A low-cost degradable plastic bag with adjustable degradation rate and a preparation method thereof

Abstract

The application discloses a low-cost degradable plastic bag with adjustable degradation rate and a preparation method thereof. The low-cost degradable plastic bag with adjustable degradation rate comprises the following raw materials in parts by weight: 100 parts of a biodegradable polymer, 5-30 parts of a degradation rate regulator and 10-30 parts of a cheapening agent. Through reasonable formula collocation, the purpose of greatly adjusting the degradation rate of the material is achieved, the material meets the degradation period requirement of different use scenes, is matched with a proper use period, is low in cost, has more excellent rapid degradation performance compared with other degradable materials with the same mechanical property, is suitable for popularization and application in the market, and effectively overcomes the plastic pollution problem caused by traditional plastics.

Description

Technical Field

[0001] This invention relates to the field of fully biodegradable materials technology. More specifically, it relates to a low-cost biodegradable plastic bag with an adjustable degradation rate and a method for preparing the same. Background Technology

[0002] Currently, plastic pollution is becoming increasingly serious, with single-use packaging materials being the main source of plastic pollution. To alleviate and completely solve the plastic problem, national and municipal governments are vigorously promoting biodegradable plastic bags to replace traditional plastic bags. However, their high cost has hindered the widespread adoption of biodegradable plastic bags. Therefore, low-cost biodegradable plastic bag manufacturing technology is a necessary technological means to overcome the current high price of biodegradable plastic bags. Significantly reducing the cost of biodegradable bags is beneficial to addressing the issue of consumer interests being harmed in current plastic pollution control efforts. Thus, it both meets the needs of plastic pollution control and promotes ecological civilization construction while protecting consumer interests.

[0003] However, solely pursuing low costs is not advisable; the diverse applications of biodegradable plastic bags should also be considered. The required degradation cycle varies depending on the usage scenario of the biodegradable plastic bag product. For example, kitchen waste bags are expected to naturally break down in 5-10 days, while long-term packaging plastic bags such as shopping bags are expected to show no significant degradation within the product's shelf life of six months. Therefore, developing biodegradable plastic bag products with different degradation cycles is one of the important technologies for promoting biodegradable plastics. Controllable degradation cycle technology can develop a series of scenario-based products according to application needs, expanding the application space of biodegradable products and contributing to the full implementation of the national plastic ban and the construction of national ecological civilization.

[0004] To regulate the degradation rate of biodegradable materials, two main approaches can be identified. One approach involves blending, introducing readily (or unfavorably) degradable or readily (or unfavorably) water-absorbing components into the biodegradable material matrix to promote (or inhibit) degradation, thus regulating the degradation rate. This method is low-cost, simple to operate, and allows for significant rate adjustment, but the presence of phase interfaces causes a substantial decrease in mechanical properties, making it difficult to meet application requirements. The other approach involves copolymerizing readily (or unfavorably) hydrophilic or readily (or unfavorably) hydrolyzable monomers along the molecular backbone to promote (or inhibit) degradation, achieving a controllable degradation rate. This method is costly, complex to operate, and allows for limited rate adjustment. Furthermore, the introduction of more monomers can easily lead to premature termination of the polymerization reaction, making it difficult to increase the polymer molecular weight and consequently affecting mechanical and thermal properties, thus failing to meet application requirements. In summary, research into regulating the degradation rate of biodegradable materials often sacrifices significant thermal and mechanical properties, especially accelerating degradation. Therefore, achieving significant rate regulation while maintaining both low cost and performance remains a challenging problem. This patented invention provides a low-cost biodegradable plastic bag with an adjustable degradation rate, which can effectively overcome the above-mentioned problems. Summary of the Invention

[0005] To address the aforementioned problems, one objective of this invention is to provide a low-cost biodegradable plastic bag with an adjustable degradation rate. The biodegradable plastic bag provided by this invention has a highly adjustable degradation rate, meeting the degradation cycle requirements of biodegradable plastic bag products in different usage scenarios. Simultaneously, it is inexpensive, suitable for widespread market application, and exhibits superior rapid degradation performance compared to other biodegradable materials with the same mechanical properties.

