Coated Metal Oxide Particles for Sunscreen Transparency and Skin Feel
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing metal oxides used in sunscreens for UV protection often have issues with coating adhesion, photoactivity, and skin feel, requiring improved coating integrity, transparency, and reduced photoactivity while maintaining effective UV absorption.
Innovation Solution
Development of particulate metal oxide particles with a core of titanium dioxide or zinc oxide, coated with inorganic materials like silica or alumina, and treated with silane coupling agents and hydrophobizing agents to enhance coating integrity, transparency, and skin feel, while reducing photoactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If metal oxide particles are coated with inorganic and/or organic coatings to reduce photoactivity, then photoactivity is reduced, but coating adhesion deteriorates and coatings are easily removed
Solution Approach 1:
The patent applies parameter changes by systematically varying coating composition (combining inorganic coatings like silica/alumina with organic coatings like silanes and waxes), coating thickness, and processing conditions (pH, temperature, surfactants) to achieve optimal balance between photoactivity reduction and coating adhesion. This multi-parameter optimization allows the coating to remain intact while effectively reducing photoactivity.
Solution Approach 2:
The patent employs composite materials by combining multiple coating layers with different properties: inorganic coatings (silica, alumina) provide structural integrity and UV filtering, while organic coatings (silanes, waxes, polymers) provide adhesion and surface modification. This composite approach allows each layer to contribute its strengths, achieving both photoactivity reduction and coating stability.
2Object-affected harmful factors
If metal oxide particles are used for UV absorption, then UV protection is provided, but transparency deteriorates and skin feel worsens
Solution Approach 1:
The patent applies segmentation by using ultrafine metal oxide particles with controlled size distributions (typically 1-100 nm range) rather than large particles. This segmentation allows the particles to be small enough to scatter less light (improving transparency) while maintaining sufficient surface area for UV absorption. The coating layers further segment the particle structure, enabling independent optimization of optical and protective properties.
Solution Approach 2:
The patent changes physical parameters including particle size (reducing to nanoscale), particle size distribution (narrowing for uniformity), and refractive index (through coating materials) to optimize the balance between UV absorption and transparency. By controlling these parameters, the patent achieves high UV protection with minimal visual impact.
3Ease of operation
If metal oxide particles are coated to improve skin feel, then skin feel is improved, but coating integrity deteriorates
Solution Approach 1:
The patent applies local quality by applying different coating materials to different regions or aspects of the particle: inorganic coatings provide structural integrity, silane coupling agents provide chemical bonding, and outer organic layers (waxes, polymers) provide skin-compatible surface properties. Each layer is optimized for its specific function while contributing to overall coating integrity.
Solution Approach 2:
The patent uses silane coupling agents as intermediaries between inorganic and organic coating layers. These silanes chemically bond to both the inorganic oxide surface and the organic coating materials, creating a strong interfacial connection that prevents coating delamination while allowing the outer layers to provide improved skin feel.
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 coated metal oxide particles provide effective UV absorption, improved skin feel, and reduced photoactivity, resulting in a sunscreen composition with enhanced performance and consumer acceptance.
Implementation Method 1
Metal oxides such as titanium dioxide, zinc oxide and iron oxide have been employed as attenuators of ultraviolet light in sunscreens
Implementation Method 2
The inorganic material of the coating layer is chemically different to the metal oxide, preferably titanium dioxide, of the core particles
Implementation Method 3
The coating layer also comprises a silane coupling agent and/or a hydrophobizing agent
Implementation Method 4
The coating layer also comprises a silane coupling agent and/or a hydrophobizing agent
Data Source
AI summary
A particulate metal oxide has a metal oxide core and a coating layer containing an inorganic material and (i) a quaternary silane coupling agent, and/or (ii) a silane coupling agent and a hydrophobizing agent. Preferred materials are titanium dioxide core particles, an amino organosilane coupling agent and a fatty acid hydrophobizing agent. The particulate metal oxide is suitable for use in forming a dispersion, and the particles and dispersion can be used in an end-use sunscreen composition which is transparent, exhibits effective UV absorption properties, reduced photoactivity, and/or improved skin feel.