A nanofiber composite filter medium and its preparation process

Abstract

The invention relates to the technical field of non-woven fiber filter materials, and discloses a nanofiber composite filter material and a preparation process thereof, comprising: synthesizing a composite antibacterial epoxy crosslinking agent, using chitosan and polyvinyl alcohol as raw materials, adopting an electrostatic spinning process, and preparing a chitosan-polyvinyl alcohol nanofiber membrane; based on an epoxy ring-opening mechanism, the epoxy functional groups of the composite antibacterial epoxy crosslinking agent react with hydroxyl and amino functional groups contained in the chitosan-polyvinyl alcohol nanofiber membrane to achieve a crosslinking modification effect of the chitosan-polyvinyl alcohol nanofiber membrane, and preparing a crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane; and using the crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane as an intermediate filter medium layer and compounding it with a PP non-woven fabric base layer to prepare a nanofiber composite filter material, wherein the composite filter material has an air filtration efficiency greater than 98%, an antibacterial rate greater than 96%, and exhibits very excellent filtration effect and antibacterial effect.

Description

Technical Field

[0001] The present invention relates to the technical field of non-woven fiber filter materials, and specifically to a nanofiber composite filter material and a preparation process thereof. Background Art

[0002] Preparing high-performance air filtration materials is an important way to reduce the harm of PM 2.5 particulates to human health, and developing green air filtration materials is a new industrial development direction.

[0003] Chitosan is a biodegradable natural polymer material. It not only has the physical adsorption and filtration functions required for nanofibers, but also has unique chemical adsorption functions and excellent antibacterial properties, and can be applied in the field of functional nanofiber filter materials.

[0004] However, due to the characteristics of low strength, high viscosity and cationic polyelectrolyte after chitosan is dissolved, it is very difficult to carry out electrospinning smoothly, thus limiting the application range of chitosan as a functional fiber. Polyvinyl alcohol is a biocompatible, biodegradable and non-toxic soluble polymer. Blending chitosan with polyvinyl alcohol with excellent spinnability is an effective way to improve the spinnability and mechanical properties of chitosan.

[0005] Since both chitosan and polyvinyl alcohol are water-soluble materials, the nanofiber membrane obtained by electrospinning is unstable in water and needs to be crosslinked. Glutaraldehyde is the most widely used crosslinking agent at present, but relevant research has confirmed its cytotoxicity. Summary of the Invention

[0006] The present invention uses fiber raw materials that are widely sourced, inexpensive, green and renewable, and prepares a chitosan-polyvinyl alcohol nanofiber membrane with antibacterial function and stable performance based on the electrospinning method. Using it as a filter medium and compounding it with a non-woven fabric substrate, a nanofiber composite filter material is prepared.

[0007] A preparation process of a nanofiber composite filter material includes the following steps:

[0008] Step 1: Synthesize a composite antibacterial epoxy crosslinking agent, and the composite antibacterial epoxy crosslinking agent is composite antibacterial epoxy crosslinking agent I or composite antibacterial epoxy crosslinking agent II;

[0009] Step 2: Using chitosan and polyvinyl alcohol as raw materials, adopt the electrospinning process to prepare a chitosan-polyvinyl alcohol nanofiber membrane;

[0010] Step 3: Based on the epoxy ring-opening mechanism, the epoxy functional groups of the composite antibacterial epoxy-based crosslinking agent react with the hydroxyl and amino functional groups contained in the chitosan-polyvinyl alcohol nanofiber membrane to achieve the crosslinking modification of the chitosan-polyvinyl alcohol nanofiber membrane, and a crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane is prepared;

[0011] Step 4: The crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane is used as an intermediate filtration medium layer and compounded with a PP non-woven fabric base layer to prepare a nanofiber composite filter material.

[0012] Preferably, the chemical structural formula of the composite antibacterial epoxy-based crosslinking agent I is:

[0013] .

