Preparation method of water-blocking polyvinyl alcohol-based coating fresh-keeping packaging material

Abstract

The present invention relates to the technical field of water-resistant modification of coated polyvinyl alcohol films, and discloses a method for preparing a water-blocking polyvinyl alcohol-based coating fresh-keeping packaging material, comprising: preparing carboxyl-terminated pyridine-type ligands and / or polypyridine-type ligands; preparing a carboxylated MOF-type antimicrobial agent by a coordination reaction between the pyridine-type ligand and silver ions; cross-linking and modifying a polyvinyl alcohol resin using the carboxylated MOF-type antimicrobial agent based on an esterification reaction mechanism to prepare a cross-linked modified polyvinyl alcohol; dissolving the cross-linked modified polyvinyl alcohol to prepare a coating liquid, which is then coated on the surface of a PLA film prepared by an extrusion blow molding process to prepare a coated polyvinyl alcohol water-blocking, antimicrobial, and biodegradable film. The present invention provides a method for preparing a coated polyvinyl alcohol water-blocking, antimicrobial, and biodegradable film. The prepared film has excellent water-blocking and antimicrobial properties and can be used in fresh-keeping packaging materials.

Description

Technical Field

[0001] The invention relates to the technical field of water-resistant modification of coated polyvinyl alcohol films, in particular to a method for preparing a water-blocking polyvinyl alcohol-based coating fresh-keeping packaging material. Background Art

[0002] In recent years, petroleum-based polymers with excellent biocompatibility and biodegradability have become a hot topic of research. Polyvinyl alcohol (PVA), an environmentally friendly polymer, is widely used in packaging, biomedicine, and other fields due to its non-toxicity, emulsification properties, and excellent mechanical and barrier properties. Dissolving it in water and coating it on biodegradable polylactic acid (PLA) packaging film can significantly improve the material's barrier properties. However, the excessive number of hydroxyl groups in PVA makes it prone to hydrogen bonding with water molecules in the air, significantly limiting its water barrier properties.

[0003] At present, the ways to enhance the water-barrier properties of polyvinyl alcohol include multi-layer co-extrusion composite and composite modification of water-barrier materials. For example, the patent with publication number CN117844031A coats the surface of a polymer film with an anti-UV high-barrier coating liquid. The coating liquid is composed of polyvinyl alcohol, dispersible graphene, a coupling agent, rutile titanium dioxide additives and other substances to prepare a composite film with excellent water-barrier properties.

[0004] The search found that metal-organic frameworks (MOFs) are a type of porous crystalline material formed by self-assembly of metal ions and organic ligands through coordination bonds. They have the characteristics of large surface area, ultra-high porosity and more than 90% pore space. They also have antibacterial, moisture absorption, ethylene scavenging, oxygen adsorption and other activities, and can be used in food water-barrier and fresh-keeping packaging. Summary of the Invention

[0005] The present invention provides a method for preparing a water-blocking polyvinyl alcohol-based coating fresh-keeping packaging material. A new pyridine-type ligand is designed and synthesized to prepare a carboxylated MOF-type antibacterial agent, which is then used to perform cross-linking modification on a polyvinyl alcohol resin. On the one hand, the water-blocking properties of the polyvinyl alcohol are improved by the large specific surface area and porous structure of the metal organic framework, and on the other hand, the polyvinyl alcohol is given antibacterial and fresh-keeping properties by the metal ions of the metal organic framework. The coating liquid is prepared and applied to the surface of a PLA film to prepare a coated polyvinyl alcohol water-blocking, antibacterial, and biodegradable film, which can be used as a fresh-keeping packaging material.

