Polyurea Microcapsule Shell Stability in Surfactant Media
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Solution Overview
Problem
The perfumery industry faces challenges in maintaining the stability and olfactive performance of microcapsules in surfactant-based consumer products, as existing microcapsules tend to leak due to diffusion through the capsule shell, especially when exposed to elevated temperatures and aggressive surfactants, leading to reduced fragrance intensity and controlled release efficiency.
Innovation Solution
A process for preparing polyurea-based microcapsules using a polyisocyanate with at least three isocyanate functional groups, without the need for additional cross-linkers like diisocyanates or polyamines, forming a stable shell that prevents leakage and maintains fragrance intensity, even in challenging media.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aminoplast microcapsules (melamine-formaldehyde resin) are used to encapsulate hydrophobic actives, then the actives are protected and controlled release is provided, but the capsules suffer from stability problems in surfactant-containing products, causing the active to leak out by diffusion through the shell
Solution Approach 1:
The invention changes the chemical composition parameters of the capsule shell by using polyisocyanate-based polymers instead of traditional melamine-formaldehyde resin. This parameter change in the shell material chemistry provides both protection against surfactant degradation and reduced active leakage while maintaining controlled release properties.
Solution Approach 2:
The invention employs composite material strategies by combining polyisocyanate polymers with specific functional groups that create a shell structure resistant to surfactant penetration. The composite nature of the shell material provides enhanced stability in challenging formulations while maintaining encapsulation efficiency.
2Reliability
If cross-linking of capsule shells with polyamines and polyisocyanates is performed to improve stability, then stability improves, but the capsules are not friable, which negatively impacts olfactive performance
Solution Approach 1:
The invention applies local quality by creating regions of differential cross-linking density within the shell structure. The shell has locally varied properties where certain regions provide stability through cross-linking while other regions maintain appropriate friability for olfactive performance, achieving both requirements simultaneously.
Solution Approach 2:
The invention uses partial cross-linking rather than complete cross-linking of the shell structure. This partial action provides sufficient stability to prevent leakage while leaving enough uncross-linked regions to maintain capsule friability and olfactive performance upon activation.
3Ease of manufacture
If polyisocyanate with three or more isocyanate groups is used to form capsule shell, then capsule formation is achieved, but the capsules show poor oil retention and high leakage when placed in organic solvent or aqueous solutions with surfactants
Solution Approach 1:
The invention changes the molecular structure parameters of the polyisocyanate polymer by selecting specific chain lengths, functional groups, and polymer architectures. These parameter changes create a shell matrix that is impermeable to surfactant penetration while maintaining excellent oil retention, overcoming the leakage problems associated with conventional polyisocyanates.
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 microcapsules that demonstrate high stability and olfactive performance, with reduced perfume leakage and sustained fragrance release in surfactant-based products, offering a cost-effective and efficient solution for perfuming compositions and consumer products.
Implementation Method 1
A process for preparing polyurea-based microcapsules using a polyisocyanate with at least three isocyanate functional groups
Data Source
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AI summary
The present invention relates to a new process for the preparation of microcapsules. Microcapsules obtainable by said process are also an object of the invention. Perfuming compositions and consumer products comprising said capsules, in particular perfumed consumer products in the form of home care or personal care products, are also part of the invention.