Spherical Silica Particles for Stannous Compatibility and Low RDA
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Solution Overview
Problem
Existing dentifrice compositions containing stannous, such as stannous fluoride, face reduced effectiveness due to interactions with silica materials, and spherical silica particles have limitations in Relative Dentin Abrasion (RDA) performance.
Innovation Solution
Development of spherical silica particles with specific characteristics, including a d50 median particle size range of 8 to 20 μm, a sphericity factor of 0.9 or higher, a BET surface area range of 0.1 to 8 m2/g, and a total mercury intrusion pore volume range of 0.35 to 0.8 cc/g, produced using a continuous loop reactor process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional non-spherical silica particles are used, then higher RDA performance is achieved, but stannous compatibility is reduced
Solution Approach 1:
The patent applies spheroidality by transforming traditional non-spherical silica particles into spherical particles with a sphericity factor of at least 0.9. This shape modification resolves the contradiction by providing both improved stannous compatibility and reduced RDA performance, as the spherical geometry reduces abrasive harshness while maintaining cleaning effectiveness.
Solution Approach 2:
The patent employs parameter changes by controlling specific physical and chemical properties of the silica particles including particle size distribution (d10, d50, d90 values), surface area (0.5-5.0 m2/g), pore volume (0.4-0.65 cc/g), and loss on ignition (3.2-5.5 wt%). These parameter optimizations simultaneously achieve improved stannous compatibility and reduced RDA performance.
2Reliability
If spherical silica particles are used, then stannous compatibility is improved, but RDA performance is reduced
Solution Approach 1:
The patent resolves this contradiction by optimizing multiple parameters simultaneously: controlling particle size distribution (d10: 3-6 μm, d50: 8-18 μm, d90: 15-30 μm), surface area (0.5-5.0 m2/g), pore volume (0.4-0.65 cc/g), and loss on ignition (3.2-5.5 wt%). These controlled parameters enable the spherical particles to achieve both improved stannous compatibility and acceptable RDA performance.
Solution Approach 2:
The patent creates a composite structure within the spherical silica particles by controlling the internal pore structure (0.4-0.65 cc/g pore volume) and surface properties (0.5-5.0 m2/g surface area). This composite approach allows the outer spherical shape to provide reduced RDA while the internal structure maintains stannous compatibility.
3Productivity
If high surface area silica particles are used, then cleaning effectiveness is improved, but stannous interaction is increased
Solution Approach 1:
The patent resolves this contradiction by precisely controlling the surface area parameter within a narrow range of 0.5-5.0 m2/g. This optimized surface area provides sufficient cleaning effectiveness through mechanical action while minimizing stannous-silica interactions that would reduce stannous compatibility.
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 achieve improved stannous compatibility and reduced RDA performance, enhancing the overall effectiveness of stannous in dentifrice compositions while maintaining low abrasivity.
Implementation Method 1
a first mineral acid and a first alkali metal silicate react to form a base silica product in the liquid medium of the loop reaction zone
Implementation Method 2
Benefits of the continuous loop reactor process include reduced particle aggregation and improved particle sphericity
Implementation Method 3
continuously recirculating the liquid medium through the loop reaction zone
Implementation Method 4
continuously discharging from the loop reaction zone a portion of the liquid medium comprising the base silica product
Data Source
AI summary
Silica particles having a d50 median particle size from 8 to 20 μm, a sphericity factor (S80) of at least 0.9, a BET surface area from 0.1 to 8 m2/g, a total mercury intrusion pore volume from 0.35 to 0.8 cc/g, and a loss on ignition from 3 to 7 wt. %, are disclosed, as well as methods for making these silica particles, and dentifrice compositions containing the silica particles.