JPH08113006A - Pneumatic tire - Google Patents

Abstract

PURPOSE: To provide the pneumatic tire for a heavy load by which a cracking by heat curing is not caused and air and water permeability becomes small and a carcass cord is not corroded. CONSTITUTION: In the pneumatic tire having at least a single layer carcass locked around a pair of left and right bead cores by folding back both ends from its inside to the outside and an inner liner composed of a rubber composition on the radial directional inside of the carcass, a rubber component constituting the inner liner is composed of butyl rubber, and contains butyl rubber halide in a range of 60 to 95wt.%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pneumatic tire. More specifically, the present invention relates to a heavy duty pneumatic tire having an inner liner capable of sufficiently blocking air and moisture without cracking due to high internal pressure and heat generated during running.

[0002]

2. Description of the Related Art Conventionally, steel cords have been mainly used for carcass cords of heavy duty pneumatic tires because of their high strength. The carcass cord made of this steel cord is corroded by air or moisture, and is likely to cause breakage of the cord or breakage of adhesion between the cord and rubber. For this reason, butyl rubber, into which air and water are less likely to permeate, is used as a main component in the inner liner of a heavy duty pneumatic tire.

Further, a natural rubber type rubber composition is preferably used for the rubber composition of the tread portion, the carcass and the like in order to reduce heat generation due to the use of heavy load. In consideration of co-vulcanizability between a carcass containing a natural rubber-based rubber composition and an inner liner made of butyl rubber in a tire manufacturing process, halogenated butyl rubber is widely used for the inner liner.

However, the inner liner made of only halogenated butyl rubber is liable to be thermally cured by oxygen in the air and heat generated by the tire during running, and the inner liner is cracked due to pressure applied by bending of the tire during running. Is likely to occur. When the inner liner crack reaches the central portion of the carcass, as described above, the carcass cord is corroded, which may lead to breakage of the carcass cord or separation due to adhesive failure between the carcass cord and rubber.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present inventors
In view of the above-mentioned prior art, even if the tire is heated to a high temperature during traveling, there is no cracking due to thermosetting, and the permeability of air and moisture is small, and the heavy load does not cause corrosion on the carcass cord. As a result of intensive research to develop a pneumatic tire, surprisingly, when an inner liner made of butyl rubber in which halogenated butyl rubber and normal butyl rubber were mixed in a specific mixing ratio was used, the above-mentioned physical properties were For the first time, it was found that a tire equipped with all of the above was obtained, and the present invention was completed.

[0006]

That is, according to the present invention, there is provided at least one layer of a carcass around which a pair of left and right bead cores are folded back and locked at both ends from inside to outside.
A pneumatic tire having an inner liner made of a rubber composition on the inner side in the radial direction of the carcass, wherein a rubber component constituting the inner liner is made of butyl rubber,
The present invention also relates to a pneumatic tire characterized by containing halogenated butyl rubber in the range of 60 to 95% by weight.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the pneumatic tire of the present invention comprises a carcass of at least one layer which is locked around a pair of left and right bead cores by folding back both ends from the inside to the outside. A pneumatic tire having an inner liner made of a rubber composition on the inner side of a carcass in a radial direction, wherein a rubber component constituting the inner liner is made of butyl rubber, and a halogenated butyl rubber is contained in an amount of 60 to 95% (% by weight, hereinafter the same. ) Is included in the range.

Since the halogenated butyl rubber contains halogen as a constituent element, it tends to be easily thermoset when heated to a high temperature. This characteristic is more remarkable as the halogen content is higher. The halogen content in one molecule is preferably 5.0% or less, preferably 3.0% or less, and more preferably 2.5% or less in order to make it hard to be thermoset when heated to a high temperature. From the viewpoint of co-vulcanization with the composition, it is preferably 0.5% or more, more preferably 1.0% or more.

Examples of the halogenated butyl rubber include chlorinated butyl rubber and brominated butyl rubber. Among them, brominated butyl rubber is preferably used because it is excellent in covulcanization.

As the butyl rubber to be halogenated, butyl rubber which is usually used for automobile tires (hereinafter,
Regular butyl rubber) is used. The regular butyl rubber is an isobutylene-isoprene copolymer, and isoprene having an unsaturation degree of usually 0.6-
It contains about 4.2 mol%.

As the butyl rubber used together with the halogenated butyl rubber, the above-mentioned regular butyl rubber is used.

In the present invention, the inner liner rubber composition contains 60 to 60 parts of halogenated butyl rubber in its rubber component.
95%, preferably 70-90%, regular butyl rubber 5
-40%, preferably 10-30%.

The content of such halogenated butyl rubber is
When it is less than 60% in the rubber component, the co-vulcanization characteristics with the carcass rubber composition tend to be deteriorated, and when it exceeds 95%, inner liner cracks are likely to occur. Tend.

The inner liner rubber composition used in the present invention is obtained by heating and kneading a predetermined amount of halogenated butyl rubber and regular butyl rubber as rubber components by a conventional method so as to have a constant composition, and molding. The rubber composition is a component used for a normal inner liner, for example, a component for improving the reinforcing property of rubber such as carbon black; for example, a process oil for improving processability and a component as a vulcanization aid; A retarder that acts as a vulcanization retarder on butyl rubber such as magnesium oxide and mercaptobenzothiazyl disulfide (hereinafter referred to as MBTS) to prevent rubber burning; a vulcanization accelerator such as zinc white; a vulcanization agent such as sulfur May be appropriately mixed.

