Polymer composition and tire

Abstract

This invention provides a polymer composition suitable for manufacturing tires that offer excellent grip performance (braking performance) on wet road surfaces, low fuel consumption, and good wear resistance. [Solution] The polymer composition according to the present invention contains a copolymer (A) having repeating units (a) derived from an aromatic vinyl compound and repeating units (b) derived from a conjugated diene compound, wherein when the total amount of repeating units contained in the copolymer (A) is 100% by mass, it contains 51 to 95% by mass of repeating units (a) derived from the aromatic vinyl compound and 5 to 48% by mass of repeating units (b) derived from the conjugated diene compound, and the weight-average molecular weight measured by gel permeation chromatography is 500 to 10,000, and a conjugated diene polymer (B).

Description

[Technical Field]

[0001] This invention relates to polymer compositions and tires. [Background technology]

[0002] Tires are required to have high braking performance (grip performance) for safety reasons, and various technologies have been proposed to improve grip performance (see, for example, Patent Documents 1 to 3). In particular, there is an increasing demand for improved grip performance when driving on wet roads (wet grip performance). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2011-93386 [Patent Document 2] Japanese Patent Publication No. 2013-79017 [Patent Document 3] Japanese Patent Publication No. 2016-37100 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Some aspects of the present invention provide polymer compositions suitable for manufacturing tires that have excellent grip performance (braking performance) on wet road surfaces, low fuel consumption performance, and good wear resistance. [Means for solving the problem]

[0005] 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.

[0006] One embodiment of the polymer composition according to the present invention is: A copolymer (A) having repeating units (a) derived from an aromatic vinyl compound and repeating units (b) derived from a conjugated diene compound, wherein when the total amount of repeating units contained in the copolymer (A) is 100% by mass, it contains 51 to 95% by mass of repeating units (a) derived from the aromatic vinyl compound and 5 to 48% by mass of repeating units (b) derived from the conjugated diene compound, and the weight-average molecular weight measured by gel permeation chromatography is 500 to 10,000, and Conjugated diene polymer (B) It contains.

[0007] In one embodiment of the polymer composition, The copolymer (A) may further contain 1 to 35% by mass of repeating units (c) derived from a hydrophilic monomer.

[0008] In one embodiment of the polymer composition, The hydrophilic monomer may have at least one functional group selected from the group consisting of hydroxyl groups, carboxyl groups, amide groups, sulfo groups, and polyalkylene glycol groups.

[0009] In any embodiment of the polymer composition, The conjugated diene polymer (B) may contain repeating units derived from 1,3-butadiene, and the 1,2-vinyl group content in the repeating units derived from 1,3-butadiene may be 7 to 70 mol%.

[0010] In any embodiment of the polymer composition, The weight-average molecular weight of the conjugated diene polymer (B), as measured by gel permeation chromatography, may be between 50,000 and 1,500,000.

[0011] In any embodiment of the polymer composition, The content of the copolymer (A) may be 1 to 100 parts by mass, when the content of the conjugated diene polymer (B) is 100 parts by mass.

[0012] In any aspect of the polymer composition, it 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 their hydrogenated resins, coumarone resin, acrylic resin, polyamide resin, and phenol resin.

[0013] In any aspect of the polymer composition, The total content of the copolymer (A), the conjugated diene polymer (B), and the extender oil (C) as an optional component may be 90% by mass or more of the whole composition.

[0014] One aspect of the tire according to the present invention is a product using the cured product of the polymer composition of any of the above aspects for the tread.

Advantages of the Invention

[0015] According to the polymer composition of the present invention, a tire excellent in grip performance (braking performance) on a wet road surface, low fuel consumption performance, and good wear resistance can be manufactured.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, preferred embodiments according to the present invention will be described in detail. It should be understood that the present invention is not limited only to the embodiments described below, but also includes various modifications implemented within the scope without changing the gist of the present invention.

[0017] In this specification, “(meth)acryl~” represents “acryl~” or “methacryl~”, and “~(meth)acrylate” represents “~acrylate” or “~methacrylate”.

[0018] In this specification, the numerical range described using “X~Y” means including the numerical value X as the lower limit value and including the numerical value Y as the upper limit value.

[0019] In this specification, the "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 " (where 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, a compound having two monovalent groups represented by "-Si(OR 1 )3" in one molecule and having 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.

[0020] 1. Polymer composition The polymer composition according to one embodiment of the present invention contains a copolymer (A) and a conjugated diene polymer (B). Hereinafter, the components that can be included in the polymer composition according to this embodiment will be described. explained.

[0021] 1.1. Copolymer (A) The polymer composition according to this embodiment contains a copolymer (A) having a repeating unit (a) derived from an aromatic vinyl compound and a repeating unit (b) derived from a conjugated diene compound. By the polymer composition according to this embodiment containing the copolymer (A), it has excellent low fuel consumption performance and improved wear resistance.

[0022] Hereinafter, the repeating units constituting the copolymer (A), the physical properties of the copolymer (A), and the production method of the copolymer (A) will be described in this order.

[0023] 1.1.1. Repeating units constituting copolymer (A) Copolymer (A) contains, when the total amount of repeating units contained in copolymer (A) is taken as 100% by mass, 51 to 95% by mass of repeating units (a) derived from aromatic vinyl compounds and 5 to 48% by mass of repeating units (b) derived from conjugated diene compounds. In addition, copolymer (A) may also contain repeating units derived from other monomers copolymerizable with these repeating units.

[0024] 1.1.1.1. Repeating units derived from aromatic vinyl compounds (a) Copolymer (A) contains 51 to 95% by mass of repeating units (a) derived from aromatic vinyl compounds, when the total amount of repeating units contained in copolymer (A) is taken as 100% by mass. The content of repeating units (a) derived from aromatic vinyl compounds is preferably 55% by mass or more, more preferably 58% by mass or more, and particularly preferably 60% by mass or more. The content of repeating units (a) derived from aromatic vinyl compounds is preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 80% by mass or less. By containing repeating units (a) derived from aromatic vinyl compounds within the above ranges, copolymer (A) becomes more likely to interact with carbon black or silica, and the dispersion of carbon black or silica becomes more uniform, which may improve the strength and wear resistance of the resulting crosslinked material or tire.

[0025] The aromatic vinyl compound is not particularly limited, but examples include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, and divinylbenzene, and one or more selected from these can be used.

[0026] 1.1.1.2. Repeating units derived from conjugated diene compounds (b) Copolymer (A) contains 5 to 48% by mass of repeating units (b) derived from the conjugated diene compound, 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 the conjugated diene compound is preferably 7% by mass or more, more preferably 10% by mass or more, and particularly preferably 12% by mass or more. The content of repeating units (b) derived from the conjugated diene compound is preferably 45% by mass or less, more preferably 40% by mass or less, and particularly preferably 38% by mass or less. By containing repeating units (b) derived from the conjugated diene compound within the above ranges in copolymer (A), flexibility can be imparted to copolymer (A), and it is expected that the processability of the resulting crosslinked material and tire will be improved.

[0027] The conjugated diene compound is not particularly limited, but examples include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-chloro-1,3-butadiene, and one or more selected from these can be used. Among these, 1,3-butadiene is particularly preferred.

[0028] 1.1.1.3. Repeating units (c) derived from hydrophilic monomers Copolymer (A) may contain 1 to 35% by mass of repeating units (c) derived from hydrophilic monomers, when the total amount of repeating units contained in copolymer (A) is taken as 100% by mass. The content of repeating units (c) derived from hydrophilic monomers is preferably 2% by mass or more, more preferably 4% by mass or more, and particularly preferably 5% by mass or more. The content of repeating units (c) derived from hydrophilic monomers is preferably 30% by mass or less, more preferably 28% by mass or less, and particularly preferably 25% by mass or less. When copolymer (A) contains repeating units (c) derived from hydrophilic monomers within the above range, it tends to interact more easily with the surface of the filler (especially silica particles), suppressing aggregation of the filler and enabling uniform dispersion of the filler. As a result, the strength of the resulting crosslinked material and tire is improved, and it exhibits even better grip performance.

