High Molecular Weight Polyamide Filaments via Solid Phase Polymerization
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Solution Overview
Problem
Existing methods for producing high molecular weight polyamide filaments face challenges such as limited chemical and abrasion resistance, process complications due to catalyst addition, and polymer degradation from high viscosity, which hinder the production of filaments with desired properties for industrial applications like papermaking machine felts.
Innovation Solution
A process involving solid phase polymerization (SPP) followed by melt phase polymerization (MPP) of polyamide flake material, where conditioned SPP flakes are melted in a non-vented extruder with a phenolic antioxidant stabilizer, and the molten polymer is conveyed through a transfer line and spinneret to produce filaments with a formic acid relative viscosity (RV) greater than 190, maintaining specific temperature and pressure ratios to achieve high tenacity and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If catalyst amount is increased to increase polymer molecular weight, then RV of filaments is improved, but process problems occur including injection port pluggage and equipment complications
Solution Approach 1:
The patent applies preliminary action by conducting solid phase polymerization (SPP) on polyamide flake material before melt spinning to increase molecular weight. This pre-treatment step builds up the polymer chains and increases RV before the actual filament formation process, thereby achieving high RV filaments without requiring excessive catalyst amounts during the main polymerization process, thus avoiding injection port pluggage and equipment complications
2Reliability
If stabilizer amount is increased to improve chemical resistance, then chemical resistance is improved, but excess foaming occurs during polymerization
Solution Approach 1:
The patent applies preliminary action by performing solid phase polymerization before melt spinning, which allows stabilizers to be incorporated during the SPP stage rather than during autoclave polymerization. This timing difference prevents excess foaming that would occur if stabilizers were added to autoclaves, while still achieving the desired chemical resistance in the final filament product
3Manufacturing precision
If polyamide flake is melt-blended with additive concentrate to increase RV, then RV of filaments is improved, but separate preparation steps are required increasing process complexity
Solution Approach 1:
The patent merges the polymerization and filament formation operations by using a non-vented extruder that performs both functions in sequence. The extruder melts the SPP-treated polyamide flake and immediately forms filaments, eliminating the need for separate preparation steps and reducing overall process complexity while maintaining high RV values
4Manufacturing precision
If post spin SPP process is used to increase RV, then RV of fibers is improved, but additional equipment and time are required increasing cost and production time
Solution Approach 1:
The patent applies preliminary action by performing solid phase polymerization on the polyamide flake material before it enters the extruder, rather than after spinning. This pre-treatment increases the molecular weight and RV of the polymer chains before filament formation, eliminating the need for post-spin SPP equipment and additional processing time while achieving the same or better RV values
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 effectively produces polyamide filaments with RV values exceeding previous reports, offering enhanced tenacity and chemical resistance, making them suitable for industrial uses such as papermaking machine felts with improved durability and performance.
Implementation Method 1
The process involves melt phase polymerizing of polyamide flake material... introducing at a flake feed end of the extruder a liquid phenolic antioxidant stabilizer
Implementation Method 2
drying at least a portion of the inert gas with a serially connected dual desiccant bed regenerative drying system
Data Source
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AI summary
Disclosed is the preparation of very high molecular weight polyamide, e.g., nylon, filaments., as indicated by such filaments exhibiting a very high Relative Viscosity (RV) value. Such filaments can be used to prepare polyamide staple fibers which are especially useful for industrial applications such as in papermachine felts. The filament preparation process involves a melt phase polymerization (MPP) procedure, optionally carried out in combination with a solid phase polymerization (SPP) procedure. Both of these procedures serve to increase the molecular weight and hence the RV of the polyamide filaments produced. These procedures are conducted under selected controlled conditions which permit realization of polyamide filaments of about 2 to 100 denier and which have RV values of greater than about 190. Such filaments also exhibit excellent tenacity and tenacity resistance properties.