[0006] A method for preparing a coated polyvinyl alcohol water-blocking and antibacterial biodegradable film comprises the following steps:

[0007] Step 1: preparing a pyridine-type ligand, wherein the pyridine-type ligand is a carboxyl-terminated pyridine-type ligand and / or a polypyridine-type ligand;

[0008] Step 2: Prepare a carboxylated MOF-type antibacterial agent by a coordination reaction between a pyridine-type ligand and silver ions;

[0009] Step 3: Based on the esterification reaction mechanism, the polyvinyl alcohol resin is cross-linked and modified using a carboxylated MOF-type antibacterial agent to prepare a cross-linked modified polyvinyl alcohol;

[0010] Step 4: prepare a PLA film by using an extrusion blow molding process, dissolve the cross-linked modified polyvinyl alcohol to prepare a coating liquid and apply it on the surface to prepare a coated polyvinyl alcohol water-blocking and antibacterial biodegradable film.

[0011] Preferably, the preparation method of the carboxyl-terminated pyridine-type ligand is:

[0012] Step S2-1: Using the Suzuki coupling reaction mechanism, under alkaline conditions, a palladium catalyst catalyzes a coupling reaction between the boronic acid pinacol ester group of 3-(ethoxyformyl)pyridine-5-boronic acid pinacol ester and the bromine functional group of 2,6-dibromopyridine to generate a tripyridyl ester monomer;

[0013] Step S2-2: In the presence of sodium hydroxide, the ester functional group of the tripyridyl ester monomer undergoes a hydrolysis reaction to generate a carboxyl-terminated pyridine-type ligand.

[0014] Preferably, the preparation method of the polypyridine ligand is:

[0015] Step S3-1: Using p-bromophenol as a nucleophilic reagent, under the catalysis of sodium hydroxide, the chlorine functional group of cyanuric chloride and the phenolic hydroxyl functional group of p-bromophenol undergo a nucleophilic substitution reaction to generate a tribromophenyl triazine monomer;

[0016] Step S3-2: Using the Suzuki coupling reaction mechanism, under alkaline conditions, a palladium catalyst catalyzes the coupling reaction between the bromine functional group of the tribromophenyltriazine monomer and 4-pyridine boronic acid to generate a polypyridine ligand.

[0017] Preferably, the alkaline condition is one of potassium carbonate, sodium carbonate, cesium carbonate, and potassium phosphate.

[0018] Preferably, the palladium catalyst is one of palladium acetate, tris(dibenzylideneacetone)dipalladium, and tetrakis(triphenylphosphine)palladium.

[0019] Preferably, the preparation method of the coated polyvinyl alcohol water-blocking and antibacterial biodegradable film in step 4 is:

[0020] Step S6-1: dissolving 0.5 to 5 parts by weight of cross-linked modified polyvinyl alcohol in a mixed solution of deionized water and N,N-dimethylformamide (the volume ratio of deionized water to N,N-dimethylformamide is 7.5 to 9.5:1) to prepare a cross-linked modified polyvinyl alcohol coating solution;

[0021] Step S6-2: 10 to 50 parts by weight of polylactic acid resin is fed into a twin-screw extruder for melting and extrusion. After pelletizing and drying, the resulting film is blown using a single-screw extruder using an upward blowing method to obtain a 50 to 150 μm PLA film. The PLA film is then pretreated by washing with an ethanol-water solution (ethanol to deionized water volume ratio of 0.5 to 1.5:1) and deionized water.

[0022] Step S6-3: Use a 20-50 μm measuring rod to evenly apply the cross-linked modified polyvinyl alcohol coating liquid on the surface of the PLA film, and dry it to obtain a coated polyvinyl alcohol water-blocking and antibacterial biodegradable film.

[0023] A coated polyvinyl alcohol water-blocking and antibacterial biodegradable film is prepared according to the above method.

[0024] Preferably, the contact angle of the coated polyvinyl alcohol water-blocking and antibacterial biodegradable film is 70-80°, and the water vapor permeability is 0.4-1.0 [g / (m 2 ·24h)].

[0025] Preferably, the coated polyvinyl alcohol water-blocking and antibacterial biodegradable film has an antibacterial effect, and the bacteria is Escherichia coli or Staphylococcus aureus.

