Rubber composition and tire using the same

Abstract

To solve the problem in which: compared with ordinary road surfaces, icy and snowy road surfaces exhibit reduced friction coefficients and become more slippery; consequently, many approaches have been proposed conventionally to improve the ice performance (braking performance on ice) of studless tires, but further improvements are still required.SOLUTION: A rubber composition contains, based on 100 pts.mass of diene rubber, 30 to 100 pts.mass of carbon black and / or white filler, and 0.5 to 30 pts.mass of hollow silica having a porous shell. This rubber composition exhibits further improved ice performance compared to the conventional art.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition and a tire using the same, and more particularly to a rubber composition having excellent ice performance and a tire using the same.

Background Art

[0002] On an icy or snowy road surface, the friction coefficient is lower than that of a general road surface, making it slippery. Therefore, conventionally, many methods have been proposed to improve the ice performance (braking performance on ice) of studless tires. For example, Patent Document 1 below discloses a rubber composition for a tire, which contains a diene rubber and porous foamed glass particles, and the porosity of the foamed glass particles is 80% or less. Also, Patent Document 2 below discloses a rubber composition characterized in that the rubber contains silica-based hollow fine particles such that a part of the hollow fine particles is exposed.

[0003] However, none of Patent Documents 1 to 2 disclose any technical idea of blending carbon black and / or a white filler and hollow silica having a porous outer shell in a specific amount with a diene rubber to enhance ice performance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, an object of the present invention is to provide a rubber composition having even higher ice performance than the prior art and a tire using the same.

Means for Solving the Problem

[0006] As a result of intensive research, the present inventors have found that the above problems can be solved by blending a specific amount of carbon black and / or white filler and hollow silica having a porous outer shell with diene rubber, and thus have completed the present invention. That is, the present invention provides a rubber composition characterized by containing 30 to 100 parts by mass of carbon black and / or white filler and 0.5 to 30 parts by mass of hollow silica having a porous outer shell with respect to 100 parts by mass of diene rubber.

Advantages of the Invention

[0007] Since the rubber composition of the present invention is characterized by containing 30 to 100 parts by mass of carbon black and / or white filler and 0.5 to 30 parts by mass of hollow silica having a porous outer shell with respect to 100 parts by mass of diene rubber, it is possible to provide a rubber composition having further improved ice performance compared with the prior art and a tire using the same.

[0008] Hollow silica having a porous outer shell has a high ability to absorb water on the road surface both in the porous part of the outer shell and in the hollow part forming the internal cavity, suppresses a decrease in the friction coefficient, and thus can provide an effect of enhancing ice performance.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described in more detail.

[0010] (Diene Rubber) The diene rubbers used in the present invention include natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and the like. The molecular weight and microstructure of the diene rubber used in the present invention are not particularly limited, and it may be end-modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, etc., or may be epoxidized. The weight average molecular weight (Mw) of the above diene rubber is not particularly limited, but for reasons such as more excellent effects of the present invention, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000. In this specification, the weight average molecular weight (Mw) is a standard polystyrene conversion value obtained by gel permeation chromatography (GPC) measurement. Also, from the viewpoint of improving ice performance, the diene rubber preferably contains natural rubber and butadiene rubber. In 100 parts by mass of the diene rubber, the butadiene rubber is preferably 30 parts by mass or more, and more preferably 40 parts by mass or more. The natural rubber (NR) referred to in the present invention includes synthetic isoprene rubber (IR). Also, the diene rubber preferably has a glass transition temperature (Tg) of -50°C or lower. By defining Tg in this way, the ice performance 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 a heating rate condition of 20°C / min to measure a thermogram, and refers to the temperature at the midpoint of the transition region. The more preferable average Tg is -60°C or lower.

[0011] (Carbon black and / or white filler) Specific examples of the carbon black used in the present invention include furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF. These may be used alone or in combination of two or more. In addition, from the viewpoint of improving ice performance, the carbon black preferably has a nitrogen adsorption specific surface area (N 2 SA) of 10 to 300 m 2 / g, more preferably 50 to 150 m 2 / g. The nitrogen adsorption specific surface area (N 2 SA) 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".

