Electret fresh-keeping nanofiber membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of fresh-keeping films, and provides an electret fresh-keeping nanofiber film as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing fluorine-containing organic matters, silver nanoparticles, water and an organic solvent to obtain a spinning solution; performing electrostatic spinning on the spinning solution to obtain micro-nano fibers, and depositing the micro-nano fibers on base cloth to obtain the electret fresh-keeping nanofiber membrane. Compared with an electret antibacterial preservative film of the same type, the electret preservative nanofiber film has antibacterial performance and high air permeability and light transmission, and the appearance and freshness of food can be maintained; better chemical stability and environmental adaptability are achieved, and the method is not affected by the use environment in general; the charges of the electret preservative film can be self-recovered, and the electret preservative film has certain charge recovery performance when used in an environment with the humidity of 30-90%, so that the antibacterial performance is greatly improved, and the service life of the electret preservative film is greatly prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of cling film, and in particular to an electret cling film and a preparation method and application thereof. Background Art

[0002] Cling film is widely used in the field of food preservation, but traditional cling film is mostly based on plastic, which has problems such as difficult degradation and release of harmful substances. Traditional cling film has limitations in antibacterial properties, cannot effectively inhibit bacterial growth, has a short service life, and has poor effects. At the same time, the material has poor light and air permeability, which limits its application.

[0003] With the development of nanotechnology and materials science, researchers have begun to explore new antibacterial cling film materials. For example, antibacterial nanofibers are prepared by electrospinning. These nanofibers are embedded with hydrogen-bonded organic frameworks (HOFs) nanocrystals, which can produce reactive oxygen species (ROS) under light irradiation, thereby achieving antibacterial effects.

[0004] Therefore, it is of great significance to provide a kind of electret fresh-keeping nanofiber membrane with improved durability and antibacterial properties. Summary of the invention

[0005] The purpose of the present invention is to provide an electret fresh-keeping nanofiber membrane and a preparation method and application thereof in view of the deficiencies in the prior art.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing an electret fresh-keeping nanofiber membrane, comprising the following steps:

[0008] 1) mixing a fluorine-containing organic compound, silver nanoparticles, water and an organic solvent to obtain a spinning solution;

[0009] 2) The spinning solution is subjected to electrostatic spinning to obtain micro-nano fibers, and the micro-nano fibers are deposited on a base fabric to obtain an electret fresh-keeping nanofiber membrane.

[0010] Preferably, in the spinning solution of step 1), the mass fraction of fluorine-containing organic matter is 20-40%, the mass fraction of silver nanoparticles is 0.5-2%, the mass fraction of water is 1-5%, and the mass fraction of organic solvent is 53-78.5%.

[0011] Preferably, the fluorine-containing organic compound comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-trifluoroethylene copolymer and polyvinylidene fluoride-hexafluoroethylene copolymer; and the organic solvent is N,N-dimethylformamide.

[0012] Preferably, the particle size of the silver nanoparticles is 1 to 10 nm.

[0013] Preferably, during the electrospinning process of step 2), the voltage is 10-30 kV, the receiving distance is 10-30 cm, the inner diameter of the spinneret is 0.1-1 mm, the spinning rate is 0.1-2.0 mL / h, the ambient temperature is 10-90° C., and the ambient humidity is 20-90%.

[0014] Preferably, the electrospinning process and the electret process are carried out simultaneously.

[0015] Preferably, in step 2), the base fabric is a single-layer meltblown nonwoven fabric; and the surface potential of the micro-nano fibers is 3 to 5 kV.

[0016] The invention also provides an electret fresh-keeping nanofiber membrane prepared by the preparation method.

[0017] The invention also provides application of the electret fresh-keeping nanofiber membrane in antibacterial fresh-keeping film.

[0018] The beneficial effects of the present invention include the following:

[0019] 1) The present invention utilizes the antibacterial properties of silver nanoparticles, combines the electrostatic spinning technology of polyvinylidene fluoride, embeds silver nanoparticles in the electrostatic spinning of polyvinylidene fluoride, and prepares a nanofiber membrane with electret properties. The electret fresh-keeping nanofiber membrane not only has excellent antibacterial properties, but also can enhance the capture and inactivation ability of microorganisms through the adsorption of electrets, while extending the service life.

[0020] 2) Due to their good antibacterial properties, silver nanoparticles can effectively inhibit the growth of bacteria, fungi and viruses, thereby improving the hygienic and safe performance of food cling film; the inhibition rate of nanofiber membrane against Escherichia coli and Staphylococcus aureus reached more than 99.9%; the antibacterial activity of the electrostatic preservation nanofiber membrane was maintained for at least 6 months under the conditions of 25°C and relative humidity of 65%.

