Rubber composition for crawler

Abstract

To obtain a rubber composition for a crawler excellent in balance of wear resistance, flex crack resistance, chipping resistance, and heat resistance.SOLUTION: The rubber composition for a crawler contains 100 pts.mass of a rubber component containing a hydrogenated conjugated diene polymer and 30 pts.mass or more of carbon black. The hydrogenated conjugated diene polymer has a hydrogenation rate of 1-99% and an aromatic vinyl monomer unit content of 0-40 mass% and has an amine-modified group at a polymer chain terminal.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for crawlers. [Background technology]

[0002] Crawlers for construction and agricultural machinery often travel on rough roads while supporting heavy loads, so improvements in abrasion resistance, chipping resistance, and resistance to flex crack growth are always required. In addition, depending on the application, high-temperature working environments are expected, so the heat resistance of crawlers is also an important property that affects the product lifespan. These abrasion resistance, chipping resistance, flex crack resistance, and heat resistance are all linked to the product lifespan, and improving them can also contribute to reducing the frequency of crawler replacement, which is a tedious task.

[0003] To meet the above-mentioned required characteristics, natural rubber, emulsion SBR, and high-cis polybutadiene have conventionally been used as raw rubber materials for general rubber crawlers (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-145137 Summary of the Invention [Problem to be solved by the invention]

[0005] However, rubber crawlers made from natural rubber, emulsion SBR, and polybutadiene rubber, which have many unsaturated bonds, are excellent in terms of abrasion resistance and resistance to flex crack growth, but they have not yet achieved sufficient heat resistance and chipping resistance, and there is a problem in that there is room for improvement in terms of the balance of all properties.

[0006] Therefore, an object of the present invention is to provide a rubber composition for crawlers that has an excellent balance of properties including abrasion resistance, flex crack growth resistance, chipping resistance, and heat resistance. [Means for solving the problem]

[0007] As a result of extensive research and investigation into solving the problems of the prior art described above, the present inventors have found that a rubber composition for crawlers, which has a specified hydrogenation rate and aromatic vinyl monomer unit content and contains specified amounts of a hydrogenated conjugated diene polymer having a specified modifying group and carbon black, can solve the problems of the prior art described above, and have thus completed the present invention. That is, the present invention is as follows.

[0008] [1] 100 parts by mass of a rubber component containing a hydrogenated conjugated diene polymer; 30 parts by mass or more of carbon black; A rubber composition for crawlers comprising: The hydrogenated conjugated diene polymer has a hydrogenation rate of 1 to 99%, an aromatic vinyl monomer unit content of 0 to 40 mass%, and an amine-modified group at a polymer chain terminal. Rubber composition for crawlers. [2] the rubber component consists solely of the hydrogenated conjugated diene polymer, The rubber composition for crawlers according to [1] above. [3] The rubber component further contains natural rubber. The rubber composition for crawlers according to [1] above. [4] The rubber component further contains natural rubber and high-cis butadiene. The rubber composition for crawlers according to [1] or [3] above. [5] Further containing N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (6PPD) as an antioxidant. The rubber composition for crawlers according to any one of [1] to [4]. [6] The content of the N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (6PPD) is 5 parts by mass or less per 100 parts by mass of the rubber component, The rubber composition for crawlers according to [5] above. [Effects of the Invention]

[0009] According to the present invention, a rubber composition for crawlers having an excellent balance of abrasion resistance, flex crack resistance, chipping resistance, and heat resistance can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. It should be noted that the following embodiments are merely examples for explaining the present invention, and the present invention is not limited to the following embodiments. The present invention can be practiced by appropriately modifying it within the scope of its gist.

[0011] [Rubber composition for crawlers] The rubber composition for crawlers of this embodiment is 100 parts by mass of a rubber component containing a hydrogenated conjugated diene polymer; 30 parts by mass of carbon black; Contains: The hydrogenated conjugated diene polymer has a hydrogenation rate of 1 to 99%, an aromatic vinyl monomer unit content of 0 to 40 mass%, and an amine-modified group at the polymer chain end. By having the above-mentioned constitution, it is possible to obtain a rubber composition for crawlers that has an excellent balance of abrasion resistance, flex crack resistance, chipping resistance, and heat resistance.

[0012] (rubber component) The rubber composition for a crawler of the present embodiment contains a rubber component, and the rubber component contains a hydrogenated conjugated diene-based polymer.

[0013] (Hydrogenated conjugated diene polymer) The hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment contains structural units derived from conjugated diene compounds (hereinafter also referred to as "conjugated diene monomer units"), and may contain structural units derived from aromatic vinyl compounds (hereinafter also referred to as "aromatic vinyl monomer units").

[0014] Examples of 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 may be used alone or in combination of two or more. 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 may be used alone or in combination of two or more.

[0015] <Hydrogenation rate> The hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment is a conjugated diene polymer to which hydrogen has been added. In this specification, the percentage (molar ratio) of hydrogenated conjugated diene monomer units relative to the total amount of conjugated diene monomer units in the conjugated diene polymer is referred to as the hydrogenation rate. The hydrogenation rate can be measured by the method described in the Examples below. From the viewpoint of the abrasion resistance and heat resistance of the rubber composition for crawlers of this embodiment, the hydrogenation rate of the hydrogenated conjugated diene polymer used in the rubber composition for crawlers is 1% or more, and from the same viewpoint, it is preferably 60% or more, more preferably 70% or more, and even more preferably 75% or more. Furthermore, from the viewpoint of compatibility and co-crosslinkability with natural rubber and high-cis polybutadiene, it is undesirable for the degree of unsaturation (hydrogenation rate) to differ significantly from that of other rubbers in the rubber composition. When a rubber composition for crawlers is produced using a hydrogenated conjugated diene polymer with an excessively high hydrogenation rate and natural rubber, the poor co-crosslinkability tends to make it difficult to benefit from the excellent ozone resistance of the hydrogenated conjugated diene rubber. From the above viewpoints, the hydrogenation rate of the conjugated diene polymer is 99% or less, preferably 90% or less, and more preferably 85% or less.

[0016] <Aromatic vinyl monomer unit content> The hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment may contain aromatic vinyl monomer units, and from the viewpoint of the chipping resistance of the rubber composition for crawlers of this embodiment, the content of aromatic vinyl monomer units is preferably more than 0 mass%, more preferably 5 mass% or more, even more preferably 10 mass% or more, even more preferably 20 mass% or more, and even more preferably 30 mass% or more. In addition, from the viewpoint of the abrasion resistance of the rubber composition for crawlers of this embodiment, the content of aromatic vinyl monomer units is 40 mass% or less, preferably 20 mass% or less, more preferably 15 mass% or less, and even more preferably 10 mass% or less. The content of the aromatic vinyl monomer unit can be measured by the method described in the Examples below, and can be controlled within the above-mentioned range by adjusting the amount of the aromatic vinyl compound added during polymerization.

