A sole and a method of manufacturing the same

Abstract

This application relates to the field of shoe sole processing technology, and more specifically, to a shoe sole and its preparation method. The shoe sole comprises a main body consisting of a forefoot section, a midfoot section, and a heel section, and an outer covering layer. The forefoot section forms a highly elastic and flexible zone with 40-60 parts of polyurethane elastomer, 20-30 parts of styrene-butadiene-ethylene block copolymer, and 10-15 parts of reinforcing agent. The midfoot section introduces 6-8 parts of ethylene-vinyl acetate copolymer and increases the reinforcing agent to 15-20 parts to construct a stable arch support zone. The heel section significantly increases the reinforcing agent to 25-35 parts to form a high-strength and durable zone. The three-section differentiated formulation, combined with a gradient crosslinking system, is integrally molded using a supercritical fluid foaming process, achieving a smooth transition of mechanical properties from front to back, improved breathability, and reduced weight. The high crosslinking density and high reinforcing agent content of the heel section effectively inhibit polymer chain slippage and cell wall creep, extending service life and overcoming the problems of heavy weight, poor breathability, and easy fatigue and collapse of traditional sports shoe soles.

Description

Technical Field

[0001] This application relates to the field of shoe sole processing technology, and more specifically, to a shoe sole and a method for preparing the same. Background Technology

[0002] The outsole of athletic shoes uses a three-layer composite structure consisting of an outsole, midsole, and insole. In practical applications, it has been found that this composite structure suffers from technical problems such as heavy weight, poor breathability, and fatigue collapse of the midsole material. The root cause lies in the inherent contradiction between the material properties, physical form, and functional requirements of the three-layer composite structure. Regarding weight, the outsole needs to use high-density, abrasion-resistant rubber to resist road wear, the midsole needs to use a considerable thickness of foamed elastomer, plus interlayer adhesives and reinforcement materials such as TPU stabilizing sheets or carbon fiber plates often inserted for arch support. The density superposition and structural redundancy of the three independent structures greatly increases the overall weight. At the same time, the need to maintain the independent integrity of each layer in traditional processes and the roughening treatment required for bonding further limits the space for thinning. Regarding breathability, although the midsole material is porous inside, it is a closed-cell structure, and air cannot flow vertically. The outsole rubber is a dense solid material that is completely impermeable. The three layers stacked together form a continuous barrier layer that blocks the air convection channel between the sole of the foot and the outside world, and the airtightness required for cushioning function is also a factor. The inherent conflict between gas space and breathability principles, coupled with the adhesive filling the interface gaps, further eliminates potential breathable microchannels, forming a closed layered barrier. Regarding the issue of midsole fatigue and collapse, as viscoelastic materials such as EVA, under long-term cyclic compressive stress, the polymer chains of foam materials undergo irreversible slippage and breakage, and the cell walls undergo creep, leading to the gradual collapse of the structure. At the same time, the encapsulated gas within the foam slowly escapes through the polymer matrix. In addition, the stress concentration caused by the sudden change in hardness at the three-layer interface and the accelerated impact of temperature environment on material performance result in the performance degradation of the midsole after 300-500 kilometers of use. These technical problems essentially reflect the engineering trade-off between protection / durability and lightweight / breathability in athletic shoe design. Summary of the Invention

[0003] To address the technical problems of composite structures, such as high weight, poor breathability, and fatigue collapse of the midsole material, this application provides a shoe sole and its preparation method.

[0004] Firstly, this application provides a shoe sole, which adopts the following technical solution: A shoe sole includes a forefoot section that contacts the forefoot, a midfoot section that contacts the arch, a heel section that contacts the heel, and an outer perimeter. The forefoot section, the midfoot section, and the heel section constitute the main body of the shoe sole. The outer perimeter covers the sides of the main shoe sole. The forefoot section is composed of the following raw materials in parts by weight: 40-60 parts of polyurethane elastomer 20-30 parts of styrene-butadiene-ethylene block copolymer 10-15 parts of reinforcing agent 1-2 parts of foam stabilizer Crosslinking agent 0.4-0.6 parts The middle section is composed of the following raw materials in parts by weight; 40-60 parts of polyurethane elastomer 10-15 parts of styrene-butadiene-ethylene block copolymer 6-8 parts of ethylene-vinyl acetate copolymer 15-20 parts of reinforcing agent Crosslinking agent 0.5-1 part 1-2 parts of foam stabilizer The latter section is composed of the following raw materials in parts by weight: 40-60 parts of polyurethane elastomer 25-30 parts of styrene-butadiene-ethylene block copolymer 25-35 parts of reinforcing agent 1-2 parts of foam stabilizer Crosslinking agent 0.5-1 part.

