JP2003039913A - Pneumatic tire having inner liner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which can reduce the road noise attributable to the tire vibration when a vehicle travels on a rough road, and improve the air impermeability of an inner liner. SOLUTION: The pneumatic tire has the inner liner consisting of a rubber composition in which >=40 mass % butyl rubber is contained in a rubber composition of 100 mass part, and hollow particles of the mean particle size of <=500 μm are mixed so that the volumetric ratio is 2-40%. The hollow particles preferably have the strength that the ratio of breakage is <=40% at the hydrostatic pressure of 500 kg/cm<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air liner in which road noise, particularly in-vehicle noise generated due to tire vibration when traveling on a poor road surface, is reduced without impairing the air impermeability and durability of the inner liner. Containing tires.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a technique for reducing in-vehicle noise, that is, road noise, caused by tire vibration when traveling on a rough road surface.

As a method of reducing road noise generated when the tire touches the ground while the vehicle is running, for example, the tread portion has a two-layer structure of a cap rubber and a base rubber, and the cap rubber has a large hysteresis loss. Or, by reducing the rigidity of the tread part using rubber with a low elastic modulus, a method of reducing tire vibration during running, or by increasing the thickness of the tread part and lowering the rigidity of the bead part A method of reducing the spring constant of the entire tire to reduce tire vibration during traveling has been proposed. However, these methods impair steering stability due to a decrease in tire rigidity, and are not practical solutions.

On the other hand, Japanese Patent Laid-Open No. 60803/1990 discloses that
A method has been proposed in which a low-hardness vulcanized rubber having a carbon black content of 20 parts by mass or less is made into particles having an average particle size of 100 to 1000 μm and uniformly dispersed in a cap rubber of a two-layer tread portion including a cap rubber and a base rubber. ing. However, in such a method, when the tire wears and the particles are exposed on the tie or the surface, the particles are not fixed to the rubber and easily fall off from the rubber. Further running causes adverse effects such as cracking of the rubber from traces of particles falling off, resulting in deterioration of wear resistance and durability. Further, when the particles are exposed on the surface, the ground contact surface becomes uneven and it is not possible to obtain a tire that satisfies both road noise and driving stability.

Further, a method of enhancing the vibration damping effect by using a material having a low rigidity and a large hysteresis loss for the constituent elements of the pneumatic tire, for example, the carcass or the side reinforcing layer, can be considered. This will increase the heat generated when the tire is running and reduce durability.

[0006]

SUMMARY OF THE INVENTION The present invention reduces road noise, particularly in-vehicle noise caused by tire vibration when traveling on a poor road surface, without impairing the air impermeability and durability of the inner liner. Pneumatic tires.

[0007]

The present invention provides a rubber component 100.
The butyl rubber is contained in an amount of 40% by mass or more, and the volume ratio of the hollow particles having an average particle diameter of 500 μm or less is 2% to 40.
The pneumatic tire is provided with an inner liner made of a rubber composition mixed so that the amount of the rubber composition becomes 100%.

Here, the hollow particles have a hydrostatic pressure of 500 kg / c.
It is desirable to have a strength with a fracture rate at m ² of 40% or less. The butyl rubber is preferably halogenated butyl rubber.

[0009]

1 shows the right half of a sectional view of an embodiment of a pneumatic tire of the present invention. In FIG. 1, a pneumatic tire 1 has a tread portion 2, a sidewall portion 3 and a bead portion 4. Further, a bead core 5 is embedded in the bead portion 4, and a carcass 6 that is locked by folding both ends around the bead core 5 from one bead portion 4 to the other bead portion, and on the outside of the crown portion of the carcass 6. Has a belt layer 7 formed of two plies. An inner liner 9 extending from one bead portion 4 to the other bead portion 4 is arranged inside the carcass 6.

The belt layer 7 comprises two plies of steel cords or cords of aramid fiber or the like crossed with each other so that the cords normally form an angle of 5 to 30 ° with respect to the tire circumferential direction. Arranged to do so. The carcass has organic fiber cords such as polyester, nylon, aramid, etc. arranged at approximately 90 ° in the tire circumferential direction, and in the area surrounded by the carcass and its folded portion,
Extending from the upper end of the bead core 5 in the sidewall direction,
The bead apex 8 made of hard rubber having a JIS-A hardness of 70 to 95 is preferably arranged.

Hollow particles are mixed in the rubber composition of the inner liner. Hollow particles having an average particle diameter of 500 μm or less are used. Average particle size is 5
If it exceeds 00 μm, the strength of the base rubber is lowered, and the hollow particles are broken when kneading with the rubber. The average particle size is 20 μm to 400 μm, particularly 40 μm to 200 μm.
A range of m is preferred. When the average particle size is small, the generation of vibration during tire running is not sufficiently suppressed and the road noise reduction effect is reduced. The hollow particles may have various particle sizes.

