Process and device for the formation of directly-formed cellulosic webs
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Solution Overview
Problem
Current lyocell melt-blown processes face challenges in washing cellulose filaments, requiring control over filament merging, diameter variation, minimizing damage, controlled liquor exchange, water consumption, and reducing equipment and energy costs, with no prior art achieving all these requirements effectively.
Innovation Solution
A process and device involving a two-stage washing system with a first stage for partial coagulation of cellulose filaments before web formation and a second stage for gentle dewatering, using modular washing modules with controlled wash liquor application and vacuum suction, optimized for line speeds from 5 to 1000 m/min, and incorporating solvent recovery and energy-efficient design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If wash liquor is applied to remove solvent from filaments, then solvent removal is improved, but filament damage increases
Solution Approach 1:
The washing process is divided into multiple sequential washing zones (first washing zone, second washing zone, third washing zone) with progressively different wash liquor temperatures and flow rates. This segmentation allows gentle initial washing to remove solvent without damaging filaments, followed by more intensive washing stages, thus resolving the contradiction between effective solvent removal and filament protection
Solution Approach 2:
The patent employs parameter changes by varying wash liquor temperature across different zones (e.g., cooler temperatures in early zones, warmer temperatures in later zones) and adjusting wash liquor flow rates. These parameter changes enable effective solvent removal while controlling the mechanical stress on filaments, preventing damage during the washing process
2Productivity
If line speed is increased to improve productivity, then production efficiency is improved, but washing quality deteriorates
Solution Approach 1:
The washing system is segmented into multiple parallel washing modules within each washing zone, allowing the wash liquor to be distributed across multiple channels. This segmentation maintains adequate washing contact time and quality even at high line speeds, as each module processes a portion of the web simultaneously
Solution Approach 2:
The washing device is designed with multi-functional capabilities that allow it to operate effectively across a wide range of line speeds (5-1000 m/min). The system can adapt its wash liquor application rate, temperature, and flow distribution to maintain washing quality regardless of the production speed, making it universally applicable to different productivity requirements
3Loss of substance
If water consumption is increased to improve solvent removal, then washing effectiveness is improved, but water consumption increases
Solution Approach 1:
The patent employs parameter changes by varying wash liquor temperature across different zones (e.g., cooler temperatures in early zones, warmer temperatures in later zones) and adjusting wash liquor flow rates. These parameter changes enable effective solvent removal while controlling the mechanical stress on filaments, preventing damage during the washing process
Solution Approach 2:
The system is designed to recover and reuse wash liquor from downstream zones in upstream zones, creating a counter-current flow pattern. This recovery approach reduces overall water consumption while maintaining effective solvent removal, as the wash liquor is utilized multiple times across different washing stages
4Manufacturing precision
If equipment complexity is increased to control filament merging and diameter variation, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The washing device is segmented into modular washing modules arranged in sequential zones, where each module performs a specific function (e.g., initial solvent removal, intermediate washing, final rinsing). This modular segmentation achieves precise control over filament properties through staged processing while keeping individual modules relatively simple and manageable
Solution Approach 2:
Different sections of the washing device are designed with locally optimized characteristics - for example, the first washing zone uses cooler temperatures and lower flow rates for gentle initial treatment, while later zones use warmer temperatures and higher flow rates for more intensive washing. This local quality differentiation achieves precise filament control without requiring the entire device to be overly complex
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 solution enables efficient production of cellulose-based webs with controlled properties, reduced solvent consumption, and minimized equipment costs, achieving line speeds and product quality not previously possible while maintaining web integrity and environmental sustainability.
Implementation Method 1
Washing of lyocell filaments is a critical process step, in which the solvent has to be removed from the thermoplastic cellulose/solvent threads in a controlled manner
Implementation Method 2
a dewatering device (10) for at least partially dewatering the web (11)
Data Source
AI summary
This invention relates to a process and a device for manufacturing cellulose-based webs which are directly formed from lyocell spinning solution and in particular for the washing of directly formed cellulose webs.