Seawater-degradable seedling raising frame and preparation method and use thereof

Abstract

This invention relates to a seawater degradable seedling raising frame and its preparation method and uses. The preparation method of the seawater degradable seedling raising frame includes the following steps: (1) Preparing modified biodegradable plastic: Mixing a non-enzymatic seawater degradation accelerator, an enzymatic seawater degradation accelerator, a surface hydrolysis inhibitor and a small amount of biodegradable resin, performing melt extrusion at a temperature of 140-180℃ to prepare a high-concentration masterbatch, mixing the masterbatch with the remaining biodegradable resin, performing melt extrusion again at a temperature of 160-190℃, cooling and granulating to obtain modified biodegradable plastic; (2) Placing the modified biodegradable plastic into an injection molding machine, heating it to a molten state, and then injecting it into the seedling raising frame mold. After injection molding is completed, demolding is performed to form a seawater degradable seedling raising frame. This seawater degradable seedling raising frame can controllably degrade to meet the needs of seagrass growth cycle, is harmless to the environment, promotes the restoration of seagrass bed ecosystem, and achieves sustainable marine ecological restoration.

Description

Technical Field

[0001] This invention belongs to the field of marine aquaculture, and particularly relates to a seawater biodegradable seedling raising frame, its preparation method and uses. Background Technology

[0002] Currently, the marine aquaculture industry commonly employs a land-based seedling cultivation and seawater transplantation model to improve seedling survival rates. For example, Japanese Patent Document JP2023048268A discloses a land-based seagrass cultivation device and method. However, this model also faces numerous technical bottlenecks. After land cultivation, the seedlings need to be removed from the cultivation substrate and repackaged, increasing manual labor and reducing production efficiency. Furthermore, the seedlings are susceptible to mechanical damage during transfer, negatively impacting their subsequent growth. In addition, plastic support frames are often used to fix the seedlings in seawater. For instance, Chinese Patent Document CN108668880A discloses a semi-submersible seagrass cultivation device and method. The support frame used to support the seagrass cultivation layer includes a base plate and a frame. The base plate is made of a biodegradable material with perforations, such as nylon mesh or other polymer materials. If these plastic products are not recycled, they may remain in the marine environment for a long time after disposal, posing a potential risk of plastic pollution. Even with recycling measures, a significant amount of resources are consumed.

[0003] Taking seagrass bed restoration as an example, the commonly used seagrass transplantation methods, such as manual transplantation, face problems such as cumbersome operation, easy damage to seedlings, and low transplantation efficiency. The paper cup counterweight transplantation method cannot meet the needs of seagrass seedling growth cycle because the paper cups are easily broken. The mesh bag counterweight seagrass transplantation method may cause secondary pollution to the environment because the mesh bags are mostly made of chemical fiber materials. The hydrolysis rate of traditional degradable plastic carriers has poor controllability.

[0004] In summary, the core problems that existing technologies have failed to solve simultaneously are: first, the transplanting process is cumbersome, and the split operation leads to high labor costs and high seedling damage rates; second, the formulation and structural design of seedling carrier materials lack specificity, resulting in poor compatibility between the seedling carrier environment and seedling needs, non-degradable plastics cause marine pollution, and materials that are prone to failure in the short term cannot match the seedling growth cycle.

