JP2000191832A - Rubber composition, vulcanized rubber and tire using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition and a vulcanized rubber capable of effectively being used in a pneumatic tire and its tread rubber which meet both of the braking performance on a rainy weather road surface and the handling safety on a dry road surface. SOLUTION: A pneumatic tire uses a rubber composition comprising a water soluble resin having a melting point of 120-200 deg.C, particularly the water soluble resin containing a blowing agent in the tread rubber to form cells of a continuous length enveloped in the water soluble resin layer in the tread vulcanized rubber. The tire having such a construction can form effectively increased micro-drainage conduits on the surface of the tread, and simultaneously can retain a high tread rigidity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition, a vulcanized rubber and a pneumatic tire using the same, and more particularly, to a pneumatic tire excellent in both braking performance on rainy roads and steering stability on dry roads. The present invention relates to a tire, a rubber composition and a vulcanized rubber which can be suitably used for a tread of the tire.

[0002]

2. Description of the Related Art In general, when pneumatic tires accumulate on the road surface, the coefficient of friction between the tires and the road surface is greatly reduced, the braking distance is increased, and an accident is caused. Demands have been increasing in recent years. Conventionally, pneumatic tires have been formed with a drain groove in order to eliminate water on the tire contact surface, and it is known that the braking performance on a rainy road surface as a tire varies greatly depending on the arrangement and volume of the groove. I have. For this reason, many tread grooves have been devised in consideration of other performances of the tire. However, when the volume of the tread groove is increased, the braking performance on a rainy road surface is improved, but the tread rigidity and the effective ground contact area of the tire are reduced, so that the steering stability on a dry road surface tends to be reduced. As a pneumatic tire with improved performance on ice, Japanese Patent Application Laid-Open No.
JP-A-613, JP-A-9-216970, JP-A-10-237226 and the like describe tires in which tread rubber is compounded with water-soluble short fibers. However, in these cases, although the braking performance on icy and snowy roads and the braking performance on rainy roads have a certain effect, if the blending amount of the short fibers is increased, the adverse effect on the rubber workability and the rubber properties is adversely affected. Due to the large size, the effect was not always sufficient, and the steering stability on a dry road had little or no improvement effect on the steering stability. on the other hand,
From the viewpoint of tire running stability, further improvement in braking performance on icy and snowy roads and rainy roads has been demanded, and at the same time, further improvement in steering stability on dry roads has been strongly demanded. ing.

[0003]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a pneumatic tire which satisfies both the high level of braking performance on rainy roads and the steering stability on dry roads required by the market. It is an object of the present invention to provide a rubber composition and a vulcanized rubber which can be effectively used as a tire tread rubber.

[0004]

