JP2003105116A - Unvulcanized rubber composition, vulcanized rubber composition and method for manufacturing the same, and tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vulcanized rubber composition suitable for use in structures required to be slip resistant on the ice, such as tires and tire treads excellent in removing water film generated on the ice without degradation in their wear resistance, high in friction coefficient when on the ice; a method for manufacturing the same; a tire using the same; and an unvulcanized rubber composition capable of producing the same. SOLUTION: The vulcanized rubber composition manufactured by this method contains tabular independent bubbles 12 covered by a resin-made protecting layer 20 and a rubber ingredient. A tire using the composition is also provided. The unvulcanized rubber composition contains at least a rubber ingredient, a resin ingredient, and a foaming agent, wherein at least part of the resin ingredient is tabular in shape.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a tire having a large coefficient of friction with ice and having excellent on-ice performance, an unvulcanized rubber composition suitable for a tread of the tire, and a vulcanized rubber composition. TECHNICAL FIELD The present invention relates to a rubber composition and a method for producing the same.

[0002]

2. Description of the Related Art Since spike tires have been regulated, tire treads have been actively researched in order to improve the braking / driving performance (ice performance) of tires on icy and snowy roads. On the ice and snow road surface, a water film is likely to be generated due to frictional heat between the ice and snow road surface and the tire, and the water film causes the friction coefficient between the tire and the ice and snow road surface to decrease. Therefore, the water film removing ability of the tread of the tire and the edge effect greatly affect the on-ice performance. Therefore, in order to improve the on-ice performance of the tire, it is necessary to improve the water film removing ability and the edge effect of the tread.

Therefore, there has been proposed a studless tire in which foamed rubber is used for the tread, and water running between the ice surface and the ground contact surface of the tread is removed to improve the running performance on ice. Further, in the field of this kind of tire, a method of forming independent bubbles like foamed rubber and a method of forming microscopic grooves on the surface are known as methods for improving the friction coefficient on ice. . As a method of forming a microscopic groove on a rubber surface, in Japanese Patent Application Laid-Open No. 4-38207, etc., by using a foamed rubber containing short fibers for the tread, the micro drainage groove is formed on the surface of the tread. Is described.

In this case, however, the short fibers are curled due to heat shrinkage or pushed into the sipes during mold vulcanization and bent, and even if the tread is worn by running, it is not substantially parallel to the worn surface. The short fibers are not easily separated from the tread, the micro drainage groove as originally intended cannot be efficiently formed, and the coefficient of friction on the ice and snow road surface is not sufficiently improved. Further, the separation of the short fibers largely depends on running conditions and the like, and the performance on ice cannot be reliably improved. Further, there is a problem that the micro drainage groove is crushed when the load applied to the tire is large.

Further, in JP-A-4-110212, etc., by dispersing hollow fibers in the tread, the water film existing between the ice and snow road surface and the tread is formed in the hollow portion of the hollow fibers. Tires that can be eliminated are disclosed. However, in the case of this tire, the hollow fiber is crushed by pressure, rubber flow, temperature, etc. during kneading and molding of the hollow fiber into rubber, and the hollow fiber may actually maintain a hollow shape. However, there is a problem in that the micro drainage channel cannot be efficiently formed, and the performance on ice is still insufficient.

Therefore, International Publication WO97 / 34776 proposes a technique for ensuring the exclusion of water by allowing long closed cells to be present in a tread rubber covered with a protective layer made of a resin. According to this technology, when the tread rubber is worn by running, a concave portion due to long closed air bubbles is formed on the ground contact surface, and this concave portion serves as a drainage channel to eliminate water in the ground contact surface and The friction coefficient with can be increased. In addition, since the resin protective layer covering the long closed cells suppresses the crushing of the concave portion, the excluded water is secured even under a high load. In other words, the technique was able to significantly improve the performance on tire ice.

In order to further improve the on-ice performance by using the technique described in the above-mentioned document, the bubble ratio in the tread rubber may be increased. By increasing the bubble ratio, the volume of the recessed portion on the tread surface is increased, so that the efficiency of removing water in the ground contact surface is improved and the performance on ice can be improved. That is, the higher the bubble rate, the higher the performance on ice. However, if the bubble ratio is increased, the distance between the bubbles is shortened correspondingly, leading to a decrease in wear resistance. Therefore, it is difficult to achieve both high performance on ice and wear resistance at a high level.

[0008]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems of the prior art. Specifically, the present invention, without reducing the wear resistance,
Suitable for a structure that has improved ability to remove the water film generated on ice, has a large coefficient of friction with an ice surface, and has a property that it is necessary to prevent slipping on ice, such as a tread of a tire having excellent ice performance. Vulcanized rubber composition and method for producing the same,
Moreover, it aims at providing the tire using the same. The present invention also provides an unvulcanized rubber composition that can be used for the production of the vulcanized rubber composition of the present invention.

[0009]

The above object can be achieved by the present invention described below. That is, the first aspect of the present invention is characterized in that at least a rubber component, a resin component, and a foaming agent are blended, and at least a part of the resin has a plate shape. It is a rubber composition. According to the first aspect of the present invention, the vulcanized rubber composition of the second aspect of the present invention can be produced by the method for producing a vulcanized rubber composition described below.

According to the unvulcanized rubber composition of the present invention, the gas produced by the foaming agent in the plate-like resin whose viscosity is lower than that of the rubber matrix during the vulcanization step is present in the rubber matrix. Vulcanization containing a rubber component and a plate-like closed cell provided with a protective layer made of the component of the plate-like resin at the interface between the rubber matrix and the gas, which is formed by collecting at least a part of the gas A rubber composition can be obtained. In the unvulcanized rubber composition of the present invention, in addition to a plate-shaped resin, when containing a long resin, the plate-shaped resin and the above-mentioned resin whose viscosity is lower than that of the rubber matrix during the vulcanization step. At the interface between the rubber matrix and the gas, which is formed by collecting at least a part of the gas existing in the unvulcanized rubber composition, such as the gas generated by the foaming agent in the long resin, the plate-like To obtain a vulcanized rubber composition containing a plate-like closed cell having a protective layer made of a resin, and a long closed cell having a protective layer made of the long resin, and a rubber component. You can

The melting point or softening point of the resin in the unvulcanized rubber composition of the present invention is preferably in the range of 70 to 200 ° C., and the rubber matrix of the rubber matrix when subjected to vulcanization is It is more preferable that the temperature is not higher than the maximum vulcanization temperature. The thickness of the plate-shaped resin in the unvulcanized rubber composition of the present invention is in the range of 0.1 to 100 μm,
The area of the plane portion is preferably in the range of 1 to 100 mm ² . Further, the resin is the rubber component 100.
It is preferably contained in an amount of 0.5 to 20 parts by mass with respect to parts by mass.

The resin in the unvulcanized rubber composition of the present invention is preferably at least one resin selected from the group consisting of polyethylene, polypropylene and polyvinylidene chloride.

A second aspect of the present invention is a vulcanized rubber composition comprising at least a plate-like closed cell covered with a protective layer made of a resin and a rubber component.

According to the second aspect of the present invention, for example, when this tread rubber is used as a rubber of a tire tread (tread rubber), when the tread rubber is worn by running, a concave portion due to plate-like closed cells appears on the ground contact surface. However, this concave portion functions as a drainage channel, drains water in the ground contact surface, and increases the coefficient of friction with the ice surface. Further, since the protective layer of the resin suppresses the crushing of the concave portion, the excluded water is secured even under a high load. At this time, since the plate-shaped closed cells form a deep concave portion from the tread surface of the tire toward the inside of the tire, it is possible to secure a large concave volume as compared with a mere spherical bubble or a long bubble. Even with the same bubble rate, high performance on ice can be achieved.

As described above, according to the second aspect of the present invention, the coefficient of friction with the ice surface is large and the ability to remove the water film generated on the ice is improved without impairing the wear resistance. It is possible to provide a vulcanized rubber composition suitable for a structure such as a tread of a tire having excellent on-ice performance that needs to suppress slip on ice. The vulcanized rubber composition of the present invention preferably further contains elongated closed cells covered with a protective layer made of a resin.

In the present invention, the rubber matrix refers to all the components except the resin in the unvulcanized rubber composition and the solid phase portion in the vulcanized rubber composition.

In the vulcanized rubber composition of the present invention, the resin forming the protective layer existing at the interface between the plate-like closed cells and the rubber matrix is at least selected from the group consisting of polyethylene, polypropylene and polyvinylidene chloride. Resin No. 1 is preferred. In the vulcanized rubber composition of the present invention, the bubble ratio Vs is 5
It is preferable to be in the range of -40%, and the ratio of the plate-like closed cells to all the contained cells is 5-95% by volume.
It is preferably within the range. The rubber component in the vulcanized rubber composition of the present invention is not particularly limited, but preferably contains at least one rubber selected from the group consisting of natural rubber and diene synthetic rubber, and as the diene rubber, , Styrene-butadiene copolymer (SBR) rubber, butadiene (BR) rubber, synthetic isoprene (IR) rubber, butyl rubber, halogenated butyl rubber, ethylene-propylene-diene terpolymer rubber, and the like.

