Core-Shell Capsule Shell Formation Using Pre-formed Polymers
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Solution Overview
Problem
Conventional core-shell capsule formation methods using in-situ polymerization result in significant unreacted monomer residues, which are undesirable, especially when encapsulating volatile agents like fragrances, and offer limited control over shell properties and release rates.
Innovation Solution
Forming shells using pre-formed polymeric materials, specifically multiple layers of polycarboxylic acids with interposed different polymers like poly(acrylic acid) and poly(vinyl pyrrolidone), allowing for precise control over shell thickness and mechanical properties, and minimizing monomeric residues to very low levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If in-situ polymerization is used to form the shell, then the shell can be formed around the core, but significant levels of unreacted monomers remain in the capsules
Solution Approach 1:
The patent applies preliminary action by pre-forming the polymeric shell material before encapsulation. Instead of performing polymerization in-situ during capsule formation, the polymer is synthesized separately to completion, ensuring no monomer residues remain, and then used to form the shell around the fragrance core. This sequential approach eliminates the harmful monomer residues that would otherwise be present.
Solution Approach 2:
The process is segmented into distinct stages: first synthesizing the polymer separately to complete conversion, then using that pre-formed polymer to create the shell. This segmentation allows the polymerization reaction to be fully completed before contact with the core material, preventing monomer contamination of the encapsulated substance.
2Object-generated harmful factors
If multiple post-treatments are performed to remove monomer residues, then monomer levels can be reduced, but the process becomes complex and time-consuming
Solution Approach 1:
The patent converts the potential harm of monomer residues into a benefit by using pre-formed polymers with defined molecular weights. The polymerization is completed beforehand under controlled conditions, transforming what would be a contamination problem into a controlled synthesis process that produces high-quality polymer material free of monomer residues.
3Ease of manufacture
If in-situ polymerization is used, then shell formation is achieved, but control over shell mechanical properties and release rates is limited
Solution Approach 1:
The patent applies parameter changes by utilizing pre-formed polymers with specifically controlled molecular weights and compositions. By selecting polymers with defined parameters (molecular weight, functional groups, composition ratios) before shell formation, precise control over the shell's mechanical properties and fragrance release characteristics is achieved, far exceeding what is possible with in-situ polymerization.
Solution Approach 2:
The shell is formed as a composite structure using pre-formed polymeric materials with specific properties. The use of composite polymer systems with controlled molecular weights and functional characteristics allows fine-tuning of the shell's mechanical strength, porosity, and release properties, providing superior manufacturing precision compared to single-phase in-situ polymerization.
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 approach enables the creation of core-shell capsules with extremely low monomeric residues and tailored properties for controlled release of fragrances, suitable for applications in personal care and laundry, while maintaining the hedonic character of the fragrance and ensuring stability at specific pH levels.
Implementation Method 1
forming shells of pre-formed polymeric material based on polycarboxylic acids, around oil droplets comprising a fragrance
Data Source
AI summary
Core-shell capsules comprising a fragrance-containing core and a shell formed around said core, wherein the shell is formed of polycarboxylic acid having a molecular weight of 1'000 to 10'000'000 Daltons.