Polyurea Microcapsule Shell Chemistry for Surfactant-Stable Fragrance Release
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Solution Overview
Problem
Existing polyurea-based microcapsules used in perfumery products suffer from stability issues in surfactant-containing consumer products, leading to leakage of encapsulated actives and inadequate olfactive performance due to their friability and mechanical properties.
Innovation Solution
A process involving the formation of polyurea microcapsules using a mixture of aromatic polyisocyanate and a specific ratio of guanidine and 3,5-diamino-1,2,4-triazole polyamines to enhance the brittleness and stability of the capsule walls, improving their mechanical properties and olfactive performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aminoplast microcapsules (melamine-formaldehyde resin) are used to encapsulate hydrophobic actives, then good olfactive performance is achieved, but stability problems occur in consumer products containing surfactants due to active leakage through the capsule wall
Solution Approach 1:
The patent uses a composite capsule wall structure combining melamine-formaldehyde resin with a shellac coating layer. The shellac layer acts as an additional barrier that prevents surfactant penetration and active leakage, while the inner melamine-formaldehyde layer provides the necessary mechanical strength and controlled release properties for good olfactive performance.
Solution Approach 2:
The shellac coating forms a thin film layer on the capsule surface that is flexible enough to allow controlled release of the active ingredient while providing a protective barrier against surfactant attack. This thin film approach maintains capsule integrity without overly restricting the release mechanism.
2Stability of the object's composition
If polyurea microcapsules are prepared using aromatic and aliphatic polyisocyanates with guanidine, then stability in surfactant-containing products is improved, but mechanical properties deteriorate as the capsules become less friable, negatively impacting olfactive performance
Solution Approach 1:
The patent modifies the chemical composition parameters of the capsule wall by incorporating shellac alongside the polyurea components. This parameter change creates a hybrid wall structure that balances the competing requirements of stability (from polyurea cross-linking) and friability (from shellac's mechanical properties), enabling both surfactant resistance and good olfactive performance.
3Reliability
If the capsule wall is made more stable through cross-linking with polyamines and polyisocyanates, then leakage resistance improves, but the capsules become less breakable during use, reducing odor intensity perceived during handling and after intentional breakage
Solution Approach 1:
The composite wall structure of melamine-formaldehyde resin with shellac coating creates a layered system where the inner cross-linked resin provides leakage resistance while the outer shellac layer contributes to controlled breakability. This composite approach ensures the capsule maintains integrity during storage but can still break effectively during consumer use to release the fragrance.
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 resulting microcapsules exhibit improved breakability and olfactive performance, maintaining stability in challenging media like surfactant-based consumer products, ensuring efficient perfume release and enhanced odor intensity.
Implementation Method 1
the shell of microcapsules is formed by the reaction between at least one aromatic polyisocyanate and a mixture of two polyamines
Implementation Method 2
dispersing the oil phase obtained in step a) into an aqueous solution comprising a emulsifier to form an oil-in-water emulsion
Implementation Method 3
the encapsulated active tends to leak out of the capsule by diffusion through the wall due to the presence of surfactants
Data Source
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AI summary
The present invention relates to a process for producing perfume-containing microcapsules with improved olfactive performance by using at least one aromatic polyisocyanate with a specific mixture of polyamines. Microcapsules obtainable by such a process and perfuming compositions or the consumer products comprising these microcapsules are also objects of the invention. In particular, the microcapsules can be used in home or personal care products.