Dynamic temperature-sensitive modified coating material for regulating evolution of pore structure and preparation method of dynamic temperature-sensitive modified coating material

Abstract

The invention discloses a dynamic temperature-sensitive modified coating material for regulating the evolution of a pore structure and a preparation method of the coating material, and belongs to the technical field of controlled-release fertilizer production. The coating material disclosed by the invention is prepared from a bio-based stock solution, a homogenizing synergist and a dynamic temperature-sensitive modifier, the homogenizing and synergist is obtained by blending microcrystalline wax and soybean oil polyol; the dynamic temperature-sensitive modifier is obtained by reaction of a first component and a second component, wherein the first component is one or more of diamyl disulfide, p-toluene disulfide and alpha-benzoin oxime; and the second component is one or more of trimethyl hexamethylene diisocyanate, 2, 4-difluorophenyl isocyanate and 3, 3-diphenyl propyl isocyanate. The problem that a bio-based controlled-release fertilizer is not intelligent is solved, and the nutrient utilization rate is increased; the problems of non-uniformity and poor quality in the industrialization process of the bio-based controlled-release fertilizer are solved, and the intelligent and sustainable development of the controlled-release fertilizer is promoted.

Description

Technical Field

[0001] This invention relates to the field of controlled-release fertilizer production technology, specifically to a coating material with dynamic temperature-sensitive modification to regulate pore structure evolution and its preparation method. Background Technology

[0002] Chemical fertilizers play a vital role in improving crop yield and quality in agricultural production. However, their irrational use can easily lead to nutrient waste and environmental pollution. The emergence of controlled-release fertilizers has effectively solved this problem. Bio-based controlled-release fertilizers have advantages such as low cost, wide availability of raw materials, and minimal environmental impact, making them a promising direction for industry development. However, bio-based controlled-release fertilizers still face the following challenges, hindering their large-scale application: (1) The nutrient release curve is simple and not intelligent, and cannot be matched with the crop's fertilizer requirement curve, resulting in low nutrient utilization.

[0003] (2) During the solidification process, the bio-based coating solution is prone to uneven film formation and many cracks after film formation, which affects the controlled release efficiency of nutrients.

[0004] (3) The bio-based coating solution is viscous. During the solidification process, the bubbles generated by chemical reactions and physical stirring are difficult to be discharged, resulting in larger and more numerous pores in the membrane shell, causing rapid loss of nutrients.

[0005] To address the aforementioned issues with bio-based coated controlled-release fertilizers, patent CN117362107A discloses a coated controlled-release fertilizer containing a temperature-sensitive block copolymer switch and its preparation method. This method involves copolymerizing three block copolymers to form a temperature-sensitive block copolymer, which is then combined with a basic membrane material to create a temperature-sensitive coated controlled-release fertilizer. The principle is that the temperature-sensitive material reacts and crosslinks into the membrane material, causing it to expand and contract with temperature changes, thus controlling nutrient release. This modification enhances the intelligence of nutrient release and improves nutrient utilization. However, the phase transition temperature of this modified material is limited, severely restricting the product's application range. The relevant patent CN116355344A discloses a temperature-responsive smart controlled-release fertilizer and its preparation method. By reacting dynamic covalent bonds, a temperature-sensitive polymer, and a basic membrane material, a temperature-responsive membrane material is prepared. The principle is that through the synergistic effect of dynamic bonds and temperature-sensitive polymer, the temperature changes in the soil are intelligently identified, and the opening and closing of the membrane pores are controlled. This modification can intelligently respond to changes in the root environment temperature, realize autonomous switching, control the release of nutrients, and improve nutrient utilization. However, the addition of dynamic covalent bonds further increases the viscosity of the coating liquid, which leads to more air bubbles and larger pores in the membrane shell, reducing nutrient utilization. The relevant patent CN116042000A discloses a coated controlled-release fertilizer that uses visible light to solidify aquatic waste and its preparation method. A novel bio-based controlled-release fertilizer is prepared by a photocuring process. The principle is to add a photoinitiator to the coating liquid and achieve solidification under ultraviolet light. This modification effectively solves the problems of viscosity and unstable nutrient release of bio-based coating liquid. However, the nutrient release curve of this product is singular and cannot match the nutrient requirement curve of crops. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a coating material with dynamic temperature-sensitive modification to regulate pore structure evolution and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a coating material for dynamically temperature-sensitive modification to regulate pore structure evolution, which is prepared from a bio-based stock solution, a homogenizing agent and a dynamically temperature-sensitive modifier in a weight ratio of (8-15):(0.5-1):(2-3). The bio-based stock solution is obtained by reacting component A and component B at a mass ratio of 20:(2-4), wherein component A is polycaprolactone diol; and component B is one or more of succinic acid and pimelic acid. The uniformity-enhancing agent is obtained by blending microcrystalline wax and soybean oil polyol; The dynamic temperature-sensitive modifier is obtained by reacting the first component and the second component in a molar ratio of 1:(3-6). The first component is one or more of dipentyl disulfide, p-toluene disulfide, and α-benzoxime; the second component is one or more of trimethylhexane diisocyanate, 2,4-difluorophenyl isocyanate, and 3,3-diphenylpropyl isocyanate.

