Bio-based waterproof moisture-permeable breathable film and preparation method thereof

Abstract

The invention discloses a bio-based waterproof moisture-permeable breathable film and a preparation method thereof, and belongs to the technical field of functional nanofiber film materials. The membrane is a four-layer composite nanofiber membrane and is constructed in situ through a multi-channel electrostatic spinning technology, and interlayer chemical crosslinking is achieved through a Ugi reaction. The preparation method comprises the following steps: preparing a bio-based polymer spinning solution, a dialdehyde-containing polyurethane spinning solution, an isonitrile-containing polyurethane spinning solution and a long-chain fatty acid-containing polyurethane spinning solution; sequentially depositing four layers of nanofibers by adopting a four-row-pipe electrostatic spinning device; initiating a Ugi reaction through heat treatment; and continuously rolling to obtain a finished product. The gram weight of the membrane is 6-30 g / m < 2 >, the air permeability is larger than or equal to 2 mm / s, the moisture permeability is larger than or equal to 12000 g / (m < 2 >. 24 h), and the hydrostatic pressure is larger than or equal to 40 kPa after 10 times of washing. The preparation method is simple in process, high in production efficiency and excellent in performance, and solves the technical problems that a bio-based waterproof membrane is poor in washing resistance and difficult to prepare on a large scale.

Description

Technical Field

[0001] This invention belongs to the field of functional nanofiber membrane material technology, and relates to a four-layer composite bio-based waterproof, breathable and breathable membrane based on in-situ chemical cross-linking and its mass production method. Background Technology

[0002] Waterproof and breathable membrane materials are functional materials that can block liquid water penetration while allowing water vapor to pass through, and have important application value in protective clothing, outdoor sportswear, medical dressings, and other fields. Existing commercial products mainly rely on petroleum-based polymer materials such as polyurethane (PU) and polytetrafluoroethylene (PTFE), which have problems such as poor biodegradability and heavy environmental burden.

[0003] In recent years, bio-based materials, represented by chitosan, cellulose, and plant proteins, have attracted much attention due to their renewability, biodegradability, and good biocompatibility. However, the inherent hydrophilicity of bio-based polymers leads to insufficient waterproofing performance, often requiring complex post-processing. For example, Chinese patent application CN119531124A discloses a method for preparing a bio-based membrane, which requires grafting silica particles onto the fiber surface using a sol-gel method, followed by prolonged immersion and multiple heat treatments (total processing time exceeding 24 hours). This cumbersome process makes continuous mass production difficult.

[0004] Therefore, developing a bio-based membrane material that is simple to process, can be continuously produced, and has excellent waterproof and breathable properties as well as water-resistant properties is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies in the preparation of bio-based waterproof and breathable membranes, such as complex processes, long production cycles, and difficulty in large-scale production. This invention provides a one-step multilayer composite bio-based waterproof, breathable, and breathable membrane prepared via in-situ chemical crosslinking, and its preparation method. This objective is achieved through the following specific technical solutions.

[0006] In a first aspect, the present invention provides a bio-based waterproof, breathable, and moisture-permeable membrane, wherein the membrane is a four-layer composite nanofiber membrane, comprising: The first layer is a base layer composed of bio-based polymer nanofibers; The second layer is a cross-linked reinforcement layer composed of polyurethane nanofibers containing dialdehyde compounds; The third layer is a cross-linked reinforcement layer composed of polyurethane nanofibers containing isonitrile compounds; The fourth layer is a hydrophobic surface layer composed of polyurethane nanofibers containing long-chain fatty acids. In this process, in-situ composite formation is achieved through chemical bonding formed by the Ugi reaction between the layers, and the basis weight of the membrane is 6~30 g / m³. 2The thickness is 8~45μm.

[0007] Furthermore, the bio-based polymer is selected from chitosan, plant protein, or a combination thereof.

[0008] Furthermore, the dialdehyde compound is selected from one or more of glutaraldehyde, succinaldehyde, and adipaldehyde.

[0009] Furthermore, the isonitrile compound is selected from one or more of cyclohexylisocyanate, tert-butylisocyanate, and benzylisocyanate.

[0010] Furthermore, the long-chain fatty acid is selected from one or more of stearic acid, lauric acid, palmitic acid, myristic acid, oleic acid, palmitoleic acid, and linoleic acid.

