Preparation method of bio-based waterproof moisture-permeable film for high-temperature-resistant and high-wear-resistant shoes

Abstract

The invention discloses a preparation method of a high-temperature-resistant and high-wear-resistant bio-based waterproof moisture-permeable membrane for shoes, which comprises the following steps: step 1, preparing a high-temperature-resistant and high-wear-resistant bio-based polyurethane membrane casting solution, namely mixing bio-based polyurethane resin, wear-resistant high-specific-heat particles, a pore-foaming agent, a modifier, a coupling agent and an auxiliary agent, and uniformly stirring to obtain the high-temperature-resistant and high-wear-resistant bio-based polyurethane membrane casting solution; a uniform membrane casting solution is formed; 2, film coating is conducted through a template method, specifically, the high-temperature-resistant nanofiber skeleton is fixed to a base material, the fixed nanofiber skeleton is filled with the film casting solution, and pre-crosslinking treatment is conducted on the film casting solution through ultraviolet light irradiation; 3, gradient coagulating bath synergistic phase separation pore forming is carried out, specifically, the film layer subjected to ultraviolet light irradiation treatment is sequentially immersed into at least two coagulating baths, the first coagulating bath is used for activating covalent bond reaction of active groups on the surface of the film layer and inhibiting the phase separation rate, and the second coagulating bath is used for activating covalent bond reaction of the active groups on the surface of the film layer; the second coagulating bath is used for quickly desolvating, inducing phase separation and forming a through microporous structure; and 4, carrying out post-curing treatment on the film layer to lock the through micropore structure and complete residual crosslinking. By adopting the technical scheme, the high temperature resistance and wear resistance of the bio-based waterproof moisture-permeable film can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of waterproof and breathable membranes, and in particular to a method for preparing a bio-based waterproof and breathable membrane for high-temperature-resistant and high-wear-resistant shoes. Background Art

[0002] With growing global environmental awareness, bio-based materials, due to their renewability and biodegradability, show great potential as a replacement for traditional petroleum-based materials in many fields. In footwear manufacturing, waterproof and breathable membranes, as core functional components, must effectively block liquid water penetration while ensuring efficient water vapor evaporation to enhance wearing comfort. However, modern footwear production processes, particularly the composite hot pressing process, typically require high temperatures of 150°C to 200°C, and the shoes are subject to repeated mechanical friction during daily wear.

[0003] Existing bio-based polyurethane (BPU)-based waterproof and breathable membranes, although they have good breathability and environmental characteristics, have significant defects in meeting the two key performance requirements of high temperature resistance and high wear resistance. Specifically, the glass transition temperature (Tg) of existing BPU materials is generally lower than 80°C, which makes them prone to softening, adhesion, and even degradation in high-temperature processes such as shoe composite hot pressing, thereby causing delamination of the composite interface between the membrane layer and the substrate. This lack of structural stability at high temperatures not only affects the overall durability of the membrane material, but also causes it to wear rapidly due to local softening of the material during dynamic friction, showing poor wear resistance (for example, the Taber abrasion value is often higher than 100mg / 1000 times, far from the requirement of less than 20mg / 1000 times for high-end shoe materials).

[0004] Therefore, existing bio-based waterproof and breathable membranes are difficult to maintain their high wear resistance and structural stability while meeting the high temperature required by the hot pressing process of shoe materials. The material softens, becomes easy to wear, and the interface is easy to delaminate at high temperatures. This seriously limits its promotion and use in high-end functional shoe materials, especially in application scenarios with strict requirements on high temperature resistance and wear resistance. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects or problems existing in the background technology and provide a method for preparing a bio-based waterproof and breathable membrane for high-temperature resistant and high-wear resistant shoes, which can improve the high-temperature resistance and wear resistance of the bio-based waterproof and breathable membrane.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] Technical Solution 1: A method for preparing a bio-based waterproof and breathable membrane for high-temperature resistant and high-wear resistant shoes, comprising the following steps:

[0008] Step 1: Prepare a high-temperature resistant and highly wear-resistant bio-based polyurethane casting liquid, including mixing a bio-based polyurethane resin, wear-resistant and high specific heat particles, a porogen, a modifier, a coupling agent and an additive to form a uniform casting liquid; Step 2: Use a template method to coat the film, including fixing a high-temperature resistant nanofiber skeleton on a substrate, filling the casting liquid into the fixed nanofiber skeleton, and pre-crosslinking the casting liquid by ultraviolet irradiation; Step 3: Perform a gradient coagulation bath to coordinate phase separation and pore formation, including immersing the membrane layer treated with ultraviolet irradiation in at least two coagulation baths in sequence, wherein the first coagulation bath is used to activate the covalent bond reaction of the surface active groups of the membrane layer and inhibit the phase separation rate, and the second coagulation bath is used for rapid desolvation to induce phase separation and form a through microporous structure; and Step 4: Post-curing the membrane layer to lock the through microporous structure and complete residual crosslinking.

[0009] Technical Solution 2 based on Technical Solution 1: In the step 1, the bio-based polyurethane resin is a polyether thermoplastic polyurethane with a bio-based content greater than or equal to 60%, and the modifier is selected from one or more combinations of acetylated lignin, cellulose nanofibers, and tannic acid. The amount of the modifier added is 1% to 5% of the mass of the bio-based polyurethane resin.

[0010] Technical solution three based on technical solution one: In step one, the wear-resistant and high specific heat particles are selected from one or more combinations of Al2O3 powder, paraffin / SiO2, and ceramic micropowder, the average particle size of the particles is 50nm to 500nm, and the addition amount is 8 to 12 parts.

[0011] Technical solution four based on technical solution one: in the step one, the preparation of the casting liquid also includes adding a solvent, a leveling agent, a penetrant and a defoaming agent, wherein the amount of the solvent is 60 to 80 parts, the amount of the leveling agent is 2 to 3 parts, the amount of the penetrant is 0.5 to 3 parts, the amount of the defoaming agent is 0.5 to 1.5 parts, the amount of the porogen is 5 to 10 parts, and the amount of the coupling agent added is 1% to 3% of the mass of the bio-based polyurethane resin.

[0012] Technical solution five based on technical solution one: in the step two, the high-temperature resistant nanofiber skeleton is selected from one of polybenzimidazole (PBI) nanofibers, cellulose nanofibers treated with a silane coupling agent, amino polyimide (PI) after alkaline hydrolysis, or carboxylated polyparaphenylene benzobisoxazole fibers (PBO) treated with aminosilane, and the porosity of the skeleton is 70% to 95%, and the pore size distribution is 100nm to 5000nm.

[0013] Technical solution six based on technical solution one: in the step two, the method of fixing the high-temperature resistant nanofiber skeleton on the substrate is hot pressing, the hot pressing temperature is 80°C, and the pressure is 0.25MPa; the method of filling the casting liquid into the nanofiber skeleton is through a slit-type sizing curtain with a gap of 0.15mm, and the sizing temperature is 80°C.

[0014] Technical Solution 7 based on Technical Solution 1: In the step 2, the ultraviolet light irradiation pre-crosslinking treatment includes multi-stage negative pressure suction of the casting liquid before ultraviolet light irradiation, and the pressures of the multi-stage negative pressure suction are 0.05MPa, 0.3MPa and 0.5MPa respectively.

[0015] Technical Solution 8 based on Technical Solution 1: In the step 3, the at least two coagulation baths include: a first coagulation bath, whose solvent is a mixed solvent of ethanol and ethyl acetate in a volume ratio of 3:1, the temperature is 40°C, and the residence time is 2 minutes to 4 minutes, and the first coagulation bath is used to activate the covalent bond reaction between the surface active groups of the high-temperature resistant nanofiber skeleton and the isocyanate groups of the bio-based polyurethane; and a second coagulation bath, whose solvent is a water / DMF mixed solvent with a water content of 70%, the temperature is 10°C, and the residence time is 3 minutes to 5 minutes, and the second coagulation bath is used to induce rapid desolvation of the bio-based polyurethane to form the through microporous structure.

