A Degradable Environmentally Friendly Packaging Material and Its Preparation Process

Abstract

The present invention provides a degradable environmental protection packaging material and its preparation process, belonging to the technical field of packaging materials; the preparation method includes the following steps: preparing modified nano-montmorillonite; preparing a composite antibacterial additive; preparing a barrier additive; preparing a degradable environmental protection packaging material. In the present invention, first, using (2-dimethylaminoethyl) methacrylate and acrylic acid as raw materials, under the initiation of benzoyl peroxide, the nano-montmorillonite is modified. After quaternization, nano-zinc oxide is in-situ synthesized on the surface of the quaternized montmorillonite through a hydrothermal reaction to prepare a composite antibacterial additive. When this composite antibacterial additive is added to polylactic acid to make a packaging material, it can not only effectively inhibit the growth of various bacteria, fungi and other microorganisms, endowing the packaging material with a strong antibacterial protection ability, but also has a more lasting antibacterial effect to extend the antibacterial validity period of the packaging material.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging materials, and particularly relates to a degradable environmental protection packaging material and a preparation process thereof. Background Art

[0002] Packaging materials are widely used in various fields, from food, medicine to daily necessities, etc., and play a key role in the protection, storage and transportation of products. Traditional packaging materials are mainly petroleum-based plastics, such as polyethylene, polypropylene, polystyrene, etc. Although these materials have the characteristics of low cost, good processing performance, excellent mechanical properties, etc., they are difficult to degrade in the natural environment. A large amount of waste plastic packaging garbage accumulates, forming pollution.

[0003] With the continuous improvement of people's environmental protection awareness and the emphasis on sustainable development, degradable materials have emerged as the times require. Degradable materials can be decomposed into small molecule substances in a relatively short time under the action of natural environment, such as soil, water, microorganisms, etc., and return to the natural cycle. Common degradable materials include polylactic acid, polyhydroxyalkanoates, starch-based materials, etc. Polylactic acid is made from renewable plant resources (such as corn, sugarcane, etc.) and has good biocompatibility and mechanical properties, and has broad application prospects in the packaging field. However, for the packaging of products with extremely high requirements for sanitary conditions, such as medicines, antibacterial properties are crucial. In pharmaceutical packaging, microbial contamination may cause the failure of medicines and even lead to serious health problems.

[0004] Most of the existing packaging materials achieve the improvement of antibacterial properties by adding antibacterial agents. However, some methods use chemically synthesized antibacterial agents, such as antibacterial agents containing heavy metals. Although the antibacterial effect is significant, it may cause potential harm to human health and the environment, and heavy metal ions are difficult to degrade in the environment and may accumulate through the food chain, causing toxic effects on organisms; while natural antibacterial agents, such as chitosan, etc., although having good biocompatibility and safety, have poor compatibility with degradable materials, are prone to problems such as uneven dispersion during the preparation process, and have poor antibacterial persistence, which is likely to affect the overall performance of the material.

[0005] Therefore, it is necessary to propose a degradable environmental protection packaging material with good antibacterial properties and long antibacterial persistence and a preparation process thereof to improve the overall performance of the packaging material. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a degradable environmental protection packaging material and a preparation process thereof.

[0007] A preparation process of a degradable environmental protection packaging material includes the following steps:

[0008] S1: Prepare modified nano-montmorillonite

[0009] First, dissolve (2-dimethylaminoethyl) methacrylate and acrylic acid in ethanol to prepare a mixed alcohol solution. At the same time, disperse nano-montmorillonite in deionized water to prepare a nano-montmorillonite suspension. Then, mix the two and add benzoyl peroxide for reaction to obtain modified nano-montmorillonite;

[0010] S2: Prepare a composite antibacterial additive

[0011] Disperse the above-mentioned modified nano-montmorillonite in absolute ethanol, add tetrahydrofuran and benzyl chloride for reaction to prepare quaternary ammonium salt montmorillonite, then disperse it in deionized water, mix it with zinc nitrate solution, and add hexamethylenetetramine solution for hydrothermal reaction to obtain a composite antibacterial additive;

[0012] S3: Prepare a barrier additive

[0013] Mix dimethyl 2,5-furandicarboxylate, dimethyl succinate, neopentyl glycol and zinc acetate for reaction, and then add antimony trioxide and octyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate to continue the reaction to obtain a barrier additive;

[0014] S4: Prepare a degradable environmental protection packaging material

[0015] First, use tannic acid and maleic anhydride as raw materials to prepare a toughening modifier. Then, melt-blend polylactic acid particles with the toughening modifier, and then add the above-mentioned composite antibacterial additive, the above-mentioned barrier additive, poly(butylene adipate-co-terephthalate) and cellulose nanocrystal aqueous suspension, and continue to melt-blend. After extrusion granulation, blown film and heat treatment, a degradable environmental protection packaging material is obtained.

[0016] Furthermore, S1 specifically includes the following steps:

[0017] S1.1: Add (2-dimethylaminoethyl) methacrylate and acrylic acid to absolute ethanol according to the solid-liquid ratio of (8.6 - 9) g: 1 g: (55 - 65) mL, and stir well to mix to obtain a mixed alcohol solution;

[0018] S1.2: Add nano-montmorillonite to deionized water according to the solid-liquid ratio of 1 g: (45 - 55) mL, and ultrasonically disperse for 20 - 30 min to obtain a nano-montmorillonite suspension;

[0019] S1.3: Add the above-mentioned mixed alcohol solution to the above-mentioned nano-montmorillonite suspension, then add benzoyl peroxide, continue to ultrasonically disperse for 10 - 20 min, and then under the protection of nitrogen, heat and react at 70 - 80 °C for 5 - 6 h. After cooling, obtain modified nano-montmorillonite through centrifugal separation and ethanol washing.

