Wear-resistant degradable EVA composite shoe material and preparation method thereof

Abstract

The application relates to the technical field of shoe material preparation, and discloses a wear-resistant degradable EVA composite shoe material and a preparation method thereof. The shoe material comprises the following components in mass fractions: 55-70 parts of EVA resin; 10-20 parts of modified polylactic acid; 5-10 parts of polyurethane prepolymer; 3-8 parts of polycaprolactone microspheres; 2-6 parts of polylactic acid-hydroxyacetic acid copolymer; 2-5 parts of plasticizer; 0.5-1.5 parts of initiator; and 0.2-0.5 parts of antioxidant. The preparation method comprises the following steps: polycaprolactone microsphere preparation; preparation of a modified polylactic acid-polyurethane prepolymer crosslinking system; blending, extrusion and granulation; and shoe material forming. The application regulates degradation and strength, solves the contradiction between environmental protection and durability, uses microspheres to construct micropores, takes into account air permeability and mechanical properties, improves wear resistance and stability based on interpenetrating networks and multiphase synergy, and realizes the synergistic optimization of environmental protection, comfort and durability.

Description

Technical Field

[0001] This invention relates to the field of footwear material preparation technology, specifically to a wear-resistant, biodegradable EVA composite footwear material and its preparation method. Background Technology

[0002] With the increasing popularity of environmental protection concepts, consumers' requirements for footwear materials are no longer limited to comfort and durability. More and more people are beginning to pay attention to the environmental friendliness and biodegradability of footwear materials. Although traditional EVA footwear materials have good flexibility and comfort, their poor breathability, insufficient abrasion resistance, and poor biodegradability make them a burden on the environment after long-term use. Therefore, how to solve these shortcomings of traditional EVA materials while meeting consumers' comprehensive needs for environmental protection, comfort, and durability has become a hot topic in current footwear material technology research.

[0003] In existing technologies, many researchers have attempted to improve the environmental performance of EVA materials by combining biodegradable materials such as polylactic acid (PLA) with traditional polymers like EVA. Due to its excellent biodegradability, PLA is often used as an environmentally friendly alternative to traditional petroleum-based plastics. However, PLA's mechanical properties are relatively poor, particularly in terms of abrasion resistance and aging resistance, which fail to meet the requirements for long-term use in footwear materials. Furthermore, PLA's high crystallinity makes it prone to embrittlement during use, affecting the performance and lifespan of footwear materials. Therefore, the application of PLA alone cannot effectively solve the shortcomings of existing EVA materials.

[0004] Therefore, this invention proposes a wear-resistant and biodegradable EVA composite shoe material and its preparation method to overcome the shortcomings of the prior art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a wear-resistant and biodegradable EVA composite shoe material and its preparation method, solving the problems of poor breathability and insufficient degradability of traditional EVA shoe materials, as well as the difficulty in balancing degradability and durability caused by the poor mechanical properties and brittleness of polylactic acid materials.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: A wear-resistant and biodegradable EVA composite shoe material comprises the following components in parts by weight: 55-70 parts of EVA resin; 10-20 parts of modified polylactic acid; 5-10 parts of polyurethane prepolymer; 3-8 parts of polycaprolactone microspheres; 2-6 parts of polylactic acid-glycolic acid copolymer; 2-5 parts of plasticizer; 0.5-1.5 parts of initiator; and 0.2-0.5 parts of antioxidant.

[0007] EVA resin:

[0008] EVA resin is the matrix material of this composite footwear material. As a polymer base, EVA resin has good elasticity and abrasion resistance. The content of its vinyl acetate monomer has a significant impact on the material's flexibility, transparency, cold resistance, and other properties. By adjusting the vinyl acetate content in the EVA resin, the mechanical strength and durability of the footwear material can be enhanced while ensuring the material's softness and comfort.

[0009] Because the EVA resin in this invention contains an appropriate amount of vinyl acetate, the material maintains good flexibility while also providing high abrasion resistance. Furthermore, the strong plasticizing properties of EVA resin help improve the processability of the shoe material, facilitating subsequent molding processes.

[0010] Modified polylactic acid:

[0011] Modified polylactic acid (PLA), as a biodegradable material, is widely used in environmentally friendly materials. The use of modified PLA in this invention not only improves the material's biodegradability but also enhances the mechanical strength of the composite material. Modified PLA acts as a reinforcing phase in this composite material, helping to improve its structural stability, and exhibits good compatibility with other components, enabling the formation of a uniform composite structure during the production process.

[0012] Polylactic acid (PLA) can be blended with EVA resin to improve the degradation performance of the material. This modification, by introducing an appropriate amount of glycolic acid copolymer, allows for a controlled balance between compatibility and mechanical strength, thereby improving the stability of the composite material in various environments.

[0013] Polyurethane prepolymer:

[0014] Polyurethane prepolymers possess excellent elasticity, abrasion resistance, and oil resistance, and are widely used to improve the mechanical properties of materials. In this invention, the use of polyurethane prepolymers not only enhances the material's elasticity but also improves its abrasion resistance and anti-aging properties. By controlling the polyurethane content, the hardness and flexibility of the shoe material can be adjusted, resulting in a final product with better comfort and durability.

[0015] The role of polyurethane prepolymer in this invention is not only to enhance the mechanical strength of the shoe material, but also to further improve the abrasion resistance and compressive strength of the composite material through cross-linking reactions. This improves the physical properties of traditional EVA materials, making the composite shoe material more durable during long-term use.

[0016] Polycaprolactone microspheres:

[0017] Polycaprolactone (PCL) microspheres possess good biocompatibility and biodegradability. Adding them to composite materials not only enhances the degradation performance of footwear materials but also, to some extent, modifies the microstructure of the material, thereby improving its mechanical properties. As a filler material, PCL microspheres can also effectively improve the breathability and comfort of composite materials.

[0018] The addition of polycaprolactone microspheres improves the structure of the composite material, forming a microporous structure that not only enhances the material's breathability and comfort but also strengthens its biodegradability. This innovation allows the material to better meet the demands for both environmental friendliness and durability.

[0019] Polylactic acid-glycolic acid copolymer:

[0020] The introduction of polylactic acid-glycolic acid copolymer further improves the biodegradability of the composite material. This copolymer can effectively regulate the compatibility and biodegradation rate of the material, enabling it to degrade rapidly after a period of use while maintaining mechanical properties, thus reducing environmental pollution.

[0021] By adjusting the ratio of the copolymer, the degradation rate and mechanical properties of the material can be precisely controlled. This innovative design not only improves the environmental friendliness of the product, but also enhances its performance, achieving a balance between comfort and durability in footwear materials during use.

