JP3661824B2 - Heavy duty pneumatic tire - Google Patents

Description

【００１３】
上記の結果より以下のことがわかる。
本発明による実施例１のタイヤは、内面保護層全体としての厚さは従来のタイヤ（比較例３）と同じで、かつ有機酸コバルト塩を含有するゴム層としては従来タイヤの１／２であるにもかかわらず、比較例３と比較した場合、接着性及びＷ／Ｂ性ふくれは従来以上の性能を維持したままで、内面保護層におけるＡ，Ｂ層全体としてのゴム破断時伸びの指数は１０５と大幅に向上している。
また、実施例２は、ゴム層Ａとゴム層Ｂの各厚さを増加した以外は、実施例１と同様にして製造したタイヤであり、比較例３と比較した場合、接着性を保持したままで、ゴム破断時伸びとＷ／Ｂ性ふくれの双方が改善されている。ただし、ゴム破断時伸びは、実施例１より劣っている。その理由は、実施例２の場合、内面保護層全体としての厚み増大により発熱が大きくなって、ゴム劣化も進んだためと考えられる。
一方、比較例１及び比較例２は、ゴム層Ｂの厚さｄＢとゴム層Ａの厚さｄＡとの比ｄＢ／ｄＡが、本発明で規定する関係式を満足していないために、いずれの場合にも、従来のタイヤ（比較例３）に比較してその改良効果は得られていない。
【００１４】
【発明の効果】
この発明によれば、重荷重用空気入りタイヤのインナーライナーとカーカスプライとの間に配置されている内面保護層について、プライコードとの接着性に悪影響を及ぼすことなく、内面保護層の耐劣化性に関係するゴム破断時伸びと、内面保護層の耐クリープ性に関係するＷ／Ｂ性ふくれの双方を改善でき、その結果、重荷重用空気入りタイヤの耐久性を著しく向上させることが可能である。また、有機酸コバルト塩の配合を必要とするゴム層を薄くすることにより、タイヤ性能を損なうことなく、高価な有機酸コバルト塩の使用量を大幅に減少することができる。さらに、内面保護層全体のゲージダウンにより、タイヤをより軽量化することも可能である。
【図面の簡単な説明】
【図１】 本発明によるタイヤの右半断面図である。
【図２】 本発明によるタイヤのサイドウォール部の断面詳細図である。
【符号の説明】
１： トレッド部
２： サイド部
２ａ： サイドゴム
３： ビード部
４： カーカスプライ
５： インナーライナー
６： 内面保護層
６ａ： 内面保護層のうちのゴム層Ａ
６ｂ： 内面保護層のうちのゴム層Ｂ
７： スチールコード[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy-duty pneumatic tire with improved durability, and more specifically, a rubber layer containing an organic acid cobalt salt and a rubber layer not containing an organic acid cobalt salt between a carcass ply and an inner liner. The present invention relates to a heavy duty pneumatic tire having a layer.
[0002]
[Prior art]
Conventionally, a butyl rubber-based rubber composition with high gas opacity is used for the inner liner of a heavy duty pneumatic tire for the purpose of maintaining the tire air pressure, and between the inner liner and the carcass ply, Usually, a squeegee rubber layer (hereinafter referred to as an inner surface protective layer) containing an organic acid cobalt salt is disposed.
By the way, this inner surface protective layer is a so-called Vashbread failure (hereinafter referred to as W / B bulge) that causes the ply cord to appear on the inner surface of the tire because the rubber creeps and thins due to running and tire internal pressure. Play an important role in preventing Therefore, from this point, it is desirable to use a rubber having good creep resistance as a characteristic of the inner surface protective layer rubber.
In addition, the carcass ply coating rubber of heavy duty pneumatic tires that use steel cord as a reinforcing material for carcass ply usually contains an organic acid cobalt salt as an adhesion promoter for the purpose of improving adhesion to the steel cord. If it is included, but the coating of the coating rubber onto the steel cord is incomplete, sufficient adhesion between the steel cord and the rubber cannot be obtained, resulting in a serious failure in tire use. For this reason, generally, the inner surface protective layer between the inner liner and the ply coating rubber is made of rubber having the same or similar composition as the ply coating rubber, and the organic acid cobalt as an adhesion promoter is used for the inner surface protective layer rubber. Inclusion of salt is unavoidable.
