Core-Shell Security Pigment Stability Against Solvents
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing core-shell particles fail to effectively stabilize feature substances against external influences, such as organic solvents and aqueous acids, and are limited in their applicability, particularly in the banknote sector, due to the lack of a robust protective shell around solvent-containing droplets and the difficulty in encapsulating solid core materials.
Innovation Solution
A method involving the formation of core-shell particles using a non-crosslinked, less polar polymer core like PMMA and a highly crosslinked, polar polymer shell like melamine-formaldehyde resin, where solvent-containing droplets are coated and the solvent is removed to precipitate the core material, followed by further crosslinking of the shell, enhancing the stability of the feature substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a non-polar polymer core is used to dissolve feature substances, then the feature substances can be evenly distributed, but the core cannot protect against polar solvents like water
Solution Approach 1:
The patent uses a composite core-shell structure combining two different polymers: a non-polar core polymer (e.g., polyolefin) that provides protection against non-polar solvents and a polar shell polymer (e.g., polyacrylic acid) that provides protection against polar solvents. This composite structure resolves the contradiction by having each layer protect against different types of solvent attacks, achieving comprehensive stability that neither single polymer could provide alone.
2Stability of the object's composition
If a polar polymer shell is used to protect against organic solvents, then protection is provided, but the shell cannot prevent diffusion of aqueous solutions
Solution Approach 1:
The patent employs a composite core-shell structure where the polar shell polymer (e.g., polyacrylic acid) protects against organic solvents while the non-polar core polymer (e.g., polyolefin) protects against aqueous solutions. This dual-polymer composite resolves the contradiction by assigning different protective functions to each layer based on their polarity characteristics.
3Stability of the object's composition
If solid core particles are encapsulated with shell material, then protection is achieved, but the process requires complex multi-step procedures
Solution Approach 1:
The patent merges the core formation and shell encapsulation steps into a single simultaneous polymerization process. Both the core polymer and shell polymer are formed in one reaction step, eliminating the need for separate core preparation, isolation, and re-encapsulation steps. This merging of operations achieves comprehensive protection while dramatically simplifying the production process.
4Stability of the object's composition
If feature substances are embedded in core material, then stability against external influences is increased, but the core material must be separated before encapsulation
Solution Approach 1:
The patent combines the embedding of feature substances with the simultaneous formation of core and shell in a single polymerization step. The feature substances are incorporated into the core polymer matrix as it forms, and the shell polymer forms around it all in the same reaction vessel without requiring separation steps. This merging eliminates the complexity of isolating and re-encapsulating core particles.
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 method significantly increases the stability of feature substances against chemical attacks, achieving high retention rates in solvents and maintaining luminescence intensity, making them suitable for applications in banknotes and other security features.
Implementation Method 1
the solvent is removed from the core (due to which the core polymer precipitates in the core together with the feature substance distributed therein)
Implementation Method 2
a highly crosslinked polar polymer such as melamine-formaldehyde resin (MF) as the shell material
Data Source
AI summary
The invention relates to a security pigment composed of core-shell particles containing an organic or organometallic distinctive substance, in particular a luminescent distinctive substance, which is dissolved or finely distributed in the core. The invention further relates to a method for producing the core-shell particles and value documents comprising the core-shell particles.