Natural plant-based degradable packaging material and preparation method thereof
By using MOF-Ag/titanium dioxide and castor oil polyether polyol in polyurethane prepolymerization reaction in packaging materials, combined with the rough structure of elemental silver and zinc and hydrogel, a porous carrier is formed, which solves the problem of insufficient antibacterial and degradable properties of existing packaging materials, and improves antibacterial durability and mechanical strength.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-30
- Publication Date
- 2026-04-03
AI Technical Summary
Existing packaging materials are inadequate in terms of antibacterial properties and biodegradability. Chemically synthesized antibacterial agents may harm the environment and human health, while natural antibacterial agents have poor compatibility and durability, affecting the overall performance of the materials.
MOF-Ag/titanium dioxide and castor oil polyether polyol are used to undergo a polyurethane prepolymerization reaction with isocyanate to form a porous and rough plant-based biodegradable carrier. Combined with the rough protruding structure of elemental silver and elemental zinc, the outer layer is a soft hydrogel structure. Through vacuum impregnation and reduction, an antibacterial plant-based biodegradable gel is formed, which improves the antibacterial durability and mechanical strength of the material.
It has achieved a natural biodegradable packaging material with good antibacterial properties. The raw materials are widely available, highly biodegradable, have long-lasting antibacterial properties, and excellent mechanical properties. It reduces the consumption of fossil resources, avoids the migration and shedding of antibacterial agents, and improves the overall performance of the material.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of packaging materials technology, specifically a natural plant-based biodegradable packaging material and its preparation method. Background Technology
[0002] Packaging materials are widely used in various fields, from food and medicine to daily necessities, playing a crucial role in the protection, storage, and transportation of products. Traditional packaging materials are mostly petroleum-based plastics, such as polyethylene, polypropylene, and polystyrene. Although these materials have the advantages of low cost, good processing performance, and excellent mechanical properties, they are difficult to degrade in the natural environment, resulting in the accumulation of large amounts of waste plastic packaging and causing pollution.
[0003] With increasing environmental awareness and emphasis on sustainable development, biodegradable materials have emerged. These materials can decompose into smaller molecules within a short time in the natural environment, such as through the action of soil, water, and microorganisms, returning to the natural cycle. Common biodegradable materials include polylactic acid (PLA), polyhydroxyalkanoates (PHA), and starch-based materials. PLA, made from renewable plant resources (such as corn and sugarcane), possesses good biocompatibility and mechanical properties, making it a promising candidate for packaging. However, for products like pharmaceuticals that require extremely high hygiene standards, antibacterial properties are crucial. In pharmaceutical packaging, microbial contamination can lead to drug inactivation and even serious health problems.
[0004] Most existing packaging materials achieve their antibacterial properties by adding antibacterial agents. However, some methods use chemically synthesized antibacterial agents, such as those containing heavy metals. Although these agents have significant antibacterial effects, they may pose potential hazards to human health and the environment. Moreover, heavy metal ions are difficult to degrade in the environment and may accumulate through the food chain, causing toxic effects on organisms. On the other hand, natural antibacterial agents, such as chitosan, have good biocompatibility and safety, but they have poor compatibility with biodegradable materials. They are prone to uneven dispersion during the preparation process, and their antibacterial durability is poor, which can easily affect the overall performance of the material.
[0005] Therefore, there is a need to develop a biodegradable and environmentally friendly packaging material with good antibacterial properties and long-lasting antibacterial activity, as well as its preparation process, in order to improve the overall performance of packaging materials. Summary of the Invention
[0006] The purpose of this invention is to provide a natural plant-based biodegradable packaging material and its preparation method. The method involves a polyurethane prepolymerization reaction of MOF-Ag / titanium dioxide and castor oil polyether polyol with isocyanate to form a porous and rough plant-based biodegradable carrier. The plant-based biodegradable carrier serves as the main stress-bearing unit. The rough, protruding structure of elemental silver and elemental zinc in the middle layer acts as an auxiliary layer, while the soft hydrogel structure of the outer layer serves as a stress buffer layer. The gap between the middle and outer layers enhances slippage capability, thereby improving the mechanical strength of the natural plant-based biodegradable packaging material.