[0020] Furthermore, S2 specifically includes the following steps:

[0021] S2.1: Add the modified nano - montmorillonite prepared in step S1.3 into absolute ethanol according to the solid - liquid ratio of 1 g:(90 - 100) mL, ultrasonically disperse for 10 - 20 min, then add tetrahydrofuran and benzyl chloride, stir and react for 20 - 24 h. After centrifugal separation, ethanol washing and drying, quaternary ammonium salt - modified montmorillonite is obtained, where the mass ratios of tetrahydrofuran and benzyl chloride to the modified nano - montmorillonite are (8 - 9):1 and (2 - 3):1 respectively;

[0022] S2.2: Add the above - mentioned quaternary ammonium salt - modified montmorillonite into deionized water according to the solid - liquid ratio of 1 g:(145 - 155) mL, ultrasonically disperse for 10 - 20 min to obtain a quaternary ammonium salt - modified montmorillonite dispersion;

[0023] S2.3: Add zinc nitrate hexahydrate into deionized water according to the solid - liquid ratio of 1 g:(12 - 14) mL, fully stir and dissolve to obtain a zinc nitrate solution;

[0024] S2.4: Add the above - mentioned zinc nitrate solution into the above - mentioned quaternary ammonium salt - modified montmorillonite dispersion, ultrasonically treat for 10 - 20 min, then add hexamethylenetetramine solution drop - by - drop while stirring to adjust the pH to 8 - 10. Then transfer it to a hydrothermal reaction kettle, heat and react at 120 - 160 °C for 6 - 8 h. After cooling, through centrifugal separation, washing and drying, a composite antibacterial additive is obtained, where the volume ratio of the zinc nitrate solution to the quaternary ammonium salt - modified montmorillonite dispersion is 1:(6 - 8), and the mass fraction of the hexamethylenetetramine solution is 2 - 3%.

[0025] Further, S3 specifically includes the following steps:

[0026] S3.1: Add dimethyl 2,5 - furandicarboxylate, dimethyl succinate and neopentyl glycol into a reaction kettle according to the molar ratio of 1:(1.2 - 1.4):(3.3 - 3.6), then add zinc acetate, and under the protection of nitrogen, heat and stir and react at 170 - 180 °C for 3 - 5 h to obtain an intermediate;

[0027] S3.2: Add antimony trioxide and octyl 3,5 - di - tert - butyl - 4 - hydroxyhydrocinnamate into the above - mentioned intermediate, and adjust the heating temperature to 220 - 240 °C. Then turn on the vacuum pump to reduce the pressure in the reaction kettle to 30 - 50 Pa, keep the temperature and react for 4 - 6 h, and then introduce nitrogen to restore the pressure in the kettle to atmospheric pressure to obtain a barrier additive.

[0028] Further, S4 specifically includes the following steps:

[0029] S4.1: Add tannic acid into N,N - dimethylformamide according to the solid - liquid ratio of 1 g:(9 - 11) mL, heat and stir at 40 - 60 °C until completely dissolved to obtain a tannic acid solution;

[0030] S4.2: Add maleic anhydride and 4-dimethylaminopyridine to the above tannic acid solution, stir well, and heat and stir under reflux at 70 - 90 °C for 4 - 6 h. After cooling, pour it into deionized water, then perform suction filtration, washing, and vacuum drying to obtain a toughening modifier;

[0031] S4.3: Add the polylactic acid particles and the above toughening modifier to a high-speed mixer, mix at 60 - 70 °C for 10 - 20 min, then add them to a twin-screw extruder, add antioxidant 1010, and melt-blend at 170 - 190 °C and 100 - 120 r / min for 1 - 2 h to obtain a precursor melt;

[0032] S4.4: Add the composite antibacterial additive prepared in step S2.4, the barrier additive prepared in step S3.2, poly(butylene adipate-co-terephthalate), and a cellulose nanocrystal aqueous suspension with a mass fraction of 1 - 3% to the above precursor melt, continue to melt-blend for 2 - 3 h, and then perform extrusion granulation to obtain a packaging material masterbatch;

[0033] S4.5: Transfer the above packaging material masterbatch to a single-screw extruder, perform blown film, and then heat-treat at 40 - 60 °C for 2 - 3 h to obtain a degradable and environmentally friendly packaging material.

[0034] Furthermore, the volume ratio of the mixed alcohol solution to the nanoclay suspension is (2 - 3):1, and the mass ratio of benzoyl peroxide to (2-dimethylaminoethyl) methacrylate is 1:(105 - 110).

[0035] Furthermore, the addition amount of zinc acetate is 0.08 - 0.1% of the total mass of dimethyl 2,5-furandicarboxylate, dimethyl succinate, and neopentyl glycol, and the mass ratios of antimony trioxide and octyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate to zinc acetate are (3.2 - 3.6):1 and (6 - 8):1 respectively.

[0036] Furthermore, the molar ratio of maleic anhydride to tannic acid is (18 - 26):1, and the addition amount of 4-dimethylaminopyridine is 3 - 5% of the mass of tannic acid.

[0037] Furthermore, by mass, the packaging material includes: 40 - 50 parts of polylactic acid particles, 15 - 25 parts of cellulose nanocrystal aqueous suspension, 10 - 15 parts of composite antibacterial additive, 8 - 12 parts of barrier additive, 5 - 10 parts of toughening modifier, 6 - 8 parts of poly(butylene adipate-co-terephthalate), and 2 - 3 parts of antioxidant 1010.

