Crosslinked rubber composition

Abstract

To provide a crosslinked rubber composition having a low dynamic-to-static modulus ratio, a small property change during repeated strain and excellent performance stability.SOLUTION: There is provided a crosslinked rubber composition comprising a rubber component containing at least one conjugated diene-based polymer, carbon black, and sulfur, wherein the storage modulus after strain ΔG'=G'(0.1% strain)-G'(10% strain) is 3.0 MPa or less, the difference in the storage modulus G'(0.1% strain) when the storage modulus after strain calculated by the following expression is measured twice is 0.4 MPa or less and the difference in the storage modulus G'(10% strain) is 0.2 MPa or less, and the change rate of the storage modulus G' at 0.1% strain and 10% strain, respectively, when the storage modulus after strain is measured twice repeatedly, is 6.0% or less. Difference in G' (0.1% strain) in two repeated measurements=First measurement G'-Second measurement G', Difference in G' (10% strain) in two repeated measurements=First measurement G'-Second measurement G', G'change rate=Difference in G' (0.1% strain) in two repeated measurements / G'in first measurement)×100, G'change rate=Difference in G' (10% strain) in two repeated measurements / G'in first measurement)×100.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a crosslinked rubber composition containing a rubber component containing at least one conjugated diene-based polymer, carbon black, and sulfur. [Background technology]

[0002] Vulcanized cross-linked rubber compositions for use in vibration-proof rubber and industrial materials generally contain rubber materials containing natural rubber, which has excellent vibration-proofing properties and rubber reinforcement properties, and carbon black is mainly used as a filler (see, for example, Patent Documents 1 and 2). In recent years, various techniques have been proposed for introducing predetermined functional groups into the terminals of conjugated diene polymers as methods for improving the performance of vulcanized crosslinked rubber compositions in these fields (see, for example, Patent Documents 3 and 4). Furthermore, vibration-isolating rubber is required to have improved dynamic magnification, which is an indication of vibration-isolating performance, and durability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2018-35253 [Patent Document 2] Patent Publication No. 2007-70582 [Patent Document 3] Patent Publication No. 5-202102 [Patent Document 4] Special Table 2023-519535 Summary of the Invention [Problem to be solved by the invention]

[0004] For anti-vibration rubbers used in engine mounts and suspension bushings for supporting engines and suppressing vibration transmission in automobiles and the like, it is required to provide a crosslinked rubber composition that has a low dynamic magnification, little change in properties under repeated strain, and excellent performance stability. [Means for solving the problem]

[0005] As a result of intensive research by the present inventors to solve the above-mentioned problems of the prior art, it has been discovered that the present inventors have discovered a crosslinked rubber composition comprising a rubber component containing at least one conjugated diene polymer, carbon black, and sulfur, wherein the storage modulus after strain ΔG′ is 3.0 MPa or less and The inventors have found that a crosslinked rubber composition in which the difference in storage modulus G' when the storage modulus is measured twice repeatedly and the rate of change are adjusted to fall within a specific range has a low dynamic magnification, small changes in properties during repeated strain, and excellent performance stability, leading to the completion of the present invention. That is, the present invention is as follows. [1] A crosslinked rubber composition comprising a rubber component containing at least one conjugated diene-based polymer, carbon black, and sulfur, Storage modulus after strain ΔG' = G' (strain 0.1%) - G' (strain 10%) is 3.0 MPa or less and When the storage modulus after strain calculated by the following formula is measured twice, the difference in storage modulus G' (0.1% strain) is 0.4 MPa or less, and the difference in storage modulus G' (10% strain) is 0.2 MPa or less, and A crosslinked rubber composition in which, when the storage modulus after strain is repeatedly measured twice, the rate of change in storage modulus G' at a strain of 0.1% and a strain of 10% is 6.0% or less. Difference between two repeated measurements G' (0.1% strain) = 1st measurement G' - 2nd measurement G' Difference between two repeated measurements G' (10% strain) = 1st measurement G' - 2nd measurement G' G' change rate = (difference between two repeated measurements of G' (strain 0.1%) / first measurement of G') x 100 G' change rate = (difference between two repeated measurements of G' (10% strain) / first measurement of G') x 100 [2] The crosslinked rubber composition according to the above item [1], wherein the volume fraction of the carbon black in the crosslinked rubber composition is 7 to 30 vol %. [3] The crosslinked rubber composition according to the above [1] or [2], wherein the glass transition temperature of the conjugated diene polymer is -110°C to -80°C. [4] The crosslinked rubber composition according to any one of [1] to [3] above, wherein the amount of 1,2-vinyl bonds in the conjugated diene monomer units of the conjugated diene polymer is 10 mol % or more and 25 mol % or less. [5] The crosslinked rubber composition according to any one of the above [1] to [4], wherein the content of aromatic vinyl monomer units in the conjugated diene polymer is 0% by mass or more and 7% by mass or less. [6] The crosslinked rubber composition according to any one of the above [1] to [5], wherein the conjugated diene polymer is a modified conjugated diene polymer obtained by reacting a modifying agent having in the molecule thereof at least one >C=O group and at least one substituted amino group that react with the active terminal, or a modified conjugated diene polymer obtained by reacting a nitrogen atom-containing coupling agent having in one molecule four or more non-halogen functional groups that react with the active terminal, and a modifying agent having in the molecule thereof at least one >C=O group and at least one substituted amino group that react with the active terminal. [7] The crosslinked rubber composition according to any one of the above [1] to [6], wherein the modified conjugated diene polymer obtained by reacting with a modifying agent having at least one >C=O group and at least one substituted amino group in the molecule that reacts with the active terminal has a modification rate measured by column adsorption GPC of 50% or more and 99% or less. [8] The crosslinked rubber composition according to the above [6] or [7], wherein the coupling ratio of the modified conjugated diene polymer with the nitrogen atom-containing coupling agent having four or more functional groups per molecule that react with the non-halogen active terminal is 7% or more and 25% or less. [9] The crosslinked rubber composition according to any one of [6] to [8] above, wherein the coupling ratio of the modified conjugated diene polymer with a nitrogen atom-containing coupling agent having four or more functional groups per molecule that react with the non-halogen active terminal is 7% or more and 15% or less.

[10] The crosslinked rubber composition according to any one of the above [1] to [9], wherein the conjugated diene polymer has a tin content of 20 ppm or less.

[11] The cross-linked rubber composition according to any one of the above [1] to

[10] , wherein the filler in the cross-linked rubber composition is carbon black only.

[12] A vibration-proof rubber comprising the crosslinked rubber composition according to any one of [1] to

[11] above.

[13] A power transmission belt and a conveyor belt comprising the crosslinked rubber composition according to any one of [1] to

[11] above. [Effects of the Invention]

[0006] The crosslinked rubber composition of the present invention has the effect of having a low dynamic magnification and little deterioration in performance during repeated strain (improved dynamic magnification and performance stability). Anti-vibration rubbers made from the crosslinked rubber composition of the present invention are suitable for use as vibration-damping materials for engine mounts, stabilizer bushings, suspension bushings, and the like used in automobiles and other vehicles. They can also be used as vibration dampers for computer hard disks, vibration dampers for general home appliances such as washing machines, and vibration-damping (vibration-damping) devices and seismic isolation devices in the construction and housing fields, such as architectural vibration-damping walls and vibration-damping (vibration-damping) dampers. DETAILED DESCRIPTION OF THE INVENTION

[0007] The following describes in detail the form for implementing the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to this, and various modifications are possible within the scope of the gist of the present invention.

[0008] <Crosslinked Rubber Composition> The crosslinked rubber composition of the present embodiment is a crosslinked rubber composition containing a rubber component containing at least one conjugated diene polymer, carbon black, and sulfur, and has a storage modulus after strain Δ G'=G'(strain 0.1%)-G'(strain 10%) is 3.0 MPa or less, preferably 2.8 MPa or less, and more preferably 2.5 MPa or less, from the viewpoint of achieving a low dynamic magnification.

[0009] In addition, in the crosslinked rubber composition of this embodiment, the difference in storage modulus G' (0.1% strain) when the storage modulus after strain is measured twice is 0.40 MPa or less, preferably 0.30 MPa or less, and more preferably 0.20 MPa or less, from the viewpoint of achieving a low dynamic magnification, and the difference in storage modulus G' (10% strain) when the storage modulus after strain is measured twice is 0.20 MPa or less, preferably 0.17 MPa or less, and more preferably 0.15 MPa or less, from the viewpoint of achieving a low dynamic magnification. Furthermore, from the viewpoint of performance stability of the crosslinked rubber composition, when the storage modulus after strain is measured twice, the rate of change in storage modulus G' at 0.1% strain and at 10% strain is 6.0% or less, preferably 5.6% or less, and more preferably 5.0% or less.

[0010] Here, the difference in storage modulus G' (strain 0.1%), the difference in storage modulus G' (strain 10%) when the storage modulus after strain is measured twice, and the rate of change in storage modulus G' at strains of 0.1% and 10% when the storage modulus after strain is measured twice are calculated using the following formulas. Difference between two repeated measurements G' (0.1% strain) = 1st measurement G' - 2nd measurement G' Difference between two repeated measurements G' (10% strain) = 1st measurement G' - 2nd measurement G' G' change rate = (difference between two repeated measurements of G' (strain 0.1%) / first measurement of G') x 100 G' change rate = (difference between two repeated measurements of G' (10% strain) / first measurement of G') x 100

[0011] The difference and rate of change in storage modulus G' can be controlled by adjusting the composition of the conjugated diene polymer and various parameters, which will be described later.

[0012] The crosslinked rubber composition of this embodiment contains a rubber component containing at least one conjugated diene polymer from the viewpoints of low dynamic magnification and performance stability, and the proportion of natural rubber in the total amount (100 parts by mass) of the rubber component is preferably 50 to 90% by mass, more preferably 50 to 70% by mass. Furthermore, from the viewpoint of improving the dispersibility of carbon black in the crosslinked rubber composition, the proportion of the at least one conjugated diene polymer in the rubber component is preferably 10 to 50% by mass, more preferably 30 to 50% by mass. In the crosslinked rubber composition of the present embodiment, by containing a certain amount of a specific modified conjugated diene polymer described below, it becomes possible to disperse carbon black well even when a relatively large amount of carbon black is blended.

