Spunbond Nonwoven Diffuser Airflow for Isotropic Fabric Strength
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Solution Overview
Problem
Spun-bonded fabrics typically exhibit higher strength in the machine direction than in the transverse direction, resulting in anisotropic properties, and achieving isotropic strength and homogeneous filament deposition remains a challenge.
Innovation Solution
The method involves spinning thermoplastic filaments, cooling them, and then passing them through a stretcher with primary air, followed by a diffuser where secondary air is introduced to create a specific air flow ratio, ensuring the filaments are deposited uniformly, with the primary air flow being significantly greater than the secondary air flow, and using a diverging diffuser with adjustable air inlets to achieve balanced tensile strengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional deposition methods are used, then the fabric achieves adequate strength properties, but the filament deposition is non-uniform, resulting in inhomogeneous fabric structure
Solution Approach 1:
The patent introduces secondary air as an intermediary element between the primary air flow and the filament deposition process. This secondary air acts as a mediator that gently redistributes filaments during deposition, creating a more uniform fabric structure while maintaining the necessary strength properties
Solution Approach 2:
By changing the air flow parameters through controlled secondary air injection at specific ratios and locations, the patent achieves more uniform filament distribution during deposition, thereby improving manufacturing precision and deposition uniformity
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 spun-bonded fabrics with tensile strength ratios between 0.8 and 1.2 in the machine direction to transverse direction, achieving isotropic strength and highly homogeneous deposition, enhancing both the strength and uniformity of the fabric.
Implementation Method 1
the primary and secondary air flow with the filaments in the travel direction through the diffuser
Implementation Method 2
a diffuser where secondary air is introduced to create a specific air flow ratio
Implementation Method 3
for cooling the spun filaments, a cooler is required with at least one cooling chamber in which the filaments are exposed to cooling air
Implementation Method 4
the filaments are spun using at least one spinner
Data Source
AI summary
A method of making a spun-bond nonwoven fabric of thermoplastic filaments has the steps of first spinning the thermoplastic filaments, then cooling the spun filaments, and then conducting the cooled and spun filaments in a travel direction through a stretcher with primary air such that the primary air exits a downstream end of the stretcher with the filaments at a predetermined primary air volume/flow VP. The filaments and substantially all of the primary air are passed together as a flow from the downstream end of the stretcher into a diffuser. Secondary air is introduced into the flow at a secondary air volume/flow VS such that a ratio VP/VS of the primary rate VP to the secondary rate is equal to at least 4.5 and the primary and secondary air flow with the filaments in the travel direction through the diffuser.