Rubber composition for sole, sole and shoe

Abstract

The present invention provides a rubber composition for shoe soles, which contains 50 to 100 parts by mass of a white filler, has a slope of an approximate straight line drawn for input energy-hysteresis loss of 0.6 or more, a gel fraction of 80% or less, and a complex elastic modulus of 30 MPa or more.

Description

Technical Field

[0001] This application claims the priority of Japanese Patent Application No. 2019-231801, and the description of the present application specification is incorporated by reference.

[0002] The present invention relates to a rubber composition for shoe soles, a shoe sole and a shoe. Background Art

[0003] Currently, mountaineering shoes such as training shoes and climbing shoes are used for walking in the mountains.

[0004] Mountaineering shoes are widely used even in applications such as climbing artificial cliffs and natural cliffs.

[0005] Such mountain climbing shoes are required to exhibit gripping properties even in locations where the ground is extremely uneven (see Patent Document 1 listed below).

[0006] However, not limited to mountaineering shoes, in conventional shoes, members constituting the outsole such as the outer sole are made of cross-linked rubber, and the rubber composition constituting the cross-linked rubber contains an inorganic filler as a reinforcing material.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent No. 3100592 Summary of the invention

[0010] Problems to be solved by the invention

[0011] The present invention aims to provide a rubber composition for shoe soles containing a white filler and capable of enabling the shoe sole to exhibit both a high elastic modulus and excellent grip, to provide a shoe sole having a high elastic modulus and excellent grip, and to provide a shoe having excellent strength and grip.

[0012] Technical solutions to solve problems

[0013] In order to solve the above problems, the present invention provides a rubber composition for shoe soles, comprising rubber and an inorganic filler.

[0014] Part or all of the above inorganic fillers are white fillers.

[0015] The ratio of the white filler to 100 parts by mass of the rubber is 50 parts by mass or more and 100 parts by mass or less.

[0016] The rubber composition has a slope (dEhys / dEin) of an approximate straight line representing the relationship between input energy (Ein) and hysteresis loss (Ehys) in a tensile cycle test of 0.6 or more,

[0017] The rubber composition has a gel fraction of 80% or less and a complex elastic modulus of 30 MPa or more.

[0018] In order to solve the above-mentioned problems, the present invention provides a shoe sole comprising a rubber composition containing rubber and an inorganic filler.

[0019] In the above rubber composition,

[0020] Part or all of the above inorganic fillers are white fillers.

[0021] The ratio of the white filler to 100 parts by mass of the rubber is 50 parts by mass or more and 100 parts by mass or less.

[0022] The rubber composition has a slope (dEhys / dEin) of an approximate straight line representing the relationship between input energy (Ein) and hysteresis loss (Ehys) in a tensile cycle test of 0.6 or more,

[0023] The rubber composition has a gel fraction of 80% or less and a complex elastic modulus of 30 MPa or more.

[0024] The present invention also provides a shoe having the above-mentioned sole. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic perspective view showing an example of a mountain climbing shoe according to an embodiment.

[0026] Figure 2 The diagram shows an example of the shape of a sample used for measuring the slope of an approximate straight line. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0028] Hereinafter, the embodiment of the present invention will be described by taking mountaineering shoes as an example.

[0029] The soles of shoes used in places with severe unevenness such as mountaineering shoes are currently made of a rubber composition for soles containing carbon black as a reinforcing material.

[0030] It is generally difficult to make a rubber composition for shoe soles containing carbon black into a color tone other than black.

[0031] It is not desirable that the components constituting the shoe be limited to a specific color tone in order to impose constraints on the design of the shoe.

[0032] In shoes such as sneakers, there is research into using a white filler such as silica as a reinforcing material in a rubber composition constituting the sole, and providing the rubber composition with a color tone other than black.

[0033] In recent years, attempts have been made to form the soles of mountaineering shoes using rubber compositions containing white fillers.

[0034] From the viewpoint of strength, etc., the sole of a shoe is sometimes preferably formed of a rubber composition having a high elastic modulus. However, in the above-mentioned attempts, an attempt was made to make the sole have gripping properties by forming the sole of a rubber composition having a low elastic modulus.

[0035] Furthermore, there is no known method for achieving high elastic modulus while achieving high grip using a white filler in a rubber composition constituting the sole of a mountaineering shoe.

[0036] Therefore, although mountain climbing shoes are exemplified below, sneakers and the like that are mainly used on paved roads are also expected to exhibit the same grip as mountain climbing shoes when used in places with severe unevenness of the ground.

[0037] That is, it is required that a high elastic modulus be exhibited while using a white filler to exhibit excellent gripping properties in places with strong unevenness, and it is not limited to the mountain climbing shoes exemplified below.

[0038] Figure 1 1 is a schematic perspective view showing an example of a mountain climbing shoe. As shown in the figure, a mountain climbing shoe 1 according to the present embodiment includes an upper 2 and a sole 3 .