A third aspect of the present invention is a kneading step of kneading a rubber matrix containing a rubber component and a foaming agent, and an unvulcanized rubber composition containing a resin component containing a plate-shaped resin, and the above-mentioned unvulcanized rubber composition. A heating step of heating the rubber composition,
An extrusion step of extruding the unvulcanized rubber composition, and a vulcanization step of vulcanizing the unvulcanized rubber composition, which is a method for producing a vulcanized rubber composition, wherein the vulcanization step comprises:
The method for producing a vulcanized rubber composition is characterized in that the viscosity of the resin becomes lower than the viscosity of the rubber matrix before the temperature of the rubber matrix reaches the maximum vulcanization temperature.

In the third aspect of the present invention, when the unvulcanized rubber composition that has undergone the kneading step, the heating step and the extruding step is vulcanized in the vulcanizing step, the rubber matrix is reached until the maximum vulcanizing temperature is reached. The viscosity of the resin becomes lower than that. On the other hand, the foaming agent starts the reaction, the gas diffuses into the rubber matrix, and the gas is distributed between the resin phase and the rubber matrix phase. Then, by collecting a part of the gas in the resin having the reduced viscosity, the phase of the resin becomes hollow, and plate-like closed cells having a protective layer made of the resin in the outer peripheral portion are formed.

As described above, according to the third aspect of the present invention, the ability to remove the water film formed on ice is improved without impairing the wear resistance, and the coefficient of friction with the ice surface is large. It is possible to produce the vulcanized rubber composition of the second present invention, which is suitable for a structure that needs to suppress slip on ice, such as a tread of a tire having excellent performance on ice.

In the method for producing a vulcanized rubber composition of the present invention, the maximum temperature of the unvulcanized rubber composition in the kneading step, the maximum temperature of the unvulcanized rubber composition in the heating step, and The maximum temperature of the unvulcanized rubber composition immediately after extrusion in the extrusion step is set below the melting point or softening point of the resin, and the maximum vulcanization temperature of the rubber matrix in the vulcanization step is the resin. Or higher than the melting point or softening point.

In the method for producing a vulcanized rubber composition of the present invention, the melting point or softening point of the resin is 70 to 20.
It is preferably in the range of 0 ° C. In the method for producing a vulcanized rubber composition of the present invention, the thickness of the plate-shaped resin is preferably in the range of 0.1 to 100 μm, and the area of the plane portion is preferably in the range of 1 to 100 mm ² . Also,
The unvulcanized rubber composition preferably contains the resin in an amount of 0.5 to 20 parts by mass based on 100 parts by mass of the rubber component.

In the method for producing a vulcanized rubber composition of the present invention, the resin is preferably at least one resin selected from the group consisting of polyethylene, polypropylene and polyvinylidene chloride, and the rubber component is Although not particularly limited, it is preferable to include at least one rubber selected from the group consisting of natural rubber and diene-based synthetic rubber.
Styrene-butadiene copolymer rubber, butadiene rubber,
Examples thereof include synthetic isoprene rubber, butyl rubber, halogenated butyl rubber, and ethylene-propylene-diene terpolymer rubber.

According to a fourth aspect of the present invention, a pair of bead portions, a carcass connected in a toroidal shape to the bead portions, a belt for tightening the crown portion of the carcass, and a belt radially outward of the belt. And a tread, wherein at least the tread contains the vulcanized rubber composition of the second aspect of the present invention.

According to the fourth aspect of the present invention, when the vulcanized rubber composition (tread rubber) of the tread is worn by running,
A recess formed by plate-like closed bubbles appears on the ground contact surface, and this recess serves as a drainage channel to eliminate water in the ground contact surface and increase the coefficient of friction with the ice surface. Further, since the protective layer of the resin suppresses the crushing of the concave portion, the excluded water is secured even under a high load. At this time, since the plate-shaped closed cells form a deep concave portion from the tread surface of the tire toward the inside of the tire, it is possible to secure a large concave volume as compared with a mere spherical bubble or a long bubble. Even with the same bubble rate, high performance on ice can be achieved. As described above, according to the fourth aspect of the present invention, a tire having an excellent ability to remove the water film formed on ice, a large friction coefficient with an ice surface, and an excellent performance on ice without impairing wear resistance. Can be provided.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The unvulcanized rubber composition, the vulcanized rubber composition and the method for producing the same, and the tire using the same in the present invention will be described in detail below.

(Unvulcanized Rubber Composition) The unvulcanized rubber composition of the present invention comprises at least a rubber component, a resin component and a foaming agent, and contains at least a part of the resin. It is characterized in that it has a plate shape. According to the unvulcanized rubber composition of the present invention, the vulcanized rubber composition of the present invention can be produced by the method for producing a vulcanized rubber composition described below. The unvulcanized rubber composition of the present invention further contains other components such as a foaming aid, if necessary.

1) Rubber Component The rubber component is not particularly limited, but preferably contains at least one rubber selected from the group consisting of natural rubber and diene synthetic rubber. Of course, only natural rubber may be included, only diene-based synthetic rubber may be included, or both may be included.

The diene synthetic rubber is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, styrene-butadiene copolymer (SBR) rubber and butadiene (BR). Examples thereof include rubber, synthetic isoprene (IR) rubber, butyl rubber, halogenated butyl rubber, and ethylene-propylene-diene terpolymer rubber. Among these diene-based synthetic rubbers,
It has a low glass transition temperature and a great effect on ice performance,
Cis-1,4-polybutadiene is preferable, and one having a cis content of 90% or more is particularly preferable.

When the vulcanized rubber composition comprising the unvulcanized rubber composition is used in a tread or the like, the rubber component preferably has a glass transition temperature of -60 ° C or lower. The use of a rubber component having such a glass transition temperature is advantageous in that the tread and the like maintain sufficient rubber elasticity even in a low temperature range and exhibit good on-ice performance.

2) Blowing agent Examples of the blowing agent include dinitrosopentamethylenetetramine (DPT) and azodicarbonamide (AD).
CA), dinitrosopentastyrene tetramine, benzenesulfonyl hydrazide derivative, oxybisbenzenesulfonyl hydrazide (OBSH), carbon dioxide generating ammonium bicarbonate, sodium bicarbonate, ammonium carbonate, nitrogen generating nitrososulfonyl azo compound, N, Examples thereof include N'-dimethyl-N, N'-dinitrosophthalamide, toluenesulfonyl hydrazide, P-toluenesulfonyl semicarbazide, P, P'-oxy-bis (benzenesulfonyl semicarbazide) and the like.

Of these foaming agents, dinitrosopentamethylenetetramine (DP
T) and azodicarbonamide (ADCA) are preferable,
Azodicarbonamide (ADCA) is particularly preferable. These may be used alone or in combination of two or more. The foaming agent allows the unvulcanized rubber composition to be foamed rubber (vulcanized rubber composition) having a high foaming rate.

3) Other components The above-mentioned other components can be used within a range that does not impair the object of the present invention. Examples thereof include carbon black and
Inorganic fillers such as silica and calcium carbonate; vulcanizing agents such as softening agents and sulfur; vulcanization accelerators such as dibenzothiazyl disulfide; N-cyclohexyl-2-benzothiazyl-sulfenamide, N-oxydiethylene-benzothiazyl- In addition to antioxidants such as sulfenamide; additives such as zinc oxide, stearic acid, and ozone deterioration inhibitor; and the like, various compounding agents ordinarily used in the rubber industry can be appropriately used. These may be used alone or in combination of two or more. In addition, in this invention, a commercial item can be used about these other components.

In the present invention, from the viewpoint of efficient foaming, it is preferable to use a foaming aid as the other component and to use the foaming aid in combination with the foaming agent. Examples of the foaming aid that can be used include urea, zinc stearate, zinc benzenesulfinate, zinc white, and the like, which are usually used in the production of foamed products. Among these, urea, zinc stearate, zinc benzenesulfinate and the like are preferable. These may be used alone or in combination of two or more.

4) Resin The resin (mainly a plate-shaped resin is referred to. When a long resin is included, both the plate-shaped resin and the long resin are included. Also includes them.
In the present invention, the same applies when simply saying "resin". )
As for the vulcanized rubber, the rubber matrix has thermal characteristics of melting (including softening) before reaching the maximum temperature of vulcanization when subjected to vulcanization. In the vulcanization step in the method for producing the composition, it is particularly preferable that the resin has thermal properties such that the viscosity of the resin becomes lower than the viscosity of the rubber matrix before the temperature of the rubber matrix reaches the maximum vulcanization temperature. preferable.

