Polymer composition and tire

Abstract

To provide a polymer composition suitable for producing a tire having excellent grip performance in a wide temperature range from a low temperature to a high temperature and maintaining the grip performance.SOLUTION: The polymer composition according to the present invention is a copolymer (A) having a repeating unit derived from an aromatic vinyl compound and a repeating unit derived from a hydrophilic monomer, the copolymer (A) containing 70 to 99% by mass of the repeating unit derived from the aromatic vinyl compound and 1 to 30% by mass of the repeating unit derived from the hydrophilic monomer when the total of the repeating units contained in the copolymer (A) is 100% by mass, the resin composition contains a copolymer (A) having a weight average molecular weight of 500 to 10,000 as measured by gel permeation chromatography, and a copolymer (B) having a repeating unit derived from an aromatic vinyl compound and a repeating unit derived from a conjugated diene compound, and having a weight average molecular weight of 100,000 to 3,000,000 as measured by gel permeation chromatography.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polymer composition and a tire. [Background technology]

[0002] Regarding racing tires, a racing tire tread rubber composition is known that is prepared by compounding 100 parts by mass of diene rubber with a total of 100 to 250 parts by mass of filler containing 20 parts by mass or more of low molecular weight diene rubber and 5 to 50 parts by mass of factice, per 100 parts by mass of diene rubber (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-199546 Summary of the Invention [Problem to be solved by the invention]

[0004] Racing tires and the like are required to have good grip performance from the moment they are fitted, but at the beginning of a race or immediately after a tire change, the tread temperature has not yet risen, and sufficient grip performance tends to be difficult to obtain. On the other hand, rubber compositions intended to improve initial grip performance will have poor wear resistance and shorten the life of the tire.

[0005] Some embodiments of the present invention provide a polymer composition suitable for producing a tire that has excellent grip performance over a wide temperature range from low to high and that maintains this grip performance. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized as any of the following aspects.

[0007] One embodiment of the polymer composition according to the present invention is A copolymer (A) having repeating units derived from an aromatic vinyl compound and repeating units derived from a hydrophilic monomer, wherein, when the total amount of repeating units contained in the copolymer (A) is taken as 100% by mass, the copolymer (A) contains 70 to 99% by mass of repeating units derived from the aromatic vinyl compound and 1 to 30% by mass of repeating units derived from the hydrophilic monomer, and has a weight average molecular weight of 500 to 10,000 as measured by gel permeation chromatography; and A copolymer (B) having a repeating unit derived from an aromatic vinyl compound and a repeating unit derived from a conjugated diene compound, and having a weight average molecular weight measured by gel permeation chromatography of 100,000 to 3,000,000. Contains:

[0008] In one embodiment of the polymer composition, The copolymer (A) may further contain 1 to 15% by mass of repeating units derived from a conjugated diene compound, when the total amount of repeating units contained in the copolymer (A) is taken as 100% by mass.

[0009] In any of the embodiments of the polymer composition, The hydrophilic monomer is selected from the group consisting of a hydroxyl group, a carboxyl group, an amide group, a sulfo group, a polyalkylene group, It may have at least one functional group selected from the group consisting of a lysine group and an amino group.

[0010] In any of the embodiments of the polymer composition, The copolymer (B) may contain 3 to 45 mass % of repeating units derived from an aromatic vinyl compound, when the total amount of repeating units contained in the copolymer (B) is taken as 100 mass %.

[0011] In any of the embodiments of the polymer composition, The copolymer (B) contains a repeating unit derived from 1,3-butadiene, The repeating units derived from 1,3-butadiene may contain 1,2-vinyl groups in an amount of 7 to 70 mol %.

[0012] In any of the embodiments of the polymer composition, The content of the copolymer (A) may be 1 to 100 parts by mass when the content of the copolymer (B) is taken as 100 parts by mass.

[0013] In any of the embodiments of the polymer composition, The composition may further contain at least one resin selected from the group consisting of C5 resin, C9 resin, C5 / C9 resin, dicyclopentadiene resin, rosin resin, terpene resin, and hydrogenated resins thereof, coumarone resin, acrylic resin, polyamide resin, and phenol resin.

[0014] In any of the embodiments of the polymer composition, The total content of the copolymer (A), the copolymer (B), and the optional extender oil (C) may be 90% by mass or more of the total composition.

[0015] One aspect of the tire according to the present invention is A cured product of the polymer composition according to any one of the above embodiments is used in a tread. [Effects of the Invention]

[0016] The polymer composition according to the present invention allows the production of a tire that exhibits good grip performance over a wide temperature range from low to high, and that maintains this grip performance. DETAILED DESCRIPTION OF THE INVENTION

[0017] Preferred embodiments of the present invention will be described in detail below. It should be understood that the present invention is not limited to the embodiments described below, but also includes various modifications that are implemented within the scope of the present invention.

[0018] In this specification, "(meth)acrylic" refers to "acrylic" or "methacrylic", and "(meth)acrylate" refers to "acrylate" or "methacrylate".

[0019] In this specification, a numerical range described using "X to Y" means that the range includes the numerical value X as the lower limit and the numerical value Y as the upper limit.

[0020] In this 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 defined as "-Si(OR 1 ) 3-w (R 2 ) w " or ">Si(OR 1 ) 2-y (R 2 ) y ” (However, 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 A compound having two monovalent groups represented by "(N-substituted methyl group)-3" in one molecule and having a nitrogen-containing group is a "compound having a nitrogen-containing group and two hydrocarbyloxysilyl groups." The expression "having two or more hydrocarbyloxysilyl groups" does not indicate the number of hydrocarbyloxy groups bonded to the silicon atom.

[0021] 1. Polymer composition A polymer composition according to one embodiment of the present invention contains a copolymer (A) and a copolymer (B). Components that can be contained in the polymer composition according to this embodiment will be described below.

[0022] 1.1.Copolymer (A) The polymer composition according to this embodiment contains a copolymer (A) that contains 70 to 99% by mass of repeating units derived from an aromatic vinyl compound and 1 to 30% by mass of repeating units derived from a hydrophilic monomer, and has a weight-average molecular weight measured by gel permeation chromatography of 500 to 10,000. By containing the copolymer (A), the polymer composition according to this embodiment has excellent grip performance over a wide temperature range from low to high temperatures, and the durability of the grip performance is improved.

[0023] The repeating units constituting the copolymer (A), the physical properties of the copolymer (A), and the method for producing the copolymer (A) will be explained below in this order.

[0024] 1.1.1. Repeating units constituting copolymer (A) Copolymer (A) contains 70 to 99 mass% of repeating units (a) derived from an aromatic vinyl compound and 1 to 30 mass% of repeating units (b) derived from a hydrophilic monomer, where the total repeating units contained in copolymer (A) is taken as 100 mass%. In addition to these repeating units, copolymer (A) may also contain repeating units derived from other monomers copolymerizable with these repeating units.

[0025] 1.1.1.1. Repeating units (a) derived from aromatic vinyl compounds Copolymer (A) contains 70 to 99 mass% of repeating units (a) derived from an aromatic vinyl compound, when the total amount of repeating units contained in copolymer (A) is taken as 100 mass%. The content of repeating units (a) derived from an aromatic vinyl compound is preferably 72 to 97 mass%, more preferably 75 to 95 mass%, and particularly preferably 78 to 90 mass%. When copolymer (A) contains repeating units (a) derived from an aromatic vinyl compound within the above range, interaction with carbon black is facilitated, and the carbon black is more uniformly dispersed, which may improve the strength of the resulting crosslinked body and tire.

[0026] The aromatic vinyl compound is not particularly limited, but examples thereof include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, and the like, and one or more selected from these can be used.

[0027] 1.1.1.2. Repeating units derived from hydrophilic monomers (b) Copolymer (A) contains 1 to 30% by mass of repeating units (b) derived from a hydrophilic monomer, when the total amount of repeating units contained in copolymer (A) is taken as 100% by mass. The content of repeating units (b) derived from a hydrophilic monomer is preferably 2 to 28% by mass, more preferably 4 to 25% by mass, and particularly preferably 5 to 23% by mass. When copolymer (A) contains repeating units (b) derived from a hydrophilic monomer within the above range, it tends to interact more easily with the surface of a filler (particularly silica particles), suppressing the aggregation of the filler and enabling the filler to be dispersed uniformly. Therefore, the crosslinked polymer obtained This improves the strength of the tire and provides better grip.

[0028] The hydrophilic monomer preferably has at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amide group, a sulfo group, a polyalkylene glycol group, and an amino group. When the copolymer (A) has such a hydrophilic functional group, it can effectively interact with the surface of a filler (particularly silica particles).

[0029] Specific examples of the repeating unit (b) derived from a hydrophilic monomer include a repeating unit (b1) derived from an unsaturated carboxylic acid ester having a hydroxyl group, a repeating unit (b2) derived from an unsaturated carboxylic acid, a repeating unit (b3) derived from (meth)acrylamide, a repeating unit (b4) derived from a compound having a sulfonic acid group, and a repeating unit (b5) derived from a compound having a polyalkylene glycol group, and it is preferable to contain at least one selected from these.

