JP2003201371A - Rubber composition, vulcanized rubber, and tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire which can always efficiently form fine drain grooves ensuring the capability of removing a water film and sufficiently exhibits an edge effect or a spike effect so that it is excellent in performances (surface braking and driving performance) on the ice, a vulcanized rubber that can be suitable used for the tread of the tire, and a rubber composition that can be suitable used for a raw material of a vulcanized rubber. <P>SOLUTION: The rubber composition contains organic short fibers containing fine particles, wherein the fine particles have a Mohs hardness higher than that of ice (Mohs hardness of 1 to 2). The tire has a tread obtained by using a vulcanized rubber made by vulcanizing the rubber composition to form specified long cells. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition, a vulcanized rubber and a tire. More specifically, the present invention relates to a tire having excellent on-ice performance, and a vulcanized rubber suitable for use in a tread of the tire. And a rubber composition that can be suitably used as a raw material for the vulcanized rubber.

[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 of tires on ice and snow roads (hereinafter referred to as "ice performance"). ing. 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 a reduction in the friction coefficient between the tire and the ice and snow road surface. For this reason,
The water film removing ability of the tread of the tire, the edge effect, and the spike effect greatly affect the performance on ice. Therefore, in order to improve the on-ice performance of the tire, it is necessary to improve the water film removing ability, the edge effect and the spike effect of the tread.

In order to provide a tread of a tire with a water film removing ability, a micro drainage groove (having a depth and a width of 1) is formed on the surface of the tire.
(About 00 μm) are provided, and the water film is eliminated by the micro drainage grooves to increase the friction coefficient of the tire on the snow and snow road surface. However, in this case, although the on-ice performance can be improved in the initial stage of use of the tire, there is a problem that the on-ice performance is gradually lowered due to wear of the tire. Therefore, in order to prevent the performance on ice from being deteriorated even if the tire is worn, it is considered to form bubbles in the tire, that is, the tread.

By the way, in Japanese Unexamined Patent Publication No. 4-38207, while increasing the bubble occupancy rate on the surface of foamed rubber having communicating bubbles, short fibers having good adhesion to the rubber are mixed with the rubber, and this is used as the tread. A method for forming a micro drainage groove on the surface of the tread by using it is described. However, in this case, even if the tread is worn by running, the short fibers that are not substantially parallel to the worn surface do not easily separate from the tread, and the micro drainage groove as originally intended is always efficiently formed. However, the friction coefficient on the ice and snow road surface was not sufficiently improved. Further, there is a problem in that the detachment of the short fibers largely depends on running conditions and the like, and the on-ice performance cannot be reliably improved.

In Japanese Patent Laid-Open No. 11-48264, etc., during vulcanization of a rubber composition of a rubber component and a foaming agent, it is necessary to measure the rubber composition until the temperature of the rubber composition reaches the maximum vulcanization temperature. It is disclosed that an organic fiber having a low viscosity is blended and vulcanized. However, in the case of such a vulcanized rubber tread tire, only micro drainage grooves are formed on the surface of the tread tire, which is effective in improving the water film removal ability, but the edge effect and the spike effect (scratch effect) There is room for improvement in improving (effect).

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention is capable of always efficiently forming a micro drainage groove capable of reliably exhibiting a water film removing property, and at the same time, providing an edge effect or a spike. A tire having excellent on-ice performance (surface braking / driving performance) that also exerts a sufficient effect, a vulcanized rubber suitable for use in a tread of the tire, and a rubber composition suitable for use as a raw material of the vulcanized rubber The challenge is to provide. Here, the unvulcanized rubber composition mixed by kneading or the like is simply a rubber composition,
The rubber composition after vulcanization is called vulcanized rubber.

[0007]

Means for Solving the Problems The present inventors have found that when the rubber composition contains fine particle-containing organic fibers, and the Mohs hardness of the fine particles is equal to or higher than the hardness of ice, the surface portion of the rubber composition is , It was found that such a fiber sufficiently exerts a certain scratching effect on the surface part, and when bubbles are formed in the rubber composition, the edge effect and the spike effect on the surface part are combined with the use of the fine particle-containing organic fiber. It is possible to provide a micro drainage groove that exerts the above, and when such a rubber composition or a vulcanized rubber thereof is used as a tread of a tire, while exhibiting an excellent edge effect and a spike effect on the snow and snow surface, , The tire has a large coefficient of friction with the ice and snow road surface in order to fully demonstrate the ability to remove the water film generated on the ice and snow road surface.
The present invention has been completed by finding that the performance on ice is comprehensively excellent.

That is, the present invention provides the following (1) to (1)
By adopting the characteristic configuration of 5), the above object is achieved. (1) A rubber composition comprising a rubber matrix and fine particle-containing organic fibers containing fine particles having a Mohs hardness of 2 or more.

(2) The rubber composition as described in (1) above, wherein the rubber component constituting the rubber matrix is at least one selected from natural rubber and diene synthetic rubber. (3) The fine particles have a diameter of 0.1 to 100.
The rubber composition according to the above (1) or (2), wherein the rubber composition has a thickness of μm.

(4) The rubber composition as described in (1) to (3) above, wherein the fine particles have a frequency of 20% by mass or more at the peak value of the particle size distribution. (5) The fine particles have an aspect ratio of 1.1 or more,
The rubber composition according to any one of (1) to (4) above, wherein the rubber composition has corners.

(6) A resin having viscosity characteristics such that the viscosity of the fine-particle-containing organic fiber becomes lower than the viscosity of the rubber matrix before the vulcanization maximum temperature during vulcanization is reached;
The rubber composition as described in (1) to (5) above, which comprises the fine particles contained in an amount of 5 to 100 parts by mass relative to 00 parts by mass. (7) The rubber composition as described in any one of (1) to (6) above, wherein the organic fibers containing fine particles are short fibers having a fiber length in the range of 0.1 to 10 mm.

