Supercritical Fluid Cleaning of Banknotes
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Solution Overview
Problem
Current protective layers for banknotes fail to provide long-lasting dirt repellence and moisture resistance, leading to high replacement costs and environmental issues due to soiling and contamination, which complicates the authentication and recycling of banknotes.
Innovation Solution
A method using supercritical fluids, such as carbon dioxide, to clean banknotes without damaging their visual data or security features, combined with additives like oxalic acid or citric acid solutions, to remove contaminants and enhance the mechanical properties of the banknotes, thereby extending their lifespan and fitness for circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional protective layers are applied to banknotes, then dirt repellence and moisture resistance are improved, but the protection duration is insufficient leading to frequent replacement
Solution Approach 1:
The patent applies parameter changes by treating banknotes with supercritical fluids at controlled temperature and pressure conditions, then maintaining them in a controlled environment to extend protection duration. The supercritical fluid treatment modifies the surface parameters of the banknote to achieve long-lasting dirt repellence without conventional protective layers.
Solution Approach 2:
The patent replaces mechanical protective layers (coatings and laminates) with a supercritical fluid treatment process. This substitution eliminates the need for additional material layers while achieving equivalent or superior protection duration through chemical-physical modification of the banknote surface.
2Object-affected harmful factors
If banknotes are frequently replaced due to soiling, then cleanliness is maintained, but replacement costs and environmental impact increase
Solution Approach 1:
The patent converts the harmful effect of soiling into a benefit by using supercritical fluid extraction to remove contaminants. The same supercritical fluid that penetrates and solubilizes dirt, oils, and stains is then evaporated, leaving the banknote cleaner without requiring replacement. This transforms the potential harm of contamination into a beneficial cleaning process.
Solution Approach 2:
The patent discards contaminants from banknotes through supercritical fluid extraction while recovering and recycling the supercritical fluid itself. The cleaning process separates harmful substances from the banknote substrate, and the fluid is recovered for repeated use, reducing waste disposal needs.
3Productivity
If supercritical fluid cleaning is applied to banknotes, then cleaning effectiveness is improved, but there is risk of damaging security features and visual data
Solution Approach 1:
The patent applies partial action by using controlled exposure to supercritical fluids for specific durations and at controlled temperatures. Rather than aggressive cleaning, the process uses mild, controlled conditions that are sufficient to remove contaminants while stopping before any damage could occur to security features or visual data.
Solution Approach 2:
The supercritical fluid acts as an intermediary between the cleaning objective and the banknote substrate. It mediates the cleaning process by solubilizing contaminants without directly contacting or damaging the security features, allowing effective cleaning while preserving the integrity of sensitive elements.
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 supercritical fluid cleaning method effectively reduces the number of replaced banknotes by 10%, saving approximately $1 billion annually and minimizing environmental impact by reducing waste disposal, while maintaining the integrity of security features and visual data.
Implementation Method 1
The present invention provides for the cleaning of secure documents such as banknotes using supercritical fluids. More specifically, the present invention provides a method of cleaning secure documents and banknotes using supercritical fluids in a manner that does not damage or otherwise compromise their visual data, inks, substrates or the security features contained therein.
Implementation Method 2
exposing the stack to a supercritical fluid at a temperature and a pressure and for a duration sufficient to clean each secure instrument and not compromise the security feature and the visual data of each secure instrument
Implementation Method 3
clean each secure instrument may include removing one or more substances from each secure instrument into the supercritical fluid
Data Source
AI summary
A method and apparatus for cleaning a stack of secure instruments is disclosed. Each secure instrument includes a substrate, visual data and a security feature. The method and apparatus include exposing the stack to a supercritical fluid at a temperature and a pressure and for a duration sufficient to clean each secure instrument and not compromise each security feature and each visual data, and maintaining a securing mechanism on the stack during exposure of the stack to the supercritical fluid such that cleaning each secure instrument includes one or more substances from each secure instrument into the supercritical fluid.