[0014] Preferably, the preparation method of the composite antibacterial epoxy-based crosslinking agent I is:

[0015] Using the Schiff base reaction mechanism, the carbonyl functional group of 4,4'-biphenyl dialdehyde reacts with the amino functional group of 3-(diphenylphosphino)propylamine to generate a dischiff base tertiary phosphine monomer;

[0016] Using the nucleophilic substitution reaction mechanism, the tertiary phosphine group of the dischiff base tertiary phosphine monomer reacts with the chlorine functional group of epichlorohydrin to generate a composite antibacterial epoxy-based crosslinking agent I.

[0017] Preferably, the chemical structural formula of the composite antibacterial epoxy-based crosslinking agent II is:

[0018] .

[0019] Preferably, the preparation method of the composite antibacterial epoxy-based crosslinking agent II is:

[0020] Using the Schiff base reaction mechanism, the carbonyl functional group of 3,3',5,5'-tetraformylbiphenyl reacts with the amino functional group of 3-(diphenylphosphino)propylamine to generate a tetrachiff base tertiary phosphine monomer;

[0021] Using the nucleophilic substitution reaction mechanism, the tertiary phosphine group of the tetrachiff base tertiary phosphine monomer reacts with the chlorine functional group of epichlorohydrin to generate a composite antibacterial epoxy-based crosslinking agent II.

[0022] Preferably, the mass ratio of chitosan to polyvinyl alcohol in the chitosan-polyvinyl alcohol nanofiber membrane in Step 2 is 1:(0.8 - 2).

[0023] Preferably, the preparation method of the cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane is: mix a composite antibacterial epoxy cross-linking agent, acetone and deionized water to prepare a composite antibacterial epoxy cross-linking agent solution with a mass fraction of 1-10wt%, completely immerse the chitosan-polyvinyl alcohol nanofiber membrane in the composite antibacterial epoxy cross-linking agent solution, keep it for 1-5 hours to carry out the cross-linking reaction, take it out, wash and dry it to obtain a cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane.

[0024] The air filtration efficiency of a nanofiber composite filter material prepared according to the above process is greater than 98%.

[0025] The antibacterial rate of a nanofiber composite filter material prepared according to the above process is greater than 96%, and the bacteria are Escherichia coli or Staphylococcus aureus.

[0026] The application of a nanofiber composite filter material prepared according to the above process in medical masks.

[0027] Beneficial effects:

[0028] The present invention firstly uses chitosan, which has excellent properties such as biocompatibility, biodegradability, antibacterial and adsorption, as a raw material for nanofiber filter material, and polyvinyl alcohol, which has biocompatibility and biodegradability, as a spinning aid, to prepare chitosan-polyvinyl alcohol nanofiber membrane through an electrospinning process;

[0029] Then, based on the epoxy ring-opening reaction, the chitosan-polyvinyl alcohol nanofiber membrane was cross-linked and modified using a composite antibacterial epoxy cross-linking agent synthesized independently to prepare a cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane;

[0030] The experimental results show that the cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane prepared by the present invention has achieved significant improvement in water resistance, antibacterial properties and mechanical properties compared with the chitosan-polyvinyl alcohol nanofiber membrane that has not been cross-linked and modified and the chitosan-polyvinyl alcohol nanofiber membrane that has been conventionally cross-linked and modified using glutaraldehyde.

[0031] Finally, the cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane was used as the intermediate filter medium layer and composited with the PP non-woven fabric base layer to prepare a nanofiber composite filter material;

[0032] The experimental results show that the air filtration efficiency of the nanofiber composite filter material prepared by the present invention is greater than 98%, and the antibacterial rate is greater than 96%, showing very excellent filtration effect and antibacterial effect. DETAILED DESCRIPTION

[0033] Experimental Example 1:

[0034] Synthesize composite antibacterial epoxy crosslinking agent Ⅰ, and its synthesis route is as follows:

[0035] ;

[0036] The synthesis process of composite antibacterial epoxy crosslinking agent Ⅰ is as follows:

[0037] (1)Synthesize the bis-Schiff base tertiary phosphine monomer. The specific synthesis method is as follows: Using the Schiff base reaction mechanism, the carbonyl functional group of 4,4'-biphenyl dialdehyde reacts with the amino functional group of 3-(diphenylphosphino)propylamine through a condensation reaction to generate the bis-Schiff base tertiary phosphine monomer. The specific experimental steps are as follows: Add 2.1 g of 4,4'-biphenyl dialdehyde and 30 mL of N,N-dimethylformamide into a three-necked flask. Under mechanical stirring, heat up to 40 °C and stir for 20 min until completely dissolved. Cool to room temperature, and then add 50 mL of N,N-dimethylformamide solution containing 4.9 g of 3-(diphenylphosphino)propylamine and 2 mL of glacial acetic acid into the three-necked flask in sequence. Heat up to 80 °C and stir for 4 h. Cool to room temperature, rotate and evaporate to remove the solvent, wash repeatedly with ethanol, and dry under vacuum to obtain the bis-Schiff base tertiary phosphine monomer;

[0038] (2)Synthesize composite antibacterial epoxy crosslinking agent Ⅰ. The specific synthesis method is as follows: Using the nucleophilic substitution reaction mechanism, the tertiary phosphine group of the bis-Schiff base tertiary phosphine monomer reacts with the chlorine functional group of epichlorohydrin through a quaternary phosphination reaction to generate composite antibacterial epoxy crosslinking agent Ⅰ. The specific experimental steps are as follows: Under the protection of nitrogen, add 3.3 g of the bis-Schiff base tertiary phosphine monomer and 40 mL of N,N-dimethylformamide into a three-necked flask, stir at room temperature until completely dissolved, then add 1.5 mL of epichlorohydrin dropwise into the three-necked flask, heat up to 60 °C and stir for 8 h. Cool to room temperature, rotate and evaporate to remove the solvent, wash repeatedly with ethanol, and dry under vacuum to obtain composite antibacterial epoxy crosslinking agent Ⅰ;

[0039] The 1H NMR characterization of composite antibacterial epoxy crosslinking agent Ⅰ is as follows: 1 H NMR(CDCl3, 400 MHz) δ: 1.90 - 1.97(m, 4H), 3.43 - 3.44(d, 4H), 3.73 - 4.03(m, 14H), 7.41 - 7.74(m, 28H), 8.49(s, 2H).

[0040] Experimental example two:

[0041] Synthesize composite antibacterial epoxy crosslinking agent Ⅱ, and its chemical structural formula is:

[0042] ;

[0043] The synthesis process of composite antibacterial epoxy crosslinking agent Ⅱ is as follows:

[0044] (1) Synthesize the tetra-Schiff base tertiary phosphine monomer. The specific synthesis method is as follows: Using the Schiff base reaction mechanism, through the condensation reaction of the carbonyl functional group of 3,3',5,5'-tetraformylbiphenyl with the amino functional group of 3-(diphenylphosphino)propylamine, the tetra-Schiff base tertiary phosphine monomer is generated. The specific experimental steps refer to the preparation experiment of the di-Schiff base tertiary phosphine monomer, and the only difference is that 1.3 g of 3,3',5,5'-tetraformylbiphenyl is used to replace 2.1 g of 4,4'-biphenyldicarboxaldehyde;

[0045] (2) Synthesize the composite antibacterial epoxy crosslinking agent II. The specific synthesis method is as follows: Using the nucleophilic substitution reaction mechanism, through the quaternary phosphonation reaction of the tertiary phosphine group of the tetra-Schiff base tertiary phosphine monomer with the chlorine functional group of epichlorohydrin, the composite antibacterial epoxy crosslinking agent II is generated. The specific experimental steps refer to the preparation experiment of the composite antibacterial epoxy crosslinking agent I, and the only difference is that 2.9 g of the tetra-Schiff base tertiary phosphine monomer is used to replace 3.3 g of the di-Schiff base tertiary phosphine monomer;

[0046] The 1H NMR characterization of the composite antibacterial epoxy crosslinking agent II is as follows: 1 H NMR(CDCl3, 400 MHz) δ: 1.92 - 1.99(m, 8H), 3.49 - 3.51(d, 8H), 3.72 - 4.02(m, 28H), 7.40 - 7.81(m, 46H), 8.42(s, 4H).

