Preparation process of supercritical foaming slippers

Abstract

The invention relates to a preparation process of supercritical foaming slippers, and belongs to the technical field of foaming materials, the materials are endowed with high-efficiency room-temperature self-repairing performance by virtue of double dynamic structure synergy of a hydrogen bond supramolecular network and a dynamic covalent bond, and rapid and reversible intermolecular repairing power is provided by multistage hydrogen bonds built in a polyurethane elastomer. A dynamic covalent bond introduced by a siloxane prepolymer realizes a stable broken bond reconnection effect, the two dynamic bonds are uniformly dispersed and fully coupled by a high-temperature mixing process, the problems of agglomeration and phase separation are avoided, and an unexpected synergistic gain is formed by quick response repair of hydrogen bonds and long-acting stable repair of the dynamic covalent bond; the damage can be quickly healed under the room temperature condition without any external stimulation, the retention rate of the mechanical property of the repaired material is greatly improved, and the service life of the slipper is remarkably prolonged.

Description

Technical Field

[0001] This invention belongs to the field of foaming material technology and relates to a preparation process for supercritical foamed slippers. Background Technology

[0002] As an essential item for multiple occasions, the market demand for slippers continues to grow with consumption upgrades. Consumers are increasingly demanding higher performance in terms of environmental protection, comfort, and durability, driving the iteration of manufacturing processes. Currently, the mainstream traditional chemical foaming process uses EVA, PVC, and other raw materials combined with chemical foaming agents. While low-cost and simple, it has many drawbacks, such as the generation of harmful byproducts during foaming, unpleasant odors and environmental pollution, poor cell control leading to poor product performance, and high energy consumption failing to meet energy conservation and emission reduction requirements, making it difficult to meet market demands. To solve these problems, supercritical fluid foaming technology has become a core development direction. This technology uses supercritical carbon dioxide or nitrogen as a physical foaming agent, producing no harmful byproducts, achieving near-zero VOC emissions, and precisely controlling the cell structure, significantly improving the resilience, cushioning, and durability of slippers.

[0003] Chinese invention patent application CN119859342A discloses a graphene-modified EVA supercritical foamed shoe sole or slipper and its preparation method. The foaming material includes the following raw materials: ethylene-vinyl acetate copolymer, modified graphene, stearic acid, zinc stearate and crosslinking agent. The prepared foamed shoe sole or slipper has higher strength and lighter material. The use of modified graphene, thermoplastic elastomer and EVA compound gives the foaming material better flexibility and slow rebound performance. After being made into shoe sole material, the shoe sole has good rebound and is softer under long-term use, which can significantly reduce the pressure on the sole of the foot.

[0004] The above-mentioned EVA supercritical foaming sole uses an irreversible chemical cross-linking network, without introducing dynamic reversible bonds and self-healing functional components. It only relies on EVA and graphene to achieve physical reinforcement. Moreover, supercritical foaming is only a physical molding process and cannot provide the material with the molecular rearrangement and bond reconstruction capabilities required for self-healing. Therefore, it does not have self-healing properties as a whole. Summary of the Invention

[0005] The purpose of this invention is to provide a manufacturing process for supercritical foamed slippers. By introducing dynamic reversible bonds and self-healing components to construct a reconfigurable cross-linked network, and combining it with supercritical foaming to achieve molecular rearrangement and bond reconstruction, the problem of traditional solutions having no self-healing properties, being easily damaged, and having a short lifespan is solved.

[0006] The objective of this invention can be achieved through the following technical solutions: A manufacturing process for supercritical foamed slippers includes the following steps: Step 1: Phenylboronic acid is subjected to a polycondensation reaction with hydroxyl-terminated polydimethylsiloxane to obtain a siloxane prepolymer.

[0007] Step 2: Polymerize polycaprolactone triblock polyol as the soft segment and hexamethylene diisocyanate and ethylenediamine as the hard segments under catalyst catalysis, and then end-cap the polymer to obtain polyurethane elastomer.

[0008] Step 3: Polyurethane elastomer, ethylene-vinyl acetate copolymer, siloxane-containing prepolymer, carbon nanotubes, graphene and zinc oxide are mixed at high temperature and hot-pressed to obtain a composite polyurethane material. The composite polyurethane material is then subjected to supercritical foaming, cooled and shaped to obtain supercritical foamed slippers.

[0009] Furthermore, the specific preparation process of the siloxane prepolymer is as follows: Phenylboronic acid and anhydrous ethanol were added to a reaction vessel and stirred at 55-60°C until completely dissolved. Then, hydroxyl-terminated polydimethylsiloxane was added and heated at 120-125°C for 4-6 hours. After drying, a siloxane-containing prepolymer was obtained.

