A rice seedling raising bio-based controlled release film material and controlled release nitrogen fertilizer, and a preparation method and application thereof

Abstract

The application discloses a rice seedling raising bio-based controlled release film material and controlled release nitrogen fertilizer and a preparation method and application thereof. The controlled release nitrogen fertilizer comprises a large particle urea and a coating layer wrapped on the surface of the large particle urea, and the coating layer is composed of a bottom layer, an inner coating layer and an outer coating layer. The bottom layer is a functional substance aqueous solution prepared from a functional substance and water, the inner coating layer is a bio-based controlled release film material prepared from castor oil, plant oil polyol, isocyanate and a sealant, and the outer coating layer is a controlled release film material prepared from a hydroxyl-containing substance, isocyanate and a sealant. The coating layer material in the controlled release nitrogen fertilizer is mainly prepared from abundant and low-cost plant oil, the bio-based raw material is applied to the coating layer material, the coating process is green, and the application meets the demand of green agriculture. In addition, the compactness of the coating layer is progressive, water can be prevented from entering the fertilizer through the film layer during the seedling raising period, and the demand for nitrogen for tillering and rice growth can be met after rice transplanting.

Description

Technical Field

[0001] This invention belongs to the field of novel fertilizers, specifically relating to a bio-based controlled-release membrane material for rice seedling raising and a controlled-release nitrogen fertilizer, as well as their preparation methods and applications. Background Technology

[0002] Agricultural practice shows that chemical fertilizers contribute over 40% to my country's grain production increase. As a crucial sector supporting agriculture, the fertilizer industry is directly related to national food security and ecological environmental protection. Controlled-release fertilizers, which use various polymer materials to coat fast-acting fertilizers, utilize a thin film to quantitatively control nutrient release. In practical applications, this allows the fertilizer's nutrient release rate to synchronize with crop nutrient absorption, thereby significantly improving fertilizer utilization, reducing labor costs, and increasing economic benefits. This lays the foundation for precision fertilization technology and the promotion of sustainable agricultural development.

[0003] Rice is a major food crop in my country. Traditional rice cultivation methods dictate that fertilization primarily relies on basal application and broadcasting, with multiple topdressings later in the season. This wastes a significant amount of labor, increases production costs, and most importantly, results in low nitrogen utilization, with most nitrogen fertilizer being lost, causing non-point source pollution and resource waste. Even with side-dip application, fertilizer cannot be directly applied to the rice roots, limiting the improvement in fertilizer utilization. One solution is to sow all or part of the nitrogen fertilizer needed for rice's growth season with the seeds during seedling cultivation. After seedling emergence, controlled-release nitrogen fertilizer can be transferred to the paddy field along with the transplanted seedlings, thereby improving nitrogen fertilizer utilization.

[0004] Controlled-release fertilizers can be classified into parabolic, linear, and delayed-release (S-type) fertilizers based on their nutrient release pattern. The nutrient release phase of S-type controlled-release fertilizers consists of a lag phase or inhibition phase with extremely low nutrient dissolution, a rapid nutrient release phase, and a decline phase with slowed nutrient release. The inhibition phase meets the slow nutrient release needs during the rice seedling stage, the release phase after transplanting ensures the nitrogen requirements of rice tillering and vegetative growth, and the nitrogen nutrient release is complete by harvest time. The nutrient release pattern of this type of fertilizer is basically synchronized with the nitrogen requirements of rice.

[0005] The composition and properties of the coating directly affect the pattern and timing of nutrient release. Therefore, one of the core aspects of controlled-release fertilizer development is the screening and optimization of coating materials. Based on the different media, polymer coating materials can be divided into three main types: organic solvent-based, water-based, and solvent-free. Considering that solvent-free coated controlled-release fertilizers have advantages such as simple equipment, ease of continuous production, and most importantly, a green process and sustainable coating materials, in the past decade, more and more research institutions at home and abroad have focused on solvent-free in-situ reaction film formation, that is, the direct reaction of small molecule monomers on the fertilizer surface to form a film for the preparation of controlled-release fertilizers. However, no reports have been found on S-type bio-based controlled-release fertilizers used for rice seedling cultivation. Summary of the Invention

[0006] The purpose of this invention is to provide a bio-based controlled-release membrane material and a controlled-release nitrogen fertilizer for rice seedling raising, as well as their preparation methods and applications.

[0007] To achieve the above objectives, the present invention first provides an S-type controlled-release nitrogen fertilizer.

[0008] The S-type controlled-release nitrogen fertilizer provided by the present invention includes large-particle urea and a coating layer wrapped around the surface of the large-particle urea. The coating layer consists of three parts: a bottom layer, an inner coating layer, and an outer coating layer.

[0009] The bottom layer is an aqueous solution of functional substances prepared from functional substances and water. The functional substances are selected from at least one of urease inhibitors, nitration inhibitors, fulvic acid, nano silica, and silicates.

[0010] The inner coating layer is a bio-based controlled-release membrane material made from castor oil, vegetable oil polyols, isocyanates, and sealants.

[0011] The outer coating layer is a controlled-release membrane material made from hydroxyl-containing substances, isocyanates, and sealants.

[0012] Furthermore, the S-type controlled-release nitrogen fertilizer consists of large urea particles and a coating layer covering the surface of the large urea particles.

[0013] Furthermore, the mass of the coating layer is 3.5% to 10% of the mass of the S-type controlled-release nitrogen fertilizer, specifically 3.8% to 6.5%. In a specific embodiment of the present invention, the mass of the coating layer is 4.8%, 3.8%, 4.3%, 5.7%, or 6.5% of the mass of the S-type controlled-release nitrogen fertilizer.