[0005] Therefore, there is an urgent need for a seagrass seedling / transplanting technology that simplifies the transplanting process, is environmentally friendly, reduces damage to seedlings during transplantation, and is controllably degradable to meet the needs of the seagrass growth cycle. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a seawater degradable seedling raising frame that is controllable and environmentally friendly, as well as the seawater degradable seedling raising frame prepared therefrom, so as to promote the restoration of seagrass bed ecosystem and achieve sustainable marine ecological restoration.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a seawater-degradable seedling raising frame, comprising the following steps: (1) Preparation of modified biodegradable plastics: Provide the following raw materials in the indicated weight ratios, Biodegradable resin: 80–95 Non-enzymatic seawater degradation accelerator: 3-7, Enzymatic seawater degradation accelerator: 3-7, Surface hydrolysis inhibitor: 0.3~2; Other functional additives: 0-3; A high-concentration masterbatch is prepared by mixing a non-enzymatic seawater degradation accelerator, an enzymatic seawater degradation accelerator, a surface hydrolysis inhibitor, and other functional additives with 10-30 parts of biodegradable resin and then performing melt extrusion at a temperature of 140-180℃. The masterbatch is mixed with the remaining biodegradable resin and then melt-extruded again at a temperature of 160-190℃. After cooling and granulation, the modified biodegradable plastic is obtained. The biodegradable resin is added in multiple batches to improve the dispersion uniformity of each component, thereby obtaining better performance.

[0008] (2) The modified biodegradable plastic is placed in the injection molding machine and heated to a molten state. It is then injected into the seedling frame mold at an injection pressure of 50-70 MPa to ensure the fluidity of the material in the mold, thereby achieving a good filling effect and avoiding molding defects. The mold temperature is controlled at (25±2)℃ to optimize the cooling rate of the material and ensure the surface smoothness and appearance quality of the molded product. The holding pressure is 30-40 MPa. By maintaining appropriate pressure to compensate for material shrinkage, the shape stability and density of the product are ensured. After injection molding is completed, the mold is stopped and the cooling time is maintained in the mold for 10-15 minutes. After the product temperature drops to room temperature, the demolding operation is carried out to form a seawater biodegradable seedling frame.

[0009] In some specific embodiments, in step (1), the biodegradable resin is selected from one or more of polybutylene succinate (PBS), polyesteramide (PEA), polycaprolactone (PCL), and polylactic acid (PLA); the above-mentioned biodegradable resin has high tensile and flexural strength, can withstand the impact of ocean currents, and has a good dispersing effect on subsequent non-enzymatic seawater degradation accelerators, enzymatic seawater degradation accelerators, and surface hydrolysis inhibitor components.

[0010] In some specific embodiments, the non-enzymatic seawater degradation accelerator is selected from oxides, hydroxides, and complexes of alkaline earth metals. Its mechanism of action is to first release hydroxide ions (OH⁻) through reaction with water molecules, increasing the alkalinity of the environment and thus accelerating the hydrolysis process. Furthermore, hydroxide ions (OH⁻) break the ester bonds in the polymer, generating carboxylate ions (-COO⁻) and hydroxyl groups (-OH), which further react with water molecules to generate carboxylic acids and low-molecular-weight alcohols, enhancing their affinity for water and promoting the hydrolysis and degradation of the polymer molecular chain, thereby accelerating the chemical degradation of the material. Simultaneously, the metal ions generated by the ionization of alkaline earth metal compounds can form coordinate bonds with the oxygen atoms of the ester bonds. This coordination further enhances the positive charge of the carbonyl carbon atom, lowers the energy barrier for nucleophilic attack by OH⁻, making the ester bonds easier to break and significantly increasing the degradation rate.

[0011] In some specific embodiments, the non-enzymatic seawater degradation accelerator is selected from one or more of calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, calcium carbonate, and calcium sulfate.

[0012] Preferably, the non-enzymatic seawater degradation accelerator is calcium hydroxide and / or calcium carbonate. These two are milder than calcium oxide among accelerators, allowing for a continuous and stable release of OH⁻, matching the service life of biodegradable plastics (60-120 days), avoiding fluctuations in the degradation rate, and unlike calcium sulfate (CaSO₄), they do not introduce SO₄²⁻. 2 ⁻ Moreover, it has a stronger alkalinity than magnesium oxide (MgO) and magnesium hydroxide (Mg(OH)2), and has a better hydrolysis catalytic effect.

