Waterproof coating for biomass-based nursery pots and methods of making and using the same

Abstract

The present application belongs to the technical field of agricultural breeding disc, and particularly relates to a waterproof coating for biomass-based seedling raising pot disc and a preparation method and application thereof. The preparation method of the waterproof coating provided by the present application uses ethyl acetate as a solvent, performs cross-linking copolymerization reaction on epoxy vegetable oil, phosphoric acid and rosin ester to obtain a coating liquid, then coats the coating liquid on the inner and outer surfaces of the pot disc, and obtains the waterproof coating through solidification. The above method can obtain a vegetable oil-based cross-linked polymerized waterproof coating with appropriate cross-linking degree. After 2 months of waterproof test, the coating does not collapse and disintegrate, has a low penetrable strength, can effectively improve the waterproofness of the biomass-based seedling raising pot disc after use, avoids collapse of the pot disc before transplanting, can ensure normal penetration of the seedling through the pot disc after transplanting, and is very suitable for use of the biomass-based seedling raising pot disc.

Description

Technical Field

[0001] This invention belongs to the field of agricultural breeding tray technology, specifically relating to a waterproof coating for biomass-based seedling trays, its preparation method, and its application. Background Technology

[0002] The pot seedling transplanting technique refers to sowing seeds in pots containing nutrient soil to promote germination, and then transferring the seedlings along with their pots to the field for transplanting when they are of suitable age. This technique can effectively extend the growth period of crops and is one of the effective ways to improve crop yield and quality, especially suitable for cold regions in northern my country (such as Heilongjiang).

[0003] Currently, plastic seedling trays are the primary seedling carrier used in pot-based seedling transplanting technology. However, plastic trays are difficult to degrade after transplanting, easily causing environmental pollution. Furthermore, as crops grow and their root systems develop, the non-degradability of plastic trays severely restricts root growth and aeration. Biomass-based seedling trays, on the other hand, are a new type of tray made from agricultural waste using hot-pressing molding technology. Replacing plastic trays with biomass trays not only solves the problems of poor water and air permeability associated with plastic trays, but also allows seedlings and biomass trays to be transplanted together in the field, meeting the agricultural production needs during crop seedling transplanting. The trays also completely degrade after being placed in the soil, providing nutrients for the transplanted seedlings. Therefore, replacing plastic seedling trays with biomass-based seedling trays will become the mainstream trend in future agricultural breeding development, and the further development and utilization of biomass-based seedling trays has attracted widespread attention from researchers.

[0004] Currently, research on biomass-based seedling trays mainly focuses on fibrous biomass. These trays are typically made from readily available and inexpensive cellulose-rich biomass materials such as straw (wheat, corn, rice), grass fiber, sawdust, and branches. They not only possess excellent air permeability but also are easily biodegradable, increasing soil fertility after degradation. Furthermore, the trays can be directly transplanted with crops, allowing seedling roots to easily penetrate the tray and absorb nutrients from the soil. However, existing fibrous biomass seedling trays are showing increasingly significant limitations in field applications: during the seedling stage, in waterlogged or high-humidity environments (such as in seedling greenhouses), the trays are prone to disintegration, losing their load-bearing capacity and collapsing before transplanting. This disrupts the transplanting process and severely restricts their application.

[0005] Therefore, how to improve the waterproofing ability of existing biomass seedling trays to ensure the smooth transplanting process, while also ensuring that the seedling roots can effectively penetrate the base of the tray after transplanting to promote the normal growth of the seedlings, has become the technical problem that this invention urgently needs to solve. Summary of the Invention

[0006] In view of this, the first objective of the present invention is to provide a method for preparing a waterproof coating for biomass-based seedling trays. The waterproof coating prepared by this method can effectively improve the waterproofness of biomass-based seedling trays, prevent the trays from disintegrating and collapsing before transplanting, and at the same time have low penetration strength, which can ensure that seedlings can normally penetrate the trays after transplanting to absorb nutrients from the soil.

[0007] The second objective of this invention is to provide a waterproof coating for biomass-based seedling trays, which can effectively improve the waterproofness of biomass-based seedling trays while having low penetration strength, making it suitable for use in biomass-based seedling trays.

[0008] A third objective of this invention is to provide an application of a waterproof coating for biomass-based seedling trays.

[0009] The fourth objective of this invention is to provide a waterproof biomass-based seedling tray, which has good waterproofness and penetration strength, and can ensure the smooth implementation of the seedling transplanting process.

