Rubber composition

Abstract

To provide a rubber composition which is superior in low-temperature properties and ozone resistance, and exhibits practically sufficient compression set characteristics and mechanical strength.SOLUTION: A rubber composition comprises a hydrogenated conjugated diene polymer and an olefin-based rubber as rubber components. The hydrogenated conjugated diene polymer has a glass transition temperature of -60°C or less as measured by means of a differential scanning calorimeter (DSC). The hydrogenated conjugated diene polymer satisfies the following formula (S). Formula (S):30≤[(b+d) / (a+b+c+d)]×100≤70. (In formula (S), a represents the composition ratio (mol%) of a structural unit represented by formula (1), b represents that of a structural unit represented by formula (2), c represents that of a structural unit represented by formula (3), and d represents that of a structural unit represented by formula (4)).SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, rubber materials have been widely used in automobiles, houses, industrial equipment, electric equipment, etc. Among them, rubber parts for automobiles such as weather strips, radiator / heater hoses, and various vibration-proof rubbers, and rubber materials such as waterproof sheets, building packings, and electric wires and cables have increasing requirements for heat resistance and ozone resistance. From such a viewpoint, ethylene-propylene-diene copolymer (EPDM) has been widely applied as these rubber materials. In recent years, more excellent low-temperature characteristics have been required for the above various rubber materials, and various developments have been made regarding rubber products having rubber elasticity even at low temperatures, that is, highly reliable rubber products having excellent low-temperature characteristics.

[0003] For example, Non-Patent Document 1 proposes a rubber material in which the component ratio of a high-ethylene-content component that becomes a crystalline component of EPDM is greatly reduced and the ratio of an amorphous component is increased in order to improve low-temperature characteristics. Further, Non-Patent Document 1 proposes a rubber material in which the crystallization of ethylene chains is suppressed and the low-temperature characteristics are improved by enhancing the alternating copolymerizability and reducing the ratio of ethylene chains.

[0004] Further, Patent Document 1 proposes a composition in which a copolymer obtained by polymerizing the propylene part of EPDM with butylene and a predetermined olefin-based polymer such as EPDM are blended, and it is disclosed that the composition is excellent in low-temperature flexibility and exhibits excellent damping performance in a wide temperature range.

[0005] Furthermore, Patent Document 2 proposes a rubber composition obtained by vulcanizing a rubber composition mainly composed of EPDM with a peroxide. By adjusting the types and amounts of the organic peroxide and carbon black contained in the rubber composition respectively, it is disclosed that a rubber material having high damping characteristics in a wide temperature range from room temperature to high temperature and a small temperature dependence of damping performance can be provided.

[0006] Furthermore, Patent Document 3 discloses that by using a rubber composition composed of a hydrogenated conjugated diene polymer and an olefin rubber, a crosslinked rubber with high strength and low wear can be provided.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

[0008]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in various conventional EPDM-based rubber materials that have been proposed, the limiting use temperature in the low-temperature region is -40°C. Nowadays, it is assumed that they will be used in a lower temperature region, and it is required to have practically good performance under such low-temperature conditions. Furthermore, it is also required to have sufficient performance in terms of ozone resistance.

[0010] Therefore, an object of the present invention is to provide a rubber composition that is excellent in low-temperature properties and ozone resistance and has practically sufficient compression set properties and mechanical strength.

Means for Solving the Problems

[0011] As a result of intensive studies to solve the above-described problems of the prior art, the present inventors have found that a rubber composition containing a conjugated diene polymer having a specific structure and an olefin rubber, and having the glass transition temperature of the hydrogenated conjugated diene polymer specified within a predetermined numerical range, provides a rubber composition that is excellent in low-temperature properties and ozone resistance and has practically sufficient mechanical strength, and thus have completed the present invention. That is, the present invention is as follows.

[0012] 〔1〕 A rubber composition containing, as a rubber component, a hydrogenated conjugated diene polymer and an olefin rubber, wherein the hydrogenated conjugated diene polymer contains the following structures (1) to (4),

[0013]

Chemical formula

[0014] the hydrogenated conjugated diene polymer has a glass transition temperature measured by a differential scanning calorimeter (DSC) of -60°C or lower, and the rubber composition in which the hydrogenated conjugated diene polymer satisfies the following mathematical formula (S). Mathematical formula (S): 30 ≦ 〔(b + d) / (a + b + c + d)〕×100 ≦ 70 (In the mathematical formula (S), a represents the structural unit represented by the above formula (1), b represents the structural unit represented by the above formula (2), c represents the structural unit represented by the above formula (3), and d represents the structural unit represented by the above formula (4), each showing the composition ratio (mol%).)

[0015] 〔2〕 The rubber composition according to the above 〔1〕, wherein the hydrogenated conjugated diene polymer has an aromatic vinyl monomer unit content of 1 to 20% by mass. [3] The rubber composition according to [1] or [2], wherein the modification rate of the hydrogenated conjugated diene polymer is 30% or more. [4] The rubber composition according to any one of [1] to [3], wherein the olefin rubber has a Mooney viscosity at 100 ° C of 25 or more and 150 or less. [5] As the rubber component, The rubber composition according to any one of [1] to [4], further comprising at least one selected from the group consisting of natural rubber, non-hydrogenated butadiene rubber, non-hydrogenated isoprene rubber, non-hydrogenated styrene-butadiene rubber, and non-hydrogenated styrene-isoprene rubber. [6] Further comprising a filler, The rubber composition according to any one of [1] to [5], wherein the content of the filler is 5 parts by mass or more and 250 parts by mass or less with respect to 100 parts by mass of the rubber component. [7] The filler is The rubber composition according to [6], which is at least one selected from the group consisting of silica, carbon black, calcium carbonate, titanium oxide, clay, and aluminum hydroxide. [8] Further comprising sulfur, The content of the sulfur is 0.2 parts by mass or less with respect to 100 parts by mass of the rubber component, The rubber composition according to any one of [1] to [7]. [Advantages of the Invention]

[0016] According to the present invention, a rubber composition excellent in low-temperature characteristics and ozone resistance and having practically sufficient compression set properties and mechanical strength can be provided. [Embodiments for Carrying Out the Invention]

[0017] Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. Note that the following embodiments are examples for explaining the present invention, and the present invention is not limited to the following embodiments. The present invention can be appropriately modified and implemented within the scope of its gist.

[0018] 〔Rubber composition〕 The rubber composition of the present embodiment contains, as a rubber component, a hydrogenated conjugated diene polymer and an olefin rubber. The hydrogenated conjugated diene polymer contains the following structures (1) to (4).

[0019]

Chemical formula

[0020] The hydrogenated conjugated diene polymer has a glass transition temperature measured by a differential scanning calorimeter (DSC) of -60°C or lower, and the hydrogenated conjugated diene polymer satisfies the following mathematical formula (S). Mathematical formula (S): 30 ≦ 〔(b + d) / (a + b + c + d)〕×100 ≦ 70 In the mathematical formula (S), a represents the structural unit represented by the formula (1), b represents the structural unit represented by the formula (2), c represents the structural unit represented by the formula (3), and d represents the structural unit represented by the formula (4), respectively showing the respective composition ratios (mol%).

[0021] According to the rubber composition of the present embodiment, excellent low-temperature properties, ozone resistance, practically sufficient compression set properties, and mechanical strength can be achieved.

[0022] The low-temperature properties of the rubber composition of the present embodiment can be evaluated using TR10 and TR70 obtained from the TR test as indices. In this specification, it is assumed that the rubber composition of the present embodiment being excellent in low-temperature properties is synonymous with low TR10 and TR70 by the TR test. Note that the TR test is a test in which, in accordance with JIS K6261-4, a 50% elongation is applied to a test piece of the rubber composition of the present embodiment, cooled to -70°C, and then the shrinkage amount as the elasticity recovers with the temperature increase is measured. The temperature at which the shrinkage rate corresponds to 10% is defined as TR10, and the temperature at which the shrinkage rate corresponds to 70% is defined as TR70. Specifically, it can be evaluated by the method described in the examples below.

[0023] The ozone resistance of the rubber composition of the present embodiment can be evaluated by subjecting a test piece of the rubber composition of the present embodiment to ozone degradation in accordance with JIS K6259-1:2015 under the conditions of 20% elongation, an ozone concentration of 50 pphm, 40 °C, and 96 hours, and then visually observing the presence or absence of cracks (ozone cracks) on the surface of the test piece. Specifically, it can be evaluated by the method described in the examples below.

[0024] (Hydrogenated conjugated diene polymer) The rubber composition of the present embodiment contains a hydrogenated conjugated diene polymer as a rubber component. The hydrogenated conjugated diene polymer includes the structures (1) to (4), and can be produced by a method including a step of polymerizing a monomer containing a conjugated diene compound to obtain a conjugated diene polymer having an active end (polymerization step) and a step of hydrogenating the conjugated diene polymer (hydrogenation step). Note that a step of modifying the ends of the conjugated diene polymer (modification step) may be performed.

[0025] Examples of the conjugated diene compound include, but are not limited to, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene. Among these, from the viewpoint of easy industrial availability, 1,3-butadiene and isoprene are preferable, and 1,3-butadiene is more preferable. These may be used alone or in combination of two or more. Here, in the present specification, the hydrogenated conjugated diene polymer is defined as a conjugated diene polymer obtained by polymerizing a monomer containing a conjugated diene compound or a conjugated diene polymer obtained by modifying the ends of the obtained conjugated diene polymer, which has been hydrogenated.

[0026] <Content of aromatic vinyl monomer unit> From the viewpoint of improving the mechanical strength such as the breaking strength and elongation of the rubber composition of the present embodiment, the hydrogenated conjugated diene polymer preferably contains an aromatic vinyl monomer unit. Further, from the viewpoint of the low-temperature properties of the rubber composition of the present embodiment, the content of the aromatic vinyl monomer unit in the hydrogenated conjugated diene polymer is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. The lower limit is not particularly limited, but it is preferably 1% by mass or more. The content of the aromatic vinyl monomer unit in the hydrogenated conjugated diene polymer can be measured by the method described in the examples described later, and can be controlled within the above numerical range by adjusting the addition amount of the aromatic vinyl compound and the polymerization time in the polymerization step.

