Seawater degradable seedling raising frame as well as preparation method and application thereof

Abstract

The invention relates to a seawater degradable seedling raising frame and a preparation method and application thereof.The preparation method of the seawater degradable seedling raising frame comprises the following steps that (1) modified biodegradable plastic is prepared, specifically, a non-enzymatic seawater degradation accelerator, an enzymatic seawater degradation accelerator, a surface hydrolysis inhibitor and a small amount of biodegradable resin are mixed and subjected to melt extrusion, and the modified biodegradable plastic is obtained; the extrusion temperature is 140-180 DEG C, high-concentration master batches are prepared, the master batches and the remaining biodegradable resin are mixed, melt extrusion is conducted again, the extrusion temperature is 160-190 DEG C, cooling and granulation are conducted, and the modified biodegradable plastic is obtained. (2) modified biodegradable plastic is placed in an injection molding machine, heated to a molten state and then injected into a seedling raising frame mold, demolding operation is conducted after injection molding is completed, and the seawater degradable seedling raising frame is formed and can be controllably degraded to meet the requirement for the growth cycle of sea grass, is harmless to the environment and promotes recovery of a sea grass bed ecological system; sustainable marine ecological restoration is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of marine aquaculture, and particularly relates to a seawater-degradable seedling raising frame and a preparation method and application thereof. BACKGROUND

[0002] At present, the mode of land-based seedling raising and seawater transplantation is generally adopted in the field of seawater aquaculture to improve the survival rate of seedlings, such as the seaweed land-based cultivation device and cultivation method disclosed in Japanese patent document JP2023048268A. However, this mode also has many technical bottlenecks. Seedlings after land-based seedling raising need to be taken out of the seedling raising substrate and re-packaged, which increases the manual operation link and reduces production efficiency, and the seedlings are prone to mechanical damage during the transfer process, which adversely affects their subsequent growth. In addition, in order to fix the seedlings in seawater, a support frame made of plastic material is often used, such as the semi-submersible seaweed cultivation device and cultivation method disclosed in Chinese patent publication document CN108668880A. The support frame for supporting the seaweed cultivation layer includes a bottom plate and a border frame. The bottom plate is made of a meshed hole degradable material, which can be a nylon net or other high molecular polymer material. If such plastic products are not recycled, they may remain in the marine environment for a long time after being discarded, posing a potential risk of plastic pollution. Even if recycling measures are taken, a large amount of resources will be consumed.

[0003] Taking seaweed bed restoration as an example, the current commonly used seaweed transplantation methods, such as manual transplantation, have problems such as complicated manual transplantation operation, easy damage to seedlings, and low transplantation efficiency. The paper cup counterweight type transplantation cannot meet the needs of the seaweed seedling growth period due to the easy breakage of the paper cup. The net bag counterweight type seaweed transplantation may cause secondary pollution to the environment due to the fact that the net bag is mostly made of chemical fiber material. The hydrolysis rate of traditional degradable plastic carriers is difficult to control.

[0004] In summary, the existing technology has not been able to solve the following core problems at the same time: first, the transplantation process is complicated, and the split type operation leads to high labor cost and high seedling damage rate; second, the formula and structural design of the seedling carrier material lack pertinence, resulting in poor compatibility of the seedling material carrier environment and the matching degree of the seedling demand, plastic that is not degradable causes marine pollution, and short-term easily failed materials cannot match the growth period of seedlings.

[0005] Therefore, there is an urgent need for a seaweed seedling / transplantation technology that can simplify the transplantation process, is environmentally friendly, reduces damage to seedlings during the transplantation process, and is controllably degradable to meet the growth period needs of seaweed. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provide a preparation method of a seawater-degradable seedling raising frame that is controllably degradable and harmless to the environment, and a seawater-degradable seedling raising frame prepared thereby, to promote the restoration of the seaweed bed ecosystem and achieve sustainable marine ecological restoration.