SUMMARY OF THE INVENTION In the present invention, as a result of studying to achieve both the drainage property and the tread rigidity having the above relationship, the tread rubber of the pneumatic tire has an adhesive property with the rubber. In addition, the present inventors have found that a tire having excellent braking performance on rainy roads and steering stability on dry roads can be obtained by the presence of a specific water-soluble resin containing bubbles in a certain range, and completing the present invention. Reached. That is, means for solving the above problems are as follows. (1) A rubber composition comprising a matrix rubber containing at least one rubber component selected from natural rubber and diene-based synthetic rubber, and a water-soluble resin having a melting point of 120C to 200C. (2) A rubber composition comprising a matrix rubber containing at least one rubber component selected from natural rubber and a diene-based synthetic rubber, and a water-soluble resin containing a foaming agent. Here, the melting point of the water-soluble resin is 120 ° C.
Preferably it is 200 ° C. It is preferable that the foaming agent is previously contained in the water-soluble resin, but a part of the foaming agent may be added alone as a rubber compounding agent. In the rubber compositions of the above (1) and (2), the water-soluble resin is preferably polyvinyl alcohol. The water-soluble resin is preferably a short fiber. Further, the water-soluble resin may contain a water-insoluble component, but is not particularly limited as long as it is a resin that is water-soluble as a whole. (3) The present invention also provides a vulcanized rubber containing a matrix rubber and a water-soluble resin layer containing bubbles. The vulcanized rubber is obtained by vulcanizing the rubber composition of (1) or (2). Here, it is preferable that the bubbles in the vulcanized rubber exist in a long shape. Further, the foaming rate of the rubber is preferably 10% or less. (4) The present invention also relates to a tire having a pair of bead portions, a carcass connected to the bead portions in a toroidal shape, and a belt portion and a tread portion for tightening a crown portion of the carcass. Is a pneumatic tire in which at least the rubber at the ground contact portion is the vulcanized rubber according to the above (3). (5) The present invention further provides a tire having a pair of bead portions, a carcass connected to the bead portions in a toroidal shape, a belt portion for tightening a crown portion of the carcass, and a tread portion. The present invention also provides a pneumatic tire in which the rubber is the vulcanized rubber described in the above (3). In the tires of (4) and (5) above, it is preferable that the bubbles in the tread portion or the tread base rubber exist in a long shape and are oriented in the tire circumferential direction.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition of the present invention comprises a specific water-soluble resin, particularly a water-soluble short fiber having a melting point of 120 to 200 ° C. The pneumatic tire of the present invention using such a rubber as a tread has many micro-groove-shaped voids due to water dissolution or desorption of water-soluble fibers on the tread surface at the time of tire wear, and with high orientation. It is formed. These micro-grooves are thought to efficiently remove water on the road surface to the main groove portion (so-called conventional drainage pattern portion) on the ground contact surface, and in particular, brake on a low friction coefficient road surface with a high accident rate. It has the effect of shortening the distance. On the other hand, regarding the tread rigidity, in the vicinity of the tread surface, although the resin is softened by the dissolution of the resin during running of the tire, the movement of the tread rubber block as a whole is suppressed by the constraint of the matrix rubber inside the block by the adhered resin. Therefore, dry road maneuverability is improved. In particular, responsiveness to handling, behavior stability at the time of lane change, and the like are improved.

Further, when the water-soluble resin layer in the tread contains bubbles, on the rainy road surface, due to detachment of the resin, a micro-volume of a volume corresponding to the sum of the volume of the detached resin and the volume of the contained bubbles. Since the drainage channel is formed, the volume of the micro drainage channel is increased as compared with the case where the water-soluble resin is simply mixed, and the braking performance on a rainy road surface can be further improved. In particular, when there are long air bubbles coated with a water-soluble resin in the ground portion of the tire tread rubber, or even if each air bubble itself is not long, a large number of independent air bubbles are formed in the fibrous resin layer in the longitudinal direction. When the air bubbles are scattered, the volume of the micro drainage channel on the tread surface increases, so that the braking performance on a rainy road surface is significantly improved.

Further, the rubber composition containing the water-soluble resin or the water-soluble resin containing a foaming agent in advance causes adhesion of the rubber composition to the matrix rubber by melting the resin by heating in the vulcanization step. The interfacial adhesion between the rubber and the fiber has the effect of suppressing block deformation and increasing the stability of dry road driving. That is, if the fiber and the rubber are not bonded, a gap is generated at the fiber / rubber interface at the time of input, and it is difficult to exhibit tread rigidity. In order to further increase the adhesiveness at the interface between the water-soluble resin and the rubber, the resin or the water-soluble fiber may be, for example, one that has been treated in advance with an adhesive liquid. A silane coupling agent may be added to the rubber to improve the adhesion between the rubber and the resin. The type of the silane coupling agent is not particularly limited, but among them, bis (3-triethoxysilylpropyl) is preferred. ) Tetrasulfide and 3-trimethoxysilylpropyl-benzothiazole-tetrasulfide are preferred.
In this case, the addition amount of the silane coupling agent is
The amount is preferably 0.5 to 20 parts by weight, particularly preferably 1 to 10 parts by weight based on 0 parts by weight. When compounding a silane coupling agent,
Even if the fiber does not melt, high adhesiveness can be exhibited, but by combining both, stronger adhesion can be obtained.

