Nanobiodegradable composite material and its application in preparing biodegradable film

Abstract

The application discloses a kind of nanobiodegradable composite material and its application in preparation biodegradable film.The preparation of the nanobiodegradable composite material is first modified to layered silicate using intercalator to obtain organic layered silicate, then the organic / inorganic material that can generate silicon dioxide and microorganism are loaded on organic layered silicate, to obtain nanobiodegradable composite material.The application ensures the survival of microorganism after high temperature in the process of granulation and film blowing by forming a multilayer micro-nano structure protective layer on the surface of microorganism, thereby playing a role in degrading plastic products;At the same time, the degradation rate of the film doped with nanobiodegradable composite material is significantly faster than that of the control group.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials technology, specifically relating to a nano-biodegradable composite material and its application in the preparation of biodegradable films. Background Technology

[0002] Currently, the main methods for disposing of waste plastic products include landfill, incineration, and ocean dumping. However, all of these methods have significant drawbacks. First, large quantities of waste plastic packaging are buried in the soil. Due to the inherent stability of non-degradable plastics, degradation would take at least several hundred years, while the corresponding plastic waste is generated at a rate of tens of thousands of tons per minute. Over time, this will severely encroach on normal living and production space, and waste plastic products mixed in the soil will also seriously affect crops' absorption of nutrients and water, potentially leading to soil compaction and reduced crop yields. Second, the incineration of plastic waste produces large amounts of toxic substances such as dioxins. These substances diffuse into the air, adhere to food and other items, and enter the human body, posing serious health risks. Furthermore, waste plastic products dumped into the ocean are partially transformed into invisible plastic fragments by the marine ecosystem. These fragments are ingested by marine life and subsequently re-enter human society, causing damage to human health and the environment. Therefore, finding a more environmentally friendly and pollution-free solution for plastic disposal has become a common issue facing the world.

[0003] Research on biodegradable films represents one of the best current solutions to plastic pollution. Using biodegradable films can achieve complete degradation of plastics, thus solving the problem of accumulated waste plastic products, and also saves significant human and material resources. Biodegradable plastics can be specifically divided into three categories: photodegradable, biodegradable, and water-degradable. Photodegradation involves adding photosensitizers to plastics, which degrade under sunlight; water degradation involves adding water-absorbing substances to plastics, but both methods are affected by climate and environmental conditions; while biodegradable plastics have become a new research hotspot. Biodegradable plastics refer to a class of plastics that are degraded by naturally occurring microorganisms such as bacteria, fungi, and algae. Ideally, biodegradable plastics are polymeric materials with excellent performance characteristics that can be completely decomposed by microorganisms in the environment after disposal and ultimately become inorganic. However, relying solely on natural microbial degradation cannot achieve controlled degradation of plastic products. Therefore, incorporating materials that can regulate the degradation of plastic products during the plastic manufacturing process is a feasible method. Summary of the Invention

[0004] In response to the current serious problem of "white pollution" and the inability to effectively degrade waste plastic products, this invention provides a nano-biodegradable composite material and its application in the preparation of controllable biodegradable films.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A nanobiodegradable composite material is prepared by the following steps: Step 1: Mix the layered silicate and the dispersant, stir to form a stable suspension, add the intercalating agent, stir under heating conditions, and the product is centrifuged, washed with water and dried to obtain organic layered silicate; The ratio of layered silicate, dispersant and intercalating agent is as follows: for every 2 to 8 g of layered silicate, use 20 to 200 mL of dispersant and add 0.5 to 5 g of intercalating agent; The layered silicate is selected from clay, hydrotalcite, pyrophyllite, kaolin, vermiculite, montmorillonite, or chlorite; the dispersant is selected from water, ethanol, or toluene; the intercalating agent is selected from quaternary ammonium salts, quaternary phosphine salts, alkyl amino acids, alkyl lactams, alkyl diamines containing unsaturated double or triple bonds, pyridine derivatives, aluminum-titanium-tin metal ions or their oxides, halides, and inorganic salts. Step 2: Mix organic layered silicate with water, disperse by ultrasonication, add organic / inorganic materials that can directly or indirectly generate silica and template solution containing microorganisms, stir under heating conditions, and obtain nano-biodegradable composite material after centrifugation, washing and drying. The ratio of organic layered silicate, water, organic / inorganic materials that can directly or indirectly generate silica, and a template solution containing microorganisms is as follows: 2-8 g of organic layered silicate is uniformly dispersed in 10-200 mL of water, and 2-10 mL of organic / inorganic materials that can directly or indirectly generate silica and OD are added dropwise. 600 =0.1 ~ 0.4% template solution of 5 ~ 50 mL of microorganisms; The template solution comprises sodium chloride, peptone, yeast, beef powder, brown sugar, chitosan, sodium alginate, and water; the ratio is 1-5 g sodium chloride, 1-3 g peptone, 1-5 g yeast, 1-5 g beef powder, 1-7 g brown sugar, 1-5 g chitosan, 1-5 g sodium alginate, and 100-500 mL water. The microorganisms are one or more of the following bacteria that can degrade plastics: Pseudomonas, Bacillus, Enterobacter, Aristolochicus, Microbacterium, and Chlorella.

