Antibacterial cellulose membrane and preparation method thereof

Abstract

Cellulose is a natural high polymer material with good barrier property and film-forming property, and attracts wide attention in the aspect of application as a packaging fresh-keeping film. However, cellulose lacks antibacterial performance, so that the application of cellulose is limited. Therefore, the oxidized regenerated cellulose membrane is prepared by adopting a simple two-step method, namely, the regenerated cellulose membrane is prepared by adopting a sol-gel method, and then the oxidized regenerated cellulose membrane is obtained by utilizing sodium periodate to oxidize. The preparation method has the advantages that the raw materials are green and environment-friendly, the preparation process is simple and convenient, and the prepared film has good antibacterial performance and has wide application prospects in the field of antibacterial food packaging.

Description

Technical Field

[0001] The invention belongs to the technical field of antibacterial films, and in particular relates to an antibacterial cellulose film and a preparation method thereof. Background Art

[0002] Traditional petroleum-based plastics such as polyethylene, polypropylene, and polyvinyl chloride are widely used in daily life because of their lightness, durability, and low price. However, since petroleum-based plastics are non-degradable, they have caused many environmental pollution and human health problems. Among many materials, natural polymers have many advantages such as renewability, biocompatibility, and degradability. Therefore, using natural polymers to replace traditional petroleum-based plastics is of great significance to alleviate environmental pollution. Among many natural polymers, cellulose has always attracted much attention because of its abundant reserves, excellent mechanical properties, low cost, and biodegradability. Cellulose is considered to be the most promising natural polymer to replace petroleum-based plastics. At present, various cellulose-based products (such as films, hydrogels, aerogels, and capsules) have been developed and widely used in packaging, energy, and smart materials.

[0003] Cellulose is a natural polymer material with good barrier and film-forming properties, and has attracted widespread attention in its application as a packaging fresh-keeping film. In addition, there are a large number of active hydroxyl sites on the cellulose chain, which enables it to undergo chemical reactions, including oxidation, esterification, etherification, cross-linking and graft copolymerization. Through these chemical reactions, cellulose films can be given more functions. Among them, antibacterial functionalization is one of the most important ways to give cellulose films new functions. It is well known that compared with some natural polymers with bactericidal properties (such as chitosan), cellulose does not have bactericidal properties, which limits the application of cellulose films.

[0004] To date, a variety of methods for antibacterial modification of cellulose films have been developed, such as physical blending, layer-by-layer self-assembly, chemical grafting, and in-situ generation. The unique chemical structure of cellulose enables it to combine with antimicrobial agents to achieve effective loading of antimicrobial agents on cellulose films, thereby improving the stability, antimicrobial efficiency, and safety of antimicrobial materials. For example, cellulose is oxidized by sodium periodate to oxidize C2 and C3 on the glucose units of cellulose to aldehyde groups to obtain dialdehyde cellulose. In the existing technology, the Chinese patent application number 202410486528, "An antibacterial nanocellulose and its preparation method, and wrapping paper based on antibacterial nanocellulose", discloses a method for preparing an efficient antibacterial nanofiber material by grafting a dialdehyde-modified guanidine salt, which has a good inhibitory effect on Escherichia coli and Staphylococcus aureus. In another Chinese patent with application number 202410694598, "A method for preparing an antibacterial cellulose film with a high aldehyde content and its application", a method for preparing dialdehyde cellulose using bamboo pulp board as raw material, and cross-linking the dialdehyde cellulose into a film through a cross-linking agent is disclosed, and a cellulose film with good antibacterial properties is prepared by this method. Although the films obtained by the above methods all have good antibacterial properties, the preparation process involved is complicated and not conducive to practical application production. Therefore, it is necessary to seek a simple method to prepare a cellulose film with good antibacterial properties. Summary of the invention

[0005] Therefore, it is necessary to provide an antibacterial cellulose membrane and a preparation method thereof to improve the performance of the cellulose membrane.