[0026] Beneficial effects

[0027] The present invention designs and synthesizes two new pyridine-type ligands, and further prepares a carboxylated MOF-type antibacterial agent based on metal coordination. Then, based on the esterification reaction mechanism, the carboxylated MOF-type antibacterial agent is used to cross-link and modify polyvinyl alcohol resin to prepare cross-linked modified polyvinyl alcohol. Finally, the cross-linked modified polyvinyl alcohol is prepared into a coating liquid and coated on the surface of a PLA film prepared by an extrusion blow molding process to prepare a coated polyvinyl alcohol water-blocking, antibacterial, and biodegradable film.

[0028] Through experiments, it was found that the coated polyvinyl alcohol water-blocking and antibacterial biodegradable film developed by the present invention has excellent water-blocking and antibacterial properties, and exhibits safe and tolerable cytotoxicity to cells. In addition, its comprehensive performance is relatively good, it has practical application value, and can be used in fresh-keeping packaging materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a synthetic route for carboxyl-terminated pyridine-type ligands;

[0030] Figure 2 This is a synthetic route for polypyridine-type ligands;

[0031] Figure 3 These are the experimental results of the water-barrier performance of the coated polyvinyl alcohol water-barrier and antibacterial biodegradable film. DETAILED DESCRIPTION

[0032] Experimental Example 1:

[0033] Synthesis of carboxyl-terminated pyridine-type ligands, such as Figure 1 As shown, it includes two synthesis processes, as follows:

[0034] (1) Synthesis of tripyridyl ester monomers: Using the Suzuki coupling reaction mechanism, under alkaline conditions, the boronic acid pinacol ester group of 3-(ethoxyformyl)pyridine-5-boronic acid pinacol ester is catalyzed by a palladium catalyst to undergo a coupling reaction with the bromine functional group of 2,6-dibromopyridine to generate tripyridyl ester monomers;

[0035] The alkaline condition is one of potassium carbonate, sodium carbonate, cesium carbonate, and potassium phosphate. Potassium carbonate is selected in this experimental example. The palladium catalyst is one of palladium acetate, tris(dibenzylideneacetone)dipalladium, and tetrakis(triphenylphosphine)palladium. Tetrakis(triphenylphosphine)palladium is selected in this experimental example.

[0036] The specific experimental steps for synthesizing a tripyridyl ester monomer are as follows: 2.4 g of 2,6-dibromopyridine, 5.6 g of 3-(ethoxyformyl)pyridine-5-boronic acid pinacol ester, 3 g of anhydrous potassium carbonate, 70 mL of 1,4-dioxane, and 20 mL of deionized water are added to a three-necked flask, the mixture is evacuated and purged with nitrogen. Under nitrogen protection and mechanical stirring, 10 mL of a tetrakis(triphenylphosphine)palladium solution (prepared with 1.5 g of tetrakis(triphenylphosphine)palladium and 10 mL of 1,4-dioxane) is added to the flask. The mixture is heated to 90° C. and refluxed for 6 h. The mixture is cooled to room temperature, poured into deionized water, washed with deionized water, extracted with ethyl acetate, dried over anhydrous sodium sulfate, and purified by silica gel column chromatography [eluent: V (cyclohexane) / V (acetone) = 2 / 1] to obtain a tripyridyl ester monomer.

[0037] (2) Synthesis of carboxyl-terminated pyridine-type ligands: In the presence of sodium hydroxide, the ester functional group of the tripyridyl ester monomer undergoes a hydrolysis reaction to generate a carboxyl-terminated pyridine-type ligand;

[0038] The specific experimental steps for synthesizing the carboxyl-terminated pyridine ligand are as follows: 1.9 g of a methyl carboxylate functional monomer, 2.0 g of sodium hydroxide, 10 mL of 1,4-dioxane, and 40 mL of deionized water were added to a three-necked flask, the temperature was raised to 70°C, and the mixture was stirred for 2 h. The pH of the solution was adjusted to 1 with concentrated hydrochloric acid, and the mixture was cooled to room temperature. The ligand was washed with deionized water and dried over anhydrous magnesium sulfate to obtain the carboxyl-terminated pyridine ligand.

