JP7664038B2 - Polymer composition, crosslinked product and tire - Google Patents

Description

The present invention relates to a polymer composition, a crosslinked body, and a tire.

Conjugated diene polymers such as styrene-butadiene copolymers have good properties such as heat resistance, abrasion resistance, mechanical strength, and moldability, and are therefore widely used in various industrial products such as pneumatic tires, anti-vibration rubber, and hoses. It has also been proposed to obtain high-strength, low-abrasion vulcanized rubber by using hydrogenated conjugated diene polymers in which some of the unsaturated bonds in the conjugated diene polymers have been hydrogenated (see, for example, Patent Document 1).

International Publication No. 2015/064646

In the manufacture of winter tires or all-season tires, polymers with a relatively low glass transition temperature (Tg) are generally used to impart flexibility to vulcanized rubber at low temperatures. In vulcanized rubber obtained using a polymer with a low Tg, there is a trade-off between abrasion resistance and grip performance on ice, and there is a tendency for abrasion resistance to decrease when attempting to impart grip performance on ice to vulcanized rubber obtained using a polymer with a low Tg. In order to develop a rubber material for winter tires or all-season tires that has a good balance between abrasion resistance and grip performance on ice, the present inventors have investigated the use of a hydrogenated conjugated diene polymer that is high in strength and exhibits high abrasion resistance.

However, vulcanized rubber containing hydrogenated conjugated diene polymers tends to have inferior grip performance on ice compared to unhydrogenated conjugated diene polymers with similar Tg. In addition, vulcanized rubber hardens with age, and there is concern that the hardening process will lead to a decline in grip performance on ice.

The present invention was made in consideration of the above problems, and its main objective is to provide a polymer composition that can improve grip performance on ice while maintaining high abrasion resistance, and can produce vulcanized rubber that suppresses increases in hardness over time.

The present inventors have conducted research to solve the above problems. They have found that the above problems can be solved by using a specific conjugated diene polymer in combination with a specific additive. The present invention provides the following means.

［２］ 上記［１］の重合体組成物を用いて得られる架橋体。
［３］ 上記［１］の重合体組成物によりトレッド及びサイドウォールの一方又は両方が形成されたタイヤ。 [1] A polymer composition comprising: (A) a conjugated diene polymer; and (B) at least one thermally expandable component selected from the group consisting of a foaming agent, a thermally expandable capsule, and a thermally expandable graphite, wherein the conjugated diene polymer (A) includes a polymer (A1) which satisfies the condition of the following mathematical formula (i) when the constituent ratios (molar ratios) in the polymer of a structural unit represented by the following formula (1), a structural unit represented by the following formula (2), a structural unit represented by the following formula (3), and a structural unit represented by the following formula (4) are p, q, r, and s, respectively:
Formula (i):
0.75≦(p+(0.5×r))/(p+q+(0.5×r)+s)≦0.97

[2] A crosslinked product obtained by using the polymer composition of [1] above.
[3] A tire having a tread and/or a sidewall formed from the polymer composition according to [1] above.

According to the present invention, it is possible to obtain vulcanized rubber that has improved grip performance on ice while maintaining high abrasion resistance. Furthermore, the vulcanized rubber is inhibited from increasing in hardness over time, and is able to maintain excellent grip performance on ice. In other words, according to the present invention, it is possible to obtain vulcanized rubber that is highly balanced in terms of abrasion resistance and grip performance on ice.

<Polymer composition>
The polymer composition of the present invention (hereinafter also simply referred to as "the composition") contains (A) a conjugated diene-based polymer and (B) a thermally expandable component (hereinafter also referred to as "thermally expandable component (B)") which is at least one selected from the group consisting of a foaming agent, a thermally expandable capsule, and a thermally expandable graphite. Each component contained in the composition and components blended as necessary will be described below. In this specification, a numerical range described using "to" means that the numerical values before and after "to" are included as the lower and upper limits.

<(A) Conjugated Diene Polymer>
The present composition contains, as a conjugated diene polymer, a polymer (hereinafter also referred to as “polymer (A1)”) that satisfies the condition of the following mathematical formula (i), where p, q, r, and s are the constituent ratios (molar ratios) in the polymer of a structural unit represented by the following formula (1), a structural unit represented by the following formula (2), a structural unit represented by the following formula (3), and a structural unit represented by the following formula (4), respectively.
Formula (i):
0.75≦(p+(0.5×r))/(p+q+(0.5×r)+s)≦0.97

As the (A1) polymer, a hydrogenated product of a polymer having a structural unit derived from a conjugated diene compound can be used. The (A1) polymer as a hydrogenated product can be produced by first polymerizing a monomer containing a conjugated diene compound to obtain an unhydrogenated conjugated diene polymer, and then subjecting the obtained polymer to a hydrogenation reaction.

As the conjugated diene compound constituting the (A1) polymer, 1,3-butadiene can be preferably used. In addition to 1,3-butadiene, conjugated diene compounds other than 1,3-butadiene may be used in the polymerization to obtain the (A1) polymer. Specific examples of conjugated diene compounds other than 1,3-butadiene include isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. Of these, isoprene is preferred as the conjugated diene compound other than 1,3-butadiene. Note that as the conjugated diene compound, one type of compound may be used alone, or two or more types of compounds may be used in combination.

The polymer (A1) is preferably a copolymer of a conjugated diene compound and an aromatic vinyl compound, from the viewpoint of increasing the strength of the crosslinked body obtained using the present composition. Examples of aromatic vinyl compounds used in the polymerization include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, N,N-dimethylaminoethylstyrene, and diphenylethylene. Among these, it is particularly preferable that the aromatic vinyl compound is at least one of styrene and α-methylstyrene. The aromatic vinyl compounds may be used alone or in combination of two or more.

When the (A1) polymer is a copolymer of a conjugated diene compound and an aromatic vinyl compound, it is preferably a copolymer of 1,3-butadiene and styrene, because it has high living properties in anionic polymerization. In order to improve the dispersibility of the filler blended in the polymer composition, it is preferable that the (A1) polymer is a random copolymer in which the distribution of the conjugated diene compound and the aromatic vinyl compound is irregular. The random copolymer of the conjugated diene compound and the aromatic vinyl compound may further have a block portion made of the conjugated diene compound or the aromatic vinyl compound, as long as the effects of the present invention are obtained.

In the copolymer of a conjugated diene compound and an aromatic vinyl compound, the content of structural units derived from the aromatic vinyl compound is preferably 3 to 45 mass% based on the total amount of monomer units constituting the copolymer, from the viewpoint of improving the strength, abrasion resistance, and low hysteresis loss properties of the crosslinked body obtained using the composition, as well as improving grip performance on ice. The content of structural units derived from the aromatic vinyl compound is more preferably 4 mass% or more, and even more preferably 5 mass% or more, based on the total amount of monomer units constituting the copolymer.

The content of the structural units derived from aromatic vinyl compounds is more preferably 40% by mass or less, even more preferably 35% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less, based on the total amount of monomer units constituting the copolymer, in order to sufficiently improve grip performance on ice. By setting the content of aromatic vinyl compound units within the above range, it is possible to achieve both productivity, strength, and abrasion resistance. The (A1) polymer preferably contains 50 to 97% by mass of 1,3-butadiene units, 3 to 45% by mass of aromatic vinyl compound units, and 0 to 30% by mass of conjugated diene compound units other than 1,3-butadiene, based on 100% by mass of the total amount of monomer units constituting the (A1) polymer. This blending ratio is advantageous in that it maintains high strength and abrasion resistance of the crosslinked body while improving grip performance on ice in a well-balanced manner.

The conjugated diene compounds and aromatic vinyl compounds exemplified above all have the same effect in that they can produce a conjugated diene polymer having an active end. Therefore, even if a compound is not described in the examples below, it can be used in the present invention.

In the polymerization, other monomers than the conjugated diene compound and the aromatic vinyl compound can be used. Examples of other monomers include acrylonitrile, methyl (meth)acrylate, and ethyl (meth)acrylate. The content of structural units derived from other monomers is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on the total amount of monomers constituting the (A1) polymer.