[0014] The bottom layer mass is 0.001 to 0.5% of the mass of the S-type controlled-release nitrogen fertilizer, specifically 0.002 to 0.2%. In a specific embodiment of the present invention, the bottom layer mass is 0.028%, 0.002%, 0.08%, 0.2%, or 0.064% of the mass of the S-type controlled-release nitrogen fertilizer.

[0015] The mass of the inner membrane layer is 2.5% to 6.5% of the mass of the S-type controlled-release nitrogen fertilizer, specifically 2.9% to 5.6%. In a specific embodiment of the present invention, the mass of the inner membrane layer is 3.8%, 3.4%, 2.9%, 4.7%, or 5.6% of the mass of the S-type controlled-release nitrogen fertilizer.

[0016] The outer coating layer comprises 0.5% to 3% of the mass of the S-type controlled-release nitrogen fertilizer, specifically 0.5% to 2.0%. In a specific embodiment of the present invention, the outer coating layer comprises 0.5%, 2.0%, 1.0%, or 0.9% of the mass of the S-type controlled-release nitrogen fertilizer.

[0017] To achieve the above objectives, the present invention also provides a method for preparing the above-mentioned S-type controlled-release nitrogen fertilizer.

[0018] The preparation method of the above-mentioned S-type controlled-release nitrogen fertilizer provided by the present invention includes the following steps:

[0019] (1) Add large urea particles into a drum and preheat to 50-70°C to obtain preheated urea particles.

[0020] (2) The functional substance aqueous solution is sprayed onto the surface of the preheated urea particles to form a bottom layer, thereby obtaining urea particles coated with the bottom layer; the functional substance is selected from at least one of urease inhibitor, nitration inhibitor, fulvic acid, nano silica, and silicate.

[0021] (3) After heating castor oil, vegetable oil polyol and sealant at 60-90°C, they are mixed with isocyanate to prepare a coating liquid. The liquid is then sprayed onto the surface of the urea particles coated with the bottom layer. After curing reaction, an inner coating layer is formed, and urea particles coated with the inner coating layer are obtained.

[0022] (4) After heating the hydroxyl-containing substance and sealant at 60-90°C, they are mixed with isocyanate to prepare a coating solution, which is then sprayed onto the surface of the urea particles coated with the inner coating layer. After curing reaction, an outer coating layer is formed, thus obtaining the S-type controlled-release nitrogen fertilizer.

[0023] In the above-mentioned S-type controlled-release nitrogen fertilizer or its preparation method, the mass ratio of the functional substance to the water in the bottom layer can be 1:(5-500). In a specific embodiment of the present invention, the mass ratio of the functional substance to the water is 1:33.3, 1:500, 1:5, or 1:7.7.

[0024] In the inner coating layer, the mass ratio of castor oil, vegetable oil polyol, isocyanate, and sealant can be (0.60–1.04):(0.40–1.00):1:(0.01–0.05). In a specific embodiment of the present invention, the mass ratio of castor oil, vegetable oil polyol, isocyanate, and sealant is 0.91:0.91:1:0.028, 0.60:0.40:1:0.01, 1.04:0.52:1:0.039, 0.77:0.77:1:0.025, or 0.90:0.89:1:0.044.

[0025] In the outer coating layer, the mass ratio of the hydroxyl-containing substance, the isocyanate, and the sealant can be (0.40–2.27):1:(0.02–0.10). In specific embodiments of the present invention, the mass ratio of the hydroxyl-containing substance, the isocyanate, and the sealant is 0.90:1:0.10, 0.42:1:0.028, 1.36:1:0.071, 1.09:1:0.08, or 2.27:1:0.067.

[0026] In the above-mentioned S-type controlled-release nitrogen fertilizer or the preparation method of S-type controlled-release nitrogen fertilizer, the preparation method of the vegetable oil polyol includes the following: mixing vegetable oil, hydrogen peroxide, organic acid and catalyst, carrying out an epoxidation reaction, removing the water layer after the reaction to obtain an epoxidation intermediate; adding an alcohol ring-opening agent to the epoxidation intermediate to carry out a ring-opening reaction, and directly rotary evaporating the product obtained after the reaction without water washing to obtain the vegetable oil polyol.

[0027] Further, the mass ratio of the vegetable oil, the hydrogen peroxide, the organic acid, and the catalyst can be 1:(0.4-0.8):(0.01-0.4):(0.001-0.005). In a specific embodiment of the present invention, the mass ratio of the vegetable oil, the hydrogen peroxide, the organic acid, and the catalyst is 1:0.8:0.3:0.005, 1:0.5:0.25:0.004, 1:0.4:0.01:0.001, 1:0.8:0.4:0.025, or 1:0.75:0.25:0.001.

[0028] The mass ratio of the epoxidation intermediate to the alcohol ring-opening agent can be 1:(0.1 to 1.0). In specific embodiments of the present invention, the mass ratio of the epoxidation intermediate to the alcohol ring-opening agent is 1:1, 1:0.4, 1:0.1, 1:0.8, or 1:0.6.

[0029] Furthermore, the vegetable oil may be at least one of palm oil, rapeseed oil, olive oil, soybean oil, corn oil, and peanut oil.

[0030] The organic acid may be formic acid or acetic acid (such as 99.8 wt% acetic acid).

[0031] The catalyst may be at least one of sulfuric acid (such as 98 wt% sulfuric acid), phosphoric acid, and hydrochloric acid.

[0032] The alcohol ring-opening agent may be any one of methanol (such as 99.5 wt% methanol), ethylene glycol, propanol, and butanol.

[0033] Furthermore, the epoxidation reaction can be carried out at a temperature of 50–70°C for a time of 3–6.5 h.

[0034] The ring-opening reaction can be carried out at a temperature of 40–60°C for 1–4 hours.

[0035] The conditions for rotary distillation can be 50–70°C for 2–4 hours.

