High-strength high-barrier degradable plastic packaging film and preparation method thereof

Abstract

The application relates to the technical field of plastic packaging films, and discloses a high-strength high-barrier degradable plastic packaging film and a preparation method thereof, the high-strength high-barrier degradable plastic packaging film comprises the following components in parts by weight: PBAT 70-85 parts, PGA 10-12 parts, modified lignin 10-20 parts, a compatibilizer 0.2-3 parts, a plasticizer 2.5-4 parts and a crosslinking agent 3.5-5 parts; the modified lignin is obtained by modifying lignin with 3-(2-hydroxyethoxy) propionic acid tert-butyl ester. The above technical scheme solves the problems of insufficient mechanical strength and poor barrier property in the related art.

Description

Technical Field

[0001] This invention relates to the field of plastic packaging film technology, specifically to a high-strength, high-barrier, degradable plastic packaging film and its preparation method. Background Technology

[0002] With increasing environmental awareness, biodegradable plastic packaging films have become an important development direction in the packaging industry because they can decompose in the natural environment after use, avoiding the long-term pollution problems caused by traditional plastics. PBAT (polybutylene adipate / terephthalate) is an ideal raw material for preparing biodegradable plastics because it can be decomposed into carbon dioxide and water by microorganisms in the natural environment. However, PBAT still has problems such as insufficient mechanical strength and poor gas barrier properties in practical applications, making it difficult to meet the high-requirement packaging needs of food, pharmaceuticals, and other industries. Therefore, developing plastic packaging films that combine high strength, high barrier properties, and good biodegradability, and exploring efficient and feasible preparation methods, is a key challenge and an important research direction for resolving the contradiction between environmental protection and performance and promoting the application of green packaging. Summary of the Invention

[0003] This invention proposes a high-strength, high-barrier degradable plastic packaging film and its preparation method, which solves the problems of insufficient mechanical strength and poor barrier properties in related technologies.

[0004] The technical solution of the present invention is as follows:

[0005] A high-strength, high-barrier, degradable plastic packaging film raw material comprises the following components by weight: 70-85 parts PBAT, 10-12 parts PGA, 10-20 parts modified lignin, 0.2-3 parts compatibilizer, 2.5-4 parts plasticizer, and 3.5-5 parts crosslinking agent; wherein the modified lignin is obtained by modifying lignin with tert-butyl 3-(2-hydroxyethoxy)propionate.

[0006] The high-strength, high-barrier degradable plastic packaging film of this invention uses PBAT and PGA as base materials. PBAT has excellent processing performance, but poor mechanical strength and barrier properties, while PGA has high mechanical strength and good barrier properties, but poor processing performance. Therefore, the combination of PBAT and PGA can complement each other's advantages and improve the mechanical strength and barrier properties of the degradable plastic packaging film.

[0007] As a further technical solution, the amount of tert-butyl 3-(2-hydroxyethoxy)propionate added is 3% to 6% of the lignin content.

[0008] As a further technical solution, the method for preparing the modified lignin includes the following steps: adding tert-butyl 3-(2-hydroxyethoxy)propionate to ethanol and dispersing it evenly, then adding lignin and mixing, and drying to obtain modified lignin.

[0009] As a further technical solution, the lignin needs to be vacuum dried at 60°C for 8 hours before use.

[0010] As a further technical solution, the amount of tert-butyl 3-(2-hydroxyethoxy)propionate added is 3% of the lignin mass, and the volume-to-mass ratio of ethanol to lignin is 10 mL: 1 g.

[0011] As a further technical solution, the compatibilizer is one of 3-tert-butyl-2-hydroxybenzaldehyde, methyl 3,4-dihydroxybenzoate, or 2,4,6-trihydroxybenzoic acid.

[0012] Due to the significant polarity difference between PBAT and PGA, their compatibility during blending is poor. This invention effectively improves this problem by adding the aforementioned compatibilizer. Adding one of 3-tert-butyl-2-hydroxybenzaldehyde, methyl 3,4-dihydroxybenzoate, or 2,4,6-trihydroxybenzoic acid as a compatibilizer can reduce the polarity difference between PBAT and PGA, improve their compatibility, and thus enhance the strength and barrier properties of the degradable plastic packaging film, achieving a synergistic improvement in both high strength and high barrier performance.

[0013] As a further technical solution, the plasticizer is at least one of tributyl citrate, triethyl acetylgic acid citrate, or polyethylene glycol.

[0014] The addition of plasticizers to the high-strength, high-barrier degradable plastic packaging film of this invention can weaken intermolecular forces during processing, enhance molecular chain movement, and improve the flexibility of the degradable plastic packaging film.

