Marine land full natural domain biodegradable plastic and method for preparing biodegradable plastic

Abstract

The invention discloses a marine land full-natural-domain biodegradable plastic and a method for preparing the biodegradable plastic, and relates to the technical field of biodegradable plastics. Polyhydroxyalkanoate, polylactic acid and poly (butylene succinate) are used as main matrixes of the material, modified alginate gel is innovatively introduced, and the biodegradable plastic is prepared. The gel has photo-thermal and ionic characteristics, and under the condition of land illumination, the photo-thermal effect of the quantum dots triggers the gel to shrink and release lipase to accelerate hydrolysis; in a marine environment, sodium ion replacement promotes gel to be disintegrated and continuously releases enzyme molecules, the gel, matrix resin, natural fibers and a plasticizer are subjected to twin-screw melt blending extrusion, and the biodegradable plastic is prepared. The technical problems of response lag, insufficient enzyme activity protection and low degradation efficiency of traditional biodegradable plastics in a complex natural environment are effectively solved, and self-adaptive efficient degradation in sea and land environments is realized.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable plastics technology, specifically referring to a biodegradable plastic that can be used in all natural environments, including marine and terrestrial environments, and a method for preparing the biodegradable plastic. Background Technology

[0002] With the global plastic pollution problem becoming increasingly serious, the development of plastic materials that can be efficiently biodegraded in all natural environments, both marine and terrestrial, has become an important research direction in the fields of environmental science and materials engineering. Current technologies are mainly based on polyester-based bio-based polymers, such as combinations of polyhydroxyalkanoates, polylactic acid, and polybutylene succinate. Although these materials show a certain degree of degradability under ideal laboratory conditions, they face significant bottlenecks in complex and variable natural environments: in terrestrial applications, fluctuations in light intensity and temperature often lead to uneven degradation rates, making it impossible to achieve a controllable response; while in marine environments, high salinity, low temperature, and differences in microbial activity further inhibit the degradation process, resulting in a longer cycle.

[0003] The core challenge lies in protecting the activity of bio-enzymes: degrading enzymes introduced by traditional methods are easily deactivated during the high-temperature extrusion process of plastic processing, losing their catalytic function and limiting the practical application of materials. In addition, enzyme molecules are difficult to diffuse in the plastic matrix, and ineffective distribution reduces the efficiency of interaction with polymer ester bonds, greatly reducing catalytic efficiency. At the same time, the dense structure of plastic reduces the specific surface area, hindering the attachment of enzyme molecules and microorganisms. The process from initial fragmentation to complete mineralization is time-consuming. These challenges, including poor stability, insufficient environmental adaptability, and low degradation efficiency, restrict the development and application of biodegradable plastics in all natural environments. Therefore, it is urgent to develop a new material system that can adapt to both marine and terrestrial environments, intelligently regulate the release of bioactive substances, and integrate physical and biological synergistic degradation mechanisms, which has become a key direction for breaking through existing technological barriers. Summary of the Invention

[0004] In view of the above situation and to overcome the shortcomings of the prior art, the present invention provides a marine and terrestrial biodegradable plastic and a method for preparing the biodegradable plastic, which effectively solves the problems of insufficient environmental adaptability and low degradation efficiency of biodegradable plastics on the market.

[0005] The technical solution adopted in this invention is as follows: This invention proposes a biodegradable plastic for all natural marine and terrestrial applications and a method for preparing the biodegradable plastic, comprising the following raw materials in parts by weight: 20-30 parts of polyhydroxyalkanoate (PHA); 15-25 parts of polylactic acid (PLA); 10-20 parts of polybutylene succinate (PBAT); 5-10 parts of chitosan; 8-12 parts of banana fiber; 5-8 parts of tetrameric castor oil ester; and 3-5 parts of modified alginate gel. The preparation method of the modified alginate gel includes the following steps: Under nitrogen protection, sodium alginate was dissolved in deionized water to form a homogeneous solution. After cooling to 4°C in an ice bath, N-isopropylacrylamide (NIPAM) was added, and a catalyst was added for isothermal reaction. The solution was purified by ethanol precipitation and freeze-dried to obtain the backbone. Under light-protected conditions, the purified low-temperature lipase was loaded onto the polymer backbone. CdSe quantum dots were added to the solution containing the polymer backbone and ultrasonically dispersed to form a mixture. Under low-temperature conditions, the mixture was added to CaCl2 solution and stirred. After the reaction was completed, the mixture was collected by centrifugation, washed with PBS containing 0.1M NaCl, and freeze-dried to obtain the modified alginate gel product.