[0008] By the way, in conventional short-fiber compound rubber for tread, kneading of unvulcanized rubber, extruding workability,
In terms of tire performance or cost, the amount of fibers is industrially limited, and thus there is a limit to increase in the volume of the micro drainage channel. However, in the present invention, by increasing the apparent volume by forming bubbles in the water-soluble resin layer in the vulcanized rubber, the surface micro drainage volume, which has a large effect on rainy road surface braking, is reduced in workability. Etc. can be greatly increased without deteriorating. In this case, the bubbles are preferably formed in the vulcanized rubber in a long shape. That is, in the conventional foamed rubber tread, there is no connectivity of the spherical bubbles, and since the bubbles are not dispersed in a long shape, the drainage property of the tread surface is low. Further, even if the foaming ratio is increased for maintaining or improving drainage, the tread rigidity of the block is greatly reduced. On the other hand, in the present invention, when air bubbles are held in a water-soluble resin having a higher elastic modulus than rubber, the concentration of deformation in the air bubbles can be particularly suppressed, and a decrease in the stability of the dry road operation can be reduced. Can be. However, when the foaming ratio of the tread rubber is larger than 10%, the block rigidity is inevitably reduced as compared with the conventional tire, and the dry road steering stability tends to be reduced. Therefore, it is preferable to adjust the setting of the foaming rate of the tread rubber according to the type, purpose, and member of the tire to be used within the range of 10% or less. Further, the foaming rate of the tread rubber of the pneumatic tire in the present invention is preferably 10% or less. That is, as described above, the tire according to the present invention is excellent in both braking performance on rainy roads and steering stability on dry roads, but especially when importance is placed on steering stability on dry roads, the top tread rubber is used. Preferably, the non-foamed (foaming rate: 0%) rubber composition is used. In particular, when importance is placed on braking performance on rainy roads, it is preferable to use a foamed rubber composition having a foaming ratio of 3 to 10%. The foaming rate here includes all cells such as long closed cells and spherical closed cells mixed in the vulcanized rubber, and the foaming rate Vs is Vs = (ρ ₀ /
ρ ₁ -1) × 100 (%). Ρ ₁ is the density of the foamed rubber (g / cm ³ ), and ρ ₀ is the density of the solid phase portion of the foamed rubber (g / cm ³ ).

[0009] In the tread rubber of the pneumatic tire of the present invention, particularly when air bubbles are present in the water-soluble resin, the air bubbles may be connected in the fibrous resin layer to form a tubular shape. Alternatively, a plurality of closed cells may be dispersed in the fibrous resin. Here, since the water-soluble resin dissolves on the tread surface, the apparent volume of the water-soluble resin containing air bubbles becomes important in order to improve braking performance on rainy road surfaces. The water-soluble resin used above preferably has a melting point of 120C to 200C. That is, especially when the fiber is blended as a short fiber, the melting point needs to be 120 ° C. or higher in order to maintain the fibrous form in the unvulcanized rubber. If the melting point is lower than 120 ° C., the rubber is melted during the kneading and extruding steps, so that the fiber shape cannot be maintained, and it is difficult to form a drainage channel on the tread surface, and the braking performance on a rainy road surface decreases, Further, the tread block rigidity is also reduced, and the steering stability on the dry road is reduced. In addition, at the time of compounding the water-soluble resin with the rubber, it is not limited at which stage of rubber kneading, but especially when a water-soluble short fiber is used, a stage at which it melts. That is, contamination at the initial mastication stage should be avoided as much as possible. In this specification, the melting point of the water-soluble resin is measured as a melting peak temperature using, for example, a differential scanning calorimeter (DSC) measuring device.

