JP2011099012A - Rubber composition for tie rubber, and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for tire rubber capable of attaining excellent durability while retaining a sufficient low heat generation property when it is adopted for the rubber tire of the pneumatic tire given with a severe use condition, and a pneumatic tire obtained from it. <P>SOLUTION: In the pneumatic tire including at least one sheet of carcass ply in which a plurality of steel cords are arranged, an inner liner arranged on a tire inner side of the carcass ply on the tire innermost side and the tire rubber arranged between the carcass ply and the inner liner, the rubber composition for tire rubber is characterized in that carbon black is formulated in a rubber component used for forming the tire rubber and containing a modified butadiene based polymer in which a butadiene based polymer manufactured under a specific condition is modified. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tie rubber suitable for forming a tie rubber disposed between a carcass ply and an inner liner, and a pneumatic tire using the same, and more particularly, excellent low heat generation and durability. TECHNICAL FIELD The present invention relates to a rubber composition for tie rubber that can exhibit properties and resistance to deterioration and a pneumatic tire using the same.

  In general, heavy-duty pneumatic tires are exposed to harsh usage environments that require long-term use under high internal pressure, so the rubber composition forming such tires has a high degree of durability and resistance to deterioration. Required. In order to improve the durability, it is known that it is effective to use a rubber composition containing carbon black, but on the other hand, loss tangent (tan δ) is increased and heat generation is increased. There is a tendency. When such a rubber composition is used for a member that can be greatly deformed, particularly a tie rubber disposed between the carcass ply and the inner liner, such a member is close to the air filled in the tire at a high internal pressure. Therefore, there is a possibility that the heat generation becomes high and the thermal deterioration is promoted.

  Under these circumstances, for example, in Patent Document 1, in order to achieve excellent durability, the rubber layer adjacent to the carcass ply contains an organic acid cobalt salt while the tie rubber is a two-layer rubber layer, and the inner liner A heavy-duty pneumatic tire is disclosed in which an organic acid cobalt salt is not contained in the rubber layer adjacent to the rubber layer. In order to achieve low heat build-up, butadiene rubber is employed as a polymer for forming tie rubber, or natural rubber capable of exhibiting higher durability is blended.

Japanese Patent Laid-Open No. 10-297209

  However, although the tie rubber described in Patent Document 1 exhibits excellent durability while significantly improving the adhesion between the steel cord and the rubber and the W / B bulge, there is room for improvement in improving low heat generation. It is left. In addition, tie rubber that employs butadiene rubber exhibiting low heat build-up as a polymer has a risk of lowering durability, and even when natural rubber is blended, it causes a decrease in heat build-up. As described above, it is still difficult to achieve a tie rubber having both excellent durability and low heat generation.

  Accordingly, the present invention provides a rubber composition for a tie rubber that can achieve excellent durability while maintaining good low heat generation when used in a tie rubber of a pneumatic tire that is subjected to severe use conditions, and a rubber composition obtained therefrom. It aims to provide a pneumatic tire.

In order to solve the above-mentioned problems, the present inventors have found a rubber composition for tie rubber containing a specific polymer and carbon black, and have completed the present invention.
That is, the rubber composition for tie rubber of the present invention is
At least one carcass ply in which a plurality of steel cords are arranged, an inner liner disposed inside the tire of the innermost carcass ply, and a tie rubber disposed between the carcass ply and the inner liner A rubber composition for tie rubber, which is used to form the tie rubber in a pneumatic tire, and is formed by blending carbon black with a rubber component containing a modified butadiene polymer obtained by modifying a butadiene polymer. Because
The butadiene-based polymer is
Component (A): a monomer containing at least 1,3-butadiene in the presence of a rare earth element-containing material having an atomic number of 57 to 71 in the periodic table or a reaction system of these compounds and a Lewis base It is characterized by being produced by polymerizing.

The catalyst system preferably further contains at least one of component (B): Lewis acid, a complex compound of a metal halide and a Lewis base, and an organic compound containing active halogen, and component (C): AlR ¹ R ² R ³ (wherein R ¹ and R ² may be the same or different, and are a hydrocarbon group or hydrogen atom having 1 to 10 carbon atoms; R ³ is a carbon atom having 1 to 10 carbon atoms) A hydrogen group, wherein R ³ may be the same as or different from R ¹ or R ² above), and / or (D) component: aluminoxane. desirable.