[0047] Example 1:

[0048] Prepare the crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane I. The preparation steps are as follows:

[0049] Step 1, prepare the chitosan / polyvinyl alcohol / acetic acid aqueous solution: First, add 0.8 g of chitosan (purchased from Shanghai Macklin Biochemical Co., Ltd., with a relative molecular mass of 1,000,000) to 10 g of acetic acid aqueous solution (the mass ratio of acetic acid to deionized water is 7:3), stir at room temperature for 12 h until completely dissolved, and prepare a chitosan / acetic acid aqueous solution with a mass fraction of 8.0 wt%. Then, add 0.8 g of polyvinyl alcohol (purchased from Shanghai Macklin Biochemical Co., Ltd., with a relative molecular mass of 250,000) to 10 g of deionized water, stir at 70 °C for 12 h until completely dissolved, and prepare a polyvinyl alcohol aqueous solution with a mass fraction of 8.0 wt%. Finally, mix the prepared chitosan / acetic acid aqueous solution and polyvinyl alcohol aqueous solution, stir at room temperature for 2 h until evenly mixed, and let stand for 5 h to defoam to obtain the chitosan / polyvinyl alcohol / acetic acid aqueous solution;

[0050] Step 2: Prepare chitosan-polyvinyl alcohol nanofiber membrane: Inject the chitosan / polyvinyl alcohol / acetic acid aqueous solution prepared in Step 1 into the feeding pump of a DXES-3 type electrospinning machine for electrospinning. The electrospinning voltage is 25 kV, the electrospinning distance is 20 cm, the perfusion speed is 0.5 mL / h, the temperature is 25 °C, and the humidity is 60% RH. Place a non-woven fabric substrate on the receiving device to collect the nanofiber membrane. After the electrospinning is completed, place the nanofiber membrane collected on the receiving substrate in a vacuum oven at 30 °C and dry it for 1 h to remove the residual solvent, obtaining a chitosan-polyvinyl alcohol nanofiber membrane with a thickness of 50 μm and a surface density of 4.5 g / m 2 of chitosan-polyvinyl alcohol nanofiber membrane;

[0051] Step 3: Prepare crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane I: Based on the epoxy ring-opening mechanism, through the ring-opening reaction of the epoxy functional groups of the composite antibacterial epoxy crosslinking agent I with the hydroxyl and amino functional groups contained in the chitosan-polyvinyl alcohol nanofiber membrane, the crosslinking modification of the chitosan-polyvinyl alcohol nanofiber membrane is realized, and crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane I is prepared;

[0052] The specific experimental steps for preparing crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane I are as follows: Mix 0.5 g of the composite antibacterial epoxy crosslinking agent I, 4 g of acetone and 6 g of deionized water evenly to prepare a 5.0 wt% composite antibacterial epoxy crosslinking agent I solution. Then, completely immerse the chitosan-polyvinyl alcohol nanofiber membrane prepared in Step 2 in the composite antibacterial epoxy crosslinking agent I solution, keep it for 2 h for crosslinking reaction, take it out and wash it repeatedly with acetone and deionized water, fully infiltrate it with ethanol, air-dry it at room temperature and then place it in a vacuum oven at 30 °C and dry it for 1 h to obtain crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane I.

[0053] Example 2:

[0054] Prepare crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane II: Based on the epoxy ring-opening mechanism, through the ring-opening reaction of the epoxy functional groups of the composite antibacterial epoxy crosslinking agent II with the hydroxyl and amino functional groups contained in the chitosan-polyvinyl alcohol nanofiber membrane, the crosslinking modification of the chitosan-polyvinyl alcohol nanofiber membrane is realized, and crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane II is prepared. The specific experimental steps refer to the preparation experiment of crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane I, and the difference is only that; the composite antibacterial epoxy crosslinking agent II is used to replace the composite antibacterial epoxy crosslinking agent I.