(8) The above-mentioned (6) or (7), wherein the resin is a crystalline polymer composed of at least one selected from polyethylene and polypropylene, and has a melting point of 190 ° C. or lower. Rubber composition. (9) The rubber composition as described in (1) to (8) above, wherein the fine particle-containing organic fiber is added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. (10) The rubber composition as described in (1) to (9) above, which comprises a foaming agent.

(11) A vulcanized rubber obtained by vulcanizing the rubber composition as described in (1) to (10) above. (12) The vulcanized rubber as described in (11) above, wherein elongated bubbles having a resin layer containing fine particles are formed at the interface with the rubber matrix. (13) The vulcanized rubber according to the above (11) or (12), which has a foaming rate Vs of 3 to 40%.

(14) A pair of beads, a carcass connected to the beads in a toroidal shape, and a belt and a tread for tightening the crown of the carcass, and at least the tread described above. (11) to (1
A tire comprising the vulcanized rubber according to 3). (15) The tire according to (14), in which the long bubbles are oriented in the tire circumferential direction.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments and examples of the present invention will be described below in detail with reference to the drawings. Figure 1
FIG. 1 is a schematic cross-sectional explanatory view of a tire according to the present invention. FIG. 2 is an explanatory view for explaining the principle of orienting the fine particle-containing organic fiber in a fixed direction. FIG. 3 is a schematic explanatory view showing a part of the peripheral surface of the tire according to the present invention. 4 (a) and (b)
FIG. 3 is a schematic cross-sectional view taken along the circumferential direction and the width direction of the tread portion of the tire according to the present invention.

The rubber composition according to the present invention is a rubber composition containing fine particle-containing organic fibers, and the Mohs hardness of the fine particles is higher than 2. The rubber composition according to the present invention contains fine-particle-containing organic fibers, and the Mohs hardness of the fine particles is equal to or higher than the hardness of ice (1 to 2), that is, equal to or higher than 2, so that a certain scratching effect can be obtained. Can be exerted on the surface part of. Further, the fine particle-containing organic fiber, by blending a foaming agent and the like described below, in combination with the use of the fine particle-containing organic fiber,
Bubbles are formed and can appear as micro long grooves on the surface. Therefore, when the rubber composition according to the present invention is used for a tread of a tire, while exhibiting an excellent edge effect and a spike effect on a snowy surface,
Exhibits the ability to remove the water film generated on ice and snow roads. For this reason, the obtained tire has a large coefficient of friction with the icy and snowy road surface, and has excellent on-ice performance (surface braking / driving performance of the tire on the icy and snowy road surface).

The Mohs hardness of the fine particles is the hardness of ice (1
To 2) or more, 2 or more, preferably 3 to 10 in hardness. The hardness of the fine particles is 2
When it is less than the above range, the edge effect and the spike effect cannot be sufficiently exhibited even when the rubber composition is used for a tire tread.

The fine particles in the fine particle-containing organic fiber may be inorganic fine particles, organic fine particles, or fine particles in which these are mixed as long as they have the hardness of ice or higher. As the inorganic fine particles, for example, gypsum, calcite,
Examples thereof include fluorite, orthoclase, quartz, and gold stone, and preferably silica glass having a Mohs hardness of 5 or more (hardness: 6.
5), quartz (hardness 7.0), fused alumina (hardness 9.
0) etc. can be mentioned. Among them, silica glass, alumina (aluminum oxide) and the like are inexpensive and can be easily used.

The fine particles have a fine particle diameter of 0.1 to 100.
It is preferably in the range of .mu.m, more preferably 0.
5 to 80 μm range, more preferably 20 to 60 μm
The range is m. When the particle size is less than 0.1 μm,
During the production of the fine particle-containing organic fiber, the particles tend to agglomerate and the dispersibility thereof tends to decrease. Further, in a tire or the like using such a fiber, it becomes impossible to exhibit a sufficient scratching effect, an edge effect, or a spike effect. On the other hand, the fine particle diameter is 100 μm
If it exceeds, problems such as fiber breakage frequently occur during the production of the fine particle-containing organic fiber, and the fine particle-containing organic fiber cannot be efficiently obtained.

The above-mentioned fine particles preferably have a frequency at the peak value of the particle size distribution of 20% by mass or more, more preferably 25% by mass or more, further preferably 30% by mass.
It is at least mass%. Here, the frequency means the mass ratio of existing particles in a particle size distribution (particle size distribution curve) in the particle size distribution (particle size distribution curve) with respect to the total particle mass when the particle size is divided by a step width of 2 μm, and is the peak value. The frequency count means the frequency count in the section width in which the above-mentioned step width in the particle size distribution curve includes the maximum peak value.

When the frequency of the fine particles at the peak value is 20% by mass or more, the particle size distribution curve of the fine particles becomes sharp and the particle diameter becomes uniform. Therefore, it is possible to obtain a good fiber in which breakage does not easily occur during the spinning of the fine particle-containing organic fiber, and when the fiber is used for a tire, the performance on ice becomes stable. On the other hand, when the frequency of the fine particles at the peak value is less than 20% by mass, the fibers are likely to be spun, and the tire performance tends to vary. Further, when the particle size is within the above range, the larger the particle size, the better the on-ice performance of the tire. For this reason,
It is desirable that the particle diameter of the peak value is as large as possible within the above-mentioned particle diameter range. However, if the particle diameters of the fine particles vary, even if an attempt is made to select fine particles having a relatively large particle diameter, it is It is not preferable because it is often present. In order to increase the frequency of such particle size distribution, classification is preferably performed. However, in order to increase the frequency, other methods besides classification can be used.