[0036] In a specific embodiment of the present invention, the method for preparing the vegetable oil polyol includes the following steps:

[0037] A. Add vegetable oil, organic acid and catalyst to a three-necked flask equipped with a stirrer, condenser and constant pressure dropping funnel, place in an oil bath for heating and stirring, then put hydrogen peroxide into the constant pressure dropping funnel and add it dropwise to the three-necked flask at a constant rate (the temperature is controlled at 40℃ during the addition). After the addition is completed, adjust the oil bath to a suitable temperature for epoxidation reaction. After the reaction is completed, use a separatory funnel to let it stand and separate into layers, remove the water layer, and obtain the epoxidation intermediate product.

[0038] B. Add the epoxidation intermediate and the alcohol ring-opening agent to a three-necked flask to carry out the ring-opening reaction. After the reaction, the product is directly obtained by rotary evaporation without water washing to obtain the vegetable oil polyol.

[0039] In the above-mentioned S-type controlled-release nitrogen fertilizer or the preparation method of S-type controlled-release nitrogen fertilizer, the nitrification inhibitor may be dicyandiamide.

[0040] The urease inhibitor may be n-butylthiophosphoric triamine.

[0041] The isocyanate may be at least one of polymethylene polyphenyl polyisocyanate, toluene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, liquefied MDI, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, a trimer of 1,6-hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, phenyldimethyl diisocyanate, and dimethylbiphenyl diisocyanate.

[0042] The hydroxyl-containing substance may be at least one of polyether polyol, castor oil, vegetable oil polyol, polyester polyol, and polyolefin polyol.

[0043] The sealant may be any one of paraffin wax, microcrystalline wax, beeswax, chlorinated paraffin wax, polyethylene wax, asphalt, and silicone wax.

[0044] The average particle size of the large-particle urea can be 2.0–8.0 mm, specifically urea particles with a particle size of 2.00–4.75 mm or urea particles with a particle size of 4.00–8.00 mm. The nitrogen content of the large-particle urea can be 46.4%.

[0045] To achieve the above objectives, the present invention also provides products for rice seedling cultivation.

[0046] The products for rice seedling cultivation provided by this invention include the above-mentioned bio-based controlled-release membrane material and / or the above-mentioned S-type controlled-release nitrogen fertilizer.

[0047] To achieve the above objectives, the present invention also provides any one of the following applications (a1)-a6):

[0048] a1) Application of the above-mentioned bio-based controlled-release membrane materials in rice seedling cultivation;

[0049] a2) Application of the above-mentioned bio-based controlled-release membrane materials in the preparation of rice seedling raising products;

[0050] a3) Application of the above-mentioned S-type controlled-release nitrogen fertilizer or the S-type controlled-release nitrogen fertilizer prepared according to the above method in rice seedling raising;

[0051] a4) Application of the above-mentioned S-type controlled-release nitrogen fertilizer or the S-type controlled-release nitrogen fertilizer prepared according to the above method in the preparation of rice seedling products;

[0052] a5) Application of the above products in rice seedling cultivation;

[0053] a6) Application of the above products in the preparation of rice seedling raising products.

[0054] To achieve the above objectives, the present invention finally provides a method for rice seedling cultivation.

[0055] The rice seedling raising method provided by the present invention includes the step of sowing and raising seedlings together with the above-mentioned S-type controlled-release nitrogen fertilizer and rice seeds.

[0056] The present invention has the following beneficial effects:

[0057] 1. Compared with the existing controlled-release nitrogen fertilizer technology for rice seedling raising, which uses petrochemical products as raw materials for the coating layer, the controlled-release nitrogen fertilizer product for rice seedling raising prepared by this invention mainly uses abundant and inexpensive vegetable oils as raw materials for the coating layer. By simplifying the vegetable oil modification process and controlling the reaction degree to optimize the structure and performance of polyols, bio-based raw materials are applied to the coating layer material for rice seedling raising, and the coating process is green, which meets the needs of green agriculture.

[0058] 2. Compared to L-type controlled-release nitrogen fertilizers or S-type controlled-release nitrogen fertilizers with short inhibition periods, which can burn rice seedlings during seedling cultivation, the controlled-release nitrogen fertilizer product for rice seedling cultivation produced by this invention, due to the progressively dense coating layers, can prevent water from entering the fertilizer through the coating layer during the seedling stage. The early nitrogen cumulative release rate is ≤5%, ensuring that the controlled-release nitrogen fertilizer will not burn the rice seedlings upon contact with the seedlings. After transplanting, water passes through the coating layer and quickly enters and exits through the membrane's channels, dissolving the fertilizer and creating a rapid nutrient release process. This meets the nitrogen requirements for tillering and rice growth until the nitrogen cumulative release rate is ≥80%. Detailed Implementation

[0059] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0060] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0061] In the following examples, the controlled-release performance of the S-type controlled-release nitrogen fertilizer was tested using the water immersion method. The specific steps are as follows: 10g of S-type controlled-release nitrogen fertilizer was weighed and placed in a 100-mesh nylon mesh bag. After sealing, the nylon mesh bag was placed in a plastic container containing 250mL of distilled water. After sealing, the container was placed in a 25℃ constant temperature incubator. Samples were taken at 1, 3, 7, 14, 21, 28, 35, 42, 49, 56, and 63 days to determine the nutrient dissolution rate. The nitrogen dissolution rate was determined using spectrophotometry.

[0062] In the examples below, the nutrient inhibition period refers to the number of days required for the cumulative release rate of the coated controlled-release fertilizer (S-type controlled-release nitrogen fertilizer) to reach 5% in water at 25°C.

[0063] In the examples below, the nutrient release period refers to the number of days required for the coated controlled-release fertilizer (S-type controlled-release nitrogen fertilizer) to achieve a cumulative release rate of 80% in water at 25°C.

