Polymer composition, crosslinked body, and tire

Abstract

Provided is a polymer composition which has excellent processability and brings about excellent production efficiency, and which is suitable for producing rubber products having improved resistance to heat aging.　The polymer composition according to the present invention includes a rubber component which comprises: a polymer (A) in which when the constituent proportions (molar proportions) of a structural unit represented by formula (1), a structural unit represented by formula (2), a structural unit represented by formula (3), and a structural unit represented by formula (4) in the polymer are expressed by p, q, r, and s, respectively, then the value α shown by expression (i) is 0.6 or greater but less than 1.0 and which has a weight-average molecular weight (Mw) in terms of polystyrene, as determined by gel permeation chromatography, of 1.0×105 to 2.0×106 and contains structural units derived from an aromatic vinyl compound in an amount of 5-50 mass% with respect to the whole polymer; and an emulsion-polymerized styrene / butadiene rubber (B). The ratio (a / b) of the content a of the polymer (A) to the content b of the emulsion-polymerized styrene / butadiene rubber (B) is 65 / 35 to 1 / 99.　(i): α=(p+(0.5×r)) / (p+q+(0.5×r)+s)

Description

Polymer compositions, crosslinked materials, and tires

[0001] This invention relates to polymer compositions, crosslinked materials, and tires.

[0002] Conjugated diene polymers obtained by polymerization using conjugated diene compounds have excellent properties such as heat resistance, abrasion resistance, mechanical strength, and moldability, and are therefore widely used in various industrial products such as vibration-damping rubber and hoses, as well as pneumatic tires.

[0003] Polymer compositions used in the manufacture of treads, sidewalls, etc., for pneumatic tires are known to incorporate inorganic fillers such as carbon black and silica as reinforcing agents along with conjugated diene polymers to improve the durability and wear resistance of the product. Furthermore, to increase the affinity between the conjugated diene polymer and the reinforcing agent, conjugated diene polymers modified with compounds containing silicon or nitrogen are used (see, for example, Patent Documents 1 to 3).

[0004] In recent years, it has been proposed to obtain tire components with high strength and excellent wear resistance using hydrogenated conjugated diene polymers, which are hydrogenated products of conjugated diene polymers having functional groups such as amino groups or alkoxysilyl groups at one or both ends (see, for example, Patent Document 4).

[0005] In hydrogenated conjugated diene polymers, thermoplastic materials exhibiting rubber elasticity are being investigated by introducing styrene blocks to create spatial constraints. However, hydrogenated conjugated diene polymers with styrene blocks may not have sufficient crosslinking properties (e.g., strength and viscoelastic properties) due to relaxation caused by the glass transition temperature of the styrene blocks. Therefore, the main method being investigated for obtaining crosslinked hydrogenated conjugated diene polymers is to use a random copolymer of 1,3-butadiene and styrene, which is then hydrogenated.

[0006] Furthermore, emulsion polymerized styrene-butadiene copolymers have long been widely used in various industrial products such as vibration-damping rubber and hoses, as well as in pneumatic tires, due to their excellent heat resistance, abrasion resistance, mechanical strength, and moldability.

[0007] International Publication No. 2008 / 123164, Japanese Patent Publication No. Hei 11-349632, International Publication No. 2017 / 221943, International Publication No. 2014 / 133097

[0008] Emulsified polymerized styrene-butadiene copolymers are susceptible to thermal and oxidative degradation due to the influence of residual unsaturated bonds. Rubber products manufactured using such copolymers have the problem of being prone to oxidative degradation due to heat during use. Generally, antioxidants are added to the polymer composition to prevent this oxidative degradation; however, simply adding antioxidants has not been sufficient to effectively prevent oxidative degradation.

[0009] Some embodiments of the present invention provide polymer compositions suitable for manufacturing rubber products that have excellent processability and productivity, as well as improved heat aging resistance.

[0010] The present invention has been made to solve at least some of the above-mentioned problems and can be realized in any of the following embodiments.

[0011] One embodiment of the polymer composition according to the present invention is a polymer composition containing a rubber component, wherein the rubber component has a composition in which, when the constituent ratio (molar ratio) of the structural units represented by the following formula (1), the structural units represented by the following formula (2), the structural units represented by the following formula (3), and the structural units represented by the following formula (4) in the polymer is p, q, r, and s, respectively, the value α represented by the following formula (i) is 0.6 or more and less than 1.0, and the weight-average molecular weight (Mw) in terms of polystyrene, as measured by gel permeation chromatography, is 1.0 × 10⁻⁶. ５ ~2.0 x 10 ６ The polymer (A) contains 5 to 50% by mass of structural units derived from aromatic vinyl compounds, and emulsion polymerized styrene-butadiene rubber (B), wherein the ratio (a / b) of the content a of polymer (A) to the content b of emulsion polymerized styrene-butadiene rubber (B) is 65 / 35 to 1 / 99. α = (p + (0.5 × r)) / (p + q + (0.5 × r) + s) (i)

[0012] In one embodiment of the polymer composition, the value β in polymer (A), represented by the following formula (ii), may be 0.2 to 0.7. β = (p + q) / (p + q + (0.5 × r) + s) (ii)

[0013] In one embodiment of the polymer composition, the polymer (A) may have at least one functional group selected from the group consisting of a carboxyl group, a hydrocarbyloxysilyl group, an epoxy group, an amino group, a hydroxyl group, a sulfo group, an iso(thio)cyanate group, a thiol group, and a halogen.

[0014] In any embodiment of the polymer composition, a filler may be further included.

[0015] In any embodiment of the polymer composition, the filler may contain either or both carbon black and silica.

[0016] In any embodiment of the polymer composition, the filler may contain silica, and the silica content may be 80 parts by mass or more when the total amount of the rubber component is 100 parts by mass.

[0017] In any embodiment of the polymer composition, the filler may contain carbon black, and the carbon black content may be 10 parts by mass or more when the total amount of the rubber component is 100 parts by mass.

[0018] In any embodiment of the polymer composition, a resin may be further included.

[0019] In any embodiment of the polymer composition, the ratio (a / b) of the content a of the polymer (A) to the content b of the emulsion polymerized styrene-butadiene rubber (B) may be 65 / 35 to 50 / 50.

[0020] One embodiment of the crosslinked body according to the present invention is obtained by crosslinking a polymer composition according to any of the above embodiments.

[0021] One embodiment of the tire according to the present invention is one in which the tread and / or sidewall are formed by a polymer composition according to any of the above embodiments.

[0022] According to the polymer composition of the present invention, rubber products having excellent processability and productivity and improved heat aging resistance can be produced.

[0023] Hereinafter, preferred embodiments according to the present invention will be described in detail. It should be understood that the present invention is not limited to only the embodiments described below, and also includes various modifications implemented within a scope that does not alter the gist of the present invention.

[0024] In the present specification, the term "rubber component" refers to a polymer capable of providing a cured product exhibiting rubber elasticity through curing by heat, light, ionic crosslinking, or the like. The cured product has the property of causing large deformation under a small force at room temperature (for example, deformation that stretches to twice or more its original length when stretched at room temperature), and rapidly returns to substantially its original shape when the force is removed.

[0025] In the present specification, "(meth)acryl-" represents "acryl-" or "methacryl-", "(thio)epoxy group" represents "epoxy group" or "thioepoxy group", and "iso(thio)cyanate group" represents "isocyanate group" or "isothiocyanate group".

[0026] In the present specification, the term "hydrocarbyloxysilyl group" refers to a monovalent or divalent group in which 1 to 3 hydrocarbyloxy groups are bonded to a silicon atom. That is, the hydrocarbyloxysilyl group is "-Si(OR １ ) ３－ｗ (R ２ ) ｗ " or ">Si(OR １ ) ２－ｙ (R ２ ) ｙ " (wherein R １ and R ２ are each independently a hydrocarbyl group, w is an integer of 0 to 2, and y is 0 or 1.) For example, "-Si(OR １ ) ３A compound having two monovalent groups represented by in one molecule and also containing a nitrogen-containing group is a "compound having a nitrogen-containing group and two hydrocarbyloxysilyl groups." The notation "having two or more hydrocarbyloxysilyl groups" does not represent the number of hydrocarbyloxy groups bonded to the silicon atom.

[0027] In this specification, a numerical range described using "X to Y" means that the numerical value X is included as the lower limit and the numerical value Y is included as the upper limit.

[0028] 1. Polymer Composition The polymer composition according to one embodiment of the present invention contains a rubber component. The components that may be included in the polymer composition according to this embodiment will be described below.

[0029] 1.1. Rubber Component 1.1.1. Polymer (A) The polymer composition according to this embodiment contains polymer (A) as a rubber component. Polymer (A) has a value α represented by the following formula (i) that is 0.6 or more and less than 1.0 when the constituent ratios (molar ratios) of the structural units represented by the following formula (1), the following formula (2), the following formula (3), and the following formula (4) in the polymer are p, q, r, and s, respectively, and the weight-average molecular weight (Mw) in polystyrene terms measured by gel permeation chromatography is 1.0 × 10 ５ ~2.0 x 10 ６ The polymer contains 5 to 50% by mass of structural units derived from aromatic vinyl compounds. α = (p + (0.5 × r)) / (p + q + (0.5 × r) + s) (i) β = (p + q) / (p + q + (0.5 × r) + s) (ii)

[0030] Polymer (A) is preferably a polymer having a random portion in which the distribution of structural units derived from the conjugated diene compound and structural units derived from the aromatic vinyl compound is irregular. Polymer (A) may also have a chain portion of structural units derived from the conjugated diene compound and / or the aromatic vinyl compound, formed by adding the conjugated diene compound and / or the aromatic vinyl compound after random copolymerization of the conjugated diene compound and / or the aromatic vinyl compound. This chain portion accounts for 10% by mass or less of the total polymer, preferably 5% by mass or less.

