JPH1180422A - Rubber composition and tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber compsn. exhibiting excellent performance on ice and abrasion resistance. SOLUTION: This rubber compsn. comprises: a rubber matrix comprising at least one rubber component selected from naturally occurring rubber and diene synthetic rubber and at least one of an unsatd. fatty acid, having in its molecule, at least two carbon-carbon double bonds, in an amt. of 0.1 to 10 pts.wt. based on 100 pts.wt. rubber component and a liq. polymer in an amt. of 0.5 to 10 pts.wt. based on 100 pts.wt. rubber component; and an org. short fiber in an at. of 0.5 to 30 pts.wt. based on 100 pts.wt., the short fiber having such a property that the viscosity becomes lower than that of the rubber matrix before, during vulcanization, the temp. of the rubber matrix reaches the highest vulcanization temp., wherein, in the unsatd. fatty acid, the proportion of protons derived from conjugated double bond in the total amount of protons derived from unsaturation is at least 10% and the liq. polymer comprises a diene polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire having excellent performance on ice, which is particularly required by the market, and a rubber composition suitable for the tread of the tire.

[0002]

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

[0003] Recently, organic short fibers which are heat-meltable have been added to a rubber composition, and when the rubber composition is vulcanized, the organic short fibers are melted to form bubbles, thereby reducing the water film removing ability and edge effect. It has been proposed that a vulcanized rubber having long bubbles that can be exhibited is obtained, and the vulcanized rubber is used for a tread or the like of a tire to improve the performance of the tire on ice. However, in this case, it is necessary to control the orientation of the elongated bubbles in the tread to increase the rate at which the elongated bubbles are exposed on the surface of the tread. For this purpose, it is desired that the orientation of the organic short fibers that form the basis for forming the long cells can be sufficiently and easily controlled in the rubber composition. Such technology has not yet been provided.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, an object of the present invention is to provide a tire excellent in ability to remove the water film, having a large coefficient of friction with an ice surface, and excellent in performance on ice and wear resistance. Further, the present invention is excellent in on-ice performance and abrasion resistance, contains long bubbles capable of exhibiting the water film removing ability and edge effect in a state where the orientation thereof is sufficiently controlled, and the tread of a tire, etc. It is an object of the present invention to provide a rubber composition suitable for a structure that needs to suppress a slip on an icy and snowy road surface.

[0005]

Means for solving the above problems are as follows. That is, <1> a rubber component composed of at least one selected from a natural rubber and a diene-based synthetic rubber, and an unsaturated fatty acid having at least two carbon-carbon double bonds in a molecule per 100 parts by weight of the rubber component. A rubber matrix containing at least one of 0.1 to 10 parts by weight and 0.5 to 10 parts by weight of a liquid polymer, and 100 parts by weight of the rubber component, the temperature of the rubber matrix at the time of vulcanization reaches the highest vulcanization temperature. And 0.5 to 30 parts by weight of organic short fibers whose viscosity is lower than the viscosity of the rubber matrix before reaching, and accounts for the total amount of protons derived from unsaturation in the unsaturated fatty acid. A rubber composition, wherein the proportion of protons derived from conjugated double bonds is at least 10%, and the liquid polymer comprises a diene-based polymer. <2> Even if the weight average molecular weight of the liquid polymer is large, 5
The rubber composition according to <1>, wherein the rubber composition is 10,000. <3> The rubber composition according to <1> or <2>, wherein the unsaturated fatty acid contains at least 25% of a conjugated diene-based acid having at least one pair of conjugated double bonds in the molecule. <4> The rubber composition according to any one of <1> to <3>, wherein the organic short fiber contains a crystalline polymer, and has a melting point lower than the maximum vulcanization temperature. <5> The above <1 wherein the organic short fiber is made of a polyolefin.
> The rubber composition according to any one of <4>. <6> The rubber composition according to <5>, wherein the polyolefin is one of polyethylene and polypropylene. <7> The rubber composition according to any one of <1> to <6>, wherein the rubber matrix contains a foaming agent. <8> From <1> to <7, wherein the foaming ratio is 3 to 40%.
> The rubber composition according to any one of the above.

<9> a pair of bead portions, a carcass connected to the bead portions in a toroidal shape, a belt and a tread for clinching a crown portion of the carcass,
A tire characterized in that at least the tread contains the rubber composition according to any one of <1> to <8>.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition and tire of the present invention will be described below in detail. (Rubber composition) The rubber composition of the present invention includes an unvulcanized rubber composition and a vulcanized rubber composition, and the rubber composition comprises a rubber matrix and organic short fibers.

--- Rubber matrix-- The rubber matrix contains components other than the organic short fibers in the rubber composition, and specifically, is composed of at least one selected from natural rubber and diene-based synthetic rubber. It contains a rubber component, at least one of an unsaturated fatty acid and a liquid polymer, and further contains other components such as a foaming agent and a foaming aid as required.

-Rubber component- The rubber component may contain only natural rubber,
It may contain only the diene-based synthetic rubber, or may contain both. The diene-based synthetic rubber is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, styrene-butadiene copolymer (SBR), polyisoprene (IR), polybutadiene ( BR) and the like. Among these diene-based synthetic rubbers, cis-1,4-polybutadiene is preferred, and those having a cis content of 90% or more are particularly preferred in that they have a low glass transition temperature and a large effect on ice.

-Unsaturated Fatty Acid-In the unsaturated fatty acid, the proportion of protons derived from conjugated double bonds in the total protons derived from unsaturation needs to be at least 10% (at least 10%). It is preferably 25% (25% or more). Further, in the present invention, the ratio is a lower limit of any one of the upper limit or lower limit of the numerical range or any one of the ratios adopted in Examples described later, and an upper limit of any one of the numerical ranges. Alternatively, a numerical range having a lower limit or any of the ratios employed in the examples described later as an upper limit is also preferable. The upper limit of the ratio is preferably 100%.

If the proportion of protons derived from conjugated double bonds in the total amount of protons derived from unsaturation in the unsaturated fatty acids is less than 10%, the viscosity of the rubber matrix cannot be reduced, Due to insufficient fluidity, the organic short fibers cannot be easily and sufficiently oriented in a certain direction during extrusion or the like. Also, the resulting vulcanized rubber may not have sufficient effects of improving the elastic modulus and the breaking strength. The content is
For example, it can be measured using NMR.

