Fluorine-free waterproof and moisture-permeable electrospun nanofiber membrane and preparation method thereof

Abstract

The application discloses a fluorine-free waterproof and moisture-permeable electrostatic spinning nanofiber membrane and a preparation method thereof, relates to the technical field of polymer materials, and is prepared through coaxial electrostatic spinning of a spinning solution, wherein the spinning solution comprises polyurethane solution and organic polysiloxane solution in a mass ratio of 100:(5-7); the polyurethane solution comprises 5-30 parts of polyurethane and 70-95 parts of solvent A by weight; the organic polysiloxide solution comprises 1-30 parts of thermosetting organic polysiloxane, 0-10 parts of a crosslinking agent and 60-99 parts of solvent B by weight; and the thermosetting organic polysiloxane is hyperbranched polydimethylsiloxane with a vinyl group or an epoxy functional group at the end. The fluorine-free waterproof and moisture-permeable membrane of the polyurethane-silicone core-shell nanofiber with polyurethane as the core and crosslinked silicone resin as the shell is prepared through coaxial electrostatic spinning and in-situ drying and crosslinking, has the advantages of small fiber diameter, large specific surface area, small pore size and high porosity, and can effectively prolong the waterproof and durable effect.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, and in particular to a fluorine-free, waterproof, breathable electrospun nanofiber membrane and its preparation method. Background Technology

[0002] Outdoor skiwear, mountaineering clothing, sailing suits, and workwear protective clothing are demanding increasingly higher performance from functional, waterproof, and breathable fabrics. Electrospun polyurethane nanofiber membranes are a new type of breathable porous fiber membrane with good mechanical properties, but their hydrostatic pressure resistance is poor.

[0003] In existing technologies, nanofiber membranes prepared by electrospinning a mixture of polyurethane and fluorinated materials can effectively improve surface hydrophobicity and thus enhance the waterproof performance of the membrane. However, research has also found that nanofiber membranes prepared by electrospinning a mixture of polyurethane and fluorine-free materials such as soluble organosilicon can effectively improve surface hydrophobicity, thereby enhancing the waterproof performance of the membrane.

[0004] However, fluorine-containing materials pose persistent pollution and irreversible health risks, and the nanofiber membranes prepared by electrospinning a mixture of polyurethane and soluble organosilicon and other fluorine-free materials have shortcomings in terms of reduced waterproof performance after repeated washing, which need to be improved. Summary of the Invention

[0005] In view of this, the first objective of this application is to provide a fluorine-free, waterproof, and breathable electrospun nanofiber membrane to significantly extend waterproof durability and improve breathability. The specific solution is as follows: A fluorine-free, waterproof, and breathable electrospun nanofiber membrane is prepared by coaxial electrospinning using a spinning solution. The spinning solution comprises a polyurethane solution and an organopolysiloxane solution in a mass ratio of 100:(5-7). The polyurethane solution comprises 5-30 parts by weight of polyurethane and 70-95 parts by weight of solvent A. The organopolysiloxane solution comprises 1-30 parts by weight of thermosetting organopolysiloxane, 0-10 parts by weight of crosslinking agent, and 60-99 parts by weight of solvent B. The thermosetting organopolysiloxane is a hyperbranched polydimethylsiloxane with vinyl or epoxy functional groups at the end groups.

[0006] Preferably, the polyurethane is a polyether-type, polyester-type, or polycarbonate-type polyurethane; the solvent A is one or a mixture of tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0007] Preferably, the polyurethane undergoes in-situ synchronous grafting treatment with isocyanate, and the grafting treatment steps include: Step ① mixing 0.3-2.5 parts by weight of hydroxysilane coupling agent with 5-10 parts by weight of solvent A, and adding 0.02-0.05 parts by weight of deionized water, stirring at a controlled temperature of 35-45℃ and a rotation speed of 250-350 r / min for 30-60 min to obtain a pre-activated silane body; Step ② mixing 5-30 parts by weight of polyurethane with 15-30 parts by weight of solvent A, stirring at a controlled temperature of 45-55℃ and a rotation speed of 350-450 r / min to dissolve, and then adding the pre-activated silane body dropwise at a controlled dropping rate of 0.5-1 mL / min. n, and after the addition is completed, continue stirring for 1-1.5h to obtain a mixture; Step ③: Add 0.5-3 parts of isocyanate modifier and 0.03-0.08 parts of crosslinking accelerator to the mixture, control the pH to 7.5-8.5, the temperature to 60-70℃, and keep stirring for 2.5-4h to obtain silane coupling agent / isocyanate graft crosslink; Step ④: Control the temperature of silane coupling agent / isocyanate graft crosslink to 30-40℃, add 0.1-0.3 parts of methanol and stir for 15-20min, and then degas at 30-40℃ and vacuum of 0.06-0.08MPa for 30-60min to obtain modified polyurethane solution.

[0008] Preferably, the weight ratio of the isocyanate modifier to the hydroxysilane coupling agent is (1.2-1.5):1; the polyurethane is a polyether-type or polycarbonate-type polyurethane.