[0013] In some specific embodiments, the enzymatic seawater degradation accelerator is selected from one or more of poly-γ-glutamic acid, β-cyclodextrin, sodium alginate, cellulose, lignin, chitin, sucrose, fructose, and whey protein powder. It should be noted that the enzymatic seawater degradation accelerator is a natural organic polymer or its derivative that can be preferentially utilized by marine microorganisms. These polymers can bind to receptors on the surface of microbial cell membranes through their polar groups such as hydroxyl, carboxyl, and amino groups, promoting rapid adsorption and colonization of microorganisms on the surface of degradable plastics. Under the induction of the accelerator components, the proliferated marine microorganisms will directionally secrete degradative enzymes (esterases) targeting the molecular chains of degradable plastics, dissolving the degradable resin to form internal defects and promoting microbial aggregation to participate in degradation. Furthermore, some components, such as sodium alginate, can undergo in-situ cross-linking or chelation reactions with non-enzymatic accelerators in the formulation (such as calcium ions), forming an 'egg-box structure' or rigid network in the matrix. This design ensures mechanical support during the seedling growth period and allows for complete disintegration due to network collapse caused by ion exchange in the later stages.

[0014] In some specific embodiments, the surface hydrolysis inhibitor is polyethylene wax. Polyethylene wax, as a lubricant, effectively reduces melt viscosity and frictional heat during processing, thereby preventing thermal degradation of the material. It has good compatibility with biodegradable resin matrices and spontaneously migrates to the plastic surface during plastic processing (such as injection molding and extrusion), forming a dense hydrophobic film. This constructs a hydrolysis protection barrier, significantly delaying the initial penetration of moisture into the material. Simultaneously, it blocks the direct interaction between hydroxyl ions (OH⁻), salt ions (Na⁺, Cl⁻) in seawater and degrading enzymes secreted by microorganisms on the plastic surface, delaying the hydrolytic breakage of surface ester bonds and preventing premature powdering, brittleness, and other failure phenomena on the plastic surface.

[0015] In some specific implementations, the other functional additives in step (1) include one or more of the following: UV stabilizers, diffusing agents, and flow promoters.

[0016] On the other hand, the present invention provides a method for preparing the aforementioned seawater-degradable seedling frame. The seawater-degradable seedling frame is an open-top, closed-bottom frame. The radius of the upper opening is 25-40 cm, the depth is 20-30 cm, and the bottom of the frame has several drainage holes with a density of 60-90 holes / m² and a diameter of 2-4 cm. The multiple drainage holes at the bottom of the frame ensure adequate water flow and drainage capacity, which helps with root oxygen penetration and growth.

[0017] In some specific embodiments, the 45-day tensile strength retention rate of the above-mentioned seawater biodegradable seedling raising frame is 60-70%, the 90-day tensile strength retention rate is 45-55%, the 180-day tensile strength retention rate is 34-43%, the 180-day weight loss is 70-90%, and the disintegration start time is 70-85 days.

[0018] Furthermore, this invention provides the application of the aforementioned seawater biodegradable seedling raising frame in mariculture or seagrass bed ecological restoration.

[0019] The present invention has achieved the following beneficial effects: The present invention discloses a method for preparing a seawater-degradable seedling raising frame and the prepared seawater-degradable seedling raising frame, which simplifies the seagrass transplanting process, reduces the need for manual operation, eliminates the need to remove seedlings from the seedling substrate, realizes an integrated operation from seedling raising to transplanting of seagrass seedlings, reduces damage to seedlings, and improves transplanting efficiency; avoids the use of non-degradable plastic support frames, reduces marine plastic pollution at the source, and protects the marine ecological environment; by optimizing the material formula and structural design of the seedling carrier, it is controllably degradable, provides a good growth environment for seagrass seedlings, covers their growth cycle (60-120 days), and improves their survival rate and growth rate after transplanting. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the seawater biodegradable seedling raising frame of the present invention. Figure 1 .

[0021] Figure 2 This is a schematic diagram of the seawater biodegradable seedling raising frame of the present invention. Figure 2 . Detailed Implementation

[0022] The embodiments of the present invention will now be clearly and completely described in conjunction with examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0023] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods; the materials, reagents, equipment, etc. used are all commercially available unless otherwise specified; and unless otherwise specified, the raw materials used in parallel experiments are from the same batch.

