Preparation method of degradable sodium alginate composite film

Abstract

The invention relates to the technical field of green composite films, in particular to a preparation method of a degradable sodium alginate composite film, which comprises the following steps: firstly, adding sodium alginate into deionized water, and fully stirring in a magnetic stirrer to prepare a sodium alginate solution; then, blending the sodium alginate solution with the glycerol and tannic acid solution, and adding the iron ion solution to carry out cross-linking reaction; iron ions and functional groups in sodium alginate and tannic acid form a stable cross-linked network, so that the mechanical property and the stability of the film are enhanced. Then, the prepared mixed solution forms a film through a tape casting method, finally, the film is dried in a drying oven, the film is placed in a calcium ion solution to be solidified after drying is completed, the residual calcium ion solution on the surface of the film is cleaned through deionized water, and the composite film can be obtained. The prepared composite film has good mechanical strength and flexibility, is suitable for various application scenes such as food packaging and daily necessity packaging, can be rapidly degraded in the natural environment, and is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of green composite films, and particularly relates to a preparation method of a degradable sodium alginate composite film. Background Art

[0002] Sodium alginate is a natural polymer that can be directly extracted from algae and can undergo ion exchange with metal cations (Ca 2+ 、Fe 3+ ), forming a dense cross-linked network structure, having good degradability, renewability and outstanding film-forming ability. Although the pure sodium alginate film has good biodegradability, its mechanical properties are poor, it is brittle, and its strength and elasticity are insufficient. In order to further make up for the defects of the pure film, functional composite films have emerged. Compared with the pure film, the composite film can not only make up for each other's strengths and weaknesses in terms of performance, but also cooperate with each other to achieve excellent performance that the pure film does not have. In addition, the tensile strength, elongation at break, water solubility, water vapor transmission rate, light transmittance, etc. of the composite film are more prominent.

[0003] Given the versatility of sodium alginate composite films, constructing an efficient preparation method has always been a key focus for researchers. For example: The Peng Shan team prepared sodium alginate / gelatin polyphenol multilayer composite films using the layer-by-layer assembly method (Peng Shan.; Kun Wang.; Fuyou Yu.; Lunzhao Yi.; Liping Sun., Gelatin / sodium alginate multilayer composite film crosslinked with green tea extract for active food packaging application. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2023, 662: 131013); The Daheng Wu team prepared composite film materials using nano mica flakes, sodium alginate, and glycerol as raw materials (Daheng Wu.; Jianing Wang.; Yuxiang Zhao.; Shengfei Li.; Haoyong Yang.; Runxiang Tan., Bio-inspired seaweed-based nanocomposite materials with excellent degradability and multifunctional barrier properties for green packaging. Chemical Engineering Journal, 2024, 479: 147285.); The Sercan Dede team prepared composite film materials by electrospinning basil oil, zein, and sodium alginate (Sercan Dede.; Omer Sadak.; Mustafa Didin.; Sundaram Gunasekaran., Basil oil-loaded electrospun biofibers: Edible food packaging material. Journal of food engineering, 2022, 319: 110914.).

[0004] In most existing studies, the functionality of composite membranes is improved by filling with various materials or modifying materials, while there are few studies on combining natural plant polyphenols and metal ions to enhance the functionality of composite membranes. Tannic acid belongs to polyphenolic compounds, has a rich source of acquisition, and has characteristics such as antioxidant activity, anti-inflammatory and antibacterial activities. In addition, there are at least two adjacent phenolic hydroxyl groups on the benzene ring of tannic acid, which can chelate metal ions, undergo complexation and electrostatic interactions with metal ions, and form a metal-phenol supramolecular network structure. This has certain significance for the research of green composite thin film materials. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies existing in the prior art, and to propose a preparation method of a degradable sodium alginate composite film. The prepared composite film has good mechanical strength and flexibility. This method is safe and simple to operate, has a rich source of raw materials, low cost, and is conducive to industrial production.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions: A preparation method of a degradable sodium alginate composite film, comprising the following steps: Step 1: Weigh the raw materials according to the components of the composite film material; Step 2: Preparation of sodium alginate solution: Add sodium alginate powder to 100 ml of deionized water, heat and stir evenly at 30 °C to obtain a sodium alginate solution; Step 3: Preparation of tannic acid solution: Dissolve tannic acid in 30 ml of deionized water and stir to dissolve to prepare a tannic acid solution; Step 4: Preparation of sodium alginate / tannic acid mixed solution: Mix the sodium alginate solution, tannic acid solution and glycerol evenly by high-speed magnetic stirring to obtain a mixed solution; Step 5: Dropwise add the iron ion solution to the above mixed solution, stir while adding to prepare a composite film solution; Step 6: Casting and drying: Pour the composite film solution into a glass mold with the same size and a clean and dry surface, and place it in a precision forced air drying oven to dry into a film; Step 7: Crosslinking and solidification: Place the dried film in 10 ml of 0.1 mol / L Ca 2+ solution for 3 minutes. After forming a crosslinked network structure, wash the residual calcium ion solution on the surface of the film with deionized water and adjust it at room temperature to obtain the composite film.