[0027] The aromatic vinyl compound is not limited to the following, and examples thereof include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, α-methylstyrene, vinyl ethylbenzene, vinyl xylene, vinyl naphthalene, and diphenylethylene. Among these, styrene is preferable from the viewpoint of easy industrial availability. These may be used alone or in combination of two or more.

[0028] The hydrogenated conjugated diene polymer may contain other monomer units in addition to the conjugated diene monomer unit and the aromatic vinyl monomer unit described above. The monomers used to form other monomer units are not limited to the following, and examples thereof include 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. These may be used alone or in combination of two or more. When the hydrogenated conjugated diene polymer contains such other monomer units, the heat resistance and ozone resistance of the rubber composition of the present embodiment tend to be further improved.

[0029] <Content of aromatic vinyl monomer block> The hydrogenated conjugated diene polymer may contain an aromatic vinyl monomer block. In the present specification, the "aromatic vinyl monomer block" refers to a structure in which 8 or more aromatic vinyl monomer units are linked in a chain. From the viewpoints of the tensile strength and elongation of the rubber composition of the present embodiment, the content of the aromatic vinyl monomer block in the hydrogenated conjugated diene polymer is preferably less than 5.0% by mass, more preferably 4.0% by mass or less, still more preferably 3.5% by mass or less, and even more preferably 3.0% by mass or less.

[0030] The method for measuring the content of the aromatic vinyl monomer block in the hydrogenated conjugated diene polymer is not particularly limited. For example, as described in WO 2014 / 133097, known methods such as measuring the amount of the structure in which styrene units are linked using NMR can be mentioned. As another method, when the hydrogenated conjugated diene polymer is a butadiene-styrene copolymer, a method of decomposing the butadiene-styrene copolymer by the method of Kolthoff (described in I.M. KOLTHOFF, et al., J. Polym. Sci. 1, 429 (1946)) and analyzing the amount of polystyrene insoluble in methanol can be mentioned. Specifically, it can be measured by the method for measuring the amount of the styrene block described in the examples described later. The content of the aromatic vinyl monomer block in the hydrogenated conjugated diene polymer can be controlled by adjusting the polymerization conditions. For example, in a method of polymerizing an aromatic vinyl compound first and then adding a conjugated diene compound to obtain a conjugated diene polymer, or in a method of adding an aromatic vinyl compound before the active terminal of the conjugated diene polymer is deactivated, by adjusting the addition amount of the aromatic vinyl compound and the addition amount of the polymerization initiator, it can be controlled within the above numerical range.

[0031] <Amount of 1,2-vinyl bond before hydrogenation> The hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment preferably has a 1,2-vinyl bond content of 20 mol% or more, more preferably 23 mol% or more, and even more preferably 25 mol% or more in the conjugated diene polymer before hydrogenation, from the viewpoint of reducing the crystallinity of the polymer upon hydrogenation. Further, from the viewpoint of improving the low-temperature properties of the rubber composition of the present embodiment, the 1,2-vinyl bond content before hydrogenation is preferably 45 mol% or less, more preferably 42 mol% or less, and even more preferably 40 mol% or less. The 1,2-vinyl bond content before hydrogenation is 1 measurable by 1H-NMR. Specifically, it can be measured by the method described in the examples below. The 1,2-vinyl bond content before hydrogenation can be controlled within the above numerical range by adjusting the polymerization temperature and the addition amount of the polar compound.

[0032] Examples of the polar compound 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 alone or in combination of two or more. The amount of the polar compound used is not particularly limited and can be selected according to the purpose, etc., but is preferably 0.01 mol or more and 100 mol or less per 1 mol of the polymerization initiator used in the polymerization step of the hydrogenated conjugated diene polymer.

[0033] <Hydrogenation rate> The hydrogenated conjugated diene polymer used in the rubber composition of this embodiment has a hydrogenation rate that satisfies the following mathematical formula (S). Mathematical formula (S): 30 ≦ [(b + d) / (a + b + c + d)] × 100 ≦ 70 In mathematical formula (S), a represents the structural unit represented by the above formula (1), b represents the structural unit represented by the above formula (2), c represents the structural unit represented by the above formula (3), and d represents the structural unit represented by the above formula (4), each showing the composition ratio (mol%). The above mathematical formula (S) represents that "the hydrogenation rate of the structural unit derived from butadiene is 30% or more and 70% or less".

[0034] From the viewpoint of the ozone resistance of the rubber composition of this embodiment, the hydrogenation rate of the hydrogenated conjugated diene polymer represented by the above mathematical formula (S) is 30% or more, preferably 35% or more, and more preferably 40% or more. On the other hand, from the viewpoint of obtaining good low-temperature characteristics of the rubber composition of this embodiment and allowing a sufficient crosslinking reaction to occur in the hydrogenated conjugated diene polymer, it is 70% or less, preferably 65% or less, and more preferably 60% or less. The hydrogenation rate of the hydrogenated conjugated diene polymer is the molar ratio in which the double bond of the structure derived from the conjugated diene monomer unit becomes a saturated bond by a hydrogenation reaction. The hydrogenation rate can be measured by the method described in the examples described later. 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.

[0035] As a method of hydrogenating after copolymerizing a conjugated diene compound and, if necessary, an aromatic vinyl compound or other monomers, for example, as described in WO 96 / 05250, JP 2000-053706 A, WO 2003 / 085010, WO 2019 / 151126, WO 2019 / 151127, WO 2002 / 002663, and WO 2015 / 006179, a method of polymerizing a conjugated diene compound by anionic polymerization under various additives and conditions, copolymerizing with other monomers if necessary, and then hydrogenating is mentioned as a preferred method.

[0036] <Weight average molecular weight> The hydrogenated conjugated diene polymer used in the rubber composition of this embodiment preferably has a weight average molecular weight of 80,000 or more, more preferably 90,000 or more, and even more preferably 100,000 or more from the viewpoints of compression set, tensile strength, and elongation of the rubber composition of this embodiment. On the other hand, from the viewpoint of the processability of the rubber composition of this embodiment, it is preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 200,000 or less.

[0037] <Molecular weight distribution> The hydrogenated conjugated diene polymer used in the rubber composition of this embodiment preferably has a molecular weight distribution (= weight average molecular weight / number average molecular weight) of 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 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.

[0038] The weight average molecular weight and molecular weight distribution of the hydrogenated conjugated diene polymer can be calculated from the polystyrene-equivalent molecular weight measured by GPC (gel permeation chromatography). Specifically, it can be measured by the method described in the examples described later. The weight average molecular weight and molecular weight distribution can be controlled within the above-described numerical ranges by adjusting the monomer addition amount, addition timing, and polymerization initiator addition amount in the polymerization step.

[0039] <Mooney viscosity> The hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment preferably has a Mooney viscosity at 100°C of 100 or less, more preferably 80 or less, and even more preferably 70 or less from the viewpoint of the processability of the rubber composition of the present embodiment when measured with an L-type rotor. On the other hand, from the viewpoints of the tensile strength and tensile elongation of the rubber composition of the present embodiment, it is preferably 20 or more, more preferably 30 or more, and even more preferably 40 or more. The Mooney viscosity of the hydrogenated conjugated diene polymer can be measured by the method described in the examples below.

[0040] <Glass transition temperature> The hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment has a glass transition temperature measured by differential scanning calorimetry (DSC) of -60°C or higher. The glass transition temperature of the rubber composition of the present embodiment greatly depends on the glass transition temperature of the hydrogenated conjugated diene polymer, but generally shifts to a higher temperature side than the glass transition temperature of the hydrogenated conjugated diene polymer. This is due to, for example, the reduction in the molecular chain mobility due to the crosslinking of the hydrogenated conjugated diene polymer in the rubber composition of the present embodiment. Also, from the viewpoint of using the rubber composition of the present embodiment in a low-temperature environment, it is necessary to lower the glass transition temperature of the rubber composition of the present embodiment and reduce the change in physical properties such as the storage elastic modulus and hardness in the use temperature range. When the rubber composition of the present embodiment is used in a low-temperature environment, it is necessary to have sufficient flexibility even in a low-temperature environment of at least lower than -40°C. In the case of an EPDM-based rubber material, which is a conventionally known rubber material with a usable temperature of -40°C, the Tg of the EPDM used was -55°C. In order to lower the usable temperature in the rubber composition of the present embodiment compared to the conventionally known EPDM-based rubber material, it is necessary to lower the Tg of the hydrogenated conjugated diene polymer contained as a rubber component. Therefore, in the rubber composition of the present embodiment, the glass transition temperature (Tg) of the hydrogenated conjugated diene polymer is preferably -60°C or lower, more preferably -65°C or lower, and even more preferably -70°C or lower. Also, from the viewpoint of the mechanical strength of the rubber composition of the present embodiment, the glass transition temperature (Tg) of the hydrogenated conjugated diene polymer is preferably -90°C or higher, more preferably -88°C or higher, and even more preferably -85°C or higher. The glass transition temperature of the hydrogenated conjugated diene polymer can be controlled within the above range by adjusting the content of the aromatic vinyl monomer unit, the amount of 1,2-vinyl bonds, and the hydrogenation rate.

[0041] Specifically, as a method for setting the glass transition temperature of the hydrogenated conjugated diene polymer to -60°C or lower, when the hydrogenated conjugated diene polymer is a hydrogenated polymer of a random copolymer of styrene and butadiene and the hydrogenation rate is 30% to 45%, the styrene content is preferably 18% by mass or less, and the amount of 1,2-vinyl bonds in the conjugated diene monomer unit before hydrogenation is preferably 15 mol% or more and 40 mol% or less. On the other hand, when the hydrogenation rate is 50% to 65%, the styrene content is preferably 10% by mass or less, and the amount of 1,2-vinyl bonds in the conjugated diene monomer unit before hydrogenation is preferably 20 mol% or more and 40 mol% or less. By setting the glass transition temperature of the hydrogenated conjugated diene polymer to -60°C or lower, a rubber composition excellent in low-temperature properties can be obtained.

[0042] Regarding the glass transition temperature of the hydrogenated conjugated diene polymer, in accordance with ISO 22768:2006, a DSC curve is recorded while raising the temperature in a predetermined temperature range, and the peak top (Inflection point) of the DSC differential curve is taken as the glass transition temperature. Specifically, it can be measured by the method described in the examples below.

