A one-way moisture-conducting antibacterial polyurethane / polyacrylonitrile Janus nanofiber membrane and a preparation method thereof

Abstract

The application provides a one-way moisture-conducting antibacterial polyurethane / polyacrylonitrile Janus nanofiber membrane and a preparation method thereof, and belongs to the field of nanofiber membranes. First, quaternary ammonium salt QAS with antibacterial effect is synthesized by N-methyldiethanolamine and bromododecane, then a bulk antibacterial polyurethane PQU is prepared by taking QAS as a chain extender, and then an antibacterial PU / PAN Janus membrane with one-way moisture-conducting characteristics is prepared by a layer-by-layer electrospinning technology. The PU / PAN Janus membrane has excellent filtering effect, bacterial blocking effect, good antibacterial performance and one-way water transmission characteristics. The PU / PAN Janus membrane can timely take the water vapor generated by breathing away from the inside of the mask, has excellent blocking effect and filtering effect on bacteria and particulate pollutants, and has antibacterial performance to avoid the secondary infection problem caused by the bacteria on the surface layer of the mask, and has potential application prospect in the application of AFM such as masks.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nanofiber membranes, and particularly relates to an antibacterial polyurethane / polyacrylonitrile Janus nanofiber membrane with unidirectional moisture transport characteristics and a preparation method thereof. BACKGROUND

[0002] In order to cope with the problem of air pollution caused by atmospheric pollution particulate matter (PM), and to avoid the pollution air carrying pollutants such as bacteria, aerosol, etc. from entering the human body through the respiratory tract, leading to respiratory diseases, stroke, cardiovascular diseases and other diseases, people choose to use masks and other personal protective articles to protect themselves.

[0003] The melt-blown fabric treated by electret is widely used in commercial masks, and PM and bacteria are captured by electrostatic adsorption. However, according to research reports, the charge of the melt-blown fabric will be quickly dissipated in a high humidity environment, resulting in a sharp decrease in filtration efficiency. Due to the hydrophobicity of the melt-blown fabric, a large amount of exhaled water vapor gas will condense into small water droplets on the inner wall of the mask, causing the filtration efficiency to decrease, and at the same time, causing an uncomfortable feeling of dampness. Especially for people wearing glasses, water vapor will also form water mist on the lenses, blurring the vision, and bringing inconvenience to daily life. Moreover, the melt-blown fabric mask cannot kill bacteria, so the bacteria on the surface of the mask will cause secondary infection. Therefore, there is an urgent need to develop a fibrous AFM air filtration membrane with high filtration efficiency, good antibacterial activity and unidirectional water transport.

[0004] The directional transport of water is triggered by asymmetric wettability and anisotropic structure. Janus textiles refer to textiles with asymmetric properties on each side, which have attracted more and more attention due to their excellent ability in water management. Janus textiles have effective water transport capacity due to the independent design and structure of each layer. There are mainly two methods to prepare Janus textiles with directional water transport capacity: one is to coat hydrophilic and hydrophobic coatings on both sides of the textile respectively to form a hydrophobic-hydrophilic gradient on the textile, for example, Guan et al. prepared a functional membrane with asymmetric wettability by spraying hydrophilic graphene oxide (GO) and hydrophobic reduced GO on different surfaces of a cotton fabric; the other is to combine materials with hydrophilic and hydrophobic properties respectively by electrospinning to form a Janus textile with a hydrophilic-hydrophobic gradient, for example, Aijaz Ahmed Babar et al. prepared a multi-stage fiber membrane connected to each other by a one-step electrospinning process, and the obtained CNW / PA-Ag nanofiber / mesh composite membrane showed excellent water management performance and considerable antibacterial activity.

[0005] However, the Janus fiber membrane still needs to be further improved, and further research is needed to obtain a Janus fiber membrane with excellent filtering effect, bacterial blocking effect, good antibacterial performance and excellent one-way water transmission characteristics. SUMMARY

[0006] The purpose of the present application is to provide a one-way moisture-conducting antibacterial polyurethane / polyacrylonitrile Janus nanofiber membrane and a preparation method thereof.

[0007] The present application provides a polyurethane / polyacrylonitrile Jauns nanofiber membrane with one-way moisture-conducting and antibacterial effects, which is prepared from polyacrylonitrile, QAS, PQU and polyurethane as raw materials.

[0008] The structure of QAS is as follows:

[0009]

[0010] The structure of PQU is as follows:

[0011]

[0012] In PQU, n is 10-20, m is 2-5, and k is 2-5.

[0013] Further, it is obtained by electrospinning of three kinds of spinning solutions layer by layer;

[0014] wherein,

[0015] The spinning solution 1 is a liquid obtained by dissolving polyacrylonitrile and QAS in an organic solvent, wherein the solid content of polyacrylonitrile in the spinning solution 1 is 5-15%, and the content of QAS is 1-3% of polyacrylonitrile;

[0016] The spinning solution 2 is a liquid obtained by dissolving polyacrylonitrile, PQU and polyurethane in an organic solvent, and the mass ratio of polyacrylonitrile, PQU and polyurethane is (1-3):(1-2):1, and the solid content is 10-20%;

[0017] The spinning solution 3 is a liquid obtained by dissolving PQU and polyurethane in an organic solvent, and the mass ratio of PQU and polyurethane is (0.5-1.5):1, and the total solid content of the two in the spinning solution 3 is 10-30%;

[0018] The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide and tetrahydrofuran.

[0019] Further, the spinning solution 1 is a liquid obtained by dissolving polyacrylonitrile and QAS in an organic solvent, wherein the solid content of polyacrylonitrile in the spinning solution 1 is 10%, and the content of QAS is 2% of polyacrylonitrile;

[0020] Spinning solution 2: liquid obtained by dissolving polyacrylonitrile, PQU and polyurethane in organic solvent, mass ratio of polyacrylonitrile, PQU and polyurethane being 2:1:1, solid content being 15%;

[0021] Spinning solution 3: liquid obtained by dissolving PQU and polyurethane in organic solvent, mass ratio of PQU and polyurethane being 1:1, solid content being 20%;

[0022] The organic solvent is N,N-dimethylacetamide.

