Degradable plastic bag and preparation method thereof

Abstract

The invention discloses a degradable plastic bag and a preparation method thereof, and belongs to the technical field of degradable plastic preparation. The method comprises the following steps: (1) preparing a ternary liquid solvent of 1, 3-propylene glycol, ethylene glycol and zinc chloride; (2) adding starch into the ternary liquid solvent system, stirring until the starch is dissolved, precipitating, drying and separating to obtain starch particles; and (3) stirring and mixing the starch particles obtained in the step (2), polylactic acid, PBAT, a heat stabilizer and an antioxidant, carrying out melt extrusion granulation through a twin-screw extruder, and carrying out film blowing and bag making in sequence to obtain the degradable plastic bag. According to the plastic bag, the degradation rate of the plastic bag can be effectively increased, and meanwhile, the toughness, the bearing capacity and the like of the plastic bag cannot be greatly lost in the using period.

Description

Technical Field

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

[0002] Plastic bags are everyday items, generally made of polymers such as polystyrene, polypropylene, and polyvinyl chloride. A large number of plastic bags are consumed annually. However, due to overuse and low recycling value, plastic bag recycling is inadequate, resulting in significant resource waste. Furthermore, the stable molecular structure of plastic bags makes them difficult for microorganisms to degrade naturally. Over time, discarded plastic bags cause substantial environmental pollution and pose a significant threat to human health. Therefore, biodegradable plastic bags are gradually replacing traditional plastic bags.

[0003] Biodegradable plastic bags are mainly composed of biodegradable plastics such as polylactic acid (PLA), regenerated cellulose, starch plastics, polyhydroxyalkanoates, polybutylene succinate, polycaprolactone, and polyethylene glycol. Among these, PLA, a polyester synthesized from plant resources, is widely used in biodegradable plastic bags due to its biodegradability, good biocompatibility, and ease of processing. However, to ensure the biodegradability of the plastic bags, they may gradually become brittle and lose strength during use, thus reducing their load-bearing capacity and toughness. Summary of the Invention

[0004] In view of the above-mentioned shortcomings in the prior art, the present invention provides a biodegradable plastic bag and a method for preparing the same, which can effectively improve the degradation rate of the plastic bag, while maintaining its toughness and load-bearing capacity during use without significant loss.

[0005] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is as follows:

[0006] A method for preparing a biodegradable plastic bag includes the following steps:

[0007] (1) Prepare a ternary liquid solvent of 1,3-propanediol, ethylene glycol and zinc chloride in a molar ratio of 1~3:0.5~1:1~2;

[0008] (2) Add starch at 3-10 wt% of the dry weight of starch in the ternary liquid solvent system, stir at 80-110℃ until the starch dissolves, and then precipitate and dry to obtain starch granules.

[0009] (3) The starch granules, polylactic acid, PBAT, heat stabilizer and antioxidant obtained in step (2) are stirred and mixed, and then melt-extruded and granulated by twin-screw extruder, and then blown film and bag making are carried out in sequence to obtain the biodegradable plastic bag.

[0010] The mass ratio of polylactic acid, PBAT, heat stabilizer and antioxidant is 1~1.5:5~10:0.5~2:0.3~1; the amount of starch granules added is 3~5wt% of PBAT.

[0011] Furthermore, in step (1), the molar ratio of 1,3-propanediol, ethylene glycol and zinc chloride is 2~3:0.5~1:1~1.5.

[0012] Furthermore, the molar ratio of 1,3-propanediol, ethylene glycol, and zinc chloride is 2.5~3:0.8~1:1.

[0013] Furthermore, the amount of starch added in step (2) is 3~wt%.

[0014] Furthermore, in step (2), the starch is corn starch, sweet potato starch, or potato starch.

[0015] Further, in step (2), anhydrous ethanol is used to precipitate and separate starch, which is then freeze-dried to obtain starch granules.

[0016] Further, in step (3), the mass ratio of polylactic acid, PBAT, heat stabilizer and antioxidant is 1~1.5:8~10:0.5~1:0.3~0.5; the amount of starch granules added is 3.8~4.2wt% of PBAT.

[0017] Furthermore, the heat stabilizer includes epoxidized soybean oil and maleate in a mass ratio of 1:2 to 3.

[0018] Furthermore, the antioxidant is antioxidant 1010 or antioxidant 1076.

[0019] A biodegradable plastic bag is prepared using the method described above.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention utilizes a ternary system of 1,3-propanediol, ethylene glycol, and zinc chloride to pretreat starch, effectively improving the mechanical properties of the prepared plastic bags. Furthermore, since the amount of starch added is positively correlated with the degradation rate to a certain extent, this invention ensures the degradation rate of the plastic bags even with a reduced starch content.

