Halide Ion Exchange in Polymeric Fibers for Sulfur Removal
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Solution Overview
Problem
The existing methods for manufacturing high tenacity fibers from copolymers of 5(6)-amino-2-(p-aminophenyl)benzimidazole, para-phenylenediamine, and terephthaloyl dichloride are expensive and inefficient, with unique challenges not addressed by processes used for para-aramid fibers, necessitating new techniques to improve tenacity and economic viability.
Innovation Solution
A method involving contacting never-dried sulfate anion-containing polymeric fibers with an aqueous acid containing halide ions to displace sulfate anions and then rinsing to remove them, reducing sulfur content in the fibers, which includes using halide anions like Cl- and Br- in acids such as hydrochloric acid, and subsequent steps to achieve low sulfur content and improved tenacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If copolymer is solutioned in sulfuric acid to spin fibers, then manufacturing economics are improved, but sulfur content in fibers increases
Solution Approach 1:
The patent applies preliminary action by treating the fiber with aqueous halide acid before final drying to displace sulfate anions with halide anions. This pre-treatment step removes sulfur while the fiber is still in a state that allows effective ion exchange, preventing sulfur from being locked into the fiber structure during subsequent drying and heat treatment processes.
Solution Approach 2:
The patent changes the chemical environment parameter by introducing aqueous halide acids (HCl, HBr, HI) to alter the anion composition in the fiber. This parameter change displaces sulfate anions with halide anions through ion exchange, effectively reducing sulfur content while maintaining the fiber's structural integrity and manufacturing process.
2Ease of manufacture
If copolymer is spun directly from polymerization solution, then manufacturing cost is reduced, but fiber tenacity is insufficient
Solution Approach 1:
The patent extracts the copolymer from the polymerization solution and redissolves it in sulfuric acid to create a optimized spinning dope. This extraction and re-dissolution step allows for better control of fiber formation parameters, leading to improved tenacity while still maintaining economic viability compared to direct spinning methods.
Solution Approach 2:
The patent changes the solvent parameter from the original polymerization solution to sulfuric acid, creating optimal conditions for spinning high tenacity fibers. This parameter change in the spinning dope composition enables better fiber alignment and strength development during the spinning process.
3Device complexity
If standard PPD-T fiber processing is used, then manufacturing simplicity is maintained, but fiber tenacity is limited
Solution Approach 1:
The patent applies parameter changes by modifying the spinning dope composition to include the copolymer solutioned in sulfuric acid, and by implementing aqueous halide acid treatment steps. These parameter changes in composition and processing conditions enable higher tenacity fibers while maintaining relatively simple processing equipment and procedures.
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 significantly reduced sulfur content, enhancing tenacity and economic efficiency by producing fibers with less than 3.0 weight percent sulfur, thereby improving the utility and production economics of high tenacity fibers.
Implementation Method 1
contacting never-dried sulfate anion-containing polymeric-fiber with an aqueous acid comprising a halide to displace at least a portion of the sulfate anions with halide anions
Data Source
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AI summary
The present invention concerns methods for removing sulfur from a fiber made from a polymer comprising imidazole groups, said method comprising: a) contacting never-dried sulfate anion-containing polymeric-fiber with an halide-containing acid to displace at least a portion of the sulfate ions with halide anions; and b) rinsing the fiber to remove the displaced sulfate ions.