Method for manufacturing a multi-material foamed midsole and multi-material foamed sole

Abstract

This invention discloses a method for preparing a multi-material foamed midsole and a multi-material foamed outsole. The multi-material foamed midsole includes the steps of preparing a welt material, preparing a filling material, preparing a midsole preform, and foaming. The welt material mainly comprises 40-50 parts of a first ethylene vinyl acetate copolymer, 10-15 parts of a second ethylene vinyl acetate copolymer, 20-25 parts of a polyolefin elastomer, 10-20 parts of a hydrogenated styrene-butadiene block copolymer, 2-10 parts of ethylene propylene diene monomer (EPDM) rubber, and other auxiliary components. The filling material mainly comprises 20-30 parts of a first ethylene vinyl acetate copolymer, 25-30 parts of a second ethylene vinyl acetate copolymer, 15-20 parts of a polyolefin elastomer, 20-25 parts of a hydrogenated styrene-butadiene block copolymer, 2-5 parts of EPDM rubber, and other auxiliary components. This preparation method can improve the deformation and cracking at the joints of multi-material midsoles after simultaneous foaming.

Description

Technical Field

[0001] This invention relates to the field of midsole material technology, specifically to a method for preparing a multi-material foamed midsole and a multi-material foamed shoe sole. Background Technology

[0002] To improve the performance of shoe midsoles in response to the different needs of various parts of the foot, different materials or midsole materials with different properties can be used in different parts of the midsole. Current midsoles are generally made of foamed materials such as EVA and TPEE. When using at least two foamed materials in the midsole, the two materials need to be joined together before foaming. This joining is usually done with glue, followed by foaming. However, because different materials have different foaming ratios under the same temperature and environment, simultaneous foaming can lead to deformation of the foamed midsole and cracking at the joints between different materials. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned defects or problems in the prior art and to provide a method for preparing a multi-material foamed midsole and a multi-material foamed shoe sole, which can improve the deformation and cracking at the joints of the multi-material midsole after foaming.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for preparing a multi-material foamed midsole includes the following steps: Preparing the welt material: Mixing the following components in parts by weight at 115±5℃ for 10-15 min: 40-50 parts of ethylene-vinyl acetate copolymer, 10-15 parts of ethylene-vinyl acetate copolymer, 20-25 parts of polyolefin elastomer, 10-20 parts of hydrogenated styrene-butadiene block copolymer, 2-10 parts of ethylene propylene diene monomer (EPDM) rubber, 0.2-0.5 parts of activator, and 4-8 parts of low-temperature foaming agent. First, add 0.5-1 parts by weight of the following additives and 0.5-1 parts by weight of the crosslinking agent, and mix at 120±5℃ for 10-15 min; Second, mix the following components at 115±5℃ for 10-15 min: 20-30 parts by weight of the first ethylene vinyl acetate copolymer, 25-30 parts by weight of the second ethylene vinyl acetate copolymer, 15-20 parts by weight of the polyolefin elastomer, 20-25 parts by weight of the hydrogenated styrene-butadiene block copolymer, and 3... Mix 2-5 parts of ethylene propylene rubber, 9-10 parts of abrasion resistant agent, 0.2-0.5 parts of activator, and 4-8 parts of low-temperature foaming agent; then add 0.5-1 parts of the following additives and 0.5-1 parts of crosslinking agent by weight, and mix at 120±5℃ for 10-15 minutes; prepare the midsole preform: inject the molten sprue and filler into the preform mold, and surround the filler with the sprue to form the sprue part and the filler body respectively, so that the sprue part and the filler body are joined together. The joints are bonded together, and then allowed to cool naturally to obtain the midsole preform; foaming: the midsole preform is placed in a foaming mold, the mold temperature is set to 172±3℃, and the mold is evacuated. After 7-8 minutes, the foaming is completed. The foamed product is taken out and allowed to cool naturally at room temperature to obtain the foamed midsole; wherein, the vinyl acetate (VA) content in the first ethylene vinyl acetate copolymer is 26%, and the vinyl acetate (VA) content in the second ethylene vinyl acetate copolymer is 33%.