[0024] As analyzed in the background section, the formulation and structural design of seedling carriers (seedling trays) used in seagrass bed restoration lack specificity, resulting in poor environmental compatibility and mismatch between the seedling carrier materials and seedling requirements. Short-term biodegradable or easily degradable materials cannot meet the needs of seedlings in their early growth stages, while non-biodegradable plastics cannot decompose in the later stages of seedling growth to promote root expansion and development, nor can they rapidly decompose after the seedling growth cycle, leading to secondary pollution. For example, the performance requirements of seedling trays (pots) for *Gnaphalium affine* during its growth stages in a seawater environment are as follows: Seedling stage (2-4 weeks): The pot (frame) should have sufficient mechanical strength to resist the mechanical force of seawater and support the healthy growth of seedling roots in seawater, ensuring that the pot is not easily cracked or deformed when immersed in seawater.

[0025] Growth stage (4-12 weeks): The pot (frame) body needs to maintain a tensile strength retention rate of more than 60% to accommodate the expansion of the root system, ensure that the root system can be well anchored and grow, and at the same time maintain an appropriate water supply to promote the normal growth of seedlings.

[0026] Accelerated growth period (12-24 weeks): The pot (frame) should gradually begin to degrade, appropriately relaxing the restraints on the roots to support the rapid growth of new algae. During this stage, the seedling pot needs to maintain orderly mechanical properties and structural stability to resist the dynamic forces of seawater and ensure the growth of new plants.

[0027] Maturity stage (24 weeks and above): At this stage, the potting mix should disintegrate to avoid hindering the natural reproduction of the seaweed and to promote rapid biological decomposition, thereby promoting the return of nutrients to the marine ecosystem.

[0028] Therefore, embodiments of the present invention have prepared a seawater-degradable seedling raising frame to solve the above-mentioned technical problems.

[0029] Example 1 This embodiment provides a method for preparing a seawater-degradable seedling raising frame, which specifically includes the following steps: (1) Preparation of modified biodegradable plastics: Provide the following raw materials in the indicated weight ratios, Polybutylene succinate (PBS): 90, calcium carbonate: 5, sucrose: 4, PE wax: 1; (2) Mix calcium carbonate, sucrose, PE wax and a small amount of PBS, and perform melt extrusion at a temperature of 150°C to produce a high-concentration masterbatch; The masterbatch was mixed with the remaining PBS to ensure that all components were evenly dispersed, and then melt-blended again. A portion of the melt-blended material was injection-molded into standard test strips. The remaining melt blended materials are melt extruded at a temperature of 190°C. The extruded materials are rapidly cooled using a cooling water tank and then cut into granules to obtain modified biodegradable plastics with the desired granular morphology. (3) Place the modified biodegradable plastic into an injection molding machine, heat it to a molten state, and then inject it into the seedling frame mold. For example... Figure 1 , Figure 2 As shown, the specifications of the seawater biodegradable seedling raising frame to be formed by the mold are as follows: The seawater biodegradable seedling raising frame is a circular frame with a circular opening at the top and a closed bottom. Upper opening radius: 30 cm, depth: 25 cm Drainage hole design: 3cm diameter, density 80 holes / square meter. Alternatively, the seawater biodegradable seedling raising frame can be a square frame with a square opening at the top and a closed bottom. The side length of the top opening is 100cm, and the depth is 25cm. Depth: 25 cm Drainage hole design: 3cm diameter, density 80 holes / square meter. The injection pressure of the injection molding machine is 60 MPa, the mold temperature is controlled at (25±5)°C, the holding pressure is 35 MPa. After the injection molding is completed, the mold heat preservation is stopped, and the cooling time in the mold is maintained for 13 minutes. After the product temperature drops to room temperature, the demolding operation is carried out to form a seawater biodegradable seedling frame.