[0039] The nuclear magnetic resonance hydrogen spectrum of the carboxyl-terminated pyridine ligand is characterized as follows: 1H NMR (CDCl3, 400 MHz) δ: 7.46-7.48 (d, 2H), 8.02-8.05 (t, 1H), 8.16 (s, 2H), 8.72 (s, 2H), 8.94 (s, 2H); the active hydrogen in the carboxyl functional group of the carboxyl-terminated pyridine ligand did not emit a peak in the CDCl3 solvent.

[0040] Experimental Example 2:

[0041] Synthesis of polypyridyl ligands, such as Figure 2 As shown, it includes two synthesis processes, as follows:

[0042] (1) Synthesis of tribromophenyl triazine monomer: Using p-bromophenol as a nucleophilic reagent, under the catalysis of sodium hydroxide, the chlorine functional group of cyanuric chloride and the phenolic hydroxyl functional group of p-bromophenol undergo nucleophilic substitution reaction to generate tribromophenyl triazine monomer;

[0043] The specific experimental steps for synthesizing tribromophenyltriazine monomer are as follows: 1.8 g of cyanuric chloride, 1.7 g of p-bromophenol, and 80 mL of ethyl acetate are added to a three-necked flask, stirred, and heated to 50°C. 1.0 g of sodium hydroxide is added to the three-necked flask, and the temperature is raised to 70°C and stirred for 1.5 hours. The mixture is cooled to room temperature and filtered, and washed with deionized water and ethyl acetate in sequence, and dried to obtain tribromophenyltriazine monomer.

[0044] (2) Synthesis of polypyridine ligands: Using the Suzuki coupling reaction mechanism, under alkaline conditions, the bromine functional group of tribromophenyltriazine monomer is catalyzed by a palladium catalyst to undergo a coupling reaction with 4-pyridine boronic acid to generate polypyridine ligands;

[0045] The alkaline condition is one of potassium carbonate, sodium carbonate, cesium carbonate, and potassium phosphate. Potassium carbonate is selected in this experimental example. The palladium catalyst is one of palladium acetate, tris(dibenzylideneacetone)dipalladium, and tetrakis(triphenylphosphine)palladium. Tetrakis(triphenylphosphine)palladium is selected in this experimental example.

[0046] The specific experimental steps for synthesizing polypyridine ligands refer to the preparation experiment of tripyridyl ester monomer. The only difference between the preparation experiment and the preparation experiment of tripyridyl ester monomer is that 3.0 g of tribromophenyl triazine monomer is used to replace 2.4 g of 2,6-dibromopyridine, and 3.6 g of 4-pyridine boronic acid is used to replace 5.6 g of 3-(ethoxyformyl)pyridine-5-boronic acid pinacol ester.

[0047] The nuclear magnetic resonance hydrogen spectrum of the polypyridine ligand is characterized as follows: 1 H NMR (CDCl3, 400MHz) δ: 6.94-6.96 (d, 6H), 7.58-7.60 (d, 6H), 7.93-7.95 (d, 6H), 8.65-8.67 (d, 6H).

[0048] Example 1:

[0049] A carboxylated MOF-type antibacterial agent was prepared. The preparation process was as follows: a carboxylated MOF-type antibacterial agent was prepared by a coordination reaction between a terminal carboxyl pyridine-type ligand and a polypyridine-type ligand and silver ions. The specific experimental steps were as follows: 3.2 g of the terminal carboxyl pyridine-type ligand, 5.9 g of the polypyridine-type ligand and 6.8 g of silver nitrate were dissolved in 100 mL of N,N-dimethylformamide, ultrasonicated for 30 minutes, and then sealed in a Teflon-lined stainless steel autoclave. The temperature was raised to 100°C and kept for reaction for 48 hours. The mixture was cooled to room temperature and centrifuged at 8000 r / min for 15 minutes. The mixture was redispersed with N,N-dimethylformamide, centrifuged, and dried to obtain the carboxylated MOF-type antibacterial agent.

