A biodegradable plastic and a method for producing the same

Abstract

This paper discloses a biodegradable plastic and its preparation method, specifically involving the combination of carbon nanotubes, cellulose, and the traditional synthetic plastic polybutylene succinate (PBS). Unlike typical starch-based biodegradable plastics, this invention uses abundant, inexpensive, and renewable corn stalks as raw material to prepare carbon nanotubes with high mechanical strength. The combination of cellulose and PBS improves the plastic's impact resistance, while the high-mechanical-strength carbon nanotubes further synergize with cellulose, enhancing the plastic's mechanical properties while increasing its heat resistance.

Description

Technical Field

[0001] This invention relates to plastic preparation and processing technology, and mainly to a biodegradable plastic, particularly a biodegradable plastic and its preparation method. Background Technology

[0002] Plastics, due to their unique and superior properties, are widely used in agricultural production and daily life, becoming one of the world's four pillar materials. However, the "white pollution" caused by the non-degradability of traditional plastics is becoming increasingly serious, leading researchers to focus on biodegradable plastics. Among them, synthetic biodegradable resins such as polylactic acid (PLA), polybutylene succinate (PBS), and polycaprolactone (PCL) have strong mechanical properties, but their poor heat resistance and high cost prevent large-scale promotion. Based on this, this invention combines carbon nanotubes prepared from corn stalks with cellulose and PBS. In addition to improving the heat resistance of PBS, the carbon nanotubes also work synergistically with cellulose to further enhance the impact resistance of the plastic. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a biodegradable plastic and its preparation method, thus solving the problems mentioned in the background. This invention uses corn stalks as raw material to extract cellulose and lignin. Through modification of the cellulose, the binding force between cellulose and polybutylene succinate (PBS) is improved, thereby enhancing the impact resistance of the plastic through compositing with PBS. Carbon nanotubes are then prepared from lignin and composited with cellulose and PBS. Due to the inherent properties of carbon nanotubes, they can further synergistically enhance the impact resistance of PBS while improving the heat resistance of the material.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] S1. After crushing the corn stalks in a universal grinder, pass them through a 50-150 mesh sieve. Add the sieved material to a Soxhlet extractor at a ratio of 1:30 or 1:35 (g / mL). -1 Add glacial acetic acid to the solution and stir thoroughly for 1.5-2.5 hours. Heat the solution to boiling and react for 3-6 hours. After the solution cools to room temperature, wash with preheated glacial acetic acid and filter. Collect the filtrate and wash the filter residue several times with deionized water. The resulting filter residue is cellulose, which should be dried for later use.

[0006] S2. Modification of cellulose: Weigh 8-10g of glutaric anhydride and add it to a round-bottom flask. After it is fully melted, add 10mL of concentrated sulfuric acid as a catalyst and add 3-5g of the cellulose prepared in step S1. Stir well and react for 3-5h. Then wash the sample after reaction with anhydrous ethanol and filter it. Then wash the sample with deionized water until it is neutral and dry it in an oven to obtain modified cellulose.

[0007] S3. Place the filtrate obtained in step S1 into a distillation apparatus for distillation. After all the glacial acetic acid is evaporated to dryness, add a large amount of deionized water to the distillation apparatus to precipitate lignin and filter it. The filtrate obtained is a hemicellulose hydrolysate, and the filter residue obtained is lignin. Dry the lignin for later use.

[0008] S4. Weigh 6-10 g of the lignin prepared in step S3, dissolve it in 20-100 mL of glacial acetic acid, sonicate for 3-10 min to fully dissolve the lignin, and then filter it using a vacuum filtration device to remove undissolved lignin, obtaining a lignin-containing glacial acetic acid solution. Immerse the anodic aluminum oxide template (AAO) in a petri dish containing the lignin-containing glacial acetic acid solution for 2 h. Place the petri dish in a vacuum oven at 50-80℃. After the solvent has completely evaporated, remove the AAO template and place it in a porcelain boat. Using argon gas as a protective atmosphere, heat it to 500-1000℃ at a rate of 8℃ / min and hold for 10 min. After the resistance furnace temperature drops to room temperature, remove the template and immerse it in a saturated sodium hydroxide solution until the template is completely dissolved. Filter it using a microporous membrane and rinse the filtrate until neutral. Dry it to obtain black carbon nanotubes.

