JP2000062407A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wet performance from the traveling initial stage to the traveling final stage by using a rubber composition containing fiber in which a foaming agent is contained in a tread. SOLUTION: Polymer obtained by adding a foaming agent to polyvinyl-alcohol polymer, the vinylalcohol unit of which is 50 mol or more and the average polymerization degree of which is 1000, and the saponification degree is under 80% is used as a raw material in the fiber used. The spun-out fiber is not subject to treatment for applying water resisting property such as formal formation, acetal formation or the like. Mixing of a foaming agent contained water soluble fiber preferably ranges from 1 pt.wt. to 40 pts.wt. to 100 pts.wt. of rubber component, and further preferably it ranges from 2 pts.wt. to 30 pts.wt.. The length of the foaming agent containing short fiber is preferably 10 mm or less, and further preferably it is 5 mm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having improved wet performance from the beginning of running to the end of running without impairing wear resistance.

[0002]

2. Description of the Related Art Tire slip during running in the rain is extremely dangerous, and various measures such as improvement of tread rubber and improvement of patterns have been made in order to avoid danger. Also, on snow,
Studless tires that have improved running performance on ice have also undergone remarkable improvements in recent years. The improvement of such performance on rainy weather, snow, and ice depends on how to remove the water film formed between the tire and the road surface, but it is effective to make a groove in the tire circumferential direction to remove the water film. Further, the area ratio of the pattern circumferential direction groove is improved and the fine groove called a sipe is formed. However, as the groove area increases, the steering stability on dry road surfaces (dry steering stability) tends to decrease, so it is not possible to increase the groove area unnecessarily for the purpose of removing the water film between the road surface and the tires. It had the drawback of not having it.

On the other hand, it has been found that it is effective to use a soft rubber for the tread as compared with an ordinary tire in order to improve the performance in rainy weather, snow, and ice, but when the rubber is soft, it is abrasion resistant. However, there is a limit to softening the rubber physical properties because of problems such as deterioration of steering stability and deterioration of pattern rigidity and block rigidity.

Further, the tread has a multi-layered structure for the purpose of ensuring rainy running, and a relatively soft rubber having a high coefficient of friction when wet is used on the outside of the tread that comes in contact with the road surface. Has also proposed a tread having a so-called cap / base structure in which rubber with high rigidity is arranged, but the friction coefficient cannot be sufficiently increased because the thickness of the base rubber is limited, or There may be problems such as the deterioration of steering stability due to softness not being compensated by the hardness of the base rubber.In addition, wear progresses and the highly rigid rubber of the base tread is exposed, and when it is extremely wet. However, there was a problem that the friction coefficient of was decreased.

As a means for solving the above problems, JP-A-9-
No. 193614 discloses an invention in which a tread rubber contains a water-soluble fiber. In this invention, the water-soluble fiber embedded in the rubber dissolves in water and a fine groove is formed in the melted part, so that it is possible to generate a microflow between the road surface and the tire, so the tire friction coefficient on ice There was an effect of improving.

However, if the amount of fiber is increased in order to further enhance the microflow effect, the rubber becomes too hard so that the performance on ice is not so improved, and the inside of the rubber that is not exposed on the surface becomes too hard. Was. Further, since a groove having a water-soluble fiber diameter (fiber thickness) or more cannot be obtained, there is only means for increasing the fiber diameter in order to increase the groove diameter, and a groove diameter of substantially φ50 μm or more is obtained. It was difficult.

Further, although the invention described above includes the invention in which the water-soluble fiber is contained in the foamed rubber, temperature distribution occurs during tire vulcanization, so that a uniform foaming ratio can be obtained in the rubber thickness direction. Not only is it difficult, but in order to secure a certain foaming rate, it was necessary to strictly control the maturity of raw rubber, moisture during storage, temperature control, etc.

[0008]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a pneumatic tire with improved wet performance from the beginning of running to the end of running without impairing wear resistance.

[0009]

Therefore, the present inventors have found that the above-mentioned drawbacks can be improved by incorporating a foaming agent into the water-soluble fiber, and have arrived at the present invention.