[0039] As shown in the figure, the shoe sole 3 of this embodiment includes a bottom portion constituting the entire lower surface 1b of the shoe and a rising portion rising from the outer peripheral edge of the lower surface 1b of the shoe.

[0040] That is, the shoe sole 3 of the present embodiment constitutes not only the lower surface 1b of the shoe but also the outer peripheral surface 1s of the lower region of the shoe.

[0041] The shoe sole 3 of the present embodiment is composed of a non-crosslinked or low-crosslinked rubber composition for shoe soles.

[0042] The above-mentioned rubber composition for shoe soles (hereinafter, also simply referred to as "rubber composition") contains rubber and inorganic filler, part or all of the above-mentioned inorganic filler is white filler, and the ratio of the above-mentioned white filler to 100 parts by mass of the above-mentioned rubber is 50 parts by mass or more and 100 parts by mass or less.

[0043] The rubber contained in the rubber composition does not need to be a single type, and may be two or more types.

[0044] When the rubber composition contains two or more rubbers, the white filler is contained in the rubber composition in a ratio of 50 parts by mass to 100 parts by mass, based on 100 parts by mass of the total content of the two or more rubbers.

[0045] The rubber composition has a slope (dEhys / dEin) of an approximate straight line representing the relationship between input energy (Ein) and hysteresis loss (Ehys) in a tensile cycle test of 0.6 or more. The rubber composition has a gel fraction of 80% or less.

[0046] The complex elastic modulus of the rubber composition is 30 MPa or more. The complex elastic modulus is obtained by a dynamic viscoelasticity test described below.

[0047] The rubber composition in the present embodiment has a loss tangent of 0.12 or more in the dynamic viscoelasticity test, and a complex elastic modulus of 90 MPa or less.

[0048] The type of the rubber in the rubber composition is not particularly limited, but it is preferred that part or all of the rubber be any one of styrene-butadiene rubber, styrene-based thermoplastic elastomer, natural rubber, isoprene rubber and isobutylene-isopropylene rubber.

[0049] As shown above, the rubber composition may contain a variety of rubbers, and the rubber contained in the rubber composition in the present embodiment at the highest mass ratio (hereinafter also referred to as "base rubber") is preferably any one of styrene-butadiene rubber, styrene-based thermoplastic elastomer, natural rubber, isoprene rubber and isobutylene-isopropylene rubber.

[0050] The ratio of the base rubber to the entire rubber is, for example, 50% by mass or more.

[0051] The ratio is preferably 60% by mass or more, more preferably 70% by mass or more.

[0052] The ratio of the base rubber to the entire rubber is, for example, 100 mass % or less.

[0053] If the rubber contained in the rubber composition is used as a base rubber, it is necessary to adjust the properties of the rubber composition using other compounding ingredients.

[0054] Therefore, the rubber composition preferably contains a rubber other than the base rubber, and preferably contains a plurality of types of rubbers.

[0055] Furthermore, the above ratio is preferably 95% by mass or less, and more preferably 90% by mass or less.

[0056] The ratio of the base rubber is preferably within a range set by selecting any one of the lower limits and any one of the upper limits.

[0057] The base rubber preferably has a small change in elastic modulus in a temperature range (for example, 0° C. or higher and 40° C. or lower) in a general shoe usage environment.

[0058] In order to achieve excellent grip performance in the shoe 1 of the present embodiment, the base rubber preferably exhibits a high loss tangent in the above-mentioned temperature range.

[0059] Furthermore, generally, the loss tangent reaches a maximum value at the glass transition temperature. Therefore, in order to exhibit the above-mentioned grip performance, the glass transition temperature of the above-mentioned base rubber is preferably higher than -15°C, and more preferably higher than -10°C.

[0060] The glass transition temperature of the base rubber is preferably lower than 20°C.

[0061] The base rubber is preferably any one of styrene-butadiene rubber, styrene-based thermoplastic elastomer, and isobutylene-isopropylene rubber (butyl rubber).

[0062] Among them, styrene butadiene rubber is preferred as the base rubber because it is excellent in strength and elasticity and also excellent in abrasion resistance.

[0063] The base rubber may be a styrene butadiene rubber obtained by solution polymerization (hereinafter also referred to as "solution polymerized SBR", "S-SBR", etc.), or a rubber formed by emulsion polymerization (hereinafter also referred to as "emulsion polymerized SBR", "E-SBR", etc.).

[0064] The base rubber may be a halogenated butyl rubber such as chlorinated butyl rubber or brominated butyl rubber.

[0065] As the rubber contained in the rubber composition, a styrene-based thermoplastic elastomer is also mentioned as a preferable rubber.

[0066] Examples of the styrene-based thermoplastic elastomer include styrene-ethylene-butylene copolymer (SEB), styrene-butadiene-styrene copolymer (SBS), hydrogenated products of SBS (styrene-ethylene-butylene-styrene copolymer (SEBS)), styrene-isoprene-styrene copolymer (SIS), hydrogenated products of SIS (styrene-ethylene-propylene-styrene copolymer (SEPS)), styrene-butadiene-isoprene-styrene copolymer (SBIS), hydrogenated products of SBIS (styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS)), styrene-isobutylene-styrene copolymer (SIBS), styrene-butadiene-styrene-butadiene copolymer (SBSB), styrene-butadiene-styrene-butadiene copolymer (SBSBS), and the like.

