Mildew-proof antibacterial degradable shoe tree and preparation method thereof

Abstract

The application discloses a kind of mildew-proof antibacterial degradable shoe stretcher and preparation method thereof, the shoe stretcher is made of raw materials including the following weight percentage: starch 15%~50%; polypropylene 40%~60%; functional additives 10%~25%; functional additives at least include mildew-proof agent, antibacterial agent, toughening agent and coupling agent.The preparation method includes: starch is dried to moisture content≤1%, polypropylene and functional additives are mixed and heated to 130~140℃ to make polypropylene wrap starch, after melt extrusion, air cooling and granulation, injection molding is formed.The application adds specific functional additives in the blending system of starch and polypropylene, so that the mildew-proof grade of shoe stretcher reaches 1 level, at the same time, the biodegradability of starch is used to make waste shoe stretcher disintegrate into fragments, long-term mildew-proof and degradable performance are considered, and the mechanical properties are excellent, which can be widely used in shoe storage, transportation packaging and daily maintenance.

Description

Technical Field

[0001] This invention belongs to the field of footwear auxiliary products technology, specifically relating to a mildew-proof, antibacterial, and biodegradable shoe tree and its preparation method. Background Technology

[0002] Shoe trees are auxiliary products used to support the inner wall of shoes, maintaining their original three-dimensional shape and preventing wrinkles on the upper. They are widely used in shoe storage, shelf display, transportation packaging, and daily home maintenance. With advancements in shoe manufacturing technology and increased awareness of shoe care, a qualified shoe tree needs to possess good rigid support, lightweight design, environmental friendliness, and anti-mold and antibacterial properties.

[0003] Currently, shoe trees on the market mainly have the following defects:

[0004] 1. Traditional shoe tree materials are non-biodegradable, causing white pollution.

[0005] Traditional shoe trees are mostly made of solid wood or rigid injection-molded plastics (such as polypropylene (PP) and acrylonitrile-butadiene-styrene copolymer ABS). While they offer good rigidity and support, the materials themselves are not biodegradable. Taking PP as an example, its molecular chains are composed of carbon-carbon single bonds, which microorganisms cannot effectively decompose, resulting in a degradation cycle of hundreds of years in the natural environment. Large quantities of discarded shoe trees persist in the environment for extended periods, causing serious white pollution. With increasingly stringent global environmental regulations and growing consumer awareness of environmental protection, there is an urgent need to develop shoe tree products with biodegradable properties.

[0006] 2. Traditional plastic shoe trees do not have anti-mold and antibacterial functions.

[0007] While plastic shoe trees, represented by PP (polypropylene), offer excellent mechanical properties and are relatively inexpensive, PP itself is a hydrophobic material and lacks the ability to inhibit microbial growth. During use, especially in humid climates or when sweat remains inside the shoe, the environment easily breeds mold (such as Aspergillus niger and Penicillium) and bacteria (such as Staphylococcus aureus and Escherichia coli). This not only produces unpleasant odors but can also damage the shoe's fibers, shortening its lifespan. For high-end footwear such as leather shoes and athletic shoes, mold can cause mildew spots on the leather surface, severely affecting its appearance and usability.

[0008] 3. Existing antibacterial shoe trees mostly use physical filling methods, which have inconsistent effects.

[0009] While there are existing technologies that incorporate antibacterial components into shoe trees, for example, patent CN218898584U discloses a low-carbon, multifunctional shoe tree that achieves sterilization and dehumidification by setting through holes at the bottom of the shoe tree and filling them with antibacterial drying particles (such as zeolite, activated carbon, antibacterial agents, etc.). However, this solution has the following shortcomings: (1) the antibacterial particles exist independently in the cavity of the shoe tree through physical filling, resulting in uneven particle distribution and easy leakage during use; (2) the antibacterial effect gradually diminishes over time, lacking long-term effectiveness; (3) the shoe tree frame is made of epoxy resin, which is not biodegradable and still causes environmental pollution after disposal. In addition, patent CN220859563U discloses a corn starch hollow shoe tree made of corn starch material. Although it has a certain degree of biodegradability, this solution does not involve anti-mildew and antibacterial functions, and the pure starch-based material has poor mechanical properties, making it difficult to provide sufficient rigid support.

[0010] 4. Most biodegradable shoe material solutions use fully biodegradable polyester, which is costly and has insufficient mechanical properties.

[0011] Existing technologies also disclose methods for preparing shoe materials using starch blends with biodegradable polyesters. For example, patent CN101235164A discloses a fully biodegradable shoe material and its preparation method, which uses plant starch blended with fully biodegradable resins (such as polylactic acid PLA, polybutylene adipate terephthalate ester ...

[0012] How to overcome the natural defects of starch's hydrophilicity and susceptibility to mold while maintaining the mechanical properties of PP substrate, and achieve both biodegradability and long-lasting mold prevention, while still maintaining excellent anti-mold and antibacterial effects at high starch content (above 15%), is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of the prior art and provide a mildew-proof, antibacterial, and biodegradable shoe tree and its preparation method, so as to solve the technical problems of existing shoe trees that are non-degradable, lack mildew-proof and antibacterial functions, have uneven distribution of antibacterial components, and are prone to mold growth on starch-based materials.