Further, it is preferable that the fine particles have an aspect ratio of 1.1 or more and that corners are present. The aspect ratio is more preferably 1.2 or more, further preferably 1.3 or more. here. The presence of a corner means that the entire surface is not a spherical surface or a smooth curved surface. The fine particles of the present invention may have fine particles having corners from the beginning, but even if the fine particles have a spherical shape, they can be used by allowing the fine particles to have corners on the surface thereof, and more particles can be used. Corners can be present. The fine particle shape can be confirmed by observing the fine particle group with an electron microscope, and it is confirmed that the fine particle shape is not spherical. The aspect ratio, which represents the ratio of the major axis to the minor axis of the particles, is 1.1.
If it is above, the existence of the corners formed on the surface of the particles can be sufficiently angular. Therefore, in a tire or the like using the fine particle-containing organic fiber containing such fine particles, the scratching effect, the edge effect, and the spike effect can be sufficiently enhanced.

The fine particles are contained in an amount of 5 to 100 parts by weight, and particularly preferably 7 to 50 parts by weight, based on 100 parts by weight of the resin forming the fine particle-containing organic fiber. When the amount of the fine particles is less than 5 parts by mass, the scratching effect on the rubber product of the rubber composition, and the edge effect and the spike effect in the tire tread may not sufficiently occur. On the other hand, when the amount of the fine particles exceeds 100 parts by mass, problems such as fiber breakage frequently occur during the production of the fine particle-containing organic fibers, and the fine particle-containing organic fibers may not be efficiently obtained.

The rubber component in the rubber composition according to the present invention is not particularly limited, but when it is used in a tire or the like described later, it is a rubber component comprising at least one selected from natural rubber and diene-based synthetic rubber. preferable. The rubber component may include only natural rubber, only diene-based synthetic rubber, or both. 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), polyisoprene (IR), polybutadiene ( BR) and the like. Among these diene synthetic rubbers, cis-1,4-polybutadiene is preferable, and one having a cis content of 90% or more is particularly preferable because of its low glass transition temperature and large effect on ice performance.

When the rubber composition of the present invention is used for a tire tread or the like, the rubber component preferably has a glass transition temperature of -60 ° C or lower. Use of a rubber component having such a glass transition temperature is advantageous in that the tread or the like maintains sufficient rubber elasticity even in a low temperature range and exhibits the above-mentioned on-ice performance.

The fine particle-containing organic fiber used in the rubber composition of the present invention has a fiber length of preferably 0.1 to 10 mm, particularly preferably 0.5 to 6 mm. In the vulcanized rubber obtained by vulcanizing the rubber composition, the presence of the fine particle-containing organic fiber in such a length effectively acts as an edge effect and a spike effect, and includes a foaming agent described later. It is also possible to sufficiently form long bubbles that can efficiently function as micro drainage channels. If the fine particle-containing organic fiber length is less than 0.1 mm,
The effect as the fine particle-containing organic fiber may not be sufficiently exhibited. Also, the length of the above-mentioned fine particle-containing organic fiber is 1
If it exceeds 0 mm, the fine particle-containing organic fibers are entangled with each other, and the dispersibility thereof tends to decrease.

In the above-mentioned fine particle-containing organic fiber,
The fineness is preferably 1 to 500 dtex. If the fineness is less than 1 dtex, the fine-particle-containing organic fiber is likely to be cut, so that the edge effect or the spike effect may not be sufficiently exhibited. Further, when the fineness of the fine particle-containing organic fiber exceeds 500 dtex, it becomes difficult to cut and there is a possibility that short fibers having a predetermined length cannot be obtained reliably.

The fine particle-containing organic fiber used in the rubber composition of the present invention is a resin having a viscosity characteristic that the viscosity becomes lower than the viscosity of the rubber matrix of the rubber component before the maximum vulcanization temperature during vulcanization is reached. It is preferable to use. The above-mentioned resin has a thermal property of melting (including softening) before the rubber composition reaches the maximum vulcanization temperature.

When the above resin has such thermal characteristics, it can function as a micro drainage groove in the vulcanized rubber obtained by vulcanizing the rubber composition containing the above-mentioned fine particle-containing organic fiber. The long bubbles can be easily formed. The maximum vulcanization temperature means the maximum temperature reached by the rubber composition during vulcanization of the rubber composition. For example, in the case of mold vulcanization, it means the maximum temperature reached by the rubber composition after the rubber composition enters the mold until it exits the mold and is cooled. The maximum vulcanization temperature can be measured, for example, by embedding a thermocouple in the rubber composition.

The viscosity of the above-mentioned rubber matrix means a flow viscosity and can be measured by using, for example, a cone rheometer, a capillary rheometer or the like.
Further, the viscosity of the resin means a melt viscosity, for example,
It can be measured using a cone rheometer, a capillary rheometer, or the like.

The material of the resin is not particularly limited and may be appropriately selected according to the purpose. In order to have the above-mentioned thermal characteristics, for example, its melting point is higher than the maximum vulcanization temperature. A resin made of a low crystalline polymer is particularly preferable. In the resin made of the crystalline polymer, the larger the difference between the melting point and the maximum vulcanization temperature of the rubber composition, the faster the resin melts during the vulcanization of the rubber composition. The viscosity of the rubber matrix becomes earlier than that of the rubber matrix. Therefore, when the resin melts, the gas existing in the rubber composition, such as the gas generated from the foaming agent mixed in the rubber composition, gathers inside the resin having a lower viscosity than the rubber matrix. As a result, in the vulcanized rubber of the rubber composition, bubbles having a resin layer containing fine particles between them and the rubber matrix, that is, capsule-like long bubbles covered with the resin do not collapse. It is efficiently formed in the state. In the tread, the capsule-shaped long air bubbles appear on the surface of the tread, and the grooves generated by friction function as the above-mentioned micro drainage grooves, and the edge effect and the spike effect are sufficiently exerted together with the water film eliminating effect. be able to.