The unsaturated fatty acid may be linear or branched. The number of carbon atoms of the unsaturated fatty acid is preferably about 10 to 22.

The component other than the conjugated diene-based acid in the unsaturated fatty acid is a non-conjugated diene-based acid. In the non-conjugated diene-based acid, at least two (two or more) carbon-carbon double bonds are mutually bonded. Not conjugated. Examples of the non-conjugated diene-based acid include linoleic acid and linolenic acid. These may be contained alone or in combination of two or more. In the present invention, the unsaturated fatty acids may contain saturated fatty acids such as stearic acid and dioxystearic acid according to the purpose.

The conjugated diene-based acid has two conjugated carbon-carbon double bonds (for example, -CH = CH-
CH = CH-) means an unsaturated monocarboxylic acid containing at least one set (one or more sets). Examples of the conjugated diene acid include 2,4-pentadienoic acid, 2,4-hexadienoic acid, 2,4-decadienoic acid, 2,4-dodecadienoic acid, 9,11-octadecadienoic acid, and eriostearic acid. , 9,11,13,15-octadecatetrienoic acid, 9,11,13-octadecatrienoic acid and the like. These may be contained alone or in combination of two or more.

Specific examples of the unsaturated fatty acids, ie, unsaturated fatty acids containing a conjugated diene-based acid, include dehydrated oil fatty acids obtained by subjecting corn oil, cottonseed oil, peanut oil, soybean oil, castor oil and the like to a dehydration reaction. Preferred among these are, among these, particularly preferred are dehydrated castor oil fatty acids obtained by subjecting castor oil to a dehydration reaction.

The castor oil is a non-drying oil obtained by squeezing from castor seeds. The castor oil contains small amounts of stearic acid and dioxystearic acid as saturated fatty acids, ricinoleic acid as unsaturated fatty acids as main components, and a small amount of other components. Oleic acid, linoleic acid, linolenic acid, etc. are included. As the dehydrated castor oil fatty acid, one containing a conjugated diene-based acid is obtained depending on the method of dehydration. In the case of this dehydrated castor oil fatty acid, the conjugated diene-based acid contained is mainly 9,11-octadecadienoic acid, and other unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid and the like.
In addition, as the unsaturated fatty acid, for example, those appropriately prepared according to a known method can be used, and may be a natural product or a synthetic product.

The content of the unsaturated fatty acid in the rubber matrix is 0.1 to 10 parts by weight, preferably 0.5 to 6 parts by weight, more preferably 1 to 4 parts by weight based on 100 parts by weight of the rubber component. Parts by weight are more preferred. Further, in the present invention, as the content of the unsaturated fatty acid in the rubber matrix, the lower limit of any one of the upper limit or lower limit of the numerical range or the value of the content employed in the examples described below. It is also preferable that the upper limit or the lower limit of any of the above-mentioned numerical ranges or the numerical range whose upper limit is any of the contents employed in the examples described later.

If the content is less than 0.1 part by weight, the viscosity of the rubber matrix cannot be reduced, and its fluidity is not sufficient. Cannot be oriented in any direction. Also, the elastic modulus of the rubber composition after vulcanization is not sufficient,
The effect of improving the breaking strength is not sufficient. On the other hand, if it exceeds 10 weight, the effect corresponding to it will not be obtained, and the wear resistance of the obtained vulcanized rubber will decrease.

-Liquid polymer- Specific examples of the liquid polymer include liquid polyisoprene rubber, liquid polybutadiene rubber, liquid styrene / butadiene copolymer, and a mixture thereof. These may be used alone or in combination of two or more.

The liquid polymer may be one prepared as appropriate according to a known method or a commercially available product. Commercially available products include, for example, LIR-20 (weight average molecular weight = 20,000) and LIR-3 manufactured by Kuraray Co., Ltd.
0 (weight average molecular weight = 30,000), LIR-50 (weight average molecular weight = 50,000) and the like.

The weight average molecular weight of the liquid polymer is preferably at most 50,000 (50,000 or less), and
25,000 is particularly preferred. Further, in the present invention, the weight-average molecular weight of the liquid polymer, as the lower limit of any of the upper limit or lower limit of the numerical value range or any value of the weight-average molecular weight adopted in Examples described below, the numerical value A numerical range in which the upper limit or lower limit of any of the ranges or the weight average molecular weight employed in the examples described later is the upper limit is also preferable. When the weight average molecular weight of the liquid polymer exceeds 50,000, the effect of lowering the viscosity of the rubber matrix is not sufficient, and the orientation of the added organic short fiber may not be sufficiently improved.

The content of the liquid polymer in the rubber matrix is 0.5 to 10 parts by weight, more preferably 1 to 6 parts by weight, based on 100 parts by weight of the rubber component. Further, in the present invention, the content is defined as a lower limit of any one of the upper limit or lower limit of the numerical range or any value of the content adopted in Examples described later, A numerical range in which the upper limit or the lower limit or any one of the contents employed in Examples described later is the upper limit is also preferable.

If the content is less than 0.5 part by weight, the viscosity of the rubber matrix cannot be reduced, and its fluidity is not sufficient. Cannot be oriented in any direction. On the other hand, if it exceeds 10 weight, the effect corresponding thereto cannot be obtained, and the abrasion resistance of the rubber composition after vulcanization may be reduced.

The unsaturated fatty acid and the liquid polymer may be used alone or in the specific amounts, or both may be used in the specific amounts. The unsaturated fatty acid and the liquid polymer function as a plasticizer or a processability improver in the rubber matrix. For this reason, the rubber composition obtained by blending the rubber matrix with the specific amount of at least one of the unsaturated fatty acid and the liquid polymer is easy to control the fluidity thereof.
The short organic fibers contained therein can be easily and sufficiently oriented in a certain direction. For example, when the rubber composition is subjected to extrusion or the like, the organic short fibers can be easily oriented in the extrusion direction.

