Rubber composition for shoe soles

Abstract

To provide a rubber composition for shoe soles, which can produce shoe soles with excellent wet grip, dry grip, and resistance to abrasion.SOLUTION: A rubber composition for shoe soles contains: a rubber component containing a modified styrene-butadiene copolymer rubber having a glass-transition temperature of -35°C or higher; and a filler containing silica. The content of the modified styrene-butadiene copolymer rubber is 70 mass% or more with respect to the entire rubber component.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition used for shoe soles.

Background Art

[0002] In shoes such as sports shoes, a material with high hardness is used for the outsole of the shoes in order to improve the grip and wear resistance during walking and running.

[0003] As such an outsole material, for example, a rubber composition containing a rubber component (A), a lignin decomposition product (B) having an aldehyde yield of 12% by mass or more by an alkaline nitrobenzene oxidation method, and an antioxidant (C) has been proposed. And it is described that by using such a rubber composition, a rubber composition for shoe soles excellent in grip force can be provided regardless of the road surface conditions (see, for example, Patent Document 1).

[0004] In addition, a rubber composition containing about 3 phr to 90 phr of a natural rubber component, about 10 phr to about 90 phr of bromobutyl rubber, about 2 phr to about 6 phr of a polyterpene resin, about 0.1 phr to about 5 phr of a sulfur curing component, about 10 phr to about 60 phr of silica, and about 1 phr to about 10 phr of a plasticizer, having a wet friction coefficient of about 0.4 to about 0.65 and a dry friction coefficient of about 0.76 to about 0.90 and having an improved DIN wear index has been proposed. And it is described that by using such a rubber composition, a rubber composition for shoe soles having good traction and durability can be provided (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the rubber composition described in Patent Document 1 above, although it is excellent in dry grip properties and wet grip properties, no consideration has been given to abrasion resistance. In the rubber composition described in Patent Document 2 above, although there is a mention regarding abrasion resistance, there is a problem that the value of the DIN abrasion volume is large and the abrasion resistance is insufficient.

[0007] Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a rubber composition for shoe soles capable of obtaining a shoe sole excellent in wet grip properties, dry grip properties, and abrasion resistance.

Means for Solving the Problems

[0008] In order to achieve the above object, the rubber composition for shoe soles of the present invention is a rubber composition for shoe soles containing a rubber component containing a modified styrene-butadiene copolymer rubber having a glass transition temperature of -35°C or higher and a filler containing silica, characterized in that the content of the modified styrene-butadiene copolymer rubber with respect to the whole rubber component is 70% by mass or more.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a rubber composition for shoe soles capable of obtaining a shoe sole excellent in wet grip properties, dry grip properties, and abrasion resistance.

Modes for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present invention will be described.

[0011] The rubber composition for shoe soles of the present invention contains a rubber component and a filler.

[0012] <Rubber Component> The rubber component in the rubber composition for shoe soles of the present invention contains a modified styrene-butadiene copolymer rubber (hereinafter sometimes referred to as "modified SBR") having a glass transition temperature of -35°C or higher.

[0013] And by using such a modified styrene-butadiene copolymer rubber, in the shoe sole manufactured using the rubber composition for shoe soles, the adhesion friction can be improved, so that the dry grip property (grip property on a dry smooth surface) can be exhibited.

[0014] Also, by using such a modified styrene-butadiene copolymer, in the shoe sole manufactured using the rubber composition for shoe soles, when the loss coefficient tanδ under specific conditions increases, the hysteresis frictional force generated when the outsole (viscoelastic body) crosses the unevenness of the water-wetted ground can be improved, so that the wet grip property (grip property on a wet surface) can be exhibited.

[0015] Here, the "glass transition temperature" refers to the temperature at which the rubber state changes to the glass state when the temperature is lowered.

[0016] In addition, in the rubber composition for shoe soles of the present invention, the content of the modified styrene-butadiene copolymer rubber with respect to the whole rubber component (that is, 100% by mass) is 70% by mass or more. This is because when the content of the modified styrene-butadiene copolymer rubber is less than 70% by mass, the above-mentioned dry grip property and wet grip property may not be fully exhibited.