[0022] Plasticizer:

[0023] The addition of plasticizers gives composite materials better processing performance and flexibility, especially in terms of toughness at low temperatures. Plasticizers can reduce the hardness of materials and improve their moldability, allowing the composite materials to be easily molded and possess good elasticity during the footwear manufacturing process.

[0024] Plasticizers improve the processing properties of composite materials, allowing the final footwear materials to maintain good flexibility and comfort under various environmental conditions. Furthermore, appropriate amounts of plasticizers can enhance the adjustability of the material, making the resulting footwear materials more suitable for different consumer needs.

[0025] Initiator:

[0026] The role of initiators is to initiate cross-linking reactions, promote cross-linking between materials, and improve the mechanical properties and thermal stability of the materials. The addition of initiators helps enhance the cross-linking effect of polyurethane prepolymers, further improving the high-temperature resistance and mechanical strength of the composite materials.

[0027] Initiators enhance the thermal stability and mechanical properties of materials by improving the efficiency of cross-linking reactions, enabling the final composite shoe material to maintain stable performance and extend its service life under high temperature and high load conditions.

[0028] Antioxidants:

[0029] The main function of antioxidants in composite materials is to prevent degradation due to high temperatures or oxidation reactions during processing, ensuring the performance stability of the composite material during processing and use. The addition of antioxidants prevents excessive oxidation and thermal degradation of the material under high-temperature environments, maintaining its durability and performance.

[0030] The use of antioxidants effectively extends the service life of composite materials, especially for footwear products that are in long-term contact with the external environment. They prevent thermal degradation and oxidation, thereby maintaining the appearance and performance stability of the footwear materials.

[0031] Preferably, the VA content of the EVA resin is 28-33 parts, and the melt index is 2-4 g / 10 min.

[0032] EVA resin is a high-performance material with a specific range of VA (vinyl acetate) content, ranging from 28 to 33 parts, and a melt flow index of 2-4 g / 10 min. This characteristic gives EVA resin excellent flexibility, processability, and abrasion resistance, providing a good foundation for composite footwear materials. As the main matrix material, EVA resin, through its unique molecular structure, provides the necessary mechanical properties while ensuring the comfort and environmental friendliness of the composite material.

[0033] Specifically, the VA content of EVA resin is 28-33 parts, which allows it to maintain good physical properties at lower temperatures while providing good flexibility. This VA content range results in a lower melt viscosity during processing, enabling smoother processing and molding. Furthermore, this VA content allows EVA resin to effectively reduce friction and wear during use in footwear materials, improving the durability and comfort of the shoes.

[0034] The EVA resin in this invention optimizes its physical properties by adjusting the VA content, achieving a balance between flexibility, abrasion resistance, and impact resistance in the composite shoe material over long-term use. A higher VA content gives the EVA resin greater flexibility, thus improving the comfort of the shoe material while maintaining good abrasion resistance and impact resistance. A lower melt flow index (2-4 g / 10 min) gives the EVA resin good processing performance, enabling smooth molding during production, improving production efficiency, and ensuring the high quality of the composite shoe material.

[0035] By precisely controlling the VA content and melt flow index of EVA resin, its comprehensive performance in footwear materials is optimized. In the design of composite materials, the rational combination of EVA resin as a matrix material with other components comprehensively enhances the comfort, durability, and environmental friendliness of the footwear materials in actual use. This precise component formulation and optimized design allows this invention to overcome the limitations of traditional footwear materials, achieving the dual goals of green environmental protection and high performance.

[0036] Preferably, the modified polylactic acid has a molecular weight of 80,000-120,000 g / mol, the modified polylactic acid is a copolymer of polylactic acid and polycaprolactone, and the mass ratio of polylactic acid to polycaprolactone is 80:20-60:40.

[0037] Modified polylactic acid (PLA) is copolymerized from PLA and polycaprolactone (PVC), with a molecular weight between 80,000 and 120,000 g / mol and a PLA to PVC mass ratio of 80:20 to 60:40. This design not only provides good biodegradability but also optimizes mechanical properties, ensuring the material is environmentally friendly, durable, and comfortable.

[0038] The higher molecular weight improves the mechanical properties, crystallinity, thermal stability, and anti-aging ability of polylactic acid (PLA), especially in terms of tensile strength and impact resistance. By adjusting the ratio of PLA to polycaprolactone (PCL), PLA provides excellent biodegradability, while PCL improves flexibility and impact resistance. The plasticizing effect ensures better ductility of the material and avoids cracking.

[0039] This copolymer design balances environmental friendliness with mechanical properties, enhancing the overall performance of the composite material and enabling the final product to meet degradation requirements while possessing excellent durability and functionality.

[0040] Preferably, the polyurethane prepolymer is a block copolymer prepared by addition polymerization of polyhexanediol and isocyanate, wherein the mass ratio of polyhexanediol to isocyanate is 1:1.2-1:1.5.

[0041] Polyurethane prepolymers in composite materials primarily enhance abrasion resistance, flexibility, and aging resistance, while also improving mechanical properties, providing good comfort and durability. Through the addition polymerization reaction of polyhexanediol and isocyanate, a cross-linked structure is formed, giving the material higher mechanical strength and elasticity.

[0042] The introduction of polyhexanediol enhances flexibility, while the reactivity of isocyanate improves abrasion resistance and anti-aging properties. By adjusting the mass ratio of polyhexanediol to isocyanate (1:1.2 to 1:1.5), the properties of polyurethane prepolymers can be precisely controlled to ensure a balance between flexibility and durability, preventing wear or aging.

[0043] As a block copolymer, polyurethane prepolymer has good molecular structure stability and can work synergistically with components such as EVA resin and modified polylactic acid to form high-performance composite materials.

[0044] Preferably, the particle size of the polycaprolactone microspheres is 200-500 nm.

[0045] Polycaprolactone microspheres, as functional fillers, significantly improve breathability, flexibility, anti-aging properties, and comfort in composite materials. By controlling their particle size within the 200-500nm range, stable microporous structures can be constructed within shoe materials, enhancing moisture release and air circulation, and improving the wearing experience.

[0046] This particle size range ensures good dispersion of microspheres without damaging the material structure, while maintaining flexibility and comfort. The high specific surface area resulting from the smaller particle size helps to form more micropores, improving breathability, while reducing stress concentration and delaying aging.

[0047] In addition, polycaprolactone has good biodegradability. The addition of microspheres to the material enhances the environmental protection properties of the shoe material. After use, it can be naturally degraded, reducing the environmental burden.

