CN115433383B - Biodegradable polylactic acid barrier film with multilayer structure and preparation method thereof - Google Patents
Biodegradable polylactic acid barrier film with multilayer structure and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of barrier film materials, and discloses a biodegradable polylactic acid barrier film and a preparation method thereof. The method comprises the steps of firstly grafting D-lactide and cellulose diacetate to obtain a CDA-g-PDLA grafted copolymer, and then preparing a multi-layer structure barrier film by taking polylactic acid and CDA-g-PDLA as raw materials. The PLA barrier film material prepared by the invention has the characteristics of excellent barrier property and high strength, can be completely biodegraded after being used and is environment-friendly.
Description
Technical Field
The invention belongs to the field of barrier film materials, and particularly relates to a biodegradable polylactic acid barrier film with a multilayer structure and a preparation method thereof.
Background
In recent years, environmental pollution caused by plastic products has caused serious influence on human living environment, and researchers have been devoted to the development of new materials to solve the environmental pollution caused by plastic products and the like. To avoid secondary pollution and excessive use of non-renewable resources, the use of degradable materials needs to be introduced. Therefore, the degradable polymer material is selected as the raw material, and the preparation of the environment-friendly barrier film material has important significance.
Polylactic acid (PLA) is a high molecular material derived from renewable plant resources, has good biocompatibility, can be completely biodegraded into water and carbon dioxide, is nontoxic and does not pollute the environment, and has a certain antibacterial function. Cellulose Diacetate (CDA) is formed by natural cellulose esterification, is an important cellulose organic ester, is biodegradable, and is nontoxic and harmless to the environment. In addition, cellulose acetate is inexpensive, has excellent properties such as spinnability, film forming property, and thermal stability, and is widely used in textile, tobacco filtration, water separation, biomedical applications, and the like. The preparation of barrier films from biodegradable PLA and CDA is of great importance.
Chinese patent CN105729967a discloses a multi-layer polylactic acid composite barrier high-strength film, which is composed of an outer layer polylactic acid hydrophobic film, a middle layer polylactic acid barrier film and a bottom layer polylactic acid barrier film. Wherein the hydrophobic layer is formed by melting and extruding a copolymer monolayer obtained by grafting polylactic acid and glycidyl methacrylate into a film and then bonding by using glue. The polylactic acid barrier film prepared by the method has better strength and barrier performance, but the preparation process is more complicated, and the glycidyl methacrylate is slightly toxic and has certain irritation to skin and mucous membrane.
Disclosure of Invention
Aiming at the defects and shortcomings of the prior art, the invention provides the biodegradable polylactic acid barrier film with the multilayer structure and the preparation method thereof, and the polylactic acid barrier film prepared by the method has high strength and high barrier property, has lower cost and is beneficial to realizing industrialization.
In order to achieve the above purpose, the invention is realized by the following technical scheme:
a preparation method of a biodegradable polylactic acid barrier film with a multilayer structure comprises the following steps:
s1, crushing cellulose diacetate into powder by using a crusher to obtain cellulose diacetate powder, and vacuum drying the cellulose diacetate powder and D-lactide;
s2, placing the cellulose diacetate powder and the D-lactide into a reaction kettle which is heated to 110-140 ℃, and stirring and dissolving under the protection of nitrogen to obtain a first mixed solution;
s3, adding Sn (Oct) into the first mixed solution 2 The catalyst is used for obtaining reaction liquid, stirring is carried out under the protection of nitrogen until the reaction is completed, heating is stopped, and the solid reaction product is taken out after the reaction kettle is cooled to room temperature;
s4, dissolving the solid reactant in chloroform, and stirring and dissolving the solid reactant by using a magnetic stirrer until the solid reactant is completely dissolved to obtain a second mixed solution;
s5, slowly pouring the second mixed solution into absolute methanol for precipitation, and vacuum-drying a solid product after suction filtration to obtain a pale yellow solid crude product;
s6, placing the solid crude product in a Soxhlet extractor, using toluene as a solvent, refluxing for 24 hours, and drying to obtain the CDA-g-PDLA grafted copolymer;
s7, respectively dissolving the CDA-g-PDLA grafted copolymer and PLLA in a mixed organic solvent to obtain a CDA-g-PDLA solution and a PLLA solution;
s8, scraping the CDA-g-PDLA solution and the PLLA solution layer by layer to form a multi-layer structure polylactic acid barrier film, wherein the outer layer of the multi-layer structure polylactic acid barrier film is a PLLA layer.