[0050] Example 2:

[0051] Preparation of cross-linked modified polyvinyl alcohol, the preparation process of which is as follows: based on the esterification reaction mechanism, polyvinyl alcohol resin is cross-linked and modified using a carboxylated MOF-type antibacterial agent to prepare the cross-linked modified polyvinyl alcohol, the specific preparation steps are: 5g of polyvinyl alcohol resin and 50mL of deionized water are added to a three-necked flask, the temperature is raised to 95°C and stirred to dissolve for 4h, a polyvinyl alcohol mother liquor is prepared, the temperature is cooled to 65°C, 2mL of concentrated sulfuric acid and 20mL of a carboxylated MOF-type antibacterial agent solution (prepared by 0.5g of a carboxylated MOF-type antibacterial agent, 10mL of N,N-dimethylformamide and 10mL of deionized water) are sequentially added dropwise to the three-necked flask, the temperature is maintained at 65°C and stirred for reaction for 3h, the mixture is cooled to room temperature, poured into ethanol for sedimentation, filtered, and dried to obtain the cross-linked modified polyvinyl alcohol;

[0052] Among them, the polyvinyl alcohol resin is Nichigo G-Polymer purchased from Mitsubishi Chemical Group TM .

[0053] Example 3:

[0054] The preparation of polyvinyl alcohol-based coatings includes three preparation steps, as follows:

[0055] Step 1: preparing a cross-linked modified polyvinyl alcohol coating solution, wherein the specific preparation steps are as follows: mixing 3 g of cross-linked modified polyvinyl alcohol, 45 mL of deionized water, and 5 mL of N,N-dimethylformamide, heating to 95° C. and stirring until completely dissolved, and cooling to room temperature to obtain a cross-linked modified polyvinyl alcohol coating solution;

[0056] Step 2: Preparation of PLA film: PLA film is prepared using polylactic acid resin as raw material by extrusion blow molding process. The specific preparation steps are as follows:

[0057] 20 g of polylactic acid resin was put into a twin-screw extruder for melting and extrusion, and then cut into 1-5 mm polylactic acid resin pellets using a pelletizer. After drying, the pellets were blown using a single-screw extruder film blowing machine using an upward blowing method to obtain a 70 μm PLA film. The PLA film was fixed on a wire frame and washed in an ethanol-water solution (ethanol and deionized water in a volume ratio of 1:1) for 2 hours, then washed with deionized water, and dried at 45°C for later use.

[0058] The temperatures of zones 1-3 of the twin-screw extruder were 160°C, 180°C, and 190°C, respectively, and the rotation speed was 100 r / min; the rotation speed of the pelletizer was 200 r / min; the temperatures of zones 1-3 of the single-screw extruder were 180°C, 190°C, and 195°C, respectively, and the rotation speed was 50 r / min. The traction speed was 6 m / min, the die diameter of the film blowing machine was 65 mm, and the blow-up ratio was 3.5.

[0059] Step 3: Fix the PLA film on the coating machine, use a 30 μm measuring rod to evenly apply the cross-linked modified polyvinyl alcohol coating liquid on the surface of the PLA film, and place it in a 70°C oven to dry for 3 hours to obtain a polyvinyl alcohol-based coating film.