On the other hand, when the melting point of the above-mentioned resin is close to the maximum vulcanization temperature of the rubber composition, the resin does not melt promptly in the initial stage of vulcanization but melts in the final stage of vulcanization. At the end of vulcanization, a part of the gas present in the rubber composition is taken into the vulcanized rubber matrix and does not collect inside the molten resin. As a result, the long bubbles that effectively function as the micro drainage channels are not efficiently formed. Further, if the melting point of the resin is too low, for example, fusion of the fine particle-containing organic fibers occurs during compounding and kneading the fine particle-containing organic fibers in the rubber composition, and dispersion of the fine particle-containing organic fibers. In some cases, defects may occur, and long bubbles that may function as the micro drainage channels may not be efficiently formed. Therefore, it is preferable that the melting point of the resin is selected within a range such that the viscosity of the rubber matrix and the viscosity of the resin are reversed during the vulcanization step without melting and softening at the temperature in each step before vulcanization.

The upper limit of the melting point of the resin is not particularly limited, but when bubbles having a resin layer between the resin and the rubber matrix are desired, it is preferable to select in consideration of the above points, and in general, Is lower than the maximum vulcanization temperature of the rubber matrix, more preferably 10 ° C. or more,
It is particularly preferable that the temperature is 20 ° C. or higher. The industrial vulcanization temperature of the rubber composition is generally about 190 ° C. at the highest, but, for example, when the maximum vulcanization temperature is set above 190 ° C., The melting point is usually 1
It is selected in the range of 90 ° C or lower, preferably 180 ° C or lower, more preferably 170 ° C or lower. The melting point of the resin 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 can be used as the melting point.

The above 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, as described above, in the present invention, it is formed from an organic material containing a large amount of crystalline polymer in that the viscosity change rapidly occurs due to the phase transition and the viscosity control is easy. It is preferable that it is formed only from a crystalline polymer.

Specific examples of the crystalline polymer include polyethylene (PE), polypropylene (PP),
Polybutylene, polybutylene succinate, polyethylene succinate, syndiotactic-1,2-polybutadiene (SPB), polyvinyl alcohol (PV
A), polyvinyl chloride (PVC) and other single composition polymers, and those whose melting point is controlled within an appropriate range by copolymerization, blending, etc. can also be used, and those obtained by adding additives to these resins can also be used. it can. 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 preferable, and the melting point is relatively low and polyethylene (PE) is easy to handle.
Is particularly preferable.

As the non-crystalline polymer resin, for example, polymethylmethacrylate (PMMA), acrylonitrile-butadiene-styrene copolymer (ABS), polystyrene (PS), polyacrylonitrile, copolymers of these, and these Blends and the like can be mentioned. These may be used alone or in combination of two or more.

The above-mentioned fine-particle-containing organic fiber is a rubber component 100.
It is preferably blended in the range of 0.5 to 30 parts by mass, particularly 1 to 20 parts by mass, and further 2
It is preferable to blend in the range of 10 to 10 parts by mass. If the amount of the fine particle-containing organic fiber is less than 0.5 part by mass, the effect of compounding the fiber cannot be sufficiently exerted, that is, in the case of vulcanized rubber, the scratching effect is sufficiently exerted. On the other hand, the tire tread does not show the edge effect or the spike effect and the corresponding improvement in the on-ice performance. On the other hand, if the blending amount exceeds 30 parts by mass, the extrusion workability of the fine particle-containing organic fiber is deteriorated, and the fiber itself is roughened to cause inconveniences such as cracks in the vulcanized rubber and the tread of the tire. It may occur and is not preferable.

A foaming agent may be added to the rubber composition according to the present invention in order to form bubbles after the application.
By blending such a foaming agent and using a resin having the above properties for the fiber, the vulcanized rubber or tread from the above rubber composition has long bubbles and forms micro drainage grooves. Water film removal ability is imparted. Examples of the foaming agent include dinitrosopentamethylenetetramine (DPT), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivatives, oxybisbenzenesulfonylhydrazide (OBSH), and carbon dioxide-generating heavy hydrocarbons. Ammonium carbonate, sodium bicarbonate, ammonium carbonate, nitrogen-generating nitrososulfonylazo compounds, N, N'-
Examples thereof include dimethyl-N, N'-dinitrosophthalamide, toluenesulfonyl hydrazide, P-toluenesulfonyl semicarbazide, P, P'-oxy-bis (benzenesulfonyl semicarbazide) and the like.

Among 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. Due to the action of the foaming agent, the obtained vulcanized rubber becomes 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 another component and use it in combination with the above foaming agent. Examples of the foaming assistant 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.

The content of the foaming agent in the rubber composition varies depending on the type and amount of each component contained in the vulcanized rubber or tread, the desired foaming ratio, etc., and cannot be unconditionally specified. Although it may be appropriately determined according to the purpose, it is generally 1 to 10 per 100 parts by mass of the rubber component.
It is preferably about parts by mass. The foaming agent may be blended in the rubber matrix or in the fine particle-containing organic fiber.

Other components to be added to the rubber composition according to the present invention can be used within a range that does not impair the effects of the present invention. For example, a vulcanizing agent such as sulfur and dibenzothiazyl disulfide can be added. Sulfurization accelerator, vulcanization acceleration aid, N-
Sulfidation inhibitors such as cyclohexyl-2-benzothiazyl-sulfenamide and N-oxydiethylene-benzothiazyl-sulfenamide, antiozonants, colorants,
In addition to antistatic agents, dispersants, lubricants, antioxidants, softeners, inorganic fillers such as carbon black and silica, various compounding agents usually used in the rubber industry are appropriately selected and used according to the purpose. be able to. These may be used alone or in combination of two or more, or may be commercially available products.

In the rubber composition according to the present invention, the above components are appropriately selected, kneaded and heated under the following conditions and methods,
It is prepared by extrusion or the like. In the kneading, various conditions such as a volume to be introduced into the kneading device, a rotation speed of the rotor, a kneading temperature, a kneading time, a kneading device and the like are not particularly limited and can be appropriately selected according to the purpose. A commercially available product can be preferably used as the kneading device. The heating or extrusion is the heating or extrusion time,
There are no particular restrictions on various conditions such as the heating or extruding device, and they can be appropriately selected according to the purpose. A commercially available product can be preferably used as the heating or extruding device. The heating or extruding temperature is appropriately selected within a range that does not cause foaming when a foaming agent is present. Generally, the extrusion temperature is preferably about 90 to 110 ° C.

