Multi-Azo Brown Paper Dyes for Improved Lightfastness
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Solution Overview
Problem
Brown papers often suffer from insufficient lightfastness due to exposure to light and weather, leading to changes in color or shade, as existing dye mixtures fail to provide adequate protection.
Innovation Solution
Development of new azo dyes containing at least three azo groups linked by aromatic structures, such as substituted benzene and/or naphthalene groups, which are water-soluble and used alone to produce materials with improved lightfastness in brownish shades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional dye mixtures (e.g., C.I. Direct Brown 44 and Direct Yellow 11) are used to produce brown shades, then the desired color can be achieved, but the lightfastness is insufficient and color changes occur under light exposure
Solution Approach 1:
The patent applies composite materials by creating a complex azo dye molecule with multiple chromophoric units (at least three azo groups) linked by aromatic structures. This composite molecular structure provides both the desired brown color and improved lightfastness, resolving the contradiction between achieving correct coloration and maintaining stability under light exposure.
Solution Approach 2:
The patent changes the molecular parameters of the dye by increasing the number of azo groups from one or two (in prior art) to at least three, and by incorporating specific aromatic linkers with defined substituents. This parameter change in molecular complexity and structure directly improves lightfastness while maintaining the brown shade, addressing the reliability issue.
2Reliability
If dye mixtures are used to achieve brown shades, then color can be produced, but the process complexity increases and lightfastness remains insufficient
Solution Approach 1:
The patent merges multiple chromophoric functions into a single azo dye molecule. Instead of using mixtures of different dyes (as in prior art), the invention combines at least three azo groups and aromatic structures into one molecular entity, simplifying the dyeing process while improving lightfastness through the synergistic effect of the multi-unit structure.
Solution Approach 2:
The complex azo dye molecule acts as a composite material at the molecular level, integrating multiple light-absorbing units and aromatic linkers into a single structure that provides both color and stability, eliminating the need for complex dye mixtures.
3Reliability
If existing azo compounds with one or two azo groups are used, then the dyeing process is simpler, but the lightfastness of the resulting brown papers is insufficient
Solution Approach 1:
The patent changes the key parameter of azo group count from one or two (prior art) to at least three (invention). This parameter change, along with incorporating specific aromatic linkers, directly improves lightfastness. The diazotization and coupling process, while requiring multiple steps, follows standard azo dye synthesis methodology, making the increased complexity manageable and justified by the performance gain.
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 new azo dyes significantly enhance the lightfastness of brownish papers, allowing them to maintain their color integrity even when exposed to light, surpassing the performance of traditional dye mixtures.
Implementation Method 1
azo dyes containing at least three azo groups which are linked by aromatic structures... enable the production of materials, in particular of organic or fiber-containing materials, e.g. paper or board, in brownish shades and with high lightfastness
Data Source
AI summary
The present invention relates to new azo dyes, a process for their preparation, and their use for dyeing or printing fibrous materials, to produce materials with brownish shades.