JP5524523B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire using a rubber composition optimal as a steel coating rubber for a tread reinforcing layer.

  Conventionally, it has been strongly desired to have excellent handling stability and wear resistance as pneumatic tires such as passenger car tires and competition tires. In order to effectively improve both of these performances, as shown in Patent Document 1, a technique is adopted in which a buffer rubber layer and a tread reinforcing layer in which a reinforcing cord is embedded are arranged in a pneumatic tire. Yes. A steel cord is generally used as the reinforcing cord, and the adhesion with other members is ensured by covering the steel cord with a coating rubber.

  The coating rubber used for the tread reinforcement layer of these pneumatic tires has the ability to suppress the development of cracks when used at high temperatures and maintains good adhesion between the steel cord and rubber against thermal history. It is required to have the performance to obtain.

  For example, Patent Document 2 discloses a steel cord coated rubber in which carbon black and silica are used in combination as a rubber reinforcing agent and a specific glycol or the like is further combined in order to impart superior durability as a coating rubber. Has been. The coated rubber can achieve both good low heat generation and heat aging resistance while suppressing a decrease in adhesion between the steel cord and the rubber.

JP 2006-151212 A JP-A-5-51491

However, even such a coated rubber does not exhibit sufficiently satisfactory durability while a higher performance rubber composition is being desired.
Accordingly, an object of the present invention is to provide a high-performance pneumatic tire using a rubber composition capable of exhibiting further excellent durability, particularly excellent crack resistance and heat-resistant adhesion, as a tread reinforcing layer. To do.

  In order to solve the above-mentioned problems, the present inventors include a specific sulfenamide-based vulcanization accelerator to obtain a rubber composition while maintaining good workability and tensile properties, and this is used as a tread reinforcing layer. By adopting it as a coating rubber, a pneumatic tire having both excellent crack resistance and heat resistant adhesiveness was found, and the present invention was completed.

That is, the pneumatic tire of the present invention is
In a pneumatic tire provided with a tread reinforcing layer (V) including a steel cord and a coating rubber,
The coating rubber is characterized by using a rubber composition which covers the steel cord and contains a sulfenamide vulcanization accelerator (C) represented by the formula (I).

（式（Ｉ）中、Ｒ¹は、炭素数３〜１２の分岐アルキル基を示し、Ｒ²は炭素数１〜１０の直鎖アルキル基を示す。Ｒ³〜Ｒ⁶は、水素原子、炭素数１〜４の直鎖アルキル基又はアルコキシ基、或いは炭素数３〜４の分岐アルキル基又はアルコキシ基であり、これらは互いに同一であっても異なっていてもよい。ｎは０または１を示し、ｘは１または２を示す。）。

(In the formula (I), R ¹ represents a branched alkyl group having 3 to 12 carbon atoms, R ² represents a linear alkyl group having 1 to 10 carbon atoms. R ^{3 to} R ⁶ represent a hydrogen atom or carbon. A linear alkyl group or alkoxy group having 1 to 4 carbon atoms, or a branched alkyl group or alkoxy group having 3 to 4 carbon atoms, which may be the same as or different from each other, and n is 0 or 1. , X represents 1 or 2.)

The rubber composition is
(A) For 100 parts by mass of a rubber component made of natural rubber and / or synthetic rubber,
(B) 40 to 80 parts by mass of carbon black having a nitrogen adsorption specific surface area of 70 to 130 m ² / g and a DBP oil absorption of 70 to 110 ml / 100 g,
(C) 0.1 to 10 parts by mass of a sulfenamide vulcanization accelerator represented by formula (I),
(D) Sulfur may be included in an amount of 0.3 to 10 parts by mass.

Also, In the above formula (I), it is preferably R ¹ is a branched alkyl group having a branched in the a position alpha, also R ¹ is tert- butyl group, is preferably n is 0, further R ¹ Is a tert-butyl group, R ² is a linear alkyl group having 1 to 6 carbon atoms, and R ^{3 to} R ⁶ are preferably hydrogen atoms. R ¹ is preferably a tert-butyl group, R ² is a linear alkyl group having 1 to 6 carbon atoms, R ^{3 to} R ⁶ are hydrogen atoms, and n is preferably 0. It is preferable that ¹ is a tert-butyl group, R ² is a methyl group, an ethyl group or an n-propyl group, R ^{3 to} R ⁶ are hydrogen atoms, and n is 0, and R ¹ is It is preferably a tert-butyl group, R ² is an ethyl group, R ^{3 to} R ⁶ are hydrogen atoms, and n is 0.

  The rubber composition preferably further includes (E) a cobalt-based component composed of a simple cobalt and / or a compound containing cobalt, and the content of the cobalt-based component (E) is the amount of cobalt as the rubber component ( A) The amount is preferably 0.03 to 3 parts by mass with respect to 100 parts by mass. The cobalt-containing compound may be a cobalt salt of an organic acid.

The rubber component (A) may include at least one of natural rubber and polyisoprene rubber.
Furthermore, it is desirable to contain natural rubber in an amount of 50% by mass or more in 100% by mass of the rubber component (A).

In addition, the pneumatic tire has a carcass layer (I) whose both ends in the width direction are folded back around the bead core and extend in a substantially toroidal shape,
A belt layer (II) composed of at least two belt plies, which are arranged radially outside the carcass layer (I) and in which a belt cord inclined in the opposite direction to the tire equator is embedded;
A tread disposed radially outward of the belt layer (II) and a non-stretch reinforcing element disposed between the tread and the carcass layer (I) and extending substantially parallel to the tire equator are embedded therein. Belt reinforcement layer (III),
A thin buffer rubber layer (IV) disposed between the tread and the belt layer (II) and between the tread and the belt reinforcing layer (III);
The tread reinforcing layer (V), which is disposed between the tread and the buffer rubber layer (IV) and in which a steel cord inclined in the range of 45 to 90 degrees with respect to the tire equator is embedded.
And may be provided.

  The rubber composition used in the pneumatic tire of the present invention employs a specific carbon black and a sulfenamide vulcanization accelerator, and therefore has excellent adhesiveness with a steel cord and has good heat resistance. In addition to exerting its properties, it has excellent durability. Therefore, it is possible to maintain excellent adhesion between the steel cord and the rubber while effectively suppressing the progress of cracks even under severe use conditions.