[0005] By adopting the above technical solutions, while maintaining or even improving traditional functions such as grip, cushioning, and arch support, the soles are made lightweight and breathable, while ensuring that they do not collapse after long-term use.

[0006] In this application, the sole body, composed of the forefoot, midfoot, and heel sections, directly undertakes the multiple functions of a traditional outsole, midsole, and insole. This eliminates the structural redundancy required for independent integrity and roughening of interlayer bonding, while also eliminating the adhesive layer necessary for each layer in a traditional three-layer structure, thus reducing the weight of the sole. Furthermore, each section's formulation uses polyurethane elastomer as the main substrate, a material that combines abrasion resistance and lightweight properties, with a lower density compared to traditional high-density abrasion-resistant rubber.

[0007] This application employs a three-stage differentiated formulation design to precisely address the mechanical requirements of different regions: the front section utilizes the highest amount of styrene-butadiene-ethylene block copolymer (20-30 parts), combined with 40-60 parts of polyurethane elastomer, imparting high elasticity and excellent flexural fatigue resistance to this region, meeting the demands of frequent bending deformation during forefoot push-off. Simultaneously, 10-15 parts of reinforcing agent ensure abrasion resistance without excessively sacrificing flexibility, giving the forefoot both flexibility and durability. 0.4-0.6 parts of crosslinking agent form a moderately crosslinked network, ensuring rapid rebound of the material during repeated stretching-compression cycles and reducing energy loss; the middle section significantly reduces the amount of styrene-butadiene-ethylene block copolymer... The amount of ethylene-vinyl acetate block copolymer is 10-15 parts, and 6-8 parts of ethylene-vinyl acetate copolymer are introduced. This material forms a ternary composite system with polyurethane elastomer and styrene-butadiene-vinyl acetate block copolymer. The polar ester groups of ethylene-vinyl acetate copolymer enhance the intermolecular forces. With the addition of 15-20 parts of reinforcing agent and 0.5-1 parts of crosslinking agent, a higher crosslinking density and modulus are formed, which precisely strengthens the arch support function, effectively disperses the concentrated stress transmitted from the heel impact to the arch, avoids the local collapse and excessive pronation caused by the single material in the arch area of ​​traditional midsoles, and maintains appropriate elasticity to adapt to the natural deformation of the arch. The latter part further increases the styrene-butadiene-ethylene block copolymer to 25-30 parts and significantly increases the reinforcing agent to 25-35 parts, forming the region with the highest modulus and structural strength among the three sections. This directly copes with the impact load of up to 3-5 times the body weight when the heel lands. The high content of styrene-butadiene-ethylene block copolymer provides excellent energy absorption and rebound performance, while the high content of reinforcing agent inhibits irreversible slippage of polymer chains and cell wall creep. Combined with 0.5-1 parts of crosslinking agent, a dense and stable network structure is formed, which effectively delays the escape of encapsulated gas through the polymer matrix and the collapse of the cell structure, ensuring the stability of the heel cushioning performance in long-term use.

[0008] By employing a gradient functional design—high elasticity and flexibility in the forefoot, stable support in the midfoot, and high strength and durability in the heel—this shoe replaces the traditional three-layer structure of outsole, midsole, and insole. Functional zones are directly integrated into the inherent properties of a single-layer material. This simplifies the structure, reduces weight, and achieves a smooth dynamic transition from heel to midfoot. It avoids stress concentration issues caused by abrupt changes in hardness at the interface of the traditional three layers, allowing the sole to form a natural mechanical transmission chain during running, improving exercise efficiency and reducing the risk of injury.

[0009] Furthermore, the single-layer integrated structure of this application fundamentally changes the traditional three-layer stacked continuous barrier layer. The outer covering is only located on the side of the main body of the sole, rather than fully covering it. This allows the upper surfaces of the forefoot, midfoot, and heel sections to be directly treated with breathable technology to form longitudinal breathable microchannels. This breaks the complete blockage of gas convection by the traditional closed-cell foam structure of the midsole and the dense rubber of the outsole. At the same time, the optimized use of the cell stabilizer in the formula can form a more uniform open-cell and closed-cell mixed structure during the foaming process. While ensuring the gas space required for the cushioning function, it creates a limited breathable path. Compared with the traditional completely closed-cell midsole material, the breathability is greatly improved, and the elimination of potential breathable channels by the adhesive filling the interface gaps is avoided.

