Preparation method of nano SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer

Abstract

The invention discloses a preparation method of a nano SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer. The preparation method comprises the following steps: S1, carrying out super-hydrophobic modification on nano SiO2 powder by using perfluorosilane; s2, continuously and simultaneously dropwise adding polyol and isocyanate to the surfaces of the fertilizer particles to obtain a polyurethane coated fertilizer; and S3, coating the surface of the polyurethane coated fertilizer with the hydrophobically modified nano SiO2 powder to obtain the super-hydrophobic polyurethane coated fertilizer with the nano SiO2. The preparation method is suitable for the technical field of coated controlled-release fertilizers, the hydrophobic nano SiO2 is directly adhered to the surface of polyurethane coated urea to form a stable, uniform and hydrophobic micro-nano structure coating, and the surface of the polyurethane coated fertilizer is coated with the hydrophobic nano SiO2 powder to obtain the super-hydrophobic polyurethane coated fertilizer with the nano SiO2. The problem that the hydrophobic effect is difficult to play due to the fact that an existing nano coating is unstable is solved, and the problem that the usage amount of a solvent for preparing the nano SiO2 hydrophobic coating is too large is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of coated controlled-release fertilizers, and is specifically a nano-SiO 2 Preparation method of superhydrophobic polyurethane coated controlled-release fertilizer. Background Art

[0002] Polyurethane is currently the main material for coated fertilizers due to its excellent mechanical properties and good controlled release properties. However, the large number of ester groups and urea groups in its structure make it less hydrophobic, thus limiting its controlled release properties. By treating the polyurethane surface with low surface energy and increasing the surface roughness, the hydrophobicity can be improved, slowing down the nutrient release process of the coated fertilizer. Nanosilica (SiO 2 ) is the most typical hydrophobic modified material. By compounding with polyurethane or directly spraying it on its surface, the polyurethane surface can be made super-hydrophobic (water contact angle greater than 150°). This technology is also used in coated fertilizers.

[0003] For example, in publication number CN107032891A, a mixed aqueous solution of micron-scale materials and nano-scale materials is sprayed on the surface of bio-based polyurethane to prepare a rough micro-nano coating on the surface, which is then immersed in an organic solvent containing low surface energy substances and dried to obtain a super-hydrophobic bio-based coated fertilizer. The controlled release period of the fertilizer can reach 1 to 4 months, which greatly improves the nutrient utilization rate of the fertilizer. However, SiO 2 The aqueous solution has poor adhesion to the polyurethane surface, and the rough micro-nano coating prepared has poor mechanical properties. The author makes improvements to this method on this basis, and provides a magnetic nano-microcapsule self-assembly super-hydrophobic additive in CN115677415A, which is added to the polyurethane prepolymer. The magnetic nano-microcapsule is subjected to magnetic action during the coating process and will spontaneously migrate from the inside of the film layer to the surface of the film layer, and finally obtains a magnetic nano-microcapsule self-assembly super-hydrophobic coated fertilizer with a layer of uniformly distributed super-hydrophobic micro-nano protrusions attached to the surface. The hydrophobic coating prepared by the method is more stable, not easy to fall off, and the fertilizer release period is extended. However, both methods use organic solvents such as chloroform, methanol, toluene, which will not only increase cost but also cause pollution to the environment.

[0004] Another example is CN113880609A, which uses a silane coupling agent as a hydrophobic agent and is added to a polyurethane prepolymer prepared from a bio-based polyol and isocyanate to successfully prepare a hydrophobically modified bio-based coated controlled release fertilizer, whose hydrophobicity is significantly improved and the release period is extended. The hydrophobic angle of the fertilizer prepared by it is only up to 137.25°, which fails to achieve super-hydrophobic properties. CN113004105A introduces nano-modified particles into bio-based polyols, and then prepares nano-modified bio-based coated fertilizers after uniform mixing and reaction with isocyanate. The coated fertilizers are placed in a solution containing low surface energy substances, and after self-assembly for 0.5 to 2 hours, the hydrophobic bio-based coated fertilizers are dried to obtain the coated fertilizers, which can be prepared by regulating different ratios to prepare coated fertilizers of corresponding controlled release periods. It uses hydrochloric acid, sulfuric acid and other catalysis, which is not only dangerous to operate but also affects the soil. And organic solvents such as n-hexane and n-propanol are also used.

[0005] The above studies all show that improving the hydrophobicity of polyurethane is of great significance to improving the release of coated fertilizers. Preparing a rough micro-nano structure on the surface of polyurethane is a widely used method. However, most methods use low surface energy organic solvents to co-construct micro-nano structures, or directly spray nanomaterial dispersions to prepare micro-nano protrusions. One is that organic solvents are used, and the other is that these micro-nano protrusions are easy to fall off. Fixatives must be added to effectively solve this problem, but this also makes the process more complicated. In summary, the current research on nano-SiO 2 The production process of spraying on the surface of polyurethane coated fertilizer has the following main disadvantages:

[0006] 1. Existing Nano-SiO 2 The hydrophobic angle is not good, and there are few reactive sites, which makes it difficult to connect closely with the membrane material;

[0007] 2. Hydrophobic Nano-SiO 2 After mixing with polyols, it reacts with isocyanate to prepare nano-SiO 2 / Polyurethane coated fertilizer, nano-SiO 2 It mainly exists inside polyurethane, which may cause film structure defects and has limited improvement on hydrophobicity;

[0008] 3. Nano-SiO 2 Particles often use organic solvents as dispersions, which are often toxic, not only requiring high equipment requirements, but also causing certain harm to the environment and human body;

[0009] 4. Preparation of Nano-SiO Using Water or Organic Solvents 2 Dispersion liquid, nano-SiO 2 Sprayed on the surface of coated fertilizer, the obtained nano-SiO 2The coating is only deposited on the surface and is easy to fall off, making it difficult to exert its hydrophobic modification advantages;

[0010] 5. Organic silicon and organic fluorine are often used as substances to reduce the surface energy of polymers and nano-SiO 2 The polymer-coated fertilizers are modified together, and their preparation is often carried out in multiple steps, which is complicated and time-consuming.