[0010] One of the objectives of this invention, and the technical solution adopted, is:

[0011] (1) Mix the epoxidized vegetable oil, ethyl acetate and rosin ester evenly to obtain a mixture;

[0012] (2) Cool the mixture to -10 to 10°C, then add phosphoric acid and shake, then react at 45 to 75°C. Repeat the shaking and reaction operations to obtain the coating solution.

[0013] (3) Apply the coating liquid obtained in step (2) evenly to the inner and outer surfaces of the biomass-based seedling tray, cure at 60-120℃ for 25-35s, and then repeat the coating and curing operation to obtain a waterproof coating for the biomass-based seedling tray.

[0014] The ratio of epoxidized vegetable oil, ethyl acetate, rosin ester, and phosphoric acid is 1g:(0.8-1.2)mL:(0.4-0.7)g:(0.06-0.08)g; in step (1), the epoxy value of the epoxidized vegetable oil is 6.2%-8.6%; in step (2), the total number of shaking and reaction operations is 5-8 times; in step (3), the total number of coating and curing operations is 4-6 times.

[0015] The waterproof coating provided by this invention is prepared by using ethyl acetate as a solvent and undergoing a crosslinking copolymerization reaction of epoxidized vegetable oil, phosphoric acid, and rosin ester to obtain a coating liquid. This coating liquid is then applied to the inner and outer surfaces of a potter's tray and cured to obtain the waterproof coating. This invention, by strictly controlling the raw material ratios and reaction conditions, can obtain a coating liquid with suitable crosslinking degree, moderate viscosity, and good coating performance on bio-based potter's trays. After coating, a vegetable oil-based crosslinked polymerized waterproof coating can be effectively prepared. The main advantages of this waterproof coating are:

[0016] Firstly, the cross-linked polymer coating uses vegetable oil fatty chains as the polymer backbone structure. Since vegetable oil fatty chains have high hydrophobicity, the resulting coating also has good waterproof performance, which can give the potting tray excellent water resistance, reduce the risk of the potting tray cracking, disintegrating and collapsing when exposed to water before transplanting, and improve the load-bearing capacity of the potting tray.

[0017] Secondly, by reasonably controlling the degree of polymerization, the plant oil-based cross-linked polymer coating has a low penetration strength, which ensures that the roots can easily penetrate the pot and take root in the field soil, ensuring the timely supply of water, air and nutrients after transplanting, and enabling the seedlings to grow normally in the soil.

[0018] Thirdly, the prepared plant oil-based coating is a green and environmentally friendly bio-based coating type. By directly transplanting the coated pots and crops together, the biomass material in the pots can provide nutrients for crop growth, while the coating material, due to its plant oil fatty acid chains as a framework, will not pollute the soil after entering it. Furthermore, degradation tests before transplanting have confirmed that the degradation rate of the coating in the soil is low (≤1%), ensuring the stability of the pots before transplanting and preventing the pots from being degraded and damaged before transplanting.

[0019] Furthermore, in this invention, the introduction of rosin ester can both increase viscosity and facilitate coating, and participate in the polymerization reaction. Therefore, the amount of rosin ester used in this invention is controlled.

[0020] Furthermore, the epoxy value of the epoxy vegetable oil has an impact on the degree of cross-linking polymerization reaction. The present invention uses epoxy vegetable oil with an epoxy value of 6.2% to 8.6%, which can further improve the waterproof effect of the coating.

[0021] The inventors discovered in their experiments that the epoxy value of the epoxy vegetable oil determines the degree of unsaturation of the oil, and the difference in unsaturation affects the degree of polymerization of the waterproof coating, thereby affecting the waterproof performance and penetration performance of the coating. Therefore, the epoxy value of the epoxy vegetable oil needs to be strictly controlled. However, this invention does not impose any special limitations on the specific type of epoxy vegetable oil, as it will not have a substantial impact on the effect of the coating. Therefore, it is only necessary to ensure that the epoxy value of the epoxy vegetable oil is within the above-mentioned range. Therefore, in the above-mentioned scheme of this invention, there are many types of epoxy vegetable oils that can be used, and technicians can select them as needed. As a preferred scheme, in step (1), the epoxy vegetable oil is one of epoxy soybean oil, epoxy sunflower seed oil, epoxy rapeseed oil, epoxy rice bran oil, epoxy cottonseed oil, and epoxy linseed oil.

[0022] As a further preferred option, the epoxidized vegetable oil is epoxidized soybean oil or epoxidized linseed oil.

[0023] Furthermore, in step (2), the oscillation time is 25–35 s; the reaction is an ultrasonic reaction, and the reaction time is 25–35 s. The above-mentioned oscillation and reaction parameters are the preferred parameters for laboratory preparation of the coating solution. If large-scale coating production and factory application are carried out on biomass-based seedling trays, the oscillation and reaction parameters can be reasonably adjusted according to the performance of the coating solution.

