Microcapsule Wall Free-Radical Polymerization Agrochemical Stability
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Solution Overview
Problem
Conventional microcapsules for agrochemicals using polyurethanes are disadvantageous due to the use of toxic isocyanates, which require safety precautions and are highly reactive, and they struggle with stability and biological effectiveness, especially when incorporating penetration-promoting compounds like oils and lipophilic surfactants.
Innovation Solution
An aqueous dispersion comprising microcapsules with a capsule wall made of free-radically polymerized monomers, specifically acrylic acid and its esters, methacrylic acid and its esters, maleic acid and its esters, styrene, butadiene, isoprene, vinyl acetate, or vinyl propionate, where the capsule core includes a lipophilic surfactant and oil, and the continuous phase contains an agrochemical, enhancing stability and biological effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyurethane microcapsules are used for agrochemical delivery, then encapsulation is achieved, but toxic isocyanates must be used which require safety precautions and reduce ease of manufacture
Solution Approach 1:
The patent changes the chemical parameters of the capsule wall material from polyurethane (requiring isocyanates) to polymers made from acrylic acid, methacrylic acid, itaconic acid, or their esters. This parameter change eliminates the need for toxic isocyanates while maintaining encapsulation functionality, directly resolving the contradiction between reliability and ease of manufacture.
2Ease of manufacture
If isocyanates are used for microcapsule production, then capsule formation is achieved, but their high reactivity towards H-acidic groups limits the selection of additives and surfactants
Solution Approach 1:
The patent changes the chemical nature of the polymerization system from isocyanate-based polyaddition to free-radical polymerization using acrylic/methacrylic acid derivatives. This parameter change eliminates the high reactivity towards H-acidic groups, thereby expanding the compatibility range of additives and surfactants that can be used in the microcapsule formulation.
3Ease of operation
If higher temperature is used to disperse surfactants or oils in polyurethane microcapsules, then dispersion is achieved, but isocyanate reactivity increases further requiring greater safety effort
Solution Approach 1:
The patent changes the polymerization mechanism from polyaddition to free-radical polymerization, which allows for lower polymerization temperatures (typically 60-80°C) compared to polyurethane synthesis. This temperature reduction decreases isocyanate reactivity and harmful effects while still achieving adequate dispersion of surfactants and oils in the capsule core.
4Device complexity
If conventional microcapsules without lipophilic surfactants are used, then simple formulation is maintained, but penetration effectiveness of agrochemicals is reduced
Solution Approach 1:
The patent merges the encapsulation function with the penetration-promoting function by incorporating lipophilic surfactants directly into the microcapsule core during manufacturing. This combination allows the microcapsules to both protect the agrochemical and enhance its penetration through plant cuticles, resolving the contradiction between formulation simplicity and biological effectiveness.
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 solution provides a stable and biologically effective agrochemical dispersion that reduces crystallization of active ingredients and increases penetration, avoiding the use of toxic isocyanates and improving the release of penetration-promoting compounds, thus enhancing the efficacy of crop protection products.
Implementation Method 1
the capsule wall of which is made up of free-radically polymerized monomers
Data Source
AI summary
The invention relates to an aqueous dispersion comprising microcapsules, the capsule wall of which is made of radically polymerised monomers and the capsule core of which comprises at least one oil and at least one lipophilic surfactant. The continuous phase of the dispersion comprises at least one agrochemical. The invention also relates to a method for producing an aqueous dispersion with the steps: i) provision of an aqueous dispersion comprising microcapsules, the capsule wall of which is made of radically polymerised monomers and the capsule core of which comprises at least one oil and at least one lipophilic surfactant (microcapsule crude dispersion), and ii) at least one agrochemical is added. The invention also relates to the use of the microcapsule crude dispersion for producing an aqueous dispersion and to a product comprising, as separate components, a microcapsule crude dispersion and at least one agrochemical for combined use in combating undesired plant growth and/or for controlling undesired insect or acaricide infestation of plants and/or for combating phytopathogenic fungi.