[0016] Technical solution nine based on technical solution one: in the step four, the temperature of the post-curing treatment is 80° C., and the treatment time is 2 minutes.

[0017] Technical solution 10 based on technical solution 1: the total duration of step 3 is no more than 7 minutes.

[0018] From the above description of the present invention, it can be seen that compared with the prior art, the present invention has the following beneficial effects:

[0019] Technical Solution 1 provides a method for preparing a bio-based waterproof and breathable membrane for high-temperature resistant and high-wear-resistant shoes. The high-temperature resistant and high-wear-resistant bio-based polyurethane casting liquid prepared in step 1 includes a bio-based polyurethane resin that has been modified to construct a branched or network structure, wear-resistant high-specific heat particles dispersed therein, as well as a coupling agent and an auxiliary agent, so that the casting liquid itself has excellent processing stability and preliminary heat-resistant and wear-resistant potential. Among them, the branched or network structure formed by introducing a specific modifier into the molecular chain of the bio-based polyurethane resin significantly enhances the cohesion and rigidity between the polymer chains, thereby increasing the glass transition temperature and thermal decomposition temperature of the material, making it less likely to soften and deform even at high temperatures, providing the membrane with basic high-temperature resistance. At the same time, the wear-resistant high-specific heat particles dispersed in the casting liquid have high hardness and high specific heat capacity characteristics. When the subsequent membrane material is subjected to friction stress, it can effectively disperse stress and quickly absorb the heat generated by local friction, delaying the thermal softening of the matrix and synergistically improving the wear resistance of the material. The template coating process used in step two precisely fixes the high-temperature resistant nanofiber skeleton on the substrate, and uses a slit sizing curtain and multi-stage negative pressure suction to ensure that the casting liquid fully fills the microporous structure of the skeleton evenly and without bubbles. Subsequently, the ultraviolet irradiation pre-crosslinking treatment forms a preliminary chemical bond between the casting liquid and the nanofiber skeleton, greatly improving the initial bonding strength between the two, effectively avoiding the interface stratification problem that may occur during the subsequent high-temperature treatment process, and further improving the temperature resistance and wear resistance of the membrane layer. This step ensures the structural integrity and uniformity of the membrane layer and the skeleton. The gradient coagulation bath synergistic phase separation pore formation in step three is the key to achieving the synergy of high moisture permeability and high hydrostatic pressure of the membrane material. This step involves designing two coagulation baths with different solvent compositions, temperatures, and immersion residence times. The first coagulation bath's solvent composition and temperature slowly induce phase separation, providing ample time for in situ covalent bonding between the bio-based polyurethane and the surface active groups of the high-temperature-resistant nanofiber backbone. This creates a strong chemically bonded interface at the microscopic level, effectively preventing delamination between the membrane and the backbone at high temperatures and laying the foundation for the final membrane's compactness and hydrostatic performance. The second coagulation bath, through rapid solvent-nonsolvent exchange, precisely induces the bio-based polyurethane to form a large number of uniform, interconnected, and through-hole micropores with controlled pore size. These micropores serve as channels for efficient water vapor transmission, ensuring the membrane's excellent moisture permeability. Furthermore, the precisely controlled pore size prevents liquid water from passing through below a certain pressure, thereby maintaining high hydrostatic performance. This gradient phase separation process cleverly resolves the dilemma of balancing moisture permeability and mechanical properties in traditional one-step methods. Finally, the post-curing treatment in step four, through appropriate temperature and time, further completes the residual cross-linking reaction in the bio-based polyurethane matrix, solidifies and locks the through-microporous structure formed inside the membrane layer, improves the dimensional stability and thermal decomposition temperature of the membrane layer, and continuously enhances the overall mechanical properties and wear resistance of the material, ensuring the long-term stability and durability of the membrane material in extreme environments.In summary, the present invention solves the core defects of existing bio-based waterproof and breathable membranes in terms of the coordination of high temperature resistance and high wear resistance through the coordinated design of the entire chain from casting liquid formula, coating process, phase separation mechanism to post-processing, and realizes the structural stability and functional efficiency of the material during the hot pressing process and use of shoe materials.

[0020] In Technical Solution 2, in Step 1, the bio-based polyurethane resin is modified by adding acetylated lignin, cellulose nanofibers, or tannic acid as a modifier, thereby constructing a branched or network structure in the bio-based polyurethane molecular chain. This structure enhances the rigidity and cross-linking density of the bio-based polyurethane molecular chain, effectively limiting the mobility of molecular segments at high temperatures, thereby significantly increasing the glass transition temperature and thermal decomposition temperature of the bio-based polyurethane matrix. This makes the membrane material more heat-resistant and stable, and can effectively cope with the high-temperature environment required by the shoe material composite hot pressing process, avoiding softening, adhesion, or degradation of the material at high temperatures, thereby ensuring the structural integrity of the membrane material during the production and processing process and the performance reliability of the final product.

[0021] In technical solution three, in step one, Al2O3 powder, paraffin wax / SiO2 or ceramic micropowder with an average particle size of 50 nanometers to 500 nanometers is selected as wear-resistant and high specific heat particles and added to the casting liquid. These nano or submicron particles can be evenly dispersed in the final film layer and effectively resist external mechanical wear through their inherent high hardness. More importantly, these particles have high specific heat capacity and thermal conductivity. When the film material is subjected to dynamic friction stress, they can quickly absorb and effectively conduct the heat generated by local friction, thereby reducing the local temperature peak of the bio-based polyurethane matrix at the friction contact point. This thermal management effect can delay the thermal softening of the matrix when friction generates heat, so that it maintains a high hardness and modulus during continuous friction, thereby significantly improving the wear resistance of the film material and effectively extending the service life of the product.

[0022] In technical solution four, in step one, the macroscopic physical and chemical properties of the casting liquid are optimized by precisely adding specified amounts of solvents, leveling agents, penetrants and defoaming agents during the preparation of the casting liquid. The specific amount of solvent ensures the full dissolution and uniform dispersion of each component. The addition of the leveling agent effectively reduces the surface tension of the casting liquid, allowing it to spread evenly during the coating process, eliminating surface defects such as brush marks, sagging or shrinkage holes, and ensuring the surface flatness of the film layer. The penetrant reduces the interfacial tension of the casting liquid on the nanofiber skeleton, allowing it to efficiently wet and fully penetrate into the fine pores of the nanofiber skeleton, avoiding the formation of "bridging" or voids, and ensuring the uniformity of the internal structure of the film layer. The introduction of the defoaming agent can effectively suppress and eliminate the bubbles generated by the casting liquid during the stirring and coating process, avoiding the appearance of hole defects in the final film material, thereby ensuring the density and mechanical properties of the film layer. The synergistic effect of these additives together provides high-quality, defect-free casting liquid, laying a solid foundation for the subsequent efficient film formation and the realization of final performance.

[0023] In Technical Solution 5, the high-temperature resistant nanofiber skeleton selected in Step 2, such as PBI nanofibers, cellulose nanofibers treated with a silane coupling agent, amino-treated PI after alkaline hydrolysis, or carboxylated PBO fibers treated with aminosilane, has a porosity set between 70% and 95%, and a pore size distribution controlled between 100 nanometers and 5000 nanometers. This precisely designed nanofiber skeleton constructs a unique and efficient three-dimensional interconnected micro-nano network structure in the membrane layer. This network not only provides a continuous and low-resistance transmission channel for water vapor molecules, thereby ensuring the high moisture permeability of the membrane material, but also enables water vapor to diffuse quickly and efficiently from one side of the membrane to the other. At the same time, the microporous structure of the skeleton and the hydrophobicity of the fiber material itself, combined with the capillary resistance effect, can effectively prevent liquid water from penetrating through the membrane layer under a certain pressure, thereby synergistically improving the waterproof ability of the membrane material and achieving a balance between waterproofness and moisture permeability.

