Rubber composition for shoe sole

Abstract

To provide a rubber composition for a shoe sole which solves the problem that conventionally, a rubber composition has been widely used in a shoe sole, the shoe sole requires various characteristics according to applications, especially a shoe sole for winter requires non-slipperiness on icy or snowy road surfaces and abrasion resistance.SOLUTION: A rubber composition for shoe sole is provided, including a rubber component (A), silica (B), a silane coupling agent (C) and a thermoplastic resin (D), wherein 70 pts.mass or more of natural rubber and butadiene rubber are blended in 100 pts.mass of the rubber component (A), and 30 pts.mass or more of the silica (B) is blended with respect to 100 pts.mass of the rubber component (A).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition for shoe soles, and more particularly to a rubber composition for shoe soles which has excellent grip performance on ice and abrasion resistance while maintaining wet grip performance. [Background technology]

[0002] Rubber compositions have been widely used for shoe soles. Various properties are required for such shoe soles depending on the application, and in particular, shoe soles for winter use are required to be slip-resistant on icy and snowy surfaces and to have abrasion resistance.

[0003] As an example of prior art relating to rubber compositions for shoe soles, Patent Document 1 listed below discloses a rubber composition for shoe soles characterized by blending 10 to 100 parts by weight of porous and amorphous granules derived from volcanic ejecta with 100 parts by weight of a rubber-like component made of natural rubber, synthetic rubber, and / or thermoplastic elastomer. Furthermore, the following Patent Document 2 discloses a rubber composition for forming shoes, which contains butadiene rubber and silica, further contains oil, and the mass average molecular weight of the oil is 1060 or more and less than 1800, and the butadiene rubber is contained in a proportion of more than 85 parts by mass when the amount of all the contained rubbers is taken as 100 parts by mass, and the butadiene rubber is a high-cis-type butadiene rubber in which 80% or more of the molecular structure is cis-1,4 units. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5565313 [Patent Document 2] Patent No. 6427596 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventional technology leaves room for improvement in terms of grip performance on ice, wet grip performance and abrasion resistance. Therefore, an object of the present invention is to provide a rubber composition for shoe soles which has excellent grip performance on ice and abrasion resistance while maintaining wet grip performance. [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 compounding a rubber component having a specific composition with silica, a silane coupling agent, and a thermoplastic resin, and by setting the compounding amount of the silica within a specific range, and have thus completed the present invention.

[0007] That is, the present invention provides a rubber composition for shoe soles comprising a rubber component (A), silica (B), a silane coupling agent (C) and a thermoplastic resin (D), characterized in that, per 100 parts by mass of the rubber component (A), 70 parts by mass or more of natural rubber and butadiene rubber are blended, and per 100 parts by mass of the rubber component (A), 30 parts by mass or more of the silica (B) is blended. Effect of the Invention

[0008] The rubber composition for shoe soles of the present invention comprises a rubber component (A), silica (B), a silane coupling agent (C) and a thermoplastic resin (D), and is characterized in that 70 parts by mass or more of natural rubber and butadiene rubber are blended per 100 parts by mass of the rubber component (A), and 30 parts by mass or more of the silica (B) are blended per 100 parts by mass of the rubber component (A).Therefore, a rubber composition for shoe soles that has excellent grip performance on ice and abrasion resistance while maintaining wet grip performance can be provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will now be described in further detail.

[0010] (Rubber component (A)) The rubber component (A) used in the present invention contains natural rubber (NR) and butadiene rubber (BR) as essential components. The rubber component (A) used in the present invention has a total amount of NR and BR of 70 parts by mass or more when the entire rubber component is taken as 100 parts by mass. From the viewpoint of improving the effects of the present invention, it is preferable to mix 5 to 70 parts by mass of NR and 5 to 70 parts by mass of BR, and more preferably mix 30 to 50 parts by mass of NR and 30 to 50 parts by mass of BR, per 100 parts by mass of the rubber component (A). Note that, in the present invention, NR includes synthetic isoprene rubber (IR). In addition to NR and BR, other rubber components can be used, such as styrene-butadiene copolymer rubber (SBR) and acrylonitrile-butadiene copolymer rubber (NBR). 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 amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl, or the like, or may be epoxidized. When SBR is used, the amount of SBR is preferably 5 to 30 parts by mass when the total rubber component (A) is 100 parts by mass. The rubber component (A) preferably has a glass transition temperature (Tg) of -65°C or lower. The rubber component (A) contains a plurality of different rubbers, and therefore the Tg referred to in this specification is a value calculated based on the sum of the products of the glass transition temperatures of the respective rubbers multiplied by the weight fractions of the respective rubbers, that is, the weighted average. In the calculation, the sum of the weight fractions of the respective components is set to 1.0. The glass transition temperature (Tg) referred to in the present invention refers to the temperature at the midpoint of the transition region when a thermogram is measured by differential scanning calorimetry (DSC) under the condition of a heating rate of 20°C / min.

