Plant-based polyurethane orthopedic shoe material and method of making same

Abstract

The application relates to the technical field of medical devices and rehabilitation engineering, and particularly discloses a plant-based polyurethane orthopedic shoe material and a preparation method thereof. The plant-based polyurethane orthopedic shoe material is prepared from the following raw materials: a plant-based polyol mixture, a polyisocyanate, a chain extender, a catalyst, a foaming agent and a foam stabilizer; and the preparation method comprises the following steps: S1, mixing part of the raw materials to obtain a polyol mixture component; S2, mixing the polyisocyanate and the polyol mixture component, and then pouring the mixture into a mold after rapid stirring; S3, performing gradient foaming on the mold by controlling the pressure and the temperature of the mold in sections; S4, after the foaming is completed, performing pressure relief, cooling and demolding to obtain the plant-based polyurethane orthopedic shoe material; and S5, coating a self-repairing coating on the surface of the shoe material, and forming an inner lining layer in the shoe material. The orthopedic shoe material can be used for preparing foot orthopedic shoe pads, arch support pieces, diabetic foot protectors and other rehabilitation aids, and has the advantages of buffering and shock-absorbing performance, high tear resistance and long-term durability.

Description

Technical Field

[0001] This application relates to the field of medical device and rehabilitation engineering technology, and more specifically, it relates to a plant-based polyurethane orthotic shoe material and its preparation method. Background Technology

[0002] Orthotic shoes are primarily used in the medical rehabilitation field to treat and improve lower limb biomechanical imbalances and functional impairments caused by foot structural abnormalities, neurological diseases, or metabolic diseases. Their advantages lie in their ability to correct abnormal gait, relieve pressure points on the soles of the feet, and prevent the progression of foot deformities and ulcer formation through personalized or adapted sole hardness, arch support, calcaneal stability control, and decompression lining design. This significantly reduces walking pain, improves joint alignment efficiency, reduces the risk of falls, and assists patients in achieving safe, comfortable, and efficient reconstruction of mobility after surgery or in chronic disease management.

[0003] Orthotic shoes improve lower limb biomechanics through structural design optimization and arch support. However, their matrix materials often have a simple molecular structure due to traditional polymers, making it difficult to achieve a balance between hardness, elasticity, and strength. This results in insufficient resilience, poor tear resistance, and limited durability, making the corrective effect easily diminish over time. It can even lead to material deformation or damage, hindering patients from obtaining lasting and stable rehabilitation support. Summary of the Invention

[0004] To address the issues of insufficient resilience, poor tear resistance, and limited durability caused by the single material used in orthopedic shoe bases, this application provides a plant-based polyurethane orthopedic shoe material and its preparation method.

[0005] In a first aspect, this application provides a plant-based polyurethane orthotic shoe material, which adopts the following technical solution: A plant-based polyurethane orthotic shoe material is made from raw materials comprising the following parts by weight: 50-80 parts of plant-based polyol mixture; 40-70 parts of polyisocyanate; 5-15 parts of chain extender; 0.1-1 parts of catalyst; 2-8 parts of foaming agent; and 1-3 parts of foam stabilizer; wherein the plant-based polyol mixture is compounded from castor oil, soybean oil, and cashew nut phenol in a weight ratio of 3-5:2-4:1-3.

[0006] By adopting the above technical solution, a plant-based polyol mixture of castor oil, soybean oil, and cashew phenol in a specific ratio is used. Castor oil provides rigid chain segments, soybean oil introduces flexibility, and the phenolic hydroxyl groups of cashew phenol enhance reactivity. The three components synergistically regulate the crosslinking density and mechanical properties of the polyurethane network, giving the shoe material a balanced hardness and elasticity. This ratio optimizes the functionality and viscosity of the polyols, ensuring sufficient reaction with polyisocyanates to form a uniform cell structure. Therefore, an orthopedic shoe material with stable mechanical properties and high comfort is obtained.

[0007] Preferably, the raw material further includes nano-reinforcing filler, which is a mixture of nanocellulose whiskers and graphene in a weight ratio of 2-5:1.

[0008] By adopting the above technical solution, the nano-reinforcing filler, which is a mixture of nanocellulose whiskers and graphene in a certain proportion, improves the rigidity and dimensional stability of the matrix, while graphene imparts conductivity and reinforcement effect. The two work together to form a three-dimensional network in the polyurethane matrix, dispersing stress and restricting molecular chain movement. This proportion balances reinforcement and processability, prevents filler agglomeration, and ensures uniform dispersion. The interfacial bonding between the filler and the polyol is enhanced, improving the wear resistance and fatigue resistance of the shoe material. Therefore, a high-strength and high-durability orthopedic shoe material is obtained.

[0009] Preferably, the surface of the orthopedic shoe material is further formed with a self-healing coating, the raw materials of which include plant-based prepolymers modified with furan groups and plant-based prepolymers modified with maleimide groups.