[0022] 2. This invention specifically defines the molar ratio of 1,3-propanediol, ethylene glycol, and zinc chloride. If the content of ethylene glycol is further reduced, it will lead to stratification and prevent the formation of a complete solvent system. If it is further increased, it will lead to increased cost of the solvent system and waste.

[0023] 3. This invention uses a compound of starch, polylactic acid (PLA), and PBAT to prepare plastic bags, and adds a heat stabilizer composed of maleic acid ester and epoxidized soybean oil, which effectively improves the thermal stability of starch and PLA during subsequent processing. Furthermore, the epoxidized soybean oil improves the interfacial bonding between starch and PLA, preventing delamination.

[0024] 4. This invention discovers that a heat stabilizer composed of maleate ester and epoxidized soybean oil has optimal efficacy. Epoxidized soybean oil possesses the ability to absorb HCl to form stable ester compounds and also has a plasticizing effect, improving the flexibility of plastic bags. Maleate ester can regulate the interactions between molecular chains, improving the compatibility of polylactic acid and PBAT, thereby enhancing the toughness of the resulting plastic bags. Simultaneously, it makes the plastic easier to mold during extrusion, blow molding, and other processing. The combined use of both can further improve the mechanical properties of plastic bags. Detailed Implementation

[0025] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0026] Example 1:

[0027] A method for preparing a biodegradable plastic bag includes the following steps:

[0028] (1) Mix 1,3-propanediol, ethylene glycol and zinc chloride in a molar ratio of 3:1:1 to form a ternary liquid solvent;

[0029] (2) Add corn starch at 3 wt% of the dry weight of starch in the ternary liquid solvent system, stir at 90°C until the starch dissolves, then precipitate the starch with anhydrous ethanol, wash repeatedly, filter and dry, and separate to obtain corn starch granules.

[0030] (3) After mixing the corn starch granules, polylactic acid, PBAT, heat stabilizer and antioxidant 1010 obtained in step (2), the mixture is melt-extruded and granulated by a twin-screw extruder, and then blown film and bag making are carried out in sequence to obtain the biodegradable plastic bag.

[0031] The mass ratio of polylactic acid, PBAT, heat stabilizer, and antioxidant is 1:5:0.5:0.3; the amount of corn starch granules added is 3 wt% of PBAT. The heat stabilizer includes epoxidized soybean oil and maleate in a mass ratio of 1:2.

[0032] A biodegradable plastic bag is prepared using the method described above.

[0033] Example 2:

[0034] A method for preparing a biodegradable plastic bag includes the following steps:

[0035] (1) Mix 1,3-propanediol, ethylene glycol and zinc chloride in a molar ratio of 1:0.5:2 to form a ternary liquid solvent;

[0036] (2) Add corn starch at 10 wt% of the dry weight of starch in the ternary liquid solvent system, stir at 80°C until the starch dissolves, then precipitate the starch with anhydrous ethanol, wash repeatedly, filter and dry, and separate to obtain corn starch granules.

[0037] (3) After mixing the corn starch granules, polylactic acid, PBAT, heat stabilizer and antioxidant 1010 obtained in step (2), the mixture is melt-extruded and granulated by a twin-screw extruder, and then blown film and bag making are carried out in sequence to obtain the biodegradable plastic bag.

[0038] The mass ratio of polylactic acid, PBAT, heat stabilizer, and antioxidant is 1.5:10:2:1; the amount of corn starch granules added is 5 wt% of PBAT. The heat stabilizer includes epoxidized soybean oil and maleate in a mass ratio of 1:3.

[0039] A biodegradable plastic bag is prepared using the method described above.

[0040] Example 3:

[0041] A method for preparing a biodegradable plastic bag includes the following steps:

[0042] (1) Mix 1,3-propanediol, ethylene glycol and zinc chloride in a molar ratio of 2:1:1 to form a ternary liquid solvent;

[0043] (2) Add corn starch at 5 wt% of the dry weight of starch in the ternary liquid solvent system, stir at 110°C until the starch dissolves, then precipitate the starch with anhydrous ethanol, wash repeatedly, filter and dry to obtain corn starch granules.

[0044] (3) After mixing the corn starch granules, polylactic acid, PBAT, heat stabilizer and antioxidant 1010 obtained in step (2), the mixture is melt-extruded and granulated by a twin-screw extruder, and then blown film and bag making are carried out in sequence to obtain the biodegradable plastic bag.

[0045] The mass ratio of polylactic acid, PBAT, heat stabilizer, and antioxidant is 1:6:1.5:0.5; the amount of corn starch granules added is 3.5 wt% of PBAT. The heat stabilizer includes epoxidized soybean oil and maleate in a mass ratio of 1:2.5.

