JP2002127719A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which is capable of reducing its mass while securing its run-flat durability sufficiently. SOLUTION: In a pneumatic tire provided with the run-flat driving performance provided with a rubber reinforcing layer 7 of a crescent-shape cross section in a sidewall part 3, the rubber reinforcing layer 7 of crescent-shape cross section is compounded of gas-filled thermoplastic resin particles of 5-300 μm in particle diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic tire having run-flat running performance, and more particularly, to a pneumatic tire having run-flat running performance.
The present invention relates to a pneumatic tire designed to reduce mass while ensuring sufficient run flat durability.

[0002]

2. Description of the Related Art Conventionally, as a pneumatic tire having run-flat running performance, a rubber reinforcing layer having a crescent cross section is provided on a side wall portion, and longitudinal deformation of the tire at the time of puncturing is suppressed based on the rigidity of the rubber reinforcing layer. In addition, there has been proposed a structure in which the destruction of the tire case structure is prevented.

The maximum thickness of the crescent rubber reinforcing layer is usually about 7 to 15 mm, which is accompanied by a large increase in mass as compared with a general tire. Moreover, the rubber reinforcing layer causes an increase in rolling resistance and a high heat storage property, so that the sidewall portion easily generates heat during run flat running. When the side wall portion generates excessive heat in this way, the modulus of the carcass layer decreases, and run-flat running becomes difficult.

[0004] In order to ensure run-flat running performance, it is important to suppress bending deformation of the sidewall portion, and for that purpose, it is important to ensure the thickness of the crescent-shaped rubber reinforcing layer. Therefore, it is necessary to lower the specific gravity to reduce the mass while maintaining the volume of the rubber reinforcing layer. It has been proposed to use foamed rubber as one of the means. However, in order to achieve a sufficient weight reduction, it is necessary to increase the foaming ratio. If the foaming ratio is increased, there is a problem that the rigidity of the rubber reinforcing layer is significantly reduced, and the reinforcing effect as a run flat tire is reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire capable of reducing mass while ensuring sufficient run flat durability.

[0006]

According to the present invention, there is provided a pneumatic tire having a run-flat running performance in which a rubber reinforcing layer having a crescent cross section is provided on a sidewall portion. It is characterized in that gas-encapsulated thermoplastic resin particles having a particle size of 5 to 300 μm are compounded in a rubber reinforcing layer having a crescent cross section.

[0007] By blending the gas-filled thermoplastic resin particles in the rubber reinforcing layer having a crescent cross section as described above, it is possible to reduce the mass while ensuring sufficient run flat durability. Moreover, when the gas-filled thermoplastic resin particles are mixed with the rubber reinforcing layer having a crescent cross section, heat generation can be suppressed, and there is an advantage that run-flat running performance is improved.

In the present invention, the volume ratio of the hollow portion contained in the gas-filled thermoplastic resin particles to the rubber reinforcing layer is in the range of 20 to 50% in order to reduce the mass while maintaining the run flat durability. Is preferred. The hardness (JIS-A) at 25 ° C. of the rubber reinforcing layer containing the gas-filled thermoplastic resin particles is preferably in the range of 70 to 90.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. In FIG. 1, 1 is a bead portion, 2 is a tread portion, and 3 is a sidewall portion connecting the bead portion 1 and the tread portion to each other. A plurality of carcass layers 4A to 4C formed by aligning a plurality of reinforcing cords in parallel are mounted between the pair of left and right bead portions 1 and 1. As the carcass cord, an organic fiber cord or a steel cord can be used.

The carcass layer 4A, which is the innermost layer, has both ends in the tire width direction wound up around the bead core 5 from the inside to the outside of the tire, and its terminal ends near the tire maximum width position. The carcass layer 4 </ b> B serving as an intermediate layer has both ends in the tire width direction wound up around the bead core 5 from the inside to the outside of the tire, and the terminal ends at a position on the outer peripheral side of the bead core 5. The outermost carcass layer 4C
Are arranged so that both ends in the tire width direction pass outside the bead core 5 and the bead filler 6, and the terminal ends at a position on the inner peripheral side of the bead core 5.

