Modified diene-based polymer, method for producing same, and rubber composition thereof

Abstract

According to the present invention, provided is a method for producing a modified diene-based polymer by melt kneading a diene-based polymer and a metal salt of an α,β-ethylenically unsaturated carboxylic acid, the method being characterized in that the metal salt of an α,β-ethylenically unsaturated carboxylic acid is at least one type of metal salt selected from a metal salt group comprising sodium acrylate, potassium acrylate, zinc acrylate, magnesium acrylate, calcium acrylate, copper acrylate and aluminum acrylate. According to the present invention, provided is a modified diene-based polymer in which the ratio of small angle X-Ray scattering intensities at q=0.04 nm-1 and q=0.7 nm-1 is 3000 or more.

Description

Modified diene polymer, its production method, and rubber composition containing the same

[0001] The present invention relates to a modified diene polymer, a method for producing the same, and a rubber composition containing the same.

[0002] In recent years, importance has been placed on the mechanical strength and durability of rubber materials, including tires, from the viewpoints of resource conservation, weight reduction, etc. As one method for improving the mechanical strength and durability of rubber materials, attempts have been made to introduce a metal carboxylate salt group into the main chain and terminals of a diene rubber (e.g., Patent Document 1).

[0003] These diene rubbers are modified in the later stages of the polymerization process, which allows for excellent control of the modification rate. However, the modification process requires multiple steps, which may require improved productivity.

[0004] International Publication No. 2020 / 230803

[0005] One aspect of the present invention is to provide a modified diene polymer that can give a rubber composition excellent in strength at break, elongation at break, and durability.

[0006] One aspect of the present invention provides a modified diene polymer having a ratio of small-angle X-ray scattering intensity at q=0.04 nm −1 to that at q=0.7 nm −1 of 3,000 or more.

[0007] Another aspect of the present invention provides a method for producing a modified diene polymer by melt-kneading a diene polymer with 0.01 to 20 parts by mass of a metal salt of an α,β-ethylenically unsaturated carboxylic acid per 100 parts by mass of the diene polymer, and a modified diene polymer obtained by such a method. The metal salt of an α,β-ethylenically unsaturated carboxylic acid is at least one metal salt selected from the group consisting of sodium acrylate, potassium acrylate, zinc acrylate, magnesium acrylate, calcium acrylate, copper acrylate, and aluminum acrylate. The metal salt may be an aqueous solution containing 0.2 to 200 parts by mass of water per part by mass of the metal salt of the α,β-ethylenically unsaturated carboxylic acid, and the melt-kneading may be carried out in the presence of a radical initiator.

[0008] Yet another aspect of the present invention provides a rubber composition obtained by compounding the modified diene polymer with a crosslinking agent, and a method for producing the same.

[0009] According to one aspect of the present invention, there is provided a modified diene polymer that can give a rubber composition excellent in strength at break, elongation at break and durability.

[0010] Hereinafter, several embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0011] (Diene Polymer) A diene polymer is a polymer having a structural unit (diene unit) based on a diene. The diene may be a conjugated diene or a non-conjugated diene, and examples thereof include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 1,3-hexadiene, 5-ethylidene-2-norbornene, dicyclopentadiene, and 5-vinyl-2-norbornene. One or more of these may be used. Preferred dienes are 1,3-butadiene, isoprene, and 5-ethylidene-2-norbornene.

[0012] The diene polymer may have, in addition to diene units, structural units based on other monomers. Examples of such other monomers include vinyl aromatic compounds, vinyl nitriles, unsaturated carboxylic acid esters, α-olefins, and vinyl compounds having functional groups capable of interacting with silica. Examples of vinyl aromatic compounds include styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene. Examples of vinyl nitriles include acrylonitrile, and examples of unsaturated carboxylic acid esters include methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. Examples of α-olefins include linear olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene; branched olefins such as 3-methyl-1-butene, 3-methyl-1-pentene, and 4-methyl-1-pentene; and vinylcyclohexane. Examples of vinyl compounds having a functional group capable of interacting with silica include bis(dimethylamino)methylvinylsilane, bis(diethylamino)methylvinylsilane, and bis(di-n-butylamino)methylvinylsilane. Preferred are vinyl aromatic compounds, and more preferred is styrene.

[0013] Examples of diene polymers include diene polymers such as poly(1,3-butadiene), polyisoprene, and 1,3-butadiene-isoprene copolymer; diene-vinyl aromatic compound copolymers such as 1,3-butadiene-styrene copolymer and isoprene-styrene copolymer; acrylonitrile-butadiene copolymer; isoprene-isobutylene copolymer; ethylene-propylene-diene copolymer; ethylene-butadiene copolymer; propylene-butadiene copolymer, etc. Preferred are diene polymers and diene-vinyl aromatic compound copolymers.

[0014] In order to enhance the strength of the rubber composition, the diene polymer preferably has a structural unit (vinyl aromatic compound unit) based on a vinyl aromatic compound. The content of the vinyl aromatic compound unit is 0% by weight or more, preferably 10% by weight or more (the content of the diene unit is 90% by weight or less), and more preferably 15% by weight or more (the content of the diene unit is 85% by weight or less), where the total amount of the diene unit and the vinyl aromatic compound unit is 100% by weight. In addition, in order to further improve the tan δ balance of the rubber composition, the content of the vinyl aromatic compound unit is preferably 50% by weight or less (the content of the diene unit is 50% by weight or more), and more preferably 45% by weight or less (the content of the diene unit is 55% by weight or more).

[0015] The vinyl bond content of the diene polymer is preferably 10 mol% or more and 80 mol% or less, more preferably 10 mol% or more and 70 mol% or less, and even more preferably 20 mol% or more and 70 mol% or less, based on the diene unit content being 100 mol%, in order to further improve the tan δ balance of the rubber composition. The vinyl bond content is measured by infrared spectroscopy using the absorption peak of the vinyl group at 910 cm －１ It can be calculated from the absorption intensity in the vicinity.

[0016] The Mooney viscosity (ML1+4) of the diene polymer is preferably 10 or more, more preferably 20 or more, in order to increase the strength of the rubber composition. Also, in order to increase the processability, it is preferably 200 or less, more preferably 150 or less. The Mooney viscosity (ML1+4) is measured at 100°C or 125°C in accordance with JIS K6300 (1994).

[0017] (Method for Producing Diene Polymer) The diene polymer used in the present invention can be obtained, for example, by polymerizing a monomer mixture containing at least a diene in an inert solvent using a polymerization initiator. The diene polymer used in the present invention is preferably polymerized by solution polymerization.

[0018] The diene contained in the monomer mixture may be the same as the diene exemplified above for use in forming the diene polymer. Furthermore, the monomer mixture may contain the above-mentioned vinyl aromatic compound, a vinyl compound containing a functional group capable of interacting with silica, or other monomers, as needed.

[0019] The inert solvent used in the polymerization is one that is commonly used in solution polymerization, and is not particularly limited as long as it does not inhibit the polymerization reaction. Specific examples of the inert solvent include chain aliphatic hydrocarbons such as butane, pentane, hexane, heptane, and 2-butene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and cyclohexene; and aromatic hydrocarbons such as benzene, toluene, and xylene. These inert solvents may be used alone or in combination of two or more. The amount of the inert solvent used is an amount that results in a monomer concentration of, for example, 1 to 50% by weight, and preferably 10 to 40% by weight.

