Wetness Indicating Ink Composition for Hygienic Articles
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Solution Overview
Problem
Existing inkjet printing technologies for hygienic articles, such as diapers, face challenges in achieving high-speed, high-quality printing with rapid dry times and smear resistance on non-porous and semi-porous substrates, particularly with binary array printers, where previous inks take more than 3 seconds to dry and are not designed for these printers.
Innovation Solution
A method using an ink composition with a ketone solvent, hydroxypropylcellulose as a water-soluble binder resin, and a water-soluble dye, which dries in one second or less on semi-porous surfaces, enabling rapid and smear-resistant printing suitable for binary array printers, and changes or dissolves upon contact with water or bodily fluids to indicate wetness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional inkjet inks are used for printing on hygienic articles, then print quality and color contrast can be achieved, but the dry time exceeds 3 seconds and smearing occurs on non-porous and semi-porous substrates
Solution Approach 1:
The patent modifies the chemical composition parameters of the ink by incorporating fast-drying solvents (isopropanol, acetone, ethyl acetate) in specific proportions (70-95% by weight), along with water-soluble resins and surfactants. This parameter change enables the ink to dry within 1 second on semi-porous substrates while maintaining smear resistance, directly resolving the contradiction between drying speed and reliability.
2Productivity
If high-speed binary array printing is implemented, then productivity increases, but existing inks are not designed for these printers and take too long to dry
Solution Approach 1:
The ink formulation uses volatile organic solvents (isopropanol, acetone, ethyl acetate) that evaporate rapidly, reducing dry time to 1 second or less. This parameter change in solvent composition enables synchronization with high-speed binary array printing processes operating at line speeds of 100-500 meters per minute, eliminating the time loss that previously limited productivity.
Solution Approach 2:
The patent leverages the vapor pressure and evaporation characteristics of the solvent system to achieve rapid drying without requiring additional pneumatic or hydraulic drying systems. The natural evaporation of isopropanol, acetone, and ethyl acetate provides sufficient drying speed for high-productivity printing operations.
3Manufacturing precision
If ink volume is increased to achieve high color contrast, then print quality improves, but dry time increases and smearing occurs
Solution Approach 1:
The patent adjusts the solvent composition parameters to include fast-evaporating components (acetone with 230 mmHg vapor pressure, isopropanol with 133 mmHg vapor pressure) that enable rapid drying even at higher ink volumes. The surfactant concentration (0.1-5% by weight) is also optimized to ensure proper wetting and distribution, allowing high color contrast without extending dry time or causing smearing.
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 ink composition allows for high-speed, high-quality printing with rapid dry times and effective wetness indication, ensuring timely detection of soiling without premature degradation, maintaining visibility and contrast on various substrates.
Implementation Method 1
The ink composition may have a dry time of one second or less when printed on a semi-porous surface using a binary array printer
Implementation Method 2
The image acts as a wetness indicator by dissolving in an aqueous fluid
Data Source
AI summary
A method of printing on a hygienic article includes applying droplets of an ink composition with an ink jet printer to a surface of a hygienic article to form a desired image. The ink composition includes an organic solvent, a water-soluble binder resin including hydroxypropylcellulose, and a water-soluble dye. The image acts as a wetness indicator by dissolving in an aqueous fluid.