[0021] 3) The tensile strength of the electrostatic fresh-keeping nanofiber membrane of the present invention reaches more than 20MPa, the elongation at break is more than 150%, and it has good flexibility and durability; the structural characteristics of the nanofiber membrane give it good air permeability and hydrophobicity, which helps to maintain the freshness of food, while reducing condensation water inside the fresh-keeping film to keep the food dry and hygienic.

[0022] 4) Compared with the same type of electret antibacterial cling film, the electret fresh-keeping nanofiber film of the present invention has both antibacterial properties and high air permeability and light transmittance. The air permeability is better than that of traditional plastic cling film, and the moisture permeability is moderate, which helps to maintain the appearance and freshness of food; it has better chemical stability and environmental adaptability, and is generally not affected by the use environment. The charge of the electret fresh-keeping nanofiber film of the present invention can be self-recovered, and it has a certain charge recovery when used in a humidity environment of 30-90%, which greatly extends the antibacterial performance and use cycle. DETAILED DESCRIPTION

[0023] The present invention provides a method for preparing an electret fresh-keeping nanofiber membrane, comprising the following steps:

[0024] 1) mixing a fluorine-containing organic compound, silver nanoparticles, water and an organic solvent to obtain a spinning solution;

[0025] 2) The spinning solution is subjected to electrostatic spinning to obtain micro-nano fibers, and the micro-nano fibers are deposited on a base fabric to obtain an electret fresh-keeping nanofiber membrane.

[0026] In the spinning solution of step 1) of the present invention, the mass fraction of the fluorine-containing organic matter is preferably 20-40%, more preferably 25-35%, and more preferably 30%; the mass fraction of the silver nanoparticles is preferably 0.5-2%, more preferably 0.8-1.5%, and more preferably 1-1.2%; the mass fraction of water is preferably 1-5%, more preferably 2-4%, and more preferably 3%; the mass fraction of the organic solvent is preferably 53-78.5%, more preferably 58-72%, and more preferably 65-70%.

[0027] In the present invention, the spinning solution has a certain conductivity.

[0028] In the present invention, the fluorine-containing organic compound preferably comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-trifluoroethylene copolymer and polyvinylidene fluoride-hexafluoroethylene copolymer; the organic solvent is preferably N,N-dimethylformamide.

[0029] In the present invention, the particle size of the silver nanoparticles is preferably 1 to 10 nm, more preferably 3 to 7 nm, and even more preferably 5 to 6 nm.

[0030] In the present invention, silver nano ions can effectively inhibit bacteria.

[0031] In the electrospinning process described in step 2) of the present invention, the voltage is preferably 10-30 kV, more preferably 15-25 kV, and more preferably 20 kV; the receiving distance is preferably 10-30 cm, more preferably 15-25 cm, and more preferably 20 cm; the inner diameter of the spinneret is preferably 0.1-1 mm, more preferably 0.3-0.7 mm, and more preferably 0.5-0.6 mm; the spinning rate (spinning solution supply rate) is preferably 0.1-2.0 mL / h, more preferably 0.5-1.5 mL / h, and more preferably 1 mL / h, the ambient temperature is preferably 10-90°C, more preferably 20-80°C, and more preferably 40-50°C; the ambient humidity is preferably 20-90%, more preferably 30-70%, and more preferably 40-50%.

[0032] In the present invention, the electrostatic spinning process and the electret process are carried out simultaneously.

[0033] In the present invention, the device used for electrospinning is preferably a multi-needle electrospinning device.

[0034] In the present invention, the base fabric in step 2) is preferably a single-layer melt-blown non-woven fabric; and the surface potential of the micro-nano fibers is preferably 3 to 5 kV.

[0035] The invention also provides an electret fresh-keeping nanofiber membrane prepared by the preparation method.

[0036] In the present invention, the charge of the electret fresh-keeping nanofiber membrane can be self-recovered, which greatly prolongs the antibacterial performance and service life; the charge content on the surface of the nanofiber membrane is mainly reflected by the surface potential, and the surface potential of the fiber membrane can reach 3 to 5 kV when the spinning process just ends.

[0037] The invention also provides application of the electret fresh-keeping nanofiber membrane in antibacterial fresh-keeping film.

