Sheath-Core Spandex Fibers for Hot Melt Adhesion
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Solution Overview
Problem
The existing methods for bonding spandex fibers to nonwoven substrates in disposable diapers face significant adhesion issues due to chemical incompatibility between hot melt adhesives and spandex fibers, leading to high adhesive consumption costs and inadequate bonding strength.
Innovation Solution
The use of sheath-core spandex fibers with a higher-melting polyurethaneurea core and a low-melting thermoplastic polymer sheath, such as polystyrene, enhances bonding by melting and softening at appropriate temperatures to form stronger adhesive sites with hot melt adhesives, reducing the required adhesive amount and improving bonding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hot melt adhesive is applied to bond spandex fibers to nonwoven substrates, then bonding strength is improved, but adhesive consumption cost increases due to chemical incompatibility
Solution Approach 1:
The patent changes the chemical composition parameters of the spandex fiber by incorporating thermoplastic polymers (such as polyethylene, polypropylene, or polyester) into the fiber structure. This parameter change makes the fiber surface more compatible with hot melt adhesives, improving bonding efficiency and reducing adhesive consumption while maintaining bonding strength.
Solution Approach 2:
The patent creates a composite fiber structure where spandex elastomer is combined with thermoplastic polymers. This composite material approach allows the fiber to possess both the elastic properties of spandex and the adhesive compatibility of thermoplastics, thereby reducing the quantity of adhesive needed while maintaining bonding strength.
2Strength
If spandex strands are overloaded with hot melt adhesive to improve bonding, then bonding strength is improved, but cost increases
Solution Approach 1:
The patent incorporates inexpensive thermoplastic polymers directly into the spandex fiber structure. These thermoplastics serve as built-in bonding agents that are already present in the fiber, eliminating the need for excessive application of separate hot melt adhesives, thereby reducing overall manufacturing costs while maintaining bonding strength.
Solution Approach 2:
By modifying the chemical composition of the spandex fiber to include thermoplastic components, the patent changes the bonding parameters of the fiber itself. This reduces the dependency on high quantities of external adhesive application, thereby lowering material costs and simplifying the manufacturing process.
3Strength
If thermoplastic polymer sheath is used in spandex fiber, then bonding strength with adhesive is improved, but fiber complexity increases
Solution Approach 1:
The patent merges the bonding function with the fiber structure itself by incorporating thermoplastic polymers into the spandex fiber. This integration eliminates the need for separate bonding mechanisms or complex multi-layer adhesive systems, as the bonding capability is built into the fiber structure, thereby reducing overall system complexity while improving bonding strength.
4Ease of manufacture
If adhesive add-on is reduced to lower cost, then manufacturing cost is reduced, but bonding strength decreases
Solution Approach 1:
The patent changes the chemical parameters of the spandex fiber by incorporating thermoplastic polymers that are chemically compatible with hot melt adhesives. This parameter change improves the inherent bonding capability of the fiber, allowing for reduced adhesive application while maintaining adequate bonding strength, thereby lowering manufacturing costs without sacrificing bond quality.
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 results in improved bonding strength between spandex fibers and substrates, reducing adhesive costs and maintaining desirable elastic properties, with enhanced bond retention and reduced tack, thus optimizing the performance of elastic fibers in disposable diapers.
Implementation Method 1
the latter melts or softens the bonding enhancing additive to form bond sites with hot melt adhesives and nonwoven substrates upon cooling
Implementation Method 2
when the melt adhesive is sprayed onto the elastic strands at temperatures range 160°C-200°C, which is above the glass transition temperature of the thermoplastic polymer sheath
Implementation Method 3
the elastic material is attached to the polyolefin nonwoven substrate when the melt adhesive is sprayed onto the elastic strands
Data Source
AI summary
An elastic fiber is provided that includes polyurethane and/or polyurethaneurea and an additive such as polystyrene, an acrylic polymer, polyvinylpyrrolidone, copolymers thereof, derivatives thereof, and combinations thereof. The elastic fiber is useful in laminate structures, such as disposable hygiene articles as wells as in knit, woven and nonwoven fabric constructions.