[0029] The hydrophilic monomer preferably has at least one functional group selected from the group consisting of hydroxyl groups, carboxyl groups, amide groups, sulfo groups, and polyalkylene glycol groups. The copolymer (A) having such a hydrophilic functional group allows it to effectively interact with the surface of the filler (especially silica particles).

[0030] Specific examples of repeating units (c) derived from hydrophilic monomers include repeating units (c1) derived from unsaturated carboxylic acid esters having hydroxyl groups, repeating units (c2) derived from unsaturated carboxylic acids, repeating units (c3) derived from (meth)acrylamide, repeating units (c4) derived from compounds having sulfonic acid groups, and repeating units (c5) derived from compounds having polyalkylene glycol groups. It is preferable to contain one or more selected from these.

[0031] <Repeating unit (c1) derived from an unsaturated carboxylic acid ester containing a hydroxyl group> Among unsaturated carboxylic acid esters having hydroxyl groups, (meth)acrylic acid esters having hydroxyl groups can be preferably used. Specific examples of (meth)acrylic acid esters having hydroxyl groups 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, it is preferable to use one or more selected from 2-hydroxyethyl (meth)acrylate, glycerin mono(meth)acrylate, and glycerin di(meth)acrylate, and 2-hydroxyethyl (meth)acrylate is particularly preferred.

[0032] <Repeating unit (c2) derived from unsaturated carboxylic acid> The unsaturated carboxylic acid is not particularly limited, but examples include monocarboxylic acids and dicarboxylic acids (including anhydrides) such as (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, and one or more selected from these can be used. Preferably, one or more selected from acrylic acid, methacrylic acid, and itaconic acid is used as the unsaturated carboxylic acid.

[0033] <(Meth)acrylamide-derived repeating unit (c3)> (Meth)acrylamide is not particularly limited, but examples 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, etc., and one or more selected from these can be used. can.

[0034] <Repeating unit (c4) derived from a compound containing a sulfonic acid group> Compounds having a sulfonic acid group are not particularly limited, but include 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, 3-alyloxy-2-hydroxypropanesulfonic acid, and alkali salts thereof, and one or more selected from these can be used.

[0035] <Repeating unit (c5) 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, methoxypolyethylene glycol mono(meth)acrylate, and one or more selected from these can be used.

[0036] 1.1.1.4. Other Repeating Units The copolymer (A) may contain, in addition to the repeating units (a) derived from the aromatic vinyl compound, the repeating units (b) derived from the conjugated diene compound, and the repeating units (c) derived from the hydrophilic monomer, repeating units derived from other monomers copolymerizable with these.

[0037] 1.1.2. Weight-average molecular weight of copolymer (A) The weight-average molecular weight of copolymer (A), as measured by gel permeation chromatography, is between 500 and 10,000. Preferably, the weight-average molecular weight of copolymer (A) is 800 or more, more preferably 1000 or more. Preferably, the weight-average molecular weight of copolymer (A) is 9500 or less, more preferably 9000 or less. A weight-average molecular weight of copolymer (A) within the above range is preferable because it allows for easy dispersion during rubber compounding and facilitates good interaction with the filler surface. The weight-average molecular weight of copolymer (A) can be measured by gel permeation chromatography using the method described in the examples below.

[0038] 1.1.3. Method for producing copolymer (A) Copolymer (A) can be produced, for example, by a method comprising a polymerization step and a recovery step.

[0039] <Polymerization process> The method for producing copolymer (A) is not particularly limited, but can be carried out by emulsion polymerization in the presence of known emulsifiers (surfactants), chain transfer agents, polymerization initiators, etc. Compounds described in Japanese Patent Publication No. 5999399, etc., can be used as emulsifiers (surfactants), chain transfer agents, and polymerization initiators.

[0040] The emulsion polymerization method for synthesizing copolymer (A) may be carried out as a single-step polymerization or as a multi-step polymerization of two or more steps.

[0041] When the copolymer (A) is synthesized by one-step polymerization, the above monomer mixture is subjected to a suitable emulsifier, chain transfer agent, polymerization initiator, etc., preferably at 40-80°C. This can be done by emulsion polymerization over a period of 4 to 36 hours.

[0042] When the copolymer (A) is synthesized by two-step polymerization, it is preferable to set the polymerization steps as follows.

[0043] The proportion of monomers used in the first stage polymerization is preferably in the range of 20 to 99% by mass, and more preferably in the range of 25 to 98% by mass, relative to the total mass of monomers (the sum of the mass of monomers used in the first stage polymerization and the mass of monomers used in the second stage polymerization). Performing the first stage polymerization with such a proportion of monomers is preferable because it is possible to obtain a copolymer (A) that has excellent dispersion stability and is less prone to agglomeration, as well as suppressing the increase in viscosity of the polymer composition over time.

[0044] The types and proportions of monomers used in the second polymerization step may be the same as, or different from, the types and proportions of monomers used in the first polymerization step.

[0045] The polymerization conditions at 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 40-80°C; preferably for a polymerization time of 2-36 hours; preferably with 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 40-80°C; preferably for a polymerization time of 2-18 hours.

[0046] By setting the total solids content concentration in emulsion polymerization to 50% by mass or less, the polymerization reaction can proceed while maintaining good dispersion stability of the resulting copolymer (A). This total solids content concentration is preferably 48% by mass or less, and more preferably 45% by mass or less.

[0047] Whether the copolymer (A) is synthesized as a single-step polymerization or as a multi-step polymerization, a neutralizing agent may be added to the polymerization mixture after the emulsion polymerization is complete. It is preferable to adjust the pH 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 ensures good stability of copolymer (A). After the neutralization treatment, the polymerization mixture can be concentrated to increase the solid content concentration while maintaining good stability of copolymer (A).

[0048] <Recovery Process> The copolymer (A) dispersion obtained by the polymerization process described above is subjected to steam stripping as needed to remove any remaining monomers. Then, a coagulant is added, and the solid content (crumb) generated by coagulation is subjected to drying operations such as dehydration or heat treatment. This allows the copolymer (A) to be recovered from the copolymer (A) dispersion obtained by the polymerization process described above.

[0049] As the copolymer (A) dispersion, the aqueous dispersion of copolymer (A) obtained by emulsion polymerization may be used as is, or a dispersion in which rubber spreading oil has been added to the copolymer (A) dispersion obtained by emulsion polymerization and dispersed as oil-spreadable rubber may be used. As the rubber spreading oil, for example, naphthenic, paraffinic, or aromatic process oils can be used. The amount of rubber spreading oil used to make oil-spreadable rubber is preferably 5 to 100 parts by mass, more preferably 10 to 60 parts by mass, per 100 parts by mass of polymer contained in the copolymer (A) dispersion. Furthermore, various additives such as antioxidants may be further added to the copolymer (A) dispersion.

[0050] 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; metal salts with a valency of 1 to 3, such as sodium chloride, calcium chloride, and magnesium sulfate; and organic acid salts such as cyclohexylamine acetate. Among these coagulants, metal salts with a valency of 1 to 3 are preferred, and sodium chloride and calcium chloride are 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 polymer contained in the copolymer (A) dispersion.

[0051] 1.1.4. Content ratio of copolymer (A) In the polymer composition according to this embodiment, the content of polymer (A) is preferably 1 to 100 parts by mass per 100 parts by mass of the conjugated diene polymer (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, it is preferable because it improves the dispersibility of the filler while also providing good compatibility with the conjugated diene polymer (B).

[0052] 1.2. Conjugated diene polymers (B) 1.2.1. Characteristics of conjugated diene polymers (B) The polymer composition according to this embodiment contains a conjugated diene polymer (B). The conjugated diene polymer (B) includes (co)polymers of conjugated diene compounds and natural rubber.