[0030] Example 2 The polybutylene succinate (PBS) in Example 1 was replaced with polycaprolactone (PCL). The raw material weight ratios were as follows: polycaprolactone (PCL): 90, calcium carbonate: 5, sucrose: 4, PE wax: 1, and the rest were the same as in Example 1.

[0031] Example 3 The calcium carbonate in Example 1 was replaced with calcium hydroxide. The raw material weight ratios were as follows: PBS: 90, calcium hydroxide: 5, sucrose: 4, PE wax: 1, and the rest were the same as in Example 1.

[0032] Example 4 The sucrose in Example 1 was replaced with sodium alginate. The raw material weight ratios are as follows: PBS: 90, calcium hydroxide: 5, sodium alginate: 4, PE wax: 1, and the rest are the same as in Example 1.

[0033] Example 5 The ratio of calcium carbonate and sucrose in Example 1 was adjusted. The total ratio of calcium carbonate and sucrose was the same as in Example 1, but the ratio of sucrose was significantly higher than that of calcium carbonate. The raw material weight ratio was as follows: PBS: 90, calcium carbonate: 3, sucrose: 6, PE wax: 1, and the rest was the same as in Example 1.

[0034] Example 6 The ratio of calcium carbonate and sucrose in Example 1 was adjusted. The total ratio of calcium carbonate and sucrose was the same as in Example 1, but the ratio of sucrose was significantly lower than that of calcium carbonate. The raw material weight ratio was as follows: PBS: 90, calcium carbonate: 7, sucrose: 2, PE wax: 1, and the rest was the same as in Example 1.

[0035] Comparative Example 1 This embodiment uses 100PBS, and the rest is the same as in Example 1.

[0036] Comparative Example 2 The calcium carbonate in Example 1 was replaced with sucrose. The raw material weight ratio was as follows: PBS: 90, sucrose: 9, PE wax: 1, and the rest was the same as in Example 1.

[0037] Comparative Example 3 The sucrose in Example 1 was replaced with calcium carbonate. The raw material weight ratios were as follows: PBS: 90, calcium carbonate: 9, PE wax: 1, and the rest were the same as in Example 1.

[0038] Comparative Example 4 In this embodiment, PE wax is not added. The raw material weight ratio is as follows: PBS: 90, calcium carbonate: 5, sucrose: 4, and the rest is the same as in Example 1.

[0039] Comparative Example 5 The total ratio of calcium carbonate and sucrose in Example 1 was reduced to 3. The weight ratio of raw materials was as follows: PBS: 96%, calcium carbonate: 2%, sucrose: 1%, PE wax: 1%, and the rest were the same as in Example 1.

[0040] Comparative Example 6 The total ratio of calcium carbonate and sucrose in Example 1 was increased to 20. The weight ratio of raw materials was as follows: PBS: 79, calcium carbonate: 12, sucrose: 8, PE wax: 1, and the rest were the same as in Example 1.

[0041] Comparative Example 7 This embodiment improves the PE wax ratio of Example 1. The raw material weight ratio is as follows: PBS: 88, calcium carbonate: 5, sucrose: 4, PE wax: 3, and the rest is the same as in Example 1.

[0042] Comparative Example 8 This embodiment uses commercially available paper seedling pots.

[0043] Test Example 1 This test example examines the mechanical properties of the standard test specimens prepared in Examples 1-6 and Comparative Examples 1-7. Specifically, tensile strength, flexural strength, and elongation at break are tested using a universal tensile testing machine according to GB / T 1040.2-2022 standard. Marine environmental performance simulation: tensile strength is tested and tensile strength retention rate is calculated after 45 days, 90 days, and 180 days. Weight loss rate is also tested after the 180-day seedling period.