-Other components- As the other components, any other components can be used without impairing the object of the present invention.
Inorganic fillers such as silica and calcium carbonate, coupling agents such as silane coupling agents, softeners, vulcanizing agents such as sulfur, vulcanization accelerators such as dibenzothiazyl disulfide, N
Antioxidants such as -cyclohexyl-2-benzothiazyl-sulfenamide, N-oxydiethylene-benzothiazyl-sulfenamide, zinc oxide, stearic acid,
In addition to additives such as an ozone deterioration inhibitor, 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 the present invention, commercially available products can be used for the other components.

In the present invention, a foaming agent can be particularly preferably used as the other component. Use of at least the foaming agent is advantageous in that desired long cells can be efficiently formed in the vulcanized rubber composition.

Examples of the foaming agent include dinitrosopentamethylenetetramine (DPT), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivative, oxybisbenzenesulfonylhydrazide (OBSH), and carbon dioxide. Generated ammonium bicarbonate, sodium bicarbonate, ammonium carbonate, a nitrososulfonylazo compound generating nitrogen, N, N′-dimethyl-N, N′-dinitrosophthalamide, toluenesulfonylhydrazide,
P-toluenesulfonyl semicarbazide, P, P'-oxy-bis (benzenesulfonyl semicarbazide) and the like can be mentioned.

Among these foaming agents, dinitrosopentamethylenetetramine (DP)
T), azodicarbonamide (ADCA) is preferred,
Particularly, azodicarbonamide (ADCA) is preferable. These may be used alone or in combination of two or more. By the foaming agent, the rubber composition after vulcanization can be made into a foamed rubber having a high foaming rate.

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 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.

-Organic short fibers-The organic short fibers have a thermal property of melting (including softening) until the rubber matrix reaches the maximum vulcanization temperature, in other words, It is preferable that the rubber composition has thermal characteristics in which the viscosity of the organic short fibers is lower than the viscosity of the rubber matrix until the temperature of the rubber matrix reaches the maximum vulcanization temperature during vulcanization of the rubber composition. Particularly preferred.

The maximum vulcanization temperature means the maximum temperature reached by the rubber matrix during vulcanization of the rubber composition. For example, in the case of mold vulcanization, it means the maximum temperature reached by the rubber matrix from when the rubber composition enters the mold to when the rubber composition exits the mold and is cooled. The maximum vulcanization temperature can be measured, for example, by embedding a thermocouple in the rubber matrix.

The viscosity of the rubber matrix means the flow viscosity, and the viscosity of the organic short fibers means the melt viscosity, which can be measured using, for example, a cone rheometer, a capillary rheometer, or the like. .

The material of the organic short fiber is not particularly limited as long as it has the above-mentioned thermal characteristics, and can be appropriately selected according to the purpose. As the material having the thermal characteristics, for example, a resin made of a crystalline polymer whose melting point is lower than the maximum vulcanization temperature is preferably exemplified.

Taking the resin made of the crystalline polymer as an example, the greater the difference between the melting point of the resin and the maximum vulcanization temperature of the rubber matrix, the faster the rubber composition is cured during vulcanization. Since the resin melts at an earlier time, the time at which the viscosity of the resin becomes lower than the viscosity of the rubber matrix is earlier. For this reason, when the resin is melted, the gas generated by the foaming agent and the like contained in the rubber composition moves into the resin having a lower viscosity than the rubber matrix and stays there. As a result, many long bubbles covered with the resin are present in the rubber composition after vulcanization.

On the other hand, when the melting point of the organic short fiber is too close to the maximum vulcanization temperature of the rubber matrix,
The organic short fibers do not melt immediately in the early stage of vulcanization, but melt in the final stage of vulcanization. In the final stage of vulcanization, a part of the gas generated by the foaming agent and the like contained in the rubber composition is taken into the vulcanized rubber, and does not move and stay inside the molten organic short fiber, and In some cases, the retention of gas in the short organic fibers becomes insufficient. On the other hand, when the melting point of the organic short fibers is too low, the organic short fibers are melted by the heat at the time of kneading the rubber composition, and the organic short fibers are fused to each other at the kneading stage, resulting in dispersibility. The organic short fibers may be divided into a plurality of pieces at the stage of kneading, or the organic short fibers may be dissolved in the rubber composition and dispersed microscopically.

The upper limit of the melting point of the organic short fiber is not particularly limited, but is preferably selected in consideration of the above points. In general, the upper limit of the rubber matrix is higher than the maximum vulcanization temperature of the rubber matrix. The temperature is preferably lower than 10 ° C.
It is more preferable that the temperature is lower than or equal to ° C. The industrial vulcanization temperature of the rubber composition is generally about 190 ° C. at maximum,
For example, when the maximum vulcanization temperature is set to 190 ° C., the melting point of the organic short fiber is usually 190.
° C or less, preferably 180 ° C or less,
70 ° C. or lower is more preferable.

On the other hand, considering the kneading of the rubber composition,
The melting point of the organic short fibers is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, and particularly preferably 20 ° C. or higher, with respect to the maximum temperature during kneading. Assuming that the maximum temperature during kneading of the rubber composition is, for example, 95 ° C., the melting point of the organic short fiber is preferably 100 ° C. or higher, more preferably 105 ° C. or higher, and particularly preferably 115 ° C. or higher. .

The melting point of the organic short fiber can be measured using a melting point measuring device known per se, and for example, the melting peak temperature measured using a DSC measuring device is defined as the melting point. it can.

The organic short fibers may be formed from a crystalline polymer, may be formed from a non-crystalline polymer, or may be formed from a crystalline polymer and a non-crystalline polymer. Although it may be, in the present invention, it is preferably formed from an organic material containing a crystalline polymer in that the viscosity change occurs abruptly at a certain temperature due to a phase transition, and viscosity control is easy. More preferably, it is formed only from a crystalline polymer.