The fine particle-containing organic fiber is blended in the rubber composition, and the fine particle-containing organic fiber is oriented in the extrusion direction by the above-mentioned extrusion or the like. In order to carry out this orientation effectively,
It suffices to control the fluidity of the rubber composition within a limited temperature range. Specifically, in the rubber composition, aroma oils, naphthene oils, paraffin oils, ester oils, etc. Plasticizer, liquid polyisoprene rubber,
By appropriately adding a processability improving agent such as a liquid polymer such as a liquid polybutadiene rubber, the viscosity of the rubber composition is lowered,
It is preferable to increase its fluidity. In this case, the above-mentioned extrusion can be satisfactorily performed, and ideally, the fine-particle-containing organic fiber can be oriented in the extrusion direction.

In particular, in the rubber composition, when a tread is produced by vulcanizing an unvulcanized tread containing the fine particle-containing organic fibers oriented in the extrusion direction, the fine particle-containing organic fibers are mixed with the tread. It is preferable to orient in a direction parallel to the ground contact surface of the tire, and it is more preferable to orient in a circumferential direction of the tire. These cases are advantageous in that the drainage in the running direction of the tire can be enhanced and the performance on ice can be effectively improved.

As a method for aligning the orientation of the fine particle-containing organic fibers, for example, as shown in FIG. 2, a rubber composition 16 containing the fine particle-containing organic fibers 15 is extruded so that the flow passage cross-sectional area decreases toward the outlet. The fine particle-containing organic fibers 15 may be oriented in a certain direction by extruding from the die 17 of the machine. In this case, the fine particle-containing organic fibers 15 in the rubber composition 16 before being extruded are arranged such that the longitudinal direction thereof is gradually aligned along the extrusion direction (arrow A direction) in the process of being extruded to the die 17. When extruded from the die 17, the longitudinal direction can be almost completely oriented in the extrusion direction (arrow A direction). In this case, the degree of orientation of the fine particle-containing organic fibers 15 in the rubber composition 16 is determined by the degree of decrease in the flow passage cross-sectional area, the extrusion rate
It can be changed depending on the viscosity of the rubber composition 16.

The rubber composition according to the present invention described above can be preferably used in various fields, but can be particularly preferably used as a raw material of the following vulcanized rubber. Hereinafter, the vulcanized rubber according to the present invention will be described in detail.

The vulcanized rubber according to the present invention has fine particles-containing elongated bubbles after vulcanization. Therefore, it is preferable that the foaming rate Vs is 3 to 40%.

The vulcanization conditions and methods are not particularly limited and may be appropriately selected depending on the type of the rubber component. Mold vulcanization is particularly preferable when manufacturing a tread or the like. . As the temperature of the vulcanization,
Generally, it is preferable that the maximum vulcanization temperature of the rubber composition during vulcanization is selected to be equal to or higher than the melting point of the resin constituting the fine particle-containing organic fiber. When the vulcanization maximum temperature is lower than the melting point of the resin, the fine particle-containing organic fibers are not melted as described above, the gas generated by foaming cannot be taken into the resin, and the vulcanized rubber has a long shape. Bubbles cannot be formed efficiently. There is no particular limitation on the device for performing the above vulcanization, and a commercially available product can be preferably used.

In the rubber composition before vulcanization, the fine particle-containing organic fiber has a higher viscosity than the rubber matrix of the rubber composition. After the start of vulcanization and before the rubber composition reaches the maximum temperature of vulcanization, the viscosity of the rubber matrix increases due to vulcanization, and the fine particle-containing organic fiber melts and has a large viscosity. Gradually decreases. During the vulcanization, the fine particle-containing organic fiber has a lower viscosity than the rubber matrix.
That is, a phenomenon occurs in which the relationship of the viscosity between the rubber matrix before vulcanization and the fine particle-containing organic fiber is reversed at the stage of vulcanization.

Accordingly, during this time, the foaming agent in the rubber composition causes a foaming reaction, and the gas such as the gas present in the rubber composition undergoes a vulcanization reaction to increase the viscosity of the rubber matrix. Compared with the above, the particles move to the inside of the fine particle-containing organic fiber, which has been melted and has a relatively reduced viscosity, and stays therein. As a result, in the vulcanized rubber, elongated bubbles are present at a high ratio in the places where the fine particle-containing organic fibers were present, and a foam layer is formed. The long bubbles in the foamed layer have a periphery (wall) covered with a resin forming the fine particle-containing organic fibers to form a capsule shape. When the material of the fine particle-containing organic fiber is the above-mentioned polyethylene, polypropylene or the like, the vulcanized rubber and the material of the fine particle-containing organic fiber are firmly adhered, but the adhesive force is not sufficient. A component that improves the adhesive strength can be added to the.

In the tread of the tire of the present invention, the concave portion due to the elongated bubbles in the foam layer, which is generated by the friction on the tread surface, has directionality.
It functions as a drainage channel for efficient drainage. Since the concave portion has the protective layer, particularly the protective layer containing fine particles, the concave portion is excellent in peeling resistance, water channel shape retention, water channel edge wear resistance, water channel retention at load input, and the like. . Further, in the tire of the present invention, since long cells are present in the entire foam layer, the various functions of the recess are exhibited from the initial stage to the final stage of use, and the on-ice performance is excellent.

The foaming ratio of the vulcanized rubber of the present invention is not particularly limited, and can be set appropriately according to its application. For example, when used for a tire tread, the foaming rate Vs is 3
It is preferably from 40 to 40%, more preferably from 5 to 35%. Further, in the present invention, as the foaming rate Vs, the lower limit value or the upper limit value of any one of the numerical value ranges or the value of the foaming rate Vs in the examples described below is set as the lower limit, and any one of the lower limit values of the numerical value range or A numerical range in which the upper limit value or the value of the foaming rate Vs in Examples described later is set as the upper limit is also preferable. The foaming rate Vs is calculated based on the formula described later, and can be appropriately changed depending on the type and amount of the foaming agent, the type and amount of the foaming auxiliary agent used in combination, the compounding amount of the resin, and the like.