[0007] The objective of this invention can be achieved through the following technical solutions:
[0008] A method for preparing a natural plant-based biodegradable packaging material includes the following steps:
[0009] Step 1: Using titanium dioxide powder as a carrier, 2,5-dihydroxyterephthalic acid as an organic ligand, and silver nitrate as a metal source, a silver metal framework is hydrothermally synthesized on its surface to obtain MOF-Ag / titanium dioxide.
[0010] Step 2: Using castor oil polyether polyol and MOF-Ag / titanium dioxide as raw materials, a polyurethane prepolymerization reaction is carried out with isocyanate to obtain a plant-based biodegradable carrier.
[0011] Step 3: Using N-isopropylacrylamide as a monomer and N,N'-methylenebispropylamide as a crosslinking agent, a free radical polymerization reaction is initiated on the surface of the plant-based biodegradable carrier to form a temperature-responsive crosslinked polyacrylamide hydrogel, thus obtaining a plant-based biodegradable gel.
[0012] Step 4: Impregnate the plant-based biodegradable gel with zinc sulfate through vacuum impregnation, and then reduce it to elemental form under the action of potassium borohydride solution to obtain an antibacterial plant-based biodegradable gel.
[0013] Step 5: Add poly(butylene adipate / terephthalate), polycaprolactone, polyvinyl alcohol, starch, triethyl citrate, dodecenyl succinic acid, and antibacterial plant-based biodegradable gel to a screw extruder for granulation to obtain natural plant-based biodegradable packaging material.
[0014] Furthermore, the mass ratio of poly(adipic acid / butylene terephthalate), polycaprolactone, polyvinyl alcohol, starch, triethyl citrate, dodecenyl succinic acid, and antibacterial plant-based biodegradable gel is 200-220:400-420:1-2:15-20:12-15:2-4:5-7.
[0015] Furthermore, the specific preparation steps of MOF-Ag / titanium dioxide are as follows:
[0016] 2,5-Dihydroxyterephthalic acid and N,N-dimethylformamide were added to a polytetrafluoroethylene-lined autoclave and stirred at 20-25℃ and 500-550 r / min for 30-40 min. Then, silver nitrate was added, and the mixture was heated to 120-130℃ and reacted for 10-12 h. Titanium dioxide powder with a particle size of 80-90 nm was then added, and the reaction was continued for 10-12 h. The mixture was allowed to cool naturally to room temperature, filtered, and the filter cake was washed 3-5 times with methanol solution and deionized water, respectively. The cake was then dried in a vacuum drying oven at 60-65℃ for 1-2 h to obtain MOF-Ag / titanium dioxide.
[0017] Furthermore, the ratio of 2,5-dihydroxyterephthalic acid, N,N-dimethylformamide, silver nitrate and titanium dioxide powder is 80.4-82.5g: 710-725mL: 30.5-31.8g: 70.1-72.5g.
[0018] Furthermore, the specific preparation steps of the plant-based biodegradable carrier are as follows:
[0019] Castor oil polyether polyol, MOF-Ag / titanium dioxide, and deionized water were added to a reaction vessel and stirred at 20-25℃ and 500-550 r / min for 30-40 min. Then, triethylenediamine, dibutyltin dilaurate, 1,4-butanediol, and isocyanate were added, and stirring was continued for 40-50 min. The mixture was poured into a mold, heated to 120-122℃, and stirred at 80-90 r / min for 10-12 min to mature. The mixture was then demolded, allowed to cool naturally to room temperature, and dried in a vacuum drying oven at 60-65℃ for 1-2 h. After pulverization, a plant-based biodegradable carrier with a particle size of 0.5-0.7 mm was obtained.