[0017] <1,2-vinyl bond content> The 1,2-vinyl bond content in the hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment is the molar ratio of the 1,2-vinyl bond content based on the content of the conjugated diene monomer units. Of the 1,2-vinyl bonds and 1,4-bonds of the conjugated diene monomer units, hydrogenation is carried out preferentially with the 1,2-vinyl bond. Therefore, when the hydrogenation rate is less than the 1,2-vinyl bond content, the hydrogenated conjugated diene polymer contains a mixture of 1,2-vinyl bonds and saturated 1,2-vinyl bonds, whereas when the hydrogenation rate is equal to or greater than the 1,2-vinyl bond content, the hydrogenated conjugated diene polymer contains only saturated 1,2-vinyl bonds. From the viewpoint of productivity of the hydrogenated conjugated diene polymer, the total amount of 1,2-vinyl bonds and saturated 1,2-vinyl bonds is preferably 13 mol % or more, and more preferably 20 mol % or more. On the other hand, as the total amount of 1,2-vinyl bonds and saturated 1,2-vinyl bonds increases, the Tg of the conjugated diene polymer increases. Therefore, from the viewpoint of abrasion resistance, the total amount is preferably 50 mol% or less, more preferably 45 mol% or less, and even more preferably 40 mol% or less. The amount of 1,2-vinyl bond and the amount of saturated 1,2-vinyl bond are, respectively, 1 It can be measured by H-NMR, specifically by the method described in the Examples. 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.

[0018] (modified polymer) The hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment is a modified polymer having an amine-modifying group at the polymer chain end. In this specification, a hydrogenated conjugated diene polymer modified with a nitrogen-containing compound is referred to as a modified polymer.

[0019] 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 the above-mentioned nitrogen atom-containing coupling agent, a method reacting a non-coupling nitrogen-containing compound with the reaction terminal, and a method of modifying the double bond of a conjugated diene polymer after polymerization by reacting a nitrogen-containing compound with the double bond.

[0020] 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.

[0021] Furthermore, examples of non-coupling nitrogen-containing compounds include, but are not limited to, 1,3-diethyl-2-imidazolinone, 1,3-dimethyl-2-imidazolinone, 1,3-dipropyl-2-imidazolinone, 1-methyl-3-ethyl-2-imidazolinone, 1-methyl-3-propyl-2-imidazolinone, 1-methyl-3-butyl-2-imidazolinone, 1,3-dihydro-1,3-dimethyl-2H-imidazol-2-one, N-methyl-2-pyrrolidone, 1-phenyl-2-pyrrolidone, and N-methyl-ε-caprolactam.

[0022] By having an amine-modified group at the end of the polymerization chain of the hydrogenated conjugated diene polymer, the dispersibility of carbon black in the crawler composition of this embodiment is improved, and the filler is dispersed more uniformly. As a result, the flex crack growth resistance of the crawler rubber composition of this embodiment tends to be improved.

[0023] <Degeneration rate> In this specification, unless otherwise specified, the "modification ratio" represents the mass ratio of the polymer having a nitrogen atom-containing functional group to the total amount of the hydrogenated conjugated diene polymer. For example, when a nitrogen atom-containing modifying agent is reacted with the terminal end of a polymer, the mass ratio of the polymer having a nitrogen atom-containing functional group due to the nitrogen atom-containing modifying agent to the total amount of the polymer is expressed as the modification rate. As mentioned above, the nitrogen atom-containing coupling agent is also included in the nitrogen atom-containing modifying agent. On the other hand, when a polymer is branched using a branching agent containing a nitrogen atom, the resulting copolymer will also have a nitrogen atom-containing functional group, and therefore this branched polymer will also be counted as a polymer having a nitrogen atom-containing functional group when calculating the modification rate. 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 formed by a nitrogen atom-containing modifying agent and a branched polymer formed by a branching agent having a nitrogen atom-containing functional group, and the total mass ratio of these is the "modification rate."

[0024] From the viewpoint of flex crack growth resistance, the hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment preferably has a modification rate (hereinafter also simply referred to as "modification rate") measured by the column adsorption GPC method described below, relative to the total amount of the hydrogenated conjugated diene copolymer, of 40% or more, more preferably 60% or more, and even more preferably 70% or more. On the other hand, from the viewpoint of easing the difficulty of removing impurities during polymerization and increasing productivity, the modification rate is preferably 99% or less, more preferably 97% or less, even more preferably 95% or less, and even more preferably 93% or less. 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.

[0025] The modification rate of the hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment can be measured, for example, by chromatography, which can separate functional group-containing modified components from unmodified components. Examples of methods using this type of chromatography include a method in which a gel permeation chromatography column filled with a polar substance such as silica that adsorbs specific functional groups is used, and the non-adsorbed components are quantified using an internal standard for comparison (column adsorption GPC method). 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. More specifically, the modification rate can be measured by the method described in the Examples. The modification rate of the hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment can be controlled within the above numerical range, for example, by controlling the amount of the modifier added and the polymerization reaction temperature to suppress deactivation of the active terminals.

[0026] <Glass transition temperature> The glass transition temperature of the hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment is preferably −40° C. or lower, more preferably −45° C. or lower, and even more preferably −50° C. or lower, from the viewpoint of abrasion resistance. The glass transition temperature can be measured by differential scanning calorimetry (DSC), specifically by the method described in the examples below. The glass transition temperature can be controlled by adjusting the ratio of conjugated diene monomer units to aromatic vinyl monomer units in the hydrogenated conjugated diene polymer, the amount of 1,2-vinyl bonds, and the hydrogenation rate, and the amount of 1,2-vinyl bonds can be controlled by adjusting the amount of polar substance added during polymerization and the polymerization temperature.

[0027] <Coupling polymer> The hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment may be a coupling 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 reactive compound (hereinafter also referred to as a "coupling agent"). 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, which is a coupled polymer.

[0028] Examples of coupling agents include, but are not limited to, 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 atom-containing coupling agents can also be used as modifiers, which will be described later.

[0029] Specific examples of the coupling agent 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.

[0030] 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.