[0010] By adopting the above technical solution, the plant-based prepolymer modified with furan and maleimide groups forms reversible covalent bonds in the coating through the Diels-Alder reaction. When the coating is damaged, heat or pressure triggers the reversible breaking and recombination of the bonds, achieving self-repair. This reaction mechanism is based on cycloaddition reaction, and the repair process does not require an external catalyst. The coating and the shoe material surface are chemically bonded, enhancing adhesion. Therefore, orthopedic shoe materials with self-repair function and extended service life are obtained.

[0011] Preferably, the orthopedic shoe material further includes an inner lining layer containing an antibacterial functional component. The antibacterial functional component is a graft of chitosan-silver ion complex and tea polyphenols, and the weight ratio of chitosan-silver ion complex to tea polyphenols is 1-3:1-2.

[0012] By adopting the above technical solution, the chitosan-silver ion complex and the grafted product of tea polyphenols are used as antibacterial functional components. Chitosan provides biocompatibility and film-forming properties, silver ions release antibacterial activity, and tea polyphenols enhance antioxidant and synergistic antibacterial effects. This ratio optimizes the release rate and persistence of the antibacterial agent, preventing bacterial growth. The components form a stable structure through grafting reaction, are uniformly dispersed in the lining layer, and bond with the polyurethane matrix. Therefore, an antibacterial, odor-resistant, and comfortable lining layer is obtained, improving the hygiene performance of the shoe material.

[0013] Secondly, this application provides a method for preparing plant-based polyurethane orthotic shoe material, using the following technical solution: A method for preparing a plant-based polyurethane orthotic shoe material includes the following steps: S1. Mix the plant-based polyol mixture, chain extender, catalyst, nano-reinforcing filler, foaming agent and foam stabilizer to obtain the polyol mixture component; S2. Mix the polyisocyanate with the polyol mixture obtained in step S1, stir quickly, and then pour into a mold. S3. Place the mold in a supercritical CO2 environment and perform gradient foaming by controlling the pressure and temperature in stages, so that the shoe material forms a density gradient structure with the density gradually increasing from the surface to the bottom layer. S4. After foaming, depressurize, cool, and demold to obtain the plant-based polyurethane orthopedic shoe material; S5. A self-healing coating is applied to the surface of the shoe material, and an inner lining layer is formed inside the shoe material. The chitosan-silver ion complex and the grafted tea polyphenol are dissolved in a solvent and applied to the inner lining of the shoe material by spraying or dipping. After drying, the inner lining layer is formed.

[0014] By adopting the above technical solution, due to the integrated process including mixing, foaming, and coating preparation, step S1 ensures uniform mixing of raw materials, providing a homogeneous system for foaming; the rapid stirring in step S2 promotes the initial reaction between polyisocyanate and polyol, controlling viscosity; the supercritical CO2 gradient foaming in step S3 forms a density gradient structure, with a dense surface layer enhancing wear resistance and a porous bottom layer providing cushioning; the depressurization rate in step S4 controls the cell structure, and cooling stabilizes the dimensions; the coating and lining layers in step S5 add functional properties; each step is interconnected, with each step laying the foundation for the next; therefore, a structurally controllable and functionally integrated orthopedic shoe material is obtained.

[0015] Preferably, in step S1, when the raw material contains nano-reinforced fillers, the nano-cellulose whiskers are first ultrasonically dispersed and blended with graphene, and then added to the plant-based polyol mixture.

[0016] By adopting the above technical solution, the ultrasonic dispersion and blending treatment of nano-reinforced fillers breaks down filler agglomeration through ultrasonic energy, promoting uniform mixing of nano-cellulose whiskers and graphene. The dispersed filler is stably suspended in polyol to prevent sedimentation. This process enhances the interfacial interaction between the filler and the matrix, improving the uniformity of the composite material. It provides uniform nucleation points for subsequent foaming and controls the cell size. Therefore, orthopedic shoe materials with good filler dispersion and consistent performance are obtained.

[0017] Preferably, in step S2, the stirring speed of the rapid stirring is 2000-4000 rpm, and the stirring time is 10-30 seconds.

[0018] By adopting the above technical solution, the high-speed stirring introduces shear force due to the use of a specific range of stirring speed and stirring time, which enables the polyisocyanate and polyol mixture to be mixed quickly and uniformly, thus initiating the reaction. This parameter ensures that the reaction system completes the molding before gelation, avoiding premature local curing. The stirring time controls the reaction process and prevents excessive stirring from causing bubble rupture. The parameters are based on fluid dynamics and reaction kinetics to optimize the mixing efficiency. Therefore, a uniformly mixed orthopedic shoe material with fine pores is obtained.

[0019] Preferably, in step S3, the specific process of gradient foaming is as follows: first, the surface layer is formed by maintaining the pressure at 15-25 MPa and the temperature at 35-45°C for 5-15 minutes; then, the core layer is formed by maintaining the pressure at 8-12 MPa and the temperature at 50-60°C for 10-20 minutes.

