Melamine-Free Microcapsule Wall via Polyisocyanate Polymerization
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Solution Overview
Problem
Existing microcapsules used in perfumery products, such as melamine-formaldehyde and polyurea-based ones, face stability issues when exposed to surfactants, leading to leakage of encapsulated fragrances, especially in consumer products like detergents, and lack optimal mechanical properties for odor retention and release.
Innovation Solution
A process for preparing melamine-formaldehyde free microcapsules using a polyisocyanate with at least three isocyanate functional groups, preferably aromatic, without a diisocyanate and additional cross-linkers, forming a stable and effective capsule wall for perfume encapsulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If melamine-formaldehyde resin is used to form capsule walls, then stability of microcapsules in surfactant-based products is improved, but leakage of encapsulated active through the wall occurs due to solubilisation by surfactants
Solution Approach 1:
The patent changes the chemical composition parameters of the capsule wall by using polyisocyanates with specific functional groups (aromatic or aliphatic) instead of melamine-formaldehyde resin. This parameter change maintains stability while preventing surfactant-induced solubilisation and leakage of encapsulated actives.
Solution Approach 2:
The patent employs composite material strategies by combining polyisocyanate polymers with specific functional groups to create a capsule wall composition that resists surfactant attack. The composite structure provides both mechanical integrity and chemical resistance to prevent active leakage.
2Object-generated harmful factors
If polyurea-based microcapsules are used instead of aminoplast, then freedom from melamine-formaldehyde is achieved, but mechanical properties are insufficient and capsules are not friable
Solution Approach 1:
The patent modifies the polyurea formulation by selecting specific polyisocyanates with defined functional groups (aromatic or aliphatic) and controlling the polymerization process to achieve optimal mechanical properties. This parameter optimization maintains melamine-free composition while achieving desired friability and strength.
Solution Approach 2:
The patent applies local quality principles by creating a capsule wall with specific regional properties - the outer layer provides mechanical strength and friability while the inner layer ensures chemical resistance and active release control. This differentiated structure achieves both mechanical performance and chemical safety.
3Reliability
If cross-linking with polyamines and polyisocyanates is applied, then stability of microcapsules is improved, but device complexity and manufacturing process complexity increase
Solution Approach 1:
The patent extracts and eliminates the need for complex multi-step cross-linking processes involving separate polyamine and polyisocyanate additions. Instead, it uses a simplified single-step polymerization approach with pre-selected polyisocyanates that provide both structural integrity and stability without requiring additional cross-linking agents or steps.
Solution Approach 2:
The patent applies multi-functionality by selecting polyisocyanates that simultaneously provide capsule wall formation, cross-linking, and stability enhancement in a single component. This universal approach replaces multiple specialized chemicals and process steps with one multifunctional polymerization system.
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 demonstrate high stability and olfactory performance in surfactant-based products, maintaining fragrance retention and intensity, even under challenging conditions like elevated temperatures, without the use of diisocyanates or additional cross-linkers.
Implementation Method 1
performing a curing step to form a microcapsule slurry
Implementation Method 2
the encapsulated active tends to leak out of the capsule by diffusion through the wall
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to a new process for the preparation of melamine-formaldehyde free 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