A one-way moisture guiding Janus fiber membrane and a method for preparing the same

Abstract

The application discloses a one-way wet guiding Janus fiber membrane and a preparation method thereof. The one-way wet guiding Janus fiber membrane is a double-layer composite two-side heterogeneous membrane material, comprising a laminated hydrophilic cotton fiber membrane and a hydrophobic polymer nanofiber membrane. The one-way wet guiding Janus fiber membrane is formed by treating the laminated hydrophilic cotton fiber membrane and the hydrophobic polymer nanofiber membrane with an ionic liquid and then performing hot press welding. The preparation method comprises the following steps: preparing a polylactic acid spinning solution; using the cotton fiber membrane as a receiving substrate, and performing electrostatic spinning on the polylactic acid spinning solution to prepare a two-side heterogeneous double-layer membrane; coating the ionic liquid on the surface of the two-side heterogeneous double-layer membrane, and then performing hot press welding to obtain the one-way wet guiding Janus fiber membrane. The one-way wet guiding Janus fiber membrane has the liquid one-way transport performance and good moisture absorption and air permeation effects. The preparation process is simple, controllable and has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of functional textile materials technology, and to a unidirectional moisture-wicking Janus fiber membrane and its preparation method. In particular, it relates to a method for achieving hydrophilic and hydrophobic membrane adhesion using an ionic liquid as an intermediate medium to complete the construction of a wettability gradient, and to a unidirectional moisture-wicking Janus fiber membrane prepared by using this method. Background Technology

[0002] Unidirectional fluid transport is a common phenomenon in nature and the human body. Materials with unidirectional moisture-wicking function are generally designed as multi-layer composite structures, and the unidirectional moisture-wicking of the fabric is achieved by the change of hygroscopic gradient in the thickness direction.

[0003] Janus membranes are materials with opposite wettability on both sides, i.e., hydrophilic (LI) on one side and hydrophobic (LO) on the other, exhibiting unique properties and functions. Janus membranes, with their asymmetric wettability gradient along the thickness direction, can be used as a liquid diode for the directional permeation of liquids in the normal direction. This allows droplets to be transported directionally and spontaneously from the hydrophobic side to the hydrophilic side in a specified direction, while transport in the opposite direction is intercepted; this property can be described as "unidirectional liquid transport."

[0004] Janus fiber fabrics, with their anisotropic wettability and ability to transport liquids in one direction, are ideal new materials for applications in biomedicine and other fields. However, existing Janus materials suffer from drawbacks such as complex preparation processes, fluorine content, and poor tolerance and controllability. Furthermore, multilayered Janus fiber membranes also present problems such as easy delamination and complex design and construction, which greatly limit their practical applications in daily life.

[0005] Therefore, developing a unidirectional moisture-wicking Janus material with a simple preparation process and high controllability is of great significance for the development and application of functional textile materials. Summary of the Invention

[0006] Due to the aforementioned deficiencies in existing technologies, this invention provides a unidirectional hygroscopic Janus material with a simple preparation process and high controllability. Specifically, it uses an ionic liquid as an intermediate medium to achieve adhesion between hydrophilic and hydrophobic membranes, thereby constructing a wettability gradient and obtaining a unidirectional hygroscopic Janus fiber membrane. Its preparation process is simple and the product has good controllability, overcoming the shortcomings of existing Janus materials, such as complex preparation processes and poor controllability.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A unidirectional moisture-wicking Janus fiber membrane is a double-layer composite membrane material with anisotropic surfaces.

[0009] It comprises a layered hydrophilic cotton fiber membrane and a hydrophobic polymer nanofiber membrane, which has an asymmetric structure and a wettability gradient, and can transport water in one direction.

[0010] The unidirectional moisture-wicking Janus fiber membrane is formed by treating a layer of hydrophilic cotton fiber membrane and hydrophobic polymer nanofiber membrane with an ionic liquid and then hot-pressing them together.

[0011] This invention utilizes ionic liquids to increase the bonding between hydrophilic and hydrophobic fibers on two different sides and the connection between hydrophilic and hydrophobic sites through hot pressing (the combination of the ionic liquid's solubility in fibers and the hot pressing process ensures a stable adhesion between the two membrane layers while simultaneously creating a wettability gradient). This enhances the adhesion and wettability gradient of the biaxially oriented composite bilayer membrane, enabling unidirectional liquid transport. The result is a biaxially oriented Janus composite fiber membrane with excellent moisture absorption and breathability, exhibiting unidirectional liquid transport properties. The application of ionic liquids avoids the use of traditional adhesives, making the manufacturing process greener and reducing the damage to the membrane morphology caused by adhesives. It achieves a more gentle and effective way to ensure a tighter connection between the bilayer membranes while maintaining the membrane's breathability, thus creating a wettability gradient in one step and achieving unidirectional moisture wicking.