[0038] Furthermore, a degradable and environmentally friendly packaging material is prepared by the preparation process of a degradable and environmentally friendly packaging material described in any one of the above.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] 1. In the present invention, first, using methyl (2-dimethylaminoethyl) acrylate and acrylic acid as raw materials, under the initiation of benzoyl peroxide, nano-montmorillonite is modified. After quaternization, nano-zinc oxide is in-situ synthesized on the surface of quaternized montmorillonite through a hydrothermal reaction to prepare a composite antibacterial additive. When this composite antibacterial additive is added to polylactic acid to form a packaging material, since the quaternized modified montmorillonite itself has antibacterial ability, the quaternary ammonium salt group can adsorb on the surface of bacteria through electrostatic interaction, destroying the cell membrane structure of bacteria. And nano-zinc oxide can bind to biomolecules such as proteins and enzymes in bacteria, affecting the normal metabolism, growth and reproduction of bacteria. Thus, the composite antibacterial additive has broad-spectrum antibacterial performance, can effectively inhibit the growth of various bacteria, fungi and other microorganisms, endowing the packaging material with strong antibacterial protection ability. In addition, nano-montmorillonite has a unique layered structure. After being modified and used as a carrier for nano-zinc oxide, it can not only improve the loading effect of nano-zinc oxide, but also effectively improve the dispersion of nano-zinc oxide in the packaging material, stably loading nano-zinc oxide on its surface and interlayer, further improving the antibacterial effect of the packaging material. When the composite antibacterial additive is added to the packaging material, this modified layered structure can slow down the release rate of antibacterial components, making the antibacterial effect more persistent, so as to extend the antibacterial validity period of the packaging material.

[0041] 2. In the present invention, first, using dimethyl 2,5-furandicarboxylate, dimethyl succinate and neopentyl glycol as raw materials, under the catalysis of zinc acetate, an esterification reaction is carried out to prepare an intermediate. Then, antimony trioxide and octyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate are added for heating and melt polycondensation to prepare a barrier additive. After this barrier additive is added to polylactic acid to form a packaging material, on the one hand, due to the presence of the rigid furan ring in the molecular chain of the barrier additive, the molecular chain movement of the packaging material is relatively restricted, making the overall structure of the material more compact and orderly, reducing the channels for small molecules such as gas and water vapor to penetrate. On the other hand, the barrier additive can act as a nucleating agent to induce the crystallization of polylactic acid, and the increase in crystallinity will form more crystalline regions inside the material, hindering the penetration of small molecules such as gas and water vapor. Thus, the barrier performance of the packaging material can be effectively improved. In addition, the barrier structure formed by the barrier additive through influencing the crystallization of polylactic acid and the molecular chain movement intersects with the lamellar barrier structure of the composite antibacterial additive to form a composite barrier network, thereby strengthening the hindering effect of the network structure on small molecules, and achieving the effect of synergistically improving the barrier performance of the packaging material.

[0042] 3. The present invention prepares a toughening modifier from tannic acid and maleic anhydride, and then melt-blends it with polylactic acid. After modifying the polylactic acid, due to the interaction between the toughening modifier and polylactic acid through hydrogen bonds and the like, a good interfacial bond can be formed between the two, so that when the packaging material is subjected to an external force, the stress can be effectively transmitted between the carboxylated tannic acid and the polylactic acid, avoiding the occurrence of stress concentration and debonding at the interface, thereby enabling the packaging material to better withstand the external force. Moreover, since the toughening modifier can be uniformly dispersed in the polylactic acid matrix, when the packaging material is subjected to an external force, the stress can be evenly dispersed throughout the packaging material system, avoiding the excessive concentration of stress in a local area, enabling the packaging material to more effectively absorb and dissipate energy, and thus improving the overall toughness of the packaging material. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings incorporated herein and constituting a part of the specification illustrate embodiments of the present disclosure and, together with the specification, are further used to explain the principles of the present disclosure and enable those skilled in the relevant art to implement and use the present disclosure.

[0044] Figure 1 It is a process flow chart of the preparation of the degradable and environmentally friendly packaging material adopted in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following describes in detail a degradable and environmentally friendly packaging material and its preparation process provided by the present invention with reference to the drawings and specific embodiments.

[0046] Example 1

[0047] A preparation process of a degradable and environmentally friendly packaging material, as Figure 1 shown, includes the following steps:

[0048] S1: Prepare modified nano-montmorillonite

[0049] S1.1: Add (2-dimethylaminoethyl) methacrylate and acrylic acid to absolute ethanol according to a solid-liquid ratio of 8.6 g: 1 g: 55 mL, and stir and mix well to obtain a mixed alcohol solution;

[0050] S1.2: Add nano-montmorillonite to deionized water according to a solid-liquid ratio of 1 g: 45 mL, and ultrasonically disperse for 20 min to obtain a nano-montmorillonite suspension;

[0051] S1.3: Add the above mixed alcohol solution to the above nano-montmorillonite suspension, then add benzoyl peroxide, continue ultrasonic dispersion for 10 min, and then under the protection of nitrogen, heat and react at 70 °C for 5 h. After cooling, perform centrifugal separation and ethanol washing to obtain modified nano-montmorillonite, where the volume ratio of the mixed alcohol solution to the nano-montmorillonite suspension is 2:1, and the mass ratio of benzoyl peroxide to (2-dimethylaminoethyl) methacrylate is 1:105;

[0052] S2: Prepare a composite antibacterial additive

[0053] S2.1: Add the modified nano-montmorillonite prepared in step S1.3 to absolute ethanol according to a solid-liquid ratio of 1 g: 90 mL, perform ultrasonic dispersion for 10 min, then add tetrahydrofuran and benzyl chloride, and stir and react for 20 h. After centrifugal separation, ethanol washing and drying, quaternary ammonium salt modified montmorillonite is obtained, where the mass ratios of tetrahydrofuran and benzyl chloride to the modified nano-montmorillonite are 8:1 and 2:1 respectively;

[0054] S2.2: Add the above quaternary ammonium salt modified montmorillonite to deionized water according to a solid-liquid ratio of 1 g: 145 mL, and perform ultrasonic dispersion for 10 min to obtain a quaternary ammonium salt modified montmorillonite dispersion;