[0031] Furthermore, examples thereof include, but are not limited to, 2-[3-(trimethoxysilyl)propyl]-1,3-dimethylimidazolidinone, 2-[3-(trimethoxysilyl)propyl]-1,3-(bistrimethylsilyl)imidazolidinone, 2-(diethoxydiethylsilyl)-1,3-diethylimidazolidinone, 2-(triethoxysilyl)-1,4-diethylpiperazine, 2-(dimethoxymethylsilyl)-1,4-dimethylpiperazine, 5-(triethoxysilyl)-1,3-dipropylhexahydropyrimidine, 5-(dieth ...ethylhexahydropyrimidine, 5-(diethoxysilyl)-1,3-dipropylhexahydropyrimidine, 5-(diethoxysilyl)-1,3-diethylhexahydropyrimidine, 5-(diethoxysilyl)-1,3-diethylhexahydropyrimidine, 5-(diethoxysilyl)-1,3-diethylhexahydropyrimidine, 5-(diethoxysilyl)-1,3-diethylhexahydropyrimidine, 5-(diethoxysilyl)-1 {2-[3-(2-dimethylaminoethyl)-2-(ethyldimethoxysilyl)-imidazolidinone-1-yl]-ethyl}-dimethylamine, 5-(trimethoxysilyl)-1,3-bis-(2-methoxyethyl)-hexahydropyrimidine, 5-(ethyldimethoxysilyl)-1,3-bis-(2-trimethylsilylethyl)-hexahydropyrimidine-1,3-dimethylimidazolidinone, 2-(3-diethoxyethylsilyl-propyl)-1,3-diethylimidazolidinone Non, 2-(3-triethoxysilyl-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)-imidazolidinon-1-yl]-ethyl}-dimethylamine, 5-(3-trimethoxysilyl-propyl)-1,4-diethylpiperazine, 5-(3-triethoxysilyl-propyl)-1,3-dipropylhexahydropyrimidine, 5-(3-diethoxyethylsilyl-propyl)-1,3-diethylhexahydropyrimidine, {2-[3-(2-dimethylaminoethyl)-2-(3-ethyldimethoxysilyl-propyl)-imidazolidinon-1-yl]-ethyl}-dimethylamine, 2-(Diethoxyethylsilyl)-1,3-bis(triethylsilyl)imidazolidinone, 2-(Diethoxyethylsilyl)-1,4-bis(trimethylsilyl)piperazine, 2-(Dimethoxymethylsilyl)-1,4-bis(trimethylsilyl)piperazine, 2-(Diethoxy ...Examples include 4-bis(trimethylsilyl)piperazine and 5-(triethoxysilyl)-1,3-bis(tripropylsilyl)hexahydropyrimidine.

[0032] 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.

[0033] 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.

[0034] 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-methylimidazolidinone, 1-[3-(diethoxysilyl)propyl]-3-ethylimidazolidinone, 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]imidazolidinone, (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)imidazolidinone, 2-(trimethoxysilanilide

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

[0035] (Method for producing hydrogenated conjugated diene polymer) The hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment is obtained by adding hydrogen gas to a conjugated diene polymer obtained by carrying out a polymerization step in which a conjugated diene compound and, if necessary, an aromatic vinyl compound are polymerized using a predetermined polymerization initiator. Preferably, the coupling reaction step and / or the modification reaction step may be carried out using the above-mentioned coupling agent or modifying agent, followed by a hydrogenation step, and a branching step may be carried out using a branching agent before the coupling reaction step or the modification step.

[0036] <Polymerization process> The polymerization method for the conjugated diene polymer used in the rubber composition for closure of this embodiment is not limited to the following, but a polymerization method based on living anionic polymerization is preferred, and an adiabatic polymerization method is preferred. From the viewpoint of increasing the reaction rate and improving productivity, the reaction temperature is preferably a polymerization initiation temperature of 25°C to 60°C, more preferably 25°C to 55°C, and even more preferably 25°C to 50°C. From the viewpoint of increasing the polymerization addition rate of the monomer, the polymerization termination temperature is preferably 65°C or higher, more preferably 68°C or higher, and even more preferably 70°C or higher. On the other hand, from the viewpoint of increasing the modification rate, the temperature is preferably 95°C or lower, more preferably 85°C or lower, even more preferably 82°C or lower, and even more preferably 80°C or lower.

[0037] As the polymerization initiator used in the polymerization step, at least an organic monolithium compound can be used. The organomonolithium compound is not limited to the following, but examples thereof include low molecular weight compounds and solubilized oligomeric organomonolithium compounds. 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. The amount of the organic monolithium compound used as the polymerization initiator is preferably determined depending on the structure of the target hydrogenated conjugated diene polymer and the molecular weight of the hydrogenated conjugated diene polymer. 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. 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.

[0038] 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 hydrogenated conjugated diene polymer. This makes it possible to obtain a conjugated diene polymer having a nitrogen atom consisting of an amino group at the polymerization initiation terminal.

[0039] 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. 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. 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. 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.

[0040] 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. 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. Examples of the alkyllithium compound include, but are not limited to, n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium. 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. These organomonolithium compounds may be used alone or in combination of two or more, or may be used in combination with other organometallic compounds. Examples of the other organometallic compounds include alkaline earth metal compounds, other alkali metal compounds, and other organometallic compounds. 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. Examples of organomagnesium compounds include dibutylmagnesium and ethylbutylmagnesium. Examples of other organometallic compounds include organoaluminum compounds.

[0041] 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. 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. 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. In the method for producing the hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment, in order to obtain a conjugated diene polymer having a high proportion of active ends in the polymerization step, a continuous method is preferred, which allows the polymer to be continuously discharged and subjected to the next reaction in a short period of time.

[0042] In the polymerization step in the method for producing the hydrogenated conjugated diene polymer used in the rubber composition for crawlers 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 hydrocarbon solvents 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.

[0043] 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.

[0044] 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. 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. 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. 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.

[0045] 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.

[0046] <Coupling step, modification step, hydrogenation step> The active terminals of the conjugated diene polymer obtained through the above-mentioned polymerization step and, if necessary, a branching step using a predetermined branching agent may be subjected to a coupling reaction using the above-mentioned coupling agent or a modification reaction using a modifying agent having a nitrogen atom-containing group. This allows the formation of an amine-modified group at the polymer chain terminal. When a nitrogen atom-containing coupling agent is used, the coupling reaction and the modification reaction proceed simultaneously. In addition, a hydrogenation step is carried out to carry out a hydrogenation reaction.

[0047] <Deactivator Addition Step, Neutralizer Addition Step> In the method for producing the hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment, a deactivator, a neutralizer, etc. may be added to the polymer solution as needed. The quenching agent is not limited to the following, but examples thereof include water; alcohols such as methanol, ethanol, and isopropanol; and the like. 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.

[0048] <Hydrogenation process> The method for producing the hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment includes a step of hydrogenating the conjugated diene polymer using a catalyst so that the hydrogenation rate is 1% or more and 99% or less. The hydrogenation rate of the hydrogenated conjugated diene polymer can be controlled, for example, by adjusting the amount of hydrogen during hydrogenation, and the hydrogenation rate can be controlled, for example, by adjusting the hydrogen feed rate, pressure, temperature, etc. The hydrogenation rate of the conjugated diene polymer can be measured by proton nuclear magnetic resonance (H-NMR), specifically, by the method described in the Examples below.

[0049] <Rubber stabilizer addition process> In the method for producing the hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment, it is preferable to add a rubber stabilizer after the hydrogenation step from the viewpoint of preventing gel formation after polymerization and improving stability during processing. As the stabilizer for rubber, it is preferable to use a hindered phenol-based antioxidant. From the viewpoint of preventing gelation due to heat generation during kneading, the hindered phenol antioxidant is added in an amount of preferably 0.55 parts by mass or more, more preferably 0.60 parts by mass or more, and even more preferably 0.65 parts by mass or more, relative to 100 parts by mass of the hydrogenated conjugated diene polymer, while from the viewpoint of cost, the amount is preferably 1.5 parts by mass or less, more preferably 1.4 parts by mass or less.