[0055] Example 3:

[0056] Prepare nanofiber composite filter material I, and its preparation steps are as follows:

[0057] Step 1, Preparation of non-woven fabric / crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane composite structure I: Refer to the preparation experiment of crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane I in Example 1, with the only difference being that during the preparation of chitosan-polyvinyl alcohol nanofiber membrane by electrospinning process, a PP non-woven fabric (purchased from Zhejiang Runjiang New Material Technology Co., Ltd., with a thickness of 100 μm and a surface density of 40 g / m 2 ) is used as the receiving substrate. The PP non-woven fabric substrate and the deposited chitosan-polyvinyl alcohol nanofiber membrane are peeled off together and immersed in the composite antibacterial epoxy crosslinking agent I solution for crosslinking modification treatment to obtain the non-woven fabric / crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane composite structure I;

[0058] Step 2, Preparation of nanofiber composite filter material I: Another layer of PP non-woven fabric is covered on the crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane in the non-woven fabric / crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane composite structure I to obtain the nanofiber composite filter material I.

[0059] Example 4:

[0060] Preparation of nanofiber composite filter material II, and the specific experimental steps refer to the preparation experiment of nanofiber composite filter material I, with the only difference being that the composite antibacterial epoxy crosslinking agent II solution is used to replace the composite antibacterial epoxy crosslinking agent I solution.

[0061] Comparative Example 1:

[0062] Preparation of a conventional crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane, and the specific preparation steps refer to the preparation experiment of crosslinked modified chitosan-polyvinyl alcohol nanofiber membrane I, with the only difference being that a conventional glutaraldehyde crosslinking agent is used to replace the composite antibacterial epoxy crosslinking agent I;

[0063] Preparation of nanofiber composite filter material a, and the specific preparation steps refer to the preparation experiment of nanofiber composite filter material I, with the only difference being that a conventional glutaraldehyde crosslinking agent solution is used to replace the composite antibacterial epoxy crosslinking agent I solution.

[0064] Comparative Example 2:

[0065] Preparation of nanofiber composite filter material b, and the specific preparation steps refer to the preparation experiment of nanofiber composite filter material I, with the only difference being that the PP non-woven fabric substrate and the deposited chitosan-polyvinyl alcohol nanofiber membrane are peeled off together, but not immersed in the composite antibacterial epoxy crosslinking agent I solution for crosslinking modification treatment (i.e., the chitosan-polyvinyl alcohol nanofiber membrane is not crosslinked and modified).

[0066] Performance test:

[0067] The following performance tests were performed on the cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane:

[0068] (1) Water resistance test: The fiber membrane sample was placed in an atmosphere of 25°C and 60% RH for 24 h. Then, the fiber membrane sample (m0g) was placed in 100 mL of deionized water and soaked for 1 h to ensure complete water absorption. The sample was taken out and filter paper was placed on the surface of the sample to absorb the surface moisture. The sample was dried to a constant weight and the mass of the fiber membrane sample (m1g) was recorded. The mass loss rate was calculated and the water resistance of the material was characterized by the mass loss rate of the fiber membrane sample. The lower the mass loss rate, the better the water resistance of the material. The specific method is as follows:

[0069] Mass loss rate (%) = (m0-m1) / m0×100%;

[0070] (2) Mechanical properties test: A YM-06E electronic single fiber strength tester was used to perform a tensile test on a fiber membrane sample with a size of 10 mm × 40 mm at a tensile speed of 5 mm / min under the conditions of 25°C and 60% RH. The gauge length was set to 20 mm, and the tensile strength of the sample was recorded.

[0071] (3) Antibacterial performance test: 200 μL of bacterial solution was transferred to 500 mL of LB broth culture medium sterilized at 120°C, and cultured in a shaker (37°C, 120 r / min) for 24 h as the test bacterial solution. The test bacterial solution was gradient diluted using sterilized test tubes on a clean bench to obtain the test bacterial solution. 100 μL of the solution with a concentration of 10 8 CFU / mL of test bacterial solution was added to LB broth solid culture medium, and the coating was evenly spread using a coating rod. Then, a 6 mm circular fiber membrane sample was attached to the surface of the LB broth solid culture medium. The LB broth solid culture medium was inverted and cultured in a 37°C biological incubator for 24 h. The diameter of the inhibition zone around the sample (including the diameter of the sample disc) was recorded.

