Stabilizing Silver Ions in Alkaline Cleansing Compositions
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Solution Overview
Problem
Silver-based antimicrobial soap compositions tend to discolour due to the instability of silver compounds in alkaline environments, leading to unwanted darkening and loss of aesthetic appeal, especially in white soap bars.
Innovation Solution
Maintaining a free alkali content below 0.01% in alkaline cleansing compositions with a pH of at least 9, combined with 20 to 85 wt% anionic surfactant and a silver(I) compound having a solubility of at least 1×10−4 mol/L, helps reduce discolouration by stabilizing silver ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver-based antimicrobial agents are used in alkaline cleansing compositions, then antimicrobial effectiveness is improved, but discolouration occurs due to silver instability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the free alkali content parameter to below 0.01% while maintaining pH of at least 9. This specific parameter control stabilizes silver compounds in the alkaline environment, preventing discolouration while preserving antimicrobial effectiveness. The composition achieves this by adjusting the balance between pH and free alkali content.
2Stability of the object's composition
If free alkali content is reduced below 0.01%, then silver compound stability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses an intermediary approach by introducing a specific silver(I) compound with controlled solubility (at least 1×10⁻⁴ mol/L) as a mediator between the alkaline environment and the silver antimicrobial agent. This intermediary compound form helps stabilize silver ions while allowing for more manageable manufacturing precision requirements compared to direct control of free alkali content alone.
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
Significantly reduces discolouration of silver-based antimicrobial soap compositions, maintaining their appearance and antimicrobial effectiveness even at high pH levels, while ensuring the silver compounds remain stable and effective.
Implementation Method 1
a silver(I) compound having silver ion solubility (in water at 25° C.) of at least 1×10−4 mol/L
Data Source
AI summary
Disclosed is a cleansing composition having pH of at least 9, said composition comprising: (i) 20 to 85 wt % anionic surfactant; and, (ii) a silver(I) compound having silver ion solubility (in water at 25° C.) of at least 1×10−4 mol/L, at a level equivalent to silver content of 0.01 to 100 ppm, wherein the free alkali content of said composition is less than 0.01%. The composition is a robust and improved cleansing composition with a stable colour.