Preparation method of degradable natural linen fiber / 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 natural linen fiber / sodium alginate composite film, which comprises the following steps: firstly, preparing a sodium alginate solution with a certain concentration, and ensuring the uniformity of the solution; thirdly, tidying and flatly laying natural linen fibers in a mold, slowly pouring the prepared sodium alginate solution into the mold paved with the linen fibers, and enabling the solution to fully infiltrate the fibers to form a uniform composite system; then, 0.1-0.3 mol / L of calcium ion solution is added into the mold, and the thin film is subjected to cross-linking forming. Finally, the formed film is placed in a drying oven to be dried, redundant water is removed, and finally the natural linen fiber / sodium alginate composite film is obtained. The composite film disclosed by the invention not only is excellent in mechanical property and environmental protection property, but also has a wide application prospect in various application scenes such as food packaging and daily necessity packaging.

Description

Technical Field

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

[0002] Sodium alginate is a natural polymer that can be directly extracted from algae. It can undergo ion exchange with metal cations to form a dense cross-linked network structure, having good degradability and outstanding film-forming ability, and is widely used in the fields of medicine, environmental protection, biochemistry, etc. Linen fibers contain different amounts of cellulose, lignin, hemicellulose, etc., making it have excellent hygroscopicity, antistatic property, degradability, mechanical properties, etc. In addition, compared with other bast fibers, the cellulose content of linen is significantly higher, up to 70%-80%, which is an ideal raw material for film preparation.

[0003] Polymer composites integrate the structures and functions of polymer matrices and functional fillers, and have the potential to become high-strength functional materials. For example, in the patent with publication number CN112812380A, "A Sodium Alginate / Aromatic Polyamide Nanofiber Composite Film and Its Preparation Method and Application" is disclosed. This method improves the performance of the sodium alginate composite film by preparing aromatic polyamide nanofibers. In the patent with publication number CN114957787B, "Preparation Method of Catechol-Functionalized Chitosan Porous Nanofiber Membrane / Sodium Alginate Composite Material" is disclosed. This method uses the thermally induced phase separation method to prepare a chitosan porous nanofiber membrane, then grafts catechol onto the fiber membrane by low-temperature plasma irradiation, and finally composites the fiber membrane with sodium alginate to obtain a multifunctional composite material. In the patent with publication number CN110452423B, "A Composite Film and Its Preparation Method" is disclosed. This method blends sodium alginate, gelatin, and graphene oxide to obtain an environmentally friendly composite film material.

[0004] The above methods can effectively obtain composite materials, but most of them have some deficiencies. For example: the raw materials are not easily available, the production process is cumbersome, the reaction conditions are relatively harsh, etc., making it difficult to be applied in industrial production. To solve these problems, it is urgent to explore a preparation process with simple method, low cost, applicable to industrial production and capable of improving the performance of composite materials. Summary of the Invention

[0005] The purpose of the present invention is to solve the drawbacks existing in the prior art, and to propose a preparation method of a degradable natural linen fiber / sodium alginate composite film. This method is safe and simple to operate, the raw materials are rich in sources, the cost is low, and it is beneficial to industrial production.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A preparation method of a degradable natural linen fiber / sodium alginate composite film, comprising the following steps: Step 1: Weigh 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 until completely dissolved to obtain a sodium alginate solution; Step 3: Laying out of linen fibers: Arrange and lay out the linen fibers flat on a glass mold; Step 4: Solution casting: Pour the sodium alginate solution evenly into a dry and clean glass mold, cast into a film to obtain a composite film solution; Step 5: Crosslinking into a film: Add a calcium ion solution to the above composite film solution to form a crosslinked network structure and crosslink into a film; Step 6: Drying and forming: Place it in a precision air blast drying oven for drying. When the film is basically formed, has no fluidity and the film can be slowly peeled off, the composite film can be obtained.

[0007] Preferably, in Step 1, the raw materials of the composite film include sodium alginate, an appropriate amount of linen fibers, and a 0.1 - 0.3 mol / L calcium ion solution.

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

[0009] Preferably, the linen fibers are natural polymer materials.

[0010] Preferably, the calcium ion solution is a crosslinking agent.

[0011] Preferably, in Step 1, the dissolution temperature of sodium alginate is 30 °C and the stirring time is 60 minutes.

[0012] Preferably, in Step 5, the crosslinking reaction time is 30 minutes to ensure the uniformity and mechanical properties of the film.

[0013] Preferably, in Step 6, the drying temperature is 60 °C and the drying time is 3 - 6 hours.

[0014] By adopting the above technical solutions: Using sodium alginate as the matrix material and natural linen fibers as the reinforcing phase, through crosslinking with calcium ions to form a stable network structure to have good mechanical properties and structural stability, a degradable bio-composite film is prepared by the solution casting method and the hot air drying method.

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

[0016] 2. The raw materials of the composite film of the present invention are all natural biomass resources, which are widely sourced, easily obtainable, inexpensive, and have high economic benefits and market competitiveness.

[0017] 3. The composite film of the present invention has good mechanical properties, is biodegradable, and can be made into different types of films through reasonable ratios and processing techniques, capable of meeting various application requirements.