[0007] To achieve the above object, the present application adopts the following technical solutions: In a first aspect, the present application provides a preparation method of seawater-degradable seedling raising frame, comprising the following steps: (1) Preparation of modified biodegradable plastic: providing the following raw materials in parts by weight, 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; Mix non-enzymatic seawater degradation accelerator, enzymatic seawater degradation accelerator, surface hydrolysis inhibitor, other functional additives with 10-30 parts of biodegradable resin, melt extrusion, extrusion temperature is 140-180℃, to make high concentration of master batch; Mix the master batch with the remaining biodegradable resin, melt extrusion again, extrusion temperature is 160-190℃, cooling and granulation, to obtain modified biodegradable plastic; wherein, the biodegradable resin is added in multiple ways to improve the uniformity of each component, thereby obtaining better performance.

[0008] (2) Put the modified biodegradable plastic into the injection molding machine, heat to the molten state, then inject into the seedling raising frame mold, the injection pressure is 50-70 Mpa, to ensure the flowability of the material in the mold, so as to achieve good filling effect and avoid molding defects, the mold temperature is controlled at (25±2)℃, to optimize the cooling rate of the material, 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, to ensure the shape stability and density of the product, after injection molding is completed, stop the mold heat preservation, maintain the cooling time in the mold for 10-15 minutes, after the product temperature drops to room temperature, carry out demolding operation, to form seawater-degradable seedling raising frame.

[0009] In some specific embodiments, in step (1), the biodegradable resin is selected from one or more of polybutylene succinate (PBS), polyester amide (PEA), polycaprolactone (PCL), and polylactic acid (PLA); the above biodegradable resin has high tensile and bending strength, can resist ocean current impact, and has good dispersion effect on subsequent non-enzymatic seawater degradation accelerator, enzymatic seawater degradation accelerator, 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 hydroxyl ions (OH⁻) by reacting with water molecules, thereby increasing the alkalinity of the environment and accelerating the hydrolysis process. In addition, the hydroxyl ions (OH⁻) break the ester bonds in the polymer, generating carboxylate ions (-COO⁻) and hydroxyl groups (-OH) after breaking, and further reacting with water molecules to generate carboxylic acid and alcohol low molecular compounds, enhancing their affinity for water, promoting the hydrolysis and degradation of the polymer molecular chain, and thus accelerating the chemical degradation of the material. At the same time, the metal ions produced by the ionization of alkaline earth metal compounds can form coordinate bonds with the oxygen atoms of the ester bond, which further enhances the positive charge of the carbonyl carbon atom, reduces the energy barrier of the OH⁻ nucleophilic attack, and makes the ester bond more prone to break, 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 somewhat milder than calcium oxide in the accelerator, allowing for the continuous and stable release of OH⁻, matching the service period (60-120 days) of degradable plastics, avoiding fluctuations in degradation rate, and not introducing SO4 2 ⁻ like calcium sulfate (CaSO4), and having stronger alkalinity and better hydrolysis catalysis than magnesium oxide (MgO) and magnesium hydroxide (Mg (OH)2).

[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. Such polymers can bind to the surface receptors of microbial cell membranes through their own polar groups such as hydroxyl, carboxyl, and amino groups, promoting the rapid adsorption, colonization, and proliferation of microorganisms on the surface of degradable plastics. Under the induction of the accelerator components, the proliferated marine microorganisms will secrete degradation enzymes (esterases) that target the molecular chains of degradable plastics, dissolve the degradable resins to form internal defects, and promote the aggregation of microorganisms to participate in degradation. In addition, certain components such as sodium alginate can undergo in-situ cross-linking or chelation reactions with non-enzymatic accelerators (such as calcium ions) in the formula, forming 'egg box structures' or rigid networks in the matrix. This design not only provides mechanical support during the seedling growth period, but also allows the network to collapse due to ion exchange in the later stage, achieving complete disintegration.

[0014] In some specific embodiments, the surface hydrolysis inhibitor is a polyethylene wax. As a lubricant, the polyethylene wax effectively reduces the melt viscosity, reduces the friction heat in the processing process, thereby avoiding thermal degradation of the material; it has good compatibility with the degradable resin matrix and will spontaneously migrate to the surface of the plastic during plastic processing (such as injection molding, extrusion) to form a dense hydrophobic film, building a hydrolysis protection barrier, significantly delaying the initial penetration of moisture into the material, while blocking the direct action of hydroxyl ions (OH⁻), salt ions (Na⁺, Cl⁻) and degradation enzymes secreted by microorganisms in seawater on the surface of the plastic, delaying the hydrolytic cleavage of the surface ester bond, and avoiding premature failure phenomena such as powdering and brittle cracking on the surface of the plastic.