[0010] Ethanol is used as a co-solvent to promote the uniform dissolution of phenylboronic acid. Low-temperature dissolution avoids the volatilization of raw materials. Heating at 120-125℃ achieves efficient polycondensation while removing ethanol and water molecules. Vacuum drying thoroughly removes small molecule residues, ensuring the purity of the prepolymer and preventing pore defects in subsequent foaming.

[0011] Furthermore, the ratio of phenylboronic acid, anhydrous ethanol, and hydroxyl-terminated polydimethylsiloxane is 50-60g: 500-700mL: 950-1150g.

[0012] This formulation ensures that phenylboronic acid and hydroxyl-terminated polydimethylsiloxane undergo equimolar polycondensation, with no monomer residue and no side reactions. The amount of ethanol used is just right to achieve complete dissolution and is easy to remove subsequently. The resulting siloxane prepolymer has a uniform molecular weight, a moderate dynamic bond content, and optimal compatibility with polyurethane and ethylene-vinyl acetate copolymer.

[0013] Furthermore, the specific preparation process of polyurethane elastomer is as follows: Polycaprolactone, hexamethylene diisocyanate, catalyst, and N,N-dimethylacetamide were added to a reactor and reacted at 75-80°C for 2-3 hours under nitrogen protection. The temperature of the reaction system was then lowered to 0°C using an ice-water bath. A 0.20-0.38 mol / L solution of ethylenediamine and N,N-dimethylacetamide was slowly added dropwise to the reactor through a constant-pressure dropping funnel. The reaction was carried out at 0°C for 6-8 hours. After the reaction was completed, anhydrous methanol was added at 75-77°C to seal the reaction for 2-3 hours. The product was then precipitated in deionized water, filtered, and dried to obtain the polyurethane elastomer.

[0014] Polycaprolactone triblock polyols provide high flexibility and room-temperature segment mobility as soft segments, while hexamethylene diisocyanate-ethylenediamine hard segments construct a high-density, multi-level hydrogen bond supramolecular network. The soft segments ensure room-temperature self-healing properties, while the hard segments provide mechanical strength, achieving a balance between self-healing and high strength, thus meeting the mechanical and durability requirements of foamed shoe materials.

[0015] Furthermore, the ratio of polycaprolactone, hexamethylene diisocyanate, catalyst, N,N-dimethylacetamide, ethylenediamine N,N-dimethylacetamide solution, and anhydrous methanol is 600-800g: 112.1-152.1g: 1.5-2.5mL: 1.5-2.5L: 2-3L: 200-300mL.

[0016] The formulation strictly controls the NCO / OH molar ratio to be 1.05-1.10, ensuring complete prepolymerization and chain extension reactions with no free monomer residue. The solvent dosage guarantees a solid content of 30%-35% in the system, with moderate viscosity and uniform stirring. The amount of end-capping agent is just right to neutralize excess -NCO, resulting in an elastomer with stable self-healing efficiency and minimal fluctuations in mechanical properties.

[0017] Furthermore, the catalyst is either dibutyltin dilaurate or bismuth isooctanoate.

[0018] Both types of catalysts efficiently catalyze the addition polymerization of hydroxyl groups with isocyanates without disrupting the hydrogen bond network or affecting self-healing properties.

[0019] Furthermore, the specific preparation process of the composite polyurethane material is as follows: Polyurethane elastomer, ethylene-vinyl acetate copolymer, and siloxane-containing prepolymer are added to a mixer at a temperature of 185-190℃ and mixed for 2-4 minutes. Carbon nanotubes are then added and mixed for another 2-4 minutes. Graphene and nano-zinc oxide are then added and mixed for 5-7 minutes. The prepared sample is left at room temperature for 24-26 hours and then vulcanized using a flat vulcanizing machine at a temperature of 190-200℃. The preheating time is 10-15 minutes, the hot pressing time is 3-5 minutes, and the molding pressure is 10-12 MPa. The mold is then placed in a cold press for 5-7 minutes to cool and set, resulting in a composite polyurethane material.

[0020] High-temperature intensive mixing enables multi-component melt blending, siloxane prepolymers act as compatibilizers to enhance interfacial bonding, carbon nanotubes and graphene synergistically enhance melt strength and mechanical properties, nano zinc oxide imparts antibacterial and deodorizing functions, and supercritical physical foaming leaves no chemical residue and produces uniform and fine pores, resulting in slippers that combine high resilience, lightweight, self-healing, antibacterial, and aging-resistant properties.