[0024] In technical solution six, in step two, by hot pressing and fixing the high-temperature resistant nanofiber skeleton at 80°C and 0.25MPa, it is ensured that the skeleton can accurately maintain its position and stability during the coating and subsequent phase separation process, effectively avoiding the displacement or deformation of the skeleton, thereby ensuring the high uniformity of the internal structure of the final membrane layer. At the same time, through a slit-type sizing curtain with a gap of 0.15 mm, the casting liquid is accurately filled into the fixed nanofiber skeleton at a sizing temperature of 80°C. This precise filling method ensures that the casting liquid can evenly and fully infiltrate and fill every micropore of the skeleton, effectively avoiding bubbles or voids caused by insufficient filling of the casting liquid, and defects such as excessively thick film layers or pore blockages caused by excessive filling, providing key process control for the preparation of high-performance, structurally uniform waterproof and breathable membranes.

[0025] In technical solution seven, in step two, before the ultraviolet irradiation pre-crosslinking treatment, the casting liquid is subjected to multi-stage negative pressure suction, and the pressures of the multi-stage negative pressure suction are 0.05MPa, 0.3MPa and 0.5MPa respectively. By applying negative pressures of different gradients, tiny bubbles that may be entrained in the casting liquid during the preparation or coating process can be thoroughly and efficiently discharged. This step-by-step increasing negative pressure can ensure that the casting liquid completely and evenly penetrates every tiny pore and corner of the nanofiber skeleton, eliminating any potential bubble traps, thereby effectively avoiding the occurrence of voids and bubble defects inside the membrane layer, and the problem of uneven filling of the casting liquid, greatly improving the density and uniformity of the final membrane layer and the reliability of its subsequent performance.

[0026] In technical solution eight, in step three, the gradient coagulation bath includes two precisely set coagulation baths, which is the key to achieving the synergy of high moisture permeability and high hydrostatic pressure of the membrane material. The first coagulation bath uses a mixed solvent of ethanol and ethyl acetate with a volume ratio of 3:1, and is immersed at 40°C for 2 to 4 minutes. This solvent system and temperature can slowly induce the phase separation of bio-based polyurethane. More importantly, it can effectively activate the in situ covalent bond reaction of the surface active groups (such as amino and carboxyl groups) of the high-temperature resistant nanofiber skeleton and the isocyanate groups of the bio-based polyurethane, and establish a strong chemical bonding interface in the early stage of membrane formation, thereby constructing a high-strength and stable bonding layer at the microscopic level, effectively preventing the delamination of the membrane layer and the skeleton at high temperature, and laying the foundation for the final membrane layer's density and high hydrostatic pressure performance. The second coagulation bath uses a water / DMF mixed solvent with a water content of 70%, and is immersed at 10°C for 3 to 5 minutes. This coagulation bath system precisely induces rapid liquid-liquid phase separation in bio-based polyurethane through rapid solvent-nonsolvent exchange, precisely controlling the nucleation and growth of micropores at low temperatures, ultimately forming a large number of uniform, interconnected, through-hole microporous structures with pore sizes controlled between 0.5 and 2 microns. These micropores form channels for efficient water vapor transmission, ensuring the membrane's excellent moisture permeability. At the same time, the precisely controlled pore size prevents liquid water from passing through under certain pressures, thereby maintaining high hydrostatic pressure performance. This gradient phase separation process cleverly resolves the conflict between moisture permeability and mechanical properties in traditional one-step methods, ensuring the membrane possesses the synergistic advantages of both high moisture permeability and high hydrostatic pressure.

[0027] In technical solution nine, in step four, the film layer is post-cured at 80°C for 2 minutes. The precisely controlled curing temperature and time can fully promote the further cross-linking reaction between the residual isocyanate groups in the bio-based polyurethane matrix and water or hydroxyl groups, thereby increasing the cross-linking density and degree of polymerization of the film layer. This effectively locks the formed through-microporous structure to prevent it from collapsing, shrinking or deforming due to thermal stress or mechanical stress during subsequent processing or use, thereby ensuring the dimensional stability and long-term moisture permeability of the film. At the same time, a higher degree of cross-linking further enhances the overall mechanical properties of the film, especially the tensile strength and modulus, and increases its thermal decomposition temperature and wear resistance, ensuring the structural integrity and durability of the film under long-term use and extreme environments.

[0028] In Technical Solution 10, the total duration of step three is controlled within 7 minutes. The reaction time of this step is determined by time limit to avoid a decrease in phase separation effect due to excessively long coagulation bath time. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is a scanning electron microscope photograph of the bio-based waterproof and breathable membrane involved in Example 1 of the present invention;

[0031] Figure 2 This is a scanning electron microscope photograph of the bio-based waterproof and moisture-permeable membrane involved in Example 2 of the present invention;

[0032] Figure 3 This is a scanning electron microscope photograph of the bio-based waterproof and moisture-permeable membrane involved in Comparative Example 1 of the present invention;

[0033] Figure 4 This is a scanning electron microscope photograph of the bio-based waterproof and breathable membrane involved in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are preferred embodiments of the present invention and should not be regarded as excluding other embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] In the claims, description and drawings of the present invention, unless otherwise clearly defined, the use of terms such as "first", "second" or "third" is for the purpose of distinguishing different objects rather than for describing a specific order.

[0036] In the claims, specification and the above-mentioned drawings of the present invention, unless otherwise expressly defined, directional words such as the terms "center", "transverse", "longitudinal", "horizontal", "vertical", "top", "bottom", "inside", "outside", "up", "down", "front", "back", "left", "right", "clockwise", "counterclockwise" and the like indicating directions or positional relationships are based on the directions and positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the specific scope of protection of the present invention.

[0037] In the claims, description and above-mentioned drawings of the present invention, unless otherwise expressly defined, the terms "fixed connection" or "fixed connection" should be understood in a broad sense, that is, any connection method without displacement relationship and relative rotation relationship between the two parties, that is, including non-detachable fixed connection, detachable fixed connection, integral connection and fixed connection through other devices or elements.

[0038] In the claims, description and drawings of the present invention, if the terms "include", "have" and their variations are used, they are intended to mean "including but not limited to".

[0039] The present invention relates to a method for preparing a bio-based waterproof and breathable membrane for high-temperature resistant and high-wear resistant shoes, which comprises the following steps:

[0040] Step 1: Prepare a high-temperature resistant and highly wear-resistant bio-based polyurethane casting liquid, including mixing a bio-based polyurethane resin, wear-resistant and high specific heat particles, a porogen, a modifier, a coupling agent and an additive to form a uniform casting liquid; Step 2: Use a template method to coat the film, including fixing a high-temperature resistant nanofiber skeleton on a substrate, filling the casting liquid into the fixed nanofiber skeleton, and pre-crosslinking the casting liquid by ultraviolet irradiation; Step 3: Perform a gradient coagulation bath to coordinate phase separation and pore formation, including immersing the membrane layer treated with ultraviolet irradiation in at least two coagulation baths in sequence, wherein the first coagulation bath is used to activate the covalent bond reaction of the surface active groups of the membrane layer and inhibit the phase separation rate, and the second coagulation bath is used for rapid desolvation to induce phase separation and form a through microporous structure; and Step 4: Post-curing the membrane layer to lock the through microporous structure and complete residual crosslinking.