[0023] Further, the QAS is prepared by the following method:

[0024] N-methylethanolamine with mass ratio of (3-8): (8-16) is reacted with bromododecane in N-dimethylformamide environment, after cooling to room temperature, adding organic solvent, freezing, washing with organic solvent, drying at room temperature under vacuum to obtain;

[0025] Preferably, the mass ratio of N-methylethanolamine to bromododecane is 1:2.4; the reaction temperature is 50-70℃, and the reaction is carried out under stirring; the freezing temperature is lower than -10℃, and the freezing time is not less than 2h;

[0026] More preferably, the reaction temperature is 60℃, the freezing temperature is -20℃, and the freezing time is 4h; the organic solvent is diethyl ether.

[0027] Further, the PQU is prepared by the following method:

[0028] 1) Prepolymer is obtained by prepolymerization of polycaprolactone and isophorone diisocyanate under catalysis of catalyst;

[0029] 2) Polymer 1 is obtained by reaction of the prepolymer with QAS dissolved in organic solvent;

[0030] 3) PQU is obtained by reaction of polymer 1 with 1,4-butanediol and then aging;

[0031] The solid content of the prepolymer in step 2) ranges from 20% to 60%;

[0032] Preferably, the molar ratio of polycaprolactone, isophorone diisocyanate, QAS and 1,4-butanediol is (0.5-2):(1-3):(1-2):(0.2-1.5); the catalyst is dibutyltin dilaurate;

[0033] In step 1), the prepolymerization temperature is (70-90)℃, and the reaction time is 1-3h;

[0034] In step 2), the solid content of the prepolymer is adjusted to 30-60% by using super-dry N,N-dimethylacetamide; the reaction temperature is (70-90)℃, and the reaction time is 1-3h;

[0035] The reaction temperature in step 3 is (70-90) °C, and the reaction time is 1-3.

[0036] Further, the mass ratio of polycaprolactone, isophorone diisocyanate, QAS, and 1,4-butanediol is 1:2.1:0.6:0.5;

[0037] In step 1), the pre-polymerization reaction temperature is 80 °C, and the reaction time is 2 h;

[0038] In step 2), the pre-polymer solid content is adjusted to 45% using super-dry N,N-dimethylacetamide; the reaction temperature is 80 °C, and the reaction time is 2 h;

[0039] In step 3), the reaction temperature is 80 °C, and the reaction time is 2 h.

[0040] The application also provides a method for preparing the nanofiber membrane as described above.

[0041] The steps are as follows:

[0042] 1) Preparation of the spinning solution:

[0043] Spinning solution 1: polyacrylonitrile and QAS are dissolved in an organic solvent, wherein the solid content of polyacrylonitrile in the spinning solution 1 is 5%-15%, and the QAS content is 1-3% of the polyacrylonitrile;

[0044] Spinning solution 2: polyacrylonitrile, PQU, and polyurethane are dissolved in an organic solvent, and the mass ratio of polyacrylonitrile, PQU, and polyurethane is (1-3):(1-2):1, and the solid content is 10-20%;

[0045] Spinning solution 3: PQU and polyurethane are dissolved in an organic solvent, and the mass ratio of PQU and polyurethane is (0.5-1.5):1, and the total solid content of the two in the spinning solution 3 is 10-30%;

[0046] 2) The three spinning solutions are sequentially electrospun in the order of spinning solution 1, spinning solution 2, and spinning solution 3, or spinning solution 3, spinning solution 2, and spinning solution 1, to obtain the product.

[0047] The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and tetrahydrofuran.

[0048] Further, the mass ratio of the spinning solution 1, the spinning solution 1, and the spinning solution 3 used in the polyurethane / polyacrylonitrile Jauns nanofiber membrane is (14-18):(8-12):(20:24), and preferably 38:22:43.

[0049] Further, the polyurethane / polyacrylonitrile Janus nanofiber membrane uses 380 mg, 220 mg and 430 mg of spinning solution 1, spinning solution 1 and spinning solution 3 respectively per 100 mg.

[0050] The application also provides a use of the above-mentioned polyurethane / polyacrylonitrile Janus nanofiber membrane in the preparation of an air filtration material or a protective device; the protective device is preferably a mask and a protective garment.

[0051] The polyacrylonitrile has a molecular weight of 80000-150000 g / mol; the polycaprolactone has a molecular weight of 1000-2000 g / mol; and the polyurethane has a molecular weight of 60000-160000 g / mol.

[0052] The application provides a one-way moisture-conducting antibacterial PU / PAN Janus nanofiber membrane and a preparation method thereof. First, a quaternary ammonium salt QAS with antibacterial effect is synthesized by N-methyldiethanolamine and bromododecane. Then, a bulk antibacterial polyurethane PQU is prepared by taking the QAS as a chain extender. Subsequently, an antibacterial PU / PAN Janus membrane with one-way moisture-conducting characteristics is prepared by a layer-by-layer electrospinning technology. The membrane has excellent filtering effect, bacterial blocking effect, good antibacterial performance and one-way moisture-conducting characteristics. The PU / PAN Janus membrane prepared by the application has potential application prospect in the application of AFM such as a mask. It can timely take the water vapor generated by breathing away from the inside of the mask, has excellent blocking effect and filtering effect on bacteria and particulate pollutants, and has antibacterial performance to avoid the secondary infection problem caused by the bacteria on the surface of the mask.

[0053] Obviously, according to the above content of the application, according to the ordinary technical knowledge and common means in the art, other various forms of modifications, replacements or changes can be made without departing from the above basic technical idea of the application.

[0054] The above content of the application will be further described in detail through the specific embodiments in the form of examples. However, this should not be understood as the range of the above subject matter of the application being limited to the following examples. Any technology realized based on the above content of the application belongs to the range of the application. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 Synthesis route of QAS.

[0056] Figure 2 Synthesis route of PQU.