[0006] Furthermore, the hydrogenated styrene-butadiene block copolymer is a star-shaped SEBS with a molecular weight of 300,000 to 350,000.

[0007] Furthermore, the polyolefin elastomer is designated as POE8003.

[0008] Furthermore, the active agent is stearic acid.

[0009] Furthermore, the wear-resistant agent is an organosilicon wear-resistant agent.

[0010] Furthermore, the additive is zinc carbonate.

[0011] Furthermore, the crosslinking agent is dicumyl peroxide.

[0012] Furthermore, the low-temperature foaming agent is white azodicarbonamide.

[0013] In addition, the present invention also provides a multi-material foamed shoe sole, characterized in that the multi-material foamed shoe sole is obtained by using a foamed midsole prepared by the preparation method of the multi-material foamed midsole as described in any one of technical solutions one to eight as raw material, and by a molding process; in the molding process, the mold heating time is 8-9 minutes, the mold heating temperature is 160±5℃, and the cooling time is 7-8 minutes.

[0014] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0015] This invention provides a method for preparing a multi-material foamed midsole and a multi-material foamed shoe sole. The multi-material foamed midsole prepared by this method has different foaming ratios for the welt material and the filling material, but the foamed midsole is basically free from deformation. There is no cracking at the joint between the welt material and the filling material. At the same time, the welt part formed by the welt material has better support performance, and the filling part formed by the filling material has better shock absorption performance, which can meet the usage requirements of the shoe sole.

[0016] In this invention, the main components of the welt and the stuffing are both ethylene-vinyl acetate copolymer, polyolefin elastomer, and hydrogenated styrene-butadiene block copolymer. However, because the welt and stuffing are applied in different positions within the midsole preform, their formulation proportions differ significantly. By finely adjusting the mass proportions of the corresponding components, the welt enhances its support performance while maintaining good resilience, and the stuffing further enhances its rebound and cushioning performance. Simultaneously, although there is a difference in the foaming ratio between the welt and stuffing during simultaneous foaming at different mass proportions, their shrinkage is essentially the same during the cooling process after foaming due to the use of essentially the same components. The deformation of the midsole after foaming is precisely due to shrinkage. This is caused by inconsistent shrinkage during the process; furthermore, polyolefin elastomers are added to the welt and stuffing materials, which help the welt and stuffing maintain good shape stability during shrinkage; in addition, if the midsole deforms after foaming, it can cause cracks at the points where the different materials were originally connected by glue. However, in this invention, the welt and stuffing are already bonded together during injection, and physical cross-linking occurs at the bonded areas during foaming to form a spatial network structure. This ensures that even if there is slight deformation during the cooling process after foaming, the bond between the welt and stuffing remains very strong, and there will be no uneven edges between the two materials at the joint.

[0017] In this invention, two ethylene vinyl acetate copolymers with different VA contents are used in the composition. EVA with a VA content of 26% provides basic hardness and wear resistance, thus giving the final material a better shock absorption effect. EVA with a VA content of 33% provides the material with better softness and elasticity, thus giving the final material better resilience. The different amounts of the two ethylene vinyl acetate copolymers in the edging material and the filling material result in different physical properties for the edging part and the filling part.

[0018] In addition, hydrogenated styrene-butadiene block copolymer is specifically added, preferably star-shaped SEBS with a molecular weight of 300,000 to 350,000. Adding a certain amount of star-shaped SEBS can improve the deformation resistance of the styrene and filler materials, allowing them to better maintain their shape during shrinkage after foaming. Furthermore, SEBS itself has good mechanical properties and can be combined with ethylene-vinyl acetate copolymers and polyolefin elastomers to improve the resilience of the final material, while also enhancing the surface finish of the product.