[0020] The polymerization initiator used in the polymerization is not particularly limited as long as it can polymerize a monomer mixture containing a diene. Specific examples include polymerization initiators using an organic alkali metal compound, an organic alkaline earth metal compound, or a lanthanide metal compound as a main catalyst. Examples of organic alkali metal compounds include organolithium compounds, organosodium compounds, and organopotassium compounds. Specific examples include organomonolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; organic polyvalent lithium compounds such as dilithiomethane, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trillithiobenzene, and 1,3,5-tris(lithiomethyl)benzene; organosodium compounds such as sodium naphthalene; and organopotassium compounds such as potassium naphthalene. Examples of organic alkaline earth metal compounds include di-n-butylmagnesium, di-n-hexylmagnesium, diethoxycalcium, calcium distearate, di-t-butoxystrontium, diethoxybarium, diisopropoxybarium, diethylmercaptobarium, di-t-butoxybarium, diphenoxybarium, diethylaminobarium, barium distearate, diketylbarium, etc. Examples of polymerization initiators using a lanthanum series metal compound as the main catalyst include polymerization initiators using a lanthanum series metal salt, such as lanthanum, cerium, praseodymium, neodymium, samarium, or gadolinium, as the main catalyst, which is composed of a lanthanum series metal salt formed from a carboxylic acid and a phosphorus-containing organic acid, etc., together with a co-catalyst such as an alkylaluminum compound, an organoaluminum hydride compound, or an organoaluminum halide compound. Among these polymerization initiators, organic monolithium compounds and organic polyvalent lithium compounds are preferably used, organic monolithium compounds are more preferably used, and n-butyllithium is particularly preferably used.The organic alkali metal compound may be used as an organic alkali metal amide compound by reacting it in advance with a secondary amine compound such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, piperidine, hexamethyleneimine, or heptamethyleneimine. By using the organic alkali metal amide compound as a polymerization initiator, the resulting cross-linked rubber product can be made to have better fuel economy and wear resistance. These polymerization initiators may be used alone or in combination of two or more.

[0021] The amount of the polymerization initiator used may be determined depending on the molecular weight distribution curve of the target diene polymer, but is usually in the range of 1 to 50 mmol, preferably 1.5 to 20 mmol, more preferably 2 to 15 mmol per 1000 g of monomer.

[0022] After initiating polymerization using a polymerization initiator, a polymerization initiator supplementation operation may be performed, in which further polymerization initiator is added to the polymerization system to continue polymerization. The timing of the polymerization initiator supplementation operation and the number of times the polymerization initiator supplementation operation is performed are not particularly limited and may be determined depending on the molecular weight distribution curve of the target diene polymer. However, the timing of the supplementation operation is preferably when the polymerization conversion rate reaches 10 to 90%, and more preferably when the polymerization conversion rate reaches 30 to 70%. From the viewpoint of excellent processability, a vinyl compound containing a functional group capable of interacting with silica is preferably copolymerized after the completion of the supplementation operation. The amount of polymerization initiator used per supplementation operation is not particularly limited and may be determined depending on the molecular weight distribution curve of the target diene polymer. However, the amount is preferably 1 to 99 moles, more preferably 1.2 to 20 moles, per mole of polymerization initiator used at the start of polymerization.

[0023] The polymerization temperature is usually in the range of −80 to +150° C., preferably 0 to 100° C., and more preferably 30 to 90° C. As the polymerization mode, any mode such as a batch mode or a continuous mode can be adopted, but a batch mode is preferred in that it is easy to control the randomness of bonding between diene units and vinyl aromatic compound units.

[0024] Furthermore, when polymerizing a monomer mixture containing a diene, it is preferable to add a polar compound to the inert organic solvent in order to adjust the amount of vinyl bonds in the diene units of the resulting diene-based polymer. Examples of polar compounds include ether compounds such as dibutyl ether and tetrahydrofuran; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; and phosphine compounds. Among these, ether compounds and tertiary amines are preferred, with tertiary amines being more preferred, and tetramethylethylenediamine being particularly preferred. These polar compounds may be used alone or in combination of two or more. The amount of polar compound used may be determined depending on the desired amount of vinyl bonds, and is preferably 0.001 to 100 mol, more preferably 0.01 to 10 mol, per mol of polymerization initiator. When the amount of polar compound used is within this range, the amount of vinyl bonds in the diene units is easily adjusted and problems due to deactivation of the polymerization initiator are less likely to occur.

[0025] In this manner, a diene polymer can be obtained in an inert solvent. The diene polymer thus obtained usually has an active terminal.

[0026] A diene polymer having an active terminal may be reacted with a coupling agent to form a coupled polymer chain. Examples of the coupling agent include, but are not limited to, silicon tetrachloride, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, tin tetrachloride, methyltrichlorotin, dimethyldichlorotin, trimethylchlorotin, tetramethoxysilane, methyltrimethoxysilane, dimethoxydimethylsilane, methyltriethoxysilane, ethyltrimethoxysilane, dimethoxydiethylsilane, diethoxydimethylsilane, tetraethoxysilane, ethyltriethoxysilane, diethoxydiethylsilane, bis(trichlorosilyl)methane, 1,2-bis(trichlorosilyl)ethane, 1,3-bis(trichlorosilyl)propane, 1,4-bis(trichlorosilyl)butane, 1,5-bis(trichlorosilyl)pentane, and 1,6-bis(trichlorosilyl)hexane. The coupling agent may be selected depending on the molecular weight distribution curve of the target diene polymer, but it is preferable to use a coupling agent having three or more functionalities, and it is more preferable to use a coupling agent having four or more functionalities.

[0027] When a coupling agent is used, it is preferable to form coupled polymer chains by coupling reaction of a portion of the polymer chains having active ends obtained by the above polymerization method, thereby obtaining a solution containing the polymer chains having active ends and the coupled polymer chains. In this case, the amount of the coupling agent used is not particularly limited and may be selected depending on the molecular weight distribution curve of the target diene polymer. However, it is preferably 0.01 to 0.4 mol, more preferably 0.02 to 0.3 mol, calculated as functional groups of the coupling agent, per mol of the polymerization initiator used during polymerization. By adding the coupling agent, the polymer chains having active ends undergo a coupling reaction at the active ends, and as a result, the active ends of the coupled polymer chains disappear, leaving them without active ends, while the polymer chains that did not undergo the coupling reaction retain their active ends.

[0028] It is preferable to convert the diene polymer into a diene polymer having a modifying group derived from the nitrogen-atom-containing compound or the silicon-atom-containing compound by reacting a modifying agent comprising a nitrogen-atom-containing compound or a silicon-atom-containing compound with an active terminal contained in the diene polymer obtained by polymerization or an active terminal that can be contained in the diene polymer after the coupling reaction.

[0029] Examples of the modifying agent include N,N-disubstituted aminoalkyl(meth)acrylamides such as dimethylaminoethyl acrylamide, diethylaminoethyl acrylamide, dimethylaminopropyl acrylamide, diethylaminopropyl acrylamide, dimethylaminobutyl acrylamide, diethylaminobutyl acrylamide, dimethylaminoethyl methacrylamide, diethylaminoethyl methacrylamide, dimethylaminopropyl methacrylamide, diethylaminopropyl methacrylamide, dimethylaminobutyl methacrylamide, and diethylaminobutyl methacrylamide; alkoxysilane compounds, siloxane compounds, and hydrocarbyloxysilane compounds having an amino group such as [3-(dimethylamino)propyl]trimethoxysilane, [3-(diethylamino)propyl]trimethoxysilane, [3-(dimethylamino)propyl]triethoxysilane, [3-(diethylamino)propyl]triethoxysilane, [3-(ethylmethylamino)propyl]trimethoxysilane, and [3-(ethylmethylamino)propyl]triethoxysilane.

[0030] When reacting the modifier comprising the nitrogen atom-containing compound or silicon atom-containing compound with the active terminal of a diene polymer, the amount of the modifier used is not particularly limited, but is preferably 0.01 to 10.0 mol, more preferably 0.02 to 5.0 mol, and particularly preferably 0.05 to 2.0 mol, relative to 1 mol of the active terminal of the polymer chain having the active terminal (when an organic alkali metal compound is used as the polymerization initiator, the amount of the modifier relative to 1 mol of metal atoms in the organic alkali metal compound). Note that the above-mentioned modifiers can be used as the modifier, and they may be used alone or in combination of two or more.

[0031] Furthermore, the method for reacting the active terminal of the diene polymer with a modifier consisting of a compound containing a nitrogen atom or a compound containing a silicon atom is not particularly limited, but examples include a method in which a polymer chain having an active terminal and the modifier are mixed in a solvent capable of dissolving them. Examples of the solvent used in this reaction include those exemplified as solvents used in the polymerization of diene polymers described above. Furthermore, in this reaction, it is preferable to leave the polymer chain having an active terminal obtained above in the state of the polymerization solution used in the polymerization and add the modifier thereto, as this is simple and preferable. In this reaction, the modifier may be dissolved in the inert solvent used in the polymerization and added to the polymerization system, and the solution concentration is preferably in the range of 1 to 50 wt %. The reaction temperature is not particularly limited, but is typically 0 to 120°C, and the reaction time is not particularly limited, but is typically 1 minute to 1 hour.

