JP2008062893A - Heavy duty radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heavy duty tire having superior degradation resistance and enhanced in durability by securing the adhesiveness between a steel cord and a coated rubber. <P>SOLUTION: In this pneumatic tire, a main cross belt is formed by so stacking at least three rubber-coated cord layers formed of substantially non-extensible steel cords buried in the coating rubber that the steel cords extend parallel with each other indoors and extend in the reverse direction on both sides of a tire equatorial plane while crossing each other between the adjacent layers. A wedge-like belt end wedge rubber formed of a three-layer structure so formed as to hold the wedge rubber 2 of the intermediate layer by the wedge rubber 1 and the wedge rubber 3 is disposed at both ends between the layers of the rubber-coated cords forming the main cross belt. An organic acid cobalt base with a cobalt quantity of 0.025 mass.% or less is contained in the wedge rubber 2 with a rubber composition of 100 mass.%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heavy load tire, and more particularly to a heavy load tire that secures adhesion between a steel cord and a covering rubber, has excellent deterioration resistance, and has improved tire durability.

Conventionally, heavy-duty pneumatic tires used for large vehicles such as large trucks and buses are used under the action of high internal pressure and heavy load. In order to increase this, the belt layers are generally laminated in order so that the steel cords cross each other to form a cross belt.
However, between the belt layers constituting such a cross belt, since the steel cords are arranged across the tire equatorial plane, a large shearing force acts between the belt layers when the tire rolls, In particular, there is a problem that separation is likely to occur between the steel cord and the rubber covering the steel cord at both ends of the belt layer where stress tends to concentrate.

As a pneumatic tire which prevents the occurrence of such separation, wedge-shaped wedge rubber having a cross-sectional wedge shape is disposed between both end portions of an adjacent belt layer constituting a cross belt in which steel cords cross each other across the tire equatorial plane, and the adjacent belt layer The steel cord interval in the tire radial direction is widened at the end position, thereby suppressing fatigue crack damage around the belt end portion and preventing occurrence of separation (for example, Patent Document 1). Or 2).
On the other hand, in order to ensure adhesion between the steel cord and the covering rubber, an organic acid cobalt salt which is an adhesion promoter and a large amount of sulfur are blended in the covering rubber and its adjacent rubber.
These compounding agents have been known to increase the adhesion between the steel cord and the coated rubber, but it is also well known that the aging characteristics due to heat and the like deteriorate. In addition, when the amount of organic acid cobalt salt or sulfur is reduced from adjacent members of steel cord coated rubber, such as wedge rubber, the organic acid cobalt salt or sulfur in the steel cord coated rubber moves to wedge rubber, which is the adjacent rubber. Because there is a decrease in adhesion, there is a contradiction performance that reduces tire durability, and although the effect of arranging the above wedge rubber is recognized, in order to further improve tire durability, deterioration resistance There remains a problem that needs to be further improved.

JP-A-9-263108 Japanese Patent Laid-Open No. 11-32224

  An object of the present invention is to provide a heavy-duty tire that secures the adhesion between a steel cord and a covering rubber and improves the durability of a tire having excellent deterioration resistance under such circumstances. is there.

As a result of intensive research to achieve the above object, the present inventor has changed the conventional wedge rubber made of a single layer of rubber into a wedge rubber made of a three-layer structure, and the wedge rubber of each layer has a specific performance and is functionally separated. By doing so, it was found that the purpose could be achieved. The present invention has been completed based on such findings.
That is, the present invention
(1) A carcass ply comprising a bead core provided in a pair of left and right bead parts, and a radial cord layer extending from the crown part to both bead parts through both side wall parts and being wound around the bead cores and moored to the bead parts. And a main cross-layer belt and a tread arranged on the outer side in the radial direction of the crown portion of the carcass ply, and the main cross-belt embeds a plurality of substantially non-extensible steel cords in the coated rubber. The at least three rubber-coated cord layers are laminated so that the cords extend parallel to each other in the layers, and the cords cross each other and extend in opposite directions across the tire equatorial plane in adjacent layers. In the pneumatic tire, the wedge rubber 2 of the intermediate layer is attached to the wedge rubber 1 and the wedge rubber at both ends between the layers of the rubber-coated cord forming the main cross belt. A wedge-shaped belt end wedge rubber having a three-layer structure formed so as to be sandwiched between the rubber layers 3 is disposed, and 0.025 by weight of an organic acid cobalt salt as a cobalt amount in 100% by mass of the rubber composition of the wedge rubber 2. A heavy duty radial tire comprising not more than mass%,
(2) The radial tire for heavy loads according to (1) above, comprising 2% by mass or less of sulfur in 100% by mass of the rubber composition of the wedge rubber 2 of the intermediate layer,
(3) The rubber composition of the wedge rubbers 1 and 3 contains 0.025 to 0.25% by mass of an organic acid cobalt salt as a cobalt amount and 1.5 to 6% by mass of sulfur. (1) or (2) heavy duty radial tire,
(4) The total thickness Da of the steel cord-covered rubber to the steel cord and the thickness D1 of the wedge rubber 1 is 0.5 mm or more, and The heavy duty radial tire according to any one of (1) to (3), wherein the total thickness Db of the thickness Dc and the thickness D3 of the wedge rubber 3 is 0.5 mm or more,
(5) The radial tire for heavy load according to (4) above, wherein the thicknesses of Da and Db are both 0.5 mm to 0.8 mm, and (6) 100% strain elastic modulus of the wedge rubber 2 is The radial tire for heavy loads according to any one of the above (1) to (5), wherein the wedge rubbers 1 and 3 are 70% or less of the 100 strain elastic modulus,
Is to provide.