[0038] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0039] Example 1

[0040] Polyvinylidene fluoride, polytetrafluoroethylene, silver nanoparticles, water and N,N-dimethylformamide are mixed to obtain a spinning solution; in the spinning solution, the mass fraction of polyvinylidene fluoride is 15%, the mass fraction of polytetrafluoroethylene is 15%, the mass fraction of silver nanoparticles (particle size is 5nm) is 1%, the mass fraction of water is 3%, and the mass fraction of N,N-dimethylformamide is 66%. Electrospinning is performed using a multi-needle electrospinning device to obtain micro-nano fibers. The process parameters of electrospinning are: voltage 20kV, receiving distance 20cm, spinneret inner diameter 0.5mm, spinning rate 1mL / h, ambient temperature 50℃, ambient humidity 50%. During the electrospinning process, the electret process is carried out at the same time, and the micro-nano fibers are deposited on a single-layer melt-blown non-woven fabric (thickness 25μm) to obtain an electret fresh-keeping nanofiber film.

[0041] The electret fresh-keeping nanofiber membrane of this embodiment has a persistent electrostatic field, and the duration of the persistent electrostatic field is 7×24h. The surface potential of the fresh-keeping nanofiber membrane is 4kV when the spinning process and the electret process are just finished, and then it begins to decay and finally stabilizes at 1.2kV; the water vapor permeability (WVP) of the electret fresh-keeping nanofiber membrane is 0.8g·mm / (m 2 ·day·kPa). The tensile strength of the electret fresh-keeping nanofiber membrane reached 22MPa, and the elongation at break was 160%.

[0042] Example 2

[0043] Polyvinylidene fluoride, polytetrafluoroethylene, silver nanoparticles, water and N,N-dimethylformamide are mixed to obtain a spinning solution; in the spinning solution, the mass fraction of polyvinylidene fluoride is 20%, the mass fraction of polytetrafluoroethylene is 15%, the mass fraction of silver nanoparticles (particle size is 3nm) is 2%, the mass fraction of water is 4%, and the mass fraction of N,N-dimethylformamide is 59%. Electrospinning is performed using a multi-needle electrospinning device to obtain micro-nano fibers. The process parameters of electrospinning are: voltage 25kV, receiving distance 25cm, spinneret inner diameter 0.8mm, spinning rate 1.5mL / h, ambient temperature 70℃, ambient humidity 70%. During the electrospinning process, the electret process is carried out at the same time, and the micro-nano fibers are deposited on a single-layer melt-blown non-woven fabric (thickness 22μm) to obtain an electret fresh-keeping nanofiber film.

[0044] The electret fresh-keeping nanofiber membrane of this embodiment has a persistent electrostatic field, and the duration of the persistent electrostatic field is 7×24h. The surface potential of the fresh-keeping nanofiber membrane is 5kV when the spinning process and the electret process are just finished, and then it begins to decay and finally stabilizes at 1.3kV; the water vapor permeability (WVP) of the electret fresh-keeping nanofiber membrane is 0.9g·mm / (m 2·day·kPa). The tensile strength of the electret fresh-keeping nanofiber membrane reached 21MPa, and the elongation at break was 155%.

[0045] Example 3

[0046] Polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, silver nanoparticles, water and N,N-dimethylformamide are mixed to obtain a spinning solution; in the spinning solution, the mass fraction of polyvinylidene fluoride is 15%, the mass fraction of polyvinylidene fluoride-trifluoroethylene copolymer is 15%, the mass fraction of silver nanoparticles (particle size is 8nm) is 0.6%, the mass fraction of water is 2%, and the mass fraction of N,N-dimethylformamide is 67.4%. Electrospinning is performed using a multi-needle electrospinning device to obtain micro-nano fibers. The electrospinning process parameters are: voltage 15kV, receiving distance 15cm, spinneret inner diameter 0.2mm, spinning rate 0.5mL / h, ambient temperature 20℃, ambient humidity 20%. During the electrospinning process, the electret process is carried out at the same time, and the micro-nano fibers are deposited on a single-layer melt-blown non-woven fabric (thickness 27μm) to obtain an electret fresh-keeping nanofiber film.

[0047] The electret fresh-keeping nanofiber membrane of this embodiment has a persistent electrostatic field, and the duration of the persistent electrostatic field is 7×24h. The surface potential of the fresh-keeping nanofiber membrane is 3kV when the spinning process and the electret process are just finished, and then it begins to decay and finally stabilizes at 1.1kV; the water vapor permeability (WVP) of the electret fresh-keeping nanofiber membrane is 0.92g·mm / (m 2 ·day·kPa). The tensile strength of the electret fresh-keeping nanofiber membrane reaches 20MPa, and the elongation at break is 150%.