[0013] From the viewpoint of reinforcing effect and processability, the crosslinked rubber composition of this embodiment preferably has a volume fraction of carbon black in the crosslinked rubber composition of 7 to 30 vol%, more preferably 8 to 25 vol%, and even more preferably 10 to 20 vol%. If the amount of carbon black is too small, the reinforcing effect tends to be small, and conversely, if the amount of carbon black is too large, the dynamic magnification tends to be high and the viscosity tends to increase, resulting in poor processability.

[0014] [Conjugated diene polymer] The conjugated diene polymer of this embodiment contains at least one conjugated diene compound and may also contain an aromatic vinyl compound. The conjugated diene polymer of this embodiment may be a polymer of structural units derived from a conjugated diene compound (hereinafter also referred to as "conjugated diene monomer units"), or a copolymer composed of structural units derived from an aromatic vinyl compound (hereinafter also referred to as "aromatic vinyl monomer units") and conjugated diene monomer units.

[0015] The conjugated diene polymer of the present embodiment is preferably a copolymer of a conjugated diene compound and an aromatic vinyl compound in which the so-called microstructure (content of aromatic vinyl monomer units, amount of 1,2-vinyl bonds, etc.) is controlled.

[0016] The conjugated diene polymer of the present embodiment preferably has an aromatic vinyl monomer unit content of 0% by mass or more and 7% by mass or less, and a 1,2-vinyl bond content in the conjugated diene monomer units of 10% by mol or more and 25% by mol or less.

[0017] Examples of aromatic vinyl compounds include, but are not limited to, styrene, p-methylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene. Among these, styrene is preferred from the viewpoint of industrial availability. These compounds may be used alone or in combination of two or more.

[0018] Furthermore, conjugated diene compounds include, but are not limited to, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene. Among these, from the viewpoint of industrial availability, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is particularly preferred. These compounds may be used alone or in combination of two or more.

[0019] (Aromatic vinyl monomer unit content) The content of aromatic vinyl monomer units in the conjugated diene polymer of this embodiment is preferably 7% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, particularly preferably 1% by mass or less, and may be 0% by mass, from the viewpoint of improving the dynamic magnification of the crosslinked rubber composition.

[0020] The content of aromatic vinyl monomer units can be measured by 1H-NMR, specifically by the method described in the examples.

[0021] The content of the aromatic vinyl monomer unit can be controlled within the above range by adjusting the amount of the aromatic vinyl compound added during polymerization.

[0022] (1,2-vinyl bond content) The 1,2-vinyl bond content in the conjugated diene polymer of this embodiment is the molar ratio of 1,2-vinyl bonds based on the content of conjugated diene monomer units, and is preferably 10 mol% or more, more preferably 13 mol% or more, and even more preferably 14 mol% or more from the viewpoint of productivity of the conjugated diene polymer. On the other hand, from the viewpoints of improving the dynamic magnification and tensile properties of the conjugated diene polymer of this embodiment, and further from the viewpoint of suppressing gelation of the conjugated diene polymer, it is 25 mol% or less, preferably 22 mol% or less, more preferably 21 mol% or less, and even more preferably 20 mol% or less.

[0023] The amount of 1,2-vinyl bonds can be measured by 1H-NMR, specifically by the method described in the Examples.

[0024] The amount of 1,2-vinyl bonds can be controlled within the above range by adjusting the reaction initiation temperature, reaction termination temperature, and the type and amount of polar substance added during polymerization.

[0025] (Weight average molecular weight Mw measured by GPC) The conjugated diene polymer of this embodiment preferably has a weight average molecular weight Mw of the entire conjugated diene polymer (including the coupling portion if coupled) measured by GPC (gel permeation chromatography) of 300,000 or more, more preferably 350,000 or more, from the viewpoints of productivity and cold flow properties of the conjugated diene polymer. From the viewpoint of gelation suppression, the weight average molecular weight Mw is preferably 1,000,000 or less, more preferably 700,000 or less, and even more preferably 500,000 or less.

[0026] (Mooney viscosity) The conjugated diene polymer of the present embodiment preferably has a Mooney viscosity measured at 100°C of 30 or more and 120 or less, more preferably 35 or more and 100 or less, and even more preferably 40 or more and 90 or less, from the viewpoints of the productivity and cold flow properties of the conjugated diene polymer, the processability when the polymer is made into a rubber composition blended with a filler such as carbon black, and the tensile strength, elongation, and hardness when the composition is vulcanized into a crosslinked rubber composition.

[0027] When the Mooney viscosity measured at 100°C is 30 or more, the tensile strength and elongation tend to be improved when the rubber is vulcanized and made into a crosslinked rubber composition, and when the Mooney viscosity measured at 100°C is 120 or less, the processability tends to be good when the rubber is made into a rubber composition blended with a filler such as carbon black.

[0028] The Mooney viscosity of the conjugated diene polymer can be measured by the method described in the examples below.

[0029] The Mooney viscosity can be controlled by the microstructure of the conjugated diene polymer, the weight average molecular weight Mw, the coupling ratio in the coupling reaction described below, and the like.

[0030] (glass transition temperature) The glass transition temperature of the conjugated diene polymer of the present embodiment is preferably −80° C. or lower, more preferably −82° C. or lower, even more preferably −84° C. or lower, and particularly preferably −86° C. or lower, from the viewpoint of dynamic magnification and low-temperature properties. On the other hand, from the viewpoint of polymerization reproducibility in living anionic polymerization, the glass transition temperature is preferably −110° C. or higher, more preferably −108° C. or higher, and even more preferably −106° C. or higher.

[0031] The glass transition temperature can be measured by the method described in the Examples below.

[0032] The glass transition temperature can be controlled within a predetermined range by adjusting the ratio of conjugated diene monomer units to aromatic vinyl monomer units in the conjugated diene polymer or the amount of 1,2-vinyl bonds, and the amount of 1,2-vinyl bonds can be controlled by adjusting the amount of polar substance added during polymerization or the polymerization temperature.

[0033] (coupling) The conjugated diene polymer of the present embodiment may be a conjugated diene polymer obtained by subjecting the active terminal of the conjugated diene polymer obtained through a polymerization step to a coupling reaction using a bifunctional or higher functional reactive compound (hereinafter also referred to as a "coupling agent").

[0034] In the coupling reaction step, a coupling agent is used to cause a coupling reaction at one active end of the conjugated diene polymer to obtain a conjugated diene polymer.

[0035] The coupling agent is not particularly limited, and examples thereof include coupling agents having one or more functional groups such as an epoxy group, a carbonyl group, a carboxylic acid ester group, a carboxylic acid amide group, an acid anhydride group, a phosphate ester group, a phosphite ester group, an epithio group, a thiocarbonyl group, a thiocarboxylic acid ester group, a dithiocarboxylic acid ester group, a thiocarboxylic acid amide group, an imino group, an ethyleneimino group, a halogen group, an alkoxysilyl group, an isocyanate group, a thioisocyanate group, a conjugated diene group, and an arylvinyl group. Among the coupling agents, nitrogen-containing coupling agents can also be used as modifiers, which will be described later.

[0036] Examples of coupling agents include, but are not limited to, halogenated silane compounds such as silicon tetrachloride, silicon tetrabromide, silicon tetraiodide, monomethyltrichlorosilicon, monoethyltrichlorosilicon, monobutyltrichlorosilicon, monohexyltrichlorosilicon, monomethyltribromosilicon, and bistrichlorosilylethane; and halogenated silane compounds such as monochlorotrimethoxysilane, monobromotrimethoxysilane, dichlorodimethoxysilane, dibromodimethoxysilane, trichloromethoxysilane, and tribromomethoxysilane.

[0037] Further, examples include, but are not limited to, alkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, and alkyltriphenoxysilane; and compounds having an imino group and an alkoxysilyl group such as tristrimethoxysilylpropylamine, triethoxysilylpropylamine, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N-(1,3-dimethylbutylidene)-3-(tributoxysilyl)-1-propanamine, N-(1-methylpropylidene)-3-(triethoxysilyl)-1-propanamine, N-ethylidene-3-(triethoxysilyl)-1-propanamine, and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole.

[0038] Furthermore, examples of the compound include, but are not limited to, 2-[3-(trimethoxysilyl)propyl]-1,3-dimethylimidazolidine, 2-[3-(trimethoxysilyl)propyl]-1,3-(bistrimethylsilyl)imidazolidine, 2-(diethoxydiethylsilyl)-1,3-diethylimidazolidine, 2-(triethoxysilyl)-1,4-diethylpiperazine, 2-(dimethoxymethylsilyl)-1,4-dimethylpiperazine, 5-(triethoxysilyl)-1,3-dipropylhexahydropyrimidine, 5-(diethoxyethylsilyl)-1,3 -Diethylhexahydropyrimidine, {2-[3-(2-dimethylaminoethyl)-2-(ethyldimethoxysilyl)-imidazolidin-1-yl]-ethyl}-dimethylamine, 5-(trimethoxysilyl)-1,3-bis-(2-methoxyethyl)-hexahydropyrimidine, 5-(ethyldimethoxysilyl)-1,3-bis-(2-trimethylsilylethyl)-hexahydropyrimidine-1,3-dimethylimidazolidine, 2-(3-diethoxyethylsilyl-propyl)-1,3-diethylimidazolidine, 2-(3-triethoxysilyl-propyl)- propyl)-1,4-diethylpiperazine, 2-(3-dimethoxymethylsilyl-propyl)-1,4-dimethylpiperazine, 5-(3-triethoxysilyl-propyl)-1,3-dipropylhexahydropyrimidine, 5-(3-diethoxyethylsilyl-propyl)-1,3-diethylhexahydropyrimidine, {2-[3-(2-dimethylaminoethyl)-2-(3-ethyldimethoxysilyl-propyl)-imidazolidin-1-yl]-ethyl}-dimethylamine, 5-(3-trimethoxysilyl-propyl)-1,3-bis-(2-methoxyethyl 1-(3-ethyldimethoxysilyl-propyl)-1,3-bis-(2-trimethylsilylethyl)-hexahydropyrimidine, 2-[3-(trimethoxysilyl)propyl]-1,3-bis(trimethylsilyl)imidazolidine, 2-(diethoxyethylsilyl)-1,3-bis(triethylsilyl)imidazolidine, 2-(triethoxysilyl)-1,4-bis(trimethylsilyl)piperazine, 2-(dimethoxymethylsilyl)-1,4-bis(trimethylsilyl)piperazine, 5-(triethoxysilyl)-1,Examples include 3-bis(tripropylsilyl)hexahydropyrimidine.