  ADVANTAGE OF THE INVENTION According to this invention, the heavy load tire which ensured the adhesiveness of a steel cord and covering rubber | gum, and improved the tire durability which has the outstanding deterioration resistance can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional schematic view showing an end of a conventional main cross belt. 1 represents a steel cord, 2 represents a steel cord-coated rubber, and 3 represents a wedge-shaped wedge rubber.
FIG. 2 is a partial cross-sectional schematic view showing an end portion of a main cross belt showing an embodiment of the present invention.
4 is a wedge rubber 1, 5 is a wedge rubber 2 of an intermediate layer, and 6 is a wedge rubber 3. As shown in FIG. 2, three wedge rubbers are laminated to form a wedge-shaped three-layer wedge rubber.
D1 represents the thickness (mm) of the wedge rubber 1, D3 represents the thickness (mm) of the wedge rubber 3, and Dc represents the thickness (mm) of the steel cord-coated rubber.
Further, Da represents the total thickness (D1 + Dc) of the thickness D1 (mm) of the wedge rubber 1 and the steel cord covering rubber thickness Dc (mm), and Db represents the thickness D3 (mm) of the wedge rubber 3 and the steel. The total thickness (D3 + Dc) of the cord-coated rubber thickness Dc (mm) is shown.

  It is necessary that the wedge rubber 2 of the intermediate layer forming the three-layer structure contains 0.025% by mass or less of the organic acid cobalt salt as a cobalt amount in 100% by mass of the rubber composition, preferably 0.01 Most preferably, the blending amount of cobalt contained in the rubber composition is 0% by mass or less. By setting the cobalt content in the above range, the excellent deterioration resistance of the wedge rubber 2 can be ensured.

Here, the organic acid cobalt salt is blended in a coated rubber having a steel cord as a reinforcing material as an adhesion promoter for adhesion between the rubber and the steel cord, and there is no particular limitation. For example, cobalt naphthenate, Examples include cobalt stearate, cobalt oleate, cobalt tall oil, and resin acid cobalt. Moreover, “manobond C” manufactured by Rhodia Co., Ltd. and the like are listed as commercial products.
The steel cord is usually plated with brass on the surface of the cord in order to ensure adhesion with the coated rubber.
In addition, the rubber component is preferably a single rubber or a blend rubber which usually contains 70% by weight or more of natural rubber, and other rubbers in the case of the blend rubber include synthetic polyisoprene rubber, polybutadiene rubber, and styrene-butadiene copolymer. For example, rubber.

Further, the wedge rubber 2 preferably contains 2% by mass or less of sulfur in 100% by mass of the rubber composition, more preferably 1.6% by mass or less.
The deterioration resistance of the wedge rubber 2 can be ensured in the same manner as when the amount of cobalt is reduced by setting the amount of sulfur within the above range.
As shown in FIG. 2, the wedge rubber 2 is sandwiched between the wedge rubber 1 and the wedge rubber 3, while the wedge rubber 1 and the wedge rubber 3 are adjacent to the steel cord-covered rubber. Since the wedge rubber 2 is adjacent to the wedge rubbers 1 and 3, even if the amount of the organic cobalt salt and sulfur in the wedge rubber 2 is reduced from the amount of the organic cobalt salt and sulfur mixed in the coated rubber, the steel is used. When there is a distance of Da or Db between the cord-covered rubber, the organic cobalt salt and sulfur transfer to the wedge rubber 2 is suppressed. Accordingly, in the steel cord-covered rubber near the steel cord, organic acid cobalt salt and sulfur for ensuring adhesion with the steel cord are sufficiently present, and a decrease in adhesion between the steel cord and the coated rubber can be suppressed.