[0006] Furthermore, the molar ratio of sodium alginate to NIPAM is 1:3.

[0007] Furthermore, the catalyst is one or more of 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS).

[0008] Furthermore, the isothermal reaction is carried out at a temperature of 55-65°C for 2 hours with stirring.

[0009] Furthermore, the low-temperature lipase is loaded onto the polymer backbone. The graft copolymer is dissolved in PBS buffer at 4°C to prepare a 3wt% solution, and then the low-temperature lipase is added. The solution is then magnetically stirred at 4°C for 2 hours to avoid foaming, allowing the enzyme to be adsorbed onto the PNIPAM chain through electrostatic interaction.

[0010] Furthermore, the ultrasonic dispersion process is set to a power of 200W, a 5s on / 5s off cycle, and a total of 3 minutes.

[0011] Furthermore, the low-temperature environment, with a temperature range of 5-8°C, maintains the expansion state of PNIPAM.

[0012] Furthermore, the stirring speed of the crosslinking reaction is 180-220 rpm.

[0013] Furthermore, the preparation method includes the following steps: PHA, PLA, PBAT, modified alginate gel, chitosan, and plasticizer were premixed and then added to a twin-screw extruder for blending. The temperature was set to 140℃ in zone I, 160℃ in zone II, and 170℃ in zone III. After blending, banana fiber was injected and the extrusion granulation was carried out at 200 rpm to obtain biodegradable plastic.

[0014] Furthermore, the plasticizer is one of acetylated tributyl citrate, epoxy acetylated ricinoleate, and tetrameric ricinoleate.

[0015] The beneficial effects achieved by the present invention using the above structure are as follows: Modified alginate gel achieves environmentally adaptive degradation through a photothermal dual-control mechanism. In terrestrial or sunlit environments, the quantum dots loaded on the gel absorb photon energy and convert it into heat energy. The thermosensitive polymer in the gel shrinks, prompting the release of low-temperature lipases and accelerating the hydrolysis of the plastic. In marine environments, sodium ions in seawater can replace the gel cross-linking sites, promoting structural dissociation and continuously releasing psychrophilic lipases. This dual action enables the plastic to achieve efficient and controllable biodegradation in both marine and terrestrial environments.

[0016] By preparing modified alginate gel, low-temperature lipase and quantum dots are co-immobilized in alginate polymer, isolating the enzyme protein from the damage caused by high processing temperatures, ensuring the integrity of bioactive components during the blending extrusion process, and continuously protecting the enzyme from inactivation by environmental factors during the plastic's service life. When the plastic enters the degradation environment, the gel achieves slow release of enzyme molecules through temperature changes, allowing the lipase to act on the ester bond sites of the polymer chain, avoiding catalytic efficiency loss caused by ineffective diffusion.

[0017] Modified alginate gel integrates a dual degradation pathway of biological enzymatic hydrolysis and physical disintegration. On the one hand, the released low-temperature lipase specifically hydrolyzes the ester bonds in the polyester molecular chain, generating oligomer fragments for further microbial metabolism. On the other hand, the gel swells and disintegrates under the action of seawater ions and microbial metabolites, destroying the dense structure of the plastic and increasing the specific surface area, providing more attachment sites for enzyme molecules and microorganisms. This synergistic effect of biological and physical processes can shorten the cycle from plastic fragmentation to mineralization. Attached Figure Description

[0018] Figure 1 The results show the weight loss rate of terrestrial samples under illumination under light conditions, which is the basis of this invention for a biodegradable plastic for all natural marine and terrestrial environments and a method for preparing the biodegradable plastic.

