Oxidation Couplers and Glutamic Acid for Persistent Grey Coverage
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Solution Overview
Problem
Existing hair dye compositions using oxidation dye precursors often result in unsatisfactory dyeing power, limited color range, insufficient color persistence, and uneven color distribution along the hair shaft, particularly failing to provide intense, uniform, and persistent color coverage of grey hair.
Innovation Solution
A composition comprising specific oxidation couplers (6-hydroxybenzomorpholine, hydroxyethyl-3,4-methylenedioxyaniline, and 2-amino-5-ethylphenol) and N,N-dicarboxymethyl glutamic acid, along with optional additional couplers and oxidation bases, is applied to keratin fibers, followed by a chemical oxidizing agent to achieve intense, uniform, and persistent coloration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional oxidation dye precursors and couplers are used, then a wide range of colours can be obtained, but the dyeing power is weak and colour intensity is insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of the coupler molecules. Specifically, it uses couplers with modified electronic properties (such as 2,6-dimethoxyaniline derivatives) that have enhanced electron-donating capabilities compared to conventional couplers. This structural parameter change results in more intense colored compounds upon oxidation, thereby increasing dyeing power while maintaining the ability to produce a wide range of colors through different coupler variants.
Solution Approach 2:
The patent employs composite material principles by combining specific oxidation bases (like 1,2-diaminobenzene derivatives) with specially selected couplers (2,6-dimethoxyaniline derivatives) to create a synergistic dyeing system. This combination produces colored compounds with superior intensity and fastness properties that exceed the performance of individual components used separately, effectively resolving the contradiction between color variety and dyeing power.
2Reliability
If oxidation dye precursors are used for permanent colouring, then colour persistence should be improved, but the colouring is insufficiently persistent against external agents such as light, shampoo or perspiration
Solution Approach 1:
The patent addresses fastness issues by changing the chemical parameters of the dye molecules. The use of 2,6-dimethoxyaniline derivatives and related couplers creates colored compounds with enhanced molecular stability and stronger bonding affinity to keratin fibers. These structural modifications result in dyes that resist fading from light exposure, washing with shampoo, and perspiration, thereby improving persistence against external harmful factors while maintaining permanent coloring capability.
3Ease of operation
If conventional dyeing compositions are applied, then colouring can be achieved, but the colour distribution is uneven along the keratin fibre (too selective)
Solution Approach 1:
The patent resolves uneven color distribution by changing the reactivity parameters of the dyeing system. The selected oxidation bases and couplers are designed with optimized reaction kinetics that ensure uniform oxidation and color development throughout the hair fiber. The 2,6-dimethoxyaniline derivatives and related compounds exhibit controlled reactivity that prevents premature or localized color formation, resulting in uniform color distribution from root to tip while maintaining effective coloring.
4Adaptability or versatility
If existing oxidation dye systems are used, then grey hair coverage can be attempted, but the coverage is not satisfactory and dyeing performance deteriorates after storage
Solution Approach 1:
The patent improves grey hair coverage and storage stability through parameter changes in the chemical composition. The use of 2,6-dimethoxyaniline derivatives and related couplers creates dye molecules with enhanced penetrability into depigmented gray hair structures. Additionally, these compounds exhibit improved chemical stability during storage, preventing premature oxidation or degradation. The optimized molecular parameters ensure both effective gray hair coverage and consistent dyeing performance after storage periods.
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 composition delivers chromatic, powerful, and sparingly selective colorings with good coverage of grey hair, offering a wide range of colors and improved fastness against external agents.
Implementation Method 1
These oxidation bases are colourless or weakly coloured compounds which, when combined with oxidizing products, can give rise to coloured compounds via a process of oxidative condensation
Data Source
AI summary
The invention relates to a composition comprising at least one oxidation dye coupler chosen from 6-hydroxy benzomorpholine of formula (I), hydroxyethyl-3.4-methy lenedioxyaniline of formula (II). 2-amino-5-ethylphenol of formula (III), one of their addition salts, their solvates and/or the solvates of their salts, and at least one compound chosen from N,N-dicarboxymethyl glutamic acid, one of its salts and mixtures thereof. The invention also relates to a process for dyeing keratin fibres, preferably the hair, comprising the application of the composition to said keratin fibres.