[0057] Figure 3 (a) NMR hydrogen spectrum of BD, NM and QAS; (b) infrared spectrum of BD, NM and QAS.

[0058] Figure 4 SEM images of (a) (d) PAN fiber membrane; (b) (e) PAN-PQU-PU fiber membrane; (c) (f) PQU-PU fiber membrane.

[0059] Figure 5 TG of nanofiber membrane, (b) DTG of nanofiber membrane.

[0060] Figure 6 Dynamic water contact angle of nanofiber membrane.

[0061] Figure 7 Water vapor permeability of nanofiber membrane at (a) 23℃ and (b) 37℃. Positive direction: Positive direction, Reverse direction: Reverse direction, Control: Bottle mouth open.

[0062] Figure 8 (a) Breakthrough pressure of nanofiber membrane; (b) Wicking height of nanofiber membrane.

[0063] Figure 9 (a) N2 isotherm adsorption line of nanofiber membrane; (b) Pore size distribution of nanofiber membrane

[0064] Figure 10 Colony growth after filtration by different membranes.

[0065] Figure 11 Air filtration performance of nanofiber membrane: (a) Filtration efficiency; (b) Pressure drop; (c) Quality factor.

[0066] Figure 12 Antibacterial performance of PAN / PAN-PQU-PU / PQU-PU membrane. DETAILED DESCRIPTION

[0067] The raw materials and equipment used in the present application are known products, which are obtained by purchasing commercially available products.

[0068] Table 1 is the relevant experimental materials used in the present application, and Table 1 is the experimental materials used in the present application

[0069]

[0070]

[0071] Among them:

[0072] Polyurethane (PU): PU3390.

[0073] Solid medium preparation method: 4.0 g of sodium chloride, 4.0 g of tryptone, 2.0 g of yeast extract powder, 8.0 g of agar were dissolved in 400 mL of deionized water, sterilized at 121°C for 15 min, poured into a plate, and allowed to cool and solidify to obtain the required solid medium plate, which was ready for inoculation.

[0074] Liquid medium preparation method: 4.0 g of sodium chloride, 4.0 g of tryptone, 2.0 g of yeast extract powder were dissolved in 400 mL of deionized water, sterilized at 121°C for 15 min, and placed on a sterile operation table or stored in a refrigerator after being sealed, which was mainly used for bacterial activation and dilution.

[0075] pH = 7.4 phosphate buffer (PBS): 4.0 g of sodium chloride, 0.1 g of potassium chloride, 1.8 g of disodium hydrogen phosphate dodecahydrate, and 0.24 g of potassium dihydrogen phosphate were dissolved in 500 mL of deionized water, sterilized at 121°C for 15 min, and placed on a sterile operation table, which was mainly used for bacterial dilution.

[0076] Example 1, preparation of the antibacterial PU / PAN Janus nanofiber membrane with one-way moisture-wicking property of the application and characterization

[0077] I. Experimental method (1) Preparation and characterization of double-hydroxy quaternary ammonium salt (QAS)

[0078] 1. Preparation of double-hydroxy quaternary ammonium salt

[0079] a) Preparation of double-hydroxy quaternary ammonium salt QAS

[0080] 5 g of N-methyl ethanolamine (NM) and 12 g of bromododecane (BD) were uniformly mixed in 25 mL of N,N-dimethylformamide (DMF) and stirred at 60°C for 8 h. After the reaction was completed, the mixture was cooled to room temperature, 50 mL of ether was added, and the mixture was placed in a -20°C refrigerator for 4 h. The product was obtained by filtration. Then the product was washed with ether three times and dried in a vacuum oven at room temperature for 12 h to obtain a white solid product, double-hydroxy quaternary ammonium salt QAS.

[0081] b) Preparation of double-hydroxy quaternary ammonium salt QAS1

[0082] Except that the amount of 8 g of N-methyl ethanolamine (NM) and 16 g of bromododecane (BD) was changed, the rest was the same as the preparation method of QAS, and a white solid product, double-hydroxy quaternary ammonium salt QAS1, was obtained.

[0083] c) Preparation of double-hydroxy quaternary ammonium salt QAS2

[0084] Except that the amount of 3 g of N-methyl ethanolamine (NM) and 8 g of bromododecane (BD) was changed, the rest was the same as the preparation method of QAS, and a white solid product, double-hydroxy quaternary ammonium salt QAS2, was obtained.

[0085] 2. Characterization of dihydroxy quaternary ammonium salt (QAS)

[0086] After the product was dried, the structure of QAS was characterized and confirmed using infrared spectroscopy and nuclear magnetic resonance. The results are as follows: Figure 3 As shown.

[0087] Figure 3 a represents the 1H NMR spectra of BD, NM, and QAS. 1 H-NMR spectrum), from Figure 3 As can be seen from the BD structure, the proton signal at ppm 3.51 belongs to methylene proton 12, the proton signal at ppm 1.78 belongs to methylene proton 11, the shift from 1.17 to 1.40 ppm belongs to methylene 2-10, and the proton signal at ppm 0.84 belongs to methyl proton 1. In the NM structure, the proton signal at ppm 4.32 belongs to hydroxyl protons 4 and 7, the triplet at approximately ppm 3.44 belongs to methylene protons 2 and 5, the triplet at approximately ppm 2.41 belongs to methylene protons 3 and 6, and the proton signal at ppm 2.18 belongs to methyl proton 8. In QAS, the multiplet at ppm 5.23–5.25 belongs to hydroxyl protons, the multiplet at ppm 3.77–3.84 belongs to methylene protons 2 and 5 bonded to O, the multiplet at ppm 3.39–3.46 belongs to methylene protons 3 and 6 bonded to N, the multiplet at ppm 3.33–3.37 belongs to methylene proton 9 bonded to N, the proton signal at ppm 3.08 belongs to methyl proton 8 bonded to N, the proton signal around ppm 1.78 belongs to methylene proton 10, the shift at ppm 1.17–1.40 belongs to methylene protons 11–19, and the proton signal at ppm 0.85 belongs to methyl proton 1. Therefore, 1 H-NMR results showed that QAS was successfully synthesized.