[0020] By adopting the above technical solution, the gradient foaming process with segmented control of pressure and temperature promotes the dissolution and nucleation of CO2 on the surface layer under high pressure and low temperature conditions, forming a dense surface layer; the medium pressure and high temperature conditions ensure sufficient foaming of the core layer, forming a loose structure; the pressure and temperature parameters are set according to the solubility and diffusion rate of CO2 to control the foaming kinetics; this process achieves a density gradient, enhances the wear resistance of the surface layer, and provides cushioning for the core layer; the connection between the front and back stages ensures a smooth structural transition; therefore, orthopedic shoe materials with a gradient structure and optimized mechanical properties are obtained.

[0021] Preferably, in step S4, the depressurization rate is 1-3 MPa / s, and the cooling is natural cooling to room temperature or forced cooling to below 30°C.

[0022] By adopting the above technical solution, the pressure relief rate is controlled and the stability of the cell growth is adjusted by using a specific pressure relief rate and cooling method, preventing cell collapse or merging; the cooling process solidifies the polyurethane structure and locks in the cell morphology; natural cooling avoids internal stress, while forced cooling improves production efficiency; the parameters are based on the thermodynamic properties of the material to ensure dimensional stability; this step consolidates the foamed structure and provides a foundation for subsequent processing; therefore, orthopedic shoe materials with uniform cell structure and stable dimensions are obtained.

[0023] Preferably, in step S5, the coating thickness of the self-healing coating is 50-200 μm, the solvent is one or more of ethanol, acetone or N,N-dimethylformamide; the spraying pressure is 0.2-0.5 MPa, the spraying distance is 15-25 cm; the immersion time is 5-15 minutes, and the lifting speed is 1-5 cm / s.

[0024] By adopting the above technical solution, the coating thickness balances protection and flexibility due to the use of specific coating parameters; the solvent selection is based on the solubility and evaporation rate of the prepolymer; the spraying pressure and distance control the coating uniformity to avoid sagging or orange peel; the immersion time and lifting speed ensure the full penetration and adhesion of the inner lining components; the parameters are based on fluid coating theory to optimize processing efficiency and quality; this step achieves uniform application of the functional coating and a firm bond with the substrate; therefore, a uniformly coated and functionally reliable orthopedic shoe material is obtained.

[0025] In summary, this application has the following beneficial effects: 1. This application uses a plant-based polyol mixture composed of castor oil, soybean oil, and cashew phenol in a specific ratio. Due to the complementary molecular structures of the long-chain structure of castor oil, the double bonds of soybean oil, and the benzene rings of cashew phenol, castor oil contributes flexible chain segments, soybean oil provides crosslinking sites to increase network density, and the rigid benzene ring structure of cashew phenol enhances overall strength. This, in turn, adjusts the crosslinking density and microphase separation structure of the final polyurethane network, enabling the material to achieve a balance of hardness, elasticity, and strength at the molecular level. Therefore, an orthopedic shoe material matrix with high resilience, high tear strength, and long-term durability is obtained.

[0026] 2. In this application, nano-reinforcing fillers composed of nano-cellulose whiskers and graphene are preferred. Due to the high crystallinity and high aspect ratio of nano-cellulose whiskers, they can form an interpenetrating three-dimensional network reinforcement skeleton through physical interaction with the two-dimensional sheet structure of graphene. This hybrid filler network is uniformly dispersed in the polyurethane matrix, which can not only improve the modulus and resistance to compression set of the material through mechanical interlocking and stress transfer, but also improve the heat dissipation efficiency of the matrix through the high thermal conductivity of graphene. Nano-cellulose and graphene produce synergy in reinforcement, dimensional stability and thermal management functions, thus obtaining a shoe material with high strength, low deformation and good heat dissipation.

[0027] 3. In this application, a self-healing coating is preferably constructed on the surface of the shoe material. Since reversible covalent bonds can be formed between furan and maleimide groups, a dynamic cross-linked network is constructed in the coating. When the coating is scratched, applying appropriate heat triggers the breaking and recombination of the reversible covalent bonds, thereby realizing the reconstruction of the covalent bond network at the damaged site. This mechanism allows the repair process to be carried out without the addition of external repair agents, and the repair behavior can be performed multiple times. Therefore, an orthopedic shoe material surface with highly efficient self-healing ability is obtained, reducing the risk of overall orthopedic function failure caused by the accumulation of surface micro-damage and extending the product's service life.

[0028] 4. The method of this application employs a gradient foaming process assisted by supercritical carbon dioxide and combined with segmented pressure-temperature control. In the high-pressure, low-temperature stage, carbon dioxide promotes the formation of bubble nuclei on the polymer surface but restricts their growth, resulting in a dense and delicate surface cell structure. In the subsequent medium-pressure, high-temperature stage, the carbon dioxide dissolved in the core layer gains foaming power and space, growing into larger pores, thus achieving a continuous gradient in pore size and density from the surface to the bottom layer. Therefore, a lightweight shoe material with a density gradient structure is obtained, whose dense surface layer provides abrasion resistance and support, and porous core layer provides cushioning. The structure is structurally matched with the biomechanics of the foot, thereby improving impact resistance and wearing comfort.

