Special coated high-tower compound fertilizer for herbal flowers and preparation method of special coated high-tower compound fertilizer

Abstract

The invention provides a special coated high-tower compound fertilizer for herbaceous flowers and a preparation method thereof, belongs to the technical field of coated compound fertilizers, and solves the problems of poor film-core binding force and poor sustained and controlled release effect of the coated high-tower compound fertilizer. The preparation method comprises the following steps: (a) preheating high-tower compound fertilizer particles; step (b), spraying a urea aqueous solution to the surfaces of the preheated high-tower compound fertilizer particles, and performing pretreatment; (c) spraying isocyanate onto the surfaces of the pretreated high-tower compound fertilizer particles, and carrying out a coupling reaction; and (d) simultaneously spraying a polyol solution containing the tannic acid chelate and a curing agent on the surfaces of the high-tower compound fertilizer particles subjected to the coupling reaction, and carrying out a solvent-free in-situ curing reaction to form a tannic acid chelate modified bio-based polyurethane film layer. The coated high-tower compound fertilizer prepared by the method is good in core film binding force, and the aim of synchronously and controllably releasing various nutrients can be achieved.

Description

Technical Field

[0001] This invention relates to the field of coated compound fertilizer technology, specifically to a coated high-tower compound fertilizer for herbaceous flowers and its preparation method. Background Technology

[0002] Currently, commercially available coated controlled-release fertilizers are mainly coated urea. The preparation methods for coated nitrogen, phosphorus, and potassium compound fertilizers still present certain challenges, including: (1) Due to the uneven physical and chemical properties of the raw materials, the membrane material is easily absorbed by the core compound fertilizer particles, and the membrane material has poor adhesion to the compound fertilizer particles, which leads to easy separation of the core and membrane. (2) The core particles are not as round and uniform in terms of nutrients as large granules of urea. The above difficulties make the coating of compound fertilizer more difficult and thicker than that of urea. In particular, when coating high-tower compound fertilizer particles, the compound fertilizer adopts the vertical spray molding technology of melt, which sprays the high-temperature molten nitrogen, phosphorus and potassium mixture slurry from the top of the tower. During the free fall process, it exchanges heat with cold air and solidifies into particles. The volume shrinkage effect when the melt cools causes the internal gas to escape, forming a through channel with a diameter of about 0.1-0.3 mm on the surface. The opening of the channel on the particle surface makes it difficult to form a uniform film layer on the surface of the coating to achieve a stable controlled release effect. (3) Due to the differences in nutrient dissolution and release of compound fertilizer particles, the challenge of precise fertilization of crops is increased.

[0003] With the increasing demand for coated compound fertilizers with good controlled-release effects on crops, the problems of membrane adhesion and the through-pores on the surface of high-tower compound fertilizer particles make it difficult to accurately control the release of nutrients after the preparation of coated high-tower compound fertilizers, and it is difficult to match them with the fertilizer requirements of crops. These problems urgently need to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a coating high-tower compound fertilizer for herbaceous flowers and its preparation method, which can fundamentally solve the core-membrane bonding problem of coating high-tower compound fertilizer and achieve the goal of simultaneous and controllable release of multiple nutrients.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, comprising: Step (a): Preheat high-tower compound fertilizer granules; Step (b): Spray urea aqueous solution onto the surface of preheated high-tower compound fertilizer granules for pretreatment; Step (c): Isocyanate is sprayed onto the surface of pretreated high-tower compound fertilizer granules to carry out a coupling reaction; Step (d) involves simultaneously spraying a polyol solution containing tannic acid chelates and a curing agent onto the surface of the high-tower compound fertilizer granules after the coupling reaction, and then performing a solvent-free in-situ curing reaction to form a bio-based polyurethane film layer modified with tannic acid chelates.

[0006] Optionally, in step (a), the preheating temperature is 50-60°C.

[0007] Optionally, in step (b), the mass concentration of urea in the urea aqueous solution is 10-30%; the amount of urea aqueous solution used is such that the mass of urea accounts for 0.5-2% of the total mass of the high-tower compound fertilizer granules.

[0008] Optionally, in step (b), the urea aqueous solution further contains an inhibitor, which is a urease inhibitor and / or a nitration inhibitor.

[0009] Optionally, the mass concentration of the inhibitor in the urea aqueous solution is 1.5-5%.

[0010] Optionally, in step (c), the amount of isocyanate used is such that the mass of the isocyanate accounts for 0.1-0.5% of the total mass of the high-tower compound fertilizer granules.

[0011] Optionally, in step (c), the coupling reaction is carried out at a temperature of 50-60°C for 2-5 minutes.

[0012] Optionally, in step (d), the method for preparing the polyol solution containing tannic acid chelate includes: dissolving tannic acid and metal ion salt in a bio-based polyol and stirring.