[0014] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0015] This invention provides a mildew-proof, antibacterial, and biodegradable shoe tree. Its core lies in the use of specific raw material combinations and ratios to enable the shoe tree to have excellent mildew-proof, antibacterial, and mechanical properties during its service life, and to have biodegradable and disintegrating properties after disposal.

[0016] Specifically, the shoe support is made of raw materials comprising the following weight percentages: starch: 15%–50%; polypropylene: 40%–60%; functional additives: 10%–25%.

[0017] In this material, starch, as a biodegradable component, imparts biodegradability; polypropylene, as the matrix resin, provides rigid mechanical support; and functional additives impart antifungal and antibacterial properties, and improve the compatibility and processing performance between starch and polypropylene. Functional additives include at least antifungal agents, antibacterial agents, toughening agents, and coupling agents. Antifungal agents and antibacterial agents inhibit the growth of mold and bacteria, overcoming the defect of starch's hydrophilicity and susceptibility to mold growth; toughening agents improve the material's impact resistance; and coupling agents improve the interfacial compatibility between starch and polypropylene, enhancing the material's mechanical properties.

[0018] In starch-polypropylene blends, the degradation effect is not significant when the starch content is too low (<15%), while the mechanical properties decrease significantly when the content is too high (>50%). This invention controls the starch content at 15%–50% and the polypropylene content at 40%–60%, achieving a good balance between biodegradability and mechanical properties. When the additive content is below 10%, the antifungal, antibacterial, and toughening effects are insufficient; when it is above 25%, it affects the mechanical properties and processing flowability of the material.

[0019] Furthermore, starch needs to be dried before being added to the ingredients to ensure that its moisture content is ≤1%, in order to avoid starch gelatinization and degradation or the generation of bubbles during high-temperature processing, which would affect the appearance and mechanical properties of the product.

[0020] Furthermore, functional additives may selectively include one or more of antioxidants, lubricants, or dispersants, depending on performance requirements. Antioxidants are used to prevent thermal oxidative degradation of materials during processing and use; lubricants are used to improve processing flowability and mold release properties; and dispersants are used to promote uniform dispersion of components in the matrix.

[0021] Through the above combination and proportion of raw materials, the shoe support of the present invention can achieve at least one of the following mechanical properties after injection molding: tensile yield strength 25-40MPa, compressive yield strength 30-50MPa, flexural modulus 1000-1800MPa, Shore hardness 65-75 (D standard), top static compressive strength 25-35kg, lateral compressive strength 8-15kg, and no cracking after repeated stepping, fully meeting the requirements of rigid support and repeated use of the shoe support.

[0022] The present invention also provides a method for preparing the above-mentioned anti-mildew, antibacterial, and biodegradable shoe tree, comprising the following steps:

[0023] Step 1: Add starch to a mixer, heat to 110-120℃, and continuously stir to fully evaporate the free water in the starch until the moisture content is reduced to ≤1%. The purpose of this step is to effectively remove free water from the starch at a temperature of 110-120℃, while preventing the starch granules from gelatinizing and sticking together at this temperature, ensuring that the starch maintains its granular shape and is evenly dispersed in the PP matrix during subsequent processing.

[0024] Step 2: Add polypropylene and functional additives to the dried starch, continue mixing and heat to 130-140℃. At this temperature, the polypropylene softens (the Vicat softening point of polypropylene is approximately 150-160℃, but significant softening can occur at 130-140℃ under shear force). The softened polypropylene gradually coats the starch granules under stirring, forming a uniformly coated mixture. The key to this step is the two-stage process of first drying the starch and then adding PP and heating to coat it, allowing the PP to uniformly coat the starch while it is in a softened state, thereby improving the interfacial bonding between the two.

[0025] Step 3: Add the above mixture to a twin-screw extruder and heat and melt it at a temperature of 160–220°C. This allows the components to be fully dispersed in the molten state, and then the mixture is extruded to form a molten strip. The shearing force of the twin-screw extruder helps to further refine the dispersion of starch granules in the PP matrix, while also promoting the uniform distribution of functional additives in the melt.

[0026] Step 4: The extruded molten material is air-cooled and solidified, then cut into cylindrical granules with a diameter of 2-4 mm using a pelletizer to obtain granules suitable for injection molding. Unlike conventional water cooling methods, this invention uses air cooling, which has the advantage of preventing the starch component from reabsorbing moisture during cooling, ensuring that the moisture content of the granules is always controlled below 1%.

[0027] Step 5: Inject the above granules into shoe tree products using an injection molding machine.