[0043] <Modification rate> The hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment preferably contains a nitrogen atom from the viewpoints of the compression set and tensile strength of the rubber composition of the present embodiment. The nitrogen atom can be introduced by using a modifier or a coupling agent. Thereby, the dispersibility of the filler in the rubber composition of the present embodiment tends to be improved. From the viewpoint of enhancing the affinity and / or reactivity of the hydrogenated conjugated diene polymer with fillers such as silica and carbon black, thereby enhancing the dispersibility of the fillers and reducing the compression set of the rubber composition of the present embodiment, the modification rate is preferably 30% or more, more preferably 45% or more, still more preferably 50% or more, even more preferably 60% or more, and even more preferably 70% or more. The upper limit of the modification rate of the hydrogenated conjugated diene polymer is not particularly limited, but from the viewpoint of the reduction in the viscosity of the formulation after kneading and good processability, it is preferably 99% or less, more preferably 98% or less, still more preferably 95% or less, and even more preferably 90% or less. In the present specification, the "coupling agent" represents a compound that generates a branched component having two or more branches. The "modifier" is a compound having a nitrogen atom and capable of bonding to a polymer to be modified. A compound having a nitrogen atom and generating a branched component having two or more branches is both a coupling agent and a modifier.

[0044] In the present specification, the "modification rate" represents the mass ratio of the polymer having a nitrogen atom-containing functional group to the total amount of the hydrogenated conjugated diene polymer. The introduction position of the nitrogen atom into the hydrogenated conjugated diene polymer may be any of the polymerization initiation terminal, in the molecular chain (including graft), and the polymerization terminal. When the hydrogenated conjugated diene polymer is produced by polymerizing a conjugated diene compound and then hydrogenating it, from the viewpoints of polymerization productivity and obtaining a high modification rate, it is preferable to apply a method of introducing a nitrogen atom using a coupling agent containing a nitrogen atom. The modification rate of the hydrogenated conjugated diene polymer can be measured by the method described in the examples described later. The modification rate of the hydrogenated conjugated diene polymer can be controlled within the above numerical range by adjusting the addition amount of the modifier.

[0045] Examples of the coupling agent containing a nitrogen atom include, from the viewpoints of polymerization productivity and high modification rate, for example, isocyanate compounds, isothiocyanate compounds, isocyanuric acid derivatives, nitrogen group-containing carbonyl compounds, nitrogen group-containing vinyl compounds, nitrogen group-containing epoxy compounds, nitrogen group-containing alkoxysilane compounds, etc., which are preferably cited. Also, from the viewpoint of reducing the viscosity of the rubber composition of the present embodiment and from the viewpoint of reducing the occurrence of cracks in the compounded sheet, it is preferable that the number of branches of the coupling agent is higher. The number of branches of the coupling agent is not particularly limited, but from the viewpoint of improving the processability when preparing the rubber composition of the present embodiment, 3 or more branches are preferable, and 4 or more branches are more preferable. The upper limit of the number of branches is not particularly limited, but from the viewpoint of productivity, 30 or less branches are preferable. As these coupling agents containing a nitrogen atom, from the viewpoint of reactivity, nitrogen group-containing alkoxysilane compounds and nitrogen group-containing polyfunctional modifiers are more preferable.

[0046] Examples of the nitrogen group-containing alkoxysilane compound include, but are not limited to, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(4-trimethoxysilylbutyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacycloheptane, 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-ethoxy-2-ethyl-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, tris(3-trimethoxysilylpropyl)amine, tris(3-methyldimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-methyldiethoxysilylpropyl)amine, tris(trimethoxysilylmethyl)amine, tris(2-trimethoxysilylethyl)amine, tris(4-trimethoxysilylbutyl)amine, tetrakis[3-(2,2-dimethoxy-1-aza-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.

[0047] Examples of the nitrogen group-containing polyfunctional modifier include, but are not limited to, compounds having at least one functional group selected from the group consisting of an epoxy group, a carbonyl group, a carboxylic acid ester group, a carboxylic acid amide group, an acid anhydride group, a phosphate ester group, a phosphite ester group, an episulfide group, a thiocarbonyl group, a thiocarboxylic acid ester group, a dithiocarboxylic acid ester group, a thiocarboxylic acid amide group, an imino group, an ethyleneimino group, a halogen group, an alkoxysilyl group, an isocyanate group, a thioisocyanate group, a conjugated diene group, and an arylvinyl group, and having at least one nitrogen atom in the compound.

[0048] In the calculation of the number of moles of the functional group, one alkoxy group in each of the epoxy group, carbonyl group, episulfide group, thiocarbonyl group, imino group, ethyleneimino group, halogen group, conjugated diene group, arylvinyl group, and alkoxysilyl group is regarded as monofunctional, each of the carboxylic acid ester group, carboxylic acid amide group, acid anhydride group, thiocarboxylic acid ester group, dithiocarboxylic acid ester group, thiocarboxylic acid amide group, isocyanate group, and thioisocyanate group is regarded as difunctional, and each of the phosphate ester group and phosphite ester group is regarded as trifunctional. As the polyfunctional modifier that can be used for modifying the hydrogenated conjugated diene polymer contained in the rubber composition of the present embodiment, those having a sum of the functionality numbers of the above functional groups in one molecule of 2 or more are preferable, and more preferably, a polyfunctional modifier having a sum of the functionality numbers of 3 or more.

[0049] When using a modified polymer as the hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment, for the preparation of such a modified polymer, in addition to the coupling agent and modifier described above, a polyfunctional modifier other than the above nitrogen group-containing polyfunctional modifier and a coupling agent not containing a nitrogen atom, which will be described later, can also be used.

[0050] Examples of the polyfunctional modifier other than the nitrogen group-containing polyfunctional modifier include, but are not limited to, polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether and glycerin 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 polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine, glycidylamine compounds such as diglycidylaniline, diglycidyl orthotoluidine, tetraglycidyl metaxylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; compounds having an epoxy group and other functional groups such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltributoxysilane, epoxy-modified silicone, epoxidized soybean oil, and epoxidized linseed oil.

[0051] In addition, examples of the coupling agent that does not contain a nitrogen atom 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, monomethyltrichlorosilane, monoethyltrichlorosilane, monobutyltrichlorosilane, monohexyltrichlorosilane, monomethyltribromosilane, and bistrichlorosilylethane; alkoxyhalogenated silane compounds such as monochlorotrimethoxysilane, monobromotrimethoxysilane, dichlorodimethoxysilane, dibromodimethoxysilane, trichloromethoxysilane, and tribromomethoxysilane; halogenated tin compounds such as tin tetrachloride, tin tetrabromide, monomethyltrichlorotin, monoethyltrichlorotin, monobutyltrichlorotin, monophenyltrichlorotin, and bistrichlorostannylethane; 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.

[0052] In addition, as a modifier for modifying the hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment, a terminal modifier may be used. Examples of the terminal modifier include, but are not limited to, 1,3 - diethyl - 2 - imidazolinone, 1,3 - dimethyl - 2 - imidazolinone, 1,3 - dipropyl - 2 - imidazolinone, 1 - methyl - 3 - ethyl - 2 - imidazolinone, 1 - methyl - 3 - propyl - 2 - imidazolinone, 1 - methyl - 3 - butyl - 2 - imidazolinone, 1,3 - dihydro - 1,3 - dimethyl - 2H - imidazol - 2 - one, and the like.

[0053] (Olefin - based rubber) The rubber composition of the present embodiment contains an olefin - based rubber as a rubber component. The olefin - based rubber refers to a rubber that uses olefin as a raw material. Since it does not contain substances that use conjugated diene compounds as raw materials, it can be clearly distinguished from hydrogenated conjugated diene-based polymers. Examples of olefin rubbers include, but are not limited to, ethylene·α-olefin copolymers, butyl rubber (IIR), halogenated butyl rubber, ethylene-vinyl acetate rubber, maleic acid-modified ethylene-propylene rubber (M-EPM), chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM), acrylic rubber (ACM), chlorosulfonated polyethylene (CSM), ethylene·α-olefin·non-conjugated polyene copolymers composed of structural units derived from ethylene, structural units derived from α-olefins having 3 to 20 carbon atoms, and structural units derived from non-conjugated polyenes, and the like. Among these, from the viewpoint of the balance between the mechanical strength and low-temperature properties of the rubber composition of the present embodiment, ethylene·α-olefin·non-conjugated polyene copolymers are preferred. Examples of α-olefins having 3 to 20 carbon atoms include, but are not limited to, propylene, butylene, etc. From the viewpoints of the low-temperature properties and cost of the rubber composition of the present embodiment, propylene or butylene is preferred. In addition, the ethylene content in the ethylene·α-olefin·non-conjugated polyene copolymer is not limited to the following, but from the viewpoint of the low-temperature properties of the rubber composition of the present embodiment, 65% by mass or less is preferred, 60% by mass or less is more preferred, and 55% by mass or less is even more preferred. Examples of non-conjugated polyenes include, but are not limited to, dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylene norbornene, units derived from ethylidene norbornene, and the like. From the viewpoint of the mechanical strength of the rubber composition of the present embodiment, ethylidene norbornene is preferred. In addition, the non-conjugated polyene content in the ethylene·α-olefin·non-conjugated polyene copolymer is not limited to the following, but from the viewpoint of the low-temperature properties of the rubber composition of the present embodiment, 10% by mass or less is preferred, 9% by mass or less is more preferred, and 8% by mass or less is even more preferred. Also, from the viewpoint of crosslinking properties, 2% by mass or more is preferred, 3% by mass or more is more preferred, and 4% by mass or more is even more preferred. From the perspective of the low-temperature properties of the rubber composition of the present embodiment, the olefin-based rubber preferably has a glass transition temperature of -50°C or lower. Also, from the perspective of the processability of the rubber composition of the present embodiment, the olefin-based rubber preferably has a Mooney viscosity at 100°C of 25 or more and 150 or less, more preferably 30 or more and 100 or less, and even more preferably 35 or more and 70 or less. The Mooney viscosity of the olefin-based rubber can be measured using an L-type rotor and can be controlled within the above numerical range by controlling the molecular weight.

