SHOE SOLE ELEMENT AND SHOE

Abstract

A shoe sole element is provided which is formed such that at least part of its outer surface serves as a ground contact surface, and which contains an elastomeric substrate and a plurality of particles distributed over the elastomeric substrate, wherein the material of the plurality of particles is at least a material selected from the group consisting of silicone, polyurethane, polystyrene, polyolefin and polyvinyl acetate.

Description

TECHNICAL FIELD

[0001] The present invention relates, for example, to a shoe sole element and a shoe containing the shoe sole element. STATE OF THE ART

[0002] Conventionally, a shoe sole element that has grip on a wet road surface and a shoe that includes the shoe sole element are known.

[0003] For example, a shoe sole element is known that contains a rubber composition containing rubber and activated carbon (PTL 1). The shoe sole element described in PTL 1 provides good grip on wet road surfaces, i.e., it is slip-resistant. CITATION LISTPatent literature

[0004] [PTL 1] International Publication No. 2021 / 176685 DISCLOSURE OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] Although the above-mentioned shoe sole element is known as a shoe sole element that has grip on wet road surface, that is, it is slip-resistant, there is a continuous demand for a shoe sole element with advantageous grip (slip resistance) on a wet road surface.

[0006] In view of the above-mentioned requirement, it is an object of the present invention to provide a shoe sole element having favorable grip (slip resistance) on a wet road surface and a shoe incorporating the shoe sole element. MEANS TO SOLVE THE PROBLEMS

[0007] A shoe sole element according to the present invention is a shoe sole element having an outer surface, at least a part of which serves as a ground contact surface, the shoe sole element comprising an elastomer substrate and a plurality of particles distributed in the elastomer substrate wherein a material for the particles is at least one selected from the group consisting of a silicone, a polyurethane, a polystyrene, a polyolefin, and a polyvinyl acetate, and is different from a material for the elastomer substrate.

[0008] A shoe according to the present invention includes the shoe sole element. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing the appearance of an example of a shoe sole element and a shoe according to an embodiment. Fig. 2 is a schematic cross-sectional view showing a cross section of the example of the shoe sole member according to the embodiment along a vertical direction when the shoe is worn. Fig.3 is a schematic cross-sectional view showing a cross section of another example of the shoe sole member according to the embodiment along a vertical direction when the shoe is worn. Fig. 4A is a photograph showing the surface condition of a shoe sole element in a test sample observed with an electron microscope. Fig. 4B is a photograph showing the surface condition of a shoe sole element in another test sample observed with an electron microscope. Fig. Figure 4C is a photograph showing the surface condition of a shoe sole element in another test sample observed with an electron microscope. Fig. Figure 5 is a graph showing the relationship between particle content and friction coefficient of shoe sole elements in a variety of test examples. Fig.Figure 6 is a graph showing the relationship between the tensile elastic modulus and the friction coefficient of the shoe sole elements in the test samples. Fig. Figure 7 is a graph showing the relationship between the Durometer A hardness and the friction coefficient of the shoe sole elements in the test samples. Fig. Figure 8 is a graph showing the relationship between the average particle diameter of the particles and the friction coefficient of the shoe sole elements in the test samples. Fig. 9 is a schematic cross-sectional view schematically showing a state in which a ground-contacting surface of an example of the shoe sole member according to the embodiment is brought into contact with the ground in a lubricating environment. Fig. 10 is a schematic view showing a state of a reference experiment. Fig.11 shows photos of the visualized results of the reference experiment. Fig. 12 shows photos of the visualized results of the reference experiment. Fig. Figure 13 is a graph showing the results of the reference experiment. Fig. Figure 14 is a graph showing the results of the reference experiment. DESCRIPTION OF THE EMBODIMENTS

[0009] Hereinafter, an embodiment of a shoe sole element and a shoe according to the present invention will be described with reference to the drawings.

[0010] A shoe 100 of the present embodiment includes a shoe sole element 10 of the present embodiment. The shoe sole element 10 of the embodiment may have an outer surface, at least a portion of which serves as a ground contact surface. In one example of the embodiment, the shoe sole element 10 may, for example, be an outsole 2, as shown in Fig.1 and Fig. 2. The shoe sole element 10 of the embodiment may be the entire outsole or a part of the outsole. In another example of the embodiment, for example, a part of the shoe sole element 10 may be arranged on the sole side of the wearer and not on the outsole 2, as in Fig. 3. For example, the shoe sole element 10 may be a midsole 3 having a ground-contacting surface. Since each view in the drawings is a schematic view, the aspect ratio of a fabric depicted in the schematic view may not necessarily correspond to that of an actual fabric.

[0011] When the shoe sole member 10 has a plate shape, the maximum thickness of the shoe sole member 10 is not particularly limited and may be, for example, 1 mm or more and 20 mm or less.

[0012] The shoe sole element 10 of the embodiment includes an elastomer substrate and a plurality of particles dispersed in the elastomer substrate. The material for the particles is at least one selected from the group consisting of a silicone, a polyurethane, a polystyrene, a polyolefin, and a polyvinyl acetate. In other words, the particles include at least one selected from the group consisting of a silicone, a polyurethane, a polystyrene, a polyolefin, and a polyvinyl acetate.

[0013] The Durometer A hardness of the shoe sole member 10 is preferably 80 or less. When the Durometer A hardness is 80 or less, the grip of the shoe sole member 10 is improved. The Durometer A hardness is preferably 75 or less, more preferably 70 or less, and further preferably 65 or less. The Durometer A hardness may be 40 or more or 50 or more. The Durometer A hardness is measured according to JIS K6253-3:2012. The measurement temperature is 23°C.

[0014] The tensile elastic modulus of the shoe sole member 10 is preferably 15 MPa or less. When the tensile elastic modulus is 15 MPa or less, the grip of the shoe sole member 10 on a wet road surface can be improved. The tensile elastic modulus is preferably 10 MPa or less, and more preferably 8 MPa or less. The tensile elastic modulus may be 3 MPa or more. The tensile elastic modulus is measured according to JIS K6251:2017. Specifically, the tensile elastic modulus is calculated from the slope of a stress-strain curve at an initial strain of 5% during strain using a No. 2 dumbbell shape. The measurement temperature is 23°C.

