Method for manufacturing shock-absorbing member for footwear

Abstract

To provide a footwear buffer member capable of rectifying separation from a sole member caused by flow deformation (creaping) while maintaining transparency and flexibility required of the footwear buffer member.SOLUTION: A method for manufacturing a footwear buffer member comprises: a step of obtaining a compact of a footwear buffer composition containing styrene thermoplastic elastomer; a step of applying a primer agent containing a styrene block copolymer to the surface of at least a part of the compact and forming a primer layer; a step of applying a coating agent containing a urethane resin to the surface of the primer layer and forming a roughly transparent protection coat layer; and a step of applying an electron beam from the outside of the protection coat layer. The styrene block copolymer contained in the primer agent used in the primer layer forming step is at least an acrylic modification styrene-butadiene-styrene block copolymer, and the application of the electron beam in the electron beam application step is carried out within the acceleration voltage range of 100-300 kV and the irradiation dose range of 100-300 kGy.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a shock-absorbing member for footwear used, for example, in shoe soles and shoe insoles. [Background technology]

[0002] In shoe design for fields requiring functionality, such as sports shoes, a shock-absorbing material with excellent shock-absorbing properties is incorporated into a sole member made of resin or the like. This type of shock-absorbing material is required to be lightweight so as not to hinder the user's movement, and also to have a high level of design, such as a transparent appearance, so that it is incorporated into the sole member in a manner that is visible from the outside so that its functionality can be appealed to consumers. For this reason, various shock-absorbing materials made of styrene-based thermoplastic elastomers, which have low specific gravity and transparency, have been proposed (Patent Documents 1 and 2).

[0003] These shock-absorbing components for footwear are bonded to a rubber-elastic sole member made of EVA or other materials. Both the shock-absorbing component and the sole member are subject to stress and deformation due to impacts and stresses during exercise. Since the adhesive surface between the shock-absorbing component and the sole member also expands and contracts, maintaining the adhesive state at the adhesive surface is important. However, the bonding between the shock-absorbing component and the sole member must be performed without impairing the transparency of the shock-absorbing component, which limits the adhesives, primers, and bonding methods that can be used. Furthermore, because the shock-absorbing component is incorporated into the sole member with a portion exposed so that it can be seen from the outside, the adhesive area between the shock-absorbing component and the sole member is also limited. Therefore, peeling of the adhesive is likely to occur at the boundary between the unglued exposed portion and the bonded interior of the sole, i.e., the periphery of the exposed portion. Because even slight peeling at the periphery of the exposed portion is directly visible, extremely reliable adhesion is required to ensure the functionality and quality of the product.

[0004] Therefore, Patent Document 3 discloses that a footwear cushioning component having excellent adhesion, flexibility, light weight, transparency, and heat resistance can be obtained by molding a footwear cushioning composition containing a styrene-based thermoplastic elastomer composed of at least styrene-ethylene-butylene-styrene block copolymer (SEBS), amine-modified styrene-ethylene-butylene-styrene block copolymer (amine-modified SEBS), and styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS) and a softener in a predetermined blending ratio, with the molecular weight, styrene content, and blending ratio of each block copolymer being within a predetermined range, applying a primer agent to the surface to form a primer-treated layer, and then applying a photo-curable urethane coating agent to form a protective layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-12886 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-281850 [Patent Document 3] Patent No. 5966110 Summary of the Invention [Problem to be solved by the invention]

[0006] The cushioning member for footwear proposed in the above-mentioned Patent Document 3 solved the problem of bonding the sole member and the cushioning member. However, in the design of new high-performance shoes, in order to pursue functionality from the cushioning member, there has been a demand to increase the size of the cushioning member incorporated into the sole member, or to incorporate the cushioning member 10 in such a way that it protrudes from the side of the sole member 20, as shown in Figures 1 and 2(a).

[0007] The styrene-based thermoplastic elastomer that constitutes the buffering member is a viscoelastic material, and softeners such as oil are also blended in to improve flexibility. Therefore, when a continuous load is applied to the buffering member, the buffering member undergoes flow deformation (creep). This creep becomes more pronounced as the size of the buffering member incorporated into the sole member increases. Furthermore, when the bonding surface 21 between the buffering member and the sole member is inclined relative to the thickness direction of the sole, as shown in Figures 1 and 2(a), the load direction is no longer perpendicular to the bonding surface 21 between the buffering member 10 and the sole member 20, as shown in Figure 2(b). Even when shear force is generated at the bonding surface 21 between the buffering member 10 and the sole member 20, the buffering member undergoes flow deformation (creep). As a result, when the sole member, which is harder than the buffering member, is unable to keep up with the flow deformation (creep) of the buffering member, a new problem arises: the buffering member peels off from the sole member, resulting in the two members becoming separated.

[0008] The present invention has been made in consideration of the above-mentioned points, and its object is to provide a shock-absorbing material for footwear that can improve separation from the sole member due to flow deformation (creep) while maintaining the adhesion to the sole member, flexibility, and transparency required for a shock-absorbing material for footwear. [Means for solving the problem]

[0009] In order to analyze the separation state between the cushioning member for footwear proposed in Patent Document 3 and the sole member due to flow deformation (creep), the present inventors analyzed the chemical bonding state of the separated surfaces of the cushioning member and the sole member where separation occurred using X-ray photoelectron spectroscopy (XPS). As shown in Figures 3(a) and 3(b), the observed peaks (285 eV) in the XPS spectrum correspond to C—C bonds and C—H bonds, and no peaks (near 290 eV) corresponding to ester bonds of the components constituting the primer layer of this cushioning member were observed. From this, it was inferred that the separation interface was near the surface of the molded cushioning member. Based on this finding, the present invention was completed.

[0010] In order to solve the above problems, the present invention provides a method for producing a footwear cushioning member having a haze value (according to JIS K7136:2000) of 20% or less and a hardness of Asker C55 or less (SRIS 0101 standard), the method comprising the steps of: a molded body-forming step of obtaining a molded body from a footwear cushioning composition containing a styrene-based thermoplastic elastomer; a primer layer-forming step of applying a primer agent containing a styrene-based block copolymer to at least a portion of the surface of the molded body to form a primer layer; a protective coating layer-forming step of applying a coating agent containing a urethane resin to the surface of the primer layer to form a substantially transparent protective coating layer; and an electron beam irradiation step of irradiating the protective coating layer from the outside with an electron beam after the protective coating layer-forming step, wherein the styrene-based block copolymer contained in the primer agent used in the primer layer-forming step is at least an acrylic-modified styrene-butadiene-styrene block copolymer, and the electron beam irradiation in the electron beam irradiation step is carried out at an acceleration voltage of 100 to 300 kV and an irradiation dose of 100 to 300 kGy.