[0044] The results are shown in Table 1 below: Standard test specimen material mechanical property test. According to the results in Table 1, compared with the blank control Comparative Example 1, the modified materials prepared in Examples 1 to 6 of the present invention showed excellent mechanical properties, and the tensile strength retention rate at 45 days all exceeded 60%, and the disintegration start time was 71-82 days, which was successfully adjusted to close to 12 weeks, meeting the needs of different growth cycles of seaweed. Finally, the weight loss at 180 days all exceeded 70%, which was significantly higher than the 14% of Comparative Example 1.

[0045] Examples 2 to 4 show that by changing different biodegradable resins, non-enzymatic seawater degradation accelerators, and enzymatic seawater degradation accelerator components, the degradation rate and mechanical properties of the material can be effectively adjusted.

[0046] In Example 2, polycaprolactone (PCL) was used instead of PBS for the biodegradable resin. The strength was slightly reduced, but the initial elongation at break was much higher than that of other examples. It had good toughness and a tensile strength retention rate of 61.5% after 45 days. The material properties can effectively ensure that the roots can be well anchored and grow. The weight loss after 180 days was 89.9%, and the material almost completely disintegrated, which will not cause secondary pollution.

[0047] In Example 3, the non-enzymatic seawater degradation accelerator was calcium hydroxide. Compared with Example 1, the tensile strength retention rate was reduced, but the weight loss after 180 days was 78.4%, which exceeded that of Example 1, meaning that it was more prone to disintegration than Example 1.

[0048] In Example 4, the enzymatic seawater degradation accelerator was sodium alginate. Compared with Example 1, the tensile strength was improved and the mechanical retention rate at 90 days was also improved. However, the weight loss at 180 days was 77.4%, which exceeded that of Example 1. That is, compared with Example 1, it can maintain mechanical strength more effectively during the functional period, but it is prone to disintegration in the long tail (180 days).

[0049] Examples 5 and 6 demonstrate that mechanical properties and degradation performance can be optimized by adjusting the ratio of non-enzymatic seawater degradation accelerator and enzymatic seawater degradation accelerator.

[0050] Example 5: The total ratio of calcium carbonate and sucrose is the same as in Example 1, but the sucrose ratio is significantly higher than that of calcium carbonate. Compared with Example 1, the tensile strength retention rate is improved, and the weight loss after 180 days is 74.5%, which is roughly the same as in Example 1.

[0051] Example 6 has the same total ratio of calcium carbonate and sucrose as Example 1, but the sucrose ratio is significantly lower than that of calcium carbonate. Compared with Example 1, the tensile strength retention rate is reduced by about 3%, and the weight loss after 180 days is 71%, which is less than that of Example 1. It is also less prone to disintegration than Example 1.

[0052] The blank control, Example 1, is a PBS product that begins to disintegrate after 35 days. Its short functional period does not meet the requirements, and its weight loss is only 14% after 180 days after the functional period, indicating that it cannot degrade rapidly.

[0053] Comparative Examples 2 to 4 verified the necessity of the non-enzymatic seawater degradation accelerator, the enzymatic seawater degradation accelerator, and the surface hydrolysis inhibitor components, demonstrating that it is impossible to precisely adjust the disintegration initiation point to 12 weeks while maintaining the initial mechanical properties.

[0054] Comparative Example 2, which does not contain the non-enzymatic seawater degradation accelerator calcium carbonate, has a 180-day tensile strength retention rate of 88% and a disintegration start time of 95 days. Compared with Examples 1-6, it is less prone to disintegration and the disintegration time is later, which is not conducive to the root development of seagrass seedlings.

[0055] Comparative Example 3, which does not contain the enzymatic seawater degradation accelerator sucrose, achieved a 180-day tensile strength retention rate of 79.4% and a disintegration start time of 58 days. Compared to Examples 1-6, it was easier to disintegrate, but the disintegration time was too early, which coincided with the growth stage of seagrass, and could not ensure that the root system could be well anchored and grow.