[0031] The content of structural units derived from aromatic vinyl compounds in polymer (A) is 5 to 50% by mass of the total polymer, preferably 5 to 45% by mass, and more preferably 5 to 40% by mass. When the content of structural units derived from aromatic vinyl compounds in polymer (A) is within the above range, it becomes easier to knead, improving the productivity of the polymer composition and allowing for the production of rubber products with high strength and excellent abrasion resistance. The content of structural units derived from aromatic vinyl compounds in polymer is not particularly limited, but for example, １ It can be measured by H-NMR.

[0032] The molecular structure of polymer (A) is not particularly limited and may be a linear polymer (hereinafter also referred to as "linear polymer"), a polymer having a multi-branched structure (hereinafter also referred to as "branched polymer"), or a mixture thereof. It is preferable that polymer (A) contains a branched polymer with four or more branches in order to maintain its shape well and facilitate transport.

[0033] Furthermore, in order to obtain rubber products with excellent fuel efficiency (rolling resistance), it is preferable that polymer (A) contains a polymer (also referred to herein as a "functional group-containing polymer") having a functional group (also referred to herein as a "specific functional group") containing at least one element selected from the group consisting of nitrogen, oxygen, sulfur, phosphorus, tin, and silicon. Here, a "functional group" is a group that has a specific structure within the molecule of an organic compound, and refers to an atomic group or bonding mode that characterizes the compound.

[0034] The position of the specific functional group in a functional group-containing polymer is not particularly limited. Examples of functional group-containing polymers include polymers having the specific functional group in the molecular chain (i.e., between the ends of the molecular chain), at the ends of the molecular chain, or both. When a functional group-containing polymer has the specific functional group at the ends of the molecular chain, the functional group-containing polymer may have the specific functional group at the polymerization initiation end, at the polymerization termination end, or at both the polymerization initiation end and the polymerization termination end.

[0035] Specific functional groups found in functional group-containing polymers include, for example, amino groups such as primary amino groups, secondary amino groups, and tertiary amino groups; nitrogen-containing groups formed by protecting two hydrogen atoms of a primary amino group; nitrogen-containing groups formed by protecting one hydrogen atom of a secondary amino group; imino groups; pyridyl groups; phosphorus-containing groups formed by protecting two hydrogen atoms of a primary phosphino group; phosphorus-containing groups formed by protecting one hydrogen atom of a secondary phosphino group; tertiary phosphino groups; epoxy groups; thioepoxy groups; carboxyl groups; hydroxyl groups; oxygen-containing groups formed by protecting a hydrogen atom of a hydroxyl group; sulfo groups; thiol groups; sulfur-containing groups formed by protecting a hydrogen atom of a thiol group; iso(thio)cyanate groups; nitrogen-containing heterocyclic groups (e.g., groups having heterocyclic rings such as pyridine rings and imide rings); hydrocarbyloxysilyl groups; hydrocarbyloxycarbonyl groups; ether bonds; thioether bonds; halogens; and the following bonding modes. These are some examples.

[0036] Among these specific functional groups, from the viewpoint of ensuring low fuel consumption performance in rubber products, it is preferable that the functional group be at least one selected from the group consisting of carboxyl groups, hydrocarbyloxysilyl groups, epoxy groups, amino groups, hydroxyl groups, sulfo groups, iso(thio)cyanate groups, thiol groups, and halogens.

[0037] The functional group-containing polymer that may be included in polymer (A) is preferably a reaction product (hereinafter also referred to as "modified polymer") of a conjugated diene polymer having an active end and a compound having a reaction site with the active end and a specific functional group. In the compound having a reaction site with the active end and a specific functional group (hereinafter also referred to as "modifying agent"), the number of reaction sites with the active end may be one or two or more. Specific examples of the specific functional group possessed by the modifying agent include the same groups and bonds as the specific functional group possessed by the functional group-containing polymer. Such a modified polymer can be obtained by using a coupling agent or end-modifying agent described later as the modifying agent in the production of the modified polymer.

[0038] When polymer (A) contains a branched polymer and a functional group-containing polymer (preferably a modified polymer), the branched polymer and the functional group-containing polymer may be separate polymers with different molecular structures and physical properties. Furthermore, polymer (A) may contain a branched polymer having a specific functional group. From the viewpoint of reducing the change in Mooney viscosity in response to differences in desolvation time and stabilizing quality, it is preferable that polymer (A) contains a branched polymer having a specific functional group.

[0039] Polymer (A) has a value α, represented by formula (i), that is 0.6 or more and less than 1.0, when the molar ratios of the structural units represented by formula (1), formula (2), formula (3), and formula (4) in the polymer are p, q, r, and s, respectively. Furthermore, it is preferable that β, represented by formula (ii), is between 0.2 and 0.7. α = (p + (0.5 × r)) / (p + q + (0.5 × r) + s) (i) β = (p + q) / (p + q + (0.5 × r) + s) (ii)

[0040] A value α represented by formula (i) above being 0.6 or more and less than 1.0 indicates that polymer (A) is a highly saturated conjugated diene polymer. The value of α is preferably 0.7 or more, more preferably 0.8 or more. The value of α is preferably 0.97 or less, more preferably 0.95 or less, and particularly preferably 0.92 or less. When the value of α is less than 0.6, the polymer has a large amount of unsaturated bonds, making it susceptible to degradation due to reactions with light and reactive oxygen species, and the quality of the polymer tends to become unstable. Furthermore, there is a concern that the instability of the polymer quality may lead to a decrease in the strength and viscoelastic properties of the rubber product. On the other hand, when the value of α reaches 1.0, crosslinking cannot proceed sufficiently, and there is a tendency for a decrease in the strength and viscoelastic properties of the rubber product to occur.

[0041] The value α represented by formula (i) above corresponds to the hydrogenation rate of the conjugated diene polymer. For example, if α is 0.60, the hydrogenation rate of the conjugated diene polymer is 60%. The hydrogenation rate and value α of the conjugated diene polymer can be adjusted by adjusting the hydrogenation reaction time or controlling the cumulative hydrogen supply. The value α represented by formula (i) above is not particularly limited, but for example, as described in the examples below. １ This can be measured using a method involving an H-NMR spectrometer.

[0042] The value β represented by the above formula (ii) corresponds to the content of 1,2-vinyl groups in the polymer before hydrogenation (hereinafter also referred to as "vinyl bond content"). For example, if β is 0.25, the content of 1,2-vinyl groups in the polymer before hydrogenation is 25 mol%. The value of β is preferably 0.22 or higher, more preferably 0.25 or higher. The value of β is preferably 0.65 or lower, more preferably 0.60 or lower, and particularly preferably 0.55 or lower. When the value of β is within the above range, the balance between viscoelasticity and strength of the rubber product is good, and the heat aging resistance and processability tend to improve. The value β represented by the above formula (ii) is not particularly limited, but for example, as described in the examples below. １ This can be measured using a method involving an H-NMR spectrometer.

[0043] In this specification, "vinyl bond content" refers to a value representing the ratio of structural units having 1,2-bonds to the total structural units of butadiene derived in the polymer before hydrogenation. The value β, represented by formula (ii) in the claim, is defined based on the composition ratio of structural units in the polymer after hydrogenation. However, this value β has a correspondence with the vinyl bond content in the polymer before hydrogenation. Through the hydrogenation reaction, specific butadiene-derived structural units contained in the polymer before hydrogenation are converted into predetermined structural units after hydrogenation. Based on this conversion relationship, a certain relationship holds between the relative abundance of each structural unit before and after hydrogenation. Thus, the value β represented by formula (ii) can also be expressed by the following formula: β = q (before hydrogenation) / (q (before hydrogenation) + s (before hydrogenation)) where q (before hydrogenation) and s (before hydrogenation) represent the amounts of structural units having 1,2-bonds and other butadiene-derived structural units in the polymer before hydrogenation, respectively. Therefore, the value β is defined based on the composition ratio of the polymer after hydrogenation, and can also be expressed as the value obtained by dividing the 1,2-vinyl bond content (mol%) measured in the polymer before hydrogenation by 100.

[0044] In formulas (i) and (ii) above, p, q, r, and s can each take values ​​from 0 to 100% (however, the sum of p, q, r, and s is 100% or less) when the constituent ratio of each structural unit of formulas (1) to (4) in the polymer is expressed in mole percent.

[0045] The polymer composition according to this embodiment is expected to provide the following effects by containing polymer (A), which is a highly saturated conjugated diene polymer: (1) Polymer (A) has a reduced number of unsaturated bonds that are vulnerable to heat, light, ozone, etc., thus improving weather resistance. (2) Polymer (A) has a reduced number of unsaturated bonds that cannot rotate, thus improving the degree of freedom of motion of the molecular chains and increasing the entanglement of rubber molecules, resulting in improved strength (stress) and abrasion resistance. (3) Polymer (A) has a controlled number of unsaturated bonds, thus suppressing the concentration of crosslinks. As a result, crosslinks become uniform and stress concentration is suppressed, thus improving strength (elongation at break) and abrasion resistance.

[0046] Polymer (A) can be obtained, for example, by hydrogenating styrene-butadiene rubber. Specifically, it can be produced by a method including the following polymerization and hydrogenation steps. Alternatively, polymer (A) may be produced by a method including, in addition to the polymerization and hydrogenation steps, at least one of the following reaction and modification steps. The method for producing polymer (A) will be described step by step below.

[0047] (Polymerization process) This process involves polymerizing monomers containing a conjugated diene compound and an aromatic vinyl compound to obtain a conjugated diene polymer having an active end.

[0048] The conjugated diene compound used for polymerization may be 1,3-butadiene alone, or it may be used in combination with other conjugated diene compounds (hereinafter also referred to as "other conjugated diene compounds"). Examples of other conjugated diene compounds include isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-heptadiene, 2-phenyl-1,3-butadiene, 3-methyl-1,3-pentadiene, and 2-chloro-1,3-butadiene. Among these, isoprene and 2,3-dimethyl-1,3-butadiene are preferred. The conjugated diene compound may be used alone, or two or more may be used in combination.