[0011] Therefore, there is an urgent need for a simple to operate nano-SiO 2 Preparation method of super hydrophobic polyurethane coated controlled release fertilizer, hydrophobic nano-SiO 2 Directly adhere to the surface of polyurethane coated urea to form a stable, uniform and hydrophobic micro-nanostructured SiO 2 Coatings are used to improve the problem that the existing nano coatings are unstable and difficult to hydrophobic. 2 The problem of excessive use of hydrophobic coating solvent. Summary of the invention

[0012] The purpose of the present invention is to overcome the defects of the prior art and provide a nano-SiO 2 Preparation method of superhydrophobic polyurethane coated controlled-release fertilizer.

[0013] To achieve the above object, the present invention adopts the following technical solutions:

[0014] A nano-SiO 2 The method for preparing a super-hydrophobic polyurethane coated controlled-release fertilizer comprises the following steps:

[0015] S1 uses perfluorosilane to treat nano-SiO 2 Perform superhydrophobic modification;

[0016] S2 continuously and simultaneously drips polyol and isocyanate onto the surface of fertilizer particles to obtain polyurethane coated fertilizer;

[0017] S3 hydrophobically modified nano-SiO 2 The powder is coated on the surface of polyurethane coated fertilizer to obtain nano-SiO 2 Superhydrophobic polyurethane coated fertilizer.

[0018] Preferably, the step S1 specifically includes:

[0019] 1-5 parts of perfluorosilane are added to a mixed solution of 50-100 parts of anhydrous ethanol and 1-10 parts of water, and an acid is added dropwise to adjust the solution pH to 3-4, and hydrolyzed at 20-25°C for 1 hour to obtain a perfluorosilane hydrolyzate; 15-25 parts of nano-SiO 2Add to a mixed solution of 300-500 parts of ethanol and 10-100 parts of water, ultrasonically disperse for 30 minutes, add perfluorosilane hydrolyzate, stir at 50-60°C for 6-8 hours, evaporate, dry and grind the product to obtain hydrophobically modified nano-SiO 2 powder.

[0020] Preferably, the nano-SiO 2 It is a white powder with a particle size between 20 and 100 nm. The perfluorosilane is one of perfluorodecyltriethoxysilane, perfluorodecyltrimethoxysilane, and perfluorooctyltriethoxysilane. The acid is one of hydrochloric acid, sulfuric acid, acetic acid, and oxalic acid.

[0021] Preferably, the step S2 specifically includes:

[0022] In the fluidized bed coating equipment, 1000-2000 parts of fertilizer granules are put in and preheated at 75°C for 10-20 minutes, 5-10 parts of liquid wax are added to lubricate the surface to remove surface defects, and 30-60 parts of polyol and isocyanate are continuously and simultaneously added to the fertilizer surface, with a mass ratio of polyol to isocyanate of 1-2:1-3, to prepare polyurethane coated fertilizer.

[0023] Preferably, the polyol and the isocyanate are TMN-450 and MDI, respectively, and the mass ratio thereof is 1:1.12.

[0024] Preferably, in step S2, the polyol is one of polycaprolactone, polypropylene glycol, and polytetramethylene glycol;

[0025] Among them, the molecular weight of polycaprolactone is 200-1000, the hydroxyl value is 110-560, and it is a colorless transparent liquid at room temperature;

[0026] Polypropylene glycol, molecular weight is 200-2000, hydroxyl value is 50-500, and it is a colorless transparent liquid at room temperature;

[0027] Polytetramethylene glycol has a molecular weight of 250 to 1000 and a hydroxyl value of 106 to 498. It is a colorless transparent liquid at room temperature.

[0028] Preferably, in step S2, the isocyanate is one of benzene-2,4-diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and diphenylmethane diisocyanate.

[0029] Preferably, in step S2, the fertilizer particles are one or more of potassium chloride, potassium sulfate, ammonium sulfate, ammonium nitrate, monoammonium phosphate, diammonium phosphate, urea, and compound nitrogen, phosphorus and potassium fertilizers.

[0030] Preferably, the step S3 specifically includes:

[0031] 1000-2000 parts of polyurethane coated fertilizer are put into the coating pot, and polyol and isocyanate are added to the surface again to react evenly. The temperature is controlled at 30-60°C to prevent too fast curing. Then 5-30 parts of hydrophobically modified nano-SiO 2 The powder is evenly coated on the surface of the above fertilizer to prepare a nano-SiO 2 Superhydrophobic polyurethane coated controlled-release fertilizer.

[0032] Preferably, in step S3, 10 to 20 parts of polyol and isocyanate are again added to the surface of the polyurethane coated fertilizer, the polyol and isocyanate are polycaprolactone (PCL) and diphenylmethane diisocyanate (MDI), respectively, the ratio of the two is 1.46:1, the reaction is uniform, and it is used as a binder.

