JPH1178416A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performance on ice in case of long-sized recessed parts appearing on the surface due to wear by making long-sized air bubbles with the inner surface covered with resin, exist in the tread of a tire. SOLUTION: Long-sized air bubbles with the internal walls covered with resin exist in a tread. When the tread is cut in a plane almost parallel with a tire ground plane, a plurality of long-sized recessed parts covered with resin exist in the cut face. Over 80% of the air bubbles or recessed parts are oriented within 45 deg. from the equator face of a tire. The long-sized recessed parts existing in the cut face at the time of cutting the tread in the plane almost parallel with the tire ground plane are 500 μm or less in the average width, and the ratio of the average width to the maximum longitudinal length is 3 or more, desirably 5-20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic tire having excellent performance on ice.

[0002]

2. Description of the Related Art Since spike tires have been regulated, researches on treads of tires have been actively conducted in order to improve braking / driving performance (on-ice performance) of tires on icy and snowy road surfaces. On the icy and snowy road surface, a water film is easily generated due to frictional heat between the icy and snowy road surface and the tire, and the water film causes a reduction in the coefficient of friction between the tire and the icy and snowy road surface. For this reason, the ability of the tire tread to remove the water film and the edge effect greatly affect the performance on ice. Therefore, in order to improve the performance on ice of the tire, it is necessary to improve the water film removing ability and the edge effect of the tread.

Therefore, Japanese Patent Application Laid-Open No. 4-38207 discloses that the micro drainage grooves are formed on the surface of the tread by using foamed rubber containing short fibers for the tread. But in this case,
The short fibers are curled by heat shrinkage or are bent by being pushed into the sipe portion during vulcanization of the mold. It is not easily detached, the micro drains as originally aimed cannot be formed efficiently, and the coefficient of friction on the ice and snow road surface is not sufficiently improved. In addition, the detachment of the short fibers greatly depends on running conditions and the like, and the performance on ice cannot be reliably improved. Further, there is a problem that the micro orientation is crushed when a load applied to the tire is large.

In Japanese Patent Application Laid-Open No. 4-110212, a hollow fiber is dispersed in the tread so that the water film existing between the ice and snow road surface and the tread is formed in a hollow portion of the hollow fiber. A tire that can be eliminated is disclosed. However, in the case of this tire, the pressure at the time of kneading or molding the hollow fiber into rubber,
The hollow fiber is crushed due to rubber flow, temperature, and the like, so that the hollow fiber cannot actually maintain a hollow shape, and there is a problem that the performance on ice is still insufficient.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, an object of the present invention is to provide a pneumatic tire that has an excellent ability to remove the water film generated on ice, a large coefficient of friction with an ice surface, and an excellent performance on ice.

[0006]

Means for Solving the Problems The present inventors have made a long tread of a tire contain long bubbles having a resin-coated inner surface, and when a long recess has appeared on the surface due to abrasion, the microbubble is formed. It has been found that the performance on ice can be improved by utilizing the function as a simple drainage ditch and the edge effect.

The present inventors have conducted intensive studies to further improve the on-ice performance of the tire. As a result, by controlling the orientation of the long bubbles more precisely,
It has been found that the performance of the tire on ice is greatly improved.

That is, according to the present invention, when the tread portion is made of foamed rubber, and the foamed rubber is cut substantially parallel to the tire grounding surface, the cut surface has a plurality of elongated concave portions coated with resin. And at least 80% of the recesses are oriented within 45 degrees, preferably within 35 degrees from the equatorial plane of the tire, wherein the average width of the elongated recesses is (W) is 500 μm or less, and a ratio L between the average width (W) and the maximum length in the longitudinal direction (L).
/ W is preferably 3 or more.

Another aspect of the present invention is a tire in which the tread is made of foamed rubber, and the ground contact portion after running includes at least a long concave portion coated with a resin. 80% or more of the pneumatic tire is oriented within 45 degrees, preferably 35 degrees from the equatorial plane of the tire, and the average width (W) of the elongated concave portion is 500 μm or less. And the average width (W)
And the maximum length in the longitudinal direction (the ratio L / W to L is preferably 3 or more.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The pneumatic tire of the present invention will be described in detail below. The pneumatic tire of the present invention, the tread, having long air bubbles whose inner wall is coated with resin, or when the tread is cut along a plane substantially parallel to the tire tread, the cut surface is coated with resin. Characterized in that there are a plurality of elongated concave portions, and 80% or more of the bubbles or the concave portions are 4% away from the equatorial plane of the tire.
Must be oriented within 5 degrees. If the amount of the oriented bubbles or the concave portions is less than 80%, the water film generated between the road surface and the tire due to frictional heat or the like cannot be sufficiently removed during running of the tire, and the performance on ice is sufficiently improved. Absent.