[0010] Additionally, depending on the requirements, the outer periphery can cover the sides and bottom of the main body of the sole, and ventilation holes can be opened in the middle section and the rear section.

[0011] Preferably, the crosslinking agent in the front section is 1,4-butanediol diglycidyl ether, the crosslinking agent in the middle section is trimethylolpropane triacrylate, and the crosslinking agent in the rear section is aziridine crosslinking agent.

[0012] By adopting the above technical solution, precise control of the crosslinking density and molecular network structure of the three-segment materials was achieved. The bifunctional 1,4-butanediol diglycidyl ether in the front segment forms a linear-to-lightly crosslinked network structure with moderate crosslinking, giving the forefoot area high flexibility and excellent resistance to bending fatigue, meeting the dynamic requirements of frequent bending deformation during push-off. The trifunctional trimethylolpropane triacrylate in the middle segment forms a three-dimensional network structure with high crosslinking density, which, in synergy with ethylene-vinyl acetate copolymer and high-content reinforcing agent, greatly enhances the rigidity and structural stability of the arch support, effectively resisting the concentrated stress transmitted from the heel impact and preventing local collapse and excessive deformation. The multifunctional trimethylolpropane triacrylate in the rear segment forms a three-dimensional network structure with high crosslinking density, which, in synergy with ethylene-vinyl acetate copolymer and high-content reinforcing agent, greatly enhances the rigidity and structural stability of the arch support, effectively resisting the concentrated stress transmitted from the heel impact and preventing local collapse and excessive deformation. The functional group aziridine crosslinking agent forms a dense, highly crosslinked network, which, together with a high content of styrene-butadiene-ethylene block copolymer and a high proportion of reinforcing agent, constructs a high-strength, high-modulus structure. This structure directly addresses the impact load during heel strike, effectively inhibiting polymer chain slippage and cell wall creep, and delaying the escape of encapsulated gas and structural collapse. The three-stage differentiated crosslinking system, combined with a gradient of raw material ratios, enables a smooth transition of mechanical properties from front to back in the single-layer integrated structure of the sole. This avoids stress concentration caused by abrupt changes in hardness at the interface of traditional three-layer structures. At the same time, it forms durability characteristics in different areas to meet their functional requirements, thereby improving the overall fatigue resistance, service life, and athletic comfort of the sole.

[0013] Preferably, the reinforcing agent in the front section is a mixture of silica and hollow glass microspheres in a mass ratio of (2-4):1; the reinforcing agent in the middle section is hollow glass microspheres; and the reinforcing agent in the rear section is a composite of carbon fiber and hollow glass microspheres in a mass ratio of 1:(3-5).

[0014] By adopting the above technical solution, a precise synergy of lightweighting, functionality, and durability is achieved across the three sections of the sole: the forefoot section uses silica to provide abrasion resistance and grip, while hollow glass microspheres reduce density and impart moderate elasticity to meet the flexible bending requirements of the forefoot; the midfoot section uses hollow glass microspheres alone to form a uniform closed-cell structure, maximizing weight reduction in the arch area while ensuring cushioning support; the rearfoot section uses carbon fiber to provide a high-strength skeleton to resist impact loads, and together with a high proportion of hollow glass microspheres, constructs a lightweight and highly rigid heel support system to delay fatigue collapse. All three reinforcement systems incorporate hollow glass microspheres, a lightweight filler, which, while reducing overall weight, adapts to the mechanical needs of each area through different compounding methods, overcoming the weight-performance contradiction in traditional reinforcement designs.

[0015] Preferably, the average particle size of the silica is 100-250 nm; the average particle size of the hollow glass microspheres is 10-40 μm; and the carbon fiber is short-cut carbon fiber with a length of 3-6 mm and a diameter of 5-10 μm.

[0016] By adopting the above technical solutions, the wear resistance and grip of the front section are further improved. The micron-sized hollow glass microspheres reduce the density while maintaining structural integrity, achieving a balance between lightweight and support. The aspect ratio of short-cut carbon fibers provides effective stress transfer, enhancing the impact resistance and creep resistance of the rear section.

