Sprayable Metal Oxide Sunscreen via Amphiphilic Polymer Network
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Solution Overview
Problem
Formulating sunscreen compositions with high levels of metal oxides that are both sprayable and stable is challenging due to the settling of dense particles, especially in products with little or no organic UV filter content, which require higher loads of metal oxides for adequate UV protection.
Innovation Solution
A composition comprising at least 10 weight percent of a metal oxide, combined with 0.1 to 5 weight percent of a branched hydrophobically modified ethoxylated urethane copolymer and 0.1 to 5.5 weight percent of a hydrophobically modified alkali swellable emulsion copolymer, achieving stability and sprayability by creating a composite network of amphiphilic polymers that suspend the metal oxides effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high levels of metal oxides are used for adequate UV protection, then UV protection capability is improved, but particle settling increases and formulation stability deteriorates
Solution Approach 1:
The patent introduces a specific polymer emulsion as an intermediary substance that mediates between the metal oxide particles and the aqueous phase. This emulsion contains hydrophobically modified alkali-swellable copolymer that adsorbs onto metal oxide particle surfaces, providing steric stabilization and preventing aggregation. The emulsion acts as a bridge that allows high levels of metal oxides to be suspended stably in the aqueous formulation without settling
Solution Approach 2:
The patent changes the physical and chemical parameters of the formulation by controlling pH levels and ionic strength to optimize the swelling behavior of the hydrophobically modified alkali-swellable copolymer. By adjusting these parameters, the polymer chains expand or contract to provide optimal steric barrier around metal oxide particles, preventing settling while maintaining high UV protection capability
2Object-affected harmful factors
If high levels of metal oxides are used for adequate UV protection, then UV protection capability is improved, but the composition becomes difficult to spray
Solution Approach 1:
The polymer emulsion serves as a lubricating intermediary between metal oxide particles, reducing inter-particle friction and creating a more fluid formulation. The emulsified polymer coating on particle surfaces prevents direct particle-to-particle contact, reducing aggregation and improving flow characteristics for spray application
Solution Approach 2:
The patent optimizes the viscosity and rheological parameters of the formulation by controlling the concentration and molecular weight of the hydrophobically modified copolymer. By adjusting these parameters, the formulation achieves optimal flow properties that enable easy spray application while maintaining high metal oxide loading for UV protection
3Duration of action of stationary object
If metal oxides are suspended in dispersions for extended time periods, then shelf life is improved, but particle settling increases
Solution Approach 1:
The hydrophobically modified alkali-swellable copolymer emulsion acts as a long-term stabilizing intermediary that continuously maintains particle dispersion. The polymer chains provide persistent steric barrier that prevents particle aggregation and settling over extended storage periods, ensuring shelf stability
Solution Approach 2:
The patent uses an excessive amount of stabilizing polymer relative to conventional formulations, ensuring that even at high metal oxide concentrations, there is sufficient polymer coating on all particle surfaces to prevent settling during extended storage. This excess polymer provides a safety margin for long-term stability
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 maintains stability and sprayability, ensuring long-term suspension of metal oxides and providing effective UV protection with an SPF of at least 15, while being free or substantially free of organic UV filters.
Implementation Method 1
a composition comprising: (a) at least about 10 weight percent of a metal oxide; (b) about 0.1 to about 5 weight percent of a branched hydrophobically modified ethoxylated urethane copolymer; and (c) about 0.1 to about 5.5 weight percent of a hydrophobically modified alkali swellable emulsion copolymer
Implementation Method 2
branched hydrophobically modified ethoxylated urethane copolymer and a hydrophobically modified alkali swellable ('HASE') emulsion copolymer
Implementation Method 3
Metal oxides, however, are difficult to formulate into sprayable compositions... for adequate UV protection
Implementation Method 4
sunscreen compositions containing inorganic sunscreen agents, i.e., metal oxides like zinc oxide or titanium dioxide
Data Source
AI summary
The present invention provides a composition comprising a high load of metal oxides that is phase stable and sprayable. It comprises a branched hydrophobically modified ethoxylated urethane copolymer and a hydrophobically modified alkali swellable emulsion copolymer comprising of one or more acrylate monomers and an ethoxylated associative comonomer.