[0006] Further, in step 1, the stirring to form a stable suspension is achieved by mechanically dispersing the layered silicates uniformly until no visible agglomerates are formed. Preferably, the mechanical stirring speed is 100-800 rpm and the stirring time is 10-30 min.

[0007] Further, in step 1, the stirring under heating conditions is carried out at a heating temperature of 50 to 150°C, a stirring speed of 100 to 800 rpm, and a stirring time of 16 to 30 h.

[0008] Furthermore, in step 2, the heating temperature is 50 ~ 70℃, and the stirring time is 1 ~ 6 h.

[0009] The above-mentioned nanobiodegradable composite material is used in the preparation of controllable biodegradable films.

[0010] A controllable biodegradable film is prepared by one of the following methods: Method 1: Mix water-soluble biodegradable material, plasticizer and coupling agent evenly, heat to high temperature until melted, then add the above-mentioned nano-biodegradable composite material, stir evenly and cast into a film; Method 2: The oil-soluble biodegradable material, plasticizer, coupling agent, and the above-mentioned nano-biodegradable composite material are mixed evenly, granulated by screw extrusion, and then the mixed masterbatch is added to a blown film machine for blown film production. The proportions of water-soluble biodegradable materials / oil-soluble biodegradable materials, plasticizers, coupling agents, and nano-biodegradable composite materials are as follows: 100 parts of water-soluble biodegradable materials / oil-soluble biodegradable materials, 1 to 5 parts of plasticizers, 1 to 20 parts of coupling agents, and 1 to 10 parts of nano-biodegradable composite materials.

[0011] Furthermore, the water-soluble biodegradable material is polyvinyl alcohol (PVA), and the oil-soluble biodegradable material is selected from polylactic acid (PLA), poly(3-hydroxyalkanoate) (PHA), poly(ε-caprolactone) (PCL), polyesters (PBS / PBSA), aliphatic aromatic copolyesters (PBAT), or carbon dioxide copolymers.

[0012] Furthermore, the plasticizer is selected from phthalates, dicarboxylic acid esters, phosphate esters, polyol esters, chlorinated compounds, or epoxidized oils.

[0013] Furthermore, the coupling agent is selected from silane coupling agents, titanate coupling agents, aluminate coupling agents, bimetallic coupling agents, phosphate coupling agents, borate coupling agents, or chromium complexes.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides a nano-biodegradable composite material for improving the high-temperature tolerance of microorganisms. By modifying the multi-layered micro / nano-structured organic / inorganic material, a multi-layered protective layer is formed on the surface of microorganisms. The protected microorganisms exhibit higher high-temperature tolerance and maintain a certain level of activity during subsequent molding and processing. Simultaneously, nutrients can pass through this protective layer, ensuring normal growth and maintaining high activity of the microorganisms. The nano-biodegradable composite material for improving the high-temperature tolerance of microorganisms provided by this invention still shows colony growth after heating in an oven at 150 °C for 9 minutes; while microorganisms without the protection of the modified multi-layered micro / nano-structured organic / inorganic material show no bacterial colony growth after heating in an oven at 100 °C for 3 minutes. This invention solves the problem that traditional encapsulation methods cannot achieve high-temperature shielding, filling a gap in the research field of microbial high-temperature tolerance.