The term "maximum vulcanization temperature" as used herein means the maximum temperature reached by the rubber matrix in the vulcanization step in the section (Production method of vulcanized rubber composition) described later. For example, in the case where the vulcanization in the vulcanization step described later is mold vulcanization, the maximum temperature reached by the rubber matrix before the unvulcanized rubber composition enters the mold and is cooled after exiting the mold. Means The maximum vulcanization temperature is
For example, it can be measured by embedding a thermocouple in the rubber matrix. The viscosity of the rubber matrix means the flow viscosity, and the viscosity of the resin means the melt viscosity, which can be measured using, for example, a cone rheometer, a capillary rheometer, or the like.

The melting point or softening point of the resin is not less than the maximum temperature of the unvulcanized rubber composition in the kneading step,
The maximum temperature of the unvulcanized rubber composition in the heating step or higher, and the maximum temperature of the unvulcanized rubber composition immediately after extrusion in the extrusion step or higher, and vulcanization of the rubber component in the vulcanization step It is preferably below the maximum temperature.

The material of the resin is not particularly limited as long as it has the above-mentioned thermal characteristics, and can be appropriately selected according to the purpose. The resin component may be a single resin or a mixture of two or more thereof. However, when two or more resins are mixed, use of those having a melting point or a softening point close to each other is effective in setting vulcanization conditions. Is preferred. Preferable examples of the resin having the thermal characteristics include a resin made of a crystalline polymer whose melting point or softening point is lower than the maximum vulcanization temperature.

Taking the resin composed of the crystalline polymer as an example, the greater the difference between the melting point or softening point of the resin and the maximum vulcanization temperature of the rubber component, the greater the difference between the unvulcanized vulcanization step and the unvulcanized resin. Since the resin melts rapidly during the vulcanization of the rubber vulcanizate, the time when the viscosity of the resin becomes lower than the viscosity of the rubber matrix becomes earlier. Therefore, when the resin melts, the gas generated by the foaming agent or the like contained in the unvulcanized rubber composition moves and stays inside the resin having a lower viscosity than the rubber matrix. as a result,
The vulcanized rubber contains many closed cells covered with the resin.

On the other hand, when the melting point or softening point of the resin becomes too close to the maximum vulcanization temperature of the rubber matrix, the resin does not melt promptly in the initial stage of vulcanization in the vulcanization process, and the end of vulcanization occurs. To melt. At the final stage of vulcanization, a part of the gas generated by the foaming agent and the like contained in the unvulcanized rubber composition is taken in the vulcanized rubber and does not move or stay inside the melted resin. As a result, the retention of gas in the molten resin may become insufficient.

On the other hand, if the melting point or softening point of the resin becomes too low, the resin is melted by the heat at the time of kneading the unvulcanized rubber composition in the kneading step in the method for producing a vulcanized rubber composition described later. However, the resins are fused and the dispersibility is lowered in the kneading stage, the resin is divided into a plurality of pieces in the kneading stage, or the resin is melted into the vulcanized rubber composition to form a microscopic structure. It may be dispersed.

The upper limit of the melting point or softening point of the resin is not particularly limited, but is preferably selected in consideration of the above points, and is preferably lower than the maximum vulcanization temperature of the rubber matrix, It is more preferable that the temperature is 10 ° C. or higher, and even more preferable that it is 20 ° C. or lower.
The industrial vulcanization temperature of a rubber composition is generally about 200 ° C. at the maximum, but for example, the maximum vulcanization temperature is 2
When the temperature is set to 00 ° C, the resin is
Selected from those having a melting point or softening point of 200 ° C. or lower,
It is preferably 190 ° C. or lower, more preferably 180 ° C. or lower, still more preferably 170 ° C. or lower.

The melting point of the resin can be measured using a melting point measuring device known per se.
The melting peak temperature measured using a DSC measuring device can be used as the melting point. The softening point of the resin is
It can be measured according to JIS K7196-1991.

The resin may be formed of a crystalline polymer, may be formed of an amorphous polymer, or may be formed of a crystalline polymer and an amorphous polymer. However, in the present invention, it is preferably formed from an organic material containing a crystalline polymer in that the viscosity change occurs rapidly at a temperature at which there is a phase transition and the viscosity can be easily controlled. More preferably, it is formed only from the volatile polymer.

Specific examples of the crystalline polymer include polyethylene (PE), polypropylene (PP),
Polyolefins such as polybutylene; polyesters such as polybutylene succinate and polyethylene succinate;
Syndiotactic-1,2-polybutadiene (SP
B), polyvinyl alcohol (PVA), and other single-component polymers, and those having a melting point controlled to an appropriate range by copolymerization, blending, or the like can also be used. Among these crystalline polymers, polyolefins and polyolefin copolymers are preferable, polyethylene (PE) and polypropylene (PP) are more preferable because they are versatile and easily available, and polyethylene (PE) and polypropylene (PP) are preferable because they have a low melting point and are easy to handle. PE) is particularly preferred.

Examples of the non-crystalline polymer include polymethyl methacrylate (PMMA), acrylonitrile-butadiene-styrene copolymer (ABS), polystyrene (PS), polyvinyl chloride (PVC), polyacrylonitrile, and the like. Examples thereof include copolymers and blends thereof. These may be used alone or in combination of two or more. Further, a crystalline polymer and an amorphous polymer may be used in combination.

If desired, known additives may be added to the resin as long as the object of the present invention is not impaired.

The molecular weight of the material of the resin differs depending on the chemical composition of the material, the branching state of the molecular chain and the like and cannot be specified unconditionally, but generally, the resin is made of the same material. The higher the molecular weight, the higher the viscosity (melt viscosity) at a certain temperature. In the present invention, the molecular weight of the material in the resin is the viscosity at the maximum vulcanization temperature of the rubber matrix (flow viscosity).
It is more preferable to select the resin within a range that does not increase the viscosity (melt viscosity) of the resin.

In one test example, the resin is 1 to 2
In the case of polyethylene having a mass average molecular weight of about × 10 ^{5, the} unvulcanized rubber after vulcanization of the unvulcanized rubber composition is more than in the case of polyethylene having a mass average molecular weight of 7 × 10 ⁵ or more. A large amount of gas generated by the foaming agent contained in the composition was taken in the resin. This difference is presumed to be due to the difference in viscosity (melt viscosity) resulting from the difference in the molecular weight of polyethylene, which is the material of the resin.

The content of the resin in the unvulcanized rubber composition is the rubber component 1 in the rubber matrix.
0.5 to 30 parts by mass is preferable with respect to 00 parts by mass,
1.0 to 10 parts by mass is more preferable. Further, as the content of the plate-shaped resin in the unvulcanized rubber composition,
0.5 to 20 parts by mass is preferable, and 1 to 5 parts by mass is more preferable, relative to 100 parts by mass of the rubber component.

When the content of the resin is less than the above preferred range, the amount of gas taken in or retained in the protective layer (in the resin) in the vulcanized rubber composition is small, and the vulcanized rubber is concerned. When the composition is used for a tire tread or the like, the performance on ice may not be sufficiently improved. On the other hand, when the content exceeds the preferable range, the dispersibility of the resin in the unvulcanized rubber composition is deteriorated, and the workability in the extrusion step is deteriorated.
Inconvenience such as cracking of the tread may occur. On the other hand, when the content is within the above-mentioned preferred numerical range, it is preferable in that such a case does not occur. Further, when the content of the plate-shaped resin is small, the effects of the present invention may not be sufficiently exhibited, and the performance on ice may not be sufficiently improved.

Regarding the shape and size of the plate-shaped resin,
It is selected according to the shape and size of the plate-shaped closed cells to be finally formed. Therefore, the shape of the plate-shaped resin is not particularly limited, triangle, polygon such as quadrangle,
It may be circular, elliptical, star-shaped, or indefinite.

The thickness of the plate-shaped resin is 0.1 to
The range is preferably 100 μm, and is 10 to 90 μm.
It is preferably in the range of m. When the thickness of the plate-shaped resin is less than 0.1 μm, it is difficult to effectively take in the bubbles generated from the foaming agent, and the original shape such as bending or curling is formed before the vulcanization step. It is difficult to hold, and it becomes difficult to form recesses having an effective volume on the surface of the finally obtained vulcanized rubber composition,
Not preferable. On the other hand, if it exceeds 100 μm, the plate-like closed cells may become too large and cracks in the vulcanized rubber composition may start to grow, which deteriorates wear resistance, which is not preferable.

The area of the plane portion of the plate-shaped resin is
It is preferably in the range of 1 to 100 mm ² , and 1 to 2
The range of 0 mm ² is more preferable. If the area of the flat portion of the plate-shaped resin is less than 1 mm ² , the depth of the recess formed on the surface of the finally obtained vulcanized rubber composition is not sufficient, and it is difficult to secure the volume of the recess. Therefore, it is not preferable. On the other hand, if it exceeds 100 mm ² , the plate-like closed cells may become too large and cracks may start to grow in the vulcanized rubber composition, and the abrasion resistance may be impaired.

The long resin to be contained in the unvulcanized rubber composition, if necessary, may be a resin originally having a long form, or may be twisted so as to have a desired thickness.
And / or, it may be cut into a desired length to have a long shape. The fineness of the long resin is not particularly limited and may be appropriately selected depending on the purpose, but from the viewpoint of improving the performance on ice, 1 to
1100 dtex is preferable, and 2 to 880 dtex is more preferable.

