Polypropylene melt-blown nonwoven fabric based on metal organic framework material and preparation method thereof

Abstract

The invention relates to the technical field of composite materials, and in particular to a polypropylene meltblown non-woven fabric based on a metal organic framework material and a preparation method thereof. The invention comprises the following steps: preparing a chitosan solution, ultrasonically dispersing MOFs in anhydrous methanol to obtain a metal organic solution, adding the chitosan solution to the metal organic solution and stirring for 0.5 to 3 hours, washing the precipitate obtained by centrifugation with DMF and methanol for 3 to 5 times, respectively, and drying the precipitate in a vacuum drying oven at 60 to 100° C. for 6 to 12 hours to obtain MOFs@CS, placing 2 to 8 wt% of MOFs@CS and 92 to 98 wt% of polypropylene in a twin-screw extruder with a screw speed of 8 to 25 Hz and a screw heating temperature of 190 to 240° C., melt-mixing the mixture, and delivering the mixture to a spinneret via a metering pump. The mixture is blown out by a fan and laid into a net, which is then collected to obtain a MOFs@CS / polypropylene flame-retardant and antibacterial meltblown non-woven fabric. The polypropylene melt-blown non-woven fabric based on the metal organic framework material of the present invention has excellent flame retardant and antibacterial properties, and the MOFs@CS therein has good biocompatibility with polypropylene and will not damage the inherent properties of polypropylene.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a polypropylene meltblown nonwoven fabric based on a metal organic framework material and a preparation method thereof. Background Art

[0002] Polypropylene nonwoven fabric is a type of nonwoven fabric. It is a nonwoven sheet of ordered or disordered fibers formed by arranging or spraying spun fibers onto a substrate and then curing them in various forms. Nonwoven fabrics offer the advantages of low cost and a wide range of applications. Polypropylene (PP) nonwoven fabrics offer numerous advantages, including light weight, small pore size, high porosity, and excellent air permeability, making them highly efficient and energy-efficient filter materials.

[0003] However, polypropylene non-woven fabrics have high crystallinity and poor hydrophilicity, making them very susceptible to bacterial growth on their surfaces, which limits their scope of use. Antibacterial finishing can reduce bacterial infection, which is beneficial for their application in the fields of medical biomaterials and air filtration materials such as medical masks, central air conditioning filtration, and clean rooms. In the prior art, non-woven fabrics generally treated with coating methods have low coating fastness and are easy to fall off. In addition, a large amount of antibacterial liquid is consumed during the treatment, resulting in poor antibacterial effect. In addition, since polypropylene is a hydrocarbon material with a low oxygen index (limiting oxygen index of only 17.4% to 18.5%), it is easy to burn and has a low charring rate. When burning, it produces molten droplets, which can easily spread flames and cause fires. The unsafe factors it presents greatly limit its scope of application.

[0004] Therefore, there is a need for an effective flame retardant and antibacterial polypropylene non-woven fabric to expand the application range of the polypropylene non-woven fabric. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a polypropylene meltblown non-woven fabric based on a metal organic framework material and a preparation method thereof, so as to solve the problem that the existing polypropylene non-woven fabric has poor flame retardant and antibacterial properties.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] The first aspect of the present invention is to provide a polypropylene meltblown non-woven fabric based on metal organic framework materials, comprising the following raw materials: 2-8 wt% MOFs@CS and 92-98 wt% polypropylene, wherein the MOFs@CS is a composite of metal organic framework materials and chitosan.

[0008] In combination with the first aspect, in some optional embodiments, the molar ratio of the metal organic framework material to chitosan in the MOFs@CS is 1 to 5:1.