[0006] Another object of the present invention is to provide a method for preparing a low-cost biodegradable plastic bag with an adjustable degradation rate as described above. The preparation method provided by the present invention has the advantages of simple operation and low cost.

[0007] To achieve the first objective mentioned above, the present invention adopts the following technical solution:

[0008] This invention discloses a low-cost biodegradable plastic bag with adjustable degradation rate, comprising the following raw materials in parts by weight:

[0009] 100 parts of biodegradable polymer;

[0010] Degradation rate regulator 5-30 parts;

[0011] 10-30 parts of the anti-corrosion agent.

[0012] In the above raw material formulation, the degradation rate of the material is controlled by adjusting the composition of the degradation rate regulator, resulting in a series of materials with different degradation cycles to meet the application requirements of different usage scenarios. Simultaneously, the introduction of a cost-reducing agent lowers the material cost, and the surfactant in the cost-reducing agent can surface-treat the cost-reducing filler, improving the compatibility between the filler and the matrix resin and enhancing the mechanical properties of the material. A drying agent reduces the impact of moisture in the filler on the material. Through the rational combination of the various raw material components, a class of degradable plastic bag products with low cost, controllable degradation rate, and good mechanical properties is ultimately obtained.

[0013] Furthermore, the degradation rate regulators include degradation inhibitors and degradation accelerators. Different combinations of degradation inhibitors and accelerators and their proportions in the raw material formulation affect the changes in the material's degradation cycle and mechanical properties. The degradation inhibitor is an amide-based crosslinking agent. Through the action of the amide crosslinking agent, it connects the biodegradable polymer molecular chains or the ends of the molecular chains, increasing the molecular weight and the interaction between the biodegradable polymer molecular chains. This slows down the degradation rate while significantly improving mechanical properties. It is worth noting that, unlike general crosslinking agents, the crosslinking agent containing amide bonds selected in this invention is itself hydrolyzable and degradable, although its hydrolysis rate is slower than that of ester bonds. The degradation accelerator is an alkaline compound. Through the reaction of the alkaline compound with water, it provides an alkaline environment. Although it sacrifices some mechanical properties, it significantly promotes the hydrolysis of polymer ester bonds, accelerating the degradation rate. In this invention, by adjusting the ratio of degradation inhibitors and degradation accelerators, a series of materials that balance mechanical properties and degradation performance are obtained.

[0014] Furthermore, in the degradation rate regulator, the mass ratio of the degradation inhibitor to the degradation accelerator is 1:0-20; exemplaryly, the mass ratio of the degradation inhibitor to the degradation accelerator can also be 1:0-5, 1:0-10, 1:0-15, 1:5-10, 1:5-15, 1:5-20, 1:10-15, 1:10-20, 1:15-20, etc., which can be adjusted by those skilled in the art according to application needs.

[0015] Furthermore, the degradation inhibitor includes, but is not limited to, one or a combination of at least two of N,N-methylenebisacrylamide, N-hydroxymethylacrylamide, and diacetoneacrylamide; preferably, the degradation promoter includes, but is not limited to, one or a combination of at least two of calcium oxide, magnesium oxide, barium oxide, potassium hydroxide, sodium hydroxide, and calcium hydroxide.

[0016] Furthermore, the combination of degradation rate regulators can be a combination of N,N-methylenebisacrylamide and calcium oxide, a combination of N,N-methylenebisacrylamide and calcium hydroxide, a combination of N-hydroxymethylacrylamide and barium oxide, a combination of N-hydroxymethylacrylamide and sodium hydroxide, a combination of diacetone acrylamide and magnesium oxide, a combination of diacetone acrylamide and potassium hydroxide, and so on.

[0017] Based on the types of degradation inhibitors and degradation promoters mentioned above, to facilitate formulation and use, the inventors further provide the following combination of degradation rate regulators, which have comparable effects:

[0018] (1) N,N-methylenebisacrylamide was selected as the inhibitor and calcium oxide was selected as the promoter. The mass ratio of N,N-methylenebisacrylamide to calcium oxide was 1:0-20.