[0020] Furthermore, the ratio of castor oil polyether polyol, MOF-Ag / titanium dioxide, deionized water, triethylenediamine, dibutyltin dilaurate, 1,4-butanediol, and isocyanate is 21.2-22.3g: 52.5-53.8g: 875-882mL: 1.1-1.12g: 0.2-0.25g: 0.1-0.15g: 32-35g.
[0021] Furthermore, the specific preparation steps of the plant-based biodegradable gel are as follows:
[0022] N-Isopropylacrylamide and N,N'-methylenebispropylamide were added to a reaction vessel and stirred for 20-30 min at 20-25℃ and 500-600 r / min. Then sodium dodecyl sulfate and deionized water were added, and the mixture was heated to 40-50℃ and stirred for another 20-30 min. Nitrogen gas was then introduced at a flow rate of 10-12 min / L for 30-40 min, and the mixture was heated to 70-80℃. Ammonium persulfate was added, and the mixture was stirred for another 6-7 h under a nitrogen atmosphere. Then, the plant-based biodegradable carrier was added to the reaction vessel and stirred for another 20-30 min. The mixture was filtered, and the filter cake was washed 2-4 times with petroleum ether and deionized water, respectively. The mixture was then vacuum dried at 60-80℃ for 1-2 h to obtain the plant-based biodegradable gel.
[0023] Furthermore, the ratio of N-isopropylacrylamide, N,N'-methylenebispropylamide, sodium dodecyl sulfate, deionized water, ammonium persulfate, and plant-based biodegradable carrier is 30-40g: 20-30g: 1-2g: 200-300mL: 1-2g: 20-30g.
[0024] Furthermore, the specific preparation steps for the antibacterial plant-based biodegradable gel are as follows:
[0025] Plant-based biodegradable gel and N,N-dimethylformamide were vacuum impregnated in a reactor under nitrogen protection at 40-50℃ and 500-600 r / min for 1-2 h. Then, zinc sulfate and potassium borohydride solution (40-45% by mass) were added dropwise to the reactor at a rate of 30 mL / min. After the addition was complete, the reaction was continued for 4-5 h. The mixture was then filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60-80℃ for 1-2 h to obtain an antibacterial plant-based biodegradable gel.
[0026] Furthermore, the ratio of plant-based biodegradable gel, N,N-dimethylformamide, zinc sulfate, and potassium borohydride solution is 20-30g: 300-400mL: 3-4g: 10-12mL.
[0027] The beneficial effects of this invention are:
[0028] 1. The natural plant-based biodegradable packaging material prepared by this invention uses castor oil polyether polyol, starch and other plant-based raw materials as core matrix components to replace the raw material system of traditional petroleum-based packaging materials. The raw materials are widely available and renewable, which not only reduces the consumption of fossil resources, but also endows the material with the basic property of biodegradability from the source.
[0029] 2. This invention utilizes castor oil polyether polyol and MOF-Ag / titanium dioxide as raw materials, reacting them with isocyanate in a polyurethane prepolymerization reaction to form a porous and rough plant-based biodegradable carrier. The rough structure of this carrier surface provides abundant sites for subsequent hydrogel adhesion, and the foaming structure of the plant-based biodegradable carrier can create gaps after hydrogel coverage. These gaps provide a basis for subsequent zinc sulfate impregnation. After zinc sulfate impregnates into the pores of the hydrogel, it is reduced by potassium borohydride to obtain an antibacterial plant-based biodegradable gel. The original silver ions of MOF-Ag / titanium dioxide are reduced to elemental form, forming elemental silver and elemental zinc in the gaps. During this process, the MOF-Ag structure collapses, leading to increased gaps, enhanced spatial confinement, improved antibacterial longevity, and prevention of migration and detachment.
