Biodegradable composite film and preparation method thereof

Abstract

The invention relates to the technical field of plastic films, in particular to a biodegradable composite film and a preparation method thereof.Sodium alginate and paper pulp serve as film forming matrixes, a calcium chloride solution serves as a cross-linking agent, glycerin serves as a plasticizer, a solution is prepared through a mechanical stirring method, the solution is spread on a mold in a curtain coating mode, and the composite film is prepared through drying. Comprising the following steps: firstly, adding deionized water into sodium alginate, and stirring in a magnetic stirrer to prepare a sodium alginate solution; dispersing paper pulp in deionized water to prepare a paper pulp suspension; blending the sodium alginate solution with the paper pulp suspension to form a uniform mixed solution; uniformly casting the prepared mixed solution into a mold, and adding a calcium ion solution for crosslinking; and drying the cross-linked film in an air dry oven, and stripping from the surface of the substrate to prepare the composite film. The prepared film has good mechanical strength and flexibility, is suitable for various packaging requirements, can be rapidly degraded in the natural environment, and is environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of plastic films, and in particular to a biodegradable composite film and a preparation method thereof. Background Art

[0002] With the rapid development of social economy and the continuous improvement of living standards, the application scope of plastic products is becoming more and more extensive, covering many fields such as food packaging, agricultural production, medical equipment, and daily life. Since the advent of plastics, due to the durability and low price of traditional petroleum-based plastic films, the production and demand of plastic films have maintained extremely high increments almost every year in the past few decades. These plastic films are usually used once, only a small part can be recycled or properly treated, and the vast majority of waste plastic films are directly discarded. Looking around the world, these waste non-degradable plastic films are being discharged into the environment at an increment of millions of tons per year, forming a serious environmental problem. Traditional plastic products are mostly made of synthetic polymer materials such as polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP) and polystyrene (PS). These materials usually take hundreds of years to completely degrade in the natural environment. The problem of waste disposal of plastic products after use has become a global challenge. Taking polyethylene as an example, although in related studies, researchers have tried to promote its degradation by using special additives, such as photodegradants, oxidants and starch particles, these special additives can only accelerate the production of microplastics and cannot promote the complete degradation of PE. Due to their tiny size, microplastics can be spread by wind, carried by water, or even accidentally ingested by marine organisms, thus entering the food chain. This situation not only has a serious impact on the marine ecosystem, but also poses risks to human health. Studies have shown that PE and PET can be degraded by catalytic pyrolysis and synthetase degradation, but these degradation processes usually require strict condition control and relatively high costs, making them difficult to promote on a large scale in practical applications.

[0003] In order to deal with the problem of plastic pollution, scientists and environmental organizations around the world are actively seeking solutions to replace traditional plastics. Biodegradable plastics have gradually become a hot topic in research and application because they can be degraded in the natural environment. In recent years, the research and application of biodegradable plastics have gradually increased. For example, the mechanical properties of biodegradable plastics can be improved by blending modification, making them more adaptable to various application requirements. Through biotechnology improvement, the efficiency of microbial synthesis of biodegradable plastics can be improved and the production cost can be reduced. By studying the degradation mechanism, biodegradable plastics that are more easily degraded in the natural environment can be developed. Common biodegradable plastics include polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polyglycolic acid (PGA), etc. However, biodegradable plastics still face some challenges in practical applications. For example, compared with traditional petroleum-based plastics, biodegradable plastics have higher production costs and are difficult to compete with them in price, which limits their large-scale application. The mechanical properties of biodegradable plastics are relatively poor, which makes it difficult to meet the needs of certain application scenarios. In addition, the degradation conditions of biodegradable plastics are harsh, requiring specific temperature, humidity and microbial environment for effective degradation, and may not be completely degraded in the natural environment. In order to solve these problems, it is urgent to explore a composite film with a simple preparation method to improve the performance of biodegradable plastics and reduce their production costs, which can be used for industrial production.

