JPS5920708A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve the resistibility for dynamic fatigue and weatherability of a large tire for bus, etc. by such an arrangement wherein a specially mixed sheet is arranged to cover the surface of the tire from its shoulder part to the sidewall in the peripheral direction of the tire. CONSTITUTION:A composite rubber sheet 3 composed by such an arrangement wherein 20-60wt. parts of natural rubber, 10-50wt. parts of polybutadiene rubber, 10-50wt. parts of halogenation butylrubber and 5-30wt. parts of copolymer rubber of ethylene propylene diene are properly mixed so that a total of 100wt. parts can be obtained is arranged to cover the surface of a tire from its shoulder C to its sidewall B in the peripheral direction of the tire. In this case, the thickness of the sheet shall be approx. 0.5-5mm.. The resistibility for dynamic fatigue and weatherability of the tire can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire, and more specifically, by improving the structure and composition of the pneumatic tire extending along the tire surface from part of the shoulder to above the sidewall part,
In particular, the present invention relates to a pneumatic tire that can improve the dynamic fatigue resistance, weather resistance, etc. of large tires such as those for trucks and buses.

As shown in Fig. 1, the conventional radial cross-sectional structure of large tires for trucks, buses, etc. is such that the rubber 1 of the cap trend part A covers the rubber 2 of the sidewall part B near the shoulder part C. The so-called cap made up of.

As shown in Fig. 2, the rubber 2 of the sidewall part B is attached to the tread side edge a of the tire.
There are tires with so-called side, over, and cap structures that extend close to the .

However, in a tire, the part extending from the shoulder part C to the upper part of the sidewall part B is the part most severely subjected to repeated bending accompanied by repeated compressive deformation during driving, and is also the part affected by sunlight, so the bending fatigue resistance is poor. sex.

Weather resistance: 9, etc. (It is desirable that an excellent rubber composition is used.

However, the portion extending from the shoulder portion C to the upper side of the sidewall portion B is actually constituted by the rubber 1 of the cap tread portion A or the rubber 2 of the sidewall portion B (as described above).

In the first place, the rubber 1 of the cap tread portion A uses a composition that emphasizes the function of the cap tread, that is, wear resistance and cut chip resistance. In order to provide the necessary functions to the shoulder part C, that is, bending fatigue resistance and weather resistance, for example, a large amount of para-phenylenediamine anti-aging agent must be added, resulting in high costs. There is. The rubber 2 of the sidewall portion B is also made of a rubber composition suitable for the elongation deformation that the sidewall portion B undergoes, and this rubber 2 is blended with a component suitable for the compression deformation that the shoulder portion C is subjected to. It is technically difficult to impart bending fatigue resistance and weather resistance in terms of rubber compounding, and there are also problems in terms of economic efficiency and the like.

The present invention was developed as a result of studies to solve the above-mentioned problems.
It was guided.

Therefore, an object of the present invention is to improve the dynamic fatigue resistance, weather resistance, etc. of large tires such as those for trucks and buses in particular by devising the structure and composition extending along the tire surface from the shoulder part to the upper part of the sidewall part. An object of the present invention is to provide an excellent pneumatic tire that can sufficiently maintain the air quality until the end of the tire's running life.

That is, in the present invention, a sheet is arranged in the circumferential direction of the tire so as to cover the surface of the tire from a shoulder part to a sidewall part, and this sheet is made of 20 to 60 parts by weight of natural comb and 10 to 50 parts by weight of polybutadiene rubber. , 10 to 50 weight of halogenated butyl rubber! and/or 5 to 30 parts by weight of ethylene, propylene, diene copolymer rubber, the total of which is 1
The gist of the present invention is a pneumatic tire characterized in that it is made of a rubber composition blended to have an amount of 0.00 parts by weight.

Hereinafter, the present invention will be explained in detail by way of examples with reference to the drawings.

FIG. 3 is a radial half-sectional view showing a pneumatic tire according to an embodiment of the present invention.

The pneumatic tire according to the embodiment of the present invention includes a pair of left and right bead portions, a pair of left and right sidewall portions B connected to the bead portions, and a shoulder portion C between the sidewall portions B. Camp tread section A arranged through
A carcass 6 is mounted between the bead wires 5 provided at each bead portion, and a play car 4 is mounted on the carcass 6 in the camp tread portion A.
is located.

In the present invention, the shoulder portion.