[0067] Among them, a styrene-based thermoplastic elastomer that is preferable as the base rubber includes a styrene-ethylene-butylene-styrene copolymer (SEBS).

[0068] In the present embodiment, the rubber composition constituting the shoe sole 3 contains a white filler in addition to the base rubber.

[0069] White fillers may have poorer dispersibility in rubber than carbon black which is generally used as a reinforcing material for rubber.

[0070] Therefore, in order to improve kneadability when preparing the rubber composition, the rubber composition may contain a liquid rubber in addition to the above-mentioned base rubber.

[0071] When solution-polymerized SBR or emulsion-polymerized SBR is used as the base rubber, the rubber that is liquid at room temperature (23° C.) and combined with these rubbers may be styrene-butadiene rubber (hereinafter also referred to as “liquid SBR”, “L-SBR”, etc.).

[0072] The rubber composition of the present embodiment exhibits a large hysteresis loss and thus exhibits excellent grip performance even on a mountain road with severe roughness.

[0073] Therefore, it is advantageous that the molecular terminals of rubber are present in a large amount in the rubber composition.

[0074] The use of the above-mentioned liquid SBR or the like is also advantageous in increasing the number of molecular terminals in the rubber composition and thus increasing the hysteresis loss.

[0075] The liquid rubber may be contained in the rubber composition at a mass ratio of 10 parts by mass or more, when the content of the base rubber in the rubber composition in the present embodiment is 100 parts by mass.

[0076] The mass ratio is preferably 15 parts by mass or more.

[0077] The above mass ratio is usually 50 parts by mass or less.

[0078] The above mass ratio is preferably 40 parts by mass or less.

[0079] The ratio of the liquid rubber is preferably within a range set by selecting any one of the lower limits and any one of the upper limits.

[0080] The total amount of the liquid rubber and the base rubber is preferably 90% by mass or more, and more preferably 95% by mass or more, of the total amount of rubber contained in the rubber composition of the present embodiment.

[0081] In order to make the molecular terminals present in a large amount in the rubber composition, the molecular weight distribution (Mw / Mn) of the base rubber is preferably wide. Therefore, of the solution-polymerized SBR and the emulsion-polymerized SBR, it is advantageous to use the emulsion-polymerized SBR as the base rubber.

[0082] The molecular weight distribution of the emulsion-polymerized SBR can be determined by gel permeation chromatography (GPC) and calculated from the mass average molecular weight (Mw) and the number average molecular weight (Mn). The mass average molecular weight (Mw) and the number average molecular weight (Mn) are each determined as a value converted to standard styrene.

[0083] The molecular weight distribution (Mw / Mn) of the emulsion-polymerized SBR is preferably 3 or more, and more preferably 3.2 or more.

[0084] The molecular weight distribution (Mw / Mn) is usually 5 or less.

[0085] The rubber composition of the present embodiment is in a non-crosslinked state or a state with a low degree of crosslinking to constitute the above-mentioned shoe sole 3 .

[0086] The emulsion-polymerized SBR generally has fewer vinyl bonds that can serve as crosslinking points in the molecule than the solution-polymerized SBR, and is therefore preferably used as the base rubber.

[0087] The rubber composition of the present embodiment may contain a cross-linking agent for cross-linking the rubber.

[0088] The crosslinking agent may be sulfur or an organic peroxide which is generally used for crosslinking of rubber.

[0089] The crosslinking agent in the rubber composition is preferably sulfur.

[0090] The sulfur may be contained in the rubber composition in an amount exceeding 0.5 parts by mass, based on 100 parts by mass of the total amount of rubber contained in the rubber composition.

[0091] The mass ratio may exceed 0.6 parts by mass.

[0092] The mass proportion is preferably less than 1 part by mass, more preferably less than 0.9 part by mass.

[0093] The mass ratio of sulfur is preferably within a range set by selecting any one of the lower limits and any one of the upper limits.

[0094] The rubber composition may further contain a compound having a polysulfide structure in its molecular structure, and the compound may function in the same manner as the cross-linking agent.

[0095] Examples of the compound include a silane coupling agent having a tetrasulfide structure.

[0096] Examples of the silane coupling agent include bis(trimethoxysilylpropyl)disulfide, bis(triethoxysilylpropyl)disulfide, bis(trimethoxysilylpropyl)tetrasulfide, and bis(triethoxysilylpropyl)tetrasulfide.

[0097] The compound may be contained in the rubber composition at a mass ratio such that sulfur exceeds 0.1 parts by mass, based on 100 parts by mass of the total amount of rubber contained in the rubber composition.

[0098] The compound may be contained in the rubber composition at the mass ratio in which sulfur is contained in excess of 0.2 parts by mass.