Further, the degree of substitution of cellulose diacetate by acetylation is 2.0 to 2.6.
Further, the melting point of D-lactide is 93-95 ℃.
In step S2, the stirring time is 30-180 min.
Further, in the step S2, the dosage ratio of the D-lactide to the cellulose diacetate powder is 5:5-7:3.
Further, sn (Oct) is contained in the reaction solution 2 The mass percentage of the catalyst is 1-4%.
Further, in step S4, the stirring time is 5 to 24 hours.
Further, in step S5, the drying temperature is 60 to 80 ℃.
Further, the mixed organic solvent is obtained by mixing chloroform and dimethylformamide, and the mass ratio of the chloroform to the dimethylformamide is 9:1.
Further, in the CDA-g-PDLA solution, the content of CDA-g-PDLA is 10-15wt%.
Further, the PLLA content in the PLLA solution is 8-13wt%.
The invention also provides the multi-layer structure polylactic acid barrier film prepared by the preparation method, wherein the layer number ratio of the PLLA layer to the CDA-g-PDLA layer in the multi-layer structure polylactic acid barrier film is 5:5-9:1.
Further, the thickness of the polylactic acid barrier film with the multilayer structure is 0.1-0.3mm.
Further, the tensile strength of the multi-layer polylactic acid barrier film is 11.2-17.5 MPa, and the water vapor transmission rate is 39.8173-45.1251 g/(m) 2 24 h), oxygen permeability of 178.56-358.65 cm 3 /(m 2 ·24h·0.1MPa)。
The biodegradable polylactic acid barrier film with the multilayer structure has the following advantages and beneficial effects:
(1) Because the PLLA and the CDA-g-PDLA have good interfacial compatibility, and the PLLA and the CDA-g-PDLA can form a three-dimensional composite structure, a more compact structure can be formed between the PLLA and the CDA-g-PDLA, so that the polylactic acid barrier film has excellent mechanical properties and simultaneously exerts the barrier property of the CDA.
(2) The polylactic acid barrier film provided by the invention can be completely biodegradable and is environment-friendly.
(3) The manufacturing process is simple, the manufacturing cost is low, the method can be well applied to the field of environment-friendly functional materials, and the production requirements of the polymer material industry are met.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
(1) Weighing D-lactide and CDA with the mass ratio of 5/5, drying in a vacuum drying oven at 60 ℃, heating a reaction kettle to 110 ℃, placing the dried CDA and D-lactide in the reaction kettle, and stirring and dissolving under the protection of nitrogen after three gas displacement is completed.
(2) Adding 1% of Sn (Oct) in the total mass fraction into the mixture obtained in the step (1) 2 And (3) continuously stirring the catalyst for 30min under the protection of nitrogen, stopping heating after the reaction time is reached, and taking out the solid reaction product after the reaction kettle is cooled to room temperature.
(3) Dissolving the solid reactant obtained in the step (2) in chloroform, and stirring and dissolving for 5 hours by using a magnetic stirrer until the dissolution is complete. Slowly pouring the obtained solution into absolute methanol for precipitation, and vacuum-drying the solid product at 60 ℃ after suction filtration to obtain a pale yellow solid crude product.
(4) And (3) taking toluene as a solvent for the solid crude product obtained in the step (3), placing the solid crude product in a Soxhlet extractor, refluxing for 24 hours, and drying to obtain the CDA-g-PDLA grafted copolymer.
