Rubber composition and studless tire using the same

Abstract

To provide a rubber composition having an excellent performance on ice while maintaining breaking elongation because an icy and snowy road surface has a lower coefficient of friction and becomes more slippery than a general road surface, and therefore, numerous techniques have conventionally been proposed in order to improve the performance on ice (braking performance on ice) of a studless tire.SOLUTION: A rubber composition includes diene rubber, carbon black, a white filler, and xyloglucan, in which 30-100 pts.mass of the white filler and 0.5-30 pts.mass of the xyloglucan are contained with respect to 100 pts.mass of the diene rubber.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition and a studless tire using the same, and more particularly to a rubber composition that has excellent performance on ice while maintaining breaking elongation, and a studless tire using the same. [Background technology]

[0002] On snowy and icy roads, the coefficient of friction is lower than on regular roads, making the tires more slippery. Therefore, numerous methods have been proposed to improve the ice performance (braking performance on ice) of studless tires. One known technique is to blend polymer microparticles into the studless tire compound, thereby creating a rough tread surface. However, these microparticles fall off during driving, raising environmental concerns. Another problem with blending polymer microparticles is that they become foreign matter in the rubber, reducing elongation at break.

[0003] As mentioned above, many techniques have been proposed to improve the performance of studless tires on ice, including, for example, the techniques disclosed in Patent Documents 1 to 3 listed below. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6544496 [Patent Document 2] Patent No. 7275526 [Patent Document 3] Patent No. 5535645 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a rubber composition that has excellent performance on ice while maintaining breaking elongation, and a studless tire using the same. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have discovered that the above problems can be solved by blending specific amounts of a white filler and xyloglucan with a diene rubber, and have thus completed the present invention.

[0007] That is, the present invention provides a rubber composition containing a diene rubber, carbon black, a white filler, and xyloglucan, characterized in that 30 to 100 parts by mass of the white filler and 0.5 to 30 parts by mass of the xyloglucan are blended with 100 parts by mass of the diene rubber. [Effects of the Invention]

[0008] The rubber composition of the present invention contains a diene rubber, carbon black, a white filler, and xyloglucan, and is characterized in that 30 to 100 parts by mass of the white filler and 0.5 to 30 parts by mass of the xyloglucan are blended per 100 parts by mass of the diene rubber.Therefore, it is possible to provide a rubber composition that maintains breaking elongation while providing excellent performance on ice, and a studless tire using the same.

[0009] The xyloglucan used in the present invention can efficiently impart surface roughness to the tire's contact surface, thereby improving performance on ice. It is believed that xyloglucan dissolves to some extent in water and falls off during driving, thereby imparting surface roughness. Furthermore, because xyloglucan is a plant-derived material, its shedding is unlikely to cause environmental problems. Furthermore, even though xyloglucan is a polymeric material, its incorporation prevents it from becoming a foreign substance in rubber, preventing a decrease in breaking elongation. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will now be described in further detail.

[0011] (Diene rubber) The diene rubber used in the present invention can be any diene rubber that can be compounded into a 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 terpolymer (EPDM). These may be used alone or in combination of two or more. There are no particular limitations on the molecular weight or microstructure, and the rubber may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, or hydroxyl group, or may be epoxidized. The molecular weight of the diene rubber is not particularly limited, but in order to obtain better 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 molecular weight is a weight average molecular weight (Mw) calculated as a standard polystyrene standard obtained by gel permeation chromatography (GPC) measurement. Furthermore, from the viewpoint of improving performance on ice, it is preferable that the butadiene rubber accounts for 30 parts by mass or more, and preferably 40 parts by mass or more, per 100 parts by mass of diene rubber, and it is even more preferable that natural rubber is used in combination. Furthermore, the diene rubber preferably has a glass transition temperature (Tg) of not more than −50° C. By specifying the Tg in this way, performance on ice is improved. In the case where multiple diene rubbers are contained, the Tg referred to in this specification is a value calculated based on the sum of the products obtained by multiplying the glass transition temperature of each rubber by the weight fraction of each rubber, i.e., 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 this invention refers to the midpoint temperature of the transition region measured by differential scanning calorimetry (DSC) at a heating rate of 20°C / min. More preferably, the average Tg is −60° C. or lower.