[0009] The second aspect of the present invention is to provide a method for preparing a polypropylene meltblown nonwoven fabric based on a metal organic framework material, comprising the following steps:

[0010] To synthesize MOFs@CS, chitosan was dissolved in an acetic acid solution to obtain a chitosan solution, the metal organic framework material was ultrasonically dispersed in anhydrous methanol to obtain a metal organic solution, the chitosan solution was added to the metal organic solution and magnetically stirred for 0.5 to 3 hours, and the precipitate obtained by centrifugation was washed with DMF and methanol for 3 to 5 times, respectively, and dried in a vacuum drying oven at 60 to 100°C for 6 to 12 hours to obtain the product MOFs@CS;

[0011] Melt spinning: 2-8 wt% MOFs@CS and 92-98 wt% polypropylene slices are placed in a twin-screw extruder with a screw speed of 8-25 Hz and a screw heating temperature of 190-240°C. After melt mixing, they are sent to the spinneret through a metering pump, blown out by a fan, and laid into a net to obtain MOFs@CS / polypropylene flame-retardant and antibacterial melt-blown non-woven fabric.

[0012] In combination with the second aspect, in some optional embodiments, in the step of synthesizing MOFs@CS, the molar volume ratio of the chitosan, metal organic framework material, acetic acid and methanol is 10-50 mmol:10 mmol:50 mL:50-300 mL.

[0013] In conjunction with the second aspect, in some optional embodiments, the preparation method of the metal organic framework material is as follows:

[0014] The metal salt is added to the solvent and stirred for 5 to 30 minutes, which is recorded as the salt solution; the organic ligand and additive are added to the solvent and stirred for 5 to 30 minutes until completely dissolved, which is recorded as the organic solution. The organic solution is added to the salt solution under stirring, and then magnetically stirred at 25 to 100° C. for 0.5 to 6.0 hours and then allowed to stand for 6 to 24 hours. The precipitate is collected and dried at 60 to 100° C. for 6 to 24 hours to obtain a metal organic framework material.

[0015] In combination with the second aspect, in some optional embodiments, the molar volume ratio of the metal salt, the organic ligand, the additive and the solvent is 1 mmol: 1 to 20 mmol: 0 to 5 mmol: 5 to 200 mL.

[0016] In combination with the second aspect, in some optional embodiments, the metal salt is one of zinc nitrate hexahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, copper nitrate trihydrate, zirconium tetrachloride, chromium trichloride hexahydrate, copper sulfate pentahydrate and ferric nitrate nonahydrate.

[0017] In combination with the second aspect, in some optional embodiments, the organic ligand is one of 2-methylimidazole, trimesic acid, terephthalic acid, and benzimidazole.

[0018] In combination with the second aspect, in some optional embodiments, the solvent is one of ethanol, methanol, deionized water, and DMF.

[0019] In combination with the second aspect, in some optional embodiments, the additive is one or more of NaOH, ethylenediamine, triethylamine, polyvinyl pyrrolidone, sodium dodecylbenzenesulfonate, and polyethylene glycol.

[0020] The flame retardant mechanism of the polypropylene melt-blown nonwoven fabric based on metal organic framework materials of the present invention is as follows: (1) the metal organic framework materials MOFs prepared by the present invention have certain flame retardant effects themselves, and their metal ion centers can be catalyzed into carbon to form a dense protective layer during combustion, and their porous structure can absorb smoke and toxic gases in the early stage of combustion; (2) chitosan itself contains a large amount of C and N elements, which can serve as a carbon source and form a dense protective layer during combustion; (3) MOFs and CS produce a synergistic flame retardant effect during combustion, and their flame retardant performance is much higher than that of either alone. The antibacterial mechanism of the polypropylene melt-blown nonwoven fabric based on metal organic framework materials of the present invention is as follows: (1) MOFs achieves continuous killing of bacteria by continuously and slowly releasing intrinsic metal ions, and imidazole organic ligands also have certain antibacterial effects; (2) the positive charge carried by the chitosan molecules interacts with the negative charge carried by the microbial cell membrane, causing bacterial proteins and other cell components to leak and produce an antibacterial effect.