[0099] The mass ratio may be less than 1.5 parts by mass.

[0100] The mass ratio is preferably less than 1 part by mass.

[0101] The mass ratio of the above-mentioned compounds is preferably within a range set by selecting any one of the above-mentioned lower limits and any one of the above-mentioned upper limits.

[0102] The rubber composition may contain a monosulfide-based silane coupling agent in addition to the polysulfide-based silane coupling agent having a polysulfide structure.

[0103] Examples of the monosulfide-based silane coupling agent include bis(trimethoxysilylpropyl methacrylate)monosulfide, bis(triethoxysilylpropyl methacrylate)monosulfide, octanoylthiopropyltrimethoxysilane, and octanoylthiopropyltriethoxysilane.

[0104] The rubber composition may contain a mercapto silane coupling agent such as mercaptopropyltrimethoxysilane and mercaptopropyltriethoxysilane in addition to a sulfide silane coupling agent such as a polysulfide silane coupling agent and a monosulfide silane coupling agent.

[0105] The rubber composition may contain a non-sulfur silane coupling agent that does not contain sulfur in its molecular structure in addition to a sulfur-based silane coupling agent such as a sulfide-based silane coupling agent and a mercapto-based silane coupling agent.

[0106] Examples of the non-sulfur silane coupling agent include alkoxysilane-based silane coupling agents such as methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, bis(trimethoxysilyl)hexane, and trifluoropropyltrimethoxysilane; vinyl-based silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; and cyclohexylethyltrimethoxysilane and glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropylmethyldimethoxysilane, glycidoxypropylmethyldiethoxysilane, and epoxycyclohexylethyltrimethoxysilane. Oxygen-based silane coupling agents; (meth)acrylic silane coupling agents such as (meth)acryloxypropyl trimethoxysilane, (meth)acryloxypropyl triethoxysilane, (meth)acryloxypropyl methyl dimethoxysilane, and (meth)acryloxypropyl methyl diethoxysilane; amino-based silane coupling agents such as aminopropyl trimethoxysilane, aminopropyl triethoxysilane, aminoethylaminopropyl trimethoxysilane, aminoethylaminopropyl triethoxysilane, aminoethylaminopropyl methyl dimethoxysilane, aminoethylaminopropyl methyl diethoxysilane, phenylaminopropyl trimethoxysilane, and phenylaminopropyl triethoxysilane; isocyanate-based silane coupling agents such as isocyanate propyl trimethoxysilane and isocyanate propyl triethoxysilane; isocyanurate-based silane coupling agents such as tris (trimethoxysilylpropyl) isocyanurate.

[0107] Examples of the white filler included in the rubber composition include silicon dioxide, calcium carbonate, magnesium carbonate, barium carbonate, etc. The white filler may be, for example, a mica mineral such as sericite, etc. The white filler may also be talc, clay, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium oxide, calcium sulfate, barium sulfate, etc.

[0108] As the white filler, for example, when a smooth flat surface is formed by compression using a glass plate, the whiteness (JIS P8148) of the flat surface is preferably 60% or more.

[0109] The whiteness may be 70% or more, 80% or more, or 90% or more.

[0110] The white filler contained in the rubber composition of the present embodiment does not need to be a single type, and may be two or more types.

[0111] When the rubber composition contains two or more white fillers, the white fillers are contained in the rubber composition in a total amount of 50 parts by mass or more and 100 parts by mass or less, based on 100 parts by mass of the total content of the rubber.

[0112] The content of the white filler is preferably 55 parts by mass or more, and more preferably 60 parts by mass or more.

[0113] The content of the white filler is preferably 95 parts by mass or less, and more preferably 90 parts by mass or less.

[0114] The content of the white filler is preferably within a range set by selecting any one of the lower limits and any one of the upper limits.

[0115] As the white filler, silicon dioxide is preferred.

[0116] The rubber composition may contain silica produced by a wet process (hereinafter also referred to as “wet-process silica”), or may contain silica produced by a dry process (hereinafter also referred to as “dry-process silica”).

[0117] In the rubber composition of the present embodiment, it is preferred that a part of the white filler constitutes aggregated particles. The rubber composition of the present embodiment preferably includes a plurality of aggregated particles constituted by the white filler.

[0118] The aggregated particles may be secondary particles formed by aggregation of a plurality of primary particles of the white filler, that is, primary aggregated particles.

[0119] The aggregated particles may be secondary aggregated particles formed by secondary aggregation of the primary aggregated particles.

[0120] By including the primary aggregated particles and the secondary aggregated particles, the rubber composition of the present embodiment exhibits high hysteresis loss by causing a part of the primary aggregated particles and the secondary aggregated particles to break when stress is applied.

[0121] In view of the above circumstances, the silica is preferably wet-process silica which easily contains primary aggregated particles.

[0122] The wet silica may be silica produced by a precipitation method (hereinafter also referred to as “precipitated silica”) or may be silica produced by a gel method (hereinafter also referred to as “gel-method silica”).