[0011] (Silica (B)) Specific examples of the silica (B) used in the present invention 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. From the viewpoint of improving the effect of the present invention, silica has a nitrogen adsorption specific surface area N 2 SA is 100~250m 2 / g, and 150 to 200m 2 It is more preferable that the molecular weight is / g. Furthermore, 2 SA shall be measured in accordance with JIS K6217-2.

[0012] (Silane coupling agent (C)) The silane coupling agent (C) used in the present invention is not particularly limited, but is preferably a sulfur-containing silane coupling agent, such as 3-octanoylthiopropyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane, bis-(3-bistriethoxysilylpropyl)-tetrasulfide, bis-(3-bistriethoxysilylpropyl)-disulfide, 3-mercaptopropyltrimethoxysilane, etc.

[0013] (Thermoplastic resin (D)) Examples of the thermoplastic resin (D) used in the present invention include natural resins such as terpene-based resins and rosin-based resins, and synthetic resins such as petroleum-based resins, coal-based resins, phenol-based resins, and xylene-based resins. Of these, petroleum-based resins and terpene-based resins are preferred. Examples of petroleum resins include C9 petroleum resins obtained by cationic polymerization of C9 fractions obtained by petroleum refining such as naphtha cracking, C5 petroleum resins obtained by thermal polymerization of C5 fractions such as cyclopentadiene and dicyclopentadiene, and C5-C9 petroleum resins obtained by polymerization of C5 fractions to C9 fractions. Examples of the terpene resin include α-pinene resin, β-pinene resin, limonene resin, hydrogenated limonene resin, dipentene resin, terpene phenol resin, terpene styrene resin, aromatic modified terpene resin, and hydrogenated terpene resin. In the present invention, from the viewpoint of further improving the effects of the present invention, it is preferable to use an aromatic modified terpene resin as the thermoplastic resin (D). Examples of the aromatic modified terpene resin include aromatic modified terpene resins obtained by polymerizing the terpene resin with an aromatic compound such as styrene, α-methylstyrene, vinyltoluene, or indene, and the content of the aromatic compound in the aromatic modified terpene resin is preferably 10 to 50 mass%. The glass transition temperature (Tg) of the thermoplastic resin (D) is preferably 40 to 90°C.

[0014] (Mixing ratio of rubber composition for shoe soles) The rubber composition for shoe soles of the present invention contains 30 parts by mass or more of the silica (B) per 100 parts by mass of the rubber component (A). If the amount of the silica (B) is less than 30 parts by mass, the abrasion resistance is deteriorated. The amount of the silica (B) added is more preferably 30 to 70 parts by mass based on 100 parts by mass of the rubber component (A). The amount of the silane coupling agent (C) added is preferably 1 to 15 mass %, and more preferably 5 to 10 mass %, based on the mass of the silica (B). The blending amount of the thermoplastic resin (D) is preferably 10 parts by mass or more, and more preferably 10 to 20 parts by mass, based on 100 parts by mass of the rubber component (A).

[0015] From the viewpoint of improving the effects of the present invention, the rubber composition for shoe soles of the present invention may further contain the following components in addition to the above-mentioned components.

