Partially Cyclized Polyacrylonitrile Flame-Resistant Fiber Production
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Solution Overview
Problem
Conventional methods for producing flame-resistant fibers and carbon fibers face challenges such as instability in thread formation, slow flame retardation processes, and difficulties in achieving high productivity due to issues with polymer viscosity and the use of corrosive solvents, leading to suboptimal quality and efficiency.
Innovation Solution
A method involving the degeneration of polyacrylonitrile (PAN) polymer with a thiolate compound in a non-protonic polar solvent, followed by oxidation with a palladium-containing compound, to create a partially cyclized polymer that is then spun into fibers using wet or dry-wet spinning techniques, resulting in a flame-resistant fiber with specific gravity and sulfur content within targeted ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PAN polymer is flame retarded in solid phase at high temperature, then flame resistance is improved, but heat accumulates in fiber causing loss of control and potential damage
Solution Approach 1:
The invention changes the flame retardation parameters by conducting the reaction in solution phase at lower temperatures (0-100°C) rather than solid phase at high temperatures (200-300°C). This parameter change allows the flame retardation to proceed without excessive heat accumulation while still achieving the desired flame resistance and cyclic structure formation in the PAN polymer.
2Reliability
If flame retardation is carried out slowly with strict process control, then flame resistance quality is improved, but productivity decreases
Solution Approach 1:
The invention introduces a solvent as an intermediary medium to facilitate the flame retardation reaction. By conducting the reaction in solution phase with appropriate solvents, the process achieves both quality control and improved productivity, as the solvent allows for better heat dissipation and more controllable reaction conditions without requiring excessively slow processing.
Solution Approach 2:
The invention changes the process parameters by using solution-phase reaction at lower temperatures with controlled addition rates, enabling faster processing while maintaining quality. The use of specific solvents and temperature control allows the reaction to proceed efficiently without the need for extremely slow processing speeds.
3Stability of the object's composition
If strongly acidic solvents are used to dissolve AN polymer powder, then solubility is improved, but apparatus corrosion increases requiring special materials
Solution Approach 1:
The invention replaces expensive corrosion-resistant apparatus materials with conventional, easier-to-handle solvents. By using solvents like DMF, DMSO, or their water mixtures instead of strongly acidic solvents, the process can be conducted in standard equipment without requiring special corrosion-resistant materials, thereby reducing capital investment and operational costs.
Solution Approach 2:
The invention changes the solvent parameters from strongly acidic to neutral or mildly polar aprotic solvents. This parameter change maintains the ability to dissolve AN polymer powder effectively while eliminating the corrosiveness issue, allowing the use of conventional apparatus materials and reducing overall process complexity.
4Stability of the object's composition
If dilute PAN solution is used for cyclization, then solubility is improved, but viscosity becomes too low for fiber formation
Solution Approach 1:
The invention optimizes the concentration parameter of the PAN solution to a specific range (5-50% by mass) that balances solubility and viscosity requirements. This parameter change allows the solution to remain sufficiently soluble while maintaining adequate viscosity for fiber formation, resolving the contradiction between solubility and shape formability.
Solution Approach 2:
The invention uses composite solvent systems, such as mixtures of DMF and water or DMSO and water, in specific proportion ranges. These composite solvent systems provide both the solubility benefits of polar aprotic solvents and the viscosity control needed for fiber formation, effectively resolving the contradiction between solubility and shape requirements.
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 approach stabilizes the production of high-performance flame-resistant fibers and carbon fibers with improved drawing properties and uniform structure, enhancing productivity and quality while minimizing solvent-related issues.
Implementation Method 1
degeneration of polyacrylonitrile (PAN) polymer with a thiolate compound
Implementation Method 2
oxidation with a palladium-containing compound
Implementation Method 3
spun into fibers using wet or dry-wet spinning techniques
Data Source
AI summary
A high-quality flame-resistant fiber and carbon fiber at low costs in preparing a flame-resistant fiber and a carbon fiber by efficiently performing a flame retardation process in a short time as compared with a conventional technology are described. [1] If a polyacrylonitrile (PAN) polymer is degenerated with an oxidizing agent containing a thiolate compound and a nitrogen atom in a polymer, and the degenerated polymer is formed into threads so as to prepare a flame-resistant PAN fiber. [2] A flame-resistant PAN fiber is prepared by degenerating a PAN precursor fiber in a solution including a thiolate compound and an oxidizing agent containing a nitrogen atom. The flame-resistant PAN fiber obtained by the preparation method is heated at 300° C. or more to 3000° C. or less, and, thus, a carbon fiber having an excellent mechanical strength can be obtained.