Washable Aqueous Ink Composition for Cold-Water Skin Washability
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Solution Overview
Problem
Existing washable ink compositions, particularly those containing conventional acid dyes, struggle with poor skin washability, especially with cold water, and offer less vivid colors compared to polymeric dyes, which are more expensive.
Innovation Solution
A combination of at least one alkali metal salt of citrate and cyclodextrin or its derivative is used in the ink formulation to enhance skin washability with cold water and maintain vivid color, allowing the use of acid dyes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional acid dyes are used in washable ink compositions, then vivid color is achieved, but skin washability deteriorates (stains are difficult to remove with cold water)
Solution Approach 1:
The patent introduces cyclodextrins as intermediary molecules that form inclusion complexes with acid dye molecules. The cyclodextrin cavity encapsulates the dye molecule, creating a host-guest complex that modifies the dye's interaction with substrates. This mediator allows the ink to maintain vivid color while improving washability, as the complexed dye can be more easily removed from skin with cold water compared to free acid dye molecules
2Ease of operation
If polymeric dyes are used to improve skin washability, then washability improves (stains can be removed with tepid water and soap), but cost increases and color vividness decreases
Solution Approach 1:
The patent employs cyclodextrins as temporary, inexpensive carriers for acid dye molecules during the writing process. These cyclodextrin-dye complexes provide improved washability without requiring expensive polymeric dyes. The cyclodextrins serve their function temporarily during application and initial drying, then naturally degrade or wash away, leaving the vibrant acid dye color while maintaining cold water washability
3Illumination intensity
If conventional acid dyes are used, then color vividness is improved, but washability with cold water deteriorates
Solution Approach 1:
The patent fundamentally changes the molecular state of the acid dye by forming inclusion complexes with cyclodextrins. This parameter change in the dye's physical-chemical state (from free molecules to complexed molecules) transforms its washing behavior. The complexed structure allows the dye to be washed away with cold water, whereas conventional acid dyes require warm or hot water for removal, thus changing the temperature parameter from 'requires warm water' to 'washable with cold water'
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 combination improves skin washability with cold water without soap and maintains vibrant color, outperforming compositions lacking these components in washability tests on fabrics and skin.
Implementation Method 1
the combined used of at least one alkali metal salt of citrate and at least one cyclodextrin or derivative thereof... this combination improves the skin washability of the ink
Implementation Method 2
The inks contain generally glycol in order to manage surface tension of the inks and to limit the drying of the nib
Data Source
AI summary
The present invention concerns a washable aqueous ink composition comprising: a) at least one alkali metal salt of citrate, b) at least one cyclodextrin or derivative thereof, c) at least one dye. It also concerns a writing instrument comprising it and the use of the association of a) at least one alkali metal salt of citrate and b) at least one cyclodextrin or derivative thereof, to improve the washability and/or vividness of the shades of a washable aqueous ink composition.