[0055] S2.3: Add zinc nitrate hexahydrate to deionized water according to a solid-liquid ratio of 1 g: 12 mL, and fully stir and dissolve to obtain a zinc nitrate solution;

[0056] S2.4: Add the above zinc nitrate solution to the above quaternary ammonium salt modified montmorillonite dispersion, perform ultrasonic treatment for 10 min, then add hexamethylenetetramine solution while stirring to adjust the pH to 8, and then transfer it to a hydrothermal reaction kettle, heat and react at 120 °C for 6 h. After cooling, perform centrifugal separation, washing and drying to obtain a composite antibacterial additive, where the volume ratio of the zinc nitrate solution to the quaternary ammonium salt modified montmorillonite dispersion is 1:6, and the mass fraction of the hexamethylenetetramine solution is 2%;

[0057] S3: Prepare a barrier additive

[0058] S3.1: Add dimethyl 2,5-furandicarboxylate, dimethyl succinate and neopentyl glycol to the reaction kettle according to a molar ratio of 1:1.2:3.3, then add zinc acetate, and under the protection of nitrogen, heat and stir and react at 170 °C for 3 h to obtain an intermediate, where the addition amount of zinc acetate is 0.08% of the total mass of dimethyl 2,5-furandicarboxylate, dimethyl succinate and neopentyl glycol;

[0059] S3.2: Add antimony trioxide and octyl 3,5 - di - tert - butyl - 4 - hydroxyhydrocinnamate to the above intermediate, adjust the heating temperature to 220 °C, then turn on the vacuum pump to reduce the pressure in the reaction kettle to 30 Pa, keep the temperature for 4 h, and then introduce nitrogen to restore the pressure in the kettle to atmospheric pressure to obtain the barrier additive. Among them, the mass ratios of antimony trioxide and octyl 3,5 - di - tert - butyl - 4 - hydroxyhydrocinnamate to zinc acetate are 3.2:1 and 6:1 respectively;

[0060] S4: Prepare the degradable environmentally friendly packaging material

[0061] S4.1: Add tannic acid to N,N - dimethylformamide according to the solid - liquid ratio of 1 g:9 mL, heat and stir at 40 °C until completely dissolved to obtain the tannic acid solution;

[0062] S4.2: Add maleic anhydride and 4 - dimethylaminopyridine to the above tannic acid solution, stir well, and heat and stir under reflux at 70 °C for 4 h. After cooling, pour it into deionized water, then perform suction filtration, washing and vacuum drying to obtain the toughening modifier. Among them, the molar ratio of maleic anhydride to tannic acid is 18:1, and the addition amount of 4 - dimethylaminopyridine is 3% of the mass of tannic acid;

[0063] S4.3: Add 40 parts by mass of polylactic acid particles and 5 parts by mass of the above toughening modifier to a high - speed mixer, mix at 60 °C for 10 min, then add them to a twin - screw extruder, add 2 parts by mass of antioxidant 1010, and melt - blend at 170 °C and 100 r / min for 1 h to obtain the precursor melt;

[0064] S4.4: Add 10 parts by mass of the composite antibacterial additive prepared in step S2.4, 8 parts by mass of the barrier additive prepared in step S3.2, 6 parts by mass of polybutylene adipate - terephthalate and 15 parts by mass of a 1% cellulose nanocrystal aqueous suspension to the above precursor melt, continue to melt - blend for 2 h, and then extrude and pelletize to obtain the packaging material masterbatch;

[0065] S4.5: Transfer the above packaging material masterbatch to a single - screw extruder, blow - film, and then heat - treat at 40 °C for 2 h to obtain the degradable environmentally friendly packaging material.

[0066] Example 2

[0067] A preparation process of a degradable environmentally friendly packaging material, as Figure 1 shown, includes the following steps:

[0068] S1: Prepare the modified nano - montmorillonite

[0069] S1.1: Add methyl (2-dimethylaminoethyl) acrylate and acrylic acid to absolute ethanol according to the solid-liquid ratio of 8.8 g: 1 g: 60 mL, and stir well to obtain a mixed alcohol solution;

[0070] S1.2: Add nanometer montmorillonite to deionized water according to the solid-liquid ratio of 1 g: 50 mL, and disperse it by ultrasonic for 25 min to obtain a nanometer montmorillonite suspension;

[0071] S1.3: Add the above-mentioned mixed alcohol solution to the above-mentioned nanometer montmorillonite suspension, then add benzoyl peroxide, continue to disperse it by ultrasonic for 15 min, and then under the protection of nitrogen, heat and react at 75 °C for 5.5 h. After cooling, centrifuge and wash with ethanol to obtain modified nanometer montmorillonite, where the volume ratio of the mixed alcohol solution to the nanometer montmorillonite suspension is 2.5:1, and the mass ratio of benzoyl peroxide to methyl (2-dimethylaminoethyl) acrylate is 1:107.5;

[0072] S2: Prepare a composite antibacterial additive

[0073] S2.1: Add the modified nanometer montmorillonite prepared in step S1.3 to absolute ethanol according to the solid-liquid ratio of 1 g: 95 mL, disperse it by ultrasonic for 15 min, then add tetrahydrofuran and benzyl chloride, and stir and react for 22 h. After centrifugation, washing with ethanol and drying, quaternary ammonium salt modified montmorillonite is obtained, where the mass ratios of tetrahydrofuran and benzyl chloride to the modified nanometer montmorillonite are 8.5:1 and 2.5:1 respectively;

[0074] S2.2: Add the above-mentioned quaternary ammonium salt modified montmorillonite to deionized water according to the solid-liquid ratio of 1 g: 150 mL, and disperse it by ultrasonic for 15 min to obtain a quaternary ammonium salt modified montmorillonite dispersion;