[0013] Optionally, the molar ratio of the tannic acid to the metal ion in the metal ion salt is 1:1 to 1:5, and the mass of the tannic acid is 1-5% of the mass of the bio-based polyol.

[0014] Secondly, the present invention provides a special coated high-tower compound fertilizer for herbaceous flowers, which is prepared by the above-described preparation method.

[0015] The above-described solution of the present invention has at least the following beneficial effects: This invention forms a bio-based polyurethane membrane modified with tannic acid chelates by pretreating high-tower compound fertilizer granules with urea, performing isocyanate coupling reaction, and solvent-free in-situ curing reaction. This specific "urea pretreatment + coupling + cross-linking modified bio-based coating" process fundamentally solves the core-membrane bonding problem of coated high-tower compound fertilizers and achieves uniform membrane layer, thereby realizing the goal of simultaneous and controllable release of multiple nutrients. Attached Figure Description

[0016] Figure 1These are the nitrogen release curves of the coated high-tower compound fertilizers prepared in the embodiments and comparative examples of the present invention; Figure 2 These are the phosphorus release curves from the coated high-tower compound fertilizers prepared according to the embodiments and comparative examples of the present invention; Figure 3 These are potted chrysanthemums 28 days after fertilization, as tested in this invention (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group, and example 1 group). Figure 4 The test examples of this invention are potted chrysanthemums 66 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group and example 1 group). Figure 5 The test examples of this invention are potted chrysanthemums 107 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group and example 1 group). Figure 6 The test examples of this invention are potted chrysanthemums 107 days after fertilization (from top to bottom: Comparative Example 1 and Example 1). Figure 7 The test examples of this invention are chrysanthemum potted plants 107 days after fertilization with slow-release fertilizer purchased from SCOTTS Company in the United States and coated high-tower compound fertilizer prepared in Example 1 (the left side is the SCOTTS slow-release fertilizer group, and the right side is the Example 1 group). Figure 8 The photos are of potted Salvia splendens plants 28 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer, comparative group 1, and example group 1). Figure 9 The following are potted Salvia splendens plants 93 days after application (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example group 1, and example group 1). Figure 10 The following are potted Salvia splendens plants 107 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example group 1, and example group 1). Figure 11 These are potted Salvia splendens plants 107 days after fertilization with slow-release fertilizer purchased from SCOTTS Company in the United States and coated high-tower compound fertilizer prepared in Example 1, respectively (the left side is the SCOTTS slow-release fertilizer group, and the right side is the Example 1 group). Figure 12 These are potted marigolds 16 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group, comparative example 2 group, and example 1 group). Figure 13The marigold potted plants were 37 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group, comparative example 2 group, and example 1 group). Figure 14 The effect of different fertilizers on leaf area 84 days after fertilization (from left to right, from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group, example 1 group, comparative example 2 group). Figure 15 These are marigold potted plants 84 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group, comparative example 2 group, and example 1 group, each with one row of photos). Figure 16 Marigold potted plants were fertilized 84 days after application of the slow-release fertilizer from SCOTTS (USA), Comparative Example 1, Comparative Example 2, and Example 1 (from left to right: SCOTTS slow-release fertilizer group, Comparative Example 1 group, Comparative Example 2 group, Example 1 group). Detailed Implementation

[0017] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0018] In a first aspect, the present invention provides a method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, comprising: Step (a): Preheat high-tower compound fertilizer granules; Step (b): Spray urea aqueous solution onto the surface of preheated high-tower compound fertilizer granules for pretreatment; Step (c): Isocyanate is sprayed onto the surface of pretreated high-tower compound fertilizer granules to carry out a coupling reaction; Step (d) involves simultaneously spraying a polyol solution containing tannic acid chelates and a curing agent onto the surface of the high-tower compound fertilizer granules after the coupling reaction, and then performing a solvent-free in-situ curing reaction to form a bio-based polyurethane film layer modified with tannic acid chelates.

[0019] For example, the preparation method further includes step (e): cooling the coated high-tower compound fertilizer granules to below 45°C, and then screening and metering them for packaging.

[0020] In this invention, the high-tower compound fertilizer is of potassium sulfate type, and the mass percentage of nitrogen, phosphorus and potassium is (18-25):(8-18):(15-20), preferably 18:18:18 or 25:10:15 or 25:8:20.

[0021] For example, the particle size of the high-tower compound fertilizer granules is 2-4 mm.

[0022] For example, in step (a), the preheating is carried out in a rotary drum coating machine for 10-20 minutes.

[0023] In step (a), the purpose of preheating is to make the subsequent urea aqueous solution adhere more evenly and the subsequent film layer more uniform. Furthermore, the preheated high-tower compound fertilizer granules are softened and can be polished in the rotary drum coating machine to further improve the uniformity of the subsequent film layer.