On the other hand, the reason why the melting point of the water-soluble resin is set to 200 ° C. or lower is that the resin is melted or softened during vulcanization,
This is because a water-soluble resin containing a bubble portion can be easily formed in the vulcanized rubber by combination with a foaming agent. That is,
By mixing a water-soluble resin and a foaming agent into an unvulcanized rubber, and further melting the resin during vulcanization, the gas generated from the foaming agent is transferred to a water-soluble resin having a lower viscosity than the matrix rubber. At the very least, after vulcanization, the desired vulcanized rubber can be obtained by causing bubbles to be present in the solidified water-soluble resin again. However, if the water-soluble resin does not melt during vulcanization, the gas generated from the foaming gas does not migrate into the resin.
Also, even if the water-soluble resin is previously hollow,
Air bubbles cannot be retained due to the vulcanization pressure. However, it is not always possible to use any temperature below 200 ° C., and vulcanization conditions (temperature,
Pressure, time, etc.) must be adjusted so that the water-soluble resin or fiber is melted. In addition, even if the melting point of the water-soluble resin is higher than the vulcanization temperature, a certain amount of predetermined bubbles can be obtained even when the melting point peak is broad and the melting point start temperature is equal to or lower than the vulcanization temperature. In order to form the encapsulated water-soluble resin in the vulcanized rubber, and also to exhibit strong and adhesive properties with the rubber, the melting point of the water-soluble resin is preferably equal to or lower than the vulcanization temperature of the rubber, and particularly preferably 130 to 1
A range of 80 ° C. is preferred.

In the vulcanized rubber obtained by using such a water-soluble resin, air bubbles may exist as closed cells in the rubber, but from the viewpoint of improving tire performance, as many air bubbles as possible are soluble in the rubber. It is preferable to be present in the resin layer from the viewpoint that the amount of anisotropic bubbles can be increased. As a technique for this, it is preferable to mix a water-soluble resin or fiber containing a foaming agent in advance with the unvulcanized rubber to cause a foaming reaction during vulcanization. The method of adding the foaming agent to the water-soluble fiber in advance is not particularly limited. For example, the foaming agent is mixed with the raw material resin of the water-soluble fiber, and the fiber is formed at a temperature at which the foaming reaction hardly occurs. It is preferable to perform hot stretching. The foaming reaction temperature varies depending on the type of the foaming agent and the foaming auxiliary, but the foaming agent having a relatively high foaming temperature is contained in the fiber. In this case, it becomes easy to cause the foaming reaction of the foaming agent in the fiber to occur selectively during vulcanization. Further, it can also be obtained by mixing a foaming agent in the middle of the process of producing a water-soluble fiber and then spinning under conditions that do not cause a foaming reaction.

Next, in the rubber composition of the present invention, a rubber composed of at least one selected from natural rubber and diene-based synthetic rubber is used as the rubber component. And any rubber commonly used as such, for example, styrene-butadiene copolymer rubber, polyisoprene rubber, cis-1,4-polybutadiene, ethylene-propylene-diene copolymer rubber, butyl rubber and the like. These rubbers can be used alone or as any blend. Further, the foaming agent that can be used in the present invention is not particularly limited, but dinitrosopentamethylenetetramine (DPT), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivative, oxybisbenzene Sulfonyl hydrazide (OBSH) and the like can be mentioned, and among them, azodicarbonamide (ADCA) is preferable in consideration of production processability. In particular, when a foaming agent is contained in the fiber in advance, it is preferable to reduce the particle diameter as much as possible from the viewpoint of operability in fiber production. Further, the compounding amount of the foaming agent used in the rubber composition of the present invention is preferably 0 to 5 parts by weight, particularly preferably 0 to 3 parts by weight based on 100 parts by weight of the rubber component. In the above rubber composition, there are no particular restrictions on the components other than those described above, and carbon black, process oil, zinc oxide, stearic acid, vulcanizing agents, vulcanization accelerators, aging agents commonly used in the rubber industry. You may mix | blend an inhibitor, an ozone deterioration inhibitor, etc.

When a water-soluble resin containing a foaming agent in advance is used in the rubber composition of the present invention, the ratio of the resin component to the foaming agent is 150 parts by weight or less, preferably 100 parts by weight of the resin. It is preferable to contain 0 to 100 parts by weight, more preferably 0 to 60 parts by weight of a foaming agent. If the amount is more than 150 parts by weight, yarn breakage occurs frequently during the fiber production process, and it becomes difficult to produce fibers. Further, when it is necessary to add a foaming aid to accelerate the foaming reaction during rubber vulcanization, it is preferable to directly blend a predetermined amount of the foaming aid into the rubber composition. A foaming aid may be contained in the fiber as long as the foaming reaction does not occur. As foaming aids, urea, zinc stearate,
Auxiliaries used in the production of normal foamed rubber products, such as zinc benzenesulfinate and zinc white, are preferably used,
Others may be used.