[0017] That is, in the rubber composition for a shoe sole of the present invention, since the rubber component contains a modified styrene-butadiene copolymer rubber having a glass transition temperature of -35°C or higher and the content of the modified styrene-butadiene copolymer rubber with respect to the whole rubber component is 70% by mass or more, the adhesion friction can be sufficiently improved and the dry grip property can be surely improved. Further, since the hysteresis friction can be sufficiently improved, the wet grip property can be surely improved.

[0018] From the viewpoint of further improving the wet grip property, the content of the modified styrene-butadiene copolymer rubber with respect to the whole rubber component is preferably 70% by mass or more, more preferably 80% by mass or more.

[0019] Further, from the viewpoint of improving the dry / wet grip property and the abrasion resistance, the bound styrene amount of the modified styrene-butadiene copolymer rubber is preferably 5 to 45% by mass, more preferably 15 to 35% by mass.

[0020] Here, the "bound styrene amount" refers to the styrene units contained in the molecular structure of the styrene-butadiene copolymer rubber.

[0021] Further, from the viewpoint of improving the mechanical strength, the vinyl bond amount of the modified styrene-butadiene copolymer rubber is preferably 15 to 65% by mass, more preferably 20 to 60% by mass.

[0022] Here, the "vinyl bond amount" refers to the 1,2-vinyl bond amount of the styrene-butadiene copolymer rubber.

[0023] Further, from the viewpoint of improving the mechanical strength and processability, the Mooney viscosity (ML 1+4 , 100°C) of the modified styrene-butadiene copolymer rubber is preferably 40 to 150.

[0024] The "Mooney viscosity" mentioned here refers to the viscosity measured in accordance with JIS K 6300-1 (2001).

[0025] Examples of the modified styrene-butadiene copolymer rubber include commercially available products such as Y031 manufactured by Asahi Kasei Corporation, SLR4502 manufactured by Synthos, and SLR4602 manufactured by Synthos.

[0026] In addition, the rubber component in the rubber composition for shoe soles of the present invention may contain other rubbers other than the above-mentioned modified styrene-butadiene copolymer rubber. Examples of other rubbers include synthetic rubbers such as butadiene rubber and isoprene rubber, and natural rubber. These rubbers may be used alone or in combination of two or more.

[0027] In the rubber composition for shoe soles of the present invention, when using the above-mentioned other rubbers, the content of the other rubbers relative to the total rubber component (i.e., 100% by mass) is preferably 30% by mass or less. This is because when the content of the other rubbers is more than 30% by mass, the proportion of the modified styrene-butadiene copolymer rubber in the total rubber component decreases, and the glass transition temperature of the total rubber component decreases. Due to this decrease in the glass transition temperature, the hysteresis friction may not be sufficiently improved, and the wet grip performance may not be fully exhibited.

[0028] From the viewpoint of further improving the wet grip performance, the content of the other rubbers relative to the total rubber component is preferably 30% by mass or less, and more preferably 20% by mass or less.

[0029] In addition, the above-mentioned synthetic rubber and natural rubber are not particularly limited, and commercially available products can be used.

[0030] <Filler> In addition, in the rubber composition for shoe soles of the present invention, a filler is contained from the viewpoints of improving dry / wet grip performance and abrasion resistance.

[0031] Examples of the filler include silica, carbon black, magnesium carbonate, calcium carbonate, clay, talc, barium sulfate, and the like. These fillers may be used alone or in combination of two or more.

[0032] Further, from the viewpoint of improving wet grip performance and abrasion resistance, a filler containing silica is used in the rubber composition for shoe soles of the present invention.

[0033] Examples of the silica include anhydrous silica and hydrous silica. Further, the BET specific surface area of the silica (measured in accordance with ISO5794 / 1) is preferably 50 m 2 / g or more, more preferably 100 m 2 / g or more, still more preferably 150 m 2 / g or more, and preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, still more preferably 250 m 2 / g or less. These silicas may be used alone or in combination of two or more.

[0034] Also, the content of silica relative to 100 parts by mass of the rubber component is preferably 40 parts by mass or more and 70 parts by mass or less. This is because when the content of silica is less than 40 parts by mass, the abrasion resistance may not be sufficiently improved, and when it is more than 70 parts by mass, the processability may decrease and the grip performance may decrease due to an increase in hardness.