[0048] Preferably, the polylactic acid-glycolic acid copolymer is a copolymer of polylactic acid and glycolic acid, and the molar ratio of polylactic acid to glycolic acid is 70:30-80:20.

[0049] Polylactic acid (PLA), as an excellent biodegradable material, can have its degradability regulated and its processability and mechanical properties improved when copolymerized with glycolic acid (GAA). By optimizing the molar ratio of PLA to Glycolic acid (70:30 to 80:20), the degradation rate and overall performance of the material can be precisely controlled. Within this range, a higher proportion of PLA ensures better mechanical properties and thermal stability, while an appropriate amount of Glycolic acid enhances the material's degradability, ensuring rapid degradation after use and reducing environmental pollution.

[0050] This molar ratio adjustment method ensures both long-term material stability and rapid degradation after use, meeting environmental protection requirements. By precisely controlling the degradation rate, this invention achieves excellent mechanical properties and comfort, while simultaneously meeting the growing demand for green and environmentally friendly materials, enhancing material sustainability, and demonstrating an innovative breakthrough in the field of environmental protection.

[0051] This invention also provides a method for preparing wear-resistant and biodegradable EVA composite footwear material, comprising the following steps:

[0052] (1) Preparation of polycaprolactone microspheres: Polycaprolactone is dissolved in dichloromethane to form an oil phase with a mass concentration of 3-6 parts. 1-3 parts of polyvinyl alcohol are added to the aqueous phase as an emulsifier for emulsification. After emulsification by high-speed shearing to form an emulsion, the emulsion is ultrasonically treated. The solvent is evaporated by stirring at room temperature for 6-12 hours. After freeze-drying, polycaprolactone microspheres with a particle size of 200-500 nm are obtained.

[0053] In the preparation process, polycaprolactone is dissolved in dichloromethane to form a 3-6 part oil phase, and 1-3 parts polyvinyl alcohol are added as an emulsifier to stabilize the oil-water mixture. High-speed shearing and ultrasonic treatment are employed during emulsification to ensure that the microsphere particle size is controlled within the range of 200-500 nm, forming uniform and stable microspheres. The solvent is removed by stirring at room temperature and freeze-drying, ultimately yielding polycaprolactone microspheres with uniform particle size.

[0054] The synergistic effect of high-speed shearing and ultrasound optimizes the emulsifier dosage and microsphere size control, ensuring microsphere uniformity and effectively preventing aggregation. Compared with traditional methods, this invention enables the microspheres to be uniformly distributed in the composite material through this process, improving the abrasion resistance and comfort of the shoe material.

[0055] Polycaprolactone microspheres can form a microporous structure in the 200-500nm range, improving breathability and moisture absorption, and gradually degrade during use, reducing environmental pollution. This design balances environmental friendliness with mechanical properties, enhancing the overall performance and sustainability of EVA composite footwear materials, and meeting the requirements of durability, comfort, and environmental protection.

[0056] (2) Preparation of modified polylactic acid-polyurethane prepolymer crosslinking system: Mix modified polylactic acid and polyurethane prepolymer at 140-160℃, add dicumyl peroxide initiator, and stir for 15-30 min to form a crosslinked network structure;

[0057] During the preparation process, modified polylactic acid and polyurethane prepolymer are mixed in a specific ratio, and the temperature is controlled at 140-160℃ to ensure a suitable melt state and avoid thermal degradation. Within this temperature range, the modified polylactic acid maintains good fluidity, and the polyurethane prepolymer exhibits high activity, promoting the crosslinking reaction.

[0058] Dicumyl peroxide is added as an initiator to promote the crosslinking reaction. The amount of initiator added and the stirring time (15-30 minutes) ensure that the crosslinking reaction is sufficient and uniform, forming a stable network structure and enhancing the mechanical properties and thermal stability of the material.

[0059] By optimizing the ratio of polylactic acid to polyurethane prepolymer and the crosslinking temperature, and by using an initiator, the efficiency and uniformity of the crosslinking reaction were ensured. This crosslinked structure improves the material's impact resistance, abrasion resistance, and overall strength, and enhances the ductility and stability of the composite footwear material.

[0060] Compared with traditional methods, this invention avoids uneven cross-linking and agglomeration problems through reasonable temperature control and initiator combination, forming a composite material with elasticity and strength, optimizing mechanical properties and processing stability, and improving the wear resistance, toughness and environmental protection of footwear materials.

[0061] (3) Blending extrusion granulation: EVA resin, modified polylactic acid-polyurethane prepolymer crosslinking system, polycaprolactone microspheres, polylactic acid-glycolic acid copolymer, plasticizer, initiator and antioxidant are mixed and then blended and granulated by twin screw extruder. After blending, the mixture is water-cooled and pelletized to obtain composite masterbatch.

[0062] During operation, the components are mixed in a specific ratio: EVA resin provides flexibility, modified polylactic acid-polyurethane crosslinking system provides high strength and durability, polycaprolactone microspheres improve air permeability and degradability, polylactic acid-glycolic acid copolymer improves biodegradability, plasticizer improves flowability, and antioxidant ensures thermal stability.

[0063] These raw materials are blended in a twin-screw extruder to ensure uniform dispersion of the components and avoid stratification. The temperature and shear force during extrusion promote melting, forming a homogeneous composite material, which is then water-cooled and pelletized to obtain granular composite masterbatch.

[0064] This blending process optimizes the dispersibility of polycaprolactone microspheres and polylactic acid-glycolic acid copolymer, improving the physical properties of the composite material. Through precise proportioning and processing control, highly uniform composite masterbatch is obtained, providing stable and high-quality raw materials for subsequent molding, ensuring that the footwear material performs excellently in terms of mechanical properties, abrasion resistance, environmental friendliness, and comfort.

[0065] (4) Shoe material molding: The composite masterbatch is placed in the mold and hot-pressed at 160-180℃. The holding pressure is controlled at 5-10MPa and the holding time is 3-6min. Then it is naturally cooled to room temperature and demolded to obtain a finished shoe material with a smooth surface and uniform internal structure.

[0066] The composite masterbatch is hot-pressed at 160-180℃. The temperature setting takes into account the softening point of the EVA matrix and the thermal stability of the polylactic acid component, ensuring that all components are fully melted and flowed while avoiding material degradation. The holding pressure during the hot pressing process is controlled at 5-10MPa to effectively fill the mold and expel gas, preventing structural defects. The holding time is 3-6 minutes to ensure that the materials are fully fused and cross-linked. After setting, the material is cooled and demolded, ultimately yielding a shoe material with a complete structure and a smooth surface.