[0028] Furthermore, the injection molding process in step 5 adopts the following conditions: barrel temperature of 200–230℃, mold temperature of 50–80℃, injection pressure of 60–90 MPa, holding pressure of 30–45 MPa, and holding time of 0.2–0.3 seconds. Too low a barrel temperature will result in excessively high melt viscosity and difficulty in mold filling, while too high a temperature may cause thermal degradation of starch. Too low a mold temperature will affect the surface quality of the product, while too high a temperature will prolong the cooling cycle. The holding pressure and holding time are used to compensate for product cooling shrinkage and prevent shrinkage marks and bubbles.

[0029] Furthermore, after injection molding, the shoe trees are annealed at a temperature of 40–50°C for 2–4 hours. Annealing eliminates internal stress generated during injection molding, preventing warping and deformation due to stress release during long-term use or degradation.

[0030] In a preferred embodiment of the present invention, the antibacterial agent in the functional additives includes bamboo extract. Bamboo extract is rich in flavonoids and polyphenols, possessing natural antibacterial activity, and can serve as a partial or complete alternative to chemical antibacterial agents, further enhancing the product's environmental friendliness.

[0031] Bamboo extract is preferably prepared by the following method, which specifically includes the following steps:

[0032] (a) Raw material pretreatment: Cut the bamboo into sections with a length of 15-20 cm, rinse them with water to remove surface impurities. Preferably, the bamboo is selected from bamboo species with high flavonoid and polyphenol content, such as dragon bamboo (Dendrocalamus giganteus) or hemp bamboo (Dendrocalamus latiflorus).

[0033] (b) Microwave-assisted extraction: The pretreated bamboo segments are placed in a reaction vessel and microwaved for 3–10 minutes to disrupt the plant cell walls. Then, a solvent is added for extraction to obtain a crude extract. Microwave treatment effectively disrupts the cellulose-lignin cell wall structure of bamboo, allowing for the full release of intracellular active components (flavonoids, polyphenols), thereby improving the efficiency of subsequent solvent extraction. Preferably, the power density of the microwave treatment is 15–20 W / g. The solvent is preferably a 50%–60% food-grade ethanol aqueous solution, with a material-to-liquid ratio of 1:20–1:30 (g:mL). The extraction temperature is controlled at 60–80℃, and the reflux extraction time is 2–3 hours.

[0034] (c) Macroporous resin purification: The crude extract is purified by adsorption through a macroporous resin column, followed by elution with 70% ethanol. The eluent is collected and concentrated to obtain the purified bamboo extract. The total polyphenol purity in the crude extract is usually only about 20%, which can be increased to over 50% after macroporous resin purification, significantly enhancing the antibacterial effect. Preferably, HPD-100 macroporous adsorption resin is used, the loading flow rate is 1-2 column volumes / hour, the total polyphenol concentration is 1.0-2.0 mg / mL, and the loading pH is 4.0-5.0.

[0035] Furthermore, the elution endpoint was determined using the elution effluent detection method: elution was terminated when the total polyphenol concentration in the elution effluent dropped below 1% of the total polyphenol concentration of the sample. Specifically, the total polyphenol concentration in the elution effluent reached its peak within 0.5 column volumes and then gradually decreased. When elution reached 3.5–5.0 column volumes, the total polyphenol concentration dropped below 1% of the peak value, indicating that the polyphenols adsorbed on the resin had been almost completely eluted, at which point elution could be terminated.

[0036] Furthermore, purified bamboo extract can be further processed through compounding to enhance its antibacterial effects and stability. Compounding can be achieved by either combining it with bamboo vinegar or with metal ions.

[0037] There are two synergistic approaches to combining polyphenols with bamboo vinegar: First, polyphenols are the main component and bamboo vinegar is the auxiliary component. The organic acids in bamboo vinegar can stabilize polyphenols and reduce oxidative degradation. The mass ratio of polyphenols to bamboo vinegar is 1:0.5 to 1:2. Second, bamboo vinegar is the main component and polyphenols are the enhancement component. The two have a synergistic effect on antibacterial activity. The mass ratio of bamboo vinegar to polyphenols is 1:0.1 to 1:0.5.

[0038] In the complex with metal ions, the metal ion is Fe. 3+ Fe 2+ Cu 2+ and Zn 2+ One of them. Zinc ions, when compounded with polyphenols at a molar ratio of 1:1 to 4:1, can enhance the stability and sustained-release properties of the antibacterial effect; Fe 3+ According to polyphenols: Fe 3+ A molar ratio of 1:1 to 3:1 can be used to form a metal-polyphenol network (MPN); Fe 2+ According to polyphenols: Fe 2+ A molar ratio of 2:1 to 5:1, when combined, exhibits a synergistic antioxidant effect; Cu 2+ According to polyphenols: Cu 2+ Combinations with a molar ratio of 1:1 to 2:1 exhibit a synergistic antibacterial effect. All of the above-mentioned combination schemes can achieve the technical effects of synergistic enhancement and reduced dosage.