Next, the components of the water-soluble resin in the present invention are not particularly limited. However, in order to develop a high friction coefficient on all road conditions, a high water-solubility is required even at a low temperature close to 0 ° C. It has mechanical properties necessary for rubber kneading, and is preferably, for example, a polyvinyl alcohol (PVA) fiber having a low saponification degree. The water-soluble temperature of the water-soluble resin or the fiber is preferably 10 ° C. or lower, particularly preferably 5 ° C. or lower. The water-soluble resin is preferably used as a short fiber. The diameter of the fiber,
Although the length is not particularly limited, it is preferable that the fiber diameter is smaller from the viewpoint of improving the tire braking performance, because when the same amount is blended, the number of grooves on the tire surface increases and the groove dispersibility becomes better. However, if the fiber is too thin in the production of fibers, thread breakage frequently occurs and the rubber scouring workability also deteriorates. The fiber diameter at the time of compounding is preferably 10 to 100 μm, particularly preferably 15 to 50 μm. In general, the fiber length is preferably longer from the viewpoint of improving the tire braking performance. However, in actuality, the longer the fiber is, the more easily the indentation due to the pattern in the tire vulcanizing kettle is likely to occur. Cannot be long. For this reason, the water-soluble resin has a fiber length of 1 to 10 mm, particularly 2 mm.
〜5 mm is preferred.

When the amount of the water-soluble resin used in the present invention is less than 1 part by weight per 100 parts by weight of the rubber component, the effect of improving the performance is small. 2 to 15 parts by weight, preferably 3 to 15 parts by weight, because such problems as poor workability during rubber extrusion (rough skin) and cracks in the tire tread occur.
10 parts by weight are preferred. Furthermore, the rubber composition containing the water-soluble resin can control the directionality of the water-soluble resin or the fiber by orienting the water-soluble fiber in one direction in a rubber extruding step. When used, it is particularly preferable to orient the water-soluble fibers in the tire circumferential direction because the water rejection to the rear side in the tire rotation direction in the ground contact surface is improved.

In the pneumatic tire of the present invention, the rubber containing the water-soluble resin is generally applied to rubber in contact with the ground, but may be used as a top tread or as a base rubber having a so-called cap / base structure. You may. When used as a base rubber, particularly high block rigidity is required, so it is desirable to set the foaming rate low, and specifically, a foaming rate of 0 to 6% is preferred. In this case, not only the stability on the dry road of the tire is improved, but also when the base rubber is exposed due to abrasion, the surface fibers dissolve and the reduction in the braking performance on rainy roads can be suppressed.

[0017]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited by these examples. <Various Measurement Methods> Various measurements on the water-soluble fiber, the rubber composition, and the test tire were performed according to the following methods. (1) Measurement of Water-Soluble Fiber Diameter Twenty locations of the fiber were randomly selected, the diameter was measured with an optical microscope, and the average value was taken as the fiber diameter. (2) Measurement of water dissolution temperature of water-soluble fiber A fiber suspended at a load of 2 mg / denier is put in water,
The temperature was raised from around 0 ° C at a rate of 2 ° C per minute, and the water temperature at the time of dissolution was taken as the water dissolution temperature. (3) Evaluation of rubber scouring workability The scouring workability of the unvulcanized tread rubber at the time of tire production was evaluated according to the following three-grade criteria of ◎, 〇, and △. ◎ Level not causing heavy problems 〇: Partially poor dispersion of fibers (lumps having a diameter of less than 5 mm) △: Failure of fibers in many places (lumps having a diameter of 5 mm or more)

(4) Evaluation of Driving Stability on Dry Road of Tire On a test course, two test drivers ran an actual vehicle, and comprehensively evaluated driving, braking, steering wheel responsiveness, and controllability during steering. And the steering stability was evaluated. Each tire of Comparative Example 1 and Comparative Example 5 was represented by an index when the tire was 100. The higher the value, the better. (5) Evaluation of the braking performance of the tire on a rainy road surface After mounting the tire on a passenger car, traveling 100 km on a dry road surface and 10 km on a wet road, performing a preliminary break-in, and then performing a water depth of 2 m.
m, and the brake was depressed at a speed of 60 km / hr to lock the tire, and the distance until the tire stopped was measured. The result is the reciprocal of the distance.
And each tire of Comparative Example 5 was set to 100 and the index was displayed.
The larger the value, the better the braking performance on a rainy road surface. For tires in which the sample rubber was applied to the base rubber, the test tires were mounted on a
After running for m times and confirming the exposure of the base rubber, the above test was performed.

