Rubber composition for crosslinking, method for producing crosslinked rubber, and tire tread

Abstract

To provide a crosslinking rubber composition that prevents the crosslinking time from increasing and that can give a crosslinked product having excellent tensile modulus, tear strength and abrasion resistance.SOLUTION: The crosslinking rubber composition contains: 100 pts.mass of a rubber polymer (A) having an iodine value of 10 to 250 (g / 100 g) and comprising 3 mass% or more of an ethylene structure, and less than 10 mass% of a vinyl aromatic monomer block; 0.1 to 5.0 pts.mass of sulfur (B); 0.1 to 5.0 pts.mass of a radical generator (C); and 0.1 to 5.0 pts.mass of a vulcanization accelerator (D).SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, in the field of rubber materials for tire treads, sheets, films, and asphalt modification, crosslinkable rubber compositions containing rubber-like polymers having an ethylene structure and into which crosslinkable unsaturated groups have been introduced have been proposed for the purpose of increasing mechanical strength and compression set (see, for example, Patent Documents 1 to 5). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2003 / 085010 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-270314 [Patent Document 3] International Publication No. 2019 / 151126 [Patent Document 4] International Publication No. 2019 / 151127 [Patent Document 5] International Publication No. 2019 / 078083 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventionally proposed rubber compositions for crosslinking containing a rubber-like polymer having an ethylene structure and a crosslinkable unsaturated group have a relatively small number of crosslinkable unsaturated groups, and therefore have the problem that the crosslinking time of the rubber composition for crosslinking is long and the crosslink density in the crosslinked product tends to be insufficient, which in turn tends to result in a low tensile modulus, low tear strength, and low abrasion resistance.

[0005] Therefore, the object of the present invention is to provide a rubber composition for crosslinking containing a rubber-like polymer having an ethylene structure and a crosslinkable unsaturated group, which is unlikely to increase the crosslinking time of the rubber composition for crosslinking and which can give a crosslinked product having excellent tensile modulus, tear strength, and abrasion resistance. [Means for solving the problem]

[0006] As a result of intensive research and investigation into solving the above-mentioned problems of the conventional art, the present inventors have found that a crosslinkable rubber composition containing a rubber-like polymer in which the iodine value, the amount of ethylene structure, and the amount of vinyl aromatic block are specified within predetermined numerical ranges can solve the above-mentioned problems of the conventional art, and have thus completed the present invention. That is, the present invention is as follows.

[0007] [1] The iodine value is 10 to 250 (g / 100g), the ethylene structure is ≥ 3 mass%, and the vinyl aromatic monomer block is < 10 mass%. and contains 5% by mass or more of vinyl aromatic monomer units. 100 parts by mass of the rubber polymer (A), 0.1 to 5.0 parts by mass of sulfur (B), 0.1 to 5.0 parts by mass of a radical generator (C), 0.1 to 5.0 parts by mass of a vulcanization accelerator (D), A rubber composition for crosslinking comprising: 〔2〕 The content of vinyl units and butylene units in the rubber-like polymer (A) is 20 mol % or more. [1] The rubber composition for crosslinking described above. 〔3〕 The rubber-like polymer (A) contains a nitrogen atom. or [2] The rubber composition for crosslinking according to claim 1. 〔4〕 Silica-based column and polystyrene column were used Measured by column adsorption GPC method The aforementioned Rubber polymer (A) is the mass ratio of the polymer having a nitrogen atom-containing functional group to the total amount The modification rate is 40% by mass or more. 〔3〕 The rubber composition for crosslinking according to claim 1. 〔5〕 The rubber composition according to any one of the above [1] to [3], wherein the average iodine value of the total amount of rubber components is 250 (g / 100g) or less. 〔4〕 The rubber composition for crosslinking according to any one of the above items. 〔6〕 The content of the sulfur (B) is greater than the content of the radical generator (C), 〔5〕 The rubber composition for crosslinking according to any one of the above items. 〔7〕 The content of the sulfur (B) / the content of the radical generator (C) is >1.67. 〔6〕 The rubber composition for crosslinking according to any one of the above items. 〔8〕 the content of the radical generator (C) / the content of the vinyl aromatic monomer unit in the rubber-like polymer (A) is ≥ 0.026; [1] to [7] The rubber composition for crosslinking according to any one of the above items. 〔9〕 (The content of sulfur (B) + the content of radical generator (C)) × 0.5 < (The content of vulcanization accelerator (D)), 〔8〕 The rubber composition for crosslinking according to any one of the above items. 〔10〕 The above-mentioned [1] to [3] further contain a polyfunctional crosslinking aid (E). 〔9〕 The rubber composition for crosslinking according to any one of the above items. 〔11〕 The rubber composition for crosslinking contains 3 to 40 parts by mass of a resin relative to 100 parts by mass of a rubber component, 〔10〕 The rubber composition for crosslinking according to any one of the above items. 〔12〕 The rubber composition for crosslinking contains 30 to 120 parts by mass of silica per 100 parts by mass of the rubber component in the rubber composition for crosslinking. 〔11〕 The rubber composition for crosslinking according to any one of the above items. 〔13〕 [1] to 〔12〕10. A method for producing a crosslinked rubber, comprising a step of kneading the rubber composition for crosslinking according to any one of the above items. 〔14〕 [1] to 〔12〕 A tire tread comprising the rubber composition for crosslinking according to any one of the above items. [Effects of the Invention]

[0008] According to the present invention, a rubber composition for crosslinking can be obtained which is unlikely to require a long crosslinking time and which provides a crosslinked product having excellent tensile modulus, tear strength, and abrasion resistance. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] [Rubber composition for crosslinking] The rubber composition for crosslinking of the present embodiment is 100 parts by mass of a rubber-like polymer (A) having an iodine value of 10 to 250 (g / 100g), an ethylene structure of 3% by mass or more, and a vinyl aromatic monomer block of less than 10% by mass; 0.1 to 5.0 parts by mass of sulfur (B), 0.1 to 5.0 parts by mass of a radical generator (C), 0.1 to 5.0 parts by mass of a vulcanization accelerator (D), Contains: By having the above constitution, it is possible to obtain a rubber composition for crosslinking which does not easily require a long crosslinking time and which provides a crosslinked product having excellent tensile modulus, tear strength, and abrasion resistance.

[0011] (Rubber polymer (A)) The rubber-like polymer (A) contained in the crosslinkable rubber composition of this embodiment has an iodine value of 10 to 250 (g / 100 g), an ethylene structure content of 3 mass% or more, and a vinyl aromatic monomer block content of <10 mass%.

[0012] <Iodine value> The rubbery polymer (A) used in the crosslinkable rubber composition of the present embodiment has an iodine value of 10 to 250 (g / 100 g). The iodine value of the rubbery polymer (A) is 10 (g / 100g) or more, preferably 15 (g / 100g) or more, more preferably 30 (g / 100g) or more, and even more preferably 50 (g / 100g) or more, from the viewpoints of co-crosslinkability when the rubbery polymer (A) is used in a rubber composition for crosslinking and flexibility when made into a tire. On the other hand, from the viewpoint of mechanical strength and abrasion resistance when used as a tire material, a value of 250 (g / 100g) or less is essential, with 200 (g / 100g) or less being preferred, 150 (g / 100g) or less being more preferred, 100 (g / 100g) or less being even more preferred, and 70 (g / 100g) or less being even more preferred. The iodine value can be measured according to the method described in "JIS K 0070:1992". The iodine value is a value that expresses the amount of halogen that reacts with 100 g of the target substance, converted into grams of iodine, so the unit of the iodine value is "g / 100 g". For example, in the method for producing a rubbery polymer described below, when a conjugated diene monomer and a vinyl aromatic monomer are copolymerized, the iodine value of the rubbery polymer decreases as the content of the conjugated diene monomer decreases, because the conjugated diene monomer has a double bond. Furthermore, when the conjugated diene monomer is hydrogenated, the iodine value decreases as the hydrogenation rate increases. The iodine value of the rubbery polymer (A) can be controlled within the above-mentioned range by adjusting the polymerization conditions such as the amount of the conjugated diene monomer having an unsaturated bond added, the polymerization time, and the polymerization temperature, and the amount of hydrogen added in the hydrogenation step, the hydrogenation time, and other conditions.

[0013] <Ethylene structure content> The rubbery polymer (A) used in the rubber composition for crosslinking of this embodiment has an ethylene structure of 3% by mass or more (ethylene structure≧3% by mass). When the ethylene structure in the rubbery polymer (A) is 3% by mass or more, the effect of preventing a decrease in the tensile strength of a rubber composition for crosslinking using the rubbery polymer (A) is obtained. The ethylene structure in the rubbery polymer (A) is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 40% by mass or more. The more ethylene structures there are in the rubbery polymer (A), the lower the sulfur (B) content and the more radical generator (C) there is, which tends to be preferable. However, the content ratio of sulfur (B) and radical generator (C) relative to the rubbery polymer (A) can be adjusted within the above-mentioned ranges. The ethylene structure in the rubbery polymer (A) is preferably 90% by mass or less, more preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. When the ethylene structure in the rubbery polymer (A) is 90% by mass or less, excellent rubber elasticity is obtained. The ethylene structure in the rubbery polymer (A) includes all ethylene structures obtained by copolymerizing ethylene monomers, ethylene structures obtained by polymerizing conjugated diene monomers and then hydrogenating them, etc. For example, when a 1,4-butadiene unit is hydrogenated, two ethylene structures are obtained, and when a 1,4-isoprene unit is hydrogenated, one propylene structure and one ethylene structure are obtained. The ethylene structure of the rubbery polymer (A) can be measured by the method described in the Examples below. The ethylene structure of the rubbery polymer (A) can be controlled within the above-mentioned range by adjusting the amount of ethylene added, the amount of conjugated diene monomer added, the hydrogenation rate, etc.

