Aramid Yarn Neutralization via Multi-Stage Heating
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Solution Overview
Problem
Copolymers derived from 5(6)-amino-2-(p-aminophenyl)benzimidazole and para-phenylenediamine and terephthaloyl dichloride fibers retain sulfuric acid, making them difficult to neutralize effectively, which affects their long-term hydrolytic stability and increases manufacturing costs.
Innovation Solution
A method involving spinning the copolymer from an inorganic acid solvent, followed by washing with a basic aqueous solution for at least 5 seconds and heating in multiple steps, specifically at temperatures ranging from 200°C to 500°C, to achieve effective neutralization and enhance hydrolytic stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If copolymer fibers are spun from sulfuric acid solutions, then fiber strength and processability are improved, but sulfuric acid retention increases making neutralization difficult
Solution Approach 1:
The neutralization process is divided into multiple sequential stages: initial neutralization with basic aqueous solution, followed by extended washing with water, then a second neutralization stage with additional base, and finally prolonged water washing. This segmented approach allows progressive removal of sulfuric acid without compromising fiber strength.
Solution Approach 2:
The patent applies preliminary neutralization treatment during the washing process by introducing basic aqueous solutions before final drying. This preliminary action prevents sulfuric acid from causing hydrolytic degradation during subsequent processing and storage, addressing the neutralization difficulty before it becomes a critical problem.
2Productivity
If copolymer fibers are not sufficiently neutralized, then processing time and cost are reduced, but long-term hydrolytic stability deteriorates
Solution Approach 1:
Basic aqueous solutions (neutralizing agents) serve as intermediaries between the sulfuric acid-containing fiber and the final product. These intermediaries facilitate the removal of harmful sulfuric acid through controlled chemical neutralization reactions, ensuring hydrolytic stability without requiring excessive processing time.
Solution Approach 2:
The patent implements continuous multi-stage washing and neutralization processes where basic solutions and water continuously act on the fiber to remove sulfuric acid. This continuous useful action ensures complete neutralization and maintains hydrolytic stability throughout the production process.
3Device complexity
If traditional neutralization techniques are used for copolymer fibers, then process simplicity is maintained, but neutralization effectiveness is insufficient
Solution Approach 1:
The patent changes multiple process parameters including washing temperature, basic solution concentration, washing duration, and sequential treatment stages. These parameter changes transform the neutralization process from ineffective to highly effective, achieving thorough sulfuric acid removal while maintaining reasonable process complexity.
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 high-tenacity aramid yarns with greater than 60% hydrolytic strength retention and improved economic viability by reducing sulfuric acid retention, leading to superior long-term physical properties.
Implementation Method 1
washing the yarn with a basic aqueous solution for at least 5 seconds
Implementation Method 2
heating the yarn; wherein the yarn is heated in at least two process steps, characterized in that (i) in a first step the yarn is heated at a temperature of 200 to 360° C. at a tension of at least 0.2 cN/dtex, followed by (ii) a second step wherein the yarn is heated at a temperature of 370 to 500° C. at a tension of less than 1 cN/dtex
Data Source
AI summary
The present invention concerns methods for obtaining high-tenacity aramid yarn, wherein the yarn is made of a copolymer obtained from a mixture of monomers comprising 5-(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic para-diamine, and an aromatic para-diacid; the method comprising: a) spinning said copolymer from an inorganic acid solvent to produce the aramid yarn; b) washing said yarn with a basic aqueous solution for at least 5 seconds; and c) heating said yarn; wherein the yarn is heated in at least two process steps, characterized in that (i) in a first step the yarn is heated at a temperature of 200 to 360° C. at a tension of at least 0.2 cN/dtex, followed by (ii) a second step wherein the yarn is heated at a temperature of 370 to 500° C. at a tension of less than 1 cN/dtex. In some embodiments, the yarn has an effective polymer cation to sulfur content molar ratio of at least 0.3. In some embodiments, the yarn has a hydrolytic strength retention of the yarn is greater than 60%.