[0012] As a preferred technical solution:

[0013] As described above, a unidirectional moisture-wicking Janus fiber membrane is a hydrophobic polymer nanofiber membrane made of polylactic acid nanofibers spun by electrospinning. The hydrophobic membrane material includes, but is not limited to, polylactic acid, and can also support functional active substances, achieving both unidirectional moisture transport and directional delivery of functional active substances.

[0014] As described above, in a unidirectional moisture-wicking Janus fiber membrane, the solvent of the electrospinning solution is a binary mixed solvent composed of dichloromethane and N,N-dimethylformamide. The volume percentage of dichloromethane in the binary mixed solvent is 75-80%, and the mass concentration of polylactic acid in the spinning solution is 80-100 g / L (the system percentage of polylactic acid in the spinning solution is 8-10% (w / v)). The polylactic acid content and the ratio of the binary mixed solvent in the spinning solution have a significant impact on whether fiber filaments can be formed and the continuity of spinning during electrospinning. If the polylactic acid content is too high, the spinning solution will be too viscous, which is not conducive to fiber filament formation. If the proportion of the highly volatile solvent dichloromethane in the binary mixed solvent is too high, the solvent will evaporate too quickly during the spinning process, clogging the spinneret. If the proportion is reduced, the solubility of polylactic acid will decrease, thus affecting fiber filament formation.

[0015] In the unidirectional moisture-wicking Janus fiber membrane described above, the ionic liquid is 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate, or 1-allyl-3-methylimidazolium room-temperature ionic liquid, including but not limited to the above ionic liquids.

[0016] The one-way moisture-wicking Janus fiber membrane described above is a commercially available product, wherein the cotton fiber membrane is a natural pure cotton mask cloth.

[0017] Furthermore, the present invention also provides a method for preparing a unidirectional moisture-wicking Janus fiber membrane as described above, comprising the following steps:

[0018] (1) Prepare polylactic acid spinning solution;

[0019] (2) Using cotton fiber membrane as receiving substrate, electrospinning was performed using polylactic acid spinning solution to prepare a bilayer membrane with anisotropic properties on both sides.

[0020] (3) After coating the surface of the bilayer membrane with anisotropic structure obtained in step (2) with an ionic liquid, hot-press welding is performed to obtain a unidirectional moisture-wicking Janus fiber membrane. The above method has a simple preparation process, does not require complicated instruments and equipment, and the materials used are all bio-based, green and pollution-free, with good application prospects.

[0021] As a preferred technical solution:

[0022] As described above, the hot-pressing process conditions are: temperature 50–80°C, time 70–150 s. Janus fiber membranes with different conductivity (conductivity and moisture wicking rate) can be obtained by adjusting the hot-pressing temperature and time under the action of ionic liquids.

[0023] The basis weight ratio (coating amount of ionic liquid) of the ionic liquid to the bilayer film with anisotropic properties is 7 to 10:1.

[0024] As described above, the electrospinning process conditions are: voltage 16–20 kV, spinning receiving distance 10 cm, spindle receiving speed 50 rpm, liquid pushing rate 0.01 mL / min, 20 G stainless steel short needle (needle length 38 mm, inner diameter 0.61 mm), and ambient humidity 40–60%. By adjusting spinning parameters such as spinning voltage, collecting distance, solution pushing rate, and the rotation speed of the cylindrical collecting column, the quality of the spun membrane is controlled, ultimately obtaining a uniform and complete hydrophobic polylactic acid nanofiber membrane on a cotton fiber membrane substrate, thereby obtaining a bilayer Janus membrane with significant differences in hydrophilicity and hydrophobicity on both sides.

[0025] As described above, after hot-press welding, the unidirectional moisture-wicking Janus fiber membrane is sequentially rinsed (rinsed in a circulating water bath to remove ionic liquid) and dried (dried in an oven at 45°C).

[0026] The specific steps for preparing polylactic acid spinning solution using the method described above are as follows:

[0027] (1.1) A binary mixed solvent is prepared by uniformly mixing dichloromethane and N,N-dimethylformamide in a certain proportion;

[0028] (1.2) A certain amount of polylactic acid masterbatch was added to a binary mixed solvent and stirred thoroughly (prepared by magnetic stirring at 500 rpm for 15 h at room temperature) to obtain polylactic acid spinning solution.