[0075] S2.3: Add zinc nitrate hexahydrate to deionized water according to the solid-liquid ratio of 1 g: 13 mL, and stir well to dissolve to obtain a zinc nitrate solution;

[0076] S2.4: Add the above-mentioned zinc nitrate solution to the above-mentioned quaternary ammonium salt modified montmorillonite dispersion, ultrasonically treat for 15 min, then add hexamethylenetetramine solution while stirring to adjust the pH to 9, and then transfer it to a hydrothermal reaction kettle, heat and react at 140 °C for 7 h. After cooling, centrifuge, wash and dry to obtain a composite antibacterial additive, where the volume ratio of the zinc nitrate solution to the quaternary ammonium salt modified montmorillonite dispersion is 1:7, and the mass fraction of the hexamethylenetetramine solution is 2.5%;

[0077] S3: Prepare a barrier additive

[0078] S3.1: Add dimethyl 2,5-furandicarboxylate, dimethyl succinate and neopentyl glycol into the reaction kettle in a molar ratio of 1:1.3:3.5, then add zinc acetate, and under the protection of nitrogen, heat and stir at 175 °C for 4 h to obtain an intermediate. The addition amount of zinc acetate is 0.09% of the total mass of dimethyl 2,5-furandicarboxylate, dimethyl succinate and neopentyl glycol;

[0079] S3.2: Add antimony trioxide and octyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate to the above intermediate, and adjust the heating temperature to 230 °C. Then turn on the vacuum pump to reduce the pressure in the reaction kettle to 40 Pa, keep the temperature and react for 5 h, and then introduce nitrogen to restore the pressure in the kettle to atmospheric pressure to obtain a barrier additive. The mass ratios of antimony trioxide and octyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate to zinc acetate are 3.4:1 and 7:1 respectively;

[0080] S4: Prepare a degradable and environmentally friendly packaging material

[0081] S4.1: Add tannic acid to N,N-dimethylformamide according to a solid-liquid ratio of 1 g:10 mL, heat and stir at 50 °C until completely dissolved to obtain a tannic acid solution;

[0082] S4.2: Add maleic anhydride and 4-dimethylaminopyridine to the above tannic acid solution, stir evenly, and heat and stir under reflux at 80 °C for 5 h. After cooling, pour it into deionized water, and then perform suction filtration, washing and vacuum drying to obtain a toughening modifier. The molar ratio of maleic anhydride to tannic acid is 22:1, and the addition amount of 4-dimethylaminopyridine is 4% of the mass of tannic acid;

[0083] S4.3: Add 45 parts by mass of polylactic acid particles and 7.5 parts by mass of the above toughening modifier into a high-speed mixer, mix at 65 °C for 15 min, then add them into a twin-screw extruder, add 2.5 parts by mass of antioxidant 1010, and melt and blend at 180 °C and 110 r / min for 1.5 h to obtain a precursor melt;

[0084] S4.4: Add 12.5 parts by mass of the composite antibacterial additive prepared in step S2.4, 10 parts by mass of the barrier additive prepared in step S3.2, 7 parts by mass of polybutylene adipate-co-terephthalate and 20 parts by mass of a 2% cellulose nanocrystal aqueous suspension to the above precursor melt, continue to melt and blend for 2.5 h, and then extrude and pelletize to obtain a packaging material masterbatch;

[0085] S4.5: Transfer the above packaging material masterbatch to a single-screw extruder, blow film, and then perform heat treatment at 50 °C for 2.5 h to obtain a degradable and environmentally friendly packaging material.

[0086] Example 3

[0087] A preparation process of a degradable and environmentally friendly packaging material, as Figure 1 shown, includes the following steps:

[0088] S1: Prepare modified nano-montmorillonite

[0089] S1.1: Add (2-dimethylaminoethyl) methacrylate and acrylic acid into absolute ethanol according to the solid-liquid ratio of 9 g: 1 g: 65 mL, stir and mix well to obtain a mixed alcohol solution;

[0090] S1.2: Add nano-montmorillonite into deionized water according to the solid-liquid ratio of 1 g: 55 mL, and ultrasonically disperse for 30 min to obtain a nano-montmorillonite suspension;

[0091] S1.3: Add the above mixed alcohol solution into the above nano-montmorillonite suspension, then add benzoyl peroxide, continue to ultrasonically disperse for 20 min, and then under the protection of nitrogen, heat and react at 80 °C for 6 h. After cooling, through centrifugal separation and ethanol washing, modified nano-montmorillonite is obtained, wherein the volume ratio of the mixed alcohol solution to the nano-montmorillonite suspension is 3:1, and the mass ratio of benzoyl peroxide to (2-dimethylaminoethyl) methacrylate is 1:110;

[0092] S2: Prepare a composite antibacterial additive

[0093] S2.1: Add the modified nano-montmorillonite prepared in step S1.3 into absolute ethanol according to the solid-liquid ratio of 1 g: 100 mL, ultrasonically disperse for 20 min, then add tetrahydrofuran and benzyl chloride, stir and react for 24 h. After centrifugal separation, ethanol washing and drying, quaternized montmorillonite is obtained, wherein the mass ratios of tetrahydrofuran and benzyl chloride to the modified nano-montmorillonite are 9:1 and 3:1 respectively;

[0094] S2.2: Add the above quaternized montmorillonite into deionized water according to the solid-liquid ratio of 1 g: 155 mL, and ultrasonically disperse for 20 min to obtain a quaternized montmorillonite dispersion;

[0095] S2.3: Add zinc nitrate hexahydrate into deionized water according to the solid-liquid ratio of 1 g: 14 mL, stir and dissolve well to obtain a zinc nitrate solution;