[0011] A primer layer made of a primer agent containing an acrylic-modified styrene-butadiene-styrene block copolymer (hereinafter also referred to as "acrylic-modified SBS") and a protective coating layer made of a coating agent containing a urethane resin are sequentially formed on the surface of a molded body made of a footwear cushioning composition containing a styrene-based thermoplastic elastomer. Then, by irradiating the protective coating layer from the outside with an electron beam, a crosslinking reaction occurs between the styrene-based thermoplastic elastomer that makes up the molded body and the acrylic-modified SBS that makes up the primer layer, improving interlayer adhesion between the surface vicinity of the molded body and the primer layer. This improves the integrity of the surface vicinity of the molded body of the cushioning material and the primer layer, and reduces separation due to flow deformation (creep). Furthermore, by setting the accelerating voltage of the electron beam to be irradiated to a range of 100 to 300 kV and the irradiation dose to a range of 100 to 300 kGy, it is possible to not only achieve interlayer crosslinking between the surface vicinity of the molded body and the primer layer but also internal crosslinking near the surface of the molded body while maintaining the physical properties required for a shock-absorbing member for footwear, such as adhesion, flexibility, and transparency, thereby suppressing flow deformation near the surface of the molded body of the shock-absorbing member and further improving separation of the shock-absorbing member due to flow deformation (creep). Thus, by adopting the above-mentioned configuration, a shock-absorbing member for footwear can be obtained that maintains adhesion to the sole member, has high transparency, and has excellent flexibility that contributes to shock-absorbing performance, and that can improve separation from the sole member due to flow deformation (creep).

[0012] In the method for producing a shock-absorbing member for footwear of the present invention, it is also preferable that the primer agent used in the primer layer-forming step further contains an acrylic monomer. The acrylic monomer contained in the primer agent contributes to interlayer crosslinking between the protective coating layer and the vicinity of the surface of the molded body upon electron beam irradiation, thereby improving the interlayer adhesion between the primer layer and the protective coating layer and between the primer layer and the molded body, thereby producing a shock-absorbing member for footwear that can further reduce separation of the member due to flow deformation (creep).

[0013] Furthermore, in the method for producing a shock-absorbing member for footwear of the present invention, it is also preferable that the styrene-based thermoplastic elastomer contained in the footwear shock-absorbing composition used in the molded body formation step is a styrene-ethylene-butylene-styrene block copolymer (hereinafter also referred to as "SEBS") and an amine-modified styrene-ethylene-butylene-styrene block copolymer (hereinafter also referred to as "amine-modified SEBS"). This allows for the selection of suitable styrene-based thermoplastic elastomer components that have the physical properties required for a shock-absorbing member for footwear, improve interlayer adhesion between the molded body and the primer layer, and also cause internal crosslinking near the surface inside the molded body, thereby improving separation of the member due to flow deformation (creep).

[0014] In the method for producing a shock-absorbing member for footwear of the present invention, it is also preferable that the footwear shock-absorbing composition used in the molded body formation step further contains a styrene-ethylene-ethylene-propylene-styrene block copolymer (hereinafter also referred to as "SEEPS"). This selects a suitable styrene-based thermoplastic elastomer component that provides even better physical properties for the shock-absorbing member for footwear, improves interlayer adhesion between the molded body and the primer layer, and also causes internal crosslinking near the surface inside the molded body, thereby improving separation of the member due to flow deformation (creep). [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a method for manufacturing a shock-absorbing member for footwear that has the following excellent effects. (1) A shock-absorbing material for footwear is obtained that has aesthetic transparency, strong adhesion to other components (mainly sole components), and excellent flexibility, while improving separation from other components due to flow deformation (creep). (2) When manufacturing the cushioning material for footwear, the cushioning material for footwear is easily manufactured because it can be obtained by simply irradiating the protective coating layer with an electron beam from the outside, thereby improving separation from other components due to flow deformation (creep). [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram schematically illustrating a sports shoe in which a shock-absorbing member for footwear is incorporated into the side surface of a sole member. [Figure 2] 2A is a partial cross-sectional view schematically illustrating the configuration of the shock absorber for footwear and the sole portion of FIG. 1, and FIG. 2B is a view illustrating a state when a load is applied. [Figure 3] FIG. 1A shows the XPS spectrum of the separated surface on the sole member side of a shoe in which separation between the cushioning member and the sole member occurred due to flow deformation (creep), and FIG. 1B shows the results of XPS analysis of the separated surface on the cushioning member side. [Figure 4] 1 is a flowchart that schematically illustrates a method for manufacturing a shock-absorbing member for footwear according to an embodiment of the present invention. [Figure 5] 1A and 1B are a plan view and a front view, respectively, schematically illustrating the configuration of test pieces prepared for creep tests and peel strength measurement tests of shock absorbers for footwear in Examples and Comparative Examples. [Figure 6] FIG. 6 is a diagram illustrating the method of a creep test performed using the test piece of FIG. 5. [Figure 7] FIG. 6 is a diagram illustrating a method for a peel strength measurement test performed using the sample piece of FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0017] First, a method for manufacturing a shock-absorbing member for footwear according to an embodiment of the present invention will be described with reference to Fig. 4. As shown in Fig. 4, the method for manufacturing a shock-absorbing member for footwear P according to this embodiment is roughly composed of a molded body forming step S1 for obtaining a molded body of a shock-absorbing composition for footwear, a primer layer forming step S2 for forming a primer layer on the surface of the molded body, a protective coating layer forming step S3 for forming a protective coating layer on the surface of the primer layer, and an electron beam irradiation step S4 for irradiating the protective coating layer from the outside with an electron beam.