(5) And (3) dissolving the CDA-g-PDLA obtained in the step (4) in a CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with 10%wt, and dissolving the PLLA in the CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with 8%wt.
(6) And (3) scraping a film on the glass plate by using the PLLA solution obtained in the step (5), and scraping the film again on the basis of the PLLA film after the PLLA film is dried and formed by using the CDA-g-PDLA solution to form a film with a double-layer structure. The resulting film had a tensile strength of 13.1MPa and a water vapor transmission rate of 44.1591 g/(m) 2 24 h), oxygen permeation of 358.65cm 3 /(m 2 ·24h·0.1MPa)。
Example 2
(1) Weighing D-lactide and CDA with the mass ratio of 7/3, drying in a vacuum drying oven at 60 ℃, heating a reaction kettle to 140 ℃, placing the dried CDA and D-lactide in the reaction kettle, and stirring and dissolving under the protection of nitrogen after three gas displacement is completed.
(2) Adding Sn (Oct) accounting for 2% of the total mass fraction into the mixture obtained in the step (1) 2 And (3) continuously stirring the catalyst for 90min under the protection of nitrogen, stopping heating after the reaction time is reached, and taking out the solid reaction product after the reaction kettle is cooled to room temperature.
(3) Dissolving the solid reactant obtained in the step (2) in chloroform, and stirring and dissolving for 24 hours by using a magnetic stirrer until the dissolution is complete. Slowly pouring the obtained solution into absolute methanol for precipitation, and vacuum-drying the solid product at 80 ℃ after suction filtration to obtain a pale yellow solid crude product.
(4) And (3) taking toluene as a solvent for the solid crude product obtained in the step (3), placing the solid crude product in a Soxhlet extractor, refluxing for 24 hours, and drying to obtain the CDA-g-PDLA grafted copolymer.
(5) And (3) dissolving the CDA-g-PDLA obtained in the step (4) in a CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with 10%wt, and dissolving the PLLA in the CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with 8%wt.
(6) And (3) scraping a film on the glass plate by using the PLLA solution obtained in the step (5), and scraping the film again on the basis of the PLLA film after the PLLA film is dried and formed by using the CDA-g-PDLA solution to form a film with a double-layer structure.
(7) And (3) repeatedly scraping one layer of PLLA on the basis of the PLLA and CDA-g-PDLA bilayer structure membrane obtained in the step (6) to obtain the polylactic acid barrier membrane with the three-layer structure. The resulting film had a tensile strength of 15.4MPa and a water vapor transmission rate of 41.6591 g/(m) 2 24 h), oxygen permeation of 298.34cm 3 /(m 2 ·24h·0.1MPa)。
Example 3
(1) Weighing D-lactide and CDA with the mass ratio of 5/5, drying in a vacuum drying oven at 60 ℃, heating a reaction kettle to 140 ℃, placing the dried CDA and D-lactide in the reaction kettle, and stirring and dissolving under the protection of nitrogen after three gas displacement is completed.
(2) Adding Sn (Oct) accounting for 2% of the total mass fraction into the mixture obtained in the step (1) 2 And (3) continuously stirring the catalyst for 90min under the protection of nitrogen, stopping heating after the reaction time is reached, and taking out the solid reaction product after the reaction kettle is cooled to room temperature.
(3) Dissolving the solid reactant obtained in the step (2) in chloroform, and stirring and dissolving for 24 hours by using a magnetic stirrer until the dissolution is complete. Slowly pouring the obtained solution into absolute methanol for precipitation, filtering, and then placing the solid product into a vacuum drying box for vacuum drying to obtain a light yellow solid crude product.
(4) And (3) taking toluene as a solvent for the solid crude product obtained in the step (3), placing the solid crude product in a Soxhlet extractor, refluxing for 24 hours, and drying to obtain the CDA-g-PDLA grafted copolymer.
(5) And (3) dissolving the CDA-g-PDLA obtained in the step (4) in a CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with 10%wt, and dissolving the PLLA in the CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with 8%wt.