[0053] The conjugated diene polymer (B) contains repeating units derived from the conjugated diene compound. Alternatively, the conjugated diene polymer (B) may be a copolymer containing repeating units derived from the conjugated diene compound and repeating units derived from the aromatic vinyl compound.

[0054] Specific examples of such conjugated diene polymers (B) include natural rubber, butadiene rubber, emulsion polymerized styrene-butadiene rubber (ESBR), solution polymerized styrene-butadiene rubber (SSBR), hydrogenated styrene-butadiene rubber, and isoprene rubber. These conjugated diene polymers (B) may be used individually or in combination of two or more types. Furthermore, the conjugated diene polymers (B) may or may not be modified.

[0055] In this specification, "modification" means giving a conjugated diene polymer consisting of repeating units derived from hydrocarbons (i.e., an unmodified conjugated diene polymer) a substructure containing heteroatoms such as nitrogen, oxygen, sulfur, and silicon.

[0056] The polymer composition according to this embodiment contains a conjugated diene polymer (B), which improves the dispersibility of the filler (especially silica) in the polymer composition, thereby improving the tire's grip performance (braking performance) and fuel efficiency on wet road surfaces. From the viewpoint of further improving the dispersibility of the filler in the polymer composition, it is preferable that the conjugated diene polymer (B) has at least one element selected from the group consisting of nitrogen, silicon, sulfur, oxygen, phosphorus, and tin (hereinafter also referred to as "specific element").

[0057] In terms of ease of introducing specific elements into the polymer, it is preferable that the conjugated diene polymer (B) has a substructure derived from a compound containing a specific element (hereinafter also referred to as "compound (M)"). Compound (M) may be a compound that can introduce a functional group containing a specific element to the polymerization initiation end (hereinafter also referred to as "initiation end modifier"), or a compound that can introduce a functional group containing a specific element to the polymerization termination end (hereinafter also referred to as "end modifier"). Furthermore, compound (M) may be a monomer that can introduce a functional group containing a specific element to the side chain of the molecular chain (hereinafter also referred to as "modified monomer"). In terms of high effectiveness in improving the dispersibility of the filler, Compound (M) preferably contains at least one selected from the group consisting of an initiating terminal denaturant and a terminal denaturant, and more preferably contains a terminal denaturant.

[0058] 1.2.2. Method for producing conjugated diene polymer (B) The conjugated diene polymer (B) included in the polymer composition according to this embodiment may preferably be a polymer produced by a method including the following polymerization and modification steps. Polymerization step: A step of polymerizing a monomer containing a conjugated diene compound and optionally an aromatic vinyl compound in the presence of a polymerization initiator to obtain a conjugated diene polymer having an active end. Modification step: A step of reacting a conjugated diene polymer having an active end with compound (M) to obtain a conjugated diene polymer (B).

[0059] The following describes a preferred method for obtaining the conjugated diene polymer (B), along with a description of preferred embodiments of the molecular structure of the conjugated diene polymer (B).

[0060] <Polymerization process> 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 for its high effectiveness in balancing processability and hysteresis loss reduction. The conjugated diene compound can be used alone or in combination of two or more.

[0061] Examples of aromatic vinyl compounds 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, styrene or α-methylstyrene are preferred as aromatic vinyl compounds.

[0062] The conjugated diene polymer obtained in the polymerization process is preferably a copolymer having repeating units derived from 1,3-butadiene and repeating units derived from styrene, due to its 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 block portions consisting of the conjugated diene compound or other aromatic vinyl compounds.

[0063] The proportion of aromatic vinyl compounds used is preferably 3 to 45% by mass, and more preferably 5 to 40% by mass, relative to the total amount of monomers used in polymerization, from the viewpoint of balancing the low hysteresis loss characteristics (low fuel consumption performance) and wet skid resistance of the resulting crosslinked material, and improving wear resistance. The proportion of repeating units derived from aromatic vinyl compounds in the polymer is 1 This value is measured by 1H-NMR.

[0064] In 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 using other monomers, the proportion of other monomers used is preferably 5% by mass or less, and more preferably 3% by mass or less, relative to the total amount of monomers used in polymerization.

[0065] Solution polymerization is particularly preferred for polymerizing monomers containing conjugated diene compounds. The polymerization method may be batch or continuous. When using solution polymerization, one example of a specific polymerization method is to polymerize the monomer in an organic solvent in the presence of a polymerization initiator and, if necessary, a vinyl group content adjuster (randomizer).

[0066] As a polymerization initiator, at least one selected from the group consisting of alkali metal compounds and alkaline earth metal compounds can preferably be used. Specific examples of these include alkyllithium, 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, calcium stearate, etc. Specific examples of alkyllithium include methyllithium, ethyllithium, n-propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, etc. Lithium compounds are preferred as polymerization initiators. The ratio of polymerization initiators used during polymerization (total amount if two or more are used) is preferably 0.2 to 20 mmol per 100 g of monomer used for polymerization.

[0067] Furthermore, the polymerization reaction may be carried out 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 (hereinafter also referred to as a "metal amide compound"). By polymerizing monomers in the presence of a metal amide compound, specific elements derived from the initiating end modifier can be introduced to the polymerization initiating end of the conjugated diene polymer.

[0068] Nitrogen-containing compounds such as secondary amine compounds can be preferably used as the starting end modifier. Specific examples of starting end modifiers include, for example, chain-like 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.

[0069] Furthermore, when polymerizing monomers 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. In either of these cases, "at least one selected from the group consisting of alkali metal compounds and alkaline earth metal compounds and the initiating end modifier" may be used. This embodiment includes "polymerizing monomers in the presence of a compound obtained by mixing them with a terminal modifying agent."

[0070] The amount of the starting end modifier used is appropriately set depending on the type of alkali metal compound or alkaline earth metal compound. For example, when using metallic lithium, from the viewpoint of improving the processability of the polymer composition and the low fuel consumption performance of the resulting crosslinked body in a balanced manner, the amount of the starting end modifier used is preferably in the range of 0.1 to 1.8 mol, and more preferably in the range of 0.2 to 1.0 mol, per 1 mol of total metallic lithium used in the polymerization. The starting end modifier can be used alone or in combination of two or more types.

[0071] Furthermore, in polymerization reactions, a nitrogen-containing alkali metal compound (hereinafter also referred to as "nitrogen-containing alkali metal compound") can be used as a polymerization initiator. An example of a nitrogen-containing alkali metal compound is the compound represented by formula (2) described in International Publication No. 2020 / 179705.

[0072] Examples of nitrogen-containing alkali metal compounds include ((2E,6E)-11-(dimethylamino)-3,7-dimethylundeca-2,6-dien-1-yl)lithium.

[0073] Furthermore, a substructure derived from a nitrogen-containing compound can be introduced to the polymerization initiation end by either a method of polymerizing monomers in the presence of a compound obtained by mixing an alkali metal compound or an alkaline earth metal compound with an initiation end modifier, or by a method of polymerizing monomers in the presence of a nitrogen-containing alkali metal compound.

[0074] Vinyl group content adjusters (randomizers) are used to adjust the vinyl group content, which represents the percentage 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 individually or in combination of two or more.

[0075] Any organic solvent that is inert to the reaction can be used as the organic solvent for polymerization. Examples of such organic solvents include linear or cyclic aliphatic hydrocarbons and aromatic hydrocarbons. Hydrocarbons having 3 to 8 carbon atoms are preferred for use as the organic solvent for polymerization. Specific examples 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 can be used individually or in combination of two or more.

[0076] When using solution polymerization, 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. By such a polymerization reaction, a conjugated diene polymer having an active end (more specifically, an alkali metal active end or an alkaline earth metal active end) can be obtained. In this specification, "active end" refers to the part of the molecular chain other than the structure derived from the monomer having a carbon-carbon double bond. It represents (more specifically, the end of a metal object).