[0041] In step 1, the bio-based polyurethane resin is a polyether-type thermoplastic polyurethane having a bio-based content of greater than or equal to 60%. The modifier is selected from one or more of acetylated lignin, cellulose nanofibers, and tannic acid, and the amount of the modifier added is 1% to 5% by weight of the bio-based polyurethane resin. Specifically, the bio-based polyurethane resin can be obtained by polymerization of castor oil polyol or soybean oil polyol with isophorone diisocyanate (IPDI) or lysine diisocyanate (LDI), and has a number average molecular weight (Mn) of 50,000 to 150,000 g / mol. The acetylated lignin can be lignin acetylated with acetic anhydride. The cellulose nanofibers can be bacterial cellulose or wood cellulose nanofibers with an average diameter of 5 to 50 nanometers and a length of 200 nanometers to 2 microns. The tannic acid can be commercially available food-grade or industrial-grade tannic acid.

[0042] In step 1, the wear-resistant, high-specific-heat particles are selected from one or more combinations of Al2O3 powder, paraffin wax / SiO2, and ceramic micropowder. The particles have an average particle size of 50 nm to 500 nm, and are added in an amount of 8 to 12 parts. Specifically, the Al2O3 powder can be α-alumina powder with an average particle size of approximately 150 nm, and can be surface-modified with an aminosilane coupling agent (such as KH-570); the paraffin wax / SiO2 can be a composite of paraffin wax and silica micropowder with an average particle size of approximately 100 nm; and the ceramic micropowder can be zirconium oxide (ZrO2) or silicon carbide (SiC) micropowder with an average particle size of approximately 300 nm, and can be surface-modified with an epoxy silane coupling agent (such as KH-560).

[0043] In the step one, the preparation of the casting solution also includes adding a solvent, a leveling agent, a penetrant and a defoaming agent, wherein the amount of the solvent is 60 to 80 parts, the amount of the leveling agent is 2 to 3 parts, the amount of the penetrant is 0.5 to 3 parts, the amount of the defoaming agent is 0.5 to 1.5 parts, the amount of the porogen is 5 to 10 parts, and the amount of the coupling agent added is 1% to 3% of the mass of the bio-based polyurethane resin. Specifically, the solvent may be selected from one or more combinations of acetone, dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran (THF) or butanone (MEK); the leveling agent may be selected from polydimethylsiloxane (PDMS) leveling agents (such as BYK-333, Dow Corning 193) or organic modified polysiloxane leveling agents (such as Shin-Etsu KF-6011); the penetrant may be selected from anionic surfactants, such as sulfosuccinate surfactants OT-50, OT-70 or OT-75; the defoamer may be selected from acrylate copolymer defoamers (such as Digo FOAMEX The defoamer can be a polyether non-silicone modified defoamer (e.g., BYK-800, BYK-051), or a plant oil derivative defoamer (e.g., BYK-088). The porogen can be selected from one or more combinations of polyvinyl pyrrolidone (PVP, K-30), sodium chloride, nano-titanium dioxide particles (average particle size less than 100 nm), light calcium carbonate powder, or wood flour. The coupling agent can be selected from one or more combinations of bio-based aminosilanes (e.g., KH-570), epoxy biosilanes (e.g., KH-560), lactic acid-modified titanates, or commercially available tannic acid. Furthermore, the casting solution can be prepared by adding 0.1% to 0.5% of a photoinitiator, which can be selected from benzophenone (BP) and its derivatives or acylphosphine oxide initiators (e.g., TPO, TPO-L, IRGACURE 184, DAROCUR 1173, OMNIRAD 2959).

[0044] In the step 2, the high-temperature resistant nanofiber skeleton is selected from one of polybenzimidazole (PBI) nanofibers, cellulose nanofibers treated with a silane coupling agent, amino polyimide (PI) after alkaline hydrolysis, or carboxylated polyparaphenylene benzobisoxazole fiber (PBO) treated with aminosilane, and the porosity of the skeleton is 70% to 95%, and the pore size distribution is 100nm to 5000nm. Specifically, the high-temperature resistant nanofiber skeleton can be prepared by electrospinning, for example, a polyimide or polybenzimidazole precursor solution (concentration 10% to 20%) is spun under the conditions of voltage 15 kV to 30 kV, needle to receiving distance 10 cm to 20 cm, and pumping rate 0.5 ml / hour to 2.0 ml / hour, and subsequently subjected to high-temperature imidization or curing treatment (such as gradually heating to 250°C to 400°C under a nitrogen atmosphere); the amino-treated polyimide (PI) nanofiber can be obtained by treating PI fibers with an amine aqueous solution; the carboxylated poly(p-phenylene benzobisoxazole) fiber (PBO) can be obtained by alkaline hydrolysis of PBO fibers.

[0045] In the step 2, the high-temperature resistant nanofiber skeleton is fixed on the substrate by hot pressing, the hot pressing temperature is 80°C, and the pressure is 0.25MPa; the casting liquid is filled into the nanofiber skeleton by a slit-type sizing curtain with a gap of 0.15mm, and the sizing temperature is 80°C. Specifically, the substrate can be selected from one of aramid woven fabric, nylon fabric, polyimide (PI) non-woven fabric, or polyphenylene sulfide (PSS) non-woven fabric; the hot pressing is achieved by a hot press to ensure the positional stability of the skeleton in subsequent processes; the slit-type sizing curtain uses a precisely processed die head to ensure uniform extrusion and filling of the casting liquid, and the sizing speed matches the substrate conveying speed.

[0046] In the step 2, the UV irradiation pre-crosslinking treatment includes performing multi-stage negative pressure suction on the casting solution before UV irradiation, and the pressures of the multi-stage negative pressure suction are 0.05MPa, 0.3MPa and 0.5MPa respectively. Specifically, the UV irradiation intensity is UVA 100mW / cm 2 and UVC 150mW / cm 2 The irradiation time is 5 seconds to 30 seconds, and the irradiation distance is 10 cm to 20 cm; the multi-stage negative pressure suction can be achieved by connecting vacuum pumps in series or in parallel, for example, the first-stage negative pressure is 0.05 MPa for 10 seconds, the second-stage negative pressure is 0.3 MPa for 15 seconds, and the third-stage negative pressure is 0.5 MPa for 20 seconds; after the ultraviolet light irradiation, a double-roller scraping treatment can be performed, in which the upper roller temperature is 40°C and the lower roller temperature is 18°C.

[0047] In step 3, the at least two coagulation baths include: a first coagulation bath, whose solvent is a mixed solvent of ethanol and ethyl acetate in a volume ratio of 3:1, a temperature of 40°C, and a residence time of 2 to 4 minutes. The first coagulation bath is used to activate the covalent bond reaction between the surface active groups of the high-temperature resistant nanofiber skeleton and the isocyanate groups of the bio-based polyurethane; and a second coagulation bath, whose solvent is a water / DMF mixed solvent with a water content of 70%, a temperature of 10°C, and a residence time of 3 to 5 minutes. The second coagulation bath is used to induce rapid desolvation of the bio-based polyurethane to form the through-hole microporous structure. Specifically, the coagulation bath can be implemented by a tank, and the solvent composition and temperature are precisely controlled by a circulation pump and a heat exchanger. The immersion residence time is controlled by adjusting the linear speed and bath length of the film layer in the coagulation bath. For example, the length of the first coagulation bath can be 3 to 5 meters, and the length of the second coagulation bath can be 4 to 6 meters, with a linear speed of 0.5 m / min to 1 m / min.

[0048] In step 4, the post-curing treatment is performed at a temperature of 80°C for 2 minutes. Specifically, the post-curing treatment can be performed using hot air drying or vacuum drying to ensure that residual solvent in the film is fully volatilized and to promote further crosslinking and curing of the bio-based polyurethane matrix, thereby improving the dimensional stability and mechanical properties of the film.