[0088] Figure 3 b is the FTIR spectrum of BD, NM, and QAS. 3293 cm⁻¹ -1 The peak at 2926 cm⁻¹ belongs to the stretching vibration peak of -OH. -1 With 2854cm -1 These are the stretching vibration peaks of methyl (-CH3-) and methylene (-CH2-), respectively, and the absorption peaks are relatively strong. 724 cm⁻¹ -1 and 625cm -1 The absorption peaks are for the bending vibrations of methylene groups with four or more carbons, at 1645.6 cm⁻¹. -1 CN in the quaternary ammonium group + The stretching vibration absorption peaks indicate the successful synthesis of QAS.

[0089] (II) Preparation of quaternary ammonium salt type polyurethane (PQU)

[0090] 1. Preparation of quaternary ammonium salt type polyurethane (PQU)

[0091] As shown in the following scheme, quaternary ammonium salt type polyurethane (PQU) was prepared using a three-step method. Figure 2

[0092] Into a flask, 65 g of polycaprolactone (PCL) was placed and vacuum dehydrated at 110 °C for 2 h, then cooled to 80 °C, 15 g of isophorone diisocyanate (IPDI) was added, and 0.1 g of dibutyltin dilaurate was added as a catalyst, and reacted at 80 °C for 2 h to obtain a prepolymer, super dry DMAc was added to control the solid content of the prepolymer in the range of 45%, then a super dry DMAc solution dissolving 7.2 g of QAS was added, and the reaction was continued at 80 °C for 2 h, then 1.5 g of 1,4-butanediol (BDO) was added, and after reacting at 80 °C for 2 h, the mixture was poured into a preheated polytetrafluoroethylene mold and placed in a blast oven at 80 °C for 24 h to obtain PQU.

[0093] 2. Preparation of quaternary ammonium salt type polyurethane (PQU1)

[0094] Into a flask, 60 g of polycaprolactone was placed and vacuum dehydrated at 110 °C for 2 h, then cooled to 80 °C, 15 g of isophorone diisocyanate was added, and 0.05 g of dibutyltin dilaurate was added as a catalyst, and reacted at 80 °C for 2 h to obtain a prepolymer, super dry DMAc was added to control the solid content of the prepolymer in the range of 20%, then a super dry DMAc solution dissolving 5 g of QAS was added, and the reaction was continued at 80 °C for 2 h, then 1 g of 1,4-butanediol was added, and after reacting at 80 °C for 2 h, the mixture was poured into a preheated polytetrafluoroethylene mold and placed in a blast oven at 80 °C for 24 h to obtain PQU1.

[0095] 3. Preparation of quaternary ammonium salt type polyurethane (PQU2)

[0096] Into a flask, 80 g of polycaprolactone was placed and vacuum dehydrated at 110 °C for 2 h, then cooled to 80 °C, 20 g of isophorone diisocyanate was added, and 0.2 g of dibutyltin dilaurate was added as a catalyst, and reacted at 80 °C for 2 h to obtain a prepolymer, super dry DMAc was added to control the solid content of the prepolymer in the range of 60%, then a super dry DMAc solution dissolving 8 g of QAS was added, and the reaction was continued at 80 °C for 2 h, then 4 g of 1,4-butanediol was added, and after reacting at 80 °C for 2 h, the mixture was poured into a preheated polytetrafluoroethylene mold and placed in a blast oven at 80 °C for 24 h to obtain PQU2.

[0097] ​(III) Preparation of PU / PAN Jauns membrane

[0098] Three kinds of spinning solutions were prepared respectively before electrospinning:

[0099] Spinning solution 1: A homogeneous solution with a solid content of 10% was prepared by dissolving polyacrylonitrile (PAN) in DMAc, and adding QAS with a mass of 2% of PAN;

[0100] Spinning solution 2: A homogeneous solution with a solid content of 15% was prepared by dissolving PAN, PQU and PU in a mass ratio of 2:1:1 in DMAc;

[0101] Spinning solution 3: A homogeneous solution with a solid content of 20% was prepared by dissolving PQU and PU in a mass ratio of 1:1 in DMAc.

[0102] Electrospinning was carried out at room temperature. The positive and negative voltages were set to 15 kV and 0.5 kV respectively, and the working distance between the needle tip and the collector was 15 cm.

[0103] Layer-by-layer spinning was carried out by first spinning the previous spinning solution and then continuing electrospinning with another spinning solution.

[0104] The fiber membrane prepared only using spinning solution 1 was named PAN membrane. The amount of spinning solution 1 used was 1000 mg per 100 mg of PAN membrane.

[0105] The fiber membrane prepared by layer-by-layer spinning using only spinning solution 1 and spinning solution 2 was named PAN / PAN-PQU-PU membrane. The amount of spinning solution 1 used was 630 mg and the amount of spinning solution 2 used was 380 mg per 100 mg of PAN / PAN-PQU-PU membrane.

[0106] The fiber membrane prepared only using spinning solution 2 and spinning solution 3 was named PAN-PQU-PU / PQU-PU membrane. The amount of spinning solution 2 used was 350 mg and the amount of spinning solution 3 used was 660 mg per 100 mg of PAN-PQU-PU / PQU-PU membrane.

[0107] The fiber membrane prepared by layer-by-layer spinning using spinning solution 1, spinning solution 2 and spinning solution 3 was named PAN / PAN-PQU-PU / PQU-PU membrane, i.e. PU / PAN Jauns membrane. The amount of spinning solution 1 used was 380 mg, the amount of spinning solution 2 used was 220 mg, and the amount of spinning solution 3 used was 430 mg per 100 mg of PAN / PAN-PQU-PU / PQU-PU membrane.

[0108] Among them, the spinning time of the PAN layer was 5 h, the spinning time of the PAN-PQU-PU layer was 2 h, and the spinning time of the PQU-PU layer was 3 h.