[0009] S5. Mix the dried polybutylene succinate (PBS), the modified cellulose prepared in step S2, and the carbon nanotubes prepared in step S4 in a plastic cup at a mass ratio of 6:4:0.3. Set the upper and lower chamber temperatures of the twin-screw extruder to 150-180℃ and the screw speed to 20-40 rpm. -1 The injection molding machine uses a mold temperature of 40-80℃ and a barrel temperature of 140-190℃ to prepare dumbbell-shaped biodegradable plastic samples.

[0010] Preferably, in step S1, the ratio of glacial acetic acid to corn straw in liquid form is 1:30 (g / mL). -1 The reaction time after heating to boiling is 2.5 hours.

[0011] Preferably, the mass of glutaric anhydride in step S2 is 10g.

[0012] Preferably, the sonication time of cellulose in glacial acetic acid in step S4 is 5 minutes.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The biodegradable plastic prepared by this invention is different from traditional plastics and is a sustainable and environmentally friendly material.

[0015] 2. The combination of modified cellulose and PBS in this invention can improve the impact resistance of the material to a certain extent.

[0016] 3. The addition of carbon nanotubes in this invention not only improves the heat resistance of the material, but also works synergistically with cellulose to further enhance the impact resistance of the material. Attached Figure Description

[0017] Figure 1 This is a scanning electron microscope image of the modified cellulose in Example 1 of the present invention.

[0018] Figure 2 This is a scanning electron micrograph of cellulose in Comparative Example 1 of the present invention.

[0019] Figure 3 This is a contact angle test of modified cellulose and distilled water in Example 2 of the present invention.

[0020] Figure 4 This is a test of the contact angle between cellulose and distilled water in Comparative Example 2 of the present invention.

[0021] Figure 5 Thermogravimetric curves of the samples prepared in Example 3, Comparative Example 1, and Comparative Examples 3 and 4 of this invention.

[0022] Figure 6 The image shows the impact resistance of the samples prepared in Example 3 and Comparative Examples 2-4 of this invention. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0024] Example 1

[0025] S1. Corn stalk raw material is pulverized in a universal pulverizer and then passed through a 100-mesh sieve. The sieved raw material is then added to a Soxhlet extractor at a ratio of 1:30 (g / mL). -1Add glacial acetic acid to the solution and stir thoroughly for 1.5 hours. Heat the solution to boiling and react for 4 hours. After the solution cools to room temperature, wash with preheated glacial acetic acid and filter. Collect the filtrate and wash the filter residue several times with deionized water. The resulting filter residue is cellulose, which is then dried for later use.

[0026] S2. Modification of cellulose: Weigh 10g of glutaric anhydride and add it to a round-bottom flask. After it is fully melted, add 10mL of concentrated sulfuric acid as a catalyst and add 3g of cellulose prepared in step S1. Stir well and react for 5h. Then wash and filter the sample after reaction with anhydrous ethanol, and then wash the sample with deionized water until neutral. Place it in an oven to dry and obtain modified cellulose.

[0027] S3. Place the filtrate obtained in step S1 into a distillation apparatus for distillation. After all the glacial acetic acid is evaporated to dryness, add a large amount of deionized water to the distillation apparatus to precipitate lignin and filter it. The filtrate obtained is a hemicellulose hydrolysate, and the filter residue obtained is lignin. Dry the lignin for later use.

[0028] S4. Weigh 9g of the lignin prepared in step S3, dissolve it in 90mL of glacial acetic acid, sonicate for 8min to fully dissolve the lignin, and then filter it using a vacuum filtration device to remove undissolved lignin, obtaining a lignin-containing glacial acetic acid solution. Immerse the anodic aluminum oxide template (AAO) in a petri dish containing the lignin-containing glacial acetic acid solution for 2h. Place the petri dish in a vacuum oven at 70℃. After the solvent has completely evaporated, remove the AAO template and place it in a porcelain boat. Using argon gas as a protective atmosphere, heat it to 800℃ at a rate of 8℃ / min and hold for 10min. After the resistance furnace temperature drops to room temperature, remove the template and immerse it in a saturated sodium hydroxide solution until the template is completely dissolved. Filter the solution using a microporous membrane and rinse the filtrate until neutral. Dry the solution to obtain black carbon nanotubes.

[0029] S5. Mix the dried polybutylene succinate (PBS), the modified cellulose prepared in step S2, and the carbon nanotubes prepared in step S4 in a plastic cup at a mass ratio of 6:4:0.3. Set the upper and lower chamber temperatures of the twin-screw extruder to 150℃ and the screw speed to 40 rpm. -1 The injection molding machine has a mold temperature of 80℃ and a barrel temperature of 170℃, which are used to prepare dumbbell-shaped biodegradable plastic samples.