[0006] To achieve the above object, the present invention provides a method for preparing an antibacterial cellulose film, comprising the following steps: (1) Cellulose activation: Microcrystalline cellulose is magnetically stirred in water, methanol and N,N-dimethylacetamide, respectively, and then filtered to obtain activated microcrystalline cellulose; (2) Preparation of cellulose solution: Anhydrous lithium chloride and N,N-dimethylacetamide are mixed, and after high temperature magnetic stirring, a lithium chloride / N,N-dimethylacetamide solution is obtained; (3) cellulose dissolution: adding the activated microcrystalline cellulose obtained in step (1) to the lithium chloride / N,N-dimethylacetamide solution obtained in step (2), and stirring by magnetic force to obtain a cellulose solution; (4) Forming a cellulose gel film: pouring the cellulose solution obtained in step (3) onto a glass plate, scraping the cellulose solution, and gelling the solution to obtain a cellulose gel film; (5) Regenerating the cellulose gel membrane: soaking the cellulose gel membrane obtained in step (4) in deionized water for regeneration to obtain a regenerated cellulose gel membrane; (6) Preparation of oxidant solution: adding sodium periodate into deionized water and stirring by magnetic force to obtain sodium periodate solution; (7) Gel membrane oxidation: immersing the regenerated cellulose gel membrane obtained in step (5) in the sodium periodate solution obtained in step (6). After the oxidation reaction is completed, the residual oxidant is washed with deionized water to obtain an oxidized regenerated cellulose gel membrane; (8) Gel film drying: The oxidized regenerated cellulose gel film obtained in step (7) is dried to obtain an oxidized regenerated cellulose film.

[0007] Furthermore, the sodium periodate oxidation time in step (6) is 2 to 8 h.

[0008] Furthermore, the cellulose membrane prepared by the above method can inhibit the growth of Staphylococcus aureus within 24 hours and achieve the effect of killing bacteria. Moreover, the oxidized regenerated cellulose membrane has an inhibitory effect on the growth of Escherichia coli.

[0009] Different from the prior art, the present invention uses sodium periodate solution as an oxidant and adopts a simple soaking method. The obtained antibacterial cellulose film has an inhibitory and killing effect on Staphylococcus aureus and can also inhibit the growth of Escherichia coli. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 These are the antibacterial results of the oxidized regenerated cellulose membranes and the regenerated cellulose membranes prepared in Examples 1 to 4 of the present invention and Comparative Example 1 and co-cultured with different bacteria.

[0011] Figure 2 These are turbidity pictures of the oxidized regenerated cellulose membranes prepared in Examples 1 to 4 of the present invention and Comparative Example 1, and the regenerated cellulose membranes co-cultured with different bacteria for 24 h. DETAILED DESCRIPTION

[0012] In order to explain in detail the technical content, features, achieved objectives and effects of the technical solution, the following is a detailed description in conjunction with specific embodiments. Example 1

[0013] A method for preparing an antibacterial cellulose film, the specific preparation method comprising the following steps: (1) Weigh 4 g of microcrystalline cellulose and add them to deionized water, anhydrous methanol, and N,N-dimethylacetamide respectively, stir magnetically for 3 h, and filter using a sand core filter to obtain activated microcrystalline cellulose; (2) 8 g of anhydrous lithium chloride and 92 mL of N,N-dimethylacetamide were mixed and magnetically stirred at 100 °C until the anhydrous lithium chloride was completely dissolved and the solution system became colorless and transparent, thereby obtaining an anhydrous lithium chloride / N,N-dimethylacetamide solvent system; (3) adding the activated microcrystalline cellulose obtained in step (1) to the anhydrous lithium chloride / N,N-dimethylacetamide solvent system obtained in step (2), and stirring under magnetic stirring at 100 °C for 12 h to obtain a transparent cellulose solution; (4) pouring the cellulose solution obtained in step (3) onto a glass plate and gelling it at room temperature for 3 h to obtain a cellulose gel film; (5) immersing the cellulose gel membrane obtained in step (4) in deionized water, regenerating for 1 h, and washing away residual salt and solvent with deionized water to obtain a regenerated cellulose gel membrane; (6) Weigh 12.83 g of sodium periodate and add it to 1 L of deionized water. Stir at room temperature in the dark until it is completely dissolved to obtain a sodium periodate solution. (7) Immerse the regenerated cellulose gel membrane obtained in step (5) in the sodium periodate solution obtained in step (6) and react for 2 h in the dark. After the reaction is completed, wash with deionized water to obtain an oxidized regenerated cellulose gel membrane; (8) The oxidized regenerated cellulose membrane obtained in the above step (7) is placed in a vacuum drying oven at 50 °C and dried for 12 h to obtain an oxidized regenerated cellulose membrane. Example 2