[0007] Preferably, in step 1, the raw materials of the composite film include 1.5 - 2.5 g of sodium alginate powder, 0.15 - 0.45 g of tannic acid powder, 0.15 mg / mL - 0.30 mg / mL of iron ion solution, an appropriate amount of glycerol and deionized water.

[0008] Preferably, the sodium alginate is a natural polysaccharide-based material.

[0009] Preferably, the tannic acid is a natural plant polyphenol material.

[0010] Preferably, the iron ion solution is a cross-linking agent.

[0011] Preferably, in step 2, the dissolution temperature of sodium alginate is 30° C. and the stirring time is 60 minutes.

[0012] Preferably, in step 5, the cross-linking reaction time is 10 minutes.

[0013] Preferably, in step 6, the drying temperature is 60° C. and the drying time is 24 hours.

[0014] By adopting the above technical scheme: first, sodium alginate is added to deionized water and fully stirred in a magnetic stirrer to prepare a sodium alginate solution. Then, the sodium alginate solution is blended with glycerol and tannic acid solution, and an iron ion solution is added for cross-linking reaction. The iron ions form a stable cross-linked network with the functional groups in sodium alginate and tannic acid, which enhances the mechanical properties and stability of the film. Next, the prepared mixed solution is formed into a film by a casting method, and finally dried in an oven. After drying, it is placed in a calcium ion solution to solidify, and the residual calcium ion solution on the surface of the film is washed with deionized water to obtain a composite film.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The main raw materials and auxiliary agents of the composite film of the present invention are non-toxic, harmless, degradable materials, and are environmentally friendly materials, which avoid the problem of long-term presence in the environment causing pollution.

[0016] 2. The raw materials of the composite film of the present invention are all natural biomass resources, which are widely available, easy to obtain, cheap, and have high economic benefits and market competitiveness.

[0017] 3. The composite film of the present invention is biodegradable and can be made into different types of films through reasonable proportions and processing techniques to meet a variety of application requirements.

[0018] 4. The composite film prepared by the present invention has good mechanical strength and flexibility, is suitable for various application scenarios such as food packaging and daily necessities packaging, and can be quickly degraded in the natural environment, and is environmentally friendly.

[0019] 5. The preparation method of the present invention is simple, low-cost, green and environmentally friendly, can be used for industrial production, and has good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1Schematic diagram of the preparation process of the present invention; Figure 2 Physical photo of the composite film prepared by the present invention; Figure 3 Mechanical property diagram of Example 1 of the present invention; Figure 4 Mechanical property diagram of Example 2 of the present invention; Figure 5 Mechanical property diagram of Example 3 of the present invention; Figure 6 Mechanical property diagram of Example 4 of the present invention; Figure 7 Mechanical property diagram of Example 5 of the present invention. Detailed implementation manners

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, and thus make a clearer definition of the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention. Embodiment

[0022] Raw material composition of the composite film: 1.5 g of sodium alginate powder, 0.15 g of tannic acid powder, 0.15 mg / ml iron ion solution, appropriate amount of glycerol and deionized water.

[0023] Preparation method of the composite film in this embodiment: Dissolve 1.5 g of sodium alginate powder in 100 mL of deionized water, stir until completely dissolved to form a homogeneous solution.

[0024] Dissolve 0.15 g of tannic acid powder in 30 mL of deionized water, stir until completely dissolved, then add it to the sodium alginate solution, and add glycerol and stir evenly.