[0012] Specific examples of the white filler used in the present invention include silica, calcium carbonate, magnesium carbonate, talc, clay, alumina, aluminum hydroxide, titanium oxide, calcium sulfate, etc. These may be used alone or in combination of two or more. Among these, silica is preferred because of better ice performance. Specific examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. These may be used alone or in combination of two or more. Note that the silica as the white filler does not include hollow silica with a porous outer shell described below.

[0013] From the viewpoint of improving ice performance, the silica preferably has a CTAB adsorption specific surface area of 50 to 300 m 2 / g, more preferably 90 to 200 m 2 / g. The CTAB adsorption specific surface area is a value measured by determining the adsorption amount of n-hexadecyltrimethylammonium bromide on the silica surface according to JIS K6217-3:2001 "Part 3: Method for determining specific surface area - CTAB adsorption method".

[0014] (Hollow silica with a porous outer shell) The hollow silica with a porous outer shell used in the present invention (hereinafter sometimes simply referred to as hollow silica) has an outer shell having a porous portion and a hollow portion forming a cavity inside thereof. The average particle diameter of the hollow silica used in the present invention is preferably from 1 μm to 1000 μm, more preferably from 10 μm to 200 μm. According to this average particle diameter range, the performance on ice can be further enhanced. The average particle diameter can be the median diameter (D50: the particle diameter of the particles at 50% in the particle diameter cumulative distribution) measured by the laser diffraction method, and can be measured, for example, with a laser diffraction scattering type particle size distribution measuring device LA-300 (manufactured by Horiba, Ltd.), a laser microscope VK-8710 (manufactured by Keyence Corporation), etc.

[0015] Also, for the hollow silica used in the present invention, the ratio of the hollow portion is preferably 30% or more, more preferably 40% or more, based on the total volume. By satisfying this ratio of the hollow portion, the performance on ice can be further enhanced. The ratio of the hollow portion can be measured by observing the cross section of the hollow silica by SEM and performing image analysis.

[0016] Also, for the hollow silica used in the present invention, the porosity is preferably 50% or more, more preferably 60% or more, based on the total volume. By satisfying this porosity, the performance on ice can be further enhanced. The porosity of the hollow silica can be determined by the following formula 1. (Formula 1) Porosity [%] = (void volume [ml]) / (bulk volume of sample [ml]) × 100 = {(bulk volume of sample [ml]) - (solid volume of sample [ml])} / (bulk volume of sample [ml]) × 100 = {1 - (solid volume of sample [ml]) / (bulk volume of sample [ml])} × 100 = {1 - (bulk specific gravity of sample [g / ml]) / (true specific gravity of sample [g / ml])} × 100 The porosity of the hollow silica is calculated as the ratio including the above-mentioned hollow portion. Confirmation of the presence of voids in the outer shell can be performed by the above formula 1 and SEM observation.

[0017] The hollow silica used in the present invention can be a commercially available product, and examples thereof include God Ball B-25C manufactured by Suzuki Oil & Fat Co., Ltd. (average particle diameter = 8 to 13 μm, ratio of hollow part = 45%).

[0018] (Other components) In the rubber composition of the present invention, in addition to the above-described components, a vulcanizing or crosslinking agent; a vulcanization or crosslinking accelerator; zinc oxide, various fillers other than those exemplified above; an antioxidant; a plasticizer; a silane coupling agent; various additives generally blended in rubber compositions such as thermally expandable microcapsules can be blended. Such additives can be kneaded by a general method to form a composition and can be used for vulcanization or crosslinking. The blending amounts of these additives can also be set to conventional general blending amounts as long as they do not conflict with the object of the present invention.

[0019] Further, the tire of the present invention can be prepared using the rubber composition of the present invention, is preferably a pneumatic tire, and can be filled with an inert gas such as air, nitrogen, and other gases. Further, the tire of the present invention is preferably applied to a tread, particularly a cap tread, and is preferably a winter tire such as a studless tire.

Examples

[0020] Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples.