A sheet 3 is arranged in the circumferential direction of the tire to cover the surface of the tire from C to above the sidewall part B, and this sheet 6 is made of 20 to 60 parts by weight of natural rubber, 10 to 50 parts of polybutadiene rubber, and halogen. The rubber composition is composed of 10 to 5 parts by weight of butyl rubber and/or 5 to 30 parts by weight of ethylene, propylene, and diene copolymer rubber so that the total amount is 100 parts by weight.

In the drawings, reference numeral 1 indicates rubber constituting the gap tread portion A, and reference numeral 2 indicates rubber constituting the sidewall portion B.

Here, the rubber composition constituting the sheet 6 described above, its shape including its wall thickness, and its arrangement method will be explained.

First, as mentioned above, the amount of natural rubber (NR) in the total 100 parts by weight of the rubber composition constituting the sheet 6 is preferably 20 to 60 parts by weight. If it is less than 20 parts by weight, the tensile strength and tear strength of the sheet 6 will be extremely reduced, and if it exceeds 60 parts by weight, polybutadiene rubber (BR), halogenated butyl rubber (e.g. Eva Ct- This is because the blending amount of IIR) and/or ethylene, propylene, diene copolymer rubber ('EPDM) decreases, resulting in a decrease in flex fatigue resistance and weather resistance.

Next, go for polybutadiene rubber (BR)! 4 [anastomosis needle 1
It is preferably 10 to 50 parts by weight out of 00 parts by weight. This is because if it is less than 10 parts by weight, the bending fatigue resistance, which is a characteristic of polybutadiene rubber, will decrease, and if it exceeds 50 parts by weight, the tensile strength and tear strength will decrease.

Matahalogenated butyl rubber (Ct-IIR) It is preferable to use 10 to 50 parts by weight in 100 parts by weight of the rubber composition. This 6
If it is less than 10 parts by weight, weather resistance and oxidative deterioration resistance decrease,
This is because if the amount exceeds 50 parts by weight, the tensile strength and tear strength will decrease rapidly.

In addition, ethylene, propylene, diene copolymer rubber (E
PDM) is 5 to 30 parts by weight of the total 100 parts by weight of the rubber composition.
Weight parts are good. If the amount is less than 5 parts by weight, the weather resistance, ozone resistance, and heat resistance effects that are the characteristics of ethylene, propylene, and diene copolymer rubber will not be exhibited.
This is because if it exceeds, the compatibility with the diene rubber will be poor, resulting in a decrease in dynamic fatigue properties, making it unsuitable.

Other compounding agents other than the above-mentioned rubber composition, such as softeners,
Antiaging agents, vulcanization accelerators, sulfur, etc. can be blended according to conventional methods, but carbon black is preferably blended in 40 to 70 parts by weight, preferably 45 to 65 parts by weight, per 100 parts by weight of the elastomer. good. This is because the sheet 6 undergoes bending fatigue deformation, so if the carbon black exceeds 70 parts by weight, the bending fatigue properties will be significantly lowered, and if it is less than 40 parts by weight, the elastic modulus will drop, making it impractical.

Moreover, the shape of the sheet 6 may be a sheet shape, or a profile shape may be used. Furthermore, the maximum thickness is 0.5
~5 pits are sufficient. If it is less than 0.5τ, the effects of bending fatigue resistance and weather resistance will decrease, and if it is more than 5τ, the rubber composition of the present invention will have poor abrasion resistance and will be prone to shoulder wear, causing uneven wear. This is because it is inappropriate. Further, the width is preferably such that it extends from near the ground contact end of the upper part of the shoulder part C to cover the joint between the trend rubber 1 and the sidewall rubber 2.

The sheet 6 may be placed in any manner as long as it is placed in the above-mentioned position, but it is preferable to attach the sheet 6 while the tire is unvulcanized. After vulcanization, the rubber/rubber with tread rubber 1 or sidewall rubber 2 [
This is because 1 tends to cause problems.

Note that the halogenated butyl rubber used in the present invention may be chlorinated butyl rubber or brominated butyl rubber.

Below, the relationship between the formulation of each example and comparative example and its physical properties is explained in the first section.
This will be explained using a table.

Table 1 shows combinations of NR, BR, ct-xxR (chlorinated butyl rubber), and EPDM, as well as zinc oxide, stearic acid, extender oil, anti-aging agent, and wax.

The physical property test results of each rubber composition containing an accelerator and sulfur are shown.

