Silica Capsule Shell Barrier Properties via Mixed-Oxide Precursors
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Solution Overview
Problem
Existing silica-based core-shell capsules lack adequate barrier properties, allowing premature leakage of active agents in solvent-rich consumer goods due to high porosity, especially when formed through interfacial polymerization where components react at different rates, leading to uneven distribution of metal oxides.
Innovation Solution
A precursor mixture of silica and a crosslinking metal-oxide is carefully selected to ensure similar reaction rates, forming a mixed-oxide shell with homogeneous distribution, reducing porosity and enhancing barrier properties by hydrolyzing and condensing at the oil/water interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silica matrix is doped with metal oxides to reduce porosity, then barrier properties improve, but homogeneous distribution of metal oxides becomes difficult to achieve in interfacial polymerization
Solution Approach 1:
The patent combines multiple metal oxide precursors (silica, titania, zirconia) into a single homogeneous precursor mixture that is added to the interfacial polymerization system at once, ensuring uniform distribution throughout the capsule shell rather than sequential addition that would create concentrated zones
Solution Approach 2:
The patent adjusts the reaction conditions including pH, temperature, and precursor ratios to control the hydrolysis and condensation rates of different metal oxide precursors, ensuring they react at similar time scales to achieve homogeneous mixed-oxide shell formation
2Reliability
If coatings are applied to increase shell thickness, then barrier properties improve, but the scaffold structure of the initial shell remains porous
Solution Approach 1:
The patent creates a composite mixed-oxide shell material combining silica with other metal oxides (titania, zirconia) that inherently forms a lower porosity structure during interfacial polymerization, eliminating the need for additional coating layers to achieve barrier properties
Solution Approach 2:
The patent inverts the approach by controlling the formation of porous structures during the primary shell formation process itself, using metal oxide doping to create a densely crosslinked network that minimizes porosity from the start rather than attempting to seal pre-formed porous structures
3Reliability
If interfacial polymerization is used to form capsules, then encapsulation efficiency improves, but premature leakage occurs due to high porosity of the formed shell
Solution Approach 1:
The patent uses a composite mixed-oxide system (silica + other metal oxides) that forms during interfacial polymerization to create a shell with inherently lower porosity and improved barrier properties, preventing premature leakage while maintaining encapsulation efficiency
Solution Approach 2:
The patent modifies the chemical composition parameters of the shell by incorporating metal oxide precursors into the polymerization mixture, changing the crosslinking density and network structure to reduce porosity and prevent solvent penetration that causes leakage
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 results in capsules with significantly improved barrier properties against small organic solvent molecules, ensuring the integrity of the encapsulated benefit agents.
Implementation Method 1
The precursor mixture hydrolyzes and condenses at an oil/water interface to create a mixed-oxide shell
Implementation Method 2
The precursor mixture hydrolyzes and condenses at an oil/water interface to create a mixed-oxide shell
Implementation Method 3
small fractions of a crosslinking metal-oxide that promote the crosslinking of silica and lower the porosity of the subsequently formed shell
Data Source
AI summary
A population of capsules comprising: a core comprising a benefit agent and a shell surrounding the core; wherein the shell surrounding the core comprises a substantially inorganic first shell; wherein the substantially inorganic first shell comprises a condensed layer comprising a condensation product of a mixture of precursors; and wherein the mixture of precursors comprises a silica precursor and a crosslinking metal-oxide precursor.