Meta-Aramid Fiber Processing to Cut Solvent Retention and Yellowing
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Solution Overview
Problem
Conventional methods for producing meta-type wholly aromatic polyamide fibers face challenges such as solvent retention, yellowing, and organic gas generation during high-temperature processing, leading to inferior heat contraction stability and mechanical properties.
Innovation Solution
A method involving wet spinning of a meta-type wholly aromatic polyamide polymer solution with a salt, followed by coagulation in an amide solvent and water bath, subsequent plastic stretching, rinsing with water, saturated steam treatment, and dry heat treatment to minimize solvent retention and enhance fiber properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wet spinning method is used to produce meta-type wholly aromatic polyamide fiber, then fiber production is achieved, but solvent remains trapped in the fiber causing yellowing and organic gas generation during high-temperature processing
Solution Approach 1:
The patent applies preliminary action by performing a saturation treatment with steam before the final drying process. This preliminary steam treatment saturates the fiber structure, allowing for more effective solvent removal during subsequent drying at elevated temperatures, thereby preventing solvent retention that causes yellowing and gas generation
Solution Approach 2:
The patent employs parameter changes by controlling the temperature progression through multiple stages: initial drying at moderate temperature, then elevated temperature drying (100-200°C), and finally high-temperature treatment (200-400°C). This staged temperature parameter change enables progressive solvent removal while maintaining fiber structural integrity
2Object-generated harmful factors
If high-temperature treatment is applied to remove solvent, then solvent retention is reduced, but fiber yellowing and mechanical property degradation occur
Solution Approach 1:
The patent applies preliminary action by conducting a saturation treatment with steam before high-temperature drying. This preliminary step prepares the fiber structure to withstand subsequent high-temperature treatment, enabling effective solvent removal while preventing the yellowing and mechanical degradation that would occur with direct high-temperature exposure
Solution Approach 2:
The patent uses steam as an intermediary medium between the solvent-trapped fiber and the high-temperature drying process. The steam saturation treatment acts as a buffer that prepares the fiber structure for high-temperature treatment, mediating the transition to enable solvent removal without direct thermal damage to the polymer structure
3Object-generated harmful factors
If rapid drying is performed to remove solvent, then solvent retention is reduced, but fiber crystallization occurs leading to poor processability
Solution Approach 1:
The patent applies preliminary action by performing steam saturation treatment before the drying process. This preliminary step creates a controlled moisture environment that prevents rapid solvent evaporation and subsequent crystallization, allowing for gradual solvent removal that maintains fiber amorphous structure and processability
Solution Approach 2:
The patent employs periodic action through a multi-stage drying process with different temperature zones and exposure times. The staged approach includes initial moderate-temperature drying, followed by elevated temperature treatment, and finally high-temperature finishing. This periodic temperature variation enables progressive solvent removal while preventing the sudden crystallization that would occur with rapid single-stage drying
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 method results in fibers with less than 1.0% solvent retention, a dry heat contraction rate of 3% or less at 300°C, and a breaking strength of 3.0 cN/dtex or more, effectively suppressing coloration and gas generation, thereby improving high-temperature performance and stability.
Implementation Method 1
the polymer solution is ejected into a coagulation bath containing an amide solvent and water to coagulate as a porous fibrous material
Implementation Method 2
subjected to a saturated steam treatment... an amount of a solvent remaining in the fiber is 1.0% by weight or less
Implementation Method 3
subjected to a heat treatment... a dry heat contraction rate at 300°C is 3% or less
Data Source
AI summary
Upon producing a meta-type wholly aromatic polyamide fiber by wet spinning a polymer solution containing a meta-type wholly aromatic polyamide containing a m-phenylenediamine isophthalamide skeleton as a major component, and an amide solvent containing a salt, (1) the polymer solution is ejected into a coagulation bath containing an amide solvent and water and containing a salt at a low concentration to coagulate as a porous thread body (fibrous material), (2) which is subsequently stretched in a plastic stretching bath containing an aqueous solution of an amide solvent, (3) is rinsed with water and then subjected to a heat treatment in a saturated steam atmosphere, and (4) is then subjected to a dry heat treatment, so as to produce a novel meta-type wholly aromatic polyamide fiber that contains an extremely small amount of a solvent remaining in the fibers, contains a small amount of a volatile substance harmful in a heat treatment step at a high temperature, is capable of suppressing coloration of a fiber product, and is capable of providing a product with high performance and high quality.