[0067] Compared to traditional hot-pressing processes, this invention ensures the coordinated molding of multi-component systems through precise design of the composite system (such as cross-linking structure and microsphere particle size) combined with meticulous control of temperature, pressure, and time. The polylactic acid-polyurethane cross-linked network provides structural support in the molten state, preventing collapse during molding, while the polycaprolactone microspheres maintain stable particle size, forming a uniform microporous structure that enhances comfort and breathability.

[0068] This hot-pressing process ensures the structural integrity, functionality, and synergy of the material, resulting in excellent performance of the final EVA composite shoe material in terms of abrasion resistance, flexibility, comfort, and biodegradability, reflecting innovative breakthroughs in molding technology and material design.

[0069] Preferably, in step 1:

[0070] The high-speed shearing speed is 8000-12000 rpm;

[0071] The emulsification time is 5-10 minutes;

[0072] The ultrasonic power is 100-300W, and the ultrasonic time is 5-15min.

[0073] By employing a synergistic emulsification process combining high-speed shearing and ultrasonic dispersion, polycaprolactone microspheres with controllable particle size and uniform distribution were successfully prepared. Specifically, high-speed shearing at 8000-12000 rpm effectively emulsified the oil-water phase within 5-10 minutes, followed by ultrasonic treatment at 100-300W (5-15 minutes) to further refine the microspheres, ensuring that their particle size remained stable between 200-500 nm, with a narrow particle size distribution and intact morphology.

[0074] This synergistic emulsification method optimizes the primary dispersion and secondary fragmentation processes of emulsion droplets, solving the problems of difficult particle size control and poor dispersibility in traditional methods. The uniform particle size of the microspheres improves the controllability of the microporous structure, contributing to enhanced breathability and softness of the material. Furthermore, this method improves the interfacial compatibility between the microspheres and the matrix material, enhancing the uniformity and overall mechanical integrity of the composite material, providing a solid technological foundation for the comfort and biodegradability of footwear materials.

[0075] Preferably, the temperature control parameters of the twin-screw extruder in step 3 are:

[0076] Feeding section: 130-140℃;

[0077] Melting zone: 155-165℃;

[0078] Mixing section: 165-175℃;

[0079] Homogenization section: 165-170℃;

[0080] Mold head area: 175-180℃.

[0081] The twin-screw extruder adopts a segmented precision temperature control system, which sets temperature gradients in the feeding section (130-140℃), melting section (155-165℃), mixing section (165-175℃), homogenization section (165-170℃), and die area (175-180℃) to ensure that the material remains stable during melting, mixing, and molding.

[0082] In the feeding section, the composite masterbatch is preheated at 130-140℃ to prevent EVA or polylactic acid degradation due to high temperatures. The melting section temperature ensures the formation of cross-linked structures between EVA, polylactic acid, and polyurethane prepolymers. The mixing section further increases the temperature to ensure uniform dispersion of polycaprolactone microspheres and other components, enhancing air permeability and flexibility. Stable temperature control in the homogenization section prevents phase separation and ensures material uniformity.

[0083] Optimized die temperature improves extrusion efficiency and ensures a smooth composite surface and consistent particle size. The overall temperature control system inhibits degradation reactions through precise temperature control points, extending the processing window and ensuring material stability and consistency. Optimization of the mixing and homogenization sections further enhances component dispersion and interfacial compatibility, providing a stable foundation for high-performance molding of footwear materials.

[0084] This invention provides a wear-resistant, biodegradable EVA composite shoe material and its preparation method. It has the following beneficial effects:

[0085] 1. This invention precisely balances the degradation rate and mechanical strength of the material by controlling the molar ratio of polylactic acid-glycolic acid copolymer. Compared with existing biodegradable materials, it resolves the contradiction between insufficient lifespan due to excessively rapid degradation and environmental pollution due to excessively slow degradation, achieving a dynamic adaptation between the lifespan of footwear materials and environmental friendliness.

[0086] 2. Based on the porous structure design of nano-sized polycaprolactone microspheres (200-500nm), a uniform microporous network is constructed inside the shoe material. Compared with traditional foaming or physical blending processes, this breaks through the bottleneck of the incompatibility between breathability and mechanical properties, while endowing the material with multiple properties such as lightweight, high resilience and moisture wicking.

[0087] 3. By constructing an interpenetrating network of polyurethane prepolymer and modified polylactic acid, a composite system combining rigidity and flexibility is formed. This addresses the shortcomings of single polymer materials in terms of mechanical properties, solving the problems of easy deformation and poor tear resistance in shoe materials, thus enabling the product to combine the elasticity of rubber with the strength of engineering plastics.

[0088] 4. A multiphase synergistic enhancement strategy using EVA / polylactic acid / polyurethane is adopted, leveraging the optimized interfacial compatibility of each component to achieve a significant performance boost. Compared to simple blending systems, this overcomes the limitations of traditional composite materials, such as weak interfacial bonding and poor stress transmission, enabling the shoe material to maintain structural stability and long-lasting functionality under complex working conditions. Attached Figure Description

[0089] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0090] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0091] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0092] Please see the appendix Figure 1

[0093] Example 1:

[0094] Component ratio (parts by mass):

[0095] 62 parts of EVA resin, of which 32 parts are vinyl acetate;

[0096] 18 parts of modified polylactic acid;

[0097] 10 parts of polyurethane prepolymer;

[0098] Five portions of polycaprolactone microspheres, with a particle size of 350 nm;

[0099] 2 parts of polylactic acid-glycolic acid copolymer;

[0100] 2 parts plasticizer (tributyl citrate);

[0101] Initiator (dicumyl peroxide) 0.7 parts;

[0102] Antioxidant 1076, 0.3 parts.

[0103] Step details:

[0104] Step 1: Preparation of polycaprolactone microspheres

[0105] Oil phase preparation: Dissolve 5 parts of polycaprolactone in 95 parts of dichloromethane and stir at 45°C until completely transparent (40 minutes).

[0106] Emulsification: Prepare 1.8 parts of polyvinyl alcohol solution in the aqueous phase, dissolve it in 100 parts of deionized water, with an oil-to-water volume ratio of 1:4. After mixing, transfer the mixture to a high-shear emulsifier and set it to 11,000 rpm for 8 minutes.

[0107] Ultrasonic treatment: The emulsion was transferred into an ultrasonic instrument and treated for 12 minutes at a power of 200W.

[0108] Curing and drying: Stir at room temperature for 10 hours to evaporate the solvent, then freeze-dry to obtain microspheres.

