Stretchable Absorbent Structure Using Dual Adhesive Zones
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Solution Overview
Problem
Existing stretchable structures in absorbent articles face challenges in achieving compatibility between flexibility and fixability due to the use of high-holding-power hot melt adhesives, which impair flexibility at bonding regions and lead to potential cohesive failure.
Innovation Solution
A stretchable structure comprising a first and second nonwoven sheet layer with elongated elastically stretchable members, where the members are fixed using a high-holding-power first hot melt adhesive at end portions and bonded using a lower-holding-power second hot melt adhesive in the stretchable direction, allowing for flexible bonding and reduced cohesive failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hot melt adhesive having high holding power is used to fix the elastically stretchable members to the sheet layer, then the fixability is improved, but the flexibility is impaired at the bonding portions
Solution Approach 1:
The patent applies different hot melt adhesives with different holding powers to different locations: a first hot melt adhesive with high holding power is used at the end portions of the elastically stretchable members where fixing is critical, while a second hot melt adhesive with lower holding power is used in the intermediate portions where flexibility is needed. This local differentiation resolves the contradiction between fixability and flexibility.
Solution Approach 2:
The bonding structure is segmented into two distinct regions: end portions requiring high holding power for reliable fixing, and intermediate portions requiring lower holding power for maintained flexibility. This segmentation allows each region to have optimized adhesive properties for its specific functional requirements.
2Reliability
If a hot melt adhesive having high holding power is used for both fixing elastically stretchable members and bonding sheet layers, then the fixability is improved, but cohesive failure occurs more easily
Solution Approach 1:
Different hot melt adhesives are selectively applied to different functions: the first hot melt adhesive with high holding power is used specifically for fixing the elastically stretchable members, while the second hot melt adhesive with lower holding power is used for bonding the sheet layers. This local quality differentiation prevents cohesive failure by matching adhesive strength to functional requirements.
Solution Approach 2:
The adhesive system is segmented into two functional components: one optimized for high-strength fixing of elastic members, and another optimized for flexible bonding of sheet layers. This segmentation prevents the cohesive failure that would result from using a single high-holding-power adhesive for both purposes.
3Strength
If the first sheet layer and the second sheet layer are continuously bonded, then the bonding strength is improved, but the flexibility and stretchability are reduced
Solution Approach 1:
The bonding between the first and second sheet layers is segmented rather than continuous. The second hot melt adhesive with lower holding power is applied at specific bonding positions, creating discrete bonding points that provide sufficient bonding strength while leaving gaps that maintain flexibility and allow stretching. This segmented bonding approach resolves the contradiction between bonding strength and flexibility.
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 ensures reliable fixability of elastically stretchable members while maintaining flexibility in the main stretchable region, reducing the risk of cohesive failure and enhancing the overall performance of the absorbent article.
Implementation Method 1
the elastically stretchable member is fixed to at least one of the first sheet layer and the second sheet layer via a first hot melt adhesive
Implementation Method 2
the first sheet layer and the second sheet layer are bonded via a second hot melt adhesive
Implementation Method 3
The elastically stretchable members incorporated between the first sheet layer and the second sheet layer play a role of creating elastically stretchable force
Data Source
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AI summary
To achieve compatibility of flexibility and fixability of elastically stretchable members when hot melt adhesives are used for fixing the elastically stretchable members and bonding a first sheet layer and a second sheet layer. To solve the above-described problem, a first sheet layer (12S) made of a nonwoven fabric; a second sheet layer (12H) made of a nonwoven fabric opposed to one side of the first sheet layer (12S); and a plurality of elongated elastically stretchable members (19) provided along the stretchable direction at intervals from each other between the first sheet layer and the second sheet layer are provided. At least a part of each end of the elastically stretchable member (19) is fixed to at least one of the first sheet layer (12S) and the second sheet layer (12H) only via a first hot melt adhesive (71). The first sheet layer (12S) and the second sheet layer (12H) are bonded via a second hot melt adhesive (72) in a range in the stretchable direction corresponding to a space between the both ends of the elastically stretchable member (19). The holding power of the first hot melt adhesive (71) is higher than the second hot meld adhesive (72).