a weight-average molecular weight of 150,000 to 1,500,000. The vinyl bond content is 0.1 moles or more and less than 10 moles. The crosslinked rubber composition satisfies the following formula (1) when the change in Shore A hardness before and after heating in air at 100°C for 72 hours. -10 < (Shore A hardness after heating) - (Shore A hardness before heating) < 5 ... (1) Any one product selected from the group consisting of vibration-damping rubber, vibration isolation rubber, conveyor belts, shoe outsoles, automotive weatherstrips, packings, gaskets, sealing materials, waterproof sheets, engine mounts, air springs, rubber gloves, medical and hygiene products, rubber rollers, industrial hoses, battery cases, adhesives, wire insulation, and window frame rubber, comprising a cross-linked rubber composition. [2] 100 parts by mass of the rubber component (A), 30 to 50 parts by mass of a filler (excluding those containing silica) containing the carbon black (B), and containing A molded article of a crosslinked rubber composition, the product according to [1] above. [3] The hydrogenated conjugated diene polymer has a glass transition temperature of -50°C or lower, and the product according to [1] or [2] above. 〔4〕 The hydrogenated conjugated diene polymer has a modification rate of 40% or more and 99% or less, and the product according to any one of [1] to 〔3〕 above. 〔5〕 The hydrogenated conjugated diene polymer has a Mooney stress relaxation (MSR) at 100°C of 0.8 or less, and the product according to any one of [1] to 〔4〕 above. 〔6〕 The crosslinked rubber composition satisfies the following formula (2), and the product according to any one of [1] to 〔5〕 above. 0.5 MPa < (storage elastic modulus at 50°C and 0.1% strain) - (storage elastic modulus at 50°C and 10% strain) < 10 MPa ··· (2) 〔7〕 The rubber component (A) contains 10% to 90% by mass of a rubber-like polymer other than the hydrogenated conjugated diene polymer, and the rubber-like polymer other than the hydrogenated conjugated diene polymer is at least one rubber selected from the group consisting of styrene-butadiene rubber, styrene-isoprene rubber, natural rubber, polybutadiene, polyisoprene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber, butyl rubber, polyurethane, epichlorohydrin rubber, silicone rubber, acrylic rubber, nitrile rubber, chloroprene rubber, and fluorine rubber, and the product according to any one of [1] to 〔6〕 above. 〔8〕 The hydrogenated conjugated diene polymer has a titanium content of 1 ppm to 100 ppm and an aluminum content of 2 ppm or less, as described in [1] to 〔7〕 Any of the products listed in one of the following. 〔9〕 The above [1] 〔8〕 A method for producing the crosslinked rubber composition contained in any one of the products described above, A method for producing a crosslinked rubber composition, comprising the step of crosslinking the hydrogenated conjugated diene polymer with sulfur and a vulcanization accelerator or an organic peroxide. 〔10〕 Contains rubber component (A) and carbon black (B), [1] A method for producing the crosslinked rubber composition contained in the product described above, The hydrogenation rate is 10% or more and 90% or less, the aromatic vinyl monomer block content is less than 5% by mass, the weight-average molecular weight is 150,000 or more and 1,500,000 or less, the glass transition temperature is -50°C or lower, and the aromatic vinyl monomer unit content is 5% by mass or more. Furthermore, the vinyl bond content is 0.1 moles or more and less than 10 moles. A step of polymerizing a hydrogenated conjugated diene polymer, A step to obtain a rubber component (A) containing 10% to 100% by mass of the hydrogenated conjugated diene polymer and having an iodine value of 10 to 370, A step of obtaining a rubber composition by mixing 100 parts by mass of the rubber component (A) and 30 to 50 parts by mass of carbon black (B), A step of crosslinking the rubber composition, It has, To obtain a crosslinked rubber composition in which the change in Shore A hardness before and after heating at 100°C for 72 hours under air satisfies the following formula (1): A method for producing a crosslinked rubber composition. -10 < (Shore A hardness after heating) - (Shore A hardness before heating) < 5 ... (1) 〔11〕 In the crosslinking step, the rubber composition containing the rubber component (A) and the carbon black (B) is crosslinked in a molded state. [9] or

[10] A method for producing the crosslinked rubber composition described above. [Effects of the Invention]

[0008] According to the present invention, a crosslinked rubber composition with a good balance of vibration damping properties and heat resistance can be provided. [Modes for carrying out the invention]

[0009] The following describes in detail an embodiment for carrying out the present invention (hereinafter referred to as "this embodiment"). The following embodiments are illustrative examples for explaining the present invention, and the present invention is not limited to these embodiments. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0010] [Crosslinked rubber composition] The crosslinked rubber composition of this embodiment is a crosslinked rubber composition obtained by crosslinking a rubber composition containing 100 parts by mass of a rubber component (A) which contains 10% to 100% by mass of a hydrogenated conjugated diene polymer and has an iodine value of 10 to 370, and 10 to 120 parts by mass of carbon black (B). The hydrogenated conjugated diene polymer has a hydrogenation rate of 10% to 99%, an aromatic vinyl monomer block content of less than 5% by mass, and a weight-average molecular weight of 150,000 to 1,500,000. Hereinafter, the hydrogenated conjugated diene polymer with the above configuration contained in rubber component (A) may be referred to as rubbery polymer 1. Furthermore, the crosslinked rubber composition of this embodiment satisfies the following equation (1) when the change in Shore A hardness, which is the durometer hardness measured according to JIS K6253-3 Type A, is observed before and after heating in air at 100°C for 72 hours. Note that Shore A hardness can be expressed as (A hardness value°), but in the following equation, only the difference in numerical values ​​is shown. -10 < (hardness after heating) - (hardness before heating) < 5 ... (1) The above-described configuration provides a good balance between vibration damping characteristics and heat resistance.

[0011] In this specification, the vibration isolation properties of a crosslinked rubber composition are evaluated using the dynamic magnification ratio as an indicator, and excellent vibration isolation properties are described as being synonymous with a low dynamic magnification ratio. The dynamic magnification ratio is the ratio of the dynamic modulus to the static modulus (dynamic modulus / static modulus) or the ratio of the dynamic spring constant to the static spring constant (dynamic spring constant / static spring constant). The dynamic spring constant, static spring constant, and dynamic magnification can be measured by the method described in JIS K6385. Generally, the lower the dynamic spring constant and the larger the static spring constant, the lower the dynamic magnification, and the better the vibration damping properties of the crosslinked rubber composition. Lowering the dynamic spring constant and improving the static spring constant are conflicting properties and difficult to achieve simultaneously. However, the inventors verified the dynamic magnification of crosslinked rubber compositions with various combinations of rubber components and fillers, and found that by adopting a specific hydrogenated conjugated diene polymer (described later) as the rubber component and incorporating an appropriate amount of carbon black, the dynamic magnification of the crosslinked rubber composition could be reduced, thus completing the present invention. The dynamic magnification of a crosslinked rubber composition deteriorates when the weight-average molecular weight of the hydrogenated conjugated diene polymer is less than 150,000, when the hydrogenation rate exceeds 99%, or when the iodine value of rubber component (A) is less than 10, as this reduces the crosslink density of the crosslinked rubber composition, lowering the static spring constant and worsening the dynamic magnification. Furthermore, when the carbon black content in the crosslinked rubber composition is less than 10 parts by mass, the elastic modulus of the crosslinked rubber composition decreases, lowering the static spring constant and worsening the dynamic magnification. On the other hand, when the molecular weight of the hydrogenated conjugated diene polymer exceeds 1.5 million, or when the carbon black content in the crosslinked rubber composition exceeds 120 parts by mass, the dynamic spring constant tends to increase and the dynamic magnification worsens due to poor dispersion of fillers caused by deterioration in processability.

[0012] The crosslinked rubber composition of this embodiment is a crosslinked rubber composition containing rubber component (A) and carbon black (B). However, if necessary, a rubbery polymer other than the hydrogenated conjugated diene polymer that is rubbery polymer 1 may also be used. Furthermore, two or more types of rubbery polymers may be used. Furthermore, in addition to carbon black, the material may contain inorganic fillers such as silica, as well as other additives such as silane coupling agents, rubber softeners, waxes, crosslinking agents such as sulfur and peroxides, vulcanization accelerators, and vulcanization aids. The following describes each ingredient.

[0013] (Rubber component (A)) The crosslinked rubber composition of this embodiment is a crosslinked body of a rubber composition containing rubber component (A). Rubber component (A) has an iodine value of 10 or more and 370 or less. The rubber component (A) constituting the crosslinked rubber composition of this embodiment contains 10% to 100% by mass of a hydrogenated conjugated diene polymer (rubbery polymer 1). The content of hydrogenated conjugated diene polymer (rubber-like polymer 1) in rubber component (A) is 10% by mass or more, preferably 15% by mass or more, and more preferably 20% by mass or more, from the viewpoint of the heat resistance of the crosslinked rubber composition of this embodiment. Furthermore, from the viewpoint of the vibration damping properties of the crosslinked rubber composition of this embodiment, it is 100% by mass or less, preferably 80% by mass or less, and more preferably 75% by mass or less. On the other hand, when the rubber composition of this embodiment is used for applications such as packing, sealing materials, and rubber rolls, it is required that there be few constraints on vibration damping properties while the compression set of the crosslinked rubber composition is small. Therefore, in this case, the content of the hydrogenated conjugated diene polymer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass in the rubber component (A). Furthermore, rubber component (A) may also contain rubber components other than the hydrogenated conjugated diene polymer (rubbery polymer 1). As the rubber component other than the hydrogenated conjugated diene polymer, rubbery polymer 2, described later, is preferred.

[0014] <Rubber-like polymer 1: Hydrogenated conjugated diene polymer> The hydrogenated conjugated diene polymer (rubber-like polymer 1) contained in rubber component (A) is obtained by polymerizing or copolymerizing at least a conjugated diene monomer and optionally an aromatic vinyl monomer, and then hydrogenating a portion of the conjugated diene monomer units. In this specification, "monomer" refers to the compound before polymerization, and "monomer unit" refers to the constituent unit that makes up the polymer. Examples of conjugated diene monomers include, but are not limited to, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene. Among these, 1,3-butadiene and isoprene are preferred from the viewpoint of ease of industrial availability, and 1,3-butadiene is more preferred. These may be used individually or in combination of two or more. Furthermore, aromatic vinyl monomers are not limited to the following, but examples include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene. Among these, styrene is preferred from the viewpoint of ease of industrial availability. These may be used individually or in combination of two or more.

[0015] The hydrogenated conjugated diene polymer preferably contains aromatic vinyl monomer units from the viewpoint of improving the tensile strength and 300% modulus properties of the crosslinked rubber composition of this embodiment, and the content of aromatic vinyl monomer units is more preferably 3% by mass or more, and even more preferably 5% by mass or more. On the other hand, from the viewpoint of improving the processability of the crosslinked rubber composition of this embodiment, it is preferably 55% by mass or less, more preferably 50% by mass or less, and even more preferably 47% by mass or less. In particular, when the crosslinked rubber composition of this embodiment is used in applications subject to high loads, such as vibration-damping rubber or vibration damping materials, it is preferable that the tensile strength and 300% modulus are high, and the content of aromatic vinyl monomer units in the hydrogenated conjugated diene polymer is preferably 3% by mass or more. Furthermore, when the glass transition temperature of the hydrogenated conjugated diene polymer is set to, for example, -50°C or lower, the content of aromatic vinyl monomer units is preferably 20% by mass or less, and more preferably 18% by mass or less. The content of aromatic vinyl monomer units in hydrogenated conjugated diene polymers can be controlled within the above numerical range by adjusting the amount of aromatic vinyl monomer added and the polymerization time during the polymerization process.

[0016] Other monomers used in the hydrogenated conjugated diene polymer include, but are not limited to, non-conjugated polyene monomers such as ethylidene norbornene, dicyclopentadiene, vinyl norbornene, and divinylbenzene; and cyclic non-conjugated polyene monomers such as dicyclopentadiene, vinyl norbornene, and ethylidene norbornene. By using these other monomers, the balance between heat resistance, ozone resistance, and vibration damping properties when the crosslinked rubber composition of this embodiment is used as vibration damping rubber tends to be further improved. These may be used individually or in combination of two or more types.

[0017] [Content of aromatic vinyl monomer blocks] The content of aromatic vinyl monomer blocks in the hydrogenated conjugated diene polymer is less than 5.0% by mass, preferably 4.0% by mass or less, more preferably 3.5% by mass or less, and even more preferably 3.0% by mass or less, from the viewpoint of lowering the dynamic magnification, which is an indicator of the abrasion resistance and vibration damping properties of the crosslinked rubber composition of this embodiment. In this specification, "aromatic vinyl monomer block" refers to a structure in which eight or more aromatic vinyl monomer units are linked together. The method for measuring the content of aromatic vinyl monomer blocks is not particularly limited, but known methods include, for example, measuring the amount of structures in which styrene units are linked using NMR, as described in International Publication No. 2014 / 133097. Another method is to decompose the butadiene-styrene copolymer using Kolthoff's method (as described in IMKOLTHOFF, et al., J. Polym. Sci. 1, 429 (1946)) and analyze the amount of methanol-insoluble polystyrene. Specifically, it can be measured by the method described in the examples below. The content of aromatic vinyl monomer blocks in the hydrogenated conjugated diene polymer can be controlled by adjusting the polymerization conditions. For example, in a method in which aromatic vinyl monomers are polymerized first and then conjugated diene monomers are added to obtain a conjugated diene polymer, or in a method in which aromatic vinyl monomers are added before the active ends are deactivated after polymerizing a conjugated diene polymer, the content can be controlled within the above numerical range by adjusting the amount of aromatic vinyl monomers added and the amount of polymerization initiator added.

[0018] [Amount of 1,2-vinyl bonds before hydrogenation] From the viewpoint of reducing the crystallinity of the polymer when hydrogenated, the amount of 1,2-vinyl bonds in the conjugated diene monomer before hydrogenation in the hydrogenated conjugated diene polymer is preferably 20 mol% or more, more preferably 23 mol% or more, and even more preferably 25 mol% or more. Furthermore, from the viewpoint of improving the flexibility of the crosslinked rubber composition of this embodiment and the processability when preparing the crosslinked rubber composition of this embodiment, the amount of 1,2-vinyl bonds in the conjugated diene monomer is preferably 65 mol% or less, more preferably 62 mol% or less, and even more preferably 59 mol% or less. The amount of 1,2-vinyl bond before hydrogenation is: 1 This can be measured by 1H-NMR. Furthermore, the amount of 1,2-vinyl bonds before hydrogenation can be controlled within the above numerical range by adjusting the polymerization temperature and the amount of polar compound added. Examples of polar compounds that can be used include, but are not limited to, ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium-tert-amylate, potassium-tert-butyrate, sodium-tert-butyrate, and sodium amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used individually or in combination of two or more. The amount of polar compound used is not particularly limited and can be selected according to the purpose, but it is preferably 0.01 moles or more and 100 moles or less per mole of polymerization initiator.