[0030] Comparative Example 1: Except for replacing the modified cellulose prepared in step S2 with the cellulose prepared in step S1 in step S5, all other steps are the same as in Example 1.

[0031] Figure 1 and 2The images show scanning electron micrographs of the cellulose and modified cellulose used in Comparative Example 1 and Example 1 of this invention, respectively. As can be seen from the figures, the cell wall microfibrils of Comparative Example 1 have clear surface textures, tight intercellular and interlayer bonding, and a relatively intact structure. The modified cellulose of Example 1 is fibrous, with a rough surface and cracks. These cracks facilitate better embedding of cellulose in the polymer, improve the interfacial adhesion between cellulose and the matrix, and enhance the performance of the composite material.

[0032] Example 2

[0033] S1. Corn stalk raw material is pulverized in a universal pulverizer and then passed through a 50-mesh sieve. The sieved raw material is then added to a Soxhlet extractor at a ratio of 1:35 (g / mL). -1 Add glacial acetic acid to the solution and stir thoroughly for 2.5 hours. Heat the solution to boiling and react for 6 hours. After the solution cools to room temperature, wash with preheated glacial acetic acid and filter. Collect the filtrate and wash the filter residue several times with deionized water. The resulting filter residue is cellulose, which is then dried for later use.

[0034] S2. Modification of cellulose: Weigh 8g of glutaric anhydride and add it to a round-bottom flask. After it is fully melted, add 10mL of concentrated sulfuric acid as a catalyst and add 5g of cellulose prepared in step S1. Stir well and react for 5h. Then wash and filter the sample after reaction with anhydrous ethanol, and then wash the sample with deionized water until neutral. Place it in an oven to dry and obtain modified cellulose.

[0035] S3. Place the filtrate obtained in step S1 into a distillation apparatus for distillation. After all the glacial acetic acid is evaporated to dryness, add a large amount of deionized water to the distillation apparatus to precipitate lignin and filter it. The filtrate obtained is a hemicellulose hydrolysate, and the filter residue obtained is lignin. Dry the lignin for later use.

[0036] S4. Weigh 10g of the lignin prepared in step S3, dissolve it in 80mL of glacial acetic acid, sonicate for 7min to fully dissolve the lignin, and then filter it using a vacuum filtration device to remove undissolved lignin, obtaining a lignin-containing glacial acetic acid solution. Immerse the anodic aluminum oxide template (AAO) in a petri dish containing the lignin-containing glacial acetic acid solution for 2h. Place the petri dish in a vacuum oven at 70℃. After the solvent has completely evaporated, remove the AAO template and place it in a porcelain boat. Using argon gas as a protective atmosphere, heat it to 1000℃ at a rate of 8℃ / min and hold for 10min. After the resistance furnace temperature drops to room temperature, remove the template and immerse it in a saturated sodium hydroxide solution until the template is completely dissolved. Filter the solution using a microporous membrane and rinse the filtrate until neutral. Dry the solution to obtain black carbon nanotubes.

[0037] S5. Mix the dried polybutylene succinate (PBS), the modified cellulose prepared in step S2, and the carbon nanotubes prepared in step S4 in a plastic cup at a mass ratio of 6:4:0.3. Set the upper and lower chamber temperatures of the twin-screw extruder to 180℃ and the screw speed to 40 rpm. -1 The injection molding machine has a mold temperature of 60℃ and a barrel temperature of 180℃, and dumbbell-shaped biodegradable plastic samples are prepared.

[0038] Comparative Example 2: In step S5, except that the cellulose prepared in step S1 is used instead of the modified cellulose prepared in step S2, all other steps are the same as in Example 2.

[0039] Figure 3 and 4 The contact angles of modified cellulose and cellulose with distilled water in Examples 2 and 2 of this invention were tested, respectively. The contact angles of modified cellulose and cellulose with water were 90.2° and 62.3°, respectively. The contact angle of esterified cellulose with distilled water increased significantly, indicating that the number of hydroxyl groups in the modified cellulose was reduced, resulting in decreased hydrophilicity. This is beneficial for effective interfacial adhesion between modified cellulose and PBS, improving the mechanical properties of the composite material.

[0040] Example 3

[0041] S1. Corn stalk raw material is pulverized in a universal pulverizer and then passed through a 150-mesh sieve. The sieved raw material is then added to a Soxhlet extractor at a ratio of 1:30 (g / mL). -1 Add glacial acetic acid to the solution and stir thoroughly for 2 hours. Heat the solution to boiling and react for 4 hours. After the solution cools to room temperature, wash with preheated glacial acetic acid and filter. Collect the filtrate and wash the filter residue several times with deionized water. The resulting filter residue is cellulose, which is then dried for later use.