[0014] <Vinyl aromatic monomer block content> The rubbery polymer (A) used in the crosslinkable rubber composition of this embodiment has a vinyl aromatic monomer block content of less than 10% by mass (vinyl aromatic monomer block<10% by mass). The vinyl aromatic monomer block refers to a block in which eight or more vinyl aromatic monomer units are chained. By making the vinyl aromatic monomer block content of the rubbery polymer (A) less than 10% by mass, fuel economy tends to be improved when the crosslinkable rubber composition of this embodiment is used as a raw material for tires. The aromatic vinyl monomer block content of the rubbery polymer (A) is preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. From the viewpoint of flexibility, it is preferred that the vinyl aromatic monomer block has few or no blocks in which 30 or more vinyl aromatic monomer units are chained. Specifically, when the rubbery polymer (A) is a butadiene-styrene copolymer, the morphology of the vinyl aromatic monomer block can be analyzed by decomposing the rubbery polymer (A) by the Kolthoff method (I.M. Kolthoff, et al., J. Polym. Sci. 1, 429 (1946)) and measuring the amount of polystyrene insoluble in methanol. Alternatively, as described in WO 2014 / 133097, the morphology can be analyzed by a known method such as measuring the chain length of styrene units using NMR. The vinyl aromatic monomer block content of the rubbery polymer (A) can be controlled within the above range by adjusting the method of adding the vinyl aromatic monomer, the addition of a polymerization aid, the polymerization temperature, and the like.

[0015] <Content of vinyl aromatic monomer units in rubbery polymer (A)> The content of vinyl aromatic monomer units in the rubber-like polymer (A) used in the cross-linkable rubber composition of this embodiment is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more, from the viewpoints of deformation resistance during transportation of a molded article of the cross-linkable rubber composition of this embodiment, and breaking strength and wet skid resistance when the cross-linkable rubber composition of this embodiment is used in a tire tread. On the other hand, from the viewpoint of the cuttability during measurement when the crosslinkable rubber composition of this embodiment is molded into a sheet-like or block-like body, the adhesion when the crosslinkable rubber composition of this embodiment is made into a packaging film and the resistance to tearing of the packaging film, and further from the viewpoint of fuel economy and abrasion resistance when the crosslinkable rubber composition of this embodiment is used in a tire tread, the content of vinyl aromatic monomer units in the rubbery polymer (A) is preferably 45 mass% or less, more preferably 30 mass% or less, and even more preferably 25 mass% or less. Furthermore, when the rubber composition for crosslinking of the present embodiment is used as a material for run-flat tire components or the like, and high modulus is required, the content of vinyl aromatic monomer units in the rubbery polymer (A) is preferably 30 mass% or more. The content of the vinyl aromatic monomer unit in the rubbery polymer (A) can be measured by the method described in the examples below. The content of the vinyl aromatic monomer units in the rubbery polymer (A) can be controlled within the above-mentioned range by adjusting the amount of the vinyl aromatic monomer added in the polymerization step.

[0016] <Vinyl unit and butylene unit content of rubber polymer (A)> The rubbery polymer (A) used in the crosslinkable rubber composition of the present embodiment preferably has a vinyl unit and butylene unit content of 20 mol % or more. The content of vinyl units and butylene units in the rubber polymer (A) is preferably 20 mol% or more, more preferably 25 mol% or more, and even more preferably 30 mol% or more, from the viewpoints of the manufacturability of the rubber polymer (A), the processability of the rubber composition for crosslinking of the present embodiment, and the wet skid resistance when the rubber composition for crosslinking of the present embodiment is used in a tire tread. In addition, from the viewpoint of heat aging resistance of the rubbery polymer (A) and fuel economy when the rubber composition for crosslinking of this embodiment is used in a tire tread, it is preferably 60 mol % or less, more preferably 50 mol % or less. The contents of vinyl units and butylene units in the rubber-like polymer (A) are as described in the examples below. 1 It can be measured by H-NMR measurement. The vinyl unit and butylene unit contents of the rubbery polymer (A) can be controlled within the above numerical range by adding a polar compound or adjusting the polymerization temperature during polymerization of the rubbery polymer (A).

[0017] <Monomer units that allow the rubber polymer (A) to contain an unsaturated group> The rubbery polymer (A) used in the crosslinkable rubber composition of the present embodiment preferably contains 2% by mass or more of conjugated diene monomer units or monomer units having an unsaturated group such as myrcene. From the viewpoint of economy and productivity, the rubbery polymer (A) more preferably contains a conjugated diene monomer unit. When the rubbery polymer (A) contains conjugated diene monomer units or myrcene as a component, the resulting rubbery polymer (A) has double bonds, which become crosslinkable unsaturated groups. The content of conjugated diene monomer units and monomer units having an unsaturated group such as myrcene in the rubbery polymer (A) is closely related to the above-mentioned iodine value. When the content of the conjugated diene monomer unit or the monomer unit having an unsaturated group such as myrcene is 2% by mass or more, the composition is excellent in terms of ease of crosslinking. The content of the conjugated diene monomer unit or the monomer unit having an unsaturated group such as myrcene is more preferably 3% by mass or more, and even more preferably 6% by mass or more. The content of conjugated diene monomer units and monomer units having an unsaturated group such as myrcene is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, which provides excellent weather resistance and resistance to deterioration over time. Of the conjugated diene monomer units and monomer units having an unsaturated group such as myrcene, the conjugated diene monomer units are preferred from the viewpoints of economy and productivity. The content of conjugated diene monomer units and monomer units having an unsaturated group such as myrcene in the rubbery polymer (A) can be measured by the method described in the Examples below, and can be controlled to fall within the above-mentioned range by adjusting the amount of conjugated diene monomer or monomer having an unsaturated group such as myrcene added or the hydrogenation rate of the conjugated diene monomer, as described in (Method for producing rubbery polymer (A)) below.

[0018] <α-olefin content in rubbery polymer (A)> The content of α-olefin in all monomer units excluding vinyl aromatic monomer units in the rubbery polymer (A) is preferably 13% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, from the viewpoint of productivity of the rubbery polymer. On the other hand, from the viewpoint of mechanical strength when the rubber composition for crosslinking of the present embodiment is used in a tire, the content of the α-olefin is preferably 70 mass% or less, more preferably 60 mass% or less, even more preferably 55 mass% or less, and even more preferably 50 mass% or less. When the rubbery polymer (A) is produced by hydrogenating a polymer or copolymer of a conjugated diene monomer, the content of the α-olefin can be controlled by adjusting the content of the conjugated diene monomer unit, the amount of vinyl bonds, or the hydrogenation rate before the hydrogenation reaction. When 1,2-vinylbutadiene is hydrogenated, it becomes butylene, which has an α-olefin structure. The α-olefin content in all monomer units excluding vinyl aromatic monomer units in the rubbery polymer (A) is as described in the examples below. 1 It can be measured by H-NMR measurement.

[0019] <Modification of the rubbery polymer (A) constituting the crosslinkable rubber composition> In the crosslinkable rubber composition of this embodiment, from the viewpoint of the peel resistance of the crosslinkable rubber composition from a molded article of the crosslinkable rubber composition and fuel economy when used in a tire, it is preferable that the rubber-like polymer (A) contains a nitrogen atom or a tin atom, and it is more preferable that it contains a nitrogen atom.

[0020] When the rubbery polymer (A) is modified with nitrogen, from the viewpoints of the mechanical strength of the rubber composition to be crosslinked and the dispersibility of silica or carbon black when producing a tire containing silica or carbon black, the modification rate of the rubbery polymer (A) measured by a column adsorption GPC method is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. In this specification, the "modification ratio" represents the mass ratio of the polymer having a nitrogen atom-containing functional group to the total amount of the rubbery polymer (A). The position at which the nitrogen atom is introduced into the rubbery polymer (A) used in the crosslinkable rubber composition of this embodiment may be any of the polymerization initiation terminal of the rubbery polymer (A), in the molecular chain (including the graft product), and the polymerization terminal. The modification rate can be controlled within the above range by adjusting the amount of modifier added to the rubbery polymer (A) and the modification process time.

[0021] When the rubbery polymer (A) used in the crosslinkable rubber composition of this embodiment is obtained by polymerizing a conjugated diene monomer and then hydrogenating it to obtain a hydrogenated polymer, it is preferable to use a method of introducing tin atoms or nitrogen atoms into the rubbery polymer (A) using a coupling agent containing tin atoms or nitrogen atoms, from the viewpoints of polymerization productivity, a high modification rate, and wear resistance and fuel economy when used as a tire material. In particular, it is more preferable to use a method of introducing nitrogen atoms into the rubbery polymer (A) using a coupling agent containing nitrogen atoms.

[0022] From the viewpoint of polymerization productivity and a high modification rate of the rubbery polymer (A), the nitrogen atom-containing coupling agent is not limited to the following, but examples thereof include isocyanate compounds, isothiocyanate compounds, isocyanuric acid derivatives, nitrogen group-containing carbonyl compounds, nitrogen group-containing vinyl compounds, nitrogen group-containing epoxy compounds, and nitrogen group-containing alkoxysilane compounds. As these nitrogen atom-containing coupling agents, nitrogen group-containing alkoxysilane compounds are more preferred from the viewpoints of polymerization productivity of the rubbery polymer (A), high modification rate, and tensile strength when used as a tire material.