[0033] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0034] In the present invention, the hydrophobic nano-SiO 2 Directly adhere to the surface of polyurethane coated urea to form a stable, uniform and hydrophobic micro-nano-scale nano-SiO 2 Coating, improve the existing nano coating instability leading to its hydrophobic effect is difficult to play the problem, solve the preparation of nano-SiO 2 The problem of excessive use of hydrophobic coating solvent. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a flow chart of the present invention;

[0036] Figure 2 is a microscopic photograph of a polyurethane coated fertilizer in an embodiment of the present invention;

[0037] Figure 3 This is a photograph of the water contact angle of the polyurethane coated fertilizer in an embodiment of the present invention;

[0038] Figure 4 It is the hydrophobic SiO in the embodiment of the present invention. 2 Microscopic photograph of a cross section of a polyurethane coated controlled-release fertilizer;

[0039] Figure 5 It is the hydrophobic SiO in the embodiment of the present invention. 2 Microscopic photos of the surface of polyurethane coated controlled-release fertilizer;

[0040] Figure 6 It is the hydrophobic SiO in the embodiment of the present invention. 2 Photo of water contact angle of polyurethane coated controlled-release fertilizer;

[0041] Figure 7 Schematic diagram of the structure of the fluidized bed used for preparing the polyurethane coated fertilizer in the embodiment of the present invention;

[0042] Figure 8 It is the hydrophobic SiO in the embodiment of the present invention. 2 Schematic diagram of the coating pan structure used for polyurethane coated controlled-release fertilizers. DETAILED DESCRIPTION

[0043] The specific embodiments of the present invention are described in detail below.

[0044] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10 to 50 is listed for a specific parameter, it is understood that the range of 10 to 40 and 20 to 50 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the range of values ​​"a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the range of values ​​"0 to 5" means that all real numbers between "0 to 5" have been fully listed in this article, and "0 to 5" is only an abbreviation of these numerical combinations.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0047] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0048] If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0049] Unless otherwise specified, the reaction is carried out at room temperature and pressure.

[0050] Unless otherwise specified, all parts or percentages are by weight.

[0051] In the present invention, all substances used are known substances and can be purchased or synthesized by known methods.

[0052] In the present invention, the devices or equipment used are all conventional devices or equipment known in the art and are commercially available.

[0053] The following is a further description of a nano-SiO 2 A specific embodiment of the method for preparing a super-hydrophobic polyurethane coated controlled-release fertilizer. 2 The preparation method of superhydrophobic polyurethane coated controlled-release fertilizer is not limited to the description in the following examples.

[0054] Embodiment 1:

[0055] A nano-SiO 2 Preparation method of super hydrophobic polyurethane coated controlled release fertilizer, such as Figure 1 As shown, the following steps are included:

[0056] S1 uses perfluorosilane to treat nano-SiO 2 Perform superhydrophobic modification;

[0057] S2 continuously and simultaneously drips polyol and isocyanate onto the surface of fertilizer particles to obtain polyurethane coated fertilizer (such as Figure 2-3 shown);

[0058] S3 hydrophobically modified nano-SiO 2 The powder is coated on the surface of polyurethane coated fertilizer to obtain nano-SiO 2 Super hydrophobic polyurethane coated fertilizer (such as Figure 4-6 shown).

[0059] Furthermore, step S1 specifically includes:

[0060] 1 part of perfluorosilane was added to a mixed solution of 50 parts of anhydrous ethanol and 1 part of water, and acid was added dropwise to adjust the solution pH to 3. The solution was hydrolyzed at 20°C for 1 hour to obtain a perfluorosilane hydrolyzate. 15 parts of nano-SiO 2The mixture was added to a mixed solution of 300 parts of ethanol and 10 parts of water and ultrasonically dispersed for 30 minutes. The perfluorosilane hydrolyzate was added and stirred at 50°C for 6 hours. The product was evaporated, dried and ground to obtain hydrophobically modified nano-SiO 2 powder.

[0061] Furthermore, nano-SiO 2 It is a white powder with a particle size of 20 nm. The perfluorosilane is perfluorodecyltriethoxysilane and the acid is hydrochloric acid.

[0062] Furthermore, step S2 specifically includes:

[0063] In the fluidized bed coating equipment, 1000 parts of fertilizer granules were put in and preheated at 75°C for 10 minutes, 5 parts of liquid wax were added to lubricate the surface to remove surface defects, and 30 parts of polyol and isocyanate were continuously and simultaneously added to the fertilizer surface. The mass ratio of polyol to isocyanate was 1:2 to prepare polyurethane coated fertilizer.

[0064] Further, such as Figure 7 As shown, the fluidized bed coating equipment includes a Roots blower 1; a gas buffer tank 2; a heater 3; an air compressor 4; and a fluidized bed 5.

[0065] Further, in step S2, the polyol is one of polycaprolactone, polypropylene glycol, and polytetramethylene glycol;

[0066] Among them, the molecular weight of polycaprolactone is 200-1000, the hydroxyl value is 110-560, and it is a colorless transparent liquid at room temperature;

[0067] Polypropylene glycol, molecular weight is 200-2000, hydroxyl value is 50-500, and it is a colorless transparent liquid at room temperature;

[0068] Polytetramethylene glycol has a molecular weight of 250 to 1000 and a hydroxyl value of 106 to 498. It is a colorless transparent liquid at room temperature.

[0069] Furthermore, in step S2, the isocyanate is one of benzene-2,4-diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and diphenylmethane diisocyanate.

[0070] Furthermore, in step S2, the fertilizer particles are one of potassium chloride, potassium sulfate, ammonium sulfate, ammonium nitrate, monoammonium phosphate, diammonium phosphate, urea, and compound nitrogen-phosphorus-potassium fertilizer.