<Production Example of PVA Fiber Prototype> Next, a method for producing the foaming agent-containing PVA fiber used in Examples and Comparative Examples will be described. (1) Sample A A saponification degree of 70 mol% of a vinyl alcohol unit, 30% of a vinyl acetate unit, and a polymerization degree of 600.
Mol% of PVA and dimethylsulfoxide (DMSO) were mixed and dissolved under stirring at 90 ° C. for 12 hours under a reduced pressure nitrogen atmosphere of 100 Torr or less, so that PVA was 40%
A DMSO solution was prepared. A predetermined amount of azodicarbonamide (ADCA) particles were added to this solution, and stirring was continued for 4 hours to obtain a mixed solution in which the blowing agent was uniformly dispersed. This mixture was extruded through a nozzle having a diameter of 0.2 mm from an extruder set at 90 ° C., wet-spun in a mixed solution bath of acetone / DMSO (weight ratio 85/15) kept at 2 ° C., and fixed. . Further, the spun fiber is drawn in a mixed solution of acetone / DMSO (weight ratio 98/2), and then the DMSO is extracted and removed in heated acetone.
The fiber was dried with a hot air drier at 80 ° C. to obtain a foaming agent-containing fiber, which was cut into a length of 3 mm. Degree of saponification of the obtained fiber 71
%, Melting point: 173 ° C. The water dissolution temperature was 2 ° C., and the water solubility was excellent at low temperatures. (2) Sample B In the production of the sample A, the same procedure as in the sample A was performed except that no blowing agent ADCA particles were added.

(3) Sample C PVA and 92% by mole of 92 mol% of vinyl alcohol units and 8% of vinyl acetate units, and having a degree of polymerization of 600 and a saponification degree of 92 mol% were mixed in the same manner as in Example 1. . A water-soluble short fiber containing a foaming agent was prepared in the same manner as in Example 1 except that methanol was used instead of acetone in this mixed solution. The obtained fiber has a degree of saponification of 91%, a melting point of 210 ° C. and a water dissolution temperature of about 10 which is worse than that of Example 1.
° C. (4) Sample D: 83 mol% of vinyl alcohol units, 17% of vinyl acetate units, and a degree of polymerization of 700 with a degree of polymerization of 700
Mol% of PVA and DMSO were mixed in the same manner as in Example 1. From this mixed solution, a water-soluble short fiber containing a foaming agent was prepared in the same manner as in Example 1. The saponification degree of the obtained fiber was 81%, the melting point was 190 ° C, and the water dissolution temperature was 5 ° C. (5) Sample E: 76 mol% of vinyl alcohol unit, 17% of maleic acid unit, 7% of vinyl acetate unit,
Maleic acid-modified PVA having a degree of polymerization of 500 and DMSO were mixed in the same manner as in Example 1. From this mixed solution, a water-soluble short fiber containing a foaming agent was prepared in the same manner as in Example 1.
The obtained fiber had a melting point of 160 ° C. and a water dissolution temperature of 2 ° C. or less.

<Manufacture of Test Tire> A rubber composition having the composition shown in Tables 1 to 3 was used as a top tread rubber or a base tread rubber and had a tire size of 205 /
A 60R15 radial tire for passenger cars was prototyped by a conventional method. The tread structure of this tire was a cap / base structure in which the height of the base rubber in the block was 50% of the total block height. The maximum temperature during vulcanization is 1
When the temperature during vulcanization of the tread portion was measured with a thermocouple at 80 ° C., the maximum temperature of the tread portion was also 180 ° C.

