Degradable packaging material and preparation method thereof

Abstract

The invention belongs to the technical field of degradable plastics, and particularly relates to a degradable packaging material and a preparation method thereof. The packaging material comprises the following raw materials in parts by mass: 60-70 parts of polylactic acid, 20-30 parts of poly (butylene terephthalate)-adipate, 2-3 parts of talcum powder, 1-3 parts of a compatilizer, 1-5 parts of a functional additive, 1-3 parts of a plasticizer, 0.2-0.5 part of a lubricant and 0.1-0.3 part of an antioxidant. According to the invention, a hydrazide modified product of chlorogenic acid and a cinnamyl aldehyde dialdehyde intermediate bridged by mercaptan are condensed to obtain the high-molecular-weight symmetric bio-based hybrid functional aid containing dynamic acylhydrazone bonds and thioether bonds. The degradable packaging material disclosed by the invention is excellent in antibacterial activity, can effectively prolong the permeation path of oxygen and water vapor, and is excellent in gas barrier property.

Description

A biodegradable packaging material and its preparation method Technical Field

[0001] This invention belongs to the field of biodegradable plastics technology, specifically relating to a biodegradable packaging material and its preparation method. Background Technology

[0002] Plastic packaging materials are widely used in the packaging of food, pharmaceuticals, cosmetics, and electronic products due to their lightweight, high strength, ease of molding, and waterproof and moisture-proof properties. With increasing environmental awareness, biodegradable plastic packaging materials have developed rapidly in recent years, among which polylactic acid (PLA) and polybutylene terephthalate (PBAT) are representative biodegradable materials that have received widespread attention. PLA is currently the world's largest-produced and most widely used bio-based biodegradable plastic. Made from renewable plant starches such as corn, cassava, and sugarcane, it possesses excellent biodegradability, biocompatibility, and processing performance, and is hailed as a "green plastic."

[0003] Although biodegradable materials degrade rapidly under composting conditions compared to traditional plastics, reducing pollution to the natural environment, they also have certain performance limitations. For example, polylactic acid (PLA) itself does not possess antibacterial properties and requires the addition of external antibacterial agents to inhibit microbial growth. Furthermore, PLA has low barrier properties against oxygen and water vapor, making it difficult to meet the high barrier performance requirements of food and pharmaceutical products. Therefore, further research is needed on the antibacterial and barrier properties of biodegradable plastics. Summary of the Invention

[0004] The primary objective of this invention is to provide a biodegradable packaging material.

[0005] The second objective of this invention is to provide a method for preparing a biodegradable packaging material.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a biodegradable packaging material comprising the following raw materials in parts by weight: 60-70 parts of polylactic acid, 20-30 parts of polybutylene terephthalate (PET), 2-3 parts of talc, 1-3 parts of compatibilizer, 1-5 parts of functional additives, 1-3 parts of plasticizer, 0.2-0.5 parts of lubricant, and 0.1-0.3 parts of antioxidant; the chemical structural formula of the functional additives is: .

[0007] Preferably, the preparation method of the functional additive includes the following steps: (1) adding chlorogenic acid to anhydrous ethanol, adding concentrated sulfuric acid for reflux reaction to obtain intermediate 1; (2) adding intermediate 1 to anhydrous ethanol, adding hydrazine hydrate for reflux reaction to obtain intermediate 2; (3) dissolving cinnamaldehyde and 1,5-pentanedithiol in dichloromethane, adding triethylamine for reaction at room temperature to obtain intermediate 3; (4) adding intermediate 3 and intermediate 2 to a mixed solvent of ethanol and dimethyl sulfoxide, and then adding glacial acetic acid for reaction to obtain the functional additive.

[0008] Preferably, in step (1), the ratio of chlorogenic acid, anhydrous ethanol, and concentrated sulfuric acid is 9-10 mmol: 60 mL: 0.5 mL; the reflux reaction temperature is 78-80 °C and the time is 12-16 h.