[0019] [Amount of vinyl bonds in hydrogenated conjugated diene polymers] The amount of vinyl bond in the hydrogenated conjugated diene polymer is preferably 0.1 mole or more, more preferably 0.5 mole or more, and even more preferably 1.0 mole or more, from the viewpoint of the crosslinkability of the hydrogenated conjugated diene polymer. On the other hand, from the viewpoint of the heat resistance of the crosslinked rubber composition of this embodiment, it is preferably less than 10 mole, more preferably 7 mole or less, and even more preferably 5 mole or less. Furthermore, "the amount of vinyl bonds in hydrogenated conjugated diene polymers" refers to the amount of 1,2-vinyl bonds present in the hydrogenated conjugated diene polymer without hydrogenation, while remaining in the 1,2-vinyl bond state, among the unhydrogenated conjugated diene monomer units and the hydrogenated conjugated diene monomer units. The amount of vinyl bond in the hydrogenated conjugated diene polymer is 1 It can be measured by 1H-NMR. Specifically, it can be measured by the method described in the examples below. Furthermore, the amount of vinyl bonds in the hydrogenated conjugated diene polymer can be controlled to the above numerical range by adjusting the amount of 1,2-vinyl bonds before hydrogenation, the hydrogenation reaction temperature, the type of catalyst used in the hydrogenation reaction, and the amount of hydrogenation.

[0020] [Hydrogenation rate] From the viewpoint of the ozone resistance of the crosslinked rubber composition of this embodiment, the hydrogenation rate of the hydrogenated conjugated diene polymer (rubber-like polymer 1) is 10% or more, preferably 20% or more, more preferably 30% or more, and even more preferably 60% or more. On the other hand, from the viewpoint of ensuring that the hydrogenated conjugated diene polymer undergoes a sufficient crosslinking reaction, the hydrogenation rate is 99% or less, preferably 97% or less, more preferably less than 90%, and even more preferably less than 80%. The hydrogenation ratio of hydrogenated conjugated diene polymers is the molar ratio in which the double bonds in the structure derived from the conjugated diene monomer unit become saturated bonds through the hydrogenation reaction. To reduce the compression set of the crosslinked rubber composition of this embodiment, the hydrogenation rate of the hydrogenated conjugated diene polymer is preferably 30% or more, more preferably 40% or more, and even more preferably 45% or more, in order to improve thermal stability. On the other hand, to increase the crosslinking density of the crosslinked rubber composition, the hydrogenation rate of the hydrogenated conjugated diene polymer is preferably 99% or less, more preferably 95% or less, and even more preferably 90% or less. As a method for hydrogenating after copolymerizing a conjugated diene monomer and, if necessary, an aromatic vinyl monomer, a preferred method is to polymerize the conjugated diene monomer by anionic polymerization under various additives and conditions, copolymerize it with other monomers as necessary, and then hydrogenate it, as described in, for example, International Publication No. 96 / 05250, Japanese Patent Publication No. 2000-053706, International Publication No. 2003 / 085010, International Publication No. 2019 / 151126, International Publication No. 2019 / 151127, International Publication No. 2002 / 002663, and International Publication No. 2015 / 006179. The hydrogenation rate can be measured by the method described in the examples below. The hydrogenation rate can be controlled within the above numerical range by adjusting the amount of hydrogen added during the hydrogenation reaction, the reaction temperature, the reaction time, the type of catalyst, and the amount of catalyst added.

[0021] [Weight average molecular weight] The weight-average molecular weight of the hydrogenated conjugated diene polymer (rubber-like polymer 1) is 150,000 or more, preferably 200,000 or more, more preferably 220,000 or more, and even more preferably 250,000 or more, from the viewpoint of the compression set, tensile strength, and elongation of the crosslinked rubber composition of this embodiment. On the other hand, from the viewpoint of the processability of the crosslinked rubber composition of this embodiment, the molecular weight is 1,500,000 or less, more preferably 1,200,000 or less, and even more preferably 1,000,000 or less.

[0022] [Molecular weight distribution] The molecular weight distribution (= weight-average molecular weight / number-average molecular weight) of the hydrogenated conjugated diene polymer (rubber-like polymer 1) is preferably 2.0 or less, more preferably 1.8 or less, and even more preferably 1.6 or less, from the viewpoint of improving polymerization reproducibility. On the other hand, from the viewpoint of the processability of the crosslinked rubber composition of this embodiment, it is preferably 1.05 or more, more preferably 1.2 or more, and even more preferably 1.4 or more. The weight-average molecular weight and molecular weight distribution can be calculated from the polystyrene-equivalent molecular weight measured by GPC (gel permeation chromatography). Specifically, they can be measured by the method described in the examples below. The weight-average molecular weight and molecular weight distribution can be controlled to the aforementioned numerical range by adjusting the amount of monomer added, the timing of addition, and the amount of polymerization initiator added during the polymerization process.

[0023] [Mooney Viscosity] The Mooney viscosity of the hydrogenated conjugated diene polymer (rubber-like polymer 1) at 100°C, when measured with an L-type rotor, is preferably 150 or less, more preferably 130 or less, and even more preferably 120 or less, from the viewpoint of the processability of the crosslinked rubber composition of this embodiment. On the other hand, from the viewpoint of the tensile strength and tensile elongation of the crosslinked rubber composition, it is preferably 30 or more, more preferably 40 or more, and even more preferably 50 or more. The Mooney viscosity of hydrogenated conjugated diene polymers can be measured by the method described in the examples below.

[0024] [Mooney stress relaxation] The Mooney stress relaxation (MSR) of the hydrogenated conjugated diene polymer (rubber-like polymer 1) at 100°C is preferably 0.80 or less, more preferably 0.75 or less, and even more preferably 0.70 or less, from the viewpoint of suppressing the cold flow properties of the crosslinked rubber composition of this embodiment and improving the modulus of the crosslinked rubber composition of this embodiment. The lower limit is not particularly limited, but it is preferably 0.10 or more from the viewpoint of processability when preparing the crosslinked rubber composition of this embodiment. The Mooney stress relaxation of hydrogenated conjugated diene polymers at 100°C can be measured by the method described in the examples below. The Mooney stress relaxation of hydrogenated conjugated diene polymers at 100°C can be controlled within the above numerical range by increasing the branching component content or increasing the hydrogenation rate.

[0025] [Glass transition temperature] The glass transition temperature (Tg) of the hydrogenated conjugated diene polymer (rubbery polymer 1) is preferably -25°C or lower, more preferably -35°C or lower, even more preferably -50°C or lower, and even more preferably -56°C or lower. The glass transition temperature of hydrogenated conjugated diene polymers can be controlled within the above range by adjusting the content of aromatic vinyl monomer units, the amount of vinyl bonds, and the hydrogenation rate. When the glass transition temperature of the hydrogenated conjugated diene polymer is within the above range, the vibration-damping rubber produced using the crosslinked rubber composition of this embodiment tends to exhibit excellent vibration damping properties and fracture characteristics under low-temperature conditions.

[0026] Regarding the control of the glass transition temperature of hydrogenated conjugated diene polymers, in order to set the glass transition temperature of a hydrogenated conjugated diene polymer to -50°C or lower, for example, if the hydrogenated conjugated diene polymer is a hydrogenated polymer of a random copolymer of styrene and butadiene with a hydrogenation rate of 10%, it is preferable to set the styrene content to 18% by mass or less, and the amount of 1,2-vinyl bonds in the conjugated diene monomer before hydrogenation to 15 mol% or more and 40 mol% or less. On the other hand, if the hydrogenation rate is 90%, it is preferable to set the styrene content to 10% by mass or less, and the amount of 1,2-vinyl bonds in the conjugated diene monomer before hydrogenation to 20 mol% or more and 40 mol% or less. By setting the glass transition temperature of the hydrogenated conjugated diene polymer to -50°C or lower, a crosslinked rubber composition with excellent low-temperature properties can be obtained.

[0027] The glass transition temperature of the crosslinked rubber composition in this embodiment largely depends on the glass transition temperature of the hydrogenated conjugated diene polymer, but generally shifts to a higher temperature than the glass transition temperature of the hydrogenated conjugated diene polymer. This is due to factors such as the reduced mobility of molecular chains caused by crosslinking. Furthermore, from the viewpoint of use in low-temperature environments, it is necessary to lower the glass transition temperature of the crosslinked rubber composition and to minimize changes in physical properties such as storage modulus and hardness in the operating temperature range. When used in low-temperature environments, the crosslinked rubber composition must have sufficient flexibility even at temperatures as low as -20°C. From the viewpoint of controlling the glass transition temperature of the crosslinked rubber composition to -20°C or lower, it is preferable to adjust the glass transition temperature of the hydrogenated conjugated diene polymer to -50°C or lower. The glass transition temperature of the hydrogenated conjugated diene polymer has a significant influence on the glass transition temperature of the crosslinked rubber composition, and by setting the glass transition temperature of the hydrogenated conjugated diene polymer to -50°C or lower, it tends to be easier to control the glass transition temperature of the crosslinked rubber composition to -20°C or lower. This ensures the flexibility of the crosslinked rubber composition under temperature conditions of -20°C, and furthermore, tends to yield a crosslinked rubber composition with little change in physical properties, including elastic modulus, from -20°C to room temperature, and with low temperature dependence. The glass transition temperature of the crosslinked rubber composition is preferably -30°C or lower, and more preferably -40°C or lower, in order to reduce low-temperature properties and temperature dependence. From the viewpoint of controlling the glass transition temperature of the crosslinked rubber composition to the above numerical range, it is preferable to set the glass transition temperature of the hydrogenated conjugated diene polymer to -50°C or lower, and furthermore, when the hydrogenated conjugated diene polymer is used in combination with other polymers, it is preferable to use materials with good compatibility.

[0028] The glass transition temperature of the hydrogenated conjugated diene polymer and the crosslinked rubber composition of this embodiment is determined in accordance with ISO 22768:2006 by recording a DSC curve while increasing the temperature within a predetermined range, and the peak top (inflection point) of the DSC differential curve is defined as the glass transition temperature. Specifically, it can be measured by the method described in the examples below.

[0029] [Degeneration rate] The hydrogenated conjugated diene polymer (rubber-like polymer 1) preferably contains nitrogen atoms from the viewpoint of compression set and abrasion resistance of the crosslinked rubber composition of this embodiment. Nitrogen atoms can be introduced by using a modifier. This tends to improve the dispersibility of the filler, carbon black (B). From the viewpoint of dispersibility of fillers such as silica and carbon black, the hydrogenated conjugated diene polymer is preferably modified to a rate of 40% or more, more preferably to 60% or more, and even more preferably to 70% or more. There is no particular upper limit to the modification rate, but from the viewpoint of lowering the viscosity of the compound after kneading and improving processability, it is preferably 99% or less, more preferably 98% or less, even more preferably 95% or less, and even more preferably 90% or less. If the compression set of the crosslinked rubber composition of this embodiment is to be reduced, it is preferable to improve the dispersibility of the filler. From this viewpoint, it is preferable to introduce functional groups with high affinity and / or reactivity with the filler into the hydrogenated conjugated diene polymer, and from the viewpoint of sufficiently increasing the affinity and / or reactivity with the filler, the modification rate of the hydrogenated conjugated diene polymer is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. In this specification, "coupling agent" refers to a compound that generates two or more branched components. "Modifying agent" refers to a compound that contains a nitrogen atom and can bond to the polymer to be modified. A compound that contains a nitrogen atom and generates two or more branched components can be both a coupling agent and a modifying agent.

[0030] In this specification, "modification rate" refers to the mass ratio of the polymer having a nitrogen atom-containing functional group to the total amount of the hydrogenated conjugated diene polymer. The nitrogen atom may be introduced into the hydrogenated conjugated diene polymer at any of the following locations: the polymerization initiation end, within the molecular chain (including grafts), or at the polymerization end. When producing hydrogenated conjugated diene polymers by polymerizing conjugated diene monomers followed by hydrogenation, it is preferable to use a method that introduces nitrogen atoms using a coupling agent containing nitrogen atoms, from the viewpoint of obtaining polymerization productivity and a high modification rate. The modification rate of hydrogenated conjugated diene polymers can be measured by the method described in the examples below. The modification rate of hydrogenated conjugated diene polymers can be controlled within the above numerical range by adjusting the amount of modification agent added.

[0031] From the viewpoint of polymerization productivity and high modification rate, preferred coupling agents containing nitrogen atoms include, for example, isocyanate compounds, isothiocyanate compounds, isocyanuric acid derivatives, nitrogen group-containing carbonyl compounds, nitrogen group-containing vinyl compounds, nitrogen group-containing epoxy compounds, and nitrogen group-containing alkoxysilane compounds. Furthermore, from the viewpoint of reducing the viscosity of the crosslinked rubber composition of this embodiment and reducing the occurrence of cracks in the compound sheet, a higher number of branches in the coupling agent is preferable. The number of branches in the coupling agent is not particularly limited, but from the viewpoint of improving the processability when preparing the crosslinked rubber composition of this embodiment, three or more branches are preferred, and four or more branches are more preferred. There is no particular upper limit to the number of branches, but from the viewpoint of productivity, 30 branches or less is preferred. From the viewpoint of reactivity, nitrogen-containing alkoxysilane compounds and nitrogen-containing polyfunctional modifiers are more preferred as coupling agents containing nitrogen atoms.

[0032] The nitrogen-containing alkoxysilane compounds are not limited to the following, but include, for example, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(4-trimethoxysilylbutyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacycloheptane, and 2,2-dimethoxy-1-(3- (Dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy-2-methyl-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-ethoxy-2-ethyl-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy-2-methyl-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, 2-E Toxy-2-ethyl-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, tris(3-trimethoxysilylpropyl)amine, tris(3-methyldimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-methyldiethoxysilylpropyl)amine, tris(trimethoxysilylmethyl)amine, tris(2-trimethoxysilylethyl)amine, tris(4-trimethoxysilylbutyl)amine, tetrakis[3-(2,2-dimethoxy-1-a Examples include [2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, and N-(3-(bis(3-(trimethoxysilyl)propyl)amino)propyl)-N-methyl-N'-(3-(methyl(3-(trimethoxysilyl)propyl)amino)propyl)-N'-(3-(trimethoxysilyl)propyl)-1,3-propanediamine.

[0033] Examples of nitrogen group-containing polyfunctional modifiers include, but are not limited to, compounds having one or more functional groups selected from the group consisting of epoxy groups, carbonyl groups, carboxylic acid ester groups, carboxylic acid amide groups, acid anhydride groups, phosphate ester groups, phosphite ester groups, epithio groups, thiocarbonyl groups, thiocarboxylic acid ester groups, dithiocarboxylic acid ester groups, thiocarboxylic acid amide groups, imino groups, ethyleneimino groups, halogen groups, alkoxysilyl groups, isocyanate groups, thioisocyanate groups, conjugated diene groups, and aryl vinyl groups, and having at least one nitrogen atom in the compound.

