High-speed process for producing acrylic fibers and relative apparatus
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Solution Overview
Problem
Current wet spinning processes for producing carbon fiber precursors face issues with high spinning speeds, leading to overflow and spray phenomena due to 'water drag' and centrifugal effects, which complicate the management of the spinning line and expose operators to splashes of hot fluids.
Innovation Solution
A wet-spinning process with a co-current washing and stretching configuration, where the washing solution moves in the same direction as the fibers, and a recycling system that heats and re-circulates the washing solution to maintain efficient solvent use and prevent overflow, combined with a spinneret immersed in a coagulation bath with a specific solvent composition and temperature, achieving a high jet stretch ratio similar to air-gap spinning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet spinning is performed at high spinning speeds, then productivity is improved, but overflow and spray phenomena occur due to water drag and centrifugal effects
Solution Approach 1:
The washing system is divided into multiple washing tanks arranged in series, with each tank handling a portion of the washing process. This segmentation allows better control of fluid dynamics in each individual tank, reducing the likelihood of overflow and spray phenomena while maintaining high spinning speeds.
Solution Approach 2:
A co-current washing configuration is introduced where washing solution flows in the same direction as the fiber tow through the spinning line. This intermediary flow pattern reduces relative velocity differences between the washing solution and fibers, minimizing water drag effects and preventing overflow while still enabling high productivity.
2Manufacturing precision
If washing solution is used in traditional counter-current configuration, then washing efficiency is improved, but centrifugal effects cause spray and exposure to hot fluids
Solution Approach 1:
The traditional counter-current washing configuration is inverted to a co-current configuration where the washing solution flows in the same direction as the fiber tow. This inversion eliminates the harmful centrifugal spray effects while maintaining washing efficiency through the series arrangement of multiple washing tanks with optimized flow rates.
3Productivity
If spinning speed is increased to 400 m/min, then productivity is improved, but management of the spinning line becomes more complex
Solution Approach 1:
The system parameters are optimized for high-speed operation, including the co-current washing configuration and series arrangement of washing tanks. These parameter changes enable stable operation at 400 m/min spinning speed while simplifying management through reduced overflow and spray issues compared to traditional configurations.
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
This process allows for high-speed spinning (150-400 m/min) while preventing overflow and splashes, resulting in fibers with excellent mechanical characteristics and surface compactness, similar to those produced by air-gap spinning, without the complexity of air-gap equipment.
Implementation Method 1
the dope coagulates immediately upon contact with the coagulation bath
Implementation Method 2
the strands of dope leaving the spinneret do not coagulate immediately upon contact with the bath, but pass for a small distance in the air, where a first stretching process (jet stretch) is effected before entering the bath where the coagulation takes place with the elimination of the solvent and formation of the fiber
Implementation Method 3
through a series of washing operations (to remove the residual solvent)
Data Source
AI summary
A process for the production of acrylic fibers, in particular a spinning process for obtaining precursor fibers of carbon fiber by the wet spinning of a polymer solution in an organic solvent and the relative apparatus.