Depilatory Substrate Surface Free Energy Adhesion
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Solution Overview
Problem
Substrate-based depilatory compositions fail to effectively adhere to the substrate rather than the skin, leading to residual depilatory composition remaining on the skin during removal, making the process messy and inefficient.
Innovation Solution
A depilatory article with a substrate having a surface free energy of at least 30 mJ/m², preferably between 31 mJ/m² to 72 mJ/m², promotes adhesion of the depilatory composition to the substrate, reducing residue and improving removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the depilatory composition is disposed on a substrate, then the need for application implements is eliminated and occlusion is improved, but the composition adheres to the skin rather than the substrate leading to residual mess
Solution Approach 1:
The patent changes the surface free energy parameter of the substrate by applying a corona treatment or plasma treatment, increasing it from typical values (20-40 mJ/m²) to at least 40 mJ/m². This parameter change modifies the substrate's surface properties to enhance its affinity for the depilatory composition, ensuring preferential adhesion to the substrate rather than the skin, thereby reducing residual mess during removal.
Solution Approach 2:
The patent replaces the mechanical adhesion mechanism (relying on physical contact and friction) with a surface energy-based adhesion mechanism. By treating the substrate surface to increase its free energy, the composition adheres through enhanced surface interactions rather than mere mechanical contact, ensuring it stays on the substrate and not the skin during application and removal.
2Reliability
If a release layer is added to protect the depilatory composition, then protection is improved, but the composition may split between substrate and release layer
Solution Approach 1:
The patent balances the surface free energy parameters of three components: the substrate (treated to at least 40 mJ/m²), the release layer (with controlled surface energy), and the depilatory composition. By carefully selecting and treating these surfaces, the patent ensures the composition adheres most strongly to the substrate, less strongly to the release layer, and maintains integrity without splitting during removal.
3Strength
If the substrate surface free energy is increased to at least 30 mJ/m², then adhesion of composition to substrate is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent replaces complex multi-step surface treatments with a single corona treatment or plasma treatment step that can be integrated into existing manufacturing lines. This substitution achieves the required surface free energy (at least 40 mJ/m²) through a well-established, relatively simple process that modifies surface chemistry without requiring multiple sequential operations.
Solution Approach 2:
The patent achieves high adhesion strength (surface free energy ≥40 mJ/m²) through controlled parameter changes in the corona or plasma treatment process, such as adjusting power, treatment duration, and atmospheric conditions. These parameter optimizations allow achieving the target surface energy with minimal treatment time and energy input, reducing manufacturing complexity while maintaining strong adhesion.
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 increased surface free energy of the substrate enhances the adhesion of the depilatory composition, allowing for cleaner removal with less residual composition on the skin, thereby simplifying the depilatory process and reducing messiness.
Implementation Method 1
the adhesion of the depilatory composition to the substrate is promoted
Data Source
Figure 1~2
Figure 3
AI summary
A depilatory article comprising a substrate and a depilatory composition disposed on said substrate forming a coated region of the substrate, wherein at least a portion of the surface of the coated region of the substrate has an average surface free energy measured by the method herein of at least 30 mJ/m2, preferably from 31 mJ/m2 to 72 mJ/m2, more preferably from 32 mJ/m2 to 55 mJ/m2, even more preferably from 33 mJ/m2 to 46 mJ/m2 and even more preferably still from 34 mJ/m2 to 38 mJ/m2.