[0009] Preferably, the thermosetting organopolysiloxane is grafted with a fluorine-free hydrophobic modifier, and the grafting modification step includes step ① mixing 1-30 parts by weight of the thermosetting organopolysiloxane and 10-35 parts by weight of solvent B, controlling the temperature at 30-40℃ and stirring at 200-300 r / min to dissolve, thereby obtaining an organopolysiloxane material solution; step ② adding 0.1-3 parts by weight of solvent B to the organopolysiloxane material solution. A fluorine-free hydrophobic modifier and 0.05-0.2 parts by weight of catalyst are added to the modified body. The temperature is raised to 50-60℃ and the mixture is kept at this temperature and stirred for 1-2 hours to obtain the modified body. In step ③, 0-10 parts by weight of crosslinking agent and the remaining solvent B are added to the modified body. After stirring evenly, the mixture is degassed at a controlled temperature of 25-35℃ and a vacuum of 0.05-0.07MPa for 20-40 minutes to obtain a modified thermosetting organopolysiloxane solution.

[0010] Preferably, the crosslinking agent is one or a mixture of organoplasmic compounds, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride.

[0011] Preferably, solvent B is one or more of cyclohexane, n-hexane, and dioxane.

[0012] The second objective of this invention is to provide a method for preparing a fluorine-free, waterproof, and breathable electrospun nanofiber membrane, comprising coaxial electrospinning a polyurethane solution and a thermosetting organopolysiloxane solution to obtain a polyurethane-silicone core-shell nanofiber membrane with a polyurethane core and a silicone resin shell, and then drying it with hot air to obtain a fluorine-free, waterproof, and breathable electrospun nanofiber membrane.

[0013] Preferably, the core layer advance speed of the coaxial electrospinning is 0.8-1.5 mL / h, the shell layer advance speed is 0.05-0.1 mL / h, the spinning voltage is 18-25 kV, the receiving distance is 15-20 cm, and the ambient temperature is 25-30℃ and the relative humidity is 40%-60%.

[0014] Preferably, the hot air drying temperature is 80-90℃ and the time is 2-10 minutes.

[0015] As can be seen from the above scheme, this application provides a fluorine-free, waterproof, and breathable electrospun nanofiber membrane and its preparation method. The fluorine-free, waterproof, and breathable electrospun nanofiber membrane has the following beneficial effects: 1. A fluorine-free waterproof and breathable membrane with polyurethane core and cross-linked silicone resin nanofibers as the core and cross-linked silicone resin as the shell was prepared by coaxial electrospinning and in-situ drying and cross-linking. It has the characteristics of small fiber diameter, large specific surface area, small pore size and high porosity, which effectively prolongs the waterproof durability. 2. By simultaneously grafting polyurethane with isocyanate in situ, hydrogen bonds are formed between the hydroxysilane coupling agent and the polyurethane molecular chain. The isocyanate simultaneously achieves grafting and cross-linking, introducing siloxane groups into the polyurethane molecular chain. Furthermore, after the thermosetting organopolysiloxane is grafted and modified with a fluorine-free hydrophobic modifier, it forms a cross-linked interpenetrating network with the modified polyurethane solution, thereby improving the compatibility between components and the stability of the membrane structure. 3. By using thermosetting organopolysiloxane, the abundant terminal functional groups enhance the thermosetting speed and allow for initial curing during spinning. It also forms a high crosslinking density in conjunction with the hyperbranched structure, resulting in a dense hydrophobic surface layer. Furthermore, it undergoes crosslinking and curing during hot air drying, tightly bonding with the modified polyurethane core layer. This prevents the loss of silicone resin during washing, ensuring that it maintains a high contact angle and waterproof rating even after multiple washes, thus maintaining long-term waterproof performance. 4. By using coaxial electrospinning, the mechanical strength and elasticity of the modified polyurethane core layer in the core-shell structure are significantly improved after cross-linking, providing good support for the membrane and preventing fiber breakage. In addition, the ether / carbonate bonds in the polyurethane molecular chain are hydrophilic, thereby enabling water vapor permeation. The microporous channels formed by the hyperbranched organosilicon shell do not hinder water vapor transfer, thus achieving good moisture permeability and good flexibility and tensile strength. Detailed Implementation

[0016] The technical solutions described below in conjunction with the embodiments of this application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0017] It should be mentioned that in the in-situ synchronous grafting treatment of polyurethane with isocyanate, the hydroxysilane coupling agent is at least one of γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, and in the embodiments of this application, the hydroxysilane coupling agent is γ-aminopropyltriethoxysilane, and the degree of hydrolysis of the silane coupling agent in the pre-activated silane body is controlled to be 30-50%, and the degree of hydrolysis is adjusted by the amount of deionized water added. The isocyanate modifier is one of toluene diisocyanate and diphenylmethane diisocyanate, and the crosslinking accelerator is one of triethylamine and dimethylbenzylamine; and in the embodiments of this application, the isocyanate modifier is toluene diisocyanate, and the crosslinking accelerator is dimethylbenzylamine.