If the foaming rate Vs is less than 3%, the volume of the recesses in the tread may be small, and the on-ice performance may not be sufficiently improved, while if it exceeds 40%, the tread may be insufficient. Although the above-mentioned performance on ice is sufficient, the number of air bubbles in the tread tends to increase and the fracture limit tends to decrease, which is not preferable in terms of durability.

In the present invention, long bubbles and spherical bubbles may be mixed, but the volume content of the long bubbles (long bubbles / total amount of bubbles) is 30% or more. It is more preferably 50% or more. With the volume content in such a range, the water removing function can be sufficiently exerted. If the volume content of the long bubbles is small outside of such a range, the drainage channel becomes small and the water removing function may not be sufficient.

In the present invention, the average diameter (μm) of the elongated bubbles is preferably about 10 to 500 μm. If the average diameter is less than 10 μm, the water drainage performance of the micro drains formed on the rubber surface may deteriorate, and if the average diameter exceeds 500 μm, the rubber cut resistance and block chipping are deteriorated. In addition, the wear resistance on a dry road surface may deteriorate.

The vulcanized rubber of the present invention can be suitably used in various fields, but it can be suitably used for a structure which needs to suppress slip on the snow and snow road surface, and is particularly preferable as a tread of a tire. Can be used. Examples of the structure required to suppress the slip on the ice, for example, a tread for replacement of retreaded tires, solid tires, the ground contact portion of a rubber tire chain used for running on ice and snow roads, crawlers for snow vehicles, shoes The bottom etc. are mentioned.

An example of the tire of the present invention will be described below with reference to the drawings. As shown in FIG. 1, 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 composed of two layers of a cap portion 6 and a base portion 7 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.

On the surface of the tread 5, as shown in FIG. 3, a plurality of blocks 10 are formed by a plurality of circumferential grooves 8 and a plurality of lateral grooves 9 intersecting with the circumferential grooves 8. Further, in the block 10, a sipe 11 extending along the width direction (B direction) of the tire is formed in order to improve braking performance and traction performance on ice. The cap portion 6 of the tread 5 is foamed rubber as shown in FIG. However, here, the long-sized bubbles 12 surrounded by the protective layer 14 in the cap tread 6A are formed by molding the fine particle-containing organic fibers (short fibers) having the above thermal characteristics so as to be oriented in the circumferential direction of the tire. Contains countless numbers. The protective layer 14 also contains fine particles 20.

The tire 4 is not particularly limited in its manufacturing method, but is vulcanized and molded in a predetermined mold under a predetermined temperature and a predetermined pressure. As a result, a tire 4 having a tread 5 formed of the vulcanized rubber (tread) of the present invention obtained by vulcanizing the above rubber composition (unvulcanized tread) is obtained. At this time, the unvulcanized cap portion 6
Is heated in the mold, the fine particle-containing organic fiber is melted (or softened), and its viscosity (melt viscosity) becomes lower than the rubber matrix viscosity (flow viscosity) of the cap portion 6, so that it is blended. The gas generated by the foaming reaction of the foaming agent also stays inside the fine particle-containing organic fiber which is melted and has a relatively reduced viscosity. As a result, as shown in FIG. 4, the cap portion 6A after cooling has a large number of elongated bubbles substantially oriented in the circumferential direction of the tire.

In this tire 4, since the cap portion 6 was formed of the rubber composition containing the fine particle-containing organic fiber of the present invention, the cap portion 6A has the elongated bubbles 12 and the spherical bubbles as shown in FIG. 18, and the surface of the cap portion 6A due to wear of the tread surface due to tire running,
The concave portion 13 due to the long bubbles 12 and the concave portion 19 due to the spherical bubbles 18 are exposed, but in the tire 4 obtained by the vulcanized rubber of the present invention, since the long bubbles are scattered throughout the cap tread 6A, the above fine particle-containing Even if the surface layer having the organic fibers disappears due to further abrasion, the newly-formed recesses 13 and 19 can maintain the above-mentioned high performance on ice. In addition, the protective layer 14 and the fine particles 20 of the fine particle-containing organic fiber not only exhibit wear resistance in the surface layer but also sufficiently exhibit the edge effect and the spike effect, so that the above-mentioned performance on ice is further improved. To do. In the above embodiment, the tread having a two-layer structure has been described as an example, but the structure of the tread is not particularly limited and may be a single layer structure. Further, it may have a multilayer structure divided in the tire radial direction, or a structure divided in the tire circumferential direction or the tread width direction, and at least a part of the surface layer of the tread is preferably constituted by the rubber composition of the present invention.

The tire according to the present invention can be suitably applied not only to so-called passenger cars but also to various vehicles such as trucks and buses. When the tire is a pneumatic tire, an inert gas such as nitrogen can be used in addition to air as the gas to be filled inside.

[0063]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. (Examples 1 to 13 and Comparative Example 1) A rubber composition having the composition shown in Table 1 was prepared.

[0064]

[Table 1] Further, the fine particle-containing PE (polyethylene) fibers compounded in the rubber matrix of the rubber composition in Examples 1 to 13 contain fine particles of the types shown in Table 2 below. The resin of the fine particle-containing organic fiber is polyethylene (HDPE,
Mass average molecular weight (Mw) 1.8 × 10 ⁵ , Dupont
DSC, temperature rising rate 10 ° C / min, sample mass about 5m
melting point peak temperature (melting point) measured under the condition of g = 135
℃). The fine-particle-containing organic fiber is formed by melt spinning with a predetermined fineness (decitex) shown in Table 2. The PE fiber length used in each example and comparative example was a short fiber length in the range of 0.1 to 10 mm.