[0030] <Repeating Unit (b1) Derived from Unsaturated Carboxylic Acid Ester Having a Hydroxyl Group> Among unsaturated carboxylic acid esters having a hydroxyl group, (meth)acrylic acid esters having a hydroxyl group can be preferably used. Specific examples of (meth)acrylic acid esters having a hydroxyl group include, for example, hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, glycerin mono(meth)acrylate, glycerin di(meth)acrylate, etc., and one or more selected from these can be used. Among these, one or more selected from 2-hydroxyethyl (meth)acrylate, glycerin mono(meth)acrylate, and glycerin di(meth)acrylate are preferred, and 2-hydroxyethyl (meth)acrylate is particularly preferred.

[0031] <Repeating Unit (b2) Derived from Unsaturated Carboxylic Acid> The unsaturated carboxylic acid is not particularly limited, but examples thereof include monocarboxylic acids and dicarboxylic acids (including anhydrides) such as (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, etc., and one or more selected from these can be used. As the unsaturated carboxylic acid, it is preferable to use one or more selected from acrylic acid, methacrylic acid, and itaconic acid.

[0032] <Repeating unit (b3) derived from (meth)acrylamide> The (meth)acrylamide is not particularly limited, but examples thereof include (meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N-methylol(meth)acrylamide, diacetone acrylamide, maleic acid amide, and acrylamide tert-butylsulfonic acid, and one or more selected from these can be used.

[0033] <Repeating Unit (b4) Derived from a Compound Having a Sulfonic Acid Group> The compound having a sulfonic acid group is not particularly limited, but examples thereof include compounds such as vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, sulfoethyl (meth)acrylate, sulfopropyl (meth)acrylate, sulfobutyl (meth)acrylate, 2-acrylamido-2-methylpropanesulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid, as well as alkali salts thereof, and one or more selected from these can be used.

[0034] <Repeating Unit (b5) Derived from a Compound Having a Polyalkylene Glycol Group> Examples of compounds having a polyalkylene glycol group include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol-polypropylene glycol mono(meth)acrylate, polyethylene glycol-polybutylene glycol mono(meth)acrylate, polypropylene glycol-polybutylene glycol mono(meth)acrylate, and methoxypolyethylene glycol mono(meth)acrylate, and one or more selected from these can be used.

[0035] 1.1.1.3. Other repeating units The copolymer (A) may contain, in addition to the repeating unit (a) derived from the aromatic vinyl compound and the repeating unit (b) derived from the hydrophilic monomer, a repeating unit derived from another monomer copolymerizable therewith, such as a repeating unit (c) derived from a conjugated diene compound.

[0036] <Repeating unit (c) derived from a conjugated diene compound> The copolymer (A) may contain repeating units (c) derived from a conjugated diene compound. The content of the repeating units (c) derived from a conjugated diene compound is preferably 1 to 15 mass% when the total of the repeating units contained in the copolymer (A) is taken as 100 mass%. The content of the repeating units (c) derived from a conjugated diene compound is more preferably 2 to 12 mass%, and particularly preferably 3 to 10 mass%. By containing the repeating units (c) derived from a conjugated diene compound in the copolymer (A) within the above range, flexibility can be imparted to the copolymer (A), and the processability of the resulting crosslinked product and tire may be improved.

[0037] The conjugated diene compound is not particularly limited, but examples thereof include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, etc., and one or more selected from these can be used. Among these, 1,3-butadiene is particularly preferred.

[0038] 1.1.2. Physical properties of copolymer (A) Glass transition temperature The copolymer (A) preferably has an endothermic peak in the temperature range of -70°C to 70°C when measured by differential scanning calorimetry (DSC) in accordance with JIS K6240:2011. The lower limit of this endothermic peak temperature (hereinafter also referred to as "glass transition temperature (Tg)") is more preferably -68°C, and particularly preferably -65°C. The upper limit of the glass transition temperature (Tg) is more preferably 68°C, and particularly preferably 65°C. When the copolymer (A) has only one endothermic peak in DSC analysis and the peak temperature is within the above range, the interaction between the copolymer (A) and the filler is improved, and re-aggregation of the filler is more easily suppressed, which is preferable.

[0039] 1.1.2.2. Weight average molecular weight The weight-average molecular weight of copolymer (A) measured by gel permeation chromatography is 500 or more and 10,000 or less. The lower limit of the weight-average molecular weight of copolymer (A) is more preferably 800, particularly preferably 1000. The upper limit of the weight-average molecular weight of copolymer (A) is more preferably 9500, particularly preferably 9000. When the weight-average molecular weight of copolymer (A) is within the above range, copolymer (A) is easily dispersed during rubber kneading and exhibits good interaction with the filler surface, which is preferable. The weight-average molecular weight of copolymer (A) can be measured by gel permeation chromatography using the method described in the Examples below.

[0040] 1.1.3. Method for producing copolymer (A) The copolymer (A) can be produced, for example, by a method including a polymerization step and a recovery step.

[0041] <Polymerization process> The method for producing the copolymer (A) is not particularly limited, but can be, for example, an emulsion polymerization method carried out in the presence of a known emulsifier (surfactant), chain transfer agent, polymerization initiator, etc. As the emulsifier (surfactant), chain transfer agent, and polymerization initiator, compounds described in Japanese Patent No. 5999399 and the like can be used.

[0042] The emulsion polymerization method for synthesizing the copolymer (A) may be carried out in a single-stage polymerization or in a multi-stage polymerization such as two or more stages.

[0043] When the copolymer (A) is synthesized by single-stage polymerization, the mixture of the above-mentioned monomers can be emulsion-polymerized in the presence of a suitable emulsifier, chain transfer agent, polymerization initiator, etc., preferably at 40 to 80°C, preferably for 4 to 36 hours.

[0044] When the copolymer (A) is synthesized by two-stage polymerization, it is preferable to set the polymerization in each stage as follows.

[0045] The proportion of the monomers used in the first-stage polymerization is preferably 20 to 99% by mass, more preferably 25 to 98% by mass, based on the total mass of the monomers (the sum of the mass of the monomers used in the first-stage polymerization and the mass of the monomers used in the second-stage polymerization). By carrying out the first-stage polymerization at such a proportion of the monomers, a copolymer (A) having excellent dispersion stability and being less likely to form aggregates can be obtained, and an increase in the viscosity of the polymer composition over time is also suppressed, which is preferable.

[0046] The types and proportions of monomers used in the second-stage polymerization may be the same as or different from the types and proportions of monomers used in the first-stage polymerization.

[0047] The polymerization conditions in each stage are preferably as follows in order to improve the dispersibility of the resulting copolymer (A). First-stage polymerization: preferably at a temperature of 40 to 80°C; preferably for a polymerization time of 2 to 36 hours; preferably at a polymerization conversion rate of 50% by mass or more, more preferably 60% by mass or more. Second-stage polymerization; preferably at a temperature of 40 to 80°C; preferably for a polymerization time of 2 to 18 hours.

[0048] By controlling the total solids concentration in the emulsion polymerization to 50% by mass or less, the polymerization reaction can proceed in a state in which the dispersion stability of the resulting copolymer (A) is good. This total solids concentration is preferably 48% by mass or less, and more preferably 45% by mass or less.

[0049] Whether the copolymer (A) is synthesized as a single-stage polymerization or a two-stage polymerization, a neutralizing agent may be added to the polymerization mixture after the emulsion polymerization is completed. The pH is preferably adjusted to about 2.5 to 10.5, preferably 3.5 to 10.0, and more preferably 5.0 to 9.5. The neutralizing agent used here is not particularly limited, but examples include metal hydroxides such as sodium hydroxide and potassium hydroxide; ammonia, etc. Setting the pH within the above range improves the stability of the copolymer (A). By concentrating the polymerization mixture after the neutralization treatment, the solids concentration can be increased while maintaining the good stability of the copolymer (A).

[0050] <Recovery process> The copolymer (A) dispersion obtained by the above polymerization step is subjected to steam stripping as necessary to remove residual monomers, and then a coagulant is added, and the solids (crumbs) generated by coagulation, etc. are subjected to drying procedures such as dehydration and heat treatment, etc. This allows the copolymer (A) to be recovered from the copolymer (A) dispersion obtained by the above polymerization step.

[0051] As the copolymer (A) dispersion, an aqueous dispersion of copolymer (A) obtained by emulsion polymerization may be used as is, or a dispersion obtained by emulsion polymerization to which a rubber extender oil has been added to disperse the copolymer (A) dispersion as an oil-extended rubber may be used. Examples of the rubber extender oil that can be used include naphthenic, paraffinic, and aromatic process oils. The amount of rubber extender oil used to prepare the oil-extended rubber is preferably 5 to 100 parts by mass, more preferably 10 to 60 parts by mass, per 100 parts by mass of the polymer contained in the copolymer (A) dispersion. The copolymer (A) dispersion may further contain various additives such as antioxidants.

[0052] The coagulant can be appropriately selected depending on the ionic functional group. Examples of coagulants include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, carbonic acid, and phosphoric acid; organic acids such as formic acid and acetic acid; hydroxides such as potassium hydroxide, sodium hydroxide, and calcium hydroxide; monovalent to trivalent metal salts such as sodium chloride, calcium chloride, and magnesium sulfate; and organic acid salts such as cyclohexylamine acetate. Among these coagulants, monovalent to trivalent metal salts are preferred, with sodium chloride and calcium chloride being more preferred. The amount of coagulant used is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, per 100 parts by mass of the polymer contained in the aqueous dispersion of copolymer (A).

[0053] 1.1.4. Content of copolymer (A) The content of polymer (A) in the polymer composition according to this embodiment is preferably 1 to 100 parts by mass relative to 100 parts by mass of copolymer (B), which will be described later. The content of copolymer (A) is more preferably 5 to 95 parts by mass, and particularly preferably 10 to 90 parts by mass. When the content of copolymer (A) is within the above range, the dispersibility of the filler is improved and compatibility with copolymer (B) is also good, which is preferable.