[0064] The materials involved in the following embodiments and their sources are as follows:

[0065] Urea particles with a particle size of 2.00–4.75 mm (nitrogen content of 46.4%) and urea particles with a particle size of 4.00–8.00 mm (nitrogen content of 46.4%) are products of Shandong Hualu Hengsheng and Jiangsu Shuangduo Chemical, respectively.

[0066] Dicyandiamide is a product of Ningxia Pengsheng Chemical.

[0067] Polymethylene polyphenyl polyisocyanate (PM200) is a product of Yantai Wanhua Company.

[0068] Paraffin wax (56#) is a product of Daqing Refining & Chemical Company of China National Petroleum Corporation.

[0069] Polyether polyol (TAE-470) is a product of Tianjin Petrochemical Company.

[0070] Polyester polyol (SKR-T5) is a product of Beijing Sike Rui.

[0071] n-Butylthiophosphoric triamine is a product of Shanghai Maclean Biochemical Technology Co., Ltd.

[0072] Microcrystalline wax (70#) is a product of Henan Yuyang Wax Industry.

[0073] Diphenylmethane diisocyanate (MDI-100) is a product of Yantai Wanhua Company.

[0074] Nano silica (DK-SiO2-30) is a product of Beijing Deco Gold.

[0075] Silicone wax (DY-803) is a product of Shandong Dayi Chemical Co., Ltd.

[0076] Toluene diisocyanate (TDI) is a product of Yantai Wanhua Company.

[0077] Sodium silicate is a product of Fuli Sodium silicate from Laizhou, Shandong.

[0078] The beeswax is a product of Hebei Xu's Beeswax.

[0079] 1,6-Hexanediisocyanate (HDI) is a product of Bayer AG, Germany.

[0080] The rice seed variety used in the following examples is Lingliangyou 179 (Approval No.: National Approval Rice 20170018).

[0081] Example 1: Preparation of Palm Oil Polyols and S-type Controlled-Release Nitrogen Fertilizer

[0082] I. Preparation of Palm Oil Polyols

[0083] 1. Weigh 200g of palm oil, 60g of acetic acid (99.8wt%) and 1g of sulfuric acid (98wt%) and add them to a 500mL three-necked flask equipped with a stirrer, condenser and constant pressure dropping funnel. Heat and stir in an oil bath at 40℃. Then add 160g of hydrogen peroxide (30wt%) into the three-necked flask at a constant pressure dropping funnel. Adjust the temperature to 65℃ and react for 6.5h. After the reaction is completed, let it stand with a separatory funnel to separate the layers. Remove the water layer to obtain the epoxidized intermediate product.

[0084] 2. Weigh 100g of epoxidation intermediate and 100g of methanol (99.5wt%) and add them to a three-necked flask. React at 60℃ for 2.5h. Then, rotary distill the product at 60℃ for 3h to obtain palm oil polyol.

[0085] II. Preparation of S-type controlled-release nitrogen fertilizer

[0086] 1. Weigh 1 kg of urea granules with a particle size of 2.00-4.75 mm, add them to the drum, and preheat to 60°C.

[0087] 2. Spray 10g of dicyandiamide aqueous solution (the mass ratio of dicyandiamide to water is 1:33.3) evenly onto the fertilizer surface to form a base layer.

[0088] 3. Mix 3.2g castor oil, 3.2g palm oil polyol prepared in step one, and 0.1g paraffin wax evenly and heat to 60℃. Then mix with 3.5g polymethylene polyphenyl polyisocyanate to prepare a coating solution and spray it onto the surface of fertilizer granules for in-situ curing reaction. This spraying process is repeated 4 times to form an inner coating layer with a bio-based content of 65%.

[0089] 4. Mix 2.5g of polyether polyol, 2g of polyester polyol, and 0.5g of paraffin wax evenly and heat to 60℃. Then, mix with 5g of polymethylene polyphenyl polyisocyanate to prepare a coating solution. Spray the solution onto the surface of the fertilizer granules and allow for in-situ curing. This spraying process is repeated once to form an outer coating layer. After spraying, cool to obtain an S-type controlled-release nitrogen fertilizer with a coating rate of 5.0%.

[0090] III. Testing the controlled-release performance of S-type controlled-release nitrogen fertilizer

[0091] The controlled-release performance of the S-type controlled-release nitrogen fertilizer prepared in step two was determined by the water immersion method.

[0092] The results showed that the initial release rate of S-type controlled-release nitrogen fertilizer was 0.1%, the nutrient inhibition period was 35 days, and the nutrient release period was 120 days.

[0093] IV. Application of S-type controlled-release nitrogen fertilizer in rice seedling raising

[0094] On May 1, 2023, in a greenhouse at the Beijing Academy of Agricultural and Forestry Sciences, the S-type controlled-release nitrogen fertilizer prepared in step two was applied at a field nitrogen application rate of 165 kg / hm². 2 The rice seedlings were sown and raised using conventional methods, with 1420 grams of S-type controlled-release nitrogen fertilizer applied to each seedling tray. No seedling burn occurred after 28 days of seedling raising. The controlled-release nitrogen fertilizer can be transferred to the paddy field along with the seedlings, eliminating the need for additional nitrogen fertilizer application.

[0095] Example 2: Preparation of rapeseed oil polyols and S-type controlled-release nitrogen fertilizer

[0096] I. Preparation of rapeseed oil polyols

[0097] 1. Weigh 200g rapeseed oil, 50g acetic acid (99.8wt%) and 0.8g sulfuric acid (98wt%) and add them to a 500mL three-necked flask equipped with a stirrer, condenser and constant pressure dropping funnel. Heat and stir in an oil bath at 40℃. Then add 100g hydrogen peroxide (30wt%) to the three-necked flask at a constant pressure dropping funnel. Adjust the temperature to 70℃ and react for 6h. After the reaction is completed, let it stand with a separatory funnel to separate the layers. Remove the water layer to obtain the epoxidized intermediate product.

