Cellulose Dyeing in Supercritical CO2 Using Organo-Urea Primers
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Solution Overview
Problem
Current methods for dyeing cellulose fibers, particularly in the paper industry, are environmentally unfriendly due to the large quantities of water and pollutants involved, and existing alternatives using supercritical CO2 face challenges in affinity with cellulose, leading to incomplete satisfaction in dyeing efficiency and compatibility with paper cellulose.
Innovation Solution
A method involving the use of primary mono-organo-urea derivatives to form carbamate bonds with cellulose fibers, allowing for efficient immobilization of hydrophobic dyes in a supercritical CO2 medium without acidic conditions, surfactants, or water, facilitating dye penetration and recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If supercritical CO2 is used as a solvent for dyeing cellulose, then environmental friendliness and ease of dye recovery are improved, but the affinity between the solvent and cellulose is insufficient
Solution Approach 1:
The patent introduces a surfactant as an intermediary substance that mediates between the supercritical CO2 solvent and the cellulose fibers. The surfactant has hydrophilic groups that interact with cellulose and hydrophobic groups that interact with the dye and CO2, thereby enabling effective dyeing in supercritical CO2 medium without compromising environmental benefits
Solution Approach 2:
The patent modifies the chemical parameters of the cellulose surface by introducing hydrophobic groups through chemical treatment or surfactant adsorption. This parameter change enables the hydrophilic cellulose to interact with the hydrophobic supercritical CO2 and dye molecules, resolving the affinity mismatch
2Quantity of substance
If conventional aqueous dyeing methods are used, then dyeing efficiency is maintained, but large quantities of water and pollutants are generated requiring complex treatment
Solution Approach 1:
The patent utilizes the phase transition properties of supercritical CO2, which can be easily converted from supercritical fluid to gas by reducing pressure. This allows for simple separation and recovery of the solvent and unreacted dye without water, eliminating the need for complex wastewater treatment while maintaining dyeing efficiency
Solution Approach 2:
The patent extracts the harmful water and pollutant components from the dyeing system by replacing the aqueous medium with supercritical CO2. The CO2 system allows dyeing to proceed effectively while enabling easy removal and recovery of the solvent, leaving no polluted water waste
3Quantity of substance
If cellulose is modified to increase hydrophobicity for better sCO2 compatibility, then affinity with supercritical CO2 is improved, but the structural integrity of cellulose may be compromised
Solution Approach 1:
The patent applies preliminary surface treatment to cellulose fibers to introduce hydrophobic groups before the dyeing process. This preliminary modification enhances affinity with supercritical CO2 while using mild treatment conditions that preserve the bulk structural integrity of the cellulose fibers
Solution Approach 2:
The patent modifies only the surface properties of the cellulose fibers locally rather than the bulk material. By introducing hydrophobic groups at the fiber surface through surfactant adsorption or controlled chemical treatment, the patent improves sCO2 compatibility while maintaining the inherent strength and integrity of the cellulose structure
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
This method enables efficient, environmentally friendly dyeing of cellulose fibers with reduced water usage, energy consumption, and avoidance of hazardous secondary products, allowing for the reuse of CO2 and dye, while maintaining the integrity of paper cellulose.
Implementation Method 1
bringing said cellulose fibers into contact with an effective quantity of at least one primary mono-organo-urea, uncharged, and substituted by a linear or branched hydrocarbon chain, saturated or unsaturated, and having at least 3 carbon atoms or by a cyclic hydrocarbon radical, saturated or unsaturated, linked directly or via a methylene or ethylene group at the nitrogen atom, substituted where appropriate, under conditions conducive to the establishment of a carbamate-type covalent bond between the cellulose and each molecule of said organo-urea
Implementation Method 2
Due to its high diffusivity, its high density, and its low viscosity, it facilitates the penetration of the dye into the cellulose fibers
Implementation Method 3
supercritical CO2 has many advantages over other solvents. It is low cost, non-toxic, non-flammable, chemically inert, and environmentally friendly
Implementation Method 4
since supercritical CO 2 is a good solvent for hydrophobic and uncharged compounds, it has little affinity for cellulose, which is rather hydrophilic and polar
Implementation Method 5
the dye, not attached to a cellulosic fiber, can be easily separated and recovered at the end of the reaction by simply reducing the pressure of the supercritical CO 2
Data Source
AI summary
The present invention relates to a method for colouring of cellulose in a supercritical C02 medium by an uncharged hydrophobic dye, comprising at least the steps consisting of: (i) provision of cellulose fibres, (ii) placing said cellulose fibres in the presence of: a) an effective quantity of at least one uncharged mono organo-urea primer of formula R-NH-CO-NH2, where R represents a linear or branched, saturated or unsaturated, hydrocarbon chain possessing at least 3 carbon atoms, or a saturated or unsaturated cyclic hydrocarbon radical, which is bonded directly or via a methylene or ethylene group to a nitrogen atom, and if appropriate substituted under conditions conducive to the forming of a covalent carbamatic bond between the cellulose and the molecules of said organo-urea; and b) at least one hydrophobic dye in a supercritical C02 medium, under conditions conducive to the immobilization of said dye on said fibres.