[0008] In some preferred embodiments of the present invention, the bio-based stock solution is prepared by the following method: Mix components A and B, add tetrabutyl titanate and concentrated sulfuric acid, and stir the mixture at 150-170℃ for 7-8 hours under nitrogen protection.

[0009] Preferably, the weight ratio of tetrabutyl titanate to component A is (0.1-0.3):20; the ratio of concentrated sulfuric acid to component A is (3-5) ml:20g.

[0010] Preferably, the stirring speed is 250-350 rap / min.

[0011] Tetrabutyl titanate and concentrated sulfuric acid act together as catalysts to induce a condensation polymerization reaction between components A and B, generating a biodegradable polyester polyol.

[0012] In some preferred embodiments of the present invention, the homogenizing and synergistic agent is prepared by the following method: The microcrystalline wax was dissolved by increasing the temperature, and the soybean oil polyol was dried in a vacuum environment. Then, the dissolved microcrystalline wax and the dried soybean oil polyol were ultrasonically mixed to prepare a uniform enhancer.

[0013] Preferably, the ratio of the added microcrystalline wax to soybean oil polyol is 1g:(20-30)ml.

[0014] In some preferred embodiments of the present invention, the dynamic temperature-sensitive modifier is prepared by the following method: Add the first component to acetone and sonicate it to distribute it evenly in the solution. Then, under nitrogen conditions, slowly add the second component to the first component and stir continuously for 5-15 minutes.

[0015] A second aspect of the present invention provides a method for preparing the above-mentioned dynamically temperature-sensitive modified coating material for regulating pore structure evolution, comprising the following steps: The bio-based stock solution and the uniformizing and enhancing agent were mixed in an organic solvent and ultrasonically stirred to promote the evaporation of the organic solvent, thus obtaining an intermediate. A dynamic temperature-sensitive modifier was added to the intermediate, followed by an organic solvent. The mixture was stirred rapidly to increase its fluidity. Then, dibutyltin dilaurate was added, and the mixture was stirred continuously under nitrogen gas. When the mixture became viscous, the stirring was stopped, and the air bubbles were removed to prepare a coating material with dynamic temperature-sensitive modification to regulate the evolution of pore structure.

[0016] Preferably, the solvent is N,N-dimethylformamide or acetone.

[0017] A third aspect of the present invention provides the application of the above-mentioned dynamically temperature-sensitive modified coating material for regulating pore structure evolution in the preparation of controlled-release fertilizers.

[0018] In a fourth aspect, the present invention provides a bio-based coated controlled-release fertilizer, comprising a fertilizer core and a coating material sprayed on the surface of the fertilizer core to regulate the evolution of its pore structure; wherein the coating material to regulate the evolution of its pore structure accounts for 1-5% of the weight of the fertilizer core.

[0019] A fifth aspect of the present invention provides a method for preparing the above-mentioned bio-based coated controlled-release fertilizer, comprising the following steps: The coating material, which is dynamically temperature-sensitive and modifies the pore structure evolution, is uniformly sprayed onto the surface of the fertilizer core at a pressure of 0.25-0.45 MPa and cured at 55-65°C for 10-15 minutes.

[0020] The beneficial effects of this invention are: (1) By adding a uniform and synergistic agent component to the coating material, the present invention effectively reduces the viscosity of the bio-based coating solution, improves the quality of the membrane shell, and ensures the stability of nutrient release.

[0021] (2) The coated controlled-release fertilizer prepared by this invention can respond to temperature changes. As the temperature changes, the molecular motion rate in the polyurethane network changes accordingly, which in turn changes the crosslinking density and porosity of the membrane structure, ultimately affecting the nutrient release rate. When the temperature increases, the molecular motion rate increases, the crosslinking density decreases, and the nutrient release rate increases, truly achieving intelligent controlled release. For crops, when the temperature is very low during the overwintering period, the crop's demand for nutrients is very small. At this time, even if nutrients are released, the crop cannot absorb them, which leads to incomplete nutrient utilization and nutrient waste. The coated controlled-release fertilizer of this invention can maintain a low nutrient release rate during the overwintering period. When the temperature rises in the second year, nutrients continue to be released, improving nutrient utilization, effectively alleviating the problem of nutrient loss, and preventing unused nutrients from entering the soil, groundwater, etc., and causing environmental pollution. Attached Figure Description

[0022] Figure 1Fourier transform infrared spectroscopy results of the membrane shells formed by curing the coating materials prepared in Examples 1-3 with dynamic temperature-sensitive modification to regulate pore structure evolution.