[0021] The polypropylene meltblown nonwoven fabric based on a metal-organic framework (MOF) material of the present invention exhibits excellent flame retardancy and antibacterial properties, with a limiting oxygen index of 30.6% and a V-0 rating in the vertical burning test (UL94). It exhibits an antibacterial rate exceeding 99% against Escherichia coli, Staphylococcus aureus, and Candida albicans, and even remains above 97% after 100 washes. The MOFs@CS exhibits excellent biocompatibility with polypropylene, does not impair the inherent properties of polypropylene, and enhances its physical and mechanical properties to a certain extent. The preparation method of the present invention utilizes readily available raw materials, is environmentally friendly and non-toxic, and has simple synthesis steps, enabling mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the vertical combustion test process of the polypropylene melt-blown non-woven fabric based on the metal organic framework material prepared in Example 1;

[0023] Figure 2 This is the vertical combustion test process of the polypropylene melt-blown non-woven fabric based on the metal organic framework material prepared in Example 2;

[0024] Figure 3 This is the vertical combustion test process of the polypropylene melt-blown non-woven fabric based on the metal organic framework material prepared in Example 3;

[0025] Figure 4 It is the limiting oxygen index LOI statistical chart;

[0026] Figure 5 It is a comparison chart of the inhibition zones of pure PP and polypropylene melt-blown nonwoven fabrics based on metal organic framework materials prepared in Examples 1-3. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the implementation of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] In the following examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All raw materials, equipment, or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0029] This application synthesizes a series of MOFs materials by a solvent thermal method, and then combines them with CS to prepare a new flame retardant antibacterial agent, which is applied to polypropylene to obtain a MOFs@CS / polypropylene flame retardant antibacterial melt-blown non-woven fabric. Chitosan (CS) is a polysaccharide containing polyhydroxyl and polyamino structures. It can react with a variety of substances to prepare chitosan derivatives. It also has excellent flame retardant and carbon-forming properties. Therefore, it is often used as a modifier for flame retardants and added to polymers to improve the flame retardancy and mechanical properties of polymers. In addition, CS has broad-spectrum antibacterial properties and has strong inhibitory ability against Escherichia coli, Staphylococcus aureus, Streptococcus and certain fungi.

[0030] In the preparation method of polypropylene melt-blown non-woven fabric based on metal-organic framework materials of the present application, the metal salt is one of zinc nitrate hexahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, copper nitrate trihydrate, zirconium tetrachloride, chromium trichloride hexahydrate, copper sulfate pentahydrate and ferric nitrate nonahydrate, the organic ligand is one of 2-methylimidazole, trimesic acid, terephthalic acid, and benzimidazole, the solvent is one of ethanol, methanol, deionized water, and DMF, and the additive is one or more of NaOH, ethylenediamine, triethylamine, polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, and polyethylene glycol.

[0031] The following examples 1-5 illustrate the polypropylene meltblown nonwoven fabric based on metal organic framework materials and the preparation method thereof of the present invention:

[0032] Example 1

[0033] (1) Synthesis of ZIF-8: 2.71 g of zinc nitrate hexahydrate was added to 60 mL of deionized water and stirred for 10 min, designated as solution A. 6.57 g of 2-methylimidazole and 0.1 g of NaOH were added to 60 mL of deionized water and stirred for 10 min, designated as solution B. Solution B was then added to solution A under magnetic stirring. The mixture was then magnetically stirred at 25°C for 30 min and allowed to stand for 12 h. The precipitate was collected and dried at 80°C for 10 h to obtain ZIF-8.

[0034] (2) Synthesis of ZIF-8@CS: 1.61 g of CS was dissolved in 50 mL of 1% acetic acid to obtain solution A. 2.3 g of ZIF-8 was ultrasonically dispersed in 50 mL of anhydrous methanol to obtain solution B. Solution A was added to solution B and magnetically stirred for 1 h. The product was then centrifuged to obtain the product. The product was washed five times with DMF and five times with methanol, respectively, and dried in a vacuum oven at 80°C for 10 h.

[0035] (3) Preparation of ZIF-8@CS / polypropylene meltblown nonwoven fabric: 4 wt% ZIF-8@CS and 96 wt% polypropylene chips were melt-mixed in a twin-screw extruder and pumped to a spinneret via a metering pump. The mixture was blown out by a fan and laid onto a web, which was then collected to obtain a flame-retardant and antibacterial ZIF-8@CS / polypropylene meltblown nonwoven fabric. The screw speed was 10 Hz, and the average temperature of the screw heating zone was 215°C.