[0049] Examples of aromatic vinyl compounds used in the above polymerization include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-tert-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-tert-butylstyrene, 3-tert-butylstyrene, vinylxylene, vinylnaphthalene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene (e.g., 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene). Among these aromatic vinyl compounds, styrene and α-methylstyrene, or both, are preferred. Aromatic vinyl compounds may be used individually or in combination of two or more.

[0050] In the polymerization described above, compounds other than conjugated diene compounds and aromatic vinyl compounds (hereinafter also referred to as "other monomers") may be used as monomers. Examples of other monomers include acrylonitrile, methyl (meth)acrylate, and ethyl (meth)acrylate. The content of other monomers is preferably 10% by mass or less, and more preferably 5% by mass or less, relative to the total amount of monomers used in polymerization.

[0051] Any polymerization method may be used, including solution polymerization, gas-phase polymerization, or bulk polymerization, but solution polymerization is particularly preferred. Furthermore, either batch or continuous polymerization can be used. When using solution polymerization, one specific example of a polymerization method involves polymerizing a monomer mixture containing a conjugated diene compound and an aromatic vinyl compound in an organic solvent in the presence of a polymerization initiator and, if necessary, a vinyl content adjuster (randomizer).

[0052] As polymerization initiators, metal compounds containing alkali metals or alkaline earth metals can be used. Specific examples include alkyllithium compounds such as methyllithium, ethyllithium, n-propyllithium, n-butyllithium, sec-butyllithium, and tert-butyllithium; 1,4-dilithiobutane, phenyllithium, stilbenithium, naphthyllithium, 1,3-bis(1-lithio-1,3-dimethylpentyl)benzene, 1,3-phenylenebis(3-methyl-1-phenylpentylidene)dilithium, sodium naphthyl, potassium naphthyl, di-n-butylmagnesium, di-n-hexylmagnesium, potassium ethoxy, and calcium stearate. Among these, lithium compounds are preferred.

[0053] Furthermore, the metal compound used as a polymerization initiator may be a metal amide compound having an alkali metal or alkaline earth metal. By carrying out polymerization to obtain a conjugated diene polymer in the presence of a metal amide compound, an amino group (preferably a secondary or tertiary amino group) can be introduced to the polymerization initiation end (free end portion in the case of a branched polymer) of the conjugated diene polymer. A conjugated diene polymer obtained by polymerizing monomers in the presence of a metal amide compound is preferable in that it can increase the strength of the crosslinked body and improve the fuel efficiency of rubber products.

[0054] The metal amide compound is preferably a compound obtained by mixing a lithium compound (for example, alkyllithium, etc.) with a compound having a nitrogen atom (hereinafter also referred to as the "initial end modifier"). The initial end modifier is preferably a secondary amine compound. Specific examples include dimethylamine, diethylamine, dipropylamine, dibutylamine, dodecamethyleneimine, N,N'-dimethyl-N'-trimethylsilyl-1,6-diaminohexane, piperidine, pyrrolidine, hexamethyleneimine, heptamethyleneimine, dicyclohexylamine, N-methylbenzylamine, di-(2-ethylhexyl)amine, diallylamine, morpholine, N-(trimethylsilyl)piperazine, N-(tert-butyldimethylsilyl)-4-piperazine, 1,3-ditrimethylsilyl-1,3,5-triazinane, and the like.

[0055] When polymerization is carried out in the presence of a metal amide compound, the metal amide compound may be prepared by pre-mixing the lithium compound and the starting-end modifier, and then the prepared metal amide compound may be added to the polymerization system and polymerization may be carried out. Alternatively, the lithium compound and the starting-end modifier may be added to the polymerization system, and the metal amide compound may be prepared by mixing the two in the polymerization system and then polymerization may be carried out. When polymerization is carried out, the amount of polymerization initiator used is preferably 0.01 to 20 mmol, and more preferably 0.05 to 15 mmol, per 100 g of monomer used for polymer synthesis.

[0056] Randomizers can be used to adjust the vinyl bond content, which represents the proportion of vinyl bonds in a polymer. Examples of randomizers include dimethoxybenzene, tetrahydrofuran, potassium dodecylbenzenesulfonate, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, 2,2-di(tetrahydrofuryl)propane, 2-(2-ethoxyethoxy)-2-methylpropane, triethylamine, pyridine, N-methylmorpholine, and tetramethylethylenediamine. These can be used individually or in combination of two or more.

[0057] Any organic solvent that is inert to the reaction can be used as the organic solvent for polymerization, such as aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. Among these, hydrocarbons having 3 to 8 carbon atoms are preferred, and specific examples include propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis-2-butene, 1-pentine, 2-pentine, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene, heptane, cyclopentane, methylcyclopentane, methylcyclohexane, 1-pentene, 2-pentene, and cyclohexene. The organic solvent can be used individually or in combination of two or more.

[0058] When solution polymerization is used, the monomer concentration in the reaction solvent is preferably 5 to 50% by mass, and more preferably 10 to 30% by mass, from the viewpoint of maintaining a balance between productivity and ease of polymerization control. The polymerization reaction temperature is preferably -20°C to 150°C, and more preferably 0°C to 120°C. Furthermore, the polymerization reaction is preferably carried out under pressure sufficient to keep the monomer substantially in the liquid phase. Such pressure can be obtained by methods such as pressurizing the reactor with a gas that is inert to the polymerization reaction.

[0059] Such polymerization reactions can yield conjugated diene polymers having active ends. The vinyl bond content in the conjugated diene compound units of the resulting conjugated diene polymer is preferably 20 to 70 mol%, more preferably 23 to 68 mol%, and particularly preferably 25 to 65 mol%. If the vinyl bond content is less than 20 mol%, the grip properties tend to be low, and if it exceeds 70 mol%, the abrasion resistance of the resulting rubber product tends to decrease.

[0060] (Reaction Step) The reaction step involves reacting a conjugated diene polymer obtained in the polymerization step with a compound having four or more functional groups that can react with the active ends of the conjugated diene polymer (hereinafter also referred to as the "coupling agent"). Through the reaction between the conjugated diene polymer having active ends and the coupling agent, four or more molecular chains of the conjugated diene polymer are bonded to one molecule of the coupling agent, thereby obtaining a polymer (A) that includes a branched polymer with four or more branches.

[0061] As a coupling agent, a compound having at least one element selected from the group consisting of nitrogen, oxygen, sulfur, phosphorus, tin, and silicon (hereinafter also referred to as "specific element") can be preferably used. When a compound having a specific element is used as a coupling agent, it is preferable in that the strength of the resulting rubber product can be increased. Furthermore, by using a compound having a specific element as a coupling agent, a modified polymer can be obtained as polymer (A).

[0062] Specific examples of such coupling agents include, for example, tetrachlorosilane and bis(trichlorosilyl)ethane. Furthermore, as coupling agents, compounds having functional groups containing specific elements can also be used, such as nitrogen-containing groups formed by protecting two hydrogen atoms of a primary amino group, nitrogen-containing groups formed by protecting one hydrogen atom of a secondary amino group, tertiary amino groups, imino groups, nitrogen-containing heterocyclic groups (e.g., groups with heterocyclic rings such as pyridine rings and imide rings), hydroxyl groups, oxygen-containing groups formed by protecting the hydrogen atom of a hydroxyl group, sulfur-containing groups formed by protecting the hydrogen atom of a thiol group, and hydrocarbyloxysilyl groups.

[0063] Specific examples of coupling agents having such functional groups include N,N,N',N'-tetra(3-trimethoxysilylpropyl)ethylenediamine, N,N,N',N'-tetra(3-triethoxysilylpropyl)ethylenediamine, N,N,N'-tris(3-trimethoxysilylpropyl)-N'-methylethylenediamine, N,N,N',N'-tetra(3-trimethoxysilylpropyl)-1,3-propanediamine, N,N,N',N'-tetra(3-trimethoxysilylpropyl)-1,4-butanediamine, bis(3-trimethoxysilylpropyl)-[2-(dimethylamino)ethyl]amine, and bis(3-trimethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silacyclopentane) Examples include bis(3-triethoxysilylpropyl)-[2-(2,2-diethoxy-1-aza-2-silacyclopentane)ethyl]amine, bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, bis(3-trimethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silacyclohexane)ethyl]amine, bis(3-trimethoxysilylpropyl)-[2-(2,2-dimethoxy-1-aza-2-silacyclooctane)ethyl]amine, N,N-bis(3-trimethoxysilylpropyl)-3-imidazolylpropylamine, and bis(3-trimethoxysilylpropyl)-(3-dimethylaminopropyl)amine.

[0064] Other specific examples of coupling agents include compounds represented by formulas (M1) to (M7) below, and compounds obtained by replacing the alkyl group and alkanediyl group in these compounds with C1-C6 alkyl groups and C1-C6 alkanediyl groups, respectively.

[0065] The reaction between the conjugated diene polymer having active ends and the coupling agent is preferably carried out as a solution reaction. The amount of coupling agent used (total amount if two or more types are used) can be appropriately set so that the content of branched polymers with four or more branches in polymer (A) is within the desired range. From the viewpoint of suppressing changes in Mooney viscosity due to differences in desolvation time and stabilizing the quality, and obtaining a high-strength crosslinked body by stabilizing the quality of the polymer, the amount of coupling agent used is preferably 0.01 mol or more, and more preferably 0.02 mol or more, per mol of metal atoms involved in polymerization in the polymerization initiator (i.e., metal compound). Furthermore, from the viewpoint of adjusting the coupling rate to a desired value to obtain a polymer composition exhibiting good processability and a crosslinked body with excellent viscoelastic properties, the amount of coupling agent used is preferably 0.4 mol or less, more preferably 0.25 mol or less, even more preferably 0.2 mol or less, and particularly preferably 0.1 mol or less, per mol of metal atoms involved in polymerization in the polymerization initiator. Furthermore, the coupling agent may be used individually or in combination of two or more types.