[0004] Alginate is a natural high molecular polymer that can be directly extracted from algae. It can exchange ions with metal cations to form a dense cross-linked network structure. It has good water solubility, degradability, renewability and outstanding film-forming ability. It is widely used in medicine, environmental protection, biochemistry and other fields. The application of alginate-based composite films is still limited by its low water barrier ability, poor UV barrier ability, lack of antioxidant activity and antibacterial activity. In order to improve biological performance, it is usually mixed with other biopolymers. Blending is one of the simple and important ways to develop new polymer materials. It is easier to operate, less polluting, and easy to industrialize than chemical modification to obtain composite materials with more ideal comprehensive performance. Pulp is a natural high molecular material made of plant fibers with good biodegradability. In the natural environment, pulp cellulose can be degraded by microorganisms and eventually decomposed into harmless substances such as carbon dioxide and water. The fiber network structure of pulp can provide support during the film forming process, promote a more uniform distribution of sodium alginate during film formation, and avoid uneven thickness of the film. In addition, pulp fibers can fill the gaps in the film, increase the density and tightness of the film, and thus improve the barrier properties and durability of the film. It has a certain softening effect during the film-forming process, so that the film has good flexibility while maintaining strength, making the film more durable and not easy to crack or break during application. At the same time, pulp is also a renewable natural resource with a wide range of sources and a relatively environmentally friendly production process. Its application meets the requirements of green environmental protection and sustainable development, helps to reduce dependence on petroleum-based plastics, and promotes the development of plastic materials towards renewable and environmentally friendly directions. Therefore, pulp and calcium ions can be effectively used for functional modification of sodium alginate films. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a biodegradable composite film and a preparation method thereof. The prepared film has good mechanical strength and flexibility, is suitable for a variety of packaging needs, and can be rapidly degraded in the natural environment and is environmentally friendly.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A biodegradable composite film is prepared by using sodium alginate and paper pulp as film-forming matrix, calcium chloride solution as crosslinking agent and glycerol as plasticizer, using mechanical stirring method to prepare solution, casting and spreading on a mold, and drying to prepare the composite film.

[0007] Preferably, the mass ratio of sodium alginate to pulp is 1-5:1, and the mass ratio of sodium alginate to pulp is preferably 1:1, 2.5:1 or 5:1; the concentration of the calcium ion solution in the calcium chloride solution is 0.1 mol / L.

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

[0009] Preferably, the pulp is a natural polymer material.

[0010] The present invention also provides a method for preparing a biodegradable composite film, comprising the following steps: Step 1, weighing raw materials according to the components of the composite film material; Step 2, preparation of sodium alginate solution: adding sodium alginate powder into 100 ml of deionized water, heating and stirring until completely dissolved, to prepare a sodium alginate solution; Step 3, preparation of pulp suspension: dissolving pulp in deionized water, heating and stirring until completely dispersed, to prepare pulp suspension; Step 4, preparation of a sodium alginate / pulp mixed solution: mixing the sodium alginate solution, glycerol and pulp suspension evenly by high-speed magnetic stirring to obtain a mixed solution; Step 5, solution casting: Pour the mixed solution into a glass mold of the same size with a dry and clean surface; Step 6, cross-linking to form a film: adding calcium chloride solution to the above mixed solution to form a cross-linked network structure to form a cross-linked film; Step 7, drying and molding: Place the mold with the film in a precision blast drying oven at a temperature of 60°C for drying. When the film is basically formed, has no fluidity and can be slowly peeled off, a composite film can be obtained.

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

[0012] Preferably, in step 6, the cross-linking reaction time is 30 minutes.

[0013] Preferably, in step 7, the drying time is 6 hours.

