Parallel Spinneret Die Layout for Stable Cellulose Filament Spinning
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Solution Overview
Problem
Existing processes for spinning cellulose dissolved in aqueous sodium hydroxide into cellulose filaments in an alkaline coagulation bath result in filaments with low structural integrity, leading to lower production rates and filament breaks due to rapid precipitation and hydrodynamic forces.
Innovation Solution
A process and system using a spinning head with rectangular spinneret dies arranged in parallel, spaced apart to allow alkaline cellulose spin dope to be extruded into an alkaline coagulation bath, minimizing hydrodynamic forces by guiding the coagulation bath flow parallel to the extrusion direction and utilizing self-convection, with optional flow directing means to stabilize the filaments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cellulose spin dope is extruded into alkaline coagulation bath at high speed, then production rate increases, but filament structural integrity deteriorates due to hydrodynamic forces and rapid precipitation
Solution Approach 1:
The patent changes the flow direction from perpendicular (radial) to parallel (axial) relative to the spinneret holes. By guiding the coagulation bath flow parallel to the extrusion direction through the spinneret holes, hydrodynamic forces are minimized while allowing high-speed extrusion, thus maintaining filament integrity at high production rates
Solution Approach 2:
The patent introduces flow directing means as an intermediary component between the coagulation bath and the spinneret. This intermediary structure controls and directs the coagulation bath flow to be parallel to the extrusion direction, mediating the interaction between the spin dope and coagulation bath to reduce mechanical strain on forming filaments
2Speed
If rapid precipitation occurs in alkaline coagulation bath, then cellulose filaments form quickly, but filament breaks due to mechanical strain from hydrodynamic forces
Solution Approach 1:
By changing the flow direction from radial to parallel relative to the spinneret holes, the patent allows rapid precipitation to occur while minimizing hydrodynamic forces that cause filament breaks. The parallel flow configuration reduces mechanical strain on the forming filaments during the quick coagulation process
3Ease of manufacture
If conventional circular spinneret dies are used, then manufacturing is simple, but filament breaks due to radial flow forces across the spinneret surface
Solution Approach 1:
The patent transitions from symmetric circular spinneret dies to asymmetric rectangular spinneret dies. This asymmetric geometry, combined with the parallel flow configuration, effectively reduces the radial flow forces that cause filament breaks while maintaining manufacturing feasibility
Solution Approach 2:
The patent changes the flow direction from radial (perpendicular to spinneret surface) to parallel (along the extrusion direction). This dimensional change in flow orientation fundamentally alters the hydrodynamic forces acting on filaments, reducing mechanical strain while allowing high-speed production
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
Enables higher production rates and maintains filament integrity by reducing mechanical strain, allowing for a wider range of draft ratios and filament diameters without breakage.
Implementation Method 1
Upon contact with the coagulation liquid, there will be a diffusion-based exchange of chemicals between the spin dope jets exiting the spinning head and the coagulation liquid
Implementation Method 2
The solvation power of alkali is thus abruptly decreased, and cellulose is precipitated, forming a dens, non-swollen network of semi-crystalline fibrils
Implementation Method 3
A wet, swollen tow is provided when the spin dope is spun into the coagulation bath. The tow of regenerated fibers may subsequently be withdrawn from the coagulation bath to provide cellulose fibers
Data Source
AI summary
Disclosed is a process for spinning an alkaline cellulose spin dope, comprising dissolved cellulose, to cellulose filaments (10). The process comprising the steps of: —feeding the alkaline cellulose spin dope to at least one spinning head (20) with a plurality of holes (21), wherein the spinning head (20) comprises at least two parallel, rectangular spinneret dies (22), each with a plurality of holes (21), the spinneret dies (22) being arranged spaced apart with a flow spacing (23) in between them; —extruding the alkaline cellulose spin dope through the plurality of holes (21) into a flow (35) of aqueous alkaline coagulation bath liquid, the aqueous alkaline coagulation bath liquid comprising a sodium coagulation salt, whereby forming cellulose filaments (10), wherein the aqueous alkaline coagulation bath liquid flows through the flow spacing (23) and then past the spinneret dies (22) in a flow direction, the flow direction of the aqueous alkaline coagulation bath liquid being parallel to the direction in which the alkaline cellulose spin dope is extruded into the aqueous alkaline coagulation bath liquid; and —withdrawing the cellulose filaments (10) from the aqueous alkaline coagulation bath liquid.