[0066] In coupling reactions, the reaction temperature is usually within the same range as that of polymerization reactions. Specifically, it is preferably -20°C to 150°C, and more preferably 0°C to 120°C. If the reaction temperature is low, the viscosity of the polymer after the reaction tends to increase, and if the reaction temperature is high, the polymerization active ends tend to be deactivated. The reaction time is preferably 1 minute to 5 hours, and more preferably 2 minutes to 1 hour.

[0067] The above coupling reaction can yield a pre-hydrogenation polymer (A) containing a branched polymer with four or more branches. The conjugated diene polymer after the coupling reaction may also contain linear polymers. The linear polymers contained in the polymer solution after the coupling reaction are unreacted polymers that did not react with the coupling agent among the linear polymers contained in the conjugated diene polymer having active ends.

[0068] (Modification Step) The conjugated diene polymer obtained by the polymerization or reaction step may be subjected to the subsequent hydrogenation step as is. Alternatively, the conjugated diene polymer obtained by the polymerization or reaction step may be subjected to a treatment before the hydrogenation step in which the active ends of the conjugated diene polymer are reacted with a compound having a specific functional group and capable of reacting with the active ends of the conjugated diene polymer (excluding coupling agents; hereinafter also referred to as "end modifiers"). By performing such a treatment, if the conjugated diene polymer obtained by the polymerization or reaction step contains polymers with active ends, polymer (A) can be made to contain polymers in which the molecular chains of the linear conjugated diene polymer are bonded to the end modifier (i.e., polymers having specific functional groups). Note that the end modifier is a compound that differs from a coupling agent in that it has 1 to 3 reaction sites with the active ends of the conjugated diene polymer.

[0069] Preferred examples of terminal denaturants include at least one selected from the group consisting of compounds represented by the following general formula (5) and compounds represented by the following general formula (6). (In formula (5), A １１ It has at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, and does not have active hydrogen, and R ３５ It is a monovalent functional group bonded to nitrogen, phosphorus, oxygen, sulfur, silicon, or a carbon atom contained in a carbonyl group, or a (thio)epoxy group. ３３ and R ３４ These are, independently, hydrocarbyl groups. ３５ R is a hydrocarbylene group. t is an integer from 0 to 2. However, if t is 2, multiple R in the formula ３３ These are either the same or different from each other. If t is 0 or 1, then multiple R in the formula ３４ (They are either identical or different from each other.) (In formula (6), A １２ It has at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, and does not have active hydrogen, and R ３９It is a monovalent functional group bonded to it by nitrogen, phosphorus, oxygen, sulfur, or silicon, or a hydrocarbyl group having 1 to 20 carbon atoms. ３６ and R ３７ These are, independently, hydrocarbyl groups. ３８ This is a hydrocarbylene group. ３９ is a single bond or a hydrocarbylene group. u is 0 or 1. However, if u is 0, multiple R in the formula ３７ (They are either identical or different from each other.)

[0070] In equations (5) and (6) above, R ３３ , R ３４ , R ３６ , R ３７ , and A in the case of a hydrocarbyl group １２ Regarding this, the hydrocarbyl group is preferably a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. ３８ and R ３９ The hydrocarbylene group represented by is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms. ３８ The hydrocarbylene group represented is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms. t is preferably 0 or 1.

[0071] A １１ When the above monovalent functional group is A １１ At least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, and A １２ When the above monovalent functional group is A １２ At least one element selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon may be protected by, for example, a trisubstituted hydrocarbylsilyl group. In this specification, "active hydrogen" refers to a hydrogen atom bonded to an atom other than a carbon atom, preferably one with a bond energy lower than the carbon-hydrogen bond of polymethylene.

[0072] A １１This may be a group that can become an onium ion by an onium salt generating agent. The terminal modifying agent may be such a group (A １１ By having ), excellent shape retention properties can be imparted to the polymer. A １１ Specific examples include nitrogen-containing groups in which two hydrogen atoms of a primary amino group are protected, nitrogen-containing groups in which one hydrogen atom of a secondary amino group is protected, tertiary amino groups, imino groups, pyridyl groups, phosphorus-containing groups in which two hydrogen atoms of a primary phosphino group are protected, phosphorus-containing groups in which one hydrogen atom of a secondary phosphino group is protected, tertiary phosphino groups, epoxy groups, thioepoxy groups, oxygen-containing groups in which a hydrogen atom of a hydroxyl group is protected, sulfur-containing groups in which a hydrogen atom of a thiol group is protected, and hydrocarbyloxycarbonyl groups. Among these, groups having a nitrogen atom are preferred in terms of good affinity with silica, and nitrogen-containing groups in which two hydrogen atoms of a tertiary amino group or primary amino group are protected are more preferred. Here, a protected group is A １１ Ya A １２ This refers to a group that has been converted to a functional group that is inactive with respect to the polymerization active end. Onium salt generating agents are Brønsted acid, or compounds that produce Brønsted acid upon contact with water.

[0073] Specific examples of compounds represented by the above general formula (5) include, for example, N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-dimethylaminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-(4-trimethylsilyl-1-piperazino)propylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyltriethoxysilane.

[0074] Specific examples of compounds represented by the above general formula (6) include, for example, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1,2-azacyloridine, 2,2-diethoxy-1-(3-trimethoxysilylpropyl)-1,2-azacyloridine, 2,2-dimethoxy-1-phenyl-1,2-azacyloridine, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, 2-(2,2-dimethoxy-1,2-azacyloridine-1-yl)-N,N-diethylethane-1-amine, 2-(2,2-dimethoxy-1,2-azacyloridine-1-yl)-N,N-dimethylethane-1-amine, and 3-(2,2-dimethoxy-1,2-azacyloridine-1-yl)-N,N-diethylpropane-1-amine.

[0075] These terminal denaturants may be used individually or in combination of two or more.

[0076] The reaction between a conjugated diene polymer having active ends and a terminal modifier can be carried out, for example, as a solution reaction. This solution reaction may be carried out using either a batch or continuous method. In this case, there are no particular restrictions on the method of adding the terminal modifier, and examples include adding it all at once, adding it in installments, or adding it continuously.

[0077] The amount of end-modifier used can be appropriately set depending on the type of compound used in the reaction. The amount of end-modifier is preferably 0.05 mol or more, and more preferably 0.1 mol or more, per 1 mol of metal atoms involved in the polymerization reaction in the polymerization initiator. By using an amount of 0.1 mol equivalent or more of end-modifier, the modification reaction can be carried out sufficiently, and the effect of improving the dispersibility of the filler can be enhanced. Alternatively, the amount of end-modifier is preferably 1.0 mol or less, and more preferably 0.8 mol or less, per 1 mol of metal atoms involved in the polymerization reaction in the polymerization initiator.

[0078] In the modification reaction with the end-modifier, the reaction temperature is usually the same as the polymerization reaction temperature, preferably -20°C to 150°C, more preferably 0°C to 120°C, and particularly preferably 20°C to 100°C. If the modification reaction temperature is low, the viscosity of the polymer solution tends to increase. If the modification reaction temperature is high, the polymerization active ends tend to be deactivated. The reaction time for end modification is preferably 1 minute to 5 hours, more preferably 2 minutes to 1 hour.

[0079] The coupling ratio of polymer (A) can be set according to the proportion of branched polymer present in polymer (A), the molecular weight of the conjugated diene polymer having active ends, the number of functional groups of the coupling agent used, and so on. From the viewpoint of suppressing changes in Mooney viscosity due to differences in desolvation time of polymer (A) and stabilizing quality, the coupling ratio of polymer (A) is preferably 10% or more, more preferably 15% or more, and particularly preferably 20% or more. Furthermore, from the viewpoint of obtaining a polymer composition with good processability and a crosslinked material with excellent viscoelastic properties, the coupling ratio of polymer (A) is preferably 70% or less, more preferably 60% or less, and particularly preferably 50% or less.

[0080] In this specification, "coupling rate" refers to the proportion (mass%) of linear conjugated diene polymers with active ends that are used in a reaction between a linear conjugated diene polymer having active ends and a coupling agent or end-modifying agent. Specifically, it represents the proportion (mass%) of polymers to which two or more linear conjugated diene polymer chains are bonded via a coupling agent or end-modifying agent, relative to the total amount of polymer (more specifically, aggregate of linear polymers having active ends) used in the reaction with a coupling agent or end-modifying agent. The coupling rate can be calculated by separating the waveform of molecules to which two or more linear conjugated diene polymer chains are bonded from a GPC curve obtained using gel permeation chromatography (GPC), and then calculating the peak area ratio.

[0081] Furthermore, if neither a reaction step nor a modification step is performed on the conjugated diene polymer having an active end obtained by the polymerization step, it is preferable to react the conjugated diene polymer having an active end with a polymerization inhibitor such as an alcohol, and then perform the following hydrogenation step. In this case, it is preferable to use an initiating end modifier in the polymerization step to obtain a conjugated diene polymer having a specific functional group.

[0082] (Hydrogenation Process) In the hydrogenation process, the conjugated diene polymer obtained by the polymerization, reaction, or modification process described above is hydrogenated (hereinafter also referred to as "hydrogenation"). The method and conditions of hydrogenation are not particularly limited as long as a conjugated diene polymer with the desired hydrogenation rate can be obtained. Examples of hydrogenation methods include using a catalyst mainly composed of an organometallic compound of titanium as a hydrogenation catalyst, using a catalyst consisting of an organometallic compound of iron, nickel, or cobalt and an organometallic compound such as alkylaluminum, using an organometallic complex of an organometallic compound such as ruthenium or rhodium, and using a catalyst in which metals such as palladium, platinum, ruthenium, cobalt, or nickel are supported on a carrier such as carbon, silica, or alumina. Among the various methods, the hydrogenation method using a titanium organometallic compound alone, or a homogeneous catalyst consisting of a titanium organometallic compound and a lithium, magnesium, or aluminum organometallic compound (for example, the catalyst described in Japanese Patent Publication No. 63-4841 and Japanese Patent Publication No. 1-37970), under mild conditions of low pressure and low temperature, is industrially preferred and also suitable due to its high hydrogenation selectivity for the double bond derived from butadiene.