[0054] 1.2.Copolymer (B) 1.2.1. Characteristics of copolymer (B) The polymer composition according to the present embodiment contains a copolymer (B) having a repeating unit derived from an aromatic vinyl compound and a repeating unit derived from a conjugated diene compound, and having a weight average molecular weight of 100,000 to 3,000,000 as measured by gel permeation chromatography.

[0055] Copolymer (B) preferably contains 3 to 45 mass% of repeating units derived from an aromatic vinyl compound, when the total repeating units contained in copolymer (B) is taken as 100 mass%. The content of repeating units derived from an aromatic vinyl compound is more preferably 5 to 43 mass%, even more preferably 8 to 41 mass%, and particularly preferably 10 to 40 mass%. When copolymer (B) contains repeating units derived from an aromatic vinyl compound within the above range, interaction with carbon black is facilitated, and the carbon black is more uniformly dispersed, which may improve the strength of the resulting crosslinked body or tire.

[0056] The aromatic vinyl compound is not particularly limited, but examples thereof include the aromatic vinyl compounds described below, and one or more selected from these compounds can be used.

[0057] Specific examples of such copolymers (B) include emulsion polymerized styrene butadiene rubber (ESBR), solution polymerized styrene butadiene rubber (SSBR), and hydrogenated styrene butadiene rubber. These copolymers (B) may be used alone or in combination of two or more. The copolymers (B) may be unmodified or modified.

[0058] In this specification, the term "modification" refers to providing a partial structure containing a heteroatom such as nitrogen, oxygen, sulfur, or silicon to a conjugated diene polymer consisting of repeating units derived from hydrocarbons (i.e., an unmodified conjugated diene polymer).

[0059] The polymer composition according to the present embodiment contains the copolymer (B), which can enhance the dispersibility of the filler (particularly silica) in the polymer composition. In order to further enhance the dispersibility of the filler in the polymer composition, the copolymer (B) preferably contains at least one element (hereinafter also referred to as "specific element") selected from the group consisting of nitrogen, silicon, sulfur, oxygen, phosphorus, and tin.

[0060] In terms of ease of introducing the specific element into the polymer, copolymer (B) preferably has a partial structure derived from a compound having the specific element (hereinafter also referred to as "compound (M)"). Compound (M) may be a compound capable of introducing a functional group having the specific element into the polymerization initiation terminal (hereinafter also referred to as "initiation terminal modifier"), or may be a compound capable of introducing a functional group having the specific element into the polymerization termination terminal (hereinafter also referred to as "terminal modifier"). Compound (M) may also be a monomer capable of introducing a functional group having the specific element into a side chain of the molecular chain (hereinafter also referred to as "modifying monomer"). In terms of a high effect of improving the dispersibility of the filler, compound (M) preferably contains at least one selected from the group consisting of initiation terminal modifiers and terminal modifiers, and more preferably contains a terminal modifier.

[0061] 1.2.2. Method for producing copolymer (B) As the copolymer (B) contained in the polymer composition according to this embodiment, for example, a polymer produced by a method including the following polymerization step and modification step can be preferably used. Polymerization step: A step of polymerizing a monomer containing a conjugated diene compound and an aromatic vinyl compound in the presence of a polymerization initiator to obtain a conjugated diene polymer having an active terminal. Modification step: A step of reacting a conjugated diene polymer having an active end with a compound (M) to obtain a copolymer (B).

[0062] A preferred production method for obtaining the copolymer (B) will be described below, along with a preferred embodiment of the molecular structure of the copolymer (B).

[0063] <Polymerization process> (Conjugated diene compounds) Examples of conjugated diene compounds include 1,3-butadiene, 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. The conjugated diene compound is preferably one or more of 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene, with 1,3-butadiene being particularly preferred due to its high effect of improving processability and reducing hysteresis loss in a well-balanced manner. The conjugated diene compounds may be used alone or in combination of two or more.

[0064] Examples of aromatic vinyl compounds include styrene, 2-methylstyrene, and 3-methylstyrene. Examples of the aromatic vinyl compound include styrene, 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). Of these, styrene or α-methylstyrene is preferred as the aromatic vinyl compound.

[0065] The conjugated diene polymer obtained in the polymerization step is preferably a copolymer having repeating units derived from 1,3-butadiene and repeating units derived from styrene, because it has high living properties in anionic polymerization. The conjugated diene polymer is preferably a random copolymer of a conjugated diene compound and an aromatic vinyl compound. The random copolymer may further have a block portion made of a conjugated diene compound or another aromatic vinyl compound.

[0066] The proportion of the aromatic vinyl compound used is preferably 3 to 45 mass %, more preferably 5 to 43 mass %, based on the total amount of monomers used in polymerization, from the viewpoint of achieving a good balance between low hysteresis loss properties (low fuel consumption performance) and wet skid resistance of the resulting crosslinked product, and also good abrasion resistance. The content of repeating units derived from the aromatic vinyl compound in the polymer is 1 This is a value measured by H-NMR.

[0067] In the polymerization, 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. When other monomers are used, the proportion of the other monomers used is preferably 5% by mass or less, and more preferably 3% by mass or less, based on the total amount of monomers used in the polymerization.

[0068] Solution polymerization is particularly preferred as a polymerization method for polymerizing a monomer containing a conjugated diene compound. The polymerization method may be either batchwise or continuous. When using solution polymerization, a specific example of the polymerization method is a method in which a monomer is polymerized in an organic solvent in the presence of a polymerization initiator and, if necessary, a vinyl group content adjuster (randomizer). From the viewpoints of improving the processability of the polymer composition, increasing the dispersibility of the filler (particularly silica), obtaining a high-strength crosslinked product, and polymer productivity, a continuous method (specifically, a method in which raw materials are continuously fed into a reactor and a product is continuously withdrawn from the reactor) is preferred.

[0069] As the polymerization initiator, at least one selected from the group consisting of alkali metal compounds and alkaline earth metal compounds can be preferably used. Specific examples thereof include alkyllithium, 1,4-dilithiobutane, phenyllithium, stilbenelithium, naphthyllithium, 1,3-bis(1-lithio-1,3-dimethylpentyl)benzene, 1,3-phenylenebis(3-methyl-1-phenylpentylidene)dilithium, naphthylsodium, naphthylpotassium, di-n-butylmagnesium, di-n-hexylmagnesium, ethoxypotassium, calcium stearate, etc. Specific examples of alkyllithium include methyllithium, ethyllithium, n-propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, etc. Polymerization The initiator is preferably a lithium compound. The proportion of polymerization initiator used in polymerization (the total amount when two or more types are used) is preferably 0.2 to 20 mmol per 100 g of monomer used in polymerization.

[0070] The polymerization reaction may also be carried out in the presence of a compound (hereinafter also referred to as a "metal amide compound") obtained by mixing at least one selected from the group consisting of alkali metal compounds and alkaline earth metal compounds with an initiation terminal modifier. By polymerizing a monomer in the presence of a metal amide compound, a specific element derived from the initiation terminal modifier can be introduced into the polymerization initiation terminal of the conjugated diene polymer.

[0071] As the initiation terminal modifying agent, nitrogen-containing compounds such as secondary amine compounds can be preferably used. Specific examples of the initiation terminal modifying agent include linear amines such as dimethylamine, diethylamine, dipropylamine, dibutylamine, dodecamethyleneimine, N,N'-dimethyl-N'-trimethylsilyl-1,6-diaminohexane, di-(2-ethylhexyl)amine, and diallylamine; and cyclic amines such as piperidine, pyrrolidine, hexamethyleneimine, heptamethyleneimine, dicyclohexylamine, N-methylbenzylamine, morpholine, N-(trimethylsilyl)piperazine, N-(tert-butyldimethylsilyl)piperazine, and 1,3-ditrimethylsilyl-1,3,5-triazinane.

[0072] When polymerizing a monomer in the presence of a compound obtained by mixing an alkali metal compound or alkaline earth metal compound with an initiating end-modifier, at least one of the alkali metal compound and alkaline earth metal compound and the initiating end-modifier may be mixed in advance, and the mixture may be added to the polymerization system to carry out polymerization. Alternatively, at least one of the alkali metal compound and alkaline earth metal compound and the initiating end-modifier may be added to the polymerization system separately or simultaneously, and the two may be mixed in the polymerization system to carry out polymerization. Both of these cases are included in the embodiment of "polymerizing a monomer in the presence of a compound obtained by mixing at least one selected from the group consisting of alkali metal compounds and alkaline earth metal compounds with an initiating end-modifier."

[0073] The amount of initiating end-modifier used is appropriately determined depending on the type of alkali metal compound or alkaline earth metal compound. For example, when metallic lithium is used, from the viewpoint of improving the processability of the polymer composition and the fuel economy performance of the resulting tire in a well-balanced manner, the amount of initiating end-modifier used is preferably in the range of 0.1 to 1.8 mol, more preferably in the range of 0.2 to 1.0 mol, per mol of metallic lithium used in the polymerization. The initiating end-modifier may be used alone or in combination of two or more.

[0074] In addition, in the polymerization reaction, a nitrogen-containing alkali metal compound (hereinafter also referred to as "nitrogen-containing alkali metal compound") can be used as a polymerization initiator. Examples of the nitrogen-containing alkali metal compound include compounds represented by formula (2) described in WO 2020 / 179705.