[0023] Examples of the nitrogen group-containing alkoxysilane compound include, but are not limited to, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(4-trimethoxysilylbutyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacyclohexane, 2,2-dimethoxy-1-(5-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(5-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(5-trimethoxysilylpropyl)-1-aza-2-silacyclohexane ... )-1-Aza-2-silacycloheptane, 2,2-dimethoxy-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, 2,2-diethoxy-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, 2-methoxy-2-methyl-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2-ethoxy-2-ethyl-1-(3-triethoxysilylpropyl)-1-aza-2-silac Clopentane, 2-methoxy, 2-methyl-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, and 2-ethoxy-2-ethyl-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane, tris(3-trimethoxysilylpropyl)amine, tris(3-methyldimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-methyldiethoxysilylpropyl)amine Amines, tris(trimethoxysilylmethyl)amine, tris(2-trimethoxysilylethyl)amine, and tris(4-trimethoxysilylbutyl)amine, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, and N 1-(3-(bis(3-(trimethoxysilyl)propyl)amino)propyl)-N 1 -methyl-N 3 -(3-(methyl(3-(trimethoxysilyl)propyl)amino)propyl)-N 3 -(3-(trimethoxysilyl)propyl)-1,3-propanediamine and the like.

[0024] When the rubber-like polymer (A) used in the rubber composition for crosslinking of this embodiment is produced by copolymerizing ethylene and a conjugated diene monomer, it is preferable that the rubber-like polymer (A) contains a tin atom, a nitrogen atom, or a silicon atom, from the viewpoints of the breaking strength of the rubber composition for crosslinking of this embodiment, and the fuel economy, abrasion resistance, and flexibility when used as a tire material. From the viewpoint of the productivity of the rubbery polymer (A), it is preferable to employ a method in which, when the conversion rate of the polymerization reaction reaches 100%, a coupling agent containing a tin atom, a nitrogen atom, or a silicon atom is used to introduce these atoms into the rubbery polymer (A). Examples of coupling agents containing a tin atom, a nitrogen atom, or a silicon atom include, but are not limited to, tin-containing compounds such as bis(1-octadecylmaleate)dioctyltin, isocyanate compounds such as 4,4-diphenylmethane diisocyanate, and alkoxysilane compounds such as glycidylpropyltrimethoxysilane.

[0025] <Glass transition temperature of rubbery polymer (A)> The glass transition temperature of the rubbery polymer (A) used in the crosslinkable rubber composition of this embodiment is preferably −90° C. or higher, more preferably −80° C. or higher, and even more preferably −75° C. or higher, from the viewpoint of the tensile strength of the crosslinkable composition of this embodiment. On the other hand, from the viewpoint of flexibility of the rubber composition for crosslinking of the present embodiment and cut resistance of the sheet during tire production, the temperature is preferably -15°C or lower, more preferably -30°C or lower, and further preferably -40°C or lower. Regarding the glass transition temperature, in accordance with ISO 22768:2006, a DSC curve is recorded while increasing the temperature within a predetermined temperature range, the peak top (inflection point) of the DSC differential curve is determined, and the temperature of the peak top is taken as the glass transition temperature.

[0026] <Weight-average molecular weight of rubber polymer (A)> The weight average molecular weight of the rubber-like polymer (A) used in the crosslinkable rubber composition of this embodiment is preferably 100,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and even more preferably 250,000 or more, from the viewpoints of compatibility with the crosslinkable rubber composition of this embodiment and the tensile elongation of the crosslinkable rubber composition. On the other hand, from the viewpoint of processability of the rubber composition for crosslinking, it is preferably 1,000,000 or less, more preferably 700,000 or less, even more preferably 600,000 or less, and even more preferably 500,000 or less. The molecular weight distribution (=weight average molecular weight / number average molecular weight) of the rubber polymer (A) used in the rubber composition for crosslinking of this embodiment is preferably 2.0 or less, more preferably 1.8 or less, and even more preferably 1.6 or less, from the viewpoint of compatibility with the rubber composition for crosslinking and fuel economy when used as a tire material. On the other hand, from the viewpoint of processability of the rubber composition for crosslinking, it is preferably 1.05 or more, more preferably 1.2 or more, and even more preferably 1.4 or more. The weight average molecular weight and molecular weight distribution of the rubbery polymer (A) can be calculated from the polystyrene-equivalent molecular weight measured by GPC (gel permeation chromatography). The weight average molecular weight and molecular weight distribution of the rubbery polymer (A) can be controlled within the above ranges by adjusting various polymerization conditions such as the amount of monomer added in the polymerization step, polymerization time, polymerization temperature, and polymerization pressure.

[0027] The rubbery polymer (A) used in the rubber composition for crosslinking of this embodiment may have two or more polymer blocks with different constituent ratios of vinyl aromatic monomer units, ethylene, α-olefin, and conjugated diene monomer units, from the viewpoints of compatibility with the rubber composition for crosslinking, flexibility over a wide temperature range from low to high temperatures, etc. Note that each polymer block may be a copolymer block containing multiple types of monomer units. From the viewpoint of flexibility, the amount of vinyl aromatic monomer units in the polymer block is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0028] (Method for producing rubbery polymer (A)) Examples of a method for producing the rubbery polymer (A) used in the crosslinkable rubber composition of this embodiment include a method in which at least a conjugated diene monomer is polymerized or copolymerized, and then a part or most of the double bonds are hydrogenated, and a method in which at least ethylene and a conjugated diene monomer are copolymerized.

[0029] Examples of the method of polymerizing or copolymerizing at least a conjugated diene monomer and then hydrogenating the resulting polymer include WO 96 / 05250, JP 2000-053706, WO 2003 / 085010, WO 2019 / 151126, WO 2019 / 151127, WO 2002 / 002663, and WO 2015 / 006179. As described above, various additives are added, and under known conditions, a conjugated diene monomer is polymerized by anionic polymerization, and if necessary, copolymerized with other monomers, followed by hydrogenation.

[0030] Examples of methods for copolymerizing at least ethylene and a conjugated diene monomer include methods of copolymerizing ethylene, a conjugated diene monomer, and, if necessary, other monomers by coordination polymerization under various additives and conditions, as described in WO 2019 / 078083, WO 2019 / 171679, and WO 2019 / 142501.

[0031] From the viewpoint of ensuring a wide degree of freedom in the polymer structure, the rubbery polymer (A) is preferably produced by polymerizing a conjugated diene monomer and then hydrogenating the polymer.

[0032] Examples of conjugated diene monomers include, but are not limited to, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene. Among these, from the viewpoint of ease of industrial availability, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred. These may be used alone or in combination of two or more.

[0033] The rubbery polymer (A) may use, as the polymerization monomer, a vinyl aromatic monomer in addition to the above-mentioned conjugated diene monomer. Examples of vinyl aromatic monomers include, but are not limited to, styrene, p-methylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, diphenylethylene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, and tertiary amino group-containing diphenylethylene (e.g., 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene). Among these, styrene is preferred from the viewpoint of industrial availability. These may be used alone or in combination of two or more.

[0034] In addition to the above-mentioned monomers, other monomers may be used as polymerization monomers for the rubbery polymer (A) as required. Examples of other monomers include, but are not limited to, unsaturated carboxylic acid esters, unsaturated carboxylic acids, α,β-unsaturated nitrile compounds, α-olefins (butylene, propylene, pentene, hexene, etc.), ethylene, myrcene, ethylidene norbornene, isopropylidene norbornene, cyclopentadiene, and divinylbenzene.

[0035] When the rubbery polymer (A) used in the rubber composition for crosslinking of this embodiment is produced by polymerizing a conjugated diene monomer, or copolymerizing it with other monomers as needed, followed by hydrogenation, the vinyl bond content of the conjugated diene monomer units of the conjugated diene-based polymer before hydrogenation is important from the viewpoint of obtaining excellent properties. The vinyl bond content is preferably 10 mol% or more, more preferably 20 mol% or more, from the viewpoints of productivity of the rubbery polymer (A) and high wet skid resistance when made into a tire. Furthermore, from the viewpoint of mechanical strength when the rubber composition for crosslinking of this embodiment is used as a tire material, the vinyl bond content is preferably 75 mol% or less, more preferably 60 mol% or less, even more preferably 45 mol% or less, and even more preferably 30 mol% or less.

[0036] The above polymerization step and hydrogenation step may each be carried out in a batch system or a continuous system.

[0037] The hydrogenation rate of the rubbery polymer (A) and the inter- and intra-molecular distribution of the monomer units consisting of monomers such as ethylene, conjugated diene monomer, myrcene, α-olefin, and vinyl aromatic monomer are not particularly limited, and may be uniform, non-uniform, or may have a specific distribution.

[0038] (Addition of additives to rubber polymer (A)) During the production of the rubbery polymer (A) used in the crosslinkable rubber composition of the present embodiment, it is preferable to add various additives.

[0039] <Rubber softener> Examples of the additives include rubber softeners, which are preferably added in an amount of 1 to 30% by mass of all materials in order to improve the productivity of the rubber polymer (A) and the processability when inorganic fillers and the like are blended during tire production. When the molecular weight of the rubbery polymer (A) is high, for example, when the weight average molecular weight exceeds 1,000,000, the rubber softener is preferably used in an amount of 15 to 30% by mass, and on the other hand, when a rubber composition containing a filler is prepared, the amount used is preferably 1 to 15% by mass in order to increase the degree of freedom in compounding. The content of the rubber softener in the rubber composition containing the rubbery polymer (A) is more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of suppressing deterioration over time when used as a tire material. The rubber softener is not particularly limited, but examples thereof include extender oil, liquid rubber, and resin. As the rubber softener, extender oils are preferred from the viewpoints of processability, productivity and economy. The method of adding a rubber softener to the rubber-like polymer (A) is not limited to the following, but a preferred method is to add the rubber softener to a polymer solution, mix, and then remove the solvent from the resulting polymer solution containing the rubber softener.