[0019] Using a low-temperature foaming agent can reduce the influence of the foaming agent's color on the final material. Furthermore, foaming at low temperatures can reduce the overall foaming ratio, thereby reducing the difference in foaming ratio between the liner material and the filler material. This also further improves the situation where the midsole deforms after foaming. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] In the claims and description of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0022] This invention provides a method for preparing a multi-material foamed midsole and a multi-material foamed shoe sole. The method for preparing the multi-material foamed midsole includes the following steps:

[0023] Step 1: Preparation of the liner material: Mix the following components in parts by weight at 115±5℃ for 10-15 min: 40-50 parts of ethylene-vinyl acetate copolymer, 10-15 parts of ethylene-vinyl acetate copolymer, 20-25 parts of polyolefin elastomer, 10-20 parts of hydrogenated styrene-butadiene block copolymer, 2-10 parts of ethylene propylene diene monomer (EPDM) rubber, 0.2-0.5 parts of activator, and 4-8 parts of low-temperature foaming agent; then add 0.5-1 parts of the following additives and 0.5-1 parts of crosslinking agent, and mix at 120±5℃ for 10-15 min.

[0024] Step 2: Preparation of filling material: Mix the following components in parts by weight at 115±5℃ for 10-15 min: 20-30 parts of first ethylene vinyl acetate copolymer, 25-30 parts of second ethylene vinyl acetate copolymer, 15-20 parts of polyolefin elastomer, 20-25 parts of hydrogenated styrene-butadiene block copolymer, 2-5 parts of ethylene propylene diene monomer (EPDM) rubber, 9-10 parts of abrasion resistant agent, 0.2-0.5 parts of activator, and 4-8 parts of low-temperature foaming agent; then add 0.5-1 parts of the following additives and 0.5-1 parts of crosslinking agent, and mix at 120±5℃ for 10-15 min.

[0025] Step 3: Preparation of midsole preform: The molten sprue and filling material are injected into the preform mold, and the sprue is wrapped around the filling material to form the sprue part and the filling part respectively. The joint of the sprue part and the filling part is bonded together, and then the preform is allowed to stand and cool to obtain the midsole preform.

[0026] Step 4, Foaming: Place the midsole preform into the foaming mold, set the mold temperature to 172±3℃, and evacuate the mold. After 7-8 minutes, foaming is complete. Take out the foamed product and let it cool naturally at room temperature to obtain the foamed midsole.

[0027] The first ethylene vinyl acetate copolymer contains 26% vinyl acetate (VA), and the second ethylene vinyl acetate copolymer contains 33% vinyl acetate (VA).

[0028] The hydrogenated styrene-butadiene block copolymer uses star-shaped SEBS with a molecular weight of 300,000 to 350,000, designated as Baling Petrochemical 604T. The wear-resistant agent is an organosilicon wear-resistant agent, specifically a silicone coupling agent. The activator is stearic acid. The additive is zinc carbonate. The crosslinking agent is dicumyl peroxide. The low-temperature foaming agent is white azodicarbonamide.

[0029] After the midsole preform is prepared, it is foamed. During the foaming process, as the temperature of the preform increases from the surface to the inside, the preform is in a molten state. The decomposition temperature of the low-temperature foaming agent is about 135℃. It decomposes rapidly in the mold, with a gas emission of 120mL / g. The decomposition gas is mainly nitrogen, with the remainder being carbon monoxide, carbon dioxide, and a small amount of ammonia. Under the action of the foaming agent, the periphery and the filling of the preform gradually expand, and the different components cross-link to form a network structure until the foaming time is completed. The foamed product can then be obtained by opening the mold.

[0030] This invention provides a method for preparing a multi-material foamed midsole and a multi-material foamed shoe sole. The multi-material foamed midsole prepared by this method has different foaming ratios for the welt material and the filling material, but the foamed midsole is basically free from deformation. There is no cracking at the joint between the welt material and the filling material. At the same time, the welt part formed by the welt material has better support performance, and the filling part formed by the filling material has better shock absorption performance, which can meet the usage requirements of the shoe sole.

