JP2002019417A - Pneumatic tire for heavy load suitable for off-road travel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for a heavy load suitable for off-road travel for improving abrasion resistance, groove bottom crack occurrunce preventive performance and heating durability by a structure of a tread part. SOLUTION: In this pneumatic tire for a heavy load suitable for off-road travel, the tread part is composed of a three-layer structure of a cap A, a cap B and a base C from a tire surface, a C layer has the tread part for gradually reducing a gauge toward a center part from the edge part, the gauge ratio of an A layer/a B layer/the C layer in a shoulder part is 35 to 80/60 to 10/3 to 21 (total 100%), the gauge ratio of the A layer/the B layer/the C layer in a crown center part is 35 to 80/61 to 11/2 to 20 (total 100%), the A layer is composed of NR/diene rubber = 100 to 60/0 to 40 (the wt.% ratio) (total 100 wt.%), the B layer and the C layer are independently composed of NR and/or IR, and tanδ (A) and tanδ (B) at 100 deg.C of the A layer, the B layer and the C layer satisfy the relationship of tanδ (A)>tanδ (B) and tanδ (B) <=0.6 tanδ (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for heavy loads, and more particularly, to running on uneven terrain having a three-layer tread having improved wear resistance, groove bottom crack prevention and heat generation durability. The present invention relates to a heavy-duty pneumatic tire suitable for a vehicle.

[0002]

2. Description of the Related Art In recent years, in heavy duty tires, ultrafine carbon particles have been blended with natural rubber (NR) alone or polybutadiene rubber (BR) / styrene-butadiene copolymer rubber (SBR) for the purpose of improving wear resistance. The used cap is frequently used in the tread portion. However, it is difficult to achieve both opposing performances such as compatibility between abrasion resistance and durability, and compatibility between on-ice performance and abrasion resistance with a single-layer tread, so use a two-layer or three-layer tread. And many patent applications have been filed for formulations and structures therefor. However, 2
In order to further improve the performance of the tread having the layered structure, there is a possibility that the workability at the time of molding is deteriorated and the adhesion to the belt portion is deteriorated.

[0003] Japanese Patent Application Laid-Open No. 11-60810 discloses a heavy duty tire having improved wear resistance, heat generation durability and wandering resistance by using a three-layer tread portion. Japanese Patent Application Laid-Open No. 6-8708 describes a studless tire in which the on-ice performance after the middle stage of wear is improved by using a rubber layer having a higher foaming ratio as the inner layer of the tread portion having a three-layer structure.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned state of the art, the present invention improves the performance of abrasion resistance, groove bottom crack generation prevention and heat generation durability and is suitable for heavy load pneumatic running on rough terrain. The purpose is to provide tires.

[0005]

According to the present invention, the tread portion has a three-layer structure of a cap-A, a cap-B and a base-C from the tire surface, and the lowermost cap-C layer has an edge. Layer A / B at the shoulder portion of a heavy-duty pneumatic tire suitable for running on rough terrain having a tread portion whose gauge gradually decreases from the portion toward the center portion
The layer / C layer gauge ratio is 35 to 80/60 to 10/3 to 2
1 (total 100%), and the gauge ratio of layer A / layer B / layer C at the crown center portion is 35 to 80/61 to 11
/ 2 to 20 (total 100%), Cap-A
Layer is natural rubber / diene rubber = 100-60 / 0-40
(By weight%) (totaling 100% by weight), the cap-B layer and the base-C layer are independently formed of natural rubber and / or polyisoprene rubber, and the cap-A layer and the cap-B The tan δ (A) and tan δ (B) at 100 ° C. of the layer satisfy the following relationship: tan δ (A)> tan δ (B) (I) tan δ (B) ≦ 0.6 tan δ (A) (II) A pneumatic tire for heavy load suitable for running on uneven terrain is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have conducted research to solve the above-mentioned problems. As a result, heavy load tires running on uneven terrain have a problem that the chipping property of the center portion particularly at the final stage of wear becomes a problem. Focus on the high number of treads
The center portion of the crown center portion is made thinner than the shoulder portion by placing a low heat generation and chipping resistant rubber on the second layer and a low heat generation rubber on the third layer. The present invention succeeded in obtaining a heavy-duty pneumatic tire with improved heat generation durability while improving wear resistance by suppressing chipping of the present invention, and led to the present invention. Hereinafter, this will be described in more detail.

