Absorbent Core Bonding Using Selective Hotmelt Adhesive
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Solution Overview
Problem
Conventional absorbent cores with high cellulose content face challenges in bond strength, especially when reduced to thinner, denser forms lacking cellulose, which increases forces during swelling, necessitating improved immobilization techniques for superabsorbent particles.
Innovation Solution
A process involving a hotmelt construction adhesive applied to a more hydrophilic nonwoven, allowing sufficient time for binding before contacting a less hydrophilic nonwoven, with optional fibrous adhesive for superabsorbent immobilization, enhancing bond strength and reducing adhesive usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If absorbent cores are made thinner and denser with reduced cellulose content, then absorbent capacity is improved, but bond strength of core seals deteriorates due to higher expansion forces
Solution Approach 1:
The adhesive is applied to the more hydrophilic nonwoven material in advance, before the bonding step. This preliminary application allows the adhesive to penetrate and bind to the hydrophilic fibers first, creating a strong foundation that can withstand the higher expansion forces generated by thin, dense absorbent cores with reduced cellulose content.
Solution Approach 2:
The patent applies adhesive selectively to the more hydrophilic nonwoven material rather than uniformly to both materials. This local quality approach targets the specific material property (hydrophilicity) that enables better adhesive binding, creating localized strong bonds at the seal interfaces where they are most needed to counteract expansion forces.
2Productivity
If hotmelt adhesive is applied and immediately bonded, then productivity is improved, but bond strength deteriorates due to insufficient binding time
Solution Approach 1:
The adhesive application and bonding operations are separated in time, with the adhesive applied first and allowed to bind to the hydrophilic nonwoven material before the actual bonding step. This time separation ensures sufficient binding occurs while maintaining production efficiency through a structured two-step process.
Solution Approach 2:
The patent controls the timing parameters of the adhesive process by specifying that bonding occurs after a sufficient time interval following adhesive application. This parameter change (time delay) allows the adhesive to transition from application to effective bonding state, ensuring strong adhesion without compromising productivity through optimized process timing.
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
This approach achieves improved bonding with reduced adhesive usage and lower bonding pressures, maintaining strength even after storage at elevated temperatures, suitable for thin absorbent cores with high absorbent capacity and minimal cellulose content.
Implementation Method 1
applying the adhesive only to the first more hydrophilic nonwoven or first part thereof... by use of a hotmelt construction adhesive... bonding the first nonwoven material or first part of the first nonwoven material via the construction adhesive to the second nonwoven material
Implementation Method 2
it has been found important to allow it to bind to the more hydrophilic nonwoven material in molten state, before binding it to the less hydrophilic nonwoven material. This cool down is for example achieved when there is a significant time/distance between the application and bonding stages
Data Source
AI summary
A process is provided for making a bond between a first, relative hydrophilic nonwoven and a second relatively less hydrophilic nonwoven by use of a construction adhesive, by applying the adhesive only to the first more hydrophilic nonwoven; also provided are absorbent cores for absorbent article comprising such bonded nonwovens, and such absorbent articles.