[0019] (2) The inhibitor is N,N-methylenebisacrylamide, and the promoter is calcium hydroxide. The mass ratio of N,N-methylenebisacrylamide to calcium hydroxide is 1:0-20.

[0020] (3) N-hydroxymethylacrylamide is selected as the inhibitor and barium oxide is selected as the promoter. The mass ratio of N-hydroxymethylacrylamide to barium oxide is 1:0-20.

[0021] (4) N-hydroxymethylacrylamide is selected as the inhibitor and sodium hydroxide is selected as the promoter. The mass ratio of N-hydroxymethylacrylamide to sodium hydroxide is 1:0-20.

[0022] (5) The inhibitor is diacetone acrylamide and the promoter is magnesium oxide. The mass ratio of diacetone acrylamide to magnesium oxide is 1:0-20.

[0023] (6) The inhibitor is diacetone acrylamide and the promoter is potassium hydroxide. The mass ratio of diacetone acrylamide to potassium hydroxide is 1:0-20.

[0024] Furthermore, the mass ratio of N,N-methylenebisacrylamide to calcium oxide can also be 1:0-5, 1:0-10, 1:0-15, 1:5-10, 1:5-15, 1:5-20, 1:10-15, 1:10-20, 1:15-20, etc.

[0025] Furthermore, the mass ratio of N,N-methylenebisacrylamide to calcium hydroxide can also be 1:0-5, 1:0-10, 1:0-15, 1:5-10, 1:5-15, 1:5-20, 1:10-15, 1:10-20, 1:15-20, etc.

[0026] Furthermore, the mass ratio of N-hydroxymethylacrylamide to barium oxide can also be 1:0-5, 1:0-10, 1:0-15, 1:5-10, 1:5-15, 1:5-20, 1:10-15, 1:10-20, 1:15-20, etc.

[0027] Furthermore, the mass ratio of N-hydroxymethylacrylamide to sodium hydroxide can also be 1:0-5, 1:0-10, 1:0-15, 1:5-10, 1:5-15, 1:5-20, 1:10-15, 1:10-20, 1:15-20, etc.

[0028] Furthermore, the mass ratio of diacetone acrylamide to magnesium oxide can also be 1:0-5, 1:0-10, 1:0-15, 1:5-10, 1:5-15, 1:5-20, 1:10-15, 1:10-20, 1:15-20, etc.

[0029] Furthermore, the mass ratio of diacetone acrylamide to potassium hydroxide can also be 1:0-5, 1:0-10, 1:0-15, 1:5-10, 1:5-15, 1:5-20, 1:10-15, 1:10-20, 1:15-20, etc.

[0030] In one specific implementation, the mass ratio of the degradation inhibitor to the biodegradable polymer should not exceed 5:100. Excessive addition of the degradation inhibitor may lead to over-crosslinking, which in turn causes a decrease in mechanical properties.

[0031] Furthermore, the cost-reducing agent includes cost-reducing filler, surface modifier, and drying agent; wherein the cost-reducing filler is a common, commercially available, low-cost filler that can significantly reduce the cost of degradable materials. The solvent-based filler includes, but is not limited to, mica, talc, hydrotalcite-like materials, glass microspheres, calcium carbonate, zinc oxide, aluminum oxide, silicon dioxide, sodium silicate, zinc borate, barium sulfate, sodium sulfate, wollastonite, kaolin, chlorite, serpentine, corn starch, sweet potato starch, urea, ammonium bicarbonate, monoammonium phosphate, diammonium phosphate, potassium nitrate, ammonium nitrate, potassium sulfate, and potassium chloride, or a combination of at least two of these. The surface modifier can treat the solvent-based filler surface to improve the compatibility between the filler and the matrix resin, thereby improving the mechanical properties of the material. This includes, but is not limited to, oleamide, erucamide, calcium stearate, zinc stearate, stearamide, and N,N'-ethylenebis-stearamide, or a combination of at least two of these. The drying agent is used to reduce the influence of moisture in the filler on the mechanical properties of the material. This includes, but is not limited to, montmorillonite powder, calcium chloride, calcium sulfate, and magnesium sulfate, or a combination of at least two of these.