[0109] Step 2: Preparation of modified polylactic acid-polyurethane prepolymer crosslinking system

[0110] Premixed heating: Modified polylactic acid and polyurethane prepolymer are fed into an internal mixer and the temperature is set to 145℃;

[0111] Initiate cross-linking: Add 0.7 parts of dicumyl peroxide, mix with a mixer at 35 rpm for 25 minutes to form a cross-linked network structure.

[0112] Step 3: Blending, extrusion, and granulation

[0113] Raw material mixing: EVA resin, crosslinking system, polycaprolactone microspheres, PLGA, plasticizer, initiator and antioxidant are premixed according to the formula;

[0114] Twin-screw extrusion:

[0115] Temperature settings: Feeding section 135℃ → Melting section 160℃ → Mixing section 170℃ → Die head 175℃

[0116] The main unit rotates at 75 rpm and feeds at 12 kg / h.

[0117] Water-cooled pelletizing: Cooling water temperature 15℃, pelletizing blade speed 3000rpm, to produce masterbatch with a diameter of 3mm.

[0118] Step 4: Shoe Material Molding

[0119] Mold preheating: Heat the mold to 175℃;

[0120] Hot pressing: 200g of masterbatch is laid in, the closing pressure is 8MPa, and the pressure is held for 5 minutes;

[0121] Cooling and demolding: After natural cooling to room temperature, the finished product has no cracks on the surface and no bubbles or delamination inside.

[0122] Example 2:

[0123] Component ratio (parts by mass):

[0124] 55 parts of EVA resin, of which 28 parts are vinyl acetate;

[0125] 25 parts of modified polylactic acid;

[0126] 8 parts of polyurethane prepolymer;

[0127] Seven parts of polycaprolactone microparticles with a particle size of 220 nm were contained.

[0128] 3 parts of polylactic acid-glycolic acid copolymer (LA:GA=70:30);

[0129] Plasticizer (polyether ester) 1.5 parts;

[0130] Initiator (dicumyl peroxide) 0.4 parts;

[0131] Antioxidant 168, 0.3 parts.

[0132] Step 1: Preparation of polycaprolactone microspheres

[0133] Oil phase preparation: Dissolve 3 parts polycaprolactone in 97 parts dichloromethane and stir at 50°C for 35 minutes until transparent;

[0134] Emulsification: Add 2 parts polyvinyl alcohol to the aqueous phase and dissolve it in 100 parts deionized water. The oil-water volume ratio is 1:3. After mixing, transfer the mixture to a high-shear emulsifier and set it to 12,000 rpm for 6 minutes.

[0135] Ultrasonic treatment: The emulsion was transferred into an ultrasonic instrument and treated for 15 minutes at a power of 300W.

[0136] Curing and drying: Stir at room temperature for 9 hours to evaporate the solvent, and freeze-dry the microspheres to a D50 of 220 nm.

[0137] Step 2: Preparation of crosslinking system

[0138] Premixed heating: Modified polylactic acid and polyurethane prepolymer are fed into an internal mixer and the temperature is set to 155℃;

[0139] Initiate crosslinking: Add 0.4 parts of dicumyl peroxide and mix with a mixer at 40 rpm for 18 minutes.

[0140] Step 3: Blending, extrusion, and granulation

[0141] Raw material mixing: EVA resin, crosslinking system, polycaprolactone microspheres, PLGA, plasticizer, initiator and antioxidant are premixed according to the formula;

[0142] Twin-screw extrusion:

[0143] Temperature settings: Feeding section 130℃ → Melting section 165℃ → Mixing section 175℃ → Die head 180℃

[0144] The main unit rotates at 90 rpm and feeds at 10 kg / h.

[0145] Water-cooled pelletizing: The cooling water temperature is 10℃, and masterbatch with a diameter of 2.5mm is obtained.

[0146] Step 4: Shoe Material Molding

[0147] Mold preheating: Heat the mold to 180℃;

[0148] Hot pressing: 200g of masterbatch is laid in, the holding pressure is 6MPa, and the holding time is 4 minutes;

[0149] Cooling and demolding: After natural cooling, the finished product has no cracks on the surface and no bubbles or delamination inside.

[0150] Example 3:

[0151] Component ratio (parts by mass):

[0152] 70 parts of EVA resin, of which 33 parts are vinyl acetate;

[0153] 15 parts of modified polylactic acid;

[0154] 6 parts of polyurethane prepolymer;

[0155] Eight portions of polycaprolactone microspheres with a particle size of 500 nm;

[0156] 3 parts of polylactic acid-glycolic acid copolymer;

[0157] 5 parts liquid silicone oil plasticizer;

[0158] 0.5 parts of dicumyl peroxide initiator;

[0159] Antioxidant 1076, 0.5 parts.

[0160] Step 1: Preparation of polycaprolactone microspheres

[0161] Oil phase preparation: Dissolve 6 parts polycaprolactone in 94 parts dichloromethane and stir at 42°C for 50 minutes;

[0162] Emulsification: Add 3 parts polyvinyl alcohol to the aqueous phase and dissolve it in 100 parts deionized water. The oil-water volume ratio is 1:5. After mixing, transfer the mixture to a high-shear emulsifier and set it to 8000 rpm for 10 minutes.

[0163] Ultrasonic treatment: The emulsion is transferred into an ultrasonic instrument and treated for 5 minutes at 100W power.

[0164] Curing and drying: Stir at room temperature for 12 hours to evaporate the solvent, and freeze dry to obtain microspheres with D50=500nm.

[0165] Step 2: Preparation of crosslinking system

[0166] Premixed heating: Modified polylactic acid and polyurethane prepolymer are fed into an internal mixer and the temperature is set to 140℃;

[0167] Initiate crosslinking: Add 0.5 parts of dicumyl peroxide and mix with a mixer at 30 rpm for 30 minutes;

[0168] Step 3: Blending, extrusion, and granulation

[0169] Raw material mixing: EVA resin, crosslinking system, polycaprolactone microspheres, PLGA, plasticizer, initiator and antioxidant are premixed according to the formula;

[0170] Twin-screw extrusion:

[0171] Temperature settings: Feeding section 140℃ → Melting section 160℃ → Mixing section 170℃ → Die head 175℃

[0172] The main unit rotates at 60 rpm and feeds at 15 kg / h.

[0173] Water-cooled pelletizing: Cooling water temperature 20℃, to obtain masterbatch with a diameter of 3.2mm.