[0019] Figure 2 The results show the weight loss rate of marine samples under illumination under light conditions, which is the basis of this invention for a biodegradable plastic that can be used in all natural environments of the ocean and land, and the method for preparing the biodegradable plastic.

[0020] Figure 3 The results show the weight loss rate of the terrestrial sample under light-free conditions for the marine and terrestrial biodegradable plastic and the method for preparing the biodegradable plastic proposed in this invention.

[0021] Figure 4 The results show the weight loss rate of marine samples under light-free conditions for a biodegradable plastic for all natural marine and terrestrial environments proposed in this invention, as well as the method for preparing the biodegradable plastic.

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example

[0024] A biodegradable plastic suitable for all natural environments, including marine and terrestrial use, and a method for preparing the biodegradable plastic. First, modified alginate gel was prepared. Under nitrogen protection, 2.0 g of sodium alginate was dissolved in 90 mL of deionized water to form a homogeneous solution. After cooling to 4°C in an ice bath, N-isopropylacrylamide (NIPAM) was added according to a molar ratio of sodium alginate to NIPAM of 1:2. 0.4 g of EDC (1-ethyl-(3-dimethylaminopropyl)carbodiimide) and 0.2 g of NHS (N-hydroxysuccinimide) were added as catalysts. The constant temperature was set at 55°C, and the reaction was stirred for 2 h. After the reaction, the gel was purified by ethanol precipitation and freeze-dried, repeated three times to obtain the framework. Under light-protected conditions, the graft copolymer was dissolved in water at 4°C. Prepare a 3wt% PBS buffer solution, add low-temperature lipase, and magnetically stir at 4°C for 2 hours to avoid foaming, allowing the enzyme to be loaded onto the polymer backbone. Add CdSe quantum dots to the solution containing the polymer backbone, place in an ice bath, set the power to 200W, turn on for 5 seconds and stop for 5 seconds, and sonicate for a total of 3 minutes to form a mixture. Add CaCl2 solution to the mixture at 5°C and stir at 180 rpm for 30 minutes. After the reaction is complete, centrifuge at 3000 rpm for 5 minutes, collect the solid product, wash the product with PBS containing 0.1M NaCl, and freeze-dry to obtain the modified alginate gel product.

[0025] Polyhydroxyalkanoate (PHA), polylactic acid (PLA), polybutylene succinate (PBAT), modified alginate gel, chitosan, and plasticizer were premixed, added to a twin-screw extruder for blending, injected into banana fiber, and extruded and granulated at 200 rpm to obtain biodegradable plastic. Example

[0026] A biodegradable plastic suitable for all natural environments, including marine and terrestrial use, and a method for preparing the biodegradable plastic. First, modified alginate gel was prepared. Under nitrogen protection, 2.0 g of sodium alginate was dissolved in 90 mL of deionized water to form a homogeneous solution. After cooling to 4°C in an ice bath, N-isopropylacrylamide (NIPAM) was added according to a molar ratio of sodium alginate to NIPAM of 1:3. 0.4 g of EDC (1-ethyl-(3-dimethylaminopropyl)carbodiimide) and 0.2 g of NHS (N-hydroxysuccinimide) were added as catalysts. The constant temperature was set at 60°C, and the reaction was stirred for 2 h. After the reaction, the gel was purified by ethanol precipitation and freeze-dried, repeated three times to obtain the framework. Under light-protected conditions, the graft copolymer was dissolved in water at 4°C. Prepare a 3wt% PBS buffer solution, add low-temperature lipase, and magnetically stir at 4°C for 2 hours to avoid foaming, allowing the enzyme to be loaded onto the polymer backbone. Add CdSe quantum dots to the solution containing the polymer backbone, place in an ice bath, set the power to 200W, turn on for 5 seconds and stop for 5 seconds, and sonicate for a total of 3 minutes to form a mixture. At 6°C, add the mixture to CaCl2 solution and stir at 200 rpm for 30 minutes. After the reaction is complete, centrifuge at 3000 rpm for 5 minutes, collect the solid product, wash the product with PBS containing 0.1M NaCl, and freeze-dry to obtain the modified alginate gel product.