[0039] The present invention, by adopting the above-described technical solution, has the following beneficial effects:

[0040] 1. This invention achieves a Grade 1 anti-mold rating on a starch-polypropylene blend by adding specific functional additives (including at least antifungal agents, antibacterial agents, toughening agents, and coupling agents) to the starch substrate, which is prone to mold growth. The rating is based on GB / T44940-2024 testing, using *Aspergillus niger* and *Penicillium cordifolium* as test species, with Grade 0 being the best and Grade 4 the worst. Comparative studies show that the starch / PP control group without antifungal and antibacterial additives achieved a Grade 4 anti-mold rating (severe growth), while the anti-mold rating of this invention is equivalent to that of the pure PP-based antibacterial material (control group 2), both being Grade 1. This invention solves the technical problem of starch's susceptibility to moisture absorption and mold growth in humid environments through the synergistic combination of antifungal agents and antibacterial agents. This allows the starch-polypropylene blend to maintain its biodegradability while achieving the same level of antifungal and antibacterial effect as pure PP-based materials, thus unifying biodegradability and long-lasting anti-mold performance.

[0041] 2. This invention introduces 15%–50% starch component into a polypropylene matrix, utilizing the biodegradability of starch in the natural environment to enable discarded shoe trees to rapidly disintegrate. Experiments show that under composting conditions, the shoe trees of this invention exhibit a mass loss rate of 10%–60% within 1–4 weeks and disintegrate into amorphous fragments within 3 months, effectively destroying the overall shape of the product.

[0042] 3. While achieving biodegradability and anti-mildew / antibacterial functions, the shoe support of this invention still maintains excellent mechanical properties: tensile yield strength 25-40 MPa, compressive yield strength 30-50 MPa, flexural modulus 1000-1800 MPa, static top compression resistance 25-35 kg, lateral compression resistance 8-15 kg, and no cracking after repeated stepping. These mechanical properties fully meet the actual needs of the shoe support for rigid support and repeated use, effectively maintaining the three-dimensional shape of the shoe and preventing wrinkles on the shoe surface.

[0043] 4. The preparation method of the present invention has been systematically optimized for the processing characteristics of the starch and polypropylene blend system: (1) A two-stage mixing process is adopted, in which starch is dried first and then PP is added and heated to coat it, so that PP softens and coats starch, improving the compatibility between starch and PP; (2) Air cooling is used as the only cooling method to avoid starch components from reabsorbing water, ensuring that the moisture content of the granules is always controlled below 1%; (3) Annealing treatment is used to eliminate internal stress, prevent product warping and deformation, and improve the yield and product dimensional stability.

[0044] 5. This invention preferably uses bamboo extract as a natural antibacterial ingredient. Through microwave-assisted extraction combined with macroporous resin purification, the purity of the active ingredient (total polyphenols) is increased from 20% to over 50%, doubling the antibacterial effect. The bamboo extract, when combined with bamboo vinegar or zinc ions, can further enhance the synergistic effect, improving the antibacterial efficacy while reducing the dosage. This approach reduces the use of chemical antibacterial agents, further enhancing the product's environmental friendliness and aligning with the industry trend of green and sustainable development. Attached Figure Description

[0045] The present invention will be further described below with reference to the accompanying drawings:

[0046] Figure 1 This is a schematic diagram of the structure of a shoe support according to the present invention;

[0047] Figure 2 for Figure 1 Top view;

[0048] Figure 3 for Figure 1 The main view.

[0049] In the diagram, 1-framework; 11-lateral support; 12-top limiting part; 13-bottom support part; 14-rounded corner;

[0050] 2-Support shell; 21-First through hole; 22-Second through hole;

[0051] 3-Connecting part; 31-Abutting end;

[0052] 4-Gap;

[0053] 5-Reinforcing ribs. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the embodiments of this invention will be described in further detail below with reference to the accompanying drawings. It should be noted that the following embodiments are only for a better understanding of this invention and do not constitute a limitation on the scope of protection of this invention.

[0055] Example 1: Raw material formula and preparation method of shoe trees.

[0056] 1. Raw material formula

[0057] This embodiment provides a mildew-proof, antibacterial, and biodegradable shoe tree, comprising the following raw materials by weight percentage: starch 30%; polypropylene 50%; and functional additives 20%. The functional additives include mildew inhibitors, antibacterial agents, toughening agents, coupling agents, antioxidants, lubricants, and dispersants.

[0058] The starch used in this embodiment is natural plant starch (corn starch), with a moisture content of 8% to 12% before use. It needs to be dried so that the moisture content of the starch is ≤1% before it can be used.

[0059] 2. Preparation method

[0060] The preparation of anti-mildew, antibacterial, and biodegradable shoe trees using the above-mentioned raw material formula includes the following steps:

[0061] Step 1, Starch drying: Put the starch into a mixer, heat it to 110-120℃, stir and mix it at a speed of 200-400 rpm, and dehydrate and dry it until the moisture content is ≤1%.