[0034] In calculating the number of moles of functional groups, each alkoxy group of epoxy, carbonyl, epithio, thiocarbonyl, imino, ethyleneimino, halogen, conjugated diene, aryl vinyl, and alkoxysilyl groups is counted as one functional group, each carboxylic acid ester, carboxylic acid amide, acid anhydride, thiocarboxylic acid ester, dithiocarboxylic acid ester, thiocarboxylic acid amide, isocyanate, and thioisocyanate groups is counted as two functional groups, and each phosphate ester and phosphite ester group is counted as three functional groups. A polyfunctional modifier that can be preferably used to modify the hydrogenated conjugated diene polymer (rubber-like polymer 1) contained in the crosslinked rubber composition of this embodiment is a polyfunctional modifier in which the sum of the number of functional groups in one molecule is 2 or more, and more preferably a polyfunctional modifier in which the sum of the number of functional groups is 3 or more.

[0035] When a modified polymer is used as the hydrogenated conjugated diene polymer in the crosslinked rubber composition of this embodiment, in addition to the coupling agent and modifying agent described above, polyfunctional modifying agents other than the nitrogen group-containing polyfunctional modifying agent described later, as well as coupling agents that do not contain nitrogen atoms, can also be used to prepare such a modified polymer.

[0036] The polyfunctional modifier is not limited to the following, but includes, for example, polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether and glycerol triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenyl groups such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxylated liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine. Examples include glycidylamino compounds such as ruaniline, diglycidyl orthotoluidine, tetraglycidylmetoxydiamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; and compounds having epoxy groups and other functional groups such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltributoxysilane, epoxy-modified silicones, epoxidized soybean oil, and epoxidized linseed oil.

[0037] Furthermore, examples of coupling agents that do not contain nitrogen atoms include, but are not limited to, alkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, and alkyltriphenoxysilane; halogenated silane compounds such as silicon tetrachloride, silicon tetrabromide, silicon tetraiodide, monomethyltrichlorosilicon, monoethyltrichlorosilicon, monobutyltrichlorosilicon, monohexyltrichlorosilicon, monomethyltribromosilicon, and bistrichlorosilylethane; and alkoxyhalogenated silane compounds such as monochlorotrimethoxysilane, monobromotrimethoxysilane, dichlorodimethoxysilane, dibromodimethoxysilane, trichloromethoxysilane, and tribromomethoxysilane. Furthermore, examples of coupling agents that do not contain nitrogen atoms include tin halogenated compounds such as tin tetrachloride, tin tetrabromide, monomethyltrichlorotin, monoethyltrichlorotin, monobutyltrichlorotin, monophenyltrichlorotin, and bistrichlorostanylethane; polyhalogenated phosphorus compounds such as trichlorophosphine and tribromophosphine; phosphite ester compounds such as trisnonylphenyl phosphite, trimethyl phosphite, and triethyl phosphite; and phosphate ester compounds such as trimethyl phosphate and triethyl phosphate.

[0038] Furthermore, as a modifying agent for modifying the hydrogenated conjugated diene polymer (rubber-like polymer 1) contained in the crosslinked rubber composition of this embodiment, a terminal modifying agent may be used. Examples of terminal modifying agents are, but are not limited to, 1,3-diethyl-2-imidazolinone, 1,3-dimethyl-2-imidazolinone, 1,3-dipropyl-2-imidazolinone, 1-methyl-3-ethyl-2-imidazolinone, 1-methyl-3-propyl-2-imidazolinone, 1-methyl-3-butyl-2-imidazolinone, 1,3-dihydro-1,3-dimethyl-2H-imidazole-2-one, and the like.

[0039] (Iodine value of rubber component (A)) The rubber component (A) used in the crosslinked rubber composition of this embodiment has an iodine value of 370 or less, preferably 350 or less, more preferably 300 or less, even more preferably 250 or less, and even more preferably 200 or less, from the viewpoint of the heat resistance and ozone resistance of the crosslinked rubber composition of this embodiment. As described later, even when the iodine value of the hydrogenated conjugated diene polymer (rubbery polymer 1) is controlled, if other rubber components with a high degree of unsaturation (high iodine value) are used in combination, the overall iodine value of rubber component (A) may increase, potentially affecting the heat resistance of the crosslinked rubber composition. Therefore, in this embodiment, the iodine value of not only the hydrogenated conjugated diene polymer (rubbery polymer 1) but also the overall iodine value of rubber component (A) is controlled to a certain range. The iodine value of the rubber composition (A) shall be 10 or more, preferably 20 or more, and more preferably 30 or more, from the viewpoint of the ease of crosslinking of the rubber component (A). The iodine value can be measured in accordance with the method described in "JIS K 0070:1992". The iodine value is a value that expresses the amount of halogen that reacts with 100g of the substance in question, converted to grams of iodine; therefore, the unit of the iodine value is "Ig / 100g". The iodine value of rubber component (A) can be controlled by adjusting the iodine value and composition ratio of the constituent rubber components, such as hydrogenated conjugated diene polymers and other rubbers.

[0040] Since conjugated diene monomers have double bonds, in the method for producing hydrogenated conjugated diene polymers (rubbery polymer 1) described later, for example, when a hydrogenated conjugated diene polymer is produced by copolymerizing a conjugated diene monomer with a vinyl aromatic monomer, the iodine value of the rubber component (A) is lower when the content of conjugated diene monomers in the polymer is lower, and also lower when the hydrogenation rate is higher. The iodine value of hydrogenated conjugated diene polymers can be controlled by adjusting polymerization conditions such as the amount of conjugated diene monomers containing unsaturated bonds added, polymerization time, and polymerization temperature, as well as conditions such as the amount and duration of hydrogenation in the hydrogenation process.

[0041] The iodine value of the hydrogenated conjugated diene polymer (rubber-like polymer 1) contained in rubber component (A) is preferably 300 or less, more preferably 250 or less, and even more preferably 200 or less, from the viewpoint of heat resistance and ozone resistance of the crosslinked rubber composition of this embodiment. Furthermore, from the viewpoint of the crosslinkability of rubber component (A), it is preferably 1 or more, more preferably 5 or more, and even more preferably 10 or more. If rubber component (A) contains a rubbery polymer 2 other than the hydrogenated conjugated diene polymer (rubbery polymer 1), the iodine value of the rubbery polymer 2 other than the hydrogenated conjugated diene polymer will depend on the type of rubber described later. For example, polybutadiene has an iodine value of 470, and polyisoprene has an iodine value of 373. When selecting a rubber component with a high iodine value as rubbery polymer 2, the iodine value of the entire rubber component (A) can be controlled to be between 10 and 370 by adjusting the ratio of the hydrogenated conjugated diene polymer (rubbery polymer 1), reducing the iodine value of the hydrogenated conjugated diene polymer (rubbery polymer 1), or by adding other rubber components with even lower iodine values.

[0042] (Hydrogenated conjugated diene polymers (rubbery polymer 1) and other rubbery polymers 2) The rubber component (A) used in the crosslinked rubber composition of this embodiment may include rubbery polymer 2 other than the hydrogenated conjugated diene polymer (rubbery polymer 1) described above. As rubbery polymer 2 other than hydrogenated conjugated diene polymers, a rubbery polymer having a glass transition temperature of -120°C or higher and 0°C or lower, and a Mooney viscosity of 20 or higher and 180 or lower at 100°C is preferred.

[0043] Other rubbery polymers 2 besides hydrogenated conjugated diene polymers (rubbery polymer 1) include, but are not limited to, at least one rubbery polymer selected from styrene-butadiene rubber, styrene-isoprene rubber, natural rubber, polybutadiene, polyisoprene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber, butyl rubber, polyurethane, epichlorohydrin rubber, silicone rubber, acrylic rubber, nitrile rubber, chloroprene rubber, and fluororubber. Polybutadiene includes low-cis-polybutadiene, high-cis-polybutadiene, and high-trans-polybutadiene; styrene-butadiene rubber includes solution-polymerized styrene-butadiene copolymer rubber and emulsion-polymerized styrene-butadiene copolymer rubber; and butyl rubber includes chlorinated butyl rubber and brominated butyl rubber.

[0044] Furthermore, depending on the application and required physical properties of the crosslinked rubber composition of this embodiment, the type of rubbery polymer 2 can be selected. For example, it is preferable to select natural rubber to improve mechanical properties such as tensile strength of the crosslinked rubber composition of this embodiment, polybutadiene to improve abrasion resistance and low-temperature properties, and ethylene-propylene-diene rubber to improve weather resistance. While not limited to the following, natural rubbers are preferred, for example, smoked sheets such as RSS3-5, SMR, and epoxidized natural rubber, due to their high molecular weight content and excellent fracture strength.

[0045] Furthermore, from the viewpoint of controlling the glass transition temperature and cold resistance of the crosslinked rubber composition of this embodiment, the rubber component (A) preferably consists only of the hydrogenated conjugated diene polymer (rubbery polymer 1) described above and the rubbery polymer 2 having the predetermined glass transition temperature and Mooney viscosity described above, but it may also contain other rubber components or polymers. For example, it may contain chloroprene rubber, styrene-butadiene-styrene block copolymer, or styrene-isoprene-styrene block copolymer.

[0046] The rubbery polymer 2, other than the hydrogenated conjugated diene polymer (rubby polymer 1), preferably has a glass transition temperature of -60 to 0°C and a Mooney viscosity of 40 to 110.

[0047] The content of rubbery polymer 2 other than hydrogenated conjugated diene polymer (rubbery polymer 1) is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, from the viewpoint of the crosslinking properties of rubber component (A) and the economic benefits of using general-purpose materials. On the other hand, from the viewpoint of heat resistance and compression set of the crosslinked rubber composition of this embodiment, it is preferable that the amount be 90% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less.

[0048] The types and blending ratios of hydrogenated conjugated diene polymers (rubbery polymer 1) and other rubbery polymers 2 are not particularly limited, but can be selected from the following perspectives. For example, if the other rubbery polymer 2 has 10% by mass or more double bonds, or if it is a rubber with an iodine value of 50 (Ig / 100g) or more, such as styrene-butadiene rubber, styrene-isoprene rubber, natural rubber, polybutadiene, or polyisoprene rubber, the viscosity during processing tends to be lower when preparing the crosslinked rubber composition of this embodiment, and the crosslinking rate when obtaining the crosslinked rubber composition of this embodiment tends to be faster, which is preferable from the viewpoint of productivity. Furthermore, the ratio of hydrogenated conjugated diene polymer (rubbery polymer 1) to other rubbery polymers 2 is preferably 10:90 to 60:40, more preferably 15:85 to 50:50, and even more preferably 20:80 to 40:60. On the other hand, when the rubbery polymer 2 has less than 10% double bonds or an iodine value of less than 50 (Ig / 100g), such as ethylene-propylene-diene rubber, ethylene-propylene rubber, or butyl rubber, the crosslinked rubber composition of this embodiment tends to be excellent in suppressing degradation under acidic and basic conditions. Furthermore, from the viewpoint of improving vibration damping properties without significantly impairing the heat resistance and ozone resistance of the crosslinked rubber composition of this embodiment, it is preferable to set the ratio of rubbery polymer 1 to rubbery polymer 2 to rubbery polymer 1:rubbery polymer 2 = 100:0 to 20:80, more preferably 80:20 to 20:80, and even more preferably 70:30 to 30:70.

[0049] The Mooney stress relaxation (MSR) of rubbery polymer 2 other than the hydrogenated conjugated diene polymer (rubbery polymer 1) is preferably 0.9 or less, more preferably 0.85 or less, even more preferably 0.80 or less, and even more preferably 0.75 or less, from the viewpoint of suppressing the cold flow properties of rubbery polymer 2 and improving the modulus of the crosslinked rubber composition of this embodiment. The lower limit is not particularly limited, but it is preferably 0.10 or more from the viewpoint of processability when preparing the crosslinked rubber composition of this embodiment. The smaller the ratio of Mooney stress relaxation at 100°C between the hydrogenated conjugated diene polymer (rubbery polymer 1) and the rubbery polymer 2, i.e., (value of Mooney stress relaxation of hydrogenated conjugated diene polymer (rubbery polymer 1)) / (value of Mooney stress relaxation of rubbery polymer 2), the greater the molecular chain entanglement of the hydrogenated conjugated diene polymer (rubbery polymer 1) than that of rubbery polymer 2. From the viewpoint of improving the reinforcing effect of the crosslinked rubber composition of this embodiment, the value of the stress relaxation ratio is preferably 0.1 or more and less than 1.0, more preferably 0.15 or more and 0.9 or less, and even more preferably 0.2 or more and 0.85 or less.

[0050] (Change in Shore A hardness of crosslinked rubber composition before and after heating) In the crosslinked rubber composition of this embodiment, Shore A hardness refers to the durometer hardness of JIS K6253-3, and is a value measured using a Type A meter. The crosslinked rubber composition of this embodiment preferably has a Shore A hardness of 40 to 80 (A40° to A80°) from the viewpoint of mechanical properties and strength, more preferably 45 to 75 (A45° to A75°), and even more preferably 48 to 73 (A48° to A73°). Furthermore, the crosslinked rubber composition of this embodiment satisfies the following formula (1) when heated at 100°C for 72 hours under air, with a change in Shore A hardness before and after heating. Note that in the following formula, only the difference in numerical values ​​is shown. -10 < (Shore A hardness after heating) - (Shore A hardness before heating) < 5 ... (1)

[0051] The upper limit of formula (1) is less than 5, preferably 4 or less, and more preferably 3 or less. A change in Shore A hardness of less than 5 suggests that the amount of residual crosslinking agent during the crosslinking reaction is reduced to a practically acceptable level, that there are few residual double bonds, and that the increase in crosslinking sites due to thermal reaction is small. This is preferable because it can be expected to suppress the increase in hardness of the crosslinked rubber composition of this embodiment over time. If equation (1) exceeds the upper limit and the hardness after heating increases, it indicates that the crosslinking points in the crosslinked rubber composition have increased due to heating, causing the crosslinked rubber composition to harden. This can lead to a change in the balance of physical properties, such as an increase in tensile strength but a decrease in tensile elongation, making it difficult to continue using the material with the properties originally designed.

[0052] The lower limit of formula (1) is greater than -10, preferably -8 or higher, more preferably -7 or higher, even more preferably -6 or higher, and even more preferably -5 or higher. The change in Shore A hardness before and after heating being greater than -10 suggests that the reduction in crosslinking points, such as polymer chain severance and vulcanization reversal, can be suppressed, and is therefore preferred because it can be expected that the decrease in hardness of the crosslinked rubber composition over time will be suppressed. If equation (1) exceeds the lower limit and the hardness after heating decreases further, it indicates that the hardness has decreased due to phenomena such as the breaking of the main chain of the polymer in the crosslinked rubber composition by heating. For example, although the tensile elongation may improve, the tensile strength decreases, changing the balance of physical properties, and making it difficult to continue using the material with the properties originally designed.

[0053] The change in Shore A hardness before and after heating satisfies the range of formula (1), and when the cross-linked rubber composition of this embodiment is used as a material for components that are subjected to heat during use, such as engine mounts for automobiles, it exhibits sufficient heat resistance and exhibits the effect of minimal deterioration over time.