[0042] S2. Modification of cellulose: Weigh 9g of glutaric anhydride and add it to a round-bottom flask. After it is fully melted, add 10mL of concentrated sulfuric acid as a catalyst and add 3g of cellulose prepared in step S1. Stir well and react for 3h. Then wash the sample after reaction with anhydrous ethanol and filter it. Then wash the sample with deionized water until it is neutral and put it in an oven to dry to obtain modified cellulose.

[0043] S3. Place the filtrate obtained in step S1 into a distillation apparatus for distillation. After all the glacial acetic acid is evaporated to dryness, add a large amount of deionized water to the distillation apparatus to precipitate lignin and filter it. The filtrate obtained is a hemicellulose hydrolysate, and the filter residue obtained is lignin. Dry the lignin for later use.

[0044] S4. Weigh 9g of the lignin prepared in step S3, dissolve it in 80mL of glacial acetic acid, sonicate for 6min to fully dissolve the lignin, and then filter it using a vacuum filtration device to remove undissolved lignin, obtaining a lignin-containing glacial acetic acid solution. Immerse the anodic aluminum oxide template (AAO) in a petri dish containing the lignin-containing glacial acetic acid solution for 2h. Place the petri dish in a vacuum oven at 80℃. After the solvent has completely evaporated, remove the AAO template and place it in a porcelain boat. Using argon gas as a protective atmosphere, heat it to 800℃ at a rate of 8℃ / min and hold for 10min. After the resistance furnace temperature drops to room temperature, remove the template and immerse it in a saturated sodium hydroxide solution until the template is completely dissolved. Filter the solution using a microporous membrane and rinse the filtrate until neutral. Dry the solution to obtain black carbon nanotubes.

[0045] S5. Mix the dried polybutylene succinate (PBS), the modified cellulose prepared in step S2, and the carbon nanotubes prepared in step S4 in a plastic cup at a mass ratio of 6:4:0.3. Set the upper and lower chamber temperatures of the twin-screw extruder to 160℃ and the screw speed to 40 rpm. -1 The injection molding machine has a mold temperature of 70℃ and a barrel temperature of 180℃, and dumbbell-shaped biodegradable plastic samples are prepared.

[0046] Comparative Example 3: In step S5, except that the cellulose prepared in step S1 is used instead of the modified cellulose prepared in step S2, all other steps are the same as in Example 2.

[0047] Comparative Example 3: In step S5, all steps are the same as in Example 3 except that the carbon nanotubes prepared in step S4 are not added.

[0048] Comparative Example 4: In step S5, all steps are the same as in Example 3 except that modified cellulose is not added.

[0049] Figure 5 The thermogravimetric analysis (TGA) curves of the samples prepared in Examples 3, 1, 3, and 4 of this invention are shown in the figure. As can be seen from the figure, the crystallization properties of PBS are improved to a certain extent with the addition of cellulose, modified cellulose, and carbon nanotubes. Compared with unmodified cellulose, modified cellulose with small pores on its surface promotes the heterogeneous nucleation process of PBS more effectively, while the addition of carbon nanotubes further synergistically enhances its heat resistance with modified cellulose. To test the impact resistance of the samples prepared in this invention, the samples were cut into strips of 80mm × 2mm × 10mm with a notch width of 2mm, and notched cantilever beam impact tests were performed according to standard GB / T 1843-1996. Figure 6The figures show the impact resistance of the samples prepared in Example 3 and Comparative Examples 2-4 of this invention. As can be seen from the figures, cellulose has a limited effect on improving the impact resistance of PBS, because cellulose has poor hydrophobicity and cannot fuse well with PBS. After modification, the hydrophilicity of cellulose decreases, and its fusion with PBS can significantly improve the impact resistance of the material. Carbon nanotubes themselves have high mechanical strength. During the fusion process with PBS, in addition to providing heterogeneous nucleation opportunities for PBS, they can also synergistically enhance the impact resistance of the composite material with modified cellulose, further improving the impact resistance of the composite material.

[0050] In summary, the biodegradable plastic prepared by this invention uses corn stalks as raw material, from which cellulose and lignin (the source of carbon nanotubes) are extracted. The hydrophobicity of cellulose is significantly improved after modification, allowing it to combine with PBS to enhance the material's impact resistance. The added carbon nanotubes not only improve the heat resistance of the modified cellulose-PBS but also synergistically enhance the material's impact resistance. This method provides a new perspective on composite material technology and a novel approach to the preparation of biodegradable plastics.