[0049] The total duration of step 3 is no more than 7 minutes.

[0050] The present invention relates to a method for preparing a bio-based waterproof and breathable membrane for high-temperature resistant and high-wear-resistant shoes. The high-temperature resistant and high-wear-resistant bio-based polyurethane casting liquid prepared in step one comprises a bio-based polyurethane resin modified to construct a branched or network structure, wear-resistant high-specific heat particles dispersed therein, and a coupling agent and an auxiliary agent, so that the casting liquid itself has excellent processing stability and preliminary heat-resistant and wear-resistant potential. Among them, the branched or network structure formed by introducing a specific modifier into the molecular chain of the bio-based polyurethane resin significantly enhances the cohesion and rigidity between the polymer chains, thereby increasing the glass transition temperature and thermal decomposition temperature of the material, making it not easy to soften and deform even at high temperatures, providing the film material with basic high-temperature resistance. At the same time, the wear-resistant high-specific heat particles dispersed in the casting liquid have high hardness and high specific heat capacity characteristics. When the subsequent film material is subjected to friction stress, it can effectively disperse stress and quickly absorb the heat generated by local friction, delay the thermal softening of the matrix, and synergistically improve the wear resistance of the material. The template coating process used in step two precisely fixes the high-temperature resistant nanofiber skeleton on the substrate, and uses a slit sizing curtain and multi-stage negative pressure suction to ensure that the casting liquid fully fills the microporous structure of the skeleton evenly and without bubbles. Subsequently, the ultraviolet irradiation pre-crosslinking treatment forms a preliminary chemical bond between the casting liquid and the nanofiber skeleton, greatly improving the initial bonding strength between the two, effectively avoiding the interface stratification problem that may occur during the subsequent high-temperature treatment process, and further improving the temperature resistance and wear resistance of the membrane layer. This step ensures the structural integrity and uniformity of the membrane layer and the skeleton. The gradient coagulation bath synergistic phase separation pore formation in step three is the key to achieving the synergy of high moisture permeability and high hydrostatic pressure of the membrane material. This step involves designing two coagulation baths with different solvent compositions, temperatures, and immersion residence times. The first coagulation bath's solvent composition and temperature slowly induce phase separation, providing ample time for in situ covalent bonding between the bio-based polyurethane and the surface active groups of the high-temperature-resistant nanofiber backbone. This creates a strong chemically bonded interface at the microscopic level, effectively preventing delamination between the membrane and the backbone at high temperatures and laying the foundation for the final membrane's compactness and hydrostatic performance. The second coagulation bath, through rapid solvent-nonsolvent exchange, precisely induces the bio-based polyurethane to form a large number of uniform, interconnected, and through-hole micropores with controlled pore size. These micropores serve as channels for efficient water vapor transmission, ensuring the membrane's excellent moisture permeability. Furthermore, the precisely controlled pore size prevents liquid water from passing through below a certain pressure, thereby maintaining high hydrostatic performance. This gradient phase separation process cleverly resolves the dilemma of balancing moisture permeability and mechanical properties in traditional one-step methods. Finally, the post-curing treatment in step four, through appropriate temperature and time, further completes the residual cross-linking reaction in the bio-based polyurethane matrix, solidifies and locks the through-microporous structure formed inside the membrane layer, improves the dimensional stability and thermal decomposition temperature of the membrane layer, and continuously enhances the overall mechanical properties and wear resistance of the material, ensuring the long-term stability and durability of the membrane material in extreme environments.In summary, the present invention solves the core defects of existing bio-based waterproof and breathable membranes in terms of the coordination of high temperature resistance and high wear resistance through the coordinated design of the entire chain from casting liquid formula, coating process, phase separation mechanism to post-processing, and realizes the structural stability and functional efficiency of the material during the hot pressing process and use of shoe materials.

[0051] In order to further illustrate the advantages of the technical solutions of the present invention, the following examples and comparative examples are provided.

[0052] The main raw materials and their brands / types or preparation methods used in the examples and comparative examples of the present invention are as follows.

[0053] The bio-based polyurethane resin is BioPU-Base type, a polyether thermoplastic polyurethane dispersion with a bio-based content greater than or equal to 60%, a number average molecular weight range of 50,000 to 150,000 g / mol, and a solid content of 30% to 35%. It is based on the reaction polymerization of soybean oil polyol or castor oil polyol with isophorone diisocyanate or lysine diisocyanate, and is purchased from Covestro.

[0054] The wear-resistant and high specific heat particles include α-alumina powder, model AluWear-150, with an average particle size of about 150 nanometers, purchased from Saint-Gobain; zirconium oxide micropowder, model ZirCon-300, with an average particle size of about 300 nanometers, purchased from Tosoh Corporation; light calcium carbonate, model CaCO3-L100, with an average particle size of about 100 nanometers, purchased from Omya; anatase nano TiO2, model TiNano-A50, with an average particle size of about 50 nanometers, purchased from Tyco.

[0055] The porogen was polyvinyl pyrrolidone, purchased from Ashland.

[0056] Solvents included acetone, analytical grade, purchased from Merck; and dimethylformamide, analytical grade, purchased from Merck.

[0057] The coupling agents include aminosilane coupling agent KH-570, purchased from Maitu High-Tech Materials Group; epoxy biosilane coupling agent KH-560, purchased from Maitu High-Tech Materials Group; and lactic acid-modified titanate, homemade in the laboratory, synthesized by ester exchange between isopropyl titanate and lactic acid under specific conditions.

[0058] The leveling agents include polydimethylsiloxane leveling agent BYK-333, purchased from BYK Chemicals; and organic modified polysiloxane leveling agent Shin-Etsu KF-6011, purchased from Shin-Etsu Chemical Co., Ltd.

[0059] The penetrants include anionic surfactant OT-50, model Aerosol OT-50, purchased from Solvay Group; anionic surfactant OT-70, model Aerosol OT-70, purchased from Solvay Group.

[0060] The defoaming agents include polyacrylate defoamer BYK-051, purchased from BYK Chemicals; and castor oil defoamer BYK-088, purchased from BYK Chemicals.

[0061] Photoinitiators include IRGACURE 184, available from BASF; DAROCUR 1173, available from BASF; and OMNIRAD 2959, available from IGM Resins.

[0062] The high-temperature resistant nanofiber skeleton includes an amino-type PI skeleton, which is homemade in the laboratory and based on the polyimide precursor solution produced by Ube Industries of Japan. It is imidized by electrospinning and gradually heated to 350°C in a nitrogen atmosphere, and then treated with a dilute amine aqueous solution for amino treatment; a carboxylated PBO fiber skeleton (made in the laboratory and based on commercially available PBO fiber) is carboxylated by alkaline hydrolysis treatment; and PBI nanofibers are homemade in the laboratory and based on polybenzimidazole solution. They are electrospun and gradually heated to 400°C in a nitrogen atmosphere for curing.

[0063] The substrate includes aramid woven fabric, model Kevlar 29, specification 200D, purchased from DuPont; nylon fabric, model Nylon 66, specification 210D, purchased from Ascend High Performance Materials; and polyimide non-woven fabric, model Kapton NW-100, purchased from DuPont.