The maximum length in the longitudinal direction of the long resin is not particularly limited and can be appropriately selected according to the purpose. Further, in order to form a long resin phase in the unvulcanized rubber composition before the vulcanization step, the form of the resin contained in the unvulcanized rubber composition in the kneading step is granular, The shape other than the long shape such as powder may be used. That is, even if a resin having a shape other than a long shape such as a granular or powdery shape is used, the conditions of the manufacturing process are appropriately controlled so that the shape of the resin finally becomes a long shape, or the physical properties of the material used are appropriately adjusted. Just select it. Details will be described later in the section (Method for producing vulcanized rubber composition).

(Vulcanized Rubber Composition) The vulcanized rubber composition of the present invention is characterized by containing at least plate-like closed cells covered with a protective layer made of a resin and a rubber component.

FIG. 1 is a schematic perspective view showing an embodiment of the vulcanized rubber composition of the present invention in a state where the surface is worn to some extent. The vulcanized rubber composition of the present invention, as shown in FIG.
In a vulcanized rubber matrix 18 containing a rubber component,
The plate-like closed cells 12 having a protective layer 20 are arranged in a dispersed state at the interface with the rubber matrix 18. In FIG. 1, the shape of the plate-like closed cells 12 exposed on the surface in the depth direction is represented by a dotted line (similar in FIGS. 2 and 3).

When the vulcanized rubber composition of the present invention is used as, for example, rubber of a tread of a tire (tread rubber), when the tread rubber is worn by running, the composition shown in FIG.
As shown in, a concave portion due to the plate-like closed bubbles 12 appears on the ground contact surface, and this concave portion functions as a drainage channel, drains water in the ground contact surface, and increases the friction coefficient with the ice surface. Further, since the protective layer 20 made of the resin suppresses the crushing of the concave portion, the excluded water is secured even under a high load.

FIG. 2 is a schematic perspective view showing another embodiment of the vulcanized rubber composition of the present invention in a state where the surface is worn to some extent. 2A, in the rubber matrix 18, as in FIG. 1, a protective layer 20 is formed at the interface with the rubber matrix 18.
2B is a vulcanized rubber composition in which the plate-like closed cells 12 having the following are arranged in a dispersed state, and the spherical closed cells 14 are also arranged in a dispersed state. FIG. The closed cells 16 are also vulcanized rubber compositions in a dispersed state. As described above, the vulcanized rubber composition of the present invention may include the closed cells other than the plate-like closed cells 12, such as the spherical closed cells 14 and the elongated closed cells 16.

FIG. 3 (a) is a schematic perspective view of a conventionally known vulcanized rubber composition in which only the spherical closed cells 14 are arranged in the rubber matrix 18, and the surface is worn to some extent. In the vulcanized rubber composition shown in FIG. 3 (a), each spherical closed cell 14 does not spread in the depth direction, and only concave portions appear on the surface. Figure 3
In (b), in addition to spherical closed cells 14, long closed cells 1
6 is a vulcanized rubber composition in which a rubber matrix 18 is arranged, and a schematic perspective view of a state where the surface is worn to some extent is shown. Also in the vulcanized rubber composition shown in FIG. 3B, each spherical closed cell 14 and each elongated closed cell 1
No. 6 does not spread in the depth direction, and only recesses are formed on the very surface.

That is, in the vulcanized rubber composition shown in FIGS. 3 (a) and 3 (b), each spherical closed cell 14
Also, the volume of each recess formed by each elongated closed bubble 16 is relatively small, and if the bubble rate is increased to improve the efficiency of removing water in the ground contact surface, the wear resistance will decrease.

The operation of the present invention will be described in more detail with reference to FIG. FIG. 4 (a) is a schematic cross-sectional view of the vulcanized rubber composition shown in FIG. 3 (a), in which the concave portions that contribute to the improvement of the water removal efficiency in the ground contact surface are spherical closed cells appearing on the surface. 1
4a, and the spherical closed cells 14b existing inside the vulcanized rubber composition do not participate in the removal of water in the ground contact surface. Since the volume of each recess formed by the spherical closed cells 14 is small, the total volume of the recesses appearing on the surface is also small.

FIG. 4 (b) shows that in order to improve the efficiency of removing water in the ground contact surface, individual bubbles are further enlarged from the vulcanized rubber composition shown in FIG. 4 (a). FIG. 3 is a schematic cross-sectional view of a vulcanized rubber composition having an increased bubble ratio, in which the concave portion due to the spherical closed cells 14a ′ that appears on the surface that contributes to the improvement of the water removal efficiency in the ground contact surface certainly has a large volume. There is. Therefore, although the total volume of the recesses appearing on the surface is also large, the spherical closed cells 14b ′ existing inside the vulcanized rubber composition still do not participate in the water removal in the ground contact surface, The volume of the voids increases in the vulcanized rubber composition as a whole. The larger the volume of the voids, the lower the wear resistance. Therefore, the vulcanized rubber composition shown in FIG. 4B also has poor wear resistance.

FIG. 4 (c) shows that the density of bubbles is further increased from the vulcanized rubber composition shown in FIG. 4 (a) in order to improve the water removal efficiency in the ground contact surface. FIG. 3 is a schematic cross-sectional view of a vulcanized rubber composition having an increased bubble ratio, in which the number of recesses due to the spherical closed cells 14a ″ appearing on the surface contributing to the improvement of the water removal efficiency in the ground contact surface is certainly increased. Therefore, although the total volume of the recesses appearing on the surface is also large, the spherical closed cells 14b ″ existing inside the vulcanized rubber composition still do not contribute to the removal of water in the ground contact surface. However, the volume of the voids increases in the vulcanized rubber composition as a whole. The larger the volume of the voids, the lower the wear resistance. Therefore, the vulcanized rubber composition shown in FIG. 4C also has poor wear resistance.

In the above description, the problem that the abrasion resistance is lowered by increasing the bubble ratio is exemplified by the vulcanized rubber composition shown in FIG. 3 (a) in which spherical closed cells are formed. However, the same applies to the vulcanized rubber composition shown in FIG. 3B in which the elongated closed cells 16 that do not spread in the depth direction are formed.

On the other hand, the vulcanized rubber composition of the present invention shown in FIG. 1 or FIG. 2 can effectively solve this problem. FIG. 4D is a schematic cross-sectional view of the vulcanized rubber composition of the present invention shown in FIG. Figure 4
As shown in (d), plate-like closed cells 1 appearing on the surface
With respect to No. 2, all the voids of the recesses that spread in the depth direction contribute to the improvement of the water removal efficiency in the ground contact surface. Therefore, the volume of each recess formed by the plate-shaped closed cells 12 is large, and the efficiency of removing water in the ground contact surface can be improved without increasing the bubble rate.

As described above, in the vulcanized rubber composition of the present invention, as shown in FIG. 2, the elongated closed cells 16 and the spherical closed cells 14 each covered with the protective layer made of resin are further added. It can also be included. In particular, the inclusion of the elongated closed cells 16 further reduces the collapse of the recess when a load is applied. In addition, the plate-shaped closed cells 12 are
It is difficult to increase the number numerically, and with only a small number of the plate-like closed cells 12, the distance between the recesses becomes large even when the surface is worn to some extent, and it is difficult to connect adjacent ones as drainage channels. On the other hand, by including the long closed cells 16 and the spherical closed cells 14, the volume of the concave portion related to the drainage water can be improved while maintaining the connection of the drainage channels. Regarding the preferable size of the long closed cells 16, paragraph No. 006 of JP-A No. 11-60811.
7 to paragraph number 0070.

The plate-like closed cells 12 and the elongated closed cells 16 in the vulcanized rubber composition of the present invention are covered with a protective layer made of a resin. The details of the specific material and the like of the resin forming the protective layer are as described in the above section (Unvulcanized rubber composition). The rubber matrix 18 in the vulcanized rubber composition of the present invention contains at least a rubber component, and further contains other various components remaining after the vulcanization step of the unvulcanized rubber composition. However, in the present invention, the term “rubber matrix” does not include plate-shaped closed cells and elongated closed cells.

The vulcanized rubber composition of the present invention shown in FIG. 1 contains, for example, before vulcanization, at least a rubber matrix containing a rubber component and a foaming agent, and a plate-shaped resin. As the plate-shaped closed cells 12 in this case, for example, a gas generated by the foaming agent in the plate-shaped resin having a viscosity lower than that of the rubber matrix during the vulcanization step and an unvulcanized rubber composition The outer peripheral portion is formed by collecting at least a part of the gas present therein, and has a protective layer made of the plate-shaped resin.

As the above-mentioned resin, the details of preferable physical properties, shape, content, specific materials and the like, and details of the rubber matrix containing the rubber component and the foaming agent are described in the above section (Unvulcanized rubber composition). It is as explained in.