[0048] The performance of the electret fresh-keeping nanofiber membranes of Examples 1 to 3 was tested

[0049] (1) Bacterial capture test: Escherichia coli and Staphylococcus aureus were prepared into bacterial suspensions, respectively, and the bacteria were cultured at 37°C for 24 h. The concentration of the bacterial suspensions was 10 6 ~10 9CFU / mL (colony forming units per milliliter). Escherichia coli suspension and Staphylococcus aureus suspension were placed on the electret fresh-keeping nanofiber membranes of Examples 1 to 3 (all with a size of 2cm×2cm) and the untreated fiber membranes, respectively, and the fiber membranes were in contact with the bacterial suspension for 30 minutes. The untreated fiber membrane (the difference from Example 1 is that the silver nanoparticles in the spinning solution of Example 1 are omitted, the mass fraction of water is 4%, only electrospinning is performed, and the electret process is not performed to obtain the nanofiber membrane, and the nanofiber membrane is obtained by high-temperature treatment at 80°C for 2h) was used as a control group to compare the effect of the electret-treated fiber membrane of Example 1. After 30 minutes of contact, the fiber membrane was removed from the bacterial suspension and gently washed with sterile saline to remove the uncaptured bacteria. The washing liquid was collected, and the number of bacteria on the surface of the fiber membrane was quantitatively analyzed by counting the colony forming units (CFU) on the culture medium to evaluate its capture efficiency.

[0050] Calculation shows that the capture rates of Escherichia coli and Staphylococcus aureus by the electret fresh-keeping nanofiber membrane of Example 1 are both 97%, the capture rates of Escherichia coli and Staphylococcus aureus by the electret fresh-keeping nanofiber membrane of Example 2 are both 96%, and the capture rates of Escherichia coli and Staphylococcus aureus by the electret fresh-keeping nanofiber membrane of Example 3 are both 95%. The capture rates of Escherichia coli and Staphylococcus aureus by the untreated fiber membrane are 10-30%.

[0051] (2) Inhibition rate and antibacterial activity test of Escherichia coli and Staphylococcus aureus: The direct contact method was used to test Escherichia coli and Staphylococcus aureus in nutrient broth (peptone 10.0 g / L, beef extract powder 3.0 g / L, sodium chloride 5.0 g / L, pH 7.2, temperature 25°C, bacterial solution concentration 5×10 7 CFU / mL) to the logarithmic growth phase, centrifuged and resuspended in sterile saline to a concentration of 10 8 CFU / mL, place the bacterial suspension in a test tube. The fiber membrane samples of Examples 1 to 3 and the control group (the control group is an untreated fiber membrane, and the untreated fiber membrane is the same as in the bacteria capture test) are directly contacted with the bacterial suspension and incubated at 37°C for 2h. After the incubation is completed, 0.5mL of the bacterial suspension is taken out from the test tube and diluted 10 times. The diluted bacterial suspension is spread on a nutrient agar plate, the plate is placed in a constant temperature incubator, cultured at 37°C for 24h, and then the colony forming units (CFU) are counted for calculation. Each example and control group are tested three times.

[0052] The inhibition rates of the electret fresh-keeping nanofiber membrane of Example 1 on Escherichia coli and Staphylococcus aureus are both 99.95%, the inhibition rates of the electret fresh-keeping nanofiber membrane of Example 2 on Escherichia coli and Staphylococcus aureus are both 99.93%, and the inhibition rates of the electret fresh-keeping nanofiber membrane of Example 3 on Escherichia coli and Staphylococcus aureus are both 99.91%. The antibacterial activity of the electret fresh-keeping nanofiber membranes of Examples 1 to 3 is maintained for at least 6 months under the conditions of 25°C and 65% relative humidity; the antibacterial activity of the untreated fiber membrane is extremely low, generally maintaining for about 7 days.

[0053] (3) Light transmittance test: Cut out 5cm×5cm samples from the electret fresh-keeping nanofiber membranes of Examples 1 to 3 to cover the test window, and clean the sample surface. Use a standard white board (diffuse reflection board) to perform zero point calibration on the spectrometer and photometer. Place the standard white board at the sample position and record the intensity of the incident light. Place the sample to be tested in the light path and record the intensity of light after passing through the sample. Transmittance = (intensity of light after passing through the sample / intensity of incident light) × 100%. It was tested that the transmittance of the electret fresh-keeping nanofiber membrane of Example 1 was 50%, the transmittance of the electret fresh-keeping nanofiber membrane of Example 2 was 45%, and the transmittance of the electret fresh-keeping nanofiber membrane of Example 3 was 35%.

