A biodegradable plastic bag and its preparation method

Abstract

This invention discloses a biodegradable plastic bag and its preparation method, belonging to the field of biodegradable plastic preparation technology. It comprises the following raw material components in parts by weight: 180-220 parts PBAT, 70-95 parts polylactic acid, 10-15 parts antioxidant, and 20-35 parts lignin-montmorillonite-sodium alginate composite. This invention specifically constructs the lignin-montmorillonite-sodium alginate composite. Through the combination of the lignin-montmorillonite-sodium alginate composite with the other components, not only can the degradation efficiency of the plastic bag be effectively improved, but its mechanical properties can also be enhanced.

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 products have advantages such as low price, light weight, durability, and good plasticity, making them widely used in industries such as construction, transportation, packaging, and agricultural production, with single-use plastic bags being the most common. However, they also have disadvantages such as extremely long degradation periods, difficulty in disposal, and a tendency to generate white pollution, thus polluting the environment. With increasing public awareness of environmental issues, the disposal of waste plastic bags has gradually attracted attention. The conventional method for disposing of waste plastic bags is landfill, but this method suffers from the problem of long-term non-degradability.

[0003] Therefore, biodegradable plastic bags have attracted much attention due to their advantages such as biodegradability, non-toxicity, and high recyclability. However, due to the inherent properties of polymers such as PBAT, currently prepared biodegradable plastic bags often suffer from insufficient mechanical properties. Summary of the Invention

[0004] To address the aforementioned shortcomings in the prior art, this invention provides a biodegradable plastic bag and a method for preparing the same.

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

[0006] A biodegradable plastic bag comprising the following raw material components in parts by weight:

[0007] 180-220 parts of PBAT, 70-95 parts of polylactic acid, 10-15 parts of antioxidant, and 20-35 parts of lignin-montmorillonite-sodium alginate complex.

[0008] Furthermore, it includes the following raw material components in parts by weight:

[0009] 180-200 parts of PBAT, 80-95 parts of polylactic acid, 10-15 parts of antioxidant, and 20-25 parts of lignin-montmorillonite-sodium alginate complex.

[0010] Furthermore, the preparation method of the lignin-montmorillonite-sodium alginate complex is as follows:

[0011] (1) Place alkali lignin and phenol in an alkaline solution and react at 60~80℃ for 1~3h. After the reaction is completed, adjust the pH of the system to acidic, filter and wash the filter cake to obtain phenolic lignin.

[0012] (2) Phenolic lignin and montmorillonite were mixed and ball-milled to obtain lignin-montmorillonite complex;

[0013] (3) Phenolic lignin was mixed with sodium alginate and then ball-milled to obtain lignin-sodium alginate complex;

[0014] (4) The lignin-montmorillonite complex and the lignin-sodium alginate complex were mixed and ball-milled to obtain the lignin-montmorillonite-sodium alginate complex.

[0015] This invention utilizes the added lignin-montmorillonite-sodium alginate complex

[0016] Montmorillonite can improve the gas barrier properties and stability of materials, but the strong van der Waals forces between its layers make it prone to aggregation, hindering its uniform dispersion in the matrix. Therefore, in preparing the lignin-montmorillonite-sodium alginate composite, this invention first reacts alkali lignin and phenol under alkaline conditions. This increases the number of reactive sites in lignin, allowing it to participate in more reactions in subsequent processes. The resulting phenolic lignin also contains a large number of phenolic hydroxyl groups, which weaken the van der Waals forces between montmorillonite layers, preventing aggregation. The introduction of numerous hydroxyl and carboxyl groups also increases the hydrophilicity of montmorillonite.

[0017] Furthermore, organic molecules such as PBAT contain ester bonds, which are prone to hydrolysis. The introduction of hydroxyl and carboxyl groups significantly enhances this process. Hydroxyl groups can form hydrogen bonds with adjacent ester bonds, weakening the stability of the CO bond, while simultaneously attracting water molecules closer to the ester bond, lowering the activation energy of the hydrolysis reaction, thus achieving the effect of "adsorbing water and weakening bond energy".

[0018] The carboxyl group is the H that dissociates. + H dissociated + It can attack the oxygen atoms in the ester bond, forming an unstable tetrahedral intermediate, accelerating the ester bond breakage into carboxylic acids and alcohols, thus playing the role of "acid catalysis-accelerated bond breaking". Through the cooperation of exogenous hydroxyl and carboxyl groups, the two can significantly improve the degradation efficiency of plastic bags.

[0019] This invention adds sodium alginate to construct a lignin-montmorillonite-sodium alginate composite, which further enhances the influence of lignin and montmorillonite on the mechanical properties of plastic bags and improves the lack of toughness in PBAT.

[0020] Furthermore, the mass ratio of alkali lignin, phenol, and alkaline solution is 5:1~3:9~13.

[0021] Furthermore, the mass ratio of alkali lignin, phenol, and alkaline solution is 5:1:13.