[0040] Preferred examples of extender oils as rubber softeners include aromatic oils, naphthenic oils, and paraffin oils. Among these, from the viewpoints of environmental safety, oil bleeding prevention, and wet grip properties, aroma substitute oils having a polycyclic aromatic (PCA) content of 3 mass% or less according to the IP346 method are preferred. Examples of aroma substitute oils include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), and RAE (Residual Aromatic Extracts), as shown in Kautschuk Gummi Kunststoffe 52(12)799(1999).

[0041] <Rubber stabilizer> The additives also include stabilizers for rubber. The rubber stabilizer is preferably added after the polymerization step of the rubbery polymer (A) from the viewpoint of preventing gel formation and improving processing stability. The rubber stabilizer is not limited to the following and known stabilizers can be used, but examples thereof include antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (hereinafter also referred to as "BHT"), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol) propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol.

[0042] (Physical properties of rubber polymer (A)) <Residual solvent amount> In the rubber polymer (A) used in the crosslinkable rubber composition of this embodiment, or in a rubber composition obtained by adding various additives to the rubber polymer (A), the residual solvent of the polymerization solvent used in the polymerization step of the rubber polymer (A) is preferably low from the viewpoint of reducing odor and VOCs. The residual solvent amount is preferably 5000 ppm, more preferably 3000 ppm, and even more preferably 1500 ppm or less. Furthermore, from the viewpoint of economical balance, it is preferably 50 ppm or more, more preferably 150 ppm or more, and even more preferably 300 ppm or more.

[0043] <Moisture content> The water content in the rubber polymer (A) used in the crosslinkable rubber composition of this embodiment, or in the rubber composition obtained by adding various additives to the rubber polymer (A), is preferably 0.05% by mass or more and 1.5% by mass or less. From the viewpoint of suppressing gel formation during drying after solvent removal, the water content in the rubber polymer (A) or the rubber composition is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more. On the other hand, from the viewpoint of suppressing condensation and discoloration resistance, the water content is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.8% by mass or less.

[0044] <Mooney viscosity> The Mooney viscosity of the rubbery polymer (A) used in the rubber composition for crosslinking of the present embodiment and of the rubber composition obtained by adding various additives to the rubbery polymer (A) is an index containing information such as the molecular weight, molecular weight distribution, branching degree, softener, residual solvent, and water content of the rubbery polymer (A). The Mooney viscosity measured at 100°C of the rubber polymer (A) and the rubber composition obtained by adding various additives to the rubber polymer (A) is preferably 40 or more, more preferably 50 or more, and even more preferably 55 or more, from the viewpoints of the abrasion resistance of the rubber composition for crosslinking of this embodiment, and the handling stability and breaking strength when used as a tire material. On the other hand, from the viewpoints of the productivity of the rubber polymer (A) and the rubber composition, and the processability of the rubber composition blended with a filler or the like, the Mooney viscosity is preferably 170 or less, more preferably 150 or less, even more preferably 130 or less, and even more preferably 110 or less. Mooney viscosity can be measured by the method specified in ISO289.

[0045] <Mooney relaxation rate> The Mooney relaxation coefficient of the rubbery polymer (A) or a rubber composition using the rubbery polymer (A) measured at 100°C is preferably 0.80 or less, more preferably 0.7 or less, and even more preferably 0.6 or less, from the viewpoint of moldability. The Mooney relaxation rate is an index of the degree of molecular entanglement of a conjugated diene polymer, and the lower the value, the greater the degree of molecular entanglement. The Mooney relaxation rate can be reduced by increasing the molecular weight of the rubbery polymer (A), increasing the degree of branching with the above-mentioned coupling agent or a predetermined branching agent, or increasing the Mooney viscosity by reducing the amount of rubber softener added. The Mooney relaxation rate was determined by preheating the rubbery polymer (A) or a rubber composition using the rubbery polymer (A) at 100°C for 1 minute, rotating the rotor at 2 rpm, and measuring the Mooney viscosity (ML) from the torque after 4 minutes. (1+4) ) is measured, the rotation of the rotor is immediately stopped, and the torque is recorded every 0.1 seconds for 1.6 to 5 seconds after stopping in Mooney units. The torque versus time (seconds) is plotted logarithmically, and the slope of the line is calculated. The absolute value of this line is used as the Mooney relaxation rate.

[0046] (Method for molding rubber polymer (A) and rubber composition) The rubbery polymer (A) used in the crosslinkable rubber composition of the present embodiment, or a rubber composition containing the rubbery polymer (A), is preferably molded into a sheet or block shape from the viewpoint of ease of handling. A block shape is more preferable, and a thickness of 1,000 cm is more preferable. 3 The above block-shaped bales are more preferred, and rectangular bales weighing 17.5 kg to 35 kg are even more preferred.

[0047] (Constituents of the rubber composition for crosslinking) The rubber composition for crosslinking of the present embodiment contains sulfur (B), a radical generator (C), and a vulcanization accelerator (D) from the viewpoint of high mechanical strength and the like. The rubber composition for crosslinking of the present embodiment is subjected to a crosslinking step to form a crosslinked product, which can be used for various applications.

[0048] The rubber composition for crosslinking of the present embodiment contains at least a rubber-like polymer (A) or a rubber composition in which various additives have been added to the rubber-like polymer (A), and may further contain other rubber components, fillers, crosslinking agents, etc., as necessary.

[0049] <Other rubber components> The other rubber components are not particularly limited and can be selected appropriately depending on the purpose. Examples include styrene-butadiene rubber (emulsion polymerization tire or solution polymerization type), natural rubber, polyisoprene, butadiene rubber (high-cis polybutadiene, low-cis polybutadiene, syndiotactic 1,2-polybutadiene, acrylonitrile-butadiene rubber (NBR)), chloroprene rubber, ethylene-α-olefin copolymer rubber such as ethylene-propylene rubber, ethylene-butene rubber, and ethylene-octene, ethylene-propylene-diene rubber (EPDM), butyl rubber, polysulfide rubber, silicone rubber, fluororubber, and urethane rubber. These may be used alone or in combination of two or more. The other rubber component may be mixed with the rubbery polymer (A) in a dry state after the polymerization step of the rubbery polymer (A), or may be mixed in a solution state during the polymerization step of the rubbery polymer (A). Among these, from the viewpoint of the tensile modulus, tear resistance, and flexibility of the rubber composition for crosslinking, an ethylene copolymer is preferred as the other rubber component, and an ethylene-α-olefin copolymer rubber such as ethylene-propylene rubber (EPM) and an ethylene-propylene-diene rubber (EPDM) are more preferred.

[0050] <Content of rubber-like polymer (A) in the total amount of rubber components> The content of the rubber-like polymer (A) relative to the total amount of rubber components in the rubber composition for crosslinking of this embodiment is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, and even more preferably 80% by mass or more.

[0051] <Average iodine value of the total rubber component> The average iodine value of the total amount of rubber components in the rubber composition for crosslinking of this embodiment is preferably 250 (g / 100g) or less, more preferably 200 (g / 100g) or less, even more preferably 130 (g / 100g) or less, and even more preferably 70 (g / 100g) or less, from the viewpoint of suppressing uneven crosslinking and obtaining high mechanical strength. The average iodine value of the rubber component can be measured in accordance with the method described in "JIS K 0070: 1992." The average iodine value of the total amount of rubber component is calculated based on the content of the polymer in the rubber composition for crosslinking of the present embodiment, after measuring the iodine value of the polymer before it is made into the rubber composition for crosslinking of the present embodiment. The iodine value is a value that expresses the amount of halogen that reacts with 100 g of the target substance, converted into grams of iodine, so the unit of the iodine value is "g / 100 g". The iodine value of the total rubber component can be controlled within the above numerical range by adjusting the amount of unsaturated bonds in the polymer constituting the rubber component constituting the crosslinkable rubber composition, the polymerization conditions for the polymer, the amount of hydrogen added, etc.

[0052] <Sulfur (B)> The rubber composition for crosslinking of the present embodiment contains sulfur (B) and a radical generator (C) from the viewpoint of making it difficult for the crosslinking time to become long and obtaining excellent tensile modulus and tear strength in the crosslinked product. The sulfur (B) is sulfur, sulfur monochloride, or sulfur dichloride. Among these, it is preferable to use sulfur in the rubber composition for crosslinking of the present embodiment from the viewpoint of providing excellent fatigue resistance over time.

[0053] The content of sulfur (B) in the rubber composition for crosslinking of this embodiment is from 0.1 parts by mass to 5.0 parts by mass per 100 parts by mass of the rubbery polymer (A) from the viewpoint of obtaining an excellent tensile modulus in the crosslinked product. From this viewpoint, it is preferably 0.5 parts by mass or more, and more preferably 1.0 part by mass or more. On the other hand, from the viewpoint of suppressing uneven crosslinking and obtaining excellent tear strength, it is preferably 5.0 parts by mass or less, and is preferably 4.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less. In the rubber composition for crosslinking of this embodiment, sulfur (B) and a radical generator (C) are used in combination on the premise that the rubbery polymer (A) has few unsaturated groups and is therefore unlikely to undergo a crosslinking reaction. Therefore, strictly speaking, it is considered preferable to set the amount of sulfur (B) and organic peroxide (C) added according to the amount of rubbery polymer (A). However, in practice, the amount of rubbery polymer (A) contained in the total amount of rubber components constituting the rubber composition for crosslinking is set to a certain amount or more (it will not be an extremely small amount) in consideration of the effect of the rubbery polymer (A) on the performance of the rubber composition for crosslinking. Therefore, even if the amounts of sulfur (B) and radical generator (C) are set relative to the total amount of rubber components, there is little effect on the performance of the rubber composition for crosslinking of this embodiment. The sulfur (B) may be used alone or in combination of two or more kinds.