[0036] Example 2

[0037] (1) Synthesis of HKUST-1: 1.50 g of Cu(NO₃)₂·3H₂O was dissolved in 100 mL of DMF and stirred for 5 min, designated as Solution A. 0.84 g of trimesic acid and 0.300 g of PVP were dissolved in 100 mL of DMF and stirred for 5 min, designated as Solution B. Solution B was added to Solution A under magnetic stirring and heated at 80°C for 24 h. The resulting blue precipitate was cooled to room temperature, collected by centrifugation, and washed alternately with DMF and ethanol three times, and finally dried in a vacuum oven at 60°C for 12 h.

[0038] (2) Synthesis of HKUST-1@CS: 2.42 g of CS was dissolved in 75 mL of 1% acetic acid to obtain solution A. 9.89 g of HKUST-1 was ultrasonically dispersed in 75 mL of anhydrous methanol to obtain solution B. Solution A was added to solution B and magnetically stirred for 1 h. The product was then centrifuged to obtain the product. The product was washed three times with DMF and methanol, respectively, and dried in a vacuum oven at 80°C for 10 h.

[0039] (3) Preparation of HKUST-1@CS / polypropylene meltblown nonwoven fabric: 4 wt% HKUST-1@CS and 96 wt% polypropylene chips were melt-mixed in a twin-screw extruder and pumped to a spinneret via a metering pump. The mixture was blown out by a fan and laid onto a web, which was then collected to obtain the HKUST-1@CS / polypropylene flame-retardant and antibacterial meltblown nonwoven fabric. In this step, the screw speed was 8 Hz, and the average screw heating temperature was 212°C.

[0040] Example 3

[0041] (1) Synthesis of UiO-66: 1.049 g of zirconium tetrachloride was dissolved in 45 mL of DMF and stirred for 5 min, which was designated as solution A. 0.748 g of terephthalic acid was also dissolved in 45 mL of DMF and stirred for 5 min, which was designated as solution B. Solution A and solution B were then mixed and stirred with a magnetic stirrer for 30 min, followed by the addition of 0.375 mL of 12 M hydrochloric acid to obtain a mixed solution C. Mixed solution C was sealed in a Teflon-coated autoclave, then reacted in an oven at 120°C for 24 h, and then allowed to stand at room temperature for 24 h. The resulting precipitate was washed three times with DMF and methanol, respectively, and finally dried at 60°C for 8 h.

[0042] (2) Synthesis of UiO-66@CS: 3.22 g of CS was dissolved in 100 mL of 1% acetic acid to obtain solution A. 17.5 g of UiO-66 was ultrasonically dispersed in 100 mL of anhydrous methanol to obtain solution B. Solution A was added to solution B and magnetically stirred for 1 h. The product was then centrifuged to obtain the product. The product was washed five times with DMF and five times with methanol, respectively, and dried in a vacuum oven at 80°C for 12 h.

[0043] (3) Preparation of UiO-66@CS / polypropylene meltblown nonwoven fabric: 4 wt% UiO-66@CS and 96 wt% polypropylene chips were melt-mixed in a twin-screw extruder and pumped to a spinneret via a metering pump. The mixture was blown out by a fan and laid onto a web, which was then collected to obtain a flame-retardant and antibacterial UiO-66@CS / polypropylene meltblown nonwoven fabric. The screw speed was 10 Hz, and the average screw heating temperature was 216°C.

[0044] Example 4

[0045] (1) Synthesis of ZIF-8: 2.71 g of zinc nitrate hexahydrate was added to 60 mL of deionized water and stirred for 30 min, designated as solution A. 6.57 g of 2-methylimidazole and 0.1 g of NaOH were added to 60 mL of deionized water and stirred for 30 min, designated as solution B. Solution B was added to solution A under magnetic stirring. The mixture was then magnetically stirred at 100°C for 0.5 min and allowed to stand for 6 h. The precipitate was collected and dried at 100°C for 6 h to obtain ZIF-8.