[0029] 5. In this application, a chitosan-silver ion complex and a graft of tea polyphenols are preferably introduced into the inner lining of the shoe material as an antibacterial functional component. The amino groups of chitosan, silver ions, and phenolic hydroxyl groups of tea polyphenols form a complex system through coordination and grafting reactions. This system is responsive to changes in the pH value of the foot microenvironment. Under acidic sweat conditions, hydrogen ions compete for coordination, which accelerates the release of silver ions to exert a rapid antibacterial effect. Under near-neutral conditions, the antioxidant and slow-release antibacterial effects of tea polyphenols are dominant, achieving controlled release of the antibacterial agent. Therefore, an inner lining with long-lasting, efficient, and pH-responsive antibacterial function is obtained, solving the problems of microbial growth and odor. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating a method for preparing a plant-based polyurethane orthotic shoe material proposed in this application. Detailed Implementation

[0031] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] Technical concept: Orthotic shoes improve lower limb biomechanics through structural design optimization and arch support. However, their matrix materials often have a simple molecular structure due to traditional polymers, making it difficult to achieve a balance between hardness, elasticity, and strength. This results in insufficient resilience, poor tear resistance, and limited durability, making the corrective effect easily diminish over time. It can even lead to material deformation or damage, hindering patients from obtaining lasting and stable rehabilitation support.

[0033] This application discloses a plant-based polyurethane orthopedic shoe material and its preparation method; it is made from the following raw materials: a plant-based polyol mixture, a polyisocyanate, a chain extender, a catalyst, a foaming agent, and a foam stabilizer; the preparation method is as follows: S1, mixing some of the raw materials to obtain a polyol mixture component; S2, mixing the polyisocyanate with the polyol mixture component, stirring rapidly, and then injecting it into a mold; S3, using the mold to perform gradient foaming by controlling the pressure and temperature in stages; S4, after foaming, depressurizing, cooling, and demolding to obtain the plant-based polyurethane orthopedic shoe material; S5, coating a self-healing coating on the surface of the shoe material, while forming an inner lining layer inside the shoe material.

[0034] This application utilizes a plant-based polyol mixture formulated from castor oil, soybean oil, and cashew phenol in a specific ratio. The long-chain structure of castor oil, the double bonds of soybean oil, and the benzene rings of cashew phenol complement each other in their molecular structures. Castor oil contributes flexible segments, soybean oil provides crosslinking sites to increase network density, and the rigid benzene ring structure of cashew phenol enhances overall strength. This, in turn, regulates the crosslinking density and microphase separation structure of the final polyurethane network, achieving a balance of hardness, elasticity, and strength at the molecular level. Therefore, an orthopedic shoe material matrix with high resilience, high tear strength, and long-lasting durability is obtained.

[0035] Example 1: This example provides a plant-based polyurethane orthopedic shoe material, which is made from the following raw materials in parts by weight: 50 parts of plant-based polyol mixture; 40 parts of polyisocyanate; 5 parts of chain extender; 0.1 parts of catalyst; 2 parts of foaming agent; and 1 part of foam stabilizer; wherein the plant-based polyol mixture is composed of castor oil, soybean oil and cashew nut phenol in a weight ratio of 3:2:1.

[0036] The raw materials also include nano-reinforcing fillers, which are a mixture of nano-cellulose whiskers and graphene in a weight ratio of 2:1.

[0037] The orthopedic shoe material also has a self-healing coating on its surface. The raw materials for the self-healing coating include plant-based prepolymers modified with furan groups and plant-based prepolymers modified with maleimide groups.

[0038] The orthopedic shoe material also has an inner lining layer, which contains antibacterial functional components. The antibacterial functional components are a graft of chitosan-silver ion complex and tea polyphenols, with a weight ratio of chitosan-silver ion complex to tea polyphenols of 1:1.

[0039] The preparation method of the above-mentioned plant-based polyurethane orthotic shoe material includes the following steps: S1. Mix the plant-based polyol mixture, chain extender, catalyst, nano-reinforcing filler, foaming agent and foam stabilizer to obtain the polyol mixture component; The process involves first ultrasonically dispersing and blending nanocellulose whiskers with graphene, and then adding them to a mixture of plant-based polyols.

[0040] S2. Mix the polyisocyanate with the polyol mixture obtained in step S1, stir quickly, and then pour into a mold. The rapid mixing speed is 2000 rpm, and the mixing time is 10 seconds.