[0021] Furthermore, the mass ratio of polyurethane elastomer, ethylene-vinyl acetate copolymer, siloxane-containing prepolymer, carbon nanotubes, graphene, and nano zinc oxide is 700-800:250-300:50-60:0-5:4-6:3-5.

[0022] Polyurethane elastomer as the main phase ensures self-healing performance, ethylene-vinyl acetate copolymer improves processability and softness, siloxane prepolymer optimizes interfacial compatibility, carbon nanotubes and graphene synergistically enhance foaming stability, and the addition of nano zinc oxide is moderate and does not affect foaming.

[0023] Furthermore, the specific preparation process of supercritical foamed slippers is as follows: Water and composite polyurethane material are added to a high-pressure reactor, the reactor is sealed, stirring is started at a speed of 300-400 r / min, high-purity nitrogen is introduced, and the gas is vented 2-3 times. The reactor is kept saturated at 138-140℃ and 12-14 MPa for 80-100 min to obtain a foamed preform. The foamed preform is quickly transferred to a special slipper foaming mold and the mold is quickly closed. The pressure is rapidly released to atmospheric pressure within 1 second, and the mold is cooled and shaped to obtain a supercritical foamed slipper.

[0024] Water serves as the heat transfer medium to ensure uniform heating. Nitrogen saturation forms a polymer and a supercritical nitrogen homogeneous system. Temperature and pressure parameters are adapted to the plasticization and gas dissolution of the composite material. Rapid pressure release (<1s) triggers pressure-induced cell nucleation and growth, resulting in fine, uniform cells with a high closed-cell rate. Cooling and shaping stabilize the cell structure, leading to slippers with high resilience.

[0025] Furthermore, the ratio of water to composite polyurethane material is 3-5L:800-900g.

[0026] The beneficial effects of this invention are: 1. This invention relies on the synergistic dynamic structure of hydrogen-bonded supramolecular networks and dynamic covalent bonds to endow materials with highly efficient room-temperature self-healing properties. The multi-level hydrogen bonds constructed within the polyurethane elastomer provide rapid and reversible intermolecular repair dynamics, while the dynamic covalent bonds introduced by the siloxane prepolymer achieve stable bond reconnection. The high-temperature mixing process ensures uniform dispersion and full coupling of the two types of dynamic bonds, eliminating agglomeration and phase separation issues. The rapid response repair of hydrogen bonds and the long-term stable repair of dynamic covalent bonds create an unexpected synergistic gain, completely breaking the inherent contradiction of traditional materials where "strong self-healing ability leads to poor mechanical properties, and excellent mechanical properties lead to inability to repair." Damage can be rapidly healed at room temperature without any external stimuli, and the retention rate of mechanical properties of the repaired material is greatly improved, significantly extending the service life of slippers.

[0027] 2. This invention significantly improves the mechanical properties and molding stability of foamed materials through the synergistic effects of dynamically bonded siloxane prepolymers, self-healing polyurethane, and polyolefin substrates, combined with the process adaptation of intensive mixing and supercritical foaming. The dynamically covalently bonded siloxane prepolymers act as highly efficient interfacial compatibilizers, fundamentally improving the interfacial compatibility between polyurethane elastomers and polyolefin substrates, eliminating the industry-wide problem of easy phase separation during blending. Carbon-based nanofillers form a dense physical cross-linked network with the polymer matrix, simultaneously achieving both mechanical reinforcement and heterogeneous nucleation. The component toughening enhancement, interfacial compatibility optimization, and process-controlled cell structure produce unexpected synergistic effects, not only significantly improving the material's strength and toughness but also resulting in uniform, fine, and highly closed-cell supercritical foam, completely solving the defects of traditional foaming such as collapse, shrinkage, and uneven cell structure, achieving a perfect balance between lightweight and high performance.

[0028] 3. This invention achieves a synergistic integration of supercritical green foaming and multifunctionality. It uses supercritical physical foaming to replace traditional chemical foaming, resulting in no harmful byproducts or odor residues throughout the process, meeting the requirements of green and environmentally friendly production. The nano-antibacterial components are uniformly distributed in the matrix under the dispersion and enhancement effect of the siloxane prepolymer. The antibacterial function and the self-repair and mechanical enhancement functions form an unexpected effect of mutual benefit without interference. The antibacterial components not only do not damage the dynamic repair structure and foaming molding, but also further stabilize the cell structure. While ensuring the core mechanical and self-repair properties of the material, it endows the product with long-lasting antibacterial and deodorizing properties, with no migration of harmful substances. It is suitable for scenarios with extremely high requirements for safety, hygiene and comfort, such as home and bathroom, greatly improving the added value and applicability of the product. Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0030] Example 1: This example provides a manufacturing process for supercritical foamed slippers, including the following steps: S1: Add 55g of phenylboronic acid and 600mL of anhydrous ethanol to the reactor and stir at 57℃ until completely dissolved. Then add 1050g of hydroxyl-terminated polydimethylsiloxane and heat at 122℃ for 5h. Place in an oven and vacuum-place at 125℃ for 74h until no more bubbles are generated in the product. Collect the product, seal it, and obtain the siloxane-containing prepolymer.