The modified butadiene polymer is preferably contained in an amount of 10 to 50% by mass in 100% by mass of the rubber component.
Furthermore, the carbon black may be blended in an amount of 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component.
The modified butadiene polymer is desirably obtained by modifying a butadiene polymer with a nitrogen-containing compound, and the nitrogen-containing compound may be a primary amine compound or a heterocyclic nitrile compound. May be.
The rubber component preferably contains natural rubber and / or polyisoprene rubber.

  The pneumatic tire of the present invention is characterized by comprising a tie rubber formed from the rubber composition for tie rubber.

According to the rubber composition for tie rubber of the present invention, it is possible to exhibit excellent low heat buildup and high durability.
Therefore, if the rubber composition is used for tie rubber, a high-performance pneumatic tire that can sufficiently withstand even a severe use environment can be realized, and such a tire is particularly suitable as a heavy-duty pneumatic tire.

It is a right half sectional view of the pneumatic tire concerning the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings as necessary.
The rubber composition for tie rubber of the present invention is
At least one carcass ply in which a plurality of steel cords are arranged, an inner liner disposed inside the tire of the innermost carcass ply, and a tie rubber disposed between the carcass ply and the inner liner A rubber composition for tie rubber, which is used to form the tie rubber in a pneumatic tire, and is formed by blending carbon black with a rubber component containing a modified butadiene polymer obtained by modifying a butadiene polymer. Because
The butadiene-based polymer is
Component (A): a monomer containing at least 1,3-butadiene in the presence of a rare earth element-containing material having an atomic number of 57 to 71 in the periodic table or a reaction system of these compounds and a Lewis base It is characterized by being produced by polymerizing. FIG. 1 is a right half sectional view of a pneumatic tire according to the present invention.

  As shown in FIG. 1, a pneumatic tire 10 according to an embodiment of the present invention includes at least one carcass ply 4, and the carcass ply 4 is coated with a plurality of steel cords arranged in parallel. It is covered with rubber (not shown). Both ends of the carcass ply 4 in the width direction are wound around and fixed to the bead cores 3a of the bead portions 3, respectively. The pneumatic tire 10 includes a carcass ply 4 straddling the bead portion 3, a tread 1 disposed on the outer side in the tire radial direction of the carcass ply 4, and a side portion 2. Further, an inner liner 5 is disposed on the inner side of the innermost carcass ply of the carcass ply 4, and a tie rubber 6 is disposed between the carcass ply 4 and the inner liner 5. The tie rubber 6 is formed of the rubber composition for tie rubber of the present invention described later.

  In particular, when the pneumatic tire 10 is a heavy duty pneumatic tire, the internal pressure of the air to be filled is very high, so that the rubber is likely to get into the steel cord forming the carcass ply 4 and cause damage to the tire. It might be. In addition, a small amount of air leakage that is likely to be induced by high internal pressure may promote rubber deterioration. Therefore, if the tie rubber formed from the rubber composition for tie rubber of the present invention to be described later is arranged in a pneumatic tire, it has an excellent low heat generation while functioning as a cushioning material that can effectively prevent the rubber cord from getting into the steel cord. And high durability.

[Catalyst system in the production of butadiene polymers]
The component (A) of the catalyst system 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 with a Lewis base. Here, among the rare earth elements having atomic numbers of 57 to 71, neodymium, praseodymium, cerium, lanthanum, gadolinium, or a mixture thereof is preferable, and neodymium is particularly preferable.

  The rare earth element-containing compound is preferably a salt or complex soluble in a hydrocarbon solvent. Specifically, the rare earth element carboxylate, alkoxide, β-diketone complex, phosphate, and phosphite are included. Among 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 (I):
(R ⁴ —CO ₂ ) ₃ M (I)
(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 rare earth element alkoxide, the following general formula (II):
(R ⁵ O) ₃ M (II)
(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). Examples of the alkoxy group represented by R ⁵ O include 2-ethyl-hexyloxy group, oleyloxy group, stearyloxy group, phenoxy group, benzyloxy group and the like. Among these, 2-ethyl-hexyloxy group and benzyloxy 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.

  As the rare earth element phosphate and phosphite, 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) phos And salts with phosphoric acid and the like. Among these, the rare earth element, bis (2-ethylhexyl) phosphate, bis (1-methylheptyl) phosphate, mono-2-ethylhexyl 2-ethylhexylphosphonate, A salt with bis (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 branch 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 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.

In the present invention, as the catalyst system,
(B) component: You may contain at least 1 sort (s) of the organic compound containing a Lewis acid, the complex compound of a metal halide and a Lewis base, and an active halogen.