[0072] The bacterial liquid was ATCC6538 Staphylococcus aureus and ATCC25922 Escherichia coli purchased from Shanghai Luwei Technology Co., Ltd.

[0073] The above experimental results are shown in Table 1 below.

[0074]

[0075] The following performance tests were performed on the nanofiber composite filter material:

[0076] (1)Air filtration performance test: The air filtration performance of the sample was tested using an 8130 automatic filter media tester from TSI, Inc., USA. During the test, compressed air enters the device in three paths: The first path enters an aerosol generator containing a 2 wt% NaCl aqueous solution to generate NaCl aerosol with an average particle size of 0.26 µm; the aerosol in this path is mixed with the compressed air in the second path in a mixer, and the dilution concentration is adjusted to 20 mg / m 3 by controlling the flow regulating valve, and then it passes through the filter element to be tested; the third path of compressed air provides a clamping force to ensure that the upper and lower jigs are tightened during the test. When the NaCl aerosol passes through the filter element to be tested, the upstream and downstream photometers respectively detect the NaCl aerosol concentration before and after passing through the filter element. The gas flow rate is 85 L / min, and the filtration efficiency of the sample is calculated as follows:

[0077] Filtration efficiency (%) = (upstream NaCl concentration - downstream NaCl concentration) × 100%;

[0078] (2)Antibacterial performance test: The antibacterial performance of the sample was evaluated with reference to GB / T 20944-2008. The specific test steps were as follows: A 6-mm-diameter sample was placed in a well plate, and 0.1 mL of a bacterial suspension with a concentration of 2×10 8 CFU / mL (phosphate buffered saline as the buffer) was dropped on the surface, and then it was placed in an MJ-250I mold incubator for 30 min. After that, 0.9 mL of phosphate buffered saline was dropped into the well plate that had been added with the bacterial suspension before. After shaking well, 0.1 mL of the phosphate buffered saline was taken from the well plate and dropped into a centrifuge tube (volume 1.5 mL) containing 0.9 mL of phosphate buffered saline, and it was serially diluted 1×10 6 times in sequence. 10 μL was taken from each dilution gradient solution and dropped on a culture medium plate, and it was cultured for 24 h. The number of bacterial colonies was recorded and the antibacterial rate of the sample was calculated as follows:

[0079] Antibacterial rate (%) = { (average colony value of the original bacterial suspension countable series - average colony value of the sample after antibacterial treatment and the corresponding gradient of the original bacterial suspension) / average colony value of the original bacterial suspension countable series} × 100%;

[0080] Among them, the bacterial suspension was Staphylococcus aureus ATCC6538 and Escherichia coli ATCC25922 purchased from Shanghai Luwei Technology Co., Ltd.;

[0081] The above experimental results are shown in Table 2 below.

[0082]

[0083] The following conclusions can be drawn through comprehensive analysis of the above experimental results:

[0084] (1) The present invention uses a self-developed composite antibacterial epoxy cross-linking agent to carry out cross-linking modification on the chitosan-polyvinyl alcohol nanofiber membrane. The cross-linked and modified chitosan-polyvinyl alcohol nanofiber membrane prepared thereby has achieved beneficial technical effects of significant improvement in water resistance, antibacterial performance, and mechanical properties compared with the uncross-linked and modified chitosan-polyvinyl alcohol nanofiber membrane and the chitosan-polyvinyl alcohol nanofiber membrane conventionally cross-linked and modified with glutaraldehyde;

[0085] Among them, the composite performance of the cross-linked and modified chitosan-polyvinyl alcohol nanofiber membrane II prepared with the composite antibacterial epoxy cross-linking agent II is better;

[0086] (2) The air filtration efficiency of the nanofiber composite filter material prepared by the present invention is >97%, and the antibacterial rate is >95%, showing very excellent filtration and antibacterial effects.

