JP4679173B2 - Rubber composition, vulcanized rubber and tire - Google Patents

Description

  The present invention relates to a rubber composition, a vulcanized rubber, and a tire, and more specifically, a tire having excellent on-ice performance particularly requested by the market, a vulcanized rubber suitable for a tread of the tire, and the vulcanized rubber. It is related with the rubber composition which can be used conveniently as a raw material of this.

  Since spike tires have been regulated, research on tire treads has been actively conducted in order to improve the braking and driving performance (on-ice performance) of tires on icy and snowy road surfaces. On such icy and snowy road surfaces, a water film is likely to be generated due to frictional heat generated between the road surface and the tire, and this water film causes a reduction in the coefficient of friction between the tire and the road surface. For this reason, the water film removing ability and the edge effect of the tire tread 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 and the edge effect of the tread.

Therefore, a lot of micro drainage grooves (depth and width of about 100 μm) are provided on the surface of the tread, and the water film is eliminated by the micro drainage grooves. It has been proposed to increase the coefficient and improve the performance on ice. However, in this case, although the performance on ice in the initial use of the tire can be improved, there is a problem that the performance on ice gradually decreases with the friction of the tire.

  It has also been proposed to improve the performance on ice by using foamed rubber for the tread and removing the water film by the recess formed by exposing the bubbles in the foamed rubber. However, a recess formed by exposing bubbles in a simple foam rubber has a spherical cross section, has no anisotropy, and cannot function as a micro drainage groove. There is a problem that the performance on ice cannot be improved to the extent. Another problem is that the cost of the foaming agent is industrially relatively high.

  Further, in Patent Document 1 and the like, it is described that a micro drainage groove as described above is formed on the surface of the tread portion by using foamed rubber containing short fibers in the tread portion. Such a drainage groove has a problem of being crushed when the load applied to the tire is large.

  On the other hand, in Patent Document 2 and the like, a tire is disclosed in which hollow fibers are dispersed in a tread portion so that a water film existing between the snowy and snowy road surface and the tread can be eliminated by the hollow portions of the hollow fibers. However, in the case of this tire, the hollow fiber is crushed by the pressure, rubber flow, temperature, etc. during kneading or molding of the hollow fiber into the rubber, and the hollow fiber cannot actually maintain the hollow shape. However, there is a problem that micro drainage grooves cannot be formed efficiently and the performance on ice is still insufficient.

Patent Documents 3 and 4 describe that hollow polyolefin fibers having specific thermal characteristics can improve performance on ice and workability during production. However, it is needless to say that it is desired to further suppress the collapse of the hollow fiber under a tire load, to secure a micro drainage channel, and to further improve the safety performance on ice.
JP-A-4-38207 (Claims etc.) JP-A-4-110212 (Claims etc.) Japanese Patent Application Laid-Open No. 11-60771 (claims, etc.) JP 11-60814 (Claims etc.)

  Accordingly, an object of the present invention is to solve the above-mentioned problems in the prior art, and is excellent in the ability to remove a water film formed on a snowy and snowy road surface, and thus has a large coefficient of friction with the snowy and snowy road surface and has excellent performance on ice. An object of the present invention is to provide a vulcanized rubber that can be suitably applied to a structure that needs to suppress slip on ice, such as a tire tread, and a rubber composition that is suitable as a raw material for the vulcanized rubber.

  As a result of intensive studies, the present inventor has found that the above problem can be solved by adopting the following configuration, and has completed the present invention.

That is, in order to solve the above problems, the rubber composition of the present invention comprises a rubber matrix containing a rubber component and a blowing agent comprising at least one selected from natural rubber and diene synthetic rubbers, in cross-sectional shape of the fiber A hollow fiber having two or more hollow parts via a cross-linked part is contained by 0.5 to 30 parts by weight of hollow fibers with respect to 100 parts by weight of the rubber matrix. .

  In the rubber composition of the present invention, the hollow fiber preferably has a hollow ratio of 10 to 70%, and the hollow fiber preferably has a branched portion in the cross-linked portion in the cross-sectional shape of the fiber. It has three or more hollow parts.

  Further, the hollow fiber contains a crystalline polymer, its melting point is lower than the maximum vulcanization temperature of the rubber matrix, and its viscosity is the temperature of the rubber matrix during vulcanization. It is preferable to use a material having a viscosity lower than that of the rubber matrix before reaching the maximum temperature, and the crystalline polymer is preferably polypropylene. Furthermore, it is also preferable that the outer peripheral surface of the hollow fiber is subjected to adhesion processing. In this case, the hollow fiber preferably includes polyester. Furthermore, as the adhesion processing, a sputtering adhesion treatment of a composition containing cobalt is preferable.