[0109] (iv) Characterization of PU / PAN Jauns membranes

[0110] 1. Morphology characterization of fiber membranes

[0111] PQU-PU fiber membranes were used as the hydrophobic inner layer, PAN-PQU-PU fiber membranes were used as the intermediate transition layer, and PAN fiber membranes were used as the hydrophilic outer layer. The surface morphology of each nanofiber membrane was characterized by scanning electron microscopy, and all samples were treated with gold spraying before testing.

[0112] The SEM photos of each fiber membrane are shown in Figure 4 . Among them, the fiber diameter of the PAN fiber membrane is about 300 nm or so, and the diameter of the PAN-PQU-PU fiber membrane is about 500 nm or so, and the diameter of the PQU-PU fiber membrane is about 280 nm or so.

[0113] Generally speaking, the diameter of the fiber will increase with the increase of the polymer concentration, because the higher the concentration, the higher the viscosity, which enhances the entanglement of the molecular chain, the surface tension and the electrostatic repulsion are inhibited, which leads to insufficient stretching of the jet in the electrostatic field, thereby forming larger diameter nanofibers. However, due to the low molecular weight of PQU, the solution viscosity is low, although the spinning solution concentration increases, the solution viscosity is lower than that of PAN, so that the diameter of the PQU-PU fiber membrane is relatively lower than that of the PAN fiber membrane.

[0114] 2. Thermal stability of fiber membranes

[0115] The thermal stability of the nanofiber membrane was investigated by thermogravimetric analysis, with a nitrogen flow rate of 50 mL / min, a heating rate of 10 ℃ / min, and a temperature test range of 30 ℃-800 ℃.

[0116] The TG curve of the fiber membrane is shown in Figure 5 . The first decomposition peak appears at about 107 ℃, which may be due to the evaporation of water. PAN has two decomposition peaks, 324 ℃ and 446 ℃, respectively. After adding a layer of PAN-PQU-PU, the decomposition peaks become 335 ℃, 409 ℃ and 455 ℃, and after adding another layer, the decomposition peaks become 334 ℃ and 433 ℃. And with the increase of PQU-PU content, the final carbon residue is decreasing, indicating that there are differences between different membranes.

[0117] The following experimental examples demonstrate the beneficial effects of the PU / PAN Jauns membranes prepared by the present application.

[0118] Experimental Example 1, mechanical property test of PU / PAN Jauns fiber membrane of the present application

[0119] I. Experimental method

[0120] The mechanical properties of the nanofiber membranes were studied using an electronic single yarn strength tester. The width of the fiber membrane sample was 5 mm, the distance between the two clamps was 50 mm, and the tensile speed was 10 mm / min. Each sample was tested in parallel for 10 times, and the average values of breaking strength (cN) and breaking elongation (%) were calculated and recorded. The thickness of the nanofiber membrane was tested using a thickness gauge.

[0121] 2. Experimental results

[0122] The results of the mechanical property test of the fiber membranes are shown in Table 2. It can be seen that the breaking elongation of the PAN fiber membrane is relatively low, only 22.25%, which is due to the relatively high rigidity of PAN itself and the high degree of orientation between the molecular chains, thus the elongation is low.

[0123] The breaking elongation of the PAN-PQU-PU / PQU-PU membrane is 72.37%, which is because the inherent elasticity of the polyurethane fiber membrane is good, and it has excellent breaking elongation and resilience. However, when combined with the PAN fiber membrane, whether it is the PAN / PAN-PQU-PU / PQU-PU fiber membrane or the PAN / PAN-PQU-PU fiber membrane, the breaking elongation is low, which is due to the poor interlayer bonding force between the PAN fiber membrane and other fiber membranes. In the stretching process, there is a difference in breaking time, the PAN fiber membrane breaks first, resulting in low breaking elongation and breaking strength of the fiber membrane, which is lower than that of the PAN-PQU-PU / PQU-PU membrane.

[0124] Table 2 Mechanical properties of nanofiber membranes

[0125]

[0126] Experimental Example 2, Dynamic water contact angle test of PU / PAN Jauns fiber membrane of the present application

[0127] I. Experimental method

[0128] 5 μL of water droplets were dropped on the fiber membrane, and the change of the water droplets on the membrane surface was observed.

[0129] II. Experimental results

[0130] The results of the change of the water droplets on the membrane surface are as follows Figure 6As shown, the water contact angle of the PAN membrane reduced to 0° within 6.6 s, and the water droplets were evenly dispersed on the membrane surface; while the water contact angle of the PAN-PQU-PU / PQU-PU fibrous membrane did not change significantly within 40 s due to the absence of the hydrophilic layer; the contact angle of the PAN / PAN-PQU-PU / PQU-PU fibrous membrane did not change significantly at the initial stage, but the water contact angle reduced at an increasingly faster rate over time, and eventually the water droplets were completely absorbed within 34.3 s, with only an initial water droplet trace on the top layer (PQU-PU fibrous membrane) and a small wetting area, while the water droplets were evenly dispersed on the bottom layer (PAN fibrous membrane) and left a large wetting trace.

[0131] When water droplets were dropped on both sides of the PAN / PAN-PQU-PU / PQU-PU fibrous membrane, it was observed that when the water droplets were dropped on the PQU-PU fibrous membrane, the water droplets could penetrate the entire fibrous membrane and wet the A4 paper placed at the bottom of the fibrous membrane, while when the water droplets were dropped on the PAN fibrous membrane, the water droplets spread on the fibrous surface and could not penetrate the entire fibrous membrane.

[0132] Although the hydrostatic pressure can push a small amount of water to penetrate the middle layer, due to the higher hydrophilicity of the PAN layer, a reverse wetting gradient force is formed, which slows down the penetration rate. In addition, even if a small amount of water penetrates the middle layer, the reverse wetting gradient force and hydrophobic force provided by the hydrophobic PQU-PU layer will hinder the water from penetrating the PQU-PU layer. Therefore, no water reaches the outer surface of the hydrophobic layer from the PAN layer.

[0133] The experimental results show that the PAN / PAN-PQU-PU / PQU-PU fibrous membrane has excellent one-way moisture guiding properties.