[0077] <Modification process> In the modification step, a conjugated diene polymer having an active end is reacted with compound (M). This reaction causes the polymer chain, which contains repeating units derived from the conjugated diene compound, to bond with compound (M) at the reaction site of compound (M), thereby obtaining a modified conjugated diene polymer having a specific element at its polymer end. The conjugated diene polymer having an active end may or may not have a modified polymerization initiation end.

[0078] Preferably, compound (M) is a compound that contains a specific element and has a functional group that can react with the active end of the conjugated diene polymer. By using such a compound, an element that contributes significantly to improving the dispersibility of the filler (especially silica) can be introduced into the polymer relatively easily. Preferably, the specific element contained in compound (M) is at least one selected from the group consisting of nitrogen, oxygen, silicon, sulfur, and phosphorus.

[0079] In order to further improve the dispersibility of the filler (especially silica) in the polymer composition, it is preferable to use a compound (M) that has one or more nitrogen-containing groups and one or more hydrocarbyloxysilyl groups in one molecule. In terms of contributing highly to improving the dispersibility of the filler (especially 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.

[0080] As specific examples of compound (M), compounds represented by formulas (6) to (9) described in Japanese Patent Publication No. 2023-147257 can be preferably used.

[0081] Specific examples of terminal denaturants include, for example, 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.

[0082] Other specific examples of terminal denaturants include, for example, 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-azasiloridine-1-yl)-N,N-diethylethane-1-amine, tris(2-triethoxysilylethyl)amine, tris(3-triethoxysilylpropyl)amine, and tris(5-triethoxysilylpentyl)amine. Examples include N,N,N',N'-tetra(2-triethoxysilylethyl)-1,2-diaminoethane, N,N,N',N'-tetra(3-triethoxysilylpropyl)-1,3-diaminopropane, N-(3-(1H-imidazole-1-yl)propyl)-3-(trimethoxysilyl)-N-(3-(trimethoxysilyl)propyl)propan-1-amine, N-(3-(1H-imidazole-1-yl)propyl)-N,N-bis(3-(trimethoxysilyl)propyl)propanamine, and compounds obtained by replacing the alkyl group and alkanediyl group in these compounds 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.

[0083] Compound (M) may be one of these compounds used alone, or two or more compounds may be used in combination.

[0084] The reaction between the polymerization active end and the end modifier is preferably carried out as a solution reaction. This solution reaction may be carried out using a solution containing unreacted monomers after the polymerization reaction is complete, or it may be carried out using a solution obtained by isolating the conjugated diene polymer having polymerization active ends contained in the solution and dissolving it in a suitable solvent such as cyclohexane. Furthermore, the above reaction may be carried out using either a batch or continuous method. The method of adding the end modifier is not particularly limited and can be done by adding it all at once, adding it in portions, or adding it continuously.

[0085] The amount of terminal modifier used in the above reaction can be appropriately set according to 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 that are involved in the polymerization reaction. By using an amount of 0.1 mol equivalent or more of terminal modifier in the above reaction, the modification reaction can proceed sufficiently, 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 that are involved in the polymerization reaction.

[0086] The reaction temperature is usually the same as the polymerization reaction temperature, preferably between -20°C and 150°C, and more preferably between 0°C and 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 ends tend to be deactivated. The reaction time is preferably 1 minute to 5 hours, more preferably 2 minutes to 1 hour.

[0087] When producing a conjugated diene polymer (B), a reaction between the polymerization active end and a coupling agent may be performed for purposes such as improving the Mooney viscosity and cold flow characteristics of the polymer. Examples of coupling agents include compounds that contain a specific element, do not contain active hydrogen, and have multiple functional groups that can react with the polymerization active end. Specific examples of coupling agents include 2,4-tolylene diisocyanate, diphenylmethane diisocyanate, N,N,N',N'-tetramethylphthalamide, tetrachlorosilicon, N,N,N',N'-tetramethyl-4,4'-diaminobenzophenone, and tetrachlorotin. The reaction using the coupling agent may be performed before or after the reaction between the polymerization active end and the end modifier, or simultaneously with the reaction between the polymerization active end and the end modifier.

[0088] When a compound having a protecting group (such as a trisubstituted hydrocarbylsilyl group) is used as a terminal modifier, some or all of the protecting groups in the modified conjugated diene polymer having the protecting groups derived from the terminal modifier may be hydrogen-substituted. Furthermore, when a compound having a protecting group is used as a terminal modifier, the conjugated diene polymer modified by the terminal modifier may be further reacted with an onium salt generating agent. In this case, a conjugated diene polymer (B) having an onium salt structure at the polymer end can be obtained. The presence of an onium salt structure in the conjugated diene polymer (B) is preferable because it can improve the shape retention of the crosslinked body obtained using the polymer composition.

[0089] 1.2.3. Physical properties of conjugated diene polymers (B) 1.2.3.1. Vinyl group content The conjugated diene polymer (B) contains structural units derived from 1,3-butadiene as the conjugated diene compound, and preferably the 1,2-vinyl group content (hereinafter also referred to as "vinyl group content") in the structural units derived from 1,3-butadiene is 7 to 70 mol%. The vinyl group content is preferably 10 mol% or more, and more preferably 15 mol% or more. When the vinyl group content is 7 mol% or more, good grip performance tends to be ensured. There is also a vinyl group content, preferably 60 mol% or less, and more preferably 50 mol% or less. When the vinyl group content is 70 mol% or less, good fuel efficiency tends to be ensured. In this specification, "vinyl group content" refers to the value indicating the ratio of repeating units having 1,2-bonds to the total repeating units of butadiene in the conjugated diene polymer. 1 This value is measured by 1H-NMR.

[0090] 1.2.3.2. Weight average molecular weight The weight-average molecular weight of the conjugated diene polymer (B), as measured by gel permeation chromatography, is preferably 50,000 to 1,500,000. The weight-average molecular weight of the conjugated diene polymer (B) is preferably 75,000 or more, more preferably 100,000 or more. The weight-average molecular weight of the conjugated diene polymer (B) is preferably 1,400,000 or less, more preferably 1,300,000 or less, and particularly preferably 1,200,000 or less. When the weight-average molecular weight of the conjugated diene polymer (B) is 50,000 or more, the dimensional stability, tensile strength, and abrasion resistance of the crosslinked material tend to be sufficiently high. When the weight-average molecular weight of the conjugated diene polymer (B) is 1,500,000 or less, the processability of the polymer composition tends to improve. The weight-average molecular weight of the conjugated diene polymer (B) can be measured by gel permeation chromatography using the method described in the examples below.

[0091] 1.2.3.3.Molecular weight distribution (Mw / Mn) The molecular weight distribution (Mw / Mn) of the conjugated diene polymer (B), expressed as the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) measured by gel permeation chromatography, is preferably between 1.0 and 10.0. When the Mw / Mn of the conjugated diene polymer (B) is 10.0 or less, it tends to maintain good fuel efficiency of the tire and good dispersibility of the filler. The Mw / Mn of the conjugated diene polymer (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.

[0092] 1.2.3.4. Glass transition temperature The glass transition temperature (Tg) of the conjugated diene polymer (B) is preferably -100°C to 0°C. When the Tg of the conjugated diene polymer (B) is -100°C or higher, the wear resistance and strength of the crosslinked material tend to improve. Furthermore, when the Tg of the conjugated diene polymer (B) is 0°C or lower, the fuel efficiency of the tire tends to improve. The Tg of the conjugated diene polymer (B) is more preferably -90°C to -10°C, and particularly preferably -80°C to -20°C. The glass transition temperature of the conjugated diene polymer (B) is a value measured in accordance with JIS K6240:2011.

