Multi-Layer Microcapsules for Low Permeability and Friction Release
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Solution Overview
Problem
Existing controlled release microcapsules face issues such as high permeability, limited encapsulation breadth, poor mechanical stability, inadequate surface deposition, and low delivery efficiency, especially in surfactant-containing solutions and rinse-off applications, leading to premature release and loss of active ingredients.
Innovation Solution
The development of controlled release particles with a multi-layered structure comprising a hydrophobic core surrounded by a copolymer outer layer, a polyurea intermediate layer, and an acrylate inner layer, which are effective in retaining active ingredients upon exposure to water and releasing them in response to friction, enhancing adhesion and delivery efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-layer microcapsules are used, then manufacturing is simpler, but permeability is high causing premature release
Solution Approach 1:
The capsule wall is segmented into three distinct layers (inner crosslinked polymer layer, intermediate shell layer, outer surfactant-resistant layer) with different functions. The inner layer provides structural integrity and low permeability, the intermediate layer provides mechanical strength, and the outer layer provides surfactant resistance. This segmentation resolves the contradiction by distributing permeability control across multiple specialized layers rather than relying on a single complex layer.
Solution Approach 2:
The capsule employs composite material construction with each layer made from different polymer compositions optimized for specific functions. The inner layer uses crosslinked polymers for low permeability, the intermediate layer uses different polymers for mechanical strength, and the outer layer uses surfactant-resistant materials. This composite approach achieves superior permeability control without requiring excessive complexity in any single layer.
2Reliability
If high crosslink density is achieved through thermal initiation, then permeability is reduced, but volatile active ingredients are lost due to boiling temperatures
Solution Approach 1:
The patent replaces thermal initiation (which requires high temperature and causes volatile loss) with mechanical shear-induced polymerization. The polymerization is triggered by applying shear force during the emulsification process, allowing crosslinking to occur at ambient or low temperatures. This substitution achieves the desired high crosslink density and low permeability without the harmful thermal effects that cause volatile active ingredient loss.
Solution Approach 2:
The patent changes the initiation parameter from temperature-based (thermal) to shear-stress-based (mechanical). By controlling the shear rate and duration during emulsification, the polymerization is triggered at low temperatures, maintaining the volatile actives in the core while still achieving high crosslink density in the shell. This parameter change resolves the contradiction between permeability reduction and volatile loss.
3Reliability
If conventional microcapsules are used in surfactant-containing solutions, then formulation flexibility is maintained, but premature release occurs due to high permeability
Solution Approach 1:
The outermost layer is specifically designed with local quality optimized for surfactant resistance, while inner layers maintain their specialized functions for permeability control and mechanical strength. This localized optimization allows the capsule to resist surfactant penetration and premature release while maintaining compatibility with various surfactant-containing formulations. The surfactant-resistant layer acts as a protective barrier without interfering with the encapsulation of diverse active ingredients.
4Area of stationary object
If smaller microcapsule size is used, then surface deposition is improved, but fracture strength increases making release difficult
Solution Approach 1:
The intermediate shell layer is designed with optimal thickness and mechanical properties to provide flexibility while maintaining integrity. This layer acts as a buffer that allows the small capsule to conform to surface topography for improved deposition, while still providing sufficient mechanical strength to protect the core until triggered. The flexible shell design resolves the contradiction by enabling small size for better surface coverage without proportionally increasing fracture resistance.
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 multi-layered structure significantly reduces permeability, improves adhesion to substrates, and enables the release of a larger quantity of active ingredients over a longer duration, addressing the limitations of existing microcapsules in surfactant-containing solutions and rinse-off applications.
Implementation Method 1
The permeability of such shell material is determined by the crosslink density of the membrane. Polymers that are used to develop a membrane around the active material need to be crosslinked to provide a sufficient barrier to retain the encapsulated active until its desired release.
Implementation Method 2
Controlled release microcapsules that provide release of active upon application of shear or friction
Implementation Method 3
An emulsion comprising the active material (dispersed phase) is stabilized in a continuous phase.
Implementation Method 4
In one mode, a shell material is deposited from the continuous phase onto a dispersed phase via precipitation of the shell material.
Data Source
AI summary
Disclosed is a composition including controlled release particles, wherein each of the controlled release particles includes: (a) a core including at least one hydrophobic active ingredient; and (b) a wall at least partially surrounding the core and including: (i) an outer layer including a copolymer of polyacrylamide and polyacrylate; (ii) an intermediate layer under the outer layer and including a polyurea; (iii) an inner layer under the intermediate layer and including an acrylate copolymer; and optionally (iv) an optional outer layer above the outer layer and including a quaternary amine containing moiety, wherein the inner layer is a mesh and the controlled release particles are effective to retain the at least one hydrophobic active ingredient upon exposure to water and effective to release the at least one hydrophobic active ingredient in response to friction. A method for preparing the composition is also disclosed.