[0071] Furthermore, step S3 specifically includes:

[0072] 1000 parts of polyurethane coated fertilizer were put into the coating pot, and polyol and isocyanate were added to the surface again to react evenly. The temperature was controlled at 30°C to prevent too fast curing. Then 5 parts of hydrophobically modified nano-SiO 2 The powder is evenly coated on the surface of the above fertilizer to prepare a nano-SiO 2 Superhydrophobic polyurethane coated controlled-release fertilizer.

[0073] Further, such as Figure 8 As shown, the coating pan includes a rotating drum 6 , an electric heating blower 7 , and a spraying device 8 .

[0074] Furthermore, in step S3, 10 parts of polyol and isocyanate are again dripped onto the surface of the polyurethane coated fertilizer, with a ratio of 1.46:1, and the reaction is uniform, and the polyurethane coated fertilizer is used as a binder.

[0075] Embodiment 2:

[0076] A nano-SiO 2 Preparation method of super hydrophobic polyurethane coated controlled release fertilizer, such as Figure 1 As shown, the following steps are included:

[0077] S1 uses perfluorosilane to treat nano-SiO 2 Perform superhydrophobic modification;

[0078] S2 continuously and simultaneously drips polyol and isocyanate onto the surface of fertilizer particles to obtain polyurethane coated fertilizer;

[0079] S3 hydrophobically modified nano-SiO 2 The powder is coated on the surface of polyurethane coated fertilizer to obtain nano-SiO 2 Superhydrophobic polyurethane coated fertilizer.

[0080] Furthermore, step S1 specifically includes:

[0081] 3 parts of perfluorosilane were added to a mixed solution of 75 parts of anhydrous ethanol and 5 parts of water, and acid was added dropwise to adjust the solution pH to 3.5. The solution was hydrolyzed at 22°C for 1 hour to obtain a perfluorosilane hydrolyzate. 20 parts of nano-SiO 2 The mixture was added to a mixed solution of 400 parts of ethanol and 55 parts of water and ultrasonically dispersed for 30 minutes. The perfluorosilane hydrolyzate was added and stirred at 55°C for 7 hours. The product was evaporated, dried and ground to obtain hydrophobically modified nano-SiO 2 powder.

[0082] Furthermore, nano-SiO 2 It is a white powder with a particle size between 20 and 100 nm. The perfluorosilane is one of perfluorodecyltriethoxysilane, perfluorodecyltrimethoxysilane, and perfluorooctyltriethoxysilane. The acid is one of hydrochloric acid, sulfuric acid, acetic acid, and oxalic acid.

[0083] Furthermore, step S2 specifically includes:

[0084] In the fluidized bed coating equipment, 1500 parts of fertilizer granules were put in and preheated at 75°C for 15 minutes, 8 parts of liquid wax were added to lubricate the surface to remove surface defects, and 50 parts of polyol and isocyanate were continuously and simultaneously added to the fertilizer surface. The mass ratio of polyol to isocyanate was 1:1.12 to prepare polyurethane coated fertilizer.

[0085] Further, in step S2, the polyol is one of polycaprolactone, polypropylene glycol, and polytetramethylene glycol;

[0086] Among them, the molecular weight of polycaprolactone is 200-1000, the hydroxyl value is 110-560, and it is a colorless transparent liquid at room temperature;

[0087] Polypropylene glycol, molecular weight is 200-2000, hydroxyl value is 50-500, and it is a colorless transparent liquid at room temperature;

[0088] Polytetramethylene glycol has a molecular weight of 250 to 1000 and a hydroxyl value of 106 to 498. It is a colorless transparent liquid at room temperature.

[0089] Furthermore, in step S2, the isocyanate is one of benzene-2,4-diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and diphenylmethane diisocyanate.

[0090] Furthermore, in step S2, the fertilizer particles are potassium chloride, potassium sulfate, ammonium sulfate, ammonium nitrate, monoammonium phosphate, diammonium phosphate, urea, and compound nitrogen-phosphorus-potassium fertilizer.

[0091] Furthermore, step S3 specifically includes:

[0092] 1500 parts of polyurethane coated fertilizer were put into the coating pot, and polyol and isocyanate were added to the surface again to react evenly. The temperature was controlled at 45°C to prevent too fast curing. Then 18 parts of hydrophobically modified nano-SiO 2 The powder is evenly coated on the surface of the above fertilizer to prepare a nano-SiO 2 Superhydrophobic polyurethane coated controlled-release fertilizer.

[0093] Furthermore, in step S3, 15 parts of polyol and isocyanate are again dripped onto the surface of the polyurethane coated fertilizer, with a ratio of 1.46:1, and the reaction is uniform, and the polyurethane coated fertilizer is used as a binder.

[0094] Embodiment 3:

[0095] A nano-SiO 2 Preparation method of super hydrophobic polyurethane coated controlled release fertilizer, such as Figure 1 As shown, the following steps are included:

[0096] S1 uses perfluorosilane to treat nano-SiO 2 Perform superhydrophobic modification;

[0097] S2 continuously and simultaneously drips polyol and isocyanate onto the surface of fertilizer particles to obtain polyurethane coated fertilizer;

[0098] S3 hydrophobically modified nano-SiO 2 The powder is coated on the surface of polyurethane coated fertilizer to obtain nano-SiO 2 Superhydrophobic polyurethane coated fertilizer.