[0015] As a further technical solution, the crosslinking agent is at least one of dicumyl peroxide, diphenylmethane diisocyanate, or triallyl isocyanurate.

[0016] The addition of a crosslinking agent to the high-strength, high-barrier biodegradable plastic packaging film of this invention can improve the mechanical strength of the film. This is because the addition of the crosslinking agent can enhance the mechanical strength of the biodegradable plastic packaging film through the formation of a network structure. Furthermore, the formation of this network structure alters the chain segment mobility of the biodegradable plastic packaging film, thereby also improving its barrier properties.

[0017] This invention also includes a method for preparing a high-strength, high-barrier, degradable plastic packaging film, comprising the following steps:

[0018] S1. After mixing PBAT, PGA and compatibilizer in the high-strength, high-barrier degradable plastic packaging film raw material, the mixture is melt-blended and extruded, and then granulated to obtain PBAT-PGA masterbatch.

[0019] S2. The PBAT-PGA masterbatch, modified lignin, and plasticizer are mixed to obtain a premix. A crosslinking agent is added to the premix, and the mixture is melt-blended, extruded, and granulated to obtain a functionalized composite masterbatch.

[0020] S3. The functionalized composite masterbatch is melt-extruded and blown into a film to obtain a high-strength, high-barrier, degradable plastic packaging film.

[0021] As a further technical solution, in step S1, the PBAT and PGA are dried at 80~85℃ for 15~20h before use.

[0022] As a further technical solution, in steps S1 and S2, the melt blending extrusion adopts a twin-screw extruder with a feed rate of 130~150g / min and the working temperature is set sequentially from zone one to zone five as 200℃, 195℃, 190℃, 185℃, and 180℃.

[0023] As a further technical solution, in step S3, the functionalized composite masterbatch is dried at 80~85℃ for 15~20h; the blown film machine used during blown film blowing has its working temperature set sequentially from zone one to zone five as 165℃, 165℃, 160℃, 155℃, and 150℃, and the screw speed is 50~60r / min.

[0024] As a further technical solution, in step S3, the thickness of the high-strength, high-barrier degradable plastic packaging film is 10~12μm.

[0025] The working principle and beneficial effects of this invention are as follows:

[0026] This invention prepares a high-strength, high-barrier degradable plastic packaging film. The film uses PBAT and PGA as masterbatches, and incorporates lignin modified with tert-butyl 3-(2-hydroxyethoxy)propionate. This results in a degradable plastic packaging film that combines high strength and high barrier properties with degradability. In existing technologies, adding lignin to degradable plastic packaging films can improve their strength and barrier properties; however, lignin is prone to aggregation due to its inherent properties. This invention uses lignin modified with tert-butyl 3-(2-hydroxyethoxy)propionate, which effectively addresses this issue. The modification improves the dispersibility of lignin, allowing it to better fulfill its function. This results in increased mechanical strength and high barrier properties in the degradable plastic packaging film, achieving a synergistic improvement in both strength and barrier performance. Detailed Implementation

[0027] 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.

[0028] In the following embodiments and comparative examples:

[0029] PBAT: Model: TH801T;

[0030] PGA: Model: F324234, Manufacturer: Huaxiang Kejie Biotechnology Co., Ltd.;

[0031] Lignin: Model: lbw, Manufacturer: Hubei Langbowan Biomedical Co., Ltd.

[0032] Example 1

[0033] A high-strength, high-barrier, degradable plastic packaging film comprises the following components in parts by weight: PBAT 85, PGA 12 parts, modified lignin 10 parts, compatibilizer 0.2 parts, tributyl citrate 2.5 parts, and dicumyl peroxide 3.5 parts; the compatibilizer is diisocyanate.

[0034] The method for preparing modified lignin includes the following steps:

[0035] First, the lignin was vacuum dried at 60℃ for 8 hours. Then, tert-butyl 3-(2-hydroxyethoxy)propionate (3% of the lignin mass) was added to anhydrous ethanol (100mL) and dispersed evenly. After that, lignin (10g) was added and mixed, and then dried to obtain modified lignin.