[0054] Methods for obtaining a crosslinked rubber composition that satisfies formula (1) include, for example, reducing the amount of crosslinking agent remaining in the crosslinked rubber composition, controlling the kneading temperature and crosslinking temperature to suppress the decomposition and gelation of rubber components due to radical generation during kneading and crosslinking, and adding an anti-aging agent. The residual amount of crosslinking agent in the crosslinked rubber composition is preferably 0.3% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less. The selection of the type of rubber used in the crosslinked rubber composition can also affect the value of formula (1). For example, natural rubber tends to have its main chain split when radicals are present, leading to a decrease in the hardness of the crosslinked rubber composition, while butadiene rubber tends to preferentially undergo crosslinking when radicals are present, leading to an increase in the hardness of the crosslinked rubber composition. Hydrogenated conjugated diene polymers (rubber-like polymer 1) are less prone to both of the above reactions, but tend to gel, increasing the hardness of the crosslinked rubber composition. Therefore, by combining rubber-like polymer 1 with natural rubber, the range of change in the hardness of the crosslinked rubber composition can be reduced. Regarding the mixing temperature, it is preferable that the maximum temperature when mixing the rubber component (A) and the additive is 150°C or less, more preferably 145°C or less, and even more preferably 140°C or less. On the other hand, it is preferable to mix at 110°C or higher in order to uniformly disperse the rubber component (A) and the additive. The crosslinking temperature is preferably 140°C to 175°C, more preferably 150°C to 175°C, and even more preferably 155°C to 175°C.

[0055] In the crosslinked rubber composition of this embodiment, if (Shore A hardness after heating) - (Shore A hardness before heating) is 5 or more, methods to control this to less than 5 include, for example, using a hydrogenated conjugated diene polymer with an iodine value of 100 or less, preferably 50 or less; using natural rubber in combination with 10 parts by mass or more per 100 parts by mass of the hydrogenated conjugated diene polymer; or reducing the amount of residual crosslinking agent in the crosslinked rubber composition to 0.1% by mass or less by raising the crosslinking temperature by about 5°C or extending the crosslinking time by about 10 minutes when obtaining the crosslinked rubber composition. On the other hand, when (Shore A hardness after heating) - (Shore A hardness before heating) is -10 or less, preferred methods for controlling it to be greater than -10 include, for example, reducing the amount of natural rubber used and increasing the proportion of hydrogenated conjugated diene polymers or polybutadiene rubber used, or using hydrogenated conjugated diene polymers with an iodine value of 30 or more and 200 or less.

[0056] Furthermore, when using a rubber component other than the hydrogenated conjugated diene polymer (rubbery polymer 1) described above as rubber component (A), selecting a rubber component with high compatibility with the hydrogenated conjugated diene polymer (rubbery polymer 1) results in a crosslinked rubber composition with less macroscopic separation, which is advantageous in terms of heat resistance. Excellent compatibility means that the solubility parameter (SP value) of the hydrogenated conjugated diene polymer (rubbery polymer 1) is close to that of the rubber component other than the rubbery polymer 1. Preferably, the absolute value of the difference in SP values ​​is 0.8 or less, more preferably 0.5 or less, and even more preferably 0.3 or less. For example, the SP values ​​of rubbery polymer 1 and rubber components can be calculated using the following method. First, the molar volume and cohesive energy of each vinyl polymer are calculated using the method of Bicerano (Reference: J. Bicerano, Prediction of Polymer Properties, 3rd edition, Marcel Dekker, 2002). For the cohesive energy, the value calculated according to the Van Krevelen method is used. Next, the SP values ​​of rubbery polymer 1 and rubber components can be determined using the method shown in equations 17.8 to 17.10 on page 615 of Jozef. Bicerano: PREDICTION OF POLYMER PROPERTIES, Marcel Dekker, AMERICA (2002). Note that microphase separation structures such as crystalline properties and block copolymers are ignored. Cohesive energy E (J / mol) / molar volume V (10 -6 m 3 Examples of / mol are given below. Polystyrene: 36932 / 97.0, 1,2-polybutadiene: 16450 / 58.3, 1,4-polybutadiene: 18579 / 59.1, 1,2-polybutylene: 17527 / 65.6, hydrogenated 1,4-polybutadiene: 18146 / 64.4, 1,4-polyisoprene: 22644 / 76.6, 1,2-polyisoprene: 19407 / 75.3, 3,4-polyisoprene: 20908 / 82.2, polyethylene: 9073 / 32.2. For example, the calculation method of the SP value in the case of an equimolar conjugated diene polymer of styrene / 1,4-butadiene is shown below. E = 36932×0.5 + 18579×0.5 = 27755 (J / mol) V = 97.0×0.5 + 59.1×0.5 = 78.1 (m 3 / mol) SP value = (27755 / 78.1) 1 / 2 = 18.6 ((J / cm 3 ) 1 / 2 )

[0057] (Flexibility of the crosslinked rubber composition under low-temperature conditions) Regarding the flexibility of the crosslinked rubber composition of this embodiment under low-temperature conditions, the viscoelastic parameters of the crosslinked rubber composition are measured, and the ratio of the storage modulus at -100°C to the storage modulus at -20°C is obtained, which can be used as an index of the flexibility under low-temperature conditions. The storage modulus can be measured in torsion mode using a viscoelasticity tester "ARES" manufactured by Rheometric Scientific, using a sheet of the crosslinked rubber composition with a thickness of 3 mm in accordance with JIS K 6394. The storage modulus (G’ (-100℃) ) measured at -100°C, a frequency of 10 Hz, and a strain of 1% and the storage modulus (G’ (-20℃) ) measured at -20°C, a frequency of 10 Hz, and a strain of 1%: the ratio (G’ (-20℃) / G’ (-100℃) ) × 100 is calculated. From the perspective of flexibility when used under low-temperature conditions, the above (G’ (-20℃) / G’ (-100℃) ) × 100 is preferably 1.5 or less, and more preferably 1.0 or less.

[0058] In this specification, the use "under low-temperature conditions" assumes use under temperature conditions of about -20°C. The above (G’ (-20℃) / G’ (-100℃)The value of ) × 100 is such that the denominator is the storage modulus when the crosslinked rubber composition is in a hard, glassy state, while the numerator is the storage modulus value that reflects the state of the crosslinked rubber composition at -20°C, i.e., whether it is soft like rubber or hard like glass, therefore (G' (-20℃) / G' (-100℃) A large value of () × 100 indicates that the storage modulus has sufficiently decreased at -20°C, and that the material can be used as a flexible material.

[0059] The above (G' (-20℃) / G' (-100℃) The value of (G') × 100 is greatly influenced by the glass transition temperature of the hydrogenated conjugated diene polymer used in the crosslinked rubber composition of this embodiment, but also depends on various conditions such as the carbon black (B) content and dispersion state described later, as well as the type and amount of additives such as oil. (-20℃) / G' (-100℃) To control the value of ), it is preferable to adjust the various conditions described above so that the glass transition temperature of the crosslinked rubber composition is -20°C or lower. The above (G' (-20℃) / G' (-100℃)In order to make the value of ) × 100 within the above-mentioned preferred numerical range, it is preferable to lower the glass transition temperature of the hydrogenated conjugated diene polymer used in the crosslinked rubber composition of this embodiment, or to lower the glass transition temperature of the crosslinked rubber composition, and to set the content of the filler containing carbon black (B) to 10 to 120 parts by mass per 100 parts by mass of rubber component (A), and more preferably to 10 to 100 parts by mass. When the filler is added in amounts of 30 parts by mass or more per 100 parts by mass of rubber component (A), it is preferable to set the glass transition temperature of the hydrogenated conjugated diene polymer to -40°C or lower. Furthermore, when the filler is added in amounts of 50 parts by mass or more per 100 parts by mass of rubber component (A), it is more preferable to set the glass transition temperature of the hydrogenated conjugated diene polymer to -50°C or lower. If the total content of the filler containing carbon black exceeds 120 parts by mass per 100 parts by mass of rubber component (A), the storage modulus of the crosslinked rubber composition may be high even at -20°C. When increasing the amount of filler added, it is preferable to highly disperse the filler. For example, using a hydrogenated conjugated diene polymer containing a modifying group that interacts with carbon black, or improving dispersibility by adjusting the temperature and kneading method during mixing, are effective methods.

[0060] (Method for producing hydrogenated conjugated diene polymers (rubbery polymer 1)) The following describes a method for producing the hydrogenated conjugated diene polymer (rubber-like polymer 1) that constitutes the rubber component (A) used in the crosslinked rubber composition of this embodiment. Unless otherwise specified, the value expressed in "parts by mass" is the value when the total amount of rubber component (A) is 100 parts by mass. Furthermore, the method for identifying the types and content ratios of rubber components contained in the crosslinked rubber composition of this embodiment is not particularly limited, but for example, NMR can be used. For example, a previously published report (JSR TECHNICAL REVIEW No. 126 / 2019) describes solids 13A method for quantitatively calculating the ratios of styrene units, 1,2-vinyl bonds, 1,4-vinyl bonds, 1,4-cis bonds, and isoprene units contained in a conjugated diene polymer composition is disclosed using CC-NMR, and this method can also be used to identify the rubber components of the crosslinked rubber composition of this embodiment.

[0061] <Method for polymerization and hydrogenation of hydrogenated conjugated diene polymers (rubbery polymer 1)> The hydrogenated conjugated diene polymer (rubber-like polymer 1) that constitutes rubber component (A) can be produced by polymerizing a conjugated diene monomer, copolymerizing an aromatic vinyl monomer as needed, and then adding a hydrogenation catalyst and hydrogenating the mixture. When the hydrogenated conjugated diene polymer is a copolymer of a conjugated diene monomer and an aromatic vinyl monomer, it is preferable that it be a random copolymer. Hydrogenated conjugated diene polymers are preferably those obtained by polymerizing at least a conjugated diene monomer, or by copolymerizing the conjugated diene monomer with other monomers, and then hydrogenating (hydrogenating) some or most of the double bonds, from the viewpoint of manufacturing cost, vibration damping properties, heat resistance, and ozone resistance. As a method for polymerizing or copolymerizing a conjugated diene monomer and then hydrogenating it, it is preferable to apply a method in which, for example, as described in International Publication No. 96 / 05250, Japanese Patent Publication No. 2000-053706, International Publication No. 2003 / 085010, International Publication No. 2019 / 151126, International Publication No. 2019 / 151127, International Publication No. 2002 / 002663, and International Publication No. 2015 / 006179, the conjugated diene monomer is polymerized by anionic polymerization under various additives and conditions, copolymerized with other monomers as needed, and then hydrogenated.

[0062] <Titanium in hydrogenated conjugated diene polymer (rubbery polymer 1)> The hydrogenated conjugated diene polymer (rubber-like polymer 1) constituting the rubber component (A) may contain titanium. The titanium in the hydrogenated conjugated diene polymer is preferably the catalyst residue from the production of the hydrogenated conjugated diene polymer. In such cases, titanium as a catalyst is preferably a hydrogenated catalyst component. As the hydrogenation catalyst component, from the viewpoint of easily adjusting the amount of metal in the hydrogenated conjugated diene polymer to a predetermined amount, for example, the Ti compounds described in Japanese Patent Publication No. 1-275605, Japanese Patent Publication No. 2-172537, Japanese Patent Publication No. 4-96904, Japanese Patent Publication No. 08-33846, Japanese Patent Publication No. 08-41081, International Publication No. 2014 / 046016, International Publication No. 2014 / 046017, International Publication No. 2014 / 065283, International Publication No. 2017 / 090714, and International Publication No. 2017 / 090714 are preferred. As the hydrogenation catalyst component, a mixture of a Ti compound and a Li compound and / or a Mg compound, or a reaction product, is more preferred. From the viewpoint of hydrogenation rate, a mixture of a Ti compound and a Li compound, or a reaction product, is even more preferred. Examples of the aforementioned Ti compound include titanocene of the following formula (I).

[0063] [ka]

[0064] In formula (I) above, R1 and R2 represent groups selected from the group consisting of C1-C12 hydrocarbon groups, allyloxy groups, alkoxy groups, halogen groups, and carbonyl groups, and R1 and R2 may be the same or different.

[0065] The aforementioned Ti compound is not limited to the following, but from the viewpoint of a high hydrogenation rate, preferred examples include bis(η5-cyclopentadienyl)titanium di(p-tolyl), bis(η5-cyclopentadienyl)titanium di(phenyl), bis(η5-cyclopentadienyl)titanium di(3,4-xylyl), bis(η5-cyclopentadienyl)titanium(furfuryloxy)chloride, and bis(η5-cyclopentadienyl)titanium dichloride. From an economic standpoint, bis(η5-cyclopentadienyl)titanium dichloride is more preferable.

[0066] The Li compound is not limited to the following, but examples include methyllithium, ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, isobutyllithium, t-butyllithium, n-pentyllithium, n-hexyllithium, phenyllithium, cyclopentadienyllithium, m-tolylllithium, p-tolylllithium, xylyllithium, dimethylaminolithium, diethylaminolithium, methoxylithium, ethoxylithium, n-propoxylithium, isopropoxylithium, n-butoxylithium, sec-butoxylithium, t-butoxylithium, pentyloxylithium, hexyloxylithium, heptyloxylithium, octyloxylithium, phenoxylithium, 4-methylphenoxylithium, benzyloxylithium, and 4-methylbenzyloxylithium.

[0067] Examples of Mg compounds include, but are not limited to, dimethylmagnesium, diethylmagnesium, dibutylmagnesium, ethylbutylmagnesium, methylmagnesium bromide, methylmagnesium chloride, ethylmagnesium bromide, ethylmagnesium chloride, phenylmagnesium bromide, phenylmagnesium chloride, t-butylmagnesium chloride, and t-butylmagnesium bromide.

[0068] <Titanium and aluminum content in hydrogenated conjugated diene polymers> When producing a hydrogenated conjugated diene polymer (rubbery polymer 1), the amount of titanium added as a hydrogenation catalyst component is preferably 150 ppm or less relative to the conjugated diene polymer before hydrogenation. The titanium content of the hydrogenated conjugated diene polymer (rubber-like polymer 1) used in the crosslinked rubber composition of this embodiment is preferably 1 ppm to 100 ppm, more preferably 5 ppm to 90 ppm, and even more preferably 10 ppm to 80 ppm. A titanium content of 100 ppm or less prevents the hydrogenated conjugated diene polymer from turning yellow, and a titanium content of 1 ppm or more eliminates the need for titanium removal equipment, thereby reducing costs. The aluminum content added during the production of the hydrogenated conjugated diene polymer (rubbery polymer 1) is preferably 6 ppm or less. The aluminum content of the hydrogenated conjugated diene polymer (rubber-like polymer 1) used in the crosslinked rubber composition of this embodiment is preferably 2 ppm or less, more preferably 1 ppm or less, and even more preferably aluminum-free, from the viewpoint of reducing the safety of the catalyst during the hydrogenation reaction. Furthermore, the function of aluminum as a co-catalyst can be complemented by using lithium or magnesium instead of aluminum. Furthermore, from the viewpoint of suppressing the increase in Mooney viscosity (ML viscosity) of hydrogenated conjugated diene polymers and the handling and safety of the hydrogenation catalyst, the hydrogenation catalyst added during the production of hydrogenated conjugated diene polymers preferably contains 0.05 moles or less of aluminum per mole of titanium, more preferably 0.04 moles or less of aluminum, even more preferably 0.03 moles or less of aluminum, and even more preferably contains no aluminum at all. By adjusting the titanium and aluminum content in the hydrogenation catalyst, the titanium and aluminum content of the hydrogenated conjugated diene polymer can be controlled to the above numerical range.