As the polymerization method for obtaining the (A1) polymer, any of solution polymerization, gas phase polymerization, and bulk polymerization may be used, but solution polymerization is particularly preferred. Furthermore, as the polymerization format, any of batch and continuous methods may be used. When using the solution polymerization method, a specific example of the polymerization method is a method in which a monomer containing a conjugated diene compound is polymerized in an organic solvent in the presence of a polymerization initiator and a randomizer that is used as needed.

As the polymerization initiator, at least one of an alkali metal compound and an alkaline earth metal compound can be used. As the alkali metal compound and the alkaline earth metal compound, those usually used as initiators for anionic polymerization can be used. Specific examples of the polymerization initiator include methyl lithium, ethyl lithium, n-propyl lithium, n-butyl lithium, sec-butyl lithium, t-butyl lithium, 1,4-dilithiobutane, phenyl lithium, stilbene lithium, naphthyl lithium, naphthyl sodium, naphthyl potassium, di-n-butyl magnesium, di-n-hexyl magnesium, ethoxy potassium, calcium stearate, and the like. Among these, lithium compounds can be preferably used as the polymerization initiator.

The polymerization reaction may be carried out in the presence of a compound (hereinafter also referred to as "initiation modifier") obtained by mixing at least one of the above-mentioned alkali metal compounds and alkaline earth metal compounds with a compound having a functional group that interacts with silica. By carrying out the polymerization in the presence of the initiation modifier, a functional group that interacts with silica can be introduced to the polymerization initiation terminal of the (A1) polymer. In addition, by introducing a functional group that interacts with silica to the initiation terminal of the (A1) polymer, it is advantageous in that the low hysteresis loss performance (low fuel consumption performance) of the vulcanized rubber can be improved.

In this specification, "interaction" means forming a covalent bond between molecules or forming an intermolecular force weaker than a covalent bond (for example, an electromagnetic force acting between molecules such as an ion-dipole interaction, a dipole-dipole interaction, a hydrogen bond, or a van der Waals force). A "functional group that interacts with silica" is a group having at least one atom that interacts with silica (for example, a nitrogen atom, a sulfur atom, a phosphorus atom, an oxygen atom, a silicon atom, etc.). The silicon atom in the "functional group that interacts with silica" is a silicon atom in a hydrocarbyloxysilyl group.

As the initiating modifier, a reaction product of a lithium compound such as an alkyl lithium with a nitrogen-containing compound such as a secondary amine compound can be used. Examples of the nitrogen-containing compound include dimethylamine, diethylamine, dipropylamine, dibutylamine, dodecamethyleneimine, N,N'-dimethyl-N'-trimethylsilyl-1,6-diaminohexane, piperidine, pyrrolidine, hexamethyleneimine, heptamethyleneimine, dicyclohexylamine, N-methylbenzylamine, di-(2-ethylhexyl)amine, diallylamine, morpholine, N-(trimethylsilyl)piperazine, N-(tert-butyldimethylsilyl)piperazine, 1,3-ditrimethylsilyl-1,3,5-triazinane, etc.

When polymerization is carried out in the presence of an initiating modifier, an alkali metal compound or an alkaline earth metal compound may be mixed with a nitrogen-containing compound in advance to prepare the initiating modifier, and the prepared modifier may be added to the polymerization system to carry out polymerization. Alternatively, an alkali metal compound or an alkaline earth metal compound and a nitrogen-containing compound may be added to the polymerization system, and the two may be mixed in the polymerization system to prepare an initiating modifier, and then polymerization may be carried out.

The randomizer can be used for the purpose of adjusting the content of 1,2-vinyl bonds (vinyl content) in the polymer obtained by the above polymerization. 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. The randomizer can be used alone or in combination of two or more.

The organic solvent used in the polymerization may be any organic solvent that is inert to the reaction, and may be, for example, an aliphatic hydrocarbon, an alicyclic hydrocarbon, or an aromatic hydrocarbon. Among these, hydrocarbons having 3 to 8 carbon atoms are preferred, and specific examples thereof include n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis-2-butene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene, n-heptane, cyclopentane, methylcyclopentane, methylcyclohexane, 1-pentene, 2-pentene, and cyclohexene. The organic solvent may be used alone or in combination of two or more.

When solution polymerization is used, 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 temperature of the polymerization reaction is preferably -20 to 150°C, more preferably 0 to 120°C, and particularly preferably 20 to 100°C. In addition, the polymerization reaction is preferably carried out under a pressure sufficient to keep the monomer substantially in a liquid phase. Such a pressure can be obtained by a method such as pressurizing the inside of a reactor with a gas inert to the polymerization reaction.

The 1,2-vinyl content (vinyl content) of the conjugated diene polymer obtained by the above polymerization is preferably 5 to 70 mol%. When the vinyl content is 5 mol% or more, the grip properties tend to be good, and when it is 70 mol% or less, the abrasion resistance tends to be good. From this viewpoint, the vinyl content is more preferably 10 mol% or more, and even more preferably 15 mol% or more. Moreover, the vinyl content is more preferably 60 mol% or less, and even more preferably 50 mol% or less. The vinyl content is a value measured by ^{a 1} H-NMR device.

The above polymerization can produce a conjugated diene polymer having an active end. When terminating the polymerization, the polymer having an active end may be reacted with alcohol or hydrogen, or may be reacted with a compound having a functional group that interacts with silica (hereinafter also referred to as a "terminal modifier") or a coupling agent. By reacting a conjugated diene polymer having an active end with a terminal modifier, a modified conjugated diene polymer in which the polymerization termination end is modified with a functional group that interacts with silica can be obtained as the (A1) polymer. In addition, by using a polymer in which a functional group that interacts with silica is introduced into the polymerization end as the (A1) polymer, it is preferable in that low hysteresis loss performance can be improved. In particular, it is preferable that the (A1) polymer has at least one functional group selected from the group consisting of an amino group, a nitrogen-containing heterocyclic group, a phosphino group, a hydroxyl group, a thiol group, and a hydrocarbyloxysilyl group. In this specification, the "active end" means a portion (more specifically, a metal end) other than the structure derived from a monomer having a carbon-carbon double bond that is present at the end of the molecular chain.

The terminal modifier is not particularly limited as long as it has a functional group that interacts with silica and can react with the active terminal of the conjugated diene polymer. As the terminal modifier, a compound having one atom selected from the group consisting of a nitrogen atom, a sulfur atom, a phosphorus atom, an oxygen atom, and a silicon atom, and having no active hydrogen bonded to the atom, can be preferably used. In particular, the terminal modifier is preferably a compound having one or more functional groups selected from the group consisting of an amino group, a group having a carbon-nitrogen double bond, a nitrogen-containing heterocyclic group, a phosphino group, a cyclic ether group, a cyclic thioether group, a protected hydroxyl group, a protected thiol group, and a hydrocarbyloxysilyl group, and capable of reacting with the polymerization active terminal. The amino group is preferably a protected primary amino group, a secondary amino group, or a tertiary amino group.

（式（５）中、Ａ^１は、窒素、リン、酸素、硫黄及びケイ素よりなる群から選択される少なくとも１種の原子を有し、活性水素を有さず、かつＲ^５に対して窒素原子、リン原子、酸素原子、硫黄原子、ケイ素原子、若しくはカルボニル基に含まれる炭素原子で結合する１価の官能基であるか、又は（チオ）エポキシ基である。Ｒ^３及びＲ^４は、それぞれ独立して、ヒドロカルビル基である。Ｒ^５は、ヒドロカルビレン基である。ｒは、０～２の整数である。ただし、ｒが２の場合、式中の複数のＲ^３は、互いに同一の基又は異なる基である。ｒが０又は１の場合、式中の複数のＲ^４は、互いに同一の基又は異なる基である。）

（式（６）中、Ａ^２は、窒素、リン、酸素、硫黄及びケイ素よりなる群から選択される少なくとも１種の原子を有し、活性水素を有さず、かつＲ^９に対して窒素原子、リン原子、酸素原子、硫黄原子若しくはケイ素原子で結合する１価の官能基であるか、又は炭素数１～２０のヒドロカルビル基である。Ｒ^６及びＲ^７は、それぞれ独立して、ヒドロカルビル基である。Ｒ^８は、ヒドロカルビレン基である。Ｒ^９は、単結合又はヒドロカルビレン基である。ｍは０又は１である。ただし、ｍが０の場合、式中の複数のＲ^７は、互いに同一の基又は異なる基である。） As the terminal modifying agent, at least one selected from the group consisting of compounds represented by the following formula (5) and compounds represented by the following formula (6) can be preferably used.