[0050] Furthermore, hindered phenol-based antioxidants can be further classified into sulfur-containing hindered phenol-based antioxidants and sulfur-free hindered phenol-based antioxidants. In the rubber composition for crawlers of this embodiment, from the viewpoints of suppressing gelation during kneading and suppressing oxidative degradation, the sulfur-containing hindered phenol-based antioxidant is preferably added in an amount of 0.10 parts by mass or more, more preferably 0.15 parts by mass or more, even more preferably 0.20 parts by mass or more, and even more preferably 0.25 parts by mass or more, per 100 parts by mass of the hydrogenated conjugated diene polymer. On the other hand, from the viewpoint of odor, the sulfur-containing hindered phenol-based antioxidant is preferably added in an amount of 1.0 part by mass or less, more preferably 0.9 parts by mass or less, and even more preferably 0.8 parts by mass or less. Furthermore, from the viewpoint of suppressing deterioration due to heat or sunlight after production, the sulfur-free hindered phenol antioxidant is added in an amount of preferably 0.2 part by mass or more, more preferably 0.3 part by mass or more, even more preferably 0.4 part by mass or more, even more preferably 0.5 part by mass or more, and even more preferably 0.6 part by mass or more, relative to 100 parts by mass of the hydrogenated conjugated diene polymer. On the other hand, from the viewpoint of colorability such as yellowing of the molded article, the sulfur-free hindered phenol antioxidant is added in an amount of preferably 1.0 part by mass or less, more preferably 0.95 part by mass or less, and even more preferably 0.9 part by mass or less.

[0051] In the rubber composition for crawlers of this embodiment, from the viewpoint of reducing the risk of gelation due to heat generation during kneading and realizing excellent productivity, it is preferable to add 0.55 parts by mass or more of a hindered phenol-based antioxidant per 100 parts by mass of the hydrogenated conjugated diene-based polymer, it is more preferable to add 0.1 part by mass or more and 1.0 part by mass or less of a sulfur-containing hindered phenol-based antioxidant, and it is even more preferable to add 0.35 part by mass or more and 1.0 part by mass or less of a sulfur-free hindered phenol-based antioxidant per 100 parts by mass of the hydrogenated conjugated diene-based polymer. The hindered phenol-based antioxidants may be used alone or in combination of two or more.Similarly, it is preferable to use one or more sulfur-containing hindered phenol-based antioxidants and one or more sulfur-free hindered phenol-based antioxidants in combination, and two or more of each may be used in combination.

[0052] Examples of the hindered phenol compound include, but are not limited to, N-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, tetrakis{methylene-3-(3',5'-di-t-butyl-4-hydroxyphenyl)propionate}methane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, distearyl(4-hydroxy-3-methyl-5-t-butylbenzyl)malonate, tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, and tetrakis(2-methyl-4-hydroxy-5-t-butylphenyl)propionate. Ethylene glycol bis{3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate}, 1,6-hexanediol bis{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate}, 2,4-bis-(N-octylthio)-6-(4-hydroxyphenyl)-3,5-di-t-butyl-anilino-1,3,5-triazine, 2,2-thiodiethylene bis{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate}, 2 ,2-thiobis(4-methyl-6-t-butylphenol), 2,2'-methylenebis-(4-ethyl-6-t-butylphenol), N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(3,5-di- t-butyl-4-hydroxybenzyl) sulfide, tris(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate, 2,4-bis{(octylthio)methyl}-o-cresol, isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, N,N'-bis{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionylhydrazine, and (meth)acrylate compounds having a hindered phenol structure.

[0053] <Solvent removal process> In the method for producing the hydrogenated conjugated diene polymer used in the rubber composition for crawlers of this embodiment, a known method can be used to obtain the resulting hydrogenated conjugated diene polymer from the polymer solution. Examples of the method include, but are not limited to, a method in which the solvent is separated by steam stripping or the like, the polymer is filtered, and then dehydrated and dried to obtain the polymer, a method in which the polymer is concentrated in a flashing tank and then devolatilized using a vent extruder or the like, and a method in which the polymer is directly devolatilized using a drum dryer or the like.

[0054] (Crawler) The term "crawler" in the rubber composition for crawlers of this embodiment means a track belt, caterpillar, crawler belt, caterpillar, or the like.

[0055] (Rubber components other than hydrogenated conjugated diene polymers) The rubber composition for a crawler of this embodiment contains the rubber component as described above, and the rubber component contains the hydrogenated conjugated diene-based polymer described above. The rubber composition for crawlers of this embodiment may contain a rubber component other than the hydrogenated conjugated diene polymer described above as the rubber component. Examples of rubber components other than the above-mentioned hydrogenated conjugated diene polymer include, but are not limited to, synthetic rubber and natural rubber. Examples of synthetic rubber include isoprene rubber, butadiene rubber and its hydrides, styrene butadiene rubber and its hydrides, nitrile rubber and its hydrides, urethane rubber, butyl rubber and its halides, ethylene-propylene-diene rubber (EPDM), chloroprene rubber, acrylic rubber, silicone rubber, and fluororubber.

[0056] The rubber component constituting the rubber composition for crawlers of this embodiment may consist solely of the above-mentioned hydrogenated conjugated diene rubber, or may further contain natural rubber, or may further contain high-cis butadiene.

[0057] In particular, when natural rubber is contained as the rubber component, the extrusion flowability of the rubber composition for crawlers of this embodiment when unvulcanized is improved, which has the advantage of facilitating the production of products with complex shapes such as crawlers. In view of the above-mentioned effects, the content of natural rubber is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 50 parts by mass or more, based on 100 parts by mass of the entire rubber component including the hydrogenated conjugated diene polymer.

[0058] On the other hand, when high-cis butadiene is contained, the glass transition temperature of the rubber composition for crawlers of this embodiment decreases, which tends to reduce the elastic modulus at low temperatures. A low elastic modulus at low temperatures is preferable because it leads to poor grip and chipping resistance when used at low temperatures. From the above perspective, the content of high-cis polybutadiene is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, based on 100 parts by mass of the total rubber component including the hydrogenated conjugated diene polymer.

[0059] (filler) The rubber composition for crawlers of this embodiment contains 30 parts by mass or more of carbon black, preferably 40 parts by mass or more, and more preferably 50 parts by mass or more, per 100 parts by mass of the rubber component, from the viewpoint of rigidity and abrasion resistance. On the other hand, from the viewpoint of sufficiently dispersing the carbon black and ensuring that the processability and mechanical strength of the rubber composition for crawlers of this embodiment are practically sufficient, the content of carbon black is preferably 300 parts by mass or less, more preferably 250 parts by mass or less, even more preferably 200 parts by mass or less, and even more preferably 100 parts by mass or less, per 100 parts by mass of the rubber component.

[0060] In addition to the above-mentioned carbon black, silica-based inorganic fillers, calcium carbonate, titanium oxide, aluminum hydroxide, clay, etc. may also be used as the filler. When carbon black is used in combination with other fillers, the preferred range of the total content of the fillers is the same as when carbon black is used alone.