[0064] Example 1

[0065] (1) Preparation of casting solution:

[0066] 60 parts of acetone, 10 parts of α-alumina powder (model AluWear-150) surface-modified with aminosilane coupling agent KH-570 and with an average particle size of 150 nm, and 5 parts of polyvinylpyrrolidone (PVP, K-30) were added to a reactor and homogenized at 5000 rpm for 30 minutes. Subsequently, 15 parts of BioPU-Base bio-based polyurethane resin, 0.45 parts of cellulose nanofiber (CNF-B01, accounting for 3% of the weight of the bio-based polyurethane resin), 0.15 parts of KH-570 aminosilane coupling agent (accounting for 1% of the weight of the bio-based polyurethane resin), and 0.045 parts of photoinitiator IRGACURE 184 (accounting for 0.3% of the weight of the bio-based polyurethane resin) were added and stirred at 80°C for 1 hour. Finally, 1.5 parts BYK-333 polydimethylsiloxane leveling agent, 1 part Aerosol OT-50 anionic surfactant, and 0.5 parts BYK-051 polyacrylate defoamer were added, and stirring was continued until a uniform casting solution with a viscosity of less than 10,000 cP was obtained.

[0067] (2) Template coating:

[0068] The amino PI nanofiber skeleton is hot-pressed and fixed to the aramid woven cloth (model Kevlar 29) substrate at 80°C and 0.25MPa for 1 minute by a hot press. The above-mentioned casting liquid is passed through a slit-type sizing curtain with a gap of 0.15mm and accurately filled into the fixed nanofiber skeleton at a sizing temperature of 80°C. Subsequently, combined with multi-stage negative pressure suction (the first stage negative pressure is 0.05MPa for 10 seconds, the second stage negative pressure is 0.3MPa for 15 seconds, and the third stage negative pressure is 0.5MPa for 20 seconds) to ensure that the casting liquid is fully penetrated and bubbles are eliminated. Then, under the ultraviolet irradiation intensity of UVA 100mW / cm 2 and UVC 150mW / cm 2 Under the conditions of , UV irradiation pre-crosslinking treatment for 15 seconds. Finally, the film surface was optimized by double roller scraping treatment (upper roller temperature 40 ° C, lower roller temperature 18 ° C).

[0069] (3) Phase separation pore formation and post-curing:

[0070] The film layer treated with ultraviolet light is immersed in two coagulation baths in sequence.

[0071] The first coagulation bath had a solvent consisting of a mixed solvent of ethanol and ethyl acetate in a volume ratio of 3:1, a temperature of 40° C., and an immersion residence time of 2 minutes.

[0072] The second coagulation bath had a solvent of a water / DMF mixed solvent with a water content of 70%, a temperature of 10° C., and an immersion residence time of 3 minutes.

[0073] After the phase separation was completed, the film was post-cured in a hot air drying oven at 80° C. for 2 minutes.

[0074] Example 2

[0075] (1) Preparation of casting solution:

[0076] 63 parts of dimethylformamide, 8 parts of zirconium oxide (ZrO2) micropowder (model ZirCon-300) with an average particle size of 300 nanometers, surface-modified with epoxy silane coupling agent KH-560, and 7 parts of light calcium carbonate (model CaCO3-L100) with an average particle size of 100 nanometers were added to a reactor and homogenized and dispersed at 5000 rpm for 30 minutes. Subsequently, 20 parts of BioPU-Base bio-based polyurethane resin, 0.1 part of commercially available industrial-grade tannic acid (brand TA-95, accounting for 0.5% of the weight of the bio-based polyurethane resin), 0.2 parts of KH-560 epoxy bio-silane coupling agent (1% of the weight of the bio-based polyurethane resin), and 0.04 parts of photoinitiator DAROCUR 1173 (0.2% of the weight of the bio-based polyurethane resin) were added, and the mixture was stirred at 60°C for 1 hour. Finally, 1 part of Dow Corning 193 polydimethylsiloxane leveling agent, 0.5 parts of Aerosol OT-70 anionic surfactant, and 0.5 parts of BYK-051 polyacrylate defoamer were added and stirred until a uniform casting solution with a viscosity of less than 10,000 cP was obtained.

[0077] (2) Template coating:

[0078] The carboxylated PBO nanofiber skeleton is hot-pressed and fixed to a nylon cloth (model Nylon66) substrate at 80°C and 0.25MPa for 1 minute using a hot press. The above-mentioned casting liquid is passed through a slit-type sizing curtain with a gap of 0.15mm and accurately filled into the fixed nanofiber skeleton at a sizing temperature of 80°C. Subsequently, combined with multi-stage negative pressure suction (the first stage negative pressure is 0.05MPa for 10 seconds, the second stage negative pressure is 0.3MPa for 15 seconds, and the third stage negative pressure is 0.5MPa for 20 seconds), it is ensured that the casting liquid is fully penetrated and bubbles are eliminated. Then, under the ultraviolet irradiation intensity of UVA 100mW / cm 2 and UVC 150mW / cm 2 Under the conditions of , UV irradiation pre-crosslinking treatment for 15 seconds. Finally, the film surface was optimized by double roller scraping treatment (upper roller temperature 40 ° C, lower roller temperature 18 ° C).

[0079] (3) Phase separation pore formation and post-curing:

[0080] The film layer treated with ultraviolet light is immersed in two coagulation baths in sequence.

[0081] The first coagulation bath had a solvent consisting of a mixed solvent of ethanol and ethyl acetate in a volume ratio of 3:1, a temperature of 30° C., and an immersion residence time of 1.5 minutes.

[0082] The second coagulation bath had a solvent of a water / DMF mixed solvent with a water content of 70%, a temperature of 10° C., and an immersion residence time of 3.5 minutes.

[0083] After the phase separation was completed, post-curing treatment was carried out on a hot press at 90° C. (pressure 0.5 MPa) for 3 minutes.

[0084] Example 3

[0085] (1) Preparation of casting solution:

[0086] A mixture of 40 parts DMF and 20 parts acetone (60 parts total), 5 parts of α-alumina powder with an average particle size of 200 nm (model AluWear-150), and 8 parts of anatase nano-TiO2 with an average particle size of 50 nm (model TiNano-A50) were added to a reactor and homogenized and dispersed at 5000 rpm for 30 minutes. Subsequently, 21 parts of BioPU-Base bio-based polyurethane resin, 0.42 parts of acetylated lignin (brand Ligno-AC80, accounting for 2% of the weight of the bio-based polyurethane resin), 0.21 parts of a laboratory-made lactic acid-modified titanate coupling agent (accounting for 1% of the weight of the bio-based polyurethane resin), and 0.084 parts of photoinitiator OMNIRAD 2959 (accounting for 0.4% of the weight of the bio-based polyurethane resin) were added, and the mixture was stirred at 80°C for 1 hour. Finally, 2 parts of Shin-Etsu KF-6011 organically modified polysiloxane leveling agent, 0.5 parts of Aerosol OT-50 anionic surfactant, and 0.5 parts of BYK-088 castor oil defoamer were added and stirred until a uniform casting solution with a viscosity of less than 10,000 cP was obtained.

[0087] (2) Template coating:

[0088] The PBI nanofiber skeleton is hot-pressed and fixed to the polyimide (PI) non-woven fabric (model Kapton NW-100) substrate at 80°C and 0.25MPa for 1 minute by a hot press. The above-mentioned casting liquid is passed through a slit-type sizing curtain with a gap of 0.15mm and accurately filled into the fixed nanofiber skeleton at a sizing temperature of 80°C. Subsequently, combined with multi-stage negative pressure suction (the first stage negative pressure is 0.05MPa for 10 seconds, the second stage negative pressure is 0.3MPa for 15 seconds, and the third stage negative pressure is 0.5MPa for 20 seconds) to ensure that the casting liquid is fully penetrated and bubbles are eliminated. Then, under the ultraviolet irradiation intensity of UVA 100mW / cm 2 and UVC 150mW / cm 2 Under the conditions of , UV irradiation pre-crosslinking treatment for 15 seconds. Finally, the film surface was optimized by double roller scraping treatment (upper roller temperature 40 ° C, lower roller temperature 18 ° C).

[0089] (3) Phase separation pore formation and post-curing:

[0090] The film layer treated with ultraviolet light is immersed in two coagulation baths in sequence.