[0054] <Radical Generator (C)> The rubber composition for crosslinking of the present embodiment contains a radical generator (C). The radical generator (C) generates peroxy radicals in the presence of heat or a redox system, and from the viewpoints of the tensile energy and compression set resistance of the rubber composition for crosslinking, organic peroxides and azo compounds are preferred, with organic peroxides being more preferred. As a radical generator (C), organic peroxides attack the double bonds contained in the unsaturated groups in the rubber-like polymer (A) to form crosslinks. Crosslinking using sulfur (B) alone is slow and the crosslink density is likely to be insufficient, so crosslinking using a radical generator (C) with a different mechanism is expected to supplement the overall crosslink density. Therefore, any compound that can generate radicals can be used as the radical generator (C).

[0055] Examples of organic peroxides include, but are not limited to, dicumyl peroxide, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butyl hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, α,α'-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-bis(t-butylperoxy)-3-hexyne, benzoyl peroxide, t-butyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxymaleic acid, and t-butylperoxyisopropyl carbonate. Particularly preferred are dicumyl peroxide, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(t-butylperoxy)-3-hexyne, and t-butyl peroxide. The organic peroxides may be used alone or in combination of two or more.

[0056] Examples of azo compounds include, but are not limited to, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile (AMBN), 2,2'-azobis-2,4-dimethylvaleronitrile (ADVN), 2,2'-azobis-4-azobiscyanovaleric acid (salt) (ACVA), etc. One azo compound may be used alone, or two or more may be used in combination.

[0057] The content of the radical generator (C) in the rubber composition for crosslinking of this embodiment is from 0.1 parts by mass to 5.0 parts by mass relative to 100 parts by mass of the rubber-like polymer (A) in the rubber composition for crosslinking, from the viewpoints of shortening the crosslinking time of the rubber composition for crosslinking and of the tensile modulus and tear strength. It is preferably from 0.4 parts by mass or more, and more preferably from 1.0 part by mass or more. On the other hand, from the viewpoints of suppressing uneven crosslinking and flexibility, it is from 5.0 parts by mass or less, and is preferably from 4.0% by mass or less, more preferably from 3.0% by mass or less, and even more preferably from 2.0% by mass or less.

[0058] From the viewpoint of the demolding properties of the vulcanizate of the rubber composition for cross-linking of the present embodiment and the hardness of the rubber composition for cross-linking, the contents of the sulfur (B) and the radical generator (C) are preferably such that the content of sulfur (B) > the content of radical generator (C), more preferably the content of sulfur (B) / the content of radical generator (C) > 1.67, and even more preferably the content of sulfur (B) / the content of radical generator (C) > 1.95.

[0059] Furthermore, from the viewpoint of sufficiently crosslinking the rubber composition for crosslinking of this embodiment and improving the tensile modulus, tear strength, and abrasion resistance, the relationship between the content of the radical generator (C) and the content of the vinyl aromatic monomer unit in the rubbery polymer (A) is preferably such that the content of the radical generator (C) / the content of the vinyl aromatic monomer unit in the rubbery polymer (A) is ≥ 0.026. The ratio of the content of the radical generator (C) / the content of the vinyl aromatic monomer unit in the rubbery polymer (A) is more preferably 0.035 or more, even more preferably 0.08 or more, and even more preferably 0.105 or more. When the content of vinyl aromatic monomer units in the rubbery polymer (A) is high, the content of crosslinkable unsaturated groups in the rubbery polymer (A) is low, but sufficient crosslinking can be achieved by adding a large amount of radical generator (C).On the other hand, when the content of vinyl aromatic monomer units in the rubbery polymer (A) is low, the content of crosslinkable unsaturated groups is high, so sufficient crosslinking can be achieved without adding a large amount of radical generator (C). In view of the above, in the present invention, the present inventors have focused on the content of the radical generator (C) and the content of the vinyl aromatic monomer unit in the rubbery polymer (A) and, as a result of extensive investigations, have obtained the above relationship. When the rubber-like polymer (A) does not contain a vinyl aromatic monomer unit, the denominator of "content of radical generator (C) / content of vinyl aromatic monomer unit in the rubber-like polymer (A)" is zero, and therefore this formula is valid when the rubber-like polymer (A) contains a vinyl aromatic monomer unit (when the content is not zero).

[0060] <Vulcanization accelerator (D)> The rubber composition for crosslinking of the present embodiment contains a vulcanization accelerator (D). As the vulcanization accelerator (D), from the viewpoint of a short crosslinking time of the rubber composition for crosslinking and abrasion resistance, preferred examples include guanidine-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, sulfenamide-based, thiourea-based, thiuram-based, dithiocarbamate-based, and xanthate-based compounds. In particular, guanidine vulcanization accelerators such as diphenylguanidine, and thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, N-cyclohexyl-2-benzothiazylsulfenamide, and Nt-butyl-2-benzothiazolylsulfenamide are more preferred. The vulcanization accelerator (D) may be used alone or in combination of two or more kinds.

[0061] The content of the vulcanization accelerator (D) in the rubber composition for crosslinking of this embodiment is 0.1 parts by mass or more, preferably 0.7 parts by mass or more, and more preferably 1.2 parts by mass or more, per 100 parts by mass of the rubber-like polymer (A) in the rubber composition for crosslinking, from the viewpoint of high crosslink density. On the other hand, from the viewpoint of flexibility of the rubber composition for crosslinking, the amount is 5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 2 parts by mass or less.

[0062] Furthermore, from the viewpoint of a short crosslinking time and hardness of the crosslinkable rubber composition of the present embodiment, it is preferable that the ratio of (content of sulfur (B) + content of radical generator (C)) × 0.5 < (content of vulcanization accelerator (D)) is satisfied. It is more preferable that (the content of sulfur (B) + the content of radical generator (C)) × 0.65 < (the content of vulcanization accelerator (D)), and it is even more preferable that (the content of sulfur (B) + the content of radical generator (C)) × 0.8 < (the content of vulcanization accelerator (D)).

[0063] <Multifunctional crosslinking aid (E)> The rubber composition for crosslinking of the present embodiment preferably contains a polyfunctional crosslinking aid (E). The polyfunctional crosslinking aid (E) is a compound having two or more radically reactive unsaturated groups from the viewpoint of uniform crosslinkability of the rubber composition for crosslinking of this embodiment and a short crosslinking time. The polyfunctional crosslinking aid (E) is not limited to the following, but preferred examples include polyfunctional vinyl monomers such as divinylbenzene and triallyl cyanurate, and polyfunctional methacrylate monomers such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate. In particular, triallyl isocyanurate and triethylene glycol dimethacrylate are preferred.

[0064] From the viewpoint of uniform crosslinking of the rubber composition for crosslinking of this embodiment, the content of the polyfunctional crosslinking aid (E) is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component in the rubber composition for crosslinking, and even more preferably equal to or greater than the content of the radical generator (C), and even more preferably 1.5 times or more the content of the radical generator (C). On the other hand, from the viewpoint of suppressing uneven crosslinking, the content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less, per 100 parts by mass of the rubber component in the rubber composition for crosslinking.

[0065] <Resin> The cross-linkable rubber composition of the present embodiment preferably contains 3 to 40 parts by mass of resin per 100 parts by mass of the rubber component in the cross-linkable rubber composition, from the viewpoint of improving the degree of cohesion when discharged from a kneader, sheet moldability, and shape stability of the extrudate during extrusion processing. The resin does not include the above-mentioned rubbery polymer (A) or other rubber components. From the viewpoint of tensile energy, the content of the resin is more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more. On the other hand, from the viewpoint of ease of mixing the rubber composition for crosslinking, the amount is more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less.

[0066] The resin contained in the rubber composition for crosslinking is preferably a compound that is solid at room temperature (23° C.) and contains carbon and hydrogen as its main components, but may contain atoms other than carbon and hydrogen. Examples of resins include aliphatic, alicyclic, aromatic, hydrogenated aromatic, and aliphatic / aromatic resins using aliphatic and / or aromatic monomers. The resin may be a petroleum-based resin or a non-petroleum-based natural or synthetic resin. Examples of the resin include, but are not limited to, a resin selected from the group consisting of a cyclopentadiene (CPD) homopolymer or copolymer resin, a dicyclopentadiene (DCPD) homopolymer or copolymer resin, a terpene homopolymer or copolymer resin, a C5 fraction homopolymer or copolymer resin, a C9 fraction homopolymer or copolymer resin, an α-methylstyrene homopolymer or copolymer resin, and a mixture of these resins. Of the above copolymer resins, particularly preferred are copolymers selected from the group consisting of (D)CPD / vinyl aromatic copolymer resins, (D)CPD / terpene copolymer resins, terpene / phenol copolymer resins, (D)CPD / C5 fraction copolymer resins, (D)CPD / C9 fraction copolymer resins, terpene / vinyl aromatic copolymer resins, terpene / phenol copolymer resins, C5 fraction / vinyl aromatic copolymer resins, and mixtures of these resins. The resins may be used alone or in combination of two or more. From the viewpoint of the tensile strength and tensile elongation of the rubber composition for crosslinking of the present embodiment, the resin preferably has a glass transition temperature of 30° C. or higher, more preferably 40° C. or higher. On the other hand, from the viewpoint of ease of mixing the rubber composition for crosslinking of the present embodiment, the glass transition temperature of the resin is preferably 100°C or lower, more preferably 80°C or lower.