Between the inner surface of the innermost carcass layer 4A and the layer between the carcass layers 4A and 4B, there is provided a rubber reinforcing layer 7 having a crescent cross section extending along the side wall portion 3, respectively. The rubber reinforcing layer 7 is made of a rubber composition which is harder than the rubber composition on the outer surface of the sidewall, and gradually becomes thinner from near the tire maximum width position toward the tread side and the bead side. The hardness of the rubber reinforcing layer 7 is JIS-A
The hardness is set in the range of 70 to 90. An inner liner layer 8 is provided on the inner surface of the tire.

On the other hand, the carcass layer 4 in the tread portion 2
On the outer peripheral side of A to 4C, there are provided two belt layers 9, 9 in which a plurality of reinforcing cords are aligned in parallel.
These belt layers 9 and 9 are arranged such that the reinforcing cords are inclined with respect to the tire circumferential direction, and the reinforcing cords intersect each other between the layers. Further, a belt cover layer 10 in which reinforcing cords are oriented in the tire circumferential direction is provided on the outer peripheral side of the belt layers 9, 9.

The pneumatic tire described above is provided with a rubber reinforcing layer 7 having a crescent cross section on the side wall portion 3, and the side wall portion 3 is prevented from bending on the basis of the rigidity of the rubber reinforcing layer 7. However, the vehicle can travel a certain distance at a certain speed. That is, it has a run flat property. About the rubber reinforcing layer 7,
As shown in FIG. 2, it may be provided integrally on the inner surface side of the innermost carcass layer 4A.

In the pneumatic tire, the rubber reinforcing layer 7 having a crescent cross section contains gas-filled thermoplastic resin particles. The gas-encapsulated thermoplastic resin particles expand thermally-expandable thermoplastic resin particles in which a liquid or solid that generates a gas by vaporizing, decomposing, or chemically reacting by heat is contained in the thermoplastic resin, by the heat during rubber vulcanization. It was made hollow. That is, it is a hollow particle in which gas is sealed in an elastic outer shell made of a thermoplastic resin. When the thermally expandable thermoplastic resin particles are previously blended with the rubber and uniformly kneaded, and then the resin is expanded simultaneously with the vulcanization of the rubber, the gas-enclosed thermoplastic resin particles can be uniformly dispersed in the rubber reinforcing layer.

As described above, the rubber reinforcing layer 7 having a crescent cross section is used.
By including the hollow particles, it is possible to reduce the mass while ensuring sufficient run-flat durability, and to improve the run-flat running performance by suppressing heat generation.

The particle size of the gas-filled thermoplastic resin particles is 5 to 5.
It is 300 μm, more preferably 10 to 200 μm.
If the particle size is too small, it is difficult to reduce the mass. Conversely, if the particle size is too large, it is difficult to ensure run-flat durability.

The volume ratio of the hollow portion contained in the gas-filled thermoplastic resin particles to the rubber reinforcing layer 7 is preferably 20 to 50%. If the volume ratio is too small, it is difficult to reduce the mass. Conversely, if the volume ratio is too large, it becomes difficult to ensure run-flat durability. In order to obtain such a volume ratio, it is preferable to mix 5 to 25 parts by weight of the gas-filled thermoplastic resin particles with respect to 100 parts by weight of rubber.

The thermoplastic resin constituting the outer shell component of the gas-filled thermoplastic resin particles has an expansion start temperature of 10%.
Those having a temperature of 0 ° C or higher, preferably 120 ° C or higher, and a maximum expansion temperature of 150 ° C or higher, preferably 160 ° C or higher are preferably used. Such thermoplastic resins include, for example, (meth) acrylonitrile polymers and (meth) acrylonitrile polymers.
A copolymer having a high acrylonitrile content is preferably used. As the other monomer (comonomer) in the case of the copolymer, monomers such as vinyl halide, vinylidene halide, styrene-based monomer, (meth) acrylate-based monomer, vinyl acetate, butadiene, vinylpyridine, and chloroprene are used. . In addition, the said thermoplastic resin is divinylbenzene, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, allyl. It may be crosslinkable with a crosslinking agent such as (meth) acrylate, triacrylformal, triallylisocyanurate and the like. The crosslinked form is preferably not crosslinked, but may be partially crosslinked so as not to impair the properties of the thermoplastic resin.