As shown in FIG. 1, a heavy-duty pneumatic tire suitable for running on uneven terrain according to the present invention is a tread portion 1.
To Cap-A layer 2, Cap-B layer 3 and Base-C
Layer 3 has a three-layer structure. As described below, three layers A, B and C have a shoulder portion 5 and a crown center portion 6.
The above-mentioned object has been achieved by specifying the gauge thickness of A and the constituent rubbers of A, B and C. FIG.
As shown in the figure, the base of the tread 1 according to the present invention
The C layer is located below the line connecting the groove bottoms 7.

[0008] In the pneumatic tire according to the present invention, the gauge ratio of the layer A / B / C at the shoulder portion and the crown center portion of the tread portion is 35 to 80/60 to 10 /, respectively.
3-21 and 35-80 / 61-11 / 2-20 (100% in total).

[0009] The rubber constituting the A, B and C layers of the tread portion of the pneumatic tire according to the present invention is a natural rubber (NR) which has conventionally been generally compounded in a rubber composition for tires.
Diene rubbers such as polyisoprene rubber (IR), various styrene-butadiene copolymer rubbers (SBR), and various polybutadiene rubbers (BR) can be used alone or as an arbitrary blend.

The cap-A layer in the tread portion of the pneumatic tire according to the present invention is composed of natural rubber / diene rubber = 100 to
60/0 to 40 (weight% ratio) (total 100%), and the following relationship of tan δ (100 ° C.) must be satisfied.

The cap-B layer and the base-C layer of the tread portion of the pneumatic tire according to the present invention are each independently composed of NR and / or IR, and have the following tan δ.
(100 ° C.).

The values of tan δ (100 ° C.) tan δ (A) and tan δ (B) of the layers A and B of the tread portion of the pneumatic tire according to the present invention are as follows in order to achieve the object of the present invention. Need to have a relationship. tan δ (A)> tan δ (B) (I) tan δ (B) ≦ 0.6 tan δ (A) (II)

The value of tan δ (A) at 100 ° C. is ta
If the value is not larger than the value of nδ (B), the wear resistance and cut resistance in the initial to middle stages become insufficient, which is not preferable, and the value of tanδ (B) at 100 ° C. If not, the heat generation durability is not sufficiently improved.

In the layers A, B and C of the present invention, carbon black is blended with the above rubber. As the carbon black used in the present invention, carbon black conventionally used in pneumatic tires for heavy loads can be used.

The rubber composition constituting the A, B and C layers of the tread for a pneumatic tire according to the present invention contains, in addition to the above-mentioned essential components, other reinforcing agents (fillers) such as carbon black and silica. Various additives conventionally used for pneumatic tires such as vulcanizing agents, vulcanization accelerators, various oils, anti-aging agents, and plasticizers can be compounded. Can be kneaded and vulcanized by a conventional method to obtain a composition and vulcanized. The compounding amounts of these additives can also be conventional general compounding amounts, as long as they do not contradict the object of the present invention.

[0016]

EXAMPLES Hereinafter, the present invention will be further described with reference to Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

Examples 1 and 2 and Comparative Examples 1 to 5 Tread layers A-1 and B-1 and C-
One layer was prepared. The rubber and carbon black used are as follows. NR: Natural rubber (RSS No. 3) IR: Nippon Zeon IR Nipol IR2200 Carbon Black SAF: Tokai Carbon Seast 9 Carbon Black ISAF: Showa Cabot Show Black N220 Antioxidant 6PPD (N-phenyl-N′-1, 3-dimethylbutyl-p-phenylenediamine)

[0018] The rubber composition constituting each layer of the tread structure layer A-1 through C-1 was blended in common the following additives (amounts are parts by weight of rubber per 100 parts by weight) Ingredients Amounts Zinc flower (JIS No. 3) 4 Industrial stearic acid 3 Powder sulfur 1.9 Vulcanization accelerator CBS (N-cyclohexyl-2-benzothiazole sulfenamide) 1.2

Sample Preparation In the composition shown in Table I and above, the components other than the vulcanization accelerator and sulfur were kneaded in a 1.8 liter closed mixer for 3 to 5 minutes, and when the temperature reached 165 ± 5 ° C. Released to give a masterbatch. This master batch was kneaded with an 8-inch open roll with a vulcanization accelerator and sulfur to obtain a rubber composition. Next, this composition was press-vulcanized in a 15 × 15 × 0.2 cm mold at 160 ° C. for 20 minutes to prepare a target test piece (rubber sheet), and the vulcanization properties were evaluated. The results are shown in Table I.