[0024] Preferably, in step (2), the reaction temperature is 50–65°C.

[0025] As a more preferred embodiment, the oscillation time is 30s; the reaction time is 30s.

[0026] Preferably, in step (3), the biomass-based seedling trays are pre-dried at 70–120°C for 3–10 minutes before coating. When placed normally, biomass-based seedling trays inevitably absorb moisture from the air, especially in rainy weather and high-humidity environments. The absorption of large amounts of water by the trays can reduce their strength. This invention, through pre-drying technology, can remove moisture from the trays, making the surface dry and more conducive to the adhesion of the coating liquid during coating.

[0027] More preferably, in step (3), the curing temperature is 70 to 105°C.

[0028] This invention does not impose any special limitations on the material of the biomass-based seedling trays suitable for waterproof coating; any biomass material commonly used in the field of seedling trays can be used. More preferably, the biomass-based seedling trays are made of fibrous materials; the fibrous materials are selected from one or more of wheat straw, corn straw, rice straw, grass fiber, sawdust, and branches.

[0029] As a further preferred option, step (3) includes a constant temperature and humidity adjustment step after repeated coating and curing operations; the constant temperature and humidity adjustment is: adjusting under constant temperature and humidity conditions of 20-30℃ and 40-60% humidity for 20-30 hours. Through constant temperature and humidity adjustment, a waterproof coating with stable performance is obtained.

[0030] More preferably, the total number of coating and curing operations is 5.

[0031] The second objective of this invention is achieved through the following technical solution:

[0032] The waterproof coating for biomass-based seedling trays is prepared by the method described above.

[0033] Currently, the seedling cultivation cycle in pot-based seedling transplanting technology is generally 30-45 days. The waterproof coating provided by this invention did not collapse or disintegrate after a two-month waterproofing test, effectively maintaining the appearance and structure of the seedling tray. Therefore, the waterproof coating of this invention effectively improves the waterproofness of biomass-based seedling trays, preventing collapse before transplanting and greatly meeting the time requirements of pot-based seedling transplanting technology for the seedling cultivation period. Furthermore, the waterproof coating of this invention has a low penetration strength, only 19.1-26.5 N / mm. Further actual seedling cultivation tests showed that the penetration strength was controlled at <40 N / mm, allowing seedling roots to easily penetrate the coating. Thus, the waterproof coating of this invention ensures that seedlings can normally penetrate the seedling tray after transplanting, guaranteeing a timely supply of water, air, and nutrients, and enabling normal seedling growth in the soil. Furthermore, accelerated degradation tests confirmed that the coating provided by this invention exhibits a degradation rate of ≤1% after a 7-day degradation test. Actual seedling trials revealed that a degradation rate of ≤1% effectively prevents the coating from being degraded by the soil during the seedling stage (before transplanting). Therefore, the coating provided by this invention is highly suitable for use in biomass-based seedling trays.

[0034] Preferably, the thickness of the waterproof coating is 100-200 μm; more preferably, the thickness of the waterproof coating is 150 μm.

[0035] The third objective of this invention is achieved through the following technical solution:

[0036] The application of the waterproof coating for biomass-based seedling trays as described above, and its application as a special coating for biomass-based seedling trays.

[0037] The waterproof coating provided by this invention is used to coat the surface of biomass-based seedling trays. It can not only effectively improve the waterproofness of biomass-based seedling trays and prevent the trays from collapsing before transplanting, but also has low penetration strength, which can ensure that seedlings can penetrate the trays normally after transplanting. It is very suitable for use in biomass-based seedling trays.

[0038] The fourth objective of this invention is to adopt the following technical solution:

[0039] A waterproof biomass-based seedling tray includes a biomass-based tray substrate and a waterproof coating applied to the inner and outer surfaces of the substrate; the waterproof coating is the waterproof coating for biomass-based seedling trays as described above; the biomass-based tray substrate is made of fibrous material; the fibrous material is selected from one or more of wheat straw, corn straw, rice straw, grass fiber, wood chips, and branches.

[0040] The waterproof biomass-based seedling tray provided by this invention, by coating the inner and outer surfaces of the substrate with a waterproof coating, can obtain a tray material that has excellent waterproof performance, puncture resistance and biodegradability, which is more conducive to the promotion and application of biomass-based tray materials and is more in line with the concept of environmental protection and green development. Attached Figure Description

[0041] Figure 1 This refers to the compression molding test system used in the preparation of biomass-based seedling trays in Examples 1-6 and Comparative Examples 1-12 of the present invention;

[0042] Figure 2 These are actual images of the uncoated biomass-based seedling trays used in Examples 1-6 and Comparative Examples 1-12 of this invention;

[0043] Figure 3 These are actual photos of biomass-based seedling trays after being coated with a waterproof coating, as shown in Examples 1 (left) and 2 (right) of the present invention.