[0015] For example, increasing the mass ratio of silica (as described later) to a rubber component in a blend composition for producing the shoe sole member 10 can improve the durometer A hardness and tensile elastic modulus of the shoe sole member 10. Conversely, decreasing the mass ratio of silica (as described later) to the rubber component can decrease the durometer A hardness and tensile elastic modulus of the shoe sole member 10.

[0016] The shoe sole member 10 preferably contains 1 vol% or more and 5 vol% or less of the particles. When the shoe sole member 10 contains 1 vol% or more of the particles, the grip of the shoe sole member 10 on a wet road surface can be improved. On the other hand, when the shoe sole member 10 contains 5 vol% or less of the particles, the strength and wear resistance of the shoe sole member 10 can be increased.

[0017] The shoe sole element 10 may contain 2 vol% or more of the particles. The shoe sole element 10 may contain 4 vol% or less of the particles.

[0018] The content (vol%) of particles in the shoe sole 10 is determined by the following equation from the volumes of the elastomer substrate and the particles, which are calculated based on the amounts of the mixed elastomer substrate and the mixed particles. Content (vol%) of a plurality of particles = [(Volume of a plurality of particles) / (Volume of the elastomer substrate + Volume of the particles)] × 100

[0019] In the above equation, the volumes of the elastomer substrate and the particles are calculated according to the equation (volume) = (mass) / (density or specific gravity). For example, the volume (unit: cm 3 ) of particles is calculated by dividing the total amount (unit: g) of particles by the density or specific gravity (unit: g / cm 3 ) is shared.

[0020] The content (vol%) of the particles in the shoe sole element 10 is determined by the following method in addition to the above-mentioned method. More specifically, a range of at least 0.01 mm 2 (10,000 µm 2 ) in a surface or cross-section of the shoe sole element 10. An electron microscope, an optical microscope, a microscope, or the like can be used as the observation means. A portion of the elastomer substrate is observed as a continuous phase, and the particles are observed as dispersion phases. The proportion of the total area of ​​the dispersion phases to the total area of ​​an observation object is calculated. The calculated value is the above-mentioned content (vol%). The content can be calculated by image analysis of an observed image.

[0021] The elastomer substrate may be a crosslinked product of a rubber composition containing at least one rubber component. Examples of the rubber component include isoprene rubber, styrene-butadiene rubber, butadiene rubber, ethylene-propylene-diene rubber (EPDM), natural rubber (NR), epoxidized natural rubber (ENR), acrylonitrile-butadiene rubber (also known as nitrile rubber or NBR), and chloroprene rubber (CR). The rubber composition may further contain a filler, a coupling agent, a crosslinker, or the like. The elastomer substrate may be formed from a thermoplastic elastomer material. The elastomer substrate may be a foam or a non-foam material.

[0022] Isoprene rubber is not particularly limited as long as it is a rubber obtained from an isoprene polymer. Isoprene rubber generally has a cis-1,4-polyisoprene structure in the molecule. Isoprene rubber can have a 1,2-polyisoprene structure, a 3,4-polyisoprene structure, a 1,2-polyisoprene structure, or a trans-1,4-polyisoprene structure in the molecule.

[0023] Styrene-butadiene rubber is not particularly limited as long as it is a rubber obtained from a copolymer of styrene and butadiene. For example, styrene-butadiene rubber is a rubber obtained from a copolymer of styrene and 1,3-butadiene.

[0024] The styrene content in the styrene-butadiene rubber is preferably 20 mass% or more, preferably 30 mass% or more, and more preferably 40 mass% or more. The styrene content may be 60 mass% or less or 50 mass% or less. The styrene content is determined according to JIS K6239.

[0025] As the styrene-butadiene rubber, a styrene-butadiene rubber obtained by emulsion polymerization, a styrene-butadiene rubber obtained by solution polymerization, or the like can be used. The styrene-butadiene rubber is preferably a styrene-butadiene rubber obtained by solution polymerization, in which the block arrangement or random arrangement in the molecule is properly adjusted by living polymerization using an organolithium catalyst or the like. For example, the number average molecular weight of the styrene-butadiene rubber may be about 10,000 or more and about 500,000 or less.

[0026] Butadiene rubber is not particularly limited as long as it is a rubber obtained from a butadiene polymer. For example, the butadiene rubber can be a so-called low-cis butadiene rubber or high-cis butadiene rubber. In low-cis butadiene rubber, one main unit constituting a molecular chain is a trans-1,4 unit, and another unit is a 1,2 unit (vinyl unit) or a cis-1,4 unit. In high-cis butadiene rubber, 80% or more of a unit constituting a molecular chain is a cis-1,4 unit. High-cis butadiene rubber is preferred.

[0027] The butadiene rubber may be a butadiene rubber other than the general butadiene rubber mentioned above. Examples of butadiene rubber include butadiene rubbers containing functional groups, in which a functional group such as a hydroxy group, a carboxyl group, an acrylic group, or an isocyanate group is introduced at the end of the molecule.

[0028] Ethylene-propylene-diene rubber (EPDM) is not particularly limited as long as it is a rubber obtained from a copolymer of ethylene, propylene, and diene. 5-ethylidene-2-norbornene (ENB) is generally used as the diene in ethylene-propylene-diene rubber (EPDM). Dicyclopentadiene (DCP) or 1,4-hexadiene (HD) can also be used as part of the diene. The mass ratio of ethylene to propylene, ethylene:propylene, can be, for example, 0.1 to 9:1. In other words, the copolymerization ratio can be 10 parts by mass or more of ethylene to 100 parts by mass of propylene. The mass ratio of the copolymerization of the total amount of ethylene and propylene to the amount of diene, (ethylene and propylene) : diene, can be, for example, 4 to 99:1.In other words, the copolymerization ratio may be a copolymerization ratio of 4 parts by mass or more and 99 parts by mass or less of total ethylene and propylene to 1 part by mass of diene.