(6) And (3) scraping a film on the glass plate by using the PLLA solution obtained in the step (5), and scraping the film again on the basis of the PLLA film after the PLLA film is dried and formed by using the CDA-g-PDLA solution to form a film with a double-layer structure.
(7) The PLLA and CDA-g-PDLA bilayer structure membrane obtained in the step (6) is used as a foundationAnd (3) repeating the step (6) again to obtain the polylactic acid barrier film with the four-layer structure. The resulting film had a tensile strength of 16.7MPa and a water vapor transmission rate of 40.5261 g/(m) 2 24 h), oxygen permeation of 213.95cm 3 /(m 2 ·24h·0.1MPa)。
Example 4
(1) Weighing D-lactide and CDA with the mass ratio of 5/5, drying in a vacuum drying oven at 60 ℃, heating a reaction kettle to 130 ℃, placing the dried CDA and D-lactide in the reaction kettle, and stirring and dissolving under the protection of nitrogen after three gas displacement is completed.
(2) Adding 3% of Sn (Oct) in the total mass fraction into the mixture obtained in the step (1) 2 And (3) continuously stirring the catalyst for 90min under the protection of nitrogen, stopping heating after the reaction time is reached, and taking out the solid reaction product after the reaction kettle is cooled to room temperature.
(3) Dissolving the solid reactant obtained in the step (2) in chloroform, and stirring and dissolving for 24 hours by using a magnetic stirrer until the dissolution is complete. Slowly pouring the obtained solution into absolute methanol for precipitation, filtering, and then placing the solid product into a vacuum drying box for vacuum drying to obtain a light yellow solid crude product.
(4) And (3) taking toluene as a solvent, placing the solid crude product in a Soxhlet extractor, refluxing for 24 hours, and drying to obtain the CDA-g-PDLA grafted copolymer.
(5) And (3) dissolving the CDA-g-PDLA obtained in the step (4) in a CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with the weight of 12 percent, and dissolving the PLLA in the CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with the weight of 10 percent.
(6) And (3) scraping a film on the glass plate by using the PLLA solution obtained in the step (5), and scraping the film again on the basis of the PLLA film after the PLLA film is dried and formed by using the CDA-g-PDLA solution to form a film with a double-layer structure.
(7) And (3) repeating the step (6) again on the basis of the PLLA and CDA-g-PDLA bilayer structure membrane obtained in the step (6) to obtain the polylactic acid barrier membrane with a four-layer structure. The resulting film had a tensile strength of 15.3MPa and a water vapor transmission rate of 40.3256 g/(m) 2 24 h), oxygen permeation of 225.67cm 3 /(m 2 ·24h·0.1MPa)。
Example 5
(1) Weighing D-lactide and CDA with the mass ratio of 6/4, drying in a vacuum drying oven at 60 ℃, heating a reaction kettle to 120 ℃, placing the dried CDA and D-lactide in the reaction kettle, and stirring and dissolving under the protection of nitrogen after three gas replacement.
(2) Adding 3% of Sn (Oct) in the total mass fraction into the mixture obtained in the step (1) 2 And (3) continuously stirring the catalyst for 120min under the protection of nitrogen, stopping heating after the reaction time is reached, and taking out the solid reaction product after the reaction kettle is cooled to room temperature.
(3) Dissolving the solid reactant obtained in the step (2) in chloroform, and stirring and dissolving for 24 hours by using a magnetic stirrer until the dissolution is complete. Slowly pouring the obtained solution into absolute methanol for precipitation, filtering, and then placing the solid product into a vacuum drying box for vacuum drying to obtain a light yellow solid crude product.
(4) And (3) taking toluene as a solvent, placing the solid crude product in a Soxhlet extractor, refluxing for 24 hours, and drying to obtain the CDA-g-PDLA grafted copolymer.
(5) And (3) dissolving the CDA-g-PDLA obtained in the step (4) in a CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with the weight of 12 percent, and dissolving the PLLA in the CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with the weight of 10 percent.