[0018] [Formation of molded body] First, the molded body forming step S1 shown in FIG. 1 will be described. In this step S1, a molded body is formed from a footwear cushioning composition containing a styrene-based thermoplastic elastomer as a main component. The styrene-based thermoplastic elastomer contained in the footwear cushioning composition is not particularly limited, but it is preferable that a styrene-ethylene-butylene-styrene block copolymer known as SEBS is blended. It is more preferable that an amine-modified styrene-ethylene-butylene-styrene block copolymer (amine-modified SEBS) is blended in addition to SEBS. This allows for the production of a cushioning material with the physical properties required for footwear cushioning, such as transparency, adhesion, and flexibility. It is even more preferable that a styrene-ethylene-ethylene-propylene-styrene block copolymer known as SEEPS is blended in addition to SEBS and amine-modified SEBS. This improves heat resistance and provides the excellent physical properties required for a cushioning material for footwear, such as strong adhesion to other components, transparency in appearance, and flexibility. By irradiating the molded body with electron beams as described below, the interlayer adhesion between the molded body and the primer layer is improved, and internal crosslinking occurs near the surface inside the molded body, resulting in a cushioning material that can improve separation of components due to flow deformation.

[0019] From the viewpoint of improving the transparency and mechanical strength of the cushioning material, the styrene content of each block copolymer constituting the styrene-based thermoplastic elastomer is preferably 20 to 55% by weight, more preferably 25 to 45% by weight, when SEBS or amine-modified SEBS is used, and is preferably 25 to 35% by weight when SEEPS is used.

[0020] Specific formulations of the styrene-based thermoplastic elastomer according to the present invention are described below. While not particularly limited, one example is a styrene-based thermoplastic elastomer according to the present invention that is a combination of three block copolymers: SEBS (a1), amine-modified SEBS (a2), and SEEPS (a3). The weight-average molecular weight Mw of each of these block copolymers a1 to a3 is preferably 50,000 or more from the viewpoint of mechanical strength, and is preferably less than 200,000 from the viewpoint of improving adhesion to the primer layer and fluidity during molding, i.e., 50,000 to 200,000. By setting the weight-average molecular weight Mw of the block copolymers a1 to a3 within this range, a molded article can be formed that is less susceptible to interfacial peeling due to improved adhesion to the primer layer, and also achieves good fluidity during molding. Note that the molecular weight in the present invention refers to the weight-average molecular weight Mw, measured by gel permeation chromatography (GPC). From the viewpoints of adhesion to the primer layer, heat resistance, and mechanical strength, the blending ratio of the styrene-based thermoplastic elastomer is preferably a2 / (a1+a2+a3)=0.08-0.8 and a3 / a1=0.35-3.5 by weight, and more preferably a2 / (a1+a2+a3)=0.1-0.7 and a3 / a1=0.45-2.5. The blending ratio a2 / (a1+a2+a3) is the blending ratio of the amine-modified SEBS (a2) among the styrene-based thermoplastic elastomers. If the blending ratio is less than 0.08, adhesion to the primer layer will be poor, and if it exceeds 0.8, mechanical strength and adhesion will decrease, and heat resistance will also tend to decrease. Furthermore, the blending ratio a3 / a1 is the blending ratio of SEEPS (a3) ​​to SEBS (a1), and if it is less than 0.35, adhesion to the primer layer tends to be poor and heat resistance also tends to decrease, while if it exceeds 3.5, the physical properties become unstable, such as reduced mechanical strength and adhesion. Therefore, by setting the blending ratio of each block copolymer within the above range, a molded product with excellent adhesion to the primer layer, mechanical strength, and heat resistance can be formed.

[0021] In addition to the styrene-based thermoplastic elastomer, the footwear cushioning composition according to the present invention also contains a softener that contributes to the flexibility of the footwear cushioning member. Examples of softeners that can be used include process oils such as paraffinic oil, naphthenic oil, or aromatic oil; synthetic resin-based softeners such as liquid polybutene or low-molecular-weight polybutadiene; and rosin. Among these, paraffinic oils are preferred among process oils in terms of external transparency. Paraffinic oils with a weight-average molecular weight of 400 to 1200 are particularly preferred in terms of improving interlayer adhesion between the surface of the molded article and the primer layer, and improving the mechanical strength of the molded article. The blend ratio of the softener is not particularly limited. For example, the blend ratio of the softener to the sum of the styrene-based thermoplastic elastomer and the softener [softener / styrene-based thermoplastic elastomer + softener] is preferably 0.5 to 0.7, and more preferably 0.55 to 0.65, by weight. If this value is less than 0.5, sufficient flexibility cannot be obtained, and if it exceeds 0.7, heat resistance and mechanical strength decrease, and the adhesiveness decreases due to the softener bleeding. Therefore, by setting the blending ratio of the softener within the above range, flexibility can be adjusted without deteriorating other physical properties.

[0022] Furthermore, the footwear cushioning composition of the present invention may contain other additives as long as the effects of the present invention are not impaired. Examples of additives include pigments, colorants, lubricants, release agents, antioxidants, antibacterial agents, UV absorbers, light stabilizers, and heat resistance agents. These may be used alone or in combination.

[0023] The footwear cushioning composition according to the present invention is produced by a known method for producing a resin composition, for example, by adding compounding ingredients such as a styrene-based thermoplastic elastomer and a softener in predetermined proportions using a melt kneader such as a single-screw extruder, a twin-screw extruder, a kneader, a Banbury mixer, or a heated roll, and then heating the compounding ingredients to uniformly knead the components in a molten state.

[0024] The footwear cushioning composition obtained as described above is molded into a predetermined shape by a known method such as injection molding, extrusion molding, blow molding, compression molding, or calendar molding to obtain a molded article of the footwear cushioning composition of the present invention. The molded article of the footwear cushioning composition of the present invention preferably has a haze value (based on JIS K7136:2000) of 20% or less, more preferably 15% or less. Furthermore, the hardness is preferably ASKER C (SRIS 0101 standard) of 55 or less, more preferably 50 or less. Therefore, the molded article is useful as a footwear cushioning member having a high transparency in appearance and sufficient flexibility to contribute to cushioning. It is preferable that these physical properties are maintained even after the electron beam irradiation process described below.

[0025] [Primer layer formation] Next, the primer layer formation step S2 will be described. In this step S2, a primer agent is applied to the surface of the molded body formed in S1 to form a primer layer. Conventionally, a primer layer is a layer provided between the surface of a molded body and a protective coating layer to enhance adhesion between the styrene-based thermoplastic elastomer constituting the molded body and the transparent urethane resin constituting the protective coating layer, since the adhesion between these two components is weak. Therefore, conventionally, primer agents have been used that contain as their main components a polyol-terminated urethane prepolymer, which dissolves the surface of the molded body and is highly reactive with the transparent urethane resin constituting the protective coating layer, an isocyanate, and a solvent (see Japanese Patent No. 5631689). However, the present invention differs significantly from previous techniques in that it uses a primer agent containing a styrene-based block copolymer.