That is, the present invention has the following configuration. (1) A pair of bead portions, a toroidal carcass extending over both bead portions, at least two belt layers in the crown portion of the carcass, and a tread portion positioned on the outer peripheral side of the belt layers. A tire having sidewall portions on the left and right of the tread portion,
A pneumatic tire comprising a rubber composition containing fibers containing a foaming agent in the tread. (2) On the outer side of the belt layer, there is at least one belt reinforcing layer formed by being endlessly spirally wound so as to be substantially parallel to the tire circumferential direction, and the belt reinforcing layer is a belt. The pneumatic tire according to (1) above, wherein the pneumatic tire is arranged on the entire part and / or on both ends. (3) The pneumatic tire according to any one of (1) or (2) above, wherein the fiber containing the foaming agent is a short fiber. (4) The foaming agent-containing fiber contains 0.5 to 100 parts by weight of a foaming agent per 100 parts by weight of resin in the fiber, according to any one of (1) to (3) above. Pneumatic tire. (5) The rubber composition used for the tread is a matrix rubber containing a rubber component composed of at least one selected from natural rubber and diene synthetic rubber, and a rubber component 100.
The pneumatic tire according to any one of (1) to (4) above, which contains 1 part by weight to 40 parts by weight of the blowing agent-containing fiber per part by weight. (6) The pneumatic tire according to any one of (1) to (5) above, wherein the matrix rubber further contains a foaming aid. (7) The pneumatic according to any one of (1) to (6), wherein the tread has two or more layers, and at least one layer of the tread contains the foaming agent-containing fiber. tire. (8) The pneumatic tire according to the above (7), wherein the rubber composition containing the foaming agent-containing fiber is used in the tread inner layer. (9) The pneumatic tire according to any one of (1) to (8), wherein the foaming agent-containing fiber is a water-soluble fiber.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the present invention is not particularly limited, but is preferably selected from natural rubber and diene synthetic rubber.
Specifically, butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene rubber (SBR), etc. are mentioned. In addition, considering the improvement of tire performance on snow and ice, in order to lower the elastic modulus at low temperature, BR
Is preferably contained in an amount of 20% by weight or more. These rubber components may be used alone or in combination of two or more.

The material of the fiber used in the present invention is not particularly limited, and well-known materials such as polyvinyl alcohol, polyester, nylon, polyethylene, polypropylene, etc. may be mentioned, but the fiber material softens and foams during tire vulcanization. It is preferable that the foaming of the agent is not hindered. Among them, blending a water-soluble fiber can effectively soften only the rubber surface when the tire is used (particularly in rainy weather), and a long water channel is formed to improve the performance on ice. Polyvinyl alcohol (hereinafter, abbreviated as PVA) is preferable because it can improve low-temperature water solubility by adjusting the molecular structure while maintaining a high fiber elastic modulus that affects block rigidity.

Generally, PVA fibers exhibit water-soluble properties when the degree of saponification is lowered, but in the present invention, a polyvinyl alcohol-based polymer having a vinyl alcohol unit of 50 mol or more and an average degree of polymerization of 1000 and a saponification degree of less than 80% is foamed. The polymer to which the agent was added was used as a raw material. A fiber that has not been subjected to a treatment for imparting water resistance such as formalization or acetalization to the spun fiber was used.

As the units other than the vinyl alcohol unit and the vinyl acetate unit, units that inhibit the crystallinity of PVA such as ethylene, allyl alcohol, itaconic acid, acrylic acid and maleic anhydride are preferable.

Next, the manufacturing method will be briefly described. First, a foaming agent AD is added to a polyvinyl alcohol polymer having a vinyl alcohol unit of 75 mol% and a vinyl acetate unit of 25 mol% and an average degree of polymerization of 500 and a saponification degree of 75%.
CA is added and dimethyl sulfoxide (DMSO) is mixed, and degassing is sufficiently performed under reduced pressure of nitrogen substitution to prepare a 45% dimethyl sulfoxide (DMSO) solution. This spinning dope was extruded from a nozzle in the same manner as ordinary polyvinyl alcohol spinning, and acetone / DMSO at 2 ° C was used.
After stretching 4.5 times in a mixed solution of (weight ratio: 95: 5), DMSO was sufficiently removed in acetone, and
Fibers were obtained by drying at 0 ° C., and then cut into desired lengths to obtain short fibers. The polyvinyl alcohol fiber is one that dissolves in water at 5 ° C.

