Disposable Wearable Article Lotion Zone Water Activity Control
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Solution Overview
Problem
Disposable wearable articles, such as disposable diapers, often cause skin problems like rashes due to friction or dryness, and water-containing hydrophilic lotions used to reduce friction can be prone to microbial growth, leading to reduced shelf life without preservatives.
Innovation Solution
A disposable wearable article with a nonwoven top sheet featuring a lotion-bearing zone containing a hydrophilic lotion with glycerin, which maintains a low water activity value and sufficient surface moisture, thereby suppressing microbial growth and extending shelf life without preservatives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a water-containing hydrophilic lotion is applied to the top sheet to reduce friction and keep skin from drying, then skin comfort is improved, but shelf life is impaired due to microbial growth
Solution Approach 1:
The patent converts the harmful effect of water (promoting microbial growth) into a beneficial effect by using glycerin to bind water molecules, reducing water activity to 0.6 or less. This prevents microbial growth while maintaining skin moisturizing effects, thus converting the harm of water-containing lotion into a benefit for both shelf life and skin comfort
Solution Approach 2:
The patent changes the key parameter of water activity from its natural state (above 0.6) to a controlled state (0.6 or less) through the addition of glycerin. This parameter change fundamentally alters the microbial growth environment while preserving the moisturizing function, resolving the contradiction between shelf life and skin comfort
2Reliability
If a preservative is added to the hydrophilic lotion to extend shelf life, then microbial growth is suppressed, but skin problems occur in some wearers
Solution Approach 1:
Instead of using preservatives that cause skin irritation, the patent uses glycerin to create an environment hostile to microorganisms by reducing water activity. This converts the approach from chemical preservation to physical/chemical environment control, eliminating preservative-related skin problems while maintaining shelf life
Solution Approach 2:
Glycerin acts as an intermediary substance that mediates between the conflicting requirements of microbial suppression and skin safety. It creates a low water activity environment that prevents microbial growth without the harmful side effects of preservatives, thus serving as a safe mediator for both shelf life extension and skin protection
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 use of glycerin in the hydrophilic lotion keeps the water activity low, ensuring sufficient surface moisture and preventing microbial growth, thus improving the shelf life of disposable wearable articles without the need for preservatives.
Implementation Method 1
the hydrophilic lotion has a water activity value of 0.8 or less
Implementation Method 2
the lotion-bearing zone has a surface moisture percentage of 3 to 10%
Data Source
AI summary
A disposable wearable article including a top sheet having a skin-touching region that is brought into contact with skin of a wearer, the top sheet being made from nonwoven fabric, wherein the skin-touching region has a lotion-bearing zone which bears a hydrophilic lotion containing water and glycerin, the lotion-bearing zone having a MD dimension of 30 mm or larger and a CD dimension of 5 mm or larger, wherein the lotion-bearing zone has a surface moisture percentage of 3 to 10%, wherein the hydrophilic lotion has a water activity value of 0.8 or less, and wherein the hydrophilic lotion is free of preservatives.