[0031] After phenylboronic acid is dissolved in an alcohol solvent, it undergoes a condensation reaction with hydroxyl-terminated polydimethylsiloxane to remove small molecules such as water or ethanol, forming a siloxane prepolymer containing Si-OB dynamic covalent bonds. Subsequent vacuum drying further removes residual solvent and unreacted small molecules to obtain a purified siloxane prepolymer.

[0032] S2: 700g of polycaprolactone (PCL-PTHF-PCL), 132.1g of hexamethylene diisocyanate, 2mL of dibutyltin dilaurate, and 2L of N,N-dimethylacetamide were added to a reaction vessel and reacted at 77°C for 2.5h under nitrogen protection. The reaction system temperature was lowered to 0°C using an ice-water bath. 2.5L of 0.29mol / L ethylenediamine N,N-dimethylacetamide solution was slowly added dropwise to the reaction vessel through a constant pressure dropping funnel. The reaction was carried out at 0°C for 7h. After the reaction was completed, to remove excess -NCO from the system, 250mL of anhydrous methanol was added at 76°C, and the end-capping reaction was carried out for 2.5h. The obtained polymer was precipitated in deionized water, filtered, and vacuum dried at 85°C for 49h to obtain polyurethane elastomer.

[0033] Using polycaprolactone (PCL-PTHF-PCL) triblock polyol as the soft segment and hexamethylene diisocyanate and ethylenediamine as the hard segment, a -NCO-terminated prepolymer was first formed under the action of a catalyst. A multi-level dynamic hydrogen bond supramolecular network was constructed by low-temperature chain extension. Finally, methanol was used to end-group stabilize the end groups to obtain a room-temperature self-healing polyurethane elastomer.

[0034] S3: Add 750g of polyurethane elastomer, 275g of ethylene-vinyl acetate copolymer and 55g of siloxane-containing prepolymer to a mixer, set the temperature to 187℃, mix for 3 minutes, add 4g of carbon nanotubes, continue mixing for 3 minutes, then add 5g of graphene and 4g of nano zinc oxide, mix for 6 minutes, remove the rubber compound, place the prepared sample at 22℃ for 25 hours, vulcanize it through a flat vulcanizing machine, set the temperature to 195℃, preheat time for 12 minutes, hot pressing time for 4 minutes, and molding pressure for 11 MPa. Then place the mold in a cold press for 6 minutes, cool and shape to obtain a 1mm composite polyurethane material.

[0035] Through high-temperature mixing and hot pressing, polyurethane elastomer, ethylene-vinyl acetate copolymer, siloxane prepolymer and carbon-based filler are melt-blended to form a uniform composite matrix.

[0036] S4: Add 4L of water and 850g of composite polyurethane material to a high-pressure reactor, seal the reactor, start stirring, set the speed to 350r / min, introduce high-purity nitrogen, exhaust twice to remove air from the reactor, maintain saturation for 90min at 139℃ and 13MPa to allow nitrogen to fully dissolve into the polymer matrix, forming a homogeneous system of polymer and supercritical nitrogen, and obtain a uniform and stable foamed preform. Quickly transfer the foamed preform to a special slipper foaming mold and close the mold rapidly. Depressurize to atmospheric pressure within <1s, using the sudden pressure drop to trigger uniform nucleation and rapid growth of cells. Keep the mold closed and allow it to cool and solidify naturally at room temperature for 7min to stabilize the cell structure, prevent collapse and shrinkage, and obtain a supercritical foamed slipper.

[0037] Example 2: This example provides a manufacturing process for supercritical foamed slippers, including the following steps: S1: Add 50g of phenylboronic acid and 500mL of anhydrous ethanol to the reaction vessel and stir at 55℃ until completely dissolved. Then add 950g of hydroxyl-terminated polydimethylsiloxane and heat at 120℃ for 4h. Place in an oven and vacuum-place at 120℃ for 72h until no more bubbles are generated in the product. Collect the product, seal it, and obtain the siloxane-containing prepolymer.