[0029] The above technical solution is only one feasible technical solution of the present invention. The scope of protection of the present invention is not limited thereto. Those skilled in the art can reasonably adjust the specific design according to actual needs.

[0030] The above invention has the following advantages or beneficial effects:

[0031] (1) The unidirectional moisture-wicking Janus fiber membrane of the present invention uses green solvent ionic liquid to build a wettability gradient in one step through hot pressing to achieve unidirectional moisture wicking and good moisture absorption and air permeability. The green solvent ionic liquid has good solubility for fibers. The fiber membrane is coated with ionic liquid, the hot pressing conditions are controlled, the two membranes are welded, and the ionic liquid is removed after rinsing to avoid the use of adhesives. The morphology, distribution state and bonding temperature of the adhesive at the interface of the composite fabric will affect the performance of the nanofiber membrane and the fabric composite. Among them, the morphology is the key influencing factor of the air permeability and moisture permeability of the composite fabric.

[0032] (2) The preparation method of the unidirectional moisture-wicking Janus fiber membrane of the present invention is simple, requires no complicated instruments and equipment, and the materials used are all bio-based, green and pollution-free, with good application prospects. Attached Figure Description

[0033] The invention, its features, shape, and advantages will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Like reference numerals denote like parts throughout the drawings. The drawings are not drawn to scale; their focus is on illustrating the gist of the invention.

[0034] Figure 1 The image shows a scanning electron microscope image of the bilayer membrane with anisotropic structure obtained in step (4) of Example 1, where A is the fiber morphology of the hydrophobic electrospun polylactic acid nanofiber membrane, B is the fiber morphology of the hydrophilic cotton fiber membrane, and C is the cross-sectional morphology of the bilayer composite membrane.

[0035] Figure 2 This is a scanning electron microscope image of the cross-section of the unidirectional moisture-wicking Janus fiber membrane prepared in Example 1;

[0036] Figure 3 On the left, a is a test image of the membrane prepared in Comparative Example 1, and b is a test image of the membrane prepared in Example 1. Figure 3 The right side is a schematic diagram of the water droplet conduction and permeation of the unidirectional moisture-wicking Janus fiber membrane prepared in Example 1, where A represents conduction from the hydrophobic side to the hydrophilic side, and B represents conduction from the hydrophilic side to the hydrophobic side.

[0037] Figure 4 The time it takes for water droplets to permeate from the hydrophobic side to the hydrophilic side on the unidirectional moisture-wicking Janus fiber membrane prepared in Example 1 is measured in seconds. The hot-pressing parameters are: temperature 60°C, time 90s, and pressure 0.7MPa.

[0038] Figure 5 The time it takes for water droplets to permeate from the hydrophobic side to the hydrophilic side on the unidirectional moisture-wicking Janus fiber membrane prepared in Example 2 is measured in seconds. The hot-pressing parameters are: temperature 80°C, time 90s, and pressure 0.7MPa.

[0039] Figure 6 The time it takes for water droplets to permeate from the hydrophobic side to the hydrophilic side on the unidirectional moisture-wicking Janus fiber membrane prepared in Example 3 is measured in seconds. The hot-pressing parameters are: temperature 60°C, hot-pressing time 130s, and pressure 0.7MPa.

[0040] Figure 7 The results show the test results of the time it takes for water droplets to permeate from the hydrophobic side to the hydrophilic side on the fiber membrane prepared in Comparative Example 2. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but these are not intended to limit the scope of the invention.

[0042] Example 1

[0043] A method for preparing a unidirectional moisture-wicking Janus fiber membrane includes the following steps:

[0044] (1) Preparation of binary mixed solvent: The ratio of dichloromethane: N,N-dimethylformamide = 3:1 (v / v) is used to mix the solvent evenly;

[0045] (2) Preparation of PLA electrospinning solution: Weigh a certain amount of polylactic acid masterbatch (the system ratio of polylactic acid in the spinning solution is 8% (w / v)), add it to the binary mixed solvent prepared in step (1) under stirring, and magnetically stir at 500 rpm for 15 h at room temperature.