[0017] Preferably, the cell stabilizer is a polyether-modified polysiloxane, wherein the viscosity of the polyether-modified polysiloxane is 500-3000 cSt, the molecular weight of the polyether segment is 1000-3000, and the degree of polymerization of the siloxane segment is 20-50.

[0018] By adopting the above technical solutions, the types and components of cell stabilizers are optimized, effectively stabilizing cell morphology, preventing collapse and merging, improving foaming uniformity and dimensional stability, and ensuring the three-stage differentiated damping function and durability.

[0019] Preferably, the styrene-butadiene-ethylene block copolymer has a molecular weight of 80,000-150,000, a styrene block content of 30-35 wt%, and a butadiene content of 40-50%.

[0020] By adopting the above technical solution and optimizing the parameters of the styrene-butadiene-ethylene block copolymer, a balance between the rigidity of the hard segment and the elasticity of the soft segment is achieved. The appropriate molecular weight ensures good compatibility and melt processability with polyurethane elastomers. The styrene hard segment provides physical crosslinking points and shape stability, while the butadiene soft segment imparts high elasticity and fatigue resistance. This parameter range allows the block copolymer to maintain the integrity of its phase structure during supercritical foaming, forming uniform micropores. At the same time, it meets the differentiated functional requirements of high elasticity and bending resistance in the front segment, stable support in the middle segment, and high strength and impact resistance in the rear segment, thereby improving the overall mechanical properties and service life of the shoe sole.

[0021] Preferably, the vinyl acetate content in the ethylene-vinyl acetate copolymer is 20-28 wt%, and the melt index is 3-8 g / 10 min at 190°C and 2.16 kg.

[0022] By adopting the above technical solution, the polarity, flowability and foaming performance of the mid-section material are synergistically optimized: the appropriate vinyl acetate content gives the block copolymer moderate polarity, enhances the interfacial compatibility with polyurethane elastomer and styrene-butadiene-ethylene block copolymer, and forms a stable ternary composite system; the appropriate melt index ensures suitable melt strength and flowability at the supercritical foaming temperature, promotes uniform nucleation and stable growth of cells, avoids cell collapse, and at the same time, this parameter range allows the mid-section to obtain a finer foam structure while maintaining the rigidity of the arch support, thereby improving shock absorption durability and stress dispersion ability.

[0023] Secondly, this application provides a method for preparing a shoe sole, employing the following technical solution: A method for preparing a shoe sole includes the following preparation steps: Prepare the front, middle and rear sections of the compound separately: add the dried base material into the internal mixer for plasticizing, then add the reinforcing agent, cell stabilizer and crosslinking agent in sequence, mix evenly, and then extrude and granulate to obtain three independent masterbatches. The substrate includes polyurethane elastomers and styrene-butadiene-ethylene block copolymers, or includes polyurethane elastomers, styrene-butadiene-ethylene block copolymers and ethylene-vinyl acetate copolymers; Supercritical fluid foaming process: Three sections of masterbatch are injected into the injection mold with zoned temperature control. Supercritical carbon dioxide or nitrogen fluid is injected into the melt through the injection molding machine nozzle to fully dissolve and diffuse the supercritical fluid. Then the pressure is quickly released to atmospheric pressure. After cooling and solidification, the mold is opened and the main blank of the shoe sole is taken out. Finished product preparation: Abrasion-resistant rubber is mixed and calendered into 2-4mm thick sheets, which are then coated onto the sides of the main body of the shoe sole through a molding vulcanization process. The vulcanization temperature is 150-170℃, the pressure is 10-15MPa, and the time is 5-8 minutes.

[0024] By combining segmented mixing and granulation with supercritical fluid foaming technology, precise control and integrated molding of the three material segments of the shoe sole are achieved: segmented mixing ensures that the raw materials in each segment are fully dispersed and pre-reacted, laying a uniform foundation for subsequent foaming; supercritical carbon dioxide or nitrogen injection enables the fluid to achieve selective solubility at different temperatures, and rapid pressure relief induces homogeneous nucleation, forming a microporous structure with a gradient pore size distribution, improving foaming uniformity and dimensional stability; the outer wear-resistant rubber molding and vulcanization coating protects the foam body and provides wear-resistant grip. The overall process avoids the residual odor and uneven pore size problems of traditional chemical foaming, and achieves a synergistic improvement in lightweight, functional zoning and durability while simplifying the three-layer composite structure.