[0134] Experimental Example 3, Water Vapor Transmission Rate (WVTR) Test of the PAN / PAN-PQU-PU / PQU-PU Fibrous Membrane of the Invention

[0135] I. Experimental Steps

[0136] The water vapor transmission rate of the composite membrane was measured in the forward direction (Positive direction) from the hydrophobic PQU-PU fibrous layer to the hydrophilic PAN layer, and in the reverse direction (Reverse direction) from the hydrophilic PAN layer to the hydrophobic PQU-PU fibrous layer.

[0137] II. Experimental Results

[0138] The water vapor transmission rate results are as follows Figure 7As shown, the PAN / PAN-PQU-PU / PQU-PU fiber membrane exhibits a higher water volume resistance (WVTR) in the forward direction than in the reverse direction, particularly at 23°C and 75% humidity, where the forward WVTR is 7.38% higher than the reverse. Meanwhile, the forward WVTR is only 1.09% lower than that of an open water bottle.

[0139] This is because at lower temperatures, the amount of water vapor volatilization is lower and the Brownian motion of water molecules is weaker. Although the PAN fiber membrane can absorb a large amount of water vapor due to its own hydrophilicity, it is more difficult for water vapor to desorb from the PAN membrane after it combines with the hydrophilic layer of the PAN fiber membrane. Therefore, it is not easy to overcome the hydrophobic barrier on the surface of the PQU-PU fiber membrane, thereby reducing the WVTR.

[0140] Experimental results show that PAN / PAN-PQU-PU / PQU-PU fiber membranes have directional moisture transport characteristics.

[0141] Experimental Example 4: Water wicking height and breakthrough pressure test of the PAN / PAN-PQU-PU / PQU-PU fiber membrane of the present invention

[0142] Breakthrough pressure is one of the most important factors determining the directional moisture transport characteristics of a membrane. The breakthrough pressure of the fiber membrane was measured by passing it through a 70cm long, 16mm inner diameter tube through the water level the membrane could withstand. Breakthrough pressures from both sides of the PQU-PU and PAN membranes, as well as from the PAN membrane alone, were verified. The results are as follows: Figure 8 As shown in Figure a, water can easily penetrate the PAN membrane, and there is no difference between the front and back sides. However, there is a difference between the front and back sides of the PAN / PAN-PQU-PU fiber membrane and the PAN / PAN-PQU-PU / PQU-PU fiber membrane. In particular, the breakthrough pressure of the PAN / PAN-PQU-PU / PQU-PU fiber membrane differs by 1.33 cm between the front and back sides.

[0143] The pressure difference results confirm that the PAN / PAN-PQU-PU / PQU-PU fiber membrane not only exhibits excellent directional moisture transport but also demonstrates significant resistance to reverse water movement. This breakthrough pressure difference across the membrane is attributed to the asymmetric wettability of the two sides of the fiber membrane, the differences in pore size between and within the fibers, and the surface energy gradient between different fiber membranes.

[0144] In addition, the wicking effect of PAN fiber membrane and PQU-PU fiber membrane was tested, and the results are as follows: Figure 8As shown in b, the wicking effect of the PAN fiber membrane is significantly better than that of the PQU-PU fiber membrane, and the wicking height reaches 4 cm within 2 min, while the PQU-PU fiber membrane is only 0.5 cm. This is because the pore size of the PAN fiber membrane is larger than that of the PQU-PU fiber membrane, which provides additional capillary force, enhances the wicking rate, and the QAS contained in the PAN fiber membrane contains a hydrophilic group, which further increases the affinity of the PAN fiber membrane, thereby further enhancing the wicking effect.

[0145] The experimental results show that the PAN / PAN-PQU-PU / PQU-PU fiber membrane of the application can directionally transport water, and the directional water transport performance of the PAN / PAN-PQU-PU / PQU-PU fiber membrane is much higher than that of PAN / PAN-PQU-PU.

[0146] Experimental Example 5, Investigation of the Pore Structure of the PAN / PAN-PQU-PU / PQU-PU Fiber Membrane of the Invention

[0147] The N2 adsorption / desorption method was used to quantitatively analyze the fiber porosity of the prepared membrane. Figure 9 The adsorption-desorption curves of the three fiber membranes are shown, and according to the IUPAC classification, all samples show pseudo-IV type isotherm curves. All fiber membrane samples show sudden adsorption at high relative pressure (P / Po greater than 0.7), indicating the presence of mesopores in the fiber membrane.

[0148] At the same time, the Barrett-Joyner-Halenda model was used for further study of the unique properties and size distribution of the pores present in the prepared composite nanofiber membrane. From Figure 9 As can be seen from b, the fiber pore size distribution of all fiber membranes is mainly concentrated in the mesopore range (2-50 nm) and macropore (greater than 50 nm), however, compared with the PAN fiber membrane, the mesopore number of the PAN / PAN-PQU-PU fiber membrane and the PAN / PAN-PQU-PU / PQU-PU fiber membrane is significantly reduced, because the PQU-PU fiber membranes are closely packed and have a certain adhesion phenomenon, resulting in partial pore collapse, so the specific surface area also decreases to a certain extent, from 12.4097 m 2 / g to 9.9379 m 2 / g and 8.5996 m 2 / g, respectively.

[0149] As can be seen from Table 3, the average pore size of the PAN fiber membrane layer is larger than that of the PQU-PU fiber membrane layer, and the difference in the number of pores and the pore size between different membrane layers can form a gradient wicking channel between the fiber membranes, thereby achieving the purpose of one-way moisture guiding and achieving a graded filtering effect, thereby improving the filtering effect.

[0150] The specific surface area and pore structure of each fiber membrane were tested using BET. The results are shown in Table 3,

[0151] Table 3 Specific surface area, average pore size and pore volume of fiber membranes

[0152]

[0153] The experimental results show that the PAN / PAN-PQU-PU / PQU-PU fiber membrane has one-way wetting characteristics and high filtration effect.