[0011] Secondly, the present invention provides a method for preparing the above-mentioned membrane, comprising the following steps: Preparation of S1 spinning solution: Four spinning solutions were prepared: Spinning solution A: Bio-based polymers were dissolved in the first solvent system, with a solid content of 10–30 wt%; Spinning solution B: Dialdehyde compound and polyurethane were dissolved in the second solvent system, with a polyurethane solid content of 10–25 wt% and a dialdehyde mass concentration of 0.2%–3%; Spinning solution C: Isonitrile compound and polyurethane were dissolved in the third solvent system, with a polyurethane solid content of 10–25 wt% and an isonitrile mass concentration of 0.4%–6%; Spinning solution D: Long-chain fatty acids and polyurethane were dissolved in the fourth solvent system, with a polyurethane solid content of 10–25 wt% and a long-chain fatty acid mass concentration of 0.4%–6%. S2 in-situ composite electrospinning: Continuous spinning is performed using a multi-channel electrospinning device. The device includes at least four electrospinning tubes arranged sequentially along the conveyor belt running direction. Each tube is equipped with an independent liquid supply system and a needle array. Spinning solution A is spun separately through the first tube, depositing a first nanofiber membrane on the conductive conveyor belt. Spinning solutions A and B are co-spun from different needles through the second tube, depositing a second nanofiber membrane on the first membrane. Spinning solutions A and C are co-spun from different needles through the third tube, depositing a third nanofiber membrane on the second membrane. Finally, spinning solutions A and D are co-spun from different needles through the fourth tube, depositing a fourth nanofiber membrane on the third membrane. S3 thermally initiated Ugi crosslinking reaction: The multilayer fiber membrane obtained in step S2 is fed into an oven via a conveyor belt for heat treatment. The oven temperature is 80~110℃ and the treatment time is 2~10 minutes to induce the Ugi reaction in the membrane. S4 Product Collection: The heat-treated membrane is collected by a winding device to obtain the bio-based waterproof, breathable and breathable membrane.

[0012] Furthermore, when the bio-based polymer in the spinning solution A is chitosan, the first solvent system is a mixture of water, ethanol and acetic acid, with a mass ratio of (0.05~0.3):1:(0.005~0.05).

[0013] Furthermore, the second solvent system is a mixed solution of acetone and DMAC containing 0.01~0.3 wt% hydrochloric acid, with a mass ratio of acetone to DMAC of (0.5~2):1.

[0014] Furthermore, both the third and fourth solvent systems are mixed solutions of ethyl acetate and DMF, with a mass ratio of ethyl acetate to DMF of (0.5~2):1.

[0015] Furthermore, the electrospinning process parameters are: spinning voltage 68~100 kV, needle-to-conveyor belt distance 10~40 cm, and 21G needles are used.

[0016] Furthermore, the needle spacing in the same row of tubes is 1~10 cm, and the spacing between adjacent rows of tubes is 5~20 cm.

[0017] Furthermore, the conductive conveyor belt is a conductive carbon fiber conveyor belt or a conductive metal conveyor belt.

[0018] Furthermore, the resulting membrane has an air permeability ≥ 2 mm / s and a moisture permeability ≥ 12000 g / (m³). 2 • 24h), after washing 10 times, the hydrostatic pressure is ≥40 kPa.

[0019] The core innovation of this invention lies in achieving in-situ construction and chemical bonding of a four-layer structure through a specific multi-channel electrospinning arrangement sequence. The mechanism is as follows: (1) Gradient structure construction: The first row of tubes is spun separately to form a hydrophilic base layer of bio-based polymer; the second and third rows of tubes are respectively introduced with polyurethane fiber layers containing dialdehyde and isonitrile; the fourth row of tubes is introduced with polyurethane fiber layers containing long-chain fatty acids to form a hydrophobic-hydrophilic gradient structure.

[0020] (2) Ugi reaction crosslinking: During the heat treatment process, the aldehyde group of the second layer and the isonitrile group of the third layer undergo a Ugi four-component reaction (aldehyde + isonitrile + carboxylic acid + amine) at the interface. At the same time, the amino group of the biological substrate also participates in the reaction, forming multiple chemical bonds such as amide bond and ester bond, which significantly improves the interlayer bonding strength.

[0021] (3) Surface hydrophobicity: The long-chain fatty acids in the fourth layer partially migrate to the surface during heat treatment and are anchored in the fiber network through the Ugi reaction, giving the membrane lasting hydrophobicity.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects: (1) Excellent performance: the hydrostatic pressure can reach more than 78 kPa, the air permeability is ≥3 mm / s, and the moisture permeability is ≥13000 g / (m³). 2 • 24h), after washing 10 times, the hydrostatic pressure retention rate is >60%; (2) Simplified process: multi-layer composite and chemical cross-linking are integrated into one-step electrospinning-heat treatment process, and the production cycle is shortened to within 30 minutes; (3) Mass production: a conveyor belt continuous device is used to realize industrial-scale production; (4) Green and environmentally friendly: the proportion of bio-based raw materials is ≥40%, and there is no need to use fluorinated hydrophobic agents. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the multi-channel electrospinning device used in this invention, wherein: 1-electrospinning needle; 2-conductive conveyor belt; 3-first row of tubes; 4-second row of tubes; 5-third row of tubes; 6-fourth row of tubes.