In the present invention, the amount of the foaming agent-containing water-soluble fiber is 1 to 4 parts by weight per 100 parts by weight of the rubber component.
It is preferably in the range of 0 parts by weight, more preferably 2 parts by weight to 30 parts by weight. When the amount of fiber is less than 1 part by weight, it becomes difficult to secure high performance on rainy weather, on snow and on ice, and when it exceeds 40 parts by weight, it becomes difficult to uniformly disperse short fibers in rubber.

The length of the foaming agent-containing short fibers is preferably 10 mm or less, more preferably 5 mm or less. If the length of the fiber is longer than 10 mm, the fibers may be entangled with each other to lower the dispersibility in the rubber.

Further, the diameter of the fiber is 0.01 mm to 0.1 m depending on the size of the long voids in the vulcanized rubber composition.
It is preferably m.

The foaming agent contained in the fiber is, for example,
Dinitropentamethylenetetramine (DPT), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivative,
Oxybisbenzenesulfonylazo compound, (OBS
H), sodium bicarbonate, ammonium carbonate, nitrososulfonylazo compound, N, N ',-dimethyl-N,
N'-dinitrosophthalamide, toluenesulfonyl hydrazide, P-toluenesulfonyl semicarbazide,
P, P'-oxy-bis (benzenesulfonyl semicarbazide) etc. are mentioned. Among these foaming agents, considering the manufacturing process, dinitropentamethylenetetramine (DPT) and azodicarbonamide (ADCA) are preferable, and azodicarbonamide (ADCA) is particularly preferable. These may be used alone or in combination of two or more.

The form of the foaming agent is not particularly limited and can be appropriately selected from particulate, liquid and the like depending on the purpose, but uneven distribution and foaming of the foaming agent in the foaming agent-containing water-soluble fiber. From the viewpoint of preventing unevenness and efficiently forming long bubbles having a uniform cross-sectional shape in the longitudinal direction in a state without being crushed, liquid or fine particles are preferable. The average particle size of the foaming agent particles is 0.1
To 10 μm is preferable, and 0.1 μm to 3 μm is more preferable.

As the content of the foaming agent, resin 1 of fiber is used.
The amount is preferably 0.5 to 100 parts by weight, more preferably 0.5 to 6 parts by weight, per 100 parts by weight.
0 parts by weight, particularly preferably 1 part by weight to 30 parts by weight. When the content of the foaming agent is more than 100 parts by weight, the amount of the foaming agent which is a foreign material is increased with respect to the fiber, and many yarn breakages occur during the production of the fiber, which is not preferable in terms of production. In addition, 0.
If the amount is less than 5 parts by weight, the volume expansion of the water-soluble fiber portion, which is the object of the present invention, after vulcanization is small, and a sufficient effect may not be expected.

The foaming aid used in the present invention may be used in combination with the foaming agent in the water-soluble fiber, but it is limited to the range in which foaming does not occur during the production of the foaming agent-containing fiber. Thus, when the foaming aid is used in combination with the foaming agent, all the foaming agents contained in the water-soluble fiber can be efficiently foamed,
Although it is advantageous in that it does not cause unevenness of foaming, the foaming auxiliary temperature is preferably added to the matrix rubber because the foaming initiation temperature is lowered and more accurate temperature control is required.

Examples of the foaming aid include urea, zinc stearate, zinc benzenesulfonate, zinc benzenesulfinate, zinc white, and other foaming aids used in the production of ordinary foaming products. Among these, urea, zinc stearate, zinc benzenesulfonate and the like are preferable, and 1
They may be used alone or in combination of two or more.