[0025] Preferably, the foaming temperature is set to 140-150℃ for the first stage, 150-160℃ for the middle stage, and 160-170℃ for the last stage.

[0026] By adopting the above technical solution, selective dissolution and controllable foaming of supercritical fluid in a differentiated temperature field are achieved: the lower temperature in the first stage reduces the solubility of supercritical fluid, promotes rapid nucleation to form a larger pore structure, and endows the forefoot with high elasticity and flexibility; the moderate temperature in the middle stage balances the nucleation rate and cell growth, forming a uniform and dense microporous structure, enhancing the stability of the arch support; the higher temperature in the later stage increases the melt strength and crosslinking reaction rate, inhibits excessive cell expansion, forms a dense microporous structure, and improves the impact resistance and creep resistance of the heel; this gradient temperature control, combined with the formulation design of low crosslinking agent in the first stage and high crosslinking agent in the later stage, ensures that the three stages achieve differentiated foaming ratios and mechanical properties in synchronous injection molding, avoiding the functional homogenization problem caused by traditional uniform temperature foaming.

[0027] Preferably, the injection pressure of the supercritical carbon dioxide or nitrogen gas is 10-20 MPa, the amount of supercritical fluid is 3-8% of the melt mass, and the pressure holding time is controlled to be 30-60 seconds.

[0028] By adopting the above technical solutions, the aggregation and collapse of foam cells are effectively suppressed, the uniform nucleation of micro-cells is promoted, the dimensional stability and mechanical property consistency of foamed materials are improved, and the excessive fluid is avoided to prevent the rupture of foam cells or insufficient foaming, thus ensuring the precise controllability of the three-segment differentiated microporous structure.

[0029] In summary, this application has the following beneficial effects: This application adopts a segmented differentiated formulation design. The front segment uses a high elastomer with an appropriate amount of reinforcing agent to achieve high elasticity, flexibility and bending resistance. The middle segment introduces ethylene-vinyl acetate copolymer and increases the crosslinking density to strengthen the arch support. The rear segment significantly increases the reinforcing agent content to form a high modulus structure to absorb impact loads. All three segments use polyurethane elastomer as the main body to achieve an integrated single-layer structure. This design replaces the traditional three-layer structure of outsole, midsole, and insole, eliminating interlayer adhesives and structural redundancy, and significantly reducing the weight of the sole. Functional zoning is achieved through the inherent properties of the material, avoiding stress concentration caused by abrupt changes in interface hardness in traditional layers, and forming a natural mechanical transmission chain for the foot. The single-layer structure breaks the continuous barrier layer formed by traditional closed-cell foam and dense rubber. Combined with partial outer wrapping on the sides, the upper surface of the sole can be treated with a breathable process to form longitudinal breathable microchannels. At the same time, the foam stabilizer is optimized to form a hybrid open-cell and closed-cell structure, which greatly improves breathability while ensuring cushioning performance, and effectively inhibits foam collapse and gas escape during long-term use, achieving a synergistic improvement in lightweight, breathability, and durability. Instruction manual illustrations

[0030] Figure 1 This is a schematic diagram of the structure of a shoe sole in Example 1.

[0031] Figure 2 This is a physical image of a shoe sole from Example 1.

[0032] Attached image labels: 1. Front section; 2. Middle section; 3. Rear section; 4. Outer perimeter. Detailed Implementation Example

[0033] The polyurethane elastomer is BASF's C95A product from Germany.

[0034] The wear-resistant rubber is SBR6250, a product from Chi Mei Corporation in Taiwan, China. Example