[0015] 2. The controllable biodegradable film provided by this invention achieves controllable regulation of plastic degradation by incorporating nano-biodegradable composite materials into a plastic system. The film doped with nano-biodegradable composite materials exhibits significant degradation within a short period of time. This demonstrates that this invention achieves effective control over plastic products.

[0016] 3. The preparation method of the present invention is simple and quick to operate, which is conducive to achieving low-cost industrial production. Moreover, the raw materials used in the experiment are all environmentally friendly consumables with high safety, which is conducive to their wide application in agriculture, manufacturing, food and other fields. Attached Figure Description

[0017] Figure 1 The figure shows the XRD pattern of the organic layered silicate material in Example 1. It can be seen from the figure that the diffraction peaks of the modified layered silicate material have shifted forward to different degrees, indicating that the interlayer spacing of the layered silicate material has changed.

[0018] Figure 2 The image shows the TGA diagram of the organic layered silicate material in Example 1. It can be seen from the diagram that the residual amount of the organic layered silicate material is about 70% after being subjected to a high temperature of 800°C, which proves that it has been successfully modified.

[0019] Figure 3 This is a scanning electron microscope image of the nano-biodegradable composite material in Example 1. The image shows that Bacillus subtilis has been successfully encapsulated by the modified multi-layered micro / nano structured organic / inorganic material, and a multi-layered uniform protective layer has been formed on the surface.

[0020] Figure 4 The image shows the Zeta potential of the nanobiodegradable composite material in Example 1, which is 8.27 mV, between that of organic layered silicates and acidic silica sols.

[0021] Figure 5 This is a colony diagram of the nano-biodegradable composite material in Example 1. It can be seen that Bacillus subtilis, protected by the modified multi-layered micro / nano structure organic / inorganic material, can continue to survive after high-temperature treatment. Even after 9 minutes at 150°C, Bacillus subtilis colonies still grew.

[0022] Figure 6 This is a degradation record diagram of the controllable biodegradable film in Example 1. It can be seen that the diameter of the film incorporating the nano-biodegradable composite material is significantly reduced in a short time compared to the ordinary film. This indicates that the incorporation of the nano-biodegradable composite material greatly accelerates the degradation rate of the plastic film.

[0023] Figure 7 This is a colony diagram of the nano-biodegradable composite material in Example 2. The diagram shows that without the protection of silica, the temperature rises to 100°C, which leads to the inactivation of Bacillus subtilis. This indicates that silica plays an indispensable role in protecting microorganisms from high-temperature damage.

[0024] Figure 8 The image shows the Molau experiment diagram of the controllable biodegradable film in Example 6. It can be seen that no phase separation occurs after standing for 2 days, indicating that the PBAT molecular chains have been successfully intercalated into the interlayer of the nano-biodegradable composite material.

[0025] Figure 9 The graph shows the degradation rate of the controllable biodegradable film in Example 6. It can be seen that when the doping amount of the nano-biodegradable composite material is 0.5%, it exhibits a higher degradation rate than the control group and BASF barrier material.

[0026] Figure 10 The graph shows the degradation rate of the controllable biodegradable film in Example 7. It can be seen that when the doping amount of the nano-biodegradable composite material is 0.5%, it exhibits a higher degradation rate than the control group and BASF barrier material. Detailed Implementation

[0027] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0029] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0030] In the following examples, a template solution was prepared by adding 1 g sodium chloride, 2 g peptone, 1 g yeast, 1 g beef powder, 3 g brown sugar, 1 g chitosan, and 1 g sodium alginate to 200 mL of water. Example 1

[0031] Preparation of nanobiodegradable composite materials Step 1: Take 5 g of montmorillonite and add it to a three-necked flask. Add 150 mL of distilled water and stir at high speed for 20 min to form a stable suspension. Then, add 1.5 g, 3 g, and 5 g of hexadecyltrimethylammonium bromide as intercalating agents, respectively. Stir at 80 °C for 24 hours, separate the solid and liquid, wash with water, dry, grind, and sieve. When the particle size is less than 63 μm, different proportions of organo-montmorillonite are obtained (denoted as 30%-OMMT, 60%-OMMT, and 100%-OMMT).