Comparative Examples 1 and 2 and Examples 1 to 4 Examples 1 to 4 are examples in which the rubber composition containing PVA fiber described in Table 1 of the present invention was applied to a top tread (cap rubber). For comparison, in Comparative Examples 1 and 2,
A rubber composition not containing PVA fiber was used. The obtained rubber composition and tire were evaluated for refining workability, vulcanized rubber foaming rate, braking performance on tires on rainy roads and steering stability on dry roads. The results are shown in Table 1. Comparative Example 1
Is an example in which a compound containing no PVA fiber and no foaming agent is used for the top rubber. Comparative Example 2 was obtained by adding a foaming agent to the compound of Comparative Example 1 and increasing the foaming rate of the tread rubber to 9%. However, although a large number of air bubbles were present on the tread surface, the block rigidity was low. Because of the decline, the block collapses greatly,
Both the wet braking performance and the dry road steering stability are lower than Comparative Example 1. Example 1 has a melting point of 173 ° C. in comparison with Comparative Example 1.
Of water-soluble short fibers. Both the wet braking performance and the steering stability on dry roads are improved compared to the comparative example.
Examples 2 to 4 are examples in which water-soluble short fibers in which the content of the foaming agent was varied at the ratios shown in Table 1 were blended. The melting point of this short fiber is 173 ° C.
The gas generated from the foaming agent migrated into the fibers whose viscosity decreased during vulcanization, and formed long bubbles after vulcanization. The long bubbles effectively increase the volume of the anisotropic void component functioning as a drainage channel on the tread surface, so that the braking performance on a rainy road surface is improved. At the same time, the handling stability of the dry road is maintained at a high level. When the surface of the test tire was observed, the water-soluble short fibers were dissolved by the water on the test road surface.

[0023]

[Table 1]

Note) * Blowing agent content: Resin part 1 in blowing agent-containing PVA fiber
1 part by weight of foaming agent with respect to 00 parts by weight 1) # 1500 manufactured by JSR Corporation 2) # 0120 manufactured by JSR Corporation (37.5% oil extension) 3) Seast 7H manufactured by Tokai Carbon Co., Ltd. 4) TMDQ: 2 5,2,4-trimethyl-1,2-dihydroquinoline polymer 5) IPPD: isopropyl-N'-phenyl-p-
Phenylenediamine 6) MBTS: bis- (benzothiazolyl-2) disulfide 7) DPG: diphenylguanidine 8) TBBS: Nt-butyl-2-benzothiazolylsulfenamide 9) benzenesulfinic acid manufactured by Otsuka Chemical Co., Ltd. Zinc 10) Urea / Zinc stearate (85/15) blend made by Otsuka Chemical Co., Ltd. 11) Prototype

Comparative Examples 3 and 4 and Examples 5 to 7 Examples 5 to 7 are the same as Example 2 except that
This is an example in which the compounded rubber composition in which the compounding amount of the fiber and the amount of the foaming aid accompanying the compounding amount were changed was applied to the top tread of a tire, and the same test as in Example 2 was performed. The results are shown in Table 2. In Examples 5 to 7, both the braking performance on rainy roads and the stability on dry roads are improved compared to Comparative Example 1.
When the amount of the foaming agent-containing water-soluble short fiber is increased to 20 parts by weight,
The dispersibility of short fibers was inferior, and the top tread became hard, so that the stickiness of the grip tended to decrease. In Comparative Example 3, a water-soluble short fiber having a high foaming agent content was blended, but the rubber foaming ratio was too high, and the rigidity of the block was reduced. Is declining. In Comparative Example 4, since the melting point of the water-soluble short fiber containing the foaming agent was too high at 210 ° C., the gas generated from the foaming agent could not be increased, and the gas was diffused into the rubber. Is higher than that of Comparative Example 1, but is not as high as that of Example 3 which differs only in the fiber melting point.
In addition, since there is no adhesiveness between the rubber and the fiber, the feeling of rigidity is insufficient. In addition, since the linearity is poor, the steering stability on a dry road is worse than in Comparative Example 1.

[0026]

[Table 2]

Examples 8 and 9 Examples 8 and 9 are the same as those of Example 3 except that the PV of melting point 173 ° C. was used.
PV with melting points of 190 ° C and 160 ° C instead of A fiber
The procedure was performed in the same manner as in Example 3 except that the A fiber was used. The results are shown in Table 3. It can be seen that both Example 8 and Example 9 are excellent in both braking performance on rainy roads and steering stability on dry roads.

