Rubber composition and studless tire using the same

Abstract

On icy and snowy roads, the coefficient of friction decreases compared to ordinary roads, making them more slippery. Therefore, numerous methods have been proposed to improve the ice performance (braking performance on ice) of studless tires. The present invention aims to provide a rubber composition that further enhances ice performance while maintaining wet performance. [Solution] 30 to 100 parts by mass of carbon black and / or silica are added to 100 parts by mass of diene rubber, and the material is hollow inside with through holes inside and outside the hollow interior, and has a bulk density of 0.3 to 1.2 g / cm³. 3 The above problem was solved by a rubber composition containing 0.5 to 30 parts by mass of hollow porous alumina particles.

Description

[Technical Field]

[0001] This invention relates to a rubber composition and a studless tire using the same, and more specifically, to a rubber composition that maintains wet performance while exhibiting excellent ice performance, and a studless tire using the same. [Background technology]

[0002] On icy and snowy roads, the coefficient of friction is lower than on normal roads, making them more slippery. Therefore, numerous methods have been proposed to improve the ice performance (braking ability on ice) of studless tires. For example, Patent Document 1 below discloses a rubber composition particularly useful as a tire tread, comprising at least a diene elastomer, more than 30 phr of liquid plasticizer, and a reinforcing filler system in an amount between 50 phr and 150 phr, characterized in that it further comprises a metal oxide hollow fine particle in an amount between 2 phr and 50 phr and a water-soluble short fiber in an amount between 2 phr and 50 phr. Patent Document 2 below discloses a rubber composition for tire treads, in which at least 1 to 30 parts by mass of hollow fine particles are blended with 100 parts by mass of rubber component such that the average number particle size in the rubber is 1 μm or more and 100 μm or less, and the particle size distribution index (PDI) in the rubber is 1.50 or less. Patent Document 3 below discloses a rubber filler consisting of porous particles having one or more through-pores within the particles, with an average diameter of the pores being 1 to 1000 nm. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2013-522427 [Patent Document 2] Japanese Patent Publication No. 2021-46775 [Patent Document 3] Japanese Patent Publication No. 2010-106144 [Overview of the project] [Problems that the invention aims to solve]

[0004] The object of the present invention is to provide a rubber composition that maintains wet performance while exhibiting excellent ice performance, and a studless tire using the same. [Means for solving the problem]

[0005] As a result of diligent research, the inventors of the present invention have discovered that a rubber composition comprising diene rubber, carbon black and / or silica, and a specific amount of hollow porous alumina particles having a specific structure can solve the above problems, and have completed the present invention.

[0006] In other words, the present invention comprises 100 parts by mass of diene rubber, 30 to 100 parts by mass of carbon black and / or silica, and a material that is hollow inside and has through holes both inside and outside the hollow interior, with a bulk density of 0.3 to 1.2 g / cm³. 3 The present invention provides a rubber composition characterized by containing 0.5 to 30 parts by mass of hollow porous alumina particles. The present invention also provides a studless tire using the aforementioned rubber composition. [Effects of the Invention]

[0007] The rubber composition of the present invention comprises 100 parts by mass of diene rubber, 30 to 100 parts by mass of carbon black and / or silica, and is hollow inside with through holes inside and outside the hollow, and has a bulk density of 0.3 to 1.2 g / cm³. 3 This rubber composition is characterized by the incorporation of 0.5 to 30 parts by mass of hollow porous alumina particles, thereby providing a rubber composition that maintains wet performance while exhibiting excellent ice performance, and a studless tire using the same. Because the hollow porous alumina particles have the aforementioned structure, they are prone to cracking in the tire tread, causing particles to fall off and creating an uneven surface, which increases surface roughness and improves ice performance. Furthermore, because the hollow porous alumina particles are hollow inside and have through-holes both inside and outside the hollow structure, they easily absorb water that has melted on the road surface, contributing to maintaining wet performance and improving ice performance. In addition, the bulk density of the hollow porous alumina particles is 0.3 to 1.2 g / cm³. 3 Therefore, they can be present in large quantities on the tire tread surface, which also contributes to improved performance on ice. Furthermore, since the aforementioned hollow porous alumina particles are not petroleum-derived substances, they have excellent environmental performance. [Modes for carrying out the invention]

[0008] The present invention will be described in more detail below.