[0032] The timing of adding the modifier consisting of a compound containing a nitrogen atom or a compound containing a silicon atom to the solution containing the polymer chains having active terminals is not particularly limited, but it is desirable to add the modifier to the solution when the polymerization reaction is not complete and the solution containing the polymer chains having active terminals also contains a monomer, more specifically, when the solution containing the polymer chains having active terminals contains 100 ppm or more, more preferably 300 to 50,000 ppm of the monomer. Adding the modifier in this manner makes it possible to suppress side reactions between the polymer chains having active terminals and impurities contained in the polymerization system, and to effectively control the reaction.

[0033] It is preferable to add a polymerization terminator such as an alcohol such as methanol or isopropanol or water to the active terminals of the diene polymer obtained by polymerization, or to active terminals that may remain after the reaction with a coupling agent or a modifying agent, as necessary, to deactivate the unreacted active terminals.

[0034] If desired, an antioxidant such as a phenol-based stabilizer, a phosphorus-based stabilizer, or a sulfur-based stabilizer may be added to the diene polymer solution obtained by the above method. The amount of antioxidant added may be determined appropriately depending on the type of antioxidant. Furthermore, if desired, an extender oil may be blended to form an oil-extended rubber. Examples of extender oils include paraffinic, aromatic, and naphthenic petroleum-based softeners, vegetable-based softeners, and fatty acids. When a petroleum-based softener is used, it is preferable that the polycyclic aromatic content extracted by the IP346 method (a testing method of the Institute Petroleum in the UK) is less than 3%. When an extender oil is used, the amount used is typically 5 to 100 parts by weight per 100 parts by weight of the diene polymer.

[0035] (Metal Salt of α,β-Ethylenically Unsaturated Carboxylic Acid) The metal salt of α,β-ethylenically unsaturated carboxylic acid is a salt containing an unsaturated carboxylic acid and a monovalent or higher metal element. The metal salt of α,β-ethylenically unsaturated carboxylic acid may be, for example, a compound represented by the following formula (1). In formula (1), R １ and R ２each independently represents a hydrogen atom or a hydrocarbon group, M represents a metal element, and n represents an integer of 1 or more. The metal salt of an α,β-ethylenically unsaturated carboxylic acid represented by formula (1) is a compound having n carboxylate ions and an n-valent metal cation M ｎ＋ and a salt formed from the above, in which some of the n carboxylate ions may be replaced by hydroxide ions.

[0036] R in formula (1) １ or R ２ The hydrocarbon group as R may be, for example, an alkyl group having 1 to 10 carbon atoms. １ and R ２ may be a hydrogen atom. n may be 1 to 3, or may be 2. M may be, for example, sodium, potassium, zinc, magnesium, calcium, strontium, barium, manganese, iron, cobalt, nickel, copper, or aluminum, and may be zinc, magnesium, or aluminum from the viewpoint of easily achieving excellent mechanical strength and durability, and the unsaturated carboxylic acid of the metal salt of an α,β-ethylenically unsaturated carboxylic acid may be acrylic acid or methacrylic acid.

[0037] Examples of metal salts of α,β-ethylenically unsaturated carboxylic acids include zinc acrylate, zinc methacrylate, magnesium acrylate, magnesium methacrylate, aluminum acrylate, aluminum methacrylate, sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate, calcium acrylate, calcium methacrylate, copper acrylate, and copper methacrylate. The metal salts of α,β-ethylenically unsaturated carboxylic acids may be used alone or in combination of two or more.

[0038] (Method for Producing Modified Diene Polymer) The modified diene polymer is produced by melt-kneading a diene polymer and a metal salt of an α,β-ethylenically unsaturated carboxylic acid. In the method of the present invention, by melt-kneading a diene polymer and a metal salt of an α,β-ethylenically unsaturated carboxylic acid, a modified structure derived from the metal salt of an α,β-ethylenically unsaturated carboxylic acid, more specifically, a metal carboxylate group, can be introduced into at least a part of the diene polymer.

[0039] From the viewpoint of easily obtaining excellent mechanical strength and durability, the amount of the metal salt of an α,β-ethylenically unsaturated carboxylic acid added to the diene polymer may be 0.01 parts by mass or more, 0.2 parts by mass or more, 0.4 parts by mass or more, 0.8 parts by mass or more, or 1.0 part by mass or more, based on 100 parts by mass of the diene polymer. The amount of the metal salt of an α,β-ethylenically unsaturated carboxylic acid added to the diene polymer may be 20 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, 3 parts by mass or less, 2 parts by mass or less, or 1.5 parts by mass or less, based on 100 parts by mass of the diene polymer.

[0040] From the viewpoint of improving dispersibility, the metal salt of an α,β-ethylenically unsaturated carboxylic acid may be added in the form of an aqueous solution during melt-kneading, and the proportion of water in the melt-kneading of the diene polymer and the metal salt of an α,β-ethylenically unsaturated carboxylic acid is 0.2 to 200 parts by mass per part by mass of the metal salt of an α,β-ethylenically unsaturated carboxylic acid. From the viewpoint of improving dispersibility in the diene polymer, the proportion of water may be 0.5 parts by mass or more, 1.0 parts by mass or more, 1.5 parts by mass or more, or 2.0 parts by mass or more. Furthermore, from the viewpoint of economy, the proportion of water may be 150 parts by mass or less, 100 parts by mass or less, 50 parts by mass or less, 20 parts by mass or less, or 5 parts by mass or less.

[0041] The temperature at which the diene polymer and the metal salt of an α,β-ethylenically unsaturated carboxylic acid are melted and kneaded may be any temperature at which the melting and kneading is possible, and may be, for example, a temperature at which the diene polymer melts or higher, such as 100 to 250° C., 120 to 200° C., or 120 to 150° C. The melting and kneading time may be 0.1 to 10 minutes, or 0.5 to 5 minutes.

[0042] The melt kneading is not limited as long as it is performed using a known kneading device. Examples of the kneading device include an extruder, a kneader, a Banbury mixer, a roll kneader, etc. Preferably, the melt kneading is performed using an extruder or a Banbury mixer.

[0043] The kneading apparatus may be equipped with a vent, and melt-kneading may be performed by removing volatile components including water from the vent during melt-kneading. In the vent, pressure is reduced using a vacuum pump or the like to remove volatile components such as organic solvents, monomers, and solvents of polyhydric alcohol solutions. The vent pressure may be 5 to 100 kPa-A or 10 to 95 kPa-A.

[0044] From the viewpoint of improving the modification rate of the metal salt of an α,β-ethylenically unsaturated carboxylic acid during melt-kneading, the melt-kneading may be carried out in the presence of a radical initiator.

[0045] The radical initiator is not limited as long as it is a known radical initiator. Examples of radical initiators that can be used include organic peroxides such as benzoyl peroxide, cumene hydroperoxide, paramenthane hydroperoxide, lauroyl peroxide, and 1,1-di(t-butylperoxy)cyclohexane, diazo compounds such as azoisobutyronitrile, inorganic compounds such as potassium peroxide, and redox catalysts typified by combinations of organic compounds with iron sulfate. One or more of these may be used, and the entire amount may be added at the start of melt-kneading, or may be added stepwise in several divided portions or continuously after the start of melt-kneading. Furthermore, melt-kneading may be carried out in the presence of an antioxidant.

[0046] The Mooney viscosity (ML1+4) of the modified diene polymer obtained by the method of the present invention may be 10 or more, or 20 or more, in order to enhance the mechanical strength of the rubber composition. Also, in order to enhance processability, it may be 250 or less, or 200 or less. The Mooney viscosity (ML1+4) is measured at 100°C in accordance with JIS K 6300 (1994).

[0047] When the modified diene polymer has a vinyl bond site, the vinyl bond amount may be 10 mol% or more and 80 mol% or less, 10 mol% or more and 70 mol% or less, or 20 mol% or more and 70 mol% or less, where the diene unit content is 100 mol%. The vinyl bond amount can be determined by infrared spectroscopy using the absorption peak of the vinyl group at 910 cm －１ It can be calculated from the absorption intensity in the vicinity.