[0003]
However, blending an organic acid cobalt salt with rubber is not preferable from the viewpoint of rubber deterioration and adversely affects the durability of the tire. In particular, since the inner surface protective layer is located close to the inner surface of the tire via the inner liner, the inner protective layer itself is a member that is relatively susceptible to rubber deterioration. When a large deformation occurs over the object, rubber breakage occurs in the inner surface protective layer, leading to tire failure such as puncture.
Accordingly, it is desirable to use a rubber having good deterioration resistance as well as the above-mentioned creep resistance as a characteristic of the inner surface protective layer rubber. However, in reality, the deterioration resistance of the inner surface protective layer rubber is not always sufficient, and in the conventional heavy load pneumatic tire inner surface protective layer, the adhesion and the creep resistance and deterioration resistance are maintained. It was difficult to further improve both sexes.
On the other hand, the present inventor has developed an inner liner containing an organic acid cobalt salt in the current production process capability, particularly by improving the detection accuracy of a hole in a rubber sheet, with the recent advancement of rolling related technology in tire production. I also learned that the rubber layer can be further gauged down.
[0004]
[Problems to be solved by the invention]
Under such circumstances, the present invention has a higher degree of adhesion to the steel cord of the inner surface protective layer located between the inner liner of the heavy duty pneumatic tire and the carcass ply and the degree of prevention of W / B swelling. An object of the present invention is to provide a heavy-duty pneumatic tire with significantly improved durability.
[0005]
[Means for Solving the Problems]
The present inventor has intensively studied to solve the above problems. As a result, the heavy-duty pneumatic tire has two inner surface protective layers, and the organic acid cobalt salt is contained only in the rubber layer adjacent to the carcass ply, and the organic acid cobalt salt is not contained in the rubber layer adjacent to the inner liner. It has been found that the use of rubber can improve both the creep resistance and the deterioration resistance of the inner surface protective layer while maintaining the level of adhesion.
That is, the present invention includes a tread portion, a pair of side portions that are continuous at both shoulders of the tread portion, a bead portion, a carcass ply that uses a steel cord straddling the bead portion as a reinforcing material, an inner liner, and a carcass ply. In a pneumatic tire having an inner surface protective layer between the inner liner and the inner liner, the inner surface protective layer includes a rubber layer A adjacent to the carcass ply and containing an organic acid cobalt salt, and an organic acid cobalt salt adjacent to the inner liner. The rubber layer B does not contain bismuth, and when the thickness of the rubber layer A is dA and the thickness of the rubber layer B is dB, there is a relationship of 1/2 <dB / dA <2. A heavy duty pneumatic tire is provided.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the rubber constituting the rubber layer A adjacent to the carcass ply in the inner surface protective layer is a rubber having the same or similar composition as the carcass ply coating rubber and contains an organic acid cobalt salt. Here, the organic acid cobalt salt is blended in a carcass ply coating 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, naphthenic acid is used. Examples include cobalt, cobalt stearate, cobalt oleate, cobalt tall oil, and resin acid cobalt. The compounding amount of the organic acid cobalt salt is usually 0.1 to 2.0 parts by weight with respect to 100 parts by weight of rubber.
The rubber of the rubber layer A 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 a blend rubber are synthetic polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer. For example, rubber.
[0007]
The carbon black blended in the rubber layer A is, for example, FEF, HAF, or ISAF grade, and the blending amount is 40 to 65 parts by weight, preferably 45 to 60 parts by weight with respect to 100 parts by weight of rubber. Part. Furthermore, the amount of sulfur compounded in the rubber layer A is usually 4 to 7 parts by weight. Further, a vulcanization accelerator, an anti-aging agent, a softening agent and the like are appropriately blended.