  The vulcanized rubber of the present invention is obtained by vulcanizing the rubber composition and contains bubbles.

Furthermore, the tire of the present invention includes a pair of bead portions, a carcass connected in a toroidal shape between the pair of bead portions, a belt for tightening the crown portion of the carcass, and a tread. At least the tread is made of a vulcanized rubber obtained by vulcanizing the rubber composition.

  According to the present invention, by using the hollow fiber having the predetermined structure, the tire has an excellent ability to remove a water film formed on the snowy and snowy road surface, and therefore has a large coefficient of friction with the snowy and snowy road surface and is excellent in performance on ice. It is possible to realize a vulcanized rubber that can be suitably applied to a structure that needs to suppress slip on ice, such as a tire tread, and a rubber composition that is suitable as a raw material of the vulcanized rubber. It became.

Hereinafter, the rubber composition, vulcanized rubber and tire of the present invention will be described in detail.
(Rubber composition)
The rubber composition of the present invention contains a predetermined rubber matrix and hollow fibers.
--Rubber matrix--
The rubber matrix contains components excluding hollow fibers in the rubber composition of the present invention, and specifically includes at least one rubber component selected from natural rubber and diene-based synthetic rubber and a foaming agent, Furthermore, other components such as a foaming aid are included as necessary.

-Rubber component-
The rubber component may contain only natural rubber, may contain only diene synthetic rubber, or may contain both. There is no restriction | limiting in particular as a diene type synthetic rubber, According to the objective, it can select suitably according to the objective, For example, a styrene-butadiene copolymer (SBR), polyisoprene (IR), polybutadiene (BR) Etc. Among these diene-based synthetic rubbers, cis-1,4-polybutadiene is preferable in that the glass transition temperature is low and the effect on performance on ice is large, and those having a cis content of 90% or more are particularly preferable.

  In addition, when using the rubber composition of this invention for the tread etc. of a tire, as this rubber component, what has a glass transition temperature of -60 degrees C or less is preferable. When a rubber component having such a glass transition temperature is used, treads and the like are advantageous in that they maintain sufficient rubber elasticity even in a low temperature range and exhibit good performance on ice.

-Foaming agent-
Examples of the foaming agent include dinitrosopentamethylenetetramine (DPT), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivatives, oxybisbenzenesulfonylhydrazide (OBSH), and bicarbonate that generates carbon dioxide. Ammonium, sodium bicarbonate, ammonium carbonate, nitrososulfonylazo compound generating nitrogen, N, N′-dimethyl-N, N′-dinitrosophthalamide, toluenesulfonyl hydrazide, P-toluenesulfonyl semicarbazide, P, P′- And oxy-bis (benzenesulfonyl semicarbazide).

  Among these foaming agents, in consideration of production processability, dinitrosopentamethylenetetramine (DPT) and azodicarbonamide (ADCA) are preferable, and azodicarbonamide (ADCA) is particularly preferable. These may be used individually by 1 type and may use 2 or more types together. By containing a foaming agent, the vulcanized rubber obtained by vulcanizing the rubber composition of the present invention can be made into a foamed rubber having a high foaming rate.

-Other ingredients-
The other components can be used as long as they do not impair the object of the present invention. For example, inorganic fillers such as carbon black, silica and calcium carbonate, coupling agents such as silane coupling agents, softeners, sulfur Vulcanizing accelerators such as dibenzothiazyl disulfide , N-cyclohexyl-2-benzothiazyl-sulfenamide, N-oxydiethylene-benzothiazyl-sulfenamide , anti-aging agent, zinc oxide, stearin In addition to additives such as acids and ozone degradation inhibitors, various compounding agents usually used in the rubber industry can be used as appropriate. These may be used individually by 1 type and may use 2 or more types together. In addition, in this invention, a commercial item can be used about these other components.

  In the present invention, from the viewpoint of efficient foaming, it is preferable to use a foaming aid as the other component and use it together with the foaming agent. Examples of such foaming aids 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 individually by 1 type, respectively, and may be used together 2 or more types.