[0048] The modified diene polymer may have a structural unit (vinyl aromatic compound unit) based on a vinyl aromatic compound in order to increase the strength of the rubber composition. The content of the vinyl aromatic compound unit may be 0% by mass or more, 10% by mass or more (diene unit content is 90% by mass or less), or 15% by mass or more (diene unit content is 85% by mass or less), where the total amount of the diene unit and the vinyl aromatic compound unit is 100% by mass. The content of the vinyl aromatic compound unit may be 50% by mass or less (diene unit content is 50% by mass or more), or 45% by mass or less (diene unit content is 85% by mass or more).

[0049] By melt-kneading the modified diene polymer obtained by the present invention, it is possible to disperse metal carboxylate salt group aggregates of an appropriate size, which has the effect of improving the tensile product and durability. The dispersibility of the metal carboxylate salt group aggregates can be characterized by the small-angle X-ray scattering intensity. q = 0.04 nm －１ and q = 0.7 nm －１ The ratio r1 of the small-angle X-ray scattering intensity (r1 is q = 0.04 nm －１ Small angle X-ray scattering intensity / q = 0.7 nm －１ The larger the small-angle X-ray scattering intensity (r1), the more aggregates with a size of about 150 nm there are. In order to improve the tensile product and durability, r1 is preferably 3000 or more. That is, according to the present invention, q=0.04 nm －１ and q = 0.7 nm －１ The modified diene polymer has a small-angle X-ray scattering intensity ratio r1 of 3,000 or more. The upper limit of r1 is not particularly limited, but is preferably 30,000 or less. In addition, the modified diene polymer has a small-angle X-ray scattering intensity ratio r1 of 3,000 or more. －１and q = 0.7 nm －１ The ratio r2 of the small-angle X-ray scattering intensity (r2 is q = 0.015 nm －１ Small angle X-ray scattering intensity / q = 0.7 nm －１ The larger the small-angle X-ray scattering intensity (q) is, the more aggregates with a size of about 400 nm are present. In order to improve the tensile product and durability, it is more preferable that the small-angle X-ray scattering intensity is 70,000 or more. That is, the modified diene polymer of the present invention has a small-angle X-ray scattering intensity (q) of 0.015 nm. －１ and q = 0.7 nm －１ The ratio r2 of the small-angle X-ray scattering intensities of the diene polymer and the carboxylic acid metal salt is preferably 70,000 or more. The upper limit of r2 is not particularly limited, but is preferably 500,000 or less. r1 and r2 can be controlled by the combination and formulation of the diene polymer and the carboxylic acid metal salt during the kneading modification.

[0050] The modified diene polymer of the present invention can be blended with other polymer components and additives to form a rubber composition for use.

[0051] Other polymer components include conventional polybutadiene, polyisoprene, styrene-butadiene copolymer, isoprene-styrene copolymer, butadiene-isoprene copolymer, acrylonitrile-butadiene copolymer, isoprene-isobutylene copolymer, ethylene-propylene-diene copolymer, and butyl rubber. Also included are natural rubber, ethylene-propylene copolymer, and ethylene-octene copolymer. One or more of these polymer components may be used.

[0052] The additives that can be used include known additives such as reinforcing agents such as silica, carbon black, and microfibrillated plant fiber; fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica; silane coupling agents; extender oils; crosslinking agents such as sulfur and organic peroxides; crosslinking aids; vulcanization accelerators such as thiazole vulcanization accelerators, thiuram vulcanization accelerators, sulfenamide vulcanization accelerators, and guanidine vulcanization accelerators; vulcanization activators such as stearic acid and zinc oxide; processing aids; antioxidants; and lubricants.

[0053] Examples of the silica include dry silica (silicic acid anhydride), wet silica (hydrated silicic acid), colloidal silica, precipitated silica, calcium silicate, and aluminum silicate. Two or more of these may be used. The BET specific surface area of ​​the silica may be 50 to 250 m / g. The BET specific surface area is measured in accordance with ASTM D1993-03. Commercially available products that can be used include ULTRASIL 7000GR and VN-3 (trade names) manufactured by Evonik, Nipsil VN3, AQ, ER, and RS-150 (trade names) manufactured by Tosoh Silica Corporation, and Zeosil 1115MP and 1165MP (trade names) manufactured by Solvay.

[0054] Examples of the carbon black include channel carbon blacks such as EPC, MPC, and CC; furnace carbon blacks such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; thermal carbon blacks such as FT and MT; acetylene carbon black; graphite; etc. Two or more of these may be used.

[0055] The nitrogen adsorption specific surface area (N2SA) of carbon black is 5 to 200 m ２ The nitrogen adsorption specific surface area may be 5 to 300 ml / 100 g, and the dibutyl phthalate (DBP) absorption of the carbon black may be 5 to 300 ml / 100 g. The nitrogen adsorption specific surface area is measured in accordance with ASTM D4820-93, and the DBP absorption is measured in accordance with ASTM D2414-93. Commercially available carbon blacks include those manufactured by Mitsubishi Chemical Corporation under the trade name Diablack N339, Tokai Carbon Co., Ltd. under the trade names SEAT 6, SEAT 7HM, and SEAT KH, and Asahi Carbon Co., Ltd. under the trade names Asahi 70 and Asahi 60U.

[0056] The microfibrillated plant fibers may be cellulose microfibrils, as they provide good reinforcing properties. The cellulose microfibrils are not particularly limited as long as they are derived from natural products, and examples include those derived from resource biomass such as fruits, grains, and root vegetables; wood, bamboo, hemp, jute, and kenaf; pulp, paper, and cloth obtained from these raw materials; waste biomass such as agricultural waste, food waste, and sewage sludge; unused biomass such as rice straw, wheat straw, and thinned wood; and cellulose produced by sea squirts, acetic acid bacteria, and the like. These microfibrillated plant fibers may be used alone or in combination of two or more.

[0057] The cellulose microfibrils may be cellulose fibers having an average fiber diameter of 10 μm or less, or may be cellulose fibers having a microstructure formed by an aggregation of cellulose molecules and having an average fiber diameter of 500 nm or less. Furthermore, the cellulose microfibrils may be formed, for example, as an aggregate of cellulose fibers having the above-mentioned average fiber diameter.

[0058] The method for producing the microfibrillated plant fibers is not particularly limited, and examples include a method in which the raw material for the cellulose microfibrils is chemically treated with an alkali such as sodium hydroxide as necessary, and then mechanically ground or beaten using a refiner, twin-screw extruder, high-pressure homogenizer, media stirring mill, millstone, grinder, vibrating mill, sand grinder, or the like. These methods separate lignin from the raw material by chemical treatment, thereby obtaining microfibrillated plant fibers that are substantially free of lignin. Another example is a method in which the raw material for the cellulose microfibrils is subjected to ultra-high pressure treatment.

[0059] The microfibrillated plant fibers may be those obtained by the above-mentioned production method and further subjected to oxidation treatment or various chemical modification treatments, or those obtained by using natural products from which the cellulose microfibrils can be derived, such as wood, pulp, bamboo, hemp, jute, kenaf, agricultural waste, cloth, paper, sea squirt cellulose, etc., as cellulose raw materials and subjecting them to oxidation treatment or various chemical modification treatments, followed by defibration treatment as necessary.

[0060] The average fiber diameter of the microfibrillated plant fibers may be 10 μm or less. From the viewpoint of further improving the dispersibility of the microfibrillated plant fibers in rubber, the average fiber diameter may be 500 nm or less, 100 nm or less, or 50 nm or less. There is no particular lower limit for the average fiber diameter of the microfibrillated plant fibers, but it may be 4 nm or more, 10 nm or more, or 20 nm or more, because the microfibrillated plant fibers are difficult to untangle and disperse.

[0061] The average fiber length of the microfibrillated plant fibers may be 100 nm or more, 300 nm or more, or 500 nm or more. The average fiber length may be 5 mm or less, 1 mm or less, 50 μm or less, or 3 μm or less. When the average fiber length is less than the lower limit or exceeds the upper limit, the same tendency as the average fiber diameter described above is observed.

[0062] When the microfibrillated plant fibers are a combination of two or more types, the average fiber diameter and the average fiber length are calculated as averages for the entire microfibrillated plant fibers.