(6) And (3) scraping a film on the glass plate by using the PLLA solution obtained in the step (5), and scraping the film again on the basis of the PLLA film after the PLLA film is dried and formed by using the CDA-g-PDLA solution to form a film with a double-layer structure.
(7) And (3) scraping 8 layers of PLLA on the basis of the PLLA and CDA-g-PDLA bilayer structure membrane obtained in the step (6) to obtain the polylactic acid barrier membrane with a ten-layer structure. The resulting film had a tensile strength of 16.3MPa and a water vapor transmission rate of 39.8173 g/(m) 2 24 h), oxygen permeation of 178.56cm 3 /(m 2 ·24h·0.1MPa)。
Example 6
(1) Weighing D-lactide and CDA with the mass ratio of 7/3, drying in a vacuum drying oven at 60 ℃, heating a reaction kettle to 120 ℃, placing the dried CDA and D-lactide in the reaction kettle, and stirring and dissolving under the protection of nitrogen after three gas displacement is completed.
(2) Adding 3% of Sn (Oct) in the total mass fraction into the mixture obtained in the step (1) 2 And (3) continuously stirring the catalyst for 180min under the protection of nitrogen, stopping heating after the reaction time is reached, and taking out the solid reaction product after the reaction kettle is cooled to room temperature.
(3) Dissolving the solid reactant obtained in the step (2) in chloroform, and stirring and dissolving for 24 hours by using a magnetic stirrer until the dissolution is complete. Slowly pouring the obtained solution into absolute methanol for precipitation, and vacuum-drying the solid product at 60 ℃ after suction filtration to obtain a pale yellow solid crude product.
(4) And (3) taking toluene as a solvent, placing the solid crude product in a Soxhlet extractor, refluxing for 24 hours, and drying to obtain the CDA-g-PDLA grafted copolymer.
(5) And (3) dissolving the CDA-g-PDLA obtained in the step (4) in a CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with the weight of 12 percent, and dissolving the PLLA in the CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with the weight of 10 percent.
(6) And (3) scraping a film on the glass plate by using the PLLA solution obtained in the step (5), and scraping the film again on the basis of the PLLA film after the PLLA film is dried and formed by using the CDA-g-PDLA solution to form a film with a double-layer structure.
(7) And (3) repeating the step (6) again on the basis of the PLLA and CDA-g-PDLA bilayer structure membrane obtained in the step (6) to obtain the polylactic acid barrier membrane with a four-layer structure. The resulting film had a tensile strength of 17.5MPa and a water vapor transmission rate of 40.8124 g/(m) 2 24 h), oxygen permeation of 181.27cm 3 /(m 2 ·24h·0.1MPa)。
Example 7
(1) Weighing D-lactide and CDA with the mass ratio of 5/5, drying in a vacuum drying oven at 60 ℃, heating a reaction kettle to 130 ℃, placing the dried CDA and D-lactide in the reaction kettle, and stirring and dissolving under the protection of nitrogen after three gas displacement is completed.
(2) Adding 4% of Sn (Oct) in total mass fraction into the mixture obtained in the step (1) 2 Catalyst, continueStirring under the protection of nitrogen, stopping heating after the reaction time is reached, and taking out the solid reaction product after the reaction kettle is cooled to room temperature.
(3) Dissolving the solid reactant obtained in the step (2) in chloroform, and stirring and dissolving for 24 hours by using a magnetic stirrer until the dissolution is complete. Slowly pouring the obtained solution into absolute methanol for precipitation, and carrying out suction filtration and then carrying out vacuum drying on a solid product at 70 ℃ to obtain a pale yellow solid crude product.
(4) And (3) taking toluene as a solvent, placing the solid crude product in a Soxhlet extractor, refluxing for 24 hours, and drying to obtain the CDA-g-PDLA grafted copolymer.
(5) And (3) dissolving the CDA-g-PDLA obtained in the step (4) in a CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with the weight of 14%, and dissolving the PLLA in the CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with the weight of 12%.