[0009] Preferably, in step (2), the ratio of intermediate 1, anhydrous ethanol, and hydrazine hydrate is 9-10 mmol: 40 mL: 15-20 mmol; the reflux reaction temperature is 78-80 °C and the time is 8-12 h.

[0010] Preferably, in step (3), the ratio of cinnamaldehyde, 1,5-pentanedithiol, dichloromethane, and triethylamine is 20-22 mmol: 9-10 mmol: 50 mL: 0.5 mL; and the reaction time is 22-24 h.

[0011] Preferably, in step (4), the ratio of intermediate 3, intermediate 2, mixed solvent, and glacial acetic acid is 4.5-5 mmol: 10-10.5 mmol: 80 mL: 0.5 mL; the reaction temperature is 70-75 °C and the reaction time is 16-20 h.

[0012] Preferably, in step (4), the volume ratio of ethanol to dimethyl sulfoxide in the mixed solvent is 4:1.

[0013] Preferably, the compatibilizer is maleic anhydride-grafted polylactic acid; and the plasticizer is tributyl acetylcitrate.

[0014] Preferably, the lubricant is ethylene bis-stearamide; the antioxidant is antioxidant 1010.

[0015] This invention provides a method for preparing the biodegradable packaging material, the method comprising the following steps: S1, firstly, mixing 80-90% by mass of polylactic acid, polybutylene terephthalate-adipate, talc, compatibilizer, plasticizer, lubricant, and antioxidant to obtain a first premix; S2, then mixing the remaining mass of polylactic acid with functional additives to obtain a second premix; S3, mixing the first premix and the second premix, and then melt-blending them using a twin-screw extruder to obtain a blend; finally, extruding and molding to obtain the final product.

[0016] Compared with existing technologies, the main advantages of this invention are as follows: This invention provides a biodegradable packaging material in which the functional additives include the polyphenolic antioxidant core of chlorogenic acid, the broad-spectrum antibacterial activity of cinnamaldehyde, and the secondary auxiliary antioxidant function of thioether bonds. By condensing the chlorogenic acid hydrazide-modified product with a thiol-bridged cinnamaldehyde dialdehyde intermediate, a high-molecular-weight symmetrical bio-based hybrid functional additive containing dynamic acylhydrazone and thioether bonds is constructed, significantly improving the thermal stability and long-lasting antibacterial rate of the biodegradable packaging material. Furthermore, in terms of barrier properties, the high-molecular-weight symmetrical rigid skeleton combined with dense polar hydroxyl groups can form a dense network with the polyester matrix through strong hydrogen bonding, greatly extending the permeation path of oxygen and water vapor, thereby endowing the packaging material with excellent gas barrier properties. Moreover, the functional additives of this invention have excellent interfacial compatibility and are difficult to migrate, solving the safety hazard of traditional additives easily leaching and contaminating food. Attached Figure Description

[0017] Figure 1. Schematic diagram of the preparation process of the functional additive of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0019] In the embodiments of the present invention, the number average molecular weight of polylactic acid is 40,000-80,000 Da; the number average molecular weight of polybutylene terephthalate-adipate is 50,000-80,000 Da; the preparation method of maleic anhydride-grafted polylactic acid (PLA-g-MAH) is as follows: polylactic acid is mixed with tert-butyl peroxide, maleic anhydride, and oxaloyl (3,5-di-tert-butyl-4-hydroxyphenyl)propionate (diimino-2,1-ethylidene ester) in a mass ratio of 100:0.05:2:0.2, and then extruded and granulated in a twin-screw extruder at 180°C, and then dried to obtain the final product.

[0020] Example 1 This example provides a biodegradable packaging material comprising the following raw materials in parts by weight: 65 parts polylactic acid, 25 parts polybutylene terephthalate-adipate, 3 parts talc, 2 parts compatibilizer (maleic anhydride-grafted polylactic acid), 3 parts functional additives, 2 parts plasticizer (acetylated tributyl citrate), 0.3 parts lubricant (ethylene bis-stearamide), and 0.2 parts antioxidant (antioxidant 1010).