[0009] (Diene-based rubber) The diene rubber used in this invention can be any diene rubber that can be blended into the rubber composition, such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and ethylene-propylene-diene polymer (EPDM). These may be used individually or in combination of two or more. Furthermore, their molecular weight and microstructure are not particularly limited, and they may be end-modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl groups, etc., or epoxidized. Furthermore, from the viewpoint of improving ice performance, it is preferable that butadiene rubber accounts for 30 parts by mass or more, preferably 40 parts by mass or more, of 100 parts by mass of diene rubber. Furthermore, it is preferable that the diene-based rubber has a glass transition temperature (Tg) of -50°C or lower. By specifying the Tg in this way, the performance on ice is improved. When a plurality of types of diene rubbers are included, the Tg referred to in this specification is a value calculated based on the sum of the products of the glass transition temperature of each rubber multiplied by the weight fraction of each rubber, that is, the weighted average. In the calculation, the sum of the weight fractions of each component is set to 1.0. The glass transition temperature (Tg) referred to in the present invention is measured by differential scanning calorimetry (DSC) under the condition of a heating rate of 20 °C / min to measure a thermogram, and refers to the temperature at the midpoint of the transition region. More preferably, the average Tg is -60 °C or lower.

[0010] (Carbon black and / or silica) Specific examples of the carbon black used in the present invention include, for example, furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF. These may be used alone or in combination of two or more. Also, from the viewpoint of improving ice performance, the carbon black preferably has a nitrogen adsorption specific surface area (N2SA) of 10 to 300 m 2 / g, and more preferably 50 to 150 m 2 / g. The nitrogen adsorption specific surface area (N2SA) is a value measured according to JIS K 6217-2:2001 "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method".

[0011] Specific examples of the silica used in the present invention include, for example, wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. These may be used alone or in combination of two or more. Also, silica made from biomass materials such as rice husks may be used.

[0012] From the viewpoint of improving ice performance, the silica preferably has a CTAB adsorption specific surface area of 50 to 300 m 2 / g, and more preferably 90 to 200 m 2 / g. The CTAB adsorption specific surface area is the value obtained by measuring the amount of n-hexadecyltrimethylammonium bromide adsorbed onto the silica surface according to JIS K6217-3:2001 "Part 3: Method for determining specific surface area - CTAB adsorption method".

[0013] (Hollow porous alumina particles) The hollow porous alumina particles used in this invention are hollow inside and have through-pores both inside and outside the hollow structure, with a bulk density of 0.3 to 1.2 g / cm³. 3 It is characterized by the following: The hollow porous alumina particles used in this invention are a known substance disclosed in Japanese Patent Publication No. 7144105, but will be described below.

[0014] The hollow porous alumina particles used in the present invention can be manufactured by a first step of dissolving an aluminum salt of a carboxylic acid in an aqueous solvent; a second step of drying and granulating the obtained solution of the aluminum salt of the carboxylic acid in air or an inert gas at a temperature of 40 to 280°C at a gas pressure of 0.01 to 1 MPa to form dried granules; and a third step of raising the temperature of the obtained dried granules at 0.3 to 10°C / min, firing them at a firing temperature in the range of 700 to 1300°C for 0.5 to 7 hours, and then lowering the temperature at 0.3 to 10°C / min.

[0015] <1st process> Hollow porous alumina particles use aluminum salts of carboxylic acids as the main raw material. Examples of carboxylic acids include monocarboxylic acids such as formic acid, acetic acid, propionic acid, lactic acid, hydroxyacetic acid, gluconic acid, and salicylic acid; dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, malic acid, and tartaric acid; tricarboxylic acids such as citric acid and aconitic acid; and α-hydroxycarboxylic acids such as lactic acid, malic acid, and citric acid. More specifically, the carboxylic acids that can be used are preferably formic acid, lactic acid, acetic acid, citric acid, glycolic acid, propionic acid, hydroxyacetic acid, tartaric acid, gluconic acid, aluminum salicylate, or mixtures thereof. The carboxylic acids that can be used in the present invention preferably have 0 to 7 carbon atoms in the portion excluding the carbon of the carboxyl group. Aluminum salts of carboxylic acids are produced by conventional methods (e.g., direct methods such as melting, slurrying, solid-phase, and solvent methods, or double decomposition methods using aqueous or alcoholic solvents).

[0016] Examples of aluminum salts of carboxylic acids that can be used in the present invention are not limited to these, but include aluminum formate, aluminum lactate, aluminum acetate, aluminum citrate, aluminum glycolate, aluminum propionate, aluminum hydroxyacetate, aluminum tartrate, aluminum gluconate, aluminum salicylate, or mixtures thereof.

