Cellulose Derivative Drying for Cold Water Dispersibility
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Solution Overview
Problem
Water-soluble cellulose derivatives often exhibit poor dispersibility in cold water due to their large surface area and fibrous nature, leading to gel-like barriers that hinder complete hydration and require time-consuming hot/cold water dissolution techniques, which are not suitable for large-scale industrial applications.
Innovation Solution
A process involving grinding and drying a moist cellulose derivative in a gas-swept impact mill with a gas temperature of 100 °C or less, followed by additional drying with a higher temperature gas outside the mill, improves flowability and cold water dispersibility without the need for extrusion or drying on trays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If water-soluble cellulose derivatives are supplied as particulate dry material with large surface area, then dissolution in water is thermodynamically favorable, but the large surface area causes outside particles to hydrate first and form gelatinous membranes that shield inside particles, leading to poor cold water dispersibility and lump formation
Solution Approach 1:
The patent applies parameter changes by controlling the moisture content of the cellulose derivative particles within a specific range (5-20 wt% water) before drying. This moisture parameter adjustment prevents excessive hydration that would form gel membranes, while maintaining enough moisture to prevent static charge accumulation. The controlled moisture level optimizes both cold water dispersibility and flowability without causing gel-blocking.
Solution Approach 2:
The patent applies local quality by creating a specific moisture distribution within the particles through controlled drying processes. The surface and interior of particles have different moisture characteristics that prevent uniform gel formation. This local moisture variation ensures that the particle surface remains sufficiently dry to avoid gel membrane formation while maintaining overall particle integrity and dispersibility.
2Ease of operation
If the cellulose derivatives are dried to low moisture content to improve flowability, then handling and transportation are facilitated, but the particles become prone to static charge accumulation and poor dispersibility
Solution Approach 1:
The patent applies parameter changes by establishing an optimal moisture content range (5-20 wt% water) that balances flowability and static charge prevention. Within this range, the moisture level is sufficient to dissipate static charges through weak conduction while low enough to maintain good flow properties. This parameter optimization resolves the contradiction between dry handling requirements and electrostatic prevention.
Solution Approach 2:
The patent uses moisture as an intermediary substance that mediates between the opposing requirements of dryness for flowability and moisture for static charge dissipation. The controlled moisture acts as a bridge, providing just enough polarity and conduction to prevent charge accumulation while maintaining particle flow characteristics through reduced inter-particle adhesion.
3Loss of energy
If traditional drying methods such as drying on trays or extrusion are used, then the cellulose derivatives can be dried, but the process is time-consuming and not suitable for large-scale industrial applications
Solution Approach 1:
The patent replaces traditional mechanical drying methods (tray drying, extrusion) with a fluidized bed drying system. In this system, hot gas flows through a fluidized bed of particles, providing uniform and rapid heat and mass transfer. This substitution of the drying mechanism dramatically reduces processing time while maintaining product quality, making the process suitable for large-scale industrial production.
Solution Approach 2:
The patent uses pneumatic principles in the fluidized bed drying system where gas flow suspends and circulates the particles, enabling efficient heat and mass transfer. The gas-particle interaction in the fluidized state provides rapid moisture removal compared to conventional thermal drying methods, significantly improving processing speed and productivity for industrial applications.
4Ease of operation
If the cellulose derivatives are ground to fine particle size to improve dispersibility, then the particles can dissolve more readily, but the fine particles have increased surface area that exacerbates gel-blocking behavior
Solution Approach 1:
The patent applies parameter changes by controlling the moisture content parameter during and after grinding operations. By maintaining moisture within the optimal range (5-20 wt%), the fine particles remain dispersed without forming gel membranes on their surfaces. This parameter control allows the benefits of fine particle size (rapid dissolution) to be realized without the harmful effects of excessive surface area (gel-blocking).
Solution Approach 2:
The patent applies preliminary action by controlling the moisture content of particles before they undergo grinding and drying operations. The pre-established moisture level prevents gel membrane formation during subsequent size reduction and drying processes, ensuring that fine particles remain dispersible without developing surface gel layers that would hinder dissolution.
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 process results in cellulose derivatives with high bulk density, good flowability, and excellent cold water dispersibility, eliminating the formation of lumps and reducing processing time, making them suitable for large-scale industrial use.
Implementation Method 1
grinding and partially drying the moist cellulose derivative in a gas-swept impact mill
Implementation Method 2
contacting the ground and partially dried cellulose derivative with an additional amount of a drying gas outside the gas-swept impact mill
Data Source
Figure 1
AI summary
A particulate cellulose derivative is obtained in a process of grinding and drying a moist cellulose derivative which comprises the steps of A) providing a cellulose derivative having a moisture content of from 60 to 95 percent, based on the total weight of the moist cellulose derivative, B) grinding and partially drying the moist cellulose derivative in a gas-swept impact mill; and C) contacting the ground and partially dried cellulose derivative with an additional amount of a drying gas outside the gas-swept impact mill. The obtained particulate cellulose derivative has a high untapped bulk density and a good flowability.