[0032] Step 2: Weigh 2 g of organo-modified montmorillonite into a three-necked flask, add 20 mL of template solution, and ultrasonically disperse to form a uniform suspension. While stirring, add 4 mL of silica sol dropwise, then add 10 mL of OD... 600 = 0.176 Bacillus subtilis template solution. Stir at 60 ℃ for 3 h, separate solid and liquid, wash with water multiple times, dry at room temperature, and seal the obtained nano-biodegradable composite material (SiO2-OMMT / Bs) for storage in a dark place at room temperature for later use.

[0033] Preparation of controllable biodegradable films Take 100 g of polyvinyl alcohol microparticles, add 1 mL of glycerol and 20 µL of vinyltriethoxysilane, heat at high temperature until all polyvinyl alcohol particles are melted, then add 5 g of nano-biodegradable composite material, stir evenly and pour into a polytetrafluoroethylene dish, and dry under natural conditions to form a film, thus obtaining a controllable biodegradable film (PVA / SiO2-OMMT / Bs).

[0034] The XRD pattern of the organic layered silicate material prepared in this embodiment is shown in the figure below. Figure 1 As shown in the figure, the diffraction peaks of the modified layered silicate material have shifted forward to varying degrees, indicating that the interlayer spacing of the layered silicate material has changed.

[0035] The TGA image of the organic layered silicate material prepared in this embodiment is shown below. Figure 2 As shown in the figure, the residual amount of the organic layered silicate material after being subjected to a high temperature of 800℃ is about 70%, which proves that it has been successfully modified.

[0036] The scanning electron microscope image of the nanobiodegradable composite material prepared in this embodiment is shown below. Figure 3As shown in the figure, Bacillus subtilis has been successfully encapsulated by modified multi-layered micro / nano-structured organic / inorganic materials, forming multiple uniform protective layers on its surface.

[0037] The zeta potential diagram of the controllable biodegradable material prepared in this embodiment is as follows: Figure 4 As shown in the figure, the Zeta potential of the prepared nanobiodegradable composite material is 8.27 mV, which is between that of organic layered silicates and acidic silica sols.

[0038] The prepared nanobiodegradable composite materials were placed in a preheated oven for high-temperature treatment for 3, 6, 9, and 12 min to simulate the high-temperature environment during film formation. Then, materials at different temperatures were transferred to 5 mL centrifuge tubes, and 4 mL of template solution was added. The mixtures were then placed in a 37°C constant-temperature shaking incubator at 120 r / min for 12 hours. 30 µL of the cultured mixture was dropped onto a solid culture medium and spread evenly with a spreader. The mixture was then incubated at 37°C for 12 hours, and photographed. Colony images are shown below. Figure 5 As shown in the figure, Bacillus subtilis protected by modified multi-layered micro / nano-structured organic / inorganic materials can continue to survive after high-temperature treatment. Even after 9 minutes at 150℃, colonies of Bacillus subtilis still grew.

[0039] The prepared biodegradable film was demolded and mixed with soil until the soil completely submerged the surface of the biodegradable film. The diameters of the two films at different times were recorded by photography, and their areas were calculated. Degradation records are shown in the figure below. Figure 6 As shown in the figure, the diameter of the film incorporating nano-biodegradable composite material is significantly reduced in a short time compared to the ordinary film, which indicates that the incorporation of nano-biodegradable composite material greatly accelerates the degradation rate of the plastic film. Example 2

[0040] Preparation of nanobiodegradable composite materials Step 1: Take 5 g of montmorillonite and add it to a three-necked flask. Add 150 mL of distilled water and stir at high speed for 20 min to form a stable suspension. Then add 1.5 g of hexadecyltrimethylammonium bromide as an intercalating agent and stir at 80 °C for 24 hours. Separate the solid and liquid, wash with water, dry, grind and sieve. When the particle size is less than 63 μm, organo-modified montmorillonite (OMMT) is obtained.