[0012] (carbon black) Examples of carbon black that can be 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, carbon black is used with a nitrogen adsorption specific surface area (N2SA) of 10 to 300 m to improve performance on ice. 2 / g, and 50 to 150m 2 / g is more preferred. The nitrogen adsorption specific surface area (N2SA) is a value measured in accordance with JIS K 6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0013] (white filler) 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., and these may be used alone or in combination of two or more. Of these, silica is preferred because of its better performance on ice.

[0014] Specific examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate, and these may be used alone or in combination of two or more.

[0015] To improve performance on ice, silica is used with a CTAB adsorption specific surface area of ​​50 to 300 m 2 / g, and 90 to 200m 2 / g is more preferred. The CTAB adsorption specific surface area is a value obtained by measuring the amount of n-hexadecyltrimethylammonium bromide adsorbed onto the silica surface in accordance with JIS K6217-3:2001 "Part 3: Determination of specific surface area - CTAB adsorption method."

[0016] (xyloglucan) As is well known, the xyloglucan used in the present invention is a polysaccharide having a main chain of glucose and a side chain of xylose, and the side chain may contain galactose. As the xyloglucan in the present invention, it is preferable to use tamarind gum produced from tamarind seeds. Although prior art discloses the blending of polysaccharides into rubber compositions, it does not disclose the technical idea of ​​using only tamarind gum to improve performance on ice. Below, we will explain the use of tamarind gum as the xyloglucan.

[0017] From the viewpoint of improving performance on ice, the tamarind gum preferably has the following features: (1) The molecular weight of the tamarind gum is 350,000 to 750,000, and preferably 450,000 to 600,000. Tamarind gum that satisfies the condition (1) above can be commercially available, and examples include Glyloid 2A (molecular weight: approximately 450,000 to 600,000) and Glyloid 3S (molecular weight: approximately 450,000 to 600,000) supplied by MP Gokyo Food & Chemical Co., Ltd. (2) Tamarind gum dissolves at least 2% by mass, preferably 2 to 5% by mass, in water at 25°C under atmospheric pressure. There is no particular upper limit to this solubility, but it is, for example, 20% by mass or less. Commercially available tamarind gums that satisfy the condition (2) above can be used, such as Glyloid 3S (trade name) supplied by MP Gokyo Food & Chemical Co., Ltd. (dissolves at least 2% by mass in water at 25°C). Glyloid 3S is tamarind gum that has been gelatinized to make it soluble in cold water. (3) Tamarind gum, when dissolved in water at a rate of 1.5% by mass at 25°C, preferably has a viscosity of 100 mPa·s to 1000 mPa·s, and more preferably a viscosity of 500 mPa·s to 800 mPa·s. Tamarind gum that satisfies the condition (3) above can be commercially available, and an example is Glyloid 3S, a product name supplied by MP Gokyo Food & Chemical Co., Ltd. (a tamarind gum solution dissolved in water at a rate of 1.5% by mass at 25°C has a viscosity of 500 mPa·s to 800 mPa·s). The more combinations of the conditions (1) to (3) are satisfied, the more the effects of the present invention are improved. Note that by satisfying the conditions (2) and / or (3), the rolling resistance of the tire can also be reduced.

[0018] (Rubber composition blending ratio) The rubber composition of the present invention contains a diene rubber, carbon black, a white filler, and xyloglucan, and is characterized in that 30 to 100 parts by mass of the white filler and 0.5 to 30 parts by mass of the xyloglucan are blended with 100 parts by mass of the diene rubber. If the amount of the white filler is less than 30 parts by mass per 100 parts by mass of the diene rubber, the mechanical properties and abrasion resistance of the rubber composition will deteriorate, and conversely, if it exceeds 100 parts by mass, the low-temperature flexibility of the rubber composition will decrease and performance on ice will deteriorate. If the amount of xyloglucan added is less than 0.5 parts by mass per 100 parts by mass of the diene rubber, the amount added is too small to achieve the effects of the present invention, and conversely, if it exceeds 30 parts by mass, the elongation at break decreases.