  Therefore, the rubber composition is optimal as a steel cord coating rubber, and the pneumatic tire of the present invention formed by using this to form a tread reinforcing layer is an extremely high performance pneumatic tire.

1 is a meridian cross-sectional view showing a pneumatic tire 11 of the present invention. It is a partially broken top view of the tread part in the pneumatic tire 11 of the present invention.

Hereinafter, the present invention will be specifically described.
The pneumatic tire of the present invention is
In a pneumatic tire provided with a tread reinforcing layer (V) including a steel cord and a coating rubber,
The coating rubber is characterized by using a rubber composition which covers the steel cord and contains a sulfenamide vulcanization accelerator (C) represented by the formula (I).

  That is, the pneumatic tire of the present invention is formed by coating a steel cord with a coating rubber using a rubber composition containing the sulfenamide vulcanization accelerator (C) represented by the formula (I). . Such a rubber composition is optimal as a rubber composition for forming a tread reinforcing layer (V) of a tire for passenger cars, trucks, buses, motorcycles, etc., which is a rubber-steel cord composite material.

  The sulfenamide vulcanization accelerator (C) represented by the above formula (I) used in the present invention is a conventional sulfenamide vulcanization accelerator represented by the following formula (X), DCBS (N , N′-dicyclohexyl-2-benzothiazylsulfenamide (hereinafter also referred to as “DCBS”) and has a vulcanization retardation effect, and also has durability in direct vulcanization adhesion to a steel cord. It is also excellent as a coating rubber composition for steel cords. The sulfenamide vulcanization accelerator (C) represented by the above formula (I) has not been reported so far, particularly in combination with a cobalt adhesive.

  Usually, when rubber and steel cords are bonded, a method of simultaneously bonding rubber and steel, that is, a direct vulcanization bonding method is known. It is considered useful to use a sulfenamide-based vulcanization accelerator such as the above-mentioned DCBS, which gives a slow effect to the vulcanization reaction, when performing the bonding simultaneously. Furthermore, when slow action is required, a sulfenamide vulcanization accelerator and a vulcanization retarder such as N- (cyclohexylthio) phthalimide (hereinafter abbreviated as “CTP”) are used in combination. Things are also done. However, when a conventional vulcanization accelerator and a vulcanization retarder as described above are used in combination, depending on the amount of the vulcanization retarder, the physical properties of the vulcanized rubber may be adversely affected, and the vulcanization There may be a problem that the appearance of the rubber is deteriorated and blooming is adversely affected.

  On the other hand, in the present invention, a vulcanization delay effect equal to or better than that of DCBS is obtained without using a vulcanization retarder such as CTP which may cause problems such as degradation of rubber physical properties after vulcanization and blooming. Since the sulfenamide-based vulcanization accelerator (C) represented by the above formula (I) having the above is used, it exhibits excellent durability in combination with carbon black (B) described later, and is directly added to the steel cord. It also has an excellent effect on adhesion durability in sulfur bonding.

In the present invention, R ¹ in the sulfenamide vulcanization accelerator (C) represents a branched alkyl group having 3 to 12 carbon atoms. When R ¹ is a branched alkyl group having 3 to 12 carbon atoms, the vulcanization accelerating performance of the sulfenamide-based vulcanization accelerator (C) is good and the adhesion performance can be further enhanced.

Specific examples of R ¹ include isopropyl, isobutyl, triisobutyl, sec-butyl, tert-butyl, isoamyl (isopentyl), neopentyl, and tert-amyl (tert-pentyl). , Isohexyl group, tert-hexyl group, isoheptyl group, tert-heptyl group, isooctyl group, tert-octyl group, isononyl group, tert-nonyl group, isodecyl group, tert-decyl group, isoundecyl group, tert-undecyl group, isododecyl Group, tert-dodecyl group and the like. Among these, a branched alkyl group having a branch at the α-position, that is, a tert-alkyl group having 3 to 12 carbon atoms is preferable from the viewpoint of obtaining a suitable scorch time, and in particular, a tert-butyl group, a tert-butyl group, -Amyl group (tert-pentyl group), tert-dodecyl group, and triisobutyl group are preferable, and tert-butyl group is most preferable from the viewpoint of improving adhesion and vulcanizing speed equivalent to DCBS in a balanced manner.

  In the sulfenamide-based vulcanization accelerator (C), n represents 0 or 1, and is preferably 0 from the viewpoint of effects such as ease of synthesis and raw material costs. X in the formula (I) represents an integer of 1 or 2. When x is 3 or more, the reactivity becomes too high, so that the stability of the sulfenamide vulcanization accelerator is lowered and workability may be deteriorated.

These are presumed to be because the more Moony scorch time tends to be imparted as the bulky group exists in the vicinity of —N— adjacent to R ¹ . Therefore, for example, when R ¹ in the above formula (I) is a tert-butyl group and n is 0, R ¹ is a cyclohexyl group, and in the vicinity of —N— as compared with DCBS where n is 0 It is considered that the former is bulkier and can provide a more preferable Mooney scorch time. Furthermore, in combination with R ² described later, by appropriately controlling the bulk height of the substituent located in the vicinity of -N-, it balances a suitable vulcanization speed and good adhesiveness while taking into account human accumulation. It is possible to perform well.

In the present invention, R ² in the sulfenamide vulcanization accelerator (C) represents a linear alkyl group having 1 to 10 carbon atoms. If R ² is a branched alkyl group, both R ¹ and R ² become a branched alkyl group, so that even if synthesized, stability may not be maintained satisfactorily, and heat resistant adhesiveness may be reduced. In particular, when both R ¹ and R ² are tert-butyl groups, even their synthesis becomes difficult. Therefore, when R ² is a linear alkyl group having 1 to 10 carbon atoms as described above, the combination with R ¹ that is a branched alkyl group is good, and the bulkiness of the substituent located in the vicinity of —N— is high. It is possible to effectively control the vulcanization rate and exhibit a suitable vulcanization rate and good adhesion performance in a well-balanced manner while taking into consideration human body accumulation.