[0174] Step 4: Shoe Material Molding

[0175] Mold preheating: Heat the mold to 160℃;

[0176] Hot pressing: 200g of masterbatch is laid in, the holding pressure is 5MPa, and the holding time is 6 minutes;

[0177] Cooling and demolding: After natural cooling, the finished product has no cracks on the surface and no bubbles or delamination inside.

[0178] Comparative Example 1:

[0179] The difference from Example 1 is as follows:

[0180] Five parts of polycaprolactone microspheres were not added; instead, they were replaced with an equal amount of EVA resin (total EVA resin 67 parts). All other components remained the same.

[0181] Preparation process:

[0182] The microsphere preparation step has been completely eliminated;

[0183] In step 3, during the co-extrusion process, only EVA resin, modified polylactic acid-polyurethane crosslinking system, PLGA, plasticizer, initiator, and antioxidant are mixed, while the remaining process parameters are the same as in Example 1.

[0184] Comparative Example 2:

[0185] The difference compared to Example 1 is as follows:

[0186] The modified polylactic acid in Example 1 was replaced with an equal amount of unmodified pure polylactic acid, while other components remained the same.

[0187] Preparation process:

[0188] In step 2, during the preparation of the crosslinking system, pure PLA was used instead of modified polylactic acid, and the other steps were completely consistent with those in Example 1.

[0189] Comparative Example 3:

[0190] The difference compared to Example 2 is as follows:

[0191] The polylactic acid-glycolic acid copolymer in Example 2 was replaced with an equal amount of ordinary polylactic acid, while other components remained the same.

[0192] Preparation process:

[0193] In step 3, during the co-extrusion process, the polylactic acid-glycolic acid copolymer component is replaced with ordinary polylactic acid, and the remaining process parameters are completely consistent with those in Example 2.

[0194] Comparative Example 4:

[0195] The difference compared to Example 3 is as follows:

[0196] The particle size of the polycaprolactone microspheres was adjusted to 800 nm, while the other components remained the same.

[0197] Preparation process:

[0198] Consistent with Example 3.

[0199] Experiment 1:

[0200] Sample preparation:

[0201] Groups and Quantities:

[0202] Example 1 group: Three circular specimens (numbered S1-1 to S1-3) with a diameter of 30 mm and a thickness of 2.0 mm were prepared according to the components and preparation process of Example 1; three square specimens (numbered S1-4 to S1-6) with a diameter of 100 × 100 mm were prepared.

[0203] Comparative Example 1: Three circular specimens with a diameter of 30 mm and a thickness of 2.0 mm (numbered C1-1 to C1-3) and three square specimens with a diameter of 100 × 100 mm (numbered C1-4 to C1-6) were prepared according to the composition and preparation process of Comparative Example 1.

[0204] Pretreatment: All samples were equilibrated for 48 hours at 23°C and 50% humidity.

[0205] Test 1: Air permeability test (water vapor transmission rate)

[0206] Testing equipment: FX3300 air permeability tester (ASTM E96 standard);

[0207] Samples tested: S1-1 to S1-3; C1-1 to C1-3;

[0208] Test period: 24-hour continuous testing;

[0209] Detection frequency: Data is recorded once per hour for a total of 24 times. The average, highest and lowest values ​​of each sample are recorded.

[0210] Method description:

[0211] The sample is clamped in the test chamber, and a pressure difference of 1 kPa is maintained on both sides of the chamber.

[0212] Constant temperature and humidity conditions (23℃±1℃, 50%±5%RH);

[0213] The water vapor permeation rate (g / (m²·h)) was collected per hour.

[0214] The experimental results are shown in Table 1:

[0215] Table 1: Comparison of Air Permeability Test Data

[0216] Sample number <![CDATA[Average transmittance (g / (m 2 ·h))]]> <![CDATA[maximum value (g / (m 2 ·h))]]> <![CDATA[minimum value (g / (m 2 ·h))]]> Remark S1-1 0.43 0.51 0.38 Uniform surface micropores S1-2 0.41 0.49 0.33 Slight edge contraction S1-3 0.47 0.54 0.42 The central area has quick moisture permeability C1-1 0.13 0.18 0.09 Smooth surface without pores C1-2 0.15 0.21 0.11 Minor scratches in some areas C1-3 0.12 0.16 0.08 Adsorption of water vapor during the test

[0217] Test 2: Test equipment: Taber 5135 abrasion tester (ISO 4649 standard);

[0218] Samples tested: S1-4 to S1-6; C1-4 to C1-6;

[0219] Test cycle: 1000 revolutions of continuous wear;

[0220] Testing frequency: Stop the machine every 250 revolutions to clean up debris and weigh it;

[0221] Method description:

[0222] Using a CS-10 grinding wheel, apply a vertical load of 1kg;

[0223] The sample is fixed on a turntable and pre-ground for 50 revolutions to eliminate surface errors;

[0224] Formal testing involved 1000 revolutions, with mass loss recorded every 250 revolutions (accuracy 0.1 mg).

[0225] The experimental results are shown in Table 2:

[0226] Table 2: Taber Wear Stage-by-Stage Quality Loss Record Table

[0227] Sample number Loss at 250 revolutions (g) Loss at 500 revolutions (g) Loss at 750 RPM (g) Total loss per 1000 revolutions (g) Wear surface condition S1-4 0.05 0.09 0.12 0.17 Shallow scratches, no peeling S1-5 0.04 0.08 0.11 0.15 Slight wear on the edges S1-6 0.06 0.1 0.14 0.19 Central region micropore exposure C1-4 0.12 0.23 0.35 0.41 Fish-scale-like peeling, powdering C1-5 0.1 0.2 0.32 0.39 Surface cracks, debris accumulation C1-6 0.14 0.27 0.38 0.43 Wear through to the substrate layer

[0228] The introduction of polycaprolactone microspheres significantly altered the internal structure of the material. Scanning electron microscopy revealed that the 350 nm microspheres in Example 1 formed a honeycomb-like pore structure with a specific surface area of ​​42 m². 2 / g. This porous network shortens the water vapor diffusion path by approximately 65%, achieving a peak transmittance exceeding 0.50 g / (m²). 2•h). In contrast, the dense structure of Comparative Example 1 hindered moisture escape, with an average permeability of only 0.13 g / (m²). 2 •h) can easily cause stuffiness when worn in practice.

[0229] The difference in wear resistance more directly reflects the mechanical reinforcing effect of the microspheres. During the wear process, the microspheres act as "miniature bearings," dispersing the shear stress of the grinding wheel. In Example 1, the wear loss was stable at 0.05-0.06g per 250 revolutions, with a total loss of 0.17g. In contrast, in Comparative Example 1, because the EVA matrix directly bears the friction, the wear loss surged with the number of revolutions, reaching as high as 0.43g after 1000 revolutions, and deep peeling appeared on the surface.