[0032] Furthermore, the mass ratio of the cost-reducing filler, surface modifier, and drying agent is 100:1.0-2.5:0.5-2.0; exemplaryly, the mass ratio of the cost-reducing filler, surface modifier, and drying agent can also be 100:1.0-2.5:1-2.0, 100:1.0-2.5:1.5-2.0, 100:1.0-2.5:1-1.5, or 100:1.5-2. 5:0.5-2.0, 100:2.0-2.5:0.5-2.0, 100:1.0-2:0.5-2.0, 100:1.0-1.5:0.5-2.0, 100:1.5-2.5:1-2.0, 100:1.5-2.5:1-1.5, 100:1.5-2.0:1-1.5, 100:1.5-2:0.5-1, etc.

[0033] Furthermore, the biodegradable polymer selected is a common commercially available biodegradable polyester, which is readily available, chemically stable, and has good mechanical properties; including but not limited to one or at least two combinations of polybutylene adipate / terephthalate (PBAT), polybutylene succinate (PBS), polybutylene adipate / terephthalate (PBSA), polylactic acid (PLA), and polycaprolactone (PCL); typical but non-limiting examples of such combinations include: combinations of polybutylene adipate / terephthalate and polybutylene succinate, combinations of polybutylene adipate / terephthalate and polylactic acid, and combinations of polybutylene adipate / terephthalate and polycaprolactone, etc.

[0034] To achieve the second objective mentioned above, the present invention adopts the following technical solution:

[0035] This invention discloses a method for preparing the above-mentioned biodegradable plastic bag, comprising the following steps:

[0036] S1: Preparation of cost-saving agent: The cost-saving filler, surface modifier and drying agent are thoroughly mixed in proportion to obtain a uniform cost-saving agent;

[0037] S2. Preparation of biodegradable plastic bags: The biodegradable polymer, degradation rate regulator and cost reducer are mixed evenly to obtain a premix, which is then melt-extruded and granulated to obtain a special modified material. Finally, the special modified material is blown into a film to obtain a biodegradable plastic bag with an adjustable degradation rate.

[0038] Furthermore, the mixing conditions described in step 2 are: low-speed stirring at room temperature for 5-10 minutes, and high-speed stirring at a temperature of 50-90℃ for 10-15 minutes; wherein the low-speed stirring rate is 50-100 rpm, and the high-speed stirring rate is 1200-1500 rpm.

[0039] Furthermore, the granulation temperature is 160-220℃; the blown film temperature is 120-180℃.

[0040] Based on the research of this invention, those skilled in the art can design various biodegradable materials with different functions and adjustable degradation rates, such as biodegradable mulch films, biodegradable lunch boxes, etc., all of which are within the scope of protection of this invention.

[0041] The beneficial effects of this invention are as follows:

[0042] This invention discloses a low-cost biodegradable plastic bag with adjustable degradation rate and its preparation method. Compared with the prior art, it has the following advantages:

[0043] (1) The biodegradable plastic bag of the present invention significantly reduces the cost of current biodegradable bags, breaks through the bottleneck of high price of current biodegradable plastic bags, and solves to a certain extent the problem of high price of biodegradable bags as a substitute for plastic pollution control, which harms the interests of consumers. It is cheaper and more suitable for promotion and application.

[0044] (2) The present invention can adjust the degradation rate of materials by adjusting the content and composition ratio of degradation rate regulators in the raw material formula, so that the materials can meet the degradation requirements of different use scenarios and match the appropriate use cycle.

[0045] (3) The degradation material provided by the present invention has superior rapid degradation performance compared with other degradation materials with the same mechanical properties. Detailed Implementation

[0046] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention. Any range described in the present invention includes endpoints, any values ​​between endpoints, and any sub-ranges formed by endpoints or any values ​​between endpoints.