[0018] In the grafting modification of thermosetting organopolysiloxanes with fluorine-free hydrophobic modifiers, the catalyst is dibutyltin dilaurate or stannous octoate. In the embodiments of this application, the selected fluorine-free hydrophobic modifier is potassium perfluorobutylsulfonylimide purchased from Haishi Chemical Co., Ltd., and the catalyst is dibutyltin dilaurate. Furthermore, the hyperbranched polydimethylsiloxane with vinyl or epoxy functional groups at the end groups in the embodiments of this application specifically uses epoxy-terminated polydimethylsiloxane purchased from Guangdong Daxiao Chemical Co., Ltd.

[0019] The following will provide a detailed description of a fluorine-free, waterproof, breathable electrospun nanofiber membrane and its preparation method.

[0020] A fluorine-free, waterproof, and breathable electrospun nanofiber membrane is prepared by coaxial electrospinning using a spinning solution. The spinning solution comprises a polyurethane solution and an organopolysiloxane solution in a mass ratio of 100:(5-7). The polyurethane solution comprises 5-30 parts by weight of polyurethane and 70-95 parts by weight of solvent A.

[0021] In the polyurethane solution, the polyurethane is a polyether-type, polyester-type, or polycarbonate-type polyurethane. Solvent A is one or a mixture of tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide. Furthermore, to further improve waterproof durability and breathability, the polyurethane undergoes in-situ simultaneous grafting treatment with isocyanate in this embodiment. The grafting treatment steps include: Step ① mixing 0.3-2.5 parts by weight of hydroxysilane coupling agent with 5-10 parts by weight of solvent A, adding 0.02-0.05 parts by weight of deionized water, and stirring for 30-60 minutes at a controlled temperature of 35-45°C and a rotation speed of 250-350 r / min to obtain a pre-activated silane body; Step ② mixing 5-30 parts by weight of polyurethane with 15-30 parts by weight of solvent A, stirring to dissolve at a controlled temperature of 45-55°C and a rotation speed of 350-450 r / min, and then adding the pre-activated silane body dropwise, controlling the dropwise addition rate to be 0. Step 3: Add 0.5-1 mL / min of isocyanate modifier and 0.03-0.08 parts of crosslinking accelerator to the mixture. Control the pH at 7.5-8.5 and the temperature at 60-70℃, and stir for 2.5-4 hours to obtain a silane coupling agent / isocyanate graft crosslink. Step 4: Control the temperature of the silane coupling agent / isocyanate graft crosslink at 30-40℃, add 0.1-0.3 parts of methanol and stir for 15-20 minutes. Then, degas at 30-40℃ and a vacuum of 0.06-0.08 MPa for 30-60 minutes to obtain a modified polyurethane solution. In the grafting treatment, the weight ratio of isocyanate modifier to hydroxysilane coupling agent is (1.2-1.5):1. The polyurethane is a polyether-type or polycarbonate-type polyurethane.

[0022] The organopolysiloxane solution comprises 1-30 parts by weight of thermosetting organopolysiloxane, 0-10 parts by weight of crosslinking agent, and 60-99 parts by weight of solvent B.

[0023] In the organopolysiloxane solution, the crosslinking agent is one or more of the following: organoplasmic compound, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride. Solvent B is one or more of the following: cyclohexane, n-hexane, and dioxane.

[0024] The thermosetting organopolysiloxane is a hyperbranched polydimethylsiloxane with vinyl or epoxy functional groups at the end groups. To further improve waterproof durability and breathability, the thermosetting organopolysiloxane is grafted with a fluorine-free hydrophobic modifier. The grafting modification process includes: Step ① mixing 1-30 parts by weight of the thermosetting organopolysiloxane and 10-35 parts by weight of solvent B, controlling the temperature at 30-40℃ and stirring at 200-300 r / min to dissolve, obtaining an organopolysiloxane material solution; Step ② adding [amount missing] by weight of [missing information] to the organopolysiloxane material solution. The modified body is obtained by adding 0.1-3 parts of fluorine-free hydrophobic modifier and 0.05-0.2 parts of catalyst by weight, raising the temperature to 50-60℃, and stirring for 1-2 hours. In step ③, 0-10 parts by weight of crosslinking agent and the remaining solvent B are added to the modified body. After stirring evenly, the body is degassed at a controlled temperature of 25-35℃ and a vacuum of 0.05-0.07MPa for 20-40 minutes to obtain a modified thermosetting organopolysiloxane solution.

[0025] A method for preparing a fluorine-free, waterproof, and breathable electrospun nanofiber membrane includes coaxial electrospinning of a polyurethane solution and a thermosetting organopolysiloxane solution to obtain a polyurethane-silicone core-shell nanofiber membrane with a polyurethane core and a silicone resin shell, followed by hot air drying to obtain the fluorine-free, waterproof, and breathable electrospun nanofiber membrane. The core layer advance speed during coaxial electrospinning is 0.8-1.5 mL / h, the shell layer advance speed is 0.05-0.1 mL / h, the spinning voltage is 18-25 kV, the receiving distance is 15-20 cm, and the ambient temperature is 25-30℃ with a relative humidity of 40%-60%. The hot air drying temperature is controlled at 80-90℃ for 2-10 min.

