JP2011099018A - 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 tire rubber 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 the cis-1,4 bonding amount in the main chain is 75% or more. <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 In the prepared pneumatic tire, carbon black is blended with a rubber component containing a modified butadiene polymer used for forming the tie rubber and having a cis-1,4 bond amount of 75% or more in the main chain. It is characterized by.

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 In the prepared pneumatic tire, carbon black is blended with a rubber component containing a modified butadiene polymer used for forming the tie rubber and having a cis-1,4 bond amount of 75% or more in the main chain. It is characterized by. 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.

[Modified butadiene polymer]
The modified butadiene polymer used in the present invention is a polymer obtained by modifying a butadiene polymer and has a so-called high cis content modified butadiene system in which the amount of cis-1,4 bonds in the main chain is 75% or more. It is a polymer. 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 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.

  Further, the amount of 1,4-cis bonds in the main chain of the modified butadiene polymer is usually 75% or more, preferably 85 to 100%, more preferably 90 to 100%. When the amount of 1,4-cis bond is within the above range, the durability can be improved and the exothermicity can be sufficiently reduced by increasing the elongation crystallinity. Further, the amount of 1,2-vinyl bonds in the main chain of the modified butadiene polymer is preferably 1.5% or less, more preferably 1.0% or less. If the 1,2-vinyl bond content is outside the above range, the crystallinity of the polymer may be lowered, which is not preferable. Accordingly, it is more desirable that the amount of 1,4-cis bond and the amount of 1,2-vinyl bond are within the above ranges. Here, the 1,4-cis bond amount in the main chain of the modified butadiene polymer refers to 1,4 in the butadiene monomer unit constituting the main chain of the modified butadiene polymer in the modified butadiene polymer. -Means the ratio of cis bonds, and the amount of 1,2-vinyl bonds refers to 1,2-vinyl bonds in the butadiene monomer units constituting the main chain of the modified butadiene polymer in the modified butadiene polymer. Means the percentage of

  Furthermore, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the modified butadiene-based 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 the catalyst or initiator is conjugated 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. As such carbon black, specifically, a grade of HAF or lower is preferable, for example, those of HAF, FF, FEF, GPF, SRF, FT grade, from the viewpoint of improving durability, Particularly preferred are HAF, FEF and GPF grades.

[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 having a low cis bond amount)]
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-based polymer having a low cis bond amount) 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.

《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 modified butadiene-based polymers are Comparative Examples 1 to 2, 6 to 7 and 11 to 12 using only natural rubber as rubber components, respectively. Comparative Examples 3 to 4, 8 to 9 and 13 to 14 using modified butadiene polymers, and Comparative Examples 5 to 10 using modified butadiene polymers having a cis-1,4 bond amount outside the predetermined range It can be seen that, as compared with 15, it has excellent durability 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 (8)

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 In the prepared pneumatic tire, carbon black is blended with a rubber component containing a modified butadiene polymer used for forming the tie rubber and having a cis-1,4 bond amount of 75% or more in the main chain. A rubber composition for tie rubber, characterized in that   2. The rubber composition for a tie rubber according to claim 1, wherein the modified butadiene-based polymer is contained in an amount of 10 to 50 mass% in 100 mass% of the rubber component.   The rubber composition for tie rubber according to claim 1 or 2, 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 3, 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 4, wherein the nitrogen-containing compound is a primary amine compound.   The rubber composition for tie rubber according to claim 4, wherein the nitrogen-containing compound is a heterocyclic nitrile compound.   The rubber composition for tie rubber according to any one of claims 1 to 6, 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 any one of claims 1 to 7.

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