[0041] Step 2: Add 1 g sodium chloride, 2 g peptone, 1 g yeast, 1 g beef powder, 3 g brown sugar, 1 g chitosan, and 1 g sodium alginate to 200 mL of water to prepare the template solution. Weigh 2 g of organo-modified montmorillonite into a three-necked flask, add 20 mL of the template solution, and ultrasonically disperse to form a uniform suspension. While stirring, add 4 mL of the template solution dropwise, then add OD... 600 10 mL of a Bacillus subtilis solution with a concentration of 0.176 was added. The mixture was stirred at 60 °C for 3 h, followed by solid-liquid separation, repeated washing with water, and drying at room temperature. The resulting nano-biodegradable composite material (OMMT / Bs) was then sealed and stored in a dark place at room temperature for later use.

[0042] Preparation of controllable biodegradable films Take 100 g of polyvinyl alcohol microparticles, add 1 mL of glycerol and 20 µL of vinyltriethoxysilane, and heat at high temperature until all the polyvinyl alcohol particles melt. After cooling, add 5 g of nano-biodegradable composite material, stir evenly, pour into a polytetrafluoroethylene dish, and dry under natural conditions to form a film, thus obtaining a controllable biodegradable film (PVA / OMMT / Bs).

[0043] The prepared nanobiodegradable composite materials were placed in a preheated oven for high-temperature treatment for 3, 6, 9, and 12 min to simulate the high-temperature environment during film formation. Then, materials at different temperatures were transferred to 5 mL centrifuge tubes, and 4 mL of template solution was added. The mixtures were then placed in a 37°C constant-temperature shaking incubator at 120 r / min for 12 hours. 30 µL of the cultured mixture was dropped onto a solid culture medium and spread evenly with a spreader. The mixture was then incubated at 37°C for 12 hours, and photographed. Colony images are shown below. Figure 7 As shown in the figure, it can be seen that without the protection of silica, the temperature rises to 100℃, which will lead to the inactivation of Bacillus subtilis. This shows that silica plays an indispensable role in protecting microorganisms from high temperature damage. Example 3

[0044] Preparation of nanobiodegradable composite materials Step 1: Take 5 g of montmorillonite and add it to a three-necked flask. Add 150 mL of distilled water and stir at high speed for 20 min to form a stable suspension. Then add 1.5 g of triphenyl[dimethyl(γ-alkyl)methoxysilane]phosphonium halide as an intercalating agent. Stir at 80 °C for 24 hours, separate the solid and liquid, wash with water, dry, grind and sieve. When the particle size is less than 63 μm, organo-montmorillonite (OMMT) is obtained.

[0045] Step 2: Add 1 g sodium chloride, 2 g peptone, 1 g yeast, 1 g beef powder, 3 g brown sugar, 1 g chitosan, and 1 g sodium alginate to 200 mL of water to prepare the template solution. Weigh 2 g of organo-modified montmorillonite into a three-necked flask, add 20 mL of the template solution, and sonicate to disperse into a uniform suspension. While stirring, add 4 mL of silica sol dropwise, then add OD... 600 10 mL of a Bacillus subtilis solution with a concentration of 0.176 was added. The mixture was stirred at 60 °C for 3 h, followed by solid-liquid separation, repeated washing with water, and drying at room temperature. The resulting nano-biodegradable composite material (SiO2-OMMT / Bs) was then sealed and stored in a dark place at room temperature for later use.

[0046] Preparation of controllable biodegradable films Take 100 g of polyvinyl alcohol microparticles, add 1 mL of glycerol and 20 µL of vinyltriethoxysilane, heat to a molten state at high temperature, and stir for half an hour until all the polyvinyl alcohol particles are melted. After cooling, add 3 g of nano-biodegradable composite material, stir evenly, pour into a polytetrafluoroethylene dish, and dry under natural conditions to form a film, thus obtaining a controllable biodegradable film (PVA / SiO2-OMMT / Bs). Example 4

[0047] Preparation of nanobiodegradable composite materials Step 1: Take 5 g of montmorillonite and add it to a three-necked flask. Add 150 mL of distilled water and stir at high speed for 20 min to form a stable suspension. Then add 1.5 g of hexadecyltrimethylammonium bromide as an intercalating agent and stir at 80 °C for 24 hours. Separate the solid and liquid, wash with water, dry, grind and sieve. When the particle size is less than 63 μm, organo-modified montmorillonite (OMMT) is obtained.