[0041] S3. Place the mold in a supercritical CO2 environment and perform gradient foaming by controlling the pressure and temperature in stages, so that the shoe material forms a density gradient structure with the density gradually increasing from the surface to the bottom layer. The specific process of gradient foaming is as follows: first, the surface layer is formed by maintaining a pressure of 15MPa and a temperature of 35℃ for 5 minutes; then, the core layer is formed by maintaining a pressure of 8MPa and a temperature of 50℃ for 10 minutes.

[0042] S4. After foaming, depressurize, cool, and demold to obtain plant-based polyurethane orthopedic shoe material; The depressurization rate is 1 MPa / s, and the cooling is natural cooling to room temperature.

[0043] S5. A self-healing coating is applied to the surface of the shoe material, while an inner lining is formed inside the shoe material. The chitosan-silver ion complex and the grafted tea polyphenols are dissolved in a solvent and applied to the shoe material lining by spraying or dipping. After drying, the inner lining is formed.

[0044] The self-healing coating has a thickness of 50 μm and uses ethanol as the solvent; the spraying pressure is 0.2 MPa and the spraying distance is 15 cm.

[0045] Example 2: This example provides a plant-based polyurethane orthopedic shoe material, which is made from the following raw materials in parts by weight: 65 parts of plant-based polyol mixture; 55 parts of polyisocyanate; 10 parts of chain extender; 0.5 parts of catalyst; 5 parts of foaming agent; and 2 parts of foam stabilizer; wherein the plant-based polyol mixture is composed of castor oil, soybean oil and cashew nut phenol in a weight ratio of 4:3:2.

[0046] The raw materials also include nano-reinforcing fillers, which are a mixture of nano-cellulose whiskers and graphene in a weight ratio of 3.5:1.

[0047] The orthopedic shoe material also has a self-healing coating on its surface. The raw materials for the self-healing coating include plant-based prepolymers modified with furan groups and plant-based prepolymers modified with maleimide groups.

[0048] The orthopedic shoe material also has an inner lining layer, which contains antibacterial functional components. The antibacterial functional components are a graft of chitosan-silver ion complex and tea polyphenols, with a weight ratio of chitosan-silver ion complex to tea polyphenols of 2:1.5.

[0049] The preparation method of the above-mentioned plant-based polyurethane orthotic shoe material includes the following steps: S1. Mix the plant-based polyol mixture, chain extender, catalyst, nano-reinforcing filler, foaming agent and foam stabilizer to obtain the polyol mixture component; The process involves first ultrasonically dispersing and blending nanocellulose whiskers with graphene, and then adding them to a mixture of plant-based polyols.

[0050] S2. Mix the polyisocyanate with the polyol mixture obtained in step S1, stir quickly, and then pour into a mold. The rapid mixing speed is 3000 rpm, and the mixing time is 20 seconds.

[0051] S3. Place the mold in a supercritical CO2 environment and perform gradient foaming by controlling the pressure and temperature in stages, so that the shoe material forms a density gradient structure with the density gradually increasing from the surface to the bottom layer. The specific process of gradient foaming is as follows: first, the surface layer is formed by maintaining the pressure at 20MPa and the temperature at 40℃ for 10 minutes; then, the core layer is formed by maintaining the pressure at 10MPa and the temperature at 55℃ for 15 minutes.

[0052] S4. After foaming, depressurize, cool, and demold to obtain plant-based polyurethane orthopedic shoe material; The depressurization rate is 2 MPa / s, and the cooling is forced cooling to below 30°C.

[0053] S5. A self-healing coating is applied to the surface of the shoe material, while an inner lining is formed inside the shoe material. The chitosan-silver ion complex and the grafted tea polyphenols are dissolved in a solvent and applied to the shoe material lining by spraying or dipping. After drying, the inner lining is formed.

[0054] The self-healing coating has a thickness of 125 μm and uses acetone as the solvent; the immersion time is 10 minutes and the lifting speed is 3 cm / s.

[0055] Example 3: This example provides a plant-based polyurethane orthopedic shoe material, which is made from the following raw materials in parts by weight: 80 parts of plant-based polyol mixture; 70 parts of polyisocyanate; 15 parts of chain extender; 1 part of catalyst; 8 parts of foaming agent; and 3 parts of foam stabilizer; wherein the plant-based polyol mixture is composed of castor oil, soybean oil and cashew nut phenol in a weight ratio of 5:4:3.

[0056] The raw materials also include nano-reinforcing fillers, which are a mixture of nanocellulose whiskers and graphene in a weight ratio of 5:1.

[0057] The orthopedic shoe material also has a self-healing coating on its surface. The raw materials for the self-healing coating include plant-based prepolymers modified with furan groups and plant-based prepolymers modified with maleimide groups.

[0058] The orthopedic shoe material also has an inner lining layer, which contains antibacterial functional components. The antibacterial functional components are a graft of chitosan-silver ion complex and tea polyphenols, with a weight ratio of chitosan-silver ion complex to tea polyphenols of 3:2.