In Table 1, Examples 1 to 5 are in accordance with the present invention, and Comparative Examples 1 to 4 are for comparison. Comparative example 1 is NR
and BR blend rubber composition In, and Comparative Example 2 is a rubber composition in which Comparative Example 1 is blended with a large amount of anti-aging agent. Comparative Example 3 is a rubber composition of NR, BR, and C6-IIR blend, and is a rubber composition containing a large amount of natural rubber (65 parts by weight). Similarly, Comparative Example 4 contains a large amount of natural rubber and B.
This is a comparative example of a rubber composition combining R and EPDM.

These results show that when a large amount of anti-aging agent is added, ozone resistance is significantly improved, but the effect of improving bending fatigue resistance is small (Comparative Examples 1 and 2). Moreover, the effect of blending C7-IIR is clearly to significantly improve ozone resistance and to improve bending fatigue resistance (Examples 1 to 3). However, even if C6-IIR is blended, if the blended amount of NR increases, BR and C4-IIR
Since the blending amount of this resin decreases, the effect of improving bending fatigue resistance and ozone resistance decreases (Example 2, Comparative Example 3).

Furthermore, in the rubber compositions blended with EPDM (Comparative Example 4, Examples 4 to 6), it is found that the flex fatigue resistance and ozone resistance are significantly improved by blending NR, BR, and EPDM. Furthermore, NR, BR, and C1-I IR
A rubber composition blended with K EPDM has a slightly lower bending fatigue resistance, but good results in ozone resistance can be obtained.

From the above, natural rubber is NR and BR at 60 parts by weight or less.
, C1-I IR tripartite blend, NR, IIIR, .
Three friends of EPDM i, and Hi NR, BR, Ct-
A rubber composition made of a four-way blend of IIR, ', and EPDM has better flex fatigue resistance, ozone resistance, etc. than a rubber composition made by blending a large amount of an antiaging agent with 100 parts by weight of an elastomer that is a blend of NR and BR. It is clear that all the characteristics can be satisfied.

(Leaving space below) Next, Table 2 shows comparative example 2 of Table 1 regarding the structure in which the sheet 6 shown in FIG. 3 is arranged. Comparative Example 4, Example 2. Example 5. Tires were prepared in which each of the comb compositions of Example 6 was arranged on sheet 6, and the results of actual vehicle running evaluation and drum evaluation (ozone irradiation) are shown. From these results, it was found that tires in which the comb composition of the present invention was disposed on the sheet 6 obtained better results in both actual vehicle running evaluation and ozone irradiation drum evaluation than those with conventional rubber compositions.

(Leaving space below unfaithfulness) In Tables 1 and 2, the evaluation of the occurrence of ozone cracks is based on JIS K6301.

Further, the judgment results shown in the upper part of Table 2 are evaluations from a part of the shoulder to the entire upper part of the sidewall, and the judgment results shown in the lower part are evaluations of the degree of occurrence of wrinkles or cracks in areas where compressive strain is concentrated.

As described above, in the present invention, a sheet is arranged in the tire circumferential direction so as to cover the surface of the tire from a part of the shoulder to a sidewall part, and this sheet is made of natural rubber of 20 to 60%.
A rubber composition containing 10 to 50 parts by weight of polybutadiene rubber, 10 to 5 omi parts of halogenated butyl rubber, and/or 5 to 30 parts by weight of ethylene, propylene, and diene copolymer rubber for a total of 100 parts by weight. Since the tire is made of a material, it is possible to sufficiently maintain the dynamic fatigue resistance, weather resistance, etc. of not only passenger car tires but especially large tires such as those for trunks and buses until the end of the tire's running life.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory radial half-sectional views showing a conventional pneumatic tire, respectively, and FIG. 3 is an explanatory radial half-sectional view showing a pneumatic tire according to an embodiment of the present invention. A...Cap tread part, B...Side wall part,
C... Shoulder part, D... Bead part, 1-Rubber of cap tread part, 2... Rubber of sidewall part, 6
... Sheet, 4. Play car, 5. Bead wire, 6. Carcass. Agent: Patent Attorney Makoto Ogawa − Patent Attorney: Ken Noguchi Patent Attorney: Kazuhiko Saishita

Claims (1)

[Claims] A sheet is arranged in the circumferential direction of the tire to cover the surface of the tire from the shoulder part to the sidewall part, and this sheet is made of 20 to 60 parts by weight of natural rubber, 10 to 50 parts by weight of polybutadiene rubber, and 10 parts by weight of halogenated butyl rubber. ~50
1. A pneumatic tire comprising a rubber composition containing 5 to 30 parts by weight of ethylene, propylene, and diene copolymer rubber in a total of 100 parts by weight.