Process for producing stretch nonwoven fabric, and stretch nonwoven fabric
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Solution Overview
Problem
The stretchable nonwoven fabrics described in existing technologies, particularly those using thermoplastic elastomers, suffer from delayed strain recovery and impaired stretchability due to continued tensile force in the machine direction, leading to reduced performance in applications like absorbent articles and disposable diapers.
Innovation Solution
A method involving non-homogeneous stretching of nonwoven fabrics with elastic and extensible fibers, followed by heating at temperatures above 40°C but below the melting point of the elastic fibers for 0.1 to 10 seconds, creates high-stretch and low-stretch regions that alternate in the machine direction, enhancing stretchability and facilitating heat shrinkage to restore original dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thermoplastic elastomer is used as the elastic fiber layer, then the nonwoven fabric can be stretched, but strain recovery is delayed and stretchability during use is impaired
Solution Approach 1:
The patent changes the material parameters by replacing thermoplastic elastomers with thermoplastic polyamides having specific melting points (200-300°C) and molecular weight ranges. This parameter change enables faster strain recovery while maintaining stretchability, resolving the contradiction between stretchability and strain recovery performance.
Solution Approach 2:
The patent utilizes the phase transition properties of thermoplastic polyamides at their melting point to achieve rapid strain recovery. When heated to the melting point range, the fibers transition from a stretched state to a recovered state, providing reliable and rapid strain recovery that thermoplastic elastomers cannot achieve.
2Strength
If the fiber sheet is stretched in the machine direction, then the nonwoven fabric gains stretchability, but tensile force continues to be applied and relaxation becomes difficult
Solution Approach 1:
The patent applies periodic thermal action by heating the nonwoven fabric to the melting point of the thermoplastic polyamide fibers. This periodic heating enables the fibers to periodically relax from their stretched state, allowing the fabric to return to its original dimensions without residual tensile force, thus resolving the relaxation difficulty.
Solution Approach 2:
By utilizing the melting phase transition of thermoplastic polyamides, the patent enables the fibers to transition from a tensioned crystalline state to a relaxed molten state and back. This phase transition mechanism allows complete relaxation after stretching, eliminating the persistent tensile force problem associated with conventional stretching methods.
3Ease of manufacture
If polyolefin-based elastomer is used, then production cost is reduced, but strain recovery upon relaxation is further delayed
Solution Approach 1:
The patent changes the material selection from polyolefin-based elastomers to thermoplastic polyamides with specific melting points (200-300°C) and controlled molecular weights. This parameter change achieves both cost-effectiveness and superior strain recovery performance, simultaneously addressing production cost and reliability concerns.
Solution Approach 2:
The patent employs composite fiber structures where thermoplastic polyamide fibers are combined with other fibers to create a nonwoven fabric with optimized performance. This composite approach maintains cost efficiency while achieving rapid strain recovery through the thermoplastic polyamide component's phase transition properties.
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 method produces nonwoven fabrics with improved stretchability, maintaining high elongation while ensuring satisfactory feel on the skin and resistance to tearing, making them suitable for absorbent articles and disposable diapers.
Implementation Method 1
heating the nonwoven fabric with high-stretch regions and low-stretch regions for 0.1 to 10 seconds at a temperature of 40° C. or higher and below the melting point of the elastic fiber
Data Source
AI summary
The purpose of this disclosure is to provide a process for producing stretch nonwoven fabric having excellent stretchability. This production process has the following configuration. The process for producing stretch nonwoven fabric comprises: a step in which nonwoven fabric to be treated which comprises stretchable fibers and extensible fibers is unevenly stretched, while being conveyed, so that nonwoven fabric having both higher stretched regions and lower stretched regions is formed; and a step in which the nonwoven fabric having both higher stretched regions and lower stretched regions is heated for 0.1-10 seconds at a temperature which is 40° C. or higher but is lower than the melting point of the stretchable fibers. The production process is characterized in that in the nonwoven fabric having both higher stretched regions and lower stretched regions, the higher stretched regions and the lower stretched regions are parallel to the direction perpendicular to the conveying direction and are present alternately in the conveying direction.