Therefore, the wedge rubbers 1 and 3 contain 0.025 to 0.25% by mass of an organic cobalt salt as a cobalt amount in 100% by mass of the rubber composition, and 1.5 to 6% by mass of sulfur. preferable. Furthermore, the more preferable content of sulfur is 2 to 4% by mass.
Further, the contents of the organic cobalt salt and sulfur contained in the wedge rubbers 1 and 3 may be the same, or may be the same as the steel cord-covered rubber.

Further, the wedge rubbers 1 and 3 are rubber layers set so as to act as a barrier for suppressing the migration of the organic cobalt salt and sulfur in the steel cord-coated rubber to the wedge rubber 2, and the steel cord-coated rubber is a steel layer. The sum of the thickness up to the cord and the thickness of the wedge rubber 1 or 3 is an important value that determines the effect. Therefore, the total thickness Da (D1 + Dc) of the thickness Dc up to the steel cord of the steel cord-coated rubber and the thickness D1 of the wedge rubber 1 is 0.5 mm or more, and up to the steel cord of the steel cord-coated rubber The total thickness Db (D3 + Dc) of the thickness Dc of the wedge rubber 3 and the thickness D3 of the wedge rubber 3 is preferably 0.5 mm or more.
Da and Db are preferably the same thickness. Moreover, although there is no restriction | limiting in particular about the upper limit of Da and Db, 0.8 mm or less is preferable.
By making the thicknesses of Da and Db within the above ranges, it is possible to suppress the transition of organic cobalt salt and sulfur to the proximity rubber, for example, the wedge rubber 2, and to secure the adhesiveness between the steel cord and the covering rubber. The amount of the organic cobalt salt and sulfur therein can be greatly reduced as compared with the amount contained in the steel cord-coated rubber, and the deterioration resistance of the wedge rubber 2 can be improved.

The 100% strain elastic modulus of the wedge rubber 2 is preferably 70% or less compared to the 100 strain elastic modulus of the wedge rubbers 1 and 3. More preferably, it is 50% or less. Although there is no restriction | limiting in particular about the lower limit, Usually, it is about 30%.
By setting the 100% strain elastic modulus of the wedge rubber within the above range, the shear stress generated at both ends of the belt layer, particularly the main cross belt layer where stress is likely to concentrate, is alleviated, and fatigue crack damage around the belt end is reduced. By suppressing the occurrence of separation at the belt end, it is possible to improve tire durability.

The method for preparing the 100% strain elastic modulus of the wedge rubber 2 is not particularly limited, and the wedge rubber 2 can be prepared by increasing or decreasing the blending amount of carbon black which is a reinforcing filler or the blending amount of sulfur.
The carbon black compounded in the wedge rubber 2 is, for example, FEF, HAF, or ISAF grade, and the compounding amount is 20 to 90 parts by mass, preferably 30 to 70 parts by mass with respect to 100 parts by mass of the rubber component. Part.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Various measurements in each example and comparative example were performed as follows.
1) Measurement of 100% strain elastic modulus The vulcanizate obtained as a sample was measured according to JIS K6251-2004. The composition A was shown as an index with 100 as the index. A smaller numerical value indicates a smaller elastic modulus. The measurement results are shown in Table 1.
2) Measurement of drum travel distance The tire was traveled under a tire internal pressure of 700 KPa and a JIS 100% load at a speed of 60 km / h until failure, and was displayed as an index when the travel distance of Comparative Example 1 was 100. The larger the value, the longer the mileage.
3) Adhesion with steel cord The main crossing belt part including the three-layer wedge rubber of the tire after running the drum is sampled, and the adhesion between the steel cord and the steel cord-coated rubber on the three-layer wedge rubber side is minus 80 ° C. The rubber adhesion rate (%) to the steel cord at that time was compared. A rubber adhesion rate of 100% was indicated as 100.

Preparation of Rubber Compositions A to E According to the blending composition described in Table 1, each component was kneaded according to a conventional method to obtain wedge rubber compositions A to E. The rubber composition was vulcanized at 145 ° C. for 60 minutes, and the 100% strain elastic modulus of the obtained vulcanizate was measured. The elastic modulus of composition A was expressed as an index with 100 as the elastic modulus. A smaller numerical value indicates a smaller elastic modulus. The results are shown in Table 1.