[0035] Examples of the silica include commercially available products such as Nipsil VN3 manufactured by Tosoh Silica Corporation.

[0036] <Silane coupling agent> Further, in the rubber composition for shoe soles of the present invention, a silane coupling agent may be contained from the viewpoint of improving the dispersibility of the filler in the rubber composition for shoe soles.

[0037] Examples of silane coupling agents include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, etc. Sulfide-based ones, and mercapto-based ones such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, NXT, NXT-Z manufactured by Momentive. These silane coupling agents may be used alone or in combination of two or more.

[0038] Examples of mercapto-based silane coupling agents include NXT-Z45 (condensate of 3-octanoylthio-1-propyltriethoxysilane) manufactured by Momentive Performance Materials Japan Co., Ltd. Examples of sulfide-based silane coupling agents include commercially available products such as Si-69 (bis[3-(triethoxysilyl)propyl]tetrasulfide) manufactured by Evonik Japan Co., Ltd.

[0039] Further, the content of the silane coupling agent with respect to 100 parts by mass of silica is preferably 5 parts by mass or more and 10 parts by mass or less. This is because when the content of the silane coupling agent is less than 5 parts by mass, the dispersibility of silica may become insufficient, and when the content of the silane coupling agent is more than 10 parts by mass, sufficient coupling effect and silica dispersion effect cannot be obtained, and the reinforcing property may decrease, so the strength of the rubber composition for shoe soles may decrease.

[0040] <Oil> Further, in the rubber composition for shoe soles of the present invention, oil may be contained from the viewpoint of improving wet grip performance. Examples of the oil include mineral oils such as paraffinic, naphthenic, and aromatic oils, vegetable oils such as castor oil, linseed oil, tall oil fatty acid, and pine tar, ester compounds such as fatty acid esters, phthalic acid esters, and phosphate esters, and chemically synthesized oils such as polyalphaolefins. These oils may be used alone or in combination of two or more.

[0041] Also, the content of the oil with respect to 100 parts by mass of the rubber component is preferably 10 parts by mass or more and 30 parts by mass or less. This is because when the content of the oil is less than 10 parts by mass, the disadvantage that the plasticizing effect by addition cannot be obtained may occur, and when it is more than 30 parts by mass, the disadvantage that the wear resistance deteriorates may occur.

[0042] <Vulcanizing agent> Further, in the rubber composition for shoe soles of the present invention, sulfur may be contained as a vulcanizing agent.

[0043] Examples of the sulfur include powdered sulfur, precipitated sulfur, insoluble sulfur, colloidal sulfur, surface-treated sulfur, etc. These sulfurs may be used alone or in combination of two or more.

[0044] Further, the content of the vulcanizing agent relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more and 5.0 parts by mass or less. This is because when the content of the vulcanizing agent is less than 0.5 part by mass, there may be a disadvantage that the hardness and mechanical strength of the outsole become insufficient, and when it is more than 5.0 parts by mass, there may be a disadvantage that the hardness of the outsole becomes too high.

[0045] <Vulcanization accelerator> In addition, the rubber composition for shoe soles of the present invention may contain a vulcanization accelerator. The vulcanization accelerator is not particularly limited, and examples thereof include sulfenamide-based, guanidine-based, thiazole-based, thiuram-based, thiourea-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, xanthate-based, and the like. These can be used alone or in combination of two or more.

[0046] Further, the content of the vulcanization accelerator relative to 100 parts by mass of the rubber component is preferably 0.1 part by mass or more and 2.5 parts by mass or less. This is because when the content of the vulcanization accelerator is less than 0.1 part by mass, there may be a disadvantage that vulcanization does not proceed sufficiently, and when it is more than 2.5 parts by mass, there may be a disadvantage that vulcanization proceeds excessively.

[0047] <Processing aid> In addition, from the viewpoint of improving the fluidity and lubricity of the rubber composition for shoe soles, suppressing adhesion to a kneader such as a roller, and improving the mold release effect, the rubber composition for shoe soles of the present invention may contain a processing aid.

[0048] Examples of the processing aid include higher fatty acid esters, stearic acid, metal soaps, polyethylene waxes, and the like.

[0049] Moreover, the content of the processing aid with respect to 100 parts by mass of the rubber component is preferably 5.0 parts by mass or less. This is because when the content of the processing aid is more than 5.0 parts by mass, the lubricity becomes too high, causing the roller and the material to slip, which may result in the problem that the material is difficult to mix during roller processing.

