Rubber composition and studless tire using same

Abstract

To solve the problem in which: on a road surface covered with ice and snow, coefficients of friction decrease compared to general road surfaces, making the road surface more slippery; and many methods have been proposed to improve the on-ice performance of studless tires, but it has been difficult to strike a balance between the on-ice performance and wet performance.SOLUTION: A rubber composition contains, (I) relative to 100 pts.mass of a diene rubber, (II) carbon black and / or white filler of 30-100 pts.mass, and (III) a water absorption-swellable polyurethane having a water absorbability of 3-50, of 0.1-20 pts.mass.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 can achieve both excellent performance on ice and excellent performance on wet surfaces, and a studless tire using the same. [Background technology]

[0002] On snowy and icy roads, the coefficient of friction is lower than on normal roads, making the roads more slippery. Thus, numerous methods have been proposed to improve the performance of studless tires on ice (braking performance on ice). For example, a method is known in which hard foreign matter or hollow polymers are blended into the studless compound, which creates microscopic irregularities on the rubber surface, thereby removing the water film that forms on the ice surface and improving friction on ice. Another method involves blending water-absorbent materials into the studless compound (see, for example, Patent Document 1).

[0003] On the other hand, in order to ensure flexibility at low temperatures, studless compounds are designed to have a low glass transition temperature (Tg) and this inevitably results in a low tan δ (0°C), which is highly correlated with braking performance on wet roads (wet performance). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3531990 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a rubber composition that can achieve both excellent performance on ice and excellent performance on wet surfaces, and a studless tire using the same. [Means for solving the problem]

[0006] As a result of extensive research, the inventors have discovered that the above-mentioned problems can be solved by a rubber composition comprising a diene rubber, carbon black and / or a white filler, and a specific amount of a water-absorbing and swelling polyurethane having a specific water absorption capacity, and have thus completed the present invention.

[0007] That is, the present invention provides: (I) per 100 parts by mass of diene rubber, (II) 30 to 100 parts by mass of carbon black and / or white filler, and (III) 0.1 to 20 parts by mass of water-absorbing swelling polyurethane having a water absorption capacity of 3 to 50 times The present invention provides a rubber composition characterized by being obtained by compounding the above-mentioned components. Effect of the Invention

[0008] The rubber composition of the present invention is characterized by comprising 100 parts by mass of (I) diene rubber, 30 to 100 parts by mass of (II) carbon black and / or white filler, and 0.1 to 20 parts by mass of (III) water-absorbing swelling polyurethane having a water absorption capacity of 3 to 50 times, and thus it is possible to provide a rubber composition that can achieve both excellent performance on ice and excellent performance on wet surfaces, and a studless tire using the same.

[0009] The water-absorbing and swelling polyurethane of the present invention has a water-absorbing capacity of 3 to 50 times, so a larger amount can be blended into the studless tire compound than in the conventional technology. For example, blending a large amount of the water-absorbing resin with extremely high water-absorbing capacity of the conventional technology causes a sudden volume expansion, resulting in breaking elongation and deterioration of appearance. In the present invention, the action of the water-absorbing polyurethane makes it easier for the studless tire to follow the road surface, improving performance on ice and wet surfaces. Furthermore, when the water-absorbing and swelling polyurethane is in the form of a foam, its softness further improves the tire's ability to conform to rough or uneven road surfaces, and the water-swelling properties further enhance this performance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will now be described in further detail. (I) Diene Rubber The diene rubber used in the present invention may be any diene rubber that can be blended in a rubber composition, such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene-diene terpolymer (EPDM), etc. These may be used alone or in combination of two or more. In addition, the molecular weight and microstructure are not particularly limited, and the end may be modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, etc., or may be epoxidized. From the viewpoint of improving performance on ice, it is preferred that polybutadiene accounts for 30 parts by mass or more, and preferably 40 parts by mass or more, per 100 parts by mass of the diene rubber (I). The diene rubber (A) 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 a plurality of diene rubbers are contained, the Tg referred to in this specification is the sum of the products of the glass transition temperatures of each rubber multiplied by the weight fraction of each rubber, i.e., a value calculated based on a 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 temperature at the midpoint 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.