[0123] The wet silica is preferably precipitated silica which is easily broken when stress is applied.

[0124] The average particle size of the white filler such as silica contained in the rubber composition is preferably 1 μm or more.

[0125] The average particle size is more preferably 2 μm or more, and further preferably 5 μm or more.

[0126] The average particle size is preferably 30 μm or less, more preferably 25 μm or less.

[0127] The average particle size refers to a volume-based median particle size (D50) determined by a laser diffraction scattering method.

[0128] The average particle size of the white filler is preferably within a range set by selecting any one of the lower limit values ​​and any one of the upper limit values.

[0129] The rubber composition may contain fillers other than the white filler.

[0130] The rubber composition preferably does not contain excessive amounts of fillers other than the white filler in order to facilitate preparation into a desired color tone.

[0131] The proportion of the white filler in the total inorganic filler of the rubber composition is preferably 95% by mass or more, more preferably 98% by mass or more.

[0132] In order to form a colored sole 3, the rubber composition may further contain a pigment such as red or blue.

[0133] The rubber composition may contain additives such as an anti-aging agent, an antioxidant, a weathering agent, an ultraviolet absorber, a light stabilizer, a flame retardant, a mold release agent, an antistatic agent, an antibacterial agent, an antifungal agent, a deodorant, and a fragrance.

[0134] As described above, the rubber composition of the present embodiment has a gel fraction of 80% or less and constitutes the shoe sole 3 .

[0135] The "gel fraction" in the present embodiment refers to the ratio of rubber that is not dissolved in a solvent extraction test (also referred to as "insoluble rubber") to the total amount of rubber.

[0136] Specifically, the gel fraction of the rubber composition is further determined as follows.

[0137] <Method for determining gel fraction>

[0138] A sample is cut from the sole. The sample is in the shape of a disk with a diameter of about 8 mm, a thickness of about 2 mm, a through hole in the center, and a mass of about 0.2 g. The mass of the sample is accurately weighed as the initial mass (M0).

[0139] Similarly, prepare another 4 samples of the above-mentioned substance with a mass of about 0.2 g, and weigh their initial masses accurately in the same manner.

[0140] Next, five sample tubes each having a volume of 50 mL and containing about 45 mL of toluene were prepared, and five sets of samples in which the samples were accommodated in the sample tubes while being immersed in toluene were prepared.

[0141] The sample was immersed in toluene in such a manner that a thin metal wire was passed through the through hole and was suspended in the interior of the sample tube.

[0142] After the sample tube was capped, it was stored at 35°C for 72 hours.

[0143] After 72 hours, the sample was taken out from the sample tube and vacuum dried, and the mass after vacuum drying was accurately weighed (M1).

[0144] The content rate (A (mass %)) of components other than rubber in the initial sample is determined by measuring the ash content of the initial sample.

[0145] The ash content is measured based on JIS K6226-1 and JIS K6226-2.

[0146] The mass of rubber contained in each initial sample (initial mass: Mi) was calculated as follows using the value of the initial mass (M0) and the content of components other than rubber (A (mass %)).

[0147] Initial mass of rubber (Mi) = M0 × (100-A) / 100

[0148] The mass of rubber contained in the sample obtained by immersing in toluene for 72 hours and then vacuum drying (insoluble rubber mass: Mb) was determined as follows.

[0149] Insoluble rubber mass (Mb) = M1 × (100-A) / 100

[0150] The ratio of the insoluble rubber mass (Mb) to the initial mass (Mi) was calculated, and the gel fraction ((Mb / Mi)×100%) in each sample was calculated.

[0151] The results of the five samples were arithmetic averaged to obtain the gel fraction of the rubber composition.

[0152] In addition, when calculating the arithmetic mean, measurement results that are considered to be outliers are excluded.

[0153] When measuring the gel fraction of the rubber composition, the arithmetic mean of five measured values ​​is calculated as described above in principle. However, when a total of five samples cannot be prepared, the number of measurement points may be reduced and the measurement may be performed.

[0154] The rubber composition preferably has a gel fraction of 77% or less, more preferably 76% or less, and still more preferably 75% or less.

[0155] The rubber composition preferably has a low gel fraction in terms of increasing hysteresis loss, but a certain degree of high gel fraction is advantageous in terms of allowing the shoe sole 3 to exhibit excellent oil resistance and chemical resistance.

[0156] Therefore, the gel fraction of the rubber composition is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more.

[0157] The gel fraction of the rubber composition is preferably within a range set by selecting any one of the lower limit values ​​and any one of the upper limit values.

[0158] The gel fraction in the rubber composition can generally be adjusted by controlling the degree of cross-linking between rubber molecules.

[0159] The rubber composition in this embodiment constitutes the sole 3 so that when a tensile cycle test is performed, the slope (dEhys / dEin) of the approximate straight line of "input energy (Ein) - hysteresis loss (Ehys)" obtained in the tensile cycle test becomes 0.6 or more.

[0160] The slope (dEhys / dEin) of the above-mentioned approximate straight line can be calculated as follows.