[0075] An example of the nitrogen-containing alkali metal compound is ((2E,6E)-11-(dimethylamino)-3,7-dimethylundeca-2,6-dien-1-yl)lithium.

[0076] It is to be noted that a partial structure derived from a nitrogen-containing compound can be introduced into the polymerization initiation terminal by either a method of polymerizing a monomer in the presence of a compound obtained by mixing an alkali metal compound or alkaline earth metal compound with an initiation terminal modifier, or a method of polymerizing a monomer in the presence of a nitrogen-containing alkali metal compound.

[0077] Vinyl group content adjusters (randomizers) are used for the purpose of adjusting the vinyl group content, which represents the content of vinyl bonds in a polymer. Examples of randomizers include dimethoxybenzene, tetrahydrofuran, 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 randomizers can be used alone or in combination of two or more.

[0078] The organic solvent used in the polymerization may be any organic solvent that is inert to the reaction. Examples of such organic solvents include linear or cyclic aliphatic hydrocarbons and aromatic hydrocarbons. The organic solvent used in the polymerization is preferably a hydrocarbon having 3 to 8 carbon atoms, and specific examples thereof include propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis-2-butene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene, heptane, cyclopentane, methylcyclopentane, methylcyclohexane, 1-pentene, 2-pentene, and cyclohexene. These organic solvents may be used alone or in combination of two or more.

[0079] When solution polymerization is performed, the monomer concentration in the reaction solvent is preferably 5 to 50% by mass, 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, more preferably 0°C to 120°C. The polymerization reaction is preferably carried out under a pressure sufficient to maintain the monomers substantially in a liquid phase. Such a polymerization reaction can produce a conjugated diene polymer having an active end (more specifically, an alkali metal active end or an alkaline earth metal active end). In this specification, the term "active end" refers to a portion (more specifically, a metal end) present at the end of the molecular chain other than the structure derived from the monomer having a carbon-carbon double bond.

[0080] <Denaturation process> In the modification step, a conjugated diene polymer having an active end is reacted with a compound (M). This reaction causes a polymer chain containing a repeating unit derived from the conjugated diene compound to bond with the compound (M) at the reaction site of the compound (M), thereby producing a modified conjugated diene polymer having a specific element at the polymer end. The conjugated diene polymer having an active end may be either modified or unmodified at the polymerization initiation end.

[0081] As the compound (M), a compound having a specific element and a functional group capable of reacting with the active terminal of the conjugated diene polymer can be preferably used. By using such a compound, an element that contributes greatly to improving the dispersibility of the filler (particularly silica) can be relatively easily introduced into the polymer. The specific element contained in the compound (M) is preferably at least one selected from the group consisting of nitrogen, oxygen, silicon, sulfur, and phosphorus.

[0082] In order to further improve the dispersibility of the filler (particularly silica) in the polymer composition, it is preferable to use a compound having one or more nitrogen-containing groups and one or more hydrocarbyloxysilyl groups in one molecule as the compound (M).In order to highly contribute to improving the dispersibility of the filler (particularly silica), it is preferable that the nitrogen-containing group is one or more selected from the group consisting of a protected primary amino group, a protected secondary amino group, a tertiary amino group, an imino group, and an imidazolyl group.

[0083] Specific examples of the compound (M) include compounds of the formula ( Compounds represented by formulas (6) to (9) can be preferably used.

[0084] Specific examples of the terminal modifying agent include N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltriethoxysilane, and 3-(4-trimethylsilyl-1-piperazino)propylmethyldimethoxysilane.

[0085] Other specific examples of the terminal modifying agent include 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, 1-triethylsilyl-2,2-diethoxy-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane, 2-(2,2-dimethoxy-1,2-azasilolidin-1-yl)-N,N-diethylethan-1-amine, tris(2-triethoxysilylethyl)amine, tris(3-triethoxysilylpropyl)amine, and tris(5-triethoxysilylpentyl)amine. , N,N,N',N'-tetra(2-triethoxysilylethyl)-1,2-diaminoethane, N,N,N',N'-tetra(3-triethoxysilylpropyl)-1,3-diaminopropane, N-(3-(1H-imidazol-1-yl)propyl)-3-(trimethoxysilyl)-N-(3-(trimethoxysilyl)propyl)propan-1-amine, N-(3-(1H-imidazol-1-yl)propyl)-N,N-bis(3-(trimethoxysilyl)propyl)propanamine, and compounds in which the alkyl group and alkanediyl group in these compounds are replaced with an alkyl group having 1 to 6 carbon atoms and an alkanediyl group having 1 to 6 carbon atoms, respectively. For example, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane is a compound having one nitrogen-containing group and two hydroxycarbyloxysilyl groups.

[0086] Other specific examples of the terminal-modifying agent include compounds represented by the following formulas (m-1-1) to (m-1-8), and compounds in which the alkyl group and alkanediyl group in the compounds are replaced with alkyl groups having 1 to 6 carbon atoms and alkanediyl groups having 1 to 6 carbon atoms, respectively. [ka]

[0087] As the compound (M), one of these may be used alone, or two or more may be used in combination.

[0088] The reaction between the polymerization active terminal and the terminal modifier is preferably carried out as a solution reaction. This solution reaction may be carried out using a solution containing unreacted monomers after the completion of the polymerization reaction, or may be carried out using a solution obtained by isolating the conjugated diene polymer having polymerization active terminals contained in the solution and dissolving it in a suitable solvent such as cyclohexane. The reaction may be carried out either batchwise or continuously. The method for adding the terminal modifier is not particularly limited, and examples thereof include a method of adding it all at once, a method of adding it in portions, and a method of adding it continuously.

[0089] The amount of terminal modifier used in the above reaction may be appropriately determined depending on the type of compound used in the reaction. The amount of terminal modifier used is preferably 0.1 mol equivalent or more, more preferably 0.3 mol equivalent or more, relative to the metal atoms of the polymerization initiator involved in the polymerization reaction. By using an amount of terminal modifier of 0.1 mol equivalent or more in the above reaction, the modification reaction can be sufficiently promoted, and the dispersibility of the filler can be suitably improved. Furthermore, the amount of terminal modifier used is preferably 1.5 mol equivalent or less, more preferably 1.2 mol equivalent or less, relative to the metal atoms of the polymerization initiator involved in the polymerization reaction.

[0090] The reaction temperature is usually the same as the polymerization reaction temperature, preferably -20°C to 150°C, and more preferably 0°C to 120°C. If the reaction temperature is too low, the viscosity of the modified conjugated diene polymer tends to increase. On the other hand, if the reaction temperature is too high, the polymerization active terminals are likely to be deactivated. The reaction time is preferably 1 minute to 5 hours, more preferably 2 minutes to 1 hour.

[0091] When producing the copolymer (B), a treatment of reacting the polymerization active terminals with a coupling agent may be carried out for the purpose of increasing the Mooney viscosity and cold flow characteristics of the polymer. Examples of the coupling agent include compounds that contain a specific element, do not contain active hydrogen, and have multiple functional groups that can react with the polymerization active terminals. Specific examples of the coupling agent include 2,4-tolylene diisocyanate, diphenylmethane diisocyanate, N,N, Examples of the coupling agent include N',N'-tetramethylphthalamide, silicon tetrachloride, N,N,N',N'-tetramethyl-4,4'-diaminobenzophenone, tin tetrachloride, etc. The reaction using a coupling agent may be carried out before or after the reaction between the polymerization active terminal and the terminal modifier, or may be carried out simultaneously with the reaction between the polymerization active terminal and the terminal modifier.

[0092] When a compound having a protecting group (such as a trisubstituted hydrocarbylsilyl group) is used as the terminal modifier, some or all of the protecting groups may be substituted with hydrogen in a modified conjugated diene polymer having protecting groups derived from the terminal modifier. Furthermore, when a compound having a protecting group is used as the terminal modifier, the conjugated diene polymer modified with the terminal modifier may be further reacted with an onium salt generating agent. In this case, a copolymer (B) having an onium salt structure at the polymer terminal can be obtained. Having an onium salt structure in the copolymer (B) is preferable in that it can improve the shape retention of a crosslinked body obtained using the polymer composition.

[0093] 1.2.3. Physical properties of copolymer (B) 1.2.3.1. Vinyl group content The copolymer (B) contains a structural unit derived from 1,3-butadiene as a conjugated diene compound, and the 1,2-vinyl group content (hereinafter also referred to as "vinyl group content") in the structural unit derived from 1,3-butadiene is preferably 7 to 70 mol%. The lower limit of the vinyl group content is preferably 10 mol%, more preferably 15 mol%. When the vinyl group content is 7 mol% or more, good grip performance tends to be ensured. Furthermore, the upper limit of the vinyl group content is preferably 60 mol%, more preferably 50 mol%. When the vinyl group content is 70 mol% or less, good fuel economy performance tends to be ensured. In this specification, the "vinyl group content" is a value indicating the content ratio of repeating units having 1,2-bonds to all repeating units of butadiene in the conjugated diene polymer, 1 This is a value measured by H-NMR.