[0014] A method for preparing an antibacterial cellulose film, the specific preparation method comprising the following steps: (1) Weigh 4 g of microcrystalline cellulose and add them to deionized water, anhydrous methanol, and N,N-dimethylacetamide respectively, stir magnetically for 3 h, and filter using a sand core filter to obtain activated microcrystalline cellulose; (2) 8 g of anhydrous lithium chloride and 92 mL of N,N-dimethylacetamide were mixed and magnetically stirred at 100 °C until the anhydrous lithium chloride was completely dissolved and the solution system became colorless and transparent, thereby obtaining an anhydrous lithium chloride / N,N-dimethylacetamide solvent system; (3) adding the activated microcrystalline cellulose obtained in step (1) to the anhydrous lithium chloride / N,N-dimethylacetamide solvent system obtained in step (2), and stirring under magnetic stirring at 100 °C for 12 h to obtain a transparent cellulose solution; (4) pouring the cellulose solution obtained in step (3) onto a glass plate and gelling it at room temperature for 3 h to obtain a cellulose gel film; (5) immersing the cellulose gel membrane obtained in step (4) in deionized water, regenerating for 1 h, and washing away residual salt and solvent with deionized water to obtain a regenerated cellulose gel membrane; (6) Weigh 12.83 g of sodium periodate and add it to 1 L of deionized water. Stir at room temperature in the dark until it is completely dissolved to obtain a sodium periodate solution. (7) Immerse the regenerated cellulose gel membrane obtained in step (5) in the sodium periodate solution obtained in step (6) and react for 4 h in the dark. After the reaction is completed, wash with deionized water to obtain an oxidized regenerated cellulose gel membrane; (8) The oxidized regenerated cellulose membrane obtained in the above step (7) is placed in a vacuum drying oven at 50 °C and dried for 12 h to obtain an oxidized regenerated cellulose membrane. Example 3

[0015] A method for preparing an antibacterial cellulose film, the specific preparation method comprising the following steps: (1) Weigh 4 g of microcrystalline cellulose and add them to deionized water, anhydrous methanol, and N,N-dimethylacetamide respectively, stir magnetically for 3 h, and filter using a sand core filter to obtain activated microcrystalline cellulose; (2) 8 g of anhydrous lithium chloride and 92 mL of N,N-dimethylacetamide were mixed and magnetically stirred at 100 °C until the anhydrous lithium chloride was completely dissolved and the solution system became colorless and transparent, thereby obtaining an anhydrous lithium chloride / N,N-dimethylacetamide solvent system; (3) adding the activated microcrystalline cellulose obtained in step (1) to the anhydrous lithium chloride / N,N-dimethylacetamide solvent system obtained in step (2), and stirring under magnetic stirring at 100 °C for 12 h to obtain a transparent cellulose solution; (4) pouring the cellulose solution obtained in step (3) onto a glass plate and gelling it at room temperature for 3 h to obtain a cellulose gel film; (5) immersing the cellulose gel membrane obtained in step (4) in deionized water, regenerating for 1 h, and washing away residual salt and solvent with deionized water to obtain a regenerated cellulose gel membrane; (6) Weigh 12.83 g of sodium periodate and add it to 1 L of deionized water. Stir at room temperature in the dark until it is completely dissolved to obtain a sodium periodate solution. (7) Immerse the regenerated cellulose gel membrane obtained in step (5) in the sodium periodate solution obtained in step (6) and react for 6 h in the dark. After the reaction is completed, wash with deionized water to obtain an oxidized regenerated cellulose gel membrane; (8) The oxidized regenerated cellulose membrane obtained in the above step (7) is placed in a vacuum drying oven at 50 °C and dried for 12 h to obtain an oxidized regenerated cellulose membrane. Example 4