[0083] Hydrogenation is carried out in a solvent that is inert to the catalyst and soluble in the conjugated diene polymer. Preferred solvents include aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclohexane and cycloheptane; aromatic hydrocarbons such as benzene and toluene; and ethers such as diethyl ether and tetrahydrofuran. The solvent used for hydrogenation may be one of the above compounds or a mixture in which they are the main components.

[0084] The hydrogenation reaction is carried out by maintaining the conjugated diene polymer at a predetermined temperature under a hydrogen or inert atmosphere, adding a hydrogenation catalyst with or without stirring, and then introducing hydrogen gas to pressurize it to a predetermined pressure. An inert atmosphere means an atmosphere that does not react with any of the substances involved in the hydrogenation reaction, and is formed by, for example, helium, neon, or argon. The hydrogenation reaction process may be a batch process, a continuous process, or a combination thereof. The amount of hydrogenation catalyst added is preferably 0.02 to 20 mmol per 100 g of the conjugated diene polymer before hydrogenation.

[0085] In the hydrogenation process, the value of α in equation (i) above (hydrogenation rate) can be adjusted by adjusting the time of the hydrogenation reaction or controlling the cumulative supply of hydrogen so that it is between 0.6 and less than 1.0.

[0086] Polymer (A) is obtained by removing the solvent from the solution obtained above and isolating the polymer. The polymer can be isolated by known solvent removal methods such as steam stripping and drying operations such as heat treatment.

[0087] A preferred method for obtaining polymer (A) involves solution polymerization of monomers containing 1,3-butadiene and styrene in the presence of a polymerization initiator (preferably a metal amide compound), adding a coupling agent to the resulting polymer solution to carry out a coupling reaction, adding a terminal modifier as needed, and then subjecting it to a hydrogenation step. This method is preferred because it allows for the production of rubber products with excellent physical properties (low fuel consumption, wear resistance, handling stability, etc.) and also improves productivity.

[0088] For polymer (A), the weight-average molecular weight (Mw) in polystyrene terms, measured using gel permeation chromatography (GPC), was 1.0 × 10⁻⁶, from the viewpoint of obtaining a rubber product with high strength and excellent abrasion resistance. ５ ~2.0 x 10 ６ The Mw of polymer (A) is more preferably 1.5 × 10 ５ The above is the most preferred, and is particularly 2.0 × 10 ５ That is all. Furthermore, Mw is more preferably 1.6 × 10 ６The following, and particularly preferably 1.4 × 10 ６ The following applies. Note that the weight-average molecular weight of polymer (A) is the value obtained from all peaks of the GPC curve measured by GPC before hydrogenation, and this weight-average molecular weight will also be referred to as the "total average molecular weight" below.

[0089] For polymer (A), the molecular weight distribution (ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (weight-average molecular weight / number-average molecular weight)) of the total amount of polymer (i.e., aggregate of different molecular weights) measured by GPC is preferably 1.1 or more and 4.0 or less. A molecular weight distribution of 1.1 or more is preferable in terms of excellent processability, and a molecular weight distribution of 4.0 or less is preferable in that the low hysteresis loss properties of the resulting rubber product can be sufficiently improved. The molecular weight distribution of polymer (A) is more preferably 1.2 or more. Furthermore, the molecular weight distribution of polymer (A) is more preferably 3.5 or less, and particularly preferably 3.0 or less.

[0090] For polymer (A), the peak top molecular weight of the peak with the smallest molecular weight, as measured by GPC (hereinafter also referred to as the "1st peak molecular weight"), is preferably 0.8 × 10⁻⁶. ５ ~1.0 x 10 ６ It is within this range. The first peak molecular weight is 0.8 × 10⁻⁶. ５ With the above conditions, the strength of the resulting rubber product can be sufficiently high while maintaining good viscoelastic properties and processability. The first peak molecular weight is more preferably 0.9 × 10⁻⁶. ５ The above is the most preferred, and is particularly preferably 1.0 × 10 ５ That concludes the explanation. Furthermore, from the viewpoint of improving viscoelastic properties and processability, the 1st peak molecular weight is more preferably 8.0 × 10⁻⁶. ５ The following, and particularly preferably 5.0 × 10 ５ The results are as follows. Note that the 1st peak molecular weight was obtained from the GPC curve measured by GPC before hydrogenation.

[0091] In the polymer composition according to this embodiment, the content of polymer (A) when the total amount of rubber components is 100 parts by mass is preferably 0.1 to 65 parts by mass, more preferably 1 to 65 parts by mass, even more preferably 10 to 65 parts by mass, even more preferably 20 to 65 parts by mass, even more preferably 30 to 65 parts by mass, even more preferably 40 to 60 parts by mass, and particularly preferably 50 to 60 parts by mass. When the content of polymer (A) in the rubber components is within the above range, it is easy to obtain rubber products that have excellent processability and productivity, as well as improved heat aging resistance.

[0092] 1.1.2. Emulsion Polymerized Styrene-Butadiene Rubber (B) The polymer composition according to this embodiment contains emulsion polymerized styrene-butadiene rubber (B) as a rubber component. Emulsion polymerized styrene-butadiene rubber (B) is not particularly limited as long as it is styrene-butadiene rubber synthesized by emulsion polymerization. Emulsion polymerized styrene-butadiene rubber (B) may also be an oil-expandable rubber.

[0093] Emulsion polymerized styrene-butadiene rubber (B) is a copolymer of butadiene and styrene. The butadiene content in emulsion polymerized styrene-butadiene rubber (B) is not particularly limited and can be adjusted as appropriate, but from the viewpoint of obtaining a rubber product with excellent abrasion resistance, it is preferably 50% by mass or more, and more preferably 60% by mass or more. Similarly, the styrene content in emulsion polymerized styrene-butadiene rubber (B) is not particularly limited and can be adjusted as appropriate, but from the viewpoint of obtaining a rubber product with excellent abrasion resistance, it is preferably 10% by mass or more, and more preferably 20% by mass or more.

[0094] Furthermore, emulsion polymerized styrene-butadiene rubber (B) may have the above-mentioned specific functional group at the polymerization initiation end, at the polymerization termination end, at both the polymerization initiation end and the polymerization termination end, or in the molecular chain (i.e., between the ends of the molecular chain). Also, emulsion polymerized styrene-butadiene rubber (B) may have the above-mentioned specific functional group at some of the ends of one polymer molecule, or at all of the ends of one polymer molecule. Furthermore, emulsion polymerized styrene-butadiene rubber (B) may have one specific functional group in the molecular chain, or it may have multiple specific functional groups.

[0095] In the polymer composition according to this embodiment, the content of emulsion polymerized styrene-butadiene rubber (B) when the total amount of rubber components is 100 parts by mass is preferably 3 to 99 parts by mass, more preferably 35 to 99 parts by mass, even more preferably 35 to 90 parts by mass, even more preferably 35 to 80 parts by mass, even more preferably 35 to 70 parts by mass, even more preferably 35 to 60 parts by mass, and particularly preferably 35 to 50 parts by mass. When the content of emulsion polymerized styrene-butadiene rubber (B) in the rubber components is within the above range, it is easy to obtain rubber products that have excellent processability and productivity, as well as improved heat aging resistance.

[0096] Emulsion polymerized styrene-butadiene rubber (B) is synthesized by emulsion polymerization, for example, by emulsifying a radically polymerizable monomer in water using an emulsifier, and then adding a radical initiator to the resulting emulsion to perform radical polymerization.

[0097] The emulsion can be prepared using an emulsifier by a known method. The emulsifier is not particularly limited, and known materials can be used. Examples include anionic surfactants, nonionic surfactants, and amphoteric surfactants. To obtain a stable emulsion dispersion, anionic surfactants are usually used. Examples of anionic surfactants include long-chain fatty acid salts with 10 or more carbon atoms, rosinates, and linear alkyl group-containing benzenesulfonates. Specifically, examples include potassium and sodium salts of capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, octylbenzenesulfonic acid, dodecylbenzenesulfonic acid, dodecyldiphenyloxidesulfonic acid, and dodecyldiphenyl ether disulfonic acid. Fluorine-based surfactants can also be used. The emulsifier can be used alone or in combination of two or more.

[0098] Furthermore, emulsion polymerization can be carried out by known methods using radical polymerization initiators. The radical polymerization initiator is not particularly limited, and known materials can be used. For example, organic peroxides such as benzoyl peroxide, lauroyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, pinan hydroperoxide, paramentane hydroperoxide, trimethylbicycloheptyl hydroperoxide, di-tert-butyl peroxide, and dicumyl peroxide can be used. In addition, diazo compounds represented by azobisisobutyronitrile, inorganic peroxides represented by potassium persulfate, and redox catalysts represented by combinations of these peroxides and ferrous sulfate can also be used.

[0099] The emulsion polymerization temperature can be appropriately adjusted depending on the type of radical initiator used, but is preferably 0 to 50°C, more preferably 0 to 20°C.

[0100] Emulsion polymerization can be stopped by adding a polymerization inhibitor to the polymerization system. The polymerization inhibitor is not particularly limited, and known materials can be used. Examples include hydroxylamine compounds such as N,N'-dimethyldithiocarbamate, hydroxylamine, diethylhydroxylamine, and N,N-diethylhydroxylamine, and hydroquinone.

[0101] Mooney viscosity (ML) of emulsion polymerized styrene-butadiene rubber (B) １＋４ The Mooney viscosity (at 100°C) is preferably 20 to 100, more preferably 30 to 80, and particularly preferably 35 to 60. When the Mooney viscosity of emulsion polymerized styrene-butadiene rubber (B) is within the above range, the heat aging resistance is improved, as well as the processability and productivity are excellent.