[0019] The amount of carbon black added is preferably 3 to 70 parts by mass, more preferably 5 to 50 parts by mass, based on 100 parts by mass of diene rubber. The amount of the white filler to be compounded is preferably 30 parts by mass or more, and more preferably 35 to 80 parts by mass, based on 100 parts by mass of the diene rubber. The amount of xyloglucan added is preferably 1 to 20 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of the diene rubber.

[0020] (Other ingredients) In addition to the above-mentioned components, the rubber composition of the present invention may contain various additives that are generally compounded in rubber compositions, such as vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, zinc oxide, antioxidants, plasticizers, silane coupling agents, and thermally expandable microcapsules, and these additives can be kneaded by a general method to form a composition, which can then be used for vulcanization or crosslinking. The amounts of these additives that can be compounded may be conventional amounts, provided that they do not deviate from the object of the present invention.

[0021] 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, an inert gas such as nitrogen, or other gases. The tire of the present invention is preferably applied to a tread, particularly a cap tread, to form a studless tire. [Example]

[0022] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0023] Standard Example 1, Examples 1 to 4, and Comparative Examples 1 to 3 Sample preparation The components (parts by mass) listed in Table 1, excluding the vulcanization system (vulcanization accelerator, sulfur), were mixed in a 1.7-liter internal Banbury mixer for 5 minutes, then discharged from the mixer and cooled to room temperature. The resulting composition was then returned to the Banbury mixer, and the vulcanization system was added and mixed to obtain a rubber composition. The resulting rubber composition was press-vulcanized at 170°C for 10 minutes, and its physical properties were measured using the following test methods.

[0024] Performance on ice: The resulting vulcanized rubber test pieces were attached to flat, cylindrical rubber bases to create samples. The samples were then immersed in room-temperature water for 24 hours. After immersion, the samples were measured for coefficient of friction on ice using an ice friction tester at a temperature of -1.5°C, a load of 98N, and a road speed of 20km / h. The obtained coefficient of friction on ice was expressed as an index, with the standard example value set at 100. A higher index indicates greater frictional force on ice and better performance on ice. Tan δ (0°C): Tan δ (0°C) was measured in accordance with JIS K6394:2007 using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho) under conditions of an elongation deformation strain rate of 10±2%, a vibration frequency of 20 Hz, and a temperature of 0°C. The results were expressed as an index, with the value of the standard example being 100. The larger the index, the better the wet performance. An index of 97 or higher can be determined to have sufficient wet performance for practical use. Breaking elongation: According to JIS K6251, No. 3 dumbbell-shaped sample pieces were punched out from the vulcanized rubber test pieces and subjected to a tensile test at a pulling rate of 500 mm / min to measure breaking elongation (%). The results were expressed as an index, with the value of Reference Example 1 being 100. A larger index indicates better breaking elongation.

[0025] The results are also shown in Table 1.

[0026] [Table 1]