[0023] Figure 2 Scanning electron microscope images of the surface and cross-section of the polyurethane coating formed by the coating material of Example 1.

[0024] Figure 3 Atomic force microscopy (AFM) results of polyurethane coatings formed by the coating materials of Example 1 and Comparative Example 1.

[0025] Figure 4 Results of hydrophobicity testing on the surface of polyurethane coatings formed by the coating materials of Examples 1-3.

[0026] Figure 5 Pore ​​distribution of the polyurethane coating formed by the coating material of Example 1 at 15°C and 35°C.

[0027] Figure 6 Nutrient release of the coated controlled-release fertilizers prepared in Example 4 and Comparative Example 1 under different temperature conditions.

[0028] Figure 7 Results of nitrogen release rate determination of the coated controlled-release fertilizers prepared in Examples 4, 5, 6 and Comparative Examples 1-4. Detailed Implementation

[0029] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0030] As mentioned earlier, although bio-based coated fertilizers have advantages such as low cost, wide availability, and low environmental pollution, bio-based controlled-release fertilizers have poor controlled-release quality, a single nutrient release curve, and cannot regulate nutrient release to match crop needs. In addition, the viscosity of bio-based coating liquid is relatively high, which leads to more air bubbles and larger gaps in the membrane shell, affecting nutrient utilization.

[0031] In view of this, the present invention has developed a coating material that dynamically modifies and regulates the evolution of pore structure by thermosensitive modification. By crosslinking thermosensitive dynamic covalent bonds into a polyurethane network, the bio-based coated controlled-release fertilizer is endowed with temperature-responsive characteristics. As the temperature changes, the molecular motion rate in the polyurethane network changes accordingly, thereby changing the crosslinking density and porosity of the membrane structure, and ultimately affecting the nutrient release rate. When the temperature increases, the molecular motion rate increases, the crosslinking density decreases, and the nutrient release rate increases, truly achieving intelligent controlled release.

[0032] The dynamically temperature-sensitive modified coating material for regulating pore structure evolution of the present invention is prepared by reacting a dynamically temperature-sensitive modifier, a uniforming agent, and a bio-based stock solution. In one embodiment of the present invention, a method for preparing the dynamically temperature-sensitive modified coating material for regulating pore structure evolution is provided as follows: The bio-based stock solution and the homogenizing and enhancing agent were mixed in an organic solvent and placed in an ultrasonic stirrer for 20 minutes to promote the evaporation of the organic solvent and generate an intermediate.

[0033] The dynamic temperature-sensitive modifier was added to the intermediate, followed by the addition of an organic solvent. The mixture was stirred rapidly to increase its fluidity. Then, dibutyltin dilaurate was added, and the mixture was stirred continuously under nitrogen gas. When the mixture became viscous, the stirring was stopped. A vacuum drying oven was used to remove air bubbles, resulting in a coating material with dynamically temperature-sensitive modification to regulate the evolution of the pore structure.

[0034] The coating material of the present invention has characteristics such as low porosity, uniform structure, and temperature response. The working mechanism of the coating material of the present invention is as follows: The bio-based stock solution and the leveling agent are mixed in an organic solvent. The dissolved microcrystalline wax has excellent smoothness and reduces the viscosity of the bio-based stock solution. The "soybean oil polyol" in the leveling agent can work synergistically with the dissolved microcrystalline wax to further reduce the viscosity.

[0035] The first component of the dynamic temperature-sensitive modifier, upon the addition of acetone, transforms the dynamic covalent bonds into a free state, allowing them to be uniformly distributed in the solution. The addition of the second component effectively connects the dynamic covalent bonds at the reaction sites on both sides. With the addition of an intermediate, a temperature-sensitive cross-linked network is synthesized. The temperature-sensitive dynamic covalent bonds are uniformly cross-linked within the network, enhancing its temperature sensitivity. Furthermore, the flowing microcrystalline wax, during the curing process, blocks large pores, significantly reducing the porosity and number of air bubbles in the bio-based membrane shell after curing. The microcrystalline wax in the uniformizing and enhancing agent synergistically improves the controlled nutrient release effect of the prepared coating material in conjunction with the first component of the dynamic temperature-sensitive modifier.