Specific examples of the crystalline polymer include, for example, polyethylene (PE), polypropylene (PP),
Polybutylene, polybutylene succinate, polyethylene succinate, syndiotactic-1,2-polybutadiene (SPB), polyvinyl alcohol (PV
A), a single composition polymer such as polyvinyl chloride (PVC), or a polymer whose melting point is controlled in an appropriate range by copolymerization, blending, or the like can be used, and a polymer obtained by adding an additive to these can also be used. These may be used alone or in combination of two or more. Among these crystalline polymers, polyolefins and polyolefin copolymers are preferable, and polyethylene (P
E) and polypropylene (PP) are more preferred, and polyethylene (PE) is particularly preferred in that it has a low melting point and is easy to handle.

Examples of the non-crystalline polymer include polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene copolymer (ABS), polystyrene (PS), polyacrylonitrile, copolymers thereof, and blends thereof. Is mentioned. These are 1
Species may be used alone or in combination of two or more.

Known additives may be added to the organic short fibers as needed, as long as the object of the present invention is not impaired.

The molecular weight of the organic short fiber material is as follows:
Although it depends on the chemical composition of the material, the state of branching of the molecular chain, and the like and cannot be specified unconditionally, in general, the organic short fibers, even if formed from the same material, have a certain temperature as the molecular weight is higher. (Melt viscosity) becomes higher. In the present invention, the molecular weight of the raw material in the organic short fiber is selected in a range such that the viscosity (melt viscosity) of the organic short fiber does not become higher than the viscosity (flow viscosity) of the rubber matrix at the highest vulcanization temperature. Is preferred.

In one test example, the organic short fiber was
In the case of polyethylene having a weight average molecular weight of about 1 to 2 × 10 ⁵ , a foaming agent and the like contained in the rubber composition after vulcanization are higher than in the case of polyethylene having a weight average molecular weight of 7 × 10 ⁵ or more. A large amount of the gas generated by the above was taken into the organic short fibers. This difference is presumed to be due to a difference in viscosity (melt viscosity) caused by a difference in molecular weight of polyethylene as a material of the organic short fiber.

The content of the organic short fiber in the rubber composition is based on 100 parts by weight of the rubber component.
0.5 to 30 parts by weight is preferable, and 1.0 to 10 parts by weight is more preferable. In the present invention, as the content of the organic short fiber in the rubber composition, any one of the lower limit or the upper limit of the numerical range or the value of the content used in Examples described below is the lower limit. It is also preferable to use a lower limit or upper limit of any of the above numerical ranges, or a numerical range having an upper limit of any one of the contents employed in Examples described later.

When the content is less than 0.5 part by weight, the amount of gas taken in or retained in the rubber composition after vulcanization is small, and the rubber composition is used for a tread of a tire or the like. In this case, the performance on ice may not be able to be sufficiently improved, and if it exceeds 30 parts by weight, dispersibility of the organic short fibers in the rubber composition is deteriorated, and workability during rubber extrusion is deteriorated. In some cases, inconveniences such as cracks in the tread may occur. On the other hand, when the content is within the preferable numerical range, it is preferable because such a case does not occur.

The denier of the organic short fiber is not particularly limited and can be appropriately selected according to the purpose. From the viewpoint of improving the performance on ice, the denier is 1 to 100.
0 denier is preferable, and 2-800 is more preferable. The average length (L) and average diameter (D) of the organic short fibers
Is not particularly limited and can be appropriately selected depending on the purpose.

-Preparation of Rubber Composition- The rubber composition is prepared by appropriately selecting the above components,
It is prepared by kneading, heating, extruding, etc. by a technique.

The maximum temperature during kneading, the maximum temperature during warming, and the maximum temperature immediately after extrusion of the rubber composition are each lower than the melting point of the organic short fiber, preferably lower by at least 5 ° C. than the melting point. It is preferable to perform kneading, warming and extrusion after setting. In this case, even after the kneading, heating and extrusion, the form of the organic short fiber can be maintained in the rubber composition.

When the maximum temperature during kneading, the maximum temperature during warming, or the maximum temperature immediately after extrusion exceeds the melting point of the organic short fibers, the form of the organic short fibers can be maintained. In some cases, after vulcanization, a rubber composition containing long bubbles may not be obtained. Even when the rubber composition is used for a tread of a tire, the performance on ice cannot be sufficiently improved.

The kneading is performed by:
There are no particular limitations on the conditions such as the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, and the kneading apparatus, which can be appropriately selected depending on the purpose. As the kneading device, a commercially available product can be suitably used.

The heating or extrusion is not particularly limited in terms of the time for heating or extrusion, the apparatus for heating or extrusion, and can be appropriately selected according to the purpose. As the heating or extruding device, a commercially available product can be suitably used. However, the heating or extrusion temperature is
It is appropriately selected according to the purpose. The extrusion temperature is:
Generally, it is about 90 to 110 ° C.

In the rubber composition, since the organic short fibers are oriented in the direction of extrusion, when this rubber composition is used for a tread of a tire, the rubber composition may be used in a direction parallel to the surface of the tread in contact with the ground. It is more preferable to use the organic short fibers oriented in the circumferential direction of the tire in that the drainage in the running direction of the tire is increased and the performance on ice can be improved.

As a method of aligning the orientation of the organic short fibers, for example, as shown in FIG. 1, a rubber composition 15 containing organic short fibers 14 is mixed with an extruder in which the cross-sectional area of the flow path decreases toward the outlet. The organic short fibers 14 may be oriented in a certain direction by extruding from the base 16. In this case, the degree of orientation of the organic short fibers 14 in the rubber composition 15 depends on the degree of decrease in the cross-sectional area of the flow path, the extrusion speed, and the rubber composition 1.
5 depending on the viscosity and the like. In the rubber composition of the present invention, the organic short fibers 14 in the rubber composition 15 before being extruded are gradually aligned in the extrusion direction (A direction) in the process of being extruded into the die 16. Thus, when extruded from the base 16, the longitudinal direction can be almost completely oriented in the extrusion direction (A direction).

-Vulcanization of Rubber Composition- The conditions and method of vulcanization of the rubber composition are not particularly limited, and can be appropriately selected according to the type of the rubber component. When vulcanization is produced, mold vulcanization is preferred. The temperature of the vulcanization is generally selected so that the maximum vulcanization temperature of the rubber composition during the vulcanization is equal to or higher than the melting point of the organic short fibers. When the vulcanization maximum temperature is less than the melting point of the organic short fiber, the organic short fiber does not melt, and gas generated by foaming or the like cannot be retained in the organic short fiber, and after vulcanization, Long bubbles cannot be efficiently formed in the rubber composition. The vulcanizing device is not particularly limited, and a commercially available product can be suitably used.