In the vulcanized rubber composition of the present invention, the bubble ratio Vs is preferably in the range of 5 to 40%, more preferably in the range of 15 to 30%. Here, "the bubble ratio Vs" means the sum of the bubble ratios of all the closed cells, regardless of the plate-shaped closed cells 12, the spherical closed cells 14 and the elongated closed cells 16, and is expressed by the following formula (1). Can be calculated by

Vs = (ρ ₀ / ρ ₁ −1) × 100 (%) (1) In the above formula (1), ρ ₁ is a vulcanized rubber composition (foamed rubber).
Of represents a density ^{(g / cm 3), ρ} 0 represents the density of the solid phase portion in the vulcanized rubber composition (foam rubber) (g / cm ^3). The density of the vulcanized rubber composition (foamed rubber) and the density of the solid phase part in the vulcanized rubber composition (foamed rubber) were determined by measuring the mass in ethanol and the mass in air,
Calculated from this.

If the bubble ratio Vs is less than 5%, a sufficient water-exclusion function cannot be obtained for the water film generated due to the absolute lack of the volume of the concave portions due to the various bubbles, and the vulcanized rubber composition may be obtained. It may not be possible to sufficiently improve the performance on ice. On the other hand, if the bubble ratio Vs exceeds 40%,
Although the performance on ice can be improved, since the volume of bubbles in the vulcanized rubber composition becomes too large,
The wear resistance and fracture limit of the vulcanized rubber composition are lowered,
Not preferable in terms of durability. The bubble rate Vs is
The types and amounts of the various foaming agents described in the section (Unvulcanized rubber composition) described above, the types of the foaming aids to be combined,
The amount can be appropriately adjusted by appropriately selecting the amount, the compounding amount of the resin, and the like.

Although the spherical closed cells 14 are not an essential component of the present invention, according to the method for producing a vulcanized rubber composition of the present invention described later, the gas generated from the foaming agent collects in the resin,
A part of the gas is not taken into the resin, and is directly placed in the rubber matrix 18 in a dispersed state. In the present invention, the ratio of the plate-shaped closed cells 12 to all the contained bubbles (the plate-shaped closed cells 12, the spherical closed cells 14 and the elongated closed cells 16) is in the range of 5 to 95% by volume. It is more preferably within the range of 10 to 90% by volume, and even more preferably within the range of 20 to 50% by volume.

If the ratio is less than 5% by volume, the effect of increasing the volume of the concave portions appearing on the surface by providing the plate-like closed cells 12 is not sufficient, and if it exceeds 95% by volume, the spherical closed cells 14 are not formed. Since the ratio becomes small and it becomes difficult for the bubbles to connect the drainage channels when the surface is worn, the water removal function may not be sufficient, which is not preferable.
The shape of the plate-like closed cells 12 is not particularly limited, and other shapes such as a triangle, a polygon such as a quadrangle, a circle, an ellipse, a star, and the like,
It may be indefinite.

The thickness of the plate-like closed cells 12 is 0.1
It is preferable that it is in the range of
It is preferably in the range of 0 μm. Plate-shaped closed cells 12
Is less than 0.1 μm, the drainage performance may not be sufficient, which is not preferable. On the other hand, 500 μm
Above, it may be the point where cracks start to grow,
It is not preferable because the wear resistance is impaired.

The area of the plane portion of the plate-like closed cells 12 is preferably in the range of 1 to 100 mm ^2.
More preferably, it is in the range of 0 to 30 mm ² . If the area of the flat portion of the plate-like closed cells 12 is less than 1 mm ² ,
The depth of the recesses appearing on the surface of the vulcanized rubber composition is not sufficient, and it becomes difficult to secure the volume of the recesses, which is not preferable. On the other hand, if it exceeds 100 mm ² , cracks may start to grow and wear resistance is impaired, which is not preferable.

(Production Method of Vulcanized Rubber Composition) The production method of the vulcanized rubber composition of the present invention comprises a rubber matrix containing a rubber component and a foaming agent, and a resin component containing a plate-shaped resin. A kneading step of kneading the vulcanized rubber composition,
The method includes a heating step of heating the unvulcanized rubber composition, an extrusion step of extruding the unvulcanized rubber composition, and a vulcanization step of vulcanizing the unvulcanized rubber composition.

In the present invention, the kneading step is a step of kneading a rubber matrix containing a rubber component and a foaming agent, and an unvulcanized rubber composition containing a resin component containing a plate-shaped resin. The details of the rubber component, the foaming agent and the resin component in the unvulcanized rubber composition are as described in the above section (Unvulcanized rubber composition).

In the method for producing a vulcanized rubber composition of the present invention, the maximum temperature of the unvulcanized rubber composition in the kneading step, the heating step and the extruding step is set below the melting point or softening point of the resin. Preferably. By doing so, the shape of the plate-shaped resin or the like can be more reliably retained even in the unvulcanized rubber composition after the kneading step. When the maximum temperature of the unvulcanized rubber composition in the kneading step is a temperature exceeding the melting point or softening point of the resin, it becomes difficult for the resin to retain its shape, and the unvulcanized rubber composition It may not be possible to form a resin phase in the desired shape therein. in this case,
Even if the obtained vulcanized rubber composition is used for a tread of a tire or the like, the above-mentioned performance on ice cannot be sufficiently improved. On the other hand, the maximum temperature of the unvulcanized rubber composition in the kneading step does not occur when it is lower than the melting point or softening point of the resin, and the obtained vulcanized rubber composition is used for a tread of a tire or the like. Then, the performance on ice can be sufficiently improved.

In the present invention, it is preferable that the maximum temperature of the unvulcanized rubber composition in the kneading step, the heating step and the extruding step is set at 5 ° C. or more lower than the melting point or softening point of the resin. This is advantageous in that the phase of the resin can be stably formed in the unvulcanized rubber composition and the performance on ice can be effectively improved.

In the present invention, the above-mentioned kneading is not limited to the above-mentioned limitation, and the above-mentioned unvulcanized rubber composition may be used as long as the resin can retain or form a desired form and the dispersibility of the resin is good. There are no particular restrictions on various conditions such as the total input volume, the rotor rotation speed, the kneading temperature, the kneading time, and the kneading device, and they can be appropriately selected according to the purpose. The kneading device may be either a closed type or an open type,
A commercial item can be used conveniently.

In the present invention, the heating step is a step of heating the unvulcanized rubber composition that has been subjected to the kneading step, and the extrusion step is the unvulcanized rubber composition that has been subjected to the heating step. It is a step of extruding.

The heating temperature is generally 70
Is about 90 ° C, and the extrusion temperature is generally 90 ° C.
It is about 110 ° C.

An unvulcanized rubber composition containing the rubber matrix and the resin is subjected to the above-mentioned kneading step, heating step and extruding step to obtain a plate-like resin in the unvulcanized rubber composition. And so on.

In the unvulcanized rubber composition obtained above, the phase of the plate-like resin or the like formed in the unvulcanized rubber composition by the extrusion or the like is orientated generally parallel to the extrusion direction. However, in order to effectively achieve this, it is sufficient to control the fluidity of the rubber matrix within a limited temperature range. Specifically, in the rubber matrix, oil, liquid polymer It is preferable to add a processability improver or the like as appropriate to reduce the viscosity of the rubber matrix and increase its fluidity. In this case, the extrusion can be carried out extremely well, and ideally the plate-like resin phase can be oriented substantially parallel to the extrusion direction.

When a vulcanized rubber composition produced from an unvulcanized rubber composition in which the phase of the plate-shaped resin or the like is oriented substantially parallel to the extrusion direction is used for a tread of a tire, the orientation direction thereof is As the above, the following modes are preferable.
The planar portion of the plate-shaped resin is oriented in a direction substantially perpendicular to the surface that contacts the ground in the tread of the tire, to form a deep recess toward the inside of the tire from the tread surface of the tire, A large volume of the concave portion can be secured, and high performance on ice can be achieved. When the flat portion of the plate-shaped resin is oriented in the circumferential direction of the tire, drainage in the running direction of the tire is enhanced, and the performance on ice can be effectively improved.

When the long resin is contained in the unvulcanized rubber composition, the long resin may be added in a direction parallel to the surface of the tread of the tire that comes into contact with the ground, more preferably in the circumferential direction of the tire. It is preferable that the resin in the form of particles is oriented because drainage in the running direction of the tire is enhanced and the performance on ice can be effectively improved.

In the unvulcanized rubber composition, a well-known method can be adopted to orient the phases of the plate-shaped resin or the like in a certain direction. For example, as shown in FIG. ,
Examples include a method of extruding the plate-shaped resin 22 and the rubber matrix 18 that have undergone the kneading step and the heating step from the die 26 of the extruder whose flow passage cross-sectional area decreases toward the outlet.

Here, FIG. 5 is an explanatory view for explaining the principle of aligning the orientation of the resin in an unvulcanized rubber prepared by mixing only a plate-shaped resin as a resin component. More specifically, FIG. It is a schematic cross section in the extruded part front-end | tip of the extruder used in an extrusion process. In addition, in FIG. 5, as the plate-shaped resin 22, two kinds, linear and planar, are drawn. However, this is because the plate-shaped resin 22 is not oriented, and the planar portion is above and below in the drawing. This is because the flat portion does not appear in the drawing for the object oriented in the direction, and it looks like a line.