[0025] Dropwise add 20 ml of 0.15 mg / ml iron ion solution to the mixed solution, stir while adding to form a cross-linked network structure, and stir evenly for 10 minutes.

[0026] Pour the mixed solution evenly onto a glass mold, dry at 60 °C for 24 hours, slowly peel it off after molding, and place it in 10 ml of 0.1 mol / L Ca 2+ Solution for cross-linking for 3 min, wash with deionized water, adjust at room temperature to obtain the composite film.

[0027] The physical photo and mechanical properties of the obtained composite film are asFigure 2 and 3 As shown, the tensile strength is 31.894 MPa and the elongation at break is 22.299%. Example

[0028] Raw material composition of the composite film: 1.5 g of sodium alginate, 0.45 g of tannic acid, 0.3 mg / ml iron ion solution, appropriate amount of glycerol and deionized water.

[0029] Preparation method of the composite film in this example: Dissolve 1.5 g of sodium alginate powder in 100 mL of deionized water, stir until completely dissolved to form a uniform solution.

[0030] Dissolve 0.45 g of tannic acid powder in 30 mL of deionized water, stir until completely dissolved, then add it to the sodium alginate solution, add glycerol, and stir evenly.

[0031] Dropwise add 0.3 mg / ml iron ion solution to the mixed solution, stir while adding to form a cross-linked network structure, and stir evenly for 10 minutes.

[0032] Pour the mixed solution evenly onto a glass mold, dry at 60 °C for 24 hours. After molding, slowly peel it off and place it in 10 ml of 0.1 mol / L Ca 2+ Solution for cross-linking for 3 min, wash with deionized water, and condition at room temperature for 24 h to obtain the composite film.

[0033] The mechanical properties of the obtained composite film are as Figure 4 shown, the tensile strength is 30.585 MPa and the elongation at break is 32.309%. Example

[0034] Raw material composition of the composite film: 1.5 g of sodium alginate, 0.3 g of tannic acid, 0.3 mg / ml iron ion solution, appropriate amount of glycerol and deionized water.

[0035] Preparation method of the composite film in this example: Dissolve 2 g of sodium alginate powder in 100 mL of deionized water, stir until completely dissolved to form a uniform solution.

[0036] Dissolve 0.3 g of tannic acid powder in 30 mL of deionized water, stir until completely dissolved, then add it to the sodium alginate solution, add glycerol, and stir evenly.

[0037] Dropwise add 0.15 mg / ml iron ion solution to the mixed solution, stir while adding to form a cross-linked network structure, and stir evenly for 10 minutes.

[0038] The mixed solution was uniformly cast in a glass mold, dried at 60 °C for 24 hours, slowly peeled off after molding, and then placed in 10 ml of 0.1 mol / L Ca 2+ solution for crosslinking for 3 min, washed with deionized water, and conditioned at room temperature to obtain a composite film.

[0039] The mechanical properties of the obtained composite film are as Figure 5 shown, the tensile strength is 28.373 MPa, and the elongation at break is 26.967%. Example

[0040] The raw material composition of the composite film: 2 g of sodium alginate, 0.45 g of tannic acid, 0.15 mg / ml iron ion solution, appropriate amount of glycerol and deionized water.

[0041] The preparation method of the composite film in this example: Dissolve 2 g of sodium alginate powder in 100 mL of deionized water, stir until completely dissolved to form a uniform solution.

[0042] Dissolve 0.3 g of tannic acid powder in 30 mL of deionized water, stir until completely dissolved, then add it to the sodium alginate solution, add glycerol, and stir evenly.

[0043] Dropwise add 0.15 mg / ml iron ion solution to the mixed solution, stir while adding to form a crosslinked network structure, and stir evenly for 10 minutes.

[0044] The mixed solution was uniformly cast in a glass mold, dried at 60 °C for 24 hours, slowly peeled off after molding, and then placed in 10 ml of 0.1 mol / L Ca 2+ solution for crosslinking for 3 min, washed with deionized water, and conditioned at room temperature to obtain a composite film.

[0045] The mechanical properties of the obtained composite film are as Figure 6 shown, the tensile strength is 30.288 MPa, and the elongation at break is 18.173%. Example

[0046] The raw material composition of the composite film: 2.5 g of sodium alginate, 0.45 g of tannic acid, 0.15 mg / ml iron ion solution, appropriate amount of glycerol and deionized water.