[0047] The raw materials used in this embodiment are all known compounds, which can be obtained commercially or prepared according to methods known in the art. In the following embodiments, the physicochemical parameters involved were measured by the following instruments:

[0048] Example 1

[0049] A low-cost biodegradable plastic bag with an adjustable degradation rate, comprising the following raw materials in parts by weight:

[0050] 100 copies of PBAT / PLA;

[0051] 20 parts of Degradation Rate Regulator #1;

[0052] 20 portions of #1 anti-corrosion agent;

[0053] The mass ratio of PBAT / PLA is 80 / 20, and the No. 1 degradation rate regulator is composed of N,N-methylenebisacrylamide and calcium oxide in a mass ratio of 1:10.

[0054] Preparation of S1:1# cost-inducing agent: Add calcium carbonate, oleamide and calcium chloride in a mass ratio of 100:2:1 to a high-speed mixer and mix at 1000 rpm for 30 minutes.

[0055] S2: Preparation of biodegradable plastic bags:

[0056] 100 parts of PBAT / PLA, No. 1 degradation rate regulator, and No. 1 cost-saving agent were simultaneously added to a high-speed mixer. The mixture was first stirred at low speed of 90 rpm for 8 minutes at room temperature, and then stirred at high speed of 1300 rpm for 12 minutes at 80°C to prepare a premix. The premix was then granulated by twin-screw extrusion at a granulation temperature of 215°C to obtain a special modified material. Finally, the special modified material was blown into a film at a blowing temperature of 160°C to obtain a low-cost biodegradable plastic bag with an adjustable degradation rate.

[0057] Example 2

[0058] The only difference from Example 1 is that the degradation rate regulator #2 is composed of N,N-methylenebisacrylamide and calcium oxide in a mass ratio of 1:5.

[0059] Example 3

[0060] The only difference from Example 1 is that the degradation rate regulator #3 is composed of N,N-methylenebisacrylamide and calcium oxide in a mass ratio of 1:15.

[0061] Example 4

[0062] A low-cost biodegradable plastic bag with an adjustable degradation rate, comprising the following raw materials in parts by weight:

[0063] 100 copies of PBAT / PBS;

[0064] 5 parts of #4 degradation rate regulator;

[0065] 30 portions of #4 anti-corrosion agent;

[0066] The mass ratio of PBAT / PBS is 80 / 20, and the degradation rate regulator #4 is composed of N-hydroxymethylacrylamide.

[0067] Preparation of S1:4# cost-inducing agent: Add talc powder, calcium stearate and montmorillonite powder in a mass ratio of 100:2.5:2.0 to a high-speed mixer and mix at 1500 rpm for 30 minutes.

[0068] S2: Preparation of biodegradable plastic bags:

[0069] 100 parts of PBAT / PBS, degradation rate regulator #4, and cost-saving agent #4 were simultaneously added to a high-speed mixer. The mixture was first stirred at low speed of 100 rpm for 10 min at room temperature, and then stirred at high speed of 1200 rpm for 15 min at 90℃ to prepare a premix. The premix was then granulated by twin-screw extrusion at a granulation temperature of 180℃ to obtain a special modified material. Finally, the special modified material was blown into a film at a blowing temperature of 160℃ to obtain a low-cost biodegradable plastic bag with an adjustable degradation rate.

[0070] Comparative Example 1

[0071] The only difference from Example 1 is that no degradation rate regulator was added.

[0072] Comparative Example 2

[0073] The only difference compared to Example 1 is that the degradation rate regulator #1 does not contain calcium oxide.

[0074] Comparative Example 3

[0075] The only difference from Example 1 is that the degradation rate regulator #1 does not contain N,N-methylenebisacrylamide.

[0076] Comparative Example 4

[0077] Compared with Example 4, the only difference is that the No. 4 cost-inducing agent is replaced with a raw material of PBAT / PBS = 80 / 20.

[0078] Test case

[0079] The degradable plastic bags prepared in Examples 1-4 and Comparative Examples 1-4 were tested, and the results are shown in Table 1.

[0080] Mechanical property testing: The test was conducted according to GB / T 1040.3 2006. Type 2 specimens were used, with a length of 150 mm and a width of 15 mm. The test speed was 200 mm / min. Data were measured in both the longitudinal and transverse directions.

