Dual-Emulsion Microcapsule Formation for Stable Water-Soluble Cores
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Solution Overview
Problem
Existing methods for producing microcapsules, particularly those with water-soluble core agents, face challenges such as instability, complexity, and inefficiency, including the need for multiple reaction steps and potential side reactions, especially when using interfacial polymerization.
Innovation Solution
A method involving the formation of two types of emulsion particles with different sizes, where one type has an average particle size of 0.1 to 300 μm and the other 0.01 to 30 μm, followed by interfacial polymerization, using monomers like isocyanate compounds and polyamines to form a film, with a reaction time of 6 hours or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If interfacial polymerization is used to produce microcapsules with water-soluble core agents, then microcapsules can be formed, but the production process becomes complex and requires multiple reaction steps
Solution Approach 1:
The production process is divided into two independent emulsion formation steps followed by a single interfacial polymerization step. The first emulsion contains the water-soluble core agent and the second emulsion contains the film-forming substance, allowing separate optimization of each component before combination.
Solution Approach 2:
Both emulsions are prepared in advance with controlled particle sizes and compositions before the actual polymerization reaction. This preliminary preparation ensures that when the emulsions are mixed, the interfacial polymerization proceeds efficiently to form stable microcapsules.
2Productivity
If conventional emulsion methods are used, then microcapsules can be produced, but side reactions occur and reaction time extends to 4-24 hours
Solution Approach 1:
The film-forming substance is concentrated at the interface between the two emulsion droplets, creating a localized reaction zone. This ensures that polymerization occurs only at the interface where the two monomers meet, preventing side reactions in the bulk aqueous phase and reducing overall reaction time to 4-24 hours.
Solution Approach 2:
The emulsion droplets serve as intermediaries that bring the two monomers into close proximity at their interfaces. This intermediary structure enables controlled interfacial polymerization while preventing unwanted side reactions between water and isocyanate that would occur in conventional mixed emulsion methods.
3Adaptability or versatility
If water-soluble substances are used as core agents, then microcapsules can encapsulate beneficial materials, but storage stability cannot be maintained
Solution Approach 1:
The problem is solved by transitioning from a single-emulsion system to a dual-emulsion system. The first emulsion contains the water-soluble core agent in an aqueous phase, while the second emulsion contains the film-forming substance in an organic phase. This dimensional separation allows the water-soluble material to be encapsulated while the organic film-forming substance provides a stable barrier, achieving both versatility and storage stability.
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 approach allows for the efficient production of stable microcapsules with high water content or pressure resistance, encapsulating various core substances, including epoxy resin curing agents, with improved storage stability and reduced leakage.
Implementation Method 1
a microcapsule-forming step of mixing and interfacial-polymerizing the emulsion (1) and the emulsion (2)
Data Source
AI summary
The present invention easily provides microcapsules by using a production method according to a more efficient and reliable interfacial polymerization method even when it is difficult to produce microcapsules by an interfacial polymerization method by adding a solution of a film-forming substance. Specifically, the present invention provides a method for producing microcapsules using two types of emulsion particles differing in size, the method comprising:an emulsion-forming step of separately forming two types of emulsions (1) and (2) whose continuous phases are common, wherein emulsion particles (1) of the emulsion (1) comprises one of two types of monomers which react with each other to form a film and emulsion particles (2) of the emulsion (2) comprises the other monomer; anda microcapsule-forming step of mixing and interfacial-polymerizing the emulsion (1) and the emulsion (2),whereinthe emulsion particles (1) of the emulsion (1) have an average particle size (R) of 0.1 to 300 μm,the emulsion particles (2) of the emulsion (2) have an average particle size (r) of 0.01 to 30 μm, andr/R≤0.1 is satisfied.