[0036] In summary, to address the problems of inaccurate nutrient release and mismatch between nutrient release and crop nutrient requirements that arise during the large-scale application of existing bio-based coated fertilizers, this invention innovatively adds a dynamic temperature-sensitive modifier and a uniformity-enhancing agent to the coating material. The added uniformity-enhancing agent not only significantly reduces the number of pores and bubbles in the bio-based membrane shell, but also increases the smoothness and hydrophobicity of the membrane shell surface; the dynamic temperature-sensitive modifier provides temperature-sensitive covalent bonds (dynamic disulfide bonds and oxime ester bonds). During the synthesis of the temperature-sensitive crosslinking network, the uniformity synergist and the dynamic temperature-sensitive modifier work synergistically. The uniformity synergist penetrates into the network structure, blocking pores and bubbles, and improving the uniformity of the bio-based membrane shell. The dynamic bonds that crosslink into the network endow the bio-based coated controlled-release fertilizer with temperature-responsive characteristics. As the temperature changes, the molecular motion rate in the network changes accordingly, thereby changing the crosslinking density and porosity of the membrane structure, and ultimately affecting the nutrient release rate. When the temperature increases, the molecular motion rate increases, the crosslinking density decreases, and the nutrient release rate increases, thus achieving intelligent controlled release.

[0037] The optimal temperature range for most crops is 15-35℃. Below 15℃, nutrient absorption by crops decreases. Within the suitable temperature range for crop growth, higher temperatures result in more vigorous growth and higher nutrient requirements. This invention has a temperature response range of 0-50℃. By crosslinking temperature-sensitive dynamic covalent bonds into a polyurethane network, the molecular motion rate within the polyurethane network changes with temperature, thereby altering the crosslinking density and porosity of the membrane structure, ultimately affecting the nutrient release rate. When the temperature increases, the molecular motion rate increases, the crosslinking density decreases, and the nutrient release rate increases, achieving intelligent controlled nutrient release that changes with temperature.

[0038] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0039] The test materials used in the embodiments and comparative examples of this invention are all conventional test materials in the art and can be purchased through commercial channels. Specifically: Soybean oil polyols were purchased from Guangzhou Haierma Vegetable Oil Co., Ltd.; CAS number for dipentyl disulfide: 112-51-6; CAS number for p-toluene disulfide: 103-19-5; CAS number for α-benzoic acid oxime: 441-38-3; CAS number for polycaprolactone diol: 36890-68-3; CAS number for trimethylhexamethylene diisocyanate: 28679-16-5; CAS number for 2,4-difluorophenyl isocyanate: 59025-55-7; CAS number for microcrystalline wax: 8001-75-0.

[0040] Example 1: Preparation of coating materials with dynamically temperature-sensitive modification to regulate pore structure evolution (1) Add 2.06g of dipentyl disulfide to 10ml of acetone and sonicate continuously for 20min in an ultrasonic stirrer to ensure that the dipentyl disulfide is evenly distributed in the solution. Then add 8.4g of trimethylhexanediisocyanate and stir continuously for 10min under nitrogen gas to prepare a dynamic temperature-sensitive modifier.

[0041] (2) Place 1g of microcrystalline wax in a small aluminum box and raise the temperature to 80℃ to dissolve the microcrystalline wax; place 20ml of soybean oil polyol in a vacuum drying oven and dry the soybean oil polyol in a vacuum environment. Then, mix the dissolved microcrystalline wax and the dried soybean oil polyol in an ultrasonic oscillator and sonicate for 3 minutes to prepare the homogenizing and enhancing agent.

[0042] (3) Add 20g of polycaprolactone diol and 2.4g of succinic acid to a three-necked flask, add 0.2g of tetrabutyl titanate and 3ml of concentrated sulfuric acid, connect the nitrogen protection system and the condensation system, place the three-necked flask in an oil bath, raise the temperature to 160℃, turn on the magnetic stirring system, and stir at a speed of 250rap / min for 8h to obtain the bio-based stock solution.

[0043] (4) Take 14g of the bio-based stock solution synthesized in step (3) and 1g of the homogenizing and enhancing agent synthesized in step (2), mix them in 5ml of acetone, place them in an ultrasonic stirrer for 20min to promote the volatilization of acetone and generate intermediates.