[0054] (4) Environmental adaptability test: Environmental adaptability refers to the high humidity and high temperature environment. The test method is to place a 15cm×20cm electret fresh-keeping nanofiber membrane of Examples 1 to 3 in an environment of 30°C and 90% relative humidity, and test the surface potential of the electret fresh-keeping nanofiber membrane every 10 minutes. After the test for 4 hours, leave the high humidity environment, place it in an environment of 30% relative humidity for 30 minutes, and test the surface potential.

[0055] The surface potential of the electret fresh-keeping nanofiber membrane of Example 1 decreased by 15% within 4 hours in a high humidity environment, and then left the high humidity environment and placed at 30% humidity for 30 minutes, and the surface potential recovery rate of the fiber membrane was 8%; the surface potential of the electret fresh-keeping nanofiber membrane of Example 2 decreased by 20% within 4 hours in a high humidity environment, and then left the high humidity environment and placed at 30% humidity for 30 minutes, and the surface potential recovery rate of the fiber membrane was 6%; the surface potential of the electret fresh-keeping nanofiber membrane of Example 3 decreased by 25% within 4 hours in a high humidity environment, and then left the high humidity environment and placed at 30% humidity for 30 minutes, and the surface potential recovery rate of the fiber membrane was 5%.

[0056] The fresh-keeping film of the present invention is subjected to electret treatment, and the persistent electrostatic field on the surface of the film can enhance the capture effect of the fresh-keeping film on bacteria and improve the barrier rate of bacteria; the raw material of the electret fresh-keeping nanofiber film has strong hydrophobicity, and the water vapor permeability of the electret fresh-keeping nanofiber film is not higher than 1.0g·mm / (m 2·day·kPa), which can significantly reduce the attachment and reproduction of bacteria on the membrane surface. The persistent electrostatic field exists in the nanofiber membrane and can last up to 7×24h. The surface potential begins to decay from 3~5kV and finally stabilizes at 1~1.3kV. The transmittance of the electret fresh-keeping nanofiber membrane reaches 35~50%; the bacteria capture rate is above 95%; the surface potential of the electret fresh-keeping nanofiber membrane drops by 15~25% within 4h in an environment with a relative humidity of 90%, and then after leaving the high humidity environment and being placed in an environment with a relative humidity of 30% for 30min, the surface potential recovery rate of the fiber membrane is 5~10%.

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an electret fresh-keeping nanofiber membrane, characterized in that: The following steps are included: 1) mixing a fluorine-containing organic compound, silver nanoparticles, water and an organic solvent to obtain a spinning solution; 2) The spinning solution is subjected to electrostatic spinning to obtain micro-nano fibers, and the micro-nano fibers are deposited on a base fabric to obtain an electret fresh-keeping nanofiber membrane.

2. The preparation method according to claim 1, characterized in that: In step 1), in the spinning solution, the mass fraction of the fluorine-containing organic matter is 20-40%, the mass fraction of the silver nanoparticles is 0.5-2%, the mass fraction of water is 1-5%, and the mass fraction of the organic solvent is 53-78.5%.

3. The preparation method according to claim 1 or 2, characterized in that: The fluorine-containing organic matter comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-trifluoroethylene copolymer and polyvinylidene fluoride-hexafluoroethylene copolymer; and the organic solvent is N,N-dimethylformamide.

4. The preparation method according to claim 3, characterized in that: The particle size of the silver nanoparticles is 1 to 10 nm.

5. The preparation method according to claim 3, characterized in that: Step 2) During the electrospinning process, the voltage is 10-30 kV, the receiving distance is 10-30 cm, the inner diameter of the spinneret is 0.1-1 mm, the spinning rate is 0.1-2.0 mL / h, the ambient temperature is 10-90° C., and the ambient humidity is 20-90%.

6. The preparation method according to claim 4 or 5, characterized in that: The electrospinning process and the electret process are carried out simultaneously.

7. The preparation method according to claim 6, characterized in that: Step 2) The base fabric is a single-layer melt-blown non-woven fabric; the surface potential of the micro-nano fibers is 3 to 5 kV.

8. The electret fresh-keeping nanofiber membrane prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the electret fresh-keeping nanofiber membrane according to claim 8 in antibacterial fresh-keeping film.