The foaming agent-containing fiber referred to here is mixed into the tread rubber of the tire during kneading of the rubber, but when the tire is vulcanized at a high temperature, the foaming agent inside foams. As a result, the tire after vulcanization does not have a fiber form, but shows a form as if hollow fibers were contained in the matrix rubber. Therefore, when this air bubble portion is exposed on the tread surface, it becomes a long cylindrical groove, which effectively acts to remove the water film existing between the tire ground contact surface and the road surface, and when it rains or snows. It will be possible to greatly improve the performance on ice. Furthermore, the detachment of fibers,
Alternatively, the dissolution can ensure a sufficient size as the water film removal path.

In addition to the above, the rubber composition used for the tread of the tire of the present invention includes fillers, vulcanizing agents, vulcanization accelerators, antioxidants, softening agents, zinc oxide, stearic acid, antioxidants. , Additives such as an ozone deterioration inhibitor, which are usually used in the rubber industry, can be appropriately blended.

The pneumatic tire of the present invention uses a rubber composition in which a tread is mixed with fibers containing a foaming agent. When the tread is composed of two or more layers, it is preferably used for at least one layer, and further for the rubber composition of the inner layer.

When the fibers are blended, the tread rubber can be made very hard. Moreover, the fibers are not detached and are not dissolved in the tire surface to maintain the hardness of the rubber without being dissolved, and the fibers are detached or melted when exposed to the tire surface, and the detached portion or the dissolved portion is Since a large number of narrow grooves that allow micro-flow of water are developed, the wet performance of the tire can be improved even though the rubber is hard.

Further, by using the rubber composition containing the foaming agent-containing fiber for the inner layer of the tread having a multi-layered structure, the steering stability can be ensured by being supported by the hard inner layer in the early stage of running of the tire, and the abrasion can be prevented. When the inner layer portion of the tread containing fibers is exposed on the tire surface, the fibers are detached,
Due to the grooves developed on the surface by melting, it becomes possible to maintain or even improve the wet performance of the tire from the middle of the row to the end of the row.

In the present invention, the tread has a multi-layered structure, and by adjusting the blending amount of the fibers in each tread layer and the content of the foaming agent in the fibers, the tread is desired in accordance with the progress of wear of the tire. It is also possible to secure wet performance and wear resistance.

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples without departing from the gist thereof.

In the examples, parts and% mean parts by weight and% by weight unless otherwise specified. Various measurements were made by the following methods.

(1) Tensile Stress of Rubber Composition The tensile stress of the rubber compositions of Examples 1, 2 and 3 and Comparative Examples 1 and 2 was partially taken out from the unvulcanized rubber used for the tread of each example. A sheet sheet having a thickness of about 2 mm is vulcanized with a vulcanization mold having a thickness of 2 mm, and a width of 5 mm, a thickness of 2 mm, and a length of 20 using a spectrometer manufactured by Toyo Seiki Co., Ltd.
The dynamic storage elastic modulus (E ′) of the rubber composition measured at an initial tension of 150 g / mm ² , a dynamic strain of 1%, a frequency of 50 Hz and a temperature of 25 ° C. was determined for each mm test piece, and the rubber of Comparative Example 1 as a control was obtained. The composition was represented by an index with E'of the composition being 100. The larger the index, the higher the tensile stress and the higher the so-called block rigidity, which tends to increase the steering stability of the tire, but simply increasing E ′ of the rubber composition lowers the performance on ice. Tensile stress of the rubber compositions of Examples 4 and 5 and Comparative Examples 3 and 4 was 10 mm when the sheets were taken out from the unvulcanized rubber used for the tread of each example and partially sheeted to a thickness of about 10 mm. After vulcanizing with the vulcanizing mold, the vulcanized rubber composition having both sides sliced to have a thickness of 2 mm was immersed in water at room temperature for about 30 minutes to completely dissolve the fibers, and the width was 5 mm, and the thickness was 2 mm. For a test piece having a length of 20 mm, a spectrometer manufactured by Toyo Seiki Co., Ltd. was used, and an initial tension of 150 g / mm ² , a dynamic strain of 1%, a frequency of 50 Hz,
E ′ of the rubber composition measured at 25 ° C. was determined and expressed by an index with E ′ of the rubber composition of Comparative Example 3 of control being 100. The larger the index, the higher the tensile stress and the higher the so-called block rigidity, which tends to increase the steering stability of the tire, but simply increasing E'of the rubber composition lowers the WET performance of the tire.