[0048] Step 2: Add 1 g sodium chloride, 2 g peptone, 1 g yeast, 1 g beef powder, 3 g brown sugar, 1 g chitosan, and 1 g sodium alginate to 200 mL of water to prepare the template solution. Weigh 2 g of organo-modified montmorillonite into a three-necked flask, add 20 mL of the template solution, and sonicate to disperse into a uniform suspension. While stirring, add 4 mL of silica sol dropwise, then add OD... 600 10 mL of a Bacillus subtilis solution with a concentration of 0.176 was added. The mixture was stirred at 60 °C for 3 h, followed by solid-liquid separation, repeated washing with water, and drying at room temperature. The resulting nano-biodegradable composite material (SiO2-OMMT / Bs) was then sealed and stored in a dark place at room temperature for later use.

[0049] Preparation of controllable biodegradable films Step 3: Take 100 g of polyvinyl alcohol microparticles, add 1 mL of glycerol and 20 µL of vinyltriethoxysilane, heat to a molten state at high temperature, and stir for half an hour until all the polyvinyl alcohol particles are melted. After cooling, add 1 g of nano-biodegradable composite material, stir evenly, pour into a polytetrafluoroethylene dish, and dry under natural conditions to form a film, thus obtaining a controllable biodegradable film (PVA / SiO2-OMMT / Bs). Example 5

[0050] Preparation of nanobiodegradable composite materials Step 1: Take 5 g of montmorillonite and add it to a three-necked flask. Add 150 mL of distilled water and stir at high speed for 20 min to form a stable suspension. Then add 1.5 g of hexadecyltrimethylammonium bromide as an intercalating agent and stir at 80 °C for 24 hours. Separate the solid and liquid, wash with water, dry, grind and sieve. When the particle size is less than 63 μm, organo-modified montmorillonite (OMMT) is obtained.

[0051] Step 2: Add 1 g sodium chloride, 2 g peptone, 1 g yeast, 1 g beef powder, 3 g brown sugar, 1 g chitosan, and 1 g sodium alginate to 200 mL of water to prepare the template solution. Weigh 2 g of organo-modified montmorillonite into a three-necked flask, add 20 mL of the template solution, and sonicate to disperse into a uniform suspension. While stirring, add 4 mL of silica sol dropwise, then add OD... 600 10 mL of a Bacillus subtilis solution with a concentration of 0.176 was added. The mixture was stirred at 60 °C for 3 h, followed by solid-liquid separation, repeated washing with water, and drying at room temperature. The resulting nano-biodegradable composite material (SiO2-OMMT / Bs) was then sealed and stored in a dark place at room temperature for later use.

[0052] Preparation of controllable biodegradable films Step 3: 1000 g of polylactic acid, 10 mL of glycerol, 200 µL of vinyltriethoxysilane and 50 g of nano-biodegradable composite material were placed in a high-speed mixer for high-speed blending for 30 minutes. The blend was then placed in a twin-screw extruder for melt extrusion granulation. The mixed masterbatch was then added to a double-layer co-extrusion laboratory blown film machine (model SJ-16×2) manufactured by Hangzhou Leibo Technology Co., Ltd. to produce a controllable biodegradable film (PLA / SiO2-OMMT / Bs). Example 6

[0053] Preparation of nanobiodegradable composite materials Step 1: Take 5 g of montmorillonite and add it to a three-necked flask. Add 150 mL of distilled water and stir at high speed for 20 min to form a stable suspension. Then add 1.5 g of hexadecyltrimethylammonium bromide as an intercalating agent and stir at 80 °C for 24 hours. Separate the solid and liquid, wash with water, dry, grind and sieve. When the particle size is less than 63 μm, organo-modified montmorillonite (OMMT) is obtained.