[0061] The silica-based inorganic filler is not limited to the following and any known filler can be used, but for example, solid particles containing SiO2 or Si3Al as a structural unit are preferred, and solid particles containing SiO2 or Si3Al as a main component of the 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 mass% or more, preferably 70 mass% or more, and more preferably 80 mass% or more. Specific 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. Other examples include silica-based inorganic fillers whose surfaces have been made hydrophobic, and mixtures of silica-based inorganic fillers and inorganic fillers other than silica-based inorganic fillers. Among these, silica and glass fiber are preferred, and silica is more preferred, from the viewpoints of strength, abrasion resistance, etc. Examples of silica include dry silica, wet silica, and synthetic silicate silica.

[0062] Examples of carbon black include, but are not limited to, carbon blacks of various classes such as SRF, FEF, HAF, ISAF, and SAF. Among these, carbon blacks with a nitrogen adsorption specific surface area of ​​50 m 2 / g or more and a dibutyl phthalate (DBP) oil absorption of 80 mL / 100 g or less is preferred. The calcium carbonate is not particularly limited, but examples thereof include calcium carbonate having an average particle size of 0.04 μm to 8.0 μm and an oil absorption of 10 to 35 g per 100 g of calcium carbonate. The filler may contain fillers other than the above-mentioned fillers, such as metal oxides and metal hydroxides. Metal oxides are compounds with the chemical formula M x O y (M represents a metal atom, and x and y each independently represent an integer of 1 to 6) as the main component of the structural unit. Examples of metal oxides include, but are not limited to, alumina, titanium oxide, magnesium oxide, and zinc oxide. Examples of metal hydroxides include, but are not limited to, aluminum hydroxide, magnesium hydroxide, and zirconium hydroxide.

[0063] (Silane coupling agent) The rubber composition for a crawler of the present embodiment may contain a silane coupling agent. The silane coupling agent has the function of strengthening the interaction between the rubber component and the filler, and has groups that have affinity or bonding properties for both the rubber component and the silica-based inorganic filler. Preferably, the silane coupling agent is a compound that has a sulfur-bonding moiety and an alkoxysilyl group or silanol group moiety in one molecule. Examples of such compounds include, but are not limited to, bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, and bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide. In the rubber composition for crawlers of this embodiment, the content of the silane coupling agent is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 20 parts by mass or less, and even more preferably 1.0 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the filler. When the content of the silane coupling agent is within the above range, the effect of adding the silane coupling agent tends to be more pronounced.

[0064] (rubber softener) The rubber composition for a crawler of the present embodiment may contain a rubber softener as needed. The rubber additive may be added to the hydrogenated conjugated diene polymer. The rubber softener is preferably added from the viewpoint of improving the productivity of the hydrogenated conjugated diene polymer and the processability of the rubber composition for crawlers containing a filler or the like. Examples of rubber softeners include, but are not limited to, extender oil, liquid rubber, and resin. The method of adding a rubber softener to a hydrogenated conjugated diene polymer or a rubber composition for crawlers is not limited to the following, but a preferred method is to add a rubber softener to a conjugated diene polymer solution, mix them, and then remove the solvent from the resulting polymer solution containing the rubber softener.

[0065] Examples of the extender oil include aromatic oil, naphthenic oil, paraffin oil, etc. Among these, from the viewpoint of environmental safety, oil bleeding prevention, and wet grip properties, aromatic substitute oils having a polycyclic aromatic (PCA) component content of 3 mass% or less according to the IP346 method are preferred. Examples of aromatic substitute oils include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), etc., as shown in Kautschuk Gummi Kunststoffe 52(12)799(1999), as well as RAE (Residual Aromatic Extracts).

[0066] The liquid rubber is not limited to the following, but examples thereof include liquid polybutadiene and liquid styrene-butadiene rubber. The effect of adding liquid rubber is that it improves the processability of the rubber composition for crawlers that is formulated with a conjugated diene polymer and a filler, etc., and also tends to shift the glass transition temperature of the rubber composition for crawlers to a lower temperature, thereby improving the abrasion resistance and low-temperature properties of the vulcanized product.

[0067] Examples of the resin include, but are not limited to, aromatic petroleum resins, coumarone-indene resins, terpene resins, rosin derivatives (including tung oil resins), tall oil, tall oil derivatives, rosin ester resins, natural and synthetic terpene resins, various hydrocarbon resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, and mixed aliphatic-aromatic hydrocarbon resins, coumarin-indene resins, phenolic resins, p-tert-butylphenol-acetylene resins, phenol-formaldehyde resins, xylene-formaldehyde resins, monoolefin oligomers, diolefin oligomers, hydrogenated aromatic hydrocarbon resins, cyclic aliphatic hydrocarbon resins, hydrogenated hydrocarbon resins, hydrogenated tung oil resins, hydrogenated oil resins, and esters of hydrogenated oil resins with monofunctional or polyfunctional alcohols. These resins may be used alone or in combination of two or more. When hydrogenating, all of the unsaturated groups may be hydrogenated, or some may remain. The effects of adding a resin include improving the processability of the rubber composition for crawlers of this embodiment, as well as improving the breaking strength when vulcanized. Also, the glass transition temperature of the rubber composition for crawlers of this embodiment can be shifted to a higher temperature, thereby improving the tensile properties at high temperatures.

[0068] The amount of extender oil, liquid rubber, resin, or the like added as a rubber softener is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, relative to 100 parts by mass of the conjugated diene-based polymer of this embodiment. When the rubber softener is added within the above range, the processability of the rubber composition for crawlers of this embodiment improves, and when vulcanized, the breaking strength and abrasion resistance tend to improve.

[0069] (anti-aging agent) The rubber composition for a crawler of the present embodiment may contain an antioxidant as needed. The antioxidant is not limited to the following, but for example, N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (6PPD) is preferred from the viewpoints of commercial availability and ozone resistance. From the viewpoint of ozone resistance, the more 6PPD added, the better, but from the viewpoint of ecological pollution, it is required that the amount used be small. From the above viewpoints, the amount of 6PPD compounded in the rubber composition for crawlers of this embodiment is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, per 100 parts by mass of the entire rubber component. The ozone resistance of the rubber composition for crawlers that is impaired in this case can be compensated for by compounding the above-mentioned hydrogenated conjugated diene rubber, and from the viewpoint of ozone resistance, the amount of hydrogenated conjugated diene polymer compounded is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 100 parts by mass, per 100 parts by mass of the entire rubber component.

[0070] (Crosslinked composition) The rubber composition for a crawler of this embodiment may be a crosslinked composition that has been subjected to a crosslinking treatment with a crosslinking agent. Examples of crosslinking agents include, but are not limited to, radical generators such as organic peroxides and azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. The sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, polymeric polysulfur compounds, and the like. In the rubber composition for crawlers of this embodiment, the content of the crosslinking agent is preferably 0.01 to 20 parts by mass, and more preferably 0.1 to 15 parts by mass, per 100 parts by mass of the rubber component containing the conjugated diene polymer. A conventionally known method can be used as the vulcanization method, and the vulcanization temperature is preferably 120°C to 200°C, and more preferably 140°C to 180°C.

