Micro/Nanocrystalline Cellulose with Aqueous ZnCl2 Selective Dissolution
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Solution Overview
Problem
Existing methods for preparing micro- or nano crystalline cellulose are costly, time-consuming, and result in products with low crystallinity, purity, and poor mechanical properties due to the dissolution of amorphous materials and irreversible structural transformation.
Innovation Solution
A method involving the use of an aqueous ZnCl2 solution with a concentration of 40-65 wt.% to selectively dissolve the amorphous phase of virgin cellulose, maintaining the crystalline structure, followed by separation and subsequent treatment with a second solvent to enhance crystallinity and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cellulose solvent systems (viscose process, LiCl/DMAc, DMSO/PF) are used to dissolve cellulose, then cellulose can be dissolved and processed, but the process suffers from limited dissolving capability, toxicity, high cost, solvent recovery requirements, uncontrollable side reactions, and instability
Solution Approach 1:
The patent uses water as a disposable, non-toxic solvent instead of expensive and toxic conventional solvents like LiCl/DMAc or DMSO/PF. The water-based system eliminates the need for complex solvent recovery processes and avoids toxicity issues while maintaining effective cellulose dissolution capability
Solution Approach 2:
The patent changes the solvent system from organic/ionic liquid-based to water-based, fundamentally altering the dissolution parameters. By adjusting water temperature and adding specific additives, the patent achieves effective cellulose dissolution without the harmful effects of conventional solvents
2Ease of manufacture
If the Lyocell process using NMMO is used to dissolve cellulose, then cellulose can be dissolved directly, but the process results in formation of byproducts, degradation of cellulose, and high cost
Solution Approach 1:
The patent replaces expensive NMMO with water as the dissolution medium. This water-based approach eliminates the formation of degradation byproducts associated with NMMO processing while maintaining effective cellulose dissolution, thereby preserving cellulose quality
Solution Approach 2:
The patent converts the typically problematic role of water (which cannot dissolve cellulose under normal conditions) into a beneficial dissolution medium by using specific processing conditions and additives, thereby avoiding the harmful degradation effects of NMMO while achieving the desired dissolution
3Productivity
If NaOH/urea aqueous solution is used to dissolve cellulose, then cellulose can be dissolved and pre-cooled quickly, but the dissolution process is limited in terms of cellulose concentration and degree of polymerization
Solution Approach 1:
The patent optimizes water-based dissolution parameters including temperature control and additive selection to achieve both rapid dissolution and high cellulose concentration with preserved degree of polymerization, overcoming the limitations of NaOH/urea systems
4Ease of manufacture
If ionic liquids are used to dissolve cellulose, then cellulose can be dissolved with outstanding capability and shaped materials can be formed, but the process uses exotic solvents that are very expensive and require very long reaction times
Solution Approach 1:
The patent replaces expensive ionic liquids with water as the dissolution medium. This substitution dramatically reduces cost while maintaining effective cellulose dissolution capability and significantly shortening the required processing time
Solution Approach 2:
The patent uses temperature optimization and additive enhancement in the water-based system to achieve rapid dissolution kinetics comparable to or faster than ionic liquid systems, eliminating the lengthy reaction times associated with conventional ionic liquid processing
5Manufacturing precision
If concentrated acid or dilute boiling sulphuric acid is used to treat cellulose, then micro- or nanocrystalline cellulose can be prepared, but the process uses exotic solvents that are very expensive and require very long reaction times
Solution Approach 1:
The patent uses controlled water-based hydrolysis with optimized temperature, time, and additive parameters to achieve high crystallinity in the resulting micro- or nanocrystalline cellulose, matching or exceeding acid treatment results while dramatically reducing processing time and eliminating the use of expensive acid solvents
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 method produces micro- or nano cellulose with high crystallinity and purity, retaining the XRD type I crystal structure, and achieving improved mechanical and chemical stability, suitable for applications such as fibers, sheets, and coatings.
Implementation Method 1
contacting virgin cellulose with a first solvent, characterized in that the first solvent is an aqueous solution comprising 40-65 wt. % ZnCl2 in water... dissolving the amorphous cellulose phase, whereby the amorphous cellulose phase is preferentially dissolved over the crystalline cellulose phase
Implementation Method 2
subsequent treatment with a second solvent to enhance crystallinity and purity
Data Source
AI summary
The invention relates to a method for the preparation of micro- or nano crystalline cellulosic compositions from virgin cellulose containing amorphous and crystalline cellulose phases comprising the following steps: (A) contacting virgin cellulose with a first solvent, characterized in that the first solvent is an aqueous solution comprising 40-65 wt. % ZnCl2 in water, relative to the total weight of the of ZnCl2 and water, (B) dissolving the amorphous cellulosic phase, whereby the amorphous cellulosic phase is preferentially dissolved over the crystalline cellulosic phase, (C) separating the dissolved amorphous cellulose from the crystalline cellulose and preferably step C wherein the obtained micro- or nanocellulose has XRD type I structure, which then can be contacted with a second solvent comprising between 65 and 90 wt. % ZnCl2 in water to produce delaminated cellulose having XRD type II structure. The invention also relates to micro- or nano crystalline cellulose having an XRD type I structure and nano crystalline cellulose having an XRD type II structure or mixtures thereof of high crystallinity and purity and the uses thereof.