[0054] Step 2: Add 1 g sodium chloride, 2 g peptone, 1 g yeast, 1 g beef powder, 3 g brown sugar, 1 g chitosan, and 1 g sodium alginate to 200 mL of water to prepare the template solution. Weigh 2 g of organo-modified montmorillonite into a three-necked flask, add 20 mL of the template solution, and sonicate to disperse into a uniform suspension. While stirring, add 4 mL of silica sol dropwise, then add OD... 600 10 mL of a Bacillus subtilis solution with a concentration of 0.176 was added. The mixture was stirred at 60 °C for 3 h, followed by solid-liquid separation, repeated washing with water, and drying at room temperature. The resulting nano-biodegradable composite material (SiO2-OMMT / Bs) was then sealed and stored in a dark place at room temperature for later use.

[0055] Preparation of controllable biodegradable films Step 3: 1000 g of butylene adipate and butylene terephthalate copolymer (PBAT), 10 mL of glycerol, 200 µL of vinyltriethoxysilane and 50 g of nano-biodegradable composite material were placed in a high-speed mixer for high-speed blending for 30 minutes. The blend was then placed in a twin-screw extruder for melt extrusion and granulation. The mixed masterbatch was then added to a double-layer co-extrusion laboratory blown film machine (model SJ-16×2) manufactured by Hangzhou Leibo Technology Co., Ltd. to produce a controllable biodegradable film (PBAT / SiO2-OMMT / Bs).

[0056] The prepared biodegradable films were placed in chloroform solution for 2 days. After 2 days, the solubility, solution state, and phase separation state of each sample were observed. Figure 8 As shown in the figure, no phase separation occurs even after standing for 2 days, indicating that the PBAT molecular chains have been successfully intercalated into the interlayer of the nano-biodegradable composite material.

[0057] The prepared biodegradable film was cut into 50 mm × 50 mm squares. Approximately 1 g of the film was mixed with 1 kg of soil and placed in a landfill container. The film was removed and weighed at different times. Figure 9 As shown in the figure, the nanobiodegradable composite material exhibits a higher degradation rate than the control group and BASF barrier material when the doping amount is 0.5%. Example 7

[0058] Preparation of nanobiodegradable composite materials Step 1: Take 5 g of montmorillonite and add it to a three-necked flask. Add 150 mL of distilled water and stir at high speed for 20 min to form a stable suspension. Then add 1.5 g of hexadecyltrimethylammonium bromide as an intercalating agent and stir at 80 °C for 24 hours. Separate the solid and liquid, wash with water, dry, grind and sieve. When the particle size is less than 63 μm, organo-modified montmorillonite (OMMT) is obtained.

[0059] Step 2: Add 1 g sodium chloride, 2 g peptone, 1 g yeast, 1 g beef powder, 3 g brown sugar, 1 g chitosan, and 1 g sodium alginate to 200 mL of water to prepare the template solution. Weigh 2 g of organo-modified montmorillonite into a three-necked flask, add 20 mL of the template solution, and sonicate to disperse into a uniform suspension. While stirring, add 4 mL of silica sol dropwise, then add OD... 600 10 mL of a Bacillus subtilis solution with a concentration of 0.176 was added. The mixture was stirred at 60 °C for 3 h, followed by solid-liquid separation, repeated washing with water, and drying at room temperature. The resulting nano-biodegradable composite material (SiO2-OMMT / Bs) was then sealed and stored in a dark place at room temperature for later use.

[0060] Preparation of controllable biodegradable films Step 3: 200 g of polylactic acid (PLA), 800 g of copolymer of butylene adipate and butylene terephthalate (PBAT), 10 mL of glycerol, 200 µL of vinyltriethoxysilane, and 50 g of nano-biodegradable composite material were placed in a high-speed mixer for high-speed blending for 30 minutes. The blend was then melt-extruded and granulated in a twin-screw extruder. The masterbatch was then blown into a double-layer co-extrusion laboratory blown film machine (model SJ-16×2) manufactured by Hangzhou Leibo Technology Co., Ltd. to obtain a controllable biodegradable film (PLA-PBAT / SiO2-OMMT / Bs).

