Polyurea Microcapsule Deposition via Cationic Cross-linking
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Solution Overview
Problem
The perfumery industry faces challenges with rapid volatility of odoriferous compounds and poor deposition of microcapsules on target surfaces, leading to weak sensory perception and short-lasting fragrance in rinse-off applications, along with issues of microcapsule aggregation during production that affect processing and aesthetic value.
Innovation Solution
A process for preparing core-shell microcapsules using a polymeric cross-linker with high molecular weight, such as polyvinylamine or polyethyleneimine, to create at least partly aggregated microcapsules that improve deposition on surfaces like hair and skin while maintaining processability, involving steps like dissolving polyisocyanate in perfume, forming an oil-in-water emulsion, and adding the cross-linker followed by a polyamine for interfacial polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If polyurea microcapsules are used for fragrance delivery, then fragrance volatility is reduced, but deposition on target surfaces deteriorates
Solution Approach 1:
The invention modifies the surface charge parameter of the microcapsules by incorporating cationic polymers (polyethyleneimine or polyvinylamine) into the shell composition. This changes the electrostatic properties of the capsule surface, enabling positive charge that promotes adhesion to negatively charged surfaces like skin and hair, thereby improving deposition while maintaining fragrance volatility control
Solution Approach 2:
The microcapsule shell is constructed as a composite material combining polyisocyanate with cationic polymers (polyethyleneimine or polyvinylamine). This composite structure provides both the protective enclosure needed for volatility control and the surface charge properties needed for improved deposition on target surfaces
2Ease of manufacture
If microcapsule aggregation is avoided during production, then processing is simplified, but deposition on target surfaces deteriorates
Solution Approach 1:
The invention applies partial aggregation rather than complete aggregation or complete dispersion. By controlling the degree of aggregation through specific cationic polymer selection and concentration, the process achieves a balance where some aggregation occurs to improve deposition, while excessive aggregation that would cause processing problems is avoided
Solution Approach 2:
The invention changes the aggregation state parameter from complete dispersion to controlled partial aggregation. This is achieved by adjusting the charge density and concentration of cationic polymers, transforming the microcapsule system from a non-aggregated state to a partially aggregated state that optimizes both deposition and processability
3Reliability
If deposition aid is added to improve microcapsule deposition, then adhesion to surface improves, but product complexity increases
Solution Approach 1:
The invention merges the deposition aid function with the microcapsule shell structure itself. The cationic polymers are incorporated directly into the shell composition during microcapsule formation, combining the protective enclosure function with the surface adhesion function in a single integrated structure, thereby eliminating the need for separate deposition aids
Solution Approach 2:
The cationic polymer-containing shell serves multiple functions simultaneously: it provides structural protection for the fragrance core, controls fragrance release, and provides surface charge for improved deposition. This multi-functional design eliminates the need for separate specialized additives for each function
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 improved deposition and retention of fragrances on target surfaces, enhancing the longevity of perfumes in consumer products without compromising industrial-scale processing, and the microcapsules exhibit a balanced release and stability, addressing the issues of volatility and aggregation.
Implementation Method 1
dispersing the oil phase obtained in step a) into an aqueous solution comprising an emulsifier to form an oil-in-water emulsion; adding to the oil-in-water emulsion obtained in step b) a polymeric cross-linker bearing amino groups with a molecular weight equal or higher than 2 000 g/mol, preferably higher than 50 000 g/mol followed by a polyamine with a molecular weight below 250 g/mol to form a microcapsule slurry
Implementation Method 2
dispersing the oil phase obtained in step a) into an aqueous solution comprising an emulsifier to form an oil-in-water emulsion
Data Source
AI summary
The present invention relates to a process for producing perfume- or flavor-containing polyurea microcapsules with improved deposition of encapsulated actives on targeted surfaces such as fiber, hair and skin, which can be used in home or personal care products, as well as to microcapsules obtainable by such a process and consumer products comprising these microcapsules.