In the rubber composition before vulcanization,
The organic short fiber has a higher viscosity than the rubber composition.
After the start of vulcanization of the rubber composition and before the rubber composition reaches the maximum vulcanization temperature, the viscosity of the rubber matrix increases by vulcanization, and the organic short fibers melt. And the viscosity is greatly reduced. During the vulcanization, the organic short fibers have a lower viscosity than the rubber matrix. That is, a phenomenon occurs in which the viscosity relationship between the rubber matrix and the organic short fibers before vulcanization is reversed at a stage during vulcanization.

During this time, foaming by the foaming agent and the like occurs in the rubber composition, and gas is generated. This gas stays inside the organic short fibers that have melted and the viscosity has relatively decreased compared to the rubber matrix whose viscosity has increased due to the progress of the vulcanization reaction. As a result, in the vulcanized rubber composition, long bubbles are formed at the place where the organic short fibers existed. The long bubble has a capsule shape with its periphery (wall surface of the long bubble) covered with the organic short fiber material. In addition, the capsule-shaped coating layer made of the organic short fibers may be hereinafter referred to as a “protective layer”. The long bubbles are independently present in the rubber composition after vulcanization. When the foaming agent or the like is used in the rubber composition, the rubber composition after vulcanization is a foamed rubber having a high foaming rate.

When the material resin of the organic short fiber is polyethylene, polypropylene or the like, the vulcanized rubber matrix and the material of the organic short fiber are firmly bonded. When it is necessary to improve the adhesive force, for example, a component capable of improving the adhesiveness to the rubber matrix may be added to the organic short fibers.

In the rubber composition after vulcanization, FIG.
As shown in the figure, long bubbles 11 are present in the vulcanized rubber matrix 6A. When the orientation of the organic short fibers 14 in the rubber composition is aligned in the extrusion direction (A direction), the long bubbles 11 exist in a state of being oriented in one direction. The elongated bubbles 11 are made of molten organic short fibers 14.
Are surrounded by a protective layer 13 adhered to the vulcanized rubber matrix 6A. The gas generated from the foaming agent or the like is taken into the protective layer 13. When the foaming agent or the like is added to the rubber matrix, in the vulcanized rubber composition (vulcanized rubber 6),
In addition to the long bubbles 11, the gas not taken into the long bubbles 11 exists as spherical bubbles 17.

When the rubber composition of the present invention is used for a tread or the like of a tire, the concave portion formed by exposing the long bubbles 11 on the surface functions as a drainage channel for efficient drainage. Further, since the surface of the concave portion is formed of the protective layer 13, the concave portion has excellent peeling resistance, excellent water channel shape retention, excellent water channel edge wear, and excellent water channel retention when a load is input. The thickness of the protective layer 13 is 0.5 to 50
μm is preferred.

In the rubber composition of the present invention, the ratio (L / D) of the maximum length (L) in the longitudinal direction (L) of each long bubble 11 (see FIG. 2) to the average diameter (D). )as,
It must be at least 3 (ie, 3 or more). The upper limit of the ratio (L / D) is not particularly limited, but is 8
~ 17 are selected. In the present invention, the ratio (L / D) is defined as a lower limit or an upper limit of any of the numerical ranges or a value of the ratio (L / D) employed in Examples described later. It is also preferable to use a lower limit or upper limit of any of the above numerical ranges or a numerical range having an upper limit of any one of the ratios (L / D) employed in Examples described later.

If the ratio (L / D) is less than 3, the length of the long bubbles 11 as long drain grooves appearing on the surface of the worn rubber composition cannot be increased, Further, since the volume cannot be increased, when the rubber composition is used for a tread or the like of a tire, it is not preferable because the water removal performance of the tire or the like cannot be improved.

When the rubber composition of the present invention is used for a tread or the like of a tire, if the maximum length (L) of the long bubbles 11 in the longitudinal direction is too short, the water-removing performance of the tire or the like is reduced and the tire is too long. And, the cut resistance of the rubber composition, the chipping of the block is deteriorated, and the wear resistance on a dry road surface is deteriorated.
Neither is preferred.

In the rubber composition of the present invention, the average diameter (D) of the elongated bubbles 11 (= the inner diameter of the protective layer 13, see FIG. 2) is preferably 20 to 500 μm. When the average diameter (D) is less than 20 μm, when the rubber composition is used for a tread or the like of a tire, the water exclusion performance of the tire or the like decreases. Both the cutting resistance and the chipping of the block deteriorate, and the abrasion resistance on a dry road surface deteriorates.

[0065] The average foaming ratio Vs in the rubber composition after vulcanization is preferably 3 to 40%, more preferably 5 to 35%. In the present invention, the lower limit or the upper limit of any one of the numerical ranges or the value of the average foaming ratio Vs employed in the examples described below is used as the lower limit as the average foaming rate Vs. It is also preferable that the lower limit or the upper limit of any one of the above or the numerical range having the upper limit of any one of the average foaming ratios Vs adopted in Examples described later.

The average foaming rate is defined as Vs.
1 means a foaming ratio Vs2 (as shown in FIG. 2,
When the bubbles 17 are formed, the spherical bubbles 17
Sum of foaming rate Vs1 and foaming rate Vs2 of long bubble 11
), And can be calculated by the following equation. Vs = (ρ₀ / Ρ₁ -1) × 100 (%) where ρ₁ Is the density of the rubber composition (foamed rubber after vulcanization).
Degree (g / cm^Three ). ρ₀ Is a rubber composition (after vulcanization)
(G / cm) ^Three )
You. The density of the rubber composition (foamed rubber after vulcanization)
And solid phase in the rubber composition (foamed rubber after vulcanization)
The density of the part is, for example, the weight in ethanol and the weight in air.
The amounts were measured and calculated from these.