[0014] By adopting the above technical scheme: a composite film made of sodium alginate, pulp and calcium ion solution. Through reasonable raw material ratio and preparation process. The raw materials of the composite film are abundant in source, low in price, simple in preparation process, good in mechanical properties and degradable, which can solve the problem that traditional plastics are difficult to degrade, overcome the shortcomings of existing biodegradable plastics in cost and performance, and have broad application prospects and important environmental significance. Among them, the composite film has the following characteristics: low cost: the raw materials of the composite film are all natural biomass resources, which are widely available, easy to obtain and low in price; good mechanical properties: through reasonable ratio and processing technology, the composite film has relatively good mechanical properties and can meet various application requirements; rapid degradation: the film can be degraded in the natural environment, avoiding the problem of long-term existence in the environment causing pollution; environmental protection and safety: the film will not produce toxic and harmful substances during the degradation process, and is harmless to the environment and human body.

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

[0016] 2. The raw materials of the present invention are widely available and inexpensive, the production process is simple, the cost is low, and it has high economic benefits and market competitiveness.

[0017] 3. The composite film prepared by the present invention has good mechanical properties and is biodegradable. It can be made into different types of films through reasonable proportions and processing techniques to meet various application requirements.

[0018] 4. The preparation method 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 It is a preparation flow chart of the present invention. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making 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, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0021] The present invention adopts the following embodiment test method and equipment: In the preparation process of the present invention, a magnetic stirrer is used for stirring, and the magnetic stirrer adopts a 08-2G constant temperature magnetic stirrer manufactured by Shanghai Meiyingpu Instrument Manufacturing Co., Ltd.; an air blast drying oven is used for drying, and the air blast drying oven adopts a BPG-9056A precision air blast drying oven manufactured by Shanghai Yiheng Technology Co., Ltd. Example

[0022] like Figure 1 As shown, a biodegradable composite film is prepared from the following raw materials: 1.5 g sodium alginate, 1.5 g paper pulp, 0.1 mol / L calcium ion solution, glycerol and deionized water.

[0023] A method for preparing a biodegradable composite film comprises the following steps: Dissolve 1.5 g of sodium alginate in 100 mL of deionized water and stir until completely dissolved to form a uniform sodium alginate solution.

[0024] 1.5 g of pulp was dissolved in 90 mL of deionized water and stirred until completely dispersed to obtain a pulp suspension.

[0025] The sodium alginate solution, glycerol and pulp suspension are uniformly mixed by high-speed magnetic stirring to obtain a mixed solution.

[0026] The mixed solution was uniformly cast on a glass mold, 0.1 mol / L calcium ion solution was added thereto to form a cross-linked network structure, and the mixture was allowed to stand for 30 minutes.

[0027] The mold containing the composite film liquid was placed in a precision air drying oven at a temperature of 60° C. and dried for 6 hours, cooled at room temperature, and slowly peeled off after molding to prepare a composite film.

[0028] The test shows that the tensile strength of the composite film of this embodiment is 34.154 MPa, and the elongation at break is 23.286%. Example

[0029] like Figure 1 As shown, a biodegradable composite film is prepared from raw materials including 1.5 g sodium alginate, 0.6 g pulp, 0.1 mol / L calcium ion solution, glycerol and deionized water.

[0030] A method for preparing a biodegradable composite film comprises the following steps: Dissolve 1.5 g of sodium alginate in 100 mL of deionized water and stir until completely dissolved to form a uniform sodium alginate solution.

[0031] 0.6 g of pulp was dissolved in 60 mL of deionized water and stirred until completely dispersed to obtain a pulp suspension.

[0032] The sodium alginate solution, glycerol and pulp suspension are uniformly mixed by high-speed magnetic stirring to obtain a mixed solution.

[0033] The mixed solution was uniformly cast on a glass mold, 0.1 mol / L calcium ion solution was added thereto to form a cross-linked network structure, and the mixture was allowed to stand for 30 minutes.

[0034] The mold containing the composite film liquid was placed in a precision air drying oven at a temperature of 60° C. and dried for 6 hours, cooled at room temperature, and slowly peeled off after molding to prepare a composite film.