[0161] <How to find the slope of an approximate straight line>

[0162] A dumbbell-shaped test piece having a thickness of about 2 mm was cut out from the shoe sole at a uniform thickness.

[0163] The dumbbell test piece is Figure 2 Shape shown.

[0164] Specifically, the width of the parallel portion of the dumbbell-shaped test piece was 5 mm and the length of the parallel portion was 2 mm.

[0165] When it is difficult to cut out a dumbbell-shaped test piece from the shoe sole, a dumbbell-shaped test piece may be cut out from a test sheet made of a rubber composition having the same formulation.

[0166] The dumbbell-shaped test piece was mounted on a tensile testing machine so that the chuck interval became 12 mm.

[0167] A test piece placed in a tensile testing machine was stretched at a stretching speed of 1 mm / min until the displacement amount reached 5% (12 mm×5%=0.6 mm), and then immediately returned to its original state at the same speed.

[0168] At this time, the integrated value of the SS curve (stress-strain curve) during stretching measured by a tensile testing machine was taken as input energy (Ein).

[0169] Then, the difference (Ein-Ein') between the integral value (Ein') of the SS curve at the time of recovery and the input energy (Ein) is defined as the hysteresis loss (Ehys).

[0170] Next, the input energy (Ein) and the hysteresis loss (Ehys) were similarly determined when the displacement was 25% (3 mm), 50% (6 mm), and 100% (12 mm).

[0171] Then, the data of the four points are plotted on a graph with the horizontal axis representing input energy (Ein) and the vertical axis representing hysteresis loss (Ehys), and the slope of the approximate straight line (dEhys / dEin) is calculated by approximating the straight line through the origin using the least squares method.

[0172] In principle, the tensile test is performed in an environment adjusted to a temperature of 23° C. and a relative humidity of 50%, and the dumbbell-shaped test piece is kept in this environment for 12 hours or more and then subjected to the tensile test.

[0173] The above-mentioned slope (dEhys / dEin) is usually less than 1, and preferably 0.9 or less.

[0174] The above-mentioned slope (dEhys / dEin) is more preferably 0.8 or less.

[0175] The above-mentioned slope (dEhys / dEin) can be generally controlled by adjusting the hysteresis loss of the rubber composition.

[0176] The hysteresis loss of the rubber composition can be adjusted by adjusting the content of the inorganic filler in a cohesive state that can be broken when stress is applied.

[0177] The hysteresis loss of the rubber composition can also be adjusted by the degree of displacement between rubber molecular chains when stress is applied.

[0178] The degree of displacement between molecular chains can be adjusted by adjusting the crosslinking density of the rubber, the amount of molecular terminals in the system, and the like.

[0179] The grip performance exhibited by the rubber composition preferably has a static friction coefficient determined by the measuring method described in Examples of 1.5 or more.

[0180] The static friction coefficient is more preferably 1.7 or more, and further preferably 1.9 or more.

[0181] The rubber composition forms the sole 3 when the loss tangent (tan δ) is 0.12 or more. The loss tangent (tan δ) of the rubber composition is determined by a dynamic viscoelasticity test at 25°C, a strain of 0.025% and a frequency of 10 Hz.

[0182] The above-mentioned rubber composition has a complex elastic modulus (E ＊ ) becomes a state of being greater than 30MPa and less than 90MPa to form the sole 3.

[0183] The dynamic viscoelasticity test can be carried out in accordance with JIS K7244-4, for example, in the following manner.

[0184] <Test method of dynamic viscoelasticity test>

[0185] A rectangular test piece of a specific size (for example, length 33±3 mm, width 5±0.3 mm, thickness 2±0.3 mm) is taken from the sole 3 .

[0186] When it is difficult to cut out a test piece from the shoe sole 3 , a rectangular test piece may be cut out from a test piece made of a rubber composition having the same formulation.

[0187] This rectangular test piece was mounted on a dynamic viscoelasticity measuring device so that the distance between chucks became 20±0.2 mm.

[0188] The measurement mode was set to the tensile mode with sinusoidal wave distortion, the load was set to the automatic static load, the dynamic strain was set to 5 μm (0.025%), and the test was performed at a frequency of 10 Hz.

[0189] The test temperature for the dynamic viscoelasticity measurement was 25° C., and the rectangular test piece was kept in an environment of 25° C. for 12 hours or more before being subjected to the dynamic viscoelasticity test.

[0190] The loss tangent of the rubber composition is preferably 0.13 or more, more preferably 0.14 or more.

[0191] The loss tangent is preferably 0.22 or less, and more preferably 0.21 or less.

[0192] The complex elastic modulus of the rubber composition is preferably 50 MPa or more, more preferably 60 MPa or more, and even more preferably 70 MPa or more.

[0193] The complex elastic modulus is preferably 85 MPa or less.

[0194] The loss tangent and the complex elastic modulus are preferably within a range set by selecting any one of the lower limit values ​​and any one of the upper limit values.