[0024] For example, in step (a), the preheating temperature is 50-60°C, preferably 50-55°C, and more preferably 50°C, 52°C or 55°C.

[0025] In step (b), by spraying urea aqueous solution onto the surface of the high-tower compound fertilizer granules, an active layer rich in amino (-NH2) and amide (-CONH2) groups is formed on the surface of the high-tower compound fertilizer granules. This reduces the absorption of the subsequent coating liquid by the core of the compound fertilizer and increases the adhesion and uniformity of the subsequent film layer.

[0026] For example, in step (b), the mass concentration of urea in the urea aqueous solution is 10-30%, preferably 15-25%.

[0027] For example, the amount of urea aqueous solution used is such that the mass of urea accounts for 0.5-2% of the total mass of the high-tower compound fertilizer granules, preferably 1-1.5%.

[0028] For example, the spraying in step (b) and the preheating in step (a) are carried out in the same equipment, and the heat preservation time after spraying is 10-20 minutes.

[0029] For example, in step (b), the urea aqueous solution further contains an inhibitor, which is a urease inhibitor and / or a nitration inhibitor. The inhibitor can slow down the conversion rate of nitrogen forms in urea, improve utilization, and extend shelf life.

[0030] For example, the nitration inhibitor is 3,4-dimethylpyrazole phosphate (DMPP).

[0031] For example, the urease inhibitor is N-butylthiophosphoric triamine (NBPT).

[0032] For example, the mass concentration of the inhibitor in the urea aqueous solution is 1.5-5%, preferably 2-4%.

[0033] For example, when nitrification inhibitors and urease inhibitors are used in combination, the mass ratio of nitrification inhibitors to urease inhibitors is 1:3 to 3:1, preferably 1:1.

[0034] In this invention, steps (a) and (b) are used to fill the pores on the particle surface, which makes the subsequently formed film layer more uniform and the film core bonding force better.

[0035] In step (c), isocyanate is sprayed onto the surface of the pretreated high-tower compound fertilizer granules. The isocyanate reacts with the urea sprayed in step (b). The urea bonds -NH-CO-NH- generated by the reaction and the urea carbamate generated by further reaction will act as a "bridge" or "coupling agent". One end of the "bridge" is anchored to the surface of the fertilizer granules, while the other end provides active chemical sites, enhancing the chemical compatibility and binding force with the coating material in the subsequent step (d).

[0036] For example, in step (c), the amount of isocyanate used is such that the mass of isocyanate accounts for 0.1-0.5% of the total mass of the high-tower compound fertilizer granules.

[0037] For example, the isocyanate is at least one of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), and polymethylene polyphenyl polyisocyanate (PAPI).

[0038] For example, in step (c), the coupling reaction is carried out at a temperature of 50-60°C for 2-5 minutes.

[0039] For example, in step (d), the method for preparing the polyol solution containing tannic acid chelate includes: dissolving tannic acid and metal ion salt in a bio-based polyol and stirring at room temperature for 15-45 minutes, preferably for 20-30 minutes.

[0040] In step (d), tannic acid forms a chelate with metal ions, which in turn plays a role in crosslinking and modifying the polymer membrane material, improving the adhesion between the membrane cores, making the membrane layer more uniform, and improving the controlled release effect; during the nutrient release process, metal ions can provide the micronutrients needed for crop growth.

[0041] For example, the molar ratio of tannic acid to metal ions in the metal ion salt is 1:1-1:5, preferably 1:2-1:3.

[0042] For example, the mass of the tannic acid is 1-5% of the mass of the bio-based polyol, preferably 2-4%.

[0043] For example, the metal ion is Fe³⁺. + Zn² + Cu² + At least one of them, which is added in the form of a soluble salt.

[0044] For example, the metal ion salt is at least one of sulfate, nitrate and chloride.

[0045] For example, the bio-based polyol is a mixture of vegetable oil polyol, bio-based butylene glycol, and straw-based polyol. The three components can produce synergy in terms of complementary polyurethane molecular structures, superimposed performance, and optimized process: vegetable oil polyol, as the main component (more than 50%), ensures the basic flexibility of the membrane material; butylene glycol is a common chain extender for polyurethane, which plays a role in regulating the viscosity and reaction rate of the system; straw-based polyol (more than 16%) contains polyhydroxy compounds obtained from the degradation of lignin, cellulose, etc., introducing rigid aromatic ring structures and polyhydroxy functional groups, which play a cross-linking role. Finally, under the action of a curing agent, a polyurethane membrane material with excellent strength, toughness, and processability is obtained.

[0046] For example, the mass ratio of vegetable oil polyol, bio-based butylene glycol and straw-based polyol is (50-80):(4-8):(42-16), preferably (60-70):(5-7):(35-23).