Specific examples of R ² include methyl group, ethyl group, n-propyl group, n-butyl group, n-amyl group (n-pentyl group), n-hexyl group, n-heptyl group, and n-octyl group. , Nonyl group, decyl group, undecyl group, dodecyl group and the like. Among these, it is preferable that it is C1-C4 from a viewpoint which considers human body accumulation | storage property by the effect of easiness of a synthesis | combination, raw material cost, etc. and holding | maintaining appropriate concentration, and it is C1-C3. Is more preferable, and it is most preferable that it is C1-C2.

Therefore, if R ² in the above formula (I) is a conventional sulfenamide vulcanization accelerator such as H, the vulcanization speed may be too high and good adhesiveness tends not to be obtained. is there. Further, when R ² is a conventional sulfenamide vulcanization accelerator such as a cyclohexyl group or a long chain group outside the above range, the vulcanization rate tends to be too slow. .

More specifically, particularly when R ¹ is a tert-butyl group and n is 0, the optimum R ² exhibits a good balance of improved adhesion and retention of vulcanization rate equivalent to DCBS. A methyl group and an ethyl group are mentioned from a viewpoint and the viewpoint which considers human body accumulation | storage property.

In addition, R ¹ in the sulfenamide vulcanization accelerator (C) is a functional group other than a branched alkyl group having 3 to 12 carbon atoms (for example, n-octadecyl group, etc.) or a branch having more than 12 carbon atoms. When it is an alkyl group, R ² is a functional group other than a linear alkyl group having 1 to 10 carbon atoms (eg, n-octadecyl group) or a linear or branched alkyl group having more than 10 carbon atoms. In this case, when n is 2 or more, the intended effect of the present invention cannot be sufficiently exerted, and the Mooney scorch time is delayed beyond a suitable range, and the vulcanization time is unnecessarily long. There is a possibility that productivity and adhesiveness may decrease, or vulcanization performance and rubber performance as an accelerator may decrease.

R ^{3 to} R ⁶ in the above formula (I) are a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms or an alkoxy group, or a branched alkyl group having 3 to 4 carbon atoms or an alkoxy group. They may be the same or different. Among them, R ³ and R ⁵ are each a linear alkyl group or alkoxy group having 1 to 4 carbon atoms, or a branched alkyl group or alkoxy group having 3 to 4 carbon atoms. Preferably there is. Further, R ³ to R ⁶ are the alkyl group or alkoxy group having 1 to 4 carbon atoms, preferably 1 carbon atoms, preferably all R ³ to R ⁶ are H. In any preferred case, it is desirable in terms of the ease of synthesis of the compound and the slowing of the vulcanization rate. Specific examples of R ^{3 to} R ^{6 in} the above formula (I) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, Examples include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, and tert-butoxy group.

Further, the log Pow value (1-octanol / water partition coefficient) of the sulfenamide-based vulcanization accelerator is preferably as small as possible from the viewpoint of maintaining appropriate concentration, and specifically, in the above formula (I) As the number of carbon atoms of R ¹ and R ² is smaller, the log Pow value tends to be smaller. For example, when R ¹ in the formula (I) used in the present invention is a t-butyl group and n is 0, a vulcanization rate equivalent to that of DCBS which is a conventional sulfenamide vulcanization accelerator is obtained. From the viewpoint of exhibiting good adhesion performance while maintaining and considering human body accumulation, R ² in formula (I) has 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms, most preferably 1 to 1 carbon atoms. Preferably, it is a linear alkyl group of 2.

The log Pow value (1-octanol / water partition coefficient) is generally a value obtained by one of the simple measuring methods for evaluating the concentration of chemical substances, and is in two solvent phases of 1-octanol and water. It means a value obtained from the chemical substance concentration ratio Pow in the two phases when a chemical substance is added to achieve a parallel state. Pow is expressed by the following equation, and the logarithmic value of Pow is the log Pow value.
Pow = Co / Cw
Co: Test substance concentration in the 1-octanol layer
Cw: Test substance concentration in water layer The log Pow value can be determined by measuring Pow using high performance liquid chromatography in accordance with JIS Z7260-117 (2006).

  In the present invention, typical examples of the sulfenamide vulcanization accelerator (C) include N-methyl-Nt-butylbenzothiazole-2-sulfenamide (BMBS), N-ethyl-Nt. -Butylbenzothiazole-2-sulfenamide (BEBS), Nn-propyl-Nt-butylbenzothiazole-2-sulfenamide, Nn-butyl-Nt-butylbenzothiazole-2- Sulfenamide (BBBS), N-methyl-N-isoamylbenzothiazole-2-sulfenamide, N-ethyl-N-isoamylbenzothiazole-2-sulfenamide, Nn-propyl-N-isoamylbenzothiazole -2-sulfenamide, Nn-butyl-N-isoamylbenzothiazole-2-sulfenamide, N-methyl N-tert-amylbenzothiazole-2-sulfenamide, N-ethyl-N-tert-amylbenzothiazole-2-sulfenamide, Nn-propyl-N-tert-amylbenzothiazole-2-sulfenamide Amides, Nn-butyl-N-tert-amylbenzothiazole-2-sulfenamide, N-methyl-N-tert-heptylbenzothiazole-2-sulfenamide, N-ethyl-N-tert-heptylbenzo Thiazole-2-sulfenamide, Nn-propyl-N-tert-heptylbenzothiazole-2-sulfenamide, Nn-butyl-N-tert-heptylbenzothiazole-2-sulfenamide;

  N-methyl-Nt-butyl-4-methylbenzothiazole-2-sulfenamide, N-methyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulfenamide, N-ethyl- Nt-butyl-4-methylbenzothiazole-2-sulfenamide, N-ethyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulfenamide, Nn-propyl-N- t-butyl-4-methylbenzothiazole-2-sulfenamide, Nn-propyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulfenamide, Nn-butyl-N- t-butyl-4-methylbenzothiazole-2-sulfenamide, Nn-butyl-Nt-butyl-4,6-dimethoxybenzothiazole-2-sulfen Amide. These may be used alone or in combination of two or more.

  Among these, N-methyl-Nt-butylbenzothiazole-2-sulfenamide (BMBS), N-ethyl-Nt-butylbenzothiazole-2-sulfene is used from the viewpoint of further improvement in adhesion performance. Amide (BEBS) and Nn-propyl-Nt-butylbenzothiazole-2-sulfenamide are preferred.