Next, the rubber layer B adjacent to the inner liner is a rubber containing no organic acid cobalt salt. In particular, in order to improve deterioration resistance, the amount of sulfur is preferably less than the amount of rubber layer A and is preferably 3 to 5 parts by weight with respect to 100 parts by weight of rubber. Also, from the viewpoint of preventing W / B blistering, the amount of carbon black in rubber layer B should be greater than the amount of rubber layer A and 50 to 65 parts by weight per 100 parts by weight of rubber. Is preferred.
[0008]
Next, it demonstrates further based on drawing as an example of this invention.
FIG. 1 is a right half sectional view of a heavy duty tire according to the present invention, in which a carcass ply 4 (only the innermost layer ply is shown) straddling a bead portion 3, a tread portion 1, a side portion 2, an inner liner 5 and an inner surface protective layer. It is comprised from 6.
FIG. 2 is a detailed cross-sectional view of the side portion 2, and the inner surface protective layer located between the carcass ply 4 and the inner liner 5 is composed of a rubber layer A indicated by 6 a and a rubber layer B indicated by 6 b. It is configured. Here, in order to ensure adhesion to the steel cord and the deterioration resistance of the inner surface protective layer rubber, when the thickness of the rubber layer A is dA and the thickness of the rubber layer B is dB, 1/2 <dB It is necessary that the relationship / dA <2 is satisfied, more preferably the relationship 2/3 ≦ dB / dA ≦ 1.
[0009]
That is, when the rubber layer A is thinned and the value of dB / dA is 2 or more, the rubber layer A sheet may be locally perforated in the manufacturing process.
On the contrary, when the A layer is thick and the value of dB / dA is 1/2 or less, the proportion of the rubber layer B with good deterioration resistance decreases, so that the entire inner surface protective layer has the rubber deterioration resistance. Improvement becomes difficult.
Further, the thickness dA of the rubber layer A is sufficient if it is about 0.5 to 1.5 mm from the viewpoint of securing adhesiveness with the steel cord.
Furthermore, in the present invention, a rubber suitable for preventing W / B blistering and deterioration resistance can be used for the B layer rubber, so that the adhesiveness, W / B blister and deterioration resistance are higher than the current level. It is also possible to reduce the weight of the tire by keeping the gauge on the entire inner surface protective layer while maintaining it.
[0010]
【Example】
Next, the present invention will be specifically described with reference to examples and comparative examples.
The test tire is a tire for trucks and buses having a size 11R22.5 rib pattern, and the structure of the inner surface protective layer is shown in Table 1. Here, cobalt naphthenate as an adhesion promoter is contained only in the rubber layer A and not contained in the rubber layer B. The rubber layer A and the rubber layer B were made according to the following basic composition.
Natural rubber 100 parts carbon black FEF 55 parts softener 1.0 part cobalt naphthenate (rubber layer A only) 2.0 parts zinc white 6.0 parts stearic acid (rubber layer B only) 2.0 Part by weight Anti-aging agent 2.0 part by weight Sulfur 5.0 part by weight Vulcanization accelerator 0.8 part by weight
The test tire was evaluated by conducting a running test of about 100,000 km, then dissecting the tire, and regarding the inner surface protective layer, the elongation at the time of rubber breakage, the adhesiveness with the W / B bulge and the ply cord were as follows: The measurement method was used.
(1) JIS # 3 samples were collected from three types of rubbers, rubber layer A, rubber layer B, and composite layers of rubber layers A and B as an inner surface protective layer that stretched at the time of rubber breakage, and measured with an Instron tensile tester. . In Comparative Example 3, the above three types of rubber are all the same rubber.
(2) W / B blister (Vashbread failure)
For the tire after the running test, only the inner liner was peeled off, the inner surface protective layer rubber (corresponding to the rubber layer B except for the comparative example 3) was exposed, and the uneven state was determined by the amount of indentation (the uneven peak and valley portions). The average value of the vertical length was evaluated. It shows that W / B property is so bad that a numerical value is large.
(3) Adhesion with ply cords The innermost ply of the tire shawler part is collected, and the adhesion between the steel cord and rubber is measured at minus 80 ° C. Compared.
In addition, in the above, evaluation of various tests was shown by the index | exponent which set the comparative example 3 by the conventional tire with one inner surface protective layer to 100. Each test shows that the larger the value, the better. The results are shown in Table 1.