[0069] <Amount of metals other than Al and Ti in the crosslinked rubber composition> The crosslinked rubber composition of this embodiment may contain metals other than Al and Ti as described above. Examples of metals other than aluminum and titanium include lithium. From the viewpoint of suppressing the aging deterioration of the crosslinked rubber composition of this embodiment, the lithium content in the crosslinked rubber composition of this embodiment is preferably 60 ppm or less, more preferably 50 ppm or less, even more preferably 40 ppm or less, and even more preferably 30 ppm or less. On the other hand, from the viewpoint of tensile elongation when crosslinked, it is preferably 2 ppm or more, more preferably 5 ppm or more, and even more preferably 10 ppm or more. Furthermore, the amounts of titanium, aluminum, lithium, and other metals mentioned above refer to the individual elemental amounts, even if these metals are present as compounds.

[0070] <Dispersion state of titanium in crosslinked rubber composition> Furthermore, when the titanium in the hydrogenated conjugated diene polymer (rubber-like polymer 1) is a residue of the hydrogenation catalyst component or polymerization catalyst component, the titanium will be finely dispersed in the crosslinked rubber composition of this embodiment, and may form compounds or complexes that are difficult to identify, potentially having a significant impact on the physical properties of the crosslinked rubber composition. Therefore, from the viewpoint of not affecting the physical properties of the crosslinked rubber composition, not making the properties difficult to define, and furthermore, mitigating the adhesion of the crosslinked rubber composition to the mold, it is preferable that the titanium in the hydrogenated conjugated diene polymer (rubber-like polymer 1) is dispersed in particulate form.

[0071] <Addition of additives> In the manufacturing process of hydrogenated conjugated diene polymers (rubbery polymer 1), deactivators, neutralizing agents, etc., may be added at the end of the polymerization process as needed. Examples of deactivators include, but are not limited to, water; and alcohols such as methanol, ethanol, and isopropanol. The end of the polymerization process, as used here, refers to the state where 95% or more of the added monomer has been consumed in polymerization. Examples of neutralizing agents include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched mixture of carboxylic acids with 9 to 11 carbon atoms, mainly around 10); aqueous solutions of inorganic acids; and carbon dioxide.

[0072] In the manufacturing process of hydrogenated conjugated diene polymers (rubber-like polymer 1), it is preferable to add a rubber stabilizer towards the end of the polymerization process, from the viewpoint of preventing gel formation and ensuring processing stability. As a rubber stabilizer, there are no limitations to those listed below, but any known stabilizers can be used. For example, antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (hereinafter also referred to as "BHT"), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propinate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol are preferred.

[0073] In the manufacturing process of hydrogenated conjugated diene polymers (rubber-like polymer 1), a rubber softener may be added as needed, such as at the end of the polymerization process, to improve the productivity and processability of the polymer. Examples of rubber softeners include, but are not limited to, stretching oils, liquid rubber, and resins. From the viewpoint of processability, productivity, and economics, stretching oils are preferred. The method for adding a rubber softener to a hydrogenated conjugated diene polymer (rubber-like polymer 1) is not limited to the following, but a preferred method is to add the rubber softener to the polymer solution, mix it, and then desolvate the resulting polymer solution containing the rubber softener.

[0074] Examples of spreading oils include aromatic oils, naphthenic oils, and paraffinic oils. Among these, aromatic substitute oils with a polycyclic aromatic (PCA) component content of 3% by mass or less according to the IP346 method are preferred from the viewpoint of environmental safety, as well as from the viewpoint of preventing oil bleeding and improving wet grip characteristics. Examples of aromatic substitute oils include TDAE (Treated Distillate Aromatic Extracts) and MES (Mild Extraction Solvate) as shown in Kautschuk Gummi Kunststoffe 52(12)799(1999), as well as RAE (Residual Aromatic Extracts). The crosslinked rubber composition of this embodiment and the rubber composition before crosslinking may contain an extensible oil. From the viewpoint of preventing deterioration over time when the crosslinked rubber composition is formed, the extensible oil content is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0075] Examples of resins, though not limited to the following, include aromatic petroleum resins, coumarone-indene resins, terpene resins, rosin derivatives (including tung oil resins), tall oil, tall oil derivatives, rosin ester resins, natural and synthetic terpene resins, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, mixed aliphatic-aromatic hydrocarbon resins, coumarin-indene resins, phenol resins, p-tert-butylphenol-acetylene resins, phenol-formaldehyde resins, xylene-formaldehyde resins, monoolefin oligomers, diolefin oligomers, hydrogenated aromatic hydrocarbon resins, cyclic aliphatic hydrocarbon resins, hydrogenated hydrocarbon resins, hydrocarbon resins, hydrogenated tung oil resins, hydrogenated oil resins, and esters of hydrogenated oil resins with monofunctional or polyfunctional alcohols. These resins may be used individually or in combination of two or more. When using hydrogenated resins, they may be those in which all unsaturated groups are hydrogenated, or those in which some unsaturated groups are retained while hydrogenation is performed. The effects of adding resin include improving the processability of rubber compositions that combine conjugated diene polymers and fillers, as well as tending to improve the fracture strength of vulcanized products.

[0076] The amount of rubber softener added, such as a stretching oil, liquid rubber, or resin, is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of the total amount of rubber component (A) including the hydrogenated conjugated diene polymer and other rubber components. Adding the softener within this range tends to result in excellent abrasion resistance and crack resistance. Furthermore, from the viewpoint of improving fuel efficiency, it is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less.

[0077] <Obtaining a hydrogenated conjugated diene polymer (rubbery polymer 1)> Known methods can be used to obtain a hydrogenated conjugated diene polymer (rubbery polymer 1) by removing the solvent from the polymer solution. Examples of such methods include separating the solvent by steam stripping, filtering the polymer, and then dehydrating and drying it; concentrating the solution in a flushing tank and then defoliating it with a vent extruder or the like; and directly defoliating it with a drum dryer or the like.

[0078] (Carbon Black (B)) The crosslinked rubber composition of this embodiment contains carbon black (B) in an amount of 10 to 120 parts by mass per 100 parts by mass of the rubber component (A) described above. The carbon black (B) is not limited to the following, but for example, carbon blacks of each class such as SRF, FEF, HAF, ISAF, and SAF can be used. Among these, from the viewpoint of the extrudeability and rolling resistance characteristics of the crosslinked rubber composition of this embodiment, a specific surface area of ​​nitrogen adsorption of 50 m² is desirable. 2 Carbon black with a concentration of 1 / g or more and a dibutyl phthalate (DBP) oil absorption capacity of 80 mL / 100 g or more is preferred. From the viewpoint of improving the hardness, modulus, and abrasion resistance of the crosslinked rubber composition of this embodiment, the carbon black (B) content is 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, per 100 parts by mass of rubber component (A). Furthermore, from the viewpoint of filler dispersibility, the carbon black (B) content is 120 parts by mass or less, preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less, per 100 parts by mass of rubber component (A).

[0079] (Silica-based inorganic filler) The crosslinked rubber composition of this embodiment may contain a silica-based inorganic filler from the viewpoint of low heat generation. The silica-based inorganic filler content is preferably 1 to 60 parts by mass, more preferably 5 to 55 parts by mass, and even more preferably 10 to 50 parts by mass, per 100 parts by mass of rubber component (A). The silica-based inorganic filler is not particularly limited and any known filler can be used, but solid particles containing SiO2 or Si3Al as constituent units are preferred, and solid particles in which SiO2 or Si3Al is the main component of the constituent units are more preferred. Here, the main component refers to a component that is contained in the silica-based inorganic filler at a concentration of 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more. Examples of silica-based inorganic fillers include, but are not limited to, silica, clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, glass fibers, and other inorganic fibrous materials. A commercially available silica-based inorganic filler is, for example, "Ultrasil 7000GR" manufactured by Evonik Degussa. Hydrophobic silica-based inorganic fillers and mixtures of silica-based and non-silica-based inorganic fillers can also be used. Among these, from the viewpoint of strength and abrasion resistance of the crosslinked rubber composition of this embodiment, silica and glass fibers are preferred as the silica-based inorganic filler, with silica being more preferred. Examples of silica include dry silica, wet silica, and synthetic silicate silica.

[0080] (Metal oxides, metal hydroxides) The crosslinked rubber composition of this embodiment may contain metal oxides or metal hydroxides in addition to the carbon black and silica-based inorganic fillers described above. Metal oxides are solid particles whose main constituent unit is the chemical formula MxOy (where M represents a metal atom, and x and y independently represent integers from 1 to 6). Examples include alumina, titanium oxide, magnesium oxide, and zinc oxide. Mixtures of metal oxides and inorganic fillers other than metal oxides can also be used. Examples of metal hydroxides include, but are not limited to, aluminum hydroxide, magnesium hydroxide, and zirconium hydroxide.

[0081] (Silane coupling agent) The crosslinked rubber composition and the rubber composition before crosslinking in this embodiment may contain a silane coupling agent. Silane coupling agents have groups that have affinity for or binding to the hydrogenated conjugated diene polymer and rubber component (A) containing other rubber components, as well as silica-based inorganic fillers, and function to tighten the interactions between them. Generally, compounds having a sulfur bond moiety and an alkoxysilyl group or silanol group moiety in a single molecule are used as silane coupling agents.

[0082] Silane coupling agents include, but are not limited to, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxacosan-1-yloxy)silane [manufactured by Evonik Degussa: Si363], and NXT-Z30, NXT-Z45, NXT-Z60, NXT-silane, etc. from Momentive. Silane coupling agents containing a pt group, bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide Examples include rasulfide, 3-triethoxysilylpropylbenzoyltetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, dimethoxymethylsilylpropylbenzothiazolyltetrasulfide, and the like. Among these, bis-[3-(triethoxysilyl)-propyl]-disulfide, ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxacosan-1-yloxy)silane [manufactured by Evonik Degussa: Si363], silane coupling agents containing mercapto groups such as NXT-Z30, NXT-Z45, NXT-Z60, and NXT-silane manufactured by Momentive, and bis-[3-(triethoxysilyl)-propyl]-tetrasulfide are preferred from the viewpoint of high reinforcing effect. Silane coupling agents may be used individually or in combination of two or more types.

[0083] From the viewpoint of further enhancing the effect of tightening the interaction between the rubber component (A) and the silica-based inorganic filler, the content of the silane coupling agent is preferably 2 to 10 parts by mass, and more preferably 3 to 9 parts by mass, per 100 parts by mass of rubber component (A). Furthermore, per 100 parts by mass of silica-based inorganic filler, it is preferably 4 to 15 parts by mass, and more preferably 6 to 12% by mass.

[0084] (Dispersibility of fillers in crosslinked rubber compositions, and storage modulus of crosslinked rubber compositions) In this embodiment, it is preferable that the filler, mainly composed of carbon black (B), in the crosslinked rubber composition is dispersed to some extent. The dispersibility of the filler can be determined by using a viscoelasticity measuring device to measure the difference in storage modulus when the strain of the crosslinked rubber composition of this embodiment is changed under constant temperature conditions. From the viewpoint of filler dispersibility, it is preferable that the crosslinked rubber composition of this embodiment satisfies the following formula (2). 0.5 MPa < (Storage modulus at 50°C with 0.1% strain) - (Storage modulus at 50°C with 10% strain) < 10 MPa ... (2)

[0085] The crosslinked rubber composition of this embodiment tends to exhibit superior dispersibility of fillers as the value obtained by subtracting the storage modulus at 10% strain at 50°C from the storage modulus at 0.1% strain at 50°C is smaller. The reason for this is that if the filler has poor dispersibility and is aggregated, it will remain aggregated in the region of low strain, resulting in a high storage modulus of the crosslinked rubber composition. However, in the region of high strain, the aggregation of the filler will break down, causing the storage modulus of the crosslinked rubber composition to decrease. In other words, the dispersibility of the filler can be determined by the difference in the storage modulus of the crosslinked rubber composition between the low-strain and high-strain conditions. The smaller the value of (storage modulus at 50°C with 0.1% strain) - (storage modulus at 50°C with 10% strain), the better the dispersibility of the filler can be judged. In this embodiment, the balance of the dispersibility of the filler is controlled from a viewpoint described later, in order to obtain a crosslinked rubber composition with excellent properties.

[0086] From the viewpoint of compression set and dynamic spring constant of the crosslinked rubber composition of this embodiment, it is preferable that the crosslinked rubber composition of this embodiment has excellent dispersibility of fillers, and the upper limit of formula (2) is preferably less than 10 MPa, more preferably 8 MPa or less, and even more preferably 7 MPa or less. On the other hand, for the reasons mentioned above, even if the filler content is the same, the better the dispersibility of the filler, the lower the storage modulus of the crosslinked rubber composition tends to be. Therefore, if the dispersibility is very good, the storage modulus decreases significantly, resulting in inferior strength. Therefore, the lower limit of formula (2) is preferably greater than 0.5 MPa, more preferably 1.0 MPa or higher, and even more preferably 1.5 MPa or higher.

[0087] The dispersibility of the filler in the crosslinked rubber composition of this embodiment can be controlled by adjusting the mixing time, mixing with high torque, using a filler that is less prone to aggregation due to hydrogen bonding, etc., when mixing various fillers such as rubber component (A), carbon black (B), and other additives, and by adding a silane coupling agent if the filler contains a silica-based inorganic filler, thereby satisfying the relationship of formula (2) above.

[0088] (Rubber softener) The crosslinked rubber composition and the rubber composition before crosslinking in this embodiment may contain a rubber softener to improve processability. Suitable rubber softeners include, for example, mineral oil-based rubber softeners and liquid or low molecular weight synthetic softeners. The aforementioned mineral oil-based rubber softeners are also called process oils or extender oils and are used to soften, increase the volume of, and improve the processability of rubber. Furthermore, the aforementioned mineral oil-based rubber softeners are mixtures of compounds having aromatic rings, naphthenic rings, and paraffinic chains, and those in which the number of carbon atoms in the paraffinic chain accounts for 50% or more of the total carbon atoms are called paraffinic, those in which the number of carbon atoms in the naphthenic ring is 30-45% are called naphthenic, and those in which the number of carbon atoms in the aromatic ring exceeds 30% are called aromatic. When the hydrogenated conjugated diene polymer used in the crosslinked rubber composition of this embodiment is a copolymer having conjugated diene monomer units and aromatic vinyl monomer units, a rubber softener having an appropriate amount of aromatic vinyl monomer units is preferred because it tends to have good affinity with the hydrogenated conjugated diene polymer. From the viewpoint of improving processability, the content of the rubber softener is preferably 0 parts by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of rubber component (A). Furthermore, from the viewpoint of suppressing bleed-out and preventing stickiness on the surface of the crosslinked rubber composition, it is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 60 parts by mass or less.

