Rubber composition and studless tire using the same

Abstract

On an icy and snowy road surface, the friction coefficient is lower than that on a general road surface, and the road surface is slippery. In order to improve the on-ice performance of studless winter tires, a number of techniques have been proposed. In addition, it is also required to reduce environmental load.SOLUTION: The rubber composition is obtained by compounding 100 pts. mass of a diene rubber with ≥ 0.5 pt. mass of a citrus juice residue powder.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 reduces environmental impact and has excellent performance on ice, 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. For example, one known method is to incorporate hard foreign matter or hollow polymers into the studless tire compound, thereby creating microscopic irregularities on the rubber surface, thereby removing the water film that forms on the ice surface and improving friction on ice (see, for example, Patent Document 1). However, the hard foreign matter and polymer compounds that fall off the tread surface are difficult to decompose, raising environmental concerns. Therefore, there is currently a need for methods that are environmentally friendly and further improve on-ice performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-35736 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a rubber composition that reduces the environmental load and has excellent performance on ice, and a studless tire using the same. [Means for solving the problem]

[0005] As a result of extensive research, the present inventors have discovered that a rubber composition in which a specific amount of citrus juice residue powder is blended with a diene rubber can solve the above-mentioned problems, and have thus completed the present invention.

[0006] That is, the present invention provides a rubber composition characterized by blending 0.5 parts by mass or more of citrus juice residue powder with 100 parts by mass of diene rubber.

[0007] The present invention also provides a studless tire using the rubber composition. [Effects of the Invention]

[0008] The rubber composition of the present invention is characterized by blending 0.5 parts by mass or more of citrus juice residue powder with 100 parts by mass of diene rubber, and therefore it is possible to provide a rubber composition that reduces environmental impact and has excellent performance on ice, as well as a studless tire using the same.

[0009] The citrus juice residue powder of the present invention has the function of foaming rubber, thereby imparting water absorption and drainage effects to the tire tread rubber and improving its performance on ice. Furthermore, the shedding of the citrus juice residue powder efficiently imparts roughness to the tire tread surface, thereby providing a high level of traction against the road surface and improving its performance on ice. Furthermore, because the citrus juice residue powder is highly biodegradable, it is rapidly biodegraded even if it falls off onto the road surface, making it environmentally friendly. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will now be described in further detail. (Diene rubber) The diene rubber used in the present invention can be any diene rubber that can be incorporated 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), or 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 weight average molecular weight (Mw) 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 weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated as standard polystyrene obtained by gel permeation chromatography (GPC) measurement. From the viewpoint of improving performance on ice, it is preferable that the butadiene rubber accounts for 30 parts by mass or more, and more preferably 40 parts by mass or more, per 100 parts by mass of the diene rubber. 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.

[0011] (Citrus juice residue powder) The citrus juice residue powder used in the present invention is known and is disclosed, for example, in Japanese Patent No. 4368911. The citrus fruit used in the present invention refers to the fruit of a plant belonging to the Rutaceae family, subfamily Rutaceae. Specific examples of citrus fruits include the fruit of plants belonging to the genera Citrus, Fortune Orange, and Trifoliate Orange in the Rutaceae family, subfamily Rutaceae. Examples include mandarin oranges such as Satsuma mandarins and mandarin oranges; oranges such as Valencia oranges and navel oranges; grapefruits; tangors; tangerines; citrus fruits such as yuzu, kabosu, sudachi, and lemons; pomelo; miscellaneous citrus fruits such as hassaku, iyokan, and hyuganatsu; kumquats; and trifoliate oranges. Among these, mandarin oranges are preferred.

[0012] The method for producing the citrus juice residue powder used in the present invention will be described below, taking Satsuma mandarin as an example of the citrus fruit. First, the unshu mandarins are washed with water. Slits are made in the peels of the washed unshu mandarins for juicing. Next, the slit mandarins are placed in a press, which presses them to extract the juice. The squeezed juice is temporarily stored in a tank or other container for use in juice, vinegar, and other seasonings. After juicing, the pomace, which contains the remaining juice, is crushed in a fine grinder and liquefied. This liquefied pomace (puree) is called mandarin puree. The pomace contains not only the outer peel, mesocarp, endocarp, fibrous residue, and sand sac, but also the remaining juice from the juicing process. At this stage, the mandarin puree has a moisture content of approximately 75% to 85%, with an average of approximately 80%. The fine grinder used may include a grinder having a cylindrical body (blade) fixed to the main body, with slits of several tens to several hundreds of micrometers in width formed at equal intervals on the peripheral wall of the cylindrical body, and a rotary blade (rotor) equipped with multiple radial sliding blades that rotate and slide along the inner peripheral wall of the cylinder, and when the material to be ground is introduced into the input section (hopper), the material is sheared by the rotating rotary blade and the slits of the fixed cylindrical body, thereby finely grinding the material. Next, the mandarin orange puree is freeze-dried in a freeze-drying machine. When the mandarin orange puree is freeze-dried, it loses moisture and becomes solidified. This solidified residue is referred to as a dried solid. The dried solid is then sieved and ground to a powder size. The powder obtained in this manner can be the squeezed pomace powder of the present invention.