[0047] For example, the vegetable oil polyol is at least one of palm oil polyol, soybean oil polyol, castor oil and castor oil polyol.

[0048] For example, in step (d), the curing agent is an isocyanate, preferably PAPI.

[0049] For example, in step (d), the mass ratio of the polyol solution containing tannic acid chelate to the curing agent is 3:7-1:1, preferably 2:3-1:1.

[0050] For example, the solvent-free in-situ curing reaction is carried out at a temperature of 50-60°C for 6-15 minutes to form a dense coating film.

[0051] For example, the solvent-free in-situ curing reaction is carried out in a rotary drum apparatus.

[0052] For example, the mass ratio of the tannic acid chelate-modified bio-based polyurethane membrane to the high-tower compound fertilizer granules is 1:50-1:25, preferably 1:40-1:30.

[0053] This invention utilizes a specific "urea pretreatment + coupling + cross-linked modified bio-based coating" process, combined with the coupling effect of the membrane layer and the built-in inhibitor, to fundamentally solve the core-membrane bonding problem of coated high-tower compound fertilizers, and achieve the goal of simultaneous and controllable release of multiple nutrients.

[0054] Secondly, the present invention also provides a special coated high-tower compound fertilizer for herbaceous flowers, which is prepared by the above-described preparation method.

[0055] The preparation method of the herbaceous flower-specific coated high-tower compound fertilizer of the present invention will be further illustrated below through specific embodiments.

[0056] In the following examples and comparative examples, the coating rate of coated high-tower compound fertilizer refers to the percentage of the film mass to the total fertilizer mass.

[0057] In the following examples and comparative examples, soybean oil polyol and castor oil polyol were purchased from Zhuochuangna New Materials (Cangzhou) Co., Ltd., with brand names Naxipol-CA1006 and Naxipol-SA2025, respectively; castor oil was purchased from Maclean Company; bio-based butylene glycol was purchased from Shandong Landian Biotechnology Co., Ltd.; palm oil polyol was purchased from Shandong Sikerui Company, with brand name SK-200; the preparation method of straw-based polyol was as follows: 70g of corn stalk powder with a particle size of 80 mesh, 70g of corn starch, a liquefying agent composed of 350g of polyethylene glycol 400 and 50g of glycerol, and 8g of sulfuric acid were mixed evenly in a reaction vessel equipped with a mechanical stirrer and a condenser, reacted at 150°C for 100min, and cooled to below approximately 100°C using an ice-water bath.

[0058] Example 1 This embodiment provides a method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, including: (a) Preheat 1 kg of high-tower compound fertilizer granules (nitrogen, phosphorus and potassium mass percentage of 18:18:18, particle size of 2-4 mm) to 50°C in a rotary drum coating machine for 20 min; (b) Pre-treating the surface of preheated high-tower compound fertilizer granules with urea: Spraying a urea aqueous solution with a urea mass concentration of 15% onto the surface of preheated high-tower compound fertilizer granules. The urea aqueous solution also contains DMPP with a mass concentration of 2%. After spraying, keep warm for 10 minutes. After pre-treatment, the urea accounts for 1% of the total mass of the high-tower compound fertilizer granules, and the DMPP accounts for 0.13% of the total mass of the high-tower compound fertilizer granules. (c) Coupling reaction on the surface of pretreated high-tower compound fertilizer granules: PAPI was sprayed onto the surface of pretreated high-tower compound fertilizer granules and reacted at 50°C for 2 min. After spraying, PAPI accounted for 0.2% of the total mass of the high-tower compound fertilizer granules. (d) Coating the surface of coupled high-tower compound fertilizer granules with a bio-based polyurethane film modified with tannic acid chelates: A polyol solution containing tannic acid chelates at a mass ratio of 2:3 and a curing agent PAPI were simultaneously sprayed onto the granule surface for solvent-free in-situ curing reaction at a reaction temperature of 50℃ and a reaction time of 15 min, forming a dense coating film. The mass ratio of the film to the high-tower compound fertilizer granules was 1:40. The polyol solution containing tannic acid chelates was prepared by dissolving tannic acid and copper sulfate at a molar ratio of 1:2 in a bio-based polyol composed of palm oil polyol, bio-based butylene glycol, and straw-based polyol at a mass ratio of 60:5:35, with the mass of tannic acid being 2% of the mass of the bio-based polyol, and stirring at room temperature for 20 min. (e) Cool the coated high-tower compound fertilizer granules to below 45°C, then screen and measure and package them.

[0059] The coating rate of the coated high-tower compound fertilizer prepared in this embodiment is 2.5%.

