Microcapsule Shell Structure for Fragrance Retention
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Solution Overview
Problem
Conventional microcapsule production methods fail to retain organic compounds, such as fragrance materials, effectively over a long period due to insufficient denseness and strength of the shell, leading to elution or diffusion through micropores.
Innovation Solution
A two-stage sol-gel process is employed to form microcapsules with a first shell of specific thickness and a second shell with a mesoporous structure, enhancing the denseness and strength of the shell, thereby retaining organic compounds within the microcapsules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single shell structure is formed by sol-gel method, then the microcapsules can be produced with simple process, but the shell lacks sufficient denseness and strength causing elution or diffusion of organic compounds
Solution Approach 1:
The single shell structure is divided into multiple concentric shells (first shell, second shell, and optionally third shell) with different functions. The first shell provides initial encapsulation, the second shell enhances denseness and strength to prevent elution, and the third shell (if present) provides additional protection, collectively solving the retention problem while maintaining process simplicity through sequential application.
Solution Approach 2:
Multiple shell layers with different compositions and structures are combined to create a composite encapsulation system. Each shell layer contributes different properties (denseness, strength, porosity control) that together provide superior retention of organic compounds compared to a single shell structure.
2Reliability
If the shell thickness is increased to improve strength and denseness, then organic compound retention improves, but the manufacturing process becomes more complex
Solution Approach 1:
Instead of forming one thick shell, the total shell thickness is segmented into multiple thinner concentric layers. Each layer is formed through controlled sol-gel reactions under different conditions, achieving the required overall thickness and strength while simplifying the formation process through staged application rather than a single complex step.
Solution Approach 2:
The shell formation process is divided into periodic stages (first shell formation, second shell formation, and optionally third shell formation), with each stage involving controlled addition of precursors, pH adjustment, and sol-gel reaction under specific conditions. This periodic action allows precise control over each layer's properties while maintaining overall process manageability.
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 enhanced shell structure effectively retains organic compounds, improving the longevity of the encapsulated fragrance materials and enhancing the physical strength of the microcapsules.
Implementation Method 1
subjecting the resulting emulsion to sol-gel reaction under acidic conditions to form capsules each including the core and the first shell
Implementation Method 2
subjecting the obtained mixture to sol-gel reaction while maintaining an initial pH value in the sol-gel reaction of the step (2) below an initial pH value in the sol-gel reaction of the step (1)
Implementation Method 3
a water phase including a surfactant
Implementation Method 4
emulsifying an organic phase including the at least one organic compound and a tetraalkoxysilane such that a content of the tetraalkoxysilane in the organic phase is not less than 10% by mass and not more than 60% by mass on the basis of the organic compound, in a water phase including a surfactant
Implementation Method 5
the second shell encapsulating the first shell has a mesoporous structure
Data Source
Figure 1
Figure 2~3
AI summary
The present invention provides a process for producing microcapsules capable of retaining an organic compound as an active ingredient such as fragrance materials therein over a long period of time. The present invention relates to process for producing microcapsules, which includes step (1) of emulsifying an organic phase including at least one organic compound and a tetraalkoxysilane such that a content of the tetraalkoxysilane in the organic phase is not less than 10% by mass and not more than 60% by mass on the basis of the organic compound, in a water phase including a surfactant, and subjecting the resulting emulsion to a sol-gel reaction under acidic conditions to form capsules each including the core and the first shell; and step (2) of further adding a tetraalkoxysilane to a water dispersion containing the capsules obtained in the step (1), and subjecting the obtained mixture to a sol-gel reaction while maintaining an initial pH value in the sol-gel reaction of the step (2) below an initial pH value in the sol-gel reaction of the step (1) to form the capsules each including the second shell encapsulating the first shell.