[0050] <Other Components> In the rubber composition for shoe soles of the present invention, other components may be contained as long as the effects of the present invention are not impaired. As the other components, known additives usually used in rubber compositions for shoe soles can be used. For example, vulcanization accelerator aids such as zinc oxide, vulcanization activators such as polyethylene glycol, anti-aging agents such as styrenated phenol, and color masterbatches such as black color masterbatch can be mentioned. These additives may be used alone or in combination of two or more.

[0051] Further, in the shoe sole manufactured using the rubber composition for shoe soles of the present invention, from the viewpoint of improving the hysteresis friction and obtaining excellent wet grip performance, the loss coefficient tanδ at a frequency of 10 Hz at -10°C is 0.3 or more.

[0052] The loss coefficient tanδ of the shoe sole can be determined by analyzing the data measured by the dynamic viscoelasticity measurement of the shoe sole using data processing software.

[0053] Specifically, for the shoe sole, based on the data obtained for a predetermined measurement temperature and measurement frequency, the value of tanδ at -10°C and 10 Hz can be extracted using data processing software. For the dynamic viscoelasticity measurement, for example, "Rheogel-E4000F" manufactured by UBE Corporation can be used, and for the data processing software, "UBE Rheo Station ver7.0" manufactured by UBE Corporation can be used.

[0054] In addition, in the sole manufactured using the rubber composition for soles of the present invention, from the viewpoint of improving the adhesion friction and improving the dry grip property, in the friction test described later, the dynamic friction coefficient μ in the dry state Kdry is preferably 1.15 or more. The larger the value of the dynamic friction coefficient μ Kdry , the greater the frictional force and the more difficult it is to slip, so it can be said that the dry grip property is improved.

[0055] In addition, in the sole manufactured using the rubber composition for soles of the present invention, from the viewpoint of improving the hysteresis friction and improving the wet grip property, in the friction test described later, the dynamic friction coefficient μ in the oil lubricated state Koil is preferably 0.38 or more. This value is considered to be the friction derived from the hysteresis friction excluding the adhesion friction, and the larger the value of the dynamic friction coefficient μ Koil , the greater the frictional force due to hysteresis and the more difficult it is to slip, so it can be said that the wet grip property is improved.

[0056] And in the sole manufactured using the rubber composition for soles of the present invention, the difference between the dynamic friction coefficient μ Kdry and the dynamic friction coefficient μ Koil (that is, μ Kdry -μ Koil ) is considered to be the friction coefficient of the adhesion friction. As described above, since μ Koil is the friction derived from the hysteresis friction, the difference from μ Kdry becomes the adhesion frictional force. Therefore, when this value is 0.7 or more, the adhesion friction is improved and excellent dry grip property can be obtained.

[0057] The "dynamic friction coefficient" mentioned here can be obtained by the method described in the examples below.

[0058] In addition, in the sole manufactured using the rubber composition for soles of the present invention, from the viewpoint of improving the wear resistance, the DIN wear volume is preferably 160 mm 3 or less. The smaller the value of the DIN wear volume, the better the durability, so it can be said that the wear resistance is improved.

[0059] Note that the "DIN wear volume" mentioned here can be obtained by the method described in the examples below.

[0060] Also, in the sole made of the rubber composition for soles of the present invention, from the viewpoint of improving strength, the tensile strength is preferably 12 MPa or more.

[0061] Note that the "tensile strength" mentioned here refers to the tensile strength measured in accordance with JIS K 6251 (2018).

[0062] <Manufacturing Method of Rubber Composition for Soles> Next, the manufacturing method of the rubber composition for soles of the present invention will be described. When manufacturing the rubber composition for soles of the present invention, first, each raw material such as the above-mentioned rubber component, filler, silane coupling agent, oil, vulcanizing agent, vulcanization accelerator, processing aid, etc. is put into a kneader, and these raw materials are kneaded to manufacture a rubber composition for soles.

[0063] Here, as the kneader, for example, a mixing roll, a calendar roll, a Banbury mixer, a kneader, etc. can be used.