[0016] A method for preparing an antibacterial cellulose film, the specific preparation method comprising the following steps: (1) Weigh 4 g of microcrystalline cellulose and add them to deionized water, anhydrous methanol, and N,N-dimethylacetamide respectively, stir magnetically for 3 h, and filter using a sand core filter to obtain activated microcrystalline cellulose; (2) 8 g of anhydrous lithium chloride and 92 mL of N,N-dimethylacetamide were mixed and magnetically stirred at 100 °C until the anhydrous lithium chloride was completely dissolved and the solution system became colorless and transparent, thereby obtaining an anhydrous lithium chloride / N,N-dimethylacetamide solvent system; (3) adding the activated microcrystalline cellulose obtained in step (1) to the anhydrous lithium chloride / N,N-dimethylacetamide solvent system obtained in step (2), and stirring under magnetic stirring at 100 °C for 12 h to obtain a transparent cellulose solution; (4) pouring the cellulose solution obtained in step (3) onto a glass plate and gelling it at room temperature for 3 h to obtain a cellulose gel film; (5) immersing the cellulose gel membrane obtained in step (4) in deionized water, regenerating for 1 h, and washing away residual salt and solvent with deionized water to obtain a regenerated cellulose gel membrane; (6) Weigh 12.83 g of sodium periodate and add it to 1 L of deionized water. Stir at room temperature in the dark until it is completely dissolved to obtain a sodium periodate solution. (7) Immerse the regenerated cellulose gel membrane obtained in step (5) in the sodium periodate solution obtained in step (6) and react for 8 h in the dark. After the reaction is completed, wash with deionized water to obtain an oxidized regenerated cellulose gel membrane; (8) The oxidized regenerated cellulose membrane obtained in the above step (7) is placed in a vacuum drying oven at 50 °C and dried for 12 h to obtain an oxidized regenerated cellulose membrane. Comparative Example 1

[0017] A method for preparing a cellulose film, the specific preparation method comprising the following steps: (1) Weigh 4 g of microcrystalline cellulose and add them to deionized water, anhydrous methanol, and N,N-dimethylacetamide respectively, stir magnetically for 3 h, and filter using a sand core filter to obtain activated microcrystalline cellulose; (2) 8 g of anhydrous lithium chloride and 92 mL of N,N-dimethylacetamide were mixed and magnetically stirred at 100 °C until the anhydrous lithium chloride was completely dissolved and the solution system became colorless and transparent, thereby obtaining an anhydrous lithium chloride / N,N-dimethylacetamide solvent system; (3) adding the activated microcrystalline cellulose obtained in step (1) to the anhydrous lithium chloride / N,N-dimethylacetamide solvent system obtained in step (2), and stirring under magnetic stirring at 100 °C for 12 h to obtain a transparent cellulose solution; (4) pouring the cellulose solution obtained in step (3) onto a glass plate and gelling it at room temperature for 3 h to obtain a cellulose gel film; (5) immersing the cellulose gel membrane obtained in step (4) in deionized water, regenerating for 1 h, and washing away residual salt and solvent with deionized water to obtain a regenerated cellulose gel membrane; (6) The regenerated cellulose membrane obtained in the above step (5) is placed in a vacuum drying oven at 50 °C and dried for 12 h to obtain a regenerated cellulose membrane.

[0018] The aldehyde content of Examples 1-4 was measured: The aldehyde content of the film was determined by the semi-micro hydroxylamine hydrochloride method. Weigh 1 g of hydroxylamine hydrochloride and dissolve it in 50 mL of methanol to prepare a 2% (w / v) hydroxylamine hydrochloride methanol solution. Add 0.5 mL of thymol blue as an indicator, and the solution will turn red. Use 0.03 mol / L NaOH-methanol solution to adjust the mixed pH to 4.5, and the solution will turn yellow. Put 0.05g of oxidized regenerated cellulose membrane into the mixed solution. If the sample contains aldehyde groups, it indicates that the sample contains aldehyde groups. After reacting for 48 h at room temperature, use 0.03 mol / L sodium hydroxide-methanol solution to titrate until pH=4.5, the solution turns yellow, and the solution does not change color within 10~15 s, otherwise continue to titrate. The calculation formula for aldehyde content is as follows: Where [CHO]——aldehyde content (mmol / g), V 2 ——Volume of NaOH-methanol solution consumed in titrating the oxidized regenerated cellulose membrane (mL), V 1 ——The volume of NaOH-methanol solution consumed in the blank (mL), c ——Concentration of NaOH-methanol solution (0.03 mol / L), m ——The mass of oxidized regenerated cellulose membrane (g). The experimental results are shown in Table 1 below:

[0019] The antibacterial properties of the cellulose films of Examples 1-4 and Comparative Example 1 were tested: The activated bacterial solution was poured into a sterilized centrifuge tube and centrifuged at 6000 rpm / min for 5 min. The supernatant was poured out and 1 mL of normal saline was added to dilute and mix. The bacterial solution of Staphylococcus aureus (S. a) and Escherichia coli (E. coli) was diluted to 10 6CFU / mL. 20 mg of oxidized regenerated cellulose membrane was added to 3 mL of diluted bacterial solution and cultured in a 37 ℃ incubator. After 12 h and 24 h, the solution was diluted to a certain multiple, and 100 μL of bacterial solution was taken out and spread on the solid culture medium, and cultured in a 37 ℃ incubator for 24 h. The number of colonies was photographed and recorded. The experimental results are shown in Figure 1 , 2 As shown in Table 2 below:

[0020] Depend on Figure 1~2 It can be concluded from Tables 1 and 2 that the antibacterial performance of the embodiment is significantly better than that of the comparative example.

[0021] In summary, the following conclusions can be drawn: cellulose film with antibacterial properties was successfully prepared by this simple sodium periodate soaking method. The cellulose film prepared by this method exhibits good antibacterial properties and has broad application prospects in the field of antibacterial food packaging.

[0022] The above descriptions are merely embodiments of the present invention, and are not intended to limit the patent protection scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing an antibacterial cellulose film, characterized in that: The following steps are involved: (1) Cellulose activation: Microcrystalline cellulose is magnetically stirred in deionized water, anhydrous methanol and N,N-dimethylacetamide, respectively, and then filtered to obtain activated microcrystalline cellulose; (2) Preparation of cellulose solution: Anhydrous lithium chloride and N,N-dimethylacetamide are mixed, and after high temperature magnetic stirring, a lithium chloride / N,N-dimethylacetamide solution is obtained; (3) cellulose dissolution: adding the activated microcrystalline cellulose obtained in step (1) to the lithium chloride / N,N-dimethylacetamide solution obtained in step (2), and stirring by magnetic force to obtain a cellulose solution; (4) Forming a cellulose gel film: pouring the cellulose solution obtained in step (3) onto a glass plate, scraping the cellulose solution, and gelling the solution to obtain a cellulose gel film; (5) Regenerating the cellulose gel membrane: soaking the cellulose gel membrane obtained in step (4) in deionized water for regeneration to obtain a regenerated cellulose gel membrane; (6) Preparation of oxidant solution: adding sodium periodate into deionized water and stirring by magnetic force to obtain sodium periodate solution; (7) Gel membrane oxidation: immersing the regenerated cellulose gel membrane obtained in step (5) in the sodium periodate solution obtained in step (6). After the oxidation reaction is completed, the residual oxidant is washed with deionized water to obtain an oxidized regenerated cellulose gel membrane; (8) Gel film drying: The oxidized regenerated cellulose gel film obtained in step (7) is dried to obtain an oxidized regenerated cellulose film.

2. The preparation method according to claim 1, characterized in that: In step (6), the sodium periodate oxidation time is 2 to 8 hours.

3. The preparation method according to claim 1, characterized in that: The cellulose membrane obtained by this method can inhibit the growth of Staphylococcus aureus within 24 hours and achieve the effect of killing bacteria. In addition, the oxidized regenerated cellulose membrane has an inhibitory effect on the growth of Escherichia coli.

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