[0195] The loss tangent and complex elastic modulus of the rubber composition can be adjusted according to the loss tangent, complex elastic modulus, etc. of the rubber used as the base rubber.

[0196] The shoe 1 of the present embodiment has a sole 3 formed of the above-mentioned specific rubber composition, and the upper 2 can be formed of a conventionally known material.

[0197] The shoe 1 of this embodiment has the sole 3 formed of the rubber composition, and therefore can exhibit high grip in situations where only a small area of ​​the sole 3 is in contact with the ground when climbing mountains, rocks, or cliffs on steep slopes.

[0198] That is, the shoe 1 of this embodiment can support the stable static posture of the wearer even when the sole 3 is in point contact with the ground.

[0199] The shoe 1 of this embodiment can also well support the static posture of the wearer in sports climbing such as climbing an artificial cliff.

[0200] That is, the mountain climbing shoes of this embodiment can be used not only in nature but also can significantly demonstrate their effects in sports climbing and the like.

[0201] In this embodiment, the crosslinking degree of rubber is lowered (or non-crosslinked) than in conventional rubber compositions for shoe soles to exhibit specific hysteresis characteristics, thereby allowing the shoe sole to exhibit both high elastic modulus and excellent grip.

[0202] The shoe 1 of the present embodiment can enable the sole 3 to exhibit excellent strength due to the high elastic modulus of the rubber composition.

[0203] Therefore, the shoe 1 of this embodiment is unlikely to cause pain to the foot even when the wearer steps on a sharp stone and the load is concentrated on one point of the shoe sole.

[0204] When viewed from a different perspective, the shoe 1 of this embodiment can also make the sole 3 thinner than conventional mountaineering shoes, and can exhibit excellent lightness.

[0205] The shoe 1 of this embodiment can maintain rich color variations on the sole 3. That is, the shoe 1 of this embodiment can express excellent design.

[0206] Furthermore, the rubber composition for shoe soles of the present invention can exert the same effect not only when constituting the soles of mountaineering shoes but also when constituting the soles of ordinary sports shoes.

[0207] In addition, the present invention can add various modifications to the above-mentioned examples as appropriate.

[0208] That is, the present invention is not limited to the above-mentioned examples at all.

[0209] [Example]

[0210] Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0211] (Example, Comparative Example)

[0212] (Compounding agent)

[0213] As raw materials for preparing the rubber composition, the following raw materials were prepared.

[0214] SBR: Styrene butadiene rubber with a styrene content of about 50% by mass (emulsion polymerized SBR)

[0215] SEBS: Styrene-ethylene-butylene-styrene copolymer

[0216] BrBR: Bromobutyl rubber

[0217] NR: Natural Rubber

[0218] ·L-SBR: Liquid SBR

[0219] PO: Paraffin oil

[0220] ·SiO2: Precipitated silica containing agglomerated particles with an average particle size (D50) of about 20 μm

[0221] CA: Bis(triethoxysilylpropyl)tetrasulfide

[0222] PEG: polyethylene glycol with a mass average molecular weight of about 2000 and a melting point of about 52°C

[0223] Vulcanizing agent 1: sulfur

[0224] ·Vulcanizing agent 2: 4,4'-dimorpholine disulfide

[0225] Vulcanization accelerator 1: di(2-benzothiazole) disulfide

[0226] Vulcanization accelerator 2: Tetramethylthiuram monosulfide

[0227] Vulcanization accelerator 3: dilaurylthiourea

[0228] (Production of cross-linked sheet)

[0229] An uncrosslinked sheet is prepared using an uncrosslinked rubber composition having the formulation shown in Table 1, and the uncrosslinked sheet is placed in the through holes of a metal frame having rectangular through holes. The metal frame is clamped between two stamping plates and hot-pressed to produce a crosslinked sheet of a specific thickness.

[0230] (Evaluation of mechanical properties and gel fraction)

[0231] A test piece was cut out from the crosslinked sheet and the complex elastic modulus (E ＊ ), loss tangent (tanδ), the slope of the approximate straight line (dEhys / dEin) drawn from the input energy (Ein)-hysteresis loss (Ehys) obtained in the tensile cycle test, and determination of the gel fraction.

[0232] (Evaluation of Friction Coefficient)

[0233] The friction coefficient was measured using a direct-acting friction tester, model "μV-1000" manufactured by TRINITY LABO CO., LTD., as an apparatus.

[0234] An uncrosslinked sheet was prepared using an uncrosslinked rubber composition, and the uncrosslinked sheet was placed in the through holes of a 2 mm thick metal frame having rectangular through holes. The metal frame was sandwiched between two pressing plates and hot pressed to produce a crosslinked sheet.

[0235] The cross-linked sheet is produced by using a mirror plate during heat pressing to make the surface sufficiently smooth.

[0236] Then, the surface of the crosslinked sheet was roughened using sandpaper (#400) to make the entire surface uniform.

[0237] A test sheet having a width of 20 mm, a length of 40 mm, and a thickness of 2 mm was cut out from the crosslinked sheet.

[0238] The test sheet is fixed on the upper surface of a stage that can move horizontally at a constant speed.