[0013] Furthermore, from the viewpoint of further enhancing the effects of the present invention, the citrus juice residue powder used in the present invention preferably has an average particle size of 200 μm or less. Having an average particle size of 200 μm or less can prevent poor tire appearance and suppress deterioration of physical properties. The average particle size is particularly preferably 20 μm to 120 μm. The average particle size can be measured according to known measurement methods, for example, using an electron microscope, laser microscope, or the like, on 100 samples. When the powder has an irregular shape, the circle-equivalent diameter can be regarded as the particle size of the powder, and the average particle size can be calculated. The citrus juice residue powder used in the present invention is commercially available from, for example, Ikata Service Co., Ltd.

[0014] (inorganic filler) Specific examples of inorganic fillers 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. The silica is not particularly limited, but examples thereof include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Silica made from biomass materials such as rice husks may also be used. 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 220m 2 / g is more preferred. The CTAB adsorption specific surface area is a value measured in accordance with JIS K6430:2008.

[0016] The rubber composition of the present invention preferably contains carbon black, specifically furnace carbon black such as SAF, ISAF, HAF, FEF, GPE, and SRF, which may be used alone or in combination of two or more.

[0017] 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."

[0018] (Rubber composition blending ratio) The rubber composition of the present invention is characterized in that 0.5 parts by mass or more of citrus juice residue powder is blended with 100 parts by mass of diene rubber. If the amount of the citrus juice residue powder 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.

[0019] The blending amount of the citrus juice residue powder is preferably 10 parts by mass or more, and more preferably 10 to 50 parts by mass, per 100 parts by mass of the diene rubber.

[0020] The amount of the inorganic filler to be compounded is preferably 30 to 100 parts by mass, and more preferably 30 to 70 parts by mass, based on 100 parts by mass of the diene rubber. When carbon black is compounded, the compounding amount is preferably 5 to 50 parts by mass per 100 parts by mass of the diene rubber.

[0021] (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 vulcanizing or crosslinking agents, vulcanizing or crosslinking accelerators, zinc oxide, antioxidants, plasticizers, and silane coupling agents, 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.

[0022] The studless tire of the present invention can be prepared using the rubber composition of the present invention, and is preferably a pneumatic tire that can be filled with air, an inert gas such as nitrogen, or other gases. The rubber composition of the present invention is preferably applied to the tread of a studless tire, particularly to a cap tread. [Example]

[0023] 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.

[0024] Standard Example 1 and Examples 1 to 4 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.

[0025] Performance on ice: The obtained vulcanized rubber test piece (2 mm thick) was attached to a flat cylindrical rubber base and tested using an inside drum type ice friction tester at a measurement temperature of -1.5°C and a load of 5.5 kg / cm. 2 The coefficient of friction on ice was measured under conditions of 25 km / h drum rotation speed. The obtained coefficient of friction on ice was expressed as an index, with the value for Standard Example 1 set to 100. A higher index indicates greater frictional force on ice and better performance on ice. The results are shown in Table 1.

[0026] [Table 1]

[0027] *1:NR (PT.NUSIRA (SAD) TSR20) *2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.) *3: Carbon black (Cabot Japan Co., Ltd. Show Black N339) *4: Silica (EVONIK WELLINK ULTRASIL VN3GR) *5: Silane coupling agent (Si69 manufactured by Evonik) *6: Citrus juice residue powder 1 (mandarin orange powder F manufactured by Ikata Service Co., Ltd., adjusted to an average particle size of 100 μm by sieving) *7: Citrus juice residue powder 2 (mandarin orange powder F manufactured by Ikata Service Co., Ltd., adjusted to an average particle size of 203 μm by sieving) *8: Vulcanization accelerator (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *9: Sulfur (Kinka brand oil-filled fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0028] As can be seen from the results in Table 1, the rubber compositions of each example contain 0.5 parts by mass or more of citrus juice residue powder per 100 parts by mass of diene rubber, and therefore have improved performance on ice compared to Standard Example 1.

[0029] The present disclosure encompasses the following embodiments. Embodiment 1: A rubber composition characterized by blending 0.5 parts by mass or more of citrus juice residue powder with 100 parts by mass of diene rubber. Embodiment 2: 2. The rubber composition according to embodiment 1, further comprising 30 to 100 parts by mass of an inorganic filler compounded with 100 parts by mass of the diene rubber. Embodiment 3: 3. The rubber composition according to claim 1 or 2, wherein the citrus pomace powder has an average particle size of 200 μm or less. Embodiment 4: A studless tire using the rubber composition according to any one of embodiments 1 to 3.

Claims

1. A rubber composition characterized by comprising 0.5 parts by mass or more of citrus juice residue powder blended with 100 parts by mass of diene rubber.

2. 2. The rubber composition according to claim 1, further comprising 30 to 100 parts by mass of an inorganic filler per 100 parts by mass of the diene rubber.

3. 2. The rubber composition according to claim 1, wherein the citrus pomace powder has an average particle size of 200 μm or less.

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

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