[0035] A type of shoe sole, reference Figure 1 and Figure 2 The sole comprises a forefoot section that contacts the forefoot, a midfoot section that contacts the arch, a heel section that contacts the heel, and an outer perimeter. The forefoot, midfoot, and heel sections are integrally molded into the main body of the sole using an injection molding process, and the outer perimeter covers the sides of the main body of the sole. It is prepared by the following method: 400g of polyurethane elastomer and 200g of styrene-butadiene-ethylene block copolymer were dried and added to a mixer for plasticizing. Then, 100g of reinforcing agent, 10g of cell stabilizer and 4g of crosslinking agent were added in sequence, mixed evenly, and then extruded and granulated to obtain the front-end masterbatch. 400g of polyurethane elastomer, 100g of styrene-butadiene-ethylene block copolymer and 60g of ethylene-vinyl acetate copolymer were dried and added to a mixer for plasticizing. Then, 150g of reinforcing agent, 10g of cell stabilizer and 5g of crosslinking agent were added in sequence, mixed evenly, and then extruded and granulated to obtain the intermediate masterbatch. 400g of polyurethane elastomer and 250g of styrene-butadiene-ethylene block copolymer were dried and added to an internal mixer for plasticizing. Then, 250g of reinforcing agent, 10g of cell stabilizer and 5g of crosslinking agent were added in sequence, mixed evenly, and then extruded and granulated to obtain the downstream masterbatch. The three masterbatches are injected into the injection mold with zoned temperature control. Supercritical carbon dioxide or nitrogen fluid is injected into the melt through the injection molding machine nozzle to fully dissolve and diffuse the supercritical fluid. Then the pressure is quickly released to atmospheric pressure. After cooling and solidification, the mold is opened and the main blank of the shoe sole is taken out. The foaming temperature is set to 140℃ for the first stage, 150℃ for the middle stage, and 160℃ for the last stage. The injection pressure of the supercritical carbon dioxide fluid is 10 MPa, the amount of supercritical fluid is 3% of the melt mass, and the holding time is controlled at 30 seconds. Finished product preparation: Abrasion-resistant rubber is mixed and calendered into a 2mm thick sheet, which is then wrapped onto the side of the main body of the shoe sole through a molding vulcanization process. The vulcanization temperature is 150℃, the pressure is 10MPa, and the time is 5 minutes.

[0036] The difference between Examples 2-3 and Example 1 lies in the types, amounts, and parameters of raw materials used to prepare the shoe soles. Specific differences are shown in Table 1. Table 1. Types, amounts, and parameters of raw materials used in the preparation of shoe soles.

[0037]

[0038]

[0039]

[0040] Example

[0041] A shoe sole, the difference between this embodiment and Embodiment 1 is that the crosslinking agent for the front, middle and rear sections is 1,4-butanediol diglycidyl ether.

[0042] Example 5 A shoe sole, the difference between this embodiment and embodiment 1 is that the reinforcing agent of the front section, middle section and rear section is a mixture of silica and hollow glass microspheres in a mass ratio of 2:1, the silica has an average particle size of 100nm and an average particle size of 10μm.

[0043] Comparative Example Comparative Example 1 A shoe sole, the difference between this comparative example and Example 1 is that the amount of styrene-butadiene-ethylene block copolymer used in the forefoot, middle and rear sections is 200g.

[0044] Comparative Example 2 A shoe sole, the difference between this comparative example and Example 1 is that the amount of reinforcing agent used in the forefoot, middle and rear sections is 150g.

[0045] Comparative Example 3 A shoe sole, the difference between this comparative example and Example 1 is that the front masterbatch, middle masterbatch and rear masterbatch are all made by adding 400g of polyurethane elastomer and 200g of styrene-butadiene-ethylene block copolymer after drying the base material into an internal mixer for plasticizing, followed by adding 100g of reinforcing agent, 10g of cell stabilizer and 4g of crosslinking agent in sequence, mixing evenly, and then extruding and granulating. The remaining steps are the same as in the example.

[0046] Comparative Example 4 A shoe sole, the difference between this comparative example and Example 1 is that the styrene-butadiene-ethylene block copolymer is replaced with an equal weight of ethylene-octene copolymer.

[0047] Comparative Example 5 A shoe sole, the difference between this comparative example and Example 1 is that the ethylene-vinyl acetate copolymer is replaced with polycaprolactone.

[0048] Polycaprolactone was purchased from Hunan Juren Chemical New Material Technology Co., Ltd., with a molecular weight of 10,000.

[0049] Detection methods / test methods Fatigue collapse resistance: Referring to GB / T 10652-2001 "Determination of compressive permanent deformation of porous polymer elastic materials under load conditions: preload 50N, peak load 1500N", a fatigue testing machine was used to apply periodic compressive loads to the later sample at a frequency of 2Hz and a cycle count of 50,000.

