A kind of vegetable oil-coated controlled-release fertilizer capable of regulating nutrient release rate and preparation method thereof

Abstract

The invention discloses a nutrient release rate adjustable plant oil coated controlled-release fertilizer and a preparation method thereof. The preparation method comprises the following step: base on total weight of a coating frame substances, firstly co-mixing and polymerizing 1-10 percent of a pore-foaming agent, 1-18 percent of a film forming aid paraffin, 0.01-0.6 percent of an organic metal catalyst and plant oil polyol to prepare a coating material A; uniformly and simultaneously spraying the coating material A and polyisocyanate on the surface of a core fertilizer in a rotational flow-spraying fluidized bed on the bottom side; performing an in-situ polymerization reaction to generate a uniform high-molecular coating layer on the surface of the core fertilizer, wherein the coating frame substances are the plant oil polyol and the polyisocyanate of which the weight ratio is 1:(0.5-1.5). The preparation method disclosed by the invention has innovation in coating material selection, coated fertilizer nutrient release performance regulation, coating material co-mixing and polymerization process and coating process; the prepared controlled-release fertilizer is stable in quality, complete in coating, controllable in nutrient release rate, low in energy consumption in the coating process and simple and easy to operate in process.

Description

technical field [0001] The invention belongs to the technical field of fertilizer and its manufacture. More specifically, it relates to a vegetable oil-coated controlled-release fertilizer capable of regulating the release rate of nutrients and a preparation method thereof. Background technique [0002] Controlled-release fertilizers are coated fertilizers that use polymer coatings, which can quantitatively control the amount and release period of nutrients released in the fertilizer, so that the supply of nutrients matches the law of fertilizer requirements in each main nutrient stage of the crop growth period, including coated urea and coated compound fertilizers. fertilizer, coated potassium fertilizer, coated ammonium phosphate, etc. After the granular water-soluble fertilizer is coated, it can reduce nutrient loss and significantly improve the utilization rate of fertilizer. Controlled-release fertilizers are the fundamental way to solve the problem of large amount of...

AI Technical Summary

Problems solved by technology

However, the biggest disadvantages of this technology and process are: first, the production process is not environmentally friendly, which is reflected in the fact that the solvents used are all volatile substances (VOC). Fertilizer release companies cannot completely recycle the volatile substances produced during the coating process, especially some companies even use odorless chloroform. Although it is odorless, it is already a VOC that is harmful to human health in the international sea area. For toluene, For solvents with strong odors such as turpentine, they are more harmful to humans; second, to achieve more than 90% recovery of VOC substances, it is necessary to first use activated carbon to absorb high-pressure air with low solvent concentration in the coating process (coating process The concentration of the solvent in the high-pressure air is less than 0.1% (volume ratio), such a low-concentration solvent cannot be recovered by a tube condenser under high-speed flow), and then the solvent adsorbed in the activated carbon is evaporated into a supersaturated solvent vapor, Recycling with tube and tube condenser

In this way, the cost of coated fertilizer will be very high

Third, companies that use fat-soluble coating materials to manufacture coated controlled-release fertilizers, except for a few large-scale enterprises, mostly borrow medical fluidized beds. Due to the mismatch between equipment and materials (core fertilizers and solvents), the coating efficiency Low, high equipment energy consumption

[0005] However, the above-mentioned patents still have certain problems in the screening of coating materials, coating technology, and nutrient release regulation of coated fertilizers.

Although the disclosed patent of CN101323545A lists dozens of kinds, most of them are isocyanate monomers, which are volatile substances. During the manufacture of coated fertilizers, volatilization of isocyanates is easy to occur and endangers human health. Moreover, the cyanate radical of each isocyanate- The number of NCO moles varies, and many are useless in the manufacture of coated fertilizers. For example, MDI and TDI have been eliminated in the manufacture of coated fertilizers; the fourteen polyether polyols listed are actually used to manufacture For foamed polyurethane, if polyurethane foaming occurs during the production of coated fertilizers, it means that the coating fails; in addition, in the stated method of preparing coated fertilizers, the process of mixing film-forming aids with isocyanate It is unscientific, because the film-forming aids described in this patent are paraffin-based substances, which generally require a temperature above 80 degrees to melt, and the isocyanates such as TDI and HDI in this patent are volatile substances (VOC). can volatilize substances harmful to humans, and this patent also needs to heat and blend it with paraffin wax, and it is inevitable that a large amount of isocyanate will volatilize during heating; First, preheat isocyanate and paraffin at 50-100°C to obtain a, mix polyols, degradable functional monomers, chain extenders and catalysts, and then preheat at 65-95°C to obtain b, a and b are mixed and sprayed to prepare the package Film fertilizer, this coating process is relatively complicated, the composition of the coating liquid is too many and too complex, and both a and b need to be heated to a molten state, a and b need to be mixed before coating, and isocyanate and poly Alcohol starts to react immediately, so the mixing time and coating material spraying time need to be strictly controlled within a relatively short period of time. It is difficult to control the mixing degree of the coating liquid and the uniformity of the film layer, and it is difficult to meet the requirements of industrial mass production (mass production The amount of a and b in this patent application is relatively large); most of the catalysts in this patent application are tertiary amine catalysts, and tertiary amine catalysts are particularly effective in promoting the reaction between isocyanate and water, so gas will be generated during film formation, which will affect the coating. In addition, the compatibility of the degradable functional monomer of the patent application and the polyurethane coating layer generated by the reaction of isocyanate and polyol needs to be studied, that is to say, the degradable functional monomer of the patent will Changing the physical and chemical properties of the film layer can accelerate the degradation of the coating material, but it will reduce the controlled release effect of the film layer; finally, the patent does not describe the coating process in detail, and the coating process is precisely the controlled release of the coating layer. The key to fertilizer quality

The disclosed patent of CN101671425A has applied for a kind of polyurethane-coated controlled-release fertilizer with improved mechanical properties, but actually improves the elasticity and toughness of polyurethane by modifying the components of isocyanate to improve the mechanical resistance of the coated fertilizer, that is, the actual There is no substantive breakthrough compared with the disclosed patent of CN101323545A

In addition, the CN101671425A patent does not describe the coating method of the coating material in detail, and the coating equipment used is a drum coating equipment, and the drum coating process is difficult to control the uniformity of the coating layer and the amount of film material. Large and other disadvantages

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