[0038] S2: 600g of polycaprolactone (PCL-PTHF-PCL), 112.1g of hexamethylene diisocyanate, 1.5mL of dibutyltin dilaurate, and 1.5L of N,N-dimethylacetamide were added to a reaction vessel and reacted at 75℃ for 2 hours under nitrogen protection. The temperature of the reaction system was then lowered to 0℃ using an ice-water bath. 2L of 0.20mol / L ethylenediamine N,N-dimethylacetamide solution was slowly added dropwise to the reaction vessel through a constant pressure dropping funnel. The reaction was carried out at 0℃ for 6 hours. After the reaction was completed, to remove excess -NCO from the system, 200mL of anhydrous methanol was added at 75℃ to seal the reaction for 2 hours. The resulting polymer was precipitated in deionized water, filtered, and vacuum dried at 80℃ for 48 hours to obtain polyurethane elastomer.

[0039] S3: Add 700g of polyurethane elastomer, 250g of ethylene-vinyl acetate copolymer and 50g of siloxane-containing prepolymer to a mixer, set the temperature to 185℃, mix for 2 minutes, add 3g of carbon nanotubes, continue mixing for 2 minutes, then add 4g of graphene and 3g of nano zinc oxide, mix for 5 minutes, remove the rubber compound, place the prepared sample at 20℃ for 24 hours, vulcanize it through a flat vulcanizing machine, set the temperature to 190℃, preheat for 10 minutes, hot press for 3 minutes, and molding pressure to 10 MPa. Then place the mold in a cold press for 5 minutes, cool and set, to obtain a 1mm composite polyurethane material.

[0040] S4: Add 3L of water (heat transfer medium) and 800g of composite polyurethane material to a high-pressure reactor, seal the reactor, start stirring, set the speed to 300r / min, introduce high-purity nitrogen, exhaust twice to remove air from the reactor, maintain saturation time for 80min at 138℃ and 12MPa to allow nitrogen to fully dissolve into the polymer matrix, forming a homogeneous system of polymer and supercritical nitrogen, and obtain a uniform and stable foamed preform. Quickly transfer the foamed preform to a special slipper foaming mold and close the mold rapidly. Depressurize to atmospheric pressure within <1s, using the sudden pressure drop to trigger uniform nucleation and rapid growth of cells. Keep the mold closed and allow it to cool and solidify naturally at room temperature for 5min to stabilize the cell structure, prevent collapse and shrinkage, and obtain a supercritical foamed slipper.

[0041] Example 3: This example provides a manufacturing process for supercritical foamed slippers, including the following steps: S1: Add 60g of phenylboronic acid and 700mL of anhydrous ethanol to the reactor and stir at 60℃ until completely dissolved. Then add 1150g of hydroxyl-terminated polydimethylsiloxane and heat at 125℃ for 6h. Place in an oven and vacuum-place at 130℃ for 76h until no more bubbles are generated in the product. Collect the product, seal it, and obtain the siloxane-containing prepolymer.

[0042] S2: 800g of polycaprolactone (PCL-PTHF-PCL), 152.1g of hexamethylene diisocyanate, 2.5mL of dibutyltin dilaurate, and 2.5L of N,N-dimethylacetamide were added to a reaction vessel and reacted at 80℃ for 3h under nitrogen protection. The temperature of the reaction system was lowered to 0℃ using an ice-water bath. 3L of 0.38mol / L ethylenediamine N,N-dimethylacetamide solution was slowly added dropwise to the reaction vessel through a constant pressure dropping funnel. The reaction was carried out at 0℃ for 8h. After the reaction was completed, to remove excess -NCO in the system, 300mL of anhydrous methanol was added at 77℃ to end-cap the reaction for 3h. The obtained polymer was precipitated in deionized water, filtered, and vacuum dried at 90℃ for 50h to obtain polyurethane elastomer.

[0043] S3: Add 800g of polyurethane elastomer, 300g of ethylene-vinyl acetate copolymer and 60g of siloxane-containing prepolymer to a mixer, set the temperature to 190℃, mix for 4min, add 5g of carbon nanotubes, continue mixing for 4min, then add 6g of graphene and 5g of nano zinc oxide, mix for 7min, remove the rubber compound, place the prepared sample at 25℃ for 26h, vulcanize it through a flat vulcanizing machine, set the temperature to 200℃, preheat time for 15min, hot pressing time for 5min, molding pressure for 12MPa, then place the mold in a cold press for 7min, cool and set, to obtain a 1mm composite polyurethane material.