In the pneumatic tire according to the present invention, the long air bubbles existing in the tread or the long concave portion present in the cut surface when the tread is cut along a plane substantially parallel to the tire contact surface is formed by It is preferable that the average width (W) is 500 μm or less, and the ratio L / W between the average (W) and the maximum length in the longitudinal direction (L) is 3 or more. If the average width (W) exceeds 500 μm, the cut resistance and the chipping resistance of the pneumatic tire decrease, and the abrasion resistance on a dry road surface deteriorates. Previous period (L / W)
Is less than 3, it is not possible to increase the length of long bubbles or long recesses as long drain grooves appearing on the surface of the worn tread, and it is not possible to increase the volume. Therefore, it is not preferable because the water removal performance of the tire cannot be improved. In addition, compared with the previous period (L / W)
There is no particular upper limit, but about 5 to 20 is selected.

[0012] The tread of the pneumatic tire of the present invention may also contain spherical bubbles in addition to the above-mentioned elongated bubbles, and the tread of the pneumatic tire of the present invention may be formed on a surface substantially parallel to the tire contact surface. The cut surface cut by the above method may include a spherical concave portion in addition to the elongated concave portion.

[0013] In the case of including a spherical bubble or a concave portion, the ratio of the long bubble or the concave portion is, respectively, the total bubble or the concave portion.
It is preferably at least 10% by volume of all the recesses, more preferably at least 50% by volume. If the proportion of the long bubbles or the concave portions is less than 10% by volume, the drainage by the long bubbles is small, and the water rejection performance may not be sufficient.

The average foaming rate (bubble content) Vs of the foamed rubber (hereinafter sometimes simply referred to as tread rubber) used for the tread of the pneumatic tire of the present invention is 3 to 40.
(Volume)% is preferable, and 5 to 35 (Volume)% is more preferable. When the average foaming rate is less than 3 (volume)%, the amount of long bubbles decreases, and the amount of drain grooves formed on the tire contact surface when the tread is worn decreases, so that the pneumatic tire on ice is reduced. Performance could not be improved, 40
When the content exceeds (volume)%, the performance on ice can be improved, but the breaking limit of the tread is greatly reduced, which is not preferable in terms of durability.

Here, the average foaming rate Vs means the foaming rate of long cells or the sum of the foaming rates of long cells and spherical cells, and can be calculated by the following equation. Vs = (ρ ₀ / ρ ₁ -1) × 100% In the formula, ρ ₁ represents the density (g / cm ² ) of the foamed rubber, and ρ ₀ represents the density (g / cm ² ) of the solid phase portion in the foamed rubber. , The weight in ethanol and the weight in air were measured and calculated from these.

The rubber component used in the tread rubber of the pneumatic tire of the present invention is not particularly limited, and natural rubber and / or synthetic rubber can be used alone or in combination as appropriate. Synthetic rubbers include styrene-butadiene copolymer (SBR) and butadiene rubber (B
R), isoprene rubber (IR), butyl rubber (II
R), ethylene-propylene terpolymer (EPDM)
And the like. Among them, cis-1,4-polybutadiene is preferable, and a cis content of 90% or more is particularly preferable, since the glass transition temperature is low and the performance on ice is large.

The type of the resin that covers the inner wall or the concave portion of the bubble is not particularly limited. For example, polyethylene (PE), polypropylene (PP), polybutylene, polybutylene succinate, polyethylene succinate,
Syndiotactic-1,2 polybutadiene (SP
B), crystalline polymers such as polyvinyl alcohol (PVA), polyvinyl chloride (PVC), etc., and non-crystalline polymers such as polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene copolymer (ABS), polystyrene, polyacrylonitrile, etc. However, from the viewpoint of ease of tire production, crystalline polymers having a melting point lower than the highest vulcanization temperature are preferable, have good adhesion to matrix rubber, and PE and PP, which are easily available as raw materials, are particularly preferable. preferable.

[0018] The tread rubber of the pneumatic tire of the present invention contains a foaming agent. Examples of the foaming agent include dinotrosopentamethylenetetramine (DPT),
Azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivative, oxybisbenzenesulfonylhydrazide (OB
SH), ammonium bicarbonate that generates carbon dioxide, sodium bicarbonate, ammonium carbonate, a nitrososulfonylazo compound that generates nitrogen, N, N-7-dimethyl-
Dinitrosophthalamide, toluenesulfonyl hydrazide, p-toluenesulfonylcarbazide, p, p'-
Oxy-bis (benzenesulfonyl semicarbazide) and the like. Among these, dinitrosopentamethylenetetramine and azodicarbonamide are preferable from the viewpoint of processability of tire production, and azodicarbonamide is particularly preferable. These foaming agents may be used alone or in combination of two or more.

