Hair Dyeing Process Using Indole Compounds and Polycyclic Couplers
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Solution Overview
Problem
Current hair dyeing methods using oxidation dye precursors and indole or indoline compounds often result in unstable color shades, particularly prone to yellowing over time, and can damage keratin fibers, while existing alternatives lack intensity and durability.
Innovation Solution
A process involving treatment of keratin fibers with a composition containing indole or indoline compounds, aromatic hydrocarbon-based polycycles like dihydroxynaphthalenes, and optional metal salts, hydrogen peroxide, and basifying agents to achieve intense, long-lasting, and uniform color without fiber damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If oxidation dye precursors (ortho- or para-phenylenediamines, ortho- or para-aminophenols) are used to obtain permanent colorings, then color intensity and resistance to external agents are improved, but problems of staining, odour, and damage to keratin fibres occur
Solution Approach 1:
The patent changes the chemical parameters by replacing traditional oxidation bases with indol(in)e compounds and using atmospheric oxygen or mild hydrogen peroxide-generating systems instead of strong oxidizing agents. This parameter change maintains color intensity while eliminating harmful effects like staining and fiber damage.
Solution Approach 2:
The patent uses colorless or weakly coloured indol(in)e compounds that temporarily deposit on hair and develop color through oxidation. These compounds are less persistent and less damaging than traditional oxidation bases, providing a disposable-like approach that minimizes long-term harm to hair fibers.
2Quantity of substance
If indole or indoline derivatives are used for dyeing keratin fibres, then color uptake is achieved, but the colorings are not intense enough and risks of bleaching and attack of keratin fibres are non-negligible
Solution Approach 1:
The patent creates a composite dyeing system combining indol(in)e compounds with specific couplers (meta-diamines, meta-aminophenols, meta-diphenols) and optionally metal salts. This composite approach enhances color intensity while maintaining good color uptake and reducing fiber damage compared to using indole derivatives alone.
Solution Approach 2:
The patent introduces couplers as intermediary substances that mediate between the indol(in)e compounds and the final colored product. These couplers facilitate color development and intensification while the indol(in)e compounds serve as gentler precursors, reducing direct damage to keratin fibers.
3Quantity of substance
If indol(in)e compounds substituted with hydroxyl groups (such as 5,6-dihydroxyindole) are used, then color uptake is achieved, but the colouring may change after several days with yellowing over time
Solution Approach 1:
The patent employs couplers that provide feedback control over the oxidation process and color development. These couplers interact with the indol(in)e compounds to produce stable colored complexes that resist yellowing and color change over time, while still achieving good initial color uptake.
Solution Approach 2:
The patent modifies the chemical parameters by selecting specific couplers with particular functional groups and structures that stabilize the final color complex. This parameter optimization prevents the yellowing and color change issues associated with using indol(in)e compounds alone, while maintaining effective color uptake.
4Reliability
If hydrogen peroxide is used as oxidizing agent in oxidation dyeing process, then permanent and resistant colorings are obtained, but damage to keratin fibres and staining problems occur
Solution Approach 1:
The patent uses atmospheric oxygen or mild hydrogen peroxide-generating systems (like percarbonates or perborates) that provide controlled oxidation. This accelerated oxidation approach achieves permanent color resistance without the harsh effects of strong hydrogen peroxide, minimizing fiber damage and staining while maintaining color reliability.
5Strength
If ortho-diphenol compounds are used with metal salts for dyeing, then intense colorings are obtained without hydrogen peroxide, but the colourings are not strong enough for hair fibres
Solution Approach 1:
The patent merges the advantages of ortho-diphenol compounds (intense coloring without strong oxidants) with indol(in)e compounds and specific couplers. This combination achieves both intense coloration and sufficient color strength on hair fibers, overcoming the limitation of ortho-diphenols alone while avoiding the harshness of traditional oxidation systems.
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 provides powerful, intense, and stable color that resists washing, perspiration, and light, maintaining uniformity from root to tip without harming the fibers, and prevents color change or yellowing, even after exposure to light.
Implementation Method 1
oxidation bases are colourless or weakly coloured compounds, which, when combined with oxidizing products, may give rise to coloured compounds via a process of oxidative condensation
Implementation Method 2
applying to the keratin fibres bases or a mixture of bases and couplers with hydrogen peroxide (H2O2 or aqueous hydrogen peroxide solution), as oxidizing agent
Implementation Method 3
treating said fibres with i) at least one indole or indoline compound; ii) at least one aromatic compound comprising a hydrocarbon-based polycycle comprising at least 10 carbon atoms... iii) at least one metal salt
Data Source
AI summary
The invention relates to a process for dyeing keratin fibres by treating said fibres with i) at least one aromatic compound comprising a hydrocarbon-based polycycle comprising at least 10 carbon atoms, at least one of the rings of which is aromatic, ii) at least one indol(in)e compound; optionally iii) at least one metal salt, iv) at least hydrogen peroxide or at least one hydrogen peroxide-generating system and v) at least one basifying agent; to a dye composition comprising ingredients i)and ii), and optionally iii) to v) as defined previously and to a kit comprising ingredients i) to v) as defined previously. This hair dyeing process makes it possible to obtain better colourings which are more uniform, chromatic and long-lasting and which do not impair the cosmetic properties of the keratin fibres, and prevents changing of the colour associated with the presence of indol(in)e derivatives.