JP5461812B2 - Rubber composition, method for producing the same, and tire using the same - Google Patents

Description

  The present invention relates to a rubber composition excellent in low heat build-up (low loss) and fracture resistance (crack growth resistance), a method for producing the same, and a tire using the same.

In recent years, tires with excellent durability have been demanded in order to save automobile fuel consumption in response to social demands for energy and resource saving, and even lower heat generation (low loss) and fracture resistance than before. A rubber composition excellent in (crack growth resistance) is strongly desired.
Under these circumstances, as a method for reducing the rolling resistance of the tire, it is common to use a rubber composition having low heat generation. In order to achieve low heat build-up, a means for reducing the filler can be taken, but there is a concern about deterioration of fracture resistance. On the other hand, in order to improve both low heat buildup and fracture resistance, a modified polymer having a functional group that interacts with a filler in the rubber composition as disclosed in Patent Document 1 is used as a rubber component. It is a very effective means to use.

International Publication No. 2006/112450 Pamphlet

  However, depending on the type of the functional group to be introduced, the reactivity with the filler is different, which may greatly affect the performance of the resulting rubber composition. Therefore, there is still room for improvement from the viewpoint of realizing a rubber composition that can further improve both low heat buildup and fracture resistance.

  Accordingly, the present invention provides a rubber composition having higher low heat generation and crack growth resistance while improving the affinity between the rubber component and the filler, a method for producing the same, and a tire using the same. The purpose is to do.

  In order to solve the above problems, the present inventors have found a rubber composition containing a rubber component containing a specific polymer and lower carbon black and a method for producing the same, and have completed the present invention.

That is, the rubber composition of the present invention has a conjugated modified group having a cis content of 40% or more, which is modified with a modifier that is a heterocyclic nitrile compound represented by formula (I) or formula (II). A rubber component containing a butadiene-based polymer having,
And carbon black having a nitrogen adsorption specific surface area of 20 to 100 m ² / g.
θ-C≡N (I)
θ-R-C≡N (II)
(In formulas (I) and (II), θ represents at least one selected from the group consisting of 2-pyridyl, 3-pyridyl, and 4-pyridyl, and R represents a divalent hydrocarbon group.)

The rubber component preferably contains natural rubber and / or polyisoprene rubber, and preferably contains 10% by mass or more of the butadiene polymer in 100% by mass of the rubber component, and the cis content of the butadiene polymer is It is desirable that it is 90% or more.
Moreover, it is preferable that the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the butadiene-based polymer is 1.3 to 3.5.
Further, 10 parts by mass or more of the carbon black may be included with respect to 100 parts by mass of the rubber component, and the nitrogen adsorption specific surface area of the carbon black is preferably 40 to 80 m ² / g.

The method for producing the rubber composition of the present invention includes a step of adding a modifier to a butadiene-based polymer having a terminal living ratio of 20% or more.
Further, the tire of the present invention is characterized by using the above rubber composition, and the rubber composition may be used for a sidewall member.

According to the rubber composition of the present invention, the butadiene-based polymer having a relatively high cis content used as a rubber component has extremely high affinity with carbon black having a specific nitrogen adsorption specific surface area, and by combining these, It is possible to realize a rubber composition having both a low heat generation property and crack growth resistance which are superior to those of conventional ones.
Further, by selecting a conjugated modifying group to be introduced into the butadiene polymer, it is possible to ensure even higher low heat generation.

Hereinafter, the present invention will be described in detail.
The rubber composition of the present invention has a conjugated modification group having a cis content of 40% or more, which is modified with a modifier which is a heterocyclic nitrile compound represented by the above formula (I) or formula (II). A rubber component containing a butadiene-based polymer;
And carbon black having a nitrogen adsorption specific surface area of 20 to 100 m ² / g.

[Butadiene polymer]
In the rubber composition of the present invention, the rubber component has a cis content (1,4-cis bond content) of 40% or more, preferably 90% or more, more preferably 96% or more, and most preferably 98% or more. A butadiene-based polymer having a conjugated modified group (hereinafter also referred to as “modified butadiene-based polymer”) is used. When the cis content is less than 40%, the effect of the present invention tends to be hardly exhibited. When the cis content is within the above range, it is possible to exhibit excellent crack growth resistance due to an increase in stretch crystallinity. In addition, cis content means the ratio of the 1, 4- cis bond in the butadiene compound unit in a butadiene-type polymer.

  The butadiene-based polymer is preferably composed of 1,3-butadiene monomer, particularly preferably composed of only 1,3-butadiene monomer, and is desirably so-called polybutadiene rubber (BR). The 1,3-butadiene monomer unit is preferably 80 to 100% by mass, and the other monomer unit copolymerizable with 1,3-butadiene is preferably 20 to 0% by mass. When the 1,3-butadiene monomer unit content in the polymer is less than 80% by mass, the 1,4-cis bond content with respect to the whole polymer is lowered, and thus the effect of the present invention is hardly exhibited.

  Here, other monomers copolymerizable with 1,3-butadiene include, for example, conjugated diene monomers having 5 to 8 carbon atoms, aromatic vinyl monomers and the like. Among these, A conjugated diene monomer having 5 to 8 carbon atoms is preferred. Examples of the conjugated diene monomer having 5 to 8 carbon atoms include 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like. Can be mentioned. Examples of the aromatic vinyl monomer include styrene, p-methylstyrene, α-methylstyrene, and vinylnaphthalene.

  In addition, the vinyl content (1,2-vinyl bond content) of the butadiene-based polymer is preferably 1.5% or less, more preferably 1.0% or less. If the vinyl content is outside the above range, the crystallinity of the polymer may be lowered, which is not preferable. Here, the vinyl content means the proportion of 1,2-vinyl bonds in the butadiene compound units in the butadiene polymer.

  Furthermore, the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the butadiene-based polymer (modified butadiene-based polymer) having the conjugated modified group is 1.3-3. 5, preferably 1.3 to 3.0. Here, Mn and Mw / Mn mean values obtained using polystyrene as a standard substance by gel permeation chromatography (GPC).

  The butadiene-based polymer having a conjugated modified group used in the present invention (modified butadiene-based polymer) is described below in detail in the presence of a catalyst system comprising a component (A), a component (B), and a component (C). A butadiene polymer before modification obtained by polymerizing a monomer containing at least a diene monomer such as 1,3-butadiene at a temperature of 25 ° C. or lower is used. Here, examples of the monomer include 1,3-butadiene and other monomers copolymerizable with the above-described 1,3-butadiene.

  The component (A) of the catalyst system used in the production of the butadiene polymer before modification is a compound containing a rare earth element having an atomic number of 57 to 71 in the periodic table, or a reaction product of these compounds and a Lewis base. It is. Here, among the rare earth elements having atomic numbers 57 to 71, neodymium, praseodymium, cerium, lanthanum, gadolinium, or the like, or a mixture thereof is preferable, and neodymium is particularly preferable.

  The rare earth element-containing compound is preferably a salt soluble in a hydrocarbon solvent, and specifically includes the rare earth element carboxylates, alkoxides, β-diketone complexes, phosphates and phosphites. Of these, carboxylates and phosphates are preferable, and carboxylates are particularly preferable. Here, examples of the hydrocarbon solvent include saturated aliphatic hydrocarbons having 4 to 10 carbon atoms such as butane, pentane, hexane and heptane, saturated alicyclic hydrocarbons having 5 to 20 carbon atoms such as cyclopentane and cyclohexane, -Monoolefins such as butene, 2-butene, aromatic hydrocarbons such as benzene, toluene, xylene, methylene chloride, chloroform, trichloroethylene, perchloroethylene, 1,2-dichloroethane, chlorobenzene, bromobenzene, chlorotoluene, etc. A halogenated hydrocarbon is mentioned.