[0029] The elastomer substrate may contain at least one selected from the group consisting of a crosslinked isoprene rubber, a crosslinked styrene-butadiene rubber, a crosslinked butadiene rubber, a crosslinked ethylene-propylene-diene rubber, a crosslinked natural rubber, a crosslinked epoxidized natural rubber, a crosslinked acrylonitrile-butadiene rubber (aka: nitrile rubber), a crosslinked chloroprene rubber, a polystyrene-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, a polybutadiene-based thermoplastic elastomer, and an ethylene-vinyl acetate copolymer (EVA).

[0030] The content of the rubber component (including isoprene rubber, styrene-butadiene rubber, butadiene rubber, ethylene-propylene-diene rubber, and the like) in the rubber composition is preferably 30 mass% or more, and more preferably 40 mass% or more. Therefore, the shoe sole member 10 can be moderately soft. Accordingly, the shoe 100 with the shoe sole member 10 can have a favorable fit to the wearer's sole and advantageous walking flexibility.

[0031] The content of the rubber component in the rubber composition may be 90 mass% or less or 80 mass% or less.

[0032] In the embodiment, the rubber composition may contain silica (silica particles) as a filler. The silica may be dry silica or wet silica. The silica contained in the rubber composition is granular.

[0033] The dry silica is obtained in a primary particle-like form by a dry process, such as a combustion process or an arc process. The dry silica is preferably fumed silica. The average particle diameter of the dry silica is preferably 5 nm or more and 50 nm or less.

[0034] The wet silica is obtained as aggregated particles by a wet process such as a sedimentation process or a gelation process.

[0035] The rubber composition preferably contains the silica in an amount of 20 parts by mass or more and 100 parts by mass or less based on a total amount of the rubber component (styrene-butadiene rubber, butadiene rubber, isoprene rubber, EPDM and the like) of 100 parts by mass.

[0036] In the embodiment, the rubber composition preferably contains at least one coupling agent and one crosslinker, and more preferably contains both the coupling agent and the crosslinker.

[0037] The coupling agent is a compound having at least one alkoxysilane structure in its molecule. The rubber composition preferably contains the coupling agent in an amount of 5 parts by mass or more and 15 parts by mass or less, based on 100 parts by mass of the silica.

[0038] Examples of the coupling agent are a mercapto-based silane coupling agent, a monosulfide-based silane coupling agent, an epoxy-based silane coupling agent, and a tetrasulfide-based silane coupling agent.

[0039] The crosslinker, which may be included in the rubber composition, is a compound that accelerates the crosslinking reaction of the rubber component in the rubber composition. Examples of crosslinkers include an organic peroxide and sulfur.

[0040] Examples of organic peroxides include 1,1-bis(1,1-dimethylethylperoxy)cyclohexane, 1,1-bis(1,1-dimethylbutylperoxy)cyclohexane, butyl 4,4-bis[(t-butyl)peroxy]petanoate, dicumyl peroxide, t-butyl-α-cumyl peroxide, 2,5-Dimethyl-2,5-bis(t-butylperoxy)hexane, 2,5-bis(t-butylperoxy)-2,5-dimethyl-3-hexyne, dibenzoyl peroxide, bis(4-methylbenzoyl) peroxide, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, t-butyl peroxybenzoate, t-hexyl peroxybenzoate and 1,1-bis(t-butyldioxy)-3,3,5-trimethylcyclohexane.

[0041] The rubber composition may contain sulfur as a crosslinking agent and a crosslinking accelerator to accelerate a crosslinking reaction with sulfur. Examples of the crosslinking accelerator include a thiazole-based crosslinking accelerator and a thiuram-based crosslinking accelerator.

[0042] Examples of thiazole-based crosslinking accelerators include 2-mercaptobenzothiazole, zinc 2-mercaptobenzothiazole, 2-mercaptothiazoline, dibenzothiazyl disulfide (di-2-benzothiazole disulfide), 2-(2,4-dinitrophenylthio)benzothiazole, 2-(N,N-diethylthiocarbamoylthio)benzothiazole, 2-(2,6-dimethyl-4-morpholinothio)benzothiazole, and 2-(4'-morpholinodithio)benzothiazole.

[0043] Examples of thiuram-based crosslinking accelerators include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide, tetramethylthiuram monosulfide, and dipentamethylenethiuram disulfide.

[0044] The rubber composition may contain a fatty acid. The fatty acid may be in the form of a salt, e.g., a metal salt or an ammonium salt. Examples of the fatty acid include lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. Examples of a fatty acid salt include a magnesium salt, a calcium salt, and a zinc salt.

[0045] In the embodiment, the rubber composition preferably contains the silicon dioxide in an amount of 40 parts by mass or more and 80 parts by mass or less, based on 100 parts by mass of the rubber component. The rubber composition may contain carbon black particles, calcium carbonate particles, magnesium carbonate particles, or the like as fillers.

[0046] In the shoe sole element 10 of the embodiment, the particles are distributed in the elastomer substrate as described above. The shape of the particles is not particularly limited. The particles may, for example, have a spherical shape, a polygonal shape, or an amorphous shape.

[0047] At least a portion of the particles preferably has a spherical shape. At least half of the particles further preferably have a spherical shape. The term "spherical shape" includes a true spherical shape and an ellipsoidal shape, such as a prolate spheroid or an oblate spheroid.

[0048] The proportion of spherical particles relative to the total particles is preferably 80% or more, preferably 90% or more, and more preferably 99% or more.

[0049] The particle shapes are determined from the observation image, in which the cut surface of the shoe sole element 10 is observed with an electron microscope. Specifically, at least 50 of the particles observed in the observation image are observed, and the particle shapes are determined by visual inspection. The electron microscope can be a transmission electron microscope or a scanning electron microscope.