[0060] Performance testing:

[0061] 1. Water barrier performance test:

[0062] (1) Contact angle: The contact angle of the film sample was measured using a Digidrop DX contact angle meter. The specific test steps are as follows: 3 μL of deionized water was dropped on the surface of the film sample as a probe, and then the contact angle instrument was used to measure 5 times at different locations on the film sample surface using the five-point fitting method, and the average value was taken;

[0063] (2) Water vapor transmission rate: The water vapor transmission rate of the film sample was tested in accordance with GB / T 1037-2021. The specific test steps are as follows: a 30 cm circular film sample was placed in a glass desiccator at an ambient temperature of 25°C and anhydrous calcium chloride was used as a desiccant for 72 hours. After that, the water barrier performance of the film sample was tested using a W3 / 060 water vapor transmission rate tester;

[0064] 2. Antibacterial water performance test:

[0065] The antibacterial performance test was conducted using an MJ-250I mold incubator. The specific test steps were as follows: the film sample was cut into a 6 mm diameter disc, irradiated with ultraviolet light for 2 h to fully sterilize, and then 100 μL of bacterial solution (concentration of 1.0×10 6 CFU / mL), place the sterile film sample flat on the culture medium, place it in an incubator at 37℃ and culture it upside down for 24 hours, and record the diameter of the inhibition zone on the film surface;

[0066] Among them, the bacterial liquid was ATCC6538 Staphylococcus aureus and ATCC25922 Escherichia coli purchased from Shanghai Luwei Technology Co., Ltd.

[0067] 3. Mechanical properties test:

[0068] The tensile strength of the film samples was tested using an Instron 5565 universal tensile testing machine. The specific test steps are as follows: 80 mm × 15 mm film samples were fixed on the tensile testing machine and tensile tests were performed at a tensile rate of 5 mm / min. The longitudinal and transverse tensile strengths of the film samples were recorded.

[0069] 4. Cytotoxicity test:

[0070] Mouse L929 fibroblasts were grown in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum at 37°C and 5% CO2 for 24 h. 5 Cells were seeded in a 96-well plate at a density of 100 μL per well. The membrane solution (prepared by dissolving 0.5 g of the membrane sample in 50 mL of deionized water) was then added. The cells were incubated for 16 h. Then, 10 μL of CCK-8 reagent was added to each well and incubated for another 1 h. The optical density was measured at 450 nm using a SpectraMax iD5 fully automated microplate reader to record the cell viability.

[0071] The above experimental results are shown in Table 1 below.

[0072] Table 1 Performance test results of coated polyvinyl alcohol water-blocking and antibacterial biodegradable membrane

[0073]

[0074] The test data in Table 1 are plotted Figure 3 , through comprehensive analysis of the above experimental results, we can draw the following conclusions:

[0075] (1) Compared with polylactic acid films, the polyvinyl alcohol-based coating prepared by the present invention can significantly increase the contact angle and reduce the water vapor permeability, showing excellent water barrier properties;

[0076] (2) The polyvinyl alcohol-based coating prepared by the present invention exhibits an inhibitory effect on Staphylococcus aureus and Escherichia coli, and has antibacterial properties;

[0077] (3) The polyvinyl alcohol-based coating prepared by the present invention also has slightly improved mechanical properties, and exhibits tolerable cytotoxicity to L929 cells, has a high dose safety threshold and biocompatibility, and the polyvinyl alcohol-based coating can be used in fresh-keeping packaging materials.

