Method for producing coloured fibrous materials and the use thereof
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Solution Overview
Problem
Current methods for dyeing m-aramid fibers require high-temperature processes and the use of hazardous carrier substances, leading to inadequate color absorption, poor light fastness, and environmental concerns, particularly when dyeing fiber mixtures with other flame-retardant fibers.
Innovation Solution
The process involves using an aqueous dispersion containing urea and/or its derivatives to apply vat dyes directly to m-aramid fibers or converting vat dyes into the leuco form in an alkaline medium, allowing for oxidative fixation without the need for carriers, thereby enhancing color absorption and fastness while maintaining environmental safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If carrier substances are used to promote chain mobility and enable dyeing at lower temperatures, then dye absorption is improved, but hazardous emissions and environmental risks increase
Solution Approach 1:
The invention extracts and eliminates the harmful carrier substances from the dyeing process. By using oxidative dyeing with vat dyes instead of carrier-based dyeing, the method removes the source of hazardous emissions while maintaining effective dye absorption through the oxidative mechanism that penetrates the m-aramid fiber structure.
Solution Approach 2:
The invention changes the fundamental parameters of the dyeing process by switching from carrier-based low-temperature dyeing to oxidative dyeing. This involves changing the dyeing mechanism from carrier-mediated diffusion to oxidative penetration, and adjusting parameters such as oxygen concentration, pH, and temperature to optimize the oxidative dyeing process without carriers.
2Manufacturing precision
If high-temperature dyeing processes are used for m-aramid fibers, then chain mobility increases for better dye penetration, but energy consumption and process complexity increase
Solution Approach 1:
The invention substitutes the thermal-mechanical dyeing mechanism (relying on heat-induced chain mobility) with a chemical-oxidative mechanism. Instead of using high temperature to physically move dye molecules into the fiber, the oxidative process chemically facilitates dye penetration and fixation, thereby reducing energy consumption while achieving effective dye penetration.
3Quantity of substance
If conventional cationic dyes are used with carriers, then color depth is achieved, but light fastness deteriorates
Solution Approach 1:
The invention converts the previously harmful effect of oxidative conditions (which can degrade dyes) into a beneficial mechanism. By using oxidative dyeing with vat dyes, the oxidation process that would normally harm the dye-fiber complex instead becomes the mechanism for creating a stable, fast-colored product. The oxidative fixation creates strong bonds between the reduced dye, fiber, and crosslinking agents, resulting in superior light fastness while maintaining color depth.
4Productivity
If carrier substances are added to dye baths, then dyeing efficiency improves, but the need for closed apparatus and emission control measures increases
Solution Approach 1:
The invention extracts and removes the carrier substances from the dyeing system, thereby eliminating the need for closed apparatus and emission control infrastructure. The oxidative dyeing process proceeds efficiently without carriers, allowing for simpler, more open dyeing systems while maintaining productivity.
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 achieves good to very good color fastness, particularly light fastness, without the negative effects of carriers, and preserves the elastic properties of knitted goods, making it suitable for producing flame-retardant textiles without the use of harmful substances.
Implementation Method 1
converting the vat dyes into the leuco form by adding reducing agents in an alkaline medium
Implementation Method 2
the vat dyes are formed oxidatively from the leuco form
Data Source
AI summary
The invention relates to a method for producing coloured fibrous material on the basis of m-aramide fibres or m-aramide-fibre-containing fibre mixtures subsequently dyed with vat dyes, wherein the use of a carrier that is harmful to health and the environment can be done away with. This method is characterised in that the m-aramide fibres are subsequently dyed with vat dyes, wherein a) vat dyes in an aqueous dispersion containing urea and/or homologues and/or derivatives of urea are applied directly to the m-aramide fibres or the m-aramide-fibre-containing fibre mixtures, and then a fixing of the vat pigment on the fibrous materials is carried out, or b) the vat dyes are transformed into the leuco form with the addition of reducing agents in an alakli medium, wherein the relevant vat contains urea and/or homologues and/or derivatives of urea, and the vat is brought into contact with the m-aramide fibres or the m-aramide-fibre-containing fibre mixtures, the vat dyes are formed oxidatively from the leuco form and a fixing of the vat dyes on the fibrous materials is carried out. The fibrous materials obtained according to this method can be used advantageously for the production of clothing and items of equipment, in particular flame-retarding or fire-protection textiles for personal protective clothing, in particular for military, fire-fighting and police personnel, workwear or for use in objects. The particular advantage of the method according to the invention is that it provides coloured fibrous materials with high colour fastness and good colour yield, without bringing about a significant loss in elastic properties.