As the rare earth element carboxylate, the following general formula (VII):
(R ⁴ -CO ₂ ) ₃ M (VII)
(Wherein, R ⁴ is a hydrocarbon group having 1 to 20 carbon atoms, and M is a rare earth element having an atomic number of 57 to 71 in the periodic table). Here, R ⁴ may be saturated or unsaturated, is preferably an alkyl group or an alkenyl group, and may be linear, branched or cyclic. The carboxyl group is bonded to a primary, secondary or tertiary carbon atom. Specific examples of the carboxylate include octanoic acid, 2-ethylhexanoic acid, oleic acid, neodecanoic acid, stearic acid, benzoic acid, naphthenic acid, versatic acid [trade names of Shell Chemical Co., Ltd. , A carboxylic acid in which a carboxyl group is bonded to a tertiary carbon atom] and the like. Among these, salts of 2-ethylhexanoic acid, neodecanoic acid, naphthenic acid, and versatic acid are preferable.

As the alkoxide of the rare earth element, the following general formula (VIII):
(R ⁵ O) ₃ M (VIII)
(Wherein, R ⁵ is a hydrocarbon group having 1 to 20 carbon atoms, and M is a rare earth element having an atomic number of 57 to 71 in the periodic table). The alkoxy group represented by R ⁵ O, 2-ethyl - hexyl alkoxy group, oleyl alkoxy group, stearyl alkoxy group, phenoxy group, and benzylalkoxy group. Among these, a 2-ethyl-hexylalkoxy group and a benzylalkoxy group are preferable.

  Examples of the rare earth element β-diketone complex include the rare earth element acetylacetone complex, benzoylacetone complex, propionitrileacetone complex, valerylacetone complex, and ethylacetylacetone complex. Among these, an acetylacetone complex and an ethylacetylacetone complex are preferable.

  Examples of the rare earth element phosphate and phosphite include the rare earth element, bis (2-ethylhexyl) phosphate, bis (1-methylheptyl phosphate), bis (p-nonylphenyl) phosphate, phosphorus Acid bis (polyethylene glycol-p-nonylphenyl), phosphoric acid (1-methylheptyl) (2-ethylhexyl), phosphoric acid (2-ethylhexyl) (p-nonylphenyl), 2-ethylhexylphosphonic acid mono-2-ethylhexyl 2-ethylhexylphosphonic acid mono-p-nonylphenyl, bis (2-ethylhexyl) phosphinic acid, bis (1-methylheptyl) phosphinic acid, bis (p-nonylphenyl) phosphinic acid, (1-methylheptyl) (2 -Ethylhexyl) phosphinic acid, (2-ethylhexyl) (p-nonylphenyl) phosphine Among these, the rare earth elements, bis (2-ethylhexyl) phosphate, bis (1-methylheptyl) phosphate, mono-2-ethylhexyl 2-ethylhexylphosphonate, bis A salt with (2-ethylhexyl) phosphinic acid is preferred.

  Among the rare earth element-containing compounds, neodymium phosphate and neodymium carboxylate are more preferable, and in particular, neodymium branching such as neodymium 2-ethylhexanoate, neodymium neodecanoate, neodymium versatate, etc. Carboxylate is most preferred.

  The component (A) may be a reaction product of the rare earth element-containing compound and a Lewis base. The reaction product has improved solubility of the rare earth element-containing compound in the solvent due to the Lewis base, and can be stably stored for a long period of time. In order to easily solubilize the rare earth element-containing compound in a solvent and to store stably for a long period of time, the Lewis base is used in a proportion of 0 to 30 mol, preferably 1 to 10 mol, per mol of rare earth element. Or as a mixture of the two or as a product obtained by reacting both in advance. Here, examples of the Lewis base include acetylacetone, tetrahydrofuran, pyridine, N, N-dimethylformamide, thiophene, diphenyl ether, triethylamine, an organic phosphorus compound, and a monovalent or divalent alcohol.

  The rare earth element-containing compound as the component (A) described above or a reaction product of these compounds and a Lewis base can be used singly or in combination of two or more.

The component (B) of the catalyst system used for the production of the butadiene polymer before the modification is represented by the following general formula (II):
AlR ¹ R ² R ³ ... (II)
(In the formula, R ¹ and R ² are the same or different and are a hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom, and R ³ is a hydrocarbon group having 1 to 10 carbon atoms, provided that R ³ represents the above R ¹ or R ² , which may be the same as or different from R ² ). Examples of the organoaluminum compound of the formula (II) include trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-t-butylaluminum, tripentylaluminum, Trihexyl aluminum, tricyclohexyl aluminum, trioctyl aluminum; diethyl aluminum hydride, di-n-propyl aluminum hydride, di-n-butyl aluminum hydride, diisobutyl aluminum hydride, dihexyl aluminum hydride, diisohexyl hydride Aluminum, dioctyl aluminum hydride, diisooctyl aluminum hydride; ethyl aluminum dihydride, n-propyl aluminum Hydride, include isobutyl aluminum dihydride and the like, among these, triethylaluminum, triisobutylaluminum, hydrogenated diethylaluminum, hydrogenated diisobutylaluminum are preferred. The organoaluminum compound as component (B) described above can be used alone or in combination of two or more.

  The component (C) of the catalyst system used for the production of the butadiene polymer before modification is selected from the group consisting of Lewis acids, complex compounds of metal halides and Lewis bases, and organic compounds containing active halogens. It is at least one halogen compound.

  The Lewis acid has Lewis acidity and is soluble in hydrocarbons. Specifically, methyl aluminum dibromide, methyl aluminum dichloride, ethyl aluminum dibromide, ethyl aluminum dichloride, butyl aluminum dibromide, butyl aluminum dichloride, dimethyl aluminum bromide, dimethyl aluminum chloride, diethyl bromide Aluminum, diethylaluminum chloride, dibutylaluminum bromide, dibutylaluminum chloride, methylaluminum sesquibromide, methylaluminum sesquichloride, ethylaluminum sesquibromide, ethylaluminum sesquichloride, dibutyltin dichloride, aluminum tribromide, antimony trichloride, Examples include antimony pentachloride, phosphorus trichloride, phosphorus pentachloride, tin tetrachloride, and silicon tetrachloride. Among these, diethylaluminum chloride, sesquiethylaluminum chloride, ethylaluminum dichloride, diethylaluminum bromide, ethylaluminum sesquibromide, and ethylaluminum dibromide are preferable. Alternatively, a reaction product of an alkylaluminum and a halogen such as a reaction product of triethylaluminum and bromine can be used.

  Examples of the metal halide constituting the complex compound of the above metal halide and Lewis base include beryllium chloride, beryllium bromide, beryllium iodide, magnesium chloride, magnesium bromide, magnesium iodide, calcium chloride, calcium bromide, iodine. Calcium chloride, barium chloride, barium bromide, barium iodide, zinc chloride, zinc bromide, zinc iodide, cadmium chloride, cadmium bromide, cadmium iodide, mercury chloride, mercury bromide, mercury iodide, manganese chloride, Manganese bromide, manganese iodide, rhenium chloride, rhenium bromide, rhenium iodide, copper chloride, copper iodide, silver chloride, silver bromide, silver iodide, gold chloride, gold iodide, gold bromide, etc. Of these, magnesium chloride, calcium chloride, barium chloride, manganese chloride, zinc chloride, and copper chloride are preferred. , Magnesium chloride, manganese chloride, zinc chloride, copper chloride being particularly preferred.