[0060] Example 2 This embodiment provides a method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, including: (a) Preheat 1 kg of high-tower compound fertilizer granules (nitrogen, phosphorus and potassium mass percentage of 25:10:15, particle size of 2-4 mm) to 52°C in a rotary drum coating machine for 15 min; (b) Pre-treating the surface of preheated high-tower compound fertilizer granules with urea: Spraying a urea aqueous solution with a urea mass concentration of 25% onto the surface of preheated high-tower compound fertilizer granules. The urea aqueous solution also contains NBPT with a mass concentration of 2%. After spraying, keep warm for 20 minutes. After pre-treatment, urea accounts for 1.5% of the total mass of high-tower compound fertilizer granules, and NBPT accounts for 0.12% of the total mass of compound fertilizer granules. (c) Coupling reaction on the surface of pretreated high-tower compound fertilizer granules: MDI was sprayed onto the surface of pretreated high-tower compound fertilizer granules and reacted at 52°C for 5 min. After spraying, MDI accounted for 0.5% of the total mass of the high-tower compound fertilizer granules. (d) Coating the surface of coupled high-tower compound fertilizer granules with a bio-based polyurethane film modified with tannic acid chelates: A polyol solution containing tannic acid chelates at a mass ratio of 1:1 and a curing agent PAPI were simultaneously sprayed onto the granule surface for solvent-free in-situ curing reaction at a reaction temperature of 60℃ and a reaction time of 6 min, forming a dense coating film. The mass ratio of the film to the high-tower compound fertilizer granules was 1:30. The polyol solution containing tannic acid chelates was prepared by dissolving tannic acid and zinc sulfate at a molar ratio of 1:3 in a bio-based polyol composed of castor oil, bio-based butylene glycol, and straw-based polyol at a mass ratio of 70:7:23, with the mass of tannic acid being 4% of the mass of the bio-based polyol, and stirring at room temperature for 30 min. (e) Cool the coated high-tower compound fertilizer granules to below 45°C, then screen and measure and package them.

[0061] The coating rate of the coated high-tower compound fertilizer prepared in this embodiment is 3.3%.

[0062] Example 3 This embodiment provides a method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, including: (a) Preheat 1 kg of high-tower compound fertilizer granules (nitrogen, phosphorus and potassium mass percentage of 25:8:20, particle size of 2-4 mm) to 55°C in a rotary drum coating machine for 10 min; (b) Pre-treating the surface of preheated high-tower compound fertilizer granules with urea: Spraying a urea aqueous solution with a urea mass concentration of 20% onto the surface of preheated high-tower compound fertilizer granules. The urea aqueous solution also contains a DMPP and NBPT composite inhibitor with a mass concentration of 4%. After spraying, keep warm for 15 minutes. After pre-treatment, the urea accounts for 1.5% of the total mass of the high-tower compound fertilizer granules, the mass ratio of DMPP and NBPT is 1:1, and the composite inhibitor is 0.3% of the total mass of the high-tower compound fertilizer granules. (c) Coupling reaction on the surface of pretreated high-tower compound fertilizer granules: TDI was sprayed onto the surface of pretreated high-tower compound fertilizer granules and reacted at 55°C for 5 min. After spraying, TDI accounted for 0.1% of the total mass of the high-tower compound fertilizer granules. (d) Coating the surface of coupled high-tower compound fertilizer granules with a bio-based polyurethane film modified with tannic acid chelates: A polyol solution containing tannic acid chelates at a mass ratio of 1:1 and a curing agent PAPI were simultaneously sprayed onto the granule surface for solvent-free in-situ curing reaction at a reaction temperature of 55℃ and a reaction time of 10 min, forming a dense coating film. The mass ratio of the film to the high-tower compound fertilizer granules was 1:35. The polyol solution containing tannic acid chelates was prepared by dissolving tannic acid and ferric chloride at a molar ratio of 1:3 in a bio-based polyol composed of castor oil polyol, bio-based butylene glycol, and straw-based polyol at a mass ratio of 64:6:30, where the mass of tannic acid was 3% of the mass of the bio-based polyol, and stirring at room temperature for 25 min. (e) The coated compound fertilizer granules are cooled to below 45°C and then screened and packaged.

[0063] The coating rate of the coated high-tower compound fertilizer prepared in this embodiment is 2.9%.