[0030] 3. The antibacterial plant-based biodegradable gel of the present invention is structurally formed by the polyurethane prepolymerization reaction of MOF-Ag / titanium dioxide and castor oil polyether polyol with isocyanate to form a porous and rough plant-based biodegradable carrier. The plant-based biodegradable carrier is the main stress-bearing unit. The rough protruding structure of elemental silver and elemental zinc in the middle layer can serve as an auxiliary layer. The soft hydrogel structure of the outer layer can serve as a stress buffer layer. The gap between the middle layer and the outer layer can improve the slippage ability, thereby improving the mechanical strength of the natural plant-based biodegradable packaging material. Detailed Implementation
[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0032] Example 1: A method for preparing a natural plant-based biodegradable packaging material, comprising the following steps:
[0033] S1: 80.4 g of 2,5-dihydroxyterephthalic acid and 710 mL of N,N-dimethylformamide were added to a polytetrafluoroethylene-lined autoclave and stirred at 20 °C and 500 r / min for 30 min. Then, 30.5 g of silver nitrate was added, and the mixture was heated to 120 °C and reacted for another 10 h. Then, 70.1 g of titanium dioxide powder with a particle size of 80 nm was added and the mixture was reacted for another 10 h. The mixture was allowed to cool naturally to room temperature, filtered, and the filter cake was washed three times with methanol solution and three times with deionized water, respectively. The cake was then dried in a vacuum drying oven at 60 °C for 1 h to obtain MOF-Ag / titanium dioxide.
[0034] S2: Add 21.2g castor oil polyether polyol, 52.5g MOF-Ag / titanium dioxide and 875mL deionized water to a reaction vessel and stir at 20℃ and 500r / min for 30min. Then add 1.1g triethylenediamine, 0.2g dibutyltin dilaurate, 0.1g 1,4-butanediol and 32g isocyanate, and continue stirring for 40min. Pour into a mold, heat to 120℃, stir at 80r / min for 10min, mature, demold, cool naturally to room temperature, dry in a vacuum drying oven at 60℃ for 1h, and pulverize to obtain a plant-based biodegradable carrier with a particle size of 0.5mm.
[0035] S3: Add 30g N-isopropylacrylamide and 20g N,N'-methylenebispropylamide to a reaction vessel and stir for 20min at 20℃ and 500r / min. Then add 1g sodium dodecyl sulfate and 200mL deionized water, heat to 40℃, continue stirring for 20min, purge with nitrogen at a flow rate of 10min / L for 30min, heat to 70℃, add 1g ammonium persulfate, and continue stirring and reacting for 6h under a nitrogen atmosphere. Then add 20g plant-based biodegradable carrier to the reaction vessel and continue stirring for 20min. Filter, wash the filter cake twice with petroleum ether and deionized water respectively, and vacuum dry at 60℃ for 1h to obtain plant-based biodegradable gel.
[0036] S4: 20g of plant-based biodegradable gel and 300mL of N,N-dimethylformamide were placed in a reactor and vacuum impregnated for 1h at 40℃ and 500r / min under nitrogen protection. Then, 3g of zinc sulfate and 10mL of 40% potassium borohydride solution were added dropwise to the reactor at a rate of 30mL / min. After the addition was complete, the reaction was continued for 4h. The mixture was then filtered, and the filter cake was washed twice with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60℃ for 1h to obtain an antibacterial plant-based biodegradable gel.
[0037] S5: Add 200g of poly(butylene adipate / terephthalate), 400g of polycaprolactone, 1g of polyvinyl alcohol, 15g of starch, 12g of triethyl citrate, 2g of dodecenyl succinic acid, and 5g of antibacterial plant-based biodegradable gel to a screw extruder for granulation to obtain natural plant-based biodegradable packaging material.
[0038] Example 2: A method for preparing a natural plant-based biodegradable packaging material, comprising the following steps:
[0039] S1: 81.45 g of 2,5-dihydroxyterephthalic acid and 717.5 mL of N,N-dimethylformamide were added to a polytetrafluoroethylene-lined autoclave and stirred at 22.5 °C and 525 r / min for 35 min. Then, 31.15 g of silver nitrate was added, and the mixture was heated to 125 °C and reacted for 11 h. Then, 71.3 g of titanium dioxide powder with a particle size of 85 nm was added and the mixture was reacted for another 11 h. The mixture was then allowed to cool naturally to room temperature, filtered, and the filter cake was washed four times with methanol solution and four times with deionized water. The cake was then dried in a vacuum drying oven at 62.5 °C for 1.5 h to obtain MOF-Ag / titanium dioxide.