[0094] 1.2.3.2. Weight average molecular weight The weight-average molecular weight of copolymer (B) measured by gel permeation chromatography is 100,000 or more and 3,000,000 or less. The lower limit of the weight-average molecular weight of copolymer (B) is preferably 120,000, more preferably 150,000. When the weight-average molecular weight of copolymer (B) is 100,000 or more, the shape stability, tensile strength, and abrasion resistance of the crosslinked product tend to be sufficiently high. The upper limit of the weight-average molecular weight of copolymer (B) is preferably 2,500,000, more preferably 2,000,000. When the weight-average molecular weight of copolymer (B) is 3,000,000 or less, the processability of the polymer composition tends to be improved. The weight-average molecular weight of copolymer (B) can be measured by gel permeation chromatography using the method described in the Examples below.

[0095] 1.2.3.3.Molecular weight distribution (Mw / Mn) The molecular weight distribution (Mw / Mn) of copolymer (B), expressed as the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) measured by gel permeation chromatography, is preferably 1.0 to 10.0. When Mw / Mn is 1.0 or more, good processability can be maintained during the production of a crosslinked product, and good filler dispersibility, rolling resistance (fuel economy), and tensile properties tend to be achieved. The Mw / Mn of copolymer (B) is more preferably 1.1 or more, even more preferably 1.2 or more, and particularly preferably 1.6 or more. When Mw / Mn of copolymer (B) is 10.0 or less, good tire fuel economy and good filler dispersibility tend to be achieved. The Mw / Mn of copolymer (B) is more preferably 3.0 or less, even more preferably 2.7 or less, even more preferably 2.5 or less, and particularly preferably 2.3 or less.

[0096] Glass transition temperature The glass transition temperature (Tg) of the copolymer (B) is preferably -100°C to 0°C. When the Tg of the copolymer (B) is -100°C or higher, the abrasion resistance and strength of the crosslinked body tend to be improved. When the Tg of the copolymer (B) is 0°C or lower, the fuel economy of the tire tends to be improved. The Tg of the copolymer (B) is more preferably -90°C or higher, and particularly preferably -80°C or higher. The Tg of the copolymer (B) is more preferably -10°C or lower, even more preferably -20°C or lower, even more preferably -30°C or lower, and particularly preferably -40°C or lower. The glass transition temperature of the copolymer (B) is a value measured in accordance with JIS K6240:2011.

[0097] 1.2.4. Content of copolymer (A) The content of copolymer (A) in the polymer composition according to the present embodiment is preferably 10 to 80% by mass, more preferably 15 to 70% by mass, and particularly preferably 20 to 60% by mass. When the content of copolymer (A) is within the above range, the dispersibility of the filler (particularly silica) can be more easily improved, and a high-strength crosslinked product can be obtained.

[0098] 1.3.Other Ingredients The polymer composition according to this embodiment may further contain the following components in addition to the above components.

[0099] 1.3.1.Extender oil (C) The polymer composition according to this embodiment may contain an extender oil (C) as an optional component. When the polymer composition according to this embodiment contains the extender oil (C), the content of the extender oil (C) is preferably 0 to 100 parts by mass per 100 parts by mass of the copolymer (B), from the viewpoint of improving processability while suppressing a decrease in rolling resistance and strength. The lower limit of the content of the extender oil (C) is more preferably 0.05 parts by mass, even more preferably 0.1 parts by mass, and particularly preferably 0.2 parts by mass per 100 parts by mass of the copolymer (B). The upper limit of the content of the extender oil (C) is more preferably 95 parts by mass, particularly preferably 90 parts by mass per 100 parts by mass of the copolymer (B).

[0100] In one embodiment of the polymer composition according to this embodiment containing the extender oil (C), the total amount of the copolymer (A), the copolymer (B), and the extender oil (C) is 90% by mass or more of the total polymer composition (hereinafter also referred to as "polymer composition Q"). The total amount of the copolymer (A), the copolymer (B), and the extender oil (C) in polymer composition Q is more preferably 93% by mass or more, and particularly preferably 95% by mass or more of the total polymer composition.

[0101] The polymer composition Q is preferably a solid from which the solvent has been removed. The polymer composition Q may be, for example, solid particles (crumbs), or may be a rubber bale obtained by compression-molding the crumbs into a desired shape (for example, a rectangular parallelepiped shape).

[0102] The extender oil (C) may be a process oil commonly used for extending elastomers. Suitable process oils include various oils known in the art, such as aromatic oils, paraffinic oils, naphthenic oils, vegetable oils (soybean oil, sunflower oil, etc.), and oils with a low content of polycyclic aromatic compounds (low PCA oils), such as mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), special residual aromatic extracts (SRAE), and heavy naphthenic oils. Examples of commercially available MES, TDAE, and SRAE include Shell's Catenex SNR (heavy paraffin obtained by solvent dewaxing distillate oil) as an MES. Examples of TDAE include Vivatec 500 manufactured by H&R Wasag AG, and examples of SRAE include NC140 manufactured by Japan Energy Corp.

[0103] The polymer composition Q is preferably produced by a method including the following mixing step and solvent removal step. Mixing step: A step of mixing a dispersion of copolymer (A) with a solution of copolymer (B) to obtain a mixed solution (hereinafter also referred to as "mixed solution SC"). Desolvation step: A step of removing the solvent from the mixed solution SC. Each step will be described in detail below.

[0104] <Mixing process> From the viewpoint of enhancing the dispersibility of the copolymer (A) in the polymer composition and sufficiently improving fuel economy and strength, it is preferable that in the mixing step, a copolymer (A) dispersion in which the copolymer (A) is dispersed in water is mixed with a copolymer (B) solution in which the copolymer (B) is dissolved in an organic solvent to obtain a mixed solution SC.

[0105] Examples of the organic solvent constituting the copolymer (B) solution include the organic solvents exemplified as solvents that can be used in the polymerization of monomers in the production of copolymer (B). As such an organic solvent, at least one selected from the group consisting of chain aliphatic hydrocarbons, cyclic aliphatic hydrocarbons, and aromatic hydrocarbons can be preferably used.

[0106] As the copolymer (A) dispersion, it is preferable to use the polymer particle dispersion obtained during the production of copolymer (A) as it is. The content of copolymer (A) in the copolymer (A) dispersion is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more, based on the total mass of the copolymer (A) dispersion. Furthermore, the content of copolymer (A) in the copolymer (A) dispersion is preferably 60% by mass or less, more preferably 50% by mass or less, and particularly preferably 45% by mass or less.

[0107] As the copolymer (B) solution, a polymer solution obtained during the production of copolymer (B) (preferably a polymer solution obtained by solution polymerization) may be used as is. Alternatively, the copolymer (B) solution may be a solution prepared by dissolving isolated solid copolymer (B) in an appropriate solvent. By using a polymer solution containing copolymer (B), the dispersibility of the filler (particularly silica) when the polymer composition Q is mixed with the filler can be further improved. Furthermore, it is preferable to use the reaction solution containing copolymer (B) obtained by the above-mentioned modification step as the polymer solution as is, in terms of reducing the number of steps and increasing productivity. Note that the details of the polymerization step and the modification step are the same as those described above.

[0108] The content of copolymer (B) in the copolymer (B) solution is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more, based on the total mass of the copolymer (B) solution. The content of copolymer (B) in the copolymer (B) solution is preferably 70% by mass or less, more preferably 50% by mass or less, and particularly preferably 30% by mass or less. By keeping the content of copolymer (B) in the copolymer (B) solution within the above range, a sufficient amount of polymer composition can be produced.

[0109] The method for mixing the copolymer (A) dispersion and the copolymer (B) solution is not particularly limited. For example, when the copolymer (A) dispersion is added to the copolymer (B) solution, the copolymer (A) dispersion may be added to the copolymer (B) solution all at once, in portions, or continuously. When the copolymer (B) solution is added to the copolymer (A) dispersion, the copolymer (B) solution may be added to the copolymer (A) dispersion all at once, in portions, or continuously.

[0110] After adding the copolymer (A) dispersion to the copolymer (B) solution, it is advisable to carry out a treatment such as stirring to uniformly disperse the copolymer (A) in the copolymer (B) solution. The temperature when mixing the copolymer (B) solution and the copolymer (A) is the same as the temperature of the polymerization reaction, preferably 10°C to 100°C, more preferably 15°C to 90°C, further preferably 20°C to 85°C, and particularly preferably 25°C to 80°C.

[0111] When obtaining the mixed solution SC, it is preferable to add a coagulant to coagulate the copolymer (A). A dispersion of the copolymer (A) and a solution of the copolymer (B) may be mixed to obtain the mixed solution SC, and then a coagulant may be added to precipitate the copolymer (A). Alternatively, a coagulant may be added to the dispersion of the copolymer (A) in advance, and the copolymer (A) may be precipitated, followed by the addition of the copolymer (B) solution to obtain the mixed solution SC. The coagulant may be the same as that described in the section "Recovery Step" in "1.1.3. Method for Producing the Copolymer (A)" above.

[0112] When adding the extender oil (C) to the polymer composition Q according to this embodiment, the method for adding the extender oil (C) is not particularly limited. For example, the extender oil (C) may be added to a polymer solution containing the copolymer (B) after polymerization, and then removed in a subsequent solvent removal step to form an oil-extended rubber. In this case, the extender oil (C) may be added before the copolymer (A) is added to the polymer solution, or the extender oil (C) may be added after the copolymer (A) is added to the polymer solution.