-Hollow fiber-
The hollow fiber used in the present invention is characterized in that it has two or more hollow parts via a bridge part in the cross-sectional shape of the fiber. By forming the bridging portion, the fibers are structurally difficult to collapse against a load such as a vehicle weight or a driving force applied to the tire, and a micro groove is easily secured. Further, even when the hollow fiber is scraped by friction due to wear associated with the use of the tire, the drainage effect is obtained by the micro grooves that the bridging portion can support the inside of the hollow hole from the road surface. Conversely, the bridging portion is pressed against the road surface by a load, so that a stronger scratching effect can be obtained. Therefore, the hollow fiber of the present invention does not include those having only one hollow portion that does not have a crosslinked portion.

  In the present invention, it is necessary for the hollow fiber to have at least two or more hollow portions via the bridging portion in the cross-sectional shape of the fiber. It is preferable to form a branched portion such as a cross. This is because the shape of the bridging portion separating the hollow holes has a branching portion such as a Y-shape or a cross shape, thereby reducing the direction in which the hollow fibers are easily crushed. This branching of the bridging portion can be formed by arranging three or more hollow portions in the fiber. For example, in the case of a fiber having a cross-sectional structure having n hollow holes (n> 3), the preferred branching configuration is such that n hollow holes are provided so that the hollow fiber has n branches near the center. And when the cross section is arbitrarily divided into left and right, the fibers are arranged at a ratio such that the left and right porosity is between 4: 6 and 6: 4. This is because, by arranging the branches at the center portion and arranging the hollow holes evenly in this way, there is no direction in which the hollow fibers are easily crushed by the input of a load.

  Further, the hollow ratio of the hollow fiber is preferably 10 to 70%, more preferably 25 to 65%, and particularly preferably 30 to 60%. When the hollow ratio is less than 10%, the amount of air taken in or retained in the rubber composition relative to the hollow fibers blended in the rubber composition is small, and the amount of air obtained by vulcanizing the rubber composition is increased. In vulcanized rubber, the performance on ice cannot be sufficiently improved. On the other hand, when the hollow ratio exceeds 70%, the productivity of the hollow fiber deteriorates and the hollow fiber is easily crushed. Due to this crushed, the rubber of air present in the hollow portion of the hollow fiber when the rubber composition is kneaded. Outflow of the composition occurs and is not preferable. On the other hand, it is preferable that the hollow ratio is within the above-mentioned preferable numerical range in that the desired effect of the present invention can be obtained without causing these problems.

  There is no restriction | limiting in particular as a denier of a hollow fiber, Although it can select suitably according to the objective, From a viewpoint of improving on-ice performance, 1-1000 denier is preferable and 2-800 denier is more preferable. The length of the hollow fiber is not particularly limited and may be appropriately selected according to the purpose. However, from the viewpoint of improving the performance on ice, 0.5 to 10 mm is preferable, and 1 to 8 mm is more preferable. .

  The hollow fiber may be an organic fiber, an inorganic fiber, or a metal fiber. These fiber materials can be used after being subjected to surface adhesion treatment by sputtering or the like on the surface of short fibers disclosed in the republished WO 01/083874, but on the other hand, rubber is not subjected to surface treatment treatment. A fiber material that can be blended and heat-sealed can also be used. Examples of the fiber material that can be heat-sealed with the rubber compound include, for example, the viscosity of the hollow fiber is higher than the viscosity of the rubber matrix until the temperature of the rubber matrix reaches the maximum vulcanization temperature at the time of vulcanization of the rubber composition. It is an organic fiber containing a crystalline polymer having low thermal properties, and it is industrially preferable to use an organic fiber containing such a crystalline polymer as a hollow fiber because the processing becomes easy.

  Here, the case of using a fiber material that can be heat-fused with a rubber compound is divided into (A) described later, and the case of using an adhesive modified by surface processing of a hollow fiber is divided into (B) described later. Will be described in turn.

  In the present invention, 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, the rubber composition is It means the maximum temperature that the rubber matrix can reach from entering the mold until it cools out of the mold. This maximum vulcanization temperature can be measured, for example, by embedding a thermocouple in a rubber matrix.

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

  Furthermore, as content of the hollow fiber in the rubber composition of this invention, 0.5-30 weight part is preferable with respect to 100 weight part of rubber matrices, 1-26 weight part is more preferable, 2-20 weight part Is particularly preferred. When the content of the hollow fiber is less than 0.5 parts by weight, the amount of the hollow fiber is too small to sufficiently improve the performance on ice. On the other hand, when the content exceeds 30 parts by weight, in the rubber composition This is not preferable because the dispersibility of the hollow fibers in the tire may deteriorate, the workability during extrusion may deteriorate, cracks may occur in the tire tread, and the cost may increase.