[0091] The first coagulation bath had a solvent consisting of a mixed solvent of ethanol and ethyl acetate in a volume ratio of 3:1, a temperature of 20° C., and an immersion residence time of 2.5 minutes.

[0092] The second coagulation bath had a solvent of a water / DMF mixed solvent with a water content of 70%, a temperature of 5° C., and an immersion residence time of 2.5 minutes.

[0093] After the phase separation was completed, the film was post-cured in a vacuum drying oven at 70° C. for 5 minutes.

[0094] Comparative Example 1

[0095] (1) Preparation of casting solution:

[0096] 60 parts of acetone, 10 parts of α-alumina powder (model AluWear-150) surface-modified with aminosilane coupling agent KH-570 and with an average particle size of 150 nm, and 5 parts of polyvinylpyrrolidone (PVP, K-30) were added to a reactor and homogenized at 5000 rpm for 30 minutes. Subsequently, 15 parts of BioPU-Base bio-based polyurethane resin, 0.45 parts of cellulose nanofiber (CNF-B01, accounting for 3% of the weight of the bio-based polyurethane resin), 0.15 parts of KH-570 aminosilane coupling agent (accounting for 1% of the weight of the bio-based polyurethane resin), and 0.045 parts of photoinitiator IRGACURE 184 (accounting for 0.3% of the weight of the bio-based polyurethane resin) were added and stirred at 80°C for 1 hour. Finally, 1.5 parts BYK-333 polydimethylsiloxane leveling agent, 1 part Aerosol OT-50 anionic surfactant, and 0.5 parts BYK-051 polyacrylate defoamer were added, and stirring was continued until a uniform casting solution with a viscosity of less than 10,000 cP was obtained.

[0097] (2) Template coating:

[0098] The amino PI nanofiber skeleton is hot-pressed and fixed to the aramid woven cloth (model Kevlar 29) substrate at 80°C and 0.25MPa for 1 minute by a hot press. The above-mentioned casting liquid is passed through a slit-type sizing curtain with a gap of 0.15mm and accurately filled into the fixed nanofiber skeleton at a sizing temperature of 80°C. Subsequently, combined with multi-stage negative pressure suction (the first stage negative pressure is 0.05MPa for 10 seconds, the second stage negative pressure is 0.3MPa for 15 seconds, and the third stage negative pressure is 0.5MPa for 20 seconds) to ensure that the casting liquid is fully penetrated and bubbles are eliminated. Then, under the ultraviolet irradiation intensity of UVA 100mW / cm 2 and UVC 150mW / cm2 Under the conditions of , UV irradiation pre-crosslinking treatment for 15 seconds. Finally, the film surface was optimized by double roller scraping treatment (upper roller temperature 40 ° C, lower roller temperature 18 ° C).

[0099] (3) Phase separation pore formation and post-curing:

[0100] The UV-irradiated film was directly immersed in a single coagulation bath consisting of water / DMF (70% water content) at 10°C for 5 minutes. After phase separation, the film was post-cured in an 80°C hot air drying oven for 2 minutes.

[0101] Comparative Example 2

[0102] (1) Preparation of casting solution:

[0103] 60 parts of acetone, 10 parts of α-alumina powder (model AluWear-150) surface-modified with aminosilane coupling agent KH-570 and with an average particle size of 150 nm, and 5 parts of polyvinylpyrrolidone (PVP, K-30) were added to a reactor and homogenized at 5000 rpm for 30 minutes. Subsequently, 15 parts of BioPU-Base bio-based polyurethane resin, 0.45 parts of cellulose nanofiber (CNF-B01, accounting for 3% of the weight of the bio-based polyurethane resin), 0.15 parts of KH-570 aminosilane coupling agent (accounting for 1% of the weight of the bio-based polyurethane resin), and 0.045 parts of photoinitiator IRGACURE 184 (accounting for 0.3% of the weight of the bio-based polyurethane resin) were added and stirred at 80°C for 1 hour. Finally, 1.5 parts BYK-333 polydimethylsiloxane leveling agent, 1 part Aerosol OT-50 anionic surfactant, and 0.5 parts BYK-051 polyacrylate defoamer were added, and stirring was continued until a uniform casting solution with a viscosity of less than 10,000 cP was obtained.

[0104] (2) Direct coating:

[0105] The casting solution was passed through a slit sizing curtain with a gap of 0.15 mm and directly coated on an aramid woven fabric (model Kevlar 29) substrate at a sizing temperature of 80°C without fixing any nanofiber skeleton, and without multi-stage negative pressure suction and ultraviolet irradiation pre-crosslinking treatment.

[0106] (3) Phase separation pore formation and post-curing:

[0107] The directly coated film layer is immersed in two coagulation baths in sequence.

[0108] The first coagulation bath had a solvent consisting of a mixed solvent of ethanol and ethyl acetate in a volume ratio of 3:1, a temperature of 40° C., and an immersion residence time of 2 minutes.

[0109] The second coagulation bath had a solvent of a water / DMF mixed solvent with a water content of 70%, a temperature of 10° C., and an immersion residence time of 3 minutes.

[0110] After the phase separation was completed, the film was post-cured in a hot air drying oven at 80° C. for 2 minutes.

[0111] The following performance tests were performed on the bio-based waterproof and breathable membranes prepared in the examples and comparative examples:

[0112] Water vapor permeability: Determined according to Method A of GB / T 12704.1-2009 “Textile fabrics test method for water vapor permeability - Part 1: Moisture absorption method”.

[0113] Hydrostatic pressure: measured in accordance with GB / T 4744-2013 Textiles - Water repellency test - Static hydrostatic pressure method.

[0114] Wear cycles: 1N load, based on GB / T 20390.1-2006 "Plastics wear test methods - Part 1: Rotating friction wheel wear test" Taber abrasion method, wear wheel CS-10F.

[0115] Temperature resistance: Determined according to GB / T 9345.1-2008 "Plastics Thermogravimetric Analysis (TGA) Part 1: General Test Methods", the 5% weight loss temperature.

[0116] The following table summarizes the performance test results of Examples 1-3 and Comparative Examples 1-2. All data are the average values of at least 5 parallel samples, and the standard deviation is reported.

[0117]

[0118] The performance comparison results of the embodiments of the present invention and the comparative examples fully demonstrate the significant advantages of the bio-based waterproof and breathable membrane prepared by the present technical solution in terms of high temperature resistance, high wear resistance, and waterproof and breathable properties.

[0119] As can be seen from Table 1, the moisture permeability of the films prepared in Example 1, Example 2 and Example 3 are much higher than that of Comparative Example 1 and Comparative Example 2, reaching 9500, 8200 and 8300 g / m2 respectively. 2 This excellent moisture permeability is mainly due to the gradient coagulation bath synergistic phase separation pore formation technology adopted by the present invention. Figure 1This is a scanning electron microscope image of the bio-based waterproof and breathable membrane prepared in Example 1. The image clearly shows a uniformly distributed and interconnected microporous network structure formed within the membrane layer, with micropore diameters controlled within the range of 0.5-2 microns. This interconnected microporous structure provides an efficient and low-resistance transmission channel for water vapor molecules, ensuring that water vapor can quickly diffuse from one side of the membrane to the other. In comparison, the moisture permeability of Comparative Example 1 is only 3500 g / m 2 24h, Figure 3 The results show that the microporous structure inside the membrane layer is unevenly distributed, with some pores blocked or too large, which hinders the effective transmission of water vapor and leads to a significant decrease in moisture permeability. The moisture permeability of comparative example 2 is even lower, reaching 2000 g / m 2 24h, Figure 4 It shows that the membrane layer is dense and lacks an effective through-microporous structure, and the water vapor channel is obviously insufficient.