[0063] When a rubber composition is prepared by blending a reinforcing agent with the modified diene polymer, the blending amount of the reinforcing agent may be 10 to 150 parts by mass per 100 parts by mass of the modified diene polymer component. Furthermore, the blending amount may be 20 parts by mass or more, or 30 parts by mass or more, in order to enhance the mechanical strength of the rubber composition. Furthermore, the blending amount may be 120 parts by mass or less, or 100 parts by mass or less, in order to enhance the processability of the rubber composition.

[0064] The reinforcing agent preferably contains silica, and the content of silica may be 30% by mass or more, 50% by mass or more, 70% by mass or more, or 80% by mass or more, relative to 100% by mass of the total amount of the reinforcing agent.

[0065] Examples of the silane coupling agent include vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, bis(3-(triethoxysilyl)propyl)disulfide, bis(3-(triethoxysilyl)propyl)tetrasulfide, γ-trimethoxysilylpropyldimethylthiocarbamyltetrasulfide, and γ-trimethoxysilylpropylbenzothiazyltetrasulfide. Two or more of these may be used. As commercially available products, Si69, Si75, etc. manufactured by Evonik Corporation can be used.

[0066] When a rubber composition is prepared by compounding a silane coupling agent with the modified diene polymer, the compounding amount of the silane coupling agent may be 1 to 20 parts by mass, 2 to 15 parts by mass, or 5 to 10 parts by mass per 100 parts by mass of silica.

[0067] Examples of the extender oil include aromatic mineral oil (viscosity specific gravity constant (V.G.C. value) 0.900 to 1.049), naphthenic mineral oil (V.G.C. value 0.850 to 0.899), and paraffinic mineral oil (V.G.C. value 0.790 to 0.849). The polycyclic aromatic content of the extender oil may be less than 3 mass% or less than 1 wt%. The polycyclic aromatic content is measured in accordance with the British Institute of Petroleum 346 / 92 method. The aromatic compound content (CA) of the extender oil may be 20 wt% or more. Two or more of these extender oils may be used.

[0068] The sulfur may be powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, or highly dispersible sulfur, and may be powdered sulfur or insoluble sulfur.

[0069] Examples of organic peroxides include ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, alkyl peresters, percarbonates, peroxydicarbonates, and peroxyesters. More specific examples include dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne, 1,3-bis(t-butylperoxyisopropyl)benzene, t-butylcumyl peroxide, di-t-butyl peroxide, 2,2,4-trimethylpentyl-2-hydroperoxide, diisopropylbenzohydroperoxide, cumene peroxide, t-butyl peroxide, 1,1-di(t-butylperoxy)3,5,5-trimethylcyclohexane, 1,1-di-t-butylperoxycyclohexane, isobutyl peroxide, 2,4-dichlorobenzoyl peroxide, o-methylbenzoyl peroxide, bis-3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, benzoyl peroxide, and p-chlorobenzoyl peroxide. These may be used alone or in combination of two or more.

[0070] The cross-linking aid may be, for example, a compound having two or more double bonds in the molecule. Examples of cross-linking aids include N,N'-m-phenylene bismaleimide, toluylene bismaleimide, triallyl isocyanurate, triallyl cyanurate, p-quinone dioxime, nitrobenzene, diphenyl guanidine, divinylbenzene, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, and allyl methacrylate. These may be used alone or in combination of two or more. The amount of cross-linking aid in the rubber composition may be 0.05 parts by mass or more, or 0.1 parts by mass or more, and may be 20 parts by mass or less, or 8 parts by mass or less, per 100 parts by mass of the modified diene polymer.

[0071] When a rubber composition is prepared by blending a crosslinking agent with the modified diene polymer, the blending amount of the crosslinking agent may be 0.1 to 15 parts by mass, 0.3 to 10 parts by mass, or 0.5 to 5 parts by mass per 100 parts by mass of the modified diene polymer.

[0072] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine.

[0073] When a rubber composition is prepared by blending a vulcanization accelerator with the modified diene polymer, the blending amount of the vulcanization accelerator may be 0.1 to 5 parts by mass, or 0.2 to 3 parts by mass, per 100 parts by mass of the polymer component.

[0074] As a method for compounding the modified diene polymer with other polymer components and additives to produce a rubber composition, a known method can be used, for example, a method for kneading each component with a known mixer such as a roll or Banbury mixer.

[0075] Regarding kneading conditions, when additives other than a crosslinking agent and a vulcanization accelerator are blended, the kneading temperature may be 50 to 200°C or 80 to 190°C, and the kneading time may be 30 seconds to 30 minutes, or 1 minute to 30 minutes. When a crosslinking agent and a vulcanization accelerator are blended, the kneading temperature may be 100°C or lower, or room temperature to 80°C. Furthermore, a composition blended with a crosslinking agent and a vulcanization accelerator is used after undergoing a crosslinking treatment such as press crosslinking. The crosslinking temperature may be 120 to 200°C or 140 to 180°C, and the crosslinking time may be 0.5 to 90 minutes, or 2 to 60 minutes.

[0076] The modified diene polymer and the rubber composition of the modified diene polymer are used for tires, shoe soles, flooring materials, vibration-proof materials, etc. They are particularly suitable for use in tires.

[0077] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0078] (Polymerization Example 1 [Diene Polymer (A)]) The atmosphere in a 20 L stainless steel polymerization reactor equipped with a stirrer was purged with dry nitrogen. Next, 8.16 kg of industrial hexane (manufactured by Sumitomo Chemical Co., Ltd., trade name: Hexane (general product), density 0.68 g / mL), 2.34 kg of cyclohexane, 238 g of 1,3-butadiene, 444 g of styrene, 8.14 mL of tetrahydrofuran, 1.16 mL of ethylene glycol diethyl ether, and 1.10 mL of ethylene glycol dibutyl ether were charged into the polymerization reactor. Next, an n-hexane solution containing 1.85 mmol of n-butyllithium (n-BuLi) was charged into the polymerization reactor, and the mixture was stirred at a stirring speed of 130 rpm and an internal temperature of the polymerization reactor of 65°C.

[0079] While continuously feeding 454 g of 1,3-butadiene to the mixture, the mixture was stirred for another 4 hours under the above conditions to obtain a polymerized solution. Next, 1.85 mmol of dimethylaminopropylacrylamide was added to the obtained polymerized solution and stirred for 15 minutes, and then 20 mL of a hexane solution containing 0.81 mL of methanol was added, and the polymerized solution was stirred for another 5 minutes to obtain a polymerized solution a1.

[0080] To the polymerization solution a1, 5.0 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumilizer GM), 2.5 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumilizer TP-D), and 284 g of extender oil (manufactured by ENEOS Corporation, trade name: Process NC140) were added, thereby obtaining a polymerization solution a2 containing a diene polymer (A).

[0081] (Polymer composition) A diene polymer (A) was obtained by evaporating most of the volatile matter from the obtained polymerization solution a2 at room temperature for 24 hours and further drying under reduced pressure at 55° C. for 12 hours. The diene polymer (A) had a styrene unit content of 39% by mass, a vinyl bond content of 38.4 mol%, a Mooney viscosity (ML1+4 (125° C.)) of 70, and contained 25 parts by mass of extender oil.

[0082] (Polymerization Example 2 [Diene Polymer (B)]) The atmosphere inside a 20 L stainless steel polymerization reactor equipped with a stirrer was purged with dry nitrogen. Next, 10.2 kg of industrial hexane (manufactured by Sumitomo Chemical Co., Ltd., trade name: Hexane (general product), density 0.68 g / mL), 357 g of 1,3-butadiene, 244 g of styrene, 11.25 mL of tetrahydrofuran, and 10.94 mL of ethylene glycol diethyl ether were charged into the polymerization reactor. Next, an n-hexane solution containing 1.60 mmol of n-butyllithium (n-BuLi) was charged into the polymerization reactor, and the mixture was stirred at a stirring speed of 130 rpm and an internal temperature of the polymerization reactor of 65°C.