[0026] The primer agent used in the present invention contains an acrylic-modified styrene-butadiene-styrene block copolymer (acrylic-modified SBS) as a styrene-based block copolymer. This allows the styrene-butadiene-styrene block copolymer contained in the primer agent to undergo a crosslinking reaction with the styrene-based thermoplastic elastomer constituting the molded article upon electron beam irradiation, as described below, thereby improving the interlayer adhesion between the surface vicinity of the molded article and the primer layer. Furthermore, the acrylic groups in the copolymer react with the transparent urethane resin constituting the protective coating layer, thereby also improving the interlayer adhesion between the primer layer and the protective coating layer. The primer agent preferably further contains an acrylic monomer. In addition to the acrylic monomer, a dimer, trimer, or the like may also be contained. The inclusion of the acrylic monomer improves the adhesion between the primer layer and the protective coating layer and also suppresses deterioration of the protective coating layer after electron beam irradiation.

[0027] This primer layer is formed by applying the above-mentioned primer agent to the surface of a molded article formed from the footwear cushioning composition, or by immersing the molded article in the primer agent and drying it. The thickness of the primer layer is not particularly limited, but it is usually formed to a thickness of about 5 μm to 100 μm, and preferably to a thickness of about 10 μm to 50 μm.

[0028] [Protective coating layer formation] Next, the protective coating layer forming step S3 will be described. In this step S3, a coating agent is applied to the surface of the primer layer formed in the previous step S2 to form a protective coating layer. A urethane resin capable of forming a substantially transparent protective coating layer is used as the coating agent. Urethane resins include, for example, photocurable, thermosetting, and moisture-curable types. However, photocurable urethane coating agents that cure upon exposure to light such as ultraviolet light are preferred because they can be cured in a short time at room temperature and offer excellent productivity. Examples of reactive urethanes that can be used for photocurable urethane coating agents include well-known substantially transparent reactive urethanes such as ether-based urethanes, ester-based urethanes, carbonate-based urethanes, and polycaprolactone-based urethanes. Carbonate-based urethanes are particularly preferred from the standpoints of solvent resistance, flexibility, and hydrolysis resistance. The photocurable urethane coating agent using carbonate-based urethanes contains a reactive carbonate-based urethane, a photopolymerization initiator, a thickener, and water. The reactive carbonate-based urethane is not particularly limited, but for example, a carbonate-based urethane having a polymerizable unsaturated bond obtained by reacting at least polycarbonate diol and polyisocyanate as raw materials can be used. Furthermore, the photopolymerization initiator may be any known one, and is not particularly limited. Examples thereof include acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, benzophenone, 2-chlorobenzophenone, p,p'-bisdiethylaminobenzophenone, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin n-butyl ether, benzoin dimethyl ketal, thioxanthone, p-isopropyl-α-hydroxyisobutylphenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,4,6-trimethylbenzophenone, 4-methylbenzophenone, and 2,2-dimethoxy-1,2-diphenylethanone.Among these, hydroxycyclohexyl phenyl ketone is preferred. Furthermore, as the thickener, any one of aliphatic alcohols such as ethanol, glycol, and ethylene glycol monoethyl ether, or a combination thereof, is preferably used. Furthermore, water functions as a dispersion medium for the above-mentioned components, and a photocurable urethane coating agent in the form of an aqueous emulsion is obtained.

[0029] Regarding the blending ratio of each component constituting the photocurable urethane coating agent, from the viewpoint of the curability of the photocurable urethane coating agent, the blending ratio C2 / C1 of the photopolymerization initiator (C2) to the reactive carbonate-based urethane (C1) is 0.01 to 0.1 by weight, and more preferably 0.025 to 0.075. If C2 / C1 is less than 0.01, the curing reaction will not proceed sufficiently, resulting in poor curing. If it exceeds 0.1, curing will be inhibited, resulting in poor curing and may leave a lingering odor after curing, which is undesirable. Furthermore, the blending ratio C4 / C1 of the water (C4) to the reactive carbonate-based urethane (C1) is preferably 1.9 to 3.0 by weight, and more preferably 2.1 to 2.7. If C4 / C1 is less than 1.9, the emulsion state of the photocurable urethane coating agent cannot be maintained, making uniform coating difficult, while if it exceeds 3.0, the viscosity of the photocurable urethane coating agent becomes too low and it is repelled by the coating surface, making uniform coating difficult, both of which are undesirable because a homogeneous protective layer cannot be formed. Furthermore, the blending ratio C3 / C1 of the thickener (C3) to the reactive carbonate urethane (C1) is preferably 0.3 to 3.5 by weight, more preferably 0.6 to 1.7, from the viewpoint of providing the coating agent with an appropriate viscosity and improving coatability when forming a protective layer.

[0030] This protective coating layer is formed by applying the above-mentioned coating agent to the surface of the primer layer, or by immersing a molded body coated with the primer layer in the coating agent and then irradiating it with light to photo-cure it. The thickness of the protective coating layer is not particularly limited, but it is usually formed to a thickness of about 1 μm to 100 μm, and preferably to a thickness of about 5 μm to 50 μm.

[0031] [Electron beam irradiation] Next, the electron beam irradiation step S4 will be described. In this step S4, electron beams are irradiated from the outside of the protective coating layer formed in the previous step S3. In the present invention, in order to improve separation of the buffer member from other members due to flow deformation (creep), electron beam irradiation is used to induce interlayer crosslinking between the surface vicinity of the molded body and the primer layer and internal crosslinking at least near the surface inside the molded body. Therefore, it was speculated that irradiating the primer layer from the outside before forming the protective coating layer, rather than irradiating the protective coating layer with electron beams from the outside, would efficiently induce the interlayer crosslinking between the molded body and the primer layer and internal crosslinking near the surface inside the molded body, thereby suppressing flow deformation of the buffer member. However, as shown in Comparative Example 1 described below, the present inventors have interestingly shown that when electron beam irradiation from the outside of the primer layer is performed followed by protective coating layer formation step S3, flow deformation of the buffer member is not suppressed.