[0067] <Filler> The rubber composition for crosslinking of the present embodiment preferably contains a filler from the viewpoint of improving reinforcement properties. The content of the filler can be appropriately selected depending on the purpose, but is preferably 10 to 130 parts by mass, more preferably 30 to 90 parts by mass, and even more preferably 40 to 85 parts by mass, per 100 parts by mass of the rubber component. The "rubber component" includes the above-mentioned rubbery polymer (A) and the above-mentioned other rubber components. When the filler content is 10 parts by mass or more, the effect of improving reinforcing properties due to the incorporation of the filler can be obtained, and when the filler content is 130 parts by mass or less, good workability can be maintained while avoiding a significant decrease in fuel efficiency when used as a tire material. Examples of fillers include, but are not limited to, carbon black, silica, aluminum hydroxide, clay, alumina, talc, mica, kaolin, glass balloons, glass beads, calcium carbonate, magnesium carbonate, magnesium hydroxide, magnesium oxide, titanium oxide, potassium titanate, and barium sulfate. Of these, carbon black is preferably used. These may be used alone or in combination of two or more. The carbon black is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include FEF, GPF, SRF, HAF, N339, IISAF, ISAF, SAF, etc. These may be used alone or in combination of two or more. The nitrogen adsorption specific surface area (N2SA, measured in accordance with JIS K6217-2:2001) of the carbon black is not particularly limited and can be appropriately selected depending on the purpose.

[0068] Among these fillers, silica is preferred, and precipitated silica is more preferred, from the viewpoint of fuel economy and wet skid resistance when the rubber composition for crosslinking is used as a material for a tire tread. The content of silica is preferably 30 to 120 parts by mass, more preferably 40 to 120 parts by mass, even more preferably 50 to 100 parts by mass, and even more preferably 60 to 80 parts by mass, per 100 parts by mass of the rubber component, from the viewpoints of fuel economy and wet skid resistance.

[0069] <Silane coupling agent> The rubber composition for crosslinking of the present embodiment preferably contains a silane coupling agent from the viewpoints of improving the dispersibility of the filler and the tensile strength of the crosslinked product. The silane coupling agent has the function of strengthening the interaction between the rubber component and the inorganic filler, and has groups that have affinity or bonding properties for both the rubber component and the filler. A compound having a sulfur-bonding moiety and an alkoxysilyl group or silanol group moiety in one molecule is preferred. Such compounds include, but are not limited to, bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide, S-[3-(triethoxysilyl)-propyl]octanethioate, condensates of S-[3-(triethoxysilyl)-propyl]octanethioate with [(triethoxysilyl)-propyl]thiol, silanes bearing at least one thiol (—SH) functional group (referred to as mercaptosilane) and / or at least one masked thiol group.

[0070] The content of the silane coupling agent in the rubber composition for crosslinking of this embodiment 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.

[0071] <Other additives> In addition to the above, various additives such as other softeners, other fillers, heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, and lubricants may be added to the crosslinkable rubber composition of the present embodiment. As other softeners, known softeners can be used. Other fillers include, for example, calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate. Known materials can be used for the heat stabilizer, antistatic agent, weather stabilizer, antioxidant, colorant, and lubricant.

[0072] [Method for producing crosslinked rubber] The method for producing a crosslinked rubber of this embodiment includes a step of kneading the above-described rubber composition for crosslinking of this embodiment. The method for kneading the rubber composition for crosslinking is not limited to the following, but examples thereof include 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, the melt kneading method using a roll, a Banbury mixer, a kneader, or an extruder is preferred from the viewpoint of productivity and good kneading properties. Rubber components other than the rubbery polymer (A), silica-based inorganic fillers, carbon black, other fillers, silane coupling agents, rubber softeners and other additives may also be mixed in the same manner. Either a method of kneading the rubber component, filler, silane coupling agent, and additives all at once or a method of mixing them in several batches can be applied. After preparing the rubber composition for crosslinking, the composition is molded as needed and heated (for example, at 140 to 180°C) to cause a crosslinking reaction. It is preferable to avoid storing the crosslinked rubber composition of this embodiment in high-temperature and high-humidity conditions and / or for long periods of time.

[0073] [Application] The rubber composition for crosslinking of the present embodiment can be used for tire components, interior and exterior parts of automobiles, vibration-proof rubber, belts, footwear, foams, various industrial goods, and the like, and these include the rubber composition for crosslinking of the present embodiment. Among these, it is preferably used for tire components. Examples of tire components include tire treads, carcasses, sidewalls, bead portions, etc. for various tires such as fuel-efficient tires, all-season tires, high-performance tires, snow tires, studless tires, etc. In particular, the rubber composition for cross-linking of the present embodiment has an excellent balance of abrasion resistance, fuel-efficient properties, wet skid resistance, and snow performance when vulcanized, and is therefore suitably used as tire treads for fuel-efficient tires, high-performance tires, and snow tires.

[0074] As a method for manufacturing a tire, a known method can be used. For example, components typically used in tire manufacturing, such as at least one carcass layer selected from the group consisting of an unvulcanized rubber composition for crosslinking and cords, a belt layer, and a tread layer, are laminated on a tire building drum in this order, and the drum is removed to produce a green tire. Next, the green tire is heated and vulcanized in a conventional manner, thereby producing a desired tire (e.g., a pneumatic tire). [Example]

[0075] 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 in any way by the following examples and comparative examples. Various physical properties in the examples and comparative examples were measured by the methods shown below.

[0076] (Physical Properties 1) Molecular Weight and Molecular Weight Distribution <Measurement condition 1>: Using the rubbery polymers obtained in the polymerization examples described below as samples, chromatograms were measured using a GPC measurement apparatus (trade name "HLC-8320GPC" manufactured by Tosoh Corporation) in which three columns packed with polystyrene gel were connected together, and an RI detector (trade name "HLC8020" manufactured by Tosoh Corporation) under the specific measurement conditions described below, and the weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) were determined based on a calibration curve obtained using standard polystyrene.

[0077] [Specific measurement conditions] GPC measuring device: Tosoh Corporation, product name "HLC-8320GPC" Eluent: 5mmol / L triethylamine in THF (tetrahydrofuran) Guard column: "TSKguardcolumn SuperMP(HZ)-H" manufactured by Tosoh Corporation Column: Three "TSKgel SuperMultiporeHZ-H" columns manufactured by Tosoh Corporation were connected. Oven temperature: 40°C Flow rate: 0.35mL / min Sample: 10 mg of the sample to be measured was dissolved in 10 mL of THF to prepare a measurement solution, and 10 μL of the measurement solution was injected into the GPC measurement device.

[0078] Among the various samples measured under the above <Measurement Condition 1>, samples whose molecular weight distribution (Mw / Mn) was less than 1.6 were measured again under the following <Measurement Condition 2>, and the results were used as the measured values. For samples that were measured under the above <Measurement Condition 1> and had a molecular weight distribution value of 1.6 or more, the result measured under <Measurement Condition 1> was used as the measured value.

[0079] <Measurement condition 2>: Using the rubbery polymers obtained in the polymerization examples described below as samples, chromatograms were measured using a GPC measurement apparatus (trade name "HLC-8320GPC" manufactured by Tosoh Corporation) equipped with three columns packed with polystyrene gel connected together under the following specific conditions, and an RI detector (trade name "HLC8020" manufactured by Tosoh Corporation). The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) were determined based on a calibration curve using standard polystyrene.

[0080] [Specific measurement conditions] Eluent: THF containing 5mmol / L triethylamine Guard column: "TSKguardcolumn SuperH-H" manufactured by Tosoh Corporation Column: Tosoh Corporation's "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" connected in this order from upstream Oven temperature: 40°C Flow rate: 0.6mL / min Sample: 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 for measurement.

[0081] (Physical Property 2) Mooney Viscosity of Rubber-like Polymers Using the rubbery polymers obtained in the polymerization examples described below as samples, Mooney viscosities were measured in accordance with ISO 289 using a Mooney viscometer (trade name "VR1132" manufactured by Ueshima Seisakusho Co., Ltd.). After preheating the sample at 100°C for 1 minute, the L-type rotor was rotated at 2 rpm, and the torque was measured after 4 minutes to determine the Mooney viscosity (ML (1+4) ) was obtained.

[0082] (Property 3) Modification rate The modification rates of the rubber-like polymers obtained in the polymerization examples described below were measured by column adsorption GPC as follows. The rubbery polymer obtained in the polymerization example was used as a sample, and measurements were carried out by applying the adsorption property of the modified basic polymer component to a GPC column packed with silica gel.

[0083] The amount of a sample solution containing the sample and low-molecular-weight internal standard polystyrene adsorbed onto the silica-based column was measured by subtracting the chromatogram measured on the polystyrene-based column from the chromatogram measured on the silica-based column, and the modification rate was calculated.

[0084] The specific measurement conditions are shown below. Furthermore, for samples in which the molecular weight distribution of the rubber-like polymer was 1.6 or more as a result of measurement under <Measurement Condition 1> in the above (Physical Property 1), measurement was carried out under the following <Measurement Condition 3>, and for samples in which the molecular weight distribution of the rubber-like polymer was less than 1.6, measurement was carried out under the following <Measurement Condition 4>.

[0085] <Measurement Condition 3: GPC Measurement Conditions Using a Polystyrene Column> GPC measuring device: Tosoh Corporation, product name "HLC-8320GPC" Eluent: THF containing 5mmol / L triethylamine Guard column: "TSKguardcolumn SuperMP(HZ)-H" manufactured by Tosoh Corporation Column: Three "TSKgel SuperMultiporeHZ-H" columns manufactured by Tosoh Corporation were connected. Oven temperature: 40°C Flow rate: 0.35mL / min RI detector (Tosoh HLC8020) Sample: 10 mg of the sample to be measured and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a measurement solution, and 10 μL of the measurement solution was injected into the GPC measurement device.