[0093] 1.3. Other ingredients The polymer composition according to this embodiment may further contain the following components in addition to the components described above.

[0094] 1.3.1.Extender oil (C) The polymer composition according to this embodiment may contain an expansive oil (C) as an optional component. When the polymer composition according to this embodiment contains an expansive oil (C), the content of the expansive oil (C) is preferably 0 to 100 parts by mass per 100 parts by mass of the conjugated diene polymer (B), from the viewpoint of improving processability while suppressing a decrease in rolling resistance and strength. The content of the expansive oil (C) is more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and particularly preferably 0.2 parts by mass or more, per 100 parts by mass of the conjugated diene polymer (B). Furthermore, the content of the expansive oil (C) is more preferably 95 parts by mass or less, and particularly preferably 90 parts by mass, per 100 parts by mass of the conjugated diene polymer (B). It is below the level of a departmental division.

[0095] One embodiment of the polymer composition according to this embodiment that contains an expansive oil (C) is a polymer composition (hereinafter also referred to as "polymer composition Q") in which the total amount of copolymer (A), conjugated diene polymer (B), and expansive oil (C) is 90% by mass or more of the total polymer composition. In polymer composition Q, the total amount of copolymer (A), conjugated diene polymer (B), and expansive oil (C) is more preferably 93% by mass or more of the total polymer composition, and particularly preferably 95% by mass or more.

[0096] 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 it may be a rubber bale obtained by compressing the crumbs into a desired shape (e.g., a rectangular parallelepiped).

[0097] As the spreading oil (C), process oils commonly used for spreading elastomers can be used. Preferred process oils include a variety of oils known in the industry, 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 Catenex SNR (heavy paraffin obtained by dewaxing distillate with a solvent) from Shell as an MES, Vivacec 500 from H&R Wasag AG as a TDAE, and NC140 from Japan Energy Corp. as an SRAE.

[0098] The polymer composition Q is preferably produced by a method comprising the following mixing and desolvation steps. Mixing step: A step of mixing a copolymer (A) dispersion with a conjugated diene polymer (B) solution to obtain a mixed solution (hereinafter also referred to as "mixed solution SC"). Desolvent removal process: A process to remove the solvent from the mixed solution SC. The following explains each step in detail.

[0099] <Mixing process> From the viewpoint of improving the dispersibility of copolymer (A) in the polymer composition and sufficiently improving fuel efficiency and strength, it is preferable that in the mixing step, a copolymer (A) dispersion in which copolymer (A) is dispersed in water and a conjugated diene polymer (B) solution in which conjugated diene polymer (B) is dissolved in an organic solvent are mixed to obtain a mixed solution SC.

[0100] The organic solvent constituting the conjugated diene polymer (B) solution is one of the organic solvents exemplified as solvents that can be used for monomer polymerization in the production of the conjugated diene polymer (B). Preferably, at least one organic solvent selected from the group consisting of linear aliphatic hydrocarbons, cyclic aliphatic hydrocarbons, and aromatic hydrocarbons can be used.

[0101] It is preferable to use the polymer particle dispersion obtained during the production of copolymer (A) as the copolymer (A) dispersion. 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.

[0102] As the conjugated diene polymer (B) solution, the polymer solution obtained during the production of the conjugated diene polymer (B) (preferably a polymer solution obtained by solution polymerization) may be used as is. Alternatively, the conjugated diene polymer (B) solution may be a solution prepared by dissolving isolated solid conjugated diene polymer (B) in a suitable solvent. By using a polymer solution containing conjugated diene polymer (B), the dispersibility of the filler (especially silica) when the polymer composition Q and the filler are mixed can be further improved. Furthermore, it is preferable to use the reaction solution containing the conjugated diene polymer (B) obtained by the modification step described above as the polymer solution, as this reduces the number of steps and increases productivity. Details of the polymerization step and modification step are described above.

[0103] The content of conjugated diene polymer (B) in the conjugated diene polymer (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 conjugated diene polymer (B) solution. Furthermore, the content of conjugated diene polymer (B) in the conjugated diene polymer (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 conjugated diene polymer (B) in the conjugated diene polymer (B) solution within the above range, a sufficient production volume of the polymer composition can be ensured.

[0104] The method for mixing the copolymer (A) dispersion and the conjugated diene polymer (B) solution is not particularly limited. For example, when adding the copolymer (A) dispersion to the conjugated diene polymer (B) solution, methods include adding the copolymer (A) dispersion to the conjugated diene polymer (B) solution all at once, adding it in stages, or adding it continuously. Similarly, when adding the conjugated diene polymer (B) solution to the copolymer (A) dispersion, methods include adding the conjugated diene polymer (B) solution all at once, adding it in stages, or adding it continuously.

[0105] After adding the copolymer (A) dispersion to the conjugated diene polymer (B) solution, it is preferable to uniformly disperse the copolymer (A) in the conjugated diene polymer (B) solution by performing a treatment such as stirring. The temperature when mixing the conjugated diene polymer (B) solution and copolymer (A) is preferably 10°C to 100°C, more preferably 15°C to 90°C, even more preferably 20°C to 85°C, and particularly preferably 25°C to 80°C.

[0106] When obtaining the mixed solution SC, it is preferable to add a coagulant to coagulate the copolymer (A). Alternatively, the copolymer (A) dispersion and the conjugated diene polymer (B) solution may be mixed to obtain the mixed solution SC, after which the coagulant may be added to precipitate the copolymer (A). Alternatively, the coagulant may be added to the copolymer (A) dispersion beforehand to precipitate the copolymer (A), and then the conjugated diene polymer (B) solution may be added to obtain the mixed solution SC. As the coagulant, the same as that described in the <Recovery Process> section of "1.1.3. Method for Producing Copolymer (A)" above can be used.

[0107] In addition, when adding the spreading oil (C) to the polymer composition Q according to this embodiment, the method of adding the spreading oil (C) is not particularly limited. For example, the spreading oil (C) may be added to the polymer solution containing the conjugated diene polymer (B) after polymerization, and then desolvated in the next desolvation step to be compounded as an oil-stretchable rubber. In this case, the spreading oil (C) may be added before adding the copolymer (A) to the polymer solution, or it may be added after adding the copolymer (A) to the polymer solution.

[0108] In the polymer composition according to this embodiment, when mixing the copolymer (A) dispersion and the conjugated diene polymer (B) solution, the conjugated diene contained in the conjugated diene polymer (B) solution It is preferable that the amount of copolymer (A) in the copolymer (A) dispersion is 1 to 100 parts by mass per 100 parts by mass of polymer (B). By keeping the content of copolymer (A) within the above range, the strength, grip performance, fuel efficiency, and processability of the crosslinked body obtained from the polymer composition can be improved in a well-balanced manner. From this viewpoint, the content of copolymer (A) is more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more, per 100 parts by mass of conjugated diene polymer (B). Furthermore, the content of copolymer (A) is more preferably 95 parts by mass or less, and particularly preferably 90 parts by mass or less, per 100 parts by mass of conjugated diene polymer (B).

[0109] <Desolvent removal process> In the desolvation step, the solvent is removed from the mixed liquid SC obtained in the mixing step, and the polymer composition Q is isolated. 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 separating the solvent by steam stripping and then dehydrating and drying the resulting polymer composition Q, defloration using a twin-screw extruder, or direct defloration using a drum dryer.

[0110] According to the manufacturing method including the mixing step and desolvation step described above, a solid polymer composition Q from which the solvent has been removed can be obtained. The resulting polymer composition Q is a crumb or rubber bale containing a copolymer (A) and a conjugated diene polymer (B).

[0111] 1.3.2. Resin The polymer composition according to this embodiment may contain resins such as thermoplastic resins and thermosetting resins in addition to the components described above. The resin is kneaded together with the copolymer (A), the conjugated diene polymer (B), and other components added as needed during the production of the polymer composition.