[0022] Furthermore, alkaline solutions are inorganic alkaline solutions, such as sodium hydroxide solution, potassium hydroxide solution, etc.

[0023] Furthermore, the mass ratio of phenolic lignin to montmorillonite is 1:3~5.

[0024] Furthermore, the mass ratio of phenolic lignin to sodium alginate is 1:2~4.

[0025] Furthermore, the mass ratio of the lignin-montmorillonite complex and the lignin-sodium alginate complex is 2~3:1.

[0026] Furthermore, the antioxidant is methylphenol, dimethylphenol, or ethylphenol.

[0027] A method for preparing the above-mentioned biodegradable plastic bag specifically includes:

[0028] The components are mixed evenly according to the formula, and then extruded and granulated to obtain a composite masterbatch. The composite masterbatch is then blown into a film and made into a bag to obtain the biodegradable plastic bag.

[0029] The beneficial effects of this invention are:

[0030] This invention, through the synergistic effect of its components, effectively improves the degradation efficiency of plastic bags and enhances their mechanical properties. Furthermore, the addition of the lignin-montmorillonite-sodium alginate complex eliminates the need for additional stabilizers or lubricants. Detailed Implementation

[0031] 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.

[0032] Example 1:

[0033] A biodegradable plastic bag comprising the following raw material components in parts by weight:

[0034] 220 parts of PBAT, 95 parts of polylactic acid, 15 parts of methylphenol, and 20 parts of lignin-montmorillonite-sodium alginate complex.

[0035] The preparation method of the lignin-montmorillonite-sodium alginate complex is as follows:

[0036] (1) Alkali lignin and phenol were placed in sodium hydroxide solution and reacted at 60°C for 1.5 h. After the reaction was completed, the pH of the system was adjusted to acidic, the filter cake was filtered and washed to obtain phenolic lignin. The mass ratio of alkali lignin, phenol and sodium hydroxide solution used was 5:1:13.

[0037] (2) Phenolic lignin and montmorillonite were mixed in a mass ratio of 1:3 and then ball-milled to obtain lignin-montmorillonite composite.

[0038] (3) Phenolic lignin and sodium alginate were mixed in a mass ratio of 1:2 and then ball-milled to obtain lignin-sodium alginate complex.

[0039] (4) The lignin-montmorillonite complex and the lignin-sodium alginate complex were mixed in a mass ratio of 3:1 and then ball-milled to obtain the lignin-montmorillonite-sodium alginate complex.

[0040] The specific method for the above-mentioned biodegradable plastic bags is as follows:

[0041] The components are mixed evenly according to the formula, and then extruded and granulated to obtain a composite masterbatch. The composite masterbatch is then blown into a film and made into a bag to obtain the biodegradable plastic bag.

[0042] Example 2:

[0043] A biodegradable plastic bag comprising the following raw material components in parts by weight:

[0044] 180 parts of PBAT, 70 parts of polylactic acid, 10 parts of ethylphenol, and 20 parts of lignin-montmorillonite-sodium alginate complex.

[0045] The preparation method of the lignin-montmorillonite-sodium alginate complex is as follows:

[0046] (1) Alkali lignin and phenol were placed in sodium hydroxide solution and reacted at 80°C for 3 hours. After the reaction was completed, the pH of the system was adjusted to acidic. The filter cake was filtered and washed to obtain phenolic lignin. The mass ratio of alkali lignin, phenol and sodium hydroxide solution used was 5:3:9.

[0047] (2) Phenolic lignin and montmorillonite were mixed in a mass ratio of 1:5 and then ball-milled to obtain lignin-montmorillonite composite.

[0048] (3) Phenolic lignin and sodium alginate were mixed in a mass ratio of 1:4 and then ball-milled to obtain lignin-sodium alginate complex.

[0049] (4) The lignin-montmorillonite complex and the lignin-sodium alginate complex were mixed in a mass ratio of 2:1 and then ball-milled to obtain the lignin-montmorillonite-sodium alginate complex.

[0050] The specific method for the above-mentioned biodegradable plastic bags is as follows:

[0051] The components are mixed evenly according to the formula, and then extruded and granulated to obtain a composite masterbatch. The composite masterbatch is then blown into a film and made into a bag to obtain the biodegradable plastic bag.

[0052] Example 3:

[0053] A biodegradable plastic bag comprising the following raw material components in parts by weight:

[0054] 200 parts of PBAT, 80 parts of polylactic acid, 12 parts of methylphenol, and 25 parts of lignin-montmorillonite-sodium alginate complex.

[0055] The preparation method of the lignin-montmorillonite-sodium alginate complex is as follows:

[0056] (1) Alkali lignin and phenol were placed in sodium hydroxide solution and reacted at 75°C for 1 h. After the reaction was completed, the pH of the system was adjusted to acidic. The filter cake was filtered and washed to obtain phenolic lignin. The mass ratio of alkali lignin, phenol and sodium hydroxide solution used was 5:2:10.

[0057] (2) Phenolic lignin and montmorillonite were mixed in a mass ratio of 1:3.5 and then ball-milled to obtain lignin-montmorillonite composite.