Claims

1. A process for preparing a nanofiber composite filter material, characterized in that: The following steps are involved: Step 1: synthesizing a composite antibacterial epoxy crosslinking agent, wherein the composite antibacterial epoxy crosslinking agent is composite antibacterial epoxy crosslinking agent I or composite antibacterial epoxy crosslinking agent II; Step 2: using chitosan and polyvinyl alcohol as raw materials, adopting electrospinning process to prepare chitosan-polyvinyl alcohol nanofiber membrane; Step 3: Based on the epoxy ring-opening mechanism, the epoxy functional groups of the composite antibacterial epoxy crosslinking agent react with the hydroxyl and amino functional groups contained in the chitosan-polyvinyl alcohol nanofiber membrane to undergo a ring-opening reaction, thereby achieving the cross-linking modification of the chitosan-polyvinyl alcohol nanofiber membrane and preparing a cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane; Step 4: Compounding the cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane as the intermediate filter medium layer with the PP non-woven fabric base layer to prepare a nanofiber composite filter material; The chemical structural formula of the composite antibacterial epoxy crosslinking agent I is: The chemical structural formula of the composite antibacterial epoxy crosslinking agent II is: .

2. The preparation process of a nanofiber composite filter material according to claim 1, characterized in that: The preparation method of the composite antibacterial epoxy crosslinking agent I is: The Schiff base reaction mechanism is used to generate a di-Schiff base tertiary phosphine monomer through a condensation reaction between the carbonyl functional group of 4,4'-biphenyldicarboxaldehyde and the amino functional group of 3-(diphenylphosphino)propylamine. The composite antibacterial epoxy crosslinking agent I is generated by utilizing the nucleophilic substitution reaction mechanism, through the quaternary phosphine group of the di-Schiff base tertiary phosphine monomer and the chlorine functional group of epichlorohydrin.

3. The preparation process of a nanofiber composite filter material according to claim 1, characterized in that: The preparation method of the composite antibacterial epoxy crosslinking agent II is as follows: Using the Schiff base reaction mechanism, the carbonyl functional group of 3,3',5,5'-tetraaldehyde biphenyl reacts with the amino functional group of 3-(diphenylphosphino)propylamine to generate tetra-Schiff base tertiary phosphine monomers; Utilizing the nucleophilic substitution reaction mechanism, the tertiary phosphine group of the tetra-Schiff base tertiary phosphine monomer reacts with the chlorine functional group of epichlorohydrin to undergo quaternary phosphination reaction to generate a composite antibacterial epoxy crosslinker II.

4. The preparation process of a nanofiber composite filter material according to claim 1, characterized in that: The mass ratio of chitosan to polyvinyl alcohol in the chitosan-polyvinyl alcohol nanofiber membrane of step 2 is 1:(0.8-2).

5. The preparation process of a nanofiber composite filter material according to claim 1, characterized in that: The preparation method of the cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane is as follows: a composite antibacterial epoxy cross-linking agent, acetone and deionized water are mixed to prepare a composite antibacterial epoxy cross-linking agent solution with a mass fraction of 1-10wt%, the chitosan-polyvinyl alcohol nanofiber membrane is completely immersed in the composite antibacterial epoxy cross-linking agent solution, and the cross-linking reaction is maintained for 1-5 hours, and the cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane is taken out, washed and dried to obtain the cross-linked modified chitosan-polyvinyl alcohol nanofiber membrane.

6. A nanofiber composite filter material prepared by the process according to any one of claims 1 to 5, characterized in that: The air filtration efficiency of the nanofiber composite filter material is greater than 98%.

7. A nanofiber composite filter material prepared by the process according to any one of claims 1 to 5, characterized in that: The antibacterial rate of the nanofiber composite filter material is greater than 96%, and the bacteria are Escherichia coli or Staphylococcus aureus.

8. Application of a nanofiber composite filter material prepared according to the process according to any one of claims 1 to 5 in a medical mask.

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