［注］
＊１．カーボンブラック：Ｎ３３０、「旭＃７０」旭カーボン社製
＊２．老化防止剤：Ｎ−（１，３ジメチルブチル）−Ｎ’−フェニル−ｐ−フェニレンジアミン「ノクラック６Ｃ」大内新興化学工業社製
＊３．有機酸コバルト塩：「マノボンドＣ：コバルト金属含有量２２質量％」ローディア社製
＊４．加硫促進剤：Ｎ，Ｎ’−ジシクロヘキシル−２−ベンゾチアゾリルスルフェンアミド「ノクセラーＤＺ」大内新興化学工業社製

[note]
* 1. Carbon black: N330, “Asahi # 70” manufactured by Asahi Carbon Co., Ltd. * 2. Anti-aging agent: N- (1,3 dimethylbutyl) -N′-phenyl-p-phenylenediamine “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd. * 3. Organic acid cobalt salt: “Manobond C: Cobalt metal content 22% by mass” manufactured by Rhodia * 4. Vulcanization accelerator: N, N'-dicyclohexyl-2-benzothiazolylsulfenamide "Noxeller DZ" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-3, Comparative Examples 1-4
Truck and bus tires (tire size) in which wedge-shaped wedge rubber composed of a single layer and a three-layer structure is provided at both end portions between the rubber-coated cord layers forming the main cross belt from each combination of wedge rubber types shown in Table 2. : 11R22.5) was manufactured by a conventional method.
The composition A shown in Table 1 was used as the steel cord-coated rubber.
Using these sample tires, the drum travel distance (index) and the rubber adhesion rate (%) to the steel cord were determined. The evaluation results are shown in Table 2.

Table 2 shows the following.
The tires (Examples 1 to 3) provided with the three-layered wedge rubber maintain the rubber adhesion rate to the steel cord in comparison with the conventional tires provided with the one-layered wedge rubber (Comparative Example 1). However, the drum mileage index can be greatly improved.

  ADVANTAGE OF THE INVENTION According to this invention, the heavy load tire which ensured the adhesiveness of a steel cord and covering rubber | gum, and improved the tire durability which has the outstanding deterioration resistance can be provided.

It is a partial cross-sectional schematic diagram which shows the main crossing belt edge part of a prior art example. It is a partial cross section schematic diagram which shows the main crossing belt edge part which shows embodiment of this invention.

Explanation of symbols

1. Steel cord 2. 2. Steel cord coated rubber Single layer wedge rubber 4. Wedge rubber 1
5. Wedge rubber 2
6). Wedge rubber 3
D1. Wedge rubber 1 thickness (mm)
D3. Wedge rubber 3 thickness (mm)
Da. Total thickness of wedge rubber 1 and steel cord coated rubber (D1 + Dc)
Db. Total thickness of wedge rubber 3 and steel cord coated rubber (D3 + Dc)
Dc. Steel cord coated rubber thickness (mm)

Claims (6)

  A bead core provided in a pair of left and right bead parts, a carcass ply formed of a radial cord layer extending from the crown part to both bead parts via both sidewall parts, and being wound around the bead core and anchored to the bead part, A main cross layer belt and a tread, which are arranged on the outer side in the radial direction of the crown portion of the carcass ply, are provided, and the main cross belt is formed by embedding a plurality of substantially non-extensible steel cords in a covering rubber. A pneumatic tire formed by laminating at least three rubber-coated cord layers so that the cords extend parallel to each other in the layers, and the cords cross each other and extend in opposite directions across the tire equatorial plane in adjacent layers. The wedge rubber 2 of the intermediate layer is attached to the both ends between the layers of the rubber-coated cord forming the main cross belt by the wedge rubber 1 and the wedge rubber 3. A wedge-shaped belt-end wedge rubber having a three-layer structure formed in such a manner is disposed, and the rubber composition of the wedge rubber 2 contains 0.025% by mass or less of an organic acid cobalt salt as a cobalt amount. A heavy duty radial tire characterized by that.   2. The heavy duty radial tire according to claim 1, wherein 2% by mass or less of sulfur is contained in 100% by mass of the rubber composition of the wedge rubber 2 of the intermediate layer.   The rubber composition of the wedge rubbers 1 and 3 contains 0.025 to 0.25% by mass of an organic acid cobalt salt as a cobalt amount and 1.5 to 6% by mass of sulfur. The radial tire for heavy loads as described in 1 or 2.   The total thickness Da of the steel cord coated rubber to the steel cord and the thickness D1 of the wedge rubber 1 is 0.5 mm or more, and the thickness Dc of the steel cord coated rubber to the steel cord is The radial tire for heavy loads according to any one of claims 1 to 3, wherein a total thickness Db of the wedge rubber 3 and the thickness D3 of the wedge rubber 3 is 0.5 mm or more.   The radial tire for heavy loads according to claim 4, wherein the thicknesses of Da and Db are both 0.5 mm to 0.8 mm.   The radial tire for heavy loads according to any one of claims 1 to 5, wherein a 100% strain elastic modulus of the wedge rubber 2 is 70% or less as compared with a 100 strain elastic modulus of the wedge rubbers 1 and 3.

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