[0113] In the polymer composition according to the present embodiment, when the polymer (A) dispersion and the copolymer (B) solution are mixed, the copolymer (A) content in the copolymer (A) dispersion is preferably 1 to 50 parts by mass per 100 parts by mass of the copolymer (B) in the copolymer (B) solution. By controlling the content of copolymer (A) within the above range, the strength, grip performance, fuel economy, and processability of the crosslinked body obtained from the polymer composition can be improved in a well-balanced manner. From this viewpoint, the upper limit of the content of copolymer (A) is preferably 2 parts by mass, more preferably 5 parts by mass, and particularly preferably 10 parts by mass per 100 parts by mass of copolymer (B). The lower limit of the content of copolymer (A) is preferably 45 parts by mass, more preferably 40 parts by mass, and particularly preferably 30 parts by mass per 100 parts by mass of copolymer (B).

[0114] <Solvent removal process> In the desolvation step, the solvent is removed from the mixed liquid SC obtained in the mixing step to isolate the polymer composition Q. The method for removing the solvent from the mixed liquid SC is not particularly limited. For example, the solvent can be removed from the mixed liquid SC by known desolvation methods, such as a method of separating the solvent by steam stripping and then dehydrating and drying the resulting polymer composition Q, a method of devolatilizing using a twin-screw extruder, or a method of directly devolatilizing using a drum dryer, etc.

[0115] According to the production method including the above-described mixing step and solvent removal step, it is possible to obtain a solid polymer composition Q from which the solvent has been removed. The obtained polymer composition Q is a crumb or rubber bale containing copolymer (A) and copolymer (B).

[0116] Resin The polymer composition according to the present embodiment may contain a resin such as a thermoplastic resin or a thermosetting resin. The resin is kneaded together with the copolymer (A), the copolymer (B), and other components added as needed during the production of the polymer composition.

[0117] As for resins, from the viewpoint of obtaining a crosslinked body (vulcanized rubber) with excellent properties such as strength, abrasion resistance, and crack growth resistance, styrene resins, polyethylene, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene resins, dicyclopentadiene / C9 resins, alkyl phenyl Examples of suitable resins include alcohol-based resins, rosin-based resins, terpene-based resins, hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated C5 / C9 resins, hydrogenated dicyclopentadiene-based resins, hydrogenated dicyclopentadiene / C9 resins, hydrogenated rosin-based resins, hydrogenated terpene-based resins, coumarone-based resins, acrylic resins, polyamide resins, phenolic resins, terpene-phenolic resins, and coumarone-indene resins. Among these, at least one resin selected from the group consisting of C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene-based resins, rosin-based resins, terpene-based resins, and hydrogenated resins thereof, as well as coumarone-based resins, acrylic resins, polyamide resins, and phenolic resins, is preferred. The resins may be used alone or in combination of two or more.

[0118] The resin content is preferably 1 part by mass or more relative to 100 parts by mass of the total mass of the rubber components contained in the polymer composition. By including 1 part by mass or more of the resin, the abrasion resistance, breaking strength, and crack growth resistance of a crosslinked product obtained using the polymer composition may be improved. The lower limit of the resin content is more preferably 3 parts by mass, and particularly preferably 5 parts by mass, relative to 100 parts by mass of the total mass of the rubber components contained in the polymer composition. Furthermore, from the viewpoint of maintaining various performance properties of the polymer composition well, the upper limit of the resin content is preferably 100 parts by mass, more preferably 90 parts by mass, and particularly preferably 80 parts by mass, relative to 100 parts by mass of the total mass of the polymer components contained in the polymer composition.

[0119] As used herein, the term "rubber component" refers to a polymer that can be cured to yield a cured product exhibiting rubber elasticity. The cured product exhibits the property of undergoing large deformation under small forces at room temperature (for example, stretching to more than twice its original size when stretched at room temperature) and rapidly returning to nearly its original shape when the force is removed.

[0120] Fillers The polymer composition according to the present embodiment may contain a filler in order to increase the strength of the crosslinked product. The filler is preferably at least one selected from the group consisting of silica and carbon black.

[0121] Examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), colloidal silica, precipitated silica, calcium silicate, and aluminum silicate. Among these, wet silica is particularly preferred from the viewpoint of improving fracture properties and achieving both grip and low rolling resistance. Highly dispersible silica is also preferred from the viewpoint of improving dispersibility in the polymer composition and improving physical properties and processability. Silica may be used alone or in combination of two or more types.

[0122] The content of silica (the total amount when two or more types are contained) is preferably 5 to 200 parts by mass, more preferably 10 to 150 parts by mass, and particularly preferably 15 to 120 parts by mass, per 100 parts by mass of the total mass of the rubber components contained in the polymer composition.

[0123] Examples of carbon black include, but are not limited to, GPF, FEF, HAF, ISAF, SAF, etc. The content of carbon black (the total amount when two or more types are contained) is preferably 1 to 80 parts by mass, more preferably 2 to 70 parts by mass, even more preferably 3 to 50 parts by mass, and particularly preferably 4 to 30 parts by mass, per 100 parts by mass of the total mass of the rubber components contained in the polymer composition.

[0124] In addition to silica and carbon black as fillers, the polymer composition according to the present embodiment may also contain an inorganic compound represented by the following formula (1) (hereinafter also referred to as "inorganic compound (N)"): Reinforcing fibers (for example, inorganic fibers such as glass fibers and carbon fibers, and organic fibers such as nylon and polyester) may be added. nM 2 mSiO k iH2O (1) (In formula (1), M 2 is at least one selected from the group consisting of a specific metal, which is any one of aluminum, magnesium, titanium, calcium, and zirconium, an oxide of the specific metal, a hydroxide of the specific metal, and a carbonate of the specific metal. n is an integer of 1 to 5, m is an integer of 0 to 10, k is an integer of 2 to 10, and i is an integer of 0 to 10.

[0125] Specific examples of the inorganic compound (N) include compounds in which the specific metal is aluminum, such as aluminum oxide, alumina monohydrate, aluminum hydroxide, aluminum silicate, and calcium aluminum oxide (Al2O3·CaO·2SiO4, etc.); compounds in which the specific metal is magnesium, such as magnesium oxide, magnesium hydroxide, magnesium silicate, calcium magnesium silicate (CaMgSiO4), and talc; compounds in which the specific metal is titanium, such as titanium oxide; compounds in which the specific metal is calcium, such as calcium oxide, calcium hydroxide, calcium silicate, and calcium carbonate; and compounds in which the specific metal is zirconium, such as zirconium oxide, zirconium hydroxide, zirconium silicate, and zirconium carbonate.

[0126] The content of the filler in the polymer composition according to this embodiment (the total amount when two or more types are contained) is preferably 25 to 300 parts by mass, more preferably 30 to 200 parts by mass, and particularly preferably 50 to 150 parts by mass, per 100 parts by mass of the total mass of the rubber components contained in the polymer composition.

[0127] 1.3.4. Crosslinking Agents The polymer composition according to the present embodiment may contain a crosslinking agent. Examples of the crosslinking agent include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, and alkylphenol resins having a methylol group, and sulfur is usually used. The content of the crosslinking agent is preferably 0.1 to 5 parts by mass, and more preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of the total mass of the rubber components contained in the polymer composition.

[0128] 1.3.5.Silane coupling agents When silica is contained in the polymer composition, the dispersibility of the silica can be further improved by adding a silane coupling agent to the polymer composition together with the silica. The silane coupling agent is not particularly limited, but sulfur-containing silane coupling agents are preferred. Examples of sulfur-containing silane coupling agents include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, γ-mercaptopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, and (3-[ethoxybis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silyl]-1-propanethiol.

[0129] The content of the silane coupling agent is preferably 1 to 20 parts by mass per 100 parts by mass of silica. By setting the content of the silane coupling agent to 1 part by mass or more, the effect of improving the dispersibility of silica can be sufficiently obtained. Furthermore, by setting the content of the silane coupling agent to 20 parts by mass or less, it is possible to suppress a decrease in the processability of the polymer composition and to suppress a decrease in the elongation at break of the crosslinked body obtained from the polymer composition. The content of the silane coupling agent is more preferably 5 to 15 parts by mass per 100 parts by mass of silica. One type of silane coupling agent may be used alone, or two or more types may be used in combination.

[0130] 1.3.6. Other additives In addition to the components described above, the polymer composition according to the present embodiment may contain various additives that are generally used to produce crosslinked products such as tires, for example, antioxidants, zinc oxide, stearic acid, softeners, vulcanization accelerators, compatibilizers, vulcanization aids, processing aids, scorch inhibitors, etc. The content ratios of these additives can be appropriately selected depending on the various components, as long as the effects of the present disclosure are not impaired.

[0131] 2. Tires A tire according to one embodiment of the present invention uses a cured product of the polymer composition described above in the tread. The tire according to this embodiment can be obtained by kneading copolymer (A), copolymer (B), and other components blended as needed using a kneader such as an open kneader (e.g., a roll) or an internal kneader (e.g., a Banbury mixer), forming the sheet, and then placing it in a predetermined position and vulcanizing it according to a conventional method. The tire according to this embodiment can be obtained by mixing and kneading the polymer composition Q described above with a filler and various additives optionally used to obtain a crosslinked product (i.e., vulcanized rubber), forming the sheet, and then placing it in a predetermined position and vulcanizing it according to a conventional method.

[0132] The polymer composition described above allows the production of tires that exhibit good grip performance over a wide temperature range from low to high and that have excellent durability of the grip performance. Therefore, the polymer composition described above is suitable as a tire tread material, and is particularly suitable as a material for tires for racing such as F1.

[0133] 3. Working Example Specific examples of the present invention will be described below, but the present invention is not limited to these examples. In the following production examples, examples, and comparative examples, "%" is based on mass unless otherwise specified.