[0062] Step 2, Mixing: Add polypropylene and functional additives to the dried starch, continue mixing and heat to 130-140℃, stir at 200-400 rpm to soften the polypropylene and coat the starch to form a uniform mixture.

[0063] Step 3, Melt Extrusion: The mixture is added to a twin-screw extruder, heated and melted, sheared and mixed, and then extruded into molten strips. The temperature range of the twin-screw extruder is 160 to 220°C, and the screw speed is 200 to 400 rpm. The twin-screw extruder is equipped with a vacuum exhaust port, and a vacuum degree of -0.06 to -0.08 MPa is maintained by a vacuum pump to remove water vapor and volatiles.

[0064] Step 4, Cooling and Pelletizing: The extruded molten strip is air-cooled and solidified, and then pelletized to obtain cylindrical particles with a diameter of 2-4 mm;

[0065] Step 5, Injection Molding: The granules are injection molded into shoe trees using an injection molding machine; the injection conditions are: barrel temperature 200~230℃, mold temperature 50~80℃, injection pressure 60~90MPa, holding pressure 30~45MPa, and holding time 0.2~0.3 seconds.

[0066] Step 6, Annealing treatment: After injection molding, the shoe tree product is annealed at a temperature of 40-50℃ for 2-4 hours to obtain anti-mildew, antibacterial and biodegradable shoe trees.

[0067] 3. The specific structure of shoe trees

[0068] like Figures 1 to 3 As shown, the shoe support made using the above-described method includes a skeleton 1, a support shell 2, and several connecting parts 3. The skeleton 1, support shell 2, and connecting parts 3 are manufactured using an integrated injection molding process. The skeleton 1 serves as a high-rigidity outer support frame, while the support shell 2 and connecting parts 3 serve as internal biomimetic support bodies. Preferably, the support shell 2 and connecting parts 3 of this invention are shaped like an octopus.

[0069] The frame 1 encloses a receiving space, which is a hollow area in the middle of the frame 1. The supporting shell 2 is located within the receiving space and is connected to the frame 1 via a connecting part 3. Gaps 4 are formed between the supporting shell 2 and the frame 1, and between the connecting part 3 and the frame 1. This invention uses a hollow structure of frame 1, supporting shell 2, and connecting part 3. The connecting part 3 suspends the supporting shell 2 within the receiving space of the frame 1, forming breathable gaps 4 around it. Compared to traditional solid shoe trees, this structure reduces material usage and achieves product lightweighting. At the same time, the gaps 4 and the receiving space effectively promote air circulation inside the shoe, allowing moisture to escape in time, slowing down mold growth, and providing good moisture-proof and breathable effects.

[0070] The frame 1 includes multiple support parts, specifically a lateral support part 11, a bottom support part 13, and a top limiting part 12. The lateral support parts 11 are located on both sides of the receiving space, and are used to abut against the inner walls of the shoe upper when the shoe support is inserted into the shoe, preventing the sides of the shoe from being squeezed and causing wrinkles or inward collapse. The bottom support part 13 is located on the front side of the receiving space and arches upward, abutting against the inner wall of the toe, preventing the front of the toe from collapsing and deforming due to long-term pressure. The top limiting part 12 is located on the rear side of the receiving space and arches upward, abutting against the inner wall of the heel, acting as a limiter to prevent the shoe support from sliding back and forth inside the shoe, while also supporting the shoe opening at the heel to prevent loosening. The lateral support parts 11, bottom support parts 13, and top limiting part 12 together form a three-dimensional support frame inside the shoe that conforms to the instep, sidewalls, inner wall of the toe, and heel.

[0071] To eliminate stress concentration during injection molding and to prevent sharp edges from scratching the inner wall of the shoe, rounded corners 14 are formed at the connection between the bottom support part 13 and the side support part 11, and at the connection between the top limiting part 12 and the side support part 11.

[0072] The connecting part 3 is an elastic connecting part, which acts as the tentacles of the octopus. One end of the connecting part 3 is connected to the outer peripheral sidewall of the supporting shell 2, and the other end of the connecting part 3 is connected to the inner wall of the lateral support part 11. Preferably, a reinforcing rib 5 can be provided between the connecting part 3 and the lateral support part 11 to enhance the connection strength between the connecting part 3 and the skeleton 1. The other end of the connecting part 3 can also be directly connected to the inner wall of the bottom support part 13. Since the connecting part 3 is made of an elastic material, the supporting shell 2 can be suspended and elastically supported in the receiving space. When the shoe support is compressed, the elastic connecting part 3 can flexibly distribute the force and rebound, which not only ensures that the supporting shell 2 fits tightly to the back of the shoe, but also avoids the shoe surface indentation caused by the rigid top, which significantly improves the adaptability to different shoe types. The end of the connecting part 3 is provided with an abutting end 31, which has an arc surface facing the skeleton 1. The abutting end 31 increases the contact area with the inner wall of the shoe, and the arc surface can effectively avoid damage to the shoe lining caused by stress concentration at the tip.