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 sesquibromide, ethylaluminum sesquibromide, ethylaluminum sesquichloride, dibutyltin dichloride, aluminum tribromide, antimony trichloride, Examples include antimony pentachloride, phosphorus trichloride, phosphorus pentachloride, tin tetrachloride, and silicon tetrachloride. Of these, diethylaluminum chloride, sesquiethylaluminum chloride, ethylaluminum dichloride, diethylaluminum bromide, ethylaluminum sesquibromide, and ethylaluminum dibromide are preferred.
Alternatively, a reaction product of an alkylaluminum and a halogen such as a reaction product of triethylaluminum and bromine can be used.

  The metal halide constituting the complex compound of the above metal halide and Lewis base includes 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 usually 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 the present invention, the catalyst system further includes
Component (C): AlR ¹ R ² R ³ (wherein R ¹ and R ² may be the same or different, a hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom, and R ³ is carbon number) 1 to 10 hydrocarbon groups, wherein R ³ may be the same as or different from R ¹ or R ² above), and / or component (D): Aluminoxane may be included.

Examples of the organoaluminum compound represented by AlR ¹ R ² R ³ which is the component (C) of the catalyst system include trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, Triisobutylaluminum, tri-t-butylaluminum, tripentylaluminum, trihexylaluminum, tricyclohexylaluminum, trioctylaluminum; diethylaluminum hydride, di-n-propylaluminum hydride, di-n-butylaluminum hydride, Diisobutylaluminum hydride, dihexylaluminum hydride, diisohexylaluminum hydride, dioctylaluminum hydride, diisooctylaluminum hydride; ethylaluminium Muzi hydride, n- propyl aluminum dihydride, include isobutyl aluminum dihydride and the like, among these, triethylaluminum, triisobutylaluminum, hydrogenated diethylaluminum, hydrogenated diisobutylaluminum are preferred. The organoaluminum compound as component (C) described above can be used alone or in combination of two or more.

  The aluminoxane as the component (D) of the catalyst system means an organic aluminoxane compound, and examples thereof include methylaluminoxane, ethylaluminoxane, propylaluminoxane, butylaluminoxane, and chloroaluminoxane. 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, per 100 g of 1,3-butadiene. 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 the halogen in (A) component and (B) component is molar ratio, and is usually 1: 0.1-1: 30, Preferably it is 1: 0.2-1: 15, More preferably, it is 1: 2.0 to 1: 5.0. Furthermore, the ratio of (A) component and (C) component is molar ratio, (A) component: (C) component is usually 1: 1-1: 700, Preferably it is 1: 3-1: 500. Moreover, the ratio of the aluminum and (A) component in (D) component is molar ratio, and is 1: 1-700: 1 normally, Preferably it is 3: 1-500: 1. It is preferable to make the amount within these catalyst amounts or the component ratio range because it acts as a highly active catalyst and there is no need for a step of removing the catalyst residue. In addition, it is preferable to include all of the components (A) to (D).
In addition to the above components (A) to (D), for the purpose of adjusting the molecular weight of the polymer, the polymerization reaction may be carried out in the presence of hydrogen gas.

  As a catalyst component, in addition to the above component (A), the component (B), the component (C) and / or the component (D) used as necessary, a conjugated diene compound such as 1,3-butadiene may be used as necessary. A small amount, specifically, a ratio of 0 to 1000 moles per mole of the component (A) compound may be used. A conjugated diene compound 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 above-mentioned catalyst can be produced, for example, by dissolving the component (A), the component (B), the component (C), or the component (D) in a solvent, -Reacting a conjugated diene compound such as butadiene. In that case, the addition order of each component is not specifically limited.

  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 about 0 to 100 ° C, preferably 20 to 80 ° C. When the temperature is less than 0 ° C., the aging is not sufficiently performed, and when the temperature exceeds 100 ° C., the catalytic activity may be reduced or the molecular weight distribution may be broadened. 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.

[Butadiene polymer]
In the production of the butadiene polymer used in the present invention, it is preferable to perform solution polymerization of a butadiene monomer in an organic solvent using a catalyst system containing the rare earth element-containing compound. Here, 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 concentration of the monomer in the solution is preferably 5 to 50% by mass, more preferably 10 to 30%.

  In the present invention, the temperature in the polymerization reaction of the butadiene-based polymer is preferably selected in the range of -80 to 150 ° C, more preferably -20 to 120 ° C. The polymerization reaction can be carried out under generated pressure, but it is usually desirable to operate at a pressure sufficient to keep the monomer in a substantially liquid phase. That is, the pressure will depend on the particular material being polymerized, the polymerization catalyst used and the polymerization temperature, but higher pressures can be used if desired, such pressure being a gas inert to the polymerization reaction and Can be obtained by an appropriate method such as pressurizing.