[0050] The average aspect ratio of the particles is preferably in the range of 1:1 to 1:10. In other words, the ratio of the maximum diameter (longest diameter) of each of the particles to the minimum diameter (shortest diameter) thereof is preferably 1 or more and 10 or less on average. When the average aspect ratio is 10 or less, the grip of the shoe sole member 10 on a wet road surface can be improved. More specifically, an average aspect ratio of 10 or less reduces the average of the differences between the maximum diameters and the minimum diameters of the particles, and therefore, when the ground-contacting surface of the shoe sole member 10 comes into contact with a wet road surface, the particles are more likely to be separated from the elastomer substrate near the ground-contacting surface.Accordingly, a void (pore) is formed at a portion where each of the particles is separated on a surface portion of the elastomer substrate. Thus, higher grip is achieved (as described in detail later). The average aspect ratio is preferably in the range of 1:1 to 1:5, and more preferably in the range of 1:1 to 1:3.

[0051] The proportion of the particles having the above-mentioned aspect ratio relative to the total particles is preferably 80% or more, preferably 90% or more, and more preferably 99% or more.

[0052] The average aspect ratio of the particles is determined from the observation image in which the cross-sectional surface of the shoe sole element 10 is observed with an electron microscope. Specifically, at least 50 particles of the particles observed in the observation image are observed, and the minimum diameters (shortest diameters) and maximum diameters (longest diameters) of the particles are measured. The aspect ratio (the ratio of the maximum diameter to the minimum diameter) of each of the particles is calculated. The arithmetic mean of the calculated aspect ratios is calculated and set as the average aspect ratio. The aspect ratio of each particle is measured regardless of the shape of the particles. The electron microscope can be a transmission electron microscope or a scanning electron microscope.

[0053] The average particle diameter of the particles is preferably 1 μm or more, and more preferably 3 μm or more. The average particle diameter of the particles is preferably 100 μm or less, and more preferably 50 μm or less. When the average particle diameter is 1 μm or more, the above-mentioned phenomenon in which the particles are separated from the elastomer substrate is more likely to occur. When the average particle diameter is 100 μm or less, this has the advantage of maintaining the strength of the shoe sole member 10 higher.

[0054] The average particle diameter of the particles is determined from the observation image in which the cross-sectional surface of the shoe sole element 10 is observed with an electron microscope. Specifically, the maximum diameters of at least 50 particles observed in the observation image are measured, and the arithmetic mean of the measured values ​​is calculated as the average particle diameter. The electron microscope can be a transmission electron microscope or a scanning electron microscope.

[0055] The material for the particles dispersed in the elastomer substrate is at least one selected from the group consisting of a silicone, a polyurethane, a polystyrene, a polyolefin, and a polyvinyl acetate, as described above. The entire material for each of the particles does not need to be the above-mentioned material, as long as at least a portion of each of the particles contains the material. For example, each of the particles may contain a core portion and a surface layer portion covering the core portion, and both the core portion and the surface layer portion may contain the above-mentioned material.

[0056] Examples of silicones include a polydimethylsiloxane or a modified product thereof, a silicone rubber and a silicone resin.

[0057] Examples of polyurethane include polyurethane elastomers such as a thermosetting polyurethane and a thermoplastic polyurethane.

[0058] Examples of polystyrene include general-purpose polystyrene (GPPS) and high-impact polystyrene (HIPS).

[0059] Examples of polyolefins include polyethylene, polypropylene, and poly(ethylene / propylene). The polyethylene can be low-density polyethylene or high-density polyethylene. The polypropylene can be isotactic polypropylene, syndiotactic polypropylene, or atactic polypropylene.

[0060] Examples of polyvinyl acetate include an ethylene-vinyl acetate copolymer.

[0061] The material for the elastomer substrate is different from the material for the particles. The term "the material is different from" means that when comparing a polymer compound that forms the elastomer substrate and a polymer compound that forms the respective particles, recurring structural units in the molecules differ from each other. If the elastomer substrate or the particles are each formed from a mixture of polymer compounds, a polymer compound that accounts for the majority of the polymer compounds contained in the elastomer substrate is compared with a polymer compound that accounts for the majority of the polymer compounds contained in the particles. If recurring structural units in the molecules differ from each other in the comparison, the material for the elastomer substrate is different from the materials for the particles.

[0062] Specifically, when comparing a monomer composition for synthesizing one of the compared polymer compounds with a monomer composition for synthesizing the other, if at least one monomer in the first monomer composition differs from at least one monomer in the second monomer composition, the polymer compound is judged to be different from the other polymer compound. Even if the first monomer composition and the second monomer composition each contain the same monomer, the above judgment is not affected.

[0063] To distinguish the monomer units that make up the polymer compounds, a method for analyzing the polymer compounds by Fourier transform infrared spectroscopy (FT-IR), pyrolysis gas chromatography mass spectrometry (Py-GCMS) or the like can be applied.

[0064] As a method for separating the particles from the shoe sole member 10, for example, a method is used in which the particles are collected with tweezers or the like while observing the surface or cross-section of the shoe sole member 10 with an optical microscope or a microscope. When the elastomer substrate is an uncrosslinked product (uncrosslinked rubber), for example, a method is used in which only the elastomer substrate is dissolved in an organic solvent to collect the undissolved particles.

[0065] The shoe sole member 10 of the embodiment may further contain a component other than the above-mentioned components, as long as the effects of the present invention are not significantly impaired. The elastomer substrate (rubber composition) may contain, for example, a hardness adjuster such as a paraffinic or naphthene-based process oil, a tackifier such as a terpene resin, an anti-aging agent, a processing aid, an inorganic filler, an antibacterial agent, a perfume, or the like.