[0099] Furthermore, step S1 specifically includes:

[0100] 5 parts of perfluorosilane were added to a mixed solution of 100 parts of anhydrous ethanol and 10 parts of water, and acid was added dropwise to adjust the solution pH to 4. The solution was hydrolyzed at 25°C for 1 hour to obtain a perfluorosilane hydrolyzate. 25 parts of nano-SiO 2 Add it to a mixed solution of 500 parts of ethanol and 100 parts of water and disperse it ultrasonically for 30 minutes. Add perfluorosilane hydrolyzate and stir at 60°C for 8 hours. The product is evaporated, dried and ground to obtain hydrophobically modified nano-SiO 2 powder.

[0101] Furthermore, nano-SiO 2 It is a white powder with a particle size between 20 and 100 nm. The perfluorosilane is one of perfluorodecyltriethoxysilane, perfluorodecyltrimethoxysilane, and perfluorooctyltriethoxysilane. The acid is one of hydrochloric acid, sulfuric acid, acetic acid, and oxalic acid.

[0102] Furthermore, step S2 specifically includes:

[0103] In the fluidized bed coating equipment, 2000 parts of fertilizer granules were put in and preheated at 75°C for 20 minutes, 10 parts of liquid wax were added to lubricate the surface to remove surface defects, and 60 parts of polyol and isocyanate were continuously and simultaneously added to the fertilizer surface. The mass ratio of polyol to isocyanate was 2:2 to prepare polyurethane coated fertilizer.

[0104] Further, in step S2, the polyol is one of polycaprolactone, polypropylene glycol, and polytetramethylene glycol;

[0105] Among them, the molecular weight of polycaprolactone is 200-1000, the hydroxyl value is 110-560, and it is a colorless transparent liquid at room temperature;

[0106] Polypropylene glycol, molecular weight is 200-2000, hydroxyl value is 50-500, and it is a colorless transparent liquid at room temperature;

[0107] Polytetramethylene glycol has a molecular weight of 250 to 1000 and a hydroxyl value of 106 to 498. It is a colorless transparent liquid at room temperature.

[0108] Furthermore, in step S2, the isocyanate is one of benzene-2,4-diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and diphenylmethane diisocyanate.

[0109] Furthermore, in step S2, the fertilizer particles are potassium chloride, potassium sulfate, ammonium sulfate, ammonium nitrate, and monoammonium phosphate.

[0110] Furthermore, step S3 specifically includes:

[0111] 2000 parts of polyurethane coated fertilizer were put into the coating pot, and polyol and isocyanate were added to the surface again to react evenly. The temperature was controlled at 60°C to prevent too fast curing. Then 30 parts of hydrophobically modified nano-SiO 2 The powder is evenly coated on the surface of the above fertilizer to prepare a nano-SiO 2 Superhydrophobic polyurethane coated controlled-release fertilizer.

[0112] Furthermore, in step S3, 20 parts of polyol and isocyanate are again dripped onto the surface of the polyurethane coated fertilizer, with a ratio of 1.46:1, and the reaction is uniform, and the polyurethane coated fertilizer is used as a binder.

[0113] Embodiment 4:

[0114] A nano-SiO 2 Preparation method for constructing a hydrophobic coating on the surface of polyurethane coated fertilizer. The method first preheats the fertilizer particles in a fluidized state in a fluidized bed for 10 minutes; adds liquid wax to pretreat the surface of the granular fertilizer; continuously and simultaneously drips polyol and isocyanate to prepare a polyurethane coated fertilizer with a stable film layer, wherein the mass ratio of polyol to isocyanate is 0.6:1. On the basis of this fertilizer, continuously and simultaneously drips polyol and its cyanate to its surface in a coating pan to react to form a new layer of polyurethane semi-cured film layer. When the film layer is not completely cured, a layer of nano-silicon dioxide powder modified by perfluorosilane is coated on the surface to obtain a uniform and stable hydrophobic nano-SiO 2 Polyurethane coated fertilizers.

[0115] Furthermore, the polyol is polypropylene glycol, polycaprolactone, and polytetramethylene glycol. The molecular weight of polypropylene glycol is 180-220, and the hydroxyl value is 400-500; the molecular weight of polycaprolactone is 400-600, and the hydroxyl value is 190-280; the molecular weight of polytetramethylene glycol is 225-275, and the hydroxyl value is 400-498.

[0116] Further, the isocyanate is toluene-2,4-diisocyanate (TDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI) and diphenylmethane diisocyanate (MDI). Preferably, diphenylmethane diisocyanate (MDI) has a grade of PM200, a viscosity of 150 to 250, and is a brown liquid at room temperature.

[0117] Furthermore, the fluorosilane is perfluorodecyltriethoxysilane, perfluorodecyltrimethoxysilane, or perfluorooctyltriethoxysilane. Preferably, perfluorodecyltrimethoxysilane has a molecular weight of 568.3 and is a colorless transparent liquid at room temperature.

[0118] Furthermore, nano-SiO 2 , is a white powder with a particle size between 20 and 100 nm.

[0119] Furthermore, surface hydrophobic coated fertilizer, nano-SiO 2 The dosage ratio with fertilizer is 0.001:1.

[0120] Furthermore, the fertilizer particles can be any granular fertilizer, such as potassium chloride (KCl), potassium sulfate (K 2 SO 4 )、Ammonium sulfate ((NH4) 2 SO 4 ), ammonium nitrate (NH 4 NO 3 ), monoammonium phosphate (NH 4 H 2 PO 4 ), diammonium phosphate ((NH 4 ) 2 HPO 4 ), urea, compound nitrogen, phosphorus and potassium fertilizers or their mixtures.

[0121] Furthermore, the fluidized bed and its supporting equipment include a Roots blower 1, a gas buffer tank 2, an electric heater 3, and an air compressor 4.

