Polyurethane nanofiber waterproof and breathable membrane and its preparation method and application

Abstract

The present invention belongs to the field of textile technology and relates to a polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on its surface, its preparation method, and its application. The membrane is primarily prepared by electrospinning and surface growth methods. The polyurethane nanofiber membrane with silicone nanofilaments grown on its surface produced by the present invention achieves surface superhydrophobicity, good moisture permeability, high resistance to hydrostatic pressure, and excellent waterproof and breathable properties. The preparation method is simple and controllable, enabling large-scale production. Furthermore, the material does not contain the element F, making it suitable for use in the textile industry as a green, environmentally friendly, high-performance waterproof and breathable membrane.

Description

Technical Field

[0001] The invention belongs to the technical field of textiles and relates to a polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on the surface, and a preparation method and application thereof. Background Art

[0002] Waterproof and breathable functional fabrics are "breathable fabrics" that prevent the penetration of liquid water droplets while allowing water vapor to pass through, achieving a waterproof and breathable effect. Therefore, they are widely used in functional clothing such as jackets, fire suits, space suits, and surgical gowns. Waterproof and breathable functional fabrics can be divided into hydrophilic non-porous membranes and hydrophobic microporous membranes based on their waterproof and breathable mechanism. Hydrophobic microporous membranes have a large number of micropores on their surface, which prevent the passage of water droplets while allowing water molecules to pass through in single-molecule form. They have better waterproof and breathable properties and a much higher market share than hydrophilic non-porous membranes. A representative product of hydrophobic microporous membranes is Gore-Tex waterproof and breathable fabric produced by the American company Gore. Its waterproof and breathable fabric uses PTFE microporous film, which has good waterproof and breathable properties. However, PTFE has low elasticity and contains a large amount of F element, making the manufacturing process complex and environmentally polluting.

[0003] Polyurethane has excellent elasticity and durability, and its structure contains no F elements, making it an ideal alternative to PTFE. Electrospinning is a novel nanofiber membrane preparation technology that can be used to produce polyurethane nanofiber membranes, which can be used as hydrophobic, microporous, waterproof, and breathable membranes in textile applications. However, simple polyurethane nanofiber membranes suffer from insufficient hydrophobicity and low water pressure resistance. To further optimize and enhance the waterproof and breathable properties of polyurethane nanofiber membranes, it is necessary to further modify the surface to enhance their hydrophobicity and improve their waterproof and breathable properties. Summary of the Invention

[0004] In view of the problems existing in the prior art, the object of the present invention is to provide a polyurethane nanofiber waterproof and breathable membrane with surface-grown silicone nanofilaments having excellent waterproof performance, moisture permeability and water pressure resistance, and a preparation method thereof.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] One of the purposes of the present invention is to provide a method for preparing a polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on the surface, comprising the following steps:

[0007] (1) Preparation of electrospinning solution:

[0008] Polyurethane was dissolved in a mixed solution of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF) by stirring, and then a certain amount of tetraethoxysilane (TEOS) and concentrated hydrochloric acid were added dropwise. After stirring for a period of time, a silica sol-polyurethane composite electrospinning solution was obtained.

[0009] Furthermore, in step (1), the mass ratio of polyurethane in the electrospinning solution is 10% to 20%, the volume ratio of DMF and THF is 1:(0.5-2), the volume ratio of TEOS and concentrated hydrochloric acid is 1:(1-3), and the total mass ratio of TEOS and concentrated hydrochloric acid is 0.1% to 1%. Among them, the mass ratio of polyurethane in the electrospinning solution and the volume ratio of DMF and THF have an important influence on the morphology of the polyurethane nanofibers formed by spinning. For example, if the polyurethane concentration is too high, the viscosity of the spinning solution will be too high and it will be difficult to spray from the needle. If the concentration is too low, the viscosity of the spinning solution will be too low, and the nanofibers will present an unfavorable beaded structure. The parameter control of TEOS and concentrated hydrochloric acid is to control the content of silica sol in the spinning solution. If the silica sol content is too low, the subsequent growth sites of silicone nanofilaments will be reduced. If the silica sol content is too high, the morphology of the nanofibers will be affected. Therefore, more preferably, the mass ratio of polyurethane is 15%, the volume ratio of DMF and THF is 1:1, the volume ratio of TEOS and concentrated hydrochloric acid is 1:2, and the total mass ratio of TEOS and concentrated hydrochloric acid is 0.5%.