[0081] Composting degradation test: The composting degradation performance of all samples was tested in accordance with the national standard GB / T 19277.1-2011.

[0082] Table 1 Test data for Examples 1-4 and Comparative Examples 1-4

[0083]

[0084] Note: The percentage of cost reduction is the percentage of the price difference between an equal number of parts of biodegradable polymer and the cost-reducing agent relative to the total number of parts of biodegradable polymer, where the total number of parts of biodegradable polymer is the sum of 100 parts of biodegradable polymer and an equal number of parts of cost-reducing agent.

[0085] Analysis of the data in Table 1 yields the following results:

[0086] (1) Test data from Examples 1, 2, and 3 revealed that adjusting the ratio of degradation inhibitor to degradation promoter in the degradation rate regulator can control the mechanical properties of the degraded plastic bag and the composting degradation rate. Compared to Example 1, in Example 2, when the ratio of degradation promoter to degradation inhibitor was reduced by 50%, the mechanical properties improved slightly by about 5%, but the degradation rate decreased significantly, and the degradation cycle was extended by 150%. In Example 3, when the ratio of degradation promoter to degradation inhibitor was increased by 50%, the mechanical properties decreased slightly by about 10%, but the degradation rate increased significantly, and the degradation cycle was shortened by 67%. This indicates that within a certain range, the ratio of degradation inhibitor to degradation promoter in the degradation rate regulator can achieve the goal of significantly adjusting the degradation rate while maintaining basically stable mechanical properties.

[0087] (2) Through comparative tests of Example 1 and Comparative Example 1, it was found that the degradation rate regulator plays a key role in regulating the degradation rate of the material and ensuring mechanical properties.

[0088] (3) Comparative tests in Example 1 and Comparative Examples 1, 2, and 3 revealed that the degradation promoter and degradation inhibitor in the degradation rate regulator play a crucial role in regulating the degradation rate and mechanical properties of the material. The addition of the degradation inhibitor can significantly improve the mechanical properties of the material while slightly slowing down the degradation rate, while the addition of the degradation promoter can significantly accelerate the degradation rate but also significantly reduce the mechanical properties. Therefore, the degradation inhibitor is an essential component in this invention, which can compensate for the loss of mechanical properties caused by the addition of degradation promoters and cost-inducing agents.

[0089] (4) Further comparison of the schemes of Example 1 and Comparative Example 2 revealed that adding too much degradation inhibitor resulted in no significant improvement in tensile strength, while the elongation at break decreased significantly. Therefore, the content of degradation inhibitor relative to biodegradable polymer was limited in this patent.

[0090] (5) Through comparative tests of Example 4 and Comparative Example 4, it was found that the cost-reducing agent can significantly reduce the cost of materials and has a great effect on market promotion and application.

[0091] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A low-cost biodegradable plastic bag with adjustable degradation rate, characterized in that, The raw materials include the following parts by weight: 100 parts of biodegradable polymer; Degradation rate regulator 5-30 parts; 10-30 parts of the cost-effective agent; The degradation rate regulator includes degradation inhibitors and degradation promoters; The inhibitor is selected from one or a combination of at least two of N,N-methylenebisacrylamide, N-hydroxymethylacrylamide, and diacetone acrylamide; The reducing agent is selected from one or a combination of at least two of the following: calcium oxide, magnesium oxide, barium oxide, potassium hydroxide, sodium hydroxide, and calcium hydroxide.

2. The biodegradable plastic bag according to claim 1, characterized in that, In the degradation rate regulator, the mass ratio of the degradation inhibitor to the degradation promoter is 1:5-20.

3. The biodegradable plastic bag according to claim 2, characterized in that, The mass ratio of N,N-methylenebisacrylamide to calcium oxide is 1:5-20.

4. The biodegradable plastic bag according to claim 2, characterized in that, The mass ratio of N,N-methylenebisacrylamide to calcium hydroxide is 1:5-20.

5. The biodegradable plastic bag according to claim 2, characterized in that, The mass ratio of N-hydroxymethylacrylamide to barium oxide is 1:5-20.