[0066] The shoe sole member 10 of the embodiment is the shoe sole member 10 having an outer surface, at least a portion of which serves as a ground contact surface, and includes the elastomer substrate and the particles dispersed in the elastomer substrate. The material for the particles is at least one selected from the group consisting of a silicone, a polyurethane, a polystyrene, a polyolefin, and a polyvinyl acetate. In this embodiment, the material of the elastomer substrate is different from that of the particles, so that the particles near the ground contact surface of the shoe sole member 10 easily detach from the elastomer substrate upon contact with a wet road surface. Accordingly, a void (pore) is formed at a portion where each of the particles is detached on a surface portion of the elastomer substrate.Furthermore, since the elastomer substrate is rubber-elastic, the elastomer substrate is easily deformed by pressure when the shoe sole member 10 is brought into contact with the ground. Accordingly, a gas is expelled from the formed void (pore), and an area near the void can be compressed by atmospheric pressure according to the amount of expelled gas. This state can be maintained for a relatively long time when the ground is wetted with water. Therefore, wet grip is considered to be exerted. This can improve the grip of the shoe sole member 10 on a wet road surface. If the water-repellent effect of the elastomer substrate is relatively high, a gas may have a higher affinity to the elastomer substrate than water.It is therefore assumed that the balance between the surface free energy of the elastomer substrate and that of the water and gas also creates a force that displaces the water between the elastomer substrate and the road surface by the gas escaping from the cavity (pore). Accordingly, it is assumed that the elastomer substrate can be easily brought into direct contact with the road surface, and the grip can be improved.

[0067] The Durometer A hardness of the shoe sole member 10 is preferably 80 or less, or the tensile elastic modulus of the shoe sole member 10 is preferably 15 MPa or less. As described above, the shoe sole member 10 becomes softer, so that the elastomer substrate is easier to deform under pressure. Accordingly, it is expected to exert higher grip. As a result, the grip of the shoe sole member 10 on a wet road surface can be further improved. The shoe sole member 10 preferably contains 1 vol% or more and 5 vol% or less of the particles. When the shoe sole member 10 contains the particles in an amount falling within the above-mentioned range, the grip of the shoe sole member 10 on a wet road surface can be improved while maintaining the strength of the shoe sole member 10 relatively high.

[0068] At least some of the particles preferably have a spherical shape. At least some of the particles have a spherical shape, such as a true sphere, an elongated sphere, or a flattened sphere, so that the above-mentioned phenomenon of the particles separating from the elastomer substrate occurs more easily. As a result, the grip of the shoe sole element 10 on a wet road surface can be improved.

[0069] The average aspect ratio of the particles is preferably in the range of 1:1 to 1:10. The aspect ratio is 10 or less so that the above-mentioned phenomenon of the particles separating from the elastomer substrate occurs more easily. As a result, the grip of the shoe sole (10) on a wet road surface can be improved.

[0070] The average particle diameter of the particles is preferably 1 µm or more and 100 µm or less. When the average particle diameter of the particles is within this range, the grip of the shoe sole member 10 on a wet road surface can be improved while maintaining the strength of the shoe sole member 10 relatively high.

[0071] Next, a method for manufacturing the shoe sole member and a method for manufacturing the shoe according to the embodiment will be described.

[0072] The shoe sole element of the embodiment is manufactured, for example, by the following steps: (I) a step of mixing raw materials such as a rubber component, a filler and a silane coupling agent (mixing step); (II) a step of adding a crosslinking agent to the mixture prepared by the mixing, further mixing the mixture, and forming a sheet from the resulting rubber composition to produce a preformed sheet in an uncrosslinked state (sheet forming step); and (III) a step of heating the preformed sheet under application of a compressive force to produce the shoe sole member 10 which is a crosslinked product of the rubber composition (crosslinking treatment step).

[0073] The shoe of the embodiment is manufactured, for example, by the following further steps: (IV) a step of pretreating a surface of the manufactured shoe sole element 10, if necessary (pretreatment step); (V) a step of disposing an adhesive between the manufactured shoe sole element 10 and another previously manufactured element, such as a midsole, and applying a compressive force in a thickness direction to a laminate of the shoe sole element 10 and the other element to bond the elements (bonding step); and (VI) a step of further connecting an upper member and the like to assemble a shoe (assembling step).

[0074] In the mixing step (I), for example, the above-mentioned raw materials are kneaded at a temperature of approximately 110°C to approximately 150°C using a kneader, such as a Banbury mixer or a pressure kneader.

[0075] In the sheet-forming step (II), the rubber composition is supplied, for example, to a calender roll or the like and further kneaded by the calender roll. The kneaded rubber composition is formed into a sheet using the calender roll or the like to produce a preformed sheet in an uncrosslinked state.

[0076] In the crosslinking treatment step (III), for example, the preformed sheet for the shoe sole element 10 placed in a mold is heat-pressed using a heat press equipped with the mold. Thus, the preformed sheet is molded into the desired shape in the mold. At the same time, the rubber composition of the preformed sheet for the shoe sole element 10 is subjected to crosslinking treatment using the heat press to produce the shoe sole element 10 formed from a crosslinked product (crosslinked rubber).

[0077] In the pretreatment step (IV), at least one of the surfaces to be bonded of the shoe sole element 10 and the surface to be bonded of the other element is pretreated, if necessary, to improve the bonding strength after bonding. For example, a surface polishing treatment or a treatment for applying a pretreatment liquid containing an organic solvent is selected as the pretreatment.

[0078] In the bonding step (V), for example, an adhesive is applied to one surface of the shoe sole member 10. Then, while a surface to which the adhesive is applied is opposed to a surface of the other sheet-like member, a compressive force is applied in the thickness direction to the laminate of the shoe sole member 10 and the other member. Thus, the shoe sole member 10 is bonded to the other member via the adhesive. A general urethane resin-based adhesive can be used as the adhesive.

[0079] The shoe 100 with the shoe sole element 10 as described above is used, for example, for a sports shoe. Furthermore, the shoe 100 can be used, for example, for a sneaker.

