Nonwoven Web Suction Gap for Thickness and Strength Balance
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Solution Overview
Problem
Existing nonwoven web production methods face challenges in achieving a balance between thickness, softness, and strength, often resulting in nonwoven webs with low strength and surface defects due to backflow effects during the deposition process.
Innovation Solution
The introduction of a suction gap between preconsolidation stages in the production process, combined with asymmetrical diffuser configurations and controlled air suction velocities, helps in relaxing the nonwoven web and preventing backflow, allowing for the creation of high-loft nonwovens with enhanced strength and homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If crimped filaments are used to achieve considerable thickness and softness, then the nonwoven web gains high loft and softness, but the tensile strength and abrasion resistance deteriorate
Solution Approach 1:
The patent divides the nonwoven web into two distinct layers: a lower layer with crimped filaments providing thickness and softness, and an upper layer with straight filaments providing strength and abrasion resistance. This segmentation allows each layer to fulfill its specific functional requirement without compromising the other properties.
Solution Approach 2:
The patent creates a composite nonwoven structure by combining two different types of filaments (crimped and straight) in a single web. The crimped filaments form the base layer for loft and softness, while straight filaments are overlaid to provide structural integrity and surface durability, achieving a synergistic combination of properties.
2Productivity
If suction velocity is increased to improve deposition efficiency, then production speed improves, but backflow effects increase causing defect sites and filament clumps
Solution Approach 1:
The patent applies different suction velocities to different regions of the deposit conveyor. The first region (upstream) operates at a lower suction velocity to prevent backflow and ensure homogeneous deposition, while the second region (downstream) operates at a higher suction velocity to maintain production efficiency. This local differentiation of suction characteristics resolves the contradiction between productivity and surface 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 enables the production of nonwoven webs with optimal thickness, softness, and strength, while minimizing surface defects and filament clumps, ensuring a consistent and high-quality product.
Implementation Method 1
at least one suction device is provided with which the air or process air in the deposit region of the filaments and/or at the first preconsolidation device can be sucked through the deposit conveyor or through the mesh belt
Implementation Method 2
at least one first preconsolidater for preconsolidating the nonwoven web is provided downstream of the deposit region of the filaments
Data Source
AI summary
A nonwoven web is made by displacing an air-permeable mesh-belt conveyor in a horizontal travel direction and spinning and then depositing crimped continuous filaments as a web at a deposit region on the air-permeable mesh-belt conveyor. A first preconsolidation stage is provided downstream of the deposit region and a second preconsolidation separated by a suction gap from the first stage. Air is drawn air through the web and the conveyor at the deposit region at a first predetermined speed, the first and second consolidation stages at a second and third predetermined speeds, and at the suction gap either not at all or at a fourth predetermined equal to at most substantially less than the second predetermined speed.