[0039] Furthermore, although not limited to the following, for example, [3-(1-hexamethyleneimino)propyl]triethoxysilane, [3-(1-hexamethyleneimino)propyl]trimethoxysilane, [2-(1-hexamethyleneimino)ethyl]triethoxysilane, [2-(1-hexamethyleneimino)ethyl]trimethoxysilane, [3-(1-pyrrolidinyl)propyl]triethoxysilane, [3-(1-pyrrolidinyl)propyl]trimethoxysilane, [3-(1-heptamethyleneimino)propyl]triethoxysilane, [3-(1-do [decamethyleneimino)propyl]triethoxysilane, [3-(1-hexamethyleneimino)propyl]diethoxymethylsilane, [3-(1-hexamethyleneimino)propyl]diethoxyethylsilane, N-[3-(triethoxysilyl)propyl]-N,N'-diethyl-N'-trimethylsilyl-ethane-1,2-diamine, N-[2-(trimethoxysilanyl)ethyl]-N,N',N'-trimethylethane-1,2-diamine, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, and the like.

[0040] Furthermore, examples of the epoxy compounds include, but are not limited to, tetraglycidyl meta-xylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, etc. Furthermore, examples of the isocyanate compounds include, but are not limited to, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, diphenylethane diisocyanate, 1,3,5-benzene triisocyanate, etc.

[0041] In addition, examples thereof include, but are not limited to, 3-(4-methylpiperazin-1-yl)propyltriethoxysilane, 1-[3-(diethoxyethylsilyl)propyl]-4-methylpiperazine, 1-[3-(trimethoxysilyl)propyl]-3-methylimidazolidine, 1-[3-(diethoxysilyl)propyl]-3-ethylimidazolidine, 1-[3-(triethoxysilyl)propyl]-3-methylhexahydropyrimidine, 1-[3-(di 3-[3-(trimethoxysilyl)propyl]-3-methylhexahydropyrimidine, 3-[3-(tributoxysilyl)propyl]-1-methyl-1,2,3,4-tetrahydropyrimidine, 3-[3-(dimethoxymethylsilyl)propyl]-1-ethyl-1,2,3,4-tetrahydropyrimidine, 1-(2-ethoxyethyl)-3-[3-(trimethoxysilyl)propyl]imidazolidine, (2-{3-[3-(trimethylsilyl)propyl]tetra hydropyrimidin-yl}ethyl)dimethylamine, 1-[3-(triethoxysilyl)propyl]-4-(trimethylsilyl)piperazine, 1-[3-(dimethoxymethylsilyl)propyl]-4-(trimethylsilyl)piperazine, 1-[3-(tributoxysilyl)propyl]-4-(trimethylsilyl)piperazine, 1-[3-(diethoxyethylsilyl)propyl]-3-(triethylsilyl)imidazolidine, 2-(trimethoxysilanilide

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

[0042] The coupling agent is not particularly limited, but from the viewpoint of reducing the dynamic magnification and reducing the load on production equipment, it is preferable to use a nitrogen atom-containing coupling agent having four or more non-halogen functional groups per molecule that react with the active terminal.

[0043] When coupling a conjugated diene polymer with a coupling agent is performed, the coupling ratio is preferably 5% or more, more preferably 7% or more, and even more preferably 10% or more, from the viewpoints of weight-average molecular weight Mw, Mooney viscosity, and cold flow properties. On the other hand, from the viewpoints of the modification rate of uncoupled portions and low dynamic magnification, the coupling ratio is preferably 35% or less, more preferably 25% or less, and even more preferably 20% or less. The coupling ratio can be measured by the method described in the Examples below.

[0044] (Modified conjugated diene polymer) The conjugated diene polymer of the present embodiment may be a modified conjugated diene polymer. Here, modification refers to modifying a conjugated diene polymer with a nitrogen-containing compound.

[0045] (denaturation rate) In this specification, unless otherwise specified, the "modification rate" refers to the mass ratio of the polymer having a nitrogen atom-containing functional group to the total amount of the conjugated diene-based polymer. For example, when a nitrogen atom-containing modifier is reacted with the terminal end of a polymer, the mass ratio of the polymer having a nitrogen atom-containing functional group by the nitrogen atom-containing modifier to the total amount of the polymer is expressed as the modification rate.

[0046] As will be described later, a nitrogen-containing coupling agent is also included in the nitrogen-containing modifier. On the other hand, when a polymer is branched using a nitrogen-containing branching agent, the resulting copolymer will have a nitrogen-containing functional group, and therefore, this branched polymer will also be counted as a polymer having a nitrogen-containing functional group when calculating the modification rate.

[0047] That is, in this specification, the polymer having a nitrogen atom-containing functional group refers to a polymer having a nitrogen atom-containing functional group by a nitrogen atom-containing modifying agent and a branched polymer by a branching agent having a nitrogen atom-containing functional group, and the total mass ratio of these is the "modification rate."

[0048] In terms of dynamic magnification, the conjugated diene polymer of this embodiment has a modification rate relative to the total amount of the conjugated diene copolymer, as measured by the column adsorption GPC method described below (hereinafter also simply referred to as "modification rate"), of preferably 50% or more, more preferably 60% or more, and even more preferably 65% ​​or more, from the viewpoints of dispersibility of fillers such as carbon black and improvement of dynamic magnification. On the other hand, from the viewpoints of processability and ease of polymerization, the modification rate is preferably 98% or less, more preferably 96% or less, and even more preferably 92% or less.

[0049] The modification rate can be controlled by keeping the amount of modifier added and the polymerization temperature low, thereby suppressing the deactivation of living ends.

[0050] The modification rate of the conjugated diene polymer of the present embodiment can be measured, for example, by chromatography, which can separate functional group-containing modified components from unmodified components. Examples of such chromatography methods include a method (column adsorption GPC method) in which a gel permeation chromatography column packed with a polar substance such as silica that adsorbs specific functional groups is used to quantify the unadsorbed components using an internal standard for comparison.

[0051] More specifically, the modification rate can be determined by measuring the amount of adsorption onto the silica column from the difference between a chromatogram obtained by measuring a sample solution containing a sample and a low-molecular-weight internal standard polystyrene on a polystyrene gel column and a chromatogram obtained by measuring the sample solution on a silica column.

[0052] More specifically, the modification rate can be measured by the method described in the Examples. The modification rate of the conjugated diene polymer of this embodiment can be controlled within the above-mentioned range, for example, by controlling the amount of modifier added and the polymerization reaction temperature to prevent deactivation of active terminals.

[0053] (Denaturation method) The modification method is not particularly limited, but examples thereof include a method using a polymerization initiator containing a nitrogen-containing compound, a method using a nitrogen-containing compound as a polymerization monomer, a method using a nitrogen-atom-containing coupling agent, a method reacting a non-coupling nitrogen-containing compound with the reaction terminal, and a method modifying the double bond of a conjugated diene polymer after polymerization by reacting a nitrogen-containing compound with the double bond.

[0054] Examples of the polymerization initiator containing a nitrogen-containing compound include, but are not limited to, reaction products of nitrogen-containing compounds such as dimethylamine, diethylamine, dibutylamine, dipropylamine, diheptylamine, dihexylamine, dioctylamine, di(2-ethylhexyl)amine, didecylamine, ethylpropylamine, ethylbutylamine, ethylbenzylamine, methylphenethylamine, piperidine, hexamethyleneimine, azacyclooctane, 1,3,3-trimethyl-6-azabicyclo[3.2.1]octane, 1,2,3,6-tetrahydropyridine, and 3,5-dimethylpiperidine with organic lithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, n-propyllithium, and i-propyllithium.

[0055] From the viewpoints of improving dynamic magnification, production stability, and environmental impact, the conjugated diene polymer of this embodiment preferably has a tin content of 50 ppm or less, more preferably 40 ppm or less, even more preferably 30 ppm or less, still more preferably 20 ppm or less, and particularly preferably 10 ppm or less. In this embodiment, the tin content in the conjugated diene polymer is the content of tin bonded to the conjugated diene polymer, and does not include the tin content when a tin-containing compound is added to the polymer as an additive. The tin content of the conjugated diene polymer of the present embodiment can be controlled by the type of monomer used in the polymerization, the type of coupling agent and the type of modifier, and the amount of addition thereof.

[0056] Examples of non-coupling nitrogen-containing compounds include, but are not limited to, 1,3-diethyl-2-imidazolidinone, 1,3-dimethyl-2-imidazolidinone, 1,3-dipropyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 1-methyl-3-propyl-2-imidazolidinone, 1-methyl-3-butyl-2-imidazolidinone, 1,3-dihydro-1,3-dimethyl-2H-imidazol-2-one, N-methyl-2-pyrrolidone, 1-phenyl-2-pyrrolidone, and N-methyl-ε-caprolactam.

[0057] Furthermore, from the viewpoint of reducing the dynamic magnification, the conjugated diene polymer of the present embodiment is preferably a modified conjugated diene polymer obtained by reacting with a modifying agent having both at least one >C=O group and at least one substituted amino group in the molecule that reacts with the active terminal, or a modified conjugated diene polymer obtained by reacting with a nitrogen atom-containing coupling agent having four or more non-halogen functional groups in one molecule that react with the active terminal, and a modifying agent having both at least one >C=O group and at least one substituted amino group in the molecule that reacts with the active terminal.