[0031] In this invention, the main components of the welt and the stuffing are both ethylene-vinyl acetate copolymer, polyolefin elastomer, and hydrogenated styrene-butadiene block copolymer. However, because the welt and stuffing are applied in different positions within the midsole preform, their formulation proportions differ significantly. By finely adjusting the mass proportions of the corresponding components, the welt enhances its support performance while maintaining good resilience, and the stuffing further enhances its rebound and cushioning performance. Simultaneously, although there is a difference in the foaming ratio between the welt and stuffing during simultaneous foaming at different mass proportions, their shrinkage is essentially the same during the cooling process after foaming due to the use of essentially the same components. The deformation of the midsole after foaming is precisely due to shrinkage. This is caused by inconsistent shrinkage during the process; furthermore, polyolefin elastomers are added to the welt and stuffing materials, which help the welt and stuffing maintain good shape stability during shrinkage; in addition, if the midsole deforms after foaming, it can cause cracks at the points where the different materials were originally connected by glue. However, in this invention, the welt and stuffing are already bonded together during injection, and physical cross-linking occurs at the bonded areas during foaming to form a spatial network structure. This ensures that even if there is slight deformation during the cooling process after foaming, the bond between the welt and stuffing remains very strong, and there will be no uneven edges between the two materials at the joint.

[0032] In this invention, two ethylene vinyl acetate copolymers with different VA contents are used in the composition. EVA with a VA content of 26% provides basic hardness and wear resistance, thus giving the final material a better shock absorption effect. EVA with a VA content of 33% provides the material with better softness and elasticity, thus giving the final material better resilience. The different amounts of the two ethylene vinyl acetate copolymers in the edging material and the filling material result in different physical properties for the edging part and the filling part.

[0033] In addition, hydrogenated styrene-butadiene block copolymer is specifically added, preferably star-shaped SEBS with a molecular weight of 300,000 to 350,000. Adding a certain amount of star-shaped SEBS can improve the deformation resistance of the styrene and filler materials, allowing them to better maintain their shape during shrinkage after foaming. Furthermore, SEBS itself has good mechanical properties and can be combined with ethylene-vinyl acetate copolymers and polyolefin elastomers to improve the resilience of the final material, while also enhancing the surface finish of the product.

[0034] Using a low-temperature foaming agent can reduce the influence of the foaming agent's color on the final material. Furthermore, foaming at low temperatures can reduce the overall foaming ratio, thereby reducing the difference in foaming ratio between the liner material and the filler material. This also further improves the situation where the midsole deforms after foaming.

[0035] Furthermore, this invention also provides a multi-material foamed shoe sole, which uses a foamed midsole prepared by the above-mentioned method as raw material, and obtains the multi-material foamed shoe sole through a molding process; in the molding process, the mold heating time is 8-9 minutes, the mold heating temperature is 160±5℃, and the cooling time is 7-8 minutes. Specifically, after the prepared foamed midsole is placed in the mold, the mold is closed and heated. After completing the hot pressing process according to the predetermined heating temperature and heating time, the mold is opened, and the hot-pressed product is cooled in the mold for 7-8 minutes. After being removed, it is left to cool naturally at room temperature for 24 hours to obtain the above-mentioned multi-material foamed shoe sole.

[0036] To further illustrate the performance of the multi-material foamed midsole provided by the present invention, the following embodiments and comparative examples are provided.

[0037] Example 1

[0038] Weigh the components according to the following parts by mass:

[0039] The styrene strip material consists of: 42 parts of first-stage ethylene-vinyl acetate copolymer; 12 parts of second-stage ethylene-vinyl acetate copolymer; 24 parts of polyolefin elastomer; 18 parts of hydrogenated styrene-butadiene block copolymer; 4 parts of ethylene propylene diene monomer (EPDM) rubber; 0.44 parts of activator; 0.8 parts of additives; 0.56 parts of crosslinking agent; and 4.5 parts of low-temperature foaming agent.

[0040] Filler: First ethylene vinyl acetate copolymer: 25 parts; Second ethylene vinyl acetate copolymer: 30 parts; Polyolefin elastomer: 20 parts; Hydrogenated styrene-butadiene block copolymer: 22 parts; EPDM rubber: 3 parts; Abrasion resistant agent: 9.23 parts; Activator: 0.46 parts; Additives: 0.9 parts; Crosslinking agent: 0.63 parts; Low-temperature foaming agent: 6.2 parts.