[0230] In practical applications, the synergistic optimization of breathability and abrasion resistance is crucial. During exercise, the feet secrete approximately 20-50 mL of sweat per hour. Example 1's moisture permeability rate can promptly wick away over 75% of sweat, extending the sole's lifespan to 1200 kilometers. Comparative Example 1's dense structure leads to sweat retention, while its abrasion resistance degrades to the level of commercially available EVA. This validates the necessity of microsphere functionalization design—it cannot be replaced by simple fillers or process adjustments.

[0231] Experiment 2:

[0232] Sample preparation:

[0233] Groups and Quantities:

[0234] Example 1 group: Three strip-shaped samples (numbered S2-1 to S2-3) of 150×20×2mm were prepared according to the components and preparation process of Example 1.

[0235] Comparative Example 2: Three strip-shaped samples (numbered C2-1 to C2-3) of 150×20×2mm were prepared according to the composition and preparation process of Comparative Example 2.

[0236] Pretreatment: All samples were equilibrated for 72 hours at 23°C and 50% humidity.

[0237] Test 1: Bending fatigue test (number of bends and fracture behavior)

[0238] Testing equipment: Bending test machine (GB / T3903.31 standard).

[0239] Tested samples: S2-1 to S2-3; C2-1 to C2-3.

[0240] Test cycle: Bending continuously until the sample breaks, and record the total number of bends.

[0241] Method description:

[0242] The sample is held in a fixture with a bending angle of 90° and a frequency of 3Hz.

[0243] Initial pre-bending 50 times eliminates internal stress;

[0244] Continue testing until the sample completely breaks.

[0245] The experimental results are shown in Table 3:

[0246] Table 3: Record of Bending Fatigue Fracture Counts

[0247] Sample number Total number of bends (times) fracture location Surface crack propagation S2-1 102,354 Irregular fracture in the middle Microcracks begin at the edges and slowly extend. S2-2 98,567 Breakage near the clamp end No obvious cracks on the surface, but it suddenly broke. S2-3 105,892 Transverse fracture in the middle Multi-directional crack convergence leads to failure C2-1 1,235 Longitudinal splitting at the edge Deep cracks appeared on the first bend C2-2 987 Brittle fracture in the middle Fracture without warning, with a smooth fracture surface. C2-3 1,504 Clamping point breakage After being bent 500 times, the crack went through.

[0248] The cross-linked network of modified polylactic acid (PLA) endows the material with exceptional toughness. In Example 1, the polyurethane prepolymer forms an interpenetrating structure with the PLA molecular chains, expanding the molecular chain slip space. In bending tests, the sample withstood over 100,000 repeated bends, with the crack propagation rate suppressed to 0.03 mm / 1000 bends. In contrast, the pure PLA molecular chains in Comparative Example 2 were stiff, and stress concentration led to fracture in less than 1500 bends, with the fracture surface exhibiting a mirror-like brittle characteristic. Simple component substitution cannot replicate the multi-scale synergistic effect of the modified system.

[0249] Experiment 3:

[0250] Groups and Quantities:

[0251] Example 2 group: Three 50×50×2mm square samples (numbered S3-1 to S3-3) were prepared according to the components and preparation process of Example 2.

[0252] Comparative Example 3: Three 50×50×2mm square samples (numbered C3-1 to C3-3) were prepared according to the composition and preparation process of Comparative Example 3.

[0253] Pretreatment: All samples were equilibrated for 72 hours at 23°C and 50% humidity.

[0254] Tests: Accelerated degradation test (weight loss rate and degradation uniformity)

[0255] Test equipment: Constant temperature and humidity composting chamber (ISO14855 standard);

[0256] Samples tested: S3-1 to S3-3; C3-1 to C3-3;

[0257] Test cycle: 60 days of continuous degradation;

[0258] Testing frequency: Samples are taken and weighed every 10 days, and the weight loss rate is recorded.

[0259] Method description:

[0260] The sample was buried in composting medium (temperature 58℃, humidity 80%).

[0261] Every 10 days, take out the sample, rinse it with distilled water, and dry it at 60°C to constant weight.

[0262] Calculate the weightlessness rate: weightlessness rate .

[0263] in, The initial mass of the sample;

[0264] For the sample to experience time Or the quality after specific treatment.

[0265] The experimental results are shown in Table 4:

[0266] Table 4: Dynamic Record of Compost Degradation Weight Loss Rate (Unit: %)

[0267] Sample number 10 days 20 days 30 days 40 days 50 days 60 days Morphological description after degradation S3-1 8.7 21.3 38.9 62.4 84.1 94.5 Completely shattered into particles <2mm S3-2 7.9 19.8 35.6 59.2 81.7 92.3 The surface is honeycomb-shaped, and the internal pores are interconnected. S3-3 9.2 22.5 40.1 65.3 85.9 95 The degradation residue is in powder form. C3-1 0.6 1.5 2.9 5.3 8.2 12.7 Localized powdering on the surface, but overall structural integrity. C3-2 0.5 1.2 2.4 4.8 7.6 11.9 Edge corrosion, no signs of internal degradation C3-3 0.8 1.8 3.1 5.7 8.9 13.4 The sample expanded but did not break.

[0268] The introduction of polylactic acid-glycolic acid copolymer significantly accelerated the degradation process. In Example 2, glycolic acid disrupted the crystalline regions of PLA, increasing the density of hydrolytic active sites by 3 times, resulting in a weight loss of over 94% after 60 days. In contrast, the pure PLA in Comparative Example 3, due to its high crystallinity, degraded only to the surface layer, resulting in a weight loss of less than 13% after 60 days.

[0269] The differences in degradation morphology confirm the structural design. Cross-sectional electron microscopy of Example 2 revealed honeycomb-like pores (50-300 μm in diameter) with a polyurethane cross-linked framework on the pore walls and interconnected enzymatic hydrolysis channels. Comparative Example 3 showed only surface powdering, while the interior remained a dense, blocky structure. The synergistic degradation of polylactic acid-glycolic acid copolymer overcomes the bottleneck of traditional PLA materials' "fast degradation on the surface, slow degradation internally," balancing environmental friendliness with controllable performance degradation.

[0270] Experiment 4:

[0271] Sample preparation:

[0272] Groups and Quantities:

[0273] Example 3 group: Three circular samples (numbered S4-1 to S4-3) with a diameter of 30 mm and a thickness of 2.0 mm were prepared according to the components and preparation process of Example 3.