[0012]
[Table 1]

[0013]
The following can be seen from the above results.
In the tire of Example 1 according to the present invention, the thickness of the entire inner surface protective layer is the same as that of the conventional tire (Comparative Example 3), and the rubber layer containing the organic acid cobalt salt is 1/2 that of the conventional tire. Nevertheless, when compared with Comparative Example 3, the adhesiveness and W / B blisters maintained the performance higher than conventional, and the index of elongation at the time of rubber breakage of the A and B layers in the inner surface protective layer as a whole. Is significantly improved to 105.
In addition, Example 2 is a tire manufactured in the same manner as Example 1 except that the thicknesses of the rubber layer A and the rubber layer B were increased. When compared with Comparative Example 3, the adhesiveness was maintained. As it is, both the elongation at break of rubber and the W / B swelling are improved. However, the elongation at break of rubber is inferior to that of Example 1. The reason for this is considered that, in the case of Example 2, the heat generation increased due to the increase in the thickness of the entire inner surface protective layer, and the deterioration of the rubber progressed.
On the other hand, in Comparative Example 1 and Comparative Example 2, since the ratio dB / dA between the thickness dB of the rubber layer B and the thickness dA of the rubber layer A does not satisfy the relational expression defined in the present invention, In this case, the improvement effect is not obtained as compared with the conventional tire (Comparative Example 3).
[0014]
【The invention's effect】
According to the present invention, the inner surface protective layer disposed between the inner liner of the heavy duty pneumatic tire and the carcass ply does not adversely affect the adhesion with the ply cord, and the deterioration resistance of the inner surface protective layer. It is possible to improve both the elongation at break of rubber related to the W / B blistering related to the creep resistance of the inner surface protective layer, and as a result, the durability of the heavy duty pneumatic tire can be remarkably improved. . Further, by reducing the thickness of the rubber layer that requires compounding of the organic acid cobalt salt, the amount of the expensive organic acid cobalt salt used can be greatly reduced without impairing the tire performance. Furthermore, the weight of the tire can be further reduced by reducing the gauge of the entire inner surface protective layer.
[Brief description of the drawings]
FIG. 1 is a right half sectional view of a tire according to the present invention.
FIG. 2 is a detailed cross-sectional view of a sidewall portion of a tire according to the present invention.
[Explanation of symbols]
1: Tread part 2: Side part 2a: Side rubber 3: Bead part 4: Carcass ply 5: Inner liner 6: Inner surface protective layer 6a: Rubber layer A of the inner surface protective layer
6b: Rubber layer B of the inner surface protective layer
7: Steel cord

Claims (3)

Between the tread part, the side part connected to both shoulders of the tread part, a pair of bead parts, a carcass ply with a steel cord straddling the bead part as a reinforcing material, an inner liner, and the carcass ply and the inner liner In the pneumatic tire having the inner surface protective layer positioned, the inner surface protective layer is adjacent to the carcass ply and contains an organic acid cobalt salt, and does not contain stearic acid, and the inner liner is adjacent to the organic acid. The rubber layer B does not contain a cobalt salt and contains stearic acid, and the amount of sulfur compounded in the rubber layer A is 4 to 7 parts by weight with respect to 100 parts by weight of the rubber. amount of sulfur to be compounded in the rubber layer B is equal to or less than the amount of the rubber layer a, the rubber per 100 parts by weight, 3 to 5 parts by weight, and the thickness of the rubber layer a dA, Gore When the thickness of the layer B and dB, 1/2 <dB / dA <heavy duty pneumatic tire, characterized in that the second relationship.   The pneumatic tire for heavy loads according to claim 1, wherein the thickness of the rubber layer A and the thickness of the rubber layer B are in a relationship of 2 / 3≤dB / dA≤1. The amount of carbon black blended in the rubber layer A is 45 to 60 parts by weight with respect to 100 parts by weight of the rubber, and the amount of carbon black blended in the rubber layer B is equal to or greater than the blending amount of the rubber layer A, The heavy-duty pneumatic tire according to claim 1 or 2, wherein the amount is 50 to 65 parts by weight with respect to 100 parts by weight of rubber.

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