Cellulose Fiber Extrusion Nozzle Array with Gas Attenuation
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Solution Overview
Problem
Current methods are unable to economically produce cellulose fibers with diameters less than 15 microns at high throughput rates, and fail to form non-woven webs with basis weights greater than 1 gram per square meter at production speeds above 30 meters per minute, especially when extruding at back pressures over 20 bar or producing fibers smaller than 5 microns at speeds of up to 750 meters per minute.
Innovation Solution
An apparatus comprising multiple nozzles arranged in rows with staggered configurations and surrounded by pressurized gas streams, which extrudes an aqueous cellulose solution through a spinnerette to form molten filaments that are then attenuated and coagulated into solid fibers, allowing for the production of fine cellulose fibers with diameters less than 5 microns at high throughput rates and efficient collection into non-woven webs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional extrusion methods are used, then equipment simplicity is maintained, but fiber diameter cannot be reduced below 15 microns at economically feasible throughput
Solution Approach 1:
The die block assembly is segmented into multiple functional components: a body with numerous individually controllable nozzles (20-100 per linear centimeter), separate gas injection channels, and distinct coagulation zones. This segmentation allows each nozzle to independently extrude ultrafine filaments while maintaining high overall throughput through parallel operation of many nozzles.
Solution Approach 2:
Pressurized gas (nitrogen or carbon dioxide) is introduced as an intermediary substance between the extruded filaments and the surrounding environment. The gas serves multiple functions: it attenuates the filaments to achieve diameters below 15 microns, provides protective atmosphere during extrusion, and facilitates solvent removal without direct contact with water until the coagulation stage.
2Manufacturing precision
If back pressure is increased above 20 bar to improve fiber formation, then fiber quality improves, but the spinnerette becomes damaged
Solution Approach 1:
The system operates at back pressures exceeding 20 bar (up to 50 bar or higher) by changing the material parameters of the spinnerette nozzles. Nozzles are constructed from high-strength, wear-resistant materials and designed with optimized wall thickness and reinforcement features that allow them to withstand the elevated pressures required for ultrafine fiber formation without deformation or failure.
Solution Approach 2:
The aqueous cellulose solution is preheated to elevated temperatures (above 100°C) before entering the die block assembly. This preliminary heating reduces the viscosity of the solution, allowing it to flow more easily through the high-pressure nozzle system and reducing the mechanical stress on the spinnerette components during extrusion.
3Productivity
If production speed is increased to 750 meters per minute, then productivity improves, but fiber diameter control becomes difficult
Solution Approach 1:
The system employs dynamic control of the pressurized gas flow rate and pressure in real-time based on production speed requirements. As the collection surface speed increases to 750 meters per minute, the gas injection parameters are adjusted to maintain optimal attenuation forces, ensuring consistent fiber diameters below 15 microns despite the high production velocity.
Solution Approach 2:
Traditional mechanical attenuation methods (such as friction or mechanical drawing) are replaced with a pneumatic system using pressurized gas. This substitution allows for contactless, highly controllable attenuation that can operate at very high speeds without mechanical wear or variability, maintaining precise fiber diameter control even at 750 meters per minute production rate.
4Manufacturing precision
If non-woven webs with basis weight less than 1 gram per square meter are produced, then product fineness improves, but collection efficiency decreases at speeds above 30 meters per minute
Solution Approach 1:
The collection system utilizes a porous conveyor belt or rotatable drum that operates in conjunction with controlled gas flow and vacuum zones. The porous structure allows for efficient fiber deposition and adhesion even at high speeds, while the gas flow patterns are optimized to ensure uniform distribution of ultrafine fibers across the collection surface, achieving basis weights below 1 gram per square meter with high collection efficiency at speeds exceeding 30 meters per minute.
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 apparatus enables the production of cellulose fibers with diameters as low as 5 microns at throughputs exceeding 0.5 grams/hole/minute and speeds of up to 750 meters per minute, achieving efficient and economical formation of non-woven webs with enhanced fiber separation and collection efficiency.
Implementation Method 1
pressurized gas can be routed through at least one passage formed in the first member... multiple corridors formed therethrough which are connected to the passage formed in the first member... pressurized gas at least partially surrounds the aqueous solution extruded from each of the nozzles
Implementation Method 2
an aqueous solution comprised of cellulose and a solvent can be extruded... through which an aqueous solution of cellulose and a solvent can be extruded
Implementation Method 3
contacted with a liquid which causes a major portion of the solvent to solvate into the liquid solution and thus allows the molten filaments to coagulate into solid cellulose fibers
Implementation Method 4
a liquid which causes a major portion of the solvent to solvate into the liquid solution
Implementation Method 5
high velocity gaseous jets to form fine cellulosic fibers... emitting pressurized gas therethrough such that the pressurized gas at least partially surrounds the aqueous solution extruded from each of the nozzles
Data Source
Figure 1~7
Figure 2
Figure 8~20
AI summary
An apparatus is disclosed for extruding cellulose fibers. The apparatus includes a first member, a second member and a third member all secured together. Multiple nozzles extend outward from the first member and each is designed to direct an aqueous cellulose solution therethrough. As the aqueous solution is extruded, it is accentuated and accelerated by pressurized gas flowing through the first member and the second member and out through first openings formed in the third member. The pressurized gas at least partially surrounds each nozzle and shelters the molten filaments extruded therefrom. The third member also has multiple second openings formed therethrough which are also connected to a source of pressurized gas. The pressurized gas streams exiting each of the second openings function to keep each of the molten filaments from contacting an adjacent molten filament.