In this case, the plate-shaped resin 22 in the rubber matrix 18 before being extruded is such that the plane portions thereof are gradually aligned along the extrusion direction (arrow A direction) in the process of being extruded to the die 26. Then, when extruded from the die 26, the plane portions thereof are almost completely aligned in the extruding direction (direction A), and become substantially parallel as a whole. The degree of orientation of the plate-shaped resin 22 in the rubber matrix 18 changes depending on the degree of reduction of the flow passage cross-sectional area, the extrusion rate, the viscosity of the rubber matrix, and the like.

In the present invention, the vulcanization step is a step of vulcanizing the unvulcanized rubber composition which has undergone the extrusion step.
Vulcanization conditions and methods in the vulcanization step are not particularly limited and may be appropriately selected depending on the type of the rubber component and the like, but mold vulcanization is preferable when manufacturing a tire tread. .

The vulcanization temperature is preferably selected so that the maximum vulcanization temperature of the rubber matrix during vulcanization is equal to or higher than the melting point or softening point of the resin. When the maximum vulcanization temperature is lower than the melting point or softening point of the resin, the resin is not sufficiently melted / softened, and gas existing in the unvulcanized rubber composition such as gas generated by the foaming agent In some cases, the resin cannot be retained in the resin, and the closed cells having a desired shape cannot be efficiently formed in the rubber. The device for performing the vulcanization is not particularly limited, and a commercially available product can be preferably used.

In the unvulcanized rubber composition used in the vulcanization step, the resin phase generally has a higher viscosity than the rubber matrix. After starting the vulcanization of the unvulcanized rubber composition and before reaching the maximum vulcanization temperature,
The viscosity of the rubber matrix increases as it is vulcanized, and the resin melts and the viscosity decreases significantly.
Then, during the vulcanization, the viscosity of the resin phase becomes lower than that of the rubber matrix. That is, there occurs a phenomenon that the viscosity relationship between the rubber matrix and the resin phase before vulcanization is reversed in the middle of vulcanization.

In the meantime, in the unvulcanized rubber composition, foaming occurs due to the foaming agent or the like to generate gas. This gas collects inside the phase of the resin, which has been melted and has a relatively reduced viscosity, as compared with the rubber matrix whose viscosity has increased due to the progress of the vulcanization reaction. As a result, the finally obtained vulcanized rubber composition may be referred to as closed cells having a desired shape (hereinafter, simply referred to as “plate-like closed cells”) where the resin phase was present. ) Has been formed.

The periphery of the plate-like closed cells (wall surface of the plate-like closed cells) is covered with a protective layer made of the material resin forming the phase of the plate-like resin or the like to form a capsule shape. ing. The vulcanized rubber composition of the present invention is manufactured as described above. The plate-like closed cells are independently present in the obtained vulcanized rubber composition of the present invention. The vulcanized rubber composition of the present invention is a foamed rubber having a high foaming rate.

When the material resin for the resin phase is at least one resin selected from the group consisting of polyethylene, polypropylene and polyvinylidene chloride, the vulcanized rubber matrix and the protective layer should be firmly bonded. It is preferable in that it can When it is necessary to improve the adhesive force, in addition to the use of these material resins, for example, a material resin that forms the phase of the resin or a component that can improve the adhesiveness is added to the rubber matrix. It may be added.

Regarding the manufacturing conditions and the like in the case of producing long closed cells using a resin other than the long shape such as granular or powdery, JP-A No. 11-60811 (particularly, paragraph 0)
040 to 0041, paragraph numbers 0046 to 0052, and paragraph numbers 0059 to 0060), together with the conditions in the case of a plate-shaped resin (including those described above and those described below), By applying the conditions described in the literature, it is possible to produce a vulcanized rubber composition containing plate-like closed cells and elongated closed cells.

In the vulcanized rubber composition of the present invention, FIG.
As shown in, the plate-shaped closed cells 12 are present in the vulcanized rubber matrix 18. In addition, in FIG.
A configuration that does not include long closed cells is illustrated. When the orientation of the plate-shaped resin in the unvulcanized rubber composition in the extrusion step is aligned with the extrusion direction (direction A),
The plate-shaped closed cells 12 exist in a state of being oriented in substantially one direction. The plate-shaped closed cells 12 are surrounded by a protective layer 20 formed by melting a plate-shaped resin and adhering it to a vulcanized rubber matrix 18. Gases present in the unvulcanized rubber composition, such as gas generated from the foaming agent, are taken into the protective layer 20. In the vulcanized rubber composition, in addition to the plate-like closed cells 12, spherical closed cells 14 due to the gas not taken into the resin phase are also present.

When a tire tread or the like is formed by using the unvulcanized rubber composition of the present invention, the recess formed by exposing the plate-like closed cells 12 on the surface drains water efficiently. It functions as a road. In the vulcanized rubber composition of the present invention, since the protective layer 20 is formed at the interface between the recess and the rubber matrix, water channel shape retention, water channel edge wear resistance, water channel retention during load input, etc. Is also excellent. Although the thickness of the protective layer 20 is not particularly limited,
It is preferably about 0.05 to 50 μm.

(Uses of Vulcanized Rubber Composition of the Present Invention) The vulcanized rubber composition of the present invention can be suitably used in various fields, but it is suitable for a structure which needs to suppress slip on ice. It can be particularly preferably used, and most preferably used for a tire tread and the like. Examples of the structure required to suppress slip on the ice include a tread for replacement of retreaded tires, a solid tire, a ground contact portion of a rubber tire chain used for running on snow and snow, a crawler for snow vehicles, shoes The bottom etc. are mentioned.

(Tire) The tire of the present invention comprises a pair of beads, a carcass straddling the beads in a toroidal shape, a belt for tightening the crown of the carcass, and a tread. At least the tread is
It is characterized by comprising the vulcanized rubber composition of the present invention. In the tire of the present invention, as long as at least the tread contains the vulcanized rubber composition of the present invention, other constitutions are not particularly limited and can be appropriately selected according to the purpose. In other words, the tire having the tread formed of the vulcanized rubber composition is the tire of the present invention.

An example of the tire of the present invention will be described with reference to the drawings. As shown in FIG. 7, a tire 4 according to the present invention includes a pair of bead portions 1, a carcass 2 connected to the pair of bead portions 1 in a toroidal shape, and a belt for tightening a crown portion of the carcass 2. 3 and a tread 5 are sequentially arranged to have a radial structure. Since the internal structure other than the tread 5 is the same as the structure of a general radial tire, description thereof will be omitted.

As shown in FIG. 8, a plurality of blocks 9 are formed on the tread 5 by a plurality of circumferential grooves 7 and a plurality of lateral grooves 8 intersecting with the circumferential grooves 7. Further, in the block 9, a sipe 10 extending along the width direction of the tire (direction of arrow B) is formed in order to improve braking performance and traction performance on ice.

As shown in FIG. 9, the tread 5 is composed of an upper layer cap portion 5A that directly contacts the road surface, and a base portion 5B that is arranged adjacent to the inner side of the cap portion 5A in the tire radial direction. , Has a so-called cap-base structure.

As shown in FIG. 9, the base portion 5B is made of normal rubber that is not foamed, and the cap portion 5A is made of rubber.
Is a foamed rubber containing innumerable plate-shaped closed cells 12.
That is, the foamed rubber is the vulcanized rubber composition of the present invention. As shown in FIG. 9, the plate-shaped closed cells 12 are substantially oriented in the circumferential direction of the tire (the direction of arrow A, like the pushing direction), and the periphery thereof is the protective layer 20 made of the plate-shaped resin. It is covered with. In the present invention, the orientation of the plate-shaped closed cells 12 may not be entirely in the circumferential direction of the tire, and may be partially in a direction other than the circumferential direction of the tire (FIG. 9). reference).

The tire 4 is not particularly limited in its manufacturing method, but can be manufactured as follows, for example. That is, first, the unvulcanized rubber composition after an extrusion step is prepared by the method for producing a vulcanized rubber composition of the present invention. In this unvulcanized rubber composition,
The phase of the plate-shaped resin is oriented in one direction. The unvulcanized rubber composition is attached to the unvulcanized base portion that is previously attached to the crown portion of the raw tire case. At this time, the orientation direction of the phase of the plate-shaped resin is made to coincide with the circumferential direction of the tire. Then, vulcanization molding is performed in a predetermined mold under a predetermined temperature and a predetermined pressure (vulcanization step). As a result, the tire 4 having the cap portion 5A made of the vulcanized rubber composition on the outer side in the tire radial direction of the base portion 5B.
Is obtained.