From the viewpoint of efficient foaming, it is preferable to use a foaming aid in combination. Examples of the foaming aid include urea, zinc stearate, zinc benzenesulfinate, and zinc white. From the viewpoint of productivity and processability, urea, zinc stearate, and zinc benzenesulfinate are preferred. These may be used alone or in combination of two or more. By appropriately selecting these foaming agents and foaming assistants, the average foaming ratio Vs can be adjusted to a desired range.

The tread rubber used for the pneumatic tire of the present invention is obtained, for example, by mixing a resin with a rubber matrix,
It can be obtained by foaming. The resin to be mixed here may be in the form of a short fiber, a long one, or the like.

The resin may itself contain a foaming agent, or may contain an additive for improving the adhesion to the matrix rubber.

The amount of the resin to be added to the foamed rubber of the tread of the pneumatic tire of the present invention is preferably 0.5 to 30 parts by weight, more preferably 1.0 to 10 parts by weight based on 100 parts by weight of the rubber component. .

The thickness of the resin layer is 0.5 to 50 μm
Is preferred. The average foaming rate Vs, and the ratio of the concave portion and the thickness of the resin layer are determined by the type and amount of the foaming agent, the type and amount of the foaming assistant to be combined, the compounding amount of the resin, the hollow ratio of the resin, and the like. By changing, it can be changed appropriately.

The tread rubber of the pneumatic tire according to the present invention may further comprise reinforcing fillers such as carbon black and silica, inorganic fillers, softeners, vulcanizing agents, vulcanization aids, aging, in addition to the above-mentioned components. Compounding agents commonly used in the rubber industry, such as inhibitors and coupling agents, can be used as appropriate.

The method for producing the pneumatic tire of the present invention is not particularly limited. For example, a rubber composition obtained by mixing and kneading a resin having a melting point lower than the maximum vulcanization temperature of the tire with a matrix rubber containing a foaming agent. Can be obtained by heating, extruding to form an unvulcanized tread, molding and vulcanizing. In this case, in manufacturing the tire, it is preferable to set the vulcanization conditions so that the melting point of the resin is lower by at least 10 ° C. than the maximum vulcanization temperature, and the difference is more preferably at least 20 ° C. .

On the other hand, if the melting point of the resin is lower than any of the kneading temperature, the warming temperature and the extrusion temperature, the shape of the resin changes during the process, and sometimes the resin is finely dispersed in the matrix rubber. Is undesirably dispersed.

The conditions other than the apparatus and temperature used in each step are not particularly limited, and can be appropriately selected depending on the purpose. Commercially available products can be suitably used for the device.

As a method for aligning the orientation of the resin,
For example, the resin may be oriented in a certain direction by extruding a rubber composition containing a resin from a die of an extruder in which a flow path cross-sectional area decreases toward an outlet. The degree of orientation of the resin in the rubber composition varies depending on the degree of decrease in the cross-sectional area of the flow path, the extrusion speed, the viscosity of the rubber composition, and the like.

The vulcanization conditions are preferably set such that the maximum temperature is higher than the melting point of the resin. By doing so, the resin melts during vulcanization and has a lower viscosity than the matrix rubber, so the gas generated by the foaming reaction of the foaming agent moves into the resin, so that the resin is efficiently elongated. Bubbles can be formed.

The tire of the present invention can be suitably applied not only to so-called passenger cars but also to various vehicles such as trucks and buses.

[0031]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention.

Preparation of Tread Rubber Composition According to the composition shown in Table 1, tread rubber compositions used in Examples and Comparative Examples were prepared. The compounded resin was polyethylene (HDPE, weight average molecular weight (Mw) 1.8 × 1).
05), and the melting point peak temperature (melting point) was 135 ° C. measured by a DuPont DSC under the conditions of a temperature rising rate of 10 ° C./min and a sample weight of about 5 mg. The resin used had an average diameter of 23 to 195 μm as shown in Table 1.
It was a solid fiber having an average length of 2 mm, and the degree of orientation was controlled by changing the flow passage reduction rate in the tread width direction of the extruder.

Production of Tire Using the rubber composition prepared above as a tread, a 185 / 70R13 radial tire for passenger cars was prepared, vulcanized and molded by a conventional method. In this tire,
The carcass has one layer and is reinforced with polyester cords arranged at an angle of 90 ° with respect to the tire circumferential direction, and the number of cords to be driven is 50/5 cm. The belt is
Two layers, reinforced by steel cord of 1x5x0.23 structure, the driving angle of the cord is 25 ° with respect to the circumferential direction of the tire, and the number of cords is 40/5
cm. As for the size of the block in the tread of the vulcanized tire, the circumferential dimension of the tire is 35 mm,
The width dimension of the tire is 30 mm. The sipe formed in the block has a width of 0.4 mm and an interval in the tire circumferential direction of about 7 mm.