[0024] Figure 2 This is a top-view schematic diagram of the needle arrangement in an electrospinning tube, showing the arrangement of multiple needle arrays within the same tube and the distribution paths of different spinning solutions.

[0025] Figure 3 This is a SEM image of the bio-based waterproof, breathable and moisture-permeable membrane prepared in Example 1. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention. Example 1

[0027] S1. Dissolve 12.5 kg of commercially available chitosan (molecular weight 250 kDa, degree of deacetylation 83%) in 50 kg of a mixed solvent of water / ethanol / acetic acid (mass ratio of the three is 0.2:1:0.02) to obtain spinning solution A. Dissolve 2 kg of glutaraldehyde and 8 kg of polyurethane (molecular weight 50,000-80,000) in 50 kg of a mixed solvent of acetone / DMAC containing 0.1% hydrochloric acid (mass ratio of the two is 2:1) to obtain spinning solution B. Dissolve 4 kg of cyclohexylisocyanate and 8 kg of polyurethane (molecular weight 50,000-80,000) in 50 kg of a mixed solvent of ethyl acetate / DMF (mass ratio of the two is 1:1) to obtain spinning solution C. Dissolve 4 kg of stearic acid and 8 kg of polyurethane (molecular weight 50,000-80,000) in 50 kg of a mixed solvent of ethyl acetate / DMF (mass ratio of the two is 1:1) to obtain spinning solution D.

[0028] S2. Pump spinning solution A into the electrostatic spinning device (e.g., Figure 1 and Figure 2 As shown, spinning solutions A and B are pumped into needles a and b, respectively, in the first row of tubes 3 of the electrospinning device. Spinning solutions A and C are pumped into needles a and c, respectively, in the third row of tubes 5 of the electrospinning device. Spinning solutions A and D are pumped into needles a and d, respectively, in the fourth row of tubes 6 of the electrospinning device. The distance between needles in the tubes is 6 cm, the distance between tubes is 8 cm, the needles are 21G needles, the spinning voltage is 98 kV, and the distance from the tubes to the conveyor belt is 32 cm.

[0029] S3. The multilayer fiber membrane obtained in step S2 is fed into an oven via conveyor belt 2 for heat treatment. The oven temperature is 80°C and the treatment time is 3 minutes to induce the Ugi reaction in the membrane.

[0030] S4. The heat-treated membrane is collected by a winding device to obtain the bio-based waterproof, breathable, and moisture-permeable membrane. SEM images are shown below. Figure 3 As shown. Example 2

[0031] S1. Dissolve 15 kg of commercially available chitosan (molecular weight 115 kDa, degree of deacetylation 83%) in 50 kg of a mixed solvent of water / ethanol / acetic acid (mass ratio of the three is 0.2:1:0.02) to obtain spinning solution A. Dissolve 2 kg of succinaldehyde and 8 kg of polyurethane (molecular weight 50,000-80,000) in 50 kg of a mixed solvent of acetone / DMAC containing 0.1% hydrochloric acid (mass ratio of the two is 2:1) to obtain spinning solution B. Dissolve 4 kg of tert-butylisocyanate and 8 kg of polyurethane (molecular weight 50,000-80,000) in 50 kg of a mixed solvent of ethyl acetate / DMF (mass ratio of the two is 1:1) to obtain spinning solution C. Dissolve 4 kg of oleic acid and 8 kg of polyurethane (molecular weight 50,000-80,000) in 50 kg of a mixed solvent of ethyl acetate / DMF (mass ratio of the two is 1:1) to obtain spinning solution D.

[0032] The remaining steps are the same as in Example 1. Example 3

[0033] S1. Dissolve 10.5 kg of soybean protein (molecular weight 300 kDa) in 50 kg of a mixed solvent of water / ethanol / acetic acid (mass ratio of the three is 0.2:1:0.02) to obtain spinning solution A. Dissolve 2 kg of glutaraldehyde and 8 kg of polyurethane (molecular weight 50,000-80,000) in 50 kg of a mixed solvent of acetone / DMAC containing 0.1% hydrochloric acid (mass ratio of the two is 2:1) to obtain spinning solution B. Dissolve 4 kg of tert-butylisocyanate and polyurethane (molecular weight 50,000-80,000) in 50 kg of a mixed solvent of ethyl acetate / DMF (mass ratio of the two is 1:1) to obtain spinning solution C. Dissolve 4 kg of oleic acid and 8 kg of polyurethane (molecular weight 50,000-80,000) in 50 kg of a mixed solvent of ethyl acetate / DMF (mass ratio of the two is 1:1) to obtain spinning solution D.