[0058] [Method of producing conjugated diene polymer] The conjugated diene polymer of this embodiment can be produced, for example, by polymerization by living anionic polymerization using an organic monolithium compound as a polymerization initiator. This allows for the production of a conjugated diene polymer having an active end, which may remain in a linear structure, or the branched structure can be appropriately controlled in a subsequent branching step using a branching agent, as described below. Furthermore, the addition of a nitrogen-containing modifier, as described below, tends to make it easier to obtain a conjugated diene polymer with a high degree of modification. When a composition containing carbon black or the like is produced, the dispersibility of the filler, such as carbon black, is improved, and a crosslinked composition with improved dynamic magnification and durability tends to be obtained. This will be explained in more detail below.

[0059] The conjugated diene polymer of this embodiment is obtained by carrying out a polymerization step in which an aromatic vinyl compound and a conjugated diene compound are polymerized using a predetermined polymerization initiator. Preferably, a coupling reaction step and / or a modification reaction step may be carried out using the above-mentioned coupling agent or modifying agent, followed by a hydrogenation step. A branching step may be carried out using a branching agent before the coupling reaction step or the modification step.

[0060] (Polymerization process) As the polymerization initiator used in the polymerization step, at least an organic monolithium compound can be used.

[0061] The organomonolithium compound is not limited to the following, but examples thereof include low molecular weight compounds and solubilized oligomeric organomonolithium compounds.

[0062] Furthermore, examples of the organic monolithium compound include compounds having a carbon-lithium bond, compounds having a nitrogen-lithium bond, and compounds having a tin-lithium bond in terms of the bonding mode between the organic group and the lithium.

[0063] The amount of the organic monolithium compound used as the polymerization initiator is preferably determined depending on the structure of the target conjugated diene polymer and the molecular weight of the conjugated diene polymer.

[0064] The amount of a monomer such as a conjugated diene compound used relative to the amount of a polymerization initiator used is related to the degree of polymerization, i.e., tends to be related to the number average molecular weight and / or weight average molecular weight, and peak top molecular weight.

[0065] Therefore, in order to increase the molecular weight, it is advisable to adjust the amount of polymerization initiator used in a direction to decrease it, and in order to decrease the molecular weight, it is advisable to adjust the amount of polymerization initiator used in a direction to increase it.

[0066] As the organic monolithium compound, an alkyllithium compound having a substituted amino group or a dialkylaminolithium is preferred from the viewpoint that it can be used as one method for introducing nitrogen atoms into a conjugated diene polymer.

[0067] In this case, a conjugated diene polymer having a nitrogen atom consisting of an amino group at the polymerization initiation terminal can be obtained.

[0068] The substituted amino group is an amino group that does not have an active hydrogen or has a structure in which the active hydrogen is protected.

[0069] Examples of alkyllithium compounds having an amino group that does not have an active hydrogen include, but are not limited to, 3-dimethylaminopropyllithium, 3-diethylaminopropyllithium, 4-(methylpropylamino)butyllithium, and 4-hexamethyleneiminobutyllithium.

[0070] Examples of alkyllithium compounds having an amino group with a structure in which an active hydrogen is protected include, but are not limited to, 3-bistrimethylsilylaminopropyllithium and 4-trimethylsilylmethylaminobutyllithium.

[0071] Examples of dialkylaminolithiums include, but are not limited to, lithium dimethylamide, lithium diethylamide, lithium dipropylamide, lithium dibutylamide, lithium di-n-hexylamide, lithium diheptylamide, lithium diisopropylamide, lithium dioctylamide, lithium-di-2-ethylhexylamide, lithium didecylamide, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide, lithium methylphenethylamide, lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, lithium morpholide, 1-lithioazacyclooctane, 6-lithio-1,3,3-trimethyl-6-azabicyclo[3.2.1]octane, and 1-lithio-1,2,3,6-tetrahydropyridine.

[0072] These organomonolithium compounds having a substituted amino group can also be used as solubilized oligomeric organomonolithium compounds by reacting them with a small amount of a polymerizable monomer, such as 1,3-butadiene, isoprene, or styrene.

[0073] The organic monolithium compound is preferably an alkyllithium compound from the viewpoints of industrial availability and ease of control of the polymerization reaction, in which case a copolymer having an alkyl group at the polymerization initiation terminal can be obtained.

[0074] Examples of the alkyllithium compound include, but are not limited to, n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium.

[0075] As the alkyllithium compound, n-butyllithium and sec-butyllithium are preferred from the viewpoints of industrial availability and ease of control of the polymerization reaction.

[0076] These organomonolithium compounds may be used alone or in combination of two or more, or may be used in combination with other organometallic compounds.

[0077] Examples of the other organometallic compounds include alkaline earth metal compounds, other alkali metal compounds, and other organometallic compounds.

[0078] Alkaline earth metal compounds include, but are not limited to, organomagnesium compounds, organocalcium compounds, and organostrontium compounds, as well as alkaline earth metal alkoxides, sulfonates, carbonates, and amides.

[0079] Examples of organomagnesium compounds include dibutylmagnesium and ethylbutylmagnesium. Examples of other organometallic compounds include organoaluminum compounds.

[0080] In the polymerization step, the polymerization reaction mode is not limited to the following, but examples thereof include a batchwise (also called a "batch type") and a continuous polymerization reaction mode.

[0081] In the continuous system, one or more connected reactors can be used. The continuous reactor may be, for example, a tank-type or tubular reactor equipped with a stirrer. In the continuous system, preferably, the monomer, the inert solvent, and the polymerization initiator are continuously fed into the reactor, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is continuously discharged.

[0082] The batch reactor may be, for example, a tank-type reactor equipped with a stirrer. In the batch reactor, preferably, a monomer, an inert solvent, and a polymerization initiator are fed, and if necessary, a monomer is added continuously or intermittently during polymerization to obtain a polymer solution in the reactor, which is then discharged after the polymerization is completed.

[0083] In the method for producing a conjugated diene polymer of the present embodiment, in order to obtain a conjugated diene polymer having active ends at a high rate, a continuous method is preferred, which allows the polymer to be continuously discharged and subjected to the next reaction in a short time.

[0084] In the polymerization step of the conjugated diene polymer of this embodiment, the polymerization is preferably carried out in an inert solvent. Examples of the inert solvent include, but are not limited to, hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific examples of the hydrocarbon solvent include, but are not limited to, aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; and hydrocarbons consisting of mixtures thereof.

[0085] By treating the impurities, that is, allenes and acetylenes, with an organometallic compound before subjecting the polymer to the polymerization reaction, a conjugated diene-based polymer having a high concentration of active ends tends to be obtained, and a modified conjugated diene-based polymer with a high modification rate tends to be obtained, which is preferable.

[0086] In the polymerization process, a polar substance (polar compound) may be added. This allows the aromatic vinyl compound to be randomly copolymerized with the conjugated diene compound, and the polar substance tends to be usable as a vinylating agent to control the microstructure of the conjugated diene portion. It also tends to be effective in accelerating the polymerization reaction.

[0087] Examples of polar substances include, but are not limited to, ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium tert-butylate, and sodium amylate; and phosphine compounds such as triphenylphosphine. These polar substances may be used alone or in combination of two or more.

[0088] The amount of polar substance used is not particularly limited and can be selected depending on the purpose, but is preferably 0.01 moles or more and 30 moles or less per mole of the polymerization initiator.

[0089] Such polar substances (vinylating agents) can be used in an appropriate amount depending on the desired amount of 1,2-vinyl bonds as modifiers for the microstructure of the conjugated diene moiety in the conjugated diene polymer. Many polar substances also have an effective randomizing effect in the copolymerization of a conjugated diene compound and an aromatic vinyl compound, and tend to be used as modifiers for adjusting the distribution of the aromatic vinyl compound and the amount of styrene blocks.

[0090] As a method for randomizing the conjugated diene compound and the aromatic vinyl compound, for example, as described in JP-A-59-140211, a copolymerization reaction may be initiated with the entire amount of styrene and a portion of 1,3-butadiene, and the remaining 1,3-butadiene may be intermittently added during the copolymerization reaction.

[0091] The polymerization temperature in the polymerization step is preferably a temperature at which living anionic polymerization proceeds, and from the viewpoint of productivity, is more preferably 0° C. or higher, even more preferably 120° C. or lower, still more preferably 30° C. or higher and 100° C. or lower, and particularly preferably 50° C. or higher and 85° C. or lower. By keeping the temperature within such a range, it tends to be possible to ensure a sufficient amount of modifying agent to react with the active terminals after completion of polymerization.

[0092] (Coupling process, modification process, hydrogenation process) The active terminals of the conjugated diene polymer obtained through the above-mentioned polymerization step and, if necessary, a coupling step using a predetermined coupling agent may be subjected to a coupling reaction using the above-mentioned coupling agent or a modification reaction using a modifier having a nitrogen atom-containing group. When a nitrogen atom-containing coupling agent is used, the coupling reaction and the modification reaction proceed simultaneously. In addition, a hydrogenation step in which a hydrogenation reaction is carried out as appropriate may be carried out.

[0093] (Deactivator addition process, neutralizer addition process) In the method for producing a conjugated diene polymer of this embodiment, a deactivator, a neutralizer, etc. may be added to the polymer solution as needed.

[0094] The quenching agent is not limited to the following, but examples thereof include water; alcohols such as methanol, ethanol, and isopropanol; and the like.

[0095] Examples of neutralizing agents include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, mainly 10 carbon atoms); aqueous solutions of inorganic acids; and carbon dioxide gas.

[0096] [Carbon Black] The crosslinked rubber composition of this embodiment contains carbon black as a filler from the viewpoint of reinforcing effect and processability. The carbon black is not particularly limited, but various grades of carbon black such as SAF grade, ISAF grade, HAF grade, MAF grade, FEF grade, GPF grade, SRF grade, FT grade, and MT grade can be used. These may be used alone or in combination of two or more types.

[0097] The amount of carbon black in the crosslinked rubber composition is preferably in the range of 20 parts by mass or more and 100 parts by mass or less, more preferably in the range of 20 to 70 parts by mass, and particularly preferably in the range of 30 to 60 parts by mass, per 100 parts by mass of the rubber component containing at least one conjugated diene polymer.