[0058] (3) Phenolic lignin and sodium alginate were mixed in a mass ratio of 1:3 and then ball-milled to obtain lignin-sodium alginate complex.

[0059] (4) The lignin-montmorillonite complex and the lignin-sodium alginate complex were mixed in a mass ratio of 2:1 and then ball-milled to obtain the lignin-montmorillonite-sodium alginate complex.

[0060] The specific method for the above-mentioned biodegradable plastic bags is as follows:

[0061] The components are mixed evenly according to the formula, and then extruded and granulated to obtain a composite masterbatch. The composite masterbatch is then blown into a film and made into a bag to obtain the biodegradable plastic bag.

[0062] Comparative Example 1

[0063] The difference from Example 1 is that phenol was not used to treat the lignin, while the rest of the process remained the same as in Example 1.

[0064] Comparative Example 2

[0065] Compared with Example 1, the difference is that phenol was not used to treat lignin, and lignin, montmorillonite and sodium alginate were added as raw materials alone, while the rest of the process was the same as in Example 1.

[0066] Comparative Example 3

[0067] Compared with Example 1, the difference is that the lignin-montmorillonite-sodium alginate complex is missing, while the rest of the process is the same as in Example 1.

[0068] Comparative Example 4

[0069] Compared with Example 1, the difference is that sodium alginate is not used, the complex is a lignin-montmorillonite complex, and the rest of the process is the same as in Example 1.

[0070] Test case

[0071] The mechanical properties and degradation rates of the plastic bags prepared in Examples 1-3 and Comparative Examples 1-4 were tested, and the results are shown in Table 1. Specific testing details are as follows:

[0072] Tensile strength: The tensile strength of the plastic bags was tested in accordance with GB / T1040.

[0073] Elongation at break: The elongation at break of plastic bags is tested according to GB / T1040.

[0074] Biodegradation rate: The biodegradation rate of plastic bags at 90 days and 120 days was tested according to GB / T20197-2006.

[0075] Table 1. Performance test results of plastic bags

[0076]

[0077] According to the test results in Table 1, the plastic bags prepared by the schemes constructed in Examples 1-3 of this invention have significantly better degradation performance and mechanical properties than those of Comparative Examples 1-3. Comparative Example 4 lacks sodium alginate, which has a certain impact on the mechanical properties of the final plastic bag. However, since the complex formed by phenol-modified lignin and montmorillonite is still retained, it does not have a significant impact on the degradation efficiency of the plastic bag.

[0078] 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 biodegradable plastic bag, characterized in that, The raw material components include the following parts by weight: The mixture comprises 180-220 parts of PBAT, 70-95 parts of polylactic acid, 10-15 parts of antioxidant, and 20-35 parts of lignin-montmorillonite-sodium alginate complex; the preparation method of the lignin-montmorillonite-sodium alginate complex is as follows: (1) Place alkali lignin and phenol in an alkaline solution and react at 60~80℃ for 1~3h. After the reaction is completed, adjust the pH of the system to acidic, filter and wash the filter cake to obtain phenolic lignin. (2) Phenolic lignin and montmorillonite were mixed and ball-milled to obtain lignin-montmorillonite complex; (3) Phenolic lignin was mixed with sodium alginate and then ball-milled to obtain lignin-sodium alginate complex; (4) The lignin-montmorillonite complex and the lignin-sodium alginate complex were mixed and then ball-milled to obtain the lignin-montmorillonite-sodium alginate complex.

2. The biodegradable plastic bag according to claim 1, characterized in that, The raw material components include the following parts by weight: 180-200 parts of PBAT, 80-95 parts of polylactic acid, 10-15 parts of antioxidant, and 20-25 parts of lignin-montmorillonite-sodium alginate complex.

3. The biodegradable plastic bag according to claim 1, characterized in that, The mass ratio of alkali lignin, phenol, and alkaline solution is 5:1~3:9~13.

4. The biodegradable plastic bag according to claim 3, characterized in that, The mass ratio of alkali lignin, phenol, and alkaline solution is 5:1:

13.

5. The biodegradable plastic bag according to claim 1, characterized in that, The mass ratio of phenolic lignin to montmorillonite is 1:3~5.

6. The biodegradable plastic bag according to claim 1, characterized in that, The mass ratio of phenolic lignin to sodium alginate is 1:2~4.

7. The biodegradable plastic bag according to claim 1, characterized in that, The mass ratio of lignin-montmorillonite complex and lignin-sodium alginate complex is 2~3:

1.

8. The biodegradable plastic bag according to claim 1 or 2, characterized in that, The antioxidants are methylphenol, dimethylphenol, or ethylphenol.

9. A method for preparing the biodegradable plastic bag according to any one of claims 1 to 8, characterized in that, The components are mixed evenly according to the formula, and then extruded and granulated to obtain a composite masterbatch. The composite masterbatch is then blown into a film and made into a bag to obtain the biodegradable plastic bag.

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