[0096] S2.4: Add the above zinc nitrate solution into the above quaternized montmorillonite dispersion, ultrasonically treat for 20 min, then while stirring, add hexamethylenetetramine solution to adjust the pH to 10, and then transfer to a hydrothermal reaction kettle, heat and react at 160 °C for 8 h. After cooling, through centrifugal separation, washing and drying, a composite antibacterial additive is obtained, wherein the volume ratio of the zinc nitrate solution to the quaternized montmorillonite dispersion is 1:8, and the mass fraction of the hexamethylenetetramine solution is 3%;

[0097] S3: Prepare barrier additives

[0098] S3.1: Dimethyl 2,5 - furandicarboxylate, dimethyl succinate and neopentyl glycol are added to a reaction kettle in a molar ratio of 1:1.4:3.6, and then zinc acetate is added. Under the protection of nitrogen, the mixture is heated and stirred at 180 °C for 5 h to obtain an intermediate. The addition amount of zinc acetate is 0.1% of the total mass of dimethyl 2,5 - furandicarboxylate, dimethyl succinate and neopentyl glycol;

[0099] S3.2: Antimony trioxide and octyl 3,5 - di - tert - butyl - 4 - hydroxyhydrocinnamate are added to the above intermediate, and the heating temperature is adjusted to 240 °C. Then, a vacuum pump is turned on to reduce the pressure in the reaction kettle to 50 Pa, and the mixture is kept at this temperature for 6 h. Then, nitrogen is introduced to restore the pressure in the kettle to atmospheric pressure to obtain barrier additives. The mass ratios of antimony trioxide, octyl 3,5 - di - tert - butyl - 4 - hydroxyhydrocinnamate to zinc acetate are 3.6:1 and 8:1 respectively;

[0100] S4: Prepare degradable and environmentally friendly packaging materials

[0101] S4.1: Tannic acid is added to N,N - dimethylformamide according to a solid - liquid ratio of 1 g:11 mL, and the mixture is heated and stirred at 60 °C until completely dissolved to obtain a tannic acid solution;

[0102] S4.2: Maleic anhydride and 4 - dimethylaminopyridine are added to the above tannic acid solution, stirred evenly, and heated and stirred under reflux at 90 °C for 6 h. After cooling, the mixture is poured into deionized water, and then filtered, washed and dried in vacuum to obtain a toughening modifier. The molar ratio of maleic anhydride to tannic acid is 26:1, and the addition amount of 4 - dimethylaminopyridine is 5% of the mass of tannic acid;

[0103] S4.3: 50 parts by mass of polylactic acid particles and 10 parts by mass of the above toughening modifier are added to a high - speed mixer, mixed at 70 °C for 20 min, and then added to a twin - screw extruder. 3 parts by mass of antioxidant 1010 is added, and the mixture is melt - blended at 190 °C and 120 r / min for 2 h to obtain a precursor melt;

[0104] S4.4: 15 parts by mass of the composite antibacterial additive prepared in step S2.4, 12 parts by mass of the barrier additive prepared in step S3.2, 8 parts by mass of poly(butylene adipate - terephthalate) and 25 parts by mass of a 3% cellulose nanocrystal aqueous suspension are added to the above precursor melt, and melt - blended for another 3 h, and then extruded and pelletized to obtain a packaging material masterbatch;

[0105] S4.5: Transfer the above-mentioned masterbatch of packaging material to a single-screw extruder, conduct blown film extrusion, and then perform heat treatment at 60 °C for 3 h to obtain a degradable and environmentally friendly packaging material.

[0106] Comparative Example 1

[0107] The difference between this Comparative Example 1 and Example 1 is that the composite antibacterial additive in Step S4.4 is removed.

[0108] Comparative Example 2

[0109] The difference between this Comparative Example 2 and Example 1 is that Steps S1.1 - S2.1 are removed, and the quaternized montmorillonite in Step S2.2 is replaced with an equal amount of nano-montmorillonite.

[0110] Comparative Example 3

[0111] The difference between this Comparative Example 3 and Example 1 is that the barrier additive in Step S4.4 is removed.

[0112] Comparative Example 4

[0113] The difference between this Comparative Example 4 and Example 1 is that the barrier additive in Step S4.4 is replaced with an equal amount of composite antibacterial additive.

[0114] Comparative Example 5

[0115] The difference between this Comparative Example 5 and Example 1 is that the composite antibacterial agent in Step S4.4 is replaced with an equal amount of barrier additive.

[0116] Comparative Example 6

[0117] The difference between this Comparative Example 6 and Example 1 is that the toughening modifier in Step S4.3 is removed.

[0118] Test Example

[0119] Test 1: Use Escherichia coli suspension and Staphylococcus aureus suspension with a concentration of 10 7 CFU / mL as test strains, and test the initial antibacterial rate of the packaging materials prepared in Examples 1 - 3 and Comparative Examples 1 - 2 according to the standard QB / T2591 - 2003. The results are shown in Table 1.

[0120] Table 1: Test Results of Initial Antibacterial Rate of Packaging Materials

[0121]

[0122] As can be seen from Table 1, after the composite antibacterial additive was not added in Comparative Example 1, the resistance of the prepared packaging material to Escherichia coli and Staphylococcus aureus was much lower than that of Example 1. This shows that by first using (2-dimethylaminoethyl) methacrylate and acrylic acid as raw materials and under the initiation of benzoyl peroxide, the nano-montmorillonite was modified, and after quaternization, nano-zinc oxide was in-situ synthesized on the surface of the quaternized montmorillonite through a hydrothermal reaction to prepare a composite antibacterial additive. When this composite antibacterial additive was added to polylactic acid to make a packaging material, it could effectively inhibit the growth of various bacteria, fungi and other microorganisms, endowing the packaging material with a strong antibacterial protection ability. In addition, in Comparative Example 2, after the nano-montmorillonite was not modified, the resistance of the prepared packaging material to Escherichia coli and Staphylococcus aureus was also lower than that of Example 1. Thus, it can be seen that after the nano-montmorillonite was modified as a carrier of nano-zinc oxide, it could not only improve the loading effect of nano-zinc oxide, but also effectively improve the dispersibility of nano-zinc oxide in the packaging material, stably load nano-zinc oxide on its surface and interlayer, and further improve the antibacterial performance of the packaging material.