When the average foaming ratio Vs is less than 3%,
For the generated water film, there is a possibility that a sufficient water exclusion function cannot be obtained due to the absolute lack of the concave volume due to the long bubbles, and the performance of the rubber composition on ice cannot be sufficiently improved. is there. On the other hand, the average foaming ratio Vs is 40%.
When it exceeds, the performance on ice can be improved, but the amount of bubbles in the rubber composition becomes too large, so that the breaking limit of the rubber composition is greatly reduced, and the durability is lowered. Not preferred. The average foaming rate Vs is the type and amount of the foaming agent, the type of the foaming auxiliary to be combined,
It can be appropriately changed depending on the amount, the amount of the resin, and the like.

In the present invention, the average foaming rate Vs is preferably 3 to 40%, and the long cells 11 preferably account for 10% or more of the average foaming rate Vs.
More preferably, it accounts for 50% or more. In other words,
The long cells 11 are at least one of all cells in the rubber composition.
Preferably occupies 0% by volume (10% by volume or more),
The long bubbles 11 are at least 5 of all the bubbles in the rubber composition.
More preferably, it occupies 0% by volume (50% by volume or more). If the ratio is less than 10%, the drainage function of the long bubbles 11 is small, and the water removal function may not be sufficient.

Although the rubber composition of the present invention can be suitably used in various fields, it can be particularly suitably used for a structure that needs to suppress slip on ice, and is most suitable for a tread of a pneumatic tire and the like. It can be suitably used. Examples of the structure required to suppress the slip on the ice include a tread for replacing a retreaded tire, a solid tire, a contact portion of a rubber tire chain used for running on an icy road, a crawler of a snowmobile, and shoes. Bottom and the like.

(Tire) The tire of the present invention has at least a tread, and other configurations are not particularly limited as long as at least the tread contains the rubber composition of the present invention. Can be selected appropriately. In other words, a tire having a tread of the rubber composition is the tire of the present invention.

An example of the tire of the present invention will be described below with reference to the drawings. As shown in FIG. 3, the tire 4 of the present invention includes a pair of bead portions 1 and the pair of bead portions 1.
A carcass 2, a belt 3 for clasping a crown portion of the carcass 2, and a tread 5
Have a radial structure in which are sequentially arranged. Note that the internal structure other than the tread 5 is the same as the structure of a general radial tire, and a description thereof will be omitted.

As shown in FIG. 4, a plurality of blocks 9 are formed in the tread 5 by a plurality of circumferential grooves 7 and a plurality of lateral grooves 8 intersecting the circumferential grooves 7.
The block 9 includes a tire width direction (B) in order to improve braking performance and traction performance on ice.
A sipe 10 extending along the direction (i.e., direction) is formed.

As shown in FIG. 5, the tread 5 includes an upper cap portion 5A directly in contact with the road surface, and a lower base portion 5B disposed adjacent to the inside of the tire of the cap portion 5A. And has a so-called cap-base structure.

As shown in FIGS. 2 and 7, the cap portion 5A is a foamed rubber containing countless long bubbles 11.
A normal rubber that is not foamed is used for the base portion 5B. The foamed rubber is the rubber composition after vulcanization. As shown in FIG. 2, the long bubbles 11 are oriented substantially in the circumferential direction of the tire (the direction of arrow A), and the periphery thereof is covered with the protective layer 13 made of the organic short fiber material. . In the present invention, the orientation of the elongated bubbles 11 covered with the protective layer 13 may not all be in the circumferential direction of the tire, and may be partially different from the circumferential direction of the tire. (See FIG. 5).

The method for producing the tire 4 is not particularly limited, but can be produced, for example, as follows. That is, first, the rubber composition is prepared. In this rubber composition, the organic short fibers are oriented in one direction. The rubber composition is stuck on an unvulcanized base which has been stuck to a crown portion of a green tire case in advance. At this time, the orientation direction of the organic short fiber,
It should be aligned with the circumferential direction of the tire. Then, vulcanization molding is performed in a predetermined mold under a predetermined temperature and a predetermined pressure. As a result, the cap portion 5A formed of the rubber composition of the present invention
Is obtained on the vulcanized base portion 5B.

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, and gas is generated. On the other hand, the organic short fibers 14 are melted (or softened), and the viscosity (melt viscosity) is lower than the viscosity (flow viscosity) of the rubber matrix (see FIG. 6). Move into the organic short fibers whose viscosity has been reduced,
Stay. As shown in FIG. 2, the cap portion 5A after cooling
Is a long bubble 11 oriented substantially in the circumferential direction of the tire.
Is a rubber composition having a high foaming ratio in which a large number of rubbers exist.
The rubber composition rich in the content of the long bubbles 11 is the rubber composition of the present invention.

Next, the operation of the tire 4 will be described.
The tire 4 is driven on an icy road. The surface of the tread 5 of the tire 4 is worn by the friction between the tire 4 and the icy and snowy road surface. Then, as shown in FIG.
The groove-shaped concave portion 12 (when a spherical bubble 17 is present, also includes the concave portion 18 due to the spherical bubble 17) is exposed on the ground surface of the cap portion 5A of the tread 5. When the tire 4 is further driven, a water film formed between the tire 4 and the icy and snowy road surface due to the contact pressure and frictional heat between the tire 4 and the contact surface thereof is exposed on the contact surface of the cap portion 5A of the tread 5. Due to the myriad of recesses 12, they are quickly removed and removed. Therefore, the tire 4 does not slip on the icy and snowy road surface.

In the tire 4, the groove-shaped concave portion 12 which is substantially oriented in the circumferential direction of the tire functions as a drain groove for draining efficiently. Since the surface (periphery) of the concave portion 12 is formed of the protective layer 13 having excellent peeling resistance, the concave portion 12 is hardly crushed even under a high load, and retains high drainage groove shape retention and water rejection performance. 12, the water rejection performance of the tire 4 at the rear side in the rotation direction is improved, so that the tire 4 is particularly excellent in the braking performance on ice. In the tire 4, the μ on the ice in the horizontal direction is improved by the scratching effect of the protective layer 13, and the handling on the ice is good.

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.