[0010] (2) Preparation of silica sol-doped polyurethane nanofiber membrane by electrospinning:

[0011] The silica sol-polyurethane composite electrospinning solution is loaded into a syringe with a metal needle, and an aluminum foil roller is selected as the receiver. Under the action of a high-voltage electric field, the spinning solution is ejected from the needle and solidified on the aluminum foil surface to form a nanofiber membrane, finally obtaining a silica sol-doped polyurethane nanofiber membrane.

[0012] Furthermore, in step (2), the high-voltage power supply voltage is 10 to 30 kV, the extrusion rate of the spinning solution is 0.1 to 1 mL / h, the distance between the needle and the aluminum foil is 10 to 40 cm, and the rolling speed of the receiving roller is 60 to 300 r / min. Among them, voltage, spinning solution extrusion rate, the distance between the needle and the aluminum foil, and the rolling speed of the receiving roller are common control parameters for electrospinning. The optimization and control of these parameters have an important influence on the morphology and size of the polyurethane nanofibers. Therefore, more preferably, the high-voltage power supply voltage is 17 kV, the extrusion rate of the spinning solution is 0.5 mL / h, the distance between the needle and the aluminum foil is 24 cm, and the rolling speed of the receiving roller is 200 r / min.

[0013] (3) Preparation of polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on the surface:

[0014] A certain amount of water and trichloromethylsilane (TCMS) are added to toluene, and then the silica sol-doped polyurethane nanofiber membrane is immersed in the solution. After sealing, it is placed in an oven for constant temperature reaction to obtain the target product, a polyurethane nanofiber waterproof and moisture-permeable membrane with silicone nanofilaments grown on the surface.

[0015] Further, in step (3), the volume ratio of water to TCMS is 1: (5-20), the total mass ratio of water to TCMS in toluene is 0.5%-2%, the isothermal reaction temperature is 30°C-80°C, and the isothermal reaction time is 2-20h. The selection of a series of parameters in this step determines the growth of silicone nanowires on the surface of polyurethane nanofibers. The thickness, length, and loading of silicone nanowires can be effectively controlled by regulating the solution, temperature, and time. Silicone nanowires have excellent hydrophobic properties. Growing silicone nanowires on the surface of polyurethane nanofiber membranes can further improve their hydrophobic properties. However, excessive growth of silicone nanowires (for example, by increasing the concentration of TCMS, reaction temperature, and reaction time) can seriously clog the pores of the nanofiber membrane and affect its moisture permeability. Therefore, taking into account both waterproof and moisture permeability, it is more preferred that the volume ratio of water to TCMS is 1: 10, the total mass ratio of water to TCMS in toluene is 1%, the isothermal reaction temperature is 60°C, and the isothermal reaction time is 8h.

[0016] The second object of the present invention is to provide a polyurethane nanofiber waterproof and moisture-permeable membrane with silicone nanofilaments grown on the surface, which is prepared by the above-mentioned preparation method.

[0017] The third purpose of the present invention is to provide a polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on the surface for use in the field of textiles, which can effectively improve the waterproof performance and water pressure resistance of the polyurethane nanofiber membrane.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) Some previously reported waterproof and breathable membranes are often constructed by surface immersion, spraying, lamination of hydrophobic materials, etc. The waterproof and breathable membrane developed in this invention is constructed by seed embedding and in-situ growth, which has higher composite structural strength and stability. In addition, the polyurethane nanofiber waterproof and breathable membrane with surface-grown silicone nanofilaments developed in this project also has the advantages of simple preparation method, controllable process conditions, good reproducibility, and high yield.

[0020] (2) Compared with the F-containing waterproof and breathable membrane material, the polyurethane nanofiber waterproof and breathable membrane with surface-grown silicone nanofilaments developed by the present invention has unique compositional advantages. The silicone nanofilaments grown on the surface of the polyurethane nanofiber membrane not only have excellent hydrophobicity, but also do not contain F elements. While keeping the raw materials green and environmentally friendly, it effectively improves the waterproof performance and water pressure resistance of the nanofiber membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the SEM image of the polyurethane nanofiber membrane.