[0123] Test 2: The packaging materials prepared in Examples 1-3 and Comparative Example 2 were added to deionized water, placed in a constant temperature water bath oscillator at 37 °C and oscillated and soaked at 150 rpm for 30 days. Then, the antibacterial rate of the packaging material after soaking for 30 days was tested according to the method in Test 1. The results are shown in Table 2.

[0124] Table 2: Test results of the antibacterial rate of the packaging material after soaking for 30 days

[0125]

[0126] As can be seen from Table 2, after the nano-montmorillonite was not modified in Comparative Example 2, the antibacterial rate of the prepared packaging material after soaking for 30 days decreased significantly compared with that of Example 1. This shows that when the composite antibacterial additive was added to the packaging material, this modified layered structure could slow down the release rate of the antibacterial component, making the antibacterial effect more persistent and extending the antibacterial validity period of the packaging material.

[0127] Test 3: The water vapor transmission rate of the packaging materials prepared in Examples 1-3 and Comparative Examples 3-5 was tested using a water vapor permeation meter, and the oxygen transmission rate of the packaging materials prepared in Examples 1-3 and Comparative Examples 3-5 was tested using an oxygen permeation meter. The results are shown in Table 3.

[0128] Table 3: Test results of the water vapor transmission rate and oxygen transmission rate

[0129]

[0130] As can be seen from Table 3, after the barrier additive is not added in Comparative Example 3, the water vapor transmission rate and oxygen transmission rate of the prepared packaging material are much higher than those in Example 1. Thus, it can be seen that by first using dimethyl 2,5-furandicarboxylate, dimethyl succinate and neopentyl glycol as raw materials, and carrying out an esterification reaction under the catalysis of zinc acetate to prepare an intermediate, and then adding antimony trioxide and octyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate for heating and melt polycondensation to prepare a barrier additive, after adding the barrier additive into polylactic acid to prepare a packaging material, the barrier performance of the packaging material can be effectively improved;

[0131] In addition, after the barrier additive is replaced with an equal amount of composite antibacterial additive or the composite antibacterial agent is replaced with an equal amount of barrier additive in Comparative Example 4 and Comparative Example 5, the water vapor transmission rate and oxygen transmission rate of the prepared packaging material are also higher than those in Example 1. Thus, it can be seen that the barrier additive and the composite antibacterial additive can synergistically improve the barrier performance of the packaging material.

[0132] Test 4: The tensile strength of the packaging materials prepared in Examples 1-3 and Comparative Example 6 was tested according to the national standard GB / T1040.3-2006, and the results are shown in Table 4.

[0133] Table 4: Tensile strength test results of packaging materials

[0134]

[0135] As can be seen from Table 4, after the polylactic acid is not modified with a toughening modifier in Comparative Example 6, the tensile strength of the prepared packaging material is lower than that in Example 1. Thus, it can be seen that by using tannic acid and maleic anhydride as raw materials to prepare a toughening modifier, and then melt-blending it with polylactic acid to modify the polylactic acid, the overall toughness of the packaging material can be effectively improved.

[0136] The above embodiments merely illustrate the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A process for preparing a degradable and environmentally friendly packaging material, characterized in that: The steps include: S1: Preparation of modified nano-montmorillonite Firstly, methacrylate (2-dimethylaminoethyl) ester and acrylic acid are dissolved in ethanol to prepare a mixed alcohol solution, and nano-montmorillonite is dispersed in deionized water to prepare a nano-montmorillonite suspension, and then the two are mixed and benzoyl peroxide is added to react to obtain modified nano-montmorillonite; S2: Preparation of composite antimicrobial additives The modified nano-montmorillonite is dispersed in anhydrous ethanol, and tetrahydrofuran and benzyl chloride are added to react to prepare quaternary ammonium salt montmorillonite, which is then dispersed in deionized water, mixed with zinc nitrate solution, and hexamethylenetetramine solution is added to perform hydrothermal reaction to obtain a composite antibacterial additive; S3: Preparation of barrier additives Dimethyl 2,5-furandicarboxylate, dimethyl succinate, neopentyl glycol and zinc acetate are mixed and reacted, and then antimony trioxide and 3,5-di-tert-butyl-4-hydroxyhydrocinnamate are added and continued to react to obtain a barrier additive; S4: Preparation of biodegradable and environmentally friendly packaging materials First, a toughening modifier is prepared with tannic acid and maleic anhydride as raw materials, and then the polylactic acid particles and the toughening modifier are melt-blended, and then the above-mentioned composite antibacterial additive, the above-mentioned barrier additive, polybutylene adipate-terephthalate and cellulose nanocrystal aqueous suspension are added, and melt-blending is continued. After extrusion granulation, film blowing and heat treatment, a degradable and environmentally friendly packaging material is obtained.

2. The process for preparing a degradable and environmentally friendly packaging material according to claim 1, characterized in that: S1 specifically includes the following steps: S1.1: Add 2-dimethylaminoethyl methacrylate and acrylic acid into anhydrous ethanol at a solid-liquid ratio of (8.6-9) g:1 g:(55-65) mL, stir and mix thoroughly to obtain a mixed alcohol solution; S1.2: Add nano-montmorillonite into deionized water at a solid-liquid ratio of 1 g: (45-55) mL, and ultrasonically disperse for 20-30 min to obtain a nano-montmorillonite suspension; S1.3: Add the mixed alcohol solution to the nano-montmorillonite suspension, then add benzoyl peroxide, continue ultrasonic dispersion for 10-20 minutes, then heat the reaction at 70-80°C for 5-6 hours under the protection of nitrogen, cool, centrifuge and wash with ethanol to obtain modified nano-montmorillonite.