[0017] Next, the first step is to dissolve the aluminum salt of the carboxylic acid in an aqueous solvent. The aqueous solvent is water or an organic solvent with a boiling point between 30°C and 200°C, or a mixture thereof. Examples of organic solvents with a boiling point between 30°C and 200°C include lower alcohols such as methanol and ethanol; ketones such as acetone and methyl ethyl ketone; and sulfoxides such as DMSO (dimethyl sulfoxide). The aqueous solvent is preferably water or a lower alcohol, and more preferably water.

[0018] The aluminum salt of the carboxylic acid is dissolved in an aqueous solvent. Dissolution is carried out by the usual method. Specifically, the aluminum salt of the carboxylic acid is heated and stirred in the aqueous solvent at a temperature of 25 to 100°C for 0.5 to 3 hours to dissolve it. Of course, this method is not limited to this one; any method that dissolves the aluminum salt of the carboxylic acid in an aqueous solvent is acceptable.

[0019] <Second process> In the second step, the obtained aluminum salt solution is dried and granulated in air or an inert gas at a temperature of 40 to 280°C under a gas pressure of 0.01 to 1 MPa. For drying and granulation, one of the following methods is selected: spray drying, fluid bed granulation, or spray freeze-drying granulation. The temperature setting is 40 to 280°C, more preferably 40 to 270°C, and higher than the boiling point of the aqueous solvent. This allows the solvent to evaporate rapidly from the inside while granulation proceeds, making it possible to obtain a hollow porous alumina precursor with through-pores on the inside and outside. Specifically, when water is used as the aqueous solvent, it is preferable to dry and granulate in air at a temperature of 100 to 280°C, preferably 120 to 260°C. In this specification, "gas pressure" is the pressure applied to the gas used, and since it is 0.01 to 1 MPa, it can be used under both negative and pressurized conditions, but if the gas is air, it can be used at atmospheric pressure of 0.1 MPa.

[0020] <3rd process> In the third step, the dried granules prepared in the second step are placed in a calcination furnace, the temperature is increased at 0.3 to 10°C / min, and the material is calcined at a desired calcination temperature within the range of 700 to 1300°C for 0.5 to 7 hours, and then the temperature is lowered at 0.3 to 10°C / min to obtain hollow porous alumina.

[0021] The firing furnace used in the third step may be any batch furnace, elevator furnace, pusher furnace, shuttle furnace, vacuum furnace, etc., that is capable of temperature control and gas control, and is more preferably a batch furnace, elevator furnace, or pusher furnace.

[0022] In the third step, the granulated particles are placed in a heat-resistant container such as a crucible or saggar made of alumina, zirconia, or the like, more preferably a heat-resistant container such as a crucible or saggar made of alumina, and fired. This process leaves through-pores on the inside and outside, resulting in hollow, porous alumina particles with minimal contamination.

[0023] The firing time is preferably 0.5 to 7 hours at the desired temperature, and more preferably 2 to 6 hours. The firing time is set according to the desired crystalline phase and specific surface area. The heating rate is preferably 0.3 to 10°C / min, and more preferably 0.5 to 8°C / min. The cooling rate is preferably 0.3 to 10°C / min, and more preferably 0.5 to 8°C / min.

[0024] In the present invention, any gas atmosphere such as air, nitrogen, vacuum, or inert gas can be selected for firing, as long as the organic matter is removed and the desired alumina crystalline phase is properly formed when firing is carried out at the predetermined firing temperature and time.

[0025] In the raw materials used in this invention, and in the wetted and powder-contacting parts of various equipment, it is preferable to use materials with low impurity content, such as Fe, Si, Ca, and Mg. Therefore, it is desirable to select materials such as FRP (fiber-reinforced plastic), stainless steel (e.g., SUS316, SUS316L), nickel alloy (e.g., Hastelloy), heat-resistant polyvinyl chloride, high-density polyethylene (HDPE), polypropylene, polyvinylidene fluoride, and polyfluorotetraethylene for the wetted and powder-contacting parts of various equipment. Furthermore, in the raw materials (e.g., aluminum salts of carboxylic acids), it is preferable to synthesize using materials with controlled Fe content of 70 ppm or less (preferably 30 ppm or less), Ca content of 70 ppm or less (preferably 30 ppm or less), Mg content of 70 ppm or less (preferably 30 ppm or less), and Si content of 70 ppm or less (preferably 30 ppm or less), as this reduces the impurity content of the resulting hollow porous alumina particles.