[0016] (Liquid butadiene rubber) The rubber composition for shoe soles of the present invention can be compounded with liquid butadiene rubber in order to further improve the effects thereof. The liquid butadiene rubber has a weight average molecular weight of 500 to 100,000, preferably 30,000 to 80,000. The weight average molecular weight in the present invention means a weight average molecular weight converted into polystyrene as analyzed by gel permeation chromatography (GPC). The liquid butadiene rubber used in the present invention is liquid at 23°C. Therefore, it is distinguished from the BR in the rubber component (A) which is solid at this temperature. The amount of the liquid butadiene rubber mixed is preferably 1 to 25 parts by mass, and more preferably 5 to 20 parts by mass, based on 100 parts by mass of the rubber component (A). The liquid butadiene rubber may be preblended with the BR in the rubber component (A). For example, BRX5000 manufactured by Zeon Corporation and used in the following examples is a preblend product obtained by mixing 71% by mass of BR having a weight average molecular weight of 600,000 and 29% by mass of liquid butadiene rubber having a weight average molecular weight of 50,000 in a cyclohexane solvent.

[0017] (Thermal expansion microcapsules) From the viewpoint of improving grip performance on ice, it is preferable to compound thermally expandable microcapsules into the rubber composition for shoe soles of the present invention. In the present invention, the thermally expandable microcapsule has a structure in which a thermally expandable substance is encapsulated in a shell material formed of a thermoplastic resin. The shell material of the thermally expandable microcapsule can be formed of a nitrile polymer. The thermally expansive substance contained in the shell material of the microcapsule has the property of vaporizing or expanding due to heat, and is exemplified by at least one selected from the group consisting of hydrocarbons such as isoalkanes and normal alkanes. Examples of isoalkanes include isobutane, isopentane, 2-methylpentane, 2-methylhexane, and 2,2,4-trimethylpentane, and examples of normal alkanes include n-butane, n-propane, n-hexane, n-heptane, and n-octane. These hydrocarbons may be used alone or in combination. A preferred form of the thermally expansive substance is one in which a hydrocarbon that is gaseous at room temperature is dissolved in a hydrocarbon that is liquid at room temperature. Examples of such thermally expandable microcapsules include those manufactured by Expancel of Sweden under the trade names "EXPANCEL 091DU-80" or "EXPANCEL 092DU-120" and those manufactured by Matsumoto Yushi Seiyaku Co., Ltd. under the trade names "Matsumoto Microsphere F-85D", "Matsumoto Microsphere F-100" and "Matsumoto Microsphere F-100D". When the thermally expandable microcapsules are compounded, the compounding amount thereof is preferably 0.5 parts by mass or more, and more preferably 0.5 to 8 parts by mass, based on 100 parts by mass of the rubber component (A).

[0018] (Oils and Antioxidants) From the viewpoint of improving the effect, the rubber composition for shoe soles of the present invention preferably contains an oil and an antioxidant. The blending amounts thereof are preferably 5 to 30 parts by mass of the oil and 1 to 10 parts by mass of the antioxidant per 100 parts by mass of the rubber component (A). As for the types of oil and anti-aging agent, non-staining oil and anti-aging agent are preferred from the viewpoint of suppressing discoloration of the sole. Examples of non-staining oils include paraffin-based oils, etc. Examples of non-staining anti-aging agents include phenol-based anti-aging agents, etc.

[0019] (Carbon Black) The rubber composition for shoe soles of the present invention may contain carbon black as a colorant. The carbon black is not particularly limited, and various grades of carbon black, such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, and FEF, may be used. The amount of carbon black to be added is preferably 1 to 10 parts by mass relative to 100 parts by mass of the rubber component (A).

[0020] (Other ingredients) In addition to the above-mentioned components, the rubber composition for shoe soles 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 selected from sulfenamide-based, guanidine-based, thiuram-based, and thiazole-based, various fillers such as clay, talc, and calcium carbonate, plasticizers, and zinc oxide, and these additives can be kneaded in a general manner to form a composition and used for vulcanization or crosslinking. The amounts of these additives may be conventional amounts, so long as they do not go against the object of the present invention.

[0021] The rubber composition for shoe soles of the present invention is useful for shoe soles and shoes equipped with the same, since it has excellent grip performance on ice and abrasion resistance while maintaining wet grip performance. The method for manufacturing the sole and the shoe is not particularly limited, and can be carried out according to a conventionally known manufacturing method using the rubber composition for shoe soles. EXAMPLES

[0022] 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.