[0059] The preparation method of the above-mentioned plant-based polyurethane orthotic shoe material includes the following steps: S1. Mix the plant-based polyol mixture, chain extender, catalyst, nano-reinforcing filler, foaming agent and foam stabilizer to obtain the polyol mixture component; The process involves first ultrasonically dispersing and blending nanocellulose whiskers with graphene, and then adding them to a mixture of plant-based polyols.

[0060] S2. Mix the polyisocyanate with the polyol mixture obtained in step S1, stir quickly, and then pour into a mold. The rapid mixing speed is 4000 rpm, and the mixing time is 30 seconds.

[0061] S3. Place the mold in a supercritical CO2 environment and perform gradient foaming by controlling the pressure and temperature in stages, so that the shoe material forms a density gradient structure with the density gradually increasing from the surface to the bottom layer. The specific process of gradient foaming is as follows: first, the surface layer is formed by maintaining the pressure at 25MPa and the temperature at 45℃ for 15 minutes; then, the core layer is formed by maintaining the pressure at 12MPa and the temperature at 60℃ for 20 minutes.

[0062] S4. After foaming, depressurize, cool, and demold to obtain plant-based polyurethane orthopedic shoe material; The depressurization rate is 3 MPa / s, and the cooling is forced cooling to below 30°C.

[0063] S5. A self-healing coating is applied to the surface of the shoe material, while an inner lining is formed inside the shoe material. The chitosan-silver ion complex and the grafted tea polyphenols are dissolved in a solvent and applied to the shoe material lining by spraying or dipping. After drying, the inner lining is formed.

[0064] The self-healing coating has a thickness of 200 μm and uses N,N-dimethylformamide as the solvent. The spraying pressure is 0.5 MPa and the spraying distance is 25 cm.

[0065] Comparative Example 1: This comparative example refers to the content of Example 1, except that the plant-based polyol mixture is composed of castor oil, soybean oil and cashew phenol in a weight ratio of 6:1:1. The rest of the contents are the same as those in Example 1.

[0066] Comparative Example 2: This comparative example refers to the content of Example 1, except that the nano-reinforcing filler is a mixture of nanocellulose whiskers and graphene in a weight ratio of 1:5. The rest of the contents are the same as in Example 1.

[0067] Comparative Example 3: This comparative example refers to the content of Example 1, except that the segmented control gradient foaming process is not used in step S3. Instead, foaming is carried out under a single condition (pressure 12MPa, temperature 50℃) for 15 minutes. The rest of the content is the same as that of Example 1.

[0068] Comparative Example 4: This comparative example refers to the content of Example 1, except that in step S5, the coating thickness of the self-healing coating is 10 μm, and the rest is the same as in Example 1.

[0069] Comparative Example 5: This comparative example refers to the content of Example 1, except that the weight ratio of the antibacterial functional component, chitosan-silver ion complex, to tea polyphenols in the inner lining layer is 1:5. The rest of the content is the same as that of Example 1.

[0070] Comparative Example 6: This comparative example refers to the content of Example 1, except that the amount of plant-based polyol mixture in the raw materials is 30 parts and the amount of polyisocyanate is 60 parts, and the rest is the same as Example 1.

[0071] Performance testing Sample Preparation: Following the raw material ratios and preparation methods disclosed in Examples 1 to 3 and Comparative Examples 1 to 6, plant-based polyurethane orthotic shoe material samples were prepared. After completing the foaming, demolding, coating, and lining processes, all samples were conditioned at a standard laboratory environment of 23°C and 50% relative humidity for at least 48 hours. Subsequently, according to the specific requirements of each testing standard, the samples were processed into specimens of specified dimensions using a standard cutter or precision cutting equipment, ensuring that the test surfaces were flat and free of defects for subsequent testing.

[0072] Intrinsic mechanical property testing of materials: A universal testing machine was used for testing. First, the prepared dumbbell-shaped specimen was precisely clamped in the upper and lower clamps of the testing machine, ensuring that the longitudinal axis of the specimen was aligned with the direction of tensile force. The equipment was started, and tension was applied at a constant speed of 500 mm / min until the specimen broke. The stress-strain curve was recorded throughout the process, and the tensile strength and elongation at break were calculated. Next, a crescent-shaped specimen was used to test its tear strength on a tensile testing machine using the same principle, and the maximum tear force was recorded. For the springback test, a spring tester was used, where a steel ball was dropped freely from a fixed height onto the specimen surface, and the percentage of the springback height to the drop height was measured. All tests were repeated at least 5 times, and the average value was taken. The testing standards for the performance parameters were the light industry standard QB / T5132-2017 and the national standard GB / T10654-2008.