[0021] The preparation process of the functional additive in this embodiment is shown in Figure 1. The preparation method includes the following steps: (1) Chlorogenic acid is added to anhydrous ethanol, and concentrated sulfuric acid is added dropwise as a catalyst. The ratio of chlorogenic acid, anhydrous ethanol and concentrated sulfuric acid is 9 mmol: 60 mL: 0.5 mL. The reaction is refluxed at 80 °C for 14 h. After the reaction is completed, most of the ethanol is removed by vacuum distillation. The remaining liquid is added to ice water, and the pH is adjusted to neutral by saturated sodium bicarbonate solution. Then, it is extracted three times with ethyl acetate. The organic phases are combined and dried with anhydrous sodium sulfate. The mixture is filtered, concentrated and purified (petroleum ether / ethyl acetate = 5:1), dried, and intermediate 1 is obtained (yield 92.8%). The obtained intermediate 1 has the following properties: 1 HNMR: (C 18 H 22 O9, 400MHz, DMSO-d6) δ: 1.21 (t, 3H), 1.96-2.06 (m, 2H), 2.21-2.31 (m, 2H), 3.54 (q, 1H), 4.13-4.21 (m, 3H), 4.4 (s, 1H), 4.61-4 .62 (m, 2H), 5.91 (s, 1H), 6.31 (d, 1H), 6.67 (d, 1H), 6.82 (d, 1H), 7.06 (d, 1H), 7.48 (d, 1H), 9.48 (s, 2H). MS (ESI) m / z=383.13[M+H] + .

[0022] (2) Intermediate 1 was added to anhydrous ethanol, and 80% hydrazine hydrate was added dropwise with stirring. The ratio of intermediate 1, anhydrous ethanol, and hydrazine hydrate was 9 mmol: 40 mL: 18 mmol. The mixture was heated to 80 °C and refluxed for 10 h. After the reaction was completed, the reaction solution was cooled to room temperature, filtered, and the precipitate was washed three times with cold ethanol and deionized water, respectively, and dried to obtain intermediate 2 (yield 85.3%). The obtained intermediate 2... 1 HNMR: (C 16 H 20 N2O8, 400MHz, DMSO-d6) δ: 1.85-1.94 (m, 2H), 2.10-2.19 (m, 2H), 3.54 (q, 1H), 4.13-4.22 (m, 3H), 4.4 (s, 1H), 4.61-4 .62 (m, 2H), 5.91 (s, 1H), 6.31 (d, 1H), 6.67 (d, 1H), 6.82 (d, 1H), 7.06 (d, 1H), 7.48 (d, 1H), 9.08 (s, 1H), 9.48 (s, 2H). MS(ESI) m / z=369.12[M+H] + .

[0023] (3) Cinnamaldehyde and 1,5-pentanedithiol were dissolved in dichloromethane, and triethylamine was added as a catalyst. The molar ratio of cinnamaldehyde, 1,5-pentanedithiol, dichloromethane, and triethylamine was 21 mmol: 9 mmol: 50 mL: 0.5 mL. The mixture was stirred at room temperature for 24 h. After the reaction was completed, the organic phase was washed successively with 5% HCl solution and saturated brine, dried over anhydrous magnesium sulfate, and the solvent was removed by vacuum distillation. The crude product was purified (petroleum ether / ethyl acetate = 5:1) to obtain intermediate 3 (yield 80.4%). The intermediate 3 was... 1 HNMR: (C 23 H 28 O2S2, 400MHz, DMSO-d6) δ: 1.55-1.64 (m, 6H), 2.60 (t, 4H), 2.94-3.19 (m, 4H), 4.04 (t, 2H), 7.20-7.30 (m, 10H), 9.72 (t, 2H). MS (ESI) m / z=401.15[M+H] + .

