Polyurea Formaldehyde Core-Shell Fertilizer Coating
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Solution Overview
Problem
Current slow/controlled-release fertilizers face issues such as resource wastage, environmental pollution, and inadequate nutrient release rates due to shortcomings in existing coating materials, including difficulty in degradation, high costs, and soil acidification.
Innovation Solution
A method for preparing a slow/controlled-release fertilizer with a core-shell structure using a polyurea formaldehyde coating layer, produced by reacting urea and formaldehyde in specific molar ratios and conditions, allowing for in-situ polymerization on fertilizer granule cores, resulting in a coating that decomposes slowly and releases nutrients in a controlled manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional coating materials (organic or inorganic) are used to coat fertilizer granules, then slow/controlled-release performance is improved to varying degrees, but the materials have shortcomings including difficulty in degradation, high costs, and environmental pollution
Solution Approach 1:
The patent changes the chemical composition parameters of the coating material by using polyurea formaldehyde with specific carbon chain lengths (2-5 carbon atoms) and controlled molecular weight, which allows the coating to degrade at appropriate rates while maintaining controlled-release functionality, thus resolving the contradiction between release performance and environmental compatibility
Solution Approach 2:
The patent employs a composite coating material formed by in-situ polymerization of urea and formaldehyde on the fertilizer granule surface, creating a polyurea formaldehyde coating that combines the benefits of controlled-release with biodegradability, eliminating the need for persistent synthetic polymers or metals that cause pollution
2Reliability
If polyurea formaldehyde coating is applied with in-situ polymerization, then nutrient release control is improved and environmental friendliness is enhanced, but the process complexity increases
Solution Approach 1:
The patent merges the coating application process with the polymerization process by applying a precursor solution containing urea and formaldehyde to the fertilizer granules, then inducing in-situ polymerization to form the final coating. This combines multiple steps into an integrated process that simplifies manufacturing while achieving reliable controlled-release performance
Solution Approach 2:
The patent uses a precursor solution containing methylol urea as an intermediary substance that is applied to the granule surface first, then undergoes polymerization to form the final polyurea formaldehyde coating. This intermediary approach allows for better process control and simplifies the overall manufacturing sequence
3Duration of action of stationary object
If coating layer thickness is increased to extend nutrient release duration, then duration of action is improved, but the decomposition time increases and may leave residues
Solution Approach 1:
The patent changes the chemical structure parameters of the polyurea formaldehyde coating by controlling the carbon chain length (2-5 carbon atoms) and molecular weight distribution, which allows the coating to maintain adequate thickness for extended release while ensuring complete biodegradation within the crop growth period, preventing residue accumulation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enhances fertilizer utilization rates, reduces environmental impact, and provides a cost-effective solution for large-scale agricultural use by ensuring slow and complete nutrient release without residue, meeting the growth needs of different crops.
Implementation Method 1
producing methylol urea from urea and formaldehyde in alkaline conditions, then adjusting to acidity and spraying onto a surface of a fertilizer granule core, then carrying out in-situ polymerization while removing water by evaporation to produce polyurea formaldehyde
Implementation Method 2
carrying out in-situ polymerization while removing water by evaporation to produce polyurea formaldehyde
Implementation Method 3
A polymerized water-insoluble component contained in the coating layer decomposes slowly through the action of microbes in soil, for absorption by crops
Data Source
Figure 1
AI summary
Provided are a sustained-release and controlled-release fertilizer having a core-shell structure and a preparation method therefor, which relate to the field of sustained-release and controlled-release fertilizer production. A sustained-release and controlled-release fertilizer having a core-shell structure comprises a core of fertilizer granules and a polyurea-formaldehyde coating layer coated on the surface of the core of fertilizer granules. The molar ratio of urea to formaldehyde in the raw material of the polyurea-formaldehyde is 1-2.5 : 1, and the polyurea-formaldehyde comprises at least polyurea-formaldehyde having 2 to 5 carbon atoms. The molecular weight of the polyurea-formaldehyde can be varied by adjusting reaction conditions so as to form a membrane structure having different carbon chain lengths. The sustained-release and controlled-release fertilizer having a core-shell structure can not only control the sustained release of a large number of nutrients such as nitrogen, phosphorus and potassium, but also can control the sustained release of trace elements such as calcium, magnesium, iron and zinc, and thus can meet nutrient requirements of different crops.