(A) When the hollow fiber is made of a fiber material that can be heat-sealed with a rubber compound. That is, the viscosity of the hollow fiber during the vulcanization of the rubber composition until the temperature of the rubber matrix reaches the maximum vulcanization temperature. Has a thermal characteristic that is lower than the viscosity of the rubber matrix, which is hereinafter referred to as “hollow fiber A”.

  The material of the hollow fiber A is not particularly limited as long as it is a fiber material containing a resin having the above thermal characteristics, and can be appropriately selected according to the purpose. Suitable examples of the fiber material having the thermal characteristics include those made of a crystalline polymer whose melting point is lower than the maximum vulcanization temperature of the rubber matrix.

  Taking hollow fiber A made of a crystalline polymer as an example, this hollow fiber A melts quickly during vulcanization of the rubber composition, so that it can be bonded to the rubber matrix by thermal fusion with rubber. Moreover, since the resin part which the hollow fiber A fuse | melted becomes difficult to peel from rubber | gum also in the case of input at the time of tire use, it is preferable.

  However, if the melting point of the hollow fiber A becomes too close to the maximum vulcanization temperature of the rubber matrix, the hollow fiber A does not melt quickly at the initial stage of vulcanization and melts at the end of vulcanization, but it is sufficiently rubber. There is a tendency not to be fused with the matrix. On the other hand, if the melting point of the hollow fiber A becomes too low, the hollow fiber A is melted by the heat at the time of kneading the rubber composition, and the hollow fibers A are fused together at the stage of kneading, resulting in poor dispersion. Inconveniences such as the hollow fiber A being divided into a plurality of parts at the kneading stage and the hollow fiber A being dissolved in the rubber composition and being dispersed microscopically are not preferable.

  In addition, since the hollow fiber A melts at the time of vulcanization, the cross-linked portion may disappear after vulcanization, but in this case as well, the protrusion of the cross-linked portion remains on the inner periphery of the hollow portion of the hollow fiber A. The projections support the hollow holes from the inside, so that the micro grooves are held, and the above-described drainage effect and scratching effect can be obtained.

  The upper limit of the melting point of the hollow fiber A is not particularly limited, but is preferably selected in consideration of the above points. In general, it is lower than the maximum vulcanization temperature of the rubber matrix, More preferably, it is 5 ° C. or more, more preferably 10 ° C. or more lower than the temperature at which it can be worn. The industrial vulcanization temperature of the rubber composition is generally about 190 ° C. at the maximum. For example, when the maximum vulcanization temperature is set to 190 ° C., the melting point of the hollow fiber A Is usually selected within a range of 190 ° C. or lower, preferably 180 ° C. or lower, and more preferably 175 ° C. or lower.

  On the other hand, considering the kneading of the rubber composition, the melting point of the hollow fiber A is preferably 5 ° C. or more, more preferably 10 ° C. or more, and particularly preferably 20 ° C. or more 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 hollow fiber A is preferably 100 ° C. or higher, more preferably 105 ° C. or higher, and particularly preferably 115 ° C. or higher. .

  The melting point of the hollow fiber A can be measured using a known melting point measuring device or the like. For example, the melting peak temperature measured using a DSC measuring device can be used as the melting point.

  The hollow fiber A may be formed from a crystalline polymer, may be formed from an amorphous polymer, or may be formed from a crystalline polymer and an amorphous polymer. However, in the present invention, it is preferably formed from an organic material containing a crystalline polymer in that the viscosity change occurs suddenly at a temperature where there is a phase transition and the viscosity can be easily controlled. More preferably it is formed from molecules only.

  Specific examples of such a crystalline polymer include, for example, polyethylene (PE), polypropylene (PP), polybutylene, polybutylene succinate, polyethylene succinate, syndiotactic-1,2-polybutadiene (SPB), polyvinyl alcohol ( A single composition polymer such as PVA) or polyvinyl chloride (PVC), or a copolymer whose melting point is controlled to an appropriate range by copolymerization, blending, or the like can be used. These may be used individually by 1 type and may use 2 or more types together. Among these crystalline polymers, polyolefins and polyolefin copolymers are preferable, and polyethylene (PE) and polypropylene (PP) are more preferable in terms of general availability and easy access. Polyethylene (PE) is particularly preferred.