[0080]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Examples 1 to 15 and Comparative Examples 1 to 5) Table 1
And each rubber composition of the composition shown in Table 2 was prepared and vulcanized. The maximum vulcanization temperature during vulcanization of each rubber composition was 175 ° C. when measured by embedding a thermocouple in the rubber composition.

The organic short fibers of Examples 1 to 8 and Comparative Examples 1 and 2 are produced according to a usual melt spinning method, and have a substantially circular cross section in a direction perpendicular to the axis. The organic short fiber is polyethylene (HDPE) in Examples 1 to 8 and Comparative Examples 1 and 2, and has a melting point measured by a Dupont DSC under the conditions of a temperature rising rate of 10 ° C./min and a sample weight of about 5 mg. The peak temperature (melting point) was 135 ° C. and 3 denier.

The organic short fibers of Examples 9 to 15 and Comparative Examples 3 to 5 were produced by a usual melt spinning method, and had a substantially circular cross section in a direction perpendicular to the axis. The organic short fiber is polypropylene in Examples 9 to 15 and Comparative Examples 3 to 5, and is a melting point peak temperature measured by a Dupont DSC under the conditions of a temperature rising rate of 10 ° C./min and a sample weight of about 5 mg ( Melting point) was 167 ° C. and 3 denier.

Therefore, the melting point of the organic short fiber in each of the above Examples and Comparative Examples is lower than the maximum vulcanization temperature at the time of vulcanization of the rubber composition. During the vulcanization of each rubber composition, the viscosity of the organic short fibers became lower than the viscosity of the rubber matrix before the temperature of each rubber composition reached the maximum vulcanization temperature. The viscosity (melt viscosity) of the organic short fiber at the maximum vulcanization temperature was measured using a cone rheometer (starting temperature was 190 ° C., and the torque generated while decreasing the temperature by 5 ° C. was used to determine the torque of the organic short fiber. As viscosity, the temperature dependence of the viscosity was measured, and the viscosity of the organic short fiber 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 in Example 1.) In Examples 1 to 8, it was 5 to 6 kg · cm.
In No. 15, it was 3 to 4 kg · cm.

The viscosity (flow viscosity) of the rubber matrix at the maximum vulcanization temperature was measured by using a cone rheometer model 1-C manufactured by Monsanto Co., and applying a constant amplitude input of 100 cycles / min while changing the temperature. When the torque was measured with time and the minimum torque value at that time was defined as viscosity (dome pressure 0.59 MPa, holding pressure 0.78 MPa, closing pressure 0.78 MPa, swing angle ± 5 °), In the comparative example, the rubber matrix in Table 1 was 26 to 27 kg · cm, and the rubber matrix in Table 2 was 24 to 25 kg · cm.

Next, rubber compositions having the compositions shown in Tables 1 and 2 were produced. A tread of a tire was formed using each of the obtained rubber compositions, and tires for each test were manufactured according to ordinary tire manufacturing conditions.

This tire is a radial tire for a passenger car, and its tire size is 185 / 70R13.
Its structure is as shown in FIG. That is, a radial structure in which a pair of bead portions 1, a carcass 2 connected in a toroidal shape to the pair of bead portions 1, a belt 3 for clinching a crown portion of the carcass 2, and a tread 5 are sequentially arranged. Having.

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 number of hits is 50/5 cm. As shown in FIG. 4, four blocks 9 are arranged in the tread 5 of the tire 4 in the width direction of the tire. The size of block 9 is
The circumferential dimension of the tire is 35 mm, and the width dimension of the tire is 30 mm. The sipe 10 formed in the block 9 has a width of 0.4 mm and a circumferential interval of the tire of about 7 mm. In addition, this tire 4
The tread 5 includes a long bubble 11 whose longitudinal direction is substantially oriented in the circumferential direction (A direction) of the tire, and the periphery of which is surrounded by a protective layer 13 made of an organic short fiber material. It is covered with.

Incidentally, for each rubber composition (unvulcanized),
A tensile test was performed. <Tensile test> The unvulcanized rubber composition after extrusion was sliced to obtain an unvulcanized rubber sheet having a gauge of 2 mm. In the extrusion direction P and the vertical direction V, a JIS-3 dumbbell sample was punched out, pulled at room temperature at a tensile strength of 100 mm / min, and subjected to a M25 stress at 25% deformation.
Tables 1 and 2 show the ratios of P and M25V. In addition, the result of a tensile test means that the larger the numerical value, the better the orientation of the organic short fibers.

The obtained tires were evaluated for performance on ice and abrasion resistance. Table 1 and Table 2 show the results.
It was shown to. In addition, the foaming rate of the foamed rubber in the tread 5 was calculated (measured) by the above-described formula.

<Performance on Ice> The tire was mounted on a domestic 1600CC class passenger car, and the passenger car was driven on a general asphalt road for 200 km, then on a flat road on ice, and the brake was depressed at a speed of 20 km / h. The distance until the tire was locked and stopped was measured. As a result, the reciprocal of the distance was set to 10 for the tires of Comparative Example 1 and Comparative Example 3.
The index was indicated as 0. The higher the value, the better the performance on ice.

<Wear Resistance> The tires were mounted on the front wheels of a domestically produced 1600cc class passenger car (FF vehicle), and the tire groove depth after traveling 20,000 km on a general road was measured to calculate the amount of wear. Table 1 shows the reciprocal index assuming that the tire of Comparative Example 1 is 100.
And 2. The larger the value, the better the wear resistance.

[0093]

[Table 1]

[0094]

[Table 2]

In Tables 1 and 2, the numerical value (amount) in the column of the content of blend means "parts by weight". "BR"
Means cis-1,4-polybutadiene (BR01, manufactured by Nippon Synthetic Rubber Co., Ltd.), and "SBR" indicates styrene-butadiene rubber (# 150, manufactured by Nippon Synthetic Rubber Co., Ltd.)
0), and carbon N220 means carbon black (Carbon N220, manufactured by Asahi Carbon Co., Ltd.)
"Antiaging agent" means Nocrack 6C manufactured by Ouchi Shinko Chemical Co., Ltd., "Vulcanization accelerator" in the upper row means dibenzothiazyl disulfide, and "Vulcanization accelerator" in the lower row.
Means N-cyclohexyl-2-benzothiazyl-sulfenamide, "blowing agent DPT" means dinitropentamethylenetetramine, and "blowing agent ADCA"
Means azodicarbonamide and "foaming aid A"
Means zinc benzenesulfinate, "foaming aid B" means a mixture of stearic acid: urea = 15: 85, and "foaming aid C" means urea.