[0054] (Other rubber components) The rubber composition of the present embodiment may contain, as a rubber component, other rubber components other than the above-described hydrogenated conjugated diene polymer and olefin-based rubber. Examples of other rubber components include, but are not limited to, non-hydrogenated conjugated diene polymers such as styrene-butadiene rubber, styrene-isoprene rubber, natural rubber, butadiene rubbers such as polybutadiene, and isoprene rubbers such as polyisoprene rubber. Styrene-butadiene rubber includes solution-polymerized styrene-butadiene copolymer rubber and emulsion-polymerized styrene-butadiene copolymer rubber. Polybutadiene includes low-cis polybutadiene, high-cis polybutadiene, and high-trans polybutadiene. Butyl rubber includes chlorinated butyl rubber and brominated butyl rubber. Other special rubbers include hydrin rubber (CO, ECO), silicone rubber (Q), methyl silicone rubber (MQ), vinyl methyl silicone rubber (VMQ), phenyl silicone rubber (PMQ), fluorosilicone rubber (FVMQ), tetrafluoroethylene propylene rubber, fluorinated rubber (FKM), polysulfide rubber (T), and urethane rubber (U). These may be used alone or in combination of two or more.

[0055] (Production method of hydrogenated conjugated diene polymer) Hereinafter, the production method of the hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment will be described. In addition, unless otherwise specified, the value expressed in "parts by mass" is the value when the total amount of the entire rubber component is 100 parts by mass. Moreover, the method for identifying the types and content ratios of the rubber components contained in the rubber composition of the present embodiment is not particularly limited. For example, NMR can be used. For example, in a previously reported document (JSR TECHNICAL REVIEW No. 126 / 2019), solid 13 By using 13C-NMR, a 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 has been disclosed, and such a method can also be used for identifying the rubber components of the rubber composition of the present embodiment.

[0056] <Polymerization Method and Hydrogenation Method of Hydrogenated Conjugated Diene Polymer> The hydrogenated conjugated diene polymer can be produced by polymerizing a conjugated diene compound, copolymerizing an aromatic vinyl compound if necessary, and then adding a hydrogenation catalyst and performing hydrogenation. When the hydrogenated conjugated diene polymer is a copolymer of a conjugated diene compound and an aromatic vinyl compound, it is preferably a random copolymer. From the viewpoints of production cost and the vibration damping properties, heat resistance, and ozone resistance of the rubber composition of the present embodiment, the hydrogenated conjugated diene polymer is obtained by polymerizing at least a conjugated diene compound or copolymerizing the conjugated diene compound and other monomers, and hydrogenating (adding hydrogen) a part or most of the double bonds. As a method of performing hydrogenation after polymerizing or copolymerizing a conjugated diene compound, for example, as described in International Publication No. 96 / 05250, JP-A-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, it is preferable to apply a method of polymerizing a conjugated diene compound by anionic polymerization under various additives and conditions, copolymerizing with other monomers if necessary, and then performing hydrogenation.

[0057] <Titanium in the hydrogenated conjugated diene polymer> The hydrogenated conjugated diene polymer used in the rubber composition of this embodiment may contain titanium. When the hydrogenated conjugated diene polymer contains titanium, the titanium is preferably a catalyst residue in the production of the hydrogenated conjugated diene polymer. In such a case, the titanium as the catalyst is preferably a hydrogenation catalyst component. As the hydrogenation catalyst component, from the viewpoint of easily adjusting the metal amount in the hydrogenated conjugated diene polymer to a predetermined amount, for example, the Ti compounds described in JP-A-1-275605, JP-A-2-172537, JP-A-4-96904, JP-A-08-33846, JP-A-08-41081, WO2014 / 046016, WO2014 / 046017, WO2014 / 065283, WO2017 / 090714, and WO2017 / 090714 are preferably mentioned. As the hydrogenation catalyst component, a mixture or reaction product of a Ti compound and a Li compound and / or a Mg compound is more preferable. From the viewpoint of the hydrogenation rate, a mixture or reaction product of a Ti compound and a Li compound is even more preferable. Examples of the Ti compound include the metallocenes of the following formula (I).

[0058]

Chemical formula

[0059] In the formula (I), R1 and R2 represent groups selected from the group consisting of C1-C12 hydrocarbon groups, aryloxy groups, alkoxyl groups, halogen groups, and carbonyl groups, and R1 and R2 may be the same or different.

[0060] As the Ti compound, from the viewpoint of high hydrogenation rate, although not limited to the following, for example, 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 can be mentioned as preferable ones. From the viewpoint of economy, bis(η5-cyclopentadienyl)titanium dichloride is more preferable.

[0061] As the Li compound, although not limited to the following, for example, methyllithium, ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, isobutyllithium, t-butyllithium, n-pentyllithium, n-hexyllithium, phenyllithium, cyclopentadienyllithium, m-tolyllithium, p-tolyllithium, 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 can be mentioned.

[0062] As the Mg compound, although not limited to the following, for example, dimethylmagnesium, diethylmagnesium, dibutylmagnesium, ethylbutylmagnesium, methylmagnesium bromide, methylmagnesium chloride, ethylmagnesium bromide, ethylmagnesium chloride, phenylmagnesium bromide, phenylmagnesium chloride, t-butylmagnesium chloride, and t-butylmagnesium bromide can be mentioned.

[0063] <Content of Titanium and Aluminum in Hydrogenated Conjugated Diene Polymer> The amount of titanium added as a hydrogenation catalyst component during the production of the hydrogenated conjugated diene polymer is preferably 150 ppm or less with respect to the conjugated diene polymer before hydrogenation. The content of titanium in the hydrogenated conjugated diene polymer used in the rubber composition of this embodiment is preferably 1 ppm or more and 100 ppm or less, more preferably 5 ppm or more and 90 ppm or less, and even more preferably 10 ppm or more and 80 ppm or less. When the content of titanium is 100 ppm or less, yellow coloring of the hydrogenated conjugated diene polymer can be prevented. When the content is 1 ppm or more, titanium removal equipment is not required, and cost reduction can be achieved. The content of aluminum added during the production of the hydrogenated conjugated diene polymer is preferably 6 ppm or less. The aluminum content of the hydrogenated conjugated diene polymer used in the 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. Also, by using lithium or magnesium instead of aluminum, the function of aluminum as a co-catalyst can be complemented. Also, from the viewpoints of suppressing the increase in the Mooney viscosity (ML viscosity) of the hydrogenated conjugated diene polymer and the handleability and safety of the hydrogenation catalyst, the hydrogenation catalyst added during the production of the hydrogenated conjugated diene polymer preferably has a content of aluminum of 0.05 mol or less per 1 mol of titanium, more preferably 0.04 mol or less, even more preferably 0.03 mol or less, and even more preferably does not contain aluminum. By adjusting the titanium content and aluminum content in the hydrogenation catalyst, the titanium content and aluminum content of the hydrogenated conjugated diene polymer can be controlled within the above numerical ranges.

[0064] <Amount of Metals Other than Al and Ti in Hydrogenated Conjugated Diene Polymer> The hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment may contain metals other than Al and Ti described above. Examples of metals other than aluminum and titanium include lithium. From the viewpoint of suppressing the aging deterioration of the rubber composition of the present embodiment, the content of lithium in the hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment is preferably 60 ppm or less, more preferably 50 ppm or less, still more preferably 40 ppm or less, and even more preferably 30 ppm or less. On the other hand, from the viewpoint of the tensile elongation when the rubber composition of the present embodiment is crosslinked, 2 ppm or more is preferable, 5 ppm or more is more preferable, and 10 ppm or more is still more preferable. In addition, the contents of other metals such as titanium, aluminum, and lithium described above are regarded as the amounts of the respective elements even when these metals are contained as compounds.

[0065] <Dispersion state of titanium in the rubber composition> When titanium in the hydrogenated conjugated diene polymer is a residue of a hydrogenation catalyst component or a polymerization catalyst component, titanium is finely dispersed in the rubber composition of the present embodiment, and it becomes a compound or complex that is difficult to specify, which may have a great influence on the physical properties of the rubber composition. Therefore, from the viewpoints of not affecting the physical properties of the rubber composition, not making the characteristics difficult, and further relaxing the adhesion of the rubber composition to the mold, it is preferable that titanium is dispersed in a particulate state in the hydrogenated conjugated diene polymer.

[0066] <Addition of additives> In the production process of the hydrogenated conjugated diene polymer, a deactivator, a neutralizing agent, etc. may be added at the end of the polymerization process as necessary. Examples of the deactivator include, but are not limited to, water; alcohols such as methanol, ethanol, and isopropanol. The end of the polymerization process here refers to a state where 95% or more of the added monomer has been consumed by polymerization. Examples of the neutralizing agent include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, versatic acid (a mixture of carboxylic acids having 9 to 11 carbon atoms, mainly 10 carbon atoms, and many branches); aqueous solutions of inorganic acids, and carbon dioxide gas.

[0067] In the production process of the hydrogenated conjugated diene-based polymer, it is preferable to add a rubber stabilizer at the end of the polymerization step from the viewpoints of preventing gel formation and improving processing stability. Examples of the rubber stabilizer include, but are not limited to, known ones, and 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-butylphenyl) propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol are preferably mentioned.

[0068] In the production process of the hydrogenated conjugated diene-based polymer, a rubber softener can be added as necessary at the end of the polymerization step or the like to improve the productivity and processability of the polymer. Examples of the rubber softener include, but are not limited to, extender oil, liquid rubber, resin, etc. From the viewpoints of processability, productivity, and economy, extender oil is preferable. Examples of the method for adding the rubber softener to the hydrogenated conjugated diene-based polymer include, but are not limited to, a method in which the rubber softener is added to a polymer solution, mixed, and then the solvent of the polymer solution containing the rubber softener is removed.