[0044] Add 2g of the dynamic temperature-sensitive modifier synthesized in step (1) to the intermediate, then add 5ml of acetone, stir rapidly to make the solution more fluid, then add 1 drop (about 0.05ml) of dibutyltin dilaurate, and continue stirring under nitrogen gas. When the mixture becomes viscous, stop stirring and use a vacuum drying oven to remove air bubbles to obtain a coating material with dynamic temperature-sensitive modification to regulate the evolution of pore structure.

[0045] Example 2: Preparation of coating materials with dynamically temperature-sensitive modification to regulate pore structure evolution (1) Add 2.46g of p-toluene disulfide to 10ml of acetone and sonicate continuously for 20min in an ultrasonic stirrer to ensure that p-toluene disulfide is evenly distributed in the solution. Then add 7.75g of 2,4-difluorophenyl isocyanate and stir continuously for 10min under nitrogen gas to prepare a dynamic temperature-sensitive modifier.

[0046] (2) Place 1g of microcrystalline wax in a small aluminum box and raise the temperature to 80℃ to dissolve the microcrystalline wax; place 25ml of soybean oil polyol in a vacuum drying oven and dry the soybean oil polyol in a vacuum environment. Then, mix the dissolved microcrystalline wax and the dried soybean oil polyol in an ultrasonic oscillator and sonicate for 3 minutes to prepare the homogenizing and enhancing agent.

[0047] (3) Add 20g of polycaprolactone diol and 2.4g of succinic acid to a three-necked flask, add 0.2g of tetrabutyl titanate and 3ml of concentrated sulfuric acid, connect the nitrogen protection system and the condensation system, place the three-necked flask in an oil bath, raise the temperature to 160℃, turn on the magnetic stirring system, and stir at a speed of 300rap / min for 7.5h to obtain the bio-based stock solution.

[0048] (4) Take 8.5g of the bio-based stock solution synthesized in step (3) and 0.8g of the homogenizing and enhancing agent synthesized in step (2), mix them in 5ml of acetone, place them in an ultrasonic stirrer for 20min to promote the volatilization of acetone and generate intermediates.

[0049] Add 2g of the dynamic temperature-sensitive modifier synthesized in step (1) to the intermediate, then add 5ml of acetone, stir rapidly to make the solution more fluid, then add 1 drop of dibutyltin dilaurate, and continue stirring under nitrogen gas. When the mixture becomes viscous, stop stirring and use a vacuum drying oven to remove air bubbles to obtain a coating material with dynamic temperature-sensitive modification to regulate the evolution of pore structure.

[0050] Example 3: Preparation of coating materials with dynamically temperature-sensitive modification to regulate pore structure evolution (1) Add 2.27g of α-benzoxime to 10ml of acetone and sonicate continuously for 20min in an ultrasonic stirrer to ensure that the α-benzoxime is evenly distributed in the solution. Then add 14.22g of 3,3-diphenylpropyl isocyanate and stir continuously for 10min under nitrogen gas to prepare a dynamic temperature-sensitive modifier.

[0051] (2) Place 1g of microcrystalline wax in a small aluminum box and raise the temperature to 80℃ to dissolve the microcrystalline wax; place 30ml of soybean oil polyol in a vacuum drying oven and dry the soybean oil polyol in a vacuum environment. Then, mix the dissolved microcrystalline wax and the dried soybean oil polyol in an ultrasonic oscillator and sonicate for 3 minutes to prepare the homogenizing and enhancing agent.

[0052] (3) Add 20g of polycaprolactone diol and 3.2g of pimelic acid to a three-necked flask, add 0.2g of tetrabutyl titanate and 5ml of concentrated sulfuric acid, connect the nitrogen protection system and the condensation system, place the three-necked flask in an oil bath, raise the temperature to 160℃, turn on the magnetic stirring system, and stir at a speed of 350rap / min for 7h to obtain the bio-based stock solution.

[0053] (4) Take 10g of the bio-based stock solution synthesized in step (3) and 1g of the uniformity enhancer synthesized in step (2), mix them in 5ml of acetone, place them in an ultrasonic stirrer for 20min to promote the volatilization of acetone and generate intermediates.

[0054] Add 2.5g of the dynamic temperature-sensitive modifier synthesized in step (1) to the intermediate, then add 5ml of acetone, stir rapidly to make the solution more fluid, then add 1 drop of dibutyltin dilaurate, and continue stirring under nitrogen gas. When the mixture becomes viscous, stop stirring and use a vacuum drying oven to remove air bubbles to obtain a coating material with dynamic temperature-sensitive modification to regulate the evolution of pore structure.