  Moreover, as a Lewis base which comprises the complex compound of the said metal halide and a Lewis base, a phosphorus compound, a carbonyl compound, a nitrogen compound, an ether compound, alcohol, etc. are preferable. Specifically, tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, triethylphosphine, tributylphosphine, triphenylphosphine, diethylphosphinoethane, diphenylphosphinoethane, acetylacetone, benzoylacetone , Propionitrile acetone, valeryl acetone, ethyl acetylacetone, methyl acetoacetate, ethyl acetoacetate, phenyl acetoacetate, dimethyl malonate, diethyl malonate, diphenyl malonate, acetic acid, octanoic acid, 2-ethyl-hexanoic acid, olein Acid, stearic acid, benzoic acid, naphthenic acid, versatic acid, triethylamine, N, N-dimethylacetamide, tetrahydrofuran, diphenyl ether, 2-ethyl-hexyl alcohol Examples include oleyl alcohol, stearyl alcohol, phenol, benzyl alcohol, 1-decanol, and lauryl alcohol. Among these, tri-2-ethylhexyl phosphate, tricresyl phosphate, acetylacetone, 2-ethylhexanoic acid, versatic acid, 2 -Ethylhexyl alcohol, 1-decanol and lauryl alcohol are preferred.

The Lewis base is reacted at a ratio of 0.01 to 30 mol, preferably 0.5 to 10 mol, per mol of the metal halide. When the reaction product with the Lewis base is used, the metal remaining in the polymer can be reduced.
Examples of the organic compound containing the active halogen include benzyl chloride.

  In addition to the components (A) to (C), an organoaluminum oxy compound, so-called aluminoxane, is further added as a component (D) to the catalyst system used for the production of the butadiene-based polymer before modification. preferable. Here, examples of the aluminoxane include methylaluminoxane, ethylaluminoxane, propylaluminoxane, butylaluminoxane, chloroaluminoxane and the like. By adding aluminoxane as the component (D), the molecular weight distribution becomes sharp and the activity as a catalyst is improved.

  The amount or composition ratio of each component of the catalyst system used in the present invention is appropriately selected according to its purpose or necessity. Of these, the component (A) is preferably used in an amount of 0.00001 to 1.0 mmol, more preferably 0.0001 to 0.5 mmol, with respect to 100 g of 1,3-butadiene, for example. When the amount of component (A) used is less than 0.00001 mmol, the polymerization activity is low, and when it exceeds 1.0 mmol, the catalyst concentration increases and a deashing step is required. Moreover, the ratio of (A) component and (B) component is molar ratio, (A) component: (B) component is 1: 1-1: 700, Preferably it is 1: 3-1: 500. Furthermore, the ratio of the halogen in the component (A) and the component (C) is in the molar ratio of 1: 0.1 to 1:30, preferably 1: 0.2 to 1:15, more preferably 1: 2. 0 to 1: 5.0. Moreover, the ratio of the aluminum in (D) component and (A) component is 1: 1-700: 1 by molar ratio, Preferably it is 3: 1-500: 1. Outside the range of these catalyst amounts or component ratios, it is not preferable because it does not act as a highly active catalyst or requires a step of removing the catalyst residue. In addition to the above components (A) to (C), the polymerization reaction may be carried out in the presence of hydrogen gas for the purpose of adjusting the molecular weight of the polymer.

  As a catalyst component, in addition to the components (A), (B), and (C), a small amount of a conjugated diene monomer such as 1,3-butadiene, if necessary, specifically (A ) You may use in the ratio of 0-1000 mol per 1 mol of compounds of a component. A conjugated diene monomer such as 1,3-butadiene as a catalyst component is not essential, but when used in combination, there is an advantage that the catalytic activity is further improved.

  The production of the catalyst is, for example, by dissolving the components (A) to (C) in a solvent and further reacting a monomer such as 1,3-butadiene as necessary. In that case, the addition order of each component is not specifically limited, Furthermore, you may add an aluminoxane as (D) component. From the viewpoint of improving the polymerization activity and shortening the polymerization initiation induction period, it is preferable that these components are mixed in advance, reacted and aged. Here, the aging temperature is 0 to 100 ° C, and preferably 20 to 80 ° C. If the temperature is less than 0 ° C., the aging is not sufficiently performed. If the temperature exceeds 100 ° C., the catalytic activity is lowered and the molecular weight distribution is widened. The aging time is not particularly limited, and can be ripened by contacting in the line before adding to the polymerization reaction tank. Usually, 0.5 minutes or more is sufficient, and stable for several days.

  The production of the butadiene-based polymer before modification is preferably performed by solution polymerization. Here, in the case of solution polymerization, an inert organic solvent is used as the polymerization solvent. Examples of the inert organic solvent include saturated aliphatic hydrocarbons having 4 to 10 carbon atoms such as butane, pentane, hexane and heptane, saturated alicyclic hydrocarbons having 5 to 20 carbon atoms such as cyclopentane and cyclohexane, 1- Monoolefins such as butene and 2-butene, aromatic hydrocarbons such as benzene, toluene and xylene, methylene chloride, chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene, 1,2-dichloroethane, chlorobenzene, bromobenzene, chloro And halogenated hydrocarbons such as toluene. Among these, a C5-C6 aliphatic hydrocarbon and alicyclic hydrocarbon are especially preferable. These solvents may be used alone or in combination of two or more.

  The production of the butadiene-based polymer before the modification needs to be performed at a polymerization temperature of 25 ° C. or less, and is preferably performed at 10 to −78 ° C. When the polymerization temperature exceeds 25 ° C., the polymerization reaction cannot be sufficiently controlled, and the cis-1,4 bond content of the produced butadiene polymer is lowered and the vinyl bond content is raised. On the other hand, when the polymerization temperature is lower than -78 ° C, the freezing point of the solvent falls below, so that the polymerization cannot be performed.

  Production of the butadiene-based polymer before the modification may be performed either batchwise or continuously. In addition, in the production of the butadiene-based polymer, in order not to deactivate the rare earth element compound-based catalyst and the polymer, mixing of a deactivating compound such as oxygen, water, carbon dioxide gas in the polymerization reaction system. Consideration to eliminate as much as possible is necessary.

  The butadiene-based polymer having a conjugated modified group (modified butadiene-based polymer) is a polymer obtained by modifying the butadiene-based polymer before modification with a specific modifying agent described later, which is a conjugated modified group. Have Here, the conjugated modification group means a functional group to be conjugated, and at least a part of the modification group and the polymer having the modification group are conjugated via the modification group. With such a butadiene-based copolymer having a conjugated modification group, delocalized electrons existing in the polymer act to improve the affinity for carbon black. It becomes possible to disperse the agent extremely effectively, and a more excellent low heat generation property can be realized.

  When the modified butadiene polymer used in the present invention is produced, the butadiene polymer before modification having a terminal living ratio of 20% or more, preferably 30% or more is used. And the said modified | denatured butadiene type polymer is obtained by throwing the modifier | denaturant shown below into the butadiene type polymer before a modification | denaturation which has such a terminal living ratio.

  Here, the “terminal living ratio” means the reactivity at the polymer terminal after the polymerization reaction, and 4,4′-dimethylaminobenzophenone is reacted under the following conditions, and the resulting polymer has UV absorption. Can be determined by measuring and quantifying.

The terminal living ratio will be specifically described with reference to FIG.
The vertical axis indicates the value of UV / RI obtained by gel permeation chromatography (GPC) measurement. UV indicates a peak area value obtained from the UV absorbance caused by the modifier that has reacted with the polymer, and RI indicates a peak area value obtained from the differential refractive index (RI) of the polymer itself.