[0089] [Method for producing crosslinked rubber composition] The crosslinked rubber composition of this embodiment can be produced by mixing the constituent materials of the crosslinked rubber composition of this embodiment, such as the rubber component (A), carbon black (B), and optionally other fillers, silane coupling agents, rubber softeners, and other additives, and then crosslinking the rubber composition. The mixing method is not limited to the following, but examples include melt-kneading methods using common mixers such as open rolls, Banbury mixers, kneaders, single-screw extruders, twin-screw extruders, and multi-screw extruders, and methods in which the solvent is removed by heating after each component has been dissolved and mixed. Of these methods, the melt-kneading method using rollers, Banbury mixers, kneaders, and extruders is preferred from the viewpoint of productivity and good kneading performance. Furthermore, both a method of kneading the materials constituting the crosslinked rubber composition of this embodiment all at once and a method of mixing them in multiple steps are applicable.

[0090] The method for producing the crosslinked rubber composition of this embodiment preferably includes a step of crosslinking the hydrogenated conjugated diene polymer (rubber-like polymer 1) with a crosslinking agent. Examples of crosslinking agents include, but are not limited to, organic peroxides and azo compounds, radical generators, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. Sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, and high molecular weight polysulfur compounds. From the viewpoint of improving tensile strength through reinforcing effect, the amount of crosslinking agent added is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of rubber component (A). Furthermore, from the viewpoint of improving flexibility and elongation at break, the amount of crosslinking agent added is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of rubber component (A).

[0091] Conventional known methods can be applied as the crosslinking method. The crosslinking temperature is not particularly limited, but from the viewpoint of shortening the crosslinking time and improving production efficiency, it is preferably 120°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. Furthermore, from the viewpoint of suppressing thermal degradation during crosslinking, it is preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 165°C or lower.

[0092] When performing sulfur crosslinking, a vulcanization accelerator may be used as needed. Conventional known materials can be used as vulcanization accelerators, and are not limited to the following, but examples include sulfenamide compounds, guanidine compounds, thiuram compounds, aldehyde-amine compounds, aldehyde-ammonia compounds, thiazole compounds, thiourea compounds, and dithiocarbamate compounds. In the method for producing the crosslinked rubber composition of this embodiment, it is preferable to have a step of crosslinking the hydrogenated conjugated diene polymer (rubber-like polymer 1) with the above-mentioned sulfur and vulcanization accelerator, or organic peroxide.

[0093] Furthermore, in the aforementioned crosslinking using sulfur, a vulcanization aid may also be used. Examples of vulcanization aids include, but are not limited to, zinc oxide and stearic acid.

[0094] In the method for producing the crosslinked rubber composition of this embodiment, various additives other than the materials described above, such as softeners, fillers, heat stabilizers, antistatic agents, weather stabilizers, anti-aging agents, colorants, and lubricants, may be added, as long as the objectives of the present invention are not impaired. Other known softeners can be used. Other fillers include, for example, calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate. For the heat-resistant stabilizer, antistatic agent, weather-resistant stabilizer, anti-aging agent, colorant, and lubricant mentioned above, known materials can be used.

[0095] (Preferred form of method for producing crosslinked rubber composition) A preferred embodiment of the method for producing the crosslinked rubber composition of this embodiment comprises the steps of: polymerizing a hydrogenated conjugated diene polymer having a hydrogenation rate of 10% to 99%, an aromatic vinyl monomer block content of less than 5% by mass, a weight-average molecular weight of 150,000 to 1,500,000, a glass transition temperature of -50°C or lower, and an aromatic vinyl monomer unit content of 5% by mass or more; obtaining a rubber component (A) containing 10% to 100% by mass of the hydrogenated conjugated diene polymer and having an iodine value of 10 to 370; mixing 100 parts by mass of the rubber component (A) with 10 to 120 parts by mass of carbon black (B) to obtain a rubber composition; and crosslinking the rubber composition, thereby obtaining a crosslinked rubber composition in which the change in Shore A hardness before and after heating under air at 100°C for 72 hours satisfies the following formula (1). -10 < (Shore A hardness after heating) - (Shore A hardness before heating) < 5 ... (1) The method for producing the crosslinked rubber composition of this embodiment makes it possible to produce a crosslinked rubber composition with a good balance between vibration damping properties and heat resistance.

[0096] In the method for producing crosslinked rubber according to this embodiment, the crosslinking of the hydrogenated conjugated diene polymer may be carried out in a molded state with the rubber composition containing the rubber component (A) and the carbon black (B). This allows for greater freedom in determining the final shape of the desired cross-linked rubber composition.

[0097] [Uses of crosslinked rubber compositions] The crosslinked rubber composition of this embodiment can be used as vibration-damping rubber, vibration isolation rubber, conveyor belts, shoe outsoles and other soles, automobile weatherstrips, packings and gaskets, sealing materials, waterproof sheets, engine mounts, air springs, rubber gloves, medical and hygiene products, rubber rollers, hoses for industrial and various applications, battery cases, adhesives, wire insulation, window frame rubber, and materials for various industrial products. In these applications, various molded products can be obtained by molding the crosslinked rubber composition of this embodiment.

[0098] The hydrogenated conjugated diene polymer used in the crosslinked rubber composition of this embodiment can have its compression set reduced by adjusting its structure and blending ratio. Crosslinked rubber compositions with low compression set are suitable for vibration-damping rubber, vibration damping materials, packings, sealing materials, rubber rollers, rubber stoppers, and medical hygiene products. For example, when the compression set of a crosslinked rubber composition after heating at 100°C for 72 hours is 10% or less, it is particularly suitable for sealing materials (packings, gaskets), medical hygiene products, and rubber rollers for printing presses. In particular, hydrogenated conjugated diene polymers can have a low glass transition temperature, making them suitable as sealing materials for parts exposed to low-temperature materials such as liquefied gases. In order to achieve the compression set of the crosslinked rubber composition of this embodiment within the aforementioned range, for example, the composition of the crosslinked rubber composition is preferably such that the hydrogenated conjugated diene polymer content is 90% by mass or more, and more preferably 100% by mass. Furthermore, the hydrogenation rate of the hydrogenated conjugated diene polymer is preferably 30% to 98%, and more preferably 40% to 95%. When the compression set of the crosslinked rubber composition after heating at 100°C for 72 hours is 30% or less, it is particularly suitable for vibration-damping rubber and vibration-reducing materials.

[0099] In order to achieve the compression set of the crosslinked rubber composition of this embodiment within the aforementioned range, for example, the composition of the crosslinked rubber composition is preferably such that the hydrogenated conjugated diene polymer content is 80% by mass or more, and more preferably 90% by mass or more. Furthermore, the hydrogenation rate of the hydrogenated conjugated diene polymer to be blended is preferably 40% to 99%, and more preferably 50% to 99%. [Examples]

[0100] The embodiment will be described in more detail below with reference to specific polymerization examples, examples, and comparative examples, but this embodiment is not limited in any way to the polymerization examples, examples, and comparative examples described below. The various physical properties in the polymerization examples, examples, and comparative examples were measured by the methods described below.

[0101] [Physical property measurement method] [Weight-average molecular weight (Mw) of polymers 1-25] Polymers 1-25 were used as samples for measurement, and chromatograms were measured using a GPC analyzer with three columns packed with polystyrene gel. The weight-average molecular weight (Mw) was determined based on a calibration curve using standard polystyrene. The specific measurement conditions are shown below. 20 μL of the following measurement solution was injected into the GPC analyzer and the measurement was performed. (Measurement conditions) Device: Tosoh Corporation product name "HLC-8320GPC" Eluent: 5 mmol / L tetrahydrofuran (THF) containing triethylamine Guard column: Product name "TSKguardcolumn SuperH-H" manufactured by Tosoh Corporation. Separation column: A combination of TSKgel SuperH5000, TSKgel SuperH6000, and TSKgel SuperH7000, manufactured by Tosoh Corporation, linked together in that order. Oven temperature: 40℃ Flow rate: 0.6mL / min Detector: RI detector (product name "HLC8020" manufactured by Tosoh Corporation) Measurement solution: A measurement solution prepared by dissolving 10 mg of the sample in 20 mL of THF.

[0102] [Degradation rate of polymers 1-25] The denaturation rates of polymers 1 to 25 were measured using the column adsorption GPC method, taking advantage of the property that denatured polymers adsorb to the column, as follows. Polymers 1 to 25 were used as samples for measurement. Using a sample solution containing the aforementioned samples and a low molecular weight internal standard polystyrene, the amount of adsorption onto the silica column was measured from the difference between the chromatogram measured on a column packed with a polystyrene gel (polystyrene column) and the chromatogram measured on a column packed with a silica gel (silica column), and the denaturation rate was determined. The GPC measurement conditions using a polystyrene column are shown below. 20 μL of the measurement solution listed below was injected into the GPC measuring device and the measurement was performed. (GPC measurement conditions using polystyrene columns): Device: Tosoh Corporation product name "HLC-8320GPC" Eluent: THF containing 5 mmol / L triethylamine Guard column: Product name "TSKguardcolumn SuperH-H" manufactured by Tosoh Corporation. Column: A combination of the product names "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" manufactured by Tosoh Corporation, in that order. Oven temperature: 40℃ Flow rate: 0.6mL / min Detector: RI detector (Tosoh Corporation HLC8020) Measurement solution: 10 mg of the sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare the sample solution. The GPC measurement conditions using a silica-based column are shown below. 50 μL of the measurement solution listed below was injected into the GPC measuring device and the measurement was performed. (GPC measurement conditions using silica columns): Device: Tosoh Corporation product name "HLC-8320GPC" Eluent:THF Guard column: DIOL 4.6×12.5mm 5micron, manufactured by GL Sciences Co., Ltd. Separation column: Agilent Technologies' Zorbax PSM-1000S, PSM-300S, and PSM-60S columns linked together in that order. Oven temperature: 40℃ Flow rate: 0.5mL / min Detector: RI detector (Tosoh Corporation HLC8020) (Method for calculating the rate of degeneration): The denaturation rate (%) was calculated using the following formula, with the total peak area of ​​the chromatogram using a polystyrene column set to 100, the peak area of ​​the sample being P1, and the peak area of ​​standard polystyrene being P2. The total peak area of ​​the chromatogram using a silica column was also set to 100, with the peak area of ​​the sample being P3 and the peak area of ​​standard polystyrene being P4. Degeneration rate (%) = [1 - (P2 × P3) / (P1 × P4)] × 100 (However, P1+P2=P3+P4=100)

[0103] [Coupling rates of polymers 1-25] The chromatograms were measured in the same manner as the weight-average molecular weight measurement method for polymers 1-25 described above, and the coupling rate of polymers 1-25 was calculated from the ratio of the peak area of ​​uncoupled (low molecular weight side peaks) to the peak area of ​​coupled (high molecular weight side peaks) polymers.

[0104] [Mooney viscosity and Mooney stress relaxation of polymers 1-25] Using a Mooney viscometer (product name "VR1132" manufactured by Ueshima Seisakusho Co., Ltd.), the Mooney viscosity and Mooney stress relaxation (relaxation rate) of polymers 1 to 25 were measured in accordance with JIS K6300 (ISO289-1) and ISO289-4. The measurement temperature was 100°C. First, the sample was preheated for 1 minute, then the rotor was rotated at 2 rpm, and the torque was measured after 4 minutes to determine the Mooney viscosity (ML). (1+4) The rotor rotation was then immediately stopped, and the torque was recorded in Mooney units every 0.1 seconds for 1.6 to 5 seconds after stopping. The slope of the line when torque and time (seconds) were plotted on a log-log scale was determined, and its absolute value was defined as Mooney stress relaxation (MSR).

[0105] [Styrene content, vinyl bond amount, and vinyl bond amount and hydrogenation rate of polymers 1-25 before hydrogenation] 1 By measuring the cumulative value of the unsaturated bonds in the polymer before hydrogenation using 1H-NMR, the content of aromatic vinyl monomer units (styrene) and the amount of vinyl bonds in the conjugated diene monomer components were calculated. Next, a large amount of methanol was added to the reaction solution after the hydrogenation reaction to precipitate and recover the polymer. Then, the polymer was extracted with acetone and vacuum dried. 1 The sample was used for 1H-NMR measurement to determine the amount of vinyl bond and hydrogenation rate. 1 The conditions for H-NMR measurement are described below. (Measurement conditions) Measuring instrument: JNM-LA400 (manufactured by JEOL) Solvent: Deuterated chloroform Measurement samples: Samples taken before and after hydrogenation of the polymer. Sample concentration: 50 mg / mL Observation frequency: 400MHz Chemical shift standard: TMS (tetramethylsilane) Pulse delay: 2.904 seconds Number of scans: 64 Pulse width: 45° Measurement temperature: 26℃

[0106] [Styrene block content of polymers 1-25] A chain of eight or more styrene structural units was defined as a styrene block, and the styrene block content was determined as follows. Polymers 1-25 were used as samples, and the 400MHz measurement was performed using deuterated chloroform as the solvent. 1 From the H-NMR spectra, the integral value ratios for each chemical shift (S) in (X) below were determined, and the styrene block content in polymers 1 to 25 was calculated. (X) Styrene structural unit chain of 8 or more: 6.00 ≤ S < 6.68

[0107] [Glass transition temperatures of polymers 1-25] Polymers 1-25 were used as samples, and DSC curves were recorded while increasing the temperature within a specified range according to ISO 22768:2006. The peak top (inflection point) of the DSC differential curve was defined as the glass transition temperature. The measurement device used was a differential scanning calorimeter DSC7020 manufactured by Hitachi High-Tech Science.

[0108] [Metal content of polymers 1-25 (amount of Al, amount of Ti)] Polymers 1-25 were used as samples, and elemental analysis was performed using inductively coupled plasma (ICP, manufactured by Shimadzu Corporation, instrument name: ICPS-7510) to measure the aluminum content (Al amount, in ppm) and titanium content (Ti amount, in ppm) in the polymers.

[0109] [Iodine value of polymers 1-25] The iodine values ​​of polymers 1 to 25 were calculated according to the method described in "JIS K 0070:1992".

[0110] [Iodine value of rubber component (A)] The iodine value (1g / 100g) of rubber component (A) was calculated according to the method described in "JIS K 0070:1992".

[0111] [Polymer production] (Preparation of hydrogenation catalyst) The hydrogenation catalyst used in preparing polymers 1 to 25, described later, was prepared by the method shown in Production Example 1 below. <Manufacturing Example 1> Two liters of dried and purified cyclohexane were charged into a nitrogen-purged reaction vessel, and 40 mmol of bis(η5-cyclopentadienyl)titanium di-(p-tolyl) and 150 grams of 1,2-polybutadiene (approximately 85 ml of 1,2-vinyl bond) with a molecular weight of approximately 1,000 were dissolved in it. Then, a cyclohexane solution containing 60 mmol of n-butyllithium was added to the reaction vessel and reacted at room temperature for 5 minutes. Immediately afterward, 40 mmol of n-butanol was added and stirred to obtain hydrogenation catalyst (T). The obtained hydrogenation catalyst was stored at room temperature.