[0018] 4. The preparation method of the composite film of the present invention is safe, has a simple process flow, low production cost, can be used for industrial production, and has good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flowchart of the present invention; Figure 2 is a photograph of the composite film prepared by the present invention; Figure 3 is a mechanical property diagram of Example 1 of the present invention; Figure 4 is a mechanical property diagram of Example 2 of the present invention; Figure 5 is a mechanical property diagram of Example 3 of the present invention; Figure 6 is a biodegradation rate diagram of Example 1 of the present invention; Figure 7 is a soil degradation result diagram of Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] 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 more clearly define 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 embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Embodiment

[0021] Composition of raw materials of the composite film: 1.5 g of sodium alginate, flax fiber, 0.1 mol / L calcium ion solution, glycerol, and deionized water.

[0022] Preparation method of the composite film in this embodiment: Dissolve 1.5 g of sodium alginate in 100 mL of deionized water, stir until completely dissolved, then add glycerol and continue to stir to form a homogeneous solution.

[0023] Lay the flax fiber flat in the mold.

[0024] The sodium alginate solution was uniformly cast in a glass mold, and 0.1 mol / L calcium ion solution was added thereto to form a cross-linked network structure, and then left standing for 30 minutes.

[0025] The mold containing the composite film solution was placed in a precision forced-air drying oven at 60 °C and dried for 3 hours, then cooled at room temperature, and slowly peeled off after molding to obtain the composite film.

[0026] The mechanical properties and degradation rate of the obtained composite film are respectively as Figure 3 and 6 shown. The tensile strength is 34.154 MPa, the elongation at break is 23.286%, and the degradation rate is 86.66%. Example

[0027] The raw material composition of the composite film: 1.5 g of sodium alginate, flax fiber, 0.1 mol / L calcium ion solution, glycerol and deionized water.

[0028] The preparation method of the composite film in this example: 1.5 g of sodium alginate was dissolved in 100 mL of deionized water and stirred until completely dissolved, then glycerol was added and stirring was continued to form a homogeneous solution.

[0029] The flax fiber was arranged and laid flat in the mold.

[0030] The sodium alginate solution was uniformly cast in a glass mold, and 0.1 mol / L calcium ion solution was added thereto to form a cross-linked network structure, and then left standing for 30 minutes.

[0031] The mold containing the composite film solution was placed in a precision forced-air drying oven at 60 °C and dried for 5 hours, then cooled at room temperature, and slowly peeled off after molding to obtain the composite film.

[0032] The mechanical properties of the obtained composite film are as Figure 4 shown. The tensile strength is 37.638 MPa, and the elongation at break is 35.110%. Example

[0033] The raw material composition of the composite film: 1.5 g of sodium alginate, flax fiber, 0.1 mol / L calcium ion solution, glycerol and deionized water.

[0034] The preparation method of the composite film in this example: 1.5 g of sodium alginate was dissolved in 100 mL of deionized water and stirred until completely dissolved, then glycerol was added and stirring was continued to form a homogeneous solution.

[0035] The flax fiber was arranged and laid flat in the mold.

[0036] The sodium alginate solution was evenly cast in a glass mold, and a 0.1 mol / L calcium ion solution was added thereto to form a crosslinked network structure, and then it was allowed to stand for 30 minutes.

[0037] The mold containing the composite film solution was placed in a precision forced-air drying oven at 60 °C and dried for 6 hours, then cooled at room temperature. After molding, it was slowly peeled off to obtain a composite film.

[0038] The mechanical properties of the obtained composite film are as Figure 5 shown, the tensile strength is 34.755 MPa, and the elongation at break is 26.591%.

[0039] In summary, in the present invention, sodium alginate is used as the matrix material, and natural flax fiber is used as the reinforcing phase. By crosslinking with calcium ions, a stable network structure is formed to have good mechanical properties and structural stability. The biodegradable biocomposite film is prepared by the solution casting method and the hot air drying method. 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 prepared by the present invention 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 the human body, and avoids the problem of pollution caused by long-term existence in the environment.

[0040] 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 also be made. Therefore, the modifications or improvements made without departing from the spirit of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A method for preparing a degradable natural flax fiber / 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 until completely dissolved, to prepare a sodium alginate solution; Step 3: Laying the flax fibers flat: Lay the flax fibers flat on the glass mold; Step 4: Solution casting: The sodium alginate solution is uniformly cast in a dry and clean glass mold to form a film to obtain a composite membrane solution; Step 5: cross-linking to form a membrane: adding a calcium ion solution to the above composite membrane solution to form a cross-linked network structure to form a cross-linked membrane; Step 6: Drying and forming: Place in a precision air drying oven for drying. When the film is basically formed, has no fluidity and can be slowly peeled off, a composite film can be obtained.

2. The method for preparing a degradable natural flax fiber / sodium alginate composite film according to claim 1, characterized in that: In step 1, the raw materials of the composite film include sodium alginate, an appropriate amount of flax fiber, 0.1-0.3 mol / L calcium ion solution, glycerol and deionized water.

3. The method for preparing a degradable natural flax fiber / 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 natural flax fiber / sodium alginate composite film according to claim 2, characterized in that: The flax fiber is a natural polymer material.

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

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

7. The method for preparing a degradable natural flax fiber / sodium alginate composite film according to claim 1, characterized in that: In step 5, the cross-linking reaction time is 30 minutes to ensure the uniformity and mechanical properties of the film.

8. The method for preparing a degradable natural flax fiber / 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 3-6 hours.

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