[0064] Example 4 This embodiment provides a method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, including: (a) Preheat 1 kg of high-tower compound fertilizer granules (nitrogen, phosphorus and potassium mass percentage of 18:18:18, particle size of 2-4 mm) to 55°C in a rotary drum coating machine for 10 min; (b) Pre-treating the surface of preheated high-tower compound fertilizer granules with urea: A urea aqueous solution with a mass concentration of 20% was sprayed onto the surface of the preheated high-tower compound fertilizer granules. The urea aqueous solution also contained a DMPP and NBPT composite inhibitor with a mass concentration of 3%. After spraying, the solution was kept warm for 10 minutes. After pre-treatment, the urea accounted for 1.2% of the total mass of the high-tower compound fertilizer granules, the mass ratio of DMPP and NBPT was 1:1, and the composite inhibitor accounted for 0.18% of the total mass of the high-tower compound fertilizer granules. (c) Coupling reaction on the surface of pretreated high-tower compound fertilizer granules: PAPI was sprayed onto the surface of pretreated high-tower compound fertilizer granules and reacted at 55°C for 3 min. After spraying, PAPI accounted for 0.4% of the total mass of the high-tower compound fertilizer granules. (d) Coating the surface of coupled high-tower compound fertilizer granules with a bio-based polyurethane film modified with tannic acid chelates: A polyol solution containing tannic acid chelates at a mass ratio of 4:5 and a curing agent PAPI were simultaneously sprayed onto the granule surface for solvent-free in-situ curing reaction at a reaction temperature of 55℃ and a reaction time of 10 min, forming a dense coating film. The mass ratio of the film to the compound fertilizer granules was 1:40. The polyol solution containing tannic acid chelates was prepared by dissolving tannic acid and zinc chloride at a molar ratio of 2:5 in a bio-based polyol composed of soybean oil polyol, bio-based butylene glycol, and straw-based polyol at a mass ratio of 65:6:29, where the mass of tannic acid was 3% of the mass of the bio-based polyol, and stirring at room temperature for 25 min. (e) Cool the coated high-tower compound fertilizer granules to below 45°C, then screen and measure and package them.

[0065] The coating rate of the coated high-tower compound fertilizer prepared in this embodiment is 2.5%.

[0066] Comparative Example 1 This comparative example provides a method for preparing a coated high-tower compound fertilizer for herbaceous flowers similar to that of Example 1. The difference is that the surface of the preheated high-tower compound fertilizer granules is not pretreated with urea, i.e., step (b) is omitted. The other steps are the same as in Example 1. The coating rate of the prepared coated high-tower compound fertilizer is 2.5%.

[0067] Comparative Example 2 This comparative example provides a method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, similar to Example 1. The difference is that the coupling reaction is not performed on the surface of the pretreated high-tower compound fertilizer particles, i.e., step (c) is omitted. The other steps are the same as in Example 1. The coating rate of the prepared coated high-tower compound fertilizer is 2.5%.

[0068] Comparative Example 3 This comparative example provides a method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, similar to Example 1. The difference is that the urea aqueous solution in step (b) does not contain the inhibitor DMPP; the other steps are the same as in Example 1. The coating rate of the prepared coated high-tower compound fertilizer is 2.5%.

[0069] Comparative Example 4 This comparative example provides a method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, similar to Example 1. The difference is that in step (d), copper sulfate is not added to the polyol solution; the other steps are the same as in Example 1. The coating rate of the prepared coated high-tower compound fertilizer is 2.5%.

[0070] Comparative Example 5 This comparative example provides a method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, similar to Example 1. The difference is that tannic acid is not added to the polyol solution in step (d), while the other steps are the same as in Example 1. The coating rate of the prepared coated high-tower compound fertilizer is 2.5%.

[0071] Test case 1. Fertilizer performance analysis The controlled-release performance of the coated high-tower compound fertilizer prepared in the examples and comparative examples was tested using the water immersion method. The specific steps are as follows: 10g of coated high-tower compound 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. The container was then sealed and placed in a 25℃ constant temperature incubator. Samples of the extract were taken at 1, 3, 7, 14, 21, 28, 35, 42, 49, 56, and 63 days, respectively, to determine the nitrogen, phosphorus, and potassium content in the extract until the cumulative release rate reached 80%. The controlled-release performance test results of commercially available coated high-tower compound fertilizer (Huaduoduo brand) are also provided. Considering that the release curves of potassium and nitrogen are basically similar, only the release curves of nitrogen and phosphorus are provided, and the results are as follows: Figure 1 and Figure 2 As shown.

[0072] Initial release rate refers to the mass fraction of nitrogen released by coated high-tower compound fertilizer after 24 hours of extraction in still water at 25℃, relative to the total nitrogen; nutrient release period refers to the number of days required for nitrogen in coated high-tower compound fertilizer to reach an 80% cumulative nutrient release rate after extraction in still water at 25℃.

[0073] Depend on Figure 1 and Figure 2 It can be seen that: (1) Compared with commercially available coated compound fertilizers, commercially available coated compound fertilizers show parabolic nutrient release characteristics. The nutrient release characteristics of Examples 1-4 show the characteristics of pre-controlled and post-promotion or uniform release, which are more in line with the fertilizer requirements of crops.

[0074] (2) Under the same membrane conditions, compared with the effect of Comparative Example 1, the release period was extended after adding the urea pretreatment process in Example 1, and phosphorus was dissolved simultaneously. Based on the analysis of the coating rate data, it was found that the high tower compound fertilizer was pretreated with urea, which reduced the absorption of the core compound fertilizer by the subsequent coating liquid and increased the adhesion and uniformity of the subsequent membrane, thereby extending the nutrient release period.