[0032] The present inventors speculate that the mechanism by which electron beam irradiation of the buffer member from the outside of the protective coating layer leads to interlayer crosslinking between the surface vicinity of the molded article and the primer layer, and internal crosslinking at least near the surface inside the molded article, is as follows: First, the crosslinking reactions caused by electron beam irradiation include (1) a first crosslinking reaction resulting from cleavage of C=C bonds in the butadiene block of the acrylic-modified SBS, the main component of the primer agent that constitutes the primer layer, and dehydrogenation of -CH groups in the styrene-based thermoplastic elastomer that constitutes the molded article; and (2) a second crosslinking reaction in which radicals are generated by the electron beam at the -CH groups in the acrylic-modified SBS, the main component of the primer agent that constitutes the primer layer, and the -CH groups in the styrene-based thermoplastic elastomer that constitutes the molded article, which then become reactive sites and react with each other accompanied by dehydrogenation. These two crosslinking reactions, (1) the first crosslinking reaction and (2) the second crosslinking reaction, strengthen the interlayer crosslinking between the surface vicinity of the molded article and the primer layer, and the internal crosslinking near the surface inside the molded article, thereby improving separation due to flow deformation (creep). Therefore, it is extremely important in the present invention to form a primer layer by applying a primer agent containing acrylic-modified SBS as a main component to a molded article containing a styrene-based thermoplastic elastomer.

[0033] The electron beam irradiation in step S4 is preferably carried out at an acceleration voltage of 100 to 300 kV and an irradiation dose of 100 to 300 kGy, and more preferably at an acceleration voltage of 150 to 250 kV and an irradiation dose of 150 to 250 kGy. By using the electron beam irradiation conditions described above, it is possible to induce internal crosslinking near the surface of the molded body in addition to interlayer crosslinking between the surface vicinity of the molded body and the primer layer, thereby improving separation of the buffer member from other components due to flow deformation (creep). In addition to this creep suppression effect, the buffer member's physical properties before electron beam irradiation, such as flexibility, external transparency, adhesion to other components, and mechanical strength, can also be maintained. On the other hand, if the acceleration voltage is less than 100 kV or the irradiation dose is less than 100 kGy, the electron beam irradiation dose is insufficient, making it difficult for the crosslinking reaction to occur, resulting in an insufficient effect of suppressing flow deformation.If the acceleration voltage is more than 300 kV or the irradiation dose is more than 300 kGy, the electron beam irradiation dose is too large, causing excessive crosslinking reaction, resulting in the generation of bubbles in the protective coating layer, impairing the transparency of the appearance, and causing problems due to significant deterioration of each layer.

[0034] The footwear cushioning material P obtained after electron beam irradiation as described above exhibits reduced flow deformation, is able to withstand shear forces, and exhibits improved separation from other components. Even after electron beam irradiation, it maintains excellent peel strength (peel adhesion strength) against other components, such as sole members bonded with shoemaking adhesives such as polyurethane adhesives and chloroprene rubber adhesives. This allows the footwear cushioning material P to withstand stress deformation during exercise, even when incorporated into a shoe designed to generate shear stress at the adhesive surface with the sole member during use, achieving high adhesive reliability. Furthermore, the footwear cushioning material P maintains excellent transparency and flexibility even after electron beam irradiation. Specifically, the haze value (based on JIS K7136:2000) relating to transparency is preferably 20% or less, more preferably 15% or less. Furthermore, the Asker C (SRIS 0101 standard) hardness relating to flexibility is preferably 55 or less, more preferably 50 or less. [Example]

[0035] The present invention will be described in detail below with reference to examples. The physical properties such as adhesiveness and transparency of the shock-absorbing member for footwear in the following examples and comparative examples were evaluated as follows.

[0036] (1) Creep test (flow deformability) A specific creep test method will be described using Figures 5 and 6. Figure 5 schematically shows the structure of test piece 50, and Figure 6 illustrates the creep test method for the test piece. The test piece 50 shown in Figure 5 was prepared as follows. Each cushioning material molded body in the Examples and Comparative Examples was molded into a strip (20 mm wide x 60 mm long x 3 mm thick). The strip surface was treated with a primer to form a primer layer, and then treated with a urethane coating to form a protective coating layer, resulting in test piece 51. A urethane piece 52 (Kuraray Co., Ltd., Kuramilon U2195, 20 mm wide x 60 mm long x 3 mm thick) similar to test piece 51 was bonded to test piece 51 with adhesive 53, thereby obtaining test piece 50. More specifically, the surfaces of test piece 51 and urethane piece 52 were wiped with Kimwipes (registered trademark) soaked in methyl ethyl ketone (MEK) and then dried at 60°C for 3 minutes. A primer (G-6626, manufactured by No Tape Industrial Co., Ltd.) was applied to the urethane-coated surface of the test piece 51 and one surface of the urethane piece 52, and then dried at 60°C for 5 minutes. An adhesive (No Tape Industrial Co., Ltd., No. 4950) was applied thereon and dried at 60°C for 5 minutes. The test piece 51 and the urethane piece 52 were then quickly bonded together. The test piece 51 was placed with the side facing up and pressed with a hand roller at a force of 2 to 3 kgf / cm2 to obtain a test piece 50. When bonding the test piece 51 and the urethane piece 52 with the adhesive 53, a 15 mm section from the end toward the other end in the longitudinal direction was left unbonded, as shown in Figure 5(b). The test piece 50 was then cured for 12 hours before being used in a creep test. Before the test, because the presence of adhesive pools at the bonded end Q0 of the test piece 50 would result in an apparent increase in strength, a notch was made by cutting approximately 1 mm along the adhesive layer with a utility knife from the bonded end Q0 of the test piece 50 toward the bonded end, as shown in Figure 5(b), before the test. As shown in Figure 6(a), the test piece 50 was fixed horizontally to a jig with the urethane piece 52 side facing up, and a 200 g weight W was fixed with vinyl tape to the end of the unbonded portion of the test piece 51, applying a tensile load in the direction of gravity. The test piece was then left in a hot air oven (Tokyo Rikakikai Co., Ltd., model number: WFO-520W) at 40°C for 24 hours.After 24 hours, the distance (distance between Q0 and Q1) from the position Q0 at the end of the bond before the test to the position Q1 at which creep-induced peeling occurred and became the end of the bond after the test was measured, as shown in Figure 6(b).

[0037] The adhesiveness in the creep test was evaluated as follows: if the measured value of the distance at which peeling occurred (the length between Q0 and Q1) was within 0 to 1 mm, it was evaluated as excellent (◎); if the measured value was more than 1 but not more than 10 mm, it was evaluated as good (○); if the measured value was more than 10 mm but not more than 20 mm, it was evaluated as fair (△); and if the measured value was more than 20 mm, it was evaluated as poor (×).