[0026] The hollow porous alumina particles obtained by the manufacturing method finally have a D50 of 4 to 50 μm and a D90 of 300 μm or less in the particle size distribution measurement, have a hollow interior and through holes in the hollow interior and the exterior, and have a specific surface area of 30 m 2 / g or more. Usually, particles are formed during granulation in the second step, and almost the final particle size distribution is obtained, which are hollow porous and have through holes. However, in the third step, they are slightly shrunk to become the final alumina particles.

[0027] The particle size distribution can be obtained by measuring, for example, with a laser diffraction particle size distribution analyzer (manufactured by Malvern Panalytical Ltd., Mastersizer 3000). D50 is the average particle diameter, which is 4 to 50 μm, preferably 6 to 40 μm, more preferably 8 to 35 μm. D90 means the particle diameter that 90% of the particles can reach. Specifically, D90 is 300 μm or less, preferably 60 μm or more and 300 μm or less, specifically 70 μm or more and 250 μm or less, and more specifically 80 μm or more and 200 μm or less.

[0028] The hollow porous alumina particles have a hollow and porous interior. There is a specific surface area to represent such performance. The specific surface area is the surface area per unit mass of an object. For example, the specific surface area can be measured with N2 using a high-precision gas / vapor adsorption measurement device (manufactured by MicrotracBEL Corp., BELSORP MAX2). The larger the specific surface area, the higher the hollowness and porosity, but the alumina particles of the present invention have a specific surface area of 30 m 2 / g or more, preferably 50 m 2 / g or more, more preferably 60 m 2 / g or more, and although the upper limit is better if it is higher, it rarely exceeds 600 m 2 / g.

[0029] The presence of through holes in the hollow porous alumina particles is difficult to analyze numerically, and the presence can be confirmed by checking the microstructure with a scanning electron microscope (SEM) or the like.

[0030] Also, the bulk specific gravity of the hollow porous alumina particles is 0.3 to 1.2 g / cm from the viewpoint of improving the effects of the present invention.3 Preferably, it is 0.5 to 0.8 g / cm³. 3 It is even more preferable that this is the case. The bulk density can be measured using a powder dynamics property measuring device such as the Powder Tester manufactured by Hosokawa Micron Corporation, according to the measurement method specified in JIS R 1628 "Method for measuring the bulk density of fine ceramic powder".

[0031] (Ratio of rubber composition) The rubber composition of the present invention comprises 100 parts by mass of diene rubber, 30 to 100 parts by mass of carbon black and / or silica, and is hollow inside with through holes inside and outside the hollow, and has a bulk density of 0.3 to 1.2 g / cm³. 3 It is characterized by containing 0.5 to 30 parts by mass of hollow porous alumina particles. If the amount of carbon black and / or silica added to 100 parts by mass of diene rubber is less than 30 parts by mass, the mechanical properties and abrasion resistance of the rubber composition deteriorate. Conversely, if it exceeds 100 parts by mass, the low-temperature flexibility of the rubber composition decreases, resulting in poor performance on ice. If the amount of hollow porous alumina particles added is less than 0.5 parts by mass per 100 parts by mass of diene rubber, the amount added is too small to achieve the effects of the present invention, while if it exceeds 30 parts by mass, the elongation at break decreases.

[0032] The amount of carbon black added is preferably 3 to 70 parts by mass per 100 parts by mass of diene rubber. The amount of silica added is preferably 30 to 100 parts by mass per 100 parts by mass of diene rubber. The amount of the hollow porous alumina particles is preferably 1 to 15 parts by mass per 100 parts by mass of diene rubber.

[0033] From the viewpoint of improving performance on ice, the rubber composition of the present invention preferably contains a resin with a softening point of 90°C to 150°C. While there are no particular limitations on the resin, specific examples include coumarone resins (e.g., coumarone resin, coumarone-indene resin, coumarone-indene-styrene resin), phenolic resins (e.g., phenolic resin, phenol-acetylene resin, phenol-formaldehyde resin), xylene resins (e.g., xylene resin, xylene-acetylene resin, xylene-formaldehyde resin), rosin resins (e.g., rosin, rosin esters, hydrogenated rosin derivatives), terpene resins (e.g., terpene resin, modified terpene resin (aromatic modified terpene resin, etc.), terpene phenolic resin, hydrogenated terpene resin), α-pinene resin, styrene resin, petroleum resin (e.g., C5 petroleum resin, C9 petroleum resin, alicyclic petroleum resin, C5 / C9 copolymer petroleum resin), and aliphatic saturated hydrocarbon resins. Among these, terpene resins and petroleum resins are preferred, and aromatic modified terpene resins are even more preferred, due to the superior effects of the present invention. As aromatic modified terpene resins, for example, aromatic modified terpene resins obtained by polymerizing terpene resins such as α-pinene, β-pinene, dipentene, and limonene with aromatic compounds such as styrene, α-methylstyrene, vinyltoluene, and indene are effectively used. The softening point shall be measured in accordance with JIS K6220-1. The amount of resin added is preferably 2 to 40 parts by mass, and more preferably 3 to 35 parts by mass, per 100 parts by mass of diene rubber.