  In particular, N-methyl-Nt-butylbenzothiazole-2-sulfenamide (BMBS), N-ethyl-Nt-butylbenzothiazole- has the longest Mooney scorch time and excellent adhesion performance. 2-sulfenamide (BEBS) is more preferred, and N-ethyl-Nt-butylbenzothiazole-2-sulfenamide (BEBS) is most preferred.

  These sulfenamide vulcanization accelerators (C) are N-tert-butyl-2-benzothiazole sulfenamide (TBBS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), dibenzothia. It can also be used in combination with a general-purpose vulcanization accelerator such as zolyl disulfide (MBTS).

As a manufacturing method of the said sulfenamide type | system | group vulcanization accelerator (C), the following method can be mentioned preferably.
That is, N-chloroamine prepared in advance by reaction of a corresponding amine and sodium hypochlorite and bis (benzothiazol-2-yl) disulfide are reacted in an appropriate solvent in the presence of an amine and a base. If an amine is used as the base, neutralize and return to the free amine, then subject to appropriate post-treatment such as filtration, washing with water, concentration and recrystallization according to the properties of the resulting reaction mixture. Sulfenamide is obtained.

  Examples of the base used in the above production method include starting amines used in excess, tertiary amines such as triethylamine, alkali hydroxides, alkali carbonates, alkali bicarbonates, sodium alkoxides, and the like. In particular, the reaction is carried out using excess raw material amine as a base or tertiary amine triethylamine, neutralizing the hydrochloride formed with sodium hydroxide, taking out the target product, and then removing the amine from the filtrate. A method of reuse is desirable.

As the solvent used in the above production method, alcohol is desirable, and methanol is particularly desirable.
For example, in N-ethyl-Nt-butylbenzothiazole-2-sulfenamide (BEBS), an aqueous sodium hypochlorite solution was added dropwise to Nt-butylethylamine at 0 ° C. or lower and the oil layer was stirred for 2 hours. Was sorted. Bis (benzothiazol-2-yl) disulfide, Nt-butylethylamine and the oil layer described above were suspended in methanol and stirred for 2 hours under reflux. After cooling, the solution is neutralized with sodium hydroxide, filtered, washed with water, concentrated under reduced pressure, and recrystallized to obtain the target BEBS (white solid).

Further, the rubber composition is
(A) For 100 parts by mass of a rubber component made of natural rubber and / or synthetic rubber,
(B) 40 to 80 parts by mass of carbon black having a nitrogen adsorption specific surface area of 70 to 130 m ² / g and a DBP oil absorption of 70 to 110 ml / 100 g,
(C) 0.1 to 10 parts by mass of a sulfenamide vulcanization accelerator represented by formula (I),
(D) It is desirable to contain sulfur in an amount of 0.3 to 10 parts by mass.

  The rubber component (A) used in the present invention is not particularly limited as long as it is a rubber used for rubber products such as tires and industrial belts, and sulfur crosslinking is possible if the rubber component has a double bond in the main chain. Therefore, the sulfenamide vulcanization accelerator represented by the above formula (I) functions effectively, and natural rubber or synthetic rubber is used, for example. Specific examples of the synthetic rubber include polyisoprene rubber, styrene-butadiene copolymer, polybutadiene rubber, ethylene-propylene-diene copolymer, chloroprene rubber, halogenated butyl rubber, and acrylonitrile-butadiene rubber.

  The rubber component (A) preferably contains at least one of natural rubber and polyisoprene rubber from the viewpoint of adhesion to a steel cord. Further, from the viewpoint of durability as a coating rubber, it is desirable to contain natural rubber in an amount of 50% by mass or more in 100% by mass of the rubber component (A). There is no restriction | limiting in particular about an upper limit, 100 mass% may be sufficient. In this case, the remainder is a synthetic rubber, and it is desirable to include at least one of the above synthetic rubbers.

The carbon black (B) used in the present invention acts as a filler, its nitrogen adsorption specific surface area is preferably 70 to 130 m ² / g, and DBP oil absorption (dibutyl phthalate oil absorption) is 70 to 110 ml / 100 g. More preferably, the nitrogen adsorption specific surface area is 70 to 100 m ² / g, and the DBP oil absorption (dibutyl phthalate oil absorption) is 70 to 110 ml / 100 g. In this specification, the nitrogen adsorption specific surface area is a value obtained by ISO 4652-1 (Single Point), and the DBP oil absorption is a value obtained by ISO 4656-1.

  When the nitrogen adsorption specific surface area and the DBP oil absorption amount are within the above ranges, the fracture resistance is improved. These carbon blacks (B), together with the sulfenamide vulcanization accelerator (C), can impart excellent durability and heat resistance to the rubber composition obtained.

  Examples of such carbon black (B) include channel black, furnace black, acetylene black, and thermal black depending on the production method, and any of them may be used as long as the above requirements are satisfied. For example, SRF, GPF, FEF, HAF , ISAF, SAF and the like.

  The content of the sulfenamide-based vulcanization accelerator (C) is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component (A). Most preferably, the amount is 0.8 to 2.5 parts by mass. If the content of the vulcanization accelerator (C) is less than 0.1 parts by mass, there is a risk that the vulcanization will not be performed sufficiently. On the other hand, if it exceeds 10 parts by mass, bloom will be a problem, which is not preferable.

  Sulfur (D) used in the present invention acts as a vulcanizing agent, and the content thereof is preferably 0.3 to 10 parts by mass, more preferably 1 with respect to 100 parts by mass of the rubber component (A). The amount is from 0.0 to 7.0 parts by mass, and most preferably from 3.0 to 7.0 parts by mass. If the content of sulfur (D) is less than 0.3 parts by mass, vulcanization may not be achieved sufficiently. On the other hand, if it exceeds 10 parts by mass, the aging performance of the rubber may be lowered, which is not preferable.

