Nonwoven Fabric Interlayer Adhesion via Localized Polypropylene
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Solution Overview
Problem
Existing underbody shielding materials face issues with peeling and elasticity due to inadequate interlayer adhesion and density, leading to compromised sound absorbing characteristics and resistance to external forces.
Innovation Solution
A nonwoven fabric with a two-layer structure comprising a long fiber polyester resin layer and a short fiber polyester resin layer, where a flow-solidified undrawn polypropylene resin is localized between them, providing enhanced interlayer adhesion and elasticity through thermal bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If one of two types of fibers having different melting points is completely melted for adhesion, or a composite-type adhesive fiber uniformly blended in a nonwoven fabric layer, then interlayer adhesion is achieved, but the density of the adhesive component between the layers cannot be sufficiently taken and peeling is liable to occur
Solution Approach 1:
The adhesive component is not uniformly distributed but localized at the interface between nonwoven fabric layers through flow-solidification of undrawn polypropylene resin. This concentrates the adhesive function where it is most needed (at the bonding interface) rather than dispersing it throughout the entire layer, achieving both strong adhesion and peeling resistance.
Solution Approach 2:
The undrawn polypropylene resin is prepared in advance as a separate component that will flow and solidify during the heating process to create the adhesive bond. This preliminary preparation of the adhesive material in a controllable state allows for optimized bonding performance.
2Strength
If polyester-based composite fibers are widely distributed in the nonwoven fabric layer for thermal adhesion, then adhesion is achieved, but it is difficult to balance both prevention of peeling and impartment of elasticity to the molded product
Solution Approach 1:
The adhesive function is segmented from the bulk nonwoven fabric structure. Instead of having adhesive fibers distributed throughout the entire layer, the undrawn polypropylene resin is positioned as a distinct component that flows and solidifies specifically at the interface, separating the adhesive function from the structural function of the nonwoven fabric.
Solution Approach 2:
The adhesive component is localized at the interface between layers rather than being uniformly distributed. This local concentration of adhesive material at the bonding interface provides strong adhesion while maintaining the elasticity and flexibility of the bulk nonwoven fabric structure.
3Quantity of substance
If no film is used for interlayer adhesion to maintain air permeability and sound absorbing characteristics, then air permeability is preserved, but density of the adhesive component between the layers cannot be sufficiently taken and peeling occurs
Solution Approach 1:
The adhesive component itself forms a porous, non-film structure through the flow-solidification of undrawn polypropylene resin. This allows the adhesive to provide bonding strength while maintaining air permeability, as the solidified resin creates a three-dimensional network rather than a continuous film that would block air flow.
Solution Approach 2:
The adhesive function is extracted from the traditional film form and implemented through a different mechanism (flow-solidification of undrawn resin). This removes the harmful effect of films blocking air permeability while retaining the beneficial adhesive function.
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 solution achieves high peeling strength, excellent sound absorbing properties, and resistance to external forces by ensuring strong interlayer bonding and maintaining air permeability, while preventing peeling and wrinkles in the molded product.
Implementation Method 1
a flow-solidified undrawn polypropylene layer is localized at an interface between the above long fiber nonwoven fabric layer and the above short fiber nonwoven fabric layer
Implementation Method 2
thermal bonding
Implementation Method 3
both the layers being compression-molded into a predetermined shape
Data Source
AI summary
An object is to realize a base material nonwoven fabric for molding excellent in handling as a material, by preventing peeling between laminated components constituting the base material for molding; and even after the base material is reheated and molded, to provide a molded product having excellent elasticity resistant to external forces such as flying debris or the like, and while maintaining peeling resistance, capable of realizing excellent sound absorbing characteristics, by suppressing air permeability inhibition due to the adhesive component. A base material nonwoven fabric for molding in a predetermined shape by heat molding, characterized by having a two-layer structure of a long fiber nonwoven fabric layer comprising at least a polyester resin and a short fiber nonwoven fabric layer comprising a polyester resin, wherein a flow-solidified undrawn polypropylene layer is localized in the vicinity of an interface between the long fiber nonwoven fabric layer and the short fiber nonwoven fabric layer.