[0122] Furthermore, the coating pot is composed of a rotating drum 6, an electric heater 7, and a spraying device 8.

[0123] Further, the hydrophobic modification method is as follows: 1 g of perfluorodecyltrimethoxysilane is added to a mixed solution of 100 mL of ethanol and water in a volume ratio of 9:1, acetic acid is added dropwise to adjust the solution pH to 3, and hydrolyzed at room temperature for 1 h to obtain a hydrolyzate; 15 g of nano-SiO 2 The mixture was added into a mixed solution of 500 mL ethanol and water with a volume ratio of 9:1 and ultrasonically dispersed for 30 min. The hydrolyzed solution of perfluorodecyltrimethoxysilane was added and stirred at 50 °C for 6 h. The product was evaporated and dried to obtain hydrophobic nano-SiO 2Granules, grind and set aside.

[0124] Further, in the production method, the amount of nano-SiO required for every 100 parts of fertilizer particles is 2 The dosage of is 0.1 parts, and the dosage of the required polyurethane is 4 parts. The coating temperature is 50°C, preferably 75°C.

[0125] Further, the production method is: polyol and isocyanate are added to the surface of the polyurethane coated fertilizer, the reaction is uniform, and the polyol and isocyanate are used as a binder to form a hydrophobic nano-SiO 2 The powder is coated on the surface of fertilizer particles to obtain a layer of hydrophobic nano-SiO 2 Coated polyurethane coated controlled release fertilizer.

[0126] Embodiment 5:

[0127] A nano-SiO 2 Preparation method for constructing a hydrophobic coating on the surface of polyurethane coated fertilizer. The method first preheats the fertilizer particles in a fluidized state in a fluidized bed for 15 minutes; liquid wax is added to pretreat the surface of the granular fertilizer; polyol and isocyanate are continuously and simultaneously added to prepare a polyurethane coated fertilizer with a stable film layer, wherein the mass ratio of polyol to isocyanate is 1:1.12. Based on this fertilizer, polyol and its cyanate are continuously and simultaneously added to its surface in a coating pan to react to form a new layer of polyurethane semi-cured film layer. When the film layer is not completely cured, a layer of nano-SiO modified by perfluorosilane is coated on the surface. 2 The powder has a uniform and stable hydrophobic nano-SiO 2 Polyurethane coated fertilizers.

[0128] Furthermore, the polyol is polypropylene glycol, polycaprolactone, or polytetramethylene glycol. Preferably, the molecular weight of polypropylene glycol is 180-220, and the hydroxyl value is 400-500; the molecular weight of polycaprolactone is 400-600, and the hydroxyl value is 190-280; and the molecular weight of polytetramethylene glycol is 225-275, and the hydroxyl value is 400-498.

[0129] Furthermore, the isocyanate is toluene-2,4-diisocyanate (TDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI) and diphenylmethane diisocyanate (MDI), diphenylmethane diisocyanate (MDI), the brand is PM200, the viscosity is 150-250, and it is a brown liquid at room temperature.

[0130] Furthermore, the fluorosilane is perfluorodecyltriethoxysilane, perfluorodecyltrimethoxysilane, or perfluorooctyltriethoxysilane. Preferably, perfluorodecyltrimethoxysilane has a molecular weight of 568.3 and is a colorless transparent liquid at room temperature.

[0131] Furthermore, nano-SiO 2 , is a white powder with a particle size of 20 to 100 nm.

[0132] Furthermore, surface hydrophobic coated fertilizer, nano-SiO 2 The dosage ratio with fertilizer is 0.004:1.

[0133] Furthermore, the fertilizer granules, with urea as the fertilizer core, have a particle size between 0.5 and 10 mm, preferably between 2 and 4 mm.

[0134] Furthermore, the fluidized bed and its supporting equipment include a Roots blower 1, a gas buffer tank 2, an electric heater 3, and an air compressor 4.

[0135] Furthermore, the coating pot is composed of a rotating drum 6, an electric heater 7, and a spraying device 8.

[0136] Further, the hydrophobic modification method is as follows: 3 g of perfluorodecyltrimethoxysilane is added to a mixed solution of 100 mL of ethanol and water in a volume ratio of 9:1, acetic acid is added dropwise to adjust the solution pH to 3.5, and hydrolyzed at room temperature for 1 h to obtain a hydrolyzate; 15 g of nano-SiO 2 The mixture was added into a mixed solution of 500 mL ethanol and water with a volume ratio of 9:1 and ultrasonically dispersed for 30 min. The hydrolyzed solution of perfluorodecyltrimethoxysilane was added and stirred at 50 °C for 6 h. The product was evaporated and dried to obtain hydrophobic nano-SiO 2 Granules, grind and set aside.

[0137] Further, in the production method, the amount of nano-SiO required for every 100 parts of fertilizer particles is 2 The dosage of is 0.5 parts, and the dosage of the required polyurethane is 4 parts. The coating temperature is 60°C, preferably 75°C.

[0138] Further, the production method is: polyol and isocyanate are added to the surface of the polyurethane coated fertilizer, the reaction is uniform, and the polyol and isocyanate are used as a binder to form a hydrophobic nano-SiO 2 The powder is coated on the surface of fertilizer particles to obtain a layer of hydrophobic nano-SiO 2 Coated polyurethane coated controlled release fertilizer.