The horizontal axis indicates a value of (1 / Mn) × 10 ³ , and Mn is the absolute molecular weight (number average molecular weight). In FIG. 1, LowCisBR was polymerized by anionic polymerization using a Li-based catalyst, and was modified with a modifier 4,4′-bis (diethylaminobenzophenone) (hereinafter also referred to as “DEAB”), which had different molecular weights Mn. Three types of UV / RI values are plotted and can be approximated as a straight line. In the case of anionic polymerization, since it is modified by 100%, the UV / RI of LowCisBR is defined as 100%, and is represented by A as shown in the following formula.
UV (Li-Br) / RI (Li-Br) = A

  On the other hand, using a catalyst containing a lanthanum series rare earth element (Nd) -containing compound according to the present invention which is coordination polymerization, high UVisRI values with different molecular weights Mn are plotted for HighCisBR modified with DEAB, Similar to the above, it can be approximated as a straight line. In the case of coordination polymerization, there are portions that are not living during polymerization, and it is difficult to modify 100%.

When the UV / RI of HighCisBR is represented by B as shown in the following formula,
UV (Nd-Br) / RI (Nd-Br) = B
The terminal living ratio in the present invention is defined as follows.
Terminal living ratio = B / A x 100 (%)

  In addition, the terminal living rate in this invention is computed from A value and B value obtained using LowCisBR of the same absolute molecular weight (number average molecular weight) as HighCisBR.

  Further, the terminal living ratio of the unmodified polymer reacted with isopropanol is set to 0%, and the UV / RI value obtained by subtracting the value of the unmodified line shown in FIG. 1 is used as the true value. The A value and B value are also shown in FIG.

  The three straight lines shown in FIG. 1 can be used as a calibration curve. For example, if the absolute molecular weight Mn (number average) of HihCisBR is known, the terminal living ratio in the present invention can be calculated.

As can be seen from FIG. 1, as the absolute molecular weight Mn (number average) increases, the terminal living ratio decreases and it becomes difficult to modify with a modifier.
Moreover, it is necessary to create a calibration curve each time the modifier changes.

Such a modifier capable of introducing a conjugated modifying group introduces a conjugated modifying group that can contribute to improving the affinity with carbon black described later, and is represented by the following formula (I) or formula (II): It is a heterocyclic nitrile compound represented.
θ-C≡N (I)
θ-R-C≡N (II)

  In the above formulas (I) and (II), θ represents a heterocyclic group. Further, θ is preferably a heterocyclic group containing a nitrogen atom, a heterocyclic group containing an oxygen atom, a heterocyclic group containing a sulfur atom, a heterocyclic group containing two or more heteroatoms, and one or more cyano groups. It is preferably at least one heterocyclic group selected from the group consisting of heterocyclic groups containing. Further, it may be a heteroaromatic group or a non-aromatic ring group such as thiophene, pyridine, furan, piperidine, dioxane, and also a monocyclic, bicyclic, tricyclic, or polycyclic heterocyclic group. It may be.

  Conventionally, the modifying groups that can be introduced into the butadiene-based polymer have been limited to specific groups such as —CN, —SiCl, —SiOR, and C═O. However, in the present invention, more excellent low heat generation is realized. From the viewpoint of conversion, a more preferable conjugated modifying group can be introduced. Such a conjugated modification group can more reliably conjugated a butadiene copolymer or the like, and contributes to an improvement in affinity for carbon black.

  Specific examples of such θ include 2-pyridyl, 3-pyridyl, 4-pyridyl, pyrazinyl, 2-pyrimidinyl, 4-pyrimidinyl, 5-pyrimidinyl, 3-pyridazinyl as a heterocyclic group containing a nitrogen atom. 4-pyridazinyl, N-methyl-2-pyrrolyl, N-methyl-3-pyrrolyl, N-methyl-2-imidazolyl, N-methyl-4-imidazolyl, N-methyl-5-imidazolyl, N-methyl-3 -Pyrazolyl, N-methyl-4-pyrazolyl, N-methyl-5-pyrazolyl, N-methyl-1,2,3-triazol-4-yl, N-methyl-1,2,3-triazol-5-yl N-methyl-1,2,4-triazol-3-yl, N-methyl-1,2,4-triazol-5-yl, 1,2,4-triazin-3-yl, , 2,4-Triazin-5-yl, 1,2,4-triazin-6-yl, 1,3,5-triazinyl, N-methyl-2-pyrrolin-2-yl, N-methyl-2-pyrroline -3-yl, N-methyl-2-pyrrolin-4-yl, N-methyl-2-pyrrolin-5-yl, N-methyl-3-pyrrolin-2-yl, N-methyl-3-pyrrolin-3 -Yl, N-methyl-2-imidazolin-2-yl, N-methyl-2-imidazolin-4-yl, N-methyl-2-imidazolin-5-yl, N-methyl-2-pyrazolin-3-yl N-methyl-2-pyrazolin-4-yl, N-methyl-2-pyrazolin-5-yl, 2-quinolyl, 3-quinolyl, 4-quinolyl, 1-isoquinolyl, 3-isoquinolyl, 4-isoquinolyl, N -Methylindole-2-y N-methylindol-3-yl, N-methylisoindol-1-yl, N-methylisoindol-3-yl, 1-indolidinyl, 2-indolidinyl, 3-indolidinyl, 1-phthalazinyl, 2-quinazolinyl 4-quinazolinyl, 2-quinoxalinyl, 3-cinnolinyl, 4-cinnolinyl, 1-methylindazol-3-yne, 1,5-naphthyridin-2-yl, 1,5-naphthyridin-3-yl, 1,5- Naphthyridin-4-yl, 1,8-naphthyridin-2-yl, 1,8-naphthyridin-3-yl, 1,8-naphthyridin-4-yl, 2-pteridinyl, 4-pteridinyl, 6-pteridinyl, 7- Pteridinyl, 1-methylbenzimidazol-2-yl, 6-phenanthridinyl, N-methyl-2-purinyl, -Methyl-6-purinyl, N-methyl-8-purinyl, N-methyl-β-carbolin-1-yl, N-methyl-β-carbolin-3-yl, N-methyl-β-carbolin-4-yl 9-acridinyl, 1,7-phenanthroline-2-yl, 1,7-phenanthroline-3-yl, 1,7-phenanthroline-4-yl, 1,10-phenanthroline-2-yl, 1,10-phenanthroline -3-yl, 1,10-phenanthroline-4-yl, 4,7-phenanthroline-1-yl, 4,7-phenanthroline-2-yl, 4,7-phenanthroline-3-yl, 1-phenazinyl, 2 -Phenazinyl, pyrrolidino, piperidino.

  Examples of the heterocyclic group containing an oxygen atom include 2-furyl, 3-furyl, 2-benzo [b] furyl, 3-benzo [b] furyl, 1-isobenzo [b] furyl, 3-isobenzo [b] furyl, 2 -Naphtho [2,3-b] furyl, 3-naphtho [2,3-b] furyl.

  Examples of the heterocyclic group containing a sulfur atom include 2-thienyl, 3-thienyl, 2-benzo [b] thienyl, 3-benzo [b] thienyl, 1-isobenzo [b] thienyl, 3-isobenzo [b] thienyl, 2 -Naphtho [2,3-b] thienyl, 3-naphtho [2,3-b] thienyl.