[0023] Examples 1 to 7 and Comparative Examples 1 to 4 Sample preparation In the formulation (parts by mass) shown in Table 1, the components other than the vulcanization accelerator and sulfur were kneaded in a 1.7-liter closed Banbury mixer for 5 minutes, and the rubber was discharged outside the mixer and cooled at room temperature. The rubber was then placed back into the mixer, and the vulcanization accelerator and sulfur were added and further kneaded to obtain a rubber composition. The obtained rubber composition was then press-vulcanized in a specified mold at 160°C for 20 minutes to obtain a vulcanized rubber test piece, and the physical properties of the vulcanized rubber test piece were measured by the test methods shown below.

[0024] Grip performance on ice: In accordance with JIS K6394:2007, the storage modulus at 0°C (E'(0°C)) was determined 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 are expressed as an index, with Comparative Example 1 being set at 100. A larger index indicates a smaller E'(0°C) and better grip performance on ice when used in shoe soles. Wet grip performance: In accordance with JIS K6394:2007, tan δ(0°C) was measured 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 are expressed as an index, with the value of Comparative Example 1 being 100. The larger the index, the larger the tan δ(0°C), which means that the wet grip performance is excellent when used for shoe soles. Abrasion resistance: Using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.), the applied force was 4.0 kg / cm in accordance with JIS K6264-2:2005. 3 The abrasion test was carried out under the conditions of a load of 1.5 N (=39 N), a slip rate of 30%, an abrasion test time of 4 minutes, and a test temperature of room temperature, and the abrasion mass was measured. An index was measured. The results were expressed as an index, with the value of Comparative Example 1 being 90. The larger the index, the better the abrasion resistance.

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

[0026] [Table 1]

[0027] *1:NR(STR20) *2: E-SBR (NIPOL 1749 manufactured by Zeon Corporation, oil extension amount = 50 parts by mass per 100 parts by mass of SBR, styrene amount = 40%. The actual amount of SBR is shown in Table 1.) *3:BR1 (NIPOL BR1220 manufactured by Zeon Corporation) *4: BR2 (NIPOL BRX5000 manufactured by Zeon Corporation. A pre-blend product obtained by mixing 71% by mass of butadiene rubber having a weight average molecular weight of 600,000 and 29% by mass of liquid butadiene rubber having a weight average molecular weight of 50,000 in a cyclohexane solvent. Of the 56 parts by mass in Table 1, the butadiene rubber having a weight average molecular weight of 600,000 is 40 parts by mass and the liquid butadiene rubber is 16 parts by mass.) *5: Carbon black (Tokai Carbon Co., Ltd., Seast 9, N 2 SA=142m 2 / g) *6: Silica (EVONIK ULTRASIL 7000GR, N 2 SA=176m 2 / g) *7: Oil (Shell Catenex Oil S523 manufactured by Shell Lubricants Japan Co., Ltd.) *8: Thermoplastic resin 1 (ExxonMobil's Escorez 2101, C5 / C9 petroleum resin) *9: Thermoplastic resin 2 (Yasuhara Chemical Co., Ltd. YS Resin TO-125, softening point = 125°C, aromatic modified terpene resin) *10: Thermally expandable microcapsules (Matsumoto Microsphere F-100 manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) *11: Anti-aging agent (Ozonone EX manufactured by Seiko Chemical Co., Ltd.) *12: Wax (paraffin wax manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *13: Silane coupling agent (Si69, bis(3-triethoxysilylpropyl)tetrasulfide, manufactured by Evonik Degussa) *14: Stearic acid (Beads Stearic Acid YR manufactured by NOF Corporation) *15: Zinc oxide (3 types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd.) *16: Sulfur (Kinka-in oil-filled fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.) *17: Vulcanization accelerator 1 (Sansera CM-G, manufactured by Sanshin Chemical Industry Co., Ltd.) *18: Vulcanization accelerator 2 (Sansera TBZTD manufactured by Sanshin Chemical Industry Co., Ltd.)

