JPH04108008A - Pneumatic tire having three layered sidewall structure - Google Patents

Abstract

PURPOSE:To improve ozone-proof ability without spoiling its external appearance by arranging a rubber constituent, in which a mixing volume of paraffin wax is increased in order of the outermost layer, the middle layer and the inner most layer, as a sidewall for covering a carcass. CONSTITUTION:A sidewall for covering a carcass 5 of a pneumatic tire is constituted in a three layered structure consisting of the innermost layer 2c adjacent to the carcass 5, the middle layer 2b arranged outside of it and the outermost layer 2a arranged outside further of it. A rubber constituent, in which a mixing volume of paraffin wax is increased in order of the outermost layer 2a, the middle layer 2b and the innermost layer 2c, is arranged as the sidewall. Furthermore, the rubber constituent of the outermost layer 2a is obtained by mixing less than 3 weight part of the paraffin wax against 100 weight part of rubber component, and also the ratios of the mixing volumes (unit weight part) of the paraffin wax into the outermost layer 2a, the middle layer 2b and the innermost layer 2c are set in such a way that the outermost layer 2a is below 0.8 and the innermost layer 2c is 1.2-3.0, assuming that the ratio of the middle layer 2b is set as 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pneumatic tire whose static ozone resistance has been improved over a long period of time without impairing the aesthetic appearance of the sidewall.

(Prior Art) Generally, rubber cracks when exposed to the atmosphere or sunlight, and the cracks become particularly noticeable when tensile stress is applied. In order to prevent this cracking, it has been known to use amine-based anti-aging agents and wax-based anti-aging agents. The former prevents aging under static and dynamic conditions by selectively chemically reacting with ozone and consuming ozone in the rubber surface layer, while the latter, when blended with rubber, oozes out to the surface and forms a thin film. This thin film prevents contact between rubber and ozone, thereby exerting an anti-aging effect, and is said to be particularly effective in preventing aging under static conditions, but generally both are used together. .

Various wax-based rubber anti-aging agents have been commercially available for a long time, but the effect of oozing out and forming a thin film depending on the temperature and the phenomenon of peeling and falling off of the thin film once formed are different, so in order to improve this, carbon Drugs with carbon numbers distributed over a wide range of numbers 16 to 41 (U.S. Patent No. 3,423,34
8), or agents containing 25 to 70% of linear hydrocarbons having 26 to 29 carbon atoms, and 30 to 75% of linear hydrocarbons having 34 to 40 carbon atoms (Japanese Patent Publication No. 1973-
25062) etc. have been proposed.

On the other hand, the sidewall has a two-layer structure, and the outer layer is provided with a rubber composition having a rubber component of 30 to 60% by weight of low unsaturation rubber and 70 to 40% by weight of high unsaturation rubber. A technique for improving ozone resistance by the effect of a good low unsaturation rubber is known (Japanese Patent Laid-Open No. 1-278805). This improves the ozone resistance of the rubber itself, and does not reduce or remove waxes.

On the other hand, in a similar two-layered wall structure,
Techniques are also known in which the anti-aging effect is maintained over a long period of time by changing the type and amount of anti-aging agent between the outer layer and the inner layer (JP-A-63112635, JP-A-63).
-112636).

(Problem B to be Solved by the Invention) The object of the present invention is to create a two-layer sidewall structure under a hitherto unknown compounding system by changing the type and amount of waxes in the outer layer and inner layer. It is an object of the present invention to provide a technology that exhibits ozone resistance even better than conventional technology and does not impair the aesthetic appearance of the sidewall.

(Means for Solving the Problems) In order to achieve the above object, the pneumatic tire of the present invention has a sidewall that covers a carcass, an innermost layer adjacent to the carcass, and an intermediate layer disposed outside of the innermost layer. A rubber composition having a triple structure consisting of a layer and an outermost layer disposed outside the sidewall, and in which the amount of petroleum paraffin wax is increased in the order of the outermost layer, middle layer, and innermost layer as the sidewall. It is characterized by being provided with.

The above petroleum paraffin wax is called petroleum microcrystalline wax, and -g contains so-called normal paraffin, which is a linear saturated hydrocarbon, and isoparaffin (branched saturated hydrocarbon) and naphthene (alicyclic hydrocarbon) as non-normal paraffin. hydrocarbons) and a small amount of aromatic hydrocarbons.

In the present invention, the rubber composition of the outermost layer contains petroleum paraffin wax in an amount of 3 parts by weight or less based on 100 parts by weight of the rubber component, and the outermost layer, the intermediate layer, and the innermost layer contain petroleum paraffin wax. The ratio of wax content (unit weight parts) is 1 for the middle layer, 0 for the outermost layer,
It is preferable that the innermost layer is 1.2 to 3.0.

As the rubber component of the rubber composition according to the present invention, in addition to diene rubber, ethylene-propylene-diene terpolymer rubber, halogenated butyl rubber, butyl rubber, etc. are used, and diene rubber and these non-diene rubbers are used. It may be a blend with.

