Spherical Silica Particle Design for RDA Control
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Solution Overview
Problem
Existing silica particles used in toothpaste compositions, particularly those with non-spherical and irregular shapes, do not effectively minimize Relative Dentin Abrasion (RDA) despite advancements in dentifrice safety testing, indicating a need for improved silica particles with enhanced RDA performance.
Innovation Solution
Development of spherical silica particles with specific characteristics, including a d50 median particle size of greater than or equal to 6 μm, a (d90−d10)/d50 ratio between 1.1 and 2.4, RDA at 20 wt.% loading between 40 and 200, and a sphericity factor of 0.9 or higher, produced using a continuous loop reactor process under low shear conditions, which results in reduced abrasiveness and improved dentin protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional non-spherical and irregularly shaped silica particles are used in toothpaste, then certain properties such as low Einlehner abrasion are achieved, but RDA performance is not improved
Solution Approach 1:
The patent applies spheroidality by transforming traditional non-spherical and irregularly shaped silica particles into spherical particles with a sphericity factor of at least 0.9. This shape transformation resolves the technical contradiction by maintaining the beneficial low Einlehner abrasion property while achieving improved RDA performance through the spherical morphology, which reduces dentin abrasion during brushing.
2Object-affected harmful factors
If spherical silica particles with smaller particle size are used, then surface area increases, but RDA performance deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the particle size of spherical silica particles to a d50 median particle size of at least 6 μm. This parameter optimization resolves the technical contradiction by finding the optimal balance between surface area and RDA performance, where particles that are not too small achieve both adequate surface area for cleaning effectiveness and reduced RDA for dentin protection.
3Shape
If conventional reactor processes are used for producing silica particles, then production efficiency is maintained, but particle sphericity and roundness are insufficient
Solution Approach 1:
The patent applies spheroidality by designing a continuous loop reactor process that inherently produces spherical particles with a sphericity factor of at least 0.9. The reactor configuration and operating conditions are optimized to achieve this high sphericity while maintaining production efficiency, resolving the technical contradiction between particle roundness and ease of manufacture.
4Shape
If high shear conditions are applied during silica particle production, then mixing efficiency improves, but particle morphology becomes less spherical
Solution Approach 1:
The patent applies parameter changes by optimizing the shear frequency during the silica particle production process to be less than 1,000,000 interactions/min. This parameter optimization resolves the technical contradiction by maintaining adequate mixing efficiency while preserving particle sphericity, as excessive shear forces would deform the spherical morphology.
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 spherical silica particles demonstrate reduced Relative Dentin Abrasion and Pellicle Cleaning Ratio, indicating enhanced safety and effectiveness in dentifrice applications, with increased particle size leading to decreased abrasiveness and improved brushing performance.
Implementation Method 1
at least a portion of the mineral acid and the alkali metal silicate react to form the silica particles in the liquid medium of the loop reaction zone
Implementation Method 2
continuously recirculating the liquid medium through the loop reaction zone
Data Source
AI summary
Silica particles having a d50 median particle size of at least 6 μm, a ratio of (d90−d10)/d50 from 1.1 to 2.4, a RDA at 20 wt. % loading from 40 to 200, and a sphericity factor (S80) of at least 0.9, are disclosed, as well as methods for making these silica particles, and dentifrice compositions containing the silica particles.