[0046] (3) Electrospun PLA fiber membrane: The cotton fiber membrane is used as the receiving substrate to receive the electrospun PLA nanofiber membrane. The electrospun process conditions are: voltage 16-20kV, spinning receiving distance 10cm, liquid pushing rate 0.01mL / min, receiving roller speed 50rpm, 20G stainless steel short needle (needle tube length 38mm, inner diameter 0.61mm), and ambient humidity 40-60%.

[0047] (4) Electrospinning for 6 hours yields a bilayer film with anisotropic properties on both sides;

[0048] (5) A green solvent ionic liquid (1-butyl-3-methylimidazolium acetate) is coated on the surface of the two-sided anisotropic bilayer film. The coating amount of the ionic liquid is 7:1 to the basis weight of the two-sided anisotropic bilayer film. Then, it is hot-pressed and welded. The hot-pressing process conditions are: hot-pressing temperature 60℃, hot-pressing time 90s, and pressure 0.7MPa.

[0049] (6) Set up a circulating water bath rinsing device to rinse the Janus fiber membrane after hot pressing in step (5) to remove ionic liquid;

[0050] (7) After rinsing with circulating water to remove ionic liquid, the membrane is placed in a 45°C oven for drying to obtain a unidirectional moisture-wicking Janus fiber membrane.

[0051] Scanning electron microscopy (SEM) was used to measure the bilayer anisotropic membrane and the unidirectional moisture-wicking Janus fiber membrane. The SEM image of the bilayer anisotropic membrane is shown below. Figure 1 As shown in the figure, a scanning electron microscope image of a unidirectional hygroscopic Janus fiber membrane is as follows. Figure 2 As shown, by Figure 1 It can be seen that the fibers in the bilayer film with anisotropic properties are arranged regularly, and the electrospun polylactic acid fibers are uniform and without beads. Figure 2 It can be seen that the composite bilayer film after hot pressing with ionic liquid as medium generates cross-links at the interface, forming a wettability gradient;

[0052] The moisture permeation performance of the unidirectional moisture-wicking Janus fiber membrane was analyzed. Specifically, a quantitative droplet permeation test was conducted using a contact angle meter. Figure 4 As can be seen from the permeation time test from the hydrophobic side to the hydrophilic side, the permeation time is measured in seconds, indicating that water can be conducted quickly.

[0053] Example 2

[0054] A method for preparing a unidirectional moisture-wicking Janus fiber membrane is basically the same as that in Example 1, except that the hot-pressing welding process conditions are as follows: hot-pressing temperature 80°C, hot-pressing time 90s, and pressure 0.7MPa.

[0055] Tests of water droplet penetration time from the hydrophobic side to the hydrophilic side on the product, such as... Figure 5 As shown.

[0056] Example 3

[0057] A method for preparing a unidirectional moisture-wicking Janus fiber membrane is basically the same as that in Example 1, except that the hot-press welding process conditions are as follows: hot-press temperature 60°C, hot-press time 130s, and pressure 0.7MPa.

[0058] Tests of water droplet penetration time from the hydrophobic side to the hydrophilic side on the product, such as... Figure 6 As shown.

[0059] Comparing the test results of Examples 1 to 3, it can be seen that by controlling the process conditions of hot-press welding, rapid unidirectional introduction of water from the hydrophobic side to the hydrophilic side and control of the penetration time can be achieved.

[0060] Comparative Example 1

[0061] A method for preparing a composite fiber membrane is basically the same as that in Example 1, except that in step (5), a green solvent ionic liquid (1-butyl-3-methylimidazolium acetate) is not coated on the surface of the bilayer membrane with anisotropic properties.

[0062] The schematic diagram of its dyed water droplet water conduction and permeation is as follows: Figure 3 As shown, Figure 3 The membrane on the left, a, is the test pattern of the membrane prepared in Comparative Example 1, and the membrane on the left, b, is the test pattern of the membrane prepared in Example 1. Figure 3 The membrane on the right is a test pattern of the membrane prepared in Example 1, where A represents conductivity from the hydrophobic side to the hydrophilic side, and B represents conductivity from the hydrophilic side to the hydrophobic side. Figure 3 It can be seen that after introducing the ionic liquid 1-butyl-3-methylimidazolium acetate to adjust the parameters and perform hot pressing, water can be rapidly introduced from the hydrophobic side to the hydrophilic side and intercepted in the opposite direction. However, the membrane droplets treated by the same preparation process without the participation of ionic liquid always remain on the hydrophobic side and do not have a unidirectional permeation effect.