[0098] [Silica-based inorganic filler] The crosslinked rubber composition of the present embodiment may contain a silica-based inorganic filler from the viewpoint of low heat buildup. The amount of the silica-based inorganic filler is preferably 1 part by mass to 60 parts by mass, more preferably 5 parts by mass to 55 parts by mass, and even more preferably 10 parts by mass to 50 parts by mass, per 100 parts by mass of the rubber component. The silica-based inorganic filler is not particularly limited and any known filler can be used, but solid particles containing SiO2 or Si3Al as a structural unit are preferred, and solid particles having SiO2 or Si3Al as the main structural unit are more preferred. Here, the main component refers to a component contained in the silica-based inorganic filler in an amount of 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more.

[0099] Examples of silica-based inorganic fillers include, but are not limited to, inorganic fibrous materials such as silica, clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, and glass fiber.

[0100] Commercially available silica-based inorganic fillers include, for example, "Ultrasil 7000GR" manufactured by Evonik Degussa. Surface-hydrophobized silica-based inorganic fillers and mixtures of silica-based inorganic fillers with non-silica-based inorganic fillers can also be used. Among these, silica and glass fiber are preferred as silica-based inorganic fillers, with silica being more preferred, from the viewpoint of the strength and abrasion resistance of the rubber composition of this embodiment. Examples of silica include dry silica, wet silica, and synthetic silicate silica.

[0101] The amount of silica-based inorganic filler in the crosslinked rubber composition is preferably in the range of 20 parts by mass or more and 100 parts by mass or less, more preferably in the range of 20 to 70 parts by mass, and particularly preferably in the range of 30 to 60 parts by mass, per 100 parts by mass of the rubber component containing at least one type of conjugated diene-based polymer.

[0102] [Metal oxides, metal hydroxides] The crosslinked rubber composition of the present embodiment may contain a metal oxide or a metal hydroxide in addition to the above-mentioned carbon black and silica-based inorganic filler. Metal oxide refers to solid particles whose main constituent unit is represented by the chemical formula MxOy (M represents a metal atom, and x and y each independently represent an integer of 1 to 6), and examples thereof include alumina, titanium oxide, magnesium oxide, zinc oxide, etc. Also, a mixture of a metal oxide and an inorganic filler other than a metal oxide can be used. Examples of metal hydroxides include, but are not limited to, aluminum hydroxide, magnesium hydroxide, and zirconium hydroxide.

[0103] In the crosslinked rubber composition of the present embodiment, from the viewpoints of dynamic magnification and cost, it is preferable that the filler is carbon black alone.

[0104] [Silane coupling agents] The crosslinked rubber composition of the present embodiment may contain a silane coupling agent. The silane coupling agent has a group that has affinity or bonding properties for the hydrogenated conjugated diene polymer, other rubber components, and silica-based inorganic filler, and functions to strengthen the interaction between them. Generally, a compound having a sulfur bond moiety, an alkoxysilyl group, and a silanol group moiety in one molecule is used as the silane coupling agent.

[0105] Examples of the silane coupling agent include, but are not limited to, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silane [Si363 manufactured by Evonik Degussa], and NXT-Z30, NXT-Z45, NXT-Z60, and NXT Silane manufactured by Momentive. butyl group-containing silane coupling agents, bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-Mercaptopropyltrimethoxysilane, 3-Mercaptopropyltriethoxysilane, 2-Mercaptoethyltrimethoxysilane, 2-Mercaptoethyltriethoxysilane, 3-Trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-Triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-Triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-Trimethoxysilylpropylbenzothiazolyltetrasulfide silane sulfide, 3-triethoxysilylpropyl benzoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, and the like.

[0106] Among these, from the viewpoint of high reinforcing effect, silane coupling agents containing a mercapto group, such as bis-[3-(triethoxysilyl)-propyl]-disulfide, ethoxy(3-mercaptopropyl)bis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silane [Si363 manufactured by Evonik Degussa], and NXT-Z30, NXT-Z45, NXTZ60, and NXT silane manufactured by Momentive, and bis-[3-(triethoxysilyl)-propyl]-tetrasulfide are preferred. The silane coupling agents may be used alone or in combination of two or more.

[0107] The content of the silane coupling agent in the crosslinked rubber composition is preferably 2 to 10 parts by mass, more preferably 3 to 9 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of further enhancing the effect of strengthening the interaction between the rubber component and the silica-based inorganic filler, and is preferably 4 to 15 parts by mass, more preferably 6 to 12 parts by mass, per 100 parts by mass of the silica-based inorganic filler.

[0108] [sulfur] The amount of sulfur in the crosslinked rubber composition is preferably in the range of 0.1 parts by mass or more and 7 parts by mass or less, more preferably in the range of 0.5 to 5 parts by mass, and particularly preferably in the range of 1 to 4 parts by mass, per 100 parts by mass of the rubber component containing at least one type of conjugated diene polymer.

[0109] (Other compounding materials) The crosslinked rubber composition of the present embodiment may contain, in addition to a rubber component containing at least one type of conjugated diene polymer, carbon black, and sulfur, fillers other than carbon black, vulcanization aids, processing aids, vulcanization accelerators, process oils, antioxidants, liquid rubbers, foaming agents, and the like, as needed.

[0110] Fillers other than carbon black include, but are not limited to, silica-based inorganic fillers, calcium carbonate, titanium oxide, aluminum hydroxide, and clay. These may be used alone or in combination of two or more.

[0111] Examples of vulcanization aids include zinc oxide (ZnO) and magnesium oxide. These may be used alone or in combination of two or more. The amount of vulcanization aid added is preferably in the range of 1 to 20 parts by mass, more preferably 3 to 10 parts by mass, per 100 parts by mass of the rubber component containing at least one conjugated diene polymer.

[0112] Examples of processing aids include stearic acid, fatty acid esters, fatty acid amides, and hydrocarbon resins. These may be used alone or in combination of two or more. The amount of processing aid added is preferably in the range of 1 to 8 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component containing at least one conjugated diene polymer.

[0113] Examples of vulcanization accelerators include thiazole-based, sulfenamide-based, thiuram-based, aldehyde ammonia-based, aldehyde amine-based, guanidine-based, and thiourea-based vulcanization accelerators. These may be used alone or in combination of two or more. Among these, sulfenamide-based vulcanization accelerators are preferred from the viewpoint of crosslinking reactivity. The amount of vulcanization accelerator blended is preferably in the range of 0.5 to 7 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the rubber component containing at least one conjugated diene polymer.

[0114] Examples of sulfenamide vulcanization accelerators include N-oxydiethylene-2-benzothiazolylsulfenamide, N-cyclohexyl-2-benzothiazolylsulfenamide, Nt-butyl-2-benzothiazoylsulfenamide, and N,N'-dicyclohexyl-2-benzothiazoylsulfenamide.

[0115] Examples of the thiazole vulcanization accelerator include dibenzothiazyl disulfide, 2-mercaptobenzothiazole, 2-mercaptobenzothiazole sodium salt, and 2-mercaptobenzothiazole zinc salt.

[0116] Examples of thiuram vulcanization accelerators include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, and tetrabenzylthiuram disulfide.

[0117] It is preferable that the content of the sulfur-based vulcanizing agent as a crosslinking agent is in the range of 0.2 to 3 parts by mass relative to the total amount (100 parts by mass) of the rubber component containing at least one type of conjugated diene polymer in the crosslinked rubber composition of this embodiment, since this results in good vulcanization crosslinking.

[0118] Examples of antioxidants include carbamate-based antioxidants, phenylenediamine-based antioxidants, phenol-based antioxidants, diphenylamine-based antioxidants, quinoline-based antioxidants, imidazole-based antioxidants, and waxes. These may be used alone or in combination of two or more. The amount of antioxidant blended is preferably in the range of 1 to 10 parts by mass, more preferably 2 to 5 parts by mass, per 100 parts by mass of the rubber component containing at least one conjugated diene polymer.

[0119] Examples of process oils include naphthenic oils, paraffinic oils, aromatic oils, etc. The amount of process oil blended is preferably in the range of 1 to 50 parts by mass, more preferably 3 to 40 parts by mass, and particularly preferably 5 to 30 parts by mass, per 100 parts by mass of the rubber component containing at least one conjugated diene polymer.

[0120] Liquid rubber may be used as a softener instead of the process oil or in combination with the process oil. The liquid rubber is not particularly limited, but examples thereof include liquid polybutadiene and liquid styrene-butadiene rubber. The effect of adding liquid rubber is to improve the processability of a conjugated diene polymer composition containing a conjugated diene polymer and carbon black, etc., and also to shift the glass transition temperature of the conjugated diene polymer composition (rubber composition) to a lower temperature, which tends to improve the low-temperature properties of the vulcanized product.

[0121] The components listed above may be used alone or in combination of two or more.

[0122] The crosslinked rubber composition of the present embodiment can be obtained by subjecting the composition (rubber composition) obtained by blending the conjugated diene polymer obtained as described above with carbon black and the like to press vulcanization under predetermined conditions, thereby obtaining the desired crosslinked rubber composition.

[0123] (Application) The uses of the crosslinked rubber composition of the present embodiment are not particularly limited, but since it has excellent properties such as a low dynamic magnification and little deterioration in performance during repeated strain (improved dynamic magnification and performance stability), it can be suitably used in engine mounts, stabilizer bushings, suspension bushings, and the like used in automobiles, vibration-proof rubber, conveyor belts, transmission belts, hoses for industrial use and various other applications, and the like. [Example]

[0124] Hereinafter, the present embodiment will be described in more detail with reference to specific examples and comparative examples, but the present embodiment is not limited to the following examples and comparative examples.