[0015] In some specific embodiments, the other functional additives in step (1) include one or more of ultraviolet light stabilizers, diffusers, and flow enhancers.

[0016] In another aspect, the application provides a seawater-degradable seedling raising frame prepared by the preparation method of the seawater-degradable seedling raising frame, wherein the seawater-degradable seedling raising frame is an open-top and closed-bottom frame, the open-top radius of the frame is 25-40 cm, the depth of the frame is 20-30 cm, and the bottom of the frame is provided with a plurality of drainage holes, the density of the drainage holes is 60-90 per square meter, and the hole diameter is 2-4 cm. The plurality of drainage holes designed at the bottom of the frame ensure appropriate water flow and drainage capacity, which is helpful for oxygen penetration and growth of root systems.

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

[0018] In still another aspect, the application provides the use of the seawater-degradable seedling raising frame described above in mariculture or ecological restoration of seaweed beds.

[0019] The application has the following beneficial effects: The preparation method of the seawater-degradable seedling raising frame and the seawater-degradable seedling raising frame prepared by the method simplify the seaweed transplanting process, reduce the need for manual operation, do not require the seedlings to be taken out of the seedling substrate, realize integrated operation of the seaweed seedlings from seedling raising to transplantation, reduce damage to the seedlings, and improve the transplantation efficiency; the use of non-degradable plastic support frames is avoided, marine plastic pollution is reduced from the source, and the marine ecological environment is protected; through optimization of the material formula and structural design of the seedling raising carrier, the degradation is controllable, a good growth environment is provided for the seaweed seedlings, the growth cycle (60-120 days) of the seaweed seedlings is covered, and the survival rate and growth speed of the seaweed seedlings after transplantation are improved. BRIEF DESCRIPTION OF DRAWINGS

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

[0021] Figure 2 This is a schematic diagram of the seawater biodegradable seedling raising frame of the present invention. Figure Two . 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] Mature stage (24 weeks and above): In this stage, the pot should enter disintegration to avoid hindering the natural propagation of Zostera marina, rapid biodegradation, so as to promote the nutrient feedback to the marine ecosystem.

[0028] Therefore, the seawater-degradable seedling raising frame prepared by the embodiments of the present application solves the above technical problems.

[0029] Embodiment 1 The present embodiment provides a preparation method of a seawater-degradable seedling raising frame, which specifically comprises the following steps: (1) Preparation of modified biodegradable plastic: the following raw materials are provided in the weight ratio: 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, with an extrusion temperature of 150°C, to prepare a high-concentration master batch; Mix the master batch with the remaining PBS to ensure uniform dispersion of all ingredients, and perform melt blending again, and a part of the melt blended material is injection molded into a standard test bar; The remaining melt blended material is melt extruded at an extrusion temperature of 190°C, and the extruded material is rapidly cooled using a cooling water tank, and then cut into particles to obtain the desired granular modified biodegradable plastic; (3) Put the modified biodegradable plastic into an injection molding machine, heat it to a molten state, and then inject it into a seedling raising frame mold. As shown in Figure 1 , Figure 2 The specifications of the seawater-degradable seedling raising frame formed by the mold are as follows: The seawater-degradable seedling raising frame is a circular frame with a circular opening at the top and a closed bottom, The upper opening has a radius of 30 cm and a depth of 25 cm, The drainage hole design has a hole diameter of 3 cm and a density of 80 holes per square meter, Or, the seawater-degradable seedling raising frame is a square frame with a square opening at the top and a closed bottom, the upper opening has a side length of 100 cm and a depth of 25 cm The depth is 25 cm, The drainage hole design has a hole diameter of 3 cm and a density of 80 holes per 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 holding is stopped, the cooling time in the mold is maintained for 13 minutes, and then the demolding operation is performed after the product temperature is reduced to room temperature, to form the seawater-degradable seedling raising frame.