[0154] Experimental Example 6, Bacterial Retention Performance of the PAN / PAN-PQU-PU / PQU-PU Fiber Membrane of the Invention

[0155] The bacterial retention performance of each fiber membrane was tested using a pressurized suction filtration method: Staphylococcus aureus was activated for 12 h using a liquid culture medium, then diluted 10 times using PBS, and the bacterial solution concentration was 5.3 x 10 7 CFU / mL, the PU / PAN Janus membrane was placed in a sand core funnel (filter core G2, average pore diameter: 40-80 μm) with a diameter of 20 mm, and a sand core funnel without adding any cloth was used as a control, 20 mL of bacterial solution was added to each group, suction filtration was performed, and then the suction-filtered bacterial solution was diluted and plated, and cultured in an incubator for 18 h.

[0156] The experimental results are shown in Table 4 and Figure 10 The influence of the sand core funnel on bacterial retention was small, and only 3.636% of the bacteria were retained, the bacterial retention effect of the commercially available PALL membrane was 99.668%, and the retention effect of the PU / PAN Janus membrane prepared by electrospinning could reach 100%, which was better than the commercially available bacterial blocking membrane, and could effectively prevent bacteria from directly penetrating the nanofiber membrane to contact the human body and cause infection.

[0157] Table 4 Number of bacteria after filtration of different membranes and bacterial retention rate

[0158]

[0159] The experimental results show that the bacterial retention performance of the PAN / PAN-PQU-PU / PQU-PU fiber membrane of the invention is extremely strong, and can reach 100%, which is much higher than that of the commercially available bacterial blocking membrane.

[0160] Experimental Example 7, Filtration Performance of the PAN / PAN-PQU-PU / PQU-PU Fiber Membrane of the Invention

[0161] The filtration efficiency and pressure drop of the fiber membrane were tested using an air filtration device, and the quality factor was calculated, and the results are shown in Figure 11

[0162] ​Fiber membranes for PM5 and PM2.5 2.5 PM 1.0 PM 0.5 PM 0.3 Filtration efficiency such as Figure 11 As shown in Figure a. PAN fiber membranes are effective against PM5 and PM2.5. 2.5 PM 1.0 PM 0.5 and PM 0.3 The filtration efficiencies were 97.17%, 97.93%, 97.87%, 97.23%, and 91.21%, respectively.

[0163] PAN-PQU-PU / PQU-PU fiber membrane for PM5, PM2.5 2.5 PM 1.0 PM 0.5 and PM 0.3 The filtration efficiencies were 98.76%, 99.00%, 98.87%, 98.00%, and 92.91%, respectively.

[0164] PAN / PAN-PQU-PU / PQU-PU fiber membranes for PM5, PM2.5 2.5 PM 1.0 PM 0.5 and PM 0.3 The filtration efficiencies were 98.44%, 99.19%, 99.21%, 98.98%, and 93.63%, respectively.

[0165] All three types of fiber membranes have excellent filtration efficiency, mainly because they have low diameters, which can effectively block PM in the air.

[0166] PAN film for PM 0.3 The filtration efficiency of PAN membranes is lower than that of the other two types of fiber membranes, and the pores of PAN membranes are easily clogged by large PM particles, causing an increase in pressure drop. Figure 11 As shown in b, the pressure drop of the PAN membrane is higher than that of the other two membranes.

[0167] To comprehensively compare the filtration performance of membranes, the membrane quality factor is calculated. The calculation formula is:

[0168]

[0169] Where: η is the filtration efficiency; ΔP is the filtration resistance, in Pa.

[0170] like Figure 11As shown in Fig. c, the PAN / PAN-PQU-PU fiber membrane has the highest quality factor, and the PAN membrane has the lowest quality factor, and the experimental results show that the PAN / PAN-PQU-PU fiber membrane has the best comprehensive filtration performance.

[0171] The polluted air also contains a variety of bacteria, such as S. aureus and E. coli. Once these bacteria are inhaled by the human body, respiratory diseases will be caused. Even if the bacteria are intercepted on the surface of the mask, they still have infective activity and can cause secondary infection. Therefore, antibacterial activity is an important property of the mask.

[0172] S. aureus and E. coli were used as representative bacteria to detect the antibacterial activity of the PAN / PAN-PQU-PU / PQU-PU fiber membrane. Figure 12 The photos showing the growth of bacterial colonies on the agar plate are shown.

[0173] The experimental results show that the PAN / PAN-PQU-PU / PQU-PU fiber membrane has excellent antibacterial performance and can kill more than 99.99% of S. aureus and E. coli.

[0174] In summary, the present application provides a one-way moisture-conducting antibacterial PU / PAN Janus nanofiber membrane and a preparation method thereof. First, a quaternary ammonium salt QAS with antibacterial effect is synthesized by N-methyldiethanolamine and bromododecane. Then, a bulk antibacterial polyurethane PQU is prepared by using QAS as a chain extender. Then, an antibacterial PU / PAN Janus membrane with one-way moisture-conducting characteristics is prepared by layer-by-layer electrospinning technology. The membrane has excellent filtration effect, bacterial barrier effect, good antibacterial performance and excellent one-way moisture-conducting characteristics. The PU / PAN Janus membrane prepared by the present application has potential application prospect in the application of AFM such as mask, which can timely take away the water vapor generated by respiration from the inside of the mask, and has excellent barrier effect and filtration effect on bacteria and particulate pollutants, and itself has antibacterial performance to avoid the problem of secondary infection caused by bacteria on the surface of the mask.

Claims

1. A polyurethane / polyacrylonitrile Jauns nanofiber membrane with unidirectional moisture-wicking and antibacterial properties, characterized in that: It is prepared from polyacrylonitrile, QAS, PQU and polyurethane as raw materials; The QAS structure is shown below: The PQU structure is shown below: In PQU, n is 10-20, m is 2-5, and k is 2-5; It is obtained by electrospinning three kinds of spinning solutions layer by layer; in, Spinning solution 1: A liquid obtained by dissolving polyacrylonitrile and QAS in an organic solvent, wherein the solid content of polyacrylonitrile in spinning solution 1 is 5-15%; and the QAS content is 1-3% of polyacrylonitrile. Spinning solution 2: A liquid obtained by dissolving polyacrylonitrile, PQU and polyurethane in an organic solvent, wherein the mass ratio of polyacrylonitrile, PQU and polyurethane is (1-3):(1-2):1, and the solid content is 10-20%; Spinning solution 3: A liquid obtained by dissolving PQU and polyurethane in an organic solvent, with a mass ratio of PQU to polyurethane of (0.5-1.5):1, and the total solid content of both in spinning solution 3 is 10-30%.