(In formula (5), A ¹ is a monovalent functional group having at least one atom selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, having no active hydrogen, and bonded to R ⁵ via a nitrogen atom, a phosphorus atom, an oxygen atom, a sulfur atom, a silicon atom, or a carbon atom contained in a carbonyl group, or is a (thio)epoxy group. ^{R 3} and R ⁴ are each independently a hydrocarbyl group. R ⁵ is a hydrocarbylene group. r is an integer of 0 to 2. However, when r is 2, multiple R ^3s in the formula are the same group or different groups. When r is 0 or 1, multiple R ^4s in the formula are the same group or different groups.)

(In formula (6), ^A2 is a monovalent functional group having at least one atom selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, having no active hydrogen, and bonded to ^R9 via a nitrogen atom, phosphorus atom, oxygen atom, sulfur atom, or silicon atom, or a hydrocarbyl group having 1 to 20 carbon atoms. ^R6 and ^R7 are each independently a hydrocarbyl group. ^R8 is a hydrocarbylene group. ^R9 is a single bond or a hydrocarbylene group. m is 0 or 1. However, when m is 0, the multiple ^R7s in the formula are the same group or different groups.)

In the above formulas (5) and (6), with respect to R ³ , R ⁴ , R ⁶ , R ⁷ , and A ² when it is a hydrocarbyl group, the hydrocarbyl group is preferably a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms.
The hydrocarbylene group of ^R5 and ^R9 is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms. The hydrocarbylene group of ^R8 is preferably a linear or branched alkanediyl group having 1 to 20 carbon atoms.
In order to enhance the reactivity with the conjugated diene polymer, r is preferably 0 or 1.
When A ¹ is the monovalent functional group, at least one atom selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon contained in A ¹ may be protected with a protective group (e.g., a tri-substituted hydrocarbylsilyl group, etc.). When A ² is the monovalent functional group, at least one atom selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon contained in A ² may be protected with a protective group (e.g., a tri-substituted hydrocarbylsilyl group, etc.). In this specification, active hydrogen refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably refers to one having a bond energy lower than that of the carbon-hydrogen bond of polymethylene. The protective group is a functional group that converts A ¹ and A ² into functional groups that are inactive against the polymerization active terminal. The (thio)epoxy group means an epoxy group and a thioepoxy group.

A ¹ may be a group that can be turned into an onium ion by an onium salt generating agent. The terminal modifying agent has such a group (A ¹ ), and thus can impart excellent shape retention to the polymer (A1). Specific examples of ^{A 1} include, for example, a nitrogen-containing group in which two hydrogen atoms of a primary amino group are replaced by two protective groups, a nitrogen-containing group in which one hydrogen atom of a secondary amino group is replaced by one protective group, a tertiary amino group, an imino group, a pyridyl group, a phosphorus-containing group in which two hydrogen atoms of a primary phosphino group are replaced by two protective groups, a phosphorus-containing group in which one hydrogen atom of a secondary phosphino group is replaced by one protective group, a tertiary phosphino group, an epoxy group, a thioepoxy group, a group in which the hydrogen atom of a hydroxyl group is replaced by a protective group, a sulfur-containing group in which the hydrogen atom of a thiol group is replaced by a protective group, and a hydrocarbyloxycarbonyl group. Among these, a group having a nitrogen atom is preferable because of its good affinity with silica, and a nitrogen-containing group in which two hydrogen atoms of a tertiary amino group or a primary amino group are substituted with two protecting groups is more preferable.

Specific examples of terminal modifiers include compounds represented by the above formula (5), such as N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N,N-dimethyl-3-(triethoxysilyl)propylamine, 3-(4-trimethylsilyl-1-piperazino)propylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropyltriethoxysilane.

Specific examples of the compound represented by the above formula (6) include, for example, 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1,2-azasilolidine, 2,2-diethoxy-1-(3-trimethoxysilylpropyl)-1,2-azasilolidine, 2,2-dimethoxy-1-phenyl-1,2-azasilolidine, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, 2-(2,2-dimethoxy-1,2-azasilolidine-1-yl)-N,N-diethylethane-1-amine, 2-(2,2-dimethoxy-1,2-azasilolidine-1-yl)-N,N-dimethylethane-1-amine, and 3-(2,2-dimethoxy-1,2-azasilolidine-1-yl)-N,N-diethylpropane-1-amine. The terminal modifying agent may be used alone or in combination of two or more.

The above-mentioned terminal modification reaction can be carried out, for example, 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 the conjugated diene polymer contained in the solution may be isolated and dissolved in an appropriate solvent such as cyclohexane before the reaction. The terminal modification reaction may be carried out either batchwise or continuously. In this case, the method of adding the terminal modifier is not particularly limited, and examples of the method include a method of adding the terminal modifier all at once, a method of adding the terminal modifier in portions, and a method of adding the terminal modifier continuously.

The amount of the terminal modification agent used may be appropriately set according to the type of compound used in the reaction, but is preferably 0.1 molar equivalent or more, more preferably 0.3 molar equivalent or more, relative to the metal atom of the polymerization initiator involved in the polymerization reaction. By using an amount of the terminal modification agent of 0.1 molar equivalent or more, the modification reaction can be sufficiently advanced, and the dispersibility of the inorganic filler can be suitably improved. The reaction temperature during terminal modification is usually the same as the temperature of the polymerization reaction, and is preferably -20 to 150°C, more preferably 0 to 120°C, and particularly preferably 20 to 100°C. If the temperature of the modification reaction is low, the viscosity of the polymer solution tends to increase. Also, if the temperature of the modification reaction is high, the polymerization active terminals are easily deactivated. The reaction time during terminal modification is preferably 1 minute to 5 hours, more preferably 2 minutes to 1 hour.

For the purpose of adjusting the Mooney viscosity of the (A1) polymer, a coupling agent such as silicon tetrachloride or a polyfunctional epoxy compound (e.g., tetraglycidyl-1,3-bisaminomethylcyclohexane) may be reacted with the conjugated diene polymer having an active terminal before or after the modification reaction using the terminal modifier, or simultaneously with the modification reaction using the terminal modifier. The amount of the coupling agent used can be appropriately set depending on the desired Mooney viscosity of the (A1) polymer and the compounds used in the reaction, but it is preferable to use 0.01 to 0.8 molar equivalents relative to the metal atoms of the polymerization initiator that participate in the polymerization reaction. The coupling agent may be used alone or in combination of two or more.

The modified or unmodified conjugated diene polymer obtained above can be hydrogenated to obtain the polymer (A1). The hydrogenation reaction method and conditions may be any method and conditions that can obtain a conjugated diene polymer with the desired hydrogenation rate (hydrogenation rate). Examples of hydrogenation methods include a method using a catalyst mainly composed of an organometallic compound of titanium as a hydrogenation catalyst, a method using a catalyst composed of an organic compound of iron, nickel, or cobalt and an organometallic compound such as an alkylaluminum, a method using an organic complex of an organometallic compound such as ruthenium or rhodium, and a method using a catalyst in which a metal such as palladium, platinum, ruthenium, cobalt, or nickel is supported on a carrier such as carbon, silica, or alumina. Among the various methods, a method in which a titanium organometallic compound alone or a homogeneous catalyst composed of a titanium organometallic compound and an organometallic compound of lithium, magnesium, or aluminum (JP-B-63-4841, JP-B-1-37970) is used to hydrogenate the polymer under mild conditions of low pressure and low temperature is industrially preferred. It also has high hydrogenation selectivity to the double bonds of butadiene, making it suitable for the purposes of the present invention.