  In these polymerizations, it is desirable to use all raw materials involved in the polymerization, such as polymerization initiators, solvents, and monomers, from which reaction-inhibiting substances such as water, oxygen, carbon dioxide, and protic compounds have been removed. . In addition, the polymerization method in the production of the butadiene polymer may be any of batch type and continuous type. However, the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the modified butadiene polymer described later are In order to make the ratio (Mw / Mn) within a suitable range, it is desirable to use a batch system.

[Modified butadiene polymer]
The modified butadiene polymer used in the present invention is a polymer obtained by modifying the butadiene polymer obtained by the above production, and is a modified butadiene polymer having a relatively high cis content. This modified butadiene-based polymer has a modifying group, whereby the affinity for carbon black can be further improved, and carbon black can be dispersed extremely effectively. As a result, low heat build-up can be realized, and it is possible to maintain good durability in combination with a relatively high cis content.

  The butadiene-based polymer before modification is a polymer obtained by polymerizing a butadiene monomer and, if necessary, another copolymerizable monomer. As such a butadiene-based polymer, The 1,3-butadiene monomer unit is preferably 80 to 100% by mass, and the other monomer units copolymerizable with 1,3-butadiene are preferably 20 to 0% by mass. If 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 modified butadiene polymer described later may be unnecessarily lowered. The effect of is difficult to express. The butadiene polymer used in the present invention is particularly preferably composed of only 1,3-butadiene monomer, that is, particularly preferably polybutadiene rubber (BR).

  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.

  The modified butadiene polymer obtained by modifying the butadiene polymer is 10 to 50% by mass, preferably 10 to 40% by mass, more preferably 20 to 40% in 100% by mass of the rubber component of the rubber composition for tie rubber. It is included in the amount of mass%. By setting it as such content, the effect made into the objective of this invention can fully be exhibited with carbon black mentioned later.

  The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the modified butadiene polymer is preferably 1.6 to 3.5, more preferably 1.6 to 3. 0.0 is desirable. Here, Mn and Mw / Mn mean values obtained using polystyrene as a standard substance by gel permeation chromatography (GPC).

[Modifier]
The modified butadiene polymer used in the present invention is preferably one obtained by modifying the butadiene polymer with a modifier, and examples of the modifier include nitrogen-containing compounds and silicon-containing compounds. Of these, nitrogen-containing compounds are suitable modifiers. These modifiers may be used alone or in combination of two or more. By modifying using such a modifier, a suitable modifying group can be introduced into the butadiene-based polymer from the viewpoint of realizing further excellent low heat generation.

(I) Nitrogen-containing compound As a modifier for modifying the butadiene-based polymer, a nitrogen-containing compound may be used. The nitrogen-containing compound means a compound containing a nitrogen atom, and examples thereof include a compound having a substituted or unsubstituted amino group, amide group, imino group, imidazole group, nitrile group or pyridyl group. More specifically, isocyanate compounds such as diphenylmethane diisocyanate, crude MDI, trimethylhexamethylene diisocyanate, tolylene diisocyanate, 4- (dimethylamino) benzophenone, 4- (diethylamino) benzophenone, 4-dimethylaminobenzylideneaniline, 4-dimethyl Aminobenzylidenebutylamine, hexamethylenediamine, 3-aminopropylmethyldiethoxysilane, heptamethylenediamine, nonamethylenediamine, dodecamethylenediamine, decamethylenediamine, 1,5-naphthalenediamine, 1,8-naphthalenediamine, 1,3 -Bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethyl Renpentamin, pentaethylenehexamine dimethylimidazolidinone, N- methylpyrrolidone, 2-cyanopyridine, and the like. Among them, hexamethylenediamine, 3-aminopropylmethyldiethoxysilane, heptamethylenediamine, nonamethylenediamine, dodecamethylenediamine, decamethylenediamine, 1,5-naphthalenediamine, 1,8-, which are compounds having an amino group. 2-naphthalenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and also a 2-nitrile group Preference is given to primary amine compounds and heterocyclic nitrile compounds such as cyanopyridine, 3-cyanopyridine and 4-cyanopyridine.

  Among these nitrogen-containing compounds, a heterocyclic nitrile compound is particularly preferable from the viewpoint of exhibiting a more suitable affinity for carbon black. The modified butadiene polymer modified with the heterocyclic nitrile compound can bind to carbon black more effectively and disperse it, suppress heat generation due to rubbing between the carbon blacks, and improve heat generation. It can be further reduced.