[0073] The outer wall of the support shell 2 is directly connected to the inner wall of the top limiting part 12. This direct connection between the support shell 2 and the frame 1 eliminates the need for an intermediate elastic transition, enhancing the overall rigidity and compressive strength of the shoe support structure, making it particularly suitable for shoes requiring rigid support. Simultaneously, the outer wall of the support shell 2 is connected to the inner wall of the lateral support part 11 via reinforcing ribs 5 to strengthen the connection between the support shell 2 and the frame 1. The support shell 2 corresponds to the octopus's body; when the shoe support is inserted into the shoe cavity, the support shell 2 primarily serves to support the instep from the inside, preventing the instep from collapsing.

[0074] Furthermore, to enhance visual appeal and breathability, the support shell 2 is equipped with decorative styling sections. In this embodiment, the decorative styling sections include two symmetrical first through holes 21 and one second through hole 22. The first through holes 21 simulate octopus eyes, and the second through hole 22 simulates octopus mouth. The first through holes 21 and the second through hole 22 not only create a vivid and adorable octopus facial expression, giving the shoe support a strong sense of fun and decoration, but also connect with the gaps 4 around the skeleton 1, forming an air convection channel inside the shoe support. This effectively promotes air circulation inside the shoe and keeps the inside dry.

[0075] Example 2: Preparation and compounding of bamboo extract.

[0076] This embodiment provides a method for preparing bamboo extract, which can be used as an antibacterial agent in shoe tree materials.

[0077] 1. Selection of bamboo raw materials

[0078] The bamboo selected is from species with high flavonoid and polyphenol content, such as *Dendrocalamus giganteus* or *Dendrocalamus latiflorus*. *Dendrocalamus giganteus* has extremely high flavonoid and polyphenol content, while *Dendrocalamus latiflorus* exhibits stronger antibacterial activity than other bamboo species, especially when harvested in July and November, with a flavonoid content of approximately 1.18%–2.02% and a total phenol content of approximately 2.21%–2.86%. Both bamboo varieties are perennial plants of the Bambusoideae subfamily of the Poaceae family, with culms 20–30 meters tall, culm diameters of 15–30 centimeters, and internode lengths of 30–50 centimeters, rich in flavonoid and polyphenolic active ingredients.

[0079] 2. Preparation of bamboo extract

[0080] Step (a) Raw material pretreatment: Select healthy bamboo materials that are 2 to 3 years old, remove branches, leaves and bamboo nodes, cut bamboo into 15 to 20 cm sections, rinse them with clean water and remove surface impurities.

[0081] Step (b) Microwave-assisted extraction: The pretreated bamboo segments are placed in a reaction vessel and microwaved for 3–10 minutes to disrupt the plant cell walls. Then, solvent is added for extraction to obtain a crude extract. Microwave treatment effectively disrupts the cellulose-lignin cell wall structure of bamboo, allowing for the full release of intracellular active ingredients (flavonoids, polyphenols), thereby improving the efficiency of subsequent solvent extraction. Preferably, the power density of the microwave treatment is 15–20 W / g (e.g., 17 W / g). A 50%–60% food-grade ethanol aqueous solution is preferred as the solvent, balancing safety and extraction rate; pure water can also be used. The material-to-liquid ratio is 1:20–1:30 (g:mL), the extraction temperature is controlled at 60–80℃ (excessive temperature will destroy the active ingredients), and the reflux extraction time is 1–12 hours, preferably 2–3 hours.

[0082] Step (c) Macroporous resin purification: The obtained crude extract is purified by adsorption through a macroporous resin column, followed by elution with 70% ethanol. The eluent is collected and concentrated to obtain purified bamboo extract. The total polyphenol purity in the crude extract is usually only about 20%, which can be increased to more than 50% after macroporous resin purification, doubling the bactericidal effect. Preferably, HPD-100 macroporous adsorption resin (produced by Cangzhou Baoen) is used, the loading flow rate is 1-2 column volumes / hour (e.g., 2.0 BV / h), the total polyphenol concentration is 1.0-2.0 mg / mL, and the loading pH is 4.0-5.0 (weakly acidic).

[0083] 3. Determining the endpoint of elution

[0084] During the elution process with macroporous resin, the elution endpoint is determined using the effluent detection method. Specifically, the total polyphenol concentration in the elution effluent is detected in stages using the Folin-Ciocalteu method or ultraviolet spectrophotometry: Within the first 0.5 column volumes, the total polyphenol concentration increases, indicating the beginning of elution; within 0.5–2.0 column volumes, the total polyphenol concentration reaches its peak, marking the main elution stage; within 2.0–3.5 column volumes, the total polyphenol concentration decreases, indicating the elution is nearing completion; and within 3.5–5.0 column volumes, the total polyphenol concentration drops to below 1% of the peak value, indicating elution is complete. The quantitative standard is: elution is terminated when the total polyphenol concentration in the effluent drops to below 1% of the total polyphenol concentration in the sample solution (or below 0.01 mg / mL). This method ensures sufficient recovery of the target polyphenols while avoiding over-elution that wastes solvent and time.