[0102] 1.1.3. Content Ratio In the polymer composition according to this embodiment, the ratio (a / b) of the content a of polymer (A) to the content b of emulsion polymerized styrene-butadiene rubber (B) is in the range of 65 / 35 to 1 / 99, preferably 65 / 35 to 10 / 90, more preferably 65 / 35 to 20 / 80, even more preferably 65 / 35 to 30 / 70, even more preferably 65 / 35 to 40 / 60, and particularly preferably 65 / 35 to 50 / 50. When the ratio (a / b) of the content a of polymer (A) to the content b of emulsion polymerized styrene-butadiene rubber (B) is within the above range, it is easy to obtain rubber products that have excellent processability and productivity, as well as improved heat aging resistance.

[0103] 1.1.4. Other Rubber Components The rubber components contained in the polymer composition according to this embodiment may consist only of polymer (A) and emulsion polymerized styrene-butadiene rubber (B), or may further contain rubber components other than polymer (A) and emulsion polymerized styrene-butadiene rubber (B) (hereinafter also referred to as "other rubber components"). Examples of other rubber components include at least one selected from the group consisting of butadiene rubber, isoprene-based rubber, solution polymerized styrene-butadiene rubber, butyl rubber, halogenated butyl rubber, ethylene-propylene rubber, and ethylene-butadiene rubber. The other rubber components can be mixed with polymer (A) and emulsion polymerized styrene-butadiene rubber (B) during kneading using a Banbury mixer, rolls, etc., as is commonly done.

[0104] Furthermore, isoprene-based rubber can be any polymer mainly composed of structural units derived from isoprene. The proportion of structural units derived from isoprene in isoprene-based rubber is preferably 90% by mass or more, and more preferably 95% by mass or more, relative to the total amount of structural units in isoprene-based rubber. Specific examples of isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), epoxidized natural rubber (ENR), hydrogenated natural rubber, grafted natural rubber, and the like.

[0105] 1.2 Other Components The polymer composition according to this embodiment may further contain the following components in addition to the rubber component.

[0106] 1.2.1. Fillers The polymer composition according to this embodiment may contain fillers. Examples of fillers include carbon black, silica, silica, and fillers other than carbon black (hereinafter also referred to as "other fillers"). Preferably, the filler contains either or both of carbon black and silica.

[0107] The filler content in the polymer composition according to this embodiment is preferably in the range of 40 to 200 parts by mass, more preferably in the range of 50 to 150 parts by mass, even more preferably in the range of 55 to 130 parts by mass, and particularly preferably in the range of 60 to 120 parts by mass, when the total amount of rubber components is 100 parts by mass. If the filler content is less than 40 parts by mass per 100 parts by mass of rubber components, the low hysteresis loss, fracture properties, and abrasion resistance of the polymer composition tend to decrease.

[0108] <Silica> The polymer composition according to this embodiment preferably contains silica from the viewpoint of low hysteresis loss, fracture properties, and wear resistance. Examples of silica include wet silica (hydrated silica), dry silica (anhydrous silica), calcium silicate, aluminum silicate, silica derived from rice husks, silica derived from rice bran, etc. Among these, wet silica is preferred. One type of silica may be used alone, or two or more types may be used in combination.

[0109] The silica content in the polymer composition according to this embodiment is preferably in the range of 30 to 180 parts by mass, more preferably in the range of 40 to 150 parts by mass, and particularly preferably in the range of 50 to 120 parts by mass, when the total amount of rubber components is 100 parts by mass. Furthermore, when the silica content is 80 parts by mass or more when the total amount of rubber components is 100 parts by mass, the processability and productivity of the polymer composition can be particularly improved.

[0110] <Carbon Black> The polymer composition according to this embodiment preferably contains carbon black from the viewpoint of fracture properties and wear resistance. The carbon black is not particularly limited, and examples include GPF, FEF, HAF, ISAF, and SAF grade carbon black. One type of carbon black may be used alone, or two or more types may be used in combination.

[0111] The nitrogen adsorption specific surface area (N2SA) of carbon black is not particularly limited, but is typically between 50 and 200 m². ２ / g is preferred, and 70 to 150m ２ / g is more preferred. The nitrogen adsorption specific surface area (N₂SA) is a value measured by measuring the amount of nitrogen adsorbed on the carbon black surface in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single-point method".

[0112] The content of carbon black in the polymer composition according to the present embodiment is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 2 to 80 parts by mass, and particularly preferably in the range of 3 to 70 parts by mass, relative to 100 parts by mass of the rubber component. When the total amount of the rubber component is 100 parts by mass and the content of carbon black is 10 parts by mass or more, the processability and productivity of the polymer composition can be particularly improved.

[0113] <Other Fillers> Examples of other fillers include aluminas (Al ２ O ３ ) such as γ-alumina and α-alumina, alumina monohydrates (Al ２ O ３ ·H ２ O) such as boehmite and diaspore, aluminum hydroxides [Al(OH) ３ such as gibbsite and bayerite, aluminum carbonate [Al ２ (CO ３ ) ３ , magnesium hydroxide [Mg(OH) ２ , magnesium oxide (MgO), magnesium carbonate (MgCO ３ ), talc (3MgO·4SiO ２ ·H ２ O), attapulgite (5MgO·8SiO ２ ·9H ２ O), titanium white (TiO ２ ), titanium black (TiO ２ｎ－１ ), calcium oxide (CaO), calcium hydroxide [Ca(OH) ２ , magnesium aluminum oxide (MgO·Al ２ O ３ ), clay (Al ２ O ３ ·2SiO ２ ), kaolin (Al ２ O ３ ·2SiO ２ ·2H２ O), pyrophyllite (Al ２ O ３ ·4SiO ２ ·H ２ O), bentonite (Al ２ O ３ ·4SiO ２ ·2H ２ O), aluminum silicate (Al ２ SiO ５ , Al ４ ·3SiO ４ ·5H ２ O, etc.), magnesium silicate (Mg ２ SiO ４ , MgSiO ３ , etc.), calcium silicate (Ca ２ SiO ４ , etc.), aluminum calcium silicate (Al ２ O ３ ·CaO·2SiO ２ , etc.), magnesium calcium silicate (CaMgSiO ４ ), calcium carbonate (CaCO ３ ), zirconium oxide (ZrO ２ ), zirconium hydroxide [ZrO(OH) ２ ·nH ２ O], zirconium carbonate [Zr(CO ３ ) ２ , and crystalline aluminosilicates containing charge-compensating hydrogen, alkali metal or alkaline earth metal, such as various zeolites.

[0114] 1.2.2. Resin The polymer composition according to the present embodiment may contain a resin. The resin may be thermoplastic or thermosetting. The resin is kneaded together with the rubber component and other optional components added as necessary during production of the polymer composition.

[0115] As for the resin, from the viewpoint of obtaining a crosslinked material (vulcanized rubber) with excellent properties in terms of strength, abrasion resistance, and crack growth resistance, it is preferable to use at least one selected from the group consisting of styrene resins, polyethylene, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene resins, dicyclopentadiene / C9 resins, terpene resins, alkylphenol resins, coumarone indene resins, hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated C5 / C9 resins, hydrogenated dicyclopentadiene resins, hydrogenated dicyclopentadiene / C9 resins, hydrogenated terpene resins, and coumarone indene resins. Of these, thermoplastic resins are preferred, and at least one selected from the group consisting of styrene resins, polyethylene, C5 resins, hydrogenated C5 resins, C9 resins, hydrogenated C9 resins, C5 / C9 resins, hydrogenated C5 / C9 resins, dicyclopentadiene / C9 resins, hydrogenated dicyclopentadiene / C9 resins, coumarone indene resins, terpene resins, and hydrogenated terpene resins is more preferred. The resin may be used alone or in combination of two or more types.

[0116] The resin content is preferably 1 part by mass or more when the total amount of rubber components is 100 parts by mass. By including 1 part by mass or more of resin, it may be possible to improve the abrasion resistance, tensile strength, and crack growth resistance of the crosslinked body obtained using the polymer composition. The resin content is more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more, when the total amount of rubber components is 100 parts by mass. Furthermore, from the viewpoint of maintaining the various properties of the polymer composition well, the resin content is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and particularly preferably 80 parts by mass or less, when the total amount of rubber components is 100 parts by mass.

[0117] 1.2.3. Other Additives The polymer composition according to this embodiment may further contain the following components in addition to the components listed above.

[0118] <Silane Coupling Agent> The polymer composition according to this embodiment may be further enhanced in silica dispersibility by incorporating a silane coupling agent. The silane coupling agent used is not particularly limited. Preferred silane coupling agents include sulfur-containing silane coupling agents such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropylbenzothiazoletetrasulfide, γ-mercaptopropyltriethoxysilane, and 3-octanoylthiopropyltriethoxysilane.

[0119] The content of the silane coupling agent in the polymer composition according to this embodiment is preferably 1 to 20 parts by mass, and more preferably 3 to 15 parts by mass, per 100 parts by mass of silica. When the content of the silane coupling agent is within the above range, an effect of improving the dispersibility of silica is obtained, as well as good processability of the polymer composition and elongation at break of the tire.

[0120] <Expanding Oil> The polymer composition according to this embodiment may contain a process oil, which is commonly used for oil-expanding elastomers, as an oil for oil-expanding (expanding oil). The method of adding the process oil is not particularly limited. For example, the process oil may be added to the conjugated diene polymer solution after polymerization and then desoluble to form an oil-expandable rubber, or the process oil may be added directly to the polymer composition during kneading to obtain a rubber compound (blended rubber).

[0121] Preferred process oils include various oils known in the industry, such as aromatic oils, paraffinic oils, naphthenic oils, vegetable oils, and oils with a low content of polycyclic aromatic compounds (low PCA oils), such as mild extraction solvates (MES), treated distillate aromatic extracts (TDAEs), special residual aromatic extracts (SRAEs) from residual oils, and heavy naphthenic oils. Examples of commercially available MES, TDAEs, and SRAEs include Shell's Catenex SNR (heavy paraffin obtained by dewaxing distillate oil with a solvent) as an MES, H&R Wasag AG's Vivacec 500 as a TDAE, and Japan Energy Corp.'s NC140 as an SRAE. The content ratio of the drawable oil in the polymer composition according to this embodiment is preferably 10 to 100 parts by mass per 100 parts by mass of the rubber component.

