Wax-Encapsulated Metal Oxide Opacifiers for Stable Rinse-Off Compositions

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Solution Overview

Problem

Existing opacifiers in aqueous personal care rinse off compositions face issues with stability, compatibility, and water content, leading to undesirable effects like spotting and residue formation, especially in concentrated detergents or unit dose packets, and they do not match the performance of styrene acrylic copolymer-based opacifiers.

Innovation Solution

Incorporation of composite opacifier particles, where metal oxide particles like zinc oxide or titanium oxide are partially or completely encapsulated by a wax with a melting point of 45 to 110°C, providing a z-average particle size of 100 to 2,000 nm, to enhance stability and sustainability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional styrene acrylic copolymer based opacifiers are used, then opacification performance is achieved, but sustainability is compromised and water content is high

Engineering Contradiction:

Improveopacification performanceVSAvoidwater content

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent changes the fundamental parameters of the opacifier system by replacing conventional styrene acrylic copolymer particles with composite particles consisting of metal oxide cores (zinc oxide, titanium oxide) encapsulated in wax. This parameter change reduces water content while maintaining opacification performance through the optical properties of metal oxide particles.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials by combining metal oxide particles with wax encapsulation. The composite structure provides both the optical properties needed for opacification (from metal oxide) and the stability/sustainability benefits (from wax encapsulation), while reducing water content compared to conventional aqueous suspensions.

Inventive Principle:

Principle #40Composite materials

2Reliability

If conventional opacifiers are used, then opacification is achieved, but stability and compatibility issues arise leading to spotting and residue formation

Engineering Contradiction:

ImproveopacificationVSAvoidformulation stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The wax acts as an intermediary substance that encapsulates the metal oxide particles and mediates their interaction with the aqueous formulation. This intermediary layer improves compatibility between the hydrophobic metal oxide particles and the hydrophilic aqueous vehicle, preventing aggregation, spotting, and residue formation while maintaining stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The wax forms a flexible shell or thin film around each metal oxide particle, creating a protective interface that prevents direct contact between the particle surface and the aqueous formulation. This shell structure enhances stability by preventing particle aggregation and interaction with other formulation components that could cause spotting or residue.

Inventive Principle:

Principle #30Flexible shells and thin films

3Shape

If conventional opacifiers are used, then aesthetic appearance is improved, but harmful effects like spotting and residue formation occur

Engineering Contradiction:

Improveaesthetic appearanceVSAvoidspotting and residue formation

Core Design Contradiction:

ShapeVSObject-generated harmful factors

Solution Approach 1:

The patent converts the potential harm of using metal oxide particles (which can cause spotting and residue) into a benefit by properly encapsulating them in wax. The wax encapsulation transforms the problematic direct particle-formulation interaction into a controlled interface, maintaining the desired aesthetic appearance while eliminating harmful effects.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 composite opacifier particles provide stable opacification comparable to conventional styrene acrylic copolymers while reducing water content, improving the overall sustainability of the personal care compositions.

Implementation Method 1

composite opacifier particles comprise metal oxide particles that are partially or completely encapsulated by a wax

Methodology Applied

Scientific EffectEncapsulation: Physical Containment

Implementation Method 2

Opacifiers are materials that make a liquid system opaque. Thus, opacifiers are used to modify the appearance or aesthetics of detergents

Methodology Applied

Scientific EffectLight scattering and absorption: Absorption (EM radiation)

Data Source

PatentUS12508214B2Personal care rinse off composition with composite opacifier particles

Publication Date: 2025.12.30 ROHM & HAAS CO

AI summary

An aqueous personal care rinse off composition is provided, comprising: a dermatologically acceptable aqueous vehicle; a dermatologically acceptable cleaning surfactant; and a plurality of composite opacifier particles, wherein the composite opacifier particles comprise metal oxide particles that are partially or completely encapsulated by a wax; wherein the metal oxide particles are selected from the group consisting of zinc oxide, titanium oxide and mixtures thereof; wherein the metal oxide particles have a z average particle size of >100 nm as measured by dynamic light scattering; wherein the wax has a melting point temperature of 50 to 110° C.; and wherein the composite opacifier particles have a z average particle size of >100 nm to 2,000 nm as measured by dynamic light scattering.