[0069] Extending oils as softeners for rubber include, for example, aroma oil, naphthenic oil, paraffin oil and the like. Among these, from the viewpoints of environmental safety, as well as prevention of oil bleed and wet grip characteristics, aroma alternative oils with a polycyclic aromatic (PCA) component of 3% by mass or less according to IP346 law are preferred. Examples of aroma alternative oils include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate) shown in Kautschuk Gummi Kunststoffe 52(12)799(1999), and RAE (Residual Aromatic Extracts). The rubber composition of this embodiment may contain an extending oil. From the viewpoint of preventing aging deterioration in the crosslinked rubber composition, the content of the extending oil is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0070] Resins as softeners for rubber are not limited to the following, but include, for example, aromatic petroleum resins, coumarone-indene resins, terpene resins, rosin derivatives (including tung oil resins), tall oil, derivatives of tall oil, rosin ester resins, natural and synthetic terpene resins, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, mixed aliphatic-aromatic hydrocarbon resins, coumarin-indene resins, phenolic resins, p-tert-butylphenol-acetylene resins, phenol-formaldehyde resins, xylene-formaldehyde resins, oligomers of monoolefins, oligomers of diolefins, hydrogenated aromatic hydrocarbon resins, cycloaliphatic hydrocarbon resins, hydrogenated hydrocarbon resins, hydrogenated tung oil resins, hydrogenated oil resins, esters of hydrogenated oil resins with monofunctional or polyfunctional alcohols, and the like. These resins may be used alone or in combination of two or more. When using hydrogenated ones of these resins, those in which all unsaturated groups are hydrogenated or those in which some unsaturated groups are left and hydrogenated may be used. As an effect of adding the resin, in addition to improving the processability when a rubber composition is prepared by blending a hydrogenated conjugated diene polymer and a filler or the like, there is a tendency to improve the breaking strength of the rubber composition.

[0071] The addition amount of an extender oil, a liquid rubber, a resin or the like as a softening agent for rubber is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of the total amount of rubber components including a hydrogenated conjugated diene polymer, an olefin rubber, and other rubber components. By setting the addition amount within this range, there is a tendency to be excellent in abrasion resistance and crack resistance. Further, 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 still more preferably 25 parts by mass or less.

[0072] <Obtaining of hydrogenated conjugated diene polymer> As a method for obtaining a hydrogenated conjugated diene polymer by removing a solvent from a polymer solution, a known method can be used. Examples of the method include a method in which after separating the solvent by steam stripping or the like, the polymer is filtered off, and then it is dehydrated and dried to obtain the polymer; a method in which it is concentrated in a flashing tank and then devolatilized by a vent extruder or the like; and a method in which it is directly devolatilized by a drum dryer or the like.

[0073] (Rubber components constituting the rubber composition) The rubber composition of the present embodiment contains, as rubber components, a hydrogenated conjugated diene polymer (rubber component A) and an olefin rubber (rubber component B). Increasing the content of the hydrogenated conjugated diene polymer can improve the low-temperature properties and compression set of the rubber composition of the present embodiment.

[0074] Increasing the content of the olefin rubber can improve the ozone resistance of the rubber composition of the present embodiment. From the perspective of the balance between the low-temperature properties and ozone resistance of the rubber composition of the present embodiment, the mass ratio of the conjugated diene polymer to the olefin rubber is preferably conjugated diene polymer: olefin rubber = 95 / 5 to 70 / 30, more preferably 90 / 10 to 70 / 30, and even more preferably 80 / 20 to 70 / 30.

[0075] If the hydrogenated conjugated diene polymer is made into a non-hydrogenated conjugated diene polymer, a difference in crosslinking efficiency occurs with the olefin rubber, deteriorating the tensile elongation and tensile strength. Further, using a non-hydrogenated conjugated diene polymer has an adverse effect on ozone resistance. Therefore, in the present embodiment, it is necessary to select a hydrogenated conjugated diene polymer.

[0076] (Filler) The rubber composition of the present embodiment may contain a filler, and it is preferable to contain 5 parts by mass or more and 250 parts by mass or less of the filler with respect to 100 parts by mass of the rubber component described above. More preferably, it is 10 parts by mass or more and 150 parts by mass or less, and even more preferably 20 parts by mass or more and 100 parts by mass or less. The filler is not limited to the following, and examples include at least one filler selected from carbon black, silica-based inorganic fillers, calcium carbonate, metal oxides such as titanium oxide, clay, and metal hydroxides such as aluminum hydroxide.

[0077] <Carbon black> The rubber composition of the present embodiment may contain carbon black as a filler from the viewpoints of processability and low cost. As the carbon black, although not limited to the following, for example, carbon blacks of each class such as SRF, FEF, HAF, ISAF, and SAF can be used. Among these, from the viewpoints of the extrusion moldability and rolling resistance characteristics of the rubber composition of the present embodiment, the nitrogen adsorption specific surface area is 50 m 2 / g or more, and carbon black having a dibutyl phthalate (DBP) oil absorption of 80 mL / 100 g or more is preferable. From the viewpoint of improving the hardness, modulus, and abrasion resistance of the rubber composition of the present embodiment, the carbon black content is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more with respect to 100 parts by mass of the rubber component. Further, from the viewpoint of filler dispersibility, the carbon black content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, still more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0078] <Silica-based inorganic filler> The rubber composition of the present embodiment may contain a silica-based inorganic filler from the viewpoint of low heat generation. The content of the silica-based inorganic filler is preferably 1 part by mass or more and 60 parts by mass or less, more preferably 5 parts by mass or more and 55 parts by mass or less, and still more preferably 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the rubber component. The silica-based inorganic filler is not particularly limited and known ones can be used, but solid particles containing SiO2 or Si3Al as a structural unit are preferred, and solid particles having SiO2 or Si3Al as a main component of the structural unit are more preferred. Here, the main component means a component contained in the silica-based inorganic filler in an amount of 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more. Examples of the silica-based inorganic filler include, but are not limited to, inorganic fibrous substances such as silica, clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, and glass fiber. Examples of commercially available silica-based inorganic fillers include, for example, the product name "Ultrasil 7000GR" manufactured by Evonik Degussa. Further, a silica-based inorganic filler with a hydrophobized surface and a mixture of a silica-based inorganic filler and an inorganic filler other than silica-based can also be used. Among these, from the viewpoint of the strength and abrasion resistance of the rubber composition of the present embodiment, silica and glass fiber are preferred as the silica-based inorganic filler, and silica is more preferred. Examples of silica include dry silica, wet silica, and synthetic silicate silica.

[0079] <Metal oxide, metal hydroxide> In addition to the carbon black and silica-based inorganic fillers described above, the rubber composition of this embodiment may contain a metal oxide or a metal hydroxide. A metal oxide has a chemical formula M x O y (where M represents a metal atom, and x and y each independently represent an integer from 1 to 6), and refers to solid particles having the main component of the structural unit. Examples include alumina, titanium oxide, magnesium oxide, zinc oxide, etc. A mixture of a metal oxide and an inorganic filler other than the metal oxide can also be used. Examples of the metal hydroxide include, but are not limited to, aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, etc.

[0080] (Silane coupling agent) The rubber composition of this embodiment may contain a silane coupling agent. The silane coupling agent has groups having an affinity or bonding property for each of the hydrogenated conjugated diene polymer, other rubber components, and silica-based inorganic filler, and has a function of tightening the interaction between them. Generally, a compound having a sulfur-bonding part, an alkoxysilyl group, and a silanol group part in one molecule is used as the silane coupling agent.

[0081] Silane coupling agents include, but are not limited to, for example, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxaoctacosane-1-yloxy)silane [manufactured by Evonik Degussa: Si363], silane coupling agents containing a mercapto group such as NXT-Z30, NXT-Z45, NXTZ60, NXT silane manufactured by Momentive, 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-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide, etc. Among these, from the viewpoint of high reinforcing effect, bis-[3-(triethoxysilyl)-propyl]-disulfide, ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silane [manufactured by Evonik Degussa: Si363], silane coupling agents containing a mercapto group such as NXT-Z30, NXT-Z45, NXT-Z60, NXT silane manufactured by Momentive, and bis-[3-(triethoxysilyl)-propyl]-tetrasulfide are preferable. The silane coupling agent may be used alone or in combination of two or more.

[0082] From the viewpoint of further enhancing the effect of tightening the interaction between the rubber component and the silica-based inorganic filler, the content of the silane coupling agent is preferably 2 parts by mass or more and 10 parts by mass or less, more preferably 3 parts by mass or more and 9 parts by mass or less, based on 100 parts by mass of the rubber component. Further, based on 100 parts by mass of the silica-based inorganic filler, it is preferably 4 parts by mass or more and 15 parts by mass or less, more preferably 6 parts by mass or more and 12 parts by mass or less.

[0083] (Softening agent for rubber) The rubber composition of this embodiment may contain a softening agent for rubber in order to improve processability. Examples of the softening agent for rubber include mineral oil-based softening agents for rubber and liquid or low molecular weight synthetic softening agents as suitable ones. The mineral oil-based softening agent for rubber is also called process oil or extender oil and is used to soften, increase the volume, and improve the processability of rubber. Further, the mineral oil-based softening agent for rubber is a mixture of compounds having an aromatic ring, a naphthene ring, a paraffin chain, etc. Those in which the carbon number of the paraffin chain occupies 50% or more of the total carbon are called paraffin-based, those in which the carbon number of the naphthene ring is 30 - 45% are called naphthene-based, and those in which the aromatic carbon number exceeds 30% are called aromatic-based. When the hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment is a copolymer having a conjugated diene monomer unit and an aromatic vinyl monomer unit, as the rubber softening agent, those having an appropriate content of aromatic vinyl monomer units are preferable because they tend to have good affinity with the hydrogenated conjugated diene polymer. From the viewpoint of improving processability, the content of the rubber softening agent 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 with respect to 100 parts by mass of the rubber component. Further, from the viewpoint of suppressing bleed-out and preventing stickiness on the surface of the 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.

[0084] (Crosslinking agent) The rubber composition of the present embodiment may contain a crosslinking agent. Examples of the crosslinking agent include, but are not limited to, radical generators such as organic peroxides and azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. Sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, and high molecular polysulfur compounds. From the viewpoint of improving the heat resistance of the rubber composition, it is preferable to use a radical generator, particularly an organic peroxide.

[0085] (Sulfur) From the viewpoint of improving heat resistance, the content of sulfur in the rubber composition of the present embodiment is preferably 0.2 parts by mass or less, more preferably 0.1 parts by mass or less, and even more preferably 0.05 parts by mass or less with respect to 100 parts by mass of the rubber component of the rubber composition. The sulfur content in the rubber composition being 0.2 parts by mass or less with respect to 100 parts by mass of the rubber component of the rubber composition means that sulfur is not used as the crosslinking agent. When sulfur is used as the crosslinking agent, crosslinking by S-S bonds is formed, but compared with the case of using a radical generator as the crosslinking agent, the bonds are more likely to be broken by heat, and the heat resistance tends to be low. Therefore, it is preferable to use a radical generator as the crosslinking agent in the rubber composition of the present embodiment, and the sulfur content is preferably within the above range.