  Examples of the non-crystalline polymer include polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene copolymer (ABS), polystyrene (PS), polyacrylonitrile, copolymers thereof, and blends thereof. It is done. These may be used individually by 1 type and may use 2 or more types together. Moreover, you may use as a composite fiber at the time of spinning.

  In addition, in the range which does not impair the objective of this invention, the well-known additive may be added to the hollow fiber A as needed.

  The molecular weight of the material of the hollow fiber A differs depending on the chemical composition of the material, the state of branching of the molecular chain, etc., and cannot be defined in general. However, even if the hollow fiber A is generally formed of the same material, its molecular weight The higher the viscosity, the higher the viscosity at a certain temperature (dissolution viscosity).

(B) In the case of a hollow fiber whose outer peripheral surface is subjected to adhesion processing (hereinafter referred to as “hollow fiber B”)
The bonding process of the hollow fiber B is not particularly limited as long as it is a known method for bonding the rubber matrix and the fiber material. For example, surface treatment with a silane coupling agent, surface treatment with a resorcin-formaldehyde-latex (common name: RFL) adhesive composition, and the like can be given. In the present invention, a method of sputtering a hollow fiber by a processing method of coating the short-fiber surface by sputtering with a rubber-adhesive metal-containing composition disclosed in the republished WO 01/083874 is preferable. For example, the sputtering adhesion process of the composition containing cobalt can be mentioned.

  According to the method described in the above publication, surface treatment is possible regardless of the type of fiber material such as organic fiber or inorganic fiber. Further, in the bonding treatment, there is no problem that the hollow fibers are bonded to each other, and static electricity that causes the hollow fibers to become dull with the metal component on the surface is less likely to be generated. Further, the fiber material to be bonded is not particularly limited as long as it is a hollow fiber having two or more hollow portions in the fiber cross-sectional shape. For example, a polyester fiber material widely used as a clothing material can be suitably used.

-Preparation of rubber composition-
The rubber composition of the present invention is prepared by kneading, heating, extruding, and the like using an apparatus, conditions, technique, and the like appropriately selected from the above components.

  The kneading is not particularly limited with respect to various conditions such as the input volume to the kneading apparatus, the rotational speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the kneading apparatus, etc., and is appropriately selected according to the purpose. be able to. Moreover, as a kneading apparatus, a commercial item can be used conveniently.

  Regarding the heating or extrusion, there are no particular limitations on the conditions such as the heating or extrusion time, the heating or extrusion apparatus, etc., and they can be appropriately selected according to the purpose. Moreover, a commercial item can be used conveniently as an apparatus for heat-injection or extrusion.

(Vulcanized rubber)
The vulcanized rubber of the present invention can be easily obtained by vulcanizing the rubber composition of the present invention and contains bubbles. There are no particular limitations on the vulcanizing apparatus, conditions, method, and the like, which can be appropriately selected according to the purpose. However, when obtaining a tire tread or the like, it is preferable to perform mold vulcanization. The vulcanization temperature is set to a temperature at which the rubber composition can be vulcanized. In addition, when using the hollow fiber A, it selects so that the vulcanization maximum temperature of the rubber matrix in the vulcanization | cure of a rubber composition may become higher than melting | fusing point of a hollow organic fiber.

  The foaming rate (average foaming rate) Vs of the vulcanized rubber of the present invention is preferably 3 to 40%, more preferably 5 to 35%. When the foaming rate Vs is less than 3%, there is a case where a sufficient water removal function cannot be obtained due to an insufficient lack of the concave volume with respect to the generated water film, and the performance on ice cannot be effectively improved. On the other hand, if it exceeds 40%, the performance on ice can be improved, but the volume ratio of bubbles in the vulcanized rubber is too high, so the fracture limit of the vulcanized rubber is greatly reduced and the durability is sufficient. May disappear.

Here, the foaming rate Vs is expressed by the following formula:
Vs = (ρ ₀ / ρ ₁ −1) × 100 (%)
( Ρ ₁ : Density (g / cm ³ ) of vulcanized rubber (foamed rubber), ρ ₀ : Density of solid phase part (g / cm ³ ) in vulcanized rubber (foamed rubber) Further, ρ ₀ and ρ ₁ can be calculated from these results by measuring the weight in ethanol and the weight in air, for example. The foaming rate Vs can be appropriately changed according to the type and amount of the foaming agent, the type and amount of the foaming aid to be combined, the blending amount of the hollow fiber, the hollow rate, and the like.