Hydrogenation of the conjugated diene polymer is carried out in a solvent that is inactive to the catalyst and in which the conjugated diene polymer is soluble. Preferred solvents include aliphatic hydrocarbons such as n-pentane, n-hexane, and n-octane; alicyclic hydrocarbons such as cyclohexane and cycloheptane; aromatic hydrocarbons such as benzene and toluene; and ethers such as diethyl ether and tetrahydrofuran, either alone or as a mixture containing these as the main components.

The hydrogenation reaction is generally carried out by maintaining the conjugated diene polymer at a predetermined temperature in a hydrogen or inert atmosphere, adding a hydrogenation catalyst with or without stirring, and then introducing hydrogen gas to pressurize to a predetermined pressure. An inert atmosphere means an atmosphere that does not react with the participants in the hydrogenation reaction, and examples of such an atmosphere include helium, neon, and argon. Air and oxygen are not preferred because they oxidize the catalyst and cause it to become inactive. Nitrogen is also not preferred because it acts as a catalyst poison during the hydrogenation reaction and reduces the hydrogenation activity. In particular, it is most preferable that the hydrogenation reactor be filled with an atmosphere of hydrogen gas alone.

The hydrogenation reaction process for obtaining a hydrogenated conjugated diene polymer can be a batch process, a continuous process, or a combination of both. When a titanocene diaryl compound is used as the hydrogenation catalyst, it may be added to the reaction solution alone or as a solution in an inert organic solvent. When the catalyst is used as a solution, the inert organic solvent used can be any solvent that does not react with the participants in the hydrogenation reaction. Preferably, the inert organic solvent used is the same solvent as that used in the hydrogenation reaction. The amount of catalyst added is 0.02 to 20 mmol per 100 g of the conjugated diene polymer before hydrogenation.

The polymer (A1) is a conjugated diene-based polymer that satisfies the above formula (i). That is, the polymer (A1) has a value (hereinafter also referred to as "value θ") defined by the following formula (ii) of 0.75 or more and 0.97 or less. By making θ 0.75 or more, a crosslinked body having sufficiently high abrasion resistance and sufficiently suppressed hardness change due to heat aging can be obtained. For these reasons, θ is preferably 0.78 or more, more preferably 0.80 or more, and even more preferably 0.85 or more. In addition, θ is 0.97 or less, preferably 0.95 or less, from the viewpoint of sufficiently carrying out the crosslinking reaction.
Formula (ii):
θ=(p+(0.5×r))/(p+q+(0.5×r)+s)

The value θ defined by the above formula (ii) corresponds to the hydrogenation rate of the polymer (A1). For example, when θ is 0.75, the hydrogenation rate of the polymer (A1) is 75%. When θ is 0.97, the hydrogenation rate of the polymer (A1) is 97%. The hydrogenation rate in the polymer can be adjusted, for example, by adjusting the time of the hydrogenation reaction to control the cumulative amount of hydrogen supplied. In this specification, the hydrogenation rate is a value measured by ^{a 1} H-NMR device.

The preferred method for obtaining polymer (A1) is to solution polymerize a monomer containing 1,3-butadiene in the presence of an alkali metal compound, and then use the resulting polymer solution as is to carry out a terminal modification reaction, followed by a hydrogenation reaction. This method is also useful industrially. In this case, polymer (A1) can be obtained by removing the solvent from the solution obtained above and isolating the polymer. The isolation of the polymer can be carried out by a known method for removing the solvent, such as steam stripping, and a drying operation such as heat treatment.

The weight average molecular weight (Mw) of the polymer (A1) is preferably 1.0×10 ⁵ to 2.0×10 ^6. When the Mw is 1.0×10 ⁵ or more, the abrasion resistance and fuel economy of the crosslinked body obtained can be sufficiently increased. In addition, when the weight average molecular weight is 2.0×10 ⁶ or less, it is preferable in that the processability of the present composition can be improved. The weight average molecular weight of the polymer (A1) is more preferably 1.1×10 ⁵ or more, and even more preferably 1.2×10 ⁵ or more. In addition, the weight average molecular weight of the polymer (A1) is more preferably 1.5×10 ⁶ or less, and even more preferably 1.2×10 ⁶ or less. In this specification, the weight average molecular weight of the polymer is a polystyrene equivalent value measured by gel permeation chromatography (hereinafter also referred to as "GPC"), and represents the weight average molecular weight by all peaks (total weight average molecular weight).

From the viewpoint of obtaining a crosslinked product with excellent grip performance on ice, the glass transition temperature (Tg) of the (A1) polymer is preferably -20°C or lower, more preferably -30°C or lower, even more preferably -35°C or lower, even more preferably -40°C or lower, and particularly preferably -45°C or lower. Furthermore, from the viewpoint of obtaining a crosslinked rubber with high strength and high abrasion resistance, the Tg of the (A1) polymer is preferably -70°C or higher. In this specification, the Tg of the polymer is a value measured by a differential scanning calorimetry (DSC) device in accordance with ASTM D3418.

The composition may contain only the (A1) polymer as the (A) conjugated diene polymer, but may further contain a polymer different from the (A1) polymer, preferably a non-hydrogenated conjugated diene polymer (hereinafter also referred to as the "(A2) polymer"). Examples of the (A2) polymer include natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR; for example, high cis BR having 90% or more cis-1,4 bonds, BR containing syndiotactic-1,2-polybutadiene (SPB), etc.), isoprene rubber (IR), styrene isoprene copolymer rubber, butadiene isoprene copolymer rubber, etc. Of these, the (A2) polymer is preferably NR, BR, or SBR.

The (A2) polymer can be produced by the same method as that described for the (A1) polymer, except that no hydrogenation reaction is performed in the production method for the (A1) polymer. The description of the (A1) polymer can be used for the preferred ranges of the monomer units constituting the (A2) polymer, and the weight average molecular weight, aromatic vinyl compound unit content, vinyl content, glass transition temperature, and other physical property values of the (A2) polymer.

From the viewpoint of obtaining a crosslinked body having excellent strength and abrasion resistance, the content of the (A1) polymer in the composition is preferably 50% by mass or more based on the total amount of the (A) conjugated diene polymer contained in the composition. From the above viewpoint, the content of the (A1) polymer is more preferably 60% by mass or more based on the total amount of the (A) conjugated diene polymer, more preferably 70% by mass or more, and even more preferably 80% by mass or more. In addition, the content of the (A1) polymer is preferably 30% by mass or more based on the total amount of the rubber component contained in the polymer composition, more preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more. As the (A) conjugated diene polymer, one type can be used alone or two or more types can be used in combination.

In this specification, the "rubber component" contained in the polymer composition refers to a polymer that can be thermally cured to obtain a cured product that exhibits rubber elasticity. The cured product exhibits the property of undergoing large deformation with a small force at room temperature (for example, deformation that stretches to more than twice its original size when stretched at room temperature) and rapidly returning to almost its original shape when the force is removed.

<(B) Thermally Expandable Component>
The thermally expandable component (B) blended in this composition is at least one selected from the group consisting of a foaming agent, a thermally expandable capsule, and a thermally expandable graphite. By blending such a component in the polymer composition together with the polymer (A1), it becomes possible to improve the friction force on ice due to the surface irregularities formed on the rubber surface after vulcanization. Therefore, this composition blended with the thermally expandable component (B) together with the polymer (A1) is particularly suitable for manufacturing winter tires or all-season tires.

The foaming agent is not particularly limited, and various chemical foaming agents such as organic foaming agents and inorganic foaming agents can be used. Specific examples of these include inorganic foaming agents such as sodium bicarbonate and ammonium carbonate; organic foaming agents such as azo foaming agents such as diazoaminebenzene, azodicarbonamide, azobisisobutyronitrile, and barium azodicarboxylate; nitroso foaming agents such as N,N'-dinitrosopentamethylenetetramine; and hydrazide foaming agents such as p,p'-oxybisbenzenesulfonylhydrazide, benzenesulfonylhydrazide, toluenesulfonylhydrazide, and hydrazodicarbonamide. In addition, as an organic foaming agent, a chemical foaming agent-containing resin, which is a composite material of a chemical foaming component such as an azo compound, a nitroso compound, a hydrazide compound, or a hydrogen carbonate salt and a resin, may be used.