Diene rubbers include natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-phtadiene copolymer rubber, isoprene-butadiene copolymer rubber, styrene-isoprene copolymer rubber, or styrene-butadiene-isoprene rubber. A rubber polymer made by polymerizing a conjugated diene such as a copolymer rubber as one of the main monomer components. In the present invention, these rubbers may be used alone or as a blend.

(Function) In order to maintain the ozone resistance of sidewall rubber in pneumatic tires that are used for a long period of time, it is essential that the ozone resistance chemicals in the sidewall rubber have a sustained effect.

However, if such chemicals are mixed into a single layer of sidewall rubber, wax may migrate to the carcass ply rubber layer that is in contact with the sidewall rubber, and the side rubber surface that requires wax bloom may initially have no problems. , after a long period of time only an insufficient wax bloom film is obtained. Furthermore, in this case, if a large amount of wax is blended into the sidewall rubber, it will often bloom and impair the appearance.

Based on this recognition, the present invention creates a concentration gradient in the amount of wax blended in the sidewall rubber layer, so that a wax bloom film is always generated on the sidewall rubber surface layer even after a long period of time. This makes it possible to prevent the occurrence of ozone crank.

In other words, the sidewall has a three-layer structure, and the amount of wax is increased in the order of the outermost layer, the middle layer, and the innermost layer, so that a sufficient wax bloom film is generated on the sidewall surface from the initial stage over a long period of time, resulting in ozone resistance. This has been designed to allow for sufficient improvement.

The pneumatic tire of the present invention is not limited to tires for passenger cars, but can also be applied to tires for heavy loads such as tires for truck buses, tires for construction vehicles, tires for aircraft, etc. It is not limited to species.

(Example) Next, the present invention will be explained by examples.

~- A radial tire for passenger cars of size 185/70-13 having a three-layer sidewall structure (Fig. We made five types of prototypes.

In Figure 1, 1 is the tread, 2-a is the outermost layer of the sidewall, 2-b is the middle layer of the sidewall, 2-C is the innermost layer of the sidewall, 3 is the bead core, 4 is the inner liner, and 5 is the carcass ply. Show each.

Both have a thickness of 0.5 as the outermost sidewall layer 2-a.
wm unvulcanized rubber sheet, sidewall intermediate layer 2-
As b, an unvulcanized rubber sheet of 1.25 mm was sequentially coated on the outside of the sidewall inner layer 2-c and then vulcanized.

After filling these five types of test tires with internal pressure, we visually evaluated their appearance after being left outdoors for 10 days, and visually observed the occurrence of ozone cranks after being left outside for 30 days and 1 year. It was evaluated.

11-Table 2 Table 1...Ethylene-propylene-diene terpolymer/
Butyl rubber bromide...manufactured by Monsanto Company, USA, product name: Santofresox 13-3...manufactured by Jumin Chemical ■, product name: Niccinol CZComparative Example 1 The above evaluations are shown in Table 2
, 2 and Examples 1 to 3, the following was confirmed.

That is, although the amount of plume was somewhat large in the tires of Comparative Example 2 and Example 2, there was no particular problem in terms of appearance. Also,
In Comparative Example 1, Example 1, and Example 3, there was no whitening phenomenon due to excessive plume on the sidewall surface.
The appearance was good.

Regarding the ozone resistance after being left for 30 days, the tires of Comparative Example 1 and Comparative Example 2 had a relatively large rack and had a somewhat poor appearance. In contrast, in the tire of Example 1, only a few small racks were observed. Further, in the tires of Example 2 and Example 3, no crank was observed and the results were extremely good.

Next, regarding ozone resistance after being left for one year, Comparative Example 1,
The tire of Comparative Example 2 had significant ozone cranking and had a poor appearance. In contrast, in the tires of Examples 1 and 2, only small racks were observed here and there. Further, the tire of Example 3 had no cracks at all and was extremely good.

(Effects of the Invention) As explained above, in the pneumatic tire having the three-layer sidewall structure of the present invention, by creating a concentration gradient in the amount of wax in the sidewall rubber layer, it is possible to maintain the appearance without impairing the appearance. It was possible to improve ozone resistance.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a pneumatic tire as an example of the present invention. 1... Tread 2-a... Sidewall outermost layer 2-b... Sidewall intermediate layer 2-c... Sidewall innermost layer 3... Bead core 4... Inner liner 5... carcass ply

Claims (1)

[Claims] 1. The sidewall covering the carcass includes an innermost layer adjacent to the carcass, and an intermediate layer disposed outside the innermost layer;
Furthermore, it constitutes a triple structure with an outermost layer disposed on the outside, and a rubber composition containing a larger amount of petroleum paraffin wax is disposed as the sidewall in the order of outermost layer, middle layer, and innermost layer. A pneumatic tire with a three-layer sidewall structure. 2. The rubber composition of the outermost layer contains petroleum paraffin wax in an amount of 3 parts by weight or less per 100 parts by weight of the rubber component, and the amount of petroleum paraffin wax blended in the outermost layer, the intermediate layer, and the innermost layer. 2. The pneumatic tire according to claim 1, wherein the ratio of (unit weight part) is 0.8 or less for the outermost layer and 1.2 to 3.0 for the innermost layer when the intermediate layer is 1.