[0022] Figure 2 This is the SEM image of the polyurethane nanofiber membrane with silicone nanofilaments grown on the surface.

[0023] Figure 3 This is the water drop contact angle diagram of polyurethane nanofiber membrane.

[0024] Figure 4 This is the contact angle diagram of a water droplet on a polyurethane nanofiber membrane with silicone nanofilaments grown on the surface. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0026] Example 1:

[0027] Synthesis of polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on the surface:

[0028] (1) Preparation of electrospinning solution:

[0029] 1.5 g of polyurethane was stirred and dissolved in a mixed solution of 9 mL of DMF and THF (4.5 mL of DMF and THF respectively), and then 0.005 mL of TEOS and 0.01 mL of concentrated hydrochloric acid were added dropwise. TEOS and hydrochloric acid underwent hydrolysis and condensation reaction, and silica sol (i.e., nanosilica) was gradually generated in the solution. After stirring for 4 h, a silica sol-polyurethane composite electrospinning solution was obtained.

[0030] (2) Preparation of silica sol-doped polyurethane nanofiber membrane by electrospinning:

[0031] An electrospinning apparatus was constructed, and the electrospinning solution was loaded into a syringe. Under the influence of a high-voltage electric field, the solution was stretched and extended in air, ultimately solidifying into nanofibers on the aluminum foil of the receiving device. The high-voltage power supply voltage was 17 kV, the extrusion rate of the spinning solution was 0.5 mL / h, the distance between the needle and the aluminum foil was 24 cm, and the receiving drum was rotated at a speed of 200 rpm. After the electrospinning process, the nanofiber membrane was vacuum dried in a drying oven to obtain a silica sol-doped polyurethane nanofiber membrane.

[0032] (3) Preparation of polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on the surface:

[0033] 100 μL of water and 1 mL of TCMS were added to 400 mL of toluene, and then the silica sol-doped polyurethane nanofiber membrane was immersed in the solution. After sealing, it was placed in an oven at a constant temperature of 60°C for reaction for 8 hours. TCMS underwent hydrolysis and condensation reaction with water in the toluene solution, and silicone nanofilaments grew on the surface of the polyurethane nanofiber membrane. The silica sol on the surface of the polyurethane nanofiber membrane provided growth sites for the in-situ growth of silicone nanofilaments. The chemical name of silicone nanofilaments is polysiloxane, which is a polymer material with excellent hydrophobic properties. Therefore, a polyurethane nanofiber waterproof and moisture-permeable membrane with silicone nanofilaments grown on the surface of the target product was obtained.

[0034] In contrast, a pure polyurethane nanofiber membrane was prepared by electrospinning. The preparation conditions were consistent with those of the silica sol-doped polyurethane nanofiber membrane, except that TEOS and concentrated hydrochloric acid were not added during the preparation of the spinning solution. Figure 1 This is an SEM image of a polyurethane nanofiber membrane. The size of the nanofibers is between 200–300 nm. The fibers are stacked on top of each other to form a large number of pores. This non-woven fiber structure is conducive to the permeation of water vapor. Figure 2 This is an SEM image of a polyurethane nanofiber membrane with silicone nanofilaments grown on the surface. It can be observed that a large number of silicone nanofilaments are grown on the surface of the polyurethane nanofibers. The size of the nanofilaments is about 30nm. Due to the small size of the nanofilaments, it has little effect on the porosity between the nanofibers.

[0035] Example 2:

[0036] The polyurethane nanofiber membrane with silicone nanofilaments grown on the surface prepared in Example 1 was used as a waterproof and breathable membrane to test its waterproof and breathable properties. A simple polyurethane nanofiber membrane was also tested as a comparative sample.

[0037] Figure 3 This is a photo of the water droplet contact angle of the polyurethane nanofiber membrane. It can be observed that the polyurethane nanofiber membrane has a certain hydrophobicity, and the water droplet contact angle is 115°. Figure 4 This photograph shows the contact angle of a water droplet on a polyurethane nanofiber membrane with silicone nanofilaments grown on its surface. Compared to the polyurethane nanofiber membrane, the membrane with silicone nanofilaments exhibits significantly enhanced hydrophobicity, with the water droplet contact angle increasing to 160°, achieving super-hydrophobic properties. This enhanced hydrophobicity is attributed to two factors: silicone itself is a highly hydrophobic material, and the growth of silicone nanofilaments on the nanofiber surface increases the overall surface roughness of the membrane, further enhancing its surface hydrophobicity.