Specifically, the heterocyclic nitrile compound is preferably a compound represented by the formula (W1) or the formula (W2).
θ-C≡N (W1)
θ−R _x −C≡N (W2)
In the above formulas (W1) and (W2), θ represents a heterocyclic group. Further, θ is 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 a heterocyclic group containing one or more cyano groups. It is preferably at least one heterocyclic group selected from the group consisting of Further, it may be a heteroaromatic ring group or a heterononaromatic ring group such as thiophene, pyridine, furan, piperidine, dioxane, etc., and further a monocyclic, bicyclic, tricyclic or polycyclic heterocyclic group. It may be.

  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 (W1) and (W2), R _x represents a divalent hydrocarbon group and corresponds to an alkylene group, alkenylene group, 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_xを示し、Ｒ_xは上記式（W1）および（W2）と同義である。θは上記式（W1）および（W2）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 _x , and R _x has the same meaning as in the above formulas (W1) and (W2). θ is synonymous with the above formulas (W1) and (W2), 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（W1）および（W2）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 (W1) and (W2). Both π ₁ and π ₂ represent a polymer chain of a butadiene polymer.

  Since the modified butadiene-based polymer can take such a structure, it is presumed that the compatibility with carbon black is further improved, and further low heat generation can be effectively realized.

[Carbon black]
In addition to the modified butadiene polymer, carbon black is blended in the rubber composition for tie rubber of the present invention. The amount of the carbon black is preferably 30 to 100 parts by mass, more preferably 30 to 80 parts by mass with respect to 100 parts by mass of the rubber component. By making the blending amount of the carbon black within the above range, the affinity with the carbon black exhibited by the modified butadiene polymer can be utilized more effectively, and the carbon black can be dispersed extremely well. It becomes.

As the carbon black is not particularly limited, it is preferable that the nitrogen adsorption specific surface area is in the range of 20~180m ² / g, more preferably in the range of 20 to 100 m ² / g. Carbon black having a nitrogen adsorption specific surface area within the above range has a large particle size and a very high effect of low heat generation. Specifically, such carbon black is preferably of the grade below HAF, for example, those of HAF, FF, FEF, GPF, SRF, FT grade, but from the viewpoint of improving durability. To HAF, FEF and GPF grades are particularly preferred.

[Rubber composition for Thai rubber]
The rubber composition for tie rubber of the present invention is obtained by blending carbon black with a rubber component containing the modified butadiene-based polymer.

  The rubber composition for tie rubber of the present invention preferably contains natural rubber and / or polyisoprene rubber (IR) as a rubber component other than the modified butadiene-based polymer. The natural rubber is not particularly limited, but is preferably a rubber obtained from a latex obtained by partially deproteinizing a protein in natural rubber latex by a mechanical separation technique, and further, the total nitrogen in the rubber The content is more preferably more than 0.1% by mass and 0.4% by mass or less. By blending the natural rubber obtained by such a mechanical separation method, unnecessary substances in the natural rubber latex that may increase exothermic properties can be effectively removed. Realization of heat generation can be made more reliable.

  The natural rubber obtained by the mechanical separation method described above is a natural rubber production process, that is, in the order of latex tapping, coagulation, washing, dehydration, drying, and packing, the latex after tapping and before coagulation is solidified. After the partial deproteinization treatment by a mechanical separation method, preferably a centrifugal concentration method, so that the total nitrogen content in the components is within a certain range, the obtained natural rubber latex is coagulated and dried. Is obtained. The natural rubber latex used as a raw material is not particularly limited, and a field latex, a commercially available latex, or the like can be used.

  Thus, it is desirable that the deproteinization of the natural rubber latex is performed by a mechanical centrifugal concentration method. When deproteinization is performed by other methods such as a degradation treatment method using a proteolytic enzyme, a method of repeatedly washing with a surfactant, a method of using an enzyme and a surfactant in combination, Although protein is reduced, at the same time, active ingredients such as tocotrienol having an anti-aging action are lost, so that the natural aging resistance of natural rubber may be lowered.