[0073] Table 1: Comparison of intrinsic mechanical properties of materials

[0074] Enhancement effect and dimensional stability testing: Compression set test requires the use of a specific fixture to compress the cylindrical sample to 50% of its original thickness and place it in a 70°C oven for 22 hours; the sample is then removed and allowed to recover for 30 minutes under standard laboratory conditions, and its final thickness is measured, and the thickness change rate is calculated to characterize the degree of permanent deformation; Thermal conductivity testing uses either the transient planar heat source method or the steady-state heat flow method; taking the steady-state heat flow method as an example, the sample is made into a flat sheet and sandwiched between a hot plate and a cold plate. When the system reaches thermal equilibrium, the heat flux density flowing through the sample, the sample thickness, and the temperature difference between the two sides are accurately measured, and the thermal conductivity is calculated according to Fourier's law; The testing standards for performance parameters are national standards GB / T6669-2008 and GB / T10297-2015.

[0075] Table 2: Comparison of Enhancement Effect and Dimensional Stability

[0076] Surface self-healing performance testing: The initial Shore hardness of the coating surface was measured using a standard hardness tester on an undamaged area. Subsequently, a scratch approximately 20 mm long and penetrating the coating was made on the surface with a sharp blade. The scratched sample was placed in a programmable temperature-controlled oven and heated at 80°C for 2 hours. After the sample cooled to room temperature, the percentage of repaired area was first observed and calculated using an optical microscope or a three-dimensional morphology analyzer. Then, the Shore hardness was measured again directly above the repaired scratch area. The self-healing efficiency of the coating can be comprehensively evaluated by the hardness recovery rate and morphology repair rate of the repaired area. This test refers to the relevant evaluation methods for the self-healing performance of coating materials, and the hardness test standard refers to GB / T531.1-2008.

[0077] Table 3: Comparison of Surface Self-Healing Efficiency

[0078] Density gradient structure and impact resistance testing: First, the density of the entire shoe material and the surface and core layers obtained using a precision slicing machine were measured using a precision electronic balance, employing the displacement method. Next, the hardness of the surface, middle, and bottom layers of the sample was measured using a Shore hardness tester, and the hardness gradient was plotted. Impact resistance testing was conducted using a drop hammer impact tester, where a 5kg impactor was dropped freely from a height of 500mm onto the central area of ​​a flat-placed sample. The maximum impact force and the force-time curve were recorded using a force sensor, and the energy absorption rate was calculated. A lower peak force and a higher energy absorption rate indicate that the material has superior shock absorption performance. The testing standards for the performance parameters were national standards GB / T6343-2009, GB / T531.1-2008, and GB / T20643.2-2006.

[0079] Table 4: Comparison of Density Gradient Structures and Impact Resistance

[0080] Antibacterial properties and pH response testing: The antibacterial activity test followed the testing method for antibacterial plastics; the sample containing the inner lining was cut into 50mm × 50mm pieces, and placed separately from the control sample without antibacterial components in a bacterial solution with a concentration of 1 × 10⁻⁶. 5 ~1×10 6 The sample was placed in a suspension of Staphylococcus aureus or Escherichia coli at CFU / mL. After 24 hours of contact at 37°C and 90% relative humidity, the viable count was calculated using the plate count method and compared with the control sample to calculate the antibacterial rate. For the pH response release test, the sample was immersed in simulated acidic sweat at pH 5.5 and neutral PBS buffer solution at pH 7.4, respectively. Samples were taken at 1h, 4h, 8h, 24h, and 48h, and the concentration of silver ions released in the solution was measured using inductively coupled plasma mass spectrometry. The cumulative release curve of silver ions under different pH conditions was plotted to verify its accelerated release under acidic conditions. The test standards for performance parameters were in accordance with the relevant provisions of the national standard GB / T21510-2008 regarding the determination of antibacterial rate.

[0081] Table 5: Comparison of antibacterial properties and pH response

[0082] Example Conclusion: As can be seen from Examples 1-3 and Comparative Example 1, and Table 1, the specific weight ratio of castor oil, soybean oil and cashew phenol in the plant-based polyol mixture, through their complementary and synergistic molecular structure, is a guarantee for optimizing the polymer network and achieving a balance between the mechanical properties and elasticity of the material, thereby obtaining a shoe material matrix with good resilience, high strength and durability.

[0083] As can be seen from Examples 1-3 and Comparative Example 2, and from Tables 1 and 2, nanocellulose whiskers and graphene are compounded in an optimized ratio to form a synergistic three-dimensional network reinforcement framework. This improves the mechanical strength of the material, enhances its resistance to compressive deformation and heat dissipation, and endows the material with high strength, low permanent deformation and heat dissipation.

[0084] As can be seen from Examples 1-3 and Comparative Example 3, and Table 4, the segmented pressure-temperature gradient foaming process assisted by supercritical CO2 is an influencing factor in achieving a gradient change in the internal pore structure of the material from the surface to the inside. This structure makes the surface layer of the material dense and wear-resistant, and the core layer porous and shock-absorbing, thereby improving impact resistance and wearing comfort.