  The vulcanized rubber of the present invention can be suitably used in various fields, but can be particularly suitably used for a structure that needs to suppress slip on ice, and is most suitable for, for example, a tread of a pneumatic tire. Can be used. Specific examples of structures that need to suppress slip on ice include, for example, treads for replacement of retreaded tires, solid tires, ground parts of rubber tire chains used for running on snowy roads, snow vehicles Examples include crawlers and shoe soles.

(tire)
The tire of the present invention has at least a tread, and as long as at least the tread includes the vulcanized rubber of the present invention, there is no particular limitation on other configurations, and the tire can be appropriately selected according to the purpose. it can. In other words, a tire having a tread containing a vulcanized rubber obtained by vulcanizing the rubber composition of the present invention is the tire of the present invention.

An example of the tire of the present invention is described below with reference to the drawings.
As shown in FIG. 1, a tire 10 according to the present invention includes a pair of bead portions 1, a carcass 2 connected in a toroidal shape between the pair of bead portions 1, and a belt for tightening a crown portion of the carcass 2. 3 and a tread 4. In the tire of the present invention, the internal structure other than the tread 4 is the same as the structure of a general radial tire, and thus the description thereof is omitted.

  As shown in the partial development view of FIG. 2, a plurality of blocks 8 are defined in the tread 4 by a plurality of circumferential grooves 6 and a plurality of lateral grooves 7 intersecting with the circumferential grooves 6. Yes. Further, a sipe 9 extending along the tire width direction (B direction) is formed on the block 8 in order to improve braking performance and traction performance on ice.

  As shown in the cross-sectional view of FIG. 3, the tread 4 is composed of an upper cap portion 4A that directly contacts the road surface and a lower base portion 4B that is disposed adjacent to the inner side in the tire radial direction of the cap portion 4A. And has a so-called cap base structure. The cap portion 4A is made of rubber containing the rubber composition of the present invention containing the hollow fiber 11, while ordinary rubber is used for the base portion 4B.

Although there is no restriction | limiting in particular about the manufacturing method, the tire 10 can be manufactured as follows, for example.
That is, first, the rubber composition of the present invention is prepared. Next, this rubber composition is affixed on an unvulcanized base portion that has been affixed in advance to the crown portion of the green tire case. Thereafter, vulcanization molding is performed in a predetermined mold under a predetermined temperature and a predetermined pressure. During this vulcanization reaction, the gas resulting from the foaming agent or the like moves to the hollow portion of the hollow fiber, so that this gas holds the hollow hole so as not to expand or collapse. In addition, when the hollow fiber melts at the vulcanization temperature, the gas in the molten resin may create new bubbles.

Next, the operation of the tire 10 of the present invention will be described.
When the tire 10 runs on an icy and snowy road surface, the surface of the tread 4 of the tire 10 is worn due to friction between the tire 10 and the icy and snowy road surface. Further, when the tire 10 is caused to travel, a water film is generated between the tire 10 and the icy and snowy road surface due to contact pressure and frictional heat between the tire 10 and the ground contact surface. This water film is quickly eliminated and removed by the hollow fibers exposed on the ground contact surface of the cap portion 4A of the tread 4 or the elongated bubbles 11 made of molten resin of the hollow fibers. For this reason, the tire 10 is less likely to slip on an icy and snowy road surface.

  In the tire 10, the hollow fibers or the elongated bubbles 11 that are substantially oriented in the circumferential direction of the tire function as drainage grooves that perform efficient drainage. Since the hollow fiber or the long bubble 11 is covered with a protective layer having excellent peel resistance on the surface (periphery), it is not easily crushed even under high load, and is excellent in drainage groove shape retention and water drainage performance. Since the hollow fiber or the long air bubbles 11 improve the water removal performance to the rear side in the rotation direction of the tire 10, the tire 10 is particularly excellent in ice braking performance. Further, in the tire 10, the on-ice μ in the lateral direction is improved by the scratching effect by the protective layer, and as a result, the on-ice handling property is improved.

  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.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
(Examples 1 to 3 and Comparative Examples 1 and 2)
The rubber compositions having the compositions shown in Table 1 below were prepared. The maximum vulcanization temperature of the rubber matrix at the time of vulcanization of each rubber composition was 180 ° C. when measured with a thermocouple embedded in the rubber matrix.