[0044] Figure 4 This is a physical image showing the waterproof effect of a biomass-based seedling tray coated with a waterproof coating in Example 2 of the present invention after a waterproof test.

[0045] Figure 5 This is a physical image showing the waterproof effect of the biomass-based seedling trays coated with the coating in Comparative Example 4 of this invention after a waterproofing test. Detailed Implementation

[0046] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of protection of the invention. Unless otherwise stated, the materials involved in this invention are all commercially available products in the art.

[0047] In the following examples, the phosphoric acid used is commercially available phosphoric acid with a concentration of 85%.

[0048] In the following embodiments, the biomass-based seedling trays used were prepared using a compression molding test system (for details on the structure of the compression molding test system, please refer to the prior art "Study on the Molding Characteristics of Seedling Trays Mixed with Corn Straw and Biogas Sludge [J]. Journal of Heilongjiang Bayi Agricultural Reclamation University, 2022(004):034"). Specifically, the compression molding test system consists of six parts: a WDW-200 micro-controlled electronic universal testing machine, a compression molding mold, a heating system, a cooling system, a temperature control system, and a computer control system (e.g., Figure 1 (As shown). During the preparation of the seedling trays, the compression molding mold used is designed based on the common 540mm × 280mm seedling tray size. The resulting seedling trays have an upper diameter of 54mm, a bottom diameter of 45mm, a height of 50mm, and a wall thickness of 5mm, forming a hollow cylindrical structure. The heating system consists of two parts: a heating rod is contained within the boss, with a temperature adjustment range of 0-700℃; the outer wall of the material frame is heated by a cast aluminum heating plate, with an operating temperature of 0-700℃. The cooling system uses circulating water cooling, with cooling pipes coiled and embedded inside the cast aluminum heating plate to quickly reduce the mold temperature. Since the compression molding test system is existing equipment, it will not be described in detail here.

[0049] In the following examples and comparative examples, the epoxidized vegetable oils involved are epoxidized soybean oil or epoxidized linseed oil, with an epoxy value ranging from 1.5% to 8.6%. More specifically, the epoxidized soybean oils used have epoxy values ​​of 1.5%, 3%, 4.5%, and 6.23%, respectively; the epoxidized linseed oil used has an epoxy value of 8.6%. The epoxidized soybean oil with an epoxy value of 6.23% is from Shanghai Maclean Biochemical Technology Co., Ltd.; the epoxidized soybean oils with epoxy values ​​of 1.5%, 3%, and 4.5% are from Shandong Baolilai Plastic Additives Co., Ltd.; and the epoxidized linseed oil with an epoxy value of 8.6% is from Wuhan Lindsay Chemical Co., Ltd.

[0050] Experimental studies revealed that the epoxy value of the epoxy vegetable oil determines its degree of unsaturation. Differences in unsaturation affect the polymerization degree of the waterproof coating, thus influencing its waterproof and permeability properties. Therefore, the epoxy value of the epoxy vegetable oil needs to be strictly controlled between 6.2% and 8.6%. However, this invention does not impose specific limitations on the particular type of epoxy vegetable oil, as it will not substantially affect the coating's effectiveness. Therefore, it is sufficient to ensure that the epoxy value of the epoxy vegetable oil is within the aforementioned range. Based on this, in other embodiments, other types of vegetable oils can also be used, such as epoxy sunflower seed oil, epoxy rapeseed oil, epoxy rice bran oil, and epoxy cottonseed oil, which can be selected by those skilled in the art as needed.

[0051] In the following embodiments, the biomass-based seedling trays used are made of fibrous materials, specifically rice straw. In other embodiments, biomass-based seedling trays made of common materials such as grass fiber, wood chips, and branches can also be selected.

[0052] More specifically, in the following embodiments, the specific preparation process of the biomass-based seedling trays is as follows: Rice straw (particle size ≤1mm, moisture content 12-14%) is used as the raw material for pressing the seedling trays, with 85g of straw used per tray. Before each experiment, the compression molding mold is preheated for 3-5 minutes to reach the target temperature (140-160℃). Then, 85±0.5g of raw material is weighed using an electronic analytical balance (JA2003) and added to the compression molding mold. The universal testing machine is run at a loading speed of 10mm / min for compression molding. The molding pressure during the compression process is automatically controlled by the computer control system, with a maximum pressure of 200kN. After reaching the required test pressure (160kN), the computer program automatically pauses and holds the pressure for 20s. After holding the pressure, the cooling system is turned on. When the mold temperature reaches below 25℃, cooling is paused, the universal testing machine's lifting program is started, the molded seedling trays are removed, and the seedling trays are marked and placed in a cool, ventilated place. The biomass-based seedling trays obtained after molding are as follows: Figure 2 As shown. The seedling tray has an upper diameter of 54mm, a bottom diameter of 45mm, a height of 50mm, and a wall thickness of 5mm, and is a hollow cylindrical structure.