[0046] A biodegradable plastic bag is prepared using the method described above.

[0047] Comparative Example 1

[0048] Compared to Example 1, no ternary liquid solvent was used for treatment, but the rest of the process remained the same as in Example 1.

[0049] Comparative Example 2

[0050] Compared to Example 1, the treatment was performed using a binary liquid solvent of ethylene glycol and zinc chloride, while the rest of the process remained the same as in Example 1.

[0051] Comparative Example 3

[0052] Compared to Example 1, this method uses 1,3-propanediol, ethylene glycol, and choline chloride liquid solvents for treatment, while the rest of the process remains the same as in Example 1.

[0053] Comparative Example 4

[0054] Compared with Example 1, the ternary liquid solvent was not used for treatment. At the same time, the amount of starch added was increased by 5 times and the amount of polylactic acid added was increased by 2 times. The rest of the process was the same as in Example 1.

[0055] Comparative Example 5

[0056] Compared to Example 1, the only heat stabilizer used was epoxidized soybean oil, while the rest of the process remained the same as in Example 1.

[0057] Comparative Example 6

[0058] Compared to Example 1, zinc stearate was used to replace the maleate component in the heat stabilizer, while the rest of the process remained the same as in Example 1.

[0059] Test case

[0060] This experiment investigates the various properties of biodegradable plastic bags in Examples 1-3 and Comparative Examples 1-6. The specific experimental procedures are as follows:

[0061] 1. Tensile properties: Tensile tests were conducted on a universal testing machine in accordance with the standard GB / T 1040.3-2006 for testing the tensile properties of plastics. The tensile rate was 2 mm / min, and 5 tests were performed for each group. The average value was taken.

[0062] 2. Biodegradability: The biodegradability of the plastic bags prepared in each example and comparative example was tested according to GB / T20197-2006 after 60 days of landfill. Five tests were conducted for each group, and the average value was taken. The test results are shown in Table 1.

[0063] Table 1 Performance Testing of Plastic Bags

[0064]

[0065] As shown in Table 1, adjusting the formulation of the ternary liquid solvent affects both the mechanical properties and degradation efficiency of the plastic bags. Furthermore, increasing the amount of starch and PLA can, to some extent, compensate for the effects of the ternary liquid solvent treatment. Changes in the heat stabilizer composition also affect the fusion of the components and their thermal stability, further impacting the mechanical properties of the plastic bags.

[0066] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a biodegradable plastic bag, characterized in that, Includes the following steps: (1) Prepare a ternary liquid solvent of 1,3-propanediol, ethylene glycol and zinc chloride in a molar ratio of 1~3:0.5~1:1~2; (2) Add starch at 3-10 wt% of the dry weight of starch in the ternary liquid solvent system, stir at 80-110℃ until the starch dissolves, and then precipitate and dry to obtain starch granules. (3) The starch granules, polylactic acid, PBAT, heat stabilizer and antioxidant obtained in step (2) are stirred and mixed, and then melt-extruded and granulated by twin-screw extruder, and then blown film and bag making are carried out in sequence to obtain the biodegradable plastic bag. The mass ratio of polylactic acid, PBAT, heat stabilizer and antioxidant is 1~1.5:5~10:0.5~2:0.3~1; the amount of starch granules added is 3~5wt% of PBAT.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of 1,3-propanediol, ethylene glycol and zinc chloride is 2~3:0.5~1:1~1.

5.

3. The preparation method according to claim 2, characterized in that, The molar ratio of 1,3-propanediol, ethylene glycol, and zinc chloride is 2.5~3:0.8~1:

1.

4. The preparation method according to claim 1, characterized in that, In step (2), the amount of starch added is 3-wt%.

5. The preparation method according to claim 1 or 4, characterized in that, In step (2), the starch is corn starch, sweet potato starch or potato starch.

6. The preparation method according to claim 1, characterized in that, In step (2), starch is separated by precipitation using anhydrous ethanol and then freeze-dried to obtain starch granules.

7. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of polylactic acid, PBAT, heat stabilizer and antioxidant is 1~1.5:8~10:0.5~1:0.3~0.5; the amount of starch granules added is 3.8~4.2wt% of PBAT.

8. The preparation method according to claim 1, characterized in that, The heat stabilizer consists of epoxidized soybean oil and maleate in a mass ratio of 1:2 to 3.

9. The preparation method according to claim 1, characterized in that, The antioxidant is antioxidant 1010 or antioxidant 1076.

10. A biodegradable plastic bag, characterized in that, It is prepared by the method described in any one of claims 1 to 9.

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