[0044] S3: Add 800g of polyurethane elastomer, 300g of ethylene-vinyl acetate copolymer and 60g of siloxane-containing prepolymer to a mixer, set the temperature to 190℃, mix for 4min, add 5g of carbon nanotubes, continue mixing for 4min, then add 6g of graphene and 5g of nano zinc oxide, mix for 7min, remove the rubber compound, place the prepared sample at 25℃ for 26h, vulcanize it through a flat vulcanizing machine, set the temperature to 200℃, preheat time for 15min, hot pressing time for 5min, molding pressure for 12MPa, then place the mold in a cold press for 7min, cool and set, to obtain a 1mm composite polyurethane material.

[0045] S4: Add 5L of water and 900g of composite polyurethane material to a high-pressure reactor, seal the reactor, start stirring, set the speed to 400r / min, introduce high-purity nitrogen, exhaust 3 times to remove air from the reactor, maintain saturation time of 100min at 140℃ and 14MPa to allow nitrogen to fully dissolve into the polymer matrix, forming a homogeneous system of polymer and supercritical nitrogen, and obtain a uniform and stable foamed preform. Quickly transfer the foamed preform to a special slipper foaming mold and close the mold quickly. Depressurize to atmospheric pressure within <1s, using the sudden pressure drop to trigger uniform nucleation and rapid growth of cells. Keep the mold closed and allow it to cool and solidify naturally at room temperature for 10min to stabilize the cell structure, prevent collapse and shrinkage, and obtain a supercritical foamed slipper.

[0046] Example 4: This example provides a preparation process for supercritical foamed slippers. The difference from Example 1 is that bismuth isooctanoate is used instead of dibutyltin dilaurate in step S2.

[0047] Example 5: This example provides a preparation process for supercritical foamed slippers. The difference from Example 1 is that carbon nanotubes are removed in step S3.

[0048] Comparative Example 1: This comparative example provides a preparation process for supercritical foamed slippers. The difference from Example 1 is that the siloxane-containing prepolymer is removed in step S3.

[0049] Comparative Example 2: This comparative example provides a preparation process for supercritical foamed slippers. The difference from Example 1 is that carbon nanotubes, graphene, and nano zinc oxide are removed in step S3.

[0050] Comparative Example 3: This comparative example provides a preparation process for supercritical foamed slippers. The difference from Example 1 is that the polyurethane elastomer is removed in step S3.

[0051] Comparative Example 4: This comparative example provides a preparation process for supercritical foamed slippers. The difference from Example 1 is that graphene and nano zinc oxide are removed in step S3.

[0052] The specifications and sources of the raw materials used in the above embodiments and comparative examples are as follows: Phenylated boric acid: 98% purity, purchased from Hubei Jianchu Biomedical Co., Ltd.

[0053] Hydroxyl-terminated polydimethylsiloxane: average molecular weight 500, viscosity 25 cSt, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0054] Polycaprolactone (PCL-PTHF-PCL, i.e., polycaprolactone-polytetrahydrofuran-polycaprolactone): molecular weight 2000, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0055] Hexamethylene diisocyanate: 99% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0056] Dibutyltin dilaurate: 95% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0057] N,N-Dimethylacetamide: 99.8% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0058] Ethylenediamine: 90% purity, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0059] Anhydrous methanol: Industrial grade, purchased from Shandong Xinyuhang Chemical Co., Ltd.

[0060] Ethylene-vinyl acetate copolymer: 99% purity, purchased from Hubei Shuaiyan Ligao Biomedical Co., Ltd.

[0061] Graphene: with an average radial size of 5-10 μm, purchased from Shanghai Maclean Biotechnology Co., Ltd.

[0062] Carbon nanotubes: 95% purity, 20-40nm diameter, 1-2μm length, purchased from Shanghai Maclean Biotechnology Co., Ltd.

[0063] Nano zinc oxide: 99% purity, particle size 30-80nm, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0064] Bismuth isooctanoate: Industrial grade, purchased from Shandong Xuchen Chemical Technology Co., Ltd.

[0065] The supercritical foamed slippers prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to performance testing: Mechanical property testing: Dumbbell-shaped standard specimens with dimensions of 35mm×12mm×2mm were used. The specimens were tested on a UTM4103 universal testing machine (Shenzhen Sun Technology Co., Ltd., China) at a tensile speed of 50mm / min, an ambient temperature of 22℃, and a relative humidity of 20%.