[0053] Example 1

[0054] This embodiment provides a waterproof coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0055] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0056] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0057] (3) Place the biomass-based seedling trays in an oven at 70°C for 5 minutes. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 70°C for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25°C and 50% humidity for 24 hours to obtain a waterproof coating for the biomass-based seedling trays with a coating thickness of 150 μm.

[0058] This embodiment also provides a waterproof biomass-based seedling tray, including a biomass-based tray substrate and a waterproof coating applied to the inner and outer surfaces of the substrate; the waterproof coating is a waterproof coating prepared by the above method.

[0059] Example 2

[0060] This embodiment provides a waterproof coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0061] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0062] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0063] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a waterproof coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0064] This embodiment also provides a waterproof biomass-based seedling tray, including a biomass-based tray substrate and a waterproof coating applied to the inner and outer surfaces of the substrate; the waterproof coating is a waterproof coating prepared by the above method.

[0065] Example 3

[0066] This embodiment provides a waterproof coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0067] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 4g of rosin ester, vortex to dissolve, and obtain a mixture.

[0068] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0069] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a waterproof coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0070] This embodiment also provides a waterproof biomass-based seedling tray, including a biomass-based tray substrate and a waterproof coating applied to the inner and outer surfaces of the substrate; the waterproof coating is a waterproof coating prepared by the above method.

[0071] Example 4

[0072] This embodiment provides a waterproof coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0073] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0074] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 65℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0075] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a waterproof coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0076] This embodiment also provides a waterproof biomass-based seedling tray, including a biomass-based tray substrate and a waterproof coating applied to the inner and outer surfaces of the substrate; the waterproof coating is a waterproof coating prepared by the above method.

[0077] Example 5

[0078] This embodiment provides a waterproof coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0079] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0080] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 8 times to obtain the coating liquid.

[0081] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a waterproof coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0082] This embodiment also provides a waterproof biomass-based seedling tray, including a biomass-based tray substrate and a waterproof coating applied to the inner and outer surfaces of the substrate; the waterproof coating is a waterproof coating prepared by the above method.

[0083] Example 6

[0084] This embodiment provides a waterproof coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0085] (1) Take 10g of epoxy linseed oil with an epoxy value of 8.6% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0086] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0087] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a waterproof coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0088] This embodiment also provides a waterproof biomass-based seedling tray, including a biomass-based tray substrate and a waterproof coating applied to the inner and outer surfaces of the substrate; the waterproof coating is a waterproof coating prepared by the above method.

[0089] Comparative Example 1

[0090] This comparative example provides a coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0091] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0092] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0093] (3) Place the biomass-based seedling trays in an oven at 25°C for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 25°C for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25°C and 50% humidity for 24 hours to obtain a coating for the biomass-based seedling trays with a coating thickness of 150 μm.

[0094] This comparative example also provides a biomass-based seedling tray, including a biomass-based tray substrate and a coating applied to the inner and outer surfaces of the substrate; the coating is a coating prepared by the above method.

[0095] Comparative Example 2

[0096] This comparative example provides a coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0097] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0098] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0099] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 2. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a coating for the biomass-based seedling trays with a coating thickness of 70μm.

[0100] This comparative example also provides a biomass-based seedling tray, including a biomass-based tray substrate and a coating applied to the inner and outer surfaces of the substrate; the coating is a coating prepared by the above method.

[0101] Comparative Example 3

[0102] This comparative example provides a coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0103] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0104] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 1% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0105] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0106] This comparative example also provides a biomass-based seedling tray, including a biomass-based tray substrate and a coating applied to the inner and outer surfaces of the substrate; the coating is a coating prepared by the above method.

[0107] Comparative Example 4

[0108] This comparative example provides a coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0109] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0110] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 4% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0111] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0112] This comparative example also provides a biomass-based seedling tray, including a biomass-based tray substrate and a coating applied to the inner and outer surfaces of the substrate; the coating is a coating prepared by the above method.

[0113] Comparative Example 5

[0114] This comparative example provides a coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0115] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then dissolve by vortexing without adding rosin ester to obtain a mixture.