[0034] The remaining steps are the same as in Example 1. Comparative Example 1

[0035] The process is basically the same as in Example 1, but without the heat treatment in step S3, it is directly wound into a film. Comparative Example 2

[0036] The process is basically the same as in Example 1, but glutaraldehyde is not added to spinning solution B. Comparative Example 3

[0037] The process is basically the same as in Example 1, but cyclohexylisocyanate is not added to spinning solution C. Comparative Example 4

[0038] The process is basically the same as in Example 1, but stearic acid is not added to the spinning solution D. Comparative Example 5

[0039] The process is basically the same as in Example 1, except that the amount of glutaraldehyde added to spinning solution B is changed to 3 kg. Comparative Example 6

[0040] The process is basically the same as in Example 1, except that the polyurethane spinning aid in spinning solution B is replaced with chitosan (molecular weight 250kDa, degree of deacetylation 83%). Comparative Example 7

[0041] The process is basically the same as in Example 1, except that the polyurethane spinning aid in spinning solution C is replaced with chitosan (molecular weight 250kDa, degree of deacetylation 83%). Comparative Example 8

[0042] The process is basically the same as in Example 1, except that the spinning aid polyurethane in spinning solution D is replaced with chitosan (molecular weight 250kDa, degree of deacetylation 83%). Comparative Example 9

[0043] The process is basically the same as in Example 1, except that spinning solution C is replaced with spinning solution D. Comparative Example 10

[0044] The process is basically the same as in Example 1, except that the chitosan (molecular weight 250kDa, degree of deacetylation 83%) in spinning solution A is replaced with commercially available guar gum (molecular weight 200kDa).

[0045] Performance testing: The bio-based waterproof and breathable membranes prepared in Examples 1-3 and Comparative Examples 1-10 were subjected to performance tests. Air permeability was tested according to GB / T 5453-1997, moisture permeability was tested according to GB / T 12704-2009 "Textiles - Test Methods for Moisture Permeability - Part 1: Moisture Absorption Method", and hydrostatic pressure was tested according to GB / T 4744-2013 "Textiles - Test and Evaluation of Waterproof Performance". Washing methods followed GB / T 8629-2017 "Textiles - Test Procedures for Household Washing and Drying", with a 4N cycle and 5 washes. Mechanical properties were tested according to GB / T 3923.1-2013 "Textiles - Tensile Properties of Fabrics - Part 1: Determination of Breaking Strength and Elongation at Break - Strip Method". The test results are shown in Table 1.

[0046] Table 1. Performance test results of the bio-based waterproof and breathable membranes prepared in Examples 1-3 and Comparative Examples 1-10

[0047] The performance test results above show that Examples 1-3 exhibit the best overall performance, with an air permeability ≥3.0 mm / s and a moisture permeability >13000 g / (m³).2 • 24h), hydrostatic pressure retention rate after washing >66%. Comparative Example 1 (no heat treatment) shows that the Ugi reaction is crucial for improving initial hydrostatic pressure and washability; Comparative Example 2 (no aldehyde component) leads to crosslinking failure, extremely low mechanical properties, and complete lack of washability; Comparative Example 3 (no isonitrile) and Comparative Example 4 (no fatty acid) affect crosslinking density and surface hydrophobicity, respectively, and significantly reduce wash retention rate; Comparative Example 5 (excess aldehyde) leads to excessive crosslinking and severely reduces air permeability; Comparative Examples 6-8 (replacement of auxiliary spinning polymer) show that polyurethane is crucial for spinning stability and fiber morphology; Comparative Example 9 (incorrect reaction order) proves that the order of isonitrile layer and fatty acid layer cannot be reversed; Comparative Example 10 (replacement of bio-based polymer) shows the superiority of the chitosan / plant protein system.

[0048] Although embodiments of the present invention have been shown and described above, it is understood that these embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and alterations to the above embodiments within the scope of the present invention without departing from its principles and spirit. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. A bio-based waterproof, breathable, and moisture-permeable membrane, characterized in that, The membrane is a four-layer composite nanofiber membrane, comprising: The first layer is a base layer composed of bio-based polymer nanofibers; The second layer is a cross-linked reinforcement layer composed of polyurethane nanofibers containing dialdehyde compounds; The third layer is a cross-linked reinforcement layer composed of polyurethane nanofibers containing isonitrile compounds; The fourth layer is a hydrophobic surface layer composed of polyurethane nanofibers containing long-chain fatty acids. In this process, in-situ composite formation is achieved through chemical bonding formed by the Ugi reaction between the layers, and the basis weight of the membrane is 6~30 g / m³. 2 The thickness is 8~45μm.