[0011] (II) Carbon black and / or white fillers 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, carbon black is required to have a nitrogen adsorption specific surface area (N2SA) of 10 to 300 m from the viewpoint of improving performance on ice. 2 / g, and 50 to 150m 2 It is even more preferred that the weight ratio is / g. 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."

[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., 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.

[0013] Specific examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc., and these may be used alone or in combination of two or more kinds.

[0014] From the viewpoint of improving performance on ice, silica is selected to have a CTAB adsorption specific surface area of ​​50 to 300 m 2 / g, and 90 to 200m 2 It is even more preferred that the weight ratio is / g. The CTAB adsorption specific surface area is a value obtained by measuring the amount of n-hexadecyltrimethylammonium bromide adsorbed on the silica surface in accordance with JIS K6217-3:2001 "Part 3: Determination of specific surface area - CTAB adsorption method."

[0015] (III) Water-absorbing and swelling polyurethane The water-absorbing and swelling polyurethane (III) used in the present invention is not particularly limited as long as it has a water absorption capacity of 3 to 50 times, and for example, a urethane resin obtained by mixing and dispersing a water-absorbing and swelling resin in a urethane resin material can be mentioned. Examples of the water-absorbing and swelling resin include polyacrylates, polysulfonates, maleic anhydrides, polyacrylamides, polyvinyl alcohols, polyethylene oxides, polyamines, polyaspartates, polyglutamates, polyalginates, starches, celluloses, polyglycols, etc., and from the viewpoint of water-absorbing swelling and stability over time, polyacrylates are preferred, for example, crosslinked polyacrylic acid. Examples of the urethane resin as the base material include polyether polyurethane resins. After blending the water-absorbing and swelling resin with the urethane resin as the base material, the polyurethane can be obtained by foaming and molding the mixture to form a foam. The water-absorbing and swelling polyurethane (III) used in the present invention is also available as a commercial product, for example, "Insuron" (water absorption capacity: about 10 times) manufactured by Nippon Spring Co., Ltd. The water absorption capacity referred to in the present invention is a value calculated by dispersing 0.5 g of a sample in 1 liter of ion-exchanged water, leaving it to stand at 20°C for 24 hours, filtering it through a 60-mesh wire screen, measuring the weight of the resulting water-swollen body, and dividing this value by the initial dry weight. The water absorption capacity in the present invention is preferably 3 to 50 times, more preferably 5 to 20 times. (III) The water-absorbing and swelling polyurethane is pulverized to an appropriate size during the kneading of the raw materials, and dispersed in the diene rubber.

[0016] (Rubber composition blend ratio) The rubber composition of the present invention is characterized in that it comprises (I) 100 parts by mass of diene rubber, (II) 30 to 100 parts by mass of carbon black and / or white filler, and (III) 0.1 to 20 parts by mass of water-swellable polyurethane. If the amount of (II) carbon black and / or white filler is less than 30 parts by mass per 100 parts by mass of (I) diene rubber, the mechanical properties and abrasion resistance of the rubber composition will deteriorate. Conversely, if the amount exceeds 100 parts by mass, the low-temperature flexibility of the rubber composition will decrease, resulting in poor performance on ice. If the amount of (III) water-swellable polyurethane is less than 0.1 parts by mass per 100 parts by mass of (I) diene rubber, the amount is too small to achieve the effects of the present invention. Conversely, if it exceeds 20 parts by mass, the breaking strength decreases.

[0017] The blending amount of the (II) carbon black and / or white filler is preferably 40 to 90 parts by mass based on 100 parts by mass of the diene rubber. The blending amount of the water-absorbing swelling polyurethane (III) is preferably 3 to 15 parts by mass based on 100 parts by mass of the diene rubber.