  The total nitrogen content in natural rubber obtained by the mechanical separation method is an index of protein content, and the content of the natural rubber latex is adjusted by adjusting the centrifugation conditions (rotation speed, time, etc.). Although it can be controlled, it is desirable that the total natural nitrogen content in the resulting natural rubber product is adjusted so as to be more than 0.1% by mass and 0.4% by mass or less. The conditions for the centrifugation are not particularly limited, but it is preferable to repeat the centrifugation several times at a rotational speed of about 7500 times, for example. If the total nitrogen content is 0.1% by mass or less, the heat aging resistance may be lowered, and if it exceeds 0.4% by mass, sufficient low heat build-up may not be obtained. That is, after adjusting the total nitrogen content in the solid content in the centrifugally concentrated latex to more than 0.1% by mass to 0.4% by mass or less, coagulation and drying to produce protein, the protein is reduced, Low exothermicity is further improved. The total nitrogen content is preferably in the range of more than 0.1% by mass and not more than 0.3% by mass, more preferably more than 0.1% by mass and not more than 0.2% by mass. Thereby, in combination with the modified butadiene polymer, the low heat build-up of the rubber composition can be improved more favorably. On the other hand, under such operating conditions for partial deproteinization, surprisingly, anti-aging active ingredients such as tocotrienol are hardly lost, so that heat resistance can be maintained at the same level as that of conventional natural rubber. it can.

Further, the non-rubber component in the natural rubber obtained by the mechanical separation method is less than 6% by mass, preferably less than 5% by mass, more preferably less than 4% by mass. The non-rubber component can cause cracking, and it is desirable to remove it as much as possible.
Furthermore, the amount of sugars in the natural rubber is 0.4% by mass or less, preferably 0.3% by mass or less.

  The rubber component obtained by coagulating the treated latex is washed with natural rubber such as a vacuum dryer, an air dryer, a drum dryer, etc., and dried using a natural rubber suitable for use in the present invention. can do.

  In addition to containing the modified butadiene copolymer in 100% by mass of the rubber component of the rubber composition for tie rubber, the natural rubber is preferably contained in an amount of 20 to 90% by mass, more preferably 30 to 90% by mass. The remainder may be polyisoprene rubber. By setting it as such content, the effect made into the objective of this invention can fully be exhibited with the said modified butadiene type polymer and carbon black. Furthermore, it is desirable that the natural rubber obtained by the mechanical separation method is contained in an amount of 30 to 100% by mass, preferably 50 to 100% by mass, in 100% by mass of the natural rubber.

  In addition to the natural rubber, the rubber component may include other diene synthetic rubbers other than the modified butadiene polymer and the polyisoprene rubber. Examples of such other diene-based synthetic rubbers include styrene-butadiene copolymer (SBR), polybutadiene (BR), butyl rubber (IIR), ethylene-propylene copolymer, and mixtures thereof. Further, some or all of the other diene-based synthetic rubber is more preferably a diene-based modified rubber having a branched structure by using a polyfunctional modifier, for example, a modifier such as tin tetrachloride. .

  Furthermore, it is desirable to mix an anti-aging agent with the rubber composition for tie rubber of the present invention. By mix | blending such an anti-aging agent, the deterioration of the rubber | gum by ozone and a heat | fever at the time of tire use environment can be suppressed effectively.

  Examples of the anti-aging agent include an amine-ketone anti-aging agent, an aromatic secondary amine anti-aging agent, a monophenol anti-aging agent, a bisphenol anti-aging agent, a polyphenol anti-aging agent, and a benzimidazole anti-aging agent. Anti-aging agents, dithiocarbamate-based anti-aging agents, thiourea-based anti-aging agents, organic thioic acid-based anti-aging agents, special wax-based anti-aging agents, etc. Emerging Chemical Industry Co., Ltd.), or Sannoc Series such as Sannock and Sannock N (made by Ouchi Emerging Chemical Industry Co., Ltd.) can be used. These may be used alone or in combination of two or more.

  These anti-aging agents are usually blended in an amount of 0.1 to 10 parts by mass, preferably 0.5 to 7 parts by mass with respect to 100 parts by mass of the rubber component. When the above upper limit is exceeded, the anti-aging agent may bleed and is not preferable from the viewpoint of cost. Moreover, there exists a possibility that effects, such as suppression of rubber deterioration, cannot fully be exhibited as it is less than the said lower limit.

  The rubber composition of the present invention includes various chemicals usually used in the rubber industry, for example, vulcanizing agents, vulcanization accelerators, process oils, scorch prevention agents, as desired, as long as the object of the present invention is not impaired. , Zinc white, stearic acid, and the like. And it can obtain by kneading | mixing using kneading machines, such as a Banbury mixer, a roll, an internal mixer, with the said mixing | blending prescription.

[Pneumatic tire]
The pneumatic tire of the present invention comprises a tie rubber formed using the above rubber composition for tie rubber, and is produced by a usual method. That is, the rubber composition for tie rubber of the present invention containing various chemicals as described above is processed into a tie rubber member at an unvulcanized stage, pasted and molded by a normal method on a tire molding machine, and a raw tire is formed. Molded. The pneumatic tire of the present invention can be obtained by heating and pressing the green tire in a vulcanizer.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
The physical properties of the modified butadiene polymer were measured according to the following methods.