[0040] S2: 21.75g castor oil polyether polyol, 53.15g MOF-Ag / titanium dioxide and 878.5mL deionized water were added to a reaction vessel and stirred at 22.5℃ and 525r / min for 35min. Then, 1.11g triethylenediamine, 0.225g dibutyltin dilaurate, 0.125g 1,4-butanediol and 33.5g isocyanate were added and stirred for another 45min. The mixture was poured into a mold, heated to 121℃, stirred at 85r / min for 11min, cured, demolded, and allowed to cool naturally to room temperature. It was then dried in a vacuum drying oven at 62.5℃ for 1.5h and pulverized to obtain a plant-based biodegradable carrier with a particle size of 0.6mm.
[0041] S3: Add 35g N-isopropylacrylamide and 25g N,N'-methylenebispropylamide to a reaction vessel and stir for 25min at 22.5℃ and 550r / min. Then add 1.5g sodium dodecyl sulfate and 250mL deionized water, heat to 45℃, and continue stirring for 25min. Purge with nitrogen at a flow rate of 11min / L for 35min, heat to 75℃, add 1.5g ammonium persulfate, and continue stirring under a nitrogen atmosphere for 6.5h. Then add 25g plant-based biodegradable carrier to the reaction vessel and continue stirring for 25min. Filter, wash the filter cake three times with petroleum ether and deionized water respectively, and vacuum dry at 70℃ for 1.5h to obtain plant-based biodegradable gel.
[0042] S4: 25g of plant-based biodegradable gel and 350mL of N,N-dimethylformamide were placed in a reactor and vacuum impregnated for 1.5h at 45℃ and 550r / min under nitrogen protection. Then, 3.5g of zinc sulfate and 11mL of 42.5% potassium borohydride solution were added dropwise to the reactor at a rate of 30mL / min. After the addition was complete, the reaction was continued for 4.5h. The mixture was then filtered, and the filter cake was washed three times with deionized water and three times with anhydrous ethanol. The mixture was then vacuum dried at 70℃ for 1.5h to obtain an antibacterial plant-based biodegradable gel.
[0043] S5: Add 210g of poly(butylene adipate / terephthalate), 410g of polycaprolactone, 1.5g of polyvinyl alcohol, 17.5g of starch, 13.5g of triethyl citrate, 3g of dodecenyl succinic acid, and 6g of antibacterial plant-based biodegradable gel to a screw extruder for granulation to obtain natural plant-based biodegradable packaging material.
[0044] Example 3: A method for preparing a natural plant-based biodegradable packaging material, comprising the following steps:
[0045] S1: 82.5g of 2,5-dihydroxyterephthalic acid and 725mL of N,N-dimethylformamide were added to a polytetrafluoroethylene-lined autoclave and stirred at 25℃ and 550r / min for 40min. Then, 31.8g of silver nitrate was added, and the mixture was heated to 130℃ and reacted for 12h. Then, 72.5g of titanium dioxide powder with a particle size of 90nm was added and the mixture was reacted for another 12h. The mixture was allowed to cool naturally to room temperature, filtered, and the filter cake was washed 5 times each with methanol solution and deionized water. The cake was then dried in a vacuum drying oven at 65℃ for 2h to obtain MOF-Ag / titanium dioxide.