[0098] 2. Weigh 100g of epoxidation intermediate and 40g of methanol (99.5wt%) and add them to a three-necked flask. React at 50℃ for 4h. Then, rotary distill the product at 50℃ for 4h to obtain rapeseed oil polyol.

[0099] II. Preparation of S-type controlled-release nitrogen fertilizer

[0100] 1. Weigh 1 kg of urea granules with a particle size of 4.00-8.00 mm, add them to the drum, and preheat to 65°C.

[0101] 2. Spray 10g of n-butylthiophosphoric triamine (NBPT) aqueous solution (NBPT to water mass ratio of 1:500) evenly onto the fertilizer surface to form a base layer.

[0102] 3. Mix 3g castor oil, 2g rapeseed oil polyol prepared in step one, and 0.05g microcrystalline wax evenly and heat to 60℃. Then mix with 4.95g diphenylmethane diisocyanate (MDI) to prepare a coating solution. Spray the solution onto the surface of the fertilizer granules and carry out an in-situ curing reaction. This spraying process is repeated 3.5 times to form an inner coating layer with a bio-based content of 60%.

[0103] 4. Mix 1.5g of polyether polyol and 0.1g of microcrystalline wax evenly and heat to 60℃. Then mix with 3.5g of diphenylmethane diisocyanate (MDI) to prepare a coating solution. Spray the solution onto the surface of the fertilizer granules and allow for in-situ curing. This spraying process is repeated once to form an outer coating layer. After spraying, cool to obtain an S-type controlled-release nitrogen fertilizer with a coating rate of 4%.

[0104] III. Testing the controlled-release performance of S-type controlled-release nitrogen fertilizer

[0105] The controlled-release performance of the S-type controlled-release nitrogen fertilizer prepared in step two was determined by the water immersion method.

[0106] The results showed that the initial release rate of the S-type controlled-release nitrogen fertilizer was 0.5%, the nutrient inhibition period was 35 days, and the nutrient release period was 90 days.

[0107] IV. Application of S-type controlled-release nitrogen fertilizer in rice seedling raising

[0108] On May 1, 2023, in a greenhouse at the Beijing Academy of Agricultural and Forestry Sciences, the S-type controlled-release nitrogen fertilizer prepared in step two was applied at a field nitrogen application rate of 165 kg / hm². 2 The rice seedlings were sown and raised using conventional methods, with 1420 grams of S-type controlled-release nitrogen fertilizer applied to each seedling tray. No seedling burn occurred after 28 days of seedling raising. The controlled-release nitrogen fertilizer can be transferred to the paddy field along with the seedlings, eliminating the need for additional nitrogen fertilizer application.

[0109] Example 3: Preparation of soybean oil polyols and S-type controlled-release nitrogen fertilizer

[0110] I. Preparation of Soybean Oil Polyols

[0111] Weigh 200g soybean oil, 2g formic acid (99wt%) and 0.2g phosphoric acid (85wt%) and add them to a 500mL three-necked flask equipped with a stirrer, condenser and constant pressure dropping funnel. Heat and stir in an oil bath at 40℃. Then add 80g hydrogen peroxide (30wt%) into the three-necked flask at a constant pressure dropping funnel. Adjust the temperature to 50℃ and react for 3h. After the reaction is completed, let it stand with a separatory funnel to separate the layers. Remove the water layer to obtain the epoxidized intermediate product.

[0112] 2. Weigh 100g of epoxidation intermediate and 10g of ethylene glycol (98wt%) and add them to a three-necked flask. React at 60℃ for 1h. Rotary distill the product at 70℃ for 2h to obtain soybean oil polyol.

[0113] II. Preparation of S-type controlled-release nitrogen fertilizer

[0114] 1. Weigh 1 kg of urea granules with a particle size of 2.00-4.75 mm, add them to the drum, and preheat to 70°C.

[0115] 2. Spray 5g of nano silica aqueous solution (the mass ratio of nano silica to water is 1:5) evenly onto the fertilizer surface to form a base layer.

[0116] 3. Mix 4g castor oil, 2g soybean oil polyol prepared in step one, and 0.15g silicone wax evenly and heat to 90℃. Then mix with 3.85g toluene diisocyanate to prepare a coating solution. Spray the solution onto the surface of the fertilizer granules to carry out in-situ curing reaction. This spraying process is carried out 3 times to form an inner coating layer with a bio-based content of 60%.

[0117] 4. Mix 1.5g of polyether polyol, 2.7g of polyester polyol, and 0.22g of silicone wax evenly and heat to 90℃. Then, mix with 3.08g of toluene diisocyanate to prepare a coating solution. Spray the solution onto the surface of the fertilizer granules and allow for in-situ curing. This spraying process is repeated twice to form an outer coating layer. After spraying, cool to obtain an S-type controlled-release nitrogen fertilizer with a coating rate of 4.5%.

[0118] III. Testing the controlled-release performance of S-type controlled-release nitrogen fertilizer

[0119] The controlled-release performance of the S-type controlled-release nitrogen fertilizer prepared in step two was determined by the water immersion method.

[0120] The results showed that the initial release rate of the S-type controlled-release nitrogen fertilizer was 0%, the nutrient inhibition period was 50 days, and the nutrient release period was 150 days.

[0121] IV. Application of S-type controlled-release nitrogen fertilizer in rice seedling raising

[0122] On May 1, 2023, in a greenhouse at the Beijing Academy of Agricultural and Forestry Sciences, the S-type controlled-release nitrogen fertilizer prepared in step two was applied at a field nitrogen application rate of 165 kg / hm². 2 The rice seedlings were sown and raised using conventional methods, with 1420 grams of S-type controlled-release nitrogen fertilizer applied to each seedling tray. No seedling burn occurred after 28 days of seedling raising. The controlled-release nitrogen fertilizer can be transferred to the paddy field along with the seedlings, eliminating the need for additional nitrogen fertilizer application.