[0064] For example, it can be carried out step by step using a plurality of kneaders. For example, after putting the rubber component, filler, silane coupling agent, and processing aid into a kneader and kneading them, the kneaded composition is moved to a roll, and at the same time, a vulcanizing agent and a vulcanization accelerator are put into the roll for kneading.

[0065] Note that all the materials may be put into a roll set at a predetermined temperature and kneaded.

[0066] In the above manner, the rubber composition for soles of the present invention can be manufactured.

Examples

[0067] The present invention will be described below based on examples. Note that the present invention is not limited to these examples, and these examples can be modified and changed based on the gist of the present invention, and they are not excluded from the scope of the invention.

[0068] The materials used for preparing the rubber composition for the shoe sole are shown below.

[0069] (1) Modified SBR1 (glass transition temperature: -30 °C, bound styrene content: 26% by mass, 1,2-vinyl bond content: 49% by mass, Mooney viscosity (ML 1+4 , 100 °C): 65, manufactured by Asahi Kasei Corporation, trade name: Y031) (2) Modified SBR2 (glass transition temperature: -25 °C, bound styrene content: 21% by mass, 1,2-vinyl bond content: 49% by mass, Mooney viscosity (ML 1+4 , 100 °C): 65, manufactured by Synthos, trade name: SLR4602) (3) Modified SBR3 (glass transition temperature: -35 °C, bound styrene content: 20% by mass, 1,2-vinyl bond content: 42% by mass, Mooney viscosity (ML 1+4 , 100 °C): 60, manufactured by Synthos, trade name: SLR4502) (4) Modified SBR4 (glass transition temperature: -62 °C, bound styrene content: 15% by mass, 1,2-vinyl bond content: 42% by mass, Mooney viscosity (ML 1+4 , 100 °C): 60, manufactured by Synthos, trade name: SLR3402) (5) Unmodified SBR (bound styrene content: 46, 1,2-vinyl bond content: 16, Mooney viscosity (ML 1+4 , 100 °C): 45, manufactured by ENEOS MATERIALS Co., Ltd., trade name: ESBR0202) (6) Butadiene rubber (manufactured by Ube Industries, Ltd., trade name: UBEPOL150L) (7) Natural rubber (trade name: SVR-CV60) (8) Silica (manufactured by Tosoh Silica Corporation, trade name: Nipsil VN3) (9) Oil (manufactured by Idemitsu Kosan Co., Ltd., trade name: PW32) (10) Silane coupling agent 1 (condensate of 3 - octanoylthio - 1 - propyltriethoxysilane, manufactured by Momentive Performance Materials Japan Co., Ltd., trade name: NXT - Z45) (11) Silane coupling agent 2 (bis[3 - (triethoxysilyl)propyl]tetrasulfide, manufactured by Evonik Japan Co., Ltd., trade name: Si - 69) (12) Vulcanization accelerator aid (activated zinc oxide, manufactured by Shodo Chemical Industry Co., Ltd., trade name: Activated Zinc White AZO) (13) Processing aid (stearic acid, manufactured by NOF Corporation, trade name: Bead Stearic Acid Tsubaki) (14) Vulcanization activator (polyethylene glycol, manufactured by Junsei Chemical Co., Ltd., trade name: PEG#4000) (15) Antioxidant 1 (styrenated phenol, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name: SP - N) (16) Antioxidant 2 (2 - mercaptobenzimidazole, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name: MB) (17) Vulcanizing agent (sulfur, manufactured by Hosoi Chemical Industry Co., Ltd., trade name: Sulfur#200) (18) Vulcanization accelerator 1 (N - oxydiethylene benzothiazole - 2 - sulfenamide, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name: MSA) (19) Vulcanization accelerator 2 (tetramethylthiuram monosulfide, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name: TS) (20) Vulcanization accelerator 3 (diphenylguanidine, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name: D(D - P)) (21) Color masterbatch (natural rubber black color masterbatch, manufactured by Shinco Co., Ltd.)

[0070] (Examples 1 - 14 and Comparative Examples 1 - 7) <Preparation of rubber composition> The rubber compositions for shoe soles of Examples 1 - 14 and Comparative Examples 1 - 7 having the compositions shown in Tables 1 - 3 (the numbers indicate parts by mass of each component) were produced by the following production method.