[0134] 3.1. Preparation of Copolymer (A) [Production Example 1-1: Synthesis of Copolymer (A-1)] A copolymer (A-1) dispersion was obtained by the following single-stage polymerization. A 7-L reactor was charged with 520 parts by mass of water, a monomer mixture consisting of 4 parts by mass of 1,3-butadiene (BD), 4 parts by mass of 2-hydroxyethyl methacrylate (HEMA), 7 parts by mass of 2-hydroxyethyl acrylate (HEA), 4 parts by mass of sodium styrenesulfonate (NaSS), 4 parts by mass of methoxypolyethylene glycol methacrylate (PME-200), 1 part by mass of polyethylene glycol monoacrylate (AE-400), and 76 parts by mass of vinyltoluene (VT), 30 parts by mass of n-dodecyl mercaptan as a chain transfer agent, and 3 parts by mass of sodium dodecylbenzenesulfonate as an emulsifier, and the atmosphere was thoroughly purged with nitrogen. 0.02 parts by mass of cumene hydroperoxide as a polymerization initiator, 0.01 parts by mass of tetrasodium salt of ethylenediaminetetraacetic acid, 0.006 parts by mass of iron (II) sulfate heptahydrate, and 0.03 parts by mass of sodium formaldehyde sulfoxylate were charged, and the mixture was polymerized with stirring at 15°C for 10 hours to obtain a dispersion of copolymer (A-1). The polymerization conversion rate at this time was 70%. The polymer dispersion was dried with hot air to obtain a solid copolymer (A-1). The composition corresponding to each monomer in copolymer (A-1) shown in Table 1 below is 1 This value was determined by H-NMR.

[0135] [Physical property evaluation] (1) Weight average molecular weight (Mw) The weight average molecular weight (Mw) of the copolymer (A-1) obtained above was measured under the following measurement conditions: The results are shown in Table 1 below. (Measurement conditions) Measuring equipment: Tosoh Corporation, GPC (Model: HLC-8220) Columns: TSKgel guard column PWXL (manufactured by Tosoh Corporation), TSK-GEL G2500PWXL (manufactured by Tosoh Corporation), TSK-GEL GMPWXL (manufactured by Tosoh Corporation) Eluent: 0.1M NaNO3 aqueous solution Calibration curve: Standard polyethylene oxide Measurement method: The copolymer (A-1) was dissolved in an eluent so that the solid content was approximately 0.3% by mass, and the solution was filtered and then measured.

[0136] [Synthesis of Copolymers (A-2) to (A-11)] Polymerization was carried out in the same manner as in Production Example 1-1, except that the types and amounts of raw materials used were changed, to obtain dispersions of copolymers (A-2) to (A-11). The compositions and physical properties of copolymers (A-2) to (A-11) are shown in Table 1 below. The compositions of copolymers (A-2) to (A-11) shown in Table 1 below are also 1 This value was determined by H-NMR.

[0137] [Table 1]

[0138] The details of each component in Table 1 above are as follows: <Aromatic vinyl compounds> ST: Styrene VT: Vinyltoluene <Unsaturated carboxylic acid esters with hydroxyl groups> HEMA: 2-hydroxyethyl methacrylate HEA: 2-hydroxyethyl acrylate <Unsaturated carboxylic acid> ·MAA: methacrylic acid AA: Acrylic acid TA: Itaconic acid <(Meth)acrylamide> AAM: Acrylamide MAM: methacrylamide <Compounds containing sulfonic acid groups> NaSS: Sodium styrene sulfonate VS: Vinyl sulfonic acid <Compounds Having a Polyalkylene Glycol Group> PME-200: Methoxypolyethylene glycol methacrylate, product name "Blenmar (registered trademark) PME-200", manufactured by NOF Corporation AE-400: Polyethylene glycol monoacrylate, product name "Blenmar (registered trademark) AE-400", manufactured by NOF Corporation <Conjugated diene compounds> BD: 1,3-butadiene IP: Isoprene

[0139] 3.2. Preparation of copolymer (B) [Production Example 2-1: Synthesis of Copolymer (B-1)] A 5-liter autoclave reactor with a nitrogen-purged atmosphere was charged with 2500 g of cyclohexane, 2.0 mL of tetrahydrofuran as a vinyl group content adjuster (randomizer), and 125 g of styrene and 325 g of 1,3-butadiene as monomers. The temperature of the reactor contents was adjusted to 40°C, and then 0.44 g of n-butyllithium was added as a polymerization initiator to initiate polymerization. After the reaction rate exceeded 80%, 50 g of 1,3-butadiene was added. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 90°C. Then, 2.08 g of 3-(N,N-bistrimethylsilyl)aminopropylmethyldiethoxysilane (M-1) as a terminal modifier was added and stirred for 10 minutes. 4.40 g of 2,6-di-tert-butyl-p-cresol as an antioxidant was added to the stirred polymer solution to obtain a polymer solution containing the modified copolymer (B-1) and the antioxidant (hereinafter referred to as "polymer solution SB-1"). The solvent was removed from this polymer solution by steam stripping, and the solution was dried using a heated roll heated to 130 °C to obtain a solid copolymer (B-1). The raw materials used in the production of copolymer (B-1) are shown in Table 2 below.

[0140] [Physical property evaluation] (1) Bound styrene content (%) Deuterated chloroform was used as the solvent, and the 1 Calculated from H-NMR measurements. (2) Vinyl group content (%) 400MHz 1 Calculated from H-NMR measurements. (3) Weight average molecular weight and molecular weight distribution of the modified polymer Gel permeation chromatography (GPC) was used to determine the molecular weight in terms of polystyrene. A chart (GPC curve) was obtained based on the above data, and the results were calculated based on the chart. The specific measurement conditions for GPC are as follows: (Measurement conditions) Measuring instrument: HLC-8020 (Tosoh Corporation) Column: Two GMH-HR-H columns (Tosoh Corporation) were connected in series. Detector: Differential refractometer RI-8020 (Tosoh Corporation) Eluent: tetrahydrofuran Column temperature: 40℃ ·Flow rate: 1.0mL / min Sample concentration: 10mg / 20mL (4) Glass transition temperature (Tg) In accordance with JIS K6240:2011, the glass transition temperature was determined from the inflection point of the DSC curve in the range of −100° C. to 100° C. The DSC measurement conditions were as follows. (DSC measurement conditions) Measurement equipment: Q1000 Differential Scanning Calorimeter (DSC) (TA Instruments) Heating rate: 10℃ / min

[0141] [Production Examples 2-2 and 2-3: Synthesis of Copolymer (B-2) and Copolymer (B-3)] Solids of copolymer (B-2) and copolymer (B-3) were obtained by polymerization, desolvation, and drying in the same manner as in Production Example 2-1, except that the types and amounts of raw materials used were as shown in Table 2. The compositions and physical properties of copolymer (B-2) and copolymer (B-3) are shown in Table 2 below.

[0142] [Table 2]

[0143] [Production Example 2-4: Synthesis of Copolymer (B-4)] A 50-liter reactor (first reactor) was charged with 1,3-butadiene as a monomer. Diene was continuously charged at a rate of 58 g / min, styrene at 17 g / min, cyclohexane as a solvent at 750 g / min, tetrahydrofuran as a vinyl group content adjuster (randomizer) at 0.57 g / min, and n-butyllithium as a polymerization initiator at 0.031 g / min, and the temperature inside the reactor was controlled at 70°C. The polymer solution was continuously discharged from the first reactor at a rate of 825 g / min, and 1,3-butadiene (additional 1,3-butadiene) was continuously introduced into the discharged polymer solution at a rate of 8 g / min into the second reactor, where the reaction was carried out. At the outlet of the third reactor, 1,1'-(1,4-phenylene)bis(N-(3-(triethoxysilyl)propyl)methanimine) (M-2) was continuously charged as a terminal modifier at a rate of 0.062 g / min. Di-tert-butyl-p-cresol was then added in an amount of 0.88 parts by mass per 100 parts by mass of polymer, yielding a polymer solution containing modified copolymer (B-4). The solvent was then removed from this polymer solution by steam stripping, and the solution was dried using a heated roll heated to 130°C to obtain a solid product of copolymer (B-4). The composition and physical properties of copolymer (B-4) are shown in Table 3 below.

[0144] [Production Example 2-5: Synthesis of Copolymer (B-5)] Polymerization was carried out in the same manner as in Production Example 2-4 to obtain a solid product of copolymer (B-5), except that the types and amounts of raw materials used were as shown in Table 3 below. The composition and physical properties of copolymer (B-5) are shown in Table 3 below.

[0145] [Table 3]

[0146] In Tables 2 and 3 above, the terminal modifying agents used are as follows: <End Modifier> M-1: 3-(N,N-bistrimethylsilyl)aminopropylmethyldiethoxysilane M-2: 1,1'-(1,4-phenylene)bis(N-(3-(triethoxysilyl)propyl)methanimine) M-3: 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza 2-Silacyclopentane

[0147] 3.3. Preparation of polymer composition PA [Polymer composition PA-1] 6 L of water was placed in a 20 L SUS container and the temperature was adjusted to 70°C. Then, 60 g of calcium chloride was added as a coagulant and thoroughly stirred to dissolve. To this, 40 parts by mass of the polymer (A-2) dispersion was added per 100 parts by mass of copolymer (B-1), and the mixture was stirred for 5 minutes. The polymer solution SB-1 prepared above was then added to the dispersion so that the total weight of copolymer (B-1) was 500 g. The solvent was then removed by steam stripping, and the mixture was then dried using a heated roll adjusted to 130°C, yielding a solid polymer composite (PA-1) containing copolymer (A-2), copolymer (B-1), and an antioxidant.