"Fiber" means an organic short fiber, and "seed"
"PE" means polyethylene and "PP" means polypropylene. Regarding "liquid polymer",
“Molecular weight” means the weight average molecular weight, and the unit of the numerical value in this column means “10,000”. The thing of 20,000 is LIR-20 manufactured by Kuraray Co., Ltd. The thing of 30000 is LIR-30 manufactured by Kuraray Co., Ltd. The thing of 50,000 is LIR-50 manufactured by Kuraray Co., Ltd. "Unsaturated fatty acids"
The term “conjugated diene-based component” means “conjugated diene-based acid having at least one conjugated double bond in the molecule” contained in the unsaturated fatty acid. The “unsaturated fatty acid” used here is prepared according to a conventional method.

From the results of Tables 1 and 2, the following is clear. That is, in Comparative Examples 1 and 3 in which the unsaturated fatty acid and the liquid polymer were not used, the orientation of the organic short fibers in the rubber composition could not be sufficiently controlled, and the vulcanized rubber composition or Tread performance on ice and abrasion resistance are not sufficient. Further, in Comparative Examples 2 and 4 in which the liquid polymer is used but the content exceeds 10 parts by weight, the orientation of the organic short fibers in the rubber composition can be sufficiently controlled, and the rubber composition after vulcanization or The performance of the tread on ice is improved, but the wear resistance is deteriorated.

Further, in the case of using the above unsaturated fatty acid, in Comparative Example 5 in which the content of the conjugated diene acid contained therein is less than 10%, the orientation of the organic short fibers in the rubber composition can be sufficiently controlled. Although the performance of the vulcanized rubber composition or tread on ice is improved, abrasion resistance is deteriorated. On the other hand, in the case of the present invention, 0.1 to 10 parts by weight of an unsaturated fatty acid in which the proportion of a proton derived from a conjugated double bond is at least 10% of the total amount of protons derived from unsaturation and / or a liquid polymer In Examples 1 to 15 using 0.5 to 10 parts by weight of the rubber composition, the orientation of the organic short fibers in the rubber composition can be sufficiently controlled, and the on-ice performance and abrasion resistance of the vulcanized rubber composition or tread. Properties can be sufficiently improved in a well-balanced manner.

[0099]

According to the present invention, the above-mentioned conventional problems can be solved. Further, according to the present invention, it is possible to provide a tire having excellent ability to remove the water film, a large coefficient of friction with an ice surface, and excellent performance on ice and abrasion resistance. Further, according to the present invention, it is excellent in on-ice performance and abrasion resistance, and includes long bubbles capable of exhibiting the water film removing ability and the edge effect in a state where the orientation is sufficiently controlled,
It is possible to provide a rubber composition suitable for a structure such as a tread of a tire, which needs to suppress the slip on the icy and snowy road surface.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating the principle of aligning the orientation of organic short fibers.

FIG. 2 is a schematic cross-sectional explanatory view of a rubber composition (after vulcanization) of the present invention.

[FIG. 3] FIG. 3 is a schematic explanatory view showing a partial cross section of a tire according to the present invention.

FIG. 4 is a partially schematic explanatory view of a peripheral surface of a tire according to the present invention.

FIG. 5 is a schematic cross-sectional view partially illustrating a tread of the tire of the present invention.

FIG. 6 is a graph showing a relationship between a vulcanization time, a viscosity of a rubber matrix, and a viscosity of an organic short fiber.

FIG. 7 is a partially enlarged schematic explanatory view of a worn tread of the tire of the present invention.

[Explanation of symbols]

 Reference Signs List 1 pair of bead portions 2 carcass 3 belt 4 tire 5 tread 5A cap portion 5B base portion 6 vulcanized rubber 6A vulcanized rubber matrix 7 circumferential groove 8 lateral groove 9 block 10 sipes 11 long bubble 12 concave portion 13 protective layer 14 Organic short fiber 15 Rubber matrix 16 Base 17 Spherical bubble 18 Depression

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 9/00 C08L 9/00

Claims (9)

[Claims] 1. A rubber component comprising at least one selected from a natural rubber and a diene-based synthetic rubber;
A rubber matrix containing at least one of 0.1 to 10 parts by weight of an unsaturated fatty acid having at least two carbon-carbon double bonds in the molecule and 0.5 to 10 parts by weight of a liquid polymer with respect to 00 parts by weight; For 100 parts by weight of the rubber component,
0.5 to 30 parts by weight of organic short fibers whose viscosity is lower than the viscosity of the rubber matrix before the temperature of the rubber matrix reaches the maximum temperature during vulcanization. In a saturated fatty acid, the proportion of protons derived from a conjugated double bond in the total proton amount derived from unsaturation is at least 10%, and the liquid polymer comprises a diene-based polymer. . 2. The rubber composition according to claim 1, wherein the weight average molecular weight of the liquid polymer is at most 50,000. 3. The unsaturated fatty acid comprises at least two conjugated diene-based acids having at least one conjugated double bond in the molecule.
The rubber composition according to claim 1, comprising 5%. 4. An organic staple fiber comprising a crystalline polymer, the melting point of which is lower than the maximum vulcanization temperature.
The rubber composition according to any one of the above. 5. The rubber composition according to claim 1, wherein the organic short fiber comprises a polyolefin. 6. The rubber composition according to claim 5, wherein the polyolefin is one of polyethylene and polypropylene. 7. The rubber composition according to claim 1, wherein the rubber matrix contains a foaming agent. 8. The rubber composition according to claim 1, which has a foaming ratio of 3 to 40%. 9. A vehicle comprising: a pair of bead portions; a carcass connected to the bead portion in a toroidal shape; a belt for tightening a crown portion of the carcass; and a tread, wherein at least the tread comprises 8. A tire, comprising the rubber composition according to any one of items 8 to 8.