[0086] [[Manufacturing method of rubber composition]] The rubber composition of the present embodiment contains at least the hydrogenated conjugated diene polymer and the olefin rubber. Further, it can contain a filler, and can be produced by mixing the constituent materials of the rubber composition of the present embodiment, such as other fillers, silane coupling agents, additives such as rubber softeners, as necessary. The mixing method is not limited to the following, but for example, a melt kneading method using a general mixer such as an open roll, Banbury mixer, kneader, single screw extruder, twin screw extruder, multi-screw extruder, etc., and a method of heating and removing the solvent after dissolving and mixing each component can be mentioned. Among these, the melt kneading method using a roll, Banbury mixer, kneader, or extruder is preferable from the viewpoints of productivity and good kneadability. Also, either a method of kneading the materials constituting the rubber composition of the present embodiment at once or a method of mixing them in a plurality of times is applicable.

[0087] When the rubber composition of the present embodiment is a crosslinked rubber composition, the manufacturing method preferably has a step of crosslinking the hydrogenated conjugated diene polymer with the crosslinking agent described above. The blending amount of the crosslinking agent differs depending on whether it contains sulfur or not. When a sulfur-containing crosslinking agent is used as the crosslinking agent, the sulfur content in the rubber composition of the present embodiment is preferably 0.2 parts by mass or less, more preferably 0.1 parts by mass or less, and even more preferably 0.05 parts by mass or less, based on 100 parts by mass of the rubber component of the rubber composition, from the viewpoint of improving heat resistance. When using a crosslinking agent that does not contain sulfur, the content of the crosslinking agent in the rubber composition of the present embodiment is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and even more preferably 3.0 part by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of improving the crosslinking density by the reinforcing effect and improving the tensile strength and elongation. Further, from the viewpoint of improving flexibility and elongation at break, the content of the crosslinking agent 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 with respect to 100 parts by mass of the rubber component.

[0088] As the crosslinking method, a conventionally known method can be applied. The crosslinking temperature is not particularly limited, but is preferably 120 °C or higher, more preferably 140 °C or higher, and even more preferably 150 °C or higher from the viewpoint of shortening the crosslinking time and increasing the production efficiency. Further, from the viewpoint of suppressing thermal deterioration during crosslinking, it is preferably 200 °C or lower, more preferably 180 °C or lower, and even more preferably 170 °C or lower.

[0089] When performing sulfur crosslinking, a vulcanization accelerator may be used as necessary. As the vulcanization accelerator, conventionally known materials can be used and are not limited to the following. For example, vulcanization accelerators such as sulfenamide compounds, guanidine compounds, thiuram compounds, aldehyde-amine compounds, aldehyde-ammonia compounds, thiazole compounds, thiourea compounds, and dithiocarbamate compounds can be mentioned. In the method for producing the crosslinked rubber composition of the present embodiment, it preferably has a step of crosslinking the hydrogenated conjugated diene polymer (rubbery polymer 1) with the sulfur and vulcanization accelerator, or organic peroxide described above.

[0090] Further, in the crosslinking using the sulfur, a vulcanization aid may be used. Examples of the vulcanization aid include, but are not limited to, zinc white and stearic acid.

[0091] In the method for producing the rubber composition of the present embodiment, within a range not impairing the object of the present invention, various additives such as other softeners, fillers, heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, and lubricants other than the above-described various materials may be added. As the other softener, a known softener can be used. Examples of the other filler include calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate. As the above-described heat stabilizer, antistatic agent, weather stabilizer, antioxidant, colorant, and lubricant, known materials can be used respectively.

[0092] In the method for producing the rubber composition of the present embodiment, when having a crosslinking step, crosslinking may be performed in a state where a rubber composition containing a rubber component and a filler is molded. Thereby, the degree of freedom of the final shape of the target crosslinked rubber composition can be increased.

[0093] 〔Use of Rubber Composition〕 The rubber composition of the present embodiment can be used as vibration-proof rubber, vibration-isolating rubber, conveyor belt, shoe soles such as shoe outsoles, weather strips of automobiles, packings, gaskets, sealing materials, waterproof sheets, engine mounts, air springs, rubber gloves, medical and sanitary products, rubber rollers, hoses for industrial and various uses, battery cases, adhesives, wire coatings, window frame rubbers, materials for various industrial products, etc. In these applications, various molded articles can be obtained by molding the rubber composition of the present embodiment.

[0094] The hydrogenated conjugated diene polymer used in the rubber composition of the present embodiment can reduce the compression set of the rubber composition of the present embodiment by adjusting its structure and blending amount. A rubber composition with a small compression set is suitable for vibration-proof rubber, vibration damping materials, packings, sealing materials, rubber rollers, rubber stoppers, and medical and sanitary products. For example, when the compression set of the rubber composition 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, since the hydrogenated conjugated diene polymer can have a low glass transition temperature, it is also suitable as a sealing material provided in a portion exposed to a low-temperature material such as liquefied gas. In order to make the compression set of the rubber composition of the present embodiment within the above range, for example, it is preferable that the composition of the rubber composition has a content of the hydrogenated conjugated diene polymer of 30% by mass or more, and more preferably 40% by mass. When the compression set of the rubber composition at 100 °C for 72 hours is 30% or less, it is particularly suitable for vibration-proof rubber and vibration damping materials.

Examples

[0095] Hereinafter, the present embodiment will be described in more detail with reference to specific production examples, examples, and comparative examples, but the present invention is not limited to the following examples and comparative examples. Here, specific examples of the hydrogenated conjugated diene polymer or non-hydrogenated conjugated diene polymer are referred to as "production examples" and "comparative production examples", and specific examples of the rubber composition are referred to as "examples" and "comparative examples". Note that various physical properties in the production examples, comparative production examples, examples, and comparative examples were measured by the methods shown below.

[0096] 〔Physical Property Measurement Method〕 (Styrene content, vinyl bond amount, hydrogenation rate) 1 From the integrated value of the unsaturated bond portion of the conjugated diene polymer before hydrogenation by H-NMR measurement, the content of the aromatic vinyl monomer unit (styrene) and the vinyl bond amount in the conjugated diene monomer unit component were calculated. Next, a large amount of methanol was added to the reaction solution after the hydrogenation reaction to precipitate and recover the hydrogenated conjugated diene polymer. The hydrogenated conjugated diene polymer was extracted with acetone and dried under vacuum. This was 1 used as a sample for H-NMR measurement to measure the 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 sample: Sampled products before and after hydrogenating the polymer Sample concentration: 50 mg / mL Observation frequency: 400 MHz Chemical shift standard: TMS (tetramethylsilane) Pulse delay: 2.904 seconds Number of scans: 64 times Pulse width: 45° Measurement temperature: 26 °C

[0097] (Calculation of Hydrogenation Rate) The hydrogenation rate of the hydrogenated conjugated diene polymer was calculated by the following formula (S). Formula (S): (b + d) / (a + b + c + d)〕× 100

[0098] (Weight-average Molecular Weight (Mw)) The hydrogenated conjugated diene polymers and non-hydrogenated conjugated diene polymers prepared in the production examples and comparative production examples described below (described as polymers 1 to 11 in the table) were used as measurement samples, and a GPC measuring device with three columns filled with polystyrene-based gel as a filler was used to measure the chromatogram, and the weight-average molecular weight (Mw) was determined based on the calibration curve using standard polystyrene. Specific measurement conditions are shown below. 20 μL of the following measurement solution was injected into the GPC measuring device for measurement. (Measurement Conditions) Device: Product name "HLC-8320GPC" manufactured by Tosoh Corporation Eluent: Tetrahydrofuran (THF) containing 5 mmol / L of 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 connected in this order. Oven temperature: 40 °C Flow rate: 0.6 mL / min Detector: RI detector (trade name “HLC8020” manufactured by Tosoh Corporation) Measurement solution: A measurement solution prepared by dissolving 10 mg of the sample for measurement in 20 mL of THF

[0099] (Measurement of styrene block content) The styrene block content was measured according to the osmium tetroxide decomposition method described in I.M. Kolthoff, et al. J. Polym. Sci. 1, 429 (1946). More specifically, 0.050 g of the hydrogenated conjugated diene polymer and the non-hydrogenated conjugated diene polymer prepared in the production examples and comparative production examples was dissolved in 10 mL of chloroform, and 16 mL of a 69% by mass aqueous solution of tert-butyl hydroperoxide and 4.0 mL of a 0.050% by mass chloroform solution of osmium tetroxide were added, and the mixture was refluxed in a 90 °C bath for 12 minutes to carry out an oxidative decomposition reaction. After completion of the reaction, the reaction solution was cooled, 200 mL of methanol was added to the reaction solution with stirring to precipitate the styrene block component, and this was filtered off through a 5-μm glass filter. The styrene block content was determined by dividing the mass of the obtained product by the total mass of the polymer.

[0100] (Measurement of ML viscosity) The measurement was carried out using a Mooney viscometer (manufactured by Shimadzu Corporation, SMV-301RT) conforming to JIS K6300-1. Using an L-type rotor, after preheating the sample at the test temperature (100 °C) for 1 minute, the rotor was rotated at 2 rpm, and the torque after 4 minutes was measured to measure the Mooney viscosity ML(1+4)(100 °C).