[0086] <Measurement Condition 4: GPC Measurement Conditions Using a Polystyrene Column> GPC measuring device: Tosoh Corporation, product name "HLC-8320GPC" Eluent: THF containing 5mmol / L triethylamine Guard column: "TSKguardcolumn SuperH-H" manufactured by Tosoh Corporation Column: Tosoh Corporation's "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000" connected in this order from upstream Oven temperature: 40°C Flow rate: 0.6mL / min RI detector (Tosoh HLC8020) Sample: 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 for measurement.

[0087] <GPC measurement conditions using a silica column> GPC measuring device: Tosoh Corporation, product name "HLC-8320GPC" Eluent:THF Guard column: "DIOL 4.6 x 12.5 mm 5 micron" Column: "Zorbax PSM-1000S", "PSM-300S", and "PSM-60S" connected in this order from upstream Oven temperature: 40°C Flow rate: 0.5mL / min RI detector (Tosoh HLC8020) Sample: 10 mg of the sample to be measured and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a measurement solution, and 50 μL of the measurement solution was injected into the GPC measurement device.

[0088] How to calculate the denaturation rate: The peak area P1 of the sample and the peak area P2 of the standard polystyrene were calculated, with the total peak area of ​​the chromatogram using the polystyrene column set to 100. Similarly, the peak area P3 of the sample and the peak area P4 of the standard polystyrene were calculated, with the total peak area of ​​the chromatogram using the silica column set to 100. Then, based on the obtained area values, 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)

[0089] (Physical Property 4) Bound Styrene Amount The rubber-like polymer obtained in the polymerization example described below was used as a sample, and 100 mg of the sample was dissolved in chloroform to make up 100 mL, to prepare a measurement sample. The amount of bound styrene (mass%) relative to 100 mass% of the rubber-like polymer sample was measured based on the amount of absorption of ultraviolet light by the phenyl group of styrene (near 254 nm) (measuring device: Shimadzu UV-2450 spectrophotometer).

[0090] (Physical Property 5) Microstructure of Butadiene Moiety (1,2-Vinyl Bond Amount) The rubber-like polymer obtained in the polymerization example described below was used as a sample, and 50 mg of the sample 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). The "content of vinyl units and butylene units" before hydrogenation corresponds to the "amount of 1,2-vinyl bonds," and the numerical value is the same. Therefore, the "content of vinyl units and butylene units" in Table 1 corresponds to the amount of 1,2-vinyl bonds before hydrogenation.

[0091] (Physical Property 6) Hydrogenation Ratio of Rubber Polymer, Ethylene Structure Content of Rubber Polymer) As a sample, the rubber-like polymer obtained in the polymerization example described below was used. 1 The hydrogenation rate and the content of ethylene structure of the rubber-like polymer were measured by H-NMR. 1 The conditions for H-NMR measurement are as follows: <Measurement conditions> Measuring equipment: JNM-LA400 (JEOL) Solvent: deuterated chloroform Measurement sample: Rubber-like 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℃

[0092] (Physical Property 7) Styrene Block Amount of Rubber Polymer A chain consisting of eight or more styrene structural units connected together is considered to be a styrene block, and the amount of the styrene block was determined as follows. 400MHz measured using deuterated chloroform as a solvent 1 From the 1 H-NMR spectrum, the integral ratio of each chemical shift range of the following (X) was determined, and the amount of styrene block contained in the rubbery polymer was calculated. (X) Aromatic vinyl compounds with 8 or more chains: 6.00≦S<6.68

[0093] (Physical Property 8) Iodine Value of Rubber Polymers The iodine value was measured as follows. After dissolving the sample in cyclohexane, add iodine monochloride solution and leave in a dark place. Then add potassium iodide and water and titrate with sodium thiosulfate solution. When the solution turns pale yellow, add starch solution and titrate until the blue color disappears to determine the iodine value.

[0094] [Production of rubbery polymer] (Preparation of hydrogenation catalyst) In the polymerization examples described below, the hydrogenation catalyst used in preparing the rubbery polymer was prepared by the following method. A nitrogen-purged reaction vessel was charged with 1 liter of dried and purified cyclohexane, 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).

[0095] (Polymerization of rubber-like polymers) <(Polymerization Example 1) Rubber Polymer 1> A 40 L internal volume, temperature-controllable autoclave equipped with a stirrer and a jacket was used as a reactor, and 2,700 g of 1,3-butadiene, 300 g of styrene, 21,000 g of cyclohexane, and 30 mmol of tetrahydrofuran (THF) and 11.6 mmol of 2,2-bis(2-oxolanyl)propane as polar substances, which had been previously removed from impurities, were placed in the reactor, and the internal temperature of the reactor was maintained at 43°C. As a polymerization initiator, 68.0 mmol of n-butyllithium was fed into the reactor. After the polymerization reaction began, the temperature inside the reactor began to rise due to heat generated by the polymerization, and the final temperature inside the reactor reached 76°C. Two minutes after this reaction temperature peak, 13.6 mmol of 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane (compound 1) was added to the reactor as a modifier, and the coupling reaction was carried out for 20 minutes. 13.3 mmol of methanol was added to this polymer solution as a reaction terminator, and a portion of the rubbery polymer solution before hydrogenation was extracted for analysis and the solvent was removed in a dryer to obtain the rubbery polymer before hydrogenation. Thereafter, the hydrogenation catalyst (TC-1) was added to the rubbery polymer solution before hydrogenation in an amount of 70 ppm (based on titanium) per 100 parts by mass of the rubbery polymer before hydrogenation, and a hydrogenation reaction was carried out for 40 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain rubbery polymer 1. The iodine value of the obtained rubbery polymer 1 was 108 (g / 100g). To the resulting rubber polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants, and the mixture was dried. The analysis results are shown in Table 1.

[0096] <(Polymerization Examples 2 and 3) Rubber Polymers 2 and 3> The hydrogenation reaction was carried out for 60 minutes and 80 minutes, respectively. Other conditions were the same as in (Polymerization Example 1), and rubbery polymer 2 and rubbery polymer 3 were obtained. The resulting rubbery polymer 2 had an iodine value of 65 (g / 100 g), and the rubbery polymer 3 had an iodine value of 22 (g / 100 g). The analysis results are shown in Table 1.

[0097] <(Polymerization Example 4) Rubber-like Polymer 4> A temperature-controllable autoclave having an internal volume of 40 L, equipped with a stirrer and a jacket, was used as a reactor. 3,000 g of 1,3-butadiene, 21,000 g of cyclohexane, and 90 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 45°C. As a polymerization initiator, 74.0 mmol of n-butyllithium was fed into the reactor. After the polymerization reaction began, the temperature inside the reactor began to rise due to heat generated by the polymerization, and the final temperature inside the reactor reached 76°C. Two minutes after this reaction temperature peak was reached, 14.8 mmol of silicon tetrachloride (compound 2) was added to the reactor as a modifier, and a coupling reaction was carried out for 20 minutes. 14.4 mmol of methanol was added to this polymer solution as a reaction terminator, and a portion of the rubbery polymer solution before hydrogenation was extracted for analysis and the solvent was removed in a dryer to obtain the rubbery polymer before hydrogenation. Thereafter, the hydrogenation catalyst (TC-1) was added to the rubbery polymer solution before hydrogenation in an amount of 70 ppm (based on titanium) per 100 parts by mass of the rubbery polymer before hydrogenation, and a hydrogenation reaction was carried out for 10 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain rubbery polymer 4. The iodine value of the obtained rubbery polymer 4 was 418 (g / 100g). To the resulting rubber polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants, and the mixture was dried. The analysis results are shown in Table 1.

[0098] <(Polymerization Example 5) Rubber-like Polymer 5> A 40 L internal volume autoclave equipped with a stirrer and a jacket and capable of temperature control was used as a reactor, and 1,000 g of 1,3-butadiene, from which impurities had been removed in advance, 1,350 g of styrene, 21,000 g of cyclohexane, and 30 mmol of tetrahydrofuran (THF) and 5.4 mmol of 2,2-bis(2-oxolanyl)propane as polar substances were placed in the reactor, and the internal temperature of the reactor was maintained at 48°C. As a polymerization initiator, 54.0 mmol of n-butyllithium was fed into the reactor. After the polymerization reaction began, the temperature inside the reactor began to rise due to heat generated by the polymerization. When the monomer conversion in the reactor reached 96%, 650 g of butadiene was added and the reaction continued. The final temperature inside the reactor reached 82°C. Two minutes after the reaction temperature reached its peak, 10.8 mmol of silicon tetrachloride (compound 2) was added to the reactor as a modifier, and the coupling reaction was carried out for 20 minutes. 10.5 mmol of methanol was added to this polymer solution as a reaction terminator, and a portion of the rubbery polymer solution before hydrogenation was extracted for analysis and desolvated in a dryer to obtain the rubbery polymer before hydrogenation. Thereafter, the hydrogenation catalyst (TC-1) was added to the rubbery block polymer solution before hydrogenation in an amount of 70 ppm (based on titanium) per 100 parts by mass of the rubbery polymer before hydrogenation, and a hydrogenation reaction was carried out for 40 minutes at a hydrogen pressure of 0.8 MPa and an average temperature of 85°C to obtain rubbery polymer 5. The iodine value of the obtained rubbery polymer 5 was 39 (g / 100g). To the resulting rubber polymer solution, 12.6 g of n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate and 3.0 g of 4,6-bis(octylthiomethyl)-o-cresol were added as antioxidants, and the mixture was dried. The analysis results are shown in Table 1.

[0099] The types of modifiers in Table 1 below are shown below. Compound 1: 2,2-Dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane Compound 2: Silicon tetrachloride

[0100] [Table 1]

[0101] [Examples 1 to 17 and Comparative Examples 1 to 3] The components shown in Tables 2 to 4 below were mixed to obtain rubber compositions for crosslinking. In the first stage of mixing, rubber polymers 1 to 5 (A), other rubber components, reinforcing filler, silane coupling agent, extender oil, zinc oxide, stearic acid, and wax were mixed using an internal mixer (capacity: 0.3 L) equipped with a temperature control device at a filling rate of 65% and a rotor rotation speed of 30 to 50 rpm. At this time, the temperature of the internal mixer was controlled so that the discharge temperature was 155 to 160°C, and each rubber composition (compound) was obtained.