Examples of the liquid or solid that generates gas by vaporization, decomposition or chemical reaction by the above-mentioned heat include, for example, n-
Liquids such as hydrocarbons such as pentane, isopentane, neopentane, butane, isobutane, hexane, petroleum ether, chlorinated hydrocarbons such as methyl chloride, methylene chloride, dichloroethylene, trichloroethane, and trichloroethylene, or azodicarbonamide , Dinitrosopentamethylenetetramine, azobisisobutyronitrile, toluenesulfonylhydrazide derivatives, and aromatic succinylhydrazide derivatives.

Examples of the rubber component used in the crescent rubber reinforcing layer include natural rubber (NR), various butadiene rubbers (BR), and various styrene-butadiene copolymer rubbers (S
BR), polyisoprene rubber (IR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (C
R), ethylene-propylene-diene copolymer rubber (E
PDM), styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, and the like.

[0022]

EXAMPLE In a pneumatic tire having a run-flat running performance of a tire size of 225 / 60R16 (FIG. 1), the rubber composition of the crescent-shaped rubber reinforcing layer is made common, while the rubber reinforcing layer is filled with gas-filled thermoplastic resin. Production of the tires 1 and 2 of the present invention containing resin particles (hollow particles), comparative tires in which bubbles were formed by a foaming agent in the rubber reinforcing layer, and conventional tires in which the rubber reinforcing layer was composed only of the rubber composition. did.

The test tires were evaluated for tire mass and run flat durability under the following conditions. The results shown in Table 1 were obtained. In Table 1, the volume ratio of the hollow portion is a percentage (%) of the volume of the hollow portion of the hollow particles or the volume of the bubbles relative to the total volume of the rubber reinforcing layer.

Tire mass: The mass of each test tire was measured. The evaluation result was calculated using the reciprocal of the measured value,
The index is set to 00. The larger the index value, the smaller the tire mass.

Run flat durability: Each test tire was mounted on a rim having a rim size of 16 × 71 / 2JJ, and then attached to the right front wheel of a rear-wheel drive vehicle with a displacement of 4000 cc in a state where air was evacuated. The vehicle was run counterclockwise at a speed of 80 km / h on the circuit course, and the test driver felt abnormal vibration due to tire failure and measured the distance until the vehicle stopped running. As a result of the evaluation, the index is shown as an index with the conventional tire being 100. The larger the index value, the better the run flat durability.

[0026]

[Table 1]

As can be seen from Table 1, the tires 1 and 2 of the present invention could be reduced in weight while maintaining the run flat durability at a level equal to or higher than that of the conventional tire. On the other hand, the run tire durability of the comparative tire was also reduced as the weight was reduced.

[0028]

As described above, according to the present invention, in a pneumatic tire having run-flat running performance in which a rubber reinforcing layer having a crescent cross section is provided on a sidewall portion,
Since gas-filled thermoplastic resin particles having a particle size of 5 to 300 μm are blended in the rubber reinforcing layer having a crescent cross section, the mass can be reduced while ensuring sufficient run flat durability, and furthermore, heat generation can be suppressed. Run flat running performance can be improved.

[Brief description of the drawings]

FIG. 1 is a half sectional view showing a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is a half sectional view showing a pneumatic tire according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead part 2 Tread part 3 Side wall part 4A-4C Carcass layer 5 Bead core 6 Bead filler 7 Rubber reinforcement layer 8 Inner liner layer 9 Belt layer 10 Belt cover layer

Claims (3)

[Claims] 1. A pneumatic tire having run-flat running performance in which a side wall portion is provided with a rubber reinforcing layer having a crescent cross section. Pneumatic tire containing particles. 2. A volume ratio of a hollow portion included in the gas-filled thermoplastic resin particles to the rubber reinforcing layer is 20 to 20.
The pneumatic tire according to claim 1, which is 50%. 3. The hardness (J) of the rubber reinforcing layer at 25 ° C.
3. The pneumatic tire according to claim 1, wherein IS-A) is 70 to 90. 4.