  Furthermore, it is preferable that the rubber composition contains a cobalt-based component (E) made of cobalt alone and / or a compound containing cobalt from the viewpoint of improving the initial adhesion performance. Examples of the cobalt-based component (E) include cobalt alone, and as a compound containing cobalt, a cobalt salt of an organic acid, a cobalt salt of an inorganic acid, cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt phosphate, There may be mentioned at least one of cobalt chromate. Of these, the use of a cobalt salt of an organic acid is desirable from the viewpoint of further improving the initial adhesion performance. These cobalt simple substance and the compound containing cobalt may be used individually by 1 type, and may be used in mixture of 2 or more types.

  More specifically, examples of the cobalt salt of the organic acid include at least one of cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tall oilate, and the like. In addition, the organic acid cobalt may be a complex salt in which a part of the organic acid is replaced with boric acid. Specifically, a commercially available product name “Manobond” manufactured by OMG may be used.

The (total) content of the cobalt-based component (E) is preferably 0.03 to 3 parts by mass, more preferably 0.03 to 1 part by mass with respect to 100 parts by mass of the rubber component (A) as the amount of cobalt. The amount is most preferably 0.05 to 0.7 parts by mass.
If the content of these cobalt amounts is less than 0.03 parts by mass, further adhesiveness cannot be exhibited. On the other hand, if it exceeds 3 parts by mass, the aging physical properties are greatly lowered, which is not preferable.

  In addition to the rubber component (A), carbon black (B), vulcanization accelerator (C), sulfur (D), and cobalt-based component (E), the rubber composition includes rubbers such as tires and conveyor belts. Compounding agents that are usually used in products can be used within the range that does not impair the effects of the present invention. For example, inorganic fillers such as silica, softeners, anti-aging agents, and the like can be appropriately blended depending on the application. . The rubber composition can be produced by kneading the above components with, for example, a Banbury mixer, a kneader or the like, and can be suitably applied as a coating rubber composition for coating a steel cord.

As a pneumatic tire provided with the tread reinforcement layer (V) containing a steel cord and the said coating rubber, the pneumatic tire 11 which consists of a structure as shown to FIG. 1 and FIG. 2 is mentioned, for example.
That is, the pneumatic tire 11 has a carcass layer (I) whose both ends in the width direction are folded back around the bead core and extend in a substantially toroidal shape,
A belt layer (II) composed of at least two belt plies, which are arranged radially outside the carcass layer (I) and in which a belt cord inclined in the opposite direction to the tire equator is embedded;
A tread disposed radially outward of the belt layer (II) and a non-stretch reinforcing element disposed between the tread and the carcass layer (I) and extending substantially parallel to the tire equator are embedded therein. Belt reinforcement layer (III),
A thin buffer rubber layer (IV) disposed between the tread and the belt layer (II) and between the tread and the belt reinforcing layer (III);
The tread reinforcing layer (V), which is disposed between the tread and the buffer rubber layer (IV) and in which a steel cord inclined in the range of 45 to 90 degrees with respect to the tire equator is embedded.
May be provided.

Hereinafter, it demonstrates more concretely based on drawing.
1 and 2, reference numeral 11 denotes a pneumatic radial tire for a passenger car capable of traveling at high speed. The pneumatic tire 11 includes a pair of bead portions 13 each having a bead core 12 embedded therein, and a radial direction extending from the bead portions 13. A sidewall portion 14 extending outward is provided, and a substantially cylindrical tread portion 15 that connects the radially outer ends of the sidewall portions 14 is provided.

  The pneumatic tire 11 has a carcass layer (I) 18 that extends between the bead cores 12 in a substantially toroidal shape and reinforces the sidewall portions 14 and the tread portions 15. Both end portions in the width direction are folded around the bead core 12 from the inner side in the axial direction toward the outer side in the axial direction. The carcass layer (I) 18 is composed of at least one carcass ply 19 here, and a plurality of carcass cords 20 extending in the radial direction (meridian direction) are embedded in these carcass plies 19. . Here, the carcass cord 20 is made of nylon, but may be made of steel or aromatic polyamide.

  Reference numeral 24 denotes a belt layer (II) disposed radially outside the carcass layer (I) 18. The belt layer (II) 24 is formed by laminating at least two (here, two) belt plies 25. In each belt ply 25, a large number of non-extensible belt cords 26 made of steel, aromatic polyamide or the like are embedded. The belt cords 26 of these belt plies 25 are inclined with respect to the tire equator S within a range of 10 to 70 degrees, and at least two belt plies 25 are inclined in the opposite direction with respect to the tire equator S.

  Reference numeral 28 denotes a tread disposed radially outward of the carcass layer (I) 18 and the belt layer (II) 24. A plurality of wide treads 28 extend continuously in the circumferential direction on the outer surface (grounding surface) of the tread 28. In this embodiment, four main grooves 29 are formed. In addition, although not shown, a large number of lateral grooves extending in the width direction may be formed on the outer surface of the tread 28. 32 is a belt reinforcing layer (III) disposed in the tread portion 15 between the tread 28 and the carcass layer (I) 18, here the belt layer (II) 24 and the carcass layer (I) 18. The belt reinforcing layer (III) 32 is wider than the belt layer (II) 24 and substantially the same width as the tread width W. As a result, the belt reinforcing layer (III) 32 is generally called a cap, and overlaps at least both ends in the width direction of the belt layer (II) 24, here, the entire width of the belt layer (II) 24.

  Here, the belt reinforcing layer (III) 32 is composed of at least one (here, one) reinforcing ply 33, and extends inside the reinforcing ply 33 substantially parallel to the tire equator S, and is made of steel, aromatic A reinforcing element 34 made of a non-extensible material such as a group polyamide is embedded. When the reinforcing element 34 is made of aromatic polyamide, it is possible to easily achieve both durability and handling stability of the pneumatic tire 11.

  For this reason, the tread portion 15 (including both end portions in the width direction of the belt layer (II) 24) overlapping the belt reinforcing layer (III) 32 is when the pneumatic tire 11 travels at a high speed. The belt reinforcing layer (III) 32 strongly suppresses the diameter growth due to centrifugal force. Thereby, the distortion generated at the outer end in the width direction of the belt layer (II) 24 is reduced, and there is almost no deterioration in durability and steering stability as compared with the conventional tire. Here, the above-described belt reinforcing layer (III) 32 is formed by, for example, winding a ribbon-like body in which one or a small number of reinforcing elements 34 are lined up and covered with rubber in a spiral manner around the outside of the carcass layer (I) 18. be able to.