2. The membrane according to claim 1, characterized in that, The bio-based polymer is selected from chitosan, plant protein, or a combination thereof.

3. The membrane according to claim 1, characterized in that, The dialdehyde compound is selected from one or more of glutaraldehyde, succinal, and adipaldehyde.

4. The membrane according to claim 1, characterized in that, The isonitrile compound is selected from one or more of cyclohexylisocyanate, tert-butylisocyanate, and benzylisocyanate.

5. The membrane according to claim 1, characterized in that, The long-chain fatty acids are selected from one or more of stearic acid, lauric acid, palmitic acid, myristic acid, oleic acid, palmitoleic acid, and linoleic acid.

6. A method for preparing a bio-based waterproof, breathable, and moisture-permeable membrane as described in any one of claims 1-5, characterized in that, Includes the following steps: Preparation of S1 spinning solution: Four spinning solutions were prepared: Spinning solution A: Bio-based polymers were dissolved in the first solvent system, with a solid content of 10-30 wt%; Spinning solution B: Dialdehyde compound and polyurethane were dissolved in the second solvent system, with a polyurethane solid content of 10-25 wt% and a dialdehyde mass concentration of 0.2%-3%; Spinning solution C: Isonitrile compound and polyurethane were dissolved in the third solvent system, with a polyurethane solid content of 10-25 wt% and an isonitrile mass concentration of 0.4%-6%; Spinning solution D: Long-chain fatty acids and polyurethane were dissolved in the fourth solvent system, with a polyurethane solid content of 10-25 wt% and a long-chain fatty acid mass concentration of 0.4%-6%. S2 in-situ composite electrospinning: Continuous spinning is performed using a multi-channel electrospinning device. The device includes at least four electrospinning tubes arranged sequentially along the conveyor belt running direction. Each tube is equipped with an independent liquid supply system and a needle array. Spinning solution A is spun separately through the first tube, depositing a first nanofiber membrane on the conductive conveyor belt. Spinning solutions A and B are co-spun from different needles through the second tube, depositing a second nanofiber membrane on the first membrane. Spinning solutions A and C are co-spun from different needles through the third tube, depositing a third nanofiber membrane on the second membrane. Finally, spinning solutions A and D are co-spun from different needles through the fourth tube, depositing a fourth nanofiber membrane on the third membrane. S3 thermally initiated Ugi crosslinking reaction: The multilayer fiber membrane obtained in step S2 is fed into an oven via a conveyor belt for heat treatment. The oven temperature is 80~110℃ and the treatment time is 2~10 minutes to induce the Ugi reaction in the membrane. S4 Product Collection: The heat-treated membrane is collected by a winding device to obtain the bio-based waterproof, breathable and breathable membrane.

7. The preparation method according to claim 6, characterized in that, When the bio-based polymer in the spinning solution A is chitosan, the first solvent system is a mixture of water, ethanol and acetic acid, with a mass ratio of (0.05~0.3):1:(0.005~0.05).

8. The preparation method according to claim 6, characterized in that, The second solvent system is a mixed solution of acetone and DMAC containing 0.01~0.3wt% hydrochloric acid, with a mass ratio of acetone to DMAC of (0.5~2):

1.

9. The preparation method according to claim 6, characterized in that, Both the third and fourth solvent systems are mixed solutions of ethyl acetate and DMF, with a mass ratio of ethyl acetate to DMF of (0.5~2):

1.

10. The preparation method according to claim 6, characterized in that, The electrospinning process parameters are: spinning voltage 68~100 kV, needle-to-conveyor belt distance 10~40 cm, and 21G needles are used.

11. The preparation method according to claim 6, characterized in that, The distance between needles in the same row of tubes is 1~10 cm, and the distance between adjacent rows of tubes is 5~20 cm.

12. The preparation method according to claim 6, characterized in that, The conductive conveyor belt is a conductive carbon fiber conveyor belt or a conductive metal conveyor belt.

13. The preparation method according to claim 6, characterized in that, The resulting membrane has an air permeability ≥ 2 mm / s and a moisture permeability ≥ 12000 g / (m³). 2 • 24h), after washing 10 times, the hydrostatic pressure is ≥40 kPa.

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