Microcapsule Composition with Differential Zeta Potential
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Solution Overview
Problem
Existing polyurea or polyurethane capsules face issues such as low olfactory intensity, low stability, high toxicity, and problematic deposition on target surfaces, particularly in applications like laundry, cleaning, and personal care, where quicker and easier release or less mechanical strength are desired.
Innovation Solution
A microcapsule composition comprising a positively charged microcapsule with a zeta potential of 10 mV or greater and a negatively charged microcapsule with a zeta potential of -10 mV or less, where the first microcapsule has a wall formed from a reaction product of branched polyethyleneimine and a polyisocyanate, and the second microcapsule has a wall formed from melamine-formaldehyde polymer, polyurea, or urea formaldehyde polymer, enhancing deposition and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyurea or polyurethane capsules are used for rugged applications requiring high mechanical strength and slow time-release, then mechanical strength and duration of action are improved, but olfactory intensity and ease of operation deteriorate
Solution Approach 1:
The invention divides the capsule system into two distinct types with different wall materials and charge characteristics. Type I capsules have cationic walls providing quick release and high olfactory intensity, while Type II capsules have anionic walls providing slow release and mechanical strength. This segmentation allows both contradictory requirements to be satisfied simultaneously through combination rather than compromise.
Solution Approach 2:
The invention merges two previously separate capsule types into a single composition system. By combining cationic capsules (providing olfactory intensity) and anionic capsules (providing mechanical strength and slow release) in specific ratios, the composition achieves both high olfactory intensity and adequate mechanical strength that neither capsule type could achieve alone.
2Duration of action of stationary object
If polyurea or polyurethane capsules are used with high mechanical strength for slow time-release, then duration of action is improved, but stability and ease of operation deteriorate
Solution Approach 1:
The invention segments the release profile into two phases: initial quick release from cationic capsules providing immediate stability and performance, followed by slow release from anionic capsules providing prolonged duration. This segmentation resolves the contradiction between rapid stability and extended duration that cannot be achieved with a single capsule type.
Solution Approach 2:
The invention changes the parameter of wall charge from uniform to differential. By assigning opposite charges to different capsule types and controlling their ratio in the composition, the system achieves both rapid initial release (stability) and prolonged sustained release (duration) that cannot be achieved with uniform wall properties.
3Strength
If polyurea or polyurethane capsules are used for rugged applications, then mechanical strength is improved, but toxicity worsens
Solution Approach 1:
The invention uses composite capsule wall materials with specific charge characteristics. The cationic and anionic polymers used in the respective capsule types are selected to provide both mechanical strength and reduced toxicity compared to conventional polyurea/polyurethane capsules, achieving a balance between strength and safety through material composition rather than single-material reliance.
4Strength
If polyurea or polyurethane capsules are used for rugged applications, then mechanical strength is improved, but deposition on target surfaces worsens
Solution Approach 1:
The invention segments the deposition function between two capsule types with opposite charges. The cationic capsules deposit readily on negatively charged surfaces providing ease of operation, while the anionic capsules provide mechanical strength. This segmentation allows deposition and strength requirements to be satisfied by different components rather than requiring a compromise in either property.
Solution Approach 2:
The invention changes the surface charge parameter of the capsule system from uniform to differential. By controlling the charge ratio and composition of cationic and anionic capsules, the system achieves improved deposition characteristics through electrostatic interactions that conventional neutral or uniformly charged capsules cannot provide, while maintaining mechanical strength through the anionic component.
Data Source
AI summary
A microcapsule composition useful in delivering an active material contains a first microcapsule and a second microcapsule. The first microcapsule has a zeta potential of 10 mV or greater, the second microcapsule has a zeta potential of 5 mV or less, and the weight ratio of the first microcapsule and the second microcapsule is between 1 : 10 and 10 : 1. Also disclosed are consumer products containing such a microcapsule composition.