[0027] Polyhydroxyalkanoate (PHA), polylactic acid (PLA), polybutylene succinate (PBAT), modified alginate gel, chitosan, and plasticizer were premixed, added to a twin-screw extruder for blending, injected into banana fiber, and extruded and granulated at 200 rpm to obtain biodegradable plastic. Example

[0028] A biodegradable plastic suitable for all natural environments, including marine and terrestrial use, and a method for preparing the biodegradable plastic. First, modified alginate gel was prepared. Under nitrogen protection, 2.0 g of sodium alginate was dissolved in 90 mL of deionized water to form a homogeneous solution. After cooling to 4°C in an ice bath, N-isopropylacrylamide (NIPAM) was added according to a molar ratio of sodium alginate to NIPAM of 1:4. 0.4 g of EDC (1-ethyl-(3-dimethylaminopropyl)carbodiimide) and 0.2 g of NHS (N-hydroxysuccinimide) were added as catalysts. The constant temperature was set at 65°C, and the reaction was stirred for 2 h. After the reaction, the gel was purified by ethanol precipitation and freeze-dried, repeated three times to obtain the framework. Under light-protected conditions, the graft copolymer was dissolved in water at 4°C. A 3wt% PBS buffer solution was prepared, and low-temperature lipase was added. The mixture was magnetically stirred at 4°C for 2 hours to prevent foaming and allow the enzyme to be loaded onto the polymer backbone. CdSe quantum dots were added to the solution containing the polymer backbone and placed in an ice bath. The mixture was ultrasonically dispersed for a total of 3 minutes at a power of 200W with a 5s on / 5s off cycle to form a mixture. The mixture was then added to a CaCl2 solution at 8°C and stirred at 220 rpm for 30 minutes. After the reaction was complete, the mixture was centrifuged at 3000 rpm for 5 minutes to collect the solid product. The product was washed with PBS containing 0.1M NaCl and freeze-dried to obtain the modified alginate gel product.

[0029] Polyhydroxyalkanoate (PHA), polylactic acid (PLA), polybutylene succinate (PBAT), modified alginate gel, chitosan, and plasticizer were premixed, added to a twin-screw extruder for blending, injected into banana fiber, and extruded and granulated at 200 rpm to obtain biodegradable plastic.

[0030] Comparative Example 1 Polyhydroxyalkanoate (PHA), polylactic acid (PLA), polybutylene succinate (PBAT), modified chitosan, and tetrameric castor oil ester were premixed and added to a twin-screw extruder. The temperature was set to 140℃ in zone I, 160℃ in zone II, and 170℃ in zone III. After melt blending, banana fiber / wollastonite powder was injected, and the screw speed was 200 rpm. The mixture was extruded and granulated to obtain the basic masterbatch. The masterbatch was then mixed with antimony trioxide and magnesium hydroxide in a mixer at 120℃ for 50 min to form a flame-retardant layer. The mixture was then calendered into a film or injection molded and cooled to set.

[0031] Comparative Example 2 Corn starch, nano-titanium dioxide, nano-calcium carbonate, and silane coupling agent are added to a ball mill according to the specified ratio and ball milled for 1-2 hours to obtain pre-modified corn starch. The pre-modified corn starch is then treated at 120-140℃ for 20-40 minutes and cooled to room temperature to obtain modified corn starch. Polylactic acid resin, polyvinyl alcohol, low-density polyethylene, and high-density polyethylene are added to a mixer according to the specified ratio, followed by the modified corn starch. The mixture is then uniformly mixed to obtain a compound. The compound is fed into a twin-screw extruder for kneading and then extruded through the die head of the twin-screw extruder to obtain a biodegradable plastic semi-finished product. The biodegradable plastic semi-finished product is then cooled in a water tank, air-dried, pelletized, and sieved to obtain biodegradable plastic.