3. The process for preparing a degradable and environmentally friendly packaging material according to claim 2, characterized in that: S2 specifically includes the following steps: S2.1: Add the modified nano-montmorillonite prepared in step S1.3 to anhydrous ethanol at a solid-liquid ratio of 1 g: (90-100) mL, ultrasonically disperse for 10-20 min, then add tetrahydrofuran and benzyl chloride, stir and react for 20-24 h, and obtain quaternary ammonium salt montmorillonite after centrifugal separation, ethanol washing and drying, wherein the mass ratios of tetrahydrofuran and benzyl chloride to the modified nano-montmorillonite are (8-9):1 and (2-3):1, respectively; S2.2: Add the above quaternary ammonium salt montmorillonite into deionized water at a solid-liquid ratio of 1 g: (145-155) mL, and ultrasonically disperse for 10-20 min to obtain a quaternary ammonium salt montmorillonite dispersion; S2.3: Add zinc nitrate hexahydrate into deionized water at a solid-liquid ratio of 1 g: (12-14) mL, stir thoroughly to dissolve, and obtain a zinc nitrate solution; S2.4: Add the above zinc nitrate solution to the above quaternary ammonium salt montmorillonite dispersion, ultrasonically treat for 10-20 minutes, then add hexamethylenetetramine solution while stirring to adjust the pH to 8-10, then transfer to a hydrothermal reactor, heat and react at 120-160°C for 6-8 hours, cool, centrifuge, wash and dry to obtain a composite antibacterial additive, wherein the volume ratio of zinc nitrate solution to quaternary ammonium salt montmorillonite dispersion is 1: (6-8), and the mass fraction of hexamethylenetetramine solution is 2-3%.

4. The process for preparing a degradable and environmentally friendly packaging material according to claim 3, characterized in that: S3 specifically includes the following steps: S3.1: Add dimethyl 2,5-furandicarboxylate, dimethyl succinate and neopentyl glycol into a reaction kettle in a molar ratio of 1: (1.2-1.4): (3.3-3.6), then add zinc acetate, and heat and stir at 170-180°C for 3-5h under the protection of nitrogen to obtain an intermediate; S3.2: Add antimony trioxide and 3,5-di-tert-butyl-4-hydroxyhydrocinnamate to the above intermediate, and adjust the heating temperature to 220-240°C. Then turn on the vacuum pump to reduce the pressure in the reactor to 30-50Pa, keep the reaction warm for 4-6 hours, and then introduce nitrogen to restore the pressure in the reactor to atmospheric pressure to obtain the barrier additive.

5. The process for preparing a degradable and environmentally friendly packaging material according to claim 4, characterized in that: S4 specifically includes the following steps: S4.1: Add tannic acid to N,N-dimethylformamide at a solid-liquid ratio of 1 g: (9-11) mL, heat and stir at 40-60°C until completely dissolved to obtain a tannic acid solution; S4.2: Add maleic anhydride and 4-dimethylaminopyridine to the above tannic acid solution, stir well, heat and stir under reflux at 70-90°C for 4-6 hours, cool, pour into deionized water, filter, wash and vacuum dry to obtain a toughening modifier; S4.3: Add the polylactic acid particles and the toughening modifier to a high-speed mixer, mix at 60-70°C for 10-20 minutes, add to a twin-screw extruder, add antioxidant 1010, and melt-blend at 170-190°C and 100-120 r / min for 1-2 hours to obtain a precursor melt; S4.4: Add the composite antibacterial additive prepared in step S2.4, the barrier additive prepared in step S3.2, polybutylene adipate-terephthalate and a 1-3% by mass aqueous suspension of cellulose nanocrystals to the above-mentioned precursor melt, continue melt blending for 2-3 hours, and then granulate by extrusion to obtain a packaging material masterbatch; S4.5: The above packaging material masterbatch is transferred to a single screw extruder for film blowing, and then heat treated at 40-60°C for 2-3h to obtain a degradable and environmentally friendly packaging material.

6. The process for preparing a degradable and environmentally friendly packaging material according to claim 2, characterized in that: The volume ratio of the mixed alcohol solution to the nano-montmorillonite suspension is (2-3):1, and the mass ratio of benzoyl peroxide to (2-dimethylaminoethyl) methacrylate is 1:(105-110).

7. The process for preparing a degradable and environmentally friendly packaging material according to claim 4, characterized in that: The amount of zinc acetate added is 0.08-0.1% of the total mass of dimethyl 2,5-furandicarboxylate, dimethyl succinate and neopentyl glycol, and the mass ratios of antimony trioxide and octyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate to zinc acetate are (3.2-3.6):1 and (6-8):1, respectively.

8. The process for preparing a degradable and environmentally friendly packaging material according to claim 5, characterized in that: The molar ratio of maleic anhydride to tannic acid is (18-26):1, and the amount of 4-dimethylaminopyridine added is 3-5% of the mass of tannic acid.

9. The process for preparing a degradable and environmentally friendly packaging material according to claim 5, characterized in that: The packaging material includes, by weight: 40-50 parts of polylactic acid particles, 15-25 parts of cellulose nanocrystal aqueous suspension, 10-15 parts of composite antibacterial additives, 8-12 parts of barrier additives, 5-10 parts of toughening modifiers, 6-8 parts of polybutylene adipate terephthalate and 2-3 parts of antioxidant 1010.

10. A degradable and environmentally friendly packaging material, characterized in that: The biodegradable environmentally friendly packaging material is prepared by the preparation process of the biodegradable environmentally friendly packaging material according to any one of claims 1 to 9.

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