Silicate Shell Microcapsule Suspension Stability
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Solution Overview
Problem
Current suspensions of microcapsules with a silicate shell and lipophilic liquid core tend to gel under certain conditions, such as increased microcapsule size, higher volume fractions, elevated temperatures, or pH changes, due to the presence of free colloidal silica particles, leading to stability issues.
Innovation Solution
Reducing the concentration of colloidal silica particles in the continuous phase or using a colloidal silicate sequestering agent, like organofunctional silanes or silicone polyethers, to prevent aggregation and gelation, thereby enhancing the stability of the microcapsule suspensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the volume fraction of microcapsules in the suspension is increased, then the concentration of active material is improved, but the suspension tends to gel and stability deteriorates
Solution Approach 1:
The patent removes the harmful component (free colloidal silica particles) from the suspension system through filtration or by preventing their formation during microcapsule synthesis. This extraction of the gelation-causing agent allows high volume fractions of microcapsules to be maintained without gelation, resolving the contradiction between concentration and stability.
Solution Approach 2:
The patent introduces sequestering agents that bind to free silica particles, preventing them from aggregating and causing gelation. These intermediary substances allow the system to tolerate higher microcapsule concentrations by neutralizing the harmful effect of colloidal silica.
2Speed
If the temperature of the suspension is elevated, then the processing speed is improved, but gelation occurs and stability decreases
Solution Approach 1:
By removing free colloidal silica particles through filtration before processing, the suspension becomes resistant to temperature-induced gelation. This allows elevated temperature processing to be performed without the stability deterioration that would normally occur.
Solution Approach 2:
Sequestering agents are added to the suspension to bind free silica particles, creating a protective effect that prevents temperature from triggering gelation. This intermediary protection enables thermal processing while maintaining suspension stability.
3Adaptability or versatility
If the pH of the suspension is changed, then the microcapsule properties are adjusted, but gelation occurs and stability is reduced
Solution Approach 1:
Filtration removes free colloidal silica particles that are responsible for pH-dependent gelation. This allows pH adjustment for microcapsule property optimization without triggering the gelation that would otherwise occur.
Solution Approach 2:
Sequestering agents act as intermediaries that bind free silica particles, preventing them from responding to pH changes by forming gels. This allows pH adjustment for property optimization while maintaining suspension stability through the protective binding effect.
4Volume of moving object
If the microcapsule size is increased, then the payload capacity is improved, but the suspension gels and stability is compromised
Solution Approach 1:
By filtering out free colloidal silica particles that cause gelation, larger microcapsules can be incorporated into the suspension without triggering gelation. This extraction enables increased payload capacity through larger capsule sizes while maintaining 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
The process results in microcapsule suspensions with improved thermal and pH stability, maintaining a high volume fraction of microcapsules without gelation at elevated temperatures for an extended period, ensuring stability and preventing viscosity increases.
Implementation Method 1
adding a colloidal silicate sequestering agent to an aqueous suspension of silicate shell microcapsules and colloidal silicate particles
Data Source
AI summary
A process for improving the stability of an aqueous suspension of silicate shell microcapsules by adding a colloidal silicate sequestering agent to an aqueous suspension of silicate shell microcapsules and colloidal silicate particles.