Next, the pneumatic tire of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view in the width direction of a heavy-duty pneumatic tire of size 11R 24.5 according to the present invention.

The tire 10 has a tread portion 3, a sidewall portion 6 extending from both ends thereof in the lateral direction of the tire, and a bead portion 5 located at the radially inner end portion of the sidewall portion 6. Both ends of the carcass 2 are folded back around the pair of left and right bead cores 1 from the inner side to the outer side in the axial direction, and are locked in the bead portion 5. In this example, the carcass 2 is composed of one steel cord layer arranged in parallel with the tire circumferential direction at an angle of approximately 90 degrees, but the carcass 2 may be composed of two or more layers if necessary.
A reinforcing layer 8 is provided on the axially outer side of the carcass cord winding portion, and a bead apex 9 is placed on the radially outer side of the bead core 1. Radially inside the tread 3,
A belt layer 4 made of steel cord is placed on the outer side of the carcass 2 in the radial direction. The belt layer 4 is composed of two or more cord layers intersecting at a relatively small angle. Carcass 2
An inner liner 7 is provided on the inner side in the radial direction of, and the inner liner 7 is blended with a rubber component containing 60 to 95% of halogenated butyl rubber and 5 to 40% of regular butyl rubber as described above, and if necessary, other components. It consists of ingredients.

Next, the pneumatic tire of the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Examples 1 to 5 and Comparative Examples 1 to 4 Halogenated butyl rubber (Bromobutyl 2255: manufactured by Exxon Chemical Co., Ltd., trade name) and butyl rubber (butyl 265: Exxon Chemical Co., Ltd.) were used in the amounts shown in Table 1. Product name), carbon black (Niteron 55S, Nippon Steel Chemical Co., Ltd. product name), process oil, stearic acid, magnesium oxide and MBTS, and then add zinc white and sulfur to the mixture. Knead and test piece (vertical: 55m
m, width: 55 mm, thickness: 4 mm) was produced.

As the physical properties of the obtained test piece, a rheometer test was conducted to (a) scorch time T _{L + 2} ,
(B) Measure 90% vulcanization time and (c) maximum torque,
The vulcanized physical properties (hardness and dematcher cut gloss) and adhesion to the carcass were examined. The methods for measuring these physical properties are shown below. The results are also shown in Table 1.

Scorch time T in rheometer test
The values of _{L + 2} , 90% vulcanization time and maximum torque were measured using Monsanto R-100 at a measurement temperature of 150 ° C. Dematcher cut gloss, which is one of the vulcanized properties, has a surface strain of 60% and a crack with a width of 2 mm on the surface of the test piece, and it is bent using a DeMatcha fatigue tester. At normal condition and 110 ℃
It was examined in an aged state by heating for 150 hours. In addition, the adhesiveness to the carcass is 30 kg / cm ^{2 when the} rubber composition for adhering the steel cord and the test piece are bonded together.
JIS K 6301 by pressure-bonding vulcanization at a temperature of 150 ° C for 6 minutes
It was tested by the method based on.

[0022]

[Table 1]

From the results shown in Table 1, in the case of the test piece obtained in Comparative Example 1 in which the content of regular butyl rubber in the butyl rubber was higher than that of the test piece obtained in the present invention, the carcass was small in aging, although the aging was small. The adhesiveness with is much inferior to that obtained in Examples 1 to 5,
On the other hand, in the case of the test piece obtained in Comparative Example 2 in which the butyl rubber does not contain any regular butyl rubber, although the adhesion to the carcass is good, it can be seen that the aging is worse than that of the test piece of the present invention. .

Example 6 and Comparative Example 5 In Example 6, the rubber composition used in Example 3 was applied to the inner liner, and in Comparative Example 5, the rubber composition used in Comparative Example 2 was applied to the inner liner. Size with 1 structure
An 11R 24.5 tire was produced. Internal pressure of this tire is 8.0
kg / cm ^2, load 6200Kg, was run for 600 hours at a speed 20 km / hr, it was examined the change in the inner liner hardness in the traveling back and forth.

In addition, a crack with a depth of 1 mm and a length of 1 mm was previously put in the buttress portion of the inner liner before running, and the amount of crack growth (m
m) was measured. The results are also shown in Table 2.

[0026]

[Table 2]

From the results shown in Table 2, it can be seen that the tire obtained in Example 6 is suitable for practical use because even if a crack occurs in the buttress portion, the crack does not grow.

[0028]

EFFECTS OF THE INVENTION The pneumatic tire of the present invention does not cause cracks due to thermosetting even when it is heated to a high temperature during running, has low air and moisture permeability, and corrodes carcass cords. Since it is not likely to occur, it can be suitably used as a tire for a heavy load truck, for example.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in the width direction of a pneumatic tire of the present invention.

[Explanation of symbols]

 7 Inner Liner

Claims (1)

[Claims] 1. A carcass having at least one layer, in which both ends are folded back from the inside to the outside around a pair of left and right bead cores, and an inner liner made of a rubber composition is provided radially inside the carcass. A pneumatic tire comprising a butyl rubber as a rubber component constituting the inner liner and containing a halogenated butyl rubber in an amount of 60 to 95% by weight.