  Further, a thin buffer rubber layer (IV) 36 is disposed in the tread portion 15 between the tread 28 and the belt layer (II) 24 and the belt reinforcing layer (III) 32. Here, the buffer rubber layer (IV) 36 is wider than the belt layer (II) 24 but slightly narrower than the tread width W. The rubber constituting the buffer rubber layer (IV) 36 preferably has a JIS hardness lower than that of the rubber constituting the tread 28 in order to effectively exert a buffering action, and its width. Is preferably not less than 0.3 times the tread width W in order to effectively exhibit the buffer action.

  Here, the wall thickness t of the buffer rubber layer (IV) 36 is preferably in the range of 0.5 to 3.0 mm. The reason is that if the thickness t is less than 0.5 mm, the circumferential shear deformation generated between the road surface and the belt layer (II) 24 (belt reinforcing layer (III) 32) is sufficiently absorbed. On the other hand, if it exceeds 3.0 mm, the centrifugal force in the tread portion 15 during high speed running increases and circumferential shear deformation increases.

  A tread reinforcing layer (V) 40 including at least one (here, one) reinforcing ply 39 is disposed in the tread portion 15 between the buffer rubber layer (IV) 36 and the tread 28, and the tread. The rubber composition described above is used for the reinforcing layer (V). Since the tread reinforcing layer (V) 40 is interposed between the shock absorbing rubber layer (IV) 36 and the tread 28, the shear deformation of the shock absorbing rubber layer (IV) 36 and the tread 28 is transmitted to the tread reinforcing layer (V) 40. Deform. However, in this embodiment, the tread reinforcing layer (V) 40 is wider than the belt layer (II) 24 and slightly narrower than the tread width W, like the buffer rubber layer (IV) 36. In the tread reinforcing layer (V) 40 (reinforcing ply 39), a plurality of linearly extending steel cords 41 having an inclination angle A with respect to the tire equator S in the range of 45 to 90 degrees are embedded over the entire width. It was.

  As a result, the steel cord 41 in the tread reinforcing layer (V) 40 is bent slightly following the deformation while functioning as a resistor against the deformation caused by the buffer rubber layer (IV) 36 and the tread 28. Thus, the widthwise distribution of slip and tangential force between the outer surface of the tread and the road surface in the entire area of the ground contact region is further dispersed and uniformized. Here, the steel cord 41 having high bending rigidity functions strongly as a resistor, and the widthwise distribution of slip and tangential force between the outer surface of the tread and the road surface in the ground contact region is strongly uniformed throughout the region. be able to.

  Thus, when the tread reinforcing layer (V) is formed using the rubber composition as a steel cord coating rubber, it not only has excellent adhesion to the steel cord, but also has excellent crack resistance and heat resistant adhesion. In order to exhibit the effect, the high performance pneumatic tire 11 is realizable.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
In addition, as above-mentioned, the log Pow value of each sulfenamide type | system | group vulcanization accelerator calculated | required by measuring Pow using a high performance liquid chromatography based on JISZ7260-117 (2006).

[Production Example 1: Synthesis of N-methyl-Nt-butylbenzothiazole-2-sulfenamide (vulcanization accelerator 1)]
To 14.1 g (0.162 mol) of Nt-butylmethylamine, 148 g of a 12% aqueous sodium hypochlorite solution was added dropwise at 0 ° C. or lower, and after stirring for 2 hours, the oil layer was separated. Bis (benzothiazol-2-yl) disulfide (39.8 g, 0.120 mol), Nt-butylmethylamine (24.3 g, 0.240 mmol) and the oil layer described above were suspended in 120 ml of methanol and refluxed. Stir for 2 hours. After cooling, the mixture was neutralized with 6.6 g (0.166 mol) of sodium hydroxide, filtered, washed with water, concentrated under reduced pressure, and then recrystallized to obtain 46.8 g (yield 82%) of the desired vulcanization accelerator 1. ) As a white solid (melting point 56-58 ° C., log Pow value 4.5).

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 1.32 (9H, s, CH ₃ (t-butyl)), 3.02 (3H, s, CH ₃ (methyl)), 7.24 (1H, m), 7.38 (1H, m), 7.77 (1H, m), 7.79 (1H, m).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 27.3, 41.9, 59.2, 120.9, 121.4, 123.3, 125.7, 135.0, 155.5, 180. 8).
Mass spectrometry (EI, 70 eV) m / z; 252 (M ⁺ ), 237 (M ⁺ -CH ₃ ), 223 (M ⁺ -C ₂ H ₆ ), 195 (M ⁺ -C ₄ H ₉ ), 167 ( _{^{M + -C 5 H 12 N)}} , 86 (M + -C 7 H 4 NS 2).

[Production Example 2: Synthesis of N-ethyl-Nt-butylbenzothiazole-2-sulfenamide (BEBS, vulcanization accelerator 2)]
The same procedure as in Production Example 1 was carried out using 16.4 g (0.162 mol) of Nt-butylethylamine instead of Nt-butylmethylamine, and 41.9 g (yield 66%) of vulcanization accelerator 2. As a white solid (melting point: 60-61 ° C., log Pow value: 4.9).
The spectrum data of the obtained BEBS is shown below.

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 1.29 (t, 3H, J = 7.1 Hz, CH ₃ (ethyl)), 1.34 (s, 9H, CH ₃ (t-butyl)), 2.9-3.4 (br-d, CH ₂ ), 7.23 (1H, m), 7.37 (1H, m), 7.75 (1H, m), 7.78 (1H, m ).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 15.12, 28.06, 47.08, 60.41, 120.70, 121.26, 123.23, 125.64, 134.75, 154. 93, 182.63.
Mass spectrometry (EI, 70 eV): m / z; 251 (M ⁺ —CH ₄ ), 167 (M ⁺ —C ₆ H ₁₄ N), 100 (M ⁺ —C ₇ H ₅ NS ₂ ): IR (KBr, cm < ^-1 >): 3061, 2975, 2932, 2868, 1461, 1429, 1393, 1366, 1352, 1309, 1273, 1238, 1198, 1103, 1022, 1011, 936, 895, 756, 727.