[0125] The physical properties of the conjugated diene polymers used in the examples and comparative examples were measured by the following methods. [Styrene Content and Vinyl Bond Amount of Conjugated Diene Polymer] Using a conjugated diene polymer as a sample, the bound styrene content and the vinyl bond content were measured by 1H-NMR measurement. The conditions for 1H-NMR measurement are as follows: <Measurement conditions> Measuring equipment: JNM-LA400 (JEOL) Solvent: deuterated chloroform Measurement sample: Conjugated diene polymer Sample concentration: 50mg / mL Observation frequency: 400MHz Chemical shift standard: TMS (tetramethylsilane) is contained at 0.05% by mass relative to deuterated chloroform. Pulse delay: 2.904 seconds Number of scans: 64 Pulse width: 45° Measurement temperature: 26℃

[0126] [Weight average molecular weight Mw] The chromatogram was measured using a GPC measuring device with three columns connected together, each packed with a polystyrene gel, and the weight-average molecular weight Mw was determined based on a calibration curve using standard polystyrene. The specific measurement conditions are shown below. 20 μL of the following measurement solution was injected into the GPC measurement device and the measurement was carried out. (Measurement conditions) Device: Tosoh Corporation, product name "HLC-8320GPC" Eluent: 5mmol / L triethylamine in tetrahydrofuran (THF) Guard column: Tosoh Corporation's product name "TSKguardcolumn SuperH-H" Separation column: Tosoh Corporation product names "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" connected in this order. Oven temperature: 40°C Flow rate: 0.6mL / min Detector: RI detector (Tosoh Corporation, product name "HLC8020") Measurement solution: 10 mg of sample dissolved in 20 mL of THF

[0127] [Coupling ratio] When a conjugated diene polymer was obtained by a coupling reaction using a coupling agent, the coupling ratio (%) was determined when the total area of ​​the uncoupled and coupled portions was taken as 100. Coupling ratio (%) = [coupling area / total area] x 100

[0128] [Modification rate of conjugated diene polymer] The modification rate was measured by the column adsorption GPC method, utilizing the property of the modified polymer to be adsorbed onto a column, as follows. The amount of adsorption onto the silica-based column was measured by subtracting the chromatogram of a sample solution containing the sample and low-molecular-weight internal standard polystyrene measured using a column packed with polystyrene-based gel from the chromatogram measured using a column packed with silica-based gel, and the modification rate was calculated. (GPC measurement conditions using a polystyrene column) The GPC measurement conditions using a polystyrene column are as follows: 20 μL of the measurement solution below was injected into the GPC measurement device and the measurement was carried out. Device: Tosoh Corporation, product name "HLC-8320GPC" Eluent: THF containing 5mmol / L triethylamine Guard column: Tosoh Corporation's product name "TSKguardcolumn SuperH-H" Column: Tosoh Corporation product names "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" connected in this order Oven temperature: 40°C Flow rate: 0.6mL / min Detector: RI detector (Tosoh HLC8020) Measurement solution: 10 mg of sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a sample solution.

[0129] (GPC measurement conditions using a silica column) The conditions for GPC measurement using a silica column are as follows: 50 μL of the measurement solution below was injected into the GPC measurement device and measurement was carried out. Device: Tosoh Corporation, product name "HLC-8320GPC" Eluent:THF Guard column: GL Sciences product name "DIOL 4.6 x 12.5 mm 5 micron" Separation column: Agilent Technologies' Zorbax PSM-1000S, PSM-300S, and PSM-60S columns connected in this order Oven temperature: 40℃, Flow rate: 0.5mL / min Detector: RI detector (Tosoh HLC8020)

[0130] (Calculation method of denaturation rate) The total peak area of ​​the chromatogram using the polystyrene column was set to 100, the peak area of ​​the sample was set to P1, the peak area of ​​the standard polystyrene was set to P2, and the total peak area of ​​the chromatogram using the silica column was set to 100, the peak area of ​​the sample was set to P3, and the peak area of ​​the standard polystyrene was set to P4. The modification rate (%) was calculated using the following formula. Total denaturation rate (%) = [1-(P2 × P3) / (P1 × P4)] × 100 (However, P1+P2=P3+P4=100) When a nitrogen atom-containing coupling agent is used, the coupling portion is also modified. In this case, the modification rate (%) of the uncoupled portion was calculated using the following formula. Uncoupled portion modification rate (%) = Total modification rate (%) - Nitrogen atom-containing coupling amount (%)

[0131] [Mooney viscosity: ML] The Mooney viscosity was measured using a Mooney viscometer (trade name "VR1132" manufactured by Ueshima Seisakusho Co., Ltd.) in accordance with JIS K6300 (ISO289-1) and ISO289-4. The measurement temperature was 100°C. Here, the sample was preheated for 1 minute, and then the rotor was rotated at 2 rpm. The torque after 4 minutes was measured and used as the Mooney viscosity (ML(1+4)).

[0132] [Glass transition temperature: Tg] Measurements were performed using a conjugated diene polymer as a sample according to ISO 22768:2006. 10 mg of sample was placed in a dedicated aluminum pan, and a Hitachi High-Tech Science DSC7020 differential scanning calorimeter was used as the measurement device. The sample was heated from 30°C to 160°C at 20°C / min and held for 2 minutes, then cooled from 160°C to -120°C at 10°C / min. The DSC curve was recorded while the temperature was then increased from -120°C to 100°C at 10°C / min. The peak (inflection point) of the DSC differential curve resulting from the glass transition of the conjugated diene polymer when the temperature was increased from -120°C to 100°C was taken as the glass transition temperature.

[0133] [Tin content] The conjugated diene polymers obtained in the polymerization examples described below were subjected to elemental analysis using inductively coupled plasma (ICP, Inductive Coupled Plasma, manufactured by Shimadzu Corporation, instrument name: ICPS-8100) to measure the tin content (unit: ppm) in the polymers, and the total content was calculated.

[0134] [Evaluation of cold flow properties] The conjugated diene-based polymers containing stabilizers obtained in the examples and comparative examples described below were used as measurement samples. A load of 1 kg was applied to a sample of 40 mm × 40 mm × thickness (H0) 50 mm at 25°C, and the thickness (H60) after leaving the sample for 60 minutes was used to calculate the change in thickness (%) using the following formula. Thickness change rate (%) = (H0-H60) x 100 / H0 If the thickness change rate was 60% or less, there was no practical problem, and therefore it was rated as "good." If it exceeded 60%, cold flow during storage was severe, resulting in poor storage and handling properties, and therefore it was rated as "poor."

[0135] [Production of Conjugated Diene Polymer] (Sample 1) Conjugated diene polymer 1 <Polymerization of modified conjugated diene polymer> To an autoclave equipped with a stirrer were added 52,500 g of cyclohexane containing 150 ppm of tetrahydrofuran, 6,655 g of 1,3-butadiene, 205 g of styrene, and 0.030 mol of n-butyllithium, and polymerization was initiated at 40°C. The maximum temperature during the polymerization reaction from the start of polymerization was 79° C. Five minutes after the maximum temperature was reached, 2.9 g (0.85 times the molar amount relative to n-butyllithium) of 1,3-dimethyl-2-imidazolidinone was added. After reacting for 15 minutes, 9.6 g of methanol (or 0.1 times the molar amount relative to n-butyllithium) was added as a polymerization terminator to obtain a polymerization solution containing a modified conjugated diene rubber. To the polymerization solution, 0.15 parts of Irganox 1520 (manufactured by BASF) and 0.3 parts of 1076 (manufactured by ADEKA) were added as antioxidants per 100 parts of rubber content, and then steam stripping was performed by heating with steam to 85 to 98° C. After the solvent was removed, the crumbs were collected, sandwiched between stainless steel plates and compressed at 30° C. for dehydration, and then dried at a roll temperature of 110° C. to obtain modified conjugated diene polymer 1 (sample 1).

[0136] (Sample 2) Conjugated diene polymer 2 <Polymerization of modified conjugated diene polymer> To an autoclave equipped with a stirrer were added 52,500 g of cyclohexane containing 150 ppm of tetrahydrofuran, 6,860 g of 1,3-butadiene, and 0.030 mol of n-butyllithium, and polymerization was initiated at 40°C. The maximum temperature during the polymerization reaction from the start of polymerization was 81° C. Five minutes after the maximum temperature was reached, 2.2 g (0.50 times the molar amount relative to n-butyllithium) of 1,3-dimethyl-2-imidazolidinone was added. After reacting for 15 minutes, 9.6 g of methanol (or 0.1 times the molar amount relative to n-butyllithium) was added as a polymerization terminator to obtain a polymerization solution containing a modified conjugated diene rubber. To the polymerization solution, 0.15 parts of Irganox 1520 and 0.3 parts of Irganox 1076 were added as antioxidants relative to 100 parts of rubber content, and then steam stripping was performed under conditions of heating with steam to 85 to 98° C. After the solvent was removed, the crumbs were collected, sandwiched between stainless steel plates and compressed at 30° C. for dehydration, and then dried at a roll temperature of 110° C. to obtain modified conjugated diene polymer 2 (sample 2).

[0137] (Sample 3) Conjugated diene polymer 3 <Polymerization of modified conjugated diene polymer> A 15% by weight solution of 1,3-butadiene in n-hexane was continuously fed into a 10-liter polymerization vessel equipped with a stirring blade and jacket at the bottom at a rate of 300 ml / min. At the same time, 0.17 parts by weight of n-butyllithium per 100 parts by weight of monomer was continuously fed. Polymerization was carried out by stirring at a rotation speed of 150 rpm and a polymerization temperature of 90°C. The overflowing living polymer solution was introduced into a Noritake static mixer (18 elements). Just before the static mixer, an amount of methanol equivalent to the amount of lithium fed was added. To the above polymerization solution, 0.15 parts of Irganox 1520 and 0.3 parts of Irganox 1076 were added as antioxidants relative to 100 parts of rubber content, and then steam stripping was performed under conditions of heating with steam to 85 to 98° C. After removing the solvent, the crumbs were collected, sandwiched between stainless steel plates and compressed at 30° C. for dehydration, and then dried at a roll temperature of 110° C. to obtain modified conjugated diene polymer 3 (sample 3).