[0024] (4) Intermediate 3 and intermediate 2 were added to a mixed solvent (ethanol and dimethyl sulfoxide in a volume ratio of 4:1), and then glacial acetic acid was added. The ratio of intermediate 3, intermediate 2, mixed solvent, and glacial acetic acid was 4.8 mmol: 10.5 mmol: 80 mL: 0.5 mL. The mixture was heated and stirred at 75 °C for 18 h. After the reaction was completed, the mixture was slowly added dropwise to deionized water to precipitate the product. The precipitate was collected by filtration. The obtained solid was washed three times with anhydrous ethanol and dried to obtain the target product, functional additive (yield 83.7%). The obtained functional additive... 1 HNMR: (C 55 H 64 N4O 16 S2, 400MHz, DMSO-d6) δ: 1.55-1.64 (m, 6H), 1.85-1.94 (m, 4H), 2.10-2.19 (m, 4H), 2. 60 (m, 4H), 2.67-2.92 (m, 4H), 3.54 (q, 2H), 3.80 (t, 2H), 4.13 (t, 2H), 4.4 (s, 2H), 4.6 1-4.62 (m, 4H), 5.91 (s, 2H), 6.31 (d, 2H), 6.67 (d, 2H), 6.82 (d, 2H), 6.97 (t, 1H), 7. 06 (d, 2H), 7.20-7.30 (m, 10H), 7.48 (d, 2H), 7.94 (t, 1H), 9.48 (s, 4H), 10.57 (s, 2H). MS (ESI) m / z=1101.38[M+H] + .

[0025] The chemical structural formula of the obtained functional additive is: .

[0026] This embodiment provides a method for preparing a biodegradable packaging material. The preparation method includes the following steps: S1, drying each raw material to remove moisture and setting it aside; first, mixing 85% by mass of polylactic acid, polybutylene terephthalate, talc, compatibilizer, plasticizer, lubricant, and antioxidant to obtain a first premix; S2, then mixing the remaining mass of polylactic acid with functional additives to obtain a second premix; S3, mixing the first premix and the second premix, and then melt-blending them at 160°C using a twin-screw extruder to obtain a blend; then extruding and molding to obtain the final product.

[0027] Example 2 This example provides a biodegradable packaging material, comprising the following raw materials in parts by weight: 70 parts polylactic acid, 30 parts polybutylene terephthalate-adipate, 3 parts talc, 3 parts compatibilizer (maleic anhydride-grafted polylactic acid), 5 parts functional additives, 3 parts plasticizer (acetylated tributyl citrate), 0.5 parts lubricant (ethylene bis-stearamide), and 0.3 parts antioxidant (antioxidant 1010).

[0028] The preparation method of the functional additive in this embodiment includes the following steps: (1) Chlorogenic acid is added to anhydrous ethanol, and concentrated sulfuric acid is added dropwise as a catalyst. The ratio of chlorogenic acid, anhydrous ethanol and concentrated sulfuric acid is 10 mmol: 60 mL: 0.5 mL. The reaction is refluxed at 80 °C for 12 h. After the reaction is completed, most of the ethanol is removed by vacuum distillation. The remaining liquid is added to ice water, and the pH is adjusted to neutral by saturated sodium bicarbonate solution. Then, it is extracted three times with ethyl acetate. The organic phases are combined and dried with anhydrous sodium sulfate. The mixture is filtered, concentrated and purified (petroleum ether / ethyl acetate = 5:1), dried, and intermediate 1 is obtained (yield 90.2%). The obtained intermediate 1 has the following properties: 1 HNMR is the same as in Example 1.

[0029] (2) Intermediate 1 was added to anhydrous ethanol, and 80% hydrazine hydrate was added dropwise with stirring. The ratio of intermediate 1, anhydrous ethanol, and hydrazine hydrate was 10 mmol: 40 mL: 20 mmol. The mixture was heated to 80 °C and refluxed for 8 h. After the reaction was completed, the reaction solution was cooled to room temperature, filtered, and the precipitate was washed three times with cold ethanol and deionized water, respectively, and dried to obtain intermediate 2 (yield 83.5%). The obtained intermediate 2... 1 HNMR is the same as in Example 1.

