JP2000233603A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability by increasing an initial and an aged rupture strengths (breaking elongation) of a protection rubber enveloping a spacer rubber and/or an end part among steel belts of a steel belt part of a breaker. SOLUTION: In a pneumatic tire comprising a breaker with steel cords, a rubber composition composed of mixing carbon black 50-90 pts.wt. sulfur 4.5-10 pts.wt. organic acid cobalt 0.01-0.8 pts.wt. (cobalt element equivalent) and metacresol resin 0.2-10 pts.wt. containing metacresol 80 wt.% or more into natural rubber or raw rubber 100 parts by weight blended of natural rubber 100 pts.wt. and diene rubber 20 pts.wt. or less is used as protection rubber enveloping space rubber and/or an end part among steel belts of a steel belt part of breaker.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which a breaker is made of a steel cord, and more particularly, to a spacer rubber and / or a terminal portion between steel belts in a steel belt portion of the breaker. The present invention relates to a pneumatic tire using a rubber composition in which a natural rubber or a blend of a natural rubber and a diene rubber is blended with a meta-cresol resin as a protective rubber to be used.

[0002]

2. Description of the Related Art In order to improve the durability of a pneumatic tire, many proposals have been made on rubber compositions for improving the adhesion to a steel cord at a breaker portion of the tire. A large amount of an organic acid cobalt / sulfur compounding system is often used as such an adhesive system, but there is no known compounding for a spacer rubber between steel belts at the end of the steel belt in the breaker portion.

Proposals for blending a resin with a large amount of cobalt / sulfur blending system include a meta-cresol resin / hexamethoxymethylmelamine (see Japanese Patent Publication No. 34582/1988), a meta-cresol / thiazole accelerator (Japanese Patent Application Laid-Open No. Sho.
See JP-A-7-178860, JP-B-62-54345.
And Japanese Patent Application Laid-Open No. 63-50 / 1988 discloses a protective rubber surrounding a belt end of a breaker using a composition containing a large amount of an organic acid cobalt / sulfur compound.
No. 201) is known.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to increase the breaking properties (elongation at break) of the spacer rubber between the steel belts of the breaker steel belt portion and / or the protective rubber surrounding the terminal portion at the initial stage and after aging. To improve tire durability.

[0005]

According to the present invention, in a pneumatic tire in which a breaker is made of a steel cord, natural rubber or 100 parts by weight of natural rubber is blended with 20 parts by weight or less of a diene rubber other than natural rubber. Carbon black 50 to 90 parts by weight, sulfur 4.5 to 10 parts by weight, organic acid cobalt 0.0 to 100 parts by weight of raw rubber
Meta-cresol resin containing 1 to 0.8 parts by weight (calculated as cobalt element) and 80% by weight or more of meta-cresol
A tire using a rubber composition containing 0 parts by weight as a spacer rubber between steel belts in a steel belt portion of a breaker and / or a protective rubber surrounding a terminal portion is provided.

[0006]

DETAILED DESCRIPTION OF THE INVENTION For example, there is a correlation between the tensile properties of spacer rubber between steel belts at the end of the steel belt at the breaker portion of a truck or bus tire and the durability of the tire. The correlation between tire and tire durability is high. This is because much of the separation between the steel belts starts from the spacer rubber part. That is, when the elongation at break falls below a certain level, separation between the steel belts may occur frequently. In general, a pneumatic tire has a reduced elongation at break due to fatigue deterioration during running. Therefore, in order to ensure the durability of the tire, a rubber composition which has a high breaking elongation when not running and which does not reduce the breaking elongation during running is desirable.

[0007] Since the spacer rubber in the tire breaker portion is in contact with the steel cord-coated rubber, a system containing a large amount of sulfur in the same manner as the steel cord-coated rubber is preferable. This is because a small amount of sulfur is not preferable because sulfur flows from the coated rubber. However,
A system containing a large amount of sulfur is not preferred because fatigue aging resistance tends to deteriorate.

However, according to the knowledge of the present inventors, when a meta-cresol resin is added to the rubber composition, the breaking elongation when not running and the retention of the breaking elongation when fatigue aging is deteriorated are improved. However, it is not preferable to use a meta-cresol resin and a formalin donor such as hexamethoxymethylmelamine as described in JP-B-63-4582, because physical properties such as elongation at break are reduced.

The raw rubber used in the rubber composition according to the present invention is natural rubber or 100 parts by weight of natural rubber and diene rubber other than natural rubber (for example, polyisoprene rubber, various polybutadiene rubbers, various styrene-butadiene copolymers). Rubber or the like) is a blend rubber of 20 parts by weight or less. If the compounding amount of the diene rubber other than the natural rubber is too large, the heat generation becomes high, which is not preferable.