[0085] As can be seen from Examples 1-3 and Comparative Example 4, and Table 3, the self-healing coating needs to reach a sufficient thickness to ensure that there is a sufficient dynamic reversible covalent network in the damaged area to participate in the repair reaction, thereby ensuring the coating's excellent self-healing performance and extending the product's service life.

[0086] Based on Examples 1-3 and Comparative Example 5, and in conjunction with Table 5, it can be seen that the chitosan-silver ion complex and tea polyphenols in the inner lining layer need to maintain an optimized ratio. Only when the two work together to construct a pH-responsive antibacterial system can they exert a highly efficient and long-lasting antibacterial effect under different environments, thus achieving efficient, long-lasting, and intelligent antibacterial protection.

[0087] As can be seen from Examples 1-3 and Comparative Example 6, and Table 1, the proportions of plant-based polyols and polyisocyanates used in the raw materials need to be kept within a reasonable range. This is the basis for forming an ideal cross-linked network structure, which has an impact on ensuring that the material obtains comprehensive mechanical properties and ensures that the material has high comprehensive performance.

[0088] 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 plant-based polyurethane orthotic shoe material, characterized in that, It is made from raw materials comprising the following parts by weight: 50-80 parts of plant-based polyol mixture; 40-70 parts of polyisocyanate; 5-15 parts of chain extender; 0.1-1 parts of catalyst; 2-8 parts of foaming agent; and 1-3 parts of foam stabilizer; wherein the plant-based polyol mixture is composed of castor oil, soybean oil and cashew nut phenol in a weight ratio of 3-5:2-4:1-3.

2. The plant-based polyurethane orthotic shoe material according to claim 1, characterized in that, The raw material also contains nano-reinforcing fillers, which are a mixture of nanocellulose whiskers and graphene in a weight ratio of 2-5:

1.

3. The plant-based polyurethane orthotic shoe material according to claim 1, characterized in that, The surface of the orthopedic shoe material is also covered with a self-healing coating, the raw materials of which include plant-based prepolymers modified with furan groups and plant-based prepolymers modified with maleimide groups.

4. The plant-based polyurethane orthotic shoe material according to claim 1, characterized in that, The orthopedic shoe material also has an inner lining layer, which contains an antibacterial functional component. The antibacterial functional component is a graft of chitosan-silver ion complex and tea polyphenols, and the weight ratio of chitosan-silver ion complex to tea polyphenols is 1-3:1-2.

5. A method for preparing a plant-based polyurethane orthotic shoe material, characterized in that, The plant-based polyurethane orthotic shoe material according to any one of claims 1-4 comprises the following steps: S1. Mix the plant-based polyol mixture, chain extender, catalyst, nano-reinforcing filler, foaming agent and foam stabilizer to obtain the polyol mixture component; S2. Mix the polyisocyanate with the polyol mixture obtained in step S1, stir quickly, and then pour into a mold. S3. Place the mold in a supercritical CO2 environment and perform gradient foaming by controlling the pressure and temperature in stages, so that the shoe material forms a density gradient structure with the density gradually increasing from the surface to the bottom layer. S4. After foaming, depressurize, cool, and demold to obtain the plant-based polyurethane orthopedic shoe material; S5. A self-healing coating is applied to the surface of the shoe material, and an inner lining layer is formed inside the shoe material. The chitosan-silver ion complex and the grafted tea polyphenol are dissolved in a solvent and applied to the inner lining of the shoe material by spraying or dipping. After drying, the inner lining layer is formed.

6. The method for preparing a plant-based polyurethane orthotic shoe material according to claim 5, characterized in that, In step S1, when the raw material contains nano-reinforced fillers, the nano-cellulose whiskers are first ultrasonically dispersed and blended with graphene, and then added to the plant-based polyol mixture.

7. The method for preparing a plant-based polyurethane orthotic shoe material according to claim 5, characterized in that, In step S2, the stirring speed of the rapid stirring is 2000-4000 rpm, and the stirring time is 10-30 seconds.

8. The method for preparing a plant-based polyurethane orthotic shoe material according to claim 5, characterized in that, In step S3, the specific process of gradient foaming is as follows: first, the surface layer is formed by maintaining the pressure at 15-25 MPa and the temperature at 35-45℃ for 5-15 minutes; then, the core layer is formed by maintaining the pressure at 8-12 MPa and the temperature at 50-60℃ for 10-20 minutes.

9. The method for preparing a plant-based polyurethane orthotic shoe material according to claim 5, characterized in that, In step S4, the depressurization rate is 1-3 MPa / s, and the cooling is natural cooling to room temperature or forced cooling to below 30°C.

10. The method for preparing a plant-based polyurethane orthotic shoe material according to claim 5, characterized in that, In step S5, the coating thickness of the self-healing coating is 50-200 μm, and the solvent is one or more of ethanol, acetone or N,N-dimethylformamide; the spraying pressure is 0.2-0.5 MPa, the spraying distance is 15-25 cm; the immersion time is 5-15 minutes, and the lifting speed is 1-5 cm / s.

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