[0083] To the mixture, 238 g of 1,3-butadiene and 162 g of styrene were continuously fed, and the mixture was stirred for an additional 4 hours under the above conditions to obtain a polymerization solution. Next, 0.19 mmol of silicon tetrachloride was added to the obtained polymerization solution and stirred for 15 minutes, and then 0.36 mmol of dimethylaminopropylacrylamide was added and stirred for 15 minutes, and then 20 mL of a hexane solution containing 0.81 mL of methanol was added, and the polymerization solution was stirred for an additional 5 minutes to obtain polymerization solution b1.

[0084] To the polymerization solution b1, 4.5 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumilizer GM), 2.3 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumilizer TP-D), and 375 g of extender oil (manufactured by ENEOS Corporation, trade name: Process NC140) were added, thereby obtaining a polymerization solution b2 containing a diene polymer B.

[0085] (Polymer composition) A diene polymer (B) was obtained by evaporating most of the volatile matter from the obtained polymerization solution b2 at room temperature for 24 hours and further drying under reduced pressure at 55° C. for 12 hours. The diene polymer (B) had a styrene unit content of 40% by mass, a vinyl bond content of 65 mol%, a Mooney viscosity (ML1+4 (100° C.)) of 62, and contained 37.5 parts by mass of extender oil.

[0086] (Polymerization Example 3 [Diene Polymer (C)]) The atmosphere in a 30 L stainless steel polymerization reactor equipped with a stirrer was purged with dry nitrogen. Next, 15.3 kg of industrial hexane (manufactured by Sumitomo Chemical Co., Ltd., trade name: Hexane (general product), density 0.68 g / mL), 13.22 mL of tetrahydrofuran, 2.73 mL of ethylene glycol dibutyl ether, 497 g of 1,3-butadiene, and 452 g of styrene were charged into the polymerization reactor. Next, an n-hexane solution containing 2.03 mmol of n-butyllithium (n-BuLi) was charged into the polymerization reactor, and the mixture was stirred at a stirring speed of 130 rpm and an internal temperature of the polymerization reactor of 43°C.

[0087] Starting 20 minutes after the start of the polymerization reaction, 755 g of 1,3-butadiene was continuously added to the above mixture over 200 minutes. Thereafter, when the polymerization conversion reached 60%, an n-hexane solution containing 2.03 mmol of n-butyllithium (n-BuLi) was added to the polymerization reactor. Then, 20 minutes after confirming that the polymerization conversion had reached the range of 95% to 100%, 10.15 mmol of [3-(diethylamino)propyl]trimethoxysilane was added and stirred for 15 minutes. Then, 1.5 equivalents of methanol relative to the total amount of lithium in the polymerization reactor were added as a polymerization terminator, and the polymerization solution was stirred for an additional 5 minutes to obtain polymerization solution c1.

[0088] To the polymerization solution c1, 9.54 g of 2,4-bis(octylthiomethyl)-6-methylphenol (manufactured by BASF Japan Ltd., trade name: Irganox 1520L) was added, to obtain a polymerization solution c2 containing a diene polymer C.

[0089] (Polymer composition) Most of the volatile matter in the obtained polymerization solution c2 was evaporated at room temperature for 24 hours, and the solution was further dried under reduced pressure at 55° C. for 12 hours to obtain a diene polymer (C). The diene polymer (C) had a styrene unit content of 26.4 mass%, a vinyl bond content of 36.4 mol%, and a Mooney viscosity (ML1+4(125° C.)) of 57.

[0090] (Polymerization Example 4 [Diene Polymer (D)]) The atmosphere in a 30 L stainless steel polymerization reactor equipped with a stirrer was replaced with dry nitrogen. Next, 15.3 kg of industrial hexane (manufactured by Sumitomo Chemical Co., Ltd., trade name: Hexane (general product), density 0.68 g / mL) and 1,810 g of 1,3-butadiene were charged into the polymerization reactor. Next, an n-hexane solution containing 30.2 mmol of n-butyllithium (n-BuLi) was charged into the polymerization reactor, and the mixture was stirred at a stirring speed of 120 rpm and an internal temperature of the polymerization reactor of 50°C.

[0091] 30 minutes after the start of the polymerization reaction, 1,810 g of 1,3-butadiene was continuously added to the above mixture over 50 minutes. 10 minutes after confirming that the polymerization conversion rate had reached the range of 95% to 100%, 1.2 mmol of 1,6-bis(trichlorosilyl)hexane was added and stirred for 10 minutes, and then a polyorganosiloxane represented by the following formula (2) was added so that the epoxy group content was 10.3 mmol, and the reaction was allowed to proceed for 20 minutes. Furthermore, 24.8 mol of trimethoxysilane was added and stirred for 15 minutes. Thereafter, 2.0 equivalents of methanol relative to the total amount of lithium in the polymerization reactor was added as a polymerization terminator, and the polymerization solution was stirred for an additional 5 minutes to obtain polymerization solution d1.

[0092] To the polymerization solution d1, 10.86 g of 2,4-bis(octylthiomethyl)-6-methylphenol (manufactured by BASF Japan Ltd., trade name: Irganox 1520L) was added to obtain a polymerization solution d2 containing a diene polymer D.

[0093] (Polymer composition) The solvent was removed from the obtained polymerization solution d2 by steam stripping, and the resulting solution was dried with hot air to obtain a diene polymer (D). The diene polymer (D) had a vinyl bond content of 10.0 mol% and a Mooney viscosity (ML1+4 (100°C)) of 50.

[0094] Example 1 125 parts by mass of a diene polymer (A), 0.2 parts by mass of 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]-2-methylphenol (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMILIZER GP), and 2.0 parts by mass of zinc acrylate (powder, purity: 98%) (manufactured by Sigma-Aldrich) were melt-kneaded at 80 rpm for 4 minutes in a 100 cc Labo Plastomill set to 130°C to produce an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer.

[0095] 127.2 parts by mass of the modified diene polymer, 3.0 parts by mass of zinc oxide (manufactured by Seido Chemical Industry Co., Ltd., product name: Zinc Oxide Type 2), and 2.0 parts by mass of stearic acid (manufactured by New Japan Chemical Co., Ltd., product name: Stearic Acid 50S) were kneaded at 80 rpm for 4 minutes in a 100 cc Laboplastomill set to 130°C to obtain a masterbatch. 132.2 parts by mass of the masterbatch, 1.5 parts by mass of sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd., trade name: Kinka Brand Fine Powder Sulfur 200 mesh), 1.5 parts by mass of N-cyclohexyl-2-benzothiazolylsulfenamide (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name: Noccela CZ-G), and 2.0 parts by mass of 1,3-diphenylguanidine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name: Noccela D) were kneaded with an open roll set at 40°C to obtain a rubber composition.

[0096] The rubber composition (uncrosslinked) was press-crosslinked in a mold (75 mm x 150 mm x 2.0 mm) at 160°C for 20 minutes to obtain a crosslinked rubber sheet.

[0097] Example 2 An α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene-based copolymer, a rubber composition, and a crosslinked rubber sheet were each produced in the same manner as in Example 1, except that the amount of zinc acrylate added during melt-kneading was changed to 4.0 parts by mass relative to 125 parts by mass of the diene-based polymer (A).

[0098] Example 3 A rubber composition and a crosslinked rubber sheet were prepared in the same manner as in Example 1, except that 125 parts by mass of the diene polymer (A) were melt-kneaded with 0.2 parts by mass of 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]-2-methylphenol (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMILIZER GP) and 5.0 parts by mass of an aqueous zinc acrylate solution (30% by mass) (manufactured by Asada Chemical Industry Co., Ltd., trade name: ZA30) in a 100 cc Labo Plastomill set to 130°C at 80 rpm for 4 minutes to prepare an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer.

[0099] Example 4 125 parts by mass of the diene polymer (A) was mixed with 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]-2-methylphenol (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMILIZER A rubber composition and a crosslinked rubber sheet were each prepared in the same manner as in Example 1, except that 0.2 parts by mass of an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer was prepared by melt-kneading 0.2 parts by mass of a zinc acrylate aqueous solution (30% by mass) (manufactured by Asada Chemical Industry Co., Ltd., trade name: ZA30), and 0.1 parts by mass of 1,1-di(t-butylperoxy)cyclohexane (manufactured by NOF Corporation, trade name: Perhexa C-40) in a 100 cc Labo Plastomill set to 130°C at 80 rpm for 4 minutes.