[0123] Example 4: Preparation of Palm Oil Polyols and S-type Controlled-Release Nitrogen Fertilizer

[0124] I. Preparation of Palm Oil Polyols

[0125] Weigh 200g of palm oil, 50g of formic acid (99wt%) and 0.5g of sulfuric acid (98wt%) and add them to a 500mL three-necked flask equipped with a stirrer, condenser and constant pressure dropping funnel. Heat and stir in an oil bath at 40℃. Then add 160g of hydrogen peroxide (30wt%) into the three-necked flask at a constant pressure dropping funnel. Adjust the temperature to 65℃ and react for 6.5h. After the reaction is completed, let it stand with a separatory funnel to separate the layers. Remove the water layer to obtain the epoxidized intermediate product.

[0126] 2. Weigh 100g of epoxidation intermediate and 80g of propanol (99.5wt%) and add them to a three-necked flask. React at 40℃ for 4h. Then, rotary distill the product at 65℃ for 2.5h to obtain palm oil polyol.

[0127] II. Preparation of S-type controlled-release nitrogen fertilizer

[0128] 1. Weigh 1 kg of urea granules with a particle size of 2.00-4.75 mm, add them to the drum, and preheat to 60°C.

[0129] 2. Spray 10g of sodium silicate aqueous solution (sodium silicate to water mass ratio of 1:5) evenly onto the fertilizer surface to form a base layer.

[0130] 3. Mix 3g castor oil, 3g palm oil polyol prepared in step one, and 0.1g beeswax evenly and heat to 70℃. Then mix with 3.9g 1,6-hexamethylene diisocyanate (HDI) to prepare a coating solution. Spray the solution onto the surface of the fertilizer granules and carry out an in-situ curing reaction. This spraying process is repeated 5 times to form an inner coating layer with a bio-based content of 60%.

[0131] 4. Mix 3g of polyether polyol, 2g of polyester polyol, and 0.4g of beeswax evenly and heat to 70℃. Then, mix with 4.6g of 1,6-hexamethylene diisocyanate (HDI) to prepare a coating solution. Spray the solution onto the surface of the fertilizer granules and allow for in-situ curing. This spraying process is repeated once to form an outer coating layer. After spraying, cool to obtain an S-type controlled-release nitrogen fertilizer with a coating rate of 6%.

[0132] III. Testing the controlled-release performance of S-type controlled-release nitrogen fertilizer

[0133] The controlled-release performance of the S-type controlled-release nitrogen fertilizer prepared in step two was determined by the water immersion method.

[0134] The results showed that the initial release rate of the S-type controlled-release nitrogen fertilizer was 0.2%, the nutrient inhibition period was 40 days, and the nutrient release period was 120 days.

[0135] IV. Application of S-type controlled-release nitrogen fertilizer in rice seedling raising

[0136] On May 1, 2023, in a greenhouse at the Beijing Academy of Agricultural and Forestry Sciences, the S-type controlled-release nitrogen fertilizer prepared in step two was applied at a field nitrogen application rate of 165 kg / hm². 2 The rice seedlings were sown and raised using conventional methods, with 1420 grams of S-type controlled-release nitrogen fertilizer applied to each seedling tray. No seedling burn occurred after 28 days of seedling raising. The controlled-release nitrogen fertilizer can be transferred to the paddy field along with the seedlings, eliminating the need for additional nitrogen fertilizer application.

[0137] Example 5: Preparation of Corn Oil Polyols

[0138] I. Preparation of Corn Oil Polyols

[0139] Weigh 200g corn oil, 50g acetic acid (99.8wt%) and 0.2g hydrochloric acid (36wt%) and add them to a 500mL three-necked flask equipped with a stirrer, condenser and constant pressure dropping funnel. Heat and stir in an oil bath at 40℃. Then add 150g hydrogen peroxide (30wt%) dropwise to the three-necked flask at a constant pressure dropping funnel. Adjust the temperature to 65℃ and react for 6h. After the reaction is completed, let it stand with a separatory funnel to separate the layers. Remove the water layer to obtain the epoxidized intermediate product.

[0140] 2. Weigh 100g of epoxidation intermediate and 60g of butanol (99.5wt%) and add them to a three-necked flask. React at 60℃ for 2.5h. Then, rotary distill the product at 60℃ for 3h to obtain corn oil polyol.

[0141] II. Preparation of S-type controlled-release nitrogen fertilizer

[0142] 1. Weigh 1 kg of urea granules with a particle size of 4.00-8.00 mm, add them to the drum, and preheat to 50°C.

[0143] 2. Spray 6g of dicyandiamide aqueous solution (the mass ratio of dicyandiamide to water is 1:7.7) evenly onto the fertilizer surface to form a base layer.

[0144] 3. Mix 3.5g castor oil, 3g corn oil polyol prepared in step one, and 0.15g paraffin wax evenly and heat to 60℃. Then mix with 3.35g polymethylene polyphenyl polyisocyanate to prepare a coating solution and spray it onto the surface of fertilizer granules for in-situ curing reaction. This spraying process is repeated 6 times to form an inner coating layer with a bio-based content of 65%.

[0145] 4. Mix 2.5g of polyether polyol, 4.3g of polyester polyol, and 0.2g of paraffin wax evenly and heat to 60℃. Then, mix with 3.0g of polymethylene polyphenyl polyisocyanate to prepare a coating solution. Spray this solution onto the surface of fertilizer granules for in-situ curing. This spraying process is repeated once to form an outer coating layer. After spraying, cool to obtain an S-type controlled-release nitrogen fertilizer with a coating rate of 7%.