[0035] The test shows that the tensile strength of the composite film of this embodiment is 25.463 MPa, and the elongation at break is 24.283%. Example

[0036] like Figure 1 As shown, a biodegradable composite film is prepared from the following raw materials: 1.5 g sodium alginate, 0.3 g pulp, 0.1 mol / L calcium ion solution, glycerol and deionized water.

[0037] A method for preparing a biodegradable composite film comprises the following steps: Dissolve 1.5 g of sodium alginate in 100 mL of deionized water and stir until completely dissolved to form a uniform sodium alginate solution.

[0038] 0.3 g of pulp was dissolved in 60 mL of deionized water and stirred until completely dispersed to obtain a pulp suspension.

[0039] The sodium alginate solution, glycerol and pulp suspension are uniformly mixed by high-speed magnetic stirring to obtain a mixed solution.

[0040] The mixed solution was uniformly cast on a glass mold, 0.1 mol / L calcium ion solution was added thereto to form a cross-linked network structure, and the mixture was allowed to stand for 30 minutes.

[0041] The mold containing the composite film liquid was placed in a precision air drying oven at a temperature of 60° C. and dried for 6 hours, cooled at room temperature, and slowly peeled off after molding to prepare a composite film.

[0042] The test shows that the tensile strength of the composite film of this embodiment is 16.232 MPa, and the elongation at break is 33.809%.

[0043] In summary, the composite film prepared by the present invention has good mechanical strength and flexibility, is suitable for various packaging needs, and can be quickly degraded in the natural environment, and is environmentally friendly. The composite film is suitable for various application scenarios such as food packaging, daily necessities packaging, and agricultural mulch.

[0044] The description and practice disclosed in the present invention are easy to think and understand for ordinary technicians in the technical field, and several improvements and modifications can be made without departing from the principles of the present invention. Therefore, 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 biodegradable composite film, characterized in that: The composite film is prepared by using sodium alginate and paper pulp as film-forming matrix, calcium chloride solution as cross-linking agent and glycerol as plasticizer, using mechanical stirring method to prepare solution, casting and spreading on a mold, and drying to prepare the composite film.

2. The biodegradable composite film according to claim 1, characterized in that: The mass ratio of the sodium alginate to the pulp is 1-5:1, and the concentration of the calcium ion solution in the calcium chloride solution is 0.1 mol / L.

3. The biodegradable composite film according to claim 1, characterized in that: The sodium alginate is a natural polysaccharide-based material.

4. The biodegradable composite film according to claim 1, characterized in that: The paper pulp is a natural polymer material.

5. The method for preparing a biodegradable composite film according to any one of claims 1 to 4, characterized in that: The steps include: Step 1, weighing raw materials according to the components of the composite film material; Step 2, preparation of sodium alginate solution: adding sodium alginate powder into 100 ml of deionized water, heating and stirring until completely dissolved, to prepare a sodium alginate solution; Step 3, preparation of pulp suspension: dissolving pulp in deionized water, heating and stirring until completely dispersed, to prepare pulp suspension; Step 4, preparation of a sodium alginate / paper pulp mixed solution: mixing the sodium alginate solution, glycerol and paper pulp suspension evenly by high-speed magnetic stirring to obtain a mixed solution; Step 5, solution casting: Pour the mixed solution into a glass mold of the same size with a dry and clean surface; Step 6, cross-linking to form a film: adding calcium chloride solution to the above mixed solution to form a cross-linked network structure to form a cross-linked film; Step 7, drying and molding: Place the mold with the film in a precision blast drying oven at a temperature of 60°C for drying. When the film is basically formed, has no fluidity and can be slowly peeled off, a composite film can be obtained.

6. The method for preparing a biodegradable composite film according to claim 5, characterized in that: In step 2, the dissolution temperature of the sodium alginate powder is 30° C. and the stirring time is 60 minutes.

7. The method for preparing a biodegradable composite film according to claim 5, characterized in that: In step 6, the cross-linking reaction time is 30 minutes.

8. The method for preparing a biodegradable composite film according to claim 5, characterized in that: In step 7, the drying time is 6 hours.

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