[0027] *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 (Rhodia Zeosil 1165MP, CTAB specific surface area = 159 m 2 / g) *5: Silane coupling agent (Si69, bis(3-triethoxysilylpropyl)tetrasulfide, manufactured by Evonik Degussa) *6: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu Co., Ltd.) *7: Tamarind gum 1 (MP Glyloid 3S manufactured by Gokyo Food & Chemical Co., Ltd., molecular weight = 450,000 to 600,000, 1.5 mass% aqueous solution (viscosity at 25°C after stirring at room temperature for 30 minutes = 500 mPa·s to 800 mPa·s) *8: Tamarind gum 2 (MP Glyloid 2A manufactured by Gokyo Food & Chemical Co., Ltd., molecular weight = 450,000 to 600,000, 1.5% by mass aqueous solution (heated at 75°C for 15 minutes to make an aqueous solution, then cooled to 25°C, viscosity = 400mPa·s to 600mPa·s) *9: Tamarind Gum 3 (MP Greate manufactured by Gokyo Food & Chemical Co., Ltd., molecular weight = 5000 to 100,000, 1.5 mass% aqueous solution (heated at 75°C for 15 minutes to make an aqueous solution, then cooled to 25°C, viscosity = 10mPa·s to 100mPa·s) *10: Guar gum (manufactured by Tokyo Chemical Industry Co., Ltd.) *11: Sulfur (Kinka brand oil-filled fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.) *12: Vulcanization accelerator (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0028] As can be seen from the results in Table 1, the rubber compositions of the examples contain diene rubber, carbon black, a white filler, and xyloglucan, and are characterized by blending 30 to 100 parts by mass of the white filler and 0.5 to 30 parts by mass of the xyloglucan per 100 parts by mass of the diene rubber. As a result, compared to Reference Example 1, performance on ice is improved while maintaining elongation at break, and the tan δ(0°C) index value is 97 or more, so substantially sufficient wet performance is also ensured. Furthermore, a decrease in elongation at break is suppressed. In contrast to this, in Comparative Example 1, the amount of white filler blended was less than the lower limit specified in the present invention, and therefore tan δ (0° C.) deteriorated. Comparative Example 2 is an example in which xyloglucan was not blended but guar gum was blended instead, and therefore the degree of improvement in breaking elongation and on-ice performance was lower than in each of the Examples. In Comparative Example 3, the amount of xyloglucan blended exceeded the upper limit specified in the present invention, and therefore the wet performance and elongation at break were reduced.

[0029] The present invention includes the following embodiments. Embodiment 1: Contains diene rubber, carbon black, white filler and xyloglucan, 30 to 100 parts by mass of the white filler and 0.5 to 30 parts by mass of the xyloglucan relative to 100 parts by mass of the diene rubber A rubber composition characterized by being compounded. Embodiment 2: 2. The rubber composition according to embodiment 1, wherein the xyloglucan has a molecular weight of 350,000 to 750,000. Embodiment 3: 3. The rubber composition according to claim 1 or 2, wherein the xyloglucan dissolves in water at 25° C. in an amount of 2% by mass or more. Embodiment 4: 4. The rubber composition according to embodiment 3, wherein an aqueous solution of the xyloglucan dissolved in water at 25° C. at a ratio of 1.5% by mass has a viscosity of 500 mPa·s to 800 mPa·s. Embodiment 5: 4. The rubber composition according to claim 3, wherein the xyloglucan is tamarind gum. Embodiment 6: 6. The rubber composition according to any one of embodiments 1 to 5, wherein the butadiene rubber accounts for 30 parts by mass or more per 100 parts by mass of the diene rubber. Embodiment 7: A studless tire using the rubber composition according to any one of embodiments 1 to 6.

Claims

1. Contains diene rubber, carbon black, white filler and xyloglucan, 30 to 100 parts by mass of the white filler and 0.5 to 30 parts by mass of the xyloglucan relative to 100 parts by mass of the diene rubber A rubber composition characterized by being compounded.

2. 2. The rubber composition according to claim 1, wherein the molecular weight of the xyloglucan is 350,000 to 750,000.

3. 2. The rubber composition according to claim 1, wherein the xyloglucan has a solubility of 2% by mass or more in water at 25°C.

4. 4. The rubber composition according to claim 3, wherein an aqueous solution of the xyloglucan dissolved in water at 25°C at a ratio of 1.5% by mass has a viscosity of 500 mPa·s to 800 mPa·s.

5. 4. The rubber composition according to claim 3, wherein the xyloglucan is tamarind gum.

6. 2. The rubber composition according to claim 1, wherein the butadiene rubber accounts for 30 parts by mass or more per 100 parts by mass of the diene rubber.

7. A studless tire using the rubber composition according to claim 1.

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