  Examples of the heterocyclic group containing two or more heteroatoms include 2-oxazolyl, 4-oxazolyl, 5-oxazolyl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, 3- Isothiazolyl, 4-isothiazolyl, 5-isothiazolyl, 1,2,3-oxadiazol-4-yl, 1,2,3-oxadiazol-5-yl, 1,3,4-oxadiazol-2- Yl, 1,2,3-thiadiazol-4-yl, 1,2,3-thiadiazol-5-yl, 1,3,4-thiadiazol-2-yl, 2-oxazolin-2-yl, 2-oxazoline- 4-yl, 2-oxazolin-5-yl, 3-isoxazolinyl, 4-isoxazolinyl, 5-isoxazolinyl, 2-thia Phosphorus-2-yl, 2-thiazoline-4-yl, 2-thiazoline-5-yl, 3-isothiazolinyl, 4-isothiazolinyl, 5- isothiazolinyl, 2-benzothiazolyl, and morpholino.

  Among these, θ is preferably a heterocyclic group containing a nitrogen atom, and 2-pyridyl, 3-pyridyl, and 4-pyridyl are particularly preferable.

  In the above formulas (I) and (II), R represents a divalent hydrocarbon group and corresponds to an alkylene group, an alkenylene group, an arylene group, or the like corresponding to a heterocyclic nitrile compound described later.

  Specific examples of such heterocyclic nitrile compounds include 2-pyridinecarbonitrile, 3-pyridinecarbonitrile, 4-pyridinecarbonitrile, and pyrazinecarbohydrate as compounds having a heterocyclic group containing a nitrogen atom. Nitrile, 2-pyrimidinecarbonitrile, 4-pyrimidinecarbonitrile, 5-pyrimidinecarbonitrile, 3-pyridazinecarbonitrile, 4-pyridazinecarbonitrile, N-methyl-2-pyrrolecarbonitrile, N-methyl-3-pyrrolecarb Nitrile, N-methyl-2-imidazolecarbonitrile, N-methyl-4-imidazolecarbonitrile, N-methyl-5-imidazolecarbonitrile, N-methyl-3-pyrazolecarbonitrile, N-methyl-4-pyrazolecarbonitrile Nitrile, N- Til-5-pyrazolecarbonitrile, N-methyl-1,2,3-triazole-4-carbonitrile, N-methyl-1,2,3-triazole-5-carbonitrile, N-methyl-1,2, 4-triazole-3-carbonitrile, N-methyl-1,2,4-triazole-5-carbonitrile, 1,2,4-triazine-3-carbonitrile, 1,2,4-triazine-5-carbonitrile Nitrile, 1,2,4-triazine-6-carbonitrile, 1,3,5-triazinecarbonitrile, N-methyl-2-pyrroline-2-carbonitrile, N-methyl-2-pyrroline-3-carbonitrile N-methyl-2-pyrroline-4-carbonitrile, N-methyl-2-pyrroline-5-carbonitrile, N-methyl-3-pyrroline-2-carbonitrile N-methyl-3-pyrroline-3-carbonitrile, N-methyl-2-imidazoline-2-carbonitrile, N-methyl-2-imidazoline-4-carbonitrile, N-methyl-2-imidazoline-5 Carbonitrile, N-methyl-2-pyrazolin-3-carbonitrile, N-methyl-2-pyrazoline-4-carbonitrile, N-methyl-2-pyrazolin-5-carbonitrile, 2-quinolinecarbonitrile, 3- Quinolinecarbonitrile, 4-quinolinecarbonitrile, 1-isoquinolinecarbonitrile, 3-isoquinolinecarbonitrile, 4-isoquinolinecarbonitrile, N-methylindole-2-carbonitrile, N-methylindole-3-carbonitrile, N- Methyl isoindole-1-carbonitrile, N-methyl iso Indole-3-carbonitrile, 1-indolizinecarbonitrile, 2-indolizinecarbonitrile, 3-indolizinecarbonitrile, 1-phthalazinecarbonitrile, 2-quinazolinecarbonitrile, 4-quinazolinecarbonitrile, 2-quinoxaline Carbonitrile, 3-cinnolinecarbonitrile, 4-cinnolinecarbonitrile, 1-methylindazole-3-carbonitrile, 1,5-naphthyridine-2-carbonitrile, 1,5-naphthyridine-3-carbonitrile, 1 , 5-naphthyridine-4-carbonitrile, 1,8-naphthyridine-2-carbonitrile, 1,8-naphthyridine-3-carbonitrile, 1,8-naphthyridine-4-carbonitrile, 2-pteridinecarbonitrile, 4 -Pteridinecarbonitrile, -Pteridinecarbonitrile, 7-pteridinecarbonitrile, 1-methylbenzimidazole-2-carbonitrile, phenanthridine-6-carbonitrile, N-methyl-2-purinecarbonitrile, N-methyl-6-purinecarbonitrile N-methyl-8-purinecarbonitrile, N-methyl-β-carboline-1-carbonitrile, N-methyl-β-carboline-3-carbonitrile, N-methyl-β-carboline-4-carbonitrile, 9-acridinecarbonitrile, 1,7-phenanthroline-2-carbonitrile, 1,7-phenanthroline-3-carbonitrile, 1,7-phenanthroline-4-carbonitrile, 1,10-phenanthroline-2-carbonitrile, 1,10-phenanthroline-3-carbonitrile 1,10-phenanthroline-4-carbonitrile, 4,7-phenanthroline-1-carbonitrile, 4,7-phenanthroline-2-carbonitrile, 4,7-phenanthroline-3-carbonitrile, 1-phenazinecarbonitrile, Examples include 2-phenazinecarbonitrile, 1-pyrrolidinecarbonitrile, and 1-piperidinecarbonitrile.

  Examples of the compound having a heterocyclic group containing an oxygen atom include 2-furonitrile, 3-furonitrile, 2-benzo [b] furancarbonitrile, 3-benzo [b] furancarbonitrile, and isobenzo [b] furan-1-carbo. Examples include nitrile, isobenzo [b] furan-3-carbonitrile, naphtho [2,3-b] furan-2-carbonitrile, and naphtho [2,3-b] furan-3-carbonitrile.

  As compounds having a heterocyclic group containing a sulfur atom, 2-thiophenecarbonitrile, 3-thiophenecarbonitrile, benzo [b] thiophene-2-carbonitrile, benzo [b] thiophene-3-carbonitrile, isobenzo [b] Examples include thiophene-1-carbonitrile, isobenzo [b] thiophene-3-carbonitrile, naphtho [2,3-b] thiophene-2-carbonitrile, and naphtho [2,3-b] thiophene-3-carbonitrile. .

  Compounds having a heterocyclic group containing two or more heteroatoms include 2-oxazolecarbonitrile, 4-oxazolecarbonitrile, 5-oxazolecarbonitrile, 3-isoxazolecarbonitrile, 4-isoxazolecarbonitrile, 5-isoxazole. Oxazolecarbonitrile, 2-thiazolecarbonitrile, 4-thiazolecarbonitrile, 5-thiazolecarbonitrile, 3-isothiazolecarbonitrile, 4-isothiazolecarbonitrile, 5-isothiazolecarbonitrile, 1,2,3-oxazole -4-carbonitrile, 1,2,3-oxazole-5-carbonitrile, 1,3,4-oxazole-2-carbonitrile, 1,2,3-thiazole-4-carbonitrile, 1,2,3 -Thiazole-5-carbo Tolyl, 1,3,4-thiazole-2-carbonitrile, 2-oxazoline-2-carbonitrile, 2-oxazoline-4-carbonitrile, 2-oxazoline-5-carbonitrile, 3-isoxazolinecarbonitrile, 4 -Isoxazoline carbonitrile, 5-isoxazoline carbonitrile, 2-thiazoline-2-carbonitrile, 2-thiazoline-4-carbonitrile, 2-thiazoline-5-carbonitrile, 3-isothiazoline carbonitrile, 4-isothiazoline carbonitrile Nitriles, 5-isothiazolinecarbonitriles, benzothiazole-2-carbonitriles, 4-morpholinecarbonitriles.