[0139] Embodiment 6:

[0140] A nano-SiO 2Preparation method for constructing a hydrophobic coating on the surface of polyurethane coated fertilizer. The method first preheats the fertilizer particles in a fluidized state in a fluidized bed for 20 minutes; adds liquid wax to pretreat the surface of the granular fertilizer; continuously and simultaneously drips polyol and isocyanate to prepare a polyurethane coated fertilizer with a stable film layer, wherein the mass ratio of polyol to isocyanate is 1. On the basis of this fertilizer, continuously and simultaneously drips polyol and its cyanate to its surface in a coating pan to react to form a new layer of polyurethane semi-cured film layer. When the film layer is not completely cured, a layer of nano-silicon dioxide powder modified by perfluorosilane is coated on the surface to obtain a uniform and stable hydrophobic nano-SiO 2 Polyurethane coated fertilizers.

[0141] Further, the polyol is polypropylene glycol, polycaprolactone, polytetramethylene glycol. Further, the isocyanate is toluene-2,4-diisocyanate (TDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI) and diphenylmethane diisocyanate (MDI).

[0142] Furthermore, the fluorosilane is perfluorodecyltriethoxysilane, perfluorodecyltrimethoxysilane, or perfluorooctyltriethoxysilane. Preferably, perfluorodecyltrimethoxysilane has a molecular weight of 568.3 and is a colorless transparent liquid at room temperature.

[0143] Furthermore, nano-SiO 2 , a white powder.

[0144] Furthermore, surface hydrophobic coated fertilizer, nano-SiO 2 The dosage ratio with fertilizer is 0.01:1.

[0145] Furthermore, the fertilizer particles can be any granular fertilizer, such as potassium chloride (KCl), potassium sulfate (K 2 SO 4 )、Ammonium sulfate ((NH4) 2 SO 4 ), ammonium nitrate (NH 4 NO 3 ), monoammonium phosphate (NH 4 H 2 PO 4 ), diammonium phosphate ((NH 4 ) 2 HPO 4 ), urea, compound nitrogen, phosphorus and potassium fertilizers.

[0146] Furthermore, the fluidized bed and its supporting equipment include a Roots blower 1, a gas buffer tank 2, an electric heater 3, and an air compressor 4.

[0147] Furthermore, the coating pot is composed of a rotating drum 6, an electric heater 7, and a spraying device 8.

[0148] Further, the hydrophobic modification method is as follows: 5 g of perfluorodecyltrimethoxysilane is added to a mixed solution of 100 mL of ethanol and water in a volume ratio of 9:1, acetic acid is added dropwise to adjust the solution pH to 4, and hydrolyze at room temperature for 1 h to obtain a hydrolyzate; 15 g of nano-SiO 2 The mixture was added into a mixed solution of 500 mL ethanol and water with a volume ratio of 9:1 and ultrasonically dispersed for 30 min. The hydrolyzed solution of perfluorodecyltrimethoxysilane was added and stirred at 50 °C for 6 h. The product was evaporated and dried to obtain hydrophobic nano-SiO 2 Granules, grind and set aside.

[0149] Further, in the production method, the amount of nano-SiO required for every 100 parts of fertilizer particles is 2 The dosage of is 1 part, and the dosage of the required polyurethane is 4 parts. The coating temperature is 80°C, preferably 75°C.

[0150] Further, the production method is: polyol and isocyanate are added to the surface of the polyurethane coated fertilizer, the reaction is uniform, and the polyol and isocyanate are used as a binder to form a hydrophobic nano-SiO 2 The powder is coated on the surface of fertilizer particles to obtain a layer of hydrophobic nano-SiO 2 Coated polyurethane coated controlled release fertilizer.

[0151] Embodiment 7:

[0152] Preparation of polyurethane coated controlled-release fertilizer, including:

[0153] In order to verify the feasibility of this process, this experiment adopted two different surface coating processes to prepare two types of fluorosilane-modified nano-silica:

[0154] (1) Adjust the parameters, start the fluidized bed, add 1 kg of large-particle urea into the fluidized bed, preheat the fluidization for 10 minutes, and add 5 g of liquid paraffin to pretreat the urea surface for 2 minutes.

[0155] (2) According to the molar ratio of polyol to isocyanate of 1:1.12, 9.43g of polypropylene glycol and 10.57g of isocyanate were weighed and simultaneously dripped into the fluidized bed. After 10 minutes of in-situ reaction, the coated fertilizer was taken out. This fertilizer was used as the modified basic fertilizer, and this ratio was used in all the following treatments.

[0156] The obtained coated fertilizers are processed as follows:

[0157] Treatment 1: 4 g hydrophobic nano-SiO 2(20nm) was added to 11.87g polycaprolactone and stirred to mix evenly; the coating pot was turned on, the parameters were adjusted, the temperature was maintained at 60°C, the prepared polyurethane coated fertilizer was added, and the hydrophobic nano-SiO 2 of polycaprolactone and 8.13g of isocyanate, wait for the reaction to be complete, take out the fertilizer and complete the experiment.

[0158] Treatment 2: Turn on the coating pan, adjust the parameters, maintain the temperature at 60°C, add the prepared polyurethane coated fertilizer, weigh 11.87g polycaprolactone and 8.13g isocyanate according to the molar ratio of polyol to isocyanate of 1.46:1, add them to the surface of the coated urea, and react for 3 minutes; when the surface of the coated urea is in a viscous state, add 4g hydrophobic nano-SiO 2 (20nm), apply evenly, wait until the surface is dry, take out the fertilizer and complete the experiment.

[0159] The specific dosage ratio is shown in Table 1:

[0160] Table 1 Nano-SiO under different preparation processes 2 Effects on the controlled release properties of polyurethane coated controlled release fertilizers

[0161]

[0162] Experimental data show that surface coating can significantly increase the release period of fertilizer.