(2) On-ice Performance The on-ice performance of Examples 1, 2, and 3 and Comparative Examples 1 and 2 was 500 when a test tire was mounted on a passenger car having a displacement of 1500 CC.
After traveling for km, the tire was locked by depressing the brake at a speed of 20 km / hr under the condition of the outside temperature of 0 to -3 ° C, and the distance until the tire was stopped was measured. The braking distance of the control tire of Comparative Example 1 was set to 100, and the braking distance of the comparative tire was divided by the braking distance of the control tire.
Indexed by the following formula. Braking distance index on ice = {(braking distance of control tire) / (braking distance of test tire)} × 100 The larger the index, the better the performance on ice.

3) WET Performance The WET performances of Examples 4 and 5 and Comparative Examples 3 and 4 are 20,000 when test tires are mounted on a passenger car having a displacement of 1500 CC.
After running for km, on the test course, four test tires were mounted on a passenger car, and two test drivers carried out actual vehicle running on a wet road surface. Driving performance, braking performance, steering response, and controllability during steering. WET
The steering stability was evaluated. The results were expressed in terms of feeling with the tire of Comparative Example 3 as a control. In addition,
Plus (minus) 1 and 2 are levels that are slightly better (or slightly worse) than the control, and scores of plus or minus 2 are levels at which the difference can be seen by general drivers. Plus (minus) 3, 4 and 5 are significantly superior (or inferior to the control) to the control, and there is a level difference that even ordinary drivers can recognize the difference.

The blowing agent-containing fibers used in the examples of the present invention are 10 denier (35 μm) thick PVA fibers.

18 are obtained in Examples 1, 2 and 3 and Comparative Examples 1 and 2.
5 / 70R13 and its structure is as shown in FIG. That is, with a pair of bead portions, a toroidal carcass extending over both bead portions, a tread portion located at the crown portion of the carcass, and a sidewall portion of the carcass, and a belt inside the tread portion. It has a radial structure with layers. In this tire, the carcass ply cord is arranged at an angle of substantially 90 degrees with respect to the circumferential direction of the tire, and the driving number is 5
The number is 0/5 cm, and has the same structure and pattern as a normal studless tire. The rubber composition (tread rubber) of the tread portion was prepared according to Table 1, respectively.

[0037]

[Table 1] 1: SBR # 1500 (trademark manufactured by JSR Corporation) 2: BR01 (trademark manufactured by JSR Corporation) 3: cast 7H (trademark manufactured by Tokai Carbon Co., Ltd., N ₂
SA 126m ² / g) 4: Seast 9 (trademark Tokai Carbon Co., Ltd., N ₂
SA 143m ² / g) 5: Nipseal AQ (trademark manufactured by Nippon Silica Industry Co., Ltd., N ₂ SA 200m ² / g) 6: Si69 (trademark Degussa AG) 7: Diphenylguanidine 8: Dibenzothiazyl disulfide 9: Bis (3-Triethoxysilylpropyl) tetrasulfide 10: dinitrosopentamethylene tetramine

Comparative Example 1 In Comparative Example 1, the tread rubber of Example 1 of JP-A-9-193613 was used as the tread rubber, and 10 parts by weight of PVA fiber containing no blowing agent was kneaded with 100 parts by weight of the rubber. It was mixed in the process, extruded like a normal tread rubber, attached to a tire, and vulcanized. The obtained tire was used as a control.

Comparative Example 2 In Comparative Example 2, a tire was manufactured using the same rubber composition as in Comparative Example 1 except that the amount of PVA fiber was doubled. When the amount of fibers is large, the tensile stress of the rubber composition is increased, and the tire performance on ice is deteriorated.