[0041] The vinyl acetate content in the first ethylene-vinyl acetate copolymer is 26%, and the vinyl acetate content in the second ethylene-vinyl acetate copolymer is 33%. The hydrogenated styrene-butadiene block copolymer uses star-shaped SEBS with a molecular weight of 300,000 to 350,000, designated as Baling Petrochemical 604T. The wear-resistant agent is an organosilicon wear-resistant agent, specifically a silicone coupling agent. The activator is stearic acid. The additive is zinc carbonate. The high crosslinking agent is dicumyl peroxide. The low-temperature foaming agent is white azodicarbonamide.

[0042] Using the above components as raw materials, a multi-material midsole preform is prepared according to the following steps:

[0043] Step 1: Preparation of the sling material: Weigh out the components of the sling material other than the additives and crosslinking agents according to the mass proportions, and mix them at 115℃ for 10 min; then add the additives and crosslinking agents, and mix them at 120℃ for 10 min.

[0044] Step 2: Preparation of filling material: Weigh out the other components of the filling material except for the additives and crosslinking agents according to the mass proportions, and mix them at 115℃ for 10 min; then add the additives and crosslinking agents, and mix them at 120℃ for 10 min.

[0045] Step 3: Preparation of midsole preform: The molten sprue and filler material are injected into the preform mold, and the sprue material is wrapped around the filler material to form the sprue part and the filler part respectively, so that the joint between the sprue material and the filler material is bonded. Then, it is allowed to stand and cool to obtain the midsole preform.

[0046] Step 4: Foaming: Place the midsole preform into the foaming mold, set the mold temperature to 172℃, and evacuate the mold. After 7.5 minutes, foaming is complete. Remove the foamed product and let it cool naturally at room temperature to obtain the foamed midsole.

[0047] Example 2

[0048] Weigh the components according to the following parts by mass:

[0049] The styrene strip material consists of: 45 parts of first-order ethylene-vinyl acetate copolymer; 10 parts of second-order ethylene-vinyl acetate copolymer; 23 parts of polyolefin elastomer; 17 parts of hydrogenated styrene-butadiene block copolymer; 5 parts of ethylene propylene diene monomer (EPDM) rubber; 0.42 parts of activator; 0.75 parts of additives; 0.6 parts of crosslinking agent; and 5 parts of low-temperature foaming agent.

[0050] Filler: First ethylene vinyl acetate copolymer: 26 parts; Second ethylene vinyl acetate copolymer: 29 parts; Polyolefin elastomer: 18 parts; Hydrogenated styrene-butadiene block copolymer: 21 parts; EPDM rubber: 4 parts; Abrasion resistant agent: 9.5 parts; Activator: 0.48 parts; Additives: 0.85 parts; Crosslinking agent: 0.65 parts; Low-temperature foaming agent: 6.5 parts.

[0051] The vinyl acetate content in the first ethylene-vinyl acetate copolymer is 26%, and the vinyl acetate content in the second ethylene-vinyl acetate copolymer is 33%. The hydrogenated styrene-butadiene block copolymer uses star-shaped SEBS with a molecular weight of 300,000 to 350,000, designated as Baling Petrochemical 604T. The wear-resistant agent is an organosilicon wear-resistant agent, specifically a silicone coupling agent. The activator is stearic acid. The additive is zinc carbonate. The high crosslinking agent is dicumyl peroxide. The low-temperature foaming agent is white azodicarbonamide.

[0052] Using the above components as raw materials, a multi-material midsole preform is prepared according to the following steps:

[0053] Step 1: Preparation of the sling material: Weigh out the components of the sling material other than the additives and crosslinking agents according to the mass proportions, and mix them at 115℃ for 15 minutes; then add the additives and crosslinking agents, and mix them at 120℃ for 15 minutes.

[0054] Step 2: Preparation of filling material: Weigh out the other components of the filling material except for the additives and crosslinking agents according to the mass proportions, and mix them at 115℃ for 15 min; then add the additives and crosslinking agents, and mix them at 120℃ for 15 min.

[0055] Step 3: Preparation of midsole preform: The molten sprue and filler material are injected into the preform mold, and the sprue material is wrapped around the filler material to form the sprue part and the filler part respectively, so that the joint between the sprue material and the filler material is bonded. Then, it is allowed to stand and cool to obtain the midsole preform.