[0116] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0117] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0118] This comparative example also provides a biomass-based seedling tray, including a biomass-based tray substrate and a coating applied to the inner and outer surfaces of the substrate; the coating is a coating prepared by the above method.

[0119] Comparative Example 6

[0120] This comparative example provides a coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0121] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, and then add 3g of hydroxylated soybean oil as a comonomer, vortex to dissolve, and obtain a mixture.

[0122] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0123] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0124] This comparative example also provides a biomass-based seedling tray, including a biomass-based tray substrate and a coating applied to the inner and outer surfaces of the substrate; the coating is a coating prepared by the above method.

[0125] Comparative Example 7

[0126] This comparative example provides a coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0127] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, and then add 5.5g of hydroxylated soybean oil as a comonomer. Vortex to dissolve and obtain a mixture.

[0128] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0129] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0130] This comparative example also provides a biomass-based seedling tray, including a biomass-based tray substrate and a coating applied to the inner and outer surfaces of the substrate; the coating is a coating prepared by the above method.

[0131] Comparative Example 8

[0132] This comparative example provides a coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0133] (1) Take 10g of epoxidized soybean oil with an epoxy value of 1.5% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, and directly vortex to dissolve to obtain a mixture.

[0134] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0135] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0136] This comparative example also provides a biomass-based seedling tray, including a biomass-based tray substrate and a coating applied to the inner and outer surfaces of the substrate; the coating is a coating prepared by the above method.

[0137] Comparative Example 9

[0138] This comparative example provides a coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0139] (1) Take 10g of epoxidized soybean oil with an epoxy value of 3% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, and directly vortex to dissolve to obtain a mixture.

[0140] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0141] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0142] This comparative example also provides a biomass-based seedling tray, including a biomass-based tray substrate and a coating applied to the inner and outer surfaces of the substrate; the coating is a coating prepared by the above method.

[0143] Comparative Example 10

[0144] This comparative example provides a waterproof coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0145] (1) Take 10g of epoxidized soybean oil with an epoxy value of 4.5% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0146] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0147] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a waterproof coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0148] This comparative example also provides a waterproof biomass-based seedling tray, including a biomass-based tray substrate and a waterproof coating applied to the inner and outer surfaces of the substrate; the waterproof coating is a waterproof coating prepared by the above method.

[0149] Comparative Example 11

[0150] This comparative example provides a waterproof coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0151] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0152] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 35℃ for 30 s. Then repeat the vortex oscillation, heating and sonication operation. The total number of vortex oscillation, heating and sonication is 5 times to obtain the coating liquid.

[0153] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a waterproof coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0154] This comparative example also provides a waterproof biomass-based seedling tray, including a biomass-based tray substrate and a waterproof coating applied to the inner and outer surfaces of the substrate; the waterproof coating is a waterproof coating prepared by the above method.

[0155] Comparative Example 12

[0156] This comparative example provides a waterproof coating for biomass-based seedling trays, the preparation method of which includes the following steps:

[0157] (1) Take 10g of epoxidized soybean oil with an epoxy value of 6.23% into a 50mL centrifuge tube, add 10mL of ethyl acetate and mix, then accurately add 7g of rosin ester, vortex to dissolve, and obtain a mixture.

[0158] (2) Cool the mixture to 0℃ and keep it for 20 min. Then add phosphoric acid at 7% of the mass of epoxidized soybean oil, vortex for 30 s, then heat and sonicate at 50℃ for 30 s. Then repeat the vortex oscillation and heating and sonication operation. The total number of vortex oscillation and heating and sonication is 2 times to obtain the coating liquid.

[0159] (3) Place the biomass-based seedling trays in an oven at 105℃ for 5 minutes before baking. Then, evenly brush the coating liquid obtained in step (2) onto the inner and outer surfaces of the biomass-based seedling trays. After each layer of coating liquid is applied, place the trays in an oven at 105℃ for 30 seconds to cure. Then repeat the brushing and curing operations. The total number of brushing and curing operations is 5 times. Finally, place the coated and cured trays in a constant temperature and humidity chamber at 25℃ and 50% humidity for 24 hours to obtain a waterproof coating for the biomass-based seedling trays with a coating thickness of 150μm.

[0160] This comparative example also provides a waterproof biomass-based seedling tray, including a biomass-based tray substrate and a waterproof coating applied to the inner and outer surfaces of the substrate; the waterproof coating is a waterproof coating prepared by the above method.