The foaming agent used in the preparation of this composition is commercially available. Specific examples of the foaming agent include Cellpowder F-10, F-35, F-35L, F-50, Cellular D, Vinihol AC, AZ, and Neo Cellvon (all manufactured by Eiwa Kasei Kogyo Co., Ltd.); Cellmic A, Cellmic A-1, Cellmic AN, Cellmic C, Cellmic S, Cellmic SX, Cellmic SX-H, Cellmic 266, and Cellmic 494 (all manufactured by Sankyo Kasei Co., Ltd.); Sponge Paste No. 4 (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.); and Uniform AZ (manufactured by Otsuka Chemical Co., Ltd.).

When a foaming agent is blended in the composition, a foaming assistant such as urea, zinc stearate, or zinc benzenesulfinate may be appropriately selected and used in combination depending on the characteristics of the foaming agent. Examples of commercially available foaming assistants include the Cellpaste series manufactured by Eiwa Kasei Kogyo Co., Ltd. and the Celton series manufactured by Sankyo Kasei Co., Ltd. When a foaming assistant is blended, the blending amount is preferably 20 to 300 parts by mass, more preferably 50 to 250 parts by mass, per 100 parts by mass of the foaming agent contained in the composition.

Thermal expansion capsules are components that contain a thermal expansion substance (e.g., aliphatic hydrocarbons) inside an outer shell formed from a thermoplastic resin. Examples of such thermal expansion capsules include product names such as Microsphere F-50D, F-85D, and F100D (all manufactured by Matsumoto Yushi Seiyaku Co., Ltd.); EXPANCEL 091DU-80 and 092DU-120 (all manufactured by Expancel Co., Ltd.), and Advancel EM series (manufactured by Sekisui Chemical Co., Ltd.).

Thermally expandable graphite is a particle that contains a substance between layers that vaporizes when heated. Conventionally known thermally expandable graphite can be used. Examples of commercially available thermally expandable graphite include Graphcard 160-50N and Graphcard 160-80N (both manufactured by Tomoe Engineering Co., Ltd.). The thermally expandable component (B) blended in the present composition is preferably at least one selected from the group consisting of foaming agents and thermally expandable capsules, with foaming agents being more preferred, in that they have a greater effect of improving grip performance on ice.

The amount of the (B) thermally expandable component in the composition is not particularly limited as long as the effects of the present invention can be obtained, but from the viewpoint of obtaining a sufficient effect of improving grip performance on ice by forming bubbles, it is preferable that the amount is 0.1% by mass or more relative to 100 parts by mass of the (A) conjugated diene polymer. If the content of the (B) thermally expandable component is in the above range, it is preferable in that a crosslinked body that can exhibit good grip performance on ice can be obtained. From this viewpoint, the content of the (B) thermally expandable component is more preferably 0.2% by mass or more, and even more preferably 0.5% by mass or more. In addition, from the viewpoint of suppressing the occurrence of defects during the production of the crosslinked body, the content of the (B) thermally expandable component is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less relative to 100 parts by mass of the (A) conjugated diene polymer. Note that, as the (B) thermally expandable component, one type may be used alone, or two or more types may be used in combination.

Here, from the viewpoint of obtaining a vulcanized rubber with excellent grip performance on ice, it is preferable that the Tg of the conjugated diene polymer (A) blended in the polymer composition is low. On the other hand, a highly hydrogenated conjugated diene polymer in which the value θ defined by the above formula (ii) is 0.75 or more has good abrasion resistance but low grip force on ice compared to a non-hydrogenated conjugated diene polymer with a similar Tg, and there is room for improvement in grip performance on ice. In this respect, the present composition in which a thermally expandable component (B) is blended together with a highly hydrogenated conjugated diene polymer is preferable in that it is possible to obtain a vulcanized rubber that combines high abrasion resistance and excellent grip performance on ice, even when a polymer with a relatively low Tg is used as the highly hydrogenated conjugated diene polymer.

<Other ingredients>
In addition to (A) the conjugated diene polymer and (B) the thermally expandable component, the present composition may further contain the following components.

- (C) Water-soluble component The present composition may further contain at least one component selected from the group consisting of water-soluble particles and water-soluble fibers (hereinafter also referred to as "(C) water-soluble component"). The present composition is suitable in that the inclusion of the (C) water-soluble component can further improve the grip performance on ice. The (C) water-soluble component is not particularly limited as long as it is soluble or swellable in water at room temperature, but for example, a substance having a solubility in water at 25°C of 1.2 g/100 g-H ₂ O or more can be used.

Examples of water-soluble particles include water-soluble inorganic particles and organic particles. Among these, examples of water-soluble inorganic particles include particles of chlorides such as sodium chloride, potassium chloride, and magnesium chloride; sulfides such as sodium sulfate, potassium sulfate, and magnesium sulfate; carbonates such as sodium carbonate and sodium hydrogen carbonate; phosphates such as sodium hydrogen phosphate; and hydroxides such as sodium hydroxide and potassium hydroxide.

Examples of water-soluble organic particles include lignin sulfonates such as sodium lignin sulfonate, potassium lignin sulfonate, calcium lignin sulfonate, magnesium lignin sulfonate, and ammonium lignin sulfonate; resins such as polyvinyl alcohol or its derivatives (e.g., partial acetates, carboxylic acid-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, etc.), alkali salts of poly(meth)acrylic acid, and alkali salts of (meth)acrylic acid/(meth)acrylic acid ester copolymers; and sugars such as monosaccharides, oligosaccharides, and polysaccharides.

Specific examples of sugars include monosaccharides such as glucose, fructose, and galactose; oligosaccharides such as sucrose, lactose, maltose, raffinose, maltotriose, trehalose, and palatinose; and polysaccharides such as starch, dextrin, glycogen, glucan, xanthan gum, galactomannan (guar gum, fenugreek gum, and the like), cyclodextrin (α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, and the like), methylcellulose, ethylcellulose, and carboxymethylcellulose. As the water-soluble particles, one of these can be used alone, or two or more can be used in combination.

The water-soluble particles may be in various forms, such as powder, granules, microbeads, etc. (C) The water-soluble particles used as the water-soluble component are preferably solid water-soluble particles. From the viewpoint of obtaining a sufficient effect of improving grip performance on ice, the water-soluble particles preferably have a median particle size of 1 μm or more, more preferably 2 μm or more. Also, from the viewpoint of achieving a good balance between grip performance on ice and abrasion resistance, the median particle size is preferably 1000 μm or less, more preferably 500 μm or less. In this specification, the median particle size of the water-soluble particles is the median diameter (D50), which is a value measured by a laser diffraction/scattering method.

As the water-soluble fiber, short fibers that can dissolve or swell in water can be used. Specifically, the fiber length of the water-soluble fiber is preferably 1 mm or more, more preferably 2 mm or more, and even more preferably 4 mm or more, from the viewpoint of obtaining a sufficient effect of improving grip performance on ice. Furthermore, the fiber length is preferably 30 mm or less, more preferably 20 mm or less, and even more preferably 15 mm or less, from the viewpoint of suppressing a decrease in abrasion resistance and processability. The diameter (average diameter) of the water-soluble fiber is preferably 5 μm or more, more preferably 10 μm or more. Furthermore, the average diameter of the water-soluble fiber is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

Examples of water-soluble fibers include fibers whose main components are the substances exemplified in the description of water-soluble organic particles. As the water-soluble fiber, at least one type selected from the group consisting of polyvinyl alcohol-based fibers and polysaccharide fibers can be preferably used. As the water-soluble fiber, one of these may be used alone, or two or more types may be used in combination.

The content of the water-soluble component (C) in the composition is not particularly limited as long as the effects of the present invention can be obtained, but is preferably 0.1 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the conjugated diene polymer (A). If the content of the water-soluble component (C) is in the above range, it is preferable that a vulcanized rubber that exhibits good grip performance on ice while maintaining abrasion resistance can be obtained. From this viewpoint, the content of the water-soluble component (C) is more preferably 0.5 parts by mass or more and even more preferably 1 part by mass or more per 100 parts by mass of the conjugated diene polymer (A). In addition, from the viewpoint of suppressing the decrease in the abrasion resistance of the crosslinked body, the content of the water-soluble component (C) is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less per 100 parts by mass of the conjugated diene polymer (A).