(Example 1) In Example 1, a foaming agent-containing PVA fiber containing 15% by weight of the amount of fiber resin mixed with a foaming agent was prepared.
A tire was produced in the same manner as in Comparative Example 1 except that a rubber composition obtained by kneading a foaming agent and an equivalent weight of a foaming aid in a matrix rubber was mixed as a tread rubber by mixing in a part by weight kneading step. The amount of fibers in the rubber is almost the same as in Comparative Example 1, but the tensile stress of the rubber is rather reduced, and the on-ice performance of the tire is significantly improved as compared with the control.

(Example 2) In Example 2, the blowing agent-containing PVA fiber prepared in Example 1 was mixed in a kneading step of 20 parts by weight per 100 parts by weight of the rubber component, and the blowing agent and the equivalent weight of the blowing aid were added. A tire was produced in the same manner as in Comparative Example 1 except that the agent was kneaded in the matrix rubber. Although the amount of fibers in the rubber is almost the same as that of Comparative Example 2, the performance on ice of the tire is significantly improved as compared with the control, although the tensile stress of the rubber is significantly increased.

Example 3 In Example 3, the foaming agent-containing PVA fiber prepared in the same manner as in Example 1 except that the content of the foaming agent was changed to 3 parts by weight per 100 parts by weight of the resin was 100 parts by weight of the rubber component. A tire was produced in the same manner as in Comparative Example 1 except that 10 parts by weight of each part were mixed in the kneading step, and the blowing agent and the equivalent amount of the foaming aid were kneaded in the matrix rubber. It can be seen that even when the amount of the foaming agent in the rubber is small, the braking performance on ice is improved.

(Examples 4, 5 and Comparative Examples 3, 4) The tires of Examples 4, 5 and Comparative Examples 3, 4 were 185 / 70R.
13 and its structure is as shown in FIG. That is, with a pair of bead portions, a toroidal carcass extending over both bead portions, a tread portion located at the crown portion of the carcass, and a sidewall portion of the carcass, and a belt inside the tread portion. It has a radial structure with layers. The difference from FIG. 1 is a cap / base structure in which the tread portion has two layers. As the tread rubber of the cap portion, a rubber composition having a composition shown in Table 2 is commonly used in each of Comparative Examples and Examples. Were prepared according to Table 3, respectively. In this tire, the angle of the carcass ply cord is arranged at an angle of 90 degrees with respect to the circumferential direction of the tire, and the driving number is 50 pieces / 5 cm, and has the same structure and pattern as a normal studless tire. .

[0044]

[Table 2] * 1: BR01 (trademark manufactured by Nippon Synthetic Rubber Co., Ltd.) * 2: Si69 (trademark manufactured by Degussa AG) * 3: Nocrac 6C (trademark manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
* 4: Nox Cellar DM (trademark Ouchi Shinko Chemical Industry Co., Ltd.)
* 5: NOXCELLER CZ (trademark Ouchi Shinko Chemical Industry Co., Ltd.)
Made)

[0045]

[Table 3] 1: SBR # 1500 (trademark manufactured by JSR Corporation) 2: cast 7H (trademark manufactured by Tokai Carbon Co., Ltd., N ₂
SA 126m ² / g) 3: Nipseal AQ (trademark manufactured by Nippon Silica Industry Co., Ltd., N ₂ SA 200m ² / g) 4: Si69 (trademark Degussa AG) 5: Diphenylguanidine 6: Dibenzothiazyl disulfide 7: Bis (3-Triethoxysilylpropyl) tetrasulfide 8: dinitrosopentamethylene tetramine

Comparative Example 3 In Comparative Example 3, 5 parts by weight of PVA fiber containing no foaming agent was mixed in a normal base rubber in a kneading step per 100 parts by weight of a rubber component, and extruded in the same manner as a normal tread rubber, It was attached to a tire and vulcanized.

Comparative Example 4 In Comparative Example 4, a tire was produced in the same manner as in Comparative Example 3 except that the amount of PVA fiber was doubled with respect to the rubber composition of Comparative Example 3. When the amount of the water-soluble fiber increases, the tensile stress of rubber increases and the WET performance of the tire deteriorates.