[0046] (2) Synthesis of ZIF-8@CS: 1.61 g of CS was dissolved in 50 mL of 1% acetic acid to obtain solution A. 2.3 g of ZIF-8 was ultrasonically dispersed in 50 mL of anhydrous methanol to obtain solution B. Solution A was added to solution B and magnetically stirred for 3 h. The product was then centrifuged to obtain the product. The product was washed three times with DMF and methanol, respectively, and dried in a vacuum oven at 100°C for 6 h.

[0047] (3) Preparation of ZIF-8@CS / polypropylene meltblown nonwoven fabric: 8 wt% ZIF-8@CS and 92 wt% polypropylene chips were melt-mixed in a twin-screw extruder and pumped to a spinneret via a metering pump. The mixture was blown out by a fan and laid onto a web, which was then collected to obtain a flame-retardant and antibacterial ZIF-8@CS / polypropylene meltblown nonwoven fabric. The screw speed was 20 Hz, and the average temperature of the screw heating zone was 190°C.

[0048] Example 5

[0049] (1) Synthesis of ZIF-8: 2.71 g of zinc nitrate hexahydrate was added to 60 mL of deionized water and stirred for 10 min, designated as solution A. 6.57 g of 2-methylimidazole and 0.1 g of NaOH were added to 60 mL of deionized water and stirred for 10 min, designated as solution B. Solution B was then added to solution A under magnetic stirring. The mixture was then magnetically stirred at 50°C for 6 h and allowed to stand for 6 h. The precipitate was collected and dried at 80°C for 10 h to obtain ZIF-8.

[0050] (2) Synthesis of ZIF-8@CS: 1.61 g of CS was dissolved in 50 mL of 1% acetic acid to obtain solution A. 2.3 g of ZIF-8 was ultrasonically dispersed in 50 mL of anhydrous methanol to obtain solution B. Solution A was added to solution B and magnetically stirred for 0.5 h. The product was then centrifuged to obtain the product. The product was washed five times with DMF and five times with methanol, respectively, and dried in a vacuum oven at 60°C for 12 h.

[0051] (3) Preparation of ZIF-8@CS / polypropylene meltblown nonwoven fabric: 2 wt% ZIF-8@CS and 98 wt% polypropylene chips were melt-mixed in a twin-screw extruder and pumped to a spinneret via a metering pump. The mixture was blown out by a fan and laid onto a web, which was then collected to obtain a flame-retardant and antibacterial ZIF-8@CS / polypropylene meltblown nonwoven fabric. The screw speed was 25 Hz, and the average temperature of the screw heating zone was 240°C.

[0052] Pure polypropylene was used as the control group to test the flame retardancy of the polypropylene meltblown nonwoven fabrics prepared in Examples 1-3. Considering that polypropylene shrinks when heated, it is not convenient to directly test the flame retardancy of the meltblown fabric. Therefore, the polypropylene composite melt was prepared into a specimen and tested according to the national standards GB / T2046.2-2009 and GB / T2048-2021. The vertical combustion test process is as follows: Figure 1-3 As shown, the oxygen index test results are as follows Figure 4 As shown, it was found that: by adding 4wt% ZIF-8@CS, 4wt% HKUST-1@CS and 4wt% UiO-66@CS to the polypropylene melt-blown non-woven fabrics in Examples 1-3, the flame retardant performance detected that the limiting oxygen index (LOI) increased from 18.0% to 30.6%, 29.8% and 29.6%, respectively, and the vertical burning test (UL94) could reach V-0, level.

[0053] The antibacterial performance of the polypropylene melt-blown nonwoven fabrics prepared in Examples 1-3 was tested, and the plate colony images were as follows: Figure 5 As shown, it was found that the antibacterial flame retardant polypropylene composite fibers prepared in Examples 1-3 had an antibacterial rate of more than 99% against Escherichia coli, Staphylococcus aureus, and Candida albicans. After washing 100 times, the antibacterial rate still reached more than 97%, showing long-lasting and high-efficiency antibacterial efficiency.