Other Rubber Components The present composition may contain only the conjugated diene polymer (A) as a rubber component, but may also contain a rubber component (hereinafter also referred to as "other rubber component") different from the conjugated diene polymer (A) in addition to the conjugated diene polymer (A) within a range that does not impair the effects of the present invention. The type of such other rubber component is not particularly limited, but examples include halogenated butyl rubber and the like. The amount of the other rubber component is preferably 60 mass% or less, more preferably 40 mass% or less, based on the total amount of the rubber components (the conjugated diene polymer (A) and the other rubber components) contained in the polymer composition.

Silica, etc. The present composition preferably contains at least one selected from the group consisting of silica and carbon black (hereinafter also referred to as "silica, etc."). Silica is preferred in that it provides a good static-dynamic ratio and low hysteresis loss characteristics, and carbon black is preferred in that it has a high effect of improving the strength of the polymer composition and vulcanized rubber. Examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), colloidal silica, etc., and among these, wet silica is preferred. Examples of carbon black include furnace black, acetylene black, thermal black, channel black, graphite, etc., and among these, furnace black is preferred.

In this composition, the total amount of silica and carbon black is preferably 40 to 150 parts by mass per 100 parts by mass of the rubber component contained in the polymer composition. If the amount of silica, etc. is 40 parts by mass or more, it is preferable in that the effect of improving the strength of the vulcanized rubber can be sufficiently obtained. Also, if the amount of silica, etc. is 150 parts by mass or less, it is preferable in that the abrasion resistance of the vulcanized rubber can be sufficiently ensured. The amount of silica, etc. is preferably 50 parts by mass or more, more preferably 55 parts by mass or more, per 100 parts by mass of the total rubber component. Also, the amount of silica, etc. is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, per 100 parts by mass of the total rubber component.

Crosslinking Agent The present composition preferably contains a crosslinking agent. The type of crosslinking agent used is not particularly limited. Specific examples of the crosslinking agent include organic peroxides, phenolic resins, sulfur, sulfur compounds, p-quinone, p-quinone dioxime derivatives, bismaleimide compounds, epoxy compounds, silane compounds, amino resins, polyols, polyamines, triazine compounds, metal soaps, and the like. Of these, the crosslinking agent used is preferably at least one selected from the group consisting of organic peroxides, phenolic resins, and sulfur. The crosslinking agent may be used alone or in combination of two or more.

Examples of organic peroxides include 1,3-bis(t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexene-3, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 2,2'-bis(t-butylperoxy)-p-isopropylbenzene, dicumyl peroxide, di-t-butyl peroxide, and t-butyl peroxide.

（式（７）中、Ｘは、ヒドロキシル基、ハロゲン化アルキル基又はハロゲン原子である。Ｒは、炭素数１～１５の１価の飽和炭化水素基である。ｎは、０～１０の整数である。） Examples of the phenol resin include p-substituted phenol compounds represented by the following formula (7), o-substituted phenol-aldehyde condensates, m-substituted phenol-aldehyde condensates, and brominated alkylphenol-aldehyde condensates. Among these, p-substituted phenol compounds are preferred. The p-substituted phenol compounds can be obtained by a condensation reaction between p-substituted phenol and an aldehyde (preferably formaldehyde) in the presence of an alkali catalyst.

(In formula (7), X is a hydroxyl group, a halogenated alkyl group, or a halogen atom. R is a monovalent saturated hydrocarbon group having 1 to 15 carbon atoms. n is an integer from 0 to 10.)

Commercially available phenolic resins include "Tackirol 201" (alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), "Tackirol 250-I" (brominated alkylphenol formaldehyde resin with a bromination rate of 4%, manufactured by Taoka Chemical Co., Ltd.), "Tackirol 250-III" (brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), and "PR-4507" (group Examples of commercially available phenolic resins include "ST137X" (manufactured by Rohm & Haas Co.), "Sumilite Resin PR-22193" (manufactured by Sumitomo Durez Co.), "Tamanol 531" (manufactured by Arakawa Chemical Industries Co.), "SP1059", "SP1045", "SP1055", "SP1056" (all manufactured by Schenectady Co.), and "CRM-0803" (manufactured by Showa Union Synthetic Co.). Of these, "Tackirol 201" is a commercially available phenolic resin that can be preferably used.

The amount of the crosslinking agent is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and even more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the total rubber components contained in the polymer composition.

Resin Component The composition may further contain a resin component together with the rubber component. The type of the resin component is not particularly limited, but examples include polyolefin resins such as polyethylene and polypropylene. When a resin component is added, the amount of the resin component is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, based on 100 parts by mass of the total amount of the rubber components contained in the polymer composition.

In addition to the above-mentioned components, the present composition can contain various additives that are generally used in rubber compositions for obtaining vulcanized rubber for various applications such as tires, hoses, vibration-proofing, and belts. Examples of such additives include antioxidants, zinc oxide, stearic acid, softeners, sulfur, and vulcanization accelerators. The amount of each of these additives can be appropriately selected according to the type of additive within a range that does not impair the effects of the present invention.

<Cross-linked body and tire>
The crosslinked body of the present invention can be obtained by subjecting the above-mentioned polymer composition to a crosslinking treatment. When obtaining a rubber molded article as a crosslinked body, the polymer composition is usually molded into a predetermined shape and then crosslinked. The rubber molded article can be produced according to a conventional method. For example, a tire is produced by mixing the above-mentioned polymer composition in a mixer such as a roll or a mixer, molding the mixture into a predetermined shape, and disposing the mixture in a predetermined position according to a conventional method to perform vulcanization molding. This forms one or both of a tread and a sidewall, and a pneumatic tire can be obtained.

The crosslinked product of the present invention (specifically, vulcanized rubber) has excellent mechanical strength and can be applied to various rubber molded products. Specifically, it can be used as a material for tire treads and sidewalls; rolls and anti-vibration rubbers for industrial machinery and equipment; various hoses and hose covers such as diaphragms, radiator hoses, and air hoses; seals such as packing, gaskets, weather strips, O-rings, and oil seals; belts such as power transmission belts; linings, dust boots, wire harnesses, shoe soles, and the like. Among these, it is suitable as a tire component, anti-vibration component, belt component, roll component, hose component, wire harness component, and shoe sole component, and is even more suitable as a tire component, anti-vibration component, roll component, and belt component.

The crosslinked body of the present invention is particularly suitable for tire components, as it has high abrasion resistance and excellent grip performance on ice, and is particularly suitable for winter tires and all-season tires. It is particularly suitable as a material for either or both of the tread and sidewall of tires.

The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. Note that "parts" and "%" in the examples and comparative examples are based on mass unless otherwise specified. The measurement methods for various physical properties are shown below.

[Bound styrene content (mass %)]: determined by a 400 MHz ¹ H-NMR apparatus.
[Vinyl content (mol %)]: Measured by a 400 MHz ¹ H-NMR apparatus.
[Hydrogenation rate (%)] and [θ]: Measured by a 500 MHz ¹ H-NMR apparatus.
[1st peak weight average molecular weight]: It was calculated in terms of polystyrene from the retention time corresponding to the apex of the maximum peak of the GPC curve obtained under the following measurement conditions using a gel permeation chromatograph (HLC-8120GPC (product name (manufactured by Tosoh Corporation))).
[Total weight average molecular weight]: The total weight average molecular weight was determined in terms of polystyrene from a GPC curve obtained under the following measurement conditions using a gel permeation chromatograph (HLC-8120GPC (product name, manufactured by Tosoh Corporation)).
(GPC Measurement Conditions)
Column: Product name "GMHXL" (manufactured by Tosoh Corporation) x 2 Column temperature: 40°C
Mobile phase: tetrahydrofuran Flow rate: 1.0 ml/min Sample concentration: 10 mg/20 ml
[Glass transition temperature Tg (° C.)]: Measured by a differential scanning calorimetry (DSC) device in accordance with ASTM D3418.