[0075] (3) Compared with the effect of Comparative Example 2, after adding the coupling step in Example 1, except for the extended release period and synchronous phosphorus dissolution, the nutrient release rate was basically the same within 20 days, indicating that the pretreatment process ensured the controllability of nutrient release in the early stage of fertilizer, and the coupling step ensured the controllability of nutrient release in the later stage of fertilizer.

[0076] (4) Under the same process conditions, comparing the effects of Comparative Example 2 and Comparative Example 3 without built-in inhibitors, the nutrient release characteristics of the coated compound fertilizers are similar, indicating that the addition of inhibitors is similar to the coupling process, both of which can ensure the controllability of nitrogen release in the later stage of the fertilizer. The difference is that the phosphorus release characteristics of the coated compound fertilizers prepared in Comparative Example 3 and Example 1 are similar, indicating that the rate of phosphorus release is not affected by the inhibitor.

[0077] (5) Compared with the effect of Comparative Example 4, the release period was extended from 50 days to 60 days after the addition of trace elements in Example 1. This is mainly because the polyphenol hydroxyl groups in tannic acid molecules not only react with the curing agent, but also form chelates with metal ions. The two work together to build a denser cross-linked network in the polyurethane structure, thereby significantly improving the controlled release performance of the membrane material.

[0078] (6) Compared with the effect of Comparative Example 5, the release period was significantly prolonged after adding tannic acid in Example 1. This once again verifies the cross-linking effect of tannic acid in the polyurethane formation process. After forming a chelate with metal ions, it undergoes double cross-linking in the polyurethane formation process, ensuring the nutrient control performance of the coated compound fertilizer.

[0079] The presence of interconnected pores on the surface of the high-tower compound fertilizer particles ensures the synchronous and controllable dissolution of nutrients.

[0080] The controlled-release performance of potassium in the coated compound fertilizers prepared in the above embodiments and comparative examples is not substantially different from that of nitrogen.

[0081] 2. Application effect of fertilizer on potted herbaceous flowers in greenhouse (1) Fertilizer effect on potted chrysanthemums There were four treatment groups: a blank control group, a commercially available uncoated high-tower compound fertilizer group (purchased from Sinochem Fertilizer, Lanlin 335), a coated high-tower compound fertilizer group prepared in Comparative Example 1, and a coated high-tower compound fertilizer group prepared in Example 1. Each group treated two rows of potted chrysanthemums, for a total of eight rows of potted chrysanthemums. All experimental instruments used 11mm diameter chrysanthemums. In the 11-color pots, except for the blank control group, 2 grams of the corresponding fertilizer were evenly mixed into each pot. Figure 3 The chrysanthemum potted plants were 28 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group and example 1 group). Figure 4 The chrysanthemum potted plants were 66 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group and example 1 group). Figure 5 The chrysanthemum potted plants were 107 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group and example 1 group). Figure 6 The chrysanthemum potted plants were 107 days after fertilization (Comparative Example 1 and Example 1). Figure 7Chrysanthemum potted plants were fertilized 107 days after application of slow-release fertilizer purchased from SCOTTS Company in the United States and coated high-tower compound fertilizer prepared in Example 1, respectively (the left side is the SCOTTS slow-release fertilizer group, and the right side is the Example 1 group).

[0082] Table 1 presents data obtained from a single destructive sampling of potted chrysanthemum plants 160 days after fertilization. Chlorophyll values ​​were measured using a SPAD Japanese handheld chlorophyll meter.

[0083] Table 1

[0084] (2) Fertilizer effect of potted plants on Salvia splendens There were four treatment groups: a blank control group, a commercially available uncoated high-tower compound fertilizer group (from the same source as above), a coated high-tower compound fertilizer group prepared in Comparative Example 1, and a coated high-tower compound fertilizer group prepared in Example 1. Each group consisted of 2 rows of 4 pots. All experimental pots had a diameter of 11 mm. In the 11-color pots, except for the blank control group, 2 grams of the corresponding fertilizer were evenly mixed into each pot. Figure 8 The following are potted Salvia splendens plants 28 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer, comparative group 1, and example group 1). Figure 9 The potted Salvia splendens plants were 93 days after application (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example group 1, and example 1 group). Figure 10 The potted Salvia splendens plants were 107 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example group 1, and example group 1). Figure 11 Potted Salvia splendens plants were fertilized 107 days after application of slow-release fertilizer purchased from SCOTTS Company, USA, and coated high-tower compound fertilizer prepared in Example 1, respectively (the left side is the SCOTTS slow-release fertilizer group, and the right side is the Example 1 group).

[0085] Table 2 shows the data obtained from a single destructive sampling of potted Salvia splendens plants 160 days after fertilization.