[0138] (Sample 4) Conjugated diene polymer 4 <Polymerization of modified conjugated diene polymer> To an autoclave equipped with a stirrer were added 52,500 g of cyclohexane containing 150 ppm of tetrahydrofuran, 6,860 g of 1,3-butadiene, and 0.036 mol of n-butyllithium, and polymerization was initiated at 40°C. The maximum temperature during the polymerization reaction from the start of polymerization was 83°C. Five minutes after reaching the maximum temperature, 0.92 g (0.07 times the molar amount relative to n-butyllithium) of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane was added as a modifier and allowed to react for 5 minutes. Then, 3.8 g (0.85 times the molar amount relative to n-butyllithium) of 1,3-dimethyl-2-imidazolidinone was added. After reacting for 15 minutes, 11.5 g of methanol (or 0.1 times the molar amount relative to n-butyllithium) was added as a polymerization terminator to obtain a polymerization solution containing a modified conjugated diene polymer. To the above polymerization solution, 0.15 parts of Irganox 1520 and 0.3 parts of Irganox 1076 were added as antioxidants relative to 100 parts of rubber content, and then steam stripping was performed under conditions of heating with steam to 85 to 98° C. After the solvent was removed, the crumbs were collected, sandwiched between stainless steel plates and compressed at 30° C. for dehydration, and then dried at a roll temperature of 110° C. to obtain modified conjugated diene polymer 4 (sample 4).

[0139] (Sample 5) Conjugated diene polymer 5 <Polymerization of modified conjugated diene polymer> To an autoclave equipped with a stirrer were added 52,500 g of cyclohexane containing 150 ppm of tetrahydrofuran, 6,860 g of 1,3-butadiene, and 0.033 mol of n-butyllithium, and polymerization was initiated at 40°C. The maximum temperature during the polymerization reaction from the start of polymerization was 79°C. Five minutes after reaching the maximum temperature, 0.60 g (0.05 times the molar amount relative to n-butyllithium) of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane was added as a modifier and allowed to react for 5 minutes. Then, 4.2 g (0.85 times the molar amount relative to n-butyllithium) of 1,3-dimethyl-2-imidazolidinone was added. After reacting for 15 minutes, 10.5 g of methanol (or 0.1 times the molar amount relative to n-butyllithium) was added as a polymerization terminator to obtain a polymerization solution containing a modified conjugated diene polymer. To the above polymerization solution, 0.15 parts of Irganox 1520 and 0.3 parts of Irganox 1076 were added as antioxidants relative to 100 parts of rubber content, and then steam stripping was performed under conditions of heating with steam to 85 to 98° C. After removing the solvent, the crumbs were collected, sandwiched between stainless steel plates and compressed at 30° C. for dehydration, and then dried at a roll temperature of 110° C. to obtain modified conjugated diene polymer 5 (sample 5).

[0140] (Sample 6) Conjugated diene polymer 6 <Polymerization of modified conjugated diene polymer> To an autoclave equipped with a stirrer were added 52,500 g of cyclohexane, 6,860 g of 1,3-butadiene, and 0.035 mol of n-butyllithium, and polymerization was initiated at 40°C. The maximum temperature during the polymerization reaction from the start of polymerization was 79°C. Five minutes after reaching the maximum temperature, 0.27 g of tetramethoxysilane (0.05 times the molar amount relative to n-butyllithium) was added as a modifier and allowed to react for 5 minutes. Then, 3.4 g of 1,3-dimethyl-2-imidazolidinone (0.85 times the molar amount relative to n-butyllithium) was added. After reacting for 15 minutes, 11.2 g of methanol (or 0.1 times the molar amount relative to n-butyllithium) was added as a polymerization terminator to obtain a polymerization solution containing a modified conjugated diene polymer. To the above polymerization solution, 0.15 parts of Irganox 1520 and 0.3 parts of Irganox 1076 were added as antioxidants relative to 100 parts of rubber content, and then steam stripping was performed under conditions of heating with steam to 85 to 98° C. After removing the solvent, the crumbs were collected, sandwiched between stainless steel plates and compressed at 30° C. for dehydration, and then dried at a roll temperature of 110° C. to obtain modified conjugated diene polymer 6 (sample 6).

[0141] (Sample 7) Conjugated diene polymer 7 <Polymerization of modified conjugated diene polymer> To an autoclave equipped with a stirrer were added 52,500 g of cyclohexane, 6,860 g of 1,3-butadiene, and 0.032 mol of n-butyllithium, and polymerization was initiated at 40°C. The maximum temperature during the polymerization reaction from the start of polymerization was 79°C. Five minutes after reaching the maximum temperature, 0.24 g of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (0.03 times the molar amount relative to n-butyllithium) was added as a modifier and allowed to react for 5 minutes. Then, 3.1 g of 1,3-dimethyl-2-imidazolidinone (0.85 times the molar amount relative to n-butyllithium) was added. After reacting for 15 minutes, 1 g of methanol (or 1 molar amount relative to n-butyllithium) was added as a polymerization terminator to obtain a polymerization solution containing a modified conjugated diene polymer. To the above polymerization solution, 0.15 parts of Irganox 1520 and 0.3 parts of Irganox 1076 were added as antioxidants relative to 100 parts of rubber content, and then steam stripping was performed under conditions of heating with steam to 85 to 98° C. After removing the solvent, the crumbs were collected, sandwiched between stainless steel plates and compressed at 30° C. for dehydration, and then dried at a roll temperature of 110° C. to obtain modified conjugated diene polymer 7 (sample 7).

[0142] (Samples 8-10) Conjugated diene polymers 8-10 <Polymerization of modified conjugated diene polymer> Modified conjugated diene polymers 8 to 10 (samples 8 to 10) were obtained in the same manner as sample 8, except that the amount of n-butyllithium and the amount of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane added were changed to the amounts shown in the table below.

[0143] [Table 1]

[0144] (Sample 11) Conjugated Diene Polymer 11 <Polymerization of modified conjugated diene polymer> To an autoclave equipped with a stirrer were added 52,500 g of cyclohexane, 6,860 g of 1,3-butadiene, and 0.034 mmol of n-butyllithium, and polymerization was initiated at 40°C. The maximum temperature during the polymerization reaction from the start of polymerization was 79°C. Five minutes after reaching the maximum temperature, 0.36 g of tin tetrachloride (0.03 times the molar amount relative to n-butyllithium) was added as a modifier and allowed to react for 10 minutes. Then, 1.9 g of 1,3-dimethyl-2-imidazolidinone (0.5 times the molar amount relative to n-butyllithium) was added. After reacting for 15 minutes, 1 g of methanol (or 1 molar amount relative to n-butyllithium) was added as a polymerization terminator to obtain a polymerization solution containing a modified conjugated diene polymer. To the polymerization solution, 0.15 parts of Irganox 1520 and 0.3 parts of Irganox 1076 were added as antioxidants relative to 100 parts of rubber content, and then steam stripping was performed under conditions of heating with steam to 85 to 98° C. After the solvent was removed, the crumbs were collected, sandwiched between stainless steel plates and compressed at 30° C. for dehydration, and then dried at a roll temperature of 110° C. to obtain modified conjugated diene polymer 11 (sample 11). The physical properties of Sample 1 (conjugated diene copolymer 1) to Sample 11 are shown in Tables 2 and 3.

[0145] [Table 2]

[0146] [Table 3]

[0147] The materials used in the examples and comparative examples are as follows. [Rubber component] Natural rubber (RSS#3) High-cis polybutadiene (UBE product name U150) Conjugated diene polymers (samples 1-6) [Combined ingredients] Filler: Carbon black (manufactured by Tokai Carbon Co., Ltd., "Seast KH (N550)") Filler: Silica (Evonik, Degussa product name "Ultrasil 7000GR") Silane coupling agent: (Evonik, Degussa brand name "Si75", bis(triethoxysilylpropyl) disulfide) Softener: Oil (JXTG Energy, PF30) Vulcanization aid: Zinc oxide (Mitsui Mining & Smelting Co., Ltd., zinc oxide type 2) Processing aid: Stearic acid (Kao Corporation, Lunac S-90V) Anti-aging agent: (Ouchi Shinko Co., Ltd., Nocrac 6C) Anti-aging agent: (Ouchi Shinko Co., Ltd., Nocrac MB) Anti-aging agent: WAX (Ouchi Shinko Chemical Industry Co., Ltd., Sunnock) Vulcanization accelerator: (Sansera NS-G, manufactured by Sanshin Chemical Industry Co., Ltd.) ·sulfur

[0148] [Proportion of ingredients] Tables 4 to 6 show the proportions of each compounding agent. [Table 4]

[0149] The volume fraction of carbon black at this time was 17.6%. [Table 5]

[0150] The volume fraction of carbon black at this time was 11.4%. [Table 6]

[0151] The volume fraction of silica at this time is 18.3%.

[0152] Example 1 In a Labo Plastomill (model: 10C100) manufactured by Toyo Seiki Seisakusho Co., Ltd. and a Banbury mixer (model: B600, capacity: 600 cc), 60 parts by mass of natural rubber (NR) and 40 parts by mass of conjugated diene polymer 1 (sample 1) were masticated for 180 seconds at a starting temperature of 5°C. Next, 50 parts by mass of carbon black (N550), process oil (PF30), 1.0 part by mass of stearic acid, 5.0 parts by mass of zinc oxide, and 2.0 parts by mass of Nocrac 6C, 1.0 part by mass of Nocrac MB, and 2.0 parts of WAX (Sunnock) were added as antioxidants, and the mixture was mixed for another 4 minutes, after which the rubber mixture was discharged from the mixer. The temperature of the rubber mixture at the end of mixing was 125°C. The above kneaded material was mixed with 2.5 parts of sulfur and 1.5 parts of a vulcanization accelerator (Suncerer NS-G) using an open roll (6-inch roll manufactured by Kansai Roll Co., Ltd.) at 75°C, and then a sheet-shaped rubber composition was taken out. The processability of this unvulcanized rubber composition was not particularly problematic. The unvulcanized rubber composition was press-crosslinked at 160°C for 20 minutes to prepare a test piece of the crosslinked rubber composition, and the hardness, tensile strength characteristics, compression set, static spring constant, dynamic spring constant, dynamic magnification, and storage modulus G' were measured. The results are shown in Table 7.