[0028] The results in Table 1 show that the rubber compositions for shoe soles of Examples 1 to 7 contain a rubber component (A), silica (B), a silane coupling agent (C) and a thermoplastic resin (D), and contain 70 parts by mass or more of natural rubber and butadiene rubber per 100 parts by mass of the rubber component (A), and contain 30 parts by mass or more of the silica (B) per 100 parts by mass of the rubber component (A). Therefore, compared to Comparative Example 1, it is clear that the rubber compositions have excellent grip performance on ice and abrasion resistance while maintaining wet grip performance. In contrast, in Comparative Example 2, since the thermoplastic resin (D) was not blended, the wet grip performance and abrasion resistance were deteriorated. In Comparative Example 3, since no natural rubber was compounded, the grip performance on ice and the abrasion resistance were deteriorated. In Comparative Example 4, since no butadiene rubber was compounded, the grip performance on ice and the abrasion resistance were deteriorated.

[0029] The present invention includes the following aspects. Embodiment 1: A rubber composition for shoe soles comprising a rubber component (A), silica (B), a silane coupling agent (C) and a thermoplastic resin (D), In 100 parts by mass of the rubber component (A), 70 parts by mass or more of natural rubber and butadiene rubber are blended, The silica (B) is blended in an amount of 30 parts by mass or more per 100 parts by mass of the rubber component (A). A rubber composition for shoe soles. Embodiment 2: The rubber composition for shoe soles according to embodiment 1, wherein 5 to 70 parts by mass of the natural rubber and 5 to 70 parts by mass of the butadiene rubber are blended in 100 parts by mass of the rubber component (A). Embodiment 3: 3. The rubber composition for shoe soles according to embodiment 1 or 2, wherein 30 to 50 parts by mass of the natural rubber and 30 to 50 parts by mass of the butadiene rubber are blended in 100 parts by mass of the rubber component (A). EMBODIMENT 4 4. The rubber composition for shoe soles according to any one of embodiments 1 to 3, wherein the thermoplastic resin (D) is an aromatic modified terpene resin. EMBODIMENT 5 5. The rubber composition for shoe soles according to any one of embodiments 1 to 4, wherein 10 parts by mass or more of the thermoplastic resin (D) is blended with respect to 100 parts by mass of the rubber component (A). Embodiment 6: 6. The rubber composition for shoe soles according to any one of embodiments 1 to 5, further comprising a liquid butadiene rubber having a weight average molecular weight of 500 to 100,000. Embodiment 7: 7. The rubber composition for shoe soles according to any one of embodiments 1 to 6, wherein 0.5 parts by mass or more of thermally expandable microcapsules are blended with respect to 100 parts by mass of the rubber component (A). Embodiment 8: A shoe sole comprising the rubber composition for shoe soles according to any one of embodiments 1 to 7. Embodiment 9: A shoe having a sole according to embodiment 8.

Claims

1. A rubber composition for shoe soles comprising a rubber component (A), silica (B), a silane coupling agent (C) and a thermoplastic resin (D), In 100 parts by mass of the rubber component (A), 70 parts by mass or more of natural rubber and butadiene rubber are blended, The silica (B) is blended in an amount of 30 parts by mass or more per 100 parts by mass of the rubber component (A). A rubber composition for shoe soles.

2. 2. The rubber composition for shoe soles according to claim 1, wherein 5 to 70 parts by mass of the natural rubber and 5 to 70 parts by mass of the butadiene rubber are blended in 100 parts by mass of the rubber component (A).

3. 2. The rubber composition for shoe soles according to claim 1, characterized in that 30 to 50 parts by mass of the natural rubber and 30 to 50 parts by mass of the butadiene rubber are blended in 100 parts by mass of the rubber component (A).

4. 2. The rubber composition for shoe soles according to claim 1, wherein the thermoplastic resin (D) is an aromatic modified terpene resin.

5. 2. The rubber composition for shoe soles according to claim 1, wherein 10 parts by mass or more of the thermoplastic resin (D) is blended with 100 parts by mass of the rubber component (A).

6. 2. The rubber composition for shoe soles according to claim 1, further comprising a liquid butadiene rubber having a weight average molecular weight of 500 to 100,000.

7. 2. The rubber composition for shoe soles according to claim 1, further comprising 0.5 parts by mass or more of thermally expandable microcapsules per 100 parts by mass of the rubber component (A).

8. A shoe sole comprising the rubber composition for shoe soles according to claim 1.

9. A shoe comprising the sole according to claim 8.

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