[0120] In terms of wear resistance, the wear cycles of Example 1, Example 2 and Example 3 reached 10,000, 11,000 and 11,500 times respectively, far exceeding the 5,000 times of Comparative Example 1 and the 3,000 times of Comparative Example 2. This significant improvement in wear resistance is due to the addition of wear-resistant high-specific heat particles to the casting solution of the present invention. The high hardness of these particles resists external wear, and at the same time, their high specific heat capacity can absorb the heat generated by friction, delaying the softening of the bio-based polyurethane matrix under local high temperature, thereby maintaining the structural integrity of the material. In addition, the bio-based polyurethane side chain or network structure constructed by the modifier also improves the fatigue resistance of the matrix. Comparative Example 2 has the worst wear resistance due to the lack of introduction of a nanofiber skeleton for reinforcement.

[0121] In terms of temperature resistance, the temperature resistance of the membrane materials of Examples 1, 2 and 3 all reached above 185°C, and Example 3 even reached 195°C. This shows that the membrane material of the present invention can fully meet the high temperature resistance requirements of the composite hot pressing process of shoe materials (usually at 150-200°C). This high-temperature stability is derived from the branched or network structure constructed by the modifier in the molecular chain of the bio-based polyurethane resin. This structure effectively enhances the cohesion and rigidity between the polymer chains, and increases the glass transition temperature and thermal decomposition temperature of the material. At the same time, the introduction of the nanofiber skeleton also provides additional thermal stability support. The temperature resistance of Comparative Example 2 is only 155°C, which is not enough to withstand high-temperature processing, and it is prone to softening at high temperatures, which confirms the limitation of the temperature resistance performance due to the lack of key reinforcing structure. Comparative Example 1 failed to undergo temperature resistance testing due to easy adhesion or degradation at high temperatures, further highlighting the superiority of the present invention in high temperature resistance.

[0122] In terms of hydrostatic pressure, the hydrostatic pressures of Example 1, Example 2, and Example 3 are 160, 165, and 160 kPa, respectively, which all meet or exceed the waterproof requirements of high-end shoe materials. Figure 1 、 Figure 2 The uniform and controlled microporous structure shown is closely related to this, where precise control of pore size ensures that liquid water cannot pass through under a certain pressure. While the hydrostatic pressure of Comparative Example 1 is relatively close at 155 kPa, its insufficient moisture permeability prevents it from achieving the overall advantage. Comparative Example 2, lacking effective structural support, failed to meet the passing standard in the hydrostatic pressure test.

[0123] also, Figure 1 and Figure 2 The scanning electron micrographs shown also indicate that a good interface bond is formed between the nanofiber skeleton and the bio-based polyurethane membrane layer, and the nanofibers are uniformly wrapped and effectively embedded in the membrane layer, which confirms the effectiveness of UV pre-crosslinking and in-situ bonding in the gradient coagulation bath, ensuring the structural stability of the composite membrane under high temperature and friction conditions, thereby avoiding the problem of interface delamination.

[0124] The above description and embodiments are intended to explain the scope of protection of the present invention, but do not constitute a limitation thereto. Modifications, equivalent substitutions, or other improvements to the embodiments of the present invention or portions thereof that can be obtained by a person of ordinary skill in the art through logical analysis, reasoning, or limited experimentation based on the teachings of the present invention or the above embodiments, combined with common knowledge, ordinary technical knowledge in the field, and / or prior art, should all be included within the scope of protection of the present invention.

Claims

1. A method for preparing a bio-based waterproof and breathable membrane for high-temperature resistant and high-wear resistant shoes, characterized in that: The following steps are involved: Step 1: preparing a high-temperature-resistant and high-wear-resistant bio-based polyurethane casting solution, including mixing a bio-based polyurethane resin, wear-resistant high-specific-heat particles, a porogen, a modifier, a coupling agent, and an additive to form a uniform casting solution; Step 2: using a template method to coat the film, including fixing a high-temperature resistant nanofiber skeleton on a substrate, filling the casting solution into the fixed nanofiber skeleton, and pre-crosslinking the casting solution by ultraviolet light irradiation; Step 3: performing gradient coagulation bath coordinated phase separation pore formation, comprising sequentially immersing the UV-irradiated membrane layer in at least two coagulation baths, wherein the first coagulation bath is used to activate the covalent bond reaction of the membrane surface active groups and inhibit the phase separation rate, and the second coagulation bath is used for rapid desolvation to induce phase separation and form a through-hole microporous structure; and Step 4: Post-curing the film layer to lock the through-microporous structure and complete the residual cross-linking.

2. The preparation method according to claim 1, characterized in that In the step 1, the bio-based polyurethane resin is a polyether thermoplastic polyurethane with a bio-based content greater than or equal to 60%, and the modifier is selected from one or more combinations of acetylated lignin, cellulose nanofibers, and tannic acid.

3. The preparation method according to claim 1, characterized in that In step 1, the wear-resistant high specific heat particles are selected from one or more combinations of Al2O3 powder, paraffin / SiO2, and ceramic micropowder, the average particle size of the particles is 50nm to 500nm, and the addition amount is 8 to 12 parts.

4. The preparation method according to claim 1, characterized in that In the step one, the preparation of the casting solution also includes adding a solvent, a leveling agent, a penetrant and a defoaming agent, wherein the amount of the solvent is 60 to 80 parts, the amount of the leveling agent is 2 to 3 parts, the amount of the penetrant is 0.5 to 3 parts, the amount of the defoaming agent is 0.5 to 1.5 parts, the amount of the porogen is 5 to 10 parts, and the amount of the coupling agent added is 1% to 3% of the mass of the bio-based polyurethane resin.

5. The preparation method according to claim 1, characterized in that In the step 2, the high-temperature resistant nanofiber skeleton is selected from one of polybenzimidazole (PBI) nanofibers, cellulose nanofibers treated with a silane coupling agent, amino polyimide (PI) after alkaline hydrolysis, or carboxylated polyparaphenylene benzobisoxazole fiber (PBO) treated with aminosilane, and the porosity of the skeleton is 70% to 95%, and the pore size distribution is 100nm to 5000nm.

6. The preparation method according to claim 1, characterized in that In the step 2, the method of fixing the high-temperature resistant nanofiber skeleton on the substrate is hot pressing, the hot pressing temperature is 80°C, and the pressure is 0.25MPa; the method of filling the casting liquid into the nanofiber skeleton is through a slit-type sizing curtain with a gap of 0.15mm, and the sizing temperature is 80°C.

7. The preparation method according to claim 1, characterized in that In the step 2, the ultraviolet irradiation pre-crosslinking treatment includes performing multi-stage negative pressure suction on the casting solution before ultraviolet irradiation, and the pressures of the multi-stage negative pressure suction are 0.05 MPa, 0.3 MPa and 0.5 MPa respectively.

8. The preparation method according to claim 1, characterized in that In the step 3, the at least two coagulation baths include: A first coagulation bath, wherein the solvent is a mixed solvent of ethanol and ethyl acetate in a volume ratio of 3:1, the temperature is 40°C, and the residence time is 2 minutes to 4 minutes, wherein the first coagulation bath is used to activate the covalent bond reaction between the surface active groups of the high-temperature resistant nanofiber skeleton and the isocyanate groups of the bio-based polyurethane; and The second coagulation bath has a solvent of a water / DMF mixed solvent with a water content of 70%, a temperature of 10°C, and a residence time of 3 to 5 minutes. The second coagulation bath is used to induce rapid desolvation of the bio-based polyurethane to form the through-microporous structure.

9. The preparation method according to claim 1, characterized in that In the step 4, the temperature of the post-curing treatment is 80° C., and the treatment time is 2 minutes.

10. The preparation method according to claim 1, characterized in that The total duration of step 3 is no more than 7 minutes.

Images