[Production Example 3: Synthesis of Nn-propyl-Nt-butylbenzothiazole-2-sulfenamide (vulcanization accelerator 3)]
In place of Nt-butylmethylamine, 18.7 g (0.162 mol) of Nn-propyl-t-butylamine was used in the same manner as in Production Example 1, and vulcanization accelerator 3 was treated as a white solid (melting point: 50 to 50). 52 ° C. and log Pow value 5.3).

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 0.92 (t, J = 7.3 Hz, 3H), 1.34 (s, 9H), 1.75 (br, 2H), 3.03 (brd , 2H), 7.24 (t, J = 7.0 Hz, 1H), 7.38 (t, J = 7.0 Hz, 1H), 7.77 (d, J = 7.5 Hz, 1H), 7 .79 (d, J = 7.5 Hz, 1H).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 11.7, 23.0, 28.1, 55.3, 60.4, 120.7, 121.3, 123.3, 125.7, 134. 7, 154.8, 181.3.

[Production Example 4: Synthesis of Nn-butyl-Nt-butylbenzothiazole-2-sulfenamide (vulcanization accelerator 4)]
The same procedure as in Production Example 1 was carried out using 20.9 g (0.162 mol) of Nt-butyl-n-butylamine instead of Nt-butylmethylamine, and 42.4 g of vulcanization accelerator 4 (yield). 60%) as a white solid (melting point 55-56 ° C., log Pow value 5.8).

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 0.89 (3H, t, J = 7.32 Hz, CH ₃ (n-Bu)), 1.2-1.4 (s + m, 11H, CH ₃ ( t-butyl) + CH ₂ (n-butyl)), 1.70 (br.s, 2H, CH ₂ ), 2.9-3.2 (br.d, 2H, N—CH ₂ ), 7.23 (1H, m), 7.37 (1H, m), 7.75 (1H, m), 7.78 (1H, m).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 14.0, 20.4, 27.9, 31.8, 53.0, 60.3, 120.6, 121.1, 123.1, 125. 5, 134.6, 154.8, 181.2.
Mass spectrometry (EI, 70 eV), m / z 294 (M ⁺ ), 279 (M ⁺ —CH ₃ ), 237 (M ⁺ —C ₄ H ₉ ), 167 (M ⁺ —C ₈ H ₁₈ N), 128 ( M ⁺ -C ₇ H ₄ NS ₂ ): IR (neat): 1707 cm ⁻¹ , 3302 cm ⁻¹ .

[Comparative Production Example 1: Synthesis of Ni-propyl-Nt-butylbenzothiazole-2-sulfenamide (vulcanization accelerator 5)]
The same procedure as in Production Example 1 was carried out using 18.7 g (0.162 mol) of Ni-propyl-t-butylamine instead of Nt-butylmethylamine, and the vulcanization accelerator 5 was treated as a white solid (melting point 68- 70 ° C.).

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 1.20-1.25 (dd, (1.22 ppm: J = 6.4 Hz, 1.23 ppm: J = 6.4 Hz) 6H), 1.37 ( s, 9H), 3.78 (m, J = 6.3 Hz, 1H), 7.23 (t, J = 7.0 Hz, 1H), 7.38 (t, J = 7.0 Hz, 1H), 7.77 (d, J = 7.5 Hz, 1H), 7.79 (d, J = 7.5 Hz, 1H).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 22.3, 23.9, 29.1, 50.6, 61.4, 120.6, 121.2, 123.2, 125.6, 134. 5, 154.5, 183.3.

[Comparative Production Example 2: Synthesis of N, N-di-i-propylbenzothiazole-2-sulfenamide (vulcanization accelerator 6)]
Using 16.4 g (0.162 mol) of N-di-i-propylamine instead of Nt-butylmethylamine, the same procedure as in Production Example 1 was carried out, and the vulcanization accelerator 6 was converted into a white solid (melting point: 57 to 59). ° C).

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 1.26 (d, J = 6.5 Hz, 12H), 3.49 (dq, J = 6.5 Hz, 2H), 7.24 (t, J = 7.0 Hz, 1H), 7.37 (t, J = 7.0 Hz, 1H), 7.75 (d, J = 8.6 Hz, 1H), 7.79 (d, J = 8.6 Hz, 1H) ).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 21.7, 22.5, 55.7, 120.8, 121.3, 123.4, 125.7, 134.7, 155.1, 182. 2.
Mass spectrometry (EI, 70 eV), m / z 266 (M ⁺ ), 251 (M ⁺ −15), 218 (M ⁺ −48), 209 (M ⁺ −57), 182 (M ⁺ −84), 167 ( M ^<+>- 99), 148 (M ^<+ > ^- 118), 100 (M ^<+ > ^- 166: base).

[Examples 1 to 12, Comparative Examples 1 to 9]
Using a 2200 ml Banbury mixer, the rubber component, carbon black, the vulcanization accelerator obtained in the above production example, sulfur, and other compounding agents were kneaded and mixed in the formulation shown in Table 1 below to obtain a rubber composition. Was prepared.
Subsequently, each rubber composition was used in accordance with the following method to evaluate the performance. The results are shown in Tables 1-3.

《Tire evaluation adhesion durability test》
In accordance with the pneumatic tire 11 shown in FIGS. 1 and 2, a tire for a passenger car of size 225 / 40R18, in which a tread reinforcing layer using the obtained rubber composition as a coating rubber of a steel cord, is formed and tested. Attached to the vehicle, the same lap was run on the test course. The tread reinforcing layer of the tire after running was taken out, the steel cord was pulled out in accordance with ASTM-D-2229, the rubber covering state was visually observed, and the value of Comparative Example 1 was displayed as an index. It shows that it is excellent in adhesion durability, so that a numerical value is large.

《Tire evaluation crack growth test》
In accordance with the pneumatic tire 11 shown in FIGS. 1 and 2, a tire for a passenger car of size 225 / 40R18, in which a tread reinforcing layer using the obtained rubber composition as a coating rubber of a steel cord, is formed and tested. The tire was mounted on a vehicle, and the same lap was run on the test course, and the crack growth length of the tread reinforcing layer of the tire after running was observed. It shows that it is excellent in crack growth resistance, so that a numerical value is large.