[0056] Comparative Example 4, which does not contain the surface hydrolysis inhibitor PE wax, had a tensile strength retention rate of 34% at 45 days, 18.2% at 90 days, and only 14.5% at 180 days. The disintegration started at 26 days. Compared with Examples 1-6, the mechanical strength was too low, and the disintegration occurred during the seedling stage of seagrass, which could not support the healthy growth of the seedling roots in seawater.

[0057] Comparative Examples 5 and 6 explored the effects of insufficient and excessive amounts of hydrolysis promoters (enzymatic and non-enzymatic), while Comparative Example 7 discussed the role of excessive surface hydrolysis inhibitors, highlighting the criticality of appropriate formulation for material performance.

[0058] Comparative Example 5 reduced the total ratio of calcium carbonate and sucrose in Example 1 to 3:1. Its 45-day tensile strength retention rate was 72.2%, its 90-day tensile strength retention rate was 65.4%, and its 180-day tensile strength retention rate still reached 54.2%, which is better than that of Examples 1-6. However, the disintegration start time was 102 days and the weight loss was 64.2% at 180 days, indicating that its degradation rate was worse than that of Examples 1-6 and it was not easy to degrade.

[0059] Comparative Example 6 increased the total ratio of calcium carbonate and sucrose in Example 1 to 20. Its tensile strength retention rate at 45 days was 60.7%, at 90 days it was 40.4%, and at 180 days it was 30.5%. Its mechanical properties were worse than those of Examples 1-6. Moreover, its disintegration started at 56 days and its weight loss at 180 days was 85.1%, indicating that its degradation rate was faster than that of Examples 1-6. It is easy to degrade, but it is right at the growth stage of seagrass, and it cannot ensure that the roots can be well anchored and grow.

[0060] Comparative Example 7 increased the proportion of PE wax from Example 1. Its tensile strength retention rate at 45 days, 90 days, and 180 days was much higher than that of Examples 1-6, and its mechanical properties were much better than those of Examples 1-6. However, the disintegration start time was 178 days, and the weight loss at 180 days was only 30.5%, indicating that its degradation rate was much worse than that of Examples 1-6, and it was not easy to degrade, which led to secondary pollution.

[0061] Test Example 2 This test case examines the growth of seagrass cultivated in the seawater biodegradable seedling trays of Examples 1-6, Comparative Examples 1-7, and the commercially available paper seedling trays of Comparative Example 8. The seagrass used in the seedling trays (traditional trays) for seagrass bed restoration was *Leptochloa macrophylla*. The experimental location was in the Bohai Sea at a temperature of 22 ± 5 degrees Celsius. The seedling cycle for *Leptochloa macrophylla* is typically 60-120 days. The seagrass growth results are shown in the table below: Table 2: Growth status of seaweed cultivated in seedling trays In Table 2, the 45-day survival rate (%) represents the proportion of seagrass seedlings that survive after transplanting into the seedling raising frame, reflecting the initial suitability of the frame. The 45-day seagrass attachment evaluation (1-5) indicates the tightness of the bond between the seagrass roots and the seedling raising frame (5 being the optimal value), reflecting the support capacity of the frame for root fixation. The 90 / 120 / 180-day seagrass stem length (cm) corresponds to the growth length of the seagrass during the corresponding period, reflecting the environmental support provided by the seedling raising frame for the long-term growth of the seagrass.

[0062] For the 45-day survival rate (%) and the 45-day seaweed adhesion evaluation, Examples 1-6 and Comparative Examples 2-7 were much better than Comparative Examples 1 and 8. This clearly shows that the mechanical properties of the seedling frame prepared by the present invention are much better than those of the 100% PBS of Comparative Example 1 and the commercially available paper seedling pot of Comparative Example 8. Therefore, the seedling frame has sufficient mechanical strength to support the healthy growth of seedling roots in seawater within 45 days, and ensures that the pot is not easily broken or deformed when soaked in seawater.