[0055] Example 4: Preparation of Coated Controlled-Release Fertilizer Take 1000g of polished urea granules and put them into a coating pan at 65℃. Keep the coating pan rotating at 15 rpm. Use a spray gun to spray the coating material prepared in Example 1, which is dynamically temperature-sensitive and regulates the evolution of pore structure, onto the surface of the rolling urea granules. Let it cure for 10 minutes. Each spraying amount is 0.5% of the mass of the urea granules. Repeat the above spraying operation until the weight of the sprayed coating material accounts for 2.5% of the total weight of the urea granules. After stabilization, the coated controlled-release fertilizer is obtained.

[0056] Example 5: Preparation of Coated Controlled-Release Fertilizer Take 1000g of polished urea granules and place them in a coating pan at 60℃. Keep the coating pan rotating at 13 rpm. Use a spray gun to spray the dynamically temperature-sensitive modified coating material prepared in Example 2 to the surface of the rolling urea granules. Let it cure for 13 minutes. Each spraying amount is 0.5% of the mass of the urea granules. Repeat the above spraying operation until the weight of the coating liquid accounts for 2.3% of the total weight of the urea granules (the last spraying amount is 0.3% of the mass of the urea granules). After stabilization, the coated controlled-release fertilizer is obtained.

[0057] Example 6: Preparation of Coated Controlled-Release Fertilizer Take 1000g of polished urea granules and put them into a coating pan at 55℃. Keep the coating pan rotating at 10 rpm. Use a spray gun to spray the coating material prepared in Example 3, which is dynamically temperature-sensitive and regulates the evolution of pore structure, onto the surface of the rolling urea granules. Let it cure for 15 minutes. Each spraying amount is 0.5% of the fertilizer mass. Repeat the above spraying operation until the weight of the coating liquid accounts for 2% of the total weight of the urea granules. After stabilization, the coated controlled-release fertilizer is obtained.

[0058] Comparative Example 1: (1) Take 3g of soybean oil polyol and 2g of trimethylhexanediisocyanate and mix them evenly at room temperature. Continue stirring until the solution changes color and then stop stirring to obtain a bio-based coating solution.

[0059] (2) Take 1000g of polished urea granules and put them into a coating pan at 65℃. Keep the coating pan speed at 15rps. After preheating, use a spray gun to spray the bio-based coating liquid prepared in step (1) onto the surface of the rolling urea granules. Let it solidify for 10min. Each spraying amount is 0.5% of the fertilizer mass. Repeat the above spraying operation until the weight of the coating liquid accounts for 2.5% of the total weight of the urea granules. After stabilization, conventional bio-based coated fertilizer is obtained.

[0060] Comparative Example 2: The preparation method of the bio-based stock solution is the same as in Example 1.

[0061] Take 14g of bio-based stock solution and 1g of soybean oil polyol, mix them in 5ml of acetone, and place them in an ultrasonic stirrer for 20min to promote the volatilization of acetone and generate an intermediate.

[0062] Add 2g of trimethylhexamethylene diisocyanate to the intermediate, then add 5ml of acetone and stir rapidly to increase the fluidity of the solution. Next, add 1 drop (about 0.05ml) of dibutyltin dilaurate and continue stirring under nitrogen gas. When the mixture becomes viscous, stop stirring and use a vacuum drying oven to remove air bubbles to obtain coating material A.

[0063] Following the method in Example 4, coating material A was sprayed onto the surface of 1000g of polished urea granules to prepare a coated controlled-release fertilizer A with a coating amount of 2.5%.

[0064] This comparative example is equivalent to the first component without the addition of "microcrystalline wax" and "dynamic temperature-sensitive modifier".

[0065] Comparative Example 3: The preparation methods for the bio-based stock solution and the dynamic temperature-sensitive modifier are the same as in Example 1.

[0066] Take 14g of bio-based stock solution and 1g of soybean oil polyol, mix them in 5ml of acetone, and place them in an ultrasonic stirrer for 20min to promote the volatilization of acetone and generate an intermediate.

[0067] Add 2g of dynamic temperature-sensitive modifier to the intermediate, then add 5ml of acetone, stir rapidly to increase the fluidity of the solution, then add 1 drop (about 0.05ml) of dibutyltin dilaurate, and continue stirring under nitrogen gas. When the mixture becomes viscous, stop stirring and use a vacuum drying oven to remove air bubbles to obtain coating material B.

[0068] Following the method in Example 4, coating material B was sprayed onto the surface of 1000g of polished urea granules to prepare coated controlled-release fertilizer B with a coating amount of 2.5%.

[0069] This comparative example is equivalent to the one without the addition of "microcrystalline wax".

[0070] Comparative Example 4: The preparation methods for the bio-based stock solution and the uniformity enhancer are the same as in Example 1.