[0112] Examples of suitable resins include styrene resins, polyethylene, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene resins, dicyclopentadiene / C9 resins, alkylphenol resins, rosin resins, terpene resins, hydrogenated C5 resins, hydrogenated C9 resins, hydrogenated C5 / C9 resins, hydrogenated dicyclopentadiene resins, hydrogenated dicyclopentadiene / C9 resins, hydrogenated rosin resins, hydrogenated terpene resins, coumarone resins, acrylic resins, polyamide resins, phenol resins, terpenephenol 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 resins, rosin resins, terpene resins, and hydrogenated versions thereof, coumarone resins, acrylic resins, polyamide resins, and phenol resins can be preferably used. The resin may be used individually or in combination of two or more types.

[0113] The resin content is preferably 1 part by mass or more per 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 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, per 100 parts by mass of the total mass of the rubber components contained in the polymer composition. 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, per 100 parts by mass of the total mass of the rubber components contained in the polymer composition.

[0114] In this specification, "rubber component" refers to a polymer from which a cured product exhibiting rubber elasticity can be obtained upon curing. The cured product exhibits large deformation with small force at room temperature (for example, at room temperature). It exhibits the characteristic of undergoing deformation (stretching to more than twice its original size) and rapidly returning to almost its original shape when the force is removed.

[0115] 1.3.3. Fillers The polymer composition according to this embodiment may contain a filler to increase the strength of the crosslinked body. Preferably, the filler is at least one selected from the group consisting of silica and carbon black.

[0116] Examples of silica include wet silica (hydrated silica), dry silica (anhydrous silica), colloidal silica, precipitated silica, calcium silicate, and aluminum silicate. Of these, wet silica is particularly preferred from the viewpoint of improving fracture properties and achieving both grip and low rolling resistance. Using highly dispersible silica is also preferred from the viewpoint of improving dispersibility in the polymer composition and improving physical properties and processability. Silica can be used alone or in combination of two or more types.

[0117] The silica content (total amount if two or more types are included) 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, based on 100 parts by mass of the total mass of the rubber components contained in the polymer composition.

[0118] The silica used is manufactured by Tosoh Silica Co., Ltd., under the product name "Nipsil AQ" (BET specific surface area = 205 m²). 2 / g), "Nipsil KQ"; manufactured by Solvay, product name "ZEOSIL 1115MP" (BET specific surface area = 115m²) 2 / g), product name "ZEOSIL 1165MP" (BET specific surface area = 160m 2 / g), product name "ZEOSIL Premium 200MP" (BET specific surface area = 220m 2 / g); Manufactured by Evonik, product name "UltraZil 360" (BET specific surface area = 50m²) 2 ( / g), Product name "Ultrazil VN3" (BET specific surface area = 175m²) 2Commercially available products such as "7000GR", "9000GR", and "9100GR" (per g) can be used.

[0119] Examples of carbon black include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited. The carbon black content (total amount if two or more types are included) 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, based on 100 parts by mass of the total mass of rubber components contained in the polymer composition.

[0120] Furthermore, in addition to silica and carbon black as fillers, the polymer composition according to this 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, or organic fibers such as nylon and polyester). nM 2 ·mSiO k • iH2O (1) (In formula (1), M 2 (where n is an integer from 1 to 5, m is an integer from 0 to 10, k is an integer from 2 to 10, and i is an integer from 0 to 10.)

[0121] Specific examples of inorganic compounds (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.); and compounds in which the specific metal is magnesium, such as magnesium oxide, magnesium hydroxide, magnesium silicate, calcium magnesium silicate (CaMgSiO4), and talc; Examples of compounds in which the metal is titanium include titanium oxide, for example; examples of compounds in which the specific metal is calcium include calcium oxide, calcium hydroxide, calcium silicate, calcium carbonate, for example; and examples of compounds in which the specific metal is zirconium include zirconium oxide, zirconium hydroxide, zirconium silicate, zirconium carbonate, for example.

[0122] The proportion of fillers in the polymer composition according to this embodiment (total amount if two or more types are included) 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, based on 100 parts by mass of the total mass of rubber components contained in the polymer composition.

[0123] 1.3.4. Crosslinking Agents The polymer composition according to this embodiment may contain a crosslinking agent. Examples of crosslinking agents include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyvalent amine compounds, and alkylphenol resins having methylol groups, with sulfur being commonly used. The content of the crosslinking agent is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, based on 100 parts by mass of the total mass of the rubber components contained in the polymer composition.

[0124] 1.3.5. Silane coupling agents When silica is included in a polymer composition, the dispersibility of silica can be further enhanced by including a silane coupling agent in the polymer composition together with the silica. The silane coupling agent is not particularly limited, but a sulfur-containing silane coupling agent is preferred. Examples of sulfur-containing silane coupling agents include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropylbenzothiazoletetrasulfide, γ-mercaptopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, and (3-[ethoxybis(3,6,9,12,15-pentaoxacosan-1-yloxy)silyl]-1-propanethol.

[0125] The preferred content of the silane coupling agent is 1 to 20 parts by mass per 100 parts by mass of silica. By including 1 part by mass or more of the silane coupling agent, a sufficient improvement in the dispersibility of silica can be obtained. Furthermore, by including 20 parts by mass or less of the silane coupling agent, a decrease in the processability of the polymer composition can be suppressed, as can a decrease in the elongation at break of the crosslinked body obtained from the polymer composition. A more preferable content of the silane coupling agent is 5 to 15 parts by mass per 100 parts by mass of silica. The silane coupling agent may be used alone or in combination of two or more types.

[0126] 1.3.6. Other Additives In addition to the components described above, the polymer composition according to this embodiment may also contain various additives commonly used to manufacture crosslinked materials such as tires, such as antioxidants, zinc oxide, stearic acid, softeners, vulcanization accelerators, compatibilizers, vulcanization aids, processing aids, and scorch inhibitors. The proportion 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. Tires A tire according to one embodiment of the present invention uses a cured product of the above-mentioned polymer composition as the tread. In this embodiment, the tire is made by kneading a copolymer (A), a conjugated diene polymer (B), and other components as needed using a kneader such as an open-type kneader (e.g., a roll kneader) or a closed-type kneader (e.g., a Banbury mixer) to form a sheet, A tire can be obtained as a tread rubber by placing it in a predetermined position according to a conventional method and vulcanizing it. In addition, in this embodiment, a tire can be obtained as a tread rubber by mixing and kneading the above-mentioned polymer composition Q with a filler and various additives optionally used to obtain a crosslinked body (i.e., vulcanized rubber), forming it into a sheet, and then placing it in a predetermined position according to a conventional method and vulcanizing it.

[0128] The polymer composition described above makes it possible to manufacture tires that have excellent grip performance (braking performance) on wet road surfaces, low fuel consumption, and good wear resistance. Therefore, the polymer composition described above is suitable as a material for tire treads.

[0129] 3. Examples The following describes specific embodiments of the present invention, but the present invention is not limited to these embodiments. In the following manufacturing examples, examples, and comparative examples, "%" refers to mass unless otherwise specified.

[0130] 3.1. Production of copolymer (A) [Production Example 1-1: Synthesis of Copolymer (A-1)] A copolymer (A-1) dispersion was obtained by the following one-step polymerization. In a 7 L reactor, 520 parts by mass of water, a monomer mixture consisting of 29 parts by mass of 1,3-butadiene (BD), 20 parts by mass of 2-hydroxyethyl methacrylate (HEMA), and 51 parts by mass of styrene (ST) was added, along with 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 reactor was thoroughly purged with nitrogen. 0.02 parts by mass of cumene hydroperoxide, 0.01 parts by mass of tetrasodium ethylenediaminetetraacetate, 0.006 parts by mass of iron(II) sulfate heptahydrate, and 0.03 parts by mass of sodium formaldehyde sulfoxylate were charged as polymerization initiators, and polymerization was carried out at 15°C for 10 hours with stirring to obtain a copolymer (A-1) dispersion. The polymerization conversion rate at this time was 70%. The polymer dispersion was dried with hot air to obtain solid copolymer (A-1). For the obtained copolymer (A-1), 400 MHz 1 Table 1 below shows the composition ratio of structural units calculated by 1H-NMR measurement and the weight-average molecular weight measured by the following method.