<< Microstructure [cis-1,4 bond amount (%), 1,2-vinyl bond amount (%)] >>
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) >>
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

<< Mooney viscosity [ML _{1 + 4} (100 ℃)] >>
In accordance with JIS K6300, measurement was performed using an L rotor under conditions of preheating for 1 minute, rotor operating time of 4 minutes, and temperature of 100 ° C.

[Production Example 1: Production of BR-2 (modified butadiene polymer with Li)]
Into an 800 ml pressure-resistant glass container that has been dried and purged with nitrogen, 300 g of cyclohexane, 50 g of 1,3-butadiene monomer, and tetrahydrofuran (THF) (1 mmol) are injected, and n-butyllithium (0.55 mmol) is added thereto. Then, hexamethyleneimine (0.5 mmol) was quickly added, and polymerization was carried out at 50 ° C. for 2 hours. The polymerization system was uniformly transparent from the start to the end of the polymerization without any precipitation. The polymerization conversion was almost 100%.

  Thereafter, 0.5 mL of an isopropanol solution (BHT concentration: 5% by mass) of 2,6-di (t-butyl) paracresol (BHT) is added to this polymerization system to stop the polymerization reaction, and further dried according to a conventional method. As a result, BR-2 (modified butadiene polymer by Li) was obtained. The obtained BR-2 had a cis-1,4 bond content of 30%, a 1,2-vinyl bond content of 20%, and Mw / Mn = 1.1.

[Production Example 2: Production of BR-3 (modified butadiene-based polymer using a nitrogen-containing compound by two-stage modification)]
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 solution of neodymium versatate (0.09 mmol) in cyclohexane, a solution of methylaluminoxane (MAO, 3.6 mmol) in toluene, 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%.

Further, the polymer solution was kept at a temperature of 60 ° C., and polymethylene polyphenyl polyisocyanate (trade name “PAPI * 135”, manufactured by Dow Chemical Japan Co., Ltd.) (hereinafter also referred to as “cMDI”) (4 in terms of isocyanate group (NCO)). .16 mmol) in toluene was added and allowed to react for 15 minutes (primary denaturation reaction). Subsequently, a toluene solution of hexamethylenediamine (hereinafter also referred to as “HMDA”) (2.08 mmol) was added and reacted for 15 minutes (secondary modification reaction). Thereafter, the reaction solution was taken out in 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 the product was dried on a roll at 110 ° C. 3 (modified butadiene-based polymer) was obtained. The resulting BR-3 had a cis-1,4 bond content of 96.2%, a 1,2-vinyl bond content of 0.59%, Mw / Mn = 2.3, Mooney viscosity [ML _{1 + 4} (100 ° C.)] = 35.

[Production Example 3: Production of BR-4 (modified butadiene polymer using nitrogen-containing compound)]
After polymerizing in the same manner according to the production of BR-3, the polymer solution was further maintained at a temperature of 60 ° C., and a toluene solution of 4.16 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. By drying, BR-4 (modified butadiene-based polymer) was obtained. The obtained BR-4 has a cis-1,4 bond content of 96.1%, a 1,2-vinyl bond content of 0.61%, Mw / Mn = 2.3, Mooney viscosity [ML _{1 + 4} (100 ° C.)] = 35.

[Production Example 4: Production of natural rubber (NR-2)]
The natural rubber latex (CT-1) added with 0.4% by mass of ammonia was concentrated by centrifuging at a rotational speed of 7500 rpm for 15 minutes using a latex separator SLP-3000 (manufactured by Saito Centrifuge Co., Ltd.). The concentrated latex was further centrifuged at 7500 rpm for 15 minutes. The resulting concentrated latex was diluted to about 20% as a solid content, then formic acid was added and allowed to stand overnight, and then the rubber obtained by coagulation was dried at 110 ° C. for 210 minutes to obtain NR-2. Manufactured. The total nitrogen content of the rubber obtained was 0.15% by mass. In addition, the total nitrogen content was obtained by accurately weighing the solid component (sample) obtained by acid coagulation and drying of the latex, measuring the total nitrogen content by the Kjeldahl method, and calculating the total nitrogen content as a ratio (mass%) to the solid component. .

[Comparative Examples 1-15, Examples 1-18]
A rubber composition having the formulation shown in Tables 1 to 3 was prepared, made into a sheet, and used as a tie rubber between a carcass ply and an inner ply, and a heavy duty tire (11R22.5) was produced by a conventional method. did. Using this tire, each item was measured according to the following method. The results are shown in Tables 1-3.