The composition according to the present invention contains a raw rubber 100
50 to 90 parts by weight of carbon black, preferably 55 to 70 parts by weight, 4.5 to 10 parts by weight of sulfur, preferably 5 to 7 parts by weight, and cobalt organic acid (cobalt element derivative) 0.005 to 0 parts by weight. 0.8 parts by weight, preferably 0.01
0.2 to 0.5 parts by weight of a meta-cresol resin containing 80% by weight or more, preferably 90% by weight or more of meta-cresol
10 to 10 parts by weight, preferably 2 to 5 parts by weight. These blending can be carried out in a conventional manner.

The carbon black used in the rubber composition according to the present invention is not particularly limited, but is preferably HAF.
Smaller grains are preferred for elongation at break. If the amount of carbon black is too small, the hardness is lowered, which is not preferable. On the other hand, if the amount is too large, heat generation is increased, which is not preferable.

When the meta-cresol content of the meta-cresol resin used in the rubber composition according to the present invention is less than 80% by weight, the effect of increasing the elongation at break is small, so that it is not preferable. On the other hand, if the amount of the cresol resin is too small, the effect of increasing the elongation at break is similarly small, so that it is not preferable.

If the amount of the organic acid cobalt used in the rubber composition according to the present invention is too small, the vulcanization is delayed, which is not preferable. On the contrary, if the amount is too large, the elongation at break is undesirably low.

In the rubber composition according to the present invention, in addition to the above essential components, any compounding agent usually used in the rubber industry,
For example, a softener, an anti-aging agent, a vulcanization accelerator, a filler, a plasticizer, and the like can be appropriately compounded within a usual range of the compounding amount as needed.

The method for producing a pneumatic tire using the rubber composition according to the present invention is not different from the conventional method and can be carried out as before.

[0016]

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

Standard Example 1, Examples 1 to 6 and Comparative Examples 1 to 2 Using a 1.7 liter closed Banbury mixer,
The vulcanization accelerator and the components excluding sulfur in the composition (parts by weight) shown in Table I were mixed at 150 ° C. for 4.5 minutes, and then the vulcanization accelerator and sulfur were mixed with an open roll to obtain a vulcanization sheet sample. I got

Initial material properties using the obtained sample,
Material properties and tire properties (tire: 11R22.5) after aging at 80 ° C. for 96 hours were measured by the following methods. The results are shown in Table I.

Hardness: JIS hardness A6301 tan δ (20 ° C.): using a viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd. 20 Hz 10 ± 2% Tensile strength, elongation at break, 100% and 300% modulus: Measured at 50 mm / min according to JIS A6301

Tire running distance: Load 14 in drum test
Distance to destruction at 0%, speed 70km / h

[0021]

[Table 1]

[0022]

[Table 2]

As is clear from the results in Table I, in Examples 1 to 6 of the present invention, tan δ (20 ° C.), elongation at break, elongation at break after 96 hours at 80 ° C., and tire running distance were all good. Tan δ (20)
C), elongation at break, and elongation at break at 80 ° C. for 96 hours were also low, and the tire running distance was also short. In Comparative Example 1, tan δ (20 ° C.), elongation at break, and elongation at break at 80 ° C. for 96 hours were all low, and the tire running distance was short. In Comparative Example 2, the hardness was high, the tensile strength was low, the breaking elongation at 80 ° C. for 96 hours was low, and the tire running distance was short.

[0024]

As described above, according to the present invention, in a pneumatic tire in which a breaker is constituted by a steel cord, a spacer rubber between steel belts in a steel belt portion of the breaker and / or a protective rubber surrounding a terminal portion. By using a rubber composition to which meta-cresol resin is added as the initial and after aging physical properties,
In particular, the breaking elongation can be increased, and the durability can be improved.

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Claims (1)

[Claims] In a pneumatic tire in which a breaker is made of a steel cord, natural rubber or natural rubber 100 is used.
50 to 90 parts by weight of carbon black, 4.5 to 10 parts by weight of sulfur, based on 100 parts by weight of raw rubber obtained by blending 20 parts by weight or less of a diene rubber other than natural rubber in parts by weight.
A rubber composition comprising 0.01 to 0.8 parts by weight of an organic acid cobalt (in terms of cobalt element) and 0.2 to 10 parts by weight of a meta-cresol resin containing 80% by weight or more of meta-cresol is used as a steel belt part of a breaker. The tire used as a spacer rubber between steel belts and / or a protective rubber surrounding a terminal portion in the above.