[0071] In the crosslinking, a vulcanization accelerator may be used as needed. As the vulcanization accelerator, a conventionally known material can be used, and examples thereof include, but are not limited to, sulfenamide-based, guanidine-based, thiuram-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, thiourea-based, and dithiocarbamate-based vulcanization accelerators. The vulcanization aid may include, but is not limited to, zinc oxide, stearic acid, and triallyl isocyanurate. The content of the vulcanization accelerator is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, per 100 parts by mass of the rubber component containing the hydrogenated conjugated diene polymer.

[0072] Examples of organic peroxides include, but are not limited to, 1,3-bis(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyne-3,2,5-dimethyl-2,5-bis(tert-butylperoxy)hexene-3,2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,2'-bis(tert-butylperoxy)-p-isopropylbenzene, dicumyl peroxide, di-tert-butyl peroxide, tert-butylperoxide, peroxide, p-menthane peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, dilauroyl peroxide, diacetyl peroxide, tert-butyl peroxybenzoate, 2,4-dichlorobenzoyl peroxide, p-chlorobenzoyl peroxide, benzoyl peroxide, di(tert-butylperoxy)perbenzoate, n-butyl-4,4-bis(tert-butylperoxy)valerate, and tert-butylperoxyisopropyl carbonate.

[0073] (Method of manufacturing rubber composition for crawlers) The rubber composition for crawlers of this embodiment is obtained by mixing the above-mentioned hydrogenated conjugated diene polymer, carbon black, and, if necessary, natural rubber, high-cis butadiene, and various additives. Examples of the mixing method include, but are not limited to, a melt-kneading method using a general mixer such as an open roll, a Banbury mixer, a kneader, a single-screw extruder, a twin-screw extruder, or a multi-screw extruder, and a method in which the components are dissolved and mixed and then the solvent is removed by heating. Among these, melt-kneading methods using a roll, a Banbury mixer, a kneader, or an extruder are preferred from the viewpoints of productivity and good kneading ability. Also applicable are a method of kneading the rubber component, the filler, the silane coupling agent, and the additives all at once, and a method of mixing them in several batches. After the mixing step, a predetermined crosslinking reaction is carried out to obtain a crosslinked composition.

[0074] (Other additives) The rubber composition for crawlers of this embodiment may contain various additives such as softeners and fillers other than those described above, heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, lubricants, and tackifiers, within the scope that does not impair the object of this embodiment. As other softeners, known softeners can be used. Known materials can be used for the heat stabilizer, antistatic agent, weather stabilizer, antioxidant, colorant, and lubricant. [Example]

[0075] Hereinafter, the present embodiment will be described in more detail with reference to specific production examples, examples, and comparative examples, but the present invention is not limited in any way to the following production examples, examples, and comparative examples. Various physical properties in the Production Examples, Examples and Comparative Examples were measured by the methods shown below.

[0076] (Microstructure of butadiene portion of conjugated diene polymer before hydrogenation (1,2-vinyl bond content)) 50 mg of the conjugated diene polymer before hydrogenation was dissolved in 10 mL of carbon disulfide to prepare a measurement sample. Using a solution cell, infrared spectra were recorded from 600 to 1000 cm -1 The absorbance at a predetermined wave number was measured in the range of 100 Hz to 100 Hz, and the microstructure of the butadiene moiety, i.e., the 1,2-vinyl bond content (mol%) was determined according to the calculation formula of Hampton's method (method described in R.R. Hampton, Analytical Chemistry 21, 923 (1949)) (measuring device: Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation).

[0077] (Styrene content (mass%) of hydrogenated conjugated diene polymer) A 100 mg sample of the unhydrogenated conjugated diene polymer was dissolved in chloroform to prepare a measurement sample. The amount of styrene (mass%) in the sample was measured based on the amount of absorption of ultraviolet light (near 254 nm) by the phenyl group of styrene (measuring device: Shimadzu UV-2450 spectrophotometer).

[0078] (Glass transition temperature of hydrogenated conjugated diene polymer (°C)) The glass transition temperature of the hydrogenated conjugated diene polymer sample was measured using a differential scanning calorimeter in accordance with JIS K6240.

[0079] (Weight-average molecular weight of hydrogenated conjugated diene polymer) The chromatogram was measured using a GPC measuring device equipped with three connected columns packed with polystyrene gel, and the weight-average molecular weight of the hydrogenated conjugated diene polymer was determined based on a calibration curve using standard polystyrene. The eluent used was tetrahydrofuran (THF) containing 5 mmol / L triethylamine. The columns used were a guard column manufactured by Tosoh Corporation under the trade name "TSKguardcolumn SuperH-H" and columns manufactured by Tosoh Corporation under the trade names "TSKgel SuperH5000," "TSKgel SuperH6000," and "TSKgel SuperH7000." An RI detector (trade name "HLC8020" manufactured by Tosoh Corporation) was used under conditions of an oven temperature of 40°C and a THF flow rate of 0.6 mL / min. 10 mg of the sample to be measured was dissolved in 20 mL of THF to prepare a measurement solution, and 20 μL of the measurement solution was injected into the GPC measurement device and measured.

[0080] (Modification rate of hydrogenated conjugated diene polymer) The modification rate of the hydrogenated conjugated diene polymer was measured by the column adsorption GPC method as follows: The measurement was carried out by utilizing the property of the conjugated diene polymer modified with a nitrogen atom-containing functional group to be adsorbed onto a column. 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. Specifically, it is as follows: <Preparation of sample solution>: 10 mg of the sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a sample solution. <GPC measurement conditions using a polystyrene column> THF containing 5 mmol / L triethylamine was used as the eluent, and 20 μL of the sample solution was injected into the device for measurement. The columns used were a guard column manufactured by Tosoh Corporation under the trade name "TSKguardcolumn SuperH-H," and columns manufactured by Tosoh Corporation under the trade names "TSKgel SuperH5000," "TSKgel SuperH6000," and "TSKgel SuperH7000." Chromatograms were obtained using an RI detector (Tosoh Corporation HLC8020) under conditions of a column oven temperature of 40°C and a THF flow rate of 0.6 mL / min. <GPC measurement conditions using a silica column>: A Tosoh HLC-8320GPC column was used, and 50 μL of the sample solution was injected into the column using THF as the eluent. Chromatograms were obtained using an RI detector at a column oven temperature of 40°C and a THF flow rate of 0.5 mL / min. Zorbax PSM-1000S, PSM-300S, and PSM-60S columns were used, with a DIOL 4.6 x 12.5 mm 5 micron guard column connected to the column. <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. Denaturation rate (%) = [1-(P2 x P3) / (P1 x P4)] x 100 (However, P1+P2=P3+P4=100)

[0081] (Hydrogenation rate of hydrogenated conjugated diene polymer) A large amount of methanol was added to the reaction solution of the hydrogenated conjugated diene polymer to precipitate and recover the hydrogenated conjugated diene polymer. Next, the hydrogenated conjugated diene polymer was washed with acetone and dried in vacuum. This, 1 The hydrogenation rate was measured using the sample for H-NMR measurement. 1 The conditions for H-NMR measurement are as follows: <Measurement conditions> Measuring equipment: JNM-LA400 (JEOL) Solvent: deuterated chloroform Measurement sample: Samples taken before and after hydrogenation of polymer Sample concentration: 50mg / mL Observation frequency: 400MHz Chemical shift standard: TMS (tetramethylsilane) Pulse delay: 2.904 seconds Number of scans: 64 Pulse width: 45° Measurement temperature: 26℃

[0082] [Production of hydrogenated conjugated diene polymer] (Preparation of hydrogenation catalyst) A hydrogenation catalyst used in preparing a hydrogenated conjugated diene polymer in a production example described later was prepared by the method of Production Example α below. <Manufacturing example α> One liter of dried and purified cyclohexane was placed in a nitrogen-purged reaction vessel, and 100 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added. With thorough stirring, an n-hexane solution containing 200 mmol of trimethylaluminum was added, and the mixture was allowed to react at room temperature for approximately 3 days to obtain a hydrogenation catalyst (TC-1).