[0056] Step 4: Foaming: Place the midsole preform into the foaming mold, set the mold temperature to 172℃, and evacuate the mold. After 7.5 minutes, foaming is complete. Remove the foamed product and let it cool naturally at room temperature to obtain the foamed midsole.

[0057] Example 3

[0058] Weigh the components according to the following parts by mass:

[0059] The styrene strip material consists of: 43 parts of first-order ethylene-vinyl acetate copolymer; 11 parts of second-order ethylene-vinyl acetate copolymer; 22 parts of polyolefin elastomer; 16 parts of hydrogenated styrene-butadiene block copolymer; 4 parts of ethylene propylene diene monomer (EPDM) rubber; 0.4 parts of activator; 0.78 parts of additives; 0.58 parts of crosslinking agent; and 4.8 parts of low-temperature foaming agent.

[0060] Filler: First ethylene vinyl acetate copolymer: 24 parts; Second ethylene vinyl acetate copolymer: 28 parts; Polyolefin elastomer: 19 parts; Hydrogenated styrene-butadiene block copolymer: 23 parts; EPDM rubber: 3 parts; Abrasion resistant agent: 9.8 parts; Activator: 0.45 parts; Additives: 0.88 parts; Crosslinking agent: 0.62 parts; Low-temperature foaming agent: 6.3 parts.

[0061] The vinyl acetate content in the first ethylene-vinyl acetate copolymer is 26%, and the vinyl acetate content in the second ethylene-vinyl acetate copolymer is 33%. The hydrogenated styrene-butadiene block copolymer uses star-shaped SEBS with a molecular weight of 300,000 to 350,000, designated as Baling Petrochemical 604T. The wear-resistant agent is an organosilicon wear-resistant agent, specifically a silicone coupling agent. The activator is stearic acid. The additive is zinc carbonate. The high crosslinking agent is dicumyl peroxide. The low-temperature foaming agent is white azodicarbonamide.

[0062] Using the above components as raw materials, a multi-material midsole preform is prepared according to the following steps:

[0063] Step 1: Preparation of the sling material: Weigh out the components of the sling material other than the additives and crosslinking agents according to the mass proportions, and mix them at 115℃ for 15 minutes; then add the additives and crosslinking agents, and mix them at 120℃ for 15 minutes.

[0064] Step 2: Preparation of filling material: Weigh out the other components of the filling material except for the additives and crosslinking agents according to the mass proportions, and mix them at 115℃ for 15 min; then add the additives and crosslinking agents, and mix them at 120℃ for 15 min.

[0065] Step 3: Preparation of midsole preform: The molten sprue and filler material are injected into the preform mold, and the sprue material is wrapped around the filler material to form the sprue part and the filler part respectively, so that the joint between the sprue material and the filler material is bonded. Then, it is allowed to stand and cool to obtain the midsole preform.

[0066] Step 4: Foaming: Place the midsole preform into the foaming mold, set the mold temperature to 172℃, and evacuate the mold. After 7.5 minutes, foaming is complete. Remove the foamed product and let it cool naturally at room temperature to obtain the foamed midsole.

[0067] Comparative Example 1

[0068] Based on Example 1, the difference is that neither the wrapping material nor the filling material in the formulation includes polyolefin elastomer components.

[0069] Comparative Example 2

[0070] Based on Example 1, the difference lies in the fact that the first ethylene vinyl acetate in the sling material is replaced with thermoplastic polyester elastomer TPEE in the formulation components.

[0071] Comparative Example 3

[0072] Based on Example 1, the difference is that neither the styrene-butadiene block copolymer component is included in the formulation components of the styrene-butadiene block copolymer for the styrene-butadiene and the filling materials.

[0073] The foamed midsoles prepared in Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3 were examined visually and tactilely. The foamed midsoles prepared in Examples 1, 2, and 3 showed virtually no deformation, with clear boundaries and no cracks at the junction of the ferrule and the filling. The foamed midsole prepared in Comparative Example 1 showed some deformation, with cracks appearing at the junction of the ferrule and the filling. The foamed midsole prepared in Comparative Example 2 showed even greater deformation than Comparative Example 1, with significant cracks appearing at the junction of the ferrule and the filling. The foamed midsole prepared in Comparative Example 3 also showed some deformation, with some cracks appearing at the junction of the ferrule and the filling. The examination revealed that, compared to Examples 1, 2, and 3, Comparative Examples 1, 2, and 3 all exhibited varying degrees of deformation and cracking, demonstrating that the multi-material foamed midsole preparation method provided by this invention can improve the deformation and cracking at the junctions of midsoles with multiple materials after simultaneous foaming.