[0061] The prepared biodegradable film was cut into 50 mm × 50 mm squares. Approximately 1 g of the film was mixed with 1 kg of soil and placed in a landfill container. The film was then removed and weighed at different times. Figure 10 As shown in the figure, the nanobiodegradable composite material exhibits a higher degradation rate than the control group and BASF barrier material when the doping amount is 0.5%.

Claims

1. A nanobiodegradable composite material, characterized in that, It is prepared by the following steps: Step 1: Mix the layered silicate and the dispersant, stir to form a stable suspension, add the intercalating agent, stir under heating conditions, and the product is centrifuged, washed with water and dried to obtain organic layered silicate; The ratio of layered silicate, dispersant and intercalating agent is as follows: for every 2 to 8 g of layered silicate, use 20 to 200 mL of dispersant and add 0.5 to 5 g of intercalating agent; The layered silicate is montmorillonite; the dispersant is water; the intercalating agent is hexadecyltrimethylammonium bromide; Step 2: Mix organic layered silicate with water, disperse by ultrasonication, add organic / inorganic materials that can directly or indirectly generate silica and template solution containing microorganisms, stir under heating conditions, and obtain nano-biodegradable composite material after centrifugation, washing and drying. The ratio of organic layered silicate, water, organic / inorganic materials that can directly or indirectly generate silica, and a template solution containing microorganisms is as follows: 2-8 g of organic layered silicate is uniformly dispersed in 10-200 mL of water, and 2-10 mL of organic / inorganic materials that can directly or indirectly generate silica and OD are added dropwise. 600 =0.1 ~ 0.4% template solution of 5 ~ 50 mL of microorganisms; The template solution is composed of sodium chloride, peptone, yeast, beef powder, brown sugar, chitosan, sodium alginate, and water, in the following proportions: sodium chloride 1-5 g, peptone 1-3 g, yeast 1-5 g, beef powder 1-5 g, brown sugar 1-7 g, chitosan 1-5 g, sodium alginate 1-5 g, and water 100-500 mL. The organic / inorganic material that can directly or indirectly generate silica is silica sol; The microorganism in question is Bacillus subtilis; In step 2, the heating temperature is 50 ~ 70℃ and the stirring time is 1 ~ 6 h.

2. The nanobiodegradable composite material according to claim 1, characterized in that, In step 1, the formation of a stable suspension is achieved by mechanically dispersing the layered silicates uniformly until there are no visible agglomerates. The mechanical stirring speed is 100-800 rpm and the stirring time is 10-30 min.

3. The nanobiodegradable composite material according to claim 1, characterized in that, In step 1, the stirring is carried out under heating conditions, with a heating temperature of 50 to 150°C, a stirring speed of 100 to 800 rpm, and a stirring time of 16 to 30 hours.

4. The application of the nanobiodegradable composite material according to claim 1 in the preparation of controllable biodegradable films.

5. A controllable biodegradable film, characterized in that, It is prepared by one of the following methods: Method 1: The water-soluble biodegradable material, plasticizer and coupling agent are mixed evenly, heated to a molten state at high temperature, and then the nano-biodegradable composite material according to any one of claims 1-3 is added, stirred evenly and cast into a film; Method 2: The oil-soluble biodegradable material, plasticizer, coupling agent, and the nano-biodegradable composite material according to any one of claims 1-3 are mixed evenly, granulated by screw extrusion, and then the mixed masterbatch is added to a blown film machine for blown film production. The proportions of water-soluble biodegradable materials / oil-soluble biodegradable materials, plasticizers, coupling agents, and nano-biodegradable composite materials are as follows: 100 parts of water-soluble biodegradable materials / oil-soluble biodegradable materials, 1 to 5 parts of plasticizers, 1 to 20 parts of coupling agents, and 1 to 10 parts of nano-biodegradable composite materials.

6. The controllable biodegradable film according to claim 5, characterized in that, The water-soluble biodegradable material is polyvinyl alcohol, and the oil-soluble biodegradable material is a copolymer of polylactic acid, butylene adipate, and butylene terephthalate.

7. The controllable biodegradable film according to claim 5, characterized in that, The plasticizer is glycerin.

8. The controllable biodegradable film according to claim 5, characterized in that, The coupling agent is a silane coupling agent, vinyltriethoxysilane.

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