Aramid Copolymer Yarn Halide-Acid Washing for Low Sulfur Tenacity
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Solution Overview
Problem
Existing processes for manufacturing copolymer fibers from 5(6)-amino-2-(p-aminophenyl)benzimidazole, para-phenylenediamine, and terephthaloyl dichloride are expensive and inefficient, with poor investment economics, and face unique challenges in achieving high tenacity due to differences from para-aramid fiber production frameworks.
Innovation Solution
A process involving contacting never-dried polymeric yarn with an aqueous base to neutralize sulfate anions, followed by treatment with an aqueous acid containing a halide, such as hydrochloric acid, and subsequent rinsing to reduce sulfur content and enhance tenacity, including heating to at least 350°C for improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copolymer fibers are manufactured using traditional processes from polymerization solution, then good product quality for ballistic and aramid end-uses is achieved, but manufacturing cost is very high with poor investment economics
Solution Approach 1:
The patent changes the processing parameters by using a different chemical pathway: isolating the copolymer from polymerization solvent and redissolving in sulfuric acid for spinning, rather than spinning directly from polymerization solution. This parameter change enables the use of common solvents and improves manufacturing economics while maintaining fiber quality
Solution Approach 2:
The patent introduces an intermediary step of isolating the copolymer from the polymerization solvent and redissolving it in sulfuric acid. This intermediary process allows for better control of the spinning parameters and improves manufacturing economics while producing high-quality fibers
2Productivity
If copolymer is solutioned in sulfuric acid and spun using conventional PPD-T processing, then fiber production is achieved, but sulfur content remains high and tenacity is insufficient
Solution Approach 1:
The patent segments the washing process into multiple distinct stages: (a) contacting with aqueous base to neutralize sulfate anions, (b) contacting with aqueous acid comprising halide to remove sulfur, and (c) rinsing. This segmentation allows each stage to target specific contaminants and achieve both low sulfur content and high tenacity
Solution Approach 2:
The patent converts the harmful effect of sulfuric acid processing (high sulfur content) into a benefit by using a controlled neutralization and removal process. The sulfate anions formed during processing are systematically removed through the multi-stage washing, turning a detrimental byproduct into a manageable intermediate that can be eliminated
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 results in copolymer yarns with sulfur content reduced to 2.5 weight percent or less, achieving tenacity levels of 32 cN/dtex or higher, providing superior strength and utility compared to traditional methods.
Implementation Method 1
contacting never-dried polymeric yarn with an aqueous base, the polymer comprising imidazole groups and said polymer comprising sulfur atoms characterized as being in the form of sulfate anions
Implementation Method 2
contacting the yarn with an aqueous acid comprising a halide... the preferred acid comprising a halide is hydrochloric acid
Implementation Method 3
further comprising heating to at least 350°C for improved mechanical properties
Data Source
AI summary
The present invention concerns methods for removing sulfur from yarn comprising the steps of: a) contacting never-dried polymeric yarn with an aqueous base, the polymer comprising imidazole groups and said polymer comprising sulfur atoms characterized as being in the form of sulfate anions; b) contacting the yarn with an aqueous acid comprising a halide; and c) rinsing the yarn.