Hydrophilic Liquid Microcapsule Wall Formation via Interfacial Polymerization
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Solution Overview
Problem
Existing microencapsulation processes face challenges in achieving consistent wall thickness, uniform deposition, controlled release rates, and charge characteristics for microcapsules with liquid hydrophilic cores, particularly when dealing with hydrophilic materials that require precise engineering of the wall chemistry and ionic properties.
Innovation Solution
A process involving the formation of microcapsules with a liquid hydrophilic core surrounded by an ionic wall material, using a low-boiling, nonflammable oil continuous phase, where monofunctional amine acrylates or methacrylates and multifunctional acrylates or methacrylates are used, along with initiators and surfactants, to create prepolymers that cross-link and adhere to the core material, ensuring uniform encapsulation and controlled properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If interfacial polymerization is used to form microcapsule walls, then capsule wall formation is achieved, but consistent wall thickness and uniform deposition are difficult to achieve
Solution Approach 1:
The patent modifies the polymerization parameters by controlling the pH gradient and using specific monomer ratios (diisocyanate to amine) to achieve uniform wall deposition. The use of buffered aqueous phases and controlled addition rates of reactive components ensures consistent wall thickness across all microcapsules in the population.
Solution Approach 2:
The patent performs preliminary emulsification of the core material in the organic phase before adding the aqueous phase containing the amine. This pre-establishes uniform droplet sizes and interfaces, which leads to consistent wall formation during the subsequent polymerization step.
2Reliability
If hydrophilic liquid core materials are encapsulated, then the core material is protected, but controlled release rates and charge characteristics are difficult to achieve
Solution Approach 1:
The patent creates local ionic characteristics in the capsule wall by selecting specific amine components with different pKa values and concentrations. This allows different regions of the wall to have tailored charge densities, enabling precise control over release rates and electrostatic properties for hydrophilic liquid cores.
Solution Approach 2:
The patent uses composite wall structures formed from multiple components (diisocyanate, amine, buffer salts) that work together to provide both mechanical integrity and controlled release properties. The composite nature of the wall allows simultaneous optimization of release rate control and charge characteristics.
3Manufacturing precision
If conventional emulsification is used, then core material dispersion is achieved, but precise engineering of wall chemistry and ionic properties is compromised
Solution Approach 1:
The patent replaces complex mechanical mixing and post-processing steps with a chemically-driven self-assembly process. The interfacial polymerization automatically directs wall material formation and ionic property development through chemical potential gradients, reducing the need for complex mechanical intervention while achieving precise wall chemistry.
4Reliability
If polymeric capsule shells are formed at phase interface, then encapsulation is achieved, but consistent charge properties and release characteristics are difficult to control
Solution Approach 1:
The patent incorporates buffer systems that provide pH feedback control during polymerization. The buffer capacity and composition are selected to maintain optimal pH ranges that ensure consistent amine ionization and wall charge development, which in turn controls release characteristics in a predictable manner.
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 process enables the formation of microcapsules with consistent wall thickness and controlled release characteristics, effectively encapsulating hydrophilic liquids with precise charge properties, enhancing the protection and delivery of sensitive materials.
Implementation Method 1
adding an oil soluble or dispersible monofunctional amine acrylate or methacrylate with a nitrogen content of at least 5% by weight; adding a multifunctional acrylate or methacrylate monomer or oligomer; adding an acid and an initiator; heating the mixture for a time sufficient to enable the monofunctional amine acrylate or methacrylate and the multifunctional acrylate or methacrylate to form a prepolymer which migrates to the liquid hydrophilic material, thereby forming prepolymers adhered to the hydrophilic core materials
Implementation Method 2
Heating or exposure to actinic radiation is then applied for a time and temperature sufficient to cross link the prepolymers
Implementation Method 3
A process involving the formation of microcapsules with a liquid hydrophilic core surrounded by an ionic wall material, using a low-boiling, nonflammable oil continuous phase, where monofunctional amine acrylates or methacrylates and multifunctional acrylates or methacrylates are used, along with initiators and surfactants
Data Source
AI summary
A process of forming a population of microcapsules is described comprising a liquid hydrophilic core material and a wall material at least partially surrounding the core material. The liquid hydrophilic core material can be anionic, cationic, or neutral but polar. The microcapsule population is formed by providing liquid hydrophilic core material; providing an oil continuous phase which is low boiling and preferably nonflammable, the oil continuous phase comprising preferably one or more organic oil materials such as esters with chain length up to about 42 carbons. A mixture is formed by dispersing the liquid hydrophilic material in the oil continuous phase. Either an oil soluble or dispersible monofunctional amine acrylate or monofunctional amine methacrylate, along with acid; or alternatively monofunctional acid acrylate or monofunctional acid methacrylate along with base; or alternatively, monofunctional amine acrylate or monofunctional amine methacrylate along with acid acrylate or methacrylate; is added. A multifunctional acrylate or methacrylate monomer or oligomer is provided along with an initiator. Optionally a surfactant is also added to form the mixture. Emulsification is achieved by subjecting the mixture to high shear agitation and heating the mixture for a time sufficient to enable forming a prepolymer which migrates to the liquid hydrophilic material, thereby forming prepolymers adhered to the hydrophilic core materials. Heating is carried out or light exposure or both for a time and temperature sufficient to crosslink the prepolymers.