[0054] The above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that the technical solutions of the present invention may be modified or replaced with equivalents without departing from the spirit and scope of the technical solutions of the present invention, and such modifications or equivalents shall be encompassed by the claims of the present invention. Any techniques, shapes, and structures not described in detail herein are well known.

Claims

1. Polypropylene meltblown nonwoven fabric based on metal organic framework material, characterized in that: The method comprises the following raw materials: 2-8 wt% MOFs@CS and 92-98 wt% polypropylene, wherein the MOFs@CS is a composite of a metal organic framework material and chitosan, and the molar ratio of the metal organic framework material to chitosan in the MOFs@CS is 1-5:

1. The method comprises the following steps: To synthesize MOFs@CS, chitosan was dissolved in an acetic acid solution to obtain a chitosan solution, the metal organic framework material was ultrasonically dispersed in anhydrous methanol to obtain a metal organic solution, the chitosan solution was added to the metal organic solution and magnetically stirred for 0.5 to 3 hours, and the precipitate obtained by centrifugation was washed with DMF and methanol for 3 to 5 times, respectively, and dried in a vacuum drying oven at 60 to 100°C for 6 to 12 hours to obtain the product MOFs@CS; Melt spinning: 2-8 wt% MOFs@CS and 92-98 wt% polypropylene slices are placed in a twin-screw extruder with a screw speed of 8-25 Hz and a screw heating temperature of 190-240°C. After melt mixing, they are sent to the spinneret through a metering pump, blown out by a fan, and laid into a net to obtain MOFs@CS / polypropylene flame-retardant and antibacterial melt-blown non-woven fabric.

2. The polypropylene meltblown nonwoven fabric based on metal organic framework material according to claim 1, characterized in that: In the step of synthesizing MOFs@CS, the molar volume ratio of the chitosan, the metal organic framework material, acetic acid and methanol is 10-50 mmol:10 mmol:50 mL:50-300 mL.

3. The polypropylene meltblown nonwoven fabric based on metal organic framework material according to claim 1, characterized in that: The preparation method of the metal organic framework material is as follows: The metal salt is added to the solvent and stirred for 5 to 30 minutes, which is recorded as the salt solution; the organic ligand and additive are added to the solvent and stirred for 5 to 30 minutes until completely dissolved, which is recorded as the organic solution. The organic solution is added to the salt solution under stirring, and then magnetically stirred at 25 to 100° C. for 0.5 to 6.0 hours and then allowed to stand for 6 to 24 hours. The precipitate is collected and dried at 60 to 100° C. for 6 to 24 hours to obtain a metal organic framework material.

4. The polypropylene meltblown nonwoven fabric based on metal organic framework material according to claim 3, characterized in that: The molar volume ratio of the metal salt, the organic ligand, the additive and the solvent is 1 mmol: 1-20 mmol: 0-5 mmol: 5-200 mL.

5. The polypropylene melt-blown nonwoven fabric based on metal organic framework material according to claim 3, characterized in that: The metal salt is one of zinc nitrate hexahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, copper nitrate trihydrate, zirconium tetrachloride, chromium trichloride hexahydrate, copper sulfate pentahydrate and ferric nitrate nonahydrate.

6. The polypropylene meltblown nonwoven fabric based on metal organic framework material according to claim 3, characterized in that: The organic ligand is one of 2-methylimidazole, trimesic acid, terephthalic acid and benzimidazole.

7. The polypropylene meltblown nonwoven fabric based on metal organic framework material according to claim 3, characterized in that: The solvent is one of ethanol, methanol, deionized water and DMF.

8. The polypropylene meltblown nonwoven fabric based on metal organic framework material according to claim 3, characterized in that: The additive is one or more of NaOH, ethylenediamine, triethylamine, polyvinyl pyrrolidone, sodium dodecylbenzenesulfonate, and polyethylene glycol.

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