Wholly Aromatic Polyamide Filament Coagulation
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Solution Overview
Problem
Conventional methods for manufacturing wholly aromatic polyamide filaments result in irregular physical properties between the surface and inside of the spun material, limiting spinning and take-up velocity, and causing environmental contamination due to the lack of a recycling system for coagulants.
Innovation Solution
A multi-stage coagulant injection process with sequentially lowered sulfuric acid concentration is employed, allowing for uniform coagulation of the surface and inside of the spun material, and the reuse of coagulants to improve the crystallinity, apparent crystal size, and reduce paracrystalline defects, thereby enhancing strength and modulus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the spun material is fed into a coagulation tank through a non-coagulation fluid layer and coagulated in the tank, then the coagulation process is simplified, but the surface of the spun material is coagulated faster and more than inside, causing irregular physical properties between surface and inside
Solution Approach 1:
The coagulation process is divided into multiple stages with different coagulants having progressively lowered sulfuric acid concentrations (e.g., first coagulant at 90-95%, second coagulant at 80-85%, third coagulant at 70-75%). This segmentation allows the surface to be coagulated by stronger coagulants while the inside is coagulated by weaker coagulants, achieving uniform coagulation throughout the spun material.
Solution Approach 2:
Different regions of the spun material (surface vs. inside) are subjected to different coagulation conditions. The surface receives stronger coagulants with higher sulfuric acid concentrations, while the inside receives weaker coagulants with progressively lowered concentrations, ensuring both surface and inside achieve uniform coagulation without excessive surface coagulation.
2Productivity
If high spinning and take-up velocity is applied, then productivity is improved, but thread cutting and staple generation occur due to irregular coagulation, limiting velocity to below 600 m/min
Solution Approach 1:
The multi-stage coagulation process is performed before the spun material is taken up at high velocity. By completing the coagulation process in advance with proper uniformity, the filament structure is stabilized, allowing subsequent high-velocity spinning and take-up operations to proceed without thread cutting or staple generation.
3Ease of operation
If coagulant is not recycled and reused, then the coagulation process is simpler to operate, but production costs increase and environmental contamination occurs
Solution Approach 1:
The coagulant solution after use is recovered and reused as a coagulant in subsequent processing stages. The spent coagulant from one stage becomes the input coagulant for the next stage, reducing waste and environmental contamination while maintaining operational simplicity through an integrated recycling system.
Solution Approach 2:
The sulfuric acid concentration of the coagulant is progressively lowered through multiple stages (e.g., 90-95% → 80-85% → 70-75%). This parameter change allows the coagulant to be effectively reused across stages, with each stage utilizing coagulant of appropriate strength for its specific coagulation requirements.
4Device complexity
If injection velocity is not controlled based on dilution level of sulfuric acid, then the injection process is simpler, but the surface and inside of the spun material cannot be evenly and uniformly coagulated
Solution Approach 1:
The injection velocity of the coagulant is controlled based on feedback regarding the dilution level of sulfuric acid in the coagulant solution. This feedback mechanism ensures that injection velocity is appropriately adjusted to achieve uniform coagulation, with the control system responding to the actual state of the coagulant solution.
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 process enables high velocity spinning without thread cutting, achieving improved strength and modulus with reduced environmental impact by uniformly coagulating the spun material and reusing coagulants, resulting in higher crystallinity and larger apparent crystal size with lower paracrystalline defects.
Implementation Method 1
passing the spun material through a non-coagulation fluid layer into a coagulant tank
Implementation Method 2
coagulated in the tank, surface of the spun material is coagulated faster and more than inside
Data Source
AI summary
Disclosed are wholly aromatic polyamide filament and a method of manufacturing the same, characterized by comprising multi-stage injection of a coagulant with sulfuric acid concentration lowered sequentially stage by stage, to a spun material fed into a coagulant injection tank. The present invention enables increase of a spinning and take-up velocity without occurrence of thread cutting by uniformly and evenly coagulating surface and inside of the spun material. In addition, the present invention recovers the coagulant or water already used and reuses the recovered coagulant or water in the earlier stages, so that it has advantages of saving production costs and reducing environmental contamination. Accordingly, the wholly aromatic polyamide filament produced according to the present invention has high crystallinity X, large apparent crystal size ACS and reduced defects in the crystal itself, thereby exhibiting more improved physical properties such as strength and modulus.