[0038] (2) Peel strength (adhesion) The peel strength of each test piece was measured in accordance with JIS K6854-3. The test piece was prepared in the same manner as the test piece 50 used in the creep test described above. After aging for 12 hours, the test piece 50 was used for the peel strength test. To prevent the apparent increase in strength due to the presence of adhesive pools at the end Q0 of the adhesive bond of the test piece 50, a notch was created by making a cutter knife approximately 1 mm along the adhesive layer from the end Q0 of the adhesive bond of the test piece 50 shown in Figure 5(b) along the adhesive bond side, as in the creep test. As shown in Figures 7(A) and (B), the test piece 51 and the urethane piece 52 of the test piece 50 were peeled off using a tensile tester (Shimadzu Corporation, Autograph (registered trademark), AT-100N), and the peel strength was measured. In Figure 7, 54 denotes a fixed-side tensile jig, and 55 denotes a movable-side tensile jig. The load cell was 1 kN (100 kgf), the test speed was 50 mm / min, and the initial gap between the fixed tensile jig 54 and the movable tensile jig 55 was 20 mm. (Note that the adhesive 53 constituting the test piece 50 is not shown in Figures 7(A) and (B).)

[0039] After measuring the peel strength, the peeling state (peel mode) of the interface between the molded body and the primer layer of each test piece 51 was evaluated as follows: The peeled surface on the urethane piece 52 side of each sample piece 50 and the peeled surface on the test piece 51 side were each measured using an FT-IR device (PerkinElmer, infrared microscope system Spotlight 200) at 380 to 4000 cm -1 The specimens were analyzed by attenuated total reflectance (ATR) in the wavenumber range of 100 Hz to 100 Hz. When the analysis detected no SEBS spectrum, a component of the molded body of each test piece 51, on the peeled surface on the urethane piece 52 side, but the SEBS spectrum was detected on the peeled surface on the test piece 51 side, the analysis was deemed "interfacial delamination." On the other hand, when the "interfacial delamination" was not met, the fracture was primarily within the molded body, or within one of the primer layer, protective coating layer, or adhesive layer, or interfacial delamination between these layers, and was therefore collectively deemed "molded body fracture." The SEBS spectrum was obtained by measuring the surface of the molded body constituting each test piece 51 using FT-IR. The presence or absence of SEBS was determined by comparing the characteristic absorption bands of the SEBS spectrum with the spectra obtained by measuring the peeled surface on the urethane piece 52 side and the peeled surface on the test piece 51 side of the specimen 50. The spectral identification method conformed to JIS K6230.

[0040] As shown in Table 1, the adhesiveness evaluation for peel strength was as follows: for test pieces in which material failure occurred inside the molded body, a measurement value of 4 kgf / 20 mm or more was evaluated as excellent (◎), a measurement value of more than 2 kgf / 20 mm but less than 4 kgf / 20 mm was evaluated as good (○), and a measurement value of 2 kgf / 20 mm or less was evaluated as fair (△). Furthermore, for test pieces in which interfacial peeling occurred, a measurement value of 4 kgf / 20 mm or more was evaluated as good (○), a measurement value of more than 2 kgf / 20 mm but less than 4 kgf / 20 mm was evaluated as fair (△), and a measurement value of 2 kgf / 20 mm or less was evaluated as poor (×).

[0041] [Table 1]

[0042] (3) Haze value (transparency) The haze of each test piece was measured using a haze meter (HZ-1, manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K7136:2000. The test pieces were prepared by molding each cushioning material molded body in the Examples and Comparative Examples into a sheet (50 mm long x 50 mm wide x 3 mm thick), treating the surface with each primer to form a primer layer, and then treating with a urethane coating agent to form a protective coating layer. A haze value of 20% or less was evaluated as excellent (○), and a haze value of more than 20% was evaluated as poor (×). Even if the haze value was 20% or less, the presence of bubbles was evaluated as poor (×).

[0043] (4) Tensile breaking strength In accordance with JIS K6252-1, Method B, five test pieces of the footwear shock absorber components having the configurations shown in the Examples and Comparative Examples, formed into an angle shape without notches (dumbbell type B), were measured for the maximum load F [N] at break at a tensile speed of 500 mm / min using a tensile tester (Autograph (registered trademark), AT-100N, manufactured by Shimadzu Corporation), and the tensile strength at break (MPa) was calculated by dividing this value by the thickness t [m] of the test piece. The tensile strength at break (MPa) was calculated by averaging the two values ​​flanking the median tensile strength of the five test pieces.

[0044] The tensile breaking strength was evaluated to assess the degree of deterioration of the protective coating layer due to electron beam irradiation of the shock-absorbing material for footwear. First, the percentage change in tensile breaking strength before and after electron beam irradiation was calculated using the formula: "Percentage change (%) = (absolute value of the difference between the measured tensile breaking strength of the test piece after electron beam irradiation and the measured tensile breaking strength of the test piece before electron beam irradiation) / (measured tensile breaking strength of the test piece before electron beam irradiation)". When the percentage change was 10% or less, it was evaluated as excellent (◎); when the percentage change was more than 10% but not more than 20%, it was evaluated as good (○); when the percentage change was more than 20% but not more than 50%, it was evaluated as fair (△); and when the percentage change was more than 50%, it was evaluated as poor (×).

[0045] (5) Tensile elongation In accordance with JIS K6251, three test pieces of each of the shock-absorbing materials for footwear having the configurations shown in the Examples and Comparative Examples were formed into a No. 3 dumbbell shape, and the tensile elongation (elongation at break) [%] was measured using a tensile tester (Autograph (registered trademark), AT-100N, manufactured by Shimadzu Corporation) at a pulling rate of 500 mm / min.

[0046] Similar to the tensile breaking strength described above, the tensile elongation was evaluated to assess the degree of deterioration of the protective coating layer due to electron beam irradiation of the shock-absorbing material for footwear. First, the percentage change in tensile elongation before and after electron beam irradiation was calculated using the formula: "Percentage change (%) = (absolute value of the tensile elongation of the test piece before electron beam irradiation minus the tensile elongation of the test piece after electron beam irradiation) / (tensile elongation of the test piece before electron beam irradiation)". When the percentage change was 10% or less, it was evaluated as excellent (◎); when it was more than 10% but not more than 20%, it was evaluated as good (○); when it was more than 20% but not more than 50%, it was evaluated as fair (△); and when it was more than 50%, it was evaluated as poor (×).