Claims

1. A method for preparing a coated polyvinyl alcohol water-blocking and antibacterial biodegradable film, characterized in that: The following steps are involved: Step 1: preparing a pyridine-type ligand, wherein the pyridine-type ligand is a carboxyl-terminated pyridine-type ligand and / or a polypyridine-type ligand; Step 2: Prepare a carboxylated MOF-type antibacterial agent by a coordination reaction between a pyridine-type ligand and silver ions; Step 3: Based on the esterification reaction mechanism, the polyvinyl alcohol resin is cross-linked and modified using a carboxylated MOF-type antibacterial agent to prepare a cross-linked modified polyvinyl alcohol; Step 4: preparing a PLA film by using an extrusion blow molding process, dissolving the cross-linked modified polyvinyl alcohol to prepare a coating liquid, and coating the liquid on the surface of the PLA film to obtain a coated polyvinyl alcohol water-blocking and antibacterial biodegradable film; Wherein, the preparation method of the carboxyl-terminated pyridine type ligand is: Using the Suzuki coupling reaction mechanism, under alkaline conditions, the boronic acid pinacol ester group of 3-(ethoxyformyl)pyridine-5-boronic acid pinacol ester is catalyzed by a palladium catalyst to undergo a coupling reaction with the bromine functional group of 2,6-dibromopyridine to form a tripyridyl ester monomer. In the presence of sodium hydroxide, the ester functional group of the tripyridyl ester monomer undergoes hydrolysis to generate a carboxyl-terminated pyridine ligand. The preparation method of polypyridine ligand is as follows: Using p-bromophenol as a nucleophilic reagent, under the catalysis of sodium hydroxide, the chlorine functional group of cyanuric chloride and the phenolic hydroxyl functional group of p-bromophenol undergo a nucleophilic substitution reaction to generate tribromophenyl triazine monomer; Using the Suzuki coupling reaction mechanism, under alkaline conditions, the bromine functional group of the tribromophenyltriazine monomer is catalyzed by a palladium catalyst to undergo a coupling reaction with 4-pyridine boronic acid to generate a polypyridine ligand. The preparation method of the coated polyvinyl alcohol water-blocking and antibacterial biodegradable film is as follows: Dissolving 0.5-5 parts by weight of cross-linked modified polyvinyl alcohol in a mixed solvent consisting of 7.5-9.5 parts by volume of deionized water and 1 part by volume of N,N-dimethylformamide to prepare a cross-linked modified polyvinyl alcohol coating solution; 10-50 parts by weight of polylactic acid resin is fed into a twin-screw extruder for melting and extrusion, pelletized, dried, and then blown using a single-screw extruder film blowing machine using an upward blowing method to obtain a 50-150 μm PLA film. The PLA film is pretreated, and the pretreatment specifically comprises the following steps: first washing with an ethanol aqueous solution and then washing with deionized water; wherein the ethanol aqueous solution comprises 0.5-1.5 parts by volume of ethanol and 1 part by volume of deionized water; The cross-linked modified polyvinyl alcohol coating liquid was evenly spread on the surface of the PLA film using a 20-50 μm measuring rod, and then dried to obtain a coated polyvinyl alcohol water-blocking and antibacterial biodegradable film.

2. The method for preparing a coated polyvinyl alcohol water-blocking and antibacterial biodegradable film according to claim 1, characterized in that: The alkaline condition is one of potassium carbonate, sodium carbonate, cesium carbonate and potassium phosphate.

3. The method for preparing a coated polyvinyl alcohol water-blocking and antibacterial biodegradable film according to claim 1, characterized in that: The palladium catalyst is one of palladium acetate, tris(dibenzylideneacetone)dipalladium and tetrakis(triphenylphosphine)palladium.

4. A coated polyvinyl alcohol water-blocking and antibacterial biodegradable film prepared according to the method according to any one of claims 1 to 3.

5. The coated polyvinyl alcohol water-blocking and antibacterial biodegradable film according to claim 4, characterized in that: The contact angle of the coated polyvinyl alcohol water-blocking and antibacterial biodegradable film is 70-80 degrees, and the water vapor permeability is 0.4-1.0 [g / (m 2 •24h)].

6. The coated polyvinyl alcohol water-blocking and antibacterial biodegradable film according to claim 4, characterized in that: The coated polyvinyl alcohol water-blocking and antibacterial biodegradable film has an antibacterial effect, and the bacteria are Escherichia coli or Staphylococcus aureus.

7. The coated polyvinyl alcohol water-blocking and antibacterial biodegradable film prepared according to the method according to any one of claims 1 to 3, characterized in that: The coated polyvinyl alcohol water-blocking and antibacterial biodegradable film is used as a fresh-keeping packaging material.

Images