[0071] Take 14g of bio-based stock solution and 1g of uniform enhancer, mix them in 5ml of acetone, and place them in an ultrasonic stirrer for 20min to promote acetone volatilization and generate intermediates.

[0072] Add 2g of trimethylhexamethylene diisocyanate to the intermediate, then add 5ml of acetone and stir rapidly to increase the fluidity of the solution. Next, add 1 drop (about 0.05ml) of dibutyltin dilaurate and continue stirring under nitrogen gas. When the mixture becomes viscous, stop stirring and remove air bubbles using a vacuum drying oven to obtain coating material C.

[0073] Following the method in Example 4, coating material C was sprayed onto the surface of 1000g of polished urea granules to prepare a coated controlled-release fertilizer C with a coating amount of 2.5%.

[0074] This comparative example is equivalent to the first component without the addition of the "dynamic temperature-sensitive modifier".

[0075] Experimental Example 1: Determination of the viscosity of coating materials The viscosity of the coating materials prepared in Example 1 and Comparative Examples 1-4 was measured using a rotational viscometer, and the results are shown in Table 1.

[0076] Table 1: Viscosity of Coating Materials The results show that the microcrystalline wax dissolved in the coating material of the present invention has excellent smoothness and reduces the viscosity of the bio-based stock solution.

[0077] Experimental Example 2: Performance Evaluation of Coated Materials with Dynamically Thermosensitive Modification to Adjust Pore Structure Evolution The coating materials prepared in Examples 1-3, which exhibited dynamic temperature-sensitive modification to regulate pore structure evolution, were cured to form a membrane shell. Fourier transform infrared spectroscopy was used to detect changes in characteristic functional groups within the membrane shell. The results are as follows: Figure 1 As shown, the two characteristic peaks of polyurethane, NH group and C=O group, appear, while -NCO group completely disappears, indicating that the polyurethane coating has been formed.

[0078] The surface and cross-section of the polyurethane coating formed by the coating material of Example 1 were observed using scanning electron microscopy (SEM); the results are as follows. Figure 2 As shown, the addition of the uniformity enhancer reduced porosity and air bubbles, improving the uniformity of the surface and cross-section.

[0079] The surface roughness of the coating material of Example 1 and the polyurethane coating formed in Comparative Example 1 were observed using atomic force microscopy (AFM); the results are as follows: Figure 3As shown, the surface roughness of the membrane shell decreases and the surface becomes more uniform after temperature-sensitive modification.

[0080] The hydrophobicity of the polyurethane coating surface formed by the coating materials in Examples 1-3 was observed using a contact angle meter, such as... Figure 4 As shown, the surface of the polyurethane coating exhibits hydrophobicity after temperature-sensitive modification.

[0081] In situ CT was used to observe the pore distribution of the polyurethane coating formed by the coating material of Example 1 at 15°C and 35°C. Figure 5 As shown, after modification, the porosity of the coating gradually increases with increasing temperature.

[0082] Experimental Example 3: Investigation of Nutrient Controlled Release Performance 1. Temperature response performance evaluation 10g of the coated controlled-release fertilizer prepared in Example 4 and the conventional bio-based coated controlled-release fertilizer prepared in Comparative Example 1 were weighed into 250ml transparent plastic bottles, 200ml of deionized water was added, and they were placed in environments of 5℃, 20℃ and 35℃ respectively to test the nutrient utilization rate as a function of temperature.

[0083] The results are as follows Figure 6 As shown, the nutrient release cycles of Example 4 at 5℃, 20℃, and 35℃ were 74 days, 61 days, and 49 days, respectively. The nutrient release cycles of conventional bio-based coated controlled-release fertilizers were 35 days, 33 days, and 28 days, respectively. The results indicate that the temperature-sensitive modified bio-based coated controlled-release fertilizer is more sensitive to temperature and can sense changes in temperature that alter the nutrient release rate.

[0084] 2. Nutrient release assay The nitrogen release rate of the coated controlled-release fertilizers prepared in Examples 4, 5, and 6, as well as Comparative Examples 1 to 4, was determined according to the National Standard for Slow-Release Fertilizers of the People's Republic of China GB / T 23348-2009.

[0085] The results are as follows Figure 7 As shown, the coating fertilizer prepared in Example 4 has a release period of 58 days; the coating fertilizer prepared in Example 5 has a release period of 52 days; and the coating fertilizer prepared in Example 6 has a release period of 45 days.