[0047] The preparation method of the composite film in this example: Dissolve 2 g of sodium alginate powder in 100 mL of deionized water, stir until completely dissolved to form a uniform solution.

[0048] Dissolve 0.3 g of tannic acid powder in 30 mL of deionized water, stir until completely dissolved, then add it to the sodium alginate solution, add glycerol, and stir evenly.

[0049] The 0.15 mg / ml iron ion solution was added dropwise to the mixed solution while stirring to form a cross-linked network structure, and stirred evenly for 10 minutes.

[0050] The mixed solution was evenly cast in a glass mold, dried at 60 °C for 24 hours, slowly peeled off after molding, and placed in 10 ml of 0.1 mol / L Ca 2+ solution for cross-linking for 3 min, washed with deionized water, and conditioned at room temperature to obtain a composite film.

[0051] The mechanical properties of the obtained composite film are as Figure 7 shown, the tensile strength is 32.698 MPa, and the elongation at break is 17.672%.

[0052] In summary, the present invention uses sodium alginate as the main film-forming matrix, plasticizer and cross-linking agent as auxiliary materials, and is prepared into a solution by mechanical stirring method. The solution casting method and hot air drying method are used to prepare a green composite film. The preparation method of the present invention is safe, the process flow is simple, the production cost is low, and it is applicable to industrial production. In addition, the composite film can be degraded in the natural environment, and no toxic and harmful substances will be generated during the degradation process, which is harmless to the environment and human body, and avoids the problem of pollution caused by long-term existence in the environment.

[0053] The descriptions and practices disclosed in the present invention are easy to think and understand for those of ordinary skill in the art. Without departing from the principle of the present invention, several improvements and refinements can be made. Therefore, the modifications or improvements made without departing from the spirit of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a degradable sodium alginate composite film, characterized in that: The steps include: Step 1: Weigh the raw materials according to the components of the composite film material; Step 2: Preparation of sodium alginate solution: Add sodium alginate powder into 100 ml of deionized water, heat and stir at 30°C to obtain a sodium alginate solution; Step 3: Preparation of tannic acid solution: dissolve tannic acid in 30 ml of deionized water and stir to dissolve to prepare a tannic acid solution; Step 4: Preparation of a sodium alginate / tannic acid mixed solution: The sodium alginate solution, the tannic acid solution and glycerol are uniformly mixed by high-speed magnetic stirring to obtain a mixed solution; Step 5: adding the iron ion solution dropwise into the mixed solution while stirring to prepare a composite membrane solution; Step 6: Casting and drying: Pour the composite film solution into equal-sized pieces, cast it into a glass mold with a dry and clean surface, and place it in a precision air drying oven to dry it into a film; Step 7: Cross-linking: Place the dried film in 10 ml of 0.1 mol / LCa 2+ After 3 minutes in the solution to form a cross-linked network structure, the residual calcium ion solution on the surface of the film is washed with deionized water and adjusted at room temperature to obtain a composite film.

2. The method for preparing a degradable sodium alginate composite film according to claim 1, characterized in that: In step 1, the raw materials of the composite film include 1.5-2.5 g of sodium alginate powder, 0.15-0.45 g of tannic acid powder, 0.15 mg / mL-0.30 mg / mL of iron ion solution, glycerol and deionized water.

3. The method for preparing a degradable sodium alginate composite film according to claim 2, characterized in that: The sodium alginate is a natural polysaccharide-based material.

4. The method for preparing a degradable sodium alginate composite film according to claim 2, characterized in that: The tannic acid is a natural plant polyphenol material.

5. The method for preparing a degradable sodium alginate composite film according to claim 2, characterized in that: The iron ion solution is a cross-linking agent.

6. The method for preparing a degradable sodium alginate composite film according to claim 1, characterized in that: In step 2, the dissolving temperature of sodium alginate is 30° C. and the stirring time is 60 minutes.

7. The method for preparing a degradable sodium alginate composite film according to claim 5, characterized in that: In step 5, the cross-linking reaction time is 10 minutes.

8. The method for preparing a degradable sodium alginate composite film according to claim 1, characterized in that: In step 6, the drying temperature is 60° C. and the drying time is 24 hours.

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