[0018] (Other ingredients) In addition to the above-mentioned components, the rubber composition of the present invention may contain various additives that are generally incorporated in rubber compositions, such as vulcanizing or crosslinking agents, vulcanizing or crosslinking accelerators, zinc oxide, antioxidants, plasticizers, silane coupling agents, and thermally expandable microcapsules, and these additives can be kneaded in a general manner to form a composition, which can be used for vulcanization or crosslinking. The amounts of these additives may be conventional amounts, provided that they do not violate the object of the present invention.

[0019] 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. EXAMPLES

[0020] 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.

[0021] Standard Example, Examples 1-4, Comparative Examples 1-2 In the formulation (parts by mass) shown in Table 1, the components other than the vulcanization system (vulcanization accelerator, sulfur) and the curing agent were mixed in a 1.7-liter closed Banbury mixer for 5 minutes, then discharged from the mixer and cooled at room temperature. The composition was then placed back into the Banbury mixer, and the vulcanization system was added and mixed to obtain a rubber composition. The rubber composition obtained was press-vulcanized at 170°C for 10 minutes, and its physical properties were measured using the test methods shown below.

[0022] Wet performance: In accordance with JIS K6394:2007, a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho) was used to measure tan δ (0°C) under conditions of an elongation deformation rate of 10±2%, a vibration frequency of 20Hz, and a temperature of 0°C. The results are expressed as an index, with the standard value set at 100. A higher index indicates better wet performance. Performance on ice: The vulcanized rubber test piece obtained was attached to a flat cylindrical rubber base and tested using an inside drum type ice friction tester at a measurement temperature of -3.0°C and a load of 5.5 kg / cm. 2 The coefficient of friction on ice was measured under conditions of a drum rotation speed of 25 km / h. The obtained coefficient of friction on ice was expressed as an index, with the standard example value set at 100. A higher index value indicates greater frictional force on ice and better performance on ice. The results are shown in Table 1.

[0023] [Table 1]

[0024] *1:NR(RSS#3) *2: BR (Nipol BR1220 manufactured by Zeon Corporation) *3: Carbon black (Seest KHA manufactured by Tokai Carbon Co., Ltd.) *4: Silica (Rhodia Zeosil 1165MP, CTAB specific surface area = 159 m 2 / g) *5: Silane coupling agent (Evonik Degussa Si69, bis(3-triethoxysilylpropyl)tetrasulfide) *6: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu K.K.) *7: Water-absorbent resin (acrylic water-absorbent resin made by Nippon Shokubai Co., Ltd., AQUALIC CA, water absorption capacity = 300-400 times) *8: Water-absorbing and swelling polyurethane (Insulon JS, water-absorbing and swelling polyurethane manufactured by NHK Spring Co., Ltd., water absorption capacity = 10 times) *9: Sulfur (Kinka-jirushi oil-containing fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.) *10: Vulcanization accelerator (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0025] As can be seen from the results in Table 1, the rubber composition of each Example is composed of 100 parts by mass of (I) diene-based rubber, 30 to 100 parts by mass of (II) carbon black and / or white filler, and 0.1 to 20 parts by mass of water-absorbing and swelling polyurethane having a water absorption capacity of 3 to 50 times, and therefore has improved wet performance and performance on ice compared to the standard example. In contrast, Comparative Examples 1 and 2 are examples using a water-absorbent resin with a water-absorbing capacity of 300 to 400 times, and therefore were unable to provide satisfactory wet performance and performance on ice compared to the standard example.

Claims

1. (I) per 100 parts by mass of diene rubber, (II) 30 to 100 parts by weight of carbon black and / or white filler, and (III) 0.1 to 20 parts by weight of water-absorbing swelling polyurethane having a water absorption capacity of 3 to 50 times It is blended, The water-absorbing and swelling polyurethane (III) is a foam. A rubber composition comprising:

2. 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 (I).

3. A studless tire using the rubber composition according to claim 1 or 2.

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