[0163] Embodiment 8:

[0164] Different nano-SiO 2 The preparation of a hydrophobic polyurethane coated fertilizer comprises:

[0165] To verify the effect of this method on different nano-SiO 2 The applicability of nano-SiO prepared with different particle sizes and different conditions 2 Preparation of different nano-SiO 2 The polyurethane coated fertilizer with a thickness of 1000 g is prepared by the same method as that of treatment 2 of Example 7. The specific dosage and proportion are shown in Table 2:

[0166] Table 2 Nano-SiO with different particle sizes 2 Effects on the controlled release properties of polyurethane coated controlled release fertilizers

[0167]

[0168] Experimental data show that adding nano-SiO 2 It can significantly increase the release period of fertilizer, and the particle size of 20nm has the best effect.

[0169] Embodiment 9:

[0170] Effects of different polyurethane film materials on the release performance of coated fertilizers:

[0171] In order to verify whether this method is applicable to different types of polyurethane membrane materials, polypropylene glycol and polytetramethylene glycol were used to replace the polycaprolactone in Example 7, and the preparation method was the same as that in Example 7. The amounts of each polyol and isocyanate were calculated according to the hydroxyl value, as shown in Table 3:

[0172]

[0173] Experimental data show that this method is applicable to different types of polyurethane-coated fertilizers.

[0174] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for preparing nano-SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer, characterized in that: The following steps are involved: S1 used perfluorosilane to modify nano-SiO2 powder into super-hydrophobic form; S2 continuously and simultaneously drips polyol and isocyanate onto the surface of fertilizer particles to obtain polyurethane coated fertilizer; S3: coating the hydrophobically modified nano-SiO2 powder on the surface of the polyurethane coated fertilizer to obtain a super-hydrophobic polyurethane coated fertilizer with nano-SiO2.

2. A method for preparing a nano-SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer as claimed in claim 1, characterized in that: The step S1 specifically includes: Add 1 to 5 parts of perfluorosilane to a mixed solution of 50 to 100 parts of anhydrous ethanol and 1 to 10 parts of water, add acid dropwise to adjust the solution pH to 3 to 4, hydrolyze at 20 to 25°C for 1 hour to obtain a perfluorosilane hydrolyzate; add 15 to 25 parts of nano-SiO2 to a mixed solution of 300 to 500 parts of ethanol and 10 to 100 parts of water, ultrasonically disperse for 30 minutes, add the perfluorosilane hydrolyzate, stir at 50 to 60°C for 6 to 8 hours, evaporate, dry and grind the product to obtain a hydrophobically modified nano-SiO2 powder.

3. A method for preparing a nano-SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer according to any one of claims 1 to 2, characterized in that: The nano-SiO2 is white powder with a particle size between 20 and 100 nm. The perfluorosilane is one of perfluorodecyltriethoxysilane, perfluorodecyltrimethoxysilane and perfluorooctyltriethoxysilane. The acid is one of hydrochloric acid, sulfuric acid, acetic acid and oxalic acid.

4. A method for preparing a nano-SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer as claimed in claim 1, characterized in that: The step S2 specifically includes: In the fluidized bed coating equipment, 1000-2000 parts of fertilizer granules are put in and preheated at 75°C for 10-20 minutes, 5-10 parts of liquid wax are added to lubricate the surface to remove surface defects, and 30-60 parts of polyol and isocyanate are continuously and simultaneously added to the fertilizer surface, with a mass ratio of polyol to isocyanate of 1-2:1-3, to prepare polyurethane coated fertilizer.

5. A method for preparing a nano-SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer as claimed in claim 4, characterized in that: In the step S2, the polyol is one of polycaprolactone, polypropylene glycol, and polytetramethylene glycol; Among them, the molecular weight of polycaprolactone is 200-1000, the hydroxyl value is 110-560, and it is a colorless transparent liquid at room temperature; Polypropylene glycol, molecular weight is 200-2000, hydroxyl value is 50-500, and it is a colorless transparent liquid at room temperature; Polytetramethylene glycol has a molecular weight of 250 to 1000 and a hydroxyl value of 106 to 498. It is a colorless transparent liquid at room temperature.

6. A method for preparing a nano-SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer as claimed in claim 4, characterized in that: In the step S2, the isocyanate is one of benzene-2,4-diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and diphenylmethane diisocyanate.

7. A method for preparing a nano-SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer as claimed in claim 4, characterized in that: In step S2, the fertilizer particles are one or more of potassium chloride, potassium sulfate, ammonium sulfate, ammonium nitrate, monoammonium phosphate, diammonium phosphate, urea, and compound nitrogen-phosphorus-potassium fertilizer.

8. The method for preparing a nano-SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer according to claim 1, characterized in that: The step S3 specifically includes: 1000 to 2000 parts of polyurethane coated fertilizer are put into a coating pan, and polyol and isocyanate are added to the surface again to react evenly. The temperature is controlled at 30 to 60°C to prevent excessive solidification, and then 5 to 30 parts of hydrophobically modified nano-SiO2 powder are evenly coated on the surface of the above fertilizer to prepare a nano-SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer.

9. A method for preparing a nano-SiO2 super-hydrophobic polyurethane coated controlled-release fertilizer as claimed in claim 8, characterized in that: In the step S3, 10 to 20 parts of polyol and 1 part of isocyanate are again dripped onto the surface of the polyurethane coated fertilizer, with the ratio of the two being 1.46:1, and the reaction is uniform, and the polyurethane coated fertilizer is used as a binder.

Images