[0071] First, each rubber component, silica, oil, silane coupling agent, and various additives (vulcanization accelerator aids, processing aids, vulcanization activators, antioxidants) shown in Table 1 were compounded and charged into a kneader set at 130°C, and the raw materials were kneaded for 10 minutes. Next, after charging the kneaded composition onto a 10-inch open roll (temperature: 60°C), the vulcanizing agent, vulcanization accelerator, and color masterbatch shown in Table 1 were added, and the raw materials were further kneaded to prepare a rubber composition.

[0072] Next, this rubber composition was pressed using a press machine under the conditions of a temperature of 160°C and a pressure of about 20 MPa for about 5 minutes to produce a rubber sheet 1 with a length of 200 mm, a width of 130 mm, and a thickness of 2 mm. Further, in the same manner, a rubber sheet 2 with a length of 100 mm, a width of 100 mm, and a thickness of 6 mm was produced.

[0073] <Evaluation of Wet Grip Performance> In the above-prepared rubber composition, dynamic viscoelasticity measurement was performed using a dynamic viscoelasticity measuring device (Rheogel-E4000F, manufactured by UBM Co., Ltd.) under the measurement conditions shown below. Specifically, first, the rubber sheet 1 obtained in Examples 1 to 14 and Comparative Examples 1 to 7 was used, cut into strip shapes with a length of 20 mm, a width of 6 mm, and a thickness of 2 mm to obtain test pieces. Next, both ends of this test piece were fixed to the fixing part of the dynamic viscoelasticity measuring device, and a load was applied so as not to loosen, and it was held while being tensioned. In this state, by driving the vibrator of the dynamic viscoelasticity measuring device, a dynamic stress was applied to the test piece to generate a dynamic strain. The dynamic stress and dynamic strain at this time were detected from the respective detectors, and the phase difference and dynamic complex elastic modulus were obtained based on the respective waveforms, and the storage elastic modulus E' and loss elastic modulus E'' were determined. The measurement conditions for the dynamic viscoelasticity measurement using the dynamic viscoelasticity measuring device are as follows.

[0074] (Measurement Conditions) ·Measurement mode: Frequency-temperature dependence ·Strain waveform: Sine wave ·Measurement frequency setting: 100 Hz, 50 Hz, 30 Hz, 10 Hz, 6 Hz, 3 Hz ·Strain control: 50 μm (automatic control) · Static load control: Automatic static load · Measurement temperature: -20°C to 50°C · Step temperature: 2°C · Heating rate: 2°C / min · Hold time: 0 sec · Offset temperature: -30°C

[0075] Next, from the data obtained by the measurement of the dynamic viscoelasticity measuring device, the data of tanδ(-10°C) at 10 Hz at -10°C was extracted, and the wet grip property was evaluated according to the following evaluation criteria. The above results are shown in Tables 1 to 3.

[0076] When tanδ(-10°C) is 0.3 or more... ○ When tanδ(-10°C) is less than 0.3... ×

[0077] <Evaluation of dry grip property> Using the test method shown below, the dynamic friction coefficient on the surface of the rubber compositions prepared in Examples 1 to 14 and Comparative Examples 1 to 7 was measured.

[0078] More specifically, using a friction tester (manufactured by Trinity Lab Co., Ltd., trade name: TL201Tt), at 23°C ± 3°C and under atmospheric pressure, a 2-mm-thick rubber sheet (each rubber sheet 1 obtained in Examples 1 to 14 and Comparative Examples 1 to 7) fixed on a sliding table was pressed with a line contact jig having a width of 10 mm under the condition of a load of 250 g. Then, the rubber sheet was slid 20 mm at a sliding speed of 10 mm / s, and the dynamic friction coefficient between 7 mm and 13 mm was measured, and the dynamic friction coefficient μ Kdry in the dry state was used.

[0079] The above measurement was performed 3 times, and the average value of the dynamic friction coefficient μ Kdry for the 3 times was calculated and used as the dynamic friction coefficient on the surface of the rubber composition.

[0080] Also, with silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., viscosity: 100 cSt), while thoroughly wetting the surface of the above-mentioned 2-mm-thick rubber sheet (each rubber sheet 1 obtained in Examples 1 to 14 and Comparative Examples 1 to 7), the coefficient of kinetic friction μ Kdry in the oil state was measured by the same measurement method as Koil above.