[0131] [Material 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. (Measurement conditions) • Measuring instrument: GPC (model number: HLC-8220) manufactured by Tosoh Corporation • 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 the eluent so that its solid content was approximately 0.3% by mass, and measured after filtration.

[0132] [Production Examples 1-2 to 1-11: Synthesis of Copolymer (A-2) to Copolymer (A-11)] Polymerization was carried out in the same manner as in Production Example 1-1, except that the type and amount of raw materials were changed, to obtain dispersions of copolymers (A-2) to (A-11). The composition and physical properties of copolymers (A-2) to (A-11) are shown in Table 1 below.

[0133] [Table 1]

[0134] The details of each component in Table 1 above are as follows: <Aromatic vinyl compounds> ·ST: Styrene VT: Vinyltoluene <Conjugated diene compounds> BD: 1,3-butadiene • IP: Isoprene <Unsaturated carboxylic acid esters containing hydroxyl groups> HEMA:2-hydroxyethyl methacrylate • HEA: 2-hydroxyethyl acrylate <Unsaturated carboxylic acids> • MAA: Methacrylic acid AA: Acrylic acid TA: Itaconic acid <(meth)acrylamide> · AAM: Acrylamide • MAM: Methacrylamide <Compounds containing a sulfonic acid group> • NaSS: Sodium styrene sulfonate VS: Vinyl sulfonic acid <Compounds containing polyalkylene glycol groups> • PME-200: Methoxypolyethylene glycol methacrylate, trade name "Bremmer (registered trademark) PME-200", manufactured by NOF Corporation. • AE-400: Polyethylene glycol monoacrylate, product name "Bremmer (registered trademark) AE-400", manufactured by NOF Corporation. <Chain movement agent> • Chain transfer agent 1: n-hexyl mercaptan • Chain transfer agent 2: n-dodecyl mercaptan • Chain transfer agent 3: Diisopropylxanthogen disulfide • Chain transfer agent 4: Tetramethylthiuram disulfide • Chain transfer agent 5: α-methylstyrene dimer

[0135] 3.2. Production of conjugated diene polymer (B) [Production Example 2-1: Synthesis of Conjugated Diene Polymer (B-1)] 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 were charged into a nitrogen-purged autoclave reactor with an internal volume of 5 liters. After adjusting the temperature of the reactor contents to 40°C, 0.44 g of n-butyllithium was added as a polymerization initiator to start polymerization. After the reaction rate exceeded 80%, 50 g of 1,3-butadiene was added. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 90°C. Subsequently, 2.08 g of 3-(N,N-bistrimethylsilyl)aminopropylmethyldiethoxysilane (M-1) was added as a terminal modifier and stirred for 10 minutes. To the stirred polymer solution, 4.40 g of 2,6-di-tert-butyl-p-cresol was added as an antioxidant to obtain a polymer solution containing the modified conjugated diene polymer (B-1) and the antioxidant (hereinafter referred to as "polymer solution SB-1"). This polymer solution was desolvated by steam stripping and dried using a hot roller heated to 130°C to obtain a solid of the conjugated diene polymer (B-1). The composition and physical properties of the obtained conjugated diene polymer (B-1) were measured. The results are shown in Table 2 below.

[0136] [Material property evaluation] (1) Bound styrene content (%) Using deuterated chloroform as the solvent, at 400 MHz 1 This was calculated from 1H-NMR measurements. (2) Vinyl group content (%) 400MHz 1 This was calculated from 1H-NMR measurements. (3) Weight-average molecular weight and molecular weight distribution of the modified polymer A chart (GPC curve) based on the molecular weight in polystyrene equivalent was obtained using gel permeation chromatography (GPC), and the results were determined based on that chart. The specific measurement conditions for GPC are as follows. (Measurement conditions) • Measuring instrument: HLC-8020 (manufactured by Tosoh Corporation) • Columns: Two GMH-HR-H columns (manufactured by Tosoh Corporation) were connected in series. • Detector: Differential refractometer RI-8020 (manufactured by Tosoh Corporation) • Eluent: Tetrahydrofuran Column temperature: 40°C ·Flow rate: 1.0mL / min • Sample concentration: 10 mg / 20 mL (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) • Measuring device: Q1000 Differential Scanning Calorimeter (DSC) (manufactured by TA Instruments) • Heating rate: 10℃ / min

[0137] [Production Example 2-2: Synthesis of conjugated diene polymer (B-2), Production Example 2-3: Synthesis of conjugated diene polymer (B-3)] Polymerization, desolvation, and drying were carried out 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 below, to obtain solid conjugated diene polymer (B-2) and conjugated diene polymer (B-3), respectively. The polymerization formulations and physical properties of conjugated diene polymer (B-2) and conjugated diene polymer (B-3) are shown in Table 2 below.

[0138] [Table 2]

[0139] [Production Example 2-4: Synthesis of Conjugated Diene Polymer (B-4)] In a 50-liter reactor (first reactor), 58 g / min of 1,3-butadiene and 17 g / min of styrene were added as monomers, 750 g / min of cyclohexane as a solvent, and 0.57 g / min of tetrahydrofuran as a vinyl group content adjuster (randomizer). n-butyllithium was continuously charged at a rate of 0.031 g / min as a polymerization initiator, 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 second reactor at a rate of 8 g / min to carry out the reaction. At the outlet of the third reactor, 1,1'-(1,4-phenylene)bis(N-(3-(triethoxysilyl)propyl)methaneimine)(M-2) was continuously charged at a rate of 0.062 g / min as a terminal modifier, followed by the addition of di-tert-butyl-p-cresol at a ratio of 0.88 parts by mass per 100 parts by mass of polymer to obtain a polymer solution containing the modified conjugated diene polymer (B-4). Next, this polymer solution was desolvated by steam stripping and dried using a hot roll heated to 130°C to obtain a solid of the conjugated diene polymer (B-4). The composition and physical properties of the conjugated diene polymer (B-4) are shown in Table 3.

[0140] [Production Example 2-5: Synthesis of Conjugated Diene Polymer (B-5)] Polymerization was carried out in the same manner as in Production Example 2-4, except that the types and amounts of raw materials used were as shown in Table 3 below, to obtain a solid conjugated diene polymer (B-5). The composition and physical properties of the conjugated diene polymer (B-5) are shown in Table 3 below.

[0141] [Table 3]

[0142] The terminal denaturing agents used in Tables 2 and 3 above are as follows: <Terminal denaturing agent> M-1:3-(N,N-bistrimethylsilyl)aminopropylmethyldiethoxysilane M-2: 1,1'-(1,4-phenylene)bis(N-(3-(triethoxysilyl)propyl)methanymine) M-3: 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane

[0143] 3.3. Production of Polymer Composition PA [Polymer composition (PA-1)] A dispersion of polymer (A-2) was added to polymer solution SB-1 in an amount of 40 parts by mass per 100 parts by mass of conjugated diene polymer (B-1), and the mixture was stirred for 5 minutes to obtain a mixed solution. 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 stirred thoroughly to dissolve it. The mixed solution prepared above was then added to the mixture in an amount of 500 g of conjugated diene polymer (B-1), the solvent was removed by steam stripping, and then the mixture was dried using a hot roll heated to 130°C to obtain a solid polymer composition (PA-1) containing copolymer (A-2), conjugated diene polymer (B-1), and an antioxidant.