[0063] Regarding the seagrass stem length at 120 days, Examples 1-6 reached 45-48 cm, with an average of 46.3 cm. Among the comparative examples, only Comparative Example 2 reached 45 cm, while the others were only 38-42 cm, with an average of 41.4 cm. Regarding the seagrass stem length at 180 days, Examples 1-6 reached 62-71 cm, with an average of 66.8 cm. Among the comparative examples, only Comparative Example 2 reached 67 cm, while the others were only 51-62 cm, with an average of 52.75 cm. Therefore, it is evident that seagrass cultivated using the seawater-degradable seedling frames prepared in Examples 1-6 exhibits significantly better growth than that of Comparative Examples 1-7 and commercially available paper seedling pots.

[0064] In summary, the seawater biodegradable seedling raising frames prepared according to Examples 1-6 of the present invention are significantly superior to Comparative Examples 1-7 and commercially available paper seedling raising pots in terms of seedling raising performance, and are suitable for marine aquaculture and ecological restoration of seagrass beds.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a seawater-degradable seedling raising frame, characterized in that, Includes the following steps: (1) Preparation of modified biodegradable plastics: Provide the following raw materials in the indicated weight ratios, Biodegradable resin: 80-95 Non-enzymatic seawater degradation accelerator: 3-7, Enzymatic seawater degradation accelerator: 3-7, Surface hydrolysis inhibitor: 0.3-2; Other functional additives: 0-3; The biodegradable resin is selected from one or more of polybutylene succinate (PBS), polyesteramide (PEA), and polylactic acid (PLA); the enzymatic seawater degradation accelerator is selected from one or more of poly-γ-glutamic acid, β-cyclodextrin, lignin, chitin, sucrose, fructose, and whey protein powder. The non-enzymatic seawater degradation accelerator is selected from one or more of calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, calcium carbonate, and calcium sulfate. The surface hydrolysis inhibitor is polyethylene wax; A high-concentration masterbatch is prepared by mixing a non-enzymatic seawater degradation accelerator, an enzymatic seawater degradation accelerator, a surface hydrolysis inhibitor, and other functional additives with 10-30 parts of biodegradable resin and then performing melt extrusion at a temperature of 140-180℃. The masterbatch is mixed with the remaining biodegradable resin and then melt-extruded again at a temperature of 160-190℃. After cooling and granulation, the modified biodegradable plastic is obtained. (2) The modified biodegradable plastic is placed in the injection molding machine, heated to the molten state, and then injected into the seedling frame mold. The injection pressure is 50-70 MPa, the mold temperature is controlled at (25±2)℃, and the holding pressure is 30-40 MPa. After the injection is completed, the mold is stopped and kept in the mold for 10-15 minutes to maintain the cooling time. After the product temperature drops to room temperature, the demolding operation is carried out to form a seawater biodegradable seedling frame.

2. The method for preparing the seawater biodegradable seedling raising frame as described in claim 1, characterized in that, The non-enzymatic seawater degradation accelerator mentioned in step (1) is calcium hydroxide and / or calcium carbonate.

3. The method for preparing the seawater biodegradable seedling raising frame as described in claim 1 or 2, characterized in that, Other functional additives in step (1) include one or more of the following: UV stabilizers, diffusing agents, and flow promoters.

4. The seawater-degradable seedling raising frame prepared by the method described in any one of claims 1-3, characterized in that, The seawater biodegradable seedling raising frame is an open frame at the top and closed frame at the bottom. The radius of the upper opening is 25-40cm, the depth of the frame is 20-30cm, and the bottom of the frame is provided with several drainage holes with a density of 60-90 holes / square meter and a hole diameter of 2-4cm.

5. The seawater biodegradable seedling raising frame as described in claim 4, characterized in that, The seawater biodegradable seedling raising frame retains 60-70% of its tensile strength at 45 days, 45-55.0% at 90 days, 34-43% at 180 days, and 70-90% of its weight at 180 days. The disintegration begins at 70-85 days.

6. The use of a seawater-degradable seedling raising frame, characterized in that, The application of the seawater biodegradable seedling raising frame as described in claim 4 or 5 in mariculture or seagrass bed ecological restoration.

Images