[0239] The test sheet is fixed so that the moving direction of the stage is the long side direction.

[0240] A rock climbing hold with an average curvature radius (R) of 14 mm and a surface roughness (maximum height roughness (Rz) = 366 μm) is brought into contact with the upper surface of the test sheet, a load of 1 kgf is applied to the test sheet at the hold, and after being stationary for 10 seconds, the stage is moved at a speed of 10 mm / sec.

[0241] The maximum value of the friction coefficient observed in the initial stage of the movement of the stage was taken as the static friction coefficient.

[0242] In the test, the preliminary friction test was performed at the same location 10 times or more. The arithmetic mean of the final three measurement results at which the measured values ​​were stable in the preliminary friction test was taken as the static friction coefficient of the test sheet.

[0243] The above evaluation results are shown in the following table.

[0244]

Table 1

[0245]

[0246] As can be seen from the above, according to the present invention, there can be provided a rubber composition for shoe soles which contains a white filler and can enable a shoe sole to exhibit both a high elastic modulus and excellent gripping properties.

[0247]

Explanation of symbols

[0248] 1: Shoe, 2: Upper, 3: Sole.

Claims

1. A rubber composition for shoe soles, characterized in that: It contains base rubber, liquid rubber and inorganic filler. Part or all of the inorganic filler is a white filler, The white filler is precipitated silica. The average particle size of the sedimentation silica is 5 μ m and above and 25 μ Below m, The rubber composition includes a plurality of agglomerated particles composed of the white filler, The ratio of the white filler to 100 parts by mass of the rubber is 50 parts by mass or more and 100 parts by mass or less, The rubber composition has a slope dEhys / dEin of an approximate straight line representing the relationship between input energy Ein and hysteresis loss Ehys in a tensile cycle test of 0.6 or more and less than 1, The rubber composition has a gel fraction of 50% to 80% and a complex elastic modulus of 30 MPa to 90 MPa, The complex elastic modulus is measured by the following dynamic viscoelasticity test method, that is, Take a rectangular test piece with a length of 33±3mm, a width of 5±0.3mm, and a thickness of 2±0.3mm from the sole. The rectangular test piece was mounted on a dynamic viscoelasticity measuring device so that the distance between the chucks became 20±0.2 mm. The measurement mode was set to tensile mode with sine wave distortion, the load was set to automatic static load, and the dynamic strain was set to 5 μ m, tested at a frequency of 10 Hz, The test temperature for the dynamic viscoelasticity measurement was 25° C., and the rectangular test piece was kept in an environment of 25° C. for 12 hours or more and then subjected to the dynamic viscoelasticity test.

2. The rubber composition for shoe soles according to claim 1, wherein The rubber composition has a loss tangent of 0.12 or more.

3. The rubber composition for shoe soles according to claim 1 or 2, wherein The base rubber includes any one of styrene-butadiene rubber, styrene-based thermoplastic resin, natural rubber, isoprene rubber, and isobutylene-isopropylene rubber.

4. A shoe sole, characterized in that: The invention is composed of a rubber composition comprising a base rubber, a liquid rubber and an inorganic filler. In the rubber composition, Part or all of the inorganic filler is a white filler, The white filler is precipitated silica. The average particle size of the sedimentation silica is 5 μ m and above and 25 μ Below m, The rubber composition includes a plurality of agglomerated particles composed of the white filler, The ratio of the white filler to 100 parts by mass of the rubber is 50 parts by mass or more and 100 parts by mass or less, The rubber composition has a slope dEhys / dEin of an approximate straight line representing the relationship between input energy Ein and hysteresis loss Ehys in a tensile cycle test of 0.6 or more and less than 1, The rubber composition has a gel fraction of 50% to 80% and a complex elastic modulus of 30 MPa to 90 MPa, The complex elastic modulus is measured by the following dynamic viscoelasticity test method, that is, Take a rectangular test piece with a length of 33±3mm, a width of 5±0.3mm, and a thickness of 2±0.3mm from the sole. The rectangular test piece was mounted on a dynamic viscoelasticity measuring device so that the distance between the chucks became 20±0.2 mm. The measurement mode was set to tensile mode with sine wave distortion, the load was set to automatic static load, and the dynamic strain was set to 5 μ m, tested at a frequency of 10 Hz, The test temperature for the dynamic viscoelasticity measurement was 25° C., and the rectangular test piece was kept in an environment of 25° C. for 12 hours or more and then subjected to the dynamic viscoelasticity test.

5. The sole according to claim 4, wherein: The rubber composition has a loss tangent of 0.12 or more.

6. The shoe sole according to claim 4 or 5, wherein: The base rubber includes any one of styrene-butadiene rubber, styrene-based thermoplastic resin, natural rubber, isoprene rubber, and isobutylene-isopropylene rubber.

7. A shoe, characterized in that: A shoe sole according to any one of claims 4 to 6 is provided.

8. The shoe according to claim 7, wherein: The shoes are mountaineering shoes.

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