[0026] Example 1

[0027] A fluorine-free, waterproof, and breathable electrospun nanofiber membrane is prepared by coaxial electrospinning using a spinning solution. The spinning solution comprises a polyurethane solution and an organopolysiloxane solution in a mass ratio of 100:6. The polyurethane solution comprises 15 parts by weight of polyurethane and 85 parts by weight of solvent A.

[0028] In the polyurethane solution, the polyurethane is a polyether-type polyurethane. Solvent A is a mixed solvent of tetrahydrofuran and N,N-dimethylformamide, with a mixing mass ratio of 1:1. Furthermore, in this application embodiment, to further improve waterproof durability and breathability, the polyurethane undergoes in-situ synchronous grafting treatment with isocyanate. The grafting treatment steps include: Step ① mixing 1.4 parts by weight of hydroxysilane coupling agent with 7 parts by weight of solvent A, adding 0.03 parts by weight of deionized water, and stirring at a controlled temperature of 40°C and a rotation speed of 300 r / min for 45 min to obtain a pre-activated silane body; Step ② mixing 15 parts by weight of polyurethane with 22 parts by weight of solvent A, stirring at a controlled temperature of 50°C and a rotation speed of 400 r / min to dissolve, and then adding the pre-activated silane body dropwise, controlling the dropwise addition. The addition rate was 0.7 mL / min, and stirring continued for 1.2 h after the addition was complete to obtain a mixture. Step ③ involved adding 1.8 parts of isocyanate modifier and 0.05 parts of crosslinking accelerator to the mixture. The pH was controlled at 8.0, the temperature at 65℃, and the mixture was stirred for 3 h to obtain a silane coupling agent / isocyanate graft crosslink. Step ④ involved controlling the temperature of the silane coupling agent / isocyanate graft crosslink at 35℃, adding 0.2 parts of methanol and stirring for 18 min, followed by degassing at 35℃ and a vacuum of 0.07 MPa for 45 min to obtain a modified polyurethane solution. In the grafting treatment, the weight ratio of isocyanate modifier to hydroxysilane coupling agent was 1.3:1. The polyurethane was a polyether-type polyurethane.

[0029] The organopolysiloxane solution comprises 15 parts by weight of thermosetting organopolysiloxane, 5 parts by weight of crosslinking agent, and 80 parts by weight of solvent B.

[0030] In the organopolysiloxane solution, the crosslinking agent is an organoplasmic compound. Solvent B is cyclohexane.

[0031] The thermosetting organopolysiloxane is a hyperbranched polydimethylsiloxane with vinyl end groups. To further improve waterproof durability and breathability, the thermosetting organopolysiloxane is grafted with a fluorine-free hydrophobic modifier. The grafting modification process includes: Step ① mixing 15 parts by weight of the thermosetting organopolysiloxane and 22 parts by weight of solvent B, stirring at 35°C and 250 r / min to dissolve, obtaining an organopolysiloxane material solution; Step ② adding 1.5 parts by weight of fluorine-free hydrophobic modifier and 0.12 parts by weight of catalyst to the organopolysiloxane material solution, raising the temperature to 55°C, and stirring for 1.5 h to obtain a modified body; Step ③ adding 5 parts by weight of crosslinking agent and the remaining solvent B to the modified body, stirring until homogeneous, and then degassing at 30°C and a vacuum of 0.06 MPa for 30 min to obtain a modified thermosetting organopolysiloxane solution.

[0032] A method for preparing a fluorine-free, waterproof, and breathable electrospun nanofiber membrane includes coaxial electrospinning of a polyurethane solution and a thermosetting organopolysiloxane solution to obtain a polyurethane-silicone core-shell nanofiber membrane with a polyurethane core and a silicone resin shell, followed by hot air drying to obtain the fluorine-free, waterproof, and breathable electrospun nanofiber membrane. The core layer advance speed during coaxial electrospinning is 1.1 mL / h, the shell layer advance speed is 0.07 mL / h, the spinning voltage is 22 kV, the receiving distance is 17 cm, and the ambient temperature is 27℃ with a relative humidity of 50%. The hot air drying temperature is controlled at 85℃ for 6 min.

[0033] Example 2

[0034] A fluorine-free, waterproof, and breathable electrospun nanofiber membrane is prepared by coaxial electrospinning using a spinning solution. The spinning solution comprises a polyurethane solution and an organopolysiloxane solution in a mass ratio of 100:5. The polyurethane solution comprises 5 parts by weight of polyurethane and 95 parts by weight of solvent A.

