Monodisperse Microcapsule Production via Controlled Shear
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Solution Overview
Problem
Industrial-scale emulsification methods for producing microcapsules result in polydisperse and large microcapsules, often requiring water and surfactants/emulsifiers, which can contaminate the active material and reduce its performance.
Innovation Solution
A method involving a double emulsion technique with controlled high shear mixing to produce monodisperse solid microcapsules below 5 µm in size, eliminating the need for water and surfactants/emulsifiers, by adding an active material to a cross-linkable liquid composition, forming a first emulsion, then a second emulsion, and applying homogeneous controlled shear to create a third emulsion that is cross-linked to form microcapsules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If industrial scale emulsification methods are used to produce microcapsules, then large volumes can be met for industrial demands, but the microcapsules become polydisperse and very large (mean size above 10 μm)
Solution Approach 1:
The invention divides the emulsification process into three distinct stages: (1) forming a first emulsion by adding composition C1 to C2, (2) forming a second emulsion by adding the first emulsion to C3, and (3) applying controlled high shear to create a third emulsion. This segmentation allows progressive control over droplet size, achieving monodispersity while maintaining industrial scale production capability.
Solution Approach 2:
The invention introduces dynamic controlled high shear mixing at a specific stage to transform the polydisperse emulsion into a monodisperse third emulsion. The dynamic application of shear force enables real-time control over droplet size distribution, converting large polydisperse droplets into uniform small droplets while maintaining production volume.
2Ease of manufacture
If water is used to form one of the phases in emulsification methods, then emulsion formation is enabled, but water may react with the active material encapsulated and provide contaminants, thus decreasing the performances of the active material
Solution Approach 1:
The invention extracts and eliminates water from the emulsion system by using only organic compositions (C1, C2, C3) that are mutually immiscible. This removal of water prevents harmful reactions with the active material while maintaining the ability to form stable emulsions through the organic phase system.
Solution Approach 2:
The invention changes the fundamental parameter of the continuous phase from aqueous to organic by using compositions C2 and C3 that are immiscible with each other and with C1. This parameter change eliminates water-related contamination while enabling emulsion formation through the organic phase system.
3Stability of the object's composition
If surfactants or emulsifiers are used to stabilize the emulsion in industrial scale methods, then emulsion stability is achieved, but surfactants may react with the active material encapsulated and provide contaminants, thus decreasing the performances of the active material
Solution Approach 1:
The invention extracts and eliminates surfactants and emulsifiers from the system by achieving emulsion stability through the mutual immiscibility of organic compositions C1, C2, and C3. The system maintains stability without requiring external stabilizing agents, thereby preventing contamination of the active material.
Solution Approach 2:
The invention enables the emulsion system to be self-stabilizing through the inherent immiscibility of the organic compositions. The system uses its own compositional properties (immiscibility of C1-C2 and C2-C3) to provide stability without external surfactants, achieving self-service stabilization.
4Productivity
If batch emulsification methods are used to meet large volumes for industrial demands, then production scale is achieved, but the microcapsules produced are polydisperse and large, requiring further processing
Solution Approach 1:
The invention segments the emulsification process into three sequential steps that can be performed in a single batch operation: (1) forming first emulsion, (2) forming second emulsion, and (3) applying controlled high shear. This segmentation achieves monodispersity without requiring multiple separate processing stages or complex equipment.
Solution Approach 2:
The invention introduces dynamic controlled high shear as a single integrated step that transforms the emulsion structure in real-time. This dynamic approach achieves size reduction and monodispersity within one process operation, avoiding the need for multiple sequential processing stages.
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
This method enables the production of monodisperse microcapsules with controlled size and shell thickness, free from contaminants, enhancing the active material's performance and stability, suitable for various industrial applications.
Implementation Method 1
a cross-linkable liquid composition C2... the middle phase of the third emulsion (composition C2) is then polymerized to form a solid shell
Implementation Method 2
loading the second emulsion obtained in step b) in a mixer which applies a homogeneous controlled shear rate to said second emulsion, said shear rate being from 1 000 s -1
Implementation Method 3
a first emulsion is obtained, said first emulsion comprising droplets of composition C1 dispersed in composition C2... the second emulsion comprising droplets dispersed in composition C3
Data Source
Figure 1
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Figure 3~4
AI summary
The present invention relates to a method for preparing solid microcapsules (20), comprising the steps of: a) adding under agitation a composition C1 comprising at least one active material to a cross-linkable liquid composition C2, wherein the active material is not an additive to be used in the lubricant, fuel or bitumen industries, or in drilling sludges or muds, or an additive to be used in oil exploration/production, composition C1 and composition C2 being immiscible with each other, so that a first emulsion is obtained, said first emulsion comprising droplets (1) of composition C1 dispersed in composition C2, b) adding under agitation the first emulsion obtained in step a) to a liquid composition C3, composition C3 and composition C2 being immiscible with each other, so that a second emulsion is obtained, said second emulsion comprising droplets (5) dispersed in composition C3, c) loading the second emulsion obtained in step b) in a mixer which applies a homogeneous controlled shear rate to said second emulsion, said shear rate being from 1 000 s-1 to 100 000 s-1, so that a third emulsion is obtained, said third emulsion comprising droplets (10) dispersed in composition C3, and d) cross-linking the droplets (10) obtained in step c), so that solid microcapsules (20) dispersed in composition C3 are obtained.