  As hollow fibers of Examples 1 and 2, polypropylene three-core hollow section yarn “Alport (registered trademark)” manufactured by Mitsubishi Rayon Co., Ltd. (hollow rate: 35%, single yarn denier number: 10d, short fiber cut length: 2 mm) was used. The melting point peak temperatures (melting points) of this fiber measured by DuPont DSC under the conditions of a heating rate of 10 ° C./min and a sample weight of about 5 mg were 175 ° C. and 177 ° C., and the maximum vulcanization of the rubber matrix The fiber material had a melting point lower than the temperature. When the hollow fiber has two melting points, the values on the low melting point side are listed in Table 1 from the viewpoint of heat fusion.

  Moreover, as the hollow fiber of Example 3, the 4-hole hollow fiber which carried out the sputtering adhesion process of the cobalt-containing composition on the outer peripheral surface was used. For the hollow fiber material to be sputtered, Toyobo Co., Ltd. polyester 4-hole hollow cross-section yarn “Dialegato (registered trademark)” (hollow rate: 30%, single yarn denier: 4d, short fiber cut length: 2 mm) It was used. Sputtering treatment was performed by the method described in Example 27 (production of short fibers for rubber reinforcement from short fiber material) in the aforementioned republished WO 01/083874, and the 4-hole hollow polyester short fibers were treated. In Example 27, a cobalt target was used and a coating layer containing cobalt / cobalt oxide was formed on the surface of the short glass fiber, but in the present invention, the 4-hole hollow polyester short fiber was used instead of the glass fiber. Processed.

  As the hollow fibers of Comparative Example 1, polypropylene short fibers (hollow rate 35%, single yarn denier number: 10d, short fiber cut length: 2 mm) were used. The fiber was obtained as follows. First, an isotactic polypropylene having a melt flow rate (conforming to JIS K 7210) of 30 g / min and an isotactic pentad fraction of 95% is hollowed at a spinning temperature of 220 ° C. using a single screw extruder. Extrusion was performed from a cross-section nozzle and wound with a feed roller at a speed of 500 m / min to obtain an undrawn yarn. Next, the undrawn yarn obtained in the spinning process was drawn in a continuous process at a draw ratio of 3 times and a drawing temperature of 140 ° C., and then wound up by a winder to obtain a single-hole hollow cross-section polypropylene fiber with a 10d single yarn cross section. It was. As a result of DSC measurement, the obtained fiber had melting point peaks at two locations of 175 ° C. and 177 ° C.

  As the hollow fiber of Comparative Example 2, a 1-hole hollow fiber whose outer periphery was sputtered was used. As the 1-hole hollow fiber material, a commercially available polyester 1-hole hollow cross-section yarn (hollow rate: 30%, single yarn denier: 4d, short fiber cut length: 2 mm) was used.

  Next, a tire tread was formed using each rubber composition, and a tire (pneumatic tire) in which the tread was formed from the vulcanized rubber of each Example and Comparative Example was manufactured according to normal tire manufacturing conditions. This tire is a radial tire for passenger cars having a tire size of 185 / 70R13, and the structure thereof is as shown in FIG. 1, that is, a pair of bead portions 1 and a pair of bead portions 1 are connected in a toroidal shape. It has a radial structure including a carcass 2, a belt 3 for tightening a crown portion of the carcass 2, and a tread 4.

  In the tire 10, the carcass 2 is disposed at an angle of 90 ° with respect to the tire circumferential direction, and the number of cords to be driven is 50/5 cm. Further, as shown in FIG. 2, four blocks 8 are arranged in the tire width direction (B direction) on the tread 4 of the tire 10. The size of the block 8 is 35 mm in the tire circumferential direction (A direction) and 30 mm in the tire width direction (B direction). Further, the sipe 9 formed in the block 8 had a width of 0.4 mm, and a distance in the tire circumferential direction (A direction) was about 7 mm.

The performance on ice of each obtained tire was evaluated according to the following. The results are also shown in Table 1 below.
<Performance on ice>
Each test tire was mounted on a domestic 1600cc class passenger car, and this passenger car was driven on a general asphalt road for 200km, then on a flat surface on ice, and the tire was locked by stepping on the brake at a speed of 20km / h, The distance to stop was measured. The results are shown 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.