[0101] (Modification rate) The modification rate of the polymer was measured by the column adsorption GPC method as follows, utilizing the property that the modified polymer is adsorbed on the column. The hydrogenated conjugated diene polymers and non-hydrogenated conjugated diene polymers (Polymers 1 to 11) prepared in the production examples and comparative production examples described below were used as samples for measurement. Using the sample and a sample solution containing low molecular weight internal standard polystyrene, the adsorption amount onto the silica-based column was measured from the difference between the chromatogram measured with a column filled with polystyrene-based gel (polystyrene-based column) and the chromatogram measured with a column filled with silica-based gel (silica-based column), and the denaturation rate was determined. The GPC measurement conditions using a polystyrene-based column are shown below. 20 μL of the following measurement solution was injected into a GPC measuring device for measurement. (GPC measurement conditions using a polystyrene-based column): Apparatus: Product name "HLC-8320GPC" manufactured by Tosoh Corporation Eluent: THF containing 5 mmol / L of triethylamine Guard column: Product name "TSKguardcolumn SuperH-H" manufactured by Tosoh Corporation Column: A combination of "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" manufactured by Tosoh Corporation in this order Oven temperature: 40 °C Flow rate: 0.6 mL / min Detector: RI detector (HLC8020 manufactured by Tosoh Corporation) Measurement solution: 10 mg of the sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a sample solution. The GPC measurement conditions using a silica-based column are shown below. 50 μL of the following measurement solution was injected into a GPC measuring device for measurement. (GPC measurement conditions using a silica-based column): Apparatus: Product name "HLC-8320GPC" manufactured by Tosoh Corporation Eluent: THF Guard column: Product name "DIOL 4.6×12.5mm 5micron" manufactured by GL Sciences Inc. Separation column: A product named "Zorbax PSM-1000S", "PSM-300S", "PSM-60S" manufactured by Agilent Technologies, connected in this order Oven temperature: 40 °C Flow rate: 0.5 mL / min Detector: RI detector (HLC8020 manufactured by Tosoh Corporation) (Calculation method of denaturation rate): Taking the total peak area of the chromatogram using a polystyrene-based column as 100, the peak area of the sample as P1, the peak area of the standard polystyrene as P2, taking the total peak area of the chromatogram using a silica-based column as 100, the peak area of the sample as P3, and the peak area of the standard polystyrene as P4, the denaturation rate (%) was determined from the following formula. Denaturation rate (%) = [1 - (P2 × P3) / (P1 × P4)] × 100 (However, P1 + P2 = P3 + P4 = 100 was set.)

[0102] (Glass transition temperature (Tg)) Using the hydrogenated conjugated diene polymer and the non-hydrogenated conjugated diene polymer (Polymers 1 to 11) prepared in the production examples and comparative production examples described below as samples, in accordance with ISO22768:2006, a DSC curve was recorded while raising the temperature in a predetermined temperature range, and the peak top (Inflection point) of the DSC differential curve was taken as the glass transition temperature. As the measuring device, a differential scanning calorimeter DSC7020 manufactured by Hitachi High-Tech Sciences was used.

[0103] [Production examples, comparative production examples, olefin rubber] In this specification, as the hydrogenated conjugated diene polymer (rubber component A) used in the examples, polymers 1 to 7 were prepared in (Production Examples 1 to 7). Also, as the hydrogenated conjugated diene polymer or non-hydrogenated conjugated diene polymer (rubber component A) used in the comparative examples, polymers 8 to 11 were prepared in (Comparative Production Examples 8 to 11). As the olefin rubber (rubber component B), an ethylene·1-butene·5-ethylidene-2-norbornene (ENB) copolymer (EBDM) was prepared.

[0104] (Production Example 1) Polymer 1 An autoclave with an internal volume of 40 L, equipped with a stirrer and a jacket and capable of temperature control, was used as a reactor. 120 g of styrene, 2,880 g of 1,3-butadiene, 21,000 g of cyclohexane, and 1.0 mmol of 2,2-bis(2-oxolanyl)propane (BOP) as a polar substance, which had been pre-removed of impurities, were placed into the reactor, and the internal temperature of the reactor was maintained at 45°C. As a polymerization initiator, 14.1 mmol of n-butyllithium (NBL) was supplied to the above reactor. After the start of the polymerization reaction, the temperature inside the reactor began to rise due to the heat generated by the polymerization, and the final temperature inside the reactor reached 78°C. 14.1 mmol of methanol (MeOH) was added to this polymer solution as a reaction terminator to obtain a polymer solution. A part of the polymer solution was withdrawn and the solvent was removed with a dryer to obtain a polymer before hydrogenation. To the polymer solution before hydrogenation, the hydrogenation catalyst (T) was added at 50 ppm on a Ti basis per 100 parts by mass of the polymer before hydrogenation, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C for 80 minutes. 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, and then the polymer solution was dropped into warm water to remove the solvent, and a drying treatment was performed with a dryer to obtain Polymer 1. The production conditions of Polymer 1 are shown in Table 1, and the physical properties are shown in Table 4.

[0105] (Production Examples 2 and 3): Polymers 2 and 3 Polymerization was carried out under the same conditions as in Polymerization Example 1 except that the hydrogen amount described in Table 1 was changed, and Polymers 2 and 3 were obtained. The physical properties are shown in Table 4.

[0106] (Production Examples 4 and 7, Comparative Production Examples 8 and 9): Polymers 4, 7, 8, and 9 Polymerization was carried out under the same conditions as in Polymerization Example 1 except that the amounts of raw materials and additives added and the hydrogen amount described in Tables 1 and 2 were changed, and Polymers 4, Polymer 7, Polymer 8, and Polymer 9 were obtained. The physical properties are shown in Tables 4 and 5.

[0107] (Production Example 5): Polymer 5 An autoclave with an internal volume of 40 L, equipped with a stirrer and a jacket and capable of temperature control, was used as a reactor. 2,880 g of 1,3-butadiene, 120 g of styrene, 21,000 g of cyclohexane, and 2.9 mmol of 2,2-bis(2-oxolanyl)propane as a polar substance, which had been purified of impurities in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 45°C. 44.5 mmol of n-butyllithium (NBL) was supplied to the reactor as a polymerization initiator. After the start of the polymerization reaction, the temperature in the reactor began to rise due to the heat generated by the polymerization, and the final temperature in the reactor reached 78°C. Two minutes after reaching the peak of this reaction temperature, 8.5 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 10 minutes. 11.1 mmol of methanol (MeOH) was added to this polymer solution as a reaction terminator to obtain a polymer solution. A part of the polymer solution was withdrawn and the solvent was removed with a dryer to obtain a polymer before hydrogenation. To the polymer solution before hydrogenation, the hydrogenation catalyst (T) was added at 50 ppm on a Ti basis per 100 parts by mass of the polymer before hydrogenation, and the hydrogenation reaction was carried out at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C for 80 minutes. 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, and then the polymer solution was dropped into warm water to remove the solvent, and a drying treatment was performed with a dryer to obtain Polymer 5. The production conditions of Polymer 5 are shown in Table 1, and the physical properties are shown in Table 4.

[0108] (Production Example 6): Polymer 6 2,2-Dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (Compound A) used as the coupling agent was changed to 1,3-dimethyl-2-imidazolidinone (Compound B), and the amount used was further adjusted. Also, the amounts of 2,2-bis(2-oxolanyl)propane (BOP) as the polar substance, n-butyllithium (NBL) as the polymerization initiator, and methanol (MeOH) as the reaction terminator were adjusted. Polymerization was carried out under the same conditions as those for the polymer 5 except for the above, and polymer 6 was obtained. The production conditions of polymer 6 are shown in Table 1, and the physical properties are shown in Table 4.

[0109] (Comparative Production Example 10): Polymer 10 Polymerization was carried out under the same conditions as those for the polymer 5 except that the amounts of the raw materials and additives added, the types of additives, and the amount of hydrogen were changed, and polymer 10 was obtained. The production conditions of polymer 10 are shown in Table 2, and the physical properties are shown in Table 5.

[0110] (Comparative Production Example 11): Polymer 11 Using an autoclave with a capacity of 40 L, equipped with a stirrer and a jacket and capable of temperature control as a reactor, 2,880 g of 1,3-butadiene, 120 g of styrene, 21,000 g of cyclohexane, and 0.9 mmol of 2,2-bis(2-oxolanyl)propane as a polar substance, which had been preliminarily purified of impurities, were placed in the reactor, and the internal temperature of the reactor was maintained at 45°C. As a polymerization initiator, 13.1 mmol of n-butyllithium (NBL) was supplied to the above reactor. After the start of the polymerization reaction, the temperature inside the reactor began to rise due to the heat generated by the polymerization, and the final temperature inside the reactor reached 78°C. To this polymer solution, 13.1 mmol of methanol (MeOH) was added as a reaction terminator to obtain a polymer solution. A part of the polymer solution was withdrawn and the solvent was removed with a dryer to obtain a polymer before hydrogenation. 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 dropped into warm water to remove the solvent, and the resulting product was dried using a dryer to obtain Polymer 11. The preparation conditions of Polymer 11 are shown in Table 2, and the physical properties are shown in Table 5.

[0111] (Polymerization Example 12): Polymer 12 As the olefin rubber, an ethylene·1-butene·5-ethylidene-2-norbornene (ENB) copolymer (EBDM) was obtained under the conditions described in JP 2022-88268. The physical properties of EBDM (Polymer 12) are shown in Table 3.

[0112] The symbols in Tables 1 and 2 below are shown. BOP: 2,2-bis(2-oxolanyl)propane NBL: n-butyllithium Compound A: 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane Compound B: 1,3-dimethyl-2-imidazolidinone MeOH: Methanol

[0113] [Table 1]

[0114] [Table 2]

[0115] [Table 3]

[0116] [Table 4]

[0117]

Table 5

[0118] 〔Rubber Composition〕 As the hydrogenated conjugated diene polymer or conjugated diene polymer (rubber component A), Polymers 1 to 11 were used. As the olefin rubber (rubber component B), ethylene propylene diene rubber (EPDM: trade name "EP33" manufactured by ENEOS MATERIALS Co., Ltd.) and ethylene butylene diene rubber (EBDM, Polymer 12) were used. Also, as the conjugated diene polymer (rubber component A) in Comparative Example 7, butadiene rubber (BR) was used. Carbon black was used as the filler. Dicumyl peroxide was used as the crosslinking agent. According to the compounding conditions and kneading method shown below, rubber compositions containing each rubber component (A) and rubber component (B), carbon black, and crosslinking agent were obtained.