[0036] A method for preparing a high-strength, high-barrier, degradable plastic packaging film includes the following steps:

[0037] S1. Dry PBAT and PGA at 80℃ for 18h; add compatibilizer and dried PBAT and PGA to a mixer and mix, melt-blend and extrude in a twin-screw extruder, and obtain PBAT-PGA masterbatch after water cooling, air drying and pelletizing; wherein, the feed rate of the twin-screw extruder is 150g / min, and the working temperature is set from zone one to zone five as 200℃, 195℃, 190℃, 185℃ and 180℃ respectively;

[0038] S2. The PBAT-PGA masterbatch, modified lignin, and plasticizer are mixed to obtain a premix. A crosslinking agent is added to the premix, and the mixture is melt-blended and extruded using a twin-screw extruder. After water cooling, air drying, and pelletizing, functionalized composite masterbatch is obtained. The feed rate of the twin-screw extruder is 150 g / min, and the operating temperature is set from zone one to zone five as 200℃, 195℃, 190℃, 185℃, and 180℃, respectively.

[0039] S3. The prepared functionalized composite masterbatch was dried at 80℃ for 18h, and then added to a blown film machine for melt extrusion blown film to obtain a high-strength, high-barrier, degradable plastic packaging film with a film thickness of 10μm. The working temperature of the blown film machine was set from zone one to zone five as 165℃, 165℃, 160℃, 155℃, and 150℃ respectively, and the screw speed was 60r / min.

[0040] Example 2

[0041] A high-strength, high-barrier, degradable plastic packaging film comprises the following components in parts by weight: 70 parts PBAT, 10 parts PGA, 20 parts modified lignin, 3 parts compatibilizer, 4 parts tributyl citrate, and 5 parts dicumyl peroxide; the compatibilizer is diisocyanate.

[0042] The method for preparing modified lignin includes the following steps:

[0043] First, the lignin was vacuum dried at 60℃ for 8 hours. Then, tert-butyl 3-(2-hydroxyethoxy)propionate (3% of the lignin mass) was added to anhydrous ethanol (100mL) and dispersed evenly. After that, lignin (10g) was added and mixed, and then dried to obtain modified lignin.

[0044] A method for preparing a high-strength, high-barrier, degradable plastic packaging film includes the following steps:

[0045] S1. Dry the raw materials PBAT and PGA at 80℃ for 18h; add the compatibilizer and the dried PBAT and PGA into a mixer and mix, then melt-blend and extrude using a twin-screw extruder, and obtain PBAT-PGA masterbatch after water cooling, air drying and pelletizing; wherein, the feed rate is 130g / min, and the extrusion temperature zone is set to 200℃, 195℃, 190℃, 185℃ and 180℃;

[0046] S2. The PBAT-PGA masterbatch, modified lignin, and plasticizer are mixed to obtain a premix. A crosslinking agent is added to the premix, and the mixture is melt-blended and extruded using a twin-screw extruder. After water cooling, air drying, and pelletizing, functionalized composite masterbatch is obtained. The feed rate of the twin-screw extruder is 150 g / min, and the operating temperature is set sequentially from zone one to zone five as 200℃, 195℃, 190℃, 185℃, and 180℃.

[0047] S3. The prepared functionalized composite masterbatch was dried at 80℃ for 18h, and then added to a blown film machine for melt extrusion blown film to obtain a high-strength, high-barrier, degradable plastic packaging film with a thickness of 10μm. The working temperature of the blown film machine was set from zone one to zone five as 165℃, 165℃, 160℃, 155℃, and 150℃ respectively, and the screw speed was 50r / min.

[0048] Example 3

[0049] The only difference between this embodiment and Example 1 is that the amount of tert-butyl 3-(2-hydroxyethoxy)propionate added is 6% of the lignin content.

[0050] Example 4

[0051] The only difference between this embodiment and Example 1 is that the amount of tert-butyl 3-(2-hydroxyethoxy)propionate added is 5% of the lignin content.

[0052] Example 5

[0053] The only difference between this embodiment and Example 1 is that the compatibilizer is 3-tert-butyl-2-hydroxybenzaldehyde.

[0054] Example 6

[0055] The only difference between this embodiment and Example 1 is that the compatibilizer is methyl 3,4-dihydroxybenzoate.

[0056] Example 7

[0057] The only difference between this embodiment and Example 1 is that the compatibilizer is 2,4,6-trihydroxybenzoic acid.

[0058] Comparative Example 1

[0059] The only difference between this comparative example and Example 1 is that the modified lignin is replaced with an equal amount of lignin in this comparative example.

[0060] Comparative Example 2

[0061] The only difference between this comparative example and Example 1 is that tert-butyl 3-(2-hydroxyethoxy)propionate is replaced with an equal amount of silane coupling agent KH-550 in this comparative example.

[0062] The plastic packaging films prepared in Examples 1-7 and Comparative Examples 1-2 were tested according to the following methods:

[0063] 1. Tensile properties: The tensile properties of the samples were tested according to the test methods specified in standard GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics"; the tensile speed was 50 mm / min.