[0030] Embodiment 2 The polybutylene succinate (PBS) of Example 1 is replaced by polycaprolactone (PCL), and the raw material weight ratio is as follows: polycaprolactone (PCL): 90, calcium carbonate: 5, sucrose: 4, PE wax: 1, and the rest is the same as Example 1.

[0031] Example 3 The calcium carbonate of Example 1 is replaced by calcium hydroxide, and the raw material weight ratio is as follows: PBS: 90, calcium hydroxide: 5, sucrose: 4, PE wax: 1, and the rest is the same as Example 1.

[0032] Example 4 The sucrose of Example 1 is replaced by sodium alginate, and the raw material weight ratio is as follows: PBS: 90, calcium hydroxide: 5, sodium alginate: 4, PE wax: 1, and the rest is the same as Example 1.

[0033] Example 5 The ratio of calcium carbonate and sucrose in Example 1 is adjusted, and the total ratio of calcium carbonate and sucrose is 9, which is the same as Example 1, but the ratio of sucrose is significantly higher than that of calcium carbonate. The raw material weight ratio is as follows: PBS: 90, calcium carbonate: 3, sucrose: 6, PE wax: 1, and the rest is the same as Example 1.

[0034] Example 6 The ratio of calcium carbonate and sucrose in Example 1 is adjusted, and the total ratio of calcium carbonate and sucrose is 9, which is the same as Example 1, but the ratio of sucrose is significantly lower than that of calcium carbonate. The raw material weight ratio is as follows: PBS: 90, calcium carbonate: 7, sucrose: 2, PE wax: 1, and the rest is the same as Example 1.

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

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

[0037] Comparative Example 3 The sucrose of Example 1 is replaced by calcium carbonate, and the raw material weight ratio is as follows: PBS: 90, calcium carbonate: 9, PE wax: 1, and the rest is the same as Example 1.

[0038] Comparative Example 4 This example does not add PE wax, and the raw material weight ratio is as follows: PBS: 90, calcium carbonate: 5, sucrose: 4, and the rest is the same as Example 1.

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

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

[0041] Comparative Example 7 In this example, the PE wax ratio of Example 1 is increased. The weight ratio of raw materials is as follows: PBS: 88, calcium carbonate: 5, sucrose: 4, PE wax: 3, and the rest is the same as Example 1.

[0042] Comparative Example 8 In this example, commercially available paper seedling pots are used.

[0043] Test Example 1 In this test example, the mechanical properties of the standard test strips prepared in Examples 1-6 and Comparative Examples 1-7 are tested. According to GB / T 1040.2-2022 standard, the tensile strength, bending strength, and elongation at break are tested using a standard strip universal tensile testing machine. After 45 days, 90 days, and 180 days of marine environment simulation, the tensile strength is tested and the tensile strength retention rate is calculated. After completing the 180-day seedling period, the weight loss rate is tested.

[0044] The results are shown in Table 1 below. According to the results in Table 1, compared with the blank control Comparative Example 1, the modified materials prepared in Examples 1-6 of the present application have excellent mechanical properties, and the tensile strength retention rate is more than 60% after 45 days, and the disintegration start time is 71-82 days, which is successfully adjusted to close to 12 weeks, meeting the needs of different growth periods of seaweed. The weight loss after 180 days is more than 70%, which is significantly higher than the 14% of Comparative Example 1.

[0045] Examples 2-4 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 materials can be effectively adjusted.

[0046] The biodegradable resin in Example 2 is replaced by polycaprolactone (PCL) instead of PBS, the strength is slightly lower, but the initial elongation at break is far more than other examples, the toughness is good, the tensile strength retention rate is 61.5% after 45 days, the material performance can effectively ensure that the root system can be well anchored and grown, and the weight loss is 89.9% after 180 days, the material is almost completely disintegrated, and will not cause secondary pollution.

[0047] In Example 3, the non-enzymatic seawater degradation accelerator is calcium hydroxide, and the tensile strength retention rate is lower than that of Example 1, but the weight loss is 78.4% after 180 days, which is higher than that of Example 1, that is, it is easier to disintegrate than Example 1.