Further, from the tread portion of each of the obtained test tires, vulcanized rubber was cut out with a razor in about 4 mm square, and the hollow ratio of the hollow fibers embedded in the vulcanized rubber pieces was measured by the following method. These results are also shown in Table 1 below.
<Hollow rate (in rubber)>
The cross section of the hollow fiber in the vulcanized rubber was observed with a scanning electron microscope, and the hollow ratio was calculated (n = 10).
<Hollow rate (under compression strain)>
The rubber was compressed by 5% using a jig for compressing the vulcanized rubber piece by sandwiching the vulcanized rubber piece between two parallel metal plates and narrowing the space between the parallel metal plates with a set screw. The side surface of the compressed rubber piece was observed with a scanning electron microscope, and the hollow ratio was calculated (n = 10) from the cross-sectional shape of the compressed hollow fiber in the rubber.

１）シス−１，４−ポリブタジエン（日本合成ゴム（株）製、ＢＲ０１）
２）カーボンＮ２２６
３）大内新興化学工業（株）製 ノクラック６Ｃ
４）ジベンズチアジルスルフィド
５）Ｎ−シクロヘキシル−２−ベンゾチアジル−スルフェンアミド
６）ジニトロソペンタメチレンテトラミン
７）氷上性能：距離の逆数を比較例１のタイヤを１００として指数表示

1) cis-1,4-polybutadiene (manufactured by Nippon Synthetic Rubber Co., Ltd., BR01)
2) Carbon N226
3) Nouchi 6C manufactured by Ouchi Shinsei Chemical Co., Ltd.
4) Dibenzthiazyl sulfide 5) N-cyclohexyl-2-benzothiazyl-sulfenamide 6) Dinitrosopentamethylenetetramine 7) Performance on ice: Represent the index of the tire of Comparative Example 1 as 100 as the reciprocal of the distance

  From the results of Table 1 above, in the tire treads of Examples 1 to 3 using a rubber composition containing a predetermined rubber matrix and hollow fibers having two or more hollow portions, As a result of observation, it was confirmed that hollow holes with less crushing were formed both in the rubber and under compressive strain, and as a result, it was confirmed that the performance on ice was improved in these tires.

1 is a cross-sectional view in the width direction of a tire according to a preferred embodiment of the present invention. 1 is a partial development view of a tire tread according to a preferred embodiment of the present invention. It is an expanded sectional view near the tread part of the tire concerning one suitable embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Carcass 3 Belt 4 Tread 4A Cap part 4B Base part 6 Circumferential groove 7 Horizontal groove 8 Block 9 Sipe 10 Tire 11 Hollow fiber or long bubble

Claims (10)

A rubber matrix containing a rubber component and a blowing agent comprising at least one selected from natural rubber and diene synthetic rubbers, a hollow fiber having two or more hollow portions via the bridge portion in the cross-sectional shape of the fibers, A rubber composition comprising 0.5 to 30 parts by weight of hollow fibers with respect to 100 parts by weight of a rubber matrix .   The rubber composition according to claim 1, wherein the hollow ratio of the hollow fiber is 10 to 70%.   The rubber composition according to claim 1, wherein the hollow fiber has three or more hollow portions so as to form a branched portion in the cross-linked portion in a cross-sectional shape of the fiber.   The hollow fiber comprises a crystalline polymer, the melting point of the hollow fiber is lower than the maximum vulcanization temperature of the rubber matrix, and the viscosity of the hollow fiber is such that the temperature of the rubber matrix during vulcanization is The rubber composition according to any one of claims 1 to 3, wherein the viscosity is lower than the viscosity of the rubber matrix before reaching the maximum vulcanization temperature.   The rubber composition according to claim 4, wherein the crystalline polymer is polypropylene.   The rubber composition according to any one of claims 1 to 3, wherein an outer peripheral surface of the hollow fiber is subjected to adhesion processing.   The rubber composition according to claim 6, wherein the hollow fiber contains polyester.   The rubber composition according to claim 6 or 7, wherein the adhesion processing is a sputtering adhesion treatment of a composition containing cobalt. A vulcanized rubber obtained by vulcanizing the rubber composition according to any one of claims 1 to 8 and containing bubbles. A pair of bead portions, a carcass connected in a toroidal shape between the pair of bead portions, a belt for tightening a crown portion of the carcass, and a tread, and at least the tread is claimed. A tire comprising a vulcanized rubber obtained by vulcanizing the rubber composition according to any one of 1 to 8 .

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