[0021] Standard Example, Examples 1 to 3, Comparative Examples 1 to 3 In the formulation (parts by mass) shown in Table 1, the components excluding the vulcanization system (vulcanization accelerator, sulfur) and the curing agent were kneaded in a 1.7-liter closed Banbury mixer for 5 minutes, then discharged outside 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 a vulcanized rubber test piece, and the physical properties were measured by the test methods shown below.

[0022] Ice performance: Samples were prepared by attaching the obtained vulcanized rubber test pieces to flat cylindrical base rubbers. Using an ice friction tester, the ice friction coefficient was measured under the conditions of a measurement temperature of -3.0 °C, a load of 98 N, and a road surface speed of 20 km / h. The obtained ice friction coefficient was indicated as an index with the value of the standard example being 100. A larger index means a greater ice friction force and better ice performance.

[0023] The results are shown together in Table 1.

[0024]

Table 1

[0025] *1: NR (STR20 manufactured by Bombardier, glass transition temperature (Tg) = -65 °C) *2: BR (Nipol BR1220 manufactured by Zeon Corporation, glass transition temperature (Tg) = -110 °C) *3: Carbon black (Shoublack N339 manufactured by Cabot Japan) *4: Silica (ULTRASIL VN3 manufactured by Evonik Degussa) *5: Silane coupling agent (Si69 manufactured by Evonik Degussa, bis(3-triethoxysilylpropyl)tetrasulfide) *6: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu KK) *7: Sulfur (Oil-treated sulfur manufactured by Hosoi Chemical Industry Co., Ltd.) *8: Vulcanization accelerator (Sunceler CM-G manufactured by Sanshin Chemical Industry Co., Ltd.) *9: Hollow silica with a porous outer shell (God Ball B-25C manufactured by Suzuki Oil & Fat Co., Ltd. (average particle diameter = 8 - 13 μm, ratio of hollow part = 45%)) *10: Porous silica without a hollow part (Aerica manufactured by Tokuyama Corporation, average particle diameter = 10 μm, porosity = 90%) *11: Hollow silica with a non-porous outer shell (Celsfiers manufactured by Pacific Cement Co., Ltd., average particle diameter = 10 μm or less, ratio of hollow part = 70%)

[0026] From the results in Table 1, the rubber compositions of Examples 1 to 3 contain 30 to 100 parts by mass of carbon black and / or white filler and 0.5 to 30 parts by mass of hollow silica having a porous outer shell with respect to 100 parts by mass of the diene rubber. Therefore, the ice performance is improved compared to the standard example. On the other hand, Comparative Example 1 uses porous silica without a hollow part, so the improvement in ice performance was not as significant as in the examples. Comparative Example 2 uses hollow silica with a non-porous outer shell, so the improvement in ice performance was not as significant as in the examples.

[0027] The present invention includes the following forms. Embodiment 1: A rubber composition comprising 30 to 100 parts by mass of carbon black and / or white filler and 0.5 to 30 parts by mass of hollow silica having a porous outer shell with respect to 100 parts by mass of the diene rubber. Embodiment 2: The rubber composition according to Embodiment 1, wherein the average particle diameter of the hollow silica having a porous outer shell is 1 μm to 1000 μm. Embodiment 3: The rubber composition according to Embodiment 1 or 2, wherein the ratio of the hollow part is 30% or more with respect to the total volume of the hollow silica having a porous outer shell. Embodiment 4: The rubber composition according to any one of Embodiments 1 to 3, wherein the diene rubber includes natural rubber and butadiene rubber. Embodiment 5: A winter tire using the rubber composition according to any one of Embodiments 1 to 4.

Claims

1. A rubber composition comprising 30 to 100 parts by mass of carbon black and / or white filler and 0.5 to 30 parts by mass of hollow silica having a porous outer shell, based on 100 parts by mass of a diene rubber.

2. The rubber composition according to claim 1, wherein the average particle diameter of the hollow silica having a porous outer shell is 1 μm to 1000 μm.

3. The rubber composition according to claim 1, wherein the ratio of the hollow portion is 30% or more based on the total volume of the hollow silica having a porous outer shell.

4. The rubber composition according to claim 1, wherein the diene rubber includes natural rubber and butadiene rubber.

5. A winter tire using the rubber composition according to claim 1.

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