At this time, when the unvulcanized cap portion is heated in the mold, foaming by the foaming agent or the like occurs in the rubber matrix to generate gas. on the other hand,
The phase of the plate-shaped resin is melted (or softened) and its viscosity (melt viscosity) is lower than that of the rubber matrix (fluid viscosity), whereby the gas is melted and the viscosity is relatively reduced. The resin moves to the inside of the plate-shaped resin phase and stays there. As shown in FIG. 6, the cap portion 5A after cooling is
The rubber composition has a large number of plate-shaped closed cells 12 substantially oriented in the circumferential direction of the tire. The rubber composition containing the plate-shaped closed cells 12 is the vulcanized rubber composition of the present invention.

Next, the operation of the tire 4 will be described.
The tire 4 is run on the ice and snow road surface. The surface of the tread 5 of the tire 4 is worn due to the friction between the tire 4 and the ice and snow road surface. Then, as shown in FIG. 10, the plate-shaped recessed portion 22 formed by the plate-shaped closed cells 12 and the recessed portion 24 formed by the spherical closed cells 14 (when elongated closed cells (not shown) are present, are formed by the elongated closed cells). The recess (also not shown)
It is exposed on the grounding surface of the cap portion 5A of the tread 5. When the tire 4 is further driven, the water film generated between the tire 4 and the ice and snow road surface due to the contact pressure and frictional heat between the tire 4 and the ground contact surface thereof is on the ground contact surface of the cap portion 5A of the tread 5. Due to the innumerable recesses 22 exposed, it is quickly eliminated,
To be removed. Therefore, the tire 4 does not slip or the like even on the ice and snow road surface.

In the tire 4, the plate-shaped recess 22 substantially oriented in the circumferential direction of the tire functions as a drain groove for efficient drainage. Since the surface of the recess 22 is covered with the protective layer 20 having excellent peeling resistance, it is difficult to be crushed even under a high load, and the drainage groove shape retention property and the water drainage performance are maintained. Since the water removal performance to the rear side in the rotation direction of the tire 4 is improved, the tire 4 is particularly excellent in ice braking performance. In the tire 4, due to the scratching effect of the protective layer 20, μ on the lateral ice
And the handling on ice is good.

Further, since the concave portion 22 deeply advances toward the inside of the tire 4 from the ground contact surface (tread surface) of the cap portion 5A of the tread 5, it is more likely to be compared with a mere spherical bubble or a long bubble. It is possible to secure a large volume of the concave portion, and it is possible to achieve a high performance on ice even with the same bubble ratio. That is, the performance on ice and the wear resistance can be balanced at a high level.

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.

[0114]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Examples 1 to 4 and Comparative Examples 1 to 8) Table 1
The rubber matrix having the composition shown in Table 1 was mixed with the resin shown in Table 2 to obtain unvulcanized rubber compositions for use in Examples and Comparative Examples.

[0116]

[Table 1]

[0117]

[Table 2]

Each of the obtained unvulcanized rubber compositions was processed under the conditions shown in Table 3 in the kneading step, the heating step, the extrusion step, and the vulcanization step, and Examples 1 to 4 and Comparative Example were carried out. 1 to
Each vulcanized rubber composition of 8 was manufactured.

[0119]

[Table 3]

The plate-like resin used in the examples and comparative examples is made of polyethylene (HDPE), and the "shape" in Table 2 means the shape of the plane portion. The long resin used in the examples and comparative examples is made of polyethylene (HDPE) produced by a usual melt spinning method, and has a cross section in a direction orthogonal to the axis that is substantially circular. Further, the melting point of each resin is 10 ° C./temperature rise rate by DSC manufactured by Dupont.
The melting point peak temperature was measured under the conditions of a minute and a sample weight of about 5 mg.

At the time of vulcanization of each of the unvulcanized rubber compositions, the viscosities of the phases of the plate-shaped resins were compared until the temperature of each of the unvulcanized rubber compositions reached the maximum vulcanization temperature. Example 1
And Examples 4 and Comparative Examples 2, 3, 5 except
In No. 8, the viscosity was lower than that of the rubber matrix (see FIG. 11).

The viscosity (fluid viscosity) of the rubber matrix at the maximum vulcanization temperature is a cone rheometer type 1-C type manufactured by Monsanto Co., Ltd., and a constant amplitude input of 100 cycles / minute is applied while changing the temperature. When the torque was measured over time and the minimum torque value at that time was taken as the viscosity (dome pressure 0.59 MPa, holding pressure 0.78 MPa, closing pressure 0.78 MPa, swing angle ± 5 °), Examples 1 to 1 No. 4 was 22 kg · cm, and Comparative Examples 2 and 3 were 22 kg · cm.

The viscosity (melt viscosity) of the resin phase at the maximum vulcanization temperature was measured using a cone rheometer (starting temperature was 200 ° C., and the torque generated was lowered by 5 ° C. at a time). As the viscosity of the resin phase,
The temperature dependence of the viscosity was measured, the viscosity of the resin phase at the maximum temperature of the tread was read from the obtained curve, and compared with the viscosity of the rubber matrix. The measurement was performed under the same conditions as the measurement of the viscosity of the rubber matrix except for the temperature. ), 5 kg · cm in Examples 1 to 4, Comparative Examples 2 and 3
Then, it was 5 kg · cm.

Next, tires (pneumatic tires) each having a cap portion (vulcanized rubber composition) of a tread formed from each of the unvulcanized rubber compositions of Examples 1 to 4 and Comparative Examples 1 to 4 were prepared.
It was manufactured under normal tire manufacturing conditions. This tire is a radial tire for passenger cars, and its tire size is 18
5 / 70R13 and its structure is as shown in FIGS. 7 and 8. That is, a pair of bead portions 1 and a carcass 2 straddling the pair of bead portions 1 in a toroidal shape,
A belt 3 for tightening the crown portion of the carcass 2,
It has a radial structure in which the tread 5 and the tread 5 are sequentially arranged.

In this tire, the cords of the carcass 2 are arranged at an angle of 90 ° with respect to the circumferential direction of the tire, and the driving number is 50 pieces / 5 cm. As shown in FIG. 8, four blocks 9 are arranged on the tread 5 of the tire 4 in the tire width direction. The size of block 9 is
The tire has a circumferential dimension of 35 mm and the tire has a lateral dimension of 30 mm. The sipes 10 formed on the blocks 9 have a width of 0.4 mm and a tire circumferential interval of about 7 mm.

In the tread 5 of the tire 4, in which the plate-shaped closed cells are contained, the plane portion thereof is substantially perpendicular to the tread surface of the tire and substantially in the tire circumferential direction (arrow). It is oriented in the A direction). Further, in the case of containing long closed cells, the longitudinal direction thereof is substantially oriented in the tire circumferential direction (arrow A direction). The periphery of the plate-shaped closed cells or the elongated closed cells is covered with a protective layer 20 made of a material resin forming the plate-shaped resin phase or the elongated resin phase.

The obtained tires were evaluated for wear resistance and on-ice performance. The evaluation method is as follows. The results are shown in Table 4. The bubble ratio of the tread 5 was calculated (measured) by the above-mentioned formula (1).

<Performance on ice> Domestic tires are 1600CC
It is installed in a passenger car of the class (total vehicle weight: 1200 kg), and the passenger car is run for 200 km on a general asphalt road, and then on a flat road on ice at a speed of 20 km / h.
At that time, the brake was suddenly pressed to lock the tire, and the distance until the tire stopped was measured. As a result, the reciprocal of the distance until the vehicle stopped was determined, and the tire of Comparative Example 1 was set as 100 and displayed as an index. The results show that the larger the index, the better the performance on ice.

<Abrasion resistance> A Lambourn abrasion tester was used to measure the abrasion amount at a slip ratio of 60% at room temperature (25 ° C), and the reciprocal of the abrasion amount of the control was set to 100, and the abrasion resistance index was expressed as an index. . The results show that the larger the index, the better the wear resistance.

[0130]

[Table 4]

From the results shown in Table 4, the following is clear. When the average bubble ratio Vs is increased without the presence of plate-like closed cells as in Comparative Example 4, the performance on ice is improved, but the wear resistance is reduced. Also, as in Comparative Examples 2 and 3,
When the long closed cells are provided, the performance on ice can be improved without lowering the abrasion resistance without increasing the average bubble ratio Vs, but further improvement on the ice performance is desired. On the other hand, in Examples 1 and 2 in which the plate-like closed cells were provided, the performance on ice could be further improved without increasing the average bubble ratio Vs and decreasing the wear resistance. Further, in Examples 3 and 4 in which both the plate-like closed cells and the elongated closed cells are provided, the performance on ice can be significantly improved without increasing the average bubble ratio Vs and decreasing the wear resistance. It was

[0132]

As described above, according to the present invention,
It is possible to provide a vulcanized rubber composition having an improved ability to remove the water film generated on ice without lowering abrasion resistance, and a method for producing the same. Further, according to the present invention,
It is possible to provide an unvulcanized rubber composition that can be used for the production of such a vulcanized rubber composition. Further, by using the vulcanized rubber composition of the present invention, a structure having a large friction coefficient with an ice surface, the tire having excellent on-ice performance, a tread of the tire, and the like, which need to suppress slip on ice, Can be provided.