[0065]

[Table 2]

The vulcanization temperature of each rubber composition shown in Tables 1 and 2 during vulcanization was measured by embedding a thermocouple in the rubber composition. By the time the vulcanization maximum temperature was reached, the melting point of the resin was exceeded, and during vulcanization of the rubber composition, the resin viscosity became lower than the rubber matrix viscosity. The viscosity (melt viscosity) of the fiber resin at the maximum vulcanization temperature is measured by using a cone rheometer (finished when the torque of the rubber reaches Max, and the torque is regarded as the rubber viscosity, and the change in torque and the foaming pressure are measured. The change was 6). On the other hand, the viscosity (fluid viscosity) of the rubber composition at the maximum temperature of vulcanization uses a cone rheometer type 1-C type manufactured by Monsanto,
The torque was measured over time by applying a constant amplitude input of 100 cycles / min while changing the temperature, and the minimum torque value at that time was taken as the viscosity (dome pressure 0.59 MPa,
The holding pressure was 0.78 MPa, the closing pressure was 0.78 MPa, and the swing angle was ± 5 °).

A tire tread was formed from the rubber composition obtained in each example, and a tire for each test was manufactured according to a normal tire manufacturing condition. This tire is a radial tire for passenger cars, and its tire size is 185 / 70R.
13 and its structure is as shown in FIG. That is,
It has a radial structure in which a pair of bead portions 1, a carcass 2 connected to the pair of bead portions 1 in a toroidal shape, a belt 3 for tightening the crown portion of the carcass 2, and a tread 5 are sequentially arranged. .

In this tire, the carcass 2 is arranged at an angle of 90 ° with respect to the circumferential direction of the tire, and the number of cords to be driven is 50 cords / 5 cm. Belt 3 is 1x
It is made of steel belt cord with a structure of 5 × 0.23, and the driving angle is 25 with respect to the tire circumferential direction.
And the number of driving is 40 lines / 5 cm. On the tread 5 of the tire 4, as shown in FIG. 3, four blocks 10 are arranged in the tire width direction. Regarding the size of the block 10, the tire has a circumferential dimension of 35 mm and the tire has a lateral dimension of 30 mm. The sipes 11 formed on the block 10 have a width of 0.4 mm and a tire circumferential direction spacing of about 7 mm.

Each of the obtained tires was evaluated for the following foaming rate (%), long cell content rate (%), long cell average diameter (μm), and on-ice performance, and the results are shown in Table 2. Indicated.

<Foaming rate> The above-mentioned foaming rate Vs means the total foaming rate in the vulcanized rubber or tread, and can be calculated by the following equation. Vs = (ρ ₀ / ρ ₁ −1) × 100 (%) where ρ ₁ is the density (g / c) of the vulcanized rubber (foamed rubber).
m ³ ). ρ ₀ represents the density (g / cm ³ ) of the solid phase portion in the vulcanized rubber (foamed rubber). The density of the rubber after vulcanization (foamed rubber) and the density of the solid phase portion in the rubber after vulcanization (foamed rubber) were calculated from, for example, the mass in ethanol and the mass in air.

<Long Bubble Content> The center block piece was cut from the tread of the tire, and the planes cut with a sharp razor perpendicular to and parallel to the longitudinal direction of the long bubbles were used as observation surfaces. did. This observation surface was photographed with a scanning electron microscope (SEM) at 100 times magnification. In addition, the place to take a picture is randomly selected.
Next, the long bubbles and the spherical bubbles in the above-mentioned photograph are separated, the respective areas are measured, and the area% of the long bubbles in a certain fixed area is calculated. The above measurement was performed 10 times, the average of the area% was calculated, and the value with respect to the total amount of bubbles was taken as the volume content of the elongated bubbles.

<Average Diameter of Long Bubbles> The cross-sectional area of the long bubbles was measured from the above photograph, and the following formula was used: {average diameter of long bubbles = (cross-sectional area of long bubbles ÷ π) ^0.5 X2}, the diameter was calculated assuming that the cross-sectional shape perpendicular to the longitudinal direction was circular. This was repeated 10 times, the average value was calculated | required, and this average value was made into the average diameter of a long bubble.

<Ice performance> Tires were mounted on a domestic 1600 CC class passenger car, the passenger car was run 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 tire was locked, and the distance to stop was measured. The result was expressed as an index with the reciprocal of the distance being 100 for the tire of Comparative Example 1. The larger the value, the better the performance on ice.

From the results of Table 2, the following is clear. That is, in the tread after vulcanization in Examples 1 to 13, long bubbles were sufficiently formed, and long bubbles were also formed, so that the water film excluding performance was sufficient. As expected, it can be seen that the performance on ice is clearly improved by improving the edge effect and spike effect. On the other hand, in Comparative Example 1, sufficient performance on ice is not obtained.

The fine particle-containing PE (polyethylene) fibers mixed in the rubber matrix of the above rubber compositions in Examples 1 to 13 contain fine particles of the types shown in Table 2. The resin of the fine particle-containing organic fiber is polyethylene. As shown in Table 2, the fine particles have a predetermined fine particle type, a fine particle shape, a predetermined diameter of a peak value in the particle size distribution of the fine particles,
And a predetermined value of the frequency of the peak value are contained and spun by a melt spinning method with a predetermined fineness. The PE fiber length used in each example was a short fiber length in the range of 0.1 to 10 mm. The shape of the fine particles and the particle size distribution of the fine particles were measured and evaluated by the following methods. A test passenger car radial tire was manufactured from the vulcanized rubber in the same manner as in Example 1. Then, the above-mentioned performance evaluation on ice was carried out for each tire, and the results are shown in Table 2.

The method of measuring the particle shape and particle size distribution of the above particles is as follows. <Particle shape> At least 10 particles in a predetermined area are observed with an electron microscope to determine an aspect ratio representing the ratio of the major axis L and the minor axis D of the particle, and a corner portion is present on the surface. Those with L / D ≧ 1.1 were defined as horns, and those without any corners on the surface were defined as spheres. Then, the set of fine particles having horns at the time of observation was made into a square shape, and the set of fine particles which were all spherical at the time of observation was made into a spherical shape.