[0112] (Polymerization example 1) Polymer 1 A temperature-controlled autoclave with an internal volume of 40 L, equipped with a stirrer and jacket, was used as the reactor. 2,760 g of 1,3-butadiene, 240 g of styrene, 21,000 g of cyclohexane, and 0.55 mol of tetrahydrofuran (THF) and 2.9 mmol of 2,2-bis(2-oxolanil)propane, which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 45°C. 37 mmol of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization, and the final temperature inside the reactor reached 77°C. Two minutes after reaching this reaction temperature peak, 7.3 mmol of 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (compound A) was added to the reactor as a coupling agent, and the coupling reaction was carried out for 20 minutes. To this polymer solution, 7.3 mmol of methanol was added as a reaction termination agent to obtain a polymer solution. To the obtained polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. Then, the polymer solution was removed dropwise by adding it to warm water, and the polymer was dried in a drying oven to obtain polymer 1. The results of the analysis are shown in Table 4.

[0113] (Polymerization example 2) Polymer 2 A temperature-controlled autoclave with an internal volume of 40 L, equipped with a stirrer and jacket, was used as the reactor. 2,760 g of 1,3-butadiene, 240 g of styrene, 21,000 g of cyclohexane, and 0.55 mol of tetrahydrofuran (THF) and 2.9 mmol of 2,2-bis(2-oxolanil)propane, which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 45°C. 37 mmol of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization, and the final temperature inside the reactor reached 77°C. Two minutes after reaching this reaction temperature peak, 7.3 mmol of 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (compound A) was added to the reactor as a coupling agent, and the coupling reaction was carried out for 20 minutes. To this polymer solution, 7.3 mmol of methanol was added as a reaction termination agent to obtain the polymer solution. A portion of the polymer solution was withdrawn and desolvented in a dryer to obtain the polymer before hydrogenation. The results of the analysis are shown in Table 4. To the polymer solution before hydrogenation, the hydrogenation catalyst (T) was added at a concentration of 50 ppm (Ti-based) per 100 parts by mass of the polymer before hydrogenation, and the hydrogenation reaction was carried out for 80 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C. To the resulting polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The polymer solution was then removed by dropping it into warm water, and the polymer was dried in a drying oven to obtain polymer 2.

[0114] (Polymerization examples 3-8, 10, 11, 13-25): Polymers 3-8, 10, 11, 13-25 Polymerization was carried out under the same conditions as Polymerization Example 2, except that the raw materials, types of additives, and their amounts were changed as listed in Tables 1 to 3, and the temperature and amount of hydrogenation were controlled during the hydrogenation reaction, to obtain polymers 3 to 8, 10, 11, and 13 to 25. The results of the analysis are shown in Tables 4 to 6.

[0115] (Polymerization example 9): Polymer 9 Polymer 9 was obtained by polymerization under the same conditions as Polymerization Example 1, except that the raw materials, types of additives, and their amounts were changed as listed in Table 2. The results of the analysis are shown in Table 5.

[0116] (Polymerization example 12) polymer12 A temperature-controlled autoclave with an internal volume of 40 L, equipped with a stirrer and jacket, was used as the reactor. 450 g of styrene, 21,000 g of cyclohexane, and 0.50 mol of tetrahydrofuran (THF) and 7.3 mmol of 2,2-bis(2-oxolanil)propane, which had been pre-treated to remove impurities, were added to the reactor, and the reactor temperature was maintained at 52°C. 61 mmol of n-butyllithium was supplied to the reactor as a polymerization initiator. After the polymerization reaction began, the temperature inside the reactor started to rise due to the heat generated by polymerization. Five minutes after detecting the temperature peak, 2,550 g of 1,3-butadiene was added. The reaction continued, and the final temperature inside the reactor reached 83°C. Two minutes after reaching this temperature peak, 16.3 mmol of tetramethoxysilane (compound C) was added to the reactor as a coupling agent, and the coupling reaction was carried out for 20 minutes. To this polymer solution, 12.2 mmol of methanol was added as a reaction termination agent to obtain the polymer solution. A portion of the polymer solution was withdrawn and desolvented in a dryer to obtain the polymer before hydrogenation. The results of the analysis are shown in Table 5. To the polymer solution before hydrogenation, the hydrogenation catalyst (T) was added at a concentration of 50 ppm (Ti-based) per 100 parts by mass of the polymer before hydrogenation, and the hydrogenation reaction was carried out for 70 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C. To the resulting polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants. The polymer solution was then removed by dropping it into warm water, and the polymer was dried in a drying oven to obtain polymer 12. The results of the analysis are shown in Table 5.

[0117] The types of coupling agents / denaturants A to E in Tables 1 to 3 below are shown below. Compound A: 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane Compound B: 1,3-dimethyl-2-imidazolidinone Compound C: Tetramethoxysilane Compound D: Silicon tetrachloride Compound E: N,N,N',N'-Tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine

[0118] [Table 1]

[0119] [Table 2]

[0120] [Table 3]

[0121] [Table 4]

[0122] [Table 5]

[0123] [Table 6]

[0124] [Manufacturing of rubber compositions] Using polymers 1 to 25 obtained in polymerization examples 1 to 25, and natural rubber, high-cis polybutadiene (BR), and ethylene-propylene-diene rubber (EPDM) as rubber component (A), rubber compositions containing each rubber component (A), carbon black (B), and crosslinking agent (C) were obtained according to the following compounding conditions and mixing method.

[0125] ((Formulation conditions 1) Example 1~ 4. Reference Example 5, Examples 6-12, Reference Example 13, Example 14. Examples 27-34 and Comparative Examples 1-9) • Rubber component (A) (polymers 1-25 of polymerization examples 1-25, RSS3 as natural rubber, U150 as BR (product name from UBE Elastomers Co., Ltd.), EP33 as EPDM (product name from ENEOS Material Co., Ltd.)): 100 parts by mass The amounts of each compounding agent listed below are in parts by mass relative to 100 parts by mass of rubber component (A) that does not contain rubber softeners, and are shown in Tables 7 to 12. • Carbon Black (B) (Manufactured by Tokai Carbon Co., Ltd., product name "Seast KH (N339)") • Anti-aging agent (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) • Naphthenic oil Zinc oxide Stearic acid • Crosslinking agent (C) sulfur • Vulcanization accelerator 1 (N-cyclohexyl-2-benzothiadylsulfinamide) • Vulcanization accelerator 2 (diphenylguanidine)

[0126] <Mixing method> The above materials were kneaded by the following method to obtain a rubber composition. Using a sealed kneader (capacity 0.3L) equipped with a temperature control device, the first stage of kneading involved mixing rubber component (A), filler (carbon black (B)), naphthenic oil, zinc oxide, stearic acid, and an antioxidant under conditions of a filling rate of 65% and a rotor rotation speed of 30-50 rpm. At this time, the temperature of the sealed mixer was controlled, and the first stage of the mixture was obtained with a discharge temperature of 125-130°C. After cooling, the mixture was kneaded in the second stage using an open roll press set to 70°C, adding sulfur (crosslinking agent (C)) and vulcanization accelerators 1 and 2. The mixture was then molded and vulcanized at 160°C for the specified time shown in Tables 5 to 7 using a vulcanization press to achieve crosslinking. The rubber composition before vulcanization and the crosslinked rubber composition after vulcanization were evaluated. Specifically, the evaluation was performed using the following method. The results are shown in Tables 13 to 18.

[0127] (Evaluation of the processability of the compound (cohesion of the rubber composition)) As an indicator of processability when obtaining the formulation, the dough's cohesiveness was evaluated based on the kneading method described above, specifically the consistency of the dough obtained in the first stage of the formulation. When the rubber composition is discharged from the sealed mixer, it is preferable for the rubber composition to be cohesive. If it is close to a powder, it will have poor processability, leading to losses in the production process and longer production times, thus reducing productivity. Insufficient mixing may also result in inadequate dispersion of fillers, potentially degrading the physical properties. From the above perspective, when the rubber composition is discharged from the sealed mixer, 1 cm 2 If the mass ratio of granular or powdery material is less than 3% by mass, it is evaluated as good processability (○); if the mass ratio of granular or powdery material is 3% by mass or more and 10% by mass or less, it is evaluated as practically acceptable processability (△); and if the mass ratio of granular or powdery material exceeds 10% by mass, it is evaluated as poor processability (×).

[0128] (Evaluation of the physical properties of the compound) The Mooney viscosity of the rubber composition before vulcanization, the tensile strength, tensile elongation, 300% modulus, compression set, static spring constant, dynamic spring constant, and dynamic magnification of the crosslinked rubber composition are shown in Table 13. For Examples 1 and 2 and Comparative Example 2, the evaluation results for Comparative Example 1 were indexed to 100. Furthermore, for Examples 3-14, Examples 27-34, and Comparative Examples 4-9, the evaluation results for Comparative Example 3 were indexed with a value of 100, and are shown in Tables 14-18. Regarding Mooney viscosity, a higher index indicates better performance. A value of 70 or higher relative to the standard is acceptable for practical use, 85 or higher is preferable, and 105 or higher indicates superiority. For all properties except Mooney viscosity, a higher index indicates better performance. We determined that a value of 85 or higher than the standard is practically acceptable, and a value of 105 or higher indicates superiority. Furthermore, the Shore A hardness of the cross-linked rubber composition described below, and the change in hardness before and after heating (the change in Shore A hardness before and after heating under air at 100°C for 72 hours using the formula (1) above), are recorded using the actual measured values ​​obtained by the method described later. Regarding the change in Shore A hardness before and after heating, it was determined that satisfying formula (1) was acceptable for practical purposes, while not satisfying formula (1) indicated practical problems.

[0129] <Tensile properties> The tensile properties were evaluated by multiplying the tensile strength and tensile elongation of the crosslinked rubber composition, as described later. A higher tensile property value indicates a better balance between tensile strength and tensile elongation, and the material is judged to be of high strength. For Examples 1 and 2 and Comparative Example 2, the evaluation results for Comparative Example 1 were indexed with 100 and are shown in Table 13. Furthermore, for Examples 3-14, Examples 27-34, and Comparative Examples 4-9, the evaluation results for Comparative Example 3 were indexed with a value of 100, and are shown in Tables 14-18. It is preferable that the value be above the standard value (100), a value of 85 to 100 is acceptable for practical purposes, a value of 75 to less than 85 may result in insufficient material strength depending on the application, and a value of less than 75 is judged to be insufficient material strength.

[0130] <Mooney viscosity of rubber compositions> In accordance with JIS K6300 (ISO289-1) and ISO289-4, the Mooney viscosity of the rubber composition before vulcanization was measured as an indicator of processability. The measurement temperature was set to 100°C. First, the sample was preheated for 1 minute, then the rotor was rotated at 2 rpm, and the torque was measured after 4 minutes to determine the Mooney viscosity (ML). (1+4) The measurement instrument used was a Mooney viscometer (product name "VR1132" manufactured by Ueshima Seisakusho Co., Ltd.).

[0131] <Tensile strength, tensile elongation, tensile properties, 300% modulus> In accordance with the tensile testing method of JIS K6251, the tensile strength, tensile elongation, and 300% modulus of the cross-linked rubber composition after vulcanization were measured. Furthermore, the tensile properties were evaluated using the method described above. The measuring instrument used was the AUTOGRAPH AGS-X manufactured by Shimadzu Corporation.

[0132] <Shore A hardness before heating> In accordance with JIS K 6253-3, the Shore A hardness (durometer type A) of the sheet was measured using six 2 mm cross-linked rubber composition sheets with smooth surfaces, stacked with their flat portions to form a test specimen approximately 12 mm thick. However, test specimens containing foreign matter, air bubbles, or scratches were not used. Furthermore, the dimensions of the measurement surface of the test specimen were set to a size that allowed measurement to be taken at a position where the tip of the indenter was 12 mm or more away from the edge of the test specimen.

[0133] <Changes in Shore A hardness before and after heating> Using the test specimens used in the pre-heating hardness measurement described above, the cross-linked rubber composition was heated at 100°C for 72 hours under normal pressure and air to obtain test specimens of the cross-linked rubber composition after heating. The Shore A hardness was measured using the same method as the pre-heating Shore A hardness measurement method described above. The value obtained from this measurement was calculated by subtracting the Shore A hardness before heating from the Shore A hardness after heating.

[0134] <Difference in storage modulus> The viscoelastic parameters of the crosslinked rubber composition were measured in torsion mode using the "ARES" viscoelasticity testing machine manufactured by Rheometrics Scientific. The difference was calculated by subtracting the storage modulus measured at 0.1% strain (50°C, 10Hz, 3% strain) from the storage modulus measured at 0.1% strain (50°C, 10Hz, 3% strain).

[0135] <Flexibility at low temperatures> In accordance with JIS K 6394, the viscoelastic parameters of a 3 mm thick cross-linked rubber composition were measured using a viscoelasticity tester "ARES" manufactured by Rheometrics Scientific Corporation in torsion mode. The ratio (G'(-100℃)) between the storage modulus measured at -100℃, frequency 10Hz, and strain 1% (G'(-20℃)) and the storage modulus measured at -20℃, frequency 10Hz, and strain 1% (G'(-20℃)) (-20℃) / G' (-100℃) The result (×100) was calculated.

[0136] <Compression permanent strain> The compression set of the crosslinked rubber composition was measured in accordance with JIS K6262.

[0137] <Static spring constant, dynamic spring constant, dynamic magnification> In accordance with JIS K6385, the static spring constant and dynamic spring constant of the cross-linked rubber composition were measured, and the dynamic ratio (dynamic spring constant / static spring constant) was calculated. The measuring instrument used was the ACUMEN3 manufactured by MTS.

[0138] <Heat resistance> The punched cross-linked rubber composition used for the aforementioned tensile strength and other measurements was heated at 100°C for 72 hours under normal pressure and air. The tensile strength and tensile elongation of the heated cross-linked rubber composition were then measured in accordance with the tensile test method of JIS K6251. The product of the tensile strength and tensile elongation of the cross-linked rubber composition after heating was calculated, with the product of the tensile strength and tensile elongation of the unheated cross-linked rubber composition set to 100. Regarding heat resistance, a higher numerical value indicates less deterioration due to heating and superior heat resistance, while a lower numerical value indicates greater deterioration due to heating and inferior heat resistance. For Comparative Example 2, Examples 1 and 2, a value of -5 or greater and less than +10 compared to the value of Comparative Example 1, and for Examples 3 to 14, Examples 27 to 34, and Comparative Examples 4 to 9, a value of -5 or greater and less than +10 compared to the value of Comparative Example 3, was judged to indicate equivalent heat resistance, a value higher than +10 indicated superior heat resistance, and a value less than -5 indicated inferior heat resistance.