[0066] Self-healing performance test: First, the prepared standard dumbbell-shaped sample (35mm×12mm×2mm) was cut in half with a scalpel. Then, the cut surfaces of the two halves were aligned, and slight pressure was applied to ensure full contact between the surfaces. The treated sample was placed at room temperature for 24 hours. The treated sample was then subjected to a tensile test on a UTM4103 universal testing machine (Shenzhen Sun Technology Co., Ltd., China) at a tensile speed of 50mm / min, an ambient temperature of 22℃, and a relative humidity of 20%. The obtained stress-strain curve was compared with that of the original sample. The repair efficiency was calculated. The calculation formula is as follows: In the formula, η is the repair efficiency, σ1 is the original fracture stress of the unrepaired specimen, and σ2 is the fracture stress of the repaired specimen. At least three parallel specimens are set for each repair time group, and the average value is taken.

[0067] Antibacterial performance test: Preparation of agar medium: Calculate the amount of medium to be prepared according to the dosage of 40 mL per culture plate. According to the instructions, prepare 20 g of agar medium per 1000 mL of water and autoclave at 121℃ for 20 min. Nutrient broth medium: According to the instructions, prepare 3 g of beef extract, 10 g of tryptone and 5 g of sodium chloride per 1000 mL of water and autoclave at 121℃ for 20 min (adjust the volume of medium, inoculation concentration, constant temperature incubation speed and incubation time according to the needs of bacterial enrichment). The samples were sterilized under ultraviolet light. The samples were cut into 3.5cm × 3.5cm pieces and placed in glass petri dishes. 50uL of bacterial suspension (Staphylococcus aureus) was dropped into the center of the sample piece. PE film was placed over the bacterial suspension. 1mL of deionized water was added to the edge of the petri dish to prevent evaporation of the bacterial suspension. The petri dishes were placed in an incubator and incubated for 4 hours. After incubation, the entire sample was transferred to a beaker containing 100mL of culture medium with tweezers. The bacteria on the sample were completely washed off to form the bacterial stock solution. 100uL of the bacterial stock solution was dropped onto agar medium and spread evenly with a spreader. After incubation, the culture medium was placed in an incubator and incubated at 37℃ for 24 hours. The total number of colonies in the sample was recorded.

[0068] The test results are as follows: Table 1 Performance Test Overview As shown in Table 1, the tensile strength and elongation at break of Examples 1-5 are higher than those of Comparative Examples 1-4. This suggests that the high-density, multi-level dynamic hydrogen bond supramolecular network composed of hard segments has been formed inside the polyurethane elastomer. This provides the material with excellent resilience and energy dissipation capabilities. During the high-temperature mixing process, the siloxane-containing prepolymer not only acts as a compatibilizer, promoting the interfacial bonding between the polyurethane elastomer and the ethylene-vinyl acetate copolymer (EVA), but the dynamic covalent bond network it introduces can also undergo reversible fracture and recombination when the material is subjected to external force, further dissipating energy and preventing crack propagation, thereby significantly improving the toughness of the composite material. At the same time, carbon nanotubes, graphene, and nano zinc oxide are uniformly dispersed in the polymer matrix, playing the role of nano-reinforcement and stress transfer points, effectively improving the mechanical properties of the material.

[0069] As shown in Table 1, the self-healing efficiency of Examples 1-5 at room temperature for 24 hours is higher than that of Comparative Examples 1-4. This may be because the polyurethane molecular chains form a high-density hydrogen bond network that can be reversibly broken and recombined at room temperature, providing rapid and initial self-healing capabilities. The siloxane-containing prepolymer contains Si-OB dynamic covalent bonds with moderate bond energy, and also has a certain degree of reversibility at room temperature or slightly above room temperature. When the material is damaged (such as being cut), after the fracture surfaces come into contact, the abundant hydrogen bonds can quickly and dynamically recombine, providing initial repair and fixation. The Si-OB dynamic covalent bonds can recombine and connect the molecular chains over a longer timescale, achieving deeper and more robust repair.

[0070] As shown in Table 1, the antibacterial rates of Examples 1-5 are higher than those of Comparative Examples 2 and 4. This may be because the nano zinc oxide is melt-blended with other polymer matrices. This process helps the nano zinc oxide particles to be more uniformly dispersed in the polymer matrix. Uniform dispersion can increase the contact area between the antibacterial agent and potential bacteria, thereby exerting the antibacterial effect more effectively.

