Metal Oxide Ester Dispersions for Stable High-Solids Sunscreen
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Solution Overview
Problem
Existing sunscreen formulations with metal oxide particles face challenges in achieving stable, low viscosity, high-solids dispersions that are non-whitening on the skin, requiring high shear mixing and surface modification, which are inefficient and costly, and do not meet consumer demand for natural and sustainable products.
Innovation Solution
The use of ester dispersing media (EDM) and broad molecular weight distribution (MWD) polyesters, synthesized from 100% biobased carbon, to create stable, low viscosity dispersions of metal oxide particles without surface modification, allowing for high solids loading and easy application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high shear mixing is employed to disperse metal oxide particles, then dispersion stability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent introduces a dispersing agent as an intermediary substance that mediates between the metal oxide particles and the dispersing medium. This dispersing agent adsorbs onto the particle surfaces and provides steric stabilization, preventing agglomeration without requiring high shear mixing equipment. The dispersing agent acts as a molecular bridge that enables stable dispersions through chemical adsorption rather than mechanical force alone.
Solution Approach 2:
The patent modifies the surface properties of metal oxide particles through surface modification treatments, changing their surface energy and chemical characteristics. By altering surface parameters such as hydrophilicity/hydrophobicity balance and surface charge, the particles achieve better compatibility with the dispersing medium, enabling stable dispersions at lower shear conditions and reducing manufacturing complexity.
2Stability of the object's composition
If surface modification is applied to metal oxide particles, then dispersion stability is improved, but manufacturing cost increases
Solution Approach 1:
The patent employs a dispersing agent as an intermediary that provides surface modification functionality. Instead of directly modifying the metal oxide particles through complex surface treatment processes, the dispersing agent adsorbs onto the particle surfaces and provides the necessary steric stabilization and surface compatibility. This approach achieves dispersion stability while maintaining simpler, lower-cost manufacturing processes.
3Ease of operation
If nonaqueous dispersing media are used, then consumer acceptance and tactile properties are improved, but viscosity increases
Solution Approach 1:
The patent modifies the physical and chemical parameters of the dispersing medium by selecting specific nonaqueous fluids with optimized viscosity characteristics. By adjusting the chemical composition and physical properties of the dispersing medium parameters, the formulation achieves low enough viscosity for easy application while maintaining the nonaqueous characteristics desired by consumers for tactile properties and skin feel.
4Productivity
If high solids loading is achieved, then product efficiency is improved, but viscosity increases
Solution Approach 1:
The patent uses a dispersing agent as an intermediary that enables high solids loading by providing steric stabilization. The dispersing agent adsorbs onto particle surfaces and prevents agglomeration, allowing high concentrations of particles to be dispersed in the liquid medium without excessive viscosity. This intermediary mechanism maintains particle separation even at high loadings, preserving fluidity and ease of application.
Solution Approach 2:
The patent optimizes the formulation parameters including the ratio of dispersing agent to particles, the molecular weight distribution of the dispersing agent, and the chemical composition of the dispersing medium. By carefully adjusting these parameters, the formulation achieves high solids loading while controlling viscosity through parameter optimization rather than simply increasing particle concentration.
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 solution provides stable, low viscosity dispersions with high metal oxide particle loadings, suitable for consumer products, meeting sustainability and performance criteria, and maintaining ease of application and stability over time.
Implementation Method 1
The MOPs are typically prepared and supplied as free-flowing powders. To effectively prepare sunscreen formulations containing ZnO and/or TiO2 MOPs that provide adequate sun protection factor ('SPF') values and that are non-whitening on skin requires creating dispersions of the MOPs that are stable against agglomeration.
Implementation Method 2
Wetting of the MOPs by the dispersing medium forms a dispersed homogeneous state that typically requires a dispersing agent to prevent reagglomeration of the MOPs.
Data Source
AI summary
The present invention relates to a nonaqueous composition for dispersing metal oxide particles. The nonaqueous composition comprises an ester dispersing media and a broad molecular weight distribution (MWD) polyester dispersing agent, each preferably synthesized from 100% biobased carbon. The ester dispersing media includes a liquid ester selected from the group consisting of: Formulas (I), (II), (III), (IV), and combinations thereof. The polyester dispersing agent has a polydispersity index (PDI) of greater than about 2.3. The present invention also relates to a nonaqueous dispersion comprising the nonaqueous composition above and metal oxide particles dispersed therein. The metal oxide particles may comprise zinc oxide, titanium oxide, or combinations thereof. Formulations using the compositions and dispersions as well as processes for preparing are also disclosed.