Various measurements were made by the following methods. (1) Size of the long recessed part Take an electron micrograph of the sliced surface or the surface of the tread after traveling about 20,000 km, and measure the width and length of only 50 recesses with the resin coating layer. , And the average value was calculated. (2) Orientation of Elongated Depression In the above photograph, the orientation angle (absolute value) of 50 elongate depressions having a resin coating layer with respect to the tire circumferential direction is determined, and the average value is calculated. Further, the number of concave portions oriented within 45 degrees and within 35 degrees is obtained, and the ratio is calculated. In addition, the photo measurement location was a location in the block, which was at least 0.5 mm away from the groove and the end of the sipe.

(3) Performance on Tire Ice After mounting the tire on a domestic 1600CC class passenger car and running the passenger car on a general asphalt road for 200 km,
The vehicle was driven on a flat road on ice, and at a speed of 20 km / h, the brakes were depressed to lock the tires, and the distance to stop was measured. The result was expressed as an index with the reciprocal of the distance taken as 100 for the control tire. The larger the value, the better the performance on ice. (4) Wear resistance The tire was mounted on the front wheels of a 1600cc class passenger car (FF vehicle) in Japan, and the tire groove depth after running 20,000 km on a general road was measured to calculate the amount of wear. The result was expressed as an index with the reciprocal of the abrasion amount as 100 for the control tire.
The larger the value, the better the wear resistance.

[0036]

[Table 1] Tread rubber compounding table * 1: BR01 (manufactured by Nippon Synthetic Rubber Co., Ltd.) * 2: Si69 (manufactured by Degussa AG) * 3: Nocrack 6C (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) * 4: Noxeller DM (Ouchi) * 5: Noxeller CZ (Ouchi Shinko Chemical Co., Ltd.) * 6: Vinyl Hall V (Eiwa Chemical Co., Ltd.) * 7: Zinc benzenesulfinate (Otsuka Chemical Co., Ltd.) * 8) Urea / zinc stearate blend (85/15)

[0037]

[Table 2]

Comparative Example 1 is completely non-oriented.
In Comparative Example 2 and Examples 1 to 5, the orientation of the elongated concave portion in the tire circumferential direction gradually increases. As can be seen from Comparative Examples 1 and 2 and Examples 1 to 5, it can be seen that the performance on ice and the abrasion resistance are improved as the orientation of the concave portion is increased. In Examples 6 to 8, the width of the obtained elongated concave portion was changed by changing the diameter of the polyethylene fiber to be blended. Example 3 and 6-
8 shows that when the orientation angle is the same, the effect is more remarkable when L / W is larger.
It can be seen that the effect is more remarkable when it is within the preferred range.

[0039]

According to the tire of the present invention, since the concave portions are oriented within 45 degrees to the left and right with respect to the circumferential direction, the performance on ice is excellent, and the surface of the concave portions is covered with a resin layer. Therefore, the abrasion of the water channel edge portion and the water channel retention during load input are also excellent.

[0040]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a state of orientation of voids in a cut surface of a tread.

[Explanation of symbols]

 a Orientation angle

Claims (6)

[Claims] The tread portion is made of foamed rubber, and when the foamed rubber is cut substantially parallel to the tire grounding surface, a plurality of elongated concave portions coated with resin are present on the cut surface, A pneumatic tire characterized in that 80% or more of the concave portions are oriented within 45 degrees with respect to the circumferential direction of the tire within the cut plane. 2. The pneumatic tire according to claim 1, wherein the orientation of the elongated concave portion is within 35 degrees with respect to the circumferential direction of the tire. 3. An average width (W) of the elongated concave portion is 500.
The air according to claim 1 or 2, wherein the ratio L / W of the average width (W) to the maximum length (L) in the longitudinal direction is 3 or more. Containing tires. 4. A tire in which a tread portion is made of foamed rubber, and a ground contact portion after traveling includes at least a long concave portion whose inner wall is coated with a resin, wherein 80% or more of the long concave portion is: A pneumatic tire characterized by being oriented within 45 degrees with respect to the circumferential direction of the tire. 5. The pneumatic tire according to claim 4, wherein the orientation of the elongated concave portion is within 35 degrees from the equatorial plane of the tire. 6. An average width (W) of the elongated concave portion is 500.
The air according to claim 4 or 5, wherein the ratio L / W between the average width (W) and the maximum length in the longitudinal direction (L) is 3 or more, and 3 μm or less. Containing tires.