[0144] [Polymer composition (PA-2)] For polymer composition (PA-2), the same procedure as for polymer composition (PA-1) was followed according to the composition shown in Table 2 below to obtain a solid polymer composition (PA-2) containing copolymer (A-9), conjugated diene polymer (B-2), and antioxidant.

[0145] 3.4. Production of polymer composition PB and crosslinked material [Examples 1-14, Comparative Examples 1-7] Each polymer composition PB was produced by blending the components according to the formulations shown in Tables 4 to 7 below and kneading them together. Kneading was carried out by the following method. Using a batch mixer equipped with a temperature control device (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name "Laboplast Mill"), the first stage of mixing was performed with the temperature set to 100°C, a rotation speed of 60 rpm, and a mixing time of 4 minutes, incorporating all components except the vulcanization accelerator and sulfur. The temperature of the mixed material discharged from the mixer was around 150°C in all cases. Next, in the second stage of mixing, the mixture obtained in the first stage was cooled to room temperature, then a vulcanization accelerator and sulfur were added to the mixer, the temperature was adjusted to 70°C, and the mixture was kneaded at a rotation speed of 60 rpm for a mixing time of 1.5 minutes to obtain polymer composition PB. The temperature of the mixture discharged from the mixer was 100°C or lower in all cases. Next, the obtained polymer composition PB was vulcanized and molded in a vulcanization press at 160°C for a predetermined time to obtain vulcanized rubber as a crosslinked body. The following physical properties were evaluated using the obtained vulcanized rubber. The results are shown in Tables 4 to 7 below.

[0146] [Material property evaluation] (1) Grip performance (tanδ at 0°C, tanδ at 50°C) Using vulcanized rubber as the measurement sample, the loss factor (tanδ(0°C)) was measured using an ARES-RDA (TA Instruments) under the conditions of shear strain 0.14%, angular velocity 100 radians / second, and 0°C. Furthermore, using the same sample and apparatus, the loss factor (tanδ(50°C)) was measured under the conditions of shear strain 3%, angular velocity 100 radians / second, and 50°C. The measurement results are shown as an index with Comparative Example 1 set to 100 in Table 4, Comparative Example 4 in Table 5, and Comparative Example 6 in Table 6. A higher value indicates better wet grip performance and fuel efficiency. Each temperature corresponds to the following physical property indicators. • 0℃ tanδ: Wet grip performance • 50℃ tanδ: Low fuel consumption performance

[0147] (2) Abrasion resistance Cross-linked rubber was used as the measurement sample, and measurements were taken using a DIN abrasion tester (manufactured by Toyo Seiki Co., Ltd.) in accordance with JIS K 6264-2:2005, under a load of 10N at 25°C. In Table 4 below, Comparative Example 1 is set to 100, in Table 5 to 100, and in Table 6 to 100, and Comparative Example 6 is set to 100, with a higher value indicating better abrasion resistance.

[0148] [Table 4]

[0149] [Table 5]

[0150] [Table 6]

[0151] [Example 15] Polymer composition PB was produced by blending each component according to the formulation shown in Table 7 below and kneading the mixture. The kneading was carried out by the following method. Using a batch-type mixer equipped with a temperature control device (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name "Laboplastmill"), for the first stage of mixing, the set temperature was adjusted to 100°C, the rotation speed was 60 rpm, and the mixing time was 4 minutes. A total of 120 parts by mass of the polymer composition (PA-1) obtained above was added, with 20 parts by mass of copolymer (A-2), 50 parts by mass of conjugated diene polymer (B-1), and 50 parts by mass of natural rubber. Further mixing was carried out by adding resin, silica, carbon black, silane coupling agent, drawstring oil, stearic acid, zinc oxide, and antioxidant. The temperature of the mixed material discharged from the mixer was around 150°C in all cases. Next, in the second stage of mixing, the mixture obtained in the first stage was cooled to room temperature, then a vulcanization accelerator and sulfur were added to the mixer, the temperature was adjusted to 70°C, and the mixture was kneaded at a rotation speed of 60 rpm for a mixing time of 1.5 minutes to obtain the polymer composition (PB-28). The temperature of the mixture discharged from the mixer was 100°C or lower in all cases. Next, the obtained polymer composition (PB-28) was vulcanized using a vulcanization press at 160°C for a predetermined time to obtain vulcanized rubber as a crosslinked body. The obtained vulcanized rubber was used to perform the same physical property evaluation as described above. The results are shown in Table 7 below. The evaluation results are expressed as an index with Comparative Example 7 set to 100. A higher value indicates better physical properties.

[0152] [Comparative Example 8] Polymer composition (PB-29) was obtained in the same manner as in Example 15, except that polymer composition (PA-2) was used instead of polymer composition (PA-1) and acrylic resin was used instead of styrene resin, and its physical properties were evaluated in the same manner. The results are shown in Table 7 below. The evaluation results are expressed as an index with Comparative Example 7 set to 100.

[0153] [Table 7]

[0154] The details of each component in Tables 4 to 7 above are as follows: *1) Manufactured by ENEOS Material Co., Ltd., product name "BR01" *2) Natural rubber *3) Manufactured by Solvay, product name "ZEOSIL 1165MP" *4) Manufactured by Mitsubishi Chemical Corporation, product name "Diablack N330" *5) Manufactured by Evonik, product name "Si75" *6) Process oil T-DAE manufactured by ENEOS Corporation. *7) Manufactured by Seiko Chemical Co., Ltd., product name "Ozonon 6C" *8) Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noxellar D" *9) Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noxellar CZ-G"

[0155] From the results in Tables 4 to 7 above, it was found that by producing vulcanized rubber using a polymer composition containing copolymer (A) having 51 to 95% by mass of repeating units (a) derived from aromatic vinyl compounds and 5 to 48% by mass of repeating units (b) derived from conjugated diene compounds, and a weight-average molecular weight of 500 to 10,000 as measured by gel permeation chromatography, and a conjugated diene polymer (B), vulcanized rubber exhibiting good wet grip performance, low fuel consumption performance, and excellent abrasion resistance can be obtained.

[0156] Furthermore, the results in Table 7 above show that when vulcanized rubber is produced using polymer composition PA obtained by pre-mixing copolymer (A) dispersion and conjugated diene polymer (B) solution, vulcanized rubber with improved wet grip performance, fuel efficiency, and abrasion resistance is obtained compared to when vulcanized rubber is produced by kneading each component in a solid state.

[0157] From the above results, it was found that the polymer composition of the present invention can produce vulcanized rubber with excellent wet grip performance, fuel efficiency, and abrasion resistance.

Claims

1. A copolymer (A) having repeating units (a) derived from an aromatic vinyl compound and repeating units (b) derived from a conjugated diene compound, wherein when the total amount of repeating units contained in the copolymer (A) is 100% by mass, it contains 51 to 95% by mass of repeating units (a) derived from the aromatic vinyl compound and 5 to 48% by mass of repeating units (b) derived from the conjugated diene compound, and the weight-average molecular weight measured by gel permeation chromatography is 500 to 10,000. Conjugated diene polymer (B) A polymer composition containing [the specified ingredient].

2. The polymer composition according to claim 1, wherein the copolymer (A) further contains 1 to 35% by mass of repeating units (c) derived from a hydrophilic monomer.

3. The polymer composition according to claim 2, 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, and a polyalkylene glycol group.

4. The polymer composition according to claim 1, wherein the conjugated diene polymer (B) contains repeating units derived from 1,3-butadiene, and the 1,2-vinyl group content in the repeating units derived from 1,3-butadiene is 7 to 70 mol%.

5. The polymer composition according to claim 1, wherein the weight-average molecular weight of the conjugated diene polymer (B), as measured by gel permeation chromatography, is 50,000 to 1,500,000.

6. 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 conjugated diene polymer (B) is 100 parts by mass.

7. The polymer composition according to claim 1, further comprising 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.

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

9. A tire using a cured polymer composition according to any one of claims 1 to 8 as the tread.

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