[0047] (6) Hardness (Asker C) The hardness of each test piece was measured using an Asker C durometer (SRIS 0101 standard) conforming to JIS K6253. Test pieces were prepared by molding each cushioning member molded body in the Examples and Comparative Examples into a size of 60 mm length x 60 mm width x 12 mm thickness, treating the surface with each primer to form a primer layer, and then treating with a urethane coating agent to form a protective coating layer. Asker C hardness of 55 or less was evaluated as excellent (○), and hardness above 55 was evaluated as poor (×).

[0048] Of the shock absorbers for footwear produced in the following Examples and Comparative Examples, Table 2 shows the specifications of the components of the molded bodies, and Table 3 shows the specifications of the components of the primer layers.

[0049] [Table 2]

[0050] [Table 3]

[0051] [Example 1] The footwear shock absorber of this example was prepared according to the following procedure, and the physical properties of both the unirradiated and irradiated samples were measured and evaluated. Of the styrene-based thermoplastic elastomer components of molded product No. a shown in Table 2, 615 g (20.5 wt%) of SEBS (styrene-ethylene-butylene-styrene block copolymer), 210 g (7 wt%) of amine-modified SEBS, and 330 g (11 wt%) of SEEPS (styrene-ethylene-ethylene-propylene-styrene block copolymer) were weighed out separately. Next, 1845 g (61.5 wt%) of paraffin oil was weighed out. Of this paraffin oil, 1020 g (34 wt%) was added to SEBS, 210 g (7 wt%) to amine-modified SEBS, and 615 g (20.5 wt%) to SEEPS. Each block copolymer and paraffin oil were mixed at room temperature and then heated at 100°C for 12 hours to absorb and disperse the paraffin oil into each styrene-based thermoplastic elastomer. The paraffin oil-absorbed SEBS, amine-modified SEBS, and SEEPS were dry-blended by hand and then kneaded for 15 minutes in a batch-type twin-screw mixer (TD3-10MDX, manufactured by Toshin Corporation) at 160-180°C and 40 rpm to obtain 3 kg of a footwear cushioning composition. This composition was injection-molded at 150-170°C into the specified test specimen shapes used in the evaluation methods for the footwear cushioning components described above to obtain molded articles. A primer (Chubu Resin P155, manufactured by Toshin Co., Ltd.) containing the components of Primer Layer No. A shown in Table 3 was applied to the surface of the resulting molded article and dried at 70°C to form a primer layer approximately 15 μm thick. Then, a coating agent containing a urethane resin having the composition shown in Table 4 below was applied to the surface of this primer layer, dried at room temperature for 20 minutes and at 70°C for 7 minutes, and then irradiated with ultraviolet light (high-pressure mercury lamp, cumulative light amount 2000 mJ / cm 2) and cured to form a protective coating layer, obtaining a test piece for a shock-absorbing material for footwear. The blending ratios of the urethane emulsion liquids (C1 and C4), photopolymerization initiator (C2), and ethanol (C3), which are components of the coating agent containing urethane resin, were C2 / C1 = 0.04, C4 / C1 = 2.3, and C3 / C1 = 0.83 by weight. Using this test piece, the physical properties of the sample without electron beam irradiation (before electron beam irradiation) were evaluated.

[0052] [Table 4]

[0053] On the other hand, another test piece was irradiated with an electron beam under conditions of an acceleration voltage of 200 kV and an exposure dose of 200 kGy. Using this test piece, the physical properties of the sample irradiated with the electron beam (after electron beam irradiation) were evaluated. The results of Example 1 are shown in Table 5.

[0054] [Examples 2 to 8] Test pieces of the footwear cushioning material of each Example were obtained in the same manner as in Example 1, except that the electron beam irradiation conditions were changed as shown in Tables 5 and 6 below. The physical properties of the obtained test pieces were evaluated before and after electron beam irradiation in the same manner as in Example 1. The results of Examples 2 to 6 are shown in Table 5, and the results of Examples 7 and 8 are shown in Table 6.

[0055] [Example 9] Test pieces for the footwear cushioning material of Example 9 were obtained in the same manner as in Example 1, except that the primer agent for forming the primer layer was changed as shown in Tables 6 and 3 below, and the electron beam irradiation conditions were changed as shown in Table 6 below. The physical properties of the obtained test pieces before and after electron beam irradiation were evaluated in the same manner as in Example 1. The results of Example 9 are shown in Table 6.

[0056] [Examples 10 and 11] Test pieces for the footwear cushioning members of Examples 10 and 11 were obtained in the same manner as in Example 1, except that the components of the footwear cushioning composition for forming the molded body were changed as shown in Tables 6 and 2 below, and the electron beam irradiation conditions were changed as shown in Table 6 below. The molded bodies used in Examples 10 and 11 were formulated to a total of 3 kg each at the blending ratios shown in No. b and No. c in Table 2. Regarding the process of absorbing and dispersing paraffin oil in the styrene-based thermoplastic elastomer constituting the footwear cushioning composition, in Example 10, a total of 1500 g (3 kg × 50 wt%) of paraffin oil was added to the SEBS listed in No. b of Table 2. In Example 11, 1560 g (3 kg × 52 wt%) of paraffin oil listed in No. c of Table 2 was added in amounts of 1212 g to the SEBS and 348 g to the amine-modified SEBS. The physical properties of the obtained test pieces were evaluated before and after electron beam irradiation in the same manner as in Example 1. The results of Examples 10 and 11 are shown in Table 6.

[0057] [Table 5]

[0058] [Table 6]

[0059] [Comparative Example 1] In Comparative Example 1, electron beam irradiation was performed on the surface of the primer layer, not on the surface of the protective coating layer, and the protective coating layer was formed after electron beam irradiation. Therefore, samples not subjected to electron beam irradiation were prepared in the same manner as in Example 1, while test pieces for samples subjected to electron beam irradiation were prepared as follows. After obtaining a molded body from the footwear cushioning composition in the same manner as in Example 1, a primer agent containing the components of primer layer No. A (product of Tomonobu Co., Ltd., Chubu Resin P155) was applied to the surface of the obtained molded body and dried at 70°C to form a primer layer of approximately 15 μm. The test piece in this state was irradiated with electron beams under conditions of an acceleration voltage of 300 kV and an exposure dose of 100 kGy. A coating agent containing a urethane resin with the same composition as in Example 1 was applied to the surface of the primer layer after electron beam irradiation, and the surface was dried at room temperature for 20 minutes and at 70°C for 7 minutes, followed by irradiation with ultraviolet light (high-pressure mercury lamp, cumulative light dose of 2000 mJ / cm). 2 ) and cured to form a protective coating layer, thereby obtaining a test piece for a shock-absorbing member for footwear. The physical properties of both test pieces obtained were evaluated. The results of Comparative Example 1 are shown in Table 7.

