Fatty Acid-Coated Zinc Oxide Particles for Stable High-Load Dispersions
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Solution Overview
Problem
Fatty acid-treated zinc oxide particles face issues with dispersion stability and thickening at high concentrations due to the formation of fatty acid soap, zinc ions, and unreacted fatty acid, limiting their use in cosmetics.
Innovation Solution
The production method involves preparing a slurry of zinc oxide particles in a dispersion medium, neutralizing fatty acid with a base to form a salt solution, and performing surface treatment at temperatures above the fatty acid's melting point, ensuring a specific ratio of IR absorbance peaks and controlling particle size to enhance dispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If fatty acid treatment is performed on zinc oxide particles, then water-repellent properties are improved, but dispersion stability deteriorates due to formation of fatty acid soap and unreacted fatty acid
Solution Approach 1:
The patent applies parameter changes by controlling the molar ratio of fatty acid to zinc oxide particles within a specific range (0.1-10 times the molar amount of zinc oxide). This parameter optimization prevents excessive formation of fatty acid soap while ensuring sufficient water-repellent treatment, thereby resolving the contradiction between water-repellent properties and dispersion stability.
Solution Approach 2:
The patent uses a base substance as an intermediary to neutralize the fatty acid and form a stable salt compound on the zinc oxide particle surface. This intermediary approach prevents direct reaction between fatty acid and zinc oxide that would produce unstable fatty acid soap, thus improving dispersion stability while maintaining water-repellent properties.
2Object-affected harmful factors
If fatty acid treatment is performed on zinc oxide particles, then water-repellent properties are improved, but viscosity increases due to presence of unreacted free fatty acid
Solution Approach 1:
The patent optimizes the fatty acid concentration parameter by controlling the molar ratio within 0.1-10 times the zinc oxide amount, and performs treatment at specific temperature ranges (50-150°C). These parameter changes ensure complete reaction of fatty acid with zinc oxide, preventing unreacted fatty acid accumulation that would cause viscosity increase, while maintaining water-repellent properties.
Solution Approach 2:
The patent converts the potentially harmful unreacted fatty acid into a beneficial stable fatty acid salt compound through controlled neutralization reaction. By optimizing reaction conditions (temperature, molar ratio), the process ensures complete conversion, transforming what would be a viscosity-increasing impurity into a stable surface coating that provides water-repellent properties without excessive thickening.
3Object-affected harmful factors
If fatty acid treatment is performed on zinc oxide particles, then water-repellent properties are improved, but precipitation of solid matter occurs
Solution Approach 1:
The patent uses a base substance as an intermediary to mediate the reaction between fatty acid and zinc oxide. This intermediary approach forms a stable soluble fatty acid salt compound on the particle surface, preventing direct precipitation of insoluble fatty acid zinc soap. The base acts as a bridge that ensures complete surface coverage without generating precipitates.
Solution Approach 2:
The patent optimizes reaction parameters including molar ratio (0.1-10 times zinc oxide amount), temperature (50-150°C), and pH conditions to ensure complete reaction of fatty acid with zinc oxide surface groups. These parameter changes prevent formation of insoluble fatty acid zinc soap that would precipitate, while maintaining sufficient water-repellent treatment.
4Reliability
If zinc oxide particles are used at high concentration, then UV shielding performance is improved, but thickening occurs due to poor dispersibility
Solution Approach 1:
The patent uses fatty acid salt compound as an intermediary surface coating on zinc oxide particles. This intermediary layer improves particle dispersibility by reducing aggregation, allowing high concentrations of zinc oxide to be used for UV shielding without excessive thickening. The surface coating acts as a spacer that prevents particle-particle aggregation at high loadings.
Solution Approach 2:
The patent optimizes particle size parameters and surface coating parameters to achieve excellent dispersibility. By controlling particle diameter (0.01-10 μm) and surface fatty acid salt coverage, the patent enables high concentration dispersions that maintain low viscosity and good flow properties, preventing thickening while achieving desired UV shielding performance.
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 method produces zinc oxide particles with improved dispersibility and temporal stability, reducing thickening and maintaining low viscosity even at high concentrations, suitable for use in cosmetics.
Implementation Method 1
performing a surface treatment by adding the obtained fatty acid salt aqueous solution to the zinc oxide slurry
Implementation Method 2
dispersed by ultrasonic irradiation using an ultrasonic homogenizer with a rated output of 600 W and a vibration amplitude of 100% at normal temperature for 3 minutes
Implementation Method 3
neutralizing a fatty acid with a base to obtain a fatty acid salt aqueous solution
Implementation Method 4
Steps (2) and (3) are performed at a temperature equal to or higher than a melting point of the fatty acid
Data Source
Figure 1
Figure 2~3
AI summary
Provided is a fatty acid-treated zinc oxide particle that has excellent dispersibility, does not exhibit excessive thickening even in a dispersion blended at a high concentration, and can provide a dispersion excellent in temporal stability. Disclosed is a fatty acid-treated zinc oxide particle characterized by having, in an FT-IR spectrum measured using a total reflection measurement method (ATR method), a ratio (I2/I1) of a maximum absorbance (I2) at from 1500 to 1600 cm-1 to a maximum absorbance (I1) at from 1350 to 1500 cm-1 of from 0.8 to 1.2, and a ratio (I3/I4) of a maximum absorbance (I3) at from 1700 to 1720 cm-1 to a maximum absorbance (I4) at from 1750 to 1800 cm-1 of 1.2 or less, wherein a primary particle size measured with a transmission electron microscope is 0.1 µm or less, and a volume-based mode diameter, according to a laser diffraction scattering method, of a dispersion liquid obtained by adding the powder to isopropyl alcohol and dispersed by ultrasonic irradiation using an ultrasonic homogenizer with a rated output of 600 W and a vibration amplitude of 100% at normal temperature for 1 minute is 0.30 µm or less.