[0050] Torsional stiffness test (arch support stability): The sole sample is inserted into a rigid metal last, and the forefoot area is completely fixed to the testing machine base using an aluminum alloy clamp and bolts to ensure that there is no relative displacement in this section; a torque transmission arm with a length of 150mm is installed at the rear edge of the heel and connected to the universal testing machine actuator through a universal joint to apply torque; the torsion axis is set to be 15mm below the sole plane, and 3 pre-cycles are performed at an angular velocity of 5° / s (torsional angle range -15° to +15°, simulating foot pronation and supination) to eliminate the Mullins effect of the material. The torque-angle curve of the 4th cycle is then formally recorded, and the torsional stiffness (K=ΔT / Δθ, unit Nm / °) is calculated by taking the slope of the 0°±5° linear segment. Five samples are tested in each group and the average value is taken. The test environment is controlled at 23±2℃ and relative humidity 50±5%.

[0051] Breathability test: Seal the shoe sole sample in the mouth of the test cup, fill the cup with desiccant, and place it in an environment of 23℃ and 50% relative humidity for 24 hours. Weigh the increase in weight of the desiccant and calculate the moisture permeability.

[0052] Grip test: The shoe sole sample was fixed to the test head of the testing machine, with the treaded side facing down in contact with the standard test surface tile. A normal force of 500N was applied and pre-contact was maintained for 30s. Then, it was pulled horizontally at a constant speed of 100mm / min. The normal force and friction force were recorded simultaneously by a three-dimensional force sensor, and the static friction coefficient was calculated. The experimental data are shown in Table 2. Table 2 Experimental data of Examples 1-5 and Comparative Examples 1-5

[0053] The experimental data above shows that by using differentiated formulas for the forefoot, midfoot, and heel sections, the sole achieves lightweight design while simultaneously addressing three major technical bottlenecks: poor breathability, insufficient arch support, and long-term collapse. This allows the sole to maintain excellent structural stability and functionality even after 50,000 compression cycles.

[0054] Comparing Example 1 with Comparative Examples 1-5, Comparative Example 1 shows that if all three sections use the same amount of styrene-butadiene-ethylene block copolymer, it is impossible to achieve the functional zoning of high elasticity and bending resistance in the front section, arch support in the middle section, and high strength and impact resistance in the rear section, resulting in reduced fatigue resistance and support stability; Comparative Example 2 shows that although using a uniform medium amount of reinforcing agent can simplify the process, it cannot simultaneously meet the differentiated needs of grip and wear resistance in the front section, lightweight support in the middle section, and high modulus creep resistance in the rear section, resulting in an imbalance between durability and functionality; Comparative Example 3 This indicates that if all three sections use a flexible formulation with low reinforcement and low cross-linking in the front section, the heel area cannot withstand high-intensity impact loads, resulting in insufficient arch support and premature collapse of the overall structure. Comparative Examples 4 and 5 demonstrate that the specific combination of styrene-butadiene-ethylene block copolymer and its combination with ethylene-vinyl acetate copolymer is irreplaceable for forming a stable ternary composite system and a microphase separation structure that adapts to the mechanical properties of each region. Simply replacing it with ethylene-octene copolymer or polycaprolactone will lead to decreased interfacial compatibility and failure of functional synergy. In other words, only through precise differentiated design of the elastomer ratio, cross-linking density, and reinforcement strategy in the front, middle, and rear sections can a synergistic improvement in lightweight, breathability, support stability, and fatigue resistance be achieved in a single-layer integrated structure.

[0055] Comparing Examples 1 with Examples 4-5, it is evident that the front-end bifunctional crosslinking agent constructs a moderately crosslinked network to ensure elasticity, the middle-end trifunctional crosslinking agent forms a high crosslinking density to enhance arch rigidity, and the rear-end multifunctional aziridine crosslinking agent constructs a dense network to delay fatigue collapse. Combined with the gradient reinforcement design of front-end silica and hollow glass microsphere composite, middle-end pure hollow glass microsphere, and rear-end carbon fiber and hollow glass microsphere composite, a smooth transition of mechanical properties from front to back and optimal matching of functions in each region are achieved. This enables the simultaneous fulfillment of multiple requirements for high elasticity, support, durability, and lightweight in a single-layer integrated structure.