[0102] Next, in the second stage of mixing, the mixture obtained above was cooled to room temperature, and then an antioxidant was added and the mixture was mixed again to improve the dispersion of the reinforcing filler. In this case, the discharge temperature of the mixture was adjusted to 155 to 160°C by controlling the temperature of the mixer. After cooling, in the third stage of kneading, sulfur (B) and other vulcanization accelerators (D) were added and kneaded using an open roll set at 70°C to obtain a rubber composition for crosslinking. A radical generator (C) and a multifunctional crosslinking aid (E) were also added in the third stage of kneading. Thereafter, the product was molded and vulcanized in a vulcanization press at 160°C for 20 minutes. The vulcanized rubber compositions were evaluated by the following methods. The results are shown in Tables 2 to 4.

[0103] (compounding material) <Rubber component> Polymers 1-5: Rubber-like polymers 1-5 obtained in polymerization examples EPDM: Ethylene-propylene rubber (Sumitomo Chemical "Esprene 505A") NR: Natural rubber (peptized)

[0104] <Reinforcing filler> Silica (product name "Ultrasil 7000GR" manufactured by Evonik Degussa, nitrogen adsorption specific surface area 170 m2 / g) Carbon black (product name "Seast KH (N339)" manufactured by Tokai Carbon Co., Ltd.)

[0105] <Silane coupling agent> Silane coupling agent (product name "Si75" manufactured by Evonik Degussa, bis(triethoxysilylpropyl) disulfide)

[0106] <Vulcanizing agent> Sulfur (B)

[0107] <Radical Generator (C)> Peroxide (PO) (40% active ingredient: NOF's "Perkmyl D") In the table, the numerical value in parentheses labeled "actual amount" is the amount of the active ingredient of the radical generator.

[0108] <Vulcanization accelerator (D)> CBS (N-cyclohexyl-2-benzothiazylsulfinamide)

[0109] <Multifunctional crosslinking aid (E)> Triallyl isocyanurate ("TAIC" manufactured by Mitsubishi Chemical Corporation)

[0110] <Vulcanization aid> zinc oxide stearic acid

[0111] <Other> Wax (paraffin wax) Antioxidant (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine)

[0112] In the table, PO represents a radical generator, the value in parentheses (actual amount (C)) is the amount of active ingredient of the radical generator, and the value without parentheses is the amount added. "S / PO (actual amount)" indicates the content of sulfur (B) / the content of radical generator (C). "PO (actual amount) / St" indicates "content of radical generator (C) / content of vinyl aromatic monomer unit of rubbery polymer (A)". D / (B+C) indicates "content of vulcanization accelerator (D) / (content of sulfur (B)+content of radical generator (C))".

[0113] (characteristic evaluation) <(Evaluation 1) Vulcanization speed> For the rubber compositions for crosslinking of the Examples and Comparative Examples, a rotorless vulcanization tester was used as a rheometer in accordance with JIS K6300-2 "Method for determining vulcanization characteristics using a vibration vulcanization tester" to measure vulcanization curves at a temperature of 160°C, with the obtained torque on the vertical axis and the vulcanization time (min.) on the horizontal axis. In the obtained vulcanization curve, the vulcanization time (min.) required from the start of vulcanization until the torque reached the maximum value MH was defined as tc(max). According to the provisions of JIS K6300-2, the difference between the minimum torque value ML and the maximum torque value MH was defined as ME (ME = MH - ML), and the vulcanization time (min.) from the start of the test until the torque reached ML + 90% ME was defined as T90, which was the vulcanization rate. The vulcanization rate of Comparative Example 1 was set to 100 and indexed. The smaller the value, the faster the vulcanization rate and the better the productivity. Tables 2 to 4 show symbols for changes within the following ranges with Comparative Example 1 as the reference. AA: Improved by 20% or more A: Improvement within the range of 15% to less than 20% B: Improvement within the range of 5% to less than 15% C: Improvement in the range of 0% to less than 5% D: Deterioration in the range of more than 0% but less than 10% E: Deterioration of 10% or more

[0114] <(Evaluation 2) Tensile modulus> Using test pieces of the vulcanized rubber compositions, the tensile modulus (M300) (MPa) was evaluated by the test method shown below. The tensile modulus results for each example were indexed with the result for Comparative Example 1 set at 100. The larger the value, the higher the tensile modulus, indicating better toughness of the rubber. [Measurement of tensile modulus (M300)] JIS No. 3 dumbbell-shaped test pieces were punched out from the test pieces of the vulcanized rubber composition, and a tensile test was carried out in accordance with JIS K6251:2010 at a tensile speed of 500 mm / min, and the tensile modulus (MPa) at 300% elongation was measured at 23°C. Tables 2 to 4 show symbols for changes within the following ranges with Comparative Example 1 as the reference. AA: Improved by 20% or more A: Improvement within the range of 15% to less than 20% B: Improvement within the range of 5% to less than 15% C: Improvement in the range of 0% to less than 5% D: Deterioration in the range of more than 0% but less than 10% E: Deterioration of 10% or more

[0115] <(Evaluation 3) Tear strength> The tear strength (MPa) of each vulcanized rubber composition was measured in accordance with JIS K 6252 using a crescent-type test piece at room temperature and a pulling rate of 500 mm / min. The tear strength of Comparative Example 1 was set as 100 and indexed. The larger the value, the higher the tear strength, indicating that the durability of the rubber composition is good. Tables 2 to 4 show symbols for changes within the following ranges with Comparative Example 1 as the reference. AA: Improved by 20% or more A: Improvement within the range of 15% to less than 20% B: Improvement within the range of 5% to less than 15% C: Improvement in the range of 0% to less than 5% D: Deterioration in the range of more than 0% but less than 10% E: Deterioration of 10% or more

[0116] <(Rating 4) Abrasion resistance> Using an Acron abrasion tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), the vulcanized rubber composition was used as a measurement sample, and the abrasion amount (cc) was measured at 1,000 revolutions under a load of 44.4 N in accordance with JIS K6264-2, and the result of Comparative Example 1 was indexed as 100. A higher index indicates better abrasion resistance. Tables 2 to 4 show symbols for changes within the following ranges with Comparative Example 1 as the reference. AA: Improved by 20% or more A: Improvement within the range of 15% to less than 20% B: Improvement within the range of 5% to less than 15% C: Improvement in the range of 0% to less than 5% D: Deterioration in the range of more than 0% but less than 10% E: Deterioration of 10% or more

[0117] [Table 2]

[0118] [Table 3]

[0119] [Table 4] [Industrial Applicability]

[0120] The rubber composition for crosslinking of this embodiment has industrial applicability in fields such as tire components, interior and exterior parts of automobiles, vibration-proof rubber, belts, footwear, foams, and various industrial goods.

Claims

1. 100 parts by mass of a rubber-like polymer (A) having an iodine value of 10 to 250 (g / 100g), an ethylene structure of 3% by mass or more, a vinyl aromatic monomer block of <10% by mass, and containing 5% by mass or more of vinyl aromatic monomer units; 0.1 to 5.0 parts by mass of sulfur (B); 0.1 to 5.0 parts by mass of a radical generator (C), 0.1 to 5.0 parts by mass of a vulcanization accelerator (D), A rubber composition for crosslinking comprising:

2. The content of vinyl units and butylene units in the rubber-like polymer (A) is 20 mol% or more. The crosslinkable rubber composition according to claim 1 .

3. The rubber-like polymer (A) contains a nitrogen atom. The crosslinkable rubber composition according to claim 1 or 2.

4. The modification rate, which is the mass ratio of the polymer having a nitrogen atom-containing functional group to the total amount of the rubbery polymer (A) measured by a column adsorption GPC method using a silica-based column and a polystyrene column, is 40 mass% or more. The crosslinkable rubber composition according to claim 3.

5. The average iodine value of the total amount of rubber components is 250 (g / 100g) or less. The rubber composition for crosslinking according to any one of claims 1 to 4.

6. The content of the sulfur (B) is greater than the content of the radical generator (C). The rubber composition for crosslinking according to any one of claims 1 to 5.

7. The content of the sulfur (B) / the content of the radical generator (C) is > 1.

67. The rubber composition for crosslinking according to any one of claims 1 to 6.

8. the content of the radical generator (C) / the content of the vinyl aromatic monomer unit in the rubber-like polymer (A) is ≥ 0.026; The rubber composition for crosslinking according to any one of claims 1 to 7.

9. (the content of sulfur (B) + the content of radical generator (C)) × 0.5 < (the content of vulcanization accelerator (D)). The rubber composition for crosslinking according to any one of claims 1 to 8.

10. Further containing a multifunctional crosslinking aid (E), The rubber composition for crosslinking according to any one of claims 1 to 9.

11. The rubber composition for crosslinking contains 3 to 40 parts by mass of a resin relative to 100 parts by mass of the rubber component. The rubber composition for crosslinking according to any one of claims 1 to 10.

12. With respect to 100 parts by mass of the rubber component in the rubber composition for crosslinking, Contains 30 to 120 parts by mass of silica, The rubber composition for crosslinking according to any one of claims 1 to 11.

13. A method for crosslinking a rubber composition according to any one of claims 1 to 12, comprising: kneading the rubber composition for crosslinking; Method for manufacturing crosslinked rubber.

14. A tread for a tire, comprising the rubber composition for crosslinking according to any one of claims 1 to 12.

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