[0074] The foregoing description of the specifications and embodiments is intended to explain the scope of protection of this invention, but does not constitute a limitation on the scope of protection of this invention. Modifications, equivalent substitutions, or other improvements to the embodiments of this invention or a portion thereof that can be obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this invention or the foregoing embodiments, in conjunction with common knowledge, general technical knowledge, and / or existing technology, should all be included within the scope of protection of this invention.

Claims

1. A method for preparing a multi-material foamed midsole, characterized in that, Includes the following steps: Preparation of the liner material: Mix the following components in parts by weight at 115±5℃ for 10-15 min: 40-50 parts of first ethylene vinyl acetate copolymer, 10-15 parts of second ethylene vinyl acetate copolymer, 20-25 parts of polyolefin elastomer, 10-20 parts of hydrogenated styrene-butadiene block copolymer, 2-10 parts of ethylene propylene diene monomer (EPDM) rubber, 0.2-0.5 parts of activator, and 4-8 parts of low-temperature foaming agent; then add 0.5-1 parts of additives and 0.5-1 parts of crosslinking agent, and mix at 120±5℃ for 10-15 min. Preparation of filling material: Mix the following components in parts by weight at 115±5℃ for 10-15 min: 20-30 parts of first ethylene vinyl acetate copolymer, 25-30 parts of second ethylene vinyl acetate copolymer, 15-20 parts of polyolefin elastomer, 20-25 parts of hydrogenated styrene-butadiene block copolymer, 2-5 parts of ethylene propylene diene monomer (EPDM) rubber, 9-10 parts of abrasion resistant agent, 0.2-0.5 parts of activator, and 4-8 parts of low-temperature foaming agent; then add 0.5-1 parts of additives and 0.5-1 parts of crosslinking agent, and mix at 120±5℃ for 10-15 min. Preparation of midsole preform: The molten sprue and filling material are injected into the preform mold, and the sprue is wrapped around the filling material to form the sprue part and the filling part respectively. The joint of the sprue part and the filling part is bonded together, and then the preform is allowed to stand and cool to obtain the midsole preform. Foaming: Place the midsole preform into the foaming mold, set the mold temperature to 172±3℃, and evacuate the mold. After 7-8 minutes, the foaming is complete. Take out the foamed product and let it cool naturally at room temperature to obtain the foamed midsole. The first ethylene vinyl acetate copolymer contains 26% vinyl acetate, and the second ethylene vinyl acetate copolymer contains 33% vinyl acetate; the additive is zinc carbonate.

2. The method for preparing a multi-material foamed midsole as described in claim 1, characterized in that, The hydrogenated styrene-butadiene block copolymer uses star-shaped SEBS with a molecular weight of 300,000 to 350,000.

3. The method for preparing a multi-material foamed midsole as described in claim 2, characterized in that, The polyolefin elastomer is designated as POE8003.

4. The method for preparing a multi-material foamed midsole as described in claim 1, characterized in that, The active agent is stearic acid.

5. The method for preparing a multi-material foamed midsole as described in claim 1, characterized in that, The wear-resistant agent is an organosilicon wear-resistant agent.

6. The method for preparing a multi-material foamed midsole as described in claim 1, characterized in that, The crosslinking agent is dicumyl peroxide.

7. The method for preparing a multi-material foamed midsole as described in claim 1, characterized in that, The low-temperature foaming agent is white azodicarbonamide.

8. A multi-material foamed shoe sole, characterized in that, Using the foamed midsole prepared by the method of any one of claims 1-7 as raw material, the multi-material foamed shoe sole is obtained by compression molding process; in the compression molding process, the mold heating time is 8-9 min, the mold heating temperature is 160 ±5℃, and the cooling time is 7-8 min.