[0038] The moisture permeability and water pressure resistance of polyurethane nanofiber membrane and polyurethane nanofiber membrane with silicone nanofilaments grown on the surface were tested. The moisture permeability of polyurethane nanofiber membrane is 13.6kg / (m 2 d), the water vapor permeability of the polyurethane nanofiber membrane with silicone nanofilaments grown on the surface is 12.8 kg / (m 2 d); The hydrostatic pressure resistance of the polyurethane nanofiber membrane is 46kPa, and the hydrostatic pressure resistance of the polyurethane nanofiber membrane with silicone nanofilaments grown on the surface is 72kPa. From the test results, it can be seen that after the silicone nanofilaments are grown on the surface, the water vapor permeability of the polyurethane nanofiber decreases slightly, from 13.6kg / (m 2 d) slightly decreased to 12.8kg / (m 2 d), indicating that silicone nanofilaments have little effect on the pore size of the polyurethane nanofiber membrane. In contrast, its hydrostatic pressure resistance has significantly increased, from 46 kPa to 72 kPa. This is primarily due to the transformation of the polyurethane nanofiber membrane's surface from hydrophobic to superhydrophobic after the silicone nanofilaments are grown, with the hydrophobic angle increasing from 115° to 160°. Comprehensively considering various performance indicators, surface-grown silicone nanofilaments can significantly enhance the waterproof and breathable properties of polyurethane nanofiber membranes. The preparation method is simple and controllable, amenable to large-scale production, and the material does not contain the element F, making it suitable for use as a green, high-performance waterproof and breathable membrane in textile applications.

Claims

1. A method for preparing a polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on the surface, characterized in that: The following steps are involved: (1) Preparation of electrospinning solution: Polyurethane was dissolved in a mixed solution of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF) by stirring, and then a certain amount of tetraethoxysilane (TEOS) and concentrated hydrochloric acid were added dropwise. After stirring for a period of time, a silica sol-polyurethane composite electrospinning solution was obtained; (2) Preparation of silica sol-doped polyurethane nanofiber membrane by electrospinning: The silica sol-polyurethane composite electrospinning solution was loaded into a syringe with a metal needle, and an aluminum foil roller was selected as a receiver. Under the action of a high-voltage electric field, the spinning solution was ejected from the needle and solidified on the aluminum foil surface to form a nanofiber membrane, ultimately obtaining a silica sol-doped polyurethane nanofiber membrane. (3) Preparation of polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on the surface: A certain amount of water and trichloromethylsilane (TCMS) are added to toluene, and then the silica sol-doped polyurethane nanofiber membrane is immersed in the solution. After sealing, it is placed in an oven for constant temperature reaction to obtain the target product, a polyurethane nanofiber waterproof and moisture-permeable membrane with silicone nanofilaments grown on the surface.

2. The method for preparing a polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on the surface according to claim 1, characterized in that: In step (1), the mass ratio of polyurethane in the electrospinning solution is 10% to 20%, the volume ratio of DMF to THF is 1:(0.5-2), the volume ratio of TEOS to concentrated hydrochloric acid is 1:(1-3), and the total mass ratio of TEOS to concentrated hydrochloric acid is 0.1% to 1%; In step (2), the voltage of the high-voltage power supply is 10 to 30 kV, the extrusion rate of the spinning solution is 0.1 to 1 mL / h, the distance between the needle and the aluminum foil is 10 to 40 cm, and the rolling speed of the receiving roller is 60 to 300 r / min; In step (3), the volume ratio of water to TCMS is 1:(5-20), the total mass ratio of water and TCMS in toluene is 0.5%-2%, the isothermal reaction temperature is 30°C-80°C, and the isothermal reaction time is 2-20h.

3. A polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on its surface, which is prepared by the preparation method according to any one of claims 1-2.

4. Application of the polyurethane nanofiber waterproof and breathable membrane with silicone nanofilaments grown on the surface as claimed in claim 3 in the field of textiles.

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