[0035] In the polyurethane solution, the polyurethane is a polycarbonate type polyurethane. Solvent A is N,N-dimethylacetamide. Furthermore, to further improve waterproof durability and breathability, the polyurethane in this application embodiment undergoes in-situ simultaneous grafting treatment with isocyanate. The grafting treatment steps include: Step ① mixing 0.3 parts by weight of hydroxysilane coupling agent with 5 parts by weight of solvent A, adding 0.02 parts by weight of deionized water, and stirring at a controlled temperature of 35°C and a rotation speed of 250 r / min for 30 min to obtain a pre-activated silane body; Step ② mixing 5 parts by weight of polyurethane with 15 parts by weight of solvent A, stirring at a controlled temperature of 45°C and a rotation speed of 350 r / min to dissolve, and then adding the pre-activated silane body dropwise, controlling the dropwise addition. The addition rate was 0.5 mL / min, and stirring continued for 1 h after the addition was complete to obtain a mixture. Step ③: 0.5 parts of isocyanate modifier and 0.03 parts of crosslinking accelerator were added to the mixture. The pH was controlled at 7.5, the temperature at 60℃, and the mixture was stirred for 2.5 h to obtain a silane coupling agent / isocyanate graft crosslink. Step ④: The temperature of the silane coupling agent / isocyanate graft crosslink was controlled at 30℃, 0.1 parts of methanol were added and stirred for 15 min, followed by degassing treatment at 30℃ and a vacuum of 0.06 MPa for 30 min to obtain a modified polyurethane solution. In the grafting treatment, the weight ratio of isocyanate modifier to hydroxysilane coupling agent was 1.2:1. The polyurethane was a polycarbonate type polyurethane.

[0036] The organopolysiloxane solution comprises 1 part by weight of a thermosetting organopolysiloxane and 99 parts by weight of solvent B.

[0037] In the organopolysiloxane solution, solvent B is n-hexane.

[0038] Thermosetting organopolysiloxanes are hyperbranched polydimethylsiloxanes with epoxy functional groups at the end groups. Furthermore, to further enhance waterproof durability and breathability, the thermosetting organopolysiloxane was grafted with a fluorine-free hydrophobic modifier. The grafting modification process included: Step ① mixing 1 part by weight of the thermosetting organopolysiloxane and 10 parts by weight of solvent B, stirring at 30°C and 200 r / min to dissolve and obtain an organopolysiloxane material solution; Step ② adding 0.1 parts by weight of fluorine-free hydrophobic modifier and 0.05 parts by weight of catalyst to the organopolysiloxane material solution, raising the temperature to 50°C, and stirring for 1 hour to obtain the modified body; Step ③ adding 0 parts by weight of crosslinking agent and the remaining solvent B to the modified body, stirring evenly, and then degassing at 25°C and a vacuum of 0.05 MPa for 20 minutes to obtain the modified thermosetting organopolysiloxane solution.

[0039] A method for preparing a fluorine-free, waterproof, and breathable electrospun nanofiber membrane includes coaxial electrospinning of a polyurethane solution and a thermosetting organopolysiloxane solution to obtain a polyurethane-silicone core-shell nanofiber membrane with a polyurethane core and a silicone resin shell, followed by hot air drying to obtain the fluorine-free, waterproof, and breathable electrospun nanofiber membrane. The core layer advance speed during coaxial electrospinning is 0.8 mL / h, the shell layer advance speed is 0.05 mL / h, the spinning voltage is 18 kV, the receiving distance is 15 cm, and the ambient temperature is 25℃ with a relative humidity of 40%. The hot air drying temperature is controlled at 80℃ for 2 min.

[0040] Example 3

[0041] A fluorine-free, waterproof, and breathable electrospun nanofiber membrane is prepared by coaxial electrospinning using a spinning solution. The spinning solution comprises a polyurethane solution and an organopolysiloxane solution in a mass ratio of 100:7. The polyurethane solution comprises 30 parts by weight of polyurethane and 70 parts by weight of solvent A.

[0042] In the polyurethane solution, the polyurethane is a polyether-type polyurethane. Solvent A is a mixed solvent of tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide, with a mixing mass ratio of 1:1:1. Furthermore, in this application embodiment, to further improve waterproof durability and breathability, the polyurethane undergoes in-situ synchronous grafting treatment with isocyanate. The grafting treatment steps include: Step ① mixing 2.5 parts by weight of hydroxyl silane coupling agent with 10 parts by weight of solvent A, adding 0.05 parts by weight of deionized water, and stirring at a controlled temperature of 45°C and a rotation speed of 350 r / min for 60 min to obtain a pre-activated silane body; Step ② mixing 30 parts by weight of polyurethane with 30 parts by weight of solvent A, stirring at a controlled temperature of 55°C and a rotation speed of 450 r / min to dissolve, and then adding the pre-activated silane body dropwise. The dropping rate was set at 1 mL / min, and stirring was continued for 1.5 h after the dropping was completed to obtain a mixture. In step ③, 3 parts of isocyanate modifier and 0.08 parts of crosslinking accelerator were added to the mixture. The pH was controlled at 8.5, the temperature at 70℃, and the mixture was stirred for 4 h to obtain a silane coupling agent / isocyanate graft crosslink. In step ④, the temperature of the silane coupling agent / isocyanate graft crosslink was controlled at 40℃, 0.3 parts of methanol were added and stirred for 20 min, followed by degassing treatment at 40℃ and a vacuum of 0.08 MPa for 60 min to obtain a modified polyurethane solution. In the grafting treatment, the weight ratio of isocyanate modifier to hydroxysilane coupling agent was 1.5:1. The polyurethane was a polyether-type polyurethane.