<Production of hydrogenation catalyst>
Synthesis of Catalyst E
A 1 L three-neck flask equipped with a stirrer and a dropping funnel was purged with dry nitrogen, and 200 ml of anhydrous tetrahydrofuran and 0.2 mol of tetrahydrofurfuryl alcohol were added. Then, a n-butyllithium/cyclohexane solution (0.2 mol) was added dropwise to the three-neck flask at 15° C. to carry out a reaction, thereby obtaining a tetrahydrofurfuryloxylithium solution in tetrahydrofuran.
Next, a 1 L three-neck flask equipped with a stirrer and a dropping funnel was purged with dry nitrogen, and 49.8 g (0.2 mol) of bis(η5-cyclopentadienyl)titanium dichloride and 250 ml of anhydrous tetrahydrofuran were added. Then, the tetrahydrofuran solution of tetrafurfuryloxylithium obtained by the method described above was added dropwise at room temperature with stirring for about 1 hour. After about 2 hours, the reddish brown liquid was filtered, and the insoluble portion was washed with dichloromethane.
Thereafter, the filtrate and the washings were combined and the solvent was removed under reduced pressure to obtain catalyst E [bis(η5-cyclopentadienyl)titanium(tetrahydrofurfuryloxy)chloride] (also referred to as "[chlorobis(2,4-cyclopentadienyl)titanium(IV) tetrahydrofurfurylalkoxide]"). The yield was 95%.

<Production of Conjugated Diene Polymer>
[Production Example 1: Synthesis of Conjugated Diene Polymer A-1]
A nitrogen-purged 50-liter autoclave reactor was charged with 25,900 g of cyclohexane, 26 g of tetrahydrofuran, 1,273 g of styrene, and 2,361 g of 1,3-butadiene. After adjusting the temperature of the reactor contents to 45°C, a cyclohexane solution containing n-butyllithium (39 mmol) was added to initiate polymerization. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 80°C.
After confirming that the polymerization conversion rate had reached 99%, 111 g of butadiene was added and polymerization was continued for another 5 minutes to obtain a reaction liquid containing a polymer. 2 mmol of silicon tetrachloride was added to the reaction liquid obtained and reacted for 10 minutes, and 28 mmol of N,N-dimethyl-3-(triethoxysilyl)propylamine was added and reacted for 20 minutes.
Next, the reaction solution was heated to 80° C. or higher and hydrogen was introduced into the system, after which 3.2 g of diethylaluminum chloride, 2.4 g of catalyst E, and n-butyllithium (15 mmol) were added, and hydrogen was supplied until a predetermined hydrogen accumulation value was reached while maintaining a hydrogen pressure of 0.7 MPa or higher to carry out a hydrogenation reaction. Thereafter, the reaction solution was returned to room temperature and pressure and withdrawn from the reaction vessel to obtain a polymer solution containing a hydrogenated conjugated diene-based polymer.
To the obtained polymer solution, 1.4 g of 2,6-di-tert-butyl-p-cresol was added. Next, an aqueous solution (temperature: 80°C) adjusted to pH 8.5 (pH at 80°C by glass electrode method) with ammonia as a pH adjuster was placed in a desolvation tank, and the above polymer solution was further added (ratio of 1000 parts by mass of the above aqueous solution to 100 parts by mass of the polymer solution), and the solvent was removed by steam stripping (steam temperature: 190°C) for 2 hours at a liquid phase temperature of 95°C in the desolvation tank, and drying was performed with a heat roll adjusted to 110°C to obtain a conjugated diene polymer A-1. Table 2 shows the analytical values of the obtained conjugated diene polymer A-1. The 1st peak weight average molecular weight of the conjugated diene polymer A-1 was 20 x 10 ⁴ , the weight average molecular weight (total weight average molecular weight) was 34 x 10 ⁴ , the hydrogenation rate was 93% (θ = 0.93), and the glass transition temperature was -34°C.

[Production Examples 2 to 7, 9: Synthesis of Conjugated Diene Polymers A-2 to A-7, A-9]
Conjugated diene polymers A-2 to A-7 and A-9 were obtained by polymerization in the same manner as in Production Example 1, except that the raw materials used were changed as shown in Table 1 and the hydrogen supply amount was changed. The analytical values of the conjugated diene polymers A-2 to A-7 and A-9 are shown in Table 2.

[Production Example 8: Synthesis of conjugated diene polymer A-8]
A nitrogen-purged 50-liter autoclave reactor was charged with 25,900 g of cyclohexane, 26 g of tetrahydrofuran, 1,273 g of styrene, and 2,361 g of 1,3-butadiene. After adjusting the temperature of the reactor contents to 45°C, a cyclohexane solution containing n-butyllithium (39 mmol) was added to initiate polymerization. The polymerization was carried out under adiabatic conditions, and the maximum temperature reached 80°C.
After confirming that the polymerization conversion rate had reached 99%, 111 g of butadiene was added and polymerization was continued for an additional 5 minutes to obtain a reaction solution containing a polymer. 2 mmol of silicon tetrachloride was added to the resulting reaction solution and reacted for 10 minutes, and 28 mmol of N,N-dimethyl-3-(triethoxysilyl)propylamine was added and reacted for 20 minutes. Next, the reaction solution was heated to 80° C. or higher and hydrogen was introduced into the system, after which the reaction solution was returned to room temperature and pressure and withdrawn from the reaction vessel to obtain a polymer solution containing a conjugated diene copolymer.
To the obtained polymer solution, 1.4 g of 2,6-di-tert-butyl-p-cresol was added. Next, an aqueous solution (temperature: 80°C) adjusted to pH 8.5 (pH at 80°C by glass electrode method) with ammonia as a pH adjuster was placed in a desolvation tank, and the polymer solution was further added (ratio of 1000 parts by mass of the aqueous solution to 100 parts by mass of the polymer solution), and the solvent was removed by steam stripping (steam temperature: 190°C) for 2 hours at a liquid phase temperature of 95°C in the desolvation tank, and drying was performed with a heat roll adjusted to 110°C to obtain a conjugated diene polymer A-8. The obtained conjugated diene polymer A-8 had a 1st peak weight average molecular weight of 20 x 10 ⁴ , a weight average molecular weight (total weight average molecular weight) of 34 x 10 ⁴ , and a glass transition temperature of -40°C. The conjugated diene polymer A-8 had a hydrogenation rate of 0% and θ of 0.

In Table 1, the abbreviations of the compounds represent the following compounds.
Compound A: piperidine Compound B: N,N-dimethyl-3-(triethoxysilyl)propylamine Compound C: silicon tetrachloride In Table 1, "-" indicates that the compound in the corresponding column was not used.

<Production and Characterization of Polymer Compositions>
[Examples 1 to 15 and Comparative Examples 1 to 4]
In the first stage of kneading, a conjugated diene polymer, (C) water-soluble component, silica, a silane coupling agent, extender oil, stearic acid, zinc oxide, and antioxidant were kneaded according to the formulations in Tables 3 and 4 at a filling rate of 72% and a rotation speed of 60 rpm using a plastomill equipped with a temperature control device. Next, in the second stage of kneading, the mixture obtained above was cooled to room temperature, and then (B) thermally expandable component, sulfur, and vulcanization accelerator were kneaded according to the formulations in Tables 3 and 4. This was molded and vulcanized at 160°C for a predetermined time in a vulcanization press. The following characteristic evaluations (1) to (3) were performed using the vulcanized rubber. The types and proportions of the conjugated diene polymer, (B) thermally expandable component, and (C) water-soluble component used in each example and comparative example are as shown in Tables 3 and 4. In Example 8, a foaming assistant was blended together with the foaming agent, which is the thermally expandable component (B), during the second stage of kneading. The values in Tables 3 and 4 represent the blending ratio (parts by mass) of each component.