6. The biodegradable plastic bag according to claim 2, characterized in that, The mass ratio of N-hydroxymethylacrylamide to sodium hydroxide is 1:5-20.

7. The biodegradable plastic bag according to claim 2, characterized in that, The mass ratio of diacetone acrylamide to magnesium oxide is 1:5-20.

8. The biodegradable plastic bag according to claim 2, characterized in that, The mass ratio of diacetone acrylamide to potassium hydroxide is 1:5-20.

9. The biodegradable plastic bag according to claim 2, characterized in that, The mass ratio of the inhibitor to the biodegradable polymer does not exceed 5:

100.

10. The biodegradable plastic bag according to claim 1, characterized in that, The cost-reducing agent includes cost-reducing filler, surface modifier, and drying agent.

11. The biodegradable plastic bag according to claim 10, characterized in that, The solvent-absorbing filler is selected from one or a combination of at least two of the following: mica, talc, hydrotalcite, glass microspheres, calcium carbonate, zinc oxide, aluminum oxide, silicon dioxide, sodium silicate, zinc borate, barium sulfate, sodium sulfate, wollastonite, kaolin, chlorite, serpentine, corn starch, sweet potato starch, urea, ammonium bicarbonate, monoammonium phosphate, diammonium phosphate, potassium nitrate, ammonium nitrate, potassium sulfate, and potassium chloride.

12. The biodegradable plastic bag according to claim 10, characterized in that, The surface modifier is selected from one or a combination of at least two of oleamide, erucamide, calcium stearate, zinc stearate, stearamide, and N,N'-ethylene bis-stearamide.

13. The biodegradable plastic bag according to claim 10, characterized in that, The drying agent is selected from one or a combination of at least two of montmorillonite powder, calcium chloride, calcium sulfate, and magnesium sulfate.

14. The biodegradable plastic bag according to claim 10, characterized in that, The mass ratio of the cost-effective filler, surface modifier, and drying agent is 100:1.0-2.5:0.5-2.

0.

15. The biodegradable plastic bag according to claim 10, characterized in that, The mass ratio of the cost-effective filler, surface modifier, and drying agent is 100:1.0-2.5:1.5-2.

0.

16. The biodegradable plastic bag according to claim 10, characterized in that, The mass ratio of the cost-effective filler, surface modifier, and drying agent is 100:1.5-2.5:0.5-2.

0.

17. The biodegradable plastic bag according to claim 10, characterized in that, The mass ratio of the cost-effective filler, surface modifier, and drying agent is 100:1.5-2:0.5-1.

18. The biodegradable plastic bag according to claim 10, characterized in that, The mass ratio of the cost-effective filler, surface modifier, and drying agent is 100:1.5-2.0:1-1.

5.

19. The biodegradable plastic bag according to claim 1, characterized in that, The biodegradable polymer is selected from one or a combination of at least two of polybutylene adipate / terephthalate, polybutylene succinate, polybutylene adipate / dibutyl succinate, polylactic acid, and polycaprolactone.

20. A method for preparing a biodegradable plastic bag as described in any one of claims 1-19, characterized in that, Includes the following steps: S1: Preparation of cost-saving agent: The cost-saving filler, surface modifier and drying agent are thoroughly mixed in proportion to obtain a uniform cost-saving agent; S2. Preparation of biodegradable plastic bags: The biodegradable polymer, degradation rate regulator and cost reducer are mixed evenly to obtain a premix, which is then melt-extruded and granulated to obtain a special modified material. Finally, the special modified material is blown into a film to obtain a biodegradable plastic bag with an adjustable degradation rate.

21. The preparation method according to claim 20, characterized in that, The mixing conditions described in step 2 are: low-speed stirring at room temperature for 5-10 minutes, and high-speed stirring at a temperature of 50-90℃ for 10-15 minutes; wherein the low-speed stirring rate is 50-100 rpm and the high-speed stirring rate is 1200-1500 rpm.

22. The preparation method according to claim 20, characterized in that, The granulation temperature is 160-220℃; the blown film temperature is 120-180℃.

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