<< Low exothermicity (tan δ) >>
Using a spectrometer (dynamic viscoelasticity measuring tester) manufactured by Toyo Seiki Co., Ltd., tan δ was measured for the test piece made of the above tie rubber at a frequency of 52 Hz, a measurement temperature of 25 ° C., and a strain of 2%. In Table 1, Comparative Example 1 is set as 100, Table 2 is set as Comparative Example 6 as 100, and Table 3 is set as Comparative Example 11 as 100, respectively. A smaller index value indicates a lower exothermic property.

《Crack resistance》
《Durability after running》
A drum running test was performed on the obtained tire, and after running for 100,000 km, a JIS K6301 tensile test method was performed on a tie rubber sample between a carcass ply and an inner ply obtained by dissecting the tire. Elongation was measured. In Table 1, Comparative Example 1 was set as 100, Table 2 as Comparative Example 6 as 100, and Table 3 as Comparative Example 11 as 100. The larger the value, the better the durability after running.

* 1: RSS # 3 natural rubber * 2: High cis butadiene rubber BR01 (unmodified butadiene polymer) manufactured by Nippon Synthetic Rubber Co., Ltd.
_{※ 3: N 2 SA: 82m} 2 / g, DBP oil ^{absorption: 102cm 3 / 100g, N-} 330
* 4: N- (1,3-dimethylbutyl) -N′-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., knock rack 6C
* 5: N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd., Noxeller CZ-G

  According to the results of Tables 1 to 3, Examples 1 to 18 using specific modified butadiene-based polymers are Comparative Examples 1 to 2, 6 to 7 and 11 to 12 using only natural rubber as a rubber component. Comparative Examples 3 to 4, 8 to 9 and 13 to 14 using an unmodified butadiene polymer, and Comparative Examples 5 to 10 and 15 using modified butadiene polymers other than the specific modified butadiene polymer In comparison, it can be seen that excellent durability is exhibited while maintaining excellent low heat generation. Among them, Examples 1-4 and 6, Examples 1-10 and 12, and Examples 13-16 containing specific modified butadiene rubber in an amount of 10-50% by mass in 100% by mass of the rubber component It is also clear that 18 can sufficiently exhibit the above characteristics.

1: Tread part 2: Side part 3: Bead part 4: Carcass ply 5: Inner liner 6: Tie rubber

Claims (10)

At least one carcass ply in which a plurality of steel cords are arranged, an inner liner disposed inside the tire of the innermost carcass ply, and a tie rubber disposed between the carcass ply and the inner liner A rubber composition for tie rubber, which is used to form the tie rubber in a pneumatic tire, and is formed by blending carbon black with a rubber component containing a modified butadiene polymer obtained by modifying a butadiene polymer. Because
The butadiene-based polymer is
Component (A): a monomer containing at least 1,3-butadiene in the presence of a rare earth element-containing material having an atomic number of 57 to 71 in the periodic table or a reaction system of these compounds and a Lewis base A rubber composition for tie rubber, which is produced by polymerizing 2. The tie rubber according to claim 1, wherein the catalyst system further comprises at least one of component (B): a Lewis acid, a complex compound of a metal halide and a Lewis base, and an organic compound containing an active halogen. Rubber composition. The catalyst system further comprises (C) component: AlR ¹ R ² R ³ (wherein R ¹ and R ² may be the same or different and each represents a hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom) , R ³ is a hydrocarbon group having 1 to 10 carbon atoms, provided that R ³ may be the same as or different from R ¹ or R ² ), and / or Or (D) component: The rubber composition for tie rubbers of Claim 2 containing an aluminoxane.   The rubber composition for tie rubber according to any one of claims 1 to 3, wherein the modified butadiene polymer is contained in an amount of 10 to 50% by mass in 100% by mass of the rubber component.   The rubber composition for tie rubber according to any one of claims 1 to 4, wherein the carbon black is blended in an amount of 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition for a tie rubber according to any one of claims 1 to 5, wherein the modified butadiene polymer is obtained by modifying a butadiene polymer with a nitrogen-containing compound.   The rubber composition for tie rubber according to claim 6, wherein the nitrogen-containing compound is a primary amine compound.   The rubber composition for tie rubber according to claim 6, wherein the nitrogen-containing compound is a heterocyclic nitrile compound.   The rubber composition for tie rubber according to any one of claims 1 to 8, wherein the rubber component contains natural rubber and / or polyisoprene rubber.   A pneumatic tire comprising a tie rubber formed from the rubber composition for a tie rubber according to claim 1.

Images