[0063] Comparative Example 2

[0064] A method for preparing a composite fiber membrane is basically the same as that in Example 1, except that the green solvent ionic liquid (1-butyl-3-methylimidazolium acetate) in step (5) is replaced with the inorganic acid phosphoric acid (inorganic acids and bases have a good dissolving effect on fibers and are similar in properties to ionic liquids);

[0065] Comparing Example 1 and Comparative Example 2 reveals that while phosphoric acid has a good dissolving effect on fibers, it is difficult to control the swelling and dissolution limits, easily causing significant damage to the fiber membrane. This results in the porous fiber membrane being dissolved and then dried and re-formed to become denser, or being completely destroyed due to over-dissolution, thus greatly reducing the moisture permeability of the membrane material. The medium was changed to phosphoric acid (85 wt%), and the coating amount was phosphoric acid:membrane (gram weight ratio) = 7:1. Then, it was welded at room temperature and a pressure of 0.5 MPa for 60 seconds. The test results of the water droplet penetration time from the hydrophobic side to the hydrophilic side on the composite fiber membrane prepared in Comparative Example 2 are as follows: Figure 7 As shown, by Figure 7 It can be seen that the moisture permeability of the fiber membrane is greatly changed after phosphoric acid treatment under mild conditions, making it impossible to support the preparation of Janus fiber membranes with unidirectional moisture conduction.

[0066] Those skilled in the art should understand that variations can be implemented by combining existing technology with the above embodiments, which will not be elaborated here. Such variations do not affect the essence of the present invention, and will not be elaborated here either.

[0067] The preferred embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and the devices and structures not described in detail should be understood as being implemented in a conventional manner in the art. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention's technical solutions still fall within the protection scope of the present invention.

Claims

1. A unidirectional moisture-wicking Janus fiber membrane, characterized in that: It is a double-layer composite membrane material with anisotropic surfaces on both sides; It comprises a layered hydrophilic cotton fiber membrane and a hydrophobic polymer nanofiber membrane; the hydrophobic polymer nanofiber membrane is a polylactic acid nanofiber membrane spun by electrospinning. The unidirectional moisture-wicking Janus fiber membrane is formed by treating a layered hydrophilic cotton fiber membrane and a hydrophobic polymer nanofiber membrane with an ionic liquid, followed by hot-pressing and welding; the ionic liquid is 1 Butyl 3 Methylimidazolium acetate, 1 Butyl 3 Methylimidazolium chloride, 1 Ethyl 3 Methylimidazolium acetate or 1 Allyl 3 Methylimidazole.

2. The unidirectional moisture-wicking Janus fiber membrane according to claim 1, characterized in that, The solvent in the electrospinning solution is dichloromethane and N,N A binary mixed solvent composed of dimethylformamide, with dichloromethane in the binary mixture The volume percentage of the solvent is 75-80%, and the mass concentration of polylactic acid in the spinning solution is 80-100 g / L.

3. The unidirectional moisture-wicking Janus fiber membrane according to claim 1, characterized in that, The cotton fiber membrane is a natural pure cotton facial mask cloth.

4. A method for preparing a unidirectional moisture-wicking Janus fiber membrane as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Prepare polylactic acid spinning solution; (2) Using cotton fiber membrane as receiving substrate, electrospinning was performed using polylactic acid spinning solution to prepare a bilayer membrane with anisotropic properties on both sides. (3) After coating the surface of the bilayer membrane with anisotropic properties obtained in step (2) with ionic liquid, hot pressing is performed to obtain a unidirectional moisture-wicking Janus fiber membrane.

5. The method according to claim 4, characterized in that, The hot pressing process conditions are: temperature 50-80℃, time 70-150s; The basis weight ratio of the ionic liquid to the bilayer membrane with anisotropic structure is 7 to 10:

1.

6. The method according to claim 4, characterized in that, The electrospinning process conditions are as follows: voltage 16-20kV, spinning receiving distance 10cm, spindle receiving speed 50rpm, and liquid pushing rate 0.01mL / min.

7. The method according to claim 4, characterized in that, After hot-press welding, the unidirectional moisture-wicking Janus fiber membrane is rinsed and dried sequentially.

8. The method according to claim 4, characterized in that, The specific steps for preparing polylactic acid spinning solution are as follows: (1.1) Mix a certain proportion of dichloromethane and N,N Dimethylformamide is mixed evenly to prepare a binary mixed solvent; (1.2) A certain amount of polylactic acid masterbatch is added to a binary mixed solvent and stirred thoroughly to obtain a polylactic acid spinning solution.

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