[0028]

[Table 3]

Comparative Example 5 and Examples 10 to 12 Examples 10 to 12 are examples in which the foaming agent-containing PVA fiber-containing rubber composition shown in Table 4 of the present invention was applied to a base tread. Comparative Example 5 is an example in which a compound containing no PVA fiber and no foaming agent was used for the base tread rubber. The results are shown in Table 4. Example 10
In the case of No. 12, the driving stability of the dry road was significantly improved as compared with the case of Comparative Example 5, and it can be seen that the short fiber reinforcement of the base portion worked effectively. In addition, the wet braking performance after exposure of the base due to wear is greatly improved.

[0030]

[Table 4]

Note) 1) # 1500 manufactured by JSR Corporation 2) Seast 7H manufactured by Tokai Carbon Co., Ltd. 3) Nip Seal AQ manufactured by Nippon Silica Co., Ltd. 4) Bis (3-triethoxysilylpropyl) tetrasulfide 5) DPG: diphenylguanidine 6) DM: dibenzothiazyl sulfide 7) NS: N-tert-butyl-2-benzothiazyl-sulfenamide 8) zinc benzenesulfinate manufactured by Otsuka Chemical Co., Ltd. 9) urea manufactured by Otsuka Chemical Co., Ltd. / Zinc stearate (8
5/15) Blend 10) Prototype

[0032]

According to the present invention, an anisotropic micro drain is effectively formed on the tread surface by using a rubber composition containing a specific water-soluble resin containing a foaming agent as a rubber for a tread. It is possible to provide a pneumatic tire excellent in both braking performance on a rainy road surface and steering stability performance on a dry road surface because high tread rigidity can be maintained by adhesion between the resin and rubber. it can.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08J 9/04 101 C08J 9/04 101 C08K 5/16 C08K 5/16 C08L 9/00 C08L 9/00 29 / 04 29/04 B

Claims (13)

[Claims] 1. A rubber composition comprising a matrix rubber containing at least one rubber component selected from natural rubber and diene-based synthetic rubber, and a water-soluble resin having a melting point of 120 ° C. to 200 ° C. 2. A rubber composition comprising a matrix rubber containing at least one rubber component selected from natural rubber and a diene-based synthetic rubber, and a water-soluble resin containing a foaming agent. 3. A matrix rubber containing at least one rubber component selected from natural rubber and a diene-based synthetic rubber, a foaming agent and a melting point of 120 ° C.
And a water-soluble resin at a temperature of from 200 ° C to 200 ° C. 4. The rubber composition according to claim 1, wherein the water-soluble resin is polyvinyl alcohol. 5. The rubber composition according to claim 1, wherein the water-soluble resin is a short fiber. 6. The rubber composition according to claim 1, wherein the amount of the foaming agent is 5 parts by weight or less based on 100 parts by weight of the rubber composition. 7. A vulcanized rubber comprising a matrix rubber and a water-soluble resin layer containing air bubbles. 8. The vulcanized rubber according to claim 7, obtained by vulcanizing the rubber composition according to any one of claims 1 to 6. 9. The vulcanized rubber according to claim 7, wherein the bubbles are present in a long shape. 10. The vulcanized rubber according to claim 9, wherein the foaming rate is 10% or less. 11. A tire having a pair of bead portions, a carcass connected to the bead portions in a toroidal shape, a belt portion for tightening a crown portion of the carcass, and a tread portion. A pneumatic tire, wherein a part of the rubber is the vulcanized rubber according to any one of claims 7 to 10. 12. A tire having a pair of bead portions, a carcass connected to the bead portions in a toroidal shape, a belt portion for tightening a crown portion of the carcass, and a tread portion, wherein a tread base rubber is provided. 7 to 10
A pneumatic tire, which is the vulcanized rubber according to any one of the above. 13. The pneumatic tire according to claim 11, wherein the bubbles in the tread are present in a long shape and are oriented in the tire circumferential direction.