[0085] 4. Compound formulation of bamboo extract

[0086] Purified bamboo extract can also undergo compounding to further enhance its antibacterial effects and stability. Compounding includes two methods: compounding with bamboo vinegar or compounding with metal ions.

[0087] There are two synergistic approaches to combining polyphenols with bamboo vinegar: First, polyphenols are the main component and bamboo vinegar is the auxiliary component. The organic acids in bamboo vinegar can stabilize polyphenols and reduce oxidative degradation. The mass ratio of polyphenols to bamboo vinegar is 1:0.5 to 1:2, which is suitable for synergistic antioxidant effects. Second, bamboo vinegar is the main component and polyphenols are the enhancement component. The two have a synergistic effect on antibacterial activity. The mass ratio of bamboo vinegar to polyphenols is 1:0.1 to 1:0.5, which is suitable for antibacterial / preservative purposes.

[0088] In the combination with metal ions, the metal ion is Fe. 3+ Fe 2+ Cu 2+ and Zn 2+ One of them. Fe 3+ According to polyphenols: Fe 3+ A molar ratio of 1:1 to 3:1 can be used to form a metal-polyphenol network (MPN); Fe 2+ According to polyphenols: Fe 2+ A molar ratio of 2:1 to 5:1, when combined, exhibits a synergistic antioxidant effect; Cu 2+ According to polyphenols: Cu 2+ A molar ratio of 1:1 to 2:1, when combined, exhibits a synergistic antibacterial effect; Zn 2+ According to polyphenols: Zn 2+ Combinations with molar ratios of 1:1 to 4:1 can enhance the stability and sustained-release properties of the antibacterial effect. All of the above-mentioned combination schemes can achieve synergistic effects and reduce dosage.

[0089] Example 3: Performance Testing.

[0090] 1. Anti-mildew performance test

[0091] The shoe tree samples prepared in Example 1, the starch / PP control group without antifungal and antibacterial additives, and the pure PP + additive control group were tested according to GB / T 44940-2024 "Qualitative Evaluation Test Method for Antifungal Performance of Footwear and Footwear Components". The test strains were *Aspergillus niger* and *Penicillium funiculosum*, which were cultured at 28±2℃ and 85%±5% humidity for 28 days and graded according to a standard of 0-4 (grade 0 indicating no growth and grade 4 indicating severe growth). The test results are shown in Table 1.

[0092] Table 1

[0093] This application (starch, PP, functional additives) Level 1 Control group 1 (starch, PP, no additives) Level 4 Control group 2 (ordinary PP + adjuvants, no starch) Level 1

[0094] The results show that this application achieves Level 1 mildew prevention on starch and PP substrates that are prone to mildew, which is comparable to the mildew prevention level of pure PP-based antibacterial materials (control group 2) and significantly better than the control group (Level 4) without additives, proving that the present invention has successfully overcome the technical defect of starch being hydrophilic and prone to mildew.

[0095] 2. Degradation performance test

[0096] The shoe tree samples prepared in Example 1 were placed under composting conditions (refer to ISO 14855) and their degradation behavior was observed, as shown in Table 2:

[0097] Table 2

[0098] Ⅰ Water absorption and swelling period 0-7 days ＜5% The material absorbs water, causing the starch component to swell and resulting in fine cracks on the sample surface. II. Rapid Disintegration Phase 1 to 4 weeks 10%～60% Microorganisms preferentially decompose starch components, causing the PP skeleton to crumble due to the loss of starch support, resulting in the loss of the overall structure of the shoe tree. III. Residue Stabilization Period 1 to 12 months 60%～80% The biodegradable starch phase has been largely depleted, and the residue is mainly PP fragments, indicating that the degradation process has essentially stopped.

[0099] In the control test, the appearance of the pure PP shoe trees remained basically unchanged after 12 months under the same conditions, with a quality loss rate of less than 1%, and they maintained their complete shape.

[0100] The results show that the starch component in the shoe tree of the present invention can be degraded by microorganisms in the natural environment, causing the PP matrix to lose its continuity and thus the shoe tree to disintegrate into amorphous fragments, effectively reducing the long-term physical impact of discarded shoe trees on the environment.

[0101] 3. Mechanical property testing

[0102] The mechanical properties of the shoe tree samples prepared in Example 1 were tested, and the results are shown in Table 3:

[0103] Table 3

[0104] Tensile yield strength 25~40MPa Compressive yield strength 30~50MPa Flexural modulus 1000~1800MPa Shore hardness 65~75 (D standard) Top static compressive strength 25-35kg (deformation <5mm) Lateral compression 8-15kg Repeated trampling simulation (10kg x 1000 times) Deformation < 2mm, no cracking

[0105] The results show that the shoe support of the present invention has good mechanical properties and fully meets the actual requirements of the shoe support for rigid support force and repeated use.