[0043] The organopolysiloxane solution comprises 30 parts by weight of thermosetting organopolysiloxane, 10 parts by weight of crosslinking agent, and 60 parts by weight of solvent B.

[0044] In the organopolysiloxane solution, the crosslinking agent is a mixture of methyltetrahydrophthalic anhydride and methylhexahydrophthalic anhydride in a mass ratio of 1:1. Solvent B is a mixture of dioxane and cyclohexane in a mass ratio of 1:1.

[0045] The thermosetting organopolysiloxane is a hyperbranched polydimethylsiloxane with vinyl end groups. To further improve waterproof durability and breathability, the thermosetting organopolysiloxane is grafted with a fluorine-free hydrophobic modifier. The grafting modification process includes: Step ① mixing 30 parts by weight of the thermosetting organopolysiloxane and 35 parts by weight of solvent B, stirring at 40°C and 300 r / min to dissolve, obtaining an organopolysiloxane material solution; Step ② adding 3 parts by weight of fluorine-free hydrophobic modifier and 0.2 parts by weight of catalyst to the organopolysiloxane material solution, raising the temperature to 60°C, and stirring for 2 hours to obtain a modified body; Step ③ adding 10 parts by weight of crosslinking agent and the remaining solvent B to the modified body, stirring until homogeneous, and then degassing at 35°C and a vacuum of 0.07 MPa for 40 minutes to obtain a modified thermosetting organopolysiloxane solution.

[0046] A method for preparing a fluorine-free, waterproof, and breathable electrospun nanofiber membrane includes coaxial electrospinning of a polyurethane solution and a thermosetting organopolysiloxane solution to obtain a polyurethane-silicone core-shell nanofiber membrane with a polyurethane core and a silicone resin shell, followed by hot air drying to obtain the fluorine-free, waterproof, and breathable electrospun nanofiber membrane. The core layer advance speed during coaxial electrospinning is 1.5 mL / h, the shell layer advance speed is 0.1 mL / h, the spinning voltage is 25 kV, the receiving distance is 20 cm, and the ambient temperature is 30℃ with a relative humidity of 60%. The hot air drying temperature is controlled at 90℃ for 10 min.

[0047] Example 4

[0048] The difference between Example 4 and Example 1 is that in Example 4, the polyurethane was not subjected to in-situ synchronous grafting treatment with isocyanate, and the thermosetting organopolysiloxane was not subjected to grafting modification treatment with fluorine-free hydrophobic modifier.

[0049] Example 5

[0050] The difference between Example 5 and Example 1 is that the polyurethane in Example 5 was not subjected to in-situ synchronous grafting treatment with isocyanate.

[0051] Comparative Example 1 The difference between Comparative Example 1 and Example 4 is that in Comparative Example 1, polydimethylsiloxane is used instead of thermosetting organopolysiloxane.

[0052] Performance testing: 1. Hydrostatic pressure: According to ISO 811-2018 "Textiles - Hydrostatic pressure test", the initial water pressure test is set with a pressurization rate of 60 cmH2O / min; after washing, the sample must be washed first before the hydrostatic pressure test is performed. 2. Moisture permeability: According to ASTM E96BW-1995 "Test method for moisture permeability of fabrics (inverted cup method)", the test temperature was set to 23℃±2℃, the relative humidity was 50%±5%, and the test time was 24h. The initial moisture permeability and the moisture permeability after 10 washes were tested respectively. 3. Air permeability: Based on ISO 9237-1995 "Textiles - Determination of air permeability of fabrics", the test pressure difference was set at 100 Pa, and the test area was 20 cm². 2 The initial air permeability and the air permeability after 10 washes were tested respectively.

[0053] The performance test results are shown in Table 1 below.