[0274] Comparative Example 4: Three circular samples (numbered C4-1 to C4-3) with a diameter of 30 mm and a thickness of 2.0 mm were prepared according to the composition and preparation process of Comparative Example 4.

[0275] Pretreatment: All samples were equilibrated for 48 hours at 23°C and 50% humidity.

[0276] Test: Air permeability test (water vapor transmission rate)

[0277] Testing equipment: FX3300 air permeability tester (ASTM E96 standard).

[0278] Tested samples: S4-1 to S4-3; C4-1 to C4-3.

[0279] Test cycle: 24-hour continuous testing.

[0280] Detection frequency: Data is recorded once per hour for a total of 24 times. The average, highest and lowest values ​​of each sample are recorded.

[0281] Method description:

[0282] The sample is clamped in the test chamber, and a pressure difference of 1 kPa is maintained on both sides of the chamber.

[0283] Constant temperature and humidity conditions (23℃±1℃, 50%±5%RH);

[0284] The water vapor permeation rate (g / (m²·h)) was collected per hour.

[0285] The experimental results are shown in Table 5:

[0286] Table 5: Comparison of Air Permeability Test Data

[0287] Sample number <![CDATA[Average transmittance (g / (m 2 ·h))]]> <![CDATA[Maximum value (g / (m 2 ·h))]]> <![CDATA[minimum value (g / (m 2 ·h))]]> Remark S4-1 0.48 0.55 0.41 Uniform micropore distribution S4-2 0.45 0.52 0.38 Slight edge contraction S4-3 0.51 0.58 0.46 The central area has quick moisture permeability C4-1 0.22 0.28 0.17 Poor pore connectivity C4-2 0.19 0.25 0.14 Localized large hole concentration C4-3 0.21 0.27 0.16 Microsphere aggregation leads to blockage

[0288] Increasing the microsphere size to 800 nm significantly reduces air permeability. In Example 3, 500 nm microspheres formed a uniform pore network with an average air permeability of 0.48 g / (m²). 2 The average air permeability of the control sample was 0.58 (·h). In contrast, the average air permeability of the control sample 4 dropped to 0.21 due to microsphere aggregation and pore blockage, and even moisture-permeable blind spots caused by the concentration of large pores appeared in some areas.

[0289] In practical applications, the 800nm ​​microspheres increased the humidity inside the shoe by 38% compared to Example 3, affecting wearing comfort. Electron microscopy showed that the microspheres in Example 3 were uniformly dispersed with a pore connectivity rate of 92%; while the pore connectivity in Comparative Example 4 was only 47%, verifying the necessity of the 200-500nm particle size limitation in the claims.

[0290] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A wear-resistant and biodegradable EVA composite shoe material, characterized in that, The components include the following parts by mass: 55-70 parts of EVA resin; 10-20 parts of modified polylactic acid; 5-10 parts of polyurethane prepolymer; 3-8 parts of polycaprolactone microspheres; 2-6 parts of polylactic acid-glycolic acid copolymer; Plasticizer 2-5 parts; Initiator 0.5-1.5 parts; Antioxidant 0.2-0.5 parts.

2. The wear-resistant and biodegradable EVA composite shoe material according to claim 1, characterized in that, The EVA resin has a VA content of 28-33 parts and a melt index of 2-4 g / 10 min.

3. The wear-resistant and biodegradable EVA composite shoe material according to claim 1, characterized in that, The modified polylactic acid has a molecular weight of 80,000-120,000 g / mol, and is a copolymer of polylactic acid and polycaprolactone, with a mass ratio of polylactic acid to polycaprolactone of 80:20-60:

40.

4. The wear-resistant and biodegradable EVA composite shoe material according to claim 1, characterized in that, The polyurethane prepolymer is a block copolymer prepared by addition polymerization of polyhexanediol and isocyanate, wherein the mass ratio of polyhexanediol to isocyanate is 1:1.2-1:1.

5.

5. The wear-resistant and biodegradable EVA composite shoe material according to claim 1, characterized in that, The polycaprolactone microspheres have a particle size of 200-500 nm.

6. The wear-resistant and biodegradable EVA composite shoe material according to claim 1, characterized in that, The polylactic acid-glycolic acid copolymer is formed by copolymerizing polylactic acid and glycolic acid, and the molar ratio of polylactic acid to glycolic acid is 70:30-80:

20.

7. A method for preparing a wear-resistant biodegradable EVA composite shoe material, used to prepare the wear-resistant biodegradable EVA composite shoe material as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Preparation of polycaprolactone microspheres: Polycaprolactone is dissolved in dichloromethane to form an oil phase with a mass concentration of 3-6 parts. 1-3 parts of polyvinyl alcohol are added to the aqueous phase as an emulsifier for emulsification. After emulsification by high-speed shearing to form an emulsion, the emulsion is ultrasonically treated. The solvent is evaporated by stirring at room temperature for 6-12 hours. After freeze-drying, polycaprolactone microspheres with a particle size of 200-500 nm are obtained. (2) Preparation of modified polylactic acid-polyurethane prepolymer crosslinking system: Mix modified polylactic acid and polyurethane prepolymer at 140-160℃, add dicumyl peroxide initiator, and stir for 15-30 min to form a crosslinked network structure; (3) Blending extrusion granulation: EVA resin, modified polylactic acid-polyurethane prepolymer crosslinking system, polycaprolactone microspheres, polylactic acid-glycolic acid copolymer, plasticizer, initiator and antioxidant are mixed and then blended and granulated by twin screw extruder. After blending, the mixture is water-cooled and pelletized to obtain composite masterbatch. (4) Shoe material molding: The composite masterbatch is placed in the mold and hot-pressed at 160-180℃. The holding pressure is controlled at 5-10MPa and the holding time is 3-6min. Then it is naturally cooled to room temperature and demolded to obtain a finished shoe material with a smooth surface and uniform internal structure.

8. The method for preparing a wear-resistant, biodegradable EVA composite shoe material according to claim 7, characterized in that, In step 1: The high-speed shearing speed is 8000-12000 rpm; The emulsification time is 5-10 minutes; The ultrasonic power is 100-300W, and the ultrasonic time is 5-15min.

9. The method for preparing a wear-resistant, biodegradable EVA composite shoe material according to claim 7, characterized in that, The temperature control parameters for the twin-screw extruder in step 3 are as follows: Feeding section: 130-140℃; Melting zone: 155-165℃; Mixing section: 165-175℃; Homogenization section: 165-170℃; Mold head area: 175-180℃.

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