[0086] The controlled-release period of the conventional bio-based coated fertilizer prepared in Comparative Example 1 was 31 days; the controlled-release period of the coated controlled-release fertilizer prepared in Comparative Example 2 was 28 days; the controlled-release period of the coated controlled-release fertilizer prepared in Comparative Example 3 was 37 days; and the controlled-release period of the coated controlled-release fertilizer prepared in Comparative Example 4 was 41 days. The results showed that the microcrystalline wax in the uniformity enhancer and the first component in the dynamic temperature-sensitive modifier could synergistically increase the nutrient controlled-release time of the coated controlled-release fertilizer.

[0087] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A coating material for dynamically temperature-sensitive modification to regulate pore structure evolution, characterized in that, It is prepared from bio-based stock solution, uniform enhancer and dynamic temperature-sensitive modifier in a weight ratio of (8-15):(0.5-1):(2-3); The bio-based stock solution is obtained by reacting component A and component B at a mass ratio of 20:(2-4), wherein component A is polycaprolactone diol; and component B is one or more of succinic acid and pimelic acid. The uniformity-enhancing agent is obtained by blending microcrystalline wax and soybean oil polyol; The dynamic temperature-sensitive modifier is obtained by reacting the first component and the second component in a molar ratio of 1:(3-6). The first component is one or more of dipentyl disulfide, p-toluene disulfide, and α-benzoxime; the second component is one or more of trimethylhexane diisocyanate, 2,4-difluorophenyl isocyanate, and 3,3-diphenylpropyl isocyanate.

2. The coating material with dynamic temperature-sensitive modification for regulating pore structure evolution according to claim 1, characterized in that, The bio-based stock solution is prepared by the following method: Mix components A and B, add tetrabutyl titanate and concentrated sulfuric acid, and stir the mixture at 150-170℃ for 7-8 hours under nitrogen protection.

3. The coating material with dynamic temperature-sensitive modification for regulating pore structure evolution according to claim 2, characterized in that, The weight ratio of tetrabutyl titanate to component A is (0.1-0.3):20; the ratio of concentrated sulfuric acid to component A is (3-5) ml:20g.

4. The coating material with dynamic temperature-sensitive modification for regulating pore structure evolution according to claim 1, characterized in that, The uniformity-enhancing agent is prepared by the following method: The microcrystalline wax was dissolved by increasing the temperature, and the soybean oil polyol was dried in a vacuum environment. Then, the dissolved microcrystalline wax and the dried soybean oil polyol were ultrasonically mixed to prepare a uniformity enhancer. Preferably, the ratio of the added microcrystalline wax to soybean oil polyol is 1g:(20-30)ml.

5. The coating material for dynamically temperature-sensitive modification and regulation of pore structure evolution according to claim 1, characterized in that, The dynamic temperature-sensitive modifier is prepared by the following method: Add the first component to acetone and sonicate it to distribute it evenly in the solution. Then, under nitrogen conditions, slowly add the second component to the first component and stir continuously for 5-15 minutes.

6. The method for preparing the coating material with dynamic temperature-sensitive modification to regulate pore structure evolution as described in any one of claims 1-5, characterized in that, Includes the following steps: The bio-based stock solution and the uniformizing and enhancing agent were mixed in an organic solvent and ultrasonically stirred to promote the evaporation of the organic solvent, thus obtaining an intermediate. A dynamic temperature-sensitive modifier was added to the intermediate, followed by an organic solvent. The mixture was stirred rapidly to increase its fluidity. Then, dibutyltin dilaurate was added, and the mixture was stirred continuously under nitrogen gas. When the mixture became viscous, the stirring was stopped, and the air bubbles were removed to prepare a coating material with dynamic temperature-sensitive modification to regulate the evolution of pore structure.

7. The preparation method according to claim 6, characterized in that, The solvent is N,N-dimethylformamide or acetone.

8. The application of the coating material with dynamic temperature-sensitive modification to regulate pore structure evolution as described in any one of claims 1-5 in the preparation of controlled-release fertilizers.

9. A bio-based coated controlled-release fertilizer, characterized in that, The fertilizer core includes a fertilizer core and a coating material for dynamically temperature-sensitive modification and regulation of pore structure evolution as described in any one of claims 1-5, which is sprayed onto the surface of the fertilizer core; the coating material for dynamically temperature-sensitive modification and regulation of pore structure evolution accounts for 1-5% of the weight of the fertilizer core.

10. The method for preparing the bio-based coated controlled-release fertilizer according to claim 9, characterized in that, Includes the following steps: The coating material with dynamic temperature-sensitive modification to regulate pore structure evolution as described in any one of claims 1-5 is uniformly sprayed onto the surface of a fertilizer core at a pressure of 0.25-0.45 MPa and cured at 55-65°C for 10-15 min.

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