[0153] Comparative Example 1 Test pieces of the crosslinked rubber composition were prepared in the same manner as in Example 1, except that the conjugated diene polymer 1 (sample 1) was changed to high-cis polybutadiene U150, and various measurements were carried out. The results are shown in Table 7.

[0154] [Examples 2 to 5, 8 to 10, Comparative Examples 2, 4 to 5] Test pieces of crosslinked rubber compositions were prepared and various measurements were carried out in the same manner as in Example 1, except that the type of conjugated diene polymer was changed to that shown in Table 4. The results are shown in Table 7.

[0155] [Examples 6 and 7, Comparative Example 3] Test pieces of the crosslinked rubber composition were prepared in the same manner as in Example 1, except that the type of conjugated diene polymer and the amount of carbon black were changed to 30 parts by mass per 100 parts by mass of the rubber component, and various measurements were carried out. The results are shown in Table 8.

[0156] Comparative Examples 6 to 8 Except for changing the carbon black filler to silica, test pieces of the crosslinked rubber composition were prepared in the same manner as in Example 1, and various measurements were carried out. The results are shown in Table 9.

[0157] The crosslinked rubber compositions of the Examples and Comparative Examples thus obtained were subjected to various measurements and evaluations according to the following standards.

[0158] [Storage modulus G', Payne effect ΔG', repeated measurements of storage modulus] Using an Anton Paar viscoelasticity testing machine (Main Unit MCR102 + Unit EVU20), the storage modulus G' (strain 0.1%) measured at a temperature of 50°C and a frequency of 10 Hz in torsion mode was used, and the difference between the storage modulus G' (strain 0.1%) measured at a strain of 0.1% and the storage modulus G' (strain 10%) measured at a strain of 10% was calculated as ΔG' = G' (strain 0.1%) - G' (strain 10%), and this was taken as the Payne effect. For the same volume fraction of carbon black, a lower Payne effect value indicates better dispersion of the carbon black. The storage modulus was measured twice on the test specimen after the above measurement (after strain). The change rates at 0.1% strain and 10% strain were calculated from the difference between the storage modulus G' (0.1% strain) and G' (10% strain) measured in the first measurement. Difference between two repeated measurements G' (0.1% strain) = 1st measurement G' - 2nd measurement G' Difference between two repeated measurements G' (10% strain) = 1st measurement G' - 2nd measurement G' G' change rate = (difference between two repeated measurements of G' (strain 0.1%) / first measurement of G') x 100 G' change rate = (difference between two repeated measurements of G' (10% strain) / first measurement of G') x 100 The smaller the rate of change, the smaller the change in performance and the better.

[0159] [Tensile properties, rate of decrease in breaking strength, rate of decrease in breaking elongation, hardness] Each unvulcanized rubber composition was press-molded at 160°C for 20 minutes and punched out with a JIS No. 5 dumbbell to prepare a 2 mm thick tensile test piece. The modulus 100% (M100), strength at break (Tb), elongation at break (Eb), and hardness (Hs: JIS A) were measured using these tensile test pieces in accordance with JIS K6251. The tensile test pieces having a thickness of 2 mm were punched out using the JIS No. 5 dumbbell and heated in an environment of 100°C for 24 hours, after which the breaking strength (Tb) and breaking elongation (Eb) were measured. The rate of decrease in the breaking strength (Tb) and breaking elongation (Eb) after heating relative to the breaking strength (Tb) and breaking elongation (Eb) before heating was calculated. The smaller the rate of decrease, the better the results.

[0160] [Compression set] According to JIS K6262, the compression set was measured after heating for 24 hours in an environment of 100°C. The smaller the compression set value, the better the performance.

[0161] [Static spring constant, dynamic spring constant, dynamic magnification] The static spring constant and dynamic spring constant of the crosslinked rubber composition were measured in accordance with JIS K6385, and the dynamic spring ratio (dynamic spring constant / static spring constant) was calculated. The measurement equipment used was ACUMEN3 manufactured by MTS. (Static spring constant: Ks) Each unvulcanized rubber composition was pressed under vulcanization conditions of 120°C x 20 minutes to prepare a cylindrical cross-linked rubber composition (diameter 50 mm, height 25 mm), and then a pair of disk-shaped metal fittings (diameter 60 mm, thickness 6 mm) was attached to the top and bottom of the cross-linked rubber composition with an adhesive to prepare a test piece. Next, the test piece was compressed 7 mm in the cylindrical axial direction, and the loads at deflections of 1.5 mm and 3.5 mm were read from the load-deflection curve of the second forward movement to calculate the static spring constant (Ks). (Dynamic spring constant: Kd100) The test piece was compressed by 2.5 mm in the axial direction of the cylinder, and a constant displacement harmonic compression vibration with an amplitude of 0.05 mm was applied from below with a frequency of 100 Hz, centered at the position of this 2.5 mm compression. The dynamic load was detected by a load cell above, and the dynamic spring constant (Kd100) was calculated and measured. (Dynamic magnification: Kd100 / Ks) The dynamic magnification was calculated as the dynamic spring constant (Kd100) / static spring constant (Ks). The lower the dynamic magnification, the better the vibration-damping properties.

[0162] [Table 7]

[0163] The results in Table 7 above show that the crosslinked rubber composition of the example containing 50 parts of carbon black (volume fraction: 17.6%) has a lower dynamic magnification and is superior in vibration-proof rubber properties than the crosslinked rubber composition of the comparative example, and is also superior in the rate of decrease in breaking strength and breaking elongation after heating and in compression set properties.

[0164] [Table 8]

[0165] The results in Table 8 above show that the crosslinked rubber composition of the example containing 30 parts of carbon black (volume fraction: 11.4%) has a lower dynamic magnification and is superior in vibration-proof rubber properties than the crosslinked rubber composition of the comparative example, and is also superior in the rate of decrease in breaking strength and breaking elongation after heating and in compression set properties.

[0166] [Table 9]

[0167] The results in Table 9 above show that the crosslinked rubber composition of the comparative example, which contains 50 parts of silica (volume fraction is 18.3%), has a high dynamic magnification and poor vibration-proof rubber properties, and is poor in the rate of decrease in breaking strength and breaking elongation after heating and in the compression set properties, compared to the crosslinked rubber compositions of the examples. [Industrial Applicability]

[0168] The crosslinked rubber composition of the present invention has industrial applicability as a forming material for engine mounts, stabilizer bushings, suspension bushings, etc. used in automobiles and the like, anti-vibration rubber, conveyor belts, power transmission belts, hoses for industrial and various uses, vibration dampers for computer hard disks, vibration dampers for general home appliances such as washing machines, and vibration dampers and seismic isolation devices such as architectural seismic damping walls and vibration dampers in the construction and housing fields.

Claims

1. A crosslinked rubber composition comprising a rubber component containing at least one conjugated diene-based polymer, carbon black, and sulfur, Storage modulus after strain ΔG' = G' (strain 0.1%) - G' (strain 10%) is 3.0 MPa or less and When the storage modulus after strain calculated by the following formula is measured twice, the difference in the storage modulus G' (strain 0.1%) is 0.4 MPa or less, and the difference in the storage modulus G' (strain 10%) is 0.2 MPa or less, and A crosslinked rubber composition in which, when the storage modulus after strain is repeatedly measured twice, the rate of change in storage modulus G' at a strain of 0.1% and a strain of 10% is 6.0% or less. Difference between two repeated measurements G' (strain 0.1%) = 1st measurement G' - 2nd measurement G' Difference between two repeated measurements G' (strain 10%) = 1st measurement G' - 2nd measurement G' G' change rate = (difference between G' measured twice (strain 0.1%) / G' measured once) x 100 G' change rate = (difference between G' measured twice (strain 10%) / G' measured once) x 100

2. 2. The crosslinked rubber composition according to claim 1, wherein the volume fraction of said carbon black in the crosslinked rubber composition is 7 to 30 vol %.

3. 3. The crosslinked rubber composition according to claim 1, wherein the conjugated diene polymer has a glass transition temperature of -110°C to -80°C.

4. 3. The crosslinked rubber composition according to claim 1, wherein the amount of 1,2-vinyl bonds in the conjugated diene monomer units of the conjugated diene polymer is 10 mol % or more and 25 mol % or less.

5. The crosslinked rubber composition according to claim 1 or 2, wherein the content of aromatic vinyl monomer units in the conjugated diene polymer is 0% by mass or more and 7% by mass or less.

6. 3. The crosslinked rubber composition according to claim 1, wherein the conjugated diene polymer is a modified conjugated diene polymer obtained by reacting a modifying agent having at least one >C=O group and at least one substituted amino group in the molecule that reacts with the active terminal, or a modified conjugated diene polymer obtained by reacting a nitrogen atom-containing coupling agent having four or more non-halogen functional groups in one molecule that react with the active terminal, and a modifying agent having at least one >C=O group and at least one substituted amino group in the molecule that reacts with the active terminal.

7. 3. The crosslinked rubber composition according to claim 1, wherein the modified conjugated diene polymer obtained by reacting with a modifying agent having at least one >C=O group and at least one substituted amino group in the molecule that reacts with the active terminal has a modification rate measured by column adsorption GPC of 50% or more and 99% or less.

8. 7. The crosslinked rubber composition according to claim 6, wherein the coupling ratio of the modified conjugated diene polymer with a nitrogen atom-containing coupling agent having four or more functional groups per molecule that react with the non-halogen active terminal is 7% or more and 25% or less.

9. 7. The crosslinked rubber composition according to claim 6, wherein the coupling ratio of the modified conjugated diene polymer with a nitrogen atom-containing coupling agent having four or more functional groups per molecule that react with the non-halogen active terminal is 7% or more and 15% or less.

10. The crosslinked rubber composition according to claim 1 or 2, wherein the conjugated diene polymer has a tin content of 20 ppm or less.

11. 3. The crosslinked rubber composition according to claim 1, wherein the filler in the crosslinked rubber composition is carbon black alone.

12. A vibration-isolating rubber comprising the crosslinked rubber composition according to claim 1 or 2.

13. A power transmission belt and a conveyor belt comprising the crosslinked rubber composition according to claim 1 or 2.

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