《Mooney viscosity, Mooney scorch time》
It measured based on JISK6300-1: 2001. In Table 2, the values of Comparative Example 1 are shown in Table 2, and the values of Comparative Example 7 are shown in Table 3 as 100. The smaller the Mooney viscosity, the better the workability, and the greater the Mooney scorch time, the better the workability.

<Tensile property evaluation>
The rubber composition obtained by vulcanizing the obtained rubber composition at 145 ° C. for 60 minutes was subjected to a measurement test at 25 ° C. in accordance with JIS K 6301-1995 (No. 3 type test piece), and fractured. Elongation (Eb) and stress (Tb) at time, and tensile stress (M300) at 300% elongation were measured. Table 2 shows the tensile properties of the rubber composition of Comparative Example 1, and Table 3 shows Comparative Example 7 The rubber composition was indexed with the tensile property as 100. Larger values indicate better tensile properties.

<Heat resistant adhesiveness>
Three steel cords (outer diameter 0.5 mm x length 300 mm) plated with brass (Cu: 63% by mass, Zu: 37% by mass) are arranged in parallel at 10 mm intervals, and each rubber composition is arranged from both the upper and lower sides. Then, this was vulcanized at 160 ° C. for 20 minutes to prepare a sample.
About each heat-resistant adhesiveness of each obtained sample, according to ASTM-D-2229, each sample was left in a gear oven at 100 ° C. for 15 days for 30 days, and then the steel cord was pulled out to visually check the rubber coating state. And displayed as 0 to 100% as an index of each heat resistant adhesiveness. It shows that it is excellent in heat-resistant adhesiveness, so that a numerical value is large.

* 1: Product name: Seest 300, manufactured by Tokai Carbon Co., Ltd., nitrogen adsorption specific surface area 84 m ² / g, DBP oil absorption 75 ml / 100 g)
* 2: N-phenyl-N′-1,3-dimethylbutyl-p-phenylenediamine (NOCRACK 6C, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 3: N, N'-dicyclohexyl-2-benzothiazylsulfenamide (Noxeller DZ, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 4: N-cyclohexyl-2-benzothiazylsulfenamide (Noxeller CZ, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 5: Nt-Butylbenzothiazole-2-sulfenamide (Noxeller NS, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 6: Product name: Manobond C22.5, manufactured by OMG, Cobalt content: 22.5% by mass
* 7: BR01
* 8: SBR # 1778

  As is apparent from the results in Table 1 above, Examples 1 to 12 containing the specific sulfenamide vulcanization accelerator are Comparative Examples 1 to 1 using only conventional sulfenamide vulcanization accelerators. Compared to 9, it has excellent adhesion durability and crack resistance, and also exhibits good workability and tensile properties. Among these examples, according to Examples 5 to 6 and 10, when the sulfenamide-based vulcanization accelerator is blended in a specific amount, even if a conventional sulfenamide-based vulcanization accelerator is used in combination, It can also be seen that the same effect is exhibited.

11: Pneumatic tire 12: Bead core 18: Carcass layer (I)
24: Belt layer (II)
25: Belt ply 26: Belt cord 28: Tread 32: Belt reinforcement layer (III)
34: Reinforcing element 36: Buffer rubber layer (IV)
40: Tread reinforcement layer (V)
41: Steel cord S: Tire equator A: Inclination angle of steel cord 41 with respect to the tire equator

Claims (10)

In a pneumatic tire provided with a tread reinforcing layer (V) including a steel cord and a coating rubber,
The coating rubber is made of a rubber composition that covers the steel cord and contains a sulfenamide-based vulcanization accelerator (C) represented by the formula (I). Tires.

(In Formula (I), R ¹ is a tert-butyl group, R ² is a linear alkyl group having 1 to 6 carbon atoms, and R ^{3 to} R ⁶ are hydrogen atoms. N represents 0 . , x is 1 or 2.). The rubber composition is
(A) For 100 parts by mass of a rubber component made of natural rubber and / or synthetic rubber,
(B) 40 to 80 parts by mass of carbon black having a nitrogen adsorption specific surface area of 70 to 130 m ² / g and a DBP oil absorption of 70 to 110 ml / 100 g,
(C) 0.1 to 10 parts by mass of a sulfenamide vulcanization accelerator represented by formula (I),
(D) The pneumatic tire according to claim 1, comprising sulfur in an amount of 0.3 to 10 parts by mass. The rubber composition according to claim 1 or 2, wherein R ² in the formula (I) is a methyl group, an ethyl group, or an n-propyl group . The rubber composition according to any one of claims 1 to 3 , wherein R ² in the formula (I) is an ethyl group . The pneumatic tire according to any one of claims 2 to 4 , wherein the rubber composition further includes (E) a cobalt-based component composed of cobalt alone and / or a compound containing cobalt. The air according to claim 5 , wherein the content of the cobalt-based component (E) is 0.03 to 3 parts by mass with respect to 100 parts by mass of the rubber component (A) as a cobalt amount. Tires. The pneumatic tire according to claim 5 or 6, wherein the cobalt-containing compound is a cobalt salt of an organic acid. The pneumatic tire according to any one of claims 2 to 7 , wherein the rubber component (A) contains at least one of natural rubber and polyisoprene rubber. The pneumatic tire according to any one of claims 2 to 8 , wherein the rubber composition contains natural rubber in an amount of 50% by mass or more in 100% by mass of the rubber component (A). The pneumatic tire has a carcass layer (I) extending in a substantially toroidal shape by folding both ends in the width direction around the bead core;
A belt layer (II) composed of at least two belt plies, which are arranged radially outside the carcass layer (I) and in which a belt cord inclined in the opposite direction to the tire equator is embedded;
A tread disposed radially outward of the belt layer (II) and a non-stretch reinforcing element disposed between the tread and the carcass layer (I) and extending substantially parallel to the tire equator are embedded therein. Belt reinforcement layer (III),
A thin buffer rubber layer (IV) disposed between the tread and the belt layer (II) and between the tread and the belt reinforcing layer (III);
The tread reinforcing layer (V) is disposed between the tread and the shock absorbing rubber layer (IV), and has a steel cord embedded therein and inclined at a range of 45 to 90 degrees with respect to the tire equator. The pneumatic tire according to any one of claims 1 to 9 , characterized in that:

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