(Example 3) In Example 3, the blowing agent-containing PVA fiber containing 15% of the amount of the fiber resin produced in Example 1 was mixed with the blowing agent in an amount of 5 parts by weight per 100 parts by weight of the rubber component. A tire was produced in the same manner as in Comparative Example 3 except that the foaming agent and an equivalent weight of the foaming auxiliary agent were mixed and kneaded in the rubber. Although the amount of fibers in the rubber is almost the same as in Comparative Example 3,
The rubber tensile stress after immersion in water was rather reduced, and the WET performance of the tire was significantly improved compared to the control.

(Example 4) In Example 4, the blowing agent-containing PVA fiber prepared in Example 1 was mixed in a kneading step of 10 parts by weight per 100 parts by weight of the rubber component to give a foaming agent and an equivalent weight of a foaming aid. A tire was produced in the same manner as in Comparative Example 3 except that was kneaded in matrix rubber. The amount of fibers in the rubber is the same as in Comparative Example 4, but the tensile stress of the rubber after soaking in water does not increase so much, and the WET performance of the tire is significantly improved compared to the control (Comparative Example 3). .

[0050]

The microflow effect of the water-soluble traces, which is a characteristic of the water-soluble fiber, is further enhanced, and since this can be achieved with a small amount of fiber, the effect of preventing the rubber from becoming hard can be obtained. Further, since only the fiber portion is foamed during rubber vulcanization, it is possible to obtain a microflow diameter suitable for desired tire performance without significantly changing the rubber physical properties by adjusting the amount of the foaming agent and selecting the fiber diameter. Become.

[Brief description of drawings]

FIG. 1 is an example of a tire of the present invention.

FIG. 2 is an example of a tire of the present invention.

[Explanation of symbols]

1: Pneumatic tire 2: Carcass ply 3: Belt 4, 4 ': Tread part 5: Sidewall part 6: Belt reinforcement layer 7: Bead core 8: Bead filler

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B60C 11/00 B60C 11/00 B C08J 5/04 CEQ C08J 5/04 CEQ 9/00 CEQ 9/00 CEQ C08L 7/00 C08L 7/00 9/00 9/00 // C08K 7/02 C08K 7/02

Claims (9)

[Claims] 1. A pair of bead portions, a toroidal carcass extending over both bead portions, at least two belt layers in a crown portion of the carcass, and a tread portion positioned on the outer peripheral side of the belt layers. And a sidewall portion on the left and right of the tread portion, wherein the rubber composition containing a foaming agent-containing fiber is used for the tread. 2. The belt reinforcing layer has at least one belt reinforcing layer formed outside the belt layer by being endlessly wound in a spiral shape so as to be substantially parallel to a tire circumferential direction. The pneumatic tire according to claim 1, wherein the belt is arranged on the entire belt portion and / or both end portions. 3. The pneumatic tire according to claim 1, wherein the foaming agent-containing fiber is a short fiber. 4. The foam-containing fiber is a resin 1 in the fiber.
The pneumatic tire according to any one of claims 1 to 3, which contains 0.5 to 100 parts by weight of a foaming agent per 00 parts by weight. 5. The rubber composition used for the tread is at least one selected from natural rubber and diene synthetic rubber.
5. A matrix rubber containing a rubber component consisting of seeds, and 1 to 40 parts by weight of a foaming agent-containing fiber per 100 parts by weight of the rubber component, according to any one of claims 1 to 4. Pneumatic tire. 6. The pneumatic tire according to claim 1, wherein the matrix rubber further contains a foaming aid. 7. The tread comprises two or more layers, and the rubber composition forming at least one layer of the tread contains the foaming agent-containing fiber, according to any one of claims 1 to 6. Pneumatic tire described. 8. The pneumatic tire according to claim 7, wherein the rubber composition containing the foaming agent-containing fiber is used in an inner layer of a tread. 9. The pneumatic tire according to any one of claims 1 to 8, wherein the foaming agent-containing fiber is a water-soluble fiber.