[0056] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A shoe sole, characterized in that, The sole includes a forefoot section that contacts the forefoot, a midfoot section that contacts the arch, a heel section that contacts the heel, and an outer perimeter. The forefoot section, midfoot section, and heel section are integrally molded into the main body of the sole using an injection molding process. The outer perimeter covers the sides of the main body of the sole. The forefoot section is composed of the following raw materials in parts by weight: 40-60 parts of polyurethane elastomer 20-30 parts of styrene-butadiene-ethylene block copolymer 10-15 parts of reinforcing agent 1-2 parts of foam stabilizer Crosslinking agent 0.4-0.6 parts The middle section is composed of the following raw materials in parts by weight; 40-60 parts of polyurethane elastomer 10-15 parts of styrene-butadiene-ethylene block copolymer 6-8 parts of ethylene-vinyl acetate copolymer 15-20 parts of reinforcing agent Crosslinking agent 0.5-1 part 1-2 parts of foam stabilizer The latter section is composed of the following raw materials in parts by weight: 40-60 parts of polyurethane elastomer 25-30 parts of styrene-butadiene-ethylene block copolymer 25-35 parts of reinforcing agent 1-2 parts of foam stabilizer Crosslinking agent 0.5-1 part.

2. The sole according to claim 1, characterized in that: The crosslinking agent in the front section is 1,4-butanediol diglycidyl ether, the crosslinking agent in the middle section is trimethylolpropane triacrylate, and the crosslinking agent in the rear section is aziridine crosslinking agent.

3. The sole according to claim 1, characterized in that: The reinforcing agent in the front section is a mixture of silica and hollow glass microspheres in a mass ratio of (2-4):1; the reinforcing agent in the middle section is hollow glass microspheres; and the reinforcing agent in the rear section is a composite of carbon fiber and hollow glass microspheres in a mass ratio of 1:(3-5).

4. The sole according to claim 3, characterized in that: The average particle size of the silica is 100-250 nm; the average particle size of the hollow glass microspheres is 10-40 μm; and the carbon fiber is short-cut carbon fiber with a length of 3-6 mm and a diameter of 5-10 μm.

5. The sole according to claim 1, characterized in that: The cell stabilizer is a polyether-modified polysiloxane, which has a viscosity of 500-3000 cSt, a molecular weight of 1000-3000 for the polyether segments, and a degree of polymerization of 20-50 for the siloxane segments.

6. The sole according to claim 1, characterized in that: The styrene-butadiene-ethylene block copolymer has a molecular weight of 80,000-150,000, a styrene block content of 30-35 wt%, and a butadiene content of 40-50%.

7. The sole according to claim 1, characterized in that: The ethylene-vinyl acetate copolymer has a vinyl acetate content of 20-28 wt% and a melt index of 3-8 g / 10 min at 190°C and 2.16 kg.

8. A method for preparing a shoe sole as described in any one of claims 1-7, characterized in that, The preparation steps include the following: Prepare the front, middle and rear sections of the compound separately: add the dried base material into the internal mixer for plasticizing, then add the reinforcing agent, cell stabilizer and crosslinking agent in sequence, mix evenly, and then extrude and granulate to obtain three independent masterbatches. The substrate includes polyurethane elastomers and styrene-butadiene-ethylene block copolymers, or includes polyurethane elastomers, styrene-butadiene-ethylene block copolymers and ethylene-vinyl acetate copolymers; Supercritical fluid foaming process: Three sections of masterbatch are injected into the injection mold with zoned temperature control. Supercritical carbon dioxide or nitrogen fluid is injected into the melt through the injection molding machine nozzle to fully dissolve and diffuse the supercritical fluid. Then the pressure is quickly released to atmospheric pressure. After cooling and solidification, the mold is opened and the main blank of the shoe sole is taken out. Finished product preparation: Abrasion-resistant rubber is mixed and calendered into 2-4mm thick sheets, which are then coated onto the sides of the main body of the shoe sole through a molding vulcanization process. The vulcanization temperature is 150-170℃, the pressure is 10-15MPa, and the time is 5-8 minutes.

9. The method for preparing a shoe sole according to claim 8, characterized in that: The foaming temperature is set to 140-150℃ for the first stage, 150-160℃ for the middle stage, and 160-170℃ for the last stage.

10. The method for preparing a shoe sole according to claim 8, characterized in that: The injection pressure of supercritical carbon dioxide or nitrogen gas is 10-20 MPa, the amount of supercritical fluid is 3-8% of the melt mass, and the holding time is controlled to be 30-60 seconds.

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