  As compounds having two or more cyano groups, 2,3-pyridinedicarbonitrile, 2,4-pyridinedicarbonitrile, 2,5-pyridinedicarbonitrile, 2,6-pyridinedicarbonitrile, 3,4- Pyridinedicarbonitrile, 2,4-pyrimidinedicarbonitrile, 2,5-pyrimidinedicarbonitrile, 4,5-pyrimidinedicarbonitrile, 4,6-pyrimidinedicarbonitrile, 2,3-pyrazinedicarbonitrile, 2,5-pyrazinedicarbonitrile, 2,6-pyrazinedicarbonitrile, 2,3-furandicarbonitrile, 2,4-furandicarbonitrile, 2,5-furandicarbonitrile, 2,3-thiophenedicarbonitrile 2,4-thiophene dicarbonitrile, 2,5-thiophene dicarbonitrile, N-methyl -2,3-pyrrole dicarbonitrile, N-methyl-2,4-pyrrole dicarbonitrile, N-methyl-2,5-pyrrole dicarbonitrile, 1,3,5-triazine-2,4-dicarb Nitrile, 1,2,4-triazine-3,5-dicarbonitrile, 3,2,4-triazine-3,6-dicarbonitrile, 2,3,4-pyridinetricarbonitrile, 2,3,5 -Pyridine tricarbonitrile, 2,3,6-pyridinetricarbonitrile, 2,4,5-pyridinetricarbonitrile, 2,4,6-pyridinetricarbonitrile, 3,4,5-pyridinetricarbonitrile, 2,4,5-pyrimidine tricarbonitrile, 2,4,6-pyrimidine tricarbonitrile, 4,5,6-pyrimidine tricarbonitrile, pyrazine tricarbonitrile Ril, 2,3,4-furantricarbonitrile, 2,3,5-furantricarbonitrile, 2,3,4-thiophenetricarbonitrile, 2,3,5-thiophenetricarbonitrile, N-methyl- 2,3,4-pyrrole tricarbonitrile, N-methyl-2,3,5-pyrrole tricarbonitrile, 1,3,5-triazine-2,4,6-tricarbonitrile, 1,2,4- Examples include triazine-3,5,6-tricarbonitrile.

  Among these, 2-cyanopyridine (2-pyridinecarbonitrile), 3-cyanopyridine (3-pyridinecarbonitrile), and 4-cyanopyridine (4-pyridinecarbonitrile) are preferable.

  As a method of modifying a butadiene-based polymer with a heterocyclic nitrile compound as described above, a polymer and a heterocyclic nitrile compound may be reacted. For example, a 1,3-butadiene monomer is required. Accordingly, a method may be mentioned in which another monomer is added and conjugated with a catalyst or an initiator to obtain a polymerization mixture, and a heterocyclic nitrile compound is added thereto. Further, a heterocyclic nitrile compound may be added to the activated polymerization mixture, or a reactive polymer formed by polymerizing a 1,3-butadiene monomer may be reacted with the heterocyclic nitrile compound. Good. Further, a heterocyclic nitrile compound may be added to the activated polymerization mixture, and a functionalizing agent may be added thereto.

  The polymerization mixture thus obtained is cooled and subjected to solvent removal and drying using a conventional method to obtain a modified butadiene-based polymer. For example, the polymer recovered from the polymer cement is poured into a solvent, and then the obtained polymer is dried using a dryer such as a drum dryer. At this time, the polymer may be directly recovered from the polymer cement dried with a drum dryer. The volatile substance in the obtained dry polymer is 1% by weight or less.

  The structure of the resulting modified butadiene-based polymer depends on the conditions used to adjust the reactive polymer, such as the type and amount of the catalyst and initiator, and the type and amount of the heterocyclic nitrile compound. Thus, it depends on the conditions used to react the reactive polymer with the heterocyclic nitrile compound.

  The modified butadiene-based polymer is presumed to have a structure represented by the following formula (X) or (Y).

式（Ｘ）および（Ｙ）中のＡは水素原子または金属原子を示し、金属原子は上記触媒に起因するものである。Ｂは単結合またはＲを示し、Ｒは上記式（I）および（II）と同義である。θは上記式（I）および（II）と同義であり、θ’はθから１つの原子が脱離した２価の置換基を示す。ただし、θ’はθが有するヘテロ原子にさらに水素原子などが付加した場合も含む。π₁およびπ₂はともにブタジエン系重合体のポリマー鎖を示す。

A in the formulas (X) and (Y) represents a hydrogen atom or a metal atom, and the metal atom originates from the catalyst. B represents a single bond or R, and R is as defined in the above formulas (I) and (II). θ is synonymous with the above formulas (I) and (II), and θ ′ represents a divalent substituent in which one atom is eliminated from θ. However, θ ′ includes a case where a hydrogen atom or the like is further added to the hetero atom of θ. Both π ₁ and π ₂ represent a polymer chain of a butadiene polymer.

  Then, when the butadiene-based polymer having the above structure is exposed to water vapor or the like, it is considered that the butadiene-based polymer is hydrolyzed and converted into a ketone-based structure such as the following formula (X ′) or (Y ′). .

式（Ｘ’）および（Ｙ’）中のＢ、θ、およびθ’は、上記式（I）および（II）と同義である。π₁およびπ₂はともにブタジエン系重合体のポリマー鎖を示す。

B, θ, and θ ′ in the formulas (X ′) and (Y ′) have the same meanings as the above formulas (I) and (II). Both π ₁ and π ₂ represent a polymer chain of a butadiene polymer.

  Since the butadiene polymer can take such a structure, it is presumed that the compatibility with the filler such as carbon black is further improved, and further excellent low heat generation can be realized.

The butadiene-based polymer is contained in an amount of 10% by mass or more, preferably 20 to 80% by mass, more preferably 30 to 70% by mass in 100% by mass of the rubber component. By setting the amount within the above range, the effects of the present invention can be sufficiently exerted. The rubber components other than the butadiene polymer having a functional group such as the butadiene polymer include natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene. Rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), halogenated butyl rubber, acrylonitrile-butadiene rubber (NBR), etc. Among these, natural rubber or polyisoprene rubber is particularly preferable. preferable. These rubber components may be used alone or in a blend of two or more.

[Carbon black]
In the rubber composition of the present invention, carbon black having a nitrogen adsorption specific surface area of 20 to 100 m ² / g, preferably 40 to 100 m ² / g, more preferably 40 to 80 m ² / g is used as a filler. Carbon black having a nitrogen adsorption specific surface area within the above range has a large particle size and a very high effect of improving low heat buildup. Such carbon black can be dispersed well due to the affinity of the butadiene-based polymer, and can sufficiently contribute to the improvement of the low heat generation. Specifically, the carbon black is preferably of the grade below HAF, and examples thereof include HAF, FF, FEF, GPF, SRF, and FT grades. From the viewpoint of improving fracture resistance, HAF, FEF and GPF grades are particularly preferred. Furthermore, you may use an inorganic filler as another filler. Examples of the inorganic filler include silica, talc, and aluminum hydroxide. In addition, these fillers may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  The carbon black is contained in an amount of 10 parts by mass or more, preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component of the rubber composition of the present invention. Although it does not specifically limit about an upper limit, Usually, it mix | blends in the quantity of 70 mass parts or less.