[0100] Example 5 A rubber composition was obtained in the same manner as in Example 1, except that 137.5 parts by mass of the diene polymer (B), 0.2 parts by mass of 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]-2-methylphenol (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMILIZER GP), and 5.0 parts by mass of an aqueous zinc acrylate solution (30% by mass) (manufactured by Asada Chemical Industry Co., Ltd., trade name: ZA30) were melt-kneaded at 80 rpm for 4 minutes in a 100 cc Labo Plastomill set at 130 ° C. to produce an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer.

[0101] The rubber composition (uncrosslinked) was press-crosslinked in a mold (75 mm x 150 mm x 2.0 mm) at 160°C for 30 minutes to obtain a crosslinked rubber sheet.

[0102] Example 6 139.2 parts by mass of the α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer obtained in the same manner as in Example 5, 80 parts by mass of silica (manufactured by Evonik Corporation, trade name: ULTRASIL 7000GR), 6.4 parts by mass of a silane coupling agent (manufactured by Evonik Corporation, trade name: Si75), 3.0 parts by mass of zinc oxide (manufactured by Seido Chemical Industry Co., Ltd., trade name: Zinc Oxide Type 2), 2.0 parts by mass of stearic acid (manufactured by New Japan Chemical Co., Ltd., trade name: Stearic Acid 50S), and 2.0 parts by mass of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name: Nocrac 6C) were kneaded for 4 minutes at 80 rpm in a 100 cc Labo Plastomill set at 130°C to obtain a masterbatch. 132.2 parts by mass of the masterbatch, 1.5 parts by mass of sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd., trade name: Kinka Brand Fine Powder Sulfur 200 mesh), 1.5 parts by mass of N-cyclohexyl-2-benzothiazolylsulfenamide (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name: Noccela CZ-G), and 2.0 parts by mass of 1,3-diphenylguanidine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name: Noccela D) were kneaded with an open roll set at 40°C to obtain a rubber composition.

[0103] The rubber composition (uncrosslinked) was press-crosslinked in a mold (75 mm x 150 mm x 2.0 mm) at 160°C for 50 minutes to obtain a crosslinked rubber sheet.

[0104] Example 7 137.5 parts by mass of the diene polymer (B) was mixed with 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]-2-methylphenol (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMILIZER A rubber composition and a crosslinked rubber sheet were each prepared in the same manner as in Example 6, except that 0.2 parts by mass of an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer was prepared by melt-kneading 0.2 parts by mass of a zinc acrylate aqueous solution (30% by mass) (manufactured by Asada Chemical Industry Co., Ltd., trade name: ZA30), and 5.0 parts by mass of 1,1-di(t-butylperoxy)cyclohexane (manufactured by NOF Corporation, trade name: Perhexa C-40) in a 100 cc Labo Plastomill set to 130°C at 80 rpm for 4 minutes.

[0105] Example 8 15 g of magnesium acrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name: Magnesium Acrylate) and 35 g of pure water were placed in a beaker and stirred at room temperature for 4 hours to obtain a 30% by mass aqueous solution of magnesium acrylate.

[0106] A rubber composition was obtained in the same manner as in Example 5, except that 137.5 parts by mass of the diene polymer (B), 0.2 parts by mass of 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]-2-methylphenol (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMILIZER GP), and 5.0 parts by mass of the magnesium acrylate aqueous solution (30% by mass) were melt-kneaded at 80 rpm for 4 minutes in a 100 cc Labo Plastomill set at 130 ° C. to produce an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer.

[0107] The rubber composition (uncrosslinked) was press-crosslinked in a mold (75 mm x 150 mm x 2.0 mm) at 160°C for 40 minutes to obtain a crosslinked rubber sheet.

[0108] Example 9 A rubber composition was obtained in the same manner as in Example 1, except that 100 parts by mass of the diene polymer (C) were melt-mixed with 0.2 parts by mass of 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]-2-methylphenol (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMILIZER GP) and 5.0 parts by mass of an aqueous zinc acrylate solution (30% by mass) (manufactured by Asada Chemical Industry Co., Ltd., trade name: ZA30) in a 100 cc Labo Plastomill set at 130 ° C. at 80 rpm for 4 minutes to produce an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer.

[0109] The rubber composition (uncrosslinked) was press-crosslinked in a mold (75 mm x 150 mm x 2.0 mm) at 160°C for 10 minutes to obtain a crosslinked rubber sheet.

[0110] Example 10 100 parts by mass of the diene polymer (C) were melt-kneaded with 0.2 parts by mass of 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]-2-methylphenol (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMILIZER GP) and 5.0 parts by mass of an aqueous zinc acrylate solution (30%) (manufactured by Asada Chemical Industry Co., Ltd., trade name: ZA30) in a 100 cc Labo Plastomill set to 130°C at 80 rpm for 4 minutes to produce an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer.

[0111] A mixture of 101.7 parts by mass of the modified diene polymer, 80 parts by mass of silica (manufactured by Evonik Corporation, trade name: ULTRASIL 7000GR), 6.4 parts by mass of a silane coupling agent (manufactured by Evonik Corporation, trade name: Si75), 3.0 parts by mass of zinc oxide (manufactured by Seido Chemical Industry Co., Ltd., trade name: Zinc Oxide Type 2), 2.0 parts by mass of stearic acid (manufactured by New Japan Chemical Co., Ltd., trade name: Stearic Acid 50S), 2.0 parts by mass of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name: Nocrac 6C), and aromatic process oil (manufactured by H&R Corporation, trade name: VivaTec A masterbatch was obtained by kneading 37.5 parts by mass of sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd., product name: Kinkajirushi Micro Powder Sulfur 200 mesh) with 37.5 parts by mass of 1,3-diphenylguanidine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name: Noccela CZ-G) for 4 minutes in a 100 cc Labo Plastomill set to 130°C at 80 rpm. 232.6 parts by mass of the masterbatch was kneaded with 1.5 parts by mass of sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd., product name: Kinkajirushi Micro Powder Sulfur 200 mesh), 1.5 parts by mass of N-cyclohexyl-2-benzothiazolylsulfenamide (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name: Noccela D) in an open roll set to 40°C to obtain a rubber composition.

[0112] The rubber composition (uncrosslinked) was press-crosslinked in a mold (75 mm x 150 mm x 2.0 mm) at 160°C for 50 minutes to obtain a crosslinked rubber sheet.

[0113] Example 11 50 parts by mass of diene polymer (D) were melt-kneaded with 0.25 parts by mass of 2,4-bis(octylthiomethyl)-6-methylphenol (manufactured by BASF Japan Ltd., product name: Irganox 1520L) and 1.67 parts by mass of an aqueous zinc acrylate solution (30%) (manufactured by Asada Chemical Industry Co., Ltd., product name: ZA30) in a 100 cc Labo Plastomill set to 130°C at 80 rpm for 4 minutes to produce an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer.

[0114] A mixture of 51.92 parts by mass of the modified diene polymer, 50 parts by mass of natural rubber, and carbon black (manufactured by Tokai Carbon Co., Ltd., trade name "SEAT SO", nitrogen adsorption specific surface area measured by the BET method: 42 m) was used. ２ / g, iodine adsorption: 44 mg / g, DBP absorption measured by Method A: 115 cm ３ A masterbatch was obtained by kneading 45 parts by mass of a hydroxypropyl methylcellulose (100g / 100g), 1 part by mass of paraffin wax (trade name "Paraffin Wax 135" manufactured by Nippon Seiro Co., Ltd.), 3.0 parts by mass of zinc oxide (trade name: Zinc Oxide Type 2 manufactured by Seido Chemical Industry Co., Ltd.), 2.0 parts by mass of stearic acid (trade name: Stearic Acid 50S manufactured by New Japan Chemical Co., Ltd.), 2.0 parts by mass of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (trade name: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), and 5 parts by mass of aromatic process oil (trade name: VivaTec 500 manufactured by H&R Corporation) at 80 rpm for 4 minutes in a 100 cc Labo Plastomill set to 130°C. 158.75 parts by mass of the masterbatch was mixed with 1.8 parts by mass of sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd., product name: Kinka Brand Fine Powder Sulfur 200 mesh) and 1.5 parts by mass of N-cyclohexyl-2-benzothiazolylsulfenamide (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name: Noccela CZ-G) using an open roll set at 40°C to obtain a rubber composition.