[0046] S2: 22.3g castor oil polyether polyol, 53.8g MOF-Ag / titanium dioxide and 882mL deionized water were added to a reaction vessel and stirred at 25℃ and 550r / min for 40min. Then, 1.12g triethylenediamine, 0.25g dibutyltin dilaurate, 0.15g 1,4-butanediol and 35g isocyanate were added and stirred for another 50min. The mixture was then poured into a mold, heated to 122℃, stirred at 90r / min for 12min, cured, demolded, and allowed to cool naturally to room temperature. The mixture was then dried in a vacuum drying oven at 65℃ for 2h and pulverized to obtain a plant-based biodegradable carrier with a particle size of 0.7mm.
[0047] S3: Add 40g N-isopropylacrylamide and 30g N,N'-methylenebispropylamide to a reaction vessel and stir for 30min at 25℃ and 600r / min. Then add 2g sodium dodecyl sulfate and 300mL deionized water, heat to 50℃, and continue stirring for 30min. Purge with nitrogen at a flow rate of 12min / L for 40min, heat to 80℃, add 2g ammonium persulfate, and continue stirring and reacting for 7h under a nitrogen atmosphere. Then add 30g plant-based biodegradable carrier to the reaction vessel and continue stirring for 30min. Filter, wash the filter cake four times with petroleum ether and deionized water respectively, and vacuum dry at 80℃ for 2h to obtain plant-based biodegradable gel.
[0048] S4: 30g of plant-based biodegradable gel and 400mL of N,N-dimethylformamide were placed in a reactor and vacuum impregnated for 2h at 50℃ and 600r / min under nitrogen protection. Then, 4g of zinc sulfate and 12mL of 45% potassium borohydride solution were added dropwise to the reactor at a rate of 30mL / min. After the addition was complete, the reaction was continued for 5h. The mixture was then filtered, and the filter cake was washed 4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 80℃ for 2h to obtain an antibacterial plant-based biodegradable gel.
[0049] S5: Add 220g of poly(butylene adipate / terephthalate), 420g of polycaprolactone, 2g of polyvinyl alcohol, 20g of starch, 15g of triethyl citrate, 4g of dodecenyl succinic acid, and 7g of antibacterial plant-based biodegradable gel to a screw extruder for granulation to obtain natural plant-based biodegradable packaging material.
[0050] Comparative Example 1: Compared with Example 3, 2,5-dihydroxyterephthalic acid in step S1 was omitted.
[0051] Comparative Example 2: Compared with Example 3, the plant-based biodegradable gel in step S4 was replaced with the plant-based biodegradable carrier prepared in step S2.
[0052] Comparative Example 3: Compared with Example 3, the antibacterial plant-based biodegradable gel in step S5 was replaced with the plant-based biodegradable gel prepared in step S3.
[0053] Use 10 7 CFU / mL *Escherichia coli* and *Staphylococcus aureus* suspensions were used as test strains. The natural plant-based biodegradable packaging materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested according to standard QB / T2591-2003. The materials were then added to deionized water and immersed in a 37°C constant temperature water bath at 150 r / min for 30 days. The antibacterial rate of the packaging materials after 30 days of immersion was then tested. The tensile strength of the natural plant-based biodegradable packaging materials was tested according to national standard GB / T1040.3-2006. The results are shown in Table 1.
[0054] Table 1
[0055]
[0056] As shown in Table 1, Comparative Example 1 omitted 2,5-dihydroxyterephthalic acid in step S1. 2,5-dihydroxyterephthalic acid is the core organic ligand for the synthesis of MOF-Ag. Without this substance, silver nitrate cannot self-assemble into the porous crystal structure of MOF-Ag through coordination. It can only undergo simple physical mixing with titanium dioxide, and cannot achieve uniform dispersion and stable loading of silver ions. Without the anchoring of the MOF porous structure, silver ions are prone to agglomeration, and cannot achieve in-situ generation and spatial confinement of elemental silver through subsequent reactions. Silver ions are rapidly lost during the soaking process, resulting in antibacterial rates before and after soaking that are much lower than those in the Example.