[0080] The shoe sole element and the shoe of the present invention are as described in the above-mentioned illustrative examples, but the present invention is not limited to the illustrative embodiment. In the present invention, a variety of forms can be adopted for a general shoe sole element, a general shoe, and the like, as long as the effects of the present invention are not impaired.

[0081] The subject matters disclosed herein include the following inventions. (1) Shoe sole element with an outer surface, at least a part of which serves as a ground contact surface, the shoe sole element contains an elastomer substrate and a plurality of particles distributed in the elastomer substrate, wherein a material for the particles includes at least one selected from the group consisting of a silicone, a polyurethane, a polystyrene, a polyolefin, and a polyvinyl acetate, and is different from a material for the elastomer substrate. (2) The shoe sole member according to (1), wherein the Durometer A hardness is 80 or less. (3) The shoe sole member according to (1) or (2), wherein a tensile elastic modulus is 15 MPa or less. (4) The shoe sole member according to any one of (1) to (3), wherein the particles are contained in an amount of 1 vol% or more and 5 vol% or less. (5) The shoe sole element according to any one of (1) to (4), wherein at least a part of the particles has a spherical shape. (6) The shoe sole element according to any one of (1) to (5), wherein the average aspect ratio of the particles is in the range of 1:1 to 1:10. (7) The shoe sole member according to any one of (1) to (6), wherein the particles have an average particle diameter of 1 µm or more and 100 µm or less. (8) The shoe sole member according to any one of (1) to (7), wherein the elastomer substrate contains at least one selected from the group consisting of a crosslinked isoprene rubber, a crosslinked styrene-butadiene rubber, a crosslinked butadiene rubber, a crosslinked ethylene-propylene-diene rubber, a crosslinked natural rubber, a crosslinked epoxidized natural rubber, a crosslinked acrylonitrile-butadiene rubber (alias: nitrile rubber), a crosslinked chloroprene rubber, a polystyrene-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, a polybutadiene-based thermoplastic elastomer, and an ethylene-vinyl acetate copolymer (EVA). (10) Shoe containing the shoe sole element according to one of (1) to (9). Examples

[0082] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to the examples.

[0083] A shoe sole element was manufactured as described below. Table 1 and Table 2 show the raw materials used to manufacture the shoe sole elements in the test examples and the compound compositions of the rubber compositions used to manufacture the shoe sole elements.

[0084] The raw materials for the production of shoe soles are described below. <Hauptrohstoffe für Elastomer-Substrat> (a) Rubber component (Isoprene rubber: IR) Product name “Nipol IR2200” (manufactured by Zeon Corporation) (b) Process oil product name “JOMO Process P200” (manufactured by JX Nippon Oil & Energy Corporation) (c) Silicon dioxide (wet silicon dioxide) product name “ULTRASIL VN3” (manufactured by Degussa AG) average particle diameter: 18 nm / specific surface area by BET method: 170 (m 2 / G ) (d) Coupling agent (tetrasulfide-based coupling agent) Chemical name: Bis[3-(triethoxysilyl)propyl]tetrasulfide Product name “Si-69” (manufactured by Degussa Japan Co., Ltd.) (e) Fatty acid (stearic acid, commercially available product) (f) Zinc oxide, product name “active zinc oxide” (manufactured by Honjo Chemical Corporation) (g) Crosslinking co-agent product name “ACTING SL”, a compound of dicyclohexylamine and ethylene glycol (manufactured by API Corporation) (h) Polyethylene glycol 4000 (commercial product) (i) Anti-aging agent product name “OZONOC33” (manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.) (j) Antioxidant (dibutylhydroxytoluene, commercially available product) (k) Titanium oxide (TiO)2 S: Crosslinker (sulfur) Product name "fine sulfur 200 mesh" (manufactured by Hosoi Chemical Industry Co., Ltd.) DM: Crosslinking accelerator (thiazole-based crosslinking accelerator) Chemical name: Di-2-benzothiazolyl disulfide Product name “NOCCELER DM-P” (manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.) TS: Crosslinking accelerator (thiuram-based crosslinking accelerator) Chemical name: Tetramethylthiuram monosulfide Product name “NOCCELER TS” (manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.) <Rohstoffe für Partikel> (X) Silicone rubber powder (average particle diameter: 5 µm, spherical, aspect ratio: 1:1) Product name “KMP-597” (manufactured by Shin-Etsu Chemical Co., Ltd.) (Y) Silicone rubber powder (average particle diameter: 13 µm, spherical, aspect ratio: 1:1) Product name “KMP-598” (manufactured by Shin-Etsu Chemical Co., Ltd.) (Test examples 1 to 15)