[0083] (Polymerization of hydrogenated conjugated diene polymer) <(Production Example 1) Hydrogenated Conjugated Diene Polymer 1> As shown in Table 1 below, a 40 L internal volume autoclave equipped with a stirrer and a jacket and capable of temperature control was used as a reactor. 2,850 g of 1,3-butadiene, 215 g of styrene, 23,000 g of cyclohexane, and 229.4 mmol of tetrahydrofuran (THF) as a polar substance, from which impurities had been removed in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. As a polymerization initiator, 22.9 mmol of n-butyllithium was fed into the reactor. After the polymerization reaction started, the temperature inside the reactor rose due to heat generated by the polymerization, and the final temperature inside the reactor was 83° C. 0.38 g of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilolidine as a modifier was added to this polymer solution, and after reacting for 3 minutes, 1.69 g of 1,3-dimethyl-2-imidazolidinone as a modifier was added, and the reaction was continued for 15 minutes. Thereafter, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the conjugated diene polymer solution before hydrogenation in an amount of 60 ppm (Ti standard) per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C, thereby obtaining a polymerization solution of hydrogenated conjugated diene polymer 1. To the obtained solution of hydrogenated conjugated diene polymer, 21.0 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate (stabilizer 1) and 9.0 g of 4,6-bis(octylthiomethyl)-o-cresol (stabilizer 2) were added as antioxidants, and then the conjugated diene polymer solution was added dropwise to warm water to remove the solvent, followed by drying in a dryer to obtain hydrogenated conjugated diene polymer 1 (referred to as polymer 1 in Table 1 below). The obtained polymer 1 was analyzed by the above-mentioned method, and the results are shown in Table 1.

[0084] <(Production Examples 2 to 4, 6 to 8) Hydrogenated Conjugated Diene Polymers 2 to 4, 6 to 8> As shown in Table 1 below, each hydrogenated conjugated diene polymer (Production Examples 2 to 4, 6 to 8) was obtained in the same manner as in the above (Production Example 1), except that the amounts of styrene and 1,3-butadiene added, the amounts of polymerization initiator and polar substance added, the amount of modifier added, and the amount of hydrogen added were changed. To each of the obtained solutions of hydrogenated conjugated diene polymers, a stabilizer shown in Table 1 was added, and then each of the hydrogenated conjugated diene polymer solutions was dropped into warm water to remove the solvent, followed by drying in a dryer to obtain hydrogenated conjugated diene polymers (polymers 2 to 4, 6 to 8). The obtained polymers 2 to 4 and 6 to 8 were analyzed by the above-mentioned methods, and the results are shown in Table 1.

[0085] <(Production Example 5) Hydrogenated Conjugated Diene Polymer 5> As shown in Table 1 below, a 40 L internal volume autoclave equipped with a stirrer and a jacket and capable of temperature control was used as a reactor. 1,950 g of 1,3-butadiene, from which impurities had been removed in advance, 1,505 g of styrene, 23,000 g of cyclohexane, and 158.1 mmol of tetrahydrofuran (THF) as a polar substance were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. As a polymerization initiator, 15.8 mmol of n-butyllithium was fed to the reactor. After the polymerization reaction started, the temperature inside the reactor rose due to heat generated by the polymerization, and the final temperature inside the reactor was 83° C. To this polymer solution, 1.73 g of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilolidine was added as a modifying agent, and the reaction was carried out for 15 minutes. Thereafter, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the conjugated diene polymer solution before hydrogenation in an amount of 60 ppm (Ti standard) per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C, thereby obtaining a polymerization solution of hydrogenated conjugated diene polymer 5. To the obtained solution of hydrogenated conjugated diene polymer 5, 21.0 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate (stabilizer 1) and 9.0 g of 4,6-bis(octylthiomethyl)-o-cresol (stabilizer 2) were added as antioxidants, and the hydrogenated conjugated diene polymer solution was then dropped into warm water to remove the solvent, followed by drying in a dryer to obtain hydrogenated conjugated diene polymer 5 (referred to as polymer 5 in Table 1). The obtained polymer 5 was analyzed by the above-mentioned method, and the results are shown in Table 1.

[0086] <(Production Example 9) Conjugated Diene Polymer 9> As shown in Table 1 below, a 40 L internal volume autoclave equipped with a stirrer and a jacket and capable of temperature control was used as a reactor. 2,700 g of 1,3-butadiene, 430 g of styrene, 23,000 g of cyclohexane, and 159.4 mmol of tetrahydrofuran (THF) as a polar substance, from which impurities had been removed in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. As a polymerization initiator, 15.9 mmol of n-butyllithium was fed to the reactor. After the polymerization reaction started, the temperature inside the reactor rose due to heat generated by the polymerization, and the final temperature inside the reactor was 83° C. 0.29 g of 2,2-dimethoxy-1-(3-(trimethoxysilyl)propyl)-1,2-azasilolidine as a modifier was added to this polymer solution, and after reacting for 3 minutes, 1.27 g of 1,3-dimethyl-2-imidazolidinone as a modifier was added, and the reaction was continued for 15 minutes. To the obtained solution of the conjugated diene polymer, 21.0 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate (stabilizer 1) and 9.0 g of 4,6-bis(octylthiomethyl)-o-cresol (stabilizer 2) were added as antioxidants, and then the conjugated diene polymer solution was added dropwise to warm water to remove the solvent, followed by drying in a dryer to obtain conjugated diene polymer 9 (referred to as polymer 9 in Table 1). The obtained polymer 9 was analyzed by the above-mentioned method, and the results are shown in Table 1.