[0119] 〔(Compounding Condition 1) Example 1〕 · As the hydrogenated conjugated diene rubber of rubber component (A), Polymer 1: 95 parts by mass · As the olefin rubber of rubber component (B), EPDM (EP33: trade name manufactured by ENEOS MATERIALS Co., Ltd.): 5 parts by mass were each used. The addition amounts of the following materials are shown in Table 6 as the number of parts by mass with respect to 100 parts by mass of rubber component (A) not containing a rubber softener. · Filler: Carbon black (trade name "SEAST KH (N550)" manufactured by Tokai Carbon Co., Ltd.) · Plasticizer: Naphthenic oil · Antioxidant: Nocrack MB (2-mercaptobenzimidazole) · Processing aid: Stearic acid · Crosslinking agent: Peroxide (dicumyl peroxide)

[0120] 〔(Compounding Condition 2) Examples 2 to 12 and Comparative Examples 1 to 7〕 · As the hydrogenated conjugated diene rubber of the rubber component (A), polymer 2 to 11 Or, high-cis BR (U150: trade name, manufactured by UBE Elastomer Co., Ltd.) As the olefin rubber of the rubber component (B), EPDM (EP33: trade name, manufactured by ENEOS Materials Co., Ltd.) or ethylene-butylene-diene rubber (EBDM) of polymer 12 was used, and the parts by mass shown in Tables 6 and 7 below were added. The addition amounts of the following materials are parts by mass with respect to 100 parts by mass of the rubber component (A) not containing a rubber softener, and are shown in Tables 6 and 7 below. · Filler: Carbon black (trade name "Seast KH (N550)", manufactured by Tokai Carbon Co., Ltd.) · Plasticizer; naphthenic oil · Antioxidant: No Crack MB (2-mercaptobenzimidazole) · Processing aid: Stearic acid · Crosslinking agent: Peroxide (dicumyl peroxide)

[0121] 〔(Mixing condition 3) Examples 13 to 15〕 · As the hydrogenated conjugated diene rubber of the rubber component (A), polymer 1 · As the olefin rubber of the rubber component (B), EPDM (EP33: trade name, manufactured by ENEOS Materials Co., Ltd.) was used, and the parts by mass shown in Table 6 below were added. The addition amounts of the following materials are parts by mass with respect to 100 parts by mass of the rubber component (A) not containing a rubber softener, and are shown in Table 6 below. · Filler: Carbon black (trade name "Seast KH (N550)", manufactured by Tokai Carbon Co., Ltd.) · Plasticizer; naphthenic oil · Antioxidant: No Crack MB (2-mercaptobenzimidazole) · Processing aid: Stearic acid · Crosslinking agent: Sulfur · Vulcanization accelerator: N-(tert-butyl)-2-benzothiazolesulfenamide (TBBS)

[0122] (Kneading method) By the above [Mixing condition 1], [Mixing condition 2], and [Mixing condition 3], a rubber composition was obtained by kneading according to the following method. Using a sealed 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 - 50 rpm, the rubber component (A), rubber component (B), filler (carbon black), naphthenic oil, antioxidant, and stearic acid were kneaded. At this time, the temperature of the sealed mixer was controlled, and the discharge temperature was 125 - 130 °C to obtain the first-stage blend. After cooling, as the second-stage kneading, dicumyl peroxide (crosslinking agent) was added and kneaded on an open roll set at 35 °C. Thereafter, it was molded and vulcanized in a vulcanization press at 170 °C for 20 minutes to effect crosslinking. The rubber composition before vulcanization and the crosslinked rubber composition after vulcanization were evaluated. Specifically, evaluation was carried out by the following method. The evaluation results are shown in Table 8 and Table 9 below.

[0123] (Physical Property Evaluation of Blend) Regarding the tensile strength, tensile elongation, and compression set of the crosslinked rubber composition after vulcanization, for Examples 1 - 15 and Comparative Examples 2 - 7, taking the evaluation result of Comparative Example 1 as 100, they were indexed and shown in the following table. Regarding TR10 and TR70, for Examples 1 - 15 and Comparative Examples 1 - 7, the measured values were shown. Regarding ozone resistance, for Examples 1 - 15 and Comparative Examples 1 - 7, the results of a four-level evaluation were shown. For Examples 1 - 15 and Comparative Examples 1 - 7, the evaluation results are shown in Table 8 and Table 9 below.

[0124] <Tensile Elongation, Tensile Strength> In accordance with the tensile test method of JIS K6251, the tensile strength and tensile elongation of the crosslinked rubber composition after vulcanization were measured. The measuring instrument used was AUTOGRAPH AGS-X manufactured by Shimadzu Corporation. The higher the values of tensile elongation and tensile strength, the higher-strength the material indicates. For Examples 1 to 15 and Comparative Examples 2 to 7, the evaluation results of Comparative Example 1 were indexed with 100 and shown in Table 8 and Table 9 below. It is preferably not less than the reference value (100), and there is no practical problem when it is not less than 85 and not more than 100. When it is not less than 75 and less than 85, the material strength may not be sufficient depending on the application, and when it is less than 75, it is evaluated that the material strength is insufficient. For Examples 1 to 15 and Comparative Examples 1 to 7, the evaluation results are shown in Table 8 and Table 9 below.

[0125] <Compression set> In accordance with JIS K6262, the compression set of the crosslinked rubber composition after vulcanization was measured under the conditions of a heating temperature of 100 °C and a heating time of 72 h. The value of the compression set was regarded as an index of heat resistance in addition to an index of resilience. For Examples 1 to 15 and Comparative Examples 2 to 7, the evaluation results of Comparative Example 1 were indexed with 100 and shown in Table 8 and Table 9 below. It is preferably not less than the reference value (100), and there is no practical problem when it is not less than 85 and not more than 100. When it is not less than 75 and less than 85, the material strength may not be sufficient depending on the application, and when it is less than 75, it is judged that the resilience is insufficient.

[0126] <TR10, TR70> In accordance with JIS K6261-4, a 50% elongation was given to the test piece, and after cooling at -70 °C, the shrinkage amount as the elasticity recovered with the temperature rise was measured. The test piece was a crosslinked rubber composition after vulcanization, and was prepared by a punching blade in the shape of a tensile No. 8 dumbbell in accordance with JIS K6251. From the state of 50% elongation, the temperature corresponding to when the shrinkage rate was 10% was taken as TR10, and the temperature corresponding to when the shrinkage rate was 70% was taken as TR70 to obtain the values. Taking the TR test result of Comparative Example 1 as the reference value, TR10 is preferably less than -50 °C. When it is not less than -50 °C and less than -40 °C, there may be problems in practical use in the low temperature region, and when it is not less than -40 °C, it is judged that it is not suitable for practical use in the low temperature region. Also, TR70 is preferably less than -30°C. When it is -30°C or more and less than -20°C, there may be problems in practical use in the low-temperature range. When it is -20°C or more, it is determined that it is not suitable for practical use in the low-temperature range. For Examples 1 to 15 and Comparative Examples 1 to 7, the evaluation results are shown in Tables 8 and 9 below.

[0127] <Ozone resistance> From the test piece of the crosslinked rubber composition after vulcanization, a JIS No. 1 dumbbell-shaped test piece conforming to JIS K6251 was cut out, and the ozone resistance was evaluated. The test piece was ozone-degraded in accordance with JIS K6259-1:2015 under the conditions of 20% elongation, an ozone concentration of 50 pphm, 40°C, and 96 hours. After that, the presence or absence of cracks (ozone cracks) on the surface of the test piece was visually observed, and the state of the cracks was evaluated in four levels based on the following criteria. [Evaluation criteria] There are 41 or more cracks less than 0.1 mm, or There are 11 or more cracks 0.1 mm or more. : 1 point There are 16 to 40 cracks less than 0.1 mm, or There are 6 to 10 cracks 0.1 mm or more. : 2 points There are 1 to 15 cracks less than 0.1 mm, or There are 1 to 5 cracks 0.1 mm or more. : 3 points There are no cracks at all. : 4 points A score of 4 is preferable for applications with ozone resistance requirements. A score of 3 or 2 may have problems in applications with ozone resistance requirements, and a score of 1 is determined to be not practical for applications with ozone resistance requirements. For Examples 1 to 15 and Comparative Examples 1 to 7, the evaluation results are shown in Tables 8 and 9 below.

[0128]

Table 6

[0129]

Table 7

[0130]

Table 8

[0131]

Table 9

Industrial Applicability

[0132] The rubber composition of the present invention has industrial applicability as materials for anti-vibration rubber, vibration isolation rubber, conveyor belts, shoe soles such as outsoles for shoes, weather strips for automobiles, packings, gaskets, sealing materials, waterproof sheets, engine mounts, air springs, rubber gloves, medical and hygienic products, hoses for industrial and various uses, battery cases, adhesives, wire coatings, window frame rubbers, rubber stoppers, rubber rollers, and various industrial products, etc.

Claims

1. A rubber composition comprising a hydrogenated conjugated diene polymer and an olefin rubber as rubber components, The hydrogenated conjugated diene polymer includes the following structures (1) to (4), 【Chemical Formula 1】 The hydrogenated conjugated diene polymer has a glass transition temperature measured by a differential scanning calorimeter (DSC) of -60°C or lower, A rubber composition in which the hydrogenated conjugated diene polymer satisfies the following mathematical formula (S). Mathematical formula (S): 30 ≦ [(b + d) / (a + b + c + d)] × 100 ≦ 70 (In the mathematical formula (S), a represents the structural unit represented by the formula (1), b represents the structural unit represented by the formula (2), c represents the structural unit represented by the formula (3), and d represents the structural unit represented by the formula (4), each showing the composition ratio (mol%) thereof.)

2. The hydrogenated conjugated diene polymer, has an aromatic vinyl monomer unit content of 1 to 20% by mass, The rubber composition according to claim 1.

3. The hydrogenated conjugated diene polymer has a modification rate of 30% or more, The rubber composition according to claim 1.

4. The olefin rubber has a Mooney viscosity at 100°C of 25 or more and 150 or less, The rubber composition according to claim 1.

5. As the rubber component, further includes at least one selected from the group consisting of natural rubber, non-hydrogenated butadiene rubber, non-hydrogenated isoprene rubber, non-hydrogenated styrene-butadiene rubber, and non-hydrogenated styrene-isoprene rubber, The rubber composition according to claim 1.

6. Further includes a filler, With respect to 100 parts by mass of the rubber component, the content of the filler is 5 parts by mass or more and 250 parts by mass or less. The rubber composition according to claim 1.

7. The filler is at least one selected from the group consisting of silica, carbon black, calcium carbonate, titanium oxide, clay, and aluminum hydroxide, The rubber composition according to claim 6.

8. further contains sulfur, with respect to 100 parts by mass of the rubber component, the sulfur content is 0.2 parts by mass or less, The rubber composition according to claim 1.

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