Keratin Fiber Bleaching With Short Pre-Reduction for Low Hair Damage
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Solution Overview
Problem
Existing bleaching and decolorization processes for keratin fibers, particularly human hair, face limitations in achieving high lightening power without causing significant damage, and existing combinations of pre-treatment steps do not adequately address this issue.
Innovation Solution
A process involving a reductive pre-treatment step with an aqueous composition containing a reducing agent, followed by an oxidative composition, where the reducing agent is applied for 0.5 to 5 minutes and the oxidative composition is applied for 1 to 45 minutes, with specific pH and concentration ranges, and optionally rinsed off, to enhance bleaching and decolorization efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If common bleaching techniques are applied to achieve high lightening power, then the lightening effect is improved, but the degree of damage to hair increases significantly
Solution Approach 1:
The patent applies a reductive pre-treatment step before the oxidative bleaching process. This preliminary action modifies the hair structure in advance by breaking disulfide bonds and opening the hair cuticle, allowing subsequent oxidative agents to penetrate more evenly and achieve lightening with reduced damage. The pre-treatment prepares the hair to receive the bleaching composition more effectively, reducing the need for aggressive bleaching.
Solution Approach 2:
The patent changes the chemical parameters by introducing a reducing agent (such as thioglycolic acid or cysteine) at a specific concentration range (0.1% to 2%) and pH level (2 to 11) before applying the oxidative bleaching composition. This parameter change creates a more favorable chemical environment for controlled lightening, reducing the harshness of the bleaching process while maintaining effectiveness.
2Illumination intensity
If pre-reduction step is extended to increase lightening power, then the bleaching performance is improved, but the degree of damage to hair increases and processing time is excessive
Solution Approach 1:
The patent optimizes the processing time parameter by limiting the reductive pre-treatment to a specific duration range (0.5 min to less than 5 min). This time parameter change ensures sufficient reduction occurs to prepare the hair for bleaching without excessive exposure that would cause damage. The patent also controls the reducing agent concentration (0.1% to 2%) to achieve the desired effect within this shortened time frame.
Solution Approach 2:
The patent applies a partial reduction action rather than complete reduction. The reductive pre-treatment is designed to only partially modify the hair structure - enough to improve bleaching penetration and performance, but not so much as to cause excessive damage or require extended processing times. This partial action achieves the optimal balance between effectiveness and hair health.
3Illumination intensity
If strong oxidative composition is applied to achieve high lightening power, then the decolorization effect is improved, but the hair structure is damaged more severely
Solution Approach 1:
The reductive pre-treatment serves as a preliminary action that weakens the hair structure in a controlled manner before oxidative exposure. By breaking some disulfide bonds and opening cuticles in advance, the hair becomes more receptive to oxidative agents, allowing milder oxidative compositions to achieve the same decolorization effect that would require harsher agents applied directly, thus preserving overall hair strength.
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 achieves enhanced bleaching and decolorization power with minimal hair damage, as demonstrated by increased lightening values and comparable hair feel across treatment groups, indicating reduced damage.
Implementation Method 1
applying to keratin fibers an aqueous composition comprising a reducing agent... The term bleaching within the meaning of the present invention is the process of lightening natural keratin fibers
Implementation Method 2
applying to keratin fibers an aqueous oxidizing composition resulting from mixing two compositions prior to application onto hair wherein one of the compositions is an anhydrous composition and comprises one or more peroxy salt(s) and/or persalt(s) and... the other composition is an aqueous composition comprising an oxidizing agent, preferably hydrogen peroxide
Data Source
AI summary
The present invention is directed to a process for bleaching and/or decolorizing keratin fibers by combining a pre-reduction step with an oxidative treatment. A short pre-reduction step (less than 5 min) boosts lightening of keratin fibers. The process was found beneficial for organic thiols and inorganic sulphur compounds as reducing agents.