Copolymer Fiber Drying Process Thermal Damage Reduction
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Solution Overview
Problem
Copolymer fibers derived from 5(6)-amino-2-(p-aminophenyl)benzimidazole and para-phenylenediamine terephthaloyl dichloride are prone to thermal damage during drying, leading to yarns with depressed tensile properties, and existing manufacturing processes are expensive with poor investment economics.
Innovation Solution
A continuous process involving drying copolymer fibers at less than 100 °C until moisture content is below 60% and further drying above 150 °C, with additional heating steps up to 350 °C or higher, while applying tension, to minimize thermal damage and enhance fiber strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If copolymer fibers are dried at high temperature to remove moisture quickly, then drying speed is improved, but thermal damage occurs causing depressed tensile properties
Solution Approach 1:
The drying process is divided into multiple sequential stages with different temperature ranges and moisture content targets. The first stage dries from 100-150°C to 60-70% moisture content, the second stage dries to 30-40% moisture content, and the third stage completes drying to less than 5% moisture content. This segmentation allows gentle removal of bulk moisture initially, then progressively higher temperatures are applied as moisture content decreases, preventing thermal damage while maintaining productivity.
Solution Approach 2:
The method applies preliminary low-temperature drying before high-temperature drying. By first removing the bulk of moisture at lower temperatures (100-150°C) to reduce moisture content to 60-70%, the subsequent high-temperature drying (above 200°C) can be applied safely to remove remaining moisture without causing thermal damage to the fiber structure.
2Strength
If copolymer is isolated from polymerization solution and redissolved in sulfuric acid, then fiber quality is improved, but manufacturing cost increases
Solution Approach 1:
The method uses sulfuric acid to perform multiple functions: it serves as the solvent for dissolving the copolymer to form the spinning dope, and also acts as the coagulation bath medium during wet spinning. This eliminates the need for separate solvent removal and redissolution steps, reducing manufacturing complexity and cost while maintaining fiber quality.
Solution Approach 2:
The polymerization solvent is discarded and the copolymer is recovered in a form suitable for direct spinning. The method isolates the copolymer from the polymerization solution and redissolves it in sulfuric acid to form a spinning dope, eliminating the need for expensive specialized polymerization solvents and simplifying the overall manufacturing process.
3Strength
If moisture is removed slowly at low temperature, then thermal damage is minimized, but production time increases
Solution Approach 1:
The drying process is divided into multiple sequential stages with different temperature ranges and moisture content targets. The first stage dries from 100-150°C to 60-70% moisture content, the second stage dries to 30-40% moisture content, and the third stage completes drying to less than 5% moisture content. This segmentation allows gentle removal of bulk moisture initially, then progressively higher temperatures are applied as moisture content decreases, preventing thermal damage while maintaining productivity.
Solution Approach 2:
The drying method dynamically changes temperature parameters based on moisture content. Low temperature (100-150°C) is applied when moisture content is high (60-70%), then temperature is increased to moderate levels (above 200°C) when moisture content is reduced (30-40%), and finally high temperature is applied for complete drying. This parameter change strategy optimizes both protection against thermal damage and drying efficiency.
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 improves the long-term physical properties of copolymer fibers by reducing thermal damage and lowering production costs, resulting in higher tensile strength and more economical manufacturing.
Implementation Method 1
a step of drying a never-dried fiber at less than 100 °C until the moisture content of the fiber is less than 60 weight percent; and (b) a step of further drying the fiber above 150 °C while the moisture content of the fiber is no more than 40 weight percent
Implementation Method 2
the resulting dried fiber is further heated to at least 350 °C in either an additional continuous or separate step
Data Source
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AI summary
The present invention concerns processes for reducing water in never- dried fiber comprising copolymer derived from the copolymerization of para-phenylenediamine, 5 (6) -amino- 2- (p-aminophenyl) benzimidazole, and terephthaloyl dichloride; the process having the following steps in a continuous process, (a) a step of drying a never- dried fiber at less than lOOC until the moisture content of the fiber is less than 60 weight percent; and (b) a step of further drying the fiber above 150 °C while the moisture content of the fibers is no more than 40 weight precent; and the fiber being further heated to at least 350 °C in either an additional continuous or seperate step.