≪Characteristics evaluation≫

(1) Abrasion Resistance Using vulcanized rubber as a measurement sample, a DIN abrasion tester (manufactured by Toyo Seiki Seisakusho) was used in accordance with JIS K6264-2:2005, and measurements were performed at 25°C under a load of 10 N. The abrasion resistance was expressed as a standardized value such that the value of Comparative Example 2 was 100, and a larger value indicates better abrasion resistance.
(2) Grip performance on ice A vulcanized rubber sample with a diameter of 50 mm and a thickness of 10 mm was used as the measurement sample, which was pressed against fixed ice and rotated at a surface pressure of 12 kgf/ ^cm2 and a main sample rotation speed of 20 cm/sec in an environment of -2°C. The frictional force generated when the sample was rotated at this pressure was detected with a load cell, and the dynamic friction coefficient μ was calculated. Evaluation was performed based on the dynamic friction coefficient μ, and the results were shown as values normalized so that the dynamic friction coefficient μ of Comparative Example 2 was 100.
(3) Hardness change (Δ hardness)
For each test piece made of each vulcanized rubber sheet before and after heat aging, the hardness (Duro-A hardness) was measured in accordance with JIS K6253, and the resistance of the vulcanized rubber to deterioration over time was evaluated based on the difference in hardness before and after heat aging. The evaluation was performed in three stages, with a difference in hardness before and after heat aging of less than 3 being "A", a difference of 3 to less than 6 being "B", and a difference of 6 or more being "C". Note that "heat aging" here refers to a process in which heat aging (100°C, 70 hours) is performed on a new vulcanized rubber in accordance with JIS K6257:2010 to obtain a heat-aged vulcanized rubber.

The results of the characteristic evaluation of Examples 1 to 15 and Comparative Examples 1 to 4 are shown in Tables 3 and 4.

In Tables 3 and 4, details of Components B and C are as follows.
B-1: Dinitrosopentamethylenetetramine, product name "Cellmike AN", manufactured by Sankyo Kasei Co., Ltd. B-2: Azodicarbonamide, product name "Vinihol AC #3", manufactured by Eiwa Kasei Kogyo Co., Ltd. B-3: Sodium bicarbonate, product name "Cellmike 266", manufactured by Sankyo Kasei Co., Ltd. B-4: Thermal expansion capsule, product name "Advancell EM (Grade EML101)", manufactured by Sekisui Chemical Co., Ltd. C-1: Magnesium sulfate, product name "MN-00", manufactured by Mai Kasei Kogyo Co., Ltd. C-2: Polyvinyl alcohol short fiber, product name "Kuralon 1239", manufactured by Kuraray Co., Ltd. C-3: Sodium lignin sulfonate, manufactured by Tokyo Kasei Kogyo Co., Ltd. Note that B-1 to B-4 are (B) thermal expansion components, and C-1 to C-3 are (C) water-soluble components.

Details of each component *1) to * 8 ) used in Tables 3 and 4 are as follows:
*1) Rhodia ZEOSIL 1165MP
*2) Diablack N339, manufactured by Mitsubishi Chemical Corporation
*3) Evonik Si75
*4) JX Nippon Oil & Energy Corporation process oil T-DAE
*5) Ozonone 6C manufactured by Seiko Chemical Co., Ltd.
*6) Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
*7) Noccela D manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
*8) Urea manufactured by Eiwa Chemical Industry Co., Ltd. (product name "Cell Paste M3")
In Tables 3 and 4, the numerical values in the formulations represent the amounts (parts by mass) blended when the polymer compositions were prepared.

As shown in Tables 3 and 4, the polymer compositions (Examples 1 to 15) containing (A) a conjugated diene polymer having a hydrogenation rate of 75% or more and (B) a thermally expandable component showed a well-balanced improvement in abrasion resistance and grip performance on ice compared to Comparative Examples 1 to 4. In particular, Examples 2 to 6, 8, and 9, which used the (A1) polymer having a Tg of -45°C or less, showed a more highly balanced improvement in abrasion resistance and grip performance on ice compared to Examples 1 and 7, which used the (A1) polymer having a Tg of -34°C and -28°C. Furthermore, a comparison between Examples 11 to 13 and Example 4 shows that the inclusion of the water-soluble component (C) further improved the grip performance on ice. In addition, the vulcanized rubber obtained using the polymer compositions of Examples 1 to 15 showed a small increase in hardness due to heat aging, and all were rated "A".

These results show that a polymer composition containing the (A1) polymer and the (B) thermally expandable component can produce a vulcanized rubber that exhibits good grip performance on ice, has excellent abrasion resistance, and exhibits reduced increase in hardness due to thermal aging. It was also found that the ice grip performance of the vulcanized rubber can be further improved by further adding the (C) water-soluble component.

Claims (12)

(A) a conjugated diene polymer, and
(B) a thermally expandable component which is at least one selected from the group consisting of a foaming agent, a thermally expandable capsule, and a thermally expandable graphite;
Contains
The conjugated diene polymer (A) includes a polymer (A1) which satisfies the condition of the following mathematical formula (i) when the constituent ratios (molar ratios) in the polymer of a structural unit represented by the following formula (1), a structural unit represented by the following formula (2), a structural unit represented by the following formula (3), and a structural unit represented by the following formula (4) are p, q, r, and s, respectively :
The polymer (A1) is a random copolymer of a conjugated diene compound and an aromatic vinyl compound, and contains structural units derived from an aromatic vinyl compound in an amount of 3 to 45 mass% based on the total amount of structural units contained in the polymer (A1) .
Formula (i):
0.75≦(p+(0.5×r))/(p+q+(0.5×r)+s)≦0.97

The polymer composition according to claim 1, wherein the proportion of the (A1) polymer in the (A) conjugated diene polymer is 50% by mass or more. The polymer composition according to claim 1 or 2, wherein the glass transition temperature of the polymer (A1) is -40°C or lower. The polymer composition according to any one of claims 1 to 3, wherein the (A1) polymer has a weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography of 1.0 x 10 ⁵ to 2.0 x 10 ⁶ . The polymer composition according to any one of claims 1 to 4 , wherein the polymer (A1) has at least one functional group selected from the group consisting of an amino group, a nitrogen-containing heterocyclic group, a phosphino group, a hydroxyl group, a thiol group, and a hydrocarbyloxysilyl group. The polymer composition according to any one of claims 1 to 5, wherein the polymer (A1) has a partial structure derived from at least one compound selected from the group consisting of compounds represented by the following formula (5) and compounds represented by the following formula ( 6 ):

(In formula (5), A ¹ is a monovalent functional group having at least one atom selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, having no active hydrogen, and bonded to R ⁵ via a nitrogen atom, a phosphorus atom, an oxygen atom, a sulfur atom, a silicon atom, or a carbon atom contained in a carbonyl group, or is a (thio)epoxy group. ^{R 3} and R ⁴ are each independently a hydrocarbyl group. R ⁵ is a hydrocarbylene group. r is an integer of 0 to 2. However, when r is 2, multiple R ^3s in the formula are the same group or different groups. When r is 0 or 1, multiple R ^4s in the formula are the same group or different groups.)

(In formula (6), ^A2 is a monovalent functional group having at least one atom selected from the group consisting of nitrogen, phosphorus, oxygen, sulfur, and silicon, having no active hydrogen, and bonded to ^R9 via a nitrogen atom, phosphorus atom, oxygen atom, sulfur atom, or silicon atom, or a hydrocarbyl group having 1 to 20 carbon atoms. ^R6 and ^R7 are each independently a hydrocarbyl group. ^R8 is a hydrocarbylene group. ^R9 is a single bond or a hydrocarbylene group. m is 0 or 1. However, when m is 0, the multiple ^R7s in the formula are the same group or different groups.) The polymer composition according to any one of claims 1 to 6 , wherein the content of the thermally expandable component (B) is 0.1 to 50 parts by mass based on 100 parts by mass of the conjugated diene polymer (A). The polymer composition according to any one of claims 1 to 7 , further comprising (C) at least one component selected from the group consisting of water-soluble particles and water-soluble fibers. The polymer composition according to any one of claims 1 to 8 , further comprising at least one selected from the group consisting of silica and carbon black. The polymer composition according to any one of claims 1 to 9 , further comprising a crosslinking agent. A crosslinked product obtained by using the polymer composition according to any one of claims 1 to 10 . A tire having a tread and/or a sidewall formed from the polymer composition according to any one of claims 1 to 10 .