[0085] The components were mixed according to the compound compositions listed in Table 1 and Table 2 to prepare each rubber composition (uncured state) for a shoe sole element. Subsequently, the rubber compositions were each heat-pressed at 160 °C and 15 MPa for 10 minutes and molded to obtain a crosslinked product. Thus, a shoe sole element (thickness: 2 mm) was manufactured. [Table 1] Unit: parts by mass (in parts, vol%) Test Example 1 Test Example 2 Test Example 3 Test Example 4 Test Example 5 Test Example 6 Test Example 7 Test Example 8 Test Example 9 (a) 100,0 100,0 100,0 100,0 100,0 100,0 100,0 100,0 100,0 (b) 20,0 20,0 20,0 20,0 20,0 20,0 20,0 20,0 20,0 (c) 44,0 51,0 60,0 69,0 80,0 60,0 60,0 44,0 51,0 (d) 4,4 5,1 6,0 6,9 8,0 6,0 6,0 4,4 5,1 (e) 2,0 2,0 2,0 2,0 2,0 2,0 2,0 2,0 2,0 (f) 5,0 5,0 5,0 5,0 5,0 5,0 5,0 5,0 5,0 (g) 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 (h) 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 (i) 0,5 0,5 0,5 0,5 0,5 0,5 0,5 0,5 0,5 (j) 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 (k) 35,0 36,1 37,2 38,3 39,7 37,2 37,2 35,0 36,1 s 2,00 2,00 2,00 2,00 2,00 2,00 2,00 2,00 2,00 DM 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 1,0 TS 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 (X) - - - - - 1,8 3,7 5,3 5,4 (Y) - - - - - - - - - Content of the particles - - - - - 1 vol.% 2 vol.% 3 vol.% 3 vol.% Physical property value Durometer hardness (A) 55 60 65 70 75 65 65 55 60 Tensile modulus of elasticity [MPa] 4,9 6,5 8,2 9,7 14,0 7,9 7,4 4,7 5,8 [Table 2] Unit: parts by mass (in parts, vol.%) Test Example 10 Test Example 11 Test Example 12 Test Example 13 Test Example 14 Test Example 15 (a) 100,0 100,0 100,0 100,0 100,0 100,0 (b) 20,0 20,0 20,0 20,0 20,0 20,0 (c) 60,0 69,0 80,0 60,0 60,0 60,0 (d) 6,0 6,9 8,0 6,0 6,0 6,0 (e) 2,0 2,0 2,0 2,0 2,0 2,0 (f) 5,0 5,0 5,0 5,0 5,0 5,0 (g) 1,0 1,0 1,0 1,0 1,0 1,0 (h) 1,0 1,0 1,0 1,0 1,0 1,0 (i) 0,5 0,5 0,5 0,5 0,5 0,5 (j) 1,0 1,0 1,0 1,0 1,0 1,0 (k) 37,2 38,3 39,7 37,2 37,2 37,2 S 2,00 2,00 2,00 2,00 2,00 2,00 DM 1,0 1,0 1,0 1,0 1,0 1,0 TS 0,1 0,1 0,1 0,1 0,1 0,1 (X) 5,6 5,8 6,0 7,5 9,5 - (Y) - - - - - 5,6 Contents of the 3 vol.% 3 vol.% 3 vol.% 4 vol.% 5 vol.% 3 vol.% particles Physical property value Durometer hardness (A) 65 70 75 65 65 65 Tensile modulus of elasticity [MPa] 7,6 8,7 12,5 7,8 7,3 7,5

[0086] For the shoe sole member sample prepared in each of the test examples, the physical properties, performance, and the like were measured as follows. <Physikalische Eigenschaften: Messung der Durometerhärte eines Schuhsohlenelementss>

[0087] The durometer hardness (Type A) was measured for the shoe sole element sample produced in each of the test examples. The measurement was based on "Vulcanized Rubber and Thermoplastic Rubber - Determination of Hardness - Part 3: Durometer Hardness (JIS K6253-3:2012)" and was conducted in an environment of 23°C. <Physikalische Eigenschaften: Messung des Zug-Elastizitätsmoduls des Schuhsohlenelements >

[0088] The tensile elastic modulus was measured for the shoe sole element sample produced in each of the test examples. The measurement was based on "Vulcanized Rubber and Thermoplastic Rubber - Determination of Tensile Properties (JIS K6251:2017)" and was conducted in an environment of 23°C. The tensile elastic modulus was calculated from the slope of a stress-strain curve at an initial strain of 5% during elongation using a No. 2 dumbbell shape. <Betrachtung der Oberfläche eines Schuhsohlenelements mit dem Elektronenmikroskop>

[0089] Fig. 4A to Fig.4C show observation images of the surfaces of the 2 mm thick sheet-like shoe sole elements (test samples) produced in Test Examples 3, 10, and 15, respectively. During the completion of sheet formation, the silicone rubber particles had already detached. A cavity (concave area) had formed in an area where the particles had detached. <Bewertung der Nassgriffigkeit: Messung des statischen Reibungskoeffizienten und des dynamischen Reibungskoeffizienten des Schuhsohlenelements >

[0090] In the water-lubricated state, the static friction coefficient and the sliding friction coefficient were each measured as follows. First, an aluminum cylinder body with a diameter of 10 mm and a width of 6 mm was prepared. Then, the side surface of the cylinder body was brought into contact with a surface of the respective test specimen for the measurement. During the measurement, the vertical load was set to 500 gf (4.91 N) and the sliding speed to 10.0 mm / s.

[0091] If the Durometer A hardness of the test sample (shoe sole element) is 65 and the average particle diameter of the particles is 5 µm, the influence of the particle content on the static friction coefficient and the dynamic friction coefficient is shown by a diagram in Fig.5 (Test Examples 3, 6, 7, 10, 13, and 14). Since the test samples (shoe sole element) contain silicone rubber particles, both the static friction coefficient and the sliding friction coefficient increase. At a content of 3 vol% or more and 4 vol% or less, the static friction coefficient and the sliding friction coefficient are particularly high.

[0092] At a particle content of 0 vol.% and an average particle diameter of 5 µm as well as a particle content of 3 vol.%, the influence of the elastic modulus (tensile elastic modulus) of the test specimen on the static friction coefficient and the sliding friction coefficient of the test specimen is shown in the diagrams in Fig. 6 and Fig.7 (Test Examples 1 to 5 and 8 to 12). An increase in the friction coefficient due to the mixed particles is particularly noticeable when the tensile elastic modulus of the test specimen (shoe sole member) is low or the hardness is low. When the tensile elastic modulus of the test specimen (shoe sole member) is 15 MPa or less, preferably 10 MPa or less, the friction coefficient is higher. When the Durometer A hardness of the test specimen (shoe sole member) is 80 or less, preferably 70 or less, the friction coefficient is higher.

[0093] When the Durometer A hardness of the test sample (shoe sole element) is 65 and the particles are mixed and unmixed, the static friction coefficient and the dynamic friction coefficient are shown by a diagram in Fig.8 (Test Examples 3, 10, and 15). Regardless of the average particle diameter, the particles mixed into the test sample (shoe sole element) increase the friction coefficient.

[0094] Increasing the proportion of silicone rubber particles in the test sample has only a minor influence on the tensile strength, tear strength and wear resistance of the test sample.