[0161] Test case

[0162] I. Waterproofing effect test of biomass-based seedling trays

[0163] Distilled water, which occupies 3 / 4 of the volume of the biomass-based seedling trays with coatings, were added to the coated trays prepared in Examples 1-6 and Comparative Examples 1-12. The trays were placed at room temperature and observed for 2 months. The collapse of the trays and the time of collapse were recorded daily.

[0164] II. Coating puncture strength test

[0165] For the puncture strength test of the coating, the samples used were PET film specimens with a coating. During specimen preparation, coatings of equal thickness were prepared on the PET film under the same coating conditions as Examples 1-6 and Comparative Examples 1-12 (the curing temperature and time corresponded to those of Examples 1-6 and Comparative Examples 1-12, respectively). After coating preparation, the coated PET film specimens corresponding to Examples 1-6 and Comparative Examples 1-12 were placed in a constant temperature and humidity chamber at 25°C and 50% humidity for 24 hours, and then their puncture strength was measured. The puncture strength test was conducted using an LT-1000 full-function material testing machine. During the test, the coated PET film specimen was cut into circular films with a diameter of approximately 10 cm according to the size of the fixture. The circular films were fixed on the fixture, and the testing speed was set to 100 mm / min. The probe was used to puncture the circular film at the set speed until it penetrated the circular film. Two parallel samples were taken from each sample, and the puncture strength data were recorded.

[0166] III. Coating Degradability Test

[0167] This experiment involved accelerating the degradation of the coating in a high-temperature and high-humidity soil environment. First, PET film samples with the coating, corresponding to Examples 1-6 and Comparative Examples 1-12, were prepared according to the coating puncture strength test. Each sample was cut into square films approximately 5cm × 5cm in size. Two parallel samples were taken from each sample, weighed sequentially, and placed in a 60℃ oven to constant weight. The weights were then recorded after removal. Plastic petri dishes and soil were prepared. Soil was evenly spread throughout each plastic petri dish. The square film sample was then placed flat on top of the soil in the plastic petri dish, and another layer of soil was evenly spread over the film. The dishes were placed in a constant temperature and humidity chamber at 40℃ and 80% RH. Water was added every 24 hours to maintain high temperature and humidity within the soil, thus simulating the soil environment after transplanting. Seven days later, the samples were removed. Due to the stickiness of the sample surface, some soil would adhere to it, so the samples needed to be rinsed clean with water before being placed in a constant-weight aluminum box. The aluminum box containing the samples was then placed in an oven at 60°C for 10 hours. After removal, the samples were immediately placed in a desiccator and allowed to cool. The samples were then weighed sequentially to obtain the mass of the degraded samples. The degradation rate (%) was calculated based on the mass of the samples before and after degradation.

[0168] IV. Test Results

[0169] The comprehensive test results for water resistance, puncture resistance, and biodegradability are shown in Table 1. Figure 3 These are actual photos of biomass-based seedling trays after being coated with a waterproof coating, as shown in Examples 1 (left) and 2 (right) of the present invention. Figure 4 This is a physical image showing the waterproof effect of a biomass-based seedling tray coated with a waterproof coating in Example 2 of the present invention after a waterproof test. Figure 5This is a physical image showing the waterproof effect of the biomass-based seedling trays coated with the coating in Comparative Example 4 of this invention after a waterproofing test.

[0170] Table 1. Test results of water resistance, puncture resistance, and degradation rate for Examples 1-6 and Comparative Examples 1-12.

[0171]

[0172]

[0173] Combining Table 1 and Figures 3-5 As can be seen from Examples 1 and 2 and Comparative Example 1, a suitable curing temperature is necessary to promote effective cross-linking of the epoxy vegetable oil itself and with other components (phosphate and rosin esters), thereby ensuring a good waterproof effect. Examples 2 and Comparative Example 2 show that insufficient curing times result in an insufficiently dense coating network structure (reduced number of layers reduces the density of each layer), allowing water molecules to penetrate the network structure into the pot and cause collapse. Examples 2 and Comparative Examples 3 and 4 show that insufficient phosphate addition significantly weakens the cross-linking of the epoxy vegetable oil itself and with other components (phosphate and rosin esters), or even results in incomplete curing, leading to an insufficiently dense coating network structure. This allows water molecules to penetrate the network structure into the pot and cause collapse, failing to meet the usage requirements. As shown in Examples 2 and 5, the absence of rosin ester resulted in excessively high cross-linking of the epoxy vegetable oil itself and with phosphoric acid, leading to low flexibility and excessive rigidity in the coating, causing direct cracking. Examples 2 and 6 & 7 showed that the introduction of hydroxylated soybean oil weakened the effective cross-linking of the epoxy vegetable oil itself and with other components (phosphoric acid, rosin ester, hydroxylated soybean oil). Furthermore, the hygroscopic nature of the hydroxyl groups in the hydroxylated soybean oil made it easier for water molecules to penetrate the pot from the network structure, causing collapse and a significant increase in degradation rate. Examples 2 and 8 & 9 showed that an excessively low epoxy value greatly reduced the effective cross-linking of the epoxy vegetable oil itself and with other components (phosphoric acid, rosin ester), preventing it from curing into a gel and thus hindering subsequent performance testing.