[0048] In Example 4, the enzymatic seawater degradation accelerator is sodium alginate, and compared with Example 1, the tensile strength is improved, and the mechanical retention rate is also improved after 90 days, but the weight loss is 77.4% after 180 days, which begins to exceed Example 1, that is, it can more effectively maintain the mechanical strength during the functional period than Example 1, but it is easy to disintegrate in the long tail (180 days).

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

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

[0051] In Example 6, the total ratio of calcium carbonate and sucrose is the same as that of Example 1, but the sucrose ratio is significantly lower than that of calcium carbonate, and the tensile strength retention rate is about 3% lower than that of Example 1, and the weight loss is 71% less than Example 1, which is not easy to disintegrate compared with Example 1.

[0052] The blank control comparative example 1 is a PBS commodity, which begins to disintegrate at 35 days, has a short functional period and does not meet the requirements, and the weight loss is only 14% after 180 days after the functional period, which cannot be quickly degraded.

[0053] Comparative examples 2 to 4 verify the necessity of non-enzymatic seawater degradation accelerator, enzymatic seawater degradation accelerator and surface hydrolysis inhibitor components, and it is shown that the disintegration start point cannot be accurately adjusted to 12 weeks under the premise of maintaining the initial mechanical properties.

[0054] Comparative example 2 does not contain non-enzymatic seawater degradation accelerator calcium carbonate, and the tensile strength retention rate is 88% after 180 days, and the disintegration start time is 95 days, which is not easy to disintegrate compared with Examples 1-6, and the disintegration time is relatively late, which is not conducive to the root development of seagrass seedlings.

[0055] Comparative Example 3 does not contain the enzymatic seawater degradation accelerator sucrose, and its 180-day tensile strength retention rate reaches 79.4%, and the disintegration starting time is 58 days. It is easy to disintegrate compared with Examples 1-6, but the disintegration time is too early, which is exactly in the growth stage of seaweed, and cannot ensure that the root system can be well anchored and grown.

[0056] Comparative Example 4 does not contain the surface hydrolysis inhibitor PE wax, and its 45-day tensile strength retention rate is 34%, the 90-day tensile strength retention rate is 18.2%, and the 180-day tensile strength retention rate is only 14.5%. The disintegration starting time is 26 days, which is too low in mechanical strength compared with Examples 1-6, easy to disintegrate, and the disintegration time is in the seedling stage of seaweed, which cannot support the healthy growth of seaweed root system in seawater.

[0057] Comparative Examples 5 and 6 discuss the influence of insufficient and excessive content of hydrolysis accelerators (enzymatic and non-enzymatic), and Comparative Example 7 discusses the effect of excessive surface hydrolysis inhibitor component, emphasizing the key of proper ratio to material performance.

[0058] Comparative Example 5 reduces the total ratio of calcium carbonate and sucrose in Example 1, and the total ratio of calcium carbonate and sucrose is 3, Its 45-day tensile strength retention rate is 72.2%, the 90-day tensile strength retention rate is 65.4%, and the 180-day tensile strength retention rate still reaches 54.2%. The mechanical properties are better than those of Examples 1-6, but the disintegration starting time is 102 days, and the 180-day weight loss is 64.2%, indicating that its degradation speed is poorer than that of Examples 1-6, and it is not easy to disintegrate.

[0059] Comparative Example 6 increases the total ratio of calcium carbonate and sucrose in Example 1, and the total ratio of calcium carbonate and sucrose is 20. Its 45-day tensile strength retention rate is 60.7%, the 90-day tensile strength retention rate is 40.4%, and the 180-day tensile strength retention rate is 30.5%. The mechanical properties are poorer than those of Examples 1-6, and the disintegration starting time is 56 days, and the 180-day weight loss is 85.1%, indicating that its degradation speed is faster than that of Examples 1-6, and it is easy to disintegrate, but it is exactly in the growth stage of seaweed, and cannot ensure that the root system can be well anchored and grown.