[Rubber composition]
The rubber composition of the present invention includes a rubber component containing the butadiene-based polymer, carbon black, a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, an anti-scorch agent, a softening agent, zinc oxide, stearic acid, A compounding agent usually used in the rubber industry, such as a silane coupling agent, can be appropriately selected and blended within a range that does not impair the object of the present invention. As these compounding agents, commercially available products can be suitably used. In addition, the said rubber composition can be manufactured by mix | blending the various compounding agent suitably selected as needed with the rubber component, kneading | mixing, heating, extrusion, etc.

[tire]
The tire using the rubber composition of the present invention can use the above-described rubber composition for any member of the tire, and is excellent in heat resistance and crack growth resistance. The tire is not particularly limited as long as the rubber composition is used for any member. Examples of the member include a tread, a sidewall, and the like, and can be manufactured by a usual method. In particular, when the rubber composition of the present invention is used for a side wall member, it is possible to obtain a high-performance tire capable of exhibiting the above effects sufficiently effectively.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
Each physical property of the butadiene polymer was measured according to the following method.

<< Microstructure [cis-1,4 bond content (%), 1,2-vinyl bond content (%)] >>
A Fourier transform infrared spectrophotometer (FT / IR-4100, manufactured by JASCO Corporation) was used, and measurement was performed by an infrared method (Morello method).

<< Ratio (Mw / Mn) of weight average molecular weight (Mw) and number average molecular weight (Mn) of butadiene-based polymer >>
Using gel permeation chromatography (trade name “HLC-8120GPC”, manufactured by Tosoh Corporation), a differential refractometer was used as a detector, and measurement was performed under the following conditions to calculate a standard polystyrene equivalent value.
Column; Trade name “GMHHXL” (manufactured by Tosoh Corporation) 2 Column temperature: 40 ° C.
Mobile phase: Tetrahydrofuran Flow rate: 1.0 ml / min
Sample concentration: 10mg / 20ml

[Production of Polymer A]
In a nitrogen atmosphere, a 5 L autoclave was charged with 2.4 kg of cyclohexane and 300 g of 1,3-butadiene under a nitrogen atmosphere. To the autoclave, as a catalyst component, a cyclohexane solution of neodymium versatate (0.09 mmol), a toluene solution of methylaluminoxane (MAO, 3.6 mmol), diisobutylaluminum hydride (DIBAH, 5.5 mmol) and diethylaluminum chloride (0. (18 mmol) in toluene and 1,3-butadiene (4.5 mmol) were aged at 40 ° C. for 30 minutes, and a pre-prepared catalyst composition was charged, followed by polymerization at 60 ° C. for 60 minutes. The reaction conversion of 1,3-butadiene was almost 100%. 200 g of this polymer solution was extracted into a methanol solution containing 0.2 g of 2,4-di-tert-butyl-p-cresol, and after the polymerization was stopped, the solvent was removed by steam stripping and dried with a roll at 110 ° C. Thus, a polymer A (butadiene-based polymer) before modification was obtained. The obtained polymer A had a cis-1,4 bond content of 96.3%, a 1,2-vinyl bond content of 0.63%, Mw / Mn = 1.8, and a terminal living ratio of 60%. there were.

[Production of polymer B]
Polymerization was carried out in the same manner according to the production of the polymer A, and then the polymer solution was kept at a temperature of 60 ° C., and a toluene solution of 4.16 mmol of 4,4′-dihydronaphthoquinone was added and reacted for 15 minutes (primary (Denaturation reaction). Thereafter, 200 g of this polymer solution was extracted into a methanol solution containing 1.3 g of 2,4-di-tert-butyl-p-cresol, and after the polymerization was stopped, the solvent was removed by steam stripping, and a roll at 110 ° C. By drying, a polymer B (modified butadiene-based polymer) was obtained. The obtained polymer B had a cis-1,4 bond content of 96.1%, a 1,2-vinyl bond content of 0.59%, and Mw / Mn = 2.3.

[Production of polymer C]
After polymerizing in the same manner according to the production of the polymer A, the polymer solution was further maintained at a temperature of 60 ° C., and a toluene solution of 2.16 mmol of 2-cyanopyridine was added and reacted for 15 minutes (primary modification reaction). I let you. Thereafter, 200 g of this polymer solution was extracted into a methanol solution containing 1.3 g of 2,4-di-tert-butyl-p-cresol, and after the polymerization was stopped, the solvent was removed by steam stripping, and a roll at 110 ° C. The polymer C (modified butadiene polymer) was obtained by drying. The obtained polymer C had a cis-1,4 bond content of 96.1%, a 1,2-vinyl bond content of 0.62%, and Mw / Mn = 2.2.

[Production of polymer D]
A glass bottle with a rubber stopper having a volume of about 1 L was dried and purged with nitrogen, and the purified and dried cyclohexane solution of butadiene and cyclohexane were added to the glass bottle, respectively, and a cyclohexane solution of 1,3-butadiene (butadiene concentration: 12) 0.0 mass%) was charged. Next, 0.30 ml of tert-butyllithium (1.57M) and 0.185 ml of 2,2-di (2-tetrahydrofuryl) propane (0.2N) were added and polymerized in a water bath at 50 ° C. for 1.5 hours. Went. The terminal living ratio of the polymer at this time was 100%. Furthermore, the polymer solution was kept at a temperature of 50 ° C., and 0.84 mmol of 2-cyanopyridine was added and reacted for 15 minutes. Thereafter, 200 g of this polymer solution was extracted into a methanol solution containing 1.3 g of 2,4-di-tert-butyl-p-cresol, and after the polymerization was stopped, the solvent was removed by steam stripping, and a roll at 110 ° C. The polymer D (modified butadiene-based polymer) was obtained by drying. The resulting polymer D had a cis-1,4 bond content of 45.4%, a 1,2-vinyl bond content of 18.33% and Mw / Mn = 1.3.

[Production of polymer E]
A 100 mL volume glass bottle with a rubber stopper was dried and purged with nitrogen. To the glass bottle, 7.11 g of a cyclohexane solution of butadiene (15.2% by mass) and a cyclohexane solution of neodymium neodecanoate (0.56 M) were sequentially added. 0.59 mL, 10.32 mL of a toluene solution of methylaluminoxane MAO (PMAO manufactured by Tosoh Akzo) (aluminum concentration: 3.23 M) and 7.77 mL of a hexane solution (0.90 M) of diisobutylaluminum hydride (manufactured by Kanto Chemical) were added. After aging for 4 minutes at room temperature, 2.36 mL of a hexane solution (0.95 M) of chlorinated diethylaluminum (manufactured by Kanto Kagaku) was added, and aging was performed for 15 minutes with occasional stirring at room temperature. The concentration of neodymium in the obtained catalyst solution was 0.011 M (mol / L).

  A glass bottle with a rubber stopper having a volume of about 1 L is dried and purged with nitrogen. A hexane cyclohexane solution and a dry cyclohexane solution are added to the glass bottle, and 40 g of a 5% strength by weight cyclohexane solution is charged. It was. Next, the prepared catalyst solution was added, and polymerization was carried out in a 10 ° C. water bath for 4 hours. At this time, the terminal living ratio of the polymer was 90%. Subsequently, a toluene solution of 4.16 mmol of 2-cyanopyridine was added and gradually heated and stirred in a water bath at each polymerization temperature. Thereafter, the reaction was stopped by adding 2 mL of a 5% solution of an anti-aging agent 2,2′-methylene-bis (4-ethyl-6-tert-butylphenol, NS-5) in isopropanol at 50 ° C., and a trace amount of NS After reprecipitation in isopropanol containing -5, it was dried on a drum to obtain a polymer E (modified butadiene polymer) with a yield of almost 100%. The obtained polymer E had a cis-1,4 bond content of 99.0%, a 1,2-vinyl bond content of 0.13%, and Mw / Mn = 2.0.