[0122] <Wax> The polymer composition according to this embodiment may contain wax from the viewpoint of maintaining the ozone resistance of rubber products. By containing wax in the polymer composition according to this embodiment, a wax bloom forms on the surface of the tire, which can prevent tire deterioration due to ozone over a long period of time.

[0123] Examples of waxes include petroleum-based waxes such as paraffin wax; plant-based waxes such as carnauba wax, jojoba wax, rice bran wax, and candelilla wax; animal-based waxes such as beeswax, lanolin, and whale wax; mineral-based waxes such as ozokerite, ceresin, and petrolactam; hydrogenated natural oils such as hydrogenated castor oil, hydrogenated soybean oil, hydrogenated rapeseed oil, and hydrogenated beef tallow oil; and refined products thereof.

[0124] The wax content in the polymer composition according to this embodiment is preferably in the range of 0.1 to 5 parts by mass, more preferably in the range of 0.5 to 4 parts by mass, and particularly preferably in the range of 0.5 to 3 parts by mass, per 100 parts by mass of rubber component. When the wax content is within the above range, the amount of bloom becomes appropriate, the ozone resistance is improved, and thus deterioration of the rubber product can be prevented.

[0125] <Crosslinking Agent> The polymer composition according to this embodiment may contain a crosslinking agent. By containing a crosslinking agent in the polymer composition according to this embodiment, rubber products with improved strength and abrasion resistance can be obtained. Examples of crosslinking agents include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyhydric amine compounds, and alkylphenol resins having methylol groups. Sulfur is usually used as the crosslinking agent. The content ratio of the crosslinking agent is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the rubber component.

[0126] <Other Components> In addition to the components described above, the polymer composition according to this embodiment may contain various additives commonly used in polymer compositions for obtaining vulcanized rubber, such as stearic acid, zinc oxide (zinc oxide), softeners, vulcanization accelerators, compatibilizers, vulcanization aids, processing aids, antioxidants, and scorch inhibitors. The proportions of these additives can be appropriately selected according to the various components, as long as the effects of this disclosure are not impaired.

[0127] 2. Method for Producing the Polymer Composition The polymer composition according to this embodiment can be obtained by mixing a rubber component and, if necessary, the above-mentioned additives. The manner in which these components are mixed to obtain the polymer composition is not particularly limited. An example of a method for producing the polymer composition according to this embodiment is described below.

[0128] First, in the first stage of mixing, the polymer composition is obtained by mixing the rubber components and additives other than the vulcanization accelerator and crosslinking agent using a mixer, preferably an open-type mixer (e.g., roll mixer) or a closed-type mixer (e.g., Banbury mixer).

[0129] Next, as a second mixing step, the polymer composition obtained above is cooled to room temperature, then a vulcanization accelerator and sulfur are added and mixed to obtain the polymer composition according to this embodiment. After the mixing process, the polymer composition is molded and then crosslinked (vulcanized) to obtain a crosslinked body (i.e., vulcanized rubber). In the polymer composition according to this embodiment, the total content of the rubber component, filler, and optionally added drawstring oil is preferably 80% by mass or more, and more preferably 85% by mass or more, based on the total composition.

[0130] The crosslinked material obtained using the polymer composition according to this embodiment is applicable to various rubber products. Such crosslinked materials can be used in applications such as tires (tire treads, undertreads, carcasses, sidewalls, bead sections, etc.), sealing materials (packings, gaskets, weatherstrips, O-rings, etc.), interior and exterior surface materials for various vehicles such as automobiles, ships, aircraft, and railways, building materials, vibration-damping rubber for industrial machinery and equipment, various hoses and hose covers (diaphragms, rolls, radiator hoses, air hoses, etc.), industrial belts (power transmission belts, etc.), blankets, linings, dust boots, medical equipment materials, fenders, electrical wire insulation materials, and other industrial products.

[0131] The polymer composition according to this embodiment makes it possible to produce rubber products with excellent processability and productivity, as well as improved heat aging resistance. Therefore, the polymer composition according to this embodiment can be suitably used as a material for tires in which one or both of the tread and / or sidewall are formed.

[0132] Tires can be manufactured according to conventional methods. For example, a polymer composition can be mixed in a kneader to form a sheet, which can then be placed in a predetermined position (for example, outside the carcass in the case of a sidewall) according to conventional methods and vulcanized to form a tread or sidewall, thereby obtaining a pneumatic tire.

[0133] 3. Examples The following describes specific examples of the present invention, but the present invention is not limited to these examples. In the following manufacturing examples, examples, and comparative examples, "%" refers to mass unless otherwise specified.

[0134] 3.1. Production of Hydrogenated Conjugated Diene Polymers [Production Example 1: Synthesis of Hydrogenated Conjugated Diene Polymer (A-1)] 25,800 g of cyclohexane, 26 g of tetrahydrofuran and 0.86 g of V-1 as vinyl content adjusters (randomizers), and 430 g of styrene and 3,784 g of 1,3-butadiene were charged into a nitrogen-purged autoclave reactor with an internal volume of 50 liters. After adjusting the temperature of the reactor contents to 42°C, 40 mmol of n-butyllithium was added as a polymerization initiator to start polymerization. After the polymerization conversion rate reached 99%, 86 g of 1,3-butadiene was added (additional butadiene), and polymerization was carried out for a further 3 minutes to obtain a reaction solution containing the polymer. 2.4 mmol of tetrachlorosilane was added to the obtained reaction solution and reacted for 5 minutes, and then 31 mmol of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was added and reacted for 15 minutes. Next, the reaction mixture was heated to over 80°C, hydrogen was introduced into the system, and the reaction was carried out for 1 hour. A small amount of the polymer solution was withdrawn from the reaction vessel to obtain the conjugated diene polymer before hydrogenation for analysis. Then, 12 mmol of bis(η5-cyclopentadienyl)titanium(furfuryloxy)chloride, 31 mmol of diethylaluminum chloride, and 24 mmol of n-butyllithium were added, and the hydrogenation reaction was carried out while maintaining a hydrogen pressure of 1.0 MPa. After the reaction, hydrogen was supplied while maintaining a hydrogen pressure of 0.7 MPa or higher until the predetermined hydrogen cumulative value was reached, and the reaction mixture was returned to room temperature and atmospheric pressure and withdrawn from the reaction vessel to obtain a polymer solution containing the hydrogenated conjugated diene polymer (A-1). A small amount of the obtained polymer solution was withdrawn, desolvated by steam stripping, and dried on a hot roll heated to 130°C to obtain the hydrogenated conjugated diene polymer (A-1). Table 1 shows the polymerization formulation of the hydrogenated conjugated diene polymer (A-1), and Table 2 shows the various physical properties of the hydrogenated conjugated diene polymer (A-1).

[0135] [Production Examples 2-13: Production of Hydrogenated Conjugated Diene Polymers and Their Physical Properties] Polymer solutions containing hydrogenated conjugated diene polymers (A-2) to (A-13) were obtained using the same method as in Production Example 1, except that the polymerization formulation was changed as shown in Table 1 below, and the amount of hydrogen supplied was changed so that the hydrogenation rate of the polymer was the value shown in Table 2 below. Various physical properties of hydrogenated conjugated diene polymers (A-2) to (A-13) are shown in Table 2 below. In Production Example 12, an initiator modifier (compound 4) was added before adding n-butyllithium as a polymerization initiator.

[0136] [Physical Property Evaluation] (1) 1st Peak Weight-Average Molecular Weight For the polymer before hydrogenation, a chart based on the molecular weight in polystyrene equivalent was obtained using a gel permeation chromatograph (GPC, product name: HLC-8020, manufactured by Tosoh Corporation), and the weight-average molecular weight was determined from the retention time of the peak with the longest retention time in the obtained GPC curve. The specific measurement conditions are as follows: (Measurement conditions) Column: Two GMH-HR-H columns (manufactured by Tosoh Corporation) connected in series. Detector: Differential refractometer RI-8020 (manufactured by Tosoh Corporation) Eluent: Tetrahydrofuran column Temperature: 40°C Flow rate: 1.0 mL / min Sample concentration: 10 mg / 20 mL (2) Total Weight-Average Molecular Weight For the polymer before hydrogenation, the total weight-average molecular weight was determined in polystyrene equivalent from all peaks of the GPC curve obtained using a GPC (product name: HLC-8020, manufactured by Tosoh Corporation). The measurement conditions are the same as above. (3) Coupling rate (mass%) For the polymer before hydrogenation, the waveform of molecules in which two or more linear conjugated diene polymer chains are bonded was separated from the GPC curve obtained using GPC (product name: HLC-8020, manufactured by Tosoh Corporation) and calculated from the peak area ratio. (4) Content of polymers with 4 or more branches (mass%) For the polymer before hydrogenation, the waveform of coupling polymers with 4 or more branches was separated from the GPC curve obtained using GPC (product name: HLC-8020, manufactured by Tosoh Corporation) and calculated from the component separation. (5) Bound styrene content (%) For the polymer before hydrogenation, at 400 MHz １ Measured by 1H-NMR spectrometer. (6) Vinyl bond content (mol%) and β-hydrogenation of the polymer before hydrogenation, measured at 400 MHz. １The measurement was performed using an H-NMR apparatus. JIS K6239-1 "Raw rubber - Method for determining the microstructure of solution-polymerized SBR (quantitative determination) - Part 1: １ The vinyl bond content was calculated based on the H-NMR and IR (cast film) methods. (7) For the hydrogenation rate (%) and the polymers before and after α-hydrogenation, deuterated chloroform was used as the solvent and 400 MHz was used. 1 The 1H-NMR spectrum was measured and the hydrogenation rate was calculated. Specifically, JIS K6239-1 "Method for determining the microstructure of solution-polymerized SBR (quantitative determination) - Part 1: １ In accordance with the 1H-NMR and IR (cast film) methods, the peak area (A) in the chemical shift range of 4.3 to 6.1 ppm was divided by the value (B) obtained by correcting the peak area in the chemical shift range of 6.1 to 7.7 ppm with the peak area of ​​deuterated chloroform (0 ppm). This value (C) was calculated for both before and after hydrogenation. Based on the ratio of these values, the hydrogenation rate (%) was determined.