[0030] (3) Cinnamaldehyde and 1,5-pentanedithiol were dissolved in dichloromethane, and triethylamine was added as a catalyst. The molar ratio of cinnamaldehyde, 1,5-pentanedithiol, dichloromethane, and triethylamine was 22 mmol: 10 mmol: 50 mL: 0.5 mL. The mixture was stirred at room temperature for 24 h. After the reaction was completed, the organic phase was washed successively with 5% HCl solution and saturated brine, dried over anhydrous magnesium sulfate, and the solvent was removed by vacuum distillation. The crude product was purified (petroleum ether / ethyl acetate = 5:1) to obtain intermediate 3 (yield 78.4%). The intermediate 3 was obtained... 1 HNMR is the same as in Example 1.

[0031] (4) Intermediate 3 and intermediate 2 were added to a mixed solvent (ethanol and dimethyl sulfoxide in a volume ratio of 4:1), and then glacial acetic acid was added. The ratio of intermediate 3, intermediate 2, mixed solvent, and glacial acetic acid was 5 mmol: 10.5 mmol: 80 mL: 0.5 mL. The mixture was heated and stirred at 75 °C for 16 h. After the reaction was completed, the mixture was slowly added dropwise to deionized water to precipitate the product. The precipitate was collected by filtration. The obtained solid was washed three times with anhydrous ethanol and dried to obtain the target product functional additive (yield 80.8%). The obtained functional additive... 1 HNMR is the same as in Example 1.

[0032] This embodiment provides a method for preparing a biodegradable packaging material. The preparation method includes the following steps: S1, drying each raw material to remove moisture and setting it aside; first, mixing 80% by mass of polylactic acid, polybutylene terephthalate-adipate, talc, compatibilizer, plasticizer, lubricant, and antioxidant to obtain a first premix; S2, then mixing the remaining mass of polylactic acid with functional additives to obtain a second premix; S3, mixing the first premix and the second premix, and then melt-blending them at 160°C using a twin-screw extruder to obtain a blend; then extruding and molding to obtain the final product.

[0033] Example 3 This example provides a biodegradable packaging material, comprising the following raw materials in parts by weight: 60 parts polylactic acid, 20 parts polybutylene terephthalate-adipate, 2 parts talc, 1 part compatibilizer (maleic anhydride-grafted polylactic acid), 1 part functional additive, 1 part plasticizer (acetylated tributyl citrate), 0.2 parts lubricant (ethylene bis-stearamide), and 0.1 parts antioxidant (antioxidant 1010).

[0034] The preparation method of the functional additive in this embodiment includes the following steps: (1) Chlorogenic acid is added to anhydrous ethanol, and concentrated sulfuric acid is added dropwise as a catalyst. The ratio of chlorogenic acid, anhydrous ethanol and concentrated sulfuric acid is 9 mmol: 60 mL: 0.5 mL. The reaction is refluxed at 78 °C for 16 h. After the reaction is completed, most of the ethanol is removed by vacuum distillation. The remaining liquid is added to ice water, and the pH is adjusted to neutral with saturated sodium bicarbonate solution. Then, it is extracted three times with ethyl acetate. The organic phases are combined and dried with anhydrous sodium sulfate. The mixture is filtered, concentrated and purified (petroleum ether / ethyl acetate = 5:1), dried, and intermediate 1 is obtained (yield 88.6%). The obtained intermediate 1 has the following properties: 1 HNMR is the same as in Example 1.

[0035] (2) Intermediate 1 was added to anhydrous ethanol, and 80% hydrazine hydrate was added dropwise with stirring. The ratio of intermediate 1, anhydrous ethanol, and hydrazine hydrate was 9 mmol: 40 mL: 15 mmol. The mixture was heated to 78 °C and refluxed for 12 h. After the reaction was completed, the reaction solution was cooled to room temperature, filtered, and the precipitate was washed three times with cold ethanol and deionized water, respectively, and dried to obtain intermediate 2 (yield 82.1%). The obtained intermediate 2... 1 HNMR is the same as in Example 1.