[0034] (Other ingredients) In addition to the components mentioned above, the rubber composition of the present invention may contain various additives commonly used in rubber compositions, such as vulcanizing or crosslinking agents; vulcanizing or crosslinking accelerators; zinc oxide; antioxidants; plasticizers; white fillers other than silica; silane coupling agents; and thermally expandable microcapsules. These additives can be mixed in a conventional manner to form a composition which can then be used for vulcanization or crosslinking. The amounts of these additives can also be conventional amounts, as long as they do not contradict the purpose of the present invention.

[0035] Furthermore, the tire of the present invention can be prepared using the rubber composition of the present invention, and is preferably a pneumatic tire, which can be filled with air, nitrogen or other inert gases, and other gases. The tire of the present invention is also preferably applied to a tread, especially a capped tread, to form a studless tire. [Examples]

[0036] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0037] Standard example, Examples 1-4, Comparative examples 1-4 In the formulations (parts by mass) shown in Table 1, the components excluding the vulcanization system (vulcanization accelerator, sulfur) and curing agent were kneaded in a 1.7-liter sealed Banbury mixer for 5 minutes, then released from the mixer and cooled to room temperature. Subsequently, the composition was put back into the same Banbury mixer, the vulcanization system was added and kneaded to obtain a rubber composition. The obtained rubber composition was press-vulcanized at 170°C for 10 minutes to obtain vulcanized rubber test pieces, and their physical properties were measured using the test method described below.

[0038] Ice Performance: Samples were prepared by attaching the obtained vulcanized rubber test pieces to a flattened cylindrical rubber base. The ice friction coefficient of the samples was measured using an ice friction tester under the conditions of a measurement temperature of -1.5°C, a load of 98N, and a road surface speed of 20km / h. The obtained ice friction coefficient is expressed as an index, with the standard example value set to 100. A larger index indicates greater ice friction and superior ice performance. Elongation at Break: In accordance with JIS K6251, a No. 3 dumbbell-shaped sample was punched out from the above vulcanized rubber test piece, and a tensile test was performed at a tensile speed of 500 mm / min to measure the elongation at break (%). The results are expressed as an index with the standard example value set to 100. A higher index indicates better elongation at break. tanδ(0℃): In accordance with JIS K6394:2007, tanδ(0℃) was measured using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho) under the conditions of tensile deformation strain of 10±2%, frequency of 20Hz, and temperature of 0℃. The results are shown as an index with the standard example value set to 100. A larger index indicates better wet performance.

[0039] The results are shown in Table 1.

[0040] [Table 1]