[0051] Finally, it should be noted that the above-described embodiments are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be pointed out that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing biodegradable plastic: characterized in that: Specifically, the following steps are included: S1. After crushing the corn stalks in a universal grinder, pass them through a 50-150 mesh sieve. Add the sieved material to a Soxhlet extractor at a ratio of 1:30 or 1:35 g / mL. -1 Add glacial acetic acid to the solution and stir thoroughly for 1.5-2.5 hours; heat the solution to boiling and react for 3-6 hours; when the solution cools to room temperature, rinse with preheated glacial acetic acid and filter; collect the filtrate and wash the filter residue several times with deionized water. The resulting filter residue is cellulose, which is then dried for later use. S2. Modification of cellulose: Weigh 8-10g of glutaric anhydride and add it to a round-bottom flask. After it is fully melted, add 10mL of concentrated sulfuric acid as a catalyst and add 3-5g of the cellulose prepared in step S1. Stir well and react for 3-5h. After that, wash the sample with anhydrous ethanol and filter it. Then wash the sample with deionized water until it is neutral and dry it in an oven to obtain modified cellulose. S3. Place the filtrate obtained in step S1 into a distillation apparatus for distillation. After all the glacial acetic acid is evaporated to dryness, add a large amount of deionized water to the distillation apparatus to precipitate lignin and filter it. The filtrate obtained is a hemicellulose hydrolysate, and the filter residue obtained is lignin. Dry the lignin for later use. S4. Weigh 6-10g of the lignin prepared in step S3, dissolve it in 20-100mL of glacial acetic acid, sonicate for 3-10 min to fully dissolve the lignin, then filter it using a vacuum filtration device to remove undissolved lignin, and obtain a glacial acetic acid solution containing lignin. Immerse the anode aluminum oxide template in a petri dish containing the lignin glacial acetic acid solution for 2 hours. Place the petri dish in a vacuum oven at 50-80℃. After the solvent has completely evaporated, remove the AAO template and place it in a porcelain boat. Using argon gas as a protective device, heat it to 500-1000℃ at a rate of 8℃ / min and hold for 10 min. After the resistance furnace temperature drops to room temperature, the template is removed and immersed in a saturated sodium hydroxide solution until the template is completely dissolved; the template is then filtered using a microporous membrane and the filtrate is rinsed until neutral, and dried to obtain black carbon nanotubes; S5. Add the dried polybutylene succinate, the modified cellulose prepared in step S2, and the carbon nanotubes prepared in step S4 to a plastic cup at a mass ratio of 6:4:0.3 and mix. Set the upper and lower chamber temperatures of the twin-screw extruder to 150-180℃ and the screw speed to 20-40 rpm. -1 The injection molding machine uses a mold temperature of 40-80℃ and a barrel temperature of 140-190℃ to prepare dumbbell-shaped biodegradable plastic samples.

2. The method for preparing a biodegradable plastic according to claim 1, characterized in that: In step S1, the stirring time is 1.5 hours, and the corn stalk raw material is crushed in a universal crusher and then passed through an 80-mesh sieve.

3. The method for preparing a biodegradable plastic according to claim 1, characterized in that: The stirring time for cellulose in step S2 is 3 hours.

4. The method for preparing a biodegradable plastic according to claim 3, characterized in that: In step S4, the mass of lignin is 6g and the mass of glacial acetic acid is 80mL.

5. The method for preparing a biodegradable plastic according to claim 3, characterized in that: In step S4, the mass of lignin is 8g and the mass of glacial acetic acid is 70mL.

6. The method for preparing a biodegradable plastic according to claim 4, characterized in that: The temperature of the vacuum oven in step S4 is 80°C, and the heating temperature of the anodized aluminum is 800°C.

7. The method for preparing a biodegradable plastic according to claim 5, characterized in that: The temperature of the vacuum oven in step S4 is 70°C, and the heating temperature of the anodized aluminum is 1000°C.

8. The method for preparing a biodegradable plastic according to claim 6, characterized in that: In step S5, the temperature of the upper and lower cavity plates is 150℃ and the screw speed is 30 r / min. -1 The mold temperature of the injection molding machine is 60℃ and the barrel temperature is 150℃.

9. A method for preparing a biodegradable plastic according to claim 7, characterized in that: In step S5, the temperature of the upper and lower cavity plates is 160℃ and the screw speed is 40 r / min. -1 The mold temperature of the injection molding machine is 80℃ and the barrel temperature is 170℃.

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