[0064] 2. Water vapor transmission rate: The water vapor transmission rate of the sample is tested according to the test method specified in GB / T 21529-2008 "Determination of water vapor transmission rate of plastic films and sheets - Electrolytic sensor method".

[0065] 3. Degradation: The composting method shall be carried out in accordance with the standard GB / T 20197-2006 "Definition, Classification, Marking and Degradation Performance Requirements of Degradable Plastics".

[0066] The measurement results are shown in the table below:

[0067] Table 1. Performance test results of plastic packaging films in Examples 1-7 and Comparative Examples 1-2

[0068]

[0069] Comparing Examples 1-7 with Comparative Examples 1-2, it is shown that the present invention can reduce the water vapor permeability of degradable plastic packaging films and improve tensile strength by adding lignin modified with tert-butyl 3-(2-hydroxyethoxy)propionate, thus solving the problems of poor barrier properties and low mechanical strength of degradable plastic packaging films.

[0070] Comparing Examples 1 and 5-7, it is shown that adding any one of 3-tert-butyl-2-hydroxybenzaldehyde, methyl 3,4-dihydroxybenzoate, or 2,4,6-trihydroxybenzoic acid can improve the tensile strength of the degradable plastic packaging film and reduce the water vapor transmission rate.

[0071] Table 2. Degradation performance test results of the degradable plastic packaging films in Examples 1-3

[0072]

[0073] As shown in Table 2, the degradation rate in Examples 1-3 of the present invention is ≥84.8% after 90 days, indicating that the degradable plastic packaging film of the present invention has excellent degradation performance.

[0074] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high strength, high barrier, degradable plastic packaging film, characterized in that, The raw materials of the high-strength, high-barrier degradable plastic packaging film include the following components by weight: 70-85 parts PBAT, 10-12 parts PGA, 10-20 parts modified lignin, 0.2-3 parts compatibilizer, 2.5-4 parts plasticizer, and 3.5-5 parts crosslinking agent; the modified lignin is obtained by modifying lignin with tert-butyl 3-(2-hydroxyethoxy)propionate. The amount of tert-butyl 3-(2-hydroxyethoxy)propionate added is 3% to 6% of the lignin content; The compatibilizer is at least one of 3-tert-butyl-2-hydroxybenzaldehyde, methyl 3,4-dihydroxybenzoate, or 2,4,6-trihydroxybenzoic acid.

2. A high strength, high barrier, degradable plastic packaging film according to claim 1, characterized in that, The method for preparing the modified lignin includes the following steps: adding tert-butyl 3-(2-hydroxyethoxy)propionate to ethanol and dispersing it evenly, then adding lignin and mixing, and drying to obtain the modified lignin.

3. A high strength, high barrier, degradable plastic packaging film according to claim 2, characterized in that, The mixing time is 40-50 minutes.

4. The high strength, high barrier, degradable plastic packaging film according to claim 1, wherein, The plasticizer includes at least one of tributyl citrate, triethyl acetylgic acid citrate, or polyethylene glycol.

5. The high strength, high barrier, degradable plastic packaging film according to claim 1, wherein, The crosslinking agent includes at least one of dicumyl peroxide, diphenylmethane diisocyanate, or triallyl isocyanurate.

6. A method for preparing a high-strength, high-barrier degradable plastic packaging film, used to prepare the high-strength, high-barrier degradable plastic packaging film according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. After mixing PBAT, PGA and compatibilizer in the high-strength, high-barrier degradable plastic packaging film raw material, the mixture is melt-blended and extruded, and then granulated to obtain PBAT-PGA masterbatch. S2. The PBAT-PGA masterbatch, modified lignin, and plasticizer are mixed to obtain a premix. A crosslinking agent is added to the premix, and the mixture is melt-blended, extruded, and granulated to obtain a functionalized composite masterbatch. S3. The functionalized composite masterbatch is melt-extruded and blown into a film to obtain a high-strength, high-barrier, degradable plastic packaging film.

7. The method for preparing a high-strength, high-barrier, degradable plastic packaging film according to claim 6, characterized in that, In steps S1 and S2, the temperature during extrusion is 180℃~200℃.

8. The method for preparing a high-strength, high-barrier, degradable plastic packaging film according to claim 6, characterized in that, In step S3, the blown film machine used in the blown film process has its working temperature set sequentially from zone one to zone five as 165℃, 165℃, 160℃, 155℃, and 150℃, and the screw speed is 50~60r / min.

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