[0095] As from Fig. 5 to Fig. As can be seen in Figure 8, the grip (sliding resistance) of the shoe sole elements containing certain particles is higher on a wet road surface than that of the shoe sole elements that do not contain particles. The reason for the high grip (sliding resistance) on a wet road surface is as follows. As shown in Fig.As schematically shown in Figure 9, when the ground contact surface of the shoe sole member is brought into contact with the wet road surface, the particles near the ground contact surface of the shoe sole member are separated from the elastomer substrate. Thus, a hollow H (pore) is formed at a portion where each of the particles is separated on a surface portion of the elastomer substrate. In addition, since the elastomer substrate has rubber elasticity, the elastomer substrate is easily deformed by pressure when the shoe sole member 10 is brought into contact with the ground. Accordingly, a gas is ejected from the formed hollow H (pore), and a region near the hollow can be pressed by atmospheric pressure according to the amount of the ejected gas. This state can be maintained for a relatively long time under a wet situation with water (represented by W). Thus, the wet grip is considered to work.As a result, the grip of the shoe sole element 10 on a wet road surface can be improved. Since the elastomer substrate in each of the test examples described above has relatively high water-repellent properties, it is assumed that a gas has a higher affinity for the elastomer substrate than water. Therefore, it is assumed that, from the balance between the surface free energy of the elastomer substrate and that of the water and the gas, a force to displace the water located between the elastomer substrate and the road surface is also exerted by the gas escaping from the cavity H (pore). Accordingly, it is assumed that the elastomer substrate is easily brought into direct contact with the road surface, and the grip can be improved.

[0096] The results of the following reference test also show that the presence of the hollow H (pore) in the elastomer substrate increases the wet grip. <Referenzversuch: Bewertung der Nassgriffigkeit von Schuhsohlenelementen>

[0097] A hemispherical silicone rubber with a radius of curvature of 7.6 mm (product name "Sylgard 184", manufactured by Dow Corning Toray Co., Ltd.) was prepared as the rubber sample. A rubber sample with a surface portion machined to form a cubic depression (recess) with a side length of approximately 100 µm was prepared, and a rubber sample with a smooth apex portion was also prepared. A friction test was conducted between each of the rubber samples and a glass plate to evaluate the grip (dry and wet grip). The test was conducted with or without water lubrication at a vertical load of 0.0981 N and a sliding speed of 0.10 mm / s. The contact state between the rubber sample and the glass was visualized by both a total internal reflection method and a light interference method, as shown in Fig. 10 is shown. Fig. 11(a) and Fig. 11(b) shows the contact condition between the rubber sample and the glass when a 5.0 mm sliding was applied under non-lubricating conditions.

[0098] Fig. 11(a) shows the results when the rubber sample was used without a void on its surface, and Fig. Figure 11(b) shows the results when the rubber sample with a cavity on its surface was used. The black part shows the contact of the rubber sample with the glass surface, the white part the contact of the air with the glass surface. As in Fig. As can be seen from Figure 11, the contact of a part of the surface of the rubber sample with the glass surface can be confirmed regardless of the presence of the cavity on the surface of the rubber sample.

[0099] Fig. 12(a) and Fig.Figure 12(b) shows the contact state between the rubber sample and the glass when a 5.0 mm sliding was applied under water lubrication. The black area shows the state in which water is brought into contact with the glass. As in Fig. 12(a) and Fig. As can be seen in Figure 12(b), the presence of numerous air bubbles in the contact surface between the rubber sample and the glass can be confirmed by the depression formed on the surface of the rubber sample. Before the application of sliding, the air remains in the cavity, and after the application of sliding, the air forms air bubbles and diffuses into the contact surface.

[0100] Fig. 13 and Fig.Figure 14 shows the actual contact area and friction coefficient when a 5.0 mm sliding was applied under lubricated and unlubricated conditions, respectively. In the unlubricated condition, the indentation in the ground contact surface of the rubber sample results in a reduction in the actual contact area, but the indentation has little effect on the friction coefficient. However, under water lubrication conditions, the indentation in the ground contact surface of the rubber sample increases the actual contact area and friction coefficient by 37.7% and 27.4%, respectively. Therefore, when there is no cavity in the ground contact surface of the rubber sample, the presence of water in the contact surface reduces the friction coefficient under water lubrication conditions.In contrast, when there is a cavity in the ground contact surface of the rubber sample, the friction coefficient increases due to the presence of water in the contact surface under the water lubrication conditions. INDUSTRIAL APPLICABILITY

[0101] The shoe sole element of the present invention is suitable for use by being arranged on the bottom of a shoe. The shoe of the present invention is suitable for use on the foot of a wearer. The shoe of the present invention is suitable for use, for example, in an application as a sports shoe. DESCRIPTION OF REFERENCE NUMBERS 100 shoes 10 shoe sole element 11 Elastomer substrate 12 particles 2 outsole 3 Midsole 5 Upper element

Claims

[1] Shoe sole element with an outer surface, at least a part of which serves as a ground contact surface, wherein the shoe sole element comprises an elastomer substrate and a plurality of particles distributed in the elastomer substrate, wherein a material for the particles contains at least one of the group consisting of a silicone, a polyurethane, a polystyrene, a polyolefin and a polyvinyl acetate, and differs from a material for the elastomer substrate. [2] The shoe sole element according to claim 1, wherein the Durometer A hardness is 80 or less. [3] The shoe sole member according to claim 1 or 2, wherein the particles are contained in an amount of 1 vol% or more and 5 vol% or less. [4] Shoe sole element according to one of claims 1 to 3, wherein at least a part of the particles has a spherical shape. [5] Shoe sole element according to one of claims 1 to 4, wherein the average aspect ratio of the particles is in the range of 1:1 to 1:

10. [6] The shoe sole element according to any one of claims 1 to 5, wherein the particles have an average particle diameter of 1 µm or more and 100 µm or less. [7] Shoe comprising the shoe sole element according to one of claims 1 to 6.

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