[0139] ((Formulation conditions 2) Example 15~ 18, Reference Example 19, Example 20~ 26. Examples 35-42, 49 and Comparative Examples 10-17) · Rubber component (A) (Polymers 1 to 25 of Polymerization Examples 1 to 25, RSS No. 3 as natural rubber, U150 (trade name, manufactured by UBE Elastomer Co., Ltd.) as BR, EP33 (trade name, manufactured by ENEOS Materials Co., Ltd.) as EPDM): 100 parts by mass The addition amounts of the following respective compounding agents are shown in Tables 19 to 22 in parts by mass with respect to 100 parts by mass of the rubber component (A) not containing a rubber softening agent. · Carbon black (B) (trade name "Seast KH (N339)" manufactured by Tokai Carbon Co., Ltd.) · Antioxidant: 2-mercaptobenzimidazole · Naphthenic oil · Zinc oxide · Stearic acid · Crosslinking agent (C) Organic peroxide (dicumyl peroxide)

[0140] <Kneading method> The above materials were kneaded by the following method to obtain a rubber composition. Using a closed kneader (internal volume 0.3 L) equipped with a temperature control device, as the first-stage kneading, under the conditions of a filling rate of 65% and a rotor rotation speed of 30 to 50 rpm, the rubber component, filler (carbon black), naphthenic oil, zinc oxide, stearic acid, and antioxidant were kneaded. At this time, the temperature of the closed mixer was controlled, and the discharge temperature was 125 to 130 °C to obtain a first-stage formulation. After cooling, as the second-stage kneading, an organic peroxide was added and kneaded using an open roll set at 35 °C. Then, it was molded and crosslinked at 170 °C for the predetermined time described in Tables 19 to 22 using a press. The rubber composition before crosslinking and the crosslinked rubber composition after crosslinking were evaluated. Specifically, they were evaluated by the following method. The evaluation results are shown in Tables 23 to 26.

[0141] (Evaluation of processability (cohesiveness) of rubber composition) Evaluation was carried out in the same manner as the evaluation of the processability (cohesiveness) of the rubber composition described above.

[0142] (Evaluation of physical properties of formulation) The Mooney viscosity of the rubber composition, the tensile strength, tensile elongation, 300% modulus, compression set, static spring constant, and dynamic spring constant of the crosslinked rubber composition were measured under the same conditions. The dynamic magnification was determined from the ratio of the dynamic spring constant to the static spring constant. For Examples 15 and 16 and Comparative Example 11, the evaluation results of Comparative Example 10 were indexed with a value of 100, and the results are shown in Table 23. Furthermore, for Examples 17-26, 35-42, 49, and Comparative Examples 13-17, the evaluation results of Comparative Example 12 were indexed with a value of 100, and the results are shown in Tables 24-26. Regarding Mooney viscosity, a higher index indicates better performance. A value of 70 or higher relative to the standard is acceptable for practical use, 85 or higher is preferable, and 105 or higher indicates superiority. For all properties except Mooney viscosity, a higher index indicates better performance. A value of 85 or higher relative to the standard is considered practically acceptable, while a value of 105 or higher indicates superiority. Furthermore, the Shore A hardness of the above-mentioned crosslinked rubber composition and the change in hardness before and after heating (the change in Shore A hardness before and after heating under air at 100°C for 72 hours using the above formula (1)) are recorded using the actual measured values ​​obtained by the method described above. The change in Shore A hardness before and after heating was evaluated as being acceptable for practical purposes if formula (1) was satisfied, and being problematic for practical purposes if formula (1) was not satisfied.

[0143] <Tensile properties> Similar to the tensile properties described above, the product of the tensile strength and tensile elongation of the crosslinked rubber composition was evaluated. A higher tensile property value indicates a better balance between tensile strength and tensile elongation, and the material is judged to be of high strength. For Examples 15 and 16 and Comparative Example 11, the evaluation results of Comparative Example 10 were indexed with a value of 100, and the results are shown in Table 23. Furthermore, for Examples 17-26, 35-42, 49, and Comparative Examples 13-17, the evaluation results of Comparative Example 12 were indexed with a value of 100, and the results are shown in Tables 24-26. It is preferably not less than the reference value (100). When it is not less than 85 and not more than 100, there is no practical problem. When it is not less than 75 and less than 85, the material strength may not be sufficient depending on the application. When it is less than 75, it is determined that the material strength is insufficient.

[0144] <Heat resistance> Regarding heat resistance, it is determined that the larger the value, the smaller the deterioration due to heating, and the better the heat resistance. The smaller the value, the larger the deterioration due to heating, and the worse the heat resistance. For Comparative Example 11, Examples 15 and 16, with respect to the value of Comparative Example 10, and for Examples 17 to 26, Examples 35 to 42, Example 49, and Comparative Examples 13 to 17, with respect to the value of Comparative Example 12, if it is not less than -5 and less than +10, the heat resistance is equivalent. If it is not less than +10, there is an advantage in terms of heat resistance. If it is less than -5, it is determined that the heat resistance is inferior.

[0145] The Shore A hardness before heating, the change in Shore A hardness before and after heating, the difference in storage modulus, and the flexibility at low temperature were measured and evaluated by the same measurement methods as described above.

[0146] [Table 7]

[0147] [Table 8]

[0148] [Table 9]

[0149] [Table 10]

[0150] [Table 11]

[0151] Table 12

[0152] Table 13

[0153] Table 14

[0154] Table 15

[0155] Table 16

[0156] Table 17

[0157] Table 18

[0158] Table 19

[0159] Table 20

[0160] Table 21

[0161] [Table 22]

[0162] [Table 23]

[0163] [Table 24]

[0164] [Table 25]

[0165] [Table 26]

[0166] Cross-linked rubber used as vibration-damping rubber must have practically acceptable heat resistance and dynamic magnification. The crosslinked rubber compositions obtained in Examples 1 to 42 and Example 49 of the present invention were found to have superior balance of tensile strength, tensile elongation, 300% modulus, compression set, and dynamic magnification compared to the crosslinked rubber compositions obtained in Comparative Examples 1 to 17, while maintaining processability, and also exhibiting equivalent or superior heat resistance.

[0167] ((Formulation Conditions 3) Example 43~ 44, Reference Example 45, Example 46~ 48. Comparative Examples 18-19) • Rubber component (A) (polymers 1-25 of polymerization examples 1-25, RSS3 as natural rubber, EP33 as EPDM (product name manufactured by ENEOS Material Co., Ltd.)): 100 parts by mass The amounts of each compounding agent listed below are shown in Table 27, per 100 parts by mass of rubber component (A) that does not contain rubber softeners. • Carbon Black (B) (Product name "Seast SO" manufactured by Tokai Carbon Co., Ltd.) • Anti-aging agent: 2-mercaptobenzimidazole • Naphthenic oil Zinc oxide Stearic acid • Crosslinking agent (C): Organic peroxide (dicumyl peroxide)

[0168] <Mixing method> The above-mentioned materials were kneaded by the following method to obtain a rubber composition. Using a sealed kneader (capacity 0.3L) equipped with a temperature control device, the first stage of kneading involved mixing rubber components, filler (carbon black), naphthenic oil, zinc oxide, stearic acid, and an antioxidant under conditions of a filling rate of 65% and a rotor rotation speed of 30-50 rpm. At this time, the temperature of the sealed mixer was controlled, and the first stage of the mixture was obtained with a discharge temperature of 125-130°C. After cooling, the second stage of mixing involved adding peroxide and kneading in an open roll oven set to 35°C. The mixture was then molded and crosslinked by pressing at 170°C for the specified time shown in Table 27. The rubber composition before crosslinking and the crosslinked rubber composition after crosslinking were evaluated. Specifically, the evaluation was performed using the following method. The evaluation results are shown in Table 28.

[0169] (Evaluation of the processability (cohesion) of rubber compositions) The rubber composition was evaluated using the same method as described above for evaluating its processability (cohesion).

[0170] (Evaluation of the physical properties of the compound) The Mooney viscosity of the rubber composition before crosslinking, and the tensile strength, tensile elongation, 300% modulus, and compression set of the crosslinked rubber composition were measured under the same conditions as described above. Examples 43-48 and Comparative Example 19 were indexed with the evaluation result of Comparative Example 18 set to 100, and the results are shown in Table 28. Regarding Mooney viscosity, a higher index indicates better performance. A value of 70 or higher relative to the standard is acceptable for practical use, 85 or higher is preferable, and 105 or higher indicates superiority. For all properties except Mooney viscosity, a higher index indicates better performance. A value of 85 or higher relative to the standard is considered practically acceptable, while a value of 105 or higher indicates superiority. The compression set was also measured using the method described above. Furthermore, a value of 100 or more relative to the standard is practically sufficient for use in packing, sealing materials, and rubber rollers, a value of 110 or more is preferable, a value of 120 or more is more preferable, and a value of 125 or more is even preferable. Furthermore, the hardness of the crosslinked rubber composition described above, and the change in hardness before and after heating (the change in Shore A hardness before and after heating under air at 100°C for 72 hours using formula (1) above), are recorded using the actual measured values ​​obtained by the method described above. Regarding the change in hardness before and after heating, it was evaluated that there were no practical problems if formula (1) was satisfied, and practical problems if formula (1) was not satisfied.

[0171] <Tensile properties> Similar to the tensile properties described above, the product of the tensile strength and tensile elongation of the crosslinked rubber composition was evaluated. A higher tensile property value indicates a better balance between tensile strength and tensile elongation, and the material is judged to be of high strength. Examples 43-48 and Comparative Example 19 were indexed with the evaluation result of Comparative Example 18 set to 100, and the results are shown in Table 28. It is preferable that the value be above the standard value (100), a value of 85 to 100 is acceptable for practical purposes, a value of 75 to less than 85 may result in insufficient material strength depending on the application, and a value of less than 75 is judged to be insufficient material strength.

[0172] <Heat resistance> Regarding heat resistance, we determined that a higher value indicates less deterioration due to heating and superior heat resistance, while a lower value indicates greater deterioration due to heating and inferior heat resistance. For Examples 43-48 and Comparative Example 18, if the value is between -5 and +10 compared to Comparative Example 19, the heat resistance is equivalent; if the value is +10 or higher, there is an advantage in terms of heat resistance; and if the value is less than -5, the heat resistance is inferior. However, for practical purposes, a value of 65 or higher is acceptable, 70 or higher is preferable, and 75 or higher is even more preferable. Cross-linked rubber compositions used as sealing materials such as packings or rubber rollers must have heat resistance, tensile properties, and compression set that are all practically acceptable. Compared to the crosslinked rubber compositions obtained in Comparative Examples 18 and 19, the crosslinked rubber compositions of Examples 43 to 48 were found to have superior balance of tensile strength, tensile elongation, 300% modulus, and compression set while maintaining processability, and their heat resistance was also confirmed to be practically acceptable.

[0173] The Shore A hardness before heating and the change in Shore A hardness before and after heating were measured and evaluated using the same measurement method as described above.

[0174] [Table 27]

[0175] [Table 28]

[0176] This application is based on Japanese Patent Application No. 2021-148431, filed with the Japan Patent Office on September 13, 2021, the contents of which are incorporated herein by reference. [Industrial applicability]

[0177] The crosslinked rubber composition of the present invention has industrial potential as a material for various industrial products, including vibration-damping rubber, vibration isolation rubber, conveyor belts, shoe outsoles and other soles, automotive weatherstrips, packings and gaskets, sealing materials, waterproof sheets, engine mounts, air springs, rubber gloves, medical and hygiene products, hoses for industrial and various applications, battery cases, adhesives, wire insulation, window frame rubber, rubber stoppers, rubber rollers, and various other industrial products.

Claims

1. 100 parts by mass of rubber component (A) containing 10% to 100% by mass of a hydrogenated conjugated diene polymer and having an iodine value of 10 to 370, Carbon black (B) 30 parts by mass or more and 50 parts by mass or less, A product comprising a crosslinked rubber composition which is a crosslinked rubber composition comprising, The hydrogenated conjugated diene polymer has a hydrogenation rate of 10% or more and 90% or less, an aromatic vinyl monomer block content of less than 5% by mass, a weight-average molecular weight of 150,000 or more and 1,500,000 or less, and a vinyl bond content of 0.1 mol% or more and less than 10 mol%. The change in Shore A hardness of the crosslinked rubber composition before and after heating in air at 100°C for 72 hours satisfies the following formula (1): -10 < (Shore A hardness after heating) - (Shore A hardness before heating) < 5 ... (1) Any one product selected from the group consisting of vibration-damping rubber, vibration isolation rubber, conveyor belts, shoe outsoles, automotive weatherstrips, packings, gaskets, sealing materials, waterproof sheets, engine mounts, air springs, rubber gloves, medical and hygiene products, rubber rollers, industrial hoses, battery cases, adhesives, wire insulation, and window frame rubber, comprising a cross-linked rubber composition.

2. The aforementioned rubber component (A) is 100 parts by mass, A filler containing the aforementioned carbon black (B) in an amount of 30 to 50 parts by mass, A molded article of a crosslinked rubber composition containing the following: The product according to claim 1.

3. The hydrogenated conjugated diene polymer has a glass transition temperature of -50°C or lower. The product according to claim 1.

4. The hydrogenated conjugated diene polymer has a modification rate of 40% to 99%. The product according to claim 1.

5. The hydrogenated conjugated diene polymer has a Mooney stress relaxation (MSR) of 0.8 or less at 100°C. The product according to claim 1.

6. The product according to claim 1, wherein the crosslinked rubber composition satisfies the following formula (2). 0.5 MPa < (Storage modulus at 50°C with 0.1% strain) - (Storage modulus at 50°C with 10% strain) < 10 MPa ... (2)

7. The rubber component (A) contains 10% by mass or more and 90% by mass or less of a rubbery polymer other than the hydrogenated conjugated diene polymer. The rubbery polymer other than the hydrogenated conjugated diene polymer is at least one rubber selected from the group consisting of styrene-butadiene rubber, styrene-isoprene rubber, natural rubber, polybutadiene, polyisoprene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber, butyl rubber, polyurethane, epichlorohydrin rubber, silicone rubber, acrylic rubber, nitrile rubber, chloroprene rubber, and fluororubber. The product according to claim 1.

8. The hydrogenated conjugated diene polymer has a titanium content of 1 ppm to 100 ppm and an aluminum content of 2 ppm or less. The product according to claim 1.

9. A method for producing the crosslinked rubber composition contained in the product described in claim 1, A method for producing a crosslinked rubber composition, comprising the step of crosslinking the hydrogenated conjugated diene polymer with sulfur and a vulcanization accelerator or an organic peroxide.

10. A method for producing the crosslinked rubber composition contained in the product according to claim 1, which contains a rubber component (A) and carbon black (B), A process of polymerizing a hydrogenated conjugated diene polymer having a hydrogenation rate of 10% or more and 90% or less, an aromatic vinyl monomer block content of less than 5% by mass, a weight-average molecular weight of 150,000 or more and 1,500,000 or less, a glass transition temperature of -50°C or lower, an aromatic vinyl monomer unit content of 5% by mass or more, and a vinyl bond content of 0.1 mol% or more and less than 10 mol%, A step to obtain a rubber component (A) containing 10% by mass or more and 100% by mass or less of the hydrogenated conjugated diene polymer, and having an iodine value of 10 or more and 370 or less, A step of obtaining a rubber composition by mixing 100 parts by mass of the rubber component (A) with 30 to 50 parts by mass of carbon black (B), A step of crosslinking the rubber composition, It has, To obtain a crosslinked rubber composition in which the change in Shore A hardness before and after heating at 100°C for 72 hours under air satisfies the following formula (1), A method for producing a crosslinked rubber composition. -10 < (Shore A hardness after heating) - (Shore A hardness before heating) < 5 ... (1)

11. In the crosslinking step, the rubber composition containing the rubber component (A) and the carbon black (B) is crosslinked in a molded state. A method for producing the crosslinked rubber composition according to claim 9 or 10.

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