[0041] *1: NR (RSS#3) *2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.) *3: Carbon black (Seast KHA manufactured by Tokai Carbon Co., Ltd.) *4: Silica (Zeosil 1165MP manufactured by Rhodia, CTAB specific surface area = 159 m²) 2 / g) *5: Silane coupling agent (Si69 manufactured by Evonik DeGussa, bis(3-triethoxysilylpropyl)tetrasulfide) *6: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu K.K.) *7: Modified terpene resin (TO-125 manufactured by Yasuhara Chemical Co., Ltd., softening point = 125°C, molecular weight = 1300, aromatic modified terpene resin) *8: Hollow porous alumina particles 1 (manufactured by Asada Chemical Industries, Ltd., hollow porous alumina particles with a hollow interior and through-pores both inside and outside the hollow interior, average particle diameter = 35 μm, specific surface area = 116 m²) 2 / g, bulk density = 0.6 g / cm³ 3 ) *9: Hollow porous alumina particles 2 (manufactured by Asada Chemical Industries, Ltd., hollow porous alumina particles with a hollow interior and through-pores both inside and outside the hollow interior, average particle diameter = 13 μm, specific surface area = 10² m²) 2 / g, bulk density = 0.6 g / cm³ 3 ) *10: Spherical alumina (Denka Co., Ltd. product name: Spherical Alumina DAW-70; not hollow inside, and does not have through-pores inside or outside the hollow interior. Average particle diameter = 76 μm, specific surface area = 0.2 m²) 2 / g, bulk density = approximately 2.0 g / cm³ 3 ) *11: Hollow inorganic particles (3M Glass Bubbles S38, manufactured by 3M Japan, have no through-pores inside or outside the hollow structure. Average particle diameter = 40 μm, specific surface area = 40 m²) 2 / g, bulk density = 0.2 g / cm³ 3 ) *12: Tubular inorganic compound (DRAGONITE-HP, manufactured by APPLIED MINERALS, hollow interior and exterior without through-pores. Halloysite, length = 0.2-2 μm, outer diameter = 50-70 nm, specific surface area = 65 m²) 2 / g, bulk density = 0.3 g / cm³ 3 ) *13: Sulfur (Finely powdered sulfur containing Kinka oil, manufactured by Tsurumi Chemical Industries Co., Ltd.) *14: Vulcanization accelerator (Noxellar CZ-G, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0042] From the results in Table 1, the rubber composition of each example contains 30 to 100 parts by mass of carbon black and / or silica per 100 parts by mass of diene rubber, and is hollow inside with through holes inside and outside the hollow, with a bulk density of 0.3 to 1.2 g / cm³. 3 Because it contains 0.5 to 30 parts by mass of hollow porous alumina particles, it maintains wet performance while improving ice performance compared to the standard example. Furthermore, no decrease in elongation at break is observed. On the other hand, Comparative Example 1 is an example in which spherical alumina was used instead of hollow porous alumina particles, so the improvement in ice performance was not as significant as in the Examples. Comparative Example 2 is an example in which hollow inorganic particles were used instead of hollow porous alumina particles, so the improvement in ice performance was not as significant as in the Examples, and the elongation at break decreased. Comparative Example 3 is an example in which a tubular inorganic compound was used instead of hollow porous alumina particles, so the improvement in ice performance was not as significant as in the Examples, and the elongation at break decreased.

[0043] The present invention encompasses the following embodiments. Embodiment 1: For every 100 parts by mass of diene rubber, 30 to 100 parts by mass of carbon black and / or silica are added, and the material is hollow inside with through-holes both inside and outside the hollow structure, and has a bulk density of 0.3 to 1.2 g / cm³. 3 0.5 to 30 parts by mass of hollow porous alumina particles. A rubber composition characterized by the incorporation of a specific compound. Embodiment 2: The specific surface area of ​​the hollow porous alumina particles is 50 m². 2 The rubber composition according to Embodiment 1, characterized in that it is 1 / g or more. Embodiment 3: The rubber composition according to Embodiment 1 or 2, characterized in that the average particle size of the hollow porous alumina particles is 4 μm to 50 μm. Embodiment 4: The rubber composition according to any one of Embodiments 1 to 3, characterized in that it contains 30 to 100 parts by mass of silica with respect to 100 parts by mass of the diene rubber. Embodiment 5: The rubber composition according to any one of Embodiments 1 to 4, further characterized by containing a resin having a softening point of 90°C to 150°C. Embodiment 6: The rubber composition according to any one of Embodiments 1 to 5, characterized in that butadiene rubber accounts for 30 parts by mass or more in 100 parts by mass of the diene rubber. Embodiment 7: A studless tire using the rubber composition described in any of Embodiments 1 to 6.

Claims

1. Each 100 parts by mass of diene rubber is mixed with 30 to 100 parts by mass of carbon black and / or silica, and a material that is hollow inside and has through holes inside and outside the hollow interior, with a bulk density of 0.3 to 1.2 g / cm³. ３ 0.5 to 30 parts by mass of hollow porous alumina particles. A rubber composition characterized by the incorporation of a specific compound.

2. The specific surface area of ​​the hollow porous alumina particles is 50 m². ２ The rubber composition according to claim 1, characterized in that it is 1 g or more.

3. The rubber composition according to claim 1, characterized in that the average particle size of the hollow porous alumina particles is 4 μm to 50 μm.

4. The rubber composition according to claim 1, characterized in that it contains 30 to 100 parts by mass of silica with respect to 100 parts by mass of the diene rubber.

5. The rubber composition according to claim 1, further characterized by containing a resin having a softening point of 90°C to 150°C.

6. The rubber composition according to claim 1, characterized in that butadiene rubber accounts for 30 parts by mass or more of 100 parts by mass of the diene rubber.

7. A studless tire using the rubber composition described in claim 1.

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