[0148] [Polymer composition PA-2] Polymer composition PA-2 was also prepared according to the composition in Table 2 above, and the same procedure as for PA-1 was carried out to obtain a solid product.

[0149] 3.4. Preparation of polymer composition PB and crosslinked product [Examples 1 to 17, Comparative Examples 1 to 10] Polymer compositions PB were produced by blending and kneading the components according to the blending recipes shown in Tables 4 to 6 below. The kneading was carried out in the following manner. Using a batch mixer equipped with a temperature control device (manufactured by Toyo Seiki Seisakusho, trade name "Labo Plastomill"), in the first stage of kneading, all components except the vulcanization accelerator and sulfur were compounded and kneaded under the conditions of a set temperature of 100°C, a rotation speed of 60 rpm, and a kneading time of 4 minutes. The temperature of the kneaded products discharged from the mixer was always around 150°C. Next, in the second stage of mixing, the kneaded material obtained in the first stage of mixing was cooled to room temperature, and then a vulcanization accelerator and sulfur were added to the mixer. The temperature was adjusted to 70°C, the rotation speed was 60 rpm, and the mixing time was 1.5 minutes to obtain polymer compositions PB. The temperature of the kneaded material discharged from the mixer was 100°C or below when discharged. Next, the obtained polymer compositions PB were vulcanized and molded in a vulcanization press at 160°C for a predetermined time to obtain vulcanized rubber as a crosslinked product. The obtained vulcanized rubber was evaluated for the following physical properties. The results are shown in Tables 4 to 6 below.

[0150] [Example 18] Using a batch mixer equipped with a temperature control device (manufactured by Toyo Seiki Seisakusho, trade name "Labo Plastomill"), for the first stage of kneading, the temperature was adjusted to 100°C, the rotation speed was 60 rpm, and the kneading time was 4 minutes. A total of 140 parts by mass of the polymer composite PA-1 obtained above was added so that the copolymer (A-2) was 40 parts by mass and the copolymer (B-1) was 100 parts by mass, and carbon black, extender oil, stearic acid, zinc oxide, and antioxidant were further added and kneaded. The temperature of the kneaded product discharged from the mixer was around 150°C. Next, in the second stage of mixing, the kneaded material obtained in the first stage was cooled to room temperature, and then a vulcanization accelerator and sulfur were added to the mixer. The temperature was adjusted to 70°C, the rotation speed was 60 rpm, and the mixing time was 1.5 minutes to obtain polymer composition PB-28. The temperature of the kneaded material discharged from the mixer was 100°C or below when discharged. Next, the obtained polymer composition was vulcanized in a vulcanization press at 160°C for a predetermined time to obtain a vulcanized rubber as a crosslinked product. The physical properties of the obtained vulcanized rubber were evaluated in the same manner as above. The results are shown in Table 6 below. Examples 17 and 18 and Comparative Example 11 were evaluated using an index where Comparative Example 10 was set to 100. The higher the index, the better the physical properties.

[0151] [Comparative Example 11] A polymer composition PB-29 was obtained and evaluated in the same manner as in Example 18, except that the formulation was as shown in Table 6 below. The formulation and physical property evaluations are shown in Table 6 below.

[0152] [Physical property evaluation] (1) Grip performance (0°C tanδ, 30°C tanδ, 100°C tanδ) Using vulcanized rubber as a measurement sample, the loss factor (tan δ(0°C)) was measured using an ARES-RDA (manufactured by TA Instruments) under conditions of shear strain of 0.14%, angular velocity of 100 radians per second, and 0°C. The measurement results are expressed as an index, with Comparative Example 1 set to 100. The larger the value, the better the grip performance (especially on dry road surfaces). Each temperature becomes a physical property index as follows: 0℃ tanδ: Initial grip performance 30℃ tanδ: Low temperature grip performance 100℃ tanδ: High temperature grip performance

[0153] (2) Strength (M300) Using vulcanized rubber as the measurement sample, a tensile test was conducted in accordance with JIS K 6251:2010. A dumbbell-shaped No. 3 was used as the test sample, and the stress at 300% elongation (M300: MPa) was measured at room temperature. The higher the M300, the higher the strength. Furthermore, a high 0°C tan δ and a high M300 indicate that grip performance will be maintained over a wide temperature range.

[0154] [Table 4]

[0155] [Table 5]

[0156] [Table 6]

[0157] Details of each component in Tables 4 to 6 above are as follows: *1) Manufactured by ENEOS Materials, product name "BR01" *2) Manufactured by ENEOS Materials, product name "HA125" *3) 1165MP: Manufactured by Solvay, product name "ZEOSIL 1165MP", 1115MP: Manufactured by Solvay, product name "ZEOSIL 1115MP" *4) Mitsubishi Chemical Corporation, product name "Diablack N330" *5) Evonik, product name "Si75" *6) ENEOS T-DAE process oil *7) Seiko Chemical Co., Ltd., product name "Ozonone 6C" *8) Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noccela D" *9) Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noccela CZ-G" In Tables 4 and 5, the parenthesized values ​​for the amount of extender oil represent the amount carried over from copolymer (B-5). In Table 6, the parenthesized values ​​for the amount of copolymer (A) represent the amount carried over from polymer compositions PA-1 and PA-2, respectively.

[0158] The results in Tables 4 to 6 above show that by producing vulcanized rubber using polymer composition PB containing copolymer (A) which contains 70 to 99 mass% of repeating units derived from an aromatic vinyl compound and 1 to 30 mass% of repeating units derived from a hydrophilic monomer and has a weight-average molecular weight of 500 to 10,000 as measured by gel permeation chromatography, and copolymer (B) which has repeating units derived from an aromatic vinyl compound and repeating units derived from a conjugated diene compound and has a weight-average molecular weight of 100,000 to 3,000,000 as measured by gel permeation chromatography, it is possible to obtain vulcanized rubber which exhibits good grip performance over a wide temperature range and has excellent grip performance durability.

[0159] Furthermore, the results in Table 6 above show that when vulcanized rubber is produced using the polymer composition PA obtained by pre-mixing the copolymer (A) dispersion and the copolymer (B), both the grip performance and the durability of the grip performance are improved compared to when the vulcanized rubber is produced by kneading each of them in the solid state.

[0160] From the above results, it was found that the polymer composition of the present invention can provide vulcanized rubber that has excellent grip performance over a wide temperature range from low to high, and that also has excellent durability of said grip performance.

[0161] The present invention is not limited to the above-described embodiments, and various modifications are possible. The present invention includes configurations that are substantially the same as 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 includes configurations in which non-essential parts of the configurations described in the above embodiments are replaced with other configurations. Furthermore, the present invention also includes configurations that achieve the same effects or purposes as the configurations described in the above embodiments. Furthermore, the present invention also includes configurations in which publicly known technology is added to the configurations described in the above embodiments.

Claims

1. A copolymer (A) having repeating units derived from an aromatic vinyl compound and repeating units derived from a hydrophilic monomer, wherein, when the total amount of repeating units contained in the copolymer (A) is taken as 100% by mass, the copolymer (A) contains 70 to 99% by mass of repeating units derived from the aromatic vinyl compound and 1 to 30% by mass of repeating units derived from the hydrophilic monomer, and has a weight average molecular weight measured by gel permeation chromatography of 500 to 10,000; A copolymer (B) having a repeating unit derived from an aromatic vinyl compound and a repeating unit derived from a conjugated diene compound, and having a weight average molecular weight measured by gel permeation chromatography of 100,000 to 3,000,000. A polymer composition comprising:

2. 2. The polymer composition according to claim 1, wherein the copolymer (A) further contains 1 to 15% by mass of a repeating unit derived from a conjugated diene compound, when the total amount of repeating units contained in the copolymer (A) is 100% by mass.

3. 3. The polymer composition according to claim 1, wherein the hydrophilic monomer has at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amide group, a sulfo group, a polyalkylene glycol group, and an amino group.

4. 3. The polymer composition according to claim 1, wherein the copolymer (B) contains 3 to 45 mass% of repeating units derived from an aromatic vinyl compound, when the total amount of repeating units contained in the copolymer (B) is 100 mass%.

5. The copolymer (B) contains a repeating unit derived from 1,3-butadiene, 3. The polymer composition according to claim 1, wherein the repeating units derived from 1,3-butadiene have a 1,2-vinyl group content of 7 to 70 mol %.

6. 3. The polymer composition according to claim 1, wherein the content of the copolymer (A) is 1 to 100 parts by mass when the content of the copolymer (B) is 100 parts by mass.

7. 3. The polymer composition according to claim 1 or claim 2, further comprising at least one resin selected from the group consisting of a C5 resin, a C9 resin, a C5 / C9 resin, a dicyclopentadiene-based resin, a rosin-based resin, a terpene-based resin, and hydrogenated resins thereof, a coumarone-based resin, an acrylic resin, a polyamide resin, and a phenolic resin.

8. 3. The polymer composition according to claim 1, wherein the total content of the copolymer (A), the copolymer (B), and the optional extender oil (C) is 90% by mass or more of the total composition.

9. A tire using a cured product of the polymer composition according to claim 1 or 2 in the tread.

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