[0081] Then, the difference between the measured coefficient of kinetic friction μ Kdry and the coefficient of kinetic friction μ Koil (i.e., μ Kdry -μ Koil ) was calculated, and the dry grip performance was evaluated according to the following evaluation criteria. The above results are shown in Tables 1 to 3.

[0082] μ Kdry -μ Koil is 0.7 or more...〇 μ Kdry -μ Koil is less than 0.7...×

[0083] <Evaluation of Abrasion Resistance> In accordance with JIS K 6264-2:2005, using a DIN abrasion tester (manufactured by GOTECH, product name: GT-7012-D), the DIN abrasion test of the rubber compositions prepared in Examples 1 to 14 and Comparative Examples 1 to 7 was performed.

[0084] A circular test piece with a diameter of 16 mm was punched out from the prepared 6-mm rubber sheet (each rubber sheet 2 obtained in Examples 1 to 14 and Comparative Examples 1 to 7), and this was used as the test piece for the DIN abrasion test.

[0085] Also, the test piece was set on the tester, and while rotating the test piece with a pressing load of 10 N, it was slid a total of 40 m to cause abrasion. The test piece was slid on a drum (diameter: 150 mm, rotation speed: 40 rpm) wrapped with #60 abrasive cloth. Then, based on the mass reduction due to abrasion of the test piece, the DIN abrasion volume [mm 3 was calculated.

[0086] Then, the abrasion resistance was evaluated according to the following evaluation criteria. The above results are shown in Tables 1 to 3.

[0087] The DIN wear volume is 160 mm 3 or less... ○ The DIN wear volume is 160 mm 3 greater than... ×

[0088] <Evaluation of Strength> In accordance with JIS K 6251 (2018), the tensile strength [MPa] of the rubber compositions prepared in Examples 1 to 14 and Comparative Examples 1 to 7 was measured. More specifically, dumbbell-shaped samples of test piece type 3 were prepared, and a tensile test was carried out using a tensile testing machine (manufactured by Instron, product name: Instron 3365) under the conditions of a temperature of 23°C and a tensile speed of 500 mm / min, and the tensile strength [MPa] at the time when the sample was cut was measured.

[0089] Then, the strength was evaluated according to the following evaluation criteria. The above results are shown in Tables 1 to 3.

[0090] The tensile strength is 12 MPa or more... ○ The tensile strength is less than 12 MPa... ×

[0091]

Table 1

[0092]

Table 2

[0093]

Table 3

[0094] As shown in Table 1, Examples 1 to 14 using a rubber composition for shoe soles containing a modified styrene-butadiene copolymer rubber having a glass transition temperature of -35°C or higher and silica, and having a content of the modified styrene-butadiene copolymer rubber of 70% by mass or more based on the total rubber component, have a tanδ(-10°C) of 0.3 or more, indicating excellent wet grip performance. Also, μ Kdry -μ Koil is 0.7 or more, indicating excellent dry grip performance. Also, since the DIN wear volume is 160 mm 3 or less, it is found to have excellent wear resistance. Also, since the tensile strength is 12 MPa or more, it is found to have excellent strength.

Industrial Applicability

[0095] As described above, the present invention is particularly useful for rubber compositions used for shoe soles.

Claims

1. A rubber composition for shoe soles containing a rubber component comprising a modified styrene-butadiene copolymer rubber having a glass transition temperature of -35°C or higher, a filler containing silica, wherein the content of the modified styrene-butadiene copolymer rubber with respect to the total rubber component is 70% by mass or more. A rubber composition for shoe soles, characterized in that the content of the modified styrene-butadiene copolymer rubber with respect to the total rubber component is 70% by mass or more.

2. containing a silane coupling agent, wherein the content of the silane coupling agent with respect to 100 parts by mass of the silica is 5 parts by mass or more and 10 parts by mass or less.

3. The rubber composition for shoe soles according to Claim 1 or Claim 2, characterized in that the content of the silica with respect to 100 parts by mass of the rubber component is 40 parts by mass or more and 70 parts by mass or less.

4. wherein the rubber component contains other rubber other than the modified styrene-butadiene copolymer rubber, and the content of the other rubber with respect to the total rubber component is 30% by mass or less.

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