[0106] 4. Long-term effectiveness test

[0107] After 50 simulated insertion and removal cycles, the anti-mold performance of the shoe support sample prepared in Example 1 was tested according to GB / T 44940-2024. The anti-mold level remained at level 1, indicating that the shoe support of the present invention has a long-lasting anti-mold and antibacterial effect.

[0108] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A mildew-proof, antibacterial, and biodegradable shoe tree, characterized in that, Including the following raw materials by weight percentage: Starch: 15%–50%; Polypropylene: 40%–60%; Functional additives: 10%–25%; The functional additives include at least antifungal agents, antibacterial agents, toughening agents, and coupling agents.

2. The anti-mildew, antibacterial, and biodegradable shoe tree according to claim 1, characterized in that: The moisture content of the starch is ≤1%.

3. The anti-mildew, antibacterial, and biodegradable shoe tree according to claim 1, characterized in that: The functional additives also include one or more of antioxidants, lubricants, and dispersants.

4. The anti-mildew, antibacterial, and biodegradable shoe tree according to claim 1, characterized in that: The shoe support has at least one of the following mechanical properties: tensile yield strength 25-40 MPa; compressive yield strength 30-50 MPa; flexural modulus 1000-1800 MPa; Shore hardness 65-75; top static compressive strength 25-35 kg; lateral compressive strength 8-15 kg; and no cracking after repeated stepping.

5. A method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Put the starch into a mixer, heat it to 110-120℃, and stir to mix it, then dehydrate and dry it until the moisture content is ≤1%; Step 2: Add polypropylene and functional additives to the dried starch, continue mixing and heat to 130-140℃ to soften the polypropylene and coat the starch to form a uniform mixture. Step 3: Add the mixture to a twin-screw extruder, heat and melt it, shear and mix it, and then extrude the molten material into strips. The temperature range of the twin-screw extruder is 160-220℃. Step 4: The extruded molten strip is air-cooled and solidified, and then cut into pellets to obtain cylindrical particles with a diameter of 2-4 mm; Step 5: The granules are injection molded into shoe trees using an injection molding machine.

6. The method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree according to claim 5, characterized in that: In step 5, the barrel temperature of the injection molding machine is 200-230°C, and the mold temperature of the injection molding machine is 50-80°C. The injection molding machine has an injection pressure of 60-90 MPa, a holding pressure of 30-45 MPa, and a holding time of 0.2-0.3 seconds.

7. The method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree according to claim 5, characterized in that: In step 5, after injection molding, the shoe tree product is annealed at a temperature of 40-50°C for 2-4 hours.

8. The method for preparing the anti-mildew, antibacterial, and biodegradable shoe tree according to any one of claims 5 to 7, characterized in that: The antibacterial agent in the functional additive comprises bamboo extract, which is prepared by the following method: (a) Cut the bamboo into sections, each 15-20 cm long, and rinse them with water. (b) Place the prepared bamboo segments into the reaction vessel, microwave them for 3 to 10 minutes to destroy the cell walls, and then extract them with solvent to obtain the crude extract. (c) The crude extract was loaded onto a macroporous resin column and eluted with 70% ethanol. The eluent was collected and concentrated to obtain the purified bamboo extract.

9. The method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree according to claim 8, characterized in that: In step (b), the power density of the microwave treatment is 15–20 W / g.

10. The method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree according to claim 8, characterized in that: In step (b), a 50%–60% food-grade ethanol solution is used for reflux extraction at a material-to-liquid ratio of 1:20–1:30 and a temperature of 60–80°C for 2–3 hours.

11. The method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree according to claim 8, characterized in that: In step (c), HPD-100 macroporous resin was used, and the sample was loaded at a flow rate of 1 to 2 column volumes per hour. The total polyphenol concentration was 1.0 to 2.0 mg / mL, and the pH was 4.0 to 5.

0.

12. The method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree according to claim 11, characterized in that: The elution endpoint was determined by the effluent detection method. Elution was terminated when the total polyphenol concentration in the effluent dropped to below 1% of the total polyphenol concentration of the sample.

13. The method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree according to claim 12, characterized in that: The total polyphenol concentration in the eluent reaches its peak within 0.5 column volumes. When elution reaches 3.5 to 5.0 column volumes, the total polyphenol concentration drops to less than 1% of the peak value, which is the elution endpoint.

14. The method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree according to claim 8, characterized in that: The purified bamboo extract underwent a compounding process.

15. The method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree according to claim 14, characterized in that: The compounding process involves mixing purified bamboo extract with bamboo vinegar at a mass ratio of 1:0.5 to 1:2, or mixing bamboo vinegar with purified bamboo extract at a mass ratio of 1:0.1 to 1:0.

5.

16. The method for preparing an anti-mildew, antibacterial, and biodegradable shoe tree according to claim 14, characterized in that: The compounding process involves combining purified bamboo extract with metal ions, wherein the metal ions are Fe. 3+ Fe 2+ Cu 2+ and Zn 2+ One of them.

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