[0087] <(Production Example 10) Hydrogenated Conjugated Diene Polymer 10> As shown in Table 1 below, a 40 L internal volume autoclave equipped with a stirrer and a jacket and capable of temperature control was used as a reactor. 2,700 g of 1,3-butadiene, 430 g of styrene, 23,000 g of cyclohexane, and 119.5 mmol of tetrahydrofuran (THF) as a polar substance, from which impurities had been removed in advance, were placed in the reactor, and the internal temperature of the reactor was maintained at 42°C. As a polymerization initiator, 11.9 mmol of n-butyllithium was fed to the reactor. After the polymerization reaction started, the temperature inside the reactor rose due to heat generated by the polymerization, and the final temperature inside the reactor was 83° C. 0.42 g of tetramethoxysilane was added to this polymer solution as a polymerization terminator, and the reaction was carried out for 15 minutes. Thereafter, the hydrogenation catalyst (TC-1) prepared in <Production Example α> was added to the conjugated diene polymer solution before hydrogenation in an amount of 60 ppm (Ti standard) per 100 parts by mass of the conjugated diene polymer before hydrogenation, and a hydrogenation reaction was carried out for 50 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C, thereby obtaining a polymerization solution of hydrogenated conjugated diene polymer 10. To the obtained solution of hydrogenated conjugated diene polymer 10, 21.0 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate (stabilizer 1) and 9.0 g of 4,6-bis(octylthiomethyl)-o-cresol (stabilizer 2) were added as antioxidants, and the hydrogenated conjugated diene polymer solution was then dropped into warm water to remove the solvent. The resulting solution was then dried in a dryer to obtain hydrogenated conjugated diene polymer 10 (referred to as polymer 10 in Table 1). The obtained polymer 10 was analyzed by the above-mentioned method, and the results are shown in Table 1.

[0088] [Table 1]

[0089] [Production of rubber composition for crawlers] [Examples 1 to 14], [Comparative Examples 1 to 5] Using the hydrogenated conjugated diene polymers 1 to 10 shown in Table 1 as raw rubbers, rubber compositions for crawlers containing each raw rubber were prepared according to the formulations shown below.

[0090] The detailed formulations are as shown in Tables 2 and 3. The details of the various materials in Tables 2 and 3 are as follows: Carbon black (N330) Oil (VIVATEC500) Resin (OPERA383) Anti-aging agent (Nocrac 6C) Wax (Sunnock N) Vulcanization accelerator (N-(tert-butyl)-2-benzothiazole sulfenamide)

[0091] The above materials were kneaded by the following method to obtain a rubber composition for crawlers. In the first stage of mixing, raw rubber, filler (carbon black), oil, resin, wax, zinc oxide, stearic acid, and antioxidant were mixed using an internal mixer (capacity: 0.3 L) equipped with a temperature control device at a filling rate of 65% and rotor rotation speeds of 50 / 57 rpm. The temperature of the internal mixer was controlled, and the discharge temperature was 150°C to obtain an unvulcanized composition. After cooling, the mixture was kneaded in the second stage using an open roll set at 70°C, after which sulfur and a vulcanization accelerator were added and kneaded. Thereafter, the mixture was molded into a predetermined shape and vulcanized in a vulcanization press at 160°C for 20 minutes. After vulcanization, the physical properties of the rubber composition for crawlers were measured. The results of the physical property measurements are shown in Tables 2 and 3.

[0092] [Physical properties of rubber composition for crawlers] After vulcanization as described above, the physical properties of the vulcanized rubber composition for crawlers were measured by the following methods.

[0093] (1) Abrasion resistance A DIN abrasion test was carried out at room temperature using a DIN abrasion tester manufactured by Ueshima Seisakusho Co., Ltd., in accordance with the measurement method specified in JIS K6264-2. The analysis results were expressed as an index, with a higher number indicating better abrasion resistance.

[0094] ((2) Heat resistance) Test pieces were heat-aged in a Geer oven at 100°C for 72 hours in accordance with JIS K6257, and the breaking strength was measured using a Strograph manufactured by Toyo Seiki Co., Ltd. in accordance with JIS K6251 to evaluate the properties. The breaking strength T0 of the sample before heat aging was compared with the breaking strength T1 of the sample after heat aging, and the value of T1 / T0 was indexed. The higher the number, the more difficult it is to undergo heat aging and the better the heat resistance.

[0095] (3) Chipping resistance The breaking elongation of the vulcanized sample was used as an index of chipping resistance, and was measured using a Strograph manufactured by Toyo Seiki Co., Ltd. in accordance with JIS K6251. The analysis results were expressed as an index, with a higher number indicating better chipping resistance.

[0096] ((4) Flex crack resistance) The evaluation was carried out in accordance with JIS K6260 using a DeMacha type bending tester manufactured by Yasuda Seiki Seisakusho Co., Ltd. The number of bending times until the sample broke was measured. The analysis results were expressed as an index, with a higher index indicating better flex crack resistance.

[0097] ((5) Low-temperature characteristics) Temperature dispersion measurements were performed using an ARES G2 rheometer manufactured by TA Instruments, and the elastic modulus at -20°C was measured. The analysis results were expressed as an index, and the higher the index, the better the low-temperature properties, that is, the more flexible the rubber composition was at low temperatures.

[0098] (6) Ozone resistance The evaluation was carried out in accordance with JIS K6259 using an ozone weather meter OMS-HN manufactured by Suga Test Instruments Co., Ltd. Dynamic testing was carried out at an ozone concentration of 50 pphm, a temperature of 40°C, a tensile strain of 10%, and a frequency of 0.5 Hz, and the time until the sample broke was expressed as an index. The larger the index, the longer the time until the sample broke, and the better the ozone resistance.

[0099] (7) Extrusion Flowability of Unvulcanized Composition The viscosity (Pa·s) of the unvulcanized composition at a shear rate of 100 (1 / s) was measured using a capillary rheometer No. 583 manufactured by Toyo Seiki Seisakusho Co., Ltd. in accordance with JIS K7199. The lower the viscosity, the better the extrusion flowability of the unvulcanized composition, and this was expressed as an index. The larger the index, the lower the viscosity, and the better the extrusion flowability.

[0100] [Table 2]

[0101] [Table 3]

[0102] The combined index values ​​showed that the rubber compositions for crawlers of Examples 1 to 14 had a better balance of abrasion resistance, heat resistance, chipping resistance, and flex cracking resistance than the rubber compositions for crawlers of Comparative Examples 1 to 5. [Industrial Applicability]

[0103] The rubber composition for crawlers of the present invention has industrial applicability as a material for crawlers.

Claims

1. 100 parts by mass of a rubber component containing a hydrogenated conjugated diene-based polymer; 30 parts by mass or more of carbon black; A rubber composition for crawlers comprising: The hydrogenated conjugated diene polymer has a hydrogenation rate of 1 to 99%, an aromatic vinyl monomer unit content of 0 to 40 mass%, and an amine-modified group at a polymer chain terminal. Rubber composition for crawlers.

2. the rubber component consists solely of the hydrogenated conjugated diene polymer, The rubber composition for crawlers according to claim 1.

3. The rubber component further contains natural rubber. The rubber composition for crawlers according to claim 1.

4. The rubber component further contains natural rubber and high-cis butadiene. The rubber composition for crawlers according to claim 1.

5. Further containing N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (6PPD) as an antioxidant. The rubber composition for crawlers according to claim 1.

6. The content of the N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (6PPD) is 5 parts by mass or less per 100 parts by mass of the rubber component, The rubber composition for crawlers according to claim 5.

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