[0086] Table 2

[0087] (3) Fertilizer effect on potted marigolds There were five treatment groups: a blank control group, a commercially available uncoated high-tower compound fertilizer group (from the same source as above), a coated high-tower compound fertilizer group prepared in Comparative Example 1, a coated high-tower compound fertilizer group prepared in Comparative Example 2, and a coated high-tower compound fertilizer group prepared in Example 1. Each group consisted of 2 rows of 4 pots. All experimental pots had a diameter of 11 mm. In the 11-color pots, except for the blank control group, 2 grams of the corresponding fertilizer were evenly mixed into each pot. Figure 12 The marigold potted plants were 16 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group, comparative example 2 group, and example 1 group). Figure 13 The marigold potted plants were 37 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group, comparative example 2 group, and example 1 group). Figure 14 The effect of different fertilizers on leaf area 84 days after fertilization (from left to right, from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group, example 1 group, comparative example 2 group). Figure 15 Marigold potted plants were photographed 84 days after fertilization (from top to bottom: blank control group, commercially available high-tower compound fertilizer group, comparative example 1 group, comparative example 2 group, and example 1 group, with one row of photos taken for each group). Figure 16 Marigold potted plants were fertilized 84 days after application of the coated high-tower compound fertilizer prepared by SCOTTS Corporation (USA), Comparative Example 1, Comparative Example 2, and Example 1 (from left to right: SCOTTS Corporation (USA) slow-release fertilizer group, Comparative Example 1 group, Comparative Example 2 group, Example 1 group).

[0088] Table 3 shows the data obtained from a single destructive sampling of potted marigolds 160 days after fertilization.

[0089]

[0090] As can be seen from Tables 1 to 3 and all the accompanying figures, the herbaceous flower-specific coated high-tower compound fertilizer prepared by this invention has undergone extensive field trials, and its field performance is superior to that of commercially available fertilizers.

[0091] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a coated high-tower compound fertilizer specifically for herbaceous flowers, characterized in that, include: Step (a): Preheat high-tower compound fertilizer granules; Step (b): Spray urea aqueous solution onto the surface of preheated high-tower compound fertilizer granules for pretreatment; Step (c): Isocyanate is sprayed onto the surface of pretreated high-tower compound fertilizer granules to carry out a coupling reaction; Step (d) involves simultaneously spraying a polyol solution containing tannic acid chelates and a curing agent onto the surface of the high-tower compound fertilizer granules after the coupling reaction, and then performing a solvent-free in-situ curing reaction to form a bio-based polyurethane film layer modified with tannic acid chelates.

2. The preparation method of the herbaceous flower-specific coated high-tower compound fertilizer according to claim 1, characterized in that, In step (a), the preheating temperature is 50-60°C.

3. The preparation method of the herbaceous flower-specific coated high-tower compound fertilizer according to claim 1, characterized in that, In step (b), the mass concentration of urea in the urea aqueous solution is 10-30%; the amount of urea aqueous solution used is such that the mass of urea accounts for 0.5-2% of the total mass of the high-tower compound fertilizer granules.

4. The preparation method of the herbaceous flower-specific coated high-tower compound fertilizer according to claim 1 or 3, characterized in that, In step (b), the urea aqueous solution also contains an inhibitor, which is a urease inhibitor and / or a nitration inhibitor.

5. The preparation method of the herbaceous flower-specific coated high-tower compound fertilizer according to claim 4, characterized in that, The mass concentration of the inhibitor in the urea aqueous solution is 1.5-5%.

6. The preparation method of the herbaceous flower-specific coated high-tower compound fertilizer according to claim 1, characterized in that, In step (c), the amount of isocyanate used is such that the mass of isocyanate accounts for 0.1-0.5% of the total mass of the high-tower compound fertilizer granules.

7. The preparation method of the herbaceous flower-specific coated high-tower compound fertilizer according to claim 1 or 6, characterized in that, In step (c), the coupling reaction is carried out at a temperature of 50-60°C for 2-5 minutes.

8. The preparation method of the herbaceous flower-specific coated high-tower compound fertilizer according to claim 1, characterized in that, In step (d), the method for preparing the polyol solution containing tannic acid chelate includes: dissolving tannic acid and metal ion salt in a bio-based polyol and stirring.

9. The preparation method of the herbaceous flower-specific coated high-tower compound fertilizer according to claim 8, characterized in that, The molar ratio of tannic acid to metal ions in the metal ion salt is 1:1 to 1:5, and the mass of tannic acid is 1-5% of the mass of the bio-based polyol.

10. A type of coated high-tower compound fertilizer specifically for herbaceous flowers, characterized in that, The herbaceous flower-specific coated high-tower compound fertilizer is prepared by the preparation method described in any one of claims 1 to 9.

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