[0036] (3) Cinnamaldehyde and 1,5-pentanedithiol were dissolved in dichloromethane, and triethylamine was added as a catalyst. The molar ratio of cinnamaldehyde, 1,5-pentanedithiol, dichloromethane, and triethylamine was 20 mmol: 9 mmol: 50 mL: 0.5 mL. The mixture was stirred at room temperature for 22 h. After the reaction was completed, the organic phase was washed successively with 5% HCl solution and saturated brine, dried over anhydrous magnesium sulfate, and the solvent was removed by vacuum distillation. The crude product was purified (petroleum ether / ethyl acetate = 5:1) to obtain intermediate 3 (yield 75.3%). The intermediate 3 was... 1 HNMR is the same as in Example 1.

[0037] (4) Intermediate 3 and intermediate 2 were added to a mixed solvent (ethanol and dimethyl sulfoxide in a volume ratio of 4:1), and then glacial acetic acid was added. The ratio of intermediate 3, intermediate 2, mixed solvent, and glacial acetic acid was 4.5 mmol: 10 mmol: 80 mL: 0.5 mL. The mixture was heated and stirred at 70 °C for 20 h. After the reaction was completed, the mixture was slowly added dropwise to deionized water to precipitate the product. The precipitate was collected by filtration. The obtained solid was washed three times with anhydrous ethanol and dried to obtain the target product, functional additive (yield 78.2%). The obtained functional additive... 1 HNMR is the same as in Example 1.

[0038] This embodiment provides a method for preparing a biodegradable packaging material, the method comprising the following steps: S1, drying each raw material to remove moisture and setting aside; firstly, mixing 90% by mass of polylactic acid, polybutylene terephthalate-adipate, talc, compatibilizer, plasticizer, lubricant, and antioxidant to obtain a first premix; S2, then mixing the remaining mass of polylactic acid with functional additives to obtain a second premix; S3, mixing the first premix and the second premix, and then melt-blending them at 160°C using a twin-screw extruder to obtain a blend; finally, extruding and molding to obtain the final product.

[0039] Comparative Example 1 differs from Example 1 in that the functional additive is replaced with intermediate 2, otherwise it is the same as Example 1.

[0040] The difference between Comparative Example 2 and Example 1 is that the functional additive is replaced with intermediate 3, otherwise it is the same as Example 1.

[0041] The antibacterial, barrier and degradable properties of the packaging materials obtained in Examples 1-3 and Comparative Examples 1-2 of the present invention were determined in the following ways: 1. Referring to GB / T31402-2023 "Determination of antibacterial activity of plastics and other non-porous materials", the inhibition rate of each group of samples against Escherichia coli, Staphylococcus aureus and Candida albicans was determined, and the results are shown in Table 1.

[0042] 2. Referring to GB / T19789-2021 "Oxygen permeability test for packaging materials, plastic films and sheets", the oxygen permeability of each group of samples was measured, and the results are shown in Table 2.

[0043] 3. Referring to GB / T1037-2021 "Determination of Water Vapor Transmission Performance of Plastic Films and Sheets", the water vapor transmission rate of each group of samples was measured, and the results are shown in Table 2.

[0044] 4. Referring to GB / T20197-2006 "Definition, Classification, Labelling and Degradation Performance Requirements of Degradable Plastics", the 180-day degradation rate of each group of samples was determined, and the results are shown in Table 2.

