Composite UV-Filter Particles for Sunscreen White Film Reduction
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Solution Overview
Problem
Current anti-UV sun protection compositions using inorganic UV-screening agents face challenges in providing efficient photoprotection without compromising cosmetic acceptability, as they often result in a white film on the skin and have insufficient efficacy.
Innovation Solution
A composition containing an aqueous phase, spherical composite particles with a mean size of 0.1 to 30 µm comprising a particulate UV-screening agent and an inorganic core, along with free particles of inorganic UV-screening agents greater than 0.07 µm, where the composite particles include SiO2, poly(methyl methacrylate), and copolymers, and the free particles are treated with surface agents like dimethicone or stearic acid, enhancing photoprotection while maintaining cosmetic acceptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic UV-screening agents with particle size greater than 0.07 μm are used, then photoprotection efficacy is improved, but cosmetic acceptability deteriorates due to white film formation on skin
Solution Approach 1:
The inorganic UV-screening agent is divided into two distinct particle size fractions: fine particles (0.005-0.07 μm) encapsulated in composite particles A, and coarse particles (>0.07 μm) as free particles B. This segmentation allows each fraction to fulfill different functional roles - the fine particles provide UV protection without white film, while the coarse particles enhance protection efficacy.
Solution Approach 2:
Fine inorganic UV-screening agent particles are nested inside composite particles A consisting of a core (organic polymer or inorganic material) and an outer shell. This encapsulation structure protects the fine particles from aggregating and depositing on skin, preventing white film formation while maintaining their UV-screening capability.
2Reliability
If inorganic UV-screening agents are used to provide high photoprotection, then UV screening efficacy is improved, but cosmeticity deteriorates
Solution Approach 1:
Different particle size ranges are assigned to different functional requirements: fine particles (0.005-0.07 μm) are optimized for cosmetic acceptability and skin feel, while coarse particles (>0.07 μm) are optimized for UV screening efficacy. The composite structure localizes the fine particles in the encapsulated form for cosmetic areas and uses free coarse particles for protection areas.
Solution Approach 2:
Composite particles A are formed by combining an organic polymer core (or inorganic core) with fine inorganic UV-screening agent particles. This composite structure integrates the benefits of both materials - the organic/inorganic core provides a carrier that prevents aggregation and improves cosmeticity, while the embedded inorganic particles provide UV protection.
3Ease of operation
If fine inorganic particles (less than 0.1 μm) are used, then cosmetic acceptability is improved, but photoprotection efficacy becomes insufficient
Solution Approach 1:
The invention merges two previously separate approaches into a single formulation: fine particles for cosmetic acceptability and coarse particles for efficacy. By combining these two particle size fractions in one composition, both cosmetic acceptability and photoprotection efficacy are simultaneously achieved.
Solution Approach 2:
The particle size parameter of the inorganic UV-screening agent is changed from a single uniform size to a bimodal distribution with two distinct size ranges. This parameter change allows the formulation to exploit the advantages of both fine particles (cosmeticity) and coarse particles (efficacy).
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 composition effectively screens out UV radiation, providing enhanced photoprotection without the drawbacks of existing formulations, such as the white film issue, while maintaining a pleasant skin feel and appearance.
Implementation Method 1
composite particles A in spherical form, having a mean size of between 0.1 and 30 μm comprising at least one particulate UV-screening agent... free particles B of inorganic UV-screening agent... effectively screens out UV radiation
Implementation Method 2
Fine inorganic particles based on a metal oxide such as titanium dioxide (TiO2) are usually used... to protect the skin against UV rays
Data Source
AI summary
The subject of the present invention is a composition containing, in a cosmetically acceptable medium, at least: a) at least one aqueous phase and b) composite particles A in spherical form, having a mean size of between 0.1 and 30 ?m comprising at least one particulate UV-screening agent and a core constituted of at least one inorganic material and/or of at least one organic material, and c) free particles B of inorganic UV-screening agent having a mean elementary size greater than 0.07 ?m.