[0032] Comparative Example 3 Polyhydroxyalkanoate, glycerol, ethylene glycol and water are added sequentially to a high-speed mixer and stirred for 10-25 minutes to form a homogeneous mixture. Thermoplastic starch, glycerol, ethylene glycol and water are added sequentially to the high-speed mixer and stirred for 10-25 minutes to form a homogeneous mixture. The mixture is then fed into a twin-screw extruder for compounding and extrusion. The material strips extruded through the die are water-cooled and air-cooled, and then pelletized to obtain biodegradable plastic particles.

[0033] Experimental Example 1 Each sample of plastic was cut into 10mm×10mm×0.5mm thin slices, weighed and recorded the initial weight, and sterilized for later use. A 10cm thick layer of sterile soil was laid in a beaker, and the water activity was adjusted to 15%. The samples were buried evenly in the soil at a depth of about 2cm, with 3 parallel samples in each group. The container was placed under a light system and the photocycle was started. Samples were taken at 0, 7, 14, 21, 28, 35 and 42 days. After cleaning the surface, the samples were vacuum dried, weighed and the weight loss rate was calculated. The test was repeated three times for each sample and the average value was taken.

[0034] like Figure 1 As shown, under terrestrial sunlight conditions, the performance evolution of biodegradable plastics exhibits phased characteristics. In the early stage, surface erosion is dominated by photocatalysis, while in the later stage, microbial activity gradually enhances the degradation process. The example groups consistently maintain the leading degradation efficiency, with Example 3 showing the most significant degradation degree. The comparative groups show lower degradation degrees, with Comparative Example 2 exhibiting superior degradation ability in the initial stage, but its degradation efficiency slows down in the later stage. The experiment demonstrates that, under terrestrial sunlight conditions, the biodegradable plastics in the examples have superior degradation ability.

[0035] Experiment Example 2 Each sample of plastic was cut into 10mm×10mm×0.5mm thin slices, weighed and recorded the initial weight, and sterilized for later use. The samples were immersed in 200mL of artificial seawater containing 0.05% NaN3 to inhibit contamination. Three parallel samples were set up for each group. The containers were placed under a light system and the photocycle was started. Samples were taken at 0, 7, 14, 21, 28, 35 and 42 days. After cleaning the surface, vacuum drying was performed, and the samples were weighed and the weight loss rate was calculated. The test was repeated three times for each sample, and the average value of the results was taken.

[0036] like Figure 2 As shown, in a simulated marine light environment, the biodegradable plastics in Examples 1-3 exhibited a significant advantage in degradation efficiency. Over time, their mass loss rate remained higher than that of all control groups. The experiment confirmed that in a marine environment, biodegradable plastics containing modified alginate can significantly accelerate material disintegration.

[0037] Experimental Example 3 Each sample of plastic was cut into 10mm×10mm×0.5mm thin slices, weighed and recorded the initial weight, and sterilized for later use. A 10cm thick layer of sterile soil was laid in a beaker, and the water activity was adjusted to 15%. The samples were buried evenly in the soil at a depth of about 2cm, with 3 parallel samples in each group. The containers were placed in a dark environment, and samples were taken at 0, 7, 14, 21, 28, 35 and 42 days. After cleaning the surface, the samples were vacuum dried, weighed and the weight loss rate was calculated. The test was repeated three times for each sample, and the average value of the results was taken.

[0038] like Figure 3 As shown, in a simulated dark terrestrial environment, although the change in weight loss rate of the biodegradable plastic samples in Examples 1-3 was not as good as that under light conditions, it was still better than that of Comparative Examples 1-3. Comparative Examples 1-3 did not have the same degradation effect as Examples 1-3 due to the lack of bioactive components. The experimental phenomena confirm that the degradation efficiency of materials under dark conditions depends on bioavailability and the intensity of enzymatic reaction. Moreover, under dark conditions, the biodegradable plastic still has a better degradation ability.