2. The nanofiber membrane according to claim 1, characterized in that... ； The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and tetrahydrofuran.

3. The nanofiber membrane according to claim 2, characterized in that: Spinning solution 1: A liquid obtained by dissolving polyacrylonitrile and QAS in an organic solvent, wherein the solid content of polyacrylonitrile in spinning solution 1 is 10%; and the content of QAS is 2% of polyacrylonitrile. Spinning solution 2: A liquid obtained by dissolving polyacrylonitrile, PQU and polyurethane in an organic solvent, with a mass ratio of polyacrylonitrile, PQU and polyurethane of 2:1:1 and a solid content of 15%; Spinning solution 3: A liquid obtained by dissolving PQU and polyurethane in an organic solvent, with a mass ratio of PQU to polyurethane of 1:1 and a solid content of 20%. The organic solvent is N,N-dimethylacetamide.

4. The nanofiber membrane according to any one of claims 1-3, characterized in that: The QAS is prepared by the following method: N-methyldiethanolamine and bromododecane in a mass ratio of (3-8):(8-16) were reacted in an N-dimethylformamide environment. After cooling to room temperature, an organic solvent was added, the mixture was frozen, washed with the organic solvent, and dried under vacuum at room temperature to obtain the final product.

5. The nanofiber membrane according to claim 4, characterized in that; The mass ratio of N-methyldiethanolamine to bromododecane is 1:2.4; the reaction temperature is 50-70℃ and carried out under stirring; the freezing temperature is below -10℃ and the freezing time is not less than 2 hours.

6. The nanofiber membrane according to claim 5, characterized in that; The reaction temperature is 60°C, the freezing temperature is -20°C, and the freezing time is 4 hours; the organic solvent is diethyl ether.

7. The nanofiber membrane according to claim 4, characterized in that: The PQU is prepared by the following method: 1) Polycaprolactone and isophorone diisocyanate were prepolymerized under catalyst to obtain a prepolymer; 2) The prepolymer reacts with QAS dissolved in an organic solvent to obtain polymer 1; 3) After polymer 1 reacts with 1,4-butanediol, it is cured to obtain PQU; In step 2), the solid content of the prepolymer ranges from 20% to 60%.

8. The nanofiber membrane according to claim 7, characterized in that: The molar ratio of polycaprolactone, isophorone diisocyanate, QAS, and 1,4-butanediol is (0.5-2):(1-3):(1-2):(0.2-1.5); the catalyst is dibutyltin dilaurate. In step 1), the prepolymerization reaction temperature is 70℃-90℃, and the reaction time is 1-3 hours; In step 2), ultra-dry N,N-dimethylacetamide is used to adjust the solid content of the prepolymer to 30-60%; the reaction temperature is 70℃-90℃, and the reaction time is 1-3h. In step 3, the reaction temperature is 70℃-90℃ and the reaction time is 1-3h.

9. The nanofiber membrane according to claim 7, characterized in that: The mass ratio of polycaprolactone, isophorone diisocyanate, QAS, and 1,4-butanediol is 1:2.1:0.6:0.

5. In step 1), the prepolymerization reaction temperature is 80℃ and the reaction time is 2 hours; In step 2), ultra-dry N,N-dimethylacetamide was used to adjust the solid content of the prepolymer to 45%; the reaction temperature was 80℃ and the reaction time was 2h. In step 3, the reaction temperature is 80℃ and the reaction time is 2 hours.

10. A method for preparing the nanofiber membrane according to any one of claims 1-9, characterized in that: The steps are as follows: 1) Preparation of spinning solution: Spinning solution 1: Polyacrylonitrile and QAS are dissolved in an organic solvent, wherein the solid content of polyacrylonitrile in spinning solution 1 is 5%-15%; and the content of QAS is 1-3% of polyacrylonitrile. Spinning solution 2: Polyacrylonitrile, PQU and polyurethane are dissolved in an organic solvent, and the mass ratio of polyacrylonitrile, PQU and polyurethane is (1-3):(1-2):1, with a solid content of 10-20%; Spinning solution 3: PQU and polyurethane are dissolved in an organic solvent, with a mass ratio of QU to polyurethane of (0.5-1.5):1, and the total solid content of both in spinning solution 3 is 10-30%. 2) The three spinning solutions are electrospun layer by layer in the order of spinning solution 1, spinning solution 2, and spinning solution 3, or spinning solution 3, spinning solution 2, and spinning solution 1, to obtain the desired spinning solution. The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and tetrahydrofuran.

11. The method according to claim 10, characterized in that: The polyurethane / polyacrylonitrile Jauns nanofiber membrane uses spinning solution 1, spinning solution 2 and spinning solution 3 in a mass ratio of (14-18):(8-12):(20-24).

12. The method according to claim 11, characterized in that: The polyurethane / polyacrylonitrile Jauns nanofiber membrane uses spinning solution 1, spinning solution 2 and spinning solution 3 in a mass ratio of 38:22:

43.

13. The method according to claim 10, characterized in that: For every 100 mg of the polyurethane / polyacrylonitrile Jauns nanofiber membrane, the mass of spinning solution 1, spinning solution 2, and spinning solution 3 is 380 mg, 220 mg, and 430 mg, respectively.

14. Use of the polyurethane / polyacrylonitrile Jauns nanofiber membrane according to any one of claims 1-9 in the preparation of air filtration materials or protective equipment.

15. The use according to claim 14, characterized in that: The protective equipment refers to masks and protective clothing.

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