<Particle size distribution> Laser beam scattered light measuring device (Microtrack particle size analyzer Model 7995-30PC SPA
Nikkiso Co., Ltd.) was used to measure the particle size distribution by measuring the scattered light hit by the particles. The measurement time was 30 seconds, and a sample was prepared by adding a surfactant to 50 to 100 ml of water and dispersing fine particles (predetermined amount) in the solution by ultrasonic waves. The mass based on the volume in each particle size was measured to determine the mass particle size distribution curve. Next, the particle size distribution curve was evaluated, and the maximum value was used as the particle size distribution peak value of the fine particles. In addition, in the particle size distribution curve, the cells are divided into 2 μm-widths, the amount of fine particles present in each division is measured, and the mass of the fine particles in each width is expressed as a percentage of the total mass. And Then, the frequency number of the division of the step width including the peak value was set as the frequency number (mass%) of the peak value in the particle size distribution.

From Table 2 above, the following was judged and evaluated. First, by comparing Example 1, Example 7 and Example 10, it is preferable that the particle diameter of the peak value in the particle size distribution is larger, and particularly, the particle diameter of 5 μm is 20 μm, more preferably 30 μm. It was seen that the performance of the tires on ice improved. Further, by comparing Example 1, Example 2 and Example 3, the frequency of the peak value in the particle size distribution is 20% by mass than 15% by mass, further 25% by mass of the tire. It was seen that the performance on ice improved. Furthermore, by comparing Example 2 with Examples 12 and 13, it was found that the particles having a rectangular shape improve the on-ice performance of the tire more than that having a spherical shape.

[0079]

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 an excellent ability to remove a water film generated on an ice / snow road surface, a coefficient of friction with the ice / snow road surface being increased by an edge effect and a spike effect, and an excellent on-ice performance. it can. Further, according to the present invention, it is possible to provide a vulcanized rubber having excellent on-ice performance, which is suitable for a structure that needs to suppress slippage on a snowy and snowy road surface, such as a tread of a tire. Furthermore, according to the present invention, it is possible to provide a rubber composition that can be suitably used as a raw material for vulcanized rubber.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a tire according to the present invention.

FIG. 2 is an explanatory view for explaining the principle of orienting organic fibers containing fine particles in a fixed direction.

FIG. 3 is a schematic explanatory view showing a part of a peripheral surface of a tire according to the present invention.

FIG. 4 (a) and FIG. 4 (b) are a schematic sectional view taken along the tire circumferential direction and a schematic sectional view taken along the tire width direction of the tread portion of the tire according to the present invention.

[Explanation of symbols]

1 pair of beads 2 carcass 3 belts 4 tires 5 tread 6 Cap section 6A vulcanized rubber 8 circumferential grooves 10 blocks 11 sipes 12 Long bubbles 13 recess 14 Protective layer 15 Fine particle-containing organic fiber 16 rubber composition 17 mouthpiece 18 Spherical bubbles 19 Spherical bubble recess 20 fine particles A tire circumferential direction B tire width direction P extrusion direction

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 9/00 C08L 9/00 F term (reference) 4F074 AA06 AA08 AA09 AA17 AA98 AC02 AC03 AC17 AC20 AC29 AC32 AC34 AC36 AC36 AD01 AD09 AE01 AE04 AE06 AG04 AG20 BA03 BA04 BA12 BA13 BA16 BA18 DA02 DA35 DA59 4J002 AC011 AC031 AC061 AC081 BB032 BB122 DE146 DE217 DG056 DJ016 DL006 EQ017 EU187 EV217 EV287 FA042 FA086 FD327 GN01

Claims (15)

[Claims] 1. A rubber composition comprising a rubber matrix and a fine particle-containing organic fiber containing fine particles having a Mohs hardness of 2 or more. 2. The rubber composition according to claim 1, wherein the rubber component constituting the rubber matrix is at least one selected from natural rubber and diene synthetic rubber. 3. The rubber composition according to claim 1 or 2, wherein the fine particles have a diameter of 0.1 to 100 μm. 4. The rubber composition according to claim 1, wherein the fine particles have a frequency number at a peak value of a particle size distribution of 20% by mass or more. 5. The rubber composition according to claim 1, wherein the fine particles have an aspect ratio of 1.1 or more and have corners. 6. A resin having viscosity characteristics such that the viscosity of the fine-particle-containing organic fiber becomes lower than the viscosity of the rubber matrix by the time the vulcanization maximum temperature is reached during vulcanization, and the resin 100.
6. The fine particles contained in the range of 5 to 100 parts by mass with respect to parts by mass of the fine particles.
The rubber composition according to any one of 1. 7. The fiber length of the organic fibers containing fine particles is 0.
7. The rubber composition according to any one of claims 1 to 6, which is a short fiber in the range of 1 to 10 mm. 8. The rubber composition according to claim 6, wherein the resin is a crystalline polymer made of at least one selected from polyethylene and polypropylene, and has a melting point of 190 ° C. or lower. . 9. The rubber component 10 is used as the fine particle-containing organic fiber.
The rubber composition according to any one of claims 1 to 8, which is compounded in an amount of 0.5 to 30 parts by mass with respect to 0 parts by mass. 10. The rubber composition according to any one of claims 1 to 9, which comprises a foaming agent. 11. A vulcanized rubber obtained by vulcanizing the rubber composition according to any one of claims 1 to 10. 12. The vulcanized rubber according to claim 11, wherein elongated cells having a resin layer containing fine particles are formed at the interface with the rubber matrix. 13. The vulcanized rubber according to claim 11, wherein the foaming rate Vs is 3 to 40%. 14. A pair of beads, a carcass connected in a toroidal shape to the beads, and a belt and a tread for tightening the crown of the carcass.
At least the tread contains the vulcanized rubber according to any one of claims 11 to 13. 15. The tire according to claim 14, wherein the elongated bubbles are oriented in the tire circumferential direction.