[0057] Comparative Example 2 replaced the plant-based biodegradable gel in step S4 with the plant-based biodegradable carrier prepared in step S2. Only the composite of MOF-Ag / titanium dioxide and polyurethane matrix was completed. Gel coating, zinc sulfate reduction, and spatial confinement construction were not performed. The silver ions in the carrier existed in the form of MOF-Ag, without the synergistic antibacterial system of elemental silver and elemental zinc. Moreover, it lacked the coating protection of the gel network. The MOF structure was easily destroyed during the soaking process, and a large amount of silver ions were dissolved and lost, resulting in a sharp drop in antibacterial rate after soaking, which was far lower than the antibacterial stability of the example. It lacked the buffer layer of the gel in S3 and the rough protruding structure of the intermediate elemental silver and elemental zinc. The material relied only on the physical bonding of polyurethane matrix and powder, without stress buffering and interfacial slip structure design. The tensile strength decreased and could not meet the mechanical requirements of packaging materials.
[0058] In Comparative Example 3, the antibacterial plant-based biodegradable gel in step S5 was replaced with the plant-based biodegradable gel prepared in step S3. The gel only completed the composite of the carrier and the temperature-responsive gel, without vacuum impregnation, zinc sulfate reduction, or other steps. No elemental zinc was introduced, and no interstitial confinement structure was formed after the MOF structure collapsed. The antibacterial component was only MOF-Ag / titanium dioxide, lacking the synergistic effect of elemental silver and elemental zinc. Moreover, there was no spatial confinement structure, and silver ions were easily migrated and lost during the soaking process, resulting in a lower antibacterial rate before and after soaking than in the example. The rough protruding structure of elemental silver / zinc formed by the reaction was lacking, the interstitial structure between the gel and the carrier was not fully expanded, the interfacial sliding ability was insufficient, and the stress buffering effect was weak.
[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.
Claims
1. A method for preparing a natural plant-based biodegradable packaging material, characterized in that, Includes the following steps: Step 1: Using titanium dioxide powder as a carrier, 2,5-dihydroxyterephthalic acid as an organic ligand, and silver nitrate as a metal source, a silver metal framework is hydrothermally synthesized on its surface to obtain MOF-Ag / titanium dioxide. Step 2: Using castor oil polyether polyol and MOF-Ag / titanium dioxide as raw materials, a polyurethane prepolymerization reaction is carried out with isocyanate to obtain a plant-based biodegradable carrier; Step 3: Using N-isopropylacrylamide as a monomer and N,N'-methylenebispropylamide as a crosslinking agent, a free radical polymerization reaction is initiated on the surface of the plant-based biodegradable carrier to form a temperature-responsive crosslinked polyacrylamide hydrogel, thus obtaining a plant-based biodegradable gel. Step 4: Zinc sulfate is impregnated into the pores of the plant-based biodegradable gel through vacuum impregnation, and then reduced to elemental form under the action of potassium borohydride solution to obtain natural plant-based biodegradable packaging material.
2. The method for preparing a natural plant-based biodegradable packaging material according to claim 1, characterized in that, The mass ratio of poly(adipic acid) / butylene terephthalate, polycaprolactone, polyvinyl alcohol, starch, triethyl citrate, dodecenyl succinic acid, and antibacterial plant-based biodegradable gel is 200-220:400-420:1-2:15-20:12-15:2-4:5-7.
3. The method for preparing a natural plant-based biodegradable packaging material according to claim 1, characterized in that, The specific preparation steps for the MOF-Ag / titanium dioxide are as follows: 2,5-Dihydroxyterephthalic acid and N,N-dimethylformamide were added to a polytetrafluoroethylene-lined autoclave and stirred at 20-25℃ and 500-550 r / min for 30-40 min. Then, silver nitrate was added, and the mixture was heated to 120-130℃ and reacted for 10-12 h. Titanium dioxide powder with a particle size of 80-90 nm was then added, and the reaction was continued for 10-12 h. The mixture was allowed to cool naturally to room temperature, filtered, and the filter cake was washed 3-5 times with methanol solution and deionized water, respectively. The cake was then dried in a vacuum drying oven at 60-65℃ for 1-2 h to obtain MOF-Ag / titanium dioxide.
