Wetness Indicator Composition for Absorbent Articles
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Solution Overview
Problem
Wetness indicator compositions in disposable absorbent articles face challenges with colorant stability due to pH changes from absorbent cores and surfactants, leading to premature color changes, especially in cellulose-free designs with high levels of adhesive and surfactants, requiring optimization of acid content and adhesion properties.
Innovation Solution
A wetness indicator composition comprising a colorant, matrix, and stabilizer, with a balanced acidic stabilizer to maintain the colorant's initial state until a wetness event, ensuring adherence and visibility of the color change without bleeding through the substrate, using a combination of rosin esters and quaternary ammonium salts for binding and stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If absorbent cores with high levels of adhesive and surfactants are used in cellulose-free designs, then absorbency and adhesion are improved, but colorant stability deteriorates due to pH changes causing premature color changes
Solution Approach 1:
The patent applies preliminary anti-action by incorporating a stabilizer into the wetness indicator composition before the wetness event occurs. This stabilizer preemptively counteracts the pH-changing effect of alkaline surfactants and adhesives in the absorbent core, preventing premature color changes while allowing the indicator to function normally when wetness occurs.
Solution Approach 2:
The stabilizer acts as an intermediary substance between the colorant and the pH-altering components of the absorbent core. It buffers the chemical interaction, allowing the wetness indicator to remain stable in the presence of high levels of adhesive and surfactant without directly interfering with the color change mechanism when urine is detected.
2Stability of the object's composition
If acid content in wetness indicator composition is increased to maintain colorant stability, then colorant stability is improved, but adhesion to substrate deteriorates due to reduced cohesive strength
Solution Approach 1:
The patent applies parameter changes by carefully controlling the amount and type of stabilizer used in the wetness indicator composition. By optimizing the stabilizer concentration and selecting specific stabilizer compounds, the formulation achieves both colorant stability and adequate adhesion to the substrate, resolving the trade-off between these two properties.
3Strength
If wetness indicator composition adheres strongly to substrate, then adhesion is improved, but fluid wicking deteriorates due to blocked fluid pathways
Solution Approach 1:
The patent applies local quality by creating a wetness indicator composition with differentiated properties: the outer surface maintains adequate adhesion to the substrate through optimized binder content, while the inner structure retains porosity and hydrophilicity to enable efficient fluid wicking. This spatial differentiation of properties allows both adhesion and wicking to function effectively.
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 composition maintains colorant stability and adhesion, ensuring timely and visible color change after a wetness event, even in challenging absorbent article designs, with improved retention and kinetic response.
Implementation Method 1
A wetness indicator composition comprising a colorant, matrix, and stabilizer, with a balanced acidic stabilizer to maintain the colorant's initial state until a wetness event
Implementation Method 2
using a combination of rosin esters and quaternary ammonium salts for binding and stabilization
Implementation Method 3
a colorant adapted to change in appearance, i.e., appear, disappear, change color, etc., upon contact with liquids such as, urine
Data Source
AI summary
An absorbent article of the present invention may comprise a backsheet, a wetness indicator composition, and an absorbent core. The wetness indicator composition may comprise a stabilizer, a colorant, and a matrix. The absorbent core may comprise a nonwoven layer and an absorbent polymer material, and optionally, a thermoplastic adhesive material. The wetness indicator composition may be in direct contact with an inner surface of the backsheet and an outer surface of the nonwoven layer. And, the absorbent polymer material, and optionally, the thermoplastic adhesive material, may be in direct contact with an inner surface of the nonwoven. Further, the absorbent core may be substantially cellulose free and may be oriented in at least one row.