The test methods for the physical properties of the compositions obtained in the respective examples are as follows. tan δ (100 ° C.): Initial strain 10%, amplitude ± 2 using a viscoelastic spectrometer manufactured by Toyo Seiki Seisaku-sho, Ltd.
%, Frequency 20 Hz, temperature 100 ° C. Abrasion resistance index: Using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.), the wear loss under the conditions of a load of 5 kg, a slip ratio of 5%, a time of 4 minutes, and room temperature was shown as an index.
The larger the index, the better.

[0021]

[Table 1]

Next, a tire tread having a three-layer structure was prepared by using the rubber compositions A-1 to C-1 for tire tread obtained above in a combination shown in Table II at a gauge ratio of SH (shoulder) portion and center portion. Parts manufactured. This time, the extrusion was carried out in one piece using a three-color extruder, but A / B / C was individually extruded and compression molded, or A / B integrated extrusion-C single extrusion (or A single extrusion-B / C integrated) (Extrusion).

[0023]

[Table 2]

The physical properties of the obtained three-layer tire tread were evaluated by the following methods, and the results are shown in Table II. Tread tan δ (100 ° C.): The sum of the values obtained by multiplying the respective shoulder portion gauge ratios of A / B / C by tan δ (100 ° C.) is calculated as tan δ (10
0 ° C). Exothermic index: Tread tan δ (100 ° C.) was shown as an index with the value of Comparative Example 1 being 100. The lower the value, the lower the heat generation of the entire tire, which is preferable from the viewpoint of heat generation durability. Tread abrasion index: The sum of the product of each of the A / B / C crown center gage ratios and the abrasion resistance index shown in Table I occupying the tread located from the groove bottom to the top is defined as the tread abrasion resistance index. . The larger the value, the better the wear resistance.

Chipping resistance: The surface condition of the remaining tread groove from the groove bottom at the time of 15% of that of a new product was visually checked, and the quality of chipping resistance was judged based on the size of chipping (chipping) in the tread portion. Evaluation criteria: ○ ... No chipping to small (chipping 0 to 2 m
m) Δ: chipping (chipping 2-5 mm) ×: large chipping (chipping more than 5 mm) Molding workability: In the work of forming a tread three days after the extrusion date and winding the tread on a molding drum, The quality of the molding workability was judged from the presence or absence of peeling off. Evaluation criteria: ○: No peeling off without applying rubber volatile oil △: No peeling off by applying rubber volatile oil ×: No peeling off by applying a wire brush in addition to applying rubber volatile oil

[0026]

As described above, according to the present invention, the heat resistance can be improved by improving the heat resistance while improving the wear resistance and the chipping resistance after the middle stage of wear. In addition, natural rubber alone or BR / SBR
B / C was made of natural rubber to ensure tackiness, with the aim of ensuring the abrasion resistance and preventing cracks at the groove bottom with A made of the blend.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of the structure of a tread portion of a heavy-duty pneumatic tire suitable for running on uneven terrain according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tread part 2 ... Cap-A layer 3 ... Cap-B layer 4 ... Base-C layer 5 ... Shoulder part 6 ... Crown center part 7 ... Groove bottom

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Claims (1)

[Claims] 1. The tire according to claim 1, wherein the tread portion is a cap from the tire surface.
A, a three-layer structure of Cap-B and Base-C,
In a heavy-duty pneumatic tire suitable for running on rough terrain having a tread portion in which a lowermost cap-C layer has a gauge gradually decreasing from an edge portion toward a center portion, an A layer / B layer / C at a shoulder portion The gauge ratio of the layer is 35 ~
80/60 to 10/3 to 21 (total 100%)
The gauge ratio of the A layer / B layer / C layer at the crown center portion is 35 to 80/61 to 11/2 to 20 (total 100%), and the cap-A layer is a natural rubber / diene rubber. =
The cap-B layer and the base-C layer are each independently composed of natural rubber and / or polyisoprene rubber. The tan δ (A) and tan δ (B) at 100 ° C. of the A-layer and the cap-B layer have the following relationship: tan δ (A)> tan δ (B) (I) tan δ (B) ≦ 0.6 tan δ (A) … A heavy duty pneumatic tire suitable for rough terrain that satisfies (II).