4. The method for preparing a natural plant-based biodegradable packaging material according to claim 3, characterized in that, The ratio of 2,5-dihydroxyterephthalic acid, N,N-dimethylformamide, silver nitrate and titanium dioxide powder is 80.4-82.5g: 710-725mL: 30.5-31.8g: 70.1-72.5g.
5. The method for preparing a natural plant-based biodegradable packaging material according to claim 1, characterized in that, The specific preparation steps of the plant-based biodegradable carrier are as follows: Castor oil polyether polyol, MOF-Ag / titanium dioxide, and deionized water were added to a reaction vessel and stirred at 20-25℃ and 500-550 r / min for 30-40 min. Then, triethylenediamine, dibutyltin dilaurate, 1,4-butanediol, and isocyanate were added, and stirring was continued for 40-50 min. The mixture was poured into a mold, heated to 120-122℃, and stirred at 80-90 r / min for 10-12 min to mature. The mixture was then demolded, allowed to cool naturally to room temperature, and dried in a vacuum drying oven at 60-65℃ for 1-2 h. After pulverization, a plant-based biodegradable carrier with a particle size of 0.5-0.7 mm was obtained.
6. The method for preparing a natural plant-based biodegradable packaging material according to claim 5, characterized in that, The ratio of castor oil polyether polyol, MOF-Ag / titanium dioxide, deionized water, triethylenediamine, dibutyltin dilaurate, 1,4-butanediol, and isocyanate is 21.2-22.3g: 52.5-53.8g: 875-882mL: 1.1-1.12g: 0.2-0.25g: 0.1-0.15g: 32-35g.
7. The method for preparing a natural plant-based biodegradable packaging material according to claim 1, characterized in that, The specific preparation steps for the plant-based biodegradable gel are as follows: N-Isopropylacrylamide and N,N'-methylenebispropylamide were added to a reaction vessel and stirred for 20-30 min at 20-25℃ and 500-600 r / min. Then sodium dodecyl sulfate and deionized water were added, and the mixture was heated to 40-50℃ and stirred for another 20-30 min. Nitrogen gas was then introduced at a flow rate of 10-12 min / L for 30-40 min, and the mixture was heated to 70-80℃. Ammonium persulfate was added, and the mixture was stirred for another 6-7 h under a nitrogen atmosphere. Then, the plant-based biodegradable carrier was added to the reaction vessel and stirred for another 20-30 min. The mixture was filtered, and the filter cake was washed 2-4 times with petroleum ether and deionized water, respectively. The mixture was then vacuum dried at 60-80℃ for 1-2 h to obtain the plant-based biodegradable gel.
8. The method for preparing a natural plant-based biodegradable packaging material according to claim 7, characterized in that, The ratio of N-isopropylacrylamide, N,N'-methylenebispropylamide, sodium dodecyl sulfate, deionized water, ammonium persulfate, and plant-based biodegradable carrier is 30-40g: 20-30g: 1-2g: 200-300mL: 1-2g: 20-30g.
9. The method for preparing a natural plant-based biodegradable packaging material according to claim 1, characterized in that, The specific preparation steps for the antibacterial plant-based biodegradable gel are as follows: Plant-based biodegradable gel and N,N-dimethylformamide were vacuum impregnated in a reactor under nitrogen protection at 40-50℃ and 500-600 r / min for 1-2 h. Then, zinc sulfate and potassium borohydride solution (40-45% by mass) were added dropwise to the reactor at a rate of 30 mL / min. After the addition was complete, the reaction was continued for 4-5 h. The mixture was then filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60-80℃ for 1-2 h to obtain an antibacterial plant-based biodegradable gel. The ratio of the plant-based biodegradable gel, N,N-dimethylformamide, zinc sulfate, and potassium borohydride solution is 20-30g: 300-400mL: 3-4g: 10-12mL.
10. A natural plant-based biodegradable packaging material, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.