The hollow particles have a hydrostatic pressure of 500 kg / c.
It is preferable that the material has a breaking rate at m ² of 40% or less. The hollow particles are kneaded with the rubber by a roll or a kneader when producing the base rubber composition, but most of the hollow particles may be destroyed by pressure, shearing force, etc. in this case. Vibration reduction effect cannot be expected.

Here, the destruction rate is measured by the following method.
In FIG. 2, hollow particles and glycerin in a volume ratio of 50:
Mix to 50 and pack into package 11. Package 1
1 into a pressure vessel 10 and set a predetermined hydrostatic pressure (500 kg
/ Cm ² ). The destruction rate is represented by the volume reduction rate of hollow particles. The calculation formula is shown below.

Destruction rate (volume reduction rate) = (1−A1 / A2) × 100 A1: True density of hollow particles before pressure treatment A2: True density of hollow particles after pressure treatment Next, hollow in base rubber Particle volume ratio is 2% to 40
% To be mixed. The volume ratio is more preferably in the range of 5% to 25%. Here, the volume ratio is calculated as a volume ratio (%) to the base rubber after vulcanization by calculating the volume of the hollow particles before kneading the hollow particles into the rubber. When the volume ratio is less than 2%, the road noise reduction effect is small.
On the other hand, if the volume ratio exceeds 40%, the durability of the base rubber deteriorates and the cost of the hollow particles increases.

The types of hollow particles used in the present invention include, but are not limited to, glass balloons, silica balloons, shirasu balloons, phenol balloons, vinylidene chloride balloons, alumina balloons, zirconia balloons and the like. The hollow particles may be used alone or in combination of two or more.

The hollow particles are made of the above materials and have a specific gravity of 1.2 to
Of what 2.5 g / cm ^2, it is preferred to use those adjusted to a specific gravity 0.7~1.5g / cm ² by hollowed.

Next, the inner liner rubber composition has a Shore A hardness of 45 to 6 in a rubber composition excluding hollow particles.
By using a relatively soft rubber in the range of 0, preferably in the range of 45 to 55, the road noise can be reduced in combination with the effect of suppressing the vibration of the tire due to the hollow particles. The Shore A hardness of the rubber composition containing the hollow particles is preferably in the range of 60 to 70.

In the present invention, the rubber composition of the inner liner contains 4 parts of butyl rubber per 100 parts by mass of the rubber component.
0 mass% or more is blended. Here, the butyl rubber is an isobutene-isobutylene copolymer, and the bound isoprene amount is usually 0.6 to 2.5 mol% and includes not only butyl rubber having a low degree of unsaturation but also halogenated butyl rubber obtained by halogenating the butyl rubber. The type of halogenation is not limited and, for example, chlorinated butyl rubber, brominated butyl rubber, etc. are used.

In the present invention, the butyl rubber is blended in an amount of 40% by mass or more based on 100 parts by mass of the component. If it is less than 40% by mass, the air impermeability becomes insufficient and it is not suitable as an inner liner. When the butyl rubber is used alone, the durability tends to decrease due to the decrease in flex resistance. Therefore, for 100 parts by mass of the rubber component, the diene rubber is 6
It is preferable to mix in a range not exceeding 0% by mass.

Here, as the diene rubber, natural rubber, polyisoprene rubber, emulsion-polymerized styrene-butadiene copolymer rubber, solution-polymerized styrene-butadiene copolymer rubber (styrene content 10 to 50 wt%, 1,2 bond amount 10 to 70).
%), High trans, styrene-butadiene copolymer rubber,
Low cis polybutadiene rubber, high cis polybutadiene rubber, styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, solution polymerization styrene-butadiene-
Examples thereof include isoprene copolymer rubber and emulsion-polymerized styrene-acrylonitrile-butadiene copolymer rubber. In particular, natural rubber, polyisoprene rubber, polybutadiene rubber or styrene-butadiene copolymer rubber is used.

In the present invention, the rubber composition of the inner liner contains carbon black such as FEF, HAF,
Various grades such as ISAF and SAF are used,
The compounding amount is usually 10 with respect to 100 parts by mass of the rubber component.
The range is from -80 parts by mass.

Other compounding agents for the rubber composition of the inner liner include, for example, vulcanizing agents such as sulfur and peroxide, vulcanizing accelerators such as thiazole type, thiuram type, sulfenamide type and guanidine type, stearic acid. And vulcanization aids such as zinc white, activators such as diethylene glycol and polyethylene glycol, fillers, plasticizers, antioxidants, process oils and the like.