[Production of polymer F]
Polymerization was carried out in a 70 ° C. water bath, and a polymer F (modified butadiene-based polymer) was obtained according to the polymer D except that the polymer solution was kept at 70 ° C. The resulting polymer F had a cis-1,4 bond content of 38.6%, a 1,2-vinyl bond content of 20.51%, and Mw / Mn = 1.8.

[Production of polymer G]
A polymer G (modified butadiene-based polymer) was obtained in accordance with the polymer C except that 2-pyridylacetonitrile was used instead of 2-cyanopyridine. The obtained polymer G had a cis-1,4 bond content of 96.0%, a 1,2-vinyl bond content of 0.61%, and Mw / Mn = 2.1.

[Comparative Examples 1-4, Examples 1-5]
A rubber composition having the compounding formulation shown in Table 1 was prepared, and crack growth resistance and low heat build-up (3% tan δ) were measured according to the following method for a vulcanized rubber obtained by vulcanizing at 145 ° C. for 33 minutes. did. The results are shown in Tables 2-4.

《Crack growth resistance》
A 0.5 mm crack was made in the center part of the JIS No. 3 test piece, fatigue was repeatedly given at a strain of 50 to 100% at room temperature, and the number of times until the sample was cut was measured. The value at each strain was determined and the average value was used. In Table 2, Comparative Example 1 in which Polymer A was blended was taken as 100, and Comparative Examples and Examples in which carbon black having the same nitrogen adsorption specific surface area was blended were displayed as indices. Further, in Table 3, the index is displayed with Comparative Example 3 as 100 including Example 1 in Table 1. Furthermore, in Table 4, the index is displayed with Comparative Example 4 as 100 including Example 1 in Table 1. A larger index value indicates better crack growth resistance.

<< Low exothermicity (3% tan δ) >>
A dynamic spectrometer (manufactured by Rheometrics, USA) was used, and measurement was performed under the conditions of tensile dynamic strain of 3%, frequency of 15 Hz, and 50 ° C. In Table 2, the comparative example 1 which mix | blended the polymer A was set to 100, and the Example and comparative example which mix | blended carbon black which has the same nitrogen adsorption specific surface area were displayed as an index | index. Further, in Table 3, the index was displayed with Comparative Example 3 as 100 including Example 1 in Table 1. Furthermore, in Table 4, the index is displayed with Comparative Example 4 as 100 including Example 1 in Table 1. It shows that it is excellent in low exothermic property (low loss property), so that an index value is small.

* 1: Polymers A to G and types of polymers used are shown in Tables 2 to 4.
* 2: Tables 2 to 4 show the nitrogen adsorption specific surface areas of the carbon blacks used.
* 3: N- (1,3-dimethylbutyl) -N′-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., NOCRACK 6C
* 4: 2,2,4-trimethyl-1,2-dihydroquinoline polymer, NOUCL 224, manufactured by Ouchi Shinsei Chemical Co., Ltd.
* 5: N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd., Noxeller CZ-G
* 6: Dibenzothiazyl disulfide, manufactured by Ouchi Shinsei Chemical Co., Ltd., Noxeller DM-P

[Examples 6 to 7]
A rubber composition having a formulation shown in Table 5 was prepared, and vulcanized rubber obtained by vulcanization at 145 ° C. for 33 minutes was subjected to crack growth resistance and low heat build-up in the same manner as in the above Examples and Comparative Examples ( 3% tan δ) was measured. The results are shown in Table 6. However, Example 6 was set as 100 and displayed as an index.

  * 1 to * 6 in the table are synonymous with Table 1.

  According to the results of Table 2, Examples 1 and 2 using a butadiene polymer modified with a modifier specified in the present invention are compared to Comparative Example 1 using an unmodified butadiene polymer. Thus, it can be seen that both the crack growth resistance and the low heat build-up have excellent effects. Moreover, these Examples 1-2 show a still higher crack growth resistance and low exothermicity than the comparative example 2 using the butadiene-type polymer modified with modifiers other than the modifier specified in the present invention. I understand that.

  According to the results of Table 3, Examples 1 and 3 to 4 having a cis content of 40% or more exhibit higher crack growth resistance and lower heat generation than Comparative Example 3 having low elongation crystallinity. I understand that. In particular, Examples 1 and 4 having a cis content of 90% or more show better crack growth resistance and low exothermicity than Example 3 having a cis content of less than 90%. . Further, Example 4 in which 98% or more is more preferable than Example 1 in which the cis content is 96% or more.

According to the results of Table 4, Examples 1 and 5 is a nitrogen adsorption specific surface area of 20 to 100 m ² / g of carbon black, crack growth resistance and than Comparative Example 4 in which the value exceeds 100 m ² / g It can be seen that both low exothermic properties are excellent.

According to the results in Table 6, Example 7 containing 10% by mass of the butadiene polymer (Polymer C) in 100% by mass of the rubber component is more than Example 6 in which the butadiene polymer is less than 10% by mass. Also, it can be seen that both the crack growth resistance and the low exothermic property show better results. On the other hand, Example 1 and Example 5 using the same polymer C as Example 7 and having a nitrogen adsorption specific surface area of carbon black in the range of 40 to 80 m ² / g are more suitable for nitrogen adsorption ratio of carbon black. It is also clear that the results are more favorable than Example 7 where the surface area is outside the above range.

It is a figure of the calibration curve for calculating the terminal living rate of one embodiment regarding the present invention.

Claims (10)

A rubber component containing a butadiene-based polymer having a cis-modified group having a cis content of 40% or more, which is modified with a modifier which is a heterocyclic nitrile compound represented by formula (I) or formula (II) ,
A rubber composition comprising a carbon black having a nitrogen adsorption specific surface area of 20 to 100 m ² / g;
θ-C≡N (I)
θ-R-C≡N (II)
(In formulas (I) and (II), θ represents at least one selected from the group consisting of 2-pyridyl, 3-pyridyl, and 4-pyridyl, and R represents a divalent hydrocarbon group.) . The rubber composition according to claim 1 , wherein the rubber component includes natural rubber and / or polyisoprene rubber. 3. The rubber composition according to claim 1, wherein the rubber component contains 10% by mass or more of the butadiene-based polymer in 100% by mass of the rubber component. The rubber composition according to any one of claims 1 to 3 , wherein a cis content of the butadiene-based polymer is 90% or more. The ratio of the weight average molecular weight of the butadiene-based polymer (Mw) to number-average molecular weight (Mn) (Mw / Mn) is one of the claims 1 to 4, characterized in that it is 1.3 to 3.5 A rubber composition according to any one of the above. The rubber composition according to claim 1 , comprising 10 parts by mass or more of the carbon black with respect to 100 parts by mass of the rubber component. The rubber composition according to claim 1 , wherein the carbon black has a nitrogen adsorption specific surface area of 40 to 80 m ² / g.   The method for producing a rubber composition according to claim 1, further comprising a step of adding a modifier to a butadiene-based polymer having a terminal living ratio of 20% or more. A tire characterized by using the rubber composition according to any one of claims 1 to 7. A tire comprising the rubber composition according to claim 1 as a sidewall member.

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