[0060] Comparative Example 2 Test pieces of a shock-absorbing member for footwear of Comparative Example 2 were obtained in the same manner as in Example 1, except that the primer agent for forming the primer layer was changed as shown in Tables 7 and 3 below, and the electron beam irradiation conditions were changed as shown in Table 7 below. The physical properties of the obtained test pieces before and after electron beam irradiation were evaluated in the same manner as in Example 1. The results of Comparative Example 2 are shown in Table 7.

[0061] [Comparative Examples 3 to 5] Test pieces of the footwear cushioning material of each comparative example were obtained in the same manner as in Example 1, except that the electron beam irradiation conditions were changed as shown in Table 7 below. The physical properties of the obtained test pieces were evaluated before and after electron beam irradiation in the same manner as in Example 1. The results of comparative examples 3 to 5 are shown in Table 7.

[0062] [Comparative Examples 6 to 9] Test pieces of footwear shock absorber materials of Comparative Examples 6 to 9 were obtained in the same manner as in Example 1, except that the primer agent for forming the primer layer was changed as shown in Tables 7, 8, and 3 below, and the electron beam irradiation conditions were changed as shown in Tables 7 and 8 below. The physical properties of the obtained test pieces were evaluated before and after electron beam irradiation in the same manner as in Example 1. The results of Comparative Examples 6 to 9 are shown in Tables 7 and 8.

[0063] [Table 7]

[0064] [Table 8]

[0065] From the results of Examples 1 to 11 shown in Tables 5 and 6 and Comparative Examples 1 to 9 shown in Tables 7 and 8, it was found that the manufacturing method of the present invention suppresses flow deformation and produces a shock-absorbing component for footwear that has excellent adhesion to other components, transparency in appearance, and flexibility.

[0066] Specifically, comparing the results of Examples 1 to 8 and Comparative Examples 3 to 5, in which electron beam irradiation conditions were varied, it was found that by setting the acceleration voltage to 100 to 300 kV and the irradiation dose to 100 to 300 kGy, flow deformation was suppressed and a cushioning member for footwear with excellent adhesion to other components, appearance transparency, and flexibility was obtained. On the other hand, when the acceleration voltage was less than 100 kV or the irradiation dose was less than 100 kGy, the electron beam irradiation dose was insufficient, making it difficult for the crosslinking reaction to occur, and flow deformation was not suppressed. On the other hand, when the acceleration voltage was more than 300 kV or the irradiation dose was more than 300 kGy, the electron beam irradiation dose was too high, causing excessive crosslinking reaction, resulting in the generation of bubbles in the protective coating layer and significant deterioration. Furthermore, the results of physical property evaluation of Examples 1 to 8 showed that a cushioning member with even better physical properties could be obtained by setting the acceleration voltage to 150 to 250 kV and the irradiation dose to 150 to 250 kGy.

[0067] Furthermore, with regard to the components of the molded body that constitutes the cushioning material, the results of Examples 8, 10, and 11 showed that by combining SEBS, amine-modified SEBS, and SEEPS, a cushioning material with highly improved flow and deformability can be obtained.

[0068] Furthermore, with regard to the components of the primer layer that constitutes the cushioning material, the results of Examples 8 and 9 and Comparative Examples 2 and 6 to 9 showed that by selecting acrylic-modified SBS, flow deformation is sufficiently suppressed and a cushioning material for footwear that is excellent in adhesion to other components, appearance transparency, and flexibility can be obtained.

[0069] Furthermore, the results of Example 6 and Comparative Example 1, which investigated the electron beam irradiation target, showed that irradiating the protective coating layer with an electron beam suppressed flow deformation more than irradiating the primer layer directly with an electron beam. This means that a buffer member that can suppress flow deformation (creep) can be obtained by simply performing an electron beam irradiation treatment after the protective coating layer has been formed, making it easy to manufacture.

[0070] The present invention is not limited to the above-described embodiments or examples, and various modified design forms are also included in the technical scope within the scope that does not deviate from the gist of the invention described in the claims. [Explanation of symbols]

[0071] 1. Shoes 10. Shock-absorbing materials for footwear 11 Molded body 12 Primer layer 13 Protective coating layer 20 Sole material 21 Adhesion surface between shock-absorbing material for footwear and sole material 50 sample pieces 51 Test piece (Buffer member of Example or Comparative Example) 52 Urethane piece 53 Adhesive 54 Fixed side tension jig 55 Movable side tension jig Q0 Edge of adhesive joint Q1 Edge of adhesive joint after test W weight

Claims

1. A method for manufacturing a shock-absorbing member for footwear having a haze value (in accordance with JIS K7136:2000) of 20% or less and a hardness of Asker C55 or less (SRIS 0101 standard), comprising: a molded body forming step of obtaining a molded body of a cushioning composition for footwear containing a styrene-based thermoplastic elastomer; a primer layer forming step of applying a primer agent containing a styrene-based block copolymer to at least a part of the surface of the molded body to form a primer layer; a protective coating layer forming step of applying a coating agent containing a urethane resin to the surface of the primer layer to form a substantially transparent protective coating layer; an electron beam irradiation step of irradiating an electron beam from outside the protective coating layer after the protective coating layer forming step, the styrene-based block copolymer contained in the primer agent used in the primer layer-forming step is at least an acrylic-modified styrene-butadiene-styrene block copolymer; The method for manufacturing a shock-absorbing member for footwear, wherein the electron beam irradiation in the electron beam irradiation step is carried out at an acceleration voltage of 100 to 300 kV and at an irradiation dose in the range of 100 to 300 kGy.

2. 2. The method for manufacturing a shock-absorbing member for footwear according to claim 1, wherein the primer agent used in the primer layer forming step further contains an acrylic monomer.

3. 3. The method for manufacturing a shock-absorbing member for footwear according to claim 1, wherein the styrene-based thermoplastic elastomer contained in the shock-absorbing composition for footwear used in the molded body formation process is a styrene-ethylene-butylene-styrene block copolymer and an amine-modified styrene-ethylene-butylene-styrene block copolymer.

4. The method for manufacturing a shock-absorbing member for footwear according to claim 3, characterized in that the shock-absorbing composition for footwear used in the molded body forming step further contains a styrene-ethylene-ethylene-propylene-styrene block copolymer.

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