(6) And (3) scraping the PLLA solution obtained in the step (5) on a glass plate by using a film scraper, repeatedly scraping the PLLA solution for 2 times after the PLLA film is dried and formed, and scraping the film again by using the CDA-g-PDLA solution on the basis of the PLLA film to form a film with a four-layer structure.
(7) And (3) scraping the PLLA film twice on the basis of the PLLA and CDA-g-PDLA four-layer structure film obtained in the step (6), and scraping a layer of CDA-g-PDLA and a layer of PLLA film. To obtain the polylactic acid barrier film with eight layers of structures. The resulting film had a tensile strength of 12.6MPa and a water vapor transmission rate of 43.1583 g/(m) 2 24 h), oxygen permeation of 281.79cm 3 /(m 2 ·24h·0.1MPa)。
Example 8
(1) Weighing D-lactide and CDA with the mass ratio of 7/3, drying in a vacuum drying oven at 60 ℃, heating a reaction kettle to 110 ℃, placing the dried CDA and D-lactide in the reaction kettle, and stirring and dissolving under the protection of nitrogen after three gas displacement is completed.
(2) Adding 4% of Sn (Oct) in total mass fraction into the mixture obtained in the step (1) 2 And (3) continuously stirring the catalyst under the protection of nitrogen, stopping heating after the reaction time is reached, and taking out the solid reaction product after the reaction kettle is cooled to room temperature.
(3) Dissolving the solid reactant obtained in the step (2) in chloroform, and stirring and dissolving for 24 hours by using a magnetic stirrer until the dissolution is complete. Slowly pouring the obtained solution into absolute methanol for precipitation, filtering, and then placing the solid product into a vacuum drying box for vacuum drying to obtain a light yellow solid crude product.
(4) And (3) taking toluene as a solvent, placing the solid crude product in a Soxhlet extractor, refluxing for 24 hours, and drying to obtain the CDA-g-PDLA grafted copolymer.
(5) And (3) dissolving the CDA-g-PDLA obtained in the step (4) in a CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with 15%wt, and dissolving the PLLA in the CHL/DMF mixed solvent with the mass ratio of 9/1 to prepare a solution with 13%wt.
(6) And (3) scraping a film on the glass plate by using the PLLA solution obtained in the step (5), and scraping the film again on the basis of the PLLA film after the PLLA film is dried and formed by using the CDA-g-PDLA solution to form a film with a double-layer structure.
(7) And (3) repeating the step (6) again on the basis of the PLLA and CDA-g-PDLA bilayer structure membrane obtained in the step (6) to obtain the polylactic acid barrier membrane with a four-layer structure. The resulting film had a tensile strength of 11.2MPa and a water vapor transmission rate of 45.1251 g/(m) 2 24 h), oxygen permeation of 302.61cm 3 /(m 2 ·24h·0.1MPa)。
Comparative example 1
(1) PLLA particles of corresponding mass were weighed, prepared into an 8% wt solution in a 9/1 mass ratio of CHL/DMF solution, scraped with a film scraper on a glass plate, and repeated four times to obtain a pure PLLA film of a multilayer structure. The resulting film had a tensile strength of 12.8MPa and a water vapor transmission rate of 42.3168 g/(m) 2 24 h), oxygen permeation of 298.75cm 3 /(m 2 ·24h·0.1MPa)。
Comparative example 2
(1) PLLA particles and CDA particles with the mass ratio of 7/3 are weighed, 10 wt% of solution is prepared in CHL/DMF solution with the mass ratio of 9/1, a film scraping device is used for scraping films on a glass plate, and the polylactic acid barrier film with a multilayer structure is obtained by repeating four times. The resulting film had a tensile strength of 14.1MPa and a water vapor transmission rate of 80.3658 g/(m) 2 24 h), oxygen permeation of 746.35cm 3 /(m 2 ·24h·0.1MPa)。
Claims (10)
1. The preparation method of the biodegradable polylactic acid barrier film with the multilayer structure is characterized by comprising the following steps of:
s1, crushing cellulose diacetate into powder by using a crusher to obtain cellulose diacetate powder, and vacuum drying the cellulose diacetate powder and D-lactide;
s2, placing the cellulose diacetate powder and the D-lactide into a reaction kettle which is heated to 110-140 ℃, and stirring and dissolving under the protection of nitrogen to obtain a first mixed solution;
s3, adding Sn (Oct) into the first mixed solution 2 The catalyst is used for obtaining reaction liquid, stirring is carried out under the protection of nitrogen until the reaction is completed, heating is stopped, and the solid reaction product is taken out after the reaction kettle is cooled to room temperature;
s4, dissolving the solid reactant in chloroform, and stirring and dissolving the solid reactant by using a magnetic stirrer until the solid reactant is completely dissolved to obtain a second mixed solution;
s5, slowly pouring the second mixed solution into absolute methanol for precipitation, and vacuum-drying a solid product after suction filtration to obtain a pale yellow solid crude product;
s6, placing the solid crude product in a Soxhlet extractor, using toluene as a solvent, refluxing for 24 hours, and drying to obtain the CDA-g-PDLA grafted copolymer;
s7, respectively dissolving the CDA-g-PDLA grafted copolymer and PLLA in a mixed organic solvent to obtain a CDA-g-PDLA solution and a PLLA solution;
s8, scraping the CDA-g-PDLA solution and the PLLA solution layer by layer to form a multi-layer structure polylactic acid barrier film, wherein the outer layer of the multi-layer structure polylactic acid barrier film is a PLLA layer.
2. The method according to claim 1, wherein the degree of substitution by acetylation of the diacetyl cellulose is 2.0 to 2.6.
3. The preparation method according to claim 1, wherein the melting point of D-lactide is 93-95 ℃.
4. The preparation method according to claim 1, wherein in the step S2, the dosage ratio of D-lactide to cellulose diacetate powder is 5:5 to 7:3.
5. The method according to claim 1, wherein Sn (Oct) is contained in the reaction solution 2 The mass percentage of the catalyst is 1-4%.
6. The preparation method according to claim 1, wherein the mixed organic solvent is obtained by mixing chloroform and dimethylformamide, and the mass ratio of the chloroform to the dimethylformamide is 9:1.
7. The method according to claim 1, wherein the content of CDA-g-PDLA in the CDA-g-PDLA solution is 10-15wt%.
8. The method of claim 1, wherein the PLLA solution has a PLLA content of 8-13wt%.
9. The multilayer polylactic acid barrier film according to any one of claims 1 to 8, wherein the layer number ratio of the PLLA layer to the CDA-g-PDLA layer is 5:5 to 9:1.
10. The multilayer-structured polylactic acid barrier film according to claim 9, wherein the multilayer-structured polylactic acid barrier film has a tensile strength of 11.2 to 17.5MPa and a water vapor transmission rate of 39.8173 to 45.1251 g/(m) 2 24 h), oxygen permeability of 178.56-358.65 cm 3 /(m 2 ·24h·0.1MPa)。
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JP2011073174A (en) * | 2009-09-29 | 2011-04-14 | Toppan Printing Co Ltd | Barrier film and method of manufacturing the same |
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CN111959080A (en) * | 2020-08-24 | 2020-11-20 | 中国科学院长春应用化学研究所 | Biodegradable multilayer composite barrier film and preparation method thereof |
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JP2011073174A (en) * | 2009-09-29 | 2011-04-14 | Toppan Printing Co Ltd | Barrier film and method of manufacturing the same |
CN105729967A (en) * | 2016-03-15 | 2016-07-06 | 湖南工业大学 | Multilayer polylactic acid composite barrier high-strength film |
CN106042502A (en) * | 2016-04-30 | 2016-10-26 | 湖南工业大学 | Environmental friendly packaging film used for fruit and vegetable packaging |
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