[0071] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A manufacturing process for supercritical foamed slippers, characterized in that, Includes the following steps: Step 1: Phenylboronic acid is subjected to a polycondensation reaction with hydroxyl-terminated polydimethylsiloxane to obtain a siloxane prepolymer; Step 2: Polymerize polycaprolactone triblock polyol as the soft segment and hexamethylene diisocyanate and ethylenediamine as the hard segment under catalyst catalysis, and then end-cap the polymer to obtain polyurethane elastomer. Step 3: Polyurethane elastomer, ethylene-vinyl acetate copolymer, siloxane-containing prepolymer, carbon nanotubes, graphene and zinc oxide are mixed at high temperature and hot-pressed to obtain a composite polyurethane material. The composite polyurethane material is then subjected to supercritical foaming, cooled and shaped to obtain supercritical foamed slippers.

2. The manufacturing process of a supercritical foamed slipper according to claim 1, characterized in that, The specific preparation process of the siloxane prepolymer mentioned in step one is as follows: Phenylboronic acid and anhydrous ethanol were added to a reaction vessel and stirred at 55-60°C until completely dissolved. Then, hydroxyl-terminated polydimethylsiloxane was added and heated at 120-125°C for 4-6 hours. After drying, a siloxane-containing prepolymer was obtained.

3. The manufacturing process of a supercritical foamed slipper according to claim 2, characterized in that, The ratio of phenylboronic acid, anhydrous ethanol, and hydroxyl-terminated polydimethylsiloxane is 50-60g: 500-700mL: 950-1150g.

4. The manufacturing process of a supercritical foamed slipper according to claim 1, characterized in that, The specific preparation process of the polyurethane elastomer described in step two is as follows: Polycaprolactone, hexamethylene diisocyanate, catalyst, and N,N-dimethylacetamide were added to a reactor and reacted at 75-80°C for 2-3 hours under nitrogen protection. The temperature of the reaction system was then lowered to 0°C using an ice-water bath. A 0.20-0.38 mol / L solution of ethylenediamine and N,N-dimethylacetamide was slowly added dropwise to the reactor through a constant-pressure dropping funnel. The reaction was carried out at 0°C for 6-8 hours. After the reaction was completed, anhydrous methanol was added at 75-77°C to seal the reaction for 2-3 hours. The product was then precipitated in deionized water, filtered, and dried to obtain the polyurethane elastomer.

5. The manufacturing process of a supercritical foamed slipper according to claim 4, characterized in that, The ratio of polycaprolactone, hexamethylene diisocyanate, catalyst, N,N-dimethylacetamide, ethylenediamine N,N-dimethylacetamide solution, and anhydrous methanol is 600-800g: 112.1-152.1g: 1.5-2.5mL: 1.5-2.5L: 2-3L: 200-300mL.

6. The manufacturing process of a supercritical foamed slipper according to claim 5, characterized in that, The catalyst is either dibutyltin dilaurate or bismuth isooctanoate.

7. The manufacturing process of a supercritical foamed slipper according to claim 1, characterized in that, The specific preparation process of the composite polyurethane material described in step three is as follows: Polyurethane elastomer, ethylene-vinyl acetate copolymer, and siloxane-containing prepolymer are added to a mixer at a temperature of 185-190℃ and mixed for 2-4 minutes. Carbon nanotubes are then added and mixed for another 2-4 minutes. Graphene and nano-zinc oxide are then added and mixed for 5-7 minutes. The prepared sample is left at room temperature for 24-26 hours and then vulcanized using a flat vulcanizing machine at a temperature of 190-200℃. The preheating time is 10-15 minutes, the hot pressing time is 3-5 minutes, and the molding pressure is 10-12 MPa. The mold is then placed in a cold press for 5-7 minutes to cool and set, resulting in a composite polyurethane material.

8. The manufacturing process of a supercritical foamed slipper according to claim 7, characterized in that, The mass ratio of the polyurethane elastomer, ethylene-vinyl acetate copolymer, siloxane-containing prepolymer, carbon nanotubes, graphene, and nano zinc oxide is 700-800:250-300:50-60:0-5:4-6:3-5.

9. The manufacturing process of a supercritical foamed slipper according to claim 1, characterized in that, The specific preparation process of the supercritical foamed slippers described in step three is as follows: Water and composite polyurethane material are added to a high-pressure reactor, the reactor is sealed, stirring is started at a speed of 300-400 r / min, high-purity nitrogen is introduced, and the gas is vented 2-3 times. The reactor is kept saturated at 138-140℃ and 12-14 MPa for 80-100 min to obtain a foamed preform. The foamed preform is quickly transferred to a special slipper foaming mold and the mold is quickly closed. The pressure is rapidly released to atmospheric pressure within 1 second, and the mold is cooled and shaped to obtain a supercritical foamed slipper.

10. The manufacturing process of a supercritical foamed slipper according to claim 9, characterized in that, The ratio of water to composite polyurethane material is 3-5L:800-900g.

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