[0146] III. Testing the controlled-release performance of S-type controlled-release nitrogen fertilizer

[0147] The controlled-release performance of the S-type controlled-release nitrogen fertilizer prepared in step two was determined by the water immersion method.

[0148] The results showed that the initial release rate of S-type controlled-release nitrogen fertilizer was 0.1%, the nutrient inhibition period was 60 days, and the nutrient release period was 150 days.

[0149] IV. Application of S-type controlled-release nitrogen fertilizer in rice seedling raising

[0150] On May 1, 2023, in a greenhouse at the Beijing Academy of Agricultural and Forestry Sciences, the S-type controlled-release nitrogen fertilizer prepared in step two was applied at a field nitrogen application rate of 165 kg / hm². 2 The rice seedlings were sown and raised using conventional methods, with 1420 grams of S-type controlled-release nitrogen fertilizer applied to each seedling tray. No seedling burn occurred after 28 days of seedling raising. The controlled-release nitrogen fertilizer can be transferred to the paddy field along with the seedlings, eliminating the need for additional nitrogen fertilizer application.

[0151] Comparative Example 1

[0152] I. Preparation of Controlled-Release Nitrogen Fertilizer

[0153] 1. Weigh 1 kg of urea granules with a particle size of 2.00-4.75 mm, add them to the drum, and preheat to 60°C.

[0154] 2. Spray 10g of 3% dicyandiamide aqueous solution evenly onto the fertilizer surface to form a base layer.

[0155] 3. Mix 3.2g castor oil, 3.2g palm oil polyol prepared in step one of Example 1, and 0.1g paraffin wax evenly and heat to 60°C. Then mix with 3.5g polymethylene polyphenyl polyisocyanate to prepare a coating solution. Spray the solution onto the surface of fertilizer granules for in-situ curing reaction. Repeat this spraying process 5 times to form a coating layer with a bio-based content of 65%. After spraying, cool to obtain an S-type controlled-release nitrogen fertilizer with a coating rate of 5.0%.

[0156] II. Testing the controlled-release performance of S-type controlled-release nitrogen fertilizer

[0157] The controlled-release performance of the S-type controlled-release nitrogen fertilizer prepared in step one was determined by the water immersion method.

[0158] The results showed that the initial release rate of the S-type controlled-release nitrogen fertilizer was 0.2%, the nutrient inhibition period was 25 days, and the nutrient release period was 110 days.

[0159] III. Application of S-type controlled-release nitrogen fertilizer in rice seedling raising

[0160] On May 1, 2023, in a greenhouse at the Beijing Academy of Agricultural and Forestry Sciences, the S-type controlled-release nitrogen fertilizer prepared in step two was applied at a field nitrogen application rate of 165 kg / hm². 2 The rice seedlings were sown and raised using conventional methods. Each seedling tray was fertilized with 1420 grams of S-type controlled-release nitrogen fertilizer. After 28 days of seedling raising, obvious seedling burn was observed.

[0161] Comparative Example 2

[0162] I. Preparation of Controlled-Release Nitrogen Fertilizer

[0163] 1. Weigh 1 kg of urea granules with a particle size of 2.00-4.75 mm, add them to the drum, and preheat to 60°C.

[0164] 2. Spray 10g of 3% dicyandiamide aqueous solution evenly onto the fertilizer surface to form a base layer.

[0165] 3. Mix 3.2g castor oil and 3.3g palm oil polyol prepared in step one of Example 1 evenly and heat to 60°C. Then mix with 3.5g polymethylene polyphenyl polyisocyanate to prepare a coating solution and spray it onto the surface of fertilizer granules to carry out in-situ curing reaction. This spraying process is carried out 4 times to form an inner coating layer with a bio-based content of 65%.

[0166] 4. Mix 2.5g of polyether polyol, 2g of polyester polyol, and 0.5g of paraffin wax evenly and heat to 60℃. Then, mix with 5g of polymethylene polyphenyl polyisocyanate to prepare a coating solution. Spray the solution onto the surface of the fertilizer granules and allow for in-situ curing. This spraying process is repeated once to form an outer coating layer. After spraying, cool to obtain an S-type controlled-release nitrogen fertilizer with a coating rate of 5.0%.

[0167] II. Testing the controlled-release performance of S-type controlled-release nitrogen fertilizer

[0168] The controlled-release performance of the S-type controlled-release nitrogen fertilizer prepared in step two was determined by the water immersion method.

[0169] The results showed that the initial release rate of S-type controlled-release nitrogen fertilizer was 0.8%, the nutrient inhibition period was 10 days, and the nutrient release period was 80 days.

[0170] III. Application of S-type controlled-release nitrogen fertilizer in rice seedling raising

[0171] On May 1, 2023, in a greenhouse at the Beijing Academy of Agricultural and Forestry Sciences, the S-type controlled-release nitrogen fertilizer prepared in step two was applied at a field nitrogen application rate of 165 kg / hm². 2 The rice seedlings were sown and raised using conventional methods. Each seedling tray was fertilized with 1420 grams of S-type controlled-release nitrogen fertilizer. After 28 days of seedling raising, obvious seedling burn was observed.

[0172] The present invention has been described in detail above. For those skilled in the art, the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments have been given, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein. Some of the essential features can be applied within the scope of the following appended claims.