[0174] Further comparison between Example 2 and Comparative Example 10 shows that while Comparative Example 10, using epoxidized soybean oil with a 4.5% epoxy value, passed the waterproof performance test and puncture strength requirements, its degradation rate in the accelerated degradation test in soil was high (41.64%). This would lead to premature degradation and failure before seedling transplanting, failing to meet the requirement of a degradation rate ≤1%, and thus also failing to meet the requirements for seedling cultivation and transplanting. Further comparison between Example 2 and Comparative Examples 11 and 12 shows that even with lower reaction temperatures or fewer reaction cycles, effective cross-linking of the epoxidized vegetable oil with other components (phosphate, rosin ester) to ensure waterproofing could still be achieved. However, the reduced degree of cross-linking resulted in a significantly increased degradation rate, leading to degradation and failure of the coating material before seedling transplanting, thus also failing to meet the requirements.

[0175] In summary, the waterproof coating prepared by this invention did not collapse or disintegrate after a two-month waterproof test, effectively maintaining the appearance and structure of the seedling tray substrate. Furthermore, the coating exhibits low penetration strength, only 19.1–26.5 N / mm, and effectively maintains its degradability for a certain period. Therefore, the waterproof coating of this invention not only effectively improves the waterproofness of biomass-based seedling trays, preventing collapse before transplanting, but also ensures that seedlings can penetrate the tray normally after transplanting, preventing premature degradation and failure of the coating. It has promising application prospects in the field of surface modification of biomass-based seedling trays.

Claims

1. A waterproof biomass-based nursery pot, characterized in that, The biomass-based seedling pot comprises a biomass-based pot base and a waterproof coating layer coated on the inner and outer surfaces of the biomass-based pot base; the biomass-based pot base is made of fiber materials; and the preparation method of the waterproof biomass-based seedling pot comprises the following steps: (1) uniformly mixing epoxy vegetable oil, ethyl acetate and rosin ester to obtain a mixed solution; (2) cooling the mixed solution to -10-10 ℃, then adding phosphoric acid and oscillating, and then reacting at 45-75 ℃, and repeatedly oscillating and reacting to obtain a coating solution; (3) uniformly coating the coating solution obtained in step (2) on the inner and outer surfaces of the biomass-based pot base, curing at 60-120 ℃ for 25-35 s, and then repeatedly coating and curing to obtain the waterproof biomass-based seedling pot; wherein, the thickness of the waterproof coating layer is 100-200 μm; the dosage ratio of the epoxy vegetable oil, ethyl acetate, rosin ester and phosphoric acid is 1 g:(0.8-1.2) mL:(0.4-0.7) g:(0.06-0.08) g; in step (1), the epoxy value of the epoxy vegetable oil is 6.2%-8.6%; in step (2), the total number of oscillation and reaction operations is 5-8 times; and in step (3), the total number of coating and curing operations is 4-6 times.

2. The waterproof biomass-based nursery pot according to claim 1, wherein, In step (1), the epoxy vegetable oil is one of epoxy soybean oil, epoxy sunflower seed oil, epoxy rapeseed oil, epoxy rice bran oil, epoxy cottonseed oil and epoxy linseed oil.

3. The waterproof biomass-based nursery pot of claim 2, wherein, The epoxy vegetable oil is epoxy soybean oil or epoxy linseed oil.

4. The waterproof biomass-based nursery pot of claim 1, wherein, In step (2), the oscillation time is 25-35 s; the reaction is ultrasonic reaction, and the reaction time is 25-35 s.

5. The waterproof biomass-based nursery pot of claim 1, wherein, In step (3), the biomass-based pot base is dried at 70-120 ℃ for 3-10 min before coating.

6. The waterproof biomass-based nursery pot of claim 1, wherein, In step (3), after the repeated coating and curing operations, a constant temperature and humidity adjustment step is further included; the constant temperature and humidity adjustment is carried out under the constant temperature and humidity conditions of 20-30 ℃ and 40-60% humidity for 20-30 h.

7. The waterproof biomass-based nursery pot of claim 1, wherein, The fiber materials are selected from one or more of wheat straw, corn straw, rice straw, grass fiber, wood chips and tree branches.

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