[0054] Table 1 Performance Test Results

[0055] As shown in Table 1 above, regarding hydrostatic pressure, in Examples 1 to 3 of this application, the synergistic effect of polyurethane isocyanate graft modification and organopolysiloxane fluorine-free hydrophobic modification increases crosslinking density, reduces surface energy, and enhances waterproof stability. Example 4, without dual modification, relies solely on thermosetting organopolysiloxane and a core-shell structure, resulting in slightly lower waterproof performance. Example 5 retains organopolysiloxane modification, with performance between Examples 1 and 4. Comparative Example 1, due to the use of polydimethylsiloxane as a substitute, suffers from poor structural stability and insufficient interfacial compatibility, leading to a significant decrease in hydrostatic pressure and failure to meet waterproof requirements. Regarding moisture permeability, in Examples 1 to 3 of this application, dual modification optimizes pore distribution and reduces water vapor blockage, resulting in higher moisture permeability and less water washing attenuation. In Example 4, without modification, pores are prone to collapse and blockage, leading to slightly lower moisture permeability. Example 5, with hydrophobic modification, has higher moisture permeability than Example 4. In Comparative Example 1, the use of polydimethylsiloxane as a substitute led to fiber agglomeration and reduced porosity, thereby decreasing moisture permeability and washability. Regarding air permeability, Examples 1 to 3 of this application exhibited superior air permeability due to dual modification that prevented fiber agglomeration and maintained high porosity. Example 4, lacking modification, suffered from fiber agglomeration and reduced porosity, resulting in decreased air permeability. Example 5, modified with organopolysiloxane, demonstrated superior air permeability compared to Example 4. In Comparative Example 1, the use of polydimethylsiloxane as a substitute led to fiber agglomeration and swelling, significantly reducing air permeability.

[0056] Based on the above performance test results and analysis, it is evident that Examples 1 to 5 of this application exhibit minimal performance degradation during water washing. This is attributed to the three-dimensional network structure of the thermosetting organopolysiloxane and the high crosslinking degree of the modified polyurethane, which resists the mechanical effects of water washing. Furthermore, although Example 4 was not modified, the thermosetting organopolysiloxane still ensured basic water washing stability. In contrast, Comparative Example 1 suffers from easy swelling and peeling after water washing, resulting in a rapid decline in performance.

[0057] In summary, this application provides a fluorine-free waterproof and breathable electrospun nanofiber membrane and its preparation method. This fluorine-free waterproof and breathable electrospun nanofiber membrane is prepared by coaxial electrospinning, which significantly enhances the mechanical strength and elasticity of the cross-linked modified polyurethane core layer in the core-shell structure, providing good support for the membrane and preventing fiber breakage. Furthermore, the ether / carbonate bonds in the polyurethane molecular chain are hydrophilic, enabling water vapor permeation, and the microporous channels formed by the hyperbranched organosilicon shell do not hinder water vapor transfer, synergistically achieving good moisture permeability, and exhibiting good flexibility and tensile strength. The preparation method of this fluorine-free waterproof and breathable electrospun nanofiber membrane, through coaxial electrospinning and in-situ drying and cross-linking, yields a polyurethane-silicone resin core-shell nanofiber membrane with a polyurethane core and a cross-linked silicone resin shell. This membrane features small fiber diameter, large specific surface area, small pore size, and high porosity, effectively extending the waterproof durability. Secondly, by simultaneously grafting polyurethane with isocyanate in situ, hydrogen bonds are formed between the hydroxyl silane coupling agent and the polyurethane molecular chain. The isocyanate simultaneously performs grafting and cross-linking, introducing siloxane groups into the polyurethane molecular chain. Furthermore, the thermosetting organopolysiloxane, after being grafted with a fluorine-free hydrophobic modifier, forms a cross-linked interpenetrating network with the modified polyurethane solution, thereby improving the compatibility between components and the stability of the membrane structure. Simultaneously, the thermosetting organopolysiloxane, with its abundant terminal functional groups, accelerates the thermosetting process and can initially cure during spinning. It also synergistically forms a high cross-linking density with the hyperbranched structure, creating a dense hydrophobic surface layer. Further cross-linking and curing occur during hot air drying, tightly bonding with the modified polyurethane core layer. This prevents the loss of silicone resin during washing, maintaining a high contact angle and waterproof rating even after multiple washes, thus ensuring long-term waterproof performance. Therefore, this application utilizes a dual-synergistic approach of in-situ simultaneous dual modification of polyurethane and optimized modification of organopolysiloxanes, combined with coaxial electrospinning and in-situ drying crosslinking processes to prepare a fluorine-free, waterproof, and breathable nanofiber membrane. This not only avoids the pollution and health risks associated with fluorine-containing materials but also solves the technical problems of poor compatibility, water resistance degradation after washing, and functional imbalance in traditional fluorine-free membranes. Thus, the fluorine-free, waterproof, and breathable electrospun nanofiber membrane prepared in this application not only possesses durable waterproofing, high-efficiency breathability, and excellent mechanical properties, but also features a simple preparation method, low production cost, small fiber diameter, and reasonable pore structure, making it suitable for various applications such as clothing and protective gear, and demonstrating significant practical value and promising prospects for widespread application.

[0058] The terms “first,” “second,” “third,” “fourth,” etc., used in this application (if applicable) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, or apparatus that includes a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, or apparatus.