[0115] The rubber composition (uncrosslinked) was press-crosslinked in a mold (75 mm x 150 mm x 2.0 mm) at 160°C for 6 minutes to obtain a crosslinked rubber sheet.

[0116] Example 12 137.5 parts by mass of diene polymer (B), 0.5 parts by mass of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumilizer GM), 0.25 parts by mass of pentaerythrityl tetrakis (3-lauryl thiopropionate) (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumilizer TP-D), and 3.3 parts by mass of aqueous zinc acrylate solution (30% by mass) (manufactured by Asada Chemical Industry Co., Ltd., trade name: ZA30) were melt-kneaded in a 20 mmφ twin-screw extruder set at 170 ° C. at 170 rpm and an hourly throughput of 5 kg / hour to produce an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer. A rubber composition and a crosslinked rubber sheet were produced in the same manner as in Example 6, except that the melt-kneading was carried out at 170 rpm and an hourly throughput of 5 kg / hour to produce an α,β-ethylenically unsaturated carboxylic acid metal salt-modified diene polymer.

[0117] Comparative Example 1 A rubber composition and a crosslinked rubber sheet were prepared in the same manner as in Example 1, except that zinc acrylate was not added.

[0118] Comparative Example 2 A rubber composition and a crosslinked rubber sheet were prepared in the same manner as in Example 5, except that zinc acrylate was not added.

[0119] Comparative Example 3 A rubber composition and a crosslinked rubber sheet were prepared in the same manner as in Example 6, except that zinc acrylate was not added.

[0120] Comparative Example 4 A rubber composition and a crosslinked rubber sheet were prepared in the same manner as in Example 7, except that zinc acrylate was not added.

[0121] Comparative Example 5 A rubber composition and a crosslinked rubber sheet were prepared in the same manner as in Example 9, except that zinc acrylate was not added.

[0122] Comparative Example 6 A rubber composition and a crosslinked rubber sheet were prepared in the same manner as in Example 10, except that zinc acrylate was not added.

[0123] Comparative Example 7 A rubber composition and a crosslinked rubber sheet were prepared in the same manner as in Example 11, except that zinc acrylate was not added.

[0124] <Evaluation> [Tensile test] JIS No. 3 dumbbell-shaped test pieces (thickness: 2 mm) were punched out of the prepared crosslinked rubber sheets in accordance with JIS K6251:2010, and the breaking strength and breaking elongation were evaluated under conditions of a temperature of 23°C and a tensile speed of 500 mm / min. The product of the breaking strength and the breaking elongation was defined as the tensile product, and each tensile product was indexed, with the result of Comparative Example 1 being set at 100. A larger value of the tensile product indicates a larger energy required to break and superior mechanical strength.

[0125] [Durability Test] According to JIS-K 6270, two No. 3 dumbbells with a thickness of 2 mm were attached to the chucks of a constant extension fatigue tester (manufactured by Mize Testing Machines Co., Ltd.) from the prepared crosslinked rubber sheets, and repeated extension and contraction of 110% at 5 Hz at a temperature of 40°C were performed until breakage. The number of times until breakage was measured, and the average value was used as an index of durability. Each measured value was indexed, with the result of Comparative Example 1 being 100. A larger index indicates better durability.

[0126] [Small-Angle X-Ray Scattering Measurement] A 3 mm thick sheet of the prepared modified diene polymer was measured using small-angle X-ray scattering. Small-angle X-ray scattering was performed according to the description in "Polymer X-Ray Diffraction, Masao Kakuto and Nobutami Kasai, Maruzen Co., Ltd., 1968" and "Polymer X-Ray Diffraction, 3.3rd Edition, Toru Masuko, Yamagata University Co-op, 1995." More specifically, the measurement was performed at room temperature of 25°C using beamline BL03XU at the Synchrotron Radiation Experimental Facility SPring-8, with an X-ray wavelength of 0.128 nm and a camera length of 8000 mm, using a Pilatus 1M detector manufactured by Dectris. X-rays were incident in a direction parallel to the thickness direction of the sheet, and measurements were taken 64 times by changing the irradiation position with an exposure time of 1 second, to obtain a total two-dimensional scattering image Ms. Simultaneously with capturing the two-dimensional scattering image, the transmitted light intensity fs was measured in an ion chamber downstream of the sheet. Measurements were taken under the same conditions except for the absence of the sheet, and a background two-dimensional scattering image Mb and transmitted light intensity fb were obtained. A two-dimensional scattering image M after background subtraction was obtained using equation (3). M = Ms / fs - Mb / fb Equation (3) A one-dimensional profile I in the radial direction was obtained from the two-dimensional scattering image M by circular averaging. At this time, the area where the scattered X-rays were blocked by a beam stop or the like installed to prevent the direct beam from entering the detector was excluded from the one-dimensional profile. The horizontal axis was calibrated to the magnitude q of the scattering vector using the standard substance collagen. q = 0.04 nm －１ and q = 0.7 nm －１ The ratio r1 of the small-angle X-ray scattering intensity is given by equation (4), q = 0.015 nm －１ and q = 0.7 nm －１ The ratio r2 of the small-angle X-ray scattering intensities of r1 and r2 was obtained by equation (5): r1 = I(q = 0.04 nm －１ ) / I (q = 0.7 nm －１ ) Formula (4) r2=I(q=0.015nm －１ ) / I (q = 0.7 nm －１ ) Formula (5)

[0127]

[0128]

Claims

1. A method for producing a modified diene polymer, which is obtained by melt-kneading a diene polymer and 0.01 to 20 parts by mass of a metal salt of an α,β-ethylenically unsaturated carboxylic acid relative to 100 parts by mass of the diene polymer.

2. 2. The method for producing a modified diene polymer according to claim 1, wherein the metal salt of an α,β-ethylenically unsaturated carboxylic acid is at least one metal salt selected from the group consisting of sodium acrylate, potassium acrylate, zinc acrylate, magnesium acrylate, calcium acrylate, copper acrylate, and aluminum acrylate.

3. The method for producing a modified diene polymer according to claim 1 or 2, characterized in that the diene polymer is melt-kneaded with an aqueous solution containing 0.2 to 200 parts by mass of water per part by mass of the metal salt of an α,β-ethylenically unsaturated carboxylic acid.

4. 3. The method for producing a modified diene polymer according to claim 1, wherein the melt-kneading is carried out in the presence of a radical initiator.

5. 3. The method for producing a modified diene polymer according to claim 1 or 2, wherein the diene polymer comprises a styrene-butadiene copolymer, an isoprene-butadiene copolymer, an isobutylene-isoprene copolymer, an ethylene-butadiene copolymer, a propylene-butadiene copolymer, an ethylene-propylene-diene copolymer, a butadiene-acrylonitrile copolymer, polyisoprene, polybutadiene, or a mixture thereof.

6. A modified diene polymer produced by the method according to claim 1 or 2.

7. A method for producing a rubber composition, comprising producing a modified diene polymer by the method according to claim 1 or 2, and compounding a crosslinking agent with the modified diene polymer.

8. The method for producing a rubber composition according to claim 7, further comprising compounding a reinforcing agent.

9. 8. The method for producing a rubber composition according to claim 7, wherein the crosslinking agent is at least one of sulfur and an organic peroxide.

10. 9. The method for producing a rubber composition according to claim 8, wherein the reinforcing agent is at least one of silica, carbon black, and microfibrillated vegetable fiber.

11. A rubber composition produced by the method of claim 7.

12. q=0.04 nm －１ and q = 0.7 nm －１ A modified diene polymer having a small-angle X-ray scattering intensity ratio of 3,000 or more.

13. q=0.015 nm －１ and q = 0.7 nm －１ The modified diene polymer according to claim 12, wherein the ratio of small-angle X-ray scattering intensities of

14. The modified diene polymer according to claim 12 or 13, wherein the diene polymer comprises a styrene-butadiene copolymer, an isoprene-butadiene copolymer, an isobutylene-isoprene copolymer, an ethylene-butadiene copolymer, a propylene-butadiene copolymer, an ethylene-propylene-diene copolymer, a butadiene-acrylonitrile copolymer, polyisoprene, polybutadiene, or a mixture thereof.