[0137]

[0138] The details of each component in Table 1 above are as follows: <Vinyl content adjuster> ・V-1: Potassium dodecylbenzenesulfonate <Terminal modifier> ・Compound 1: N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane <Coupling agent> ・Compound 2: Tetrachlorosilane ・Compound 3: N,N'-bis(3-triethoxysilylpropyl)terephthaldiimine <Initial modifier> ・Compound 4: Piperidine <Hydrogenation> ・Ti compound: Bis(η5-cyclopentadienyl)titanium(furfuryloxy)chloride ・Al compound: Diethylaluminum chloride ・Li compound: n-butyllithium

[0139]

[0140] 3.2. Production of Polymer Compositions and Crosslinked Products Polymer compositions were produced by mixing the hydrogenated conjugated diene polymers (A-1) to (A-13) produced above with the components according to the formulations shown in Table 3 or Table 4 below, and then kneading the mixture. The kneading was carried out by the following method. Using a Plastmill (capacity: 250 mL) equipped with a temperature control device, the first stage of kneading was performed at a filling rate of 72% and a rotation speed of 60 rpm, mixing emulsion polymerized styrene-butadiene rubber (ESBR1, ESBR2), hydrogenated modified conjugated diene polymers (A-1 to A-13), silica, carbon black, silane coupling agent, spreading oil, stearic acid, zinc oxide, and antioxidant to obtain polymer composition A. In Examples 13 and 14, resin was also included in the formulation. Next, in the second stage of mixing, the obtained polymer composition A was cooled to room temperature, then vulcanization accelerators 1 and 2 and sulfur were added and mixed to obtain polymer composition B. The obtained polymer composition B was molded and vulcanized at 160°C for a predetermined time using a vulcanization press to obtain a crosslinked body (vulcanized rubber).

[0141] 3.3. Evaluation of Physical Properties Processability, productivity, and heat aging resistance were evaluated as follows. The results are shown in Table 3 or Table 4 below.

[0142] (1) Processability The pre-vulcanization rubber (polymer composition B) obtained above was used as a sample for measurement, and the Mooney viscosity was measured in accordance with JIS K6300 using an L rotor under the conditions of preheating for 1 minute, rotor operating time for 4 minutes, and temperature of 100°C. When expressed as an index with Example 2 set to 100, a value of 110 or more was evaluated as "A", a value of 90 or more and less than 110 as "B", a value of 80 or more and less than 90 as "C", and a value of less than 80 as "D". A larger index value indicates lower Mooney viscosity and better processability.

[0143] (2) Productivity The rubber (polymer composition B) obtained above before vulcanization was used as a sample for measurement, and in accordance with JIS K6300-2, the torque was measured by heating it at a temperature of 160°C for 30 minutes using a rotorless vulcanization tester to obtain a vulcanization curve. When the maximum value of the torque is MH and the minimum value is ML, the time required to reach 90% of (MH-ML) was defined as the "90% vulcanization time". When the "90% vulcanization time" of Example 19 was expressed as an index of 100, it was evaluated as "A" if it was 110 or more, "B" if it was 90 or more and less than 110, "C" if it was 80 or more and less than 90, and "D" if it was less than 80. The larger the index value, the shorter the 90% vulcanization time and the better the productivity.

[0144] (3) Heat aging resistance A 2 mm thick rubber sheet was obtained from the vulcanized rubber obtained above, and a test specimen was prepared by punching out the obtained rubber sheet into a dumbbell shape No. 3 as specified in JIS K6251. The tensile strength TB1 of this test specimen was measured in accordance with JIS K6251, at a measurement temperature of 23°C and a tensile speed of 500 mm / min. Next, in accordance with JIS K6257, this test specimen was subjected to a heat aging test using the normal oven method at 100°C for 336 hours. The tensile strength TB2 of the test specimen after this heat aging test was measured under the same conditions as above, and the TB retention rate (%), which is an indicator of heat aging, was calculated using the following formula. A larger value indicates a better TB retention rate. TB retention rate (%) = (TB2 / TB1) × 100 When the TB retention rate of Example 2 is expressed as an index with 100, a value of 110 or more is evaluated as "A", a value of 90 or more but less than 110 is evaluated as "B", a value of 80 or more but less than 90 is evaluated as "C", and a value less than 80 is evaluated as "D". A larger index value indicates a smaller TB retention rate and better heat aging resistance.

[0145]

[0146]

[0147] The details of each component in Tables 3 and 4 above are as follows:・ESBR-1: Manufactured by ENEOS Material, product name "ESBR 1502", emulsion polymerized styrene-butadiene rubber ・ESBR-2: Manufactured by ENEOS Material, product name "ESBR 1723", emulsion polymerized styrene-butadiene rubber, 27.3% oil additive ・Silica: Manufactured by Rhodia, product name "ZEOSIL 1165MP" ・Carbon black: Manufactured by Tokai Carbon, product name "Seast 3" ・Resin 1: Manufactured by ENEOS, product name "T-REZ PR802", C5 / C9 resin ・Resin 2: Manufactured by ENEOS, product name "T-REZ PR803", hydrogenated dicyclopentadiene / C9 resin ・Silane coupling agent: Manufactured by Evonik, product name "Si75" ・Drawing oil: Manufactured by ENEOS, product name "Process Oil T-DAE" • Stearic acid: Manufactured by Kao Chemical Co., Ltd., product name "Lunaq S-98" • Zinc oxide: Manufactured by Seido Chemical Industry Co., Ltd., product name "Zinc Oxide Type 2" • Anti-aging agent: Manufactured by Seiko Chemical Co., Ltd., product name "Ozonone 6C", N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) • Vulcanization accelerator 1: Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noxellar CZ-G", N-cyclohexylbenzothiazole-2-sulfenamide • Vulcanization accelerator 2: Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noxellar D", diphenylguanidine • Sulfur: Manufactured by Tsurumi Chemical Industry Co., Ltd., product name "Precipitated Sulfur"

[0148] 3.4. Evaluation Results From the results in Tables 3 and 4 above, it was found that polymer compositions containing polymer (A) and emulsion polymerized styrene-butadiene rubber (B) in a content ratio of 65 / 35 to 1 / 99 had no D ratings, and the number of evaluation items with a C rating or lower was one or less, indicating that a crosslinked material with an excellent balance of processability, productivity, and heat aging resistance could be obtained. On the other hand, Comparative Example 1, in which the content ratio of polymer (A) to emulsion polymerized styrene-butadiene rubber (B) was 70 / 30, and Comparative Example 3, which did not contain (B) emulsion polymerized styrene-butadiene rubber, had good heat aging resistance, but had difficulties with processability and productivity. Furthermore, Comparative Example 2, which did not contain polymer (A), had poor heat aging resistance.

[0149] The present invention is not limited to the embodiments described above, and various modifications are possible. The present invention encompasses configurations that are substantially identical to those described in the embodiments (for example, configurations with the same function, method, and result, or configurations with the same purpose and effect). The present invention also encompasses configurations in which non-essential parts of the configurations described in the embodiments are replaced with other configurations. Furthermore, the present invention also encompasses configurations that produce the same effects or achieve the same purpose as the configurations described in the embodiments. Furthermore, the present invention also encompasses configurations that add known technology to the configurations described in the embodiments.

Claims

1. A polymer composition containing a rubber component, wherein the rubber component has a composition ratio (molar ratio) of structural units represented by the following formula (1), the following formula (2), the following formula (3), and the following formula (4) in the polymer, where p, q, r, and s are respectively, the value α represented by the following formula (i) is 0.6 or more and less than 1.0, and the weight-average molecular weight (Mw) in polystyrene terms, measured by gel permeation chromatography, is 1.0 × 10⁻⁶. ５ ~2.0 x 10 ６ A polymer composition comprising: a polymer (A) containing 5 to 50% by mass of structural units derived from aromatic vinyl compounds; and an emulsion polymerized styrene-butadiene rubber (B), wherein the ratio (a / b) of the content a of polymer (A) to the content b of emulsion polymerized styrene-butadiene rubber (B) is 65 / 35 to 1 / 99. α = (p + (0.5 × r)) / (p + q + (0.5 × r) + s) (i) 2. The rubber composition according to claim 1, wherein the value β in the polymer (A) represented by the following formula (ii) is 0.2 to 0.

7. β = (p + q) / (p + q + (0.5 × r) + s) (ii) 3. The polymer composition according to claim 1, wherein the polymer (A) has at least one functional group selected from the group consisting of a carboxyl group, a hydrocarbyloxysilyl group, an epoxy group, an amino group, a hydroxyl group, a sulfo group, an iso(thio)cyanate group, a thiol group, and a halogen.

4. The polymer composition according to claim 1, further comprising a filler.

5. The polymer composition according to claim 4, wherein the filler contains one or both of carbon black and silica.

6. The polymer composition according to claim 5, wherein the filler contains silica, and the silica content is 80 parts by mass or more when the total amount of the rubber component is 100 parts by mass.

7. The polymer composition according to claim 5, wherein the filler contains carbon black, and the carbon black content is 10 parts by mass or more when the total amount of the rubber component is 100 parts by mass.

8. The polymer composition according to claim 4, further containing a resin.

9. The polymer composition according to claim 1, wherein the ratio (a / b) of the content a of the polymer (A) to the content b of the emulsion polymerized styrene-butadiene rubber (B) is 65 / 35 to 50 / 50.

10. A crosslinked body obtained by crosslinking a polymer composition according to any one of claims 1 to 9.

11. A tire having one or both of the tread and / or sidewall formed by the polymer composition according to any one of claims 1 to 9.

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