[0045] Table 1 Table 2 As shown in Tables 1-2, the packaging materials obtained in Examples 1-3 of this invention exhibit better antibacterial and barrier properties compared to Comparative Examples 1-2. This is because the packaging materials of this invention incorporate functional additives. The condensation of the chlorogenic acid hydrazide-modified product with a cinnamaldehyde dialdehyde intermediate bridged by thiol results in a high-molecular-weight symmetrical bio-based hybrid containing dynamic acylhydrazone and thioether bonds. The polyphenolic antioxidant core of chlorogenic acid and the broad-spectrum antibacterial activity of cinnamaldehyde enhance the antibacterial rate of the packaging material. The high-molecular-weight symmetrical rigid skeleton combined with dense polar hydroxyl groups forms a dense network with the polyester matrix through strong hydrogen bonding, significantly extending the permeation path of oxygen and water vapor, thereby endowing the packaging material with excellent gas barrier properties.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A biodegradable packaging material, characterized in that, The raw materials include the following parts by weight: 60-70 parts polylactic acid, 20-30 parts polybutylene terephthalate (PET), 2-3 parts talc, 1-3 parts compatibilizer, 1-5 parts functional additives, 1-3 parts plasticizer, 0.2-0.5 parts lubricant, and 0.1-0.3 parts antioxidant; the chemical structural formula of the functional additives is: 。 2. The biodegradable packaging material according to claim 1, characterized in that, The preparation method of the functional additive includes the following steps: (1) adding chlorogenic acid to anhydrous ethanol, adding concentrated sulfuric acid for reflux reaction to obtain intermediate 1; (2) adding intermediate 1 to anhydrous ethanol, adding hydrazine hydrate for reflux reaction to obtain intermediate 2; (3) dissolving cinnamaldehyde and 1,5-pentanedithiol in dichloromethane, adding triethylamine for reaction at room temperature to obtain intermediate 3; (4) adding intermediate 3 and intermediate 2 to a mixed solvent of ethanol and dimethyl sulfoxide, then adding glacial acetic acid for reaction to obtain the functional additive.

3. The biodegradable packaging material according to claim 2, characterized in that, In step (1), the ratio of chlorogenic acid, anhydrous ethanol, and concentrated sulfuric acid is 9-10 mmol: 60 mL: 0.5 mL; the reflux reaction temperature is 78-80℃ and the time is 12-16 h.

4. The biodegradable packaging material according to claim 2, characterized in that, In step (2), the ratio of intermediate 1, anhydrous ethanol, and hydrazine hydrate is 9-10 mmol: 40 mL: 15-20 mmol; the reflux reaction temperature is 78-80 °C and the time is 8-12 h.

5. The biodegradable packaging material according to claim 2, characterized in that, In step (3), the ratio of cinnamaldehyde, 1,5-pentanedithiol, dichloromethane, and triethylamine is 20-22 mmol: 9-10 mmol: 50 mL: 0.5 mL; the reaction time is 22-24 h.

6. The biodegradable packaging material according to claim 2, characterized in that, In step (4), the ratio of intermediate 3, intermediate 2, mixed solvent, and glacial acetic acid is 4.5-5 mmol: 10-10.5 mmol: 80 mL: 0.5 mL; the reaction temperature is 70-75℃ and the reaction time is 16-20 h.

7. The biodegradable packaging material according to claim 2, characterized in that, In step (4), the volume ratio of ethanol to dimethyl sulfoxide in the mixed solvent is 4:

1.

8. The biodegradable packaging material according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polylactic acid; the plasticizer is tributyl acetylacetate.

9. The biodegradable packaging material according to claim 1, characterized in that, The lubricant is ethylene bis-stearamide; the antioxidant is antioxidant 1010.

10. A method for preparing the biodegradable packaging material according to any one of claims 1-9, characterized in that, The preparation method includes the following steps: S1, firstly, 80-90% by mass of polylactic acid, polybutylene terephthalate-adipate, talc, compatibilizer, plasticizer, lubricant, and antioxidant are mixed to obtain a first premix; S2, then the remaining mass of polylactic acid is mixed with functional additives to obtain a second premix; S3, the first premix and the second premix are mixed and melt-blended using a twin-screw extruder to obtain a blend; then, the blend is extruded and molded to obtain the final product.

Images