[0059] It should be noted that the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0060] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A fluorine-free, waterproof, and breathable electrospun nanofiber membrane, prepared by coaxial electrospinning of a spinning solution, characterized in that: The spinning solution comprises a polyurethane solution and an organopolysiloxane solution in a mass ratio of 100:(5-7); wherein the polyurethane solution comprises 5-30 parts by weight of polyurethane and 70-95 parts by weight of solvent A; the organopolysiloxane solution comprises 1-30 parts by weight of thermosetting organopolysiloxane, 0-10 parts by weight of crosslinking agent and 60-99 parts by weight of solvent B; the thermosetting organopolysiloxane is a hyperbranched polydimethylsiloxane with vinyl or epoxy functional groups at the end groups.

2. The fluorine-free, waterproof, and breathable electrospun nanofiber membrane according to claim 1, characterized in that: The polyurethane is a polyether-type, polyester-type, or polycarbonate-type polyurethane; the solvent A is one or a mixture of tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide.

3. The fluorine-free, waterproof, breathable, electrospun nanofiber membrane according to claim 2, characterized in that: The polyurethane is subjected to in-situ synchronous grafting treatment with isocyanate. The grafting treatment steps include: Step ① mixing 0.3-2.5 parts by weight of hydroxysilane coupling agent with 5-10 parts by weight of solvent A, and adding 0.02-0.05 parts by weight of deionized water. The mixture is stirred for 30-60 minutes at a controlled temperature of 35-45℃ and a stirring speed of 250-350 r / min to obtain a pre-activated silane body; Step ② mixing 5-30 parts by weight of polyurethane with 15-30 parts by weight of solvent A, and stirring to dissolve the mixture at a controlled temperature of 45-55℃ and a stirring speed of 350-450 r / min. The pre-activated silane body is then added dropwise at a controlled dropping rate of 0.5-1 mL / min. After the addition is complete, continue stirring for 1-1.5 hours to obtain a mixture; Step ③: Add 0.5-3 parts of isocyanate modifier and 0.03-0.08 parts of crosslinking accelerator to the mixture, control the pH to 7.5-8.5, the temperature to 60-70℃, and keep stirring for 2.5-4 hours to obtain a silane coupling agent / isocyanate graft crosslink; Step ④: Control the temperature of the silane coupling agent / isocyanate graft crosslink at 30-40℃, add 0.1-0.3 parts of methanol and stir for 15-20 minutes, then degas at 30-40℃ and a vacuum of 0.06-0.08 MPa for 30-60 minutes to obtain a modified polyurethane solution.

4. The fluorine-free, waterproof, and breathable electrospun nanofiber membrane according to claim 1, characterized in that: The weight ratio of the isocyanate modifier to the hydroxysilane coupling agent is (1.2-1.5):1; the polyurethane is a polyether-type or polycarbonate-type polyurethane.

5. The fluorine-free, waterproof, breathable, electrospun nanofiber membrane according to claim 1, characterized in that: The thermosetting organopolysiloxane is grafted with a fluorine-free hydrophobic modifier. The grafting modification process includes: Step ① mixing 1-30 parts by weight of the thermosetting organopolysiloxane and 10-35 parts by weight of solvent B, stirring at 30-40°C and 200-300 r / min to dissolve and obtain an organopolysiloxane material solution; Step ② adding 0.1-3 parts by weight of fluorine-free hydrophobic modifier and 0.05-0.2 parts by weight of catalyst to the organopolysiloxane material solution, raising the temperature to 50-60°C, and stirring for 1-2 hours to obtain a modified body; Step ③ adding 0-10 parts by weight of crosslinking agent and the remaining solvent B to the modified body, stirring evenly, and then degassing at 25-35°C and a vacuum of 0.05-0.07 MPa for 20-40 minutes to obtain a modified thermosetting organopolysiloxane solution.

6. The fluorine-free, waterproof, and breathable electrospun nanofiber membrane according to claim 1, characterized in that: The crosslinking agent is one or a mixture of organoplasmic compounds, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride.

7. The fluorine-free, waterproof, breathable, electrospun nanofiber membrane according to claim 1, characterized in that: Solvent B is one or more of cyclohexane, n-hexane, and dioxane.

8. A method for preparing a fluorine-free, waterproof, and breathable electrospun nanofiber membrane, characterized in that: This includes obtaining a polyurethane-silicone core-shell nanofiber membrane with a polyurethane core and a silicone resin shell by coaxial electrospinning of a polyurethane solution and a thermosetting organopolysiloxane solution, and then obtaining a fluorine-free, waterproof, and breathable electrospun nanofiber membrane by hot air drying.

9. The method for preparing a fluorine-free, waterproof, and breathable electrospun nanofiber membrane according to claim 8, characterized in that: The coaxial electrospinning core layer advance speed is 0.8-1.5 mL / h, the shell layer advance speed is 0.05-0.1 mL / h, the spinning voltage is 18-25 kV, the receiving distance is 15-20 cm, and the ambient temperature is 25-30℃ and the relative humidity is 40%-60%.

10. The method for preparing a fluorine-free, waterproof, and breathable electrospun nanofiber membrane according to claim 8, characterized in that: The hot air drying temperature is 80-90℃, and the time is 2-10 minutes.

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