Vibration noise is input to the pneumatic tire from the tread ground contact portion during traveling. By softening the rubber component forming the tire, the vibration absorption efficiency is increased, and noise can be reduced. Therefore, the vibration absorbing effect is enhanced by incorporating a predetermined amount of hollow particles into the rubber composition of the relatively soft inner liner. That is, by blending the hollow particles, the hollow particles have the effect of vibrating and absorbing the vibration transmitted through the rubber component inside the rubber component. Further, since the particles are hollow, vibration noise is not transmitted inside the particles, and effective noise reduction can be achieved. On the other hand, when the porous composition is blended with the rubber composition, the rubber component enters the irregularities on the surface of the particle, and the particle is fixed by the rubber component so that the particle does not easily vibrate, and noise reduction cannot be sufficiently achieved as in the present invention. . Further, the hollow particles block the permeation of air in the inner liner, and the air impermeability of the pneumatic tire can be increased.

In the present invention, the inner liner is a known tire manufacturing method, for example, a sheet-like material is extruded separately from an unvulcanized rubber composition, and the two are laminated to form an inner liner, which is laminated with other tire constituent materials. It is possible to adopt a method in which a green tire is produced by molding and vulcanization is performed.

The cross-sectional shape, structure, and
The material of the reinforcing material can be appropriately changed according to the tire category, for example, passenger car tires, light truck tires, and truck bus tires. Furthermore, the present invention is not limited to pneumatic radial tires, but can be applied to bias tires and belted bias tires.

[0026]

[Embodiment] The tire size is TL225 with the structure shown in FIG.
/ 55R16 radial tires for passenger cars were prototyped. A polyester cord layer was used for the tire carcass, cord angles were arranged at 90 ° in the tire circumferential direction, and two plies in which steel cords were crossed between the plies at 22 ° in the tire circumferential direction were used for the belt layer. .

Table 1 shows the basic composition of the inner liner, and Table 2 shows the mixing specifications of the hollow particles in the rubber composition.
The air impermeability, road noise and durability of the inner liner of the prototype tire were measured by the following methods.

[0028]

[Table 1]

[0029]

[Table 2]

(1) Air impermeable tire Size TL225 / 55R16 pneumatic tire was filled with air, room temperature was kept at 21 ° C., air pressure was measured after leaving for 6 months, and air permeability was measured. The degree was evaluated. The air pressure before standing in Comparative Example 1 was set to 1000 and displayed as an index. Higher numbers indicate less air permeation.

(2) A pneumatic tire of road noise tire size TL225 / 55R16 was prototyped and evaluated by the driver's feeling in the vehicle when traveling on a poor road surface at 50-80 km / h. Comparative Example 1 was evaluated on a scale of 10 with 5 points. The larger the number, the better.

(3) Durability of inner liner A pneumatic tire of tire size TL225 / 55R16 was prototyped and accelerated in an oven (4 days at 80 ° C).
Then, drum running (internal pressure: 140 KPa, load: 470
0N, speed: 80km / h, mileage: 10,000k
The damage state of the inner liner after m) was visually evaluated. The comparative example 1 was set to 100 and displayed as an index. The higher the number, the better the durability.

In Comparative Example 1, since the hollow particles were not mixed with the inner liner, the road noise was not good. In Comparative Example 2, since the rubber hardness of the inner liner is low and the hollow particles are not mixed, the road noise and the durability of the inner liner are not good. In Comparative Example 3, since the volume ratio of the hollow particles is as small as 1%, the effect of reducing road noise is small. In Comparative Example 4, since the destruction rate of the hollow particles blended in the inner liner is as high as 90%, the effects of road noise reduction and inner liner durability cannot be expected. In Comparative Example 5, glass beads were mixed instead of the hollow particles, so that the effect of reducing road noise cannot be expected.

In the first embodiment, the glass balloon has a volume ratio of 5
% To improve air impermeability, road noise and durability of the inner liner.

Example 2 uses glass balloons in a volume ratio of 2
Since the mixture was mixed so as to be 0%, the air impermeability and the road noise were improved as compared with Example 1, but the durability of the inner liner was slightly inferior.

The embodiments and examples disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

[0037]

As described above, the pneumatic tire of the present invention has an inner liner in which a rubber composition containing butyl rubber is blended with a predetermined amount of hollow particles, so that it is impermeable to air.
Road noise and overall durability of the inner liner are improved.

[Brief description of drawings]

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

FIG. 2 shows a schematic diagram of a method of measuring the destruction rate.

[Explanation of symbols]

1 pneumatic tire, 2 tread part, 3 sidewall part, 4 bead part, 5 bead core, 6 carcass, 7 belt layer, 8 bead apex, 9 inner liner.

Claims (3)

[Claims] 1. A rubber composition comprising 100 parts by mass of a rubber component containing 40% by mass or more of butyl rubber and hollow particles having an average particle size of 500 μm or less mixed in a volume ratio of 2% to 40%. A pneumatic tire with an inner liner. Wherein the hollow particles are hydrostatic pressure 500 kg / cm ²
The pneumatic tire according to claim 1, which has a strength at a fracture rate of 40% or less. 3. The pneumatic tire according to claim 1, wherein the butyl rubber is halogenated butyl rubber.