[Brief description of drawings]

1 is an embodiment of a vulcanized rubber composition of the present invention,
It is a schematic perspective view of the state where the surface was worn to some extent.

FIG. 2 is a schematic perspective view of another embodiment of the vulcanized rubber composition of the present invention, in which the surface is worn to some extent,
(A) is a vulcanized rubber composition in which spherical closed cells are arranged in a rubber matrix together with plate-like closed cells,
In addition to this, (b) is a vulcanized rubber composition in which elongated closed cells are arranged in a rubber matrix.

FIG. 3 (a) is a schematic perspective view of a conventionally known vulcanized rubber composition in which only spherical closed cells are arranged in a rubber matrix, and the surface is worn to some extent; FIG. 3 is a schematic perspective view of a vulcanized rubber composition in which long closed cells are arranged in a rubber matrix in addition to spherical closed cells, and the surface of which is worn to some extent.

4 (a) is a schematic cross-sectional view of the vulcanized rubber composition shown in FIG. 3 (a), and FIG. 4 (b) is a schematic cross-sectional view of the vulcanized rubber composition shown in FIG. 3 (a). FIG. 3 is a schematic cross-sectional view of a vulcanized rubber composition in which the bubble ratio is increased by enlarging the bubbles, and (c) is a vulcanized rubber composition shown in (a),
FIG. 2 is a schematic cross-sectional view of a vulcanized rubber composition in which the bubble ratio is increased by further increasing the density of bubbles, and (d) is a schematic cross-sectional view of the vulcanized rubber composition of the present invention shown in FIG. 1. is there.

FIG. 5 is an explanatory diagram for explaining the principle of aligning the orientation of the plate-shaped resin.

FIG. 6 is a schematic cross-sectional view of a vulcanized rubber composition of the present invention.

FIG. 7 is a partial cross-sectional schematic explanatory view of the tire of the present invention.

FIG. 8 is a partial schematic explanatory view of the peripheral surface of the tire of the present invention.

FIG. 9 is a partial cross-sectional schematic explanatory view of the tread of the tire of the present invention.

FIG. 10 is a schematic partial enlarged cross-sectional view of a worn tread of the tire of the present invention.

FIG. 11 is a graph showing the relationship between the vulcanization time and the viscosity of the rubber matrix and the viscosity of the resin.

[Explanation of symbols]

2 carcass 3 belt 4 tire 5 tread 5A cap portion 5B base portion 7 circumferential groove 8 lateral groove 9 block 10 sipes 12 plate-like closed cells 14, 14a, 14b, 14a ', 14b', 14
a ”, 14b” Spherical closed cells 16 Long closed cells 18 Rubber matrix 20 Protective layers 22, 24 Recesses 22 Resin 26 Base

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 27/08 C08L 27/08 F term (reference) 4F074 AA05 AA17 AA24 AA37 AB03 AE02 AE06 AG20 BA01 BA13 BA16 BA17 BA18 BB01 BB05 CA23 CC04Y CC06Z CC32X CC32Z DA02 DA12 DA59 4J002 AC01W AC011 AC03W AC031 AC08W AC081 BB03X BB032 BB12X BB122 BB15W BB151 BB24W BB241 BD10X BD102 DA047 EQ016 EQ026 FD147 FD326GN

Claims (21)

[Claims] 1. A rubber component and a resin component,
An unvulcanized rubber composition comprising a foaming agent and at least a part of the resin having a plate shape. 2. The melting point or softening point of the resin is 70 to
The unvulcanized rubber composition according to claim 1, which is in a range of 200 ° C. 3. The unvulcanized rubber according to claim 1, wherein the melting point or softening point of the resin is not higher than the maximum vulcanization temperature of the rubber matrix when subjected to vulcanization. Composition. 4. The thickness of the plate-shaped resin is 0.1 to 100.
4. The area of the flat portion is in the range of 1 to 100 mm ² , and the area of the plane portion is in the range of 1 to 100 mm ^2.
The unvulcanized rubber composition described in 1. 5. The unvulcanized rubber composition according to any one of claims 1 to 4, wherein the resin is contained in an amount of 0.5 to 20 parts by mass with respect to 100 parts by mass of the rubber component. . 6. The unvulcanized rubber composition according to any one of claims 1 to 5, wherein the resin is at least one resin selected from the group consisting of polyethylene, polypropylene and polyvinylidene chloride. object. 7. A vulcanized rubber composition comprising at least plate-like closed cells covered with a protective layer made of a resin and a rubber component. 8. The method according to claim 7, further comprising elongated closed cells covered with a protective layer made of resin.
The vulcanized rubber composition described in 1. 9. Before vulcanization, a rubber matrix containing at least a rubber component and a foaming agent, and a plate-shaped resin are included, and the plate-shaped resin has a viscosity lower than that of the rubber matrix during a vulcanization step. And a rubber component, which is formed by collecting at least a part of the gas generated by the foaming agent in the resin, and has a closed closed cell provided with a protective layer having an outer peripheral portion made of the plate-shaped resin, and a rubber component. A vulcanized rubber composition comprising: 10. Before vulcanization, at least a rubber matrix containing a rubber component and a foaming agent, a plate-shaped resin, and a long resin are contained, A protective layer formed by collecting at least a part of the gas generated by the foaming agent in the plate-shaped resin and the long-shaped resin having a reduced viscosity, the outer peripheral portion of which is composed of the plate-shaped resin A vulcanized rubber composition comprising: a plate-shaped closed cell, a long closed cell having an outer peripheral portion provided with a protective layer made of the long resin, and a rubber component. 11. The vulcanized rubber composition according to any one of claims 7 to 10, wherein the bubble ratio Vs is in the range of 5 to 40%. 12. The vulcanized rubber composition according to claim 7, wherein the ratio of the plate-like closed cells to all the contained cells is in the range of 5 to 95% by volume. . 13. A kneading step of kneading a rubber matrix containing a rubber component and a foaming agent, and an unvulcanized rubber composition containing a plate-shaped resin, and a heating step of heating the unvulcanized rubber composition. And an extrusion step of extruding the unvulcanized rubber composition, and a vulcanization step of vulcanizing the unvulcanized rubber composition, wherein the vulcanization step is In the method for producing a vulcanized rubber composition, the viscosity of the resin becomes lower than the viscosity of the rubber matrix before the temperature of the rubber matrix reaches the maximum vulcanization temperature. 14. The maximum temperature of the unvulcanized rubber composition in the kneading step, the maximum temperature of the unvulcanized rubber composition in the heating step, and the unvulcanized rubber immediately after extrusion in the extrusion step. The maximum temperature of the composition is set below the melting point or softening point of the resin, and the maximum vulcanization temperature of the rubber matrix in the vulcanization step is
The method for producing a vulcanized rubber composition according to claim 13, wherein the melting point or softening point of the resin is equal to or higher than the melting point or softening point of the resin. 15. A kneading step of kneading a rubber matrix containing a rubber component and a foaming agent, a plate-shaped resin, and an unvulcanized rubber composition containing a long resin, and the unvulcanized rubber composition. A method for producing a vulcanized rubber composition, comprising a heating step of heating, an extrusion step of extruding the unvulcanized rubber composition, and a vulcanization step of vulcanizing the unvulcanized rubber composition. In the vulcanization step, the viscosity of the plate-shaped resin and the elongated resin becomes lower than the viscosity of the rubber matrix until the temperature of the rubber matrix reaches the maximum vulcanization temperature, The method for producing a vulcanized rubber composition, wherein the maximum vulcanization temperature of the rubber matrix in the vulcanization step is equal to or higher than the melting point or softening point of the resin. 16. The maximum temperature of the unvulcanized rubber composition in the kneading step, the maximum temperature of the unvulcanized rubber composition in the heating step, and the unvulcanized rubber immediately after extrusion in the extrusion step. The method for producing a vulcanized rubber composition according to claim 15, wherein the maximum temperature of the composition is set to be lower than the melting point or softening point of the resin. 17. The melting point or softening point of the resin is 70.
14. It is in the range of -200 degreeC, It is characterized by the above-mentioned.
A method for producing the vulcanized rubber composition according to any one of 1 to 16. 18. The thickness of the plate-shaped resin is 0.1-10.
The area of the plane portion is 1 to 100 mm ^{2 in} the range of 0 μm.
The method for producing a vulcanized rubber composition according to any one of claims 13 to 17, characterized in that 19. The unvulcanized rubber composition contains the plate-shaped resin in an amount of 0.5 to 20 parts by mass with respect to 100 parts by mass of the rubber matrix.
The method for producing the vulcanized rubber composition according to any one of 3 to 18. 20. The vulcanized rubber composition according to any one of claims 13 to 19, wherein the resin is at least one resin selected from the group consisting of polyethylene, polypropylene and polyvinylidene chloride. Manufacturing method. 21. A pair of beads, a carcass connected to the beads in a toroidal shape, a belt and a tread for tightening the crown of the carcass, and at least the tread. A tire comprising the vulcanized rubber composition according to any one of 1 to 12.