Claims

1. An S-type controlled-release nitrogen fertilizer, the S-type controlled-release nitrogen fertilizer comprising large-particle urea and a coating layer covering the surface of the large-particle urea, the coating layer comprising three parts: a bottom layer, an inner coating layer and an outer coating layer; in, The bottom layer is an aqueous solution of functional substances made from functional substances and water, wherein the functional substances are selected from at least one of urease inhibitors, nitration inhibitors, fulvic acid, nano silica, and silicates; The inner coating layer is a bio-based controlled-release membrane material made from castor oil, vegetable oil polyol, isocyanate, and sealant. Castor oil, vegetable oil polyol, and sealant are heated at 60-90°C, then mixed with isocyanate to form a coating solution. This solution is sprayed onto the surface of urea particles coated with a base layer, and after curing, the inner coating layer is formed. In the inner coating layer, the mass ratio of castor oil, vegetable oil polyol, isocyanate, and sealant is (0.60-1.04):(0.40-1.00):1:(0.01-0.05). The outer coating layer is a controlled-release membrane material made from hydroxyl-containing substances, isocyanates, and sealants; in the outer coating layer, the mass ratio of the hydroxyl-containing substances, the isocyanates, and the sealants is (0.40~2.27):1:(0.02~0.10); the hydroxyl-containing substances are polyether polyols and / or polyester polyols.

2. The S-type controlled-release nitrogen fertilizer according to claim 1, characterized in that: The mass of the coating layer is 3.5% to 10% of the mass of the S-type controlled-release nitrogen fertilizer; The bottom layer mass is 0.001% to 0.5% of the mass of the S-type controlled-release nitrogen fertilizer; The mass of the inner coating layer is 2.5% to 6.5% of the mass of the S-type controlled-release nitrogen fertilizer; The outer coating layer has a mass of 0.5% to 3% of the mass of the S-type controlled-release nitrogen fertilizer.

3. The S-type controlled-release nitrogen fertilizer according to claim 1 or 2, characterized in that: In the bottom layer, the mass ratio of the functional substance to the water is 1:(5-500); The method for preparing the vegetable oil polyol includes the following steps: mixing vegetable oil, hydrogen peroxide, organic acid, and catalyst, and carrying out an epoxidation reaction; after the reaction, removing the aqueous layer to obtain an epoxidation intermediate; adding an alcohol ring-opening agent to the epoxidation intermediate to carry out a ring-opening reaction; and directly rotary evaporating the product obtained after the reaction without water washing; the mass ratio of the vegetable oil, hydrogen peroxide, organic acid, and catalyst is 1:(0.4~0.8):(0.01~0.4):(0.001~0.005); the mass ratio of the epoxidation intermediate to the alcohol ring-opening agent is 1:(0.1~1.0); the organic acid is formic acid or acetic acid; the catalyst is at least one of sulfuric acid, phosphoric acid, and hydrochloric acid; and the alcohol ring-opening agent is any one of methanol, ethylene glycol, propanol, and butanol.

4. The S-type controlled-release nitrogen fertilizer according to claim 3, characterized in that: The vegetable oil is at least one of palm oil, rapeseed oil, olive oil, soybean oil, corn oil, and peanut oil.

5. The S-type controlled-release nitrogen fertilizer according to claim 3, characterized in that: The epoxidation reaction is carried out at a temperature of 50–70°C for a time of 3–6.5 h. The ring-opening reaction is carried out at a temperature of 40–60°C for 1–4 hours. The conditions for rotary distillation are 50–70°C for 2–4 hours.

6. The S-type controlled-release nitrogen fertilizer according to any one of claims 1-5, characterized in that: The nitration inhibitor is dicyandiamide; The urease inhibitor is n-butylthiophosphoric triamine; The isocyanate is at least one selected from polymethylene polyphenyl polyisocyanate, toluene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, liquefied MDI, isophorone diisocyanate, a trimer of 1,6-hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, phenyl diisocyanate, and dimethylbiphenyl diisocyanate. The sealant is any one of paraffin wax, microcrystalline wax, beeswax, chlorinated paraffin wax, polyethylene wax, asphalt, and silicone wax; The average particle size of the large-particle urea is 2.0–8.0 mm.

7. A method for preparing the S-type controlled-release nitrogen fertilizer according to any one of claims 1-6, comprising the following steps: (1) Add the large urea particles as described in any one of claims 1-6 into a rotating drum and preheat it to 50-70°C to obtain preheated urea particles. (2) Spray the aqueous solution of the functional substance described in any one of claims 1-6 onto the surface of the preheated urea particles to form a bottom layer, thereby obtaining urea particles coated with the bottom layer. (3) Castor oil, any of the vegetable oil polyols described in claims 1-6 and any of the sealants described in claims 1-6 are heated at 60-90°C and then mixed with any of the isocyanates described in claims 1-6 to prepare a coating liquid. The coating liquid is then sprayed onto the surface of the urea particles coated with the bottom layer. After curing reaction, an inner coating layer is formed, and urea particles coated with the inner coating layer are obtained. (4) The hydroxyl-containing substance and the sealant described in any one of claims 1-6 are heated at 60-90°C and then mixed with the isocyanate described in any one of claims 1-6 to prepare a coating liquid. The mixture is then sprayed onto the surface of the urea particles coated with the inner coating layer. After curing reaction, an outer coating layer is formed to obtain the S-type controlled-release nitrogen fertilizer.

8. A product for rice seedling cultivation, comprising S-type controlled-release nitrogen fertilizer; wherein the S-type controlled-release nitrogen fertilizer is the S-type controlled-release nitrogen fertilizer according to any one of claims 1-6 or the S-type controlled-release nitrogen fertilizer prepared according to the method of claim 7.

9. Any one of the following applications (a1)-a4): a1) Application of the S-type controlled-release nitrogen fertilizer prepared according to the method of claim 7 in rice seedling raising; a2) The application of the S-type controlled-release nitrogen fertilizer prepared according to the method of claim 7 in the preparation of rice seedling products; a3) The application of the product according to claim 8 in rice seedling cultivation; a4) The application of the product according to claim 8 in the preparation of rice seedling raising products.

10. A method for raising rice seedlings, comprising the step of sowing and raising seedlings together with rice seeds using the S-type controlled-release nitrogen fertilizer as described in any one of claims 1-6 or the S-type controlled-release nitrogen fertilizer prepared according to the method described in claim 7.