[0039] Experiment Example 4 Each sample of plastic was cut into 10mm×10mm×0.5mm thin slices, weighed and recorded the initial weight, and sterilized for later use. The samples were immersed in 200mL of artificial seawater containing 0.05% NaN3 to inhibit contamination. Three parallel samples were set up for each group. The containers were placed in a dark environment and samples were taken at 0, 7, 14, 21, 28, 35 and 42 days. After cleaning the surface, the samples were vacuum dried, weighed and the weight loss rate was calculated. The test was repeated three times for each sample and the average value was taken.

[0040] like Figure 4As shown, in a simulated dark marine environment, the degradation process of all samples showed a slowing trend. However, although Examples 1-3 containing photocatalytic components could not take advantage of photodegradation, their modified gel structure still maintained a higher mass loss rate than the control group and showed continuous degradation ability in the later stage of the experiment. Comparative Examples 1-3 showed a continuous degradation inhibition state, and the degradation tended to level off in the later stage. The experimental phenomena show that the degradation of materials under dark conditions depends on the synergistic effect of salt water infiltration and biological enzymatic hydrolysis, and still has a better degradation ability.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0042] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A biodegradable plastic suitable for both marine and terrestrial environments, characterized in that: The raw materials include the following parts by weight: 20-30 parts of polyhydroxyalkanoate (PHA); 15-25 parts of polylactic acid (PLA); 10-20 parts of polybutylene succinate (PBAT); 5-10 parts of chitosan; 8-12 parts of banana fiber; 5-8 parts of tetrameric ricinoleate; and 3-5 parts of modified alginate gel. The preparation method of the modified alginate gel includes the following steps: Under nitrogen protection, sodium alginate was dissolved in deionized water to form a homogeneous solution. After cooling to 4°C in an ice bath, N-isopropylacrylamide (NIPAM) was added, and a catalyst was added for isothermal reaction. The solution was purified by ethanol precipitation and freeze-dried to obtain the framework. Under light-protected conditions, the purified low-temperature lipase was loaded onto the polymer framework. CdSe quantum dots were added to the solution containing the polymer framework and ultrasonically dispersed to form a mixture. Under low-temperature conditions, the mixture was added to CaCl2 solution and stirred. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain the modified alginate gel product.

2. The marine and terrestrial biodegradable plastic according to claim 1, characterized in that: The molar ratio of sodium alginate to NIPAM is 1:(2-4).

3. The marine and terrestrial biodegradable plastic according to claim 2, characterized in that: The catalyst is one or more of 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS).

4. The marine and terrestrial biodegradable plastic according to claim 3, characterized in that: The isothermal reaction was carried out at a temperature of 55-65℃ for 2 hours with stirring.

5. A biodegradable plastic suitable for both marine and terrestrial environments according to claim 4, characterized in that: The low-temperature lipase was loaded onto the polymer backbone. The graft copolymer was dissolved in PBS buffer at 4°C to prepare a 3wt% solution, and then the low-temperature lipase was added. The mixture was then magnetically stirred at 4°C for 2 hours.

6. A biodegradable plastic suitable for both marine and terrestrial environments according to claim 5, characterized in that: The ultrasonic dispersion process was set to a power of 200W, with a 5s on / 5s off cycle, for a total of 3 minutes.

7. A marine and terrestrial biodegradable plastic according to claim 6, characterized in that: The low-temperature environment is in the temperature range of 5-8℃.

8. A biodegradable plastic suitable for both marine and terrestrial environments according to claim 7, characterized in that: The stirring speed for the crosslinking reaction is 180-220 rpm.

9. A marine and terrestrial biodegradable plastic and a method for preparing the biodegradable plastic according to claims 1-8, characterized in that: The preparation method includes the following steps: PHA, PLA, PBAT, modified alginate gel, chitosan, and plasticizer were premixed, added to a twin-screw extruder for blending, and then injected into banana fiber. The mixture was extruded and granulated at 200 rpm to obtain biodegradable plastic.

10. A marine and terrestrial biodegradable plastic according to claim 9, characterized in that: The plasticizer is one of acetylated tributyl citrate, epoxy acetylated ricinoleate, and tetrameric ricinoleate.

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