[0060] Comparative Example 7 increases the ratio of PE wax in Example 1, and its 45-day, 90-day, and 180-day tensile strength retention rates are much higher than those of Examples 1-6, and the mechanical properties are much better than those of Examples 1-6, but the disintegration starting time is 178 days, and the 180-day weight loss is only 30.5%, indicating that its degradation speed is much poorer than that of Examples 1-6, and it is not easy to disintegrate and cause secondary pollution.

[0061] Test Example 2 The seawater degradable seedling raising frame of Examples 1-6 and Comparative Examples 1-7 and the commercially available paper seedling raising pot of Comparative Example 8 were used to cultivate the growth conditions of sea grass, and the sea grass selected was Zostera marina. The experimental site was in the Bohai Sea, the temperature was 22+-5 degrees, and the sea grass seedling period was usually 60-120 days. The sea grass growth condition results are as follows: Table 2: Sea grass growth conditions in the seedling raising frame In Table 2, the 45-day survival rate (%) indicates the survival rate of sea grass seedlings after planting in the seedling raising frame, reflecting the initial adaptability of the seedling raising frame. The 45-day sea grass adhesion evaluation (1-5) indicates the tightness of the sea grass root system and the seedling raising frame (5 is the best), reflecting the support ability of the seedling raising frame to the root system.

[0062] For the 45-day survival rate (%) and the 45-day sea grass adhesion evaluation, Examples 1-6 and Comparative Examples 2-7 are much better than Comparative Example 1 and Comparative Example 8, which obviously shows that the mechanical properties of the seedling raising frame prepared by the present application are much better than the 100% PBS of Comparative Example 1 and the commercially available paper seedling raising pot of Comparative Example 8, so that the seedling raising frame has sufficient mechanical strength to support the healthy growth of seedling roots in seawater within 45 days, and ensures that the pot body is not easy to break or deform under seawater soaking.

[0063] For the 120-day sea grass stem length, Examples 1-6 reached 45-48 cm, with an average of 46.3 cm, and in the comparative examples, only Comparative Example 2 was 45 cm, and the rest were only 38-42 cm, with an average of 41.4 cm. For the 180-day sea grass stem length, Examples 1-6 reached 62-71 cm, with an average of 66.8 cm, and in the comparative examples, only Comparative Example 2 was 67 cm, and the rest were only 51-62 cm, with an average of 52.75 cm. As can be seen, the seawater degradable seedling raising frame prepared using Examples 1-6 to cultivate sea grass has significantly better sea grass growth conditions than Comparative Examples 1-7 and the commercially available paper seedling raising pot.

[0064] In summary, the seawater degradable seedling raising frame prepared according to Examples 1-6 of the present application is significantly better than Comparative Examples 1-7 and the commercially available paper seedling raising pot in terms of seedling raising performance, and is suitable for seawater aquaculture and ecological restoration of sea grass beds.

[0065] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

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; 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-degradable seedling raising frame as described in claim 1, characterized in that, In step (1), the biodegradable resin is selected from one or more of polybutylene succinate (PBS), polyesteramide (PEA), polycaprolactone (PCL), and polylactic acid (PLA); and / or, the non-enzymatic seawater degradation accelerator is selected from oxides, hydroxides, and complexes of alkaline earth metals; and / or, 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.

3. The method for preparing the seawater biodegradable seedling raising frame as described in claim 1 or 2, characterized in that, The surface hydrolysis inhibitor mentioned in step (1) is polyethylene wax.

4. The method for preparing the seawater biodegradable seedling raising frame as described in claim 1 or 2, characterized in that, The non-enzymatic seawater degradation accelerator mentioned in step (1) is selected from one or more of calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, calcium carbonate, and calcium sulfate.

5. The method for preparing the seawater biodegradable seedling raising frame as described in claim 4, characterized in that, The non-enzymatic seawater degradation accelerator mentioned in step (1) is calcium hydroxide and / or calcium carbonate.

6. The method for preparing the seawater-degradable 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.

7. The seawater-degradable seedling raising frame prepared by the method described in any one of claims 1-6, 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.

8. The seawater biodegradable seedling raising frame as described in claim 7, 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.

9. 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 8 or 9 in mariculture or seagrass bed ecological restoration.

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